title: Abiotic oxidation of Mn(II) induced oxidation and mobilization of As(III) in the presence of magnetite and hematite.
abstract: Manganese (hydr)oxides are powerful oxidants mediating the transformation of As(III) to As(V) under natural conditions, however, the presence of Mn(II) on the oxidation of As(III) in the pH range of 7.0-9.0 has not been reported so far. In this study, abiotic oxidation of Mn(II) to amorphous Mn(III, IV) (hydr)oxides (MnOx) on magnetite and hematite was confirmed, and the impact of newly formed MnOx on the fate of As(III) was investigated. With the addition of Mn(II) into As(III)-preloaded systems, the dissolved and the adsorbed As(III) was oxidized to As(V) at high pH, and Mn(II) mobilized the adsorbed As(III) and As(V) in hematite system. High production of dissolved As(V) and significant mobilization of As(III) were even more significant in hematite suspension (total As was 18.96 mgL(-1) after 60 h at pH 8.62) with simultaneous addition of Mn(II) and As(III), while magnetite showed a higher capacity for the retention of As(III) and As(V). It could therefore be deduced that the newly formed MnOx on iron oxides could oxidize the dissolved and the adsorbed As(III) to As(V). In addition, the MnOx formed at high pH would take up the sorption sites previously occupied by the adsorbed As(III), and then mobilized a fraction of the adsorbed As(III) into solution. The present study reveals that MnOx formed via abiotic oxidation on iron oxides plays an important role in the oxidation and mobilization of both dissolved and adsorbed As(III) in aquatic environment.
authors.affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China.
authors.forename: Hai-Tao
authors.initials: HT
authors.lastname: Ren
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: Song-Hai
authors.initials: SH
authors.lastname: Wu
authors.affiliation: School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin, PR China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Science, Beijing, PR China.
authors.forename: Chao
authors.initials: C
authors.lastname: Hua
authors.affiliation: State Key Laboratory of Hollow Fiber Membrane Materials and Processes, Tianjin Polytechnic University, Tianjin, PR China; School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin, PR China. Electronic address: hanxu_mail@yahoo.com.cn.
authors.forename: Xu
authors.initials: X
authors.lastname: Han
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; C000499:ferric oxide; D008345:Manganese; D001151:Arsenic; D052203:Ferrosoferric Oxide