Uranyl Research Articles

Binding of uranyl cations to a Zr-based metal-organic framework by density functional theory

Zr-based metal–organic frameworks (Zr-MOFs) have been widely used as ion adsorbents for the removal or extraction of toxic and/or radionuclide species from aqueous solutions. However, the mechanisms by which uranyl cations (UO22+) interact with Zr-MOFs have not been established. In this work, the nature of the bonding of uranyl cations with a Zr-MOF was determined using density functional theory for nineteen structurally distinct candidate complexes. The results showed that in all cases the binding energy was of the order of 1.5 eV, but depended on the specific bonding site. The most stable structure involved coordination of the uranyl cation and two structurally distinct oxygens in the Zr-MOF metal node. It was also found that higher degree of deprotonation in Zr-MOF correlated with higher binding energy between the Zr-MOF and uranyl cations. These insights can aid in the design of Zr-MOFs with optimized features for efficient capture of uranyl cations.

Dual-Ligand ZIF-8 Bearing the Cyano Group for Efficient and Selective Uranium Capture from Seawater.

Uranium extraction from seawater is a potential technique that will change the world. Adsorption capacity, selectivity, and antibacterial ability for high-performance uranium adsorbents remain the major challenges. In this study, a dual-ligand zeolitic imidazolate framework 8 (ZIF-8) decorated with cyano groups (ZIF-8-CN) is prepared via a facile blend strategy at room temperature. Owing to the abundant mesopores and nitrogen functional groups, ZIF-8-CN shows an extremely high uranium uptake of 1000 mg/g at pH = 6, which is 2.42 times that of pristine ZIF-8. Noteworthily, ZIF-8-CN possesses a 16.2 mg/g uranium adsorption in natural seawater within 28 days, and the distribution coefficient (Kd = 3.25 × 106 mL/g) is far greater than that for other coexisting metal ions, demonstrating a marked preference for uranyl ions. Except for the coordination between uranium and nitrogen in imidazole, the cyano groups provide additional adsorption sites and preferentially bind to uranyl, thereby strengthening the affinity for uranyl. Notably, ZIF-8-CN displays ultrastrong antimicrobial ability against both Escherichia coli and Staphylococcus aureus, which is greatly desired for the scale-up marine tests. Our study demonstrates the high potential of ZIF-8-CN in uranium capture and provides a wide scope for the application of mixed-ligand MOFs.

Flexible self-supporting Na3MnTi(PO4)3@C fibers for uranium extraction from seawater by electro sorption

As an eco-friendly technique with the superior adsorption performance, electroadsorption has shown great potential for application in uranium (U(VI)) recovery in recent years. However, the electrodes used in the electrosorption generally suffer the adsorbent to be loaded on the conductors, which greatly limited the adsorption performance of the electrodes for uranyl ions. In present study, a flexible self-supporting Na3MnTi(PO4)3@C fibers (NMTP@C fibers) electrode material was rationally designed and prepared by electrostatic spinning method and annealing technique, and its ability to capture U(VI) efficiently was preliminarily demonstrated by batch adsorption and electro sorption. The plentiful phosphate groups provide sufficient active sites for adsorption, while the axially continuous electron conduction and radially short-range ion transport give NMTP@C fibers fast charge/ion transport capability. The NMTP@C fiber can remove 99% of 5 ppm U(VI) in seawater by electro absorption within 1 h. After several cycles of adsorption under seawater conditions, the adsorbent can still maintain a stable adsorption capacity. The adsorption mechanism of NMTP@C nanofibers for U(VI) was investigated by XPS, FT-IR, Raman, SEM-EDS, and XRD, which was electrostatic interactions and surface complexation. These results suggest that NMTP@C fibers are promising high-capacity adsorbents for efficient and selective capture of U(VI) from seawater.

