Interaction of actinides(III) with aluminosilicate colloids in “statu nascendi”

An average size of HAS colloids, as determined by laser-induced breakdown detection (LIBD), is found to be in the range of 10-20 nm in diameter, increasing with lowering pH. The SEM-EDXS analysis results in an atomic Si/Al ratio of 1.23 ± 0.03. The TRLFS speciation shows the formation of three different colloid-borne Cm species: Cm-HAS(I), Cm-HAS(II) and Cm-HAS(III). These results are different from the HAS colloid formation with monosilanol, in which only two species - Cm-HAS(I) and Cm-HAS(II) - are observed. The number of hydration water molecules in the three colloid-borne Cm species, as confirmed by measuring the fluorescence lifetime with TRLFS, varies from 7 for Cm-HAS(I), to 6 for Cm-HAS(II) and to 0-1 for Cm-HAS(III), which infers bi-dentate and tri-dentate oxo-bridging and structural incorporation of Cm, respectively. The prevailing Cm-HAS(III) species at pH 9 converts by decreasing pH first to Cm-HAS(II) and then to Cm-HAS(I), revealing a gradual dissociation of Cm from HAS colloids upon acidification.