Hydrometallurgy 94 (2008) 58–68

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Hydrometallurgy

j ourna l homepage: www.e lsev ie r.com/ locate /hydromet

Progress after three years of BioMinE—Research and Technological Developmentproject for a global assessment of biohydrometallurgical processes applied toEuropean non-ferrous metal resources

D. Morin a,⁎, T. Pinches b, J. Huisman c, C. Frias d, A. Norberg e, E. Forssberg f

a Ecotechnology Unit, Environment and Process Division, BRGM, BP6009, 45060 Orléans Cedex 2, Franceb Mintek, Randburg, South Africac Paques, AB Balk, The Netherlandsd Técnicas Reunidas, Madrid, Spaine Skeria, Skellefteå, Swedenf Luleå University, Luleå, Sweden

⁎ Corresponding author.E-mail addresses: d.morin@brgm.fr (D. Morin), Tony

anders.norberg@skeria.skelleftea.se (A. Norberg), Eric.Fo

0304-386X/$ – see front matter © 2008 Elsevier B.V. Adoi:10.1016/j.hydromet.2008.05.050

A B S T R A C T

A R T I C L E I N F O

Available online 6 June 2008

Keywords:

BioMinE is an integrated pEuropean Commission, whi2005-500329). It is dedicat

BiohydrometallurgyBiominingBioleachingNon-ferrous metalsGoldCopperNickelZincEuropean integrated project

ed to the evaluation of biohydrometallurgy to improve the exploitation of theEuropean non-ferrous metal resources in a sustainable way. At the end of 2007, the Consortium of BioMinEcomprised 37 partners from industry (13 including 6 Small or Medium Enterprises), research organisations(8), universities (15), and government (1). The participants are from 13 EU member states and from Serbiaand South Africa (INCO Countries). For more details see http://biomine.brgm.fr.The three main kinds of resources considered for bioleaching studies are:- Copper polymetallics (concentrates and tailings),- Zinc polymetallics (zinc and zinc polymetallic concentrates)- Secondary wastes (tailings, rock and metallurgical wastes, etc.)

roject under the sixth framework programme of research supported by thech started in November 2004 and will last until October 2008 (Ref. NMP2-CT-

For each of these resources, amenability studies of application of bioleaching technologies by variousapproaches have been undertaken or still ongoing. Further processing assessment will be conducted up tothe demonstration scale. Technological improvements have been made to apply bioleaching in the contextof the European resources in terms of complexity and sustainability requirements. The relevantfundamental studies covering bio-prospecting, molecular ecology, biochemistry, and genetics areasaimed at improving the understanding and the control of the selected technologies have given originalresults.Much progress has also been obtained in the use of the microbial sulfate-reducing process to polisheffluents and to recover metals from leachates containing low concentrations of metals. The finding ofmicro-organisms thriving at low and high temperature, respectively 8 and 65 °C, leads to an extension ofthe application range of the process. It has been also observed that this process could be pushed down topH 4.5 and 4 creating opportunities of selective metal recovery as metal sulphides. It has also beendemonstrated that sulphate can be removed at high concentrations, as well as arsenic or selenium. Thenext step in this work is pilot testing. This will allow to determine scale-up criteria and to assess theresidual metal concentration under actual conditions.The pilot-scale demonstration operations, as well as the techno-economic and comparative sustain-ability assessments will be achieved during 2008, the last year of the project.The prototypes of the learning objects for training about biohydrometallurgy accessible by internet havebeen elaborated. A public output of this work is accessible at http://wiki.biomine.skelleftea.se/wiki. Thebasic knowledge thus delivered is aimed at disseminating the understanding of the origins and use ofbiohydrometallurgy.Contacts with mining operators in Europe have been taken and collaboration schemes have beenestablished in various ways according to the respective contexts. When a high potential of technical

P@mintek.co.za (T. Pinches), J.Huisman@paques.nl (J. Huisman), cfrias@tecnicasreunidas.es (C. Frias),rssberg@km.luth.se (E. Forssberg).

ll rights reserved.

59D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

involvement could be foreseen, a direct participation of the mining operators in the project wasfavoured, this led to integrate KGHM (Pol), Boliden (Sw) and Copper Institute of Bor (Serbia) into theconsortium of partners.When no direct technical commitment was conceivable at the first stage, collaboration was establishedwith companies with the most urgent requirement to have access to the relevant resource.

© 2008 Elsevier B.V. All rights reserved.

1. Introduction

The European non-ferrous metals mining industry has initiatedand developed the BioMinE project as they identified the need to findnew processes for metal extraction from resources of today and oftomorrow.

Currently, the extracting and metallurgical industries can copewith the huge demands of the emerging countries but the prices ofmetals have soared at unexpected sky-high values. Many metalmarket analysts predict that a new area has begun and that the priceswill remain high for an extended period. They will most probably notgo down to levels before the recent increase in metal prices.

Large orebodies of natural metal resources that can be processedeasily with conventional techniques are becoming scarce. In addition,recently discovered deposits have a more complex mineralogy thanbefore.

In the present context, some mining regions of the world arebecomingwealthier as their resources are still relatively abundant andhave the right characteristics to serve as feed for current metallurgicaltechnologies. Chile is an example in case of copper. Others regions, likeEurope, are (nowadays) poor in primary resources and have a growingeconomic dependence on substances that are absolutely necessary totheir industry. From the point of view of the European extractivemetallurgy, Europe has two converging ways to loosen the grip. One isto discover new resources on its own territory and the other is todevelop its own technologies for its own resources. By the means ofexploring all the options for a sustainable development and investingin research in innovative technologies able to deal with difficult-to-treat resources, Europe is getting ahead for the production of metals inthe future.

Conventional technologies to extract base metals are mainly basedon pyrometallurgy. This is, compared to hydrometallurgy ratherrestricted with regard to ranges of metals grades and impurities it canprocess.

Hydrometallurgy has provided many alternatives that are more orless universally applicable at various costs and profits. The aim to keepelements in their aqueous phase reduces the risks of uncontrolledemissions. Many technologies have been developed to selectivelyrecover impurities and valuable metals. However, the efficiency ofthese technologies has a cost in energy and in complexity.

Biohydrometallurgy results in lower energy expenses and simpli-fies the treatment of complex materials due to the catalytic effectexerted by the microbiological processes on the oxidizing reactions ofthe metal-bearing sulfides.

This initial picture of the base metal metallurgy sector guided thedesigners of the BioMinE project in the organisation of the projectfocused on the evaluation of processes to be applied in Europe toEuropean resources.

BioMinE is an integrated project under the sixth frameworkprogramme of research supported by the European Commission,which started in November 2004 and will last until October 2008. Atthe end of 2007, the Consortium of BioMinE comprised 37 partnersfrom industry (13 including 6 SMEs), research organisations (8),universities (15), and government (1). The participants are from 13 EUmember states and from Serbia and South Africa (INCO Countries). Formore details see http://biomine.brgm.fr. The names of the organiza-tions partners of BioMinE, which are quoted in the text, are listed inTable 1.

After having described in a previous paper the context and theobjectives of the project at its beginning (Morin et al., 2006), this onegives an overview of the progress of BioMinE after three years.