Response of Photonic Hydrogels of Homogeneous Particles to Uranyl Ions in Aqueous Solutions

We study here the response of photonic hydrogels (PHs), made of photonic crystals of homogeneous silica particles in polyacrylamide hydrogels (SPHs), to the uranyl ions UO22+ in aqueous solutions. It is found that the reflection spectra of the SPH show a peak due to the Bragg diffraction, which exhibits a blue shift in the presence of UO22+. Upon exposure to the SPH, UO22+ gets adsorbed on the SPH and forms complex coordinate bonds with multiple ligands on the SPH, which causes shrinking of hydrogel and leads to the blue shift in the diffraction peak. The amount of the blue shift in the diffraction peak increases monotonically up to UO22+ concentrations as high as 2300µM. The equilibration time for the shift in the Bragg peak upon exposure to UO22+ is found to be ~30 min. These results are in contrast to the earlier reports on photonic hydrogels of inhomogeneous microgel particles hydrogel (MPH), which shows the threshold UO22+ concentration of ~600 µM, below which the diffraction peak exhibits a blue shift and a change to a red shift above it. The equilibration time for MPH is ~300min. The observed monotonic blue shift and the faster time response of the SPH to UO22+ as compared to the MPH are explained in terms of homogeneous nature of silica particles in the SPH, against the porous and polymeric nature of microgels in the MPH. We also study the extraction of UO22+ from aqueous solutions using the SPH. The extraction capacity estimated by the arsenazo-III analysis is found to be 112 mM/kg.

Electric field gradients at rubidium sites in rubidium uranyl nitrate and quadrupole moments of 85Rb and 87Rb

The electronic structure along the axial direction of the uranyl ion in rubidium uranyl nitrate (RbUO2(NO3)3) has been probed by nuclear quadrupole resonance and nuclear magnetic resonance measurements of 85Rb and 87Rb quadrupole couplings. The parameter of interest in these experiments is the electric field gradient at the Rb sites, which may be compared with values computed by various theoretical approaches. From this analysis a refinement of the ratio of the quadrupole moments of 85Rb and 87Rb has also been obtained.

Tubular LDHS@TCN composites for photo-assisted uranium extraction

The extraction of uranium (VI) from uranium solutions is an attractive means in the context of increasing demand for uranium resources. Multiple photocatalysis can convert uranyl ions to UO2 precipitation by adjusting the valence of uranium species, which makes it one of the effective means of uranium extraction. In this paper, LDHS@TCN composites were prepared by in-situ growth method, and the II-scheme heterojunction photocatalyst was successfully constructed. The LDHS@TCN composites has photo-assisted uranium reduction ability, and the photo-assisted uranium extraction reaches 1719.12 mg g−1. In addition, XPS and DFT calculations were used to verify the formation mechanism of II-scheme heterojunction and the photoelectron transfer pathway during the reduction of U(VI) to U(IV).

Evidence for Uranium(VI/V) Redox Supported by 2,2'-Bipyridyl-6,6'-dicarboxylate.

The 2,2'-bipyridyl-6,6'-dicarboxylate ligand (bdc) has been shown in prior work to effectively capture the uranyl(VI) ion, UO22+, from aqueous solutions. However, the redox properties of the uranyl complex of this ligand have not been addressed despite the relevance of uranium-centered reduction to the nuclear fuel cycle and the presence of a bipyridyl core in bdc, a motif long recognized for its ability to support redox chemistry. Here, the bdc complex of UO22+ (1-UO2) has been synthetically prepared and isolated under nonaqueous conditions for the study of its reductive chemical and electrochemical behavior. Spectrochemical titration data collected using decamethylcobaltocene (Cp*2Co) as the reductant demonstrate that 1e- reduction of 1-UO2 is accessible, and companion near-infrared and infrared spectroscopic data, along with theoretical findings from density functional theory, provide evidence that supports the accessibility of the U(V) oxidation state. Data obtained for control ruthenium complexes of bdc and related polypyridyl dicarboxylate ligands provide a counterpoint to these findings; ligand-centered reduction of bdc in these control compounds occurs at potentials more negative than those measured for reduction of 1-UO2, further supporting the generation of uranium(V) in 1-UO2. Taken together, these results underscore the usefulness of bdc as a ligand for actinyl ions and suggest that it could be useful for further studies of the reductive activation of these unique species.

Ion-imprinted nanocellulose aerogel with comprehensive optimized performance for uranium extraction from seawater

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

Green and Simple Synthesis of a Nonflammable and Broad‐Spectrum Adsorbent for Uranyl and Other Metal Ions

AbstractAdsorption is an effective technology widely used in the removal of radioactive and other heavy metal ions, the adsorbent plays critical role and development of novel adsorbents is being in urgent demand. In this work, phytic acid (PA)‐modified melamine sponge (MS) adsorbent MS@PDA@PA is prepared conveniently in green solvent water. A wide spectrum of metal ions including radioactive uranyl and transition heavy metal ions can be effectively adsorbed by the MS@PDA@PA due to non‐selectivity of phosphoric acid groups in PA. Different factors including pH of aqueous solution, contact time, and initial concentration of ions on the effect of adsorption of the resultant materials are investigated in detail, and the maximum adsorption capacities for U(VI), Pb(II), Cu(II), Cr(III) are 166.7, 168.5, 114.3, and 101.0 mg g−1 respectively at 298 K. It is notable that the MS@PDA@PA is nonflammable due to employment of MS as frame material, and the thermal stability is even improved after incorporation of PA, greatly reduce the risk of the adsorbent in the processes of storage and usage. The green yet simple synthesis and fire resistance of MS@PDA@PA make it a competitive material for practical treatment of wastewater consisting of toxic metal ions.

