Search Results (55)

Nuclear technology, while offering significant benefits across various sectors, poses potential health risks due to uranium (U) contamination, particularly through its internalization and subsequent interactions with biological systems. This study investigates the binding of uranyl (UO₂²⁺) and zinc (Zn²⁺) ions to Human Serum Albumin (HSA) that is already bound to fatty acids (FAs), using all-atom molecular dynamics (MD) simulations. The analysis focuses on the structural and dynamic alterations in the protein’s multi-metal binding site (MBS-A) caused by FA binding. Results reveal that FA binding induces a conformational change in HSA, disrupting the pre-formed MBS-A binding site, while still allowing uranyl and zinc ions to interact with residue D249 through strong Coulombic interactions. Secondary binding sites, associated with calcium and zinc binding, remain largely unaffected by FAs, providing alternative coordination for metal ions. This study also explores the binding and unbinding pathways of the metal ions using well-tempered meta-dynamics (WT-MtD), showing that while FA binding disrupts the primary metal binding site, it does not completely inhibit the binding of both uranyl and zinc ions. These findings offer new insights into the nature of uranium’s interactions with blood serum proteins and the role of fatty acids in modulating these interactions, which may help in designing future strategies for managing uranium contamination in biological systems. Full article

Uranium plays an important role in the modern nuclear industry. However, such a radioactive element can also cause severe damage to the environment once leaked or discharged into water or air, having a huge impact on the safety of the biosphere. In this work, we pioneered the use of fluorescent monomers as imprinted units, which promoted fluorescence emission of the material. A novel porous aromatic framework was obtained with uranyl ion chelating sites, namely MIPAF-15. The unique N-O chelating pockets on the 4-bromo-1-H-indole-7-carboxylic acid gave rise to high coordination affinity toward uranyl ions, which enabled the fast adsorption rate of uranyl ions and a uranyl ion adsorption capacity of 44.88 mg·g⁻¹ at 298 K with an initial pH value of 6.0 and the uranyl concentration of 10 ppm. At the same time, the fluorescence quenching effect of MIPAF-15 was observed upon its adsorption of uranyl ions, which allowed the selective detection of uranyl ions with a detection limit of 5.04 × 10⁻⁸ M, lower than the maximum concentration of uranyl ions in drinking water specified by the World Health Organization (6.30 × 10⁻⁸ M) and United States Environmental Protection Agency (1.11 × 10⁻⁷ M). This kind of multifunctional porous material produces a favorable pathway for the detection, removal and degeneration of highly pollutive ions, promoting the overall sustainable development of the natural environment. Full article

Thorium is a notable candidate for resolving uranium shortage caused by the global application of nuclear power generation. Uranium extraction from seawater is another attempt to handle its source deficiency, however, vanadium is one of the main competitive elements in that process. Exploration of probes which can discriminatively detect thorium and vanadium from uranium has primary significance for their further separation and for environmental protection. Herein, N′-(2,4-dihydroxybenzylidene)-4-hydroxylphenylhydrazide, AOH, is used as sensor for Th⁴⁺ and vanadyl (VO²⁺) determination. AOH demonstrates a specific “turn-on” fluorescence selectivity towards Th⁴⁺ over f-block and other foreign metal ions, with a detection limit (LOD) of 7.19 nM in acidic solution and a binding constant of 9.97 × 10⁹ M⁻². Meanwhile, it shows a “turn-off” fluorescence response towards VO²⁺ over other metal ions at the coexistence of Th⁴⁺, with a LOD of 0.386 μM in the same media and a binding constant of 4.54 × 10⁴ M⁻¹. The recognition mechanism, based on HRMS, ¹H NMR, and FT-IR results, demonstrates that VO²⁺ causes the fluorescence quenching by replacing Th⁴⁺ to coordinate with AOH. In real water detection tests, Th⁴⁺ and VO²⁺ exhibited satisfying recoveries. These findings expand the application of sensors in nuclide pollution control. Full article

