Showing papers on "Uranyl published in 2016"
TL;DR: Density functional theory calculations, in combination with X-ray absorption fine structure characterizations, suggest that the uranyl ions prefer to coordinate with hydroxyl groups bonded to the V-sites of the nanosheets via forming bidentate inner-sphere complexes.
Abstract: Efficient nuclear waste treatment and environmental management are important hurdles that need to be overcome if nuclear energy is to become more widely used. Herein, we demonstrate the first case of using two-dimensional (2D) multilayered V2CTx nanosheets prepared by HF etching of V2AlC to remove actinides from aqueous solutions. The V2CTx material is found to be a highly efficient uranium (U(VI)) sorbent, evidenced by a high uptake capacity of 174 mg g–1, fast sorption kinetics, and desirable selectivity. Fitting of the sorption isotherm indicated that the sorption followed a heterogeneous adsorption model, most probably due to the presence of heterogeneous adsorption sites. Density functional theory calculations, in combination with X-ray absorption fine structure characterizations, suggest that the uranyl ions prefer to coordinate with hydroxyl groups bonded to the V-sites of the nanosheets via forming bidentate inner-sphere complexes.
189 citations
TL;DR: Thermodynamic investigations revealed that the adsorption of uranyl ions by the adsorbents was spontaneous and endothermic and the maximum adsorbent capacity was 54 and 105.3 mg uranyl/g adsorent, respectively.
174 citations
TL;DR: In this paper, the authors present a periodic table of metal coordination chemistry in hydrothermal fluids based on a review of the literature and new XAS data on the hydration of the uranyl ion.
168 citations
TL;DR: This work provides a facile and purposeful approach for developing MOFs toward a highly efficient and selective extraction of uranium(VI) in aqueous solution, and it further facilitates the structure-based design of nanomaterials for radionuclide-containing-medium pretreatment.
Abstract: A novel carboxyl-functionalized metal–organic framework for highly efficient uranium sorption was prepared through a generic postsynthetic strategy, and this MOF’s saturation sorption capacity is found to be as high as 314 mg·g–1 The preliminary application illustrated that the grafted free-standing carboxyl groups have notably enhanced the sorption of uranyl ions on MIL-101 In addition, we have performed molecular dynamics simulation combined with density functional theory calculations to investigate the molecular insights of uranyl ions binding on MOFs The high selectivity and easy separation of the as-prepared material have shown tremendous potential for practical applications in the nuclear industry or radioactive water treatment, and the functionalized MOF can be extended readily upon the versatility of click chemistry This work provides a facile and purposeful approach for developing MOFs toward a highly efficient and selective extraction of uranium(VI) in aqueous solution, and it further facili
147 citations
TL;DR: Electrocatalytic water reduction observed with a trisaryloxide U(iii) complex [((Ad,MeArO)3mes)U] is reported—the first homogeneous uranium catalyst for H2 production from H2O.
Abstract: Depleted uranium is a mildly radioactive waste product that is stockpiled worldwide. The chemical reactivity of uranium complexes is well documented, including the stoichiometric activation of small molecules of biological and industrial interest such as H2O, CO2, CO, or N2 (refs 1 - 11), but catalytic transformations with actinides remain underexplored in comparison to transition-metal catalysis. For reduction of water to H2, complexes of low-valent uranium show the highest potential, but are known to react violently and uncontrollably forming stable bridging oxo or uranyl species. As a result, only a few oxidations of uranium with water have been reported so far; all stoichiometric. Catalytic H2 production, however, requires the reductive recovery of the catalyst via a challenging cleavage of the uranium-bound oxygen-containing ligand. Here we report the electrocatalytic water reduction observed with a trisaryloxide U(III) complex [(((Ad,Me)ArO)3mes)U] (refs 18 and 19)--the first homogeneous uranium catalyst for H2 production from H2O. The catalytic cycle involves rare terminal U(IV)-OH and U(V)=O complexes, which have been isolated, characterized, and proven to be integral parts of the catalytic mechanism. The recognition of uranium compounds as potentially useful catalysts suggests new applications for such light actinides. The development of uranium-based catalysts provides new perspectives on nuclear waste management strategies, by suggesting that mildly radioactive depleted uranium--an abundant waste product of the nuclear power industry--could be a valuable resource.
137 citations
TL;DR: Burns et al. as discussed by the authors presented a structure hierarchy of hexavalent uranium (U 6+ ) compounds, with the first two being those of Burns et al., which considered 180 and 368 structures, respectively.
