New insight into the ternary complexes of uranyl carbonate in seawater.

PubMed

Beccia, M R; Matara-Aho, M; Reeves, B; Roques, J; Solari, P L; Monfort, M; Moulin, C; Den Auwer, C

2017-11-01

Uranium is naturally present in seawater at trace levels and may in some cases be present at higher concentrations, due to anthropogenic nuclear activities. Understanding uranium speciation in seawater is thus essential for predicting and controlling its behavior in this specific environmental compartment and consequently, its possible impact on living organisms. The carbonato calcic complex Ca 2 UO 2 (CO 3 ) 3 was previously identified as the main uranium species in natural seawater, together with CaUO 2 (CO 3 ) 3 2- . In this work, we further investigate the role of the alkaline earth cation in the structure of the ternary uranyl-carbonate complexes. For this purpose, artificial seawater, free of Mg 2+ and Ca 2+ , using Sr 2+ as a spectroscopic probe was prepared. Combining TRLIF and EXAFS spectroscopy, together with DFT and theoretical thermodynamic calculations, evidence for the presence of Sr alkaline earth counter ion in the complex structure can be asserted. Furthermore, data suggest that when Ca 2+ is replaced by Sr 2+ , SrUO 2 (CO 3 ) 3 2- is the main complex in solution and it occurs with the presence of at least one monodentate carbonate in the uranyl coordination sphere. Copyright © 2017 Elsevier Ltd. All rights reserved.

Rational Ligand Design for U(VI) and Pu(IV)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szigethy, Geza

2009-08-12

Nuclear power is an attractive alternative to hydrocarbon-based energy production at a time when moving away from carbon-producing processes is widely accepted as a significant developmental need. Hence, the radioactive actinide power sources for this industry are necessarily becoming more widespread, which is accompanied by the increased risk of exposure to both biological and environmental systems. This, in turn, requires the development of technology designed to remove such radioactive threats efficiently and selectively from contaminated material, whether that be contained nuclear waste streams or the human body. Raymond and coworkers (University of California, Berkeley) have for decades investigated the interactionmore » of biologically-inspired, hard Lewis-base ligands with high-valent, early-actinide cations. It has been established that such ligands bind strongly to the hard Lewis-acidic early actinides, and many poly-bidentate ligands have been developed and shown to be effective chelators of actinide contaminants in vivo. Work reported herein explores the effect of ligand geometry on the linear U(IV) dioxo dication (uranyl, UO 2 2+). The goal is to utilize rational ligand design to develop ligands that exhibit shape selectivity towards linear dioxo cations and provides thermodynamically favorable binding interactions. The uranyl complexes with a series of tetradentate 3-hydroxy-pyridin-2-one (3,2-HOPO) ligands were studied in both the crystalline state as well as in solution. Despite significant geometric differences, the uranyl affinities of these ligands vary only slightly but are better than DTPA, the only FDA-approved chelation therapy for actinide contamination. The terepthalamide (TAM) moiety was combined into tris-beidentate ligands with 1,2- and 3,2-HOPO moieties were combined into hexadentate ligands whose structural preferences and solution thermodynamics were measured with the uranyl cation. In addition to achieving coordinative saturation, these ligands exhibited increased uranyl affinity compared to bis-Me-3,2-HOPO ligands. This result is due in part to their increased denticity, but is primarily the result of the presence of the TAM moiety. In an effort to explore the relatively unexplored coordination chemistry of Pu(IV) with bidentate moieties, a series of Pu(IV) complexes were also crystallized using bidentate hydroxypyridinone and hydroxypyrone ligands. The geometries of these complexes are compared to that of the analogous Ce(IV) complexes. While in some cases these showed the expected structural similarities, some ligand systems led to significant coordination changes. A series of crystal structure analyses with Ce(IV) indicated that these differences are most likely the result of crystallization condition differences and solvent inclusion effects.« less

Thiocyanate complexes of uranium in multiple oxidation states: a combined structural, magnetic, spectroscopic, spectroelectrochemical, and theoretical study.

PubMed

Hashem, Emtithal; Platts, James A; Hartl, František; Lorusso, Giulia; Evangelisti, Marco; Schulzke, Carola; Baker, Robert J

2014-08-18

A comprehensive study of the complexes A4[U(NCS)8] (A = Cs, Et4N, (n)Bu4N) and A3[UO2(NCS)5] (A = Cs, Et4N) is described, with the crystal structures of [(n)Bu4N]4[U(NCS)8]·2MeCN and Cs3[UO2(NCS)5]·O0.5 reported. The magnetic properties of square antiprismatic Cs4[U(NCS)8] and cubic [Et4N]4[U(NCS)8] have been probed by SQUID magnetometry. The geometry has an important impact on the low-temperature magnetic moments: at 2 K, μeff = 1.21 μB and 0.53 μB, respectively. Electronic absorption and photoluminescence spectra of the uranium(IV) compounds have been measured. The redox chemistry of [Et4N]4[U(NCS)8] has been explored using IR and UV-vis spectroelectrochemical methods. Reversible 1-electron oxidation of one of the coordinated thiocyanate ligands occurs at +0.22 V vs Fc/Fc(+), followed by an irreversible oxidation to form dithiocyanogen (NCS)2 which upon back reduction regenerates thiocyanate anions coordinating to UO2(2+). NBO calculations agree with the experimental spectra, suggesting that the initial electron loss of [U(NCS)8](4-) is delocalized over all NCS(-) ligands. Reduction of the uranyl(VI) complex [Et4N]3[UO2(NCS)5] to uranyl(V) is accompanied by immediate disproportionation and has only been studied by DFT methods. The bonding in [An(NCS)8](4-) (An = Th, U) and [UO2(NCS)5](3-) has been explored by a combination of DFT and QTAIM analysis, and the U-N bonds are predominantly ionic, with the uranyl(V) species more ionic that the uranyl(VI) ion. Additionally, the U(IV)-NCS ion is more ionic than what was found for U(IV)-Cl complexes.

Infrared Multiphoton Dissociation Spectroscopy of a Gas-Phase Complex of Uranyl and 3-Oxa-Glutaramide: An Extreme Red-Shift of the [O=U=O]²⁺ Asymmetric Stretch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gibson, John K.; Hu, Hanshi; Van Stipdonk, Michael J.

2015-04-09

The gas-phase complex UO₂(TMOGA)₂²⁺ (TMOGA = tetramethyl-3-oxa-glutaramide) prepared by electrospray ionization was characterized by infrared multiphoton dissociation (IRMPD) spectroscopy. The IRMPD spectrum from 700–1800 cm⁻¹ was interpreted using a computational study based on density functional theory. The predicted vibrational frequencies are in good agreement with the measured values, with an average deviation of only 8 cm⁻¹ (<1%) and a maximum deviation of 21 cm⁻¹ (<2%). The only IR peak assigned to the linear uranyl moiety was the asymmetric ν₃ mode, which appeared at 965 cm⁻¹ and was predicted by DFT as 953 cm⁻¹. This ν₃ frequency is red-shifted relative tomore » bare uranyl, UO₂²⁺, by ca. 150 cm⁻¹ due to electron donation from the TMOGA ligands. Based on the degree of red-shifting, it is inferred that two TMOGA oxygen-donor ligands have a greater effective gas basicity than the four monodentate acetone ligands in UO₂(acetone)₄²⁺. The uranyl ν₃ frequency was also computed for uranyl coordinated by two TMGA ligands, in which the central Oether of TMOGA has been replaced by CH₂. The computed ν₃ for UO₂(TMGA)₂²⁺, 950 cm⁻¹, is essentially the same as that for UO₂(TMOGA)₂²⁺, suggesting that electron donation to uranyl from the Oether of TMOGA is minor. The computed ν₃ asymmetric stretching frequencies for the three actinyl complexes, UO₂(TMOGA)₂²⁺, NpO₂(TMOGA)₂²⁺ and PuO₂(TMOGA)₂²⁺, are comparable. This similarity is discussed in the context of the relationship between ν₃ and intrinsic actinide-oxygen bond energies in actinyl complexes.« less

Structural characterization of environmentally relevant ternary uranyl citrate complexes present in aqueous solutions and solid state materials.

PubMed

Basile, Madeline; Unruh, Daniel K; Flores, Erin; Johns, Adam; Forbes, Tori Z

2015-02-14

Organic acids are important metal chelators in environmental systems and tend to form soluble complexes in aqueous solutions, ultimately influencing the transport and bioavailability of contaminants in surface and subsurface waters. This is particularly true for the formation of uranyl citrate complexes, which have been utilized in advanced photo- and bioremediation strategies for soils contaminated with nuclear materials. Given the complexity of environmental systems, the formation of ternary or heterometallic uranyl species in aqueous solutions are also expected, particularly with Al(iii) and Fe(iii) cations. These ternary forms are reported to be more stable in aqueous solutions, potentially enhancing contaminant mobility and uptake by organisms, but the exact coordination geometries of these soluble molecular complexes have not been elucidated. To provide insight into the nature of these species, we have developed a series of geochemical model compounds ([(UO(2))(2)Al(2)(C(6)H(4)O(7))(4)](6-) (U(2)Al(2)), [(UO(2))(2)Fe(2)(C(6)H(4)O(7))(4)](6-) (U(2)Fe(2)-1) and [(UO(2))(2)Fe(2)(C(6)H(4)O(7))(4)(H(2)O)(2)](6-) (U(2)Fe(2)-2) and [(UO(2))(2)Fe(4)(OH)(4)(C(6)H(4)O(7))(4)](8-) (U(2)Fe(4))) that were characterized by single-crystal X-ray diffraction and vibrational spectroscopy. Mass spectroscopy was then employed to compare the model compounds to species present in aqueous solutions to provide an enhanced understanding of the ternary uranyl citrate complexes that could be relevant in natural systems.

Gas-Phase Coordination Complexes of UVIO{2/2+}, NpVIO{2/2+}, and PuVIO{2/2+} with Dimethylformamide

NASA Astrophysics Data System (ADS)

Rutkowski, Philip X.; Rios, Daniel; Gibson, John K.; van Stipdonk, Michael J.

2011-11-01

Electrospray ionization of actinyl perchlorate solutions in H2O with 5% by volume of dimethylformamide (DMF) produced the isolatable gas-phase complexes, [AnVIO2(DMF)3(H2O)]2+ and [AnVIO2(DMF)4]2+, where An = U, Np, and Pu. Collision-induced dissociation confirmed the composition of the dipositive coordination complexes, and produced doubly- and singly-charged fragment ions. The fragmentation products reveal differences in underlying chemistries of uranyl, neptunyl, and plutonyl, including the lower stability of Np(VI) and Pu(VI) compared with U(VI).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schoendorff, George E.; De Jong, Wibe A.; Gordon, Mark S.

The formation of uranyl dicationic complexes containing water and nitrile (acetonitrile, propionitrile, and benzonitrile) ligands, [UO2(H2O)n(RCN)m]2+, has been studied using density functional theory (DFT) with a relativistic effective core potential (RECP) to account for scalar relativistic effects on uranium. It is shown that nitrile addition is favored over the addition of water ligands. Decomposition of these complexes to [UO2OH(H2O)n(RCN)m]+ by the loss of either H3O+ or (RCN+H)+ is also examined. It is found that this reaction occurs when the coordination sphere of uranyl is unsaturated. Additionally, this reaction is influenced by the size of the nitrile ligand with reactions involvingmore » acetonitrile being the most prevalent.« less

Photochemical water oxidation and origin of nonaqueous uranyl peroxide complexes.

PubMed

McGrail, Brendan T; Pianowski, Laura S; Burns, Peter C

2014-04-02

Sunlight photolysis of uranyl nitrate and uranyl acetate solutions in pyridine produces uranyl peroxide complexes. To answer longstanding questions about the origin of these complexes, we conducted a series of mechanistic studies and demonstrate that these complexes arise from photochemical oxidation of water. The peroxo ligands are easily removed by protonolysis, allowing regeneration of the initial uranyl complexes for potential use in catalysis.

Molecular-scale characterization of uranium sorption by bone apatite materials for a permeable reactive barrier demonstration

USGS Publications Warehouse

Fuller, C.C.; Bargar, J.R.; Davis, J.A.

2003-01-01

Uranium binding to bone charcoal and bone meal apatite materials was investigated using U LIII-edge EXAFS spectroscopy and synchrotron source XRD measurements of laboratory batch preparations in the absence and presence of dissolved carbonate. Pelletized bone char apatite recovered from a permeable reactive barrier (PRB) at Fry Canyon, UT, was also studied. EXAFS analyses indicate that U(VI) sorption in the absence of dissolved carbonate occurred by surface complexation of U(VI) for sorbed concentrations ??? 5500 ??g U(VI)/g for all materials with the exception of crushed bone char pellets. Either a split or a disordered equatorial oxygen shell was observed, consistent with complexation of uranyl by the apatite surface. A second shell of atoms at a distance of 2.9 A?? was required to fit the spectra of samples prepared in the presence of dissolved carbonate (4.8 mM total) and is interpreted as formation of ternary carbonate complexes with sorbed U(VI). A U-P distance at 3.5-3.6 A?? was found for most samples under conditions where uranyl phosphate phases did not form, which is consistent with monodentate coordination of uranyl by phosphate groups in the apatite surface. At sorbed concentrations ??? 5500 ??g U(VI)/g in the absence of dissolved carbonate, formation of the uranyl phosphate solid phase, chernikovite, was observed. The presence of dissolved carbonate (4.8 mM total) suppressed the formation of chernikovite, which was not detected even with sorbed U(VI) up to 12 300 ??g U(VI)/g in batch samples of bone meal, bone charcoal, and reagent-grade hydroxyapatite. EXAFS spectra of bone char samples recovered from the Fry Canyon PRB were comparable to laboratory samples in the presence of dissolved carbonate where U(VI) sorption occurred by surface complexation. Our findings demonstrate that uranium uptake by bone apatite will probably occur by surface complexation instead of precipitation of uranyl phosphate phases under the groundwater conditions found at many U-contaminated sites.

Uranyl extraction by N,N-dialkylamide ligands studied using static and dynamic DFT simulations.

PubMed

Sieffert, Nicolas; Wipff, Georges

2015-02-14

We report DFT static and dynamic studies on uranyl complexes [UO(2)(NO(3))x(H(2)O)(y)L(z)](2-x) involved in the uranyl extraction from water to an "oil" phase (hexane) by an amide ligand L (N,N-dimethylacetamide). Static DFT results "in solution" (continuum SMD models for water and hexane) predict that the stepwise formation of [UO(2)(NO(3))(2)L(2)] from the UO(2)(H(2)O)(5)(2+) species is energetically favourable, and allow us to compare cis/trans isomers of penta- and hexa-coordinated complexes and key intermediates in the two solvents. DFT-MD simulations of [UO(2)(NO(3))(2)L(2)], [UO(2)(NO(3))(2)(H(2)O)L(2)], and [UO(2)(NO(3))(H(2)O)L(2)](+) species in explicit solvent environments (water, hexane, or the water/hexane interface) represented at the MM or full-DFT level reveal a versatile solvent dependent binding mode of nitrates, also evidenced by metadynamics simulations. In water and at the interface, the latter exchange from bi- to monodentate, via in plane rotational motions in some cases. Remarkably, structures of complexes at the interface are more "water-like" than gas phase- or hexane-like. Thus, the order of U-O(NO(3))/U-O(L) bond distances observed in the gas phase (U-O(nit) < U-OL) is inverted at the interface and in water. Overall, the results are consistent with the experimental observation of uranyl extraction from nitric acid solutions by amide analogues (bearing "fatty" substituents), and allow us to propose possible extraction mechanisms, involving complexation of L "right at the interface". They also point to the importance of the solvent environment and the dynamics on the structure and stability of the complexes.

Two actinide-organic frameworks constructed by a tripodal flexible ligand: Occurrence of infinite {(UO2)O2(OH)3}4n and hexanuclear {Th6O4(OH)4} motifs

NASA Astrophysics Data System (ADS)

Liang, Lingling; Zhang, Ronglan; Zhao, Jianshe; Liu, Chiyang; Weng, Ng Seik

2016-11-01

Two new actinide metal-organic frameworks were constructed by using a tripodal flexible ligand tris (2-carboxyethyl) isocyanurate (H3tci) under hydrothermal condition. The combination of H3tci and uranyl nitrate hexahydrate in aqueous solution leads to the isolation of [(UO2)2(H2O)4]0.5(tci)2(UO2)4(OH)4·18H2O (1), which contains two distinct UO22+ coordination environments. Four uranyl cations, linked through μ3-OH respectively, result in the edge-sharing ribbons. Then, the layer structure is constructed by U-O clusters linked through other eight-coordinated uranyl unions, giving rise to a porous structure in the space. Topological analysis reveals that complex 1 belongs to a (4, 8)-connected net with a schläfli symbol of (34.26.3)2(34.46.56.68.73.8). Th3(tci)2O2(OH)2(H2O)3·12H2O (2) generated by the reaction of H3tci and thorium nitrate tetrahydrate, possesses nine-fold coodinated Th(IV) centers with a monocapped square antiprismatic geometry. The hexamers "Th6O4(OH)4" motifs are connected together by the carboxylate groups, showing a three-dimensional structures. Complex 2 takes on an 8-connected architecture and the point symbol is (424.64).

COORDINATION COMPOUND-SOLVENT EXTRACTION PROCESS FOR URANIUM RECOVERY

DOEpatents

Reas, W.H.

1959-03-10

A method is presented for the separation of uranium from aqueous solutions containing a uranyl salt and thorium. Thc separation is effected by adding to such solutions an organic complexing agent, and then contacting the solution with an organic solvent in which the organic complexing agent is soluble. By use of the proper complexing agent in the proper concentrations uranium will be complexed and subsequently removed in the organic solvent phase, while the thorium remains in the aqueous phase. Mentioned as suitable organic complexing agents are antipyrine, bromoantipyrine, and pyramidon.

Surface catalysis of uranium(VI) reduction by iron(II)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liger, E.; Charlet, L.; Van Cappellen, P.

1999-10-01

Colloidal hematite ({alpha}-Fe{sub 2}O{sub 3}) is used as model solid to investigate the kinetic effect of specific adsorption interactions on the chemical reduction of uranyl (U{sup VI}O{sub 2}{sup 2+}) by ferrous iron. Acid-base titrations and Fe(II) and uranyl adsorption experiments are performed on hematite suspensions, under O{sub 2}- and CO{sub 2}-free conditions. The results are explained in terms of a constant capacitance surface complexation model of the hematite-aqueous solution interface. Two distinct Fe(II) surface complexes are required to reproduce the data: ({equivalent{underscore}to}Fe{sup III}OFe{sup II}){sup +} (or {equivalent{underscore}to}Fe{sup III}OFe{sup II}(OH{sub 2}){sub n}{sup +}) and {equivalent{underscore}to}Fe{sup III}OFe{sup II}OH{sup 0} (or {equivalent{underscore}to}Fe{sup III}OFe{supmore » II}(OH{sub 2}){sub n{minus}1}OH{sup 0}). The latter complex represents a significant fraction of total adsorbed Fe(II) at pH {gt} 6.5. Uranyl binding to the hematite particles is characterized by a sharp adsorption edge between pH 4 and pH 5.5. Because of the absence of competing aqueous carbonate complexes, uranyl remains completely adsorbed at pH {gt} 7. A single mononuclear surface complex accounts for the adsorption of uranyl over the entire range of experimental conditions. Although thermodynamically feasible, no reaction between uranyl and Fe(II) is observed in homogeneous solution at pH 7.5, for periods of up to three days. In hematite suspensions, however, surface-bound uranyl reacts on a time scale of hours. Based on Fourier Transformed Infrared spectra, chemical reduction of U(VI) is inferred to be the mechanism responsible for the disappearance of uranyl. The kinetics of uranyl reduction are quantified by measuring the decrease with time of the concentration of U(VI) extractable from the hematite particles by NaHCO{sub 3}. In the presence of excess Fe(II), the initial rate of U(VI) reduction exhibits a first-order dependence on the concentration of adsorbed uranyl. The pseudo-first-order rate constant varies with pH (range, 6--7.5) and the total (dissolved + adsorbed) concentration of Fe(II) (range, 2--160 {micro}M). When analyzing the rate data in terms of the calculated surface speciation, the variability of the rate constant can be accounted for entirely by changes in the concentration of the Fe(II) monohydroxo surface complex {equivalent{underscore}to}Fe{sup III}OFe{sup II}OH{sup 0}. Therefore, the rate law is derived for the hematite-catalyzed reduction of uranyl by Fe(II), where the bimolecular rate constant {kappa} has a value of 399 {+-} 25 M{sup {minus}1} min{sup {minus}1} at 25 C. The hydroxo surface complex is the rate-controlling reductant species, because it provides the most favorable coordination environment in which electrons are removed from Fe(II). Natural particulate matter collected in the hypolimnion of a seasonally stratified lake also causes the rapid reduction of uranyl by Fe(II), Ferrihydrite, identified in the particulate matter by X-ray diffraction, is one possible mineral phase accelerating the reaction between U(VI) and Fe(II). At near-neutral pH and total Fe(II) levels less than 1 mM, the pseudo-first-order rate constants of chemical U(VI) reduction, measured in the presence of the hematite and lake particles, are of the same order of magnitude as the highest corresponding rate coefficients for enzymatic U(VI) reduction in bacterial cultures. Hence, based on the results of this study, surface-catalyzed U(VI) reduction by Fe(II) is expected to be a major pathway of uranium immobilization in a wide range of redox-stratified environments.« less

Water structure and aqueous uranyl(VI) adsorption equilibria onto external surfaces of beidellite, montmorillonite, and pyrophyllite: results from molecular simulations.

PubMed

Greathouse, Jeffery A; Cygan, Randall T

2006-06-15

Molecular dynamics simulations were performed to provide a systematic study of aqueous uranyl adsorption onto the external surface of 2:1 dioctahedral clays. Our understanding of this key process is critical in predicting the fate of radioactive contaminants in natural groundwaters. These simulations provide atomistic detail to help explain experimental trends in uranyl adsorption onto natural media containing smectite clays. Aqueous uranyl concentrations ranged from 0.027 to 0.162 M. Sodium ions and carbonate ions (0.027-0.243 M) were also present in the aqueous regions to more faithfully model a stream of uranyl-containing groundwater contacting a mineral system comprised of Na-smectite. No adsorption occurred near the pyrophyllite surface, and there was little difference in uranyl adsorption onto the beidellite and montmorillonite, despite the difference in location of clay layer charge between the two. At low uranyl concentration, the pentaaquouranyl complex dominates in solution and readily adsorbs to the clay basal plane. At higher uranyl (and carbonate) concentrations, the mono(carbonato) complex forms in solution, and uranyl adsorption decreases. Sodium adsorption onto beidellite occurred both as inner- and outer-sphere surface complexes, again with little effect on uranyl adsorption. Uranyl surface complexes consisted primarily of the pentaaquo cation (85%) and to a lesser extent the mono(carbonato) species (15%). Speciation diagrams of the aqueous region indicate that the mono(carbonato)uranyl complex is abundant at high ionic strength. Oligomeric uranyl complexes are observed at high ionic strength, particularly near the pyrophyllite and montmorillonite surfaces. Atomic density profiles of water oxygen and hydrogen atoms are nearly identical near the beidellite and montmorillonite surfaces. Water structure therefore appears to be governed by the presence of adsorbed ions and not by the location of layer charge associated with the substrate. The water oxygen density near the pyrophyllite surface is similar to the other cases, but the hydrogen density profile indicates reduced hydrogen bonding between adsorbed water molecules and the surface.

Composition for detecting uranyl

DOEpatents

Baylor, Lewis C.; Stephens, Susan M.

1995-01-01

A composition for detecting the presence and concentration of a substance such as uranyl, comprising an organohalide covalently bonded to an indicator for said substance. The composition has at least one active OH site for forming a complex with the substance to be detected. The composition is made by reacting equimolar amounts of the indicator and the organohalide in a polar organic solvent. The absorbance spectrum of the composition-uranyl complex is shifted with respect to the absorbance spectrum of the indicator-uranyl complex, to provide better spectral resolution for detecting uranyl.

Polymorphism in alkali metal uranyl nitrates: Synthesis and crystal structure of gamma-K(UO2)(NO3)3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jouffret, Laurent J.; Krivovichev, Sergey V.; Burns, Peter C.

2011-07-20

Single crystals of γ-K(UO₂)(NO₃)₃ were prepared from aqueous solutions by evaporation. The crystal structure [orthorhombic, Pbca (61), a = 9.2559(3) Å, b = 12.1753(3) Å, c = 15.8076(5) Å, V = 1781.41(9) ų, Z = 8] was determined by direct methods and refined to R₁ = 0.0267 on the basis of 3657 unique observed reflections. The structure is composed of isolated anionic uranyl trinitrate units, [(UO₂)(NO₃)₃] –, that are linked through eleven-coordinated K + cations. Both known polymorphs of K(UO₂)(NO₃)₃ (α- and γ-phases) can be considered as based upon sheets of isolated complex [(UO₂)(NO₃)₃] – ions separated by K +more » cations. The existence of polymorphism in the two K[UO₂(NO₃)₃] polymorphs is due to the different packing modes of uranyl trinitrate clusters that adopt the same two-dimensional but different three-dimensional arrangements.« less

D.C. electrical conductivity and conduction mechanism of some azo sulfonyl quinoline ligands and uranyl complexes.

PubMed

El-Ghamaz, N A; Diab, M A; El-Sonbati, A Z; Salem, O L

2011-12-01

Supramolecular coordination of dioxouranium(VI) heterochelates 5-sulphono-7-(4'-X phenylazo)-8-hydroxyquinoline HL(n) (n=1, X=CH(3); n=2, X=H; n=3, X=Cl; n=4, X=NO(2)) have been prepared and characterized with various physico-chemical techniques. The infrared spectral studies showed a monobasic bidentate behavior with the oxygen and azonitrogen donor system. The temperature dependence of the D.C. electrical conductivity of HL(n) ligands and their uranyl complexes has been studied in the temperature range 305-415 K. The thermal activation energies E(a) for HL(n) compounds were found to be in the range 0.44-0.9 eV depending on the nature of the substituent X. The complexation process decreased E(a) values to the range 0.043-045 eV. The electrical conduction mechanism has been investigated for all samples under investigation. It was found to obey the variable range hopping mechanism (VRH). Copyright © 2011 Elsevier B.V. All rights reserved.

Synthesis and Characterization of Templated Ion Exchange Resins for the Selective Complexion of Actinide Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murrray, George M.; Uy, O. Manuel

The purpose of this research is to develop polymeric extractants for the selective complexation of uranyl ions (and subsequently other actinyl and actinide ions) from aqueous solutions. Selectivity for a specific actinide ion is obtained by providing the polymers with cavities lined with complexing ligands so arranged as to match the charge, coordination number, coordination geometry, and size of the actinide ion. These cavity-containing polymers are produced by using a specific actinide ion (or surrogate) as a template around which monomeric complexing ligands are polymerized. The polymers provide useful sequestering agents for removing actinide ions from wastes and will formmore » the basis for a variety of analytical techniques for actinide determination.« less

Partitioning of uranyl between ferrihydrite and humic substances at acidic and circum-neutral pH

NASA Astrophysics Data System (ADS)

Dublet, Gabrielle; Lezama Pacheco, Juan; Bargar, John R.; Fendorf, Scott; Kumar, Naresh; Lowry, Gregory V.; Brown, Gordon E.

2017-10-01

As part of a larger study of the reactivity and mobility of uranyl (U(VI)O22+) cations in subsurface environments containing natural organic matter (NOM) and hydrous ferric oxides, we have examined the effect of reference humic and fulvic substances on the sorption of uranyl on 2-line ferrihydrite (Fh), a common, naturally occurring nano-Fe(III)-hydroxide. Uranyl was reacted with Fh at pH 4.6 and 7.0 in the presence and absence of Elliott Soil Humic Acid (ESHA) (0-835 ppm) or Suwanee River Fulvic Acid (SRFA) (0-955 ppm). No evidence was found for reduction of uranyl by either form of NOM after 24 h of exposure. The following three size fractions were considered in this study: (1) ≥0.2 μm (Fh-NOM aggregates), (2) 0.02-0.2 μm (dispersed Fh nanoparticles and NOM macro-molecules), and (3) <0.02 μm (dissolved). The extent to which U(VI) is sorbed in aggregates or dispersed as colloids was assessed by comparing U, Fe, and NOM concentrations in these three size fractions. Partitioning of uranyl between Fh and NOM was determined in size fraction (1) using X-ray absorption spectroscopy (XAS). Uranyl sorption on Fh-NOM aggregates was affected by the presence of NOM in different ways depending on pH and type of NOM (ESHA vs. SRFA). The presence of ESHA in the uranyl-Fh-NOM ternary system at pH 4.6 enhanced uranyl uptake more than the presence of SRFA. In contrast, neither form of NOM affected uranyl sorption at pH 7.0 over most of the NOM concentration range examined (0-500 ppm); at the highest NOM concentrations (500-955 ppm) uranyl uptake in the aggregates was slightly inhibited at pH 7.0, which is interpreted as being due to the dispersion of Fh aggregates. XAS at the U LIII-edge was used to characterize molecular-level changes in uranyl complexation as a result of sorption to the Fh-NOM aggregates. In the absence of NOM, uranyl formed dominantly inner-sphere, mononuclear, bidentate sorption complexes on Fh. However, when NOM concentration was increased at pH 4.6, the proportion of uranyl-Fh inner-sphere sorption complexes decreased relative to uranyl-ESHA or uranyl-SRFA complexes, which comprised up to ∼60% of the total uranyl in the systems studied. At pH 7.0, uranyl-NOM complexes were also present in the Fh-NOM aggregates in the concentration ranges of ESHA or SRFA considered; however, the proportion of these complexes was smaller at pH 7.0 than at pH 4.6 and did not increase significantly with increasing NOM concentration.

Formic acid interaction with the uranyl(VI) ion: structural and photochemical characterization.

PubMed

Lucks, Christian; Rossberg, André; Tsushima, Satoru; Foerstendorf, Harald; Fahmy, Karim; Bernhard, Gert

2013-10-07

Complex formation between the uranyl(VI) ion and formic acid was studied by infrared absorption (IR) and X-ray absorption (EXAFS) spectroscopy as well as density functional theory (DFT) calculations. In contrast to the acetate ion which forms exclusively a bidentate complex with uranyl(VI), the formate ion binds to uranyl(VI) in a unidentate fashion. The photochemistry of the uranyl(VI)-formic acid system was explored by DFT calculations and photoreduction of uranyl(VI) in the presence of formic acid was found to occur via an intermolecular process, that is, hydrogen abstraction from hydrogenformate by the photo-excited uranyl(VI). There is no photo-induced decarboxylation of uranyl(VI) formate via an intramolecular process, presumably due to lack of a C=C double bond.

Coordination trends in alkali metal crown ether uranyl halide complexes: the series [A(crown)]2[UO(2)X(4)] where A=Li, Na, K and X=Cl, Br.

PubMed

Danis, J A; Lin, M R; Scott, B L; Eichhorn, B W; Runde, W H

2001-07-02

UO(2)(C(2)H(3)O(2))(2).2H(2)O reacts with AX or A(C(2)H(3)O(2) or ClO(4)) (where A = Li, Na, K; X = Cl, Br) and crown ethers in HCl or HBr aqueous solutions to give the sandwich-type compounds [K(18-crown-6)](2)[UO(2)Cl(4)] (1), [K(18-crown-6)](2)[UO(2)Br(4)] (2), [Na(15-crown-5)](2)[UO(2)Cl(4)] (3), [Na(15-crown-5)](2)[UO(2)Br(4)] (4), [Li(12-crown-4)](2)[UO(2)Cl(4)] (5), and [Li(12-crown-4)](2)[UO(2)Br(4)] (6). The compounds have been characterized by single-crystal X-ray diffraction, powder diffraction, elemental analysis, IR, and Raman spectroscopy. The [UO(2)X(4)](2-) ions coordinate to two [A(crown)](+) cations through the four halides only (2), through two halides only (3), through the two uranyl oxygens and two halides (3, 4), or through the two uranyl oxygen atoms only (5, 6). Raman spectra reveal nu(U-O) values that correlate with expected trends. The structural trends are discussed within the context of classical principles of hard-soft acid-base theory.

XAFS investigation of polyamidoxime-bound uranyl contests the paradigm from small molecule studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayes, Richard T.; Piechowicz, Marek; Lin, Zekai

In this study, 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 η 2 motifs proposed by small molecule andmore » computational studies. Samples exposed to environmental seawater also display a feature consistent with a μ 2-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.« less

XAFS investigation of polyamidoxime-bound uranyl contests the paradigm from small molecule studies

DOE PAGES

Mayes, Richard T.; Piechowicz, Marek; Lin, Zekai; ...

2015-11-12

In this study, 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 η 2 motifs proposed by small molecule andmore » computational studies. Samples exposed to environmental seawater also display a feature consistent with a μ 2-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.« less

Polymorphism in Alkali Metal Uranyl Nitrates: Synthesis and Crystal Structure of γ-K(UO2)(NO3)3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jouffret, Laurent J.; Krivovichev, Sergey V.; Burns, Peter C.

2011-07-20

Single crystals of γ-K(UO2)(NO3)3 were prepared from aqueous solutions by evaporation. The crystal structure [orthorhombic, Pbca (61), a = 9.2559(3) Å, b = 12.1753(3) Å, c = 15.8076(5) Å, V = 1781.41(9) Å3, Z = 8] was determined by direct methods and refined to R1 = 0.0267 on the basis of 3657 unique observed reflections. The structure is composed of isolated anionic uranyl trinitrate units, [(UO2)(NO3)3]–, that are linked through eleven-coordinated K+ cations. Both known polymorphs of K(UO2)(NO3)3 (α- and γ-phases) can be considered as based upon sheets of isolated complex [(UO2)(NO3)3]– ions separated by K+ cations. The existence ofmore » polymorphism in the two K[UO2(NO3)3] polymorphs is due to the different packing modes of uranyl trinitrate clusters that adopt the same two-dimensional but different three-dimensional arrangements.« less

Synthesis, X-ray crystallography, thermal studies, spectroscopic and electrochemistry investigations of uranyl Schiff base complexes.

PubMed

Asadi, Zahra; Shorkaei, Mohammad Ranjkesh

2013-03-15

Some tetradentate salen type Schiff bases and their uranyl complexes were synthesized and characterized by UV-Vis, NMR, IR, TG, C.H.N. and X-ray crystallographic studies. From these investigations it is confirmed that a solvent molecule occupied the fifth position of the equatorial plane of the distorted pentagonal bipyramidal structure. Also, the kinetics of complex decomposition by using thermo gravimetric methods (TG) was studied. The thermal decomposition reactions are first order for the studied complexes. To examine the properties of uranyl complexes according to the substitutional groups, we have carried out the electrochemical studies. The electrochemical reactions of uranyl Schiff base complexes in acetonitrile were reversible. Copyright © 2012 Elsevier B.V. All rights reserved.

Europium, uranyl, and thorium-phenanthroline amide complexes in acetonitrile solution: an ESI-MS and DFT combined investigation.

PubMed

Xiao, Cheng-Liang; Wang, Cong-Zhi; Mei, Lei; Zhang, Xin-Rui; Wall, Nathalie; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

2015-08-28

The tetradentate N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) ligand with hard-soft donor atoms has been demonstrated to be promising for the group separation of actinides from highly acidic nuclear wastes. To identify the formed complexes of this ligand with actinides and lanthanides, electrospray ionization mass spectrometry (ESI-MS) combined with density functional theory (DFT) calculations was used to probe the possible complexation processes. The 1 : 2 Eu-L species ([EuL2(NO3)](2+)) can be observed in ESI-MS at low metal-to-ligand ([M]/[L]) ratios, whereas the 1 : 1 Eu-L species ([EuL(NO3)2](+)) can be observed when the [M]/[L] ratio is higher than 1.0. However, ([UO2L(NO3)](+)) is the only detected species for the uranyl complexes. The [ThL2(NO3)2](2+) species can be observed at low [M]/[L] ratios; the 1 : 2 species ([ThL2(NO3)](3+)) and a new 1 : 1 species ([ThL(NO3)3](+)) can be detected at high [M]/[L] ratios. Collision-induced dissociation (CID) results showed that Et-Tol-DAPhen ligands can coordinate strongly with metal ions, and the coordination moieties remain intact under CID conditions. Natural bond orbital (NBO), molecular electrostatic potential (MEP), electron localization function (ELF), atoms in molecules (AIM) and molecular orbital (MO) analyses indicated that the metal-ligand bonds of the actinide complexes exhibited more covalent character than those of the lanthanide complexes. In addition, according to thermodynamic analysis, the stable cationic M-L complexes in acetonitrile are found to be in good agreement with the ESI-MS results.

Probing hydrogen and halogen-oxo interactions in uranyl coordination polymers: a combined crystallographic and computational study

DOE PAGES

Carter, Korey P.; Kalaj, Mark; Kerridge, Andrew; ...

2018-01-01

Four uranyl compounds containing either benzoic acid ( 1 ), m -chlorobenzoic acid ( 2 ), m -bromobenzoic acid ( 3 ), or m -iodobenzoic acid ( 4 ) are described, and the latter two compounds are used to probe non-covalent interaction strengths via structural, vibrational, and computational means.

Modulating Uranium Binding Affinity in Engineered Calmodulin EF-Hand Peptides: Effect of Phosphorylation

PubMed Central

Pardoux, Romain; Sauge-Merle, Sandrine; Lemaire, David; Delangle, Pascale; Guilloreau, Luc; Adriano, Jean-Marc; Berthomieu, Catherine

2012-01-01

To improve our understanding of uranium toxicity, the determinants of uranyl affinity in proteins must be better characterized. In this work, we analyzed the contribution of a phosphoryl group on uranium binding affinity in a protein binding site, using the site 1 EF-hand motif of calmodulin. The recombinant domain 1 of calmodulin from A. thaliana was engineered to impair metal binding at site 2 and was used as a structured template. Threonine at position 9 of the loop was phosphorylated in vitro, using the recombinant catalytic subunit of protein kinase CK2. Hence, the T9TKE12 sequence was substituted by the CK2 recognition sequence TAAE. A tyrosine was introduced at position 7, so that uranyl and calcium binding affinities could be determined by following tyrosine fluorescence. Phosphorylation was characterized by ESI-MS spectrometry, and the phosphorylated peptide was purified to homogeneity using ion-exchange chromatography. The binding constants for uranyl were determined by competition experiments with iminodiacetate. At pH 6, phosphorylation increased the affinity for uranyl by a factor of ∼5, from Kd = 25±6 nM to Kd = 5±1 nM. The phosphorylated peptide exhibited a much larger affinity at pH 7, with a dissociation constant in the subnanomolar range (Kd = 0.25±0.06 nM). FTIR analyses showed that the phosphothreonine side chain is partly protonated at pH 6, while it is fully deprotonated at pH 7. Moreover, formation of the uranyl-peptide complex at pH 7 resulted in significant frequency shifts of the νas(P-O) and νs(P-O) IR modes of phosphothreonine, supporting its direct interaction with uranyl. Accordingly, a bathochromic shift in νas(UO2)2+ vibration (from 923 cm−1 to 908 cm−1) was observed upon uranyl coordination to the phosphorylated peptide. Together, our data demonstrate that the phosphoryl group plays a determining role in uranyl binding affinity to proteins at physiological pH. PMID:22870263

Structural determination of individual chemical species in a mixed system by iterative transformation factor analysis-based X-ray absorption spectroscopy combined with UV-visible absorption and quantum chemical calculation.

PubMed

Ikeda, Atsushi; Hennig, Christoph; Rossberg, André; Tsushima, Satoru; Scheinost, Andreas C; Bernhard, Gert

2008-02-15

A multitechnique approach using extended X-ray absorption fine structure (EXAFS) spectroscopy based on iterative transformation factor analysis (ITFA), UV-visible absorption spectroscopy, and density functional theory (DFT) calculations has been performed in order to investigate the speciation of uranium(VI) nitrate species in acetonitrile and to identify the complex structure of individual species in the system. UV-visible spectral titration suggests that there are four different species in the system, that is, pure solvated species, mono-, di-, and trinitrate species. The pure EXAFS spectra of these individual species are extracted by ITFA from the measured spectral mixtures on the basis of the speciation distribution profile calculated from the UV-visible data. Data analysis of the extracted EXAFS spectra, with the help of DFT calculations, reveals the most probable complex structures of the individual species. The pure solvated species corresponds to a uranyl hydrate complex with an equatorial coordination number (CNeq) of 5, [UO2(H2O)5]2+. Nitrate ions tend to coordinate to the uranyl(VI) ion in a bidentate fashion rather than a unidentate one in acetonitrile for all the nitrate species. The mononitrate species forms the complex of [UO2(H2O)3NO3]+ with a CNeq value of 5, while the di- and trinitrate species have a CNeq value of 6, corresponding to [UO2(H2O)2(NO3)2]0 (D2h) and [UO2(NO3)3]- (D3h), respectively.

Electrospray ionization of uranyl-citrate complexes

NASA Astrophysics Data System (ADS)

Somogyi, Árpád; Pasilis, Sofie P.; Pemberton, Jeanne E.

2007-09-01

Results presented here demonstrate the usefulness of electrospray ionization and gas-phase ion-molecule reactions to predict structural and electronic differences in complex inorganic ions. Electrospray ionization of uranyl citrate solutions generates positively and negatively charged ions that participate in further ion-molecule reactions in 3D ion trap and FT-ICR mass analyzers. Most ions observed are derived from the major solution uranyl-citrate complexes and involve species of {(UO2)2Cit2}2-, (UO2)3Cit2, and {(UO2)3Cit3}3-, where Cit indicates the citrate trianion, C6H5O73-. In a 3D ion trap operated at relatively high pressure, complex adducts containing solvent molecules, alkali and ammonium cations, and nitrate or chloride anions are dominant, and proton/alkali cation (Na+, K+) exchange is observed for up to six exchangeable protons in an excess of alkali cations. Adduct formation in a FT-ICR cell that is operated at lower pressures is less dominant, and direct detection of positive and negative ions of the major solution complexes is possible. Multiply charged ions are also detected, suggesting the presence of uranium in different oxidation states. Changes in uranium oxidation state are detected by He-CID and SORI-CID fragmentation, and certain fragments undergo association reactions in trapping analyzers, forming "exotic" species such as [(UO2)4O3]-, [(UO2)4O4]-, and [(UO2)4O5]-. Ion-molecule reactions with D2O in the FT-ICR cell indicate substantial differences in H/D exchange rate and D2O accommodation for different ion structures and charge states. Most notably, the positively charged ions [H2(UO2)2Cit2(H)]+ and [(UO2)2(Cit)]+ accommodate two and three D2O molecules, respectively, which reflects well the structural differences, i.e., tighter uranyl-citrate coordination in the former ion than in the latter. The corresponding negatively charged ions accommodate zero or two D2O molecules, which can be rationalized using suggested solution phase structures and charge state distributions.

Six uranyl-organic frameworks with naphthalene-dicarboxylic acid and bipyridyl-based spacers: syntheses, structures, and properties.

PubMed

Xu, Wei; Ren, Ya-Nan; Xie, Miao; Zhou, Lin-Xia; Zheng, Yue-Qing

2018-03-28

A new series of uranium coordination polymers have been hydrothermally synthesized by using 1,4-naphthalene dicarboxylic acid (H 2 NDC), namely, (H 3 O) 2 [(UO 2 ) 2 (NDC) 3 ]·H 2 O (1), (H 2 -bpp)[(UO 2 ) 2 (NDC) 3 ]·EtOH·5H 2 O (2), (H 2 -bpe) 2/2 [(UO 2 ) 2 (NDC) 3 ]·EtOH (3), (H 2 -bpp)[(UO 2 ) 2 (NDC) 3 ]·5H 2 O (4), (H 2 -bpp)[(UO 2 )(HNDC)(NDC)] 2 ·2H 2 O (5), and (H 2 -bpy)[(UO 2 )(NDC) 2 ] (6) [bpp = 1,3-di(4-pyridyl) propane, bpe = 4,4'-vinylenedipyridine, bpy = 4,4'-bipyridine]. Single-crystal X-ray diffraction demonstrates that complex 1 represents the uranyl-organic polycatenated framework derived from a simple two-dimensional honeycomb grid network structure via a H 2 NDC linker. Complexes 2-4 contain the dinuclear motifs of the two UO 7 pentagonal and one UO 8 hexagonal bipyramids which are linked by NDC 2- anions creating a (UO 2 ) 4 (NDC) 2 unit, and further extend to a 2D layer through NDC 2- anions. Complex 5 displays a 1D zigzag double chain structure, in which the carboxylate groups of the NDC 2- anions adopt a chelate mode and further extends to a 2D framework via hydrogen bonds. The 1D structure of complex 6 is similar to the zigzag chain of complex 5. In addition, powder X-ray diffraction, elemental analysis, IR, thermal stability and luminescence properties of all complexes have also been investigated in this paper. The photocatalytic properties of the six complexes for the degradation of tetracycline hydrochloride (TC) under UV irradiation have been examined. Moreover, density functional theory (DFT) calculations were carried out to explore the electronic structural and bonding properties of the uranyl complexes 1-6.

UO₂²⁺ uptake by proteins: understanding the binding features of the super uranyl binding protein and design of a protein with higher affinity.

PubMed

Odoh, Samuel O; Bondarevsky, Gary D; Karpus, Jason; Cui, Qiang; He, Chuan; Spezia, Riccardo; Gagliardi, Laura

2014-12-17

The capture of uranyl, UO2(2+), by a recently engineered protein (Zhou et al. Nat. Chem. 2014, 6, 236) with high selectivity and femtomolar sensitivity has been examined by a combination of density functional theory, molecular dynamics, and free-energy simulations. It was found that UO2(2+) is coordinated to five carboxylate oxygen atoms from four amino acid residues of the super uranyl binding protein (SUP). A network of hydrogen bonds between the amino acid residues coordinated to UO2(2+) and residues in its second coordination sphere also affects the protein's uranyl binding affinity. Free-energy simulations show how UO2(2+) capture is governed by the nature of the amino acid residues in the binding site, the integrity and strength of the second-sphere hydrogen bond network, and the number of water molecules in the first coordination sphere. Alteration of any of these three factors through mutations generally results in a reduction of the binding free energy of UO2(2+) to the aqueous protein as well as of the difference between the binding free energies of UO2(2+) and other ions (Ca(2+), Cu(2+), Mg(2+), and Zn(2+)), a proxy for the protein's selectivity over these ions. The results of our free-energy simulations confirmed the previously reported experimental results and allowed us to discover a mutant of SUP, specifically the GLU64ASP mutant, that not only binds UO2(2+) more strongly than SUP but that is also more selective for UO2(2+) over other ions. The predictions from the computations were confirmed experimentally.

Surface complexation model of uranyl sorption on Georgia kaolinite

USGS Publications Warehouse

Payne, T.E.; Davis, J.A.; Lumpkin, G.R.; Chisari, R.; Waite, T.D.

2004-01-01

The adsorption of uranyl on standard Georgia kaolinites (KGa-1 and KGa-1B) was studied as a function of pH (3-10), total U (1 and 10 ??mol/l), and mass loading of clay (4 and 40 g/l). The uptake of uranyl in air-equilibrated systems increased with pH and reached a maximum in the near-neutral pH range. At higher pH values, the sorption decreased due to the presence of aqueous uranyl carbonate complexes. One kaolinite sample was examined after the uranyl uptake experiments by transmission electron microscopy (TEM), using energy dispersive X-ray spectroscopy (EDS) to determine the U content. It was found that uranium was preferentially adsorbed by Ti-rich impurity phases (predominantly anatase), which are present in the kaolinite samples. Uranyl sorption on the Georgia kaolinites was simulated with U sorption reactions on both titanol and aluminol sites, using a simple non-electrostatic surface complexation model (SCM). The relative amounts of U-binding >TiOH and >AlOH sites were estimated from the TEM/EDS results. A ternary uranyl carbonate complex on the titanol site improved the fit to the experimental data in the higher pH range. The final model contained only three optimised log K values, and was able to simulate adsorption data across a wide range of experimental conditions. The >TiOH (anatase) sites appear to play an important role in retaining U at low uranyl concentrations. As kaolinite often contains trace TiO2, its presence may need to be taken into account when modelling the results of sorption experiments with radionuclides or trace metals on kaolinite. ?? 2004 Elsevier B.V. All rights reserved.

Iron (III) Matrix Effects on Mineralization and Immobilization of Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cynthia-May S. Gong; Tyler A. Sullens; Kenneth R. Czerwinski

2006-01-01

Abstract - A number of models for the Yucca Mountain Project nuclear waste repository use studies of actinide sorption onto well-defined iron hydroxide materials. In the case of a waste containment leak, however, a complex interaction between dissolved waste forms and failed containment vessel components can lead to immediate precipitation of migratory iron and uranyl in the silicate rich near-field environment. Use of the Fe(III) and UO22+ complexing agent acetohydroxamic acid (AHA) as a colorimetric agent for visible spectrophotometry is well-known. Using the second derivative of these spectra a distinct shift in iron complexation in the presence of silicate ismore » seen that is not seen with uranyl or alone. Silica also decreases the ability of uranyl and ferric solutions to absorb hydroxide, hastening precipitation. These ferric silicate precipitates are highly amorphous and soluble. Precipitates formed in the presence of uranyl below ~1 mol% exhibit lower solubility than precipitates from up to 50 mol % and of uranyl silicates alone.« less

Efficient tetracycline adsorption and photocatalytic degradation of rhodamine B by uranyl coordination polymer

NASA Astrophysics Data System (ADS)

Ren, Ya-Nan; Xu, Wei; Zhou, Lin-Xia; Zheng, Yue-Qing

2017-07-01

Two mixed uranyl-cadmium malonate coordination polymers [(UO2)2Cd(H-bipy)2(mal)4(H2O)2]·4H2O 1 and [(UO2)Cd(bipy)(mal)2]·H2O 2 (H2mal = malonic acid, bipy =4,4‧-bipyridine) have been synthesized in room temperature. Compound 1 represents a one-dimensional (1D) chain assembly of Cd(II) ions, uranyl centers and malonate ligands. Compound 2 exhibits a two-dimensional (2D) 2D +2D → 3D polycatenated framework based on inclined interlocked 2D 44 sql grids. The two compounds have been characterized by elemental analysis, IR and UV-vis spectroscopy, thermal analysis, powder X-ray diffraction and photoluminescence spectroscopy. And the ferroelectric property of 2 also has been studied. Moreover, compound 2 exhibits good photocatalytic activity for dye degradation under UV light and is excellent adsorbent for removing tetracycline antibiotics in the aqueous solution.

Theoretical study of the coordination behavior of formate and formamidoximate with dioxovanadium( v ) cation: implications for selectivity towards uranyl

DOE PAGES

Mehio, Nada; Johnson, J. Casey; Dai, Sheng; ...

2015-10-28

Poly(acrylamidoxime)-based fibers bearing random mixtures of carboxylate and amidoxime groups are the most widely utilized materials for extracting uranium from seawater. However, the competition between uranyl (UO 2 2+) and vanadium ions poses a significant challenge to the industrial mining of uranium from seawater using the current generation of adsorbents. To design more selective adsorbents, a detailed understanding of how major competing ions interact with carboxylate and amidoxime ligands is required. In this work, we employ density functional theory (DFT) and wave-function methods to investigate potential binding motifs of the dioxovanadium ion, VO 2 +, with water, formate, and formamidoximatemore » ligands. Employing higher level of theory calculations (CCSD(T)) resolve the existing controversy between the experimental results and previous DFT calculations for the structure of the hydrated VO 2 + ion. Consistent with the EXAFS data, CCSD(T) calculations predict higher stability of the distorted octahedral geometry of VO 2 +(H 2O) 4 compared to the five-coordinate complex with a single water molecule in the second hydration shell, while all seven tested DFT methods yield the reverse stability of the two conformations. Analysis of the relative stabilities of formate-VO 2 + complexes indicates that both monodentate and bidentate forms may coexist in thermodynamic equilibrium in solution, with the equilibrium balance leaning more towards the formation of monodentate species. Investigations of VO 2 + coordination with the formamidoximate anion has revealed the existence of seven possible binding motifs, four of which are within ~ 4.0 kcal/mol of each other. Calculations establish that the most stable binding motif entails the coordination of oxime oxygen and amide nitrogen atoms via a tautomeric rearrangement of amidoxime to imino hydroxylamine. Lastly, the difference in the most stable VO 2 + and UO 2 2+ binding conformation has important implications for the design of more selective UO 2 2+ ligands.« less

Potassium and magnesium succinatouranilates – Synthesis and crystal structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novikov, S.A., E-mail: serg.alex.novikov@gmail.com; Grigoriev, M.S.; Serezhkina, L.B.

2017-04-15

Single crystal X-ray diffraction has been applied to determine the structures of two new uranyl coordination polymers: K{sub 2}[(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}] (1) and [Mg(H{sub 2}O){sub 6}] [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]·2H{sub 2}O (2), where C{sub 4}H{sub 4}O{sub 4}{sup 2-} is succinate anion. Crystals of 1 and 2 contain polymeric complex anions [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]{sup 2-} with the same A{sub 2}Q{sup 02}{sub 3} crystallochemical formula (A=UO{sub 2}{sup 2+}, Q{sup 02}=C{sub 4}O{sub 4}H{sub 4}{sup 2-}), and have layered (1) or chain (2) structure. It has been found, that conformation of succinate ionsmore » is one of the factors, which affects the structure of [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]{sup 2-} anions. IR spectra of these new compounds are in good agreement with crystallographic data. Topological analysis of the uranium dicarboxylates with A{sub 2}Q{sup 02}{sub 3} crystallochemical formula has shown the presence of five isomers which differ from each other in coordination sequences and / or dimensionality. - Graphical abstract: Crystal structures of two new uranium(VI) coordination polymers with succinate linkers, namely K{sub 2}[(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}] (1) and [Mg(H{sub 2}O){sub 6}][(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]·2H{sub 2}O (2), were determined by single-crystal XRD. Crystals of studied compounds are based on 2D or 1D structural units with the same composition and crystallochemical formula. Topological isomerism in A{sub 2}Q{sup 02}{sub 3} crystallochemical group and conformations of succinate anions in uranyl complexes are under discussion. - Highlights: • Two new uranium coordination polymers were synthesized. • Their structural units have the same composition and crystallochemical formula. • In spite the same composition and CCF dimensionality of units is different. • Structural features of uranyl CPs are affected by linker conformations.« less

Expanding the Library of Uranyl Amide Derivatives: New Complexes Featuring the tert-Butyldimethylsilylamide Ligand.

PubMed

Pattenaude, Scott A; Coughlin, Ezra J; Collins, Tyler S; Zeller, Matthias; Bart, Suzanne C

2018-04-16

New uranyl derivatives featuring the amide ligand, -N(SiHMe 2 ) t Bu, were synthesized and characterized by X-ray crystallography, multinuclear NMR spectroscopy, and absorption spectroscopies. Steric properties of these complexes were also quantified using the computational program Solid-G. The increased basicity of the free ligand -N(SiHMe 2 ) t Bu was demonstrated by direct comparison to -N(SiMe 3 ) 2 , a popular supporting ligand for uranyl. Substitutional lability on a uranyl center was also demonstrated by exchange with the -N(SiMe 3 ) 2 ligand. The increased basicity of this ligand and diverse characterization handles discussed here will make these compounds useful synthons for future reactivity.

Precipitation characteristics of uranyl ions at different pHs depending on the presence of carbonate ions and hydrogen peroxide.

PubMed

Kim, Kwang-Wook; Kim, Yeon-Hwa; Lee, Se-yoon; Lee, Jae-Won; Joe, Kih-Soo; Lee, Eil-Hee; Kim, Jong-Seung; Song, Kyuseok; Song, Kee-Chan

2009-04-01

This work studied the dissolution of uranium dioxide and precipitation characteristics of uranyl ions in alkaline and acidic solutions depending on the presence of carbonate ions and H2O2 in the solutions at different pHs controlled by adding HNO3 or NaOH in the solution. The chemical structures of the precipitates generated in different conditions were evaluated and compared by using XRD, SEM, TG-DT, and IR analyses together. The sizes and forms of the precipitates in the solutions were evaluated, as well. The uranyl ions were precipitated in the various forms, depending on the solution pH and the presences of hydrogen peroxide and carbonate ions in the solution. In a 0.5 M Na2CO3 solution with H2O2, where the uranyl ions formed mixed uranyl peroxy-carbonato complexes, the uranyl ions were precipitated as a uranium peroxide of UO4(H20)4 at pH 3-4, and precipitated as a clarkeite of Na2U2Ox(OH)y(H2O)z above pH 13. In the same carbonate solution without H2O2, where the uranyl ions formed uranyl tris-carbonato complex, the uranyl ions were observed to be precipitated as a different form of clarkeite above pH 13. The precipitate of uranyl ions in a nitrate solution without carbonate ions and H2O2 at a high pH were studied together to compare the precipitate forms in the carbonate solutions.

Ions generated from uranyl nitrate solutions by electrospray ionization (ESI) and detected with Fourier transform ion-cyclotron resonance (FT-ICR) mass spectrometry.

PubMed

Pasilis, Sofie; Somogyi, Arpád; Herrmann, Kristin; Pemberton, Jeanne E

2006-02-01

Electrospray ionization (ESI) of uranyl nitrate solutions generates a wide variety of positively and negatively charged ions, including complex adducts of uranyl ions with methoxy, hydroxy, and nitrate ligands. In the positive ion mode, ions detected by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry are sensitive to instrumental tuning parameters such as quadrupole operating frequency and trapping time. Positive ions correspond to oligomeric uranyl nitrate species that can be characterized as having a general formula of [(UO(2))(n)(A)(m)(CH(3)OH)(s)](+) or [(UO(2))(n)(O)(A)(m)(CH(3)OH)(s)](+) with n = 1-4, m = 1-7, s = 0 or 1, and A = OH, NO(3), CH(3)O or a combination of these, although the formation of NO(3)-containing species is preferred. In the negative ion mode, complexes of the form [(UO(2))(NO(3))(m)](-) (m = 1-3) are detected, although the formation of the oxo-containing ions [(UO(2))(O)(n)(NO(3))(m)](-) (n = 1-2, m = 1-2) and the hydroxy-containing ions [(UO(2))(OH)(n)(NO(3))(m)](-) (n = 1-2, m = 0-1) are also observed. The extent of coordinative unsaturation of both positive and negative ions can be determined by ligand association/exchange and H/D exchange experiments using D(2)O and CD(3)OD as neutral reaction partners in the gas-phase. Positive ions are of varying stability and reactivity and may fragment extensively upon collision with D(2)O, CD(3)OD and N(2) in sustained off-resonance irradiation/collision-induced dissociation (SORI-CID) experiments. Electron-transfer reactions, presumably occurring during electrospray ionization but also in SORI-CID, can result in reduction of U(VI) to U(V) and perhaps even U(IV).

Structure and Bonding in Uranyl(VI) Peroxide and Crown Ether Complexes; Comparison of Quantum Chemical and Experimental Data.

PubMed

Vallet, Valérie; Grenthe, Ingmar

2017-12-18

The structure, chemical bonding, and thermodynamics of alkali ions in M[12-crown-4] + , M[15-crown-5] + , and M[18-crown-6] + , M[UO 2 (O 2 )(OH 2 ) 2 ] + 4,5 , and M[UO 2 (O 2 )(OH)(OH 2 )] n 1-n (n = 4, 5) complexes have been explored by using quantum chemical (QC) calculations at the ab initio level. The chemical bonding has been studied in the gas phase in order to eliminate solvent effects. QTAIM analysis demonstrates features that are very similar in all complexes and typical for electrostatic M-O bonds, but with the M-O bonds in the uranyl peroxide systems about 20 kJ mol -1 stronger than in the corresponding crown ether complexes. The regular decrease in bond strength with increasing M-O bond distance is consistent with predominantly electrostatic contributions. Energy decomposition of the reaction energies in the gas phase and solvent demonstrates that the predominant component of the total attractive (ΔE elec + ΔE orb ) energy contribution is the electrostatic component. There are no steric constraints for coordination of large cations to small rings, because the M + ions are located outside the ring plane, [O n ], formed by the oxygen donors in the ligands; coordination of ions smaller than the ligand cavity results in longer than normal M-O distances or in a change in the number of bonds, both resulting in weaker complexes. The Gibbs energies, enthalpies, and entropies of reaction calculated using the conductor-like screening model, COSMO, to account for solvent effects deviate significantly from experimental values in water, while those in acetonitrile are in much better agreement. Factors that might affect the selectivity are discussed, but our conclusion is that present QC methods are not accurate enough to describe the rather small differences in selectivity, which only amount to 5-10 kJ mol -1 . We can, however, conclude on the basis of QC and experimental data that M[crown ether] + complexes in the strongly coordinating water solvent are of outer-sphere type, [M(OH 2 ) n + ][crown ether], while those in weakly coordinating acetonitrile are of inner-sphere type, [M-crown ether] + . The observation that the M[UO 2 (O 2 )(OH)(OH 2 )] n 1-n complexes are more stable in solution than those of M[crown ether] + is an effect of the different charges of the rings.

Selectivity in Ligand Binding to Uranyl Compounds: A Synthetic, Structural, Thermodynamic and Computational Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnold, John

The uranyl cation (UO 2 2+) is the most abundant form of uranium on the planet. It is estimated that 4.5 billion tons of uranium in this form exist in sea water. The ability to bind and extract the uranyl cation from aqueous solution while separating it from other elements would provide a limitless source of nuclear fuel. A large body of research concerns the selective recognition and extraction of uranyl. A stable molecule, the cation has a linear O=U=O geometry. The short U-O bonds (1.78 Å) arise from the combination of uranium 5f/6d and oxygen 2p orbitals. Due tomore » the oxygen moieties being multiply bonded, these sites were not thought to be basic enough for Lewis acidic coordination to be a viable approach to sequestration. We believe that the goal of developing a practical system for uranium separation from seawater will not be attained without new insights into our existing fundamental knowledge of actinide chemistry. We posit that detailed studies of the kinetic and thermodynamic factors that influence interactions between f-elements and ligands with a range of donor atoms is essential to any major advance in this important area. The goal of this research is thus to broaden the coordination chemistry of the uranyl ion by studying new ligand systems via synthetic, structural, thermodynamic and computational methods. We anticipate that this fundamental science will find use beyond actinide separation technologies in areas such as nuclear waste remediation and nuclear materials.« less

Synthesis and spectroscopic studies of binuclear metal complexes of a tetradentate N2O2 Schiff base ligand derived from 4,6-diacetylresorcinol and benzylamine.

PubMed

Shebl, Magdy

2008-09-01

A tetradentate N2O2 donor Schiff base ligand, H2L, was synthesized by the condensation of 4,6-diacetylresorcinol with benzylamine. The structure of the ligand was elucidated by elemental analyses, IR, 1H NMR, electronic and mass spectra. Reaction of the Schiff base ligand with nickel(II), cobalt(II), iron(III), cerium(III), vanadyl(IV) and uranyl(VI) ions in 1:2 molar ratio afforded binuclear metal complexes. Also, reaction of the ligand with several copper(II) salts, including Cl-, NO3-, AcO-, ClO4- and SO42- afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO(4)(-) anion as compared to the strongly coordinating power of SO42- and Cl- anions. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, 1H NMR, electronic, mass and ESR spectra as well as magnetic susceptibility measurements. The metal complexes exhibited different geometrical arrangements such as square planar, octahedral, square pyramidal and pentagonal bipyramidal arrangements. The variety in the geometrical arrangements depends on the nature of both the anion and the metal ion.

Synthesis and characterization of heterometallic uranyl pyridinedicarboxylate compounds

NASA Astrophysics Data System (ADS)

Jayasinghe, Ashini S.; Payne, Maurice K.; Forbes, Tori Z.

2017-10-01

The incorporation of transition metals into hybrid uranyl materials can result in more diverse structural topologies and variations in physical and chemical properties. To explore the impact of transition metals on the uranyl cation, five uranium containing bimetallic chain compounds, [(UO2)M(PDC)2(H2O)4]·4(H2O) (PDC = 2,6 pyridinedicarboxylate; M = Ni2+, Co2+, Fe2+, Zn2+, and Cu2+) were synthesized by evaporation of aqueous solutions at room temperature. The uranyl cation is complex by two PDC ligands and the transition metal cations bond to the complex to form a one-dimensional chain topology. The presence of the transition metal leads to the presence of a stronger uranyl oxo bonds as shown by the single-crystal X-ray diffraction data and the Raman spectra. Solid state diffuse reflectance UV/Visible spectra confirmed the presence of the transition metals in the structure by the broad bands that appeared at relevant wavelengths.

Predicting Stability Constants for Uranyl Complexes Using Density Functional Theory

DOE PAGES

Vukovic, Sinisa; Hay, Benjamin P.; Bryantsev, Vyacheslav S.

2015-04-02

The ability to predict the equilibrium constants for the formation of 1:1 uranyl:ligand complexes (log K 1 values) provides the essential foundation for the rational design of ligands with enhanced uranyl affinity and selectivity. We also use density functional theory (B3LYP) and the IEFPCM continuum solvation model to compute aqueous stability constants for UO 2 2+ complexes with 18 donor ligands. Theoretical calculations permit reasonably good estimates of relative binding strengths, while the absolute log K 1 values are significantly overestimated. Accurate predictions of the absolute log K 1 values (root mean square deviation from experiment < 1.0 for logmore » K 1 values ranging from 0 to 16.8) can be obtained by fitting the experimental data for two groups of mono and divalent negative oxygen donor ligands. The utility of correlations is demonstrated for amidoxime and imide dioxime ligands, providing a useful means of screening for new ligands with strong chelate capability to uranyl.« less

A procedure for quantitation of total oxidized uranium for bioremediation studies

USGS Publications Warehouse

Elias, Dwayne A.; Senko, John M.; Krumholz, Lee R.

2003-01-01

A procedure was developed for the quantitation of complexed U(VI) during studies on U(VI) bioremediation. These studies typically involve conversion of soluble or complexed U(VI) (oxidized) to U(IV) (the reduced form which is much less soluble). Since U(VI) freely exchanges between material adsorbed to the solid phase and the dissolved phase, uranium bioremediation experiments require a mass balance of U in both its soluble and adsorbed forms as well as in the reduced sediment bound phase. We set out to optimize a procedure for extraction and quantitation of sediment bound U(VI). Various extractant volumes to sediment ratios were tested and it was found that between 1:1 to 8:1 ratios (v/w) there was a steady increase in U(VI) recovered, but no change with further increases in v/w ratio.Various strengths of NaHCO3, Na-EDTA, and Na-citrate were used to evaluate complexed U(VI) recovery, while the efficiency of a single versus repeated extraction steps was compared with synthesized uranyl-phosphate and uranyl-hydroxide. Total recovery with 1 M NaHCO3 was 95.7% and 97.9% from uranyl-phosphate and uranyl-hydroxide, respectively, compared to 80.7% and 89.9% using 450 mM NaHCO3. Performing the procedure once yielded an efficiency of 81.1% and 92.3% for uranyl-phosphate and uranyl-hydroxide, respectively, as compared to three times. All other extractants yielded 7.9–82.0% in both experiments.

A Family of Uranyl Coordination Polymers Containing O-Donor Dicarboxylates and Trispyridyltriazine Guests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thangavelu, Sonia G.; Cahill, Christopher L.

Four uranyl coordination polymers [UO2(C6H8O4)(H2O)2](C18H12N6)2 (1), [UO2(C8H4O4)(H2O)2](C18H12N6)2 (2), Na[(UO2)(C12H6O4)2](C18H13N6)·H2O (3), and Na[(UO2)(C16H8O4)(C6H3NO2)](C18H12N6)·H2O (4) containing aliphatic (adipic acid) or aromatic linkers (1,4-benzene dicarboxylic acid (BDC), 1,4-napthalene dicarboxylic acid (NDC), anthracene 9,10-dicarboxylic acid (ADC)) were synthesized and characterized using single crystal X-ray diffraction, powder X-ray diffraction, and luminescence spectroscopy. The π-stacking distances or the number of π–π interactions present between trispyridyltriazine (TPTZ) guests or the host framework in 1–4 may be affected by the size of the O-donor linker (adipic acid < BDC < NDC < ADC). Luminescence studies show that substitution between adipic acid and BDC influences the emission of 1more » and 2, in which the emission of 1 shows a red shift relative to that of 2. Uranyl emission was not observed in 3 and 4, and may be attributed to the position of the NDC and ADC triplet state relative to the emissive uranyl species.« less

A Family of Uranyl Coordination Polymers Containing O-Donor Dicarboxylates and Trispyridyltriazine Guests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thangavelu, Sonia G.; Cahill, Christopher L.

2016-01-06

Four uranyl coordination polymers [UO2(C6H8O4)(H2O)2](C18H12N6)2 (1), [UO2(C8H4O4)(H2O)2](C18H12N6)2 (2), Na[(UO2)(C12H6O4)2](C18H13N6)·H2O (3), and Na[(UO2)(C16H8O4)(C6H3NO2)](C18H12N6)·H2O (4) containing aliphatic (adipic acid) or aromatic linkers (1,4-benzene dicarboxylic acid (BDC), 1,4-napthalene dicarboxylic acid (NDC), anthracene 9,10-dicarboxylic acid (ADC)) were synthesized and characterized using single crystal X-ray diffraction, powder X-ray diffraction, and luminescence spectroscopy. The π-stacking distances or the number of π–π interactions present between trispyridyltriazine (TPTZ) guests or the host framework in 1–4 may be affected by the size of the O-donor linker (adipic acid < BDC < NDC < ADC). Luminescence studies show that substitution between adipic acid and BDC influences the emission of 1more » and 2, in which the emission of 1 shows a red shift relative to that of 2. Uranyl emission was not observed in 3 and 4, and may be attributed to the position of the NDC and ADC triplet state relative to the emissive uranyl species.« less

Dehydration-driven evolution of topological complexity in ethylamonium uranyl selenates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gurzhiy, Vladislav V., E-mail: vladgeo17@mail.ru; Krivovichev, Sergey V.; Tananaev, Ivan G.

Single crystals of four novel uranyl selenate and selenite-selenate oxysalts with protonated ethylamine molecules, (C{sub 2}H{sub 8}N){sub 2}[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)](H{sub 2}O) (I), (C{sub 2}H{sub 8}N){sub 3}[(UO{sub 2})(SeO{sub 4}){sub 2}(HSeO{sub 4})] (II), (C{sub 2}H{sub 8}N)[(UO{sub 2})(SeO{sub 4})(HSeO{sub 3})] (III), and (C{sub 2}H{sub 8}N)(H{sub 3}O)[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)] (IV) have been prepared by isothermal evaporation from aqueous solutions. Uranyl-containing 1D and 2D units have been investigated using topological approach and information-based complexity measurements that demonstrate the evolution of structural units and the increase of topological complexity with the decrease of H{sub 2}O content. - Graphical abstract: Single crystals ofmore » four novel uranyl selenate and selenite-selenate oxysalts with protonated ethylamine molecules have been prepared by isothermal evaporation from aqueous solutions. Structural analysis and information-based topological complexity calculations points to the possible sequence of crystalline phases formation, showing both topological and structural branches of evolution. - Highlights: • Single crystals of four novel uranyl oxysalts were prepared by evaporation method. • The graph theory was used for investigation of topologies of structural units. • Dehydration processes drives the evolution of topological complexity of 1D and 2D structural units.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thangavelu, Sonia G.; Butcher, Ray J.; Cahill, Christopher L.

Thiophene 2,5-dicarboxylic acid (TDC) was reacted with uranyl acetate dihydrate and one (or none) of six N-donor chelating ligands (2,2'-bipyridine (BPY), 4,4'-dimethyl-2,2'-bipyridine (4-MeBPY), 5,5'-dimethyl-2,2'-bipyridine (5-MeBPY), 6,6'-dimethyl-2,2'-bipyridine (6-MeBPY), 4,4',6,6'-tetramethyl-2,2'-bipyridine (4,6-MeBPY), and tetrakis(2-pyridyl)pyrazine (TPPZ) to result in the crystallization of seven uranyl coordination polymers, which were characterized by their crystal structures and luminescence properties. The seven coordination polymers, Na2[(UO2)2(C6H2O4S)3]·4H2O (1), [(UO2)4(C6H2O4S)5(C10H8N2)2]·C10H10N2·3H2O (2), [(UO2)(C6H2O4S)(C12H12N3)] (3), [(UO2)(C6H2O4S)(C12H12N3)]·H2O (4), [(UO2)2(C6H2O4S)3]·(C12H14N2)·5H2O (5), [(UO2)3(CH3CO2)(C6H2O4S)4](C14H17N2)3·(C14H16N2)·H2O (6), and [(UO2)2(C6H2O4S)3](C24H18N6) (7), consist of either uranyl hexagonal bipyramidal or pentagonal bipyramidal coordination geometries. In all structures, structural variations in the local and global structures of 1–7 are influenced by the positionsmore » (or number) of methyl groups or pyridyl rings on the N-donor species, thus resulting in a wide diversity of structures ranging from single chains, double chains, or 2-D sheets. Direct coordination of N-donor ligands to uranyl centers is observed in the chain structures of 2–4 using BPY, 4-MeBPY, and 5-MeBPY, whereas the N-donor species participate as guests (as either neutral or charge balancing species) in the chain and sheet structures of 5–7 using 6-MeBPY, 4,6-MeBPY, and TPPZ, respectively. Compound 1 is the only structure that does not contain any N-donor ligands and thus crystallizes as a 2-D interpenetrating sheet. The luminescent properties of 1–7 are influenced by the direct coordination or noncoordination of N-donor species to uranyl centers. Compounds 2–4 exhibit typical UO22+ emission upon direct coordination of N-donors, but its absence is observed in 1, 5, 6, and 7, when N-donor species participate as guest molecules. These results suggest that direct coordination of N-donor ligands participate as chromophores, thus resulting in possible UO22+ sensitization. The lack of emission in 1, 5, 6, and 7 may be explained by the extended conjugation of the TDC ligands within their structures.« less

Uranyl Coordination Polymers Incorporating η5-Cyclopentadienyliron-Functionalized η6-Phthalate Metalloligands: Syntheses, Structures and Photophysical Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerr, Andrew T.; Kumalah, Sayon A.; Holman, K. T.

2013-10-06

The reaction of two η5-cyclopentadienyliron(II)-functionalized terephthalate and phthalate metalloligands, namely [(η5-C5H5)FeII(η6-1,4-HO2CC6H4CO2H)][(η5-C5H5)FeII(η6-1,4-HO2CC6H4CO2)][PF6] and [(η5-C5H5)FeII(η6-1,2-HO2CC6H4CO2H)][(η5-C5H5)FeII(η6-1,2-HO2CC6H4CO2)][PF6]—hereafter [H2 CpFeTP][HCpFeTP][PF6] and [H2 CpFeP][HCpFeP][PF6], respectively—with [UO2(NO3)2]·6H2O under hydrothermal conditions yielded four new coordination polymers; (1) [(UO2)F(HCpFeTP)(PO4H2)]·2H2O, (2) [(UO2)2(CpFeTP)4]·5H2O, (3) [(UO2)2F3(H2O)(CpFeP)], and (4) [H2 CpFeP][UO2F3]. The use of metalloligands has proven to be a viable route towards the incorporation of a secondary metal center into uranyl bearing materials. Depending upon the protonation state, the iron sandwich metalloligands may vary from zwitterionic neutral or monoanionic coordinating species as observed in compounds 1–3, or a positively charged species that hydrogen bonds with anionic [UO2F3]- chains as observed in 4.more » Further, the hydrolysis of the charge balancing PF6 - anion increases the diversity of UO2 2+ coordinating species by contributing both F- and PO4 3- anions (1, 3, 4). The luminescent properties of 1–4 were also studied and revealed the absence of uranyl emission, suggestive of a possible energy transfer from the uranyl cation to the iron(II) metal center.« less

Metal complexes of the fourth generation quinolone antimicrobial drug gatifloxacin: Synthesis, structure and biological evaluation

NASA Astrophysics Data System (ADS)

Sadeek, Sadeek A.; El-Shwiniy, Walaa H.

2010-08-01

Three metal complexes of the fourth generation quinolone antimicrobial agent gatifloxacin (GFLX) with Y(ΙΙΙ), Zr(ΙV) and U(VΙ) have been prepared and characterized with physicochemical and spectroscopic techniques. In these complexes, gatifloxacin acts as a bidentate deprotonated ligand bound to the metal through the ketone oxygen and a carboxylato oxygen. The complexes are six-coordinated with distorted octahedral geometry. The kinetic parameters for gatifloxacin and the three prepared complexes have been evaluated from TGA curves by using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. The calculated bond length and force constant, F(U dbnd O), for the UO 2 bond in uranyl complex are 1.7522 Å and 639.46 N m -1. The antimicrobial activity of the complexes has been tested against microorganisms, three bacterial species, such as Staphylococcus aureus ( S. aureus), Escherichia coli ( E. coli) and Pseudomonas aeruginosa ( P. aeruginosa) and two fungi species, penicillium ( P. rotatum) and trichoderma ( T. sp.), showing that they exhibit higher activity than free ligand.

Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

DOE PAGES

Miskowiec, Andrew J.; Kirkegaard, Marie C.; Huq, Ashfia; ...

2015-11-17

We report a novel production method for uranium oxy uoride [(UO 2) 7F 14(H 2O) 7] 4H 2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl uoride, UO 2F 2, through the gas phase at ambient temperatures fol- lowed by desiccation by equilibration with a dry environment. We follow the structure of [(UO 2) 7F 14(H 2O) 7] 4H 2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous struc- ture), and a water molecule binds as an equatorialmore » ligand to the uranyl ion. Quasielas- tic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform re- stricted motion on a length scale commensurate with the O{H bond (r = 0.92 A). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps -1) than their hydrogen-bonded partners (Dr = 28.7 ps -1).« less

Two actinide-organic frameworks constructed by a tripodal flexible ligand: Occurrence of infinite ((UO{sub 2})O{sub 2}(OH){sub 3}){sub 4n} and hexanuclear (Th{sub 6}O{sub 4}(OH){sub 4}) motifs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Lingling; Zhang, Ronglan; Zhao, Jianshe, E-mail: jszhao@nwu.edu.cn

Two new actinide metal-organic frameworks were constructed by using a tripodal flexible ligand tris (2-carboxyethyl) isocyanurate (H{sub 3}tci) under hydrothermal condition. The combination of H{sub 3}tci and uranyl nitrate hexahydrate in aqueous solution leads to the isolation of [(UO{sub 2}){sub 2}(H{sub 2}O){sub 4}]{sub 0.5}(tci){sub 2}(UO{sub 2}){sub 4}(OH){sub 4}·18H{sub 2}O (1), which contains two distinct UO{sub 2}{sup 2+} coordination environments. Four uranyl cations, linked through μ{sub 3}-OH respectively, result in the edge-sharing ribbons. Then, the layer structure is constructed by U-O clusters linked through other eight-coordinated uranyl unions, giving rise to a porous structure in the space. Topological analysis reveals thatmore » complex 1 belongs to a (4, 8)-connected net with a schläfli symbol of (3{sup 4.}2{sup 6.}3){sub 2}(3{sup 4.}4{sup 6.}5{sup 6.}6{sup 8.}7{sup 3.}8). Th{sub 3}(tci){sub 2}O{sub 2}(OH){sub 2}(H{sub 2}O){sub 3}·12H{sub 2}O (2) generated by the reaction of H{sub 3}tci and thorium nitrate tetrahydrate, possesses nine-fold coodinated Th(IV) centers with a monocapped square antiprismatic geometry. The hexamers “Th{sub 6}O{sub 4}(OH){sub 4}” motifs are connected together by the carboxylate groups, showing a three-dimensional structures. Complex 2 takes on an 8-connected architecture and the point symbol is (4{sup 24.}6{sup 4}). - Graphical abstract: Two new 3D actinide metal-organic frameworks were constructed by using a tripodal flexible ligand tris (2-carboxyethyl) isocyanurate (H3tci) and their topological structures were displayed. The infinite ((UO{sub 2})O{sub 2}(OH){sub 3}){sub 4n} and hexanuclear (Th{sub 6}O{sub 4}(OH){sub 4}) motifs were found in the title actinides networks.« less

Uranyl mediated photofootprinting reveals strong E. coli RNA polymerase--DNA backbone contacts in the +10 region of the DeoP1 promoter open complex.

