Showing papers on "Uranyl published in 2017"

A half-wave rectified alternating current electrochemical method for uranium extraction from seawater

Abstract: In total there is hundreds of times more uranium in sea water than on land, but extracting it for use in nuclear power generation is challenging due to its low concentration (∼3 ppb) and the high salinity background. Current approaches based on sorbent materials are limited due to their surface-based physicochemical adsorption nature. Here we use a half-wave rectified alternating current electrochemical (HW-ACE) method for uranium extraction from sea water based on an amidoxime-functionalized carbon electrode. The amidoxime functionalization enables surface specific binding to uranyl ions, while the electric field can migrate the ions to the electrode and induce electrodeposition of uranium compounds, forming charge-neutral species. Extraction is not limited by the electrode surface area, and the alternating manner of the applied voltage prevents unwanted cations from blocking the active sites and avoids water splitting. The HW-ACE method achieved a ninefold higher uranium extraction capacity (1,932 mg g−1) without saturation and fourfold faster kinetics than conventional physicochemical methods using uranium-spiked sea water. The large amount of uranium in the oceans could be exploited for nuclear fuel, but existing physicochemical extraction methods are limited in terms of capacity and rates of removal. Here the authors use an electrochemical extraction technique, demonstrating improved uptake capacity and kinetics.

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.

Abstract: 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 A × 23 A 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...

Ultrafast and Efficient Extraction of Uranium from Seawater Using an Amidoxime Appended Metal-Organic Framework.

Abstract: Enrichment of uranyl from seawater is crucial for the sustainable development of nuclear energy, but current uranium extraction technology suffers from multiple drawbacks of low sorption efficiency, slow uptake kinetics, or poor extraction selectivity. Herein, we prepared the first example of amidoxime appended metal–organic framework UiO-66-AO by a postsynthetic modification method for rapid and efficient extraction of uranium from seawater. UiO-66-AO can remove 94.8% of uranyl ion from Bohai seawater within 120 min and 99% of uranyl ion from Bohai seawater containing extra 500 ppb uranium within 10 min. The uranyl sorption capacity in a real seawater sample was determined to be 2.68 mg/g. In addition, the recyclability of the UiO-66-AO framework was demonstrated for at least three adsorption/desorption cycles. The origin for the superior sorption capability was further probed by extended X-ray absorption fine structure (EXAFS) analysis on the uranium-sorbed sample, suggesting multiple amidoxime ligands ...

Highly Sensitive Detection of Ionizing Radiations by a Photoluminescent Uranyl Organic Framework

Abstract: Precise detection of low-dose X- and γ-radiations remains a challenge and is particularly important for studying biological effects under low-dose ionizing radiation, safety control in medical radiation treatment, survey of environmental radiation background, and monitoring cosmic radiations. We report here a photoluminescent uranium organic framework, whose photoluminescence intensity can be accurately correlated with the exposure dose of X- or γ-radiations. This allows for precise and instant detection of ionizing radiations down to the level of 10−4 Gy, representing a significant improvement on the detection limit of approximately two orders of magnitude, compared to other chemical dosimeters reported up to now. The electron paramagnetic resonance analysis suggests that with the exposure to radiations, the carbonyl double bonds break affording oxo-radicals that can be stabilized within the conjugated uranium oxalate-carboxylate sheet. This gives rise to a substantially enhanced equatorial bonding of the uranyl(VI) ions as elucidated by the single-crystal structure of the γ-ray irradiated material, and subsequently leads to a very effective photoluminescence quenching through phonon-assisted relaxation. The quenched sample can be easily recovered by heating, enabling recycled detection for multiple runs.

Functionalized Porous Aromatic Framework for Efficient Uranium Adsorption from Aqueous Solutions

Abstract: We demonstrate the successful functionalization of a porous aromatic framework for uranium extraction from water as exemplified by grafting PAF-1 with the uranyl chelating amidoxime group. The resultant amidoxime-functionalized PAF-1 (PAF-1-CH2AO) exhibits a high uranium uptake capacity of over 300 mg g–1 and effectively reduces the uranyl concentration from 4.1 ppm to less than 1.0 ppb in aqueous solutions within 90 min, well below the acceptable limit of 30 ppb set by the US Environmental Protection Agency. The local coordination environment of uranium in PAF-1-CH2AO is revealed by X-ray absorption fine structure spectroscopic studies, which suggest the cooperative binding between UO22+ and adjacent amidoxime species.

Ion-Imprinted Mesoporous Silica for Selective Removal of Uranium from Highly Acidic and Radioactive Effluent.

