Binding Of Uranyl Ions Research Articles

Overcoming Chemical Dissociation Processes: Electrochemical Modulation of High‐Affinity Binding Sites for Rapid Uranium Extraction from Seawater

AbstractCurrently reported adsorption (hydroxyl or amidoxime) groups must dissociate hydrogen ions to form ─O− units for the coordination with uranyl ions. However, this process suffers a high energy barrier for bond dissociation, leading to the sluggish uptake speed and low adsorption capacity for uranium extraction from natural seawater. Herein, this study proposes a strategy for electrochemical modulation of adsorption sites, which overcomes the chemical dissociation processes of hydrogen ions. Poly‐2,5‐dihydroxy‐1,4‐benzoquinone containing redox carbonyl groups is intercalated into the channels of a covalent organic framework (COF) through in situ cross‐linking of 2,5‐dihydroxy‐1,4‐benzoquinone. Under electrochemical modulation, the C═O groups are transformed into adjacent phenol–oxygen anions to cooperate with the coordination atoms (O and N) on the COF channel for rapid binding of uranyl ions, which gave an absorption rate of 4.2 mg g−1 d−1 (≈3.3 ppb of uranium in natural seawater). Notably, the COF‐based electrodes delivered an average capacity of ≈20.8 mg‐U per g for uranyl ion adsorption during 5 days of extraction, ≈3000 times larger than that of classical tannin‐based adsorbents. The proposed method for preparing electrochemically modulated binding sites is expected to provide guidance for designing high‐efficiency adsorbents in the future.

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.

Characterization of Uranyl (UO22+) Ion Binding to Amyloid Beta (Aβ) Peptides: Effects on Aβ Structure and Aggregation.

Uranium (U) is naturally present in ambient air, water, and soil, and depleted uranium (DU) is released into the environment via industrial and military activities. While the radiological damage from U is rather well understood, less is known about the chemical damage mechanisms, which dominate in DU. Heavy metal exposure is associated with numerous health conditions, including Alzheimer's disease (AD), the most prevalent age-related cause of dementia. The pathological hallmark of AD is the deposition of amyloid plaques, consisting mainly of amyloid-β (Aβ) peptides aggregated into amyloid fibrils in the brain. However, the toxic species in AD are likely oligomeric Aβ aggregates. Exposure to heavy metals such as Cd, Hg, Mn, and Pb is known to increase Aβ production, and these metals bind to Aβ peptides and modulate their aggregation. The possible effects of U in AD pathology have been sparsely studied. Here, we use biophysical techniques to study in vitro interactions between Aβ peptides and uranyl ions, UO22+, of DU. We show for the first time that uranyl ions bind to Aβ peptides with affinities in the micromolar range, induce structural changes in Aβ monomers and oligomers, and inhibit Aβ fibrillization. This suggests a possible link between AD and U exposure, which could be further explored by cell, animal, and epidemiological studies. General toxic mechanisms of uranyl ions could be modulation of protein folding, misfolding, and aggregation.

Threonine Phosphorylation of an Electrochemical Peptide-Based Sensor to Achieve Improved Uranyl Ion Binding Affinity

We have successfully designed a uranyl ion (U(VI)-specific peptide and used it in the fabrication of an electrochemical sensor. The 12-amino acid peptide sequence, (n) DKDGDGYIpTAAE (c), originates from calmodulin, a Ca(II)-binding protein, and contains a phosphothreonine that enhances the sequence's affinity for U(VI) over Ca(II). The sensing mechanism of this U(VI) sensor is similar to other electrochemical peptide-based sensors, which relies on the change in the flexibility of the peptide probe upon interacting with the target. The sensor was systematically characterized using alternating current voltammetry (ACV) and cyclic voltammetry. Its limit of detection was 50 nM, which is lower than the United States Environmental Protection Agency maximum contaminant level for uranium. The signal saturation time was ~40 min. In addition, it showed minimal cross-reactivity when tested against nine different metal ions, including Ca(II), Mg(II), Pb(II), Hg(II), Cu(II), Fe(II), Zn(II), Cd(II), and Cr(VI). Its reusability and ability to function in diluted aquifer and drinking water samples were further confirmed and validated. The response of the sensor fabricated with the same peptide sequence but with a nonphosphorylated threonine was also analyzed, substantiating the positive effects of threonine phosphorylation on U(VI) binding. This study places emphasis on strategic utilization of non-standard amino acids in the design of metal ion-chelating peptides, which will further diversify the types of peptide recognition elements available for metal ion sensing applications.

