rtion

tiongh cbyim

deder fchinlorrga

the chloride from the organic system with water at an appropriate pH, the copper is proposed to be re-nge mechanism by the same organic system.

was agher cl conceuch as

chlocell dalso fo

Hydrometallurgy 113114 (2012) 155159

Contents lists available at SciVerse ScienceDirect

Hydrome

l senot suitable to extract copper from chloride solutions due totheir low extraction capability and small separation factors of cop-per over iron. So far no solvent extraction systems are available ona commercial scale to recover copper effectively from chloride so-lutions and to transfer it to sulfate solutions for electrowinning.To overcome this problem, an aromatic hydroxyoxime reagentLIX64N was used to extract copper from chloride leach solutions,but failed due to its low loading capacity and the transfer of chlo-ride to the electrolyte (Paynter, 1973). As a result, electrowinning

ping with sulphuric acid, the amine was protonated to formhydrosulphate and therefore, the organic system could not berecycled to the extraction step without prior conditioning withchloride solution. Although a combination of LIX54 with AcorgaCLX50 showed improvement during the copper stripping stepwith sulphuric acid compared to the above mentioned mixture,the same drawback existed due to the formation of hydrosulphatein the organic phase. Kyuchoukov and Szymanowski (2000) andKyuchoukov et al. (2000) reported the use of a bi-functional re-of copper from chloride solutions had to bin copper powder product which is difcnew extractant called ACORGA DS5443 or Ction capacity and high selectivity for copp

Corresponding author.E-mail address: chu.cheng@csiro.au (C.Y. Cheng).

0304-386X/$ see front matter. Crown Copyright 20doi:10.1016/j.hydromet.2011.12.016und that the commer-tants to extract copperd Acorga M5640, were

Alamine 336 were tested (Kyuchoukov and Szymanowski, 2000;Kyuchoukov et al., 2000; Ryszard and Jan, 2001). This mixture ef-ciently extracted copper from chloride solutions. However, in strip-cially used aromatic hydroxyoxime extracfrom sulfate solutions, such as LIX 984N an1. Introduction

Copper chloride hydrometallurgythe 1970s and 1980s due to the hiand recovery and less environmentaing and leaching with other media ser, the electrowinning of copper fromproblematic due to the difculties inof a copper powder product. It washot research topic inopper leaching kineticsrn compared to smelt-sulphuric acid. Howev-ride solutions was veryesign and the handling

was developed and patented (Dalton et al., 1982). However,CLX50 also transferred chloride to the electrowinning step, result-ing in the unfavourable copper powder product (Atmore et al.,1984). This reagent was abandoned and has never been commer-cialised. Methods to extract copper from chloride solutions and totransfer it to sulphate solutions for electrowinning were exploredby a number of researchers. Mixed extractants consisting of a che-lating reagent, LIX54, and a basic extractant, tri-alkylamine such asCrown Copyright 2011 Published by Elsevier B.V. All rights reserved.Iron extracted via a cation exchaA synergistic solvent extraction system fochloride concentration solutions

Z. Zhu, W. Zhang, C.Y. Cheng The Parker Centre, CSIRO Process Science and Engineering, CSIRO Minerals Down Under Na

a b s t r a c ta r t i c l e i n f o

Article history:Received 2 November 2011Received in revised form 22 December 2011Accepted 22 December 2011Available online 29 December 2011

Keywords:Synergistic solvent extractionLIX63Versatic 10Copper

A synergistic solvent extracarate copper from iron in hiphate solution for recoverycopper over iron and otheriron and chloride in the loalyte is used to strip the coppprocess ow sheet from leaIt is proposed that in high chforms complexes with the o

j ourna l homepage: www.ee undertaken, resultingult to be marketed. ALX50 with high extrac-er in chloride solutions

11 Published by Elsevier B.V. All rigseparating copper from iron in high

al Research Flagship, Australia

(SSX) system consisting of Versatic 10 and LIX 63 has been developed to sep-hloride concentration solutions and to transfer the extracted copper to a sul-conventional electrowinning. The SSX system is able to selectively extractpurity metals from chloride solutions in extraction stages. The co-extractedorganic solution are scrubbed in two separate scrub circuits. A spent electro-rom the scrubbed organic solution for conventional copper electrowinning. Ag with chloride solutions to copper conventional electrowinning is proposed.ide concentration solutions, copper exists as neutral molecule of CuCl2, whichnic components of the SSX system via a solvating mechanism. After scrubbing

tallurgy

v ie r .com/ locate /hydrometagent such as Kelex 100 and LIX26 to transfer copper from chlo-ride to sulphate solutions for electrowinning. However, thesereagents extract iron(III) more strongly than copper and cannotbe used for the separation of copper from iron(III).

