Thermochemistry and Solubilities of Oxides in Sodium Sulfate-Vanadate Solutions

Thermodynamic calculations for the equilibrium concentrations of Na₃VO₄, NaVO₃, and V₂O₅ in a mixed sodium sulfate-vanadate solution containing 30 mol% vanadate as a function of melt basicity have been made. The dependences on melt basicity and oxygen partial pressure of the proportions of the V⁵⁺ and V^4 + states of vanadate in the sulfate-vanadate solution have been calculated. The solubilities of Al₂O₃ and Cr₂O₃ in a Na₂SO₄-30 mol% NaVO₃ melt, and the effect of vanadate content on the solubilities of CeO₂ and Y₂O₃ in fused sulfate-vanadate solutions have also been estimated. Vanadate ions greatly increase the acidic solubilities of all metal oxides compared to that in pure Na₂SO₄. This effect decreases but does not become negligible with decreasing vanadate content.