Atmospheric Chloride Leaching of Base Metal Sulphides

Atmospheric Chloride Leaching of Base Metal Sulphides… 197

Atmospheric Chloride Leaching of Base Metal Sulphides Bryn Harris (1), V Lakshmanan(2), T. Magee(1), R. Sridhar(2) (1) Jaguar Nickel Inc., Toronto Canadá (2) Process Research Ortech Inc., Missisauga Canadá [email protected]

Abstract The Jaguar Nickel Atmospheric Chloride Leach Process, recently developed for nickel laterite ores, has been successfully adapted to the atmospheric leaching of base metal sulphide feeds. Results are presented showing that greater than 95% of the contained copper, nickel and cobalt can be solubilised from base metal sulphide concentrates irrespective of the PGM content of the feed, and that substantially all of the sulphur can be removed and recovered as an elemental product suitable for sale. The paper discusses the roles of the important parameters, net chloride concentration, pH, Eh and temperature, on the extraction kinetics and overall recovery of the metals. Speciation of sulphur and the deportment of PGMs is also discussed. A conceptual flowsheet is presented.

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Bryn Harris 198

Introduction Jaguar Nickel Inc., with the assistance of Process Research ORTECH, has been developing a novel chloride-based flowsheet for the recovery on nickel and cobalt from Guatemalan laterites [1,2,3]. A logical consequence of this development was to see if the chemistry could be equally applied to sulphide ores as well as oxide ores, and this paper reports on results obtained in the laboratory using a modified version of the chloride-based circuit developed for oxidic feeds. The immediately obvious differences are that sulphide feeds both require an oxidant to effect leaching and also have much higher values of paymetals relative to gangue and impurities than do laterites, and cognizance of these differences has been taken into account in looking at sulphide feeds. Chloride chemistry, particularly in strong salt solutions, is complex, and can be quite different from that found in corresponding sulphate systems. The two most important factors in concentrated chloride salt solutions (brines) to note are firstly that the activity of water is <<1, and secondly, that the activity of the hydrogen ion, H+ (or, more importantly, H3O+), is significantly increased. It follows, then, that in concentrated brines such as magnesium chloride considered for the Jaguar Process, in general, a small amount of acid can achieve much more than a similar amount in more dilute chloride solutions or in sulphate systems. It is also necessary to appreciate that base metals, with the exception of nickel, form a variety of chloro-complexes, and that these also have a bearing on the properties of the system, and, hence, efficient impurity removal and better product recovery. Considering the above, the behaviour of ferric iron is of great interest. The reduced activity of water offers the opportunity to readily hydrolyze any iron that enters solution, and at a significantly lower apparent pH1 than can be achieved in sulphate. Provided that the overall chloride concentration is maintained such that FeCl4

- does not form to any extent, in which case hydrolysis would be very difficult, then it should be possible to leach out base metals from sulphide feeds, and with appropriate control of the redox manipulate the form of sulphur produced, and such has formed the basis of the flowsheet presented in this paper. The Chemistry of Chloride Systems The fundamental background to the chloride chemistry which forms the basis of the work reported in this paper has been discussed at some length in a previous publication [3], and is therefore not reproduced here. Nevertheless, it is pertinent to revisit certain of these fundamentals as they apply to base metal sulphide feeds. Chloride metallurgy has for many years been primarily the domain of precious metals production, but is increasingly being considered as an alternative process for the production of base and refractory metals. Many metal chlorides are found to be considerably more soluble than their corresponding sulphate salts, thus allowing the use of more concentrated solutions. The solubility of CuSO4.5H2O, for example, is about one fifth that of CuCl2.2H2O, and both nickel and ferrous chlorides are also more soluble than their sulphate counterparts [4]. Additionally, and with particular relevance to sulphide feeds, the enhanced leachability of minerals in chloride solutions can be attributed to, in part, the high oxidizing potential of both the Fe(III)/Fe(II) and Cu(II)/Cu(I) couples, as well as the high stability of the chloro-complexes of many transition metals. This lowers ionic activities and potentials for sulphide corrosion, as well as imparting moderate solubility of these complex species in stronger brine solutions. Redox Potentials and Chloride Complexation The standard reduction potentials for some of the reactions of interest are provided below: Oxygen ½O2 + 2H+ + 2e- = H2O 1.23V (1) Iron Fe2+ + e- = Fe(s) -0.44 V (2)Fe3+ + e- = Fe2+ 0.73V (1.0N HCl) (3)FeOOH + 3H+ + e-= Fe2+ + 2H2O 0.74V (4)

1 It should be noted that pH can be a very misleading term when applied to strong brines due to both the low activity of water

and the enhanced activity of the hydrogen ion.

Hydro-Sulfides 2004


FeO42- + 3H2O + 3e- = FeOOH + 5OH- 0.80V (5)

Nickel Ni2+ + 2e- = Ni -0.24V (6) Cobalt Co2+ + 2e- = Co -0.28V (7)Co3+ + e- = Co2+ 1.92V (8) Copper Cu+ + e- = Cu 0.52V (9)Cu2+ + e- = Cu+ 0.16V (10)Cu2+ + 2e- = Cu 0.34V (11) Magnesium Mg2+ + 2e- = Mg -2.36V (12)

The potential-log [Cl-] shown in Figure 1 indicates that at a concentration of 10M Cl- (354.5 g/L of Cl-) and 0.73V, iron will be present as ferric chloride, whereas ferrous chloride is the most predominant from 1.0M Cl- (35.45 g/L of Cl-) and higher and between –0.4V and 0.73V. The reduction potential for the Ni++/Ni couple is –0.3V as against its standard reduction potential of -0.24V [5], and, therefore, the dissolution of nickel is highly favorable in this system, where the reduction of oxygen will provide the required dissolution potential for nickel and iron. A similar argument also holds for cobalt and for copper. Furthermore, it can be seen that the oxidation of iron to the ferric state is also favorable under these conditions, which in turn could contribute to the dissolution of nickel and other base metals as it reduces to the ferrous state.

