用于氙氪吸附分离的金属-有机骨架材料耐辐照性能的初步研究

Background: The adsorption and separation of Xenon (Xe)/Krypton (Kr) has received increasing attention due to the concern of reprocessing radioactive isotopes of Xe and Kr from off-gas of used nuclear fuel as well as the commercial value of high purity Xe gas. At present, the separation of Xe/Kr is mainly through cryogenic distillation, which is energy and capital intensive. Porous materials such as metal-organic frameworks (MOFs) have shown the ability to selectively adsorb xenon and krypton at relative high temperature, hence are expected to replace cryogenic distillation to achieve low-cost Xe/Kr separation. Purpose: This study aims to investigate the gamma radiation stability of three MOFs (Co/DOBDC, Ni/DOBDC, Co₃(HCOO)₆) used for Xe and Kr adsorption separation. Methods: First of all, three MOFs, i.e., Co/DOBDC, Ni/DOBDC, and Co₃(HCOO)₆, were synthesized and activated according to the preparation methods in the published literature, and the adsorption isotherms of Xe and Kr in three MOFs samples were measured by using physical adsorption instrument with a specially designed water circulating system to maintain a constant temperature (273 K). Then, these samples were irradiated with γ-ray (1.322 MeV) at a gamma dose rate of 0~1 kGy·h^-1 at ambient temperature. Samples' properties, such as Henry constant, Henry selectivity and ideal adsorbed solution theory (IAST) selectivity of Xe/Kr, before and after irradiation, were characterized by X-ray diffraction (XRD) patterns and N₂ adsorption measurements. Finally, the γ-ray radiation stability of Co/DOBDC, Ni/DOBDC and Co₃(HCOO)₆ were studied, and the pore properties (specific surface area and pore volume) before and after irradiation were compared. Results & Conclusions: Experimental results from the observed single-component Xe and Kr isotherms, Henry's constants, Henry's constant ratio and IAST selectivity of the sample, show that Co/DOBDC and Ni/DOBDC as adsorbents have the potential to adsorb and storage high concentration Xe whilst Co₃(HCOO)₆ has the potential for adsorption separation of Xe and Kr in low concentration. Radiation resistance test results show that the pore properties of Co/DOBDC and Ni/DOBDC change significantly after different doses of γ-ray irradiation, and the change degree of pore properties of Co/DOBDC is large than that of Ni/DOBDC whilst the pore properties of Co₃(HCOO)₆ basically do not change after γ-ray radiation at a total dose of 9 kGy, indicating that Co₃(HCOO)₆ can be considered as a potential adsorbent for Xe/Kr separation under radioactive conditions.