2. Selection of resources and roadmap for the RTD studies

Not all the European resources would be good candidates for theassessment of the application of biotreatments and a rationalscreening was required. Two objectives had to converge. The firstwas to characterise what a typically European resource amenable forbiotreatment would mean. The second was to make available samplesof such typical resources for testing within the project.

The first was mainly based on existing knowledge and the use ofdata base of geological information. This was done during the firstyear of the project in the frame of the workpackage 1 of the projectwith the support of the know-how of the experts in the application ofthe relevant biotechnologies (Lips and the BioMinE Consortium,2006). This screening was unique for Europe and was even the firstone of its kind in the world. The result was a selection of potentialresources to which application of the biotechnologies could be thesolution for a more profitable exploitation than with conventionaltechnologies. A roadmap of the major part of the work in the projectcould then be designed. Since the first year it has thus been agreedthat low-grade complex copper and zinc concentrates and secondaryresources of the mining activities would be the targeted resources ofthe project. The existing biotechnologies that fit to the Europeantargets were identified like for example tank leaching for copperconcentrates. New technologies to be developed for new resourceswere determined, for instance indirect bioleaching for certain zincconcentrates. New concepts of equipment to fit the characteristics oflow-grade resources had to be elaborated with for example the designof a low-cost bioreactor. The possibility to recover more metal fromprocess and bleed streams by integrating a biotechnological treatmentbased on metal sulfide precipitation was planned to be assessed.

Some fundamental research has been isolated at the beginning ofthe project that would allow a progress for the developmentof biohydrometallurgy specifically in Europe. An example is thestudy of genomics. This is justified by the expectation that thisknowledge will clarify the real capacities of the micro-organisms.Furthermore, Europe has the potential to carry out consistent work inthis area on the long term. The investigation in the bio-flotationtechnique has the same kind of justification. There is clearly no hopeto develop a commercial applicationwithin the time frame of BioMinEbut on the long term Europe will benefit of the advantages of a realbreakthrough if viable technology could result from the research inthis area and if interesting spin-off could be developed. However,some other fundamental work could be bent to the objectives of theproject in terms of resources like the search for new species and thedesign of consortia for the treatment of selected resources in pre-defined conditions. More practically, from the beginning of the projecta specific effort was made to better use molecular techniques foridentifying and monitoring the population of micro-organisms withthe aim to identify what each technique will be most appropriate toobtain specific information.

The second objective of workpackage 1 (WP1) at the end of thescreening of the resources was to make benchmark resourcesavailable. This was possible through a regular dialogue with themining operators recognized as the potential end-users of the

Table 1List of the 37 BioMinE organizations participating in BioMinE project in 2007

Partner name and short name Countries

Bureau de Recherches Géologiques et Minières (BRGM) FrTampere University of Technology (TUT) FinTechnische Universitaet Berlin (TUB) GerUniversitaet Duisburg-Essen (UDE) GerInstitute of Geology and Mineral Exploration (IGME) GrNational Technical University of Athens (NTUA) GrBioclear B.V. (Bioclear) NlPaques B.V. (Paques) NlWageningen University (WU) NlInstityt Metali Niezelaznych (IMN) PolInstituto National De Engeharia (INETI) PortDe Beers Consolidated (DBCM) RSAMintek (Mintek) RSAUniversity of Cape Town (UCT) RSAUniversity of Stellenbosch (Stellenbosch) RSAUniversidad Autonoma de Madrid (UAM) SpLuleå University of Technology (Ltu) SwMEAB Metallextraktion AB (MEAB) GerUmeå University (Umu) SwCellFacts Instruments Ltd (CIL) UKImperial College of Science and Technology (Imperial) UKRio Tinto (Rio Tinto) UKUniversity of Wales, Bangor (UWB) UKUniversity of Warwick (Warwick) UKTecnicas Reunidas (TR) SpOutotec (OTT) FinUmicore (Umicore) BelSkeria Untvecklung, Skellefteå (Skeria) SwCentre National de la Recherche Scientifique (CNRS) FrUniversity of Stuttgart (USTUTT) GerPE International (PE Int) GerInstitute for Non-ferrous and Rare Metals (IMNR) RomMilton Roy Mixing (MRM) FrNew Boliden (Boliden) SwCopper Institute Bor (CIB) SerKGHM Polska Miedź, S.A. (KGHM) PolUniversity of Seville (US) Sp

60 D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

technologies developed. By capturing the interest of Boliden, KGHM,Rio Narcea, Somincor, Lunding Mining, Bor District and some othercompanies, a large part of the major operators in this field in Europecould contribute in giving access to samples of the relevant resources.

This is during the second year of the project that the work plan onapplications could be drawn up per resource and per technology fromthe amenability test work (Workpackages 2 and 3) to the possibledemonstration of validated treatments (Workpackage 4). Since then,this roadmap (based on ‘Exploitable results’) has been the mainstructure for the activities of resources assessment from the technicalpoint of view and the guide for the exploitation of applied results ofthe project.

In the same time, the structure of management of the exploitableresults has been much improved on the basis of a screening of themain potential outcomes of the project aligned with the vision of theapplications on which our work has been focused. The implementa-tion of the concept of clusters of partners associated in thedevelopment of specific results to exploit has been undertaken andformalized during the third year of the project (Workpackage 5).

3. Bioleaching

From a practical point of view, two dominant aspects havecharacterized the project at the end of the third year:

• The first is the achievement of a large bulk of preliminaryassessments of resources and technologies screened and selectedduring the two first years of the project (in WP1, 2 and 3).

• The second is the focus on bench-scale experiments towards pilot-scale demonstration operations on the selected resources.

In the background of this major stream of development activities,research work has been continued on specific subjects of interestmainly in the area of bioleaching and for the benefit of a betterunderstanding and control of the processes.

Test work on the application of bioleaching has been carried out inthe frame of WP2 for quite a large range of European resources withthe various techniques previously selected for their presumedappropriateness. Direct or indirect bioleaching were assessed on Ni–Cu, Cu, Zn, Pb and Zn/Pb concentrates and wastes (tailings and slags).The technical results of the bench-scale studies are satisfactory andgenerally confirm the validity of undertaking operations at pilot scaleand subsequent calculation of costs at a pre-feasibility level for thetechnologies applied to the benchmark resources selected.

The benchmark resources concerned are particularly a Ni–Cuconcentrate of the Aguablanca mine (Spain, Rio Narcea), a Cuconcentrate of the Majdanpeck-Veliki Krivelj mines of the Bor district(Serbia), Zn and Pb concentrates of the Tara Mine (Ireland, Boliden),and secondary resources of Bor and Lubin (Poland).