Abstract: It is strategically important to recycle uranium from radioactive liquid wastes for future uranium supply of nuclear energy. However, it is still a challenge to adsorb uranium selectively from highly acidic and radioactive waste. In this paper, we report a novel strategy for effective uranium removal from highly acidic and radioactive media by surface ion-imprinted mesoporous silica sorbent. The sorbent was successfully synthesized by a co-condensation method with uranyl as the template ion and diethylphosphatoethyltriethoxysilane as the functional ligands. The pseudo-second-order model and Langmuir model showed better correlation with the sorption kinetic and isotherm data, and the sorption equilibrium could be reached within 40 min, the maximum adsorption capacity from Langmuir model was 80 mg/g in 1 mol/L nitric acid (HNO3) solution at 298.15 K. The sorbent showed faster kinetics and higher selectivity toward uranium over other ions compared with nonimprinted mesoporous and other previous sorbents. Fur...

Smart Photonic Crystal Hydrogel Material for Uranyl Ion Monitoring and Removal in Water

Abstract: Uranyl ion (UO22+) pollution is a serious environmental problem, and developing novel adsorption materials is essential for UO22+ monitoring and removal. Although some progress is achieved, it is still a challenging task to develop an adsorption material with indicating signal for real-time evaluation of the adsorption degree and the UO22+ concentration. Herein, this paper describes a smart photonic crystal hydrogel (PCH) material, which not only can be used for real-time monitoring function but also can be utilized for UO22+ removal based on the chelation of UO22+ with ligand groups in PCH material. The working principle is based on the binding of a uranyl ion to multiple ligand groups, which results in the shrinkage of PCH material and triggers a blue-shift of diffraction wavelength. Consequently, the adsorption degree and the UO22+ concentration can be sensitively evaluated by measuring the diffraction shift or observing the color change with naked eye. With this PCH material, the lowest detectable concentration for UO22+ is 10 × 10−9m, and the maximum adsorption capacity at 298 K is 169.67 mmol kg−1. In addition, this material also holds good selectivity and regeneration feature, and shows desirable performance for UO22+ analysis in real water samples.

Protein Hydrogel Microbeads for Selective Uranium Mining from Seawater.

Abstract: Practical methods for oceanic uranium extraction have yet to be developed in order to tap into the vast uranium reserve in the ocean as an alternative energy. Here we present a protein hydrogel system containing a network of recently engineered super uranyl binding proteins (SUPs) that is assembled through thiol-maleimide click chemistry under mild conditions. Monodisperse SUP hydrogel microbeads fabricated by a microfluidic device further enable uranyl (UO22+) enrichment from natural seawater with great efficiency (enrichment index, K = 2.5 × 103) and selectivity. Our results demonstrate the feasibility of using protein hydrogels to extract uranium from the ocean.

Recent advances in structural studies of heterometallic uranyl-containing coordination polymers and polynuclear closed species

Abstract: An overview is given of recent structural studies on heterometallic uranyl-containing species, with particular emphasis on those formed with carboxylate ligands, showing the effect of the additional metal cations and ancillary ligands on the dimensionality, geometry and topology of the assemblies generated. These examples illustrate the level of elaboration which is now possible in the design and synthesis of both uranyl clusters and coordination polymers, properties and potential applications of which are also briefly discussed.

Highly Efficient Interception and Precipitation of Uranium(VI) from Aqueous Solution by Iron-Electrocoagulation Combined with Cooperative Chelation by Organic Ligands.

Abstract: A new strategy combining iron-electrocoagulation and organic ligands (OGLs) cooperative chelation was proposed to screen and precipitate low concentrations (0-18.52 μmol/L) of uranium contaminant in aqueous solution. We hypothesized that OGLs with amino, hydroxyl, and carboxyl groups hydrophobically/hydrophilically would realize precuring of uranyl ion at pH < 3.0, and the following iron-electrocoagulation would achieve faster and more efficient uranium precipitation. Experimentally, the strategy demonstrated highly efficient uranium(VI) precipitation efficiency, especially with hydrophilic macromolecular OGLs. The uranium removal efficiency at optimized experimental condition reached 99.65%. The decrease of zeta potential and the lattice enwrapping between U-OGLs chelates and flocculation precursor were ascribed to the enhanced uranium precipitation activity. Uranium was precipitated as oxides of U(VI) or higher valences that were easily captured in aggregated micelles under low operation current potential. The actual uranium tailing wastewater was treated, and a satisfied uranium removal efficiency of 99.02% was discovered. After elution of the precipitated flocs, a concentrated uranium solution (up to 106.52 μmol/L) with very few other metallic impurities was obtained. Therefore, the proposed strategy could remove uranium and concentrate it concurrently. This work could provide new insights into the purification and recovery of uranium from aqueous solutions in a cost-effective and environmentally friendly process.

