Synthesis Of Amidoxime Styrene Acrylonitrile Hypercrosslinked Copolymer And Its Uranium Adsorption Properties

In recent years,in order to meet the growing energy demand,nuclear energy,as an energy with great potential,has been vigorously developed.However,the radioactive wastewater containing uranium produced by the nuclear industry has a great impact on the environment.In order to prevent the diffusion of radionuclides in the environment,effective uranium pollution control methods are needed.Adsorption technology has the characteristics of simple process,easy operation and high removal rate.It is considered to be a feasible method to remove radioactive elements from aqueous solution.Hypercrosslinked polymer is a three-dimensional microporous polymer with rich microporous structure,high specific surface area and adjustable pore size.It is a good adsorption material.Because of its excellent selectivity for uranium ions,the adsorbent with amidoxime group is considered to be a suitable adsorbent for the removal of uranium in water,and has been widely studied.In this paper,hypercrosslinked styrene acrylonitrile polymer was prepared with styrene acrylonitrile copolymer（SAN）as raw material,anhydrous ferric chloride（Fe Cl₃）as catalyst,1,2-dichloroethane（DCE）and biphenyl dichlorobenzyl（BCMBP）as crosslinking agents,respectively（HCPSAN-D,HCPSAN-B）,and then further amidoximation and alkali treatment were carried out to obtain the products,which are recorded as HCPSAN-D-AO-KOH and HCPSAN-B-AO-KOH.The products were characterized by FT IR,water contact angle,TG,BET and XPS,indicating the successful preparation of the materials.According to the characterization results,it can be seen that HCPSAN-B-AO has a larger specific surface area and pore volume than HCPSAN-D-AO,which is mainly due to cross-linking The molecular size of BCMBP is larger than that of DCE and the molecular structure is more rigid,which makes the chain spacing of SAN larger,the pore size larger and the pore structure more stable after hypercrosslinking,which is conducive to improving the amidoximation degree of the material and the adsorption performance of the material.The uranium adsorption properties of HCPSAN-D-AO-KOH and HCPSAN-B-AO-KOH were studied.When the amount of adsorbent was 5 mg,the temperature T=25℃,the p H value was 8,the adsorption time was 60 min,and the concentration of uranium solution was100 ppm,the maximum uranium adsorption capacity of HCPSAN-D-AO-KOH was 122 mg/g,and the maximum uranium adsorption capacity of HCPSAN-B-AO-KOH was 227 mg/g.The increase of adsorption capacity is because HCPSAN-B-AO-KOH has a higher degree of amidoximation than HCPSAN-D-AO-KOH,and the hydrophilicity,specific surface area and pore structure of the material are greatly improved.The adsorption kinetics and thermodynamics of U（VI）adsorption of HCPSAN-D-AO-KOH and HCPSAN-B-AO-KOH were studied.The results showed that the adsorption of U（VI）by HCPSAN-D-AO-KOH and HCPSAN-B-AO-KOH accorded with quasi second-order kinetic model and Langmuir model,so the adsorption process belongs to monolayer chemisorption.According to the thermodynamic fitting diagram and parameters,ΔG⁰<0 indicates that the adsorption process of U（VI）ions is a spontaneous process.in additionΔH⁰>0 indicates that the adsorption process of U（VI）ions is an endothermic process.