A Universally Applicable Strategy for Construction of Anti-Biofouling Adsorbents for Enhanced Uranium Recovery from Seawater

MOFs-Based Materials with Confined Space: Opportunities and Challenges for Energy and Catalytic Conversion

Metal-Organic Frameworks (MOFs) are a very promising material in the fields of energy and catalysis due to their rich active sites, tunable pore size, structural adaptability, and high specific surface area. The concepts of "carbon peak" and "carbon neutrality" have opened up huge development opportunities in the fields of energy storage, energy conversion, and catalysis, and have made significant progress and breakthroughs. In recent years, people have shown great interest in the development of MOFs materials and their applications in the above research fields. This review introduces the design strategies and latest progress of MOFs are included based on their structures such as core-shell, yolk-shell, multi-shelled, sandwich structures, unique crystal surface exposures, and MOF-derived nanomaterials in detail. This work comprehensively and systematically reviews the applications of MOF-based materials in energy and catalysis and reviews the research progress of MOF materials for atmospheric water harvesting, seawater uranium extraction, and triboelectric nanogenerators. Finally, this review looks forward to the challenges and opportunities of controlling the synthesis of MOFs through low-cost, improved conductivity, high-temperature heat resistance, and integration with machine learning. This review provides useful references for promoting the application of MOFs-based materials in the aforementioned fields.

Application of Natural Antibacterial Plants in the Extraction of Uranium from Seawater

Marine biofouling directly affects the performance and efficiency of uranium (U(VI)) extraction from seawater. Compared to traditional chemical methods, natural plant extracts are generally biodegradable and nontoxic, making them an environmentally friendly alternative to synthetic chemicals in solving the marine biofouling problem. The effectiveness of natural antibacterial plants (i.e., pine needle, peppermint, Acorus gramineus Soland, Cacumen platycladi, and wormwood) in solving the marine biofouling problem was evaluated in this work. Experimental results showed that natural antibacterial plants could kill Vibrio alginolyticus in solution and effectively solve the marine biofouling problem of U(VI) extraction. To improve the adsorption capacity of natural plants for U(VI) in seawater, poly(vinylphosphonic acid) (PVPA) was modified on natural antibacterial plant surfaces by irradiation grafting technology. PVPA and natural antibacterial plants work as active sites and base materials for the U(VI) extraction material, respectively. The recovery performance of PVPA/pine needle for U(VI) was preliminarily studied. Results show that the adsorption of U(VI) on PVPA/pine needle follows pseudo-second-order and Langmuir models, and the maximum adsorption capacity is 111 mg/g at 298 K and pH 8.2.

Highly sensitive and specific uranyl ion detection by a fluorescent sensor containing uranyl-specific recognition sites

Uranium pollution has become a serious threat to human health and environmental safety, making the detection of environmental uranium contamination of great importance. The sensitive and specific detection of uranyl ions, which are the dominant form of uranium in the environment, depends on the specific recognition of uranyl ions by chemical groups. In this study, a novel fluorescent sensor containing a highly specific uranyl ion recognition group is synthesized via the reaction of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and 1,1,2,2-tetra(4-carboxylphenyl)ethylene (TPE-(COOH)4). Owing to the effects of aggregation-induced emission (AIE) and intramolecular charge transfer (ICT), the fluorescent sensor, named TPE-EDC, exhibits significant fluorescent properties in aqueous environments. The binding of uranyl ions by specific recognition groups in TPE-EDC leads to a decrease in the ICT effect, thus causing a significant reduction in the emission intensity of TPE-EDC. The attenuation of the fluorescence intensity of TPE-EDC shows an excellent linear relationship with an increase in uranyl ion concentration. TPE-EDC exhibits ultra-sensitive and ultra-selective detection ability for uranyl ions with an ultra-low detection limit of 69 pmol/L and an ultrashort response time of 30 s. These high detection performances render the fluorescent sensor TPE-EDC a promising candidate for early warning of uranium pollution.

Emerging Nanomaterials toward Uranium Extraction from Seawater: Recent Advances and Perspectives

Nuclear energy holds great potential to facilitate the global energy transition and alleviate the increasing environmental issues due to its high energy density, stable energy output, and carbon-free emission merits. Despite being limited by the insufficient terrestrial uranium reserves, uranium extraction from seawater (UES) can offset the gap. However, the low uranium concentration, the complicated uranium speciation, the competitive metal ions, and the inevitable marine interference remarkably affect the kinetics, capacity, selectivity, and sustainability of UES materials. To date, massive efforts have been made with varying degrees of success to pursue a desirable UES performance on various nanomaterials. Nevertheless, comprehensive and systematic coverage and discussion on the emerging UES materials presenting the fast-growing progress of this field is still lacking. This review thus challenges this position and emphatically focuses on this topic covering the current mainstream UES technologies with the emerging UES materials. Specifically, this review elucidates the causality between the physiochemical properties of UES materials induced by the intellectual design strategies and the UES performances and further dissects the relationships of materials-properties-activities and the corresponding mechanisms in depth. This review is envisaged to inspire innovative ideas and bring technical solutions for developing technically and economically viable UES materials.

