Changes in U(VI) speciation upon sorption onto montmorillonite from aqueous and organic solutions

摘要

The speciation of UO(sub 2)(sup 2+) and UO(sub 2)(sup 2+) Tributylphosphate (TBP) mixtures has been investigated in solution and intercalated with the reference smectite clay SAz-1 using x-ray absorption, Raman, and luminescence spectroscopies. Neither aquated UO(sub 2)(sup 2+) nor its TBP complex undergoes any detectable changes in uranium oxidation state on intercalation. Further, at the pH values employed in this work, there is no evidence for hydrolysis of the uranium species to generate dimeric or higher order uranium oligomers. However, we do find indications that the structures of the solution complexes are altered on intercalation, particularly for the UO(sub 2)(sup 2+)/TBP system. In addition, several lines of evidence suggest that, at the loading levels used in this study, the uranyl species may be interacting with two or more spectroscopically distinguishable sites on SAz-1. 29 refs., 3 figs., 2 tabs.