Journal
WATER RESEARCH
Volume 43, Issue 17, Pages 4412-4420Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2009.06.056
Keywords
Binary oxide systems; Selenium oxyanions; Pseudo-second-order kinetic model; X-ray absorption spectroscopy (XAS)
Funding
- National Science Council, Taiwan [NSC 91-2313-B-002-361, 92-2313-B-002-090, 93-2313-B-002-008, 94-2313-B-002-091, 95-2313-B-002-041, 96-2313-B-002-021]
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Removal of selenium oxyanions by the binary oxide systems, Al- or Fe-oxides mixed with X-ray noncrystalline SiO2, was previously not well understood. This study evaluates the adsorption capacity and kinetics of selenium oxyanions by different metal hydroxides onto SiO2, and uses X-ray absorption spectroscopy (XAS) to assess the interaction between selenium oxyanions and the sorbents at pH 5.0. The binary oxide systems of Al(III)- or Fe(III)-oxides mixed with SiO2 were prepared, and were characterized for their surface area, point of zero charge (PZC), pH envelopes, X-ray diffraction analysis (XRD), and then macroscale adsorption isotherm and kinetics of selenite and selenate, micro-scale adsorption XAS. The adsorption capacity of selenite and selenate on Al(III)/SiO2 is greater than on Fe(III)/SiO2. Adsorption isothermal and kinetic data of selenium can be well fitted to the Langmuir isotherm and pseudo-second-order kinetic models. Based on simple geometrical constraints, selenite on both the binary oxide systems forms bidentate inner-sphere surface complexes, and selenate on Fe(III)/SiO2 forms stronger complexes than on Al(III)/SiO2. (c) 2009 Elsevier Ltd. All rights reserved.
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