Statistical study of the influence of some variables on cobalt electrowinning

A major concern in cobalt electrowinning is the generation of H2 along with cobalt deposition on the cathode, which results in current efficiency drop, specific energy consumption increase, as well as poor deposit quality. In this paper, the influence of initial pH, temperature, current density, and Co2+ ions concentration on current efficiency and specific energy consumption for cobalt electrowinning in a batch cell for 24-h electrolysis was investigated through a two-level factorial design. Preliminary analysis from cyclic voltammograms and current-time curves indicated a current efficiency of 86.2%, with 60 g/L of Co2+ at pH 4.0. The statistical study indicated that temperature presented the greatest significant contribution for the response variables. The best result was achieved with initial pH 4.0, 70°C 100 A/m2 and 60 g/L of Co2+, leading to a current efficiency of 78.8% and a specific energy consumption of 2.3 kWh/kg. As the pH drops considerably during the tests, its influence demands further studies.