|
|||||
|
|
Arsenite sequestration at the surface of nano-Fe(OH)2, ferrous-carbonate hydroxide, and green-rust after bioreduction of arsenic-sorbed lepidocrocite by Shewanella putrefaciens |
|
| Authors: | Georges Ona-Nguema Guillaume Morin Yuheng Wang Farid Juillot Giuliana Aquilanti Christian Ruby François Guyot Gordon E Brown Jr |
| Institution: | a Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), Université Paris 6, Université Paris 7, IPGP, CNRS, 140, rue de Lourmel, 75015 Paris, France b Department of Geological and Environmental Sciences, Surface & Aqueous Geochemistry Group, Stanford University, Stanford, CA 94305-2115, USA c XAFS Beamline, ELETTRA, AREA Science Park, 34012 Basovizza, Trieste, Italy d BM29 European Synchrotron Radiation Facility (ESRF) BP220, 38043 Grenoble Cedex, France e Laboratoire de Chimie Physique et Microbiologie pour l’Environnement (LCPME), UMR 7564 CNRS, Université Nancy 1, 405, rue de Vandœuvre, 54600 Villers-lès-Nancy, France f Stanford Synchrotron Radiation Laboratory, SLAC, MS 69, 2575 Sand Hill Road, Menlo Park, CA 94025, USA |
| Abstract: | X-ray Absorption Fine Structure (XAFS) spectroscopy was used in combination with high resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), X-ray energy dispersive spectroscopy (XEDS), X-ray powder diffraction, and Mössbauer spectroscopy to obtain detailed information on arsenic and iron speciation in the products of anaerobic reduction of pure and As(V)- or As(III)-adsorbed lepidocrocite (γ-FeOOH) by Shewanella putrefaciens ATCC 12099. We found that this strain of S. putrefaciens is capable of using Fe(III) in lepidocrocite and As(V) in solution or adsorbed on lepidocrocite surfaces as electron acceptors. Bioreduction of lepidocrocite in the absence of arsenic resulted in the formation of hydroxycarbonate green rust 1 FeII4FeIII2(OH)12CO3: GR1(CO3)], which completely converted into ferrous-carbonate hydroxide (FeII2(OH)2CO3: FCH) over nine months. This study thus provides the first evidence of bacterial reduction of stoichiometric GR1(CO3) into FCH. Bioreduction of As(III)-adsorbed lepidocrocite also led to the formation of GR1(CO3) prior to formation of FCH, but the presence of As(III) slows down this transformation, leading to the co-occurrence of both phases after 22-month of aging. At the end of this experiment, As(III) was found to be adsorbed on the surfaces of GR1(CO3) and FCH. After five months, bioreduction of As(V)-bearing lepidocrocite led directly to the formation of FCH in association with nanometer-sized particles of a minor As-rich Fe(OH)2 phase, with no evidence for green rust formation. In this five-month experiment, As(V) was fully converted to As(III), which was dominantly sorbed at the surface of the Fe(OH)2 nanoparticles as oligomers binding to the edges of Fe(OH)6 octahedra at the edges of the octahedral layers of Fe(OH)2. These multinuclear As(III) surface complexes are characterized by As-As pairs at a distance of 3.32 ± 0.02 Å and by As-Fe pairs at a distance of 3.50 ± 0.02 Å and represent a new type of As(III) surface complex. Chemical analyses show that the majority of As(III) produced in the experiments with As present is associated with iron-bearing hydroxycarbonate or hydroxide solids, reinforcing the idea that, at least under some circumstances, bacterial reduction can promote As(III) sequestration instead of mobilizing it into solution. |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ | |