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Uranium is a strategic resource which is found in quantities of 4.5 billion tons in seawater. For exacting U(VI) efficiently from seawater, this study involves the preparation of a polysulfone (PSF)-based phytic acid-silica blended membrane (PA-SiO 2 /PSF) through the incorporation of silicon dioxide particles (SiO 2) and phytic acid (PA) into the polysulfone ultrafiltration membrane. A large number of adsorption sites was contributed by PA, serving as the primary factor in enhancing the U(VI) adsorption performance of PSF. Meanwhile, silica can be used as a carrier of PA to improve the performance of PSF. The addition of hydrophilic SiO 2 and PA increases the water flux (380 L·h−1·m−2) and hydrophilicity (contact angle = 61.8°) of PSF. The modified PSF demonstrates a negative potential under neutral pH conditions. Notably, at pH = 7, PA-SiO 2 /PSF exhibits the highest adsorption performance (q e = 1052.01 mg/m2) and selectivity (K d = 16161.96 mL/m2) for U(VI), with an 82 % recovery ratio of U(VI) achieved after five adsorption-desorption cycles. Moreover, the dynamic adsorption effect of PA-SiO 2 /PSF surpasses that of static adsorption. Therefore, this study presents a straightforward method of modifying polysulfone membranes, with potential applicability in uranium adsorption from seawater. [Display omitted] • PA-SiO 2 /PSF is synthetized by blending with phytic acid functional particles. • PA-SiO 2 /PSF has excellent water flux with silicon dioxide as a modified carrier by phytic acid. • Compared with PSF, PA-SiO 2 /PSF has higher adsorption capacity. • PA-SiO 2 /PSF has higher adsorption selectivity for uranium than other metal cations. • PA-SiO 2 /PSF has high removal rate in simulated sea with dynamic adsorption. [ABSTRACT FROM AUTHOR]

Effectively extracting uranium (VI) [U(VI)] from seawater requires efficient adsorbents. Generally, there are two major factors that affect the adsorption efficiency of adsorbents, including the biofouling around the adsorbents and the relative density of adsorption active sites. To enhance the practical application value of powdered polyamidoxime-based materials, macro-braidable and hierarchical porous bamboo strips (BS) with antibacterial properties are selected to synthetize polyamidoximized bamboo strips (PAOBS) by in-situ polymerization methods. On the one hand, natural BS have a bamboo quinone structure, and their intrinsic structure is not destroyed during the reaction process, which endows PAOBS with excellent antibacterial properties. In addition, PAOBS retains the hierarchical porous structure of BS, providing channels for the adsorption process, which is beneficial to achieve the maximum utilization of adsorption active sites. On the other hand, PAOBS increases the relative density of amidoxime functional groups, and its adsorption capacity (233 mg g−1) is approximately 2.14 times higher than that of pure PAO at pH= 6.0, including electrostatic effect and chelation mechanism. After PAOBS is floated in the Yellow Sea Basin for 30 days, its adsorption capacity for U(VI) reaches 1.03 mg g−1. Importantly, the addition of BS increases the coordination modes with the uranyl ion, and the single coordination mode of CH(NH 2)= N - O H from PAO is translated to the three mixed coordination modes of CH(NH 2)= N - O H, CH(N H 2)=N - O H, and CH(N H 2)=N - OH and adjacent CH(N H 2)=N - OH from PAOBS. Construction of PAOBS plays a role in the design of novel adsorbents with high relative density of adsorption active sites and biofouling-resistant, laying the steady foundation for further realizing sustainable U(VI) extraction from seawater. [Display omitted] • PAOBS was synthetized by in-situ polymerization method for the first time. • The outstanding anti-biofouling ability of PAOBS was due to bamboo quinone itself. • Compared with PAO, the adsorption capacity of PAOBS was increased by 2.1 times. • PAOBS was floated in Yellow Sea for 30 d to solve the issue from pure powder PAO. [ABSTRACT FROM AUTHOR]

Graphical abstract An anti-algae adsorbent Ag-L-Arg-rGH composites were synthesized for removing uranium (VI) from simulated seawater. Abstract Uranium (VI) is very essential element in nuclear technique and the enrichment uranium has attracted lots of attention. In this work, l -Arginine and Ag nanoparticles (AgNPs) functionalized reduced graphene oxide ternary hydrogel composites (Ag- l -Arg-rGH) were successfully synthesized, which combined the insertion of AgNPs with one-step thermal reduction and an assembly of graphene oxide nanosheets, using l -Arginine (l -Arg) as both a functional and cross-linking agents. The Ag- l -Arg-rGH composites exhibited great enhanced sorption capacity. Kinetic data best fitted the pseudo-second-order model. The thermodynamic data fitted the Langmuir isotherm model and the calculated maximum adsorption capacity is 434.78 mg/g. In addition, the anti-algae experimental results indicated adsorbent showed marked algal inhibition with the presence of AgNPs in the Ag- l -Arg-rGH composites. In the simulated seawater experiments, The distribution coefficient (K d) value of uranium(VI) with other competing ions was 2.41 × 104 mL g−1. Thereby, the Ag- l -Arg-rGH composites possessed a promising potential for the enrichment uranium (VI) from nature seawater. [ABSTRACT FROM AUTHOR]

