| Nuclear energy,as a relatively green and efficient new energy,has made great progress in the past three decades.However,at the current rate of nuclear fuel consumption,the world’s uranium reserves will be exhausted within decades,and the process of mining uranium poses a potential threat to the environment.The 21 st century is the century of the ocean.Compared with the limited land resources,the ocean resources to be exploited are extremely rich.Extracting uranium in large quantities from seawater,which contains about1,000 times as much uranium as that on land,will be an effective way to cope with the current shortage of uranium resources and avoid the environmental pollution caused by current uranium mining.Although many highly efficient uranium sorbents have been developed,the vast majority of their uranium extraction capacity studies have been carried out in the laboratory using purified seawater.However,in the real Marine environment,the serious bioadhesion of bacteria/microorganisms and various shellfish will greatly reduce or even destroy the uranium extraction performance of the adsorbent.In addition,the complex environments such as waves,tides,ocean currents and so on also requires the adsorbent to have high enough strength.Therefore,it is urgent to develop a new type of bio-adhesive and high-strength adsorbent with high efficiency for uranium adsorption in natural seawater.In this study,the antimicrobial quaternary ammonium salt functionalized chitosan/ramie fiber was combined with polyamidoxime to design the ultrathin films and hydrogel films with good anti-bacterial(anti-biofouling)properties,high strength and high uranium adsorption,respectively.This study will provide a highly efficient and low-cost adsorbent for uranium extraction in natural marine environment,and will also inspire the development of other novel highly efficient uranium adsorption,which has important theoretical significance and potential application value.The main research contents of this study are as follows:(1)By dispersive quaternized chitosan(Q-CS)and polyamidoxime(PAO)in crosslinked sulfonated cellulose nanocrystalline(S-CNC)network,an ultra-thin polyamidoxime film(AUPM)with high adsorption performance was prepared.Cross-linked S-CNC can not only improve the hydrophilicity of AUPM,improve its uranium adsorption efficiency,but also enhance the mechanical strength,forming a self-supporting ultrathin film(10 μm thickness,tensile strength 17.21 MPa).More importantly,because the Q-CS has a large number of quaternary ammonium groups,AUPM has a broad spectrum of anti-bacterial properties and subsequently good anti-bioadhesion.Compared with the blank membrane without Q-CS,the uranium adsorption capacity of AUPM increased by 37.4% to 8.78 mg/g after 25 days of immersion in natural seawater.In addition,the mechanical strength of AUPM remained basically unchanged during the 10 cycles of adsorption-desorption.(2)Furthermore,a high-performance composite hydrogel membrane uranium adsorbent(RPHM)with good bioadhesion resistance and high strength was prepared by combining ramie natural fiber fabric with amidoxime functionalized polymer.Ramie fiber has a wide spectrum of effective antibacterial properties,which can effectively resist various kinds of biological adhesion in the sea for a long time.The extremely high strength gives the composite hydrogel membrane very high mechanical properties(340 μm thickness,tensile strength 35.26 MPa).Compared with blank hydrogel membrane without composite ramie fiber,the adsorption capacity of uranium increased by 33.5% after 25 days of RPHM immersion in natural seawater,reaching 5.18 mg/g.In addition,the mechanical strength of RPHM remained basically unchanged during the 10 cycles of adsorptiondesorption. |
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