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Sample records for uranium vi complexes

  1. Method of purifying uranium tetrafluoride hydrate and preparing uranium (VI) peroxide hydrate using a fluoride complexing agent

    International Nuclear Information System (INIS)

    Barreiro, A.J.; Lowe, C.M.T.; Lefever, J.A.; Pyman, R.L.

    1983-01-01

    The annual production of phosphate rock, on the order of about 30-40 million tons yearly, represents several million pounds of uranium. The present invention provides a process of purifying uranium tetrafluoride hydrate to produce a uranium (VI) peroxide product meeting 'yellow cake' standards using a double precipitation procedure. A fluoride complexing agent is used in the precipitation

  2. A coupled mass transfer and surface complexation model for uranium (VI) removal from wastewaters

    International Nuclear Information System (INIS)

    Lenhart, J.; Figueroa, L.A.; Honeyman, B.D.

    1994-01-01

    A remediation technique has been developed for removing uranium (VI) from complex contaminated groundwater using flake chitin as a biosorbent in batch and continuous flow configurations. With this system, U(VI) removal efficiency can be predicted using a model that integrates surface complexation models, mass transport limitations and sorption kinetics. This integration allows the reactor model to predict removal efficiencies for complex groundwaters with variable U(VI) concentrations and other constituents. The system has been validated using laboratory-derived kinetic data in batch and CSTR systems to verify the model predictions of U(VI) uptake from simulated contaminated groundwater

  3. Bioreduction of Uranium(VI) Complexed with Citric Acid by Clostridia Affects its Structure and Mobility

    International Nuclear Information System (INIS)

    Francis, A.; Dodge, C.

    2008-01-01

    Uranium contamination of the environment from mining and milling operations, nuclear-waste disposal, and ammunition use is a widespread global problem. Natural attenuation processes such as bacterial reductive precipitation and immobilization of soluble uranium is gaining much attention. However, the presence of naturally occurring organic ligands can affect the precipitation of uranium. Here, we report that the anaerobic spore-forming bacteria Clostridia, ubiquitous in soils, sediments, and wastes, capable of reduction of Fe(III) to Fe(II), Mn(IV) to Mn(II), U(VI) to U(IV), Pu(IV) to Pu(III), and Tc(VI) to Tc(IV); reduced U(VI) associated with citric acid in a dinuclear 2:2 U(VI):citric acid complex to a biligand mononuclear 1:2 U(IV):citric acid complex, which remained in solution, in contrast to reduction and precipitation of uranium. Our findings show that U(VI) complexed with citric acid is readily accessible as an electron acceptor despite the inability of the bacterium to metabolize the complexed organic ligand. Furthermore, it suggests that the presence of organic ligands at uranium-contaminated sites can affect the mobility of the actinide under both oxic and anoxic conditions by forming such soluble complexes.

  4. Spectroscopic Confirmation of Uranium (VI)-Carbonato Adsorption Complexes on Hematite

    International Nuclear Information System (INIS)

    Bargar, John R

    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 FeO surface -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

  5. Spectroscopic confirmation of uranium(VI)-carbonato adsorption complexes on hematite

    Science.gov (United States)

    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 carbonato complexes may be of major importance to the groundwater transport of similar actinide contaminants such as neptunium and plutonium.

  6. Extraction of uranium (VI) sulphate complexes by Adogen amines

    Energy Technology Data Exchange (ETDEWEB)

    Elyamani, I S; Abd Elmessieh, E N [Nuclear chemistry department, hot laboratories center, atomic energy authority, Cairo, (Egypt)

    1995-10-01

    The distribution of U(VI) between aqueous H{sub 2} So{sub 4} solutions and organic phases of adogen-368 has been described. The dependence of extraction on acidity, diluent type, metal and extractant concentrations was investigated. The possible extraction mechanism is discussed in the light of results obtained. The separation of U(VI) from rare earths is suggested. 5 figs., 1 tab.

  7. Synthesis, characterization, and reactivity of a uranium(VI) carbene imido oxo complex

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Erli; Cooper, Oliver J.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T. [Nottingham Univ. (United Kingdom). School of Chemistry; Tuna, Floriana; McInnes, Eric J.L. [Manchester Univ. (United Kingdom). School of Chemistry and Photon Science Inst.

    2014-06-23

    We report the uranium(VI) carbene imido oxo complex [U(BIPM{sup TMS})(NMes)(O)(DMAP){sub 2}] (5, BIPM{sup TMS}=C(PPh{sub 2}NSiMe{sub 3}){sub 2}; Mes=2,4,6-Me{sub 3}C{sub 6}H{sub 2}; DMAP=4-(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two-electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T-shaped motif with respect to the carbene, which is consistent with an inverse trans-influence. Complex 5 reacts with tert-butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPM{sup TMS})(O){sub 2}(DMAP){sub 2}] (6).

  8. Synthesis, characterization, and reactivity of a uranium(VI) carbene imido oxo complex

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Erli; Cooper, Oliver J.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T. [School of Chemistry, University of Nottingham (United Kingdom); Tuna, Floriana; McInnes, Eric J.L. [School of Chemistry and Photon Science Institute, University of Manchester (United Kingdom)

    2014-06-23

    We report the uranium(VI) carbene imido oxo complex [U(BIPM{sup TMS})(NMes)(O)(DMAP){sub 2}] (5, BIPM{sup TMS}=C(PPh{sub 2}NSiMe{sub 3}){sub 2}; Mes=2,4,6-Me{sub 3}C{sub 6}H{sub 2}; DMAP=4-(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two-electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T-shaped motif with respect to the carbene, which is consistent with an inverse trans-influence. Complex 5 reacts with tert-butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPM{sup TMS})(O){sub 2}(DMAP){sub 2}] (6). (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Complex formation between uranium(VI) and α-D-glucose 1-phosphate

    International Nuclear Information System (INIS)

    Koban, A.; Geipel, G.; Bernhard, G.

    2003-01-01

    The complex formation of uranium(VI) with α-D-glucose 1-phosphate (C 6 H 11 O 6 PO 3 2- , G1P) was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at pH 4 and potentiometric titration in the pH range from 3 to 10. Both measurements show the formation of a 1 : 1 complex at lower pH values. The formation constant of UO 2 (C 6 H 11 O 6 PO 3 ) was calculated from TRLFS measurements to be log β 11 = 5.72±0.12, and from potentiometric titration log β 11 = 5.40±0.25, respectively. It was found by potentiometric titration that at higher pH values the complexation changes to a 1 : 2 complex. The stability constant for this complex was calculated to be log β 12 = 8.96±0.18. (orig.)

  10. Sorption of uranium (VI) on homoionic sodium smectite experimental study and surface complexation modeling.

    Science.gov (United States)

    Korichi, Smain; Bensmaili, Aicha

    2009-09-30

    This paper is an extension of a previous paper where the natural and purified clay in the homoionic Na form were physico-chemically characterized (doi:10.1016/j.clay.2008.04.014). In this study, the adsorption behavior of U (VI) on a purified Na-smectite suspension is studied using batch adsorption experiments and surface complexation modeling (double layer model). The sorption of uranium was investigated as a function of pH, uranium concentration, solid to liquid ratio, effect of natural organic matter (NOM) and NaNO(3) background electrolyte concentration. Using the MINTEQA2 program, the speciation of uranium was calculated as a function of pH and uranium concentration. Model predicted U (VI) aqueous speciation suggests that important aqueous species in the [U (VI)]=1mg/L and pH range 3-7 including UO(2)(2+), UO(2)OH(+), and (UO(2))(3)(OH)(5)(+). The concentration of UO(2)(2+) decreased and that of (UO(2))(3)(OH)(5)(+) increased with increasing pH. The potentiometric titration values and uptake of uranium in the sodium smectite suspension were simulated by FITEQL 4.0 program using a two sites model, which is composed of silicate and aluminum reaction sites. We compare the acidity constants values obtained by potentiometric titration from the purified sodium smectite with those obtained from single oxides (quartz and alpha-alumina), taking into account the surface heterogeneity and the complex nature of natural colloids. We investigate the uranium sorption onto purified Na-smectite assuming low, intermediate and high edge site surfaces which are estimated from specific surface area percentage. The sorption data is interpreted and modeled as a function of edge site surfaces. A relationship between uranium sorption and total site concentration was confirmed and explained through variation in estimated edge site surface value. The modeling study shows that, the convergence during DLM modeling is related to the best estimation of the edge site surface from the N(2

  11. Characterization of the sorption of uranium(VI) on different complexing resins

    International Nuclear Information System (INIS)

    Pesavento, Maria; Biesuz, Raffaela; Alberti, Giancarla; Sturini, Michela

    2003-01-01

    The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with logβ 110i =-1.16, in more acidic solution, and ML 2 with log β 120i =-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML 2 , in more acidic solution, with log β 120i =-3.16. In the presence of the ligand EDTA, the complex ML 2 (OH) 2 was characterized with log β 12-2i =-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)

  12. Uranium (VI) complexing by macrocyclic or chelating ligands in aqueous solutions stability, formation kinetics, polarographic properties

    International Nuclear Information System (INIS)

    Brighli, M.

    1984-07-01

    Stability of chelates (with EDTA,N,N ethylenediamine diacetic acid EDDA nitrilotriacetic acid NTA and iminodiacetic acid) of UO 2 2+ and UO 4 species of uranium VI is studied in aqueous solution (NaClO 4 3M at 25 deg celcius). Structure in solution are proposed and discussed for mononuclear species. Only complexing kinetics (formation and acid hydrolysis) of UO 4 with EDDA and NTA are studied by spectrophotometry (other reactions are too fast). Besides UO 2 2+ complexes are formed with crown ethers I5C5 and I8C6 in aqueous solution (TEA ClO 4 M/10 at 25 deg celcius. Complexes are probably stabilized by solvation. Results are confirmed by voltametry and reduction mechanisms of UO 2 2+ and its complexes on mercury drop are proposed. 143 refs [fr

  13. Peroxo complexes of molybdenum(VI), tungsten(VI), uranium(VI), zirconium(IV) and thorium(IV) ions containing tridentate Schiff bases derived from salicylaldehyde and amino acids

    International Nuclear Information System (INIS)

    Tarafder, M.T.H.; Khan, A.R.

    1997-01-01

    The synthesis of peroxo complexes of molybdenum(VI), tungsten(VI), uranium(VI), zirconium(IV), thorium(IV) and their possible oxygen transfer reactions is presented. An attempt has also been made to study the size of the metal ions and the electronic effect derived from the tridentate Schiff bases on the v 1 (O-O) mode of the complexes in their IR spectra

  14. Approaches to surface complexation modeling of Uranium(VI) adsorption on aquifer sediments

    Science.gov (United States)

    Davis, J.A.; Meece, D.E.; Kohler, M.; Curtis, G.P.

    2004-01-01

    Uranium(VI) adsorption onto aquifer sediments was studied in batch experiments as a function of pH and U(VI) and dissolved carbonate concentrations in artificial groundwater solutions. The sediments were collected from an alluvial aquifer at a location upgradient of contamination from a former uranium mill operation at Naturita, Colorado (USA). The ranges of aqueous chemical conditions used in the U(VI) adsorption experiments (pH 6.9 to 7.9; U(VI) concentration 2.5 ?? 10-8 to 1 ?? 10-5 M; partial pressure of carbon dioxide gas 0.05 to 6.8%) were based on the spatial variation in chemical conditions observed in 1999-2000 in the Naturita alluvial aquifer. The major minerals in the sediments were quartz, feldspars, and calcite, with minor amounts of magnetite and clay minerals. Quartz grains commonly exhibited coatings that were greater than 10 nm in thickness and composed of an illite-smectite clay with occluded ferrihydrite and goethite nanoparticles. Chemical extractions of quartz grains removed from the sediments were used to estimate the masses of iron and aluminum present in the coatings. Various surface complexation modeling approaches were compared in terms of the ability to describe the U(VI) experimental data and the data requirements for model application to the sediments. Published models for U(VI) adsorption on reference minerals were applied to predict U(VI) adsorption based on assumptions about the sediment surface composition and physical properties (e.g., surface area and electrical double layer). Predictions from these models were highly variable, with results overpredicting or underpredicting the experimental data, depending on the assumptions used to apply the model. Although the models for reference minerals are supported by detailed experimental studies (and in ideal cases, surface spectroscopy), the results suggest that errors are caused in applying the models directly to the sediments by uncertain knowledge of: 1) the proportion and types of

  15. Characterization of the sorption of uranium(VI) on different complexing resins

    Energy Technology Data Exchange (ETDEWEB)

    Pesavento, Maria; Biesuz, Raffaela; Alberti, Giancarla; Sturini, Michela [Dipartimento di Chimica Generale dell' Universita degli Studi di Pavia, Via Taramelli 12, 27100, Pavia (Italy)

    2003-08-01

    The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with log{beta}{sub 110i}=-1.16, in more acidic solution, and ML{sub 2}with log {beta}{sub 120i}=-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML {sub 2}, in more acidic solution, with log {beta}{sub 120i}=-3.16. In the presence of the ligand EDTA, the complex ML {sub 2}(OH) {sub 2}was characterized with log {beta}{sub 12-2i}=-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)

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

    Science.gov (United States)

    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.

  17. Ternary uranium(VI) carbonato humate complex studied by cryo-TRLFS

    International Nuclear Information System (INIS)

    Steudtner, R.; Sachs, S.; Schmeide, K.; Brendler, V.; Bernhard, G.

    2011-01-01

    The complex formation of U(VI) with humic acid (HA) in the presence of carbonate was studied by time-resolved laser-induced fluorescence spectroscopy at low temperature (cryo-TRLFS) at pH 8.5. In the presence of HA, a decrease of the luminescence intensity of U(VI) and no shift of the emission band maxima in comparison to the luminescence spectrum of the UO 2 (CO 3 ) 3 4- complex, the dominating U(VI) species under the applied experimental conditions in the absence of HA, was observed. The formation of a ternary U(VI) carbonato humate complex of the type UO 2 (CO 3 ) 2 HA(II) 4- starting from UO 2 (CO 3 ) 3 4- was concluded from the luminescence data. For this complex a complex stability constant of log K=2.83 ± 0.17 was determined. Slope analysis resulted in a slope of 1.12 ± 0.11, which verifies the postulated complexation reaction. The results agree very well with literature data. Speciation calculations show that the formation of the ternary U(VI) carbonato humate complex can significantly influence the U(VI) speciation under environmental conditions. (orig.)

