Recovery of manganese and zinc via sequential precipitation from spent zinc-MnO_2 dry cells after fusion with potassium hydrogenosulfate

摘要

This work describes a route for processing the electroactive components of spent zinc-MnO_2 dry cells via fusion with potassium hydrogenosulfate (KHSO_4). The fused mass was dissolved in water. Lead remained in the insoluble matter. Soluble zinc and manganese were isolated by a two-step precipitation procedure. Zinc was precipitated as oxalate after addition of aqueous H_2C_2O_4 at pH around 1. Manganese was isolated as MnO(OH)_2 after adjusting pH at 11 using aqueous KOH + H_2O_2. pH control is essential for a successful separation of the elements. Both were recovered in high yields (>92 wt.%). About 75 wt.% of potassium was recovered as K_2SO_4 after treatment of the final effluent with sulfuric acid (pH 7) followed by slow evaporation.