Functional Modification Of MIL-101 And Study On Uranium Adsorption Performance

As a kind of energy with low pollution and high efficiency,nuclear energy has been widely used in all aspects of production and life.Uranium is the main source of nuclear energy,but China’s rare land uranium resources will limit the development of nuclear energy in China.There are a lot of uranium resources in seawater,so reasonable development and extraction of uranium from seawater will greatly alleviate the current situation of uranium shortage in China.Efficient uranium adsorption material is the key to the extraction of uranium from seawater,which requires both high specific surface area and efficient chelating groups.In this paper,a series of highly efficient,selective and recyclable uranium adsorption materials were prepared by combining metal organic frameworks with amidoxime or amino acids.（1）The amidoxime modified MIL-101 adsorbent（MIL-101-AO）was prepared by chloromethylation of MIL-101 and reaction with diaminomaleonitrile and hydroxylamine hydrochloride.The synthesized materials were characterized by SEM,FT-IR,BET and XPS.The results of morphology analysis show that the crystal structure of the original MOF is preserved,and the disruption to the crystal morphology caused by the post modification process is minimized,by carefully controlling the reagent concentration and experimental temperature.MIL-101-AO has a high adsorption efficiency for U（VI）in aqueous solution,with a uranium adsorption capacity of 549 mg·g^-1,according to the results of uranium adsorption experiments.The adsorption process of uranium conforms to the Langmuir and pseudo-second-order kinetics model,which indicates that it is a monolayer chemical adsorption process.MIL-101-AO also showed excellent selective adsorption capacity for U（VI）in artificial seawater（removal rate of 96%）.The results of XPS suggest that amidoxime group can effectively coordinate with uranyl ion.MIL-101-AO is a highly efficient and recyclable adsorbent for uranium extraction from seawater.（2）Three new types of uranium adsorbents,MIL-101-Gly,MIL-101-His and MIL-101-Cys,were prepared by the reaction of environmentally friendly amino acids（glycine,histidine and cysteine）with MIL-101-CM and characterized systematically.The results of morphology analysis indicate that although the specific surface area of the three materials decreases,the crystal morphology remains intact.The results of adsorption experiments indicate that all three adsorbents have strong uranium adsorption capacity and selectivity,with MIL-101-His having the better two outputs(adsorption capacity of 345mg·g^-1,uranium removal rate of 75.2%under coexisting ions);in comparison,MIL-101-Gly and MIL-101-His have good recycling performance.The results show that the adsorption process of uranium on the three new adsorbents conforms to the Langmuir model and the pseudo-second-order kinetics model,indicating that the adsorption process is monolayer and dominated by chemical action.XPS analysis results prove nitrogen and oxygen in amino acids participate in the coordination with uranyl ion,which endows the adsorbent with high efficiency of uranium adsorption.