Fundamental issues about bioleaching which have been addressedfor their pertinence in the case of European context have significantlyprogressed towards a better efficiency and sustainability of theapplications of the processes. A non-exhaustive selection of thesetechnical studies is as follows:

• Use of wastes as reagents• Enhancement of bioreactors for regenerating ferric as oxidant in theconfiguration of the indirect bioleaching process

• Prevention of passivation of chalcopyrite during bioleaching• Biostabilisation of arsenic in solid bioresidues• Reduction of elemental sulfur in the solid residues of bioleachedrefractory gold ores to lower the consumption of cyanide requiredfor the recovery of the precious metal

• Determination of the operating conditions of bioleaching of slagsand tailings

• Identification and characterisation of low-temperature micro-organisms

• Understanding of the biochemical mechanisms of tolerance to highconcentrations of inhibiting elements

• Selection of bacterial cultures able to tolerate high Zn concentrationsin solution (up to 75 g/l).

3.1. Tank bioleaching of Cu and Cu polymetallic concentrates

Themain thrust of the RTD activities using the copper concentrateswas conventional “direct” tank bioleaching. Furthermore, it was clearthat the use of thermophilic cultures enabling faster leach kinetics,particularly for the leaching of chalcopyrite, would be a keyrequirement. Taken together with downstream processing studiescarried out under workpackage 4, these results were being used forpreliminary techno-economic evaluations to plan the scope ofintegrated piloting campaigns to be completed during the latter partof year 3 and year 4 of the project.

The Aguablanca Cu–Ni concentrate (Cu; 7.5%, Ni; 5.6%, Fe; 32.7%,S=; 32.3%) had also been subjected to preliminary amenability testingusing “indirect” bioleaching. However, for this concentrate, techno-economic studies indicated that conventional “direct” bioleachingwasthe preferred technology.

While Ni (pentlandite) and Cu (chalcopyrite) bioleaching have beenstudied fairly extensively in the past, there have been no knownpublished studies on the bioleaching of polymetallic Ni–Cu concen-trates. The current biohydrometallurgical studies therefore representnovel technology development. Bioleaching design criteria for thepiloting campaign were based on an extended period of laboratory andbench-scale RTD activities. This confirmed the requirement for use ofthermophilic cultures for effective bioleaching of the chalcopyritecomponent. Novel bioleaching operating conditions and control

Fig. 1. CARD-FISH (Catalysed Reporter Deposition–Fluorescent In Situ Hybridization) hybridized bacteria with specific probes in R2. A: CARD-FISH with THC642, specific for membersof the A. caldus specie. B: CARD-FISH with LEP154, specific for members of the L. ferriphilum species. Tendency of L. ferriphilum to form clusters can be observed (B) against theplanktonic A. caldus (A). Scale bar, 2 µm (Universidad Autonoma de Madrid).

61D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

strategies have been identifiedwhich have the potential to significantlyincrease the rates of Cu and Ni leaching. It has also been shown that useof these operational strategies has the potential to reduce process(energy) costs by allowing control of chalcopyrite-sulfide oxidation(elemental sulfur production) and of the amount of pyrite oxidised.

The bench-scale and integrated piloting results on the copperconcentrate will also provide the experimental data for the ongoingdevelopment of a tank bioleaching model being undertaken by theUniversity of Cape Town. Up to now UCT have tested the model formesophilic bioleaching systems and this is now being expanded toinclude thermophilic systems, where the model would allowinvestigation of hypothetically different reactor configurations andoperating strategies.

During the third year of the project, samples of copper concen-trateswere received from theMajdanpek and the Veliki Krievelj minesof RTB-Bor, Serbia. A sample of copper sulfide concentrate from RTB-Bor smelter slag was also received. Initial tests have confirmed that allthese resources show good amenability to bioleaching. Bench-scalebioleaching development and optimisationwork has now startedwiththe intention of generating design criteria for an integrated pilotingcampaign using the RTB-Bor Cu resources to be started in early 2008.INETI has also carried out laboratory bioleaching amenability testing

Fig. 2. Combination of atomic force and epifluorescence microscopy for visualization

on the Neves Corvo chalcopyrite concentrate using thermophiliccultures isolated and characterised from hot springs in the Azores.

In the Aguablanca Ni–Cu and the Majdanpek and Veliki Krievelj Cuconcentrates, the major copper mineral is chalcopyrite. This is also thecase for other BioMinE concentrate resources such as those from theBoliden district and Neves Corvo. Chalcopyrite does not generallyleach well in acid-sulfate leach environments due to surfacepassivation and the use of thermophilic cultures (up to 80 °C) isusually necessary to achieve acceptable leach kinetics. As a result,further RTD activities have now started to provide molecular tools toidentify and enumerate thermophiles in the high-temperature copperbioleaching systems. Specifically, Q-PCR (Quantitative PolymeraseChain Reaction, used by Bioclear) and CARD-FISH (Catalysed ReporterDeposition–Fluorescent In Situ Hybridization, used by UniversidadAutonoma de Madrid, see Fig. 1) methods will be developed usingsamples generated during the ongoing piloting and bench-scaleresearch activities.

In addition, Bioclear are developing a biomolecular tool formonitoring the level of microbial “activity” and Warwick Universityfunctional gene probes to investigate and monitor specific activitiessuch as Fe and S oxidation (Bathe and Norris, 2007). The role ofextracellular polysaccharide and cell attachment in bioleaching

of leaching bacteria on pyrite developed by the University of Duisburg-Essen.

Fig. 3. Different approaches for optimising and designing bioleaching consortia(University of Wales, Bangor).

62 D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

systems using thermophiles is presently unknown. Related research istherefore being undertaken in conjunction with the bench- and pilotscale using Cu concentratesmentioned above in particular in using themethod of combination of atomic force microscopy and fluorescent insitu hybridisation developed by the University of Duisburg-Essen(illustrated in Fig. 2, Mangold et al., 2008).

Other innovative approaches to bioleaching of copper concentratesare being undertaken by Boliden and Technical University of Lulea(Ltu). The main objective here is to investigate bioleaching strategiesfor the selective removal of impurities such as arsenic and antimonyfrom copper concentrates.

A broad range of research investigations related to bioleachingconsortia applicable to the various BioMinE resources has now beencompleted. It should be noted that prior to BioMinE there was verylittle published information available on the microbial consortiaoccurring in tank bioleaching processes. A major study by UWB(Johnson et al., 2007) has investigated the structure of consortiaestablished on eleven types of sulfide concentrates using 23 differentspecies and strains. These studies show that a “one size fits all”approach is inappropriate and that theremay be considerable benefitsarising from the use of optimised microbial consortia for specificconcentrates and the operating conditions chosen with scenarios asillustrated in Fig. 3.

Another relevant finding from the microbial genetics studies atStellenbosch University is that metals resistance in the microbialconsortia is aided by mobile metal resistance genes, which may berecruited from the horizontal gene pool acquired via metal resistanceplasmids or transposons (Tuffin et al., 2006). It appears that genesconferring high levels of resistance to arsenic previously found instains of Leptospirilli from South Africa are also present in isolatesfrom different parts of Europe (Kloppers et al., 2007).

