Effects of copper ion on cobalt re-dissolution from zinc sulphate solution

The factors affecting the cobalt re-dissolution from zinc sulphate solution in zinc hydrometallurgy,including the reaction time, oxidation,particle size of zinc powder,and Cu2+ concentration,are summarized in the article.It was shown that the re-dissolution did not occur at all when very large-sized zinc powder was employed,but it occurred markedly with small-sized zinc powder.Meanwhile,the re-dissolution was aggravated with copper ions added,whereas no re-dissolution occurred without copper ion addition.The role the copper ion played in the cobalt re-dissolution is however unclear yet.The reaction of cobalt re-dissolution was assumed to be Zn+Co2+→Zn2++Co(s),Co(s)+2OH-→Co(OH)2+2e.