Minerals Engineering by Sushanta K Sahu

Minerals Engineering 17 (2004) 949–951

Technical Note

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Recovery of copper, nickel and cobalt from the leach liquor of a sulphide concentrate by solvent extraction S.K. Sahu *, A. Agrawal, B.D. Pandey, V. Kumar Metal Extraction and Forming Division, National Metallurgical Laboratory, Jamshedpur 831 007, India Received 4 September 2003; accepted 12 March 2004

Abstract The pressure acid leach liquor of copper concentrate generated at Uranium Corporation of India Limited (UCIL), Jaduguda was processed by solvent extraction for the recovery of valuable metals such as copper, nickel and cobalt. Copper from the leach liquor was extracted with LIX 84 in kerosene. From the copper free raﬃnate cobalt and nickel were separated with sodium salt of Cyanex 272. A scheme was developed to simulate the counter-current extraction of copper and cobalt–nickel. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Solvent extraction; Sulphide ores; Leaching

1. Introduction

2. Experimental

The Jaduguda uranium ore contains signiﬁcant amounts of valuable metals (Rao, 1998). The by-product recovery plant of UCIL at Jaduguda produces 600 t/y copper sulphide concentrate analysing 15% Cu, 10.85% Ni, 0.37% Co, 26.6% Fe, 33.3% S etc. To process the sulphide concentrate, options that have been explored in India include salt roasting-water leaching (Mukherjee et al., 1985) followed by metal separation with di-2-ethylhexyl phosphoric acid (D2EHPA) (Murthy and Mishra, 1986) and sulphuric acid pressure leaching (Pandey et al., 2002). For the extractive separation of copper, nickel and cobalt from aqueous solutions, either oxime (Aminian and Bazin, 2000) or organophosphorus (Rickelton et al., 1983) based extractants are often employed. The separation ability of organophosphorus extractants for Co–Ni follows the order: phosphinic > phosphonic > phosphoric acid (Preston, 1982). In the present work extraction of copper with LIX 84 and Co–Ni with Cyanex 272 from the pressure acid leach liquor of copper concentrate has been reported. The study also aims at investigating the species extracted into the organic phase and separating the metals in counter-current mode.

The aqueous solution obtained from the pressure sulphuric acid leaching of copper concentrate contained 2.8 g/L Cu, 6.16 g/L Ni, 0.156 g/L Co and 5.96 g/L Fe. After iron precipitation at pH 4.5 and aeration for 6 h at 40 °C, the composition of the purified leach solution was found to be 2.47 g/L Cu, 5.98 g/L Ni, 0.14 g/L Co and 0.035 g/L Fe. LIX 84 supplied by Henkel Corporation was used for the extraction of copper from the purified leach liquor. For the extraction of cobalt and nickel Cyanex 272, obtained from Cytec, was used in the form of sodium salt. Sodium salt of Cyanex 272 was prepared by reacting 1 M Cyanex 272 with the required amount of sodium hydroxide solution (Eq. (1)). Cyanex 272 was saponified to a level of 80% at O/A ratio of 10:1 for the extraction of cobalt whereas it was 60% for nickel extraction.

* Corresponding author. Tel.: +91-657-227-1806; fax: +91-657-2270527. E-mail address: sushanta_sk@yahoo.com (S.K. Sahu).

þ Naþ aq þ ½1=2ðHRÞ2 org ! NaRorg þ Haq

ð1Þ

Desired concentration of Na-Cyanex 272 was obtained by diluting it with kerosene while adding isodecanol as phase modiﬁer. Distribution ratios were determined by mixing 50 mL each of aqueous and organic phases for 15 min in a 250 mL glass beaker with the help of a glass stirrer. For obtaining distribution data metal in both the organic and aqueous phases were analysed by Atomic Absorption Spectrometer; in the former case stripping

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S.K. Sahu et al. / Minerals Engineering 17 (2004) 949–951

of the metal was carried out with dilute sulphuric acid (10 V%) prior to analysis.

