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Utilization of uranium resource in seawater are highly possible to meet the growth demands for the sustainable development of nuclear energy industry. Bio-adsorbents exhibit high performance in terms of adsorption selectivity, equilibrium speed, and environmental friendliness, while the high fabrication cost hinders their practical application. In this study, a low-cost soy protein isolate (SPI) is used to fabricate adsorbent named SPI hydrogel for uranium extraction. This is the first report on applying bio-adsorbents derived from low-cost natural proteins for uranium extraction. The SPI hydrogel showed high uranium adsorption capacity of 53.94 mg g -1 in simulated nuclear wastewater and 5.29 mg g -1 is achieved in natural seawater, which is higher than all currently available adsorbents based on non-modified natural biomolecules. The amino and oxygen-containing groups are identified as the functional groups for uranyl binding by providing four oxygen and two nitrogen atoms to form equatorial coordination with uranyl, which guarantees the high binding selectivity and affinity to uranyl ions. The low cost for accessing the raw material together with the environmental friendliness, high salt tolerance, high uranium adsorption ability, and high selectivity to uranium, make SPI hydrogel a promising adsorbent for uranium extraction from seawater and nuclear wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Electrochemical techniques are considered promising applications to immobilize uranium in alkaline wastewater in order to prevent its migration into groundwater and soil. In this work, the results of electrochemical and Atomic Force Microscope (AFM) demonstrate a successful immobilization of uranyl in the carbonate system by U(VI)-U(V), U(V)-U(IV) reduction, and U(V) disproportionation reactions. The results indicated that the electrochemical fixation rate in alkaline system could reach more than 99%. The valence state of uranium is the key factor affecting its migration in the working system. Where, the analysis of the immobilized samples by X-ray photoelectron spectroscopy (XPS) revealed that pHs, current density, and the presence of foreign cations significantly affect the valence state of uranium in the immobilized samples. Under same conditions, the reduction reactions of U(VI)-U(V) and U(V)-U(IV) occurred easily. Where, at pH higher than 3.4 or the current density in the range of 0.5-20 mA/cm 2 , high content of U(V) and U(IV) in the immobilized products was obtained. Other conditions favored the occurrence of the electrolytic water reaction, and the immobilized samples were dominated by U(VI). It was found that the temperature showed the greatest effect on the electrochemical immobilization rate. Where, the electrochemical immobilization rate increased by about 1.8 times when the ambient temperature increased from 293.15 to 328.15 K. This study provides a new idea for the immobilization of uranium in alkaline wastewater and demonstrates the feasibility of electrochemical immobilization of uranium in alkaline systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Owing to the abundant uranium reserves in the oceans, the collection of uranium from seawater has aroused the widespread interest. Compared to the uranium extraction from ore, uranium collection from seawater is a more environmentally friendly strategy. The amidoxime (AO) functional group has been considered as one of the most efficient chelating groups for uranium capture. In this work, by drawing upon the photothermal character and antibacterial activity of cuttlefish ink, a cuttlefish ink loaded polyamidoxime (CI-PAO) membrane adsorbent is developed. Under one-sun illumination, the CI-PAO membrane shows a high extraction capacity of 488.76 mg-U/g-Ads in 500 mL 8 ppm uranium spiked simulated seawater, which is 1.24 times higher than PAO membrane. The adsorption rate of CI-PAO membrane is increased by 32.04%. Furthermore, exhibiting roughly 75% bacteriostatic rate in composite marine bacteria, the CI-PAO shows a dramatically antibacterial activity, which effectively prevents the functional sites on the adsorbent surface from being occupied by the biofouling blocks. After immersing in natural seawater for 4 weeks, light-irradiated CI-PAO gave high uranium uptake capacity of 6.17 mg-U/g-Ads. Hence, the CI-PAO membrane adsorbent can be considered as a potential candidate for the practical application for uranium extraction from seawater., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Marine biofouling is one of the most significant challenges hindering practical uranium extraction from seawater. Single atoms have been widely used in catalytic applications because of their remarkable redox property, implying that the single atom is highly capable of catalyzing the generation of reactive oxygen species (ROS) and acts as an anti-biofouling substance for controlling biofouling. In this study, the Co single atom loaded polyacrylamidoxime (PAO) material, PAO-Co, is fabricated based on the binding ability of the amidoxime group to uranyl and cobalt ions. Nitrogen and oxygen atoms from the amidoxime group stabilize the Co single atom. The fabricated PAO-Co exhibits a broad range of antimicrobial activity against diverse marine microorganisms by producing ROS, with an inhibition rate up to 93.4%. The present study is the first to apply the single atom for controlling biofouling. The adsorbent achieves an ultrahigh uranium adsorption capacity of 9.7 mg g -1 in biofouling-containing natural seawater, which decreased only by 11% compared with that in biofouling-removed natural seawater. These findings indicate that applying single atoms would be a promising strategy for designing biofouling-resistant adsorbents for uranium extraction from seawater., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The detection of environmental uranyl is attracting increasing attention. However, the available detection strategies mainly depend on the selective recognition of uranyl, which is subject to severe interference by coexisting metal ions. Herein, based on the unique uranyl-triggered photocleavage property, the protein BSA is labelled with fluorescent molecules that exhibit an aggregation-induced emission effect for uranyl detection. Uranyl-triggered photocleavage causes the separation of the fluorescent-molecule-labelled protein fragments, leading to attenuation of the emission fluorescence, which is used as a signal for uranyl detection. This detection strategy shows high selectivity for uranyl and an ultralow detection limit of 24 pM with a broad detection range covering five orders of magnitude. The detection method also shows high reliability and stability, making it a promising technique for practical applications in diverse environments., (© 2022 Wiley-VCH GmbH.)

