Kinetic and Mechanistic Aspects of the Reactions of Iodide and Hypoiodous Acid with Permanganate: Oxidation and Disproportionation

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• 作者：Xiaodan Zhao ; Elisabeth Salhi ; Huiling Liu ; Jun Ma ; Urs von Gunten
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：April 19, 2016
• 年：2016
• 卷：50
• 期：8
• 页码：4358-4365
• 全文大小：556K
• 年卷期：0
• ISSN：1520-5851

文摘

Oxidation kinetics of iodide and HOI/OI^– by permanganate were studied in the pH range of 5.0–10.0. Iodide oxidation and iodate formation were faster at lower pH. The apparent second-order rate constants (k_obs) for iodide oxidation by permanganate decrease with increasing pH from 29 M^–1 s^–1 at pH 5.0 and 6.9 M^–1 s^–1 at pH 7.0 to 2.7 M^–1 s^–1 at pH 10.0. k_obs for HOI abatement are 56 M^–1 s^–1 at pH 5.0, 2.5 M^–1 s^–1 at pH 7.0, and 173 M^–1 s^–1 at pH 10.0. Iodate yields over HOI abatement decrease from 98% at pH 6.0 to 33% for pH ≥ 9.5, demonstrating that HOI disproportionation dominates HOI transformation by permanganate at pH ≥ 8.0. MnO₂ formed as a product from permanganate reduction, oxidizes HOI to iodate for pH < 8.0, and promotes HOI disproportionation for pH ≥ 8.0. The rate of HOI oxidation or disproportionation induced by MnO₂ is much lower than for permanganate. During treatment of iodide-containing waters, the potential for iodinated disinfection byproducts (I-DBPs) formation is highest at pH 7.0–8.0 due to the long lifetime of HOI. For pH < 6.0, HOI/I₂ is quickly oxidized by permanganate to iodate, whereas for pH ≥ 8.0, HOI/OI^– undergoes a fast permanganate-mediated disproportionation.