Polyguanidine-modified adsorbent to enhance marine applicability for uranium recovery from seawater

Efficient and stable adsorption uranium from wastewater by P-ZBCT composite adsorbent at low dosage

In this research, a new synthesis approach was developed for an adsorbent, namely the phosphorylated ZIF-8/bamboo charcoal/chitosan/tannic acid (P-ZBCT) composite, for the efficient adsorption of uranyl ions from wastewater at low dosages. Impressively, the uranium adsorption rate of P-ZBCT reaches up to 98 % at a low dosage of 0.056 g/L in a 10-mg/L uranium solution, outperforming most reported uranium adsorption materials. The theoretical maximum adsorption capacity of P-ZBCT for uranium at 308 K and pH 6.0 is 2357.69 mg/g, with uranium adsorption being a spontaneous endothermic chemical reaction. Mechanistic analysis reveals that surface functional groups such as PO, amino group, and CN play a pivotal role in uranium adsorption. A competitive adsorption experiment shows that zinc is the most competitive with uranium adsorption; however, the partition coefficient of U is 11 times that of zinc, indicating that the absorption of uranium is more selective than that of other metal ions, such as zinc. Adsorption treatment using P-ZBCT successfully reduces the uranium content in real uranium tailings-containing pond wastewater to 34 μg/L. P-ZBCT demonstrates exceptional recycling performance, maintaining an adsorption rate of 85 % even after 10 sorption-desorption cycles. Therefore, P-ZBCT exhibits significant potential for efficiently extracting uranium from low-concentration uranium-containing wastewater.

Superhydrophilic Amidoxime-Modified Poly(vinyl alcohol) Fibers for Enhanced Uranium Extraction from Seawater

The efficient extraction of uranium from seawater is an important step in the sustainable development of nuclear energy. Polymer-based absorbents are considered to be ideal materials due to their high adsorption properties and industrialization feasibility. Their adsorption performance could be further improved by enlarging the specific surface area and enhancing hydrophilicity. Here, an amidoxime-modified poly(vinyl alcohol) fiber (PVA-g-PAO) with a high specific surface area and superhydrophilicity was prepared by a one-step grafting method. The hydrophilicity was conducive to the infiltration of ions into the adsorbent, and the pore structure constructed by grafting an adsorption functional layer on the surface of fibers increased the specific surface area. The adsorption capacity of PVA-g-PAO can be arrived at 11.3 mg/g in simulated seawater (uranium concentration: 330 ppb) with a high adsorption selectivity of uranium. Furthermore, more than 95% of uranium in a 5 ppm uranium solution can be adsorbed within 6 days, indicating the fast adsorption ability of PVA-g-PAO, which is further confirmed by the fast adsorption capacity in natural seawater (3.37 mg/g for 30 days). Such PVA-g-PAO gel fiber adsorbents with superhydrophilicity and high specific surface area are promising adsorbents for uranium extraction from natural seawater.

Uranium Extraction from Seawater: A Novel Approach Using Aluminum Fumarate-Based Metal-Organic Framework Aerogels

Efficient extraction of uranyl ions from seawater is crucial for the commercialization of nuclear technology. Metal-organic frameworks (MOFs), with their superior uranium extraction properties, face challenges in large-scale applications due to their powdery nature and the difficulty of assembling them into mechanically stable macroscopic composites. To address this, successfully synthesized 90 wt % nanoMOF (aluminum fumarate) loaded directional aerogels (AlFA-3-10) using polyvinyl alcohol (PVA) as an adhesive, which demonstrates robust strength longitudinally and transversely. Our uranium adsorption experiments reveal that at a pH of 8 (akin to that of seawater), the AlFA-3-10 achieves a maximum adsorption capacity of 1146.25 mg g-1, maintaining this exceptional performance over five cycles. Notably, in simulated seawater, AlFA-3-10 exhibits high selectivity for uranyl ions with minimal interference from other ions. The directional pores within AlFA-3-10 facilitate fluid transmission and exchange, ensuring optimal contact between the MOF and uranyl ions, thereby enhancing electrostatic attraction and electron transport for improved capture efficiency. This streamlined approach maximizes the intrinsic potential of nano-MOFs and heralds a new era for their integration into macroscopic composite materials.