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6

-2 -1 0 1 2

log[Cl-]

Eh / VCl2

Au

H2O

Cl-

AuCl4-

O2

Fe2+

Fe3+ FeCl2+FeCl2

+ FeCl3

FeCl+ FeCl2NiNi2+

Zn

Zn2+ ZnCl

+

ZnCl42-

ZnCl

3-

Pb2+

Pb

PbCl+

PbCl42-

FeFe2+

H+

H2

Cu

Cu2+

Ag

AgCl2-

AgCl32-

CuCl+ CuCl2

CuCl2-

CuCl32-

ZnCl

2

BiCl

2+

BiCl4-

Bi BiCl

52-

BiCl63-

Figure 1. Eh-log[Cl-] diagram at 25oC [5]

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Chloride Hydrometallurgical Practices Apart from the precious metals plants (which of necessity have to operate in chloride), there have been relatively few commercial hydrometallurgical operations treating sulphide feeds which have been conducted entirely in chloride media. A review of these processes can be found in an earlier publication [3]. Despite this, a chloride-based atmospheric leach process, whilst unusual, is far from unique. Noranda operated the Brenda Leach Process, employing a high temperature (105-110oC), high-strength chloride (CaCl2+NaCl+HCl) atmospheric leach of copper-molybdenum sulphide concentrates until the mine shut down in the 1990s [6]. The process essentially leached out all of the copper, lead and calcium from molybdenum, and the only real factor of concern was to maintain the lagging on the piping in winter to prevent the high strength brine from crystallizing [7]. Falconbridge operates a chloride process at its nickel-cobalt refinery in Kristiansand, Norway, which was initially a hydrochloric acid leach, but more latterly a chlorine leach [8,9,10]. These and other plants such as those operated by Jinchuan [11], Sumitomo [12] and SLN [13] in a mixed chloride-sulphate medium, clearly demonstrate that chloride-based circuits are perfectly feasible, and that any material-handling issues associated with a chloride environment can be and are being overcome. One major unit operation sometimes associated with chloride flowsheets is pyrohydrolysis of the final chloride liquor, and over the years, this has become a very mature technology, particularly in the steel pickling industry for the treatment of ferrous chloride solutions. There are essentially two ways of operating, in a spray roaster or in a fluid bed [14]. When treating a magnesium chloride feed solution, the former generates a fine, caustic powder, suitable for use as a neutralizing and precipitating agent within the process, whereas the latter generates coarser particles, more suitable for handling and sale. Significant work has been recently reported on the pyrohydrolysis of such solutions, a process which is operating successfully on predominantly magnesium chloride liquors at Rio Tinto Iron and Titanium (QIT) in Quebec [15,16]. It is also worth noting that at its Goro plant in New Caledonia, Inco plans to use pyrohydrolysis for the production of nickel oxide and to recycle HCl within the solvent extraction circuit [17]. Chloride Metallurgy for Base Metal Sulphide Feeds Beginning in the 1970s and early 1980s, when it was firmly believed by hydrometallurgists that aqueous processing would confine smelting to the history books, there was a great deal of interest in and research into developing chloride-based hydrometallurgical processes for the treatment of (primarily) copper sulphide concentrates [18,19,20]. Of these early attempts, only Duval’s CLEAR (Copper (chloride) Leach Electrowin And Regeneration) Process [21,22,23,24,25,26] attained commercial operation, and this only from 1976 until 1982, when it was shut down for economic reasons. The Cyprus CYMET Process [27,28,29,30,31,32] attained a pilot operation at 45kg/h, but none of the others, those of Minemet Recherche (Imetal) in France [33,34,35], Dextec in Australia [36,37,38,39,40,41], Elkem in Norway [42,43], the USBM Process [44,45,46,47], the Canadian Great Central Mines Process [48,49,50], Phelps Dodge [51], and UBC/Cominco [52], with the exception of Dextec which has transmogrified itself into the Intec Process [53,54,55,56,57], seem to have progressed at all. Although the literature contains many references to ferric and cupric chloride leaching of chalcopyrite concentrates [20], of which the studies by Dutrizac [58,59], Majima et al.[60], and Holdich and Broadbent [61] are of interest, none of the processes really overcame the difficulties associated with precious metals recovery, electrowinning of copper from a chloride medium, and the effective recycle of lixiviant, whether ferric or cupric. The following summarises some of the salient features of these early processes.

CLEAR Process (Duval) [21,22,23,24,25,26] The CLEAR (Copper (chloride) Leach Electrowin And Regeneration) was probably the most developed of all of the sulphide hydrometallurgical copper processes [18,21,22]. It comprised a two-stage leach, with 50% of the copper in concentrate being recovered in a ‘reduction’ leach with CuCl2, generating a cuprous chloride solution suitable for electrowinning. The balance of the copper was recovered in an oxidation leach with ferric chloride; iron leached from the concentrate was precipitated as goethite, and the recirculating load of iron was oxidized with oxygen in a pressurized reactor at 140°C. The only major consumable was oxygen, and virtually all of the sulphur in the feed reported to the leach residue in elemental form. A small proportion of the sulphur was oxidized to sulphate, which was precipitated as jarosite. Solvent extraction was introduced into the flowsheet for the control of impurities such as zinc [23,24], and arsenic, antimony and bismuth remained largely in the leach residue. However, concentrations above 50 mg/L As, Sb or Bi resulted in unacceptable copper [25]. Silver in the concentrate leached and reported to the copper product [25,26], although efforts were made to recover it from solution by amalgamation [26]. Gold normally reported to the leach residue, although it was shown that it could be recovered by leaching with high chloride cupric chloride solution, with subsequent electrowinning of the gold [62]. The process operated from 1976 until 1982, and was shut down for economic reasons (along with a number of other U.S. copper operations, it might be added).

Hydro-Sulfides 2004


CYMET Process (Cyprus Metallurgical Processes) [27,28,29,30,31,32] This was one of the first copper hydrometallurgical processes treating a sulphide feed and proceeded as far as a 45 kg/h pilot plant [27]. The process that was piloted was not the original one, (which was based on anodic dissolution and suffered from pollution problems [27]). In the revised flowsheet [27,28,29,30,31,32], copper was leached by a mixed cupric/ferric chloride solution in two stages at 90-95°C. Copper was recovered by cuprous chloride crystallization followed by hydrogen reduction. The lixiviant was regenerated by oxydrolysis of the crystallizer mother liquor, which also yielded jarosite and ferric hydroxide for disposal. Reagent requirements were for hydrogen, oxygen and alkali (for jarosite precipitation). According to Flett [18], the process did not appear to have been investigated for complex sulphides, and it would seem that any feed with substantial lead and bismuth contents caused serious impurity problems in the cuprous chloride crystals. A separate recovery step (amalgamation) was included for silver recovery, but any gold was lost with the residue. MINEMET Process [33,34,35] This process was developed by Minemet Recherche (Imetal) for the recovery of cathode copper from chalcopyrite concentrates [33,34]. For copper concentrates, leaching was by two stages of cupric chloride/sodium chloride at close to the boiling point. Copper was recovered by solvent extraction and conventional sulphate electrowinning; any cuprous copper present in the leach liquor being oxidized by air sparging during solvent extraction. For more complex sulphide concentrates [33], especially those containing lead, the lixiviant was ferric chloride/sodium chloride, and the copper was removed from solution along with silver and bismuth by lead cementation. Lead was recovered by electrowinning. DEXTEC Process [36,37,38,39,40,41] In this Australian-developed process, chalcopyrite concentrate was converted to copper powder, ferric oxide and elemental sulphur in an electrolytic diaphragm cell. The reaction was carried out at 90°C in near-saturated sodium chloride solution under air sparging. For lead concentrates, the temperature was 70°C without air sparging [38]. Silver was leached and reported with the copper powder, but gold reported to the leach residue, where it could be recovered by cyanidation or a proprietary Dextec process [40]. Bismuth, lead and zinc were leached selectively from the concentrate, and arsenic reported to the leach residue (presumably as a ferric arsenate-type material). The process was tested on a number of concentrates at the pilot scale (100-L cells), and a commercial cell (8 m3) was reported to be operating at Port Kembla [40], with the pilot lead version subsequently operating at a European smelter.

