Skip to Main content Skip to Navigation
Journal articles

Interaction between U(VI) and SrTiO3 surfaces versus temperature

Abstract : The purpose of this work is the study of the interaction mechanisms between U(VI) ions and SrTiO3 surfaces as a function of pH and temperature (25, 50, 75 and 90 °C) by coupling thermodynamic and spectroscopic approaches. First, the reactivity towards U(VI) for both surface sites of the strontium titanate (triple bond; length of mdashTisingle bondO and triple bond; length of mdashSrsingle bondO) has been investigated as a function of the temperature. The N2-BET specific area was measured: View the MathML source. The surface site density has been determined from potentiometric titrations (6 sites/nm2 for each site triple bond; length of mdashTisingle bondO and triple bond; length of mdashSrsingle bondO). The potentiometric titration data have been simulated, for each temperature, using the FITEQL 4.0 software and the constant capacitance model, taking into account both protonation of the triple bond; length of mdashSrsingle bondOH surface sites and deprotonation of the triple bond; length of mdashTisingle bondOH ones (one pK model). The intrinsic strontium protonation constant increases with an increasing temperature, while the titanate deprotonation one decreases. Moreover, both enthalpy and entropy changes corresponding to the surface acid–base reactions have been evaluated using the van't Hoff relation. The uranium(VI) ions are sorbed onto SrTiO3 surfaces in the 0.5–5.0 pH range with an initial cation concentration equal to 10−4 M. The U(VI) surface complexes were identified by using time-resolved laser-induced fluorescence spectroscopy (TRLFS). For all the studied samples, the fluorescence spectra and the corresponding lifetime values do not change with the pH and the temperature. Two U(VI) complexes sorbed onto SrTiO3 were detected and the corresponding lifetimes are 60±5 and 12±2 μs whatever the temperature (25, 50, 75 and 90 °C). The sorption edges were simulated with the FITEQL 4.0 code. The sorption equilibrium constants of the U(VI)/SrTiO3 system between 25 and 90 °C were obtained with the constant capacitance model (CCM), considering two reactive surface sites. According to the spectroscopic characterization, two types of surface complexes, namely [(triple bond; length of mdashSrOH)(triple bond; length of mdashTiOH)UO2]2+ and [(triple bond; length of mdashTiOH)(triple bond; length of mdashTiO)UO2]2+, were considered. Finally, enthalpy (ΔrH°) and entropy (ΔrS°) changes were calculated from the temperature-dependent sorption constants, by the application of the van't Hoff formalism. The formation of the [(triple bond; length of mdashSrOH)(triple bond; length of mdashTiOH)UO2]2+ surface complex was found to present an endothermic character associated to an increase in the disorder of the system. On the contrary, the formation of the [(triple bond; length of mdashTiOH)(triple bond; length of mdashTiO)UO2]2+ surface complex led to an exothermic process with only a slight increase in the disorder of the system.
Document type :
Journal articles
Complete list of metadatas

http://hal.in2p3.fr/in2p3-00380064
Contributor : Sophie Heurteau <>
Submitted on : Wednesday, April 29, 2009 - 5:09:40 PM
Last modification on : Wednesday, September 16, 2020 - 4:08:24 PM

Identifiers

Collections

Citation

G. García-Rosales, R. Drot, F. Mercier-Bion, G. Lagarde, E. Simoni. Interaction between U(VI) and SrTiO3 surfaces versus temperature. Journal of Colloid and Interface Science, Elsevier, 2009, 333, pp.104-113. ⟨10.1016/j.jcis.2009.01.049⟩. ⟨in2p3-00380064⟩

Share

Metrics

Record views

126