3.2. Tank bioleaching of Zn and Zn polymetallic concentrates

For the zinc and zinc polymetallic RTD activities, the main subjectwas the application of indirect bioleaching technology. A keychallenge that had been successfully addressed was the intensificationof the ferrous iron bio-oxidation step in the process. A preliminarytechno-economic assessment for indirect bioleaching of zinc and zincpolymetallic concentrates was produced, which indicated some scale-up challenges to be addressed but indicated the potential forfavourable economics. For comparative purposes, RTD on direct tankbioleaching was also carried out. In this case, three technicalchallenges were identified to achieve improved economics. Thesewere the need for microbial tolerance to high quantities of silvercommonly occurring in these types of concentrates, maximisingmicrobial tolerance to high Zn tenors which could facilitate directelectrowinning of Zn metal (eliminates solvent extraction step), and areduction in energy requirements by control of the amount of sulfideoxidised to sulfate. A zinc concentrate from the Boliden Petiknäsmine,Sweden, was supplied and used in these studies. While the ability tocontrol sulfide oxidation had not shown any success, good progresswas made in adapting the culture to higher metal concentrations.

Due to the lower value of Zn compared to Cu and Ni, the keyobjective for ZnS bioleaching is to minimise costs associated with theZn bioleaching-metals recovery circuit. One way to do this is tomaximise the Zn tenor obtained to the extent (N50 g/l) that a simplifiedhydrometallurgical circuit involving direct electrowinning of Znmightbe an option. Bench-scale testing at Mintek using mesophilic andmoderately thermophilic cultures bioleaching Petiknäs Zn concentrateachieved Zn concentrations of 75 g/l. An alternative approachinvestigated is to limit the energy costs for sulfide oxidation bypromoting sulfideoxidation to the level of elemental sulfur, rather thanits complete oxidation to sulfate. In the “indirect” bioleaching processthis is achieved because the chemical oxidation of base metal sulfideyields largely an elemental sulfur product. In “direct” bioleaching the

objective has been to devise strategies that promote bacterial ironoxidation but which might significantly reduce the level of bacterialsulfur oxidation. The strategies investigated were (i) use of a low-residence-time bioleaching process fed with an Fe-oxidising culture(bio-generator concept) (Ltu, Boliden), (ii) the use of various selectivebioleaching process operating conditions (Mintek), and (iii) the use ofmetabolic blockers (Umu, UDE and CNRS). To date, only the firstapproach has provided indications of potential success. Some partners(CNRS, UDE andUmu) are nowadopting a genomics approach to betterdefine sulfur oxidation pathways and consequently ways in whichthese might be manipulated.

RTD activities by IMNR have established an effective tankbioleaching process to treat the Baia Mare Pb–Zn-precious metalsconcentrate. The major emphasis over the reporting period has beento provide sufficiently large residue samples to Técnicas Reunidas forPb and precious metals recovery work under workpackage 4.

3.3. Tank bioleaching of Au concentrates

Bioleaching of refractory sulfide gold concentrates is a commer-cialised technology and the challenges under BioMinE have been toaddress environmental issues arising from the use of cyanide torecover the gold and the safe disposal of arsenic-containing wasteresidues. Good progress had been made in the use of thermophiliccultures capable of reducing final residue sulfur content and aconcomitant decrease in cyanide consumption. Gold concentratesderived from the Petiknäs Norra mine, Sweden and the Sheba mine,South Africa, have been employed in these studies. Other ideasintroduced were the use of bioleaching process configurations whichmight achieve selective leaching of arsenopyrite over pyrite, wherearsenopyrite is the main gold-hosting mineral.

The work on bioleaching of gold concentrates by Mintek on Shebaand Petiknäs Norra gold concentrates in bench-scale piloting usingmesophile, moderate thermophile and thermophile cultures has beencompleted. Results using a thermophile culture have identifiedoptimum operating conditions which allow for at least a ten-folddecrease in cyanide consumption for gold leaching compared to thecurrent commercial process using the lower temperature cultures.This results from a significant reduction in the bioleach residueelemental sulfur content. The ability to minimise cyanide usage maybe a significant factor in meeting statutory environmental impactrequirements for the use of this technology in Europe. The cyanideconsumptions obtained were at or below the levels normallyassociated with non-sulfide-free-milling gold ores. The results alsoshow final waste leach liquors where the level of As(III) is twenty-foldless than the minimum achievable using the lower temperaturecultures. A related technology advance, which has been furtherconsolidated over the reporting period, is conversion of wastebioleach solids to “controlled low-strength materials” (CLSM) withapplication for encapsulated systems underground (studied by

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Imperial College see Bouzalakos et al., 2008 and Chan and Dudeney,2008). This would facilitate potential structural applications as analternative to conventional disposal in tailings dams.

In the longer term, the ongoing studies being carried out byStellenbosch on the molecular biology of metals resistance mechanismsmay have significant impact on developing strategies for designing andoperating bioleaching processes to tolerate high concentrations ofinhibitory metals such as arsenic found in refractory gold concentrates.Similarly, the progress being made by Warwick, CNRS and Umu inunderstanding and cellular sulfur oxidation mechanisms will impact onthe development of process options for sulfur management.

At the biological level, the major immediate contribution, which isclosely related to the foregoing research areas, in advancing refractoryAu bioleaching technology is the ability to monitor and characterisethe microbial consortia and relating the changes to consortiacomposition to the concentrate characteristics and to the processoperating conditions (d'Hugues et al., 2007).

3.4. Indirect tank bioleaching of base metal concentrates

BioMinE is addressing the development of the bio-oxidation unitoperation in the indirect bioleaching process i.e. an intensive processfor bacterial oxidation of ferrous to ferric iron. Tempere University ofTechnology and Outotec participated in progressing the developmentof a high-rate fluidised bed bioreactor with optimum performancewith respect to Fe tolerance and low pH (b1.0) to maximise Fesolubility (Puhakka et al., 2007). Process operation using a Leptospir-illum ferriphilum dominated fluidised bed reactor at an Fe concentra-tion of 60 g/l was feasible.

This has been extended to experimentation coupled to kineticmodellingaddressing the simultaneouseffects of Fe3+ concentration andvariousbasemetals (Ni andZn)on reactor performance. Thesedatawereused by Outotec to assess the techno-economic feasibility of applyingindirect bioleaching to treat basemetal ores and concentrates and as thebasis for comparison with different technology processing options.Special focuswas to compare and evaluate the techno-economic aspectsof indirect bioleaching with other process options for treating theFinnish low-grade Ni concentrate from the Hitura mine. Conclusionsreached by Outotec to date are that indirect bioleaching will requireoptimum project scenarios for financial success.

University of Seville has been collaborating with Técnicas Reunidasin a similar way to develop an enhanced bio-oxidation reactor forferric iron production. In this case the RTD activities have focussed onbioreactor culture adaptation simultaneously to high ferrous iron andZn. These activities are being carried out primarily as a contribution tothe integrated piloting campaign and techno-economic study forindirect bioleaching of zinc sulfide concentrates.

3.5. Heap bioleaching of base metal sulfide ores

While no significant European target resources had emerged at thebeginning of the reporting period, it is recognised that one potentialopportunity for heap bioleaching in Europe is heap bioleaching of low-grade chalcopyrite-containing ores. In commonwith tank bioleaching ofchalcopyrite-containing concentrates, the challenge for heap bioleachingis the slow copper leaching kinetics due to the passivation of thechalcopyrite mineral surface. For this reason, a testwork programmewasdeveloped and started by Outotec to investigate the passivationphenomenon and to developmethods for potential processmanagementprocedures to overcome it using ore from Boliden's Aitik mine, Sweden.