Abstract: Over the past four decades, the number of inorganic oxide and oxy-salt phases containing stoichiometric quantities of hexavalent uranium has increased exponentially from a few dozen to well over 700, and these structures have become well-known for their remarkable compositional diversity and topological variability. Considering the entirety of these compounds ( i . e ., crystal structures, conditions of synthesis, and geological occurrences) offers significant insight into the behavior of uranium in the solid state and in the nascent (typically aqueous) fluids. The structure hierarchy approach adopted here aims specifically to facilitate the recognition of useful patterns in the crystal-chemical behavior of hexavalent uranium (U 6+ ). This work represents the third attempt at a structure hierarchy of U 6+ compounds, with the first two being those of Burns et al . (1996) and Burns (2005), which considered 180 and 368 structures, respectively. The current work is expanded to include the structures of 727 known, well-refined synthetic compounds (610) and minerals (117) that contain stoichiometric quantities of U 6+ . As in the previous works, structures are systematically ordered on the basis of topological similarity, as defined predominantly by the polymerization of high-valence cations. The updated breakdown is as follows: (1) isolated polyhedra (24 compounds/0 minerals); (2) finite clusters (70 compounds/10 minerals); (3) infinite chains (94 compounds/15 minerals); (4) infinite sheets (353 compounds/79 minerals); and (5) frameworks (186 compounds/13 minerals). Within each of these major categories, structures are sub-divided on the basis of increasing connectivity of uranium (nearly always uranyl) polyhedra. In addition to elucidating common trends in U 6+ crystal chemistry, this structure hierarchy will serve as a comprehensive introduction for those not yet fluent in the domain of uranium mineralogy and inorganic, synthetic uranium chemistry.
133 citations
TL;DR: A new series of amidoxime-based polymer adsorbents were synthesized at the Oak Ridge National Laboratory (ORNL) by electron beam induced grafting of acrylonitrile and itaconic acid onto polyethylene fiber as mentioned in this paper.
130 citations
TL;DR: Uranyl nitrate hexahydrate is described as a convenient, hydrogen atom abstraction catalyst that can mediate fluorinations of certain alkanes upon activation with visible light.
Abstract: The fluorination of unactivated C(sp(3) )-H bonds remains a desirable and challenging transformation for pharmaceutical, agricultural, and materials scientists. Previous methods for this transformation have used bench-stable fluorine atom sources; however, many still rely on the use of UV-active photocatalysts for the requisite high-energy hydrogen atom abstraction event. Uranyl nitrate hexahydrate is described as a convenient, hydrogen atom abstraction catalyst that can mediate fluorinations of certain alkanes upon activation with visible light.
116 citations
TL;DR: This work reports the first XAFS investigation of polyamidoxime-bound uranyl, with EXAFS fits suggesting a cooperative chelating model, rather than the tridentate or η2 motifs proposed by small molecule and computational studies.
Abstract: Limited resource availability and population growth have motivated interest in harvesting valuable metals from unconventional reserves, but developing selective adsorbents for this task requires structural knowledge of metal binding environments. Amidoxime polymers have been identified as the most promising platform for large-scale extraction of uranium from seawater. However, despite more than 30 years of research, the uranyl coordination environment on these adsorbents has not been positively identified. We report the first XAFS investigation of polyamidoxime-bound uranyl, with EXAFS fits suggesting a cooperative chelating model, rather than the tridentate or η2 motifs proposed by small molecule and computational studies. Samples exposed to environmental seawater also display a feature consistent with a μ2-oxo-bridged transition metal in the uranyl coordination sphere, suggesting in situ formation of a specific binding site or mineralization of uranium on the polymer surface. These unexpected findings challenge several long-held assumptions and have significant implications for development of polymer adsorbents with high selectivity.
108 citations
TL;DR: Hydroxylated titanium carbide Ti3C2(OH)2, a representative of the two-dimensional transition metal carbides, has been predicted to be an effective adsorbent for uranyl ions in aqueous environments for the first time using density functional theory simulations.
107 citations
01 Jan 2016
TL;DR: In this article, the assignment problem of metal/I-ketoenolates is considered. But the assignment is not addressed in this paper, since it is assumed that one or both 0 atoms have been substituted by NH, S or Se.