  18. Ternary uranium(VI) carbonato humate complex studied by cryo-TRLFS

    Energy Technology Data Exchange (ETDEWEB)

    Steudtner, R.; Sachs, S.; Schmeide, K.; Brendler, V.; Bernhard, G. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany). Inst. of Radiochemistry

    2011-07-01

    The complex formation of U(VI) with humic acid (HA) in the presence of carbonate was studied by time-resolved laser-induced fluorescence spectroscopy at low temperature (cryo-TRLFS) at pH 8.5. In the presence of HA, a decrease of the luminescence intensity of U(VI) and no shift of the emission band maxima in comparison to the luminescence spectrum of the UO{sub 2}(CO{sub 3}){sub 3}{sup 4-} complex, the dominating U(VI) species under the applied experimental conditions in the absence of HA, was observed. The formation of a ternary U(VI) carbonato humate complex of the type UO{sub 2}(CO{sub 3}){sub 2}HA(II){sup 4-} starting from UO{sub 2}(CO{sub 3}){sub 3}{sup 4-} was concluded from the luminescence data. For this complex a complex stability constant of log K=2.83 {+-} 0.17 was determined. Slope analysis resulted in a slope of 1.12 {+-} 0.11, which verifies the postulated complexation reaction. The results agree very well with literature data. Speciation calculations show that the formation of the ternary U(VI) carbonato humate complex can significantly influence the U(VI) speciation under environmental conditions. (orig.)

  19. Surface complexation modeling of the effects of phosphate on uranium(VI) adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Romero-Gonzalez, M.R.; Cheng, T.; Barnett, M.O. [Auburn Univ., AL (United States). Dept. of Civil Engeneering; Roden, E.E. [Wisconsin Univ., Madison, WI (United States). Dept. of Geology and Geophysics

    2007-07-01

    Previous published data for the adsorption of U(VI) and/or phosphate onto amorphous Fe(III) oxides (hydrous ferric oxide, HFO) and crystalline Fe(III) oxides (goethite) was examined. These data were then used to test the ability of a commonly-used surface complexation model (SCM) to describe the adsorption of U(VI) and phosphate onto pure amorphous and crystalline Fe(III) oxides and synthetic goethite-coated sand, a surrogate for a natural Fe(III)-coated material, using the component additivity (CA) approach. Our modeling results show that this model was able to describe U(VI) adsorption onto both amorphous and crystalline Fe(III) oxides and also goethite-coated sand quite well in the absence of phosphate. However, because phosphate adsorption exhibits a stronger dependence on Fe(III) oxide type than U(VI) adsorption, we could not use this model to consistently describe phosphate adsorption onto both amorphous and crystalline Fe(III) oxides and goethite-coated sand. However, the effects of phosphate on U(VI) adsorption could be incorporated into the model to describe U(VI) adsorption to both amorphous and crystalline Fe(III) oxides and goethite-coated sand, at least for an initial approximation. These results illustrate both the potential and limitations of using surface complexation models developed from pure systems to describe metal/radionuclide adsorption under more complex conditions. (orig.)

  20. Surface complexation modeling of the effects of phosphate on uranium(VI) adsorption

    International Nuclear Information System (INIS)

    Romero-Gonzalez, M.R.; Cheng, T.; Barnett, M.O.; Roden, E.E.

    2007-01-01

    Previous published data for the adsorption of U(VI) and/or phosphate onto amorphous Fe(III) oxides (hydrous ferric oxide, HFO) and crystalline Fe(III) oxides (goethite) was examined. These data were then used to test the ability of a commonly-used surface complexation model (SCM) to describe the adsorption of U(VI) and phosphate onto pure amorphous and crystalline Fe(III) oxides and synthetic goethite-coated sand, a surrogate for a natural Fe(III)-coated material, using the component additivity (CA) approach. Our modeling results show that this model was able to describe U(VI) adsorption onto both amorphous and crystalline Fe(III) oxides and also goethite-coated sand quite well in the absence of phosphate. However, because phosphate adsorption exhibits a stronger dependence on Fe(III) oxide type than U(VI) adsorption, we could not use this model to consistently describe phosphate adsorption onto both amorphous and crystalline Fe(III) oxides and goethite-coated sand. However, the effects of phosphate on U(VI) adsorption could be incorporated into the model to describe U(VI) adsorption to both amorphous and crystalline Fe(III) oxides and goethite-coated sand, at least for an initial approximation. These results illustrate both the potential and limitations of using surface complexation models developed from pure systems to describe metal/radionuclide adsorption under more complex conditions. (orig.)

  1. Extraction of Uranium (VI) Nitrate Complexes By Adogen 464. Vol. 3

    International Nuclear Information System (INIS)

    El-Yamani, I.S.; Abd El-Messieh, E.N.

    1996-01-01

    Long-chain amines are frequently used for the extraction of actinides and offer several advantages for their use in the reprocessing of high burn-up nuclear fuels. The present investigation was undertaken to obtain some information on the extraction of Uranium (VI)by adogen 464 from nitrate medium. Extraction parameters studied include: acidity, salting agent, metal and extractant concentrations, diluent type, and temperature. Extraction mechanism was proposed on the basis of results obtained. Best results were attained at 6 M H N O 3 and sodium nitrate was found to increase appreciably the extraction. It was infrared that extraction was dominated by solvation, and ion exchange reaction mechanisms at lower (<6 M) and higher acidities, respectively. As far as diluents are concerned, the dielectric constant, solvation power and donor characteristics were used to explain the variation in the extraction efficiency of the diluents. Kerosene, the most economic particularly when used on industrial scale, was recommended as optimal diluent. Extractability decreases markedly with rise of temperature, suggesting that the extraction behaviour is exothermic; the thermodynamic functions were also calculated and discussed. A method for the separation of uranium (VI) from some fission products existing in high liquid waste was outlined. 3 figs., 2 tabs

  2. Electronic structure, fluorescence and photochemistry of the uranyl ion, and comparison with octahedral uranium (VI), ruthenyl (VI), rhenium (V) and osmium (VI) complexes

    Energy Technology Data Exchange (ETDEWEB)

    Joergensen, C K [Geneva Univ. (Switzerland)

    1977-01-01

    The highly anisotropic uranyl complexes (with very short U-O distances and very long distances to the ligating atoms in the equatorial plane) are compared with trans-dioxo complexes of 4d/sup 2/Ru(VI) and 5d/sup 2/Re(V) and Os(VI). A major difference is the low-lying empty 5f orbitals, and the first excited state is highly oxidizing, and sufficiently long-lived to abstract hydrogen atoms from most organic molecules. It is argued that even the low concentrations of uranyl carbonate present in sea water is excited by solar radiation roughly every 10 minutes. Octahedral U(VI)O/sub 6/ in perovskites and UF/sub 6/ are also discussed, as well as trans-lawrencium chemistry.

  3. Spectrophotometric study of the complexation equilibria of uranium(VI) with 1,4-bis(4'-methylanilino)anthraquinone and determination of uranium(VI)

    International Nuclear Information System (INIS)

    Idriss, K.A.; Seleim, M.M.; Abu-Bakr, M.S.; Sedaira, H.

    1985-01-01

    The reaction of U(VI) with 1,4-bis(4'-methylanilino)anthraquinone (quinizarin green) in water-dimethylformamide medium was investigated spectrophotometrically. The complexation equilibria in solution were demonstrated. The study of the reaction in presence of equimolar concentrations or in solutions containing metal or ligand excess gave evidence for the formation of complexes with stoichiometric ratios of UO 2 :L = 1:1 and 1:2 in dependence on the pH of the medium. Their thermodynamic stabilities and the values of their molar absorption coefficients were determined. The optimum conditions for spectrophotometric determination of U(VI) with this reagent were found. (author)

  4. Surface complexation modeling of uranium (Vi) retained onto zirconium diphosphate in presence of organic acids

    International Nuclear Information System (INIS)

    Almazan T, M. G.; Garcia G, N.; Ordonez R, E.

    2010-10-01

    In the field of nuclear waste disposal, predictions regarding radionuclide migration through the geosphere, have to take account the effects of natural organic matter. This work presents an investigation of interaction mechanisms between U (Vi) and zirconium diphosphate (ZrP 2 O 7 ) in presence of organic acids (citric acid and oxalic acid). The retention reactions were previously examined using a batch equilibrium method. Previous results showed that U (Vi) retention was more efficient when citric acid or oxalic acid was present in solid surface at lower ph values. In order to determine the retention equilibria for both systems studied, a phosphorescence spectroscopy study was carried out. The experimental data were then fitted using the Constant Capacitance Model included in the FITEQL4.0 code. Previous results concerning surface characterization of ZrP 2 O 7 (surface sites density and surface acidity constants) were used to constraint the modeling. The best fit for U (Vi)/citric acid/ZrP 2 O 7 and U (Vi)/oxalic acid/ZrP 2 O 7 systems considered the formation of a ternary surface complex. (Author)

  5. Effect of denaturants on the speciation of uranium(VI) complexes of malonic acid in micellar media

    International Nuclear Information System (INIS)

    Sailaja, B.B.V.; Kebede, Tesfahun; Nageswara Rao, G.; Prasada Rao, M.S.

    2001-01-01

    A computer assisted investigation has been made on the nature of complexes of uranium(VI) with malonic acid. The formation constants have been determined experimentally by monitoring hydrogen ion concentration. The distribution of the metal ion amongst the complexes formed with the above carboxylic acid has also been computed. The formation constants have been refined with the computer program, MINIQUAD75 using the primary alkalimetric data. The predominant complexes formed are UO 2 (H 2 C 3 O 4 ) 2 ) 2- , UO 2 (H 2 C 3 O 4 ) and UO 2 (H 2 C 3 O 4 )(H 2 C 3 O 4 H) - . The distribution pattern of different species varies with the relative concentrations of the metal ion and the ligand. The variation of stability with surfactant concentrations is found to be the cumulative effect of various factors like electrostatic interactions. dilution effect and competition for hydrogen ion associated with the nature of micelles. (author)

  6. Complex formation of uranium(VI) with fructose and glucose phosphates

    International Nuclear Information System (INIS)

    Koban, A.; Geipel, G.; Bernhard, G.; Fanghaenel, T.

    2002-01-01

    The uptake of heavy metals into plants is commonly quantified by the soil-plant transfer factor. Up to now little is known about the chemical speciation of actinides in plants. To compare the obtained spectroscopic data of uranium complexes in plants with model compounds, we investigate the complexation of uranium with relevant bioligands of various functionalities. A very important class of ligands consists of phosphate esters, which serve as phosphate group and energy transmitters as well as energy storage media in biological systems. Heavy metal ions bound to the phosphate esters can be transported into living cells and then deposited. Therefore, in our study we present the results of uranium complexation with glucose-6-phosphate (G6P), and fructose-6-phosphate (F6P) obtained by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The experiments were performed at a fixed uranyl concentration (10 -5 M) as a function of the ligand concentrations (10 -5 to 10 -3 M) in a pH range from 2 to 4.5. For the glucose phosphate system we observed, using increasing ligand concentrations, a decrease in the fluorescence intensity and a small red shift of the emission bands. From this we conclude that the complexed uranyl glucose phosphate species show only minor or no fluorescence properties. The TRLFS spectra of the glucose phosphate samples indicated the presence of a single species with fluorescence properties. This species has a lifetime of approximately 1.5 μs and was identified as the free uranyl ion. An opposite phenomenon was observed for the fructose phosphate system: there was no decrease in fluorescence intensity. However, a strong red shift of the spectra was observed, illustrating the fluorescence properties of the uranyl fructose phosphate complex. The TRLFS spectra of the fructose phosphate system showed a second lifetime ( 2 2+ UO 2 (lig) x (2-y)+ + y H + (lig = sugar phosphate). Applying the mass action law and transformation to the logarithmic

  7. Multisensor system for determination of iron(II), iron(III) and uranium(VI) in complex solutions

    International Nuclear Information System (INIS)

    Legin, A.V.; Seleznev, B.L.; Rudnitskaya, A.M.; Vlasov, Yu.G.

    1998-01-01

    The aim of the present paper is the development and analytical evaluation of a multisensor system for determination of low content of iron(II), iron(III) and uranium(VI) in complex aqueous media. Sensor array included sensors on the basis of chalcogenide vitreous materials with redox and ionic cross-sensitivities, crystalline silver sulphide electrode, noble metal electrodes Pt, Au, Ag and redox sensor on the basis of oxide glass. Potentiometric measurements have been taken in a conventional electrochemical cell vs. a standard Ag/AgCl reference electrode. All measurements have been taken at room temperature. Calibration solutions contained UO 2 (NO 3 ) 2 in concentration range 10 -6 -1,610 -5 mol/L, K 3 Fe(CN) 6 and K 4 Fe(CN) 6 or FeSO 4 (NH 4 ) 2 SO 4 and FeCl 3 , with the ratio of Fe(II)/Fe(III) concentration from 100:1 to 1:100, the total concentration of Fe was 10 -4 and 10 -5 mol/L. All solutions have been made on the background electrolyte of calcium and magnesium chlorides and sulphates with the fixed content of 5-27 mmol/L of each component which is a typical one for groundwater or mining water. Sensor potentials have been processed by a back-propagation artificial neural net. Average error of determination of Fe(II) and Fe(III) is about 20 %, of uranium(VI) - 40 %. It was found that sensitivity of the sensor array to iron and uranium is irrespective of the chemical form of these species

  8. Radiochemical investigations to the complex formation of uranium (VI) with silicic acid

    International Nuclear Information System (INIS)

    Hrnecek, E.

    1997-12-01

    The complexation of tracer amounts of UO 2 2+ by silicic acid was investigated by an extraction method using 2,5. 10 -3 M 1-(2-thenoyl)-3,3,3-trifloroacetone (IMA) in benzene as extractant at 25 degree C. The tracer used in the experiments was uranium-232, which has been separated from its daughter nuclides by ion exchange from 10 M HCl on Dowex 1x2. The ionic strength in the aqueous phase for the extractions was kept constant at 0,2 M (Na, H)ClO 4 and the pH was varied between pH 2,5 and pH 4,5. For the determination of the stability constants, a silicic acid concentration of 0,01 M, 0,03 M and 0,067 M in the (Na, H)ClO 4 solution was used. The time- and pH- dependence of the polymerization of these silicic acid solutions was determined by kinetical investigations with an ammoniumheptamolybdate-reagent. The uranium concentration in the aqueous and organic phases was determined by liquid scintillation counting using α/β -discrimination. The stability constants determined were log Q1, = -2,20 for the reaction UO 2 2+ Si(OH) 4 = UO 2 OSi(OH) 3 + + H + and Q 2 = -5,87 for the reaction of the polymeric silicate UO 2 2+ (-SiOH) j (-SiOH) j-2 (SiO) 2 UO 2 +2 H + . The influence of silicate on the speciation calculations for uranium in a model natural water is also discussed. (author)

  9. Multisensor system for determination of iron(II), iron(III), uranium(VI) and uranium(IV) in complex solutions

    International Nuclear Information System (INIS)

    Legin, A.V.; Seleznev, B.L.; Rudnitskaya, A.M.; Vlasov, Yu.G.; Tverdokhlebov, S.V.; Mack, B.; Abraham, A.; Arnold, T.; Baraniak, L.; Nitsche, H.

