HKUST-1和Co-MOF-74颗粒的稳定性及其分离低浓度氙氪的实验研究

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

  • 摘要: Xe和Kr的分离对放射性Xe同位素活度的准确测量具有重要意义。为研究HKUST-1和Co-MOF-74在核数据测量用气体源制备工况条件下的稳定性及其分离低浓度Xe和Kr的性能,本文首先使用粘结剂聚乙烯醇对HKUST-1和Co-MOF-74粉末样品进行造粒,并表征了造粒前后HKUST-1和Co-MOF-74样品的晶体结构,分析了造粒过程对晶体结构的影响;然后采用静态吸附法测定了N2、Xe和Kr在粉末样品和颗粒样品上的吸附等温线;随后研究对比了粉末样品和颗粒样品的水稳定性、热循环稳定性和γ射线辐照稳定性;最后采用固定床吸附-脱附法开展了HKUST-1颗粒样品分离低浓度Xe和Kr的初步研究。结果表明:使用聚乙烯醇粘结剂造粒未对HKUST-1和Co-MOF-74粉末的晶体结构造成明显损伤,HKUST-1和Co-MOF-74颗粒样品的BET比表面积较造粒前分别减小11%和6%;HKUST-1和Co-MOF-74样品造粒前后在25 ℃时对低压下的Xe(Kr)吸附量基本相同,HKUST-1和Co-MOF-74颗粒样品的Xe/Kr亨利选择性分别为9.70和9.15;HKUST-1颗粒样品的水稳定性和热循环稳定性好于Co-MOF-74颗粒样品,HKUST-1和Co-MOF-74颗粒样品均具有良好的耐γ射线辐照性能;采用固定床吸附-脱附法,HKUST-1颗粒样品可将低浓度的Xe和Kr分离,Xe和Kr的柱分离度为0.96。

     

    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.

     

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