• Poly(amidoxime)/Polyzwitterionic adsorbent is fabricated for uranium extraction. • The adsorbent can be easily prepared by free-radical polymerization. • The adsorbent shows high salt shrinkage resistance. • The adsorbent exhibits excellent antibacterial activity. • A high uranium extraction capacity of 6.26 mg g−1 in natural seawater. Effective uranium extraction from seawater can contribute greatly for meeting the needs of low carbon energy. Extensive studies have been conducted on polyamidoxime-based (PAO-based) adsorbents for their exceptional uranium adsorption capabilities. However, the salt-shrinkage effect severely hinders the extraction of uranium from seawater using traditional PAO-based adsorbents. This study synthesizes a novel semi-interpenetrating polymer network hydrogel, designated as PAO/PMPC-SH, using a free-radical polymerization approach utilizing PAO and zwitterionic poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC). The incorporation of the PMPC component endows the adsorbent with exceptional resistance to salt shrinkage owing to the antipolyelectrolyte effect. This characteristic facilitates the diffusion of uranyl ions within PAO/PMPC-SH, even in a high-salt environment with a salt concentration as high as 25 wt%, thereby exposing the uranium binding sites in the adsorbent. Moreover, PAO/PMPC-SH exhibits exceptional antibacterial activity. After 28 days of test in natural seawater, PAO/PMPC-SH demonstrates a high uranium extraction capacity of 6.26 mg g−1, representing only a 9.14 % decrease compared with the capacity of adsorbing in marine microorganism-removed natural seawater. Overall, the notable performance of PAO/PMPC-SH in uranium extraction highlights its potential as a highly effective adsorbent for uranium extraction from seawater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ion-imprinting and chemical cross-linking are cooperated to fabricate the adsorbent. • The adsorbent exhibits outstanding mechanical properties and antibiofouling ability. • The adsorbent achieves a high uranium adsorption capacity of 9.46 mg g−1 in seawater. • The adsorbent shows an ultra-high selectivity of 19.01 to uranium against vanadium. • The performance of adsorbent is comprehensively optimized. Significantly abundant uranium resources in seawater are considered promising alternatives to terrestrial uranium reserves. The adsorption capacity and speed, binding selectivity, mechanical properties, and antibiofouling ability are the most important features for practical uranium adsorbent applications. Herein, a new nanocellulose aerogel, which contains specific binding spatial structures for uranyl ions, designated as I-CNF aerogel, is fabricated by combining ion-imprinting and chemical cross-linking strategies. The ion-imprinted and chemically stabilized functional sites endow the I-CNF aerogel with robust binding affinity and selectivity for uranyl ions. The ordered lamellar structure, porosity, and high hydrophilicity together facilitate uranyl ion access to the functional sites in the adsorbent and endow the adsorbent with a high uranium adsorption capacity. Furthermore, owing to the chemical cross-linking process and the generated Schiff base groups, the adsorbent exhibits high mechanical strength, excellent reusability, and effective antibiofouling activity. Benefitting from these optimized properties, I-CNF aerogel demonstrates a high uranium extraction capacity of 9.46 mg g−1 with an ultrahigh selectivity of 19.01 to uranium against vanadium in natural seawater, making it a highly potential candidate for practical uranium extraction in natural seawater. [ABSTRACT FROM AUTHOR]

• The external electric field is used to enhance the adsorption capacity of the material. • The graphite electrode modified by amidoxime was prepared by coating technology and heterogeneous reaction. • Using sodium bicarbonate as eluent and adding reverse voltage can realize the effective recycling of materials. Electrode materials have an important influence on the performance of electroadsorption. In this paper, Polyacrylonitrile was introduced to the graphite surface by coating method, then amidoxime reaction was carried out by one-step hydrothermal method. The results of material analysis showed that the nitrile group were transformed to amidoxime group and the electrode had good thermal stability. The electrochemical test results demonstrated that the amidoxime-modified graphite felt electrode displayed a good specific capacitance of 46.5 F·g−1 in 1 M NaCl solution at a scan rate of 5 mV·s−1. The results of batch adsorption experiments showed that the adsorption capacity of uranium could reach 164.75 mg·g−1 at −0.9 V (vs SCE). When sodium carbonate was used as eluent, the elution efficiency was 95% under the influence of reverse voltage (0.9 V). The adsorption capacity could reach 90% of the initial value after 5 times of reuse. The results indicated that the amidoxime-modified graphite felt had a good application prospect for removing uranium from water by electroadsorption method. [ABSTRACT FROM AUTHOR]

