Solubility of Metal Oxides under Control of Basicity by Electrolysis in Fused Na<SUB>2</SUB>SO<SUB>4</SUB>

Abstract

The dissolution behavior of NiO, Co3O4, Fe2O3, Fe3O4, SiO2, Al2O3 and Cr2O3 powders under the control of the O2− activity of fused Na2SO4 by electrochemical polarization was investigated. As a result, the increase in the quantity of electricity for the anodic reaction with increasing polarization potential for the platinum electrode caused an increase in the basicity(−log aNa2O) of the fused Na2SO4, while the increase in the quantity of electricity for cathodic reaction with decreasing polarization potential caused a decrease in basicity of the fused Na2SO4. The solubility of NiO and Co3O4 in fused Na2SO4 increased in the anodic potential region. However, their solubility did not increase in the cathodic potential region. The solubility of Fe2O3 and Fe3O4 slightly increased in the anodic potential region. The solubility of SiO2 did not increase in the anodic potential region, whereas the solubility of SiO2 increased with a decrease in the polarization potential in the cathodic potential region. The solubility of Al2O3 and Cr2O3 increased in the cathodic and anodic potential regions. The solubility of Al2O3 was larger than that of Cr2O3. We found that the resistance of acid and basic dissolution for oxides could be estimated by the electrochemical polarization method.