Hydrometallurgy 121-124 (2012) 116–119

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Technical note

Extraction of copper from bacterial leach liquor of a low grade chalcopyrite test heapusing LIX 984N-C

S. Panda a,c, P.K. Parhi b,⁎, N. Pradhan a, U.B. Mohapatra c, L.B. Sukla a, K.H. Park b

a Bioresources Engineering Department, Institute of Minerals & Materials Technology (IMMT), CSIR, Bhubaneswar-751013, Indiab Mineral Resources Research Division, Korea Institute of Geoscience & Mineral Resources (KIGAM), Daejeon, 305-350, Republic of Koreac North Orissa University, Baripada-757003, Odisha, India

⁎ Corresponding author. Tel.: +82 42 868 3604.E-mail address: parhi_pankaj@yahoo.co.in (P.K. Parh

0304-386X/$ – see front matter © 2012 Elsevier B.V. Aldoi:10.1016/j.hydromet.2012.03.008

a b s t r a c t

a r t i c l e i n f o

Article history:Received 13 March 2012Accepted 27 March 2012Available online 5 April 2012

Keywords:Low grade oreHeap bioleachingCopperSolvent extractionLIX 984N-C

Low grade copper ore (ball mill spillage) obtained from Malanjkhand Copper Mine was processed throughheap bioleaching at pilot scale. Bioleach liquor (Pregnant Leach Solution) from the heap contains (g/L of) Cu(II) 0.45, Fe (III) 0.838, Zn (II) 0.006, Ni (II) 0.0014, Mn (II) 0.011 and Pb (IV) 0.004. Solvent extraction ofcopper from Pregnant Leach Solution was carried out using LIX 984N-C. Effect of different operational factorssuch as equilibrium pH (pHe), extractant concentration, strip solution concentration, phase ratio wasexamined to optimize the condition for selective and quantitative extraction of copper. Based on the resultsof extraction as well as stripping isotherm, a 6-cycle counter current simulation study (CCS) was conductedfor the conformational study. The extraction of copper was quantitative in 2-stages using 1.5% (v/v) LIX984N-C at A: O ratio of 1:2 and pHe 1.85. The CCS condition (two stages, phase ratio A:O=1:4) obtained fromthe stripping isotherm study, further attributes to the enrichment (4 folds) of copper concentration in thestrip solution.

© 2012 Elsevier B.V. All rights reserved.

1. Introduction

Over the past few years, hydrometallurgical copper productionfrom low grade ores is being routed through bioleaching–solventextraction–electrowinning (BL–SX–EW) (Wenjian et al., 1995). Atabout 20–25% of the world's total copper production is throughsolvent extraction followed by electrowinning processes (Munoz etal., 2007). Heap bioleaching of low grade chalcopyrite ore is gainingimportance for waste treatment vis-à-vis with a substantial recoveryof the valuable metals (Pradhan et al., 2008; Sukla et al., 2009).During heap bioleaching of chalcopyrite, some other metal ionimpurities also get leached and are present along with the copper.Iron is found as one of the major impurities in the leach solution sinceits concentration is as high as compared to the other impurities. Theseparation of copper by solvent extraction process from the ironbearing solution is well proven and a suitable method in hydromet-allurgy (Cvetkovski et al., 2009; Minango et al., 2005; Stevanovic etal., 2009). Stevanovic et al. (2009) have developed the processingflow sheet to recover the copper from overburden of an abandonedmine Cerovo in Eastern Serbia which follows the hydrometallurgicalroute including leaching–SX–EW methods. In view of the industrialand economic importance of copper extraction process, there is agreat need for separation and recovery of the metal values using cost

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l rights reserved.

effective commercial extractants. A considerable amount of workhave been devoted towards the investigation on solvent extraction ofcopper from acid or ammoniacal medium using LIX series extractants(Lazarova and Lazarova, 2005, 2007; Panigrahi et al., 2009; Parija andSarma, 2000). Off these LIX reagents, LIX 984N-C is found to be anefficient and effective extractant owing to its exclusive applications inextraction of several metals (Cu, Ni, Fe and Zn) by solvent extractionprocesses (Kul and Cetinkaya, 2009a, 2009b, 2010). In addition, theselectivity of the LIX 984N-C towards any of the above metals wasagain governed by the change of suitable pH range of the aqueoussolutions (Kul and Cetinkaya, 2009b).

