Preparation of Mn-Zn Ferrite from Spent Zinc-Carbon Batteries by Alkali Leaching, Acid Leaching and Co-Precipitation

The treatment of spent zinc-carbon batteries for the recovery of valuable metals followed by conversion to Mn-Zn ferrite has been conducted employing two-stage alkali and acid leaching and co-precipitation method. In the first stage, leaching process was carried out with 4 M NaOH, which resulted in a recovery of 63.4 % Zn and 0.1 % Mn. Electrowinning of alkali leaching solution containing 12.75 g/L Zn at a current density of 0.2 A/cm(2) produced Zn metal of 15 nm to 30 nm size and 99.9 % purity. The second stage leaching of residue with 3 M H2SO4 and 6 vol.% H2O2 at a solid/liquid ratio of 1: 10 indicated the leaching efficiency of 98.0 % Zn, 97.9 % Mn and 55.2 % Fe. The obtained leaching solution was finally adjusted to suitable mole ratios of Mn:Zn:Fe (1:1:4) by the addition of Zn and Fe sulfate salts followed by pH control to produce Mn-Zn ferrite powder. The characterization of the ferrite powder showed uniform nano-crystal line particles of about 20 rim size with spinet structure.