title: The Sorption Processes of U(VI) onto SiO2in the Presence of Phosphate: from Binary Surface Species to Precipitation.
abstract: The ternary system containing aqueous U(VI), aqueous phosphate and solid SiO2was comprehensively investigated using a batch sorption technique, in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy, time-resolved luminescence spectroscopy (TRLS), and surface complexation modeling (SCM). The batch sorption studies on silica gel (10 g/L) in the pH range 2.5 to 5 showed no significant increase in U(VI) uptake in the presence of phosphate at equimolar concentration of 20 μM, but significant increase in U(VI) uptake was observed for higher phosphate concentrations. In situ infrared and luminescence spectroscopic studies evidence the formation of two binary U(VI) surface species in the absence of phosphate, whereas after prolonged sorption in the presence of phosphate, the formation of a surface precipitate, most likely an autunite-like phase, is strongly suggested. From SCM, excellent fitting results were obtained exclusively considering two binary uranyl surface species and the formation of a solid uranyl phosphate phase. Ternary surface complexes were not needed to explain the data. The results of this study indicate that the sorption of U(VI) on SiO2in the presence of inorganic phosphate initially involves binary surface-sorption species and evolves toward surface precipitation.
authors.affiliation: Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia.
authors.forename: M Josick
authors.initials: MJ
authors.lastname: Comarmond
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, D-01328 Dresden, Germany.
authors.forename: Robin
authors.initials: R
authors.lastname: Steudtner
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, D-01328 Dresden, Germany.
authors.forename: Madlen
authors.initials: M
authors.lastname: Stockmann
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, D-01328 Dresden, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Heim
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, D-01328 Dresden, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Müller
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, D-01328 Dresden, Germany.
authors.forename: Vinzenz
authors.initials: V
authors.lastname: Brendler
authors.affiliation: Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia.
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Payne
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, D-01328 Dresden, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Foerstendorf
mesh_terms: D000327:Adsorption; D010710:Phosphates; D012822:Silicon Dioxide; D017550:Spectroscopy, Fourier Transform Infrared; D014501:Uranium / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D010710:Phosphates; D014867:Water; D014501:Uranium; D012822:Silicon Dioxide