    1999-01-01

    Development and analytical evaluation of a multisensor system based on the principles of 'electronic tongue' for the determination of low contents of uranium(VI), uranium(IV), iron(II) and iron(III) in complex aqueous media have been carried out. A set of 29 different chemical sensors on the basis of all- solid-state crystalline and vitreous materials with enhanced electronic conductivity and redox and ionic cross-sensitivity have been incorporated into the sensor array. Multidimensional data have been processed by pattern recognition methods such as artificial neural networks and partial least squares. It has been demonstrated that Fe(II) and Fe(III) contents in the range from 10 -7 to 10 -4 mol L -1 of total iron concentration can be determined with the average precision of about 25 %. U(VI) and U(IV) contents can been determined with the average precision of 10-40% depending on the concentration. The developed multisensor system can be applied in future for the analysis of mining and borehole waters as well other contaminated natural media, including on-site measurements. (author)

  10. Uranium(VI) sorption on iron oxides in Hanford Site sediment: Application of a surface complexation model

    International Nuclear Information System (INIS)

    Um, Wooyong; Serne, R. Jeffrey; Brown, Christopher F.; Rod, Kenton A.

    2008-01-01

    Sorption of U(VI) on Hanford fine sand (HFS) with varying Fe-oxide (especially ferrihydrite) contents showed that U(VI) sorption increased with the incremental addition of synthetic ferrihydrite into HFS, consistent with ferrihydrite being one of the most reactive U(VI) sorbents present in natural sediments. Surface complexation model (SCM) calculations for U(VI) sorption, using only U(VI) surface-reaction constants obtained from U(VI) sorption data on freshly synthesized ferrihydrite at different pHs, were similar to the measured U(VI) sorption results on pure synthetic ferrihydrite and on HFS with high contents of ferrihydrite (5 wt%) added. However, the SCM prediction using only U(VI) sorption reactions and constants for synthetic ferrihydrite overestimated U(VI) sorption on the natural HFS or HFS with addition of low amounts of added ferrihydrite (1 wt% added). Over-predicted U(VI) sorption was attributed to reduced reactivity of natural ferrihydrite present in Hanford Site sediments, compared to freshly prepared synthetic ferrihydrite. Even though the SCM general composite (GC) approach is considered to be a semi-quantitative estimation technique for contaminant sorption, which requires systematic experimental data on the sorbent-sorbate system being studied to obtain credible SCM parameters, the general composite SCM model was still found to be a useful technique for describing U(VI) sorption on natural sediments. Based on U(VI) batch sorption results, two simple U(VI) monodentate surface species, SO U O 2 HCO 3 and SO U O 2 OH on ferrihydrite and phyllosillicate in HFS, respectively, can be successfully used to describe U(VI) sorption onto Hanford Site sediment contacting varying geochemical solutions

  11. Solvothermal synthesis of uranium(VI) phases with aromatic carboxylate ligands: A dinuclear complex with 4-hydroxybenzoic acid and a 3D framework with terephthalic acid

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yingjie, E-mail: yzx@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Karatchevtseva, Inna [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Bhadbhade, Mohan [Mark Wainwright Analytical Centre, University of New South Wales, Kensington, NSW 2052 (Australia); Tran, Toan Trong; Aharonovich, Igor [School of Physics and Advanced Materials, University of Technology Sydney, Ultimo, NSW 2007 (Australia); Fanna, Daniel J.; Shepherd, Nicholas D. [School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 (Australia); Lu, Kim [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Li, Feng [School of Science and Health, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 (Australia); Lumpkin, Gregory R. [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia)

    2016-02-15

    With the coordination of dimethylformamide (DMF), two new uranium(VI) complexes with either 4-hydroxybenzoic acid (H{sub 2}phb) or terephthalic acid (H{sub 2}tph) have been synthesized under solvothermal conditions and structurally characterized. [(UO{sub 2}){sub 2}(Hphb){sub 2}(phb)(DMF)(H{sub 2}O){sub 3}]·4H{sub 2}O (1) has a dinuclear structure constructed with both pentagonal and hexagonal bipyramidal uranium polyhedra linked through a µ{sub 2}-bridging ligand via both chelating carboxylate arm and alcohol oxygen bonding, first observation of such a coordination mode of 4-hydroxybenzoate for 5 f ions. [(UO{sub 2})(tph)(DMF)] (2) has a three-dimensional (3D) framework built with pentagonal bipyramidal uranium polyhedra linked with µ{sub 4}-terephthalate ligands. The 3D channeled structure is facilitated by the unique carboxylate bonding with nearly linear C–O–U angles and the coordination of DMF molecules. The presence of phb ligands in different coordination modes, uranyl ions in diverse environments and DMF in complex 1, and tph ligand, DMF and uranyl ion in complex 2 has been confirmed by Raman spectroscopy. In addition, their thermal stability and photoluminescence properties have been investigated. - Graphical abstract: With the coordination of dimethylformamide, two new uranyl complexes with either 4-hydroxybenzoate or terephthalate have been synthesized under solvothermal conditions and structurally characterized. - Highlights: • Solvent facilitates the synthesis of two new uranium(VI) complexes. • A dinuclear complex with both penta- and hexagonal bipyramidal uranium polyhedral. • A unique µ{sub 2}-bridging mode of 4-hydroxybenzoate via alcohol oxygen for 5 f ions. • A 3D framework with uranium polyhedra and µ{sub 4}-terephthalate ligands. • Vibration modes and photoluminescence properties are reported.

  12. Analytical method of uranium (IV) and uranium (VI) in uranium ores and uranium-bearing rocks

    International Nuclear Information System (INIS)

    Shen Zhuqin; Zheng Yongfeng; Li Qingzhen; Zhong Miaolan; Gu Dingxiang

    1995-11-01

    The best conditions for keeping the original valences of uranium during the dissolution and separation procedure of geological samples (especially those micro uranium-bearing rock) were studied. With the exist of high concentration protectants, the sample was decomposed with concentration HF at 40 +- 5 degree C. The U(VI) was dissolved completely and formed stable complex UO 2 F 2 , the U(IV) was precipitated rapidly and carried by carrier. Quantitative separation was carried out immediately with suction. The decomposition of sample and separation of solid/liquid phases was completed within two minutes. After separation, the U(IV) and U(VI) were determined quantitatively with laser fluorescence or voltametry respectively according to the uranium content. The limit of detection for this method is 0.7 μg/g, RSD is 10.5%, the determinate range of uranium is 2 x 10 -6 ∼10 -1 g/g. The uranium contents and their valence state ratio were measured for more than one hundred samples of sand stone and granite, the accuracy and precision of these results are satisfactory for uranium geological research. (12 tabs.; 11 refs.)

  13. The study of complex equilibria of uranium(VI) with selenate

    International Nuclear Information System (INIS)

    Lubal, P.; Havel, J.

    1997-01-01

    Uranyl (M)-selenate (L) complex equilibria in solution were investigated by spectrophotometry in visible range and potentiometry by means of uranyl ion selective electrode. The formation ML and ML 2 species was proved and the corresponding stability constants calculated were: log β 1 = 1.57 6 ± 0.01 6 , log β 2 = 2.42 3 ± 0.01 3 (I 3.0 mol 1 -1 Na(ClO 4 , SeO 4 ) (spectrophotometry) at 298.2 K. Using potentiometry the values for infinite dilution (I → 0 mol 1 -1 ) were: log β 1 = 2.64 ± 0.01, log β 2 ≤ 3.4 at 298.2 K. Absorption spectra of the complexes were calculated and analysed by deconvolution technique. Derivative spectrophotometry for the chemical model determination has also been successfully applied. (author)

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

    Science.gov (United States)

    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.

  15. A comparative study of the complexation of uranium(VI) with oxydiacetic acid and its amide derivatives

    International Nuclear Information System (INIS)

    Rao, Linfeng; Tian, Guoxin

    2005-01-01

    There has been significant interest in recent years in the studies of alkyl-substituted amides as extractants for actinide separation because the products of radiolytic and hydrolytic degradation of amides are less detrimental to separation processes than those of organophosphorus compounds traditionally used in actinide separations. Stripping of actinides from the amide-containing organic solvents is relatively easy. In addition, the amide ligands are completely incinerable so that the amount of secondary wastes generated in nuclear waste treatment could be significantly reduced. One group of alkyl-substituted oxa-diamides have been shown to be promising in the separation of actinides from nuclear wastes. For example, tetraoctyl-3-oxa-glutaramide and tetraisobutyl-oxa-glutaramide form actinide complexes that can be effectively extracted from nitric acid solutions. To understand the thermodynamic principles governing the complexation of actinides with oxa-diamides, we have studied the complexation of U(VI) with dimethyl-3-oxa-glutaramic acid (DMOGA) and tetramethyl-3-oxa-glutaramide (TMOGA) in aqueous solutions, in comparison with oxydiacetic acid (ODA) (Figure 1). Previous studies have indicated that the complexation of U(VI) with ODA is strong and entropy-driven. Comparing the results for DMOGA and TMOGA with those for ODA could provide insight into the energetics of amide complexation with U(VI) and the relationship between the thermodynamic properties and the ligand structure

  16. Uranium(VI) transport modeling: geochemical data and submodels

    International Nuclear Information System (INIS)

    Tripathi, V.S.

    1984-01-01

    Understanding the geochemical mobility of U(VI) and modeling its transport is important in several contexts including ore genesis, uranium exploration, nuclear and mill-tailings waste management, and solution mining of uranium ores. Adsorption is a major control on partitioning of solutes at the mineral/solution interface. The effect of carbonate, fluoride, and phosphate complexing on adsorption of uranium was investigated. A critical compilation of stability constants of inorganic complexes and solid compounds of U(VI) necessary for proper design of experiment and for modeling transport of uranium was prepared. The general features of U(VI) adsorption in ligand-free systems are similar to those characteristic of other hydrolyzable metal ions. The adsorption processes studied were found to be reversible. The adsorption model developed in ligand-free systems, when solution complexing is taken into account, proved remarkably successful in describing adsorption of uranium in the presence of carbonate and fluoride. The presence of phosphate caused a much smaller decrease in the extent of adsorption than expected; however, a critical reassessment of the stability of UO 2 2+ .HPO 4 2- complexes, showed that phosphato complexes, if any, are extremely weak under experimental conditions. Removal of uranium may have occurred due to precipitation of sodium uranyl phosphates in addition to adsorption

  17. Uranium(VI) speciation by spectroscopy

    International Nuclear Information System (INIS)

    Meinrath, G.

    1997-01-01

    The application of UV-Vis and time-resolved laser-induced fluorescence (TRLF) spectroscopies to direct of uranium(VI) in environmental samples offers various prospects that have, however, serious limitations. While UV-Vis spectroscopy is probably not sensitive enough to detect uranium(VI) species in the majority of environmental samples, TRLFS is principially able to speciate uranium(VI) at very low concentration levels in the nanomol range. Speciation by TRLFS can be based on three parameters: excitation spectrum, emission spectrum and lifetime of the fluorescence emission process. Due to quenching effects, the lifetime may not be expected to be as characteristics as, e.g., the emission spectrum. Quenching of U(VI) fluorescence by reaction with organic substances, inorganic ions and formation of carbonate radicals is one important limiting factor in the application of U(VI) fluorescence spectroscopy. Fundamental photophysical criteria are illustrated using UV-Vis and fluorescence spectra of U(VI) hydrolysis and carbonato species as examples. (author)

  18. Investigation of uranium (VI) adsorption by polypyrrole

    Energy Technology Data Exchange (ETDEWEB)

    Abdi, S. [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Nasiri, M., E-mail: mnasiri@semnan.ac.ir [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Mesbahi, A. [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Khani, M.H. [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, Tehran, 14395-836 (Iran, Islamic Republic of)

    2017-06-15

    Highlights: • The adsorbent (polypyrrole) was synthesized by a chemical method using PEG, DBSNa and CTAB as the surfactant. • The solution pH was one of the most important parameters affecting the adsorption of uranium. • The CTAB provided higher removal percentage compared with the other surfactants. • The maximum adsorption capacity obtained from Langmuir isotherm was 87.72 mg/g. • The pseudo second-order model fitted well with the adsorption kinetic of polypyrrole to uranium. - Abstract: The purpose of this study was to investigate the adsorption of uranium (VI) ions on the polypyrrole adsorbent. Polypyrrole was synthesized by a chemical method using polyethylene glycol, sodium dodecylbenzenesulfonate, and cetyltrimethylammonium bromide as the surfactant and iron (III) chloride as an oxidant in the aqueous solution. The effect of various surfactants on the synthesized polymers and their performance as the uranium adsorbent were investigated. Adsorbent properties were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The effect of different parameters such as pH, contact time, initial metal ion concentrations, adsorbent dose, and the temperature was investigated in the batch system for uranium adsorption process. It has been illustrated that the adsorption equilibrium time is 7 min. The results showed that the Freundlich model had the best agreement and the maximum adsorption capacity of polypyrrole for uranium (VI) was determined 87.72 mg/g from Langmuir isotherm. In addition, the mentioned adsorption process was fast and the kinetic data were fitted to the Pseudo first and second order models. The adsorption kinetic data followed the pseudo-second-order kinetic model. Moreover, the thermodynamic parameters ΔG{sup 0}, ΔH{sup 0} and ΔS{sup 0} showed that the uranium adsorption process by polypyrrole was endothermic and spontaneous.

  19. Extractive separation of uranium(VI) as perchlorate/chloroacetate complexes with 1-phenyl-2,3 dimethyl-5-pyrazolone and its applications

    International Nuclear Information System (INIS)

    Bose, R.; Murty, D.S.R.

    2003-01-01

    The extraction of U(VI) with 1-phenyl 2,3 dimethyl-5-pyrazolone, at a pH of 2.5, in the presence of common anions, like perchlorate and tri-, di-, and monochloroacetates has been investigated. The optimum experimental conditions have been evaluated by studying various parameters such as pH, equilibration period, reagent concentration, metal concentration, and solvents. Effect of diverse anions and cations on the extraction has also been studied. The extracted species, determined by log D - log R plots are represented as, [UO 2 (Apy) 4 (ClO 4 ) 2 ], [UO 2 (Apy) 2 (TCA) 2 ], [UO 2 (Apy) 2 (DCA) 2 ], [UO 2 (Apy)(H 2 O)(MCA) 2 ]. The conditional stability constants of the quantitatively extracted complexes are calculated. The proposed method allows the selective separation of uranium(VI) from multicomponent mixtures and geological matrices and is also applied for the separation and chemical characterization of impurities at trace and ultratrace levels. (author)

  20. Studies on extraction of uranium (VI) with petroleum sulfoxides

    International Nuclear Information System (INIS)

    Yang Yanzhao; Sun Sixiu; Bao Borong

    1999-01-01

    The extraction of uranium(VI) with petroleum sulfoxides(PSO) in different diluents is studied. The extraction ability of U(VI) decreases in the following order: benzene, toluene, cyclohexane, heptane, kerosene, carbon tetrachloride and chloroform. The influence of the concentrations of nitric acid, PSO, salting out agent, complexing anion and temperature on the extraction equilibrium is also investigated, and the enthalpy of the extraction reaction is obtained. The relationship between the extraction equilibrium constants K ex and the physical parameters of diluents is derived. The extraction mechanism and equilibrium are examined by measurement of IR spectrophotometry

  1. Complexation study of a tert-butyl-calix[4]arene-based 2-hydroxynaphthalene ligand with uranium(VI) in non-aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Anne; Schmeide, Katja [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

    2017-06-01

    The actinide uranium, well known from nuclear power cycle, plays also a role in rare earth production as it is an undesired constituent of the respective ores. To facilitate the production of rare earth elements, uranium has to be removed. Due to their modifiable selectivity and solubility calix[n]arenes are interesting compounds for the extraction of actinides and lanthanides. The mechanism of uranium(VI) interaction with a tert-butyl-calix[4]arene-based 2-hydroxynaphthalene ligand (L1) was studied by TRLFS, UV-vis spectroscopy and isothermal calorimetry.