The leach characteristics of gangue minerals, particularly silicateminerals, in heap leaching operations can be of major significance.Umu has now completed the studies on the leaching of a range ofsilicate minerals in bioleaching chemical environments. A key findingis that fluoride leached from silicate minerals may have an inhibitoryeffect on acidophiles.

The RTD activities supported by Rio Tinto have sought to addressone of the major challenges that often cause heap leaching operationsto fail, namely, methods of construction that impact negatively onfluid flow during heap operation. This has been addressed through amodelling approach to investigate the mechanisms that lead toparticle segregationwithin heaps, allowing methods for the control ofthis phenomenon at bulk scale to be identified.

Another opportunity considered for heap bioleaching technologywas the treatment of tailings. However, the need to agglomeratetailings prior to heap leaching raises uncertainties regarding cost.

3.6. Tank bioleaching of flotation tailings and slags

The choice of metallurgical wastes, such as tailings and slags, forbioleaching testing was guided by the techno-economic filterdeveloped and reported during year 1 under WP1. Thus, wasteresources were chosen that contained metal values which couldjustify their exploitation or, alternatively, where the possibility of co-or parallel-processing of wastes with a hydrometallurgical operationis an option. Preliminary techno-economic studies on Ni-containingtailings from Aguablanca mine gave reasonably encouraging resultsbut it was concluded that a more detailed study using project-specificdata would be necessary to confirm this. Although no testwork hadbeen undertaken at this point, after a visit to the RTB-Bor mine anddiscussions with the mine management, it was concluded that anintegrated (bio)hydrometallurgical approach to treating primaryconcentrates, slag concentrates and tailings from the RTB-Bor minesin Serbia could represent a promising application opportunity. Inother studies, the comparative characteristics of a range of metallur-gical and industrial oxidic wastes which could be co-processed and/orused as alternative low-cost neutralisation agents in bioleachingprocesses was established.

It was noted that while agglomeration or pelletisation of tailingsfollowed by heap bioleaching is technically feasible, the costimplications will need to be further assessed on a project-specificbasis. The alternative approach now being investigated by BRGM isthe application of a concept of low duty bioreactor. The targetresources under consideration are RTB-Bor copper tailings, Agua-blanca Ni tailings and KGHM Cu tailings and low-grade middlingsconcentrate fraction. Bioleaching amenability has been carried out sofar on RTB-Bor tailings and KGHM middlings. The low copperextractions observed for the RTB-Bor tailings using the mesophiliccultures used are related to the poor leachability of the chalcopyrite atthe low temperature. Optimisation studies on the KGHM middlingsshowed a trend of decreasing Cu extraction with increasing feedsolids.

CIB more recently supplied Mintek with a characterised RTB-BorCu concentrate obtained by upgrading of the smelter slag (concentratecurrently re-smelted). Bioleach testing on this material showed itsready amenability to bioleaching, and with increased Cu recoverieswith increasing process temperature. These results confirm that theco-treatment of the slag with the RTB-Bor Cu concentrates would bean option for an integrated biohydrometallurgical plant at RTB-Bor.The other option being pursued by Seville is the indirect bioleaching ofslags. University of Seville are testing a representative range of slagand slag products from reverberatory, electric and flash smelters,including from the Huelva smelter, Spain.

Ltu has completed the neutralisation studies of 10 different oxidicbyproducts from Swedish industry. Ltu and Boliden are nowcollaborating to test the use of selected oxidic wastes added as analternative low-cost neutralisation agent to a refractory gold pyrite–arsenopyrite bioleaching system and the effects of this on bioleachingperformance, gold recovery and cyanide consumption.

IMN have shown that the total bio-degradation of organicsstripped from Pb-bearing slimes was technically feasible to upgradethe slimes.

64 D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

3.7. Heap bioleaching of kimberlite ores

Another ongoing related activity has been the biotransformation(accelerated weathering) of diamond-hosting kimberlite ore whichmay allow the use of less intensive comminution methods. Laboratoryresults under idealised conditions in the presence of Fe, S and bacteriahave clearly demonstrated the potential for biotransformation of theclay components in kimberlite ores (Gericke et al., 2007). Compressiontests on treated ore samples clearly demonstrated a direct relationshipbetween the degree of “weathering” and the compression stressmeasured, although XRD analyses of the mineralogical composition offeed and treated ore particles were shown to be similar.

3.8. General research activities

Significant RTD effort by a number of partners during years 1 and 2had gone into bio-prospecting and as a result a microbial cultureregister was created to support needs arising from bioleachingresearch on the various identified target resources and for otherresearch purposes. Over this period, it was also recognised that thebio-prospecting activities were intimately inter-related with themicrobial consortia and biomolecular tools activities. The majortechnology advance arising from these combined studies was theprovision of a range of tools tomore rigorously define andmonitor themesophilic and moderately thermophilic consortia that exist inbioleaching systems. In view of the emerging importance of thermo-philic bioleaching processes, it was considered important to nowextend these capabilities to include the thermophilic processes. Anotable advance was the isolation of psychrotolerant acidophiles,which may have previously unrecognised importance for the start-upof heap bioleaching processes in cold conditions (Dopson et al., 2007).Other key advances were studies using “constructed” consortia of fourkey types of mesophilic micro-organisms found in the tank bioleach-ing systems. This work has begun to provide improved understandingof the consortia dynamics for the bioleaching of a number of the targetconcentrate resources. Ongoing studies have also addressed the role ofextracellular polysaccharides in cell-mineral attachment and theirrelation to bioleaching performance (Harneit and Sand, 2007).

An important advance regarding an improved understanding ofthe molecular biology (genetics, transcriptomics and proteomics) hasbeen promising research results on functional gene probes which mayenable the detection of key specific activities in thermophiles, such asiron and sulfur oxidation, to be monitored during bioleaching. Relatedongoing research was the use of a transcriptomics approach toinvestigate the expression of iron and sulfur oxidation pathways inmesophilic bioleaching species (Bruscella et al., 2007). Steady progresswas also made in developing genetic systems for the importantbioleaching micro-organisms, with specific focus on achieving animproved understanding of the metals resistance mechanisms. This isstate-of-the-art research and there are no other known researchgroups carrying out similar work.

4. Metal separation and recovery from solids and liquids

A major driver for the work on bioleaching (WP2) is to reduce theenvironmental impact of the mineral industry. However, that cannotbe completely prevented.

The aim of thework package 3 of BioMinE is to develop technologiesthat can tackle environmental issues that remain despite these efforts.The technologies (like treatment or polishing of the final effluents)should fill the gaps or interact with existing treatment technologies toensure that the overall metal extraction process is environmentallybenign. But, WP3 goes further than just a developing treatmenttechnique. The aim is also to integrate treatment and metal recovery.This can be especially attractive for metal of secondary importance inconcentrates; metals that are often wasted to the tailings dam.

4.1. Metal sulfide separation and recovery

The blue-sky research in WP3 is the development of beneficiationtechnology using the properties of bacteria, in particular for theseparation of metal sulfides. An open mind is definitely kept to assesswhether this know-how is applicable in other fields.

