Estudo estatístico do efeito de variáveis influentes na eletrorrecuperação de cobalto

Abstract

Pure metallic cobalt is mainly obtained by electrowinning process, which most important parameters are current efficiency, specific energy consumption and product quality. In this work cobalt electrowinning by cyclic voltammetry and batch electrolysis tests in sulfate solutions was studied. The effect of pH, temperature, current density and cobalt concentration effects on current efficiency and specific energy consumption were evaluated statiscally. Voltammetric tests at 25 °C indicated that the increase of cobalt concentration elevated current density, while at pH 4 higher current efficiencies were achieved. In 24-h electrolysis tests, the highest current efficiency (78,76 %) and the lowest specific energy consumption (3,04 kWh.kg-1 ) were obtained with initial pH 4, temperature of 70 °C, current density of 100 A.m-2 and cobalt concentration of 60 g.L-1 . Macroscopically, the best morphology was obtained with initial pH 2, at 70 °C, with a current density of 400 A.m-2 and cobalt concentration of 60 g.L-1 . Through the statistical study, all variables individual effects were found to be significant. Temperature was the most significant, while initial pH the least. The main deposit impurities were carbon and sulfur, probably from the sodium lauryl sulfate, besides Pb, Ag and Sb from the anode.