title: Formation of iodinated organic compounds by oxidation of iodide-containing waters with manganese dioxide.
abstract: This study shows that iodinated organic compounds can be produced when iodide-containing waters are in contact with manganese oxide birnessite (delta-MnO2) in the pH range of 5-7. In the absence of natural organic matter (NOM), iodide is oxidized to iodate that is also adsorbed onto delta-MnO2. In the presence of iodide and NOM, adsordable organic iodine compounds (AOI) are formed at pH < 7 because of the oxidation of iodide to iodine by delta-MnO2 and the reactions of iodine with NOM. In addition, iodoacetic acid and iodoform have been identified as specific iodinated byproducts. Formation of iodoform is not observed for high NOM/delta-MnO2 ratios due to inhibition of the catalytic effect of delta-MnO2 by NOM poisoning. Experiments with model compounds such as resorcinol and 3,5-heptanedione confirmed that the delta-MnO2/l(-) system is very effective for the formation of iodinated organic compounds. These results suggest that birnessite acts as a catalyst through the oxidation of iodide to iodine and the polarization of the iodine molecule, which then reacts with NOM moieties. Furthermore, our results indicate that during water treatment in the presence of manganese oxide, iodinated organic compounds may be formed, which may lead to taste and odor or toxicological problems.
authors.affiliation: Laboratoire de Chimie er Microbiologie de l'Eau UMR CNRS 6008, ESIP-Université de Poitiers, 40 avenue du Recteur Pineau 86 022 POITIERS Cedex, France. herve.gallard@univ-poitiers.fr
authors.forename: Hervé
authors.initials: H
authors.lastname: Gallard
authors.forename: Sébastien
authors.initials: S
authors.lastname: Allard
authors.forename: Rudy
authors.initials: R
authors.lastname: Nicolau
authors.forename: Urs
authors.initials: U
authors.lastname: von Gunten
authors.forename: Jean Philippe
authors.initials: JP
authors.lastname: Croué
mesh_terms: D000327:Adsorption; D054879:Halogenation; D006847:Hydrocarbons, Iodinated / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007454:Iodides / Q000737:chemistry*; D017613:Iodine Compounds / Q000138:chemical synthesis*; D017895:Manganese Compounds / Q000737:chemistry*; D008956:Models, Chemical; D009930:Organic Chemicals / Q000138:chemical synthesis*; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D006847:Hydrocarbons, Iodinated; D007454:Iodides; D017613:Iodine Compounds; D017895:Manganese Compounds; D009930:Organic Chemicals; D010087:Oxides; D014867:Water; C010473:iodoform; C016552:manganese dioxide