Rapid Enrichment And Detection Of Radionuclide Iodine Using Novel Metal Organic Gel Materials

With the increasingly prominent problem of environmental pollution and the depletion of non-renewable resources,China will vigorously develop nuclear power as a strategic development goal.The rapid development of nuclear power industry has brought great pressure to the disposal of radioactive waste in China.In radioactive waste,I¹²⁹,I¹³¹and other iodine isotopes have strong radioactivity and migration.Therefore,it is of great significance to quickly remove and detect radioactive iodine vapor from nuclear waste.In this study,a fluorescent metal-organic gel material with high quantum yield（named YTU-1000）was designed and prepared,and its adsorption performance and fluorescence detection performance against iodine vapor were systematically studied.The specific research contents of this study are as follows:（1）The effect of synthesis conditions on the yield of the material and the basic physical properties of the material were studied.A novel luminescent metal-organic gel material was synthesized from zirconium nitrate and 1,1,2,2-tetra（4-carboxybenzene）ethylene ligand under mild solvothermal conditions.By adjusting the doping ratio of zirconium nitrate and organic ligand,the ratio of nitrogen,nitrogen dimethylformamide（DMF）and water in the solvent,and temperature,the yield and forming condition of the gel material were optimized.The optimal experimental conditions for preparing gel materials were obtained.The basic structure,morphology and luminescence characteristics of the materials were analyzed by powder diffraction（PXRD）,scanning electron microscopy（SEM）,nitrogen adsorption,infrared spectroscopy（IR）and fluorescence spectroscopy（PL）.Thermogravimetric analysis（TG）and dissolution test were used to test the thermal stability and solution stability of the gel.In this part,the metal-organic gel material was found to be amorphous,with particle size distribution ranging from 1 to 5μm.In addition,N₂adsorption tests show that the material is non-porous and dense structure,which is one of the main reasons for the material’s high quantum efficiency（IQE=95.45%,EQE=88.15%）.Thermogravimetric tests and dissolution tests show that the material not only has good thermal stability,but also has good hydrolysis stability in a wide p H range of（2～12）.（2）The adsorption performance and mechanism of metal-organic gel material YTU-1000 for iodine vapor were studied.The possibility of using the metal-organic gel material as radioactive iodine vapor adsorbent was studied by testing its adsorption kinetics,adsorption capacity,desorption performance and adsorption stability.The adsorption capacity of the material for iodine vapor can reach 3.01 g/g,which is better than most commercial iodine adsorption materials.In addition,at 75℃,the material can reach 80%of the maximum adsorption capacity in about 10 hours,indicating that it has a fast adsorption kinetics.In the experiment of adsorption and desorption,it was found that the material could still maintain more than 80%of the initial adsorption performance after5 cycles.The weight test of iodine-loaded material shows that the iodine fixation rate of iodine-saturated material is still above 93%after 96 hours at room temperature and pressure,indicating that the material has a strong binding force with iodine.The XPS analysis of the material before and after the adsorption of iodine shows that the direct interaction between N atom and iodine molecule is the main reason for the material’s good adsorption performance.（3）The fluorescence detection performance of the material for iodine vapor was studied.The fluorescence spectra,excitation spectra and fluorescence lifetime of metal-organic gel materials and organic ligands before and after iodine vapor adsorption were studied.The fluorescence spectra of the material loaded with different amounts of iodine showed that the sensitivity of the material to iodine vapor reached 17.03μg/g.In addition,the fluorescence intensity of the material has good stability,which can maintain more than 67%of the initial intensity in high humidity environment.（4）Electrospinning technology was studied and the metal-organic gel material was used to prepare membrane material.Based on the good mechanical properties and stability of the metal-organic gel material,the metal-organic gel material was prepared by electrospinning technology using polyvinylpyrrolidone（PVP）as the matrix material and methanol as the diluent.