Research On Bio-Based Materials For Uranium Extraction From Seawater

As a clean energy,nuclear energy has been listed as an important direction of China’s future energy development strategy.As an important raw material of nuclear energy industry,uranium is related to the stable operation of China’s nuclear power and the implementation of national strategic security.Compared with terrestrial uranium deposits,the ocean is rich in uranium resources,which is nearly a thousand times that of terrestrial uranium deposits.In addition,the extraction process of uranium from seawater is more environmentally friendly than that of land uranium mining.Therefore,the extraction of uranium from seawater is considered to be a nuclear fuel resource project with good return and good development prospects,which is of great strategic and practical significance to China’s economic construction and energy self-sufficiency.At present,researchers from various countries have developed a variety of adsorbents for uranium extraction from seawater,including inorganic material adsorbents,nano material adsorbents and polymer adsorbents.Although they show good adsorption performance,there are still some problems,such as low selectivity,long adsorption cycle,low mechanical strength,serious biological fouling and so on.Owing to the merits of environmental friendliness,short regeneration cycle,high selectivity and fast adsorption rate biomaterials have attracted more and more attention.They are considered to be one of the most promising adsorbents for uranium extraction from seawater.In addition,there are a large number of microorganisms in the ocean,and there is serious marine biological fouling in the process of uranium extraction from seawater,which not only has a significant impact on the adsorption performance of the adsorbent,but also the biological enzymes and other active substances produced by the organisms will lead to the damage of the uranium extraction adsorbent and seriously reduce the reuse performance of the adsorbent,Thus,the economic cost of the technology development is increased.Therefore,it is urgent to develop biosorbents with high adsorption performance,high mechanical strength,high specificity,fast saturation time and anti biofouling activity.Based on the problems of low selectivity,long adsorption cycle,low mechanical strength and serious biological fouling of the existing adsorbents for uranium extraction from seawater,the main contents of this study are as follows:(1)Herein,a kind of spidroin-based functional protein fiber was developed for the first time by strategies of genetic engineering and biomimetic spinning.A chimeric spidroin-based super uranyl-binding protein(SSUP)fiber was designed by fusing the gene of super uranyl-binding protein(SUP)with the gene of spidroin.SUP endowed the SSUP fiber with high affinity and selectivity to uranium,and spidroin gave the SSUP fiber with high mechanical strength and high reusability.The wet SSUP fiber is a water-rich hydrogel-like structure,which provided abundant hydrophilic intermolecular space for the entrance of uranyl ions,and could accelerate the rate for uranium adsorption.In seawater,the SSUP fiber achieved a break-through uranium extraction capacity of 12.33 mg/g with an ultrashort equilibration time of 3.5 days.(2)Inspired by the similar three-dimensional structures of superb-uranyl binding proteins(SUPs)and spider proteins,a dual-SUP(DSUP)chimeric protein fiber with high tensile strength was designed.The unique loofah-like structure of DSUP hydrogel fibers fully exposes abundant functional uranyl binding sites,enabling DSUP fibers with a groundbreaking uranium extraction capacity of 17.45 mg/g and an ultra-short saturation time of 3 days in natural seawater.This study reports an approach to the design of an adsorbent with ultrahigh uranium extraction capacity and explores a strategy for fabricating artificial high-strength functional non-spidroin protein fiber.(3)Aiming at the problems of serious biofouling in the process of uranium extraction from seawater,a strategy to construct an anti-biofouling adsorbent with enhanced uranium adsorption capacity in natural seawater was proposed.This strategy is realized by a simple one-step covalent cross-linking reaction between antimicrobial compounds and adsorbents,and can be widely applied to currently available carboxyl-containing adsorbents.The anti-biofouling adsorbent constructed in this study is not only safe and efficient,but also has good reusability and wide antibacterial spectrum.After a 30-day field test in real seawater,the uranium recovery capacity of Anti-Ui O-66 was 4.62 mg/g,which was 24.4%higher than that of the non-antibacterial material Ui O-66.(4)The peptides with broad-spectrum antibacterial activities were screened from the antimicrobial peptide database and cross-linked into polymeric peptide hydrogel PPH-OP.PPH-OP not only possesses the properties of strong binding affinity and selectivity to uranium in seawater,but also has remarkable resistance to biological pollution,the growth inhibition rate of marine microorganisms reaches 99%.Amino acids in the peptide provided a large number of active sites for the coordination of uranium,and the extraction capacity of uranium in natural seawater was 7.12 mg/g.This work opens up a new direction for designing low-cost and sustainable nuclear fuel recycling materials.