The effect of additives and impurities on the cobalt electrowinning process.

A rotating electrochemical quartz crystal microbalance was used to study the effect of experimental variables on the efficiency of the electrowinning process. The technique provided a useful means of differentiating between the cobalt deposition and hydrogen evolution reactions, which cannot be achieved using conventional methods. The major effects on the deposition reaction were found to be pH, temperature and Co concentration, whilst for H2 evolution temperature and pH were important. It was shown that current efficiency is highest at high pH values, due to a combination of inhibited H2 evolution and enhanced Co deposition. Of additives and impurities, Zn did affect Co deposition but only when present at more than 100 ppm.
A rotating electrochemical quartz crystal microbalance was used to study the effect of experimental variables on the efficiency of the electrowinning process. The technique provided a useful means of differentiating between the cobalt deposition and hydrogen evolution reactions, which cannot be achieved using conventional methods. The major effects on the deposition reaction were found to be pH, temperature and Co concentration, whilst for H2 evolution temperature and pH were important. It was shown that current efficiency is highest at high pH values, due to a combination of inhibited H2 evolution and enhanced Co deposition. Of additives and impurities, Zn did affect Co deposition but only when present at more than 100 ppm.