From the reported literatures (Kul and Cetinkaya, 2009b; Lazarovaand Lazarova, 2005), LIX 984N-C was notably found as a veryselective chelating extractant towards the extraction of coppermetal ion despite of the presence of other impurities in the aqueoussolution, while separating the copper ion from the leach solutionbearing other metals such as Zn, Pd and Ni. Nevertheless, LIX 984N-Cis considered as a strong extractant towards the extraction of copperbecause of its very good physical performance property. Its predom-inance performances by mean of extraction efficiency and selectivity,is due to the mixed effect of LIX 860N-C and LIX 84-IC in LIX 984N-C(Asghari et al., 2009; Cheng et al., 2000; Fouad, 2009).

The mixed reagent for example LIX 984N, shows faster kineticsbecause of the synergism behavior as compared with other LIXreagents (LIX 860N-I, LIX 84-I, LIX 65N) during the investigation onthe extraction of copper from the nitrate/nitric acid solution (Lazarovaand Lazarova, 2005). LIX® 984N acts as a very good synergist with

Table 2Mineralogical analysis of low grade Malanjkhand Copper ore (Mill Spillage).

Silicate minerals Quartz, orthoclase, microcline, plagioclase, biotite and chloriteMuscovite, sericite, epidote, hornblende and clay minerals

Sulphideminerals

Chalcopyrite, bornite, pyrite, chalcocite, sphalerite,covellite, molybdenite

Accessoryminerals

Malachite, apatite, fluorite, pyrophyllite, titanite, zircontourmaline, zoisite and clinozoisite

117S. Panda et al. / Hydrometallurgy 121-124 (2012) 116–119

Cyanex 301 and their mixture lead to enhance the metal strippingefficiency more effectively from the loaded organic with H2SO4.Nonetheless, it could also lower the acid consumption rate whilestripping the metal ion from the loaded organic phase (Fouad, 2009).Unlike solvent extraction, several authors have also proposed for theuse of LIX 984N in dispersive (ELM and BLM) as well as non dispersivetype liquid membranes (SLM) separation process, in which LIX 984Nprovides a very good overall transport performance for copper fromthe acidic and dilute solutions (Sengupta et al., 2006; Yang and Fane,1999a, 1999b).

Copper extraction was obtained to be quantitative with 30% LIX984N-C at an equilibrium pH 2, O: A ratio of 8:1 in 2 stages to enhancethe loading of copper (20.4 g/L) into the organic phase and subsequentstripping of copper from loaded organic using 550 g/L H2SO4 in twocounter current stages (Kul and Cetinkaya, 2009b). Xie et al.(2008)have developed the process flow diagram for the separation of Cu(II),Zn(II), and Cd(II) from a rich sulfate leachate of zinc slag by solventextraction in which the copper extraction was carried out with LIX984N followed by separation of Zn and Cd using of mixture of D2EHPAand tri-butyl-phosophate. Extraction of copper from the rich sulphateleach solution was carried out as the function of the factors namelyextraction time, pH, LIX 984 concentration and phase ratio and theoptimal condition for copper extraction was determined as: concen-tration of LIX 984N 25%(v/v), extraction time 7 min., phase ratio O/A3:2 and pH=1.7. Furthermore, from the results of it was observed thatLIX 984N is highly selective and very efficient in the extraction of Cu(II) in presence of the metal like Zn (II) and Cd (II).

The purpose of the present paper is to explore the optimalcondition for selective extraction of copper from the Pregnant LeachSolution (PLS) obtained through heap bioleaching of low grade copperore (ball mill spillage) using LIX 984N-C. The effect of differentoperating parameters such as equilibrium pH (pHe), LIX 984N-Cconcentration, strip solution (H2SO4) concentration, phase ratio, werestudied. A suitable extraction and stripping condition was establishedto enrich the copper concentration more effectively and that attributesto achieve a high copper concentration the final strip solution.

