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Abstract

A process for producing cobalt metal powder from nickel-cobalt sulphides wherein said nickel-cobalt sulphides are leached in an ammoniacal ammonium sulphate solution under an elevated pressure of an oxygen bearing gas, at a temperature of at least 80.degree. C., with an effective ammonia to metals mole ratio in the range of 5:1 to 6.5:1 to oxidize the nickel and cobalt sulphides to sulphates, and to produce an ammoniacal leach liquor in which dissolved cobalt is predominantly in the (III) oxidation state, and an ammoniacal ammonium sulphate leach residue containing a cobalt (III) hexammine sulphate-calcium sulphate double salt. The improvement comprises repulping the ammoniacal ammonium sulphate leach residue, containing the cobalt (III) hexammine sulphate-calcium sulphate double salt, with a solution containing an effective amount of ammonium carbonate to dissolve the cobalt (III) hexammine sulphate in the repulp leach liquor and precipitate calcium carbonate; and separating the repulp leach liquor containing cobalt (III) hexammine sulphide from the repulp leach residue containing calcium carbonate.

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