PubMed Central

Jeppesen, C; Nielsen, P E

1989-01-01

Employing a newly developed uranyl photofootprinting technique (Nielsen et al. (1988) FEBS Lett. 235, 122), we have analyzed the structure of the E. coli RNA polymerase deoP1 promoter open complex. The results show strong polymerase DNA backbone contacts in the -40, -10, and most notably in the +10 region. These results suggest that unwinding of the -12 to +3 region of the promoter in the open complex is mediated through polymerase DNA backbone contacts on both sides of this region. The pattern of bases that are hyperreactive towards KMnO4 or uranyl within the -12 to +3 region furthermore argues against a model in which this region is simply unwound and/or single stranded. The results indicate specific protein contacts and/or a fixed DNA conformation within the -12 to +3 region. Images PMID:2503811

Thermal stability of uranyl complexes with neutral oxygen-containing organic bases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobets, L.V.

1987-03-01

The thermal stability of uranyl chloride, nitrate, and oxalate with a series of neutral oxygen-containing organic ligands is discussed. It was found that the temperatures of removal of chlorine are higher than the stripping of the first molecule of the base in complexes UO/sub 2/Cl/sub 2/ x 2L. This is an indication of greater strength of the bonds of the Cl/sup -/ ions to the uranyl group in comparison with the investigated bases. It was shown that the temperatures of removal of a mole of neutral ligands depend little on the nature of the anions and exhibit a correlation withmore » the donor capacity of the bases: Ac < TBP < DMFA similarly ordered DMSO < TBPO similarly ordered PyO. The chemistry of the decomposition of the complexes and the strength of the binding of the acido- and neutral ligands in them are discussed.« less

Density functional theory and molecular dynamics study of the uranyl ion (UO₂)²⁺.

PubMed

Rodríguez-Jeangros, Nicolás; Seminario, Jorge M

2014-03-01

The detection of uranium is very important, especially in water and, more importantly, in the form of uranyl ion (UO₂)²⁺, which is one of its most abundant moieties. Here, we report analyses and simulations of uranyl in water using ab initio modified force fields for water with improved parameters and charges of uranyl. We use a TIP4P model, which allows us to obtain accurate water properties such as the boiling point and the second and third shells of water molecules in the radial distribution function thanks to a fictitious charge that corrects the 3-point models by reproducing the exact dipole moment of the water molecule. We also introduced non-bonded interaction parameters for the water-uranyl intermolecular force field. Special care was taken in testing the effect of a range of uranyl charges on the structure of uranyl-water complexes. Atomic charges of the solvated ion in water were obtained using density functional theory (DFT) calculations taking into account the presence of nitrate ions in the solution, forming a neutral ensemble. DFT-based force fields were calculated in such a way that water properties, such as the boiling point or the pair distribution function stand. Finally, molecular dynamics simulations of a water box containing uranyl cations and nitrate anions are performed at room temperature. The three peaks in the oxygen-oxygen radial distribution function for water were found to be kept in the presence of uranyl thanks to the improvement of interaction parameters and charges. Also, we found three shells of water molecules surrounding the uranyl ion instead of two as was previously thought.

Excited States and Luminescent Properties of UO 2F 2 and Its Solvated Complexes in Aqueous Solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Jing; Wang, Zheming; Pan, Duoqiang

2014-07-21

The electronic absorption and emission spectra of free UO 2F 2 and its water solvated complexes below 32 000 cm –1 are investigated at the levels of ab initio CASPT2 and CCSD(T) with inclusion of scalar relativistic and spin–orbit coupling effects. The influence of the water coordination on the electronic spectra of UO 2F 2 is explored by investigating the excited states of solvated complexes (H 2O) nUO 2F 2 (n = 1–3). In these uranyl complexes, water coordination is found to have appreciable influence on the 3Δ (Ω = 1 g) character of the luminescent state and on themore » electronic spectral shape. The simulated luminescence spectral curves based on the calculated spectral parameters of (H 2O) nUO 2F 2 from CCSD(T) approach agree well with experimental spectra in aqueous solution at both near-liquid-helium temperature and room temperature. The possible luminescence spectra of free UO 2F 2 in gas phase are predicted on the basis of CASPT2 and CCSD(T) results, respectively, by considering three symmetric vibration modes. Finally, the effect of competition between spin–orbit coupling and ligand field repulsion on the luminescent state properties is discussed.« less

A Uranyl Peroxide Dimer in the Gas Phase

DOE PAGES

Dau, Phuong D.; Dau, Phuong V.; Rao, Linfeng; ...

2017-03-14

For this study, the gas-phase uranyl peroxide dimer, [(UO 2) 2(O2)(L) 2] 2+ where L = 2,2'-trifluoroethylazanediyl)bis(N,N'-dimethylacetamide), was synthesized by electrospray ionization of a solution of UO 2 2+ and L. Collision-induced dissociation of this dimer resulted in endothermic O atom elimination to give [(UO 2) 2(O)(L) 2] 2+, which was found to spontaneously react with water via exothermic hydrolytic chemisorption to yield [(UO 2) 2(OH) 2(L) 2] 2+. Density functional theory computations of the energies for the gas-phase reactions are in accord with observations. The structures of the observed uranyl dimer were computed, with that of the peroxide ofmore » particular interest, as a basis to evaluate the formation of condensed phase uranyl peroxides with bent structures. The computed dihedral angle in [(UO 2) 2(O 2)(L) 2] 2+ is 145°, indicating a substantial deviation from the planar structure with a dihedral angle of 180°. Energies needed to induce bending in the most elementary gas-phase uranyl peroxide complex, [(UO 2) 2(O 2)] 2+, were computed. It was found that bending from the lowest-energy planar structure to dihedral angles up to 140° required energies of <10 kJ/mol. The gas-phase results demonstrate the inherent stability of the uranyl peroxide moiety and support the notion that the uranyl-peroxide-uranyl structural unit is intrinsically planar, with only minor energy perturbations needed to form the bent structures found in studtite and uranyl peroxide nanostructures.« less

Uranium: A Dentist's perspective

PubMed Central

Toor, R. S. S.; Brar, G. S.

2012-01-01

Uranium is a naturally occurring radionuclide found in granite and other mineral deposits. In its natural state, it consists of three isotopes (U-234, U-235 and U-238). On an average, 1% – 2% of ingested uranium is absorbed in the gastrointestinal tract in adults. The absorbed uranium rapidly enters the bloodstream and forms a diffusible ionic uranyl hydrogen carbonate complex (UO2HCO3+) which is in equilibrium with a nondiffusible uranyl albumin complex. In the skeleton, the uranyl ion replaces calcium in the hydroxyapatite complex of the bone crystal. Although in North India, there is a risk of radiological toxicity from orally ingested natural uranium, the principal health effects are chemical toxicity. The skeleton and kidney are the primary sites of uranium accumulation. Acute high dose of uranyl nitrate delays tooth eruption, and mandibular growth and development, probably due to its effect on target cells. Based on all previous research and recommendations, the role of a dentist is to educate the masses about the adverse effects of uranium on the overall as well as the dental health. The authors recommended that apart from the discontinuation of the addition of uranium to porcelain, the Public community water supplies must also comply with the Environmental Protection Agency (EPA) standards of uranium levels being not more than 30 ppb (parts per billion). PMID:24478959

Effects of aqueous uranyl speciation on the kinetics of microbial uranium reduction

DOE PAGES

Belli, Keaton M.; DiChristina, Thomas J.; Van Cappellen, Philippe; ...

2015-02-16

The ability to predict the success of the microbial reduction of soluble U(VI) to highly insoluble U(IV) as an in situ bioremediation strategy is complicated by the wide range of geochemical conditions at contaminated sites and the strong influence of aqueous uranyl speciation on the bioavailability and toxicity of U(VI) to metal-reducing bacteria. In order to determine the effects of aqueous uranyl speciation on uranium bioreduction kinetics, incubations and viability assays with Shewanella putrefaciens strain 200 were conducted over a range of pH and dissolved inorganic carbon (DIC), Ca 2+, and Mg 2+ concentrations. A speciation-dependent kinetic model was developedmore » to reproduce the observed time series of total dissolved uranium concentration over the range of geochemical conditions tested. The kinetic model yielded the highest rate constant for the reduction of uranyl non-carbonate species (i.e., the ‘free’ hydrated uranyl ion, uranyl hydroxides, and other minor uranyl complexes), indicating that they represent the most readily reducible fraction of U(VI) despite being the least abundant uranyl species in solution. In the presence of DIC, Ca 2+, and Mg 2+ is suppressed during the formation of more bioavailable uranyl non-carbonate species and resulted in slower bioreduction rates. At high concentrations of bioavailable U(VI), however, uranium toxicity to S. putrefaciens inhibited bioreduction, and viability assays confirmed that the concentration of non-carbonate uranyl species best predicts the degree of toxicity. The effect of uranium toxicity was accounted for by incorporating the free ion activity model of metal toxicity into the bioreduction rate law. These results demonstrate that, in the absence of competing terminal electron acceptors, uranium bioreduction kinetics can be predicted over a wide range of geochemical conditions based on the bioavailability and toxicity imparted on U(VI) by solution composition. Finally, these findings also imply that the concentration of uranyl non-carbonate species, despite being extremely low, is a determining factor controlling uranium bioreduction at contaminated sites.« less

A route to oligosaccharide-appended salicylaldehydes: useful building blocks for the synthesis of metal-salophen complexes.

PubMed

Bedini, Emiliano; Forte, Gianpiero; De Castro, Cristina; Parrilli, Michelangelo; Dalla Cort, Antonella

2013-08-16

A simple and general synthetic protocol to obtain oligosaccharide-appended salicylaldehydes, key intermediates for the synthesis of water-soluble metal-salophen complexes, is here reported. Six new aldehydes have been prepared and fully characterized as well as the corresponding zinc- and uranyl-salophen complexes. These new derivatives show very good solubility in water. Preliminary studies on the association of compound 19-U, that is, the uranyl maltotetraose derivative, with hydrogen phosphate and fluoride provide very encouraging results and open up the possibility of using such compounds for the efficient recognition of anions in pure water.

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

PubMed

Carter, Korey P; Kalaj, Mark; Surbella, Robert G; Ducati, Lucas C; Autschbach, Jochen; Cahill, Christopher L

2017-11-02

Engaging the nominally terminal oxo atoms of the linear uranyl (UO 2 2+ ) cation in non-covalent interactions represents both a significant challenge and opportunity within the field of actinide hybrid materials. An approach has been developed 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, a family of uranyl hybrid materials was generated 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 through single crystal X-ray diffraction, Raman, Infrared (IR), and luminescence spectroscopy, as well as through density functional calculations of electrostatic potentials. Looking comprehensively, these results are compared with recently published analogues featuring 2,5-diiodobenzoic acid which indicate that although 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. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and X-ray diffraction study of new uranyl malonate and oxalate complexes with carbamide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medvedkov, Ya. A.; Serezhkina, L. B., E-mail: Lserezh@samsu.ru; Grigor’ev, M. S.

2016-05-15

Two new malonate-containing uranyl complexes with carbamide of the formulas [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Urea){sub 2}] (I) and [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Urea){sub 3}] (II), where Urea is carbamide, and one uranyl oxalate complex of the formula [UO{sub 2}(C{sub 2}O{sub 4})(Urea){sub 3}] (III) were synthesized, and their crystals were studied by X-ray diffraction. The main structural units in crystals I are the electroneutral chains [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Urea){sub 2}]{sub ∞} belonging to the crystal-chemical group AT{sup 11}M{sub 2}{sup 1} (A = UO{sub 2}{sup 2+}, T{sup 11} = C{sub 3}H{sub 2}O{sub 4}{sup 2-}, M{sup 1} = Urea) of uranyl complexes.more » Crystals II and III are composed of the molecular complexes [UO{sub 2}(L)(Urea){sub 3}], where L = C{sub 3}H{sub 2}O{sub 4}{sup 2-} or C{sub 2}O{sub 4}{sup 2-}, belonging to the crystal-chemical group AB{sup 01}M{sub 3}{sup 1} (A = UO{sub 2}{sup 2+}, B{sup 01} = C{sub 3}H{sub 2}O{sub 4}{sup 2-} or C{sub 2}O{sub 4}{sup 2-}, M{sup 1} = Urea). The characteristic features of the packing of the uranium-containing complexes are discussed in terms of molecular Voronoi–Dirichlet polyhedra. The effect of the Urea: U ratio on the structure of uranium-containing structural units is considered.« less

Interaction of Uranium with Bacterial Cell Surfaces: Inferences from Phosphatase-Mediated Uranium Precipitation.

PubMed

Kulkarni, Sayali; Misra, Chitra Seetharam; Gupta, Alka; Ballal, Anand; Apte, Shree Kumar

2016-08-15

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. 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. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Interaction of Uranium with Bacterial Cell Surfaces: Inferences from Phosphatase-Mediated Uranium Precipitation

PubMed Central

Kulkarni, Sayali; Misra, Chitra Seetharam; Gupta, Alka; Ballal, Anand

2016-01-01

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. PMID:27287317

Analysis of vibration frequencies of uranyl ion in complexes with neutral bases (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobets, L.V.; Umreiko, D.S.

1986-12-01

It has been shown that any estimate of the changes in vibration frequencies of UO/sub 2//sup 2 +/ applies only to the series of isostructural compounds with similar stoichiometry. Either the same values of stretching vibration frequencies of uranyl correspond to complexes with ligands that have different donor abilities, or changes in these frequencies are not great and do not reflect the real increase in the donor ability of the bases with respect to proton-containing acceptors. When the acido ligands are replaced or the stoichiometry of the complexes is changed, no correlations can be carried out, since, besides the basicitiesmore » of donors, other parameters such as the dentateness of the ligand, and hence the symmetry and the structure of the compound, are also varied. In this paper, the authors evaluate the contributions of the ligands to the shift of the vibration frequencies of uranyl that have been made and do not take into account the characteristic features of the compounds which therefore led to very different values of the contributions for one and the same ligand in different compounds. To evaluate the shifts produced by the ligands, the value of 1065 cm/sup -1/ was taken as the vibration frequency of a hypothetical fee uranyl ion, not perturbed by bonds with equatorial ligands. The authors also evaluate the contributions of ions able to form polymer structures.« less

2,6-Diiminopiperidin-1-ol: an overlooked motif relevant to uranyl and transition metal binding on poly(amidoxime) adsorbents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kennedy, Zachary C.; Cardenas, Allan Jay P.; Corbey, Jordan F.

2016-01-01

Glutardiamidoxime, a structural motif on sorbents used in uranium extraction from seawater, was discovered to cyclize in situ at room temperature to 2,6-diimino-piperidin-1-ol in the presence of uranyl nitrate. The new diimino motif was also generated when exposed to competing transition metals Cu(II) and Ni(II). Multinuclear μ-O bridged U(VI), Cu(II), and Ni(II) complexes featuring bound diimino ligands were isolated. A Cu(II) complex with the historically relevant cyclic imide dioxime motif is also reported for structural comparison to the reported diimino complexes.

Selective colorimetric and fluorescent quenching determination of uranyl ion via its complexation with curcumin

NASA Astrophysics Data System (ADS)

Zhu, Jing-Hui; Zhao, Xin; Yang, Jidong; Tan, Yu-Ting; Zhang, Lei; Liu, Shao-Pu; Liu, Zhong-Fang; Hu, Xiao-Li

2016-04-01

Under pH 4.0 HAc-NaAc buffer medium, curcumin alone possesses extraordinary weak fluorescence emission. Nevertheless, the introduction of Triton X-100 micelles can largely enhance the fluorescence intensity of curcumin. Uranyl ions can complex with micelles-capped curcumin, along with the slight red shift of curcumin fluorescence (about 1-7 nm), a clear decrement of absorbance (424 nm) and fluorescence (507 nm) intensities, and a distinct color change from bright yellow to orange. The fluorescence decrements (ΔF, 507 nm) are positively correlated to the amount of uranyl ions in the concentration range of 3.7 × 10- 6-1.4 × 10- 5 mol L- 1. The detection limit of this fluorescence quenching methods is 3.7 × 10- 6 mol L- 1, which is nearly 9000 times lower than the maximum allowable level in drinking water proposed by World Health Organization. Good selectivity is achieved because of a majority of co-existing substances (such as Ce4 +, La3 +, and Th4 +) do not affect the detection. The content of uranyl ions in tap water samples was determined by the proposed method with satisfactory results.

Synthesis of microspheres of triuranium octaoxide by simultaneous water and nitrate extraction from ascorbate-uranyl sols.

PubMed

Brykala, M; Deptula, A; Rogowski, M; Lada, W; Olczak, T; Wawszczak, D; Smolinski, T; Wojtowicz, P; Modolo, G

A new method for synthesis of uranium oxide microspheres (diameter <100 μm) has been developed. It is a variant of our patented Complex Sol-Gel Process, which has been used to synthesize high-quality powders of a wide variety of complex oxides. Starting uranyl-nitrate-ascorbate sols were prepared by addition of ascorbic acid to uranyl nitrate hexahydrate solution and alkalizing by aqueous ammonium hydroxide and then emulsified in 2-ethylhexanol-1 containing 1v/o SPAN-80. Drops of emulsion were firstly gelled by extraction of water by the solvent. Destruction of the microspheres during thermal treatment, owing to highly reactive components in the gels, requires modification of the gelation step by Double Extraction Process-simultaneously extraction of water and nitrates using Primene JMT, which completely eliminates these problem. Final step was calcination in air of obtained microspheres of gels to triuranium octaoxide.

Recovery of Uranium from Seawater: Preparation and Development of Polymer-Supported Extractants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spiro, Alexandratos

2013-12-01

A new series of polymer-supported extractants is proposed for the removal and recovery of uranium from seawater. The objective is to produce polymers with improved stability, loading capacity, and sorption kinetics compared to what is found with amidoximes. The target ligands are diphosphonates and aminomethyldiphosphonates. Small molecule analogues, especially of aminomethyldiphos-phonates, have exceptionally high stability constants for the uranyl ion. The polymeric diphosphonates will have high affinities due to their ability to form six-membered rings with the uranyl ion while the aminomethyldiphosphonates may have yet higher affinities due to possible tridentate coordination and their greater acidity. A representative set ofmore » the polymers to be prepared are indicated.« less

Perrhenate complexation by uranyl in traditional solvents and in ionic liquids: a joint molecular dynamics/spectroscopic study.

PubMed

Chaumont, Alain; Klimchuk, Olga; Gaillard, Clotilde; Billard, Isabelle; Ouadi, Ali; Hennig, Christoph; Wipff, Georges

2012-03-15

The complexation of perrhenate (ReO(4)(-)) anions by the uranyl (UO(2)(2+)) cation has been investigated by joint molecular dynamics simulations and spectroscopic (UV-vis, TRLFS, and EXAFS) studies in aqueous solution, acetonitrile, and three ionic liquids (ILs), namely, [Bmi][Tf(2)N], [Me(3)BuN][Tf(2)N], and [Bu(3)MeN][Tf(2)N] that are based on the same Tf(2)N(-) anion (bis(trifluoromethylsulfonyl)imide) and either Bmi(+) (1-butyl,3-methylimidazolium), Me(3)BuN(+), or Bu(3)MeN(+) cations. They show that ReO(4)(-) behaves as a weak ligand in aqueous solution and as a strong ligand in acetonitrile and in the ILs. According to MD simulations in aqueous solution, the UO(2)(ReO(4))(2) complex quickly dissociates to form UO(2)(H(2)O)(5)(2+), while in acetonitrile, a stable UO(2)(ReO(4))(5)(3-) species forms from dissociated ions. In the ILs, the UO(2)(ReO(4))(n)(2-n) complexes (n = 1 to 5) remained stable along the dynamics, and to assess their relative stabilities, we computed the free energy profiles for stepwise ReO(4)(-) complexation to uranyl. In the two studied ILs, complexation is favored, leading to the UO(2)(ReO(4))(5)(3-) species in [Bmi][Tf(2)N] and to UO(2)(ReO(4))(4)(2-) in [Bu(3)MeN][Tf(2)N]. Furthermore, in both acetonitrile and [Bmi][Tf(2)N] solutions, MD and PMF simulations support the formation of dimeric uranyl complexes [UO(2)(ReO(4))(4)](2)(4-) with two bridging ReO(4)(-) ligands. The simulation results are qualitatively consistent with spectroscopic observations in the different solvents, without firmly concluding, however, on the precise composition and structure of the complexes in the solutions. © 2012 American Chemical Society

Kinetics of triscarbonato uranyl reduction by aqueous ferrous iron: a theoretical study.

PubMed

Wander, Matthew C F; Kerisit, Sebastien; Rosso, Kevin M; Schoonen, Martin A A

2006-08-10

Uranium is a pollutant whose mobility is strongly dependent on its oxidation state. While U(VI) in the form of the uranyl cation is readily reduced by a range of natural reductants, by contrast complexation of uranyl by carbonate greatly reduces its reduction potential and imposes increased electron transfer (ET) distances. Very little is known about the elementary processes involved in uranium reduction from U(VI) to U(V) to U(IV) in general. In this study, we examine the theoretical kinetics of ET from ferrous iron to triscarbonato uranyl in aqueous solution. A combination of molecular dynamics (MD) simulations and density functional theory (DFT) electronic structure calculations is employed to compute the parameters that enter into Marcus' ET model, including the thermodynamic driving forces, reorganization energies, and electronic coupling matrix elements. MD simulations predict that two ferrous iron atoms will bind in an inner-sphere fashion to the three-membered carbonate ring of triscarbonato uranyl, forming the charge-neutral ternary Fe(2)UO(2)(CO(3))(3)(H(2)O)(8) complex. Through a sequential proton-coupled electron-transfer mechanism (PCET), the first ET step converting U(VI) to U(V) is predicted by DFT to occur with an electronic barrier that corresponds to a rate on the order of approximately 1 s(-1). The second ET step converting U(V) to U(IV) is predicted to be significantly endergonic. Therefore, U(V) is a stabilized end product in this ET system, in agreement with experiment.

Adsorption of uranium(VI) to manganese oxides: X-ray absorption spectroscopy and surface complexation modeling.

PubMed

Wang, Zimeng; Lee, Sung-Woo; Catalano, Jeffrey G; Lezama-Pacheco, Juan S; Bargar, John R; Tebo, Bradley M; Giammar, Daniel E

2013-01-15

The mobility of hexavalent uranium in soil and groundwater is strongly governed by adsorption to mineral surfaces. As strong naturally occurring adsorbents, manganese oxides may significantly influence the fate and transport of uranium. Models for U(VI) adsorption over a broad range of chemical conditions can improve predictive capabilities for uranium transport in the subsurface. This study integrated batch experiments of U(VI) adsorption to synthetic and biogenic MnO(2), surface complexation modeling, ζ-potential analysis, and molecular-scale characterization of adsorbed U(VI) with extended X-ray absorption fine structure (EXAFS) spectroscopy. The surface complexation model included inner-sphere monodentate and bidentate surface complexes and a ternary uranyl-carbonato surface complex, which was consistent with the EXAFS analysis. The model could successfully simulate adsorption results over a broad range of pH and dissolved inorganic carbon concentrations. U(VI) adsorption to synthetic δ-MnO(2) appears to be stronger than to biogenic MnO(2), and the differences in adsorption affinity and capacity are not associated with any substantial difference in U(VI) coordination.

Failure of ESI Spectra to Represent Metal-Complex Solution Composition: A Study of Lanthanide-Carboxylate Complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDonald, Luther W.; Campbell, James A.; Clark, Sue B.

2014-01-21

Electrospray ionization - mass spectrometry (ESI-MS) was used for the characterization of uranyl complexed to tributyl phosphate (TBP) and dibutyl phosphate (DBP). The stoichiometry of uranyl with TBP and DBP was determined, and the gas phase speciation was found to be dependent on the cone voltage applied to induce fragmentation on the gas phase complexes. To quantitatively compare the gas phase distribution of species to solution, apparent stability constants were calculated. With a cone voltage of 80V, the apparent stability constants for the complexes UO2(NO3)2•2TBP, UO2(NO3)2(H2O)•2TBP, and UO2(DBP)+ were determined. With a lower cone voltage applied, larger complexes were observedmore » and stability constants for the complexes UO2(NO3)2•3TBP and UO2(DBP)42- were determined.« less

Uranyl adsorption and surface speciation at the imogolite-water interface: Self-consistent spectroscopic and surface complexation models

USGS Publications Warehouse

Arai, Y.; McBeath, M.; Bargar, J.R.; Joye, J.; Davis, J.A.

2006-01-01

Macro- and molecular-scale knowledge of uranyl (U(VI)) partitioning reactions with soil/sediment mineral components is important in predicting U(VI) transport processes in the vadose zone and aquifers. In this study, U(VI) reactivity and surface speciation on a poorly crystalline aluminosilicate mineral, synthetic imogolite, were investigated using batch adsorption experiments, X-ray absorption spectroscopy (XAS), and surface complexation modeling. U(VI) uptake on imogolite surfaces was greatest at pH ???7-8 (I = 0.1 M NaNO3 solution, suspension density = 0.4 g/L [U(VI)]i = 0.01-30 ??M, equilibration with air). Uranyl uptake decreased with increasing sodium nitrate concentration in the range from 0.02 to 0.5 M. XAS analyses show that two U(VI) inner-sphere (bidentate mononuclear coordination on outer-wall aluminol groups) and one outer-sphere surface species are present on the imogolite surface, and the distribution of the surface species is pH dependent. At pH 8.8, bis-carbonato inner-sphere and tris-carbonato outer-sphere surface species are present. At pH 7, bis- and non-carbonato inner-sphere surface species co-exist, and the fraction of bis-carbonato species increases slightly with increasing I (0.1-0.5 M). At pH 5.3, U(VI) non-carbonato bidentate mononuclear surface species predominate (69%). A triple layer surface complexation model was developed with surface species that are consistent with the XAS analyses and macroscopic adsorption data. The proton stoichiometry of surface reactions was determined from both the pH dependence of U(VI) adsorption data in pH regions of surface species predominance and from bond-valence calculations. The bis-carbonato species required a distribution of surface charge between the surface and ?? charge planes in order to be consistent with both the spectroscopic and macroscopic adsorption data. This research indicates that U(VI)-carbonato ternary species on poorly crystalline aluminosilicate mineral surfaces may be important in controlling U(VI) mobility in low-temperature geochemical environments over a wide pH range (???5-9), even at the partial pressure of carbon dioxide of ambient air (pCO2 = 10-3.45 atm). ?? 2006 Elsevier Inc. All rights reserved.

Removal of toxic uranium from synthetic nuclear power reactor effluents using uranyl ion imprinted polymer particles.

PubMed

Preetha, Chandrika Ravindran; Gladis, Joseph Mary; Rao, Talasila Prasada; Venkateswaran, Gopala

2006-05-01

Major quantities of uranium find use as nuclear fuel in nuclear power reactors. In view of the extreme toxicity of uranium and consequent stringent limits fixed by WHO and various national governments, it is essential to remove uranium from nuclear power reactor effluents before discharge into environment. Ion imprinted polymer (IIP) materials have traditionally been used for the recovery of uranium from dilute aqueous solutions prior to detection or from seawater. We now describe the use of IIP materials for selective removal of uranium from a typical synthetic nuclear power reactor effluent. The IIP materials were prepared for uranyl ion (imprint ion) by forming binary salicylaldoxime (SALO) or 4-vinylpyridine (VP) or ternary SALO-VP complexes in 2-methoxyethanol (porogen) and copolymerizing in the presence of styrene (monomer), divinylbenzene (cross-linking monomer), and 2,2'-azobisisobutyronitrile (initiator). The resulting materials were then ground and sieved to obtain unleached polymer particles. Leached IIP particles were obtained by leaching the imprint ions with 6.0 M HCl. Control polymer particles were also prepared analogously without the imprint ion. The IIP particles obtained with ternary complex alone gave quantitative removal of uranyl ion in the pH range 3.5-5.0 with as low as 0.08 g. The retention capacity of uranyl IIP particles was found to be 98.50 mg/g of polymer. The present study successfully demonstrates the feasibility of removing uranyl ions selectively in the range 5 microg - 300 mg present in 500 mL of synthetic nuclear power reactor effluent containing a host of other inorganic species.

Behavior of Colorado Plateau uranium minerals during oxidation

USGS Publications Warehouse

Garrels, Robert Minard; Christ, C.L.

1956-01-01

Uranium occurs as U(VI) and U(IV) in minerals of the Colorado Plateau ores. The number of species containing U(VI) is large, but only two U(IV) minerals are known from the Plateau: uraninite, and oxide, and coffinite, a hydroxy-silicate. These oxidize to yield U(VI) before reacting significantly with other mineral constituents. Crystal-structure analysis has shown that U(VI) invariable occurs as uranyl ion, UO2+2. Uranyl ion may form complex carbonate or sulfate ions with resulting soluble compounds, but only in the absence of quinquevalent vanadium, arsenic, or phosphorous. In the presence of these elements in the +5 valence state, the uranyl ion is fixed in insoluble layer compounds formed by union of uranyl ion with orthovanadate, orthophosphate, or orthoarsenate. Under favorable conditions UO2+2 may react to form the relatively insoluble rutherfordine, UO2CO3, or hydrated uranyl hydroxides. These are rarely found on the Colorado Plateau as opposed to their excellent development in other uraniferous areas, a condition which is apparently related to the semiarid climate and low water table of the Plateau. Uranium may also be fixed as uranyl silicate, but little is known about minerals of this kind. In the present study emphasis has been placed on a detailing of the chemical and crystal structural changes which occur in the oxidation paragenetic sequence.

ELECTRON STAINS

PubMed Central

Zobel, C. Richard; Beer, Michael

1961-01-01

Chemical studies have been carried out on the interaction of DNA with uranyl salts. The effect of variations in pH, salt concentration, and structural integrity of the DNA on the stoichiometry of the salt-substrate complex have been investigated. At pH 3.5 DNA interacts with uranyl ions in low concentration yielding a substrate metal ion complex with a UO2++/P mole ratio of about ½ and having a large association constant. At low pH's (about 2.3) the mole ratio decreases to about ⅓. Destruction of the structural integrity of the DNA by heating in HCHO solutions leads to a similar drop in the amount of metal ion bound. Raising the pH above 3.5 leads to an apparent increase in binding as does increasing the concentration of the salt solution. This additional binding has a lower association constant. Under similar conditions DNA binds about seven times more uranyl ion than bovine serum albumin, indicating useful selectivity in staining for electron microscopy. PMID:13788706

Supramolecular structures for determination and identification of the bond lengths in novel uranyl complexes from their infrared spectra

NASA Astrophysics Data System (ADS)

El-Sonbati, A. Z.; Diab, M. A.; Morgan, Sh. M.; Seyam, H. A.

2018-02-01

Novel dioxouranium (VI) heterochelates with neutral bidentate compounds (Ln) have been synthesized. The ligands and the heterochelates [UO2(Ln)2(O2NO)2] were confirmed and characterized by elemental analysis, 1H NMR, UV.-Vis, IR, mass spectroscopy, X-ray diffraction and thermogravimetric analysis (TGA). IR spectral data suggest that the molecules of the Schiff base are coordinated to the central uranium atom (ON donor). The nitrato groups are coordinated as bidentate ligands. The thermodynamic parameters were calculated using Coats-Redfern and Horowitz-Metzger methods. The ligands (Ln) and their complexes (1-3) showed the υ3 frequency of UO22+ has been shown to be an excellent molecular probe for studying the coordinating power of the ligands. The values of υ3 of the prepared complexes containing UO22+ were successfully used to calculate the force constant, FUO (1n 10-8N/Å) and the bond length RUO (Å) of the Usbnd O bond. A strategy based upon both theoretical and experimental investigations has been adopted. The theoretical aspects are described in terms of the well-known theory of 5d-4f transitions. Wilson's, matrix method, Badger's formula, and Jones and El-Sonbati equations were used to calculate the Usbnd O bond distances from the values of the stretching and interaction force constants. The most probable correlation between Usbnd O force constant to Usbnd O bond distance were satisfactorily discussed in term of Badger's rule and the equations suggested by Jones and El-Sonbati. The effect of Hammett's constant is also discussed.

Sorption of uranium in uranyl nitrate solutions on strong cationic resins and its elution with ammonium sulfate. II. Effects of EDTA on thorium decontamination; Estudos de sorpcao de uranio contido em solucoes de nitrato de uranilo por resina cationica forte e sua eluicao com sulfato de amonio. Parte II: efeito de EDTA na descontaminacao do torio (in Portuguese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ribas, Antonio G.S.; Abrao, Alcidio

1970-05-15

This paper describes the studies of decontamination of thorium present as impurity in uranyl nitrate solutions, which was carried out through strong cationic resin where the thorium was partially retained. Then, the final decontamination was performed percolating the uranyl solution on a second cationic resin, after complexation of thorium (and other impurities) with EDTA. The thorium decontamination and the uranium retention were studied as a function of EDTA/U ratio, uranium concentration and acidity of the influent uranyl nitrate. The elution conditions were also studied as a function of eluent flow rate, concentration and acidity. Several tables and graphs showing themore » final results are included. (tr-auth)« less

Synthesis and characterization of new ion-imprinted polymer for separation and preconcentration of uranyl (UO2(2+)) ions.

PubMed

Ahmadi, Seyed Javad; Noori-Kalkhoran, Omid; Shirvani-Arani, Simindokht

2010-03-15

UO(2)(2+) ion-imprinted polymer materials used for solid-phase extraction were prepared by copolymerization of a ternary complex of uranyl ions with styrene and divinyl benzene in the presence of 2,2'-azobisisobutyronitrile. The imprinted particles were leached by HCl 6M. Various parameters in polymerization steps such as DVB/STY ratio, time of polymerization and temperature of polymerization were varied to achieve the most efficient uranyl-imprinted polymer. X-ray diffraction (XRD), infra-red spectroscopy (IR), thermo gravimetric analysis (TGA), UV-vis and nitrogen sorption were used to characterize the polymer particles. The XRD results showed that uranyl ions were completely removed from the polymer after leaching process. IR Analysis indicated that the N,N'-ethylenebis(pyridoxylideneiminato) remained intact in the polymer even after leaching. Some parameters such as pH, weight of the polymer, elution time, eluent volume and aqueous phase volume which affects the efficiency of the polymer were studied. (c) 2009 Elsevier B.V. All rights reserved.

Chemical controls on uranyl citrate speciation and the self-assembly of nanoscale macrocycles and sandwich complexes in aqueous solutions.

PubMed

Basile, M; Unruh, D K; Gojdas, K; Flores, E; Streicher, L; Forbes, T Z

2015-03-28

Uranyl citrate forms trimeric species at pH > 5.5, but exact structural characteristics of these important oligomers have not previously been reported. Crystallization and structural characterization of the trimers suggests the self-assembly of the 3 : 3 and 3 : 2 U : Cit complexes into larger sandwich and macrocyclic molecules. Raman spectroscopy and ESI-MS have been utilized to investigate the relative abundance of these species in solution under varying pH and citrate concentrations. Additional dynamic light scattering experiments indicate that self-assembly of the larger molecules does occur in aqueous solution.

A ω-mercaptoundecylphosphonic acid chemically modified gold electrode for uranium determination in waters in presence of organic matter.

PubMed

Merli, Daniele; Protti, Stefano; Labò, Matteo; Pesavento, Maria; Profumo, Antonella

2016-05-01

A chemically modified electrode (CME) on a gold surface assembled with a ω-phosphonic acid terminated thiol was investigated for its capability to complex uranyl ions. The electrode, characterized by electrochemical techniques, demonstrated to be effective for the determination of uranyl at sub-μgL(-1) level by differential pulse adsorptive stripping voltammetry (DPAdSV) in environmental waters, also in presence of humic matter and other potential chelating agents. The accuracy of the measurements was investigated employing as model probes ligands of different complexing capability (humic acids and EDTA). Copyright © 2016 Elsevier B.V. All rights reserved.

Cation–cation interactions and cation exchange in a series of isostructural framework uranyl tungstates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balboni, Enrica; Burns, Peter C., E-mail: pburns@nd.edu; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556

2014-05-01

The isotypical compounds (UO{sub 2}){sub 3}(WO{sub 6})(H{sub 2}O){sub 5} (1), Ag(UO{sub 2}){sub 3}(WO{sub 6})(OH)(H{sub 2}O){sub 3} (2), K(UO{sub 2}){sub 3}(WO{sub 6})OH(H{sub 2}O){sub 4} (3), Rb(UO{sub 2}){sub 3}(WO{sub 6})(OH)(H{sub 2}O){sub 3.5} (4), and Cs(UO{sub 2}){sub 3}(WO{sub 6})OH(H{sub 2}O){sub 3} (5) were synthesized, characterized, and their structures determined. Each crystallizes in space group Cc. (1): a=12.979 (3), b=10.238 (2), c=11.302 (2), β=102.044 (2); (2): a=13.148 (2), b=9.520 (1), c=11.083 (2), β=101.568 (2); (3): a=13.111 (8), b=9.930 (6), c=11.242 (7), β=101.024 (7); (4): a=12.940 (2), b=10.231 (2), c=11.259(2), β=102.205 (2); (5): a=12.983 (3), b=10.191 (3), c=11.263 (4), β=101.661 (4). Compounds 1–5 are amore » framework of uranyl and tungsten polyhedra containing cation–cation interactions. The framework has three symmetrically distinct U(VI) cations, one tungsten, sixteen to eighteen oxygen atoms, and in 2–5, one monovalent cation. Each atom occupies a general position. Each U(VI) cation is present as a typical (UO{sub 2}){sup 2+} uranyl ion in an overall pentagonal bipyramidal coordination environment. Each pentagonal bipyramid shares two equatorial edges with two other pentagonal bipyramids, forming a trimer. Trimers are connected into chains by edge-sharing with WO{sub 6} octahedra. Chains are linked through cation–cation interactions between two symmetrically independent uranyl ions. This yields a remarkably complex system of intersecting channels that extend along [0 0 1] and [−1 1 0]. The cation exchange properties of 2 and 3 were characterized at room temperature and at 140 °C. - Graphical abstract: Chains of uranium and tungsten polyhedra are connected into a three dimensional framework by cation–cation interactions occurring between two symmetrically independent uranyl pentagonal bipyramids. Monovalent cations present in channels within the structure can be exchanged by room temperature or mild hydrothermal treatments. The framework of these compounds is robust to cation exchange and heat. (yellow polyhedra=uranium pentagonal bipyramids; blue polyhedra=tungsten octahedral, purple balls=K; yellow balls=Na; grey balls=Tl). - Highlights: • Five isostructural uranyl tungstates compounds were synthesized hydrothermally. • The structures consist of a chains of uranium and tungstate polyhedral. • Chains are connected into a framework by cation–cation interactions. • Cation exchange does not alter the structural integrity of the compounds. • Cation exchange was successful at room temperature and mild hydrothermal conditions.« less

Construction of Uranyl Selective Electrode Based on Complex of Uranyl Ion with New Ligand Carboxybenzotriazole in PVC Matrix Membrane

NASA Astrophysics Data System (ADS)

Abu-Dalo, M. A.; Al-Rawashdeh, N. A. F.; Al-Mheidat, I. R.; Nassory, N. S.

2015-10-01

In the present study uranyl selective electrodes in polyvinyl chloride (PVC) matrix membrane were prepared based on a complex of uranyl ion (UO2) with carboxybenzotriazole (CBT) as ligand. The effect of the nature of plasticizer in PVC matrix were evaluated using three different plasticizers, these are dibutyl phthalate (DBP), dioctyl phthalate (DOP) and bis(2-ethylhexyl) sebacate (BHS). The results of this study indicated that the best plasticizer could be used is the DBP, which may be attributed to its lowest viscosity value compared to DOP and BHS. The electrodes with DBP as plasticizer exhibits a Nernstian response with a slope of 28.0 mV/ decade, over a wide range of concentration from 3.0×10-5-6.0×10-2 M and a detection limit of 4.0×10-6 M. It can be used in the pH range of 4.0-10.0 with a response time of less than 10 s for DBP and 25 s for both DOP and BHS. The effects of ions interferences on the electrode response were evaluated. The di- and tri-valent cations were found to interfere less than univalent cations, which was attributed to the high diffusion and the exchange rate between the univalent ions and the uranyl ion solution. The electrodes were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron microscopy (SEM). The results of the standard addition method were satisfactory with errors less than 7%. The developed electrode was found to be fast, sensitive and reliable indicated its potential use in measuring the uranly ion concentration in the field.

Response to the comment “Uranyl-chloride speciation and uranium transport in hydrothermal brines: Comment on Migdisov et al. (2018)” by Dargent et al.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Migdisov, A. A.; Runde, W.; Williams-Jones, A. E.

We welcome the comments provided by Dargent et al. (2018) and appreciate the effort they have made to evaluate our recently reported data on the stability of uranyl(VI) chloride complexes as function of temperature (Migdisov et al., 2018). We also appreciate the opportunity provided by the editor to clarify issues in our paper that were not clearly articulated or in error.

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Veelen, Arjen; Bargar, John R.; Law, Gareth T. W.

Polarization-dependent grazing incidence X-ray absorption spectroscopy (XAS) measurements were completed on oriented single crystals of magnesite [MgCO 3] and brucite [Mg(OH) 2] reacted with aqueous uranyl chloride above and below the solubility boundaries of schoepite (500, 50, and 5 ppm) at pH 8.3 and at ambient (P CO2 = 10 –3.5) or reduced partial pressures of carbon dioxide (P CO2 = 10 –4.5). X-ray absorption near edge structure (XANES) spectra show a striking polarization dependence (χ = 0° and 90° relative to the polarization plane of the incident beam) and consistently demonstrated that the uranyl molecule was preferentially oriented withmore » its O axial = U(VI) = O axial linkage at high angles (60–80°) to both magnesite (101¯4) and brucite (0001). Extended X-ray absorption fine structure (EXAFS) analysis shows that the “effective” number of U(VI) axial oxygens is the most strongly affected fitting parameter as a function of polarization. Furthermore, axial tilt in the surface thin films (thickness ~ 21 Å) is correlated with surface roughness [σ]. Our results show that hydrated uranyl(-carbonate) complexes polymerize on all of our experimental surfaces and that this process is controlled by surface hydroxylation. Lastly, these results provide new insights into the bonding configuration expected for uranyl complexes on the environmentally significant carbonate and hydroxide mineral surfaces.« less

Uranium immobilization and nanofilm formation on magnesium-rich minerals

DOE PAGES

van Veelen, Arjen; Bargar, John R.; Law, Gareth T. W.; ...

2016-03-18

Polarization-dependent grazing incidence X-ray absorption spectroscopy (XAS) measurements were completed on oriented single crystals of magnesite [MgCO 3] and brucite [Mg(OH) 2] reacted with aqueous uranyl chloride above and below the solubility boundaries of schoepite (500, 50, and 5 ppm) at pH 8.3 and at ambient (P CO2 = 10 –3.5) or reduced partial pressures of carbon dioxide (P CO2 = 10 –4.5). X-ray absorption near edge structure (XANES) spectra show a striking polarization dependence (χ = 0° and 90° relative to the polarization plane of the incident beam) and consistently demonstrated that the uranyl molecule was preferentially oriented withmore » its O axial = U(VI) = O axial linkage at high angles (60–80°) to both magnesite (101¯4) and brucite (0001). Extended X-ray absorption fine structure (EXAFS) analysis shows that the “effective” number of U(VI) axial oxygens is the most strongly affected fitting parameter as a function of polarization. Furthermore, axial tilt in the surface thin films (thickness ~ 21 Å) is correlated with surface roughness [σ]. Our results show that hydrated uranyl(-carbonate) complexes polymerize on all of our experimental surfaces and that this process is controlled by surface hydroxylation. Lastly, these results provide new insights into the bonding configuration expected for uranyl complexes on the environmentally significant carbonate and hydroxide mineral surfaces.« less

Uranium Immobilization and Nanofilm Formation on Magnesium-Rich Minerals.

PubMed

van Veelen, Arjen; Bargar, John R; Law, Gareth T W; Brown, Gordon E; Wogelius, Roy A

2016-04-05

Polarization-dependent grazing incidence X-ray absorption spectroscopy (XAS) measurements were completed on oriented single crystals of magnesite [MgCO3] and brucite [Mg(OH)2] reacted with aqueous uranyl chloride above and below the solubility boundaries of schoepite (500, 50, and 5 ppm) at pH 8.3 and at ambient (PCO2 = 10(-3.5)) or reduced partial pressures of carbon dioxide (PCO2 = 10(-4.5)). X-ray absorption near edge structure (XANES) spectra show a striking polarization dependence (χ = 0° and 90° relative to the polarization plane of the incident beam) and consistently demonstrated that the uranyl molecule was preferentially oriented with its Oaxial═U(VI)═Oaxial linkage at high angles (60-80°) to both magnesite (101̅4) and brucite (0001). Extended X-ray absorption fine structure (EXAFS) analysis shows that the "effective" number of U(VI) axial oxygens is the most strongly affected fitting parameter as a function of polarization. Furthermore, axial tilt in the surface thin films (thickness ∼ 21 Å) is correlated with surface roughness [σ]. Our results show that hydrated uranyl(-carbonate) complexes polymerize on all of our experimental surfaces and that this process is controlled by surface hydroxylation. These results provide new insights into the bonding configuration expected for uranyl complexes on the environmentally significant carbonate and hydroxide mineral surfaces.

Uranyl(VI) nitrate salts: modeling thermodynamic properties using the binding mean spherical approximation theory and determination of "fictive" binary data.

PubMed

Ruas, Alexandre; Bernard, Olivier; Caniffi, Barbara; Simonin, Jean-Pierre; Turq, Pierre; Blum, Lesser; Moisy, Philippe

2006-02-23

This work is aimed at a description of the thermodynamic properties of highly concentrated aqueous solutions of uranyl nitrate at 25 degrees C. A new resolution of the binding mean spherical approximation (BIMSA) theory, taking into account 1-1 and also 1-2 complex formation, is developed and used to reproduce, from a simple procedure, experimental uranyl nitrate osmotic coefficient variation with concentration. For better consistency of the theory, binary uranyl perchlorate and chloride osmotic coefficients are also calculated. Comparison of calculated and experimental values is made. The possibility of regarding the ternary system UO(2)(NO(3))(2)/HNO(3)/H(2)O as a "simple" solution (in the sense of Zdanovskii, Stokes, and Robinson) is examined from water activity and density measurements. Also, an analysis of existing uranyl nitrate binary data is proposed and compared with our obtained data. On the basis of the concept of "simple" solution, values for density and water activity for the binary system UO(2)(NO(3))(2)/H(2)O are proposed in a concentration range on which uranyl nitrate precipitates from measurements on concentrated solutions of the ternary system UO(2)(NO(3))(2)/HNO(3)/H(2)O. This new set of binary data is "fictive" in the sense that the real binary system is not stable chemically. Finally, a new, interesting predictive capability of the BIMSA theory is shown.

Molecular dynamics simulations of uranyl adsorption and structure on the basal surface of muscovite

DOE PAGES

Teich-McGoldrick, Stephanie L.; Greathouse, Jeffery A.; Cygan, Randall T.

2014-02-05

Anthropogenic activities have led to an increased concentration of uranium on the Earth’s surface and potentially in the subsurface with the development of nuclear waste repositories. Uranium is soluble in groundwater, and its mobility is strongly affected by the presence of clay minerals in soils and in subsurface sediments. We use molecular dynamics simulations to probe the adsorption of aqueous uranyl (UO 2 2+) ions onto the basal surface of muscovite, a suitable proxy for typically ultrafine-grained clay phases. Model systems include the competitive adsorption between potassium counterions and aqueous ions (0.1 M and 1.0 M UO 2Cl 2 ,more » 0.1 M NaCl). We find that for systems with potassium and uranyl ions present, potassium ions dominate the adsorption phenomenon. Potassium ions adsorb entirely as inner-sphere complexes associated with the ditrigonal cavity of the basal surface. Uranyl ions adsorb in two configurations when it is the only ion species present, and in a single configuration in the presence of potassium. Finally, the majority of adsorbed uranyl ions are tilted less than 45° relative to the muscovite surface, and are associated with the Si 4Al 2 rings near aluminum substitution sites.« less

Mixed-Ligand Uranyl Polyrotaxanes Incorporating a Sulfate/Oxalate Coligand: Achieving Structural Diversity via pH-Dependent Competitive Effect.

PubMed

Xie, Zhen-Ni; Mei, Lei; Hu, Kong-Qiu; Xia, Liang-Shu; Chai, Zhi-Fang; Shi, Wei-Qun

2017-03-20

A mixed-ligand system provides an alternative route to tune the structures and properties of metal-organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1'-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO 2 (L) 0.5 (SO 4 )(H 2 O)·2H 2 O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl polyrotaxane compounds, UPO1-UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO 2 (L) 0.5 (C 2 O 4 ) 0.5 (NO 3 )·3H 2 O) in one-dimensional chain was obtained at a low pH value range (1.47-1.89) and UPO2 (UO 2 (L)(C 2 O 4 )(H 2 O)·7H 2 O)obtained at a higher pH value range (4.31-7.21). By lowering the amount of oxalate, another two uranyl polyrotaxane network UPO3 ((UO 2 ) 2 (L) 0.5 (C 2 O 4 ) 2 (H 2 O)) and UPO4 ((UO 2 ) 2 O(OH)(L) 0.5 (C 2 O 4 ) 0.5 (H 2 O)) could be acquired at a low pH value of 1.98 and a higher pH value over 6, respectively. The UPO1-UPO4 compounds, which display structural diversity via pH-dependent competitive effect of oxalate, represent the first series of mixed-ligand uranyl polyrotaxanes with organic ligand as the coligand. Moreover, the self-assembly process and its internal mechanism concerning pH-dependent competitive effect and other related factors such as concentration of the reagents and coordination behaviors of the coligands were discussed in detail.

In situ ligand synthesis with the UO22+ cation under hydrothermal conditions

NASA Astrophysics Data System (ADS)

Frisch, Mark; Cahill, Christopher L.

2007-09-01

A novel uranium (VI) coordination polymer, (UO 2) 2(C 2O 4)(C 5H 6NO 3) 2 ( 1), has been prepared under the hydrothermal reaction of uranium nitrate hexahydrate and L-pyroglutamic acid. Compound 1 (monoclinic, C2/ c, a=22.541(6) Å, b=5.7428(15) Å, c=15.815(4) Å, β=119.112(4)°, Z=4, R1=0.0237, w R2=0.0367) consists of uranium pentagonal bipyramids linked via L-pyroglutamate and oxalate anions to form an overall two-dimensional (2D) structure. With the absence of oxalic acid within the starting materials, the oxalate anions are hypothesized to form in situ whereby decarboxylation of L-pyroglutamic acid occurs followed by coupling of CO 2 to form the oxalate linkages as observed in the crystal structure. Addition of copper (II) to this system appears to promote oxalate formation in that synthetic moolooite (Cu(C 2O 4)· nH 2O; 0⩽ n⩽1) and a known uranyl oxalate [(UO 2) 2(C 2O 4)(OH) 2(H 2O) 2·H 2O], co-crystallize in significant quantity. Compound 1 exhibits the characteristic uranyl emission spectrum upon either direct uranyl excitation or ligand excitation, the latter of which shows an increase in relative intensity. This subsequent increase in the intensity indicates an energy transfer from the ligand to the uranyl cations thus illustrating an example of the antenna effect in the solid state.

In situ ligand synthesis with the UO{sub 2}{sup 2+} cation under hydrothermal conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frisch, Mark; Cahill, Christopher L.; Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC

A novel uranium (VI) coordination polymer, (UO{sub 2}){sub 2}(C{sub 2}O{sub 4})(C{sub 5}H{sub 6}NO{sub 3}){sub 2} (1), has been prepared under the hydrothermal reaction of uranium nitrate hexahydrate and L-pyroglutamic acid. Compound 1 (monoclinic, C2/c, a=22.541(6) A, b=5.7428(15) A, c=15.815(4) A, {beta}=119.112(4){sup o}, Z=4, R{sub 1}=0.0237, wR{sub 2}=0.0367) consists of uranium pentagonal bipyramids linked via L-pyroglutamate and oxalate anions to form an overall two-dimensional (2D) structure. With the absence of oxalic acid within the starting materials, the oxalate anions are hypothesized to form in situ whereby decarboxylation of L-pyroglutamic acid occurs followed by coupling of CO{sub 2} to form the oxalatemore » linkages as observed in the crystal structure. Addition of copper (II) to this system appears to promote oxalate formation in that synthetic moolooite (Cu(C{sub 2}O{sub 4}).nH{sub 2}O; 0{<=}n{<=}1) and a known uranyl oxalate [(UO{sub 2}){sub 2}(C{sub 2}O{sub 4})(OH){sub 2}(H{sub 2}O){sub 2}.H{sub 2}O], co-crystallize in significant quantity. Compound 1 exhibits the characteristic uranyl emission spectrum upon either direct uranyl excitation or ligand excitation, the latter of which shows an increase in relative intensity. This subsequent increase in the intensity indicates an energy transfer from the ligand to the uranyl cations thus illustrating an example of the antenna effect in the solid state. - Graphical abstract: A novel homometallic coordination polymer (UO{sub 2}){sub 2}(C{sub 2}O{sub 4})(C{sub 5}H{sub 6}NO{sub 3}){sub 2}, in the uranium-L-pyroglutamic acid system has been synthesized under hydrothermal conditions. The title compound consists of uranium pentagonal bipyramids bridged through both L-pyroglutamate and oxalate linkages to produce a 3D crystal structure. The oxalate anions are theorized to result from decarboxylation of L-pyroglutamic acid followed by subsequent coupling of CO{sub 2}.« less

Hydrothermal syntheses, structures, and properties of the new uranyl selenites Ag(2)(UO(2))(SeO(3))(2), M[(UO(2))(HSeO(3))(SeO(3))] (M = K, Rb, Cs, Tl), and Pb(UO(2))(SeO(3))(2).

PubMed

Almond, Philip M; Albrecht-Schmitt, Thomas E

2002-03-11

The transition metal, alkali metal, and main group uranyl selenites, Ag(2)(UO(2))(SeO(3))(2) (1), K[(UO(2))(HSeO(3))(SeO(3))] (2), Rb[(UO(2))(HSeO(3))(SeO(3))] (3), Cs[(UO(2))(HSeO(3))(SeO(3))] (4), Tl[(UO(2))(HSeO(3))(SeO(3))] (5), and Pb(UO(2))(SeO(3))(2) (6), have been prepared from the hydrothermal reactions of AgNO(3), KCl, RbCl, CsCl, TlCl, or Pb(NO(3))(2) with UO(3) and SeO(2) at 180 degrees C for 3 d. The structures of 1-5 contain similar [(UO(2))(SeO(3))(2)](2-) sheets constructed from pentagonal bipyramidal UO(7) units that are joined by bridging SeO(3)(2-) anions. In 1, the selenite oxo ligands that are not utilized within the layers coordinate the Ag(+) cations to create a three-dimensional network structure. In 2-5, half of the selenite ligands are monoprotonated to yield a layer composition of [(UO(2))(HSeO(3))(SeO(3))](1-), and coordination of the K(+), Rb(+), Cs(+), and Tl(+) cations occurs through long ionic contacts. The structure of 6 contains a uranyl selenite layered substructure that differs substantially from those in 1-5 because the selenite anions adopt both bridging and chelating binding modes to the uranyl centers. Furthermore, the Pb(2+) cations form strong covalent bonds with these anions creating a three-dimensional framework. These cations occur as distorted square pyramidal PbO(5) units with stereochemically active lone pairs of electrons. These polyhedra align along the c-axis to create a polar structure. Second-harmonic generation (SHG) measurements revealed a response of 5x alpha-quartz for 6. The diffuse reflectance spectrum of 6 shows optical transitions at 330 and 440 nm. The trailing off of the 440 nm transition to longer wavelengths is responsible for the orange coloration of 6.

Carbonate-H2O2 Leaching for Sequestering Uranium from Seawater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Horng-Bin; Weisheng, Liao; Wai, Chien

Uranium adsorbed on amidoxime-based polyethylene fiber in simulated seawater can be quantitatively eluted at room temperature using 1M Na2CO3 containing 0.1 M H2O2. This efficient elution process is probably due to formation of an extremely stable uranyl-peroxo-carbonato complex in the carbonate solution. After washing with water, the sorbent can be reused with little loss of uranium loading capacity. Possible existence of this stable uranyl species in ocean water is also discussed.

Carbonate-H₂O₂ leaching for sequestering uranium from seawater.

PubMed

Pan, Horng-Bin; Liao, Weisheng; Wai, Chien M; Oyola, Yatsandra; Janke, Christopher J; Tian, Guoxin; Rao, Linfeng

2014-07-28

Uranium adsorbed on amidoxime-based polyethylene fiber in simulated seawater can be quantitatively eluted at room temperature using 1 M Na2CO3 containing 0.1 M H2O2. This efficient elution process is probably due to the formation of an extremely stable uranyl-peroxo-carbonato complex in the carbonate solution. After washing with water, the sorbent can be reused with minimal loss of uranium loading capacity. Possible existence of this stable uranyl species in ocean water is also discussed.

PROCESS FOR SEPARATION OF HEAVY METALS

DOEpatents

Duffield, R.B.

1958-04-29

A method is described for separating plutonium from aqueous acidic solutions of neutron-irradiated uranium and the impurities associated therewith. The separation is effected by adding, to the solution containing hexavalent uranium and plutonium, acetate ions and the ions of an alkali metal and those of a divalent metal and thus forming a complex plutonium acetate salt which is carried by the corresponding complex of uranium, such as sodium magnesium uranyl acetate. The plutonium may be separated from the precipitated salt by taking the same back into solution, reducing the plutonium to a lower valent state on reprecipitating the sodium magnesium uranyl salt, removing the latter, and then carrying the plutonium from ihe solution by means of lanthanum fluoride.

Use of spectroscopic techniques for uranium(VI)/montmorillonite interaction modeling.

PubMed

Kowal-Fouchard, A; Drot, R; Simoni, E; Ehrhardt, J J

2004-03-01

To experimentally identify both clay sorption sites and sorption equilibria and to understand the retention mechanisms at a molecular level, we have characterized the structure of hexavalent uranium surface complexes resulting from the interaction between the uranyl ions and the surface retention groups of a montmorillonite clay. We have performed laser-induced fluorescence spectroscopy (LIFS) and X-ray photoelectron spectroscopy (XPS) on uranyl ion loaded montmorillonite. These structural results were then compared to those obtained from the study of uranyl ions sorbed onto an alumina and also from U(VI) sorbed on an amorphous silica. This experimental approach allowed for a clear determination of the reactive surface sites of montmorillonite for U(VI) sorption. The lifetime values and the U4f XPS spectra of uranium(VI) sorbed on montmorillonite have shown that this ion is sorbed on both exchange and edge sites. The comparison of U(VI)/clay and U(VI)/oxide systems has determined that the interaction between uranyl ions and montmorillonite edge sites occurs via both [triple bond]AlOH and [triple bond]SiOH surface groups and involves three distinct surface complexes. The surface complexation modeling of the U(VI)/montmorillonite sorption edges was determined using the constant capacitance model and the above experimental constraints. The following equilibria were found to account for the uranyl sorption mechanisms onto montmorillonite for metal concentrations ranged from 10(-6) to 10(-3) M and two ionic strengths (0.1 and 0.5 M): 2[triple bond]XNa + UO2(2+) <==> ([triple bond]X)2UO2 + 2Na+, log K0(exch) = 3.0; [triple bond]Al(OH)2 + UO2(2+) <==> [triple bond]Al(OH)2UO2(2+), log K0(Al) = 14.9; [triple bond]Si(OH)2 + UO2(2+) <==> [triple bond]SiO2UO2 + 2H+, log K0(Si1) = -3.8; and [triple bond]Si(OH)2 + 3UO2(2+) + 5H2O <==> [triple bond]SiO2(UO2)3(OH)5- + 7H+, log K0(Si2) = -20.0.

Interfacial Interaction of Titania Nanoparticles and Ligated Uranyl Species: A Relativistic DFT Investigation.

PubMed

Zhao, Hong-Bo; Zheng, Ming; Schreckenbach, Georg; Pan, Qing-Jiang

2017-03-06

To understand interfacial behavior of actinides adsorbed onto mineral surfaces and unravel their structure-property relationship, the structures, electronic properties, and energetics of various ligated uranyl species adsorbed onto TiO 2 surface nanoparticle clusters (SNCs) were examined using relativistic density functional theory. Rutile (110) and anatase (101) titania surfaces, experimentally known to be stable, were fully optimized. For the former, models studied include clean and water-free Ti 27 O 64 H 20 (dry), partially hydrated (Ti 27 O 64 H 20 )(H 2 O) 8 (sol) and proton-saturated [(Ti 27 O 64 H 20 )(H 2 O) 8 (H) 2 ] 2+ (sat), while defect-free and defected anatase SNCs involving more than 38 TiO 2 units were considered. The aquouranyl sorption onto rutile SNCs is energetically preferred, with interaction energies of -8.54, -10.36, and -2.39 eV, respectively. Energy decomposition demonstrates that the sorption is dominated by orbital attractive interactions and modified by steric effects. Greater hydrogen-bonding involvement leads to increased orbital interactions (i.e., more negative energy) from dry to sol/sat complexes, while much larger steric interaction in the sat complex significantly reduces the sorption interaction (i.e., more positive energy). For dry SNC, adsorbates were varied from aquo to aquo-carbonato, to carbonato, to hydroxo uranyl species. Longer U-O surf /U-Ti distances and more positive sorption energies were calculated upon introducing carbonato and hydroxo ligands, indicative of weaker uranyl sorption onto the substrate. This is consistent with experimental observations that the uranyl sorption rate decreases upon raising solution pH value or adding carbon dioxide. Anatase SNCs adsorbing aquouranyl are even more exothermic, because more bonds are formed than in the case of rutile. Moreover, the anatase sorption can be tuned by surface defects as well as its Ti and O stoichiometry. All the aquouranyl-SNC complexes show similar character of molecular orbitals and energetic order although differing in highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps and orbital energy levels, but changes can be accomplished by adding carbonato and hydroxo ligands.

Genesis of kasolite associated with aplite-pegmatite at Jabal Sayid, Hijaz region, Kingdom of Saudi Arabia

NASA Astrophysics Data System (ADS)

Dawood, Yehia H.; Harbi, Hesham M.; Abd El-Naby, Hamdy H.

2010-01-01

In this study, we report kasolite Pb(UO 2)SiO 4·(H 2O) for the first time as a main uranyl mineral in the mineralized aplite-pegmatite of Jabal Sayid, Hijaz region. It commonly forms clusters of yellow acicular crystals in the voids and fractures. The mineral chemistry and mineralogical characteristics of kasolite were investigated using different techniques. Calcium, iron and phosphorus are detected in kasolite in addition to its major constituents; uranium, lead and silicon. Lead does not exist as a radiogenic product and not even as a substitute for uranium in the mineral structure. Alternatively, galena mineralization could be considered as a source for lead. The fluoride and carbonate complexes played a significant role in the formation of kasolite. High temperature hydrothermal solutions reacted with pre-existing uranium-bearing metamictized accessory minerals such as pyrochlore, U-rich thorite and zircon to form uranous fluoride complexes. These complexes are predominant in reducing environment and at pH 4. When the fluids approached the surface passing through fracture system, the oxygen fugacity ( fO 2) and the pH increased because of the loss of volatile components. At these conditions, uranous fluorides would convert to uranyl fluoride complexes UO 2F 3-. Further decrease in temperature was associated with the decay of the activity of fluorine ion by the dilution of hydrothermal solutions and precipitation of fluorite. At this condition, uranyl-carbonate complexes are favoured. These complexes were combined later with silica and lead to form kasolite.

Solid state and aqueous behavior of uranyl peroxide cage clusters

NASA Astrophysics Data System (ADS)

Pellegrini, Kristi Lynn

Uranyl peroxide cage clusters include a large family of more than 50 published clusters of a variety of sizes, which can incorporate various ligands including pyrophosphate and oxalate. Previous studies have reported that uranyl clusters can be used as a method to separate uranium from a solid matrix, with potential applications in reprocessing of irradiated nuclear fuel. Because of the potential applications of these novel structures in an advanced nuclear fuel cycle and their likely presence in areas of contamination, it is important to understand their behavior in both solid state and aqueous systems, including complex environments where other ions are present. In this thesis, I examine the aqueous behavior of U24Pp 12, as well as aqueous cluster systems with added mono-, di-, and trivalent cations. The resulting solutions were analyzed using dynamic light scattering and ultra-small angle X-ray scattering to evaluate the species in solution. Precipitates of these systems were analyzed using powder X-ray diffraction, X-ray fluorescence spectrometry, and Raman spectroscopy. The results of these analyses demonstrate the importance of cation size, charge, and concentration of added cations on the aqueous behavior of uranium macroions. Specifically, aggregates of various sizes and shapes form rapidly upon addition of cations, and in some cases these aggregates appear to precipitate into an X-ray amorphous material that still contains U24Pp12 clusters. In addition, I probe aggregation of U24Pp12 and U60, another uranyl peroxide cage cluster, in mixed solvent water-alcohol systems. The aggregation of uranyl clusters in water-alcohol systems is a result of hydrogen bonding with polar organic molecules and the reduction of the dielectric constant of the system. Studies of aggregation of uranyl clusters also allow for comparison between the newer uranyl polyoxometalate family and century-old transition metal polyoxometalates. To complement the solution studies of uranyl cage clusters, solid state analyses of U24Pp12 are presented, including single crystal X-ray diffraction and preliminary single crystal neutron diffraction. Solid state analyses are used to probe the complicated bonding environments between U24Pp12 and crystallized counterions, giving further insight into the importance of cluster protonation and counterions in uranyl cluster systems. The combination of solid state and solution techniques provides information about the complicated nature of uranyl peroxide nanoclusters, and insight towards future applications of clusters in the advanced nuclear fuel cycle and the environment.

Highly Preorganized Ligand 1,10-Phenanthroline-2,9-dicarboxylic Acid for the Selective Recovery of Uranium from Seawater in the Presence of Competing Vanadium Species

DOE PAGES

Lashley, Mark A.; Ivanov, Alexander S.; Bryantsev, Vyacheslav S.; ...

2016-09-30

Studies of the complexation of new promising ligands with uranyl (UO 2 2+) and other seawater cations can aid the development of more efficient, selective, and robust sorbents for the recovery of uranium from seawater. Here, we propose that the ligand design principles based on structural preorganization can be successfully applied to obtain a dramatic enhancement in UO 2 2+ ion binding affinity and selectivity. This concept is exemplified through the investigation of the com-plexes of UO 2 2+, VO 2+, and VO 2+ with the highly preorganized ligand PDA (1,10-phenanthroline-2,9-dicarboxylic acid) using a combination of fluores-cence and absorbance techniques,more » along with den-sity functional theory (DFT) calculations. Moreover, the measured stability constant value, log K1, of 16.5 for the UO 2 2+/PDA complex is very high compared to uranyl complexes with other dicarboxylic ligands. Moreover, PDA exhibits strong selectivity for uranyl over vanadium ions, since the determined sta-bility constant values of the PDA complexes of the vanadium ions are quite low (V(IV) log K1 = 7.4, V(V) = 7.3). Finally, the structures of the corresponding UO 2 2+, VO 2+, and VO 2+ complexes with PDA were identified by systematic DFT calculations, and helped to interpret the stronger binding affinity for uranium over the vanadium ions. Due to its high chemical stability, selectivity, and structural preor-ganization for UO 2 2+ complexation, PDA is a very promising candidate that can be potentially used in the development of novel adsorbent materials for the selective extraction of uranium from sea-water.« less

Highly Preorganized Ligand 1,10-Phenanthroline-2,9-dicarboxylic Acid for the Selective Recovery of Uranium from Seawater in the Presence of Competing Vanadium Species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lashley, Mark A.; Ivanov, Alexander S.; Bryantsev, Vyacheslav S.

Studies of the complexation of new promising ligands with uranyl (UO 2 2+) and other seawater cations can aid the development of more efficient, selective, and robust sorbents for the recovery of uranium from seawater. Here, we propose that the ligand design principles based on structural preorganization can be successfully applied to obtain a dramatic enhancement in UO 2 2+ ion binding affinity and selectivity. This concept is exemplified through the investigation of the com-plexes of UO 2 2+, VO 2+, and VO 2+ with the highly preorganized ligand PDA (1,10-phenanthroline-2,9-dicarboxylic acid) using a combination of fluores-cence and absorbance techniques,more » along with den-sity functional theory (DFT) calculations. Moreover, the measured stability constant value, log K1, of 16.5 for the UO 2 2+/PDA complex is very high compared to uranyl complexes with other dicarboxylic ligands. Moreover, PDA exhibits strong selectivity for uranyl over vanadium ions, since the determined sta-bility constant values of the PDA complexes of the vanadium ions are quite low (V(IV) log K1 = 7.4, V(V) = 7.3). Finally, the structures of the corresponding UO 2 2+, VO 2+, and VO 2+ complexes with PDA were identified by systematic DFT calculations, and helped to interpret the stronger binding affinity for uranium over the vanadium ions. Due to its high chemical stability, selectivity, and structural preor-ganization for UO 2 2+ complexation, PDA is a very promising candidate that can be potentially used in the development of novel adsorbent materials for the selective extraction of uranium from sea-water.« less

Proteogenomic insights into uranium tolerance of a Chernobyl's Microbacterium bacterial isolate.

PubMed

Gallois, Nicolas; Alpha-Bazin, Béatrice; Ortet, Philippe; Barakat, Mohamed; Piette, Laurie; Long, Justine; Berthomieu, Catherine; Armengaud, Jean; Chapon, Virginie

2018-04-15

Microbacterium oleivorans A9 is a uranium-tolerant actinobacteria isolated from the trench T22 located near the Chernobyl nuclear power plant. This site is contaminated with different radionuclides including uranium. To observe the molecular changes at the proteome level occurring in this strain upon uranyl exposure and understand molecular mechanisms explaining its uranium tolerance, we established its draft genome and used this raw information to perform an in-depth proteogenomics study. High-throughput proteomics were performed on cells exposed or not to 10μM uranyl nitrate sampled at three previously identified phases of uranyl tolerance. We experimentally detected and annotated 1532 proteins and highlighted a total of 591 proteins for which abundances were significantly differing between conditions. Notably, proteins involved in phosphate and iron metabolisms show high dynamics. A large ratio of proteins more abundant upon uranyl stress, are distant from functionally-annotated known proteins, highlighting the lack of fundamental knowledge regarding numerous key molecular players from soil bacteria. Microbacterium oleivorans A9 is an interesting environmental model to understand biological processes engaged in tolerance to radionuclides. Using an innovative proteogenomics approach, we explored its molecular mechanisms involved in uranium tolerance. We sequenced its genome, interpreted high-throughput proteomic data against a six-reading frame ORF database deduced from the draft genome, annotated the identified proteins and compared protein abundances from cells exposed or not to uranyl stress after a cascade search. These data show that a complex cellular response to uranium occurs in Microbacterium oleivorans A9, where one third of the experimental proteome is modified. In particular, the uranyl stress perturbed the phosphate and iron metabolic pathways. Furthermore, several transporters have been identified to be specifically associated to uranyl stress, paving the way to the development of biotechnological tools for uranium decontamination. Copyright © 2017. Published by Elsevier B.V.

Synthesis, spectral and magnetic studies of mono- and bi-nuclear metal complexes of a new bis(tridentate NO2) Schiff base ligand derived from 4,6-diacetylresorcinol and ethanolamine.

PubMed

Shebl, Magdy

2009-07-15

A new bis(tridentate NO2) Schiff base ligand, H(4)L, was prepared by the reaction of the bifunctional carbonyl compound; 4,6-diacetylresorcinol (DAR) with ethanolamine. The ligand reacted with iron(III), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), cerium(III) and uranyl(VI) ions, in absence and in presence of LiOH, to yield mono- and bi-nuclear complexes with different coordinating sites. The ligand and its metal complexes were characterized by elemental analyses, IR, (1)H NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. In absence of LiOH, mononuclear complexes (2, 3 and 5-9) as well as binuclear complexes (1 and 4) were obtained. In mononuclear complexes, the ligand acted as a neutral, mono- and di-basic/bi- and tetra-dentate ligand while in binuclear complexes (1 and 4), the ligand acted as a bis(mono- or di-basic/tridentate) ligand. On the other hand, in presence of LiOH, only binuclear complexes (10-15) were obtained in which the ligand acted as a bis(dibasic tridentate) ligand. The metal complexes exhibited different geometrical arrangements such as octahedral, tetrahedral, square planar, square pyramidal and pentagonal bipyramidal arrangements.

Correlation between ionic radii of metals and thermal decomposition of supramolecular structure of azodye complexes

NASA Astrophysics Data System (ADS)

El-Sonbati, A. Z.; Diab, M. A.; El-Bindary, A. A.; Eldesoky, A. M.; Morgan, Sh. M.

2015-01-01

An interesting azodye heterocyclic ligand of copper(II), cobalt(II), nickel(II) and uranyl(II) complexes have been synthesized by the reaction of metal salts with 5-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-2-thioxo-4-thiazolidinone (HL) yields 1:1 and 1:2 (M:L) complexes depending on the reaction conditions. The elemental analysis, magnetic moments, spectral (UV-Vis, IR, 1H and 13C NMR and ESR) and thermal studies were used to characterize the isolated complexes. The molecular structures of the ligand tautomers are optimized theoretically and the quantum chemical parameters are calculated. The IR spectra showed that the ligand (HL) act as monobasic tridentate/neutral bidentate through the (sbnd Ndbnd N), enolic (Csbnd O)- and/or oxygen keto moiety groups forming a five/six-membered structures. According to intramolecular hydrogen bond leads to increasing of the complexes stability. The molar conductivities show that all the complexes are non-electrolytes. The ESR spectra indicate that the free electron is in dxy orbital. The calculated bonding parameter indicates that in-plane σ-bonding is more covalent than in-plane π-bonding. The coordination geometry is five/six-coordinated trigonal bipyramidal for complex (1) and octahedral for complexes (2-6). The value of covalency factor β12 and orbital reduction factor K accounts for the covalent nature of the complexes. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. The synthesized ligand (HL) and its Cu(II) complexes (1, 2 and 4) are screened for their biological activity against bacterial and fungal species. The ligand (HL) showed antimicrobial activities against Escherichia coli. The ligand (HL) and its Cu(II) complexes (2 and 4) have very high antifungal activity against Penicillium italicum. The inhibitive action of ligand (HL), against the corrosion of C-steel in 2 M HCl solution has been investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).

Alteration, adsorption and nucleation processes on clay-water interfaces: Mechanisms for the retention of uranium by altered clay surfaces on the nanometer scale

NASA Astrophysics Data System (ADS)

Schindler, Michael; Legrand, Christine A.; Hochella, Michael F.

2015-03-01

Nano-scale processes on the solid-water interface of clay minerals control the mobility of metals in the environment. These processes can occur in confined pore spaces of clay buffers and barriers as well as in contaminated sediments and involve a combination of alteration, adsorption and nucleation processes of multiple species and phases. This study characterizes nano-scale processes on the interface between clay minerals and uranyl-bearing solution near neutral pH. Samples of clay minerals with a contact pH of ∼6.7 are collected from a U mill and mine tailings at Key Lake, Saskatchewan, Canada. The tailings material contains Cu-, As-, Co-, Mo-, Ni-, Se-bearing polymetallic phases and has been deposited with a surplus of Ca(OH)2 and Na2CO3 slaked lime. Small volumes of mill-process solutions containing sulfuric acid and U are occasionally discharged onto the surface of the tailings and are neutralized after discharge by reactions with the slaked lime. Transmission electron microscopy (TEM) in combination with the focused ion beam (FIB) technique and other analytical methods (SEM, XRD, XRF and ICP-OES) are used to characterize the chemical and mineralogical composition of phases within confined pore spaces of the clay minerals montmorillonite and kaolinite and in the surrounding tailings material. Alteration zones around the clay minerals are characterized by different generations of secondary silicates containing variable proportions of adsorbed uranyl- and arsenate-species and by the intergrowth of the silicates with the uranyl-minerals cuprosklodowskite, Cu[(UO2)2(SiO3OH)2](H2O)6 and metazeunerite, Cu[(UO2)(AsO4)2](H2O)8. The majority of alteration phases such as illite, illite-smectite, kaolinite and vermiculite have been most likely formed in the sedimentary basin of the U-ore deposit and contain low amounts of Fe (<5 at.%). Iron-enriched Al-silicates or illite-smectites (Fe >10 at.%) formed most likely in the limed tailings at high contact pH (∼10.5) and their structure is characterized by a low degree of long-range order. Adsorption of U and nucleation of metazeunerite and cuprosklodowskite are strongly controlled by the presence of the adsorbed oxy-anion species arsenate and silica on the Fe-enriched silicates. Heterogeneous nucleation of nano-crystals of the uranyl minerals occurs most likely on adsorption sites of binary uranyl-, arsenate- and silica-complexes as well as on ternary uranyl-arsenate or uranyl-silicate complexes. The uranyl minerals occur as aggregates of misoriented nano-size crystals and are the result of supersaturated solutions and a high number of nucleation sites that prevented the formation of larger crystals through Oswald ripening. The results of this study provide an understanding of interfacial nano-scale processes between uranyl species and altered clay buffers in a potential Nuclear Waste repository as similar alteration conditions of clays may occur in a multi-barrier system.

Self-assembly of [UO{sub 2}X{sub 4}]{sup 2−} (X=Cl, Br) dianions with γ substituted pyridinium cations: Structural systematics and fluorescence properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Surbella, Robert G.; Andrews, Michael B.; Cahill, Christopher L., E-mail: cahill@gwu.edu

2016-04-15

Room temperature self-assembly of [UO{sub 2}X{sub 4}]{sup 2−} (X=Cl, Br) with γ substituted pyridinium cations has resulted in the formation of twelve compounds that were studied via single crystal X-ray diffraction and fluorescence spectroscopy. Systematic variation of electron donating groups on the pyridinium species is shown to influence the presence and/or strength of various supramolecular synthons, including hydrogen bonding and pi interactions. Combinations of such non-covalent interactions (NCIs) have given rise to a range of supramolecular assemblies, and are shown to influence uranyl emission by way of second sphere coordination to equatorial ligands. - Graphical abstract: Supramolecular assembly of themore » [UO{sub 2}Cl{sub 4}]{sup 2−} dianion with pyridinium cations is a viable synthetic route to the growth of uranyl containing single crystals.« less

Spectroscopic studies and thermal analysis of mononuclear metal complexes with moxifloxacin and 2,2‧-bipyridine and their effects on acute lung injury induced by hydrochloric acid in rats

NASA Astrophysics Data System (ADS)

El-Hamid, S. M. Abd; El-Demerdash, R. S.; Arafat, H. F. H.; Sadeek, S. A.

2017-12-01

The article describes the interaction of Y(III), Zr(IV), La(III), Ce(IV) and U(VI) with moxifloxacin hydrochloride and 2,2‧-bipyridine. Characterization of complexes was made by elemental analyses, molar conductivity, magnetic moment measurements and spectral measurements e.g. IR, UV-Vis., 1H NMR and mass as well as thermal analyses (TG and DTG). The molar conductivity shows that the complexes are electrolytes nature. Spectroscopic investigation of the solid complexes studied here indicate that moxifloxacin hydrochloride and 2,2‧-bipyridine are coordinated to the metal ions in a neutral bidentate manner. After complete characterization, the chemical formulae of the complexes were established. The calculated bond length and force constant, F(Udbnd O), in the uranyl complex are 1.756 Å and 637.90 Nm-1, respectively. Kinetic and thermodynamic parameters were determined using Coats-Redfern and Horowitz-Metzger equations. Establishment of hydrochloric acid that induce acute lung injury (ALI) in rats by intratracheal administration through damaging the alveolar epithelium and activation of the neutrophil and subsequent oxidative stress by increasing malondialdehyde (MDA), tumor necrosis factor (TNF-α) and neutrophil, which were confirmed by histopathological investigation while decreasing in antioxidant enzymes and lymphocytes. Whereas treatment with mixed-ligand metal complexes significantly decrease MDA, TNF-α and neutrophils and increase antioxidant and lymphocytes.

Liquid-liquid extraction of uranyl by TBP: the TBP and ions models and related interfacial features revisited by MD and PMF simulations.