Anti-biofouling bio-adsorbent with ultrahigh uranium extraction capacity: One uranium resource recycling solution

Uranium extraction from seawater is an effective solution to the shortage of uranium resources on land. However, because of the high salinity in seawater, an extremely low uranium concentration (~3.3 ppb) and biofouling caused drastically decrease the performance of adsorbents, and the practical development of uranium extraction from seawater still faces major challenges. Here, we demonstrated a simple strategy to utilize waste feather fiber (FF) to prepare anti-biofouling amidoxime functionalized FF (FF-Cu2O/AO), which was applied to the extraction uranium from seawater. The introduction of Cu2O endows FF-Cu2O/AO with anti-biofouling and enhances the binding of uranyl ions to amidoxime. FF-Cu2O/AO exhibited outstanding uranium adsorption performance, adsorbing 816 mg-U/g-Ads from 8 ppm uranium-spiked water. Following immersion in natural seawater for 30 days, the uranium extraction capacity of FF-Cu2O/AO reached 7.73 mg-U/g-Ads. More importantly, the strategy can be used for the preparation of other uranium adsorbents based on amidoxime functionalized polymer fibers to provide antibacterial and improved adsorption performance. Economic analysis shows that the cost of FF-Cu2O/AO adsorption of uranium from natural seawater is much lower than that of conventional adsorbents. Therefore, FF-Cu2O/AO would be an outstanding candidate for extracting uranium from seawater because of its high uranium extraction capacity, anti-biofouling and low-cost.

Molecular Structure of the Surface-Immobilized Super Uranyl Binding Protein

Recently, a super uranyl binding protein (SUP) was developed, which exhibits excellent sensitivity/selectivity to bind uranyl ions. It can be immobilized onto a surface in sensing devices to detect uranyl ions. Here, sum frequency generation (SFG) vibrational spectroscopy was applied to probe the interfacial structures of surface-immobilized SUP. The collected SFG spectra were compared to the calculated orientation-dependent SUP SFG spectra using a one-excitonic Hamiltonian approach based on the SUP crystal structures to deduce the most likely surface-immobilized SUP orientation(s). Furthermore, discrete molecular dynamics (DMD) simulation was applied to refine the surface-immobilized SUP conformations and orientations. The immobilized SUP structures calculated from DMD simulations confirmed the SUP orientations obtained from SFG data analyzed based on the crystal structures and were then used for a new round of SFG orientation analysis to more accurately determine the interfacial orientations and conformations of immobilized SUP before and after uranyl ion binding, providing an in-depth understanding of molecular interactions between SUP and the surface and the effect of uranyl ion binding on the SUP interfacial structures. We believe that the developed method of combining SFG measurements, DMD simulation, and Hamiltonian data analysis approach is widely applicable to study biomolecules at solid/liquid interfaces.

Synthesis ofpara-linked azacalix[n]pyridine[n]pyrazines and their uranyl ion binding properties

Based on the fragment coupling strategy, the novel macrocycles,para-linked azacalix[n]pyridine[n]pyrazines (n= 2 and 4) with coexisting different heteroaromatics, were synthesized readily starting from 2,5-dibromopyrazine and 2,6-dibromopyridine.

Assorted functionality-appended UiO-66-NH2 for highly efficient uranium(vi) sorption at acidic/neutral/basic pH.

