| In the electrolytic production of zinc, cobalt is removed from zinc electrolyte by cementation with zinc dust Prior to electrowinning. Although the thermodynamics for this reaction are favourable, kinetic barriers to cobalt reduction render the method impractical unless activators such as antimony or arsenic in conjunction with copper are used. There is a large body of work studying the effect of these additives, yet the mechanism by which they act is still poorly understood. Moreover, regardless of the beneficial effect of the activators, from time to time the process fails to meet the target level of 0.1 mg/L cobalt in the purified electrolyte, with negative consequences in the electrowinning operation. Even when the target conditions are met, zinc dust consumption is excessively high: satisfactory operation requires up to 300 times the stoichiometric amount of zinc dust.;In the present work the role of the antimony/copper activators was investigated in a batch cementation process using synthetic electrolyte. The objectives were to study the fundamentals of cobalt cementation in zinc sulfate electrolyte with conventional additives, to clarify the action of additives and their role in cementation, and to identify and test novel additives. (Abstract shortened by UMI.). |
