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Journal of the Southern African Institute of Mining and Metallurgy

On-line version ISSN 2411-9717
Print version ISSN 0038-223X

J. S. Afr. Inst. Min. Metall. vol.109 n.6 Johannesburg Jun. 2009




A cobalt solvent extraction investigation in Africa's Copper Belt



T. KönighoferI; S.J. ArcherII; L. BradfordIII

ITWP Matomo Process Plant (Pty) Ltd, South Africa
IIMDM Technical Africa (Pty) Ltd, South Africa
IIIMetorex Ltd, South Africa




Processing of copper-cobalt orebodies in Africa's Copper Belt has received much recent attention with various flowsheet options being developed specifically for the refining of cobalt. The upfront leach and copper refining routes are well understood whereas the refining of cobalt is more complex, requiring numerous impurity removal steps to produce high purity metal. This paper describes an investigation into one of the possible processing steps in the refining of cobalt, namely, cobalt solvent extraction.
The paper emphasizes the importance of upstream impurity removal to achieve the required cobalt solvent extraction feed composition. 18% (v/v) Cyanex 272 in an aliphatic diluent is used as the organic phase. The pH profiles in the various stages are evaluated in order to obtain a raffinate containing <10 mg/l cobalt and with a low magnesium content reporting to the stripping section. The pH profile is also used to minimize the impurity deportment to the cobalt electrolyte. The effect of adding a preneutralization stage before feeding the organic phase to the extraction circuit is investigated. Zinc build-up in the stripping stages is also looked at.
It is recommended for the purpose of this study that four extraction stages at an O:A ratio of 1 with a pH profile from 4.9 to 5.7 be employed. The pH is controlled with 40 g/l NaOH. A preneutralization stage is required, where the organic phase is contacted with 10 M NaOH. Two scrubbing stages are recommended at an O:A ratio of 40, using the cobalt electrowinning advance electrolyte as the scrub liquor. Three strip stages are to be employed at an O:A ratio of 0.67.



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1. 31 August 2008.         [ Links ]

2. SOLE, K.C., FEATHER, A.M., and COLE, P.M. Solvent Extraction in Southern Africa: An update of some recent hydrometallurgical developments, Hydrometallurgy 78, Elsevier, 2005. pp. 52-78.         [ Links ]

3. ROUX, L.M., MINNAAR, E., CILLIERS, P.J., BELLINO, M., and DYE, R. Comparison of Solvent Extraction and Selective Precipitation for the Purification of Cobalt Electrolytes at the Luilu Refinery, DRC, The South African Institute of Mining and Metallurgy Base Metal Conference, Symposium Series S47, 2007. pp. 343-364.         [ Links ]

4. Cyanex 272®Handbook, Solvent Extraction Reagent, Cytec Industries, pp. 1-37.         [ Links ]

5. DAUDINOT, A.M.M. and LIRANZA, E.G. Proceeding of the International Solvent Extraction Conference, ISEC 2002, Johannesburg, pp. 964-969.         [ Links ]

6. BOURGET, C. and JAKOVLJEVIC, B. Operational Practices for Cyanex 272 Extractant Circuits, Proceedings of ISEC 2008, vol. I, pp. 447-452.         [ Links ]

7. COLE, P.M. and FEATHER, A.M. Processing of African Copper-Belt Copper- Cobalt Ores: Flowsheet Alternatives and Options, Proceedings of ISEC 2008, vol. I, pp. 131-138.         [ Links ]

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