• Hemp fiber with optimal adsorption capacity and optimal fouling resistance of amidoxime-quaternized polyethyleneimine (HFAO-QPEI) were prepared using simple fiber surface modification grafting. • HFAO-QPEI exhibits excellent uranium selectivity and recyclability. • Quaternization gives HFAO-QPEI significant biofouling resistance, especially inhibiting the adhesion of mussels. • DFT calculation results indicate that the HFAO-QPEI-U mode exhibits the most stable structure. Nuclear energy plays a key role in the global energy supply. The adsorption and extraction of uranium from seawater is key to the rapid development of nuclear energy. In this paper, quaternary aminated polyethyleneimine/amidoxime-modified hemp fiber (HFAO-QPEI) with high adsorption capacity and anti-biofouling properties were successfully synthesized by immersion and hydrothermal methods. Upon systematic evaluation, HFAO-QPEI possessed high adsorption capacity and good reusability with fast adsorption kinetics, as well as good adsorption selectivity and affinity for uranyl ions. Furthermore, HFAO-QPEI not only reached a maximum adsorption capacity of 364.7 mg/g but also demonstrated a short adsorption equilibrium time of 200 min. In contrast, HFAO-QPEI demonstrated high selectivity for uranyl ions, removing up to 95.1 % of uranium with K d value of 4.69 × 104 mL/g, which was 256.3 times greater than that of hemp fiber (HF). After the fifth adsorption–desorption cycle, the recovery of U(VI) was 91.38 %. DFT calculations proved that HFAO-QPEI-U was the most stable model. The quaternary ammonium salt functionalization not only makes HFAO-QPEI have excellent anti-biofouling ability (anti-diatom rate up to 87.22 %, anti-bacterial rate up to 97 % or more, anti-adhesion of large fouling organisms mussels with a certain effect), but also modifies its surface charge, making it more suitable for the marine environment. In addition, HFAO-QPEI showed a high adsorption capacity of 2.45 mg/g in natural seawater. The results suggest that the HFAO-QPEI adsorbent holds great promise for extracting uranium from seawater. [ABSTRACT FROM AUTHOR]

[Display omitted] Polyacrylonitrile (PAN)-based materials have been studied for decades as uranium (U(VI)) adsorbents, because the further products of abundant nitrile groups, amidoxime (AO) groups, show great affinity for U(VI) ions. However, excessive amidoximation could cause the shrinkage of PAN fibers, resulting in decreased adsorption performance. Hence, an amino-reinforced amidoxime (ARAO) swelling layer was constructed on the PAN fiber surface (PAN-NH 2 -AO) by modification of the strongly hydrophilic amino group to prevent shrinkage. The molecular chains in the ARAO swelling layer would be swelled due to the adsorption of a large amount of water. Simultaneously, U(Ⅵ) ions can penetrate into the ARAO swelling layer with water molecules and coordinate with amino or AO groups, leading to increased adsorption performance. PAN-NH 2 -AO exhibited maximum U(VI) and water adsorption capacities of 492.61 mg g−1 and 20.32 g g−1 at 25 ℃ with a swelling ratio of 20.73%, respectively. The adsorption capacity of PAN-NH 2 -AO was 0.312 mg g−1 after a 91-day immersion in Yellow Sea, China. The study of the adsorption thermodynamics and kinetics of PAN-NH 2 -AO showed that the adsorption process was spontaneous homogeneous chemical adsorption. This paper proposes a novel method to obstruct amidoximation induced shrinkage and to maximize the potential application of PAN-based materials. [ABSTRACT FROM AUTHOR]

• PDA and PEI co-deposition combined with electrostatic self-assembly realizes mild surface modification. • The membrane with 3 functional layers exhibits the best adsorption performance (adsorption capacity = 142.25 mg·g−1). • This membrane can achieve over 90 % uranium removal within 90 min in dynamic filtration. • DFT calculation results indicate that the PEI/PA-U mode exhibits the most stable structure. Developing simple and efficient new strategies for uranium extraction from seawater (UES) is crucial for addressing the energy crisis. Here, we proposed a mild strategy to prepare a layer-by-layer assembly membrane (LAM) by polydopamine (PDA) and polyethyleneimine (PEI) co-deposition coupled with polyethyleneimine/phytic acid self-assembly for efficient uranium extraction. By regulating the number of self-assemblies, the performance of the membrane could be easily adjusted. The functional coating's rich active groups (–NH 2 , -PO 4 3-, –OH) provided a good adsorption performance for the modified membrane, with a static adsorption capacity of 142.25 mg·g−1. Meanwhile, it possessed excellent dynamic removal rate, which could achieve over 90 % uranium removal within 90 min. The LAM also exhibited exceptional adsorption selectivity, boasting a remarkable 9:1 ratio in extracting uranium and vanadium. Furthermore, the strong adhesion of PDA endowed the material with good stability, and the adsorption capacity only decreased by 23 % after 5 cycles. DFT calculations proved that PEI/PA-U was the most stable model. Particularly, the adsorption capacity of LAM in natural seawater can reach 0.99 mg·g−1. With the simple and mild preparation process, along with the excellent adsorption performance, the LAM membrane holds great promise for seawater uranium enrichment. [ABSTRACT FROM AUTHOR]