2. Experimental

2.1. Description of the heap bioleaching pilot plant set up

A heap of low grade ore copper ore (ball mill spillage material) of1000 t capacity was constructed at Malanjkhand, India. Chemicalcomposition of the sample showed 0.26% Cu, 1.5% Fe, 0.46% S, and92.8% of acid insoluble material. Chemical composition of each sizefraction with their percentage weight in construction of the heap isshown in Table 1. The detailed mineralogical analysis of the sample ispresented in Table 2. The ore material was stacked on an imperviousleach pad. Bottom of the heap had layered network of pipelines foraeration of heap. Sprinklers were fitted at the top for spraying of thelixiviant. The heap was acid conditioned prior to the start of theexperiment. A specially designed BACFOX tank (Bacterial Film Oxida-tion Unit) of 108 m3 capacity was built for the growth of microorgan-isms. A mixed culture of mesophillic acidophillic chemolithotrophicconsortia, predominantly Acidithiobacillus ferrooxidans acted asinoculum. The BACFOX tank was also used for collection of pregnant

Table 1Chemical composition of each size fraction used in heap.

Size (mm) Weight % Cu (O)a Cu(S)b Cu (Total) Si as SiO2

+12 24 Nil 0.50 0.50 77.72−12+6 43 Nil 0.23 0.23 73.88−6+4 33 Nil 0.09 0.09 61.96

a Cu (O)—copper oxides.b Cu(S)—copper sulphides.

leach solution (PLS) from the heap. The heap was operated at ambienttemperature. The tank also had a compressed air supply. Initial volumeof the bacterial solution was 30 m3 and was pumped at the rate of1.1 L/min/m2. The concentration of copper and other elements in thePLS was analyzed by Atomic Absorption Spectrophotometer (PerkinElmer Model AA-400).

2.2. Extraction of copper from pregnant heap leaching solution

2.2.1. ReagentsThe organic solvents such as LIX 984N-C (Cognis, Ireland) and

commercial grade kerosene were used as obtained from the supplier.The kerosene was used as the diluent in all cases. The organicextractant namely LIX 984N-C used in present investigation, is thewell known as the combination of 1:1 volume of LIX 860N-C and LIX84-IC. (Asghari, et al., 2009). The pH adjustment of the aqueoussolution was made to a desired value before extraction by addition ofdilute H2SO4 or NaOH and all the pH readings were recorded using apH meter (pH meter Orion, USA, provided with combined glasselectrode). All the chemical reagents used were of analytical grade(Merck, German).

2.2.2. Solvent extraction procedureAll the solvent extraction experiments were performed manually

by contacting the desired volume of aqueous and organic phases in aseparating funnel (shake flask) for time period of 5 min. After phasedisengagement, the two phases were allowed to separate followed bymeasurement of equilibrium pH (pHe) and analysis of metal ionconcentration of raffinate using atomic absorption spectrophotome-ter. The metal ion concentration in the organic phase was determinedfrom the difference between the concentration of metal before andafter extraction. As and when required, the metal concentrations inthe organic phase were estimated after filtration through 1PS phaseseparation paper and stripping a suitable aliquot of it with 10% (v/v)H2SO4 followed by dilution and analysis. All the experiments wereconducted at the ambient temperature (25±1 °C). The distributioncoefficient D (ratio of metal ion concentrations in the organic andaqueous phases) and the percentage (%) of metal extraction weredetermined accordingly. Some of the solvent extraction experimentsin present investigation were repeated in order to assure reproduc-ibility and the experimental error was found to be of ±2%.

3. Results and discussion

The bacterial lixiviant prepared in the BACFOX tank wasrecirculated, which allowed the copper to dissolute from the oreand build up in the BACFOX tank. The composition of PLS from heap,used for copper solvent extraction study was presented in Table 3.The bioleach liquor (PLS) was then subjected to various optimization

Table 3Analysis result of pregnant leach solution of heap used for solvent extraction studies.

Cu(II),g/L

Fe(III),g/L

Zn(II),g/L

Ni (II),g/L

Mn (II),g/L

Pb (IV),g/L

0.45 0.838 0.006 0.0014 0.011 0.004

0

20

40

60

80

100

0 0.5 1 1.5 2 2.5 3

[LIX 984N-C], %

Co

pp

er e

xtra

ctio

n, %

Fig. 2. Effect of LIX 984N-C concentration on copper extraction, Conditions: pHe 1.85,time: 5 min and A:O=1.

118 S. Panda et al. / Hydrometallurgy 121-124 (2012) 116–119

studies using LIX 984N-C as the extractant. The major impurity in theleach liquor was Fe while other metals namely Ni, Zn, Mn and Pb,were present in minor amount (b0.012 g/L).

