Reductive acid leaching of spent zinc-carbon batteries and oxidative precipitation of Mn-Zn ferrite nanoparticles

The non-magnetic 8-mesh undersize material obtained by crushing, magnetic separation and sieving of spent zinc-carbon batteries assayed 23.9% Mn, 14.9% Zn, and 4% Fe. Reductive acid leaching of this material at a solid/liquid ratio of 1: 10, and 60 degrees C with 2 mol dm(-3) H2SO4 and 0.39 mol H2O2 extracted 97.9% Mn, 98.0% Zn and 55.2% Fe after 60 min. The leach liquor composition was then adjusted to a Mn:Zn:Fe molar ratio of 1: 1:4 suitable for producing MnZnFe4O8 ferrite powder by adding Mn(II), Zn(II) and Fe(II) sulfates. The effect of pH in the range pH 5-12 on the precipitation of Mn-Zn ferrite powder was investigated over 60 min using O-2 gas flow rate of 1.3 dm(3) min(-1) at 80 degrees C. The precipitated Mn-Zn ferrite at pH 12 were 20 nm particles that had a spinel structure. The saturation magnetizations of Mn-Zn ferrite powder (Mn1-xZnxFe2O4) were determined to be 39-91 emu/g with various zinc contents (x=0.2-0.8). (C) 2008 Elsevier B.V. All rights reserved.