Etude multi-échelle des mécanismes d'interaction des ions aquo uranyle avec les surfaces de l'oxyde de titane (poudres et monocristaux)

Abstract : The aim of this work is the study, at a molecular scale of the sorption mechanisms corresponding to UO_2^{2+}/TiO_2 system. The first step of the study is the hydrated solid characterization and the second step is the sorption mechanisms study. The work is performed usind a multi-scale approach, which is composed by three parts. At first, we have obtained macroscopic data corresponding to the uranyl retention on the solid. Moreover, we have used CD-MUSIC model in order to calculate the surface acidity constants of the hydrated solid.In a second part, we have performed a multi-spectroscopic study (TRLFS, XPS, DRIFT, SHG) in order to characterize the system at a molecular scale. Finally, all these results were obtained on the solid TiO-2 under different forms (rutile or anastase phases and (110), (001), (111) rutile single crystals). From the structural results, we have determined that there are two sorption sites towards the free uranyl ion into the titania surface, whatever the sudied solid (powder or single crystal). Moreover, these two reactive sorption sites don't present the same reactivity towards free uranyl ion : the more reactive sorption site is assigned to a bridging-oxygen atoms and the less reactive sorption site is assigned to a bridging-top oxygen atoms. Thus, using this methodology, we can conclude that it is possible to understand the powder surface properties using the single crystals surface results.
Keywords : sorption
Document type :
Theses
Nuclear Theory. Université Paris Sud - Paris XI, 2005. French


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Submitted on : Thursday, January 26, 2006 - 4:14:12 PM
Last modification on : Wednesday, February 1, 2006 - 9:31:34 AM

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Johan Vandenborre. Etude multi-échelle des mécanismes d'interaction des ions aquo uranyle avec les surfaces de l'oxyde de titane (poudres et monocristaux). Nuclear Theory. Université Paris Sud - Paris XI, 2005. French. <tel-00011473>

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