  2. Modification of zirconium diphosphate with salicylic acid and its effect on the uranium (Vi) sorption

    International Nuclear Information System (INIS)

    Almazan T, M. G.; Garcia G, N.; Simoni, E.

    2014-10-01

    The surface of zirconium diphosphate (ZrP 2 O 7 ) was modified with salicylic acid and its effect was evaluated on the uranium (Vi) sorption. The modified surface of the material was analyzed with different analytical techniques among which are included the atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. This analysis allowed showing that the salicylic acid is being held on the surface of the zirconium diphosphate. The reactivity of modified zirconium diphosphate compared with uranium (Vi) was investigated using the classical method of batch sorption. The analysis of sorption isotherms shows that the salicylic acid has an important effect in the uranium (Vi) sorption. According to the study conducted, the interaction among the uranium (Vi) and the surface of zirconium diphosphate modified with the salicylic acid most likely leads to the complexes formation of binary (U(Vi)/ZrP 2 O 7 ) and ternary (U(Vi)/salicylate/ZrP 2 O 7 ) surface. (Author)

  3. Uranium (Vi) sorption onto zirconium diphosphate chemically modified

    International Nuclear Information System (INIS)

    Garcia G, N.; Ordonez R, E.

    2010-10-01

    This work deals with the uranium (Vi) speciation after sorption onto zirconium diphosphate (ZrP 2 O 7 ) surface, hydrated and in a surface modified with organic acids. Oxalic and citric acids were chosen to modify the ZrP 2 O 7 surface because they have poly carboxylic groups and they mimic the organic matter in nature. Thus the interest of this work is to evaluate the uranium (Vi) sorption edge at different s ph values in natural and modified surfaces. The luminescence technique (fluorescence and phosphorescence, respectively) was used for the quantification and speciation of uranyl sorbed at the zirconium diphosphate interface. The fluorescence experiment, showed that adsorption of uranyl on surface of zirconium diphosphate tends to 100%. The speciation shows that there are different complexes in surface which were formed between zirconium diphosphate and uranyl, since it is produced a displacement of wavelength in fluorescence spectra of each system. (Author)

  4. Uranium nucleophilic carbene complexes

    International Nuclear Information System (INIS)

    Tourneux, Jean-Christophe

    2012-01-01

    The only stable f-metal carbene complexes (excluding NHC) metals f present R 2 C 2- groups having one or two phosphorus atoms in the central carbon in alpha position. The objective of this work was to develop the chemistry of carbenes for uranium (metal 5f) with the di-anion C{Ph 2 P(=S)} 2 2- (SCS 2- ) to extend the organometallic chemistry of this element in its various oxidation states (+3-+6), and to reveal the influence of the 5f orbitals on the nature and reactivity of the double bond C=U. We first isolated the reactants M(SCHS) (M = Li and K) and demonstrated the role of the cation M + on the evolution of the di-anion M 2 SCS (M = Li, K, Tl) which is transformed into LiSCHS in THF or into product of intramolecular cyclization K 2 [C(PhPS) 2 (C 6 H 4 )]. We have developed the necessary conditions mono-, bis- and tris-carbene directly from the di-anion SCS 2- and UCl 4 , as the precursor used in uranium chemistry. The protonolysis reactions of amides compounds (U-NEt 2 ) by the neutral ligand SCH 2 S were also studied. The compounds [Li(THF)] 2 [U(SCS)Cl 3 ] and [U(SCS)Cl 2 (THF) 2 ] were then used to prepare a variety of cyclopentadienyl and mono-cyclo-octa-tetra-enyliques uranium(IV) carbene compounds of the DFT analysis of compounds [M(SCS)Cl 2 (py) 2 ] and [M(Cp) 2 (SCS)] (M = U, Zr) reveals the strong polarization of the M=C double bond, provides information on the nature of the σ and π interactions in this binding, and shows the important role of f orbitals. The influence of ancillary ligands on the M=C bond is revealed by examining the effects of replacing Cl - ligands and pyridine by C 5 H 5 - groups. Mulliken and NBO analyzes show that U=C bond, unlike the Zr=C bond, is not affected by the change in environment of the metal center. While the oxidation tests of carbene complexes of U(IV) were disappointing, the first carbene complex of uranium (VI), [UO 2 (SCS)(THF) 2 ], was isolated with the uranyl ion UO 2 2+ . The reactions of compounds UO 2 X 2

  5. Phospholyl-uranium complexes

    International Nuclear Information System (INIS)

    Gradoz, Philippe

    1993-01-01

    After having reported a bibliographical study on penta-methylcyclopentadienyl uranium complexes, and a description of the synthesis and radioactivity of uranium (III) and (IV) boron hydrides compounds, this research thesis reports the study of mono and bis-tetramethyl-phospholyl uranium complexes comprising chloride, boron hydride, alkyl and alkoxide ligands. The third part reports the comparison of structures, stabilities and reactions of homologue complexes in penta-methylcyclopentadienyl and tetramethyl-phospholyl series. The last part addresses the synthesis of tris-phospholyl uranium (III) and (IV) complexes. [fr

  6. Interactions of uranium (VI) with biofilms

    International Nuclear Information System (INIS)

    Brockmann, Sina; Arnold, Thuro; Bernhard, Gert

    2013-01-01

    In this study a detailed investigation was made of natural biofilms from two uranium-contaminated sites, namely the former uranium mine in Koenigstein (Saxony) and the ground surface of the former Grassenhalde tailing heap in Thuringia. A predominance of uranyl sulphate (UO 2 SO 4 ), a highly mobile, solute uranium species, was found in the mine waters of both sites. In this study an investigation was made of the capacity of Euglena mutabilis cells for bioaccumulation of uranium in a pH range of 3 to 6 using living cells and sodium perchlorate (9 g/l) or sodium sulphate (3.48 g/l) as background media. At acidic pH values in the range from 3 to 4 it was possible to remove more than 90% of the original uranium content from the test solution regardless of the medium being used. The speciation of the uranium accumulated in the Euglena cells was investigated by laser-induced fluorescence spectroscopy (LIFS). It was found that a new uranium species of low variability forms on the cells independent of the background medium, state of life of the cells and pH value. By comparing the data from the LIFS measurements with reference values it was possible to narrow down the identity of the uranium species to one bonded to (organo) phosphate and/or carboxylic functional groups. Using time-resolved FT-IR spectroscopy it was possible to demonstrate carboxylic bonding of uranium to dead cells. However it was not possible to exclude (organo) complexation with this method. An investigation of the specific location of the uranium on or in the cells using combined CLSM/LIFS technology yielded first indications of intracellular accumulation of uranium in the living cells. Supplementary TEM/EDX measurements confirmed the intracellular uptake, showing it to occur in round to oval cell organelles which are thought to be vacuoles or vacuole-like vesicles. It was not possible to detect uranium on dead cells using these methods. This points to passive, homogeneously distributed biosorption of

  7. (VI) ML6 Complexes

    African Journals Online (AJOL)

    A geometric analysis revealed that beta-(C-H) and alpha-(C-C) can occupy the seventh and eighth coordination sites in the title Fischer carbene complexes as agostic interactions, which allows classifying the carbene as a η3 ligand in these cases. This theory was supported by the relative energies of the conformers and an ...

  8. Extraction behavior of uranium(VI) with polyurethane foam

    International Nuclear Information System (INIS)

    Tingchia Huang; Donghwang Chen; Muchang Shieh; Chingtsven Huang

    1992-01-01

    The extraction of uranium(VI) from aqueous solution with polyether-based polyurethane (PU) foam was studied. The effects of the kinds and concentrations of nitrate salts, uranium(VI) concentration, temperature, nitric acid concentration, pH, the content of poly(ethylene oxide) in the polyurethane foam, and the ratio of PU foam weight and solution volume on the extraction of uranium(VI) were investigated. The interferences of fluoride and carbonate ions on the extraction of uranium(VI) were also examined, and methods to overcome both interferences were suggested. It was found that no uranium was extracted in the absence of a nitrate salting-out agent, and the extraction behaviors of uranium(IV) with polyurethane foam could be explained in terms of an etherlike solvent extraction mechanism. In addition, the percentage extraction of a multiple stage was also estimated theoretically

  9. Anaerobic bio-removal of uranium (VI) and chromium (VI): Comparison of microbial community structure

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Monica [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Faleiro, Maria Leonor [IBB - Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Chaves, Sandra; Tenreiro, Rogerio [Universidade de Lisboa, Faculdade de Ciencias, Centro de Biodiversidade, Genomica Integrativa e Funcional (BioFIG), Campus de FCUL, Campo Grande 1749-016 Lisboa (Portugal); Santos, Erika [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Costa, Maria Clara, E-mail: mcorada@ualg.pt [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)

    2010-04-15

    Several microbial communities, obtained from uranium contaminated and non-contaminated samples, were investigated for their ability to remove uranium (VI) and the cultures capable for this removal were further assessed on their efficiency for chromium (VI) removal. The highest efficiency for removal of both metals was observed on a consortium from a non-contaminated soil collected in Monchique thermal place, which was capable to remove 91% of 22 mg L{sup -1} U(VI) and 99% of 13 mg L{sup -1} Cr(VI). This study revealed that uranium (VI) removing communities have also ability to remove chromium (VI), but when uranium (VI) was replaced by chromium (VI) several differences in the structure of all bacterial communities were observed. TGGE and phylogenetic analysis of 16S rRNA gene showed that the uranium (VI) removing bacterial consortia are mainly composed by members of Rhodocyclaceae family and Clostridium genus. On the other hand, bacteria from Enterobacteriaceae family were detected in the community with ability for chromium (VI) removal. The existence of members of Enterobacteriaceae and Rhodocyclaceae families never reported as chromium or uranium removing bacteria, respectively, is also a relevant finding, encouraging the exploitation of microorganisms with new abilities that can be useful for bioremediation.

  10. Anaerobic bio-removal of uranium (VI) and chromium (VI): Comparison of microbial community structure

    International Nuclear Information System (INIS)

    Martins, Monica; Faleiro, Maria Leonor; Chaves, Sandra; Tenreiro, Rogerio; Santos, Erika; Costa, Maria Clara

    2010-01-01

    Several microbial communities, obtained from uranium contaminated and non-contaminated samples, were investigated for their ability to remove uranium (VI) and the cultures capable for this removal were further assessed on their efficiency for chromium (VI) removal. The highest efficiency for removal of both metals was observed on a consortium from a non-contaminated soil collected in Monchique thermal place, which was capable to remove 91% of 22 mg L -1 U(VI) and 99% of 13 mg L -1 Cr(VI). This study revealed that uranium (VI) removing communities have also ability to remove chromium (VI), but when uranium (VI) was replaced by chromium (VI) several differences in the structure of all bacterial communities were observed. TGGE and phylogenetic analysis of 16S rRNA gene showed that the uranium (VI) removing bacterial consortia are mainly composed by members of Rhodocyclaceae family and Clostridium genus. On the other hand, bacteria from Enterobacteriaceae family were detected in the community with ability for chromium (VI) removal. The existence of members of Enterobacteriaceae and Rhodocyclaceae families never reported as chromium or uranium removing bacteria, respectively, is also a relevant finding, encouraging the exploitation of microorganisms with new abilities that can be useful for bioremediation.

  11. Uranium thiolate complexes

    International Nuclear Information System (INIS)

    Leverd, Pascal C.

    1994-01-01

    This research thesis proposes a new approach to the chemistry of uranium thiolate complexes as these compounds are very promising for various uses (in bio-inorganic chemistry, in some industrial processes like oil desulphurization). It more particularly addresses the U-S bond or more generally bonds between polarizable materials and hard metals. The author thus reports the study of uranium organometallic thiolates (tricyclo-penta-dienic and mono-cyclo-octa-tetraenylic complexes), and of uranium homoleptic thiolates (tetra-thiolate complexes, hexa-thiolate complexes, reactivity of homoleptic thiolate complexes) [fr

  12. Uranium(VI) sorption onto magnetite. Increasing confidence in surface complexation models using chemically evident surface chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Bok, Frank [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

    2017-06-01

    Surface complexation models have made great efforts in describing the sorption of various radionuclides on naturally occurring mineral phases. Unfortunately, many of the published sorption parameter sets are built upon unrealistic or even wrong surface chemistry. This work describes the benefit of combining spectroscopic and batch sorption experimental data to create a reliable and consistent surface complexation parameter set.

  13. Extraction and Separation of Uranium (VI) and Thorium (IV) Using Tri-n-dodecylamine Impregnated Resins

    International Nuclear Information System (INIS)

    Metwally, E.; Saleh, A.Sh.; El-Naggar, H.A.

    2005-01-01

    Extraction of U(VI) and Th(IV) from chloride and nitrate solutions with tri-n- dodecylamine impregnated on Amberlite XAD4, was investigated. The distribution of U(VI) and Th(IV) was studied at different concentrations of acid, salting-out agent, extractant, aqueous metal ion and other parameters. Absorption spectral studies have been investigated for uranium species in both aqueous HCl solution and the resin phase. From these studies, it is suggested that the tetrachloro complex of U(VI) is formed in the extraction of uranium (VI) from hydrochloric acid solutions by TDA impregnated resin. Stripping of the extracted U(VI) and Th(IV) was assayed with HCl and HNO 3 . Finally, the separation of uranium from thorium and fission products in HCl media was achieved

  14. A spectroscopic study of uranium(VI) interaction with magnetite

    International Nuclear Information System (INIS)

    El Aamrani, S.; Gimenez, J.; Rovira, M.; Seco, F.; Grive, M.; Bruno, J.; Duro, L.; Pablo, J. de

    2007-01-01

    The uranium sorbed onto commercial magnetite has been characterized by using two different spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS). Magnetite samples have been put in contact with uranium(VI) solutions in conditions in which a high uranium uptake is expected. After several days, the magnetite surface has been analysed by XPS and EXAFS. The XPS results obtained are not conclusive regarding the uranium oxidation state in the magnetite surface. On the other hand, the results obtained with the EXAFS technique show that the uranium-magnetite sample spectrum has characteristics from both the UO 2 and schoepite spectra, e.g. a relatively high coordination number of equatorial oxygens and two axial oxygens, respectively. These results would indicate that the uranium sorbed onto magnetite would be a mixture of uranium(IV) and uranium(VI)

  15. Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

    Science.gov (United States)

    Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; Davis, J. A.

