title: As(III) removal and speciation of Fe (Oxyhydr)oxides during simultaneous oxidation of As(III) and Fe(II).
abstract: Abiotic oxidation of Fe(II) is an important pathway in the formation of Fe (oxyhydr)oxides. However, how can As(III) affect the oxidation rate of Fe(II) and the speciation of Fe (oxyhydr)oxides, and what's the extent of the newly formed Fe (oxyhydr)oxides on the removal of aqueous arsenic are still poorly understood. Oxidation of Fe(II) under neutral pH conditions was therefore investigated under different molar ratios of As:Fe. Our results suggest that co-existence of aqueous As(III) significantly slows down the oxidation rate of Fe(II). Speciation of Fe (oxyhydr)oxides is dependent on pH and As:Fe ratios. At pH 6.0, formation of lepidocrocite and goethite is apparently inhibited at low As:Fe ratios, and ferric arsenate is favored at high As:Fe ratios. At pH 7.0, lepidocrocite gradually degenerates with the increasing As:Fe ratios. At pH 8.0, arsenite significantly inhibits the development of magnetite and favors a formation of lepidocrocite. XPS analysis further reveals that more than half of As(III) is oxidized to As(V) at pH 6.0 and 7.0, whereas at pH 8.0, the rapid oxidation of Fe(II) as well as the rapid formation of Fe (oxyhydr)oxides facilitate a rapid removal of dissolved As(III) before its further oxidation to As(V).
authors.affiliation: School of Environmental Science and Engineering, Tianjin University, Tianjin, PR China; China Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, Tianjin, PR China. Electronic address: xuhan@tju.edu.cn.
authors.forename: Xu
authors.initials: X
authors.lastname: Han
authors.affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China.
authors.forename: Jia
authors.initials: J
authors.lastname: Song
authors.affiliation: Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China.
authors.forename: Yi-Liang
authors.initials: YL
authors.lastname: Li
authors.affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China.
authors.forename: Shao-Yi
authors.initials: SY
authors.lastname: Jia
authors.affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China.
authors.forename: Wen-Hui
authors.initials: WH
authors.lastname: Wang
authors.affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China.
authors.forename: Fu-Gen
authors.initials: FG
authors.lastname: Huang
authors.affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China.
authors.forename: Song-Hai
authors.initials: SH
authors.lastname: Wu
mesh_terms: D001151:Arsenic / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D058085:Iron Compounds; D010087:Oxides; D014874:Water Pollutants, Chemical; D001151:Arsenic
keywords: As(III); Fe (oxyhydr)oxides; Immobilization; Oxidation; Speciation