title: Selenium(IV) uptake by maghemite (γ-Fe2O3).
abstract: The mechanism of selenium(IV) uptake by maghemite was investigated on both the macroscopic and the molecular level. Maghemite nanoparticles exhibited fast adsorption kinetics toward selenium(IV). Batch experiments showed a decreased sorption with increasing pH (3.5-11). Ionic strength variations (0.01 to 0.1 M NaCl) had no significant influence on selenium(IV) uptake. Electrophoretic mobility measurements revealed a significant shift toward lower values of the isoelectric point of maghemite upon selenium(IV) uptake, suggesting the formation of inner-sphere surface complexes. At the molecular level, using X-ray Absorption Fine-Structure Spectroscopy (EXAFS), the formation of both bidentate binuclear corner-sharing ((2)C) and bidentate mononuclear edge-sharing ((1)E) inner-sphere surface complexes was observed, with a trend toward solely (1)E complexes at high pH. The absence of a tridentate surface complex as observed for arsenic(III) and antimonite(III) might be due to the relatively small size of the Se(IV)O3 unit. These new spectroscopic results can be implemented in reactive transport models to improve the prediction of selenium migration behavior in the environment as well as its monitoring through its interaction with maghemite or maghemite layers at the surface of magnetite. Due to its chemical stability even at low pH and its magnetization properties allowing magnetic separation, maghemite is a promising sorbing phase for the treatment of Se polluted waters.
authors.affiliation: Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf e.V. , 01328 Dresden, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Jordan
authors.forename: Aline
authors.initials: A
authors.lastname: Ritter
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Scheinost
authors.forename: Stephan
authors.initials: S
authors.lastname: Weiss
authors.forename: Dieter
authors.initials: D
authors.lastname: Schild
authors.forename: René
authors.initials: R
authors.lastname: Hübner
mesh_terms: D000327:Adsorption; D005290:Ferric Compounds / Q000737:chemistry*; D012643:Selenium / Q000737:chemistry*; D013816:Thermodynamics; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; C000499:ferric oxide; D012643:Selenium