A series of functionalized metal organic frameworks (MOFs) were synthesized by the post-synthetic modification (PSM) of Zr(iv)-containing UiO-66-NH2 MOFs using covalent grafting with various functional groups utilizing pendant –NH2 moieties. The tethering of amide (with/without pendant carboxylic acid), iminopyridine, phoshinic amide and sulphur-containing functionalities produced a library of eight different UiO-66-NH2 derivatives. The functionalized MOFs were characterized by FT-IR spectroscopy, NMR, PXRD, TGA, SEM-EDX and BET surface area analysis. Uranyl ion extraction with the functionalized MOFs was investigated in acidic/neutral/basic conditions (pH 1 to 9). This work presents a comprehensive study of different functionalized MOFs to investigate the effects of various analytical parameters, including pH, contact time, and desorption process. The MOFs as solid phase extractants (SPEs) provide a direct comparison of the sorption efficiencies of different functional groups on a common solid support. A phosphorous-functionalized material, UiO-66-PO-Ph, with enhanced thermal stability (∼500 °C) exhibits the best sorption capacity (∼96%) in an acidic medium (pH 3). The parent MOF UiO-66-NH2 (92%) and iminopyridine-functionalized UiO-66-IMP (90%) showed excellent sorption in neutral conditions (pH 7). Amide-containing MOFs UiO-66-AM1 (40%), UiO-66-AMMal (31%) and UiO-66-AMGlu (70%), sulfur-based MOFs UiO-66-SMA (65%) and UiO-66-SSA (27%), and phosphorous-functionalized UiO-66-PO-OPh (50%) displayed maximum sorption in basic conditions (pH 8). The kinetics studies revealed rapid uranium sorption in about 2 h due to the effective binding of uranyl ions with the anchored functional groups of MOFs; quantitative elution of uranyl ions from the MOF framework was carried out with 0.1/0.01 M HNO3. The MOFs also exhibit moderate recyclability for uranium sorption and can be regenerated by an acidic solution. The functionalized MOFs alter the stability in acidic/basic media; thus, UiO-66-NH2 is a versatile MOF material employed as an SPE for the extraction of radionuclides from aqueous media. This work also provides a platform for the development of new functionalized MOF materials for the efficient sorption of uranium as well as moderate recyclability for its removal, and the potential applications include the removal of uranium from aqueous waste streams.

Pyrolytic temperature evaluation of macauba biochar for uranium adsorption from aqueous solutions

This study aims to evaluate the effect of the pyrolytic temperature on the biochar derived from the macauba endocarp for the removal of uranium (VI) from aqueous solutions. The endocarp was subjected to six different pyrolytic temperatures, ranging from 250 °C to 750 °C. The biochars obtained at each temperature were evaluated for their adsorption capacities (“q”). The highest adsorption capacities were obtained for the biochar produced at 250 °C (BC250), followed by the one obtained at 350 °C (BC350), with removal efficiencies of 86% and 80%, respectively. The best condition was achieved when the endocarp was subjected to temperatures between 300 and 350 °C, at which it was possible to obtain a satisfactory balance among adsorption capacity, gravimetric yield and fixed carbon content. This characteristic, combined with the high removal efficiency, points to an ideal working temperature of 350 °C. Elemental analysis showed a decrease of the H/C and O/C ratios when higher pyrolytic temperatures were applied, indicating an inverse relationship between the carbonization and the surface polar functional groups, which were likely responsible for an increased adsorptive capacity in biochars produced at lower temperatures. Both FTIR and XPS analysis indicated that oxygen-containing groups such as hydroxyls and carboxylic acids were involved with the binding of uranyl ions.