New insight into the mechanism of biofouling-resistant thiazole-linked covalent organic frameworks for selective uranium capture from seawater

The extraction of uranium from seawater is crucial for the sustainable production of nuclear fuel. Traditional amidoxime-functionalized adsorbents suffer from competitive adsorption of vanadium ion and biofouling. These challenges motivate the development of novel adsorbents for selective uranium extraction from seawater. Herein, four kinds of thiazole-linked covalent organic frameworks (COFs) were investigated to harvest uranium from seawater. The selectivity and anti-biofouling performance were systematically investigated through the molecular dynamics (MD) simulations. Driven by the pore size sieving effect and electrostatic interaction, the Ca2UO2(CO3)3 complex and vanadate anions were selectively separated by different COFs in special areas. On one hand, benefits from the small steric partition factor, the Ca2UO2(CO3)3 complex can stick on the surface of COFs. On the other hand, the dispersive negatively and positively charged areas of studied COFs work as potential binding sites for the Ca2UO2(CO3)3 complex and vanadate anions, respectively. Moreover, an analysis of pulling force and desorption time between uranium and vanadium ions further confirmed the selectivity of various thiazole-linked COFs. The anti-biofouling property was comparatively investigated by dynamic trajectory and solvent accessible surface area. Our outcomes illustrate that the hydroxyl and zwitterionic groups in the thiazole-linked COFs endow their strong surface hydrations to resist marine biofouling. In particular, the TpBdsaPa is identified as a promising candidate due to charge dispersed zwitterionic group as well as remarkable anti-biofouling ability. The present study sheds an atomic-level understanding of the thiazole-linked COFs for selective uranium uptaking from seawater, which will provide aid to design novel adsorbent with highly selective uranium extraction capacity and strong anti-biofouling property.

Enhanced uranium extraction from seawater: from the viewpoint of kinetics and thermodynamics

Uranium extraction from seawater (UES) is recognized as one of the seven pivotal chemical separations with the potential to revolutionize global paradigms. The forthcoming decade is anticipated to witness a surge in UES, driven by escalating energy demands. The oceanic reservoirs, possessing uranium quantities approximately 1000-fold higher than terrestrial mines, present a more sustainable and environmentally benign alternative. Empirical evidence from historical research indicates that adsorption emerges as the most efficacious process for uranium recovery from seawater, considering operational feasibility, cost-effectiveness, and selectivity. Over the years, scientific exploration has led to the development of a plethora of adsorbents with superior adsorption capacity. It would be efficient to design materials with a deep understanding of the adsorption from the perspective of kinetics and thermodynamics. Here, we summarize recent advancements in UES technology and the contemporary challenges encountered in this domain. Furthermore, we present our perspectives on the future trajectory of UES and finally offer our insights into this subject.

Elimination of uranium pollution from coastal nuclear power plant by marine microorganisms: Capability and mechanism

Uranium is one of the sensitive radionuclides in the wastewater of nuclear powers. Due to the fact that nuclear powers are mainly located in coastal areas, the elimination of uranium (U(VI)) pollution from coastal nuclear power is ultimately rely on marine microorganisms. The fixing of U(VI) on V. alginolyticus surface or converting it into sediments is an effective elimination strategy for U(VI) pollution. In this work, typical marine microorganism V. alginolyticus was used to evaluate the elimination of U(VI) pollution by marine microorganisms. Effects of solution conditions (such as pH, temperature, and bacterium concentrations) on the physicochemical properties and elimination capabilities of V. alginolyticus were studied in detail. FT-IR, XPS and XRD results reveal that COOH, NH2, OH and PO4 on V. alginolyticus were main functional groups for U(VI) elimination and formed (UO2)3(PO4)2·H2O. The elimination of U(VI) by V. alginolyticus includes two stages of adsorption and biomineralization. The theoretical maximum adsorption capacity (Cs,max) of V. alginolyticus for U(VI) can reach up to 133 mg/g at pH 5 and 298 K, and the process reached equilibrium in 3 h. Results show that V. alginolyticus play important role in the elimination of U(VI) pollution in seawater.

Ultra-selective uranium separation by in-situ formation of π-f conjugated 2D uranium-organic framework

With the rapid development of nuclear energy, problems with uranium supply chain and nuclear waste accumulation have motivated researchers to improve uranium separation methods. Here we show a paradigm for such goal based on the in-situ formation of π-f conjugated two-dimensional uranium-organic framework. After screening five π-conjugated organic ligands, we find that 1,3,5-triformylphloroglucinol would be the best one to construct uranium-organic framework, thus resulting in 100% uranium removal from both high and low concentration with the residual concentration far below the WHO drinking water standard (15 ppb), and 97% uranium capture from natural seawater (3.3 ppb) with a record uptake efficiency of 0.64 mg·g-1·d-1. We also find that 1,3,5-triformylphloroglucinol can overcome the ion-interference issue such as the presence of massive interference ions or a 21-ions mixed solution. Our finds confirm the superiority of our separation approach over established ones, and will provide a fundamental molecule design for separation upon metal-organic framework chemistry.