    2018-01-01

    The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonite edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites ('spillover' effect). A series of U(VI) - Na-montmorillonite batch adsorption experiments was conducted as a function of pH, with variable U(VI), Ca, and dissolved carbonate concentrations. Based on the experimental data, a new type of surface complexation model (SCM) was developed for montmorillonite, that specifically accounts for the spillover effect using the edge surface speciation model by Tournassat et al. (2016a). The SCM allows for a prediction of U(VI) adsorption under varying chemical conditions with a minimum number of fitting parameters, not only for our own experimental results, but also for a number of published data sets. The model agreed well with many of these datasets without introducing a second site type or including the formation of ternary U(VI)-carbonato surface complexes. The model predictions were greatly impacted by utilizing analytical measurements of dissolved inorganic carbon (DIC) concentrations in individual sample solutions rather than assuming solution equilibration with a specific partial pressure of CO2, even when the gas phase was

  16. Polarography of uranium(VI)-salicylic acid system

    International Nuclear Information System (INIS)

    Salah, El-Maraghy B.

    1980-01-01

    Uranium(VI)-salicylic acid system has been studied polarographically in perchloric acid medium. Varying concentrations of HClO 4 and salicylic acid have been used. The nature of the polarographic waves is irreversible. (author)

  17. Polarography of uranium(VI)-salicylic acid system

    Energy Technology Data Exchange (ETDEWEB)

    Salah, E M.B. [Ain Shams Univ., Cairo (Egypt). Faculty of Education

    1980-08-01

    Uranium(VI)-salicylic acid system has been studied polarographically in perchloric acid medium. Varying concentrations of HClO/sub 4/ and salicylic acid have been used. The nature of the polarographic waves is irreversible.

  18. A Spectroscopic Study of the effect of Ligand Complexation on the Reduction of Uranium(VI) by Anthraquinone-2,6-disulfonate (AH2DS)

    International Nuclear Information System (INIS)

    Wang, Zheming; Wagnon, Ken B.; Ainsworth, Calvin C.; Liu, Chongxuan; Rosso, Kevin M.; Fredrickson, Jim K.

    2008-01-01

    In this project, the reduction rate of uranyl complexes with hydroxide, carbonate, EDTA, and Desferriferrioxamine B (DFB) by anthraquinone-2,6-disulfonate (AH2DS), a potential electron shuttle for microbial reduction of metal ions (Newman and Kolter 2000), is studied by stopped-flow kinetics techniques under anoxic atmosphere. The apparent reaction rates varied with ligand type, solution pH, and U(VI) concentration. For each ligand, a single largest kobs within the studied pH range was observed, suggesting the influence of pH-dependent speciation on the U(VI) reduction rate. The maximum reaction rate found in each case followed the order of OH- > CO32- > EDTA > DFB, consistent with the same trend of the thermodynamic stability of the uranyl complexes and ionic sizes of the ligands. Increasing the stability of uranyl complexes and ligand size decreased the maximum reduction rate. The pH-dependent rates were modeled using a second-order rate expression that was assumed to be dependent on a single U(VI) complex and AH2DS species. By quantitatively comparing the calculated and measured apparent rate constants as a function of pH, species AHDS3- was suggested as the primary reductant in all cases examined. Species UO2CO3(aq) , UO2HEDTA-, and (UO2)2(OH)22+ were suggested as the principal electron acceptors among the U(VI) species mixture in carbonate, EDTA, and hydroxyl systems, respectively

  19. A spectroscopic study of the effect of ligand complexation on the reduction of uranium(VI) by anthraquinone-2,6-disulfonate (AH2DS)

    International Nuclear Information System (INIS)

    Wang, Z.; Wagnon, K.B.; Ainsworth, C.C.; Liu, C.; Rosso, K.M.; Fredrickson, J.K.

    2008-01-01

    In this paper, the reduction rate of uranyl complexes with hydroxide, carbonate, EDTA, and desferriferrioxamine B (DFB) by anthraquinone-2,6-disulfonate (AH 2 DS) is studied by stopped-flow kinetic technique under anoxic atmosphere. The apparent reaction rates varied with ligand type, solution pH, and U(VI) concentration. For each ligand, a single largest pseudo-1 st order reaction rate constant, k obs , within the studied pH range was observed, suggesting the influence of pH-dependent speciation on the U(VI) reduction rate. The maximum reaction rate found in each case followed the order of OH - > CO 3 2- > EDTA > DFB, in reverse order of the trend of the thermodynamic stability of the uranyl complexes and ionic sizes of the ligands. The pH-dependent rates were modeled using a second-order rate expression that was assumed to be dependent on a single U(VI) complex and an AH 2 DS species. By quantitatively comparing the calculated and measured apparent rate constants as a function of pH, species AHDS 3- was suggested as the primary reductant in all cases examined. Species UO 2 CO 3 (aq), UO 2 HEDTA - , and (UO 2 ) 2 (OH) 2 2+ were suggested as the principal electron acceptors among the U(VI) species mixture in each of the carbonate, EDTA, and hydroxyl systems, respectively. (orig.)

  20. Extraction equilibrium of uranium (VI) from phosphoric solution with HDEHP and TOPO in cyclohexane

    International Nuclear Information System (INIS)

    You Jianzhang; Zhou Zuming; Qin Qizong

    1988-01-01

    The extraction equilibrium of uranium(VI) from phosphoric acid solution with HDEHP and TOPO in cyclohexane has been investigated to examine the effects of extractant concentration, hydrogen ion concentration and temperature on the extraction of uranium(VI). Experimental results suggest that the composition of synergistic complex species is UO 2 (HA 2 ) 2 ·TOPO and the extraction equilibrium constant β 21 is 10 9.52 at 30 deg C. In addition, the thermodynamic functions of the extraction reaction (ΔG,ΔH,ΔS) and the infra-red spectra of synergistic complexes have also been determined

  1. Magnetic chitosan for removal of uranium (VI)

    International Nuclear Information System (INIS)

    Stopa, Luiz Claudio Barbosa

    2007-01-01

    The chitosan, an aminopolysaccharide formed for repeated units of D-glucosamine, is a deacetylation product of chitin. It presents favorable ionic properties acting as chelant, being considered a removing ionic of contaminants from water effluents. It has ample bioactivity, that is, is biocompatible, biodegradable, bioadhesive and biosorbent. The chitosan interacts for crosslinked by means of its active groups with other substances, can still coat superparamagnetic materials as magnetite nanoparticles producing one conjugated polymer-magnetite. Superparamagnetic materials are susceptible for the magnetic field, thus these particles can be attracted and grouped by a magnetic field and as they do not hold back the magnetization, they can be disagrouped and reused in processes for removal of contaminants from industrial effluents and waste water. The present work consisted of preparing coated magnetic magnetite particles with chitosan (PMQ). The PMQ powder has showed a magnetic response of intense attraction in the presence of a magnetic field without however becoming magnetic, a typical behavior of superparamagnetic material. It was characterized by Fourier transform infrared spectrometry and measurements of magnetization. Its performance of Uranium (VI) adsorption as uranyl species, U0 2 2+ , was evaluated with regard to the influence of adsorbent dose, speed of agitation, pH, the contact time and had studied the isotherms of adsorption as well as the behavior of desorption using ions of carbonate and oxalate. The optimal pH to the best removal occurred in pH 5 and that the increase of the dose increases the removal, becoming constant above of 20 g.L -1 . In the kinetic study the equilibrium was achieved after 20 minutes. The results of equilibrium isotherm agreed well with the Langmuir model, being the maximum adsorption capacity equal 41.7 mg.g -1 . In the desorption studies were verified 94% of U0 2 2+ recovered with carbonate ion and 49.9% with oxalate ion

  2. Uranium(VI) speciation: modelling, uncertainty and relevance to bioavailability models. Application to uranium uptake by the gills of a freshwater bivalve

    International Nuclear Information System (INIS)

    Denison, F.H.

    2004-07-01

    The effects of varying solution composition on the interactions between uranium(VI) and excised gills of the freshwater bivalve Corbicula fluminea have been investigated in well defined solution media. A significant reduction in the uptake of uranium was observed on increasing the concentrations of the uranium complexing ligands citrate and carbonate. Saturation kinetics as a function of uranium concentration at a pH value of 5.0 were observed, indicating that the uptake of uranium is a facilitated process, probably involving one or several trans-membrane transport systems. A relatively small change in the uptake of uranium was found as a function of pH (factor of ca. 2), despite the extremely large changes to the solution speciation of uranium within the range of pH investigated (5.0 - 7.5). A comprehensive review of the thermodynamic data relevant to the solution composition domain employed for this study was performed. Estimates of the uncertainties for the formation constants of aqueous uranium(VI) species were integrated into a thermodynamic database. A computer program was written to predict the equilibrium distribution of uranium(VI) in simple aqueous systems, using thermodynamic parameter mean-values. The program was extended to perform Monte Carlo and Quasi Monte Carlo uncertainty analyses, incorporating the thermodynamic database uncertainty estimates, to quantitatively predict the uncertainties inherent in predicting the solution speciation of uranium. The use of thermodynamic equilibrium modelling as a tool for interpreting the bioavailability of uranium(VI) was investigated. Observed uranium(VI) uptake behaviour was interpreted as a function of the predicted changes to the solution speciation of uranium. Different steady-state or pre-equilibrium approaches to modelling uranium uptake were tested. Alternative modelling approaches were also tested, considering the potential changes to membrane transport system activity or sorption characteristics on

  3. Ion-exchanger ultraviolet spectrophotometry for uranium(VI)

    International Nuclear Information System (INIS)

    Waki, H.; Korkisch, J.

    1983-01-01

    A sensitive method based on solid-phase spectrophotometry has been developed for the microdetermination of uranium(VI) in water samples. Uranium is sorbed on the anion-exchanger QAE-Sephadex from thiocyanate solution and the absorbance of the exchanger is measured at 300 nm. This method is about 30 times more sensitive than solution spectrophotometry. Absorption spectra of various metals in the anion-exchanger phase are presented and their interferences discussed. A procedure for the cation-exchange separation of uranium from accompanying elements before spectral measurement of uranium is proposed. (author)

  4. Effect of pH and uranium concentration on interaction of uranium(VI) and uranium(IV) with organic ligands in aqueous solutions

    International Nuclear Information System (INIS)

    Li, W.C.; Victor, D.M.; Chakrabarti, C.L.

    1980-01-01

    The effect of pH and uranium concentration on the interactions of uranium(VI) and uranium(IV) with organic ligands was studied by employing dialysis and ultrafiltration techniques. The interactions of U(VI) and U(IV) with organic ligands in nitrate or chloride aqueous solution have been found to be pH-dependent. The stability constants of uranium-organic complexes decrease in the order: fulvic acid>humic acid>tannic acid for U(VI) and humic acid>tannic acid>fulvic acid for U(IV). Scatchard plots for the uranium-organic acid systems indicate two types of binding sites with a difference in stability constants of about 10 2 . Ultrafiltration of uranium-humic acid complexes indicates that U(VI) and U(IV) ions are concentrated in larger molecular size fractions (>5.1 nm) at pH less than or equal to 3 and in smaller molecular size fractions (in the range 5.1 to 3.1 nm and 2.4 to 1.9 nm) at pH greater than or equal to 5. 7 figures, 4 tables

  5. Extraction kinetics of uranium (VI) with polyurethane foam

    International Nuclear Information System (INIS)

    Huang, Ting-Chia; Chen, Dong-Hwang; Huang, Shius-Dong; Huang, Ching-Tsven; Shieh, Mu-Chang.

    1993-01-01

    The extraction kinetics of uranium(VI) from aqueous nitrate solution with polyether-based polyurethane foam was investigated in a batch reactor with automatic squeezing. The extraction curves of uranium(VI) concentration in solution vs. extraction time exhibited a rather rapid exponential decay within the first few minutes, followed by a slower exponential decay during the remaining period. This phenomenon can be attributed to the presence of two-phase structure, hard segment domains and soft segment matrix in the polyurethane foam. A two-stage rate model expressed by a superposition of two exponential curves was proposed, according to which the experimental data were fitted by an optimization method. The extraction rate of uranium (VI) was also found to increase with increasing temperature, nitrate concentration, and hydration of the cation of nitrate salt. (author)

  6. Mechanism of uranium (VI) removal by two anaerobic bacterial communities

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Monica [Centro de Ciencias do Mar, Universidade do Algarve, FCT-DQF (edificio 8), Campus de Gambelas, 8005-139 Faro (Portugal); Faleiro, Maria Leonor [IBB - Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, FCT, Campus de Gambelas, 8005-139 Faro (Portugal); Costa, Ana M. Rosa da [Centro de Investigacao em Quimica do Algarve, Universidade do Algarve, FCT, DQF, Campus de Gambelas, 8005-139 Faro (Portugal); Chaves, Sandra; Tenreiro, Rogerio [Universidade de Lisboa, Faculdade de Ciencias, Centro de Biodiversidade, Genomica Integrativa e Funcional (BioFIG), Campus de FCUL, Campo Grande, 1749-016 Lisboa (Portugal); Matos, Antonio Pedro [Servico de Anatomia Patologica, Hospital Curry Cabral, Lisboa (Portugal); Costa, Maria Clara, E-mail: mcorada@ualg.pt [Centro de Ciencias do Mar, Universidade do Algarve, FCT-DQF (edificio 8), Campus de Gambelas, 8005-139 Faro (Portugal)

    2010-12-15

    The mechanism of uranium (VI) removal by two anaerobic bacterial consortia, recovered from an uncontaminated site (consortium A) and other from an uranium mine (consortium U), was investigated. The highest efficiency of U (VI) removal by both consortia (97%) occurred at room temperature and at pH 7.2. Furthermore, it was found that U (VI) removal by consortium A occurred by enzymatic reduction and bioaccumulation, while the enzymatic process was the only mechanism involved in metal removal by consortium U. FTIR analysis suggested that after U (VI) reduction, U (IV) could be bound to carboxyl, phosphate and amide groups of bacterial cells. Phylogenetic analysis of 16S rRNA showed that community A was mainly composed by bacteria closely related to Sporotalea genus and Rhodocyclaceae family, while community U was mainly composed by bacteria related to Clostridium genus and Rhodocyclaceae family.