Challenges and Opportunities of Uranium Extraction From Seawater: a Systematic Roadmap From Laboratory to Industry

Uranium extraction from seawater (UES) is crucial for ensuring the sustainable development of nuclear power and has seen significant advancements in recent years. However, natural seawater is a highly complex biogeochemical system, characterized by an extremely low uranium (U) concentration (≈3.3 µg L-1), abundant competitive ions, and significant marine biological pollution, making UES a formidable challenge. This review addresses the challenges encountered in UES and explores potential methods for enhancing the industrial UES system, including membrane separation, electrochemistry, photocatalysis, and biosorption. Additionally, several representative marine tests are summarized and restrictive factors of large-scale UES are analyzed. Finally, the further development of UES from laboratory to industry applications is promoted, with a focus on technological innovation. The goal is to stimulate innovative ideas and provide fresh insights for the future development of the UES system, bridging the gap between laboratory research and industrial implementation.

Nano-tentacled interconnected channels organic gel for rapid uranium extraction from seawater

Due to dwindling terrestrial uranium resources and escalating ecological pressures, the long-term viability of uranium supply has become a critical concern. The immense uranium reserves in seawater present a potential solution, yet extraction technology faces dual challenges of efficiency and adaptability to complex marine environments. Current interconnected porous adsorbents, despite their high flux properties, are limited by low specific surface area and weak mechanical strength, which constrain their effectiveness. Here, inspired by the unique hierarchical structures of marine organisms, we describe an organic gel adsorbent with supermacroporous and interconnected channels (10 ∼ 100 µm) adorned with "nano-tentacle" structures. This design significantly enhances the specific surface area by 18 times, increasing adsorption sites and imparting antibacterial properties. Notably, this adsorbent maintains structural integrity and superior mechanical strength (1.32 MPa tensile and 2.44 MPa compressive strength) even when fully saturated. During a 23-day trial in natural seawater, a uranium adsorption rate of 0.332 mg g⁻¹ day⁻¹ was achieved. This work offers a pioneering approach for the design and fabrication of hierarchical structured adsorbents, highlighting the immense potential of extracting uranium from seawater for sustainable energy production.

Bis-substituted amino acid functionalized chitosan aerogels: High uranium adsorption capacity and antibacterial properties

Based on the goal of "carbon neutralization and carbon peaking", it is still challenging to develop a high adsorption performance and environmentally friendly material for uranium extraction. We proposed a new idea of "Three-Dimensional Environmental-Friendly". A series of amino acid bis-substituted chitosan aerogels (C-1, C-2, C-3, C-4 and C-5) were prepared by ice template method and selective substitution reaction in water environment. Among them, C-3 adsorbent has the antibacterial properties of gram-positive bacteria, gram-negative bacteria and marine bacteria, which is more suitable for uranium adsorption in complex environments. Also, C-3 adsorbent solves the shortcomings of poor adsorption property and easy to cause secondary pollution during modification of traditional chitosan materials. The selectivity and adsorption capacity of uranium are further improved by the unique functional groups of serine residues. At pH = 7, the maximum adsorption capacity reaches 606.32 mg/g. In addition, C-3 adsorbent have excellent selectivity and stability. The synergistic effect of coordination, electrostatic interaction and intraparticle diffusion between C-3 adsorbent and uranium may be the key to its high adsorption performance. The high performance of chitosan adsorbent provides a new idea for the design and application of green and efficient uranium adsorption materials.

Insights into enhanced immobilization of uranyl carbonate from seawater by Fe-doped MXene

Extracting uranium from seawater not only reduces radioactive contamination in seawater but also provides a source of uranium energy. However, due to the low concentration of uranium in seawater and the high salinity of seawater, extraction of uranium from seawater is challenging. In this work, we demonstrated a simple strategy to synthesize Fe-doped MXene (Fe@Ti3C2Tx) via a hydrothermal method and applied for uranium enrichment in seawater. The Fe@Ti3C2Tx exhibited excellent adsorption performance in high salinity environments. The removal capacity of Fe@Ti3C2Tx was determined to be 526.6 mg/g for UO2(CO3)22- at 328 K with quick reaction equilibrium (∼ 30 min). Kinetic and thermodynamic analyses of UO2(CO3)22- elimination process on Fe@Ti3C2Tx surface revealed it to be a spontaneous and endothermic single-phase elimination process. FT-IR and XPS analyses further indicated that the removal mechanism of UO2(CO3)22- by Fe@Ti3C2Tx was surface complexation. Our study suggests that Fe@Ti3C2Tx can provide a feasible solution for uranium enrichment in seawater.