In this study, a hyperbranched chelated hydrophilic swollen-layer was constructed on the surface of polyacrylonitrile (PAN) fiber with amino trimethylene phosphoric acid (ATMP) as a terminal group, which applied as an adsorbent for seawater uranium U(VI) extraction. This shows that U(VI) enter the gel-like swollen-layer to form a more complex body structure. The molecular chain conformational extension in the swollen-layer reduces the resistance of the uranyl ion to enter the swollen-layer, which is conducive to the adsorption behavior. The adsorption performance on the U(VI) by the adsorption experiment were found to be consistent with the Langmuir isotherm adsorption model and the pseudo-second-order kinetics, indicating that the adsorption of U(VI) by this material is uniform single-layer chemical adsorption. Ion competition experiments and cyclic adsorption experiments verify the practical application potential of the materials. In the dynamic simulation of seawater adsorption experiments, the adsorption capacity of the adsorbent reached 7.4 mg/g. Studies on the adsorption mechanism have found that a large number of hydroxyl groups in the swollen-layer and ATMP as an end machine have a chelation effect on U(VI). [ABSTRACT FROM AUTHOR]

The preparation of powder adsorbent into microsphere adsorbent is one of the effective methods for the industrialization of uranium extraction from seawater. Herein, a MOF-derived Co-Ni layered double hydroxides/polyethyleneimine modified chitosan micro-nanoreactor (DNPM) was prepared by a simple method in this work. The microstructure and chemical structure of DNPM were comprehensively characterized. The pH value, adsorption time, initial solution concentration, temperature, competitive ions, regeneration performance, and bed column heights were investigated for the adsorption performance of DNPM by batch adsorption and fixed-bed column continuous adsorption experiments. When the contact time was 8 h, the initial concentration was 150 mg/L, and the pH value was 6, the adsorption capacity of DNPM was 334.67 mg/g. The uranium adsorption by DNPM fits with the pseudo-second-order kinetic and Langmuir models, which was a spontaneous and endothermic process. In addition, DNPM has good adsorption selectivity and reusability. The fixed-bed column continuous adsorption experiment shows that the adsorption capacity increased with the increase of bed column height. The adsorption mechanism can be attributed to coordination chelation and electrostatic interaction. In general, this work provides an effective strategy for developing environmentally friendly uranium adsorbent that can be industrially used. [Display omitted] [ABSTRACT FROM AUTHOR]

• A hyperbranched structure with multi-active sites on PAN fibers was constructed. • The adsorption amount reached 1.3 mg/g in dynamic simulated seawater. • The adsorption amount reached 0.6 mg/g in real marine environment. • The adsorption mechanism is chemisorption and N forms a coordination with U(VI). • The branched structure increased the molecular chain rigidity and h →. With the depletion of terrestrial uranium deposits, a large amount of uranium(VI) (U(VI)) in seawater has attracted the attention of researchers and energy suppliers. However, the extremely low concentration of U(VI) and the complex environment enhance the difficulty of extracting U(VI) from seawater. In this study, a multi-active polyacrylonitrile (PAN) adsorbent was constructed to extract U(VI) from seawater. Poly(amido)amine (PAMAM) with hyperbranched topology was grown onto the surface of PAN fiber by a multi-step method, forming a swollen layer in water. The highest adsorption capacity of the material reached 555.5 mg/g. Importantly, during a continuous 50-day simulated seawater dynamic adsorption process, the material reached an adsorption equilibrium in 15 days, with the adsorption amount of 1.3 mg/g. The ocean test in the Yellow Sea of China showed that the adsorption capacity of the material was 0.6 mg/g in 34 days in seawater environment. The effect of molecular chain conformation and swelling behavior on adsorption properties were investigated. The study on the adsorption mechanism of the material shows that the lone pair of electrons of the N atom coordinates with U(VI). [ABSTRACT FROM AUTHOR]