In preliminary study for kinetics on extraction of copper from thepregnant heap was studied and from the results it was ensured thatcopper extraction occurs rapidly (with in contact time limit asmentioned in Experimental section) indicating very fast extractionkinetics. The observation is quite similar to the behavior of othercommercial LIX reagents such as LIX 84-I, LIX 622N and LIX 64(Lazarova and Lazarova, 2007; Panigrahi et al., 2009; Parija andSarma, 2000).

3.1. Effect of equilibrium pH

To study the copper extraction as the function of pH, the pHe

values of the aqueous leach solution was varied from 0.38 to 2.24with using 1.0%(v/v) LIX 984N-C, at the phase ratio: A:O=1:1 andcontact time 5 min. From the results of Fig. 1, it can be seen that theextraction of copper was increased from 37.78% to 97.56% withincrease in pHe from 0.38 to 1.85 and on further increase in the pHe to2.24, the copper extraction was more or less remains constant. Co-extraction of Fe(III) was not observed up to the pHe of 1.85, however,at pHe 2.24, a small quantity of Fe (3.25 mg/L) was extracted toorganic phase along with copper. The separation factor of copperfrom Fe (SFCu–Fe=DCu/DFe) at the solution pHe 2.24 was determinedto be 16,254.7, indicating the selectivity of the LIX 984N-C onextraction of copper. The co-extraction of other metals such as Mn(II), Zn (II), Ni (II) and Pb (IV), are not observed within the studied pHrange. The suitable pH ranges of present investigation was capable ofavoiding iron precipitation (since Fe (III) starts precipitation greaterthan equilibrium pH 2.24) (Nathasarma, and Sarma, 1987; Parhi et al,2011) and minimizing the co-extraction of other metal ions from theleach solution.

From the above results it is cleared that, the Initial pH value oforiginal leach solution (pH 2.0) is well within the optimum solventextraction pH range and also consistent with the observations ofprevious work (Sukla et al., 2009).

3.2. Effect of LIX 984N-C concentration

The extraction of copper from the leach solution was carried out withdifferent concentration of LIX 984N-C (0.25–2.5%) and at pHe 1.85 andphase ratio of 1. As shown in Fig. 2, the copper extraction was increasedfrom 22.67% to 97.56% with increase in extractant concentration from0.25% to 1.5%(v/v) LIX 984N-C. The extraction of copper seems to beplateau beyond 1.5% (v/v) LIX 984N-C. The co-extraction of Mn (II), Fe(III), Zn (II), Ni (II) and Pb (IV)was not observedwithin the above studiedLIX 984N-C concentration range. Thus, from the above study, 1.5% (v/v) of

0

20

40

60

80

100

0 0.5 1 1.5 2 2.5

Equilibrium pH (pHe)

Met

al e

xtra

ctio

n,%

Cu

Fe

Fig. 1. Effect of pHe on copper extraction, Conditions: A:O=1, time: 5 min and 1%(v/v)LIX 984N-C.

LIX 984N-C was sufficient to recover 99.56% of copper from the leachsolution in a single contact of aqueous and organic phases.

3.3. Extraction isotherm

The extraction isotherm was studied to find out the number ofstages required for a quantitative extraction of copper at a chosen A:Ophase ratio. Both aqueous and organic phases were contacted atdifferent phase ratios (A: O=1:5 to 5:1), while keeping rest of theparameters like pHe 1.85, 1.5%( v/v) LIX 984N-C and total volume ofphases constant. After phase separation, the two phases were analyzedand based on the results, concentration of copper in organic and theaqueous phases, were plotted to obtainMcCabe–Thiele diagram (Fig. 3).It illustrated the quantitative extraction of copper in 2 stages at A: Oratio of 2:1. Furthermore, to confirm this, a 2-stage counter-currentsimulation (CCS) study was carried out up to 6 cycles, at the abovepredicted conditions. The analysis of the raffinate obtained in CCS studyreads to contain 0.009 mg/L of copper, confirming ~99.9% of copperextraction. Desired quantity of loaded organic containing 0.9 g/L ofcopper was generated for stripping study.

3.4. Effect of H2SO4 concentration on stripping of copper

The efficiency of H2SO4 on stripping of copper from the copperloaded organic was examined and presented. The concentration ofH2SO4 was varied from 10 to 200 g/L while other parameters like phaseratio of A: O=1:1 and contact time of 5 minutes were kept fixed. Therate of copper stripping as the function of H2SO4 concentration wasshown in Fig. 4. This showed that the percentage of copper strippingwas linearly increased from 19.24 to 99.55% with increase in H2SO4

0

0.4

0.8

1.2

1.6

0 0.1 0.2 0.3 0.4 0.5

[Cu

] org

, g/L

O:A=1:2

[Cu]aq, g/L

Fig. 3. McCabe–Thiele plot on extraction of copper, Conditions: pHe 1.85, time: 5 min1.5% (v/v) LIX 984N-C.