  7. Mechanism of uranium (VI) removal by two anaerobic bacterial communities

    International Nuclear Information System (INIS)

    Martins, Monica; Faleiro, Maria Leonor; Costa, Ana M. Rosa da; Chaves, Sandra; Tenreiro, Rogerio; Matos, Antonio Pedro; Costa, Maria Clara

    2010-01-01

    The mechanism of uranium (VI) removal by two anaerobic bacterial consortia, recovered from an uncontaminated site (consortium A) and other from an uranium mine (consortium U), was investigated. The highest efficiency of U (VI) removal by both consortia (97%) occurred at room temperature and at pH 7.2. Furthermore, it was found that U (VI) removal by consortium A occurred by enzymatic reduction and bioaccumulation, while the enzymatic process was the only mechanism involved in metal removal by consortium U. FTIR analysis suggested that after U (VI) reduction, U (IV) could be bound to carboxyl, phosphate and amide groups of bacterial cells. Phylogenetic analysis of 16S rRNA showed that community A was mainly composed by bacteria closely related to Sporotalea genus and Rhodocyclaceae family, while community U was mainly composed by bacteria related to Clostridium genus and Rhodocyclaceae family.

  8. Application of Calixarenes as Macrocyclic Ligands for Uranium(VI: A Review

    Directory of Open Access Journals (Sweden)

    Katarzyna Kiegiel

    2013-01-01

    Full Text Available Calixarenes represent a well-known family of macrocyclic molecules with broad range of potential applications in chemical, analytical, and engineering materials fields. This paper covers the use of calixarenes as complexing agents for uranium(VI. The high effectiveness of calix[6]arenes in comparison to other calixarenes in uranium(VI separation process is also presented. Processes such as liquid-liquid extraction (LLE, liquid membrane (LM separation, and ion exchange are considered as potential fields for application of calixarenes as useful agents for binding UO22+ for effective separation from aqueous solutions containing other metal components.

  9. Recovery of uranium (VI) from low level aqueous radioactive waste

    International Nuclear Information System (INIS)

    Kulshrestha, Mukul

    1996-01-01

    Investigation was undertaken to evaluate the uranium (VI) removal and recovery potential of a naturally occurring, nonviable macrofungus, Ganoderma Lucidum from the simulated low level aqueous nuclear waste. These low level waste waters discharged from nuclear mine tailings and nuclear power reactors have a typical U(VI) concentration of 10-100 mg/L. It is possible to recover this uranium economically with the advent of biosorption as a viable technology. Extensive laboratory studies have revealed Ganoderma Lucidum to be a potential biosorbent with a specific uptake of 2.75 mg/g at an equilibrium U(VI) concentration of 10 mg/L at pH 4.5. To recover the sorbed U(VI), the studies indicated 0.2N Na 2 CO 3 to be an effective elutant. The kinetics of U(VI) desorption from loaded Ganoderma Lucidum with 0.2N Na 2 CO 3 as elutant, was found to be rapid with more than 75% recovery occurring in the first five minutes, the specific metal release rate being 0.102 mg/g/min. The equilibrium data fitted to a linearised Freundlich plot and exhibited a near 100% recovery of sorbed U(VI), clearly revealing a cost-effective method of recovery of precious uranium from low level wastewater. (author). 7 refs., 3 figs., 1 tab

  10. Towards a consistent geochemical model for prediction of uranium(VI) removal from groundwater by ferrihydrite

    International Nuclear Information System (INIS)

    Gustafsson, Jon Petter; Daessman, Ellinor; Baeckstroem, Mattias

    2009-01-01

    Uranium(VI), which is often elevated in granitoidic groundwaters, is known to adsorb strongly to Fe (hydr)oxides under certain conditions. This process can be used in water treatment to remove U(VI). To develop a consistent geochemical model for U(VI) adsorption to ferrihydrite, batch experiments were performed and previous data sets reviewed to optimize a set of surface complexation constants using the 3-plane CD-MUSIC model. To consider the effect of dissolved organic matter (DOM) on U(VI) speciation, new parameters for the Stockholm Humic Model (SHM) were optimized using previously published data. The model, which was constrained from available X-ray absorption fine structure (EXAFS) spectroscopy evidence, fitted the data well when the surface sites were divided into low- and high-affinity binding sites. Application of the model concept to other published data sets revealed differences in the reactivity of different ferrihydrites towards U(VI). Use of the optimized SHM parameters for U(VI)-DOM complexation showed that this process is important for U(VI) speciation at low pH. However in neutral to alkaline waters with substantial carbonate present, Ca-U-CO 3 complexes predominate. The calibrated geochemical model was used to simulate U(VI) adsorption to ferrihydrite for a hypothetical groundwater in the presence of several competitive ions. The results showed that U(VI) adsorption was strong between pH 5 and 8. Also near the calcite saturation limit, where U(VI) adsorption was weakest according to the model, the adsorption percentage was predicted to be >80%. Hence U(VI) adsorption to ferrihydrite-containing sorbents may be used as a method to bring down U(VI) concentrations to acceptable levels in groundwater

  11. Study of electrolytic reduction of uranium VI to uranium IV in nitrate systems

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, B.F. de; Almeida, S.G. de; Forbicini, S; Matsuda, H T; Araujo, J.A. de [Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo (Brazil). Centro de Engenharia Quimica

    1980-01-01

    Experimental parameters are optimized in order to obtain uranium (IV) nitrate solutions at maximum yield, using hydrazine as stabilizer. Uranium (VI) electrolytic reduction was chosen because: there is no increase in the volume of radioactive effluents; there are no secondary reactions; there is no need for further separations; all reagents used are not inflammable. The method is, therefore, efficient and of low cost.

  12. Isolation and characterization of a uranium(VI)-nitride triple bond

    Science.gov (United States)

    King, David M.; Tuna, Floriana; McInnes, Eric J. L.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T.

    2013-06-01

    The nature and extent of covalency in uranium bonding is still unclear compared with that of transition metals, and there is great interest in studying uranium-ligand multiple bonds. Although U=O and U=NR double bonds (where R is an alkyl group) are well-known analogues to transition-metal oxo and imido complexes, the uranium(VI)-nitride triple bond has long remained a synthetic target in actinide chemistry. Here, we report the preparation of a uranium(VI)-nitride triple bond. We highlight the importance of (1) ancillary ligand design, (2) employing mild redox reactions instead of harsh photochemical methods that decompose transiently formed uranium(VI) nitrides, (3) an electrostatically stabilizing sodium ion during nitride installation, (4) selecting the right sodium sequestering reagent, (5) inner versus outer sphere oxidation and (6) stability with respect to the uranium oxidation state. Computational analyses suggest covalent contributions to U≡N triple bonds that are surprisingly comparable to those of their group 6 transition-metal nitride counterparts.

  13. Biosorption behaviors of uranium (VI) from aqueous solution by sunflower straw and insights of binding mechanism

    International Nuclear Information System (INIS)

    Lian Ai; Xuegang Luo; Xiaoyan Lin; Sizhao Zhang

    2013-01-01

    Uranium (VI)-containing water has been recognized as a potential longer-term radiological health hazard. In this work, the sorptive potential of sunflower straw for U (VI) from aqueous solution was investigated in detail, including the effect of initial solution pH, adsorbent dosage, temperature, contact time and initial U (VI) concentration. A dose of 2.0 g L -1 of sunflower straw in an initial U (VI) concentration of 20 mg L -1 with an initial pH of 5.0 and a contact time of 10 h resulted in the maximum U (VI) uptake (about 6.96 mg g -1 ) at 298 K. The isotherm adsorption data was modeled best by the nonlinear Langmuir-Freundlich equation. The equilibrium sorption capacity of sunflower straw was observed to be approximately seven times higher than that of coconut-shell activated carbon as 251.52 and 32.37 mg g -1 under optimal conditions, respectively. The positive enthalpy and negative free energy suggested the endothermic and spontaneous nature of sorption, respectively. The kinetic data conformed successfully to the pseudo-second-order equation. Furthermore, energy dispersive X-ray, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that U (VI) adsorption onto sunflower straw was predominantly controlled by ion exchange as well as complexation mechanism. The study revealed that sunflower straw could be exploited for uranium remediation of aqueous streams as a promising adsorbent. (author)

  14. Polarographic behaviour of uranium (VI) in tributyl phosphate organic solutions

    International Nuclear Information System (INIS)

    Degueldre, C.A.; Meklati, M.

    1984-01-01

    U(VI) determination by D.C. and differential pulse polarography was studied in the organic solutions derived from tributyl phosphate - diluent extracts (after separation from nitric acid media) along with a selected aprotic solvent (i.e.: propylene carbonate and N,N-dimethylacetamide). Miscibility of the TBP-diluent (e.g. cyclohexane, n-hexane, kerosene, n-dodecane) phase with nitric acid as supporting electrolyte, either by addition or already present in the extract was larger in DMA than in PC. In the DMA organic mixture, U(VI) exhibited a DPP peak due to a one electron step, with Esub(p)=-0.4 V (position connected with H 2 O and HNO 3 concentrations). This peak which was proportionnel to the U(VI) concentration from 5x10 -6 to 10 -3 M can be used to determinate directly hexavalent uranium in the industrial organic extraction phases TBP-diluent. (orig.)

  15. Uranium(VI) retention on quartz and kaolinite. Experiments and modelling

    International Nuclear Information System (INIS)

    Mignot, G.

    2001-01-01

    The behaviour of uranium in the geosphere is an important issue for safety performance assessment of nuclear waste repositories, or in the context of contaminated sites due to mining activity related to nuclear field. Under aerobic conditions, the fate of uranium is mainly governed by the ability of minerals to sorb U(VI) aqueous species. Hence, a thorough understanding of U(VI) sorption processes on minerals is required to provide a valuable prediction of U(VI) migration in the environment. In this study, we performed sorption/desorption experiments of U(VI) on quartz and kaolinite, for systems favouring the formation in solution (i) of UO 2 2+ and monomeric hydrolysis products or (ii) of di-/tri-meric uranyl aqueous species, and / or U(VI)-colloids or UO 2 (OH) 2 precipitates, or (iii) of uranyl-carbonate complexes. Particular attention was paid to determine the surface characteristics of the solids and their modification due to dissolution/precipitation processes during experiments. A double layer surface complexation model was applied to our experimental data in order to derive surface complexation equilibria and intrinsic constants which allow a valuable description of U(VI) retention over a wide range of pH, ionic strength, initial concentration of uranium [0.1-10μM] and solid - solution equilibration time. U(VI) sorption on quartz was successfully modeled by using two sets of adsorption equilibria, assuming (i) the formation of the surface complexes SiOUO 2 + , SiOUO 2 OH and SiO(UO 2 ) 3 (OH) 5 , or (ii) the formation of the mono-dentate complex SiO(UO 2 ) 3 (OH) 5 and of the bidentate complex (SiO) 2 UO 2 . Assumptions on the density of each type of surface sites of kaolinite and on their acid-base properties were made from potentiometric titrations of kaolinite suspensions. We proposed on such a basis a set of surface complexation equilibria which accounts for U(VI) uptake on kaolinite over a wide range of chemical conditions, with aluminol edge sites as

  16. Uranium(VI) adsorption properties of a chelating resin containing polyamine-substituted methylphosphonic acid moiety

    International Nuclear Information System (INIS)

    Matsuda, Masaaki; Akiyoshi, Yoshirou

    1991-01-01

    Uranium(VI) adsorption and desorption properties of a chelating resin containing polyamine-substituted methylphosphonic acid moiety of 2.29 mmol/g-resin (APA) were examined. Uranium(VI) adsorption properties of several ion exchange resins and extractant agents which were known as excellent adsorbents for uranium(VI), were examined together for a comparison with those of APA. Uranium(VI) adsorption capacity of APA at the concentration of 100 mg·dm -3 -uranium(VI) in 100 g·dm -3 -H 2 SO 4 aq. soln., 190 g·dm -3 -H 3 PO 4 aq. soln. and uranium enriched sea water, was 0.2, 0.05 and 0.05 mmol·g -1 respectively. The adsorption capacity of APA for uranium(VI) in these solutions was larger than that of another adsorbents, except the adsorption of uranium(VI) in enriched sea water on ion exchange resin containing phosphoric acid moiety (adsorption capacity ; 0.2 mmol·g -1 ). Uranium(VI) adsorption rate on APA was high and the relation between treatment time (t : min) and uranium(VI) concentration (y : mg·dm -3 ) in 100 g·dm -3 H 2 SO 4 aq. soln. after treatment, was shown as following equation, y=20 0.048t+1.90 (0≤t≤30). The adsorbed uranium(VI) on APA was able to be eluted with a mixed aq. soln. of hydrogen peroxide and sodium hydroxide and also was able to be eluted with an aq. alkaline soln. dissolved reduction agents such as sodium sulfite and hydrazine. From these results, it was thought that uranium(VI) adsorbed on APA was eluted due to the reduction to uranium(VI) by these eluents. (author)

  17. Remediation of uranium contaminated soils with bicarbonate extraction and microbial U(VI) reduction

    International Nuclear Information System (INIS)

    Phillips, E.J.P.; Landa, E.R.; Lovley, D.R.

    1995-01-01

    A process for concentrating uranium from contaminated soils in which the uranium is first extracted with bicarbonate and then the extracted uranium is precipitated with U(VI)-reducing microorganisms was evaluated for a variety of uranium-contaminated soils. Bicarbonate (100 mM) extracted 20-94% of the uranium that was extracted with nitric acid. The U(VI)-reducing microorganism, Desulfovibrio desulfuricans reduced the U(VI) to U(IV) in the bicarbonate extracts. In some instances unidentified dissolved extracted components, presumably organics, gave the extract a yellow color and inhibited U(VI) reduction and/or the precipitation of U(IV). Removal of the dissolved yellow material with the addition of hydrogen peroxide alleviated this inhibition. These results demonstrate that bicarbonate extraction of uranium from soil followed by microbial U(VI) reduction might be an effective mechanism for concentrating uranium from some contaminated soils. (author)

  18. Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite.

    Science.gov (United States)

    Meng, Fande; Yuan, Guodong; Larson, Steven L; Ballard, John H; Waggoner, Charles A; Arslan, Zikri; Han, Fengxiang X

    2017-12-01

    The occurrence of uranium (U) and depleted uranium (DU)-contaminated wastes from anthropogenic activities is an important environmental problem. Insoluble humic acid derived from leonardite (L-HA) was investigated as a potential adsorbent for immobilizing U in the environment. The effect of initial pH, contact time, U concentration, and temperature on U(VI) adsorption onto L-HA was assessed. The U(VI) adsorption was pH-dependent and achieved equilibrium in 2 h. It could be well described with pseudo-second-order model, indicating that U(VI) adsorption onto L-HA involved chemisorption. The U(VI) adsorption mass increased with increasing temperature with maximum adsorption capacities of 91, 112 and 120 mg g -1 at 298, 308 and 318 K, respectively. The adsorption reaction was spontaneous and endothermic. We explored the processes of U(VI) desorption from the L-HA-U complex through batch desorption experiments in 1 mM NaNO 3 and in artificial seawater. The desorption process could be well described by pseudo-first-order model and reached equilibrium in 3 h. L-HA possessed a high propensity to adsorb U(VI). Once adsorbed, the release of U(VI) from L-HA-U complex was minimal in both 1 mM NaNO 3 and artificial seawater (0.06% and 0.40%, respectively). Being abundant, inexpensive, and safe, L-HA has good potential for use as a U adsorbent from aqueous solution or immobilizing U in soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Selective Adsorption of Uranium (VI) on NaHCO Leached ...

