Arkema SodiumDichromate AoA - Public -R2

ANALYSIS OF ALTERNATIVES

Public Version

Legal name of applicant(s): Arkema France

Submitted by: Arkema France

Substance: Sodium dichromate

Use title: Use of sodium dichromate as an additive for suppressing parasiticreactions and oxygen evolution, pH buffering and cathode corrosionprotection in the electrolytic manufacture of sodium chlorate withor without subsequent production of chlorine dioxide or sodiumchlorite

Use number: 1

Disclaimer

This report has been prepared by Risk & Policy Analysts Ltd, with reasonable skill, care and diligenceunder a contract to the client and in accordance with the terms and provisions of the contract. Risk& Policy Analysts Ltd will accept no responsibility towards the client and third parties in respect ofany matters outside the scope of the contract. This report has been prepared for the client and weaccept no liability for any loss or damage arising out of the provision of the report to third parties.Any such party relies on the report at their own risk.

Note

This public version of the Analysis of Alternatives includes some redacted text. The letters indicatedwithin each piece of redacted text correspond to the type of justification for confidentiality claimswhich is included as an Annex (Section 7) in the complete version of the document.

Table of contents

1 Summary.............................................................................................................................. 1

1.1 Use applied for................................................................................................................................1

1.2 Potential alternatives for sodium dichromate................................................................................1

1.3 Suitability of potential alternatives to sodium dichromate............................................................4

1.4 Feasibility and availability of potential alternatives for sodium dichromate .................................6

1.5 Actions needed to improve the suitability and availability of potential alternatives...................11

2 Analysis of substance function ............................................................................................ 15

2.1 The chlorate process.....................................................................................................................15

2.2 Conditions of use and technical feasibility criteria .......................................................................22

2.3 Summary of functionality of sodium dichromate in the “Applied for Use” .................................29

3 Annual tonnage .................................................................................................................. 31

3.1 Tonnage band ...............................................................................................................................31

3.2 Trends in the consumption of sodium dichromate ......................................................................31

3.3 Form and usage of sodium dichromate ........................................................................................31

4 Identification of possible alternatives.................................................................................. 33

4.1 List of possible alternatives...........................................................................................................33

4.2 Description of efforts made to identify possible alternatives ......................................................33

4.3 Screening of identified alternatives..............................................................................................63

5 Suitability and availability of possible alternatives............................................................... 85

5.1 Introduction ..................................................................................................................................85

5.2 Chromium(III) chloride..................................................................................................................85

5.3 Sodium molybdate........................................................................................................................95

5.4 Molybdenum-based coatings .....................................................................................................105

5.5 Two-compartment electrolytic systems .....................................................................................111

6 Overall conclusions on suitability and availability of possible alternatives.......................... 117

6.1 Technical feasibility of shortlisted alternatives ..........................................................................117

6.2 Economic feasibility of shortlisted alternatives..........................................................................119

6.3 Reduction of risks from the use of shortlisted alternatives........................................................120

6.4 Availability of shortlisted alternatives ........................................................................................121

6.5 Overall conclusion.......................................................................................................................122

7 Annex – Justifications for confidentiality claims................................................................. 123

8 Appendix 1 – Information Sources..................................................................................... 125

9 Appendix 2 – Comparative hazard and risk characterisation of alternatives........................ 129

9.1 Background .................................................................................................................................129

9.2 Reference values for sodium dichromate and alternative substances.......................................129

9.3 Exposure Assessment..................................................................................................................152

9.4 Comparative risk characterisation ..............................................................................................156

9.5 References for this Appendix......................................................................................................158

10 Appendix 3 – Economic feasibility ..................................................................................... 161

10.1 Economic feasibility of sodium molybdate.................................................................................161

10.2 Economic feasibility of molybdenum-based coatings ................................................................167

10.3 Economic feasibility of two-compartment electrolytic systems.................................................171

Use number: 1 Legal name of applicant(s): Arkema France1

1 Summary

1.1 Use applied for

This Analysis of Alternatives (AoA) is part of an Application for the Authorisation (AfA) for thecontinued use of sodium dichromate (CAS No. 7789-12-0 & 10588-01-9; EINECS No. 234-190-3,hereafter referred to as “SD”) by the applicant, Arkema France (hereafter referred to as Arkema), inthe sodium chlorate (NaClO3) manufacturing process, where it acts as a crucial additive to theprocess. Generation of sodium chlorate is based on the electrolysis of sodium chloride (NaCl), at acontrolled pH range, where the sodium chloride is converted into sodium chlorate while hydrogenevolves as a co-product. SD acts to increase the current efficiency of the conversion process bysuppressing unwanted (parasitic cathodic) reactions and thus reducing the use of electrical energy,and acts as a pH buffer to ensure optimal process conditions are maintained. Another crucial role islimiting the amount of oxygen generated during the process, as the presence of oxygen poses aserious hazard because it forms explosive atmospheres in the presence of hydrogen.

Arkema is using '''#B#''' tonnes of SD out of a total consumption of <40 tonnes consumed in this useby EU-based manufacturers of sodium chlorate. This overall volume represents less than 1% of theentire amount of SD used each year in the EU.

This AoA has been prepared by an independent third party working on behalf of Arkema. Arkemaand a further six EU-based users of SD collectively formed the Sodium Dichromate AuthorisationConsortium (hereafter referred to as SDAC). While there is notable overlap in the informationpresented and the argumentation made in the AoA documents of all seven applicants, each AoAdocument, including the present one, is tailored to the specific applicant and describes the specificsituation for Arkema. It must be noted that each of the company-specific AoA documents mayinclude information which is available only to the applicant and which (a) is confidential, and (b)does not appear in the AoA documents of the remaining SDAC applicants.

1.2 Potential alternatives for sodium dichromate

This AoA details an extensive search of literature carried out by the independent third party. Inaddition, consultation with all seven SDAC members regarding their R&D efforts has been used inconjunction with the publicly available information to ensure all relevant alternatives have beenconsidered. In total, ten alternative substances and technologies were identified and evaluated, andthese are summarised in Table 1-1.

Table 1-1: Master list of identified potential alternatives for SD in sodium chlorate manufacture

No Potential alternative substances

1 Chromium (III) chloride

2 Sodium molybdate

3 Rare Earth Metal (III) salts

No Potential alternative cathode coatings

4 Molybdenum-based cathode coatings

5 Ruthenium-based cathode coatings

6 Zirconium- based cathode coatings


Table 1-1: Master list of identified potential alternatives for SD in sodium chlorate manufacture

No Potential alternative cathode materials

7 Ruthenium alloy cathodes

No Potential alternative electrolytic processes

8 Two-compartment electrolytic systems

9 Two-compartment electrolytic cells with oxygen-consuming gas diffusion electrodes

10 Polymeric cathode film coatings

The screening of the identified alternatives included the following steps:

Commercialisation status: this step looked into whether each of the alternatives is commerciallyavailable. If yes, the question was how quickly could it be implemented on an industrial scale bythe applicant; if no, the analysis looked into how quickly it might become available on anindustrial scale. This step eliminated Alternatives 9 and 10 as they are currently very far awayfrom any foreseeable commercialisation scenario;

Suitability for SD replacement: this step looked into the fundamental criterion of whether eachidentified alternative is able to eliminate the handling of - and exposure of workers to - SD. Asfar as is known at this time, some of the identified alternatives (Alternatives 2, 5 and 7) cannotperform to an acceptable level unless SD is present in the electrolyte (in the sodium chloratecell), as is described in detail in Section 4.3.3. Additionally it should be noted that the use ofAlternative 1 results in the formation of SD in the electrolyte (although, compared to the use ofSD, it eliminates worker exposure arising from the handling of SD during the dosing task, the firststep in the use of SD to produce sodium chromate);

Technical feasibility criteria comparison: this step utilised a list of seven criteria to compare thetechnical feasibility of the identified alternatives. The criteria are:

- Formation of a protective film permeable to H2 but impermeable to hypochlorite- Control of oxygen formation- Cathode protection- pH buffering- Current efficiency and overall energy consumption- Solubility in the electrolyte (for alternative substances only)- Lack of impurities in the sodium chlorate product

This screening identified specific technical shortcomings for some of the potential alternatives,e.g. poor energy efficiency (Alternative 2), generation of excessive amounts of O2 (Alternative 2),very low solubility (Alternative 3), poor pH buffering (Alternatives 2, 4, 5, 7) and poor reactionselectivity (Alternative 7)

Engineering and economic feasibility: this step looked at the practical (incl. engineering) stepsrequired for each of the identified alternatives and the key complexities of these practical steps.A series of alternatives were found to be practically impossible to implement due to inherentand, to the applicant’s best knowledge, insurmountable problems, e.g. poor solubility(Alternative 3), unavailability of suitable cathodes (Alternatives 5 and 6), and lack of industrialscale proof of concept and experience (Alternatives 3, 5, 6 and 7).

An overview of results is given in Table 1-2. The table identifies the shortlisted potential alternativeswhich form the core of the assessment in Section 5 of this AoA:

Alternative 1 (substance): Chromium (III) chloride for completeness, given the lack of suitabilityin eliminating Cr(VI) exposure


Alternative 2 (substance): Sodium molybdate Alternative 4 (technology): Molybdenum-based cathode coatings, and Alternative 8 (technology): Two-compartment electrolytic systems.

Table 1-2: Summary of the screening of identified potential alternatives for SD in the manufacture ofsodium chlorate

AlternativeCommercialisationstatus

Suitability asSDreplacement(exposure)

Compared toSD in termsof technicalfeasibilitycriteria

Engineeringandeconomicfeasibility

Shortlisted forfurtheranalysis?


1 Chromium (III)compounds

Not immediatelyavailable and mostlikely unavailable atsunset date

Unsuitableas it onlyleads to avery smallreduction toexposure (ca.20% forsomeworkers)

Uncertaindue to lackofknowledgeof conditionsandparametersof use

Uncertainfeasibilityand costwhile 3rdparty patentapplicationpending

Yes – butunsuitable forreducingworkerexposure

2 Sodiummolybdate

Unproven on theindustrial scale;uncertain future

Low SDlevels maybe required

Worse Not availableon industrialscale

Yes

3 Rare EarthMetal (III)salts

Impossible to use Acceptable Worse Impossible No

No Potential alternative cathodic coatings

4 Molybdenum-basedcathodecoatings


SD additionmay berequired

Probablyworse;betterclaimedenergyefficiency

Infeasiblaandunavailableat onindustrialscale

Yes

5 Ruthenium-basedcathodecoatings


SD additionrequired

Worse Impossible No

6 Zirconium-basedcathodecoatings

Unproven on theindustrial scale

SD additionmay berequired

Worse Impossible No


7 Rutheniumalloy cathodes


SD additionrequired

Worse Impossible No


8 Two-compartmentelectrolyticsystems

Not used forchlorate production

Acceptable Worse thanSD

Feasible butvery costly

Yes


1.3 Suitability of potential alternatives to sodium dichromate

1.3.1 Risks to human health and the environment from direct substitution

A detailed comparative risk assessment for environmental and human health effects has beenundertaken to assess the suitability of chromium (III) compounds and sodium molybdate whichcould in theory act as ‘drop-in’ replacements for SD. This assessment, included in this AoA asAppendix 2 (Section 8), also looked into the risks to human health and the environment from sodiumphosphates. These would need to be added to the electrolyte in the absence of SD if sodiummolybdate (or molybdenum-coated cathodes) is used to act as a pH buffer.

For the comparative assessment of the human health and environmental risks of SD and thepotential alternative substances, the following approach was followed:

Available reference values (DNELs, PNECs) were analysed Where there are no feasible reference values, (i.e. none that had been derived by similar

methodologies to allow for a comparison), tentative reference values were derived An exposure scenario was established similar to the actual exposure scenario for SD Exposure modelling input data were compiled for all alternative substances and SD Exposure levels and risk characterisation ratios for the environment were calculated using

ECETOC TRA Exposure levels for workers were modelled using ART (Advanced REACH Tool).

Comparison of hazard data (classifications) reveals that none of the alternatives investigated areCMR substances and that none of the alternatives has been classified for environmental hazards.Moreover, the tentative risk characterisation shows that the alternative substances (chromium(III)chloride, sodium molybdate and sodium phosphates) have lower RCRs for both human healthendpoints (workers) and the environment; therefore, the alternative substances assessed in detailare beneficial with regard to human health considerations and fulfil the REACH Authorisationrequirement of leading to a reduction in overall risks to human health and the environmentcompared to the Annex XIV substance SD, based on the assumptions used in Appendix 2.

However, the use of chromium(III) chloride does not avoid the presence of Cr(VI) species in theelectrolyte. Use of a Cr(III) compound instead of SD would eliminate exposure during Task 1 (feedingliquid SD solution into the process, i.e. dosing, see Table 5-7). All other Tasks, in terms of workerexposure to Cr(VI) species, would remain unchanged. Importantly, any worker who is involved indosing SD (a generally infrequent task), is also involved in one or more other Tasks which may resultin exposure to Cr(VI). As a result, the use of a Cr(III) compound in the place of SD would onlyeliminate a very small percentage (ca. 20%) of aggregate exposure of some workers (see Section5.2.4), but the exposure of other workers would not be affected.

Therefore, despite chromium(III) chloride resulting in a reduction in risk, this alternative cannot beconsidered suitable as its use only marginally reduces worker exposure to the Cr(VI) anion thatconfers the SVHC (CMR) properties to SD.

For the two alternative technologies, molybdenum-coated cathodes and two-compartmentelectrolytic cells, a direct comparison of risks against SD is not possible. In the case of molybdenum-coated cathodes, it is assumed that no additives would be required apart from a sodium phosphatebuffer. For two-compartment electrolytic cells, no additives are assumed to be added. It is


therefore assumed that the risks from the use of SD would be eliminated and new hazards wouldnot be introduced to the operation of the cells (although, the extent to which molybdenum-coatedcathodes would control the evolution of oxygen is uncertain), hence, both alternative technologiesare assumed to reduce the overall risk to human health and the environment.

1.3.2 Environmental externalities from changes in energy consumption

Electricity is the most significant component of the production cost of sodium chlorate. With theexception of chromium(III) chloride that largely acts in the electrolyte as SD, the use of any of theother three alternatives would result in notable increases in energy consumption. Increased energyconsumption is expected for sodium molybdate and two-compartment cells, which would result inincreased indirect emissions of greenhouse gases due to the need to generate additional electricity.

In contrast, if claims made in the patent literature were to be confirmed at the industrial scale, theuse of molybdenum-coated electrodes could theoretically result in a modest reduction in indirectgreenhouse gas emissions due to increased energy efficiency. However, such claims are impossibleto verify without trialling this alternative on an industrial scale over a test period much longer thanthat documented in the relevant patent literature. Moreover, the concomitant use of phosphatebuffers would increase oxygen generation and reduce the efficiency and yield of the process. Giventhese uncertainties, a calculation of environmental externalities resulting from change(s) in energyconsumption is not provided for this alternative.

A summary of the calculated changes in energy consumption and associated changes to the releaseof greenhouse gases (CO2) is presented in Table 1-3.

Table 1-3: Environmental externalities from changes in energy consumption under the shortlistedalternatives for Arkema

Alternative''''''''#G#''''''''

''''''''''''''''' '''''''''''' '''''''''''''''''''

'''''''''''''''''''''''''''''''''''''''''''''

'''''''''''''''''''''''''''''''''''''''' ''''''' '''''''''''

''''''''''''''''' '''' '''''''''''''''''''' '''''''''''''''''''''''''

''''''''''''''''''' '''' '''''

Chromium(III)chloride

''''' ''' ''''''''''''''' ''''' ''' '''''''''''''''' '''''' ''' '''''''''''''''' '''''' ''' '''''''''''''''''

Sodiummolybdate

'''''''''' ''''''''''''' ''''''''''''''''' '''''''''' ''' '''''''' '''''''''''' '''''''''''' '''''' '''''''''''''''''''''''

''''''''''''''''''

Molybdenum-based coatings

'''''''' '''''''''''''''''''' '''''''' '''' ''''''''''''''''''''''' '''''''' '''''''''''''' '''' '''''''''''''' ''''''''''''''''''''''''

Two-compartmentelectrolyticsystems

'''''''''' ''''''''''''' ''''''''''''''''' ''''''''''' ''' '''''''' '''''''''''''''''''''''''' ''''''

''''''''''''''''''''''''

'''''''''''''''''

Important note: these figures are based on simple assumptions on energy consumption increases (changes incathode potential) and do not take into account effects that may exacerbate energy consumption such as theaddition of phosphates. For instance, the increased oxygen release due to the phosphate addition whichresults in anodic losses is not included. This is particularly important for Mo-based coatings which may inreality not result in energy savings (certainly not of the magnitude implied in published lab-based research)


1.4 Feasibility and availability of potential alternatives for sodiumdichromate

1.4.1 Assessment of technical feasibility

The potentially feasible alternatives have all been proposed in academic literature and in patents aspotential alternatives to the use of SD as an additive or, in the case of molybdenum-based coatingsand two-compartment cells, as an alternative way of producing sodium chlorate. Despite theirproposed use, only the chromium(III) chloride alternative is believed to have been implemented on acommercial scale use by the holder of the relevant patent application. The applicant has noexperience of the technical feasibility of these potential alternatives and this AoA relies substantiallyon the descriptions and claims made in the relevant published research, some of which has beenperformed by direct competitors. The conclusions of the assessment of technical feasibility aresummarised in Table 1-4.

Table 1-4: Overview of technical feasibility of shortlisted alternatives for Arkema

Alternative Technical advantages Technical disadvantagesConclusion on

technicalfeasibility


Once in the electrolyte, itis oxidised to Cr(VI) andmay behave as if SD hadbeen dosed in

Details unknown to the applicant.Does not eliminate current workerexposure to Cr(VI)

Potentiallyfeasible, butapplicant hasno access totechnology

Sodiummolybdate

- Sufficiently soluble- Relatively simple,

‘drop-in- substitute

- Unstable protective film on thecathode

- Poor pH buffer requiring the additionof phosphates which interfere withand adversely affect the stability andlongevity of the anode and mayincrease oxygen evolution

- High evolution of oxygen gaspotentially leading to explosivemixtures with hydrogen

- Worse current efficiency andelectricity consumption than SD

- Unproven on an industrial scale

Infeasible


- Patent literatureclaims a lowerelectricityconsumption than SD

- Poor pH buffer requiring the additionof phosphates which interfere withand adversely affect the stability andlongevity of the anode and mayincrease oxygen evolution

- Potential issues with high evolution ofoxygen gas

- Would still require Cr(VI)- Unproven on an industrial scale,

hence great uncertainty over controlof parasitic reactions and cathodelifetime

- Necessary cathodes not presentlyavailable

Infeasible


Table 1-4: Overview of technical feasibility of shortlisted alternatives for Arkema

Alternative Technical advantages Technical disadvantagesConclusion on

technicalfeasibility


- Solubility, cathodicfilm formation andoxygen evolutionissues inherentlyresolved

- pH control requiredbut can be addressedwithout the use ofadded buffers

- Worse current efficiency andelectricity consumption than SD

- Unproven on an industrial scalespecifically for chlorate manufacture

- Would require complete plant rebuild

''''''''''''''''''''''' '''#E#''''' '''''''''''''''' '''''''

''''''''''''''''''''''''''' ''''''' '''''''''''''''''''''' ''''''''''' ''''''''''''''''''

Infeasible

1.4.2 Assessment of economic feasibility

From the assessment of technical feasibility, it is clear that the alternatives other than theChromium(III) chloride are not technically feasible. However, for the sake of completeness, thepotential economic feasibility of the shortlisted alternatives has been considered. These are basedon early patent trials, and we have assumed that the data presented in these is reliable:

The initial capital investment required for the conversion from SD to an alternative substance ortechnology, which would need to be recouped through increases in the end price to customersof the sodium chlorate

Undertaking the capital investment in the unproven technologies would also result in significantdowntime and the likely loss of customers for the sodium chlorate

The change in operating costs, primarily represented by the cost of energy which is by far thelargest component of production costs in the sodium chlorate industry. Any increase in theconsumption and therefore the cost of energy would have a significant impact on on-goingoperating costs and also lead to potentially significant increases in end product prices tocustomers in order to retain profitability; this would impact on the competitiveness of theindividual companies vis a vis non-EU suppliers of sodium chlorate.

Table 1-5 summarises the findings of the assessment of the economic feasibility of the shortlistedalternatives. Cr(III) may potentially be an economically feasible alternative, as it is straightforward tosubstitute it directly into the current process; however, the cost is uncertain as the applicant is notfamiliar with the parameters and conditions of the relevant technology. The remaining threeunproven alternatives would require substantial investment costs (particularly the two-compartment electrolytic systems, which require a new plant to be built), which would have to berecouped through potentially very large increases in the price of sodium chlorate. As noted above,as far as on-going operating costs are concerned, these are dominated by the cost of energy. Forsodium molybdate and two-compartment electrolytic systems, the energy consumption of theprocess would show a notable increase, which would result in significant increases in CO2 and otheratmospheric emissions, as well as the need to further increase the price of the end sodium chlorateto customers. At a company level, the combined effect of one of the companies not gainingauthorisation would be a significant deterioration in profit margins and the likely inability to remaincompetitive within the EU market. For molybdate-based coating systems, the information availablein the patent literature would suggest a reduction in energy consumption, however, it is uncertain


whether this would materialise on the industrial scale in the presence of phosphates, which wouldresult in anodic losses and increased maintenance costs due to the impaired longevity of the anodes.Even if it were to be assumed that this unproven technology could deliver a reduction in operatingcosts, the very high investment costs and downtime period required to shift to new plant wouldrender this alternative economically infeasible.


Table 1-5: Overview of economic feasibility of shortlisted alternatives for Arkema

AlternativeInvestment costs Changes to operating costs Conclusion on

economicfeasibilityDescription Estimate Description Estimate


- Patent licence fees- Uncertain plant conversion

and downtime

Not costed - Generally minimal changesassumed

- Unclear cost of REACH compliance

+'''''''#D#''''''/y

(assumed)

Uncertain

Sodium molybdate - Patent licence fees- Disposal of old electrolyte

and generation of new- Downtime

>'''''''''' #D#'''''''''''''

Turnover of ancillaryoperations (''''''''' '''''''''''''''''''''''''''' ''''''''''''''''') alsoaffected

- Increased energy costs- Increased use of more costly

Mo(VI) additive and addition ofphosphate buffer

- Addition of phosphate bufferaffecting anode durability

- Increased controls of O2 evolution- Increased insurance premiums- Reduced cost of REACH

compliance

+''''''''' ''''''''''''/y

''''''''''''''''' '''''''''''''''''''''''''''''''''' '''''''''''''''''''''''''''''''''

Infeasible

High investmentcosts and reduced

profitability

Molybdenum-basedcoatings

- Patent licence fees- Disposal of old electrolyte

and generation of new- Replacement cathodes- Downtime

>''''''''' ''''''''''''

Turnover of ancillaryoperations ('''''''''''''' ''''''''''''''''''''''''''''''' '''''''''''''''''')also affected

- Theoretically reduced energy costs- Addition of phosphate buffer

affecting anode durability- Potentially, increased controls of

O2 evolution- Reduced cost of REACH

compliance

-'''''''''' '''''''''''''/y

''''''''''''''''''''''''''''''''''' '''''''''''''''''''''''''''''''''' ''''''''''''''''''''''''''''''''

Infeasible

High investmentcosts, unprovenand uncertainongoing costs

Two-compartmentelectrolytic systems

- Old plant to be replaced bynew plant

>'''''''''' ''''''''''''' - Increased energy costs- No need to SD or other additives- Increased material and

maintenance costs (membranereplacement)

- Lower environmental control costsand reduced cost of REACHcompliance

+'''''''' ''''''''''''''/y Infeasible

Very highinvestment costs

and reducedprofitability


1.4.3 Assessment of availability

Table 1-6 summarises the findings of this AoA with regard to the availability of the shortlistedalternatives for SD. None of the shortlisted alternatives are currently available, because either theyhave not been proven on the industrial scale, and/or access to the (pending) patents by the sunsetdate is not known and therefore cannot be assessed.

Table 1-6: Overview of availability of shortlisted alternatives

Alternative Quantity availability Quality availabilityAccess to requiredtechnology (rights)

Conclusion onavailability


- CrCl3 not REACHregistered

- Quantity neededis less than 10 t/y

- No issueidentified

- Access to patentedtechnologyrequired; licenseterms not knownas awaiting patent

- Patent filed butnot yet granted

- Access totechnology notpossible by thesunset date

Unavailable atpresent and

probablyunavailable at

sunset date

Sodiummolybdate

- Sodiummolybdate isREACH registered

- Quantity neededis less than 10 t/y

- No issueidentified buttechnology isunproven on theindustrial scale

- Existing (known)patent rights heldby third parties

Unavailable


- Raw materialsavailable on themarket

- Requiredcathodes notcurrentlyavailable

- Unknown atpresent, astechnology isnot proven onthe industrialscale

- Existing (known)patent rights heldby third parties

Unavailable


- Chlor-alkalitechnologywidely availableon market

- Unknown atpresent, astechnology isnot proven forchloratemanufacture

- Technology is notproven forchloratemanufacture onthe industrial scale

''''''''''''''''''' ''''''

'''''''#E#'''''''''''''''''

''''''''' ''''''''''''''''

Unavailable


1.4.4 Summary of feasibility and availability of shortlisted alternatives

The findings of the analysis on the technical and economic feasibility and availability of alternativesare briefly summarised in Table 1-7 below.

Table 1-7: Overall conclusions on suitability and availability of shortlisted alternatives for Arkema

AlternativeTechnicalFeasibility

EconomicFeasibility

Reductionin risk

Availability Conclusion


(-) ?HH: ENV: -

Does not remove allexposure to Chromium (VI),

uncertain availability andof uncertain economic

feasibility

Sodiummolybdate

(unproven, pH

buffering,energy

consumption,O2 evolution)

(high energy

cost)

HH:ENV:

Not CMR thereforesuitable, increased

environmentalexternalities.

Technically andeconomically infeasible and

unavailable


(unproven, pH

buffering,uncertain

energyconsumption,

possible O2

issues)

(high plantconversion

cost,uncertain

profitability)

HH:ENV: ?

Not CMR thereforesuitable, technically and

economically infeasible andunavailable


(unproven,high energy

use)

(very high

plantconversioncost, high

energy costs,poor

profitability)

HH:ENV:

Not CMR thereforesuitable, increased

environmentalexternalities.

Technically andeconomically infeasible and

unavailable

: better than SD; : worse than SD; - : no change compared to SDParentheses indicate a degree of uncertainty

1.5 Actions needed to improve the suitability and availability ofpotential alternatives

The actions and timescale that would theoretically be required before the shortlisted availablebecame feasible and suitable are presented in Table 1-8.

The alternatives that have been identified have already been the subject of significant R&D effortsby members of the SDAC and by other entities. Despite this, the identified shortcomings are yet tobe overcome. Their transition from the laboratory to the industrial scale has not been possible norcan the timeframe for such a transition be predicted with any degree of accuracy.

The use of chromium(III) chloride in the production of sodium chlorate is patented by a competitor;this alternative might become available to the applicant in the future after negotiation with the


patent (application) holder, but the terms of any licence are uncertain. In any event, this alternativeis not considered suitable due (a) to the continued presence of Cr(VI) species in the electrolyte and(b) the very small reduction in worker inhalation exposure that could be achieved in comparison tothe use of SD.

The use of two-compartment electrolytic systems would currently result in unacceptable increases inelectrical consumption and would not be economically feasible due to the need to construct anentirely new production facility. Given the impending increases in the cost of electricity in the EU inthe long term (EC, 2013), energy prices would need to decrease significantly for investment in suchlarge-scale projects to become attractive.

The most promising technology might be implied to be molybdenum-based coatings, as these havebeen suggested to result in significantly reduced energy consumption. However, current indicationssuggest that this technology may still result in increased oxygen levels and compromise processsafety unless small amounts of SD are used. In addition, the expected lifetime of these coatedcathodes has not been evaluated. In particular, the scientific community needs to undertake furtherR&D on this technology and then demonstrate it on a commercially relevant scale in a pilot plantfacility before any suggestion of economic feasibility can be confirmed. The technology that hasbeen described in the known patents is protected until 2028, and it is unlikely that further R&D willyield results before then.

In conclusion, the Authorisation is applied so that Arkema can continue to produce sodium chlorateuntil a technically and economically feasible alternative is developed. The benefits from thecontinued use of SD under closely controlled conditions and with minimisation of worker exposuresignificantly outweigh the risks to human health posed by the use of SD in the applicant’s plant, asshown in the accompanying Socio-economic Assessment (SEA) document. It is not realistic forArkema to aim towards the adoption of any one of the known, published technologies as theirfeasibility is uncertain and the time required for their industrial scale-up is unclear.


Table 1-8: Actions and timescale required for improving the suitability and availability of shortlisted alternatives

Alternative Actions for improving of feasibilityActions for improving of

suitabilityActions for improving of

availability

Potential timeframe for thealternative becoming feasible

and suitable

Chromium(III) chloride

Uncertain what actions would berequired, as the applicant has noaccess to the particulars of the

technology

Cannot improve; the alternativewill always result in largely

similar Cr(VI) exposure as SD

Need to obtain access topatented technology oncepatent has been granted

Time is required for granting ofpatent to patent holder andnegotiations by Arkema for

securing access rights topatented technology on

commercially and economicallyacceptable terms.

However, alternative is not along-term solution due topresence of Cr(VI) in the

electrolyte

Sodium molybdateFurther R&D is required before energy

use, pH buffering and O2 issues areaddressed

Already suitable for CMR effects;technical improvements required

for control of energyconsumption increases

Technology needs to bedeveloped further to become

commercially viableUncertain


Further R&D is required before pHbuffering and possible O2 issues areaddressed and reduction of energy

consumption is proven underindustrial scale operating conditions

Already suitable for CMR effects;reduction in energy consumptionnot certain, needs to be verified

Technology needs to bedeveloped further to become

commercially viable.Mo-coated cathodes need to

become available on the market

Uncertain


Chlor-alkali technology is known butneeds to be proven on an industrial

scale for chlorate manufacture

Already suitable for CMR effects;increased environmental

externalities are difficult to avoid

Technology already available,but for use in chlorate

manufacture it is unlikely toimprove due to very high initial

costs and increasinglyunappealing electricity costs in

the EU

Uncertain(will probably never become an

attractive solution)


2 Analysis of substance function

2.1 The chlorate process

2.1.1 Description of chlorate production and electrochemical reactions

The “Applied for Use” is the use of SD as an additive in the manufacture of sodium chlorate fromsodium chloride by electrolysis, with no SD presence in the sodium chlorate product. In short,chlorate is produced in undivided cells with oxidation of chloride to chlorine on the anodes, andhydrogen evolution on the cathodes made of steel or titanium (Cornell, 2002). The manufacture ofsodium chlorate in the EU is the same as anywhere else in the world and involves the following steps(note that the chlorate process is detailed in the IPPC BREF - Best Available Techniques for theManufacture of Large Volume Inorganic Chemicals; the potential steps where exposure can occurare described in the Chemical Safety Report alongside photographs showing some tasks):

Brine preparation: saturated sodium chloride brine needs to be used and the electrolyticprocess requires high purity brine. Therefore, after the preparation of the brine by dissolvingthe solid sodium chloride salt in hot water, impurities in the salt (e.g. Ca2+, Mg2+, SO4

2-) areremoved through precipitation (using NaOH, Na2CO3 and CaCl2) and filtration (IPPC, 2007)

Electrolysis: the brine is transferred to an electrolysis cell along with SD as an additive (andpotentially hydrochloric acid or chlorine for pH adjustment). As will be discussed in more detailbelow, SD is used to ensure suitable conditions for promoting sodium chlorate formation andavoiding side reactions during electrolysis

The electrolysis of sodium chloride into sodium chlorate takes place in a controlled range oftemperatures, 60-90 °C, and a pH of 6.0-6.5 (IPPC, 2007). The anodes are typically made oftitanium covered with a noble metal coating and cathodes are generally made of steel (IPPC,2007). Cathode materials in the first years of chlorate manufacture were copper, nickel andplatinum. Today, apart from steel, some plants use titanium or a Ti-0.2% Pd alloy (Cornell, 2002)

The production of chlorate relies on the electrolysis of chloride (eqs. 1-4), also producinghydrogen as a co-product (eq. 5) (Mendiratta & Duncan, 2003). Chlorine, due to the pHconditions, remains in solution forming hypochlorous acid and hypochlorite ions. The liquor (thesolution from cells) is continuously circulated between the cells and the reaction tanks (IPPC,2007). The overall reaction can be summarised by equation 6 (eq. 6):

2Cl- ⇄ Cl2 + 2e- (1)

Cl2 +H2O ⇄ HOCl + HCl (2)

2HOCl + ClO- ⇄ ClO3- + 2Cl- + 2H+ (3)

6ClO- + 3H2O ⇄ 2ClO3- + 4Cl- + 1.5 O2 + 6H+ + 6e- (4)

2H+ + 2e- ⇄ H2 (this equation is often presented as 2H2O + 2e- ⇄ H2 + O2) (5)

NaCl + 3H2O ⇄ NaClO3 + 3H2 (6)


The production of protons (eqs. 3 and 4) and their conversion into hydrogen (eq. 5) indicate thatthe control of electrolyte pH is a key variable in the process. A further issue is the evolution ofoxygen during the process by another competing electrochemical reaction (eq. 7).

2H2O ⇄ O2 + 4H+ + 4e- (7)

Inhibition of this side-reaction is an important part of the process, both for current efficiencyand safety reasons due to the explosive atmospheres potentially formed in the presence ofhydrogen. The anodic selectivity can be disturbed by certain compounds in the electrolyte, thusfurther increasing oxygen formation (Kus, 2000).

Crystallisation and drying: sodium chlorate is recovered from the liquors in a crystallisation unitvia precipitation of crystals of sodium chlorate. These are then separated from the liquor bycentrifugal filtration. The crystals are dried, commonly using fluidised bed dryers using heatedair (IPPC, 2007).

This process is illustrated in Figure 2-1.

Figure 2-1: The Sodium Chlorate Process Showing Outputs and Emissions, adapted from Tilak & Chen (1999),Mendritta & Duncan (2003) and IPPC (2007)

Two key characteristics of the process must be noted:

Use of closed loop systems and recycling of liquors: a predominantly closed system is used.Where this is not possible, a high degree of recycling of chlorate and liquors (containing SD) ismaintained to minimise the output of Cr(VI) in the chlorate and the release of Cr(VI) to theaquatic environment. Efficient dewatering and washing of the chlorate crystals also enables alow output of chromium with the product. The process has been highly optimised over thecourse of its operation (Tilak & Chen, 1999) and produces large amounts of chlorate incomparison to the amount of SD consumed (IPPC, 2007)).


High hydrogen utilisation to improve the economics of the process: besides the main product,a co-product of approximately 57 kg of hydrogen1 is produced per tonne of chlorate as indicatedin the relevant BREF document (IPPC, 2007). This co-product is also collected and, for overallenergy and economic efficiency, it is important to utilise hydrogen to a high degree. Thisdepends on local conditions and the possibility of finding an outlet for using the hydrogen, eitheras a source of energy or as a raw material for chemical reactions. The possibility of utilisinghydrogen outside of the sodium chlorate plant substantially reduces the amount of the fossilfuels required either for the production of the equivalent amount of energy or hydrogen used inchemical synthesis or both. This improves the overall economics of the chlorate productionplant.

Typical conditions for the process are shown in Table 2-1, as described in literature. The valuesshown are approximate and other concentrations of sodium chloride and final chlorate can be used.The example uses a platinum-iridium anode but other electrode materials may also be used.Typically, these are ruthenium oxide, platinum-iridium coated titanium based anodes (Tilak & Chen,1999).

Table 2-1: Example operating conditions for a chlorate cell (steel cathode and Pt/Ir anode)

Parameter Valuea

Valueb Unit

Current density 2-3 1-3 kA/m2

Current efficiency 94 - %

Average cell voltage 3-3.5 2.6-3.5 V

Electrical energy requirement 5,700 5,000-6,000 kWh/t

Process temperature 80 - °C

Electrolyte Composition Valuea Unit

NaCl 150 g/L

Na2Cr2O7 2-5 g/L

NaOCl 3-5 g/L

NaClO3 500-600* g/L

Source:a

Mendiratta & Duncan (2003);b

IPPC (2007)* based on Cornell (2002)

With particular regard to energy requirements, electricity consumption is typically in the range of5000 – 6000 kWh/t, depending on the current density (IPPC, 2007).

1Theoretical production 56.9 kg of hydrogen per 1000 kg of sodium chlorate according to: NaCl + 3H2O NaClO3 + 3H2.


2.1.2 The role of sodium dichromate

Overview

SD plays four interlinked roles in the sodium chlorate production process::

1. It acts as a pH buffer

2. It suppresses the production of oxygen, thus preventing the creation of explosive mixtureswith hydrogen

3. It passivates the steel cathodes, thus protecting them from corrosion

4. It increases the overall efficiency and the energy efficiency of the chlorate process bysuppressing certain parasitic reactions at the cathode.

The suppression of cathode reactions appears to be by far the most critical task for SD and isexplained under Point 4 below.

Function 1: pH buffering

SD acts as a buffer, i.e. a weak acid or base which maintains the acidity of a solution at a chosenvalue that resists changes to the pH from the addition of another acid or base. The dichromateanion has the ability to react with both hydrogen cations and hydroxide anions in accordance to eqs.8 and 9.

Cr2O72- + 2H+ ⇄ H2Cr2O7 ⇄ H2CrO4 + CrO3 (8)

Cr2O72- + 2OH- ⇄ 2CrO4

- + H2O (9)

Speciation of SD varies with pH in a water solution, as shown in the above equations and in Figure 2-2. Thespecies will be the same in the chlorate electrolyte but the pH scale might differ slightly. As can be seen, in thepH range relevant to chlorate production (pH 6.0-6.5, as explained in Section 2.2.4), all three species (HCrO4

-,

Cr2O7-2

and CrO4-2

) will be present. At alkaline conditions the chromate ion CrO4-2

with sodium as counter ion(Na2CrO4) will dominate, whereas in the acidic pH range the sodium dichromate (SD) Na2Cr2O7 and or NaHCrO4

will dominate. Therefore, when reference is made in this AoA to the “presence of SD in the electrolyte”, it ismeant that Cr(VI) may be found in a variety of forms which, in co-existence, deliver the required functionalityat an concentration equivalent to 3 g SD per litre of electrolyte


Figure 2-2: The distribution of Cr(VI) species in aqueous solution as a function of pH. The lines representH2CrO4 (…), Cr2O7

-2(- - -), HCrO4

-(_.._), and CrO4

-2(̶̶ ̶ ̶). A Cr(VI) concentration of 0.05 M applies

Source: Ramsay et al (2001)

According to Tilak & Chen (1999), to maximise the electrolytic cell efficiency and ensure the safety ofthe plant, the pH must be controlled within a narrow range, 6.0-6.5, as shown in the BREF Documentreferred to above. Controlling the pH can be beneficial because at low pH the evolution of oxygendecreases (eq. 7) but that of Cl2 increases (eq. 1); at high pH, the opposite occurs. Moreover,maintaining the pH of the cell solution at the given range helps in avoiding the corrosion of theanode due to oxygen evolution.

Function 2: Suppression of oxygen production

As shown above, at low pH the evolution of oxygen decreases. In chlorate producing cells, becausethere is no separating membrane to confine the anodic and cathodic products, the oxygen becomesmixed with the hydrogen evolved at the cathode and, therefore, there is a danger of forming anexplosive mixture. Similarly, the evolution of too much chlorine could make the cell combustible orexplosive (Tilak & Chen, 1999). It is not desirable to operate chlorate production cells with greaterthan 2.5% oxygen in the evolved hydrogen. Thus, the amount of oxygen evolved from an anode usedfor the electrolysis of halide solutions is important for both safety reasons and current efficiency(Alford & Warren, 1994).

Function 3: Passivation of steel cathodes-

Cr(VI) is known to passivate steel, as its reduction forms a Cr(III) oxide/hydroxide film (eq. 10)(Brasher & Mercer, 1965) on the cathode in chlorate cells (Tilak & Chen, 1999). This helps slow thecorrosion of the electrodes down, thus resulting in savings and reduced contamination of thesodium chlorate product by iron compounds.

Cr2O72- + 14H+ + 6e- ⇄ 2Cr3+ + 7H2O (10)


The purity of the sodium chlorate product is important when it is used to generate ClO2 from sodiumchlorate for bleaching. In addition, the purity of sodium chlorate is crucial for the final purity ofsodium perchlorate produced by Arkema (see the SEA for further information on the use of sodiumperchlorate). The higher purity sodium chlorate that is obtained when SD is used in the electrolytehas superior performance and is thus preferable for downstream use of sodium chlorate.

Iron oxides may also cause short-circuits and poor electrolyte circulation due to obstruction in thenarrow (2-4 mm) electrode gaps. However, a benefit of this corrosion phenomenon is that thesurface is continuously renewed, thereby removing deposits consisting of mainly calcium andmagnesium compounds (Cornell, 2002)2.

Function 4: Increase of the overall efficiency and the energy efficiency of the chlorate process

Suppression of parasitic reactions at the cathode

The main reaction on the cathode is hydrogen evolution from water, eq. 11. Two important sidereactions are the reduction of hypochlorite and of chlorate, eqs. 12 and 13. These compete with thechemical (eqs. 2 and 3) and electrochemical reactions of hypochlorite and chlorate (eq. 4) (Cornell,2002).

2H2O + 2e- H2 + 2OH- (11)

ClO- + H2O + 2e- ⇄ Cl- + 2OH- (12)

ClO3- + 3H2O + 6e- ⇄ Cl- + 6OH- (13)

The reduction of hypochlorite and chlorate ions on the cathode by parasitic reactions may cause alowered current efficiency, thus leading to increased energy consumption.

Additions of SD to the electrolyte have long been known to suppress reactions (12) and (13). A thinfilm, less than 10 nm thick, of chromium hydroxide, Cr(OH)3·xH2O is formed by reduction of Cr(VI)during cathodic polarisation (see eq. 8). Cornell (2002) has documented that the filmelectrochemically hinders the reduction of hypochlorite and chlorate; on the other hand, thehydrogen evolution reaction can still take place on the cathode after SD addition. During cathodicpolarisation, the film grows at a rate that decreases with time until a final film thickness is reached.Thus, the film inhibits not only the reduction of hypochlorite and chlorate but also limits its owngrowth (Cornell, 2002).

The Cr(III) film acts as a temporary diaphragm that is permeable to H2 and OH- but prevents access ofhypochlorite ions to the cathode. As hypochlorite is less available to the cathode surface, itselectrochemical reduction (eq. 12) is hindered. Notably, this diaphragm is present only duringproduction i.e. when the electrolysis current is on. It is oxidised immediately to SD after theelectrolysis current is stopped by the active chlorine species present in the electrolyte.

2Salt contains sulphate and it accumulates in the cell solution. When the sulphate level becomes highenough, a part of the cell solution is taken out of the process circuit and sulphate is precipitated by calciumsalts (batch process): Ca

2++ SO4

2- CaSO4(s). The precipitate is settled and filtered out. This calcium

sulphate “cake” may contain small amounts of SD. The second step of the process is to remove excess Caby precipitating it out by sodium carbonate. Ca

2++ CO3

2- CaCO3(s). This precipitate is also filtered out of

system. The amount of calcium sulphate (and calcium carbonate) formed depends on salt quality.


Another important cause of lowered current efficiency is oxygen production, as discussed earlier.Oxygen production normally results in <2.5% oxygen content in hydrogen. By control andoptimisation of the process parameters, including the addition of SD as described above, theproduction of oxygen can be minimised (IPPC, 2007) resulting in increased current efficiency andreducing safety risks.

Energy consumption at a sodium chlorate plant

Usually, in a production plant, the chlorate cells are operated in the cell voltage range 2.75 – 3.6 V atan average current efficiency of 95% (IPPC, 2007)3. Energy consumption is directly proportional tothe voltage and inversely proportional to the current efficiency (IPPC, 2007). From a historicalperspective, it is possible to say that the energy consumption of chlorate manufacture decreased toone-third during a little more than 100 years. The first sodium chlorate plant started 1886 and theenergy consumption was 15,000 kWh/t of crystallised product. In addition to the electrical energyrequirement for electrolysis, additional energy is required to drive other plant equipment such aspumps, compressors and centrifuges amongst other operations. This can contribute significantly tothe total energy requirement. With modern technology, the total consumption of electrical energyis 5,000 – 6,000 kWh/t of crystal product. Typical ranges of energy consumption for electrolysis andancillary equipment are shown in the Table 2-2 below.

Table 2-2: Electricity consumption parameters in a chlorate plant (according to BREF)

Parameter Typical ranges

Electrical energy use for electrolysis 4,700-5,200 kWh/t chlorate

Electrical energy use for other electrical equipment (pumps, compressors, etc.) 100-500 kWh/t chlorate

Total energy use 5,000-6,000 kWh/t chlorate

Source: BREF (IPPC, 2007)

Finally, energy consumption can also be controlled by controlling the impurities in the salt (NaCl).These impurities can ‘blind’ both the anode and cathode surface and deactivate the anode. Efficientbrine purification is, therefore, important even if it generates an increased amount of solid waste(IPPC, 2007).

Conclusion

Overall, the beneficial action of the SD can be summarised in Table 2-3.

Table 2-3: Important roles of sodium dichromate in the chlorate process

Effect

Action

Reaction with H+

and OH-

(pH buffering)Formation of Cr(III) on the cathode

Improvement of current energyefficiency and thus of yield andreduction in operating costs

Controlling the evolution of O2

reduces the consumption ofenergy

Cr(III) film prevents competingparasitic reactions at the cathode

3The IPPC (2007) quotes a range of 2.75 – 3.6 V and 2.6 – 3.5 V. To ensure consistency in the analysis, thisAoA will use the latter range and 3.1 V as a mid-range cell voltage value.


Table 2-3: Important roles of sodium dichromate in the chlorate process

Effect

Action

Reaction with H+

and OH-

(pH buffering)Formation of Cr(III) on the cathode

Improvement of safety of process Controlling the evolution of O2

and Cl2 and explosive mixtures

Protection of anode Controlling the evolution of O2

provides corrosion protection

Protection of cathode Cr(III) passivates steel and protectsit from corrosion

Improvement of sodium chlorateproduct quality

Avoidance of corrosion preventscontamination of the chlorate

product by iron compounds

Improvement of chlorine dioxideproduct quality

Prevention of contamination ofchlorate product ensures high

quality ClO2 product indownstream use

2.2 Conditions of use and technical feasibility criteria

2.2.1 Approach to information collection and overview of technicalfeasibility criteria

The development of technical feasibility criteria for SD and its alternatives has been based on acombination of consultation between the independent third party that has authored this AoA andthe applicants, and the review of available scientific literature.

Through the use of a detailed written questionnaire (disseminated in December 2012) the applicantwas asked to provide details of the (ideally) measurable, quantifiable technical performance criteriawhich SD (or the SD-based technology) meets and that any alternatives (substances andtechnologies) would also need to meet before being considered potentially feasible replacements.These criteria could relate to issues such as molecular structure, solubility, transformation products,product purity, energy consumption, etc., so to everything and anything that is relevant andimportant to the process in which SD is used and the roles it plays in that process.

In parallel, scientific literature delving into the parameters of the chlorate process and theassessment of the technical suitability of specific alternative technologies was collected andanalysed (with the assistance of the applicants) and has been incorporated into the analysis. Therole of SD in meeting the four main tasks in the production of sodium chlorate has been describedabove in Section 2.1.2. The technical feasibility criteria that shall be used in the assessment of thetechnical feasibility of selected alternatives are as follows.

Formation of protective film that is permeable to hydrogen and impermeable to hypochlorite Control of oxygen formation Cathode protection pH buffering Current efficiency and energy consumption Solubility in electrolyte Impurities control.


The discussion below explains the relevance and importance of the criteria for the chlorate processand presents in more detail the threshold values (or ranges) that will be used in Sections 4 and 5 forthe comparison of alternatives to SD.

2.2.2 Formation of protective film permeable to hydrogen

Importance of the technical criterion

As explained earlier, SD acts to limit side reactions, which themselves limit the achievable processefficiency (both electrical and chemical) and can cause potential safety concerns due to theformation of oxygen. During the chlorate production process, SD, a source of Cr(VI), is reduced toCr(III) by cathodic polarisation (Cornell, 2002). The equation for the reduction from Cr(VI) to Cr(III)can be found in section 2.1.2, equation 10. This Cr(III) is present only during production i.e. whenthe electrolysis current is on as it is oxidised immediately to SD if the electrolysis current is stoppeddue to the presence of hypochlorite. This less than 10 nm thick Cr(III) hydroxide film on the cathodeacts as a temporary diaphragm that is permeable to H2 and OH-, but prevents hypochlorite ions fromaccessing the cathode (Ahlberg Tidblad & Lindberg, 1991). This hinders the electrochemicalreduction of hypochlorite and chlorate, yet allows for hydrogen evolution (Lindbergh & Simonsson,1991) that is an inherent by-product of the process. The hydrogen evolution equation is:

2H+ + 2e- H2 (14)

ClO3- + 3H2O + 6e- Cl- +6OH- (15)

On the other hand, in relation to hypochlorite, as stated above, the Cr(III) hydroxide film on thecathode effectively hinders the undesired hypochlorite and chlorate reductions, while still allowingfor the required hydrogen evolution reaction to occur (Lindbergh & Simonsson, 1991). This isimportant because it enables increases in production and current efficiency, and minimises cathodecorrosion. For this effect to take place, as well as the limiting of oxygen production at the anode, theconcentration of SD should be a minimum of 3 g/L. Hindering hypochlorite reductions (eq. 16) isalso important in controlling the rate of oxygen formation reactions (see below, eq. 17). (Cornell,2002).

ClO- + H2O + 2e- Cl- + 2OH- (16)

Threshold value

There is no suitable threshold value that can be used in the comparison of alternatives to SD. A thin,permeable, film must be generated by any alternative substance or technology, in a fashion similarto the film generated in the presence of >3 g/L SD in the electrolyte.

