Hydrometallurgical recovery of cadmium and nickel from spent Ni–Cd batteries

The paper is concerned with a simple hydrometallurgical method for the selective recovery of cadmium and nickel from spent Ni–Cd batteries. The following consecutive stages are proposed: dismantling, leaching in sulphuric acid, cadmium electrowinning, Fe3+ removal and nickel electrowinning. The influence of H2O2 addition to the leaching solution on the efficiency of the dissolution process was investigated. The electrowinning of cadmium was carried out at various pH and current densities (100 and 400 A/m2). Fe3+ ions were removed from the bath by hydroxide precipitation. Nickel electrolyses were conducted at pH of 9 and two current densities (100 and 400 A/m2). Concentrations of Ni2+, Cd2+ and Fe3+ ions as well as cathode potentials and electrolysis voltages were monitored during the electrowinning. Efficiencies of leaching and electrolysis were calculated. Final products were metals of high purity (98–100% Cd, 98–99% Ni). Maximum total recoveries of cadmium and nickel from spent Ni–Cd batteries were 92% and 67%, respectively. A preliminary assessment of an economic viability of the proposed treatment was undertaken.