Inner-sphere vs. outer-sphere reduction of uranyl supported by a redox-active, donor-expanded dipyrrin

Abstract: The uranyl(vi) complex UO2Cl(L) of the redox-active, acyclic diimino-dipyrrin anion, L- is reported and its reaction with inner- and outer-sphere reductants studied Voltammetric, EPR-spectroscopic and X-ray crystallographic studies show that chemical reduction by the outer-sphere reagent CoCp2 initially reduces the ligand to a dipyrrin radical, and imply that a second equivalent of CoCp2 reduces the U(vi) centre to form U(v) Cyclic voltammetry indicates that further outer-sphere reduction to form the putative U(iv) trianion only occurs at strongly cathodic potentials The initial reduction of the dipyrrin ligand is supported by emission spectra, X-ray crystallography, and DFT; the latter also shows that these outer-sphere reactions are exergonic and proceed through sequential, one-electron steps Reduction by the inner-sphere reductant [TiCp2Cl]2 is also likely to result in ligand reduction in the first instance but, in contrast to the outer-sphere case, reduction of the uranium centre becomes much more favoured, allowing the formation of a crystallographically characterised, doubly-titanated U(iv) complex In the case of inner-sphere reduction only, ligand-to-metal electron-transfer is thermodynamically driven by coordination of Lewis-acidic Ti(iv) to the uranyl oxo, and is energetically preferable over the disproportionation of U(v) Overall, the involvement of the redox-active dipyrrin ligand in the reduction chemistry of UO2Cl(L) is inherent to both inner- and outer-sphere reduction mechanisms, providing a new route to accessing a variety of U(vi), U(v), and U(iv) complexes

Novel Viologen Derivative Based Uranyl Coordination Polymers Featuring Photochromic Behaviors

Abstract: A series of novel uranyl coordination polymers have been synthesized by hydrothermal reactions. Both complexes 1 and 2 prosess two ipbp- ligands (H2 ipbpCl=1-(3,5-dicarboxyphenyl)-4,4'-bipyridinium chloride), one uranyl cation, and two coordination water molecules, which can further extend to 2D networks through hydrogen bonding. In complex 1, two sets of equivalent nets are entangled together, resulting in a 2D + 2D → 3D polycatenated framework. In complex 2, the neighbouring equivalent nets interpenetrate each other, forming a twofold interpenetrated network. Complexes 3 and 4 are isomers, and both of them are constructed from (UO2 )2 (OH)2 dinuclear units, which are connected with four ipbp- ligands. The 3D structures of complexes 3 and 4 are similar along the b axis. Similar to other viologen-based coordination polymers, complexes 3 and 4 exhibit photochromic and thermochromic properties, which are rarely observed in actinide coordination polymers. Unlike the monotonous coordination mode in complexes 1-4, the ipbp- ligands feature a μ3 -bridge through two kinds of coordination modes in complex 5. Notably, complex 5 presents a unique example in which terminal pyridine nitrogen atom is involved in the coordination.

Experimental and Theoretical Approaches to Three Uranyl Coordination Polymers Constructed by Phthalic Acid and N,N′-Donor Bridging Ligands: Crystal Structures, Luminescence, and Photocatalytic Degradation of Tetracycline Hydrochloride

Abstract: Three uranyl coordination polymers have been synthesized by using phthalic acid (H2PHA) in the presence of N,N′-donor ligands, and namely, (UO2)(BPP)0.5(PHA) (1), (UO2)(BPE)0.5(PHA) (2), and [(UO2)(H2O)(PHA)](PYZ)0.5·H2O (3) [BPP = 1,3-di(4-pyridyl)- propane, BPE = 4,4′-vinylenedipyridine, and PYZ = pyrazine]. X-ray analysis of single crystal structure determined that compounds 1 and 2 exhibit a three-dimentional (3D) framework, and compound 3 exhibits a two-dimentional (2D) network. Compound 1 is linked by PHA2– anions to form a one-dimensional ribbon and bridged by BPP ligands to build a 3D framework of cds CdSO4 topological type. Compound 2 is bridged by PHA2– anions into layers of a 4-connected dinodal net topology of (44;62) and connected through BPE ligands to form a 3D framework of pcu alpha-Po primitive cubic topological type. Compound 3 is assembled into 2D layers via PHA2– anions; the PYZ ligands and lattice water molecules only stabilize the 3D supramolecular structure. Considering the effect o...

