Electrowinning of cobalt at high cathodic current densities (400-1000 A M-2)

Abstract

Current densities from 40O Am to 1000 Am were used to investigate the electrowinning of cobalt from sulfate solutiaiie. The cell used was a cylindrical beaker of 1000 ml capacity. Two lead anodes and one stainless steel cathode were used as - electrodes. The cathode was prepared electrolytically with a solution of orthophospheric acid, rinsed with distilled water and acetone, then dried in a dessicator before IISG.A magnetic stirrer was used while heating up and stirring the solution. The cell voltage, the current efficiency for cobalt deposition, the deposit purity, the electrical energy consumption, and the deposit appearance were measured as a function of Current density, additive (gelatin) concentration, temperature, acid concentration, cobalt ions content and speed of a,gitation. Reasonable results were observed by a careful control of these parameters. It was found that low operating current densities were afficient in the sense that the current efficiency 8.nd the deposit purity were high while the applied cell voltage and the electrical energy consumption were low. The current densities suggested were between 4OO - 70O Am~^,Other goad operating conditions we found are near neutral solutions of pE5-5,4, vigorous agitation to avoid precipitation of cobalt hydroxide, addition of a chemical agent at a concentration of 4 mg/l gelatin as optimum quantity and high temperature of 85°Cc