Construction of amidoxime-functionalized magnetic hydroxyapatite with enhanced uranium extraction performance from aqueous solution and seawater

A novel amidoxime-functionalized magnetic hydroxyapatite (AFNH) was successfuly fabricated to extract uranium from aqueous solution and seawater. The introduction of amidoxime group not only increased the number of active site of AFNH to speed up the adsorption rate and increase the extraction capacity, but also adjusted the optimal extraction pH from 4 to 8, which was beneficial for capturing uranium from seawater. The maximum adsorption capacity and adsorption efficiency at pH 8 were 945.2 mg g-1 and 99.2%, respectively. AFNH still had good removal efficiency (above 90%) after five cycles, indicating the good regeneration of AFNH. After uranium adsorption, AFNH could be easily recycled by magnetic separation due to its magnetism. In simulated seawater, AFNH also showed excellent uranium removal performance with high adsorption efficiency (84.9%) and adsorption capacity (1.70 mg g-1). Furthermore, the 14-day uranium extraction capacity of AFNH in natural seawater could reach 5.93 mg g-1. The SEM, FTIR, XRD and XPS analyses showed that the enhanced uranium extraction performance of AFNH was mainly attributed to electrostatic interaction, complexation and co-precipitation. In conclusion, AFNH was expected to be a candidate as adsorbent with great potential in extracting uranium from seawater.

Photocatalytic Antimicrobials: Principles, Design Strategies, and Applications

Nowadays, the increasing emergence of antibiotic-resistant pathogenic microorganisms requires the search for alternative methods that do not cause drug resistance. Phototherapy strategies (PTs) based on the photoresponsive materials have become a new trend in the inactivation of pathogenic microorganisms due to their spatiotemporal controllability and negligible side effects. Among those phototherapy strategies, photocatalytic antimicrobial therapy (PCAT) has emerged as an effective and promising antimicrobial strategy in recent years. In the process of photocatalytic treatment, photocatalytic materials are excited by different wavelengths of lights to produce reactive oxygen species (ROS) or other toxic species for the killing of various pathogenic microbes, such as bacteria, viruses, fungi, parasites, and algae. Therefore, this review timely summarizes the latest progress in the PCAT field, with emphasis on the development of various photocatalytic antimicrobials (PCAMs), the underlying antimicrobial mechanisms, the design strategies, and the multiple practical antimicrobial applications in local infections therapy, personal protective equipment, water purification, antimicrobial coatings, wound dressings, food safety, antibacterial textiles, and air purification. Meanwhile, we also present the challenges and perspectives of widespread practical implementation of PCAT as antimicrobial therapeutics. We hope that as a result of this review, PCAT will flourish and become an effective weapon against pathogenic microorganisms and antibiotic resistance.

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 biomass fiber adsorbent grafted with phosphate/amidoxime for efficient extraction of uranium from seawater by synergistic effect

There are approximately 4 billion tons of uranium in the ocean, which is unmatched by the surface. Nevertheless, it's very challenging to extract uranium from the ocean due to the exceedingly low concentration of uranium in the ocean (about 3.3 μg L^-1) as well as high salinity level. Current methods are often limited by selectivity, sustainability, economics, etc. Herein, phosphoric acid group and amidoxime group were grafted to skin collagen fibers through " initiated access" to design a new uranium extraction material, abbreviated as CGPA. Through laboratory simulation experiments, it is concluded that the maximum adsorption capacity of CGPA for uranium reaches 263.86 mg g^-1. It has high adsorption, selectivity, and reusability for uranium. In the actual seawater extraction experiment, CGPA obtained 29.64 μg of uranium after extracting 10.0 L of seawater, and the extraction rate was 90.1%. The adsorbent has excellent effects in kinetics, selectivity, extraction capacity, renewability, etc. In the extraction of uranium from seawater, and is an economically feasible and industrially expandable adsorbent.

Modeling and spectroscopic investigation of U(VI) removal on porous amidoxime-functionalized metal organic framework derived from macromolecular carbohydrate

The investigation of interaction mechanism of U(VI) selective removal on amidoxime-functionalized metal organic framework (i.e., UiO-66(Zr)-AO) derived from macromolecular carbohydrate is conducive to apply metal organic frameworks in actual environmental remediation. The batch experiments showed that UiO-66(Zr)-AO displayed the fast removal rate (equilibrium time of 0.5 h), high adsorption capacity (384.6 mg/g), excellent regeneration performance (<10 % decrease after three cycles) towards U(VI) removal due to the unprecedented chemical stability, large surface area and simple fabrication. U(VI) removal at different pH can be satisfactorily fitted by diffuse layer modeling with cation exchange at low pH and an inner-sphere surface complexation at high pH. The inner-sphere surface complexation was further demonstrated by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analysis. These findings revealed that UiO-66(Zr)-AO can be an effective adsorbent to remove the radionuclides from aqueous solution, which is crucial for recycling of uranium resource and decreasing the uranium harm to the environment.