Until recently, most commercialised leaching processes for cop-per sulphide ores were carried out in sulphate systems. After therecovery of copper from the leach solutions, large volumes ofwaste solutions containing a large amount of sulphate salts are

hts reserved.

JenniferResaltado

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discharged, resulting in environmental pollution. To overcome thisdrawback, the development of leaching processes with hydrochloricacid and chloride salts has made great progress for the treatment ofcopper, zinc, nickel and cobalt containing ores (Harris and White,2008; Harris et al., 2003, 2004; Krebs et al., 2007; Kyung-Ho et

2.2.2. Scrubbing pH isothermsThe loaded organic solution and a selected scrub solution were

mixed at an A/O ratio of 1:4 for iron scrubbing and 1:2 for chloridescrubbing and 40 C. 6 M HCl or 10% NaOH solution was used to ad-just the pH during testing. Solution mixture samples were taken at0.5 pH intervals for assay.

2.2.3. Stripping kineticsThe loaded organic solution was stripped with the aqueous solu-

tion containing 53 g/L Cu and 180 g/L H2SO4 at an O/A ratio of 4:1and 40 C. Timing started immediately when the strip solution wasadded to the loaded organic solution. Solution mixture sampleswere taken at 0.5, 1, 2, 3, 5 and 10 min for assay.

3. Results and discussions

3.1. Metal extraction acidity isotherms

156 Z. Zhu et al. / Hydrometallurgy 113114 (2012) 155159al., 2006). More than 90% of copper can be leached by hydrochloricacid and chloride salts at atmospheric pressure. Another advantageof hydrochloric acid and chloride salts leaching is that they can berecycled by pyrohydrolysis of iron as commonly practised in thesteel making industry. However, the efcient separation and recov-ery of copper, from chloride solutions has not been established.Copper hydroxyl-chloride and cuprous hydroxyl-chloride precipita-tions have been proposed (Krebs et al., 2007). However, these in-termediate products have to be treated in extra processes torecover copper as pure metal. Ion exchange technology has beenproposed in process ow sheets (Harris and White, 2008). Howev-er, it suffers disadvantages including small throughput and compli-cated operation.

A novel SSX systems has been developed to separate and recovercobalt and zinc from leach solutions (Cheng, 2006; Cheng andUrbani, 2005; Cheng et al., 2010). This paper presents the further de-velopment and application of the novel SSX system for the separation,purication and recovery of copper from chloride leach solutions.

2. Experimental

2.1. Aqueous and organic solutions

The synthetic leach solution was prepared by dissolving AR ortechnical grade sulphates of copper, iron(III), aluminium and calciumchlorides in distilled water. The metal concentrations in the syntheticleach solution were determined by Inductively Coupled PlasmaAtomic Emission Spectrometry (ICP-AES). The composition of the re-sultant feed solution is shown in Table 1.

The reagent Versatic 10 acid (neodecanoic acid) and the diluentShellsol D70 (100% aliphatic) were provided by Shell Chemicals Aus-tralia and LIX63 by Cognis Australia (now part of BASF). The compo-sition of the LIX63 was reported by Cognis to be 70% activecomponent (5,8-diethyl-7-hydroxy-6-dodecanone oxime) in a dilu-ent. The actual concentration of the oxime in LIX63 was only 54%(Barnard and Urbani, 2007). For consistency, 70% oxime in theLIX63 was used as a nominal concentration in the current paper. Allreagents were used as received.

2.2. Batch test procedures

All tests were carried out in 0.5 L or 1.0 L stainless steel rectangu-lar boxes immersed in a temperature controlled water bath. The solu-tion temperature was maintained at 401 C during testing. Eurostardigital overhead stirrers and 30 mm (for 0.5 L box) or 40 mm (for1.0 L box) diameter impellers were used for mixing.

2.2.1. Extraction acidity isothermsTo determine metal extraction acidity isotherms, the acidity of the

aqueous solution was adjusted by adding concentrated HCl and mea-sured by titration with standard NaOH solution. The organic solutionwas mixed with the synthetic solution at a particular A/O ratio and40 C. The solutionmixture (20 mL) was sampled at different aciditiesfor assay by ICP-AES. The system was allowed to equilibrate at eachacidity point before sampling.