Study on uranium ion adsorption property of porous glass modified with amidoxime group

In this paper, we prepared three types of porous glasses (PGs) with specific surface areas of 311.60 m2/g, 277.60 m2/g, and 231.38 m2/g, respectively, via borosilicate glass phase separation. These glasses were further modified with amidoxime groups (AO) using the hydroxylamine method, yielding adsorbents named 1.5-PG-AO, 2-PG-AO, and 3-PG-AO. The adsorption performance of these adsorbents under various conditions was investigated, including sorption kinetics and adsorption mechanisms. The results reveal that the number of micropores and specific surface area of PG are significantly reduced after AO modification. All three adsorbents exhibit similar adsorption capabilities. Particularly, pH has a pronounced effect on U (VI) adsorption of PG-AO, with a maximum value at pH = 4.5. Equilibrium adsorption is achieved within 2 h, with a maximum adsorption capacity of 129 mg/g. Notably, a uranium removal rate of 99.94% is attained. Furthermore, the adsorbents show high selectivity in uranium solutions containing Na+ or K+. Moreover, the adsorbents demonstrate exceptional regeneration ability, with the removal rate remaining above 80% even after undergoing five adsorption-desorption cycles. The adsorption reaction of uranium on PG-AO involves a combination of multiple processes, with monolayer chemisorption being the dominant mechanism. Both the complex adsorption of AO and the ion exchange and physical adsorption of PG contribute to the adsorption of uranyl ions on the PG-AO adsorbents.

In-situ constructing amidoxime groups on metal-free g-C3N4 to enhance chemisorption, light absorption, and carrier separation for efficient photo-assisted uranium(VI) extraction

The development of inexpensive and efficient semiconductor catalysts for photo-assisted uranium extraction from seawater remains a huge challenge. Herein, we have successfully synthesized amidoxime-rich g-C3N4 (AO-C3N4) by simply amidoximing a cyano-rich precursor for photo-assisted uranium extraction from seawater. The amidoxime groups not only served as the U(VI) binding sites for efficient uranium adsorption, but also significantly improved the visible light absorption capacity and carrier separation efficiency via introducing defect energy level, resulting in the excellent photocatalytic activity for AO-C3N4 towards photo-assisted uranium extraction. In the process of photo-assisted uranium extraction, U(VI) was first adsorbed by the amidoxime groups on the AO-C3N4 and then reduced to U(IV), while (UO2)O2·2H2O and (UO2)O2·4H2O were further formed by the oxidation of U(IV) by superoxide radicals (·O2-). Moreover, the generated reactive oxygen species (ROS) under light endowed AO-C3N4 with outstanding antibacterial properties, preventing the limitation of uranium extraction capacity from marine biofouling.

Recent Advances in Antibiofouling Materials for Seawater-Uranium Extraction: A Review

Nuclear power has experienced rapid development as a green energy source due to the increasing global demand for energy. Uranium, as the primary fuel for nuclear reactions, plays a crucial role in nuclear energy production, and seawater-uranium extraction has gained significant attention. However, the extraction of uranium is usually susceptible to contamination by microorganisms, such as bacteria, which can negatively affect the adsorption performance of uranium adsorption materials. Therefore, an important challenge lies in the development of new antibacterial and antiadhesion materials to inhibit the attachment of marine microorganisms. These advancements aim to reduce the impact on the adsorption capability of the adsorbent materials. This paper reviews the antibiofouling materials used for extracting seawater uranium, and corresponding mechanisms are discussed.

