title: Natural montmorillonite induced photooxidation of As(III) in aqueous suspensions: roles and sources of hydroxyl and hydroperoxyl/superoxide radicals.
abstract: Photooxidation of arsenite(As(III)) in a suspension of natural montmorillonite under the irradiation of metal halide lamp (λ ≥ 313 nm)has been investigated. The results showed that the natural montmorillonite induced the photooxidation of As(III) by generating hydroxyl radicals (HO·) and hydroperoxyl/superoxide radicals (HO₂·/O₂⁻·). HO· which was responsible for the As(III) photooxidation. Approximately 38% of HO· was generated by the photolysis of ferric ions, and the formation of the remaining 62% was strongly dependent on the HO₂·/O₂⁻·. The presence of free ironions (Fe(2+) and Fe(3+)), made significant contributions to the photogeneration of these reactive oxygen species (ROS). The photooxidation of As(III) in natural montmorillonite suspensions was greatly influenced by the pH values. The photooxidation of As(III) by natural montmorillonite followed the Langmuir-Hinshelwood equation. In addition, the photooxidation of As(III) could be enhanced by the addition of humic acid. This work demonstrates that photooxidation may be an important environmental process for the oxidation of As(III) and may be a way to remove As(III) from acidic surface water containing iron-bearing clay minerals.
authors.affiliation: Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, 430079, PR China.
authors.forename: Yajie
authors.initials: Y
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.forename: Jinjun
authors.initials: J
authors.lastname: Li
authors.forename: Feng
authors.initials: F
authors.lastname: Wu
mesh_terms: D001151:Arsenic / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D007477:Ions; D007501:Iron / Q000737:chemistry; D008027:Light; D008670:Metals / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D055668:Photochemical Processes; D017382:Reactive Oxygen Species / Q000737:chemistry; D013481:Superoxides / Q000737:chemistry; D013535:Suspensions; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification / Q000379:methods
chemical_list: D006812:Humic Substances; D007477:Ions; D008670:Metals; D017382:Reactive Oxygen Species; D013535:Suspensions; D014874:Water Pollutants, Chemical; D013481:Superoxides; D001546:Bentonite; D017665:Hydroxyl Radical; D007501:Iron; D001151:Arsenic; D010100:Oxygen
keywords: Arsenite; Hydroperoxyl/superoxide radical; Hydroxyl radical; Iron species; Natural montmorillonite; Photooxidation