Showing papers on "Uranyl published in 2021"

Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C-H Bonds Elaboration

Abstract: Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration of aliphatic C-H bonds. In this manifold, a photocatalyst (PCHAT) exploits the energy of a photon to trigger the homolytic cleavage of such bonds in organic compounds. Selective C-H bond elaboration may be achieved by a judicious choice of the hydrogen abstractor (key parameters are the electronic character and the molecular structure), as well as reaction additives. Different are the classes of PCsHAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, a metal-oxo porphyrin and a tris(amino)cyclopropenium radical dication. The processes (mainly C-C bond formation) are in most cases carried out under mild conditions with the help of visible light. The aim of this review is to offer a comprehensive survey of the synthetic applications of photocatalyzed d-HAT.

Functionalized Iron-Nitrogen-Carbon Electrocatalyst Provides a Reversible Electron Transfer Platform for Efficient Uranium Extraction from Seawater.

Abstract: Uranium extraction from seawater provides an opportunity for sustainable fuel supply to nuclear power plants. Herein, an adsorption-electrocatalysis strategy is demonstrated for efficient uranium extraction from seawater using a functionalized iron-nitrogen-carbon (Fe-Nx -C-R) catalyst, comprising N-doped carbon capsules supporting FeNx single-atom sites and surface chelating amidoxime groups (R). The amidoxime groups bring hydrophilicity to the adsorbent and offer surface-specific binding sites for UO2 2+ capture. The site-isolated FeNx centres reduce adsorbed UO2 2+ to UO2 + . Subsequently, through electrochemical reduction of the FeNx sites, unstable U(V) ions are reoxidized to U(VI) in the presence of Na+ resulting in the generation of solid Na2 O(UO3 ·H2 O)x , which can easily be collected. Fe-Nx -C-R reduced the uranium concentration in seawater from ≈3.5 ppb to below 0.5 ppb with a calculated capacity of ≈1.2 mg g-1 within 24 h. To the best of the knowledge, the developed system is the first to use the adsorption of uranyl ions and electrodeposition of solid Na2 O(UO3 .H2 O)x for the extraction of uranium from seawater. The important discoveries guide technology development for the efficient extraction of uranium from seawater.

Selective extraction of uranium from seawater with biofouling-resistant polymeric peptide

Abstract: Nuclear power could continue to be a reliable and carbon-free energy source at least from a near-term perspective. In addition to the safety issues, another risk that may threaten the sustainability of this technology is the uranium supply disruption. As opposed to the land-based deposits, the ocean contains 1,000 times more uranium reserves and provides a more abundant resource for uranium. However, due to the very low concentration and presence of many other metal ions as well as the accumulation of microorganisms, the development of uranium extraction technology faces enormous challenges. Here we report a bifunctional polymeric peptide hydrogel that shows not only strong affinity to and selectivity for uranium in seawater but also remarkable resistance against biofouling. Detailed characterizations reveal that the amino acid in this peptide material serves as the binding ligand, and uranyl is exclusively bound to the oxygen atoms. Benefiting from its broad-spectrum antimicrobial activity, the present polymeric adsorbent can inhibit the growth of approximately 99% of marine microorganisms. Measurements in natural seawater show that this peptide material delivers an impressive extraction capacity of 7.12 mg g−1 and can be reused. This work opens a new direction for the design of low-cost and sustainable materials for obtaining nuclear fuel. The oceans contain 1,000 times more uranium than terrestrial resources, which could contribute to the sustainability of nuclear power. Here the authors report a polymeric adsorbent that can capture uranium from seawater selectively with an extraction capacity of 7.12 mg g–1. It is even resistant against biofouling and can be reused.

Sunlight-induced uranium extraction with triazine-based carbon nitride as both photocatalyst and adsorbent

Abstract: Extracting uranium from high salinity seawater at ultralow concentrations would beneficially contribute to the sustainable utilization of nuclear energy, but it poses a significant challenge. Here we report a sunlight-driven photocatalysis-assisted extraction (SUPER) method by utilizing a bifunctional carbon nitride material, CN550, which has shown about a tenfold improvement in both adsorption capacity and photocatalytic activity compared to g-C3N4. Uranyl ions could be captured on the surface of CN550, and then deposited as metastudtite nanoparticles with light illumination. Compared with the pure physicochemical adsorption (PA) method, a tenfold higher uranium extraction capacity, up to 1556 mg g−1, has been attained. Additionally, a 25 times improvement of the partition coefficient (PC), from 0.312 to 7.778 L g−1, has also been achieved. In spiked real seawater, the extraction capacity can still achieve more than 1000 mg g−1, and the SUPER method has been found to work under natural sunlight illumination as well.

