模拟吸附放射性同位素137Cs和90Sr的Cd-MOFs材料合成及评价

为吸附后处理产生的高放废液玻璃固化过程中大量的放射性同位素⁹⁰Sr和¹³⁷Cs，采用溶剂热法合成阴离子型金属有机骨架［DMA］2［Cd₃(FDC)₄］·2H₂O，并评价其对锶、铯离子的吸附能力。采用粉末X-射线衍射、傅里叶红外和热重等方法确认Cd-MOFs的结构。扫描电子显微镜结果显示，在吸附Cs和Sr元素后，Cd-MOFs形貌没有发生明显变化。同时荧光发射光谱证实，Cd-MOFs吸附铕离子后，能够很好敏化铕离子，使材料发射出红色荧光。对锶、铯离子吸附实验结果显示，对锶、铯离子在前50 min即可完成超过50%的吸附，对铯离子的最大吸附量为63.94 mg/g，对锶离子的最大吸附量为53.06 mg/g。通过吸附动力学研究发现，Cd-MOFs对Cs和Sr离子的吸附均符合准二级动力学模型，证明对Cs和Sr离子的速率决策步为化学吸附。推测水合离子半径、有机骨架螺旋链间螺距等因素均对吸附效果有影响。

Synthesis and Evaluation of Cd-MOFs Materials for Adsorption of Simulated Radioisotopes 137Cs and 90Sr

In medical science and industry field, radioisotopes ⁹⁰Sr and ¹³⁷Cs have extensive utilization, whilst large amounts of them require separating in the vitrification process of high level radioactive liquid waste from spent fuel reprocessing. Through a solvothermal process, anionic metal-organic frameworks, ［DMA］2［Cd₃(FDC)₄］·2H₂O, have been synthesized, whose structure has been characterized via powder X-ray diffraction, fourier-transform infrared spectroscopy and thermogravimetric analysis. Scanning electron microscope analysis has been carried out to compare the morphologies of the structures before and after the adsorption of Cs and Sr ions, indicating Cd-MOFs stability during the removal process. In addition, fluorescence spectroscopy has evidenced that europium ions have been sensitizated by Cd-MOFs adsorption, enabling the materials to emit fluorescent red. Furthermore, the adsorption experimental studies of Cs and Sr ions adsorption demonstrate that over 50% of adsorption has been achieved within the first 50 min contact time, obtaining the maximum adsorption of Cs⁺ and Sr²⁺, 63.94 mg/g and 53.06 mg/g, respectively. Additionally, kinetic analysis points out that the adsorption of Cs⁺ and Sr²⁺ ions on Cd-MOFs obeys the pseudo-second-order kinetics, suggesting that the rate-determining step is chemisorption. Theoretically, ions’ hydrated radius, helix pitch of the organic frameworks, and their interactions have effects on adsorption capacities and kinetics.