The objective is to develop know-how and potential applicationsfor the separation of minerals and metals using the selectivity of theinteractions of micro-organisms with surfaces.

The following raw materials were chosen for the fundamentalresearch: sphalerite and galena. These minerals are often togethermineralised in sulfidic deposits.

A first approach that was followed was to use complete microbialcell. One group worked with yeast cells, the other with bacteria. Thesecond approach was to synthesise the particular extracellularpolymer that are involved in the attachment process.

With the yeast cell, several column flotation tests were done. ThepH value, pulp density of the sulfidic particles and biomassconcentration were varied.

It could be shown by the team of the Technical University of Berlin(Kuyumcu et al., 2007) that due to different surface charges of theseveral micro-organisms and mineral particles surface attachmentoccurs (Heterocoagulation = Biocoagulation). A yeast species likeYarrowia lipolytica was suitable. The process is selective. Y. lipolyticaacts as collector for galena and sphalerite at different pH values.

Flotation tests with the biocoagulates showed acceptable resultswith averaged recovery up to 90% for single minerals. The yeasts act ascollectors for galena and sphalerite at pH-values of about 6 withoutadditional chemicals. Loading densities of approximately one gramsphalerite per 5 to 10 grams yeast were obtained.

In research conducted by Ltu (Vilinskaa et al., 2007) wherebacterial cells are used, Acidithiobacillus ferrooxidans cells for thesurface modification of chalcopyrite and pyrite relevant tothe separation of metal sulfides from pyrite has been undertaken.The use of cells adapted to minerals by serial sub-culturing in thepresence of minerals is also investigated.

The cells exhibited an iso-electric point (iep) at pH 3 while the iep ofchalcopyrite and pyrite found to be at pH 6 and 7.5 respectively. Thepresence of cells shifted theminerals iep close to cells iep, illustrating cellsspecific interactionwith theminerals. The Leptospirillum ferrooxidans cellsbehaved differently in chalcopyrite–pyrite system than A. ferrooxidanscells where pyrite depressed and chalcopyrite floated with xanthatecollector. The differences in the oxidation of mineral surfaces caused bytheir varied catalytic activity and the production of OH⁎ radical besidesbacterial oxidation of the surfaces played a significant role for xanthateadsorption and flotation responses of the minerals.

A second approach that is followed by UDE is not to work withcomplete organisms, but to try to extract and synthesise the EPS that isthought to be responsible for the selective binding to the metalsulfides. Experiments to stimulate EPS production by adding quorumsensing active agents have been started. Preliminary results indicatethat two compound groups can be distinguished showing either anegative or a positive effect on attachment. So far, only the systempyrite with A. ferrooxidans ATCC 23270 has been investigated.Elucidation of EPS biosyntheses genes and regulation by themicroarray technique (in cooperation with CNRS) in the systemspyrite with either A. ferrooxidans ATCC 23270 or strain A2 has beenstarted.

4.2. Dissolved metal recovery from bioleachates

This exploitable result and the cluster around are focused on threepossible applications:

1) Recovery of metals secondary metals from bioleach stream (orother leached streams like autoclave). ‘Secondary metals’ are for

65D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

example nickel from a Cu/Ni concentrate or copper and zinc from agold leaching operation.

2) Recovery ofmetals fromwastes and tailings treatment. The techno-economical filter that was developed and applied in the first year ofBioMinE indicated that the wastes and tailings represent a massiveresource in Europe. In WP2 the focus is on dissolving these metalswith low-cost and low-intensity bioreactors. A SX-EW metalrecovery system will be uneconomic when such technology isapplied on a small scale or with low intensity. An economicalternative is to produce a pure intermediate product (a sulfide orcarbonate) that can be sold as a high-value concentrate to a smelteror a hydrometallurgical plant.

3) Recovery of metals from naturally leached streams. A large opportu-nity actually exists to recover metals from run-offs from old mines,tailings etc. This so-called acid mine/rock drainage can contain metalconcentration of up to 1000mg/l copper at flows of a dozen to several100 m3/h. However, the Cu load is often too small for a conventionalSX-EW so the stream is at best neutralised and the metals are wastedto the tailings dam. A biologically driven metal recovery can recoverthese metals at an attractive price. So, acid mine drainage with arelativelyhighmetal contents (i.e. 500mg/l of copper) couldbe turnedinto a resource or asset instead of being a problem.

The objective for this exploitable result is to collect technology thatcan economically and efficiently recover valuable metals of mediumconcentration from aqueous streams.

The work under this “exploitable result” is directed both to theabiotic precipitation of metals (for example nickel precipitation fromCu/Ni tank leach after Cu SX-EW) and to the (selective) precipitation ofmetals inside a bioreactor with sulfidogenic biomass. Both rely on thesame principles with regard to the metals because the selectiverecovery of metals from either bioleaching or waste streams can beachieved through exploitation of the different solubilities of variousmetal sulfides, e.g. the Ksp CubbZnbFe.

The major control parameter is the pH. In off-line systems, severalprecipitation stages can be operated at different pHs that are all fedwith either gaseous or dissolved sulfide.

Key to commercial and/or large-scale deployment of such atechnology is the development of systems with better process controle.g. ability to achieve selective precipitation from mixed metalsolutions. Acidophilic sulfate-reducing bacteria (aSRB) have beentargeted as interesting agents for use in such selective metal recoverysystems. One important objective of the project was to increase theunderstanding of the physiology of these microbes, relative to theirpotential metal precipitation.

The practical work in BioMinE with acidophilic sulfate-reducingbacteria (aSRB) showed that recovery of Zn from a Zn and Fecontaining solution was successful in a bench-scale system. Thebacteria isolated in the bioreactor were identified as Desulfosporosinussp. that grew better at pH 5 than at pH 6, indicating that they areacidophiles. However, the conversion of the electron donor glycerol isincomplete and the by-product acetate becomes easily toxic at the lowpH of the experiment. It is almost certain that a second organism ispresent that converts the acetate.

Novel strains of aSRB have previously been isolated by UWB from amine site in southern Spain. Phylogenetic analysis indicated that theseare distinct from the Desulfosporosinus sp. isolate M1 that have beentested under lower pHs. Growth was seen on plates at a pH as low as2.5. The aSRB cultures were further assessed for their use of variousorganic electron donors using a 96-well plate assay. A variety ofcompounds was tested with the mixed culture to see if they couldsupport sulfate reduction by the co-culture. These included a varietyof sugars that Acidocella PFBC can use for growth aerobically (but notanaerobically) such as fructose and sucrose, as well as some aromaticcompounds including benzoate and phenol. In addition, othercompounds that did not support growth of either micro-organism

were tested, including sugars such a glucose and galactose, as well asmethanol. In no case, however, was sulfate reduction apparent,indicating that the syntrophic partnership was limited by theprovision of acetate to Acidocella PFBC by the aSRB, and that onlyacetate can be catabolised by PFBC in the absence of oxygen. It appearsthat selective metal recovery systems based on these aSRB are limitedto a small range of potential electron donors, notably only those thatcan be used by the aSRB.

