Dissolution of alkaline batteries in reductive acidic media

In this paper, recovery of manganese and zinc from alkaline battery paste by leaching under atmospheric condition using elemental sulfur as a reductive agent and sulfuric acid was investigated. Different dissolution parameters, acid concentrations, liquid-to-solid ratios, reaction temperatures, leaching times and amounts of elemental sulfur were studied in detail. According to results, the Mn dissolution in reductive acidic media was an intermediate-controlled process with activation energy of 10.21±2.60 kJ/mol. After the leaching step, Mn and Zn were selectively precipitated from the leaching solution using sodium hydroxide. After solid/liquid separation, manganese(II, III) oxide (Mn₃O₄) was obtained by drying at 105 °C in air. Next, Mn₃O₄ was converted to manganese(IV) oxide (MnO₂) by heating at 800 °C in air. After that the solution containing Zn(OH)^2-₄ was treated with sulfuric acid to form zinc hydroxide, separated and next converted to zinc oxide by heating at 600 °C in air. The final products were characterized by XRD. The results showed that the proposed process can be effectively used for recovery of Mn and Zn from alkaline batteries.