Formation of iodinated organic compounds by oxidation of iodide-containing waters with Manganese Dioxide
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This study shows that iodinated organic compounds can be produced when iodide-containing waters are in contact with manganese oxide birnessite (d-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 d-MnO2. In thepresence of iodide and NOM, adsordable organic iodine compounds (AOI) are formed at pH<7 because of the oxidation of iodide to iodine by d-MnO2 and the reactions of iodine with NOM. In addition, iodoacetic acid and iodoform have been identified as specific iodinated byproducts. Formation ofiodoform is not observed for high NOM/d-MnO2 ratios due to inhibition of the catalytic effect of d-MnO2 by NOM poisoning. Experiments with model compounds such as resorcinol and 3,5- heptanedione confirmed that the d-MnO2/I- 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.
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Allard, Sebastien; Gallard, H.; Fontaine, C.; Croue, J. (2010)This paper demonstrates that manganese oxides can initiate the formation of methyl iodide, a volatile compound that participates to the input of iodine into the atmosphere. The formation of methyl iodide was investigated ...
Allard, Sebastien; Von Gunten, Urs; Salhi, E.; Nicolau, R.; Gallard, H. (2009)The oxidation of iodide by synthetic birnessite (δ-MnO2) was studied in perchlorate mediain the pH range 4-8. Iodine (I2) was detected as an oxidation product that was subsequently further oxidized to iodate (IO3). The ...
Allard, Sebastien; Gallard, H. (2013)Methyl iodide is a well-known volatile halogenated organic compound that contributes to the iodine content in the troposphere, potentially resulting in damage to the ozone layer. Most methyl iodide sources derive from ...