2.2.3 Solubility in electrolyte


SD is very soluble, with a water solubility of 2355 g/L at 20 °C (Munn, et al., 2005). SD’s solubilityallows it to be present in solution in the electrolyte and thus be reduced to Cr(III) on the cathode.An insoluble substance limits the rate at which it is able to partake in reactions with other species insolution and thus its ability to act as an effective pH buffer is drastically reduced. Furthermore,


insoluble particles contribute to sludge and may interfere with the flow of electrolytes and productsolutions during the process4.

Threshold value

No specific threshold can be set; in general, the solubility of any alternative substance must be ashigh as possible.

2.2.4 pH buffering and control of oxygen formation


One of SD’s key functions is as a pH buffer and equations 8 and 9, under section 2.1.2, illustrate howSD acts as one. The buffering of the pH allows for many SD benefits as it facilitates corrosioninhibition, oxygen evolution control, and maximisation of current efficiency. Without effectivebuffering, pH-influenced reaction inefficiencies would increase; a decrease in pH would result inmore chlorine being formed, and, an increase would result in more oxygen being formed.Electrochemically produced oxygen in a chlorate cell may be detrimental to the anode, limiting thecoating lifetime (Cornell, 2002). Additionally, chlorine and oxygen gases would contaminate thehydrogen gas co-product and might not only decrease its value (if used as a raw material for latersyntheses or sold) but also decrease process safety (as discussed elsewhere). Therefore, it is veryimportant to maintain the optimum pH to maximise the electrolytic cell efficiency and ensure thesafety of the plant (Tilak & Chen, 1999). Finally, unfavourable pH may also result in undesiredprecipitation of compounds in the electrolyte (Hedenstedt & Edvinsson-Albers, 2012).

There are several possible side reactions leading to the formation of oxygen, and the selectivity foroxygen formation depends on several factors: the concentration of hypochlorite, the currentdensity, the chloride concentration, the temperature, and on the anode coating (Cornell, 2002).Hypochlorite is an important source for oxygen in chlorate electrolysis, and can form oxygen via anumber of reactions (eqs. 17 and 18):

2ClO- O2 + 2Cl- (17)

ClO- + H2O 2H+ + Cl- + O2 + 2e- (18)

Without hypochlorite, and at potentials lower than the reversible potential for chlorine evolution,oxygen evolution from water discharge is the main reaction (eq. 7, see Section 2.1.1), and is anelectrochemical reaction (Cornell, 2002). However, it has been pointed out that there are difficultiesin separating the different contributions that generate oxygen (Nylén, 2006).

These processes occur at the anode and thus the Cr(III) film that is formed at the cathode does notlimit these reactions. However, SD is still important in minimising these reactions due to its pHbuffering properties and because, when the other side-reactions are limited, there is less HClO/ClO-

available to decompose into oxygen.

4E.g. the reason for the removal of cathode corrosion sludges is in part due to their insolubility.


Threshold value

The pH is kept between 6.0 and 6.5 to minimise anodic oxygen formation (Cornell, 2002). The acidicanode surface not only suppresses oxygen evolution, but also favours chloride oxidation. Having thepH more acidic would suppress oxygen evolution further, but would also decrease the rate ofchlorate-producing reactions (Nylén, 2006). Importantly, a minimum SD concentration of >3 g/L inthe solution is required to hold the pH in the range of 6.0 to 6.5 and below this value SD begins tofail as a pH buffer. ''''''''''''''''''' ''' ''' '''' ''''''''' '''''''' '''''''''''#A#'''' ''''''' '''''''''''''' '''' '''''''''''''''' ''''''''' ''''''''''''' '''''''''''' '''''' '''''''''' '''' '''''''''''''' ''''''' ''''''' '''''''''' ''''''' ''''' '''''''''''''''''''''' '''' '''''' '''''''''''''''''''' '''' ''''''''''''''''''''''

According to the relevant BREF Document, under the conditions used in the sodium chlorateindustry, a 2-2.5% oxygen content in hydrogen can be achieved. The explosive limits of H2 in O2 are4.65% the lower and 93.9% the upper (Li, et al., 2007). From an applicant-specific perspective, whenconsidering alternatives the safety limit for oxygen in hydrogen should remain below 3% and be nomore than 0.2% higher than SD to properly manage the risk of explosions. Therefore, while theconcentration of O2 should ideally be below 2.5% (to be on par with SD), 3.0% will be assumed to bethe safety limit which an alternative must not exceed at the applicant’s plant.

2.2.5 Cathode protection


The Cr(III) hydroxide film that forms on the cathode in chlorate cells passivates the steel, and slowsthe corrosion of the electrode which occurs at shutdown in the presence of hypochlorite. As hasbeen mentioned before, this effect limits the side reactions that reduce process efficiency but filmformation also has other beneficial effects. It also reduces contamination of the sodium chlorateproduct and reduces cost by decreasing the time required for maintenance of the equipment. Thecorrosion of steel cathodes produces sludge (e.g. iron oxides) over time and these must beperiodically removed. The greater the rate of corrosion, the more often this process must be carriedout. Maintaining an effective concentration of SD in the system helps prolong the time betweenmaintenance; the operating limit for the concentration of SD required for the prevention ofcorrosion is a minimum of 3 g/L. Below this value, cathodic corrosion in the presence ofhypochlorous acid will occur at an increased rate (Speight, 2002).

Threshold value

No threshold for the degree of tolerable corrosion has been set. However, sodium chloratemanufacturers may have a minimum acceptable lifetime of a single cathode that may be companyspecific. This can be assumed to be 8-16 years based on experience. This lower end of this range, 8years, will be used as a technical feasibility criterion when comparing alternatives to SD.

2.2.6 Current efficiency and energy consumption


The presence of SD limits electrochemical side reactions which consume electrical energy anddecrease the overall process efficiency. The current efficiency and energy consumption of theprocess are important measures that are critical to both the technical and economic feasibility of theprocess. As electrical energy represents the largest part of the overall cost of sodium chloratemanufacture, maintaining a high current efficiency is of paramount importance. Theoretically, the


amount of electrical charge required to produce a tonne of sodium chlorate is 1,511 A.h per kg ofchlorate5. However, the efficiency of any process is not 100% and thus the actual energy required isgreater. Cell current efficiency is a function of the cell operating characteristics and cell design. Celloperating characteristics include flow rate, pH, and temperature, for example. Generally, cellcurrent efficiencies in the range of 93-96% can be achieved using metal electrodes (Tilak & Chen,1999). The overall energy consumption of a chlorate cell is in turn a function of current efficiencyand cell voltage (Tilak & Chen, 1999):

P = 1511E / (ԑ/100) (19)

where P is energy consumption (kWh/tonne), ԑ is the current efficiency (%), and E is cell voltage (volts). As can be seen, the energy consumption is inversely proportional to the current efficiency(IPPC, 2007).

As stated in Table 2-1, a typical operating voltage for a cell is between 2.6-3.5 V. Assuming a voltageof 3.1 V and a cell efficiency of 90% would predict an energy consumption of 5,204 kWh/tonne ofchlorate compared to a 4930 kWh/tonne if the cell was 95% efficient. This is a potential saving of ca.274 kWh/tonne if a high efficiency can be achieved with a concomitant reduction in the release ofgreenhouse gases.

SD must be maintained in the range of 3-6.5 g/L of electrolyte and in this range, the efficiency of theprocess is acceptable6; above that range, no benefit may be apparent and, in fact, a higherconcentration may hinder the electrical efficiency of the anode (Cornell, 2002). Thus, it is beneficialfor the process to keep the SD concentration as low as possible while still enabling the performanceof its other tasks (e.g. pH buffering, corrosion inhibition).

In addition to the electrical power consumed by the electrolysis cell, a smaller amount of additionalenergy is required to run ancillary equipment such as pumps, mixers and centrifuges to prepare andtransport electrolyte as well as to recover the chlorate product (IPPC, 2007). The mid-range value forelectricity consumption of other electrical equipment is assumed to be 300 kWh/tonne bringing thetotal theoretical energy consumption at 95% cell efficiency to 5,230 kWh/tonne chlorate when usingSD.

Threshold value

The minimum acceptable current efficiency or power consumption values for the applicant maydiffer to those of other manufacturers of sodium chlorate depending on the specific productionparameters of each plant. Specific information from the applicant is considered confidential. Takinginto account what is shown in the relevant BREF Document, the following threshold values will beconsidered in this analysis.

5Equation 6 shows the overall reaction for the production of NaClO3. This reaction requires 6 electrons perchlorate atom produced or 6 Faradays (160.8 A.h/mol) per mol of chlorate or 1,510.8 A.h/kg.

6In some references, slightly different SD concentration ranges are quoted. To ensure consistency in theanalysis, this range will be used to represent typical chlorate manufacture conditions.


Table 2-4: Energy efficiency and consumption thresholds for potential alternatives for SD

Parameter Literature thresholdsApplicant-specific thresholds used

in this analysis

Minimum energy efficiency Minimum: 90%Ideal: >95%

Minimum: ''#A#'''%

Maximum energyconsumption

5,700 kWh/t chlorate (see Table 2-2) '''''#A#''''''' kWh/t chlorate

2.2.7 Control of impurities


Chlorate chemistry is highly vulnerable to the presence of impurities; therefore, the presence ofimpurities is of great concern both to the chlorate manufacturer and to the users of the chlorate.

At present, with the use of SD, the typical level of impurities is below 0.5% by weight with chromiumpresent at very low levels, typically below 5 ppm, as shown in Table 2-5.

Table 2-5: Typical sodium chlorate product specification

Attribute Limit

NaClO3 overall purity 99.5 wt%

NaCl 0.12 wt%

Moisture 0.20 wt%

Chromium <5 ppm

Source: Mendiratta & Duncan (2003)

If SD were to be replaced by an alternative substance or technology, a different impurity profilewould arise for the chlorate product and these new impurities might well affect the efficiency andstability of the ClO2 generation reaction on the premises of the customers of the applicant (i.e.during the bleaching processes used in the pulp and paper industry). An undesired reaction that canresult is known as a ClO2 ‘puff’, which is the thermal decomposition of ClO2 in a heterogeneous,exothermic and autocatalytic reaction. This reaction might be rather violent given high partialpressures of ClO2 in the air, exceeding 10.1 kPa (Kack & Lundberg, 2010). Initiators of ClO2 puffs mayinclude (Ragauskas, undated):

Reactive metals, such as iron An electric spark or static electricity A temperature rise above 100°C Organic contaminants, especially hydrocarbon greases, oils, and rubber Dust and rust particles Sunlight Sudden pressure fluctuations Contact with certain chemicals, apart from hydrocarbons, might also cause decomposition.

These chemicals include carbon monoxide (CO), mercury (Hg), sulphur (S), phosphorous (P) andpotassium hydroxide (KOH) (Lewis, 2000).

Moreover, when sodium chlorate is used for treatment of water intended for human consumptiononly levels of up to 1 ppm/kg sodium chlorate is allowed for seven specified heavy metals (inaccordance with standard EN 15028).


In conclusion, any new impurity has to be evaluated as to whether it is compatible with the ClO2

process.

Threshold value

Each impurity has to be considered separately. With alternatives to SD, particular attention needs tobe paid to the risks for the ClO2 process from the presence of metals even at the ppm level.

2.2.8 Summary of technical feasibility criteria

Table 2-6 summarises the analysis presented above on the technical feasibility criteria that will beused for the assessment of the technical feasibility of alternatives to SD. Where applicant-specificinformation diverges from the literature values, the former is provided instead, but it is confidential.

Table 2-6: Summary of technical performance criteria of sodium dichromate

Technical feasibilitycriteria

Primary relevance

Relevant thresholdvalue or ideal range

Notes

SD andreplacementsubstances

Chlorateprocess and

quality ofchlorateoutput

Formation of protectivefilm that is permeable tohydrogen andimpermeable tohypochlorite

No specific thresholdcan be identified

A sufficiently robustdiaphragm must be

deposited to preventparasitic reactions

Solubility in electrolyte Highly soluble – ashigh as possible

Solubility of SD:ca. 2355 g/L

pH buffering and controlof oxygen formation

pH: '''''' ''#A#''' '''''''O2: ideally, less than

2.5% by volume of O2

in H2 with amaximum of 3.0%

This links to thepresence of a minimum

of 3 g/L Cr(VI) in theelectrolyte

Cathode protection Minimum cathodelifetime of 8 years

Current efficiency andenergy consumption

Energy efficiency:''#A#'''% or more,

ideally >95%'''''''''' '''''''''''''''''''''''''''''''''''''''

''''''''''''''#A#''''''''' ''''''''''''''''''''''''''' ''''''''''''''''''''''''' '''''''''''''''''

Threshold values mayvary by chlorate plant

Control of impurities

Each impurity mustbe considered

separately. Metalscould be particularlydetrimental to ClO2

generation

When used fortreatment of waterintended for humanconsumption, only

levels of up to 1 ppm/kgsodium chlorate isallowed for seven

specified heavy metals(EN 15028)


2.3 Summary of functionality of sodium dichromate in the“Applied for Use”

The information in the preceding parts of Section 2 are summarised in the Table 2-7 below.

Table 2-7: Parameters for SD use in sodium chlorate manufacture and assessment of alternatives

Functional aspect Explanation

Tasks performed bythe substance

pH buffer for the electrolyte, to maintain process parameters to ensure rate of ClO3-

forming reactions remains feasibleSuppression of oxygen evolution to prevent formation of explosive atmospheresCathode protection to minimise maintenance costs and to maintain product purityMaintain current efficiency to ensure economic feasibility

Physical form of theproduct

SD is purchased by the applicant in solution form to minimise (to the extent possible)worker exposure from handling solid SD. SD is added as an aqueous solution (60-70%w

/w)

The sodium chlorate product is sold as a white crystalline solid or as aqueoussolutions

Concentration of thesubstance in themarketed product

Unintentional presence in the chlorate product. <5 ppm (<0.0005%) total chromium,of which only some is Cr(VI), is present in the sodium chlorate product

Critical properties andquality criteria thesubstance must fulfil

Ability to form a protective film which is permeable to hydrogen and impermeableto hypochlorite – this suppresses the side (parasitic) reactions. If these side reactionstake place, they will limit the evolution of hydrogen, reduce current efficiency andresult in increased oxygen concentration which can lead to explosion mixtures withhydrogen

Solubility in electrolyte – must be highly soluble and must not interfere with processor increase the frequency of sludge removal

pH buffering and control of oxygen formation- must provide a stable pH whichensures corrosion inhibition, oxygen evolution control, and maximisation of theefficiency of the process

Cathode protection (corrosion inhibition) – must limit frequency of maintenance ofcathodes and sludge removal

Current efficiency and energy consumption – must maintain high current efficiencyand low energy consumption, to ensure the economic viability of the process (energyis the largest production cost component)

Control of impurities – must not introduce impurities in the chlorate product andprevents the presence of impurities which may affect the efficiency of the chlorinedioxide production reaction by downstream users

Frequency ofsubstance use andusage quantities

SD is added to the process periodically when process monitoring indicates that itsconcentration needs to be adjusted. Typically, this occurs a few times a year asindicated in the CSR. Small amounts of SD are lost during the process, requiring theaddition of '''#B#''''' kg/tonne of sodium chlorate product. The total tonnage of SDused by the applicant is 1-10 t/y (see further detail in Section 3.1)

Process andperformanceconstraints concerningthe use of thesubstance

Process pHand O2

generation

Between pH '''''''#A#''''''''Ideally less than 2.5% O2 in H2 by volume with 3.0% as a safety limitfor the applicant

Acceptablecathodelifetime

Minimum 8 years


Table 2-7: Parameters for SD use in sodium chlorate manufacture and assessment of alternatives

Functional aspect Explanation

Energyconsumptionand efficiency

Greater than '''#A#'%, for the applicant, ideally over 95%; totalenergy consumption less than '''''#A#'''''' kWh/t chlorate ''''''''''''''''''''''''''''''' ''''''''' ''''''' ''''''''''' ''''''#A#''''' ''''''''''''' ''''''''''''''''' '''' '''''''''''''''''''

Concentrationin electrolyte

The concentration of SD in the electrolyte and an ideal range ofconcentrations has been established, 3-6.5 g/L. Below that range,SD cannot perform its intended tasks (energy consumptionincreases affecting the economics of the process, pH is notbuffered sufficiently this making the process unstable, corrosionphenomena increase). Above the ideal range, no discerniblebenefit may arise.

Impurities Each impurity has to be considered separately due to its variableeffect on the reactions the chlorate will participate in

Currentdensity

1-3 kA/m2

Temperature Process temperatures may vary and are confidential but typically inthe region of 60-90 °C

Conditions underwhich the use of thesubstance could beeliminated

The use of SD fulfils many roles and if it were to be eliminated, alternative methodsof controlling pH, corrosion and process efficiency would need to be found in orderto have a feasible process without the use of SD. Without a way of fulfilling theseroles, the use of SD cannot be eliminated, as the chlorate production process wouldbecome too inefficient, thus uneconomical

Customerrequirementsassociated with theuse of the substance

The presence of specific impurities may be of particular importance for the efficiencyof the chlorine dioxide production process by downstream users. For example: totalchromium content <5 ppm in sodium chlorate

Industry sector andlegal requirements fortechnical acceptabilitythat must be met

Other than contractual requirements on the purity of the final sodium chlorateproduct, there are no industry sector or legal requirements that require the use ofSD. Application for water purification intended for human consumption sets a limiton heavy metals <1 ppm (EN 15028)


3 Annual tonnage

3.1 Tonnage band

Confidential annual tonnage (2012): '''#B#''' tonnes of anhydrous SD

Annual tonnage band: 1-10 tonnes per year based on anhydrous SD

It is worth noting that in 2012, the consumption of SD in the manufacture of sodium chlorate by theconsortium of companies of which the applicant is a member was at the low end of the 10-100 t/yrange. This tonnage is very low compared to the overall tonnage registered: ECHA’s DisseminationPortal7 indicates that the substance was registered at the 10,000-100,000 t/y band. This makes the“Applied for Use” of the substance one of the rather ‘niche’ applications for SD. The CSR alsoexplains the use of predominantly closed loop systems in the industry which greatly reduce releasesof and exposure to chromates during the manufacture of sodium chlorate.

3.2 Trends in the consumption of sodium dichromate

In the period 2007-2012, the applicant’s consumption of SD in the chlorate process generally''''''''''''''''' ''''' '''''''''' '''''''''' '''''''' '''''''#C#' '''''''' ''''' ''''''''''''''''' ''''''''''''''''' ''''''' '''''''''''''''''''''' '''' ''''' ''''''''''''''''''''''''''''''''''' '''''''''' ''''''' '''''''''' '''''''' ''''' ''''''''''''''''''''''''''' '''' '''''''''''''''''' '''' '''''' '''''''''

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3.3 Form and usage of sodium dichromate

During the chlorate production process, SD is dosed when required to keep a constant level in theelectrolytic cell. The number of times that SD is added varies by production plant but generally takesplace a few times per year and the quantities added are very small, as described in the CSR. Theaddition is done to compensate for small losses due to:

Chlorate product: the final product contains traces (<5 ppm or 0.0005% w/w) of chromium(Mendiratta & Duncan, 2003)

7Available at: http://echa.europa.eu/information-on-chemicals/registered-substances (accessed on 6November 2013).


Filter sludge: solids (typically corrosion products) accumulate at the bottom of the electrolyticcell and the process tanks as sludge. The sludge is removed from the cells during scheduledmaintenance and the electrolytic cells are periodically washed using hydrochloric acid. Thewaste acid is filtered and the sludge containing iron and chromium is filtered off. The motherliquor (the part of a solution that is left over after crystallisation) is sometimes filtered beforethe crystallisation stage. This adds to the chromium-containing sludge (IPPC, 2007).

The substance is added in the form of solution, the concentration of which is typically 60-70% w/w (asNa2Cr2O7·2H2O). The final concentration of SD in the chlorate cell is 3-6.5 g/L. According to the BREFDocument for Large Volume Inorganic Chemicals (Solids), the dose rate for SD is 0.01-0.15 kg/tonneof sodium chlorate product (IPPC, 2007). Information from the applicant confirms that hisconsumption of SD is within this range at ''''#A#''''' kg/tonne of sodium chlorate.


4 Identification of possible alternatives

4.1 List of possible alternatives

This AoA evaluates a broad range of alternatives, as the applicant wishes to demonstrate that verythorough search for the identification of suitable alternatives has been undertaken.

This section presents an assessment from a screening of the available information. The alternativesubstances and technologies presented in Table 4-1 were identified through literature research andindustry consultation, have been screened as, in principle, realistic potential alternatives for thereplacement of SD and are further assessed in Section 5 of this AoA. Several other alternatives havebeen identified (see rest of Section 4) but were subsequently eliminated as infeasible and/orunsuitable.

Table 4-1: Shortlisted potential alternatives for the replacement of sodium dichromate

Alternative substances

Chromium (III) chlorideCrCl3 (other trivalent chromium substances are apossibility, such as Cr(OH)3, Cr2O3)

Sodium molybdate Na2MoO4

Cathodic coatings based on metals

Molybdenum-based coatingsCathodes coated using Na2MoO4, FeCl3 (not present inthe electrolyte)

Other technologies

Two-compartment electrolytic cell systems

It must be noted that the use of SD in the manufacture of sodium chlorate is the current ‘state-of-the-art’ not only within the EU but also elsewhere in the world. As will be discussed later, the abovealternatives are currently not used commercially; indeed, EU-based chlorate producers are at theforefront of research for the development of low-Cr(VI) or Cr(VI)-free processes for the manufactureof sodium chlorate.

4.2 Description of efforts made to identify possible alternatives

4.2.1 Overview

This AoA document has been prepared by an independent third party. This Section presents boththe efforts made by the applicant to research and develop alternatives and those by theindependent third party to identify in the literature efforts by various stakeholders towards thedevelopment of alternatives.

4.2.2 Research and development by the applicants

Introduction

The process of chlorate manufacture is well understood and has been described extensively in theIPPC BREF - Best Available Techniques for the Manufacture of Large Volume Inorganic Chemicals(2007). The BREF describes the historic improvements that have been made to the chlorate process


and highlights the importance of SD as a necessary additive, as well as the steps taken to reduce itsuse (recirculation and recycling of solutions) and minimise exposure.

The removal of SD and other Cr(VI) species from processes is and has been of high interest for manydecades, but in spite of extensive research, an alternative that fulfils the role of SD in amanufacturing process environment has not been developed at the industrial scale. Instead, thetrend has been to minimise the output of chromium from the process and work towards apredominantly closed loop system.

Some members of the SDAC have been actively involved in research and development. Several PhDprojects and a number of published papers have been sponsored in part by SDAC companies. Inaddition to academic research, attempts to apply alternative technologies to the production ofsodium chlorate have been made, including pilot production scale trials. Although the removal andreduction of the use of Cr(VI) has been an objective of these trials, they have not succeeded incompletely removing its presence.

Past and current R&D activities of the applicant

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Future R&D activities of the applicant

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Table 4-2: Past R&D work on the development of a suitable alternative for sodium dichromate

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4.2.3 Literature searches

Introduction

The following paragraphs summarise information that is available in the scientific literature onefforts that have been made towards identifying and developing alternatives to SD and to SD-basedchlorate cells. The tables provided below summarise the key findings of the identified literaturesources.

Alternative substances used as additives to the chlorate process

Alternative 1: In-situ generation of dichromate from trivalent chromium (chromium (III) chloride)

Patent applications have been published describing the use of trivalent chromium (Cr(III)) as areplacement of SD in the chlorate process. Two are the key sources of information:

A patent by Dobosz (1987), associated with Canadian interests A patent application by Hedenstedt & Edvinsson-Albers (2012), associated with AkzoNobel

(EKA).

A number of key points have been highlighted in this research:

Engineering requirements: a separate vessel, for example a tank, for the in situ formation ofCr(VI) from a Cr(III) compound might be required;

pH levels: according to Hedenstedt & Edvinsson-Albers, Cr(III) can be oxidised to Cr(VI) bysodium chlorate and hypochlorite under acidic conditions and at elevated temperatures. On theother hand, Dobosz described the process as most effective at pH values between ca. 8 and ca.10. Generally, its assumed that pH conditions similar to the applicant’s current operatingconditions would be sufficient;

Chromate use and presence: Cr(VI) is formed in situ from the addition of a suitable Cr(III)compound. Such a compound is oxidised in a vessel to hexavalent chromium by means ofhypochlorite, chlorine, chlorite or chlorate. Suitable Cr(III) substances that could be addedinclude chromic chloride, chromic oxide and chromic hydroxide; CrCI3·6H2O has been suggestedas a suitable option. The dosage of the Cr(III) compound could be similar to that of SD in thecurrent conditions of use (2-6 SD equivalents per litre).

Overall, under the processes outlined by these patents and patent applications, Cr(VI) is still presentthe electrolyte but is not handled by the workers in the make-up and dosing of the electrolytesolution. This would reduce potential exposures of workers to Cr(VI). However, exposure to Cr(VI)would still result from other processes involving the electrolyte such as sampling/testing, cleaningand maintenance and washing of filter cakes. It is estimated that using a Cr(III) compound instead ofSD would reduce exposure by approximately 20%.


Table 4-3: Research into the use of in-situ oxidation of Cr(III) Dobosz, 1987

Parameter Details

Year 1987

Source (Dobosz, 1987)- Patent

Associated company/research organisation

Tenneco Canada Inc.

Objective of research orinvention (Extracts fromsource document

- Developing a method for formation of Cr(VI) useful in the electrolysis of chloridesto form chlorates by reaction between a Cr(III) compound and hypochloritepresent in an effluent from the chloride electrolysis. In this way, at least part ofthe hypochlorite ions are converted to harmless chloride ions while providing theneeded Cr(VI) from readily-available trivalent chromium compounds

- The process of the invention can be used to effect treatment of the hypochlorous-acid-containing condensate, to effect treatment of aqueous chlorate solution toachieve dehypoing (hypochlorite removal), or a combination depending on thehexavalent chromium ion requirement and the amount of oxidising agentavailable for oxidation. When the condensate is treated with Cr(III), the resultingdeactivated condensate containing only chloride ions and chromate ions, thencan be used in brine preparation for the cell

Relevance to the chlorateprocess

High, but priority seems to have been the removal of hypochlorite to make theprocess more efficient rather than the elimination of Cr(VI) for environmental/healthreasons

Key changes to currentchlorate process andnotable improvements andshortcomings. (Extractsfrom source document)

- Cr(III) substances that could be added include chromic chloride, chromic oxideand chromic hydroxide.

- The process may be effected over a wide range of pH but is most effective at pHvalues between ca. 8 and ca. 10. These pH conditions facilitate dissolution of theCr(III) and oxidative conversion to Cr(VI). It is preferable to add sodium hydroxideor other suitable alkali to the condensate prior to reaction with the Cr(III)compound.

- Cr(III) is used to effect dehypoing in the tank to remove hypochlorite and againform Cr(VI) and chloride ions. The Cr(VI) ions so produced are recycled to thebrine preparation tank with the mother liquor

Presence of Cr(VI) in theelectrolyte

Handling of Cr(VI): the invention demonstrates a manner of providing Cr(VI) for usein the electrolytic production of chlorates which uses by-product hypochlorite fromthe chlorate production to oxidise Cr(III) to Cr(VI)Presence of Cr(VI) in electrolyte: Cr(VI) is still present as a result of the oxidation ofCr(III) to Cr(VI)

Table 4-4: Research into the in-situ oxidation of Cr(III) – Hedenstedt & Edvinsson-Albers, 2012

Parameter Details

Year 2012

Source (Hedenstedt & Edvinsson-Albers, 2012) - Patent


AkzoNobel (EKA)

Objective of research orinvention

- Development of a process of producing alkali metal chlorate in an electrolytic cellcomprising an anode and a cathode, where substantially no hexavalentchromium is added to the process from an external source

- Provision of an alternative compound entirely substituting or to a large extentsubstituting Cr(VI) compounds as raw material, while safeguarding a controlledsupply of Cr(VI)in the cell electrolyte which is independent on the amount ofhypochlorite in condensate streams for example

- Provision of a process which facilitates production of alkali metal chlorate whereCr(VI) can be provided at an acidic pH whereby necessary pH adjustment can bereduced or eliminated


Table 4-4: Research into the in-situ oxidation of Cr(III) – Hedenstedt & Edvinsson-Albers, 2012

Parameter Details


Highly relevant

Key changes to currentchlorate process andnotable improvements andshortcomings

- At least one chromium compound having a valence lower than +6 may be addedto at least one process stream containing either alkali metal chloride or alkalimetal chlorate or to at least one process stream containing both alkali metalchlorate and alkali metal chlorate

- Formation of Cr(VI) results from the addition of a chromium compound with avalence lower than +6 in a separate vessel, for example a tank, and oxidised inthis vessel to hexavalent chromium (in-situ generation thereof), for example bymeans of hypochlorite, chlorine, chlorite, chlorate, etc.

- Example dosage for the chromium compound having a valence lower than +6 is2 g to about 6 g (calculated as SD equivalents)/L electrolyte solution or from ca. 2g to ca. 20 g chromium/t chlorate product

- Chromium compounds having a valence lower than +6 may for example bechromium halides such as chromium(III) chloride, chromium(III)chloridehexahydrate, and several others, or their mixtures

- The examples shown in the patent utilise chromium trichloride hexahydrate(CrCl3·6H2O)

- The chromium compounds can for example be added as salts, aqueous solutionsor as melts if the melting point is sufficiently low, for example chromiumtrichloride hexahydrate having a melting point of 83 °C

- It can be concluded that CrCI3·6H2O crystals can be easily dissolved and that pH isreduced on dissolution of acidic CrCI3·6H2O. Precipitation occurred close toneutral pH and in weakly alkaline solutions, presumably due to formation ofCr(OH)3(s) or CrO2(s). Sodium chlorate was found to oxidize Cr(III) to Cr(VI) underacidic conditions and at elevated temperatures. Sodium hypochlorite can oxidiseCr(III) to Cr(VI) in strongly alkaline solutions and down to to at least pH 5 orbelow pH 5. Hypochlorite can even dissolve precipitations formed in neutralsolutions and oxidise chromium with a valence lower than +6 to hexavalent state

- The molar ratio of hexavalent chromium to chromium having a valence lowerthan +6 ranges from about 0:10000 to about 1:10000


Handling of Cr(VI): several examples do not involve Cr(VI), some doPresence of Cr(VI) in electrolyte: Cr(VI) always present as a result of oxidation

Alternative 2: Sodium molybdate

Sodium molybdate (Na2MoO4 or its dihydrate Na2MoO4·2H2O) or the Mo(VI) oxide have beenproposed as an alternative to SD in the chlorate process. Key sources of information in the openliterature include:

A journal article by Li et al (2007), associated with Canadian interests A patent by Rosvall et al (2010), associated with AkzoNobel (EKA) A thesis and journal articles by Gustafsson and colleagues in 2012, associated with the Royal

Technical Institute of Stockholm (KTH) and AkzoNobel (EKA).


Oxygen evolution: sodium molybdate interferes with the anodic reactions and results in therelease of significant volumes of oxygen, even when used at low concentrations. In the work ofLi et al, the measured off-gas O2 level was observed to be high and the H2 explosive upper limit(4.8%) was nearly reached. In the Rosvall et al patent, additions of MoO3 as low as 1-10 mg/L led


to oxygen release in excess of 3.5% and in some cases well above 4% (Li et al used aconcentration of Na2MoO4 of 8 g/L). There is a clear need for adding as little Mo(VI) as possible

Buffering: according to Li et al, SD has a better buffer “fit” for the chlorate reaction andGustafsson et al assert that, to fully replace Cr(VI) or significantly lower the Mo(VI) concentrationin the electrolyte, a buffer agent such as phosphate will be needed. Investigation of the filmsformed on the cathode by co-additions of molybdate and phosphate showed that themolybdenum-containing cathode films became thinner if the electrolyte also containedphosphate during the film build-up. With 80 mM molybdate in the electrolyte a cracked filmwas formed on the cathode surface. The cathode film that was formed in presence of bothmolybdate and phosphate looked similar but was thinner, yet the activation of hydrogenevolution was still as effective. If the amount of molybdate was low (4 mM) and the electrolytealso contained between 10 and 40 mM phosphate, no molybdenum film was visible withScanning Electron Microscopy (SEM) or detectable with Energy-dispersive X-ray spectroscopy(EDX) on the cathode surface. This may be due to competitive adsorption of molybdate andphosphate, where the higher molybdate concentration is necessary for the molybdate to befavoured. Addition of molybdate was found to activate the hydrogen evolution reaction evenwhen no film could be detected, suggesting that a catalytic film was formed which thendissolved, detached or was too thin to be detected by EDX (Hummelgard, 2012).

Current efficiency (CE): efficiencies documented in the literature are not ideal. Li et al referredto 91% efficiency, while Gustafsson and his colleagues showed that 80 mM Mo(VI), onlyincreased the CE from 80% to about 83% despite being present in a concentration about 30,000times higher to a comparison cell that contained a small concentration of Cr(VI) (the latterincreased current efficiency to 94%). Adding 80 mM Mo(VI) to the Cr(VI)-containing electrolytedid not have a negative effect on the CE, but instead a small positive effect.

Chromate use and presence: in the work of Rosvall et al and Gustafsson, small additions of SD(ca. 3 mg/L) were deemed necessary for the efficient operation of the cell. Gustafsson et al alsosuggest that it will be difficult to replace Cr(VI) in the existing process without replacing the steelcathodes with a more dimensionally stable material.

Overall, the use of Mo(VI) ions shows some promise but there are also significant shortcomings withthe evolution of oxygen, its poorer buffering, and a current efficiency which may not be ideal. Theelimination of Cr(VI) cannot be guaranteed under the conditions demonstrated in the literature.Evidence of commercial use of this alternative could not be established, and the applicant has noknowledge of any such commercial use.

Table 4-5: Research into sodium molybdate – Li et al, 2007

Parameter Details

Year 2007

Source (Li, et al., 2007) – Journal article


Aker Kvaerner Chemetics, CanadaNatural Science and Engineering Research Council of Canada (NSERC) for its IndustrialR&D Fellowship Fund


- Identification of a suitable alternative with similar buffering characteristics todichromate and without adverse effect on the electrolytic performance ofsodium chlorate production is important to reduce the environmental impact


High; sodium molybdate is examined as a replacement for SD in the chlorate process


Table 4-5: Research into sodium molybdate – Li et al, 2007

Parameter Details


- 8 g/L Na2MoO4 were used- At 22–23 °C, without electrolysis occurring, buffer regions were observed to be

pH 5.0–6.0 for molybdate and 5.0-6.5 for dichromate. Dichromate has a betterbuffer “fit” for the chlorate reaction

- The current efficiency ranged from 85% to 92% at pH lower than 5.7 andincreases to ca. 98% in the pH range 5.75 to 5.95 and drops again above pH 5.95.At a lower pH of 5.4, Mo oxides are likely to form at the cathode and adverselyaffect the current efficiency. At a higher pH of 7–10, Mo electrode positionbecomes a main cathodic parasitic reaction which significantly lowers thecurrent efficiency

- The measured off-gas O2 level was observed to fluctuate between 3.7% and4.8%. At these values, the current efficiency was only about 91% after 55 hoursof operation and the H2 explosive upper limit was nearly reached (with 4.8% O2).The high off-gas O2 levels clearly show the adverse influence of molybdate on theDSA® anode, because O2 is only generated from the anodic parasitic reactions

- In an effort to minimize and control this adverse anodic effect of molybdate onthe anode, silica solution was added to the chlorate cell to formpolysilicamolybdate anions; the O2 level in the cell off-gas dropped from 4.8% to4.3%

- Mixed additives based on Mo(VI) and Cr(VI) were also trialled. Although cathodesurface potential was lowered substantially at pH 6.7, this pH was outside thebuffer region and is not optimum for the chlorate reaction. On the other hand,increased complexity resulting from adding one more compound wouldcounteract the advantage of the reduction of Hydrogen Evolution Reaction (HER)overpotential


Handling of Cr(VI): in the absence of SD, molybdenum interferes with the anodicreaction and leads to increased evolution of O2

Presence of Cr(VI) in electrolyte: SD not present (but results not favourable, seepoint above)

Table 4-6: Research into sodium molybdate – Rosvall et al, 2010

Parameter Details

Year 2010

Source (Rosvall, et al., 2010) – Patent


AkzoNobel (EKA)


- Developing a process for activation of a cathode which reduces the cell voltage,while using low amounts of chromium and activating metal(s)

- A further object of the invention is to provide a process with high cathodiccurrent efficiency, in which the formation of oxygen is decreased and energylosses and the risk of explosions in the cell also are decreased


Significant; the key aim was not to eliminate the presence of Cr(VI) in the electrolyte


Table 4-6: Research into sodium molybdate – Rosvall et al, 2010

Parameter Details


- Titanium cathodes were used in the presence of SD in the electrolyte. Theaddition of SD was at the level of 9 μM Na2Cr2O7•2H2O (ca. 0.003 g/L)

- MoO3 was added at variable (low) concentrations ca. 1-10 mg/L. Despite thelow Mo addition, significant cathode activation was noted but also significantrelease of oxygen (oxygen evolution of 3.5-3.8%)

- Long term effects were studied with 1 mg/L and 100 mg/L MoO3 added to theelectrolyte. This resulted in cathode activation but also a release of oxygen whichwould exceed 3.5% and might even reach more than 4%

- Experiments made it clear that small amounts of molybdenum species reducesthe voltage on the titanium cathode


Handling of Cr(VI): the experiments did not eliminate the use of SD, but the amountadded was very limited, well below the typical operating conditions of a chlorate cellPresence of Cr(VI) in electrolyte: SD still present but at very low levels

Table 4-7: Research into sodium molybdate – Gustafsson et al, 2012

Parameter Details

Year 2012

Source (Gustafsson, 2012) – Thesis(Gustafsson, et al., 2012) – Journal article(Gustafsson, et al., 2012b) – Journal article(Hummelgard, 2012) – Thesis


Royal Technical Institute, StockholmAkzoNobel (EKA)


- The goal was to better understand how molybdate (and Rare Earth Mineral salts(REMs) can be used as additives to pH neutral electrolytes to activate theHydrogen Evolution Reaction (HER)


High; the ability of molybdenum to replace SD was considered


- Additions of 4 mM Mo(VI) were made into the electrolyte- Addition of molybdate to neutral and alkaline electrolytes activate the

electrolytic HER (on electrode substrates with poor activity for the HER). Theadded molybdate ions are reduced on the cathode forming for example films ofoxides or alloys. These films give different electrode substrates a similar activityfor HER

- The activation for neutral electrolytes was larger with 4 mM molybdate aselectrolyte additive than with 100 mM. Large amounts of molybdate appear tobe detrimental to the activation. Molybdate also increased the overpotential onthe anode due to either adsorption or precipitation of film. Side reactions to theHER can be inhibited by the molybdate additive. The additive is more efficientwhen added to neutral than to alkaline electrolytes. In alkaline electrolytes, filmsof molybdenum oxides are not stable and are thus less efficient at hindering forexample hypochlorite reduction. For inhibiting side reactions, molybdate is farless efficient than dichromate

- Increased cathode potential, increased anode potential, and increased oxygenlevels in the presence of high Mo(VI) concentrations give a very strongmotivation to use a low level of Mo(VI) in the process. Even though the partialcurrent for the side reaction of Mo(VI) reduction appeared to be quite low for100 mM Mo(VI), the current efficiency of the HER would probably be even higherif a low Mo(VI) level was used, thus giving another motivation to use a lowMo(VI) level

- Comparisons were made of the changes to current efficiency (CE) with Cr andMo. The addition of 2.7 μM Cr(VI) increased the CE, as measured after 20


Table 4-7: Research into sodium molybdate – Gustafsson et al, 2012

Parameter Details

minutes of electrolysis, from about 80% to over 94%. However, 80 mM Mo(VI)only increased the CE to about 83% despite being present in a concentrationabout 30,000 times higher. Adding 80 mM Mo(VI) to the Cr(VI)-containingelectrolyte did not have a negative effect on the CE, but instead a small positiveeffect

- A low concentration of Mo(VI) alone will not be sufficient to achieve a highcurrent efficiency in the chlorate process. Some other additive therefore also hasto be used, for example low levels of Cr(VI). To fully replace Cr(VI) orsignificantly lower the concentration, a buffer agent such as phosphate will beneeded

- It will be difficult to replace Cr(VI) in the existing process without replacing thesteel cathodes with a more dimensionally stable material


Handling of Cr(VI): a significant reduction in the use of SD could be achieved, butother issues would remain (e.g. need to replace cathodes)Presence of Cr(VI) in electrolyte: SD would still be present in low concentrations

Alternative 3: Rare Earth Metal salts

Rare Earth Metal (REM)8 salts have been investigated as an alternative to SD in the chlorate process.Among rare earth metals, yttrium has been given particular attention in relation to the manufactureof sodium chlorate but lanthanum and samarium have also been discussed. The metals are added inthe form of their chlorides.

Key sources of information in the open literature include:

A thesis and associated journal articles by Nylén and colleagues in 2007-2008, associated withthe Royal Technical Institute of Stockholm (KTH) and AkzoNobel (EKA)

A thesis and associated journal articles by Gustafsson and colleagues in 2010-2012, similarlyassociated with the Royal Technical Institute of Stockholm (KTH) and AkzoNobel (EKA).


Effectiveness of REM salts: the addition of Y(III)/La(III)/Sm(III) ions to a suitable (NaCl)electrolyte results in the formation of a hydroxide film on the cathode during hydrogenevolution. According to Nylén and colleagues, a gel-like Y(OH)3 film formed on the iron surfacehas been found to inhibit the reduction of protons, nitrate ions and of hypochlorite ions. Undercertain conditions the film also catalyses hydrogen evolution from the reduction of water;

Permanence of the REM hydroxide film: the Y(OH)3 film has been found to be sensitive tocertain operating parameters; (a) temperature: at 25 °C, additions of 10 mM YCl3, SmCl3 andLaCl3, the REM hydroxide film could easily be seen by the naked eye on the electrode surfaceafter experiments at this temperature, but not after trials at, 70 °C. It probably dissolved at thehigher temperature as the current was switched off; (b) current density and concentration: a

8Rare earth metals as defined by IUPAC are a set of seventeen chemical elements in the periodic table,specifically the fifteen lanthanides plus scandium and yttrium. Scandium and yttrium are considered rareearth elements since they tend to occur in the same ore deposits as the lanthanides and exhibit similarchemical properties.


low concentration of Y(III) or a high current density when extensive gas evolution disturbs thefilm formation, hinders the reduction of ions but the film does not activate water reduction. Athigher Y(III) concentration (5 M) and lower current densities, the film formed has inhibiting aswell as catalytic properties. In addition, when adding Y(III) to chlorate electrolyte atconcentrations higher than those experimented with, yttrium precipitates immediately, mostlikely as Y(OH)3. Higher concentrations may also lead to thicker diffusion layers and concomitantprecipitation of Y(OH)3 at a distance from the electrode and no film formation on the surface; (c)pH: at the optimal pH for the chlorate process, Y(III), Sm(III) and La(III) will be very close toprecipitation. The exact solubility of REM salts was not determined but REMs started toprecipitate at pH 4.8 and therefore it was not possible to perform trials at the normal operatingcondition of pH 6.5 (Gustafsson, et al., 2010);

Chromate use and presence: not all of this research has focused specifically on the replacementof chromates from the sodium chlorate process. Nevertheless, the experiments undertaken didnot involve the use of SD , hence Cr(VI) would be eliminated from the electrolyte

Overall, REM salts pose insurmountable problems to their implementation as additives to thechlorate process. At low concentrations, they give a thin cathode film, while at higherconcentrations (and lower current densities) the film formed has inhibiting as well as catalyticproperties. Given the problems with solubility, temperature and concentration, trivalent metal ionssuch as REM salts cannot be recommended as an additive to the chlorate process at normal chlorateprocess conditions.

This alternative is not known to be employed in any commercial application.

Table 4-8: Research into REM salts – Nylén et al, 2007-2008

Parameter Details

Year 2007-2008

Source (Nylén, 2008) – Thesis(Nylén, et al., 2008) – Journal article(Nylén, et al., 2007) – Journal article




- The purpose of this work was to identify possible improvements in chlorateelectrolysis, with the long-term goal of reducing its energy consumption


High, but replacement of Cr(VI) not the main focus of the research


- The addition of Y(III) ions to a 0.5 M NaCl electrolyte resulted in the formation ofan yttrium hydroxide film on the cathode during hydrogen evolution. Thehydrous, gel-like Y(OH)3 film formed on the iron surface inhibits the reduction ofprotons, nitrate ions and of hypochlorite ions. Under certain conditions the filmalso catalyses hydrogen evolution from the reduction of water. The reactant ofthe catalysed water reduction is most likely water molecules coordinated to Y(III)within the yttrium hydroxide film

- Two forms of film may be distinguished. A film formed at conditions expected tofavour a relatively thin film, i.e. a low concentration of Y(III) or a high currentdensity when extensive gas evolution disturbs the film formation and hinders thereduction of ions but the film does not activate water reduction. At higher Y(III)concentrations and lower current densities the film formed has inhibiting as wellas catalytic properties. Loss of activation at high current densities may be aproblem in electrolysis applications

- When adding Y(III) to chlorate electrolyte having a higher ionic strength than the


Table 4-8: Research into REM salts – Nylén et al, 2007-2008

Parameter Details

electrolyte in this work, yttrium precipitates immediately, most likely as Y(OH)3 inthe bulk. Another problem might be the mass transport in industrial cells, whichhas to be good enough for developing a thin diffusion layer of OH-. Thickerdiffusion layers may lead to precipitation of Y(OH)3 at a distance from theelectrode and no film formation on the surface


Handling of Cr(VI): no SD was used in the experimental systems that used YCl3Presence of Cr(VI) in electrolyte: SD is not present (but the Y(OH)3 film does notsurvive under the typical operating conditions of a chlorate cell)

Table 4-9: Research into REM salts – Gustafsson et al, 2010-2012

Parameter Details

Year 2010-2012

Source (Gustafsson, 2012) – Thesis(Gustafsson, et al., 2010) – Journal article




- The goal was to better understand how (molybdate and) trivalent cations can beused as additives to pH neutral electrolytes to activate the Hydrogen EvolutionReaction (HER)


Highly relevant; successful results could open a pathway to the elimination of SD


- The addition of Y(III) to a pH neutral electrolyte has been found to catalyse theHER. Addition of Y(III) results in the formation of a Y(OH)3 film at the cathode.Experiments suggest that the efficiency for yttrium hydroxide deposition basedon the transport of yttrium was about 7%, so the film appears to be destroyed byvigorous gas evolution

- At 25°C, additions of 10 mM YCl3, SmCl3 and LaCl3, the REM hydroxide film couldeasily be seen by the naked eye on the electrode surface after experiments atthis temperature, but not after trials at 70°C. It was probably dissolved at thehigher temperature as the current was switched off

- The optimal pH of the chlorate process is close to neutral pH. Y(III), Sm(III) andLa(III) will be very close to precipitation around neutral pH. Experimentobservations showed that Y(III) precipitated at pH 4.8 in 550 g/L NaClO3 at 70°C,which means that the Y(III) will be in precipitated form at pH 6.5. It is possiblethat the trivalent cations also form precipitations with anions in the electrolyte.In the chlorate process, the sodium chlorate is separated from the electrolytewith crystallization at alkaline pH. If added to an industrial chlorate electrolysisprocess, the trivalent cations would precipitate in this step and potentiallycontaminate the chlorate product

- High chloride concentrations form complexes with Y(III) and probably also withother trivalent metal ions and thus decrease the activation of the HER. Hightemperatures also decrease the degree of activation achieved by addition oftrivalent cations

- Given these problems with solubility, temperature and chlorides, trivalentmetal ions cannot be recommended as an additive to the chlorate process.Trivalent cations could be a promising additive to activate the HER at roomtemperature and chloride levels below 0.5 M


Handling of Cr(VI): the experiments did not involve SD; however, this is of limitedrelevance given the shortcomings of REMs detailed abovePresence of Cr(VI) in electrolyte: in theory, absent, but not relevant due to technicalshortcomings


Alternative technologies for the sodium chlorate process

Introduction to alternative electrode materials and coatings

Section 2.1.2 describes that SD is added to the electrolyte to form a thin film of chromium hydroxideon the cathode, and the film electrochemically hinders the reduction of the hypochlorite andchlorate and thus improves the current efficiency of the chlorate process. It also affects the rate ofthe hydrogen evolution reaction (HER). There has been research that has specifically aimed atimproving current efficiency and/or control over the hypochlorite reaction by means of developingnovel coatings for electrodes or novel electrode materials. Relevant technologies suggested in theliterature include:

Coatings based (primarily) on

Molybdenum

Ruthenium

Zirconium Electrodes based on

Ruthenium-titanium alloys

Ruthenium-based, titanium-free alloys.

A summary of the available literature information regarding to alternative electrode materials andcoatings is presented below.

Alternative 4: Molybdenum-based cathode coatings

The use of molybdenum-based coatings has been investigated as an alternative to SD in the chlorateprocess, although some of the relevant research was not specifically aimed at eliminating the use ofSD. The material deposited on the cathode in one patent was made out of a bath comprising FeCI3,Na2MoO4, NaHCO3 and Na2P2O7 or RuCl3 and MoCl3. Another patent has also been filed on cathodescoated with Ni-Mo but that does not address the use of SD in chlorate cells.


A patent by Krstajic et al in 2007, associated with Industrie De Nora S.p.A., a leading electrodesupplier

A patent by Rosvall et al in 2009, associated with AkzoNobel (EKA).


Current efficiency and oxygen evolution: molybdenum-based coatings show some promise asregards the achieved oxygen evolution, cell voltage and cathodic current efficiency

pH buffering: to ensure adequate buffering of pH at the desired level (achieve an initial pH 6.4),sodium acid phosphates (3 g/L) need to be added to the electrolyte

Chromate use and presence: in the Krstajic et al patent, a low addition of SD (0.1 g/L) wasrequired to ensure acceptable (equivalent) current efficiency. In the Rosvall et al patent, SD wasused at typical concentrations (4.4 g/L).