ELKEM Process [42,43] This process was developed by Elkem in Norway, specifically to treat concentrate from a small Norwegian copper mine [18]. It was piloted at 150 and 1500 kg/day on a number of concentrates, and comprised a two-stage ferric chloride leach, crystallization of lead chloride and electrowinning of copper/silver powder. Zinc was recovered from the spent catholyte by solvent extraction with TBP. As with the other processes, sulphur reported to the leach residue in elemental form, iron was oxidized and precipitated as goethite, jarosite (from the small amount of sulphur oxidation) and ferric arsenate (along with arsenic). Impurity control was by neutralization of a bleed stream. Behaviour of gold was not mentioned, but it is likely that it remained in the leach residue. USBM Process [44,45,46,47] This was also a ferric chloride leach process at 104°C, followed by copper recovery by electrowinning in a diaphragm cell. The copper product also contained the silver leached from the concentrate. Gold remained in the leach residue along with elemental sulphur. Iron was controlled (presumably also arsenic) by oxydrolysis and precipitation as hydrated oxide, which also appeared to act as scavenger for all other impurities, except sulphate and lead [47]. The process, as described, was only tested on chalcopyrite concentrates. GREAT CENTRAL MINES Process [48,49,50,51] This could be regarded as the being the last of the plethora of processes developed in the late seventies and early eighties, and was developed by Bacon, Donaldson and Associates [48,49] using HBMS concentrates. The process [49] was basically a two-stage cupric chloride leach, with elemental sulphur reporting to the residue, as with the other processes. Silver was recovered from the leach liquor by a proprietary process, and copper was recovered by electrowinning. Iron was removed by hydrolysis and precipitation of spent catholyte. Gold was not mentioned, but again presumably reported to the leach

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•

residue. A proprietary modification of the leach chemistry when dealing with complex concentrates dealt with impurities [51].

More Recent Developments The late 1980s and early 1990s saw a renewed interest in chloride-based processes, primarily for the treatment of complex base metal sulphide feeds which were not amenable to smelting. Those of particular interest in addition to the advent of the Intec Process mentioned earlier, were the CANMET FCL (Ferric Chloride Leach) Process [63], the Cuprex process of ICI and Tecnicas Reunidas in Spain [64,65], otherwise known as CMEP or later, Cuzclor [78], and the CENIM-LNETI Process, developed in Portugal, and which interestingly employs an oxidising leach in a strong ammonium chloride solution [66]. However, to date, once again, none of these appears to have reached commercialisation. The past few years has seen the continued development of the Intec Process, which uses a mixed bromine/chlorine oxidant, BrCl2

-, denoted Halex™, and the advent of Outokumpu’s HydroCopper™ Process, which makes novel use of a chlor-alkali cell [67,68,69,70]. Also being pursued at the present time is chloride-assisted sulphate pressure leaching, originally developed as Noranda’s Antlerite Process in the 1970s [71], a variation and modification of which is the CESL Process [72,73,74], and most recently the basis of the process proposed by Inco for Voisey’s Bay [75]. There have also been processes reported for simply the upgrading of chalcopyrite concentrates, particularly from complex sulphides, the most interesting of which in the context of the Jaguar Process was that described by Dyson and Scott using acidic magnesium chloride solutions [76]. In these processes, the copper component of the concentrate largely remains unaltered, while the iron (and zinc) components are selectively removed. Finally, one other process of interest was that proposed by Adamson and Naden [77], wherein sulphide feeds were pressure leached in a magnesium chloride medium under an oxygen atmosphere. The purpose of the magnesium chloride was to promote the formation of elemental sulphur, as well as the retention of iron in the leach residue. However, as with all of the other processes mentioned above, it seems not to have progressed beyond the developmental stage.

DISCUSSION OF PUBLISHED PROCESSES Flett [78] recently published a review of the applications of chloride hydrometallurgy to complex sulphides, concluding that whilst there were no current operating processes, the Intec Process seemed the most likely, if any, to achieve commercialisation. Even more recently, Senanayake and Muir [5] have looked at the fundamentals of processing sulphide feeds, demonstrating that it should, indeed, be possible, to develop a chloride-based process for sulphide feedstocks. The chloride-based processes essentially solubilise base metals with either cupric and/or ferric ions, with copper recovery generally being proposed by electrowinning from cuprous chloride, which is theoretically less energy intensive than conventional sulphate electrowinning, but which has never really been made to operate satisfactorily. Iron was rejected as goethite (which acts as an impurity scavenger), or as jarosite if appreciable sulphate formation occurred. Most of the deleterious impurities (As, Sb, Bi) were claimed to remain in the leach residue along with elemental sulphur. Zinc, if present, could be recovered by solvent extraction/electrowinning after copper recovery, and lead crystallized as chloride from the hot leach liquor by cooling. Silver was usually leached and reported to the copper, if a separate recovery step was not introduced. Gold and the PGMs generally remained in the leach residue, and were difficult to separate and recover. The three major problem areas were therefore copper recovery, sulphur production and PGM recovery. As noted above, direct electrolysis of cuprous chloride was never really successful, but this is easily overcome by employing solvent extraction, transferring into sulphate and carrying out conventional electrowinning. The issues of sulphur formation and PGM recovery were never satisfactorily addressed. Whilst appearing to be logically attractive, the formation of elemental sulphur directly in the leach process always led to subsequent problems, whether they were environmental in nature or were related to the subsequent separation and recovery of both the sulphur and the precious metals. In developing the process outlined in this paper, the authors have taken cognizance of the particular difficulties associated with elemental sulphur, as well as generating an intermediate concentrate from which it is relatively simple to isolate and recover the precious metals. Effluent treatment has been minimized by recycling the lixiviant, leading to an environmentally friendly flowsheet. Magnesium Chloride as a Lixiviant Medium It is apparent from the discussion presented in a previous paper [3] that high strength chloride brines, and in particular those of magnesium chloride, have some unusual properties that can be advantageous in leaching circuits:

High H+ activity – enables only a small amount of acid (HCl) to effect leaching of the value metals. This is because the high hydrogen ion activity provides a very much higher driving force than for equivalent acid strength in more

Hydro-Sulfides 2004


dilute solutions, and in many instances, the amount of acid added need be only marginally higher than the stoichiometric amount required for the base metals.

