title: Characterization of hexavalent chromium interaction with Sargassum by X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and quantum chemistry calculation.
abstract: Hexavalent chromium represents higher toxicity in aqueous solutions. It can be removed by such low-cost biosorbents as Sargassum sp. In this study, X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and quantum chemistry (QC) calculation were used to study the interactions between hexavalent chromium and Sargassum sp. during the biosorption. It was found that most of the adsorbed Cr(VI) ions were reduced to Cr(III) after the biosorption. The electrons for the reduction of Cr(VI) were possibly supplied from the Sargassum biomass, some organic compounds of which were oxidized. Cr(III) ions were coordinated with the oxygen atoms from either carboxyl or hydroxyl functional groups to form an octahedral structural metal complex. The coordination numbers of the formed Cr complex were 4-6, and bond length of Cr-O was 1.98Å. QC calculation proved the possible formation of the Cr(III) metal complex, and revealed that carboxyl from biomass could be strongly bound with Cr(III). A three-step removal mechanism of Cr(VI) by Sargassum was proposed.
authors.affiliation: Department of Civil and Environmental Engineering, National University of Singapore, Singapore, Singapore.
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Zheng
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.forename: Jianwen
authors.initials: J
authors.lastname: Jiang
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Yanping
authors.initials: Y
authors.lastname: Fan
authors.forename: Andrew T S
authors.initials: AT
authors.lastname: Wee
authors.forename: J Paul
authors.initials: JP
authors.lastname: Chen
mesh_terms: D002857:Chromium / Q000302:isolation & purification* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D056951:Photoelectron Spectroscopy; D044647:Sargassum / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification* / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D010100:Oxygen