Preparation Of Functional Mental Organic Frameworks And Adsorption Properties For U(?)

Uranium is one of the most important industrial and military materials with 17isotopes in nature,most of which are ²³⁸U and ²³⁵U.However,many applications of nuclear materials will produce radioactive pollution,such as:nuclear power plants will produce radioactive waste water,raw material mining,nuclear accidents and nuclear leakage,in addition,the technology of extracting uranium from seawater and salt lake brine has been a difficult problem to solve.Therefore,reasonable treatment of nuclear pollutants is of great significance to environmental protection and human health,as well as to promote the recycling of resources and the development of modern nuclear industry.Metal-organic frameworks?Mental-Organic-Frameworks?have the characteristics of large specific surface area,easy adjustment of pore size and easy modification of functional groups.They are very suitable as U???adsorbents in water to enrich uranyl in aqueous solution.In this paper,easily available of two simple UiO-66 materials were synthesized by changing different ligands.Using different characterization methods and intermittent adsorption experiments,the adsorption process of U???was explored,and the adsorption mechanism was speculated.The experimental results show that the maximum adsorption capacity of UiO-66 for U???is 327.3 mg/g,the maximum adsorption capacity of UiO-66-PYDC is 565.6 mg/g,and the material adsorption process is spontaneous.Because UiO-66 has the characteristics of small adsorption pH range and low adsorption capacity,we tried to synthesize NH₂-MIL-125 material,and tried to make the material loaded with TiO2 and then phosphorylated to obtain a functionalized new composite material NH₂-MIL-125-P@TiO₂,by loading TiO₂ in the voids of MOF and preparing phosphoric acid shell on the surface to strengthen the adsorption capacity of uranyl.The static adsorption experiment shows that the pH range of the modified material's optimal adsorption has been significantly expanded,from 7-8 to 5-10,and the material's adsorption capacity has been doubled compared with the material before modification.The experimentally obtained thermodynamic model parameters such as?G,?H,and?S indicate that the material's adsorption of uranium is a spontaneous endothermic process,and the maximum adsorption capacity of the simulated parameter fitting is up to 614.82 mg/g.In order to find a kind of uranium adsorbent which can adapt to the complex environment of various ions and has larger adsorption capacity to extract uranium from seawater and salt lake brine,we tried to calcinate the material with MOFs as a template and synthesize new porous materials while retaining the original framework structure of MOFs.Since the uranium core commonly used in the world is UO₂·Gd₂O₃ material,if gadolinium salt can be used as raw material to make adsorbent,it is of great significance for uranium extraction in nuclear industry and environmental protection.In the experiment,synthetic MOF-76?Gd?was used as template,and porous layered gadolinium oxide??-Gd₂O₃?material was obtained by high-temperature calcination.The adsorption capacity of the material in different aqueous solutions was investigated.Compared with the ordinary nano-Gd₂O₃,the specific surface area of the material was more than doubled,and the adsorption capacity was increased by 30%.Compared with MOF-76?Gd?,the adsorption capacity of the material It has been improved by nearly6 times,and the adsorption effect of the material in groundwater and seawater is still very good.The optimal adsorption pH range is 3-4.5,which is calculated by kinetic fitting and thermodynamic models.The equilibrium adsorption time is 180 min,and the adsorption process is a spontaneous endothermic reaction.