title: Reduction of As(V) to As(III) by commercial ZVI or As(0) with acid-treated ZVI.
abstract: Zero-valent iron (ZVI) consists of an elemental iron core surrounded by a shell of corrosion products, especially magnetite. ZVI is used for in situ removal or immobilization of a variety of contaminants but the mechanisms for removal of arsenic remain controversial and the mobility of arsenic after reaction with ZVI is uncertain. These issues were addressed by separately studying reactions of As(V) with magnetite, commercial ZVI, and acid-treated ZVI. Strictly anoxic conditions were used. Adsorption of As(V) on magnetite was fast with pH dependence similar to previous reports using oxic conditions. As(V) was not reduced by magnetite and Fe(II) although the reaction is thermodynamically spontaneous. As(V) reactions with ZVI were also fast and no lag phase was observed which was contrary to previous reports. Commercial ZVI reduced As(V) to As(III) only when As(V) was adsorbed, i.e., for pH<7. As(III) was not released to solution. Acid-treated ZVI reduced As(V) to As(0), shown using wet chemical analyses and XANES/EXAFS. Comparisons were drawn between reactivity of acid-treated ZVI and nano-ZVI; if true then acid-treated ZVI could provide similar reactive benefits at lower cost.
authors: Department of Civil and Environmental Engineering, Penn State University, UP, PA, USA.
authors: Fenglong
authors: F
authors: Sun
authors: Kwadwo A
authors: KA
authors: Osseo-Asare
authors: Yongsheng
authors: Y
authors: Chen
authors: Brian A
authors: BA
authors: Dempsey
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry / Q000302:isolation & purification*; D001152:Arsenicals / Q000737:chemistry / Q000302:isolation & purification*; D003343:Corrosion; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D006851:Hydrochloric Acid / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D056928:X-Ray Absorption Spectroscopy; D014961:X-Ray Diffraction
chemical_list: D001152:Arsenicals; D014874:Water Pollutants, Chemical; D007501:Iron; D001151:Arsenic; D006851:Hydrochloric Acid; D052203:Ferrosoferric Oxide