•

•

•

•

•

•

Low water activity – coupled with the high solubility of base metal chloride salts, permits more effective control of iron in the liquor through hydrolysis and re-precipitation. Essentially, there is “insufficient capacity” for the brine to hold high levels of ferric iron in solution, since ferric has the lowest pH of hydrolysis amongst any of the ions present, although the low iron levels in sulphide feeds relative to oxides still results in high iron extraction.

High magnesium concentration – leading to low water activity and, through the common ion effect, minimises the dissolution potential of magnesium.

High chloride concentration – stabilises base metals in solution and leads to increased solubility. However, care has to be taken that the chloride levels are not so high as to promote the formation of ferric anion complexes such as FeCl4

-, which are difficult to hydrolyse and precipitate from solution once formed.

Pyrohydrolysis – the alkali and alkaline earth chlorides do not decompose during pyrohydrolysis, unlike magnesium chloride. Therefore, using MgCl2 permits the recovery and recycle of both hydrochloric acid and caustic (highly reactive) magnesia, the acid being recycled to the leaching step, and the MgO being used for neutralisation and precipitation within the flowsheet downstream of the leach circuit.

Sulphur removal – the high proton activity achievable with low acid concentration means that reductive leaching can readily be attained, enabling the elimination of sulphur as hydrogen sulphide very easily and efficiently.

A further, and often overlooked, property of magnesium chloride is that it is a very effective desiccant. The result of this is that the leach solids tend to be partially dehydrated by the leaching medium, and thus both settle and filter somewhat more efficiently than might be anticipated from their behaviour in sulphate media.

Testwork and Results Initial laboratory testing has been conducted in order to test the hypotheses discussed above with reference to sulphide concentrates. Unfortunately, the timing of the conference (April, 2004) means that only limited data can be reported in this paper, but they nevertheless confirm that the magnesium chloride system potentially offers a viable route to treating base metal sulphides. Based on work conducted with the laterite project [1,2,3], process conditions were chosen as 95oC, 4 hours leaching time, with an initial lixiviant solution of 400 g/L total chloride, comprising 4N HCl, with the balance of the chloride from MgCl2. Feed solids pulp density was 5%, this level being chosen to ensure that salt crystallization did not take place. The analysis of the first two sulphide concentrates tested is shown below in Table 1, one of which was from the northern hemisphere, and the other from the southern. Concentrate II contained appreciable values of precious metals, whereas Concentrate I had negligible PGM content.

Table 1. Analysis of Sulphide Feeds Used in Testwork Fee

d Ni Fe Cu Co Zn So S2- Au Ag Pt Pd Rh

% % % % % % % ppm

ppm

ppm

ppm

ppm

I 18.7

26.6

1.38

0.19 0.01 - 20.

1 - - - - -

II 18.0

29.0

1.40

0.25

0.013

1.43

23.8

0.27 7.0 1.1

4 3.88

0.44

A series of leach tests was carried out for each concentrate, using a variety of oxidants, and the results obtained to date are summarized below in

Table 2. The results clearly show that:

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Bryn Harris 204

•

•

• •

•

•

•

High base metal extraction can be achieved with several different oxidants, although this is undoubtedly a function of the concentrate and the oxidant used. Test 11 gave the best results with concentrate I, using oxidant F. Unfortunately, the results for concentrate II with oxidant F were not available for inclusion in the paper.

Sulphur elimination was generally >99.9% (as hydrogen sulphide). Negligible elemental sulphur was seen in the leach residues, and very low levels of sulphate were observed in the final leach liquor (

Table 2). This is a highly effective and efficient means of eliminating sulphur from base metal sulphide concentrates.

Iron extraction was high (predominantly as ferrous), but such is not a problem in this flowsheet compared to laterites, since the Fe/base metals ratio is very much lower with sulphide feeds. High iron extractions still give relatively low iron in solution compared to the base metal content, and this can very easily be removed in a chloride medium by precipitation with recycled reactive magnesia with almost negligible co-precipitation of base metals.

As anticipated, no dissolution of gold, platinum or palladium was observed. In the test conducted where there were significant precious metals values in the concentrate, minor rhodium was seen to dissolve, but silver dissolution was high. Unless recovered separately, by, for example, cementation or with activated carbon, this silver will likely report with the copper.

Table 2. Results of Initial Base Metal Sulphide Leaching Experiments Metal Extraction, % Sulphur Final

ORP Tes

t No

Con Oxidant

mV Cu Ni Co Fe Au Ag Pd Pt Rh

Removal

%

SO42-

mg/L

T1 I A 190 47.4

79.4

67.7

80.4 - - - - - >99.9 10.5

T2 B 475 30.1

12.3 0.7 61.

0 - - - - - >99.9 18.4

T5 C 440 81.3

90.0

77.4

85.2 - - - - - >99.9 3.7

T8 D 405 99.9

89.5

73.0

88.6 - - - - - >99.9 3.8

T3 E 250 58.7

46.5

30.3

64.1 - - - - - >99.9 42.4

T11 F 398 99.9

94.9

82.7

95.0 - - - - - >99.9 23.1

T9 G 365 99.9

89.6

99.9

72.0 - - - - - >99.9 6.9

T17 II C 425 50.0

53.4

56.7

71.4 0 66.

7 0 0 13.7 >99.9 *

T18 G 260 78.8

99.3

87.1

92.5 * * * * * >99.9 *

T16 H 575 58. 58. 37. 83. * * * * * >99.9 *

Hydro-Sulfides 2004


5 6 3 4 - results not available at the time of publication. flowsheet The flowsheet shown in Figure 2 is a generic version for using the atmospheric chloride leach process for treating sulphide feeds. The main operations to be considered are:

•

•

•

•

•

•

•

Leaching of the sulphide feed at 90-100oC in recycled magnesium chloride/hydrochloric acid with the addition of an oxidant to control the redox potential. This is crucial both to ensure that the sulphur is eliminated as hydrogen sulphide gas, and that no precious metals dissolve. Direct oxidation to elemental sulphur occurs at a higher redox potential, one that is often commensurate with effecting dissolution of the precious metals. This has always been a drawback of previous chloride-based leaching flowsheets. The use of different oxidants over and above the normal choices of oxygen and/or chlorine permits the manipulation of the redox potential and kinetics. However, this has to be weighed against the introduction and possible build-up of alkali and alkaline earth metal cations in the circuit, and furthermore, the impact of any such cations on the pyrohydrolysis reaction.