PubMed

Benay, G; Wipff, G

2014-03-20

We report a molecular dynamics (MD) study of biphasic systems involved in the liquid-liquid extraction of uranyl nitrate by tri-n-butylphosphate (TBP) to hexane, from "pH neutral" or acidic (3 M nitric acid) aqueous solutions, to assess the model dependence of the surface activity and partitioning of TBP alone, of its UO2(NO3)2(TBP)2 complex, and of UO2(NO3)2 or UO2(2+) uncomplexed. For this purpose, we first compare several electrostatic representations of TBP with regards to its polarity and conformational properties, its interactions with H2O, HNO3, and UO2(NO3)2 species, its relative free energies of solvation in water or oil environments, the properties of the pure TBP liquid and of the pure-TBP/water interface. The free energies of transfer of TBP, UO2(NO3)2, UO2(2+), and the UO2(NO3)2(TBP)2 complex across the water/oil interface are then investigated by potential of mean force (PMF) calculations, comparing different TBP models and two charge models of uranyl nitrate. Describing uranyl and nitrate ions with integer charges (+2 and -1, respectively) is shown to exaggerate the hydrophilicity and surface activity of the UO2(NO3)2(TBP)2 complex. With more appropriate ESP charges, mimicking charge transfer and polarization effects in the UO2(NO3)2 moiety or in the whole complex, the latter is no more surface active. This feature is confirmed by MD, PMF, and mixing-demixing simulations with or without polarization. Furthermore, with ESP charges, pulling the UO2(NO3)2 species to the TBP phase affords the formation of UO2(NO3)2(TBP)2 at the interface, followed by its energetically favorable extraction. The neutral complexes should therefore not accumulate at the interface during the extraction process, but diffuse to the oil phase. A similar feature is found for an UO2(NO3)2(Amide)2 neutral complex with fatty amide extracting ligands, calling for further simulations and experimental studies (e.g., time evolution of the nonlinear spectroscopic signature and of surface tension) on the interfacial landscape upon ion extraction.

Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite–selenates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gurzhiy, Vladislav V., E-mail: vladgeo17@mail.ru; Kovrugin, Vadim M.; Tyumentseva, Olga S.

2015-09-15

Single crystals of seven novel uranyl oxysalts of selenium with protonated methylamine molecules, [C{sub 2}H{sub 8}N]{sub 2}[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)] (I), [C{sub 2}H{sub 8}N]{sub 2}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}(H{sub 2}O)] (II), [C{sub 4}H{sub 15}N{sub 3}][H{sub 3}O]{sub 0.5}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 2.93}(SeO{sub 3}){sub 0.07}(H{sub 2}O)](NO{sub 3}){sub 0.5} (III), [C{sub 2}H{sub 8}N]{sub 3}[H{sub 5}O{sub 2}][(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}(H{sub 2}O){sub 2}]{sub 2}(H{sub 2}O){sub 5} (IV), [C{sub 2}H{sub 8}N]{sub 2}[H{sub 3}O][(UO{sub 2}){sub 3}(SeO{sub 4}){sub 4}(HSeO{sub 3})(H{sub 2}O)](H{sub 2}SeO{sub 3}){sub 0.2} (V), [C{sub 4}H{sub 12}N]{sub 3}[H{sub 3}O][(UO{sub 2}){sub 3}(SeO{sub 4}){sub 5}(H{sub 2}O)] (VI), and [C{sub 2}H{sub 8}N]{sub 3}(C{sub 2}H{sub 7}N)[(UO{sub 2}){sub 3}(SeO{sub 4}){submore » 4}(HSeO{sub 3})(H{sub 2}O)] (VII) have been prepared by isothermal evaporation from aqueous solutions. Their crystal structures have been solved by direct methods and their uranyl selenate and selenite–selenate units investigated using black-and-white graphs from the viewpoints of topology of interpolyhedral linkages and isomeric variations. The crystal structure of IV is based upon complex layers with unique topology, which has not been observed previously in uranyl selenates. Investigations of the statistics and local distribution of the U–O{sub br}–Se bond angles demonstrates that shorter angles associate with undulations, whereas larger angles correspond to planar areas of the uranyl selenite layers. - Graphical abstract: Crystal structures of the seven novel Se-contaning uranyl oxysalts that contain protonated organic molecules as interlayer species have been investigated from the viewpoints of topology of interpolyhedral linkages, isomeric variations and flexibility of structural units. - Highlights: • Single crystals of seven novel uranyl oxysalts were prepared by evaporation method. • The graph theory was used for investigation of topologies of structural units. • The method of orientation matrices was applied to distinguish geometrical isomers. • The flexibility of structural complexes specifies the undulation of layered structural units.« less

Unusual Versatility of the Filamentous, Diazotrophic Cyanobacterium Anabaena torulosa Revealed for Its Survival during Prolonged Uranium Exposure

PubMed Central

Chandwadkar, Pallavi; Nayak, Chandrani

2017-01-01

ABSTRACT Reports on interactions between cyanobacteria and uranyl carbonate are rare. Here, we present an interesting succession of the metabolic responses employed by a marine, filamentous, diazotrophic cyanobacterium, Anabaena torulosa for its survival following prolonged exposure to uranyl carbonate extending up to 384 h at pH 7.8 under phosphate-limited conditions. The cells sequestered uranium (U) within polyphosphates on initial exposure to 100 μM uranyl carbonate for 24 to 28 h. Further incubation until 120 h resulted in (i) significant degradation of cellular polyphosphates causing extensive chlorosis and cell lysis, (ii) akinete differentiation followed by (iii) extracellular uranyl precipitation. X-ray diffraction (XRD) analysis, fluorescence spectroscopy, X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopy established the identity of the bioprecipitated uranium as a U(VI) autunite-type mineral, which settled at the bottom of the vessel. Surprisingly, A. torulosa cells resurfaced as small green flakes typical of actively growing colonies on top of the test solutions within 192 to 240 h of U exposure. A consolidated investigation using kinetics, microscopy, and physiological and biochemical analyses suggested a role of inducible alkaline phosphatase activity of cell aggregates/akinetes in facilitating the germination of akinetes leading to substantial regeneration of A. torulosa by 384 h of uranyl incubation. The biomineralized uranium appeared to be stable following cell regeneration. Altogether, our results reveal novel insights into the survival mechanism adopted by A. torulosa to resist sustained uranium toxicity under phosphate-limited oxic conditions. IMPORTANCE Long-term effects of uranyl exposure in cyanobacteria under oxic phosphate-limited conditions have been inadequately explored. We conducted a comprehensive examination of the metabolic responses displayed by a marine cyanobacterium, Anabaena torulosa, to cope with prolonged exposure to uranyl carbonate at pH 7.8 under phosphate limitation. Our results highlight distinct adaptive mechanisms harbored by this cyanobacterium that enabled its natural regeneration following extensive cell lysis and uranium biomineralization under sustained uranium exposure. Such complex interactions between environmental microbes such as Anabaena torulosa and uranium over a broader time range advance our understanding on the impact of microbial processes on uranium biogeochemistry. PMID:28258135

Cellular distribution of uranium after acute exposure of renal epithelial cells: SEM, TEM and nuclear microscopy analysis

NASA Astrophysics Data System (ADS)

Carrière, Marie; Gouget, Barbara; Gallien, Jean-Paul; Avoscan, Laure; Gobin, Renée; Verbavatz, Jean-Marc; Khodja, Hicham

2005-04-01

The major health effect of uranium exposure has been reported to be chemical kidney toxicity, functional and histological damages being mainly observed in proximal tubule cells. Uranium enters the proximal tubule as uranyl-bicarbonate or uranyl-citrate complexes. The aim of our research is to investigate the mechanisms of uranium toxicity, intracellular accumulation and repartition after acute intoxication of rat renal proximal tubule epithelial cells, as a function of its chemical form. Microscopic observations of renal epithelial cells after acute exposure to uranyl-bicarbonate showing the presence of intracellular precipitates as thin needles of uranyl-phosphate localized in cell lysosomes have been published. However the initial site of precipitates formation has not been identified yet: they could either be formed outside the cells before internalization, or directly inside the cells. Uranium solubility as a function and initial concentration was specified by ICP-MS analysis of culture media. In parallel, uranium uptake and distribution in cell monolayers exposed to U-bicarbonate was investigated by nuclear microprobe analyses. Finally, the presence of uranium precipitates was tested out by scanning electron microscopic observations (SEM), while extracellular and/or intracellular precipitates were observed on thin sections of cells by transmission electron microscopy (TEM).

Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments.

PubMed

Stewart, Brandy D; Mayes, Melanie A; Fendorf, Scott

2010-02-01

Adsorption on soil and sediment solids may decrease aqueous uranium concentrations and limit its propensity for migration in natural and contaminated settings. Uranium adsorption will be controlled in large part by its aqueous speciation, with a particular dependence on the presence of dissolved calcium and carbonate. Here we quantify the impact of uranyl speciation on adsorption to both goethite and sediments from the Hanford Clastic Dike and Oak Ridge Melton Branch Ridgetop formations. Hanford sediments were preconditioned with sodium acetate and acetic acid to remove carbonate grains, and Ca and carbonate were reintroduced at defined levels to provide a range of aqueous uranyl species. U(VI) adsorption is directly linked to UO(2)(2+) speciation, with the extent of retention decreasing with formation of ternary uranyl-calcium-carbonato species. Adsorption isotherms under the conditions studied are linear, and K(d) values decrease from 48 to 17 L kg(-1) for goethite, from 64 to 29 L kg (-1) for Hanford sediments, and from 95 to 51 L kg(-1) for Melton Branch sediments as the Ca concentration increases from 0 to 1 mM at pH 7. Our observations reveal that, in carbonate-bearing waters, neutral to slightly acidic pH values ( approximately 5) and limited dissolved calcium are optimal for uranium adsorption.

Adsorption of Fe(II) and U(VI) to carboxyl-functionalized microspheres: The influence of speciation on uranyl reduction studied by titration and XAFS

NASA Astrophysics Data System (ADS)

Boyanov, Maxim I.; O'Loughlin, Edward J.; Roden, Eric E.; Fein, Jeremy B.; Kemner, Kenneth M.

2007-04-01

The chemical reduction of U(VI) by Fe(II) is a potentially important pathway for immobilization of uranium in subsurface environments. Although the presence of surfaces has been shown to catalyze the reaction between Fe(II) and U(VI) aqueous species, the mechanism(s) responsible for the enhanced reactivity remain ambiguous. To gain further insight into the U-Fe redox process at a complexing, non-conducting surface that is relevant to common organic phases in the environment, we studied suspensions containing combinations of 0.1 mM U(VI), 1.0 mM Fe(II), and 4.2 g/L carboxyl-functionalized polystyrene microspheres. Acid-base titrations were used to monitor protolytic reactions, and Fe K-edge and U L-edge X-ray absorption fine structure spectroscopy was used to determine the valence and atomic environment of the adsorbed Fe and U species. In the Fe + surface carboxyl system, a transition from monomeric to oligomeric Fe(II) surface species was observed between pH 7.5 and pH 8.4. In the U + surface carboxyl system, the U(VI) cation was adsorbed as a mononuclear uranyl-carboxyl complex at both pH 7.5 and 8.4. In the ternary U + Fe + surface carboxyl system, U(VI) was not reduced by the solvated or adsorbed Fe(II) at pH 7.5 over a 4-month period, whereas complete and rapid reduction to U(IV) nanoparticles occurred at pH 8.4. The U(IV) product reoxidized rapidly upon exposure to air, but it was stable over a 4-month period under anoxic conditions. Fe atoms were found in the local environment of the reduced U(IV) atoms at a distance of 3.56 Å. The U(IV)-Fe coordination is consistent with an inner-sphere electron transfer mechanism between the redox centers and involvement of Fe(II) atoms in both steps of the reduction from U(VI) to U(IV). The inability of Fe(II) to reduce U(VI) in solution and at pH 7.5 in the U + Fe + carboxyl system is explained by the formation of a transient, "dead-end" U(V)-Fe(III) complex that blocks the U(V) disproportionation pathway after the first electron transfer. The increased reactivity at pH 8.4 relative to pH 7.5 is explained by the reaction of U(VI) with an Fe(II) oligomer, whereby the bonds between Fe atoms facilitate the transfer of a second electron to the hypothetical U(V)-Fe(III) intermediate. We discuss how this mechanism may explain the commonly observed higher efficiency of uranyl reduction by adsorbed or structural Fe(II) relative to aqueous Fe(II).

Uranyl Ion Complexes with Long-Chain Aliphatic α,ω-Dicarboxylates and 3d-Block Metal Counterions.

PubMed

Thuéry, Pierre; Harrowfield, Jack

2016-03-07

Twelve new complexes were obtained from reaction of uranyl ions with the aliphatic dicarboxylic acids HOOC-(CH2)n-2-COOH (H2Cn; n = 7-10 and 12) under solvo-hydrothermal conditions, in the presence of 3d-block metal ions (Mn(2+), Fe(3+), Co(2+), Ni(2+), and Cu(2+)) and 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen). In contrast to previously reported triple-stranded helicates obtained with C9(2-) and C12(2-), all these complexes crystallize as polymeric one-dimensional (1D) or two-dimensional (2D) species. [Fe(bipy)3][(UO2)2(C7)3]·3H2O (1), [Cu(phen)2]2[(UO2)3(C7)4(H2O)2]·2H2O (2), and [Cu(bipy)2]2[(UO2)2(C9)3] (6), in which the 3d cation was reduced in situ, are 1D ladderlike polymers displaying tetra- or hexanuclear rings, of sufficient width to encompass two counterions in 2 and 6. The three complexes [Co(phen)3][(UO2)3(C8)3(O)]·H2O (3), [Ni(phen)3][(UO2)3(C8)3(O)]·H2O (4) and [Co(phen)3][(UO2)3(C9)3(O)]·H2O (5) contain bis(μ3-oxo)-bridged tetranuclear secondary building units, and they crystallize as deeply furrowed 2D assemblies. Depending on the nature of the counterion, C10(2-) gives [Ni(bipy)3][(UO2)2(C10)3]·2H2O (7), a 2D network displaying elongated decanuclear rings containing the counterions, or [Mn(phen)3][(UO2)2(C10)3]·6H2O (8), [Co(phen)3][(UO2)2(C10)3]·7H2O (9), and [Ni(phen)3][(UO2)2(C10)3]·7H2O (10), which consist of 2D assemblies with honeycomb topology; the hexanuclear rings in 8-10 are chairlike and occupied by one counterion and two uranyl groups from neighboring layers. Two complexes of the ligand with the longest chain, C12(2-), are reported. [UO2(C12)(bipy)] (11) is a neutral 1D species in which bipy chelates the uranyl ion and plays an important role in the packing through π-stacking interactions. Two polymeric units, 1D and 2D, coexist in the complex [Ni(bipy)3][(UO2)2(C12)3][UO2(C12)(H2O)2]·H2O (12); the 2D network has the honeycomb topology, but the hexanuclear rings are markedly convoluted, with local features akin to those in helicates, and the counterions are embedded in intralayer cavities. Emission spectra measured in the solid state show in most cases various degrees of quenching, with intense and well-resolved uranyl emission being observed only for complexes 2 and 11.

URANIUM RECOVERY PROCESS

DOEpatents

Hyman, H.H.; Dreher, J.L.

1959-07-01

The recovery of uranium from the acidic aqueous metal waste solutions resulting from the bismuth phosphate carrier precipitation of plutonium from solutions of neutron irradiated uranium is described. The waste solutions consist of phosphoric acid, sulfuric acid, and uranium as a uranyl salt, together with salts of the fission products normally associated with neutron irradiated uranium. Generally, the process of the invention involves the partial neutralization of the waste solution with sodium hydroxide, followed by conversion of the solution to a pH 11 by mixing therewith sufficient sodium carbonate. The resultant carbonate-complexed waste is contacted with a titanated silica gel and the adsorbent separated from the aqueous medium. The aqueous solution is then mixed with sufficient acetic acid to bring the pH of the aqueous medium to between 4 and 5, whereby sodium uranyl acetate is precipitated. The precipitate is dissolved in nitric acid and the resulting solution preferably provided with salting out agents. Uranyl nitrate is recovered from the solution by extraction with an ether such as diethyl ether.

PROCESS FOR RECOVERY OF URANIUM VALUES FROM IMPURE SOLUTIONS THEREOF

DOEpatents

Kilner, S.B.

1959-11-01

A process is presented for the recovery of uraninm values from impure solutions which are obtained, for example, by washing residual uranium salt or uranium metal deposits from stainless steel surfaces using an aqueous or certain acidic aqueous solutions. The solutions include uranyl and oxidized iron, chromium, nickel, and copper ions and may contain manganese, zinc, and silver ions. In accordance with one procedure. the uranyl ions are reduced to the uranous state, and the impurity ions are complexed with cyanide under acidic conditions. The solution is then treated with ammonium hydroxide or alkali metal hydroxide to precipitate uranous hydroxide away from the complexed impurity ions in the solution. Alternatively, an excess of alkali metal cyanide is added to the reduced solution until the solution becomes sufficiently alkaline for the uranons hydroxide to precipitate. An essential feature in operating the process is in maintaining the pH of the solution sufficiently acid during the complexing operation to prevent the precipitation of the impurity metal hydroxides.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, I-Ting; Sessler, Jonathan L.; Gambhir, Sanjiv Sam

Chemical tools that can report radioactive isotopes would be of interest to the defense community. Here in this paper we report –250 nm polymeric nanoparticles containing porphyrinoid macrocycles with and without pre-complexed depleted uranium and demonstrate that the latter species may be detected easily and with high sensitivity via photoacoustic imaging. The porphyrinoid macrocycles used in the present study are non-aromatic in the absence of the uranyl cation, but aromatic after cation complexation. We solubilized both the freebase and metalated forms of the macrocycles in poly(lactic-co-glycolic acid) and found a peak in the photoacoustic spectrum at 910 nm excitation inmore » the case of the uranyl complex. The signal was stable for at least 15 minutes and allowed detection of uranium concentrations down to 6.2 ppb (5.7 nM) in vitro and 0.57 ppm (19 fCi; 0.52 μM) in vivo. Furthermore, to the best of our knowledge, this is the first report of a nanoparticle that detects an actinide cation via photoacoustic imaging.« less

The geometric structures, vibrational frequencies and redox properties of the actinyl coordination complexes ([AnO2(L)n](m); An = U, Pu, Np; L = H2O, Cl-, CO3(2-), CH3CO2(-), OH-) in aqueous solution, studied by density functional theory methods.

PubMed

Austin, Jonathan P; Sundararajan, Mahesh; Vincent, Mark A; Hillier, Ian H

2009-08-14

The geometric and electronic structures of the aqua, chloro, acetato, hydroxo and carbonato complexes of U, Np and Pu in both their (VI) and (V) oxidation states, and in an aqueous environment, have been studied using density functional theory methods. We have obtained micro-solvated structures derived from molecular dynamics simulations and included the bulk solvent using a continuum model. We find that two different hydrogen bonding patterns involving the axial actinyl oxygen atoms are sometimes possible, and may give rise to different An-O bond lengths and vibrational frequencies. These alternative structures are reflected in the experimental An-O bond lengths of the aqua and carbonato complexes. The variation of the redox potential of the uranyl complexes with the different ligands has been studied using both BP86 and B3LYP functionals. The relative values for the four uranium complexes having anionic ligands are in surprisingly good agreement with experiment, although the absolute values are in error by approximately 1 eV. The absolute error for the aqua species is much less, leading to an incorrect order of the redox potentials of the aqua and chloro species.

F-element metalated dipyrrins: synthesis and characterization of a family of uranyl bis(dipyrrinate) complexes.

PubMed

Bolotaulo, Duer; Metta-Magaña, Alejandro; Fortier, Skye

2017-03-07

Using an improved, chromatography-free dipyrrin synthesis, the α,β-unsubstituted dipyrrins [RC(C 4 H 2 N) 2 H] (2) (R = tolyl (2toly l ), p-OMe-C 6 H 4 (2anis), mesityl (2mes), ferrocenyl (2Fc)) were isolated in good to excellent yields. Deprotonation of 2 with Na[N(SiMe 3 ) 2 ] gives the alkali metal salts [Na(DME) n ][RC(C 4 H 2 N) 2 ] (3) which reacts with UO 2 Cl 2 (THF) 3 to give the uranyl bis(dipyrrinates) UO 2 [RC(C 4 H 2 N) 2 ] 2 (L) (L = THF (4R-THF); DMAP (4R-DMAP)) (R = tolyl, p-OMe-C 6 H 4 , mesityl, ferrocenyl). The THF adducts, 4R-THF, are unstable in aromatic and nonpolar solvents and rapidly decompose to 2 and an intractable uranium-containing solid. On the other hand, the DMAP adducts, 4R-DMAP, are indefinitely stable in solution. The solid-state structures of 4R-THF and 4R-DMAP reveal distorted trigonal bipyramidal geometries. In the solid-state, the dipyrrinate ligands exhibit significant distortions including bowing and, in some instances, out-of-plane equatorial N-atom coordination, likely as a consequence of steric crowding and interligand repulsion. The complexes, 4R-DMAP, have been fully characterized by NMR, UV/Vis, and fluorescence spectroscopies, and their electrochemical properties have been investigated through cyclic voltammetry. The cyclic voltammograms of 4R-DMAP display several redox features but present a reversible wave at ca. -1.9 V (vs. Fc 0/+ ) attributable to a ligand centred reduction. Fluorescence measurements of all compounds reveal that only the mesityl derivatives 2mes, 3mes, and 4mes fluoresce with modest Stokes shift that ranges from ca. 30-70 nm, with 4mes displaying the greatest relative emission intensity.

Uranium(iii) complexes supported by hydrobis(mercaptoimidazolyl)borates: synthesis and oxidation chemistry.

PubMed

Maria, Leonor; Santos, Isabel C; Santos, Isabel

2018-05-23

The reaction of [UI3(thf)4] with the sodium or lithium salts of hydrobis(2-mercapto-1-methylimidazolyl)borate ligands ([H(R)B(timMe)2]-) in a 1 : 2 ratio, in tetrahydrofuran, gave the U(iii) complexes [UI{κ3-H,S,S'-H(R)B(timMe)2}2(thf)2] (R = H (1), Ph (2)) in good yields. Crystals of [UI{κ3-H,S,S'-H(Ph)B(timMe)2}2(thf)2] (2) were obtained by recrystallization from a tetrahydrofuran/acetonitrile solution, and the ion-separated uranium complex [U{κ3-H,S,S'-H(Ph)B(timMe)2}2(CH3CN)3][I] (3-I) was obtained by dissolution of 2 in acetonitrile followed by recrystallization. One-electron oxidation of 2 with AgBPh4 or I2 resulted in the formation of the cationic U(iv) complexes [U{κ3-H,S,S'-H(Ph)B(timMe)2}3][X] (X = BPh4 (6-BPh4), I (6-I)), due to a ligand redistribution process. These complexes are the first examples of homoleptic poly(azolyl)borate U(iv) complexes. Treatment of complex 2 with azobenzene led to the isolation of crystals of the U(iv) compound [UI{κ3-H(Ph)B(timMe)2}2(κ2-timMe)] (7). Treatment of 2 with pyridine-N oxide (pyNO) led to the formation of the uranyl complex [UO2{κ2-S,S'-H(Ph)B(timMe)2}2] (8) and of complex 6-I, while from the reaction of [U{κ3-H(Ph)B(timMe)2}2(thf)3][BPh4] (5) with pyNO, the oxo-bridged U(iv) complex [{U{κ3-H(Ph)B(timMe)2}2(pyNO)}2(μ-O)][BPh4]2 (9) was also obtained. In the U(iii) and U(iv) complexes, the bis(azolyl)borate ligands bind to the uranium center in a κ3-H,S,S' coordination mode, while in the U(vi) complex the ligands bind to the metal in a κ2-S,S' mode. The presence of UH-B interactions in the solid-state, for the nine-coordinate complexes 1, 2, 3, 6 and 7 and for the eight-coordinate complex 9, was supported by IR spectroscopy and/or X-ray diffraction analysis.

Incorporation of Uranium into Hematite during Crystallization from Ferrihydrite

PubMed Central

2014-01-01

Ferrihydrite was exposed to U(VI)-containing cement leachate (pH 10.5) and aged to induce crystallization of hematite. A combination of chemical extractions, TEM, and XAS techniques provided the first evidence that adsorbed U(VI) (≈3000 ppm) was incorporated into hematite during ferrihydrite aggregation and the early stages of crystallization, with continued uptake occurring during hematite ripening. Analysis of EXAFS and XANES data indicated that the U(VI) was incorporated into a distorted, octahedrally coordinated site replacing Fe(III). Fitting of the EXAFS showed the uranyl bonds lengthened from 1.81 to 1.87 Å, in contrast to previous studies that have suggested that the uranyl bond is lost altogether upon incorporation into hematite. The results of this study both provide a new mechanistic understanding of uranium incorporation into hematite and define the nature of the bonding environment of uranium within the mineral structure. Immobilization of U(VI) by incorporation into hematite has clear and important implications for limiting uranium migration in natural and engineered environments. PMID:24580024

RECOVERY OF URANIUM BY SECONDARY XANTHATE COMPLEXING

DOEpatents

Neville, O.K.

1959-09-01

A method is described for separating and recovering uranium values contained in an acidic aqueous solution together with thorium or protactinium values. In accordance with the invention, the acidic solution containing uranium in the uranyl form is contacted with an organic xanthate. The xanthate forms a urano-xanthate complex but is substantially non-reactive with thorium and protactinium. The urano-xanthate complex is recovered by organic solvent extraction.

[An electron microscopic study on the RNA component of synaptonemal complexes in spermatocytes of Mus musculus].

PubMed

Xing, M; Jing, D Z; Hao, S

1991-01-01

The ultrastructural and cytochemical features of synaptonemal complexes (SC) in sections of spermatocytes of Mus musculus were studied under electron microscope. In specimens stained with uranyl acetate and lead citrate the SC was found consisting of three main elements. the lateral element (LE), the central element (CE) and the transverse filament (L-C filament). When stained with the Bernhard's technique, the SC was recognized as a contrasted, tripartite structure which was usually located in the bleached area occupied by the condensed chromatin and composed of highly electron-dense LEs and medium electron-dense CE and L-C filaments. The SC and the LE, stained either by uranyl acetate-lead citrate or by the Bernhard's technique, always showed diameters of about 210 nm and 60 nm, respectively. The results suggest that RNA may be an important component of the SC.

A roadmap to uranium ionic liquids: anti-crystal engineering.

PubMed

Yaprak, Damla; Spielberg, Eike T; Bäcker, Tobias; Richter, Mark; Mallick, Bert; Klein, Axel; Mudring, Anja-Verena

2014-05-19

In the search for uranium-based ionic liquids, tris(N,N-dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1-butyl-3-methylimidazolium (C4mim) cation. As dithiocarbamate ligands binding to the UO2(2+) unit, tetra-, penta-, hexa-, and heptamethylenedithiocarbamates, N,N-diethyldithiocarbamate, N-methyl-N-propyldithiocarbamate, N-ethyl-N-propyldithiocarbamate, and N-methyl-N-butyldithiocarbamate have been explored. X-ray single-crystal diffraction allowed unambiguous structural characterization of all compounds except N-methyl-N-butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X-ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase-transition behavior depending on the N,N-dialkyldithiocarbamato ligand with the aim to establish structure-property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N-dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N-methyl-N-propyldithiocarbamato)uranylate, tris(N-ethyl-N-propyldithiocarbamato)uranylate, and tris(N-methyl-N-butyldithiocarbamato)uranylate, lead to the formation of (room-temperature) ionic liquids, which confirms that low-symmetry ions are indeed suitable to suppress crystallization. These materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stewart, B.D.; Mayes, Melanie; Fendorf, Scott

2010-01-01

Adsorption on soil and sediment solids may decrease aqueous uranium concentrations and limit its propensity for migration in natural and contaminated settings. Uranium adsorption will be controlled in large part by its aqueous speciation, with a particular dependence on the presence of dissolved calcium and carbonate. Here we quantify the impact of uranyl speciation on adsorption to both goethite and sediments from the Hanford Clastic Dike and Oak Ridge Melton Branch Ridgetop formations. Hanford sediments were preconditioned with sodium acetate and acetic acid to remove carbonate grains, and Ca and carbonate were reintroduced at defined levels to provide a rangemore » of aqueous uranyl species. U(VI) adsorption is directly linked to UO{sub 2}{sup 2+} speciation, with the extent of retention decreasing with formation of ternary uranyl-calcium-carbonato species. Adsorption isotherms under the conditions studied are linear, and K{sub d} values decrease from 48 to 17 L kg{sup -1} for goethite, from 64 to 29 L kg{sup -1} for Hanford sediments, and from 95 to 51 L kg{sup -1} for Melton Branch sediments as the Ca concentration increases from 0 to 1 mM at pH 7. Our observations reveal that, in carbonate-bearing waters, neutral to slightly acidic pH values ({approx}5) and limited dissolved calcium are optimal for uranium adsorption.« less

A roadmap to uranium ionic liquids: Anti-crystal engineering

DOE PAGES

Yaprak, Damla; Spielberg, Eike T.; Bäcker, Tobias; ...

2014-04-15

In the search for uranium-based ionic liquids, tris(N,N-dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1-butyl-3-methylimidazolium (C 4mim) cation. As dithiocarbamate ligands binding to the UO 2 2+ unit, tetra-, penta-, hexa-, and heptamethylenedithiocarbamates, N,N-diethyldithiocarbamate, N-methyl-N-propyldithiocarbamate, N-ethyl-N-propyldithiocarbamate, and N-methyl-N-butyldithiocarbamate have been explored. X-ray single-crystal diffraction allowed unambiguous structural characterization of all compounds except N-methyl-N-butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X-ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase-transition behavior depending on the N,N-dialkyldithiocarbamato ligand withmore » the aim to establish structure–property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N-dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N-methyl-N-propyldithiocarbamato)uranylate, tris(N-ethyl-N-propyldithiocarbamato)uranylate, and tris(N-methyl-N-butyldithiocarbamato)uranylate, lead to the formation of (room-temperature) ionic liquids, which confirms that low-symmetry ions are indeed suitable to suppress crystallization. As a result, these materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery.« less

Unusual Versatility of the Filamentous, Diazotrophic Cyanobacterium Anabaena torulosa Revealed for Its Survival during Prolonged Uranium Exposure.

PubMed

Acharya, Celin; Chandwadkar, Pallavi; Nayak, Chandrani

2017-05-01

Reports on interactions between cyanobacteria and uranyl carbonate are rare. Here, we present an interesting succession of the metabolic responses employed by a marine, filamentous, diazotrophic cyanobacterium, Anabaena torulosa for its survival following prolonged exposure to uranyl carbonate extending up to 384 h at pH 7.8 under phosphate-limited conditions. The cells sequestered uranium (U) within polyphosphates on initial exposure to 100 μM uranyl carbonate for 24 to 28 h. Further incubation until 120 h resulted in (i) significant degradation of cellular polyphosphates causing extensive chlorosis and cell lysis, (ii) akinete differentiation followed by (iii) extracellular uranyl precipitation. X-ray diffraction (XRD) analysis, fluorescence spectroscopy, X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopy established the identity of the bioprecipitated uranium as a U(VI) autunite-type mineral, which settled at the bottom of the vessel. Surprisingly, A. torulosa cells resurfaced as small green flakes typical of actively growing colonies on top of the test solutions within 192 to 240 h of U exposure. A consolidated investigation using kinetics, microscopy, and physiological and biochemical analyses suggested a role of inducible alkaline phosphatase activity of cell aggregates/akinetes in facilitating the germination of akinetes leading to substantial regeneration of A. torulosa by 384 h of uranyl incubation. The biomineralized uranium appeared to be stable following cell regeneration. Altogether, our results reveal novel insights into the survival mechanism adopted by A. torulosa to resist sustained uranium toxicity under phosphate-limited oxic conditions. IMPORTANCE Long-term effects of uranyl exposure in cyanobacteria under oxic phosphate-limited conditions have been inadequately explored. We conducted a comprehensive examination of the metabolic responses displayed by a marine cyanobacterium, Anabaena torulosa , to cope with prolonged exposure to uranyl carbonate at pH 7.8 under phosphate limitation. Our results highlight distinct adaptive mechanisms harbored by this cyanobacterium that enabled its natural regeneration following extensive cell lysis and uranium biomineralization under sustained uranium exposure. Such complex interactions between environmental microbes such as Anabaena torulosa and uranium over a broader time range advance our understanding on the impact of microbial processes on uranium biogeochemistry. Copyright © 2017 American Society for Microbiology.

ON THE REACTION OF COMPONENETS IN MeNO$sub 3$-UO$sub 2$(NO$sub 3$)$sub 2$- H$sub 2$O TYPE SYSTEMS (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yakimov, M.A.; Nosova, N.F.; Degtyarev, A.Ya.

1963-01-01

Solubility in ternary systems TlNO/sub 3/--UO/sub 2/(NO/sub 3/)/sub 2/-- H/sub 2/ O and CsNO/sub 3/--UO/sub 2/(NO/sub 3/)/sub 2/--H/sub 2/O at 0 to 25 c- C was studi ed by the isothermal method. The first system did not form solid phase compounds; the second system formed two compounds Cs/sub 2/UO/ sub 2/(NO/sub 3/)/sub 4/ and CsUO/sub 2/(NO/sub 3/)/sub 3/ at 25 c- and of water vapor pressure over the systems at 25 c- showed that water activity in the ternary systems at certain concentrations does not exceed the water activity in binary uranyl nitratewater system (at identical uranyl nitrate concentrations) confirmingmore » the observed complex formation in the solution. The mechanism of complex formation was analyzed and expanded for alkali metal - metal salt-complexing agent water systems. (R.V.J.)« less

Parts per billion detection of uranium with a porphyrinoid-containing nanoparticle and in vivo photoacoustic imaging

DOE PAGES

Ho, I-Ting; Sessler, Jonathan L.; Gambhir, Sanjiv Sam; ...

2015-04-01

Chemical tools that can report radioactive isotopes would be of interest to the defense community. Here in this paper we report –250 nm polymeric nanoparticles containing porphyrinoid macrocycles with and without pre-complexed depleted uranium and demonstrate that the latter species may be detected easily and with high sensitivity via photoacoustic imaging. The porphyrinoid macrocycles used in the present study are non-aromatic in the absence of the uranyl cation, but aromatic after cation complexation. We solubilized both the freebase and metalated forms of the macrocycles in poly(lactic-co-glycolic acid) and found a peak in the photoacoustic spectrum at 910 nm excitation inmore » the case of the uranyl complex. The signal was stable for at least 15 minutes and allowed detection of uranium concentrations down to 6.2 ppb (5.7 nM) in vitro and 0.57 ppm (19 fCi; 0.52 μM) in vivo. Furthermore, to the best of our knowledge, this is the first report of a nanoparticle that detects an actinide cation via photoacoustic imaging.« less

A spectroscopic study of uranyl speciation in chloride-bearing solutions at temperatures up to 250 °C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Migdisov, A. A.; Boukhalfa, H.; Timofeev, A.

The speciation of U in NaCl-bearing solutions at temperatures up to 250 °C and concentrations of NaCl up to 1.5 m has been investigated using an in situ spectroscopic technique. The recorded spectra permit us to identify the species present in the solutions as UO 2 2+, UO 2Cl +, and UO 2Cl 2°. UO 2Cl 3 - is also likely present at high temperatures and NaCl concentrations, but concentrations of this species are insufficient for derivation of the formation constants. No evidence was found for species of higher ligand (Cl-) number. Thermodynamic stability constants derived for these species showmore » fair agreement with published data for 25 °C, but differ significantly from those predicted by an earlier high-temperature study (Dargent et al., 2013), which suggested that UO 2Cl 4 2- and UO 2Cl 5 3- contribute significantly to the mass balance of uranyl chloride complexes, especially at high temperature. In contrast, our data suggest that the main uranyl-chloride complex present in aqueous solutions at T >150 °C and concentrations of NaCl relevant to natural hydrothermal systems is UO 2Cl 2°. The values of the logarithms of thermodynamic formation constants (β) for the reaction UO 2 2+ + Cl - = UO 2Cl + are 0.02, 0.25, 0.55, 1.09, 1.59, and 2.28 derived at 25, 50, 100, 150, 200, and 250 °C, respectively. For the reaction UO 2 2+ + 2Cl - = UO 2Cl 2° the values of log β derived at these temperatures are 0.4, 0.58, 0.74, 1.44, 2.18, and 3.42. Values of the formation constant estimated for uranyl-chloride species predict the high concentrations of U observed by Richard et al. (2011) in fluid inclusions of the giant McArthur River unconformity-type uranium deposit.« less

A spectroscopic study of uranyl speciation in chloride-bearing solutions at temperatures up to 250 °C

DOE PAGES

Migdisov, A. A.; Boukhalfa, H.; Timofeev, A.; ...

2017-10-24

The speciation of U in NaCl-bearing solutions at temperatures up to 250 °C and concentrations of NaCl up to 1.5 m has been investigated using an in situ spectroscopic technique. The recorded spectra permit us to identify the species present in the solutions as UO 2 2+, UO 2Cl +, and UO 2Cl 2°. UO 2Cl 3 - is also likely present at high temperatures and NaCl concentrations, but concentrations of this species are insufficient for derivation of the formation constants. No evidence was found for species of higher ligand (Cl-) number. Thermodynamic stability constants derived for these species showmore » fair agreement with published data for 25 °C, but differ significantly from those predicted by an earlier high-temperature study (Dargent et al., 2013), which suggested that UO 2Cl 4 2- and UO 2Cl 5 3- contribute significantly to the mass balance of uranyl chloride complexes, especially at high temperature. In contrast, our data suggest that the main uranyl-chloride complex present in aqueous solutions at T >150 °C and concentrations of NaCl relevant to natural hydrothermal systems is UO 2Cl 2°. The values of the logarithms of thermodynamic formation constants (β) for the reaction UO 2 2+ + Cl - = UO 2Cl + are 0.02, 0.25, 0.55, 1.09, 1.59, and 2.28 derived at 25, 50, 100, 150, 200, and 250 °C, respectively. For the reaction UO 2 2+ + 2Cl - = UO 2Cl 2° the values of log β derived at these temperatures are 0.4, 0.58, 0.74, 1.44, 2.18, and 3.42. Values of the formation constant estimated for uranyl-chloride species predict the high concentrations of U observed by Richard et al. (2011) in fluid inclusions of the giant McArthur River unconformity-type uranium deposit.« less

A spectroscopic study of uranyl speciation in chloride-bearing solutions at temperatures up to 250 °C

NASA Astrophysics Data System (ADS)

Migdisov, A. A.; Boukhalfa, H.; Timofeev, A.; Runde, W.; Roback, R.; Williams-Jones, A. E.

2018-02-01

The speciation of U in NaCl-bearing solutions at temperatures up to 250 °C and concentrations of NaCl up to 1.5 m has been investigated using an in situ spectroscopic technique. The recorded spectra permit us to identify the species present in the solutions as UO22+, UO2Cl+, and UO2Cl2°. UO2Cl3- is also likely present at high temperatures and NaCl concentrations, but concentrations of this species are insufficient for derivation of the formation constants. No evidence was found for species of higher ligand (Cl-) number. Thermodynamic stability constants derived for these species show fair agreement with published data for 25 °C, but differ significantly from those predicted by an earlier high-temperature study (Dargent et al., 2013), which suggested that UO2Cl42- and UO2Cl53- contribute significantly to the mass balance of uranyl chloride complexes, especially at high temperature. In contrast, our data suggest that the main uranyl-chloride complex present in aqueous solutions at T > 150 °C and concentrations of NaCl relevant to natural hydrothermal systems is UO2Cl2°. The values of the logarithms of thermodynamic formation constants (β) for the reaction UO22+ + Cl- = UO2Cl+ are 0.02, 0.25, 0.55, 1.09, 1.59, and 2.28 derived at 25, 50, 100, 150, 200, and 250 °C, respectively. For the reaction UO22+ + 2Cl- = UO2Cl2° the values of log β derived at these temperatures are 0.4, 0.58, 0.74, 1.44, 2.18, and 3.42. Values of the formation constant estimated for uranyl-chloride species predict the high concentrations of U observed by Richard et al. (2011) in fluid inclusions of the giant McArthur River unconformity-type uranium deposit.

Selective Se-for-S substitution in Cs-bearing uranyl compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gurzhiy, Vladislav V., E-mail: vladgeo17@mail.ru; Tyumentseva, Olga S.; Krivovichev, Sergey V.

Phase formation in the mixed sulfate-selenate aqueous system of uranyl nitrate and cesium nitrate has been investigated. Two types of crystalline compounds have been obtained and characterized using a number of experimental (single crystal XRD, FTIR, SEM) and theoretical (information-based complexity calculations, topological analysis) techniques. No miscibility gaps have been observed for Cs{sub 2}[(UO{sub 2}){sub 2}(TO{sub 4}){sub 3}] (T= S, Se), which crystallizes in tetragonal system, P-42{sub 1}m, a =9.616(1)–9.856(2), c =8.105(1)–8.159(1) Å, V =749.6(2)–792.5(3) Å{sup 3}. Nine phases with variable amount of S and Se have been structurally characterized. The structures of the Cs{sub 2}[(UO{sub 2}){sub 2}(TO{sub 4}){sub 3}]more » (T= S, Se) compounds are based upon the [(UO{sub 2}){sub 2}(TO{sub 4}){sub 3}]{sup 2-} layers of corner-sharing uranyl pentagonal bipyramids and TO{sub 4} tetrahedra. The layers contain two types of tetrahedral sites: T1 (3-connected, i.e. having three O atoms shared by adjacent uranyl polyhedra) and T2 (4-connected). The Se-for-S substitution in tetrahedral sites is highly selective with smaller S{sup 6+} cation showing a strong preference for the more tightly bonded T2 site. Crystallization in the pure Se system starts with the formation of Cs{sub 2}[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)](H{sub 2}O) crystals, its subsequent dissolution and formation of Cs{sub 2}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}]. The information-based structural complexity calculations for these two phases support the rule that more topologically complex structures form at the latest stages of crystallization. - Graphical abstract: Nine phases representing the Cs{sub 2}[(UO{sub 2}){sub 2}(TO{sub 4}){sub 3}] (T= S, Se) solid solution series with variable amount of S and Se have been prepared by isothermal evaporation from aqueous solutions and characterized using a number of experimental and theoretical techniques. No immiscibility is observed between the pure sulfate and selenate compounds. The Se-for-S substitution in tetrahedral sites is highly selective with smaller S{sup 6+} cation showing a strong preference for the more tightly bonded 4-connected site. - Highlights: • Single crystals of novel mixed sulfate-selenate uranyl oxysalts were prepared by evaporation method. • Topological analysis and information-based complexity calculations were used for structure description. • The selective Se-for-S substitution was observed. • Evolution of phase formation in the aqueous Cs{sup +}–UO{sub 2}{sup 2+}–SO{sub 4}{sup 2–}–SeO{sub 4}{sup 2–} system was analyzed.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilgrim, Corey D.; Zavarin, Mavrik; Casey, William H.

Here, the rates of ligand exchange into the geochemically important [NpO 2(CO 3) 3] 4– aqueous complex are measured as a function of pressure in order to complement existing data on the isostructural [UO 2(CO 3) 3] 4– complex. Experiments are conducted at pH conditions where the rate of exchange is independent of the proton concentration. Unexpectedly, the experiments show a distinct difference in the pressure dependencies of rates of exchange for the uranyl and neptunyl complexes.

Micro-SHINE Uranyl Sulfate Irradiations at the Linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Youker, Amanda J.; Kalensky, Michael; Chemerisov, Sergey

2016-08-01

Peroxide formation due to water radiolysis in a uranyl sulfate solution is a concern for the SHINE Medical Technologies process in which Mo-99 is generated from the fission of dissolved low enriched uranium. To investigate the effects of power density and fission on peroxide formation and uranyl-peroxide precipitation, uranyl sulfate solutions were irradiated using a 50-MeV electron linac as part of the micro-SHINE experimental setup. Results are given for uranyl sulfate solutions with both high and low enriched uranium irradiated at different linac powers.

Determination of uranyl incorporation into biogenic manganese oxides using X-ray absorption spectroscopy and scattering

USGS Publications Warehouse

Webb, S.M.; Fuller, C.C.; Tebo, B.M.; Bargar, J.R.

2006-01-01

Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO22+ (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (2 mol % U, >4 ??M U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. ?? 2006 American Chemical Society.

The U(VI) speciation influenced by a novel Paenibacillus isolate from Mont Terri Opalinus clay.

PubMed

Lütke, Laura; Moll, Henry; Bachvarova, Velina; Selenska-Pobell, Sonja; Bernhard, Gert

2013-05-21

Bacterial cell walls have a high density of ionizable functional groups available for U(VI) binding, hence have a great potential to affect the speciation of this contaminant in the environment. The studied strain of the genus Paenibacillus is a novel isolate originating from the Mont Terri Opalinus clay formations (Switzerland) which are currently investigated as a potential host rock for future nuclear waste storage. U(VI) binding to the cell surface functional groups was studied by potentiometry combined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). Four bacterial U(VI) surface complexes were identified: R-COO-UO2(+), R-O-PO3-UO2, R-O-PO3H-UO2(+), and (R-O-PO3)2-UO2(2-). The corresponding complex stability constants were calculated to be 5.33 ± 0.08, 8.89 ± 0.04, 12.92 ± 0.05, and 13.62 ± 0.08, respectively. Hence UO2(2+) displays a moderate to strong interaction with the bacterial surface functional groups. In the acidic pH range (pH 3) UO2(2+) binding onto the cell envelope is governed by coordination to hydrogen phosphoryl sites. Upon increasing the pH an increasing coordination of UO2(2+) to carboxylic and deprotonated phosphoryl sites was found. At a pH greater than 7 uranyl hydroxides dominate the speciation. Additionally the bacteria-mediated release of inorganic phosphate in dependence on [U(VI)] at different pH values was studied to assess the influence of phosphate release on U(VI) mobilization.

Preparation, characterization and cytotoxicity studies of some transition metal complexes with ofloxacin and 1,10-phenanthroline mixed ligand

NASA Astrophysics Data System (ADS)

Sadeek, S. A.; El-Hamid, S. M. Abd

2016-10-01

[Zn(Ofl)(Phen)(H2O)2](CH3COO)·2H2O (1), [ZrO(Ofl)(Phen)(H2O)]NO3·2H2O (2) and [UO2(Ofl)(Phen)(H2O)](CH3COO)·H2O (3) complexes of fluoroquinolone antibacterial agent ofloxacin (HOfl), containing a nitrogen donor heterocyclic ligand, 1,10-phenathroline monohydrate (Phen), were prepared and their structures were established with the help of elemental analysis, molar conductance, magnetic properties, thermal studies and different spectroscopic studies like IR, UV-Vis., 1H NMR and Mass. The IR data of HOfl and Phen ligands suggested the existing of a bidentate binding involving carboxylate O and pyridone O for HOfl ligand and two pyridine N atoms for Phen ligand. The coordination geometries and electronic structures are determined from electronic absorption spectra and magnetic moment measurements. From molar conductance studies reveals that metal complexes are electrolytes and of 1:1 type. The calculated bond length and force constant, F(Udbnd O), in the uranyl complex are 1.751 Å and 641.04 Nm-1. The thermal properties of the complexes were investigated by thermogravimetry (TGA) technique. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. Antimicrobial activity of the compounds was evaluated against some bacteria and fungi species. The activity data show that most metal complexes have antibacterial activity than that of the parent HOfl drug. The in vitro cytotoxicities of ligands and their complexes were also evaluated against human breast and colon carcinoma cells.

Uranium(VI) Scavenging by Amorphous Iron Phosphate Encrusting Sphaerotilus natans Filaments.

PubMed

Seder-Colomina, Marina; Morin, Guillaume; Brest, Jessica; Ona-Nguema, Georges; Gordien, Nilka; Pernelle, Jean-Jacques; Banerjee, Dipanjan; Mathon, Olivier; Esposito, Giovanni; van Hullebusch, Eric D

2015-12-15

U(VI) sorption to iron oxyhydroxides, precipitation of phosphate minerals, as well as biosorption on bacterial biomass are among the most reported processes able to scavenge U(VI) under oxidizing conditions. Although phosphates significantly influence bacterially mediated as well as iron oxyhydroxide mediated scavenging of uranium, the sorption or coprecipitation of U(VI) with poorly crystalline nanosized iron phosphates has been scarcely documented, especially in the presence of microorganisms. Here we show that dissolved U(VI) can be bound to amorphous iron phosphate during their deposition on Sphaerotilus natans filamentous bacteria. Uranium LIII-edge EXAFS analysis reveals that the adsorbed uranyl ions share an equatorial oxygen atom with a phosphate tetrahedron of the amorphous iron phosphate, with a characteristic U-P distance of 3.6 Å. In addition, the uranyl ions are connected to FeO6 octahedra with U-Fe distances at ~3.4 Å and at ~4.0 Å. The shortest U-Fe distance corresponds to a bidentate edge-sharing complex often reported for uranyl adsorption onto iron oxyhydroxides, whereas the longest U-Fe and U-P distances can be interpreted as a bidentate corner-sharing complex, in which two adjacent equatorial oxygen atoms are shared with the vertices of a FeO6 octahedron and of a phosphate tetrahedron. Furthermore, based on these sorption reactions, we demonstrate the ability of an attached S. natans biofilm to remove uranium from solution without any filtration step.

U(VI) uranyl cation-cation interactions in framework germanates.

PubMed

Morrison, Jessica M; Moore-Shay, Laura J; Burns, Peter C

2011-03-21

The isomorphous compounds NH(4)[(UO(6))(2)(UO(2))(9)(GeO(4))(GeO(3)(OH))] (1), K[(UO(6))(2)(UO(2))(9)(GeO(4))(GeO(3)(OH))] (2), Li(3)O[(UO(6))(2)(UO(2))(9)(GeO(4))(GeO(3)(OH))] (3), and Ba[(UO(6))(2)(UO(2))(9)(GeO(4))(2)] (4) were synthesized by hydrothermal reaction at 220 °C. The structures were determined using single crystal X-ray diffraction and refined to R(1) = 0.0349 (1), 0.0232 (2), 0.0236 (3), 0.0267 (4). Each are trigonal, P(3)1c. 1: a = 10.2525(5), c = 17.3972(13), V = 1583.69(16) Å(3), Z = 2; 2: a = 10.226(4), c = 17.150(9), V = 1553.1(12) Å(3), Z = 2; 3: a = 10.2668(5), c = 17.0558(11), V = 1556.94(15) Å(3), Z = 2; 4: a = 10.2012(5), c = 17.1570(12), V = 1546.23(15) Å(3), Z = 2. There are three symmetrically independent U sites in each structure, two of which correspond to typical (UO(2))(2+) uranyl ions and the other of which is octahedrally coordinated by six O atoms. One of the uranyl ions donates a cation-cation interaction, and accepts a different cation-cation interaction. The linkages between the U-centered polyhedra result in a relatively dense three-dimensional framework. Ge and low-valence sites are located within cavities in the framework of U-polyhedra. Chemical, thermal, and spectroscopic characterizations are provided.

Cleaving Off Uranyl Oxygens through Chelation: A Mechanistic Study in the Gas Phase

DOE PAGES

Abergel, Rebecca J.; de Jong, Wibe A.; Deblonde, Gauthier J. -P.; ...

2017-10-11

Recent efforts to activate the strong uranium-oxygen bonds in the dioxo uranyl cation have been limited to single oxo-group activation through either uranyl reduction and functionalization in solution, or by collision induced dissociation (CID) in the gas-phase, using mass spectrometry (MS). Here, we report and investigate the surprising double activation of uranyl by an organic ligand, 3,4,3-LI(CAM), leading to the formation of a formal U 6+ chelate in the gas-phase. The cleavage of both uranyl oxo bonds was experimentally evidence d by CID, using deuterium and 18O isotopic substitutions, and by infrared multiple photon dissociation (IRMPD) spectroscopy. Density functional theorymore » (DFT) computations predict that the overall reaction requires only 132 kJ/mol, with the first oxygen activation entailing about 107 kJ/mol. Here, combined with analysis of similar, but unreactive ligands, these results shed light on the chelation-driven mechanism of uranyl oxo bond cleavage, demonstrating its dependence on the presence of ligand hydroxyl protons available for direct interactions with the uranyl oxygens.« less

EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS

DOEpatents

Furman, N.H.; Mundy, R.J.

1957-12-10

An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

Synthesis and SMM behaviour of trinuclear versus dinuclear 3d-5f uranyl(v)-cobalt(ii) cation-cation complexes.

PubMed

Chatelain, Lucile; Tuna, Floriana; Pécaut, Jacques; Mazzanti, Marinella

2017-05-02

Trinuclear versus dinuclear heterodimetallic U V O 2 + Co 2+ complexes were selectively assembled via a cation-cation interaction by tuning the ligand. The trimeric complex 2, with a linear [Co-O[double bond, length as m-dash]U[double bond, length as m-dash]O-Co] core, exhibits magnetic exchange and slow relaxation with a reversal barrier of 30.5 ± 0.9 K providing the first example of a U-Co exchange-coupled SMM.

Production and Characterization of Desmalonichrome Relative Binding Affinity for Uranyl Ions in Relation to Other Siderophores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mo, Kai-For; Dai, Ziyu; Wunschel, David S.

2016-06-24

Siderophores are Fe binding secondary metabolites that have been investigated for their uranium binding properties. Much of the previous work has focused on characterizing hydroxamate types of siderophores, such as desferrioxamine B, for their uranyl binding affinity. Carboxylate forms of these metabolites hold potential to be more efficient chelators of uranyl, yet they have not been widely studied and are more difficult to obtain. Desmalonichrome is a carboxylate siderophore which is not commercially available and so was obtained from the ascomycete fungus Fusarium oxysporum cultivated under Fe depleted conditions. The relative affinity for uranyl binding of desmalonichrome was investigated usingmore » a competitive analysis of binding affinities between uranyl acetate and different concentrations of iron(III) chloride using electrospray ionization mass spectrometry (ESI-MS). In addition to desmalonichrome, three other siderophores, including two hydroxamates (desferrioxamine B and desferrichrome) and one carboxylate (desferrichrome A) were studied to understand their relative affinities for the uranyl ion at two pH values. The binding affinities of hydroxymate siderophores to uranyl ion were found to decrease to a greater degree at lower pH as the concentration of Fe (III) ion increases. On the other hand, lowering pH has little impact on the binding affinities between carboxylate siderophores and uranyl ion. Desmalonichrome was shown to have the greatest relative affinity for uranyl at any pH and Fe(III) concentration. These results suggest that acidic functional groups in the ligands are critical for strong chelation with uranium at lower pH.« less

URANIUM PURIFICATION PROCESS

DOEpatents

Ruhoff, J.R.; Winters, C.E.

1957-11-12

A process is described for the purification of uranyl nitrate by an extraction process. A solution is formed consisting of uranyl nitrate, together with the associated impurities arising from the HNO/sub 3/ leaching of the ore, in an organic solvent such as ether. If this were back extracted with water to remove the impurities, large quantities of uranyl nitrate will also be extracted and lost. To prevent this, the impure organic solution is extracted with small amounts of saturated aqueous solutions of uranyl nitrate thereby effectively accomplishing the removal of impurities while not allowing any further extraction of the uranyl nitrate from the organic solvent. After the impurities have been removed, the uranium values are extracted with large quantities of water.

A Solution-Based Approach for Mo-99 Production: Considerations for Nitrate versus Sulfate Media

DOE PAGES

Youker, Amanda J.; Chemerisov, Sergey D.; Kalensky, Michael; ...

2013-01-01

Molybdenum-99 is the parent of Technetium-99m, which is used in nearly 80% of all nuclear medicine procedures. The medical community has been plagued by Mo-99 shortages due to aging reactors, such as the NRU (National Research Universal) reactor in Canada. There are currently no US producers of Mo-99, and NRU is scheduled for shutdown in 2016, which means that another Mo-99 shortage is imminent unless a potential domestic Mo-99 producer fills the void. Argonne National Laboratory is assisting two potential domestic suppliers of Mo-99 by examining the effects of a uranyl nitrate versus a uranyl sulfate target solution configuration onmore » Mo-99 production. Uranyl nitrate solutions are easier to prepare and do not generate detectable amounts of peroxide upon irradiation, but a high radiation field can lead to a large increase in pH, which can lead to the precipitation of fission products and uranyl hydroxides. Uranyl sulfate solutions are more difficult to prepare, and enough peroxide is generated during irradiation to cause precipitation of uranyl peroxide, but this can be prevented by adding a catalyst to the solution. A titania sorbent can be used to recover Mo-99 from a highly concentrated uranyl nitrate or uranyl sulfate solution; however, different approaches must be taken to prevent precipitation during Mo-99 production.« less

Partitioning of uranyl between ferrihydrite and humic substances at acidic and circum-neutral pH

DOE PAGES

Dublet, Gabrielle; Lezama Pacheco, Juan; Bargar, John R.; ...

2017-07-14

As part of a larger study of the reactivity and mobility of uranyl (U(VI)O 2 2+) cations in subsurface environments containing natural organic matter (NOM) and hydrous ferric oxides, we have examined the effect of reference humic and fulvic substances on the sorption of uranyl on 2-line ferrihydrite (Fh), a common, naturally occurring nano-Fe(III)-hydroxide. Uranyl was reacted with Fh at pH 4.6 and 7.0 in the presence and absence of Elliott Soil Humic Acid (ESHA) (0–835 ppm) or Suwanee River Fulvic Acid (SRFA) (0–955 ppm). Here, no evidence was found for reduction of uranyl by either form of NOM aftermore » 24 h of exposure.« less

Partitioning of uranyl between ferrihydrite and humic substances at acidic and circum-neutral pH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dublet, Gabrielle; Lezama Pacheco, Juan; Bargar, John R.

As part of a larger study of the reactivity and mobility of uranyl (U(VI)O 2 2+) cations in subsurface environments containing natural organic matter (NOM) and hydrous ferric oxides, we have examined the effect of reference humic and fulvic substances on the sorption of uranyl on 2-line ferrihydrite (Fh), a common, naturally occurring nano-Fe(III)-hydroxide. Uranyl was reacted with Fh at pH 4.6 and 7.0 in the presence and absence of Elliott Soil Humic Acid (ESHA) (0–835 ppm) or Suwanee River Fulvic Acid (SRFA) (0–955 ppm). Here, no evidence was found for reduction of uranyl by either form of NOM aftermore » 24 h of exposure.« less

Uranyl interaction with the hydrated (001) basal face of gibbsite: a combined theoretical and spectroscopic study.

PubMed

Veilly, Edouard; Roques, Jérôme; Jodin-Caumon, Marie-Camille; Humbert, Bernard; Drot, Romuald; Simoni, Eric

2008-12-28

The sorption of uranyl cations and water molecules on the basal (001) face of gibbsite was studied by combining vibrational and fluorescence spectroscopies together with density functional theory (DFT) computations. Both the calculated and experimental values of O-H bond lengths for the gibbsite bulk are in good agreement. In the second part, water sorption with this surface was studied to take into account the influence of hydration with respect to the uranyl adsorption. The computed water configurations agreed with previously published molecular dynamics studies. The uranyl adsorption in acidic media was followed by time-resolved laser-induced fluorescence spectroscopy and Raman spectrometry measurements. The existence of only one kind of adsorption site for the uranyl cation was then indicated in good agreement with the DFT calculations. The computation of the uranyl adsorption has been performed by means of a bidentate interaction with two surface oxygen atoms. The optimized structures displayed strong hydrogen bonds between the surface and the -yl oxygen of uranyl. The uranium-surface bond strength depends on the protonation state of the surface oxygen atoms. The calculated U-O(surface) bond lengths range between 2.1-2.2 and 2.6-2.7 A for the nonprotonated and protonated surface O atoms, respectively.

PROCESS FOR THE SEPARATION OF HEAVY METALS

DOEpatents

Gofman, J.W.; Connick, R.E.; Wahl, A.C.

1959-01-27

A method is presented for thc separation of plutonium from uranium and the fission products with which it is associated. The method is based on the fact that hexavalent plutonium forms an insoluble complex precipitate with sodium acetate, as does the uranyl ion, while reduced plutonium is not precipitated by sodium acetate. Several embodiments are shown, e.g., a solution containing plutonium and uranium in the hexavalent state may be contacted with sodium acetate causing the formation of a sodium uranyl acetate precipitate which carries the plutonium values while the fission products remain in solution. If the original solution is treated with a reducing agent, so that the plutonium is reduced while the uranium remains in the hexavalent state, and sodium and acetate ions are added, the uranium will precipitutc while the plutonium remains in solution effecting separation of the Pu from urarium.

Scale-Dependent Rates of Uranyl Surface Complexation Reaction in Sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chongxuan; Shang, Jianying; Kerisit, Sebastien N.

Scale-dependency of uranyl[U(VI)] surface complexation rates was investigated in stirred flow-cell and column systems using a U(VI)-contaminated sediment from the US Department of Energy, Hanford site, WA. The experimental results were used to estimate the apparent rate of U(VI) surface complexation at the grain-scale and in porous media. Numerical simulations using molecular, pore-scale, and continuum models were performed to provide insights into and to estimate the rate constants of U(VI) surface complexation at the different scales. The results showed that the grain-scale rate constant of U(VI) surface complexation was over 3 to 10 orders of magnitude smaller, dependent on themore » temporal scale, than the rate constant calculated using the molecular simulations. The grain-scale rate was faster initially and slower with time, showing the temporal scale-dependency. The largest rate constant at the grain-scale decreased additional 2 orders of magnitude when the rate was scaled to the porous media in the column. The scaling effect from the grain-scale to the porous media became less important for the slower sorption sites. Pore-scale simulations revealed the importance of coupled mass transport and reactions in both intragranular and inter-granular domains, which caused both spatial and temporal dependence of U(VI) surface complexation rates in the sediment. Pore-scale simulations also revealed a new rate-limiting mechanism in the intragranular porous domains that the rate of coupled diffusion and surface complexation reaction was slower than either process alone. The results provided important implications for developing models to scale geochemical/biogeochemical reactions.« less

Pressure dependence of carbonate exchange with [NpO 2(CO 3) 3] 4– in aqueous solutions

DOE PAGES

Pilgrim, Corey D.; Zavarin, Mavrik; Casey, William H.

2016-12-13

Here, the rates of ligand exchange into the geochemically important [NpO 2(CO 3) 3] 4– aqueous complex are measured as a function of pressure in order to complement existing data on the isostructural [UO 2(CO 3) 3] 4– complex. Experiments are conducted at pH conditions where the rate of exchange is independent of the proton concentration. Unexpectedly, the experiments show a distinct difference in the pressure dependencies of rates of exchange for the uranyl and neptunyl complexes.

METAL PHTHALOCYANINES

DOEpatents

Frigerio, N.A.

1962-03-27

A process is given for preparing heavy metal phthalocyanines, sulfonated or not. The process comprises mixing an inorganic metal salt with dimethyl formamide or methyl sulfoxide; separating the metal complex formed from the solution; mixing the complex with an equimolar amount of sodium, potassium, lithium, magnesium, or beryllium sulfonated or unsulfonated phthalocyanine whereby heavy-metal phthalocyanine crystals are formed; and separating the crystals from the solution. Uranyl, thorium, lead, hafnium, and lanthanide rare earth phthalocyanines can be produced by the process. (AEC)

Preparation of U.sub.3 O.sub.8

DOEpatents

Johnson, David R.

1980-01-01

A method is described for the preparation of U.sub.3 O.sub.8 nuclear fuel material by direct precipitation of uranyl formate monohydrate from uranyl nitrate solution. The uranyl formate monohydrate precipitate is removed, dried and calcined to produce U.sub.3 O.sub.8 having a controlled particle size distribution.

Structure and Reactivity of X-ray Amorphous Uranyl Peroxide, U 2O 7

DOE PAGES

Odoh, Samuel O.; Shamblin, Jacob; Colla, Christopher A.; ...

2016-03-14

Recent accidents resulting in worker injury and radioactive contamination occurred due to pressurization of uranium yellowcake drums produced in the western USA. The drums contained an unexpected X-ray amorphous reactive form of uranium oxide, U 2O7. Heating hydrated uranyl peroxides produced during in situ mining unintentionally produced U 2O 7. It is a hygroscopic anhydrous uranyl peroxide that reacts rapidly with water to release O 2 gas and form metaschoepite, a uranyl-oxide hydrate. Quantum chemical calculations indicate that the most stable U 2O 7 conformer consists of two bent (UO 2) 2+ uranyl ions bridged by a peroxide group bidentatemore » 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. The reactivity of U 2O 7 in water and with water in air is much higher than other uranium oxides, and this can be both hazardous and potentially advantageous in the nuclear fuel cycle.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

WANG,YIFENG; XU,HUIFANG

Correctly identifying the possible alteration products and accurately predicting their occurrence in a repository-relevant environment are the key for the source-term calculation in a repository performance assessment. Uraninite in uranium deposits has long been used as a natural analog to spent fuel in a repository because of their chemical and structural similarity. In this paper, a SEM/AEM investigation has been conducted on a partially alternated uraninite sample from a uranium ore deposit of Shinkolobwe of Congo. The mineral formation sequences were identified: uraninite {yields} uranyl hydrates {yields} uranyl silicates {yields} Ca-uranyl silicates or uraninite {yields} uranyl silicates {yields} Ca-uranyl silicates.more » Reaction-path calculations were conducted for the oxidative dissolution of spent fuel in a representative Yucca Mountain groundwater. The predicted sequence is in general consistent with the SEM observations. The calculations also show that uranium carbonate minerals are unlikely to become major solubility-controlling mineral phases in a Yucca Mountain environment. Some discrepancies between model predictions and field observations are observed. Those discrepancies may result from poorly constrained thermodynamic data for uranyl silicate minerals.« less

Uranyl sulfate irradiations at the Van de Graaff: A means to combat uranyl peroxide precipitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Youker, Amanda J.; Kalensky, Michael; Quigley, Kevin J.

As part of an effort to support SHINE Medical Technologies in developing a process to produce Mo-99 by neutron-induced fission, a series of irradiation experiments was performed with a 3 MeV Van de Graaff accelerator to generate high radiation doses in 0.5–2 mL uranyl sulfate solutions. The purpose was to determine what conditions result in uranyl peroxide precipitation and what can be done to prevent its formation. The effects of temperature, dose rate, uranium concentration, and the addition of known catalysts for the destruction of peroxide were determined.

Structural evolution of a uranyl peroxide nano-cage fullerene: U60, at elevated pressures

NASA Astrophysics Data System (ADS)

Turner, K. M.; Lin, Y.; Zhang, F.; McGrail, B.; Burns, P. C.; Mao, W. L.; Ewing, R. C.

2015-12-01

U60 is a uranyl peroxide nano-cage that adopts a highly symmetric fullerene topology; it is topologically identical to C60. Several studies on the aqueous-phase of U60 clusters, [UO2(O2)(OH)]6060-, have shown its persistence in complex solutions and over lengthy time scales. Peroxide enhances corrosion of nuclear fuel in a reactor accident-uranyl peroxides often form near contaminated sites. U60 (Fm-3) crystallizes with approximate formula: Li68K12(OH)20[UO2(O2)(OH)]60(H2O)310. Here, we have used the diamond anvil cell (DAC) to examine U60 to understand the stability of this cluster at high pressures. We used a symmetric DAC with 300 μm culet diamonds and two different pressure-transmitting media: a mixture of methanol+ethanol and silicone oil. Using a combination of in situ Raman spectroscopy and synchrotron XRD, and electrospray ionization mass spectroscopy (ESI-MS) ex situ, we have determined the pressure-induced evolution of U60. Crystalline U60 undergoes an irreversible phase transition to a tetragonal structure at 4.1 GPa, and irreversibly amorphizes at 13 GPa. The amorphous phase likely consists of clusters of U60. Above 15 GPa, the U60 cluster is irreversibly destroyed. ESI-MS shows that this phase consists of species that likely have between 10-20 uranium atoms. Raman spectroscopy complements the diffraction measurements. U60 shows two dominant vibrational modes: a symmetric stretch of the uranyl U-O triple bond (810 cm-1), and a symmetric stretch of the U-O2-U peroxide bond (820 cm-1). As pressure is increased, these modes shift to higher wavenumbers, and overlap at 4 GPa. At 15 GPa, their intensity decreases below detection. These experiments reveal several novel behaviors including a new phase of U60. Notably, the amorphization of U60 occurs before the collapse of its cluster topology. This is different from the behavior of solvated C60 at high pressure, which maintains a hcp structure up to 30 GPa, while the clusters disorder. These results suggest that uranyl peroxide nano-cage clusters are persistent once formed, regardless of the state of the cluster: crystalline, amorphous, or in solution. These results add to the body of evidence suggesting that uranyl peroxides are important compounds to consider when dealing with environmental impacts of nuclear waste contamination.

Theoretical insights into the uranyl adsorption behavior on vanadium carbide MXene

NASA Astrophysics Data System (ADS)

Zhang, Yu-Juan; Zhou, Zhang-Jian; Lan, Jian-Hui; Ge, Chang-Chun; Chai, Zhi-Fang; Zhang, Peihong; Shi, Wei-Qun

2017-12-01

Remediation of the contamination by long-lived actinide wastes is extremely important but also challenging. Adsorption based techniques have attracted much research attention for their potential as low-cost and effective methods to reduce the radioactive waste from solution. In this work, we have investigated the adsorption behavior of uranyl species [with the general form UO2(L1)x(L2)y(L3)z, where L1, L2 and L3 stand for ligands H2O, OH and CO3, respectively] on hydroxylated vanadium carbide V2C(OH)2 MXene nanosheets using density functional theory based simulation methods We find that all studied uranyl species can stably bond to hydroxylated MXene with binding energies ranging from -3.3 to -4.6 eV, suggesting that MXenes could be effective adsorbers for uranyl ions. The strong adsorption is achieved by forming two Usbnd O bonds with the hydroxylated Mxene. In addition, the axial oxygen atoms from the uranyl ions form hydrogen bonds with the hydroxylated V2C, further strengthening the adsorption. We have also investigated the effects of F termination on the uranyl adsorption properties of V2C nanosheets. Usbnd F bonds are in general weaker than Usbnd O bonds on the adsorption site, suggesting that F terminated Mexne is less favorable for uranyl adsorption applications.

Self-assembly of silver nanoparticles as high active surface-enhanced Raman scattering substrate for rapid and trace analysis of uranyl(VI) ions

NASA Astrophysics Data System (ADS)

Wang, Shaofei; Jiang, Jiaolai; Wu, Haoxi; Jia, Jianping; Shao, Lang; Tang, Hao; Ren, Yiming; Chu, Mingfu; Wang, Xiaolin

2017-06-01

A facile surface-enhanced Raman scattering (SERS) substrate based on the self-assembly of silver nanoparticles on the modified silicon wafer was obtained, and for the first time, an advanced SERS analysis method basing on this as-prepared substrate was established for high sensitive and rapid detection of uranyl ions. Due to the weakened bond strength of Odbnd Udbnd O resulting from two kinds of adsorption of uranyl species (;strong; and ;weak; adsorption) on the substrate, the ν1 symmetric stretch vibration frequency of Odbnd Udbnd O shifted from 871 cm- 1 (normal Raman) to 720 cm- 1 and 826 cm- 1 (SERS) along with significant Raman enhancement. Effects of the hydrolysis of uranyl ions on SERS were also investigated, and the SERS band at 826 cm- 1 was first used to approximately define the constitution of uranyl species at trace quantity level. Besides, the SERS intensity was proportional to the variable concentrations of uranyl nitrate ranging from 10- 7 to 10- 3 mol L- 1 with an excellent linear relation (R2 = 0.998), and the detection limit was 10- 7 mol L- 1. Furthermore, the related SERS approach involves low-cost substrate fabrication, rapid and trace analysis simultaneously, and shows great potential applications for the field assays of uranyl ions in the nuclear fuel cycle and environmental monitoring.

Fiber optic detector and method for using same for detecting chemical species

DOEpatents

Baylor, Lewis C.; Buchanan, Bruce R.

1995-01-01

An optical sensing device for uranyl and other substances, a method for making an optical sensing device and a method for chemically binding uranyl and other indicators to glass, quartz, cellulose and similar substrates. The indicator, such as arsenazo III, is immobilized on the substrate using a chemical binding process. The immobilized arsenazo III causes uranyl from a fluid sample to bind irreversibly to the substrate at its active sites, thus causing absorption of a portion of light transmitted through the substrate. Determination of the amount of light absorbed, using conventional means, yields the concentration of uranyl present in the sample fluid. The binding of uranyl on the substrate can be reversed by subsequent exposure of the substrate to a solution of 2,6-pyridinedicarboxylic acid. The chemical binding process is suitable for similarly binding other indicators, such as bromocresol green.

Dynamic interplay between uranyl phosphate precipitation, sorption, and phase evolution

DOE PAGES

Munasinghe, P. Sumudu; Elwood Madden, Megan E.; Brooks, Scott C.; ...

2015-04-17

We report that natural examples demonstrate uranyl-phosphate minerals can maintain extremely low levels of aqueous uranium in groundwaters due to their low solubility. Thus, greater understanding of the geochemical factors leading to uranyl phosphate precipitation may lead to successful application of phosphate-based remediation methods. However, the solubility of uranyl phosphate phases varies over >3 orders of magnitude, with the most soluble phases typically observed in lab experiments. To understand the role of common soil/sediment mineral surfaces in the nucleation and transformation of uranyl phosphate minerals under environmentally relevant conditions, we carried out batch experiments with goethite and mica at pHmore » 6 in mixed electrolyte solutions ranging from 1–800 μM U and 1–800 μM P. All experiments ended with uranium concentrations below the USEPA MCL for U, but with 2–3 orders of magnitude difference in uranium concentrations.« less

Separation of uranium from technetium in recovery of spent nuclear fuel

NASA Astrophysics Data System (ADS)

Friedman, H. A.

1984-06-01

A method for decontaminating uranium product from the Purex 5 process is described. Hydrazine is added to the product uranyl nitrate stream from the Purex process, which contains hexavalent (UO2(2+)) uranium and heptavalent technetius (TcO4-). Technetium in the product stream is reduced and then complexed by the addition of oxalic acid (H2O2O4), and the Tc-oxalate complex is readily separated from the 10 uranium by solvent extraction with 30 vol % tributyl phosphate in n-dodecane.

Bicarbonate Elution of Uranium from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Horng-Bin; Wai, Chien M.; Kuo, Li-Jung

Uranium adsorbed on amidoxime-based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO3 at 40°C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris-carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (~10-3 M) in seawater. In real seawater experiments, the bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent. Usingmore » the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.« less

Bicarbonate Elution of Uranium from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Horng-Bin; Wai, Chien M.; Kuo, Li-Jung

Uranium adsorbed on amidoxime-based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO 3 at 40°C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris-carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (~10 -3 M) in seawater. The bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent, in real seawatermore » experiments. Furthermore, by using the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.« less

Bicarbonate Elution of Uranium from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

DOE PAGES

Pan, Horng-Bin; Wai, Chien M.; Kuo, Li-Jung; ...

2017-05-02

Uranium adsorbed on amidoxime-based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO 3 at 40°C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris-carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (~10 -3 M) in seawater. The bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent, in real seawatermore » experiments. Furthermore, by using the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.« less

75 FR 36701 - Issuance of Environmental Assessment and Finding of No Significant Impact for Modification of...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-28

... in the form of highly water soluble uranyl fluoride. EnergySolutions also proposed the addition of...; the concentration of residual uranyl fluoride in the K-25 piping waste in the railcars would likely... soluble uranyl fluoride in quantities in excess of the limits in Condition 4 of the 2006 Order (i.e., up...

Evidence of a Nonphotochemical Mechanism for the Solid-State Formation of Uranyl Peroxide.

PubMed

Kirkegaard, Marie C; Miskowiec, Andrew; Ambrogio, Michael W; Anderson, Brian B

2018-05-21

We have demonstrated the solid-state formation of a uranyl peroxide (UP) species from hydrated uranyl fluoride via a uranyl hydroxide intermediate, the first observation of a UP species formed in a solid-state reaction. Water vapor pressure is shown to be a driving factor of both the loss of fluorine and the subsequent formation of peroxo units. We have ruled out a photochemical mechanism for formation of the UP species by demonstrating that the same reaction occurs in the dark. A radiolytic mechanism is unlikely because of the low radioactivity of the sample material, suggesting the existence of a novel UP formation mechanism.

METHOD OF INHIBITING CORROSION IN URANYL SULFATE SOLUTIONS

DOEpatents

Bohlmann, E.G.; Griess, J.C. Jr.

1960-08-23

A method is given for treating a uranyl sulfate solution to inhibit the corrosiveness of the solution and elevate the phase separation temperature of the solution. Lithium sulfate is added to the solution in an amount ranging from 0.25 to 1.3 times the uranyl sulfate concentration. The corrosiveness of the solution with respect to stainless steel is substantially decreased by this means. This treatment also serves to raise the phase separation temperature of the solution (above 250 deg C), at which time the uranyl sulfate solution separates into two liquid phases of unequal uranium concentration and thus becomes unsuitable as nuclear reactor fuel.

Evidence of a Nonphotochemical Mechanism for the Solid-State Formation of Uranyl Peroxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirkegaard, Marie C.; Miskowiec, Andrew J.; Ambrogio, Michael W.

Here, we have demonstrated the solid-state formation of a uranyl peroxide (UP) species from hydrated uranyl fluoride via a uranyl hydroxide intermediate, the first observation of a UP species formed in a solid-state reaction. Water vapor pressure is shown to be a driving factor of both the loss of fluorine and the subsequent formation of peroxo units. We have ruled out a photochemical mechanism for formation of the UP species by demonstrating that the same reaction occurs in the dark. A radiolytic mechanism is unlikely because of the low radioactivity of the sample material, suggesting the existence of a novelmore » UP formation mechanism.« less

Evidence of a Nonphotochemical Mechanism for the Solid-State Formation of Uranyl Peroxide

DOE PAGES

Kirkegaard, Marie C.; Miskowiec, Andrew J.; Ambrogio, Michael W.; ...

2018-05-10

Here, we have demonstrated the solid-state formation of a uranyl peroxide (UP) species from hydrated uranyl fluoride via a uranyl hydroxide intermediate, the first observation of a UP species formed in a solid-state reaction. Water vapor pressure is shown to be a driving factor of both the loss of fluorine and the subsequent formation of peroxo units. We have ruled out a photochemical mechanism for formation of the UP species by demonstrating that the same reaction occurs in the dark. A radiolytic mechanism is unlikely because of the low radioactivity of the sample material, suggesting the existence of a novelmore » UP formation mechanism.« less

Uranium luminescence in La2 Zr2 O7 : effect of concentration and annealing temperature.

PubMed

Mohapatra, M; Rajeswari, B; Hon, N S; Kadam, R M

2016-12-01

The speciation of a particular element in any given matrix is a prerequisite to understanding its solubility and leaching properties. In this context, speciation of uranium in lanthanum zirconate pyrochlore (La 2 Zr 2 O 7  = LZO), prepared by a low-temperature combustion route, was carried out using a simple photoluminescence lifetime technique. The LZO matrix is considered to be a potential ceramic host for fixing nuclear and actinide waste products generated during the nuclear fuel cycle. Special emphasis has been given to understanding the dynamics of the uranium species in the host as a function of annealing temperature and concentration. It was found that, in the LZO host, uranium is stabilized as the commonly encountered uranyl species (UO 2 2+ ) up to a heat treatment of 500 °C at the surface. Above 500 °C, the uranyl ion is diffused into the matrix as the more symmetric octahedral uranate species (UO 6 6- ). The uranate ions thus formed replace the six-coordinated 'Zr' atoms at regular lattice positions. Further, it was observed that concentration quenching takes place beyond 5 mol% of uranium doping. The mechanism of the quenching was found to be a multipolar interaction. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

First Cationic Uranyl-Organic Framework with Anion-Exchange Capabilities.

PubMed

Bai, Zhuanling; Wang, Yanlong; Li, Yuxiang; Liu, Wei; Chen, Lanhua; Sheng, Daopeng; Diwu, Juan; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao

2016-07-05

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.

URANIUM EXTRACTION

DOEpatents

Harrington, C.D.; Opie, J.V.

1958-07-01

The recovery of uranium values from uranium ore such as pitchblende is described. The ore is first dissolved in nitric acid, and a water soluble nitrate is added as a salting out agent. The resulting feed solution is then contacted with diethyl ether, whereby the bulk of the uranyl nitrate and a portion of the impurities are taken up by the ether. This acid ether extract is then separated from the aqueous raffinate, and contacted with water causing back extractioa of the uranyl nitrate and impurities into the water to form a crude liquor. After separation from the ether extract, this crude liquor is heated to about 118 deg C to obtain molten uranyl nitrate hexahydratc. After being slightly cooled the uranyl nitrate hexahydrate is contacted with acid free diethyl ether whereby the bulk of the uranyl nitrate is dissolved into the ethcr to form a neutral ether solution while most of the impurities remain in the aqueous waste. After separation from the aqueous waste, the resultant ether solution is washed with about l0% of its volume of water to free it of any dissolved impurities and is then contacted with at least one half its volume of water whereby the uranyl nitrate is extracted into the water to form an aqueous product solution.