A cascade electro-dehydration process for simultaneous extraction and enrichment of uranium from simulated seawater

Uranium extraction from seawater has become a crucial issue that has raised tremendous attention. The transport of water molecules along with salt ions through an ion-exchange membrane is a common phenomenon for typical electro-membrane processes such as selective electrodialysis (SED). In this study, a cascade electro-dehydration process was proposed for the simultaneous extraction and enrichment of uranium from simulated seawater by taking advantage of water transport through ion-exchange membranes and the high permselectivity of membranes for monovalent ions against uranate ions. The results indicated that the electro-dehydration effect in SED allowed 1.8 times the concentration of uranium with a loose structure CJMC-5 cation-exchange membrane at a current density of 4 mA/cm². Thereafter, a cascade electro-dehydration by a combination of SED with conventional electrodialysis (CED) enabled approximately 7.5 times uranium concentration with the extraction yield rate reaching over 80% and simultaneously desalting the majority of salts. Overall, a cascade electro-dehydration is a viable approach, creating a novel route for highly effective uranium extraction and enrichment from seawater.

Uranium extraction from seawater: material design, emerging technologies and marine engineering

Uranium extraction from seawater (UES), a potential approach to securing the long-term uranium supply and sustainability of nuclear energy, has experienced significant progress in the past decade. Promising adsorbents with record-high capacities have been developed by diverse innovative synthetic strategies, and scale-up marine field tests have been put forward by several countries. However, significant challenges remain in terms of the adsorbents' properties in complex marine environments, deployment methods, and the economic viability of current UES systems. This review presents an up-to-date overview of the latest advancements in the UES field, highlighting new insights into the mechanistic basis of UES and the methodologies towards the function-oriented development of uranium adsorbents with high adsorption capacity, selectivity, biofouling resistance, and durability. A distinctive emphasis is placed on emerging electrochemical and photochemical strategies that have been employed to develop efficient UES systems. The most recent achievements in marine tests by the major countries are summarized. Challenges and perspectives related to the fundamental, technical, and engineering aspects of UES are discussed. This review is envisaged to inspire innovative ideas and bring technical solutions towards the development of technically and economically viable UES systems.

High-strength and anti-biofouling nanofiber membranes for enhanced uranium recovery from seawater and wastewater

Ultrathin fibers can increase the contact area between adsorbents and seawater during the uranium extraction process; however, their construction usually aggravates the complex spinning technology and lowers their mechanical strength. Meanwhile, high strength and antifouling ability are essential for ocean adsorbents to withstand the complex natural environment and microbial systems. Herein, we design high-strength and anti-biofouling poly(amidoxime) nanofiber membranes (HA-PAO NFMs) via a supramolecular crosslinking. Bacterial cellulose supplies the NFMs with ultrathin fiber structure, and large amounts of adsorption ligands are immobilized on the framework via the crosslinking with antibacterial ions. Thus, different from other fibers, HA-PAO NFMs achieve ultrathin diameter (20-30 nm), high BET area (51 m² g^-1), and excellent mechanical strength (13.6 MPa). The uranium adsorption capacity reaches to 409 mg-U/g-Ads in the simulated seawater, 99.2% uranium can be removed from the U-contained wastewater, and the adsorption process can be observed by the naked eye due to the significant color changes. The inhibition zones indicate their excellent anti-biofouling ability, which contributes to 1.83 times more uranium extraction amount from natural seawater than the non-antifouling adsorbents. Furthermore, they display a long service life and can be large-scale prepared, and the HA-PAO NFMs have potential in the massive uranium recovery.

Facile synthesis of low-cost MnPO4 with hollow grape-like clusters for rapid removal uranium from wastewater

