Incipient wetness impregnation to prepare bismuth-modified all-silica beta zeolite for efficient radioactive iodine capture

Abstract

The economical and effective capture of radioactive iodine has always been an important field of research in the reprocessing of spent fuel. In this work, we successfully prepared a novel bismuth-modified all-silica beta zeolite material (Bi@Si-BEA) though a modified incipient wetness impregnation method. A series of iodine sorption and desorption experiments and characterization methods (PXRD, SEM, TEM, TG, XPS, FTIR, ²⁹Si NMR, Raman, PDF, and DFT calculation) were performed to reveal the structural characteristics and the mechanism of iodine capture of Bi@Si-BEA. The results showed that the sorption mechanism generally involved the preferential enrichment of iodine molecules in the 12-ring channels of the Si-BEA, for which the adsorption energy was −0.23 ​eV. The enriched iodine molecules subsequently reacted with the active bismuth sites (Bi⁰ and β-Bi₂O₃) on the surface of Si-BEA to form bismuth iodine compounds (BiI₃ and BiOI), thereby achieving immobilization of iodine through strong chemical interactions. Through a combination of physical and chemical effects, Bi@Si-BEA could reach a sorption capacity of 600 ​mg/g, of which the chemisorption accounts for approximately 350 ​mg/g, in approximately 2 ​h. In addition, we explored the effects of different loadings of bismuth and experimental temperatures on the iodine sorption performance and scaled up the preparation of Bi@Si-BEA.