URANIUM PURIFICATION PROCESS

DOEpatents

Winters, C.E.

1957-11-12

A method for the preparation of a diethyl ether solution of uranyl nitrate is described. Previously the preparation of such ether solutions has been difficult and expensive, since crystalline uranyl nitrate hexahydrate dissolves very slowly in ether. An improved method for effecting such dissolution has been found, and it comprises adding molten uranyl nitrate hexahydrate at a temperature of 65 to 105 deg C to the ether while maintaining the temperature of the ether solvent below its boiling point.

FY-15 Progress Report on Cleanup of irradiated SHINE Target Solutions Containing 140g-U/L Uranyl Sulfate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, Megan E.; Bowers, Delbert L.; Vandegrift, George F.

2015-09-01

During FY 2012 and 2013, a process was developed to convert the SHINE Target Solution (STS) of irradiated uranyl sulfate (140 g U/L) to uranyl nitrate. This process is necessary so that the uranium solution can be processed by the UREX (Uranium Extraction) separation process, which will remove impurities from the uranium so that it can be recycled. The uranyl sulfate solution must contain <0.02 M SO 4 2- so that the uranium will be extractable into the UREXsolvent. In addition, it is desired that the barium content be below 0.0007 M, as this is the limit in the Resourcemore » Conservation and Recovery Act (RCRA).« less

Laser induced phosphorescence uranium analysis

DOEpatents

Bushaw, B.A.

1983-06-10

A method is described for measuring the uranium content of aqueous solutions wherein a uranyl phosphate complex is irradiated with a 5 nanosecond pulse of 425 nanometer laser light and resultant 520 nanometer emissions are observed for a period of 50 to 400 microseconds after the pulse. Plotting the natural logarithm of emission intensity as a function of time yields an intercept value which is proportional to uranium concentration.

Laser induced phosphorescence uranium analysis

DOEpatents

Bushaw, Bruce A.

1986-01-01

A method is described for measuring the uranium content of aqueous solutions wherein a uranyl phosphate complex is irradiated with a 5 nanosecond pulse of 425 nanometer laser light and resultant 520 nanometer emissions are observed for a period of 50 to 400 microseconds after the pulse. Plotting the natural logarithm of emission intensity as a function of time yields an intercept value which is proportional to uranium concentration.

Uranyl carboxyphosphonates that incorporate Cd(II)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alsobrook, Andrea N.; Alekseev, Evgeny V.; Depmeier, Wulf

2011-05-15

The hydrothermal treatment of UO{sub 3}, Cd(CH{sub 3}CO{sub 2}){sub 2}.2H{sub 2}O, and triethyl phosphonoacetate results in the formation of Cd{sub 2}[(UO{sub 2}){sub 6}(PO{sub 3}CH{sub 2}CO{sub 2}){sub 3}O{sub 3}(OH)(H{sub 2}O){sub 2}].16H{sub 2}O (CdUPAA-1), [Cd{sub 3}(UO{sub 2}){sub 6}(PO{sub 3}CH{sub 2}CO{sub 2}){sub 6}(H{sub 2}O){sub 13}].6H{sub 2}O (CdUPAA-2), and Cd(H{sub 2}O){sub 2}[(UO{sub 2})(PO{sub 3}CH{sub 2}CO{sub 2})(H{sub 2}O)]{sub 2} (CdUPAA-3). CdUPAA-1 adopts a cubic three-dimensional structure constructed from planar uranyl oxide clusters containing both UO{sub 7} pentagonal bipyramids and UO{sub 8} hexagonal bipyramids that are linked by Cd(II) cations and phosphonoacetate to yield large cavities approximately 16 A across that are filled with disordered watermore » molecules. CdUPAA-2 forms a rhombohedral three-dimensional channel structure that is assembled from UO{sub 7} pentagonal bipyramids that are bridged by phosphonoacetate. CdUPAA-3 is layered with the hydrated Cd(II) cations incorporated directly into the layers linking one-dimensional uranyl phosphonate substructures together. In this structure, there are complex networks of hydrogen bonds that exist within the sheets, and also stitch the sheets together. -- Graphical abstract: A view of part of the cubic structure of Cd{sub 2}[(UO{sub 2}){sub 6}(PO{sub 3}CH{sub 2}CO{sub 2}){sub 3}O{sub 3}(OH)(H{sub 2}O){sub 2}].16H{sub 2}O. Display Omitted highlights: > High symmetry uranyl compounds. > Three-dimensional structures. > Porous materials. > Heterobimetallic compounds.« less

Separation of uranium from technetium in recovery of spent nuclear fuel

DOEpatents

Friedman, H.A.

1984-06-13

A method for decontaminating uranium product from the Purex 5 process comprises addition of hydrazine to the product uranyl nitrate stream from the Purex process, which contains hexavalent (UO/sub 2//sup 2 +/) uranium and heptavalent technetium (TcO/sub 4/-). Technetium in the product stream is reduced and then complexed by the addition of oxalic acid (H/sub 2/C/sub 2/O/sub 4/), and the Tc-oxalate complex is readily separated from the 10 uranium by solvent extraction with 30 vol % tributyl phosphate in n-dodecane.

Separation of uranium from technetium in recovery of spent nuclear fuel

DOEpatents

Friedman, Horace A.

1985-01-01

A method for decontaminating uranium product from the Purex process comprises addition of hydrazine to the product uranyl nitrate stream from the Purex process, which contains hexavalent (UO.sub.2.sup.2+) uranium and heptavalent technetium (TcO.sub.4 -). Technetium in the product stream is reduced and then complexed by the addition of oxalic acid (H.sub.2 C.sub.2 O.sub.4), and the Tc-oxalate complex is readily separated from the uranium by solvent extraction with 30 vol. % tributyl phosphate in n-dodecane.

Identification of Uranyl Minerals Using Oxygen K-Edge X Ray Absorption Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Jesse D.; Bowden, Mark E.; Resch, Charles T.

2016-03-01

Uranium analysis is consistently needed throughout the fuel cycle, from mining to fuel fabrication to environmental monitoring. Although most of the world’s uranium is immobilized as pitchblende or uraninite, there exists a plethora of secondary uranium minerals, nearly all of which contain the uranyl cation. Analysis of uranyl compounds can provide clues as to a sample’s facility of origin and chemical history. X-ray absorption spectroscopy is one technique that could enhance our ability to identify uranium minerals. Although there is limited chemical information to be gained from the uranium X-ray absorption edges, recent studies have successfully used ligand NEXAFS tomore » study the physical chemistry of various uranium compounds. This study extends the use of ligand NEXAFS to analyze a suite of uranium minerals. We find that major classes of uranyl compounds (carbonate, oxyhydroxide, silicate, and phosphate) exhibit characteristic lineshapes in the oxygen K-edge absorption spectra. As a result, this work establishes a library of reference spectra that can be used to classify unknown uranyl minerals.« less

RECOVERY OF URANIUM FROM PITCHBLENDE

DOEpatents

Ruehle, A.E.

1958-06-24

The decontamination of uranium from molybdenum is described. When acid solutions containing uranyl nitrate are contacted with ether for the purpose of extracting the uranium values, complex molybdenum compounds are coextracted with the uranium and also again back-extracted from the ether with the uranium. This invention provides a process for extracting uranium in which coextraction of molybdenum is avoided. It has been found that polyhydric alcohols form complexes with molybdenum which are preferentially water-soluble are taken up by the ether extractant to only a very minor degree. The preferred embodiment of the process uses mannitol, sorbitol or a mixture of the two as the complexing agent.

Uranyl adsorption kinetics within silica gel: dependence on flow velocity and concentration

NASA Astrophysics Data System (ADS)

Dodd, Brandon M.; Tepper, Gary

2017-09-01

Trace quantities of a uranyl dissolved in water were measured using a simple optical method. A dilute solution of uranium nitrate dissolved in water was forced through nanoporous silica gel at fixed and controlled water flow rates. The uranyl ions deposited and accumulated within the silica gel and the uranyl fluorescence within the silica gel was monitored as a function of time using a light emitting diode as the excitation source and a photomultiplier tube detector. It was shown that the response time of the fluorescence output signal at a particular volumetric flow rate or average liquid velocity through the silica gel can be used to quantify the concentration of uranium in water. The response time as a function of concentration decreased with increasing flow velocity.

Combination of solid phase extraction and dispersive liquid-liquid microextraction for separation/preconcentration of ultra trace amounts of uranium prior to its fiber optic-linear array spectrophotometry determination.

PubMed

Dadfarnia, Shayessteh; Shabani, Ali Mohammad Haji; Shakerian, Farid; Shiralian Esfahani, Golnaz

2013-12-15

A simple and sensitive method for the separation and preconcentration of the ultra trace amounts of uranium and its determination by spectrophotometry was developed. The method is based on the combination of solid phase extraction and dispersive liquid-liquid microextraction. Thus, by passing the sample through the basic alumina column, the uranyl ion and some cations are separated from the sample matrix. The retained uranyl ion along with the cations are eluted with 5 mL of nitric acid (2 mol L(-1)) and after neutralization of the eluent, the extracted uranyl ion is converted to its anionic benzoate complex and is separated from other cations by extraction of its ion pair with malachite green into small volume of chloroform using dispersive liquid-liquid microextraction. The amount of uranium is then determined by the absorption measurement of the extracted ion pair at 621 nm using flow injection spectrophotometry. Under the optimum conditions, with 500 mL of the sample, a preconcentration factor of 1980, a detection limit of 40 ng L(-1), and a relative standard deviation of 4.1% (n=6) at 400 ng L(-1) were obtained. The method was successfully applied to the determination of uranium in mineral water, river water, well water, spring water and sea water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

PREPARATION OF URANIUM TRIOXIDE

DOEpatents

Buckingham, J.S.

1959-09-01

The production of uranium trioxide from aqueous solutions of uranyl nitrate is discussed. The uranium trioxide is produced by adding sulfur or a sulfur-containing compound, such as thiourea, sulfamic acid, sulfuric acid, and ammonium sulfate, to the uranyl solution in an amount of about 0.5% by weight of the uranyl nitrate hexahydrate, evaporating the solution to dryness, and calcining the dry residue. The trioxide obtained by this method furnished a dioxide with a considerably higher reactivity with hydrogen fluoride than a trioxide prepared without the sulfur additive.

ELECTROLYTIC PRODUCTION OF URANIUM TETRAFLUORIDE

DOEpatents

Lofthouse, E.

1954-08-31

This patent relates to electrolytic methods for the production of uranium tetrafluoride. According to the present invention a process for the production of uranium tetrafluoride comprises submitting to electrolysis an aqueous solution of uranyl fluoride containing free hydrofluoric acid. Advantageously the aqueous solution of uranyl fluoride is obtained by dissolving uranium hexafluoride in water. On electrolysis, the uranyl ions are reduced to uranous tons at the cathode and immediately combine with the fluoride ions in solution to form the insoluble uranium tetrafluoride which is precipitated.

Sorption of uranyl ions from various acido systems by amphoteric epoxy amine ion-exchange resins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rychkov, V.N.; Radionov, B.K.; Molochnikov, L.S.

1995-03-01

Sorption of uranyl ions by epoxy amine ampholytes with N-monomethylenephosphonic acid groups modified with pyridine or quaternary ammonium groups was studied under dynamic conditions. Heterocyclic nitrogen favors sorption of uranyl ion from fluoride, sulfate, and fluoride-sulfate solutions. The ESR studies of mono- and bimetallic forms of nitrogen-containing ampholytes with copper(II) as paramagnetic marker revealed the characteristics of uranium(VI) interaction with cation- and anion-exchange groups and its dependence on the fluoride content in solution.

Multilinear analysis of Time-Resolved Laser-Induced Fluorescence Spectra of U(VI) containing natural water samples

NASA Astrophysics Data System (ADS)

Višňák, Jakub; Steudtner, Robin; Kassahun, Andrea; Hoth, Nils

2017-09-01

Natural waters' uranium level monitoring is of great importance for health and environmental protection. One possible detection method is the Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS), which offers the possibility to distinguish different uranium species. The analytical identification of aqueous uranium species in natural water samples is of distinct importance since individual species differ significantly in sorption properties and mobility in the environment. Samples originate from former uranium mine sites and have been provided by Wismut GmbH, Germany. They have been characterized by total elemental concentrations and TRLFS spectra. Uranium in the samples is supposed to be in form of uranyl(VI) complexes mostly with carbonate (CO32- ) and bicarbonate (HCO3- ) and to lesser extend with sulphate (SO42- ), arsenate (AsO43- ), hydroxo (OH- ), nitrate (NO3- ) and other ligands. Presence of alkaline earth metal dications (M = Ca2+ , Mg2+ , Sr2+ ) will cause most of uranyl to prefer ternary complex species, e.g. Mn(UO2)(CO3)32n-4 (n ɛ {1; 2}). From species quenching the luminescence, Cl- and Fe2+ should be mentioned. Measurement has been done under cryogenic conditions to increase the luminescence signal. Data analysis has been based on Singular Value Decomposition and monoexponential fit of corresponding loadings (for separate TRLFS spectra, the "Factor analysis of Time Series" (FATS) method) and Parallel Factor Analysis (PARAFAC, all data analysed simultaneously). From individual component spectra, excitation energies T00, uranyl symmetric mode vibrational frequencies ωgs and excitation driven U-Oyl bond elongation ΔR have been determined and compared with quasirelativistic (TD)DFT/B3LYP theoretical predictions to cross -check experimental data interpretation. Note to the reader: Several errors have been produced in the initial version of this article. This new version published on 23 October 2017 contains all the corrections.

Uranyl nitrate-exposed rat alveolar macrophages cell death: Influence of superoxide anion and TNF α mediators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orona, N.S.; Tasat, D.R., E-mail: deborah.tasat@unsam.edu.ar; School of Dentistry, University of Buenos Aires, M. T. de Alvear 2142

2012-06-15

Uranium compounds are widely used in the nuclear fuel cycle, military and many other diverse industrial processes. Health risks associated with uranium exposure include nephrotoxicity, cancer, respiratory, and immune disorders. Macrophages present in body tissues are the main cell type involved in the internalization of uranium particles. To better understand the pathological effects associated with depleted uranium (DU) inhalation, we examined the metabolic activity, phagocytosis, genotoxicity and inflammation on DU-exposed rat alveolar macrophages (12.5–200 μM). Stability and dissolution of DU could differ depending on the dissolvent and in turn alter its biological action. We dissolved DU in sodium bicarbonate (NaHCO{submore » 3} 100 mM) and in what we consider a more physiological vehicle resembling human internal media: sodium chloride (NaCl 0.9%). We demonstrate that uranyl nitrate in NaCl solubilizes, enters the cell, and elicits its cytotoxic effect similarly to when it is diluted in NaHCO{sub 3}. We show that irrespective of the dissolvent employed, uranyl nitrate impairs cell metabolism, and at low doses induces both phagocytosis and generation of superoxide anion (O{sub 2}{sup −}). At high doses it provokes the secretion of TNFα and through all the range of doses tested, apoptosis. We herein suggest that at DU low doses O{sub 2}{sup −} may act as the principal mediator of DNA damage while at higher doses the signaling pathway mediated by O{sub 2}{sup −} may be blocked, prevailing damage to DNA by the TNFα route. The study of macrophage functions after uranyl nitrate treatment could provide insights into the pathophysiology of uranium‐related diseases. -- Highlights: ► Uranyl nitrate effect on cultured macrophages is linked to the doses and independent of its solubility. ► At low doses uranyl nitrate induces generation of superoxide anion. ► At high doses uranyl nitrate provokes secretion of TNFα. ► Uranyl nitrate induces apoptosis through all the range of doses tested.« less

Fluorimetric determination of some sulfur containing compounds through complex formation with terbium (Tb+3) and uranium (U+3).

PubMed

Taha, Elham Anwer; Hassan, Nagiba Yehya; Aal, Fahima Abdel; Fattah, Laila El-Sayed Abdel

2007-05-01

Two simple, sensitive and specific fluorimetric methods have been developed for the determination of some sulphur containing compounds namely, Acetylcysteine (Ac), Carbocisteine (Cc) and Thioctic acid (Th) using terbium Tb+3 and uranium U+3 ions as fluorescent probes. The proposed methods involve the formation of a ternary complex with Tb+3 in presence of Tris-buffer method (I) and a binary complex with aqueous uranyl acetate solution method (II). The fluorescence quenching of Tb+3 at 510, 488 and 540 nm (lambda(ex) 250, 241 and 268 nm) and of uranyl acetate at 512 nm (lambda(ex) 240 nm) due to the complex formation was quantitatively measured for Ac, Cc and Th, respectively. The reaction conditions and the fluorescence spectral properties of the complexes have been investigated. Under the described conditions, the proposed methods were applicable over the concentration range (0.2-2.5 microg ml(-1)), (1-4 microg ml(-1)) and (0.5-3.5 microg ml(-1)) with mean percentage recoveries 99.74+/-0.36, 99.70+/-0.52 and 99.43+/-0.23 for method (I) and (0.5-6 microg ml(-1)), (0.5-5 microg ml(-1)), and (1-6 microg ml(-1)) with mean percentage recoveries 99.38+/-0.20, 99.82+/-0.28 and 99.93+/-0.32 for method (II), for the three cited drugs, respectively. The proposed methods were successfully applied for the determination of the studied compounds in bulk powders and in pharmaceutical formulations, as well as in presence of their related substances. The results obtained were found to be in agree statistically with those obtained by official and reported ones. The two methods were validated according to USP guidelines and also assessed by applying the standard addition technique.

Protein scaffolds for selective enrichment of metal ions

DOEpatents

He, Chuan; Zhou, Lu; Bosscher, Michael

2016-02-09

Polypeptides comprising high affinity for the uranyl ion are provided. Methods for binding uranyl using such proteins are likewise provided and can be used, for example, in methods for uranium purification or removal.

Structure of complexes of uranyl succinate with carbamide and dimethylurea

NASA Astrophysics Data System (ADS)

Serezhkina, L. B.; Grigor'ev, M. S.; Seliverstova, N. V.; Serezhkin, V. N.

2017-09-01

Three new succinate-containing complexes of uranyl with carbamide ( Urea) and N,N'-dimethylurea ( s-Dmur) are synthesized and studied by IR spectroscopy and X-ray diffraction. Structures of the same type, [UO2( Urea)4(H2O)][(UO2)2(C4H4O4)3] · 3H2O and [UO2( Urea)4(H2O)][(UO2)2(C4H4O4)3] · 2 Urea contain two sorts of uranium-containing complex groups, namely, mononuclear [UO2( Urea)4(H2O)]2+ cations and two-dimensional [(UO2)2(C4H4O4)3]2- anions described by crystal-chemical formulas AM 5 1 and A 2 Q 3 02, respectively ( A = UO2 2+, M 1 = Urea or H2O, Q 02 = C4H4O4 2-), and differ only in the nature of noncoordinated molecules—water and carbamide. The main structural groups of the [(UO2)2(C4H4O4)2( s-Dmur)3] crystals are [(UO2)2(C4H4O4)2( s-Dmur)3] chains belonging to the A 2 Q 2 02 M 3 1 ( A = UO2 2+, Q 02 = C4H4O4 2-, M 1 = s-Dmur) crystal-chemical group. Specific features of intermolecular interactions in the crystal structures are revealed using the Voronoi-Dirichlet method of molecular polyhedra.

Engineered nano-magnetic iron oxide-urea-activated carbon nanolayer sorbent for potential removal of uranium (VI) from aqueous solution

NASA Astrophysics Data System (ADS)

Mahmoud, Mohamed E.; Khalifa, Mohamed A.; El Wakeel, Yasser M.; Header, Mennatllah S.; Abdel-Fattah, Tarek M.

2017-04-01

A novel magnetic nanosorbent was designed using chemical grafting of nano-magnetite (Nano-Fe3O4) with nanolayer of activated carbon (AC) via urea intermediate for the formation of Nano-Fe3O4-Urea-AC. Characterizing was carried out using FT-IR, SEM, HR-TEM, TGA, point of zero charge (Pzc) and surface area analysis. The designed sorbent maintained its magnetic properties and nanosized structure in the range of 8.7-14.1 nm. The surface area was identified as 389 m2/g based on the BET method. Sorption of uranyl ions from aqueous solutions was studied and evaluated in different experimental conditions. Removal of uranyl ions increased with increasing in pH value and the maximum percentage removal was established at pH 5.0. The removal and sorption processes of uranyl ions by Nano-Fe3O4-Urea-AC sorbent were studied and optimized using the batch technique. The key variables affecting removal of uranyl ions were studied including the effect of the contact time, dosage of Nano-Fe3O4-Urea-AC sorbent, reaction temperature, initial uranyl ions concentration and interfering anions and cations.

Immobilization of selenate by iron in aqueous solution under anoxic conditions and the influence of uranyl

NASA Astrophysics Data System (ADS)

Puranen, Anders; Jonsson, Mats; Dähn, Rainer; Cui, Daqing

2009-08-01

In proposed high level radioactive waste repositories a large part of the spent nuclear fuel (SNF) canisters are commonly composed of iron. Selenium is present in spent nuclear fuel as a long lived fission product. This study investigates the influence of iron on the uptake of dissolved selenium in the form of selenate and the effect of the presence of dissolved uranyl on the above interaction of selenate. The iron oxide, and selenium speciation on the surfaces was investigated by Raman spectroscopy. X-ray Absorption Spectroscopy was used to determine the oxidation state of the selenium and uranium on the surfaces. Under the simulated groundwater conditions (10 mM NaCl, 2 mM NaHCO 3, <0.1 ppm O 2) the immobilized selenate was found to be reduced to oxidation states close to zero or lower and uranyl was found to be largely reduced to U(IV). The near simultaneous reduction of uranyl was found to greatly enhance the rate of selenate reduction. These findings suggest that the presence of uranyl being reduced by an iron surface could substantially enhance the rate of reduction of selenate under anoxic conditions relevant for a repository.

Free energies and mechanisms of water exchange around Uranyl from first principles molecular dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atta-Fynn, Raymond; Bylaska, Eric J.; De Jong, Wibe A.

2012-02-01

From density functional theory (DFT) based ab initio (Car-Parrinello) metadynamics, we compute the activation energies and mechanisms of water exchange between the first and second hydration shells of aqueous Uranyl (UO{sub 2}{sup 2+}) using the primary hydration number of U as the reaction coordinate. The free energy and activation barrier of the water dissociation reaction [UO{sub 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) {yields} [UO{sub 2}(OH{sub 2})4]{sup 2+}(aq) + H{sub 2}O are 0.7 kcal and 4.7 kcal/mol respectively. The free energy is in good agreement with previous theoretical (-2.7 to +1.2 kcal/mol) and experimental (0.5 to 2.2 kcal/mol) data. The associative reaction [UO{submore » 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) + H{sub 2}O {yields} [UO{sub 2}(OH{sub 2})6]{sup 2+}(aq) is short-lived with a free energy and activation barrier of +7.9 kcal/mol and +8.9 kca/mol respectively; it is therefore classified as associative-interchange. On the basis of the free energy differences and activation barriers, we predict that the dominant exchange mechanism between [UO{sub 2}(OH{sub 2}){sub 5}]{sup 2+}(aq) and bulk water is dissociative.« less

Molecular Simulations of the Diffusion of Uranyl Carbonate Species in Nanosized Mineral Fractures

NASA Astrophysics Data System (ADS)

Kerisit, S.; Liu, C.

2010-12-01

Uranium is a major groundwater contaminant at uranium processing and mining sites as a result of intentional and accidental discharges of uranium-containing waste products into subsurface environments. Recent characterization has shown that uranium preferentially associates with intragrain and intra-aggregate domains in some of the uranium-contaminated sediments collected from the US Department of Energy Hanford Site [1, 2]. In these sediments, uranium existed as precipitated and/or adsorbed phases in grain micropores with nano- to microscale sizes. Desorption and diffusion characterization studies and continuum-scale modeling indicated that ion diffusion in the microfractures is a major mechanism that led to preferential uranium concentration in the microfracture regions and will control the future mobility of uranium in the subsurface sediments [1, 3-4]. However, the diffusion properties of uranyl species in the intragrain regions, especially at the solid-liquid interface, are still poorly understood. Therefore, a general aim of this work is to provide atomic-level insights into the contribution of microscopic surface effects to the slow diffusion process of uranyl species in porous media with nano- to microsized fractures. In this presentation, we will first present molecular dynamics (MD) simulations of feldspar-water interfaces to investigate their interfacial structure and dynamics and establish a theoretical framework for subsequent simulations of water and ion diffusion at these interfaces [5]. We will then report on MD simulations carried out to probe the effects of confinement and of the presence of the mineral surface on the diffusion of water and electrolyte ions in nanosized feldspar fractures [6]. Several properties of the mineral-water interface were varied, such as the fracture width, the ionic strength of the contacting solution, and the surface charge. Our calculations reveal a 2.0-2.5 nm interfacial region within which the diffusion properties of water and that of the electrolyte ions differ significantly from those in bulk aqueous solutions. We will then present MD simulations of the diffusion of a series of alkaline-earth uranyl carbonate species in aqueous solutions [7]. The MD simulations show that the alkaline-earth uranyl carbonate complexes have distinct water exchange dynamics, which could lead to different reactivities. Finally, we will present recent results on the diffusion and adsorption of uranyl carbonate species in intragrain micropores, modeled with the feldspar-water interfaces mentioned in the above, to help interpret the diffusion behavior of uranium in contaminated sediments. [1] Liu C. et al. Geochim. Cosmochim. Acta 68 4519 (2004) [2] McKinley J. P. et al. Geochim. Cosmochim. Acta 70 1873 (2006) [3] Liu C. et al. Water Resour. Res. 42 W12420 (2006) [4] Ilton E. S. et al. Environ. Sci. Technol. 42 1565 (2009) [5] Kerisit S. et al. Geochim. Cosmochim. Acta 72 1481 (2008) [6] Kerisit S. and Liu C. Environ. Sci. Technol. 43 777 (2009) [7] Kerisit S. and Liu C. Geochim. Cosmochim. Acta 74 4937 (2010)

Exploring New Assembly Modes of Uranyl Terephthalate: Templated Syntheses and Structural Regulation of a Series of Rare 2D → 3D Polycatenated Frameworks

DOE PAGES

Mei, Lei; Wang, Cong-zhi; Zhu, Liu-zheng; ...

2017-06-23

In this paper, the reaction of uranyl nitrate with terephthalic acid (H 2TP) under hydrothermal conditions in the presence of an organic base, 1,3-(4,4'-bispyridyl)propane (BPP) or 4,4'-bipyridine (BPY), provided four uranyl terephthalate compounds with different entangled structures by a pH-tuning method. [UO 2(TP) 1.5](H 2BPP) 0.5·2H 2O (1) obtained in a relatively acidic solution (final aqueous pH, 4.28) crystallizes in the form of a noninterpenetrated honeycomb-like two-dimensional network structure. An elevation of the solution pH (final pH, 5.21) promotes the formation of a dimeric uranyl-mediated polycatenated framework, [(UO 2) 2(μ-OH) 2(TP) 2] 2(H 2BPP) 2·4.5H 2O (2). Another new polycatenatedmore » framework with a monomeric uranyl unit, [(UO 2) 2(TP) 3](H 2BPP) (3), begins to emerge as a minor accompanying product of 2 when the pH is increased up to 6.61, and turns out to be a significant product at pH 7.00. When more rigid but small-size BPY molecules replace BPP molecules, [UO 2(TP) 1.5](H 2BPP) 0.5 (4) with a polycatenated framework similar to 3 was obtained in a relatively acidic solution (final pH, 4.81). The successful preparation of 2–4 represents the first report of uranyl–organic polycatenated frameworks derived from a simple H 2TP linker. Finally, a direct comparison between these polycatenated frameworks and previously reported uranyl terephthalate compounds suggests that the template and cavity-filling effects of organic bases (such as BPP or BPY), in combination with specific hydrothermal conditions, promote the formation of uranyl terephthalate polycatenated frameworks.« less

Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, Jesse D.; Bowden, Mark; Tom Resch, C.

2017-01-01

Uranium ores mined for industrial use are typically acid-leached to produce yellowcake and then converted into uranium halides for enrichment and purification. These anthropogenic chemical forms of uranium are distinct from their mineral counterparts. The purpose of this study is to use soft X-ray absorption spectroscopy to characterize several common anthropogenic uranium compounds important to the nuclear fuel cycle. Non-destructive chemical analyses of these compounds is important for process and environmental monitoring and X-ray absorption techniques have several advantages in this regard, including element-specificity, chemical sensitivity, and high spectral resolution. Oxygen K-edge spectra were collected for uranyl nitrate, uranyl fluoride,more » and uranyl chloride, and fluorine K-edge spectra were collected for uranyl fluoride and uranium tetrafluoride. Interpretation of the data is aided by comparisons to calculated spectra. These compounds have unique spectral signatures that can be used to identify unknown samples.« less

Preliminary experiments on the reduction of the uranyl ion to uraninite by carbonaceous substances

USGS Publications Warehouse

Breger, Irving A.; Moore, Richard T.

1955-01-01

An aqueous solution of uranyl sulfate containing a suspension of subbituminous coal has been heated at 210 C for three days. Examination of the coal at the end of the experiment showed it to contain 31.8 percent uranium recognizable as uraninite by a sharp, strong X-ray diffraction pattern. A similar experiment with degraded spruce wood also led to the formation of uraninite but in lesser quantity and with broader lines in the X-ray diffraction pattern. The ability of coal or wood to reduce the uranyl ion is a critical factor in the correlation of studies of uraniferous coals containing the uranyl ion with studies of uraninite-bearing coalified wood from the Colorado Plateau. Although these results are based an preliminary experiments, they are extremely important geochemically and warrant the development of the series of controlled studies that are proposed.

The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels.

PubMed

Ivanov, Peter; Griffiths, Tamara; Bryan, Nick D; Bozhikov, Gospodin; Dmitriev, Serguei

2012-11-01

The effect of humic acid (HA) on U(VI) sorption on bentonite was studied in batch experiments at room temperature and ambient atmosphere at a (237)U(VI) concentration of 8.4 × 10(-11) M and HA concentration of 100 mg L(-1). The distribution of U(VI) between the liquid and solid phases was studied as a function of pH and ionic strength both in the absence and presence of HA. It was shown that the uranyl sorption on bentonite is strongly dependent on pH and the presence of humics, and the effect of the addition order was negligible. In the absence of HA an enhancement in the uptake with increasing pH was observed and a sharp sorption edge was found to take place between pH 3.2 and 4.2. The presence of HA slightly increases uranium(VI) sorption at low pH and curtails it at moderate pH, compared to the absence of HA. In the basic pH range for both the presence and absence of HA the sorption of uranium is significantly reduced, which could be attributed to the formation of soluble uranyl carbonate complexes. The influence of ionic strength on U(VI) and HA uptake by bentonite were investigated in the range of 0.01-1.0 M, and while there was an enhancement in the sorption of humic acid with increasing ionic strength, no significant effect of the ionic strength on the U(VI) sorption was observed in both the absence and presence of HA.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yingjie, E-mail: yzx@ansto.gov.au; Bhadbhade, Mohan; Karatchevtseva, Inna

Three new coordination polymers of uranium(VI) with pyromellitic acid (H{sub 4}btca) have been synthesized and structurally characterized. (ED)[(UO{sub 2})(btca)]·(DMSO)·3H{sub 2}O (1) (ED=ethylenediammonium; DMSO=dimethylsulfoxide) has a lamellar structure with intercalation of ED and DMSO. (NH{sub 4}){sub 2}[(UO{sub 2}){sub 6}O{sub 2}(OH){sub 6}(btca)]·~6H{sub 2}O (2) has a 3D framework built from 7-fold coordinated uranyl trinuclear units and btca ligands with 1D diamond-shaped channels (~8.5 Å×~8.6 Å). [(UO{sub 2}){sub 2}(H{sub 2}O)(btca)]·4H{sub 2}O (3) has a 3D network constructed by two types of 7-fold coordinated uranium polyhedron. The unique μ{sub 5}-coordination mode of btca in 3 enables the formation of 1D olive-shaped large channels (~4.5more » Å×~19 Å). Vibrational modes, thermal stabilities and fluorescence properties have been investigated. - Graphical abstract: Table of content: three new uranium(VI) coordination polymers with pyromellitic acid (H{sub 4}btca) have been synthesized via room temperature and hydrothermal synthesis methods, and structurally characterized. Two to three dimensional (3D) frameworks are revealed. All 3D frameworks have unique 1D large channels. Their vibrational modes, thermal stabilities and photoluminescence properties have been investigated. - Highlights: • Three new coordination polymers of U(VI) with pyromellitic acid (H{sub 4}btca). • Structures from a 2D layer to 3D frameworks with unique 1D channels. • Unusual µ{sub 5}-(η{sub 1}:η{sub 2}:η{sub 1}:η{sub 2:}η{sub 1}) coordination mode of btca ligand. • Vibrational modes, thermal stabilities and luminescent properties reported.« less

Uranyl peroxide enhanced nuclear fuel corrosion in seawater.

PubMed

Armstrong, Christopher R; Nyman, May; Shvareva, Tatiana; Sigmon, Ginger E; Burns, Peter C; Navrotsky, Alexandra

2012-02-07

The Fukushima-Daiichi nuclear accident brought together compromised irradiated fuel and large amounts of seawater in a high radiation field. Based on newly acquired thermochemical data for a series of uranyl peroxide compounds containing charge-balancing alkali cations, here we show that nanoscale cage clusters containing as many as 60 uranyl ions, bonded through peroxide and hydroxide bridges, are likely to form in solution or as precipitates under such conditions. These species will enhance the corrosion of the damaged fuel and, being thermodynamically stable and kinetically persistent in the absence of peroxide, they can potentially transport uranium over long distances.

M4FT-15OR03100415 - Update on COF-based Adsorbent Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayes, Richard T.; Dai, Sheng

2015-02-01

This letter report provides an update on activities focused on generating nanoporous adsorbents involving covalent organic frameworks (COF) and zeolitic imidazolium frameworks (ZIF). The adsorbents have been generated and screened in a uranyl-spiked brine (6 ppm U) to understand uranyl-binding behavior. Porous organic polymers (POP) also qualify under this title and are similar to the COF PPN-6 that is discussed herein. Seven COF/POP and one 1 ZIF were synthesized and screened for uranyl adsorption. Seawater screening is on-going via batch testing while flow screening systems are being developed at PNNL.

Method for loading resin beds

DOEpatents

Notz, Karl J.; Rainey, Robert H.; Greene, Charles W.; Shockley, William E.

1978-01-01

An improved method of preparing nuclear reactor fuel by carbonizing a uranium loaded cation exchange resin provided by contacting a H.sup.+ loaded resin with a uranyl nitrate solution deficient in nitrate, comprises providing the nitrate deficient solution by a method comprising the steps of reacting in a reaction zone maintained between about 145.degree.-200.degree. C, a first aqueous component comprising a uranyl nitrate solution having a boiling point of at least 145.degree. C with a second aqueous component to provide a gaseous phase containing HNO.sub.3 and a reaction product comprising an aqueous uranyl nitrate solution deficient in nitrate.

Uranyl peroxide enhanced nuclear fuel corrosion in seawater

PubMed Central

Armstrong, Christopher R.; Nyman, May; Shvareva, Tatiana; Sigmon, Ginger E.; Burns, Peter C.; Navrotsky, Alexandra

2012-01-01

The Fukushima-Daiichi nuclear accident brought together compromised irradiated fuel and large amounts of seawater in a high radiation field. Based on newly acquired thermochemical data for a series of uranyl peroxide compounds containing charge-balancing alkali cations, here we show that nanoscale cage clusters containing as many as 60 uranyl ions, bonded through peroxide and hydroxide bridges, are likely to form in solution or as precipitates under such conditions. These species will enhance the corrosion of the damaged fuel and, being thermodynamically stable and kinetically persistent in the absence of peroxide, they can potentially transport uranium over long distances. PMID:22308442

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.

PubMed

Liu, Wei; Dai, Xing; Bai, Zhuanling; Wang, Yanlong; Yang, Zaixing; Zhang, Linjuan; Xu, Lin; Chen, Lanhua; Li, Yuxiang; Gui, Daxiang; Diwu, Juan; Wang, Jianqiang; Zhou, Ruhong; Chai, Zhifang; Wang, Shuao

2017-04-04

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.

Crystal Chemistry of the Potassium and Rubidium Uranyl Borate Families Derived from Boric Acid Fluxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.

2010-07-19

The reaction of uranyl nitrate with a large excess of molten boric acid in the presence of potassium or rubidium nitrate results in the formation of three new potassium uranyl borates, K{sub 2}[(UO{sub 2}){sub 2}B{sub 12}O{sub 19}(OH){sub 4}]·0.3H{sub 2}O (KUBO-1), K[(UO{sub 2}){sub 2}B{sub 10}O{sub 15}(OH){sub 5}] (KUBO-2), and K[(UO{sub 2}){sub 2}B{sub 10}O{sub 16}(OH){sub 3}]·0.7H{sub 2}O (KUBO-3) and two new rubidium uranyl borates Rb{sub 2}[(UO{sub 2}){sub 2}B{sub 13}O{sub 20}(OH){sub 5}] (RbUBO-1) and Rb[(UO{sub 2}){sub 2}B{sub 10}O{sub 16}(OH){sub 3}]·0.7H{sub 2}O (RbUBO-2). The latter is isotypic with KUBO-3. These compounds share a common structural motif consisting of a linear uranyl, UO{sub 2}{sup 2+},more » cation surrounded by BO{sub 3} triangles and BO{sub 4} tetrahedra to create an UO{sub 8} hexagonal bipyramidal environment around uranium. The borate anions bridge between uranyl units to create sheets. Additional BO{sub 3} triangles extend from the polyborate layers and are directed approximately perpendicular to the sheets. All of these compounds adopt layered structures. With the exception of KUBO-1, the structures are all centrosymmetric. All of these compounds fluoresce when irradiated with long-wavelength UV light. The fluorescence spectrum yields well-defined vibronically coupled charge-transfer features.« less

Grain-Size Based Additivity Models for Scaling Multi-rate Uranyl Surface Complexation in Subsurface Sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xiaoying; Liu, Chongxuan; Hu, Bill X.

The additivity model assumed that field-scale reaction properties in a sediment including surface area, reactive site concentration, and reaction rate can be predicted from field-scale grain-size distribution by linearly adding reaction properties estimated in laboratory for individual grain-size fractions. This study evaluated the additivity model in scaling mass transfer-limited, multi-rate uranyl (U(VI)) surface complexation reactions in a contaminated sediment. Experimental data of rate-limited U(VI) desorption in a stirred flow-cell reactor were used to estimate the statistical properties of the rate constants for individual grain-size fractions, which were then used to predict rate-limited U(VI) desorption in the composite sediment. The resultmore » indicated that the additivity model with respect to the rate of U(VI) desorption provided a good prediction of U(VI) desorption in the composite sediment. However, the rate constants were not directly scalable using the additivity model. An approximate additivity model for directly scaling rate constants was subsequently proposed and evaluated. The result found that the approximate model provided a good prediction of the experimental results within statistical uncertainty. This study also found that a gravel-size fraction (2 to 8 mm), which is often ignored in modeling U(VI) sorption and desorption, is statistically significant to the U(VI) desorption in the sediment.« less

Design of a Fission 99 Mo Recovery Process and Implications toward Mo Adsorption Mechanism on Titania and Alumina Sorbents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stepinski, Dominique C.; Youker, Amanda J.; Krahn, Elizabeth O.

2017-03-01

Molybdenum-99 is a parent of the most widely used medical isotope technetium-99m. Proliferation concerns have prompted development of alternative Mo production methods utilizing low enriched uranium. Alumina and titania sorbents were evaluated for separation of Mo from concentrated uranyl nitrate solutions. System, mass transfer, and isotherm parameters were determined to enable design of Mo separation processes under a wide range of conditions. A model-based approach was utilized to design representative commercial-scale column processes. The designs and parameters were verified with bench-scale experiments. The results are essential for design of Mo separation processes from irradiated uranium solutions, selection of support materialmore » and process optimization. Mo uptake studies show that adsorption decreases with increasing concentration of uranyl nitrate; howeveL, examination of Mo adsorption as a function of nitrate ion concentration shows no dependency, indicating that uranium competes with Mo for adsorption sites. These results are consistent with reports indicating that Mo forms inner-sphere complexes with titania and alumina surface groups.« less

Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

NASA Astrophysics Data System (ADS)

Ward, Jesse D.; Bowden, Mark; Tom Resch, C.; Eiden, Gregory C.; Pemmaraju, C. D.; Prendergast, David; Duffin, Andrew M.

2017-01-01

Uranium ores mined for industrial use are typically acid-leached to produce yellowcake and then converted into uranium halides for enrichment and purification. These anthropogenic chemical forms of uranium are distinct from their mineral counterparts. The purpose of this study is to use soft X-ray absorption spectroscopy to characterize several common anthropogenic uranium compounds important to the nuclear fuel cycle. Chemical analyses of these compounds are important for process and environmental monitoring. X-ray absorption techniques have several advantages in this regard, including element-specificity, chemical sensitivity, and high spectral resolution. Oxygen K-edge spectra were collected for uranyl nitrate, uranyl fluoride, and uranyl chloride, and fluorine K-edge spectra were collected for uranyl fluoride and uranium tetrafluoride. Interpretation of the data is aided by comparisons to calculated spectra. The effect of hydration state on the sample, a potential complication in interpreting oxygen K-edge spectra, is discussed. These compounds have unique spectral signatures that can be used to identify unknown samples.

Insight into hydrogen bonding of uranyl hydroxide layers and capsules by use of 1H magic-angle spinning NMR spectroscopy [Insight into the hydrogen bonding for uranyl hydroxides using 1H MAS NMR spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alam, Todd M.; Liao, Zuolei; Nyman, May

Solid-state 1H magic-angle spinning (MAS) NMR was used to investigate local proton environments in anhydrous [UO 2(OH) 2] (α-UOH) and hydrated uranyl hydroxide [(UO 2) 4O(OH) 6·5H 2O (metaschoepite). For the metaschoepite material, proton resonances of the μ 2-OH hydroxyl and interlayer waters were resolved, with two-dimensional (2D) double-quantum (DQ) 1H– 1H NMR correlation experiments revealing strong dipolar interactions between these different proton species. The experimental NMR results were combined with first-principles CASTEP GIPAW (gauge including projector-augmented wave) chemical shift calculations to develop correlations between hydrogen-bond strength and observed 1H NMR chemical shifts. Furthermore, these NMR correlations allowed characterization ofmore » local hydrogen-bond environments in uranyl U 24 capsules and of changes in hydrogen bonding that occurred during thermal dehydration of metaschoepite.« less

Insight into hydrogen bonding of uranyl hydroxide layers and capsules by use of 1H magic-angle spinning NMR spectroscopy [Insight into the hydrogen bonding for uranyl hydroxides using 1H MAS NMR spectroscopy

DOE PAGES

Alam, Todd M.; Liao, Zuolei; Nyman, May; ...

2016-04-27

Solid-state 1H magic-angle spinning (MAS) NMR was used to investigate local proton environments in anhydrous [UO 2(OH) 2] (α-UOH) and hydrated uranyl hydroxide [(UO 2) 4O(OH) 6·5H 2O (metaschoepite). For the metaschoepite material, proton resonances of the μ 2-OH hydroxyl and interlayer waters were resolved, with two-dimensional (2D) double-quantum (DQ) 1H– 1H NMR correlation experiments revealing strong dipolar interactions between these different proton species. The experimental NMR results were combined with first-principles CASTEP GIPAW (gauge including projector-augmented wave) chemical shift calculations to develop correlations between hydrogen-bond strength and observed 1H NMR chemical shifts. Furthermore, these NMR correlations allowed characterization ofmore » local hydrogen-bond environments in uranyl U 24 capsules and of changes in hydrogen bonding that occurred during thermal dehydration of metaschoepite.« less

Uranium XAFS analysis of kidney from rats exposed to uranium

PubMed Central

Kitahara, Keisuke; Numako, Chiya; Terada, Yasuko; Nitta, Kiyohumi; Homma-Takeda, Shino

2017-01-01

The kidney is the critical target of uranium exposure because uranium accumulates in the proximal tubules and causes tubular damage, but the chemical nature of uranium in kidney, such as its chemical status in the toxic target site, is poorly understood. Micro-X-ray absorption fine-structure (µXAFS) analysis was used to examine renal thin sections of rats exposed to uranyl acetate. The U L III-edge X-ray absorption near-edge structure spectra of bulk renal specimens obtained at various toxicological phases were similar to that of uranyl acetate: their edge position did not shift compared with that of uranyl acetate (17.175 keV) although the peak widths for some kidney specimens were slightly narrowed. µXAFS measurements of spots of concentrated uranium in the micro-regions of the proximal tubules showed that the edge jump slightly shifted to lower energy. The results suggest that most uranium accumulated in kidney was uranium (VI) but a portion might have been biotransformed in rats exposed to uranyl acetate. PMID:28244440

Uranium XAFS analysis of kidney from rats exposed to uranium.

PubMed

Kitahara, Keisuke; Numako, Chiya; Terada, Yasuko; Nitta, Kiyohumi; Shimada, Yoshiya; Homma-Takeda, Shino

2017-03-01

The kidney is the critical target of uranium exposure because uranium accumulates in the proximal tubules and causes tubular damage, but the chemical nature of uranium in kidney, such as its chemical status in the toxic target site, is poorly understood. Micro-X-ray absorption fine-structure (µXAFS) analysis was used to examine renal thin sections of rats exposed to uranyl acetate. The U L III -edge X-ray absorption near-edge structure spectra of bulk renal specimens obtained at various toxicological phases were similar to that of uranyl acetate: their edge position did not shift compared with that of uranyl acetate (17.175 keV) although the peak widths for some kidney specimens were slightly narrowed. µXAFS measurements of spots of concentrated uranium in the micro-regions of the proximal tubules showed that the edge jump slightly shifted to lower energy. The results suggest that most uranium accumulated in kidney was uranium (VI) but a portion might have been biotransformed in rats exposed to uranyl acetate.

Removal of uranyl ions by p-hexasulfonated calyx[6]arene acid

NASA Astrophysics Data System (ADS)

Popescu (Hoştuc), Ioana-Carmen; Petru, Filip; Humelnicu, Ionel; Mateescu, Marina; Militaru, Ecaterina; Humelnicu, Doina

2014-10-01

Radioactive pollution is a significant threat for the people's health. Therefore highly effective radioactive decontamination methods are required. Ion exchange, biotechnologies and phytoremediation in constructed wetlands have been used as radioactive decontamination technologies for uranium contaminated soil and water remediation. Recently, beside those classical methods the calix[n]arenic derivatives' utilization as radioactive decontaminators has jogged attention. The present work aims to present the preliminary research results of uranyl ion sorption studies on the p-hexasulfonated calyx[6]arenic acid. The effect of temperature, contact time, sorbent amount and uranyl concentration variation on sorption efficiency was investigated. Isotherm models revealed that the sorption process fit better Langmuir isotherm.

Process for the extraction of technetium from uranium

DOEpatents

Gong, Cynthia-May S.; Poineau, Frederic; Czerwinski, Kenneth R.

2010-12-21

A spent fuel reprocessing method contacts an aqueous solution containing Technetium(V) and uranyl with an acidic solution comprising hydroxylamine hydrochloride or acetohydroxamic acid to reduce Tc(V) to Tc(II, and then extracts the uranyl with an organic phase, leaving technetium(II) in aqueous solution.

Negative Stains Containing Trehalose: Application to Tubular and Filamentous Structures

NASA Astrophysics Data System (ADS)

Harris, J. Robin; Gerber, Max; Gebauer, Wolfgang; Wernicke, Wolfgang; Markl, Jürgen

1996-02-01

Several examples are presented that show the successful application of uranyl acetate and ammonium molybdate negative staining in the presence of trehalose for TEM studies of filamentous and tubular structures. The principal benefit to be gained from the inclusion of trehalose stems from the considerably reduced flattening of the large tubular structures and the greater orientational freedom of single molecules due to an increased depth of the negative stain in the presence of trehalose. Trehalose is likely to provide considerable protection to protein molecules and their assemblies during the drying of negatively stained specimens. Some reduction in the excessive density imparted by uranyl acetate around large assemblies is also achieved. Nevertheless, in the presence of 1% (w/v) trehalose, it is desirable to increase the concentration of negative stain to 5% (w/v) for ammonium molybdate and to 4% for uranyl acetate to produce satisfactory image contrast. In general, the ammonium molybdate-trehalose negative stain is more satisfactory than the uranyl acetate-trehalose combination, because of the greater electron beam sensitivity of the uranyl negative stain. Reassembled taxol-stabilized pig brain microtubules, together with collagen fibrils, sperm tails, helical filaments, and reassociated hemocyanin (KLH2), all from the giant keyhole limpet Megathura crenulata, have been studied by negative staining in the presence of trehalose. In all cases satisfactory TEM imaging conditions were readily obtained on the specimens, as long as regions of excessively deep stain were avoided.

Inhibition of poly(ADP-ribose)polymerase-1 and DNA repair by uranium

PubMed Central

Cooper, Karen L.; Dashner, Erica J.; Tsosie, Ranalda; Cho, Young Mi; Lewis, Johnnye

2015-01-01

Uranium has radiological and non-radiological effects within biological systems and there is increasing evidence for genotoxic and carcinogenic properties attributable to uranium through its heavy metal properties. In this study, we report that low concentrations of uranium (as uranyl acetate; <10 μM) is not cytotoxic to human embryonic kidney cells or normal human keratinocytes; however, uranium exacerbates DNA damage and cytotoxicity induced by hydrogen peroxide, suggesting that uranium may inhibit DNA repair processes. Concentrations of uranyl acetate in the low micromolar range inhibited the zinc finger DNA repair protein poly(ADP-ribose) polymerase (PARP)-1 and caused zinc loss from PARP-1 protein. Uranyl acetate exposure also led to zinc loss from the zinc finger DNA repair proteins Xeroderma Pigmentosum, Complementation Group A (XPA) and aprataxin (APTX). In keeping with the observed inhibition of zinc finger function of DNA repair proteins, exposure to uranyl acetate enhanced retention of induced DNA damage. Co-incubation of uranyl acetate with zinc largely overcame the impact of uranium on PARP-1 activity and DNA damage. These findings present evidence that low concentrations of uranium can inhibit DNA repair through disruption of zinc finger domains of specific target DNA repair proteins. This may provide a mechanistic basis to account for the published observations that uranium exposure is associated with DNA repair deficiency in exposed human populations. PMID:26627003

Inhibition of poly(ADP-ribose)polymerase-1 and DNA repair by uranium.

PubMed

Cooper, Karen L; Dashner, Erica J; Tsosie, Ranalda; Cho, Young Mi; Lewis, Johnnye; Hudson, Laurie G

2016-01-15

Uranium has radiological and non-radiological effects within biological systems and there is increasing evidence for genotoxic and carcinogenic properties attributable to uranium through its heavy metal properties. In this study, we report that low concentrations of uranium (as uranyl acetate; <10 μM) is not cytotoxic to human embryonic kidney cells or normal human keratinocytes; however, uranium exacerbates DNA damage and cytotoxicity induced by hydrogen peroxide, suggesting that uranium may inhibit DNA repair processes. Concentrations of uranyl acetate in the low micromolar range inhibited the zinc finger DNA repair protein poly(ADP-ribose) polymerase (PARP)-1 and caused zinc loss from PARP-1 protein. Uranyl acetate exposure also led to zinc loss from the zinc finger DNA repair proteins Xeroderma Pigmentosum, Complementation Group A (XPA) and aprataxin (APTX). In keeping with the observed inhibition of zinc finger function of DNA repair proteins, exposure to uranyl acetate enhanced retention of induced DNA damage. Co-incubation of uranyl acetate with zinc largely overcame the impact of uranium on PARP-1 activity and DNA damage. These findings present evidence that low concentrations of uranium can inhibit DNA repair through disruption of zinc finger domains of specific target DNA repair proteins. This may provide a mechanistic basis to account for the published observations that uranium exposure is associated with DNA repair deficiency in exposed human populations. Copyright © 2015 Elsevier Inc. All rights reserved.

Synthesis and structure of R{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (R = Rb or Cs)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serezhkin, V. N., E-mail: lserezh@samsu.ru; Peresypkina, E. V.; Grigor’eva, V. A.

2015-01-15

Crystals Rb{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (I) and Cs{sub 2}[UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}] (II) have been synthesized and studied by IR spectroscopy and X-ray diffraction. Crystals I are monoclinic, with the following parameters: a = 12.2118(5) Å, b = 10.2545(3) Å, c = 11.8754(4) Å, β = 110.287(1)°, sp. gr. C2/c, Z = 4, and R = 0.0523. Crystals II are orthorhombic, with a = 13.7309(3) Å, b = 10.5749(2) Å, c = 10.1891(2) Å, sp. gr. Pnma, Z = 4, and R = 0.0411. The basic structural units of crystals I and II are one-core complexes [UO{submore » 2}(NO{sub 3}){sub 2}(NCS){sub 2}]{sup 2−}, which belong to the crystallochemical group cis-AB{sub 2}{sup 01}M{sub 2}{sup 1} (A = UO{sub 2}{sup 2+}, B{sup 01} = NO{sub 3}{sup −}, M{sup 1} = NCS{sup −}), which are combined into a framework via electrostatic interactions with ions of alkaline metals R (R = Rb or Cs). The structural features of crystals I and II, which condition the formation of [UO{sub 2}(NO{sub 3}){sub 2}(NCS){sub 2}]{sup 2−} complexes with a cis rather than a trans position of isothiocyanate ions in the coordination sphere of uranyl ions, are discussed.« less

Influence of uranyl speciation and iron oxides on uranium biogeochemical redox reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stewart, B.D.; Amos, R.T.; Nico, P.S.

2010-03-15

Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous- and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO{sub 2}{sup 2+} and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO{sub 2}. However, various factors within soils and sediments may limit biological reduction of U(VI), inclusive of alterations in U(VI) speciation and competitive electron acceptors. Here we elucidate themore » impact of U(VI) speciation on the extent and rate of reduction with specific emphasis on speciation changes induced by dissolved Ca, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction. The amount of uranium removed from solution during 100 h of incubation with S. putrefaciens was 77% with no Ca or ferrihydrite present but only 24% (with ferrihydrite) and 14% (no ferrihydrite) were removed for systems with 0.8 mM Ca. Imparting an important criterion on uranium reduction, goethite and hematite decrease the dissolved concentration of calcium through adsorption and thus tend to diminish the effect of calcium on uranium reduction. Dissimilatory reduction of Fe(III) and U(VI) can proceed through different enzyme pathways, even within a single organism, thus providing a potential second means by which Fe(III) bearing minerals may impact U(VI) reduction. We quantify rate coefficients for simultaneous dissimilatory reduction of Fe(III) and U(VI) in systems varying in Ca concentration (0 to 0.8 mM), and using a mathematical construct implemented with the reactive transport code MIN3P, we reveal the predominant influence of uranyl speciation, specifically the formation of uranyl-calcium-carbonato complexes, and ferrihydrite on the rate and extent of uranium reduction in complex geochemical systems.« less

SEPARATION OF URANYL AND RUTHENIUM VALUES BY THE TRIBUTYL PHOSPHATE EXTRACTION PROCESS

DOEpatents

Wilson, A.S.

1961-05-01

A process is given for separating uranyl values from ruthenium values contained in an aqueous 3 to 4 M nitric acid solution. After the addition of hydrogen peroxide to obtain a concentration of 0.3 M, the uranium is selectively extracted with kerosene-diluted tributyl phosphate.

U-EXTRACTION--IMPROVEMENTS IN ELIMINATION OF Mo BY USE OF FERRIC ION

DOEpatents

Clark, H.M.; Duffey, D.

1958-06-10

An improved solvent extraction process is described whereby U may be extracted by a water immiscible organic solvent from an aqueous solution of uranyl nitrate. It has been found that Mo in the presence of phosphate ions appears to form a complex with the phosphate which extracts along with the U. This extraction of Mo may be suppressed by providing ferric ion in the solution prior to the extraction step. The ferric ion is preferably provided in the form of ferric nitrate.

Unprecedented reduction of the uranyl ion [UO2]2+ into a polyoxo uranium(IV) cluster: synthesis and crystal structure of the first f-element oxide with a M6(micro3-O)8 core.

PubMed

Berthet, Jean-Claude; Thuéry, Pierre; Ephritikhine, Michel

2005-07-21

The smooth comproportionation reaction of the U(VI) and U(III) complexes UO2(OTf)2 and U(OTf)3, afforded the hexanuclear U(IV) oxide cluster [U6(micro3-O)8(micro2-OTf)8(py)8], a rare example of a metal oxide with a M6(micro3-O)8 core.

Precipitation and Dissolution of Uranyl Phosphates in a Microfluidic Pore Structure

NASA Astrophysics Data System (ADS)

Werth, C. J.; Fanizza, M.; Strathmann, T.; Finneran, K.; Oostrom, M.; Zhang, C.; Wietsma, T. W.; Hess, N. J.

2011-12-01

The abiotic precipitation of uranium (U(VI)) was evaluated in a microfluidic pore structure (i.e. micromodel) to assess the efficacy of using a phosphate amendment to immobilize uranium in groundwater and mitigate the risk of this contaminant to potential down-gradient receptor sites. U(VI) was mixed transverse to the direction of flow with hydrogen phosphate (HPO42-), in the presence or absence of calcium (Ca2+) or sulfate (SO42-), in order to identify precipitation rates, the morphology and types of minerals formed, and the stability of these minerals to dissolution with and without bicarbonate (HCO3-) present. Raman backscattering spectroscopy and micro X-ray diffraction (μ-XRD) results both showed that the only mineral precipitated was chernikovite (also known as hydrogen uranyl phosphate; UO2HPO4), even though the formation of other minerals were thermodynamically favored depending on the experimental conditions. Precipitation and dissolution rates varied with influent conditions. Relative to when only U(VI) and HPO42- were present, precipitation rates were 2.3 times slower when SO42- was present, and 1.4 times faster when Ca2+ was present. These rates were inversely related to the size of crystals formed during precipitation. Dissolution rates for chernikovite increased with increasing HCO3- concentrations, consistent with formation of uranyl carbonate complexes in aqueous solution, and they were the fastest for chernikovite formed in the presence of SO42-, and slowest for the chernikovite formed in the presence of Ca2+. These rates are related to the ratios of mineral-water interfacial area to mineral volume. Fluorescent tracer studies and laser confocal microscopy images showed that densely aggregated precipitates blocked pores and reduced permeability. The results suggest that changes in the solute conditions evaluated affect precipitation rates, crystal morphology, and crystal stability, but not mineral type.

CONTINUOUS PRECIPITATION METHOD FOR CONVERSION OF URANYL NITRATE TO URANIUM HEXAFLUORIDE

DOEpatents

Reinhart, G.M.; Collopy, T.J.

1962-11-13

A continuous precipitation process is given for converting a uranyl nitrate solution to uranium tetrafluoride. A stream of the uranyl nitrate solution and a stream of an aqueous ammonium hydroxide solution are continuously introduced into an agitated reaction zone maintained at a pH of 5.0 to 6.5. Flow rates are adjusted to provide a mean residence time of the resulting slurry in the reaction zone of at least 30 minutes. After a startup period of two hours the precipitate is recovered from the effluent stream by filtration and is converted to uranium tetrafluoride by reduction to uranium dioxide with hydrogen and reaction of the uranium dioxide with anhydrous hydrogen fluoride. (AEC)

ANALYTICAL METHOD FOR THE DETERMINATION OF BORON IN URANYL NITRATE SOLUTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1962-01-01

A method was developed for the determination of boron in uranyl nitrate solutions. The boron is separated from uranium and other impurities by distillation of methyl borate. It is determined absorptiometrically by means of curcumin in the presence of orthochlorophenol, perchloric acid, and acetic anhydride. The limit of detection is judged to be not greater than 0.05 mu g, but is dependent on the purity of the reagents used. The coefficient of variation on 210 results at the 0.2 mu g boron level was 26% with a bias of -25%. The method may be applied to depleted uranyl nitrate solutionsmore » and uranium slag recovery liquors. (auth)« less

Biosensing for the Environment and Defence: Aqueous Uranyl Detection Using Bacterial Surface Layer Proteins

PubMed Central

Conroy, David J.R.; Millner, Paul A.; Stewart, Douglas I.; Pollmann, Katrin

2010-01-01

The fabrication of novel uranyl (UO22+) binding protein based sensors is reported. The new biosensor responds to picomolar levels of aqueous uranyl ions within minutes using Lysinibacillus sphaericus JG-A12 S-layer protein tethered to gold electrodes. In comparison to traditional self assembled monolayer based biosensors the porous bioconjugated layer gave greater stability, longer electrode life span and a denser protein layer. Biosensors responded specifically to UO22+ ions and showed minor interference from Ni2+, Cs+, Cd2+ and Co2+. Chemical modification of JG-A12 protein phosphate and carboxyl groups prevented UO22+ binding, showing that both moieties are involved in the recognition to UO22+. PMID:22399904

ELECTROLYTIC PREPARATION OF UF$sub 4$

DOEpatents

Allen, A.L.; Anderson, R.W.; Powell, E.W.

1958-11-01

A method is presented for converting hexavalent aranium to uranium tetrafluoride. The method consists of electrolyzing a solution of uranyl fluoride in hydrofluoric acld at about 90 icient laborato C. The uranyl ions are reduced at the cathode and a hydrated uranium tetrafluoride precipitates. The precipitate is separated and subsequently dehydrated to UF/sub 4/.

Ultrasensitive detection of uranyl by graphene oxide-based background reduction and RCDzyme-based enzyme strand recycling signal amplification.

PubMed

Li, Ming-Hui; Wang, Yong-Sheng; Cao, Jin-Xiu; Chen, Si-Han; Tang, Xian; Wang, Xiao-Feng; Zhu, Yu-Feng; Huang, Yan-Qin

2015-10-15

We proposed a novel strategy which combines graphene oxide-based background reduction with RCDzyme-based enzyme strand recycling amplification for ultrahigh sensitive detection of uranyl. The RCDzyme is designed to contain a guanine (G)-rich sequence that replaces the partial sequence in an uranyl-specific DNAzyme. This multifunctional probe can act as the target recognition element, DNAzyme and the primer of signal amplification. The presence of UO2(2+) can induce the cleavage of the substrate strands in RCDzyme. Then, each released enzyme strand can hybridize with another substrate strands to trigger many cycles of the cleavage by binding uranyl, leading to the formation of more G-quadruplexes by split guanine-rich oligonucleotide fragments. The resulting G-quadruplexes could bind to N-methyl-mesoporphyrin IX (NMM), causing an amplified detection signal for the target uranyl. Next, graphene oxide-based background reduction strategy was further employed for adsorbing free ssDNA and NMM, thereby providing a proximalis zero-background signal. The combination of RCDzyme signal amplification and proximalis zero-background signal remarkably improves the sensitivity of this method, achieving a dynamic range of two orders of magnitude and giving a detection limit down to 86 pM, which is much lower than those of related literature reports. These achievements might be helpful in the design of highly sensitive analytical platform for wide applications in environmental and biomedical fields. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of maleic acid and uranyl on mercurial diuresis in dogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nigrovic, V.; Koechel, D.A.; Cafruny, E.J.

1973-01-01

The effects of two nephrotoxic agents were studied in anesthetized dogs undergoing mercurial diuresis. One of the agents, uranyl, accumulates in the kidneys when administered as the acetate salt but does not readily react with sulfhydryl groups. In acute experiments uranyl acetate in doses up to 5 ..mu..mol/kg produced no change in the urinary excretion of sodium or chloride. Uranyl acetate given before the injection of mercury(II) did not reduce the diuretic response to inorganic mercury. The other compound, maleic acid, accumulates in the kidneys and also reacts readily with sulfhydryl groups. The administration of small doses of maleic acidmore » did not change the excretion of sodium but it decreased the excretion of chloride. The administration of maleic acid either before or after the administration of mercury completely abolished the diuretic response. The inhibition occurred without significant changes in urinary pH. Diuretic responses to ethacrynic acid, furosemide, hydrochlorothiazide or acetazolamide were preserved in maleate-treated dogs. Both the lack of any effect of uranyl on mercurial diuresis and the specific inhibition of mercurial diuresis by maleic acid support the presently accepted view that the renal diuretic receptor for mercury(II) has at least one sulfhydryl binding site. Although the inhibition is ascribed to competition between mercury(II) and maleate for binding on the receptor, it is conceivable that the reduction in urinary chloride excretion produced by maleate may be responsible, in part, for refractoriness to mercury(II).« less

Hydrothermal synthesis of uranyl squarates and squarate-oxalates: hydrolysis trends and in situ oxalate formation.

PubMed

Rowland, Clare E; Cahill, Christopher L

2010-07-19

We report the synthesis of two uranyl squarates and two mixed-ligand uranyl squarate-oxalates from aqueous solutions under hydrothermal conditions. These products exhibit a range of uranyl building units from squarates with monomers in (UO(2))(2)(C(4)O(4))(5).6NH(4).4H(2)O (1; a = 16.731(17) A, b = 7.280(8) A, c = 15.872(16) A, beta = 113.294(16) degrees , monoclinic, P2(1)/c) and chains in (UO(2))(2)(OH)(2)(H(2)O)(2)(C(4)O(4)) (2; a = 12.909(5) A, b = 8.400(3) A, c = 10.322(4) A, beta = 100.056(7) degrees , monoclinic, C2/c) to two squarate-oxalate polymorphs with dimers in (UO(2))(2)(OH)(C(4)O(4))(C(2)O(4)).NH(4).H(2)O (3; a = 9.0601(7) A, b = 15.7299(12) A, c = 10.5108(8) A, beta = 106.394(1) degrees , monoclinic, P2(1)/n; and 4; a = 8.4469(6) A, b = 7.7589(5) A, c = 10.5257(7) A, beta = 105.696(1) degrees , monoclinic, P2(1)/m). The dominance at low pH of monomeric species and the increasing occurrence of oligomeric species with increasing pH suggests that uranyl hydrolysis, mUO(2)(2+) + nH(2)O right harpoon over left harpoon [(UO(2))(m)(OH)(n)](2m-n) + nH(+), has a significant role in the identity of the inorganic building unit. Additional factors that influence product assembly include in situ hydrolysis of squaric acid to oxalic acid, dynamic metal to ligand concentration, and additional binding modes resulting from the introduction of oxalate anions. These points and the effects of uranyl hydrolysis with changing pH are discussed in the context of the compounds presented herein.

Synthesis and characterization of UO(2)(2+)-ion imprinted polymer for selective extraction of UO(2)(2+).

PubMed

Singh, Dhruv K; Mishra, Shraddha

2009-06-30

Ion-imprinted polymers (IIPs) were prepared for uranyl ion (imprint ion) by formation of binary (salicylaldoxime (SALO) or 4-vinylpyridine (VP)) or ternary (salicylaldoxime and 4-vinylpyridine) complex in 2-methoxy ethanol (porogen) following copolymerization with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking monomer using 2,2'-azobisisobutyronitrile as initiator. Control polymers (CPs) were also prepared under identical experimental conditions without using imprint ion. The above synthesized polymers were characterized by surface area measurement, microanalysis and FT-IR analysis techniques. The imprinted polymer formed with ternary complex of UO(2)(2+)-SALO-VP (1:2:2, IIP3) showed quantitative enrichment of uranyl ion from dilute aqueous solution and hence was chosen for detailed studies. The optimal pH for quantitative enrichment is 3.5-6.5. The adsorbed UO(2)(2+) was completely eluted with 10 mL of 1.0 M HCl. The retention capacity of IIP3 was found to be 0.559 mmol g(-1). Further, the distribution ratio and selectivity coefficients of uranium and other selected inorganic ions were also evaluated. Five replicate determinations of 25 microg L(-1) of uranium(VI) gave a mean absorbance of 0.032 with a relative standard deviation of 2.20%. The detection limit corresponding to three times the standard deviation of the blank was found to be 5 microg L(-1). IIP3 was tested for preconcentration of uranium(VI) from ground, river and sea water samples.

The crystal structure of ianthinite, [U 24+(UO 2) 4O 6(OH) 4(H 2O) 4](H 2O) 5: a possible phase for Pu 4+ incorporation during the oxidation of spent nuclear fuel

NASA Astrophysics Data System (ADS)

Burns, Peter C.; Finch, Robert J.; Hawthorne, Frank C.; Miller, Mark L.; Ewing, Rodney C.

1997-10-01

Ianthinite, [U 24+(UO 2) 4O 6(OH) 4(H 2O) 4](H 2O) 5, is the only known uranyl oxide hydrate mineral that contains U 4+, and it has been proposed that ianthinite may be an important Pu 4+-bearing phase during the oxidative dissolution of spent nuclear fuel. The crystal structure of ianthinite, orthorhombic, a = 0.7178(2), b = 1.1473(2), c = 3.039(1) nm, V = 2.5027 nm 3Z = 4, space group P2 1cn, has been solved by direct methods and refined by least-squares methods to an R index of 9.7% and a wR index of 12.6% using 888 unique observed [| F| ≥ 5 σ | F|] reflections. The structure contains both U 4+. The U 6+ cations are present as roughly linear (U 6+O 2) 2+ uranyl ion (Ur) that are in turn coordinated by five O 2- and OH - located at the equatorial positions of pentagonal bipyramids. The U 4+ cations are coordinated by O 2-, OH - and H 2O in a distorted octahedral arrangement. The Ur φ5and U 4+| 6 (φ: O 2-, OH -, H 2O) polyhedra l sharing edges to for two symmetrically distinct sheets at z ≈ 0.0 and z ≈ 0.25 that are parallel to (001). The sheets have the β-U 3O 8 sheet anion-topology. There are five symmetrically distinct H 2O groips located at z ≈ 0.125 between the sheets of U φn polyhedra, and the sheets of U φn polyhedra are linked together only by hydrogen bonding to the intersheet H 2O groups. The crystal-chemical requirements of U 4+ and Pu 4+ are very similar, suggesting that extensive Pu 4+ ↔ U 4+ substitution may occur within the sheets of U φn polyhedra in trh structure of ianthinine.

Construction of the Syngonium podophyllum-Pseudomonas sp. XNN8 Symbiotic Purification System and Investigation of Its Capability of Remediating Uranium Wastewater.

PubMed

Deng, Qin-Wen; Wang, Yong-Dong; Ding, De-Xin; Hu, Nan; Sun, Jing; He, Jia-Dong; Xu, Fei

2017-02-01

The endophyte Pseudomonas sp. XNN8 was separated from Typha orientalis which can secrete indole-3-acetic acid and 1-aminocyclopropane-1-carboxylate deaminase and siderophores and has strong resistance to uranium it was then colonized in the Syngonium podophyllum; and the S. podophyllum-Pseudomonas sp. XNN8 symbiotic purification system (SPPSPS) for uranium-containing wastewater was constructed. Afterwards, the hydroponic experiments to remove uranium from uranium-containing wastewater by the SPPSPS were conducted. After 24 days of treatment, the uranium concentrations of the wastewater samples with uranium concentrations between 0.5 and 5.0 mg/L were lowered to below 0.05 mg/L. Furthermore, the uranium in the plants was assayed using Fourier transform infrared spectroscopy (FTIR) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The Pseudomonas sp. XNN8 was found to generate substantial organic groups in the roots of the Syngonium podophyllum, which could improve the complexing capability of S. podophyllum for uranium. The uranium in the roots of S. podophyllum was found to be the uranyl phosphate (47.4 %) and uranyl acetate (52.6 %).

FLAME DENITRATION AND REDUCTION OF URANIUM NITRATE TO URANIUM DIOXIDE

DOEpatents

Hedley, W.H.; Roehrs, R.J.; Henderson, C.M.

1962-06-26

A process is given for converting uranyl nitrate solution to uranium dioxide. The process comprises spraying fine droplets of aqueous uranyl nitrate solution into a hightemperature hydrocarbon flame, said flame being deficient in oxygen approximately 30%, retaining the feed in the flame for a sufficient length of time to reduce the nitrate to the dioxide, and recovering uranium dioxide. (AEC)

SHINE and Mini-SHINE Column Designs for Recovery of Mo from 140 g-U/L Uranyl Sulfate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stepinski, Dominique C.; Vandegrift, George F.

Argonne is assisting SHINE Medical Technologies (SHINE) in their efforts to develop an accelerator-driven process that utilizes a uranyl-sulfate solution for the production of fission Mo-99. In an effort to design a Mo-recovery system for the SHINE project using low-enriched uranium (LEU), we conducted batch, breakthrough, and pulse tests to determine the Mo isotherm, mass-transfer zone (MTZ), and system parameters for a 130 g-U/L uranyl sulfate solution at pH 1 and 80°C, as described previously. The VERSE program was utilized to calculate the MTZ under various loading times and velocities. The results were then used to design Mo separation andmore » recovery columns employing a pure titania sorbent (110-μm particles, S110, and 60 Å pore size). The plant-scale column designs assume Mo will be separated from 271 L of a 141 g-U/L uranyl sulfate solution, pH 1, containing 0.0023 mM Mo. The VERSE-designed recovery systems have been tested and verified in laboratory-scale experiments, and this approach was found to be very successful.« less

Structure, Kinetics, and Thermodynamics of the Aqueous Uranyl(VI) Cation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerisit, Sebastien N.; Liu, Chongxuan

2013-08-20

Molecular simulation techniques are employed to gain insights into the structural, kinetic, and thermodynamic properties of the uranyl(VI) cation (UO22+) in aqueous solution. The simulations make use of an atomistic potential model (force field) derived in this work and based on the model of Guilbaud and Wipff (Guilbaud, P.; Wipff, G. J. Mol. Struct. (THEOCHEM) 1996, 366, 55-63). Reactive flux and thermodynamic integration calculations show that the derived potential model yields predictions for the water exchange rate and free energy of hydration, respectively, that are in agreement with experimental data. The water binding energies, hydration shell structure, and self-diffusion coefficientmore » are also calculated and discussed. Finally, a combination of metadynamics and transition path sampling simulations is employed to probe the mechanisms of water exchange reactions in the first hydration shell of the uranyl ion. These atomistic simulations indicate, based on two-dimensional free energy surfaces, that water exchanges follow an associative interchange mechanism. The nature and structure of the water exchange transition states are also determined. The improved potential model is expected to lead to more accurate predictions of uranyl adsorption energies at mineral surfaces using potential-based molecular dynamics simulations.« less

Uranium(VI) interactions with mackinawite in the presence and absence of bicarbonate and oxygen.

PubMed

Gallegos, Tanya J; Fuller, Christopher C; Webb, Samuel M; Betterton, William

2013-07-02

Mackinawite, Fe(II)S, samples loaded with uranium (10(-5), 10(-4), and 10(-3) mol U/g FeS) at pH 5, 7, and 9, were characterized using X-ray absorption spectroscopy and X-ray diffraction to determine the effects of pH, bicarbonate, and oxidation on uptake. Under anoxic conditions, a 5 g/L suspension of mackinawite lowered 5 × 10(-5) M uranium(VI) to below 30 ppb (1.26 × 10(-7) M) U. Between 82 and 88% of the uranium removed from solution by mackinawite was U(IV) and was nearly completely reduced to U(IV) when 0.012 M bicarbonate was added. Near-neighbor coordination consisting of uranium-oxygen and uranium-uranium distances indicates the formation of uraninite in the presence and absence of bicarbonate, suggesting reductive precipitation as the dominant removal mechanism. Following equilibration in air, mackinawite was oxidized to mainly goethite and sulfur and about 76% of U(IV) was reoxidized to U(VI) with coordination of uranium to axial and equatorial oxygen, similar to uranyl. Additionally, uranium-iron distances, typical of coprecipitation of uranium with iron oxides, and uranium-sulfur distances indicating bidentate coordination of U(VI) to sulfate were evident. The affinity of mackinawite and its oxidation products for U(VI) provides impetus for further study of mackinawite as a potential reactive medium for remediation of uranium-contaminated water.

Uranium(VI) interactions with mackinawite in the presence and absence of bicarbonate and oxygen

USGS Publications Warehouse

Gallegos, Tanya J.; Fuller, Christopher C.; Webb, Samuel M.; Betterton, William J.

2013-01-01

Mackinawite, Fe(II)S, samples loaded with uranium (10-5, 10-4, and 10-3 mol U/g FeS) at pH 5, 7, and 9, were characterized using X-ray absorption spectroscopy and X-ray diffraction to determine the effects of pH, bicarbonate, and oxidation on uptake. Under anoxic conditions, a 5 g/L suspension of mackinawite lowered 5 × 10-5 M uranium(VI) to below 30 ppb (1.26 × 10-7 M) U. Between 82 and 88% of the uranium removed from solution by mackinawite was U(IV) and was nearly completely reduced to U(IV) when 0.012 M bicarbonate was added. Near-neighbor coordination consisting of uranium–oxygen and uranium-uranium distances indicates the formation of uraninite in the presence and absence of bicarbonate, suggesting reductive precipitation as the dominant removal mechanism. Following equilibration in air, mackinawite was oxidized to mainly goethite and sulfur and about 76% of U(IV) was reoxidized to U(VI) with coordination of uranium to axial and equatorial oxygen, similar to uranyl. Additionally, uranium-iron distances, typical of coprecipitation of uranium with iron oxides, and uranium-sulfur distances indicating bidentate coordination of U(VI) to sulfate were evident. The affinity of mackinawite and its oxidation products for U(VI) provides impetus for further study of mackinawite as a potential reactive medium for remediation of uranium-contaminated water.

Periodic density functional theory investigation of the uranyl ion sorption on three mineral surfaces: a comparative study.

PubMed

Roques, Jérôme; Veilly, Edouard; Simoni, Eric

2009-06-04

Canister integrity and radionuclides retention is of prime importance for assessing the long term safety of nuclear waste stored in engineered geologic depositories. A comparative investigation of the interaction of uranyl ion with three different mineral surfaces has thus been undertaken in order to point out the influence of surface composition on the adsorption mechanism(s). Periodic DFT calculations using plane waves basis sets with the GGA formalism were performed on the TiO(2)(110), Al(OH)(3)(001) and Ni(111) surfaces. This study has clearly shown that three parameters play an important role in the uranyl adsorption mechanism: the solvent (H(2)O) distribution at the interface, the nature of the adsorption site and finally, the surface atoms' protonation state.

Periodic Density Functional Theory Investigation of the Uranyl Ion Sorption on Three Mineral Surfaces: A Comparative Study

PubMed Central

Roques, Jérôme; Veilly, Edouard; Simoni, Eric

2009-01-01

Canister integrity and radionuclides retention is of prime importance for assessing the long term safety of nuclear waste stored in engineered geologic depositories. A comparative investigation of the interaction of uranyl ion with three different mineral surfaces has thus been undertaken in order to point out the influence of surface composition on the adsorption mechanism(s). Periodic DFT calculations using plane waves basis sets with the GGA formalism were performed on the TiO2(110), Al(OH)3(001) and Ni(111) surfaces. This study has clearly shown that three parameters play an important role in the uranyl adsorption mechanism: the solvent (H2O) distribution at the interface, the nature of the adsorption site and finally, the surface atoms’ protonation state. PMID:19582222

Sensitivity analysis of high resolution gamma-ray detection for safeguards monitoring at natural uranium conversion facilities

DOE PAGES

Dewji, Shaheen A.; Croft, Stephen; Hertel, Nolan E.