Overall, the use of Mo-based cathode coatings shows some promise but may need to beaccompanied by the addition of phosphate to ensure adequate pH buffering which can beproblematic, as discussed in Section 5. The elimination of Cr(VI) cannot be guaranteed under theconditions demonstrated in the literature but a (significant) reduction in the concentration of SD tothe electrolyte seems plausible. Evidence of commercial use of this alternative could not beestablished, and the applicant has no knowledge of any such commercial use.

Table 4-10: Research into molybdenum-based cathode coatings – Krstajic et al, 2007

Parameter Details

Year 2007

Source (Krstajic, et al., 2007) – Patent


Industrie De Nora S.p.A.


- The patent relates to a process for the industrial electrolytic production ofsodium chlorate, characterised by a high yield and a high electrical efficiency

- The patent is aimed at developing a system for sodium chlorate production withlow energy consumption making use of a nil or extremely limited amount ofchromium compounds


High relevance; elimination of SD was among the objectives of the patent


- Activation of the carbon steel cathodes was achieved through a bath prepared bydissolution of 9 g/L FeCI3, 40 g/L Na2MoO4, 75 g/L NaHCO3 and 45 g/L Na2P2O7 indistilled water, and the deposition was carried out at a constant current densityof 100 mA/cm2 and at a temperature of 60 °C, making use of a platinum finemesh as the counterelectrode, under stirring. The deposition was protracteduntil a 20 micrometre thick alloy comprised of 47% by weight molybdenum and53% by weight iron was obtained, as detected by a subsequent X-ray energydispersion spectroscopy test

- The voltage and energy efficiency of the cells with and without Mo-activatedelectrodes are shown below

Electrolyte Conditions Cell with activatedcathodes

Cell with non-activated cathodes

300 g/L NaCI3 g/L SD

pH = 6.412.5 kA/m

2

61°C

Voltage: 3.01-3.02Efficiency: 98%


300 g/L NaCI3 g/L sodium acidphosphates (Na2HPO4 andNaH2PO4)0.1 g/L SD

pH = 6.402.5 kA/m

2

60-61°C



300 g/L NaCI3 g/L sodium acidphosphates (Na2HPO4 andNaH2PO4)

pH = 6.412.5 kA/m

2

61°C




Handling of Cr(VI): one of the embodiments does not include the use of SD, butresults in lower current efficiency and lower voltagePresence of Cr(VI) in electrolyte: an option was investigated where SD was notpresent in the electrolyte

Notes: Another patent (Krstajic, et al., 2010) has also been filed on cathodes coated with Ni-Mo but that does not address the use of SD in chlorate cells


Table 4-11: Research into molybdenum-based cathode coatings – Rosvall et al, 2009

Parameter Details

Year 2009

Source (Rosvall, et al., 2009)


AkzoNobel (EKA)


- The patent relates to the process of preparing an electrode for the production ofalkali metal chlorate and improving the electrolytic process. Emphasis is given toproviding a cell in which a bipolar electrode or hybrids of bipolar and monopolarelectrodes are mounted and to investigating a cell in which the polarity of theelectrodes can be reversed such that the electrodes successively work as anodeand cathode within a given period of time.

- A further objective of the invention is to provide an electrode improving thecathodic current efficiency when in operation in an electrolytic cell, particularlywhile reducing the cell voltage

- A further objective of the invention is to provide electrodes which may lower themetal loading of precious metals on an electrode substrate while substantiallymaintaining the performance of commercial electrodes


High; but invention not aimed at replacing or reducing the use of SD; SD was used inthe experiments


- Experiments were based on an electrolyte containing 120 g/L NaCI, 580 g/LNaCIO3, and 4.4 g/L SD

- RuCl3 and MoCl3 were used to deposit a layer on a Ti-based electrode- The results of oxygen evolution, cell voltage and cathodic current efficiency are

shown below- In this experiment, the current efficiency of the titanium cathodes coated with

molybdenum oxide were superior to the current efficiency of the baselineelectrodes (PSC 120). For the molybdenum oxide-coated cathode, a decrease inoxygen formation was also observed

Oxygen (%) CCE (%) Cell voltage (V) Comment

2.3 95 2.87 Baseline

2.3 96 2.85 After stop

2.0 100 3.14 Mo/Ru-oxide on Ti (Grade 1)

2.1 99 3.18 After stop


Handling of Cr(VI): SD was used as normalPresence of Cr(VI) in electrolyte: SD was present at typical operating levels

Alternative 5: Ruthenium-based cathode coatings

The use of ruthenium-based coatings has been investigated in the context of the chlorate process,however, the research has so far focused on the development of new cathode coatings that wouldallow more efficient operation of the cell and reduced energy consumption, rather than thereduction or elimination of the use of SD in industrial chlorate cells. The material deposited on thecathode is RuO2, although a patent has provided a comparison of the RuO2 coatings to Ru/W oxideand Ru/Mo coatings (on Ti3SiC2 ceramic material).


A thesis and journal articles by Cornell and colleagues, associated with the Royal Institute ofTechnology in Stockholm (KTH) and AkzoNobel (EKA)

The aforementioned 2009 Rosvall et al patent, associated with AkzoNobel (EKA).



Oxygen evolution: when RuO2 coatings were used in experiments (Ti0.7Ru0.3O2) in the presenceof chromates, oxygen evolution somewhat increased (as shown by Rosvall et al). On the otherhand, when in the presence of molybdenum or tungsten, such an issue did not arise;

Current efficiency: RuO2 coatings on titanium electrodes have a current efficiency poorer thanunder typical SD use. However, current efficiency may improve when mixtures of other oxides(TiO2, MoO2, WO2) are used alongside RuO2;

Stability concerns: thicker RuO2 coatings may be eroded by the vigorous gas evolution andimproved stability is necessary before RuO2-based activated cathodes can be used industrially;

Chromate use and presence: hypochlorite and chlorate ions are reduced on RuO2 in the absenceof the chromium hydroxide film, under typical conditions (70 °C, 3 kA/m2). An addition of SD tothe chlorate electrolyte is necessary in order to keep a high current efficiency on the cathode.The level of SD addition would appear to be similar to that of current practices (3-6.5 g/L).

Overall, the conclusion so far has been that the use of SD cannot be eliminated as the RuO2 coatingslead to the reduction of chlorate at fast rates. There is no available evidence that the dosage of SDcan be reduced compared to the current state-of-the-art process. Evidence of commercial use ofthis alternative could not be established, and the applicant has no knowledge of any suchcommercial use.

Table 4-12: Research into ruthenium-based cathode coatings –Cornell et al, 1993-2006

Parameter Details

Year 1993, 2002, 2006

Source (Cornell & Simonsson, 1993) – Journal article(Cornell, 2002) – Thesis(Nylén & Cornell, 2006) – Journal article


AkzoNobel (EKA)Royal Institute of Technology, Stockholm


- Investigation of Ru-based DSA® anodes and how the concentrations of chloride,chlorate, chromate, as well as pH, mass-transport and temperature affect theanode potential

- Investigation of RuO2 coatings on activated cathodes and their role in reducingenergy consumption

- Investigation of the role of the Cr(III) hydroxide film around the cathode

Relevance to the use andreplacement of Cr(VI) in thechlorate process

Limited; the research was not focused on the replacement of Cr(Vi) but didinvestigate its role in the electrolyte and around the anodes

Key differences to currentchlorate process andnotable improvements andshortcomings

- The rate of the hydrogen evolution reaction in the chlorate process stronglydepends on the electrode material. Thermally prepared RuO2 coatings arerelatively active due to a favourable reaction mechanism in combination withlarge real surface areas. At a current density of 3 kA/m2, typical for industrialelectrolysis, the overvoltage for hydrogen evolution is about 300 mV lower onRuO2 than on corroded iron

- In a chlorate electrolyte, the 100 % RuO2 electrodes are more active than theDSA®s, and the overpotential depends on the coating thickness

- Ina chlorate electrolyte, the effect of the film on hydrogen evolution on an iron


Table 4-12: Research into ruthenium-based cathode coatings –Cornell et al, 1993-2006

Parameter Details

or a RuO2 cathode is difficult to estimate, since the current in a chromate-freesolution is a sum of currents from hydrogen evolution, chlorate reduction andhypochlorite reduction

- The thicker RuO2 coatings prepared in the laboratory were eroded by thevigorous gas evolution and improved stability is necessary before RuO2-basedactivated cathodes could be used industrially

- A thin film of Cr(III)hydroxide is formed on the RuO2 cathode in the chlorateprocess. The film efficiently hinders the reduction of hypochlorite and chlorate

- Hypochlorite and chlorate ions are reduced on RuO2 in the absence of thechromium hydroxide film, the chlorate reduction reaction being relatively fast onRuO2 and by far the dominating reaction in chromate-free chlorate electrolyte at70 °C, 3 kA/m2. Chlorate reduction on iron is faster if the electrode is corroded.In the chlorate process, chlorate reduction is activation controlled. Therefore, amass transport barrier as an alternative to dichromate addition on the RuO2

cathode will not efficiently hinder chlorate reduction. An addition of SD to thechlorate electrolyte is necessary in order to keep a high current efficiency on thecathode

- Catalytic electrode materials, such as RuO2, were deactivated after dichromateaddition whereas the film activated inferior electrocatalysts, such as gold

- RuO2 showed relatively good resistance to iron poisoning and other electrolyteimpurities


Handling of Cr(VI): the addition of Cr(VI) was necessary in order to suppress parasiticreactions (an addition of 0.015M of Na2CrO4 is described (ca. 2-3g/L))Presence of Cr(VI) in electrolyte: Cr(VI) is still present, probably at similarconcentrations to current practices

Table 4-13: Research into ruthenium-based cathode coatings – Rosvall et al, 2009

Parameter Details

Year 2009

Source (Rosvall, et al., 2009) – Patent


AkzoNobel (EKA)


- Development of an electrode which has improved performance in an electrolyticcell, notably improving the cathodic current efficiency when in operation in anelectrolytic cell, particularly while reducing the cell voltage, showing reducedthickness resulting in material savings and optimisation enabling an increasednumber of 5 electrodes arranged in the same cell space whereby production maybe increased without up-scaling an existing plant

- Development of an electrode that does not corrode where sludge which could bedeposited on the anodes is not formed

- Development of an electrode that is resistant to hydrogen evolving conditionsand reducing conditions in an alkaline environment and at least shorterexposures in an oxidative environment

- Development of an electrolytic cell and a process for the production of alkalimetal chlorate. It was a particular objective to develop a cell in which theformation of oxygen and therefore the associated danger of explosion isdecreased while the operating conditions are facilitated

- Development of an electrolytic cell in which a bipolar electrode or hybrids ofbipolar and monopolar electrodes are mounted

- Development of an electrolytic cell in which the polarity of the electrodes can bereversed such that the electrodes can work successively as anode and cathodewithin a given period of time


Table 4-13: Research into ruthenium-based cathode coatings – Rosvall et al, 2009

Parameter Details


Highly relevant to the chlorate process, but not relevant to the removal of SD fromthe process/electrolyte


A series of experiments were conducted under different configurations and theresults are summarised below.

Ru-basedcathode coating

Cathodematerial

SD Cathodiccurrent

efficiency*

Cell voltage* Oxygen*

No coating Ti No SD 92%96% AS

3.30 V 3.7%

No coating Mildsteel

No SD 86%Failed AS

3.01 V 4.2%N/A AS

No coating Ti3SC2 No SD 100% 3.24 V 3.9%

No coating Ti 4.4 g/L 99%Failed AS

3.37 V 2.3%

No coating Mildsteel

4.4 g/L 97%90% AS

3.00 V3.01 V AS

2.2%2.4% AS

No coating Ti3SC2 4.4 g/L 100% 3.28 V3.23 V AS

2.3%

No coating,machined

Ti3SC2 4.4 g/L 100% 3.35 V3.33 V AS

1.8%

No coating,sandblasted

Ti3SC2 4.4 g/L 100% 3.29 V3.28 V AS

2.1%

No coating,polished

Ti3SC2 4.4 g/L 100% 3.36 V3.34 V AS

1.7%

Ti0.7Ru0.3O2 Ti 4.4 g/L 95%96% AS

2.87 V2.85 V AS

2.3%

Mo/Ru oxide Ti 4.4 g/L 100%99% AS

3.14 V3.18 V AS

2.0%2.1% AS

W/Ru oxide Ti 4.4 g/L 99% 3,22 V3.27 V AS

2.2%

1st

, 2nd

, 3rd

layerRu0.83Mo0.17O2

Ti3SC2 4.4 g/L 100% 2.85 V2.89 V AS

2.1%

1st

Ru0.3Ti0.7O2;2

ndand 3

rdlayer

Ru0.83Mo0.17O2

Ti3SC2 4.4 g/L 100% 2.93 V2.94 V AS

2.2%

1st

2nd

and 3rd

RuO2

Ti3SC2 4.4 g/L 95%(no result AS)

2.80 V2.93 V AS

2.8%

* AS = after stop


Handling of Cr(VI): SD needs to be used at concentrations within the typicaloperating range of the current state-of-the-art processPresence of Cr(VI) in electrolyte: Cr(VI) still present in the electrolyte

Notably, older research focused on the potential benefits of replacing iron cathodes with titaniumones coated in oxides such as RuO2 and the results were encouraging (see the table that follows),but the state of the art described in the relevant patent is outdated compared to currentdevelopments and the invention based on RuO2 and other metal oxides has not developed into anindustrially-proven alternative.


Table 4-14: Research into ruthenium-based cathode coatings – Yoshida et al, 1981

Parameter Details

Year 1981

Source (Yoshida, et al., 1981) – Patent


Hodogaya Chemical Co., Ltd


- Development of an activated cathode which is capable of preventing a cathodecurrent loss due to the reducing reaction in the aqueous solution electrolysis, hasa low overvoltage, a high corrosion resistance and a high mechanical strengthand is easy to handle

- Prevention of the contamination of the product and effluent by metal salt addedto the electrolytic bath in the aqueous solution electrolysis


High relevance; reduction of use of chromate is presented as one of the benefits ofthe invention


The patent refers to an activated cathode which comprises:- A base plate, e.g. titanium- A metal oxide layer formed on the surface of the base plate, e.g. ruthenium,

rhodium, palladium, osmium, iridium and platinum, the most efficient appearingto be ruthenium

- An oxide of one or more metal elements selected from the group consisting ofcalcium, magnesium, strontium, barium and zinc in the group II and chromium,molybdenum, tungsten, selenium and tellurium in the group VI

- Titanium cathodes coated with Ru or Rh were accompanied by considerablecathode current loss in the absence of chromate

- Titanium cathodes with Ru+Rh coatings and the addition of metal oxides such asCaO, MgO, BaO, SrO and Cr2O3 showed cathode current loss lower than ironcathodes in the presence of 2 g/L SD


Handling of Cr(VI): the use of 2 g/L SD could be eliminated with the use of acombination of metal oxides on a titanium base.However, according to (Lindbergh & Simonsson, 1991), these cathodes only allow thekinetics of the hypochlorite ion reduction reaction to be slowed down but do notallow the reaction to be eliminated (Andolfatto & Delmas, 2002)Presence of Cr(VI) in electrolyte: Cr(VI) would still be present in the electrolyte toensure the efficiency of the process

Alternative 6: Zirconium-based cathode coatings

The use of zirconium-based coatings has been investigated in the context of the chlorate process;however, the relevant research may not have aimed at the reduction or elimination of the use of SDin industrial chlorate cells. The material deposited on the cathode is ZrO2 (the layer can be appliedon a zirconium surface by thermal decomposition of a Zr-containing solution), although patentsdescribe external layers of ZrTiO4 accompanied by RuO2 (and optionally by ZrO2 and/or TiO2) andZrO2 modified with Y2O3 on a zirconium plate.


A journal article by Herlitz et al in 2001, associated with the Royal Institute of Technology (KTH)in Stockholm

A patent by Andolfatto & Delmas in 2002, associated with Atofina A patent by Brown et al in 2010, associated with Industrie De Nora, S.p.A.



Suppression of parasitic reactions: ZrO2 reduces the rate of hypochlorite reduction, but doesnot entirely inhibit it. Combinations of Zr with Ti and/or Ru are required for a better suppression

Cathodic current efficiency: when ZrO2 modified with Y2O3 was deposited on a zirconium plate,a cathodic efficiency of up to ca. 91% (after 104 days) was recorded. However, this was in ahypochlorite cell without direct linkages to the use of SD for the manufacture of chlorate,therefore, the applicability of the described system to the chlorate cell is unclear

Chromate use and presence: no chromate was used in the experiments described in thepatents above.

Overall, the conclusion so far has been that Zr-based coatings may be used in the absence ofchromate, but the achieved cathodic current efficiency may not necessarily be as high as in a typicalchlorate cell in the presence of a cathodic chromium hydroxide film. Efforts have been made toimplement a Zr-coated cathode on an industrial scale, but these were unsuccessful and led to theabandonment of the relevant research.

Table 4-15: Research into zirconium-based cathode coatings – Herlitz, 2001

Parameter Details

Year 2001

Source (Herlitz, 2001) – Journal article


Royal Institute of Technology, Stockholm


To clarify the effect of oxidised zirconium on parasitic cathodic reactions in thechlorate process, electrochemical studies were carried out at laboratory scale. Thetechniques used were cyclic voltammetry and recording of polarisation curves


Significantly relevant; oxidised zirconium was considered as a means for suppressingthe hypochlorite parasitic reaction, but not as a direct replacement additive for SD


- Oxidised zirconium cathodes reduce the rate of hypochlorite reduction, althoughnot entirely inhibiting it, which is mainly related to a lowered active area due tothe porous layer of zirconium dioxide

- The oxidised samples are partly passivated, giving high overvoltages for thehydrogen evolution reaction. These overvoltages gradually decrease duringcathodic polarisation due to the simultaneous reduction of the zirconium oxide

- Studies of the selectivity indicate that hypochlorite reduction occurs on theoxidised zirconium cathodes to a high extent, the thermal oxide being somewhatbetter

- It is concluded that zirconium oxide is not a suitable cathode material for thesodium chlorate process


Not relevant, the alternative has not proven to be technically feasible


Table 4-16: Research into zirconium-based cathode coatings – Andolfatto & Delmas, 2002

Parameter Details

Year 2002

Source (Andolfatto & Delmas, 2002) – Patent


Atofina


Development of a cathode which allows the chlorate of an alkali metal to beelectrolytically synthesised with a high coulombic yield and in the absence of SD


Highly relevant; Zr/Ru coatings were considered in order to eliminate the parasitichypochlorite reduction and eliminate the need for SD


- This specific cathode comprises a titanium substrate with an external layer ofZrTiO4 accompanied by RuO2 and optionally by ZrO2 and/or TiO2

- Depending on the ratio of Zr/Ti and Ru/(Zr+Ti+Ru), different suppression of thehypochlorite reduction can be achieved in the absence of SD

- For a ratio Zr/Ti equal to 1 and Ru/(Zr+Ti+Ru) equal to 0.001, the new electrodewould appear to limit the hypochlorite reduction to the same extent as SD on amild-steel electrode


Handling of Cr(VI): SD was eliminated in the examples shown in the patent; someembodiments achieved results similar to those obtained with SD and steel cathodesPresence of Cr(VI) in electrolyte: Cr(VI) would not be present in the electrolyte

Table 4-17: Research into zirconium-based cathode coatings – Brown et al, 2010

Parameter Details

Year 2010

Source (Brown, et al., 2010) – Patent


Industrie De Nora, S.p.A.


A cathodic member for electrochemical cells used in hypochlorite productioncomprises a zirconium plate coated with a zirconium oxide layer, which is particularlysuitable for minimising the decomposition of the hypochlorite product while ensuringa prolonged lifetime. The coated zirconium plate can be used as the cathodic plate ina monopolar cell, or can be welded to a titanium plate for use in a bipolarconfiguration


The invention relates to electrochemical cells for the production of hypochloritesolutions; although reference is made to chlorate cells, the applicability of theinvention is uncertain.It is mentioned that the addition of SD in hypochlorite systems for water disinfectionis not relevant, as the presence of chromium is not acceptable


- Although ZrO2 is very stable in the caustic environment established on cathodesurfaces, the cathodically-evolved hydrogen tends to detach the protective layerfrom the titanium body in a short time

- The invention comprises a zirconium-oxide coated zirconium plate for use as acathode in an electrolytic cell for the production of hypochlorite

- While titanium has always been the valve metal of choice for valve metal-basedcathode plates of hypochlorite cells due to its lower cost and its superiorresistance against corrosion, it has been found that ZrO2 layers grown onzirconium surfaces are much more resistant to detachment induced bycathodically-evolved hydrogen compared to similar layers grown on titanium

- In thermal-sprayed layers, ZrO2 can be mixed with other suitable oxides tomodify the structure of the layer, for instance to obtain an adequate porosity.Zirconium oxide modified with a small amount of Y2O3, usually less than 10%


Table 4-17: Research into zirconium-based cathode coatings – Brown et al, 2010

Parameter Details

molar, is sometimes used on titanium plates and proves beneficial also onzirconium plates.

The results on current efficiency using different versions of Zr plates are detailedbelow.

Cathode material InitialCE

CE after104days

Cathode material InitialCE

CE after104days

Zr plate with ZrO2

deposited withthermaldecomposition ofZr acetate

93.0% 88.4% Ti plate uncoated 78.4% 72.5%

Zr plate withplasma-spraying ofZrO2 modified with8% of Y2O3

87.2% 91.3% Ti plate withplasma-spraying ofZrO2 modified with8% of Y2O3

89.3% Failedafter 44days

Zr plate withthermally grownZrO2 layer

93.4% 90.0% Pt plate withplasma-spraying ofZrO2 modified with8% of Y2O3

91.8% Failedafter 44days

Bipolar Ti/Zrcathode with 4coats of Ru/Ir/Ti

88.5-92.7%


Not relevant to the replacement of SD from the chlorate process

Alternative 7: Ruthenium alloy cathodes

The use of ruthenium-titanium-based alloys as cathode materials has been investigated in the pastas a means for reducing energy consumption, rather than with the aim of eliminating SD from theelectrolyte.

Key sources of information in the open literature include patents and journal articles associated withCanadian interests, particularly the Canadian Institut de recherche d'Hydro-Québec, as shown inTable 4-18 and Table 4-19.


Hydrogen overpotential reduction: Ru-Ti alloy cathodes significantly reduce the hydrogenoverpotential by 300 mV more than the steel cathodes;

Suppression of hypochlorite decomposition and oxygen evolution: the speed of hypochloritedecomposition (2 ClO- 2 Cl- +O2) was found to be low, even lower than the speed measuredon the steel electrodes, which meant that very little molecular oxygen was released;

Chromate use and presence: the use of SD is uncertain. The patents and journal articlepublished in the 1990s suggest that SD may not be used but the alloy may comprise up to 50%chromium. On the other hand, the 2006 patent by Schulz et al refers to an aluminium-containing nanocrystalline alloy, which, apparently, might be used in the presence of a cathodicCr(OH)3 film.


Overall, these ruthenium-titanium alloys show some good performance in terms of currentefficiency and suppression of parasitic reactions, however, they seem unable to guarantee theelimination of the use of SD or the presence of chromium in the electrolyte. Evidence of commercialuse of this alternative could not be established, and the applicant has no knowledge of any suchcommercial use.

Table 4-18: Research into ruthenium/titanium alloy cathodes – Van Neste al al, 1996, Boily et al, 1997,Schulz et al, 1997 & 2006

Parameter Details

Year 1996, 1997, 2006

Source (Van Neste, et al., 1996) –Journal article(Boily, et al., 1997) – Patent(Schulz, et al., 1997) – Patent(Schulz, et al., 2006) – Patent


Institut de recherche d'Hydro-QuébecEKA Chimie Canada


- The present invention relates to new nanocrystalline alloys containing Ti, Ru, Feand O. The invention also relates to a process of preparation of these new alloys

- The patent was the result of a research carried out to improve the electricefficiency of the cells used for the electrochemical synthesis of sodium chlorate,the electricity consumption of which is very high (about 50 to 100 MW per plant)


High, but no mention to the presence of SD in the electrolyte is made


- According to the 1997 patents, a method of producing sodium chlorate byelectrochemical synthesis in an electrolysis cell having cathodes made of acomplex alloy according to of the formula:Ti30+x Ru15+y Fe25+z O3u+t Mu

where M is preferably chromium andx is between -5 and +5y is between -5 and +5z is between -5 and +5t is between -28 and +5u is between 0 and +10,x + y + z + t + u = 0

- The alloy may comprise up to 50% chromium. This addition could substantiallyreduce or even eliminate the use of SD

- When measured under a current of density 250 mA/cm2 at 70 °C in an electrolytecell, the overpotential of hydrogen was approximately 300 mV lower than that ofthe steel cathodes. The latter have an overpotential of hydrogen equal toapproximately 900 mV while the cathodes made from the alloys according to theinvention have an overpotential of hydrogen equal to about 600 mV. Whenmultiplied by the number of cathodes and the number of cells in a sodiumchlorate production plant, this reduction in the overpotential of hydrogenrepresents a net gain of electric energy of more than 10%

- The speed of decomposition of the hypochlorite in contact with the materialforming the cathodes was very low, even lower than the speed measured on thesteel electrodes, which meant that there was very little molecular oxygenreleased. This reduced the risks of simultaneous release of molecular hydrogenand oxygen even further and therefore also reduced the inherent risks ofexplosion

- The cathodes made from the alloy can be welded directly on titanium anodes- The 2006 patent refers to an alloy of the formula Ti2+t(Ru(1-x_Al(1+x))(1-u/2)MuTy,

wherein: t is a number preferably between -0.5 and +0.5; x is a numberpreferably between +0.5 and +0.9; u is a number preferably less than 0.25; y is anumber preferably equal to 2; M represents one or more elements selectedamong Ag, Pd, Rh, Fe, Cr and V, the elements being preferably, Ag, Pd or Rh; and


Table 4-18: Research into ruthenium/titanium alloy cathodes – Van Neste al al, 1996, Boily et al, 1997,Schulz et al, 1997 & 2006

Parameter Details

T represents one or more elements selected among O, B, S, C, N, Si, P and H, theelements being preferably oxygen. Said alloy is preferably in nanocrystalline form

- This latter patent suggests that suitable alloys should not interfere with theCr(OH)3 film on the cathode, suggesting that SD may still be used


Handling of Cr(VI): it is implied that SD may not need to be used, but the cathodewould contain significant levels of chromium in the older Schulz et al patent. For thesecond patent, Cr may comprise up to 50% of the alloyPresence of Cr(VI) in electrolyte: uncertain

Table 4-19: Research into ruthenium/titanium alloy cathodes – Gebert et al, 2000

Parameter Details

Year 2000

Source (Gebert, et al., 2000) – Journal article


École Polytechnique de MontréalIFW DresdenInstitut de recherche d'Hydro-Québec


Development of cathodes that will allow a reduction in energy consumption


Uncertain; cathodes for chlorate electrolysis are discussed but it is uncertain if this isin light of the use of Cr(VI) in the electrolyte


- Cathodes for chlorate electrolysis were prepared by mixing nanocrystalline Ti–Ru–Fe–O catalyst powder with small amounts of Teflon and subsequent hotpressing the mixture on a carbon–Teflon sub-layer

- The behaviour of electrodes with catalyst loadings from 300 mg/cm2 reduced to10 mg/cm2 was investigated in a chlorate electrolyte with pH 6.5 and in part, forcomparison, in a 1 M sodium hydroxide solution at 70 °C

- The as-milled catalyst powder electrodes showed a high activity for the HER inthe chlorate electrolyte particularly expressed in low overpotentials of about 580mV at −250 mA/cm2 for catalyst loadings down to 20 mg/cm2 and high doublelayer capacitances in the freshly prepared state. These electrodes showincreased activity at low polarisation. The long-term stability during electrolysiswas also analysed


Handling of Cr(VI): uncertainPresence of Cr(VI) in electrolyte: uncertain

Later research by scientists at the Canadian Institut de recherche d'Hydro-Québec focused on a newfamily of electrocatalytic materials consisting of an iron aluminide (Fe3Al) alloy doped withruthenium and with the potential addition of tantalum. Experiments with these new alloys stillrequire the use of SD, the addition of which is described at 3 g/L.

These alloys have not yet found commercial use. On the Institut de recherche d'Hydro-Québec’swebsite an invitation for Expressions of Interest was available in early 2014 aimed at the attributionof a worldwide exclusive license for the valorisation of the technology based on the Ru-alloys, atechnology entitled “Chlorate Efficient Cathode Technology”. The call for expressions of interest hasbeen issued to selected parties that have interests in sodium chlorate production technologies. TheCanadian Institute claims that, “the new cathodes can provide up to approximately 10% of energysavings to the sodium chlorate production process, depending on operating conditions. These


electrocatalytic electrodes, which are highly resistant to corrosion, are dimensionally stable and leadto very low levels of iron impurities as a result of their utilization”9.

Overall, these alloys cannot guarantee the elimination of SD use or the presence of chromium in theelectrolyte and have not yet found commercial use.

Table 4-20: Research into ruthenium alloy cathodes – Schulz & Savoie, 2009-2013

Parameter Details

Year 2009, 2010, 2013

Source (Schulz & Savoie, 2009) – Journal article(Schulz & Savoie, 2010) – Journal article(Schulz & Savoie, 2010b) – Patent(Schulz & Savoie, 2013) – Patent


Institut de recherche d'Hydro-Québec


The journal articles and patents discuss a new family of electrocatalytic materialsconsisting of an iron aluminide (Fe3Al) alloy doped with a catalytic element such asruthenium. High energy ball milling is used to prepare these new metastablenanocrystalline alloys. Their cathodic overvoltages for the hydrogen evolutionreaction in a chlorate electrolyte are about 400 mV lower than that of iron cathodes


Substantially relevant, but not aimed at replacing SD


- The catalysed iron aluminide nanocrystalline powders were prepared by highenergy ball milling starting from mixtures of Fe3Al and Ru powders

- The electrochemical set-up consisted of a two-compartment cell with a capacityof about one litre. The counter electrode was a DSA anode. The electrolyte wasa synthetic standard chlorate electrolyte containing 550 g/L of NaClO3, 110 g/L ofNaCl, 3 g/L of SD and 1 g/L of NaClO. The pH was regularly adjusted at 6.5 usingNaOH or HCl.

- The electrodes made of compacted ball milled powders have overpotentialvalues for the HER at 250 mA/cm2 in a chlorate electrolyte about 400 mV lowerthan that of iron cathodes

- The 2010 patent does not describe the use of SD, but this is implied as itmentions “One sees on this figure the characteristic peaks of Fe, Al, and Ru butalso of Na and Cr coming from the electrolyte”

- The 2013 patent discusses the corrosion resistance of the alloys describedearlier. This was found to be good at pH 6.5 but poor in acidic conditions(standard industrial practises use acid wash from time to time to cleanelectrochemical cells and electrodes). To solve this problem, the inventorsdiscovered that the addition of a small amount of Ta to these materials couldmake these new alloys not only highly resistant to corrosion in chlorateelectrolyte but also in acidic (HCl) solutions without losing performanceregarding the electrochemical synthesis of sodium chlorate. The alloys ofinterest are Fe3-xAl1+xMyTzTat (x is between -1 and +1, y is between 0 and +1, z is abetween 0 and +1 and t is between 0 and +1). The electrolyte again contains 3g/L SD


Handling of Cr(VI): SD is still added to the electrolyte at typical concentrationsPresence of Cr(VI) in electrolyte: SD is still present in the electrolyte

9Information on the Call for Expressions of Interest is available athttp://www.hydroquebec.com/innovation/en/partenariats.html (accessed on 11 April 2014).


Other technologies

Alternative 8: Two-compartment electrolytic systems

Other technologies that may be considered alternatives to chromate-based solutions go beyond theelectrode level. These could include variations of two-compartment cells (for example, membrane-type ‘chlor-alkali’ cells).

The key sources of information regarding this alternative are a number of patents. These include:

A patent by Cook in 1975, associated with Hooker Chemicals Plastics Corp A patent by Millet in 1990, associated with Atochem (now Arkema) A patent by Delmas & Ravier in 1993, associated with ELF Atochem (now Arkema)

The chlor-alkali process is a process related to a chlorate cell but with some important differences.The electrodes in a chlorate cell are in one compartment, allowing the anode and cathode reactionproducts to mix and to react together. This allows chlorine to react with hydroxide to formhypochlorite and finally sodium chlorate. In a two compartment-cell, such as a chlor-alkali cell, theelectrodes are physically separated and thus their products cannot react together. These cells canbe operated without SD and can produce sodium chlorate under certain conditions (Millet, 1990)(Delmas & Ravier, 1993). The usual electrolytic reactions operating in chlor-alkali cells are as follows:

6Cl- 3Cl2 + 6e- (20)

6H2O + 6e- 3H2 + 6OH- (21)

Overall: 6NaCl + 6H2O 3Cl2 + 3H2 + 6NaOH (22)

If the process is modified so that the chlorine gas is reacted with the hydroxide solution, sodiumchlorate can also be generated as shown in eq. 23 below (Tilak & Chen, 1999):

3Cl2 + 6OH- 5Cl- +ClO3- + 3H2O (23)

with counter-ions: 3Cl2 + 6NaOH 5NaCl + NaClO3 + 3H2O (24)Combined (22 & 24): 6NaCl + 6H2O + 6NaOH 5NaCl + NaClO3 + 3H2O + 3H2 (25)Eq. 25 simplified: NaCl + 3H2O NaClO3 + 3H2 (6)

It can be seen that overall the process is chemically identical to the conventional undivided cellprocess but in practice quite different. Chlorine is produced in the anode compartment of amembrane chlor-alkali cell and hydrolysed into hypochlorous acid (eq. 2) (Hakansson, et al., 2004).The pH and temperature of the solution of hypochlorous acid is then maintained so that theformation of chlorate is maximised (pH 6-6.5 at around 80 °C). At this pH, the correct ratio ofhypochlorite and hypochlorous acid is achieved. Equation 26 shows the balanced equation, in thiscase showing sodium hydroxide acting as a base. The cathode compartment would serve as thesource of sodium hydroxide that would be introduced into the chlorate reactor and in limitedamounts to a chlorine absorption unit or anode compartment (Delmas & Ravier, 1993). The use ofsodium hydroxide for pH control in this manner potentially avoids the need for further bufferingagents to be added to the electrolyte.


3Cl2 + 3H2O ⇄ 3HOCl + 3HCl (2)

3HOCl + NaOH ⇄ 2HOCl + NaClO (26)

The current process involving SD uses undivided electrolysis cells while chlor-alkali cells usemembrane cells and would also involve separate chlorate reactors and gas processing equipment. Achange to this type of cell would require a rebuild of current plant technology, as all existing singlecompartment cells would need to be scrapped.

It is considered that modified chlor-alkali type-cells could be technically feasible for the productionof chlorate without the use of SD. For this reason, further consideration to production of chloratevia two-compartment cells and reaction of chlorine with sodium hydroxide will be given, althoughthe high cost of the associated production plant replacement is of note.

Table 4-21: Research into two-compartment electrolytic systems – Cook, 1975

Parameter Details

Year 1975

Source Cook (1975)


Hooker Chemicals Plastics Corp


- A process for producing alkali metal chlorate using two different cells. he firstbeing a two-compartment membrane cell and the second being a conventionalsingle-compartment chlorate cell.

- The patent describes a process that produces sodium hydroxide, chlorine,sodium chlorate and hydrogen as outputs of one overall process.


High relevance, but no mention is made of the use of SD in the electrolyte. Aconventional cell is used so use of Cr(VI) can be expected.


- The examples describe a process producing 1.7 tons per day of sodium chlorateusing the linked cells. The first cell produces a concentration of 100 g/L of sodiumchlorate and this is increased to 430 g/L in the second cell.

- The process has a current efficiency of 94%, at a cell voltage of 4.2 V and acurrent density of 4 A/sq. inch (0.62 kA/m2).

- Part of the hydrogen generated is burned with part of the chlorine produced togenerate hydrogen chloride. This is then used for pH control at some stages. It isnot clear how much of the hydrogen produced is diverted in this manner


Handling of Cr(VI): the patent does not mention the use of any electrolyte additivesnor describe any steps to limit corrosion. As the chlorate is primarily manufactured ina conventional chlorate cell, it is expected that Cr(VI) would be used as normal.Presence of Cr(VI) in electrolyte: Cr(VI) could be expected to be present in theelectrolyte.

Table 4-22: Research into two-compartment electrolytic systems – Millet, 1990

Parameter Details

Year 1990

Source Millet (1990)


Atochem (Arkema)


- Production of alkali metal chlorates or perchlorates using a two-compartmentmembrane cell

- Avoiding the use of Cr(VI) was a stated objective of the patent


High relevance to both the chlorate production process and the elimination of the useof Cr(VI)


Table 4-22: Research into two-compartment electrolytic systems – Millet, 1990

Parameter Details


- The patent claims processes carried out at pH 6.2-6.6 controlled by introducingsodium hydroxide from the cathode compartment into the anode compartment.

- The examples employ an electrolyte consisting of 150-160 g/L NaCl and 500 gNaClO3 at a temperature of 63-71 °C and pH 6.3-6.4.

- A current of 10 A was applied to a 0.5 dm2 electrode (equivalent to 2 kA/m2) butno mention of cell voltage is made.

- The yield of sodium chlorate is claimed at 87.3%-93% based on the oxygenpresent in the chlorine in the absence of SD.

- A yield of pure hydrogen is claimed at practically equal to 100%.- No mention is made of how long the process was operated for nor the scale of

the process- Two examples are shown with the following chlorate generation efficiencies

based on amount of oxygen formed

Temp Anolyte pH Anolyterecycling flowrate

Membrane (byDupont)

Sodiumchlorateefficiency

63 °C 6.3-6.4 70 L/h Nafion 117 87.3%

71 °C 6.3-6.4 160 L/h Nafion 902 93%


Handling of Cr(VI): the invention is claimed without the use of chromates.Presence of Cr(VI) in electrolyte: No SD present in the electrolyte

Table 4-23: Research into two-compartment electrolytic systems –Delmas & Ravier, 1993

Parameter Details

Year 1993

Source Delmas & Ravier (1993)


ELF Atochem (Arkema)


- Method of manufacturing chlorate alkali metal by electrolysis in a membrane cellwithout adding chromium


High relevance to both chlorate process and the elimination of the use of Cr(VI)


- The invention comprises two linked chlor-alkali cells and a scrubbing column anddoes not involve the use of Cr(VI)

- The process preferably runs at pH 6.5-7 and temperature of 70-90 °C- Chlorate production is carried out by transfer of chlorine gas and the solution of alkali

metal hydroxide from a chlor-alkali cell to react in a scrubbing column- pH is maintained at 6.5-7 in the scrubbing tower by addition of sodium hydroxide

from cathode compartments- Column output is recycled by circulating in a second chlor-alkali cell- The output of the anode compartment of the second cell is diverted to a crystalliser

to obtain the chlorate and to recycle mother liquors back to the second chlor-alkalicell

- The method is claimed to result in a reduction in water consumption: the usualmethod of production of sodium chlorate requires the introduction of 1,563 kg ofwater per tonne of NaClO₃, associated with sodium chloride fed in the form of brine containing 26% by weight of NaCl. In the process disclosed, the second cell is fed by astream from the reaction between chlorine and the aqueous solution at 33% byweight of soda with the introduction of 719 kg of water per tonne of NaClO₃ product. There is a saving of 844 kg of water that would otherwise need to be evaporated in asodium chlorate crystallisation facility


Handling of Cr(VI): no use of SDPresence of Cr(VI) in electrolyte: no presence of SD in the electrolyte


Alternative 9: Oxygen-consuming gas diffusion electrodes

A recently developed technology for an improved chlor-alkali process replaces the conventional steelor titanium cathodes in chlor-alkali membrane cells with an oxygen-consuming electrode,fundamentally changing the chemistry of the process. This change results in the production ofchlorine and sodium hydroxide without the production of hydrogen. The process is claimed to resultin up to 30% reduction in electricity requirements in laboratory trials (Chlistunoff, 2004). However,this is at the cost of a valuable hydrogen co-product and significant technical barriers to limitcathode corrosion are yet to be overcome. The use of oxygen-consuming electrodes in theproduction of chlorate is currently under patent (Hakansson, et al., 2004). Although the patentstates that an embodiment of the patent does not necessitate the use of chromates, the examples inthe patent use SD at a concentration of 3 g/L, as shown in Table 4-24.

The purpose of the project was continuation of the development of new chlor-alkali electrochemicalreactors (ECRs) that employ oxygen-depolarised cathodes. Due to their lower operating voltages,the oxygen-depolarised reactors consume up to 30% less electrical energy per unit weight of theproducts (chlorine and caustic soda) than the state-of-the-art membrane electrolysers withhydrogen-evolving cathodes.

Evidence of commercial use of this alternative could not be established, and the applicant has noknowledge of any such commercial use. The elimination of the use of SD under this method has notbeen demonstrated; therefore this cannot be considered a realistic alternative for the purposes ofthis AfA.

Table 4-24: Research into oxygen-consuming gas diffusion electrodes – Hakansson et al, 2004

Parameter Details

Year 2004

Source (Hakansson, et al., 2004)


AkzoNobel (EKA)


- A process for producing alkali metal chlorate in an electrolytic cell that is dividedby a cation selective separator into an anode compartment in which an anode isarranged and a cathode compartment in which a gas diffusion electrode isarranged

- The patent is aimed at developing a chlorate cell where the cost and handling ofHCl and NaOH are reduced while improving energy efficiency


High relevance, but the embodiments described use SD at typical electrolyteconcentrations


- The experiment was run as a batch process with a start volume in the reactorvessel of 2 litres. The start concentration of the electrolyte in the anodecompartment was 110 g of NaCl/L, 550 g of NaClO3 and 3 g/L SD. This solutionwas pumped through the anode compartment of an electrolytic cell at a rate of25 L/h corresponding to an approximate linear velocity across the anode of 2cm/s

- An excess of oxygen gas was fed to the gas compartment. The cell was alaboratory cell containing an anode compartment with a dimensionally stable(DSA) chlorine anode and a cathode compartment with a silver plated nickel wiregas diffusion electrode loaded with uncatalysed carbon (5-6 mg/cm2). The anodeand cathode compartments were separated by a cation selective membrane,Nafion 450, and the distance between each electrode and the membrane was 8mm

- Electrolysis was conducted at a temperature of 70 °C in the electrolysis cell, witha current density of 0.2-3 kA/m2 and at a pH of 6.2. The current was varied


Table 4-24: Research into oxygen-consuming gas diffusion electrodes – Hakansson et al, 2004

Parameter Details

between 0.5- 6.3 A. The electrolysis was run for 30 h- The achieved efficiencies under two examples are shown below.

Example – conditions Currentefficiency forelectrolysis

(based on OH-

)

Currentefficiency for

chlorine

Currentefficiency for

chlorate

50 g/L NaOH solution waspumped through the cathodecompartment at linear velocityacross the cathode of 2 cm/s

92% 100% 95%

Solid sodium chloride was addedto the reactor vessel and fed tothe anode compartment at a rateof 0.71 g/Ah

100% 97%

The cell voltage for the overall chemical reaction in the gas diffusion electrode cell isabout 2V, which implies that considerable operation costs can be saved by replacingthe hydrogen evolving cathode with a gas diffusion electrode acting as cathode


Handling of Cr(VI): the invention is claimed with and without the use of chromates.However, example embodiments in the patent use SD at 3 g/LPresence of Cr(VI) in electrolyte: as per typical operating conditions, where SD isused

Alternative 10: Polymeric cathode film coatings

Finally, the use of polymeric films as cathode coatings has been discussed in the literature in thepast. A 1981 patent by Bommaraju et al discussed the elimination of chromates from the electrolytein favour of a polymeric cathodic film made of chlorinated or fluorinated polymers and copolymers.An example shown based on a proprietary tetrafluoroethylene fluorocarbon showed comparablereductions in current efficiency for chlorate and/or hypochlorite reduction when compared to theuse of a conventional steel cathode in a chlorate electrolyte which includes a chromate additive.

Nevertheless, this patent is now more than 30 years old; evidence of commercial use of thisalternative could not be established, and the applicant has no knowledge of any such commercialuse. This novel method cannot be considered a realistic option for the replacement of SD and will begiven no further consideration in favour of other options discussed in this AoA.

Table 4-25: Research into polymer cathode film coatings – Bommaraju et al, 1981

Parameter Details

Year 1981

Source (Bommaraju, et al., 1981)


Hooker Chemicals & Plastics Corp.


Provision of a viable alternative to the use of chromates in chlorate cells, withoutsacrificing cell performance and efficiency through the use of a protective porous filmon the surface of the cathode


High relevance


Table 4-25: Research into polymer cathode film coatings – Bommaraju et al, 1981

Parameter Details


- A non-conductive material is used to generate a cathode film with an averagethickness of from about 10-4 μm to about 103 μm, and with sufficient porosity to permit the transport of hydrogen molecules leaving the cathode

- Materials include those that are substantially nonconductive and chemicallyresistant or inert to the chlorate solution, remaining stable in the solution duringconditions of prolonged operation include various halogenated polymers,copolymers and resins, both of the thermosetting and thermoplastic variety, andparticularly chlorinated and fluorinated polymers and copolymers, such aspolyvinyl chloride, Teflon, Kel-F (proprietary chlorotrifluoroethylene), andKalgard (proprietary tetrafluoroethylene fluorocarbon). The polymeric materialmay also be a thermoplastic polymer, such as polysulphone, or an elastomericmaterial, such as neoprene rubber or a silicone material. Also suitable as film-forming materials are various metallic and non-metallic oxides such as zirconiumdioxide, titanium dioxide, tantalum oxide, chromic oxide (Cr2O3), vanadiumtrioxide, iron oxide, cobalt oxide, aluminium oxide, hafnium dioxide, niobiumpentoxide, and silicon dioxide

- The film-forming material can be applied to the substrate by plasma or thermalspraying, chemical vapour deposition, emulsion techniques, or other suitabletechniques which will form a thin, porous surface on the substrate material

- Examples of the invention have been described where the film is formed eitherwith Kalgard or Cr2O3. These examples showed comparable reductions in currentefficiency for chlorate and/or hypochlorite reduction when compared to the useof a conventional steel cathode in a chlorate electrolyte which includes achromate additive


Handling of Cr(VI): SD was eliminated in the examples shown in the patentPresence of Cr(VI) in electrolyte: Cr(VI) would not be present in the electrolyte

4.2.4 Consultation with the supply chain

Given that SD is only used as a process aid and does not play a role in the final product (in whichchromium is present as an impurity at levels below 5ppm), consultation with customers of theapplicant was not deemed necessary for the purposes of the AoA and was not undertaken.

On the other hand, this AoA document is the result of extensive consultation between theindependent third party that was contracted to develop this AoA and the applicant. The applicantwas specifically consulted regarding the alternatives identified through data searches in order toensure that the information in the open literature is relevant and accurate and to gauge the level ofinternal knowledge regarding the feasibility of alternative technologies. Questionnaires, emailcommunications and face-to-face meetings were used for the purposes of information gathering andverification.

4.3 Screening of identified alternatives

4.3.1 Screening of identified alternatives for commercialisation status

As already explained, the applicant has been a member of a consortium of sodium chloratemanufacturers (SDAC) who have worked together towards the preparation of their individual AfAs,within the confines of Competition Law and with an independent third party in the role of a trustee.Each individual applicant within this consortium has supported the development of the AoA byproviding information on the current commercialisation status of the identified alternatives. Theaim of this analysis was two-fold:


Establish which alternatives (if any) are immediately or otherwise readily available for adoptionas a replacement for SD

Collect information on the availability of the alternatives that would be shortlisted, to inform theanalysis presented in Section 4 of the AoA.

The analysis prepared on the basis of consortium members’ submissions has been used in thepreparation of all members’ AoA documents.

The overall conclusion from Table 4-26 is that none of the identified alternatives is commerciallyavailable at present and will not become available by the sunset date. Several of the identifiedalternatives are invariably solutions that have only been trialled at the laboratory scale with oftenunsatisfactory results. With the exception of Cr(III) compounds (in this AoA, represented by CrCl3),none of the other alternatives has found commercial use in the manufacture of sodium chlorate andamong the manufacturers of sodium chlorate who are applying for Authorisation, Cr(III) has onlybeen used by the competitor who has filed the relevant patent application. Certain alternatives thatmight be considered as being closer than others to commercialisation because of some existingexperience with them (e.g. use of Ru-based anodes which would be adapted to work as cathodes, ortwo-compartment cells that have been used in the chlor-alkali industry) require a considerablelength of time before they could be implemented.

Conclusion: two of the identified alternatives, two-cell systems with oxygen-consuming diffusionelectrodes and polymeric film coatings, are eliminated on the basis of commercialisation issues; theformer has not been proven beyond the lab scale and only in the presence of SD, while the latter hasnot found commercial applications for over 30 years, therefore, cannot be considered a realisticoption. The remaining alternatives will be subject to further screening.

4.3.2 Screening of identified alternatives for suitability in eliminating Cr(VI)exposure

An alternative to SD in the applied for use should ideally eliminate the use of SD and any associatedworker exposure to the Cr(VI) anion that confers to SD its SVHC properties during the sodiumchlorate production process (worker exposure for downstream users as well as consumer exposureare of no relevance to the applied for use, as discussed in the CSR). However, it is not always thecase that alternatives may eliminate the use of SD or indeed the exposure to Cr(VI). Somealternatives may limit the handling of SD solution but may still result in the presence of Cr(VI) in theelectrolyte; other alternatives may simply need the addition of SD (possibly, at variableconcentrations) otherwise they would not be able to ensure the required current and processefficiency of the chlorate process. It is clear that if an alternative requires the addition of a similardose of SD into the electrolyte, it could not be assumed a suitable option for the replacement of SD.


