J. Phys. Chem. 1982, 86,4224-4228
4224
Oxidation of Aqueous Sulfur Dioxide. 1. Homogeneous Manganese( I I ) and Iron( I I ) Catalysis at Low pH A. Hum, Jr., P. K. Llm, and C. A. Eckert’ Depertment of Chemical Engineering, University of Il//nols, Urbana, Illinois 6 180 1 (Received: March 2, 198 1; I n Final F m : May IO, 1982)
The kinetics of the homogeneously catalyzed oxidation of aqueous sulfur dioxide solutions was investigated. Of the first-row transition-metal ions, only manganese and iron were found to be catalytically active. The Mn(I1)-catalyzedreaction showed no induction period, and the initial rate was described by the following rate expression: d[S(VI)]/dt = 10[6~3~”z1’z/(1+z’’z)I[Mn(II)]~ + 10~3~4g’””~~1+z’’~~[Mn(II)]0[HS03~] In contrast, the Fe(I1)-catalyzed reaction showed induction periods of up to 2 h, and the overall reaction rate following the 0.43} [Fe(II)]01.16 [HS03-] / ( [H+]l.ll [S042-] induction period was described by d[S(VI)]/dt = 10[0~7~~””2~(1+z”2)~ at low oxygen pressures (