0

1

2

3

4

5

0 0.2 0.4 0.6 0.8 1

[Cu

] SS, g

/L

O:A=4:1

[Cu]LO, g/L

Fig. 5. McCabe–Thiele plot on stripping of copper from loaded organic, Conditions:180 g/L H2SO4 and time 5 min.

119S. Panda et al. / Hydrometallurgy 121-124 (2012) 116–119

concentration from 10 to 180 g/L and thereafter it reached to a plateauvalue. As the summary of the above results, 180 g/L of H2SO4 waschosen to be the suitable concentration for quantitative stripping ofcopper from the loaded organic phase and therefore this concentrationwas fixed for further experimental investigations.

3.5. Stripping isotherm study

The stripping isotherm for copper was constructed to find out thenumber of stages required for stripping at chosen phase ratio (A: O).The Cu-loaded LIX 984N-C and 180 g/L H2SO4 was contacted atdifferent phase ratio (A: O=1:5 to 5:1), while keeping the totalvolume of the phases constant. After phase separation, both phasesare analyzed for metal concentration The McCabe–Thiele plot (Fig. 5)illustrated the possibility of >99% of copper stripping at 2 counter-current stages at A: O ratio of 1:4. To confirm the above prediction, a2-stages counter-current simulation (CCS) study was performed (up to6 cycles) at the above mentioned conditions, which resulted aquantitative stripping of copper. Spent organic analysis result reveals92% and 99.9% of stripping in the first and second stages, respectively.The final stripped solution obtained after two stage CCS study whichreads to contain 3.6 g/L copper (>99.9% stripping efficiency), confirm-ing the copper enrichment in the stripped solutionwas up to 4 times ascompared to copper concentration in the loaded organic.

4. Conclusions

Solvent extraction of copper was carried out using LIX 984N-C fromthe pregnant leach solution obtained from a test heap bioleachingexperiment on low grade copper ore (ballmill spillage) ofMalanjkhand.Copperwas preferentially extracted from pregnant leach solution using1.5% (v/v) LIX 984N-C and it shows quantitative with 2-extractionstageswith A: O ratio of 2:1 at solution pHe 1.85. Co-extraction of Fe, Zn,Co, Ni was not observed under the optimum conditions, indicating theselectivity extraction behavior of LIX 984N-C towards copper. Strippingisotherm study was carried out using 180 kg/m3 H2SO4 which predictsthe optimum stripping condition (2-stage at A:O ratio of 1: 4) andfurthermore, it was confirmed by CCS study. Subsequently, the strippedsolution, generated after CCS study contains 3.6 g/L of copper, wasensuring about the copper enrichment up to 4 folds and 8 folds ascompared to the copper concentration in loaded organic and initialleach solution phase, respectively.

Acknowledgments

The authors are thankful to M/s Hindustan Copper Limited forfinancial support for carrying out heap bioleaching. They also thankstaff of Institute of Minerals and Materials Technology and HindustanCopper Limited involved in this project. The first author, S. Panda is

10

30

50

70

90

0 50 100 150 200

Co

pp

er s

trip

pin

g, %

[H2SO4], g/L

Fig. 4. Effect of contact time on stripping of copper from loaded organic, Conditions:[H2SO4] :180 g/L and A: O=1.

thankful to CSIR for the award of Senior Research Fellowship and oneof the co-author, P.K. Parhi is grateful to KIGAM for the award ofpostdoctoral fellowship.

References

Asghari, H., Safarzadeh, M.S., Asghari, G., Moradkham, D., 2009. The effect of impuritieson the extraction of copper from sulfate medium using LIX®984N in kerosene.Russ. J. Non-Ferr. Met. 50, 89–96.

Cheng, C.Y., Hughes, C.A., Barnard, K.R., Larcombe, K., 2000. Manganese in coppersolvent extraction and electrowinning. Hydrometallurgy 58, 135–150.

Cvetkovski, V.B., Conic, V.T., Vukovic, M.V., Stojanovski, G.P., Cvetkovska, M.V., 2009.Construction of isotherms in solvent extraction of copper. Hemijska Industrija 63,309–312.