0.8

3. Results and discussion

0.4

Copper complex formed with LIX 84 (HA) was characterized by Job’s method (Pazos et al., 1991). In this method the concentrations of the metal in the aqueous phase and active oxime of the organic phase were varied so as to get their sum equal to 0.1 M. At an initial aqueous phase pH of 2.0, copper to organic phase molar ratio: [Cu]/[active oxime] was found to be 1/2 indicating the extraction of CuA2 species, which was conﬁrmed by slope analysis method. Plots of log D vs log [HA] + pH for the extraction of copper from a synthetic solution (2.54 g/L) and from the leach liquor with 0.1 M LIX 84 had slopes of 1.87 and 1.78, respectively indicating the release of two Hþ ions as represented by Eq. (2) þ Cu2þ aq þ 2HAorg () ½CuA2 org þ 2Haq

ð2Þ

The extraction of cobalt and nickel from the leach liquor was studied by using 0.03 M Na-Cyanex 272 (80% neutralised) for cobalt and 0.4 M Na-Cyanex 272 (60% neutralised) for nickel. The initial pH was varied from 2.0 to 6.0 for cobalt and 1.75–6.25 for nickel, corresponding to the equilibrium pH of 5.20–6.75 and 5.75– 6.60, respectively. Extraction of both cobalt and nickel increased with increase in equilibrium pH. The plots of log D vs pH had slopes of 1.1 for the two metals indicating the exchange of one Hþ ion with one mole of the extracted metal species. The eﬀect of Na-Cyanex 272 concentration on the extraction of cobalt and nickel from the copper free raﬃnate was studied in the range 0.015–0.035 M for cobalt at pH 6.15, and 0.3–0.5 M for nickel at pH 6.5. Extraction of both the metal ions increased with increase in Cyanex 272 concentration. Plots (Fig. 1) of log D vs log [Na-Cyanex 272] had slopes of 1.78 and 2.1 for Co and Ni indicating the association of two moles of extractant with the extracted metal (M2þ :Co2þ /Ni2þ ). As Cyanex 272 exists as monomer in neutral form and dimer in the acidic form (Sarangi et al., 1999), the metal extraction may follow the reaction: þ M2þ aq þ Rorg þ ½2ðHRÞ2 org () MR2 3HRorg þ Haq

ð3Þ As regards the number of stages required for countercurrent extraction, copper extraction was possible in two stages with 0.1 M LIX 84, whereas cobalt and nickel were extracted in three-stages with Na-Cyanex 272. From the loaded organic phase copper could be quantitatively stripped with 180 g/L sulphuric acid in one stage, whereas 10 g/L sulphuric acid could strip cobalt/ nickel in two stages.

Log D

Slope = 1.78

Slope = 2.1 Co

pH = 6.5

pH = 6.15

-0.4 -2

-1.5

-1

-0.5

Log [Na-Cyanex 272] Fig. 1. Eﬀect of Na-Cyanex 272 concentration on the extraction of cobalt and nickel from leach liquor. Aqueous feed: pH ¼ 6.15 for cobalt and pH ¼ 6.5 for nickel.

Results on counter current extraction of copper at an aqueous phase pH of 2 with 0.1 M LIX 84 are given in Fig. 2(a). In the first stage 87% copper was extracted and 2.466 g/L copper was loaded into the organic phase at the end of second stage. The final raffinate contained 0.004 g/L copper, 5.90 g/L nickel, 140 ppm cobalt and 17 ppm iron. Similarly, counter current extraction of cobalt at an aqueous pH of 6.6 with 80% saponified 0.03 M Cyanex 272 and nickel at an aqueous pH of 6.66 with 60% saponified 0.45 M Cyanex 272 are shown in Fig. 2(b) and (c). In two stages major quantity of the desired metal was extracted. However, at the end of fourth stage for cobalt extraction, 138.57 ppm Co, 10 ppm Ni and 18 ppm Fe entered to the organic phase (LO4 ) with 5.89 g/L Ni and 1.43 ppm Co left out in the raffinate. In case of nickel, 5.882 g/L Ni was loaded into the organic phase at the end of fourth stage. Thus fairly good separation of copper, nickel and cobalt from the leach liquor was achieved in counter current extraction.