Self‐assembled biogenic melanin modulated surface chemistry of biopolymers‐colloidal silica composite porous matrix for the recovery of uranium

ABSTRACTA new composite porous matrix surface modulated by self‐assembled melanin was developed and investigated for its affinity to bind uranium from an aqueous medium. The composite matrix was synthesized using biopolymers (i.e., agarose and alginate) and inorganic colloidal silica nanoparticles (AACS) by the process of cryotropic‐gelation at subzero‐temperature. Post‐synthesis surface modification of AACS matrix with melanin (MAACS) was performed by green chemistry. The in situ sequestrial conversion of l‐Dopa by the biocatalytic activity of tyrosinase enzyme allows the formation of melanin on the surface of AACS matrix. The functional moieties on the matrix display fast kinetics and high binding capacity with respect to uranium. MAACS matrix showed high porosity (~90%) with interconnected pores, high swelling kinetics and permeability. Other physicochemical properties of the matrix, such as thermal stability, storage modulus, and surface charge potential were found to be increased, while percent degradation decreased, which demonstrate improved properties of the matrix after impregnation of silica nanoparticles and surface functionalization with melanin. Thermodynamic parameters suggest that the binding of uranyl ions is passive and spontaneous. The concentrated recovery of uranium was achieved with reusability potential of adsorbent. These results suggest an environment friendly and safer method for the recovery of uranium. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46937.

Higher uranium(VI) biosorption capacity and repeated use of PA-ZZF51 prepared by marine mangrove endophytic fungus ZZF51 and phytic acid

The grafted mangrove endophytic fungus Fusarium sp. #ZZF51 by phytic acid with polyphosphate groups (PA-ZZF51) was successfully synthesized by esterification reaction, and its uranium(VI) biosorption conditions, models, mechanism and regeneration property were also obtainted. The uranium(VI) removal from aqueous solution by PA-ZZF51 was optimized at pH (5.0), S/L ratio (0.2 g L−1), time (45 min), and the initial uranyl ions concentration (100 mg L−1) with 453.70 mg g−1 of biosorption capacity and 90.74% of removal percentage, respectively. Kinetic and equilibrium biosorption studies showed pseudo-second-order equation and Langmuir isotherm model could better fit with the experiment data. FTIR and SEM of the prepared material indicated the various functionalities on the mycelium surface including hydroxyl, carboxyl, phosphate groups and so on were responsible for the binding of uranyl ions.

Highly Sensitive and Selective Uranium Detection in Natural Water Systems Using a Luminescent Mesoporous Metal-Organic Framework Equipped with Abundant Lewis Basic Sites: A Combined Batch, X-ray Absorption Spectroscopy, and First Principles Simulation Investigation.

Uranium is not only a strategic resource for the nuclear industry but also a global contaminant with high toxicity. Although several strategies have been established for detecting uranyl ions in water, searching for new uranium sensor material with great sensitivity, selectivity, and stability remains a challenge. We introduce here a hydrolytically stable mesoporous terbium(III)-based MOF material compound 1, whose channels are as large as 27 Å × 23 Å and are equipped with abundant exposed Lewis basic sites, the luminescence intensity of which can be efficiently and selectively quenched by uranyl ions. The detection limit in deionized water reaches 0.9 μg/L, far below the maximum contamination standard of 30 μg/L in drinking water defined by the United States Environmental Protection Agency, making compound 1 currently the only MOF material that can achieve this goal. More importantly, this material exhibits great capability in detecting uranyl ions in natural water systems such as lake water and seawater with pH being adjusted to 4, where huge excesses of competing ions are present. The uranyl detection limits in Dushu Lake water and in seawater were calculated to be 14.0 and 3.5 μg/L, respectively. This great detection capability originates from the selective binding of uranyl ions onto the Lewis basic sites of the MOF material, as demonstrated by synchrotron radiation extended X-ray adsorption fine structure, X-ray adsorption near edge structure, and first principles calculations, further leading to an effective energy transfer between the uranyl ions and the MOF skeleton.