• A novel multi-activity graphene oxide platelets was successfully synthesized. • GO-DM-AO exhibits excellent adsorption towards U(VI) at pH = 8. • Adsorption equilibrium time was shortened by 50% than that of GO-DM. • GO-DM-AO displayed superior adsorption at low concentration of U(VI). The introduction of organic groups onto graphene oxide (GO) platelets can supply additional active sites for adsorption of uranium(VI) (U(VI)) to improve the adsorption capacity. However, as a result of the existence of stabilizing π-conjugation system, a facile and effective modification method remains a challenge. Therefore, a novel strategy is exploited by nano-sized architectural design of multi-activity GO through post-decoration with amidoxime functionalized diaminomaleonitrile (DM-AO). The post-modification of DM-AO successfully activated the inert sites in GO platelets. Meanwhile, the amidoxime group in DM-AO can improve the adsorption selectivity. Adsorption amount of U(VI) on the as prepared GO-DM-AO reached at 935 mg g−1, which is increased by 209% increment compared with that of pristine GO at the same concentration. The adsorption efficiency of GO-DM-AO is greatly improved, and the time to reach the adsorption equilibrium is half of that of GO. Excitingly, the excellent removal efficiency could still maintained even after 5 cycles of adsorption-desorption. The outstanding adsorption amount, short adsorption equilibrium time, and excellent removal efficiency can provide a theoretical guidance for further immobilization of U(VI) from seawater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel phosphonate-functionalized DFNS adsorbent was successfully synthesized. • Adsorption capacity of PA-DFNS increased by 163% than that of unmodified DFNS. • Adsorption equilibrium time was shortened by 33% than that of the unmodified DNFS. • PA-DFNS displayed superior adsorption at low concentration of U(VI). Abstract A novel phosphonate assisted fabrication dendritic fibrous nanosilica (DFNS)-based adsorbing material was successfully synthesis via organic modification with 3-aminopropyltriethoxysilane (KH550), epichlorohydrin (ECH) and phytic acid (PA) on the grounds of hard-soft-acid-base theory, in which organic phosphorous can be applied for efficient chelating uranium(VI) (U(VI)). The adsorption properties can be evaluated by setting a series parameters (pH, adsorbent dose, contact time, initial U(VI) concentration). It is clear that uranium as a "hard" lewis acid can easily form chelating bond with "hard" donor-ligands so that as-papered PA-DFNS has an excellent adsorption capacity (q m = 1106 mg g−1, 298.15 K), which exhibits a 163% increment compared with that of original DNFS under the same condition. In the meantime, the adsorption equilibrium time of PA-DNFS (t = 60 min) was shortened by 33% compared with that of pristine DNFS. Besides, the PA-DFNS exhibited good removal efficiency and stability under the 0.1 M HNO 3 after 6 cycles, extending the application of PA-DFNS in the field of adsorption. [ABSTRACT FROM AUTHOR]

The efficient extraction of uranium (U(VI)) from seawater has been a significant challenge for the nuclear industry. In this study, we prepared a robust quaternized polyethyleneimine-polyacrylonitrile crosslinked membrane (QPEI-PAN) using homogeneous cross-linking reaction and quaternary ammonium salt functionalization. PEI was uniformly dispersed inside the membrane by cross-linking with PAN molecular chains, providing QPEI-PAN with a robust structure and abundant active sites for U(VI) capture. The batch adsorption data obtained for QPEI-PAN modelled well using the Langmuir adsorption isotherm, and the maximum theoretical adsorption capacity was determined as 8198.2 mg·m−2. Particularly, QPEI-PAN reached a maximum dynamic adsorption capacity of 6823.1 mg·m−2 within 90 min. The robust membrane structure allowed for efficient regeneration, with a U(VI) recovery rate of 88 % over seven adsorption-desorption cycles. Quaternary ammonium salt functionalization not only gave the QPEI-PAN membrane an excellent anti-biofouling ability but also modified its surface charge, making it more suitable for the marine environment, where its adsorption capacity in unfiltered seawater (containing bacteria and microorganisms) was only 5.6 % lower than that of the filtered seawater. These findings suggest that this novel, anti-biofouling membrane-type adsorbent has significant potential for application in the field of uranium extraction from seawater (UES). [Display omitted] • QPEI-PAN functional membrane was successfully prepared by homogeneous crosslinking and quaternary ammonium grafting reaction. • Compared to the original PAN, the tensile strength of 40PEI-PAN have been increased by 1.6 times. • QPEI-PAN has high U(VI) adsorption capacity in both static (8198.2 mg·m-2) and dynamic (6823.1 mg·m-2) modes. • Compared with deionized water, the adsorption capacity in natural seawater has only decreased by 10%. [ABSTRACT FROM AUTHOR]