Treatment of the hydrogen sulphide gas in a Claus Reactor to recover elemental sulphur, suitable for sale or direct storage, and recovery of the intrinsic energy contained in the sulphide as it is oxidised to elemental sulphur. The recovered energy can be used elsewhere in the flowsheet, notably in the pre-evaporative step for pyrohydrolysis. An option would be to use the gas as a precipitant within the flowsheet to form separate base metal sulphide products for sale if desirable.

Solid/liquid of the leach slurry, optimally on a vacuum belt filter. The residue contains all of the PGMs, and can either be sold as-is, upgraded in a second chloride leach with a higher oxidation potential, or be fed directly to a PGM processing plant.

Solvent extraction of copper. In a chloride medium, this can be achieved with relatively high levels of iron and base metals in solution. At a given pH, solvent extraction is more efficient than in the corresponding sulphate medium, and in fact extraction can occur at a much lower pH due to the lower water activity and enhanced hydrogen ion activity [79,80,81,82]. Stripping can be into sulphate followed by conventional electrowinning, since copper recovery by electrolysis from a chloride medium is somewhat more difficult than it is from sulphate, and the potential advantages of the single electron change are rarely realised.

Precipitation of impurities by lime and recycled magnesia (from the pyrohydrolysis step). Depending on the feed, this will likely be a two or three-stage process. Initially, iron will be precipitated by magnesia – experience with the laterite flowsheet has shown that this can be very effective using magnesia in a magnesium chloride matrix, to give a pure, easily settleable and readily filterable goethite product. Arsenic, if present, is easily removed as scorodite, whereas antimony and bismuth can be precipitated as the respective oxychlorides as the pH is raised. Selenium and tellurium may require separate treatment in a bleed stream by, for example, reductive precipitation.

Zinc, if present in commercially viable levels, can be recovered by a separate solvent extraction step, analogous to copper. Such a step would likely be incorporated after iron removal. Otherwise, the laterite flowsheet has indicated that zinc can be removed to low levels simply by pH adjustment with magnesia.

Although the test data obtained to date indicate virtually no sulphate formation, any that is formed can easily be controlled by replacing some of the magnesia used for pH control with lime in order to precipitate gypsum. This will also control minor lead impurities as well as barium, should it be present. Significant lead values can be controlled by cooling crystallization of lead chloride from the leach liquor. Calcium in pyrohydrolysis is not a problem, although if calcium chloride shows signs of building up too high, then it too can readily be treated in a bleed stream.

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Bryn Harris 206

BASE METALSATMOSPHERIC LEACH

SL

COPPER SOLVENTEXTRACTION

2-3 STAGEPURIFICATION

SL

NICKEL/COBALTPRECIPITATION

LS

PYROHYDROLYSIS

MgCl2 Brine

18% HCl

Chloride Lixiviant

Precious Metals ConcentrateUpgrade, refine or sell

Loaded OrganicTo Copper Circuit

Stripped OrganicFrom Copper Circuit

Copper Raffinate

Sulphide FeedOxidantHCl from

Copper Circuit

Nickel/CobaltHydroxide Product

MgO

MgO

To Disposalor Recycle

(Lime)

H2SCLAUSREACTOR

O2

Energy ElementalSulphur

Energy

Figure 2. Conceptual Flowsheet for the Treatment of Sulphide Feeds •

•

Recovery of nickel and cobalt. The flowsheet of Figure 2 indicates precipitation with recycled magnesia as a mixed nickel/cobalt hydroxide, which is the currently preferred option for the laterite flowsheet. However, in a chloride medium, separation of nickel and cobalt is relatively easily by solvent extraction with amines, phosphine oxides, phosphate esters., etc offering the option of separate nickel and cobalt products, should such prove to be attractive. The final step is pyrohydrolysis of a portion of the final magnesium chloride brine, consistent with the hydrochloric acid and magnesia requirements of the flowsheet. Pyrohydrolysis is normally quite energy intensive, but in this flowsheet, there is considerable energy available from the sulphur formation step, and this will significantly reduce the energy requirements of pyrohydrolysis.

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As can be seen, this flowsheet is not only extremely efficient, but it also extremely environmentally friendly. Elemental sulphur is formed in a separate dedicated step, and it will likely be of sufficiently high purity such that it may be sold. Otherwise, it can be melted and blocked, making it easily disposable. There will be a small amount of leach residue, comprising mostly gangue minerals, which is a small volume for disposal. Should PGMs be present, then this will form a concentrate suitable for sale, upgrading in a second chloride leach or direct feed to a PGM refinery. The point to note here is that this residue can also be readily processed in a chloride medium even if the precious metals comprise mostly gold, and therefore that no cyanidation step is required. There will also be intermediate precipitates, and although these will be of relatively small volume, they will nevertheless require dedicated disposal areas. The magnesium chloride process is able to handle most of the common impurities by suitable control of redox and/or pH. The only possible problems normally encountered in sulphide feed concentrates are likely to be selenium and tellurium, and these only if they attain their higher valence states. conclusions This paper has presented some initial results on the application of the Jaguar Nickel Atmospheric Chloride Leach Process to sulphide feedstocks. The process, initially developed for laterite feeds, involves leaching of the sulphide in a mixed magnesium chloride/hydrochloric acid lixiviant together with an appropriate oxidant. A number of oxidants have been tested, and the choice revolves around ensuring that the redox potential is kept within a range to ensure that sulphur is eliminated as hydrogen sulphide, and at the same time preventing any precious metals in the concentrate from being solubilised. It is considered that the formation of hydrogen sulphide, and its subsequent conversion to elemental sulphur, at the same time liberating all of its intrinsic energy, is a major step forward in the processing of base metal sulphides. Eliminating the sulphur in this manner avoids any risk of coating the base metal and PGM minerals with molten sulphur, and simultaneously effects a very clean separation of sulphur from the solids. Treating the hydrogen sulphide in a Claus Reactor is very common practice, generating both a clean sulphur product and liberating substantial quantities of energy for use elsewhere in the flowsheet. As an alternative, the hydrogen sulphide could be used to precipitate separate copper, nickel, cobalt and zinc sulphides, should the marketing of these prove more attractive. This would depend on the location of the mine and associated infrastructure to a large extent. Coincidentally, adjusting the redox potential to promote the formation of hydrogen sulphide also maintains it at a level which is not conducive to any precious metals leaching. Therefore, this process overcomes two of the major problems previously encountered with chloride-based base metal sulphide leach processes, by eliminating the sulphur from the leach residue, and leaving a precious-metals rich concentrate after the base metals have been leached out. The precious metals concentrate can be sold as-is, treated directly in a PGM refinery, or upgraded in a second, more oxidizing leach step, again depending upon the economics of the particular location. Finally, the process is extremely environmentally friendly. A separate elemental sulphur product, minimal leach residue, and low volume intermediate precipitates are produced. No effluent treatment is required, since the magnesium chloride lixiviant is recycled within the process flowsheet. The authors believe that an approach based on this flowsheet offers appreciable advantages over both conventional smelting and/or pressure oxidation processes for the treatment of base metal sulphide feeds, both with and without precious metal values.

