title: Equilibria, kinetics, and spectroscopic analyses on the uptake of aqueous arsenite by two-line ferrihydrite.
abstract: Arsenite sorption from aqueous solutions was investigated using two-line ferrihydrite at room temperature, as a function of solution pH and arsenite loading. The isotherms, pH envelopes, and kinetics of arsenite sorption were characterized and its mechanism was elucidated via X-ray absorption spectroscopic studies. Arsenite sorption showed only slight pH dependence with a sorption maximum centered around pH 8.0. The Langmuir isotherm is most appropriate for arsenite sorption over the wide range of pH, indicating the homogenous and monolayer sorption of arsenite. The kinetic study demonstrated that arsenite sorption onto two-line ferrihydrite is considerably fast and the equilibrium is achieved within the reaction time of 3 h. X-ray absorption near-edge structure spectroscopy elucidated a slight change in oxidation state of arsenite for the initial concentration of 13.35 mM at pH 4. The extended X-ray absorption fine structure (EXAFS) spectroscopy results indicate that types of surface complexes of arsenite appeared to be very similar to those proposed by the previous studies in that the bidentate binuclear corner-sharing (2C) complex is predominant at all the surface loadings. However, our EXAFS results suggest that regardless ofpH, the mixed complexes of2C and bidentate mononuclear edge-sharing surface complex (2E) as well as the 2C complex are favoured at low and intermediate surface loadings, but only the 2C complex is dominant at high surface loading. Overall, the EXAFS results support the efficient removal of arsenite by the two-line ferrihydrite through the formation of highly stable inner-sphere surface complexes, such as 2C complex.
authors.affiliation: Department of Earth and Environmental Sciences and Research Institute of Natural Science (RINS), Gyeongsang National University, Jinju 660-701, Republic of Korea.
authors.forename: Soon-Oh
authors.initials: SO
authors.lastname: Kim
authors.affiliation: Department of Earth and Environmental Sciences and Research Institute of Natural Science (RINS), Gyeongsang National University, Jinju 660-701, Republic of Korea.
authors.forename: Woo Chun
authors.initials: WC
authors.lastname: Lee
authors.affiliation: Department of Earth and Environmental Sciences and Research Institute of Natural Science (RINS), Gyeongsang National University, Jinju 660-701, Republic of Korea.
authors.forename: Hyen Goo
authors.initials: HG
authors.lastname: Cho
authors.affiliation: School of Environmental Science and Engineering, Gwangju Institute of Science and Technology(GIST), Gwangju 500-712, Republic of Korea.
authors.forename: Byung-Tae
authors.initials: BT
authors.lastname: Lee
authors.affiliation: Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350, Republic of Korea.
authors.forename: Pyeong-Koo
authors.initials: PK
authors.lastname: Lee
authors.affiliation: Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea
authors.forename: Sun Hee
authors.initials: SH
authors.lastname: Choi
mesh_terms: D000327:Adsorption; D018053:Arsenites / Q000737:chemistry* / Q000302:isolation & purification*; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D056951:Photoelectron Spectroscopy / Q000379:methods*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D018053:Arsenites; D005290:Ferric Compounds; D014867:Water; C092844:ferric oxyhydroxide; C015001:arsenite