Rapid and selective uranium extraction from aqueous solution under visible light in the absence of solid photocatalyst

Abstract: Extraction of uranium from radioactive waste-water is of significant importance for environmental protection and the recovery of uranium resource. Different from the previous reports to use the solid absorbent/photocatalyst for U(VI) removal, herein, we proposed a new eco-friendly method for the rapid and selective extraction of uranium from aqueous solutions under visible light without solid materials. At optimal pH value and in the presence of organics like alcohols, the U(VI) could be extracted efficiently to form brown uranium solid over wide uranium concentrations under anaerobic condition and visible light, by utilizing the excitation of the given U(VI) species. With comprehensive modelling of the electronic ultraviolet-visible (UV-Vis) properties, it is proved that pH adjusting towards U(VI) could induce efficient ligand-to-metal-charge-transfer (LMCT) within the uranyl complex under visible light and the reduction of U(VI) to form U(V), which can be transformed into U(IV) via disproportionation reaction. The resulting U(IV) in solid phase makes the extraction much more convenient in operation. More importantly, the excellent selectivity for uranium extraction over interfering alkali metal ions, transition metal ions and the lanthanide metal ions shows a powerful application potential.

Bioinspired hierarchical porous membrane for efficient uranium extraction from seawater

Abstract: The oceans offer a virtually infinite source of uranium and could sustain nuclear power technology in terms of fuel supply. However, the current processes to extract uranium from seawater remain neither economically viable nor efficient enough to compete with uranium ore mining. Microporous polymers are emerging materials for the adsorption of uranyl ions due to their rich binding sites, but they still fall short of satisfactory performance. Here, inspired by the ubiquitous fractal structure in biology that is favourable for mass and fluid transfer, we describe a hierarchical porous membrane based on polymers of intrinsic microporosity that can capture uranium in seawater. This biomimetic membrane allows for rapid diffusion of uranium species, leading to a 20-fold higher uranium adsorption capacity in a uranium-spiked water solution (32 ppm) than the membrane with only intrinsic microporosity. Furthermore, in natural seawater, the membrane can extract as much uranium as 9.03 mg g−1 after four weeks. This work suggests a strategy to be extended to the rational design of a large family of microporous polymer adsorbents that could fulfil the vast promise of the oceans to fuel a reliable and potentially sustainable energy source. The vast amount of uranium in seawater is driving a shift from the use of mined ore to seawater extraction. Here the authors describe an adsorbent design based on polymers of intrinsic microporosity that adopts a bioinspired structure and allows efficient uranium capture.

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

Abstract: 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 A), the interlayer spacing of graphene sheets was covalently pillared with phenyl-based units into twice the ionic length (13 A) 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.

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

Abstract: 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.

Intrinsic Semiconducting Behavior in a Large Mixed-Valent Uranium(V/VI) Cluster

Abstract: We disclose the intrinsic semiconducting properties of one of the largest mixed-valent uranium clusters, [H3 O+ ][UV (UVI O2 )8 (μ3 -O)6 (PhCOO)2 (Py(CH2 O)2 )4 (DMF)4 ] (Ph=phenyl, Py=pyridyl, DMF=N,N-dimethylformamide) (1). Single-crystal X-ray crystallography demonstrates that UV center is stabilized within a tetraoxo core surrounded by eight uranyl(VI) pentagonal bipyramidal centers. The oxidation states of uranium are substantiated by spectroscopic data and magnetic susceptibility measurement. Electronic spectroscopy and theory corroborate that UV species serve as electron donors and thus facilitate 1 being a n-type semiconductor. With the largest effective atomic number among all reported radiation-detection semiconductor materials, charge transport properties and photoconductivity were investigated under X-ray excitation for 1: a large on-off ratio of 500 and considerable charge mobility lifetime product of 2.3×10-4 cm2 V-1 , as well as a high detection sensitivity of 23.4 μC Gyair-1 cm-2 .

In Vivo Uranium Sequestration using a Nanoscale Metal-Organic Framework.

Abstract: An agent for actinide sequestration with fast uranium uptake kinetics and efficient in vivo uranium removal using a nanoscale metal-organic framework (nano-MOF) is proposed. UiO-66 nanoparticles post-synthetically functionalized with carboxyl groups, UiO-66-(COOH)4 -180, exhibit the fastest uranium uptake kinetics reported with more than 65 % of uranyl in fetal bovine serum (FBS) removed within 5 min. Moreover, the in vivo bio-distribution studies show that the material partially accumulates in kidneys and femurs where uranium mainly deposits facilitating the in vivo sequestration of uranium. The results of the in vivo uranium decorporation assays with mice show that UiO-66-(COOH)4 -180 could successfully reduce the amounts of uranyl deposited in kidneys and femurs by up to 55.4 % and 36.5 %, respectively, and is significantly more efficient than the commercial actinide decorporation agent, ZnNa3 -DTPA.