Table 4-26: Commercialisation status of identified alternatives for SD in the sodium chlorate process

Alternatives

Commercial availability for the sodium chlorate processIs this a realistic

alternative option?Currently used?If commercially used, timeframe for

implementationIf not commercially used, timeframe

for becoming available


1 Chromium (III)chloride

Not by the applicant Uncertain. Relevant patentapplication (by a direct competitor) isat an early stage of the process which

can typically take several years

- Not immediately availableand most likely

unavailable at the sunsetdate

2 Sodium molybdate No - Impossible to estimate; still underresearch with significant shortcomings

Not currently

3 Rare Earth metal(III) salts

No - Impossible to estimate; still underresearch with significant shortcomings

Not currently, overcomingthe poor solubility is a

major challenge


4 Molybdenum-based cathodecoatings

No - Uncertain; depends on the rate ofreplacing of cathodes at the affected

plant

Not currently

5 Ruthenium-basedcathode coatings

There are Ru-coated DSA-type anodes on the market;

these cannot be used ascathodes since they are not

stable due to hydrideformation on the titaniumsubstrate, which ‘peels off’the coating. The availability

of Ru-coated cathodes islimited

Impossible to estimate.If the technology would be effective in replacing SD (not so far the case), the

first stage of implementation could potentially take less than a year, forcompanies with access to Ru-based electrode technology.

Full implementation would depend on the rate of replacing of cathodes at theaffected plant

Not currently


Table 4-26: Commercialisation status of identified alternatives for SD in the sodium chlorate process

Alternatives

Commercial availability for the sodium chlorate processIs this a realistic

alternative option?Currently used?If commercially used, timeframe for

implementationIf not commercially used, timeframe

for becoming available

6 Zirconium- basedcathode coatings

No Impossible to estimate, as past trials have been unsuccessful.If the technology would be effective in replacing SD (not so far the case,

concerns exist over the coating’s lifetime), the first stage of implementationcould potentially take less than a year, for companies with access to the

electrode technology.Full implementation would depend on the rate of replacing of cathodes at the

affected plant

Not currently


7 Ruthenium alloycathodes

Not for cathodes, already inuse as anodes

Uncertain; depends on the rate of replacing of cathodes at each affected plant;uncertain commercial availability of the required alloys

Not currently; may noteliminate the use of SD


8 Two-cellelectrolyticsystems

Not for chlorate production Uncertain; entire new plant would berequired

- Not currently'' '''''''''''''''''''''''' #E#'''' ''''''

'''''''''''''''' ''''''' '''''''''''''''''''''''''' '''''''''''''

9 Two-compartmentelectrolytic cellswith oxygen-consuming gasdiffusionelectrodes

No - Impossible to estimate; still underresearch. Lab trials used SD in the

electrolyte

Not foreseeably; will notbe considered further

given the use of SD

10 Polymeric cathodefilm coatings

No - Impossible to estimate Given the date of thepatent (1981), this cannot

be considered realisticand will not be considered

further


The following table summarises the available information on the identified alternatives andidentifies those that would not eliminate worker exposure to Cr(VI), thus in principle would notmake suitable alternatives for SD in the applied-for-use. The colours signify elimination of exposure(green), reduction of exposure or uncertain change (orange) and no change on current exposureconditions (red).

Table 4-27: Preliminary screening of the suitability of the identified alternatives in eliminating workerexposure to SD

AlternativesCurrent

situationComparison to SD


1 Chromium (III) chloride Addition of SDleading to 3-6.5

g SD/L inelectrolyte

Better but not optimal: eliminates handling of SD duringloading, worker exposure to Cr(VI) largely remains

unchanged

2 Sodium molybdate Better but not optimal: to achieve acceptable processefficiency, low presence of Cr(VI) needed

3 Rare Earth metal (III) salts Better: no Cr(VI) required


4 Molybdenum-basedcathode coatings

As above Uncertain: past research has shown that SD is either notreplaced or may still need to be present at lower

concentrations (0.1 g/L)

5 Ruthenium-basedcathode coatings

No improvement: Cr(VI) is required and a SD dosagesimilar to the current process would be required. Theshortcomings identified in the published research will

need to be overcome

6 Zirconium- basedcathode coatings

Uncertain: could eliminate the use of SD but this is notcertain, as some of the past research was not aimed at

replacing SD



As above No improvement: some alloys used in lab tests maycontain up to 50% Cr which would reduce the

consumption of SD but might not eliminate the presenceof Cr(VI) in the electrolyte. Later research indicates use

of 3 g/L SD


8 Two-cell electrolyticsystems

As above Better: would eliminate the use of SD and the presenceof Cr(VI) in the electrolyte

The table suggests that ruthenium-based cathode coatings and ruthenium alloy cathodes wouldoffer no improvement; therefore they cannot be considered realistic alternatives for SD. In addition,molybdenum-based cathode coatings and zirconium-based cathode coatings are likely to requireaddition of SD at typical concentrations of SD in order for performance to be maintained atacceptable standards. Cr(III) chloride and, possibly, sodium molybdate may indeed reduce workerexposure to SD but certainly do not eliminate exposure to Cr(VI); CrCl3 in particular reduces thehandling and exposure to Cr(VI), as SD does not need to be physically handled and dosed into thesystem, but it does not eliminate exposure to Cr(VI), as it is oxidised into Cr(VI) in the electrolytethus generating a Cr(VI) concentration essentially identical to that obtained from the addition of SDunder the applied-for-use scenario. The result is that with CrCl3 the estimated exposure reductionamounts to only ca. 20% of aggregate exposure of day workers only. All other employees (unitworkers and central laboratory workers) would not benefit from reduced exposure to Cr(VI). This isfurther elaborated in Section 5.2.


Only REM salts and two-cell electrolytic systems may claim that they require neither the addition northe presence of SD in the electrolyte (but the former is clearly technically infeasible, as discussedbelow).

4.3.3 Screening of identified alternatives against the technical feasibilitycriteria

Comparison of SD to potential alternative substances

A list of technical feasibility criteria was developed and discussed in Section 2 (see Table 2-6). Thisdevelopment involved all members of the SDAC. The applicants were asked to:

Provide quantitative values or qualitative descriptions of how each of the technical feasibilitycriteria are met by SD along with a minimum value or threshold that must be achieved by analternative

Use the technical feasibility criteria and their thresholds or ideal values/ranges to (a) compareeach alternative substance to SD, and (b) compare the SD-based state-of-the-art chloratetechnology to the alternative technologies identified, in support of the information obtainedfrom the literature review.

In some cases, the values provided by individual applicants within the consortium varied. Wherenecessary, clarification was sought to identify the reasons for any deviation and to establish the levelof knowledge and practical experience of each applicant with the alternatives under consideration.Where appropriate, applicant-specific information is provided in the following table and this hasbeen marked as confidential.

Generally, a semi-quantitative approach was taken where applicants assessed each alternative to SDin turn as “Similar”, “Better” or “Worse” and, where possible, additional justification and explanationwas provided.

This systematic comparison of alternatives is shown in Table 4-28. The colouring code of the cells isas follows:

Green colour indicates an alternative that meets and notably exceeds the value achieved by SDunder the criterion (i.e. the substance is “Better” than SD)

White colour indicates an alternative that meets the threshold/range of a criterion (i.e. thesubstance is “Similar” than SD)

Orange colour indicates an alternative that may or may not meet the threshold/range of acriterion, i.e. there is uncertainty or it may marginally fail the criterion

Red colour indicates an alternative that does not meet the threshold/range of a criterion (i.e.the substance is “Worse” than SD).


Table 4-28: Comparison of alternative substances to SD against the technical performance criteria

Criteria Sodium dichromate Alternative substances

Result or numericalvalue achieved by

sodium dichromate

Threshold oracceptable range for

replacing sodiumdichromate

Chromium (III) chloride Sodium molybdate Rare Earth metal (III) salts

Formation ofprotective filmpermeable tohydrogen

No suitablenumerical value, buthydrogen efficiency

>98 %

2 % Similar: Cr(III) is oxidised toCr(VI) immediately (in the

presence of active chlorine)and acts as if SD had been used

as an additive

Uncertain: it creates aprotective film but the

thickness of the film grows toothick and energy consumption

will increase

Worse: salts are not soluble atprocess conditions. In trials,rare earth metals started to

precipitate at pH 4.8 and trialsat normal operating pH 6.5were not even possible to

perform. REM hydroxide film isnot permanent at typical

operating conditions

Formation ofprotective filmimpermeable tohypochlorite

No numerical value Ideally, similar to SD Similar (assumed) Worse: worse currentefficiency implies lower

selectivity

Worse: salts are not soluble atprocess conditions

Control of oxygenformation (andcontrol of oxygencontent inhydrogen)

SD achieves <2.5% O2

evolutionIdeally, less than

2.5% by volume of O2

in H2 with amaximum of 3.0%

Similar (assumed) Worse: research indicates 3.6-4.8% O2 generation, suggesting

Mo(VI) needs to be as low aspossible


Cathode protection(corrosioninhibition)

Cannot bequantified; minimumlifetime of cathode isassumed to be 8 yrs

At least 8 yearscathode lifetime

Similar (assumed) Uncertain Worse: salts are not soluble atprocess conditions

pH buffering '''#A#''' '''''''#A#'''''''' Similar (assumed) Worse: addition of phosphatebuffer is required; this leads tocracks on the cathodic film and

affects the durability of theanodes



Table 4-28: Comparison of alternative substances to SD against the technical performance criteria

Criteria Sodium dichromate Alternative substances

Result or numericalvalue achieved by

sodium dichromate

Threshold oracceptable range for

replacing sodiumdichromate

Chromium (III) chloride Sodium molybdate Rare Earth metal (III) salts

Current efficiencyand energyconsumption

>95%, 5,230 kWh/ttheoretical>'''''#A#''''

''''#A#'''''' kWh/t forthe applicant

Energy efficiency:''#A#'''% or more,

ideally >95%.Total energy

consumption:''''''#A#'' '''''''''' kWh/t

chlorate or less

Similar (assumed) Worse: 80-91% or lower.However, similar process

efficiency can be reached byonly partially replacing SD with

molybdate


Solubility inelectrolyte

Highly solubleSolubility of SD:

ca. 2355 g/L

(Highly) soluble Similar (assumed) Similar Worse: salts are not soluble atprocess conditions

Impurities inchlorate product

<5ppm Cr in solidchlorate product


separately. Metalsare particularly

detrimental to ClO2

generation

Similar (assumed) Worse: presence ofmolybdenum in the chlorate

product would destabilise theClO2 reaction

Uncertain but probably worse:probably higher impurity

content due to lack of solubility


The conclusions from this analysis are as follows:

The only alternative substance that generally meets the technical feasibility criteria is CrCl3

(more accurately, Cr(III)), as it is assumed to effectively give Cr(VI) in the electrolyte and thusdeliver the technical functions of the chromates within the chlorate cell). However, theapplicant does not have access to the details of this technology and therefore the exactconditions and parameters under which such performance equivalence can be obtained are notknown

Rare Earth Metal salts are clearly infeasible replacements for SD. Their solubility at processconditions is very poor and prevents them from performing their intended role. No solution hasbeen found so far to making the solubility of these compounds acceptable for the purposes ofsodium chlorate production. These substances cannot be considered technically feasiblealternatives

Sodium molybdate is accompanied by a major hazard concern, the generation of O2 in quantitiesthat may lead to explosive mixtures with H2, which is also released. This inherent hazard doesnot exist in the current technology that is based on SD. Sodium molybdate is a poorer pH buffer,which requires the addition of phosphates; however, the presence of phosphates has an adverseeffect on the stability of the cathodic film and the durability of the anodes. In addition, Mo(VI) isaccompanied by poorer current efficiency, which may be around or below 90%, unless some SDis added to the electrolyte. Finally, the presence of metal impurities in the chlorate productwould have adverse effects on the stability of the processes of the applicant’s customers (e.g.ClO2 formation).

Comparison of the SD-based chlorate production process to potential alternative technologies

A similar comparison of the SD-based chlorate process was performed for alternative technologies.The overview of comparison against the technical feasibility criteria is shown in Table 4-29. Thecolour coding is similar to the one in the previous table on alternative substances. The followingconclusions may be reached:

All of the alternative technologies have technical disadvantages, for example, poor pH bufferingwould require in each and every case the use of phosphate additives which could causeproblems at the anode

Alternatives other than two-cell electrolytic systems are shrouded by uncertainty as regardstheir ability to generate a film around the cathode of ‘equivalent’ impermeability to hypochloriteand permeability to hydrogen

The control of O2 formation is likely to be worse for Ru-based coatings The use of two-cell electrolytic systems might lead to higher energy consumption The stability of cathode coatings will define whether metal impurities would be found in the

chlorate product, thus causing safety concerns for the subsequent use of the chlorate by theapplicant’s customers

Technologies other than two-cell electrolytic systems may not be able to eliminate the use of SD.Notably, relevant past research has not really focused on the elimination of SD and for Ru-basedcathode coatings and Ru alloys there are well-founded concerns that Cr(VI) will continue to bepresent in the electrolyte.

Conversely, from a more positive perspective,

Mo-based coatings may be accompanied by improvements in current efficiency (this may also bethe case for Ru-based coatings and Ti-Ru alloys, but this is uncertain)


Two-cell electrolytic systems use separated electrodes, thus they eliminate the need for theformation of selective films on the cathode and would prevent the development of explosiveatmospheres as the generated gases (H2 and O2) would not be allowed to mix.

Overall, it would seem that two-cell electrolytic systems would have some distinct advantages overother technologies but would not be ‘trouble-free’. Ru-based coatings and Ru alloys would appearto be the least appropriate alternative technologies.


Table 4-29: Comparison of alternative technologies to SD-based chlorate process against the technical performance criteria

Criteria Sodium dichromate Alternative technologies

Result ornumerical

value achievedby sodium

dichromate

Threshold oracceptable range

for replacingsodium

dichromate

Mo-basedcoatings

Ru-based coatings Zr-based coatings Ru alloy cathodes Two-cell electrolyticsystems

Formation ofprotectivefilmpermeableto hydrogen

No suitablenumericalvalue, buthydrogen

efficiency >98%

2 % Uncertain:different

technology to SD.The film is not

formedelectrolytically

but imposed as acoating

Uncertain: differenttechnology to SD. It

may perform well if SDis present. RuO2

may reduce cathodicoverpotential to

hydrogen evolution.Coating has shown

poor stability

Uncertain:different

technology. Thefilm is not formedbut imposed; itseffectiveness is

unclear

Uncertain: differenttechnology. The film is

not formed butimposed; its

effectiveness is unclear

Not relevant to thistechnology:

cells/electrodes areseparated

Formation ofprotectivefilmimpermeabletohypochlorite

No numericalvalue

Ideally, similar toSD

Uncertain:different

technology to SD.The film is not

formedelectrolytic ally

but imposed as acoating

Worse: differenttechnology to SD.

RuO2 coatingeffectiveness in

preventing parasiticreactions is poor

(reduction ofhypochlorite and

chlorate ions)

Worse: differenttechnology. The

film is not formedbut imposed; ZrO2

based coatingsreduce the rate of

hypochloritereduction, but do

not entirelyinhibit it (unless

perhapscombined withother oxides)

Uncertain: differenttechnology. The film is

not formed butimposed; its

effectiveness is unclear.Lab tests with Ru-Ti

alloys would suggest alow rate of hypochlorite

reduction

Not relevant to thistechnology:

cells/electrodes areseparated '''''''

'''''''''''''''''''''''' '''' '''''''''''''''''''''' '''''''

''''''''''''''''#E#''''''''''''''''''''' '''''''''''''''''''''''' ''''

''''''''''''''''''''''''' ''''''''''''''' ''''''''''''''

''''''''''''''''''''''''''''




Result ornumerical


dichromate


for replacingsodium

dichromate

Mo-basedcoatings


Control ofoxygenformation(and controlof oxygencontent inhydrogen)

SD achieves<2.5% O2

evolution

Ideally, less than2.5% by volume

of O2 in H2 with amaximum of

3.0%

Uncertain Marginally worse: Rureleased from the

coating can increasethe bulk formation of

oxygen

Uncertain Similar: Ru-Ti alloyshave shown low

evolution of oxygen,but generally

the bulk of anodicformation of oxygen is

not influenced bychange of the cathode

coating/material

Better: cathode andanode are physically

separated by amembrane and

produced gases (H2 &O2) do not mix

Cathodeprotection(corrosioninhibition)

Cannot bequantified;minimumlifetime of

cathode is 8years

At least 8 yearscathode lifetime

Uncertain,possibly similar,

depends onadditives

replacing SD

Uncertain: requiresfurther study

Uncertain'' ''''''''''''''''''''''' ''''''

''''''''''''''#E#'' ''' '''''''''''''' '''''''''''''''''

Worse: no film orcoating at all; presenceof iron in the alloy may

lead to corrosioneffects. Ru alloys with

Fe/Al show poorstability in acidic pH and

require addition ofmetals such as Ta toimprove corrosion

resistance

Better: no particularneed for this. The

special materials usedare not easily

corroded




Result ornumerical


dichromate


for replacingsodium

dichromate

Mo-basedcoatings


pH buffering '#A#''''' '''''''#A#''''' Worse: need foraddition of

buffering agent,e.g. sodium

phosphate (3g/L). Phosphatesas Cr replacement

may causeproblems at the

anode

Worse: need foraddition of buffering

agent, e.g. sodiumphosphate.

Phosphates as Crreplacement may

cause problems at theanode

Worse: need foraddition of

buffering agent,e.g. sodiumphosphate,expected

Worse: need foraddition of buffering

agent, e.g. sodiumphosphate, expected

Worse: need foradjustment of pH

(e.g. NaOH/HClfeedback loops)

Currentefficiencyand energyconsumption

>95%5,700 kWh/ttheoretical;>''''#A#''%'''#A#''''''''

kWh/t for theapplicant

Energy efficiency:'''#A#''% or more,

ideally >95%.Total energy

consumption:''''''''''' '#A#'''''''''''kWh/t chlorate or

less

Better accordingto patents, a

lower cell voltagecan be achieved

using thistechnology,

resulting in alower energyconsumption

Uncertain: pastresearch would

suggest it is possiblybetter (activated

cathodes decreaseenergy consumption),if RuO2 used alongsideother oxides but onlyin the presence of SD

Uncertain,probably worse:

91% currentefficiency

reported for ZrO2

modified withY2O3 on a

zirconium plate ina hypochlorite

cell

Uncertain, probablyworse: past research

would suggest it ispossibly better by

reducing specific energyconsumption (Ru alloyslead to a reduction of

the hydrogenoverpotential).

Materials based onFe3Al alloy doped with

Ru and Ta may stillrequire SD (3 g/L)

Worse: using typicalelectricity

consumption figuresfor a chlor-alkaliplant, the overall

energy consumptioncan be calculated to

be worse than what isachieved with SD.

''''''''''''''''' '''''''''''''''''''''''''#E#'' ''''''''''''''

'''''''' '''''''''''''''''''''''''''''''''' ''''''''''' '''''

''''''''''''




Result ornumerical


dichromate


for replacingsodium

dichromate

Mo-basedcoatings



Highly solubleSolubility of SD:

ca. 2355 g/L

(Highly) soluble Not relevant Not relevant Not relevant Not relevant Not relevant

Impurities inchlorateproduct

<5ppm Cr insolid chlorate

product

Each impuritymust be

consideredseparately.Metals areparticularly

detrimental toClO2 generation

Uncertain butprobably worse:it will depend on

any additivesused and the

stability of thecoating.

Presence ofmetals in the

electrolyte(released from

the coating)would give rise to

concern

Uncertain butprobably worse: itwill depend on any

additives used and thestability of the

coating. Presence ofmetals in the

electrolyte (releasedfrom the coating)would give rise to

concern

Uncertain butprobably worse:it will depend on

any additivesused and the

stability of thecoating. Presence

of metals in theelectrolyte

(released fromthe coating)

would give rise toconcern

Uncertain but probablyworse: it will dependon any additives usedand the stability of thecoating. Presence of

metals in theelectrolyte (released

from the coating) wouldgive rise to concern

Better quality due tofewer impurities


4.3.4 Screening of identified alternatives for practicality and (preliminary)economic feasibility

Members of the SDAC, including the applicant, were requested to outline the practical (engineering)steps that would be required for the implementation of each alternative. They were also asked toidentify the most critical of these steps and highlight any issues that would require substantialexpenditure or extended timelines. The results are shown in Table 4-30. The conclusion on therealism of each alternative solution is highlighted in colour:

Green, for feasible and readily implementable solutions Orange, for alternative solutions with distinct engineering challenges and/or practicality issues Red, for alternatives that are infeasible from a practical and engineering perspective.

We therefore can identify the following ‘groups’ of alternatives that may be feasible alternatives interms of practicality:

CrCl3 is the only solution that could theoretically be feasible to implement (in comparison toother alternatives), on the basis of its similarities to SD and the (limited) information that ispublicly available. However, as the applicant does not have access to the relevant patent, accessrights need to be secured first, after the patent has been granted, before the ease or not ofimplementation can be confirmed

Sodium molybdate, molybdenum-based cathode coatings, ruthenium-based cathode coatings,ruthenium alloy cathodes and two-cell electrolytic systems are technically demanding and notimmediately available, but could theoretically be implemented in the longer term. Of these, theuse of sodium molybdate as an additive would be the relatively simpler option. On the otherhand, the use of new cathode coatings and alloys would require the gradual replacement ofexisting cathodes; due to the number of cathodes involved, this can only be undertaken over along period. In addition, the implementation of two-cell systems would practically require a newplant to be set up

Rare Earth Metal salts and zirconium-based cathode coatings are not considered realistic. Theformer simply cannot work as additives to the electrolyte, and the latter have not been provenas their industrial upscale failed in the past.

4.3.5 Summary of screening process for alternatives

A summary of the entire screening approach presented above is given in Table 4-31. The colourcode is as follows:

Green: acceptable/feasible Orange: feasible with complications and/or disadvantages in comparison to SD Red: infeasible/unrealistic.


Table 4-30: Practical and economic feasibility screening of potential alternatives

Alternatives Practical steps required Key complexities of practical steps Conclusion



- Exact changes are unclear as the applicant has noaccess to the details of the technnology which is underpatent application. It can be assumed that somechanges to dosing so that Cr(III) can added to the celland thus be oxidised to Cr(VI) in the electrolyte wouldbe required

- Securing access to relevant patent once it is granted

- Need to wait for patent to be granted and becomeavailable for licensing

- Unclear complexity but probably less complex thanother alternatives that are less similar to SD

- The cost of licensing is uncertain; reliance on thistechnology would also mean reliance on a patent heldby a direct competitor

Uncertain feasibilityand cost, while 3

rd

party patentapplication andaccess to patentpending

2 Sodiummolybdate

- Needs to be scaled up from lab scale- Substitution of overall volume of the electrolyte

(solution of chlorate) available in a plant; potentiallypossible to have both substances in the sameelectrolyte, cutting off one and adding the other

- Redesign of safety measures and hazard controls withregard to hydrogen handling (vis-à-vis the increasedgeneration of O2 gas)

- In theory, technically feasible but scaling up fraughtwith uncertainties

- Separation of SD from electrolyte and management ofthe waste

- Changes to the equipment for handling hydrogen- Equipment clean-up and preparation of new solution

would require downtime

From an engineeringperspective feasiblebut yet unavailableon an industrial scale

3 Rare EarthMetal (III) salts


(solution of chlorate) available in a plant; unclear ifpossible to have both substances in the sameelectrolyte, cutting off one and adding the other

- Very difficult to address the issue of poor solubility- Separation of SD from electrolyte and management of

the waste- Changes to the equipment for handling hydrogen- Equipment clean-up and preparation of new solution

would require downtime

From an engineeringperspectiveinfeasible andunavailable on anindustrial scale




(solution of chlorate) available in a plant- Activation of new iron cathodic sheets would be

necessary*- Assembly of new cathodic sheets and replacement of

all cathodes currently in use


- Existing cathode replacement would be very costly andwill only be possible to undertake over several years orinvolve a significant plant shutdown

- Known patents are held by third parties

From an engineeringperspective verydemanding andcostly; unavailableon an industrial scale




5 Ruthenium-based cathodecoatings


(solution of chlorate) available in a plant- Activation of new Ti sheets would be necessary to give

them the morphology (physical dimensions) of actualcathodes (current Ru-coated electrodes are used asanodes)

- Assembly of new cathodic sheets and replacement ofall cathodes currently in use



- Compared to Mo-based coatings, additional cost fortitanium rather than iron electrodes plus activation-related costs for the use of precious metals

From an engineeringperspective verydemanding andcostly; unavailableon an industrial scale

6 Zirconium-based cathodecoatings


(solution of chlorate) available in a plant- Activation of new iron cathodic sheets would be

necessary- Assembly of new cathodic sheets and replacement of


- Past attempts at industrial scale-up have failed- Separation of SD from electrolyte and management of

the waste- Existing cathode replacement would be very costly and

will only be possible to undertake over several years orinvolve a significant plant shutdown

- '''''''''''''''' ''''''''''''''#E# ''' ''' ''''''''''' ''''''''''''''''' '''' ''''''''''''''''''''' ''''''''' '''''''''''''''''' ''''' '''''' ''''''''''''''''

From an engineeringperspective verydemanding andcostly. unavailableon an industrialscale'' '''''#E#''' '''''''''''''''''' '''''''''' '''''''''''''''''''''


7 Rutheniumalloy cathodes


(solution of chlorate) available in a plant- Activation of new alloy cathodic sheets would be

necessary- Assembly of new cathodic sheets and replacement of




- Compared to Mo-based coatings, additional cost fortitanium rather than iron electrodes plus activation-related costs for the use of precious metals

- Uncertain commercial availability of alloys- May need to obtain access to patents held by 3

rdparties

From an engineeringperspective verydemanding andcostly; unavailableon an industrial scaleand issues withmarket availability






- Substitution of overall volume of the electrolyte(solution of chlorate) available in a plant

- Replacement of all the cells would be necessary. Thebrine treatment would require consequent overhauling,the crystallisation section debottlenecked and theelectrical power supply increased without increasingcapacity

- New retention systems for Cl2 on the production ofchlorate would be required

- Significant number of HAZOP studies and additionaltraining of personnel due to fundamental changes tothe chlorate production process

- Effectively, a new plant would be required

'''''''''' ''''''''''''''''''''''' ''''' #E#'''''' '''''''''''''''' ''''''' '''''' ''''''''''''''''''''''''''''''''''' '''''''''''''

- To the applicant’s knowledge, this technology has notbeen used anywhere in the world for chloratemanufacture

- In theory, technically feasible but scaling up fraughtwith uncertainties

- Replacement of all the electrolysers with newelectrolysis cell-rooms and long period of shut-down

- Several years may be required for design planning andscaling; even engineering implementation after allother steps have been taken could require several years

- Costs will be several millions of Euros (including costlymembranes)

- The suitability of membranes (currently available forchlor-alkali cells) would be the critical factor in thefeasibility of two-cell solutions for chlorate production

From an engineeringperspective feasiblebut requires a newplant; very costlyand time-consuming

* Activation refers to the coating a base metal (Fe, Ti) with an active layer which acts as a catalyst for the generation of hydrogen. This active layer is composed of variousmetals and requires a treatment process of the surface base and its components. Also, the composition and morphology of the active layer must match very strict rangesof variation, i.e. an anode and a cathode, whether or not coated, are not interchangeable in their functions


Table 4-31: Summary of the screening of identified potential alternatives for SD in the manufacture of sodium chlorate

AlternativeCommercialisation

status

Suitability as SDreplacement(exposure)

Comparison to SDagainst technicalfeasibility criteria

Engineering andeconomic feasibility

Overall commentaryShortlisted for

furtheranalysis?



Not immediatelyavailable and mostlikely unavailable at

sunset date

Leads to a very smallreduction (ca. 20 % forsome workers) but not

elimination of Cr(VI)exposure; eliminates

handling of SD

Uncertain due to lackof knowledge ofconditions and

parameters of use.Could prove similar to

Cr(VI)

Uncertain feasibilityand cost while 3

rdparty

patent applicationpending

The option that couldprove to be the mostsimilar to current useof SD but with only aminor reduction inworker exposure toCr(VI), it cannot be

considered a suitableoption

Yes – forcompleteness

only, as notconsideredsuitable for

worker healthprotection

2 Sodiummolybdate

Unavailable;unknown future

To achieve acceptableprocess efficiency, low

concentrations ofCr(VI) in the electrolyte

may be needed

Poorer currentefficiency and releaseof O2 that may lead to

explosiveatmospheres;

phosphate presencehas a serious effect on

anodes; metalimpurities

From an engineeringperspective feasible

but yet unavailable onan industrial scale

A simple alternative;however, wiith worseperformance than SDand not proven on an

industrial scale

Yes

3 Rare Earth Metal(III) salts


In theory, no Cr(VI)required

Poorly soluble;technically infeasible

From an engineeringperspective infeasibleand unavailable on an

industrial scale

Not soluble at normalchlorate productionconditions; unusable

No; cannot beused




status





furtheranalysis?




SD is either notreplaced or may still

need to be present atlower concentrations

(0.1 g/L)

Poorer pH buffering;unclear reaction

selectivity; betterclaimed energy

efficiency; phosphatepresence has a serious

effect on anodes;metal impurities

From an engineeringperspective very

demanding and costly;unavailable on an

industrial scale

Patent literaturesuggests reduced

energy consumptionand avoidance of SD(but uncertain); not

proven on an industrialscale

Yes

5 Ruthenium-based cathodecoatings


Cr(VI) is required and adosage similar tocurrent would be

required

Poorer pH bufferingand reaction

selectivity; metalimpurities


demanding and costly;existing electrodes areused as anodes rather

than cathodes;unavailable on an

industrial scale

Unrpoven andinfeasible; still requires

the use of SD;unsuitable

No; it is not asuitable

alternative,neither is ittechnically

feasible

6 Zirconium-based cathodecoatings

Unavailable;''''''''''''' '''' '''''''''''''''''

'''''''''''''''#E#'' '''''''''''' '''''''''''' ''''''''''''''''''' ''''''''

'''''''''''''''''

Could eliminate theuse of SD but this is not

certain

Generally uncertain;poorer pH buffering;may still require SD;

metal impurities


demanding and costly;unavailable at the

industrial scale'' ''''''''''''''' '''''''''''#E# ''''' '''''''''''''''''''''''' '''''''''' ''''''''''

'''''''''

Costly and demandingalternative '''''''

''''''''''''''''' '''''''''''''''' '''''''''''''''' ''''''#E#'''' '''' '''''''''''''''' '''''''''''''''''' '''''''''''

'''''''''''''''' '''''''''''''

No'' '''''''''''''''''

'''''''''''#E#'''''''''' '''' ''''''''''

'''' ''''''''''''''''''''''''

'''''''''




status





furtheranalysis?




Some alloys used in labtests may contain up to

50% Cr. More recentresearch indicates use

of 3 g/L SD

Poorer pH buffering,cathode corrosion

protection andreaction selectivity;

metal impurities


demanding and costly;unavailable on an

industrial scale andissues with market

availability

Technically interestingdue to its potential to

reduce energyconsumption but,

unproven, costly, raisesconcerns on cathode

lifetime and alternativebuffering agents may

also cause unexpectedproblems (e.g. higherO2 evolution). Would

still require SD

No; it is not asuitable

alternative,neither is ittechnically

feasible



Unavailable forchlorate manufacture;

unknown future

Would eliminate theuse of SD and the

presence of Cr(VI) inthe electrolyte

Better separation ofelectrodes and gases

and lower productimpurities but poorer

current efficiency''''''''''''''#E#'''''' '''' '''''''''''''''''''''''''''' ''''' ''''''

'''''''''''''''''''

From an engineeringperspective feasiblebut requires a new

plant; very costly andtime-consuming;increased energy

consumption can becalculated '''''''''''#E#'''''

'''' '''''' '''''''''''''''''''' '''''''''''' '''''''''''''''''''

Theoretically feasible;however, not without

disadvantages andextremely costly

Yes


Based on the above findings and using expert judgement, some of the identified alternatives can beexcluded from further consideration:

Rare Earth Metal salts (due to their poor solubility) Ruthenium-based cathode coatings (as they could not reduce or eliminate the use of/exposure

to Cr(VI)) Zirconium-based cathode coatings (as their industrial scale-up has failed in the past and they

cannot guarantee the elimination of SD use), and Ru-based alloy cathodes (as they are found to be fraught with uncertainty and unable to reduce

or eliminate the use of/exposure to Cr(VI)).

In conclusion, the following alternatives are considered – in principle – realistic and will be assessedfurther in Section 5 of this AoA:

Alternative 1 (substance): Chromium (III) compounds (CrCl3) – for completeness, given the lackof suitability in eliminating Cr(VI) exposure

Alternative 2 (substance): Sodium molybdate Alternative 4 (technology): Molybdenum-based cathode coatings, and Alternative 8 (technology): Two-compartment electrolytic systems.


5 Suitability and availability of possible alternatives

5.1 Introduction

As mentioned earlier, the preparation of the analysis of alternatives for SD in the manufacture ofsodium chlorate has been undertaken by an independent third party on behalf of the consortium,but the AoA for each applicant has been customised to their individual needs. As a result, theanalysis below includes the following elements:

Analysis which applies equally to all applicants within the SDAC, including the submitter of thepresent document. This has to a great extent been based on publicly available information

Where available and appropriate, applicant-specific information has been included. This mayinclude areas where the applicant needs to deviate from the joint analysis in order to explaintheir particular situation or the feasibility of an alternative for example, or where the applicant isable to provide additional company-specific, thus invariably commercially sensitive, information.

It must be therefore clear that some overlap between this AoA and the AoA documents of the othermembers of the SDAC should be expected. On the other hand, it needs to be remembered that eachmember of the consortium may have different needs and access to alternative technologies. Thismeans that the information available to each consortium member company regarding each specificalternative and the detail of the assessment varies by necessity.

5.2 Chromium(III) chloride

5.2.1 Substance ID and properties

Table 5-1 presents the identity of chromium (III) chloride which is used here as a representativeCr(III) compound.

Table 5-1: Identity of chromium(III) chloride

Properties Chromium(III) chloride Chromium(III) chloride hexahydrate

EC Number 233-038-3 919-095-3 / 919-229-0

CAS Number 10025-73-7 10060-12-5

IUPAC Name: Chromium(III) chloride Chromium(III) chloride hexahydrate

Formula CrCl3 CrCl3·6H2O

Molecular weight 158.36 266.48

Structure

Source: Chemspider Internet site (http://www.chemspider.com)


Table 5-2 provides an overview of the physicochemical properties of chromium(III) chloride .

Table 5-2: Physicochemical properties of chromium(III) chloride

PropertyValue

NotesAnhydrous Hexahydrate

Physical state at 20 °Cand 101.3 kPa

Purple hexagonal plates1

Green monoclinic crystals1

Melting/freezing point 1152 °C1

83 °C2

Boiling point 1300 °C1

No data

Density 2.873

1.784

At 25 °C

Water solubilitySlightly soluble

7.12 g/L6

Soluble5

585 g/L7 Hygroscopic

1

Auto-flammability No data No data

Flammability No data No data

Explosiveness No data No data

Oxidising properties No data No data

Granulometry No data No data

Sources:1: CRC (2003)2: Alfa Aesar: http://www.alfa.com/en/catalog/42113, accessed on 29 September 20143: Sigma-Aldrich: http://www.sigmaaldrich.com/catalog/product/aldrich/450790, accessed on 29 September20144: Sigma-Aldrich: http://www.sigmaaldrich.com/catalog/product/aldrich/27096, accessed on 29 September20145: Alfa Aesar: http://www.alfa.com/en/GP100W.pgm?DSSTK=42113, accessed on 20 August 20146: EPISuite: http://www.chemspider.com/Chemical-Structure.23193.html, accessed on 29 September 20147: http://en.wikipedia.org/wiki/Chromium(III)_chloride, accessed on 29 September 2014

5.2.2 Technical feasibility

Assessment of technical feasibility

The use of chromium compounds at a lower oxidation state than 6+ is an approach that has beenrecently developed to reduce exposure to Cr(VI), however it does not eliminate Cr(VI) from theprocess. Instead, Cr(III) salts act as a source of in-situ generated SD (by “SD” it is here meant severalforms of Cr(VI), depending on the pH value, as per equations (8) and (9) in Section 2.1.2, so that theoverall presence of Cr(VI) is equivalent to an effective SD concentration of 3-6.5 g/L). Potentialworker exposure to Cr(VI) is marginally lower due to elimination of handling neat SD at the dosingstage. Because Cr(VI) is intended to be present in the system at a similar concentration to theapplied for use of SD, it has the potential to fulfil the technical feasibility criteria and on this basis, itmight be expected that the changes to the process that would need to be made might be lesscomplex in comparison to other alternatives. Yet, as the applicant does not have access to thedetails of the technology (currently under patent application filed by a competitor), there isuncertainty over the robustness of this assessment. Table 5-3 summarises the use of chromium(III)chloride according to the technical feasibility criteria.


Table 5-3: Comparison of chromium(III) chloride and sodium dichromate according to technical feasibilitycriteria

Technical feasibilitycriteria

Result or value achievedCriteria pass?

*Sodiumdichromate

ThresholdChromium(III)

chloride

Formation of protectivefilm permeable to H2

and impermeable tohypochlorite

Sufficient Similar to SDExpected similar to

SD()

pH buffering and controlof oxygen formation

pH ''#A#''''; <2.5%O2

pH '''''''#A#''; <3.0%O2 in H2 by volume

Expected similar toSD

()

Cathode protection(corrosion inhibition)

SufficientMinimum cathode

lifetime: 8 yrsExpected similar to

SD()

Current efficiency andenergy consumption

>95%, 5,230 kWh/ttheoretical;

''#A#'''%, ''''''''''''''''#A#''''''' ''''''''''''''''

>'''#A#''%;<''#A#'''''''''' kWh/t


()

Solubility in electrolyte Highly soluble SufficientSufficient; soluble

in water**()

Impurities in chlorateproduct




detrimental to ClO2

generation


()

* parentheses indicate uncertainty over the conclusion reached due to lack of data** information from http://www.alfa.com/en/GP100W.pgm?DSSTK=42113 (accessed on 20 August 2014)

Overall, Cr(III) compounds might be considered technically feasible alternatives for SD on the basis ofthe similarities between these substances and SD but they do not eliminate the presence of Cr(VI)anions in the electrolyte.

Conclusion and required steps to make the alternative technically feasible

To a certain extent, chromium(III) chloride might be considered a replacement for SD as it marginallyreduces potential worker exposure at the dosing stage, but this technology remains to be provenand the applicant has no specific knowledge of the conditions and parameters of the use of thesubstance.

To implement this alternative, the applicant would need to:

Acquire access rights to the relevant patented technology, the patent application of which wassubmitted in 2012 and has not yet been granted

Introduce yet unknown changes to the existing equipment that would allow the optimisation ofthe dosing of chromium(III) chloride

Develop in-house company knowledge and expertise, through testing and training of thepersonnel.

The issue of access to the patent that describes the use of Cr(III) needs to be considered and isdiscussed further below.


5.2.3 Economic feasibility

The cost of converting from SD to CrCl3 needs to consider both investment costs and changes tooperating costs.

Investment costs for the implementation of the alternative

Arkema operates one sodium chlorate production plants in Jarrie (France). For a conversion of thisplant to Cr(III) technology, the following costs would be involved:

Access to technology and R&D: it is understood that a direct competitor, AkzoNobel, has filedan application for the patent protection of the Cr(III) technology (Hedenstedt & Edvinsson-Albers, 2012). This patent application has been published and is subject to examination.Arkema would need to secure access to the patent before implementing this alternative. Theterms under which Arkema might be granted access to the technology would be subject tonegotiations between the two parties. No further detail on the associated cost can be providedhere but the implications of reliance on a direct competitor’s licensed technology must be noted

Plant conversion costs: Arkema is not certain of what conversion actions would be required tobe undertaken at the Jarrie plant if CrCl3 were to replace SD, whether any production stoppagemight be required, what additional equipment might be needed (and what additionalrunning/maintenance cost they would attract) and how easy or quick the optimisation of thedosing stage might be. Given the technical similarities between SD and Cr(III) compounds, thetime and cost required could be lower in comparison to the other alternatives discussed in thisAoA but it has not been possible to estimate at this stage.

Operating costs

There are many elements that contribute to operating costs, but as already noted, energy is themain cost of the production process. The following table presents the range of different operatingcost elements and provides a comparison of the costs arising under SD and under CrCl3. A quantifiedbreakdown of cost components is not available, however, it must be noted that the most importantcost, which defines the overall production cost, is the cost of electricity. The assumption made inTable 5-4 is that CrCl3 would be able to generate in the electrolyte the required concentration of SDand that the electrolytic process could proceed as if SD had been dosed. This is an unprovenassumption, as the applicant has no access to the particulars of the Cr(III) technology.


Table 5-4: Comparison of operating costs for production of sodium chlorate between SD and chromium(III)chloride

Operating cost category

Current process costin € per tonne ofsodium chlorate

product

Change due to use ofchromium(III) chloride

Energy costs for producing 1 tonne of sodium chlorate

Electricity ''''''''#C#' '''''''''' No change assumed, as SD isformed in the electrolyteOil and gas Minor component

Materials and service costs for producing 1 tonne of sodium chlorate

Cost of SD Minor component'''''#C#''''''', based onSD consumption andsodium chloratetonnage

''''''#D#'''''''

Raw materials (salts, additives, etc., excludingwater and sodium dichromate)

Minor component No change assumed

Water Minor component No change assumed

Environmental service costs (e.g. wastetreatment and disposal services)


Transportation of product to customer Minor component No change assumed

Replacement parts and any other materialsneeded for the operation of the plant


Labour costs for producing 1 tonne of sodium chlorate

Salaries, for workers on the production line(incl. supervisory roles)


Costs of meeting worker health and safetyrequirements (e.g. disposable gloves, masks,etc.)

Minor component No change assumed, as SD wouldbe present in the majority ofprocess steps

Maintenance and laboratory costs for producing 1 tonne of sodium chlorate

Sampling, testing and monitoring cost (incl. labworker cost)

Minor component No change expected, as SD wouldstill be present

Costs associated with equipment downtime forcleaning or maintenance (incl. maintenancecrew costs)

Minor component Uncertain, as it will depend on thechanges to be introduced to theplant (new equipment mayintroduce new maintenancerequirements)

Other costs for producing 1 tonne of sodium chlorate

Insurance premiums Minor component No change assumed

Marketing, license fees and other regulatorycompliance activities

Minor component No change assumed, REACHAuthorisation fees still requireddue to presence of Cr(VI)

Other general overhead costs (e.g.administration)

Minor component No change expected

Overall costs (% change) ''''#C#'''''''' '''''''''''' '''''''''''#D#' ''''''''''''' '''''''''''''

Source: Applicant’s data

Energy: on the assumption of a high degree of technical similarity between the use of SD and thealternative, the cost of energy would be unlikely to change noticeably as a result of transfer to thealternative.


Materials and services: this is where the main operating cost difference might arise, based on therelative cost of the price of chromium(III) chloride in comparison with SD. The following two tablespresent publicly available price data for SD and CrCl3. It can roughly be assumed that SD is availableat €1,540/t while CrCl3 is sold at €2,000/t (median prices, see Table 5-5 and Table 5-6 below), i.e. a30% increase per tonne. It must be noted that the quality of incoming raw materials is of extremelyhigh importance, as any impurity will accumulate in the predominantly closed loop chlorate process.Prices for approved raw materials may therefore differ from the examples in the table, which aresolely used for the purposes of calculating the economic costs of conversion to Cr(III)10.

Table 5-6: Cost of sodium dichromate dihydrate (Alibaba.com, 2 April 2014)

Source Location PuritySupply ability

(t/y)

Minimumorder

quantity (t)Price (€/t) (FOB)

1 China 98 10,000 5 1,098-1,464

2 China 99 48,000 3 1,830-2,048

3 China 98.5 60,000 25 1,794-2,013

4 China 98.3 10,000 5 1,098-1,464

5 China 99.5 96,000 1 1,830-2,048

6 China 98-99.3 60,000 1 1,391-1,611

7 China 98 5,000 5 1,501-1,574

8 China 98 2,500 10 1,318-1,464

9 China 98.5 72,000 3 1,830-2,050

10 China 98.3 30,000 5 1,098-1,464

11 China 99 36,000 5 1,830-2,048

12 China 98 35,000 10 1,245-1,464

13 China 98.3 6,000 1 1,464-1,830

Range (€/t) 1,098-2,050

Average price (€/t) 1,610

Median price (€/t) 1,538

10Arkema may purchase SD at a different price to the one used in the calculations here. This analysis usesthe price information available from Alibaba to ensure that it is, to the extent possible, comparable to theAlibaba-sourced prices of the alternatives (chromium(III) chloride and sodium molybdate). Using the actualprice paid for by Arkema would make a small difference to the calculations, but not to the overallconclusions of the analysis, as the additive represents a very small proportion of the overall productioncosts.

Table 5-5: Cost of chromium(III) chloride hexahydrate (Alibaba.com, 2 April 2014)

Source Location PuritySupply Ability

(t/y)

MinimumOrder

Quantity (t)Price (€/t) (FOB)

1 China 98 12,000 1 2,270

2 China 98 6,000 0.001 1,098-2,050

3 China 98 12,000 1 1,908

4 China 99 12,000 1 2,021

5 China 99 12,000 1 3,902

6 China 99 12,000 1 1,830

7 China 99 12,000 1 3,851

Range (€/t) 1,098-3,902




It is assumed that SD is used at 4.5 g/L of electrolyte (mid-range of 3-6 g/L in the BREF Document)and that sufficient chromium(III) chloride hexahydrate would be used to achieve an equivalentconcentration of Cr(VI) in the electrolyte. Taking into account the following molecular weights:

SD anhydrous: 261.97, SD dehydrate: 297.97 CrCl3 anhydrous: 158.36, CrCl3 hexahydrate: 266.48

The replacement ratio for the hydrated salts SD:CrCl3 is 1:2 and for the anhydrous salts: 1:1.2.

Given the applicant’s consumption of anhydrous SD of ca. '''#B#''''' kg/t sodium chlorate, theconsumption of anhydrous CrCl3 would be ''''''#G#'''''' kg per tonne of sodium chlorate. This wouldbe equivalent to a production cost increase of €''#D#'''''''/t sodium chlorate. With an annualproduction of sodium chlorate of ca. ''''''#B#''''''' tonnes (in 2012), the additional annual cost fromthe conversion would be ca. €''''#D#''''''.

Labour costs: on the assumption of a high degree of similarity between SD and CrCl3, no substantialcost changes would be likely to arise. There is still Cr(VI) in the electrolyte so despite the eliminationof handling SD, the cost of worker protection will not show any discernible decline.

Maintenance costs: it is unclear whether any cost increases might arise as a result of theintroduction of new equipment.

Other costs: it is explained below that the use of a Cr(III) substance that is oxidised to Cr(VI) in theelectrolyte would only have a small positive effect to the overall potential exposure of workers toCr(VI) during the operation of a sodium chlorate plant. Therefore, whilst the use of SD would indeedbe eliminated by using the Cr(III) alternative, the source of exposure to the Cr(VI) anion that confersto SD its SVHC properties would largely remain, particularly for inhalation worker exposure.Therefore, a conversion to Cr(III) would be an insufficient step towards the removal of the need for aREACH Authorisation. Also, because SD is formed during the use of this alternative, its use wouldnot forego the need to apply for Authorisation.

Conclusion and required steps to make the alternative economically feasible

The investment costs associated with the implementation of this alternative are currently unknown.The changes to the applicant’s plant could possibly be more straightforward and of a lower costcompared to the other alternatives assessed in this AoA, but there will also be a cost for acquiringthe rights to use the patented technology (after the patent has been granted) which is currentlyunknown. The changes to operating costs would probably be low (assumed above to be anestimated €''''#D#''''''' per year), excluding any yet uncertain cost increases for the maintenance ofany new equipment required.

In light of the existing uncertainties, particularly, the economic feasibility of acquiring a license forusing this technology in the future, it is not possible to conclusively assess whether the alternative iseconomically feasible for Arkema.

5.2.4 Reduction of overall risk due to transition to the alternative

Overview

Appendix 2 (Section 8) to this AoA document presents a detailed analysis of the hazards and risks ofthe selected potential alternative substances. The reader is referred to the Appendix, while here ashort summary of findings is presented only. For this alternative, the analysis in the Appendix looks


beyond CrCl3 into other Cr(III) compounds to ensure that an adequate dataset has been used in thecomparison to SD.

Classification and labelling

For chromium (III) chloride hexahydrate, self-classified notifications according to the classificationand labelling inventory suggest a hazard profile more benign than SD (Skin Irrit, Eye Irrit 2, STOT SE 3(respiratory), Acute Tox 4), see Figure 9-3 in Appendix 2. Other Cr(III) compounds may havedifferent hazard profiles. For example, chromium trinitrate has been classified in its registrationdossier as

Oxidising solid Cat 3 (H272: May intensify fire; oxidiser) Skin sensitising Cat 1A (H317: May cause an allergic skin reaction) Acute toxic Cat 4 after inhalation (H332: Harmful if inhaled) Aquatic Chronic toxic Cat 2 (H411: Toxic to aquatic life with long lasting effects).

Chromium triacetate has been classified as skin sensitising Cat 1B (H317: May cause an allergic skinreaction) in the registration dossier. All three substances are soluble Cr(III) salts and human healthhazards are probably due to Cr(III).

Generally, however, when seen in isolation, Cr(III) compounds can be considered more benign thanSD or other Cr(VI) compounds.

Comparative risk characterisation

Ecotoxicity – PNEC values

Information on the ecotoxicity of Cr(III) compounds is available from registration dossiers, the EURisk Assessment Report (EU RAR) for Cr(VI) compounds and a Concise International ChemicalAssessment Document (CICAD). Appendix 2 explains that the PNECfreshwater as derived within the EURAR of 4.7 µg Cr(III)/L has been used for the comparative assessment to SD. Additionally, arecalculated PNECSTP of 490 µg Cr(III)/L has been used based on the chromium triacetate dossier.

Mammalian toxicity – DN(M)EL values

Appendix 2 explains that the most critical effects for the evaluation of long-term toxicity of Cr(III) arelocal effects in the lung seen after inhalation exposure towards soluble Cr(III). Therefore, a tentativeDNEL for comparative risk assessment was derived on basis of a 90-day inhalation toxicity study withchromium sulphate in a comparative manner to the procedure described for chromium trinitrate.Starting from a LOAEC of 3 mg Cr(III)/m3 (corresponding to a human equivalent concentration of 1.5mg Cr(III)/m3) and an assessment factor (AF) of 75, a tentative DNEL value of 0.02 mg Cr(III)/m3 hasbeen calculated for local effects after long term inhalation exposure.