    African Journals Online (AJOL)

    NICO

    with a variety of organic and inorganic ligands to form complex species of different ... approach for the synthesis of magnetic particles for uranium .... equations (1) and (2), respectively. Extraction efficiency. (C. C ). C o e o. = −. × 100. (1).

  20. Characterization of U(VI)-carbonato ternary complexes on hematite: EXAFS and electrophoretic mobility measurements

    Science.gov (United States)

    Bargar, John R.; Reitmeyer, Rebecca; Lenhart, John J.; Davis, James A.

    2000-01-01

    We have measured U(VI) adsorption on hematite using EXAFS spectroscopy and electrophoresis under conditions relevant to surface waters and aquifers (0.01 to 10 μM dissolved uranium concentrations, in equilibrium with air, pH 4.5 to 8.5). Both techniques suggest the existence of anionic U(VI)-carbonato ternary complexes. Fits to EXAFS spectra indicate that U(VI) is simultaneously coordinated to surface FeO6 octahedra and carbonate (or bicarbonate) ligands in bidentate fashions, leading to the conclusion that the ternary complexes have an inner-sphere metal bridging (hematite-U(VI)-carbonato) structure. Greater than or equal to 50% of adsorbed U(VI) was comprised of monomeric hematite-U(VI)-carbonato ternary complexes, even at pH 4.5. Multimeric U(VI) species were observed at pH ≥ 6.5 and aqueous U(VI) concentrations approximately an order of magnitude more dilute than the solubility of crystalline β-UO2(OH)2. Based on structural constraints, these complexes were interpreted as dimeric hematite-U(VI)-carbonato ternary complexes. These results suggest that Fe-oxide-U(VI)-carbonato complexes are likely to be important transport-limiting species in oxic aquifers throughout a wide range of pH values.

  1. Extraction equilibrium of uranium(VI) with dicyclohexano-18-crown-6 and its application for separating uranium and thorium

    International Nuclear Information System (INIS)

    Wang Wenji; Sun Quing; Chen Bozhong

    1986-01-01

    The extraction of uranium with dicyclohexano-18-crown-6 (mixed isomers) is described. The extraction equilibrium of uranium(VI) from aqueous hydrochloric acid solution with dicyclohexano-18-crown-6 isomer A (Isub(a)) and isomer B (Isub(b)) in 1,2-dichloroethane is presented. The extracted species were found to be 1:2 (metal/crown) for Isub(a) and 2:3 for Isub(b) from slope analysis and direct determination of extracted complexes. The extraction equilibrium constants (Ksub(ex)) were determined at 25 deg C and are equal to 29.5 and 0.208, respectively. It is concluded that Isub(a) has a stronger coordination ability for uranium than Isub(b). The different orientation of lone pairs of the oxygen atoms in both isomers has to be taken into account for interpereting the above results. (author)

  2. Effect of uranium (VI) on two sulphate-reducing bacteria cultures from a uranium mine site

    International Nuclear Information System (INIS)

    Martins, Monica; Faleiro, Maria Leonor; Chaves, Sandra; Tenreiro, Rogerio; Costa, Maria Clara

    2010-01-01

    This work was conducted to assess the impact of uranium (VI) on sulphate-reducing bacteria (SRB) communities obtained from environmental samples collected on the Portuguese uranium mining area of Urgeirica. Culture U was obtained from a sediment, while culture W was obtained from sludge from the wetland of that mine. Temperature gradient gel electrophoresis (TGGE) was used to monitor community changes under uranium stress conditions. TGGE profiles of dsrB gene fragment demonstrated that the initial cultures were composed of SRB species affiliated with Desulfovibrio desulfuricans, Desulfovibrio vulgaris and Desulfomicrobium spp. (sample U), and by species related to D. desulfuricans (sample W). A drastic change in SRB communities was observed as a result of uranium (VI) exposure. Surprisingly, SRB were not detected in the uranium removal communities. Such findings emphasize the need of monitoring the dominant populations during bio-removal studies. TGGE and phylogenetic analysis of the 16S rRNA gene fragment revealed that the uranium removal consortia are composed by strains affiliated to Clostridium genus, Caulobacteraceae and Rhodocyclaceae families. Therefore, these communities can be attractive candidates for environmental biotechnological applications associated to uranium removal.

  3. Remediation of uranium contaminated soils with bicarbonate extraction and microbial U(VI) reduction

    Science.gov (United States)

    Philips , Elizabeth J.P.; Landa, Edward R.; Lovely, Derek R.

    1995-01-01

    A process for concentrating uranium from contaminated soils in which the uranium is first extracted with bicarbonate and then the extracted uranium is precipitated with U(VI)-reducing microorganisms was evaluated for a variety of uranuum-contaminated soils. Bicarbonate (100 mM) extracted 20–94% of the uranium that was extracted with nitric acid. The U(VI)-reducing microorganism,Desulfovibrio desulfuricans reduced the U(VI) to U(IV) in the bicarbonate extracts. In some instances unidentified dissolved extracted components, presumably organics, gave the extract a yellow color and inhibited U(VI) reduction and/or the precipitation of U(IV). Removal of the dissolved yellow material with the addition of hydrogen peroxide alleviated this inhibition. These results demonstrate that bicarbonate extraction of uranium from soil followed by microbial U(VI) reduction might be an effective mechanism for concentrating uranium from some contaminated soils.

  4. Uranium(VI) retention by Ca-bentonite under (hyper)alkaline conditions

    Energy Technology Data Exchange (ETDEWEB)

    Philipp, Thimo; Schmeide, Katja [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

    2017-06-01

    The sorption behavior of U(VI) on Ca-bentonite was studied in saline, (hyper)alkaline solution via batch experiments. At pH 8.5-9.5 sorption is low in the presence of CO{sub 2} due to the formation of weakly sorbing uranyl carbonate species, which have been observed to dominate speciation up to pH 10 by time-resolved laser-induced fluorescence spectroscopy (TRLFS). In the pH region 10-12, U(VI) retention is almost complete. The retention can either be attributed to strongly sorbing uranyl hydroxo complexes or to a partial precipitation of uranium due to an altered solubility of U(VI) induced by ions leached out of the bentonite.

  5. Extraction separation studies of uranium(VI) by amine oxides

    International Nuclear Information System (INIS)

    Ejaz, M.

    1975-01-01

    The extraction of uranium(VI) by two amine oxides, 4-(5-nonyl)pyridine oxide and trioctylamine oxide has been studied. The extraction behavior of these two N-oxides is compared. The dependence of extraction on the type of amine oxide and acid, nature of organic diluent, and amine oxide concentration has been investigated. The influence of the concentration of the metal and salting-out agents is described. The possible mechanism of extraction is discussed in the light of the results of extraction isotherms, loading radiodata, and log-log plots of amine oxide concentration vs distribution ratio. The separation factors for a number of metal ions are reported, and the separation of uranium from some fission elements has also been achieved

  6. Interaction of uranium(VI) with bioligands present in human biological fluids. The case study of urea and uric acid

    International Nuclear Information System (INIS)

    Osman, A.A.A.; Geipel, G.; Bernhard, G.

    2013-01-01

    The complexation of uranium(VI) with bioligands found in human biological fluids, viz, urea and uric acid in aqueous solutions, has been investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature, I = 0.1 M (NaClO4) and pH (3 for uric acid; 4 for urea). In both complex systems a static quench effect with increasing ligand concentration and no peaks shift upon complexation were observed. With uranium(VI) both ligands formed a fairly weak 1:1 complex with average stability constants of log β 110 = 4.67 ± 0.29 for uric acid and log β 110 = 3.79 ± 0.15 and 2.12 ± 0.18 for relatively low and relatively high urea concentrations, respectively. Application of the newly generated data on the U(VI) speciation modelling in biofluids, e.g., human urine was also discussed.

  7. Interaction of uranium(VI) with bioligands present in human biological fluids. The case study of urea and uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Osman, A.A.A.; Geipel, G.; Bernhard, G. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany). Inst. of Resource Ecology

    2013-05-01

    The complexation of uranium(VI) with bioligands found in human biological fluids, viz, urea and uric acid in aqueous solutions, has been investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature, I = 0.1 M (NaClO4) and pH (3 for uric acid; 4 for urea). In both complex systems a static quench effect with increasing ligand concentration and no peaks shift upon complexation were observed. With uranium(VI) both ligands formed a fairly weak 1:1 complex with average stability constants of log {beta}{sub 110} = 4.67 {+-} 0.29 for uric acid and log {beta}{sub 110} = 3.79 {+-} 0.15 and 2.12 {+-} 0.18 for relatively low and relatively high urea concentrations, respectively. Application of the newly generated data on the U(VI) speciation modelling in biofluids, e.g., human urine was also discussed.

  8. On the uptake and binding of uranium (VI) by the green alga Chlorella Vulgaris

    International Nuclear Information System (INIS)

    Vogel, Manja

    2011-01-01

    the algae cells during the sorption experiment and a behavior analogue to initially heat killed cells. Differences in the contribution of functional groups to the uranium binding depending on the metabolic activity of the algal biomass were also shown by the difference spectra of the ATR-FTIR measurements calculated between uranium contaminated and untreated biomass. All together the spectroscopic investigations showed in case of Chlorella vulgaris a mixture of functional groups is responsible for the coordination of U(VI). The metabolic activity of the cells influences the binding of uranium under the given experimental conditions. Models of the structure of the formed U(VI)-algae complexes in dependence of the metabolic activity were created. For living algal cells, mainly carboxylic and organic phosphate groups are involved in the binding of uranium, whereas in dead algal biomass additionally inorganic phosphates are involved to some extend in the interaction of uranium with algal cells. The transferability of the obtained findings concerning the experiments in mineral medium to natural occurring mining related waters was verified exemplary with the surface water of ''Gessenwiese'' (former ''Gessenhalde'' at Ronneburg). The obtained results of this study contribute to the prediction of the migration behavior of uranium under environmental conditions, the radiological risk assessment of geogenic and anthropogenic appearing uranium and a reliable estimation of the accumulation of uranium in the food chain.

  9. Examination of Uranium(VI) Leaching During Ligand Promoted Dissolution of Waste Tank Sludge Surrogates

    Energy Technology Data Exchange (ETDEWEB)

    Powell, Brian; Powell, Brian A.; Rao, Linfeng; Nash, Kenneth. L.

    2008-06-10

    The dissolution of synthetic boehmite (?-AlOOH) by 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) was examined in a series of batch adsorption/dissolution experiments. Additionally, the leaching behavior of {sup 233}U(VI) from boehmite was examined as a function of pH and HEDPA concentration. The results are discussed in terms of sludge washing procedures that may be utilized during underground tank waste remediation. In the pH range 4 to 10, complexation of Al(III) by HEDPA significantly enhanced dissolution of boehmite. This phenomenon was especially pronounced in the neutral pH region where the solubility of aluminum, in the absence of complexants, is limited by the formation of sparsely soluble aluminum hydroxides. At pH higher than 10, dissolution of synthetic boehmite was inhibited by HEDPA, likely due to sorption of Al(III):HEDPA complexes. Addition of HEDPA to equilibrated U(VI)-synthetic boehmite suspensions yielded an increase in the aqueous phase uranium concentration. Partitioning of uranium between the solid and aqueous phase is described in terms of U(VI):HEDPA speciation and dissolution of the boehmite solid phase.

  10. Liquid-liquid extraction of uranium(VI) with cryptand-222 and Eosin as the counter ion

    International Nuclear Information System (INIS)

    Viji Jacob Mathew; Khopkar, S.M.

    1995-01-01

    Uranium(VI), (5 μg) was quantitatively extracted at pH 6.0 with 0.01M cryptand-222 in chloroform in the presence of 0.005M Eosin as the counter ion. The metal from the organic phase was stripped with 0.1M perchloric acid. Uranium(VI) from the aqueous phase was determined spectrophotometrically at 430 nm as its complex with oxine. The extraction was quantitative between pH 5.5-6.5. Nitrobenzene, chloroform and dichloromethane were the best diluents. The optimum extractant concentration was 0.01M, while that of Eosin was 0.005M. Except for perchloric acid (0.01M), other acids could not strip uranium. Uranium was separated from manganese, cadmium, lead, thallium and nickel, etc., in the multicomponent mixtures. The relative standard deviation was ±1%. (author). 18 refs., 1 fig., 6 tabs

  11. Interactions of uranium (VI) with biofilms; Wechselwirkung von Uran(VI) mit Biofilmen

    Energy Technology Data Exchange (ETDEWEB)

    Brockmann, Sina; Arnold, Thuro; Bernhard, Gert

    2013-07-01

    In this study a detailed investigation was made of natural biofilms from two uranium-contaminated sites, namely the former uranium mine in Koenigstein (Saxony) and the ground surface of the former Grassenhalde tailing heap in Thuringia. A predominance of uranyl sulphate (UO{sub 2}SO{sub 4}), a highly mobile, solute uranium species, was found in the mine waters of both sites. In this study an investigation was made of the capacity of Euglena mutabilis cells for bioaccumulation of uranium in a pH range of 3 to 6 using living cells and sodium perchlorate (9 g/l) or sodium sulphate (3.48 g/l) as background media. At acidic pH values in the range from 3 to 4 it was possible to remove more than 90% of the original uranium content from the test solution regardless of the medium being used. The speciation of the uranium accumulated in the Euglena cells was investigated by laser-induced fluorescence spectroscopy (LIFS). It was found that a new uranium species of low variability forms on the cells independent of the background medium, state of life of the cells and pH value. By comparing the data from the LIFS measurements with reference values it was possible to narrow down the identity of the uranium species to one bonded to (organo) phosphate and/or carboxylic functional groups. Using time-resolved FT-IR spectroscopy it was possible to demonstrate carboxylic bonding of uranium to dead cells. However it was not possible to exclude (organo) complexation with this method. An investigation of the specific location of the uranium on or in the cells using combined CLSM/LIFS technology yielded first indications of intracellular accumulation of uranium in the living cells. Supplementary TEM/EDX measurements confirmed the intracellular uptake, showing it to occur in round to oval cell organelles which are thought to be vacuoles or vacuole-like vesicles. It was not possible to detect uranium on dead cells using these methods. This points to passive, homogeneously distributed

  12. Study of new complexes of uranium and comba radical. I.- Complexes defective in sodium carbonate

    International Nuclear Information System (INIS)

    Vera Palomino, J.; Galiano Sedano, J. A.; Parellada Bellod, R.; Bellido Gonzalez, A.

