The effect of additives and impurities on the cobalt electrowinning process

Despite the fact that most of the world's cobalt is produced by electrowinning, there is very little fundamental knowledge of this process. In the present study a rotating electrochemical quartz crystal microbalance (REQCM) was used to study the effect of experimental variables on the efficiency of the electrowinning process. Use of the REQCM allows the cobalt deposition reaction to be differentiated from hydrogen evolution, something which can not be achieved using conventional electrochemical techniques. It will be shown that increasing pH enhances the cobalt deposition reaction and reduces the amount of hydrogen evolved, thus resulting in a high current efficiency. It was also found that increases in temperature enhanced the cobalt deposition reaction, along with the rate of hydrogen evolution, resulting in little change to the current efficiency. The effect of other variables, such as additives and impurities have also been studied.