Structural Consequences of 1,4-Cyclohexanedicarboxylate Cis/Trans Isomerism in Uranyl Ion Complexes: From Molecular Species to 2D and 3D Entangled Nets.

Abstract: trans-1,4-Cyclohexanedicarboxylic acid (t-1,4-chdcH2) or the commercially available mixture of the cis and trans isomers (c,t-1,4-chdcH2) has been used in the synthesis of a series of 14 uranyl ion complexes, all obtained under solvohydrothermal conditions, some in the presence of additional metal cations and/or 2,2′-bipyridine (bipy). With its two isomeric forms having very different shapes and its great sensitivity to the experimental conditions, 1,4-chdc2– appears to be suitable for the synthesis of uranyl ion complexes displaying a wide range of architectures. Under the conditions used, the pure trans isomer gives only the complexes [UO2(t-1,4-chdc)(H2O)2] (1) and [UO2(t-1,4-chdc)] (2), which crystallize as one- and two-dimensional (1D and 2D) species, respectively. Complexes containing either the cis isomer alone or mixtures of the two isomers in varying proportion were obtained from the isomer mixture. The neutral complexes [UO2(c-1,4-chdc)(DMF)] (3) and [UO2(c-1,4-chdc)(bipy)] (4) are 2D and 1D ass...

Elucidating bonding preferences in tetrakis(imido)uranate(VI) dianions

Abstract: Actinyl species, [AnO2]2+, are well-known derivatives of the f-block because of their natural occurrence and essential roles in the nuclear fuel cycle. Along with their nitrogen analogues, [An(NR)2]2+, actinyls are characterized by their two strong trans-An–element multiple bonds, a consequence of the inverse trans influence. We report that these robust bonds can be weakened significantly by increasing the number of multiple bonds to uranium, as demonstrated by a family of uranium(VI) dianions bearing four U–N multiple bonds, [M]2[U(NR)4] (M = Li, Na, K, Rb, Cs). Their geometry is dictated by cation coordination and sterics rather than by electronic factors. Multiple bond weakening by the addition of strong π donors has the potential for applications in the processing of high-valent actinyls, commonly found in environmental pollutants and spent nuclear fuels. The field of high-valent uranium chemistry has been dominated by the linear uranyl moiety [UO2]2+ and its imido analogues. A family of tetrakis(imido)uranate dianions has now been developed that displays four uranium–nitrogen multiple bonds. Their geometry is dictated by cation coordination and steric factors rather than electronic ones.

Superparamagnetic Adsorbent Based on Phosphonate Grafted Mesoporous Carbon for Uranium Removal

Abstract: A direct approach was presented to graft phosphonate groups on magnetic mesoporous carbon by an impregnation method with environmentally friendly precursors unlike the conventional methods involving a series of complicated steps and harsh conditions. Through the in situ reduction of Fe3+, magnetite particles of ∼10 nm were successfully embedded into the mesopores, which was confirmed by HR-TEM. Surface characterization by X-ray photoelectron spectroscopy and Fourier transform infrared revealed phosphonate functional groups anchored through multidentate bonding with the surface of P–Fe–CMK-3. Due to the combined advantages of mesoporous pore size (5.5 nm), phosphonate ligands (1.42 mmol g–1), and magnetic sensitivity (5.20 emu g–1), this multifunctional adsorbent captured >85% of UO22+ within 5 min and the maximum adsorption capacity was 150 mg g–1 at pH 4. The exceptionally high selectivity and efficiency of P–Fe–CMK-3 toward uranyl capture even in groundwater (Kd = 1 × 105 mL g–1), radioactive wastewater...

Peptide-Mediated Nanopore Detection of Uranyl Ions in Aqueous Media

Abstract: Uranium is one of the most common radioactive contaminants in the environment. As a major nuclear material in production, environmental samples (like soil and groundwater) can provide signatures on uranium production activity inside the facility. Thus, developing a new and portable analytical technology for uranium in aqueous media is significant not only for environmental monitoring, but also for nonproliferation. In this work, a label-free method for the detection of uranyl (UO22+) ions is developed by monitoring the translocation of a peptide probe in a nanopore. Based on the difference in the number of peptide events in the absence and presence of uranyl ions, nanomolar concentration of UO22+ ions could be detected in minutes. The method is highly selective; micromolar concentrations of Cd2+, Cu2+, Zn2+, Ni2+, Pb2+, Hg2+, Th4+, Mg2+, and Ca2+ would not interfere with the detection of UO22+ ions. In addition, simulated water samples were successfully analyzed.

