Sulfite Oxidation Catalyzed by Manganese(II) Ions: Reaction Kinetics in Excess of Metal Ions

Abstract The paper gives a summary of data on the kinetics of oxygen oxidation of sulfite in the presence of manganese(II) salts at ambient temperature in a medium with pH 2–4. The results of data analysis have revealed contradictions and errors in determining the partial orders of this reaction when metal ions are present in excess to sulfite. It is shown that the kinetics of oxidation of sulfite under such conditions actually is of zero order with respect to manganese ions and one and a half order with respect to sulfite, and the reaction rate slightly depends on pH. The averaged observed reaction rate constant is 12 ± 4 L1/2 mol–1/2 s–1. The found new partial orders agree with a common free radical mechanism of this reaction. Using the partial orders redefined in this study for components, it is possible to bring into agreement various data obtained by numerous authors on the kinetics of this environmentally important reaction.