Developing a cost-effective approach for the remediation of wastewater containing uranyl [U(VI)] ions is essentially important to ecosystems and human health. In this study, a Zn-based ZIF-8 framework was fabricated from wasted batteries through an environmentally friendly ball milling process featuring a distinct microstructure compared to those synthesized from commercial Zn(II) sources. The as-obtained Zn-based ZIF-8 framework can effectively remove U(VI) ions from water, and a high removal efficiency of up to 99% is achieved across different process parameters, including initial dosage, pH values, and the presence of interfering ions. The superior U(VI) removal performance is attributed to the synergistic effect of microstructural features (e.g., crystallite size, specific surface area and pore diameter) and chemical interaction within the framework of Zn-based ZIF-8, resulting in the formation of the U···N chelates. This study integrates waste upcycling and hazardous U(VI) removal in an environmentally sound way, thereby promoting a circular economy. Full article

Bentonite has been considered as backfill material in the long-term deep geological disposal sites for radioactive waste. The performance of raw and irradiated bentonite based on the retention of radioactive nuclides, such as U(VI), is a critical factor for its application. Herein, the intrinsic features and adsorption behavior of Gao Miao Zi (GMZ) bentonite based on uranyl ions was investigated. In aqueous solutions, bentonite can achieve an adsorption rate of up to 100% for U(VI). The primary mechanism of U(VI) adsorption by GMZ bentonite is ion exchange, supplemented by surface complexation. Strong irradiation can introduce slight structural changes and framework fractures in bentonite, reducing its adsorption capacity for U(VI). This study provides an in-depth analysis of the adverse effects of high doses of radiation (100 kGy) on the microstructure and adsorption properties of bentonite, offering important insights for the safe storage of radioactive waste. Full article

The most promising material for uranium extraction from saltwater is generally acknowledged to be fibrous adsorbents. An irradiation-modified anti-biofouling ultra-high-molecular-weight polyethylene (UHMWPE-g-PGAO) fibrous adsorbent with a hyperbranched structure was synthesized. It exhibited adsorption capacities of 314.8 mg-U/g-Ads in aqueous solution and 4.04 mg-U/g-Ads in simulated seawater over a 28-day period. The ultra-high-molecular-weight polyethylene (UHMWPE) fiber was functionalized by covalently linking hyperbranched polyethyleneimine (h-PEI) to facilitate the migration of uranyl ions within the fibers. Additionally, amidoxime and quaternary ammonium groups were immobilized on the fiber surface to enhance uranium affinity and provide defense against marine organisms. This three-dimensional design of amidoxime and h-PEI-modified UHMWPE fiber retained more than 91.0% of its maximum adsorption capacity after undergoing five adsorption-desorption cycles. The UHMWPE-g-PGAO adsorbent exhibits significant antibacterial activity against Escherichia coli and Staphylococcus aureus, achieving an inactivation efficiency of over 99.9%. It is proved to be an innovative fiber adsorbent for uranium extraction from seawater for its biofouling resistance, robustness, and reusability. Full article

2,6-Dipicolinoylbis(N,N-dialkylthioureas) and H₂L^R2 react with uranyl salts and a supporting base (e.g., NEt₃) under formation of monomeric or oligomeric complexes of the compositions [UO₂(L^R2)(solv)] (solv = donor solvents) or [{UO₂(L^R2)(µ₂-OMe)}₂]^2–. In such complexes, the uranyl ions are commonly coordinated by the “hard” O,N,O or N,N,N donor atom sets of the central ligand unit and the lateral sulfur donor atoms remain uncoordinated. Their individual structures, however, depend on the reaction conditions, particularly on the equivalents of NEt₃ used. An unprecedented, selective hydrolysis of the uranium-coordinating bis(thioureato) ligands results in an S/O donor atom exchange at exclusively one thiourea side-arm, when an excess of NEt₃ is used. The resulting trimeric uranyl complexes are isolated in fair yields and have a composition of [(UO₂)₃(L^2Et2)₂(µ₂–OR)(µ₃-O)]^–. H₂L^2Et2 represents the newly formed 2,6-dipicolinoyl(N,N-diethylthiourea)(N,N-diethylurea) and R = H, Me, or Et. {L^2Et2}^2– binds to the uranyl units via the pyridine ring, the dialkylurea arm, and the central carbonyl groups, while the thiourea unit remains uncoordinated. The central cores of the products consist of oxido-centered triangular {(UO₂)₃O}⁴⁺ units. The observed reactivity is metal-driven and corresponds mechanistically most probably to a classical metal-catalyzed hydrodesulfurization. The hydrolytic thiourea/urea conversion is only observed in the presence of uranyl ions. The products were isolated in crystalline form and studied spectroscopically and by X-ray diffraction. The experimental findings are accompanied by DFT calculations, which help to understand the energetic implications in such systems. Full article