MOF-implanted poly (acrylamide-co-acrylic acid)/chitosan organic hydrogel for uranium extraction from seawater

In this study, a composite hydrogel with a low swelling ratio, excellent mechanical properties, and good U (VI) adsorption capacity was developed by incorporating a metal-organic framework (MOF) with a poly (acrylamide-co-acrylic acid)/chitosan (P(AM-co-AA)/CS) composite. The CS chain, which contains NH₂, reduces the swelling ratio of the hydrogel to 4.17 after 5 h of immersion in water. The coordinate bond between the MOF and carboxyl group on the surface of P(AM-co-AA)/CS improves the mechanical properties and stability of P(AM-co-AA)/CS. The U(VI) adsorption capacity of P(AM-co-AA)/CS/MOF-808 is 159.56 mg g^-1 at C₀ = 99.47 mg L^-1 and pH = 8.0. The adsorption process is well fitted by the Langmuir isotherm and pseudo-second-order model. The P(AM-co-AA)/CS/MOF-808 also exhibits good repeatability and stability after five adsorption-desorption cycles. The uranium adsorption capacity of the developed adsorbent after one month in natural seawater is 6.2 mg g^-1, and the rate of uranium adsorption on the hydrogel is 0.21 mg g^-1 day^-1.

Highly efficient extraction of uranium from seawater by polyamide and amidoxime co-functionalized MXene

Uranium mainly exists in the form of uranyl carbonate in seawater. [UO₂(CO₃)₃]^4- has strong stability, which increases the difficulty of uranium extraction from seawater. Meanwhile, the complex marine environment, a large number of coexisting competing ions and biological pollution are all non-negligible disturbing factors. Herein, we introduced amidoxime (AO) groups into the surface of Ti₃C₂ and grafted polyamides (PA) by a simple one-step hydrothermal method to produce an efficient seawater uranium extraction adsorbent Ti₃C₂-AO-PA. Owing to the amidoxime groups, the material was highly selective for uranium. And the large number of amino groups in the polyamides gave it ideal resistance to biofouling. The possibility of Ti₃C₂-AO-PA as an adsorbent for uranium extraction from seawater was confirmed by various characterization techniques, numerous adsorption batch experiments, simulated seawater experiments and antibacterial performance tests. It was demonstrated that the uptake of [UO₂(CO₃)₃]^4- by Ti₃C₂-AO-PA showed fast reaction kinetics (about 120 min), brilliant absorption capacity (81.1 mg·g^-1 at pH 8.3), significant high selectivity (32.8 mg-U/g-Ads) and outstanding anti-biological contamination performance (92.9% antibacterial rate). XPS and DFT further indicated that the high extraction ability of Ti₃C₂-AO-PA for uranium was mainly attributed to the strong complexation of AO and -NH₂ with [UO₂(CO₃)₃]^4-. These conclusions showed that Ti₃C₂-AO-PA not only had an ideal application prospect for uranium extraction from seawater, but also provided an available strategy for rapid and selective uranium adsorption from real 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.

Metal-Organic Framework Confined Solvent Ionic Liquid Enables Long Cycling Life Quasi-Solid-State Lithium Battery in Wide Temperature Range

Solid-state Li batteries are receiving increasing attention as a prospective energy storage system due to the high energy density and improved safety. However, the high interfacial resistance between solid-state electrolyte and electrode results in sluggish Li⁺ transport kinetics. To tackle the interfacial problem and prolong the cycle life of solid-state Li batteries, a quasi-solid-state electrolyte (QSSE) based on a solvate ionic liquid (SIL) space-restricted in nanocages of UIO-66 (SIL/UIO-66) is prepared in this study. Benefiting from the effective spatial confinement of the TFSI^- by the pore UIO-66 and the strong chemical interactions between the SIL and metal atoms, SIL/UIO-66 QSSE exhibits high ionic conductivity and good compatibility with electrodes. As a result, Li|QSSE|LFP cells demonstrate excellent rate capability and cycle stability in a wide temperature range of 25-90 °C. This study provides a realistic strategy for the fabrication of safe solid electrolytes with excellent compatibility and long cycle life for high-performance QSSE Li-ion batteries.