Abstract: A. Scope of the review 173 B. The assignment problem 174 C. Metal fi-ketoenolates 187 D. Metal /I-ketoenolates 192 E. Ligand substitution in metal /I-ketoenolates 195 F. Adducts of transition metal B-ketoenolates 208 G. Uranyl and vanadyl /I-ketoenolates 227 H. Derivatives of metal acetylacetonates in which one or both 0 atoms have been substituted by NH, S or Se 239 Acknowledgements 246 References 246
TL;DR: By controlling the extent of hydrolysis during the self-assembly process of a zwitterionic-based ligand with uranyl cations, a structural evolution from the neutral uranyl-organic framework to the first cationic uranyl -organic framework with the formula of [(UO2)(HTTTPC)(OH)]Br·1.5DMF·4H2O (SCU-7).
Abstract: By controlling the extent of hydrolysis during the self-assembly process of a zwitterionic-based ligand with uranyl cations, we observed a structural evolution from the neutral uranyl–organic framework [(UO2)2(TTTPC)(OH)O(COOH)]·1.5DMF·7H2O (SCU-6) to the first cationic uranyl–organic framework with the formula of [(UO2)(HTTTPC)(OH)]Br·1.5DMF·4H2O (SCU-7). The crystal structures of SCU-6 and SCU-7 are layers built with tetranuclear and dinuclear uranyl clusters, respectively. Exchangeable halide anions are present in the interlaminar spaces balancing the positive charge of layers in SCU-7. Therefore, SCU-7 is able to effectively remove perrhenate anions from aqueous solution. Meanwhile, the H2PO4–-exchanged SCU-7 material exhibits a moderate proton conductivity of 8.70 × 10–5 S cm–1 at 50 °C and 90% relative humidity, representing nearly 80 times enhancement compared to the original material.
TL;DR: The synthesized material was found to show an increase in adsorption activity with respect to uranyl ions in comparison with the initial compounds, and the highest adsorptive capacity for the obtained modified silica was found at the neutral pH, where one gram of the adsorbent can extract 176mg of uranium.
TL;DR: The purpose of introducing a second ligand is to enhance the affinity of the amidoxime (AO) ligand via two possible mechanisms: by acting directly upon the AO to increase its ability to ion exchange or providing additional coordination sites to the uranyl ion.
Abstract: Bifunctional amidoxime fibers are synthesized from commercially available polyacrylonitrile as sorbents for the recovery of U(VI) from seawater. The purpose of introducing a second ligand is to enhance the affinity of the amidoxime (AO) ligand via two possible mechanisms: by acting directly upon the AO to increase its ability to ion exchange or providing additional coordination sites to the uranyl ion. Amines are chosen as the second ligand since they have a high affinity for U(VI) at ppm levels from synthetic seawater. Diethylenetriamine (DETA) is utilized as the amine because it is sufficiently flexible to interact with AO and able to bind metal ions. Along with AO and AO-DETA fibers, the primary NH2 moieties were modified with phosphonic acid ligands (AO-phon-DETA). All fibers have high affinities (>99% sorption) for the uranyl ion when initially present at 0.90 ppm in synthetic seawater. When contacted with actual seawater at the Pacific Northwest National Laboratory for 20.8 days, the loadings for th...
TL;DR: In this paper, an ultrahigh molecular weight polyethylene (UHMWPE) fibrous adsorbent with amidoxime (AO) groups was prepared by pre-radiation-induced graft copolymerization of acrylonitrile (AN) and acrylic acid (AA), followed by amidoximation.
Abstract: An ultrahigh molecular weight polyethylene (UHMWPE) fibrous adsorbent with amidoxime (AO) groups, denoted as AO-UHMWPE, was prepared by preirradiation-induced graft copolymerization of acrylonitrile (AN) and acrylic acid (AA) on UHMWPE fibers, followed by amidoximation. The chemical structure, thermal stability, and mechanical strength were evaluated by means of Fourier transform infrared spectrometry, thermogravimetric analysis, and tensile tests, respectively. The adsorption behaviors of the AO-UHMWPE fiber were studied by batch adsorption in 331 ppb uranium solution, and flow-though adsorption experiments in simulated and natural seawater. It was found that the adsorption conditions (i.e., contact time and manner, temperature, and uranyl ion initial concentration) significantly influence the amount of uranyl ions binding to the AO-UHMWPE fibers. The adsorption of uranium in the batch adsorption experiment was 4.54 g-U/kg-ad in the presence of massive amounts of interference ions.
