title: Kinetic and Mechanistic Aspects of the Reactions of Iodide and Hypoiodous Acid with Permanganate: Oxidation and Disproportionation.
abstract: 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.
authors.affiliation: State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology , Harbin 150090, China.|Eawag, Swiss Federal Institute of Aquatic Science and Technology , Ueberlandstrasse 133, CH-8600 Dübendorf, Switzerland.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , Ueberlandstrasse 133, CH-8600 Dübendorf, Switzerland.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Salhi
authors.affiliation: State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology , Harbin 150090, China.
authors.forename: Huiling
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology , Harbin 150090, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , Ueberlandstrasse 133, CH-8600 Dübendorf, Switzerland.|School of Architecture, Civil and Environmental Engineering (ENAC), Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: von Gunten
mesh_terms: D004203:Disinfection; D054879:Halogenation; D006863:Hydrogen-Ion Concentration; D007452:Iodates / Q000737:chemistry; D007454:Iodides / Q000737:chemistry*; D017613:Iodine Compounds / Q000737:chemistry*; D007700:Kinetics; D017895:Manganese Compounds / Q000737:chemistry*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis; D018508:Water Purification / Q000379:methods
chemical_list: D007452:Iodates; D007454:Iodides; D017613:Iodine Compounds; D017895:Manganese Compounds; D010087:Oxides; D014874:Water Pollutants, Chemical; D014867:Water; C048856:permanganic acid; C081961:hypoiodous acid