Inspired by the easy availability and modification of fiber-like materials for water treatment and sorption applications, the functionalized natural fiber luffa cylindrica (LC) and synthetic fiber polyacrylonitrile (PAN) have been designed for the uranium adsorption. Seawater desalination brine has a significantly higher concentration of uranyl ion, so it is very meaningful to extract uranyl ions from it. In this paper, the seawater from seawater desalination plant at various treatment stages was collected to evaluate uranium adsorption performance. The effect of flocculant and scale inhibitors on uranium adsorption performance of functional fibers was also studied. The oxime/guanidine co-modified luffa cylindrica fiber (WGLC), guanidine/amidoxime co -modified polyacrylonitrile fiber (PAN-G-AO) and polyethyleneimine modified polyacrylonitrile fiber (PAN-PEI) were synthesized. PAN-G-AO showed excellent uranium capture performance with a high saturation adsorption capacity of 490.20 mg g−1 and rapid adsorption equilibrium at 15 min. Amount of uranium adsorption of three materials declined when flocculant and scale inhibitors were added. The results of adsorption experiments in various stages of seawater desalination solution for 30 days showed that adsorption materials PAN-G-AO had the largest adsorption capacity (18.6 μg g−1) in the concentrated desalinated seawater, which demonstrate promising application potential of the functionalized fiber materials for uranium adsorption from desalinated concentrated seawater. • The WGLC, PAN-G-AO and PAN-PEI were successfully synthesized. • The adsorption capacity was decreased in the presence of scale inhibitors. • The fastest adsorption equilibrium was achieved by PAN-G-AO in the flocculant system. • The PAN-G-AO adsorption capacity in desalinated concentrated seawater was18.60 μg g−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • The casein hydrolysates were grafted on AOBS to construct a degradable adsorbent. • The adsorption capacity of AHCAOBS-3 for U was 15.3 times that of V in the sea. • The construction of biaxial adsorption sites lower the interference of V. • The findings of this study broaden the application range of proteins. Amidoxime-based materials are currently the most promising adsorbents for sustainable extraction uranium from seawater. However, in practical applications, the strong affinity of amidoxime-based materials for vanadium seriously interferes with the extraction uranium from seawater. Herein, a novel environmentally friendly and degradable adsorbent is firstly designed through grafting animal protein on natural bamboo strips (BS). In detail, the casein hydrolysates (sodium caseinate, acid hydrolyzed casein and casein phosphopeptide) are grafted with amidoximated bamboo strips (SCAOBS, AHCAOBS and CPPAOBS) by chemical cross-linking and amide reactions to construct biaxial adsorption sites, including amidoxime and amino acid branched chains. The optimal adsorption pH of SCAOBS, AHCAOBS and CPPAOBS were 5, 7 and 7, the adsorption capacities were 186.3, 204.0 and 68.6 mg g−1, and the attenuation was 23.1%, 17.7% and 20.2% after 5 cycles, respectively. Utilizing the weavability of BS, SCAOBS, AHCAOBS and CPPAOBS adsorbents are woven and floated in the Yellow Sea Basin, exhibiting that the adsorption capacity of uranium is 0.84, 1.21 and 0.81 mg g−1, respectively, much higher than that of vanadium. Evenly, the adsorption capacity of AHCAOBS for uranium is about 15.3 times that of vanadium (0.077 mg g−1). Through DFT spatial structure optimization, there are indeed biaxial dual adsorption sites (–CO O H from amino acid and C = N - O H from amidoxime groups) between amino acids and amidoxime branched chains, and even the spatial structure of biaxial triple adsorption sites (–CO O H from amino acid, O = C-N from amide bond and C = N -OH from amidoxime groups) is more stable, thereby breaking this bottleneck from the vanadium interference for the amidoxime-based adsorption materials. [ABSTRACT FROM AUTHOR]

Schematic representation of AL-PNIPAM hydrogels for uranium adsorption and desorption. [Display omitted] • Aminated lignin-based thermo-responsive hydrogels (AL-PNIPAM) was prepared by radical polymerization to remove uranium. • The maximum uranium adsorption capacity of AL-PNIPAM hydrogels reached 285.5 mg·g−1 at 298 K. • AL-PNIPAM hydrogels had the larger K d value (3.82 × 105 mL·g−1) in the simulated seawater. In this work, triethylenetetramine (TETA) functional lignin (AL) has been prepared, and the aminated lignin-based thermo-responsive (AL-PNIPAM) hydrogels were prepared by radical polymerization. AL-PNIPAM hydrogels exhibited a satisfactory adsorption performance for uranium aqueous solution, with a maximum uranium adsorption capacity of 285.5 mg·g−1 at 298 K. The study of adsorption kinetics showed that the adsorption model of AL-PNIPAM hydrogels was more consistent with pseudo-second-order kinetic equation, confirming the prominent chemical adsorption of the adsorption process. More importantly, it showed high selectivity towards uranium (VI), and the K d was 3.82 × 105 mL·g−1 in simulated seawater. And uranium (VI) can be effectively desorbed, the best desorption was achieved at 15 °C using dilute nitric acid solution with a maximum resolution efficiency of 76 %. Therefore, AL-PNIPAM hydrogels could be considered as a potential candidate in the field of uranium extraction from seawater. [ABSTRACT FROM AUTHOR]

Efficiently capturing of uranium (VI) [U(VI)] from seawater elicits unparalleled attraction for sustaining the uplifted requirement for nuclear fuel. However, obtaining the abundant U(VI) resource from seawater has always seriously restricted by competitive adsorption from higher concentrations of competitors, especially vanadium (V) [V(V)]. Herein, based on amidoximized natural bamboo strips with hierarchical porous structure, the molecular-level uranyl-specific "nano-holes" was co-constructed by the intramolecular hydrogen bonds for specifically trapping U(VI) from seawater. Manipulating the branched degrees of amino groups enabled the creation of a series of the molecular-level uranyl-specific "nano-holes" that exhibit ultrahigh affinity and selective adsorption of U(VI) with a adsorption capacity 1.8 fold higher compared to that of V(V) after 30 days floating in the Yellow Sea basin, conquering the long-term challenge of the competitive adsorption of V(V) for amidoxime-based adsorbents applied to extract U(VI) from seawater. The diameter of the molecular-level uranyl-specific "nano-holes" is approximately 12.07 Å, significantly larger than (UO 2) 3 (OH) 3 + (10.37 Å) and smaller than HV 10 O 28 5-, thereby exhibiting specifically trapping of U(VI) in a series of adsorption experiments with different U(VI)-V(V) ratios. Besides, the adsorption model based on the combination of experimental and theoretical results is accompanied by "hydrogen bond breaking and coordination bond formation". [Display omitted] [ABSTRACT FROM AUTHOR]