TL;DR: Results indicate that SERS signals using functionalized Au nanostar substrates can provide quantitative detection of small molecules and that the tip architecture plays an important role in understanding the resulting SERS intensities.
Abstract: The radius of curvature of gold (Au) nanostar tips but not the overall particle dimensions can be used for understanding the large and quantitative surface-enhanced Raman scattering (SERS) signal of the uranyl (UO2)2+ moiety. The engineered roughness of the Au nanostar architecture and the distance between the gold surface and uranyl cations are promoted using carboxylic acid terminated alkanethiols containing 2, 5, and 10 methylene groups. By systematically varying the self-assembled monolayer (SAM) thickness with these molecules, the localized surface plasmon resonance (LSPR) spectral properties are used to quantify the SAM layer thickness and to promote uranyl coordination to the Au nanostars in neutral aqueous solutions. Successful uranyl detection is demonstrated for all three functionalized Au nanostar samples as indicated by enhanced signals and red-shifts in the symmetric U(VI)–O stretch. Quantitative uranyl detection is achieved by evaluating the integrated area of these bands in the uranyl fingerprint window. By varying the concentration of uranyl, similar free energies of adsorption are observed for the three carboxylic acid terminated functionalized Au nanostar samples indicating similar coordination to uranyl, but the SERS signals scale inversely with the alkanethiol layer thickness. This distance dependence follows previously established models assuming that roughness features associated with the radius of curvature of the tips are considered. These results indicate that SERS signals using functionalized Au nanostar substrates can provide quantitative detection of small molecules and that the tip architecture plays an important role in understanding the resulting SERS intensities.
TL;DR: In this paper, a porous aromatic framework (PAF) was surface functionalized with poly(acrylonitrile) through atom-transfer radical polymerization (ATRP) to obtain a maximum capacity of 4.81 g-U/kg-ads.
Abstract: In order to ensure a sustainable reserve of fuel for nuclear power generation, tremendous research efforts have been devoted to developing advanced sorbent materials for extracting uranium from seawater. In this work, a porous aromatic framework (PAF) was surface-functionalized with poly(acrylonitrile) through atom-transfer radical polymerization (ATRP). Batches of this adsorbent were conditioned with potassium hydroxide (KOH) at room temperature or 80 °C prior to contact with a uranium-spiked seawater simulant, with minimal differences in uptake observed as a function of conditioning temperature. A maximum capacity of 4.81 g-U/kg-ads was obtained following 42 days contact with uranium-spiked filtered environmental seawater, which demonstrates a comparable adsorption rate. A kinetic investigation revealed extremely rapid uranyl uptake, with more than 80% saturation reached within 14 days. Relying on the semiordered structure of the PAF adsorbent, density functional theory (DFT) calculations reveal coopera...
TL;DR: The instrumental method of analysis based on photoluminescence spectroscopy confirmed the feasibility for quantitative analysis of ultratrace concentrations of uranyl ions as implied from a very low limit of detection and limit of quantification.
Abstract: Detection of ultratrace levels of aqueous uranyl ions without using sophisticated analytical instrumentation and a tedious sample preparation method is a challenge for environmental monitoring and mitigation. Here we present a novel yet simple analytical method for highly sensitive and specific detection of uranyl ions via photoluminescence quenching of CdS quantum dots. We have demonstrated a new approach for synthesizing highly water-soluble and strong photoluminescence-emitting CdS quantum dots (i.e., CdS-MAA and CdS-MAA-TU) of sizes less than 3 nm. The structural, morphological, and optical properties of both the batches of CdS quantum dots were thoroughly characterized by XRD, high-resolution transmission electron microscopy (HRTEM), zeta potential, UV–visible absorption, and photoluminescence spectroscopy. Compared to the batch of CdS quantum dots prepared by capping with only mercaptoacetic acid (CdS-MAA), the batch prepared by capping with mercaptoacetic acid and thiourea in tandem (CdS-MAA-TU) ex...
TL;DR: It is shown that a consideration of the properties of both the one-electron and electron-pair densities is required to understand and rationalize the variation in axial bonding effected by equatorial complexation.
