Electrowinning of Cobalt from a sulfate-chloride solution

Cobalt electrowinning has been proposed as a first step to treat industrial effluents containing significant Co concentrations. In this paper, the effects of various process parameters such as cobalt concentration, electrolyte pH, current density, electrolyte temperature, chloride concentration and electrode spacing on cobalt electrowinning from a sulfate-chloride electrolyte simulating an industrial effluent were studied. Experimental results showed that cobalt concentration had a significant influence on cobalt deposition from this specific system. Current efficiency decreased considerably when the cobalt concentration was reduced to less than 10 g.L^-1. The desired cobalt concentration should be greater than 40 g.L^-1. Current efficiency decreased with an increase in current density from 100 to 800 A.m^-2, while a sharp increase in the current efficiency was noted when the current density was raised from 50 to 100 A.m^-2. Generally, the current efficiency increased with an increase in electrolyte pH. In the concentration range studied, the effect of chloride ions on the current efficiency was not significant. Scanning electron microscopy (SEM) examinations of the Co deposits indicated that the above factors have an influence on the structures and surface morphology of the electrowon cobalt. In particular, X-ray diffraction (XRD) studies revealed that the chloride concentration in the solution plays a major role in the preferred orientations of the cobalt deposits.