X-ray Absorption Studies of the Interaction between Uranium(VI) and Silica-Gel-Bound Tetraazamacrocycles

The development of separation processes aimed at the selective uptake of toxic metal ions from dilute wastewaters and industrial process streams is of paramount importance for preventing environmental contamination but still remains a challenging scientific task. In that viewpoint, solid-liquid extraction using chelating agents grafted on hydrophilic supports is appealing, mainly because the affinity and selectivity of the scavenging material towards the targeted species can be fine-tuned by molecular design.1,2 We have synthesized a series of N-functionalized tetraazamacrocyclic ligands covalently bound on the surface of amorphous silica-gel beads for the selective extraction of actinides.2,3 In collaboration with the CEA Centre of Valduc, one of these materials has been prepared on a semi-industrial scale (Scheme 1) and used in the final decontamination step of real effluents for removing the residual α-emitters (U, Pu, Am) contained at the sub-ng/L level.