Leaching of MnO 2 with mixed non‐aqueous solvent dimethyl sulfoxide–sulfur dioxide

Electrolytic manganese dioxide is dissolved in the mixed non‐aqueous solvent dimethyl sulfoxide–sulfur dioxide (DMSO–SO 2 ) to form manganese disulfate as a final product. Sulfur dioxide does not change the oxidation state of the metal cations in DMSO–SO 2 solvent. However, oxidation of sulfur(IV) to sulfur(VI) is possible. The complete MnO 2 dissolution occurs in 50 min at a stirring speed of 650 rpm, pH 1, 0.2% solids concentration, 35 × 44 mesh particle size, and 36°C. IR and FTIR evidence has been presented in favor of the formation of SO   3 2− , S 2 O   5 2− , (CH 3 ) 2 S + as intermediate species for the proposed mechanism. In the mixed non‐aqueous solvent system the kinetics of leaching is controlled by a mass transport process. The equation 1–⅔α–(1–α) 2/3 = kt fits the experimental data very well. This is further supported by scanning electron micrographs, which show a product layer formation on the surface of the MnO 2 particle, and by the dependence of k on 1/r   0 2 .