Catalytic oxidation of sulphite in diluted aqueous solutions

The rate of reaction of dissolved oxygen and sulphite ions in diluted aqueous solutions, which has industrial importance in abatement of air pollution by sulphur dioxide, was investigated in homogeneous and in heterogeneous systems. Cobaltous sulphate was used as a catalyst.The rate of sulphite oxidation was found to be zero order with respect to oxygen and three-halves order with respect to sulphite. The influence of the catalyst concentration was found to follow a square root dependence. The reaction rate constant increased with pH. The heterogeneous conditions resulted in a reaction rate that was about one order of magnitude lower than that under homogeneous conditions. This difference indicates an induction period of the sulphite oxidation.