ELECTROCHEMICAL BEHAVIOUR OF METALLIC TITANIUM IN MnO2 ELECTROSYNTHESIS FROM SYNTHETIC SOLUTIONS SIMULATING SPENT BATTERY LEACH LIQUORS

Electrochemical power cells with MnO2 cathode represent an important waste group. After discharge, trough leaching and anodic electrosynthesis, this oxide can be recovered. Pure titanium represents an interesting substrate for this process both economically and environmentally. In H2SO4 electrolytes titanium exhibits active corrosion, active-passive transition and passive voltage regions. At higher polarization, dielectric breakdown of the passive layer occurs, resulting in oxygen evolution. In the presence of Mn2+ ions the titanium active corrosion is inhibited and at higher potentials oxidation of the manganese ions occurs. Anodic surface modification by potentiostatic sweeping is proposed in presence of Mn2+ ions. During MnO2 electrosynthesis tests on the modified electrode, no passivation was observed, which is not in agreement with the literature. Our measurements prove the feasibility of titanium usage as an anode in the electrolytic recovery route of MnO2 from spent household Zn-Mn battery leach liquors.