title: Adsorption of Selenium and Strontium on Goethite: EXAFS Study and Surface Complexation Modeling of the Ternary Systems.
abstract: Knowledge of the geochemical behavior of selenium and strontium is critical for the safe disposal of radioactive wastes. Goethite, as one of the most thermodynamically stable and commonly occurring natural iron oxy-hydroxides, promisingly retains these elements. This work comprehensively studies the adsorption of Se(IV) and Sr(II) on goethite. Starting from electrokinetic measurements, the binary and ternary adsorption systems are investigated and systematically compared via batch experiments, EXAFS analysis, and CD-MUSIC modeling. Se(IV) forms bidentate inner-sphere surface complexes, while Sr(II) is assumed to form outer-sphere complexes at low and intermediate pH and inner-sphere complexes at high pH. Instead of a direct interaction between Se(IV) and Sr(II), our results indicate an electrostatically driven mutual enhancement of adsorption. Adsorption of Sr(II) is promoted by an average factor of 5 within the typical groundwater pH range from 6 to 8 for the concentration range studied here. However, the interaction between Se(IV) and Sr(II) at the surface is two-sided, Se(IV) promotes Sr(II) outer-sphere adsorption, but competes for inner-sphere adsorption sites at high pH. The complexity of surfaces is highlighted by the inability of adsorption models to predict isoelectric points without additional constraints.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry and Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University , Beijing, 100871, China.|Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology , Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Nie
authors.affiliation: Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology , Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Finck
authors.affiliation: Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology , Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Frank
authors.identifier: 0000-0002-2650-2071
authors.initials: F
authors.lastname: Heberling
authors.affiliation: Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology , Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.|Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology , Engesserstr. 20, 76131 Karlsruhe, Germany.
authors.forename: Tim
authors.identifier: 0000-0002-7903-9199
authors.initials: T
authors.lastname: Pruessmann
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry and Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University , Beijing, 100871, China.
authors.forename: Chunli
authors.identifier: 0000-0003-1400-3758
authors.initials: C
authors.lastname: Liu
authors.affiliation: Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology , Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Lützenkirchen
mesh_terms: D000327:Adsorption; D006863:Hydrogen-Ion Concentration; D008903:Minerals / Q000737:chemistry; D012643:Selenium / Q000737:chemistry*; D018036:Selenium Compounds; D013324:Strontium
chemical_list: D008903:Minerals; D018036:Selenium Compounds; D012643:Selenium; D013324:Strontium