title: Formation of bromate in sulfate radical based oxidation: mechanistic aspects and suppression by dissolved organic matter.
abstract: Sulfate radical based oxidation is discussed being a potential alternative to hydroxyl radical based oxidation for pollutant control in water treatment. However, formation of undesired by-products, has hardly been addressed in the current literature, which is an issue in other oxidative processes such as bromate formation in ozonation of bromide containing water (US-EPA and EU drinking water standard of bromate: 10 μg L(-1)). Sulfate radicals react fast with bromide (k = 3.5 × 10(9) M(-1) s(-1)) which could also yield bromate as final product. The mechanism of bromate formation in aqueous solution in presence of sulfate radicals has been investigated in the present paper. Further experiments were performed in presence of humic acids and in surface water for investigating the relevance of bromate formation in context of pollutant control. The formation of bromate by sulfate radicals resembles the well described mechanism of the hydroxyl radical based bromate formation. In both cases hypobromous acid is a requisite intermediate. In presence of organic matter formation of bromate is effectively suppressed. That can be explained by formation of superoxide formed in the reaction of sulfate radicals plus aromatic moieties of organic matter, since superoxide reduces hypobromous acid yielding bromine atoms and bromide. Hence formation of bromate can be neglected in sulfate radical based oxidation at typical conditions of water treatment.
authors.affiliation: University Duisburg-Essen, Instrumental Analytical Chemistry, Universitätsstr. 5, D-45141 Essen, Germany; IWW Water Centre, Moritzstr. 26, D-45476 Mülheim an der Ruhr, Germany. Electronic address: holger.lutze@uni-due.de.
authors.forename: Holger V
authors.initials: HV
authors.lastname: Lutze
authors.affiliation: University Duisburg-Essen, Instrumental Analytical Chemistry, Universitätsstr. 5, D-45141 Essen, Germany.
authors.forename: Rani
authors.initials: R
authors.lastname: Bakkour
authors.affiliation: University Duisburg-Essen, Instrumental Analytical Chemistry, Universitätsstr. 5, D-45141 Essen, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Kerlin
authors.affiliation: University Duisburg-Essen, Instrumental Analytical Chemistry, Universitätsstr. 5, D-45141 Essen, Germany; Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, Mülheim an der Ruhr, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: von Sonntag
authors.affiliation: University Duisburg-Essen, Instrumental Analytical Chemistry, Universitätsstr. 5, D-45141 Essen, Germany; IWW Water Centre, Moritzstr. 26, D-45476 Mülheim an der Ruhr, Germany; University Duisburg-Essen, Centre for Water and Environmental Research (ZWU), Universitätsstr. 2, D-45141 Essen, Germany.
authors.forename: Torsten C
authors.initials: TC
authors.lastname: Schmidt
mesh_terms: D001959:Bromates / Q000737:chemistry*; D006812:Humic Substances; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification
chemical_list: D001959:Bromates; D006812:Humic Substances; D013431:Sulfates; D014874:Water Pollutants, Chemical; C069025:sulfate radical; C027664:hypobromous acid
keywords: Bromate; Ozone; Pollutant degradation; Sulfate radicals; Water treatment