| Nuclear power,as a new type of clean energy,has continuously improved its importance in the global energy strategy,and it is expected to be used to solve the energy and environmental pollution problems that mankind is facing at this stage.In order to ensure the sustainable development of nuclear energy,it is urgent to solve the shortage problem of nuclear fuel uranium resources.Seawater contains about 4.5 billion tons of uranium,which is approximately 1,000 times that of terrestrial uranium resources.Therefore,extraction of uranium from seawater has become a key strategy to deal with the shortage of terrestrial uranium resources,and the researches on this topic have been developed for six or seven decades.In recent years,more and more countries have paid attention to it and made great progress.However,the adsorbents used for uranium extraction from seawater are severely contaminated by the ocean,resulting in a significant decrease in the mechanical properties and adsorption properties.Up to now,there have been related researches on anti-biofouling adsorbents for extracting uranium from seawater,and the anti-biofouling mechanisms mainly contain antibacterial/anti-algae and anti-adhesion.The antibacterial/anti-algae mechanism is to affect or destroy the structure of the organism,leading to the death of the organism;the anti-adhesion mechanism is to give the material surface super-hydrophilicity,leading to reduced interaction force between the material and the organism,and preventing the organism from being on the surface of the material Attached.However,the reported antibacterial/anti-algae adsorbents are mostly modified by caducous antibacterial nano particles,antibiotics,or single molecule antibacterial groups with relatively poor antibacterial activity.Moreover,the reported anti-adhesion adsorbents with relatively low degree of functionalization,resulting in poor anti-adhesion property.Therefore,the anti-biofouling activity and long-term stability of the anti-biofouling adsorbents need to be improved at this stage,and they are far from reaching the requirements for long-term uranium extraction from seawater.In addition,the reported anti-biofouling adsorbents have poor adsorption performance,which makes such adsorbents unable to be used for large-scale marine tests.Therefore,it is highly urgent to carry out research work on uranium adsorbents with enhanced anti-biofouling activity and adsorption performance.In view of the poor anti-biofouling and adsorption performance of adsorbents for uranium extraction from seawater at this stage,in this paper,it is proposed to introduce functional groups with better antibiofouling and adsorption affinity with uranyl into the matrix material to improve the comprehensive performance of the adsorbents.In this paper,three anti-biofouling adsorbents for uranium extraction from seawater were prepared with antibacterial polymers and anti-adhesion phosphorylcholine functional group by chemical methods.Based on the results of the systematically characterization and tests on adsorbents,the problem of poor anti-biofouling and adsorption performance of uranium extraction materials from seawater at this stage have been solved.This paper proved that the introduction of antibacterial polymers endows the adsorbents with good antibacterial properties and improves the adsorption performance of the adsorbents at the same time.By cross-linking the antibacterial polymer polyhexamethylene guanidine hydrochloride(PHGC)with the polyacrylamide-acrylonitrile(PAM-AN)polymer matrix,and followed by the amidoximation of the cyano groups,the polyguanidine modified antibacterial uranium adsorbent PAM-AO-PHGC is prepared.This is the first time that antibacterial polymers are used in uranium adsorbent.The experimental results prove that the introduction of antibacterial polymer PHGC endows the adsorbent with excellent antibacterial properties,and the adsorbent has good antibacterial properties against four typical bacteria with high antibacterial rate reached 100%.Compared with the adsorbent without grafting PHGC,the adsorption capacity of PAM-AO-PHGC is improved.And the adsorption capacity of PAM-AO-PHGC reaches 231.0 mg/g in simulated seawater with high ionic concentration.This paper obtained anti-biofouling uranium adsorbents with the best comprehensive performance and practicality at this stage.And the anti-biofouling adsorbents are used for the kilogram-grade marine test for the first time.By grafting PHGC onto commercial acrylic fiber with hydrothermally methods,and followed by the amidoximation of the cyano groups,the polyguanidine modified antibacterial adsorbent,PAO-G-A,is finally prepared.This is the first time that antibacterial polymers are introduced into fibrous adsorbents for uranium extraction.The experimental results show that the introduction of guanidine groups gives PAO-G-A excellent antibacterial properties.PAO-G-A shows good antibacterial broad-spectrum properties against five common bacteria,and its antibacterial rate against high-concentration marine bacteria is as high as 99.46%.Since the guanidine group contains a large number of amine groups,it has a synergistic effect with the amidoxime group,which effectively improves the adsorption performance of the adsorbent.The theoretical value of the saturated adsorption capacity of PAO-G-A in uranium solution at 25? is 684.3mg/g,and the adsorption capacity in simulated seawater with high ionic concentration is 261.1 mg/g.Moreover,it has good selectivity for uranium in a multi-competitive adsorption system.In addition,after five cycles of testing,PAO-G-A maintains good adsorption efficiency,elution efficiency and antibacterial activity after five cycles of testing,which proves that PAO-G-A has good recycling performance.In view of the excellent comprehensive performance of PAO-G-A,kilogram-grade adsorbent was prepared and used in 35 d marine tests.After the tests,PAO-G-A maintained good appearance,mechanical properties and anti-biofouling performance.Its adsorption capacity for uranium reached 3.63 mg/g,exceeding the data of 1.5 mg/g in the marine tests by Japanese researchers.This paper solved the problem of poor functionality and adsorption performance of the existing anti-adhesion uranium adsorbents,and constructed a highly efficient uranium adsorbent with "coordination-electrostatic" dual adsorption mechanism synergistic effect.By using ethylenediamine(EDA)as the "bridge" and tert-butyl hydroperoxide(TBHP)initiated surface graft polymerization,2-methacryloyloxyethyl phosphorylcholine(MPC)is grafted onto the matrix of commercial acrylic fibers with highly functionalization.Finally obtained the anti-adhesion uranium adsorbent PAN-ED A-MPC.The experimental results show that the grafting rate of MPC monomer in the adsorbent is as high as 130%,and the adsorption capacity of PAN-EDA-MPC in 200 ppm U solution reachs 2657.57 mg/g.Moreover,the adsorption capacity of PAN-EDA-MPC reached 2.73 mg/g after 14-day adsorption in real seawater.By comparing the adsorption performance and anti-adhesion performance of the adsorbents with or without the grafting of phosphorylcholine,it is found that the introduction of phosphorylcholine not only helps to improve the adsorption performance of the adsorbents,but also endows the adsorbents with good hydrophilicity and anti-adhesion properties.Phosphorylcholine is a novel and efficient functional group,which has good prospects in the study of uranium extraction from seawater.In summary,this paper systematically introduces the research on adsorbents with different anti-biofouling mechanisms for the first time.It is proved that the introduction of antibacterial polymers endows the adsorbents with good antibacterial properties and enhanced adsorption performance.And an anti-biofouling uranium adsorbent with good comprehensive performance and practicality is obtained.Moreover,it is solved that the problems of poor functionality and adsorption performance of the existed anti-adhesion uranium adsorbents.Faced with the need for practical use of uranium extraction from seawater,the anti-biofouling uranium extraction adsorbents have also been used for the large-scale marine tests for the first time.The research results of this paper have guiding significance for solving the problem of serious damaged by marine biofouling on adsorbents for uranium extraction from seawater,and also have important reference value for the future engineered marine tests. |
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