Graphene Oxide Membranes for Tunable Ion Sieving in Acidic Radioactive Waste.

Abstract: Graphene oxide (GO) membranes with unique nanolayer structure have demonstrated excellent separation capability based on their size-selective effect, but there are few reports on achieving ion-ion separation, because it is difficult to inhibit the swelling effect of GO nano sheets as well as to precisely control the interlayer spacing d to a specific value between the sizes of different metal ions. Here, selective separation of uranium from acidic radioactive waste containing multication is achieved through a precise dual-adjustment strategy on d. It is found that GO swelling is greatly restricted in highly acidic solution due to protonation effect. Then the interlayer spacing is further precisely reduced to below the diameter of uranyl ion by increasing the oxidation degree of GO. Sieving uranyl ions from other nuclide ions is successfully realized in pH =3-3 mol L-1 nitric acid solutions.

Nanospace Decoration with Uranyl-Specific "Hooks" for Selective Uranium Extraction from Seawater with Ultrahigh Enrichment Index.

Abstract: Mining uranium from seawater is highly desirable for sustaining the increasing demand for nuclear fuel; however, access to this unparalleled reserve has been limited by competitive adsorption of a wide variety of concentrated competitors, especially vanadium. Herein, we report the creation of a series of uranyl-specific "hooks" and the decoration of them into the nanospace of porous organic polymers to afford uranium nanotraps for seawater uranium extraction. Manipulating the relative distances and angles of amidoxime moieties in the ligands enabled the creation of uranyl-specific "hooks" that feature ultrahigh affinity and selective sequestration of uranium with a distribution coefficient threefold higher compared to that of vanadium, overcoming the long-term challenge of the competing adsorption of vanadium for uranium extraction from seawater. The optimized uranium nanotrap (2.5 mg) can extract more than one-third of the uranium in seawater (5 gallons), affording an enrichment index of 3836 and thus presenting a new benchmark for uranium adsorbent. Moreover, with improved selectivity, the uranium nanotraps could be regenerated using a mild base treatment. The synergistic combination of experimental and theoretical analyses in this study provides a mechanistic approach for optimizing the selectivity of chelators toward analytes of interest.

Tuning gold nanostar morphology for the SERS detection of uranyl.

Abstract: The impact of tunable morphologies and plasmonic properties of gold nanostars are evaluated for the surface enhanced Raman scattering (SERS) detection of uranyl. To do so, gold nanostars are synthesized with varying concentrations of the Good's buffer reagent, 2-[4-(2-hydroxyethyl)-1-piperazinyl]propanesulfonic acid (EPPS). EPPS plays three roles including as a reducing agent for nanostar nucleation and growth, as a nanostar-stabilizing agent for solution phase stability, and as a coordinating ligand for the capture of uranyl. The resulting nanostructures exhibit localized surface plasmon resonance (LSPR) spectra that contain two visible and one near-infrared plasmonic modes. All three optical features arise from synergistic coupling between the nanostar core and branches. The tunability of these optical resonances are correlated with nanostar morphology through careful transmission electron microscopy (TEM) analysis. As the EPPS concentration used during synthesis increases, both the length and aspect ratio of the branches increase. This causes the two lower energy extinction features to grow in magnitude and become ideal for the SERS detection of uranyl. Finally, uranyl binds to the gold nanostar surface directly and via sulfonate coordination. Changes in the uranyl signal are directly correlated to the plasmonic properties associated with the nanostar branches. Overall, this work highlights the synergistic importance of nanostar morphology and plasmonic properties for the SERS detection of small molecules.

Covalent organic framework hydrogels for synergistic seawater desalination and uranium extraction

Abstract: Meeting the demand for fresh water and energy is among the major challenges to the development of human civilization. Herein, we report the concept of a covalent organic framework hydrogel (named CPP) as a synergistic platform for seawater desalination and uranium extraction. In natural seawater, CPP shows an exceptional evaporation rate (0.744 kg m−2 h−1) and uranium extraction capacity (4.15 mg g−1), which benefits from the hydrophilic 3D hydrogel network and capillary microporous channels of CPP providing adequate water transport, improving the mass transfer of uranyl ions, and increasing the binding sites of uranyl ions. In addition, CPP exploits interfacial solar heating to limit heat, increases solar energy utilization, and further accelerates the coordination between uranium and binding sites. The excellent photocatalytic effects endow CPP with high anti-biofouling activity, achieving long-term solar desalination and highly efficient uranium extraction. The connection between freshwater and nuclear energy is realized in a new material providing an opportunity to meet the growing needs of mankind.

