title: Oxidation of trichloroethylene by the hydroxyl radicals produced from oxygenation of reduced nontronite.
abstract: Reduction by Fe(II)-bearing silicate minerals has been proposed as an important mechanism for the attenuation of chlorinated hydrocarbons (CHCs) in anoxic subsurfaces. The redox condition of subsurface often changes from anoxic to oxic due to natural processes and human activities, but little is known about the transformation of CHCs induced by Fe(II)-bearing silicate minerals under oxic conditions. This study reveals that trichloroethylene (TCE) can be efficiently oxidized during the oxygenation of reduced nontronite at pH 7.5, whereas the reduction was negligible under anoxic conditions. The maximum oxidation of TCE (initially 1 mg/L) attained 89.6% for 3 h oxygenation of 2 g/L nontronite with 50% reduction extent. TCE oxidation is attributed to the strongly oxidizing hydroxyl radicals (OH) produced by the oxygenation of Fe(II) in nontronite. Fe(II) on the edges is preferentially oxygenated for OH production, and the interior Fe(II) serves as an electron pool to regenerate the Fe(II) on the edges. Oxidation of TCE could be sustainable through chemically or biologically reducing the oxidized silicate minerals. Our findings present a new mechanism for the transformation of CHCs and other redox-active substances in the redox-fluctuation environments.
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan 430074, PR China.
authors.forename: Xixiang
authors.initials: X
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan 430074, PR China. Electronic address: yuansonghu622@cug.edu.cn.
authors.forename: Songhu
authors.initials: S
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan 430074, PR China.
authors.forename: Man
authors.initials: M
authors.lastname: Tong
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan 430074, PR China.
authors.forename: Deng
authors.initials: D
authors.lastname: Liu
mesh_terms: D017665:Hydroxyl Radical; D007501:Iron / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D010084:Oxidation-Reduction; D014241:Trichloroethylene / Q000737:chemistry*
chemical_list: D008903:Minerals; D014241:Trichloroethylene; D017665:Hydroxyl Radical; D007501:Iron
keywords: Chlorinated hydrocarbons; Hydroxyl radicals; Iron-bearing silicate minerals; Oxidative transformation; Oxygenation