Preparation Of Amidoximed Polyethylene Nanofiber Membrane And Application Research Of Uranium Extraction From Seawater

With the development of economy,human society will be more dependent on the stability of energy.Meanwhile,the establishment of the goal of "carbon peak and carbon neutrality" also puts forward new requirements for energy use,namely reducing the proportion of fossil energy use and expanding the proportion of clean non-carbon energy use.Nuclear energy,a kind of green non-carbon energy with high energy density,can solve the energy crisis and environmental problems very well.To ensure a steady supply of nuclear energy,it is necessary to ensure a steady supply of nuclear fuel uranium.As much as 450 million tons of uranium are stored in the seawater,1000 times the reserves on land,which can ensure human use for nearly 10,000 years.It will be an inexhaustible nuclear energy treasure house!Therefore,this paper studies and explores the main scientific problems in the process of seawater uranium extraction,namely,the efficient adsorption of uranium in the ocean with very low uranium concentration,the preparation of uranium extraction materials with high mechanical strength in response to complex marine environment and the preparation of uranium extraction materials with rapid adsorption to cope with biological deposition.Polyethylene nanofiber membrane (named PENFM) has large specific surface area and high mechanical strength,which is a good base material for uranium extraction from seawater.This paper focuses on the modification of PENFM to prepare functionalized membrane adsorbents.The main research contents and results of this paper are as follows:(1) By using radiation induced graft polymerization (RIGP) method,acrylonitrile(AN)/acrylic acid (AA) monomer was grafted onto the surface of PENFM,and then the functionalized PENFM was prepared by amidoximation reaction.In this paper,the maximum adsorption capacity can reach 163.18 mg/g for 72 h under the experimental conditions,which can be reused for 10 times,and the mechanical properties are up to 54.59 MPa.The AM adsorbent prepared in this paper is adsorbed in seawater for 70 days,and its uranium extraction performance is up to 6.03 mg/g.The results of this paper show that the AM adsorbent prepared by one-step RIGP method has high performance of uranium extraction from seawater and reusability.(2) The amidoximed PENFM adsorbents were fabricated using a two-step graft polymerization involving the RIGP of HEA onto the commercial PENFM to form polyhydroxyethyl acrylate chain (PHEA) and the CAN initiated graft polymerization(CIGP) of AN and AA onto the PHEA chains.Finally,the functionalized PENFM was prepared by amidoximation reaction.In this paper,the adsorption-desorptionregeneration experiments in laboratory conditions show that AFM has the properties of efficient adsorption,rapid desorption and multiple use.Under the experimental conditions in this paper,the adsorption performance of the AFM can reach 156.2 mg/g for 96 h,the adsorption can be repeated 12 times,and the mechanical properties can reach 75 MPa.The AFM adsorbent prepared in this paper has a 70 day sea test result of 8.34 mg/g.The results of this paper show that AFM prepared by two-step RIGPCIGP method has great application potential in uranium extraction from seawater.(3) Using RIGP-CIGP grafting method to modify functional groups on the surface of PENFM,membrane adsorbent materials with different degree of grafting,different membrane thicknesses and different molecular chain conformations were prepared.The study on the properties of uranium extraction from seawater showed that:(i) Adsorbents with degree of grafting of 37.03%,52.46%,71.26%,106.32%,180.74%,313.90% and 401.86% were prepared,and the results of 30-day sea test were 3.09,3.67,3.65,3.87,3.33,2.68 and 2.35 mg/g,respectively.The results show that there is not a simple linear relationship between adsorption performance and degree of grafting,and there is an optimal degree of grafting.(ii) 5-AFM,9-AFM,16-AFM and 20-AFM adsorption materials with substrate membrane thickness of 5,9,16 and 20 μm were prepared,and the real seawater adsorption results of 56 days were 7.46,3.85,2.25 and 2.05 mg/g,respectively,indicating that the ultra-thin membrane is beneficial to improve the adsorption performance.(iii) AFM-15k,AFM-55k,AFM-110k and AFM-180k with different surface structures were prepared by irradiating PENFM at doses of 15,55,110 and 180 kGy.The adsorption properties of simulated seawater under laboratory conditions for 96 h are 156.42.220.94,198.88 and 1 84.73 mg/g,respectively,indicating that too dense and sparse functional adsorption groups are not conducive to the adsorption of uranium by the adsorbent.(4) Ultrathin PENFM (named UTPENFM) was prepared by biaxial tensile method.and ultrathin membrane adsorption material (named AO-UTPENFM) was prepared by RIGP-CIGP grafting method,which has a rapid adsorption property for uranium.The adsorption performance was as high as 172.88 mg/g after adsorption in 8 ppm simulated seawater for 6 h.The adsorption capacity of AO-UTPENFM adsorbent prepared in this paper is 3.38 mg/g in the 7-day sea test.The results of this paper show that the AOUTPENFM adsorption material has high efficiency and rapid adsorption capacity,which provides a new idea for the preparation of seawater uranium extraction materials.