Kinetics of the reactions of the SO ? 4 radical with SO ? 4 , S2O 2? 8 , H2O and Fe2+
- 1 January 1990
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions
- Vol. 86 (14) , 2557-2564
- https://doi.org/10.1039/ft9908602557
Abstract
The sulphate radical anion, SO– 4, is known to be a key intermediate in the aqueous aerobic oxidation of SO2 initiated by free radicals. The absorption spectrum of SO– 4 has been obtained following photolysis of K2S2O8 solutions at 248 nm. Kinetic spectrophotometric techniques have been employed to investigate the decay of SO– 4 in the presence of S2O2– 8 and FeII. Several rate constants have been determined at 293 K: 2k(SO– 4+ SO– 4)=(8.9 ± 0.3)× 108 dm3 mol–1 s–1(at infinite dilution), k(SO– 4+ S2O2– 8)=(6.1 ± 0.6)× 108 dm3 mol–1 s–1(at infinite dilution) and k(SO– 4+ H2O)=(500 ± 60) s–1. The reaction of SO– 4 with FeII proceeds via a rapid equilibration step followed by electron transfer, which is rate-determining SO– 4+ Fe2+ [graphic omitted] [FeII(SO4)]+ [graphic omitted] [FeIII(SO4)]+ [graphic omitted] Fe3++ SO2– 4. Values of k1,k–1 and k2 at 293 K are (3.0 ± 1.9)× 108 dm3 mol–1 s–1, (4.8 ± 3.0)× 104 s–1 and (6.5 ± 2.1)× 103 s–1 respectively. The implications of these results for current cloud and precipitation chemistry models are discussed.Keywords
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