Abstract: The molecular structures of a series of uranyl (UO22+) complexes in which the uranium center is equatorially coordinated by a first-row species are calculated at the density functional theory level and binding energies deduced. The resulting electronic structures are investigated using a variety of density-based analysis techniques in order to quantify the degree of covalency in the equatorial bonds. It is shown that a consideration of the properties of both the one-electron and electron-pair densities is required to understand and rationalize the variation in axial bonding effected by equatorial complexation. Strong correlations are found between density-based measures of the covalency and equatorial binding energies, implying a stabilizing effect due to covalent interaction, and it is proposed that uranyl U–Oyl stretching vibrational frequencies can serve as an experimental probe of equatorial covalency.
TL;DR: A novel tetraphenylethene-based fluorescent sensor could be used to visually distinguish UO2(2+) from lanthanides, transition metals, and alkali metals under UV light; the presence of other metal ions did not interfere with the detection of uranyl ions.
TL;DR: The use of metal halide reagents and reactions with small surface area to volume ratios are found to favor the growth of salt-inclusion compounds over pure oxides and thus enable a more targeted synthetic route for their preparation.
Abstract: Salt-inclusion compounds (SICs) are known for their structural diversity and their potential applications, including luminescence and radioactive waste storage forms. Currently, the majority of salt-inclusion phases are grown serendipitously and the targeted growth of SICs has met with only moderate success. We report an enhanced flux growth method for the targeted growth of SICs. Specifically, the use of (1) metal halide reagents and (2) reactions with small surface area to volume ratios are found to favor the growth of salt-inclusion compounds over pure oxides and thus enable a more targeted synthetic route for their preparation. The Cs–X–U–Si–O (X = F, Cl) pentanary phase space is used as a model system to demonstrate the generality of this enhanced flux method approach. Single crystals of four new salt-inclusion uranyl silicates, [Cs3F][(UO2)(Si4O10)], [Cs2Cs5F][(UO2)2(Si6O17)], [Cs9Cs6Cl][(UO2)7(Si6O17)2(Si4O12)], and [Cs2Cs5F][(UO2)3(Si2O7)2], were grown using this enhanced flux growth method. A det...
TL;DR: In this paper, the effects from environmental pollution by uranium compounds have been overviewed and the necessity of prohibiting the use of depleted uranium shells as chemical weapons of mass destruction has been substantiated.
Abstract: Studies into the effects from environmental pollution by uranium compounds have been overviewed. Analysis of the impact of uranium oxides resulted from military operations using armor-piercing shells made of depleted uranium shows a predominance of chemical toxicity caused by the strong oxidizing power of uranyl ions. They induce oxidative stress through the generation of reactive oxygen species. As a result, oxidative damage to biomolecules and disruption of metabolic processes occur. Oxidative DNA damage causes long-term genotoxic effects in the form of mutagenesis, carcinogenesis, and other pathologies. The necessity of prohibiting the use of depleted uranium shells as chemical weapons of mass destruction has been substantiated.
TL;DR: The biosorption mechanisms of uranium on an aerobic bacterial strain Streptomyces sporoverrucosus dwc-3, isolated from a potential disposal site for (ultra-)low uraniferous radioactive waste in Southwest China, were evaluated and results confirmed that ion exchange also contributed to the adsorption process of uranium.
Abstract: The biosorption mechanisms of uranium on an aerobic bacterial strain Streptomyces sporoverrucosus dwc-3, isolated from a potential disposal site for (ultra-)low uraniferous radioactive waste in Southwest China, were evaluated by using transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), proton induced X-ray emission (PIXE) and enhanced proton backscattering spectrometry (EPBS) Approximately 60% of total uranium at an initial concentration of 10mg/L uranium nitrate solution could be absorbed on 100mg S sporoverrucosus dwc-3 with an adsorption capacity of more than 30mg/g (wet weight) after 12hr at room temperature at pH30 The dynamic biosorption process of S sporoverrucosus dwc-3 for uranyl ions was well described by a pseudo second-order model S sporoverrucosus dwc-3 could accumulate uranium on cell walls and within the cell, as revealed by SEM and TEM analysis as well as EDX spectra XPS and FT-IR analysis further suggested that the absorbed uranium was bound to amino, phosphate and carboxyl groups of the cells Additionally, PIXE and EPBS results confirmed that ion exchange also contributed to the adsorption process of uranium
TL;DR: The effects of aqueous speciation of U on the biosorption of U and the localization pattern of uranyl phosphate precipitated as a result of phosphatase action are demonstrated.