Removal of aqueous uranyl ions using titania-supported mesoporous silica composite with the synergistic effect of coupled adsorption and photocatalytic reduction of U(VI)

The aim of this study is to determine and compare the adsorption capacities, kinetic and thermodynamic parameters of the adsorption process of uranyl ions from aqueous solution on nanotube titania impregnated mesoporous silica SBA-15 (TNT-SBA-15) and naked SBA-15 (nSBA-15) adsorbents. The TNT-SBA-15 composite containing various molar ratio of nanotube titania to silica (TNT-SBA-15(m:n)) in the matrix was synthesized by the sol–gel/impregnation method using sodium silicate as a silica precursor, sulphuric acid and nanotube titania. Batch adsorption experiments showed that the maximum adsorption capacity (qmax) of the TNT-SBA-15(m:n = 1:1) composite under indoor light be as high as 2.65 mMoleU g−1 that was 1.4 times higher than that of nSBA-15 under the same conditions. Under UV (300 W) illumination the qmax of TNT-SBA-15(1:1) adsorbent reached 3.49 mMoleU g−1 that was 2 times higher than the qmax in the dark. The increase in qmax of the TNT-SBA-15(1:1) composite in the two experiments was attributed to the synergistic effect of coupled sorption and photocatalytic reduction of U(VI) by titania following the deposition of uranium (IV) (hydr)oxide on the surface of the adsorbent. The adsorption process followed a pseudo-second kinetic model. The activation energy was found to be 160 and 135 kJ Mole−1 for the adsorption on nSBA-15 and TNT-SBA-15(1:1), respectively. The isotherm of the adsorption process follows the Langmuir as well as Freundlich models. The adsorption is an endothermic and spontaneous process. Adsorbed TNT-SBA-15 can be easily regenerated in 0.3 M HNO3 solution, and the qmax of the adsorbent was maintained at 95% the initial qmax after three consecutive adsorption–desorption cycles. These results revealed that, though TNT-SBA-15 made from inexpensive reagents could be an effective adsorbent for uranyl removal from wastewater.

Preparation of solar photo-thermal driven aerogel and clarification of the mechanism for enhanced uranium adsorption

The oceans contain a significant amount of uranium, a valuable resource for nuclear power and fuel applications. However, current technologies for extracting uranium from seawater have limitations, including low efficiency and high energy consumption. Aerogels are promising materials for uranyl ion adsorption due to their high porosity and abundant active sites. This study presents a novel approach for efficient uranium extraction from seawater using a full-fiber-based PAO/PPy aerogel. This aerogel enables rapid diffusion of uranium and accelerated adsorption in the presence of heat generated by sun irradiation, achieving a high adsorption capacity of 69.66 mg g−1 under 1 kW m−2 in 50 mg L−1 solution. The dynamical and thermodynamic simulations indicate the presence of both chemisorption and physisorption throughout the adsorption process. Additionally, the composite aerogel is demonstrated antifouling performance and excellent selectivity of U(VI) in a mixed ionic solution. The present study offers a novel approach for the rational design of aerogel adsorbents that can effectively extract uranium from seawater in outdoor environments, without the need for additional energy input.

Novel potentiometric carbon paste electrodes for trace detection of uranyl(II) ions in petroleum water samples

Two different phosphine sulfide derivatives have been explored as electroactive materials to modify carbon paste electrodes for the accurate detection of uranyl(II) ions. The optimized electrodes based on triphenylphosphine sulfide (L1) and triisobutylphosphine sulfide (L2) responded linearly towards uranyl(II) ions within the range of 1.0 × 10-7 – 1.0 × 10-1 M. Good sensitivity (29.32 ± 0.53 and 27.99 ± 0.61 mV per decade) and detection capability up to 7.9 × 10-8 and 1.0 × 10-7 M uranyl(II) were observed for L1- and L2-based electrodes, respectively. The effect of solution temperature on uranyl(II) determination was studied within 10–60 °C. Selectivity studies showed that the electrodes are capable to discriminate uranyl(II) ions over a large number of possible co-existing inorganic interferents. Moreover, they exhibited speedy response, thermal and long-term stability, and significant reusability. Petroleum water samples spiked with uranyl(II) ions were analyzed utilizing the developed electrodes where good recovery and accuracy were achieved, demonstrating the real-life applicability of the developed electrodes.