2,6-Dipicolinoylbis(N,N-dialkylthioureas), H₂L^R, readily react with uranyl salts under formation of monomeric or dimeric complexes of the compositions [UO₂(L^R)(solv)] (solv = donor solvents such as H₂O, MeOH or DMF) or [{UO₂(L^R)(µ-OMe)}₂]²⁻ (1). In such complexes, the uranyl ions are exclusively coordinated by the “hard” O,N,O or N,N,N donor atom sets of the central ligand unit and the lateral sulfur donor atoms do not participate in the coordination. Different conformations have been found for the dimeric anions. The bridging methanolato ligands and the four uncoordinated sulfur atoms can adopt different orientations with respect to the equatorial coordination spheres of the uranyl units. The presence of non-coordinated sulfur atoms offers the opportunity for the coordination of additional, preferably “soft” metal ions. Thus, reactions with [AuCl(PPh₃)], lead acetate or acetates of transition metal ions such as Ni²⁺, Co²⁺, Fe²⁺, Mn²⁺, Zn²⁺, or Cd²⁺, were considered for the syntheses of bimetallic complexes. Various oligometallic complexes with uranyl units were prepared: [{UO₂(L^R)(μ-OMe)(Au(PPh₃)}₂] (2), [(UO₂)₃Pb₂(L^R)₄(MeOH)₂(μ-OMe)₂] (3), [M{UO₂(L^R)(OAc)}₂] (M= Zn, Ni, Co, Fe, Mn or Cd) (R = Et: 5, RR = morph: 6), or [(UO₂)(NiI)₂(L^R)₂] (7). The products were extensively studied spectroscopically and by X-ray diffraction. Full article

A novel biomass-based magnetic nanoparticle (Fe₃O₄-P-CMC/PAMAM) was synthesized by crosslinking carboxymethyl chitosan (CMC) and poly(amidoamine) (PAMAM), followed by phosphorylation with the incorporation of magnetic ferric oxide nanoparticles. The characterization results verified the successful functionalization and structural integrity of the adsorbents with a surface area of ca. 43 m²/g. Batch adsorption experiments revealed that the adsorbent exhibited a maximum adsorption capacity of 1513.47 mg·g⁻¹ for U(VI) at pH 5.5 and 298.15 K, with Fe₃O₄-P-CMC/G1.5-2 showing the highest affinity among the series. The adsorption kinetics adhered to a pseudo-second-order model (R² = 0.99, q_e,exp = 463.81 mg·g⁻¹, k₂ = 2.15×10⁻² g·mg⁻¹·min⁻¹), indicating a chemically driven process. Thermodynamic analysis suggested that the adsorption was endothermic and spontaneous (ΔH° = 14.71 kJ·mol⁻¹, ΔG° = −50.63 kJ·mol⁻¹, 298. 15 K), with increasing adsorption capacity at higher temperatures. The adsorbent demonstrated significant selectivity for U(VI) in the presence of competing cations, with Fe₃O₄-P-CMC/G1.5-2 showing a high selectivity coefficient. The performed desorption and reusability tests indicated that the adsorbent could be effectively regenerated using 1M HCl, maintaining its adsorption capacity after five cycles. XPS analysis highlighted the role of phosphonate and amino groups in the complexation with uranyl ions, and validated the existence of bimodal U4f peaks at 380.1 eV and 390.1 eV belonging to U 4f_7/2 and U 4f_5/2. The results of this study underscore the promise of the developed adsorbent as an effective and selective material for the treatment of uranium-contaminated wastewater. Full article

