1987 Volume 22 Issue 6 Pages 389-396
The oxidation of S (N) ion in rain water containing Fe3+ and Mn2+ was investigated in test solutions, and rain water samples. The rate of oxidation reaction of S (IV) ion both in test solutions and rain water was of the first order. The rate of oxidation of S (N) ion was 0.12-1.6×10-6s-1 without the catalyst, while it became larger, 1.7-16×10-4 s-1, by the order of 2 to 4 by the existence of Fe3+ and Mn2+. Therefore, Fe3+ and Mn2+ strongly contribute as catalysts for the oxidation of S (IV), and the positive correlationship was found between the concentrations of Fe3+ and/or Mn2+ and the oxidation rate. The increase of the oxidation rate at lower pH of solution was also found at pH4 to 6. This could be due to the change of chemical form of each catalytic ion by the pH of solution. As the results of these experiments, catalytic oxidation reaction of S (IV) ion was expressed as a function of concentrations of Fe3+ and Mn2+ and pH of solution.
The oxidation rate of S (N) ion in 11 rain water samples collected at Hiyoshi, Yokohama, May through November, 1985 was 3.4-92×10-5 s-1. These measured values were almost agreed with the values, 3.5-140×10-5 s-1, calculated by the experimental equation.