Previously it was shown that two different aSRB isolates (M1 andPFB) were capable of using the same range of electron donors,including glycerol, ethanol, mannitol, fumarate, citrate, succinate,glutamate, propionate and yeast extract. Isolate PFB was also able toreduce sulfate, using malate as electron donor. Previous work alsoidentified that the two aSRB produce acetate from organic electrondonors, which can inhibit aSRB at low pH. However, in consortiumconsisting of the aSRB and a second heterotrophic acidophile(Acidocella PFBC), no acetate was detected due to syntrophicinteractions between the two acidophiles.

Paques and WU worked on acidophilic or acido-tolerant sulfate-reducing bacteria with H2 as electron donor and CO2 as carbon source.Here, the aim is to precipitate nickel selectively from a streamcontaining iron and nickel. First, a test was run at pH 6 to separate zincand iron. That proved feasible. Then, the samewas done for nickel andiron. The results were also promising although the systemwas slightlyless stable. Both the nickel and zinc sulfide could be removed from thebioreactor effluent by settling. An investigation was also done in thetoxicity of sulfide at a pH of 5 in a gas-lift reactor. The removal ofsulfate became incomplete at a sulfide concentration of N500 mg/l.The population in these bioreactors has also been studied. Consider-able progress has been achieved with the molecular phylogeny of thepH 5 (16S rRNA), pH 4.5 (16S rRNA and dsrB), and low and highsulfate-reducing bioreactors (16S rRNA) are now completed.

An experimental set-up has been operated for biological sulfurreduction for those systems where the metal is precipitated in aseparate compartment (contactor) from the bioreactor. The processcould be further improved. An H2S concentration of N15% in the richgas to the contactor could be achieved and this could be maintained.

The sulfide precipitation was also tested for nickel. Good recoveryrates (N99%) from a 5 g/l solution could be obtained at a pHb5.

4.3. Water purification, recovery and reuse

Themetal andmining industry is well known (and criticised) for itslarge impact on local water conditions in the widest sense. Effects ongroundwater levels, consumption of water for processing plant, acidmine drainage and the release of water with a quality that is ofteninsufficient to allow reuse, are the main issues.

Developed technologies are aimed at improving the quality ofdischarge for a variety of applications and particularly the effluents ofbioleaching operations. They are focussed on the use of biologicalprocesses but also take interactions with other processes likemembrane technology also into account.

As a first step, as much as possible of valuable metals should berecovered. Then, the water should be processed to remove remainingmetals and salts. The aim is to process water to a level that is suited forthe envisioned reuse.

The objective of this exploitable result is to collect technology topurify water for different types of reuse, with biotechnologicalprocesses as a core component.

The microbial population in fluidised bed reactors that wereprimarily aimed to remove sulfate from water has been investigated.The water that is released from bioleaching operations is often of ahigh temperature. A biological sulfate removal/sulfide generation athigh temperature is beneficial when processes are coupled.

Work has primarily been done on both thermophillic (65 °C) andpsychrophillic (9 °C) organisms. The electron donor of a fluidised bed

Fig. 4. Treatment flowsheet devised by Imperial College using filtration and reverse osmosis for recycling water in the process of bioleaching of refractory gold concentrates.

66 D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

reactor (FBR) was switched from ethanol to formic acid to testwhether the volumetric activity could be increased. This provedindeed the case as the activity increased two-fold to a maximum850 mg/l/d rate of sulfate, although after a long lag period. Thepopulation was studied with PCR-DGGE (Polymerase Chain Reaction-Denaturing gradient gel electrophoresis). The population was stillsurprisingly diverse despite the high temperature. A second newthermophillic SRB genus was described: Desulfurispora thermophilagen. nov., sp. nov. and deposited into public databases (DeutscheSammlung für Mikroorganismen, DSM and Japan Collection ofMicroorganisms, JCM). Additionally a manuscript on the descriptionof another new sulfate-reducing species, Desulfotomaculum alcoholo-vorum, sp. nov., was submitted.

The increase in activity upon a change of ethanol to formiate wasmore pronounced under psychrophillic conditions; an increase from0.4 to 1.4 g/l/d of SO4 conversion was observed at a residence time ofapproximately 20 h. The conversion of sulfate was not always stable asit fluctuated between 50 and 90%. The reactor operation could bestabilised by applying a slightly higher influent pH from 3 to 4.5 andby lowering the free sulfide concentration through precipitation. APCR-DGGE analysis indicated that all bacteria present in this culturehad a resemblance with previously known bacteria of 98% or more.

The picture in Fig. 4 shows in a simple way imagined by Imperial'steam howmembrane technology can be introduced into a bioleachingflowsheet to upgrade the water quality. The work on membranetechnology with synthetic liquors, based on data from an industrialprocess, were subjected to filtration, reverse osmosis and/or resin ionexchange processes under designed conditions in a re-circulatingsystem. Arsenical ferrihydrite precipitated from the synthetic liquorswith lime retained most of the arsenic(V) (Asb100 ppb). Over 90% ofresidual As(V) was removed by reverse osmosis thus achieving theWHO standard (Asb50 ppb for discharge). Drinking water standardswere readily achieved by reverse osmosis and ion exchange employedin sequence. Arsenic(III) was poorly retained by the RO membrane

(only 20–55% removal) because arsenite existed as neutral molecule(which readily penetrated the membrane). Therefore prior oxidationof As(III) to As(V) is a pre-requisite.

The ecotoxicological assessment (Algaltoxkit) that was used in thebeginning of the project by Umicore proved also useful in this researchalthough theanalyseswere timeconsumingandrequiredexperiencewithalgal cultures. The algae became insensitive to arsenic below 100 ppb.

With regard to the removal of heavy metals, synthetic mine liquorwas spiked with high concentration of Cu, Ni, Zn, Cd (1 g/l) and Pb, Hg(0.5 g/l). The percentage of heavy metal removal with neutralisationandprecipitationwas approximately 98–99% for Cu, Pb andHg, but lessfor Ni, Zn and Cd. Reverse osmosis achieved more than 90% removal ofCu, Ni, Zn and Cd but very poor removal of (un-ionised) Hg. Concerningwaste from cyanidation, cyanide residues (typically 2 g/l and 0.18 g/Lfor 35 and 70 °C bioleach) could be destroyed (e.g., by hydrogenperoxide); complexed (e.g. with iron salts); or recycled. Preparation ofPrussian blue with iron from bioleaching was successful in thelaboratory at initial low pH but the complex did not surviveneutralisation. This work is also useful for effluent polishing.

4.4. Effluent polishing

The demands on the quality of the final effluent of industries,includingmetal andmining, are becomingmore strict as the EuropeanWater Directive is coming into force. The way the water quality isdetermined is also likely to change. Currently the quality is basicallydetermined based on concentrations of compounds. However,ecotoxicity tests, which determine the quality of an effluent with atest on organisms like bacteria, algae, fish, etc., are expected to berequired. Furthermore, the type, quantity and quality of the receivingwater will be taken into account.

