title: Sulfate radical-based water treatment in presence of chloride: formation of chlorate, inter-conversion of sulfate radicals into hydroxyl radicals and influence of bicarbonate.
abstract: Sulfate radical (SO4(-)) based oxidation is discussed as a potential water treatment option and is already used in ground water remediation. However, the complex SO4(-) chemistry in various matrices is poorly understood. In that regard, the fast reaction of SO4(-) with Cl(-) is of high importance since Cl(-) belongs to the main constituents in aqueous environments. This reaction yields chlorine atoms (Cl) as primary products. Cl initiate a cascade of subsequent reactions with a pH dependent product pattern. At low pH (<5) formation of chlorine derived oxidation products such as chlorate (ClO3(-)) is favoured. This is undesired because ClO3(-) may reveal adverse effects on the environment and human health. At pH > 5 Cl mainly react with water yielding hydroxyl radicals. Thus, at moderate Cl(-) concentrations (mM range) the SO4(-)-based process may be converted into a conventional (hydroxyl radical -based) advanced oxidation process. The conversion of SO4(-) into OH, however, is interrupted in presence of bicarbonate by scavenging of Cl.
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. Electronic address: n.kerlin@Krohne.com.
authors.forename: Nils
authors.initials: N
authors.lastname: Kerlin
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. 5, D-45141 Essen, Germany. Electronic address: torsten.schmidt@uni-due.de.
authors.forename: Torsten C
authors.initials: TC
authors.lastname: Schmidt
mesh_terms: D001639:Bicarbonates / Q000737:chemistry*; D002704:Chlorates / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry*; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry; D018508:Water Purification
chemical_list: D001639:Bicarbonates; D002704:Chlorates; D002712:Chlorides; D013431:Sulfates; C069025:sulfate radical; D014867:Water; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide
keywords: Advanced oxidation; Chlorate; Chloride; Hydroxyl radical; Ozone; Sulfate radical; UV/persulfate