Preparation Of Modified Polyacrylonitrile Membrane And Its Removal Performance For Uranium In Simulated Uranium-Containing Wastewater

The closed nuclear fuel cycle is of great significance for ensuring the long-term stable development of nuclear industry.However,in this cycle,a large amount of uranium-containing waste liquid is generated,and direct discharge of these waste liquid not only affects the ecological environment but also endangers human health.Effectively extracting and recovering uranium from uranium-containing waste liquid is not only beneficial for environmental protection,but also can further meet the strategic needs of nuclear power development for uranium resources.Membrane adsorption method is a newly emerging method for wastewater treatment in recent years.In the process of material preparation,the separation membrane not only needs to have good adsorption performance,but also strong mechanical properties to withstand the driving force generated by external pressure or concentration difference on both sides of the membrane.In order to prepare separation membrane with good adsorption performance and high mechanical strength,this paper first prepared polyacrylonitrile separation membrane（PM）using impregnation precipitation phase conversion method,and then prepared aminated polyacrylonitrile separation membrane（DPM）and amidoxime polyacrylonitrile separation membrane（APM）using bulk modification method.The static adsorption performance,dynamic filtration performance,and uranium removal performance of the two kinds of membranes were experimentally tested.At the same time,this article also compared the uranium removal performance of DPM,APM,PM,and commercial ultrafiltration membrane,and analyzed the advantages and disadvantages of the two modified membranes.The specific exploration content and main conclusions were as follows:Using Diethylenetriamine（DETA）for bulk modification of PM,the DPM was prepared.The nitrile conversion rate of the DPM was 17.72%,and the tensile fracture stress was 0.6650MPa.During static adsorption,the equilibrium adsorption capacity was 63.16 mg·g^-1.After continuous filtration for 5 hours under different pressures,the rejection rate of uranium by the DPM remained above 95%,with a maximum of 100%.When the operating pressure was 0.5MPa,the maximum membrane flux was 20.7 L/（m²·h）.In addition,the removal rate of uranium by DPM in simulated uranium-containing wastewater was 96.50%,and the removal rates of Cr,Cu,and Fe elements were also as high as 95.58%,86.52%,and 62.75%,respectively.To further improve the adsorption performance of the membrane,hydroxylamine hydrochloride（NH₂OH·HCl）was used to modify the PM and the APM was prepared.The nitrile conversion rate of APM was 43.90%,and the tensile fracture stress was 0.3350 MPa.The equilibrium adsorption capacity during static adsorption was 152.23 mg·g^-1.After continuous filtration for 5 hours under different pressures,the rejection rate of uranium by APM remained above 95%,with a maximum of 100%.When the operating pressure was 0.5 MPa,the maximum membrane flux was 6.21 L/（m²·h）.In addition,the APM had a high removal rate of 96.96%for uranium in simulated uranium-containing wastewater,and the removal rates for Cr,Fe,and Cu elements were also as high as 99.22%,84.85%,and 54.24%,respectively.In the comparison of uranium removal efficiency among DPM,APM,PM,and commercial ultrafiltration membrane,it was found that APM had the best static and dynamic uranium removal efficiency,with an adsorption capacity of 158 mg·g^-1 at static state and a rejection rate of 100%at dynamic state.However,the removal efficiency of uranium by PM membrane and commercial ultrafiltration membrane was almost zero.The above experimental results indicated that both the prepared DPM and APM had good mechanical properties and high uranium removal performance.However,the modification conditions of APM were milder,and the uranium removal effect was better.Besides,the preparation process of APM was simple,and it had better application prospects in the field of uranium-containing waste liquid treatment.