If U(VI) in seawater (unconventional uranium resource) can be extracted efficiently, it can provide important supplies and guarantees for the stable development of nuclear power. In this study, a mixing melting method without condensation agent was proposed to prepare ultra-high flexibility and different proportions DAMN modified EAA resin film (EAA-DAMN) through the condensation reaction between -COOH and -NH 2 and the uniform mixing of liquid EAA and DAMN. In addition, the dense film structure and -C N of EAA-DAMN were transformed into multiple pores structure and amidoxime groups of the amidoximated EAA (AO-EAA) by amidoxime reaction. The AO-EAA-3 showed the most excellent adsorption performance (q e =146.40 mg g−1) at pH = 5, which was 2.33 times that of EAA. Moreover, a hypothesis was proposed for the first time that -NH 2 in the material could combine with H+ ionized by water to form -NH 3 +, and then adsorbed NO 3 - in the solution through electrostatic attraction, and O element from NO 3 - adsorbed on the surface and N-O from amidoxime groups of material as the adsorption active sites performed coordination with U(VI), thereby improving the adsorption performance of AO-EAA. [Display omitted] • The AO-EAA were synthesized by a mixed melting method without condensation agent. • The synthesis mechanism included the condensation reaction and liquid mixing. • The AO-EAA-3′s adsorption capacity was 5.30 μg g−1 in 3 μg L−1 simulated seawater. • The O from NO 3 - and N-O from amidoxime groups acted as adsorption sites. [ABSTRACT FROM AUTHOR]

[Display omitted] • The C N (C N , C N hydrolysis and itself) were used to synthesize AOBS. • The flexibility of BS was utilized to woven and shaped. • The AOBS showed ultra-high adsorption capacity and ultra-fast adsorption rate. • The crude U(VI) (m U = 40.45 mg) was recovered by AOBS-M placing in the Yellow Sea. The uranium(VI) (U(VI)) extraction from seawater was crucial for future energy problems such as increasingly depleted fossil fuels and serious environmental pollution, and it could improve the current situation of limited U(VI) reserves on land. In this study, the natural material bamboo strips (BS) were utilized due to the flexibility and richness of various functional groups, and the amidoximized bamboo strips (AOBS) could be directly prepared by a simple one-step method. The amidoximation of materials not only adjusted the optimal adsorption pH from 4 to 6, but also advanced the hydrophilicity, speeded up the reaction rate (adsorption equilibrium within 1 h, about 0.17 times of BS), and increased the adsorption capacity (q e = 268.41 mg g−1 at pH = 6, about 1.7 times of BS). Importantly, the AOBS maintained its initial stitchability through flexibility adjustment, and was woven into a macro-shaped adsorbent (AOBS-M). After being placed in the Yellow Sea basin for 30 days, approximately 44.75 g of crude U(VI) (U(VI) content = 40.45 mg) was obtained (q e = 0.97 mg g−1), and it showed the excellent selectivity for U(VI). The AOBS-M not only overcame the problem that the existing adsorption materials were difficult to achieve macroscopic large-area molding, but also realized the flexibility adjustment during the modification process by controlling the reaction conditions, and promoted the industrial development of U(VI) extraction from seawater. [ABSTRACT FROM AUTHOR]

• 3D macroscopic g-C 3 N 4 sponge have been designed by thermal polymerization. • Thermodynamic analysis was best described by Langmuir model. • The maximum adsorption capacity of MFCN-DETA composites was 658.57 mg/g at pH 6. • MFCN-DETA showed selective U(VI) adsorption from simulated seawater. Uranium is the key fuel for nuclear power and there is 4.5 billion tons of uranium in the oceans. However, it is a significant challenge for the current adsorbent with powder form to extract uranium from seawater. In this study, we report a facile method for the synthesis of three-dimensional macroscopic g-C 3 N 4 sponge from melamine-formaldehyde (MFCN) resin by thermal polymerization, which can easily be extracted from aqueous solution. Different organic amino (diethylenetriamine, triethylenetetramine and tetraethylenepentamine) modified g-C 3 N 4 sponge composites (MFCN-DETA, MFCN-TETA and MFCN-TEPA) has been designed by schiff base reaction. The uranium adsorption performance of the products from aqueous solutions and simulated seawater was investigated. MFCN, MFCN-DETA and MFCN-TEPA achieved the maximum adsorption capacity at pH 6 and the optimum pH for MFCN-TETA was 5.0. The results showed that the maximum adsorption capacity of MFCN-DETA composites was 658.57 mg/g at pH 6. Furthermore, the MFCN-DETA composites was effectively regenerated using 0.1 N HNO 3 , which could be reused for enrichment of uranium (VI) and the adsorption efficiency could maintain 83% after 5 cycles of adsorption and desorption. The distribution coefficie(K d) value of uranium was 9.1 × 104 mL g−1 for MFCN-DETA in simulating seawater. Thus, MFCN-DETA composites are believed to have promising potential applications in removal of uranium (VI) from seawater. [ABSTRACT FROM AUTHOR]

