Research On The Stability Of Functionalized MOF Materials Against Radiation And The Effective Recovery Of Radionuclides

With the rapid development of human society and modern industry,the problem of energy supply and demand has become more and more serious.Nuclear energy is recognized as one of the preferred energy sources for alternatives to fossil fuels.In the process of using nuclear energy,a variety of radionuclides will inevitably be produced,which seriously endangers the sustainable development of the ecological environment.Adsorption is one of the most effective methods for removing radionuclides from nuclear waste.Metal-organic frameworks（MOFs）materials are expected to play an important role in the adsorption,removal and recycling of radionuclides in nuclear wastewater environments due to their high specific surface area,easily adjustable pore structure and chemical properties,but they are required to maintain structural stability in high irradiation environments.Therefore,it is of great scientific and practical significance in the field of nuclear wastewater treatment to study the anti-irradiation stability of MOF materials and obtain adsorbents with strong anti-irradiation stability.In this study,the anti-irradiation stability of MOFs was systematically studied and analyzed,and the radioactive metal nuclide adsorption experiment was carried out based on the selected MOF materials with excellent irradiation stability.The main contents of the paper are as follows:1.Using MIL-101（Cr）as the parent material,the functional modification design and material preparation of the ligand were carried out by using amino and sulfonic acid groups,and the influence of functional groups on the anti-irradiation stability of the material was investigated.Comparative studies based on X-ray diffraction（XRD）patterns and BET specific surface area characterization have shown that the order of the material’s anti-irradiation stability is:-H>-NH₂>-SO₃H.Further Fourier infrared spectroscopy（FT-IR）and X-ray photoelectron spectroscopy（XPS）characterization analysis showed that although the inorganic unit centered on the metal with high atomic number（Cr）as the metal center had strong anti-irradiation stability in a high-doseβ-irradiated environment,the difference in irradiation stability for the material structure modified by functional groups was mainly attributed to the change in the stability of the coordination chemical bond between the organic ligand and the metal ion.For different organic ligands functionalized by-H,-NH₂and-SO₃H,due to their different non-polar surface areas（-H>-NH₂>-SO₃H）,the chemical bond strength between the organic ligand and the metal cluster is different,which in turn makes the material show different structural stability.2.Using Ui O-66（Zr）as the parent material,the anti-irradiation stability of seven modified functional groups on the material structure and their removal performance on radioactive metal nuclides were systematically studied.The stability sequence based on XRD and BET specific surface area characterization analysis is:-（OH）₂>-（COOH）₂>-H>-NH₂>-COOH>-OH>-NO₂.Through FT-IR and XPS characterization analysis,it can be seen that Zr-based inorganic clusters have excellent anti-irradiation stability,and it is found that the effects of functional group modification on improving the structural stability of materials are:functionalization of double groups>functionalization of no groups>functionalization of single groups.This result can also be mainly attributed to the difference in the non-polar surface area of organic ligands:the larger the non-polar surface area,the greater the interaction with metal ions,the higher the chemical bond strength,which in turn makes the huge energy generated byβparticles during inelastic scattering more difficult to damage the chemical bond between metal and organic ligand.In addition,based on Ui O-66 and Ui O-66-（COOH）₂,two materials with excellent irradiation stability,uranium ion adsorption experiments were carried out on the material samples exposed to different intensity irradiation,and it was found that the adsorption capacity did not change significantly before and after irradiation,indicating that these two MOF materials have good application potential in the removal of radionuclides.3.Based on the Al-MOF material synthesized by solvothermal method,its anti-irradiation behavior and selective removal and recovery properties of thorium ions were studied.The experimental results show that under the conditions of p H=5.0 and room temperature,when the initial concentration of thorium ions in the aqueous solution is 400 mg/L,after about 100 min,the material shows adsorption equilibrium behavior,and the saturated adsorption capacity can reach 1302.42 mg/g,and it is found that the adsorbed material had good elution and cyclic adsorption effects in 0.01M nitric acid（HNO₃）solution.Since the adsorption experimental data are suitable for description by Langmuir model,it is indicated that Th（IV）mainly forms monolayer adsorption in Al-MOF materials.The adsorption process of kinetic experiments is more consistent with the quasi-secondary kinetic equation,indicating that chemical action plays a dominant role in its adsorption process.In addition,under the competitive adsorption conditions of multiple metal ions,the adsorption efficiency and selectivity of Al-MOF for Th（IV）ions can still be maintained at a high level,thereby showing good separation selectivity for Th（IV）,and the adsorption performance of the material afterβirradiation at a dose of 1000 k Gy is comparable to that of the sample before irradiation.These research results show that Al-MOF is an excellent adsorbent material with broad potential application value in the field of radionuclide adsorption and recovery.