Comparative risk assessment

Appendix 2 shows that the ecotoxicity RCR of CrCl3 is considerably lower than the RCR for SD. Inaddition, the human health RCR is several orders of magnitude lower than the RCR for SD. Althoughthe risk characterisation is based on assumptions for release and exposure, calculations are tentativeand are not meant to represent real conditions at the applicant’s production sites, use of CrCl3 wouldappear to be beneficial with regard to human health considerations. Under the conditions of use


assumed here also the comparative environmental risk characterisation leads to the conclusion thatthere is less risk associated with the use of the Cr(III) compound. It must be noted that the RCRs forSD are also below 1 both for ecotoxicity and human health toxicity.

Discussion on elimination of exposure to Cr(VI) from the use of Cr(III) compounds

The CSR describes six Tasks for workers, which may result in some exposure to SD, see Table 5-7.Not all Tasks are relevant to all workers exposed to SD during the manufacture of sodium chlorate;instead, realistic shift patterns have been established and are used in the CSR (see Table 5-8). Thislatter table also presents the estimates of long-term inhalation and dermal exposure of workersunder the three different shift patterns or worker roles, during which a variety of tasks might beundertaken.

Table 5-7: Worker tasks (CSR) during which SD (Cr(VI)) exposure may occur

Task Description

Task 1 Feeding liquid SD solution into the process (PROC 8b)

Task 2 Use in closed batch process: Sampling electrolyte solution (PROC 3)

Task 3 Laboratory analyses (production lab) (PROC 15)

Task 4 Maintenance and cleaning (PROC 8a)

Task 5 Waste handling (filter press) (PROC 8b)

Task 6 Laboratory analyses (central lab) (PROC 15)

Source: CSR, Section 9

Some important points need to be considered (and these need to be seen in the light of the muchmore detailed analysis presented in the CSR):

Use of a Cr(III) compound in the place of SD would aim to eliminate exposure during Task 1(feeding liquid SD solution into the process, i.e. dosing). All other Tasks, in terms of workerexposure to Cr(VI) species, would remain unchanged

Task 1 is performed by “day workers”. This is a very infrequent task. These workers also carryout Tasks 4 and 5 that may also involve exposure to Cr(VI)

The CSR provides the exposure estimates for each type of shift pattern. As shown in Table 5-8,the aggregate inhalation exposure for day workers is calculated at 1.23 ng/m3 (long-term TWA).The total exposure for day workers is calculated as T1+T4+T5, however, as there are twoworkers who share these roles, the exposure is divided by two. The total exposure usingsodium dichromate is ((T1+T4+T5)/2 = 0.62 ng/m3 as a long term TWA. When the exposure isrecalculated without Task 1, the exposure for day workers becomes ((T4+T5)/2) = 0.495 ng/m3.Therefore, Task 1 (dosing) represents only ca. 20% of the aggregated inhalation exposure.

Conclusion on suitability

In conclusion, whilst the comparative risk assessment of Cr(III) compounds indicates a more benignprofile than SD, due to the transformation of Cr(III) into Cr(VI) in the electrolyte, no real reduction inworker exposure would be likely to arise. This of course must not detract from the key conclusion ofthe CSR that existing risks to worker health are very low (risk characterisation ratio for inhalationexposure for day workers is ''''''''''#H#' '' ''''''''' while continuing to use sodium dichromate and that


measurements are so low that the measurements process required the use of the newesttechniques to be able to determine if there was in fact any exposure at all.

The use of Cr(III) compounds would not be a suitable alternative as the existing (very low) risks fromexposure to SD would still largely remain unchanged. The use of Cr(III) compounds cannot beviewed as a viable long-term replacement for SD that would eliminate exposure to Cr(VI).

Table 5-8: Task-specific and aggregated long-term TWA inhalation exposure estimates for unit operatorsand day workers (CSR)

Task N N (sites) N<LoQ

Long-termTWA Cr(VI)

concentration [ng/m3]

Comments

T1 2 1 100% 0.25 Based on modelling

T2 31 8 58% 1.4Based on 90

thpercentile of

monitoring

T3 18 8 78% 0.48Based on 90

thpercentile of

monitoring

T4 3 1 0% 0.53 Based on maximum of monitoring(cleaning) and modelling

(maintenance)

T5 8 4 50% 0.46Based on 90

thpercentile of

monitoring

Aggregated estimates

Unit operator (two working at any one time) 1.23 = ((T2 + T3 + T4) / 2)

Day worker (two working at any one time) 0.620 = ((T1 + T4 + T5) / 2 )

Cr(III) Day worker (without T1 exposure)* 0.495 = ((T4 + T5) / 2 )*

Source: CSR, Section 9* calculated here, not discussed in CSR.

5.2.5 Availability

Three elements of availability can be considered:

Availability of the alternative in quantities sufficient for the applicant’s production processes Availability of the alternative in the quality required by the applicant’s production processes Access to the technology that allows the implementation of the alternative as a SD replacement.

With regard to the quantity required, CrCl3 is not yet registered under REACH (although other Cr(III)compounds have been registered). However, the tonnage of CrCl3 that would be required is''''#D#''''' ''''''''''; previously, it was estimated that Arkema might need '''#D#'''''' kg of CrCl3 per tonneof sodium chlorate produced. Therefore, the tonnage of CrCl3 required would be well below 10 t/y.

Issues of quality have not been identified.

Finally, with regard to access to the technology required, it has been shown earlier that a processusing Cr(III) compounds instead of SD has had a patent application filed by a direct competitor. Thepatent application is undergoing examination and therefore it may be granted (and consequentlymight become available for licensing by the patent holder) after a period of notable length which willbe after the sunset date.


Conclusion and required steps to make the alternative available

The technology is not currently available to the applicant and will remain unavailable until after therelevant patent has been granted to the competitor who filed the application and thereafter only ifthe license becomes available to Arkema on commercially and economically acceptable terms. It isvery unlikely that the situation on availability will change by the sunset date.

5.2.6 Conclusion on suitability and availability for chromium(III) chloride

The most critical disadvantage of chromium(III) compounds is that they cannot be consideredsuitable. The use of this alternative generates sodium dichromate during the process and so its usewould not forego the need to apply for Authorisation. The use of this alternative would eliminatethe handling of SD, but overall they would reduce the estimated aggregate worker inhalationexposure for day workers by a factor of only 20% and would make no discernible difference to thecurrent Cr(VI) exposure of other unit operators or laboratory workers. Therefore, they cannot beconsidered valid alternatives for the purposes of this AoA.

Chromium(III) chloride (and Cr(III) compounds more generally) might be a technically feasiblealternative substance to the use of SD, but this is currently uncertain as the applicant does not haveaccess to the particulars of the Cr(III) technology. Similarly, chromium(III) chloride might beeconomically more feasible than the rest of the alternatives presented in Section 5 of this AoA, butthere is uncertainty over the changes that would be required to the applicant’s plant as well as overthe economic terms of acquiring a use license from the competitor who has applied for a patent onit. Finally, this alternative is currently unavailable to the applicant, and will only become available inthe future if licensed on commercially and economically acceptable terms.

Overall, chromium(III) compounds are not acceptable as replacements for SD in the applied for use.

5.3 Sodium molybdate

5.3.1 Substance ID and properties

Sodium molybdate is available in two forms. These are shown in Table 5-9.

Table 5-9: Identity of available forms of disodium molybdate

Properties Disodium molybdate Sodium molybdate di-hydrate

EC Number 231-551-7 600-158-6

CAS Number 7631-95-0

IUPAC Name: Disodium dioxide-dioxomolybdenumSodium dioxide(dioxo)molybdenumhydrate (2:1:2)

Formula MoO4·2Na Na2MoO4·2H2O

Molecular weight 205.92 241.92

Structure


Table 5-9: Identity of available forms of disodium molybdate

Properties Disodium molybdate Sodium molybdate di-hydrate

Sources:1: http://esis.jrc.ec.europa.eu/2: ECHA dissemination portal: http://apps.echa.europa.eu/registered/data/dossiers/DISS-9eb7d44e-5b59-695c-e044-00144f67d031/AGGR-d3c96bda-6117-42e7-bf76-918c545cb4f7_DISS-9eb7d44e-5b59-695c-e044-00144f67d031.html#section_1.13: https://upload.wikimedia.org/wikipedia/commons/0/08/Natriummolybdaat.png4: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=16211258

Table 5-10 provides an overview of the physicochemical properties of disodium molybdate.

Table 5-10: Physicochemical properties of disodium molybdate

Property Value Note

Physical state at 20°C and101.3 kPa

Crystalline solid colourless towhite

at 20 °C and at 1013 hPa

Melting/freezing point No data Decomposes >100 °C

Boiling point - -

Density 2.59 at 23.3 °C

Water solubility ca. 654.2 g/L at 20 °C at pH 8.8 OECD Guideline 105 (Water Solubility)

Auto-flammability Not justified

Flammability Not justified

Explosiveness Not justified

Oxidising properties No oxidising properties

Recommendations on the Transport ofDangerous Goods, Manual of Tests andCriteria, Part 34.4.1, Test O.1: Test foroxidizing solids

Granulometry% ile: D10, Mean: 34.5 µm% ile: D50, Mean: 143.1 µm% ile: D90, Mean: 295.9 µm

Guideline 67/548(EEC (Council Directive92/69/EEC)OECD Guideline 110 (Particle SizeDistribution / Fibre Length and DiameterDistributions)CIPAC MT 187: Particle Size Analysis by LaserDiffractionISO13320-1: Particle Size Analysis-LaserDiffraction Methods

Sources:ECHA dissemination portal: http://apps.echa.europa.eu/registered/data/dossiers/DISS-9eb7d44e-5b59-695c-e044-00144f67d031/AGGR-e8329392-562d-40df-96dc-082576cf46a0_DISS-9eb7d44e-5b59-695c-e044-00144f67d031.html#AGGR-e8329392-562d-40df-96dc-082576cf46a



The use of sodium molybdate as a potential alternative to the use of SD has been proposed due to acombination of its buffering properties and its ability to form a protective film on the cathode. Theavailable information indicates that the use of sodium molybdate has not yet been demonstrated ona commercial scale and that academic R&D efforts have identified significant limitations.


Important differences with SD have been found that influence the ability of sodium molybdate tomeet the technical feasibility criteria, as shown in the available scientific literature. In general,sodium molybdate is lacking in performance, in comparison to SD and this has led some researchersto trial the use of sodium molybdate in parallel with reduced amounts of SD with the aim ofachieving the required process parameters. As the aim of the alternative in this case is to eliminateSD, the comparison between sodium molybdate and SD that is shown in Table 5-11 has been carriedout assuming no SD is present. Once again, the reader is reminded that this comparison has beenjointly generated for the members of the SDAC, but where applicant-specific information isavailable, this has been used to ‘overrule’ the more generic analysis.

Table 5-11: Comparison of sodium molybdate and sodium dichromate according to technical feasibilitycriteria

Technicalfeasibility criteria

Result or value achievedCriteria pass?

Sodium dichromate Threshold Sodium molybdate

Formation ofprotective film thatis permeable tohydrogen andimpermeable tohypochlorite

Sufficient Similar to SD

It creates a protectivefilm but published

research suggests itgrows too quickly andis potentially unstable

pH buffering andcontrol of oxygenformation

pH '''#A#'''; <2.5%O2

pH ''''''''#A#'''''';<3.0% O2 in H2 by

volume

pH 5.0-6.0; O2 in H2

3.6-4.8%Additional buffer is

required



lifetime 8 yearsUnknown (laboratory

scale only)?



''#A#'''%, '''#A#''''''''''''''' ''''''' '''''''''''''''''

>''#A#'''%;<'''''#A#''''' kWh/t

86% currentefficiency; 5,746

kWh/t theoretical


Highly soluble Sufficient654.2 g/LSufficient





detrimental to ClO2

generation

Presence of metal(Mo) impurities wouldact as a ClO2 process

‘poison’

Overall, the comparison suggests that sodium molybdate meets one criterion, under the currentstate of knowledge fails four criteria and for a sixth criterion no conclusion can be reached on thebasis of available information. The following paragraphs explain the shortcomings of this alternativein more detail.

Detailed presentation of technical characteristics of the alternative

Formation of a protective film: the substance is capable of forming a protective film around thecathodes; however, its thickness may grow excessively quickly, thus affecting the efficiency of theelectrochemical reactions by increasing energy consumption. In comparison, the dichromate filmonly grows to a certain extent (it is self-limiting) depending on current density and chromate


content. Also, as discussed in Section 4.2.3, the presence of phosphates (the necessity of which isdiscussed below) interfered with the formation of the molybdate film. At high Mo concentrations,80 mM molybdate in the electrolyte, a cracked film was formed on the cathode surface. If theamount of molybdate in the lab tests was low (4 mM) and the electrolyte also contained between 10and 40 mM phosphate no molybdenum film was visible with Scanning Electron Microscopy (SEM) ordetectable with Energy-dispersive X-ray spectroscopy (EDX) on the cathode surface. Generally,there are great uncertainties surrounding the technical feasibility of sodium molybdate and theapplicant does not have first-hand experience with the alternative, even at the lab scale.

pH buffering and oxygen formation: the ability of sodium molybdate to function as a pH buffer inthe region required for the chlorate reaction (see Section 2.1.1) is limited and may require theaddition of an additional phosphate buffer. However, such an addition would cause very serioustechnical problems. While typically a maximum of 5 mg PO4/L cell solution can be acceptable, theconcentration that might be required if sodium molybdate were to replace SD would be 4.9 g/L, i.e.ca. 1,000% higher than what is currently assumed acceptable. Several problems might arise fromthe addition of a phosphate buffer at such high levels:

Side reactions at the anode: phosphates would cause precipitations on the anode surface in thepresence of Fe and Si, potentially leading to a failure of the coating of the anodes. The durabilityof the anodes would be seriously compromised in the presence of 4.9 g/L phosphates undernormal conditions of use. This has been documented in the scientific literature; for example,Krstajić et al (1984) have documented that the standard mixed RuO2·TiO2 coated titaniumanodes deteriorates very quickly in the presence of ionic phosphate species (and go on torecommend the development of a different type of anode containing palladium and tin oxides inthe coating mixture which are not currently state of the art). Such high concentration may havebeen suitable for lab experiments such as those described in the patent literature but these aretypically very short and not representative of the continuous operation of a chlorate plant

Increase in the release of oxygen: literature suggests that deposits on the anode associatedwith phosphate impurities in the brine cause an increase in production of oxygen at plant scale11

(Kus, 2000) Increased maintenance requirements: acid washing of the electrolysers would need to be

undertaken more frequently Higher energy consumption: the above adverse effects would result in an increase to the

consumption of electricity during the electrolysis.

Overall, the use of phosphates at the required concentration is technically a “non-starter” under thecurrent technological knowledge and with existing anodes. In this regard, the remainder of thediscussion on the technical feasibility of sodium molybdate is largely theoretical and academic.

Meanwhile, molybdate itself also causes higher levels of oxygen production, thus increasedconcentration of oxygen in the hydrogen gas stream, far higher than what is possible to achievewhen using SD. This represents a serious process safety concern related to the risk of explosion. Forthese reasons, the use of both molybdate and phosphate should ideally be as low as possible.

11The effects have been found to affect large scale production in very low levels of phosphate (down to 1-5ppm) but short duration laboratory scale trials had not reproduced the effect (Nylén & Cornell, 2006).


If the oxygen generation increased in comparison to the present SD-based technology to a level thatwould pose a safety risk (and this would indeed be the case with an oxygen concentration inhydrogen of 3.6-4.8%), action would need to be taken to dilute the generated gas. This couldinclude a nitrogen purge, a fairly well-established method of dilution. However, operation of theplant with a continuous purge of nitrogen to decrease oxygen concentration below the explosionlimit would pose significant problems:

Additional instrumentation would need to be introduced The amount of nitrogen required would be significant The use of the H2/N2 mixture in reactions where H2 is needed as a raw material would be

impossible, particularly as the flow of variable content H2/N2 mixtures cannot be measured. Thepresence of nitrogen limits the purity of the hydrogen, and compressing and using the hydrogenwhen it contains high amounts of nitrogen would be technically very challenging.

''''''''''''''' '''' '''''''''''''''''' '''''''''' ''''' ''''''''''''''''''' ''#C#'''''''''''''''' '''' '''''' '''''''''''''''''''' '''' ''''''''''''''''''' ''''''''''''''''''''''''''''''' ''''''' '''''' '''''''''''''''''' '''' '''''' ''''''''''' '''''''''' ''''''' ''''''''''''''''''''''''''''' ''''''''''''''''''' ''''''' ''''''''' '''' '''''''''''''''''''''''' '''' '''''' '''''''''''''''''' '''''' ''''''' ''''''''''''''' ''''''''''''''''''''''' '''''''''''''''''''' ''''''''''' '''''''''' '''' ''''' ''''''''''''''' ''''''''''''''''''''''''' ''''''''' '''''''''''''''' '''''''' '''''''''''''''''''' ''''''' ''''' '''''''''' '''''' ''''' ''''''''''

Cathode protection: the long-term effect over multiple years on cathode protection is not knowndue to lack of large-scale trials outside of the laboratory.

Current efficiency and energy consumption: publicly available information suggests that whensodium molybdate is used, in the absence of any Cr(VI) in the electrolyte, it is unlikely that a currentefficiency above 80-91% could be achieved (Li et al. (2007); Gustafsson (2012)). If a mid-range valueof 86% were to be assumed, the loss of efficiency relative to SD would be significant and technicallyinfeasible as the current efficiency is below ''#A#''''%. The total theoretical anticipated energyconsumption would be 5,746 kWh/t of chlorate produced12.

Impurities in the chlorate product: the use of sodium molybdate is likely to result in traces of Mo inthe chlorate product, in a similar way that Cr traces can presently be found in the chlorate (less than5 ppm, see Table 2-5). This is certainly a cause for concern; whilst presence of chromium in thechlorate product does not affect the customers’ processes (ClO2 generation), a metal such as Mowould act as a ‘poison’ to the ClO2 manufacturing process. Therefore, the use of sodium molybdatemight cause unnecessary and unwelcome problems to the applicant’s customers.

Conclusion and required steps to allow use of sodium molybdate as an alternative to sodiumdichromate

As shown above, poor pH buffering, increased oxygen formation, impaired current efficiency andunwanted metal impurities are the key issues faced by sodium molybdate. While the addition of a

12The following conditions for a chlorate cell employing SD were used to enable a comparison t to atheoretical change to sodium molybdate. A cell voltage of 3.1 V (mid-range value from BREF (IPPC, 2007))and current efficiency of 95% gives a theoretical energy requirement of 4,930 kWh/tonne of chlorate + 300kWh/tonne (mid-range value for other electrical equipment) = 5,230 kWh/tonne chlorate using SD. Usingsodium molybdate, the literature indicates a current efficiency in the range 80-91% efficiency. Using themid-range value of 86% and the same cell voltage, an electrical consumption of 5,446 kWh/tonne can becalculated + 300 kWh/tonne = 5,746 kWh/tonne of chlorate or a 9.9% increase in electrical consumption.


phosphate buffer would address the issue of pH, it would seriously impact upon anode performance(Kus, 2000) and would further increase in oxygen formation, thus affecting the stability andeconomics of the electrolysis process. The addition of phosphates at the high concentrationsdescribed in the patent literature make this alternative entirely infeasible.

The most practical way of addressing these problems may be to introduce SD at a lower level (<3g/L) in combination with a lower level of molybdate without the presence of phosphate. However,the use of SD would still require a REACH Authorisation, thus this cannot be a realistic solution to theproblems faced by sodium molybdate.

Consequently, for sodium molybdate to be considered a viable replacement for SD, further researchwill be needed in order to improve the identified shortcomings. Elements of further R&D mightinclude the following:

1. R&D phase using existing electrolyte to verify robustness

2. R&D to optimise the mixture of molybdate and phosphate

3. R&D to scale-up to (a) long-term tests, lab pilot (b) intermediate scale, (c) commercial scale

4. Possible change from steel cathode to alternative dimensionally stable cathode technology

5. Replacement of the existing Cr(VI) containing electrolyte solution with newly developedelectrolyte

6. Implementation of additional safety measures to decrease oxygen concentration to anacceptable level (such as a hydrogen DeOxo plant (BASF, 2014) and/or use of inert gas)

7. Implementation of systems for gas treatment to ensure clean-up of hydrogen before furtheruse.

The applicant is aware of R&D on molybdate additives in chlorate production that has already takenplace by third parties and that the reduction and removal of Cr(VI) from the chlorate processthrough the use of molybdates has been the goal for more than a decade. Only limited progress hasbeen made so far towards the total removal of Cr(VI) from the process but potential reductions inthe level of Cr(VI) have been suggested. The applicant assumes that, in order to make significantgains to a commercially feasible alternative using this technology, substantial further R&D will berequired. This would then need to be followed by process scale-up trials before commissioning anychanges required to existing plant technology.


This alternative has been found to be technically infeasible to implement. Therefore it cannot beconsidered economically feasible for the applicant.

Appendix 3 describes the implications for the applicants if the technical feasibility is ignored and thecosts calculated based on the claimed performance of the alternatives. This is provided for sake ofclarity.



Overview

This sub-section presents a comparison of risks from the alternative and SD with regard to workerexposure during the manufacture of sodium chlorate and further estimates and monetises theenvironmental impacts arising from the increase in energy consumption that would arise from thereplacement of SD with the alternative.

Appendix 2 (Section 8) to this AoA document presents a detailed analysis of the hazards and risks ofthe selected potential alternative substances. The reader is referred to the Appendix, while here ashort summary of findings is presented only. For this alternative, the analysis in the Appendix looksnot only into sodium molybdate but also sodium phosphates which might be used as pH buffersalongside the molybdate salt.

Classification and Labelling

Sodium molybdate does not have a harmonised classification under CLP (EC No 1272/2008). In theC&L inventory a total of 13 aggregated notifications have been identified. Most commonly, noclassification is notified followed by the classes presented in Figure 9-4 in Appendix 2.

Appendix 2 explains that while sodium molybdate(VI) dihydrate is a possible alternative to sodiumdichromate, also data on sodium molybdate(VI) (anhydrous, CAS: 7631-95-0) are reported as toxicityis independent from water of hydration of the substance. Where toxicity is related to elemental Mo,no explicit reference is made in every instance to what exactly was the species used in the test.

On the other hand, sodium phosphates have been looked at as required additives alongside themolybdate. Appendix 2 looks at disodium hydrogen orthophosphate (CAS No. 7558-79-4) andsodium dihydrogen orthophosphate (CAS No. 7558-80-7), both of which are in equilibrium with eachother in aqueous solution and the state of equilibrium solely depends on the pH of the solution.Therefore, they have been assessed together.

For sodium phosphates, no Harmonised Classification according to Annex VI of the CLP Regulation isavailable. In the registration dossiers of both substances, no classification has been recommended.For disodium hydrogen orthophosphate and sodium dihydrogen orthophosphate, classificationaccording to the classification and labelling inventory is as shown in Figure 9-5 in Appendix 2.

According to their respective joint entries (REACH registration), these compounds are not classified.

Comparative risk characterisation

Ecotoxicity – PNEC values

Information on PNEC values for sodium molybdate is available from the ECHA Dissemination Portal(ECHA-CHEM). A PNECfreshwater of 12.7 mg/L (based on elemental Mo) and a PNECSTP of 21.7 mg/L(based on elemental Mo) have been used in the assessment of alternatives to SD.

PNEC values for the two sodium phosphates have also been obtained (PNECfreshwater: 100 µg/L,PNECSTP: 100 mg/L). However, in acute aquatic toxicity tests with sodium phosphates (sodiumdihydrogen orthophosphate and disodium hydrogen orthophosphate) up to the limit concentration(100 mg/L) no toxic effects were observed and comparing real phosphate concentrations with the


PNECfreshwater will always result in RCRs > 1. Taking into account that huge amounts of phosphate arereleased into the environment by the use of inorganic fertilisers and that phosphates are excretedfrom the human body, a further quantification of phosphate exposure in the context of this use hasnot been performed as the total amount released into the environment from this use is regarded asnegligible in comparison to the other phosphate sources.

Mammalian toxicity – DN(M)EL values

Based on the data documented in Appendix 2 a tentative DNEL for systemic effects after long-terminhalation exposure was derived for molybdenum(VI) on basis of a 90-day repeated dose inhalationtoxicity study performed with molybdenum trioxide (66.7 mg Mo(VI)/m3: NOAEC systemic effects).As there is no evidence for local effects after inhalation exposure, no such tentative DNEL is derived.The tentative DNEL value for systemic effects after long term inhalation exposure used for thecomparative assessment is 1.3 mg Mo(VI)/m3.

For phosphates, the tentative DNEL was derived by route-to-route extrapolation on basis of a 90-dayrepeated dose oral toxicity study with sodium aluminium phosphate in dogs (NOAEL of 322.88mg/kg bw/day). Appendix 2 explains that the extrapolation results in a tentative DNEL for systemiceffects after long-term inhalation exposure of 32.29 mg sodium aluminium phosphate/m3

corresponding to 21.1 mg phosphate/m3 or 6.9 mg phosphor/m3.

Comparative risk assessment

Appendix 2 shows that the ecotoxicity RCR of sodium molybdate is far lower than the respective RCRfor SD. In addition, the human health RCRs for both the molybdate and the phosphates are severalorders of magnitude lower than the RCR for SD. Although the risk characterisation is based onassumptions for release and exposure calculations are tentative and are not meant to represent realconditions at the applicant’s production sites, use of sodium molybdate in combination withphosphate buffer would appear to be beneficial with regard to human health considerations. Underthe conditions of use assumed here, the comparative environmental risk characterisation leads tothe conclusion that there is less risk associated with the use of the molybdate compound. Again, itmust be noted that the RCRs for SD are also below 1 both for ecotoxicity and human health toxicity.

Externalities from energy usage

The use of sodium molybdate is expected to increase the energy consumption of the process byconsiderable amount due to a lower current efficiency. As described in Section 5.3.2, an additional'''''''''' ''' #G#'''''''''''' ''' ''''''' kWh/t chlorate produced of electricity is required. Considering theapplicant’s annual production of '''''#B#''''''' tonnes, this equates to an additional '''''''#G#' ''' '''''''kWh per year. Using greenhouse gas emission factors available from UK Department forEnvironment, Food and Rural Affairs13, it can be calculated that the generation of the equivalentamount of electricity would result in the release of ''''#G#'''''''' tonnes of CO2e per year14.

13Available at: http://www.ukconversionfactorscarbonsmart.co.uk/, accessed 29 September 2014.

14The DEFRA 2013 overseas electricity generation factor of 0.07909 kg CO2e/kWh of electricity for Francewas used. Using this factor, the generation of '''''''' '#G#'' '''''''' kWh of electricity would generate anadditional emission of '''''#G#''''' tonnes of CO2e per year.


Monetisation of greenhouse gas emissions is based on the methodology developed by the UKgovernment for carbon valuation in public policy appraisal15. The shadow price of carbon is closer towhat would be the full social cost of carbon emissions in terms of the damages caused by carbonemissions, but also takes into account estimates of marginal abatement costs, etc. Thus, it alsotakes into account policy commitments and technological issues. The value used in this assessmentis £31/tonne CO2 for the year 2017 (year of the sunset date), as shown in the relevant UKGovernment document16. The present day exchange rate (£1 = €1.25) was used to convert the valuein £ to € (€38.8/t).

Therefore, the externalities of the increased energy consumption and concomitant CO2 emissionswould be ''''''''''' ''' ''''#G#''''' '' '''''' '''''''''' million per year.

Other environmental impacts

Hydrogen that could no longer be used in ancillary operations and would have to be vented to theatmosphere. Hydrogen is an indirect greenhouse gas (IPCC, 2007).


Sodium molybdate when used alongside a phosphate buffer is a more benign substance than SD.The substance is considered to be a suitable alternative for SD in the applied for use. However, itsuse would require additional energy thus would result in an increase in CO2 emissions to the tune of''''#G#'''''' t/y.

5.3.5 Availability

Three elements of availability can be considered:


With regard to the quantity required, Table 5-12 summarises the available information on the statusof REACH Registration for disodium molybdate.

Table 5-12: REACH registration status of disodium molybdate

Status Tonnage band Date of search

Registered 100 – 1,000 tonnes per annum 27 March 2013

Sources: ECHA Dissemination Portal: http://apps.echa.europa.eu/registered/data/dossiers/DISS-9eb7d44e-5b59-695c-e044-00144f67d031/DISS-9eb7d44e-5b59-695c-e044-00144f67d031_DISS-9eb7d44e-5b59-695c-e044-00144f67d031.html

15Available at https://www.gov.uk/government/publications/updated-short-term-traded-carbon-values-used-for-uk-policy-appraisal-2014 (accessed on 13 December 2014).

16Shadow value of carbon, available athttps://www.gov.uk/government/uploads/system/uploads/attachment_data/file/243825/background.pdf.


The tonnage of sodium molybdate that would be required is very small; previously, it was estimatedthat Arkema may need ''''#D#'''' kg of sodium molybdate per tonne of sodium chlorate produced.Therefore, the tonnage of sodium molybdate required would be '''''''' ''''''#D#'''''' ''''' ''''''.

Issues of quality have not been identified.

Finally, with regard to access to the technology required' '''''' '''''''''''''''''' ''''''' ''''''' ''#E#'''''''''''''''''''''' '''''''''''' ''''''' ''''''' '''' '''''''''''''''''''' '''' ''''''' ''''''''''''''''''''''''''' '''' ''''''''''''''' ''''''''''''''' As already explained, therequired technology that would render this alternative feasible is not currently available.

5.3.6 Conclusion on suitability and availability for sodium molybdate

Sodium molybdate was investigated as an alternative substance that would replace the use of SD inthe production of sodium chlorate. The substance (used in combination with a phosphate buffer) isa suitable alternative as it has a more benign hazard profile than SD. The comparative riskassessment performed for the purposes of this AoA suggests a lowering of risk from the replacementof SD by the molybdate salt. Nevertheless, environmental impacts from an increased release of CO2

are to be expected as a result of increased electricity consumption.

It was found that sodium molybdate fails the majority of the technical feasibility criteria and its poorpH buffering capabilities necessitate the addition of phosphate buffers at concentrations muchhigher than the electrolysis cell can tolerate. It is particularly the addition of phosphates that renderthis alternative unrealistic: their presence in the electrolysis cells is currently kept at a minimumlevel and if addition of several g/L would be required, the stability and durability of the anodeswould be severely impacted.

In addition, sodium molybdate would result in the generation of excessive volumes of oxygen in thehydrogen co-product at levels close to the explosion limit. The presence of phosphates wouldexacerbate the generation of oxygen. This would raise serious safety risks and would necessitate theintroduction of processes that would allow the dilution of the generated gas mixture, typically bymeans of nitrogen purging.

In terms of economic feasibility, the implementation of sodium molybdate would require significant(one-off) investment costs, including the costs of developing or acquiring access to the relevanttechnology (when and if this materialises in the future), the disposal of the existing electrolyte andthe generation of new electrolyte, the losses of chlorate sales and economic impacts on ancillaryoperations from the stoppage of the production during conversion, and the cost ofintroducing/expanding oxygen controls. These costs are substantial and unjustifiable, in light of thepoor technical feasibility of the alternative.

As regards operating (on-going) costs, sodium molybdate is accompanied by impaired energyefficiency, which is significantly lower than what is achieved using SD. This fact alone wouldsignificantly increase production costs for the chlorate plant and would significantly affect theapplicant’s profitability. Notably, the cost of electricity is expected to rise over the long term (EC,2013) and as such, this cost component, which is the single most important cost component, willonly increase in importance. In addition, severe economic losses would arise from the inability ofthe applicant to use the generated hydrogen gas when mixed with nitrogen, as a direct effect ofnitrogen purging aimed at the control of oxygen generation. Therefore, the use of sodiummolybdate cannot be considered economically feasible to the applicant.


Finally, in terms of availability, the molybdate substance itself is available on the EU market;however, the technology that would allow its implementation under conditions that wouldguarantee a minimum level of technical feasibility and economic viability is not available.

Overall, sodium molybdate has not been found to be a technically or economically feasiblealternative to the use of SD in the applicant’s production of sodium chlorate. Even if significantfurther R&D were to overcome the technical barriers, its economic feasibility would be unlikely tosubstantially improve. In practice, already extensive R&D presented in the open literature indicatesthat this is only likely if it is employed alongside a reduced level of Cr(VI).

5.4 Molybdenum-based coatings

5.4.1 Description of alternative technology and properties

This alternative technology involves the use of cathodes that have been coated with molybdenumprior to use in the chlorate process. The aim of the coating is to improve the current efficiency ofthe process by providing a coating to supress parasitic reactions that can occur during the process,as described in Section 2.1.2. The patents describing the use of molybdenum-coated cathodes aresummarised in Section 4.2.3. These patents indicate that molybdate salts (such as those shown inTable 4-11), would be required initially to prepare the coated-cathodes but they would not be addedinto the process electrolyte afterwards. As a result of this, the buffering effect provided by thepresence of sodium molybdate will not be present and will entirely need to be replaced with anotheragent. The Rosvall et al (2009) patent continues to use SD in the process while the Krstajic et al(2007) patent application replaces the buffering effect of SD using sodium acid phosphates.Therefore, the analysis of the technical and economic feasibility of this alternative assumes thatsodium acid phosphates are required if this alternative is being employed without the presence ofCr(VI) in the process.



Research into molybdenum-based coatings for chlorate cathodes has focused more on increasingcurrent efficiency than reduction of SD content in the electrolyte. However, some patentsnonetheless claim no SD content, and therefore the analysis below has been carried out assumingthis can be achieved.

A comparison of technical performance of molybdate-coated cathodes to the identified technicalfeasibility criteria is shown in Table 5-13.

Table 5-13: Comparison of molybdenum-based coatings and sodium dichromate according to technicalfeasibility criteria


Result or value achieved

Criteria pass?*Sodium dichromate Threshold



Sufficient Similar to SD

Uncertain: differenttechnology to SD. The

film is not formedelectrolytically but

imposed as a coating

()


Table 5-13: Comparison of molybdenum-based coatings and sodium dichromate according to technicalfeasibility criteria






pH ''#A#'''''; <2.5%O2

pH '''''#A#'''''''''';<3.0% O2 in H2 by

volume

Separate phosphatebuffer required;

uncertain effect onoxygen concentration



lifetime 8 years

Uncertain: lab testsare generally very

short and notrepresentative of

continuous operationat the industrial scale

?



''#A#'''%, '''''#A#'''''''''''''''' ''''''''''''''''

>''#A#''''%;<''''#A#''''''' kWh/t

94%; 4,342 kWh/ttheoretical

()


Highly soluble SufficientNot relevant to this

technologyNot relevant





detrimental to ClO2

generation

Uncertain: presenceof metal (Mo)

impurities would actas a ClO2 process

‘poison’

()

* parentheses indicate uncertainty over the conclusion reached due to lack of data. A tick is given only if theentire criterion is met


Formation of protective film: the technology differs in that the film is not formed electrolyticallybut imposed as a coating on the electrode substrate. The evidence available from past R&D is notsufficient to conclusively confirm the technical equivalence of this technology, but it may beassumed that it could perform to an acceptable level.

pH buffering and control of oxygen formation: the relevant embodiment of the patent applicationavoids the use of SD but requires phosphate as a buffer. As discussed in Section 5.3.2, the presenceof phosphate in the electrolyte is of concern because it can result in increased oxygen levels. Thepatent, however, does not discuss the level of oxygen achieved. Therefore, taking these factors intoconsideration, this alternative seems unlikely to fulfil this technical feasibility criterion, althoughfurther R&D would be required to determine this conclusively.

Cathode protection: cathode durability would be a concern. The patent applications describing theuse of this alternative reference tests lasting four (Rosvall, et al., 2009) or eight hours (Krstajic, et al.,2007), and no long-duration trials are known. Therefore, the effect of this technology on long termcorrosion inhibition and cathode lifetime is highly uncertain. Long-duration pilot plant trials wouldbe required to establish the likely rate of corrosion.

Impurities in chlorate product: the effect of transfer to this alternative on the purity of the resultingsodium chlorate is not known due to the lack of pilot scale trials. It seems probable that chloratepurity could be linked, in large part, to any corrosion observed and on the presence of any additive


other than chromium that may be used to take over any of the roles of SD in the process. Asdiscussed earlier in relation to sodium molybdate, traces of Mo in the chlorate product could be acause for concern, since heavy metals are considered as “poison” in the ClO2 manufacturing process.Therefore, the use of molybdate coatings might cause unnecessary and unwelcome problems to theapplicant’s customers.

On the other hand, the use of this technology could in theory have notable benefits in comparison tothe use of SD-based cells, on the basis of published test results.

Current efficiency and energy consumption: according to the patent application by Krstajic et al(2007), lower cell voltages and hence lower energy consumption can be achieved usingmolybdenum-based cathode coatings. In the patent, a cell voltage of 2.50-2.53 V with a currentefficiency of 94% is implied. Yet, the patent application examples are run over a very short period oftime, 8 hours. After such short a period of time, corrosion of the electrodes may not be apparent. Asnoted by Kus (2000), phosphate may cause negative effects at the anode. These may only becomeapparent after longer periods of operation time as would be expected in a commercial setting.However, if the results indicated by the patent are used for the sake of a conservative estimate, atheoretical energy consumption of 4,042 kWh per tonne of chlorate can be calculated for theelectrolysis. This results in a theoretical energy consumption of 4,342 kWh per tonne of chlorate,assuming 300 kWh/t is required for ancillary equipment, representing a considerable decrease inelectrical consumption relative to the use of SD17.

Although promising, the publicly available information does not provide sufficient guarantee thatthese limited results can translate to energy savings at the industrial scale and, to the best of theapplicant’s knowledge, this technology has not come any closer to commercialisation. Arkema doesnot consider molybdenum-based cathode coatings to be a realistic technically feasible alternative tothe use of SD and can certainly not be implemented by SD’s sunset date.

Conclusion and required steps to allow use of molybdenum coatings as an alternative to sodiumdichromate

Overall, while this alternative promises complete removal of Cr(VI) from the system, without Cr(VI)in the electrolyte, additional buffer must be used. The phosphate buffer would have a detrimentaleffect on the stability and durability of the anodes and could lead to increased oxygen generation; itis not clear whether additional controls on oxygen would be required. A relevant patent applicationhas claimed a reduction in cell voltage and a concomitant reduction in energy consumption.However, this has not been proven at the industrial scale, especially during continuous operation ofthe electrolysis cells. Overall, this yet unproven alternative is not considered technically feasible.

Due to the lack of commercial scale applications known to the applicant, significant uncertaintiesexist regarding the commercialisation of the technology and whether or not it would work in

17The following conditions for a chlorate cell employing SD were used to enable a comparison to be made toa theoretical change to molybdenum-coated cathodes. A cell voltage of 3.1 V (mid-range value from BREF(IPPC, 2007)) and current efficiency of 95% gives a theoretical energy requirement of 4,930 kWh/tonne ofchlorate + 300 kWh/tonne (mid-range value for other electrical equipment) = 5,230 kWh/tonne chlorateusing SD. Using molybdenum-coated cathodes, the patent indicates a current efficiency of 94% and avoltage between 2.50-2.53 V. Using these data; a mid-range cell voltage of 2.515 V and 94% efficiency, anelectrical consumption of 4,042 kWh/tonne can be calculated + 300 kWh/tonne = 4,342 kWh/tonne ofchlorate or a 9.9% increase in electrical consumption.


practice. In particular, the cathode lifetime must be long enough to consider the technologytechnically feasible, but no data on the cathode lifetime has been found. Although this technology ispromising, it can be expected that considerable R&D would still be required to demonstrate that thistechnology is technically feasible for commercial production of sodium chlorate. The typical steps inundertaking the required R&D and implementation steps may include:

1. R&D phase in existing electrolyte (without SD) to verify robustness

2. R&D phase to optimise buffer system needed, and effects on anodes

3. R&D to scale-up to (a) long-term tests, lab pilot (b) intermediate scale, (c) commercial scaleincluding demonstration of cathode lifetime

4. Replacement of all Cr(VI) containing electrolyte

5. Replacement of all existing electrolytic cell cathodes

6. Process optimisation

7. Preparation of new buffered electrolyte and its maintenance

8. Investigation of oxygen evolution and potentially implementation of safety measures toreduce the oxygen content of hydrogen stream

9. Potentially, implementation of systems for gas treatment to ensure clean-up of hydrogenbefore further use.





Overview

Due to the nature of this alternative, a direct comparison of hazards and risks to SD cannot beperformed here. However, it is of note that sodium molybdate would be the basis of the coatingand the new cathodes would be used alongside a sodium phosphate buffer. Due to the lack ofexperience with this technology at the industrial scale, it cannot be predicted whether otheradditives might be needed or what species may be found in the electrolyte during the use of achlorate cells that uses molybdenum-coated cathodes. We therefore tentatively assume that nofurther substance would be added to the electrolyte and no releases due to corrosion or othereffects might occur. Under this assumption and in light of the findings of Appendix 2 (on sodiumphosphates and sodium molybdate), it can be assumed that this alternative would have a morebenign risk profile than SD.



There is significant uncertainty on how energy consumption might change were molybdenum-coated cathodes to be used in the continuous operation of industrial-scale chlorate plants. Somevery tentative assumptions were made above on how energy might theoretically decrease incomparison to SD, but these were only used to illustrate the potential changes to the operating costsof the applicant. In light of such significant uncertainty, a detailed calculation of externalities is notprovided as it, in all likelihood, would be of dubious accuracy.


Molybdenum-coated cathodes could reduce risks to workers during the manufacture of sodiumchlorate but environmental impacts are uncertain.

5.4.5 Availability

As noted above, three elements of availability can be considered:


According to the patent describing the manufacture of molybdenum-based cathodes, they are madeusing iron(III) chloride and sodium molybdate in a buffer solution. It can safely be assumed thatthese materials would be available to any company (other than the applicant) that would wish tomanufacture coated cathodes. The applicant would not coat the cathodes themselves, as this is nottheir core business. The applicant has no knowledge of any supplier of suitable cathodes.

With regard to quality, given that the technology is not proven and unavailable on the market,assumptions on quality would be based on speculation.

Most importantly, access to the technology is the key issue. The aforementioned patent applicationhas been filed by Industrie De Nora (Krstajic, et al., 2007). The patent is yet to be granted and thetechnology is yet to be proven outside the laboratory. Therefore, the alternative technology cannotbe considered available to the applicant, certainly not by the sunset date for SD. In theory, assumingthat the Industrie De Nora18 (or other Mo-based coating) technology would develop into analternative suitable for use on the industrial scale without reliance on Cr(VI), it would need to belicenced from the patent holder.

5.4.6 Conclusion on suitability and availability for molybdate-based coatings

Molybdate-coated cathodes are not sued anywhere in the world for sodium chlorate manufacture.

18The Industrie De Nora patent protection will elapse in 2026, 20 years from filing date, 29 November 2006(Krstajic, et al., 2007). See terms of European patents here: http://www.epo.org/law-practice/legal-texts/html/epc/2013/e/ar63.html (accessed on 3 September 2014).


Molybdate-coated cathodes were investigated as an alternative technology that would replace theuse of SD in the production of sodium chlorate. The coated cathodes (used in combination with aphosphate buffer) could be considered to be a suitable alternative, although a direct comparison tothe hazard profile of SD cannot be made. Calculations on the environmental externalities that wouldaccompany the implementation of this alternative technology have not been made due to thesignificant uncertainties over the technical characteristics of molybdate-based coatings in anindustrial environment.

It was found that molybdenum-based coatings fail to meet the majority of the technical feasibilitycriteria and their poor pH buffering capabilities necessitate the addition of phosphate buffers atconcentrations much higher than the electrolysis cell can tolerate. It is particularly the addition ofphosphates that render this alternative unrealistic: their presence in the electrolysis cells is currentlykept at a minimum level and if addition of several g/L were required, the stability and durability ofthe anodes would be seriously impacted, unless new, more durable types of anodes could bedeveloped.

It is unclear whether molybdenum-based coatings would result in the generation of excessivevolumes of oxygen in the hydrogen co-product. Certainly, the presence of phosphates wouldexacerbate the generation of oxygen. Whether this would raise safety risks and would necessitatethe introduction of processes that would allow the dilution of the generated gas mixture (typically bymeans of nitrogen purging), it remains to be seen. The presence of metal impurities in the finalproduct is also a concern which is not possible to allay or confirm under the current state ofknowledge.

In terms of economic feasibility, the implementation of molybdenum-coated cathodes would requiresignificant investment (one-off) costs, including the costs of developing or acquiring access to therelevant technology (when and if this materialises in the future), the disposal of the existingelectrolyte and the generation of new electrolyte, the purchase and installation of new cathodes,the losses of chlorate sales and economic impacts on ancillary operations from the stoppage of theproduction during conversion, and, potentially, the cost introducing/expanding oxygen controls.These costs are substantial and unjustifiable, in light of the uncertain technical feasibility of thealternative.

As far as operating (on-going) costs are concerned, molybdenum-coated cathodes have beenclaimed in a relevant patent application to be capable of decreasing cell voltage and thus reduceenergy consumption. This has not been possible to demonstrate at the industrial scale and suchclaims cannot be relied upon, although information from said patent application has been used inthe calculation of the potential theoretical energy savings from the use of the molybdenum-coatedcathodes. Beyond the issue of energy consumption, adverse effects on the durability of the anodescoupled with uncertainty on the long-term durability of the cathode coating paint a picture of poorlong-term economics for the chlorate production process. If nitrogen purging were to be needed,the costs associated with impacts on ancillary operations would be very severe. Therefore, the useof molybdenum-coated cathodes cannot be considered economically feasible to the applicant.

Finally, in terms of availability, the substances needed for the generation of the coatings areavailable on the EU market; however, the technology that would allow their implantation underconditions that would guarantee a minimum level of technical feasibility and economic viability isnot available.

Overall, molybdenum-based coatings have not been found to be a technically or economicallyfeasible alternative to the use of SD in the applicant’s production of sodium chlorate. Even if


significant further R&D were able to overcome the technical barriers, their economic feasibilitywould still remain highly uncertain without first implementing this technology at the industrial scale.

5.5 Two-compartment electrolytic systems

5.5.1 Description of alternative technology and properties

Two-compartment electrolytic systems are a different technology to the existing sodium chlorateproduction method employing SD. As described in Section 4.2.3, there are patents describing theuse of modified chlor-alkali type cells to generate sodium chlorate. This process is currently used bysome of the manufacturers of sodium chlorate to generate sodium hydroxide, sodium hypochlorite,chlorine and hydrogen. It involves combining the output streams of the process in separatechemical reactors in order to produce hypochlorite and convert it into sodium chlorate. The processis preferably carried out in a separate reactor at a different pH and temperature to an ordinarychlor-alkali cell. Figure 5-1 below shows an example process diagram for a membrane chlor-alkalitype cell employed for the production of sodium chlorate. The technology is not limited only to thisconfiguration. Potentially, it could also consist of two or more membrane cells linked in series. ThepH ranges shown in the diagram are indicative but the anode compartment pH would besubstantially lower than the cathode compartment.

Figure 5-1: Example chlor-alkali type chlorate production process. Based on (Cook, 1975) (Millet, 1990)(Delmas & Ravier, 1993) (Hakansson, et al., 2004)




Table 5-14 presents the comparison of the two-cell technology to the technical feasibility criteria forthe replacement of SD in the sodium chlorate production process. As this alternative is a differenttechnology, some of the criteria are not relevant to this comparison.

Table 5-14: Comparison of two-compartment electrolytic technology and sodium dichromate according totechnical feasibility criteria




Two-compartmentsystems


Sufficient Similar to SDNot relevant to



pH ''#A#''''; <2.5%O2

pH '''''''#A#'''''''';<3.0% O2 in H2 by

volume

pH control required;oxygen producedseparately from

hydrogen

()



lifetime 8 yearsUncertain: likely to be

acceptable()



''#A#'''%, ''''#A#''''''''''' ''''''' '''''''''''''''''

>'''#A#''%;<''''''#A#''''' kWh/t

5,880 kWh/ttheoretical


Highly soluble SufficientNot relevant to






detrimental to ClO2

generation

Better quality due tofewer impurities

* parentheses indicate uncertainty over the conclusion reached due to lack of data. A tick is given only if theentire criterion is met


Formation of protective film & solubility in electrolyte: these criteria are not of relevance to thistechnology.

pH buffering and oxygen formation: ordinarily, chlor-alkali cells do not require pH buffers as theyoperate at a different pH range to the chlorate reaction. For the chlor-alkali process, the anodecompartment is maintained at a low pH specifically to prevent formation of chlorate (IPPC, 2001),while the cathode compartment is at a high pH due to the formation of sodium hydroxide. In orderto effectively produce chlorate; however, the chlorate reactor or anode compartment must be at pH


'''#A#'''' and thus pH adjustment is needed. Therefore, pH control is required in the modified chlor-alkali technology. This can be, at least in part, achieved by addition of sodium hydroxide andhydrochloric acid produced from the product streams. This would involve careful processoptimisation to balance the pH by the use of online monitoring and feedback loops betweendifferent process stages. Alternatively, non-Cr(VI) pH buffers could be used but their presence maycomplicate the electrochemistry in the electrolysis cell in a similar fashion to conventional systems.While the applicant is familiar with chlor-alkali technology in general, their experience concerns theoptimal production of chlorine and sodium hydroxide and the prevention of chlorate formation(normally an unwanted by-product in chlor-alkali plants). Both of these approaches – pH balancethrough process optimisation and the use of non-Cr(VI) buffers – would therefore demandsignificant R&D for the applicant in order to optimise the conditions required.

With regard to oxygen generation, this is released in a separate compartment to hydrogen,therefore, the hazard of explosive mixtures formation is eliminated.

Cathode protection: the protection of the cathodes is less of a concern with this alternative becausechlor-alkali cells are resistant to corrosion due to their requirement to handle chlorine gas. They areconstructed from more expensive materials (e.g. titanium) than chlorate cells. The technicalcriterion for cathode protection is therefore met by this alternative. Membrane chlor-alkali cellsrequire relatively frequent maintenance due to the short (2-5 years, according to literature) lifetimeof the selective membrane that divides the cell compartments, but does not introduce additionalcorrosion products that have a potential effect on product quality in the same way as steel cathodecorrosion in chlorate cells. This consideration would also affect the economic feasibility of theprocess as described in Appendix 3.

