Conversion kinetics of cerium oxide into sodium cerium sulfate in Na₂SO₄-H₂SO₄-H₂O solutions

Abstract

The conversion of cerium oxide (CeO₂) into sodium cerium sulfate (NaCe(SO₄)₂·H₂O) in Na₂SO₄–H₂SO₄–H₂O solutions was studied at elevated temperatures using a batch-type glass reactor under atmospheric pressure. Sodium sulfate (Na₂SO₄) concentration, sulfuric acid (H₂SO₄) concentration and reaction temperature were chosen as dependent variables, and the effects of these three variables on the conversion of cerium oxide into sodium cerium sulfate in Na₂SO₄–H₂SO₄–H₂O solutions were investigated. The conversion includes two chemical reactions: cerium oxide dissolution and sodium cerium sulfate synthesis. The experimental data showed that increases of sodium sulfate concentration and sulfuric acid concentration decreased the conversion rate, whereas the conversion rate increased with increasing reaction temperature. The conversion kinetics of cerium oxide into sodium cerium sulfate for these three variables was analyzed and the fitted equation to the experimental data was determined. The variations of rate constant in dissolution and synthesis with temperature obeyed the Arrhenius equation with activation energies of 120 and 200 kJ/mol, respectively. In addition, the rate constant of cerium oxide dissolution was a function of the sodium sulfate concentration and sulfuric acid concentration at N−⁰.³ and C⁶.⁵, respectively, and for sodium cerium oxide synthesis at N−⁰.² and C−⁴.³.