An efficient Ni-based adsorbent for selective removal of 85Kr and 14CH4 in radioactive contaminants from nuclear process off-gas stream

Efficient adsorbents for radioactive gas treatment in nuclear energy cycle is crucial for eliminating negative environmental impacts caused by wide nuclear applications. A Ni-based MOF material called JUC-86(Ni) which is based on 1-H-benzimidazole-5-carboxylic acid (HBIC) linker was synthesized for adsorbing the 85Kr, 14CH4 from off-gas stream. It was disclosed that there is a suitable pore environment for 85Kr and 14CH4 preferred adsorption in JUC-86 and the adsorption capacity could even reach 2.79 mmol/g (85Kr) and 2.54 mmol/g (14CH4) which are almost higher than all the adsorbents. The 85Kr/N2 and 14CH4/N2 IAST selectivities of the resulting sample are satisfactory (11.63 and 9.43) and well matched with the breakthrough experiments where the breakthrough times of 85Kr and 14CH4 are much longer than N2. What’s more, the adsorption heats of 85Kr and 14CH4 are less than 30 kJ/mol which indicated a stronger affinity than N2 and a low-energy regeneration. As simulation results showed that the adsorption distribution follows a-spiral-pattern which could be attributed to the N atom in the CN, this is also the dominant factor of the 85Kr and 14CH4 preferable adsorption. [Display omitted] •JUC-86 have top-rank adsorption capacity of 85Kr (62.60 mL/g) and 14CH4 (56.97 mL/g).•85Kr/N2 and 14CH4/N2 selectivities on JUC-86 reach up to 11.63 and 9.43 respectively.•Novel structure of ligand provides a low isosteric heats for 85Kr/14CH4 adsorption.•DFT simulation reveals a-spiral-pattern adsorption behavior attributed to the N in CN.