Current efficiency and energy consumption: the theoretical energy consumption of the process canbe estimated using typical consumption figures for a chlor-alkali plant BREF (IPPC, 2001) andassuming the process of converting chlorine to chlorate is 100% efficient, which means the resultingestimate will be highly conservative. A chlor-alkali plant requires 1,750 kg NaCl and 2,790 kWh ofelectricity to produce one tonne of chlorine gas (Cl2). Ordinarily, this energy would also producesodium hydroxide (1.128 t/t Cl2) but it is converted into sodium chlorate in this alternative process.As discussed in Section 4.2.3 on “Other technologies”, 3 moles of Cl2 are required to produce 1 moleof NaClO3 or, if converted to tonnes, 2 tonnes of Cl2 is required to produce 1 tonne of sodiumchlorate. In electrical consumption alone, a modified chlor-alkali plant would require 2,790 × 2 =5,580 kWh/t of sodium chlorate produced. In addition to this, further energy would be required toheat solutions and concentrate them for crystallisation. Using the same assumption as for thetheoretical calculation of the energy requirement for auxiliary processes used for SD of 300 kWh/tchlorate gives a total energy consumption of 5,880 kWh/t sodium chlorate produced. This is wellabove the ideal threshold making the alternative less technically and economically feasible than theSD-based process.

''''''''''''' ''''''' ''''''''''''''''''' '''''''''''''''''''''' ''''''' ''''' '''''''''''''''''''' '''' ''''''''''''''' ''''''''' '''' '''''''' '''''''''' ''''''''''''''' ''''''''''''''''''''''' '''''''''''''' '''''' ''' '''''''''''''''' ''''''''''' '''''' ''''''' ''''''''''''''''''' ''''' ''''''' '''' '''''''''' '''''''' ''''' ''''''''''' '''''''' ''''''''''''''''''''''''''''''' '''''''' '''''''''' ''''''''''''''''''''''''''''#E#''''''''' ''''''' ''''''''''''''''''''''' ''''''''' '''''''''''''''''' '''''''''''''''''''''' ''''''''''''''''''''''''''' ''''' ''''''''' ''''''''''''' '''''''''''''' ''''''''' ''' '''''''''''''''' ''''''''''''''''''' '''''''''''''''''''''' ''''' '''''''''''' '''''''''''' ''''''''''''''''''''''''' '''' '' '''''''' ''''''''''''''''''''''''''' ''''''' '''' ''''''''''' ''' ''''''''''' ''' '''''''''' ''''''''''''' '''''''''''''' '''''''''''''''' '''''''' ''' ''''''''''''''''''' '''' '''''' ''''''''''''''''''''' '''''''''''' '''''''''''' '''''''''''' ''''''''' ''''''''''''''''' '''''' '''''''''''' '''' '''''''''' ''''''''''' '''''' ''''' '''''''''''''' '''''''''''''''''' '''''''''''''''''''''''''

Impurities in the chlorate product: ''''''''''''''' ''''''''''''''' '''''''' '''''''''''''#E#'''''' '''''''' ''''' ''''''''''' '''''' ''''''''''''''''' '''''' '''''''''' '''''''''''''''''' ''''''''''''''''' '''''' '''''''''''' ''''''''''''''' '''''''''''''' '''' ''''''' '''''''''''''' ''''''''''''''' ''''''''''''''''


Conclusion and required steps to allow use of two-compartment electrolytic systems as analternative to sodium dichromate

The chlor-alkali technology is widely known in the industry. This technology is optimised for theproduction of chlorine and sodium (or potassium) hydroxide and not for the production of sodiumchlorate. The use of two-compartment electrolysis cells is largely theoretical.

If this technology were to be adapted for the production of sodium chlorate, it can safely beassumed that further R&D would be required. As identified above, the energy consumption of theprocess must be improved for this alternative to become technically feasible. This would involve at aminimum:

1. Selection of the most appropriate ion-selective membrane for compatibility with chlorate

Identification of appropriate membrane suppliers

2. Optimisation of process conditions for any electrolysis cells and chemical reactors:

Temperature, concentration, pH at each stage

Identity and concentration of buffers (if found necessary or beneficial)

Flow rate (or residence times) for solutions at each stage

3. Evaluation in the lab before scaling-up to the pilot scale.

''''''''''''''''''' '''''''''''''''''''''''''''' '''' ''''''' ''''''''''''''''''' '''''''''''' '''''' ''''''' '''''''' ''''''''' ''''''' ''''''''''''''''''''''

#E#

As with all R&D efforts, the outcome of the research is not certain to result in improved technicalfeasibility. ''''''''''''''' '''''''''' '''''''''''''' '''''''''''' ''''''' '''''''''' ''''' ''''''' ''''''''''''''''' '''' '''''' '''''''''' ''''''''''''''' ''' ''''''''''''''''''''''''''''''' ''''''''''' ''''''' ''''''''''''''' ''''''''' '''' ''''''' ''''#E#'''''''' '''''''' '''''''''''' '''' ''''''' '''''''''' '''''''''' '''''''''''''''' '''''''''''' '''''''''''''''''''' '''''''''''''' '''''''''''''''''''''''''' '''''''''''''''''' ''''''''''''''''''' '''''''''''''''' '''''''' ''''''' ''''''''''''''''''' ''''''''' ''''''''''''''''''''''''' ''''''''''''' ''''''''''''''''''''''' '''''''' ''''''''''''''''''''' ''''''''''''' '''''''''''' ''''' '''''''''''''''''''

Generally, the technology cannot be considered a technically realistic alternative for large-scaleproduction of sodium chlorate.






Overview

The comparison of hazards and risks between two different technologies is not as straightforward asin the case of the other three alternatives assessed above. The two-compartment system removesthe need for SD without introducing any new substances and without generating significantoperating hazards. It would appear that the use of the technology could be beneficial in terms ofeliminating exposure to and risks from SD.

The following analysis estimates and monetises the reduction in environmental damage impactsarising from the increase in energy consumption that would arise from the replacement of the SD-based technology with the alternative.


The use of two-compartment cell technology is expected to increase the energy consumption of theprocess by considerable amount due to a higher voltage. As described in Section 5.5.2, an additional'''''''''''' ''' ''#G#'''''''''' ''' ''''''' kWh/t chlorate produced of electricity is required. Considering theapplicant’s annual production of '''''#B#''''''' tonnes, this equates to an additional '''''''''#G# ''' '''''''kWh per year. Using greenhouse gas emission factors available from UK Department forEnvironment, Food and Rural Affairs19, it can be calculated that the generation of the equivalentamount of electricity would result in the release of '''''#G#'''''' tonnes of CO2 per year20.

Monetisation of greenhouse gas emissions is based on the methodology developed by the UKgovernment for carbon valuation in public policy appraisal21. The shadow price of carbon is closer towhat would be the full social cost of carbon emissions in terms of the damages caused by carbonemissions, but also takes into account estimates of marginal abatement costs, etc. Thus, it alsotakes into account policy commitments and technological issues. The value used in this assessmentis £31/tonne CO2 for the year 2017 (year of the sunset date), as shown in the relevant UKGovernment document22. The present day exchange rate (£1 = €1.25) was used to convert the valuein £ to € (€38.8/t).

Therefore, the externalities of the increased energy consumption and concomitant CO2 emissionswould be '''''''''' ''' '''''''' ''' #G#''''''' '''''''''' million per year.

19Available at: http://www.ukconversionfactorscarbonsmart.co.uk/, accessed 29 September 2014.

20The DEFRA 2013 overseas electricity generation factor of 0.07909 kg CO2e/kWh of electricity for Francewas used. Using this factor, the generation of '''''''' #G#'' '''''''' kWh of electricity would generate anadditional emission of ''''''#G#''''' tonnes of CO2e per year.

21Available at https://www.gov.uk/government/publications/updated-short-term-traded-carbon-values-used-for-uk-policy-appraisal-2014 (accessed on 13 December 2014).

22Shadow value of carbon, available athttps://www.gov.uk/government/uploads/system/uploads/attachment_data/file/243825/background.pdf.



Two-compartment cell technology would eliminate the use of SD without introducing chemicalsubstances of notable concern, therefore, the technology may be considered to be a suitablealternative for SD in the applied-for-use. However, its use would require the use of additionalelectricity in the production process and thus would result in increased CO2 emissions to the tune of''''''#G#'''''' t/y.

5.5.5 Availability

In general, chlor-alkali technology is available on the open market, but technology specificallyadapted to chlorate production is not. ''''''''''''''' ''''''' ''''''''''''' '''''''''''''''''''' ''''''''''''''''''' '''''''''''''''' '''''''''''''''''''' '''''''' '' ''''''''''''''''''' '''''''''' '''''' '''''''' '''''''''''''''''''''' ''''''''''''''' ''''''''''' '''''''' ''''''''''''''' '''''''''''''''' ''''''''''''''''''''' '''''''''''''''''' ''''''''''''''''''''''' '''''''''' ''''''''''''''''''' '''''''''''''''''''''' '''''''''' '''''''''''''''''''''' '''' ''''''' '''''''''''' ''''''''''''''' '''''''''''''' ''''''''''''''''''' '''''''''''' ''''''' '''''''''''''''''''' '''''''' '''''''''''''''''''''''''' '''' ''''''' '''''''''''''''''''''' ''''''''''''''''''' '''' '''''''''''''' ''''' '''''''''''''''''''''''' '''''''''''''''' ''''''''''''''''' '''''''''''''''' '''''''' ''''''' ''''''''#E#''''''''''' ''''''''''''''''' '''''' ''''''''''''''''''''''''''''' ''''''''''''''''''''''' ''' ''''''' ''''''''''''''''''' '''''''''' ''' ''' '''''''''' '''' '''' '''''''''''''''' '''''''' ''''''' '''''''''''''''''''''''''''''''''''''''''' '''''''''' ''''' '''''''''''''''' '''''''''''''' ''''''''''' ''''''''''' ''''' ''' '''''''''''''''''''''' '''''''''''' '''''' ''''''''''''' ''' '''''''''''''''''''''''' '''' '''''''''''' ''''''' ''''' '''' '''''''''' ''''''' '''''''''''''' '''''' '''''''''''''''''''''''''''''''''''''''''''''''''''''''''' ''''''''''''' '''''''''' '''''''''' '''''''''''''''''''''''' '''' '''''''''''' '''''' ''''''''''''''''''' '''''''''''' ''''''''''' ''''' '''''''''''''''''''''''''' ''''''' ''''''''''''''''' ''''''''''''''''''''''''' ''''''' ''''''' '''''''''''''''' '''''''''''''''''''' '''''''''''' '''''''''''''''''''' '''''''''''' ''' '''''''''' ''''''''' ''''''''''' ''''''' ''''''''''' ''''''''''''''''''''''''' '''' '''''''''''''' '''' '''''''''''''''''''''''''''''''' ''''''''''''''''''''' ''''' ''''''' ''''''''''''' ''''''''''

5.5.6 Conclusion on suitability and availability for two-compartmentelectrolytic systems

The use of this alternative would most likely result in a reduction of risk to human health. However,it would result in increased electricity consumption, by ca. '''#D#'''%, and this would result inincreased greenhouse gas emissions and associated environmental damage costs.

The two-compartment cell technology is not currently available in a form that can be implementedby the applicant and its technical feasibility is poor. From a practical perspective, demolition ofexisting chlorate plant and erection of a new production plant would be accompanied by anindicative cost of over €''''#D#''' million. In addition, the increase in energy costs would dramaticallyreduce the profitability of Arkema’s operations.

Overall, this is not a feasible alternative for Arkema.


6 Overall conclusions on suitability and availability ofpossible alternatives

6.1 Technical feasibility of shortlisted alternatives

The production of sodium chlorate has been carried out by industry since 1886 (Tilak & Chen, 1999)and has seen continual improvements over its long history of use but no realistic alternative to theuse of SD has been found despite significant R&D efforts (see Section 4.2.1). According to theresearch undertaken, nowhere in the world is any technology or substance other than SD used as aprocess aid in the production of sodium chlorate. Given the inability to identify a suitable alternativeor technology despite extensive global research, the trend among sodium chlorate manufacturerssuch as Arkema has been to maximise efficiency and therefore reduce the volume of Cr(VI) used, tominimise the release of Cr(VI) from the process and work towards a closed loop system to minimisethe release of Cr(VI) to the environment.

Four potential alternatives have been considered in detail in this AoA:

Alternative substance: Chromium (III) compounds (CrCl3) Alternative substance: Sodium molybdate Alternative technology: Molybdenum-based cathode coatings, and Alternative technology: Two-compartment electrolytic systems.

A summary of the assessment of technical feasibility of the shortlisted alternatives is presented inTable 6-1. More specifically:

Cr(III) compounds: Cr(III) compounds have the potential to show equivalent performance to SD,but the applicant does not have access to the particulars of the relevant technology

Sodium molybdate: sodium molybdate has been studied by industry and academia but resultshave been poor and further development is required. The addition of the molybdate salt hasshown issues with poor energy efficiency and pH buffering, the latter requiring the addition ofphosphate buffers. The addition of such buffers, at considerably elevated concentrations, wouldcause major problems to the stability and durability of the anodes and would contribute to anincrease in the generation of oxygen at plant scale. The evolution of increased concentrations ofoxygen in hydrogen (above the limit of explosion) raises serious process safety concerns. Thistechnology has not been proven at the industrial scale, where continuous operation putssignificant strain on the electrodes, and the very presence of high concentrations of phosphatesmakes this alternative technically unrealistic

Molybdenum-based coatings: claims have been made in relevant patent applications that thistechnology could lead to a reduction of cell voltage and, consequently, of energy consumption.This has not been proven at the industrial scale, as the lab tests described in the literature onlylasted for a few hours. On the other hand, the new cathodes would also need the addition ofhigh concentrations of phosphates, which would have a very detrimental effect on the anodes.As mentioned above for sodium molybdate, this technology has not been proven at theindustrial scale, where continuous operation puts significant strain on the electrodes and thedurability of the electrodes in the cell is a parameter on which little specific information isavailable


Table 6-1: Summary of technical feasibility of shortlisted alternatives for SD (NB. grey cells show problematic areas, parentheses show areas of uncertainty)

Technical feasibility criteriaThreshold based on SD

performanceChromium(III) chloride Sodium molybdate


Two-compartment systems

Formation of protective filmthat is permeable to hydrogenand impermeable tohypochlorite

Similar to SD () () Not relevant

pH buffering and control ofoxygen formation

pH '''''#A#''''''''; <3.0% O2 inH2 by volume

()

Poor buffering, phosphates

affect anodesOxygen evolution

Poor buffering, phosphates

affect anodesOxygen evolution (?)

()pH control required

Cathode protection (corrosioninhibition)

Minimum cathode lifetime 8years

() ? ? ()

Current efficiency and energyconsumption

'''''''''''' '#A#''''''''''' '''''''''''>95%; 5,230 kWh/t

theoretical

86%; 5,746 kWh/t

theoretical

()94%; 4,342 kWh/t

theoretical

5,880 kWh/ttheoretical

Solubility in electrolyte Sufficient () Not relevant Not relevant

Impurities in chlorate product

Each impurity must beconsidered separately.Metals are particularly

detrimental to ClO2

generation

()

Presence of metal impuritieswould act as a ClO2 process

‘poison’

()Presence of metal impuritieswould act as a ClO2 process

‘poison’

#E#''

Current state of knowledge of technical parametersUncertain; patent

application filed by acompetitor

Not used, globally. Researchpast and ongoing; much

R&D still needed

Not used, globally.Research past and ongoing;

much R&D still needed

Not used, globally forchlorate production.

Significant R&D required''

'''''''' '''''''''''''#E# '''''''''' '''''''

''''''''' ''''''''' ''''''''''''''''''

Expected time for achieving technical feasibility forcommercialisation at industrial scale

Uncertain; patent licensingissue pending

Impossible to estimate; many years would be needed for R&D, pilot scale andcommercialisation, if R&D results are positive

Conclusion and technical shortcomings

Potentially technicallyfeasible, but currentlyuncertain

Requires access to a 3rd

party (competitor)patent

Poor energy efficiency

Phosphate effects onanode

Explosion hazards

Not a feasible solution

Poor pH buffering

Phosphate effects onanode

New cathodes needed


Poor energy efficiency

Requires completeplant rebuild



Two-compartment electrolytic systems: such systems have been used industrially for the chlor-alkali process since the late 1800s (IPPC, 2001). As a result of their long history, this technologyis very well understood; the process has many similarities to the production of sodium chlorateand it is operated by the applicant (and other companies) for the production of chlorine,hydrogen and caustic soda, but, here, a variation of the known technology would be required.The available information ''''''''' ''''''' '''''''#E#'''''''''''' ''''''' ''''''' would suggest that this technologywould result in a more expensive manufacturing process due to higher electricity consumption,more complex equipment and higher maintenance requirements. Its requirement for acomplete rebuild of the sodium chlorate plants makes this a very unrealistic solution for theelimination of SD.

In conclusion, there is no certainty that any of the alternatives could demonstrate technicalfeasibility.

6.2 Economic feasibility of shortlisted alternatives

Table 6-2 summarises the available information on the economic feasibility of the shortlistedalternatives. The conclusions that may be reached are:

Chromium (III) compounds: Chromium (III) compounds could be a solution that is economicallymore feasible than the other alternatives, as it might require fewer and/or smaller changes tothe applicant’s plant and lower increases in operating costs. However, the conversion costs andin particular the cost of access to the rights to use the relevant technology that is subject to apatent application are uncertain

Sodium molybdate: sodium molybdate would be accompanied by notable investment costs,namely the disposal and replacement of the existing electrolyte, the improvement of oxygencontrols (to reduce the risk of explosion) and downtime, which would affect not only thechlorate plant but also ancillary operations of the applicant. In terms of on-going costs, sodiummolybdate would result in considerably increased energy consumption, increased maintenanceand materials costs due to the adverse effect of phosphates on the stability and durability of theanodes and significant operating difficulties for the applicant’s ancillary operations that dependon high quality hydrogen gas. The economic feasibility of this alternative is very poor

Molybdenum-based coatings: as with sodium molybdate, the introduction of these coatingswould be accompanied by notable investment costs, namely the disposal and replacement ofthe existing electrolyte, the purchase and installation of new cathodes and downtime of severalmonths, which will affect not only the chlorate plant but also ancillary operations of theapplicant. In terms of on-going costs, molybdenum-coated cathodes would result in uncertainchanges to energy consumption, possibly a reduction, according to a relevant patent application,increased maintenance and materials costs due to the adverse effect of phosphates on thestability and durability of the anodes and unclear impacts on ancillary operations (as it is notclear what oxygen controls would be required). The economic feasibility of the alternative isvery poor, particularly in light of the significant investment costs

Two-compartment electrolytic systems: for this alternative, the investment costs are fargreater and, realistically, prohibitive, than the previously described alternatives, as demolition ofthe existing chlorate plant and erection of a new plant would be required at a cost of severalmillions of Euros. Even if such investment were feasible, the new plants would have increased


maintenance requirements (the periodic replacement of membranes, higher energyconsumption and are the most critical component of chlorate plant operating costs. Two-compartment solutions are the most economically infeasible solution and cannot be consideredas a realistic proposition. ''''''''''''''''' '''''''' '''''' ''''''' '''''''''#E#'''''''''''''' '''''''''''''''''' ''''''''

In general, alternatives other than Cr(III) compounds do not come even close to being proven at theindustrial, commercial scale; therefore, issues of economic feasibility are purely of theoreticalnature, as these alternatives cannot possibly be implemented by the applicant sunset date. Twoimportant points need to made: (a) investment costs particularly for alternatives other than Cr(III)compounds would be very high, and (b) electricity (primarily for electrolysis and for ancillary tasks)accounts for – by far – the largest proportion of the production cost of the applicant. Therefore,profitability crucially depends on electricity prices and costs. Recent analysis on the projectedchanges in the electricity market between 2010 and 2020 and beyond indicates that “thedevelopments in the EU28 power sector have significant impacts on energy costs and electricityprices, in particular in the short term. Power generation costs are expected to significantly increaseby 2020 relative to 2010, mainly as a consequence of higher investments due to the need forsignificant capital replacement and higher fuel costs (because of the large increase in internationalfossil fuel prices). Grid costs also increase to recover high investment costs in grid reinforcementsand interconnectors. Smaller components of the cost increase are national taxes and ETS allowanceexpenditures (…) As a result, average electricity price in the period 2010-20 increases by 31% (isestimated)” (EC, 2013). Against this backdrop, the switch to an unproven technology that couldincrease electricity consumption is not a viable option for the applicant, as they cannot guaranteethe profitability and long-term viability of the chlorate (and certain ancillary) operations.

6.3 Reduction of risks from the use of shortlisted alternatives

There is a mixed picture with regard to the capacity of the shortlisted alternatives to reduce risksfrom the use of SD in the applied for use. Two-compartment systems do not use any replacementadditives and do not appear to introduce notable hazards, therefore they could be consideredcapable of eliminating the risks from SD, and as such, to be a suitable alternative for SD.

For molybdenum-based solutions, Appendix 2 explains that the use of sodium molybdate andsodium phosphate buffers results in a reduction of risks, as shown by the lower RCR valuesestimated. Therefore, the two molybdenum-based alternatives could be considered suitablealternatives for SD. However, past research has shown that some of the technical shortcomings ofthese alternatives can be addressed by the addition of SD into the electrolyte. Under such acondition, the two shortlisted alternatives would evidently not be considered suitable alternatives.

Conversely, Cr(III) substances may not be considered suitable alternatives for SD under the existingstate of knowledge. As discussed in Section 5.2.4, the CSR describes six Tasks for workers, whichmay result in some exposure to SD, see Table 5-7. The use of CrCl3 (or other Cr(III) substance) wouldeliminate exposure under Task 1 (Feeding liquid SD solution into the process), however, based on theworker shift patterns assumed in the CSR (see Table 5-8), no worker would avoid exposure to SD, asall workers who may be involved in Task 1 are assumed to be involved in other tasks during whichexposure to SD (via the electrolyte) will remain. The calculations made in Section 5.2.4 show that forinhalation exposure, which is the critical element of overall worker exposure, the use of a Cr(III)compound which would be oxidised into SD in the electrolyte, would only eliminate a very smallpercentage (5%) of aggregate exposure of all workers, except those exclusively working in thelaboratory for whom, no exposure reduction would be achieved. Therefore, Cr(III) compounds


cannot be considered suitable replacements for SD even if they would result in a very smallreduction in worker exposure to Cr(VI).

On the other hand, the use of some of the alternatives would result in increased use of energy andthis would in turn result in increased indirect greenhouse gas emissions. These can be summarisedas follows:

'''''''''''' ''''''''''''''''''''#G# '''''''''''''''''' ''''''' ''''''''''''''''' '''' '''''' ''''''''''' ''''''' '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' ''''' '''''' '''''''''' '''''''''''''''''

'''''''''''''''''''''''''''''''''''' ''''''''''''''''' ''''''' '''''''''''''''''' ''''''' '''' ''''''''''''''''''''''''''' ''''''''' ''''''''''''''''' '''' ''''''''''''''''''''''''''''''''''''

'''''''''''''''''''''''''''''''' '''''''''''''''''''' ''''''''''''''''' ''''''''''''''''''' '''''''' ''''''''''''''''' '''' '''''' ''''''''''' '''''''''''''''''''''''''''''''''''''''''''''''''''''''''' '''''''''''''''''' '''' '''''' ''''''''''' ''''''''''''''''''

It is important to note that these values do not take into account any changes in emissions arisingfrom the need to control the oxygen concentration in hydrogen nor from the loss of the use ofhydrogen in related ancillary operations.

6.4 Availability of shortlisted alternatives

Table 6-3 summarises the previously presented discussion on the availability of the shortlistedalternatives. With the exception of Cr(III) compounds for which a competitor has filed a patentapplication, the other technologies are not available at the industrial/commercial scale.

Table 6-3: Summary of availability of shortlisted alternatives for SD (NB. grey cells show problematic areas)

Availabilitycriterion


Sodium molybdateMolybdenum-based coatings


Quantityavailability

Small quantities

required(NB. CrCl3 not

REACH registeredyet)

Small quantities

required, sodiummolybdate is REACH

registered

()Required reagents

available on themarket but coatedcathodes not yet

available

Not relevant

Quality availability

No issues identified

No issues identifiedwith the quality ofthe substance but

technology notavailable for use atthe industrial scale

Technology not

available for use atthe industrial scale

Technology

specifically adoptedto chlorate

production notavailable for use atthe industrial scale


Table 6-3: Summary of availability of shortlisted alternatives for SD (NB. grey cells show problematic areas)

Availabilitycriterion


Sodium molybdateMolybdenum-based coatings


Access totechnology rights

Relevant patent

application filed bya 3

rdparty and a

license will berequired once

patent is granted;commercial and

business terms oflicense areuncertain.

Unlikely to beavailable by sunset

date

3

rdparty patents

have been appliedfor but the required

technology thatwould render this

alternative feasible,is not currently

available

A 3

rdparty has filed

a relevant patentapplication. Patentprotection elapses

in 2026

()

Technologyspecifically adapted

to chlorateproduction not

available for use atthe industrial scale.''''''' ''''''''''''''''' ''''''

''''''''''''''''''''''''''''''''''''#E#'' '''''''''''

'''''''''''' '''''''''''''''''''''''''''' ''''''''''''''

Is the alternativeavailable to theapplicant

No No No No

Note: Parentheses indicate a degree of uncertainty

6.5 Overall conclusion

The overall outcome of this analysis is shown in Table 6-4.

Table 6-4: Overall conclusions on suitability and availability of shortlisted alternatives for Arkema

AlternativeTechnicalFeasibility

EconomicFeasibility

Reduction in risk Availability

Chromium(III) chloride (-) ?HH: ENV: -

Sodium molybdate HH:ENV:


HH:ENV: ?


HH:ENV:

: better than SD; : worse than SD; - : no change compared to SD

Parentheses indicate a degree of uncertainty

None of the shortlisted alternatives are feasible alternatives for SD that would eliminate theexposure of workers to the Cr(VI) species responsible for SD’s SVHC status, and this conclusionsupports the applicant’s request for the Authorisation of the continued use of SD in the manufactureof sodium chlorate, as is standard practice in the chlorate industry across the world.

Arkema believes that the practical implementation at the industrial scale of the above or more novelsolutions may lie many years into the future. A long review period for the Authorisation would notonly allow time to attempt to overcome the limitations of the currently known technologies, but alsoto explore potentially better long-term solutions.


7 Annex – Justifications for confidentiality claims

This Annex is available in the complete version of this document.


Table 7-1: Justifications for confidentiality claims

Reference type Commercial Interest Potential Harm Limitation to Validity of Claim


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Andolfatto, F. & Delmas, F., 2002. Specific cathode, used for preparing an alkaline metal chlorate andmethod for making same. US, Patent No. US6352625 B1.

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Bommaraju, T. V., Dexter, T. H. & Charles, G., 1981. Film-coated cathodes for halate cells. US, PatentNo. 4295951 A.

Brasher, D. M. & Mercer, A. D., 1965. Radiotracer Studies of the Passivity of Metals in InhibitorSolutions. Transactions of the Faraday Society, Volume 61, pp. 803-811.

Brown, C. W., Carlson, R. C. & Hardee, K. L., 2010. Cathode member and bipolar plate forhypochlorite cells. International application, Patent No. WO 2010/037706 A1.

Chlistunoff, J., 2004. Final Technical Report - Advanced Chlor-Alkali Technology, Los Alamos: LosAlamos National Laboratory.

Cook, E. H., 1975. ELECTROLYTIC MANUFACTURE OF CHLORATES, USING A PLURALITY OFELECTROLYTIC CELLS. US, Patent No. 3,897,320.

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Cornell, A. & Simonsson, D., 1993. Ruthenium Dioxide as Cathode Material for hydrogen Evolution inHydroxide and Chlorate Solutions.. Journal of the Electrochemical Society, 140(11), pp. 3124-3129.

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9 Appendix 2 – Comparative hazard and riskcharacterisation of alternatives

9.1 Background

Article 60 (5) of REACH requires the applicant to investigate whether the use of the alternativesubstance “would result in reduced overall risks to human health and the environment” (ascompared to the Annex XIV substance).

In order to comply with this requirement in this document the hazard profiles of those substancesselected to be evaluated in detail are presented and suitable reference values for a quantitativecomparison (DNELs for human health assessment, PNECs for an assessment of environmentaltoxicity) are either identified or (if no such reliable basis could be found in the public domain)derived.

Three substances were selected for in-depth analysis:

Chromium (III) chloride hexahydrate Sodium molybdate (VI) dihydrate Phosphate buffer containing sodium dihydrogen orthophosphate and disodium hydrogen

phosphate to be used in combination with molybdenum coated cathodes.

Literature searches (up to May 2014) were performed for alternative substances in bibliographicdatabases as appropriate (after consultation of existing assessments) and assessments availablefrom eChemPortal and other sources were screened.

As not only a comparison of hazard profiles is required but a comparison of substance properties ona risk basis, a human health and environmental exposure scenario is developed (Section 9.3).Exposure within this scenario is estimated using the Tier I tool ECETOC TRA v.3. This approach isdifferent to that used in the CSR, as it should be applicable in a similar way for all substancesassessed. For an indicative comparison of occupational exposure, task 2 (sampling) was selected,since this constitutes the task carried out most frequently (daily).

Section 9.4 presents the comparative risk characterisation and the overall conclusions on risks fromusing the alternative substances.

9.2 Reference values for sodium dichromate and alternativesubstances

9.2.1 Sodium dichromate

Classification

Sodium dichromate, CAS 10588-01-9

According to Annex VI of the CLP Regulation SD is classified as follows:


Figure 9-1: Classification of sodium dichromate


Sodium dichromate dihydrate, CAS 7789-12-0

No classification according to Annex VI of the CLP Regulation is available. Classification according toclassification and labelling inventory (no joint entry, highest number of notifiers) is as follows:

Figure 9-2: Classification of sodium dichromate dihydrate

Ecotoxicity

Existing reference values

Predicted no effect concentrations as derived in the registration dossier as presented in ECHA-CHEM, the EU-RAR (ECB, 2005) and the CICAD assessment (WHO, 2013) are given in Table 9-1. Thenumerical values for the freshwater PNECs presented in all three sources are nearly identical,however the underlying basis is different. Using the species sensitivity distribution approach (SSD)the EU-RAR (ECB, 2005) and CICAD assessment (WHO, 2013) derived a PNECfreshwater of 3.4 µg/L and 4µg/L, respectively. The value presented in the CICAD document is based on the lower 95%confidence limit on the hazardous concentration for the protection of 95% of species (HC5-95%). Thevalue presented in the EU-RAR is based on the lower 95% confidence limit on the hazardousconcentration for the protection of 50% of species (HC5-50%) using an additional assessment factorof 3. The underlying basis for the PNECfreshwater presented in the registration dossier in ECHA-CHEM(ECHA, 2014) is unclear. Most probably – as can be concluded from the data presented in theregistration dossier – it refers to Ceriodaphnia dubia NOEC for reproduction of 4.7 µg Cr(VI)/L.According to EU-RAR (ECB, 2005) an assessment factor of 10 should be applied resulting in aPNECfreshwater of 0.47 µg/L chromium (VI) documented, which is a factor 10 lower than the valuedocumented in the table below. The reason for this discrepancy remains unclear.


Identical PNECs were derived in all three sources for PNECSTP and PNECsoil (slight differences are dueto rounding). According to EU-RAR in soil Cr(VI) would be reduced to Cr(III), and this would beexpected to have been the case also in many of the soil toxicity tests.

Numerical values for PNECsediment are also identical in the registration dossier and in the EU-RAR, butthe one in the registration dossier refers to dry weight and the one in the EU-RAR to wet weight.Probably there is a mistake in the registration dossier as it refers to the EU-RAR for the assessmentof sediment toxicity. The EU-RAR points out that the PNECsediment is very tentative based onfreshwater toxicity and equilibrium partitioning, as most of Cr(VI) will be transformed to Cr(III) underconditions found in most sediments, and Cr(III) formed would be expected to be poorly soluble andthus of reduced bioavailability.

Table 9-1: Predicted no effect concentrations for different environmental compartments – values fromECHA-CHEM compared to EU RAR (ECB, 2005) and a CICAD assessment (WHO, 2013)

ECHA-CHEMbased on Cr(VI)

EU RAR (2005)based on Cr(VI)

CICAD (2013)based on Cr(VI)

PNECfreshwater 4.7 µg/L, AF 10 (0.47 µg/L, AF 10); SSD(HC5-50%, AF 3): 3.4 µg/L

SSD (HC5-95%): 4 µg/L

PNECmarine-water not derived not derived 0.09 µg/L (AF 50)

PNECintermittent-releases not derived not derived not derived

PNECSTP 0.21 mg/L, AF 1 0.21 mg/L, AF 1 0.2 mg/L, AF 1

PNECsediment 0.15 mg/kg sed. dw (EPM) 0.15 mg/kg sed. ww (0.69mg/kg sed. dw.)

not derived

PNECsoil 35 µg/kg soil dw., AF 10 35 µg/kg soil dw., AF 10 0.04 mg/kg soil dw., AF 10

Discussion of suitability of reference values for comparative assessment

The most relevant reference value for comparison with alternative substances is the PNECfreshwater. Incontrast to PNECsoil it is largely attributable solely to Cr(VI) species. It is based on a large chronic dataset from a wide range of aquatic taxa, while the sediment value is based on the freshwater data andEPM only.

In regard to STP microorganism toxicity, also the PNECSTP as derived within EU-RAR (ECB, 2005) isvalid (this value is also referred to by ECHA-CHEM). It is based on a review of several studies onsingle microbial strains as well as an activated sludge respiration inhibition test. With appropriateassessment factors, resulting PNECs were mostly of similar magnitude, and the lowest value basedon a single-organism study was used to derive the value.

Conclusions: PNECs for comparative assessment

The PNECfreshwater of 3.4 µg Cr(VI)/L derived within the EU risk assessment (ECB, 2005) is the mostvalid value as derivation is very well documented and corresponds to the methodology outlined inREACH guidance on information requirements and chemical safety assessment, part R.10 (ECHA,2008). This value will be used for comparative assessment of alternatives to SD.

Regarding sewage treatment plant microorganisms, the PNECSTP derived within the EU riskassessment (ECB, 2005) of 0.21 mg Cr(VI)/L is valid and will be used for comparative assessment ofalternatives to SD.


Human Health


Sodium dichromate (CAS 10588-01-9) has been registered in the tonnage band 10,000-100,000tons/year (ECHA, 2014). The DMELs/DNELs reported in the following table are taken form theapplication CSR. Values are presented for the Cr(VI) ion which is the molecular entity that drivescarcinogenicity of SD and is released when the substance solubilises and dissociates.

Table 9-2: Worker DMELs/DNELs for sodium dichromate (CAS 10588-01-9) – values from authorisation CSR

Route ofexposure

Systemic effects Local effects

Acute Long-term Acute Long-term

Chromium triacetate*

Inhalation High hazard (nothreshold derived)

Not derived High hazard (nothreshold derived)

DMEL 0.0025 µg/m3

*

(effect) (lethality, Cat 2) (severe skin burnsand eye damage)

(lung cancer)

Dermal No hazard identified Not derived High hazard (nothreshold derived)

Not derived(skin corrosion)

(effect) (lethality, Cat 4) (severe skin burnsand eye damage)

* associated with an excess risk of 1 x 10E-5

Long-term inhalation to chromium (VI) causes lung tumours in humans and animals. There is noevidence that inhalation exposure to chromium (VI) causes tumours at other localisations.Therefore, chromium (VI) is a local acting carcinogen and for local effects after long-term inhalationexposure a DMEL was derived on basis of epidemiological data in humans assuming a linear dose-response relationship.

No DNEL was derived for local effects after acute inhalation exposure. This exposure is characterisedby a ‘High hazard’ according to the ‘Guidance on Information Requirements and Chemical SafetyAssessment Part E: Risk Characterisation’ (ECHA, 2012a) and due to the classification of SD as ‘Skincorrosive Cat 1B (H314: Causes severe skin burns and eye damage). This hazard was treated in aqualitative but not a quantitative manner.

In a subchronic inhalation study with rats local effects in the lung and effects on the humoralimmune response were observed (LOAEC 25 µg/m3, continuous exposure 22 h/d, 7 d/w). Althoughthis study has some shortcomings for the purpose of comparison a calculation has been performedin the CSR to see which DNEL would result for systemic effects after long-term inhalation exposure.The resulting value was above the DMEL for local effects. As the DMEL for local effects protects fromsystemic effects no DNEL was derived for systemic long-term effects after inhalation exposure.

SD is classified as acute toxic Cat 2 after inhalation exposure (H330: Fatal if inhaled). Therefore a‘High hazard’ was assigned for systemic effects after acute inhalation exposure according to the‘Guidance on Information Requirements and Chemical Safety Assessment Part E: RiskCharacterisation’ (ECHA, 2012a). This hazard was treated in a qualitative but not a quantitativemanner.

No DNELS were derived with respect to local effects after dermal exposure. Due to the skin corrosiveproperties and its classification as skin sensitising substance (category 1) a ‘High hazard’ was


assigned for systemic effects after acute inhalation exposure according to the ‘Guidance onInformation Requirements and Chemical Safety Assessment Part E: Risk Characterisation’ (ECHA,2012a). No quantification of this hazard is possible and the risk possibly associated with this route ofexposure has to be controlled by appropriate risk management measures.

SD elicits only very low acute toxicity after dermal contact. It is classified as acutely toxic (category 4)after dermal exposure (H312: Harmful in contact with skin), therefore no hazard was attributed forsystemic effects after acute dermal exposure according to ‘Guidance on Information Requirementsand Chemical Safety Assessment Part E: Risk Characterisation’ (ECHA, 2012a). Acute dermal effectsare dominated by corrosive reactions to the skin which were treated in a qualitative manner. It canreasonably be assumed that protection from local effects will also protect from systemic effectsafter dermal exposure.

Systemic toxic effects may occur in the context of extensive dermal exposure which areaccompanied by local reactions. As the local effects are dominating overall toxicity, no DNEL forsystemic effects after long-term dermal exposure has been derived and a qualitative assessment ofthe local effects after long-term dermal exposure has been performed.


The relevant endpoint for comparing effects after long-term exposure is carcinogenicity afterinhalation exposure. The DMEL reported in the CSR and in Table 9-2 is the same as reported byRAC23 in its ‘Application for authorisation: establishing a reference dose response relationship forcarcinogenicity of hexavalent chromium’, which has been derived by linear extrapolation to the lowdose range. As RAC recognised that ‘mechanistic evidence is suggestive on non-linearity, it isacknowledged that the excess risk in the low exposure range might be an overestimate’ this valuebears some uncertainty which cannot be further quantified at the moment.

Conclusions: Tentative DNELs for comparative assessment

For a comparative risk characterisation of human health after inhalation exposure the DMEL forlong-term inhalation exposure, local effects (DMEL: 0.0025 µg/m3 associated with an excess risk of 1x 10E-5) is used.

9.2.2 Chromium(III) chloride hexahydrate, CAS 10060-12-5

Classification

For chromium (III) compounds, no Harmonised Classification according to Annex VI of the CLPRegulation is available. For chromium (III) chloride hexahydrate (CAS 10060-12-5), classificationaccording to classification and labelling inventory (highest and second highest number of notifiers) isas follows:

23See http://echa.europa.eu/documents/10162/13579/rac_carcinogenicity_dose_response_crvi_en.pdf.


Figure 9-3: Classification of chromium (III) chloride hexahydrate

Deviating from this classification for chromium chloride hexahydrate chromium trinitrate has beenclassified as

Oxidising solid Cat 3 (H272: May intensify fire; oxidiser), Skin sensitising Cat 1A (H317: May cause an allergic skin reaction) Acute toxic Cat 4 after inhalation (H332: Harmful if inhaled) Aquatic Chronic toxic Cat 2 (H411: Toxic to aquatic life with long lasting effects)

In the registration dossier, chromium triacetate has been classified as skin sensitising Cat 1B (H317:May cause an allergic skin reaction) in the registration dossier. All three substances are soluble Cr(III)salts and human health hazards are probably due to Cr(III).

Ecotoxicity


Chromium (III) chloride is not registered under REACH. Instead, predicted no effect concentrationsfor the soluble chromium (III) compounds chromium triacetate (CAS: 1066-30-4) and chromiumtrinitrate (CAS: 13548-38-4) are available in ECHA-CHEM. Further, PNECs for soluble chromium (III)compounds in general are reported in EU-RAR (ECB, 2005) (the report is on Cr(VI), but Cr(III) was alsoassessed) and the CICAD assessment (WHO, 2009) on inorganic chromium (III) compounds. Studieson chromium trichloride were included in both of these assessments, as observed toxicities areobviously independent of the counter-ions. PNEC values from these four sources are summarised inTable 9-3.

Chromium trinitrate is a soluble Cr(III) compound with a comparatively large (chronic) datasetavailable according to ECHA-CHEM, while for chromium triacetate only acute data are reported.These acute data were largely derived in medium to hard water, while toxicity of chromium (III) mostlikely increases with decreasing hardness and decreasing salinity, i.e. highest toxicity is observed insoft freshwater, and lower toxicity in marine water compared to freshwater (ECB, 2005; WHO,


2009). This may explain the difference seen in the PNEC values for freshwater which are between22.7 µg Cr(III)/L for chromium triacetate and around 5 µg Cr(III)/L for chromium trinitrate as well aschromium (III) compounds in general according to EU-RAR (ECB, 2005) or the CICAD assessment(WHO, 2009) (identical values, rounded in case of CICAD), where different chromium (III) compoundswere assessed together.

As mentioned above, EU-RAR and CICAD evaluate ecotoxicity studies for (soluble) Cr(III) compounds,independently from the counter ions. Studies evaluated in EU-RAR were mainly conducted withchromium trichloride, chromium trinitrate and chromium potassium sulphate.

Table 9-3: Predicted no effect concentrations for different environmental compartments – values fromECHA-CHEM (chromium triacetate and trinitrate) compared to EU RAR (ECB, 2005) and CICAD (WHO, 2009)

ECHA-CHEM,chromiumtriacetatebased on Cr(III)

ECHA-CHEM,chromiumtrinitratebased on Cr(III)

EU RAR (2005)based on Cr(III)

CICAD (2009)based on Cr(III)

PNECfreshwater 22.7 µg/L, AF 1000 4.87 µg/L, AF 10 4.7 µg/L, AF 10, forsoft water

SSD (HC1-50%): 10µg/L (<100 mg/LCaCO3);5 µg/L, AF 10, forsoft water

PNECmarine-water 2.27 µg/L, AF 10000 0.97 µg/L, AF 50 not derived 2 µg/L, AF 1000

PNECintermittent-releases 227 µg/L, AF 100 4.03 µg/L, AF 100 not derived not derived

PNECSTP 1.13 mg/L, AF 100 506.6 µg/L, AF 100 not derived not derived

PNECsediment not derived 70.8 µg/kg sed. dw,AF 100.

31 mg/kg sed. ww(143 mg/kg sed.dw), EPM for acidicconditions (lowerads.)

not derived

PNECsoil not derived 70.8 µg/kg soil dw.,AF 100

3.2 mg/kg soil dw,AF 10

3.2 mg/kg soil dw,AF 10

Using chromium triacetate in medium to hard water, in the available acute fish test (96 h; hardness:ca. 202 mg/L CaCO3) as well as the acute test with daphnia magna (48 h; hardness: 250 mg/L CaCO3),no effects were observed up to the limit concentration of 100 mg/L nominal (mean measured 87.8mg/L), corresponding to a nominal Cr(III) concentration of 22.7 mg/L. No data are available for algaefor this compound. While the aquatic PNEC derived for chromium trinitrate is based on a 72 daysNOEC (reproduction & behaviour) of 48 µg Cr(III)/L established with freshwater fish Salmo gairdneri(hardness: 25 mg/L CaCO3), practically the same value results from the assessments performedwithin EU-RAR and CICAD based on a NOEC derived from a life-cycle test on Daphnia magna (47µg/L; hardness: 52 mg/L CaCO3) using also chromium trinitrate. Both of these decisive tests wereperformed using soft water.

The test for STP microorganisms reported for chromium triacetate is based on read across tochromium sulphate. The activated sludge respiration inhibition test leads to an EC50 based on Cr(III)of 49 mg/L. By application of an AF of 100, a PNECSTP of 490 µg Cr(III)/L would result , pronouncedlydiffering from the PNECSTP of 5 mg/L available from ECHA-CHEM for chromium triacetate(corresponding to 1.13 mg Cr(III)/L). This may be due to a mistake in molecular weight calculations.The recalculated PNECSTP of 490 µg Cr(III)/L based on the chromium triacetate dossier is practicallythe same size like the one reported for chromium trinitrate (506.6 µg Cr(III)/L), which is based onTetrahymena pyriformis IC50 (9 h) of 50 mg Cr(III)/L.



For PNECfreshwater, reference values derived based on chronic test data using soft water are to bepreferred over acute data derived using medium to hard water. Thus, PNECfreshwater values reportedaccording to ECHA-CHEM for chromium trinitrate and according to EU-RAR (ECB, 2005) and theCICAD assessment (WHO, 2009) for Cr(III) compounds in general are all valid. PNECSTP as presented inECHA-CHEM for chromium triacetate cannot be used due to obvious mistakes in molecular weightcalculations, but the value of 490 µg Cr(III)/L derived by recalculation from key study results is valid.This value (490 µg Cr(III)/L) is practically identical to the PNECSTP reported for chromium trinitrate, inspite of being based on different key studies.

Values for sediment and soil are given as reported but will not be used for the comparativeassessment.


The PNECfreshwater as derived within the EU risk assessment (ECB, 2005) of 4.7 µg Cr(III)/L) is used forthe comparative assessment.

Regarding sewage treatment plant microorganisms: as the respiration inhibition test is most widelyaccepted as an indicator for combined microbial inhibition in STPs, the PNECSTP according to therecalculated PNEC-value from the chromium triacetate dossier of 490 µg Cr(III)/L will be used in theassessment of alternatives to SD.

Human toxicity


Chromium(III) chloride hexahydrate is not registered under REACH. However, the closely relatedsubstances chromium triacetate (CAS: 1066-30-4) and chromium trinitrate (CAS: 13548-38-4) areregistered in the tonnage band 10-100 tons/year and 100-1000 tons/year, respectively. Additionalinformation is available from the CICAD assessment (WHO, 2009) on chromium (III), an EFSAevaluation on chromium(III) picolinate and the German MAK evaluation of chromium (III) (Hartwig,2009).

The DNELs as reported in ECHA-CHEM for chromium triacetate (CAS: 1066-30-4) and chromiumtrinitrate (CAS: 13548-38-4) are outlined in Table 9-4.


Table 9-4: Worker DNELs for chromium triacetate (CAS 1066-30-4) and chromium trinitrate (CAS 13548-38-4) – values from ECHA-CHEM (ECHA, 2014)

Route ofexposure



Chromium triacetate*

Inhalation 1097 mg/m3

4.24 mg/m3

36 mg/m3

0.141 mg/m3

(effect) (248.9 mg/m3)

(repeated dosetoxicity)

(0.96 mg/m3)


(8.2 mg/m3)


(0.03 mg/m3)


Dermal 40.3 mg/kg bw/d 20.2 mg/kg bw/d 8 mg/cm2

Not derived(effect) (9.1 mg/kg bw/d)


(4.6 mg/kg bw/d)(repeated dose

toxicity)

(1.8)(skin

irritation/corrosion)

(skin sensitisation)

Chromium trinitrate*

Inhalation 0.619 mg/m3

(0.08 mg/m3)

0.464 mg/m3

(0.06 mg/m3)

0.21 mg/m3

(0.026 mg/m3)

0.155 mg/m3

(0.02 mg/m3)

(effect) (repeated dosetoxicity)




Dermal 0.32 mg/kg bw/d(0.07 mg/kg bw/d)

0.32 mg/kg bw/d(0.07 mg/kg bw/d)

High hazard High hazard



(qualitativeassessment)

(qualitativeassessment)

*values for Cr(III) are presented in brackets; values for Cr(III) as presented for chromium triacetate werecalculated considering the molecular weight of chromium triacetate (229.13 g/mol); Cr(III) concentrations aspresented for chromium trinitrate were calculated on basis of the Cr(III) content of the underlying NOAELconcentrations/doses and considering the applied assessment factors

Evaluation of long-term inhalation exposure of chromium triacetate and chromium trinitrate isbased on a 90-day inhalation toxicity study in rats performed with basic chromium sulphate assurrogate for soluble Cr(III) salts (Derelanko et al., 1999). Animals were exposed to 17, 54, 164mg/m3 basic chromium sulphate (corresponding to 3, 10, 30 mg Cr(III)/m3) for 6 hours/day on 5days/week. Local effects (especially inflammation) were already observed in the lowest dose group.Systemic effects (decreased body weight and haematological findings) were obvious in the middleand high dose group. According to WHO (2009) a concentration of 3 mg Cr(III)/m3 can therefore beregarded as NOAEC for systemic effects and LOAEC for local effects. The results were interpreted in asimilar way in the registration dossier for chromium trinitrate, but interpretation was different in theregistration dossier of chromium triacetate.

The DNEL for systemic effects after long-term inhalation exposure for chromium trinitrate is basedon the study of Derelanko et al. (1999) assuming a NOAEC of 17 mg/m3 soluble basic chromiumsulphate (corresponding to 3 mg Cr(III)/m3 and to 23.1 mg/m3 chromium trinitrate nonahydrate).The human equivalent concentration (6 h exposure of rats to 8 h human exposure: factor 2) wasgiven as a NAEC of 11.61 mg chromium trinitrate/m3. The DNEL was derived by application of adefault assessment factor of AF 25 (2 subchronic to chronic, 2.5 interspecies and 5 intraspeciesvariability). The DNEL for systemic effects after acute exposure was extrapolated from the long termDNEL, but no further information was provided.