2016-12-16

Under the policies proposed by recent International Atomic Energy Agency (IAEA) circulars and policy papers, implementation of safeguards exists when any purified aqueous uranium solution or uranium oxides suitable for isotopic enrichment or fuel fabrication exists. Under IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed in previous work to develop and validate gamma-ray nondestructive assay monitoring systemsmore » in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UO 2(NO 3) 2) solution exiting solvent extraction was identified as a key measurement point (KMP). Passive nondestructive assay techniques using high resolution gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely manner. Building upon the aforementioned previous validation work on detector sensitivity to varying concentrations of uranyl nitrate via a series of dilution measurements, this work investigates detector response parameter sensitivities to gamma-ray signatures of uranyl nitrate. The full energy peak efficiency of a detection system is dependent upon the sample, geometry, absorption, and intrinsic efficiency parameters. Perturbation of these parameters translates into corresponding variations of the 185.7 keV peak area of the 235U in uranyl nitrate. Such perturbations in the assayed signature impact the quality or versatility of the safeguards conclusions drawn. Given the potentially high throughput of uranyl nitrate in NUCPs, the ability to assay 1 SQ of material requires uncertainty «1%. Accounting for material self-shielding properties, pipe thickness, and source-detector orientation is instrumental in determining the robustness of gamma-ray detection in the process monitoring of uranyl nitrate in NUCPs. Monte Carlo models and ray-tracing models were employed to determine the sensitivity of the detected 185.7 keV photon to self-shielding properties, pipe thickness, and source-detector geometry. Considering the implementation of the detection of 1 SQ, diversion of 1 SQ becomes essentially undetectable given the systematic uncertainty, in addition to considerations such as propagating uncertainties due to pipe offset/position, as well as minor variations in pipe thickness. Consequently, pipe thickness was the most sensitive variable in affecting full energy efficiency of the 185.7 keV signature peak with up to 8% variation in efficiency for ±0.5 mm changes in Schedule 40 304L stainless steel piping. Furthermore, computation of the attenuation correction factor of the uranyl nitrate solution [CF(AT) (i.e. εsample)] using Parker's method using with the approximation for the geometrical factor κ≈π/4 was validated through experimental, Monte Carlo and ray-tracing calculations for a uranyl nitrate filled transfer pipe segment. Furthermore, quantifying sensitivity in detector position, as well as voiding effects due to bubbly flow or laminar flow with an air gap in the uranyl nitrate becomes increasingly important as considerations from (static) design-scale measurements translate into (dynamic) field operations tests.« less

Sensitivity analysis of high resolution gamma-ray detection for safeguards monitoring at natural uranium conversion facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dewji, Shaheen A.; Croft, Stephen; Hertel, Nolan E.

Under the policies proposed by recent International Atomic Energy Agency (IAEA) circulars and policy papers, implementation of safeguards exists when any purified aqueous uranium solution or uranium oxides suitable for isotopic enrichment or fuel fabrication exists. Under IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed in previous work to develop and validate gamma-ray nondestructive assay monitoring systemsmore » in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UO 2(NO 3) 2) solution exiting solvent extraction was identified as a key measurement point (KMP). Passive nondestructive assay techniques using high resolution gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely manner. Building upon the aforementioned previous validation work on detector sensitivity to varying concentrations of uranyl nitrate via a series of dilution measurements, this work investigates detector response parameter sensitivities to gamma-ray signatures of uranyl nitrate. The full energy peak efficiency of a detection system is dependent upon the sample, geometry, absorption, and intrinsic efficiency parameters. Perturbation of these parameters translates into corresponding variations of the 185.7 keV peak area of the 235U in uranyl nitrate. Such perturbations in the assayed signature impact the quality or versatility of the safeguards conclusions drawn. Given the potentially high throughput of uranyl nitrate in NUCPs, the ability to assay 1 SQ of material requires uncertainty «1%. Accounting for material self-shielding properties, pipe thickness, and source-detector orientation is instrumental in determining the robustness of gamma-ray detection in the process monitoring of uranyl nitrate in NUCPs. Monte Carlo models and ray-tracing models were employed to determine the sensitivity of the detected 185.7 keV photon to self-shielding properties, pipe thickness, and source-detector geometry. Considering the implementation of the detection of 1 SQ, diversion of 1 SQ becomes essentially undetectable given the systematic uncertainty, in addition to considerations such as propagating uncertainties due to pipe offset/position, as well as minor variations in pipe thickness. Consequently, pipe thickness was the most sensitive variable in affecting full energy efficiency of the 185.7 keV signature peak with up to 8% variation in efficiency for ±0.5 mm changes in Schedule 40 304L stainless steel piping. Furthermore, computation of the attenuation correction factor of the uranyl nitrate solution [CF(AT) (i.e. εsample)] using Parker's method using with the approximation for the geometrical factor κ≈π/4 was validated through experimental, Monte Carlo and ray-tracing calculations for a uranyl nitrate filled transfer pipe segment. Furthermore, quantifying sensitivity in detector position, as well as voiding effects due to bubbly flow or laminar flow with an air gap in the uranyl nitrate becomes increasingly important as considerations from (static) design-scale measurements translate into (dynamic) field operations tests.« less

Sensitivity analysis of high resolution gamma-ray detection for safeguards monitoring at natural uranium conversion facilities

NASA Astrophysics Data System (ADS)

Dewji, S. A.; Croft, S.; Hertel, N. E.

2017-03-01

Under the policies proposed by recent International Atomic Energy Agency (IAEA) circulars and policy papers, implementation of safeguards exists when any purified aqueous uranium solution or uranium oxides suitable for isotopic enrichment or fuel fabrication exists. Under IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed in previous work to develop and validate gamma-ray nondestructive assay monitoring systems in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UO2(NO3)2) solution exiting solvent extraction was identified as a key measurement point (KMP). Passive nondestructive assay techniques using high resolution gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely manner. Building upon the aforementioned previous validation work on detector sensitivity to varying concentrations of uranyl nitrate via a series of dilution measurements, this work investigates detector response parameter sensitivities to gamma-ray signatures of uranyl nitrate. The full energy peak efficiency of a detection system is dependent upon the sample, geometry, absorption, and intrinsic efficiency parameters. Perturbation of these parameters translates into corresponding variations of the 185.7 keV peak area of the 235U in uranyl nitrate. Such perturbations in the assayed signature impact the quality or versatility of the safeguards conclusions drawn. Given the potentially high throughput of uranyl nitrate in NUCPs, the ability to assay 1 SQ of material requires uncertainty «1%. Accounting for material self-shielding properties, pipe thickness, and source-detector orientation is instrumental in determining the robustness of gamma-ray detection in the process monitoring of uranyl nitrate in NUCPs. Monte Carlo models and ray-tracing models were employed to determine the sensitivity of the detected 185.7 keV photon to self-shielding properties, pipe thickness, and source-detector geometry. Considering the implementation of the detection of 1 SQ, diversion of 1 SQ becomes essentially undetectable given the systematic uncertainty, in addition to considerations such as propagating uncertainties due to pipe offset/position, as well as minor variations in pipe thickness. Consequently, pipe thickness was the most sensitive variable in affecting full energy efficiency of the 185.7 keV signature peak with up to 8% variation in efficiency for ±0.5 mm changes in Schedule 40 304L stainless steel piping. Furthermore, computation of the attenuation correction factor of the uranyl nitrate solution [CF(AT) (i.e. εsample)] using Parker's method using with the approximation for the geometrical factor κ≈π/4 was validated through experimental, Monte Carlo and ray-tracing calculations for a uranyl nitrate filled transfer pipe segment. Quantifying sensitivity in detector position, as well as voiding effects due to bubbly flow or laminar flow with an air gap in the uranyl nitrate becomes increasingly important as considerations from (static) design-scale measurements translate into (dynamic) field operations tests.

PROCESS OF SEPARATING URANIUM FROM AQUEOUS SOLUTION BY SOLVENT EXTRACTION

DOEpatents

Warf, J.C.

1958-08-19

A process is described for separating uranium values from aqueous uranyl nitrate solutions. The process consists in contacting the uramium bearing solution with an organic solvent, tributyl phosphate, preferably diluted with a less viscous organic liquida whereby the uranyl nitrate is extracted into the organic solvent phase. The uranvl nitrate may be recovered from the solvent phase bv back extracting with an aqueous mediuin.

PROCESS FOR EXTRACTING NEPTUNIUM AND PLUTONIUM FROM NITRIC ACID SOLUTIONS OF SAME CONTAINING URANYL NITRATE WITH A TERTIARY AMINE

DOEpatents

Sheppard, J.C.

1962-07-31

A process of selectively extracting plutonium nitrate and neptunium nitrate with an organic solution of a tertiary amine, away from uranyl nitrate present in an aqueous solution in a maximum concentration of 1M is described. The nitric acid concentration is adjusted to about 4M and nitrous acid is added prior to extraction. (AEC)

[La(UO{sub 2})V{sub 2}O{sub 7}][(UO{sub 2})(VO{sub 4})] the first lanthanum uranyl-vanadate with structure built from two types of sheets based upon the uranophane anion-topology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mer, A.; Obbade, S.; Rivenet, M.

2012-01-15

The new lanthanum uranyl vanadate divanadate, [La(UO{sub 2})V{sub 2}O{sub 7}][(UO{sub 2})(VO{sub 4})] was obtained by reaction at 800 Degree-Sign C between lanthanum chloride, uranium oxide (U{sub 3}O{sub 8}) and vanadium oxide (V{sub 2}O{sub 5}) and the structure was determined from single-crystal X-ray diffraction data. This compound crystallizes in the orthorhombic system with space group P2{sub 1}2{sub 1}2{sub 1} and unit-cell parameters a=6.9470(2) A, b=7.0934(2) A, c=25.7464(6) A, V=1268.73(5) A{sup 3}, Z=4. A full matrix least-squares refinement yielded R{sub 1}=0.0219 for 5493 independent reflections. The crystal structure is characterized by the stacking of uranophane-type sheets {sup 2}{sub {infinity}}[(UO{sub 2})(VO{sub 4})]{sup -}more » and double layers {sup 2}{sub {infinity}}[La(UO{sub 2})(V{sub 2}O{sub 7})]{sup +} connected through La-O bonds involving the uranyl oxygen of the uranyl-vanadate sheets. The double layers result from the connection of two {sup 2}{sub {infinity}}[La(UO{sub 2})(VO{sub 4}){sub 2}]{sup -} sheets derived from the uranophane anion-topology by replacing half of the uranyl ions by lanthanum atoms and connected through the formation of divanadate entities. - Graphical abstract: A view of the three-dimensional structure of [La(UO{sub 2})V{sub 2}O{sub 7}][(UO{sub 2})(VO{sub 4})]. Highlights: Black-Right-Pointing-Pointer New lanthanum uranyl vanadate divanadate has been synthesized. Black-Right-Pointing-Pointer Structure was determined from single-crystal X-ray diffraction data. Black-Right-Pointing-Pointer Structure is characterized by uranophane-type sheets and double layers {sup 2}{sub {infinity}}[La(UO{sub 2})(V{sub 2}O{sub 7})]{sup +}.« less

Inhibition of poly(ADP-ribose)polymerase-1 and DNA repair by uranium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooper, Karen L.; Dashner, Erica J.; Tsosie, Ranalda

Uranium has radiological and non-radiological effects within biological systems and there is increasing evidence for genotoxic and carcinogenic properties attributable to uranium through its heavy metal properties. In this study, we report that low concentrations of uranium (as uranyl acetate; < 10 μM) is not cytotoxic to human embryonic kidney cells or normal human keratinocytes; however, uranium exacerbates DNA damage and cytotoxicity induced by hydrogen peroxide, suggesting that uranium may inhibit DNA repair processes. Concentrations of uranyl acetate in the low micromolar range inhibited the zinc finger DNA repair protein poly(ADP-ribose) polymerase (PARP)-1 and caused zinc loss from PARP-1 protein.more » Uranyl acetate exposure also led to zinc loss from the zinc finger DNA repair proteins Xeroderma Pigmentosum, Complementation Group A (XPA) and aprataxin (APTX). In keeping with the observed inhibition of zinc finger function of DNA repair proteins, exposure to uranyl acetate enhanced retention of induced DNA damage. Co-incubation of uranyl acetate with zinc largely overcame the impact of uranium on PARP-1 activity and DNA damage. These findings present evidence that low concentrations of uranium can inhibit DNA repair through disruption of zinc finger domains of specific target DNA repair proteins. This may provide a mechanistic basis to account for the published observations that uranium exposure is associated with DNA repair deficiency in exposed human populations. - Highlights: • Low micromolar concentration of uranium inhibits polymerase-1 (PARP-1) activity. • Uranium causes zinc loss from multiple DNA repair proteins. • Uranium enhances retention of DNA damage caused by ultraviolet radiation. • Zinc reverses the effects of uranium on PARP activity and DNA damage repair.« less

Cyanex based uranyl sensitive polymeric membrane electrodes.

PubMed

Badr, Ibrahim H A; Zidan, W I; Akl, Z F

2014-01-01

Novel uranyl selective polymeric membrane electrodes were prepared using three different low-cost and commercially available Cyanex extractants namely, bis(2,4,4-trimethylpentyl) phosphinic acid [L1], bis(2,4,4-trimethylpentyl) monothiophosphinic acid [L2] and bis(2,4,4-trimethylpentyl) dithiophosphinic acid [L3]. Optimization and performance characteristics of the developed Cyanex based polymer membrane electrodes were determined. The influence of membrane composition (e.g., amount and type of ionic sites, as well as type of plasticizer) on potentiometric responses of the prepared membrane electrodes was studied. Optimized Cyanex-based membrane electrodes exhibited Nernstian responses for UO₂(2+) ion over wide concentration ranges with fast response times. The optimized membrane electrodes based on L1, L2 and L3 exhibited Nernstian responses towards uranyl ion with slopes of 29.4, 28.0 and 29.3 mV decade(-1), respectively. The optimized membrane electrodes based on L1-L3 showed detection limits of 8.3 × 10(-5), 3.0 × 10(-5) and 3.3 × 10(-6) mol L(-1), respectively. The selectivity studies showed that the optimized membrane electrodes exhibited high selectivity towards UO₂(2+) ion over large number of other cations. Membrane electrodes based on L3 exhibited superior potentiometric response characteristics compared to those based on L1 and L2 (e.g., widest linear range and lowest detection limit). The analytical utility of uranyl membrane electrodes formulated with Cyanex extractant L3 was demonstrated by the analysis of uranyl ion in different real samples for nuclear safeguards verification purposes. The results obtained using direct potentiometry and flow-injection methods were compared with those measured using the standard UV-visible and inductively coupled plasma spectroscopic methods. © 2013 Published by Elsevier B.V.

Incorporation of Np(V) and U(VI) in Carbonate and Sulfate Minerals Crystallized from Aqueous Solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balboni, Enrica; Morrison, Jessica M.; Wang, Zheming

2015-02-15

The neptunyl Np(V)O2 + and uranyl U(VI)O2 2+ ions are soluble in groundwater, although their interaction with minerals in the subsurface may impact their mobility. One mechanism for the immobilization of actinyl ions in the subsurface is coprecipitation in low-temperature minerals that form naturally, or that are induced to form as part of a remediation strategy. Important differences in the crystal-chemical behavior of the Np(V) neptunyl and U(VI) uranyl ions suggest their behavior towards incorporation into growing crystals may differ significantly. Using a selection of low temperature minerals synthesized in aqueous systems under ambient conditions, this study examines the factorsmore » that impact the structural incorporation of the Np(V) neptunyl and U(VI) uranyl ions in carbonate and sulfate minerals.« less

PROCESSES OF RECOVERING URANIUM FROM A CALUTRON

DOEpatents

Baird, D.O.; Zumwalt, L.R.

1958-07-15

An improved process is described for recovering the residue of a uranium compound which has been subjected to treatment in a calutron, from the parts of the calutron disposed in the source region upon which the residue is deposited. The process may be utilized when the uranium compound adheres to a surface containing metals of the group consisting of copper, iron, chromium, and nickel. The steps comprise washing the surface with an aqueous acidic oxidizing solvent for the uranium whereby there is obtained an acidic aqueous Solution containing uranium as uranyl ions and metals of said group as impurities, treating the acidic solution with sodium acetate in the presenee of added sodium nitrate to precipitate the uranium as sodium uranyl acetate away from the impurities in the solution, and separating the sodium uranyl acetate from the solution.

In Situ Bioremediation of Perchlorate in Vadose Zone Soil Using Gaseous Electron Donors

DTIC Science & Technology

2009-11-01

National Aeronautics and Space Administration ND Non-detect NDMA N-Nitrosodimethylamine No. Number NO3- Nitrate OD Outside diameter O&M...Nitrite xv • Selenate • Arsenate • Chromate and dichromate (i.e., hexavalent chromium) • Uranylate • Pertechnetate • N-Nitrosodimethylamine ( NDMA ...Arsenate • Chromate and dichromate (i.e., hexavalent chromium) • Uranylate • Pertechnetate • N-Nitrosodimethylamine ( NDMA ) • Trichloroethene (TCE

Recuperation of uranyl ions from effluents by means of microbiological collectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cecal, A.; Palamaru, I.; Humelnicu, D.

1997-12-31

This paper deals with the study of bioaccumulation of uranyl ions (UO{sub 2}{sup 2+}) from industrial effluents, using microbiological collectors: Nostoc linkia sp., Tolipotrix sp., Spirulina sp., Porphyridium cruentum and also the glucide extract of P. cruentum. The values of retaining degree of UO{sub 2}{sup 2+} on the biomass, for several experimental conditions, were established between 14.22 and 91.99%.

Patch testing with uranyl acetate in veterans exposed to depleted uranium during the 1991 Gulf war and the Iraqi conflict.

PubMed

Shvartsbeyn, Marianna; Tuchinda, Papapit; Gaitens, Joanna; Squibb, Katherine S; McDiarmid, Melissa A; Gaspari, Anthony A

2011-01-01

The Depleted Uranium Follow-Up Program is a clinical surveillance program run by the Baltimore Veterans Affairs Medical Center since 1993 for veterans of the Gulf and Iraqi wars who were exposed to depleted uranium (DU) as a result of "friendly-fire" incidents. In 2009, 40 veterans from this cohort were screened for skin reactivity to metals by patch-testing with extended metal series and uranyl acetate (0.25%, 2.5%, and 25%). A control arm comprised 46 patients without any known occupational exposures to DU who were seen at the University of Maryland Dermatology Clinic for evaluation of allergic contact dermatitis. Excluding irritant reactions, no patch-test reactions to uranyl acetate were observed in the participants. Irritant reactions to DU were more common in the clinic cohort, likely reflective of the demographic differences between the two arms of the study. Biologic monitoring of urine uranium concentrations in the DU program participants with 24-hour urine samples showed evidence of percutaneous uranium absorption from the skin patches. We conclude that dermatitis observed in a subset of the veterans was unrelated to their military DU exposure. Our data suggest that future studies of skin testing with uranyl acetate should utilize 0.25%, the least irritating concentration.

KINETICS OF THE DISSOLUTION OF URANIUM DIOXIDE IN CARBONATE-BICARBONATE SOLUTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schortmann, W.E.; DeSesa, M.A.

The kinetics of the dissolution of uranium dioxide in sodium carbonate- sodium bicarbonate solutions were determined. The study was undertaken in order to obtain fundamental information about the commercial carbonate process for leaching uranium from its ores. A rate equation incorporating the effects of surface area oxygen partial pressure, temperature, and reagent concentrations was empirically developed. A mechanism consisting essentially of two consecutive reactions at steady state is proposed. These reactions are the oxidation of U/ sup 4+/ to U/sup 6+/ and the subsequent formation of the uranyl dicarbonate complexion. Depending on the conditions, either or both of these reactionsmore » can determine the over-all rate. The conversion of uranyl dicarbonate to the uranyl tricarbonate complexion is postulated to be very rapid. In the suggested mechanism, the rate-determining phase of the oxidation is the dissociation of adsorbed molecular oxygen. and both the carbonate and bicarbonate ions play equivalent roles in the formation of the uranyl dicarbonate. As indicated by their high activation energies of about 13 and 14 kcal per mole uranium, both reactions are chemical rather than diffusional processes. A mathematical examination of the proposed mechanism produced a rate equation consistent with the experimental information. The credibility of the mechanism was thereby strengthened. (auth)« less

A Raman spectroscopic study of the uranyl sulphate mineral johannite.

PubMed

Frost, Ray L; Erickson, Kristy L; Cejka, Jirí; Reddy, B Jagannadha

2005-09-01

Raman spectroscopy at 298 and 77K has been used to study the secondary uranyl mineral johannite of formula (Cu(UO2)2(SO4)2(OH)2 x 8H2O). Four Raman bands are observed at 3593, 3523, 3387 and 3234cm(-1) and four infrared bands at 3589, 3518, 3389 and 3205cm(-1). The first two bands are assigned to OH- units (hydroxyls) and the second two bands to water units. Estimations of the hydrogen bond distances for these four bands are 3.35, 2.92, 2.79 and 2.70 A. A sharp intense band at 1042 cm(-1) is attributed to the (SO4)2- symmetric stretching vibration and the three Raman bands at 1147, 1100 and 1090cm(-1) to the (SO4)2- anti-symmetric stretching vibrations. The nu2 bending modes were at 469, 425 and 388 cm(-1) at 77K confirming the reduction in symmetry of the (SO4)2- units. At 77K two bands at 811 and 786 cm(-1) are attributed to the nu1 symmetric stretching modes of the (UO2)2+ units suggesting the non-equivalence of the UO bonds in the (UO2)2+ units. The band at 786cm(-1), however, may be related to water molecules libration modes. In the 77K Raman spectrum, bands are observed at 306, 282, 231 and 210cm(-1) with other low intensity bands found at 191, 170 and 149cm(-1). The two bands at 282 and 210 cm(-1) are attributed to the doubly degenerate nu2 bending vibration of the (UO2)2+ units. Raman spectroscopy can contribute significant knowledge in the study of uranyl minerals because of better band separation with significantly narrower bands, avoiding the complex spectral profiles as observed with infrared spectroscopy.

Uptake and speciation of uranium in synthetic gypsum (CaSO4•2H2O): Applications to radioactive mine tailings.

PubMed

Lin, Jinru; Sun, Wei; Desmarais, Jacques; Chen, Ning; Feng, Renfei; Zhang, Patrick; Li, Dien; Lieu, Arthur; Tse, John S; Pan, Yuanming

2018-01-01

Phosphogypsum formed from the production of phosphoric acid represents by far the biggest accumulation of gypsum-rich wastes in the world and commonly contains elevated radionuclides, including uranium, as well as other heavy metals and metalloids. Therefore, billions-of-tons of phosphogypsum stockpiled worldwide not only possess serious environmental problems but also represent a potential uranium resource. Gypsum is also a major solid constituent in many other types of radioactive mine tailings, which stems from the common usage of sulfuric acid in extraction processes. Therefore, management and remediation of radioactive mine tailings as well as future beneficiation of uranium from phosphogysum all require detailed knowledge about the nature and behavior of uranium in gypsum. However, little is known about the uptake mechanism or speciation of uranium in gypsum. In this study, synthesis experiments suggest an apparent pH control on the uptake of uranium in gypsum at ambient conditions: increase in U from 16 μg/g at pH = 6.5 to 339 μg/g at pH = 9.5. Uranium L 3 -edge synchrotron X-ray absorption spectroscopic analyses of synthetic gypsum show that uranyl (UO 2 ) 2+ at the Ca site is the dominant species. The EXAFS fitting results also indicate that uranyl in synthetic gypsum occurs most likely as carbonate complexes and yields an average U-O distance ∼0.25 Å shorter than the average Ca-O distance, signifying a marked local structural distortion. Applications to phosphogypsum from the New Wales phosphoric acid plant (Florida, USA) and uranium mine tailings from the Key Lake mill (Saskatchewan, Canada) show that gypsum is an important carrier of uranium over a wide range of pH and controls the fate of this radionuclide in mine tailings. Also, development of new technologies for recovering U from phosphogypsum in the future must consider lattice-bound uranyl in gypsum. Copyright © 2017 Elsevier Ltd. All rights reserved.

The geochemistry of water near a surficial organic-rich uranium deposit, northeastern Washington State, U.S.A.

USGS Publications Warehouse

Zielinski, R.A.; Otton, J.K.; Wanty, R.B.; Pierson, C.T.

1987-01-01

The chemistry of three stream, three spring and six near-surface waters in the vicinity of a Holocene organic-rich uranium deposit is described, with particular emphasis on the chemistry of U. Results characterize the solution behavior of uranium as U-bearing water interacts with relatively undecomposed, surficial organic matter. Of the measured major and trace chemical species, only U is consistently highly enriched (17-318 ppb) relative to reported values for regional waters, or to literature values for waters in largely granitic terrains. R-mode factor analysis of the chemical data suggests that most U is present in a soluble form, but that some U is also associated with fine suspended particulates of clay, organic matter, or hydrous oxides. Calculations that apply thermodynamic data to predict U speciation in solution indicate the relative importance of uranyl carbonate and uranyl phosphate complexes. Analysis of more finely filtered samples (0.05 ??m vs. 0.45 ??m), and direct radiographic observations using fission-track detectors suspended in the waters indicate the presence of some uraniferous particulate matter. Application of existing thermodynamic data for uranous- and uranyl-bearing minerals indicates that all waters are undersaturated with U minerals as long as ambient Eh ??? +0.1 v. If coexisting surface and near-surface waters are sufficiently oxidizing, initial fixation of U in the deposit should be by a mechanism of adsorption. Alternatively, more reducing conditions may prevail in deeper pore waters of the organic-rich host sediments, perhaps leading to direct precipitation or diagenetic formation of U4+ minerals. A 234U 238U alpha activity ratio of 1.08 ?? 0.02 in a spring issuing from a hillslope above the deposit suggests a relatively soluble source of U. In contrast, higher activity ratios of 234U 238U (??? 1.3) in waters in contact with the uraniferous valley-fill sediments suggest differences in the nature of interaction between groundwater and the local, U-rich source rocks. ?? 1987.

Validation of gamma-ray detection techniques for safeguards monitoring at natural uranium conversion facilities

NASA Astrophysics Data System (ADS)

Dewji, S. A.; Lee, D. L.; Croft, S.; Hertel, N. E.; Chapman, J. A.; McElroy, R. D.; Cleveland, S.

2016-07-01

Recent IAEA circulars and policy papers have sought to implement safeguards when any purified aqueous uranium solution or uranium oxides suitable for isotopic enrichment or fuel fabrication exists. Under the revised policy, IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed to develop and validate concepts of nondestructive assay monitoring systems in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UO2(NO3)2) solution exiting solvent extraction was identified as a key measurement point (KMP), where gamma-ray spectroscopy was selected as the process monitoring tool. The Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory was employed to simulate the full-scale operating conditions of a purified uranium-bearing aqueous stream exiting the solvent extraction process in an NUCP. Nondestructive assay techniques using gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely way. This work investigated gamma-ray signatures of uranyl nitrate circulating in the UNCLE facility and evaluated various gamma-ray detector sensitivities to uranyl nitrate. These detector validation activities include assessing detector responses to the uranyl nitrate gamma-ray signatures for spectrometers based on sodium iodide, lanthanum bromide, and high-purity germanium detectors. The results of measurements under static and dynamic operating conditions at concentrations ranging from 10-90 g U/L of natural uranyl nitrate are presented. A range of gamma-ray lines is examined, including attenuation for transmission measurement of density and concentration. It was determined that transmission-corrected gamma-ray spectra provide a reliable way to monitor the 235U concentration of uranyl nitrate solution in transfer pipes in NUCPs. Furthermore, existing predictive and analysis methods are adequate to design and realize practical designs. The 137Cs transmission source employed in this work is viable but not optimal for 235U densitometry determination. Validated simulations assessed the viability of 133Ba and 57Co as alternative densitometry sources. All three gamma-ray detectors are viable for monitoring natural uranium feed; although high-purity germanium is easiest to interpret, it is, however, the least attractive as an installation instrument. Overall, for monitoring throughput in a facility such as UNCLE, emulating the uranium concentration and pump speeds of the Springfields conversion facility in the United Kingdom, an uncertainty of less than 0.17% is required in order to detect the diversion of 1 SQ of uranyl nitrate through changes in uranium concentration over an accountancy period of one year with a detection probability of 50%. Although calibrated gamma-ray detection systems are capable of determining the concentration of uranium content in NUCPs, it is only in combination with verifiable operator declarations and supporting data, such as flow rate and enrichment, that safeguards conclusions can be drawn.

Comparative density functional study of the complexes [UO2(CO3)3]4- and [(UO2)3(CO3)6]6- in aqueous solution.

PubMed

Schlosser, Florian; Moskaleva, Lyudmila V; Kremleva, Alena; Krüger, Sven; Rösch, Notker

2010-06-28

With a relativistic all-electron density functional method, we studied two anionic uranium(VI) carbonate complexes that are important for uranium speciation and transport in aqueous medium, the mononuclear tris(carbonato) complex [UO(2)(CO(3))(3)](4-) and the trinuclear hexa(carbonato) complex [(UO(2))(3)(CO(3))(6)](6-). Focusing on the structures in solution, we applied for the first time a full solvation treatment to these complexes. We approximated short-range effects by explicit aqua ligands and described long-range electrostatic interactions via a polarizable continuum model. Structures and vibrational frequencies of "gas-phase" models with explicit aqua ligands agree best with experiment. This is accidental because the continuum model of the solvent to some extent overestimates the electrostatic interactions of these highly anionic systems with the bulk solvent. The calculated free energy change when three mono-nuclear complexes associate to the trinuclear complex, agrees well with experiment and supports the formation of the latter species upon acidification of a uranyl carbonate solution.

Characterization of UO2(2+) binding to osteopontin, a highly phosphorylated protein: insights into potential mechanisms of uranyl accumulation in bones.

PubMed

Qi, Lei; Basset, Christian; Averseng, Olivier; Quéméneur, Eric; Hagège, Agnès; Vidaud, Claude

2014-01-01

Bones are one of the few organs in which uranyl (UO2(2+)) accumulates. This large dioxo-cation displays affinity for carboxylates, phenolates and phosphorylated functional groups in proteins. The noncollagenous protein osteopontin (OPN) plays an important role in bone homeostasis. It is mainly found in the extracellular matrix of mineralized tissues but also in body fluids such as milk, blood and urine. Furthermore, OPN is an intrinsically disordered protein, which, like other proteins of the SIBLING family, contains a polyaspartic acid sequence and numerous patterns of alternating acidic and phosphorylated residues. All these properties led to the hypothesis that this protein could be prone to UO2(2+) binding. In this work, a simple purification procedure enabling highly purified bovine (bOPN) and human OPN (hOPN) to be obtained was developed. Various biophysical approaches were set up to study the impact of phosphorylations on the affinity of OPN for UO2(2+) as well as the formation of stable complexes originating from structural changes induced by the binding of this metal cation. The results obtained suggest a new mechanism of the interaction of UO2(2+) with bone metabolism and a new role for OPN as a metal transporter.

Method for photochemical reduction of uranyl nitrate by tri-N-butyl phosphate and application of this method to nuclear fuel reprocessing

DOEpatents

De Poorter, Gerald L.; Rofer-De Poorter, Cheryl K.

1978-01-01

Uranyl ion in solution in tri-n-butyl phosphate is readily photochemically reduced to U(IV). The product U(IV) may effectively be used in the Purex process for treating spent nuclear fuels to reduce Pu(IV) to Pu(III). The Pu(III) is readily separated from uranium in solution in the tri-n-butyl phosphate by an aqueous strip.

Study of Pulsed Columns with the System. Uranyl Nitrate-Nitric Acid-Water- Tributylphosphate; ETUDE DES COLONNES A PULSATIONS A L'AIDE DU SYSTEME NITRATE D'URANYLE-ACIDE NITRIQUEEAU-TRIBUTYLPHOSPHATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durandet, J.; Defives, D.; Choffe, B.

1959-10-31

The performsnce of a pulsed column with perforated plates was studied with the aid of a uranyl nitrate-nitric acid --water --tributyl phosphate system. The extraction of uranium from an aqueous acidic solution by an organic solvent and the extraction of uranium from organic solutions by water were the two cases investigated. The variation of the efficiency and the capacity of the pulsed column was determined as a function of the pulse amplitude and frequency, of the total flow rate, of the diameter of the holes, and of the choice of dispersed phase. The results showed that for a given amplitudemore » and total flow rate the efficiency has a maximum with an increase in frequency. (J.S.R.)« less

Neptunium incorporation into select uranyl phases and thermal analysis of select uranyl phases

NASA Astrophysics Data System (ADS)

Klingensmith, Amanda Leigh

Alteration of spent nuclear fuel in a geological repository under oxidizing conditions is likely to result in abundant uranyl compounds. The proposed repository at Yucca Mountain, Nevada is intended to store about 70,000 metric tons of spent nuclear fuel in the unsaturated zone of a welded tuff sequence. Following failure of canisters that encapsulate the waste, contents may be exposed both to air and water and undergo repetitive wetting and drying events. Incorporation of radionuclides into the uranyl alteration phases may significantly reduce their mobility, thereby impacting repository performance. Of particular interest is 237Np owing to its long half-life (2.14 x 106 years) and potential mobility in groundwater. Powders of the synthetic uranyl phase soddyite, (UO2) 2(SiO4)(H2O)2, a framework type structure, and uranophane, Ca[(UO2)(SiO3OH)]2(H 2O)5, kasolite, Pb[(UO2)(SiO4)]H 2O, Na compreignacite, Na2[(UO2)3O 2(OH)3]2(H2O)7, and becquerelite, Ca[(UO2)3O2(OH)3]2(H 2O)8, all of which are sheet type structures, were synthesized in the presence of Np5+ under varying temperature and pH conditions. Uranophane, kasolite, boltwoodite K[(UO2)(SiO3OH)](H 2O)1.5, and Na boltwoodite K,Na[(UO2)(SiO 3OH)](H2O)1.5 were synthesized in the presence of Np as well as P, Ca and/or Mg. Single crystals of Na metaschoepite, Na[(UO 2)4O2(OH)5]˙5H2O were synthesized in the presence of Np5+ and laser ablation verified that Np can be incorporated within the structure of a uranyl phase. Incorporation of Np5+ into soddyite increased steadily with synthesis temperature. Np incorporation into uranophane, becquerelite, and kasolite was not dependent on synthesis temperature. Np uptake in uranophane and kasolite was found to be dependent on synthesis pH, with an increase in Np uptake with higher pH. Uranophane, boltwoodite and Na boltwoodite showed an increase in Np incorporation in the presence of P. Boltwoodite showed an even higher Np uptake when Mg and P were both present in the synthesis. Thermal analysis was completed for the uranyl phases soddyite, becquerelite, Na compreignacite, uranophane, and kasolite. TGA curves for becquerelite, Na compreignacite and uranophane showed loss of interlayer water groups by 100°C. Soddyite and kasolite showed more gradual TGA curves and retention of water groups up to 400°C for soddyite and 550°C for kasolite, with agreement shown by high temperature powder XRD data.

A report on emergent uranyl binding phenomena by an amidoxime phosphonic acid co-polymer

DOE PAGES

Abney, C. W.; Das, S.; Mayes, R. T.; ...

2016-08-01

Development of technology to harvest the uranium dissolved in seawater would enable access to vast quantities of this critical metal for nuclear power generation. Amidoxime polymers are the most promising platform for achieving this separation, yet design of advanced adsorbents is hindered by uncertainty regarding the uranium binding mode. In this work we use XAFS to investigate the uranium coordination environment in an amidoxime-phosphonic acid copolymer adsorbent. In contrast to the binding mode predicted computationally and from small molecule studies, a cooperative chelating model is favoured, attributable to emergent behavior resulting from inclusion of amidoxime in a polymer. Samples exposedmore » to seawater also display a feature consistent with a 2-oxo-bridged transition metal, suggesting formation of an in situ specific binding site. As a result, these findings challenge long held assumptions and provide new opportunities for the design of advanced adsorbent materials.« less

SEPARATION OF THORIUM FROM URANIUM

DOEpatents

Bane, R.W.

1959-09-01

A description is given for the separation of thorium from uranium by forming an aqueous acidic solution containing ionic species of thorium, uranyl uranium, and hydroxylamine, flowing the solution through a column containing the phenol-formaldehyde type cation exchange resin to selectively adsorb substantially all the thorium values and a portion of the uranium values, flowing a dilute solution of hydrochloric acid through the column to desorb the uranium values, and then flowing a dilute aqueous acidic solution containing an ion, such as bisulfate, which has a complexing effect upon thortum through the column to desorb substantially all of the thorium.

PLUTONIUM SEPARATION METHOD

DOEpatents

Beaufait, L.J. Jr.; Stevenson, F.R.; Rollefson, G.K.

1958-11-18

The recovery of plutonium ions from neutron irradiated uranium can be accomplished by bufferlng an aqueous solutlon of the irradiated materials containing tetravalent plutonium to a pH of 4 to 7, adding sufficient acetate to the solution to complex the uranyl present, adding ferric nitrate to form a colloid of ferric hydroxide, plutonlum, and associated fission products, removing and dissolving the colloid in aqueous nitric acid, oxldizlng the plutonium to the hexavalent state by adding permanganate or dichromate, treating the resultant solution with ferric nitrate to form a colloid of ferric hydroxide and associated fission products, and separating the colloid from the plutonlum left in solution.

Effects of sulfate ligand on uranyl carbonato surface species on ferrihydrite surfaces

USGS Publications Warehouse

Arai, Yuji; Fuller, C.C.

2012-01-01

Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on ferrihydrite surfaces were studied in 0.01 M Na2SO4 solutions to simulate the major chemical composition of U-contaminatedgroundwater (i.e., [SO42-]~13 mM L-1) at the site. Uranyl sorption was greater at pH 7.5 than that at pH 4 in both air- and 2% pCO2-equilibrated systems. While there were negligible effects of sulfate ligands on the pH-dependent U(VI) sorption (<24 h) in both systems, X-ray absorption spectroscopy (XAS) analysis showed sulfate ligand associated U(VI) surface species at the ferrihydrite–water interface. In air-equilibrated systems, binary and mono-sulfate U(VI) ternary surface species co-existed at pH 5.43. At pH 6.55–7.83, a mixture of mono-sulfate and bis-carbonato U(VI) ternary surface species became more important. At 2% pCO2, there was no contribution of sulfate ligands on the U(VI) ternary surface species. Instead, a mixture of bis-carbonato inner-sphere (38%) and tris-carbonato outer-sphere U(VI) ternary surface species (62%) was found at pH 7.62. The study suggests that the competitive ligand (bicarbonate and sulfate) coordination on U(VI) surface species might be important in evaluating the U solid-state speciation in the AFO PRB at the study site where pCO2 fluctuates between 1 and 2 pCO2%.

Topologically identical, but geometrically isomeric layers in hydrous α-, β-Rb[UO{sub 2}(AsO{sub 3}OH)(AsO{sub 2}(OH){sub 2})]·H{sub 2}O and anhydrous Rb[UO{sub 2}(AsO{sub 3}OH)(AsO{sub 2}(OH){sub 2})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Na; Klepov, Vladislav V.; Villa, Eric M.

2014-07-01

The hydrothermal reaction of uranyl nitrate with rubidium nitrate and arsenic (III) oxide results in the formation of polymorphic α- and β-Rb[UO{sub 2}(AsO{sub 3}OH)(AsO{sub 2}(OH){sub 2})]·H{sub 2}O (α-, β-RbUAs) and the anhydrous phase Rb[UO{sub 2}(AsO{sub 3}OH)(AsO{sub 2}(OH){sub 2})] (RbUAs). These phases were structurally, chemically and spectroscopically characterized. The structures of all three compounds are based upon topologically identical, but geometrically isomeric layers. The layers are linked with each other by means of the Rb cations and hydrogen bonding. Dehydration experiments demonstrate that water deintercalation from hydrous α- and β-RbUAs yields anhydrous RbUAs via topotactic reactions. - Graphical abstract: Three differentmore » layer geometries observed in the structures of Rb[UO{sub 2}(AsO{sub 3}OH)(AsO{sub 2}(OH){sub 2})] and α- and β- Rb[UO{sub 2}(AsO{sub 3}OH)(AsO{sub 2}(OH){sub 2})]·H{sub 2}O. Two different coordination environments of uranium polyhedra (types I and II) are shown schematically on the top of the figure. - Highlights: • Three new uranyl arsenates were synthesized from the hydrothermal reactions. • The phases consist of the topologically identical but geometrically different layers. • Topotactic transitions were observed in the processes of mono-hyrates dehydration.« less

Effects of sulfate ligand on uranyl carbonato surface species on ferrihydrite surfaces.

PubMed

Arai, Yuji; Fuller, C C

2012-01-01

Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on ferrihydrite surfaces were studied in 0.01 M Na(2)SO(4) solutions to simulate the major chemical composition of U-contaminated groundwater (i.e., [SO(4)(2-)] ~13 mM L(-1)) at the site. Uranyl sorption was greater at pH 7.5 than that at pH 4 in both air- and 2% pCO(2)-equilibrated systems. While there were negligible effects of sulfate ligands on the pH-dependent U(VI) sorption (<24 h) in both systems, X-ray absorption spectroscopy (XAS) analysis showed sulfate ligand associated U(VI) surface species at the ferrihydrite-water interface. In air-equilibrated systems, binary and mono-sulfate U(VI) ternary surface species co-existed at pH 5.43. At pH 6.55-7.83, a mixture of mono-sulfate and bis-carbonato U(VI) ternary surface species became more important. At 2% pCO(2), there was no contribution of sulfate ligands on the U(VI) ternary surface species. Instead, a mixture of bis-carbonato inner-sphere (38%) and tris-carbonato outer-sphere U(VI) ternary surface species (62%) was found at pH 7.62. The study suggests that the competitive ligand (bicarbonate and sulfate) coordination on U(VI) surface species might be important in evaluating the U solid-state speciation in the AFO PRB at the study site where pCO(2) fluctuates between 1 and 2 pCO(2)%. Copyright © 2011 Elsevier Inc. All rights reserved.

URANIUM RECOVERY AND PURIFICATION PROCESS AND PRODUCTION OF HIGH PURITY URANIUM TETRAFLUORIDE

DOEpatents

Bailes, R.H.; Long, R.S.; Grinstead, R.R.

1957-09-17

A process is described wherein an anionic exchange technique is employed to separate uramium from a large variety of impurities. Very efficient and economical purification of contamimated uranium can be achieved by treatment of the contaminated uranium to produce a solution containing a high concentration of chloride. Under these conditions the uranium exists as an aniomic chloride complex. Then the uranium chloride complex is adsorbed from the solution on an aniomic exchange resin, whereby a portion of the impurities remain in the solution and others are retained with the uramium by the resin. The adsorbed impurities are then removed by washing the resin with pure concentrated hydrochloric acid, after which operation the uranium is eluted with pure water yielding an acidic uranyl chloride solution of high purity.

METHOD FOR DECONTAMINATION OF REACTOR SOLUTIONS

DOEpatents

Maraman, W.J.; Baxman, H.R.; Baker, R.D.

1959-05-01

A process for U recovery from phosphate fuel solutions is described. To fuel solution drawn from the reactor is added Fe(NO/sub 3/)/sub 3/ which destroys the U complex and forms ferric phosphate complex. The UO/sub 2/(NO/sub 3/)/sub 2/ formed is extracted into TBP-kerosene in a countercurrent column. The TBP contalning UO/sub 2/(NO/sub 3/)/sub 2/ is further purified by an aqueous Al(NO/ sub 3/)/sub 3/ scrub solution. The pregnant solution then goes to an H/sub 3/PO/ sub 4/ stripping and kerosene washing column. The H/sub 3/PO/sub 4/--uranyl phosphate solution is separated at the bottom and boiled to remove HNO/sub 3/ then diluted to fuel solution make-up strength. (T.R.H.)

Validation of gamma-ray detection techniques for safeguards monitoring at natural uranium conversion facilities

DOE PAGES

Dewji, Shaheen A.; Lee, Denise L.; Croft, Stephen; ...

2016-03-28

Recent IAEA circulars and policy papers have sought to implement safeguards when any purified aqueous uranium solution or uranium oxides suitable for isotopic enrichment or fuel fabrication exists. Under the revised policy, IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed to develop and validate concepts of nondestructive assay monitoring systems in a natural uranium conversion plant (NUCP).more » In particular, uranyl nitrate (UO 2(NO 3) 2) solution exiting solvent extraction was identified as a key measurement point (KMP), where gamma-ray spectroscopy was selected as the process monitoring tool. The Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory was employed to simulate the full-scale operating conditions of a purified uranium-bearing aqueous stream exiting the solvent extraction process in an NUCP. Nondestructive assay techniques using gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely way. This work investigated gamma-ray signatures of uranyl nitrate circulating in the UNCLE facility and evaluated various gamma-ray detector sensitivities to uranyl nitrate. These detector validation activities include assessing detector responses to the uranyl nitrate gamma-ray signatures for spectrometers based on sodium iodide, lanthanum bromide, and high-purity germanium detectors. The results of measurements under static and dynamic operating conditions at concentrations ranging from 10–90 g U/L of natural uranyl nitrate are presented. A range of gamma-ray lines is examined, including attenuation for transmission measurement of density and concentration. It was determined that transmission-corrected gamma-ray spectra provide a reliable way to monitor the 235U concentration of uranyl nitrate solution in transfer pipes in NUCPs. Furthermore, existing predictive and analysis methods are adequate to design and realize practical designs. The 137Cs transmission source employed in this work is viable but not optimal for 235U densitometry determination. Validated simulations assessed the viability of 133Ba and 57Co as alternative densitometry sources. All three gamma-ray detectors are viable for monitoring natural uranium feed; although high-purity germanium is easiest to interpret, it is, however, the least attractive as an installation instrument. Overall, for monitoring throughput in a facility such as UNCLE, emulating the uranium concentration and pump speeds of the Springfields conversion facility in the United Kingdom, an uncertainty of less than 0.17% is required in order to detect the diversion of 1 SQ of uranyl nitrate through changes in uranium concentration over an accountancy period of one year with a detection probability of 50%. As a result, calibrated gamma-ray detection systems are capable of determining the concentration of uranium content in NUCPs, it is only in combination with verifiable operator declarations and supporting data, such as flow rate and enrichment, that safeguards conclusions can be drawn.« less

Bicarbonate Impact on U(VI) Bioreduction in a Shallow Alluvial Aquifer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Philip E.; Williams, Kenneth H.; Davis, James A.

Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contaminated, shallow alluvial aquifer have provided insight into the coupling of microbiology, biogeochemistry, and hydrogeology that control U mobility in the subsurface. Initial experiments successfully tested the concept that Fe-reducing bacteria such as Geobacter sp. could enzymatically reduce soluble U(VI) to insoluble U(IV) during in situ electron donor amendment (Anderson et al. 2003, Williams et al. 2011). In parallel, in situ desorption tracer tests using bicarbonate amendment demonstrated rate-limited U(VI) desorption (Fox et al. 2012). These results and prior laboratory studies underscored the importance of enzymatic U(VI)-reduction and suggestedmore » the ability to combine desorption and bioreduction of U(VI). Here we report the results of a new field experiment in which bicarbonate-promoted uranium desorption and acetate amendment were combined and compared to an acetate amendment-only experiment in the same experimental plot. Results confirm that bicarbonate amendment to alluvial aquifer desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, that the rate of acetate-promoted enzymatic U(VI) reduction was greater in the presence of added bicarbonate in spite of the increased dominance of Ca-uranyl-carbonato aqueous complexes. A model-simulated peak rate of U(VI) reduction was ~3.8 times higher during acetate-bicarbonate treatment than under acetate-only conditions. Lack of consistent differences in microbial community structure between acetate-bicarbonate and acetate-only treatments suggest that a significantly higher rate of U(VI) reduction the bicarbonate-impacted sediment may be due to a higher intrinsic rate of microbial reduction induced by elevated concentrations of the bicarbonate oxyanion. The findings indicate that bicarbonate amendment may be useful in improving the engineered bioremediation of uranium in aquifers.« less

Bicarbonate impact on U(VI) bioreduction in a shallow alluvial aquifer

NASA Astrophysics Data System (ADS)

Long, Philip E.; Williams, Kenneth H.; Davis, James A.; Fox, Patricia M.; Wilkins, Michael J.; Yabusaki, Steven B.; Fang, Yilin; Waichler, Scott R.; Berman, Elena S. F.; Gupta, Manish; Chandler, Darrell P.; Murray, Chris; Peacock, Aaron D.; Giloteaux, Ludovic; Handley, Kim M.; Lovley, Derek R.; Banfield, Jillian F.

2015-02-01

Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contaminated, shallow alluvial aquifer have provided insight into the coupling of microbiology, biogeochemistry, and hydrogeology that control U mobility in the subsurface. Initial experiments successfully tested the concept that Fe-reducing bacteria such as Geobacter sp. could enzymatically reduce soluble U(VI) to insoluble U(IV) during in situ electron donor amendment (Anderson et al., 2003; Williams et al., 2011). In parallel, in situ desorption tracer tests using bicarbonate amendment demonstrated rate-limited U(VI) desorption (Fox et al., 2012). These results and prior laboratory studies underscored the importance of enzymatic U(VI)-reduction and suggested the ability to combine desorption and bioreduction of U(VI). Here we report the results of a new field experiment in which bicarbonate-promoted uranium desorption and acetate amendment were combined and compared to an acetate amendment-only experiment in the same experimental plot. Results confirm that bicarbonate amendment to alluvial aquifer sediments desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, the rate of acetate-promoted enzymatic U(VI) reduction was greater in the presence of added bicarbonate in spite of the increased dominance of Ca-uranyl-carbonato aqueous complexes. A model-simulated peak rate of U(VI) reduction was ∼3.8 times higher during acetate-bicarbonate treatment than under acetate-only conditions. Lack of consistent differences in microbial community structure between acetate-bicarbonate and acetate-only treatments suggest that a significantly higher rate of U(VI) reduction in the bicarbonate-impacted sediment may be due to a higher intrinsic rate of microbial reduction induced by elevated concentrations of the bicarbonate oxyanion. The findings indicate that bicarbonate amendment may be useful in improving the engineered bioremediation of uranium in aquifers.

NMR shielding calculations across the periodic table: diamagnetic uranium compounds. 2. Ligand and metal NMR.

PubMed

Schreckenbach, Georg

2002-12-16

In this and a previous article (J. Phys. Chem. A 2000, 104, 8244), the range of application for relativistic density functional theory (DFT) is extended to the calculation of nuclear magnetic resonance (NMR) shieldings and chemical shifts in diamagnetic actinide compounds. Two relativistic DFT methods are used, ZORA ("zeroth-order regular approximation") and the quasirelativistic (QR) method. In the given second paper, NMR shieldings and chemical shifts are calculated and discussed for a wide range of compounds. The molecules studied comprise uranyl complexes, [UO(2)L(n)](+/-)(q); UF(6); inorganic UF(6) derivatives, UF(6-n)Cl(n), n = 0-6; and organometallic UF(6) derivatives, UF(6-n)(OCH(3))(n), n = 0-5. Uranyl complexes include [UO(2)F(4)](2-), [UO(2)Cl(4)](2-), [UO(2)(OH)(4)](2-), [UO(2)(CO(3))(3)](4-), and [UO(2)(H(2)O)(5)](2+). For the ligand NMR, moderate (e.g., (19)F NMR chemical shifts in UF(6-n)Cl(n)) to excellent agreement [e.g., (19)F chemical shift tensor in UF(6) or (1)H NMR in UF(6-n)(OCH(3))(n)] has been found between theory and experiment. The methods have been used to calculate the experimentally unknown (235)U NMR chemical shifts. A large chemical shift range of at least 21,000 ppm has been predicted for the (235)U nucleus. ZORA spin-orbit appears to be the most accurate method for predicting actinide metal chemical shifts. Trends in the (235)U NMR chemical shifts of UF(6-n)L(n) molecules are analyzed and explained in terms of the calculated electronic structure. It is argued that the energy separation and interaction between occupied and virtual orbitals with f-character are the determining factors.

GRAPHITE PRODUCTION UTILIZING URANYL NITRATE HEXAHYDRATE CATALYST

DOEpatents

Sheinberg, H.; Armstrong, J.R.; Schell, D.H.

1964-03-10

ABS>The graphitizing of a mixture composed of furfuryl alcohol binder and uranyl nitrate hexahydrate hardener and the subsequent curing, baking, and graphitizing with pressure being initially applied prior to curing are described. The pressure step may be carried out by extrusion, methyl cellulose being added to the mixture before the completion of extrusion. Uranium oxide may be added to the graphitizable mixture prior to the heating and pressure steps. The graphitizable mixture may consist of discrete layers of different compositions. (AEC)

Method of precipitating uranium from an aqueous solution and/or sediment

DOEpatents

Tokunaga, Tetsu K; Kim, Yongman; Wan, Jiamin

2013-08-20

A method for precipitating uranium from an aqueous solution and/or sediment comprising uranium and/or vanadium is presented. The method includes precipitating uranium as a uranyl vanadate through mixing an aqueous solution and/or sediment comprising uranium and/or vanadium and a solution comprising a monovalent or divalent cation to form the corresponding cation uranyl vanadate precipitate. The method also provides a pathway for extraction of uranium and vanadium from an aqueous solution and/or sediment.

Criticality experiments and analysis of molybdenum reflected cylindrical uranyl fluoride water solution reactors

NASA Technical Reports Server (NTRS)

Fieno, D.; Fox, T.; Mueller, R.

1972-01-01

Clean criticality data were obtained from molybdenum-reflected cylindrical uranyl-fluoride-water solution reactors. Using ENDF/B molybdenum cross sections, a nine energy group two-dimensional transport calculation of a reflected reactor configuration predicted criticality to within 7 cents of the experimental value. For these reactors, it was necessary to compute the reflector resonance integral by a detailed transport calculation at the core-reflector interface volume in the energy region of the two dominant resonances of natural molybdenum.

SEPARATION OF BARIUM VALUES FROM URANYL NITRATE SOLUTIONS

DOEpatents

Tompkins, E.R.

1959-02-24

The separation of radioactive barium values from a uranyl nitrate solution of neutron-irradiated uranium is described. The 10 to 20% uranyl nitrate solution is passed through a flrst column of a cation exchange resin under conditions favoring the adsorption of barium and certain other cations. The loaded resin is first washed with dilute sulfuric acid to remove a portion of the other cations, and then wash with a citric acid solution at pH of 5 to 7 to recover the barium along with a lesser amount of the other cations. The PH of the resulting eluate is adjusted to about 2.3 to 3.5 and diluted prior to passing through a smaller second column of exchange resin. The loaded resin is first washed with a citric acid solution at a pH of 3 to elute undesired cations and then with citric acid solution at a pH of 6 to eluts the barium, which is substantially free of undesired cations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abrao, Alcidio.; Araujo, Jose Adroaldo de; Franca Junior, J.M.

This paper describes a technique for the production of nuclear grade ammonium diuranate (ADU) using uranyl sulfate solutions obtained as eluate from the ion exchange (strong cationic resin) purification of uranium, by precipitation with NH{sub 3} gas. The precipitation of ADU by direct introduction of NH{sub 3} gas into acid uranyl sulfate solution has as consequence a high coprecipitation of sulfate ion, reaching ratios as high as 10 to 14% SO{sub 4}/ADU. To overcome this serious inconvenience, the reverse order of addition of reagents was studied, the ADU precipitation being done in such a way that the pH of themore » mixture was kept higher than 6 during the whole precipitation. This modification, in conjunction with the adjustment of other precipitation parameters, like temperature, precipitation time, aging time, concentration of uranium in uranyl sulfate and pH, allowed a sucessful precipitation of ADU with low sulfate content. The technique was applied at pilot plant scale, using batch and continuous precipitation, in both cases the obtained ADU was low in sulfate.« less

Recovery of uranium from an irradiated solid target after removal of molybdenum-99 produced from the irradiated target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reilly, Sean Douglas; May, Iain; Copping, Roy

A process for minimizing waste and maximizing utilization of uranium involves recovering uranium from an irradiated solid target after separating the medical isotope product, molybdenum-99, produced from the irradiated target. The process includes irradiating a solid target comprising uranium to produce fission products comprising molybdenum-99, and thereafter dissolving the target and conditioning the solution to prepare an aqueous nitric acid solution containing irradiated uranium. The acidic solution is then contacted with a solid sorbent whereby molybdenum-99 remains adsorbed to the sorbent for subsequent recovery. The uranium passes through the sorbent. The concentrations of acid and uranium are then adjusted tomore » concentrations suitable for crystallization of uranyl nitrate hydrates. After inducing the crystallization, the uranyl nitrate hydrates are separated from a supernatant. The process results in the purification of uranyl nitrate hydrates from fission products and other contaminants. The uranium is therefore available for reuse, storage, or disposal.« less

First-principles molecular dynamics simulation of the Ca 2UO 2(CO 3) 3 complex in water

DOE PAGES

Priest, Chad; Tian, Ziqi; Jiang, De-en

2016-01-22

Recent experiments have shown that the neutral Ca 2UO 2(CO 3) 3 complex is the dominant species of uranium in many uranyl-containing streams. However, the structure and solvation of such a species in water has not been investigated from first principles. Herein we present a first principles molecular dynamics perspective of the Ca 2UO 2(CO 3) 3 complex in water based on density functional theory and Born–Oppenheimer approximation. We find that the Ca 2UO 2(CO 3) 3 complex is very stable in our simulation timeframe for three different concentrations considered and that the key distances from our simulation are inmore » good agreement with the experimental data from extended X-ray absorption fine structure (EXAFS) spectroscopy. More important, we find that the two Ca ions bind differently in the complex, as a result of the hydrogen-bonding network around the whole complex. Furthermore, this finding invites confirmation from time-resolved EXAFS and has implications in understanding the dissociative equilibrium of the Ca 2UO 2(CO 3) 3 complex in water.« less

Functionalized Sugarcane Bagasse for U(VI) Adsorption from Acid and Alkaline Conditions.

PubMed

Su, Shouzheng; Liu, Qi; Liu, Jingyuan; Zhang, Hongsen; Li, Rumin; Jing, Xiaoyan; Wang, Jun

2018-01-15

The highly efficient removal of uranium from mine tailings effluent, radioactive wastewater and enrichment from seawater is of great significance for the development of nuclear industry. In this work, we prepared an efficient U(VI) adsorbent by EDTA modified sugarcane bagasse (MESB) with a simple process. The prepared adsorbent preserves high adsorptive capacity for UO 2 2+ (pH 3.0) and uranyl complexes, such as UO 2 (OH) + , (UO 2 ) 2 (OH) 2 2+ and (UO 2 ) 3 (OH) 5 + (pH 4.0 and pH 5.0) and good repeatability in acidic environment. The maximum adsorption capacity for U(VI) at pH 3.0, 4.0 and 5.0 is 578.0, 925.9 and 1394.1 mg/g and the adsorption capacity loss is only 7% after five cycles. With the pH from 3.0 to 5.0, the inhibitive effects of Na + and K + decreased but increased of Mg 2+ and Ca 2+ . MESB also exhibits good adsorption for [UO 2 (CO 3 ) 3 ] 4- at pH 8.3 from 10 mg/L to 3.3 μg/L. Moreover, MESB could effectively extract U(VI) from simulated seawater in the presence of other metals ions. This work provided a general and efficient uranyl enriched material for nuclear industry.

Different biosorption mechanisms of Uranium(VI) by live and heat-killed Saccharomyces cerevisiae under environmentally relevant conditions.

PubMed

Wang, Tieshan; Zheng, Xinyan; Wang, Xiaoyu; Lu, Xia; Shen, Yanghao

2017-02-01

Uranium adsorption mechanisms of live and heat-killed Saccharomyces cerevisiae in different pH values and biomass concentrations were studied under environmentally relevant conditions. Compared with live cells, the adsorption capacity of heat-killed cells is almost one order of magnitude higher in low biomass concentration and highly acidic pH conditions. To explore the mesoscopic surface interactions between uranium and cells, the characteristic of uranium deposition was investigated by SEM-EDX, XPS and FTIR. Biosorption process of live cells was considered to be metabolism-dependent. Under stimulation by uranyl ions, live cells could gradually release phosphorus and reduce uranium from U(VI) to U(IV) to alleviate uranium toxicity. The uranyl-phosphate complexes were formed in scale-like shapes on cell surface. The metabolic detoxification mechanisms such as reduction and "self-protection" are of significance to the migration of radionuclides. In the metabolism-independent biosorption process of heat-killed cells: the cells cytomembrane was damaged by autoclaving which led to the free diffusion of phosphorous from intracellular, and the rough surface and nano-holes indicated that the dead cells provided larger contact area to precipitate U(VI) as spherical nano-particles. The high biosorption capacity of heat-killed cells makes it become a suitable biological adsorbent for uranium removal. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of the Organic Species and Oxoanion in the Synthesis of two Uranyl Sulfate Hydrates, (H 3 O) 2 [(UO 2 ) 2 (SO 4 ) 3 ­(H 2 O)]·7H 2 O and (H 3 O) 2 [(UO 2 ) 2 (SO 4 ) 3 (H 2 O)]·4H 2 O, and a Uranyl Selenate-Selenite [C 5 H 6 N][(UO 2 )(SeO 4 )(HSeO 3 )

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jouffret, Laurent J.; Wylie, Ernest M.; Burns, Peter C.

2012-08-08

Two uranyl sulfate hydrates, (H3O)2[(UO2)2(SO4)3(H2O)]·7H2O (NDUS) and (H3O)2[(UO2)2(SO4)3(H2O)]·4H2O (NDUS1), and one uranyl selenate-selenite [C5H6N][(UO2)(SeO4)(HSeO3)] (NDUSe), were obtained and their crystal structures solved. NDUS and NDUSe result from reactions in highly acidic media in the presence of L-cystine at 373 K. NDUS crystallized in a closed vial at 278 K after 5 days and NDUSe in an open beaker at 278 K after 2 weeks. NDUS1 was synthesized from aqueous solution at room temperature over the course of a month. NDUS, NDUS1, and NDUSe crystallize in the monoclinic space group P21/n, a = 15.0249(4) Å,b = 9.9320(2) Å, c = 15.6518(4)more » Å, β = 112.778(1)°, V = 2153.52(9) Å3,Z = 4, the tetragonal space group P43212, a = 10.6111(2) Å,c = 31.644(1) Å, V = 3563.0(2) Å3, Z = 8, and in the monoclinic space group P21/n, a = 8.993(3) Å, b = 13.399(5) Å, c = 10.640(4) Å,β = 108.230(4)°, V = 1217.7(8) Å3, Z = 4, respectively.The structural units of NDUS and NDUS1 are two-dimensional uranyl sulfate sheets with a U/S ratio of 2/3. The structural unit of NDUSe is a two-dimensional uranyl selenate-selenite sheets with a U/Se ratio of 1/2. In-situ reaction of the L-cystine ligands gives two distinct products for the different acids used here. Where sulfuric acid is used, only H3O+ cations are located in the interlayer space, where they balance the charge of the sheets, whereas where selenic acid is used, interlayer C5H6N+ cations result from the cyclization of the carboxyl groups of L-cystine, balancing the charge of the sheets.« less

Assessment of calcium addition on the removal of U(VI) in the alkaline conditions created by NH 3 gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katsenovich, Yelena; Cardona, Claudia; Szecsody, Jim

Remediation of uranium (U) contamination in the deep vadose zone (VZ) sediments abundant in calcite mineral is a challenging task considering the formation of highly stable and mobile uranyl complexes with carbonate and calcium in pore water composition. There is a concern that uranium contamination in the VZ can serve as a continued source for groundwater pollution, creating a risk to human health and the environment through the groundwater pathway. This requires in-situ remediation of the radionuclide-contaminated VZ to convert soluble U species to low solubility precipitates that are stable in the natural environment. Injection of reactive gasses (e.g., NHmore » 3) is a promising technology to decrease U mobility in the unsaturated zone without the addition of liquid amendments. The NH 3 injection creates alkaline conditions that can alter the sediment pore water composition due to a release of elements from minerals (via desorption and dissolution) that are present in the sediment. However, it is not known how VZ pore water constituents (Si, Al 3+, HCO 3 -, and Ca 2 +) would affect U(VI) removal/precipitation in alkaline conditions. This study quantified the role of major pore water constituents typically present in the arid and semi-arid environments of the western regions of the U.S and identified solid uranium-bearing phases that could potentially precipitate from solutions approximating pore water compositions after pH manipulations via ammonia gas injections. Triplicate samples were prepared using six Si (5, 50 100, 150, 200, and 250 mM), six HCO 3 - (0, 3, 25, 50, 75, and 100 mM), and two Ca 2+ (5 and 10 mM) concentrations. The concentration of aluminum and uranium was kept constant at 5 mM and 0.0084 mM, respectively, in all synthetic formulations tested. Results showed that the percentage of U(VI) removal was controlled by the Si/Al molar ratios and Ca 2+ concentrations. Regardless of the bicarbonate concentration tested, the percentage of U(VI) removed increased as the Si/Al ratios were increased. However, higher Ca concentrations correlated with higher U(VI) removal, ranging between 96% and 99%, at low Si/Al ratios. The SEM images of dried precipitates displayed dense amorphous regions high in silica content, where EDS elemental analysis unveiled higher U atomic percentages. The formation of uranyl silicate and carbonate minerals was also predicted by the speciation modeling. XRD analysis revealed the presence of uranyl carbonate mineral phases (andersonite, grimselite); however, uranyl silicates predicted (Na-boltwoodite) were not identified experimentally, possibly due to the amorphous nature of the silica solid phases observed in our experiments.« less

The effect of Si and Al concentrations on the removal of U(VI) in the alkaline conditions created by NH3 gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katsenovich, Yelena P.; Cardona, Claudia; Lapierre, Robert

2016-10-01

Remediation of uranium in the deep unsaturated zone is a challenging task, especially in the presence of oxygenated, high-carbonate alkalinity soil and pore water composition typical for arid and semi-arid environments of the western regions of the U.S. This study evaluates the effect of various pore water constituencies on changes of uranium concentrations in alkaline conditions, created in the presence of reactive gases such as NH3 to effectively mitigate uranium contamination in the vadose zone sediments. This contaminant is a potential source for groundwater pollution through slow infiltration of soluble and highly mobile uranium species towards the water table. Themore » objective of this research was to evaluate uranium sequestration efficiencies in the alkaline synthetic pore water solutions prepared in a broad range of Si, Al, and bicarbonate concentrations typically present in field systems of the western U.S. regions and identify solid uranium-bearing phases that result from ammonia gas treatment. In previous studies (Szecsody et al. 2012; Zhong et al. 2015), although uranium mobility was greatly decreased, solid phases could not be identified at the low uranium concentrations in field-contaminated sediments. The chemical composition of the synthetic pore water used in the experiments varied for silica (5–250 mM), Al3+ (2.8 or 5 mM), HCO3- (0–100 mM) and U(VI) (0.0021–0.0084 mM) in the solution mixture. Experiment results suggested that solutions with Si concentrations higher than 50 mM exhibited greater removal efficiencies of U(VI). Solutions with higher concentrations of bicarbonate also exhibited greater removal efficiencies for Si, Al, and U(VI). Overall, the silica polymerization reaction leading to the formation of Si gel correlated with the removal of U(VI), Si, and Al from the solution. If no Si polymerization was observed, there was no U removal from the supernatant solution. Speciation modeling indicated that the dominant uranium species in the presence of bicarbonate were anionic uranyl carbonate complexes (UO2(CO3)2-2 and UO2(CO3)3-4) and in the absence of bicarbonate in the solution, U(VI) major species appeared as uranyl-hydroxide (UO2(OH)3- and UO2(OH)4-2) species. The model also predicted the formation of uranium solid phases. Uranyl carbonates as rutherfordine [UO2CO3], cejkaite [Na4(UO2)(CO3)3] and hydrated uranyl silicate phases as Na-boltwoodite [Na(UO2)(SiO4)·1.5H2O] were anticipated for most of the synthetic pore water compositions amended from medium (2.9 mM) to high (100 mM) bicarbonate concentrations.« less

Assessment of calcium addition on the removal of U(VI) in the alkaline conditions created by NH 3 gas

DOE PAGES

Katsenovich, Yelena; Cardona, Claudia; Szecsody, Jim; ...

2018-03-06

Remediation of uranium (U) contamination in the deep vadose zone (VZ) sediments abundant in calcite mineral is a challenging task considering the formation of highly stable and mobile uranyl complexes with carbonate and calcium in pore water composition. There is a concern that uranium contamination in the VZ can serve as a continued source for groundwater pollution, creating a risk to human health and the environment through the groundwater pathway. This requires in-situ remediation of the radionuclide-contaminated VZ to convert soluble U species to low solubility precipitates that are stable in the natural environment. Injection of reactive gasses (e.g., NHmore » 3) is a promising technology to decrease U mobility in the unsaturated zone without the addition of liquid amendments. The NH 3 injection creates alkaline conditions that can alter the sediment pore water composition due to a release of elements from minerals (via desorption and dissolution) that are present in the sediment. However, it is not known how VZ pore water constituents (Si, Al 3+, HCO 3 -, and Ca 2 +) would affect U(VI) removal/precipitation in alkaline conditions. This study quantified the role of major pore water constituents typically present in the arid and semi-arid environments of the western regions of the U.S and identified solid uranium-bearing phases that could potentially precipitate from solutions approximating pore water compositions after pH manipulations via ammonia gas injections. Triplicate samples were prepared using six Si (5, 50 100, 150, 200, and 250 mM), six HCO 3 - (0, 3, 25, 50, 75, and 100 mM), and two Ca 2+ (5 and 10 mM) concentrations. The concentration of aluminum and uranium was kept constant at 5 mM and 0.0084 mM, respectively, in all synthetic formulations tested. Results showed that the percentage of U(VI) removal was controlled by the Si/Al molar ratios and Ca 2+ concentrations. Regardless of the bicarbonate concentration tested, the percentage of U(VI) removed increased as the Si/Al ratios were increased. However, higher Ca concentrations correlated with higher U(VI) removal, ranging between 96% and 99%, at low Si/Al ratios. The SEM images of dried precipitates displayed dense amorphous regions high in silica content, where EDS elemental analysis unveiled higher U atomic percentages. The formation of uranyl silicate and carbonate minerals was also predicted by the speciation modeling. XRD analysis revealed the presence of uranyl carbonate mineral phases (andersonite, grimselite); however, uranyl silicates predicted (Na-boltwoodite) were not identified experimentally, possibly due to the amorphous nature of the silica solid phases observed in our experiments.« less

Experiments on Anion Exchange with Amberlite Ir-120 Resin; ENSAYOS DE INTERCAMBIO ANIONICO CON RESINA AMBERLITA Ir-120

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cellini, R.F.; Palomino, J.V.

1956-01-01

The ion exchange of the uranyl ion on Amberlite Ir-120 resin was studied with different uranyl ion concentrations. Elution with sulfuric acid was investlgated and the elution curve for the experimental conditions was determined. From the concentrations of the ions of Cu/sup 2+/, Ni/sup 2+/, Fe/sup 3+/, Cd/sup 2+/, Mn/sup 2+/, and Cr/sup 3+/ the maximum exchange capacity was tested and elation curves with 4 N sulfuric acid were obtained. (tr-auth)

Reductive stripping process for the recovery of uranium from wet-process phosphoric acid

DOEpatents

Hurst, Fred J.; Crouse, David J.

1984-01-01

A reductive stripping flow sheet for recovery of uranium from wet-process phosphoric acid is described. Uranium is stripped from a uranium-loaded organic phase by a redox reaction converting the uranyl to uranous ion. The uranous ion is reoxidized to the uranyl oxidation state to form an aqueous feed solution highly concentrated in uranium. Processing of this feed through a second solvent extraction cycle requires far less stripping reagent as compared to a flow sheet which does not include the reductive stripping reaction.

Competing retention pathways of uranium upon reaction with Fe(II)

NASA Astrophysics Data System (ADS)

Massey, Michael S.; Lezama-Pacheco, Juan S.; Jones, Morris E.; Ilton, Eugene S.; Cerrato, José M.; Bargar, John R.; Fendorf, Scott

2014-10-01

Biogeochemical retention processes, including adsorption, reductive precipitation, and incorporation into host minerals, are important in contaminant transport, remediation, and geologic deposition of uranium. Recent work has shown that U can become incorporated into iron (hydr)oxide minerals, with a key pathway arising from Fe(II)-induced transformation of ferrihydrite, (Fe(OH)3·nH2O) to goethite (α-FeO(OH)); this is a possible U retention mechanism in soils and sediments. Several key questions, however, remain unanswered regarding U incorporation into iron (hydr)oxides and this pathway's contribution to U retention, including: (i) the competitiveness of U incorporation versus reduction to U(IV) and subsequent precipitation of UO2; (ii) the oxidation state of incorporated U; (iii) the effects of uranyl aqueous speciation on U incorporation; and, (iv) the mechanism of U incorporation. Here we use a series of batch reactions conducted at pH ∼7, [U(VI)] from 1 to 170 μM, [Fe(II)] from 0 to 3 mM, and [Ca] at 0 or 4 mM coupled with spectroscopic examination of reaction products of Fe(II)-induced ferrihydrite transformation to address these outstanding questions. Uranium retention pathways were identified and quantified using extended X-ray absorption fine structure (EXAFS) spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Analysis of EXAFS spectra showed that 14-89% of total U was incorporated into goethite, upon reaction with Fe(II) and ferrihydrite. Uranium incorporation was a particularly dominant retention pathway at U concentrations ⩽50 μM when either uranyl-carbonato or calcium-uranyl-carbonato complexes were dominant, accounting for 64-89% of total U. With increasing U(VI) and Fe(II) concentrations, U(VI) reduction to U(IV) became more prevalent, but U incorporation remained a functioning retention pathway. These findings highlight the potential importance of U(V) incorporation within iron oxides as a retention process of U across a wide range of biogeochemical environments and the sensitivity of uranium retention processes to operative (bio)geochemical conditions.

Competing retention pathways of uranium upon reaction with Fe(II)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massey, Michael S.; Lezama Pacheco, Juan S.; Jones, Morris

Biogeochemical retention processes, including adsorption, reductive precipitation, and incorporation into host minerals, are important in contaminant transport, remediation, and geologic deposition of uranium. Recent work has shown that U can become incorporated into iron (hydr)oxide minerals, with a key pathway arising from Fe(II)-induced transformation of ferrihydrite, (Fe(OH)3•nH2O) to goethite (α-FeO(OH)); this is a possible U retention mechanism in soils and sediments. Several key questions, however, remain unanswered regarding U incorporation into iron (hydr)oxides and this pathway’s contribution to U retention, including: (i) the competitiveness of U incorporation versus reduction to U(IV) and subsequent precipitation of UO2; (ii) the oxidation statemore » of incorporated U; (iii) the effects of uranyl aqueous speciation on U incorporation; and, (iv) the mechanism of U incorporation. Here we use a series of batch reactions conducted at pH ~7, [U(VI)] from 1 to 170 μM, [Fe(II)] from 0 to 3 mM, and [Ca] at 0 or 4 mM) coupled with spectroscopic examination of reaction products of Fe(II)-induced ferrihydrite transformation to address these outstanding questions. Uranium retention pathways were identified and quantified using extended x-ray absorption fine structure (EXAFS) spectroscopy, x-ray powder diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy. Analysis of EXAFS spectra showed that 14 to 89% of total U was incorporated into goethite, upon reaction with Fe(II) and ferrihydrite. Uranium incorporation was a particularly dominant retention pathway at U concentrations ≤ 50 μM when either uranyl-carbonato or calcium-uranyl-carbonato complexes were dominant, accounting for 64 to 89% of total U. With increasing U(VI) and Fe(II) concentrations, U(VI) reduction to U(IV) became more prevalent, but U incorporation remained a functioning retention pathway. These findings highlight the potential importance of U(V) incorporation within iron oxides as a retention process of U across a wide range of biogeochemical environments and the sensitivity of uranium retention processes to operative (bio)geochemical conditions.« less

PROCESS OF RECOVERING URANIUM

DOEpatents

Kilner, S.B.

1959-12-29

A method is presented for separating and recovering uranium from a complex mixure of impurities. The uranium is dissolved to produce an aqueous acidic solution including various impurities. In accordance with one method, with the uranium in the uranyl state, hydrogen cyanide is introduced into the solution to complex the impurities. Subsequently, ammonia is added to the solution to precipitate the uraniunn as ammonium diuranate away from the impurities in the solution. Alternatively, the uranium is precipitated by adding an alkaline metal hydroxide. In accordance with the second method, the uranium is reduced to the uranous state in the solution. The reduced solution is then treated with solid alkali metal cyanide sufficient to render the solution about 0.1 to 1.0 N in cyanide ions whereat cyanide complex ions of the metal impurities are produced and the uranium is simultaneously precipituted as uranous hydroxide. Alternatively, hydrogen cyanide may be added to the reduced solution and the uranium precipitated subsequently by adding ammonium hydroxide or an alkali metal hydroxide. Other refinements of the method are also disclosed.

Amine templating effect absent in uranyl sulfates synthesized with 1,4-n-butyldiamine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jouffret, Laurent J., E-mail: ljouffret@nd.edu; Wylie, Ernest M.; Burns, Peter C.

2013-01-15

Two new uranyl sulfates, (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2}){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS2) and (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2})(SO{sub 4}){sub 2}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS3), were synthesized and their crystal structures determined. NDUS2 was obtained in highly acidic media heat-treated at 373 K and subsequently maintained at 278 K until crystals formed after two months. NDUS3 results from the degradation of NDUS2 over the course of a few days. NDUS2 and NDUS3 crystallize in the monoclinic space group P2{sub 1}/n, a=10.9075(4) A, b=10.4513(4) A, c=17.7881(7) A, {beta}=97.908(2) Degree-Sign , V=2008.52(13) A{sup 3}, Z=4, at 140 K and a=8.8570(4) A,more » b=7.3299(3) A, c=20.4260(9) A, {beta}=95.140(2) Degree-Sign , V=1320.74(10) A{sup 3}, Z=4, at 140 K, respectively. The compounds contain interlayer 1,4-n-butyldiammonium cations that charge-balance the anionic structural units. - Graphical abstract: Amine templating effect absent in uranyl sulfates synthesized with 1,4-diaminobutane, as shown by the synthesis of two new uranyl sulfates, (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2}){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS2) and (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2})(SO{sub 4}){sub 2}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS3). Highlights: Black-Right-Pointing-Pointer Two layered uranyl sulfates were synthesized. Black-Right-Pointing-Pointer Amine molecules are located in the interlayers of the compounds. Black-Right-Pointing-Pointer No templating effect of the amine was observed. Black-Right-Pointing-Pointer Amine molecules are only charge balancing cations in the structures.« less

Vibrational Properties of Anhydrous and Partially Hydrated Uranyl Fluoride

DOE PAGES

Anderson, Brian B.; Kirkegaard, Marie C.; Miskowiec, Andrew J.; ...