Encapsulating Amidoximated Nanofibrous Aerogels within Wood Cell Tracheids for Efficient Cascading Adsorption of Uranium Ions

Continuous filtering adsorption has drawn growing interest in the exploration of uranium resources in seawater and reduction in the environmental risks of uraniferous wastewater from nuclear industries. For most filtering adsorbents, repeated filtration, high membrane thickness, and high pressure are normally essential to achieve both a high rejection ratio and high filtration flux. Herein cellulose fibrils were preferentially exfoliated from the lignin-poor layer of secondary cell walls of balsa wood during an in situ amidoximation process. By maintaining honeycomb-like cellular microstructures and cellulose aerogel stuffing in their cell tracheids, the resultant nanowoods showed superior mechanical properties (e.g., compressive strength ∼1.3 MPa in transverse direction) with large surface areas (∼80 m² g^-1). When their cell tracheids were aligned perpendicular to the flow and the edges sealed with a thermoset polymer, they could serve as efficient and high-pressure filtration membranes to capture aquatic uranium ions. In analogy to a typical cascading filtration system, the filtrate passed successively the layered-organized cell tracheids through abundant micropores on their cell walls, enabling a high rejection ratio of >99% and flux of ∼920 L m^-2 h^-1 under pressure up to 6 bar (membrane thickness of 2 mm). Thus, this study not only provides an in situ approach to producing robust woods with functional nanocellulose encapsulated into their cell tracheids but also offers a sustainable route for high-efficiency extraction of aqueous uranium.

Superrepellent Doubly Reentrant Geometry Promotes Antibiofouling and Prevention of Coronavirus Contamination

The fomite transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has drawn attention because of its highly contagious nature. Therefore, surfaces that can prevent coronavirus contamination are an urgent and unmet need during the coronavirus disease 2019 (COVID-19) pandemic. Conventional surfaces are usually based on superhydrophobic or antiviral coatings. However, these coatings may be dysfunctional because of biofouling, which is the undesired adhesion of biomolecules. A superhydrophobic surface independent of the material content and coating agents may serve the purpose of antibiofouling and preventing viral transmission. Doubly reentrant topology (DRT) is a unique structure that can meet the need. This study demonstrates that the DRT surfaces possess a striking antibiofouling effect that can prevent viral contamination. This effect still exists even if the DRT surface is made of a hydrophilic material such as silicon oxide and copper. To the best of our knowledge, this work first demonstrates that fomite transmission of viruses may be prevented by minimizing the contact area between pathogens and surfaces even made of hydrophilic materials. Furthermore, the DRT geometry per se features excellent antibiofouling ability, which may shed light on the applications of pathogen elimination in alleviating the COVID-19 pandemic.

Cuttlefish ink loaded polyamidoxime adsorbent with excellent photothermal conversion and antibacterial activity for highly efficient uranium capture from natural seawater

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.

Theory-Guided Design of a Method to Obtain Competitive Balance between U(VI) Adsorption and Swaying Zwitterion-Induced Fouling Resistance on Natural Hemp Fibers

The competitive balance between uranium (VI) (U(VI)) adsorption and fouling resistance is of great significance in guaranteeing the full potential of U(VI) adsorbents in seawater, and it is faced with insufficient research. To fill the gap in this field, a molecular dynamics (MD) simulation was employed to explore the influence and to guide the design of mass-produced natural hemp fibers (HFs). Sulfobetaine (SB)- and carboxybetaine (CB)-type zwitterions containing soft side chains were constructed beside amidoxime (AO) groups on HFs (HFAS and HFAC) to form a hydration layer based on the terminal hydrophilic groups. The soft side chains were swayed by waves to form a hydration-layer area with fouling resistance and to simultaneously expel water molecules surrounding the AO groups. HFAS exhibited greater antifouling properties than that of HFAO and HFAC. The U(VI) adsorption capacity of HFAS was almost 10 times higher than that of HFAO, and the max mass rate of U:V was 4.3 after 35 days of immersion in marine water. This paper offers a theory-guided design of a method to the competitive balance between zwitterion-induced fouling resistance and seawater U(VI) adsorption on natural materials.

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.

Ion cross-linking assisted synthesis of ZIF-8/chitosan/melamine sponge with anti-biofouling activity for enhanced uranium recovery

A ZIF-8/chitosan/melamine sponge (CMZ8) uranium adsorbent was prepared using chitosan and zinc ions as adjuvants to achieve the integration of anti-fouling, adsorption and separation properties.

Hydrous titanium oxide and bayberry tannin co-immobilized nano collagen fibrils for uranium extraction from seawater and recovery from nuclear wastewater

Extraction uranium from complicated aqueous solutions (seawater and nuclear wastewater) has been promoting the development of multi-functional adsorbents with high adsorption capacities and high selectivity. Here, we proposed a co-immobilization approach to preparing uranium adsorbents. Due to specific recognition and binding between functional groups, bayberry tannin (BT) and hydrous titanium oxide (HTO) were co-immobilized onto nano collagen fibrils (NCFs). The adsorption performances of NCFs-HTO-BT to uranium were systematically investigated in two aqueous systems, including nuclear wastewater and seawater. Results proved that NCFs-HTO-BT possessed the remarkable adsorption capacities and affinities for uranium in wastewater (393.186 mg g^-1) and spiked seawater (14.878 mg g^-1) with the uranium concentration of 320 mg g^-1 and 8 mg g^-1, respectively. Based on characteristic analysis of the adsorbent before and after uranium adsorption, the hydroxyl groups of HTO, the adjacent phenolic hydroxyl groups of BT, and nitrogen-containing and oxygen-containing functional groups of NCFs were active sites for uranium adsorption.