[Display omitted] • • Highly hydrophilic phosphate functionalized silicide was obtained by one-step covalent grafting. • • The as-prepared adsorbent at ultralow dosage showed a rapid uranium removal rate. • • The as-prepared adsorbent showed an outstanding uranium adsorption capacity. • • The as-prepared adsorbent at ultralow dosage showed remarkable salt tolerance. Highly efficient removal of uranium from uranium-containing nuclear wastewater is important both for utilizing the uranium resource and protecting the environment from the hazards of uranium. However, the hypersaline environment of nuclear wastewater makes the removal of uranium a great challenge. Herein, a highly hydrophilic phosphate-functionalized silicide (VTES-PA 4) is prepared by a one-step covalent grafting method for highly efficient uranium removal from hypersaline nuclear wastewater. Impressively, the uranium removal of VTES-PA 4 reaches up to 97.4% within 7 min at an ultra-low dosage of 0.06 g/L in 12 ppm uranium solution, which outperforms most reported uranium removal materials. More importantly, the VTES-PA 4 exhibits excellent removal rates of 86.6% and 76.9% in hypersaline wastewater containing 5 M NaNO 3 and NaCl, respectively. Satisfactory uranium removal is due to the full exposure of the functional sites for binding of uranyl, endowing VTES-PA 4 with a high uranium uptake capacity of 413.2 mg/g. The adsorption mechanism has been investigated by EXAFS and XPS, which reveals that uranyl is adsorbed by coordinating with six oxygen atoms from the phosphate groups. This work enriches the study on the development of uranium adsorbents from hypersaline nuclear wastewater and can contribute to the sustainable development of the nuclear energy industry. [ABSTRACT FROM AUTHOR]

• A pre-hydrolysis strategy is used to boost the uranium extraction performance. • The strategy is universally applicable for the PAO-based adsorbents. • The pre-treated adsorbent exhibits significant resistance to salt-shrinkage. • The pre-treated adsorbent shows 60.3% enhanced extraction capacity. • The pre-treated adsorbent realizes more than 1-fold accelerated extraction rate. Utilization of the seawater uranium (U) resource is a prospective strategy to satisfy the requirements of nuclear energy industry. Poly(amidoxime) (PAO)-based adsorbents are the most prospective candidates for extracting seawater U resource. However, owing to its innate shortcoming of salt shrinkage in seawater, the channels between the polymer chains in PAO-based adsorbents are shrinkage, hindering the entry of uranyl ions into the adsorbent. Therefore, amidoxime groups in PAO-based adsorbents are not utilized efficiently. Herein, a universally applicable pre-hydrolysis strategy is designed to boost the U extraction performance of PAO-based adsorbents. Pre-hydrolyzed polyacrylonitrile is used to fabricate PAO with higher hydrophilicity, namely h -PAO. Due to the existence of more hydrophilic groups generated by the pre-hydrolysis process, h -PAO hydrogel exhibits enhanced interaction with water and reduced salt-shrinkage behavior compared with that of PAO hydrogel. As a result, h -PAO hydrogel exhibits increased (6.5-fold) seawater migration ability to facilitate the transport of uranyl ions to the functional groups inside the adsorbent. In filtered real seawater, h -PAO hydrogel shows 60.3% enhanced U extraction capacity, which is 9.86 mg g−1, and more than 1-fold accelerated U extraction rate. Collectively, our results indicate that the pre-hydrolysis strategy is a promising approach to boost the U extraction performance of PAO-based adsorbents in real seawater. [ABSTRACT FROM AUTHOR]