2017-01-01

Uranyl fluoride (UO 2F 2) is a hygroscopic powder with two main structural phases: an anhydrous crystal and a partially hydrated crystal of the same R¯3m symmetry. The formally closed-shell electron structure of anhydrous UO 2F 2 is amenable to density functional theory calculations. We use density functional perturbation theory (DFPT) to calculate the vibrational frequencies of the anhydrous crystal structure and employ complementary inelastic neutron scattering and temperature-dependent Raman scattering to validate those frequencies. As a model closed-shell actinide, we investigated the effect of LDA, GGA, and non-local vdW functionals as well as the spherically-averaged Hubbard +U correction onmore » vibrational frequencies, electronic structure, and geometry of anhydrous UO 2F 2. A particular choice of U eff = 5.5 eV yields the correct U Oyl bond distance and vibrational frequencies for the characteristic Eg and A1g modes that are within the resolution of experiment. Inelastic neutron scattering and Raman scattering suggest a degree of water coupling to the lattice vibrations in the more experimentally accessible partially hydrated UO 2F 2 system, with the symmetric O-U-O stretching vibration shifted approximately 47 cm -1 lower in energy compared to the anhydrous structure. Evidence of water interaction with the uranyl ion is present from a two-peak decomposition of the uranyl stretching vibration in the Raman spectra and anion hydrogen stretching vibrations in the inelastic neutron scattering spectra. A first-order dehydration phase transition temperature is definitively identified to be 125 °C using temperature-dependent Raman scattering.« less

Dehydration of the Uranyl Peroxide Studtite, [UO 2(η 2-O 2)(H 2O) 2]·2H 2O, Affords a Drastic Change in the Electronic Structure: A Combined X-ray Spectroscopic and Theoretical Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vitova, Tonya; Pidchenko, Ivan; Biswas, Saptarshi

The dehydration of studtite, [UO 2(2-O 2)(H 2O)2]·2H 2O, to metastudtite, [UO 2(2-O 2)(H 2O) 2], uranyl peroxide minerals that are major oxidative alteration phases of UO2 under conditions of geological storage, has been studied using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy. XPS of the U 4f region shows small but significant differences between studtite and metastudtite, with the 4f binding energy of studtite the highest reported for a uranyl mineral studied by this technique. Further information on the changes in the electronic structure was elucidated using U M4-edge High Energy Resolution XANES (HR-XANES) spectroscopy, which directly probesmore » f-orbital states. The transition from the 3d to the 5f* orbital is sensitive to variations of the U=Oaxial bond length and to changes in the bond covalency. We report evidences that the covalence in the uranyl fragment decreases upon dehydration. Photoluminescence spectroscopy at near liquid helium temperatures reveals significant spectral differences between the two materials, correlating with the X-ray spectroscopy results. A theoretical investigation has been conducted on the structures of both studtite and metastudtite and benchmarked to the HR-XANES spectra. These illustrate the sensitivity of the 3d to the 5f * transition towards U=Oaxial bond variation.« less

Influence of Background H2O on the Collision-Induced Dissociation Products Generated from [UO2NO3]+

NASA Astrophysics Data System (ADS)

Van Stipdonk, Michael J.; Iacovino, Anna; Tatosian, Irena

2018-04-01

Developing a comprehensive understanding of the reactivity of uranium-containing species remains an important goal in areas ranging from the development of nuclear fuel processing methods to studies of the migration and fate of the element in the environment. Electrospray ionization (ESI) is an effective way to generate gas-phase complexes containing uranium for subsequent studies of intrinsic structure and reactivity. Recent experiments by our group have demonstrated that the relatively low levels of residual H2O in a 2-D, linear ion trap (LIT) make it possible to examine fragmentation pathways and reactions not observed in earlier studies conducted with 3-D ion traps (Van Stipdonk et al. J. Am. Soc. Mass Spectrom. 14, 1205-1214, 2003). In the present study, we revisited the dissociation of complexes composed of uranyl nitrate cation [UVIO2(NO3)]+ coordinated by alcohol ligands (methanol and ethanol) using the 2-D LIT. With relatively low levels of background H2O, collision-induced dissociation (CID) of [UVIO2(NO3)]+ primarily creates [UO2(O2)]+ by the ejection of NO. However, CID (using He as collision gas) of [UVIO2(NO3)]+ creates [UO2(H2O)]+ and UO2 + when the 2-D LIT is used with higher levels of background H2O. Based on the results presented here, we propose that product ion spectrum in the previous experiments was the result of a two-step process: initial formation of [UVIO2(O2)]+ followed by rapid exchange of O2 for H2O by ion-molecule reaction. Our experiments illustrate the impact of residual H2O in ion trap instruments on the product ions generated by CID and provide a more accurate description of the intrinsic dissociation pathway for [UVIO2(NO3)]+. [Figure not available: see fulltext.

Impact of pore size on the sorption of uranyl under seawater conditions

DOE PAGES

Mayes, Richard T.; Gorka, Joanna; Dai, Sheng

2016-04-05

The extraction of uranium from seawater has received significant interest recently, because of the possibility of a near-limitless supply of uranium to fuel the nuclear power industry. While sorbent development has focused primarily on polymeric sorbents, nanomaterials represent a new area that has the potential to surpass the current polymeric sorbents, because of the high surface areas that are possible. Mesoporous carbon materials are a stable, high-surface-area material capable of extracting various chemical species from a variety of environments. Herein, we report the use of a dual templating process to understand the effect of pore size on the adsorption ofmore » uranyl ions from a uranyl brine consisting of seawater-relevant sodium, chloride, and bicarbonate ions. It was found that pore size played a more significant role in the effective use of the grafted polymer, leading to higher uranium capacities than the surface area. Furthermore, the pore size must be tailored to meet the demands of the extraction medium and analyte metal to achieve efficacy as an adsorbent.« less

Probing the oxygen environment in UO(2)(2+) by solid-state 17O nuclear magnetic resonance spectroscopy and relativistic density functional calculations.

PubMed

Cho, Herman; de Jong, Wibe A; Soderquist, Chuck Z

2010-02-28

A combined theoretical and solid-state (17)O nuclear magnetic resonance (NMR) study of the electronic structure of the uranyl ion UO(2)(2+) in (NH(4))(4)UO(2)(CO(3))(3) and rutherfordine (UO(2)CO(3)) is presented, the former representing a system with a hydrogen-bonding environment around the uranyl oxygens and the latter exemplifying a uranyl environment without hydrogens. Relativistic density functional calculations reveal unique features of the U-O covalent bond, including the finding of (17)O chemical shift anisotropies that are among the largest for oxygen ever reported (>1200 ppm). Computational results for the oxygen electric field gradient tensor are found to be consistently larger in magnitude than experimental solid-state (17)O NMR measurements in a 7.05 T magnetic field indicate. A modified version of the Solomon theory of the two-spin echo amplitude for a spin-5/2 nucleus is developed and applied to the analysis of the (17)O echo signal of U (17)O(2)(2+).

Approaches to modelling uranium (VI) adsorption on natural mineral assemblages

USGS Publications Warehouse

Waite, T.D.; Davis, J.A.; Fenton, B.R.; Payne, T.E.

2000-01-01

Component additivity (CA) and generalised composite (GC) approaches to deriving a suitable surface complexation model for description of U(VI) adsorption to natural mineral assemblages are pursued in this paper with good success. A single, ferrihydrite-like component is found to reasonably describe uranyl uptake to a number of kaolinitic iron-rich natural substrates at pH > 4 in the CA approach with previously published information on nature of surface complexes, acid-base properties of surface sites and electrostatic effects used in the model. The GC approach, in which little pre-knowledge about generic surface sites is assumed, gives even better fits and would appear to be a method of particular strength for application in areas such as performance assessment provided the model is developed in a careful, stepwise manner with simplicity and goodness of fit as the major criteria for acceptance.

Investigation of uranium binding forms in selected German mineral waters.

PubMed

Osman, Alfatih A A; Geipel, Gerhard; Bernhard, Gert; Worch, Eckhard

2013-12-01

Cryogenic time-resolved laser-induced fluorescence spectroscopy was successfully used to identify uranium binding forms in selected German mineral waters of extremely low uranium concentrations (<2.0 μg/L). The measurements were performed at a low temperature of 153 K. The spectroscopic data showed a prevalence of aquatic species Ca2UO2(CO3)3 in all investigated waters, while other uranyl-carbonate complexes, viz, UO2CO3(aq) and UO2(CO3)2 (2-), only existed as minor species. The pH value, alkalinity (CO3 (2-)), and the main water inorganic constituents, specifically the Ca(2+) concentration, showed a clear influence on uranium speciation. Speciation modeling was performed using the most recent thermodynamic data for aqueous complexes of uranium. The modeling results for the main uranium binding form in the investigated waters indicated a good agreement with the spectroscopy measurements.

The fundamental ribosomal RNA transcription initiation factor-IB (TIF-IB, SL1, factor D) binds to the rRNA core promoter primarily by minor groove contacts.

PubMed

Geiss, G K; Radebaugh, C A; Paule, M R

1997-11-14

Acanthamoeba castellanii transcription initiation factor-IB (TIF-IB) is the TATA-binding protein-containing transcription factor that binds the rRNA promoter to form the committed complex. Minor groove-specific drugs inhibit TIF-IB binding, with higher concentrations needed to disrupt preformed complexes because of drug exclusion by bound TIF-IB. TIF-IB/DNA interactions were mapped by hydroxyl radical and uranyl nitrate footprinting. TIF-IB contacts four minor grooves in its binding site. TIF-IB and DNA wrap around each other in a right-handed superhelix of high pitch, so the upstream and downstream contacts are on opposite faces of the helix. Dimethyl sulfate protection assays revealed limited contact with a few guanines in the major groove. This detailed analysis suggests significant DNA conformation dependence of the interaction.

Structural analysis of the coordination of dinitrogen to transition metal complexes.

PubMed

Peigné, Benjamin; Aullón, Gabriel

2015-06-01

Transition-metal complexes show a wide variety of coordination modes for the nitrogen molecule. A structural database study has been undertaken for dinitrogen complexes, and geometrical parameters around the L(n)M-N2 unit are retrieved from the Cambridge Structural Database. These data were classified in families of compounds, according to metal properties, to determine the degree of lengthening for the dinitrogen bonding. The importance of the nature of the metal center, such as coordination number and electronic configuration, is reported. Our study reveals poor activation by coordination of dinitrogen in mononuclear complexes, always having end-on coordination. However, partial weakening of nitrogen-nitrogen bonding is found for end-on binuclear complexes, whereas side-on complexes can be completely activated.

Cytotoxicity of Cyclometalated Platinum Complexes Based on Tridentate NCN and CNN-coordinating ligands: Remarkable Coordination Dependence

PubMed Central

Vezzu, Dileep A. k.; Lu, Qun; Chen, Yan-Hua; Huo, Shouquan

2014-01-01

A series of cyclometalated platinum complexes with diverse coordination patterns and geometries were screened for their anticancer activity. It was discovered that the NʌCʌN-coordinated platinum complex based on 1,3-di(pyridyl)benzene displayed much higher cytotoxicity against human lung cancer cells NCI-H522, HCC827, and NCI-H1299, and human prostate cancer cell RV1 than cisplatin. In a sharp contrast, the CʌNʌN-coordinated platinum complex based on 6-phenyl-2,2′-bipyridine was ineffective on these cancer cells. This remarkable difference in cytotoxicity displayed by NʌCʌN- and CʌNʌN-coordinated platinum complexes was related to the trans effect of the carbon donor in the cyclometalated platinum complexes, which played a crucial role in facilitating the dissociation of the chloride ligand to create an active binding site. The DNA binding was studied for the NʌCʌN-coordinated platinum complex using electrophoresis and emission titration. The cellular uptake observed by fluorescent microscope showed the complex is largely concentrated in the cytoplasm. The possible pathways for the cell apoptosis was studied by western blot analysis and the activation of PARP via caspase 7 was observed. PMID:24531534

SEPARATION OF URANYL NITRATE BY EXTRACTION

DOEpatents

Stoughton, R.W.; Steahly, F.L.

1958-08-26

A process is presented for obtaining U/sup 233/ from solutions containing Pa/sup 233/. A carrier precipitate, such as MnO/sub 2/, is formed in such solutions and carries with it the Pa/sup 233/ present. This precipitate is then dissolved in nitric acid and the solution is aged to allow decay of the Pa/ sup 233/ into U/sup 233/. After a sufficient length of time the U/sup 233/ bearing solution is made 2.5 to 4.5 Molar in manganese nitrate by addition thereof, and the solution is then treated with ether to obtain uranyl nitrate by solvent extraction techniques.

ADSORPTION METHOD FOR SEPARATING THORIUM VALUES FROM URANIUM VALUES

DOEpatents

Boyd, G.E.; Russell, E.R.; Schubert, J.

1959-08-01

An improved ion exchange method is described for recovery of uranium and thorium values as separate functions from an aqueous acidic solution containing less than 10/sup -3/ M thorium ions and between 0.1 and 1 M uranyl ions. The solution is passed through a bed of cation exchange resin in the acid form to adsorb all the thorium ions and a portion of the uranyl ions. The uranium is eluted by means of aqueous 0.1 to 0.4 M sulfuric acid. The thorium may then be stripped from the resin by elution with aqueous 0.5 M oxalic acid.

ADSORPTION METHOD FOR SEPARATING THORIUM VALUES FROM URANIUM VALUES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, G.E.; Russell, E.R.; Schubert, J.

An improved ion exchange method is described for recovery of uranium and thorium values as separate functions from an aqueous acidic solution containing less than 10/sup -3/ M thorium ions and between 0.1 and 1 M uranyl ions. The solution is passed through a bed of cation exchange resin in the acid form to adsorb all the thorium ions and a portion of the uranyl ions. The uranium is eluted by means of aqueous 0.1 to 0.4 M sulfuric acid. The thorium may then be stripped from the resin by elution with aqueous 0.5 M oxalic acid.

A smart T(1)-weighted MRI contrast agent for uranyl cations based on a DNAzyme-gadolinium conjugate.

PubMed

Xu, Weichen; Xing, Hang; Lu, Yi

2013-11-07

Rational design of smart MRI contrast agents with high specificity for metal ions remains a challenge. Here, we report a general strategy for the design of smart MRI contrast agents for detecting metal ions based on conjugation of a DNAzyme with a gadolinium complex. The 39E DNAzyme, which has high selectivity for UO2(2+), was conjugated to Gd(III)-DOTA and streptavidin. The binding of UO2(2+) to its 39E DNAzyme resulted in the dissociation of Gd(III)-DOTA from the large streptavidin, leading to a decrease of the T1 correlation time, and a change in the MRI signal.

Element speciation during nuclear glass alteration

NASA Astrophysics Data System (ADS)

Galoisy, L.; Calas, G.; Bergeron, B.; Jollivet, P.; Pelegrin, E.

2011-12-01

Assessing the long-term behavior of nuclear glasses implies the prediction of their long-term performance. An important controlling parameter is their evolution during interaction with water under conditions simulating geological repositories. After briefly recalling the major characteristics of the local and medium-range structure of borosilicate glasses of nuclear interest, we will present some structural features of this evolution. Specific structural tools used to determine the local structure of glass surfaces include synchrotron-radiation x-ray absorption spectroscopy with total electron yield detection. The evolution of the structure of glass surface has been determined at the Zr-, Fe-, Si- and Al-K edges and U-LIII edge. During alteration in near- or under-saturated conditions, some elements such as Fe change coordination, as other elements such as Zr only suffer structural modifications in under-saturated conditions. Uranium exhibits a modification of its speciation from an hexa-coordinated U(VI) in the borosilicate glass to an uranyl group in the gel. These structural modifications may explain the chemical dependence of the initial alteration rate and the transition to the residual regime. They also illustrate the molecular-scale origin of the processes at the origin of the glass-to-gel transformation. Eventually, they explain the provisional trapping of U by the alteration gel: the uranium retention factors in the gel depend on the alteration conditions, and thus on the nature of the resulting gel and on the trapping conditions.

Attenuation and Transport Mechanisms of Depleted Uranium in Groundwater at Lawrence Livermore National Laboratory Site 300

NASA Astrophysics Data System (ADS)

Danny, K. R.; Taffet, M. J.; Brusseau, M. L. L.; Chorover, J.

2015-12-01

Lawrence Livermore National Laboratory (LLNL) Site 300 was established in 1955 to support weapons research and development. Depleted uranium was used as a proxy for fissile uranium-235 (235U) in open-air explosives tests conducted at Building 812. As a result, oxidized depleted uranium was deposited on the ground, eventually migrating to the underlying sandstone aquifer. Uranium (U) groundwater concentrations exceed the California and Federal Maximum Contaminant Level of 20 pCi L-1 (30 ug L-1). However, the groundwater plume appears to attenuate within 60 m of the source, beyond which no depleted U is detected. This study will determine the relative contribution of physical (e.g. dilution), chemical (e.g. surface adsorption, mineral precipitation), and biological (e.g. biotransformation) processes that contribute to the apparent attenuation of U, which exists as uranyl (UO22+) complexes, at the site. Methods of investigation include evaluating 15 yr of hydrogeologic and chemical data, creating a site conceptual model, and applying equilibrium (e.g. aqueous species complexation, mineral saturation indices) and reactive transport models using Geochemist's WorkbenchTM. Reactive transport results are constrained by direct field observations, including U major ion, and dissolved O2 concentrations, pH, and others, under varying chemical and hydraulic conditions. Aqueous speciation calculations indicate that U primarily exists as anionic CaUO2(CO3)32- or neutral Ca2UO2(CO3)30 species. Additionally, nucleation and growth of Ca/Mg uranyl carbonate solids are predicted to affect attenuation. Initial reactive transport results suggest surface adsorption (e.g. ion exchange, surface complexation) to layer silicate clays is limited under the aqueous geochemical conditions of the site. Current and future work includes XRD analysis of aquifer solids to constrain iron and aluminum (oxy)hydroxides, and coupling advective-dispersive transport with the chemical and physical processes. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675707.

Experimental measurements of U60 nanocluster stability in aqueous solution

NASA Astrophysics Data System (ADS)

Flynn, Shannon L.; Szymanowski, Jennifer E. S.; Gao, Yunyi; Liu, Tianbo; Burns, Peter C.; Fein, Jeremy B.

2015-05-01

In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)-19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16 days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0 g/L. The aqueous concentrations of U, Li, and K, determined after 10 kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24 h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2 + 0.2/-0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the dissociation behavior of nanoclusters under a range of aqueous conditions.

Spectroscopic confirmation of uranium(VI)-carbonato adsorption complexes on hematite

USGS Publications Warehouse

Bargar, John R.; Reitmeyer, Rebecca; Davis, James A.

1999-01-01

Evaluating societal risks posed by uranium contamination from waste management facilities, mining sites, and heavy industry requires knowledge about uranium transport in groundwater, often the most significant pathway of exposure to humans. It has been proposed that uranium mobility in aquifers may be controlled by adsorption of U(VI)−carbonato complexes on oxide minerals. The existence of such complexes has not been demonstrated, and little is known about their compositions and reaction stoichiometries. We have used attenuated total reflectance Fourier transform infrared (ATR-FTIR) and extended X-ray absorption fine structure (EXAFS) spectroscopies to probe the existence, structures, and compositions of ≡FeOsurface−U(VI)−carbonato complexes on hematite throughout the pH range of uranyl uptake under conditions relevant to aquifers. U(VI)−carbonato complexes were found to be the predominant adsorbed U(VI) species at all pH values examined, a much wider pH range than previously postulated based on analogy to aqueous U(VI)−carbonato complexes, which are trace constituents at pH < 6. This result indicates the inadequacy of the common modeling assumption that the compositions and predominance of adsorbed species can be inferred from aqueous species. By extension, adsorbed carbonato complexes may be of major importance to the groundwater transport of similar actinide contaminants such as neptunium and plutonium.

Molecular and polymeric uranyl and thorium hybrid materials featuring methyl substituted pyrazole dicarboxylates and heterocyclic 1,3-diketones

NASA Astrophysics Data System (ADS)

Carter, Korey P.; Kerr, Andrew T.; Taydakov, Ilya V.; Cahill, Christopher L.

2018-02-01

A series of seven novel f-element bearing hybrid materials have been prepared from either methyl substituted 3,4 and 4,5-pyrazoledicarboxylic acids, or heterocyclic 1,3- diketonate ligands using hydrothermal conditions. Compounds 1, [UO2(C6H4N2O4)2(H2O)], and 3, [Th(C6H4N2O4)4(H2O)5]·H2O feature 1-Methyl-1H-pyrazole-3,4-dicarboxylate ligands (SVI-COOH 3,4), whereas 2, [UO2(C6H4N2O4)2(H2O)], and 4, [Th(C6H5N2O4)(OH)(H2O)6]2·2(C6H5N2O4)·3H2O feature 1-Methyl-1H-pyrazole-4,5-dicarboxylate moieties (SVI-COOH 4,5). Compounds 5, [UO2(C13H15N4O2)2(H2O)]·2H2O and 6, [UO2(C11H11N4O2)2(H2O)]·4.5H2O feature 1,3-bis(4-N1-methyl-pyrazolyl)propane-1,3-dione and 1,3-bis(4-N1,3-dimethyl-pyrazolyl)propane-1,3-dione respectively, whereas the heterometallic 7, [UO2(C11H11N4O2)2(CuCl2)(H2O)]·2H2O is formed by using 6 as a metalloligand starting material. Single crystal X-ray diffraction indicates that all coordination to either [UO2]2+ or Th(IV) metal centers is through O-donation as anticipated. Room temperature, solid-state luminescence studies indicate characteristic uranyl emissive behavior for 1 and 2, whereas those for 5 and 6 are weak and poorly resolved.

Identification of different coordination geometries by XAFS in copper(II) complexes with trimesic acid

NASA Astrophysics Data System (ADS)

Gaur, A.; Klysubun, W.; Soni, Balram; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

2016-10-01

X-ray absorption spectroscopy (XAS) is very useful in revealing the information about geometric and electronic structure of a transition-metal absorber and thus commonly used for determination of metal-ligand coordination. But XAFS analysis becomes difficult if differently coordinated metal centers are present in a system. In the present investigation, existence of distinct coordination geometries around metal centres have been studied by XAFS in a series of trimesic acid Cu(II) complexes. The complexes studied are: Cu3(tma)2(im)6 8H2O (1), Cu3(tma)2(mim)6 17H2O (2), Cu3(tma)2(tmen)3 8.5H2O (3), Cu3(tma) (pmd)3 6H2O (ClO4)3 (4) and Cu3(tma)2 3H2O (5). These complexes have not only Cu metal centres with different coordination but in complexes 1-3, there are multiple coordination geometries present around Cu centres. Using XANES spectra, different coordination geometries present in these complexes have been identified. The variation observed in the pre-edge features and edge features have been correlated with the distortion of the specific coordination environment around Cu centres in the complexes. XANES spectra have been calculated for the distinct metal centres present in the complexes by employing ab-initio calculations. These individual spectra have been used to resolve the spectral contribution of the Cu centres to the particular XANES features exhibited by the experimental spectra of the multinuclear complexes. Also, the variation in the 4p density of states have been calculated for the different Cu centres and then correlated with the features originated from corresponding coordination of Cu. Thus, these spectral features have been successfully utilized to detect the presence of the discrete metal centres in a system. The inferences about the coordination geometry have been supported by EXAFS analysis which has been used to determine the structural parameters for these complexes.

Long-term Kinetics of Uranyl Desorption from Sediments Under Advective Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shang, Jianying; Liu, Chongxuan; Wang, Zheming

2014-02-15

Long-term (> 4 months) column experiments were performed to investigate the kinetics of uranyl (U(VI)) desorption in sediments collected from the Integrated Field Research Challenge (IFRC) site at the US Department of Energy (DOE) Hanford 300 Area. The experimental results were used to evaluate alternative multi-rate surface complexation reaction (SCR) approaches to describe the short- and long-term kinetics of U(VI) desorption under flow conditions. The SCR stoichiometry, equilibrium constants, and multi-rate parameters were independently characterized in batch and stirred flow-cell reactors. Multi-rate SCR models that were either additively constructed using the SCRs for individual size fractions (e.g., Shang et al.,more » 2011), or composite in nature could effectively describe short-term U(VI) desorption under flow conditions. The long-term desorption results, however, revealed that using a labile U concentration measured by carbonate extraction under-estimated desorbable U(VI) and the long-term rate of U(VI) desorption. An alternative modeling approach using total U as the desorbable U(VI) concentration was proposed to overcome this difficulty. This study also found that the gravel size fraction (2-8 mm), which is typically treated as non-reactive in modeling U(VI) reactive transport because of low external surface area, can have an important effect on the U(VI) desorption in the sediment. This study demonstrates an approach to effectively extrapolate U(VI) desorption kinetics for field-scale application, and identifies important parameters and uncertainties affecting model predictions.« less

Uranium extraction from TRISO-coated fuel particles using supercritical CO2 containing tri-n-butyl phosphate.

PubMed

Zhu, Liyang; Duan, Wuhua; Xu, Jingming; Zhu, Yongjun

2012-11-30

High-temperature gas-cooled reactors (HTGRs) are advanced nuclear systems that will receive heavy use in the future. It is important to develop spent nuclear fuel reprocessing technologies for HTGR. A new method for recovering uranium from tristructural-isotropic (TRISO-) coated fuel particles with supercritical CO(2) containing tri-n-butyl phosphate (TBP) as a complexing agent was investigated. TRISO-coated fuel particles from HTGR fuel elements were first crushed to expose UO(2) pellet fuel kernels. The crushed TRISO-coated fuel particles were then treated under O(2) stream at 750°C, resulting in a mixture of U(3)O(8) powder and SiC shells. The conversion of U(3)O(8) into solid uranyl nitrate by its reaction with liquid N(2)O(4) in the presence of a small amount of water was carried out. Complete conversion was achieved after 60 min of reaction at 80°C, whereas the SiC shells were not converted by N(2)O(4). Uranyl nitrate in the converted mixture was extracted with supercritical CO(2) containing TBP. The cumulative extraction efficiency was above 98% after 20 min of online extraction at 50°C and 25 MPa, whereas the SiC shells were not extracted by TBP. The results suggest an attractive strategy for reprocessing spent nuclear fuel from HTGR to minimize the generation of secondary radioactive waste. Copyright © 2012 Elsevier B.V. All rights reserved.

Computer simulation of uranyl uptake by the rough lipopolysaccharide membrane of Pseudomonas aeruginosa.

PubMed

Lins, Roberto D; Vorpagel, Erich R; Guglielmi, Matteo; Straatsma, T P

2008-01-01

Heavy metal environmental contaminants cannot be destroyed but require containment, preferably in concentrated form, in a solid or immobile form for recycling or final disposal. Microorganisms are able to take up and deposit high levels of contaminant metals, including radioactive metals such as uranium and plutonium, into their cell wall. Consequently, these microbial systems are of great interest as the basis for potential environmental bioremediation technologies. The outer membranes of Gram-negative microbes are highly nonsymmetric and exhibit a significant electrostatic potential gradient across the membrane. This gradient has a significant effect on the uptake and transport of charged and dipolar compounds. However, the effectiveness of microbial systems for environmental remediation will depend strongly on specific properties that determine the uptake of targeted contaminants by a particular cell wall. To aid in the design of microbial remediation technologies, knowledge of the factors that determine the affinity of a particular bacterial outer membrane for the most common ionic species found in contaminated soils and groundwater is of great importance. Using our previously developed model for the lipopolysaccharide (LPS) membrane of Pseudomonas aeruginosa, this work presents the potentials of mean force as the estimate of the free energy profile for uptake of sodium, calcium, chloride, uranyl ions, and a water molecule by the bacterial LPS membrane. A compatible classical parameter set for uranyl has been developed and validated. Results show that the uptake of uranyl is energetically a favorable process relative to the other ions studied. At neutral pH, this nuclide is shown to be retained on the surface of the LPS membrane through chelation with the carboxyl and hydroxyl groups located in the outer core.

Dehydration of Uranyl Nitrate Hexahydrate to Uranyl Nitrate Trihydrate under Ambient Conditions as Observed via Dynamic Infrared Reflectance Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.

2015-05-22

the hexahydrate [UO 2(NO 3) 2(H 2O) 6] (UNH) and the trihydrate [UO 2(NO 3) 2(H 2O) 3] (UNT) forms. Their stabilities depend on both relative humidity and temperature. Both phases have previously been studied by infrared transmission spectroscopy, but the data were limited by both instrumental resolution and the ability to prepare the samples as pellets without desiccating them. We report time-resolved infrared (IR) measurements using an integrating sphere that allow us to observe the transformation from the hexahydrate to the trihydrate simply by flowing dry nitrogen gas over the sample. Hexahydrate samples were prepared and confirmed via knownmore » XRD patterns, then measured in reflectance mode. The hexahydrate has a distinct uranyl asymmetric stretch band at 949.0 cm -1 that shifts to shorter wavelengths and broadens as the sample dehydrates and recrystallizes to the trihydrate, first as a blue edge shoulder but ultimately resulting in a doublet band with reflectance peaks at 966 and 957 cm -1. The data are consistent with transformation from UNH to UNT since UNT has two non-equivalent UO 2 2+ sites. The dehydration of UO 2(NO 3) 2(H 2O) 6 to UO 2(NO 3) 2(H 2O) 3 is both a morphological and structural change that has the lustrous lime green crystals changing to the dull greenish yellow of the trihydrate. Crystal structures and phase transformation were confirmed theoretically using DFT calculations and experimentally via microscopy methods. Both methods showed a transformation with two distinct sites for the uranyl cation in the trihydrate, as opposed to a single crystallographic site in the hexahydrate.« less

Cytotoxicity of cyclometalated platinum complexes based on tridentate NCN and CNN-coordinating ligands: remarkable coordination dependence.

PubMed

Vezzu, Dileep A K; Lu, Qun; Chen, Yan-Hua; Huo, Shouquan

2014-05-01

A series of cyclometalated platinum complexes with diverse coordination patterns and geometries were screened for their anticancer activity. It was discovered that the N^C^N-coordinated platinum complex based on 1,3-di(pyridyl)benzene displayed much higher cytotoxicity against human lung cancer cells NCI-H522, HCC827, and NCI-H1299, and human prostate cancer cell RV1 than cisplatin. In a sharp contrast, the C^N^N-coordinated platinum complex based on 6-phenyl-2,2'-bipyridine was ineffective on these cancer cells. This remarkable difference in cytotoxicity displayed by N^C^N- and C^N^N-coordinated platinum complexes was related to the trans effect of the carbon donor in the cyclometalated platinum complexes, which played a crucial role in facilitating the dissociation of the chloride ligand to create an active binding site. The DNA binding was studied for the N^C^N-coordinated platinum complex using electrophoresis and emission titration. The cellular uptake observed by fluorescent microscope showed that the complex is largely concentrated in the cytoplasm. The possible pathways for the cell apoptosis were studied by western blot analysis and the activation of PARP via caspase 7 was observed. Copyright © 2014 Elsevier Inc. All rights reserved.

Linking clinician interaction and coordination to clinical performance in Patient-Aligned Care Teams.

PubMed

Hysong, Sylvia J; Thomas, Candice L; Spitzmüller, Christiane; Amspoker, Amber B; Woodard, LeChauncy; Modi, Varsha; Naik, Aanand D

2016-01-15

Team coordination within clinical care settings is a critical component of effective patient care. Less is known about the extent, effectiveness, and impact of coordination activities among professionals within VA Patient-Aligned Care Teams (PACTs). This study will address these gaps by describing the specific, fundamental tasks and practices involved in PACT coordination, their impact on performance measures, and the role of coordination task complexity. First, we will use a web-based survey of coordination practices among 1600 PACTs in the national VHA. Survey findings will characterize PACT coordination practices and assess their association with clinical performance measures. Functional job analysis, using 6-8 subject matter experts who are 3rd and 4th year residents in VA Primary Care rotations, will be utilized to identify the tasks involved in completing clinical performance measures to standard. From this, expert ratings of coordination complexity will be used to determine the level of coordinative complexity required for each of the clinical performance measures drawn from the VA External Peer Review Program (EPRP). For objective 3, data collected from the first two methods will evaluate the effect of clinical complexity on the relationships between measures of PACT coordination and their ratings on the clinical performance measures. Results from this study will support successful implementation of coordinated team-based work in clinical settings by providing knowledge regarding which aspects of care require the most complex levels of coordination and how specific coordination practices impact clinical performance.

Electronic structure and reactivity of three-coordinate iron complexes.

PubMed

Holland, Patrick L

2008-08-01

[Reaction: see text]. The identity and oxidation state of the metal in a coordination compound are typically thought to be the most important determinants of its reactivity. However, the coordination number (the number of bonds to the metal) can be equally influential. This Account describes iron complexes with a coordination number of only three, which differ greatly from iron complexes with octahedral (six-coordinate) geometries with respect to their magnetism, electronic structure, preference for ligands, and reactivity. Three-coordinate complexes with a trigonal-planar geometry are accessible using bulky, anionic, bidentate ligands (beta-diketiminates) that steer a monodentate ligand into the plane of their two nitrogen donors. This strategy has led to a variety of three-coordinate iron complexes in which iron is in the +1, +2, and +3 oxidation states. Systematic studies on the electronic structures of these complexes have been useful in interpreting their properties. The iron ions are generally high spin, with singly occupied orbitals available for pi interactions with ligands. Trends in sigma-bonding show that iron(II) complexes favor electronegative ligands (O, N donors) over electropositive ligands (hydride). The combination of electrostatic sigma-bonding and the availability of pi-interactions stabilizes iron(II) fluoride and oxo complexes. The same factors destabilize iron(II) hydride complexes, which are reactive enough to add the hydrogen atom to unsaturated organic molecules and to take part in radical reactions. Iron(I) complexes use strong pi-backbonding to transfer charge from iron into coordinated alkynes and N 2, whereas iron(III) accepts charge from a pi-donating imido ligand. Though the imidoiron(III) complex is stabilized by pi-bonding in the trigonal-planar geometry, addition of pyridine as a fourth donor weakens the pi-bonding, which enables abstraction of H atoms from hydrocarbons. The unusual bonding and reactivity patterns of three-coordinate iron compounds may lead to new catalysts for oxidation and reduction reactions and may be used by nature in transient intermediates of nitrogenase enzymes.

Spectroscopic studies of uranium species for environmental decontamination applications

NASA Astrophysics Data System (ADS)

Eng, Charlotte

After the Cold War, Department of Energy began to concentrate its efforts on cleanup of former nuclear material processing facilities, especially uranium-contaminated groundwater and soil. This research aims to study uranium association to both organic and inorganic compounds found in the contaminated environment in the hopes that the information gathered can be applied to the development and optimization of cost-effective remediation techniques. Spectroscopic and electrochemical methods will be employed to examine the behavior of uranium in given conditions to further our understanding of its impact on the environment. Uranium found in groundwater and soil bind with various ligands, especially organic ligands present in the environment due to natural sources (e.g. metabolic by-products or degradation of plants and animals) or man-made sources (e.g. chelating agents used in operating or cleanup of uranium processing facilities). We selected reasonable analogs of naturally occurring matter and studied their structure, chemical and electrochemical behavior and found that the structure of uranyl complexes depends heavily on the nature of the ligand and environmental factors such as pH. Association of uranium-organic complexes with anaerobic bacteria, Clostridium sp. was studied to establish if the bacteria can effectively bioreduce uranium while going through normal bacterial activity. It was found that the nature of the organic ligand affected the bioavailability and toxicity of the uranium on the bacteria. In addition, we have found that the type of iron corrosion products and uranyl species present on the surface of corroded steel depended on various environmental factors, which subsequently affected the removal rate of uranium by a citric acid/hydrogen peroxide/deionized water cleaning process. The method was found to remove uranium from only the topmost corrosion layers and residual uranium could be found (a) deeper in the corrosion layers where it is occluded by the steel corrosion products or (b) in areas where the dissolved uranium/iron species, the products generated by the dissolution power of citric acid, was not properly rinsed away.

Grain-Size Based Additivity Models for Scaling Multi-rate Uranyl Surface Complexation in Subsurface Sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xiaoying; Liu, Chongxuan; Hu, Bill X.

This study statistically analyzed a grain-size based additivity model that has been proposed to scale reaction rates and parameters from laboratory to field. The additivity model assumed that reaction properties in a sediment including surface area, reactive site concentration, reaction rate, and extent can be predicted from field-scale grain size distribution by linearly adding reaction properties for individual grain size fractions. This study focused on the statistical analysis of the additivity model with respect to reaction rate constants using multi-rate uranyl (U(VI)) surface complexation reactions in a contaminated sediment as an example. Experimental data of rate-limited U(VI) desorption in amore » stirred flow-cell reactor were used to estimate the statistical properties of multi-rate parameters for individual grain size fractions. The statistical properties of the rate constants for the individual grain size fractions were then used to analyze the statistical properties of the additivity model to predict rate-limited U(VI) desorption in the composite sediment, and to evaluate the relative importance of individual grain size fractions to the overall U(VI) desorption. The result indicated that the additivity model provided a good prediction of the U(VI) desorption in the composite sediment. However, the rate constants were not directly scalable using the additivity model, and U(VI) desorption in individual grain size fractions have to be simulated in order to apply the additivity model. An approximate additivity model for directly scaling rate constants was subsequently proposed and evaluated. The result found that the approximate model provided a good prediction of the experimental results within statistical uncertainty. This study also found that a gravel size fraction (2-8mm), which is often ignored in modeling U(VI) sorption and desorption, is statistically significant to the U(VI) desorption in the sediment.« less

A surface structural model for ferrihydrite I: Sites related to primary charge, molar mass, and mass density

NASA Astrophysics Data System (ADS)

Hiemstra, Tjisse; Van Riemsdijk, Willem H.

2009-08-01

A multisite surface complexation (MUSIC) model for ferrihydrite (Fh) has been developed. The surface structure and composition of Fh nanoparticles are described in relation to ion binding and surface charge development. The site densities of the various reactive surface groups, the molar mass, the mass density, the specific surface area, and the particle size are quantified. As derived theoretically, molecular mass and mass density of nanoparticles will depend on the types of surface groups and the corresponding site densities and will vary with particle size and surface area because of a relatively large contribution of the surface groups in comparison to the mineral core of nanoparticles. The nano-sized (˜2.6 nm) particles of freshly prepared 2-line Fh as a whole have an increased molar mass of M ˜ 101 ± 2 g/mol Fe, a reduced mass density of ˜3.5 ± 0.1 g/cm 3, both relatively to the mineral core. The specific surface area is ˜650 m 2/g. Six-line Fh (5-6 nm) has a molar mass of M ˜ 94 ± 2 g/mol, a mass density of ˜3.9 ± 0.1 g/cm 3, and a surface area of ˜280 ± 30 m 2/g. Data analysis shows that the mineral core of Fh has an average chemical composition very close to FeOOH with M ˜ 89 g/mol. The mineral core has a mass density around ˜4.15 ± 0.1 g/cm 3, which is between that of feroxyhyte, goethite, and lepidocrocite. These results can be used to constrain structural models for Fh. Singly-coordinated surface groups dominate the surface of ferrihydrite (˜6.0 ± 0.5 nm -2). These groups can be present in two structural configurations. In pairs, the groups either form the edge of a single Fe-octahedron (˜2.5 nm -2) or are present at a single corner (˜3.5 nm -2) of two adjacent Fe octahedra. These configurations can form bidentate surface complexes by edge- and double-corner sharing, respectively, and may therefore respond differently to the binding of ions such as uranyl, carbonate, arsenite, phosphate, and others. The relatively low PZC of ferrihydrite can be rationalized based on the estimated proton affinity constant for singly-coordinated surface groups. Nanoparticles have an enhanced surface charge. The charging behavior of Fh nanoparticles can be described satisfactory using the capacitance of a spherical Stern layer condenser in combination with a diffuse double layer for flat plates.

Molten salt flux synthesis and crystal structure of a new open-framework uranyl phosphate Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}: Spectroscopic characterization and cationic mobility studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yagoubi, S., E-mail: said.yagoubi@cea.fr; Renard, C.; Abraham, F.

2013-04-15

The reaction of triuranyl diphosphate tetrahydrate precursor (UO{sub 2}){sub 3}(PO{sub 4}){sub 2}(H{sub 2}O){sub 4} with a CsI flux at 750 °C yields a yellow single crystals of new compound Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}. The crystal structure (monoclinic, space group C2/c, a=13.6261 (13) Å, b=8.1081(8) Å, c=12.3983(12) Å, β=114.61(12)°, V=1245.41(20) Å{sup 3} with Z=4) has been solved using direct methods and Fourier difference techniques. A full-matrix least-squares refinement on the basis of F{sup 2} yielded R1=0.028 and wR2=0.071 for 79 parameters and 1352 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a charge-coupledmore » device detector. The crystal structure is built by two independent uranium atoms in square bipyramidal coordination, connected by two opposite corners to form infinite chains {sup 1}{sub ∞}[UO{sub 5}] and by one phosphorus atom in a tetrahedral environment PO{sub 4}. The two last entities {sup 1}{sub ∞}[UO{sub 5}] and PO{sub 4} are linked by sharing corners to form a three-dimensional structure presenting different types of channels occupied by Cs{sup +} alkaline cations. Their mobility within the tunnels were studied between 280 and 800 °C and compared with other tunneled uranyl minerals. The infrared spectrum shows a good agreement with the values inferred from the single crystal structure analysis of uranyl phosphate compound. - Graphical abstract: Arrhenius plot of the electrical conductivity of tunneled compounds Cs{sub 3}U{sub 2}PO{sub 10} and CsU{sub 2}Nb{sub 2}O{sub 11.5}. Highlights: ► The reaction of (UO{sub 2}){sub 3}(PO{sub 4}){sub 2}(H{sub 2}O){sub 4} in excess of molten CsI leads to single-crystals of new tunneled compound Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}. ► Ionic conductivity measurements and crystal structure analysis indicate a strong connection of the Cs{sup +} cations to the tunnels. ► A low symmetry in Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2} is the cause of IR activation and splitting of the bands in the IR spectrum.« less

Protein Hydrogel Microbeads for Selective Uranium Mining from Seawater.

PubMed

Kou, Songzi; Yang, Zhongguang; Sun, Fei

2017-01-25

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 (UO 2 2+ ) enrichment from natural seawater with great efficiency (enrichment index, K = 2.5 × 10 3 ) and selectivity. Our results demonstrate the feasibility of using protein hydrogels to extract uranium from the ocean.

METHOD FOR DISSOLVING ZIRCONIUM-URANIUM COMPOSITIONS

DOEpatents

Gens, T.A.

1961-07-18

A method is descrioed for treating a zirconium-- uranium composition to form a stable solution from which uranium and other values may be extracted by contacting the composition with at least a 4 molar aqueous solution of ammonium fluoride at a temperature of about 100 deg C, adding a peroxide, in incremental amounts, to the heated solution throughout the period of dissolution until all of the uranium is converted to soluble uranyl salt, adding nitric acid to the resultant solution to form a solvent extraction feed solution to convert the uranyl salt to a solvent extractable state, and thereafter recovering the uranium and other desired values from the feed solution by solvent extraction.

Observation of a brine layer on an ice surface with an environmental scanning electron microscope at higher pressures and temperatures.

PubMed

Krausko, Ján; Runštuk, Jiří; Neděla, Vilém; Klán, Petr; Heger, Dominik

2014-05-20

Observation of a uranyl-salt brine layer on an ice surface using backscattered electron detection and ice surface morphology using secondary-electron detection under equilibrium conditions was facilitated using an environmental scanning electron microscope (ESEM) at temperatures above 250 K and pressures of hundreds of Pa. The micrographs of a brine layer over ice grains prepared by either slow or shock freezing provided a complementary picture of the contaminated ice grain boundaries. Fluorescence spectroscopy of the uranyl ions in the brine layer confirmed that the species exists predominately in the solvated state under experimental conditions of ESEM.

Simultaneous reduction of arsenic(V) and uranium(VI) by mackinawite: role of uranyl arsenate precipitate formation.

PubMed

Troyer, Lyndsay D; Tang, Yuanzhi; Borch, Thomas

2014-12-16

Uranium (U) and arsenic (As) often occur together naturally and, as a result, can be co-contaminants at sites of uranium mining and processing, yet few studies have examined the simultaneous redox dynamics of U and As. This study examines the influence of arsenate (As(V)) on the reduction of uranyl (U(VI)) by the redox-active mineral mackinawite (FeS). As(V) was added to systems containing 47 or 470 μM U(VI) at concentrations ranging from 0 to 640 μM. In the absence of As(V), U was completely removed from solution and fully reduced to nano-uraninite (nano-UO2). While the addition of As(V) did not reduce U uptake, at As(V) concentrations above 320 μM, the reduction of U(VI) was limited due to the formation of a trögerite-like uranyl arsenate precipitate. The presence of U also significantly inhibited As(V) reduction. While less U(VI) reduction to nano-UO2 may take place in systems with high As(V) concentrations, formation of trögerite-like mineral phases may be an acceptable reclamation end point due to their high stability under oxic conditions.

Spectroscopy and DFT studies of uranyl carbonate, rutherfordine, UO2CO3: a model for uranium transport, carbon dioxide sequestration, and seawater species

NASA Astrophysics Data System (ADS)

Kalashnyk, N.; Perry, D. L.; Massuyeau, F.; Faulques, E.

2017-12-01

Several optical microprobe experiments of the anhydrous uranium carbonate—rutherfordine—are presented in this work and compared to periodic density functional theory results. Rutherfordine is the simplest uranyl carbonate and constitutes an ideal model system for the study of the rich uranium carbonate family relevant for environmental sustainability. Micro-Raman, micro-reflectance, and micro-photoluminescence (PL) spectroscopy studies have been carried out in situ on native, micrometer-sized crystals. The sensitivity of these techniques is sufficient to analyze minute amounts of samples in natural environments without using x-ray analysis. In addition, very intense micro-PL and micro-reflectance spectra that were not reported before add new results on the ground and excited states of this mineral. The optical gap value determined experimentally is found at about 2.6-2.8 eV. Optimized geometry, band structure, and phonon spectra have been calculated. The main vibrational lines are identified and predicted by this theoretical study. This work is pertinent for optical spectroscopy, for identification of uranyl species in various environmental settings, and for nuclear forensic analysis.

Effects of a low-radiotoxicity uranium salt (uranyl acetate) on biochemical and hematological parameters of the catfish, Clarias gariepinus

NASA Astrophysics Data System (ADS)

Al-Ghanim, Khalid A.; Ahmad, Zubair; Al-Kahem Al-Balawi, Hmoud F.; Al-Misned, Fahad; Maboob, Shahid; Suliman, El-Amin M.

2016-01-01

Specimens of Clarias gariepinus were treated with lethal (70, 75, 80, 85, 90, and 95 mg/L) and sub-lethal concentrations (8, 12 and 16 mg/L) of uranyl acetate, a low-radiotoxicity uranium salt. The LC 50 value was registered as 81.45 mg/L. The protein and glycogen concentrations in liver and muscles were decreased in the fish exposed to sub-lethal concentrations. The red blood cell (RBC) and white blood cell (WBC) counts, haemoglobin (Hb) concentration and haematocrit (Hct) values were decreased. Different blood indices like mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were negatively affected. Level of plasma glucose was elevated whereas protein was decreased. The level of calcium concentration (Ca) was declined in the blood of exposed fish whereas magnesium (Mg) remains unchanged. The activity level of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) was elevated in exposed fish. These effects were more pronounced in the last period of exposure and in higher concentrations. Results of the present study indicate that uranyl acetate has adverse effects on Clarias gariepinus and causes changes in the biochemical and hematological parameters of the fish.

Site-specific incorporation of uranyl carbonate species at the calcite surface

NASA Astrophysics Data System (ADS)

Reeder, Richard J.; Elzinga, Evert J.; Tait, C. Drew; Rector, K. D.; Donohoe, Robert J.; Morris, David E.

2004-12-01

Spatially resolved luminescence spectra from U(VI) co-precipitated at the (101¯4) growth surface of synthetic calcite single crystals confirm heterogeneous incorporation corresponding to the distribution of structurally non-equivalent steps composing the vicinal surfaces of spiral growth hillocks. Spectral structure from U(VI) luminescence at the "-" vicinal regions and featureless, weak luminescence at the "+" vicinal regions are consistent with previously reported observations of enrichment at the former sites during calcite growth. Luminescence spectra differ between the non-equivalent regions of the crystal, with the spectral features from the "-" vicinal region corresponding to those observed in bulk calcite samples. Subtle spectral shifts are observed from U(VI) co-precipitated with microcrystalline calcite synthesized by a different method, and all of the U(VI)-calcite sample spectra differ significantly from that of U(VI) co-precipitated with aragonite. The step-selective incorporation of U(VI) can be explained by a proposed model in which the allowed orientation for adsorption of the dominant calcium uranyl triscarbonate species is controlled by the atomic arrangement at step edges. Differences in the tilt angles of carbonate groups between non-equivalent growth steps favor adsorption of the calcium uranyl triscarbonate species at "-" steps, as observed in experiments.

Nuclear forensics investigation of morphological signatures in the thermal decomposition of uranyl peroxide.

PubMed

Schwerdt, Ian J; Olsen, Adam; Lusk, Robert; Heffernan, Sean; Klosterman, Michael; Collins, Bryce; Martinson, Sean; Kirkham, Trenton; McDonald, Luther W

2018-01-01

The analytical techniques typically utilized in a nuclear forensic investigation often provide limited information regarding the process history and production conditions of interdicted nuclear material. In this study, scanning electron microscopy (SEM) analysis of the surface morphology of amorphous-UO 3 samples calcined at 250, 300, 350, 400, and 450°C from uranyl peroxide was performed to determine if the morphology was indicative of the synthesis route and thermal history for the samples. Thermogravimetic analysis-mass spectrometry (TGA-MS) and differential scanning calorimetry (DSC) were used to correlate transitions in the calcined material to morphological transformations. The high-resolution SEM images were processed using the Morphological Analysis for Material Attribution (MAMA) software. Morphological attributes, particle area and circularity, indicated significant trends as a result of calcination temperature. The quantitative morphological analysis was able to track the process of particle fragmentation and subsequent sintering as calcination temperature was increased. At the 90% confidence interval, with 1000 segmented particles, the use of Kolmogorov-Smirnov statistical comparisons allowed discernment between all calcination temperatures for the uranyl peroxide route. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Oxo-exchange of gas-phase uranyl, neptunyl, and plutonyl with water and methanol.

PubMed

Lucena, Ana F; Odoh, Samuel O; Zhao, Jing; Marçalo, Joaquim; Schreckenbach, Georg; Gibson, John K

2014-02-17

A challenge in actinide chemistry is activation of the strong bonds in the actinyl ions, AnO2(+) and AnO2(2+), where An = U, Np, or Pu. Actinyl activation in oxo-exchange with water in solution is well established, but the exchange mechanisms are unknown. Gas-phase actinyl oxo-exchange is a means to probe these processes in detail for simple systems, which are amenable to computational modeling. Gas-phase exchange reactions of UO2(+), NpO2(+), PuO2(+), and UO2(2+) with water and methanol were studied by experiment and density functional theory (DFT); reported for the first time are experimental results for UO2(2+) and for methanol exchange, as well as exchange rate constants. Key findings are faster exchange of UO2(2+) versus UO2(+) and faster exchange with methanol versus water; faster exchange of UO2(+) versus PuO2(+) was quantified. Computed potential energy profiles (PEPs) are in accord with the observed kinetics, validating the utility of DFT to model these exchange processes. The seemingly enigmatic result of faster exchange for uranyl, which has the strongest oxo-bonds, may reflect reduced covalency in uranyl as compared with plutonyl.

True and masked three-coordinate T-shaped platinum(II) intermediates.

PubMed

Ortuño, Manuel A; Conejero, Salvador; Lledós, Agustí

2013-01-01

Although four-coordinate square-planar geometries, with a formally 16-electron counting, are absolutely dominant in isolated Pt(II) complexes, three-coordinate, 14-electron Pt(II) complexes are believed to be key intermediates in a number of platinum-mediated organometallic transformations. Although very few authenticated three-coordinate Pt(II) complexes have been characterized, a much larger number of complexes can be described as operationally three-coordinate in a kinetic sense. In these compounds, which we have called masked T-shaped complexes, the fourth position is occupied by a very weak ligand (agostic bond, solvent molecule or counteranion), which can be easily displaced. This review summarizes the structural features of the true and masked T-shaped Pt(II) complexes reported so far and describes synthetic strategies employed for their formation. Moreover, recent experimental and theoretical reports are analyzed, which suggest the involvement of such intermediates in reaction mechanisms, particularly C-H bond-activation processes.

A bis(amido) ligand set that supports two-coordinate chromium in the +1, +2, and +3 oxidation states†

PubMed Central

Cai, Irene C.; Lipschutz, Michael I.

2014-01-01

The amido ligand –N(SiiPr3)DIPP (DIPP = 2,6-diisopropylphenyl) has been used to prepare two-coordinate complexes of CrI, CrII, and CrIII. The two-coordinate CrII complex has also been used to prepare a three-coordinate CrIII iodide complex, which can be used to access a stable CrIII methyl species. PMID:25222516

The coordination structure of the extracted copper(II) complex with a synergistic mixture containing dinonylnaphthalene sulfonic acid and n-hexyl 3-pyridinecarboxylate ester

NASA Astrophysics Data System (ADS)

Zhu, Shan; Hu, Huiping; Hu, Jiugang; Li, Jiyuan; Hu, Fang; Wang, Yongxi

2017-09-01

In continuation of our interest in the coordination structure of the nickel(II) complex with dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (4PC), it was observed that the coordination sphere was completed by the coordination of two N atoms of pyridine rings in ligands 4PC and four water molecules while no direct interaction between Ni(II) and deprotonated HDNNS was observed. To investigate whether the coordination structure of nickel(II) with the synergistic mixture containing HDNNS and 4PC predominates or not in the copper(II) complex with the synergistic mixtures containing HDNNS and pyridinecarboxylate esters, a copper(II) synergist complex with n-hexyl 3-pyridinecarboxylate ester (L) and naphthalene-2-sulfonic acid (HNS, the short chain analogue of HDNNS), was prepared and studied by X-ray single crystal diffraction, elemental analyses and thermo gravimetric analysis (TGA), respectively. It was shown that the composition of the copper(II) synergist complex was [Cu(H2O)2(L)2(NS)2] and formed a trans-form distorted octahedral coordination structure. Two oxygen atoms of the two coordinated water molecules and two N atoms of the pyridine rings in the ligands L defined the basal plane while two O atoms from two sulfonate anions of the deprotonated HNS ligands occupied the apical positions by direct coordination with Cu(II), which was distinguished from the coordination structure of the nickel(II) synergist complex as reported in our previous work. In the crystal lattice, neighboring molecules [Cu(H2O)2L2(NS)2] were linked through the intermolecular hydrogen bonds between the hydrogen atoms of the coordinated water molecules and the oxygen atoms of the sulfonate anions in the copper(II) synergist complex to form a 2D plane. In order to bridge the gap between the solid state structure of the copper(II) synergist complex and the solution structure of the extracted copper(II) complex with the actual synergistic mixture containing L and HDNNS in the non-polar organic phase, the structures of the two copper(II) complexes were further investigated by Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS), and the results indicated that the extracted copper(II) complex in the non-polar organic phase might possess a similar coordination structure as the copper(II) synergist complex.

Reactivity of the Donor-Stabilized Silylenes [iPrNC(Ph)NiPr]2 Si and [iPrNC(NiPr2 )NiPr]2 Si: Activation of CO2 and CS2.

PubMed

Mück, Felix M; Baus, Johannes A; Nutz, Marco; Burschka, Christian; Poater, Jordi; Bickelhaupt, F Matthias; Tacke, Reinhold

2015-11-09

Activation of CO2 by the bis(amidinato)silylene 1 and the analogous bis(guanidinato)silylene 2 leads to the structurally analogous six-coordinate silicon(IV) complexes 4 (previous work) and 8, respectively, the first silicon compounds with a chelating carbonato ligand. Likewise, CS2 activation by silylene 1 affords the analogous six-coordinate silicon(IV) complex 10, the first silicon compound with a chelating trithiocarbonato ligand. CS2 activation by silylene 2, however, yields the five-coordinate silicon(IV) complex 13 with a carbon-bound CS2 (2-) ligand, which also represents an unprecedented coordination mode in silicon coordination chemistry. Treatment of the dinuclear silicon(IV) complexes 5 and 6 with CO2 also affords the six-coordinate carbonatosilicon(IV) complexes 4 and 8, respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Four coordination polymers based on 5-tert-butyl isophthalic acid and rigid bis(imidazol-1yl)benzene linkers: Synthesis, luminescence detection of acetone and optical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arıcı, Mürsel, E-mail: marici@ogu.edu.tr; Zafer Yeşilel, Okan; Büyükgüngör, Orhan

Four coordination polymers including, [Co(µ-Htbip){sub 2}(µ-dib)]{sub n} (1), [Co(µ-tbip)(µ-dmib){sub 0.5}]{sub n} (2), [Zn{sub 2}(µ-tbip)(µ{sub 3}-tbip)(µ-dmib){sub 1.5}]{sub n} (3) and [Cd(µ{sub 3}-tbip)(µ-dib){sub 0.5} (H{sub 2}O)]{sub n} (4) (tbip: 5-tert-butylisophthalate, dib: 1,4-bis(imidazol-1yl)benzene, dmib: 1,4-bis(imidazol-1yl)-2,5-dimethylbenzene), were hydrothermally synthesized and characterized by elemental analysis, IR spectra, single crystal and powder X-ray diffraction and thermal analysis (TG/DTA). The structural diversity is observed depending on ligands and coordination number of metal centers in the synthesized complexes. The tbip ligand displayed five different coordination modes in its complexes. In 1 and 2, complex 1 is 3D framework with the dia topology while complex 2 has 2D structuremore » with the sql topology depending on coordination geometries of Co ions. Complex 3 is 3D framework with the fsh 4,6-conn topology and complex 4 has 2D 4-connected sql topology. Photoluminescent properties of complex 3 dispersed in various organic solvents were investigated and the results showed that 3 dispersed in methanol could be used as a fluorescent sensor for the detection of acetone. Moreover, thermal and optical properties of the complexes were also studied. - Graphical abstract: Four coordination polymers were hydrothermally synthesized and characterized by various techniques. The complexes showed the structural diversity depending on ligands and coordination number of metal centers. The tbip ligand displayed four different coordination modes in its complexes. In 1 and 2, complexes 1 and 2 are 3D and 2D structures with the dia and sql topologies depending on coordination geometries of Co ions, respectively. Complexes 3 and 4 are 3D and 2D structures with the fsh 4,6-conn and sql topology, respectively. Photoluminescent properties of complex 3 dispersed in various organic solvents were investigated and the results showed that 3 dispersed in methanol could be used as a fluorescent sensor for the detection of acetone. Moreover, thermal and optical properties of the complexes were also studied. - Highlights: • Four new 2D and 3D coordination polymers with 5-tert-butyl isophthalic acid and rigid bis(imidazol-1yl)benzene linkers. • The structural diversity depending on ligands and coordination number of metal centers. • Fluorescent sensor for the detection of acetone.« less

Polymer complexes.. XXXX. Supramolecular assembly on coordination models of mixed-valence-ligand poly[1-acrylamido-2-(2-pyridyl)ethane] complexes

NASA Astrophysics Data System (ADS)

El-Sonbati, A. Z.; El-Bindary, A. A.; Diab, M. A.

2003-02-01

The build-up of polymer metallic supramolecules based on homopolymer (1-acrylamido-2-(2-pyridyl)ethane (AEPH)) and ruthenium, rhodium, palladium as well as platinum complexes has been pursued with great interest. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes [( 11)+( 12)] in the paper and in mononuclear polymer complexes ( 1)-( 5) it acts as a neutral bidentate ligand coordinating through the N-pyridine and NH-imino atoms, while in the mixed ligand diamagnetic poly-chelates, which are obtained from the reaction of AEPH with PdX 2 and KPtCl 4 in the presence of N-heterocyclic base consisting of polymer complexes ( 9)+( 10), and in monouclear compounds ( 6)-( 8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds ( 13)+( 14) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. The poly-chelates are of 1:1, 1:2 and 3:2 (metal-homopolymer) stoichiometry and exhibit six coordination. The values of ligand field parameters were calculated. The homopolymer and their polymer complexes have been characterized physicochemically.

Polymer complexes. XXXX. Supramolecular assembly on coordination models of mixed-valence-ligand poly[1-acrylamido-2-(2-pyridyl)ethane] complexes.

PubMed

El-Sonbati, A Z; El-Bindary, A A; Diab, M A

2003-02-01

The build-up of polymer metallic supramolecules based on homopolymer (1-acrylamido-2-(2-pyridyl)ethane (AEPH)) and ruthenium, rhodium, palladium as well as platinum complexes has been pursued with great interest. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes [(11)+(12)] in the paper and in mononuclear polymer complexes (1)-(5) it acts as a neutral bidentate ligand coordinating through the N-pyridine and NH-imino atoms, while in the mixed ligand diamagnetic poly-chelates, which are obtained from the reaction of AEPH with PdX2 and KPtCl4 in the presence of N-heterocyclic base consisting of polymer complexes (9)+(10), and in monouclear compounds (6)-(8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds (13)+(14) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. The poly-chelates are of 1:1, 1:2 and 3:2 (metal-homopolymer) stoichiometry and exhibit six coordination. The values of ligand field parameters were calculated. The homopolymer and their polymer complexes have been characterized physicochemically.

PROCESS OF PREPARING URANIUM-IMPREGNATED GRAPHITE BODY

DOEpatents

Kanter, M.A.

1958-05-20

A method for the fabrication of graphite bodies containing uniformly distributed uranium is described. It consists of impregnating a body of graphite having uniform porosity and low density with an aqueous solution of uranyl nitrate hexahydrate preferably by a vacuum technique, thereafter removing excess aqueous solution from the surface of the graphite, then removing the solvent water from the body under substantially normal atmospheric conditions of temperature and pressure in the presence of a stream of dry inert gas, and finally heating the dry impregnated graphite body in the presence of inert gas at a temperature between 800 and 1400 d C to convert the uranyl nitrate hexahydrate to an oxide of uranium.

The synaptinemal complex in Rhoeo spathacea.

PubMed

McQuade, H A; Wells, B

1975-03-01

The synaptinemal complex in meiocytes of Rhoeo spathacea is described. Unpaired zygotene chromosomes do not exhibit well defined axial cores under the ordinary fixations of electron microscopy and appear diffuse. However, the axial core is defined by ethanolic phosphotungstic acid (PTA) although it does not respond to uranyl-EDTA-lead. Thus the core appears to contain histone but not RNA and presents a condition which is modified later in pairing when lateral elements of the synaptinemal complex respond positively to both tests. The total number of attachments of synaptinemal complexes to the nuclear envelope was determined in several nuclei from serial sections. Eleven of the twelve possible attachments were found in one nucleus. It thus seems certain that all must be so attached. In the same manner all chromosomes can be seen to have an attachment to a chromocentre. Chromocentres are often very large and compound in that two kinds of heterochromatin can be distinguished. These states of chromatin within the chromocentre are considered to be a function of the degree of condensation. Segments of synaptinemal complexes are distributed randomly through sections of pachytene nuclei and long uncoiled segments of complexes are frequently found in or near the centres of median nuclear sections. Synaptinemal complexes are also found in chromocentres. Our findings suggest that on completion of pairing, which begins distally, homologous chromosomes in Rhoeo are paired throughout their entire lengths, rather than in small terminal segments only.

Reversible five-coordinate ⇄ six-coordinate transformation in cobalt(II) complexes

NASA Astrophysics Data System (ADS)

Xiao, Linda; Bhadbhade, Mohan; Baker, Anthony T.

2018-04-01

The heterocyclic ligands 2,6-bis(pyrazol-1-yl)pyridine (L1) and 2,6-bis(benzimidazol-2-yl)pyridine (L2) and their cobalt(II) complexes were synthesized. The blue five-coordinate complex [Co(L1)Cl2] isolated initially from the reaction mixture rapidly absorbed water vapour from the atmosphere to yield the pink six-coordinate complex [Co(L1)(H2O)3]Cl2. This change is reversible upon desiccation or transferring [Co(L1)(H2O)3]Cl2 into acetonitrile. The five coordinate complex [Co(L2)Cl2], however, remains stable under similar conditions. The structures of the complexes [Co(L1)Cl2], [Co(L1)(H2O)3]Cl2 and [Co(L2)Cl2] have been determined by x-ray crystallography. The magnetic susceptibilities and the electronic spectra for [Co(L1)Cl2], [Co(L2)Cl2] and [Co(L1)(H2O)3]Cl2 are presented.

Evolution of uranium distribution and speciation in mill tailings, COMINAK Mine, Niger.

PubMed

Déjeant, Adrien; Galoisy, Laurence; Roy, Régis; Calas, Georges; Boekhout, Flora; Phrommavanh, Vannapha; Descostes, Michael

2016-03-01

This study investigated the evolution of uranium distribution and speciation in mill tailings from the COMINAK mine (Niger), in production since 1978. A multi-scale approach was used, which combined high resolution remote sensing imagery, ICP-MS bulk rock analyses, powder X-ray diffraction, Scanning Electron Microscopy, Focused Ion Beam--Transmission Electron Microscopy and X-ray Absorption Near Edge Spectroscopy. Mineralogical analyses showed that some ore minerals, including residual uraninite and coffinite, undergo alteration and dissolution during tailings storage. The migration of uranium and other contaminants depends on (i) the chemical stability of secondary phases and sorbed species (dissolution and desorption processes), and (ii) the mechanical transport of fine particles bearing these elements. Uranium is stabilized after formation of secondary uranyl sulfates and phosphates, and adsorbed complexes on mineral surfaces (e.g. clay minerals). In particular, the stock of insoluble uranyl phosphates increases with time, thus contributing to the long-term stabilization of uranium. At the surface, a sulfate-cemented duricrust is formed after evaporation of pore water. This duricrust limits water infiltration and dust aerial dispersion, though it is enriched in uranium and many other elements, because of pore water rising from underlying levels by capillary action. Satellite images provided a detailed description of the tailings pile over time and allow monitoring of the chronology of successive tailings deposits. Satellite images suggest that uranium anomalies that occur at deep levels in the pile are most likely former surface duricrusts that have been buried under more recent tailings. Copyright © 2015 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, Alexander S.; Bryantsev, Vyacheslav S.

Uranium is used as the basic fuel for nuclear power plants, which generate significant amounts of electricity and have life cycle carbon emissions that are as low as renewable energy sources. However, the extraction of this valuable energy commodity from the ground remains controversial, mainly because of environmental and health impacts. Alternatively, seawater offers an enormous uranium resource that may be tapped at minimal environmental cost. Nowadays, amidoxime polymers are the most widely utilized sorbent materials for large-scale extraction of uranium from seawater, but they are not perfectly selective for uranyl, UO 2 2+. In particular, the competition between UOmore » 2 2+ and VO 2+/VO2+ cations poses a significant challenge to the effi-cient mining of UO 2 2+. Thus, screening and rational design of more selective ligands must be accomplished. One of the key components in achieving this goal is the establishment of computational techniques capable of assessing ligand selec-tivity trends. Here, we report an approach based on quantum chemical calculations that achieves high accuracy in repro-ducing experimental aqueous stability constants for VO 2+/VO 2+ complexes with ten different oxygen donor lig-ands. The predictive power of the developed computational protocol was demonstrated for amidoxime-type ligands, providing greater insights into new design strategies for the development of the next generation of adsorbents with high selectivity toward UO 2 2+over VO 2+/VO 2+ ions. Furthermore, the results of calculations suggest that alkylation of amidox-ime moieties present in poly(acrylamidoxime) sorbents can be a potential route to better discrimination between the uranyl and competing vanadium ions within seawater.« less

An artificially constructed Syngonium podophyllum-Aspergillus niger combinate system for removal of uranium from wastewater.

PubMed

He, Jia-dong; Wang, Yong-dong; Hu, Nan; Ding, Dexin; Sun, Jing; Deng, Qin-wen; Li, Chang-wu; Xu, Fei

2015-12-01

Aspergillus niger was inoculated to the roots of five plants, and the Syngonium podophyllum-A. niger combinate system (SPANCS) was found to be the most effective in removing uranium from hydroponic liquid with initial uranium concentration of 5 mg L(-1). Furthermore, the hydroponic experiments on the removal of uranium from the hydroponic liquids with initial uranium concentrations of 0.5, 1.0, and 3.0 mg L(-1) by the SPANCS were conducted, the inhibitory effect of A. niger on the growth of S. podophyllum in the SPANCS was studied, the accumulation characteristics of uranium by S. podophyllum in the SPANCS were analyzed, and the Fourier transform infrared (FT-IR) and extended X-ray absorption fine structure (EXAFS) spectra were measured. The results show that the removal of uranium by the SPANCS from the hydroponic liquids with initial uranium concentrations of 0.5, 1.0, and 3.0 mg L(-1) reached 98.20, 97.90, and 98.50%, respectively, after 37 days of accumulation of uranium; that the uranium concentrations in the hydroponic liquids decreased to 0.009, 0.021, and 0.045 mg L(-1), respectively, which are lower than the stipulated concentration for discharge of 0.050 mg L(-1) by the People's Republic of China; that A. niger helped to generate more groups in the root of S. podophyllum which can improve the complexing capability of S. podophyllum for uranium; and that the uranium accumulated in the root of S. podophyllum was in the form of phosphate uranyl and carboxylic uranyl.

Can we predict uranium bioavailability based on soil parameters? Part 2: soil solution uranium concentration is not a good bioavailability index.

PubMed

Vandenhove, H; Van Hees, M; Wannijn, J; Wouters, K; Wang, L

2007-01-01

The present study aimed to quantify the influence of soil parameters on uranium uptake by ryegrass. Ryegrass was established on eighteen distinct soils, spiked with (238)U. Uranium soil-to-plant transfer factors (TF) ranged from 0.0003 to 0.0340kgkg(-1). There was no significant relation between the U soil-to-plant transfer (or total U uptake or flux) and the uranium concentration in the soil solution or any other soil factor measured, nor with the U recovered following selective soil extractions. Multiple linear regression analysis resulted in a significant though complex model explaining up to 99% of variation in TF. The influence of uranium speciation on uranium uptake observed was featured: UO(2)(+2), uranyl carbonate complexes and UO(2)PO(4)(-) seem the U species being preferentially taken up by the roots and transferred to the shoots. Improved correlations were obtained when relating the uranium TF with the summed soil solution concentrations of mentioned uranium species.

Uranium Biominerals Precipitated by an Environmental Isolate of Serratia under Anaerobic Conditions.

PubMed

Newsome, Laura; Morris, Katherine; Lloyd, Jonathan R

2015-01-01

Stimulating the microbially-mediated precipitation of uranium biominerals may be used to treat groundwater contamination at nuclear sites. The majority of studies to date have focussed on the reductive precipitation of uranium as U(IV) by U(VI)- and Fe(III)-reducing bacteria such as Geobacter and Shewanella species, although other mechanisms of uranium removal from solution can occur, including the precipitation of uranyl phosphates via bacterial phosphatase activity. Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK. When supplied with glycerol phosphate, this Serratia strain was able to precipitate 1 mM of soluble U(VI) as uranyl phosphate minerals from the autunite group, under anaerobic and fermentative conditions. Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI), via reduction to nano-crystalline U(IV) uraninite. Some evidence for the reduction of solid phase uranyl(VI) phosphate was also observed. This study highlights the potential for Serratia and related species to play a role in the bioremediation of uranium contamination, via a range of different metabolic pathways, dependent on culturing or in situ conditions.

Uranium Biominerals Precipitated by an Environmental Isolate of Serratia under Anaerobic Conditions

PubMed Central

Newsome, Laura; Morris, Katherine; Lloyd, Jonathan. R.

2015-01-01

Stimulating the microbially-mediated precipitation of uranium biominerals may be used to treat groundwater contamination at nuclear sites. The majority of studies to date have focussed on the reductive precipitation of uranium as U(IV) by U(VI)- and Fe(III)-reducing bacteria such as Geobacter and Shewanella species, although other mechanisms of uranium removal from solution can occur, including the precipitation of uranyl phosphates via bacterial phosphatase activity. Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK. When supplied with glycerol phosphate, this Serratia strain was able to precipitate 1 mM of soluble U(VI) as uranyl phosphate minerals from the autunite group, under anaerobic and fermentative conditions. Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI), via reduction to nano-crystalline U(IV) uraninite. Some evidence for the reduction of solid phase uranyl(VI) phosphate was also observed. This study highlights the potential for Serratia and related species to play a role in the bioremediation of uranium contamination, via a range of different metabolic pathways, dependent on culturing or in situ conditions. PMID:26132209

Probing the Oxygen Environment in UO22+ by Solid-State O-17 Nuclear Magnetic Resonance Spectroscopy and Relativistic Density Functional Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Herman M.; De Jong, Wibe A.; Soderquist, Chuck Z.

A combined theoretical and solid-state O-17 NMR study of the electronic structure of the uranyl ion UO22+ in (NH4)4UO2(CO3)3 and rutherfordine UO2CO3 is presented, the former representing a system with a hydrogen-bonding environment around the uranyl oxygens, and the latter exemplifying a uranyl environment without hydrogens. A fully relativistic ab initio treatment reveals unique features of the U-O covalent bond, including the finding of O-17 chemical shift anisotropies that are among the largest ever reported (>1200 ppm). Computational results for the oxygen electric field gradient tensor are found to be consistently larger in magnitude than experimental solid-state O-17 NMR measurementsmore » in a 7.05 T magnetic field indicate. A modified version of the Solomon theory of the two-spin echo amplitude for a spin-5/2 nucleus is developed and applied to the analysis of the O-17 echo signal of UO22+. The William R. Wiley environmental Molecular Sciences Laboratory is a US Department of Energy national scientific user facility located at Pacific Northwest National Laboratory (PNNL) in Richland, Washington. PNNL is operated by Battelle for the US Department of Energy.« less

Time-dependent water dynamics in hydrated uranyl fluoride

DOE PAGES

Miskowiec, Andrew J.; Anderson, Brian B.; Herwig, Kenneth W.; ...

2015-09-15

In this study, uranyl fluoride is a three-layer, hexagonal structure with significant stacking disorder in the c-direction. It supports a range of unsolved ‘thermodynamic’ hydrates with 0–2.5 water molecules per uranium atom, and perhaps more. However, the relationship between water, hydrate crystal structures, and thermodynamic results, collectively representing the chemical pathway through these hydrate structures, has not been sufficiently elucidated. We used high-resolution quasielastic neutron scattering to study the dynamics of water in partially hydrated uranyl fluoride powder over the course of 4 weeks under closed conditions. The spectra are composed of two quasielastic components: one is associated with translationalmore » diffusive motion of water that is approximately five to six times slower than bulk water, and the other is a slow (on the order of 2–300 ps), spatially bounded water motion. The translational component represents water diffusing between the weakly bonded layers in the crystal, while the bounded component may represent water trapped in subnanometre ‘pockets’ formed by the space between uranium-centred polymerisation units. Complementary neutron diffraction measurements do not show any significant structural changes, suggesting that a chemical conversion of the material does not occur in the thermodynamically isolated system on this timescale.« less

Synthesis and structure determination of uranyl peroxide nanospheres in the presence of organic structure directing agents

NASA Astrophysics Data System (ADS)

Forbes, T. Z.; Burns, P. C.

2007-12-01

Recently, actinyl peroxide nanoclusters containing 20, 24, 28, or 32 actinyl polyhedra have been synthesized and their structures identified with single crystal X-ray diffraction [1]. Most nanomaterials are composed of main group elements or transition metals, therefore, these actinyl nanospheres may display vastly different chemical and physical properties due to the presence of filled f-orbitals. A major goal of our research group is to create novel actinyl materials, focusing on nano- and mesoporous materials. The original nanosphere syntheses were limited to inorganic crystallization agents, such as monovalent cations. Over the last decade, the use of organic compounds and surfactants have received increased attention as structure-directing agents for the generation of novel inorganic materials. Using structure-directing organic amines we have successfully synthesized and determined the structures of uranyl nanospheres containing 40 and 50 uranyl polyhedra. The topology of the skeletal U-50 nanosphere is identical to the C50Cl10 fullerene [2]. The topographical relationship between the actinyl nanospheres and fullerene or fullerene-like material may provide additional insight into stable configurations for lower fullerenes. [1] Burns et al., Actinyl peroxide nanospheres. Angewandte Chemie, International Edition, 2005. 44(14): p. 2135. [2] Xie et al., Capturing the Labile Fullerene[50] as C50Cl10. Science, (2004) 305(5671): p. 699.

Establishing the traceability of a uranyl nitrate solution to a standard reference material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, C.H.; Clark, J.P.

1978-01-01

A uranyl nitrate solution for use as a Working Calibration and Test Material (WCTM) was characterized, using a statistically designed procedure to document traceability to National Bureau of Standards Reference Material (SPM-960). A Reference Calibration and Test Material (PCTM) was prepared from SRM-960 uranium metal to approximate the acid and uranium concentration of the WCTM. This solution was used in the characterization procedure. Details of preparing, handling, and packaging these solutions are covered. Two outside laboratories, each having measurement expertise using a different analytical method, were selected to measure both solutions according to the procedure for characterizing the WCTM. Twomore » different methods were also used for the in-house characterization work. All analytical results were tested for statistical agreement before the WCTM concentration and limit of error values were calculated. A concentration value was determined with a relative limit of error (RLE) of approximately 0.03% which was better than the target RLE of 0.08%. The use of this working material eliminates the expense of using SRMs to fulfill traceability requirements for uranium measurements on this type material. Several years' supply of uranyl nitrate solution with NBS traceability was produced. The cost of this material was less than 10% of an equal quantity of SRM-960 uranium metal.« less

Nuclear proliferomics: A new field of study to identify signatures of nuclear materials as demonstrated on alpha-UO3.

PubMed

Schwerdt, Ian J; Brenkmann, Alexandria; Martinson, Sean; Albrecht, Brent D; Heffernan, Sean; Klosterman, Michael R; Kirkham, Trenton; Tasdizen, Tolga; McDonald Iv, Luther W

2018-08-15

The use of a limited set of signatures in nuclear forensics and nuclear safeguards may reduce the discriminating power for identifying unknown nuclear materials, or for verifying processing at existing facilities. Nuclear proliferomics is a proposed new field of study that advocates for the acquisition of large databases of nuclear material properties from a variety of analytical techniques. As demonstrated on a common uranium trioxide polymorph, α-UO 3 , in this paper, nuclear proliferomics increases the ability to improve confidence in identifying the processing history of nuclear materials. Specifically, α-UO 3 was investigated from the calcination of unwashed uranyl peroxide at 350, 400, 450, 500, and 550 °C in air. Scanning electron microscopy (SEM) images were acquired of the surface morphology, and distinct qualitative differences are presented between unwashed and washed uranyl peroxide, as well as the calcination products from the unwashed uranyl peroxide at the investigated temperatures. Differential scanning calorimetry (DSC), UV-Vis spectrophotometry, powder X-ray diffraction (p-XRD), and thermogravimetric analysis-mass spectrometry (TGA-MS) were used to understand the source of these morphological differences as a function of calcination temperature. Additionally, the SEM images were manually segmented using Morphological Analysis for MAterials (MAMA) software to identify quantifiable differences in morphology for three different surface features present on the unwashed uranyl peroxide calcination products. No single quantifiable signature was sufficient to discern all calcination temperatures with a high degree of confidence; therefore, advanced statistical analysis was performed to allow the combination of a number of quantitative signatures, with their associated uncertainties, to allow for complete discernment by calcination history. Furthermore, machine learning was applied to the acquired SEM images to demonstrate automated discernment with at least 89% accuracy. Copyright © 2018 Elsevier B.V. All rights reserved.

Incorporation mechanisms of actinide elements into the structures of U 6+ phases formed during the oxidation of spent nuclear fuel

NASA Astrophysics Data System (ADS)

Burns, Peter C.; Ewing, Rodney C.; Miller, Mark L.

1997-05-01

Uranyl oxide hydrate and uranyl silicate phases will form due to the corrosion and alteration of spent nuclear fuel under oxidizing conditions in silica-bearing solution. The actinide elements in the spent fuel may be incorporated into the structures of these secondary U6+ phases during the long-term corrosion of the UO 2 in spent fuel. The incorporation of actinide elements into the crystal structures of the alteration products may decrease actinide mobility. The crystal chemistry of the various oxidation states of the actinide elements of environmental concern is examined to identify possible incorporation mechanisms. The substitutions Pu 6+U 6+ and (Pu 5+, Np 5+)U 6+ should readily occur in many U 6+ structures, although structural modification may be required to satisfy local bond-valence requirements. Crystal-chemical characteristics of the U 6+ phases indicate that An 4+ (An: actinide)U 6+ substitution is likely to occur in the sheets of uranyl polyhedra that occur in the structures of the minerals schoepite, [(UO 2) 8O 2(OH) 12](H 2O) 12, ianthinite, [U 24+ (UO 2) 4O 6(OH) 4(H 2O) 4](H 2O) 5, becquerelite, Ca[(UO 2) 3O 2(OH) 3] 2(H 2O) 8, compreignacite, K 2[(UO 2) 3O 2(OH) 3] 2(H 2O) 8, α-uranophane, Ca[(UO 2)(SiO 3OH)] 2(H 2O) 5, and boltwoodite, K(H 2O)[(UO 2)(SiO 4)], all of which are likely to form due to the oxidation and alteration of the UO 2 in spent fuel. The incorporation of An 3+ into the sheets of the structures of α-uranophane and boltwoodite, as well as interlayer sites of various uranyl phases, may occur.

The coordination- and photochemistry of copper(i) complexes: variation of N^N ligands from imidazole to tetrazole.

PubMed

Bergmann, Larissa; Braun, Carolin; Nieger, Martin; Bräse, Stefan

2018-01-02

The prediction of coordination modes is of high importance when structure-property relationships are discussed. Herein, the coordination chemistry of copper(i) with pyridine-amines with a varying number of coordinating N-atoms, namely pyridine-benzimidazole, -triazole and -tetrazole, or their deprotonated analogues, and different phosphines was systematically studied and the photoluminescence properties of all synthesized complexes examined and related to DFT data. Each complex was characterized by single-crystal X-ray analysis and elemental analysis, and a set of prediction rules derived for the coordination chemistry of copper(i) with these ligands. A mononuclear cationic coordination motif was found for PPh 3 or DPEPhos with all N^N ligands, which exhibits blue to green luminescence of MLCT character d(Cu) → π*(pyridine-amine ligand) with quantum yields up to 46%. With the deprotonated N^N ligands, mononuclear neutral complexes were only expected with DPEPhos. The emission's nature of this complex type is strongly dependent on the electronic effects of the N^N ligand and was characterized as (ML + IL)CT transition. In contrast to the high quantum yields up to 78% for the tetrazolate complexes (as reported before), the triazolate and imidazolate based complexes show much lower emission efficiencies below 10%. Besides the mononuclear copper(i) complexes, cluster-type complexes were obtained, which show moderate luminescence in the blue to green region of the visible spectrum (469-505 nm).

