The oxidative leaching reactions of cobalt sulfides are interesting in connection with a hydrometallurgical treatment of cobalt sulfide as well as complex cobalt sulfide ores such as cobaltite (CoAsS), carrollite (CuS,Co
2S) and pentlandite (Ni,Fe,Co)S. The chemical compositions of the complex sulfide ores vary over a wide range, and thus there still remains some ambiguity in the leaching mechanism.
The synthetic three kinds of cobalt sulfide, whose chemical compositions were CoS, CoS
2 and Co
3S
4, were used in this study. The oxidative leaching reactions of those cobalt sulfide samples in aqueous nitric acid solution are discussed from both a thermodynamic and a kinetic aspect based on the experimental results obtained on the leaching rates, the stoichiometry of the reaction and X-ray analysis of the reaction products.
From the experimental results, the following conclusion is obtained. The oxidative leaching reaction is a simultaneous one of the formation of sulfate ion and elemental sulfur, and general equations are expressed by the following formlas.
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oindentThe overall reaction of the oxidative leaching of the samples used is controlled by a chemical surface reaction step, and the rate equation is given by the following formula.
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