不同吸附剂对低浓度 Kr 气的选择性吸附与纯化

Kr-85 is a widely used and valuable β -radionuclide, mainly present in the tail gas of spent fuel reprocessing. The recovery and purification of Kr-85 not only mitigate the environmental impact of radioactive gases, but also yield high-activity radiation sources. This study proposes a method to concentrate trace amounts of Kr in off-gas streams via low-temperature adsorption using different porous adsorbents, followed by further purification through chromatography to obtain high-purity Kr gas. Nano-scale pure silica MFI zeolite (Si-MFI) was synthesized, and its low-temperature adsorption-separation capacity for Kr gas was compared with various other adsorbents. The results indicate that Si-MFI exhibits the best adsorption-separation performance for Kr gas at 195 K. Consequently, Si-MFI was selected as the adsorbent for this study. Furthermore, the feasibility of the proposed approach was validated through breakthrough experiments in a fixed-bed setup and a custom-designed low-temperature Kr recovery apparatus. The results demonstrate that the device and the cryogenic enrichment-chromatographic purification process can effectively recover Kr from simulated exhaust gas with a concentration of 0.005% (vol). The purified Kr product is virtually free of nitrogen and oxygen impurities, thereby confirming the feasibility of the process.