Graphene oxide based ion-imprinted polymers for selective uranium adsorption from seawater

The project for the uranium adsorption from seawater provides a new idea for acquisition of uranium resources. However, the low concentration of uranium in seawater, the presence of multiple metal ions, and the attachment of microorganisms all affect the adsorption of uranium by the material. To solve these problems, graphene oxide (GO)-based uranium imprinted polymers with antibacterial properties and specific selectivity for uranium were prepared. β-1,3 glucan was selected as the functional monomer for grafting GO, followed by the imprinting process with uranyl ions as the target template. After elution of the target ions by hydrochloric acid, the ion-imprinted polymer was prepared (GOG-RE). The results of ion-competition adsorption experiments showed that the imprinted material had a high adsorption selectivity for uranyl ions, the Kd value of 1.28 × 105 mL∙g−1. The calculated maximum adsorption capacity was 806.45 mg·g−1. Antibacterial experiments have proven its significant inhibitory effect on E. coli (Gram-negative), S. Aureus (Gram-positive) and Pseudoalteromonas marina. The above results indicate that GOG-RE has excellent application prospects in the field of uranium adsorption from seawater.

Biomineralization of uranium by Desulfovibrio desulfuricans A3-21ZLL under various hydrochemical conditions

Uranium pollution in groundwater environment has become an important issue of global concern. In this study, a strain of Desulfovibrio desulfuricans was isolated from the tailings of acid heap leaching, and was shown to be able to remove uranium from water via biosorption, bio-reduction, passive biomineralization under uranium stress, and active metabolically dependent bioaccumulation. This research explored the effects of nutrients, pH, initial uranium and sulfate concentration on the functional groups, uranium valence, and crystal size and morphology of uranium immobilization products. Results showed that tetravalent and hexavalent phosphorus-containing uranium minerals was both formed. In sulfate-containing water where Desulfovibrio desulfuricans A3-21ZLL can grow, the sequestration of uranium by bio-reduction was significantly enhanced compared to that with no sulfate loading or no growth. Ungrown Desulfovibrio desulfuricans A3-21ZLL or dead ones released inorganic phosphate group in response to the stress of uranium, which associated with soluble uranyl ion to form insoluble uranium-containing precipitates. This study revealed the influence of hydrochemical conditions on the mineralogy characteristics and spatial distribution of microbial uranium immobilization products. This study is conducive to the long-term and stable bioremediation of groundwater in decommissioned uranium mining area.

Decorated xanthan gum/alginate mingled hydrogel beads@La(III)-MOFs@reduced graphene oxide@graphene quantum dots nanohybrid for adsorptive capture and recovery of U(VI)

Uranium as an example of radionuclide toxic heavy metal has shown serious impacts on human and living systems causing well-known sever diseases and therefore, proper attention should be directed and given to safely store and remove uranium hazardous species from the environment especially water resources by finding effective approaches for remediation and capturing uranium from water or wastewater. Therefore, the present investigation is designed to fabricating and combining of xanthan gum and alginate mingled hydrogel beads with reduced graphene oxide (rGO)/graphene quantum dots (GQDs) and lanthanum 1,4-benzene di-carboxylate (La-MOFs) in a single nanocomposite (La-BDC/rGO/GQDs@mingled hydrogel) for direct application in adsorptive capturing of U(VI) from water. The assembled nanocomposite was found into crystalline structure as well as characterized and detected with multiple correlated active functional groups to the constituting units from the FT-IR analysis, while the HR-TEM analysis showed uniformly distributed particles with 25.3 nm as the average nanocomposite size. The effectiveness behavior of La-BDC/rGO/GQDs@mingled hydrogel nanocomposite in adsorptive capturing of uranyl ions (50 and 100 mg/L) was explored and optimized in a number of experimental conditions and revealed to the optimum pH = 7.12, nanocomposite dose = 20 mg and reaction time = 30 min. The adsorptive capture interaction of U(VI) by La-BDC/rGO/GQDs@mingled hydrogel nanocomposite perfectly fitted with the linear and nonlinear pseudo-second order expressions giving 0.96 and 0.93 as well as the linear and nonlinear Freundlich isotherm expressions yielded 0.997 and 0.997 correlation factors, respectively. The computed thermodynamic parameters provided good evidence for the endothermic capture type of U(VI) interaction with La-BDC/GQDs-rGO@mingled hydrogel. The nanocomposite was subjected to more than three regeneration processes with satisfactory results. Finally, La-BDC/rGO/GQDs@mingled hydrogel nanocomposite achieved excellent capture percentage of U(VI) from sea, tap and wastewaters providing 91.19 %, 90.78 % and 91.53 % from 100 mg/L concentration to deliver a direct confirmation for its potential superior performance in adsorptive capturing of U(VI) from contaminated waters.