Table 1Chemical composition of the synthetic leach solution.

Element Cu Fe(III) Al Ca Cl

Concentration (g/L) 14.2 4.74 2.07 126 224In Fig. 1, it can be seen that the extraction of copper was inde-pendent of the solution acidity between 0.1 and 0.5 M HCl with aconstant value. However, the extraction of iron was slightly aciditydependent, showing an increasing trend when the solution acidityincreased. This suggests that the iron can be scrubbed by a lowacidity solution, e.g. 0.2 M HCl solution. Due to the high chlorideconcentration in the scrub solution, copper remained in the loadedorganic solution.

With 0.1 M HCl, 350 g/L CaCl2 at an A/O ratio of 1:2 and 40 C, over95% Cu but only 14% Fe were extracted by the SSX system consistingof 0.3 M LIX 63 and 0.33 M Versatic 10 in Shellsol D70 after a singlecontact (Fig. 1). The extraction of aluminium was negligible. Thisclearly shows that the SSX system can be used to separate copperfrom other metals, including Fe(III), in chloride solutions with a fewextraction stages.

3.2. Iron scrubbing

The co-extracted iron was scrubbed with a scrub solution con-taining 350 g/L CaCl2 and 0.2 M HCl. A total of 4 batch scrubbingtests were successively conducted at an A/O ratio of 1:4 and40 C. This means that the same organic solution was mixed withfresh scrub solution 4 times. As shown in Table 2 and Fig. 2, afterthe rst two scrubbing stages, over 99.8% Fe(III) was scrubbedwithb1 mg/L Fe(III) left in the organic solution. About 11% Cu wasalso scrubbed in each of the rst two scrubbing stages. In acounter-current operation, it would be expected that all the

0.0 0.1 0.2 0.3 0.4 0.5 0.6HCl concentration (M)

Extr

actio

n (

)

Cu

Fe

Al

0.010.020.030.040.050.060.070.080.090.0

100.0

Fig. 1. Effect of HCl concentration onmetal extraction with the SSX system consisting of0.3 M LIX 63 and 0.33 M Versatic 10 in Shellsol D70 and the synthetic aqueous solutioncontaining 14 g/L Cu, 4.7 g/L Fe(III), 2 g/L Al and 350 g/L CaCl2 at an A/O ratio of 1:2 and

40 C.

JenniferResaltado

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JenniferResaltado

scrubbed copper would be extracted again by the organic solutionin the subsequent scrub stages.

3.3. Chloride scrubbing

The co-extracted chloride was scrubbed with water under con-

Copper is readily separated from iron in the high chloride concen-tration solution by the novel SSX system;

Iron is readily scrubbed from the copper-loaded SSX system with aweak acid (0.2 M HCl) solution containing high concentration ofCaCl2;

Chloride is scrubbed with water in a pH range of 3.54 and the pH isadjusted by adding ammonia solution;

the following calculation. In the current loaded organic solution,

Table 2Scrubbing iron from the loaded organic solution with a scrub solution containing350 g/L CaCl2 and 0.2 M HCl at an A/O ratio of 1:4 and 40 C.

Scrubstage

Cu concentration (g/L) Fe concentration (g/L) Scrubbing (%)

In aq. soln. In org. soln. In aq. soln. In org. soln. Cu Fe

0 6.796 0.324 1 2.218 6.026 1.299 0.014 11.33 95.812 1.855 6.072 0.118 b0.001 10.66 >99.83 1.483 5.444 0.018 b0.001 19.89 >99.94 1.244 5.183 b0.001 b0.001 23.74 >99.9

Table 3Scrubbing chloride from the loaded organic solution with water under different pHvalues at an A/O ratio of 1:2 and 40 C.

ScrubpH

Cu concentration (g/L) Cl concentration (g/L) Scrubbing (%)

In aq. soln. In org. soln. In aq. soln. In org. soln. Cu Cl

6.550 8.815 3.04 0.554 6.119 15.97 0.321 6.58 96.363.53 0.090 6.508 18.37 0.144 0.65 98.374.03 0.014 6.500 18.58 0.039 0.75 99.55

157Z. Zhu et al. / Hydrometallurgy 113114 (2012) 155159trolled pH with 10% NaOH solution. The chloride scrubbing at pH3.04, 3.53 and 4.03 and the chloride scrubbing pH isotherm areshown in Table 3 and Fig. 3, respectively. At pH 4, over 99.5%chloride was scrubbed with only 39 mg/L Cl left in the scrubbedorganic solution, while the scrub efciency of copper was only0.75%. In a counter-current operation, the scrubbed copperwould be extracted again by the organic solution in the subse-quent scrub stages.

