Oxidation-precipitation of Co from Zn-Cd-Co-Ni sulphate solution using Caro's acid

A process utilizing Care's acid to precipitate cobalt from a Zn-Cd-Co-Ni sulphate solution has been investigated. Care's acid oxidizes Co(II) to Co(III) species. About 98-99% of the cobalt contained in the feed solution was precipitated as Co(OH)(3) at pH 3.5-4.0. However, at pH less than or equal to 2.5, less than 8% of the cobalt present in the feed was precipitated. At such law pH's, a dark green colloidal suspension was generated and this was difficult to filter. Results obtained from both batch and continuous experiments were similar. The cobalt content of the Co(OH)(3), precipitate was 47-49% which is fairly close to the theoretical value of 53.6%. The impurities consisted of 3-4% Zn, about 1% Cd and less than 0.005% Ni. (C) 1998 Elsevier Science B.V.