Selective extraction of uranium from seawater on amidoximated MXene/metal-organic framework architecture under an electric field

Seawater holds tremendous uranium resources, which can sustain the global nuclear industry for thousands of years. However, the existing technologies for uranium extraction from seawater (UES) are constrained by the ultra-low uranium concentration and high interference background. A three-dimensional amidoximated Ti3C2Tx/ZIF-67 architecture (TAZ) is fabricated for highly efficient uranium capture via electrosorption. Besides the excellent electrical conductivity of Ti3C2Tx, the introduction of amidoxime groups and ZIF-67 nanoparticles endows TAZ with porous structure and abundant active sites, which favors the rapid uranyl ions diffusion and enhanced electrosorption. TAZ displays a remarkable uranium extraction uptake of 2224.54 mg/g under an applied voltage of 1 V. Meanwhile, TAZ possesses prominent uranium selectivity resulting from amidoxime groups and imidazole N. TAZ also maintains a good reusability of 63.51% after 10 cycles. Furthermore, the bactericidal rates of TAZ against both Escherichia coli and Staphylococcus aureus achieve nearly 100%. The excellent properties have made TAZ apt for UES with a high uranium uptake of 11.40 mg/g in 24 h under an electric field, which is 5.3 times higher than the physicochemical adsorption. Our work provided a strategy to design high-performance nanomaterials for efficient uranium mining from seawater.

Strengthening Fe(II)/Fe(III) Dynamic Cycling by Surface Sulfation to Achieve Efficient Electrochemical Uranium Extraction at Ultralow Cell Voltage.

Electrochemically mediated Fe(II)/Fe(III) redox-coupled uranium extraction can efficiently reduce the cell voltage of electrochemical uranium extraction (EUE). How to regulate the surface structure to enhance the uranium acyl ion adsorption capacity and strengthen the Fe(II)/Fe(III) redox cycle process is crucial for EUE. In this work, we developed surface sulfated nanoreduced iron (S-NRI) for EUE and exhibited improved properties for EUE at an ultralow cell voltage (-0.1 V). Compared with a nanoreduced iron (NRI) adsorbent, S-NRI displayed faster electrochemical extraction kinetics properties and higher extraction efficiency and capacity for uranium. In a more complex seawater electrolyte containing uranyl ion concentration ranging from 1 to 20 ppm, the removal efficiency could reach almost ∼100% after EUE for 24 h. At a higher 50 ppm uranium acyl ion concentration in a seawater electrolyte, S-NRI exhibited higher extraction capacity (755.03 mg/g), which is better than 528.53 mg/g of NRI at a cell voltage of -0.1 V. Outstanding EUE property could be attributed to the fact that sulfate species (M-SO42-) on the S-NRI surface not only enhanced selective adsorption of uranyl ions but also strengthened the Fe(II)/Fe(III) redox cycle, which accelerated electron transfer between Fe(II) and U(VI), promoted the regeneration of Fe(II) active sites, and finally enhanced the EUE property.

In Silico Simulations Reveal Molecular Mechanism of Uranyl Ion Toxicity towards DNA-Binding Domain of PARP-1 Protein.