In order to deal with the environmental resource problems caused by nuclear pollution and uranium mine wastewater, it is particularly important to develop uranium removal adsorbent materials with low cost, high efficiency and controllable rapid preparation. In this work, the hollow grape-like manganese phosphate clusters (h-MnPO₄) were synthesized in 4 h by in-situ etching without template at room temperature, which can quickly and effectively remove uranium ions from wastewater. Due to the reasonable hollow structure, more effective adsorption sites are exposed. The obtained sample h-MnPO₄-200 reaches adsorption equilibrium in 1 h and can remove 97.20% uranyl ions (initial concentration is 100 mg L^-1). Under the condition of 25 ℃ and pH= 4, the maximum adsorption capacity of h-MnPO₄-200 for uranium was 751.88 mg g^-1. The FT-IR, XPS and XRD analysis showed that -OH and PO₄^3- groups played a key role in the adsorption process. Thanks to the synergistic adsorption mechanism of surface complexation and dissolution-precipitation, h-MnPO₄-200 maintained a high removal rate in the presence of competitive anions and cations. In a word, h-MnPO₄-200 can be rapidly synthesized through a facile and low-cost method and has a great application prospect in the practical emergency treatment of uranium-containing wastewater.

Nanoemulsion assembly toward vaterite mesoporous CaCO3 for high-efficient uranium extraction from seawater

Uranium extraction from seawater is particularly significant and regarded as an indispensable strategy for satisfying the increasing demand for nuclear fuel owing to the high uranium reserves (about 4.5 billion tons) in seawater, while remains great challenges due to the low concentration, the interference of various cations and the complexity of the marine environment. Thus, developing a highly efficient adsorbent with high adsorption capacity, excellent selectivity, low cost, and facile synthesis method is significant and urgently required. Inorganic materials show many advantages in adsorption such as low cost, fast response, high stability, etc, while conventionally, have poor capacity and selectivity especially in real seawater. Herein, mesoporous CaCO₃ (mCaCO₃) with vaterite phase is synthesized by a facile nanoemulsion strategy and "ready-to-use" for uranium adsorption without functionalization and post treatment. Surfactant Pluronic F127 not only assembles into reverse micelles to form mesopores, but also stabilizes the active vaterite phase. The obtained mCaCO₃ with high surface area (48.2 m²/g), interconnected mesopores (11 nm), and unique vaterite phase achieves highly efficient uranium adsorption with a maximum adsorption capacity of 850 ± 20 mg-U/g in uranium-spiked seawater and 6.5 ± 0.5 mg-U/g in 700 L of natural seawater for one week, as well as excellent selectivity, matching the state-of-the-art U adsorbents. After adsorption, mCaCO₃-U is dissolved with a simple acid elution to obtain concentrated uranyl solution for purification, avoiding the disposal of adsorbents. To the best of our knowledge, this is the first case to report mesoporous CaCO₃ for uranium adsorption from seawater with such a good performance. The facile synthesis, abundant raw materials and eco-friendly adsorption-desorption processes endow the mCaCO₃ as a promising candidate for large-scale uranium extraction from seawater.

Enhanced uranium photoreduction on Ti3C2Tx MXene by modulation of surface functional groups and deposition of plasmonic metal nanoparticles

Photocatalytic reduction of soluble hexavalent uranium (U(VI)) is a novel and efficient avenue to enriching U(VI), where the free U(VI) is firstly bound on the surface of photocatalysts and then reduced to insoluble tetravalent uranium (U(IV)) by photoelectrons. Therefore, constructing the efficient U(VI) binding sites on photocatalysts is an efficient strategy to boost catalytic activity toward U(VI) photoreduction. Herein, we successfully constructed an efficient catalyst for U(VI) photoreduction by depositing Ag nanoparticles on Ti₃C₂T_x MXene with abundant U(VI) binding sites (Ag/Ti₃C₂T_x-O). Impressively, the U(VI) extracting mass over Ag/Ti₃C₂T_x-O under light reached up to 1257.6 mg/g in 120 min, which was almost 11 times as high as that without light. Further mechanistic studies indicated that the U(VI) binding sites on Ti₃C₂T_x MXene in Ag/Ti₃C₂T_x-O were beneficial to the reduction of U(VI) by significantly decreasing its reduction potential. More importantly, hot electrons generated by Ag nanoparticles were transferred into the binding sites to easily reduce the bound U(VI), resulting in the remarkable performance of Ag/Ti₃C₂T_x-O during U(VI) enrichment.