Adsorption uranium [U(VI)] from U-containing radioactive wastewater (URW) is a critical strategy for solving the resource shortage and environmental pollution in pace with the sustainable development of nuclear energy. However, the URW universally exhibits acidity and contains co-existing metal ions with high concentration. Herein, the amidoximation ethylene-acrylic acid copolymer balls (EAA-AO) with aciduric and super-high mechanical property were successfully synthesized through grafting diaminomaleonitrile and further treatment of amidoximation. Significantly, the mechanical properties of EAA-AO were not affected by the grafting process and maintained super-high mechanical properties. Furthermore, the –NH 2 and unreacted –C N groups in diaminomaleonitrile adjusted the pK a to make the optimal pH be 4. In addition, the microstructure of EAA-AO was transformed from the original dense to multi-layer porous structure, which promoted the mass transfer process and the contact between uranyl ions (UO 2 2+) and internal adsorption active sites. The adsorption capacity of EAA-AO was about 1.78 times that of EAA at pH = 4, and the adsorption capacity for U(VI) was about 8.17 times that of Ba2+ with the second highest adsorption capacity. Therefore, the EAA-AO exhibited ultra-high adsorption performance (q e = 3.196 mg g−1) in the artificial radioactive wastewater, laying a good foundation for subsequent large-scale industrial adsorption of U(VI) in nuclear industrial wastewater. The amidoximation ethylene-acrylic acid copolymer balls (EAA-AO) with ultra-high mechanical property and multi-layer porous structure was revealed for the first time the modulation of hot alkali ethanol water mixed solution on the structure, and exhibited superior adsorption performance and specific selectivity for U(VI) from radioactive wastewater. [Display omitted] • The EAA-AO were successfully synthetized through two-step approach: the dehydration condensation reaction and amidoximation reaction, and the ultra-high mechanical and aciduric property didn't be destroyed by preparation process. • The hot alkaline ethanol-water mixed solution transformed the original dense structure of EAA into a multi-layer porous structure of EAA-AO, which accelerated the mass transfer process and maximized utilization of adsorption active sites. • The EAA-AO showed superior adsorption performance for U(VI) in radioactive wastewater because -NH 2 and unreacted -C≡N groups from diaminomaleonitrile adjusted the pK a of adsorbents. • Based on -N=C-, -O-N- from amidoxime groups, and unreacted -C≡N groups participating in the chemical coordination process, the EAA-AO exhibited specific selectivity for U(VI) in radioactive wastewater with high concentration interfering metal ion. [ABSTRACT FROM AUTHOR]

It is still a challenge to obtain uranium (U) adsorbents with high selectivity, excellent cycle stability and excellent performance through design and synthesis. In this paper, the TiO 2 /CPAN-AO catalyst was prepared by the hydrothermal method combined with high temperature cyclization dehydrogenation. TiO 2 /CPAN-AO has excellent photocatalytic properties, which can reduce U(VI) to U(IV) quickly and selectively. The generated Z-type heterojunction promotes the reduction ability of photogenerated electrons, and obtains great selectivity to UO 2 2+ (Uranyl ions) through the AO group. TiO 2 /CPAN-AO with π-electron conjugated structure broadens the spectral range through surface hybridization and prolongs the lifetime of photo-generated charges. Under the induction of light, the uranium extraction capacity of TiO 2 /CPAN-AO after 5 h of irradiation is about 2.38 g/g. TiO 2 /CPAN-AO is a catalyst with enhanced adsorption capacity, making it possible to extract uranium from large-scale natural seawater in the future. [Display omitted] • Radial microspherical TiO 2 and cyclized polyacrylonitrile have a clear structure and interface. • The material has abundant reaction sites and long photogenerated carrier lifetime. • Further broaden the corresponding spectral range, and improve the light stability of the photocatalyst. • The material has excellent photocatalytic conversion efficiency of U(VI) to U(IV). • This strategy opens up a new way to extract uranium from seawater. [ABSTRACT FROM AUTHOR]

In this study, a swelling layer was constructed on the surface of the nano-polyacrylonitrile (PAN) fiber fabric prepared by electrospinning to enrich uranium (U (VI)) adsorption from seawater. The constructed swelling layer composes of a polyethyleneimine (PEI) containing a huge amount of amino groups and imino groups with strong hydrophilicity. The molecular chain swelled in an aqueous solution by forming a swelling layer on the PAN surface. In addition, p-aminobenzenesulfonic acid (SA) was used as the side chain end group grafted on the PAN surface, the benzene ring as the side chain can hinder the rotation of the PEI chain, thereby increasing the rigidity. The increasing of the rigidity leads to stretch the conformation of the PEI molecular chain, increasing the probability of collision with U (VI), which is beneficial for adsorption. The adsorption capacity of the prepared adsorbent in the adsorption experiment reached 215.25 mg g−1, and the adsorption capacity in the 8 ppm spiked simulated seawater reached 144.5 mg g−1. The adsorption mechanism of U (VI) was analyzed by XPS. The sulfonic acid group in SA as the terminal group and amino group in the swelling layer formed a coordination structure with U (VI). The swelling layer constructed on the surface of polyacrylonitrile fibers is used to effectively extract uranium from seawater. • Nano PAN nonwoven fabric prepared by electrospinning. • A large amount of amino hyperbranched swelling layer grafted on the nano-PAN cloth. • The swelling behavior reduces the resistance of uranium to enter the swelling layer. • The swelling layer can increase the collision probability of end groups and uranyl ions. [ABSTRACT FROM AUTHOR]