3.4. Copper stripping kinetics

Copper stripping kinetic tests were conducted with the scrubbedorganic solution containing 3.78 g/L Cu using a strip solution contain-ing 53 g/L Cu and 180 g/L H2SO4 at an O/A ratio of 4 and 40 C(Table 4). After two minutes of stripping, over 81% Cu was strippedand after three minutes of stripping, nearly 94% Cu was stripped, indi-cating fast stripping kinetics.

4. Process owsheet development

With the above solvent extraction circuit, copper can be separatedfrom iron in chloride solutions, transferred to sulphate solution andrecovered as pure copper cathodes by conventional electrowinning.A proposed owsheet is shown in Fig. 4.

This process, consisting of chloride leaching, copper solvent ex-traction and electrowinning, and iron hydrolysis would have the fol-lowing main features:

Hydrochloric acid leaching provides faster leaching kinetics andhigher copper recovery compared with sulphuric acid leaching;

ing

()

Cu

Fe60.070.080.090.0

100.00 1 2 3 4 5Scrubbing stage

Scru

bb

0.010.020.030.040.050.0

Fig. 2. Scrubbing iron from the loaded organic solution consisting of 0.3 M LIX 63and 0.33 M Versatic 10 in Shellsol D70 with chloride solution contained 350 g/LCaCl2 and 0.2 M HCl in 4 batch scrubbing stages at an A/O ratio of 1:4 and 40 C.The loaded organic solution contained 6.80 g/L Cu and 0.32 g/L Fe(III).the chloride concentration was 8.82 g/L, and that of copper andiron, 6.55 g/L and 0.82 g/L, respectively (Table 5). The aluminiumextraction was negligible (Fig. 1). The total molar concentrationof copper calculated was 0.103 M and that of iron and chloride0.015 M and 0.249 M, respectively. Based on the molecule formulaof CuCl2 and HFeCl4, 0.265 M Cl is required, resulting inthe calculated chloride to the measured chloride ratio of 1.07.This is consistent with a chloride to copper mole ratio of 2:1and a chloride to iron mole ratio of 4:1, and hence the extraction

ing

() Cu

Cl

50.060.070.080.090.0

100.0 The ammonia is regenerated by lime boiling and recycled for pH ad-justment in the chloride scrub stage;

Copper is readily stripped from the loaded SSX system to obtainloaded strip liquor suitable for conventional electrowinning;

Part of the rafnate of the SSX circuit is subjected to iron hydrolysisto regenerate HCl and CaCl2 for leaching and to obtain an environ-mentally friendly product of iron oxide;

Part of the rafnate is recycled to the leach process to form a closedcircuit.

5. Proposed extraction mechanism

It is well-known that copper and iron can form complexeswith chloride ions such as CuCl2 and HFeCl4 in acidic solutionswith high chloride concentrations (Jackson, 1986). When the SSXsystem extracts copper and iron, it is most likely that they areextracted as neutral molecules; this is indirectly supported bypH

Scru

bb

0.010.020.030.040.0

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Fig. 3. Scrubbing chloride from the loaded organic solution consisting of 0.3 M LIX 63and 0.33 M Versatic 10 in Shellsol D70 with water under different pH values at an A/O ratio of 1:2 and 40 C. The loaded organic solution contained 6.55 g/L Cu and8.82 g/L Cl.

mechanism of the SSX system for the extraction of copper andiron in high chloride concentration solutions is suggested to besolvating as shown in Eqs. (1) and (2).

CuCl2 SSX SSXCuCl2 1

HFeCl4 SSX SSX HFeCl4 2

where the bars denote organic species.When the loaded organic solution was subjected to scrubbing

with water, the chloride concentration in the loaded scrub liquorwas low. For example, if the above mentioned loaded organic solutionwas scrubbed at an A/O ratio of 1:1 and all chloride entered the aque-ous solution, the maximum chloride concentration would be 8.8 g/L,indicating a low chloride concentration compared with the chlorideconcentration of 224 g/L in the feed solution (Table 1). Therefore,the SSXCuCl2complex would dissociate to release the chloride ions

6. Conclusions

A novel SSX system consisting of Versatic 10 and LIX 63 has beendeveloped to separate copper from iron in high chloride concentra-tion solutions and transfer the copper into sulphate solutions, therebyenabling conventional electrowinning.

