The Study On The Adsorption Behavior Of U(Ⅵ) By Hydrostability Metal-Organic-Framework HKUST-1@Polymer Composite

Metal-Organic-Frameworks（MOFs）is a new type of porous material that has developed rapidly in recent years.Because of the advantages of high porosity,controllable structure and easy modification,it has shown broad application prospects in the fields of proton conduction,chemical sensing,catalysis,energy storage and adsorption separation.However,the relatively low metal coordination bond strength of MOFs（such as HKUST-1）leads to poor hydrostability of the framework,which limits the application of MOFs in water environments to a certain extent.In this paper,HKUST-1 is used as the base MOFs material,and the covalent compounding and foaming strategies are used to compound with polyacrylic acid（PAA）and carboxymethyl cellulose（CMC）.Two kinds of materials with different quality are obtained.Compared with the HKUST-1@PAA and HKUST-1@CMC composites,it intends to break through the bottleneck restricting the practical application of the poor hydrostability of MOFs,and is used for the adsorption and separation of radionuclide U（VI）.The physical and chemical properties of HKUST-1@PAA and HKUST-1@CMC were characterized by SEM,FT-IR,Raman spectroscopy and N₂ adsorption-desorption isotherms.The results show that the crystal form of HKUST-1 in the composite is intact and maintains a high degree of crystallinity.The introduction of PAA and CMC can significantly improve the hydrostability of HKUST-1.HKUST-1 began to collapse after being suspended in water for 30 min,while HKUST-1@polymer composites can exist stably for 12 h,and even maintain high crystallinity at p H 3.0.The effects of p H value,contact time,initial concentration of U（VI）and competing ions on the adsorption of U（VI）on HKUST-1@PAA and HKUST-1@CMC composites were investigated through static batch experiments.The results show that the adsorption process is greatly affected by the p H value and is p H-dependent.Different polymers also have a greater impact on the adsorption rate.PAA can extend the adsorption equilibrium time to180 min,while CMC can allow adsorption to reach equilibrium within 10 min.The adsorption of U（VI）by HKUST-1@PAA and HKUST-1@CMC is in accordance with the pseudo-second-order kinetics,indicating that the adsorption is greatly affected by chemical action.When HKUST-1 is dominant in the composites,the adsorption conforms to the Langmuir isotherm model,which is a single homogeneous adsorption process.In the presence of a series of competing ions,the two composites both show better affinity and higher selective adsorption capacity for U（VI）.In addition,a mixed derivative membrane of HKUST-1@CMC was prepared by casting method and a dynamic membrane separation experiment was carried out.The results showed that in the range of p H 2.0-4.5,the removal percentage of U（VI）by the derivatized membrane was above 90%.Using 0.1 mol·L^-1 Na₂CO₃ as the eluent,the removal percentage of U（VI）by the derivative membrane remained stable above 80%after 4 adsorption-desorption cycles,showing the potential for practical applications.The above results show that the introduction of polymers PAA and CMC can significantly improve the hydrostability of HKUST-1,and the composite exhibits good adsorption and separation capabilities for U（VI）.In addition,due to the characteristics of polymers,composites can also be made into hybrid derivative membranes.Derivative membranes have good dynamic membrane separation capabilities for U（VI）.This research provides a new idea for the development and application of MOFs with hydrostability that can be used for the adsorption and separation of radionuclides.The above results show that by combining PAA and CMC with HKUST-1,the hydrostability of HKUST-1 can be significantly improved,and the material exhibits good adsorption and separation ability for U（VI）.In addition,due to the characteristics of polymers,composite materials can also be made into hybrid derivative membranes.Derivative membranes have good dynamic membrane separation capabilities for U（VI）.This research provides a new idea for the development and application of MOFs materials with hydrostability that can be used for the adsorption and separation of radionuclides.