Preparation And Adsorption For Uranium Of Pore Aromatic Framework Anion Exchange Resin

Uranium is mainly used to provide fuel for nuclear power plants.Alkaline wastewater will be produced at the front of the nuclear fuel cycle,in which uranium mainly exists in the form of uranyl carbonate anion.Removing the radioactive element uranium in the wastewater will reduce the long-term radioactive harm to various organisms and human beings,and at the same time,uranium resources can be saved.Porous aromatic framework?PAF?material has strong all carbon framework,high specific surface area,water stability and chemical stability.It can be used as a good matrix material in harsh environment.PPN-6 is a kind of porous aromatic skeleton material.Ionic liquid can be fixed on PPN-6 through chemical reaction with benzene ring on the skeleton to prepare supported solid ionic liquid?SILs?,which can be used as anion exchange resin for uranium separation in alkaline uranium-containing wastewater.In this paper,two kinds of quaternary phosphonium and two kinds of quaternary ammonium salts were fixed on the porous aromatic skeleton materials to form four kinds of ionic liquid functionalized materials,which were used for the adsorption of uranium in alkaline solution.In order to explore the influence of the length of carbon chain on the adsorption properties of uranium,the functional materials P-C2 and P-C4were synthesized with triethylphosphine and tributylphosphine respectively.In addition,the functional materials N-C2 and N2-C4 were synthesized by triethylamine and butanediamine,and compared with the materials of quaternary phosphonium.The functionalized ionic liquid synthesized by butanediamine increases the reaction site and plays a role in the cross-linking of materials.The structures of the four materials and PAF were characterized by FT-IR,SEM,EDS,N₂ adsorption and desorption,and the adsorption of[UO₂?CO₃?₃]^4-ion by four materials was studied.Among the four materials,P-C4,P-C2,N2-C4 and N-C2,P-C4 and P-C2 have good adsorption capacity for uranium,the maximum adsorption capacity is about 670mg/g,and the length of carbon chain has little effect on the adsorption performance of uranium.The maximum adsorption capacity of N2-C4 and N-C2 are 360 mg/g and140 mg/g,respectively,It can be seen that the adsorption performance of N2-C4 and N-C2 for uranium is not as good as that of P-C4 and P-C2,because the adsorption mechanism of the two kinds of materials is different.The adsorption property of N2-C4 is higher than that of N-C2,which indicates that the density of adsorption site of functionalized ionic liquid increases after crosslinking with butanediamine,and it can be seen from the SEM figure that the particle size of cross-linked functionalized material is larger than that of uncrosslinked material.Through the exploration of the equilibrium time of adsorption of uranium by four kinds of materials,it is found that two kinds of quaternary phosphonium reach equilibrium in 4 hours,triethylamine functional materials reach equilibrium in 20minutes,and butanediamine functional materials reach equilibrium in 4 hours The equilibrium was reached in one hour,and their adsorption kinetic data were fitted.The adsorption of the four materials was in accordance with the pseudo second-order kinetic model.It was revealed that the adsorption process was chemical adsorption,and it was confirmed by element analysis that this process was an ion exchange process,[UO₂?CO₃?₃]^4-ion exchanged Cl^-out of the material.When a variety of salts with different concentrations coexist with[UO₂?CO₃?₃]^4-ion,the quaternary phosphonium functional materials can effectively capture[UO₂?CO₃?₃]^4-ion,and their ion selectivity is better than that of the quaternary ammonium functional materials.All the four materials after uranium absorption can be eluted with dilute HCl easily,because[UO₂?CO₃?₃]^4-reacts with HCl to form UO₂²⁺,which is eluted from the material,and the Cl^-is exchanged again to achieve the purpose of desorption and regeneration.These advantages make quaternary phosphonium salt functionalized meterial a promising material for uranium separation from alkaline solution.