title: Redox stability of As(III) on schwertmannite surfaces.
abstract: As(III)-enriched mine discharge often drains through Fe(III)-mineral abundant land covers which makes the understanding of its fate and redox behaviour extremely important. We therefore conducted batch kinetic and equilibrium studies at pH 3.0±0.05 in anoxic media coupled with spectroscopic and microscopic examinations at variable conditions to understand possible As(III) binding mechanisms and the redox stability of As(III) on schwertmannite, a prominent ferric mineral in acid mine drainage environments. Schwertmannite acted as an efficient scavenger for As(III) compared to goethite at identical sorbent:solute ratios. As K-edge X-ray absorption near-edge structure (XANES) demonstrated partial oxidation of sorbed As(III) to As(V) on both the minerals depending on the Fe(III)/As(III) ratios (goethite acted as a better oxidant than schwertmannite). Sorbed As(III) and As(V) coordinated in a bidentate binuclear binding mechanism with As(III)/As(V)-O and As(III)/As(V)-Fe interatomic distances as 1.78/1.69 and 3.37/3.31Å, respectively. Scanning (SEM-EDX) and transmission (TEM) electron microscopic, and IR spectroscopic measurements revealed the formation of As-containing surface coatings by sorbed As on schwertmannite.
authors.affiliation: Department of Hydrology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany; Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Bhopal, Madhya Pradesh 462023, India. Electronic address: susanta@iiserb.ac.in.
authors.forename: Susanta
authors.initials: S
authors.lastname: Paikaray
authors.affiliation: Department of Geological Sciences, University of Saskatchewan, SK S7N 5E2, Canada.
authors.forename: Joseph
authors.initials: J
authors.lastname: Essilfie-Dughan
authors.affiliation: Institute for Synchrotron Radiation, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Göttlicher
authors.affiliation: Institute of Geosciences, Friedrich Schiller University of Jena, Carl-Zeiss-Promenade 10, 07745 Jena, Germany.
authors.forename: Kilian
authors.initials: K
authors.lastname: Pollok
authors.affiliation: Department of Hydrology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Peiffer
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry*; D007220:Industrial Waste; D058085:Iron Compounds / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008903:Minerals / Q000737:chemistry; D008906:Mining; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D007220:Industrial Waste; D058085:Iron Compounds; D008903:Minerals; D014874:Water Pollutants, Chemical; C511969:schwertmannite; C094886:goethite; D001151:Arsenic
keywords: As immobilization; As redox stability; Iron oxyhydroxy sulphate; Mine drainage; Surface precipitation