Metal phosphonate sorbents: Enhancement of actinide sorption performance by gamma irradiation

Abstract

The effect of irradiation on actinide sorbents potentially employed in nuclear waste management, should be investigated to evaluate their feasibility in real-world applications. In this study, hafnium-amino trismethylene phosphonate (Hf-ATMP), which is a type of organic–inorganic hybrid sorbents for actinides, was exposed to 60Co gamma rays, and the effects of ionising radiation on actinide sorption performance and its microstructure were investigated. Thereafter, the irradiation effect on other materials of this type was studied. The results revealed that the actinide sorption performance of Hf-ATMP was significantly enhanced by irradiation; the saturated Th(IV) sorption capacity of Hf-ATMP increased by 58.1% after irradiation with a dose of 2.4 MGy. The selectivity for actinides and the sorption performance for trace amounts of radioactive 239Pu and 237Np were also comparable to those of pristine Hf-ATMP. The structural characterisation of Hf-ATMP before and after irradiation indicated that the P-O–H groups in Hf-ATMP were converted into P-O-Hf groups upon irradiation. The pore volume and BET surface area of Hf-ATMP decreased, but the bulk chemical structure of Hf-ATMP was not damaged by gamma irradiation. Additionally, the enhancement of actinide sorption performance by gamma irradiation was observed with several other metal phosphonates. The results indicated the application potential of metal phosphonates as actinide sorbents in practical nuclear processes. Besides, this study opens a new door for improving the sorption performance of metal phosphonate sorbents using irradiation techniques.