references

1. Harris, Bryn; Magee, John and Valls, Ricardo, “Beyond PAL: The Chesbar Option, AAL”, Presented at ALTA Nickel-Cobalt-9, Perth, WA, (May 18-20, 2003).

2. Harris, Bryn and Magee, John; “Atmospheric Chloride Leaching: the Way Forward for Nickel Laterites”, In Hydrometallurgy 2003, Proceedings of the 5th International Symposium Honoring Professor Ian M. Ritchie (Courtney Young, et al., Editors), 2003 Fall TMS/EPD Meeting and 33rd Annual CIM Hydrometallurgical Meeting, Vancouver, B.C., Canada, (August 24-27, 2003), p 501.

3. Harris, G.B., Magee, T.J., Lakshmanan, V.I. and Sridhar, R., “The Jaguar Nickel Inc. Sechol Laterite Project Atmospheric Chloride Leach Process”, Paper Presented at International Laterite Nickel Symposium, 2004 TMS Annual Meeting, (March 14-18, 2004), Charlotte, North Carolina.

4. Gupta, C.K. and Mukherjee, T.K., “Hydrometallurgy in Extraction Processes”, CRC Press, Volume I (1990), p. 11.

5. Senanayake, G. and Muir, D.M., “Chloride Processing of Metal Sulphides: Review of Fundamentals and Applications”, In Hydrometallurgy 2003, Proceedings of the 5th International Symposium Honoring Professor Ian M. Ritchie (Courtney Young, et al., Editors), 2003 Fall TMS/EPD Meeting and 33rd Annual CIM Hydrometallurgical Meeting, Vancouver, B.C., Canada, (August 24-27, 2003), p. 517.

Bryn Harris 208

Hydro-Sulfides 2004

6. Jennings, P.H., Stanley, R.W. and Ames, H.L., “Development of a Process for Purifying Molybdenite Concentrates”,. in Proceedings of

Second International Symposium on Hydrometallurgy, (D.J.I. Evans, Editor), AIME, New York (1973), p. 868.

7. Stanley, R.W., Noranda Research Centre, Personal Communication, (April, 1985).

8. Thornhill, P.G. Wigstol, E. and Van Weert, G., “The Falconbridge Matte Leach Process”, Journal of Metals, 23(7), (1971), p. 13.

9. Stensholt, E.O., Zachariasen, H. and Lund J.H., “The Falconbridge Chlorine Leach Process”, in Nickel Metallurgy, Volume I - Extraction and Refining of Nickel, (E. Ozberk and H. Marcusson, Editors), CIM Montreal, (1986), p. 442.

10. Stensholt, E.O., Zachariasen, H., Lund, J.H. and Thornhill, P.G., “Recent Improvements in the Falconbridge Nickel Refinery”, in Extractive Metallurgy of Nickel and Cobalt, TMS-AIME, Warrendale, (1988), p. 403.

11. Yang Yuhua and Meng Xianxuan, “Operating Practice and Technical Developments in Nickel Refining and Cobalt Recovery at Jinchuan Non-Ferrous Metal Company”, in Electrometallurgical Plant Practice, (P.L. Claessens and G.B. Harris, Editors), Proceedings of the 20th Annual CIM Hydrometallurgical Meeting, Pergamon Press (1990), p.253.

12. Fujimori, M., Ono, N., Itasako, S. and Fukui, I., “Solvent Extraction in Sumitomo's Cobalt Refining Process”, Paper presented at Cobalt 80, 10th Annual CIM Hydrometallurgical Meeting, Edmonton, Alberta, (October 26-28, 1980).

13. Demarthe, J.M., Gandon, L. and Goujet, M., “Hydrometallurgical Method For Treating Nickel Mattes”, Canadian Patent 1 126 201, to Société Métallurgique le Nickel-SLN, (22 June, 1982).

14. Steinbach, W. and Baerhold, F., “Comparison of Spray Roasting and Fluid Bed Granulation for the Recovery of Hydrochloric Acid from Metallurgical Processes Through Pyrohydrolysis”, in Chloride Metallurgy 2002 Volume 2, (E. Peek and G. van Weert, Editors), Proceeding of the 32nd Annual CIM Hydrometallurgical Conference, CIM, Montreal (2002), p. 643.

15. Coscia, C. and Kozinski, J.A., “Pyrohydrolysis of an Al-Fe-Mg-Cl Solution – Characterization of the Transformation Process”, ibid p. 683.

16. Patoine, M.-C., De Mori, A., Borowiec, K. and Coscia, C., “Pyrohydrolysis of a Calcium and Magnesium Bearing FeCl2 Leach Liquor”, ibid p. 699.

17. Bacon, Gord and Mihaylov, Indje, “Solvent Extraction as an Enabling Technology in the Nickel Industry”, in ISEC 2002, Proceedings of the International Solvent Extraction Conference (Kathryn C. Sole, et al., Editors), Cape Town (March, 2002), p. 1.

18. Flett, D.S., Melling, J. and Derry, R., “Chloride Hydrometallurgy for the Treatment of Complex Sulphide Ores”, Warren Spring Laboratory Report LR 461 (ME), U.K. (1983).

19. McLean, D.C., “Chloride Leaching of Copper Concentrates: Practical Operational Aspects”, Paper presented at 111th AIME Annual Meeting, Dallas, (February, 1982).

20. Wadsworth, M.E., “Trends and Developments in Copper Metallurgy Research”, in Copper ’84 Symposium, CIM 23rd Annual Conference of Metallurgists, Quebec City, (August, 1984).

21. Atwood, G.E., and Curtis, C.H., “Hydrometallurgical Process for the Production of Copper”, U.S. Patent 3,785,944 (to Duval), (15 January, 1974).

22. Atwood, G.E. and Livingston, R.W., “The CLEAR process: a Duval Corporation Development”, Erzmetall 33(5), (1980), p. 251.

