Potential-Selective Deposition of Copper from Chloride Solutions Containing Iron

Abstract

The hydrometallurgy of copper may involve leaching of the metal from itsore with an aqueous solution containing cupric and ferric chloride. The subsequentdeposition of copper from such a process stream is modeled here in anidealized electrochemical cell with a rotating-disk electrode. The potential distributionand concentration profiles within the diffusion layer are predictedfor given potential differences between the electrode and the solution. Thecuprous ion, which is formed by the reduction of the complexed cupric ion atthe electrode, is stabilized in the chloride solution and can react either at theelectrode or with ferric species within the diffusion layer. The assumption isthat this fast and irreversible homogeneous reaction generates a reaction plane,whose position is shown in the concentration and potential profiles. In addition,the position of the reaction plane is plotted as a function of the potentialdifference between the electrode and the adjacent solution. Predicted current-potentialand current efficiency-potential curves are also reported. Finally, theiron contamination of the deposited copper is estimated to be less than 10–5atom percent for some cases. Also, because some of the partial current densitiesare below their limiting values, the analysis is strictly valid only atthe center of the disk.