Abstract: Deinococcus radiodurans and Escherichia coli expressing either PhoN, a periplasmic acid phosphatase, or PhoK, an extracellular alkaline phosphatase, were evaluated for uranium (U) bioprecipitation under two specific geochemical conditions (GCs): (i) a carbonate-deficient condition at near-neutral pH (GC1), and (ii) a carbonate-abundant condition at alkaline pH (GC2). Transmission electron microscopy revealed that recombinant cells expressing PhoN/PhoK formed cell-associated uranyl phosphate precipitate under GC1, whereas the same cells displayed extracellular precipitation under GC2. These results implied that the cell-bound or extracellular location of the precipitate was governed by the uranyl species prevalent at that particular GC, rather than the location of phosphatase. MINTEQ modeling predicted the formation of predominantly positively charged uranium hydroxide ions under GC1 and negatively charged uranyl carbonate-hydroxide complexes under GC2. Both microbes adsorbed 6- to 10-fold more U under GC1 than under GC2, suggesting that higher biosorption of U to the bacterial cell surface under GC1 may lead to cell-associated U precipitation. In contrast, at alkaline pH and in the presence of excess carbonate under GC2, poor biosorption of negatively charged uranyl carbonate complexes on the cell surface might have resulted in extracellular precipitation. The toxicity of U observed under GC1 being higher than that under GC2 could also be attributed to the preferential adsorption of U on cell surfaces under GC1. This work provides a vivid description of the interaction of U complexes with bacterial cells. The findings have implications for the toxicity of various U species and for developing biological aqueous effluent waste treatment strategies. IMPORTANCE The present study provides illustrative insights into the interaction of uranium (U) complexes with recombinant bacterial cells overexpressing phosphatases. This work demonstrates the effects of aqueous speciation of U on the biosorption of U and the localization pattern of uranyl phosphate precipitated as a result of phosphatase action. Transmission electron microscopy revealed that location of uranyl phosphate (cell associated or extracellular) was primarily influenced by aqueous uranyl species present under the given geochemical conditions. The data would be useful for understanding the toxicity of U under different geochemical conditions. Since cell-associated precipitation of metal facilitates easy downstream processing by simple gravity-based settling down of metal-loaded cells, compared to cumbersome separation techniques, the results from this study are of considerable relevance to effluent treatment using such cells.
TL;DR: Quantitative chemical calculations indicate that the most stable U2O7 conformer consists of two bent (UO2)(2+) uranyl ions bridged by a peroxide group bidentate and parallel to each uranyl ion, and a μ2-O atom, resulting in charge neutrality.
Abstract: Recent accidents resulting in worker injury and radioactive contamination occurred due to pressurization of uranium yellowcake drums produced in the western U.S.A. The drums contained an X-ray amorphous reactive form of uranium oxide that may have contributed to the pressurization. Heating hydrated uranyl peroxides produced during in situ mining can produce an amorphous compound, as shown by X-ray powder diffraction of material from impacted drums. Subsequently, studtite, [(UO2)(O2)(H2O)2](H2O)2, was heated in the laboratory. Its thermal decomposition produced a hygroscopic anhydrous uranyl peroxide that reacts with water to release O2 gas and form metaschoepite, a uranyl-oxide hydrate. Quantum chemical calculations indicate that the most stable U2O7 conformer consists of two bent (UO2)(2+) uranyl ions bridged by a peroxide group bidentate and parallel to each uranyl ion, and a μ2-O atom, resulting in charge neutrality. A pair distribution function from neutron total scattering supports this structural model, as do (1)H- and (17)O-nuclear magnetic resonance spectra. The reactivity of U2O7 in water and with water in air is higher than that of other uranium oxides, and this can be both hazardous and potentially advantageous in the nuclear fuel cycle.
TL;DR: In this paper, an electrochemical sensor by combining sol-gel processing and paste electrode was developed, which was first synthesized and reacted with tetramethoxysilane to obtain polymer solgel and then used as a receptor for selecting and sensing of uranyl ion in aqueous solution.
