Catalyzed oxidation of sulfur dioxide in solution: The iron-manganese synergism

Abstract

Abstract At concentrations of sulfur(IV) of 10 −5 molesl −1 and lower, there is a synergism between iron(III) and manganese(II) catalysis of the autoxidation. This synergism has a different rate law from the synergism seen at higher concentrations of sulfur. At pH 3.0, we obtained the rate law: −d[S(IV)]/[S(IV)]d t = k 1 [Fe(III)]+ k 3 [Fe(III)][Mn(II)], where k 1 =2600 M −1 s −1 , k 3 =750 M −1 s −1 , and k 3 =1.0 × 10 10 M −2 s −1 . A similar relation is found at pH 5.0. This is in substantial agreement with the work of Ibusuki and Takeuchi ( Atmospheric Environment 21 , 1555 (1987)). We estimate that this effect will raise the catalyzed oxidation rate of sulfur in clouds several times over the iron rate taken separately, for typical atmospheric concentrations of iron, sulfur, and manganese.