Stability and Low Concentration Xe/Kr Mixtures Separation on HKUST-1 and Co-MOF-74 Pellets

Abstract

Nuclear data, as the basis for the study of nuclear reaction and nuclear structure, are used to describe the properties of the nucleus and the reactions of the nucleus with other particles. The accuracy and reliability of nuclear data play important roles in nuclear fundamental research and nuclear technology application. The noble gas Xe can be used for neutron activation analysis of nuclear materials. However, it is necessary to separate radioactive Xe from Kr because of the interference of radioactive Kr isotopes when measuring radioactive Xe isotopes. Metal-organic framework (MOF) is a kind of porous crystalline material built with coordinate bonds between metal ions and organic ligands. The modular synthesis strategy of MOF makes them possessing adjustable pore size and adsorption performance, which provides the possibility for customized application. HKUST-1 and Co-MOF-74 are two representative MOFs that received extensive attention in the field of Xe/Kr separation due to the open metal sites in their pores. However, the stability of the two MOFs, especially in practical application environment close to radioactive Xe/Kr separation, still has not yet been studied. In this work, the HKUST-1 and Co-MOF-74 powders were shaped with polyvinyl alcohol as a binder, and the impact on the crystal structures of HKUST-1 and Co-MOF-74 in the shaping process was characterized by PXRD. The adsorption isotherms of N2, Xe and Kr on powder and pellets were tested by static adsorption method. The results show that the crystal structures of HKUST-1 powder and Co-MOF-74 powder are not obviously changed during the shaping process, and the BET surface areas of HKUST-1 pellets and Co-MOF-74 pellets decrease by 11% and 6% respectively. The capacity of Xe (Kr) at low pressure and 25 ℃ on HKUST-1 (Co-MOF-74) powder is almost the same as that of HKUST-1 (Co-MOF-74) pellets, and Xe/Kr Henry selectivity of HKUST-1 pellets and Co-MOF-74 pellets is 9.70 and 9.15 respectively. The stability of powder and pellets was studied by comparing the changes of specific surface area and infrared spectrum before and after the circumstance of 50% relative humidity, thermal cycling and γ ray radiation, according to the actual operating conditions of radioactive Xe/Kr separation. The stabilities of HKUST-1 pellets are better than those of Co-MOF-74 pellets in the circumstance of water and thermal cycling. HKUST-1 pellets and Co-MOF-74 pellets have good γ ray radiation resistance. A preliminary study on the separation of low concentration Xe and Kr using HKUST-1 pellets was carried out by adsorption-desorption experiment using fix-bed breakthrough column. Low concentration Xe and Kr can be efficiently separated by using HKUST-1 pellets as adsorbent in the fixbed breakthrough column using adsorption-desorption method, which provides a basis for establishing Xe/Kr separation procedure of MOFs required for the preparation of Xe source for nuclear data measurement.

Keywords

• hkust-1
• co-mof-74
• pellet
• stability
• xe
• kr
• adsorption