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

Abstract

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 C=N, this is also the dominant factor of the ⁸⁵Kr and ¹⁴CH₄ preferable adsorption.