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

摘要

The non-magnetic 8-mesh undersize material obtained by crushing, magnetic separation and sieving of spent zinc-carbon batteries assayed 23.9 percent Mn, 14.9 percent Zn, and 4 percent Fe. Reductive acid leaching of this material at a solid/liquid ratio of 1:10, and 60 deg C with 2 mol dm~(-3) H_2SO_4 and 0.39 mol H_2O_2 extracted 97.9 percent Mn, 98.0 percent Zn and 55.2 percent 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 MnZnFe_4O_8 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 deg 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 (Mn_(1-x)Zn_xFe_2O_4) were determined to be 39-91 emu/g with various zinc contents (x=0.2-0.8).