Identifiant pérenne de la notice : 210612762
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Note publique d'information : This study deals with the understanding of the uranyl chemistry at the 0.1 M NaNO3
solution/mineral (quartz and aluminium hydroxide) interface. The aims are:(i) to identify
and to characterize the different uranyl surface species (mononuclear, polynuclear
complexes and/or precipitates...), i.e. the coordination environments of sorbed/precipitated
uranyl ions, by using X-ray photoelectron spectroscopy (XPS), extended X-ray absorption
fine structure (EXAFS) and time-resolved laser-induced fluorescence spectroscopy (TRLFS),
and;(ii) to investigate the influence of pH, initial uranyl aqueous concentration
and hydroxyl ligand concentration on the uranyl surface speciation.Our study on the
speciation of uranyl ions at the quartz surface (i) confirms the formation of uranyl
polynuclear/oligomers on quartz from moderate (1 mol/m2) to high (26 mol/m2) uranyl
surface concentrations and (ii) show that theses polynuclear species coexist with
uranyl mononuclear surface species over a pH range 5-8.5 and a wide range of initial
uranyl concentration of the solutions (10-100 M). The uranyl concentration of these
surface species depends on pH and on the initial uranyl aqueous concentration.Hydrate
(surface-) precipitates and/or adsorbed polynuclear species and monomeric uranyl surface
complexes are formed on aluminium hydroxide. Uranyl mononuclear complexes are predominant
at acidic pH, as well as uranyl in solution or on the surface. Besides mononuclear
species, precipitates and/or adsorbed polynuclear species are predominantly formed
at neutral pH values on aluminium hydroxide. A main contribution of our investigations
is that precipitation and/or adsorption of polynuclear species seem to occur at low
uranyl surface concentrations (0.01-0.4 mol/m2). The uranyl surface speciation is
mainly dependent on the pH and the aluminol ligand concentration.
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