Uranium(VI) is an important strategic resource in the development of nuclear energy with 4.5 billion tons in the seawater. However, because of the low concentration of U(VI) and the presence of multiple competing ions in seawater. It is a significant challenge for extracting U(VI) from seawater. In this study, a series of multi-branched HF-PAA-AO n(n =1,2,3,4,5) adsorption materials were prepared for the extraction of U(VI) from solution, and the adsorption properties of the adsorbents were investigated by batch experiments. The experimental results indicated that the HF-PAA-AO 5 material exhibits an excellent removal rate and the maximum adsorption capacity of HF-PAA-AO 5 is of 550.28 mg/g. Moreover, the adsorbent still maintains a high adsorption efficiency after five adsorption-desorption recycles. Meanwhile, the adsorbent showed superior selectivity and adsorption properties (removal rate > 89%) in modified artificial seawater. Therefore, the HF-PAA-AO 5 composite is considered to be a favorable potential adsorbent for capturing U(VI) from seawater. Unlabelled Image • The agglomeration after adsorption of U(VI) is overcome in the HF-PAA-AO 5 material. • 3D multi-branched adsorbent is prepared with PAA and DAMN for the removal of U(VI). • HF-PAA-AO 5 exhibits excellent selectivity and adsorption capacity towards U(VI). • HF-PAA-AO 5 still presents favorable adsorption properties in the modified artificial seawater containing high salinity and low concentration of U(VI). • HF-PAA-AO 5 is a promising adsorbent for the adsorption of U(VI) from seawater. [ABSTRACT FROM AUTHOR]

A polysaccharide-graphene oxide/ZIF (GCZ8A) foam was first designed with macrostructure, antibiofouling and anti-adhesion properties for seawater uranium extraction. • A GCZ8A foam was prepared with macrostructure, anti-biofouling and anti-adhesion. • The GCZ8A adsorbent displays cell growth inhibitory and anti- adhesion behavior. • The maximum U-capacity of GCZ8A is 1.9 times (361.01 mg g−1) for ZIF-8 at pH 8.0. • The removal rate of U(VI) reaches nearly 70% in natural seawater. • Adsorption mechanism is mainly the co-effects of the three type's interactions. Biofouling is the most affecting factor in the recovery of uranium due to the presence of large number of marine microorganisms in the seawater. Herein, a chitosan – graphene oxide/ZIF (GCZ8A) foam adsorbent with antifouling properties was prepared via in situ growth of silver ions doped ZIF-8 on a chitosan-GO foam substrate to overcome the challenges of traditional powder types for real applications. The mechanical properties and degradation tests was investigated to confirm that the GCZ8A adsorbent exhibited high mechanical properties with nearly 352.41 KPa of compression stress and low degradation with 3.26% of mass loss in seawater. Moreover, for Nitzschia , the GCZ8A composites not only displayed growth inhibitory behavior (more than 70% cell death rate), but also inhibited cell adhesion on its surface. The maximum U -uptake capacity of antibiofouling adsorbent (361.01 mg g−1) was 1.9 times than pure ZIF-8 (189.75 mg g−1) at pH 8.0, owing to its large specific surface area (200.79 m2/g) and nitrogen/oxygen functional groups. The adsorbent displayed an excellent reusability and achieved the 121.7 mg g−1 adsorption capacity at fifth cycles. Moreover, GCZ8A adsorbent exhibited high U-uptake capacity (12.24 μg g−1) with 66.31% of U (VI)-removal rate in natural seawater (Bohai, China). All of uranium removal rate of GCZ8A was nearly 70% in simulated contaminated seawater, which further affirmed its potential for actual application. [ABSTRACT FROM AUTHOR]

• An anti-biofouling and robust MMT-PDA/PAM nanocomposite hydrogel was first proposed. • The interpenetrating network lead to high water permeability and stability. • A high adsorption amount of 44 mg g−1 was achieved in lab-scale dynamic adsorption. • The MMT-PDA/PAM displayed excellent anti-adhesion ability without killing algae. • It also showed superior adsorption capacity in algae-contained simulated seawater. A major challenge of uranium extraction from seawater (UES) is to effectively block the biofouling without destroying the ecological balance, especially prevent the attachment of macroalgae on the surface of the adsorbent. Herein, a robust montmorillonite-polydopamine/polyacrylamide nanocomposite hydrogel is reported by a two-step method, including PDA intercalation MMT and further free radical polymerization with AM monomers. The interpenetrating structure of hydrogel lead to high water permeability with the swelling ratio of 51, which could fully facilitate the internal accessible sites exposure and increase the uranium diffusion. As a result, a high adsorption capacity of 44 mg g−1 was achieved in lab-scale dynamic adsorption. Most importantly, the prepared anti-biofouling hydrogel adsorbents display excellent anti-adhesion ability towards Nitzschia after 8 days contact. The adsorption capacity of uranium can reach 2130 μg g−1 in algae-contained simulated seawater. This hydrogel also exhibited a long service life of acceptable mechanical strength and adsorption capacity after at least 6 adsorption-desorption cycles. This new anti-biofouling nanocomposite hydrogel shows great potential as a new generation adsorbent for UES. [ABSTRACT FROM AUTHOR]