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.

Amidoxime modified Fe3O4@TiO2 particles for antibacterial and efficient uranium extraction from seawater

Uranium extraction and recovery play a critical role in guaranteeing the sustainable nuclear energy supply and protecting the environmental safety. The ideal uranium sorbents possess high adsorption capacity, excellent selectivity and reusability, as well as outstanding antimicrobial property, which are greatly desired for the real application of uranium extraction from seawater. To address this challenge, a novel magnetic core-shell adsorbent was designed and fabricated by a facile method. The obtained amidoximed Fe₃O₄@TiO₂ particles (Fe₃O₄@TiO₂-AO) achieved equilibrium in 2 h and the maximum adsorption capacity calculated from Langmuir model is 217.0 mg/g. The adsorption kinetics followed the pseudo-second-order model. Meanwhile, the Fe₃O₄@TiO₂-AO exhibited great selectivity when competitive metal ions and anions coexisted. In addition, the magnetic Fe₃O₄@TiO₂-AO could be conveniently separated and collected by an external magnetic field, the regeneration efficiency maintained at 78.5% even after ten adsorption-desorption cycles. In natural seawater, the uranium uptake reached 87.5 μg/g in 33 days. Furthermore, the TiO₂ contained adsorbent showed effective photo induced bactericidal properties against both E. coli and S. aureus. The Fe₃O₄@TiO₂-AO with great U(VI) adsorption performance is highly promising in uranium extraction and reclamation.

Accelerated Chemical Thermodynamics of Uranium Extraction from Seawater by Plant-Mimetic Transpiration

The extraction of uranium from seawater, which is an abundant resource, has attracted considerable attention as a viable form of energy-resource acquisition. The two critical factors for boosting the chemical thermodynamics of uranium extraction from seawater are the availability of sufficient amounts of uranyl ions for supply to adsorbents and increased interaction temperatures. However, current approaches only rely on the free diffusion of uranyl ions from seawater to the functional groups within adsorbents, which largely limits the uranium extraction capacity. Herein, inspired by the mechanism of plant transpiration, a plant-mimetic directional-channel poly(amidoxime) (DC-PAO) hydrogel is designed to enhance the uranium extraction efficiency via the active pumping of uranyl ions into the adsorbent. Compared with the original PAO hydrogel without plant-mimetic transpiration, the uranium extraction capacity of the DC-PAO hydrogel increases by 79.33% in natural seawater and affords the fastest reported uranium extraction average rate of 0.917 mg g^-1 d^-1 among the most state-of-the-art amidoxime group-based adsorbents, along with a high adsorption capacity of 6.42 mg g^-1 within 7 d. The results indicate that the proposed method can enhance the efficiency of solar-transpiration-based uranium extraction from seawater, particularly in terms of reducing costs and saving processing time.

Metal-organic frameworks as superior porous adsorbents for radionuclide sequestration: Current status and perspectives

Efficient separation of hazardous radionuclides from radioactive waste remains a challenge to the global acceptance of nuclear power due to complex nature of the waste, high radiotoxicities and presence of large number of interfering elements. Sorption of radioactive elements from liquid phase, gas phase or their solid particulates on various synthetic organic, inorganic or biological sorbents is looked as one of the options for their remediation. In this context, highly porous materials, termed as metal-organic frameworks (MOFs), have shown promise for efficient capturing of various types of radioactive elements. Major advantages that have been advocated for the application of MOFs in radionuclide sorption are their excellent chemical stability, and their large surface area due to abundant functional groups, and porosity. In this review, recent developments on the application of MOFs for radionuclide sequestration are briefly discussed. Focus has been devoted to address the separation of few crucial radioactive elements such as Th, U, Tc, Re, Se, Sr and Cs from aqueous solutions, which are important for liquid radioactive waste management. Apart from these radioactive metal ions, removal of radionuclide bearing gases such as I₂, Xe, and Kr are also discussed. Aspects related to the interaction of MOFs with the radionuclides are also discussed. Finally, a perspective for comprehensive investigation of MOFs for their applications in radioactive waste management has been outlined.