23. Fletcher, A.W. and Gage, R.C., “Dealing with a Siliceous Crud Problem in Solvent Extraction”, Paper 16 in Impurity Control and Disposal, CIM 15th Annual Hydrometallurgical Meeting, Vancouver, (August 1985).

24. Fletcher, A.W., “Modification of the CLEAR Process to Treat Complex Materials”, in Complex Sulfides, Proceedings of an International Symposium, San Diego, (November 1985), TMS-AIME, p. 485.

25. Wilson, A.T. et al., “The Production of Electrolytic Grade Copper from a Chloride Leach Solution”, ibid, p. 473.

26. Schweitzer, F.W. and Livingston, R.W., “Duval’s CLEAR Hydrometallurgical Process”, in Chloride Electrometallurgy, (P.O. Parker, Editor), Proceedings of a symposium at the 111th AIME Annual Meeting, Dallas, (February, 1982), p. 221.

27. McNamara, J.H., Ahrens, W.A. and Franek, J.G., “A Hydrometallurgical Process for the Extraction of Copper”, CIM Bulletin 73(815), (March 1980), p. 201.

28. Allen, E.S., Kruesi, P.R. and Goens, D.N., “Treatment of Chalcopyrite Copper Concentrate using the CYMET Process”, Paper A74-7 presented at 103rd AIME Annual Meeting, Dallas, (February, 1974).

29. Kruesi, P.R., Allen, E.S. and Lake, J.J., “CYMET Process - Hydrometallurgical Conversion of Base Metal Sulphides to Pure Metals”, CIM Bulletin 66(734), (June, 1973), p. 81.

30. Anon., “Copper Hydrometallurgy: the Third Generation Plants”, E/MJ, (June, 1975), p. 104.

31. Peters, M.A. and Kazell, W.G., “Improvements in and Relating to the Recovery of Copper and/or Silver”, British Patent 1,598,250 (to Cyprus), (16 September, 1981).


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32. Allen, E.S. and Horn, R.C., “Process for the Ferric Chloride Leaching of Sulphide Ores”, Canadian Patent 1,044,022 (to Cyprus), (12

December ,1978).

33. Demarthe, J.M., Gandon, L. and Georgeaux, A., “A New Hydrometallurgical Process for Copper”, in Extractive Metallurgy of Copper, (J.C. Yannopoulos, J.C. Agarwal, Editors) TMS-AIME, New York, (1976), p. 825.

34. Demarthe, J.M., Georgeaux, A. and Sonntag, A., “Method of Obtaining Copper from Sulphurized Concentrate”, Canadian Patent 1,105,410 (to Penarroya), (21 July, 1981).

35. Demarthe, J.M. and Georgeaux, A., “Hydrometallurgical Treatment of Complex Sulphides”, in Complex Metallurgy '78, IMM, London, (1978), p. 113.

36. Everett, P.K., “The Single Step Conversion of Chalcopyrite to Copper, Iron Oxide and Elemental Sulphur”, Paper presented at Extractive Metallurgy Symposium, University of NSW, (8 November, 1977).

37. Everett, P.K., “Recovery of Copper from Ores and Concentrates”, U.S. Patent 4,107,009 (to Dextec) (15 August, 1978).

38. Everett, P.K., “Extraction of Copper by Mixing Finely Dispersed Oxygen with Material Slurry”, Canadian Patent 1,068,643 (to Dextec), (25 December, 1979).

39. Everett, P.K., “Refining of Ferrous and Base Metal Sulphide Ores and Concentrates”, Canadian Patent 1,092,365 (to Dextec), (30 December, 1980).

40. Everett, P.K., “The Dextec Copper Process”, in Extraction Metallurgy '81, IMM, London, (1981), p. 149.

41. Anon., “Pollution-Free, Cost-Effective Smelting Process Developed”, Mining Engineering 37(4), (April, 1985), p. 353.

42. Andersen, E. et al., “Production of Base Metals from Complex Sulphide Concentrates by the Ferric Chloride Route in a Small, Continuous Pilot Plant”, in Complex Sulphide Ores, IMM, London, (1980), p. 186.

43. Boe, G.H., Krogh, S. and Ydstie, B., “Notes on the Treatment of Complex Sulfide Ores”, Paper A82-8 presented at 111th AIME Annual Meeting, Dallas, (February, 1982).

44. Haver, F.P. and Wong, M.M., “Recovering Elemental Sulphur from Non-Ferrous Minerals”, USBM RI 7474, (January, 1971).

45. Haver, F.P. and Wong, M.M., “Recovery of Copper, Iron and Sulphur from Chalcopyrite Concentrate Using a Ferric Chloride Leach”, J. Metals, (February, 1971), p. 25.

46. Haver, F.P. and Wong, M.M., “Making Copper Without Pollution”, Mining Engineering (June, 1972), p. 52.

47. Haver, F.P., Baker, R.D. and Wong, M.M., “Improvements in Ferric Chloride Leaching of Chalcopyrite Concentrate”, USBM RI 8007, (1975).

48. Beattie, M.J.V., Craigen, W.J.S. and Sarkar, K.M., “The Great Central Mines Hydrometallurgical Copper Process”, Paper presented at CIM 14th Annual Hydrometallurgical Meeting, Timmins, (October, 1984).

49. Beattie, M.J.V., Bacon, Donaldson and Associates, Personal Communication, (21 November, 1984).

50. Raudsepp, R. and Beattie, M.J.V., “Iron Control in Chloride Systems”, Iron Control in Hydrometallurgy, (Dutrizac, J.E. and Monhemius, A.J., Editors), Ellis Horwood, Chichester, England (1986), p. 163.

51. Clevenger, G.W. and Pepple, G.W., “Cupric Chloride Leaching of Copper Sulfides”, U.S. Patent 4,384,890, (24 May, 1983).

52. Peters, E., Swinkels, G.M. and Vizsolyi, A., “Copper Recovery from Sulfide Concentrates by the UBC-Cominco Ferric Chloride Leach Route”, in Process and Fundamental Considerations of Selected Hydrometallurgical Systems, (M.C. Kuhn, Editor), SME-AIME, New York, (1981), p. 71.

53. Everett, P.K., “Production of Metals”, European Patent EP 0,646,185 B1, (June 25, 1993).

54. Bhappu, R.B. and Severs, K.J., “Technological Advances in Treating Copper Concentrates: the Intec Copper Process”, SME Preprint 99-165, SME (1999).

55. Moyes, J. and Houllis, F., “Intec Base Metals Process Realising the Potential of Chloride Hydrometallurgy”, in op. cit. reference14, Volume 2, (2002), p. 577.

