Electrohydrometallurgical recovery of Zinc and Manganese from spent batteries.

The present experimental work involves the application of electrohydrometallurgical processes for Mn-Zn recovery from wastes originated by spent batteries. Disposal of spent batteries constitutes a serious environmental problem in terms of heavy metals content when these devices are disposed off under inadequate way. Alkaline and zinc-carbon batteries represent about 80% of the market. In particular, alkaline batteries have an average content of manganese dioxide (MnO2) of 35%, while zinc content is of 14%. The high Mn and Zn content justify the interest to recover the metals. Main processes applied are the pyrometallurgical processes, that involve high energetic consumption and pollution problems; and hydrometallurgical processes, chipper and at low energetic cost. In this work, hydrometallurgical processes have been applied, starting from spent alkaline batteries. Zn and Mn recovery from the aqueous solutions has been carried out electrochemically. The composition of the alkaline batteries utilised was 14 % Zn and 27 % Mn, as MnO2. Main aim of the research was the development of an experimental work to recover selectively MnO2 and Zn from leaching solution containing Mn and Zn, both at concentration of 10 g dm-3, by electrolysis, with the scope to apply electrochemical technologies for Zn and Mn recovery from exhaust batteries. The results have demonstrated the technical feasibility of the application of the mentioned technologies; in fact, high recovery of manganese and zinc dissolved in solution were achieved (96% MnO2 and 98% Zn).