Anodic Formation of Cobalt Oxide during Electrowinning of Cobalt in a Chloride Electrolyte

摘要

During electrowinning of cobalt, in addition to anodic chlorine and oxygen evolution, deposition of a black substance was observed on the DSA electrode. The black substance was investigated by means of XRD, and found to be trivalent cobalt oxy-hydroxide (α-CoOOH). The deposition of cobalt oxy-hydroxide and possible ways to prevent its formation were studied. Experiments showed that deposited cobalt oxy-hydroxide could be dissolved cathodically. The amount of charge for cathodic dissolution was used to estimate the deposited amount of cobalt oxy-hydroxide. In agreement with thermodynamic predictions, the deposition of cobalt oxy-hydroxide decreased with decreasing pH. The results also showed that deposition of CoOOH could be suppressed by addition of H_2O_2.