Separation of minor actinides from highly acidic solutions using diglycolamide modified mesoporous silica synthesized via a novel "ring-opening click" reaction

Solid-phase extraction represents a promising approach for partitioning of trivalent minor actinides (MAs) from high-level liquid waste, which is crucial for the decontamination of radioactive waste. However, highly acidic effluents pose a formidable challenge for extraction materials. Herein, the diglycolamide ligands functionalized mesoporous silica robust matrixs were prepared, resulting in rapid and efficient separation of MAs from strong nitric acid media. This paper reports the first modification of SBA-15-type mesoporous silica through a "ringopening click" reaction under mild conditions. Five modified silica materials with monolayer diglycolamide ligands containing different terminal groups were obtained using low temperature (0-25 degrees C) procedures. The rigid and open pore structure of SBA-15 is retained under such mild conditions, allowing facile diffusion and open access to the monolayer ligands. The functionalized product SBA-15-DEDGA exhibited a strong affinity for trivalent MAs in highly acidic solutions and could separate trace amounts of radioactive Am(III) from 1 to 8 M nitric acid solutions with high efficiency (> 98%) within 1 min; the largest distribution coefficient exceeded 5 x 104 mL/g. Solid-state nuclear magnetic resonance spectroscopy combined with X-ray photoelectron spectroscopy of Eu(III) revealed that the binding mechanism involves direct coordination of Eu(III) to a tridentate oxygenbinding site. Additionally, selective separation of americium from curium was achieved with separation factors up to 191 +/- 20 through oxidation of Am(III) by sodium persulfate. The superlative and efficient sorption performance of these materials demonstrates their utility in the immobilization of trivalent actinides and the separation of americium from curium.