Journal ArticleDOI
Arsenate and Chromate Retention Mechanisms on Goethite. 1. Surface Structure
TLDR
In this paper, the authors used Extended X-ray absorption fine structure (EXAFS) spectroscopy to deduce the local coordination environment of two environmental contaminants, arsenate and chromate, on the mineral goethite (α-FeOOH).Abstract:
The molecular structure of ions retained on mineral surfaces is needed to accurately model their sorption process and to determine their stability. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used in this study to deduce the local coordination environment of two environmental contaminants, arsenate and chromate, on the mineral goethite (α-FeOOH). Based on the oxyanion−Fe distances, it was concluded that three different surface complexes exist on goethite for both oxyanions: a monodentate complex, a bidentate-binuclear complex, and a bidentate-mononuclear complex. At low surface coverages, the monodentate complex was favored while at higher coverages the bidentate complexes were more prevalentthe bidentate-binuclear complex appears to be in the greatest proportion at these highest surface coverages. Therefore, modeling efforts for chromate or arsenate retention on goethite need to consider a monodentate complex at very low coverages, both the monodentate and bidentate complexes at in...read more
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Journal ArticleDOI
Enhanced exopolymer production and chromium stabilization in Pseudomonas putida unsaturated biofilms.
John H. Priester,Scott G. Olson,Samuel M. Webb,Mary P. Neu,Larry E. Hersman,Patricia A. Holden +5 more
TL;DR: It is demonstrated that Cr accumulation in unsaturated biofilms occurs with enzymatic reduction of Cr, cellular lysis, cellular association, and extracellular DNA binding of Cr(III), which altogether can facilitate localized biotic stabilization of Cr in contaminated vadose zones.
Journal ArticleDOI
Predicting Boron Adsorption by Soils Using Soil Chemical Parameters in the Constant Capacitance Model
TL;DR: In this paper, a constant capacitance model was used to fit arsenate adsorption on all soils by optimizing either three monodentate or two bidentate As(V) surface complexation constants.
Journal ArticleDOI
Adsorption, sequestration, and bioaccessibility of As(V) in soils.
TL;DR: The results indicate the bioaccessibility, and thus, potentially the bioavailability of otherwise soluble As(V) added to soils is significantly reduced in some soils over time, particularly those with lower pH and higher Fe oxide content.
Journal ArticleDOI
X-ray absorption fine structure study of As(V) and Se(IV) sorption complexes on hydrous Mn oxides
TL;DR: X-ray absorption fine structure (XAFS) spectroscopic analysis at the As, Se, and Mn K-edges was used to study arsenate [As(V)O43−] and selenite [Se(IV)O32−] sorption complexes on the synthetic hydrous manganese oxides (HMOs) vernadite (δ-MnO2) and K-birnessite (nominal composition: K4Mn14O27 · 9H2O) as discussed by the authors.
Journal ArticleDOI
TiO2-Photocatalyzed As(III) Oxidation in Aqueous Suspensions: Reaction Kinetics and Effects of Adsorption
TL;DR: The selective use of hydroxyl radical quenchers and superoxide dismutase demonstrated that superoxide, O2-, plays a major role in the oxidation of As(III) to As(V).
References
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Book
Environmental Chemistry of Soils
TL;DR: In this article, an introduction to modern soil chemistry describes chemical processes in soils in terms of established principles of inorganic, organic, and physical chemistry, providing an understanding of the structure of the solid mineral and organic materials from which soils are formed.
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Iron Oxides in the Laboratory: Preparation and Characterization
Udo Schwertmann,R. M. Cornell +1 more
TL;DR: In this paper, the main aim of the second edition is to present reliable, well-tested, up-to-date methods of synthesizing pure iron oxides, including monodispersed particles, presently of great interest to industry.
Journal ArticleDOI
Theoretical X-ray Absorption Fine Structure Standards
John J. Rehr,John J. Rehr,J. Mustre de Leon,S. I. Zabinsky,S. I. Zabinsky,R. C. Albers,R. C. Albers +6 more
Journal ArticleDOI
Surface chemistry of ferrihydrite: Part 1. EXAFS studies of the geometry of coprecipitated and adsorbed arsenate
TL;DR: In this article, the As and Fe K-edges were collected from samples of two-line ferrihydrite with adsorbed (ADS) and coprecipitated (CPT) arsenate prepared over a range of conditions and arsenate surface coverages.