Study On The Preparation And Uranium Adsorption Properties Of Functionalized MIL-101 Metal Organic Framework Material

With the increased of global environmental pollution caused by the large-scale use of fossil energy,nuclear energy as a clean energy has received more and more attention from all countries in the world.As a main source of nuclear energy,uranium resources urgently need to find a stable and sustainable supply method.There are 4.5 billion tons of uranium in the ocean,which is 1000 times of terrestrial uranium.However,the existence of low concentrations of uranium resources in seawater and the interference of multiple coexisting ions severely restrict the extraction of uranium resources from the ocean.Therefore,the development of adsorption materials with high selectivity,high adsorption capacity and rapid adsorption rate is of great significance for the development and utilization of uranium resources in the ocean.In this paper,MIL-101?Cr?metal-organic framework materials were used as raw materials to prepare three kinds of adsorbent materials by functional treatment:MIL-101-AO,DSHM-DAMN,MIL-101/PVA,and their structures and uranium adsorption performance were studied respectively.The amidoxime functionalized MIL-101 adsorbent?MIL-101-AO?was prepared by unsaturated metal site coordination method and amine deuteration treatment.The synthesized material has regular octahedral structure and the surface area is2103 m² g^-1.when the pH is 8 at25?,the adsorption equilibrium time is 25 min,which has a fast adsorption rate.The saturated adsorption capacity is 476 mg g^-1,the adsorption mode accords with quasi-secondary kinetic adsorption model and Langmiur isotherm adsorption model;ion competition experiments shows that MIL-101-AO has excellent selectivity to uranyl ions which the removal rate of uranyl ions exceeds 90%.Double-shelled hollow MIL-101 metal organic framework material?DSHM?was prepared by step-by-step synthesis and subsequent acid etching.The diaminomaleonitrile functionalized double layer hollow MIL-101 adsorbent material?DSHM-DAMN?was prepared by unsaturated metal site coordination method.The optimum adsorption pH of DSHM-DAMN is8 and its adsorption performance is better than MIL-101-AO material.The saturated uranium adsorption capacity is 601 mg g^-1 at 25?.The adsorption mode also accords with quasi-secondary kinetic adsorption model and Langmiur isotherm adsorption model which accords with quasi-secondary kinetic adsorption model and Langmiur isotherm adsorption model;By XPS analysis,it is speculated that the nitrile group and the amino group in the diaminomaleonitrile functional group participate in the coordination of the uranyl ion.MIL-101/polyvinyl alcohol composite hydrogel material?MIL-101/PVA?was synthesized by doping physical cross-linking method.The composite material has a porous three-dimensional network structure,and MIL-101 crystal particles are accumulated in the pores.When the pH of the material is 8 at 25?,the adsorption capacity of saturated uranium can reach 511 mg g^-1,which exceeds the adsorption capacity of pure MIL-101 and PVA materials,and also accords with quasi-secondary kinetic adsorption model and Langmiur isotherm adsorption model.In the dynamic adsorption process,MIL-101/PVA reached the adsorption amount saturation within 20 days,and its equilibrium adsorption amount was about 1.25 mg g^-1.After five cycles of adsorption,the adsorption performance only slightly decreased,thus MIL-10/PVA has good practical application ability,overcoming the difficulty that the powdered MIL-101 material is hard to recycle.