Homogeneous Catalysis of Oxalic Acid Oxidation Reaction by Ozone in Strongly Acidic Solutions

The possibility of catalysis by VO2+, Cr3+, Cr2O72–, Mn2+, MnO4–, Fe3+, Co2+, Ni2+, Cu2+, Ce3+, BrO3–, or IO3– ions of oxalic acid oxidation reaction with ozone in strongly acidic aqueous solutions at pH 0.3–1.7 has been studied. The final product of the oxidation is carbon dioxide. The kinetic regularities of the reaction have been determined from the rates of ozone consumption and carbon dioxide release. Without a catalyst, oxalic acid does not interact with ozone. It has been found that Mn2+, MnO4– and Co2+ ions are effective catalysts, while the catalytic effect of VO2+, Cr3+, Cr2O72–, Fe3+, Ni2+, Cu2+, Ce3+, BrO3–, or IO3– is weak or does not manifest itself at all. The effects of acidity and concentrations of the catalyst in solution and ozone in the gas phase on the kinetics of the process have been studied. Kinetic schemes of catalytic reactions and leading intermediates are proposed. The data obtained will help in choosing the optimal conditions for the process of oxidative mineralization of oxalic acid under the action of ozone in strongly acidic media.