Application of innovative processes for the valorization of alkaline spent batteries

Disposal of spent batteries constituted a serious environmental problem in terms of heavy metals content when these devices are disposed off in 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 37%, while zinc content is of 16%. The high Mn and Zn content justify the interest to recover the metals. The present experimental work involves the utilisation of technologies well know in the framework of the mineral processing and the metal dissolution by bio-hydrometallurgical processes for Mn-Zn recovery from wastes. The wastes were constituted from spent alkaline batteries. Main aim of the research was to develop a preliminary experimental work to recover selectively MnO2 and Zn from leaching and/or bioleaching solutions containing Mn and Zn by electrolysis, with the scope to apply electrochemical technologies for Zn and Mn recovery from exhaust batteries. Results have demonstrated the technical feasibility of the application of electrochemical technologies for Zn and Mn recovery from exhaust batteries, after leaching and/or integrated bio-leaching of the powders achieved by manual dismantling and subsequent grinding and milling. About 98% of MnO2 and Zinc recovery from the leaching and/or bioleaching solutions has been achieved. In all the operative conditions, a MnO2 and Zn deposit at high grade of purity has been attained; this fact was demonstrated from the results of the analyses conducted by diffractometric techniques.