Guanidinium-based ionic covalent organic frameworks for capture of uranyl tricarbonate

Abstract: Uranium, which was abundant in the ocean but existed in the form of uranyl tricarbonate ([UO2(CO3)3]4−) with an extremely low concentration of 3.3 ppb, was a significant element of nuclear energy. It is of immediate significance to the research into uranium extraction by the exploration of adsorbents for environment and resource sustainability. Herein, the new ionic covalent organic frameworks (iCOFs) named COF-DG containing the guanidine groups was designed and synthesized via Schiff base reaction between diaminoguanidine hydrochloride and 1,3,5-triformylphloroglucinol. The adsorption performance indicated that the COF-DG possessed an uptake capacity of 65.6 mg g−1 toward the [UO2(CO3)3]4−, attributed to the chemical interaction and anion exchange between [UO2(CO3)3]4− and the cationic COF-DG with Cl−, as well as the electrostatic attraction. Besides, the COF-DG exhibited a higher affinity and selectivity toward [UO2(CO3)3]4− in the presence of the competing anions. Furthermore, the COF-DG displayed an antibacterial rate of 82% against Gram-negative bacteria Escherichia coli owing to the guanidine groups. This work contributes new insights into the further development of iCOFs, for applying as a potential candidate in uranium extraction from seawater in practical engineering. The new ionic covalent organic frameworks named COF-DG was designed and exploited via Schiff base reaction, which exhibited a higher affinity and selectivity toward the [UO2(CO3)3]4−.

Adsorption of uranium(VI) from aqueous solution by phosphorylated luffa rattan activated carbon

Abstract: Phosphorylated activated carbon was prepared from silk gourd loofah rattan by phosphoric acid modification. The effect of pH value, original content of uranyl ions, time and temperature on the adsorption of uranium by phosphorylated activated carbon were studied by static experiments. In this paper, the adsorption process was analyzed by thermodynamics, kinetics and isotherm model. The adsorbent was characterized using infrared spectroscopy and scanning electron microscopy. The results showed that the pH of the solution can significantly affect the adsorption performance and the pH value of the best adsorption was 5.0. The adsorption equilibrium time was about 240 min and when the adsorption quantity was 197 mg/g, it reaches the summit, and the pseudo-second-order equation and Langmuir equation were more suitable to describe the adsorption process.

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

Abstract: 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.

Anhydrous Superprotonic Conductivity of a Uranyl-Based MOF from Ambient Temperature to 110 °C

Abstract: Developing proton–conducting electrolytes that are usable over a wide temperature range (25–150 °C) is highly desirable to enhance the efficiency of fuel cells for on-board automotive applications....

Reticular exploration of uranium-based metal—organic frameworks with hexacarboxylate building units

Abstract: The rational reticular design of metal—organic frameworks (MOFs) from building units of known geometries is essential for enriching the diversity of MOF structures. Unexpected and intriguing structures, however, can also arise from subtle changes in the rigidity/length of organic linkers and/or synthetic conditions. Herein, we report three uranium-based MOF structures—i.e., NU-135X (X = 0, 1, 2)—synthesized from trigonal planar uranyl nodes and triptycene-based hexacarboxylate ligands with variable arm lengths. A new chiral 3,6-connected nuc net was observed in NU-1350, while the extended versions of the ligand led to 3-fold catenated MOFs (NU-1351 and NU-1352) with rare 3,6-connected cml-c3 nets. The differences in the topology of NU-1350 and NU-1351/NU-1352 could be attributed to the slight distortions of the shorter linker in the former from the ideal trigonal prism geometry to an octahedral geometry when coordinated to the trigonal planar uranyl nodes.

Synthesis and Characterization of Water Stable Uranyl(V) Complexes

Abstract: The importance of uranyl(V) (UO2+ ) species associated with environmental and geologic applications is becoming increasingly evident, but the tendency of the uranyl(V) cation to disproportionate in water has prevented the isolation of stable complexes. Here we demonstrate that in the presence of the tridentate complexing dipicolinate (dpa2- ), a ligand highly abundant in soil, the uranyl(V) species can be stabilized and isolated in anoxic basic water. Stable uranyl(V) dipicolinate complexes are readily formed from the reduction of the uranyl(VI) analogue both in organic solution and in basic water, and their solution and solid-state structure were determined. A bis-dpa UV O2+ complex was obtained from water at pH 10, while at higher pH values, a trinuclear mono-dpa cation-cation complex was isolated. These results present the second ever isolated water stable uranyl(V) complex. Moreover, we demonstrate that dipicolinate complexes of UVI O22+ , UV O2+ and UIV are strongly luminescent with a signature characteristic of each oxidation state. This provides unique examples of luminescent UV and UIV compounds.