Recovery Zinc and Manganese from Spent Battery Powder by Hydrometallurgical Route

Spent Zn-MnO2 battery electrode powder, containing 30.1% of Mn and 25.6% Zn was was treated via reductive leaching by H2SO4 and selective precipitation by NaOH at pH 13 for Mn(OH)2 and then pH 10 for Zn(OH)2, and the hydroxides converted respectively to MnO2 and ZnO by calcination. The effects of H2SO4 concentration, leaching time, solid-liquid ratio, reaction temperature were investigated. H2SO4 can totally dissolve Zn, but leaching rate of manganese is only 60% because of the existence of Mn (IV). Ascorbic, citric and oxalic acids were tested as the reducing agent, and ascorbic acid performs the better efficiency. The optimal reductive leaching condition were determined as 0.5 mol/L of H2SO4, 20 ml/g, 25°C, ascorbic acid dosage 10g/L for 2hours. Yielding up to 98% leaching efficiency of the two metals. The recovery rates are about 91% for Zn and 94% for Mn with high purity.