Preparation Of SiO₂-functionalized UiO-66-（OH）₂ And Its Adsorption Properties For Uranyl Ions

Traditional fossil energy is a non renewable resource,and it will produce a large number of greenhouse gases when used,which will endanger the earth’s environment.With the increasingly serious problem of global warming and China’s goal of carbon neutrality by 2060,nuclear energy has become an important part of China’s energy structure.Uranium mining produces a large amount of wastewater containing uranium,which is characterized by complex components,low uranium concentration and many coexisting ions.If it is not reasonably disposed,radionuclide uranium will migrate and diffuse to the biosphere with surface runoff and underground seepage,causing radioactive pollution to the ecological environment and waste of uranium resources.Therefore,the separation of wastewater containing uranium enrichment process,for the environmental protection and uranium resources of our country economy has the vital significance.In 2007,Lillerud et al.Found a MOFs material Ui O-66（Ui O=University of Oslo）with ultra-high stability.Since then,the research focus of uio-66 has mainly focused on grafting new chemical groups on uio-66 skeleton to expand its application field.SiO₂ is regarded as an excellent functional material with rich morphology and pores,good compatibility and easy modification.In order to further improve the performance of SiO₂,many scholars introduce SiO₂ into MOFs and combine their advantages to obtain a stable and efficient new functional nanocomposite.Therefore,a new MOFs composite was synthesized and functionalized with SiO₂.By SEM,XRD,FT-IR and TGA for characterizing the structure of the two materials,inspected the two materials under different conditions of U（VI）adsorption performance.The main research contents and conclusions are as follows:（1）In this paper,the metal organic framework material Ui O-66-（OH）2 was synthesized by hydrothermal synthesis.The adsorption properties of Ui O-66-（OH）2 for U（VI）under different initial conditions were studied.The results show that the optimum adsorption conditions are p H=6,adsorption time 5 h,adsorption temperature 303 K,initial uranium concentration 40 mg·L^-1 and Ui O-66-（OH）2 dosage 5 mg.Under these conditions,the maximum equilibrium adsorption capacity can reach 205.74 mg·g^-1.The adsorption conforms to the quasi second-order kinetics and Langmuir adsorption model,which reflects the characteristics of monolayer chemical adsorption,and Ui O-66-（OH）2 shows good selectivity for U（VI）under the condition of coexistence of multiple ions.The above results show that Ui O-66-（OH）2 has good adsorption performance for U（VI）.（2）UiO-66-（OH）2 was functionalized with SiO2 and 3-aminotrimethylsila ne as raw materials.The effects of SiO2/Ui O-66-（OH）2 on the adsorption of U（VI）under different initial conditions were studied.The results show that the o ptimum adsorption conditions are p H=6,adsorption time 2h,adsorption temp erature 303 K,initial uranium concentration 35 mg·L^-1 and adsorbent dosage 5mg.Under these conditions,the maximum equilibrium adsorption capacity ca n reach 263.93 mg·g^-1.Compared with Ui O-66-（OH）2,the adsorption capacity is increased by 58.19 mg/g.The adsorption conforms to the quasi second-order kinetics and Langmuir adsorption model,which reflects the characteristics of monolayer chemical adsorption.Under the condition of coexistence of multipl e ions,SiO2/Ui O-66-（OH）2 shows good selectivity for U（VI）.The above resul ts show that SiO2/Ui O-66-（OH）2 has good adsorption performance for U（VI）,s o it can be regarded as an economic and practical U（VI）adsorption material.