Abstract: In this work, an electrochemical sensor by combining sol–gel processing and paste electrode was developed. Functional precursor was first synthesized and reacted with tetramethoxysilane to obtain polymer sol–gel and then used as a receptor for selective binding and sensing of uranyl ion in aqueous solution. Ion-imprinted polymer sol–gel synthesized in the presence of uranyl ion was characterized by Fourier transform-infrared spectroscopy, scanning electron microscopy and N 2 adsorption–desorption analysis by comparing with non-imprinted sol–gel obtained in the absence of uranyl ion. Surface area, pore volume and diameter were analyzed from the profile of nitrogen adsorption. Uranyl ion imprinted network was employed to achieve a suitable conformation for electrochemical reduction of uranyl ion and also to improve the selectivity of the sensor. The results showed that the ion imprinted polymer sol–gel modified carbon paste electrode exhibited selectivity toward uranyl ion compared to electrode containing non-imprinted polymer sol–gel. The ion-imprinted sensor was also successfully employed to detect uranyl ion in real samples and exhibited distinctive change in current upon interaction with uranyl ion. The corresponding selectivity factors of the sensor toward uranyl ion against the other analogues were evaluated.
TL;DR: In this paper, the effects of fluorine doping of HAp and fluoride ions concentration on the sorption behavior of U(VI) by hydroxyapatite (HAp) were investigated.
TL;DR: The synthesis and crystal structures of six new compounds containing the UO22+ cation, 3,5-dichlorobenzoic acid, and a chelating N-donor were reported in this article.
Abstract: The syntheses and crystal structures of six new compounds containing the UO22+ cation, 3,5-dichlorobenzoic acid, and a chelating N-donor [2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (dimethylphen), 2,2′:6′,2″-terpyridine (terpy), 4′-chloro-2,2′:6′,2″-terpyridine (Cl–terpy), or 2,4,6-tris(2-pyridyl)-s-triazine (TPTZ)] are reported. Single-crystal X-ray diffraction analysis of these materials enabled the exploration of the structural relationship between the benzoic acids and the chelating N-donor as well as providing a platform to evaluate the effects of ligand choice on uranyl hydrolysis and subsequent oligomerization. At an unadjusted pH (ca. 3), a mix of uranyl monomers and dimers are observed, dimer formation resulting from both bridging carboxylate linkers and hydroxo bridges. Assembly by halogen- and hydrogen-bonding interactions as well as π–π interactions was observed depending on the experimental conditions utilized. Further, spectroscopic characterization (both vibrational and luminescence) of complexes 1, 4, and 5 to explore the effects of the electron-donating ability of the capping ligand on the corresponding uranyl luminescence and vibrational spectra suggests that there is a relationship between the observed bathochromic shifts and the electron-donating ability of the capping ligands.
TL;DR: In this paper, the authors presented experimental data taken using extended X-ray absorption fine structure at the U L 3 edge and theoretical calculation results. But they did not consider the effect of the covalent effect in the extraction process.
Abstract: To shed some light on the uranium extraction mechanism of amidoximate (AO) ligands from uranyl carbonate solution, we present experimental data taken using extended X-ray absorption fine structure at the U L3 edge and theoretical calculation results. The EXAFS data were well simulated and confessedly shows that AO ligands directly substitute the CO32– group in the equatorial plane to form a stable [UO2(CO3)3-x(AO)x](4-x)– complex. Density functional theory calculation indicates that although they have a slightly weaker electrostatic attraction than CO32– ligands, AO ligands display stronger binding capability to uranyl because of the remarkable orbital hybridization between U 5f/6d and (N,O)2p in the uranyl–AO complex. This finding provides strong evidence supporting the substitutional mechanism, which implies that cationic adsorbents are preferred in the further design of higher efficient adsorbents, and furthermore highlights the crucial role of the covalent effect in the extraction process.
TL;DR: It was possible to show that the branched alkyl chain amides form partly outer-sphere complexes with protonated ligands hydrogen bonded to nitrate ions.
Abstract: The structures of plutonium(IV) and uranium(VI) ions with a series of N,N-dialkyl amides ligands with linear and branched alkyl chains were elucidated from single-crystal X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and theoretical calculations In the field of nuclear fuel reprocessing, N,N-dialkyl amides are alternative organic ligands to achieve the separation of uranium(VI) and plutonium(IV) from highly concentrated nitric acid solution EXAFS analysis combined with XRD shows that the coordination structure of U(VI) is identical in the solution and in the solid state and is independent of the alkyl chain: two amide ligands and four bidentate nitrate ions coordinate the uranyl ion With linear alkyl chain amides, Pu(IV) also adopt identical structures in the solid state and in solution with two amides and four bidentate nitrate ions With branched alkyl chain amides, the coordination structure of Pu(IV) was more difficult to establish unambiguously from EXAFS Density func