A hydrometallurgical process that involves solvent extraction and selective precipitation has been used to selectively recover Co2+ from an aqueous filtrate containing mostly Co2+, NH4+ and NO3- ions and trace amounts of Pt2+, Al3+ and Fe3+ ions. The effect of pH on the precipitation efficiencies of Al3+ and Fe3+ ions from the leach liquor was investigated. Solvent extraction exhibited good performance in terms of both Co2+ and Pt2+ ions extraction efficiency and phase separation when ammonium salt of di(2-ethyl-hexyl)phosphoric acid was used as an extractant in the presence of a tributylphosphate modifier. Cobalt was stripped from the organic phase with nitric acid to yield cobalt nitrate. (C) 2003 Elsevier Ltd. All rights reserved.