A Bridge to Coordination Isomer Selection in Lanthanide(III) DOTA-tetraamide Complexes

PubMed Central

Vipond, Jeff; Woods, Mark; Zhao, Piyu; Tircso, Gyula; Ren, Jimin; Bott, Simon G.; Ogrin, Doug; Kiefer, Garry E.; Kovacs, Zoltan; Sherry, A.Dean

2008-01-01

Interest in macrocyclic lanthanide complexes such as DOTA is driven largely through interest in their use as contrast agents for MRI. The lanthanide tetraamide derivatives of DOTA have shown considerable promise as PARACEST agents, taking advantage of the slow water exchange kinetics of this class of complex. We postulated that water exchange in these tetraamide complexes could be slowed even further by introducing a group to sterically encumber the space above the water coordination site, thereby hindering the departure and approach of water molecules to the complex. The ligand 8O2-bridged-DOTAM was synthesized in a 34% yield from cyclen. It was found that the lanthanide complexes of this ligand did not possess a water molecule in the inner coordination sphere of the bound lanthanide. The crystal structure of the ytterbium complex revealed that distortions to the coordination sphere were induced by the steric constraints imposed on the complex by the bridging unit. The extent of the distortion was found to increase with increasing ionic radius of the lanthanide ion, eventually resulting in a complete loss of symmetry in the complex. Because this ligand system is bicyclic, the conformation of each ring in the system is constrained by that of the other, in consequence inclusion of the bridging unit in the complexes means only a twisted square antiprismatic coordination geometry is observed for complexes of 8O2-bridged-DOTAM. PMID:17295475

Correlation of Solid State and Solution Coordination Numbers with Infrared Spectroscopy in Five-, Six-, and Eight-Coordinate Transition Metal Complexes of DOTAM.

PubMed

Nagata, Maika K C T; Brauchle, Paul S; Wang, Sen; Briggs, Sarah K; Hong, Young Soo; Laorenza, Daniel W; Lee, Andrea G; Westmoreland, T David

2016-08-16

Three new DOTAM (1,4,7,10-tetrakis(acetamido)-1,4,7,10-tetraazacyclododecane) complexes have been synthesized and characterized by X-ray crystallography: [Co(DOTAM)]Cl 2 •3H 2 O, [Ni(DOTAM)]Cl 2 •4H 2 O, and [Cu(DOTAM)](ClO 4 ) 2 •H 2 O. Solid state and solution IR spectroscopic features for a series of [M(DOTAM)] 2+ complexes (M=Mn, Co, Cu, Ni, Ca, Zn) correlate with solid state and solution coordination numbers. [Co(DOTAM)] 2+ , [Ni(DOTAM)] 2+ , and [Zn(DOTAM)] 2+ are demonstrated to be six-coordinate in both the solid state and in solution, while [Mn(DOTAM)] 2+ and [Ca(DOTAM)] 2+ are eight-coordinate in the solid state and remain so in solution. [Cu(DOTAM)] 2+ , which is five-coordinate by X-ray crystallography, is shown to increase its coordination number in solution to six-coordinate.

Method for monitoring stack gases for uranium activity

DOEpatents

Beverly, C.R.; Ernstberger, E.G.

1985-07-03

A method for monitoring the stack gases of a purge cascade of gaseous diffusion plant for uranium activity. A sample stream is taken from the stack gases and contacted with a volume of moisture-laden air for converting trace levels of uranium hexafluoride, if any, in the stack gases into particulate uranyl fluoride. A continuous strip of filter paper from a supply roll is passed through this sampling stream to intercept and gather any uranyl fluoride in the sampling stream. This filter paper is then passed by an alpha scintillation counting device where any radioactivity on the filter paper is sensed so as to provide a continuous monitoring of the gas stream for activity indicative of the uranium content in the stack gases. 1 fig.

Method for monitoring stack gases for uranium activity

DOEpatents

Beverly, Claude R.; Ernstberger, Harold G.

1988-01-01

A method for monitoring the stack gases of a purge cascade of a gaseous diffusion plant for uranium activity. A sample stream is taken from the stack gases and contacted with a volume of moisture-laden air for converting trace levels of uranium hexafluoride, if any, in the stack gases into particulate uranyl fluoride. A continuous strip of filter paper from a supply roll is passed through this sampling stream to intercept and gather any uranyl fluoride in the sampling stream. This filter paper is then passed by an alpha scintillation counting device where any radioactivity on the filter paper is sensed so as to provide a continuous monitoring of the gas stream for activity indicative of the uranium content in the stack gases.

SEPARATION OF URANIUM FROM THORIUM AND PROTACTINIUM

DOEpatents

Musgrave, W.K.R.

1959-06-30

This patent relates to the separation of uranium from thorium and protactinium; such mixtures of elements usually being obtained by neutron irradiation of thorium. The method of separating the constituents has been first to dissolve the mixture of elements in concertrated nitric acid and then to remove the protactinium by absorption on manganese dioxide and the uranium by solvent extraction with ether. Prior to now, comparatively large amounts of thorium were extracted with the uranium. According to the invention this is completely prevented by adding sodium diethyldithiocarbamate to the mixture of soluble nitrate salts. The organic salt has the effect of reacting only with the uranyl nitrate to form the corresponding uranyl salt which can then be selectively extracted from the mixture with amyl acetate.

Performance of a hydrogen uranyl phosphate-carbon double-layer solid capacitor

NASA Astrophysics Data System (ADS)

Pham-Thi, M.; Adet, Ph.; Velasco, G.; Colomban, Ph.

1986-05-01

A mixture of commercially available carbon black (C) powders and hydrogen uranyl phosphate (HUP) precipitate can be used as the electrode material for miniaturized double-layer capacitors. A solid cell of C-HUP/HUP/C-HUP has a capacitance of 1 F which, given the device area and thickness of 0.8 sq cm and 0.2 cm respectively, corresponds to an energy density of more than 5 J/cu cm. The charge x voltage factor is higher than 5 x 10 to the -6th s and the working voltage is over 1.6 V. The leakage current is lower than 3 microamps at room temperature. The electrolyte can be operated up to about 120 C if the device is hermetically sealed.

Laser removal of loose uranium compound contamination from metal surfaces

NASA Astrophysics Data System (ADS)

Roberts, D. E.; Modise, T. S.

2007-04-01

Pulsed laser removal of surface contamination of uranyl nitrate and uranium dioxide from stainless steel has been studied. Most of the loosely bound contamination has been removed at fluence levels below 0.5 J cm -2, leaving about 5% fixed contamination for uranyl nitrate and 15% for uranium dioxide. Both alpha and beta activities are then sufficiently low that contaminated objects can be taken out of a restricted radiation area for re-use. The ratio of beta to alpha activity is found to be a function of particle size and changes during laser removal. In a separate experiment using technetium-99m, the collection of removed radioactivity in the filter was studied and an inventory made of removed and collected contamination.

Growth, structural, optical, thermal and dielectric properties of lanthanum chloride—thiourea—L tartaric acid coordinated complex

NASA Astrophysics Data System (ADS)

Slathia, Goldy; Bamzai, K. K.

2017-11-01

Lanthanum chloride—thiourea—l tartaric acid coordinated complex was grown in the form of single crystal by slow evaporation of supersaturated solutions at room temperature. This coordinated complex crystallizes in orthorhombic crystal system having space group P nma. The crystallinity and purity was tested by powder x-ray diffraction. Fourier transform infra red and Raman spectroscopy analysis provide the evidences on structure and mode of coordination. The scanning electron microscopy (SEM) analysis shows the morphology evolution as brought by the increase in composition of lanthanum chloride. The band transitions due to C=O and C=S chromophores remain active in grown complexes and are recorded in the UV-vis optical spectrum. The thermal effects such as dehydration, melting and decomposition were observed by the thermogravimetric and differential thermo analytical (TGA/DTA) analysis. Electrical properties were studied by dielectric analysis in frequency range 100-30 MHz at various temperatures. Increase in values of dielectric constant was observed with change in lanthanum concentration in the coordinated complex.

Identifying and Coordinating Care for Complex Patients

PubMed Central

Rudin, Robert S.; Gidengil, Courtney A.; Predmore, Zachary; Schneider, Eric C.; Sorace, James; Hornstein, Rachel

2017-01-01

Abstract In the United States, a relatively small proportion of complex patients---defined as having multiple comorbidities, high risk for poor outcomes, and high cost---incur most of the nation's health care costs. Improved care coordination and management of complex patients could reduce costs while increasing quality of care. However, care coordination efforts face multiple challenges, such as segmenting populations of complex patients to better match their needs with the design of specific interventions, understanding how to reduce spending, and integrating care coordination programs into providers' care delivery processes. Innovative uses of analytics and health information technology (HIT) may address these challenges. Rudin and colleagues at RAND completed a literature review and held discussions with subject matter experts, reaching the conclusion that analytics and HIT are being used in innovative ways to coordinate care for complex patients but that the capabilities are limited, evidence of their effectiveness is lacking, and challenges are substantial, and important foundational work is still needed. PMID:28845354

New water soluble heterometallic complex showing unpredicted coordination modes of EDTA

NASA Astrophysics Data System (ADS)

Mudsainiyan, R. K.; Jassal, A. K.; Chawla, S. K.

2015-10-01

A mesoporous 3D polymeric complex (I) having formula {[Zr(IV)O-μ3-(EDTA)Fe(III)OH]·H2O}n has been crystallized and characterized by various techniques. Single-crystal X-ray diffraction analysis revealed that complex (I) crystallized in chiral monoclinic space group Cc (space group no. 9) with unexpected coordination modes of EDTA and mixture of two transition metal ions. In this complex, the coordination number of Zr(IV) ion is seven where four carboxylate oxygen atoms, two nitrogen atoms, one oxide atom are coordinating with Zr(IV). Fe(III) is four coordinated and its coordination environment is composed of three different carboxylic oxygen atoms from three different EDTA and one oxygen atom of -OH group. The structure consists of 4-c and 16-c (2-nodal) net with new topology and point symbol for net is (336·454·530)·(36). TGA study and XRPD pattern showed that the coordination polymer is quite stable even after losing water molecule and -OH ion. Quenching behavior in fluorescence of ligand is observed by complexation with transition metal ions is due to n-π* transition. The SEM micrograph shows the morphology of complex (I) exhibits spherical shape with size ranging from 50 to 280 nm. The minimum N2 (SBET=8.7693 m2/g) and a maximum amount of H2 (high surface area=1044.86 m2/g (STP)) could be adsorbed at 77 K. From DLS study, zeta potential is calculated i.e. -7.94 shows the negative charges on the surface of complex. Hirshfeld surface analysis and fingerprint plots revealed influence of weak or non bonding interactions in crystal packing of complex.

Crystal structures of copper(II) chloride, copper(II) bromide, and copper(II) nitrate complexes with pyridine-2-carbaldehyde thiosemicarbazone

NASA Astrophysics Data System (ADS)

Chumakov, Yu. M.; Tsapkov, V. I.; Jeanneau, E.; Bairac, N. N.; Bocelli, G.; Poirier, D.; Roy, J.; Gulea, A. P.

2008-09-01

The crystal structures of chloro-(2-formylpyridinethiosemicarbazono)copper dimethyl sulfoxide solvate ( I), bromo-(2-formylpyridinethiosemicarbazono)copper ( II), and (2-formylpyridinethiosemicarbazono)copper(II) nitrate dimethyl sulfoxide solvate ( III) are determined using X-ray diffraction. In the crystals, complexes I and II form centrosymmetric dimers in which the thiosemicarbazone sulfur atom serves as a bridge and occupies the fifth coordination site of the copper atom of the neighboring complex related to the initial complex through the center of symmetry. In both cases, the coordination polyhedron of the complexing ion is a distorted tetragonal bipyramid. Complex III in the crystal structure forms polymer chains in which the copper atom of one complex forms the coordination bond with the thicarbamide nitrogen atom of the neighboring complex. In this structure, the coordination polyhedron of the central atom is an elongated tetragonal bipyramid. It is established that complexes I III at a concentration of 10-5 mol/l selectively inhibit the growth of 60 to 90 percent of the cancer tumor cells of the human myeloid leukemia (HL-60).

The coordination chemistry of group 15 element ligand complexes--a developing area.

PubMed

Scheer, Manfred

2008-09-07

A survey of the contemporary challenges of the field of unsubstituted group 15 element ligand complexes (excluding N) is given. The focus of the article is on the coordination chemistry behaviour of such E(n) ligand complexes. This field is subdivided into two areas of reactivity: E(n) ligand complexes with (i) noncoordinated Lewis-acidic cations and (ii) Lewis-acidic coordination compounds containing at least one permanently coordinating ligand. In the latter case, insoluble 1D and 2D polymers respectively are obtained; however, under special conditions soluble, spherical, fullerene-like giant molecules are formed. These nano-sized molecules are up to 2.4 nm in diameter and are able to encapsulate small molecules in their holes. In contrast, the first-mentioned field uses weakly coordinating anions to obtain readily soluble di- and polycationic products. These show depolymerisation tendencies in solution under the formation of oligomer-monomer equilibria and thus reveal dynamic supramolecular aggregation processes.

The impact of ionic liquids on the coordination of anions with solvatochromic copper complexes.

PubMed

Kuzmina, O; Hassan, N H; Patel, L; Ashworth, C; Bakis, E; White, A J P; Hunt, P A; Welton, T

2017-09-28

Solvatochromic transition metal (TM)-complexes with weakly associating counter-anions are often used to evaluate traditional neutral solvent and anion coordination ability. However, when employed in ionic liquids (IL) many of the common assumptions made are no longer reliable. This study investigates the coordinating ability of weakly coordinating IL anions in traditional solvents and within IL solvents employing a range of solvatochromic copper complexes. Complexes of the form [Cu(acac)(tmen)][X] (acac = acetylacetonate, tmen = tetramethylethylenediamine) where [X] - = [ClO 4 ] - , Cl - , [NO 3 ] - , [SCN] - , [OTf] - , [NTf 2 ] - and [PF 6 ] - have been synthesised and characterised both experimentally and computationally. ILs based on these anions and imidazolium and pyrrolidinium cations, some of which are functionalised with hydroxyl and nitrile groups, have been examined. IL-anion coordination has been investigated and compared to typical weakly coordinating anions. We have found there is potential for competition at the Cu-centre and cases of anions traditionally assigned as weakly associating that demonstrate a stronger than expected level of coordinating ability within ILs. [Cu(acac)(tmen)][PF 6 ] is shown to contain the least coordinating anion and is established as the most sensitive probe studied here. Using this probe, the donor numbers (DNs) of ILs have been determined. Relative donor ability is further confirmed based on the UV-Vis of a neutral complex, [Cu(sacsac) 2 ] (sacsac = dithioacetylacetone), and DNs evaluated via 23 Na NMR spectroscopy. We demonstrate that ILs can span a wide donor range, similar in breadth to conventional solvents.

Applications of several spectral techniques to characterize coordination compounds derived from 2,6-diacetylpyridine derivative

NASA Astrophysics Data System (ADS)

Chandra, Sulekh; Sharma, Amit Kumar

2009-09-01

The coordination compounds of Cr III, Mn II and Co II metal ions derived from quinquedentate 2,6-diacetylpyridine derivative have been synthesized and characterized by using the various physicochemical studies like stoichiometric, molar conductivity and magnetic, and spectral techniques like IR, NMR, mass, UV and EPR. The general stoichiometries of the complexes are found to be [Cr(H 2L)X] and [M(HL)X], where M = Mn(II) and Co(II); H 2L = dideprotonated ligand, HL = monodeprotonated ligand and X = NO 3-, Cl - and OAc -. The studies reveal that the complexes possess monomeric compositions with six coordinated octahedral geometry (Cr III and Mn II complexes) and six coordinated tetragonal geometry (Co II complexes).

Mathematical model and coordination algorithms for ensuring complex security of an organization

NASA Astrophysics Data System (ADS)

Novoseltsev, V. I.; Orlova, D. E.; Dubrovin, A. S.; Irkhin, V. P.

2018-03-01

The mathematical model of coordination when ensuring complex security of the organization is considered. On the basis of use of a method of casual search three types of algorithms of effective coordination adequate to mismatch level concerning security are developed: a coordination algorithm at domination of instructions of the coordinator; a coordination algorithm at domination of decisions of performers; a coordination algorithm at parity of interests of the coordinator and performers. Assessment of convergence of the algorithms considered above it was made by carrying out a computing experiment. The described algorithms of coordination have property of convergence in the sense stated above. And, the following regularity is revealed: than more simply in the structural relation the algorithm, for the smaller number of iterations is provided to those its convergence.

From {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} to {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} infinite chains in A{sub 6}U{sub 2}Mo{sub 4}O{sub 21} (A=Na, K, Rb, Cs) compounds: Synthesis and crystal structure of Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yagoubi, S.; Groupe de Radiochimie, Institut de Physique Nucleaire d'Orsay, Universite Paris-Sud XI, 91406 Orsay Cedex; Obbade, S., E-mail: said.obbade@phelma.grenoble-inp.f

2011-05-15

A new caesium uranyl molybdate belonging to the M{sub 6}U{sub 2}Mo{sub 4}O{sub 21} family has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the other alkali uranyl molybdates of this family (A=Na, K, Rb) where molybdenum atoms adopt only tetrahedral coordination and which can be formulated A{sub 6}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}], the caesium compound Cs{sub 6}U{sub 2}Mo{sub 4}O{sub 21} should be written Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] with molybdenum atoms in tetrahedral and square pyramidal environments. Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] crystallizes in the triclinic symmetry withmore » space group P1-bar and a=10.4275(14) A, b=15.075(2) A, c=17.806(2) A, {alpha}=70.72(1){sup o}, {beta}=80.38(1){sup o} and {gamma}=86.39(1){sup o}, V=2604.7(6) A{sup 3}, Z=4, {rho}{sub mes}=5.02(2) g/cm{sup 3} and {rho}{sub cal}=5.08(3) g/cm{sup 3}. A full-matrix least-squares refinement on the basis of F{sup 2} yielded R{sub 1}=0.0464 and wR{sub 2}=0.0950 for 596 parameters with 6964 independent reflections with I{>=}2{sigma}(I) collected on a BRUKER AXS diffractometer with Mo(K{alpha}) radiation and a CCD detector. The crystal structure of Cs compound is characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} parallels chains built from U{sub 2}O{sub 13} dimeric units, MoO{sub 4} tetrahedra and MoO{sub 5} square pyramids, whereas, Na, K and Rb compounds are characterized by {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}O(MoO{sub 4}){sub 4}]{sup 6-} parallel chains formulated simply of U{sub 2}O{sub 13} units and MoO{sub 4} tetrahedra. Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction, confirm the structural results. The thermal stability and the electrical conductivity are also studied. The four compounds decompose at low temperature (between 540 and 610 {sup o}C). -- Graphical abstract: The staking of {sub {infinity}}{sup 1}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})]{sup 6-} infinite uranyl molybdate ribbons in the Cs{sub 6}[(UO{sub 2}){sub 2}(MoO{sub 4}){sub 3}(MoO{sub 5})] structure. Display Omitted Highlights: {yields} Cs{sub 6}U{sub 2}Mo{sub 4}O{sub 2} a new compound with bidimensional crystal structure, characterized by infinite uranyl molybdate chains. {yields} Crystal structure similar to these of the compounds containing Na, K, Rb. {yields} Molybdenum atoms surrounded by five oxygen atoms to form an original and strongly distorted MoO{sub 5} environment. {yields} The chains arrangement illustrates the key role of the alkaline ionic radius, in the crystal structure distortion for Cs compound.« less

Synthesis and X-ray Crystallography of [Mg(H2O)6][AnO2(C2H5COO)3]2 (An = U, Np, or Pu).

PubMed

Serezhkin, Viktor N; Grigoriev, Mikhail S; Abdulmyanov, Aleksey R; Fedoseev, Aleksandr M; Savchenkov, Anton V; Serezhkina, Larisa B

2016-08-01

Synthesis and X-ray crystallography of single crystals of [Mg(H2O)6][AnO2(C2H5COO)3]2, where An = U (I), Np (II), or Pu (III), are reported. Compounds I-III are isostructural and crystallize in the trigonal crystal system. The structures of I-III are built of hydrated magnesium cations [Mg(H2O)6](2+) and mononuclear [AnO2(C2H5COO)3](-) complexes, which belong to the AB(01)3 crystallochemical group of uranyl complexes (A = AnO2(2+), B(01) = C2H5COO(-)). Peculiarities of intermolecular interactions in the structures of [Mg(H2O)6][UO2(L)3]2 complexes depending on the carboxylate ion L (acetate, propionate, or n-butyrate) are investigated using the method of molecular Voronoi-Dirichlet polyhedra. Actinide contraction in the series of U(VI)-Np(VI)-Pu(VI) in compounds I-III is reflected in a decrease in the mean An═O bond lengths and in the volume and sphericity degree of Voronoi-Dirichlet polyhedra of An atoms.

Bioreduction of U(VI)-Phthalate to a Polymeric U(IV)-Phthalate Colloid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vazquez, G.; Dodge, C; Francis, A

2009-01-01

Phthalic acid, a ubiquitous organic ligand, formed soluble mono- and biligand complexes with a uranyl ion that was then reduced to a U(IV)-phthalate by a Clostridium species under anaerobic conditions. We confirmed the reduction of the hexavalent uranium to the tetravalent oxidation state by UV-vis absorption and X-ray absorption near edge structure spectroscopy. Sequential micro- and ultrafiltration of the solution revealed that the bioreduced uranium was present as a colloid with particles between 0.03 and 0.45 {mu}m. Analysis with extended X-ray absorption fine structure revealed the association of the reduced uranium with the phthalic acid as a repeating biligand 1:2more » U(IV):phthalic acid polymer. This is the first report of the formation of a U(IV) complexed to two phthalic acid molecules in the form of a polymeric colloid. Although it was proposed that the bioreduction and the precipitation of uranium might be an invaluable strategy to immobilize uranium in contaminated environments, our results suggest that the organic ligands present there might hinder the precipitation of the bioreduced uranium under anaerobic conditions and, thereby, enhance its environmental mobility as uranium organic complexes or colloids.« less

Oxidation and Hydration of U 3O 8 Materials Following Controlled Exposure to Temperature and Humidity

DOE PAGES

Tamasi, Alison L.; Boland, Kevin S.; Czerwinski, Kenneth; ...

2015-03-18

Chemical signatures correlated with uranium oxide processing are of interest to forensic science for inferring sample provenance. Identification of temporal changes in chemical structures of process uranium materials as a function of controlled temperatures and relative humidities may provide additional information regarding sample history. In our study, a high-purity α-U 3O 8 sample and three other uranium oxide samples synthesized from reaction routes used in nuclear conversion processes were stored under controlled conditions over 2–3.5 years, and powder X-ray diffraction analysis and X-ray absorption spectroscopy were employed to characterize chemical speciation. We measured signatures from the α-U 3O 8 samplemore » indicated that the material oxidized and hydrated after storage under high humidity conditions over time. Impurities, such as uranyl fluoride or schoepites, were initially detectable in the other uranium oxide samples. After storage under controlled conditions, the analyses of the samples revealed oxidation over time, although the signature of the uranyl fluoride impurity diminished. The presence of schoepite phases in older uranium oxide material is likely indicative of storage under high humidity and should be taken into account for assessing sample history. Finally, the absence of a signature from a chemical impurity, such as uranyl fluoride hydrate, in an older material may not preclude its presence at the initial time of production.« less

Inducing fluorescence of uranyl acetate as a dual-purpose contrast agent for correlative light-electron microscopy with nanometre precision.

PubMed

Tuijtel, Maarten W; Mulder, Aat A; Posthuma, Clara C; van der Hoeven, Barbara; Koster, Abraham J; Bárcena, Montserrat; Faas, Frank G A; Sharp, Thomas H

2017-09-05

Correlative light-electron microscopy (CLEM) combines the high spatial resolution of transmission electron microscopy (TEM) with the capability of fluorescence light microscopy (FLM) to locate rare or transient cellular events within a large field of view. CLEM is therefore a powerful technique to study cellular processes. Aligning images derived from both imaging modalities is a prerequisite to correlate the two microscopy data sets, and poor alignment can limit interpretability of the data. Here, we describe how uranyl acetate, a commonly-used contrast agent for TEM, can be induced to fluoresce brightly at cryogenic temperatures (-195 °C) and imaged by cryoFLM using standard filter sets. This dual-purpose contrast agent can be used as a general tool for CLEM, whereby the equivalent staining allows direct correlation between fluorescence and TEM images. We demonstrate the potential of this approach by performing multi-colour CLEM of cells containing equine arteritis virus proteins tagged with either green- or red-fluorescent protein, and achieve high-precision localization of virus-induced intracellular membrane modifications. Using uranyl acetate as a dual-purpose contrast agent, we achieve an image alignment precision of ~30 nm, twice as accurate as when using fiducial beads, which will be essential for combining TEM with the evolving field of super-resolution light microscopy.

Distribution of ciprofloxacin into the central nervous system in rats with acute renal or hepatic failure.

PubMed

Naora, K; Ichikawa, N; Hirano, H; Iwamoto, K

1999-05-01

Pharmacokinetic changes of various drugs have been reported in renal or hepatic failure. The present study employed ciprofloxacin, a quinolone antibiotic having neurotoxic side effects, to assess the influence of these diseases on distribution of ciprofloxacin into the central nervous system (CNS). After intravenous dosing of ciprofloxacin (10-30 mg kg(-1)), ciprofloxacin levels in plasma and brain were measured in normal rats (Wistar, male, 10-week-old) and those with acute renal and hepatic injuries which were induced by uranyl nitrate and carbon tetrachloride (CCl4), respectively. In the uranyl nitrate-treated rats, the plasma elimination half-life of ciprofloxacin was prolonged and the total body clearance was reduced when compared with those in the normal rats. Similar but smaller changes were observed in the CCl4-treated group. Brain levels of ciprofloxacin were significantly increased by both uranyl nitrate and CCl4 treatments. A proportional correlation between serum unbound levels and brain levels of ciprofloxacin was observed in the normal group. However, brain-to-serum unbound concentration ratios of ciprofloxacin were reduced in the rats with renal or hepatic failure. These results suggest that renal failure as well as hepatic failure retards elimination of ciprofloxacin from the blood, leading to elevation of the CNS level, and also that ciprofloxacin distribution in the brain is reduced in these disease states.

Oxidation and Hydration of U 3 O 8 Materials Following Controlled Exposure to Temperature and Humidity

DOE PAGES

Tamasi, Alison L.; Boland, Kevin S.; Czerwinski, Kenneth; ...

2015-03-18

Chemical signatures correlated with uranium oxide processing are of interest to forensic science for inferring sample provenance. Identification of temporal changes in chemical structures of process uranium materials as a function of controlled temperatures and relative humidities may provide additional information regarding sample history. In our study, a high-purity α-U 3O 8 sample and three other uranium oxide samples synthesized from reaction routes used in nuclear conversion processes were stored under controlled conditions over 2–3.5 years, and powder X-ray diffraction analysis and X-ray absorption spectroscopy were employed to characterize chemical speciation. We measured signatures from the α-U 3O 8 samplemore » indicated that the material oxidized and hydrated after storage under high humidity conditions over time. Impurities, such as uranyl fluoride or schoepites, were initially detectable in the other uranium oxide samples. After storage under controlled conditions, the analyses of the samples revealed oxidation over time, although the signature of the uranyl fluoride impurity diminished. The presence of schoepite phases in older uranium oxide material is likely indicative of storage under high humidity and should be taken into account for assessing sample history. Finally, the absence of a signature from a chemical impurity, such as uranyl fluoride hydrate, in an older material may not preclude its presence at the initial time of production. LA-UR-15-21495.« less

The effects of intramolecular H-bond formation on the stability constant and water exchange rate of the Gd(III)-diethylenetriamine-N'-(3-amino-1,1-propylenephosphonic)-N, N,N'',N''-tetraacetate complex.

PubMed

Baranyai, Zsolt; Gianolio, Eliana; Ramalingam, Kondareddiar; Swenson, Rolf; Ranganathan, Ramachandran; Brücher, E; Aime, Silvio

2007-01-01

The binding interaction of metal chelates to biological macromolecules, though driven by properly devoted recognition synthons, may cause dramatic changes in some property associated with the coordination cage such as the thermodynamic stability or the exchange rate of the metal coordinated water. Such changes are due to electrostatic and H-bonding interactions involving atoms of the coordination cage and atoms of the biological molecule at the binding site. To mimic this type of H-bonding interactions, lanthanide(III) complexes with a DTPA-monophosphonate ligand bearing a propylamino moiety (H6NP-DTPA) were synthesized. Their thermodynamic stabilities and the exchange lifetime of the coordinated water molecule (for the Gd-complex) were compared with those of the analog complexes with DTPA and the parent DTPA-monophosphonate derivative (H6P-DTPA). It was found that the intramolecular H-bond between the epsilon-amino group and the phosphonate moiety in NP-DTPA complexes causes displacements of electric charges in their coordination cage that are markedly pH dependent. In turn, this affects the characteristic properties of the coordination cage. In particular it results in a marked elongation of the exchange lifetime of the coordinated water molecule. (c) 2007 John Wiley & Sons, Ltd.

Mechanics of metal-catecholate complexes: The roles of coordination state and metal types

PubMed Central

Xu, Zhiping

2013-01-01

There have been growing evidences for the critical roles of metal-coordination complexes in defining structural and mechanical properties of unmineralized biological materials, including hardness, toughness, and abrasion resistance. Their dynamic (e.g. pH-responsive, self-healable, reversible) properties inspire promising applications of synthetic materials following this concept. However, mechanics of these coordination crosslinks, which lays the ground for predictive and rational material design, has not yet been well addressed. Here we present a first-principles study of representative coordination complexes between metals and catechols. The results show that these crosslinks offer stiffness and strength near a covalent bond, which strongly depend on the coordination state and type of metals. This dependence is discussed by analyzing the nature of bonding between metals and catechols. The responsive mechanics of metal-coordination is further mapped from the single-molecule level to a networked material. The results presented here provide fundamental understanding and principles for material selection in metal-coordination-based applications. PMID:24107799

Multispecies diffusion models: A study of uranyl species diffusion

NASA Astrophysics Data System (ADS)

Liu, Chongxuan; Shang, Jianying; Zachara, John M.

2011-12-01

Rigorous numerical description of multispecies diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication in imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multispecies diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multispecies diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multispecies U(VI) diffusion under a steady state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that for multispecies U(VI) diffusion under transient chemical conditions, a fully coupled diffusion model could be well approximated by a component-based diffusion model when the diffusion coefficient for each chemical component was properly selected. The component-based diffusion model considers the difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be enforced, if necessary, by adding a secondary migration term resulting from model simplification. The effect of ion activity coefficient gradients on multispecies diffusion is also discussed. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from U.S. Department of Energy's Hanford 300A, where intragranular diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that had been previously described using a semiempirical, multirate model. Compared with the multirate model, the diffusion models have the advantage to provide spatiotemporal speciation evolution within the diffusion domains.

Attributes of advanced practice registered nurse care coordination for children with medical complexity.

PubMed

Cady, Rhonda G; Kelly, Anne M; Finkelstein, Stanley M; Looman, Wendy S; Garwick, Ann W

2014-01-01

Care coordination is an essential component of the pediatric health care home. This study investigated the attributes of relationship-based advanced practice registered nurse care coordination for children with medical complexity enrolled in a tertiary hospital-based health care home. Retrospective review of 2,628 care coordination episodes conducted by telehealth over a consecutive 3-year time period for 27 children indicated that parents initiated the majority of episodes and the most frequent reason was acute and chronic condition management. During this period, care coordination episodes tripled, with a significant increase (p < .001) between years 1 and 2. The increased episodes could explain previously reported reductions in hospitalizations for this group of children. Descriptive analysis of a program-specific survey showed that parents valued having a single place to call and assistance in managing their child's complex needs. The advanced practice registered nurse care coordination model has potential for changing the health management processes for children with medical complexity. Copyright © 2014 National Association of Pediatric Nurse Practitioners. Published by Mosby, Inc. All rights reserved.

Magnetic beads-based DNAzyme recognition and AuNPs-based enzymatic catalysis amplification for visual detection of trace uranyl ion in aqueous environment.

PubMed

Zhang, Hongyan; Lin, Ling; Zeng, Xiaoxue; Ruan, Yajuan; Wu, Yongning; Lin, Minggui; He, Ye; Fu, FengFu

2016-04-15

We herein developed a novel biosensor for the visual detection of trace uranyl ion (UO2(2+)) in aqueous environment with high sensitivity and specificity by using DNAzyme-functionalized magnetic beads (MBs) for UO2(2+) recognition and gold nano-particles (AuNPs)-based enzymatic catalysis oxidation of TMB (3,3',5,5'-tetramethylbenzidine sulfate) for signal generation. The utilization of MBs facilitates the magnetic separation and collection of sensing system from complex sample solution, which leads to more convenient experimental operation and more strong resistibility of the biosensor to the matrix of sample, and the utilization of AuNPs-based enzymatic catalysis amplification greatly improved the sensitivity of the biosensor. Compared with the previous DNAzyme-based UO2(2+) sensors, the proposed biosensor has outstanding advantages such as relative high sensitivity and specificity, operation convenience, low cost and more strong resistibility to the matrix of sample. It can be used to detect as low as 0.02 ppb (74 pM) of UO2(2+) in aqueous environment by only naked-eye observation and 1.89 ppt (7.0 pM) of UO2(2+) by UV-visible spectrophotometer with a recovery of 93-99% and a RSD ≤ 5.0% (n=6) within 3h. Especially, the visual detection limit of 0.02 ppb (74 pM) is much lower than the maximum allowable level of UO2(2+) (130 nM) in the drinking water defined by the U.S. Environmental Protection Agency (EPA), indicating that our method meets the requirement of rapid and on-site detection of UO2(2+) in the aqueous environment by only naked-eye observation. Copyright © 2015 Elsevier B.V. All rights reserved.

Platinum blue as an alternative to uranyl acetate for staining in transmission electron microscopy.

PubMed

Inaga, Sumire; Katsumoto, Tetsuo; Tanaka, Keiichi; Kameie, Toshio; Nakane, Hironobu; Naguro, Tomonori

2007-04-01

This paper introduces an aqueous solution of platinum blue (Pt-blue) as an alternative to uranyl acetate (UA) for staining in transmission electron microscopy (TEM). Pt-blue was prepared from a reaction of cis-dichlorodiamine-platinum (II) (cis-platin) with thymidine. When Pt-blue was dried on a microgrid and observed by TEM it showed a uniform appearance with tiny particles less than 1 nm in diameter. The effect of Pt-blue as an electron stain was then examined not only for positive staining of conventional ultrathin resin sections and counterstaining of post-embedding immuno-electron microscopy but also for negative staining. In ultrathin sections of the rat liver and renal glomerulus, Pt-blue provided good contrast images, especially in double staining combined with a lead stain (Pb). Almost all cell organelles were clearly observed with high contrast in these sections. Glycogen granules in the hepatic parenchymal cells were particularly electron dense in Pt-blue stained sections compared with those treated with UA. In longitudinal and transverse sections of budding influenza A viruses, a specific arrangement of rod-like structures, which correspond to the ribonucleoprotein complexes, was clearly shown in each virion stained with Pt-blue and Pb. When post-embedding immunoelectron microscopy was performed in ultrathin sections of HeLa cells embedded in Lowicryl K4M, the localization of Ki-67 protein was sufficiently detected even after Pt-blue and Pb staining. The present study also revealed that Pt-blue could be used for the negative staining of E. coli, allowing the visualization of a flagellum. These findings indicate that Pt-blue is a useful, safe, and easily obtainable electron stain that is an alternative to UA for TEM preparations.

Assessing ligand selectivity for uranium over vanadium ions to aid in the discovery of superior adsorbents for extraction of UO 2 2+ from seawater

DOE PAGES

Ivanov, Alexander S.; Bryantsev, Vyacheslav S.

2016-06-06

Uranium is used as the basic fuel for nuclear power plants, which generate significant amounts of electricity and have life cycle carbon emissions that are as low as renewable energy sources. However, the extraction of this valuable energy commodity from the ground remains controversial, mainly because of environmental and health impacts. Alternatively, seawater offers an enormous uranium resource that may be tapped at minimal environmental cost. Nowadays, amidoxime polymers are the most widely utilized sorbent materials for large-scale extraction of uranium from seawater, but they are not perfectly selective for uranyl, UO 2 2+. In particular, the competition between UOmore » 2 2+ and VO 2+/VO2+ cations poses a significant challenge to the effi-cient mining of UO 2 2+. Thus, screening and rational design of more selective ligands must be accomplished. One of the key components in achieving this goal is the establishment of computational techniques capable of assessing ligand selec-tivity trends. Here, we report an approach based on quantum chemical calculations that achieves high accuracy in repro-ducing experimental aqueous stability constants for VO 2+/VO 2+ complexes with ten different oxygen donor lig-ands. The predictive power of the developed computational protocol was demonstrated for amidoxime-type ligands, providing greater insights into new design strategies for the development of the next generation of adsorbents with high selectivity toward UO 2 2+over VO 2+/VO 2+ ions. Furthermore, the results of calculations suggest that alkylation of amidox-ime moieties present in poly(acrylamidoxime) sorbents can be a potential route to better discrimination between the uranyl and competing vanadium ions within seawater.« less

Synthesis, crystal structures and Hirshfeld surface analyses of two new Salen type nickel/sodium heteronuclear complexes

NASA Astrophysics Data System (ADS)

Mahlooji, Niloofar; Behzad, Mahdi; Tarahhomi, Atekeh; Maroney, Michael; Rudbari, Hadi Amiri; Bruno, Giuseppe; Ghanbari, Bahram

2016-04-01

Two new heteronuclear Nickel(II)/Sodium(I) complexes of a side-off compartmental Schiff base ligand were synthesized and characterized by spectroscopic methods. Crystal structures of both of the complexes were also obtained. The Schiff base ligand was synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with 2-hydroxy-3-methoxybenzaldehyde. In both of the complexes the Ni(II) ion is coordinated to the inner N2O2 coordination sphere with square-planar geometry and the Na(I) ion is coordinated to the outer O2 O2‧ coordination sphere. In Complex (1) with general formula [Ni(L)Na(CH3OH)(ClO4)] the sodium ion is seven coordinated while in (2) with general formula [{Ni(L)Na(OH2)}2(μ-Ni(CN)4)] the sodium ion is six coordinated. Intermolecular interactions in two studied complexes were analyzed using 3D Hirshfeld surfaces and corresponding 2D fingerprint plots. This analysis showed that the H … H and C … H/H … C contacts for both structures (altogether 67.5% of total Hirshfeld surface area for (1) and 77.6% for (2)) and the O … H/H … O (24.2%) for (1) and the N … H/H … N (8.1%) contacts for (2) were the characteristic intermolecular contacts in the related crystal structures.

Syntheses and structures of [UO2( L)5](ClO4)2 and [U( L')4(H2O)4](ClO4)4 ( L is dimethylformamide, L' is N,N-dimethylcarbamide)

NASA Astrophysics Data System (ADS)

Serezhkin, V. N.; Vologzhanina, A. V.; Pushkin, D. V.; Astashkina, D. A.; Savchenkov, A. V.; Serezhkina, L. B.

2017-09-01

The reaction of aqueous solutions of uranyl perchlorate with selected organic amides was studied in the dark and under the sunlight. The complexes [UVIO2(C3H7NO)5](ClO4)2 ( I) and [UIV(C3H8N2O)4(H2O)4](ClO4)4 ( II), where C3H7NO is N,N-dimethylformamide ( Dmfa) and C3H8N2O is N,N-dimethylcarbamide ( a-Dmur), were studied by X-ray diffraction. Complex II and the complex UIV( s-Dmur)4(H2O)4(ClO4)4 ( III), where s-Dmur is N,N'-dimethylcarbamide, were studied by IR spectroscopy. Crystals I and II are composed of mononuclear [UO2( Dmfa)5]2+ and [U( Dmur)4(H2O)4]4+ groups as uranium-containing structural units belonging to the crystal-chemical groups AM 7 1 ( A = UVI, M 1 = O2- and Dmfa) and AM 8 1 ( A = UIV, M 1 = Dmur and H2O) of uranium complexes, respectively. The mononuclear uranium- containing complexes in the crystals of U(IV) and U(VI) perchlorates were found to obey the 14 neighbors rule.

Composition for detecting uranyl

DOEpatents

Baylor, L.C.; Stephens, S.M.

1994-01-01

The present invention relates to an indicator composition for use in spectrophotometric detection of a substance in a solution, and a method for making the composition. Useful indicators are sensitive to the particular substance being measured, but are unaffected by the fluid and other chemical species that may be present in the fluid. Optical indicators are used to measure the uranium concentration of process solutions in facilities for extracting uranium from ores, production of nuclear fuels, and reprocessing of irradiated fuels. The composition comprises an organohalide covalently bonded to an indicator for the substance, in such a manner that the product is itself an indicator that provides increased spectral resolution for detecting the substance. The indicator is preferably arsenazo III and the organohalide is preferably cyanuric chloride. These form a composition that is ideally suited for detecting uranyl.

Pt(II) and Pd(II) complexes with ibuprofen hydrazide: Characterization, theoretical calculations, antibacterial and antitumor assays and studies of interaction with CT-DNA

NASA Astrophysics Data System (ADS)

Manzano, Carlos M.; Bergamini, Fernando R. G.; Lustri, Wilton R.; Ruiz, Ana Lúcia T. G.; de Oliveira, Ellen C. S.; Ribeiro, Marcos A.; Formiga, André L. B.; Corbi, Pedro P.

2018-02-01

Palladium(II) and platinum(II) complexes with a hydrazide derivative of ibuprofen (named HIB) were synthesized and characterized by chemical and spectroscopic methods. Elemental and thermogravimetric analyses, as well as ESI-QTOF-MS studies for both complexes, confirmed a 1:2:2 metal/HIB/Cl- molar ratio. The crystal structure of the palladium(II) complex was solved by single crystal X-ray diffractometric analysis, which permitted identifying the coordination formula [PdCl2(HIB)2]. Crystallographic studies also indicate coordination of HIB to the metal by the NH2 group. Nuclear magnetic resonance and infrared spectroscopies reinforced the coordination observed in the crystal structure and suggested that the platinum(II) complex presents similar coordination modes and structure when compared with the Pd(II) complex. The complexes had their structures optimized with the aid of DFT methods. In vitro antiproliferative assays showed that the [PdCl2(HIB)2] complex is active over ovarian cancer cell line OVCAR-03, while biophysical studies indicated its capacity to interact with CT-DNA. The complexes were inactive over Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa bacterial strains.

New water soluble heterometallic complex showing unpredicted coordination modes of EDTA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mudsainiyan, R.K., E-mail: mudsainiyanrk@gmail.com; Jassal, A.K.; Chawla, S.K., E-mail: sukhvinder.k.chawla@gmail.com

2015-10-15

A mesoporous 3D polymeric complex (I) having formula ([Zr(IV)O-μ{sup 3}-(EDTA)Fe(III)OH]·H{sub 2}O){sub n} has been crystallized and characterized by various techniques. Single-crystal X-ray diffraction analysis revealed that complex (I) crystallized in chiral monoclinic space group Cc (space group no. 9) with unexpected coordination modes of EDTA and mixture of two transition metal ions. In this complex, the coordination number of Zr(IV) ion is seven where four carboxylate oxygen atoms, two nitrogen atoms, one oxide atom are coordinating with Zr(IV). Fe(III) is four coordinated and its coordination environment is composed of three different carboxylic oxygen atoms from three different EDTA and onemore » oxygen atom of –OH group. The structure consists of 4-c and 16-c (2-nodal) net with new topology and point symbol for net is (3{sup 36}·4{sup 54}·5{sup 30})·(3{sup 6}). TGA study and XRPD pattern showed that the coordination polymer is quite stable even after losing water molecule and –OH ion. Quenching behavior in fluorescence of ligand is observed by complexation with transition metal ions is due to n–π⁎ transition. The SEM micrograph shows the morphology of complex (I) exhibits spherical shape with size ranging from 50 to 280 nm. The minimum N{sub 2} (S{sub BET}=8.7693 m{sup 2}/g) and a maximum amount of H{sub 2} (high surface area=1044.86 m{sup 2}/g (STP)) could be adsorbed at 77 K. From DLS study, zeta potential is calculated i.e. −7.94 shows the negative charges on the surface of complex. Hirshfeld surface analysis and fingerprint plots revealed influence of weak or non bonding interactions in crystal packing of complex. - Graphical abstract: The complex (I) crystallized with unexpected coordination modes of EDTA having 4-c, 16-c net with new topology and point symbol is (3{sup 36}·4{sup 54}·5{sup 30})·(3{sup 6}). TGA study and XRPD pattern proved its stability with high preference of H{sub 2} uptake by complex. - Highlights: • 3D complex having unexpected coordination modes of EDTA with Zr(IV) and Fe(III). • The structure consists of 4-c and 16-c (2-nodal) net with new topology. • Reasonable S{sub BET} (8.7693 m{sup 2}/g) but high H{sub 2} uptake (1044.86 m{sup 2}/g) due to limited pore size. • Quenching behavior due to n–π⁎ transition by complexation with transition metal ions. • From DLS study, zeta potential value is −7.94.« less

Parent Perspective on Care Coordination Services for Their Child with Medical Complexity

PubMed Central

Cady, Rhonda G.; Belew, John L.

2017-01-01

The overarching goal of care coordination is communication and co-management across settings. Children with medical complexity require care from multiple services and providers, and the many benefits of care coordination on health and patient experience outcomes have been documented. Despite these findings, parents still report their greatest challenge is communication gaps. When this occurs, parents assume responsibility for aggregating and sharing health information across providers and settings. A new primary-specialty care coordination partnership model for children with medical complexity works to address these challenges and bridge communication gaps. During the first year of the new partnership, parents participated in focus groups to better understand how they perceive communication and collaboration between the providers and services delivering care for their medically complex child. Our findings from these sessions reflect the current literature and highlight additional challenges of rural families, as seen from the perspective of the parents. We found that parents appreciate when professional care coordination is provided, but this is often the exception and not the norm. Additionally, parents feel that the local health system’s inability to care for their medically complex child results in unnecessary trips to urban-based specialty care. These gaps require a system-level approach to care coordination and, consequently, new paradigms for delivery are urgently needed. PMID:28587274

Parent Perspective on Care Coordination Services for Their Child with Medical Complexity.

PubMed

Cady, Rhonda G; Belew, John L

2017-06-06

The overarching goal of care coordination is communication and co-management across settings. Children with medical complexity require care from multiple services and providers, and the many benefits of care coordination on health and patient experience outcomes have been documented. Despite these findings, parents still report their greatest challenge is communication gaps. When this occurs, parents assume responsibility for aggregating and sharing health information across providers and settings. A new primary-specialty care coordination partnership model for children with medical complexity works to address these challenges and bridge communication gaps. During the first year of the new partnership, parents participated in focus groups to better understand how they perceive communication and collaboration between the providers and services delivering care for their medically complex child. Our findings from these sessions reflect the current literature and highlight additional challenges of rural families, as seen from the perspective of the parents. We found that parents appreciate when professional care coordination is provided, but this is often the exception and not the norm. Additionally, parents feel that the local health system's inability to care for their medically complex child results in unnecessary trips to urban-based specialty care. These gaps require a system-level approach to care coordination and, consequently, new paradigms for delivery are urgently needed.

Facial and meridional isomers of holmium-nitrate N-tert-butylacetamide complexes

NASA Astrophysics Data System (ADS)

Chang, Ye-Di; Xue, Jun-Hui; Kang, Xiao-Yan; Yang, Li-Min; Li, Wei-Hong; Xu, Yi-Zhuang; Zhao, Guo-Zhong; Zhang, Gao-Hui; Liu, Ke-Xin; Chen, Jia-Er; Wu, Jin-Guang

2018-06-01

Two Ho(C6H13NO)3(NO3)3 complexes formed by holmium nitrate and N-tert-butylacetamide (NtBA) (Ho-NtBA(I) in a Cc space group, and Ho-NtBA(II) in a P21/c space group) are reported here to investigate the coordination of lanthanide ions with amide groups. Using X-ray single crystal diffraction, FTIR, Raman, FIR and THz methods the structures of the two complexes were identified, in which Ho3+ is 9-coordinated to three carbonyl oxygen atoms provided by three NtBA ligands and three bidentate nitrate ions to form the "facial" and "meridional" isomers. Their FTIR and Raman spectra indicate the formation of two holmium complexes, the variations of NtBA after holmium coordination and the spectra are similar for the isomers in some extent. Their FIR and THz spectroscopic results show the coordination of holmium ions and THz maybe more sensitive to isomers. The results demonstrate the coordination behaviors of holmium ions and NtBA ligand.

A Monofunctional Platinum Complex Coordinated to a Rhodium Metalloinsertor Selectively Binds Mismatched DNA in the Minor Groove

PubMed Central

Weidmann, Alyson G.; Barton, Jacqueline K.

2015-01-01

We report the synthesis and characterization of a bimetallic complex derived from a new family of potent and selective metalloinsertors containing an unusual Rh—O axial coordination. This complex incorporates a monofunctional platinum center containing only one labile site for coordination to DNA, rather than two, and coordinates DNA non-classically through adduct formation in the minor groove. This conjugate displays bifunctional, interdependent binding of mismatched DNA via metalloinsertion at a mismatch as well as covalent platinum binding. DNA sequencing experiments revealed that the preferred site of platinum coordination is not the traditional N7-guanine site in the major groove, but rather N3-adenine in the minor groove. The complex also displays enhanced cytotoxicity in mismatch repair-deficient and mismatch repair-proficient human colorectal carcinoma cell lines compared to the chemotherapeutic cisplatin, and triggers cell death via an apoptotic pathway, rather than the necrotic pathway induced by rhodium metalloinsertors. PMID:26397309

A monofunctional platinum complex coordinated to a rhodium metalloinsertor selectively binds mismatched DNA in the minor groove.

PubMed

Weidmann, Alyson G; Barton, Jacqueline K

2015-10-05

We report the synthesis and characterization of a bimetallic complex derived from a new family of potent and selective metalloinsertors containing an unusual Rh-O axial coordination. This complex incorporates a monofunctional platinum center containing only one labile site for coordination to DNA, rather than two, and coordinates DNA nonclassically through adduct formation in the minor groove. This conjugate displays bifunctional, interdependent binding of mismatched DNA via metalloinsertion at a mismatch as well as covalent platinum binding. DNA sequencing experiments revealed that the preferred site of platinum coordination is not the traditional N7-guanine site in the major groove, but rather N3-adenine in the minor groove. The complex also displays enhanced cytotoxicity in mismatch repair-deficient and mismatch repair-proficient human colorectal carcinoma cell lines compared to the chemotherapeutic cisplatin, and it triggers cell death via an apoptotic pathway, rather than the necrotic pathway induced by rhodium metalloinsertors.

Time-Resolved Infrared Reflectance Studies of the Dehydration-Induced Transformation of Uranyl Nitrate Hexahydrate to the Trihydrate Form

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.

Uranyl nitrate is a key species in the nuclear fuel cycle. However, this species is known to exist in different states of hydration, including the hexahydrate ([UO2(NO3)2(H2O)6] often called UNH), the trihydrate [UO2(NO3)2(H2O)3 or UNT], and in very dry environments the dihydrate form [UO2(NO3)2(H2O)2]. Their relative stabilities depend on both water vapor pressure and temperature. In the 1950s and 1960s the different phases were studied by infrared transmission spectroscopy, but were limited both by instrumental resolution and by the ability to prepare the samples for transmission. We have revisited this problem using time-resolved reflectance spectroscopy, which requires no sample preparationmore » and allows dynamic analysis while the sample is exposed to a flow of N2 gas. Samples of known hydration state were prepared and confirmed via X-ray diffraction patterns of known species. In reflectance mode the hexahydrate UO2(NO3)2(H2O)6 has a distinct uranyl asymmetric stretch band at 949.0 cm-1 that shifts to shorter wavelengths and broadens as the sample desiccates and recrystallizes to the trihydrate, first as a shoulder growing in on the blue edge but ultimately results in a doublet band with reflectance peaks at 966 and 957 cm-1. The data are consistent with transformation from UNH to UNT as UNT has two inequivalent UO22+ sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a structural and morphological change that has the lustrous lime green UO2(NO3)2(H2O)6 crystals changing to the matte greenish yellow of the trihydrate solid. The phase transformation and crystal structures were confirmed by density functional theory calculations and optical microscopy methods, both of which showed a transformation with two distinct sites for the uranyl cation in the trihydrate, with but one in the hexahydrate.« less

Time-resolved infrared reflectance studies of the dehydration-induced transformation of uranyl nitrate hexahydrate to the trihydrate form

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Timothy J.; Sweet, Lucas E.; Meier, David E.

2015-09-08

Uranyl nitrate is a key species in the nuclear fuel cycle. However, this species is known to exist in different states of hydration, including the hexahydrate ([UO 2(NO 3) 2(H 2O) 6] often called UNH), the trihydrate [UO 2(NO 3) 2(H 2O) 3 or UNT], and in very dry environments the dihydrate form [UO 2(NO 3) 2(H 2O) 2]. Their relative stabilities depend on both water vapor pressure and temperature. In the 1950s and 1960s, the different phases were studied by infrared transmission spectroscopy but were limited both by instrumental resolution and by the ability to prepare the samples formore » transmission. We have revisited this problem using time-resolved reflectance spectroscopy, which requires no sample preparation and allows dynamic analysis while the sample is exposed to a flow of N 2 gas. Samples of known hydration state were prepared and confirmed via X-ray diffraction patterns of known species. In reflectance mode the hexahydrate UO 2(NO 3) 2(H 2O) 6 has a distinct uranyl asymmetric stretch band at 949.0 cm –1 that shifts to shorter wavelengths and broadens as the sample desiccates and recrystallizes to the trihydrate, first as a shoulder growing in on the blue edge but ultimately results in a doublet band with reflectance peaks at 966 and 957 cm –1. The data are consistent with transformation from UNH to UNT as UNT has two inequivalent UO 2 2+ sites. The dehydration of UO 2(NO 3) 2(H 2O) 6 to UO 2(NO 3) 2(H 2O) 3 is both a structural and morphological change that has the lustrous lime green UO 2(NO 3) 2(H 2O) 6 crystals changing to the matte greenish yellow of the trihydrate solid. As a result, the phase transformation and crystal structures were confirmed by density functional theory calculations and optical microscopy methods, both of which showed a transformation with two distinct sites for the uranyl cation in the trihydrate, with only one in the hexahydrate.« less

Four-coordinate, 14-electron Ru(II) complexes: unusual trigonal pyramidal geometry enforced by bis(phosphino)silyl ligation.

PubMed

MacInnis, Morgan C; McDonald, Robert; Ferguson, Michael J; Tobisch, Sven; Turculet, Laura

2011-08-31

Unprecedented diamagnetic, four-coordinate, formally 14-electron (Cy-PSiP)RuX (Cy-PSiP = [κ(3)-(2-R(2)PC(6)H(4))(2)SiMe](-); X = amido, alkoxo) complexes that do not require agostic stabilization and that adopt a highly unusual trigonal pyramidal coordination geometry are reported. The tertiary silane [(2-Cy(2)PC(6)H(4))(2)SiMe]H ((Cy-PSiP)H) reacted with 0.5 [(p-cymene)RuCl(2)](2) in the presence of Et(3)N and PCy(3) to afford [(Cy-PSiP)RuCl](2) (1) in 74% yield. Treatment of 1 with KO(t)Bu led to the formation of (Cy-PSiP)RuO(t)Bu (2, 97% yield), which was crystallographically characterized and shown to adopt a trigonal pyramidal coordination geometry in the solid state. Treatment of 1 with NaN(SiMe(3))(2) led to the formation of (Cy-PSiP)RuN(SiMe(3))(2) (3, 70% yield), which was also found to adopt a trigonal pyramidal coordination geometry in the solid state. The related anilido complexes (Cy-PSiP)RuNH(2,6-R(2)C(6)H(3)) (4, R = H; 5, R = Me) were also prepared in >90% yields by treating 1 with LiNH(2,6-R(2)C(6)H(3)) (R = H, Me) reagents. The solid state structure of 5 indicates a monomeric trigonal pyramidal complex that features a C-H agostic interaction. Complexes 2 and 3 were found to react readily with 1 equiv of H(2)O to form the dimeric hydroxo-bridged complex [(Cy-PSiP)RuOH](2) (6, 94% yield), which was crystallographically characterized. Complexes 2 and 3 also reacted with 1 equiv of PhOH to form the new 18-electron η(5)-oxocyclohexadienyl complex (Cy-PSiP)Ru(η(5)-C(6)H(5)O) (7, 84% yield). Both amido and alkoxo (Cy-PSiP)RuX complexes reacted with H(3)B·NHRR' reagents to form bis(σ-B-H) complexes of the type (Cy-PSiP)RuH(η(2):η(2)-H(2)BNRR') (8, R = R' = H; 9, R = R' = Me; 10, R = H, R' = (t)Bu), which illustrates that such four-coordinate (Cy-PSiP)RuX (X = amido, alkoxo) complexes are able to undergo multiple E-H (E = main group element) bond activation steps. Computational methods were used to investigate structurally related PCP, PPP, PNP, and PSiP four-coordinate Ru complexes and confirmed the key role of the strongly σ-donating silyl group of the PSiP ligand set in enforcing the unusual trigonal pyramidal coordination geometry featured in complexes 2-5, thus substantiating a new strategy for the synthesis of low-coordinate Ru species. The mechanism of the activation of ammonia-borane by such low-coordinate (R-PSiP)RuX (X = amido, alkoxo) species was also studied computationally and was determined to proceed most likely in a stepwise fashion via intramolecular deprotonation of ammonia and subsequent borane B-H bond oxidative addition steps.

Electronic Structure of Transition Metal Clusters, Actinide Complexes and Their Reactivities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnan Balasubramanian

2009-07-18

This is a continuing DOE-BES funded project on transition metal and actinide containing species, aimed at the electronic structure and spectroscopy of transition metal and actinide containing species. While a long term connection of these species is to catalysis and environmental management of high-level nuclear wastes, the immediate relevance is directly to other DOE-BES funded experimental projects at DOE-National labs and universities. There are a number of ongoing gas-phase spectroscopic studies of these species at various places, and our computational work has been inspired by these experimental studies and we have also inspired other experimental and theoretical studies. Thus ourmore » studies have varied from spectroscopy of diatomic transition metal carbides to large complexes containing transition metals, and actinide complexes that are critical to the environment. In addition, we are continuing to make code enhancements and modernization of ALCHEMY II set of codes and its interface with relativistic configuration interaction (RCI). At present these codes can carry out multi-reference computations that included up to 60 million configurations and multiple states from each such CI expansion. ALCHEMY II codes have been modernized and converted to a variety of platforms such as Windows XP, and Linux. We have revamped the symbolic CI code to automate the MRSDCI technique so that the references are automatically chosen with a given cutoff from the CASSCF and thus we are doing accurate MRSDCI computations with 10,000 or larger reference space of configurations. The RCI code can also handle a large number of reference configurations, which include up to 10,000 reference configurations. Another major progress is in routinely including larger basis sets up to 5g functions in thee computations. Of course higher angular momenta functions can also be handled using Gaussian and other codes with other methods such as DFT, MP2, CCSD(T), etc. We have also calibrated our RECP methods with all-electron Douglas-Kroll relativistic methods. We have the capabilities for computing full CI extrapolations including spin-orbit effects and several one-electron properties and electron density maps including spin-orbit effects. We are continuously collaborating with several experimental groups around the country and at National Labs to carry out computational studies on the DOE-BES funded projects. The past work in the last 3 years was primarily motivated and driven by the concurrent or recent experimental studies on these systems. We were thus significantly benefited by coordinating our computational efforts with experimental studies. The interaction between theory and experiment has resulted in some unique and exciting opportunities. For example, for the very first time ever, the upper spin-orbit component of a heavy trimer such as Au{sub 3} was experimentally observed as a result of our accurate computational study on the upper electronic states of gold trimer. Likewise for the first time AuH{sub 2} could be observed and interpreted clearly due to our computed potential energy surfaces that revealed the existence of a large barrier to convert the isolated AuH{sub 2} back to Au and H{sub 2}. We have also worked on yet to be observed systems and have made predictions for future experiments. We have computed the spectroscopic and thermodynamic properties of transition metal carbides transition metal clusters and compared our electronic states to the anion photodetachment spectra of Lai Sheng Wang. Prof Mike Morse and coworkers(funded also by DOE-BES) and Prof Stimle and coworkers(also funded by DOE-BES) are working on the spectroscopic properties of transition metal carbides and nitrides. Our predictions on the excited states of transition metal clusters such as Hf{sub 3}, Nb{sub 2}{sup +} etc., have been confirmed experimentally by Prof. Lombardi and coworkers using resonance Raman spectroscopy. We have also been studying larger complexes critical to the environmental management of high-level nuclear wastes. In collaboration with experimental colleague Prof Hieno Nitsche (Berkeley) and Dr. Pat Allen (Livermore, EXAFS) we have studied the uranyl complexes with silicates and carbonates. It should be stressed that although our computed ionization potential of uranium oxide was in conflict with the existing experimental data at the time, a subsequent gas-phase experimental work by Prof Mike Haven and coworkers published as communication in JACS confirmed our computed result to within 0.1 eV. This provides considerable confidence that the computed results in large basis sets with highly-correlated wave functions have excellent accuracies and they have the capabilities to predict the excited states also with great accuracy. Computations of actinide complexes (Uranyl and plutonyl complexes) are critical to management of high-level nuclear wastes.« less

Syntheses, Characterization, Resolution, and Biological Studies of Coordination Compounds of Aspartic Acid and Glycine

PubMed Central

Akinkunmi, Ezekiel; Ojo, Isaac; Adebajo, Clement; Isabirye, David

2017-01-01

Enantiomerically enriched coordination compounds of aspartic acid and racemic mixtures of coordination compounds of glycine metal-ligand ratio 1 : 3 were synthesized and characterized using infrared and UV-Vis spectrophotometric techniques and magnetic susceptibility measurements. Five of the complexes were resolved using (+)-cis-dichlorobis(ethylenediamine)cobalt(III) chloride, (+)-bis(glycinato)(1,10-phenanthroline)cobalt(III) chloride, and (+)-tris(1,10-phenanthroline)nickel(II) chloride as resolving agents. The antimicrobial and cytotoxic activities of these complexes were then determined. The results obtained indicated that aspartic acid and glycine coordinated in a bidentate fashion. The enantiomeric purity of the compounds was in the range of 22.10–32.10%, with (+)-cis-dichlorobis(ethylenediamine)cobalt(III) complex as the more efficient resolving agent. The resolved complexes exhibited better activity in some cases compared to the parent complexes for both biological activities. It was therefore inferred that although the increase in the lipophilicity of the complexes may assist in the permeability of the complexes through the cell membrane of the pathogens, the enantiomeric purity of the complexes is also of importance in their activity as antimicrobial and cytotoxic agents. PMID:28293149

Formation of ternary CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) complexes under neutral to weakly alkaline conditions.

PubMed

Lee, Jun-Yeop; Yun, Jong-Il

2013-07-21

The chemical behavior of ternary Ca-UO2-CO3 complexes was investigated by using time-resolved laser fluorescence spectroscopy (TRLFS) in combination with EDTA complexation at pH 7-9. A novel TRLFS revealed two distinct fluorescence lifetimes of 12.7 ± 0.2 ns and 29.2 ± 0.4 ns for uranyl complexes which were formed increasingly dependent upon the calcium ion concentration, even though nearly indistinguishable fluorescence peak shapes and positions were measured for both Ca-UO2-CO3 complexes. For identifying the stoichiometric number of complexed calcium ions, slope analysis in terms of relative fluorescence intensity versus calcium concentration was employed in a combination with the complexation reaction of CaEDTA(2-) by adding EDTA. The formation of CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) was identified under given conditions and their formation constants were determined at I = 0.1 M Na/HClO4 medium, and extrapolated to infinitely dilute solution using specific ion interaction theory (SIT). As a result, the formation constants for CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) were found to be log β113(0) = 27.27 ± 0.14 and log β213(0) = 29.81 ± 0.19, respectively, providing that the ternary Ca-UO2-CO3 complexes were predominant uranium(vi) species at neutral to weakly alkaline pH in the presence of Ca(2+) and CO3(2-) ions.

Solid-state polymerisation via [2+2] cycloaddition reaction involving coordination polymers.

PubMed

Medishetty, Raghavender; Park, In-Hyeok; Lee, Shim Sung; Vittal, Jagadese J

2016-03-14

Highly crystalline metal ions containing organic polymers are potentially useful to manipulate the magnetic and optical properties to make advanced multifunctional materials. However, it is challenging to synthesise monocrystalline metal complexes of organic polymers and single-phase hybrid materials made up of both coordination and organic polymers by traditional solution crystallisation. This requires an entirely different approach in the solid-state by thermal or photo polymerisation of the ligands. Among the photochemical methods available, [2+2] cycloaddition reaction has been recently employed to generate cyclobutane based coordination polymers from the metal complexes. Cyclobutane polymers have also been integrated into coordination polymers in this way. Recent advancements in the construction of polymeric chains of cyclobutane rings through photo-dimerisation reaction in the monocrystalline solids containing metal complexes, coordination polymers and metal-organic framework structures are discussed here.

Care coordination of multimorbidity: a scoping study

PubMed Central

Burau, Viola

2015-01-01

Background A key challenge in healthcare systems worldwide is the large number of patients who suffer from multimorbidity; despite this, most systems are organized within a single-disease framework. Objective The present study addresses two issues: the characteristics and preconditions of care coordination for patients with multimorbidity; and the factors that promote or inhibit care coordination at the levels of provider organizations and healthcare professionals. Design The analysis is based on a scoping study, which combines a systematic literature search with a qualitative thematic analysis. The search was conducted in November 2013 and included the PubMed, CINAHL, and Web of Science databases, as well as the Cochrane Library, websites of relevant organizations and a hand-search of reference lists. The analysis included studies with a wide range of designs, from industrialized countries, in English, German and the Scandinavian languages, which focused on both multimorbidity/comorbidity and coordination of integrated care. Results The analysis included 47 of the 226 identified studies. The central theme emerging was complexity. This related to both specific medical conditions of patients with multimorbidity (case complexity) and the organization of care delivery at the levels of provider organizations and healthcare professionals (care complexity). Conclusions In terms of how to approach care coordination, one approach is to reduce complexity and the other is to embrace complexity. Either way, future research must take a more explicit stance on complexity and also gain a better understanding of the role of professionals as a prerequisite for the development of new care coordination interventions. PMID:29090157

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

NASA Astrophysics Data System (ADS)

Reinoso-Maset, Estela; Steefel, Carl I.; Um, Wooyong; Chorover, Jon; O'Day, Peggy A.

2017-06-01

Uranyl oxyhydroxide minerals are important weathering products in uranium-contaminated surface and subsurface environments that regulate dissolved uranium (U) concentrations. However, dissolution rates for this class of minerals and associated dissolution mechanisms have not been previously reported for circumneutral pH conditions, particularly for the case of flow through porous media. In this work, the dissolution rates of K- and Na-compreignacite (K2(UO2)6O4(OH)6·8H2O and Na2(UO2)6O4(OH)6·8H2O, respectively) were measured using flow-through columns reacted with two simulated background porewater (BPW) solutions of low and high dissolved carbonate concentration (ca. 0.2 and 2.8 mmol L-1). Column materials were characterized before and after reaction with electron microscopy, bulk chemistry, and EXAFS to identify structural and chemical changes during dissolution and to obtain insight into molecular-scale processes. The reactive transport code CrunchFlow was used to calculate overall dissolution rates while accounting for fluid transport and changes in mineral volume and reactive surface area, and results were compared to steady-state dissolution rate calculations. In low carbonate BPW systems, interlayer K and Na were initially leached from both minerals, and in Na-compreignacite, K and minor divalent cations from the input solution were incorporated into the mineral structure. Results of characterization analyses suggested that after reaction both K- and Na-compreignacite resembled a disordered K-compreignacite with altered surfaces. A 10-fold increase in dissolved carbonate concentration and corresponding increase in pH (from 6.65 to 8.40) resulted in a net removal of 58-87% of total U mass from the columns, compared to <1% net loss in low carbonate BPW systems. Steady-state release of dissolved U was not observed with high carbonate solutions and post-reaction characterizations indicated a lack of development of leached or altered surfaces. Dissolution rates (normalized to specific surface area) were 2.5-3 orders-of-magnitude faster in high versus low carbonate BPW systems, with Na-compreignacite dissolving more rapidly than K-compreignacite under both BPW conditions, possibly due to greater ion exchange (1.57 · 10-10 vs. 1.28 · 10-13 mol m-2 s-1 [log R = -9.81 and -12.89] and 5.79 · 10-10 vs. 3.71 · 10-13 mol m-2 s-1 [log R = -9.24 and -12.43] for K- and Na-compreignacite, respectively). Experimental and spectroscopic results suggest that the dissolution rate is controlled by bond breaking of a uranyl group and detachment from polyhedral layers of the mineral structure. With higher dissolved carbonate concentrations, this rate-determining step is accelerated by the formation of Ca-uranyl carbonate complexes (dominant species under these conditions), which resulted in an increase of the dissolution rates. Optimization of both dissolution rate and mineral volume fraction in the reactive transport model to account for U mass removal during dissolution more accurately reproduced effluent data in high carbonate systems, and resulted in faster overall rates compared with a steady-state dissolution assumption. This study highlights the importance of coupling reaction and transport processes during the quantification of mineral dissolution rates to accurately predict the fate of contaminants such as U in porous geomedia.

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinoso-Maset, Estela; Steefel, Carl I.; Um, Wooyong

Uranyl oxyhydroxide minerals are important weathering products in uranium-contaminated surface and subsurface environments that regulate dissolved uranium concentrations. However, dissolution rates for this class of minerals and associated dissolution mechanisms have not been previously reported for circumneutral pH conditions, particularly for the case of flow through porous media. In this paper, the dissolution rates of K- and Na-compreignacite (K 2(UO 2) 6O 4(OH) 6·8H 2O and Na 2(UO 2) 6O 4(OH) 6·8H 2O respectively) were measured using flow-through columns reacted with two simulated background porewater (BPW) solutions of low and high dissolved total carbonate content (ca. 0.2 and 2.8 mmolmore » L -1). Column materials were characterized before and after reaction with electron microscopy, bulk chemistry, and EXAFS to identify structural and chemical changes during dissolution and to obtain insight into molecular-scale processes. The reactive transport code CrunchFlow was used to calculate overall dissolution rates while accounting for fluid transport and changes in mineral volume and reactive surface area and results were compared to steady-state dissolution rate calculations. In low carbonate BPW systems, interlayer K and Na were initially leached from both minerals, and in Na-compreignacite, K and minor divalent cations from the input solution were incorporated into the mineral structure. Results of characterization analyses suggested that after reaction both K- and Na-compreignacite resembled a disordered K-compreignacite with altered surfaces. A 10-fold increase in dissolved carbonate concentration and corresponding increase in pH (from 6.65 to 8.40) resulted in a net removal of 58-87% of total uranium mass from the columns, compared to <1% net loss in low carbonate BPW systems. Steady-state release of dissolved uranium was not observed with high carbonate solutions and post-reaction characterizations indicated a lack of development of leached or altered surfaces. Dissolution rates (normalized to specific surface area) were about 2.5-3 orders-of-magnitude faster in high versus low carbonate BPW systems, with Na-compreignacite dissolving more rapidly than K-compreignacite under both BPW conditions, possibly due to greater ion exchange (1.57·10 -10 vs. 1.28·10 -13 mol m -2 s -1 [log R = -9.81 and -12.89] and 5.79·10 -10 vs. 3.71·10 -13 mol m -2 s -1 [log R = -9.24 and -12.43] for K- and Na-compreignacite respectively). Experimental and spectroscopic results suggest that the dissolution rate is controlled by bond breaking of a uranyl group and detachment from polyhedral layers of the mineral structure. With higher dissolved carbonate concentrations, this rate-determining step is accelerated by the formation of Ca-uranyl carbonate complexes (dominant species under these conditions), which resulted in an increase of the dissolution rates. Optimization of both dissolution rate and mineral volume fraction in the reactive transport model to account for uranium mass removal during dissolution more accurately reproduced effluent data in high carbonate systems, and resulted in faster overall rates compared with a steady-state dissolution assumption. Finally, this study highlights the importance of coupling reaction and transport processes during the quantification of mineral dissolution rates to accurately predict the fate of contaminants such as uranium in porous geomedia.« less

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

DOE PAGES

Reinoso-Maset, Estela; Steefel, Carl I.; Um, Wooyong; ...

2017-06-01

Uranyl oxyhydroxide minerals are important weathering products in uranium-contaminated surface and subsurface environments that regulate dissolved uranium concentrations. However, dissolution rates for this class of minerals and associated dissolution mechanisms have not been previously reported for circumneutral pH conditions, particularly for the case of flow through porous media. In this paper, the dissolution rates of K- and Na-compreignacite (K 2(UO 2) 6O 4(OH) 6·8H 2O and Na 2(UO 2) 6O 4(OH) 6·8H 2O respectively) were measured using flow-through columns reacted with two simulated background porewater (BPW) solutions of low and high dissolved total carbonate content (ca. 0.2 and 2.8 mmolmore » L -1). Column materials were characterized before and after reaction with electron microscopy, bulk chemistry, and EXAFS to identify structural and chemical changes during dissolution and to obtain insight into molecular-scale processes. The reactive transport code CrunchFlow was used to calculate overall dissolution rates while accounting for fluid transport and changes in mineral volume and reactive surface area and results were compared to steady-state dissolution rate calculations. In low carbonate BPW systems, interlayer K and Na were initially leached from both minerals, and in Na-compreignacite, K and minor divalent cations from the input solution were incorporated into the mineral structure. Results of characterization analyses suggested that after reaction both K- and Na-compreignacite resembled a disordered K-compreignacite with altered surfaces. A 10-fold increase in dissolved carbonate concentration and corresponding increase in pH (from 6.65 to 8.40) resulted in a net removal of 58-87% of total uranium mass from the columns, compared to <1% net loss in low carbonate BPW systems. Steady-state release of dissolved uranium was not observed with high carbonate solutions and post-reaction characterizations indicated a lack of development of leached or altered surfaces. Dissolution rates (normalized to specific surface area) were about 2.5-3 orders-of-magnitude faster in high versus low carbonate BPW systems, with Na-compreignacite dissolving more rapidly than K-compreignacite under both BPW conditions, possibly due to greater ion exchange (1.57·10 -10 vs. 1.28·10 -13 mol m -2 s -1 [log R = -9.81 and -12.89] and 5.79·10 -10 vs. 3.71·10 -13 mol m -2 s -1 [log R = -9.24 and -12.43] for K- and Na-compreignacite respectively). Experimental and spectroscopic results suggest that the dissolution rate is controlled by bond breaking of a uranyl group and detachment from polyhedral layers of the mineral structure. With higher dissolved carbonate concentrations, this rate-determining step is accelerated by the formation of Ca-uranyl carbonate complexes (dominant species under these conditions), which resulted in an increase of the dissolution rates. Optimization of both dissolution rate and mineral volume fraction in the reactive transport model to account for uranium mass removal during dissolution more accurately reproduced effluent data in high carbonate systems, and resulted in faster overall rates compared with a steady-state dissolution assumption. Finally, this study highlights the importance of coupling reaction and transport processes during the quantification of mineral dissolution rates to accurately predict the fate of contaminants such as uranium in porous geomedia.« less

The role of uranium-arene bonding in H2O reduction catalysis

NASA Astrophysics Data System (ADS)

Halter, Dominik P.; Heinemann, Frank W.; Maron, Laurent; Meyer, Karsten

2018-03-01

The reactivity of uranium compounds towards small molecules typically occurs through stoichiometric rather than catalytic processes. Examples of uranium catalysts reacting with water are particularly scarce, because stable uranyl groups form that preclude the recovery of the uranium compound. Recently, however, an arene-anchored, electron-rich uranium complex has been shown to facilitate the electrocatalytic formation of H2 from H2O. Here, we present the precise role of uranium-arene δ bonding in intermediates of the catalytic cycle, as well as details of the atypical two-electron oxidative addition of H2O to the trivalent uranium catalyst. Both aspects were explored by synthesizing mid- and high-valent uranium-oxo intermediates and by performing comparative studies with a structurally related complex that cannot engage in δ bonding. The redox activity of the arene anchor and a covalent δ-bonding interaction with the uranium ion during H2 formation were supported by density functional theory analysis. Detailed insight into this catalytic system may inspire the design of ligands for new uranium catalysts.

Voltammetric Determination of Cocaine in Confiscated Samples Using a Carbon Paste Electrode Modified with Different [UO2(X-MeOsalen)(H2O)] · H2O Complexes

PubMed Central

de Oliveira, Laura Siqueira; dos Santos Poles, Ana Paula; Balbino, Marco Antonio; Teles de Menezes, Matheus Manoel; de Andrade, José Fernando; Dockal, Edward Ralph; Tristão, Heloísa Maria; de Oliveira, Marcelo Firmino

2013-01-01

A fast and non-destructive voltammetric method to detect cocaine in confiscated samples based on carbon paste electrode modified with methoxy-substituted N,N'-ethylene-bis(salcylideneiminato)uranyl(VI)complexes, [UO2(X-MeOSalen)(H2O)].H2O, where X corresponds to the positions 3, 4 or 5 of the methoxy group on the aromatic ring, is described. The electrochemical behavior of the modified electrode and the electrochemical detection of cocaine were investigated using cyclic voltammetry. Using 0.1 mol·L−1 KCl as supporting-electrolyte, a concentration-dependent, well-defined peak current for cocaine at 0.62 V, with an amperometric sensitivity of 6.25 × 104 μA·mol·L−1 for cocaine concentrations ranging between 1.0 × 10−7 and 1.3 × 10−6 mol·L−1 was obtained. Chemical interference studies using lidocaine and procaine were performed. The position of the methoxy group affects the results, with the 3-methoxy derivative being the most sensitive. PMID:23771156

Electrochemically fabricated polypyrrole-cobalt-oxygen coordination complex as high-performance lithium-storage materials.

PubMed

Guo, Bingkun; Kong, Qingyu; Zhu, Ying; Mao, Ya; Wang, Zhaoxiang; Wan, Meixiang; Chen, Liquan

2011-12-23

Current lithium-ion battery (LIB) technologies are all based on inorganic electrode materials, though organic materials have been used as electrodes for years. Disadvantages such as limited thermal stability and low specific capacity hinder their applications. On the other hand, the transition metal oxides that provide high lithium-storage capacity by way of electrochemical conversion reaction suffer from poor cycling stability. Here we report a novel high-performance, organic, lithium-storage material, a polypyrrole-cobalt-oxygen (PPy-Co-O) coordination complex, with high lithium-storage capacity and excellent cycling stability. Extended X-ray absorption fine structure and Raman spectroscopy and other physical and electrochemical characterizations demonstrate that this coordination complex can be electrochemically fabricated by cycling PPy-coated Co(3)O(4) between 0.0 V and 3.0 V versus Li(+)/Li. Density functional theory (DFT) calculations indicate that each cobalt atom coordinates with two nitrogen atoms within the PPy-Co coordination layer and the layers are connected with oxygen atoms between them. Coordination weakens the C-H bonds on PPy and makes the complex a novel lithium-storage material with high capacity and high cycling stability. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Near-unity thermally activated delayed fluorescence efficiency in three- and four-coordinate Au(i) complexes with diphosphine ligands.

