Surface structures and stability of arsenic(III) on goethite: Spectroscopic evidence for inner-sphere complexes
- Agricultural Research Service, Riverside, CA (United States). Salinity Lab.
- Univ. of Idaho, Moscow, ID (United States). Soil Science Div.
The adsorption and stability of arsenite [As(III)] on goethite ({alpha}-FeOOH) was investigated using a combination of standard batch techniques and X-ray absorption spectroscopy (XAS). The reactivity of As(III) with {alpha}-FeOOH at varying pH and As(III) concentration provided macroscopic evidence for strong complexation on the {alpha}-FeOOH surface. Extended X-ray absorption fine structure (EXAFS) spectroscopy gave an average As(III)-Fe interatomic distance of 3.378 {+-} 0.014 {angstrom}, which is indicative of bidentate binuclear bridging As(III) complexes on the {alpha}-FeOOH surface and which is similar to other oxyanions which adsorb on {alpha}-FeOOH by an inner-sphere mechanism. X-ray absorption near-edge structure (XANES) analysis indicated that the As(III)-{alpha}-FeOOH surface complex is stable toward heterogeneous oxidation to As(V), as determined by the energy position of the X-ray absorption edge. The structural information from EXAFS was included in the description of As(III) adsorption on the {alpha}-FeOOH surface using a surface complexation model (the constant capacitance model). These results suggest that As(III) surface complex formation on iron(III) oxides may plan an important role in the environmental behavior of arsenic.
- OSTI ID:
- 653155
- Journal Information:
- Environmental Science and Technology, Vol. 32, Issue 16; Other Information: PBD: 15 Aug 1998
- Country of Publication:
- United States
- Language:
- English
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