With the organic system consisting of 0.3 M LIX 63 and 0.33 MVersatic 10 in Shellsol D70, over 95% Cu but only 14% Fe(III) wereextracted at an A/O ratio of 1:2 and 40 C after a single contact.Over 99% co-extracted Fe(III) was scrubbed using a scrub solutioncontaining 350 g/L CaCl2 and 0.2 M HCl after two successive scrub-bing stages with only 1 mg/L Fe(III) remaining in the organic solu-tion. Over 99.5% of the co-extracted chloride was scrubbed withwater at pH 4, with only 39 mg/L remaining in the scrubbed organ-ic solution. The copper stripping kinetics was fast with nearly 94%Cu being stripped after 3 minutes of mixing at 40 C using 180 g/L

Acknowledgements

Table 4Copper stripping kinetics.

Time (min) 0.0 0.5 1.0 2.0 3.0 5.0 10.0

Cu strip (%) 0.0 15.1 59.8 81.4 93.7 97.5 98.3

electrolyte

d o

le

Spentelectrolyte

Lime

Table 5Copper, iron and chloride mole concentrations in the organic solution.

In organic solution (g/L) In organic solution (mol/L) Clcalc.(mol/L)

[Clcalc.]/[Cl]

Cu Fe Cl Cu Fe Cl

6.55 0.82 8.82 0.103 0.015 0.249 0.265 1.07

158 Z. Zhu et al. / Hydrometallurgy 113114 (2012) 155159and the copper ions Eq. (3). At an appropriate pH, the organic solutionwould extract the cationic copper ions to form complexes such asSSX2Cu2Eq. (4) and release hydrogen ions to the aqueous solution.In Fig. 3, it can be seen that copper was scrubbed from the organic so-lution at low pH and extracted when the pH increased, indicating thatthe extraction mechanism of the SSX system for copper became pHdependent, which is indicative of a cation exchange mechanismEq. (4). Because of this change in mechanism, chloride can be releasedfrom the copperchloride complex and the copper can be transferredfrom a chloride medium to a sulphate medium for conventional elec-trowinning, which is an important feature of this system.

SSXCuCl2SSX Cu2 2Cl 3

SSX Cu2 SSX2Cu2 2H 4

Leachsolution Strippe

Loaded organic

HCl/CaCl2 recyc

Raffinate

Bleed

Copper ores

Chloride leaching

Extraction Fe Scrubbing

To leaching CaCl2Fig. 4. A schematic of a proposed process owsheet for the separation of copper from ironsystem and conventional electrowinning.The authors would like to thank Dr Keith Barnard and Mr YokoPranolo for reviewing this paper and providing valuable comments.The support of the Minerals Down Under National Research Flag-ship and Parker CRC for Integrated Hydrometallurgy Solutions isgratefully acknowledged.

Advanced

rganic

Scrubbed organic

Iron hydrolysis

Iron oxide

StrippingCl Scrubbing

Water

NH3sulphuric acid.It is proposed that in high chloride concentration solutions, the

copper would form a complex containing CuCl2 with the SSX systemvia a solvating mechanism. After scrubbing the chloride with water,the copper is proposed to be re-extracted via a cation exchangemechanism by the same organic system.Cu cathodes

Cu EWLime boiling

and the recovery of copper from chloride solutions by a synergistic solvent extraction

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159Z. Zhu et al. / Hydrometallurgy 113114 (2012) 155159

A synergistic solvent extraction system for separating copper from iron in high chloride concentration solutions1. Introduction2. Experimental2.1. Aqueous and organic solutions2.2. Batch test procedures2.2.1. Extraction acidity isotherms2.2.2. Scrubbing pH isotherms2.2.3. Stripping kinetics

3. Results and discussions3.1. Metal extraction acidity isotherms3.2. Iron scrubbing3.3. Chloride scrubbing3.4. Copper stripping kinetics

4. Process flowsheet development5. Proposed extraction mechanism6. ConclusionsAcknowledgementsReferences