Effect of di-(2-ethylhexyl)phosphoric acid on microstructure, cloud point and uranyl ion binding competence of Triton X-100 micelles

The incorporation of an extracting agent di-(2-ethylhexyl)phosphoric acid (D2EHPA) into non-ionic surfactant, Triton X-100 (TX-100) micelles was investigated by monitoring the microstructural changes using light scattering (LS) and small angle neutron scattering (SANS) techniques. Dynamic light scattering (DLS) studies indicate a gradual increase in the apparent diffusion coefficient (Da) of the micelles upon addition of D2EHPA, suggesting the incorporation of D2EHPA molecules into TX-100 micelles. Quantitative analysis of the SANS data for D2EHPA containing micelles indicates that the effective surface charge on the micelles increases with increasing concentration of D2EHPA, while the dimensions of the micelles remain almost same. Thus, the observed increase in Da of the micelles is attributed to the changes in the intermicellar interactions. The increase in repulsive interaction with addition of D2EHPA is also evident from an increase in the cloud point of the micellar solutions. The microstructural and cloud point changes occurred in D2EHPA containing micelles in the presence of an inorganic salt, sodium chloride (NaCl) further support the inclusion of D2EHPA molecules into TX-100 micelles. The binding of uranyl ions (UO22+) to TX-100–D2EHPA mixed micelles was ensured by monitoring a decrease in the intermicellar repulsion upon addition of uranyl nitrate hexahydrate and a subsequent decrease in the cloud point of the micelles. A red-shift in the absorption peaks of uranyl nitrate hexahydrate in the presence of TX-100–D2EHPA mixed micelles also confirms the binding of UO22+ to mixed micelles. The quantitative estimation of UO22+ bound to TX-100–D2EHPA mixed micelles was carried by cloud point extraction (CPE) method followed by spectrophotometric determination.

Designing Novel Nanomaterials through Functionalization of Carbon Nanotubes with Supramolecules for Application in Nuclear Waste Management

We have investigated the possible interaction between functionalized carbon nanotubes (CNT) and uranyl using density functional theory (DFT). Due to the apparent solubility problems of CNT, we have taken the oxidized CNT and we have functionalized it with a supramolcule, curcurbituril (CB). Further, the supramolecule itself has solubility issue and hence, we have taken the hydroxylated CB (OH-CB). The CNT and OH-CB molecule interacts with each other through hydrogen bonding. Our calculations show that functionalized carbon nanotubes and cucurbituril can be used not only for improving the solubilities, but is also much more efficient for binding of uranyl ion as compared to their unfunctionalized counterpart. These findings are new and can open up a new era for actinide speciation and separation chemistry using CNT.

Noncovalent surface grafting of uranium complexed cucurbit[5]uril oligomer onto palm shell powder: a novel approach for selective uranyl ion extraction

Biomass - that is a new feather in your cap: palm shell powder was used as support for novel uranyl complexed cucurbit[5]uril oligomer to obtain a selective extractant for uranium. The key to the selectivity lies in the perfect environment of the two portals of cucurbit[5]uril for uranyl ion binding.

Insights into Uranyl Ion Binding to Ubiquitin from Molecular Modeling and Dynamics Simulations

Uranium is toxic to the human body with mechanisms not fully understood. The interaction between uranyl ion (UO22+) and ubiquitin (Ub) was predicted by molecular modeling, molecular dynamics (MD) s...

Interactions of uranyl ion with cytochrome b 5 and its His39Ser variant as revealed by molecular simulation in combination with experimental methods

The biological toxicity of uranyl ion (UO (2) (2+) ) lies in interacting with proteins and disrupting their native functions. The structural and functional consequences of UO (2) (2+) interacting with cytochrome b (5) (cyt b (5)), a small membrane heme protein, and its heme axial ligand His39Ser variant, cyt b (5) H39S, were investigated both experimentally and theoretically. In experiments, although cyt b (5) was only slightly affected, UO (2) (2+) binding to cyt b (5) H39S with a K (D) of 2.5 μM resulted in obvious alteration of the heme active site, and led to a decrease in peroxidase activity. Theoretically, molecular simulation proposed a uranyl ion binding site for cyt b (5) at surface residues of Glu37 and Glu43, revealing both coordination and hydrogen bonding interactions. The information gained in this study provides insights into the mechanism of uranyl toxicity toward membrane protein at an atomic level.