The molecular toxicity of the uranyl ion (UO22+) in living cells is primarily determined by its high affinity to both native and potential metal-binding sites that commonly occur in the structure of biomolecules. Recent advances in computational and experimental research have shed light on the structural properties and functional impacts of uranyl binding to proteins, organic ligands, nucleic acids, and their complexes. In the present work, we report the results of the computational investigation of the uranyl-mediated loss of DNA-binding activity of PARP-1, a eukaryotic enzyme that participates in DNA repair, cell differentiation, and the induction of inflammation. The latest experimental studies have shown that the uranyl ion directly interacts with its DNA-binding subdomains, zinc fingers Zn1 and Zn2, and alters their tertiary structure. Here, we propose an atomistic mechanism underlying this process and compute the free energy change along the suggested pathway. Our Quantum Mechanics/Molecular Mechanics (QM/MM) simulations of the Zn2-UO22+ complex indicate that the uranyl ion replaces zinc in its native binding site. However, the resulting state is destroyed due to the spontaneous internal hydrolysis of the U-Cys162 coordination bond. Despite the enthalpy of hydrolysis being +2.8 kcal/mol, the overall reaction free energy change is -0.6 kcal/mol, which is attributed to the loss of domain's native tertiary structure originally maintained by a zinc ion. The subsequent reorganization of the binding site includes the association of the uranyl ion with the Glu190/Asp191 acidic cluster and significant perturbations in the domain's tertiary structure driven by a further decrease in the free energy by 6.8 kcal/mol. The disruption of the DNA-binding interface revealed in our study is consistent with previous experimental findings and explains the loss of PARP-like zinc fingers' affinity for nucleic acids.

TiO2/CPAN-AO heterojunction in-situ grow on carbonized melamine sponge for photocatalytic reduction of uranium (VI)

Extraction of uranium from seawater is of great significance to the development of nuclear energy. Photocatalytic reduction technology offers an innovative solution for the uranium recovery. However, traditional photocatalysts in powder form are limited by recyclable issue. Herein, a constructed novel composite sponge with TiO2/CPAN-AO binary photocatalyst that improved performance in uranium recovery from seawater on account of its exceptional photocatalytic performance, high selectivity, and recyclability. In addition, a new adsorption system called "Diffusion-Capture-Anchoring" was developed for photocatalytic reduction of uranyl ions. The removal rate of uranium within 105 min was 98%, when the initial uranium concentration was 100 mg/L. The selectivity and specificity of the material for uranium were established by the addition of interfering cations. Antimicrobial experiment proved that a great inhibitory effect on Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pseudoalteromonas xiamenensis (P. xiamenensis). More importantly, the excellent recycling property of the CS/TiO2/CPAN-AO was tested via the ten cycles of experiment. As an efficient and recyclable adsorbent, the CS/TiO2/CPAN-AO composite sponge demonstrates great potential for extracting uranium from the seawater.

Poly(vinylphosphonic acid) grafted hollow microspheres with nanoparticles-stacked polymer shell for uranium selective extraction: Dynamic role translation of ethyl α-cyanoacrylate

Hollow polymer microspheres (MPs) have attracted much attention in the field of separation science and technology due to their low density, high specific surface area, easy chemical modification, and abundant binding sites. However, traditional methods for preparing hollow microspheres typically involve surfactants and expensive templates, which are time-consuming and uneconomical, and are not suitable for large-scale production. Oil-soluble α-ethyl cyanoacrylate (ECA), a highly reactive monomer, has been employed to prepare hollow microspheres efficiently in the current study. Self-stabilizing encapsulation via fast interfacial polymerization of ECA would confer a special Pickering-like emulsion droplet reactor for rapid microcapsule formation. The ECA acts as both a monomer and a Pickering emulsifier during the reaction, in which case the newly formed polyECA (PECA) nanoparticles accumulate at the interface, forming a shell of PECA layer eventually. Excellent mechanical property of the PECA layers prevent droplets from coalescence, resulting in hollow PECA MPs after drying. To provide adsorption sites for chelating of uranyl ions, a water-soluble vinyl monomer grafted with ethylene phosphate (vinylphosphonic acid) was then introduced onto the non-reactive double bonds of the polyECA chain under mild reaction conditions, owning to the slightly amphiphilic nature of the PECA chain. The obtained adsorbent for uranium extraction is thus named as PECA-PO43− MPs. Owing to the accessible affinity sites and hollow structure, PECA-PO43− MPs displayed high adsorption capacities at pH = 7–9, showing remarkable selectivity for uranium even in the presence of various competition ions. Moreover, PECA-PO43− MPs exhibited high stability as well as excellent recyclability toward uranium capture after five regeneration cycles. Therefore, this work not only presents a new clue to fabricate novel functional MPs in a high-efficiency way, but also provides a novel platform for efficient uranium extraction.