Trace Uranium Partitioning in a Multiphase Nano-FeOOH System

Abstract: The characterization of trace elements in minerals using extended X-ray absorption fine structure (EXAFS) spectroscopy constitutes a first step toward understanding how impurities and contaminants interact with the host phase and the environment. However, limitations to EXAFS interpretation complicate the analysis of trace concentrations of impurities that are distributed across multiple phases in a heterogeneous system. Ab initio molecular dynamics (AIMD)-informed EXAFS analysis was employed to investigate the immobilization of trace uranium associated with nanophase iron (oxyhydr)oxides, a model system for the geochemical sequestration of radiotoxic actinides. The reductive transformation of ferrihydrite [Fe(OH)3] to nanoparticulate iron oxyhydroxide minerals in the presence of uranyl (UO2)2+(aq) resulted in the preferential incorporation of U into goethite (α-FeOOH) over lepidocrocite (γ-FeOOH), even though reaction conditions favored the formation of excess lepidocrocite. This unexpected result is sup...

Engaging the Terminal: Promoting Halogen Bonding Interactions with Uranyl Oxo Atoms

Abstract: Engaging the nominally terminal oxo atoms of the linear uranyl (UO22+) cation in non-covalent interactions represents both a significant challenge and opportunity within the field of actinide hybrid materials. We have developed an approach for promoting oxo atom participation in a range of non-covalent interactions through judicious choice of electron donating equatorial ligands and appropriately polarizable halogen-donor atoms. As such, we have generated a family of uranyl hybrid materials based on a combination of 2,5-dihalobenzoic acid and aromatic, chelating N-donor ligands. Delineation of criteria for oxo participation in halogen bonding interactions has been achieved by preparing materials containing 2,5-dichloro- (25diClBA) and 2,5-dibromobenzoic acid (25diBrBA) coupled with 2,2'-bipyridine (bipy) (1 and 2), 1,10-phenanthroline (phen) (3-5), 2,2':6',2''-terpyridine (terpy) (6-8), or 4'-chloro-2,2':6',2''-terpyridine (Cl-terpy) (9-10), which have been characterized via single crystal X-ray diffraction, Raman, Infrared (IR), and luminescence spectroscopy, as well as via density functional calculations of electrostatic potentials. Looking comprehensively, these results are compared with recently published 2,5-diiodobenzoic acid analogues indicating that while inclusion of a capping ligand in the uranyl first coordination sphere is important, it is the polarizability of the selected halogen atom that ultimately drives halogen bonding interactions with the uranyl oxo atoms.

Carboxylated graphene as a sensing material for electrochemical uranyl ion detection

Abstract: The present study is focused on the application of graphene modified with carboxylic groups in the development of sensor for electrochemical detection for uranyl ion. After the graphene synthesis and its characterization, the optimization of the measurement conditions and working parameters of sensors were evaluated. Uranyl ion concentration was determined with the use of voltammetric techniques by comparison of current change of redox indicator hexaammineruthenium(III) chloride. The prepared sensor demonstrated linear response within the range of 5 × 10 −8 to 5 × 10 −6 mol L −1 and significant selectivity towards UO 2 2+ ions over other examined cations (e.g. Cd 2+ , Ca 2+ , Sr 2+ , Co 2+ , Mg 2+ , Pb 2+ and for Fe 3+ ).

Engineering Nanoscale Iron Oxides for Uranyl Sorption and Separation: Optimization of Particle Core Size and Bilayer Surface Coatings

Abstract: Herein, we describe engineered superparamagnetic iron oxide nanoparticles (IONPs) as platform materials for enhanced uranyl (UO22+) sorption and separation processes under environmentally relevant conditions. Specifically, monodispersed 8–25 nm iron oxide (magnetite, Fe3O4) nanoparticles with tailored organic acid bilayered coatings have been systematically evaluated and optimized to bind, and thus remove, uranium from water. The combined nonhydrolytic synthesis and bilayer phase transfer material preparation methods yield highly uniform and surface tailorable IONPs, which allow for direct evaluation of the size-dependent and coating-dependent sorption capacities of IONPs. Optimized materials demonstrate ultrahigh sorption capacities (>50% by wt/wt) at pH 5.6 for 8 nm oleic acid (OA) bilayer and sodium monododecyl phosphate (SDP) surface-stabilized IONPs. Synchrotron-based X-ray absorption spectroscopy shows that iron oxide core particle size and stabilizing surface functional group(s) substantially affec...

