Metal Recovery from Aqueous Solutions

Metal recovery by reduction of metal ions present in model solutions, containing one or more heavy metals, was performed. To prepare the model solutions, sulfates and/or chlorides of Cu(II), Cd(II), Pb(II) and Zn(II) were used, at pH 3.5. Assays were run in a one or two compartments cell, at different applied potentials, using a steel plate as cathode, a platinum plate as anode and an Ag/AgCl, KClsat as reference electrode. The metal recovery yield was determined by atomic absorption spectroscopy. The phases corresponding to the metallic deposits were identified by X-ray diffraction. For the solutions containing just one metal ion, the best metal recoveries and the corresponding applied potentials, obtained in a one cell compartment, were the following: Cu2+ 99% at E = - 100 mV; Pb2+ 99% at E = - 800 mV; Cd2+ 93% at E = 900 mV; and Zn2+ 38% at E = - 1300 mV. The metal removals from the mixed solution of four heavy metals, after 4 consecutive chronoamperometries, performed in a one compartment cell, at the best applied potentials determined with the solutions containing only one metal ion, were the following: Cu2+ 99%; Pb2+ 68%; Cd2+ 92%; and Zn2+ 10%.