Constructing Uranyl-Specific Nanofluidic Channels for Unipolar Ionic Transport to Realize Ultrafast Uranium Extraction

High-speed capturing of uranyl (UO₂²⁺) ions from seawater elicits unprecedented interest for the sustainable development of the nuclear energy industry. However, the ultralow concentration (∼3.3 μg L^-1) of uranium element leads to the slow ion diffusion inside the adsorbent particle, especially after the transfer paths are occupied by the coexisted interfering ions. Considering the geometric dimension of UO₂²⁺ ion (a maximum length of 6.04-6.84 Å), the interlayer spacing of graphene sheets was covalently pillared with phenyl-based units into twice the ionic length (13 Å) to obtain uranyl-specific nanofluidic channels. Applying a negative potential (-1.3 V), such a charge-governed region facilitates a unipolar ionic transport, where cations are greatly accelerated and co-ions are repelled. Notably, the resulting adsorbent gives the highest adsorption velocity among all reported materials. The adsorption capacity measured after 56 days of exposure in natural seawater is evaluated to be ∼16 mg g^-1. This novel concept with rapid adsorption, high capacity, and facile operating process shows great promise to implement in real-world uranium extraction.

Anti-bacterial and super-hydrophilic bamboo charcoal with amidoxime modified for efficient and selective uranium extraction from seawater

With the growing demand for nuclear energy, uranium extraction from seawater (UES) is becoming increasingly important due to the ocean reserves 4.5 billion tons for uranium(VI) [U(VI)]. Herein, two kinds of amidoxime modified bamboo charcoal (AOOBCS and AOOBCH) with porous structure, anti-bacterial, and super-hydrophilic properties were successfully synthetized by two etching methods (soaking and hydrothermal). The super-hydrophilic property of AOOBCH accelerated the contact between the amidoxime group and uranyl ions (UO₂²⁺), and promoted the action of anti-bacterial substances (bamboo-quinone) on bacteria to restrain the form of bacterial membrane. In addition, the amidoxime groups not only didn't destroy the super-hydrophilic surface, but also adjusted the adsorbents' pK_a by changing the amidoxime grafting rate. Under PH = 7, the adsorption capacity of AOOBCH was about 1.97 times that of AOOBCS and 2.95 times that of BC. Importantly, the AOOBCH exhibited ultra-high uptake capacity (6.37 mg g^-1) and exceptional selectivity for U(VI) in 100-fold interfering ions simulated seawater system due to the chelation between C(NH₂)NOH and UO₂²⁺ to form a more stable coordination structure (E_ads = -36.56 eV). Benefiting from the superior performance and selectivity, the AOOBCH is a potential candidate for UES.

Facile carboxylation of natural eggshell membrane for highly selective uranium (VI) adsorption from radioactive wastewater

With the commercial nuclear technology rising in society nowadays, it is of paramount importance to remove uranium (VI) in radioactive wastewater through a cost-effective and efficient way. Due to simple operation, low cost and abundant adsorbents, the adsorption method has been widely used to treat the radioactive wastewater. However, unsatisfactory selectivity and potential secondary pollution of most adsorbents hamper their practical large-scale application. To overcome these limitations, an effective and green absorbent is developed by functionalizing the waste eggshell membrane (ESM) with carboxyl-rich agents. This design concept transfers waste ESM (or "trash") into a unique "treasure" absorbent for directly handling radioactive wastewater. The resultant ESM-COOH shows excellent adsorption selectivity toward uranium (VI) with the selectivity coefficient of 75%, exceeding a majority of reported adsorbents. Moreover, its adsorption capacity still maintains 84% of the initial value after six cycles, suggesting good reusability. These excellent features enable the ESM-COOH to adsorb uranium (VI) highly selectively and efficiently. This work offers a concept to transfer biological wastes into treasure for the mass remediation of water body.

Carbon materials for extraction of uranium from seawater

With the rapid growth of population and industrialization, the energy crisis and environmental pollution as two main difficulties urgently need to be solved nowadays. The development and utilization of nuclear energy is of great significance for solving energy support, national security and environmental protection. As the raw material of nuclear energy, a lot of uranium in seawater provide a guarantee for the sustainable and green development of nuclear power plants. Recently, various new carbon-based materials (e.g., carbon nanofibers, multiwalled carbon nanotube, graphene) have been attracted widely intense interest in extraction of uranium from seawater due to large specific surface area, excellent acid-base resistance, high adsorption performance, environmental friendly and low cost. Thus, the systematic reviews concerning the extraction of uranium from seawater on various carbon-based materials were highly desirable. In this review, the extraction methods of uranium from seawater, including electrochemical, photocatalytic and adsorption methods are briefly introduced. Then the application and mechanism of four generation carbon-based materials on the extraction of uranium from seawater are systematically reviewed in details. Finally, the current challenges and future trends of uranium extraction from seawaters are proposed. This review provides the guideline for designing carbon-based materials with high adsorption capacity and exceptional selectivity for U(VI) extraction from seawater.