4. Conclusions For the extractive separation of copper, cobalt and nickel from the leach liquor of the copper concentrate, LIX 84 and Na-Cyanex 272 were eﬀectively utilised as solvents. The species extracted into the organic phase were determined to be CuA2 for copper with LIX 84, and MR2 3HR for cobalt and nickel with Na-Cyanex 272. Counter current extraction of copper with LIX 84, and cobalt–nickel with Na-Cyanex 272 showed almost quantitative loading into the organic phase in two and four stages, respectively. The extraction of cobalt with 80% saponiﬁed 0.03 M Cyanex 272 at an equilibrium pH of 6.6 resulted in limited nickel (10 ppm) and iron (18 ppm) contamination. High nickel extraction (99.9%) was achieved in four stages using 60% sodium salt of 0.45 M Cyanex 272 at an equilibrium pH of 6.6.

S.K. Sahu et al. / Minerals Engineering 17 (2004) 949–951 LO2 Cu = 2.466 g/L Fe = 17 ppm

951

O LO1 Cu = 0.326 g/L

Stage 1

Stage 2 Rf1 Cu = 0.33 g/L

A Cu = 2.47 g/L Co = 140 ppm Ni = 5.96 g/L Fe = 35 ppm

Rf2 Cu = 0.004 g/L Co = 140ppm Ni = 5.90 g/L Fe = 18 ppm

(a) LO4 Co = 138.57 ppm Ni = 10 ppm Fe = 18 ppm

LO3 Co = 12.09 ppm

LO2 Co = 3.4 ppm

Stage 3

Stage 2

Stage 1

Rf2 Rf1 Co = 13.52 ppm Co = 4.83 ppm

A Co = 140 ppm Ni = 5.90 g/L Fe = 18 ppm

LO1 Co = 0.3 ppm Stage 4

Rf3 Co = 1.73 ppm

Rf4 Co = 1.43 ppm Ni = 5.89 g/L

(b) LO4 Ni = 5.882 g/L

LO3 LO2 Ni = 0.483 g/L Ni = 0.048 g/L

Stage 1

A Co = 1.43 ppm Ni = 5.89 g/L

Stage 2

O LO1 Ni = 0.035 g/L

Stage 3

Rf1 Rf2 Ni = 0.491 g/L Ni = 0.056 g/L

Stage 4

Rf3 Ni = 0.043 g/L Rf4 Ni = 0.008 g/L

(c) Fig. 2. Counter current extraction for copper, cobalt and nickel: (a) copper with 0.1 M LIX 84, (b) cobalt with 80% saponiﬁed 0.03 M Cyanex 272 and (c) nickel with 60% saponiﬁed 0.45 M Cyanex 272.

References Aminian, H., Bazin, C., 2000. Solvent extraction equilibria in copper(II)–iron(II)–LIX 984 system. Minerals Eng. 13, 667–672. Mukherjee, T.K., Menon, P.R., Shukla, P.P., Gupta, C.K., 1985. Chloridizing roasting process for a complex sulphide concentrate. J. Met. (June), 28–33. Murthy, T.K.S., Mishra, S.L., 1986. Recovery of copper and nickel from a complex solution using di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant. Trans. Indian Inst. Met. 39, 130–136. Pandey, B.D., Bagchi, D., Kumar, V., Agrawal, A., Premchand, 2002. Pressure sulphuric acid leaching of a sulphide concentrate to recover copper, nickel and cobalt. Trans. Inst. Min. Metall. C 111, 106–109. Pazos, C., Curieses, J.P.S., Coca, J., 1991. Solvent extraction equilibrium of nickel from ammonical solutions by LIX 64N. Solvent Extr. Ion Exc. 9, 569–591.

Preston, J.S., 1982. Solvent extraction of cobalt and nickel by organophosphorus acids. I. Comparison of phosphoric, phosphonic and phosphinic acid systems. Hydrometallurgy 9, 115– 133. Rao, N.K., 1998. Strategy for the beneﬁciation of ores of some strategic metals in India. Met. Mater. Process. 10, 21–40. Rickelton, W.A., Flett, D.S., West, D.W., 1983. Cobalt and nickel separation by solvent extraction with dialkyl phosphinic acid. In: Proc. Int. Solvent Extraction Conf., Denver, Colorado, American Institute of Chemical Engineers, New York, pp. 195– 196. Sarangi, K., Reddy, B.R., Das, R.P., 1999. Extraction studies of cobalt and nickel from chloride solutions using Na-Cyanex 272. Separation of Co(II)/Ni(II) by the sodium salts of D2EHPA, PC 88A and Cyanex 272 and their mixtures. Hydrometallurgy 52, 252– 265.