Potentiostatic control of a rotating cylinder electrode reactor enabled copper retrieval from a solution containing multiple metallic ions. The treated solution (pH 4 sulphuric acid) was obtained from a mine tailing. A batch process was used in laboratory experiments to simulate possible industrial treatments. Oxygen reduction was the major parasitic reaction at the cylinder cathode since the reactor was not separated, allowing the gas produced at the anode to dissolve in the electrolyte. A higher current therefore generated an increase in oxygen production and an increase in dissolved oxygen concentration. Since the oxygen reduction proceeded under diffusion control, the oxygen reduction current efficiency also increased. Reduction of ferric ions to a ferrous state and arsenic deposition were other less important side reactions decreasing current efficiency. Polarization experiments were conducted using a rotating disk electrode to study the reactions encountered at the cylinder cathode.