Binding of uranyl ion by a DNA aptamer attached to a solid support

A UO(2)(2+)-specific DNA aptamer was attached to aminopolystyrene (aminoPS) using sulfo-SMCC as a crosslinking agent in view of high affinity of DNA for uranyl ion. Capacity of the aptamer-conjugated aminoPS resins for uranyl uptake was measured, revealing that about 0.63 μg of uranium can be complexed to 1g of the resins, which clearly demonstrates that most of DNA aptamers introduced to the resins can strongly bind to uranyl ion. In the presence of 21 mM bicarbonate ion at pH 8.01, apparent dissociation constant (K(d)(app)) of about 84.6 pM and log formation constant (K(f)) of about 22.9 were obtained. Results of the present study strongly suggest that modification of the aptamer-containing resins can improve uranyl-binding ability, probably leading to economical recovery of uranium from seawater.

Polyelectrolyte CASA hydrogels for uptake of uranyl ions from aqueous solutions

AbstractIn this study, uranyl ion adsorption from aqueous solutions has been investigated by chemically crosslinked acrylamide/sodium acrylate (CASA) hydrogels. Adsorption studies were investigated by the spectroscopic method. CASA hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), sodium acrylate (SA), and water by free radical polymerization in aqueous solution, using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA). Uranyl ion adsorption from aqueous solutions was studied by the batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of adsorbent on the uranyl ion adsorption were examined. In experiments of sorption, L‐type sorption in the Giles classification system was found. Some binding parameters, such as initial binding constant (Ki), equilibrium constant (K), monolayer coverage (n), site‐size (u), and maximum fractional occupancy (Ô) for the CASA hydrogel–uranyl ion binding system, were calculated using the Langmuir linearization method. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 4.44 × 10−4–14.86 × 10−4 mol uranyl ion per gram for CASA hydrogels. Adsorption of uranyl ion (percentage) was changed within a range of 12.86–46.71%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 200–204, 2007

Interaction of uranium(VI) with various modified and unmodified natural and synthetic humic substances studied by EXAFS and FTIR spectroscopy

The complexation of uranium(VI) by humic acids (HAs) and fulvic acids (FAs) was studied to obtain information on the binding of uranium(VI) onto functional groups of humic substances. For this, various natural and synthetic HAs were chemically modified resulting in HAs with blocked phenolic OH groups. Both from the original and from the modified humic substances, solid uranyl humate complexes were prepared at pH 2. FTIR and extended X-ray absorption fine structure (EXAFS) spectroscopy were applied to study the chemical modification process of humic substances, to study the structure of uranyl humate complexes and to evaluate the effect of individual functional groups of humic substances (carboxylic and phenolic OH groups) on the complexation of uranyl ions. The results confirmed the predominant blocking of phenolic OH groups in the modified HAs. These modified HAs are suitable model substances to study the role of phenolic OH groups of HAs in dependence on pH. By EXAFS spectroscopy, identical structural parameters were determined for all uranyl humates. Axial UO bond distances of 1.78 Å were determined. In the equatorial plane approximately five oxygen atoms were found at a mean distance of 2.39 Å. The blocking of phenolic OH groups of HAs did not change the near-neighbor surrounding of uranium(VI) in uranyl humate complexes. Thus, the results confirmed that predominantly HA carboxylate groups are responsible for binding of uranyl ions and that the influence of phenolic OH groups is insignificant under the applied experimental conditions. The carboxylate groups are monodentate coordinated to uranyl ions.