Sulfur dioxide oxidation by oxygen catalyzed by mixtures of manganese(II) and iron(III) in aqueous solutions at environmental reaction conditions

Abstract

The reaction kinetics of SO 2 oxidation by oxygen catalyzed by mixtures of Mn(II) and Fe(III) in aqueous solutions over a wide range of pH from 2.6 to 6.5 have been studied at low concentrations of S(IV) and the metal ions. The catalytic synergism between the two catalysts as a function of [Mn(II)]. [Fe(III)] has been confirmed. The following rate expression is obtained with a rate constant of k s = (3.6 ± 0.6) × 10 10/ mole s −1 − d[S(IV)] dt = k s[Mn(II)]·[Fe(III)]·[S(IV)] at a pH of 4.2 and a temperature of 23.8°C. The pH and temperature dependences of the reaction rate have also been evaluated. The reaction mechanism is briefly discussed on the basis of the rate law and the activation energy for this reaction.