PubMed

Osawa, Masahisa; Aino, Masa-Aki; Nagakura, Takaki; Hoshino, Mikio; Tanaka, Yuya; Akita, Munetaka

2018-05-14

The synthesis and photoluminescence properties of three-coordinate Au(i) complexes with rigid diphosphine ligands LMe {1,2-bis[bis(2-methylphenyl)phosphino]benzene}, LEt {1,2-bis[bis(2-ethylphenyl)phosphino]benzene}, and LiPr {1,2-bis[bis(2-isopropylphenyl)phosphino]benzene} are investigated. The LMe and LEt ligands afford two types of complexes: dinuclear complexes [μ-LMe(AuCl)2] (1d) and [μ-LEt(AuCl)2] (2d) with an Au(i)-Au(i) bond and mononuclear three-coordinate Au(i) complexes LMeAuCl (1) and LEtAuCl (2). On the other hand, the bulkiest ligand, LiPr, affords three-coordinate Au(i) complexes, LiPrAuCl (3) and LiPrAuI (4), but no dinuclear complexes. X-ray analysis suggests that both 3 and 4 possess a highly distorted trigonal planar geometry. Moreover, luminescence data reveal that at room temperature, 3 and 4 exhibit yellow-green thermally activated delayed fluorescence in the crystalline state with maximum emission wavelengths at 558 and 549 nm, respectively. The emission yields are close to unity. Quantum chemical calculations suggest that the emission of 4 originates from the (σ + X) → π* excited state that possesses strong intraligand charge-transfer character. The luminescent properties of four-coordinate Au(i) complex (5) possessing a tetrahedral geometry are discussed on the basis of the emission spectra and decay times measured in a temperature range of 309-77 K.

Uranyl-Peroxide Clusters Incorporating Iron Trimers and Bridging by Bisphosphonate- and Carboxylate-Containing Ligands.

PubMed

Qiu, Jie; Dong, Sining; Szymanowski, Jennifer E S; Dobrowolska, Malgorzata; Burns, Peter C

2017-04-03

A hybrid uranium-iron cage nanocluster, [(UO 2 ) 24 (FeOH) 24 (O 2 ) 24 (PO 4 ) 8 (CH(COO)(PO 3 ) 2 ) 24 ] 96- (U 24 Fe 24 ), was synthesized using bridging ligands containing bisphosphonate and carboxylate groups. U 24 Fe 24 contains six tetramers of uranyl hexagonal bipyramids and eight iron trimers, each of which consists of three corner-sharing Fe 3+ octahedra and is stabilized by in situ formed phosphate and 2,2-bis(phosphonato)acetate (C 2 P 2 ) groups. Tetramers and trimers are bridged by 24 C 2 P 2 groups into a cage cluster. Crystals of U 24 Fe 24 present a paramagnetic-like behavior. X-ray scattering showed that U 24 Fe 24 forms in the reactant solution prior to crystallization and is stable upon dissolution in water.

Uranyl peroxide nanoclusters at high-pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Katlyn M.; Szymanowski, Jennifer E. S.; Zhang, Fuxiang

Here, U 60 ([UO 2(O 2)(OH)] 60 60– in water) is a uranyl peroxide nanocluster with a fullerene topology and O h symmetry. U 60 clusters can exist in crystalline solids or in liquids; however, little is known of their behavior at high pressures. We compressed the U 60-bearing material: Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 ( Fm3¯; a = 37.884 Å) in a diamond anvil cell to determine its response to increasing pressure. Three length scales and corresponding structural features contribute to the compression response: uranyl peroxide bonds (<0.5 nm), isolated single nanoclusters (2.5 nm), andmore » the long-range periodicity of nanoclusters within the solid (>3.7 nm). Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 transformed to a tetragonal structure below 2 GPa and irreversibly amorphized between 9.6 and 13 GPa. The bulk modulus of the tetragonal U 60-bearing material was 25 ± 2 GPa. The pressure-induced amorphous phase contained intact U 60 clusters, which were preserved beyond the loss of long-range periodicity. The persistence of U 60 clusters at high pressure may have been enhanced by the interaction between U 60 nanoclusters and the alcohol pressure medium. Once formed, U 60 nanoclusters persist regardless of their associated long-range ordering—in crystals, amorphous solids, or solutions.« less

Rapid Dissolution of Soluble Uranyl Phases in Arid, Mine-Impacted Catchments Near Church Rock, NM

DOE Office of Scientific and Technical Information (OSTI.GOV)

deLemos, J.L.; Bostick, B.C.; Quicksall, A.N.

2009-05-14

We tested the hypothesis that runoff of uranium-bearing particles from mining waste disposal areas was a significant mechanism for redistribution of uranium in the northeastern part of the Upper Puerco River watershed (New Mexico). However, our results were not consistent with this hypothesis. Analysis of >100 sediment and suspended sediment samples collected adjacent to and downstream from uranium source areas indicated that uranium levels in the majority of the samples were not elevated above background. Samples collected within 50 m of a known waste disposal site were subjected to detailed geochemical characterization. Uranium in these samples was found to bemore » highly soluble; treatment with synthetic pore water for 24 h caused dissolution of 10-50% of total uranium in the samples. Equilibrium uranium concentrations in pore water were >4.0 mg/L and were sustained in repeated wetting events, effectively depleting soluble uranium from the solid phase. The dissolution rate of uranium appeared to be controlled by solid-phase diffusion of uranium from within uranium-bearing mineral particles. X-ray adsorption spectroscopy indicated the presence of a soluble uranyl silicate, and possibly a uranyl phosphate. These phases were exhausted in transported sediment suggesting that uranium was readily mobilized from sediments in the Upper Puerco watershed and transported in the dissolved load. These results could have significance for uranium risk assessment as well as mining waste management and cleanup efforts.« less

Rapid Dissolution of Soluble Uranyl Phases in Arid, Mine-Impacted Catchments near Church Rock, NM

PubMed Central

DELEMOS, JAMIE L.; BOSTICK, BENJAMIN C.; QUICKSALL, ANDREW N.; LANDIS, JOSHUA D.; GEORGE, CHRISTINE C.; SLAGOWSKI, NAOMI L.; ROCK, TOMMY; BRUGGE, DOUG; LEWIS, JOHNNYE; DURANT, JOHN L.

2008-01-01

We tested the hypothesis that runoff of uranium-bearing particles from mining waste disposal areas was a significant mechanism for redistribution of uranium in the northeastern part of the Upper Puerco River watershed (New Mexico). However, our results were not consistent with this hypothesis. Analysis of >100 sediment and suspended sediment samples collected adjacent to and downstream from uranium source areas indicated that uranium levels in the majority of the samples were not elevated above background. Samples collected within 50 m of a known waste disposal site were subjected to detailed geochemical characterization. Uranium in these samples was found to be highly soluble; treatment with synthetic pore water for 24 h caused dissolution of 10–50% of total uranium in the samples. Equilibrium uranium concentrations in pore water were >4.0 mg/L and were sustained in repeated wetting events, effectively depleting soluble uranium from the solid phase. The dissolution rate of uranium appeared to be controlled by solid-phase diffusion of uranium from within uranium-bearing mineral particles. X-ray adsorption spectroscopy indicated the presence of a soluble uranyl silicate, and possibly a uranyl phosphate. These phases were exhausted in transported sediment suggesting that uranium was readily mobilized from sediments in the Upper Puerco watershed and transported in the dissolved load. These results could have significance for uranium risk assessment as well as mining waste management and cleanup efforts. PMID:18589950

Uranyl peroxide nanoclusters at high-pressure

DOE PAGES

Turner, Katlyn M.; Szymanowski, Jennifer E. S.; Zhang, Fuxiang; ...

2017-08-14

Here, U 60 ([UO 2(O 2)(OH)] 60 60– in water) is a uranyl peroxide nanocluster with a fullerene topology and O h symmetry. U 60 clusters can exist in crystalline solids or in liquids; however, little is known of their behavior at high pressures. We compressed the U 60-bearing material: Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 ( Fm3¯; a = 37.884 Å) in a diamond anvil cell to determine its response to increasing pressure. Three length scales and corresponding structural features contribute to the compression response: uranyl peroxide bonds (<0.5 nm), isolated single nanoclusters (2.5 nm), andmore » the long-range periodicity of nanoclusters within the solid (>3.7 nm). Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 transformed to a tetragonal structure below 2 GPa and irreversibly amorphized between 9.6 and 13 GPa. The bulk modulus of the tetragonal U 60-bearing material was 25 ± 2 GPa. The pressure-induced amorphous phase contained intact U 60 clusters, which were preserved beyond the loss of long-range periodicity. The persistence of U 60 clusters at high pressure may have been enhanced by the interaction between U 60 nanoclusters and the alcohol pressure medium. Once formed, U 60 nanoclusters persist regardless of their associated long-range ordering—in crystals, amorphous solids, or solutions.« less

Silver nanoparticle decorated reduced graphene oxide (rGO) nanosheet: a platform for SERS based low-level detection of uranyl ion.

PubMed

Dutta, Soumen; Ray, Chaiti; Sarkar, Sougata; Pradhan, Mukul; Negishi, Yuichi; Pal, Tarasankar

2013-09-11

Herein, a simple wet-chemical pathway has been demonstrated for the synthesis of silver nanoparticle conjugated reduced graphene oxide nanosheets where dimethylformamide (DMF) is judiciously employed as an efficient reducing agent. Altogether, DMF reduces both silver nitrate (AgNO3) and graphene oxide (GO) in the reaction mixture. Additionally, the presence of polyvinylpyrolidone (PVP) assists the nanophasic growth and homogeneous distribution of the plasmonic nanoparticle Ag(0). Reduction of graphene oxide and the presence of aggregated Ag NPs on reduced graphene oxide (rGO) nanosheets are confirmed from various spectroscopic techniques. Finally, the composite material has been exploited as an intriguing platform for surface enhanced Raman scattering (SERS) based selective detection of uranyl (UO2(2+)) ion. The limit of detection has been achieved to be as low as 10 nM. Here the normal Raman spectral (NRS) band of uranyl acetate (UAc) at 838 cm(-1) shifts to 714 and 730 cm(-1) as SERS bands for pH 5.0 and 12.0, respectively. This distinguished Raman shift of the symmetric stretching mode for UO2(2+) ion is indicative of pronounced charge transfer (CT) effect. This CT effect even supports the higher sensitivity of the protocol toward UO2(2+) over other tested oxo-ions. It is anticipated that rGO nanosheets furnish a convenient compartment to favor the interaction between Ag NPs and UO2(2+) ion through proximity induced adsorption even at low concentration.

Additional studies on mixed uranyl oxide-hydroxide hydrate alteration products of uraninite from the palermo and ruggles granitic pegmatites, grafton county, New Hampshire

USGS Publications Warehouse

Foord, E.E.; Korzeb, S.L.; Lichte, F.E.; Fitzpatrick, J.J.

1997-01-01

Additional studies on an incompletely characterized secondary uranium "mineral" from the Ruggles and Palermo granitic pegmatites, New Hampshire, referred to as mineral "A" by Frondel (1956), reveal a mixture of schoepite-group minerals and related uranyl oxide-hydroxide hydrated compounds. A composite chemical analysis yielded (in wt.%): PbO 4.85 (EMP), UO3 83.5 (EMP), BaO 0.675 (av. of EMP and ICP), CaO 0.167 (av. of EMP and ICP), K2O 2.455 (av. of EMP and ICP), SrO 0.21 (ICP), ThO2 0.85 (ICP), H2O 6.9, ??99.61. Powder-diffraction X-ray studies indicate a close resemblance in patterns between mineral "A" and several uranyl oxide-hydroxide hydrated minerals, including the schoepite family of minerals and UO2(OH)2. The powder-diffraction data for mineral "A" are most similar to those for synthetic UO2.86??1.5H2O and UO2(OH)2, but other phases are likely present as well. TGA analysis of both mineral "A" and metaschoepite show similar weight-loss and first derivative curves. The dominant losses are at 100??C, with secondary events at 400?? and 600??C. IR spectra show the presence of (OH) and H2O. Uraninite from both pegmatites, analyzed by LAM-ICP-MS, shows the presence of Th, Pb, K and Ca.

Resolving Confined 7Li Dynamics of Uranyl Peroxide Capsule U 24

DOE PAGES

Xie, Jing; Neal, Harrison A.; Szymanowski, Jennifer; ...

2018-04-18

Here, we obtained a kerosene-soluble form of the lithium salt [UO 2(O 2)(OH) 2] 24 phase (Li-U 24), by adding cetyltrimethylammonium bromide surfactant to aqueous Li-U 24. Interestingly, its variable-temperature solution 7Li NMR spectroscopy resolves two narrowly spaced resonances down to –10 °C, which shift upfield with increasing temperature, and finally coalesce at temperatures > 85 °C. Comparison with solid-state NMR demonstrates that the Li dynamics in the Li-U 24-CTA phase involves only exchange between different local encapsulated environments. This behavior is distinct from the rapid Li exchange dynamics observed between encapsulated and external Li environments for Li-U 24 inmore » both the aqueous and the solid-state phases. Density functional theory calculations suggest that the two experimental 7Li NMR chemical shifts are due to Li cations coordinated within the square and hexagonal faces of the U 24 cage, and they can undergo exchange within the confined environment, as the solution is heated. Very different than U 24 in aqueous media, there is no evidence that the Li cations exit the cage, and therefore, this represents a truly confined space.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Sadananda; Brown, Suree S.; Mayes, Richard T.

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. Hydroxylamine derivatives of poly(acrylonitrile) (PAN) moiety are demonstrated to possess two kinds of functional groups: open-chain amidoxime and cyclic imide dioxime. The open-chain amidoxime is shown to convert to imide dioxime on heat treatment in the presence of an aprotic solvent, like dimethylsulfoxide (DMSO). The formation of amidoxime and imide dioxime was confirmed by 13-C CPMAS spectra. The adsorbents were evaluated for uranium adsorption efficiency at ORNL with simulated seawater spikedmore » with 8 ppm uranium and 5 gallon seawater in a batch reactor, and in flow-through columns with natural seawater at the Marine Science Laboratory (MSL) of Pacific Northwest National Laboratory (PNNL) at Sequim Bay, WA. The DMSO-heat-treated sorbents adsorbed uranium as high as 4.48 g-U/kg-ads. from seawater. Experimental evidence is presented that the poly(imide dioxime) is primarily responsible for enhanced uranium adsorption capacity from natural seawater. The conjugated system in the imide dioxime ligand possesses increased electron donation ability, which is believed to significantly enhance the uranyl coordination in seawater« less

Resolving Confined 7Li Dynamics of Uranyl Peroxide Capsule U 24

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Jing; Neal, Harrison A.; Szymanowski, Jennifer

Here, we obtained a kerosene-soluble form of the lithium salt [UO 2(O 2)(OH) 2] 24 phase (Li-U 24), by adding cetyltrimethylammonium bromide surfactant to aqueous Li-U 24. Interestingly, its variable-temperature solution 7Li NMR spectroscopy resolves two narrowly spaced resonances down to –10 °C, which shift upfield with increasing temperature, and finally coalesce at temperatures > 85 °C. Comparison with solid-state NMR demonstrates that the Li dynamics in the Li-U 24-CTA phase involves only exchange between different local encapsulated environments. This behavior is distinct from the rapid Li exchange dynamics observed between encapsulated and external Li environments for Li-U 24 inmore » both the aqueous and the solid-state phases. Density functional theory calculations suggest that the two experimental 7Li NMR chemical shifts are due to Li cations coordinated within the square and hexagonal faces of the U 24 cage, and they can undergo exchange within the confined environment, as the solution is heated. Very different than U 24 in aqueous media, there is no evidence that the Li cations exit the cage, and therefore, this represents a truly confined space.« less

CW EPR parameters reveal cytochrome P450 ligand binding modes.

PubMed

Lockart, Molly M; Rodriguez, Carlo A; Atkins, William M; Bowman, Michael K

2018-06-01

Cytochrome P450 (CYP) monoxygenses utilize heme cofactors to catalyze oxidation reactions. They play a critical role in metabolism of many classes of drugs, are an attractive target for drug development, and mediate several prominent drug interactions. Many substrates and inhibitors alter the spin state of the ferric heme by displacing the heme's axial water ligand in the resting enzyme to yield a five-coordinate iron complex, or they replace the axial water to yield a nitrogen-ligated six-coordinate iron complex, which are traditionally assigned by UV-vis spectroscopy. However, crystal structures and recent pulsed electron paramagnetic resonance (EPR) studies find a few cases where molecules hydrogen bond to the axial water. The water-bridged drug-H 2 O-heme has UV-vis spectra similar to nitrogen-ligated, six-coordinate complexes, but are closer to "reverse type I" complexes described in older liteature. Here, pulsed and continuous wave (CW) EPR demonstrate that water-bridged complexes are remarkably common among a range of nitrogenous drugs or drug fragments that bind to CYP3A4 or CYP2C9. Principal component analysis reveals a distinct clustering of CW EPR spectral parameters for water-bridged complexes. CW EPR reveals heterogeneous mixtures of ligated states, including multiple directly-coordinated complexes and water-bridged complexes. These results suggest that water-bridged complexes are under-represented in CYP structural databases and can have energies similar to other ligation modes. The data indicates that water-bridged binding modes can be identified and distinguished from directly-coordinated binding by CW EPR. Copyright © 2018 Elsevier Inc. All rights reserved.

Pediatric Care Coordination: Lessons Learned and Future Priorities.

PubMed

Cady, Rhonda G; Looman, Wendy S; Lindeke, Linda L; LaPlante, Bonnie; Lundeen, Barbara; Seeley, Amanda; Kautto, Mary E

2015-09-30

A fundamental component of the medical home model is care coordination. In Minnesota, this model informed design and implementation of the state's health care home (HCH) model, a key element of statewide healthcare reform legislation. Children with medical complexity (CMC) often require care from multiple specialists and community resources. Coordinating this multi-faceted care within the HCH is challenging. This article describes the need for specialized models of care coordination for CMC. Two models of care coordination for CMC were developed to address this challenge. The TeleFamilies Model of Pediatric Care Coordination uses an advanced practice registered nurse care (APRN) coordinator embedded within an established HCH. The PRoSPer Model of Pediatric Care Coordination uses a registered nurse/social worker care coordinator team embedded within a specialty care system. We describe key findings from implementation of these models, and conclude with lessons learned. Replication of the models is encouraged to increase the evidence base for care coordination for the growing population of children with medical complexities.

Divergent Coordination Chemistry: Parallel Synthesis of [2×2] Iron(II) Grid-Complex Tauto-Conformers.

PubMed

Schäfer, Bernhard; Greisch, Jean-François; Faus, Isabelle; Bodenstein, Tilmann; Šalitroš, Ivan; Fuhr, Olaf; Fink, Karin; Schünemann, Volker; Kappes, Manfred M; Ruben, Mario

2016-08-26

The coordination of iron(II) ions by a homoditopic ligand L with two tridentate chelates leads to the tautomerism-driven emergence of complexity, with isomeric tetramers and trimers as the coordination products. The structures of the two dominant [Fe(II) 4 L4 ](8+) complexes were determined by X-ray diffraction, and the distinctness of the products was confirmed by ion-mobility mass spectrometry. Moreover, these two isomers display contrasting magnetic properties (Fe(II) spin crossover vs. a blocked Fe(II) high-spin state). These results demonstrate how the coordination of a metal ion to a ligand that can undergo tautomerization can increase, at a higher hierarchical level, complexity, here expressed by the formation of isomeric molecular assemblies with distinct physical properties. Such results are of importance for improving our understanding of the emergence of complexity in chemistry and biology. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Syntheses, structures and luminescence of three copper(I) cyanide coordination polymers based on trigonal 1,3,5-tris(1H-imidazol-1-yl)benzene ligand

NASA Astrophysics Data System (ADS)

Shao, Min; Li, Ming-Xing; Lu, Li-Ruo; Zhang, Heng-Hua

2016-09-01

Three Cu(I)-cyanide coordination polymers based on trigonal 1,3,5-tris(1H-imidazol-1-yl)benzene (tib) ligand, namely [Cu3(CN)3(tib)]n (1), [Cu4(CN)4(tib)]n (2), and [Cu2(CN)2(tib)]n (3), have been prepared and characterized by elemental analysis, IR, PXRD, thermogravimetry and single-crystal X-ray diffraction analysis. Complex 1 displays a 3D metal-organic framework with nanosized pores. Complex 2 is a 3D coordination polymer assembled by three μ2-cyanides and a μ3-cyanide with a very short Cu(I)···Cu(I) metal bond(2.5206 Å). Complex 3 is a 2D coordination polymer constructing from 1D Cu(I)-cyanide zigzag chain and bidentate tib spacer. Three Cu(I) complexes are thermally stable up to 250-350 °C. Complexes 1-3 show similar orange emission band at 602 nm originating from LMCT mechanism.

[Raman spectra of complexes of rare earth nitrate with histidine].

PubMed

Gao, S; Ji, M; Liu, J; Hou, Y; Chen, S

1999-12-01

Raman spectra of solid complexes RE(His)(NO3)3 x H2O (RE = La-Nd, Sm-Lu, Y; His = L-alpha-histidine ) have been investigated. The results indicate that RE3+ coordinates with one O atome of carboxyl group in the complex, while amino group and imidazole ring do not take part in coordination and NO3 is double coordination. The vibration peaks of carboxyl group delta(v)COO-(as-s) were plotted against the atomic number of the lanthanoids, which obeys Oddo-Harkins law.

Coordinating properties of uridine 5'-monophosphate with selected Ln(3+) ions in ionic micellar media.

PubMed

Sudhiranjan Singh, M; Homendra, Naorem; Lonibala, R K

2012-12-01

Coordinating properties of uridine 5'-monophosphate (UMP) towards trivalent La, Pr, Nd, Sm, Eu and Gd ions in presence of cationic and anionic micelles have been investigated by potentiometric pH-titration and spectroscopic methods. Stability constants of the 2:1 complexes have been determined and the change in free energy, enthalpy and entropy associated with the complexation are also calculated. Nd(III) complexes isolated from aqueous and aqueous-micellar media do not show any significant structural difference. Formation of Ln(III) complexes in all cases completes below pH 7.5 showing that UMP best interacts with Ln(3+) ions at the physiological pH range 7.3-7.5. The nucleobase is not involved in the complexation and the metal ion coordination of UMP is through the phosphate moiety only. Coordinating tendency of UMP with lanthanides, Nd(III) ion in particular, at different pH is also discussed. Luminescent properties of Eu(III) complex and its decay lifetime are also presented. This information may prove helpful regarding the use of lanthanides as biological probes for calcium/magnesium ions.

Dramatic Influence of an Anionic Donor on the Oxygen-Atom Transfer Reactivity of a MnV–Oxo Complex

PubMed Central

Neu, Heather M; Quesne, Matthew G; Yang, Tzuhsiung; Prokop-Prigge, Katharine A; Lancaster, Kyle M; Donohoe, James; DeBeer, Serena; de Visser, Sam P; Goldberg, David P

2014-01-01

Addition of an anionic donor to an MnV(O) porphyrinoid complex causes a dramatic increase in 2-electron oxygen-atom-transfer (OAT) chemistry. The 6-coordinate [MnV(O)(TBP8Cz)(CN)]− was generated from addition of Bu4N+CN− to the 5-coordinate MnV(O) precursor. The cyanide-ligated complex was characterized for the first time by Mn K-edge X-ray absorption spectroscopy (XAS) and gives Mn–O=1.53 Å, Mn–CN=2.21 Å. In combination with computational studies these distances were shown to correlate with a singlet ground state. Reaction of the CN− complex with thioethers results in OAT to give the corresponding sulfoxide and a 2e−-reduced MnIII(CN)− complex. Kinetic measurements reveal a dramatic rate enhancement for OAT of approximately 24 000-fold versus the same reaction for the parent 5-coordinate complex. An Eyring analysis gives ΔH≠=14 kcal mol−1, ΔS≠=−10 cal mol−1 K−1. Computational studies fully support the structures, spin states, and relative reactivity of the 5- and 6-coordinate MnV(O) complexes. PMID:25256417

Transition Manifolds of Complex Metastable Systems: Theory and Data-Driven Computation of Effective Dynamics.

PubMed

Bittracher, Andreas; Koltai, Péter; Klus, Stefan; Banisch, Ralf; Dellnitz, Michael; Schütte, Christof

2018-01-01

We consider complex dynamical systems showing metastable behavior, but no local separation of fast and slow time scales. The article raises the question of whether such systems exhibit a low-dimensional manifold supporting its effective dynamics. For answering this question, we aim at finding nonlinear coordinates, called reaction coordinates, such that the projection of the dynamics onto these coordinates preserves the dominant time scales of the dynamics. We show that, based on a specific reducibility property, the existence of good low-dimensional reaction coordinates preserving the dominant time scales is guaranteed. Based on this theoretical framework, we develop and test a novel numerical approach for computing good reaction coordinates. The proposed algorithmic approach is fully local and thus not prone to the curse of dimension with respect to the state space of the dynamics. Hence, it is a promising method for data-based model reduction of complex dynamical systems such as molecular dynamics.

Transition Manifolds of Complex Metastable Systems

NASA Astrophysics Data System (ADS)

Bittracher, Andreas; Koltai, Péter; Klus, Stefan; Banisch, Ralf; Dellnitz, Michael; Schütte, Christof

2018-04-01

We consider complex dynamical systems showing metastable behavior, but no local separation of fast and slow time scales. The article raises the question of whether such systems exhibit a low-dimensional manifold supporting its effective dynamics. For answering this question, we aim at finding nonlinear coordinates, called reaction coordinates, such that the projection of the dynamics onto these coordinates preserves the dominant time scales of the dynamics. We show that, based on a specific reducibility property, the existence of good low-dimensional reaction coordinates preserving the dominant time scales is guaranteed. Based on this theoretical framework, we develop and test a novel numerical approach for computing good reaction coordinates. The proposed algorithmic approach is fully local and thus not prone to the curse of dimension with respect to the state space of the dynamics. Hence, it is a promising method for data-based model reduction of complex dynamical systems such as molecular dynamics.

Comparative studies of mononuclear Ni(II) and UO2(II) complexes having bifunctional coordinated groups: Synthesis, thermal analysis, X-ray diffraction, surface morphology studies and biological evaluation

NASA Astrophysics Data System (ADS)

Fahem, Abeer A.

2012-03-01

Two Schiff base ligands derived from condensation of phthalaldehyde and o-phenylenediamine in 1:2 (L1) and 2:1 (L2) having bifunctional coordinated groups (NH2 and CHO groups, respectively) and their metal complexes with Ni(II) and UO2(II) have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibilities and spectral data (IR, 1H NMR, mass and solid reflectance) as well as thermal, XRPD and SEM analysis. The formula [Ni(L1)Cl2]·2.5H2O, [UO2(L1)(NO3)2]·2H2O, [Ni(L2)Cl2]·1.5H2O and [UO2(L2)(NO3)2] have been suggested for the complexes. The vibrational spectral data show that the ligands behave as neutral ligands and coordinated to the metal ions in a tetradentate manner. The Ni(II) complexes are six coordinate with octahedral geometry and the ligand field parameters: Dq, B, β and LFSE were calculated while, UO2(II) complexes are eight coordinate with dodecahedral geometry and the force constant, FUsbnd O and bond length, RUsbnd O were calculated. The thermal decomposition of complexes ended with metal chloride/nitrate as a final product and the highest thermal stability is displayed by [UO2(L2)(NO3)2] complex. The X-ray powder diffraction data revealed the formation of nano sized crystalline complexes. The SEM analysis provides the morphology of the synthesized compounds and SEM image of [UO2(L2)(NO3)2] complex exhibits nano rod structure. The growth-inhibiting potential of the ligands and their complexes has been assessed against a variety of bacterial and fungal strains.

Zinc(II)-methimazole complexes: synthesis and reactivity.

PubMed

Isaia, Francesco; Aragoni, Maria Carla; Arca, Massimiliano; Bettoschi, Alexandre; Caltagirone, Claudia; Castellano, Carlo; Demartin, Francesco; Lippolis, Vito; Pivetta, Tiziana; Valletta, Elisa

2015-06-07

The tetrahedral S-coordinated complex [Zn(MeImHS)4](ClO4)2, synthesised from the reaction of [Zn(ClO4)2] with methimazole (1-methyl-3H-imidazole-2-thione, MeImHS), reacts with triethylamine to yield the homoleptic complex [Zn(MeImS)2] (MeImS = anion methimazole). ESI-MS and MAS (13)C-NMR experiments supported MeImS acting as a (N,S)-chelating ligand. The DFT-optimised structure of [Zn(MeImS)2] is also reported and the main bond lengths compared to those of related Zn-methimazole complexes. The complex [Zn(MeImS)2] reacts under mild conditions with methyl iodide and separates the novel complex [Zn(MeImSMe)2I2] (MeImSMe = S-methylmethimazole). X-ray diffraction analysis of the complex shows a ZnI2N2 core, with the methyl thioethers uncoordinated to zinc. Conversely, the reaction of [Zn(MeImS)2] with hydroiodic acid led to the formation of the complex [Zn(MeImHS)2I2] having a ZnI2S2 core with the neutral methimazole units S-coordinating the metal centre. The Zn-coordinated methimazole can markedly modify the coordination environment when changing from its thione to thionate form and vice versa. The study of the interaction of the drug methimazole with the complex [Zn(MeIm)4](2+) (MeIm = 1-methylimidazole) - as a model for Zn-enzymes containing a N4 donor set from histidine residues - shows that methimazole displaces only one of the coordinated MeIm molecules; the formation constant of the mixed complex [Zn(MeIm)3(MeImHS)](2+) was determined.

Stereochemistry of complexes with double and triple metal-ligand bonds: a continuous shape measures analysis.

PubMed

Alvarez, Santiago; Menjón, Babil; Falceto, Andrés; Casanova, David; Alemany, Pere

2014-11-17

To each coordination polyhedron we can associate a normalized coordination polyhedron that retains the angular orientation of the central atom-ligand bonds but has all the vertices at the same distance from the center. The use of shape measures of these normalized coordination polyhedra provides a simple and efficient way of discriminating angular and bond distance distortions from an ideal polyhedron. In this paper we explore the applications of such an approach to analyses of several stereochemical problems. Among others, we discuss how to discern the off-center displacement of the metal from metal-ligand bond shortening distortions in families of square planar biscarbene and octahedral dioxo complexes. The normalized polyhedron approach is also shown to be very useful to understand stereochemical trends with the help of shape maps, minimal distortion pathways, and ligand association/dissociation pathways, illustrated by the Berry and anti Berry distortions of triple-bonded [X≡ML4] complexes, the square pyramidal geometries of Mo coordination polyhedra in oxido-reductases, the coordination geometries of actinyl complexes, and the tetrahedricity of heavy atom-substituted carbon centers.

Reductive Elimination from Phosphine-Ligated Alkylpalladium(II) Amido Complexes To Form sp3 Carbon-Nitrogen Bonds.

PubMed

Peacock, D Matthew; Jiang, Quan; Hanley, Patrick S; Cundari, Thomas R; Hartwig, John F

2018-04-11

We report the formation of phosphine-ligated alkylpalladium(II) amido complexes that undergo reductive elimination to form alkyl-nitrogen bonds and a combined experimental and computational investigation of the factors controlling the rates of these reactions. The free-energy barriers to reductive elimination from t-Bu 3 P-ligated complexes were significantly lower (ca. 3 kcal/mol) than those previously reported from NHC-ligated complexes. The rates of reactions from complexes containing a series of electronically and sterically varied anilido ligands showed that the reductive elimination is slower from complexes of less electron-rich or more sterically hindered anilido ligands than from those containing more electron-rich and less hindered anilido ligands. Reductive elimination of alkylamines also occurred from complexes bearing bidentate P,O ligands. The rates of reactions of these four-coordinate complexes were slower than those for reactions of the three-coordinate, t-Bu 3 P-ligated complexes. The calculated pathway for reductive elimination from rigid, 2-methoxyarylphosphine-ligated complexes does not involve initial dissociation of the oxygen. Instead, reductive elimination is calculated to occur directly from the four-coordinate complex in concert with a lengthening of the Pd-O bond. To investigate this effect experimentally, a four-coordinate Pd(II) anilido complex containing a flexible, aliphatic linker between the P and O atoms was synthesized. Reductive elimination from this complex was faster than that from the analogous complex containing the more rigid, aryl linker. The flexible linker enables full dissociation of the ether ligand during reductive elimination, leading to the faster reaction of this complex.

Lanthanide complex coordination polyhedron geometry prediction accuracies of ab initio effective core potential calculations.

PubMed

Freire, Ricardo O; Rocha, Gerd B; Simas, Alfredo M

2006-03-01

lanthanide coordination compounds efficiently and accurately is central for the design of new ligands capable of forming stable and highly luminescent complexes. Accordingly, we present in this paper a report on the capability of various ab initio effective core potential calculations in reproducing the coordination polyhedron geometries of lanthanide complexes. Starting with all combinations of HF, B3LYP and MP2(Full) with STO-3G, 3-21G, 6-31G, 6-31G* and 6-31+G basis sets for [Eu(H2O)9]3+ and closing with more manageable calculations for the larger complexes, we computed the fully predicted ab initio geometries for a total of 80 calculations on 52 complexes of Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III) and Tm(III), the largest containing 164 atoms. Our results indicate that RHF/STO-3G/ECP appears to be the most efficient model chemistry in terms of coordination polyhedron crystallographic geometry predictions from isolated lanthanide complex ion calculations. Moreover, both augmenting the basis set and/or including electron correlation generally enlarged the deviations and aggravated the quality of the predicted coordination polyhedron crystallographic geometry. Our results further indicate that Cosentino et al.'s suggestion of using RHF/3-21G/ECP geometries appears to be indeed a more robust, but not necessarily, more accurate recommendation to be adopted for the general lanthanide complex case. [Figure: see text].

Syntheses and Characterization of Ruthenium(II) Tetrakis(pyridine)complexes: An Advanced Coordination Chemistry Experiment or Mini-Project

ERIC Educational Resources Information Center

Coe, Benjamin J.

2004-01-01

An experiment for third-year undergraduate a student is designed which provides synthetic experience and qualitative interpretation of the spectroscopic properties of the ruthenium complexes. It involves the syntheses and characterization of several coordination complexes of ruthenium, the element found directly beneath iron in the middle of the…

η6-Cycloparaphenylene transition metal complexes: synthesis, structure, photophysical properties, and application to the selective monofunctionalization of cycloparaphenylenes.

PubMed

Kubota, Natsumi; Segawa, Yasutomo; Itami, Kenichiro

2015-01-28

The synthesis, structure, photophysical properties, and reactivity of cycloparaphenylenes (CPPs) coordinated to group 6 transition metal fragments are described. The η(6)-coordination of [9]CPP or [12]CPP with M(CO)6 (M = Cr, Mo, W) afforded the corresponding [n]CPP-M(CO)3 complexes (n = 9, 12; M = Cr, Mo, W). In the (1)H NMR spectra of these complexes, characteristic upfield-shifted singlet signals corresponding to the four hydrogen atoms attached to the coordinated C6H4 ring of the CPPs were observed at 5.4-5.9 ppm. The complex [9]CPP-Cr(CO)3 could be successfully isolated in spite of its instability. X-ray crystallographic analysis and computational studies of [9]CPP-Cr(CO)3 revealed that chromium-CPP coordination occurs at the convex surface of [9]CPP both in the solid state and in solution. TD-DFT calculations suggested that the emerging high-wavenumber absorption peak upon coordination of [9]CPP to Cr(CO)3 should be assigned to a weak HOMO-LUMO transition. Moreover, by using the complex [9]CPP-Cr(CO)3, a rapid and highly monoselective CPP functionalization has been achieved. The established one-pot method, consisting of complexation, deprotonation, nucleophilic substitution, and decomplexation steps, yielded silyl-, boryl-, and methoxycarbonyl-substituted CPPs in up to 93% yield relative to reacted starting material.

Potentiometric and DFT studies of Cu(II) complexes with glycylglycine and methionine of interest for the brain chemistry

NASA Astrophysics Data System (ADS)

Vilhena, Felipe S.; Felcman, Judith; Szpoganicz, Bruno; Miranda, Fabio S.

2017-01-01

A large number of copper (II) complexes have been used as mimetic models for metalloproteins and metalloenzymes. Due to the lack of structural information about copper (II) complexes in aqueous solution, the coordination environment of this metal is not well established. In this work, pKa values of the complexes in the Cu:GlyGly, Cu:Met and Cu:GlyGly:Met systems were calculated by potentiometric titration at 25 °C and ionic strength of 0.1 mol L-1. The coordination modes of the ligands were explored for the main hydrolytic species throught RI-PBE/def2-SVP/COSMO level. In the Cu:GlyGly system, DFT results indicated that the NamineNpept coordination of dipeptide is 2.1 kcal mol-1 more stable than the tridentate NamineNpeptOcarboxy coordination moiety. The deprotonation of the peptide nitrogen is 13.7 kcal mol-1 more favorable than the hydrolysis of the water molecule coordinated to the metal. In the Cu:GlyGly:Met system, the sulfur atom does not belong to the copper (II) coordination sphere. Once the copper ion is incorporated into peptides, another ligand as methionine could bind to this system and carry an antioxidant site to different brain regions.

The coordinating evaluation and spatial correlation analysis of CSGC: A case study of Henan province, China.

PubMed

Xie, Mingxia; Wang, Jiayao; Chen, Ke

2017-01-01

This study investigates the basic characteristics and proposes a concept for the complex system of geographical conditions (CSGC). By analyzing the DPSIR model and its correlation with the index system, we selected indexes for geographical conditions according to the resources, ecology, environment, economy and society parameters to build a system. This system consists of four hierarchies: index, classification, element and target levels. We evaluated the elements or indexes of the complex system using the TOPSIS method and a general model coordinating multiple complex systems. On this basis, the coordination analysis experiment of geographical conditions is applied to cities in the Henan province in China. The following conclusions were reached: ①According to the pressure, state and impact of geographical conditions, relatively consistent measures are taken around the city, but with conflicting results. ②The coordination degree of geographical conditions is small among regions showing large differences in classification index value. The degree of coordination of such regions is prone to extreme values; however, the smaller the difference the larger the coordination degree. ③The coordinated development of geographical conditions in the Henan province is at the stage of the point axis.

Efficient uranium capture by polysulfide/layered double hydroxide composites.

PubMed

Ma, Shulan; Huang, Lu; Ma, Lijiao; Shim, Yurina; Islam, Saiful M; Wang, Pengli; Zhao, Li-Dong; Wang, Shichao; Sun, Genban; Yang, Xiaojing; Kanatzidis, Mercouri G

2015-03-18

There is a need to develop highly selective and efficient materials for capturing uranium (normally as UO2(2+)) from nuclear waste and from seawater. We demonstrate the promising adsorption performance of S(x)-LDH composites (LDH is Mg/Al layered double hydroxide, [S(x)](2-) is polysulfide with x = 2, 4) for uranyl ions from a variety of aqueous solutions including seawater. We report high removal capacities (q(m) = 330 mg/g), large K(d)(U) values (10(4)-10(6) mL/g at 1-300 ppm U concentration), and high % removals (>95% at 1-100 ppm, or ∼80% for ppb level seawater) for UO2(2+) species. The S(x)-LDHs are exceptionally efficient for selectively and rapidly capturing UO2(2+) both at high (ppm) and trace (ppb) quantities from the U-containing water including seawater. The maximum adsorption coeffcient value K(d)(U) of 3.4 × 10(6) mL/g (using a V/m ratio of 1000 mL/g) observed is among the highest reported for U adsorbents. In the presence of very high concentrations of competitive ions such as Ca(2+)/Na(+), S(x)-LDH exhibits superior selectivity for UO2(2+), over previously reported sorbents. Under low U concentrations, (S4)(2-) coordinates to UO2(2+) forming anionic complexes retaining in the LDH gallery. At high U concentrations, (S4)(2-) binds to UO2(2+) to generate neutral UO2S4 salts outside the gallery, with NO3(-) entering the interlayer to form NO3-LDH. In the presence of high Cl(-) concentration, Cl(-) preferentially replaces [S4](2-) and intercalates into LDH. Detailed comparison of U removal efficiency of S(x)-LDH with various known sorbents is reported. The excellent uranium adsorption ability along with the environmentally safe, low-cost constituents points to the high potential of S(x)-LDH materials for selective uranium capture.

Insights into aquatic toxicities of the antibiotics oxytetracycline and ciprofloxacin in the presence of metal: complexation versus mixture.

PubMed

Zhang, Yu; Cai, Xiyun; Lang, Xianming; Qiao, Xianliang; Li, Xuehua; Chen, Jingwen

2012-07-01

Co-contamination of ligand-like antibiotics (e.g., tetracyclines and quinolones) and heavy metals prevails in the environment, and thus the complexation between them is involved in environmental risks of antibiotics. To understand toxicological significance of the complex, effects of metal coordination on antibiotics' toxicity were investigated. The complexation of two antibiotics, oxytetracycline and ciprofloxacin, with three heavy metals, copper, zinc, and cadmium, was verified by spectroscopic techniques. The antibiotics bound metals via multiple coordination sites and rendered a mixture of various complexation speciations. Toxicity analysis indicated that metal coordination did modify the toxicity of the antibiotics and that antibiotic, metal, and their complex acted primarily as concentration addition. Comparison of EC(50) values revealed that the complex commonly was highest toxic and predominately correlated in toxicity to the mixture. Finally, environmental scenario analysis demonstrated that ignoring complexation would improperly classify environmental risks of the antibiotics. Copyright © 2012 Elsevier Ltd. All rights reserved.

Copper(II) and zinc(II) as metal-carboxylate coordination complexes based on (1-methyl-1H-benzo[d]imidazol-2-yl) methanol derivative: Synthesis, crystal structure, spectroscopy, DFT calculations and antioxidant activity

NASA Astrophysics Data System (ADS)

Benhassine, Anfel; Boulebd, Houssem; Anak, Barkahem; Bouraiou, Abdelmalek; Bouacida, Sofiane; Bencharif, Mustapha; Belfaitah, Ali

2018-05-01

This work presents a combined experimental and theoretical study of two new metal-carboxylate coordination compounds. These complexes were prepared from (1-methyl-1H-benzimidazol-2-yl)methanol under mild conditions. The structures of the prepared compounds were characterized by single-crystal X-ray analysis, FTIR and UV-Vis spectroscopy. In the Cupper complex, the Cu(II) ion is coordinated by two ligands, which act as bidentate chelator through the non-substituted N and O atoms, and two carboxylicg oxygen atoms, displaying a hexa-coordinated compound in a distorted octahedral geometry, while in the Zinc complex the ligand is ligated to the Zn(II) ion in monodentate fashion through the N atom, and the metal ion is also bonded to carboxylic oxygen atoms. The tetra-coordinated compound displays a distorted tetrahedral shape. The density functional theory calculations are carried out for the determination of the optimized structures. The electronic transitions and fundamental vibrational wave numbers are calculated and are in good agreement with experimental. In addition, the ligand and its Cu(II) and Zn(II) complexes were screened and evaluated for their potential as DPPH radical scavenger.

Statistical Determinants of Selective Ionic Complexation: Ions in Solvent, Transport Proteins, and Other “Hosts”

PubMed Central

Bostick, David L.; Brooks, Charles L.

2009-01-01

To provide utility in understanding the molecular evolution of ion-selective biomembrane channels/transporters, globular proteins, and ionophoric compounds, as well as in guiding their modification and design, we present a statistical mechanical basis for deconstructing the impact of the coordination structure and chemistry of selective multidentate ionic complexes. The deconstruction augments familiar ideas in liquid structure theory to realize the ionic complex as an open ion-ligated system acting under the influence of an “external field” provided by the host (or surrounding medium). Using considerations derived from this basis, we show that selective complexation arises from exploitation of a particular ion's coordination preferences. These preferences derive from a balance of interactions much like that which dictates the Hofmeister effect. By analyzing the coordination-state space of small family IA and VIIA ions in simulated fluid media, we derive domains of coordinated states that confer selectivity for a given ion upon isolating and constraining particular attributes (order parameters) of a complex comprised of a given type of ligand. We demonstrate that such domains may be used to rationalize the ion-coordinated environments provided by selective ionophores and biological ion channels/transporters of known structure, and that they can serve as a means toward deriving rational design principles for ion-selective hosts. PMID:19486671

The Behavior of the Ru-bda Water Oxidation Catalysts at Low Oxidation States.

PubMed

Matheu, Roc; Ghaderian, Abolfazl; Francas, Laia; Chernev, Petko; Ertem, Mehmed; Benet-Buchholz, Jordi; Batista, Victor; Haumann, Michael; Gimbert-Suriñach, Carolina; Sala, Xavier; Llobet, Antoni

2018-06-13

The Ru complex [RuII(bda-κ-N2O2)(N-NH2)2], 1, (bda2- = (2,2'-bipyridine)-6,6'-dicarboxylate; N-NH2 = 4-(pyridin-4-yl)aniline) is used as a synthetic intermediate to prepare Ru-bda complexes that contain the NO+, acetonitrile (MeCN) or H2O ligands at oxidation states II and III. Complex 1 reacts with excess NO+ to form a Ru complex where the aryl amine ligands N-NH2 in 1 are transformed into diazonium salts (N-N2+ = 4-(pyridin-4-yl)benzenediazonium)) together with the formation of a new Ru-NO group at the equatorial zone, to generate [RuII(bda-κ-N2O)(NO)(N-N2)2]3+, 23+. Similarly, complex 1 can also react with a coordinating solvent, such as MeCN, at room temperature leading to complex [RuII(bda-κ-N2O)(MeCN)(N-NH2)2], 3. Finally in acidic aqueous solutions solvent water coordinates the Ru center forming {[RuII(bda-κ-(NO)3)(H2O)(N-NH3)2](H2O)n}2+, 42+, that is strongly hydrogen bonded with additional water molecules at the second coordination sphere. We have additionally characterized the one electron oxidized complex {[RuIII(bda-κ-(NO)3.5)(H2O)(N-NH3)2](H2O)n}3+, 53+. The coordination mode of the complexes has been studied both in the solid state and in solution through single-crystal XRD, X-ray absorption spectroscopy, variable-temperature NMR and DFT calculations. While the κ-N2O is the main coordination mode for 23+ and 3, an equilibrium that involves isomers with κ-N2O and κ-NO2 coordination modes and neighboring hydrogen bonded water molecules is observed for 42+ and 53+. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bending nanofibers into nanospirals: coordination chemistry as a tool for shaping hydrophobic assemblies.

PubMed

Kossoy, Elizaveta; Weissman, Haim; Rybtchinski, Boris

2015-01-02

In the current work, we demonstrate how coordination chemistry can be employed to direct self-assembly based on strong hydrophobic interactions. To investigate the influence of coordination sphere geometry on aqueous self-assembly, we synthesized complexes of the amphiphilic perylene diimide terpyridine ligand with the first-row transition-metal centers (zinc, cobalt, and nickel). In aqueous medium, aggregation of these complexes is induced by hydrophobic interactions between the ligands. However, the final shapes of the resulting assemblies depend on the preferred geometry of the coordination spheres typical for the particular metal center. The self-assembly process was characterized by UV/Vis spectroscopy, zeta potential measurements, and cryogenic transmission electron microscopy (cryo-TEM). Coordination of zinc(II) and cobalt(II) leads to the formation of unique nanospiral assemblies, whereas complexation of nickel(II) leads to the formation of straight nanofibers. Notably, coordination bonds are utilized not as connectors between elementary building blocks, but as directing interactions, enabling control over supramolecular geometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Meaningful Use of Data in Care Coordination by the Advanced Practice Registered Nurse: The TeleFamilies Project

PubMed Central

Looman, Wendy S.; Erickson, Mary M.; Garwick, Ann W.; Cady, Rhonda G.; Kelly, Anne; Pettey, Carrie; Finkelstein, Stanley M.

2012-01-01

Meaningful use of electronic health records to coordinate care requires skillful synthesis and integration of subjective and objective data by practitioners to provide context for information. This is particularly relevant in the coordination of care for children with complex special health care needs. The purpose of this paper is to present a conceptual framework and example of meaningful use within an innovative telenursing intervention to coordinate care for children with complex special health care needs. The TeleFamilies intervention engages an advanced practice nurse in a full-time care coordinator role within an existing hospital-based medical home for children with complex special health care needs. Care coordination is facilitated by the synthesis and integration of internal and external data using an enhanced electronic health record and telehealth encounters via telephone and videoconferencing between the advanced practice nurse and the family at home. The advanced practice nurse’s ability to maintain an updated plan of care that is shared across providers and systems and build a relationship over time with the patient and family supports meaningful use of these data. PMID:22948406

A diketiminate-bound diiron complex with a bridging carbonate ligand

PubMed Central

Sadique, Azwana R.; Brennessel, William W.; Holland, Patrick L.

2009-01-01

Reduction of carbon dioxide by a diiron(I) complex gives μ-carbonato-κ3 O:O′,O′′-bis­{[2,2,6,6-tetra­methyl-3,5-bis­(2,4,6-triisopropyl­phenyl)heptane-2,5-diiminate(1−)-κ2 N,N′]iron(II)} toluene disolvate, [Fe2(C41H65N)2(CO3)]·2C7H8, a diiron(II) species with a bridging carbonate ligand. The asymmetric unit contains one diiron complex and two cocrystallized toluene solvent mol­ecules that are distributed over three sites, one with atoms in general positions and two in crystallographic sites. Both FeII atoms are η2-coordinated to diketiminate ligands, but η1- and η2-coordinated to the bridging carbonate ligand. Thus, one FeII center is three-coordinate and the other is four-coordinate. The bridging carbonate ligand is nearly perpendicular to the iron–diketiminate plane of the four-coordinate FeII center and parallel to the plane of the three-coordinate FeII center. PMID:19407402

New insight into UO 2F 2 particulate structure by micro-Raman spectroscopy

DOE PAGES

Stefaniak, Elzbieta A.; Darchuk, Larysa; Sapundjiev, Danislav; ...

2013-02-19

Uranyl fluoride particles produced via hydrolysis of uranium hexafluoride have been deposited on different substrates: polished graphite disks, silver foil, stainless steel and gold-coated silicon wafer, and measured with micro-Raman spectroscopy (MRS). All three metallic substrates enhanced the Raman signal delivered by UO 2F 2 in comparison to graphite. The fundamental stretching of the U–O band appeared at 867 cm –1 in case of the graphite substrate, while in case of the others it was shifted to lower frequencies (down to 839 cm –1). All applied metallic substrates showed the expected effect of Raman signal enhancement; however the gold layermore » appeared to be most effective. Lastly, application of new substrates provides more information on the molecular structure of uranyl fluoride precipitation, which is interesting for nuclear safeguards and nuclear environmental analysis.« less

Direct Electrodeposition of UO2 from Uranyl Bis(trifluoromethanesulfonyl)imide Dissolved in 1-Ethyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide Room Temperature Ionic Liquid System

DOE PAGES

Freiderich, John W.; Wanigasekara, Eranda P.; Sun, Xiao-Guang; ...

2013-11-11

Our study demonstrates a direct electrodeposition of UO 2 at a Pt cathode from a solution of uranyl bis(trifluoromethanesulfonyl)imide [UO 2(NTf 2) 2)] in a bulk room-temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM +NTf 2 –). Cyclic voltammetry (CV) studies revealed two reduction waves corresponding to the conversion of uranium(VI) to uranium(IV), and a mechanism for the overall electroreduction is proposed. A controlled-potential experiment was performed, holding the reduction potential at–1.0 V for 24 h to obtain a brown-black deposit of UO 2 on the Pt cathode. The Faradaic efficiency of the reduction process was determined to be >80%. Themore » UO 2deposit was characterized by powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).« less

Fission-Produced 99Mo Without a Nuclear Reactor.

PubMed

Youker, Amanda J; Chemerisov, Sergey D; Tkac, Peter; Kalensky, Michael; Heltemes, Thad A; Rotsch, David A; Vandegrift, George F; Krebs, John F; Makarashvili, Vakho; Stepinski, Dominique C

2017-03-01

99 Mo, the parent of the widely used medical isotope 99m Tc, is currently produced by irradiation of enriched uranium in nuclear reactors. The supply of this isotope is encumbered by the aging of these reactors and concerns about international transportation and nuclear proliferation. Methods: We report results for the production of 99 Mo from the accelerator-driven subcritical fission of an aqueous solution containing low enriched uranium. The predominately fast neutrons generated by impinging high-energy electrons onto a tantalum convertor are moderated to thermal energies to increase fission processes. The separation, recovery, and purification of 99 Mo were demonstrated using a recycled uranyl sulfate solution. Conclusion: The 99 Mo yield and purity were found to be unaffected by reuse of the previously irradiated and processed uranyl sulfate solution. Results from a 51.8-GBq 99 Mo production run are presented. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

Radiolysis of hexavalent plutonium in solutions of uranyl nitrate containing fission product simulants

NASA Astrophysics Data System (ADS)

Rance, Peter J. W.; Zilberman, B. Ya.; Akopov, G. A.

2000-07-01

The effect of the inherent radioactivity on the chemical state of plutonium ions in solution was recognized very shortly after the first macroscopic amounts of plutonium became available and early studies were conducted as part of the Manhattan Project. However, the behavior of plutonium ions, in nitric acid especially, has been found to be somewhat complex, so much so that a relatively modern summary paper included the comment that, "The vast amount of work carried out in nitric acid solutions can not be adequately summarized. Suffice it to say results in these solutions are plagued with irreproducibility and induction periods…" Needless to say, the presence of other ions in solution, as occurs when irradiated nuclear fuel is dissolved, further complicates matters. The purpose of the work described below was to add to the rather small amount of qualitative data available relating to the radiolytic behavior of plutonium in solutions of irradiated nuclear fuel.

Bioremediation of uranium contamination with enzymatic uranium reduction

USGS Publications Warehouse

Lovley, D.R.; Phillips, E.J.P.

1992-01-01

Enzymatic uranium reduction by Desulfovibrio desulfuricans readily removed uranium from solution in a batch system or when D. desulfuricans was separated from the bulk of the uranium-containing water by a semipermeable membrane. Uranium reduction continued at concentrations as high as 24 mM. Of a variety of potentially inhibiting anions and metals evaluated, only high concentrations of copper inhibited uranium reduction. Freeze-dried cells, stored aerobically, reduced uranium as fast as fresh cells. D. desulfuricans reduced uranium in pH 4 and pH 7.4 mine drainage waters and in uraniumcontaining groundwaters from a contaminated Department of Energy site. Enzymatic uranium reduction has several potential advantages over other bioprocessing techniques for uranium removal, the most important of which are as follows: the ability to precipitate uranium that is in the form of a uranyl carbonate complex; high capacity for uranium removal per cell; the formation of a compact, relatively pure, uranium precipitate.

Electron binding energy of uranium-ligand and uranyl-ligand anions

NASA Astrophysics Data System (ADS)

Wang, Lei; Horowitz, Steven; Marston, Brad

2012-02-01

Electron binding energies of the early actinide element uranium in gas-phase anion complexes are calculated by relativistic density functional theory (DFT) with two different exchange-correlation functions (RPBE and B3LYP) and also in the Hartree-Fock (HF) approximationootnotetextADF2010.02, SCM.com. Scalar and spin-orbit calculations are performed, and the calculated energies are compared to available experimental measurements and shown to disagree by energies of order 1 eV. Strong correlations that are poorly treated in DFT and HF can be included by a hybrid approach in which a generalized Anderson impurity model is numerically diagonalized. Reduction-oxidation (redox) potentials of aqueous actinide ions show improved agreement with measured values in the hybrid approachootnotetextS. E. Horowitz and J. B. Marston, J. Chem. Phys 134 064510 (2011).. We test whether or not similar improvements are found in the gas-phase.

Metal complexes of diisopropylthiourea: synthesis, characterization and antibacterial studies.

PubMed

Ajibade, Peter A; Zulu, Nonkululeko H

2011-01-01

Co(II), Cu(II), Zn(II) and Fe(III) complexes of diisopropylthiourea have been synthesized and characterized by elemental analyses, molar conductivity, magnetic susceptibility, FTIR and electronic spectroscopy. The compounds are non-electrolytes in solution and spectroscopic data of the complexes are consistent with 4-coordinate geometry for the metal(II) complexes and six coordinate octahedral for Fe(III) complex. The complexes were screened for their antibacterial activities against six bacteria: Escherichia coli, Pseudomonas auriginosa, Klebsiella pneumoniae, Bacillus cereus, Staphylococcus aureus and Bacillus pumilus. The complexes showed varied antibacterial activities and their minimum inhibitory concentrations (MICs) were determined.

Coordination Complexes as Catalysts: The Oxidation of Anthracene by Hydrogen Peroxide in the Presence of VO(acac)[subscript 2

ERIC Educational Resources Information Center

Charleton, Kimberly D. M.; Prokopchuk, Ernest M.

2011-01-01

A laboratory experiment aimed at students who are studying coordination chemistry of transition-metal complexes is described. A simple vanadyl acetylacetonate complex can be used as a catalyst in the hydrogen peroxide oxidation of anthracene to produce anthraquinone. The reaction can be performed under a variety of reaction conditions, ideally by…

Metal–organic coordination architectures of tetrazole heterocycle ligands bearing acetate groups: Synthesis, characterization and magnetic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Bo-Wen, E-mail: bowenhu@hit.edu.cn; Zheng, Xiang-Yu; Ding, Cheng

2015-12-15

Two new coordination complexes with tetrazole heterocycle ligands bearing acetate groups, [Co(L){sub 2}]{sub n} (1) and [Co{sub 3}(L){sub 4}(N{sub 3}){sub 2}·2MeOH]{sub n} (2) (L=tetrazole-1-acetate) have been synthesized and structurally characterized. Single crystal structure analysis shows that the cobalt-complex 1 has the 3D 3,6-connected (4{sup 2}.6){sub 2}(4{sup 4}.6{sup 2}.8{sup 8}.10)-ant topology. By introducing azide in this system, complex 2 forms the 2D network containing the [Co{sub 3}] units. And the magnetic properties of 1 and 2 have been studied. - Graphical abstract: The synthesis, crystal structure, and magnetic properties of the new coordination complexes with tetrazole heterocycle ligands bearing acetate groupsmore » are reported. - Highlights: • Two novel Cobalt(II) complexes with tetrazole acetate ligands were synthesized. • The magnetic properties of two complexes were studied. • Azide as co-ligand resulted in different structures and magnetic properties. • The new coordination mode of tetrazole acetate ligand was obtained.« less

Spectral characterization of novel ternary zinc(II) complexes containing 1,10-phenanthroline and Schiff bases derived from amino acids and salicylaldehyde-5-sulfonates

NASA Astrophysics Data System (ADS)

Boghaei, Davar M.; Gharagozlou, Mehrnaz

2007-07-01

A series of new ternary zinc(II) complexes [Zn(L 1-10)(phen)], where phen is 1,10-phenanthroline and H 2L 1-10 = tridentate Schiff base ligands derived from the condensation of amino acids (glycine, L-phenylalanine, L-valine, L-alanine, and L-leucine) and salicylaldehyde-5-sulfonates (sodium salicylaldehyde-5-sulfonate and sodium 3-methoxy-salicylaldehyde-5-sulfonate), have been synthesized. The complexes were characterized by elemental analysis, IR, UV-vis, 1H NMR, and 13C NMR spectra. The IR spectra of the complexes showed large differences between νas(COO) and νs(COO), Δ ν ( νas(COO) - νs(COO)) of 191-225 cm -1, indicating a monodentate coordination of the carboxylate group. Spectral data showed that in these ternary complexes the zinc atom is coordinated with the Schiff base ligand acts as a tridentate ONO moiety, coordinating to the metal through its phenolic oxygen, imine nitrogen, and carboxyl oxygen, and also with the neutral planar chelating ligand, 1,10-phenanthroline, coordinating through nitrogens.

Memory for Negation in Coordinate and Complex Sentences

ERIC Educational Resources Information Center

Harris, Richard J.

1976-01-01

Two experiments were run to test memory for the negation morpheme "not" in coordinate sentences (e.g., The ballerina had twins and the policewoman did not have triplets) and complex sentences (e.g., The ghost scared Hamlet into not murdering Shakespeare). (Editor)

Synthesis and reactivity of TADDOL-based chiral Fe(II) PNP pincer complexes-solution equilibria between κ(2)P,N- and κ(3)P,N,P-bound PNP pincer ligands.

PubMed

Holzhacker, Christian; Stöger, Berthold; Carvalho, Maria Deus; Ferreira, Liliana P; Pittenauer, Ernst; Allmaier, Günter; Veiros, Luis F; Realista, Sara; Gil, Adrià; Calhorda, Maria José; Müller, Danny; Kirchner, Karl

2015-08-07

Treatment of anhydrous FeX2 (X = Cl, Br) with 1 equiv. of the asymmetric chiral PNP pincer ligands PNP-R,TAD (R = iPr, tBu) with an R,R-TADDOL (TAD) moiety afforded complexes of the general formula [Fe(PNP)X2]. In the solid state these complexes adopt a tetrahedral geometry with the PNP ligand coordinated in κ(2)P,N-fashion, as shown by X-ray crystallography and Mössbauer spectroscopy. Magnetization studies led to a magnetic moment very close to 4.9μB reflecting the expected four unpaired d-electrons (quintet ground state). In solution there are equilibria between [Fe(κ(3)P,N,P-PNP-R,TAD)X2] and [Fe(κ(2)P,N-PNP-R,TAD)X2] complexes, i.e., the PNP-R,TAD ligand is hemilabile. At -50 °C these equilibria are slow and signals of the non-coordinated P-TAD arm of the κ(2)P,N-PNP-R,TAD ligand can be detected by (31)P{(1)H} NMR spectroscopy. Addition of BH3 to a solution of [Fe(PNP-iPr,TAD)Cl2] leads to selective boronation of the pendant P-TAD arm shifting the equilibrium towards the four-coordinate complex [Fe(κ(2)P,N-PNP-iPr,TAD(BH3))Cl2]. DFT calculations corroborate the existence of equilibria between four- and five-coordinated complexes. Addition of CO to [Fe(PNP-iPr,TAD)X2] in solution yields the diamagnetic octahedral complexes trans-[Fe(κ(3)P,N,P-PNP-iPr,TAD)(CO)X2], which react further with Ag(+) salts in the presence of CO to give the cationic complexes trans-[Fe(κ(3)P,N,P-PNP-iPr,TAD)(CO)2X](+). CO addition most likely takes place at the five coordinate complex [Fe(κ(3)P,N,P-PNP-iPr,TAD)X2]. The mechanism for the CO addition was also investigated by DFT and the most favorable path obtained corresponds to the rearrangement of the pincer ligand first from a κ(2)P,N- to a κ(3)P,N,P-coordination mode followed by CO coordination to [Fe(κ(3)P,N,P-PNP-iPr,TAD)X2]. Complexes bearing tBu substituents do not react with CO. Moreover, in the solid state none of the tetrahedral complexes are able to bind CO.

Structure of thallium(III) chloride, bromide, and cyanide complexes in aqueous solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blixt, J.; Glaser, J.; Sandstroem, M.

1995-05-10

The structures of the hydrated thallium(III) halide and pseudohalide complexes, [TlX{sub n}(OH{sub 2}){sub m}]{sup (3-d)+}, X = Cl, Br, CN, in aqueous solution have been studied by a combination of X-ray absorption fine structure spectroscopy (XAFS), large-angle X-ray scattering (LAXS), and vibrational spectroscopic (Raman and IR) techniques including far-infrared studies of aqueous solutions and some solid phases with known structures. The vibrational Tl-X frequencies of all complexes are reported, force constants are calculated using normal coordinate analysis, and assignments are given. The structural results are consistent with octahedral six-coordination for the cationic complexes Tl(OH{sub 2}){sub 6}{sup 3$PLU}, TlX(OH{sub 2}){sub 5}{supmore » 2+}, and trans-TlX{sub 2}(OH{sub 2}){sub 4}{sup +}. The coordination geometry changes to trigonal bipyramidal for the neutral TlBr{sub 3}(OH{sub 2}){sub 2} complex and possibly also for TlCl{sub 3}(OH{sub 2}){sub 2}. The TlX{sub 4}{sup -} complexes are all tetrahedral. Higher chloride complexes, TlCl{sub 5}(OH{sub 2}){sup 2-} and TlCl{sub 6}{sup 3-}, are formed and have again octahedral coordination geometry. 65 refs., 7 figs., 5 tabs.« less

Chitosan-Copper (II) complex as antibacterial agent: synthesis, characterization and coordinating bond- activity correlation study

NASA Astrophysics Data System (ADS)

Mekahlia, S.; Bouzid, B.

2009-11-01

The antimicrobial activity of chitosan is unstable and sensitive to many factors such as molecular weight. Recent investigations showed that low molecular weight chitosan exhibited strong bactericidal activities compared to chitosan with high molecular weight. Since chitosan degradation can be caused by the coordinating bond, we attempt to synthesize and characterize the chitosan-Cu (II) complex, and thereafter study the coordinating bond effect on its antibacterial activity against Salmonella enteritidis. Seven chitosan-copper complexes with different copper contents were prepared and characterized by FT-IR, UV-vis, XRD and atomic absorption spectrophotometry (AAS). Results indicated that for chitosan-Cu (II) complexes with molar ratio close to 1:1, the inhibition rate reached 100%.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Brian B.; Kirkegaard, Marie C.; Miskowiec, Andrew J.

Uranyl fluoride (UO 2F 2) is a hygroscopic powder with two main structural phases: an anhydrous crystal and a partially hydrated crystal of the same R¯3m symmetry. The formally closed-shell electron structure of anhydrous UO 2F 2 is amenable to density functional theory calculations. We use density functional perturbation theory (DFPT) to calculate the vibrational frequencies of the anhydrous crystal structure and employ complementary inelastic neutron scattering and temperature-dependent Raman scattering to validate those frequencies. As a model closed-shell actinide, we investigated the effect of LDA, GGA, and non-local vdW functionals as well as the spherically-averaged Hubbard +U correction onmore » vibrational frequencies, electronic structure, and geometry of anhydrous UO 2F 2. A particular choice of U eff = 5.5 eV yields the correct U Oyl bond distance and vibrational frequencies for the characteristic Eg and A1g modes that are within the resolution of experiment. Inelastic neutron scattering and Raman scattering suggest a degree of water coupling to the lattice vibrations in the more experimentally accessible partially hydrated UO 2F 2 system, with the symmetric O-U-O stretching vibration shifted approximately 47 cm -1 lower in energy compared to the anhydrous structure. Evidence of water interaction with the uranyl ion is present from a two-peak decomposition of the uranyl stretching vibration in the Raman spectra and anion hydrogen stretching vibrations in the inelastic neutron scattering spectra. A first-order dehydration phase transition temperature is definitively identified to be 125 °C using temperature-dependent Raman scattering.« less

Adsorption of gluconate and uranyl on C-S-H phases: Combination of wet chemistry experiments and molecular dynamics simulations for the binary systems

NASA Astrophysics Data System (ADS)

Androniuk, Iuliia; Landesman, Catherine; Henocq, Pierre; Kalinichev, Andrey G.

2017-06-01

As a first step in developing better molecular scale understanding of the effects of organic additives on the adsorption and mobility of radionuclides in cement under conditions of geological nuclear waste repositories, two complementary approaches, wet chemistry experiments and molecular dynamics (MD) computer simulations, were applied to study the sorption behaviour of two simple model systems: gluconate and uranyl on calcium silicate hydrate phases (C-S-H) - the principal mineral component of hardened cement paste (HCP). Experimental data on sorption and desorption kinetics and isotherms of adsorption for gluconate/C-S-H and U(VI)/C-S-H binary systems were collected and quantitatively analysed for C-S-H samples synthesised with various Ca/Si ratios (0.83, 1.0, 1.4) corresponding to various stages of HCP aging and degradation. Gluconate labelled with 14C isotope was used in order to improve the sensitivity of analytical detection technique (LSC) at particularly low concentrations (10-8-10-5 mol/L). There is a noticeable effect of Ca/Si ratio on the gluconate sorption on C-S-H, with stronger sorption at higher Ca/Si ratios. Sorption of organic anions on C-S-H is mediated by the presence of Ca2+ at the interface and strongly depends on the surface charge and Ca2+ concentration. In parallel, classical MD simulations of the same model systems were performed in order to identify specific surface sorption sites most actively involved in the sorption of gluconate and uranyl on C-S-H and to clarify molecular mechanisms of adsorption.

Synthesis and Fluorescence Properties of Structurally Characterized Heterobimetalic Cu(II)⁻Na(I) Bis(salamo)-Based Complex Bearing Square Planar, Square Pyramid and Triangular Prism Geometries of Metal Centers.

PubMed

Dong, Xiu-Yan; Zhao, Qing; Wei, Zhi-Li; Mu, Hao-Ran; Zhang, Han; Dong, Wen-Kui

2018-04-25

A novel heterotrinuclear complex [Cu₂(L)Na( µ -NO₃)]∙CH₃OH∙CHCl₃ derived from a symmetric bis(salamo)-type tetraoxime H₄L having a naphthalenediol unit, was prepared and structurally characterized via means of elemental analyses, UV-Vis, FT-IR, fluorescent spectra and single-crystal X-ray diffraction. The heterobimetallic Cu(II)⁻Na(I) complex was acquired via the reaction of H₄L with 2 equivalents of Cu(NO₃)₂·2H₂O and 1 equivalent of NaOAc. Clearly, the heterotrinuclear Cu(II)⁻Na(I) complex has a 1:2:1 ligand-to-metal (Cu(II) and Na(I)) ratio. X-ray diffraction results exhibited the different geometric behaviors of the Na(I) and Cu(II) atoms in the heterotrinuclear complex; the both Cu(II) atoms are sited in the N₂O₂ coordination environments of fully deprotonated (L) 4− unit. One Cu(II) atom (Cu1) is five-coordinated and possesses a geometry of slightly distorted square pyramid, while another Cu(II) atom (Cu2) is four-coordination possessing a square planar coordination geometry. Moreover, the Na(I) atom is in the O₆ cavity and adopts seven-coordination with a geometry of slightly distorted single triangular prism. In addition, there are abundant supramolecular interactions in the Cu(II)⁻Na(I) complex. The fluorescence spectra showed the Cu(II)⁻Na(I) complex possesses a significant fluorescent quenching and exhibited a hypsochromic-shift compared with the ligand H₄L.

Carbonate formation within a nickel dimer: synthesis of a coordinatively unsaturated bis(mu-hydroxo) dinickel complex and its reactivity toward carbon dioxide.

PubMed

Wikstrom, Jeffrey P; Filatov, Alexander S; Mikhalyova, Elena A; Shatruk, Michael; Foxman, Bruce M; Rybak-Akimova, Elena V

2010-03-14

The tridentate aminopyridine ligand bearing a bulky tert-butyl substituent at the amine nitrogen, tert-butyl-dipicolylamine (tBuDPA), occupies three coordination sites in six-coordinate complexes of nickel(ii), leaving the remaining three sites available for additional ligand binding and activation. New crystallographically characterized complexes include two mononuclear species with 1:1 metal:ligand complexation: a trihydrate solvate (1.3H(2)O) and a monohydrate biacetonitrile solvate (1.H(2)O.2CH(3)CN). Complexation in the presence of sodium hydroxide results in a bis(mu-hydroxo) complex (2), the bridging hydroxide anions of which are labile and become displaced by methoxide anions in methanol solvent, affording bis-methoxo-bridged (4). Nickel(II) centers in 2 are five-coordinate and antiferromagnetically coupled (with J = -31.4(5) cm(-1), H = -2JS(1)S(2), in agreement with Ni-O-Ni angle of 103.7 degrees). Bridging hydroxide or alkoxide anions in coordinatively unsaturated dinuclear nickel(II) complexes with tBuDPA react as active nucleophiles. 2 readily performs carbon dioxide fixation, resulting in the formation of a bis(mu-carbonato) tetrameric complex (3), which features a novel binding geometry in the form of an inverted butterfly-type nickel-carbonate core. Temperature-dependent magnetic measurements of tetranuclear carbonato-bridged revealed relatively weak antiferromagnetic coupling (J(1) = -3.1(2) cm(-1)) between the two nickel centers in the core of the cluster, as well as weak antiferromagnetic pairwise interactions (J(2) = J(3) = -4.54(5) cm(-1)) between central and terminal nickel ions.

DNA/RNA binding and anticancer/antimicrobial activities of polymer-copper(II) complexes

NASA Astrophysics Data System (ADS)

Lakshmipraba, Jagadeesan; Arunachalam, Sankaralingam; Riyasdeen, Anvarbatcha; Dhivya, Rajakumar; Vignesh, Sivanandham; Akbarsha, Mohammad Abdulkader; James, Rathinam Arthur

2013-05-01

Water soluble polymer-copper(II) complexes with various degrees of coordination in the polymer chain were synthesized and characterized by elemental analysis, IR, UV-visible and EPR spectra. The DNA/RNA binding behavior of these polymer-copper(II) complexes was examined by UV-visible absorption, emission and circular dichroism spectroscopic methods, and cyclic voltammetry techniques. The binding of the polymer-copper(II) complexes with DNA/RNA was mainly through intercalation but some amount of electrostatic interaction was also observed. This binding capacity increased with the degree of coordination of the complexes. The polymer-copper(II) complex having the highest degree of coordination was subjected to analysis of cytotoxic and antimicrobial properties. The cytotoxicity study indicated that the polymer-copper(II) complexes affected the viability of MCF-7 mammary carcinoma cells, and the cells responded to the treatment with mostly through apoptosis although a few cells succumbed to necrosis. The antimicrobial screening showed activity against some human pathogens.

Zn and Fe complexes containing a redox active macrocyclic biquinazoline ligand.

PubMed

Banerjee, Priyabrata; Company, Anna; Weyhermüller, Thomas; Bill, Eckhard; Hess, Corinna R

2009-04-06

A series of iron and zinc complexes has been synthesized, coordinated by the macrocyclic biquinazoline ligand, 2-4:6-8-bis(3,3,4,4-tetramethyldihydropyrrolo)-10-15-(2,2'-biquinazolino)-[15]-1,3,5,8,10,14-hexaene-1,3,7,9,11,14-N(6) (Mabiq). The Mabiq ligand consists of a bipyrimidine moiety and two dihydropyrrole units. The electronic structures of the metal-Mabiq complexes have been characterized using spectroscopic and density-functional theory (DFT) computational methods. The parent zinc complex exhibits a ligand-centered reduction to generate the metal-coordinated Mabiq radical dianion, establishing the redox non-innocence of this ligand. Iron-Mabiq complexes have been isolated in three oxidation states. This redox series includes low-spin ferric and low-spin ferrous species, as well as an intermediate-spin Fe(II) compound. In the latter complex, the iron ion is antiferromagnetically coupled to a Mabiq-centered pi-radical. The results demonstrate the rich redox chemistry and electronic properties of metal complexes coordinated by the Mabiq ligand.

Evolutionary dynamics of the traveler's dilemma and minimum-effort coordination games on complex networks.

PubMed

Iyer, Swami; Killingback, Timothy

2014-10-01

The traveler's dilemma game and the minimum-effort coordination game are social dilemmas that have received significant attention resulting from the fact that the predictions of classical game theory are inconsistent with the results found when the games are studied experimentally. Moreover, both the traveler's dilemma and the minimum-effort coordination games have potentially important applications in evolutionary biology. Interestingly, standard deterministic evolutionary game theory, as represented by the replicator dynamics in a well-mixed population, is also inadequate to account for the behavior observed in these games. Here we study the evolutionary dynamics of both these games in populations with interaction patterns described by a variety of complex network topologies. We investigate the evolutionary dynamics of these games through agent-based simulations on both model and empirical networks. In particular, we study the effects of network clustering and assortativity on the evolutionary dynamics of both games. In general, we show that the evolutionary behavior of the traveler's dilemma and minimum-effort coordination games on complex networks is in good agreement with that observed experimentally. Thus, formulating the traveler's dilemma and the minimum-effort coordination games on complex networks neatly resolves the paradoxical aspects of these games.

Evolutionary dynamics of the traveler's dilemma and minimum-effort coordination games on complex networks

NASA Astrophysics Data System (ADS)

Iyer, Swami; Killingback, Timothy

2014-10-01

The traveler's dilemma game and the minimum-effort coordination game are social dilemmas that have received significant attention resulting from the fact that the predictions of classical game theory are inconsistent with the results found when the games are studied experimentally. Moreover, both the traveler's dilemma and the minimum-effort coordination games have potentially important applications in evolutionary biology. Interestingly, standard deterministic evolutionary game theory, as represented by the replicator dynamics in a well-mixed population, is also inadequate to account for the behavior observed in these games. Here we study the evolutionary dynamics of both these games in populations with interaction patterns described by a variety of complex network topologies. We investigate the evolutionary dynamics of these games through agent-based simulations on both model and empirical networks. In particular, we study the effects of network clustering and assortativity on the evolutionary dynamics of both games. In general, we show that the evolutionary behavior of the traveler's dilemma and minimum-effort coordination games on complex networks is in good agreement with that observed experimentally. Thus, formulating the traveler's dilemma and the minimum-effort coordination games on complex networks neatly resolves the paradoxical aspects of these games.

Coordination of a complex welfare system case: rehabilitation entity in Finland.

PubMed

Miettinen, Sari; Ashorn, Ulla; Lehto, Juhani; Viitanen, Elina

2011-01-01

The main purpose of this article is to analyse the institutional and political structures of the Finnish rehabilitation entity and the governmental efforts to improve the governance of the rehabilitation policy. Rehabilitation in Finland is a complex welfare system which has undergone several coordination attempts during the last two decades. The centrality of the coordination of this welfare system is obvious. Based on the content analysis of three Government's rehabilitation reports from 1994 to 2002 and their background papers, this article provides two main findings. First, the rehabilitation entity seems to be based on different funding strategies, different governing and different coordination models between the rehabilitation subsystems. Second, the governance discourse in the reports seems to be unchanging with a predominantly hierarchical mode. The article concludes with a discussion on the challenges to coordinate this kind of a complex welfare system as an entity and also how to overcome those challenges. Copyright © 2010 John Wiley & Sons, Ltd.

Generalization of the Activated Complex Theory of Reaction Rates. I. Quantum Mechanical Treatment

DOE R&D Accomplishments Database

Marcus, R. A.

1964-01-01

In its usual form activated complex theory assumes a quasi-equilibrium between reactants and activated complex, a separable reaction coordinate, a Cartesian reaction coordinate, and an absence of interaction of rotation with internal motion in the complex. In the present paper a rate expression is derived without introducing the Cartesian assumption. The expression bears a formal resemblance to the usual one and reduces to it when the added assumptions of the latter are introduced.

Supramolecular complexes of Co(II), Ni(II) and Zn(II) p-hydroxybenzoates with caffeine: Synthesis, spectral characterization and crystal structure

NASA Astrophysics Data System (ADS)

Taşdemir, Erdal; Özbek, Füreya Elif; Sertçelik, Mustafa; Hökelek, Tuncer; Çelik, Raziye Çatak; Necefoğlu, Hacali

2016-09-01

Three novel complexes Co(II), Ni(II) and Zn(II) containing p-hydroxybenzoates and caffeine ligands were synthesized and characterized by elemental analysis, FT-IR and UV-vis Spectroscopy, molar conductivity and single crystal X-ray diffraction methods. The thermal properties of the synthesized complexes were investigated by TGA/DTA. The general formula of the complexes is [M(HOC6H4COO)2(H2O)4]·2(C8H10N4O2)·8H2O (where: M: Co, Ni and Zn). The IR studies showed that carboxylate groups of p-hydroxybenzoate ligands have monodentate coordination mode. The M2+ ions are octahedrally coordinated by two p-hydroxybenzoate ligands, four water molecules leading to an overall MO6 coordination environment. The medium-strength hydrogen bondings involving the uncoordinated caffeine ligands and water molecules, coordinated and uncoordinated water molecules and p-hydroxybenzoate ligands lead to three-dimensional supramolecular networks in the crystal structures.

2-and 1-D coordination polymers of Dy(III) and Ho(III) with near infrared and visible luminescence by efficient charge-transfer antenna ligand

NASA Astrophysics Data System (ADS)

Oylumluoglu, Gorkem; Coban, Mustafa Burak; Kocak, Cagdas; Aygun, Muhittin; Kara, Hulya

2017-10-01

Two new lanthanide-based coordination complexes, [Dy(2-stp).2(H2O)]n (1) and {[Ho(2-stp).3(H2O)]·(H2O)}n (2) [2-stp = 2-sulfoterephthalic acid] were synthesized by hydrothermal reaction and characterized by elemental analysis, UV, IR, single crystal X-ray diffraction and solid state photoluminescence. DyIII and HoIII atoms are eight-coordinated and adopt a distorted square-antiprismatic geometry in complexes 1 and 2, respectively. In compound 1, Dy atoms are coordinated by four bridging 2-stp ligands forming two-dimensional (2D) layer, while Ho atoms by three bridging 2-stp ligands creating one dimensional (1D) double chains in 2. In addition, complexes 1 and 2 display in the solid state and at room temperature an intense yellow emission, respectively; this photoluminescence is achieved by an indirect process (antenna effect). The excellent luminescent performances make these complexes very good candidates for potential luminescence materials.