Advancing Strategies of Biofouling Control in Water-Treated Polymeric Membranes

Polymeric membranes, such as polyamide thin film composite membranes, have gained increasing popularity in wastewater treatment, seawater desalination, as well as the purification and concentration of chemicals for their high salt-rejection and water flux properties. Membrane biofouling originates from the attachment or deposition of organic macromolecules/microorganisms and leads to an increased operating pressure and shortened service life and has greatly limited the application of polymeric membranes. Over the past few years, numerous strategies and materials were developed with the aim to control membrane biofouling. In this review, the formation process, influence factors, and consequences of membrane biofouling are systematically summarized. Additionally, the specific strategies for mitigating membrane biofouling including anchoring of hydrophilic monomers, the incorporation of inorganic antimicrobial nanoparticles, coating/grafting of cationic bactericidal polymers, and the design of multifunctional material integrated multiple anti-biofouling mechanisms, are highlighted. Finally, perspectives on the challenges and opportunities in anti-biofouling polymeric membranes are shared, shedding light on the development of even better anti-biofouling materials in near future.

Application of poly(vinylphosphonic acid) modified poly(amidoxime) in uptake of uranium from seawater

To enhance the anti-biofouling properties and adsorption capability of poly(amidoxime) (PAO), vinylphosphonic acid (VPA, CH2[double bond, length as m-dash]CH-PO3H2) was polymerized on poly(acrylonitrile) (PAN) surface by plasma technique, followed by amidoximation treatment to convert the cyano group (-C[triple bond, length as m-dash]N) into an amidoxime group (AO, -C(NH2)[double bond, length as m-dash]N-OH). The obtained poly(vinylphosphonic acid)/PAO (PVPA/PAO) was used as an adsorbent in the uptake of U(vi) from seawater. The effect of environmental conditions on the anti-biofouling property and adsorption capability of PVPA/PAO for U(vi) were studied. Results show that the modified PVPA enhances the anti-biofouling properties and adsorption capability of PAO for U(vi). The adsorption process is well described by the pseudo-second-order kinetic model and reached equilibrium in 24 h. Adsorption isotherms of U(vi) on PVPA/PAO can be well fitted by the Langmuir model, and the maximum adsorption capability was calculated to be 145 mg g-1 at pH 8.2 and 298 K. Experimental results highlight the application of PVPA/PAO in the extraction of U(vi) from seawater.

Polyamidoxime grafting on ultrahigh-strength cellulose-based jute fabrics for effectively extracting uranium from seawater

Ultrahigh-strength cellulose-based jute fabric (jute–TMC–PAO) for the highly effective extraction of uranium from seawater.

Ion-imprinted guanidine-functionalized zeolite molecular sieves enhance the adsorption selectivity and antibacterial properties for uranium extraction

The important properties in the development of adsorbents for uranium extraction from seawater include specific selectivity to uranium ions and anti-biofouling ability in the ocean environment. In this paper, we report a novel strategy for efficient selective extraction of uranium from aqueous solutions and good anti-bacterial properties by surface ion-imprinted zeolite molecular sieves. Guanidine-modified zeolite molecular sieves 13X (ZMS-G) were synthesized and used as the support for the preparation of uranium(vi) ion-imprinted adsorbents (IIZMS-G) by ligands with phosphonic groups. The prepared IIZMS-G adsorbent was characterized via Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The results showed that guanidine groups have been successfully introduced onto the support while its morphology structure was maintained. The adsorption performance and selectivity to U(vi) ions, antibacterial property, and reusability of IIZMS-G were evaluated. The results showed that the maximum adsorption capacity reached 141.09 mg g⁻¹ when the initial concentration of metal ions was 50 mg L⁻¹ at pH 6 and 20 °C. The adsorption process followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. The IIZMS-G exhibits an efficient selective adsorption of U(vi) ions from aqueous solutions with competing ions. In addition, the IIZMS-G exhibited excellent inhibitory effects on Escherichia coli and Staphylococcus aureus, and the inhibitory rate was 99.99% and 98.96% respectively. These results suggest that the prepared IIZMS-G adsorbent may promote the development strategy of novel high selectivity and antifouling adsorbents for uranium recovery from seawater.

The important properties in the development of adsorbents for uranium extraction from seawater include specific selectivity to uranium ions and anti-biofouling ability in the ocean environment.