Preparation Of Functionalized Graphene Oxide-Based Materials And Study On Uranium Adsorption Properties

The safe supply of energy is related to the steady progress of society,the sustainable development of the economy and the successful application of high-tech technologies.The global increase in energy demand has led to the emergence of an energy crisis,which requires technicians,scientists and engineers to explore other new energy sources to meet this challenge.Among them,nuclear energy has become the most potential alternative energy source due to its clean and efficient characteristics.As one of the raw materials for nuclear energy,uranium is an extremely precious energy.Considering that our country's terrestrial uranium resources are poor and our country's geographical advantages are surrounded on three sides by the sea,it is of great significance to develop and utilize the abundant uranium resources in the sea rationally.The most critical step in the development of marine uranium resources is to design an efficient and low-cost adsorbent for uranium extraction from seawater.In this paper,graphene oxide is used as a substrate and functionally modified to synthesize three composite adsorption materials.The microscopic morphology and element composition of the adsorbent are analyzed by SEM,BET,TEM,FT-IR and XRD methods;The effect of p H of the solution,contact time of the adsorbent,initial concentration and system temperature on the adsorption performance was investigated through batch adsorption experiments;the adsorption process of the adsorbent is studied through the kinetic model and the thermodynamic model;the practical performance of the adsorbent is further investigated through the ion competition experiment and simulated seawater adsorption experiment.The experiment further investigates the practical performance of the adsorbent;finally,an in-depth exploration of the adsorption mechanism of the adsorbent material is carried out through XPS analysis technology.Using a simple one-step hydrothermal method,using phosphomolybdic acid as the source of molybdenum,and using thiourea as the source of sulfur and nitrogen,Mo S₂ was grown on the surface of GO under hydrothermal temperature of 160?to obtain a stable Mo S₂/N-r GO composite material.The optimal adsorption p H value of Mo S₂/N-r GO is 6.0,and the saturated adsorption capacity can reach 185.8 mg·g^-1 under the adsorption equilibrium time of 75 min,and the adsorption process conforms to the quasi-second-order kinetic equation and Langmuir adsorption model.In the ion competition experiment,Mo S₂/N-r GO showed good adsorption and selectivity to uranyl ions,and the partition coefficient could reach 1.29×10⁴m L·g^-1.After 6 cycles of adsorption and desorption experiments,Mo S₂/N-r GO still showed good removal efficiency.Under different low-concentration simulated seawater conditions,the removal rate of uranyl ions by Mo S₂/N-r GO was greater than 90.1%.XPS analysis results show that the adsorption process is mainly the S,O and N atoms on Mo S₂/N-r GO participate in coordination with uranium,thereby adsorbing uranium.The guanidine-based polymer polyhexamethylenediamine-polyethyleneimine(GHPEI)was synthesized by polycondensation,and then grafted on the surface of graphene oxide through the immobilization of polydopamine to obtain a material with a large amount of guanidine and amine groups on the surface.Compared with GO and DGO,GHPEI-DGO exhibits superior adsorption performance.Its optimal adsorption p H value is 6.0,adsorption equilibrium time is 78 min,saturated adsorption capacity is 192.62 mg·g^-1,and the adsorption process conforms to the quasi-second-order kinetic equation and Langmuir adsorption model.GHPEI-DGO has a high affinity for uranyl ions,and after 6 cycles of desorption,the removal rate can still be maintained at 77.2%.In low-concentration simulated seawater,GHPEI-DGO still shows a good removal performance of more than 87.14%for uranyl ions.XPS analysis results show that the nitrogen-containing functional groups(-N=,-NH and-NH₂)and oxygen-containing functional groups(-OH and-COOH)in GHPEI-DGO participate in the adsorption process of uranium.The tannin is cured by formaldehyde,and the urea containing amine groups is added through the polymerization reaction,and then the adhesion of the tannin is used to make it adhere to the surface of graphene oxide through covalent bonds to prepare urea-cured tannin Graphene oxide composite material(CBT-GO).The optimal adsorption p H of CBT-GO is 7.0,the saturated adsorption capacity is 188.56 mg·g^-1,and the adsorption process conforms to the pseudo-second-order kinetic equation and Langmuir adsorption model.After 6consecutive cycles of adsorption and desorption experiments,the removal rate of uranium by CBT-GO remained above 79.1%,and at the same time,it showed high affinity and selectivity for uranyl ions,with a distribution coefficient of up to 1.39×10⁴m L·g^-1.The removal rate of uranyl ions by CBT-GO measured in low-concentration simulated seawater can exceed86.42%.Finally,XPS spectrum analysis showed that the nitrogen-containing functional groups(-N=,-NH and-NH₂)and oxygen-containing functional groups(-OH and-COOH)in CBT-GO participated in the adsorption process of uranium.