Starting from a LOAEC of 17 mg/m3 soluble basic chromium sulphate (corresponding to 3 mgCr(III)/m3 and to 23.1 mg/m3 chromium trinitrate nonahydrate) for local effects a DNEL of 0.155mg/m3 was derived for local effects after long-term inhalation exposure (AF 75: 3 LAEC to NAEC, 2subchronic to chronic, 2.5 interspecies and 5 intraspecies variability). The DNEL for the acute local


effects (0.21 mg/m3) after inhalation exposure was extrapolated from the long-term DNEL, but nofurther information has been provided for the extrapolation.

The DNELs for long-term and acute systemic effects after dermal exposure are based on an oralsubchronic (20 week) toxicity study with chromium trichloride in rats, with a NOAEL of 21.3 mgchromium trichloride/kg bw/d (corresponding to 7 mg Cr(III) /kg bw/d corresponding to 32 mgchromium trinitrate/kg bw/d). For the long-term DNEL an overall assessment factor of 100 was used(2 subchronic to chronic, 4 scaling rat, 2.5 remaining interspecies and 5 intraspecies variability). Noadditional factor for route to route extrapolation was applied as for both routes, oral and dermal, avery low absorption (10%) was assumed. The acute DNEL value was extrapolated from the long termDNEL value. As both values are numerically identical there seems to be an error in thedocumentation.

Chromium trinitrate has been classified as skin sensitising substance in the registration dossier (Cat1A, H317: May cause an allergic skin reaction) based on the results of a guinea pig maximisation testperformed with chromium trichloride. Due to this classification no DNEL for dermal local effectsafter long term exposure was derived and a qualitative hazard assessment was performed for localeffects. As stated in the CICAD document Cr(III) ‘acts as the ultimate haptenic determinant forchromium sensitisation in the skin; however, especially because of their lower penetration into theskin, trivalent chromium compounds are less potent sensitisers than hexavalent chromiumcompounds’.

The DNEL for systemic effects after long-term inhalation exposure for chromium triacetate is basedon the subchronic repeated dose toxicity study in rats performed with soluble basic chromiumsulphate (Derelanko et al., 1999). The highest dose applied was selected as NOAEC for systemictoxicity (NOAEC: about 210 mg chromium acetate/m3). The human equivalent concentration (6 hexposure of rats to 8 h human exposure: factor 2) is a NAEC of 106 mg/m3. The DNEL was derived byapplication of an overall default assessment factor of AF 25 (2 subchronic to chronic, 2.5 interspeciesand 5 intraspecies variability). The DNEL for systemic effects after acute exposure is based on arepeated dose inhalation toxicity study (NAEC 13718 mg/m3; AF 12.5: 2.5 interspecies and 5intraspecies variability). The underlying study could not be identified in the registration dossier. ADNEL of 0.141 mg/m3 has been derived for local effects after long-term inhalation exposure (AF 75: 3LAEC to NAEC, 2 subchronic to chronic, 2.5 interspecies and 5 intraspecies variability). Theunderlying study is the same as used for derivation of DNEL long-term systemic which resulted in aDNEL for local effects of 21 mg chromium acetate/m3, which corresponds to a human equivalentconcentration of 10.5 mg chromium acetate/m3. The DNEL for the acute local effects after inhalationexposure is based on a repeated dose study with an (adjusted) LOAEC of 1370 mg/m3 (AF 38: 3 LAECto NAEC, 2.5 interspecies and 5 intraspecies variability). The underlying study could not be identifiedin the registration dossier.

The DNELs for long-term and acute systemic effects after dermal exposure are based on an oralsubchronic toxicity study in rats performed with chromium picolinate monohydrate. No adverseeffects were observed up to the highest dose tested (50000 ppm) (Rhodes et al., 2005). The dosewas converted to basic acetate monohydrate (NOAEL of 2015 mg/kg bw/d). For the long-term DNELan overall assessment factor of 100 was used (2 subchronic to chronic, 4 scaling rat, 2.5 remaininginterspecies and 5 intraspecies variability) without any further factor for route-to-routeextrapolation. The derivation of the acute value was performed in a similar manner without the timeextrapolation factor. Chromium triacetate has been classified as skin sensitising substance in theregistration dossier (Cat 1B, H317: May cause an allergic skin reaction) based on the results of amouse local lymph node assay performed with basic chromium acetate. The EC3 value determinedin the LLNA assay was < 5% (not further specified, because even the lowest concentration tested


(5%) resulted in SI values of > 3%. Due to this classification no DNEL for dermal local effects afterlong term exposure was derived.

A DNEL of 8 mg/cm2 was derived for dermal local effects after acute exposure. This value is obviouslybased on human data, because only an intraspecies assessment factor of 5 was applied. However, itis not obvious from the registration dossier on which data this DNEL is based.


Values for long-term DNELs for inhalation exposure are based on a subchronic inhalation studyperformed with basic chromium sulphate as surrogate for soluble Cr(III) salts in rats (Derelanko etal., 1999). The values for the systemic DNEL differ by a factor of 10 which is due to the differentinterpretation of the study in the registration dossiers for chromium trinitrate and chromiumtriacetate. Effects observed in the mid and high dose group were not regarded as toxicologicalrelevant in the context of the evaluation of chromium triacetate. But, in accordance with theevaluation of WHO (2009), it is concluded that effects on body weight and haematology should beregarded as relevant. Therefore, the NOAEC for systemic effects derived from this study is 3 mgCr(III)/m3. Local effects in the lung were observed in all three dose groups. In accordance with theevaluation of WHO (2009) and the evaluation of the chromium trinitrate and triacetate the lowestconcentration tested (3 mg Cr(III)/m3) is regarded as LOAEC for local effects.

No adequate study could be identified for the evaluation of acute systemic or local effects afterinhalation exposure. The basis for the derivation of the DNELs for systemic and local effects afteracute exposure of both substances is unclear.

No toxicity studies after repeated dermal exposure could be identified. According to this, the DNELsfor systemic long-term and acute exposure were derived by route-to-route extrapolation from oralstudies for both chromium(III) compounds. Whereas in the case of chromium acetate a subchronicstudy performed with chromium picolinate in rats was used the DNELs for chromium trinitrate forlong-term and acute systemic effects after dermal exposure are based on an oral subchronic (20week) toxicity study with chromium trichloride in rats with a NOAEL of 21.3 mg chromiumtrichloride/kg bw/d (corresponding to 7 mg Cr(III) /kg bw/d corresponding to 32 mg chromiumtrinitrate/kg bw/d). Rats were fed a diet supplemented with 0, 5, 25, 50, or 100 mg Cr(III)/kg aschromium chloride for a period of 20 weeks. According to WHO (WHO, 2009) this corresponds to0.35 to 7 mg Cr(III)/kg bw/day. As no adverse effects were observed in this study a NOAEL of 7 mgCr(III) can be deduced for Cr(III) as chromium trichloride.

Taking into account the results of the study with chromium picolinate where no toxic effects wereobserved up to the highest dose tested (50000 ppm corresponding to 4240 mg of chromiumpicolinate monohydrate/kg bw/day for rats) according to EFSA (2010) the NOAEL of Cr(III) seems tobe much higher than 7 mg/kg bw/d. From the study with chromium picolinate a NOAEL of about 500mg Cr(III)/kg bw/d resulted, which was used as basis for the evaluation of chromium picolinate byEFSA (2010).

No reliable studies on the reproductive toxicity of chromium trichloride could be identified in ECHA-CHEM. Repeated dose toxicity studies did not indicate any effects on reproductive organs or spermparameters. In a developmental toxicity study with chromium chloride no effects were observed at200 mg/kg bw/day (rats, exposure from GD 6-17, only one dose). Additional investigations withchromium picolinate do not indicate a risk for reproduction by Cr(III) (EFSA, 2010; WHO, 2009). In adrinking water study male Swiss mice (9-10 per group) were exposed to chromium(III) chloridehexahydrate of 2000 or 5000 mg/l (corresponding to chromium doses of about 82 or 204 mg/kg


body weight and day) 12 weeks before mating with untreated females (Hartwig, 2009). Males of thelow and high dose showed a statistically significant decrease in body weights and relative preputialgland weights, relative testis weights were significantly increased. In the high dose group fertilitywas significantly reduced. In addition, female mice given chromium(III) chloride with the drinkingwater in concentrations of 2000 and 5000 mg/L (chromium doses of about 85 and 212 mg/kg bodyweight and day), respectively, were mated with untreated males. Body weight of the females wasnot affected. Females of the high dose group had statistically significant decreased relative ovarianand uterus weights. A statistically significant reduction in the number of implants and the number ofviable foetuses was observed (Hartwig, 2009). In male rats treated with chromium(III) chloridehexahydrate in concentrations of 1000 mg/L drinking water (chromium doses of about 24 mg/kgbody weight and day) for 12 weeks before mating with untreated females (1:2) there was astatistically significant decrease in body weights, absolute testis weights, and the absolute andrelative weights of the preputial glands and seminal vesicles. The number of pregnant dams, ofimplants per animal and of living offspring was comparable with the numbers in the controls(Hartwig, 2009).

Chromium (III) has been identified as skin sensitising agent according to WHO (2009) and Hartwig(2009). As reported above, chromium (III) chloride induced skin sensitisation in a guinea pigmaximisation test. Therefore, Cr(III) should be classified as skin sensitising. Therefore, noquantitative and only a qualitative hazard assessment can be performed for local effects afterdermal exposure.


Most critical for the evaluation of long-term toxicity of Cr(III) are local effects in lung seen afterinhalation exposure towards soluble Cr(III). Therefore, a tentative DNEL for comparative riskassessment was derived on basis of the 90-day inhalation toxicity study with chromium sulphate in acomparative manner to the procedure described for chromium trinitrate.

DNEL long-term inhalation exposure, local effects

LOAEC: 3 mg Cr(III)/m3

Dose descriptor starting point: 1.5 mg Cr(III)/m3

AF: 75 (default according to Reach Guidance R.8)

(3 LOAEC to NOAEC, 2 subchronic to chronic exposure, 2.5 interspecies and 5 intraspecies variability)

DNEL: 0.02 mg Cr(III)/m3

9.2.3 Sodium molybdate(VI) dihydrate, CAS 10102-40-6

While sodium molybdate(VI) dihydrate is a possible alternative to SD, also data on sodiummolybdate(VI) (anhydrous, CAS: 7631-95-0) will be reported as toxicity is independent from water ofhydration. Where toxicity is related to elemental Mo, no explicit reference is made in every instanceto what exactly was the species used in the test.


Classification

For sodium molybdate(VI), no harmonised classification according to Annex VI of the CLP Regulationis available. Sodium molybdate(VI) (anhydrous, CAS: 7631-95-0) is registered under REACH. In theregistration dossier, it was recommended to not classify the substance. In addition, no classificationwas recommended in the joint entry of the classification and labelling inventory. Another group ofnotifiers recommended classification as follows:

Figure 9-4: Classification of disodium molybdate

Ecotoxicity


Predicted no effect concentrations (PNECs) as derived according to ECHA-CHEM for sodiummolybdate(VI) (anhydrous, CAS: 7631-95-0) are outlined in Table 9-5. These values are (on anelemental basis) identical to the ones available from ECHA-CHEM for MoO3 (CAS 1313-27-5), whichin aqueous solution is rapidly transformed to the molybdate ion (MoO4

2-) according to the SIDS InitialAssessment Profile for Highly Soluble Molybdenum Salts (SIAP, OECD, 2013).

Table 9-5: Predicted no effect concentrations for different environmental compartments – values fromECHA-CHEM (sodium molybdate(VI) anhydrous)

ECHA-CHEM, based on elemental Mo*

PNECfresh water 12.7 mg/L, AF 3, statistical extrapolation

PNECmarine-water 1.9 mg/L, AF 3, statistical extrapolation

PNECintermittent-releases not derived

PNECSTP 21.7 mg/L, AF 10, assessment factor

PNECsediment 22600 mg/kg sed. dw, EPM

PNECsoil 9.5 mg/kg soil dw, AF 1, statistical extrapolation

* values from ECHA-CHEM were recalculated based on a MW of 205.92 for MoO4Na2 (conversion factor1/2.146)


Derivation of PNECs by species sensitivity distribution is described in detail in the publication byHeijerick et al. (2012). All requirements according to REACH guidance R.10 (ECHA, 2008) are met.The additional assessment factor of 3 on the derived HC5-50% took account of a further NOEC notincluded in the distribution.

PNECSTP is derived by AF 10 from the 3-h EC10 value of an activated sludge respiration inhibition testaccording to the standard.


The PNECfreshwater of 12.7 mg/L (based on elemental Mo) as available from ECHA-CHEM is valid.Derivation of the value is outlined in detail by Heijerick et al. (2012). It is supported by experimentaldata summarised in the SIAP document (OECD, 2013) and the associated conclusion, that “Highlysoluble molybdenum salts category substances do not present a hazard for the environment basedon their low hazard profile.”

Based on the quite extensive data review provided within SIAP (OECD, 2013) we derived aprovisional PNEC for the fresh water environment within this document using the AF method forchronic data based on three trophic levels as outlined in REACH guidance R.10 (ECHA, 2008) forcomparison. A provisional PNECfreshwater derived on basis of the data review included in the SIAPdocument (OECD, 2013) of 4 mg/L could be derived, which is lower by a factor of 3 but of the sameorder of magnitude as the value reported in the registration dossier. This is due to the higher AFapplied when using the AF-method.

With regard to STP microorganism toxicity, also the PNECSTP available from ECHA-CHEM is valid. It isbased on the activated sludge respiration inhibition test, which is most widely accepted as anindicator for combined microbial inhibition in STPs.


The PNECfreshwater of 12.7 mg/L (based on elemental Mo) as available from ECHA-CHEM is valid andwill be used for comparative assessment of sodium molybdate(VI) dihydrate as an alternative to SD.

Regarding sewage treatment plant microorganisms, the PNECSTP available from ECHA-CHEM of 21.7mg/L (based on elemental Mo) is valid and will be used in the assessment of alternatives to SD.

Human toxicity


Sodium molybdate dihydrate (CAS: 10102-40-6) itself is not registered under REACH, but the closelyrelated sodium molybdate (anhydrous, CAS: 7631-95-0) is registered in the tonnage band of 1000-10000 tons/year. The DNELs as derived according to ECHA-CHEM for sodium molybdate(VI)(anhydrous, CAS: 7631-95-0) are outlined in Table 9-6. Further information is given in the SIAP onhighly soluble molybdenum salts (SIAP, OECD, 2013).


Table 9-6: Worker DNELs for sodium molybdate anhydrous (CAS 7631-95-0) – values from ECHA-CHEM(ECHA, 2014)

Route ofexposure



Inhalation not derived 23.97 mg/m3

(about 11.2 mgMo(VI)/m

3)

not derived not derived


Dermal not derived not derived not derived not derived(effect)


No dose-response or assessment factor information is available for the DNEL derivation.

The information on repeated inhalation toxicity in the registration dossier is read across from dataon MoO3 (CAS 1313-27-5). As this substance is rapidly transformed to the molybdate ion (MoO4

2-) inaqueous solution (SIAP, OECD, 2013), it was concluded that molybdenum trioxide can be used asread-across substance for the evaluation of systemic toxicity of molybdate. Information on repeateddose inhalation toxicity is based on the NTP study TR 462: Toxicology and Carcinogenesis Studies ofMolybdenum Trioxide in F344/N Rats and B6C3F1 Mice (Inhalation Studies) (NTP, 1997). The 13-weeks study part of the NTP study (also the registration dossier) reports, both for rats and mice, nochemical related lesions at concentrations up to 100 mg/m3 MoO3 (corresponding to 66.7 mgMo(VI)/m³), the highest concentration tested (6.5 h/d, 5 d/w). However, there were significantincreases in liver copper concentrations in female mice exposed to 30 mg/m3 and 100 mg/m³, as wellas in male mice exposed to 100 mg/m³ compared to those of the control groups. Without anytoxicological or histopathological correlate, these increases are not considered to be adverse (SIAP,OECD, 2013). Thus, the 13-week inhalation study on mice yielded a NOAEC of 100 mg MoO3/m³ (66.7mg Mo(VI)/m³), and a NOEC of 10 mg MoO3/m³ (6.7 mg Mo(VI)/m³).

The chronic study was performed with concentrations of 10, 30 and 100 mg MoO3/m³. The NOAEC inthis study was 10 mg/m3 (6.7 mg Mo(VI)/m³) with respect to alveolar inflammation in the rat. Inaddition, the study report documented a statistically significant and dose related hyalinedegeneration of the nasal respiratory epithelium in all exposed females (0, 10, 30, 100 mg/m3: 1/48,13/49; 50/50, 50/50), which was also evident in males, reaching the level of significance at 30 mg/m3

(2/50, 7/49, 48/49, 49/50).

The local effects observed in the respiratory tract following inhalation of MoO3 were considered inthe SIAP (and obviously also by the authors of the registration dossier) as specific to MoO3 and werenot read across to the soluble molybdenum compounds. Therefore the SIAP focused only onsystemic effects, and the NOAEC value for systemic effects in rats and mice is 100 mg/m3 (66.7 mgMo(VI)/m³).


No information was provided on the toxicological basis of the DNEL for long-term inhalationexposure of workers derived in the registration dossier. Based on the available information from theregistration dossier it is assumed that the DNEL for systemic effects was derived on basis of thechronic toxicity study with molybdenum trioxide in rats and mice, which revealed a NOAEC of 100


mg MoO3/m³ (66.7 mg Mo(VI)/m³), applying a default overall assessment factor of 3 after conversionto a human equivalent concentration of 33.35 mg Mo(VI)/m³).

The underlying study is regarded valid. In line with the SIAP molybdenum trioxide is regarded areasonable read-across substance for the assessment of systemic effects and the default procedureseems to be appropriate in the absence of substance specific data.

There are no data on repeated dose toxicity after dermal application of soluble molybdenum saltsavailable. Dermal absorption can be considered low to negligible (about 0.2%) (SIAP, OECD, 2013).

The registration dossier and the SIAP report a reliable repeated dose rat feeding study (90 daysstudy according to OECD guideline 408, extended for some reproductive endpoints, according toguideline 416). Rats were exposed to 5, 17, 60 mg Mo(VI)/kg bw/d, applied as disodium molybdatedihydrate. This study yielded a NOAEL of 60 mg Mo(VI)/kg bw/day regarding testicular, sperm andoestrous cycle effects. Due to reduced body weight in animals of the high dose group and slightkidney effects (slight diffuse hyperplasia of the proximal tubules) in two females of the high dosegroup the overall NOAEL is 17 mg Mo(VI)/kg bw/day.

A study from the fifties of the past century, cited by EPA IRIS (EPA, 2014), reports retarded weightgain in rats exposed to 2, 8 or 14 mg/kg bw/day as sodium molybdate dihydrate. This effect was notevident in the more actual studies, which are considered to be more reliable as the former data.

Further information on reproductive toxicity is available from an OECD guideline 414 developmentaltoxicity study with rats. Rats were exposed from day 6-20 of gestation to 0, 100, 338, 675, and 1350ppm sodium molybdate(VI) dihydrate in the diet (corresponding to 0, 3, 10, 20 and 40 mg Mo(VI)/kgbw/d) no developmental or maternal effects were observed, resulting in an NOAEL fordevelopmental and maternal toxicity of 40 mg Mo(VI)/kg bw/d (ECHA, 2014; OECD, 2013).

Under consideration of the calculation factors in ECHA guidance R.8 (ECHA, 2012b), the NOAEL ofthe developmental toxicity study can be converted to 70 mg Mo(VI)/m3, (40 mg Mo/kg bw/day : 4(interspecies factor) x 70 kg bw : 10 m3 (respiratory volume per shift)) and supports the findings fromthe inhalation study which reported a NOAEC of 66.7 mg Mo/m3. If the NOAEL of 17 mg/kg bw/dfrom the 90-day oral toxicity study would be converted in a similar manner this would result in a ca.twofold lower NOAEC. However, without in depth evaluation of the original study report the toxicrelevance of the effects in the high dose group, which were obviously not accompanied byhistopathological alterations, remains unclear. Therefore, these data are not considered to be incontrast to the findings in the developmental toxicity and inhalation toxicity study.

There is no inhalation toxicity study available for soluble molybdates. According to the SIAP, localeffects observed after inhalation exposure to molybdenum trioxide are not regarded to be predictivefor soluble molybdates, because for local effects the strong acidification during thedissolution/dissociation reaction of molybdenum trioxide with water is considered to impart theunique irritation potential of molybdenum trioxide, which is probably not observed with solubledisodium molybdate. However, a final evaluation of possible local effects of disodium molybdateafter inhalation exposure is not possible with the toxicity data at hand.

The NTP long-term study further reports a marginally positive trend for alveolar/bronchial adenomaand/or carcinoma in female rats (“equivocal evidence for carcinogenicity”) and increased incidencesfor alveolar/bronchial adenoma and/or carcinoma in male mice (“some evidence forcarcinogenicity”), but MoO3 is not classified with respect to carcinogenicity, neither in the EU (seeabove) nor by EPA or IARC


Acute toxicity of disodium molybdate anhydrate is low. For the rat a dermal LD50 of > 2000 mg/kgbw, an oral LD50 of 4233 mg/kg bw and an inhalation LC50 of 1930 mg/m3 has been reported (ECHA,2014; OECD, 2013). None of the acute inhalation toxicity studies performed with several solublemolybdenum compounds including disodium molybdate revealed any toxic lesion of the lung (ECHA,2014; OECD, 2013) indicating that disodium molybdate does not induce local effects after acuteinhalation exposure.

In addition, no local effects were observed after application of several soluble molybdenumcompounds, including disodium molybdate, to the skin or eyes. Therefore, it was concluded thatdisodium molybdate is not irritating to skin or eyes. In a guinea pig maximisation assay withdisodium molybdate a negative result was obtained, i.e. disodium molybdate dihydrate wasconsidered not to cause skin sensitisation (ECHA, 2014; OECD, 2013).


Based on the data documented above a tentative DNEL for systemic effects after long-terminhalation exposure was derived for molybdenum(VI) on basis of a 90-day repeated dose inhalationtoxicity study performed with molybdenum trioxide (66.7 mg Mo(VI)/m3: NOAEC systemic effectseffects). As there is no evidence for local effects after inhalation exposure, no such tentative DNEL isderived.

DNEL long-term inhalation exposure, systemic effects

NOAEC: 66.7 mg Mo(VI)/m3

Dose descriptor starting point (human equivalent concentration): 33.35 mg Mo(VI)/m3


(2 subchronic to chronic exposure, 2.5 interspecies and 5 intraspecies variability)

DNEL: 1.3 mg Mo(VI)/m3

9.2.4 Sodium Phosphates, CAS 7558-79-4 and 7558-80-7

Sodium phosphates in general are evaluated as (part) of a possible alternative to SD. REACHregistered compounds are disodium hydrogen orthophosphate (CAS 7558-79-4) and sodiumdihydrogen orthophosphate (CAS 7558-80-7), both of which are in equilibrium with each other inaqueous solution and the state of equilibrium solely depends on the pH of the solution. Therefore,they are assessed here together.

Classification

For sodium phosphates, no Harmonised Classification according to Annex VI of the CLP Regulation isavailable. In the registration dossiers of both substances no classification has been recommended.For disodium hydrogen orthophosphate (CAS 7558-79-4) and sodium dihydrogen orthophosphate(CAS 7558-80-7), classification according to classification and labelling inventory (highest to thirdhighest number of notifiers including joint entry) is as follows:


Figure 9-5: Classification of disodium hydrogen orthophosphate and sodium dihydrogen orthophosphate

According to their respective joint entries (REACH registration), these compounds are not classified.

Ecotoxicity


Beyond the REACH registration documents for disodium hydrogen orthophosphate (CAS 7558-79-4)and sodium dihydrogen orthophosphate (CAS 7558-80-7), no further assessment reports coveringecotoxicity could be identified.

REACH dossiers are identical for both compounds with regard to key studies for aquatic ecotoxicityincluding toxicity to STP microorganisms. In addition, the hazard assessment part (derived PNECvalues and assessment factors used) are identical. Therefore, both compounds are treated togetheras “sodium phosphates” without further discrimination.


Table 9-7: Predicted no effect concentrations for different environmental compartments – values fromECHA-CHEM

ECHA-CHEM, sodium phosphates (CAS 7558-79-4 and 7558-80-7)

PNECfresh water 50 µg/L, AF 2000

PNECmarine-water 5 µg/L, AF 20,000

PNECintermittent-releases 0.5 mg/L, AF 200

PNECSTP 50 mg/L, AF 20

PNECsediment not derived

PNECsoil not derived

No toxic effects were observed for both sodium phosphates in reliable acute tests with freshwaterfish, aquatic invertebrates and algae (NOEC ≥ 100 mg/L). Also with sewage treatment plant microorganisms, the NOEC (3h) determined in a reliable activated sludge respiration inhibition testaccording to OECD 209 equals the limit concentration of 1000 mg/L. It is not clear, as to why for bothcompounds in deriving PNECs consistently 2fold higher assessment factors compared to thoserecommended by REACH guidance document R.10 (ECHA, 2008) were used (e.g. for aquatic PNECbased on acute data for three trophic levels AF of 2000 instead of 1000).


Aquatic PNEC values are based on acute aquatic studies for freshwater fish, green algae, andinvertebrates which are regarded as valid. These studies were used as basis for the derivation of thedifferent aquatic PNEC values by applying different assessment factors. The PNECSTP is based on areliable study on activated sludge respiration inhibition according to the standard. As discussedabove it is not clear why generally two-fold higher assessment factors were applied for thederivation of the PNEC values than recommended by REACH guidance document R.10 (ECHA, 2008).

As the decisive PNECs suitable for comparative assessments are PNECfreshwater and PNECSTP these PNECvalues were calculated using standard AF as given in REACH Guidance on Information Requirementsand CSA, R.10 for comparison. The resulting values are:

PNECfreshwater: 100 µg/L

PNECSTP: 100 mg/L


PNECs used for comparative assessments are PNECfreshwater and – for risk assessment regardingsewage treatment plants – PNECSTP.

However, deviating from PNECs reported in the registration dossiers for both sodium phosphates,values derived using standard AFs according to REACH Guidance on Information Requirements andCSA, R.10 are used to provide for comparability of reference values across different compounds:

PNECfreshwater: 100 µg/L

PNECSTP: 100 mg/L


Human toxicity


Disodium hydrogen orthophosphate (CAS 7558-79-4) and sodium dihydrogen orthophosphate (CAS7558-80-7) are both registered in the tonnage band of 10,000-100,000 tons/year. Besides the REACHregistration documents for disodium hydrogen orthophosphate (CAS 7558-79-4) and sodiumdihydrogen orthophosphate (CAS 7558-80-7), there is an older JECFA evaluation on phosphoric acidsand phosphate salts (WHO, 1982).

The DNELs as reported in ECHA-CHEM for disodium hydrogen orthophosphate and sodiumdihydrogen orthophosphate are outlined in Table 9-8.

Table 9-8: Worker DNELs for disodium hydrogen orthophosphate (CAS 7558-79-4) and sodium dihydrogenorthophosphate (CAS 7558-80-7) – values from ECHA-CHEM (ECHA, 2014)

Route ofexposure



Inhalation No-threshold effectand/or no dose-

response informationavailable

4.07 mg/m3

No-threshold effect and/or no dose-responseinformation available

(effect) Repeated dosetoxicity (NOAEC),

overall assessmentfactor: 140

Dermal No-threshold effectand/or no dose-

response informationavailable

Exposure basedwaiving

No-threshold effect and/or no dose-responseinformation available

(effect)


Only a DNEL for systemic effects after long-term inhalation exposure was derived. The DNELs forboth phosphates are identical. As there were no repeated dose inhalation toxicity studies reportedin the registration dossiers, the DNEL was obviously derived by route-to-route extrapolation on basisof an oral study. The key study for repeated oral exposure is a subchronic toxicity study with beagledogs which received sodium aluminium phosphate in concentrations of 0.3, 1.0 and 3.0% in the diet(corresponding to 94.23, 322.88 and 1107.12 mg/kg bw/d in males and 129.31, 492.77 and 1433.56mg/kg bw/d in females). Due to nephrotoxicity observed in animals of the highest dose group (renalconcretions) a NOAEL of 322.88 mg/kg bw/day was derived. The read across was considered to bejustified by the authors of the registration dossier as observed toxicity effects were typical forphosphate but not for aluminium (‘Sodium aluminium phosphate is essentially a sodiumorthophosphate that also contains an aluminium ion. Although aluminium is known to have toxiceffects, the only systemic toxicity observed in the tests performed on sodium aluminium phosphateare not indicative of aluminium toxicity. The addition of aluminium in the phosphate compound isunlikely to have an impact on the use of this data for the sodium and potassium phosphates as anytoxicity observed is due to the phosphate content of the test material.’)

The DNEL was derived by applying an overall assessment factor of 140. No further information wasprovided.


Taking into account the different molecular weights for sodium dihydrogen orthophosphate anddisodium hydrogen orthophosphate (see below) it is astonishing that identical DNEL values werepresented in both registration dossiers. As DNELs are substance based, different numerical valuesshould result for the two phosphates.


The DNEL for systemic effects after long-term inhalation exposure was based on an oral study, asthere are no repeated dose toxicity studies after dermal or inhalation application for phosphates.

The DNEL was derived by applying an overall assessment factor of 140 and probably by conversion ofan oral rat N(L)OAEL into a corrected inhalatory N(L)OAEC to assess human inhalatory exposure aspresented in Figure R.8-3 of ECHA guidance R.8 (ECHA, 2012b). This seems to be an inaccurateness inthe registration dossier, as the conversion for the rat was applied but not the correct conversion fordog data. It is not evident from the dossier how the assessment factor is composed.

Starting from a subchronic oral dog toxicity study a default procedure according to ECHA guidanceR.8 (ECHA, 2012b) to derive a DNEL for systemic effects after long-term inhalation exposure ofworkers would be to convert the dog NOAEL of 322.88 mg/kg bw/day into a human equivalent airconcentration (workers) of 1614.4 mg/m3 (NOAEL : 1.4 (allometric factor dog/man) x 70 kg bw : 10m3/person). Applying an assessment factor of 50 (2.5 for remaining interspecies differences, 5 forintraspecies variability, 2 for extrapolation from subchronic study and 2 for route-to-routeextrapolation), a DNEL of 32.23 mg sodium aluminium phosphate/m3 would result. As DNELs alwaysrefer to the registered substance the DNEL calculated for sodium aluminium phosphate has to betransformed into a DNEL for disodium hydrogen orthophosphate or sodium dihydrogenorthophosphate taking into account the molecular weights of these substances (144.94, 141.96, and119.98 g/mol, respectively). This results in DNEL values of 31.57 mg/m3 and 26.7 mg/m3 for disodiumhydrogen orthophosphate and sodium dihydrogen orthophosphate, respectively, or a DNEL of 21.1mg phosphate/m3 or 6.9 mg phosphor/m3.

The reason for the discrepancy between the default calculation as presented above and the values inthe registration dossiers remains unclear.

The study selected as key study for DNEL derivation seems to be reliable. Several older rat studieswith different phosphates (mostly published before 1970) are reported in WHO (1982), where thelowest level of phosphate that produced nephrocalcinosis in rats was 1% P in the diet. This level wasused as the basis for the evaluation by JECFA: Assuming a daily food intake of 2800 calories a doselevel of 6600 mg P per day was calculated as the best estimate of the lowest level that mightconceivably cause nephrocalcinosis in humans. WHO (1982) derived a Maximum Tolerable DailyIntake of 70 mg/kg bw as phosphor, which is equivalent to 271.2 mg/kg bw/day as NaH2PO4 or 327.6mg/kg bw/day as Na2HPO4. In view of a high susceptibility of the rat to nephrocalcinosis (WHO,1982), these data are in good agreement with the NOAEL of the dog study, used as key study in theregistration dossier.

Acute inhalation toxicity has only been investigated with sodium dihydrogen orthophosphate. Ratswere exposed to dust concentrations of 0.83 ± 0.065 mg/L (gravimetric concentration; nominalconcentration 37.35 mg/L; maximum attainable concentration). No mortality was observed. Duringexposure lacrimation and squinting eyes were observed. Clinical signs noted following the exposureincluded chromodacryorrhea, lacrimation, nasal discharge and squinting eyes. No histopathologicalinvestigations were performed (ECHA, 2014).


Both phosphates are not classified as acutely toxic after oral or dermal exposure, as experimentalinvestigations revealed LD50 values > 2000 mg/kg bw/d (ECHA, 2014).

Tests with both phosphates did not reveal any evidence of skin or eye irritating properties. Nosensitising properties were observed in a Mouse Local Lymph Node Assay with sodium dihydrogenorthophosphate (ECHA, 2014).

Information on reproductive toxicity is available from an OECD Guideline 422 study in rats(Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity ScreeningTest) with dipotassium hydrogen orthophosphate tested at the limit dose of 1000 mg/kg bw/d. Thisstudy did not reveal any effect on fertility or offspring development. The NOAEL for fertility anddevelopmental toxicity derived from this study is 1000 mg/kg bw/d. Developmental toxicity hasbeen investigated with pregnant rats and mice, which received sodium dihydrogen orthophosphateon GD 6-15 by oral intubation in doses up to 410 and 370 mg/kg bw/d, respectively. No maternaleffects or effects on the offspring were observed indicating that the highest dose tested can beregarded as NOAEL for developmental toxicity. Taking these data into consideration the NOAEL fromthe dog study seems also to be protective of possible reproductive toxic effects.


For a comparative risk characterisation of human health after inhalation exposure a tentative DNELfor systemic effects after long-term inhalation exposure was derived. The DNEL was derived byroute-to-route extrapolation on basis of a 90-day repeated dose oral toxicity study with sodiumaluminium phosphate in dogs (NOAEL of 322.88 mg/kg bw/day). In the absence of specific data 50%absorption after oral exposure and 100% absorption after inhalation exposure is assumed.Therefore, a route-to-route extrapolation factor of 2 is used for oral to inhalation extrapolation.

DNEL long-term inhalation exposure, systemic effects

NOAEL: 322.88 mg sodium aluminium phosphate/kg bw/day

Dose descriptor starting point (human equivalent concentration): 1614.4 mg sodium aluminiumphosphate/m3


(2.5 remaining interspecies and 5 intraspecies variability, 2 subchronic to chronic, 2 route-to-route)

DNEL: 32.29 mg sodium aluminium phosphate/m3

corresponding to

31.57 mg disodium hydrogen orthophosphate/m3

26.7 mg sodium dihydrogen orthophosphate /m3

21.1 mg phosphate/m3 or

6.9 mg phosphor/m3


9.2.5 Summary on hazard profiles of alternative substances

In Table 9-9, the tentative PNECs derived for SD and the alternative substances are summarised. Itshould be mentioned that none of the possible alternatives was classified for environmental toxicityhazards whereas SD is classified as very toxic to aquatic organisms after acute (H400) and chronic(H410) exposure. The higher toxicity is reflected in the PNECfreshwater, which is in a similar range as forchromium (III) but at least two orders of magnitude lower than those for phosphate buffer andsodium molybdate.

Table 9-9: Summary of tentative PNECs used for comparative assessment of sodium dichromate andalternative substances

Sodium dichromate(Cr(VI))

Chromiumtrichloride (Cr(III))

Sodium molybdate(Mo(VI))

Phosphates(PO4

3-)

PNECSTP [mg/L] 0.21 0.49 21.7 100

PNECfreshwater

[mg/L]0.0034 0.0047 12.7 0.100

Table 9-10 summarises the tentative D(M)NELs for alternative substances used for the comparativeassessment. The DMEL and DNEL for chromium (VI) and (III), respectively, are based on local effectsas most critical endpoints. The DNELs for sodium molybdate and sodium phosphates are based onsystemic effects, as there was no evidence of any local effects.

The DMEL for chromium (VI) (0.0000025 mg/m3, associated with a remaining risk of 1 x 10E-5) issubstantially lower than the tentative DNELs used for the other substances. Additionally, it should betaken into consideration that none of the possible alternatives is classified for CMR endpoints.Whereas chromium (VI) and (III) may cause skin sensitisation neither sodium molybdate nor sodiumphosphates were classified for skin sensitising properties.

Table 9-10: Summary of tentative worker DNELs long-term exposure used for comparative assessment ofsodium dichromate and alternative substances

Sodium dichromate(Cr(VI))

Chromiumtrichloride (Cr(III))

Sodium molybdate(Mo(VI))

Phosphate buffer(PO4

3-)#

Inhalation D(M)NEL– systemic effectslong-term [mg/m³]

n.d. 0.06 1.3 21.1

Inhalation D(M)NEL– local effects long-term [mg/m³]

0.0000025 0.02 n.d. n.d.

n.d. not derived; the values marked in bold were used for the comparative risk assessment

9.3 Exposure Assessment

9.3.1 Comparative environmental Exposure Assessment

Exposure scenario for use as a processing aid in the production of sodium chlorate and chlorinedioxide

A scenario oriented on ERC4 (Industrial use of processing aids) but based on specific releasefractions was used as outlined in Table 9-11.


Table 9-11: Specific release fractions and STP parameters used for exposure estimation (ECETOC-TRA)

Input parameter Value Unit Comment

Daily amount used at site[kg/d] (release fractions)

[Annual EU tonnage] *1000 / [Releasetimes per year]

kg default according toREACH guidance R.16

Release times per year(d/year)

240 d worst case: 242 to 362for different sites

Local release fraction toair

0 no release to air

Local release fraction tosewage

0.01 1% release to sewage

Local release fraction tosoil

0 No direct release to soil

Use of local STP (yes/no) yes

Local STP with primarysettler?

yes

Sludge to Soil? (yes/no) no The sludge is recycled,incinerated or sent tolandfill

River flow (m3/d) 18000 m3/d default according to

REACH guidance R.16

Effluent discharge rate oflocal STP (m

3/d)

2000 m3/d default according toREACH guidance R.16

Following REACH guidance R.7.13-2 (Environmental risk assessment for metals and metalcompounds), the vapour pressure was set to a very low value (1*10-6 Pa). Estimations wereperformed on the elemental level (i.e. for Cr(VI), Cr(III) and Mo(VI), as also PNEC values were basedon the element.

Input data for exposure modelling

Physico-chemical and environmental fate properties data for SD and alternative substances used forthe exposure estimation are given in Table 9-12.

Table 9-12: Physico-chemical and environmental fate properties data for sodium dichromate andalternative substances (ECHA, 2014, if not stated otherwise)

Substance MW (g/mol) Kpsusp [L/kg] Kpsed [L/kg] Kpsoil [L/kg] Elimination STP Watersolubility[mg/L]

Sodiumdichromatedihydrate

51.996 (Cr) 2,000(acidic)200(alkaline)(ECB, 2005)

1,000(acidic)100(alkaline)(ECB, 2005)

50 (acidic)2 (alkaline)(ECB, 2005)

50% adsorbedto STP sludge50% in effluent(ECB, 2005):Kpsludge 3500(54% sludgeadsorption)

2355 *103

Cr(VI)(20°C)(ECB, 2005)

Chromium(III) chloridehexahydrate

51.996 (Cr) 30,000(acidic)300,000(alkaline)(ECB, 2005)

11,000(acidic)120,000(alkaline)(ECB, 2005)

800 (acidic)15,000(alkaline)(ECB, 2005)

50% adsorbedto STP sludge50% in effluent(ECB, 2005):Kpsludge 20000(82% sludgeadsorption)

585 *103

Cr(III)(20°C)(WHO,2009)


Table 9-12: Physico-chemical and environmental fate properties data for sodium dichromate andalternative substances (ECHA, 2014, if not stated otherwise)

Substance MW (g/mol) Kpsusp [L/kg] Kpsed [L/kg] Kpsoil [L/kg] Elimination STP Watersolubility[mg/L]

Sodiummolybdate(VI)dihydrate

241.95;95.94 (Mo)

2793(OECD,2013)

1778(OECD,2013)

871(OECD,2013)

Assumption:Kp raw SS, Kpsettled SS, Kpactivated SS, Kpeffluent SS =Kpsusp

654.2*103

(20°C)corr. to259.41*10

3

(Mo)

Sodiumphosphates

96.986(H2PO4

-)

Chemical and/orbiologicalphosphateelimination toapprox. 0.5 –1.0 mg/L STPeffluentconcentration

107 (23°C)

Sodium phosphates are used as buffer in combination with molybdate coatings and in combinationwith the processing aid sodium molybdate. In acute aquatic toxicity tests with sodium phosphates(sodium dihydrogen orthophosphate and disodium hydrogen orthophosphate) up to the limitconcentration (100 mg/L) no toxic effects were observed. Based on the investigations up to the limitconcentration a PNECfreshwater of 0.1 mg/L was derived for the phosphate compounds. This value isgenerally below the phosphate concentration, down to which phosphates are eliminated in STPs. I.e.comparing real phosphate concentrations with the PNECfreshwater will always result in RCRs > 1. Takinginto account that huge amounts of phosphate are released into the environment by use of inorganicfertilisers and that phosphates are excreted from the human body a further quantification ofphosphate exposure in the context of this use scenario will not be performed as the total amountreleased into the environment from this use is regarded negligible in comparison to the otherphosphate sources. For example, the European Pollutant Release and Transfer Register reports thatseveral hundred tons of total phosphorus are released per year into the single communal sewagetreatment plants, whereas less than 1 ton phosphate/year would be needed per plant for thisapplication. Further, phosphate is routinely reduced in sewage works to limit eutrophication ofreceiving waters. The resulting phosphate concentration leaving the STP is always above thePNECfreshwater.

Assumed tonnages for the environmental exposure assessment are given in Table 9-13. Based on arealistic default amount of sodium dichromate dihydrate, relative amounts sufficient forreplacement in the relevant process were chosen for the alternatives. Because the exposureestimation was performed on the elemental level, corresponding tonnage levels for the element arealso given for convenience.

Table 9-13: Assumed annual tonnages used for the comparative exposure assessment

Substance Estimated tonnage (tonnes/year)Based on the element

(tonnes/year)

Sodium dichromate dihydrate 1.5 0.52

Chromium(III) chloridehexahydrate

2.7 0.52

Sodium molybdate(VI) dihydrate 2.4 0.95


These annual tonnages were calculated based on the knowledge on the molar concentrations ofCr(VI), Cr(III) and Mo(VI) necessary in the electrolyte for sodium chlorate production and using arealistic default assumption for the yearly amount of SD.

Specific considerations for sodium dichromate and chromium(III) chloride

Scenario for sodium dichromate

For the exposure estimation it has to be considered that chromium VI (Cr(VI)) is converted tochromium III (Cr(III) in the environment), the extent of which being dependant on prevailingenvironmental conditions (ECB, 2005). Under the conditions of acidic soils, sediments and waters (orneutral conditions with high concentrations of reductants) rapid reduction of chromium VI tochromium III is assumed, giving an estimated net result of 97% Cr(III) converted from Cr(VI) and 3%Cr(VI) remaining (ECB, 2005). However, under alkaline conditions (or neutral conditions with lowconcentrations of reductants) a slow rate is assumed for the reduction of Cr(VI) to Cr(III). This holdstrue e.g. for sea water (ECB, 2005). Correspondingly, for comparative risk assessment, we assumealkaline conditions as a worst case scenario (100% Cr(VI), respective Kp-values for suspended matter,sediment and soil were used, see Table 9-12). Alkaline conditions as a worst case scenario issubstantiated by the following reasoning:

Cr(III) is generally less ecotoxic compared to Cr(VI) Cr(VI) is removed by adsorption to sludge to a considerable lower extent in STPs (approx. 50%)

compared to Cr(III) (approx. 80%) (ECB, 2005), leading to a higher relative STP effluentconcentration.

Because there are insufficient data to derive a PNECsediment from experimental studies, per defaultequilibrium partitioning is applied. Because this same method is applied for estimatingconcentrations in sediment, RCRs will by default be identical to the ones calculated for thefreshwater department. Therefore, for comparison to possible alternatives no separate assessmentof sediment will be performed. It has to be considered however that this is, again, a worst caseassumption (same RCR for sediment like the one for freshwater), because the anoxic and reducingconditions in deeper sediment layers will actually lead to a rapid reduction of Cr(VI) to Cr(III).

Scenarios for chromium(III) chloride hexahydrate

Cr(III) is assumed to be essentially stable under environmentally relevant conditions, notransformation reactions to other redox states is assumed (100% Cr(III)).

For the purpose of comparison, two separate exposure estimations were performed, assuming acidicand alkaline conditions, respectively, and using respective Kp-values for suspended matter, sedimentand soil (see Table 9-12). The considerably lower adsorption constants for suspended matter,sediment and soil under acidic conditions leads to a higher RCRfreshwater (approximately factor of 4)compared to alkaline conditions. Therefore, as a worst case, PEC and RCR values calculated for acidicconditions are used for the further comparative assessment.

9.3.2 Comparative human exposure assessment

For an indicative comparison of occupational exposure, task 2 (sampling) was selected since thisconstitutes the task carried out most frequently (daily). SD and all alternatives are non-volatile sothat modelling within ART (Advanced REACH Tool) reflects exposure to aerosol. If all other


determinants, such as the transfer rate of the sampling solution, the room volume and the airchanges per hour are identical (as assumed for this comparison) the exposure concentrationestimated by the model is solely dependent on the concentration of the substance in the electrolytesolution and increases linearly with it. The task-based concentration shown in the following tablewas converted to a time-weighted average (TWA) concentration assuming exposure duration of 30minutes.

Table 9-14: Comparison of occupational exposure during sampling

Substance

Concentration of substance in electrolytesolution

Concentration in air based on ARTmodelling

g/L %* Task-based [ng/m3] TWA [ng/m

3]

Use applied for:sodium dichromate

1.77 (Cr(VI)) 0.126 (Cr(VI)) 11 0.69

Alternative:chromium (III)chloride

1.77 (Cr(III)) 0.126 (Cr(III)) 11 0.69

Alternative: sodiummolybdate

3.17 (Mo(VI)) 0.226 (Mo(VI)) 20 1.2

Alternative:phosphate buffer

3 0.214 19 1.2

* Calculated with a density of 1400 g/L assumed for the electrolyte solution; while this information is specificto current conditions, the same density was also assumed when the alternatives are used, since these are notexpected to alter the density at these low concentrations

Overall, the higher concentrations of (some of) the alternatives in the electrolyte solution directlytranslate into higher exposure concentrations, but the difference is moderate (factor 1.8).

The same holds true for dermal exposure. As solids dissolved in liquids are outside the applicabilitydomain of ECETOC TRA (ECETOC, 2012) a simplified calculation has been performed within the CSRfor dermal exposure. Assuming that the handling of the substance would be comparable to thesituation with SD the final result of dermal exposure depends on the concentration of thealternatives in the electrolyte solution, i.e. the relative dermal exposure between SD and thealternative would be comparable to the inhalation situation.

9.4 Comparative risk characterisation

9.4.1 Results of comparative assessment

Ecotoxicity

Results of environmental exposure and risk assessment are given in Table 9-15. As mentionedabove, RCR values for sediment are identical, because equilibrium partitioning is used to estimateboth, PEC sediment and PNEC sediment. No terrestrial exposure is estimated, because there will beneither direct exposure of soil nor exposure by the sludge to soil pathway (sewage sludge is recycled,incinerated or sent to landfill).


Table 9-15: Local exposure concentrations and risks for the freshwater environment

Compound, assumed environmental conditions Exposure concentration (PEC), [mg/L] RCR

Sodium dichromate dihydrate as Cr(VI) 4.95E-04 1.46E-01

Chromium (III) chloride hexahydrate as Cr(III) 1.38E-04 2.95E-02

Sodium molybdate(VI) dihydrate as Mo(VI) 9.61E-04 7.57E-05

It must be emphasised that assumptions for release and exposure calculations are tentative and arenot meant to represent real conditions at production sites. Rather, the assessment is meant to becomparative and assumptions are identical for all three compounds (with the exception that forboth, sodium dichromate dihydrate and chromium(III) chloride, hexahydrate, worst case scenarioswere calculated by assuming alkaline and acidic environmental conditions, respectively (seeexplanations above)).

Human Health

Table 9-16: Exposure concentrations and risks for workers exemplified for the sampling task

Compound, assumed environmentalconditions

PredictedExposureConcentration[mg/L]

D(M/N)ELLong-term,inhalation exposure[mg/L]

RCR

Sodium dichromate dihydrate as Cr(VI) 0.69 E-07 0.0000025 0.276

Chromium (III) chloride hexahydrate asCr(III)

0.69 E-07 0.02 3.45 x 10E-05

Sodium molybdate(VI) dihydrate as Mo(VI) 1.2 E-06 1.3 9.23 x 10E-07

Sodium phosphates 1.2 E-0631.57 Na2HPO4

26.7 NaH2PO4

21.1 PO43-

3.8-5.6 x 10E-08*

*depending on the basis of comparison (Na2HPO4, NaH2PO4, or PO43-

)

This comparison reveals that the alternatives would result in RCRs several orders of magnitude lowerthan the RCR for SD.

9.4.2 Conclusions

For the comparative assessment of human health and environmental risks of SD and the alternativesubstances the following approach was used:

Available reference values (DNELs, PNECs) were analysed Where no reference values were available, which were derived by similar methodologies to

allow for a comparison, tentative reference values were derived in this report (these values arefor use for this comparative assessment only and are not intended to represent a full assessmentof the substances concerned)

In order to be able to compare substances on a risk basis, an exposure scenario was establishedsimilar to the actual exposure scenario, but generic enough to be applicable to the alternatives

Exposure modelling input data were compiled for all substances Exposure levels and risk characterisation ratios for the environment were calculated using

ECETOC TRA Exposure levels for workers were modelled with ART (Advanced REACH Tool).


Comparison of hazard data (classifications) reveals that none of the alternatives investigated areCMR substances and that none of the alternatives has been classified for environmental hazards.

The tentative risk characterisation shows that the alternative substances have lower RCRs for bothhuman health endpoints (workers) and the environment.

Relevant uncertainties are associated with the rather generic exposure assessment applied here.However, differences between RCRs of SD and the alternative substances are at least one order ofmagnitude for all endpoints and therefore it can be reasonably assumed that this conclusion wouldhold true also under conditions of a refined exposure assessment.