The study of small synthetic models for the highly selective removal of uranyl ions from seawater with amidoxime-containing materials is a valuable means to enhance their recovery capacity, leading to better extractants. An important issue in such efforts is to design bifunctional ligands and study their reactions with trans-{UO₂}²⁺ in order to model the reactivity of polymeric sorbents possessing both amidoximate and another adjacent donor site on the side chains of the polymers. In this work, we present our results concerning the reactions of uranyl and pyrimidine-2-amidoxime, a ligand possessing two pyridyl nitrogens near the amidoxime group. The 1:2:2 {UO₂}²⁺/pmadH₂/external base (NaOMe, Et₃N) reaction system in MeOH/MeCN provided access to complex [UO₂(pmadH)₂(MeOH)₂] (1) in moderate yields. The structure of the complex was determined by single-crystal X-ray crystallography. The U^VI atom is in a distorted hexagonal bipyramidal environment, with the two oxo groups occupying the trans positions, as expected. The equatorial plane consists of two terminal MeOH molecules at opposite positions and two N,O pairs of two deprotonated η² oximate groups from two 1.11000 (Harris notation) pmadH⁻ ligands; the two pyridyl nitrogen atoms and the –NH₂ group remain uncoordinated. One pyridyl nitrogen of each ligand is the acceptor of one strong intramolecular H bond, with the donor being the coordinated MeOH oxygen atom. Non-classical C_aromatic-H⋯X (X=O, N) intermolecular H bonds and π–π stacking interactions stabilize the crystal structure. The complex was characterized by IR and Raman spectroscopies, and the data were interpreted in terms of the known structure of 1. The solid-state structure of the complex is not retained in DMSO, as proven via ¹H NMR and UV/Vis spectroscopic techniques as well as molar conductivity data, with the complex releasing neutral pmadH₂ molecules. The to-date known coordination chemistry of pmadH₂ is critically discussed. An attempt is also made to discuss the technological implications of this work. Full article

The development of microbial biofilms increases the survival of microorganisms in the extreme conditions of ecosystems contaminated with components of liquid radioactive waste (LRW) and may contribute to the successful bioremediation of groundwater. The purpose of this work was to compare the composition of the microorganisms and the exopolysaccharide matrix of the biofilms formed on sandy loams collected at the aquifer from a clean zone and from a zone with nitrate and radionuclide contamination. The aquifer is polluted from the nearby surface repository for liquid radioactive waste (Russia). The phylogenetic diversity of prokaryotes forming biofilms on the sandy loams’ surface was determined during 100 days using high-throughput sequencing of the V4 region of the 16S rRNA genes. Scanning electron microscopy was used to study the development of microbial biofilms on the sandy loams. The ratio of proteins and carbohydrates in the biofilms changed in the course of their development, and the diversity of monosaccharides decreased, depending on the contamination of the sites from which the rocks were selected. The presence of pollution affects biofilm formation and EPS composition along with the dominant taxa of microorganisms and their activity. Biofilms establish a concentration gradient of the pollutant and allow the microorganisms involved to effectively participate in the reduction of nitrate and sulfate; they decrease the risk of nitrite accumulation during denitrification and suppress the migration of radionuclides. These biofilms can serve as an important barrier in underground water sources, preventing the spread of pollution. Pure cultures of microorganisms capable of forming a polysaccharide matrix and reducing nitrate, chromate, uranyl, and pertechnetate ions were isolated from the biofilms, which confirmed the possibility of their participation in the bioremediation of the aquifer from nonradioactive waste components and the decrease in the radionuclides’ migration. Full article

