scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Arsenate and Chromate Retention Mechanisms on Goethite. 1. Surface Structure

30 Jan 1997-Environmental Science & Technology (American Chemical Society)-Vol. 31, Iss: 2, pp 315-320
TL;DR: 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...
Citations
More filters
Journal ArticleDOI
TL;DR: The scale of the problem in terms of population exposed to high As concentrations is greatest in the Bengal Basin with more than 40 million people drinking water containing ‘excessive’ As as mentioned in this paper.

6,741 citations

Journal ArticleDOI
Imran Ali1

1,531 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compared the adsorption behavior of arsenite and arsenate on ferrihydrite, under carefully controlled conditions, with regard to adaption kinetics and the influence of pH.
Abstract: Because of its toxicity, arsenic is of considerable environmental concern. Its solubility in natural systems is strongly influenced by adsorption at iron oxide surfaces. The objective of this study was to compare the adsorption behavior of arsenite and arsenate on ferrihydrite, under carefully controlled conditions, with regard to adsorption kinetics, adsorption isotherms, and the influence of pH on adsorption. The adsorption reactions were relatively fast, with the reactions almost completed within the first few hours. At relatively high As concentrations, arsenite reacted faster than arsenate with the ferrihydrite, i.e., equilibrium was achieved sooner, but arsenate adsorption was faster at low As concentrations and low pH. Adsorp tion maxima of approximately 0.60 (0.58) and 0.25 (0.16) molAs molFe-1 were achieved for arsenite and arsenate, respectively, at pH 4.6 (pH 9.2 in parentheses). The high arsenite retention, which precludes its retention entirely as surface adsorbed species, indicates the likel...

1,428 citations

Journal ArticleDOI
TL;DR: In this study in situ Raman and Fourier transform infrared (FTIR) spectroscopic methods were combined with sorption techniques, electrophoretic mobility measurements, and surface complexation modeling to study the interaction of As(III) and As(V) with amorphous oxide surfaces.

1,181 citations

Journal ArticleDOI
TL;DR: In this article, the authors developed and tested a sequential extraction procedure (SEP) for As by choosing extraction reagents commonly used for sequential extraction of metals, Se and P, including NH 4 NO 3, NaOAc, NH 2 OH·HCl, EDTA, NH 4 OH and NH 4 F, were shown to either have only low extraction efficiency for As, or to be insufficiently selective or specific for the phases targeted.

1,137 citations

References
More filters
Book
17 Mar 1994
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.
Abstract: This introduction to modern soil chemistry describes chemical processes in soils in terms of established principles of inorganic, organic, and physical chemistry. The text provides an understanding of the structure of the solid mineral and organic materials from which soils are formed, and explains such important processes as cation exchange, chemisorption and physical absorption of organic and inorganic ions and molecules, soil acidification and weathering, oxidation-reduction reactions, and development of soil alkalinity and swelling properties. Environmental rather than agricultural topics are emphasized, with individual chapters on such pollutants as heavy metals, trace elements, and inorganic chemicals.

6,735 citations

Book
01 Jan 1945

5,804 citations

Book
01 Mar 1991
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.
Abstract: Iron Oxides play an important role in numerous disciplines. Since the publication of the first edition, there has been a surge of interest in synthetic fine to ultrafine iron oxides in a wide range of scientific and technological disciplines, especially in mineralogy, geosciences and environmental science and in various branches of technology. As before, the main aim of the second edition is to present reliable, well-tested, up-to-date methods of synthesizing pure iron oxides. The section on monodispersed particles, presently of great interest to industry, has been expanded. Furthermore the methods of characterization have been focused on their relevance to iron oxides. The well tried syntheses have been retained and some new ones have been incorporated.

2,286 citations

Journal ArticleDOI
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.

1,123 citations