• A new strategy of cooperative reaming is used to prepare macroporous hydrogel. • The pore size on the novel MP-PAO hydrogel membrane reaches up to 40 µm. • The MP-PAO membrane shows both high uranium sorption capacity and good reusability. • The high adsorption rate can be gained with 24-day extraction equilibrium time. As nuclear power plant fuel, nearly 4.5 billion tons of uranium is reserved in the ocean with a low concentration of 3.3 ppb. Uranium capture from natural seawater relies heavily on the development of highly efficient uranium adsorbent. By combination of the water-soluble pore-forming agent (sodium bicarbonate, NaHCO 3) and alkali treatment technology, a novel macroporous polyamidoxime (MP-PAO) hydrogel membrane is prepared for highly efficient uranium sorption. The macropores with a size of about 40 µm in diameter contribute to the exposure of previously hidden coordination bond sites and fast diffusion of uranyl ion. As a result, the MP-PAO membrane adsorbent delivers superior uranium sorption capacity of 5.80 mg-U/g-Ads, almost 1.76 times that of the pristine polyamidoxime (PAO) membrane adsorbent. Strikingly, the adsorption equilibrium of uranium on the MP-PAO membrane can be reached within 24 days. The adsorption rate of MP-PAO membrane is 14.29% faster than that of the reference PAO membrane. In addition, the MP-PAO membrane also shows a good reusability and long service life. The strategy applied in this work is widely suitable for the preparation of macroporous adsorbents. MP-PAO membrane holds tremendous potential for uranium capture from natural seawater. [ABSTRACT FROM AUTHOR]

[Display omitted] • KIST hydrogel shows shortest equilibrium adsorption time among existed adsorbents. • High uranium extraction capacity of 1.18 mg g−1 is achieved in natural seawater. • KIST hydrogel shows high antibiofouling activity against marine microorganisms. • KIST hydrogel exhibits high mechanical properties. Highly efficient extraction of uranium from seawater is vital for meeting the growth demands of uranium resources for the development of nuclear energy industry. However, currently available uranium adsorbents encounter multiple challenges, including the ultralong extraction period, severe marine biofouling, and violent impact of ocean motions. Targeting on these challenges and inspiring by the high tolerance of kelp to marine biofouling and motions, a kelp inspired super-toughness (KIST) bio-hydrogel is fabricated for uranium extraction from seawater. The hydrogel KIST is prepared by compositing the biofriendly and low-cost bacterial cell debris with polyvinyl alcohol, making the KIST hydrogel possesses high environment friendly. Attributing to the fast uranium adsorption rate of the bacterial cell debris, the KIST hydrogel realizes a uranium extraction capacity of 1.18 mg g−1 in biofouling-containing natural seawater with an ultrafast equilibrium adsorption time of 28 h, which is the shortest among all available uranium adsorbents in natural seawater. The antimicrobial activity of the bacterial cell debris empowers KIST hydrogel with as high as 99.21% inhibition rate to the growth of a broad range marine biofouling microorganisms, including the marine bacteria and marine algae. The KIST hydrogel also possesses outstanding tensile ability, flexibility, and rheological property, endowing the hydrogel with high resistance to the ocean current. Taking into consideration these advantages, the KIST hydrogel would be a promising adsorbent for practical uranium extraction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crab carapace is used for uranium extraction from seawater for the first time. • High uranium extraction capacity of 1.38 mg g−1 is achieved natural seawater. • CaCO 3 is identified as functional uranium adsorption component for the first time. • Marine crab carapace binds uranium by forming coordination bonds. The sustainable access to uranium resource is critical for the sustainable development of nuclear energy industry. The global seawater contains thousands of times more uranium reserves than that on the land and can be a promising supply of uranium. Nevertheless, extraction of uranium from seawater is challenging due to the complex seawater environment and it's urgent to develop adsorbents that suitable for being used in seawater environment. Herein, inspired by the high uranium concentrations in natural marine animal carapaces, the grinded marine crab carapace is used for uranium extraction. The crystalline calcium carbonate in crab carapace is identified as functional components for uranium adsorption for the first time. The grinded crab carapace achieves a high uranium extraction capacity of 1.38 mg g−1 in natural seawater. The EXAFS analysis and DFT calculations reveal that uranyl ion from seawater is bound by forming coordination bonds between uranium atom and oxygen atoms from the carbonate group and between axial oxygen atom from uranyl ion with calcium atom. Considering the promising uranium binding ability in natural seawater, the marine crab carapaces are highly potential for being used in uranium extraction from seawater. [ABSTRACT FROM AUTHOR]