A quantitative understanding of the molecular-scale mechanisms of radionuclide sorption on different clay minerals is crucial for the development and safe implementation of geological nuclear waste disposal technologies. We apply classical molecular dynamics (MD) computer simulations to study the adsorption of uranyl on the external basal surfaces of two typical clay models. In the illite model, negative charge is primarily localized in the tetrahedral sheets, while in the lower-charge smectite model, the isomorphic substitutions are introduced in the octahedral sheet. The comparison of atomic density distributions at the clay surfaces and adsorption-free energies profiles as a function of distance from these surfaces demonstrates that overall U behavior at the basal clay surface is quite similar for illite and smectite. Uranyl is sorbed as a mixture of outer-sphere aqua complexes [UO₂(H₂O)₅]²⁺ and hydrolyzed aqua complexes [UO₂(H₂O)_4–5OH]⁺ on both surfaces. The structural and compositional differences between the models do not greatly affect the uranyl’s nearest coordination environment and are mainly reflected in the specific localization and orientation of the uranyl ions at both surfaces and in the magnitude of the adsorption-free energies. The observed quantitative characteristics of uranyl interactions with illite and smectite surfaces will help to better understand U behavior during the sorption process on clay minerals for the entire range of mixed-layer illite–smectite structures. A comparison of two versions of the ClayFF force field in the simulations made it possible to more accurately and quantitatively evaluate some subtle features of the uranyl–clay interactions and to obtain a more precise composition of uranyl complex with the modified ClayFF force field (ClayFF-MOH). Full article

Renewable and biodegradable polysaccharides have attracted interest for their wide applicability, among them their use as sorbents for heavy metal ions. Their high sorption capacity is due mainly to the acidic groups that populate the polysaccharide backbone, for example, carboxylic groups in alginate and sulfate ester groups in the iota and lambda carrageenans. In this study, these three polysaccharides were employed, alone or in different mixtures, to recover different heavy metal ions from aqueous solutions. All three polysaccharides were capable of adsorbing Eu³⁺, Sm³⁺, Er³⁺, or UO₂²⁺ and their mixtures, findings that were also confirmed using XPS, TGA, and FTIR analyses. In addition, the highest sorption yields of all the metal ions were obtained using alginate, alone or in mixtures. While the alginate with carboxylic and hydroxyl groups adsorbed different ions with the same selectivity, carrageenans with sulfate ester and hydroxyl groups exhibited higher adsorption selectivity for lanthanides than for uranyl, indicating that the activity of the sulfate ester groups toward trivalent and smaller ions was higher. Full article

It is a central issue to eliminate radioactive uranium (U(VI)) efficiently from water. In this manuscript, β-cyclodextrin was cross-linked with 2,3,5,6-tetrafluoro-1,4-benzenedicarbonitrile, and then a carboxylation reaction was used to prepare porous cross-linked polymers rich in carboxyl groups (CA-PCDPs). Subsequently, magnetic nanoparticles (MNPs) were loaded onto the CA-PCDPs via coprecipitation, and magnetic porous β-cyclodextrin polymer nanoparticles (CA-PCDP@MNPs) were successfully obtained, which were used for efficient elimination of U(VI) from nuclear wastewater solution. Moreover, SEM, FTIR, VSM, BET, and XRD were employed to investigate the CA-PCDP@MNP and found that it had a well-developed porous structure, high specific surface area, and abundant oxygen-containing functional groups (carboxyl, hydroxyl, C-O-C, Fe-O, etc.), providing sufficient active sites for chelating uranyl ions. Experiments illustrated that the CA-PCDP@MNP had efficient removal ability for U(VI), and the maximum theoretical adsorption amount for U(VI) reached 245.66 mg/g at pH 6.0 and 303 K. Moreover, the adsorption process was more suitable for the quasi second-order kinetic model and Langmuir adsorption isotherm model, indicating that the adsorption process was chemical adsorption. Meanwhile, the CA-PCDP@MNPs also exhibited fast response magnetic recovery ability and excellent regeneration and recycling ability. In addition, the data of the adsorption mechanism demonstrated that oxygen-containing functional groups, which were rich on the surface of CA-PCDP@MNPs, were the main binding active sites of U(VI). From the above results, it can be deduced that the CA-PCDP@MNP has a good application prospect in the practical application of nuclear wastewater treatment. Full article

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. Full article