Periodic Density Functional Theory Investigation of the Uranyl Ion Sorption on the TiO₂ Rutile (110) Face

Abstract

Periodic density functional theory calculations have been performed in order to study the uranyl ion sorption on the TiO2 rutile (110) face. From experimental measurements, two uranyl surface complexes have been observed and the two corresponding sorption sites have been identified. However, from a crystallographic point of view, three different sorption sites can be considered on this face. The corresponding three surface bidentate complexes were modeled and optimized, and their relative energies were calculated. Only 5 kJ/mol separates the two most stable structures, which correspond to the experimental ones. The third surface complex is nearly 10 kJ/mol less stable, in agreement with the fact that it was not observed experimentally.

Sorption of U(VI) at the TiO2–water interface: An in situ vibrational spectroscopic study

“…Under oxidizing environmental conditions, the hexavalent form is the most prominent. The sorption of U(VI) on a multiplicity of naturally occurring and artificial substrates has been intensively studied in the last decades, using macroscopic batch and column experiments, spectroscopic and microscopic analysis, theoretical calculations and modeling (Waite et al, 1994;Bargar et al, 2000;Duff et al, 2002;Catalano et al, 2005;Arai et al, 2006;Perron et al, 2006;Ulrich et al, 2006;Chardon et al, 2008;Pasilis and Pemberton, 2008;Sherman et al, 2008;Hattori et al, 2009;Rossberg et al, 2009).…”

“…Furthermore, the type of dominant complexes for U(VI) sorption onto rutile are reported to depend on the U(VI) surface concentration. At lower concentrations, a bidentate inner-sphere complex onto two bridging oxygen atoms has been proposed, with another complex at higher U(VI) surface concentration bound onto one top and one bridging oxygen atom (Perron et al, 2006;Drot et al, 2007;Vandenborre et al, 2007). Recently, the formation of only one type of surface complex, possibly a trimer was proposed for a mixed anatase and rutile sample with a higher percentage of sorbed U(VI) (Lefèvre et al, 2008).…”

Uranyl adsorption at (010) edge surfaces of kaolinite: A density functional study

“…Thus far mostly force-field based molecular dynamics was used to explore adsorption at the water-mineral interface (Arab et al, 2004;Cygan, 2005, 2006). Only few density functional studies addressed uranyl adsorption at mineral surfaces, (Moskaleva et al, 2006;Perron et al, 2006;Kremleva et al, 2008) but edge surfaces of clay minerals were not among them.…”

Comparison between batch and column experiments to determine the surface charge properties of rutile TiO2 powder

“…It was thus necessary to obtain its surface charge properties in batch experiments, but also in column experiments, since our intention was to compare the sorption of several ionic pollutants (selenium oxoanions and uranyle) under hydrostatic and hydrodynamic conditions of the sorption. Rutile was chosen due to its stability in a wide pH range (2)(3)(4)(5)(6)(7)(8)(9)(10) to avoid any interfering dissolution effects. The rutile form has until recently been the only polymorph available in the single-crystal phase [1] and has thus been intensively studied both experimentally and theoretically.…”

“…The rutile form has until recently been the only polymorph available in the single-crystal phase [1] and has thus been intensively studied both experimentally and theoretically. This polymorph of TiO 2 was thus selected in the framework of our research consortium to compare the results obtained for rutile powder with those obtained with rutile single crystals of several crystallographic orientations and with ab initio calculations [2,3].…”