Fouad, E.A., 2009. Improvement of Cu (II) stripping utilizing a mixture of CYANEX 301and LIX984N. J. Eng. Appl. Sci. 56, 581–598.

Kul, M., Cetinkaya, U., 2009a. Recovery of zinc by LIX 984N-C from electroplating rinsebath solution. Solvent Extr. Ion Exch. 27, 536–550.

Kul, M., Cetinkaya, U., 2009b. Recovery of copper by LIX 984N-C from electroplatingrinse bath solution. Hydrometallurgy 98, 86–91.

Kul, M., Cetinkaya, U., 2010. Recovery of nickel by solvent extraction fromelectroplating rinse bath solution. Solvent Extr. Ion Exch. 28, 225–243.

Lazarova, Z., Lazarova, M., 2005. Solvent extraction of copper from nitrate media withchelating LIX-reagents: comparative equilibrium study. Solvent Extr. Ion Exch. 23,695–711.

Lazarova, Z., Lazarova, M., 2007. Kinetic aspects of copper-LIX® extraction from nitrate/nitric acid aqueous solutions. Solvent Extr. Ion Exch. 25, 619–638.

Minango, R., Bwalya, E., Bukunkwe, D., Grinbaum, B., 2005. Development of a novelthree-step SX process to recover copper from an acidic solution. J. S. Afr. Inst. Min.Metall. 105, 593–598.

Munoz, J.A., Dreisinger, D.B., Cooper, W.C., Young, S.K., 2007. Silver catalyzedbioleaching of low grade ores. Part I. Shake flasks tests. Hydrometallurgy 88, 3–18.

Nathasarma, K.C., Sarma, P.V.R.B., 1987. Separation of iron and manganese from sulphatesolutions obtained from Indian Ocean nodules. Hydrometallurgy 17, 239–249.

Panigrahi, S., Parhi, P.K., Sarangi, K., Nathsarma, K.C., 2009. A study on extraction ofcopper using LIX 84-I and LIX 622N. Sep. Purif. Technol. 70, 58–62.

Parhi, P.K., Park, K.H., Kim, H.I., Park, J.T., 2011. Recovery ofmolybdenum from the sea noduleleach liquor by solvent extraction using Alamine 304-I. Hydrometallurgy 105, 195–200.

Parija, C., Sarma, P.V.R.B., 2000. Separation of nickel and copper from ammoniacalsolutions through co-extraction and selective stripping using LIX 84 as theextractant. Hydrometallurgy 54, 195–204.

Pradhan, N., Nathsarma, K.C., Rao, K.S., Sukla, L.B., Mishra, B.K., 2008. Heap bioleachingof chalcopyrite: a review. Miner. Eng. 21, 355–365.

Sengupta, B., Sengupta, R., Subrahmanyam, N., 2006. Copper extraction into emulsionliquid membranes using LIX 984N-C. Hydrometallurgy 81, 67–73.

Stevanovic, Z., Antonijevic, M., Jonovic, R., Avramovic, L., Markovic, R., Bugarin, M.,Trujic, V., 2009. Leach–SX–EW copper revalorization from overburden ofabandoned copper mine Cerovo, Eastern Serbia. J. Min. Metall. Sect. B. 45, 45–57.

Sukla, L.B., Nathsarma, K.C., Mahanta, J.R., Singh, S., Behera, S., Rao, K.S., Subbaiah, T.,Mishra, B.K., 2009. Recovery of copper values from bio-heap leaching of low gradeMalanjkhand chalcopyrite ore. Korean J. Chem. Eng. 26 (6), 1668–1674.

Wenjian, W.U., Hanying, J., Songqing, Y., 1995. Extractive separation of copper andnickel with LIX 984N. Min. Metall. Eng. 15, 43–47.

Xie, K., Wen, J., Hua, Y., Ruan, R., 2008. Selective separation of Cu (II), Zn(II), and Cd (II)by solvent extraction. Rare Met. 27, 228–232.

Yang, X.J., Fane, A.G., 1999a. Performance and stability of supported liquid membranesusing LIX 984N for copper transport. J. Membr. Sci. 156, 251–263.

Yang, X.J., Fane, A.G., 1999b. Facilitated transport of copper in bulk liquid membranescontaining LIX 984N. Sep. Sci. Technol. 34, 1873–1890.