title: Photochemical oxidation of chloride ion by ozone in acid aqueous solution.
abstract: The experimental investigation of chloride ion oxidation under the action of ozone and ultraviolet radiation with wavelength 254 nm in the bulk of acid aqueous solution at pH 0-2 has been performed. Processes of chloride oxidation in these conditions are the same as the chemical reactions in the system O3 - OH - Cl(-)(aq). Despite its importance in the environment and for ozone-based water treatment, this reaction system has not been previously investigated in the bulk solution. The end products are chlorate ion ClO3(-) and molecular chlorine Cl2. The ions of trivalent iron have been shown to be catalysts of Cl(-) oxidation. The dependencies of the products formation rates on the concentrations of O3 and H(+) have been studied. The chemical mechanism of Cl(-) oxidation and Cl2 emission and ClO3(-) formation has been proposed. According to the mechanism, the dominant primary process of chloride oxidation represents the complex interaction with hydroxyl radical OH with the formation of Cl2(-) anion-radical intermediate. OH radical is generated on ozone photolysis in aqueous solution. The key subsequent processes are the reactions Cl2(-) + O3 → ClO + O2 + Cl(-) and ClO + H2O2 → HOCl + HO2. Until the present time, they have not been taken into consideration on mechanistic description and modelling of Cl(-) oxidation. The final products are formed via the reactions 2ClO → Cl2O2, Cl2O2 + H2O → 2H(+) + Cl(-) + ClO3(-) and HOCl + H(+) + Cl(-) ⇄ H2O + Cl2. Some portion of chloride is oxidized directly by O3 molecule with the formation of molecular chlorine in the end.
authors.affiliation: Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskiye Gory 1, building 3, 119991, Moscow, Russia. levanov@kge.msu.ru.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Levanov
authors.affiliation: A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prospect 29, 119991, Moscow, Russia.
authors.forename: Oksana Ya
authors.initials: OY
authors.lastname: Isaykina
authors.affiliation: Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskiye Gory 1, building 3, 119991, Moscow, Russia.
authors.forename: Nazrin K
authors.initials: NK
authors.lastname: Amirova
authors.affiliation: Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskiye Gory 1, building 3, 119991, Moscow, Russia.
authors.forename: Ewald E
authors.initials: EE
authors.lastname: Antipenko
authors.affiliation: Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskiye Gory 1, building 3, 119991, Moscow, Russia.|A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky prospect 29, 119991, Moscow, Russia.
authors.forename: Valerii V
authors.initials: VV
authors.lastname: Lunin
mesh_terms: D002384:Catalysis; D002712:Chlorides / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*; D010782:Photolysis; D012996:Solutions; D014466:Ultraviolet Rays; D018508:Water Purification / Q000379:methods*
chemical_list: D002712:Chlorides; D012996:Solutions; D017665:Hydroxyl Radical; D010126:Ozone; D006861:Hydrogen Peroxide
keywords: Chemical kinetics; Chlorate; Chloride; Mechanism of chemical reaction; Molecular chlorine; Ozone