AgI and PbII as Additional Assembling Cations in Uranyl Coordination Polymers and Frameworks

Abstract: Five mono- or polycarboxylic acids have been used to generate a series of eight heterometallic uranyl complexes involving silver(I) or lead(II) cations, all synthesized under (solvo)-hydrothermal conditions. Pimelic acid (H2pim) gave complexes [Ag(bipy)2]2[UO2(pim)(NO3)]2 (1) and [UO2Pb(pim)2(bipy)(H2O)]·0.5bipy·H2O (2) (bipy = 2,2′-bipyridine), which both crystallize as one-dimensional (1D) polymers, but differ in that the silver(I) cations are separate counterions, while carboxylate-bound lead(II) cations are an essential component of the polymer. Only silver(I)-containing species were obtained with all-cis-1,3,5-cyclohexanetricarboxylic acid (H3chtc), [UO2Ag(chtc)(H2O)2] (3) and [Ag(bipy) (CH3CN)]2[UO2(chtc)]2 (4); both contain two-dimensional (2D) uranyl carboxylate subunits with honeycomb {63} topology, these being united into a three-dimensional (3D) framework with the lonsdaleite {66} topology by bridging, oxo-bound silver(I) cations in 3. Both silver- and lead-containing complexes were obtained wi...

Influence of Pyrazine/Piperazine Based Guest Molecules in the Crystal Structures of Uranyl Thiophene Dicarboxylate Coordination Polymers: Structural Diversities and Photocatalytic Activities for the Degradation of Organic Dye

Abstract: The reaction of uranyl acetate dihydrate with 2,5-thiophenedicarboxylic acid (H2TDC) as the main ligand and pyrazine (PYZ); piperazine (PZ); 1,4 pyridyl piperazine (PYPZ); 1,4-di(pyridin-4-yl) piperazine (DPYZ); 1,2 pyrimidyl piperazine (PMPZ) as auxiliary ligand leads to the formation of five new compounds [UO2(TDC)(H2O)]·(PYZ)0.5·H2O, (I); [(UO2)2(TDC)3]·(HPZ)·4(H2O), (II); [UO2(TDC)2(H2O)]·(H2DPYZ)·H2O, (III); [UO2(TDC)3]·(H2DPYZ), (IV); [(UO2)2(TDC)3(H2O)]·(H2PMPZ).H2O, (V). They were analyzed by IR, UV–vis, thermogravimetric analysis, X-ray diffraction analysis, powder X-ray diffraction, and fluorescence spectroscopy. Depending on the countercation, uranyl thiophene dicarboxylate is shown to crystallize as 2D layer in (I, IV), 2D layer with twofold interpenetrated (6,3) nets in (II), 1D chains in (III), and 2D layer without 2-fold interpenetrated (6,3) nets in (V). The coligand DPYZ in structures of (III and IV) had not been added to the reaction but has been formed by the N-arylation of the PYPZ lig...

Grafting of arginine and glutamic acid onto cellulose for enhanced uranyl sorption

Abstract: The grafting of arginine and glutamic acid on cellulose (through an intermediary step of chlorination) allows improving uranyl sorption of the biopolymer. The sorbents (Arg-Cell and Glu-Cell) were characterized by elemental analysis, FTIR spectrometry, XRD, SEM-EDX analysis and TGA. The sorption efficiency increases with pH; this can be attributed to the deprotonation of carboxylic acid and amine groups and to the formation of polynuclear hydrolyzed uranyl species. Sorption isotherms (fitted by the Langmuir equation) show sorption capacities at saturation of the monolayer of 147 and 168 mg U g−1 for Arg-Cell and Glu-Cell, respectively (compared to 78 mg U g−1 for raw cellulose); maximum sorption capacities at equilibrium (experimental values) reach 138, 160 and 73.4 for Arg-Cell, Glu-Cell and cellulose, respectively. Uranyl sorption is endothermic and is spontaneous for amino acid derivatives of cellulose (contrary to exothermic for cellulose). Uptake kinetics for the different sorbents are fitted by the pseudo-second-order rate equation. Uranium can be desorbed using sulfuric acid solutions, and the sorbents can be recycled for a minimum of five cycles of sorption/desorption: the decrease in sorption capacities at the fifth cycle does not exceed 13%.