The experimental work in the first year of BioMinE showed that abiological treatment resulted in less ecotoxicity than a physico-chemical treatment. However, metals like arsenic, selenium, thallium

67D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

etc. that are noxious at low concentrations receive more attention asproblematic metals in final effluents.

Experiments of sulfate reduction carried out by BRGM on acidicinfluent as high as 100 mg/l of As have shown the capacity ofefficiently removing arsenic down to 1 mg/l.

Molecular biology analyses were performed at different levelsinside the fixed film bioreactor. Liquid samples were considered asrepresentative of the biofilm colonizing the column. Biodiversitystudies (16S rRNA gene for phylogenetic identification and arrA genefor arsenate reductase detection)were focused on the biofilm from themiddle of the column. Analysis of 16S rRNA gene sequences revealed adiverse population composed of at least of 4 Gram+ genera. A newDesulfosporosinus strain (96% id. with Dsp. orientis) was selected inthe column. Only one arrA sequence, related to Desulfosporosinus arrAsequence, was detected. Those results suggest that the new SRB is theonly one responsible for As(V) reduction in the process. In theglycerol-fed bioreactor, the Desulfosporosinus ratio was important atthe bioreactor bottom, near the feeding point, and decreased from thispoint to the outlet. This result is consistent with the sulfate reductionoccurring in the first one third of the column, where the energeticsubstrate glycerol is available. Feeding with H2 increased the ratio ofDesulfosporosinus and Sporomusa-like bacteria along the column,probably because H2 (energetic substrate for SRB) is uniformlydistributed in the bioreactor.

On another hand, a new sulfate-reducer was isolated from thebioreactor. Species description including determination of optimumpH, ability to use As(V) as terminal electron acceptor, substratesutilization, etc. is ongoing.

NTUA's work is focussed on base metal removal from effluent ofmetallurgical processing (Kousi et al., 2007) with the main followingobjectives:

• Residence time optimisation for both nutrient and waste stream,• Efficiency optimisation of the reactors in terms of metal removal forboth synthetic and real wastewater.

The solid phase inside the bioreactors was more closely investi-gated. Both XRD and SEM-EDX analyses show that metals like zinc andiron had precipitated as fine amorphous sulfides. This had as adrawback that bacterial cells become encapsulated by zinc and ironsulfides as observed by SEM-EDX. However, this did not appear toaffect the bioreactor columnperformance. This is explained by the factthat the bacteria are continuously growing, thereby created newsurface area for exchange of products and nutrients.

5. Studies of the integrated process flowsheets (WP4)

This is during the third year of the project that the activity in theworkpackage 4 has started being significant with the determination of

Fig. 5. Time schedule from amenability test work to

the specifications of the operating conditions and of the equipment ofthe applications that include a processing step with the use of thebioleach technologies to be techno-economically evaluated.

A focus on indirect bioleaching of zinc/lead bulk and polymetallicconcentrates has demonstrated very attractive results and thecombination of expertise in WP2 on microbial aspects and in WP4on the process side have had a synergetic effect on the developmentstudies.

Work on the optimisation of the metal recovery from the pregnantsolutions (Zn/Cu/Ni) or from the solid residues (Pb/Ag) according tothe resources treated has progressed towards a reliable knowledge ofthe performances of the technologies used.

The exploitation of the data obtained at bench-scale has allowedestablishing the design of process flowsheets from the attack of themineral resources by bioleaching to the recovery of pure metals andwater recycling.

The time schedule of this workpackage aiming at the demonstra-tion operations during the fourth year of the project is quite respectfulof the planning as shown in Fig. 5.

6. Training and dissemination of knowledge

The work of design and implementation of learning objects on theweb covered by the workpackage 6 has now a close and direct contactwith the R&D activities, since this work has been fully accepted amongthe partners and is used by them. Many other partners than WP6partners are now contributing to the work as extra services. This isespecially true for the BioMineWiki (http://wiki.biomine.skelleftea.se/wiki), which was launched during the spring of 2007. The wiki is ongood way to develop into a ‘living’ instrument, a network communitytool and a reference tool to be presented as a service for peoplestarting a professional career in biohydrometallurgy. The wiki isexpected to play a vital role in the dissemination and exploitationwork also.

7. Economy and sustainability

The study of themacro-economy of themarkets of copper and zinc,which are the twomainmetals targeted in the project in the Europeanperspective, have shown that the demand of those metals is so highthat local mine-to-metal installations using biotechnological pro-cesses are particularly attractive, even if the viability of theimplementation of such installations is site specific. Europe doeshave a lot of existing refining capacities and some are to be upgraded.Biotechnologies could be considered here not to replace the refiningprocess but to overcome some problematic steps of the existingcapacities. The successful development of a bioleaching route wouldenable existing facilities to expand their output without installing

pilot-scale operations in the frame of BioMinE.

Fig. 6. Conceptual cost comparison for base metal production route alternatives.

68 D. Morin et al. / Hydrometallurgy 94 (2008) 58–68

additional roasters. A further advantage would be the ability to accepta broader range of concentrates, including those unsuitable forroasting for example, those with high copper levels in the case ofzinc concentrate for instance.

After screening all the processing routes for extracting zinc fromsulfide concentrate, it appears that the mine-to-metal route could becompetitive depending on Treatment Charges/Refining Charge'sforecasts and cost estimates. One should bare in mind that betterrecoveries can probably be obtained with a more basic concentrationstep in the mine-to-metal route than in the traditional one (see Fig. 5).Thismay be not only away to raise the yield of recovery of metals fromthe mineral resources and to increase the diversity of the resources,but also to improve the sustainability of the whole process chain ofproduction of metals from primary or secondary materials (Fig. 6).

This will be during the fourth year of the project and whileobtaining the results of techno-economic evaluation of the selectedprocesses that the sustainability of the different routes will beassessed by USTUTT and PE International in comparison withconventional ways of recovering metals.

8. Conclusion

While the market pull becomes more and more visible on a long-term basis with the high price levels of the non-ferrous metals, thetechnology push as developed in BioMinE is more and more self-assured and ready to match the needs. At the end of the first year, theobjective of having selected benchmark resources was reached.Within the second year, the technologies for treating the typicalEuropean resources selected were established. The third year wasparticularly dedicated to achieving most part of the amenabilitytesting and defining through bench-scale studies the operatingconditions for pilot-scale demonstration operations to be mainlyundertaken during the last year of the project.

This is also during this last year of the project that the screening ofthe exploitable results has given more opportunity to the partners tofocus their involvement and their efforts on subjects that represent atrue European challenge. The clusters of partners around a limitednumber of exploitable results targeting real evaluation of processingroutes have allowed rationalizing the work and reinforcing themotivation about the success in terms of applicability of the processdeveloped.

Acknowledgements

The mining owners and operators that have provided samples ofthe benchmark materials tested in the frame of the BioMinE aregratefully acknowledged as well as for the relevant information totheir resources. These are Rio Narcea (Spain), Boliden (Sweden), RTB-Bor Grupa Mine (Serbia), KGHM (Poland) and Somincor (Portugal).

This paper is a contribution to the coordination activities of theBioMinE project co-financed by the European Commission (through acontract under the reference NMP2-CT-2005-500329).

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