56. Moyes, John and Houllis, Frank, “The Development of the Intec Nickel Process to Treat a Low-Grade Ni/Cu/Co/PGM Concentrate”, in op. cit. reference 1, (2003).

57. Wood, Philip R., “The Intec Copper Process: (Electro) Winning Against the Odds”, Presented at ALTA Copper-8, Perth, WA, (May 22-23, 2003).

58. Dutrizac, J.E., “Ferric Ion Leaching of Chalcopyrite from Different Localities”, Met. Trans. B, l3B, (September, 1982), p. 303.

59. Dutrizac, J.E., “Sulphate Control in Chloride Leaching Processes”, Hydrometallurgy 23, (1989), p. 1.

Bryn Harris 210

Hydro-Sulfides 2004

60. Majima, H. et al., “The Leaching of Chalcopyrite in Ferric Chloride and Ferric Sulphate Solutions”, in Copper '84 Symposium, CIM 23rd

Annual Conference of Metallurgists, Quebec City, (August, 1984).

61. Holdich, R.G. and Broadbent, C.P., “Investigation of the Dissolution of Pyrite in Copper(II) Chloride Solutions”, in Extraction Metallurgy '85, IMM, London, (1985), p. 695.

62. Wilson, A.T., “An Economical Method for the Recovery of Gold from the Sulphur-Containing Residue of a Hydrometallurgical Process”, op. cit. ref.24, p. 143.

63. Craigen, W.J.S., Kelly, F.J., Bell, D.H. and Wells, J.A., “Evaluation of the CANMET Ferric Chloride Leach (FCL) Process for Treatment of Complex Base-Metal Sulfide Ores”, in Sulphide Deposits – Their Origin and Processing, (Gray, P.M.J., et al., Editors) IMM, London, UK, (1990), p. 255.

64. Dalton, R.F., Hermana, E. and Hoffman, B., “The Cuprex Process - A New Chloride-Based Hydrometallurgical Process for the Extraction of Copper from Sulfide Ores”, in Separation Processes in Hydrometallurgy, (Davies, G.A., Editor), Ellis Horwood Ltd, Chichester, U.K., (1987), p. 466.

65. Dalton, R.F., Diaz, G., Hermana, E., Price, R. and Zunkel, A.D., “The Cuprex Metal Extraction Process Pilot Plant Experience and Economics of a Chloride-Based Process for the Recovery of Copper from Sulphide Ores”, in Hydrometallurgy and Electrometallurgy of Copper, Proceedings of the Copper 91-Cobre 91 International Symposium, Volume III, (Cooper, W.C., Kemp, D.J., Lagos, G.E. and Tan, K.G., Editors), Pergamon Press, (August 18-21, 1991).

66. Limpo, J.L., Figueiredo, Amer, S. and Luis, A., “The CENIM-LNETI Process: A New Process for the Hydrometallurgical Treatment of Complex Sulphides in Ammonium Chloride Solutions”, Hydrometallurgy 28, (1992), P. 149.

67. Hyvärinen, O. and Hämäläinen, M., “Method for Producing Copper in Hydrometallurgical Process”, U.S. Patent 6,007,600 (to Outokumpu), (December 28, 1999).

68. Hyvärinen, O., Hämäläinen, M. and Leimala, R., “Outokumpu HydroCopper™ Process – A Novel Concept in Copper Production”, in op. cit. reference14, Volume 2, (2002), p. 609.

69. Hietala, Kari and Hyvärinen, Olli, “HydoCopper™ - A New Technology for Copper Production”, Presented at ALTA Copper-8, Perth, WA, (May 22-23, 2003).

70. Hämäläinen, M., Hyvärinen, O. and Jyrälä, M., “Solution Purification in the Outokumpu HydoCopper™ Process”, in op. cit. reference 2, Volume 1, (2003), p. 545.

71. Stanley, R.W. and Subramanian, K.N., “Recovering Copper from Concentrates with Insoluble Sulfate Forming Leach”, U.S. Patent 4,039,406 (to Noranda Mines Ltd.) (August 2, 1977).

72. Jones, D.L., Hestrin, J. and Moore, R., “CESL Process for Nickel/Cobalt/Copper Sulphides, Testing in an Integrated Pilot Plant”, Presented at ALTA Nickel-Cobalt Pressure Leaching and Hydrometallurgy Forum, Perth, WA, (1998).

73. Jones, David L., “Pressure-Oxidation Treatment of Copper Sulfide Ores for Sulfur Removal and Chloride-Assisted Leaching of Metal Values”, U.S. Patent 5,902,474 (to Cominco Engineering Services Ltd.), May 11,1999).

74. Jones, David L., “Process for the recovery of nickel and/or cobalt from a concentrate”, U.S. Patent 6,383,460 (to Cominco Engineering Services Ltd.), (May 7, 2002),

75. Kerfoot, D.G.E., Krause, E., Love, B.J. and Singhal, A., “Hydrometallurgical Process for the Recovery of Nickel and Cobalt Values from a Sulfidic Flotation Concentrate”, U.S. Patent 6,569,224, (to Inco Limited), (May 27, 2003).

76. Dyson, N.F. and Scott, T.R., “The Beneficiation of Chalcopyrite Concentrates by Leaching with HCl-CaCl2 and HCl-MgCl2 Solutions”, op. cit. reference 36.

77. Adamson, D.V. and Naden, D., “Metal Sulphide Extraction”, U.S. Patent 4,378,275 (to Saudi-Sudanese Red Sea Joint Commission), (March 29, 1983).

78. Flett, D.S., “Chloride Hydrometallurgy for Complex Sulphides: A Review”, in op. cit reference 14, Volume I, (2002), p. 255.

79. Carpenter, J.C., et al., “A Study of the Extraction of Copper and Iron from Chloride Solutions with Commercial Extractants”, Proceedings AIME International Symposium on Copper Extraction and Refining, Las Vegas, NV, (1976) p. 1025.

80. Christie, P.G., Lakshmanan, V.I., and Lawson G.J., “The Liquid-Liquid Extraction of Copper(II) and Iron(III) from Chloride Solutions Using LIX 64N in Kerosene”, Proceedings ISEC, (1974) Vol. 1, p 685.

81. Lakshmanan, V.I., Lawson, G.J. and Nyholm, P.S., “The Extraction of Copper(II) and Iron(III) with Kelex 100 from Aqueous Media Containing Chloride Ions”, Proceedings ISEC, (1974), Vol. 1, p 699.

82. Lakshmanan, V.I. and Lawson, G.J., “The Extraction of Copper from Aqueous Chloride Solutions with LIX-70 in Kerosene”, Jnl. Inorg. Nucl. Chem., 37, (1975), p 207.


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