It can be concluded that the alternative substances assessed in detail are beneficial with regard tohuman health considerations. Under the conditions of use assumed here also the comparativeenvironmental risk characterisation leads to the conclusion that there is less risk associated with theuse of the alternative substances.

In conclusion, the analysed alternative substances fulfil the requirement of leading to a reduction inoverall risks to human health and the environment compared to the Annex XIV substance SD, basedon the assumptions used here.

9.5 References for this Appendix

Derelanko, M.J.; Rinehart, W.E.; Hilaski, R.J.; Thompson, R.B.; Löser, E. (1999)Thirteen-week subchronic rat inhalation toxicity study with a recovery phase of trivalent chromiumcompounds, chromic oxide, and basic chromium sulfateToxicological Sciences, 52, 278-288

ECB, European Chemicals Bureau (2005)European Union Risk Assessment Report: Chromium Trioxide, Sodium Chromate, SodiumDichromate, Ammonium Dichromate, Potassium Dichromate. 3rd Priority List, Vol. 53.EUR 21508 EN. European Commission. Joint Research Centre

ECETOC, European Centre for Ecotoxicology and Toxicology of Chemicals (2012)Technical Report No. 114. ECETOC TRA version 3: Background and Rationale for the ImprovementsBrussels, Belgium

ECHA, European Chemicals Agency (2008)Guidance on information requirements and chemical safety assessment. Chapter R.10:Characterisation of dose [concentration]-response for environmenthttp://guidance.echa.europa.eu/

ECHA, European Chemicals Agency (2012a)Guidance on information requirements and chemical safety assessment. Part E: RiskCharacterisation. Version 2.0Helsinki, Finland

ECHA, European Chemicals Agency (2012b)Guidance on information requirements and chemical safety assessment. Chapter R.8:Characterisation of dose [concentration]-response for human health. Version: 2.1online: http://echa.europa.eu/documents/10162/17224/information_requirements_r8_en.pdf


ECHA, European Chemicals Agency (2014)Information on Chemicals - Registered SubstancesOnline: http://echa.europa.eu/web/guest/information-on-chemicals/registered-substances

EFSA, European Food Safety Authority (2010)Scientific Opinion on the safety of chromium picolinate as a source of chromium added fornutritional purposes to foodstuff for particular nutritional uses and to foods intended for the generalpopulation. EFSA Panel on Food Additives and Nutrient Sources added to food (ANS)The EFSA Journal, 8(12):1883, 1-49

EPA, Environmental Protection Agency (2014)Integrated Risk Information System (IRIS)online: http://www.epa.gov/IRIS/

Hartwig, A. (2009)Gesundheitsschädliche Arbeitsstoffe, Toxikologisch-arbeitsmedizinische Begründungen von MAK-Werten, Loseblattsammlung, 46. LfgDFG Deutsche Forschungsgemeinschaft, WILEY-VCH Verlag Weinheim

Heijerick, D.G.; Regoli, L.; Carey, S. (2012)The toxicity of molybdate to freshwater and marine organisms. II. Effects assessment of molybdatein the aquatic environment under REACHScience of the Total Environment, 435–436, 179-187

NTP, National Toxicology Program (1997)Toxicology and Carcinogenesis Studies of Molybdenum Trioxide in F344/N Rats and B6C3F1 Mice(Inhalation Studies). TR 462U.S. Department of Health and Human Services; Public Health Service

OECD, Organisation for Economic Co-Operation and Development (2013)SIDS Initial Assessment Profile for Highly Soluble Molybdenum Salts. CoCAM 5, 15-17 October 2013http://webnet.oecd.org/hpv/ui/handler.axd?id=7584FAAE-4CC2-41F1-AEDD-E3134ACB47A7

Rhodes, M.C.; Hébert, C.D.; Herbert, R.A.; Morinello, E.J.; Roycroft, J.H.; Travlos, G.S.; Abdo, K.M.(2005)Absence of toxic effects in F344/N rats and B6C3F1 mice following subchronic administration ofchromium picolinate monohydrateFood and Chemical Toxicology, 43, 21-29

WHO, World Health Organization (1982)Toxicological Evaluation of Certain Food Additives and Contaminants. Twenty-sixth Meeting of theJoint FAO/WHO Expert Committee on Food Additives. WHO Food Additives Series, No. 17

WHO, World Health Organization (2009)Concise International Chemical Assessment Document No. 76. Inorganic Chromium(III) CompoundsGeneva, Switzerland

WHO, World Health Organization (2013)


Concise International Chemical Assessment Document No. 78. Inorganic Chromium(VI) CompoundsGeneva, Switzerland


10 Appendix 3 – Economic feasibility

The AoA has found that, with the exception of chromium(III) chloride, no alternative to sodiumdichromate has been found to be technically feasible and that for this reason the alternative cannothave any economic feasibility for the applicant. This section explores the situation should thealternatives be assumed to have technical feasibility and the economic feasibility assessed based onthe claims made in the R&D.

10.1 Economic feasibility of sodium molybdate


There are four key investment costs for switching from SD to sodium molybdate:

Access to technology and R&D: Arkema will have to undertake further R&D work before it iscapable of switching to sodium molybdate, as discussed earlier, or acquire rights of access to athird party’s R&D on the technology. '''' ''''''''''''' '''' ''''''''''''''' '''''''#E#''' '''''''''''''' ''''''''' ''''''' ''''''''' ''''''''''''''''''''''''' '''''''' '''''' '''''' ''''' '''''''' ''''''''''''''''''''''

Plant conversion costs: there are two key steps under this:

Disposal of existing electrolyte: the implementation of sodium molybdate would, at aminimum, entail replacing the existing electrolyte brine solution that contains Cr(VI) with anew brine solution containing sodium molybdate and buffer. The existing brine solution thatcontains Cr(VI) would need to be disposed of. In addition, after the removal of the chlorateSD-rich solution, pipes and tanks must be washed; this washing water would contain a lowerconcentration of Cr(VI) and would still require disposal. The cost of the emptying andwashing of the system and of the disposal of the Cr(VI)-containing brine and the wash waterscannot be estimated but it is expected to be modest

Preparation of a new electrolyte: the new electrolyte would need to be generated andwould comprise sodium chlorate, sodium molybdate and phosphate buffer.

Literature suggests that a sodium molybdate concentration of 8 g/L (Li, et al., 2007) wouldbe needed.

Sodium phosphate buffer would also be required due to the poorer buffer range fit ofsodium molybdate in comparison to SD. Based on the patent held by Industrie De Nora(Krstajic, et al., 2007), it is assumed that around 3 g/L of phosphates (32 mmol of PO4

3-)would be required to provide an effective buffer in a chlorate electrolyte. This concentrationcan be achieved by addition of various sodium phosphate salts, such as sodium dihydrogenorthophosphate.

In addition, a concentration of sodium chlorate of 450 g/L would need to be achieved (seeTable 2-1).

The applicant cannot provide a detailed breakdown of the cost of preparing the newelectrolyte but this can be assumed to be modest, yet not insignificant.


Downtime: the time required for the aforementioned actions could be ca. 5 weeks, on theassumption that electrodes would not need to be replaced. If this is assumed to represent5/52 = ca. 10% of the year, then an estimated 10% of turnover (and profit) associated withproduction and sales of sodium chlorate may be assumed to be lost. Based on the actualtonnage sold by Arkema (ca. '#B#''' kt) the overall turnover made in 2012 was ca. €'''#C#'''million. With a production cost of €'''#C#''''' per tonne and a profit margin of ''#C#'%, theaverage market price per tonne of sodium chlorate made by Arkema is ca. €''#C#''''' and theprofit is €''#C#'''/t chlorate. A 5-week downtime would mean two things: ('''' #D#'''''''''' ofthe annual turnover might be lost. This would represent €''''#D#''' million in turnover and€'''#D#''''' million in profit; (b) fixed costs over the same period would still be incurred. Toprovide an indication of this cost, we may consider the on-going costs presented in Table10-1. Of the cost elements included in that table, the following may be considered fixedcosts that would continue even during a period of downtime: Salaries, Costs of meetingworker health and safety requirements, Costs associated with equipment downtime forcleaning or maintenance, Insurance premiums, Marketing, license fees and other regulatorycompliance activities, Other general overhead costs (e.g. administration)24. As the applicantcannot provide detailed information about these costs, a quantified estimate of the fixedcosts over the given downtime period cannot be provided, but such costs should not bedisregarded

- Improvement of oxygen controls: the introduction of N2 gas purging would requireinvestment costs for altering the equipment used for purging and the compression ofhydrogen. This cost has not been estimated yet as the sodium molybdate technology is notconsidered technically suitable. For the purposes of this analysis, it is assumed that thischange would, theoretically, be completed within the 5-week period indicated above.''''''''''''''''''''''' '''''''''' '''''''''''''''''''''' '''' '''''' '''''''''''''''' '''' ''''''''' '''''''''''''''''''''' '''' '''''' ''''''''' '''' '''''''''''''''''''''''' '''' '''''' ''''''''''' ''''' ''''''''''''''''''''#A#''' '''' ''' ''''''''''' ''''''''''''''' '''''''''''''' ''''''''' '''''''''' '''''' ''''''''''''''''''''''''''''' ''''''''''''' ''''''''''''' '''''''''''''''''''''''''

As noted above, total period of downtime of 5 weeks is assumed. During this period, sodiumchlorate production would cease and operations that are linked to the production of sodiumchlorate would also be affected, '''''''''''''' ''''''' '''''''''''''''''''''''''' '''' ''''''''''''''''''' ''''''''''''''''' ''''' '''''''''' ''''''''''''''''''''''''' ''''''''''''''''''' ''''''''' '''''' '''''''''''''''''''''''' '''' ''''''' '#D#''''''''''''''' ''' ''' '''''''''''''''''' '''''''' '''''' '''''''' ''''' ''''''''''''''''''' ''''''''''''''' '''''''' ''''''''''''''' ''''''''''''' ''''''''' ''''''''' ''''' ''''''''''''''''''' '''''''''''''''' ''''''''''''' '''''' ''''''' '''''''''''' ''''''' ''''''''''''''' '''' '''''''''''''''''''

Operating costs

There are many elements that contribute to operating costs, but as already noted, energy is themain cost of the production process. The following table presents the range of different operatingcost elements and provides a comparison of the costs arising under SD and under sodiummolybdate. This table has been jointly developed for the members of the consortium of sodium

24Clearly some of the other variable costs would still be incurred during downtime (i.e. the plant will stillconsume some electricity, water, etc.) but for simplicity, this is disregarded.


chlorate manufacturers, but where appropriate the information has been replaced with applicant-specific information, which is claimed as confidential.

Table 10-1: Comparison of operating costs for production of sodium chlorate between sodium dichromateand sodium molybdate



product

Change due to use of sodiummolybdate


Electricity '''''''''#C# ''''''''''' ''''''''''''' ''#D#''''''''''''''''*

Oil and gas Minor component No change expected


Cost of SD Minor component '''''#D#'''''''', +1,170% formolybdate salt.'''''#D#''''''' for addition ofphosphate buffer


Minor component Increase due to the use of inert gasto limit oxygen concentration inhydrogen gas to safe levels

Water Minor component No change expected


Minor component Elimination of Cr(VI) in sludge, butwaste would still be hazardous

Transportation of product to customer Minor component No change expected


Minor component Increased cost for anoderecoating/replacement due to thepresence of phosphates





Minor component No major change expected



Minor component Short-term cost increases forsampling and monitoring; unclearmaintenance requirements


Minor component Cost increases likely due to morefrequent anode recoating/replacement


Insurance premiums Minor component Additional costs cannot bequantified


Minor component Reduced with respect to REACHregulation (no need for anAuthorisation)



Overall costs (% change) '''''#C#'''''''' '''''''''''''''#D# '''''''''''''''''''' ''''''''''''

* Assuming electricity consumption is directly proportional to cost


Energy cost: Arkema does not consider sodium molybdate as a technically feasible alternative to SDand they cannot estimate their specific costs with certainty. As described in the above section ontechnical feasibility, the use of sodium molybdate would result in a '''#D#'''''% increase in electricityconsumption (from '''''#C#''''' kWh/t for the applicant to 5,746 kWh/t theoretical). If it is assumedthat the cost of electricity is directly proportional to consumption, this also represents a '''#D#''%increase in the cost of electricity. If we also take that '#C#''''% of the total production cost of sodiumchlorate for Arkema is due to electricity, the total increase in production cost would be ''#D#''''% dueto electricity alone. In money terms, a '''''#D#''''% increase in energy costs would translate into aproduction cost increase of €'''''''' '' '''#D#''''''' ''' ''''''''''' per tonne of sodium chlorate.

The increase in electricity costs would therefore increase the total cost of production from €''''#C#''''to €'''#D#'''' per tonne of sodium chlorate. To give the magnitude of this additional cost for theapplicant, it is worth remembering that Arkema’ sodium chlorate production in 2012 was ''#B#''' kt.Using the ''#B#''' kt figure, the additional cost of €''#D#'''/t sodium chlorate would mean anadditional cost/reduction in profits of ca. €''#D#'''''''''''' per year. '''''''' ''''''''''''' ''''''''''''#D#'''' ''''''''''''''''''''''' '''''''''''''''' ''''''''''''' '''''''' ''''''''''''''' '''''''''''''''' ''''' ''''''' '''''''''''''''''''''

Material and service costs: other process cost components are generally minor and it would beexpected that most of them would not change significantly with the use of sodium molybdate. Thefollowing may be noted:

Cost of sodium molybdate: the cost of the additive itself however would change. Publiclyavailable price data is provided in Table 10-2. This suggests a price of ca. €11,000 per tonne,significantly higher than the assumed price for SD of €1,540/tonne. If it is assumed that SD isused at 4.5 g/L of electrolyte (mid-range of 3-6 g/L in the BREF) and that sodium molybdate isused at 8 g/L of electrolyte as proposed by Li et al (2007) and that the average prices of SD andsodium molybdate are €1,540/t and €11,000/t respectively, then the percentage increase inadditive per litre of electrolyte is ca. 1,170%. As noted earlier (under the discussion on CrCl3),given the consumption of SD of '''#B#''''' kg/t sodium chlorate, the consumption of sodiummolybdate would be 8/4.5 = 1.78 times higher than SD, or ''#D#''''' kg per tonne of sodiumchlorate. With an annual production of sodium chlorate of ca. ''#B#''' kt, the additional annualcost from the replacement of SD by sodium molybdate would be ca. €'''''''' ''#D#'''''''''' per year or€''''#D#''''' per tonne of sodium chlorate. This is clearly much lower than the main cost elementof increased energy consumption.

Table 10-2: Cost of sodium molybdate (Alibaba.com, 2 April 2014)


(t/y)Minimum order


1 China 99 600 0.1 8,786-10,250

2 China 99 800 0.001 10,982-18,304

3 China 99 24,000 1 9,225-10,250

4 China 99 18,000 0.1 8,786-10,103

5 China 99 5,000 0.001 5,857-13,179

6 China 99 500 0.001 7,321-21,964

7 China 99 1,200 0.1 13,179-18,304

8 China 99 6,000 0.001 8,786-13,179

9 China 99.5 5,000 0.001 7,321-14643

10 China 99 3,600 1 10,982-21,964

11 China 99.9 3,000 0.001 10,250-14,643

Range (€/t) 5,857-21,964




Cost of phosphate buffer: the use of sodium molybdate as an alternative would require theaddition of additional buffer, due to the poorer buffer range fit of sodium molybdate incomparison to SD. Based on the patent held by De Nora (Krstajic, et al., 2007), it is assumedthat around 3 g/L of phosphates (32 mmol of PO4

3-) would be required to provide an effectivebuffer in a chlorate electrolyte – it must be noted that such a very high concentration (by typicalstandards in electrolytic cells, would have significant adverse effects on the durability of theanodes (Kus, 2000). This concentration can be achieved by addition of various sodiumphosphate salts, such as sodium dihydrogen orthophosphate. In order to achieve thisconcentration of phosphate (PO4

3-), 4.9 g/L (32 mmol) of sodium dihydrogen orthophosphatedihydrate (NaH2PO4·2H2O) is required. The rate of consumption of the phosphate is not knownbut it can be assumed to be similar to that of SD, with proportionality to the concentration in theelectrolyte: for a consumption of ''#B#'''' t/y of SD, the corresponding consumption of phosphatewould be around ''#D#'''' t/y.

At the median price shown in Table 10-3, this amounts to some €''''''#D#''''' per year or €''''#D#''''per tonne of sodium chlorate produced (using a sodium chlorate production tonnage of'''''#B#''''''' t/y). Clearly, this is a minor additional cost element.

Cost of environmental services: it might be construed that the environmental service costscould decrease because there would no longer be a need to dispose of Cr(VI)-containing sludge.However, the amount of hazardous waste would arguably not decrease. The same amount ofsludge would be formed and due to the presence of NaClO3 the waste would remain hazardouseven in the absence of dichromate.

Cost of inputs for control of oxygen evolution: there would also be an increase in costs due tothe need to provide nitrogen gas to limit the oxygen concentration in the hydrogen. This costhas not been possible to quantify. On the other hand, the use of N2 purging with the aim tocontrol the concentration of O2 in H2, would have an impact on the quality of hydrogen'' '''''''' ''''''''''' '''''''' '''' ''''''''''''''''' '''''''''''''''''' ''''' ''''' '''' #A# & #D#'''''' ''''''''''' ''''' '''''''''''''''''''''' '''' ''''''' '''''''''''''''''''''''' '''''''''''' '''''' '''''''''''' ''''' '''''''''''''''''''''' '''' ''''''' ''''''''''''''' ''''''' '''''' '''''''''''''''''''''' '''' ''''''' '''''''''''''''' '''''''''''''''''''''''' '''''''' ''''''''''''''''''''''''' ''''''''''' '''''' ''''''''''''''''''''' ''''''''' '''''''' '''''''''''''''''''''' ''''' ''''''' '''''''''''''''''''''''''''''''''''' '''''''''''''''''''''' '''''''''''''''''''''' ''''' '''''' ''''''' '''''''''''''''' '''''''' '''''' '''''''''''''''' '''''''''''' ''''''''''' '''''''''''''''''''''''''''''' ''''''''''''''''''''''''' ''' ''''''''''''''''''' '''''''''' '''' ''''' '''''''''''''''''' ''''''''' ''' ''''''''' ''''''''''.

Table 10-3: Cost of sodium dihydrogen orthophosphate dihydrate (Alibaba.com, 2 September 2014)


(t/y)

Minimumorder


1 China 98% 10,000 1 763-1,525

2 China 98-99% 600 1 771-1,125

3 China 99% 3,000 20 991-1,085

Range (€/t) 763-1,525

Average price (€/t) 1043

Median price (€/t) 948


Replacement parts: anode recoating and replacement is likely to occur more often due to thepossible need to add phosphate. This cost has not been quantified.

Labour costs: no real changes would arise in labour costs.

Maintenance costs: the long term-effect of sodium molybdate and phosphate buffer on the lifetimeof electrodes and equipment has not been evaluated, as the applicant is not aware of any scale-uptrials that would allow this to be evaluated. In the short term, the cost of sampling and monitoringthe process could be foreseen to increase in order to gain further process experience. Followingthis, it is expected that the significantly adverse effects of increased concentrations of phosphateson the anodes would require more frequent replacement of the anodes, thus increasing the overallcost of maintenance.

Other costs: if sodium molybdate and phosphate were used in high concentrations to avoid any useof Cr(VI), there would be a reduction in the cost of meeting REACH Regulation requirements asfuture Authorisation applications would be avoided. Finally, the increased generation of oxygen (tobe controlled by N2 purging) would clearly increase the explosion hazard profile of the plant and thiscould affect the insurance premiums for the applicant. All these administrative costs are notpossible to quantify, but are likely to be lower than the key cost of increased energy consumption.


The use of sodium molybdate (in conjunction with phosphates) is clearly an economically infeasiblealternative. Apart from the cost of further developing and implementing this alternative, its usewould increase the cost of energy by a significant margin (ca. '#D#'''''%) which will increase theoverall production cost by ca. '''#D#''''%. This would have a serious impact on the profitability ofArkema’s operations. Sodium chlorate is a commodity chemical available from both EU-based andnon-EU suppliers and is sold on the basis of margin and logistics. When sodium molybdate is used,the production cost increases from €''#C#''''' to €'''''#D#'''''' per tonne of sodium chlorate. The priceat which the applicant was selling sodium chlorate in 2012 was, on average, €'''#C#'''' per tonne. Itmust be noted that not all cost increases have been quantified; therefore, this is a conservativeestimate. ''''''' '''''''''''''''''''' ''''''''' '''''''''''''''' ''''''''''''''''''' '#D#''''' '''''''''''''''''''''' '''' ''''''''''''' '''''''''''''''''''' '''''''''''''''''''''''''''''''' '''''' '''''''''''''''''' ''''''''''' '''''''''''''' '''' '''''' ''''''' '''''''''''' '''''''''' ''''''' ''''''''''''''''''' '''' ''''''''''''' '''''''''''''''''''''''''''''''''''''' The commodity nature of the chlorate means that passing on the additional productioncost to customers would be very difficult. Moreover, ancillary operations that rely on the hydrogenreleased from the chlorate reaction would be impacted. ''''''' '''''''' ''''''''''''' '''' '''''''''''''''''''' '''''''''''''''''''''''''' '''' ''''''' '''''''''''''''''''' ''''''''''''' ''''''''' ''''''''''''''''' '''''''''''' '''''''''' '''#D#' '''''' '''''''' '''' ''''''' '''''''''''''''' '''''''''''''''' '''''''''''''' ''''''''' ''''''' ''''''''''''''''''' ''''''''''''''' '''''''''''' ''''''''''''' ''''''''''''' ''''' ''''''''''''' ''''' '''''''' '''' ''''''' ''''''''''''''''''''''''' ''''''''''''''''' '''''' ''''''''''''''''''''''''

Unless R&D identifies, develops and scales up the use of sodium molybdate at an optimalconcentration and, potentially, in the presence of additives which help control the increase in energyconsumption and oxygen generation without the need for a phosphate buffer at highconcentrations, it would appear impossible to substantially improve the economic feasibility of thisalternative.


10.2 Economic feasibility of molybdenum-based coatings


There are two key investment costs for switching from SD to molybdate-coated cathodes:

Access to technology and R&D: the molybdenum-coated cathodes technology is far from beingmature as it has not been successfully demonstrated at a scale relevant to the commercialproduction of sodium chlorate. Therefore, R&D further to what is currently published will berequired before this technology could be implemented on the applicant’s plant. If suchtechnology that can deliver SD-free chlorate production is patented by a third party, the cost ofobtaining the rights to the patent would need to be factored in but it is impossible to estimate atpresent. ''''' '''''''''''' '''' ''''''''''''''' ''''''''''' '''''''''''''''' '''''''' #E#''''''' '''''''''' '''''' '''''''''''''''''''''' ''''''''' '''''' '''''''''' ''''''' ''''''''''''''''''''

Plant conversion costs: there are six key steps under this:

Disposal of existing electrolyte: as in the case of the implementation of sodium molybdate,the implementation of molybdate-coated cathodes would, at a minimum, entail replacingthe existing electrolyte brine solution that contains Cr(VI) with a new brine solutioncontaining buffer. The existing brine solution that contains Cr(VI) would need to be disposedof. In addition, after the removal of the chlorate SD-rich solution, pipes and tanks must bewashed; this washing water would contain a lower concentration of Cr(VI) and would stillrequire disposal. The cost of the emptying and washing of the system and of the disposal ofthe Cr(VI)-containing brine and the wash waters cannot be estimated but it is expected to bemodest.

- Preparation of a new electrolyte: the new electrolyte would need to be generated andwould comprise: sodium chlorate and phosphate buffer. The discussion presented above forsodium molybdate would be relevant here. The applicant cannot provide a detailedbreakdown of the cost of preparing the new electrolyte but this can be assumed to bemodest, yet not insignificant.

Plant downtime: in order to begin using this technology, all of the electrodes and cathodicboxes (electrolysers) would need to be replaced. ''''''' ''''''''' '''''''''''''' ''''' ''''''''''''''''' '''' ''''''''''''''''''''' ''''''''''''''''' ''''''''' ''' ''''''''''' ''''''' ''''''' '''''''''' '''''''''''''''' '''' '''''''''''''''''''''' '''' ''''''''''''''''' ''' '''''''''''''''''''''' ''''''' '''''''''''''' ''''''' ''''''''''' '''''' ''''' ''''''''''''''' ''''''''''''''' ''''''' ''''''''' '''''''''''''''''''''''''''''''' '''''''''''''''''''''''' ''''''''''' ''''''''''''''''''' '''' ''''''''''''''' '''''''''' '''' ''''''' ''''''''' ''''''' ''''''' ''''''''''''''''''' '''''''''''''''''''''''''''''''''''''''''' '''''''''''''''' ''''''' ''''' '''''''''''''''''''''''''''''''' '''''''''''''''' '''''''''''''' '''''''' '''''' '''''''''' ''''''''''' ''''''''''''''''''' '''''''''''''''''''' '''''''''''#A# & #D#''''''' ''''''''''' ''''''' ''''''' '''''''''''''' '''' ''''''''''''''''''''''''''''''''''''''' '''''''''''' '''''''''''''' '''''' '''''''''''''''''''''''' '''' ''''' '''''''''''''' '''''''''''''''''' '''' '''''''''''''''''''' ''''''''''''''''''''''''''''''' '''''' ''''''''''''''''' '''' '''''''''''''' ''''''''''''' ''''' ''''''''' '''''''''''''''''''''' ''''''' '''''''''' ''''''''''''''''''''' '''''''''''''''''' ''''''''''''''' '''''''''''''''''''''''''' ''''''''''''''''''' ''' ''''''''''' ''''''''' '''''''''''''''' ''''''''''''''''''''''''''''' ''''' ''''''''' '''''''''''''''''''''''' ''''''' ''''''' ''''' '''''''' '''''''''''''''''''''''''''''''''''' ''''''''''''''''''''' ''''''''''''''''' ''' '''' '''''''''' ''''''''' ''''''''''''''' '''''' ''''' '''''''''''''' '''' ''''''''''''''''''' ''''''''''''' ''''' '''''''''' '''''''''''''''''''' '''' ''' ''' '''''' '''''''''''''''''' ''''''''''''''' '''''''''''''''''' ''''''''''''''''''' '''''''''''' '''''' '''''''''''''''''''''' ''''''''' '''''' ''''''''''''''' ''''''''''''''''''''' ''''''' ''''''''''''''''''''''''' ''''' ''''''''' ''''''''''''''''''' '''' '''''''' '''''''''' ''' '''''''''''''''''''' '''' ''''''' ''''''''''' '''''''''''' '''''''''' '''''''''''''''''''''''''''''''''' '''''' '''''''''''''''' ''''''''''' '''' ''''''''''''''''''' ''''''''''''' ''''''''''''''' ''''''' ''''''' ''''''''''' ''''''''''''''''''''''''''''''''''''' ''''''' '''''''''''''' '''''''''''''''''' ''''''' '''''''''''''''''' ''''''''''''''''''''' ''''''''''' ''''' ''''''''''''''' '''' '''''''''''''' '''' '''''''''''''''''''''' '''''' ''''''''''''''''''''''''' '''''''''' ''''' ''' '''''''' '''''''''' '''''''''''''''''''''' '''''''''''


Assuming a X#D#X month period, the reduction in annual chlorate production caused by aloss of X#D#XX months production is equivalent to a loss of ''''''''''#D#''''''' kt of chlorateproduction (assumed to equate sales) for the applicant (based on production/sales of ''#C#'''kt/year). This would reduce turnover by ca. €'''''''''''''''#D# ''''''''''''''' Based on a profit marginof ''''''' ''''''''' ''''''' ''''#D#'''''' '''' ''''''''''''' '''''''''''''''' as mentioned above, the lost profit duringdowntime from loss of sodium chlorate sales alone would be €'''''''''''''''''''#D# '''''''''''''''Additional fixed costs over the given downtime period would also arise but cannot bequantified. Arkema does not believe that its chlorate business unit could sustain a ''#D#'''''month shutdown; therefore, the implementation of this technology would risk the entireplant.

Acquisition of replacement equipment: the cost of materials (new electrodes) is challengingto estimate due to the experimental nature of the technology in its current state. It is alsonot known whether it would be best to replace either the cathodes boxes alone or the entireelectrolysers. We hereby provide a simple calculation of the cost of replacing the cathodesalone, which may be a gross underestimation of the actual cost.Based on existing technology, the typical cost of a single anode is in the region of €120, witha similar cost for a cathode. Coated cathodes could be expected to be more costly, but inthe absence of information on this, we will assume that the new, coated cathodes would beof a similar price per unit. The applicant is a large producer of sodium chlorate and employs'''#A#''''''' cathodes. Therefore, a conservative estimate of the cost of the new cathodesalone could be ca. €''''''' ''' '''''''''#D#' '' '''''''' '''''''''''''

Cost of installing new equipment (engineering cost): it is assumed that the applicant wouldaim to replace all cathodes within the timeframe of the aforementioned downtime, i.e. 3-6months, and this would include the activation of the new cathodes. This cost has not beenquantified

Impacts on ancillary operations: other integrated facilities would be affected. For theapplicant these include ''''''' '''''''''''''''''''''''''' ''''' ''''''''''''''''''' ''''''''''''''''' ''''''' ''''''''''''''''' ''''''''''''''''''''' ''''''' '''''' ''''''''''''''''''' ''''''''''''' ''''''' ''''''''''''''''''''' '''' ''''''' '''''''''''''''' '''''''''' ''''' ''' ''''''''''' '''''''' ''''''''''''''''''''''''''' ''''''' '''''''' '''''''''''''''''' ''''''' ''' ''''''''''''''#A# & #D#' ''''''''' '''''' ''''''''''''''' '''''''''''''''''''''''''''''''' '' ''''''''''''''''''' '''' ''''''' '''''''''''''''' '''''''''' '''''' '''''' '''''''''''''''' '''''''''''' '''''''''' '''''''' '''''''''''''' '''''''''' '''''''''''''' '''''''''''''''' '''''''''' '''' ''''''' '''''''''''''''' ''''''''''''''' ''''''''''' '''''''''''' '''''''' ''''' '''''''.

Finally, the control of oxygen evolution might need to be improved, possibly through the use of N2.The changes required have not been costed as it is not clear what intervention would in fact beneeded.

Operating costs

There are many elements that contribute to operating costs, but as already noted, energy is themain cost of the production process. Table 10-4 presents the range of different operating costelements and provides a comparison of the costs arising under SD and under the use of molybdate-coated cathodes. This table has been jointly developed for the members of the consortium ofsodium chlorate manufacturers, but where appropriate the information has been replaced withapplicant-specific information, which is claimed as confidential.


Table 10-4: Comparison of operating costs for production of sodium chlorate between sodium dichromateand molybdate based coatings



product

Change due to use of molybdatebased coatings


Electricity '''''''''#C# ''''''''''' ''''''''''' #D# ''''''''''''''*

Oil and gas Minor component No change envisaged


Cost of SD Minor component '''''#D#''''''' - Assumed that no SDwould be required (this has notbeen proven yet).''''''#D#'''''''' for Addition ofphosphate buffer


Minor component No change envisagedPotentially increase due to the useof inert gas to limit oxygenconcentration in hydrogen gas tosafe levels

Water Minor component No change envisaged


Minor component Elimination of Cr(VI) in sludge, butwaste would still be hazardous

Transportation of product to customer Minor component No change envisaged


Minor component Increased cost for anoderecoating/replacement due to thepresence of phosphates



Minor component No change envisaged


Minor component No significant change envisaged



Minor component Increased until sufficient processexperience has been gained


Minor component Unknown


Insurance premiums Minor component No change envisaged





Overall costs (% change) '''''#C# '''''' '''''''''''''' ''''''#D# ''''''''''' ''''''''''


Energy cost: as already discussed in the above section on technical feasibility, the use ofmolybdenum-based coatings has the theoretical potential to reduce the energy consumption of the


process by ''''#D# '''% (from an applicant-specific '''''#C# ''''' kWh/t down to a theoretical 4,342kWh/t). In the absence of information from the use of the technology at the industrial scale, we mayapply this reduction to the electricity bill for the applicant (assuming that electricity accounts for''#C# ''''% of Arkema’s production costs). This, would suggest that production costs could reduce by€''''''' ''' '''#D#'''''''' ''' '''''' '''''''''' per tonne of sodium chlorate produced, representing a reduction ofoverall production costs of ''#D#''''%.

If it were to be assumed that Arkema would not reduce the sale price of sodium chlorate, which iscurrently assumed to stand, on average, at €''''#C#''' per tonne, and thus translate the reduction inproduction costs into additional profit, at the new increased margin Arkema would earn anadditional €''''#D#''''/tonne of chlorate sold which at a sodium chlorate production/sales level of''#D#''' kt/y would translate into an additional ca. €''#D#'''' million per year. This is clearly atheoretical calculation because the technology has not been proven at the industrial scale. Thistheoretical reduction in costs should not detract from the fact that implementation of thetechnology would require a significant investment cost.

Cost of materials and service costs: the initial cost of materials is discussed above. Additional on-going costs (or savings) would include:

Savings from the non-use of SD: it has been explained that the consumption of SD is ''''#B#'''''kg/t sodium chlorate, so with an annual production of ''''#B#''''''''' tonnes and an assumed marketprice of SD of €1,540 per tonne, the cost savings would be ca. €''''#D#''''''''/y

Cost of phosphate buffers: as described above for sodium molybdate, sodium phosphate bufferat a concentration of 4.9 g/L would need to be employed in the electrolyte. Using the sameapproach the cost of additional buffer can be expected to be €'''''#D#'''''' per year or around€'''#D#''''' per tonne of chlorate produced

Cost of environmental services: it might be construed that the environmental service costscould decrease because there would no longer be a need to dispose of Cr(VI)-containing sludge.However, the amount of hazardous waste would arguably not decrease. The same amount ofsludge would be formed and due to the presence of NaClO3 the waste would remain hazardouseven in the absence of dichromate

Cost of inputs for control of oxygen evolution: there might also be an increase in costs due tothe need to provide nitrogen gas to limit the oxygen concentration in the hydrogen'' '''' ''''''''''''''''' ''''' ''''''''''' ''''''''''''' '''''''''''' '''''''' '''''' '''''''''''' '#D#''' ''''''' '''''' '''''''''''''''''' '''''' '''' ''''''' ''''''''''''''''''''''''''''' '''''''''''. Given the uncertainty over whether such oxygen controls would indeed be needed, anestimate of the impacts on ancillary operations/revenue streams is not elaborated here

Replacement parts: anode recoating and replacement is likely to occur more often due to thepossible need to add phosphate. This cost has not been quantified.

Labour costs: no significant changes are envisaged.

Maintenance costs: there are no data available on the likely lifetime of molybdenum-coatedcathodes, as the technology has not yet been demonstrated.

Other costs: if this technology were to be technically feasible and avoid any use of Cr(VI), therewould be an elimination of the cost of meeting REACH Regulation requirements, as future


Authorisation applications would be avoided. On the other hand, if the applicant needed to obtain alicence for using patented technology developed by a third party (as noted earlier, Industrie De Norahave filed a patent application (Krstajic, et al., 2007) which, as of 14 October 2014, does not appearto have been granted yet25), this may have require the ongoing payment of fees. These are notpossible to estimate at present.


As this technology is unproven with a third-party patent application on this technology pending, thediscussion on its economic feasibility can only be a theoretical one.

Even if the very significant technical hurdles were to be overcome with additional research and scaleup of the technology, which would certainly require a significant time, a sufficiently longtransition/conversion period would be needed for the orderly gradual replacement of electrodeunits that respects the typical electrode lifetime at a sodium chlorate plant. If such a conversionperiod were not be available, the costs associated with an accelerated cathode replacement wouldbe very significant, as this would result in loss of production and sales of sodium chlorate. For theapplicant, the cost of downtime and of the replacement of the existing cathodes would be very high.Revenues from ancillary operations would also be affected during conversion with a significantturnover potentially lost in the assumed 3-6 months of downtime. These very high upfront costsmake this, as yet unproven, technology economically infeasible.

With regard to operating costs, if assertions made in a relevant published patent application provecorrect and if elimination of Cr(VI) were to become possible, this technology could reduceproduction costs. However, this has not been proven at the industrial scale and any reliance onthese claims would certainly be premature. Irrespective of the potential changes in energyconsumption, the periodic replacement of anodes would be necessary due to their impaireddurability in the presence of significant concentrations of phosphates. Moreover, if there was aneed for better controls on oxygen evolution, the costs associated with such controls (cost of N2

purging and impacts on ancillary operations) could seriously impact upon the applicant’s profitabilityand revenue streams.

These costs make this – yet unproven – technology economically infeasible.

10.3 Economic feasibility of two-compartment electrolytic systems


There are four key investment costs for switching from SD to two-compartment electrolytic systems:

Access to technology and R&D: ''''''''''''' '''''' ''''''''''''' '''''#E#'''''''''''''''''' '''''' '''''' ''''''' ''''''''''''''''''''''''''''''''''''''' '''''''' ''''''' ''''''''''''' '''''''''' '''''''''' ''''''''''''''''''' '''''''''''''' ''''''''''''''''' ''''''''''''' ''''' '''''''' '''''''''''''''' ''''''''''''''''' ''''' ''''''' '''''''''''' '''' ''''''' ''''''''''''''''''' ''''''''''' ''''''''''' ''''''''''''''''''''''

Building a new plant: the existing single-cell electrolysers would become obsolete and wouldneed to be replaced. A new membrane-based two-compartment plant similar to a chlor-alkali

25Based on the data available at the European Patent Office,https://register.epo.org/application?number=EP06819847 (accessed on 14 October 2014)


plant would need to be constructed and retention systems for Cl2 for the production of chloratewould be necessary. Essentially, the implementation of a new plant by Arkema would involvethe replacement of its existing facilities, at a very significant cost.

''''''''''''''''' '''' ''''''''''''''''''' ''''''''''''''''''' ''''''''''''''''''''''''''''''' '''' ''' ''''''''' ''''''''''''''''''' '''''''''' ''''''''''' '''''''''' '''''''''''''''''''''''' ''''''''''''''''' '''' ''''''' ''''''''''''''' '''''''' ''''#E#'''''''''''''' '''''''' '''' ''''' ''''''''''''''''''' ''''''''''''' '''''''''''''''''''''' ''''''' '''''''''''''''' '''''''''''''''' ''''''''' ''' '''' '''''''''''''' ''''''' ''''''''' '''''''''''''''' ''''''''''''''''' '''''''''''' '''''''''''' '''''''''''''''''''''''''' ''' '''''''''''''''''' '''''''''' ''''''''''''' '''''' ''''''''''''''''''''' ''''' '''''''''''''' ''''' ''''''''''' '''''''''''''''''' ''' '''''''' ''''''''''''' ''''''' ''''''''''''' '''''' ''' '''''' ''''''''''''''' '''''''''' '''' '''''''''' '''''''' ''''''''''''''''''''''' '''''''' ''''''' ''''''''''''''''''' ''''''' ''''''''''''''''''''''''''''''''''' '''''''''''''''''''''' ''' '''''''' ''''''''''' '''''''''' ''''''' ''''''''' '''' '''''''''''''''''''' '''''''''''''''''''''' '''' ''''''''''''''''''''''''' ''''''''''''''''' ''''''' ''''''' ''''''' '''''''''''''''''''''''''' '''''''''' ''''' ''''''' '''''''''''''''' '''''''''''''' '''''''''''''' '''''''''' '''''''''''''''' ''''''''''''' ''''' ''''''' ''''''''''''''' ''''''''''''''''''' ''''''''''' ''''' ''''''''''' '''''''''''' '''' ''''''''''''''''''''' '''' ''' ''''''''''''''' '''''''''''''''' '''''''' '''' ''' '''''''' '''''''''' ''''''''''''' '''''' '''''''''''''''''''''''''''''''' ''''''''''''''''''' '''''''' ''' '''''''''''''''''''' ''''''''''''''''''''''''''''''''''' '''' ''''''' '''''''''''''''' '''''''''''''' '''' ''''''' ''''''''''''' ''''''''''''''' '''''''''' '''''''''' '''''''''''' ''''''''' ''''''''''''' '''''''''''' '''''''''''' ''''''''''' ''''' ''''''' '''''''''''''''' ''''''''' '''''''''''' ''''' '''''''''''''' Additionally, during the period ofdemolition-construction, the turnover made from ancillary operations ''''''''''''''#C#'''''''''''''' '''''''''''''''''''''' '''''''''''''''''' would be lost

Worker training: there would be a requirement to retrain workers in the operation of a newand unfamiliar plant

Existing equipment/plants becoming redundant: as noted above, the existing sodium chlorateplant of Arkema would need to be replaced and past investment would be lost, although someparts of the plant could potentially be reused. ''''''' '''''''''''''''''''' '''''''' '#D#''' ''''''' ''''''' ''''''''''''''''''''''''''''' ''''''''''''' '''''''' ''''''' '''''''''''''''''''' '''''''''''''' '''''' ''''''''''''''''''''''' ''''''' '''''''''' ''''''''''''''''''''' ''''''' '''''''''''''''''' ''''''''''''' ''''''''''''' ''''' ''''''''''''' '''''' ''''''''''''''' ''''' ''''''' '''' ''''''''' ''''''''''''''' ''''''''''

The above discussion shows that the investment costs for the conversion to this alternativetechnology are extremely high. ''' '''''''''''' ''''' ''''''''' '''''''''''''' '''''#C#' '''''''''''''''' ''''' '''''''''''' '''' ''' ''''''''''''''''''''' '''''''' ''''''''''' ''''''' ''''''''''''''''''''' '''' '''''' ''''''''''''' '''''''''''''''''''

Operating costs

There are many elements that contribute to operating costs, but as already noted, energy is themain cost of the production process. Table 10-5 presents the range of different operating costelements and provides a comparison of the costs arising under SD and under the use of the two-celltechnology. This table has been jointly developed for the members of the consortium of sodiumchlorate manufacturers, but where appropriate the information has been replaced with applicant-specific information, which is claimed as confidential.


Table 10-5: Comparison of operating costs for production of sodium chlorate between sodium dichromateand two-compartment electrolytic cells



product

Change due to implementation oftwo-cell technology


Electricity '''''''''' #C#'''''''''''' ''''''''''''#D#'' ''''''''''''*

Oil and gas Minor component No change envisaged


Cost of SD Minor component '''''#D#''''''''' - Cost of SD eliminated



Water Minor component No change envisaged


Minor component Reduced due to elimination ofCr(VI) sludge disposal costs

Transportation of product to customer Minor component No change envisaged


Minor component Significant increase due toreplacement of cell membrane(every 2-5 years)



Minor component Initial training requirement but nochange over continued operation


Minor component No significant change envisaged





Minor component Significant increase overconventional process due toreplacement of cell membrane


Insurance premiums Minor component No change envisaged





Overall costs (% change) ''''''#C#'''''' ''''''''''''''''' '''#D#''''''''''''''' '''''''''''''


Energy consumption: the energy consumption of the sodium chlorate process would increasesubstantially and, as this is the major cost component for the production of sodium chlorate, it willalso have a significant impact on the overall cost of the process. This alternative process could beexpected to use approximately of 5,880 kWh/t chlorate produced in electricity (see calculation madeearlier). This would mean an increase of ''#D#''''' kWh/t over the current '''''#A#''''' kWh/tconsumption of the applicant or ''''#D#''''%.


If other costs are disregarded, a ''''#D#'''''% increase in energy costs alone would result in a '''#D#''''%overall increase in the production cost of sodium chlorate for Arkema or ca. €''''''#D#'' per tonne ofsodium chlorate. To give the magnitude of this additional cost for the applicant, it is worthremembering that Arkema’s sodium chlorate production in 2012 was '#B#''' kt. The additional costof €'''#D#'''''/tonne would mean an additional cost of ca. €''''''' '#D#''''''''''''' per year. A ''#D#''''%overall increase in production costs '''''''''''' ''''''''' ''''''' ''''''' ''''''''''''' '''''''''''#C# ''''''''''''' '''' '''''''''''''' ''''' '''''',making production of sodium chlorate unsustainable. Beyond this theoretical calculation, thefeasibility study that Arkema has conducted suggested that the overall production cost increase atthe time of the study would be ''''''' ''''''''''' ''''''''''''''''''' ''''''''''''' '''''''' ''''''''' '''''''' '''' '''''''''''''''''''''' '''' ''''''''''''''''' ''''''' ''''''''''''' ''''' ''''''''''''''' '''''''' '''''''''''''' '''' '''''''''' ''''''''' ''''''' '''''''''''''''''' ''''''''''''''' '''' ''''''''' '''''' '''''''''''''''''' ''''''''''''''''' ''''''''''''''''''' '''''''''''''''''''' '''''''''''' '''''''' '''''' '''''''''''''''' '''' '''''''''''''''''''''' ''''''''''' '''''''''''' ''''''''' ''''''''''''''''' ''''' ''''''''' ''''''' ''''''''''' ''''''''''' '''''''''''' '''''''''' '''''''''#D#'' '''''''''''''''' ''''''''''''' '''''''''' ''''' '''''''''''' ''''''''''''''''''''''''''' '''''''' '''''''''''''''''' '''' '''''''''' '''''''''''''''' ''''''' ''''''''''''''''''''' '''' ''''''' '''''''''' ''' '''''' ''''''''''''' '''''''''''' ''''''''''''''' '''''' '''''''''''''''''''' '''''''''''' ''''''''''' '''''''''''' '''''''''''''''''' ''''' ''''''''''' ''''''''''''' '''''' ''''''''' ''''' '''''' ''''''''''''''' ''''''''''''' ''''''' '''''''''''''''''''' '''''''''''''' ''''''''''''''''' ''''''''' '''''''''''''''''''' '''' ''''''''''''''''''''''' ''' '''' ''''''''' '''''''' ''' '''''''''''' ''''''''''''''''''''''''' '''''' ''''''' '''''''''''''' '''''''''''' '''' '''''''''''' '''''' ''''''''''''''''''''''''' ''''''''''' '''' ''''''''''''''''''' ''''' ''''''''''''''''''''''''''''' '''''''''' ''''''''' ''' ''''''''' ''''''''' '''''''''''''''''''''

Materials and services: the applicant would avoid the cost of SD. It has been explained that theconsumption of SD is ''''#B#''''''' kg/t sodium chlorate, so with an annual production of '''#B#'' ktsodium chlorate and an assumed market price of SD of €1,540 per tonne, the cost savings would beca. €'''''#D#''''''/y.

On the other hand, maintenance costs would also rise, as the operation of a membrane chlor-alkalicell is more expensive than undivided chlorate cells. This is due to the relatively low service life ofthe membrane. According to the chlor-alkali BREF, the membrane needs to be replaced every 2-5years (IPPC, 2001), in addition to this, the electrodes will need periodic replacement, as is the casefor undivided cells. ''' ''''''''''''' ''''' '''''''''''' '''''''' ''''''' ''''''''''''''''''''''''' '''' ''''''' '''''''' '''''''''''''''''''''' ''''''''''''''''''''''''''' '''''' '''''''''''''' ''''''''''''''' ''''''' ''''''''''''''''''''''''''''''' #D#'''''''''''''''' '''''''''''' ''''' '''''''' '''''''''''''''''' ''''''''''''''''''''''' '''''''''''''''''''' '''' ''''''' '''''''''''''''''''' ''''''''''''' '''''' ''''' ''''''''''''' ''''''''''' ''''''''''''''' ''''''' ''''''' ''''''''''''' '''''''''''''''' ''''''''''' '''' '''''''''''''''' '''' '''''' '''''''''''''''''''''' ''''''' ''''''''' ''''''''''''' '''' '''''' '''''''''''''''''''' ''''''''''''''''''''''''''

Labour costs: no significant changes are envisaged.

Other costs: other costs would likely stay similar to the current process employing SD with theexception of reduced REACH compliance costs for Authorisation.


The use of the two-cell production technology is clearly an economically infeasible alternative. Itsimplementation would require the demolition of the existing sodium chlorate plant and the buildingof new plant. A preliminary estimation of the cost of this engineering work would suggest a cost ofprobably over €'''''''' ''#D#'''''''''''' to obtain a plant of a capacity similar to the existing chlorate plant.

Even if the building of new plants could be financed, the operation of the new plants would behindered by the considerable increase of the most important production cost component, energyconsumption by ''''#D#''''%, which would increase Arkema’s overall production cost by ca. '''#D#''''%.Furthermore, the cost of electricity is expected to rise in the future (EC, 2013) and as such, this costcomponent will only increase in importance.


As mentioned earlier, sodium chlorate is a commodity chemical available from both EU-based andnon-EU suppliers and is sold on the basis of margin and logistics. '''''''''''' ''''''''''''''''''''''''''''''''''''''''''''''''''''' ''''''''''''''' ''''''' '''''''''' ''''''' ''''''''''''''''''' ''''''''' ''''''''''''''''''' ''''''''' ''''''''' ''''' '''''''''''' ''''' '''' ''''''' '''''''''''''''''''' ''''''''''''''''''' '''' ''''''' '''''''''''''#D# & #E#'''' '''''''''' '''''''''''''''''' ''''' ''''''''''''' '''' ''''''''''' ''''''' '''''''''' '''''''''''''''''''' '''''''''''''''''' ''''''' '''''''''' '''' ''''''''''''' ''''''' '''''''''''''''''' ''''''' ''''''''''''' ''''''''''''''' '''''''''''''''' '''' '''''''''' ''''''''''''' '''''''''''''''''''' ''''''''' '''''' ''''''''''''' ''''' ''''''''''''''' '''''''' '''''''''''''''''''''' ''''''''' '''''''''''''''' ''''''''''''''''' ''''''''''''''''''''''''''' ''''' ''' ''''''''''''''''''''''''''''''''' '''''''''''''''''''''' ''''''' ''''''''''' '''''''''''''''' ''''''' ''''''''''' ''''''' '''''''''''''' ''''''''''''''''''''''''''''''''''' The commodity nature of the chlorate means that passing on the additional productioncost to its customers would be very difficult.

The need to construct a new plant at a very high cost, coupled with an increased cost of production,renders this alternative clearly economically infeasible for Arkema in both the short and longer term.

Arkema SodiumDichromate AoA - Public -R2

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