Metal-Organic-Framework Based Functional Materials for Uranium Recovery: Performance Optimization and Structure/Functionality-Activity Relationships

Uranium recovery has profound significance in both uranium resource acquisition and pollution treatment. In recent years, metal-organic frameworks (MOFs) have attracted much attention as potential uranium adsorbents owing to their tunable structural topology and designable functionalities. This review explores the research progress in representative classic MOFs (MIL-101, UiO-66, ZIF-8/ZIF-67) and other advanced MOF-based materials for efficient uranium extraction in aqueous or seawater environments. The uranium uptake mechanism of the MOF-based materials is refined, and the structure/functionality-property relationship is further systematically elucidated. By summarizing the typical functionalization and structure design methods, the performance improvement strategies for MOF-based adsorbents are emphasized. Finally, the present challenges and potential opportunities are proposed for the breakthrough of high-performance MOF-based materials in uranium extraction.

Smart Adsorbents for Aquatic Environmental Remediation

A noticeable interest and steady rise in research studies reporting the design and assessment of smart adsorbents for sequestering aqueous metal ions and xenobiotics has occurred in the last decade. This motivates compiling and reviewing the characteristics, potentials, and performances of this new adsorbent generation's metal ion and xenobiotics sequestration. Herein, stimuli-responsive adsorbents that respond to its media (as internal triggers; e.g., pH and temperature) or external triggers (e.g., magnetic field and light) are highlighted. Readers are then introduced to selective adsorbents that selectively capture materials of interest. This is followed by a discussion of self-healing and self-cleaning adsorbents. Finally, the review ends with research gaps in material designs.

Bioinspired Durable Antibacterial and Antifouling Coatings Based on Borneol Fluorinated Polymers: Demonstrating Direct Evidence of Antiadhesion

Substituting natural products for traditional poison-killing antifouling agents is an efficient and promising method to alleviate the increasingly serious ecological crisis and aggravate the loss due to marine biofouling. Herein, the successful synthesis of poly(methyl methacrylate-co-ethyl acrylate-co-hexafluorobutyl methacrylate-co-isobornyl methacrylate) copolymer (PBAF) with borneol monomers and fluorine by a free radical polymerization method is reported. The PBA_0.09F coating exhibits outstanding antibacterial and antifouling activity, achieving 98.2% and 92.3% resistance to Escherichia coli and Staphylococcus aureus, respectively, and the number of Halamphora sp. adhesion is only 26 (0.1645 mm²) in 24 h. This remarkable antibacterial and antifouling performance is attributed to the incorporation of fluorine components into the copolymer, which induces a low surface energy and hydrophobicity and the complex molecular structure of the natural nontoxic antifouling agent borneol. In addition, the results showed that the contents of the adhesion-related proteins mfp-3, mfp-5, and mfp-6 were significantly reduced, which proved that natural substances affect the secretion of biological proteins. Importantly, the PBAF coating exhibits excellent environmental friendliness and long-term stability. The antifouling mechanism is clarified, and an effective guide for an environmentally friendly antifouling coating design is proposed.

Covalent Organic Framework Sponges for Efficient Solar Desalination and Selective Uranium Recovery

Energy and fresh water are essential for the sustainable development of human society, and both could be obtained from seawater. Herein, we explored the first covalent organic framework (COF) sponge (named BHMS) by in situ loading the benzoxazole-linked COF (DBD-BTTH) onto a porous polymer scaffold (polydimethylsiloxane) as a synergistic platform for efficient solar desalination and selective uranium recovery. In natural seawater, BHMS shows a high evaporation rate (1.39 kg m^-2 h^-1) and an exceptional uranium recovery capacity (5.14 ± 0.15 mg g^-1) under 1 sun, which are due to its desirable inbuilt structural hierarchy and elastic macroporous open cells providing adequate water transport, increased evaporation sites of seawater, and selective binding sites of uranyl. Besides, the excellent photothermal performance and photocatalytic activity endow the BHMS with high solar desalination efficiency and excellent anti-biofouling activity and promote selective coordination of uranyl.

In-situ synthesis of uranyl-imprinted nanocage for selective uranium recovery from seawater

Adaptive coordination structure is vital for selective uranium extraction from seawater. By strategy of molecular imprinting, uranyl is introduced into the  m ultivariate metal-organic framework (MOF) during the synthesis process to guide the  in-situ  construction of proper nanocage structure for targeting uranyl binding. Except for  the  coordination between uranium with four oxygen from the materials, the axial oxygen of uranyl also forms hydrogen bonds with hydrogen from the phenolic hydroxyl group, which enhances the binding affinity of the material to uranyl. Attributing to the high binding affinity, the adsorbent shows high uranium binding selectivity to uranyl against not only the interfering metal ions, but also the carbonate group that coordinates with uranyl to form [UO 2 (CO) 3 ] 4 -  in seawater. In natural seawater, the adsorbent realizes a high uranium adsorption capacity of 7.35 mg g -1 , t ogether with an 18.38 times higher selectivity to vanadium.  Integrated into account the high reusability, this adsorbent is a promising alternative for uranium recovery from seawater.