Effect of manganese(II) and boric acid on the electrowinning of cobalt from acidic sulfate solutions

Abstract

The effect of Mn(II) and boric acid on the electrowinning of cobalt from acidic sulfate electrolyte was investigated by electrochemical methods. The results indicated that the presence of Mn(II) or boric acid alone increased the current efficiency by 2 to 3 pct but that their combination had no additional effect. The preferred crystal orientation pattern changed from (110) (100) (101) to (100) (110) (101) in the presence of 0.1 to 10 g dm−3 Mn(II); an additional change, to (110) as the only preferred orientation, occurred at a very high concentration of Mn(II) (100 g dm−3). Boric acid had no effect on the crystal pattern of the cobalt deposits. In general, the presence of boric acid increased the brightness of all the deposits, irrespective of the presence of Mn(II) in the electrolyte, and had no effect on the deposit morphology. The cathode polarization behavior of the cobalt electrocrystallization was affected only marginally by the presence of Mn(II) in the electrolyte, but the presence of boric acid with or without Mn(II) had a significant effect. Boric acid was found to suppress the rate of electroreduction of cobalt on stainless steel by an order of magnitude, irrespective of the presence of Mn(II).