    1975-01-01

    Some complexes formed in presence of defect of sodium carbonate with respect to the stoichiometric ratio (U): (C0 3 ) = 1:3 are studied. This ratio corresponds to the main complex which is responsible for the uranium extraction with CDMBAC organic solutions and from U(VI) aqueous solutions with an excess of sodium carbonate. (Author) 10 refs

  13. Complex formation in the system uranium(VI) - alpha-substituted carboxylic acids studied by TRLFS. Pt. III. Alpha-aminoisobutyric acid at pH 4

    International Nuclear Information System (INIS)

    Moll, H.; Geipel, G.; Bernhard, G.; Fanghaenel, Th.; Grenthe, I.

    2002-01-01

    At higher ligand concentrations a 1:2 complex between UO 2 2+ and α-aminoisobutyric acid was observed at pH 4. Fluorescence lifetimes and spectra were obtained for UO 2 [NH 3 C(CH 3 ) 2 COO] 2 2+ . The complex formation constant was found to be log β 1:2 = 2.07±0.25. (orig.)

  14. Investigation on Microbial Dissolution of Uranium (VI) from Autunite Mineral - 13421

    Energy Technology Data Exchange (ETDEWEB)

    Sepulveda, Paola; Katsenovich, Yelena; Lagos, Leonel [Applied Research Center, Florida International University. 10555 West Flagler St. Suite 2100, Miami Fl 33175 (United States)

    2013-07-01

    Precipitating autunite minerals by polyphosphate injection was identified as a feasible remediation strategy for sequestering uranium in contaminated groundwater and soil in situ at the Hanford Site. Autunite stability under vadose and saturated zone environmental conditions can help to determine the long-term effectiveness of this remediation strategy. The Arthrobacter bacteria are one of the most common groups in soils and are found in large numbers in Hanford soil as well as other subsurface environments contaminated with radionuclides. Ubiquitous in subsurface microbial communities, these bacteria can play a significant role in the dissolution of minerals and the formation of secondary minerals. The main objective of this investigation was to study the bacterial interactions under oxidizing conditions with uranium (VI); study the potential role of bicarbonate, which is an integral complexing ligand for U(VI) and a major ion in groundwater compositions; and present data from autunite dissolution experiments using Arthrobacter strain G968, a less U(VI)-tolerant strain. Sterile 100 mL glass mixed reactors served as the major bioreactor for initial experimentation. These autunite-containing bioreactors were injected with bacterial cells after the autunite equilibrated with the media solution amended with 0 mM, 3 mM 5 mM and 10 mM concentrations of bicarbonate. G968 Arthrobacter cells in the amount of 10{sup 6} cells/mL were injected into the reactors after 27 days, giving time for the autunite to reach steady state. Abiotic non-carbonate controls were kept without bacterial inoculation to provide a control for the biotic samples. Samples of the solution were analyzed for dissolved U(VI) by means of kinetic phosphorescence analyzer KPA-11 (Chemcheck Instruments, Richland, WA). Analysis showed that as [HCO{sub 3}{sup -}] increases, a diminishing trend on the effect of bacteria on autunite leaching is observed. Viability of cells was conducted after 24 hours of cell

  15. Investigation on Microbial Dissolution of Uranium (VI) from Autunite Mineral - 13421

    International Nuclear Information System (INIS)

    Sepulveda, Paola; Katsenovich, Yelena; Lagos, Leonel

    2013-01-01

    Precipitating autunite minerals by polyphosphate injection was identified as a feasible remediation strategy for sequestering uranium in contaminated groundwater and soil in situ at the Hanford Site. Autunite stability under vadose and saturated zone environmental conditions can help to determine the long-term effectiveness of this remediation strategy. The Arthrobacter bacteria are one of the most common groups in soils and are found in large numbers in Hanford soil as well as other subsurface environments contaminated with radionuclides. Ubiquitous in subsurface microbial communities, these bacteria can play a significant role in the dissolution of minerals and the formation of secondary minerals. The main objective of this investigation was to study the bacterial interactions under oxidizing conditions with uranium (VI); study the potential role of bicarbonate, which is an integral complexing ligand for U(VI) and a major ion in groundwater compositions; and present data from autunite dissolution experiments using Arthrobacter strain G968, a less U(VI)-tolerant strain. Sterile 100 mL glass mixed reactors served as the major bioreactor for initial experimentation. These autunite-containing bioreactors were injected with bacterial cells after the autunite equilibrated with the media solution amended with 0 mM, 3 mM 5 mM and 10 mM concentrations of bicarbonate. G968 Arthrobacter cells in the amount of 10 6 cells/mL were injected into the reactors after 27 days, giving time for the autunite to reach steady state. Abiotic non-carbonate controls were kept without bacterial inoculation to provide a control for the biotic samples. Samples of the solution were analyzed for dissolved U(VI) by means of kinetic phosphorescence analyzer KPA-11 (Chemcheck Instruments, Richland, WA). Analysis showed that as [HCO 3 - ] increases, a diminishing trend on the effect of bacteria on autunite leaching is observed. Viability of cells was conducted after 24 hours of cell incubation with

  16. Microbial reduction of uranium(VI) by anaerobic microorganisms isolated from a former uranium mine

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, Ulrike; Krawczyk-Baersch, Evelyn [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biogeochemistry; Arnold, Thuro [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Resource Ecology; Scheinost, Andreas C. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures

    2017-06-01

    The former uranium mine Koenigstein (Germany) is currently in the process of controlled flooding by reason of remediation purposes. However, the flooding water still contains high concentrations of uranium and other heavy metals. For that reason the water has to be cleaned up by a conventional waste water treatment plant. The aim of this study was to investigate the interactions between anaerobic microorganisms and uranium for possible bioremediation approaches, which could be an great alternative for the intensive and expensive waste water treatment. EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements were performed and revealed a complete reduction of U(VI) to U(IV) only by adding 10 mM glycerol.

  17. Microbial reduction of uranium(VI) by anaerobic microorganisms isolated from a former uranium mine

    International Nuclear Information System (INIS)

    Gerber, Ulrike; Krawczyk-Baersch, Evelyn; Arnold, Thuro; Scheinost, Andreas C.

    2017-01-01

    The former uranium mine Koenigstein (Germany) is currently in the process of controlled flooding by reason of remediation purposes. However, the flooding water still contains high concentrations of uranium and other heavy metals. For that reason the water has to be cleaned up by a conventional waste water treatment plant. The aim of this study was to investigate the interactions between anaerobic microorganisms and uranium for possible bioremediation approaches, which could be an great alternative for the intensive and expensive waste water treatment. EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements were performed and revealed a complete reduction of U(VI) to U(IV) only by adding 10 mM glycerol.

  18. Liquid-liquid extraction of uranium (VI) using Cyanex 272 in kerosene from sodium salicylate medium

    International Nuclear Information System (INIS)

    Kamble, Pravin N.; Mohite, Baburao S.; Suryavanshi, Vishal J.; Salunkhe, Suresh T.

    2015-01-01

    Liquid-liquid extraction of uranium (VI) from sodium salicylate media using Cyanex 272 in kerosene has been carried out. Uranium (VI) was quantitatively extracted from 1x10 -4 M sodium salicylate with 5x10 -4 M Cyanex 272 in kerosene. It was stripped quantitatively from the organic phase with 4M HCl and determined spectrophotometrically with arsenazo(III) at 600 nm. The effects of concentrations of sodium salicylate, metal ions and strippants have been studied. Separation of uranium (VI) from other elements was achieved from binary as well as from multicomponent mixtures. The method is simple, rapid and selective with good reproducibility (approximately ±2%). (author)

  19. Effect of uranium (VI) on the growth of yeast and influence of metabolism of yeast on adsorption of U (VI)

    International Nuclear Information System (INIS)

    Sakamoto, Fuminori; Ohnuki, Toshihiko; Kozai, Naofumi; Wakai, Eiichi; Francis, A.J.

    2005-01-01

    We have carried out the growth experiments of 3 strains of yeast in a medium containing uranium (VI) to elucidate the effect of U (VI) on the growth of microorganisms. Hansenula fabianii J640 grew in the liquid medium containing 0.1 mM U (VI) at lower rate than the control, but Saccharomyces cerevisiae did not grow under this condition. The H. fabianii J640 pre-cultured for 21 h in the liquid medium without U (VI) grew even after the exposure to 1 mM U (VI), but did not grow without pre-cultivation. For the pre-cultured H. fabianii J640, radioactivity of U in the medium was the same as the initial one for 110 h, and then gradually decreased. TEM-EDS analysis of H. fabianii J640 exposed to 1 mM U (VI) for 165 h showed accumulation of U (VI) on the cells. When H. fabianii J640 was not pre-cultured, radioactivity of U in the medium was lower than the initial one. These results indicated that U (VI) inhibits the growth of yeast, and that the adsorption of U (VI) by the cells depends on the metabolism of yeast. (author)

  20. Bio sorption process for uranium (VI) by using algae-yeast-silica gel composite adsorbent

    International Nuclear Information System (INIS)

    Turkozu, D. A.; Aytas, S.

    2006-01-01

    Many yeast, algae, bacteria and various aquatic flora are known to be capable of concentrating metal species from dilute aqueous solution. Many researcher have found that non-living biomaterials can be used to accumulate metal ions from environment. In recent studies, mainly two process are used in biosorption experiments. These are the use of free cells and the use of immobilized cells on a solid support. A variety of inert supports have been used to immobilize biomaterials either by adsorption or physical entrapment. This uptake is often considerable and frequently selective, and occurs via a variety of mechanisms including active transport, ion exchange or complexation, and adsorption or inorganic precipitation. Biosorbent may be used as an ion exchange material. Adsorption occurs through interaction of the metal ions with functional groups that are found in the cell wall biopolymers of either living or dead organisms. In this study, the algae-yeast-silica gel composite adsorbent was tested for its ability to recover U(VI) from diluted aqueous solutions. Macro marine algae (Jania rubens.), yeast (Saccharomyces cerevisiae) and silica gel were used to prepare composite adsorbent. The ability of the composite biosorbent to adsorb uranium (VI) from aqueous solution has been studied at different optimized conditions of pH, concentration of U(VI), temperature, contact time and matrix ion effect was also investigated. The adsorption patterns of uranium on the composite biosorbent were investigated by the Langmuir, Freundlich and Dubinin-Radushkhevic isotherms. The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated. The results suggested that the macro algae-yeast-silica gel composite sorbent is suitable as a new biosorbent material for removal of uranium ions from aqueous solutions

  1. On the uptake and binding of uranium (VI) by the green alga Chlorella Vulgaris; Zur Aufnahme und Bindung von Uran(VI) durch die Gruenalge Chlorella Vulgaris

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, Manja

    2011-07-01

    of the algae cells during the sorption experiment and a behavior analogue to initially heat killed cells. Differences in the contribution of functional groups to the uranium binding depending on the metabolic activity of the algal biomass were also shown by the difference spectra of the ATR-FTIR measurements calculated between uranium contaminated and untreated biomass. All together the spectroscopic investigations showed in case of Chlorella vulgaris a mixture of functional groups is responsible for the coordination of U(VI). The metabolic activity of the cells influences the binding of uranium under the given experimental conditions. Models of the structure of the formed U(VI)-algae complexes in dependence of the metabolic activity were created. For living algal cells, mainly carboxylic and organic phosphate groups are involved in the binding of uranium, whereas in dead algal biomass additionally inorganic phosphates are involved to some extend in the interaction of uranium with algal cells. The transferability of the obtained findings concerning the experiments in mineral medium to natural occurring mining related waters was verified exemplary with the surface water of ''Gessenwiese'' (former ''Gessenhalde'' at Ronneburg). The obtained results of this study contribute to the prediction of the migration behavior of uranium under environmental conditions, the radiological risk assessment of geogenic and anthropogenic appearing uranium and a reliable estimation of the accumulation of uranium in the food chain.

  2. Studies on new complexes of dioxo uranium(VI) and thorium(IV) with some schiff bases derived from trimethoprime salicyldehyde and o-vanillin (Paper No. AL-50)

    International Nuclear Information System (INIS)

    Pujar, M.A.; Pirgonde, B.R.

    1990-02-01

    Dioxouranium(VI) and thorium(IV) form 1:1(Metal:Ligands) complexes with some schiff bases. The complexes have been characterized through elemental analyses, electronic and IR spectral, conductance and magnetic susceptibility measurements. They are considered dimeric or polymeric hexa or octa-coordinated arrangement around metal ion moiety. Force constants and U-O bond lengths have been calculated. (author). 1 tab

  3. Synthesis, characterization and oxidative behaviour of dioxoruthenium(VI) complexes

    International Nuclear Information System (INIS)

    Agarwal, D.D.; Rastogi, Rachana

    1995-01-01

    Dioxoruthenium(VI) complexes are found to give low yield of epoxide but good yield of cyclohexanone. The complexes are electro active giving metal centered Ru VI /Ru V couple. Cis-stilbene gives trans epoxide and benzaldehyde. Norbornene gives exo epoxy norbornene. The selectivity for allylic oxidation is high. In the present note the synthesis of dioxoruthenium(VI) complexes and their oxidation behaviour is reported. The dioxoruthenium(VI) complexes have been stoichiometrically found to be good oxidants. (author). 21 refs., 1 tab

  4. Comparative EXAFS study of uranium(VI) and neptunium(V) sorption onto kaolinite

    International Nuclear Information System (INIS)

    Reich, T.; Amayri, S.; Reich, Ta.; Jermolajev, J.

    2005-01-01

    Full text of publication follows: We investigated the surface sorption process of U(VI) and Np(V) on kaolinite by extended X-ray absorption fine structure (EXAFS) spectroscopy in the 10 μM concentration range. Batch experiments with kaolinite in CO 2 -equilibrated systems showed that the adsorption edge of U(VI) occurs at pH 5.5, i.e., near the pH PZC of kaolinite. The adsorption edge of Np(V) occurs well above the pH PZC value at pH 8.5. This may indicate that the bonds between Np(V) and the surface functional groups of kaolinite are not as strong as in the case of U(VI). U(VI) and Np(V) have in common that the amount which is adsorbed decreases when the pH is increased beyond the absorption maximum. This behavior can be attributed to the formation of U(VI) and Np(V) carbonato complexes in the aqueous solutions. The aim of this comparative EXAFS study was to investigate the reason for the different affinities of U(VI) and Np(V) for kaolinite by measuring their local environments at the clay surface. Samples were prepared from 4 g/L kaolinite, 0.1 M NaClO 4 , pH 3.0 - 10.5, presence and absence of ambient CO 2 . The U L 3 - and Np L 2 -edge EXAFS spectra of the wet paste samples were measured at room temperature in fluorescence mode at the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility. The measured U-O and U-Al/Si distances indicate inner-sphere sorption of U(VI) on kaolinite. There was no evidence of uranium neighbors in the EXAFS spectra, suggesting that the adsorbed U(VI) complexes were predominantly monomeric. The average distance between uranium and its equatorial oxygen atoms, O eq , increased from 2.32 to 2.38 Angstrom in the presence of atmospheric CO 2 when the pH was increased from 5.0 to 8.5. In the CO 2 -free system, the U-O eq distance was independent from pH and equal to 2.32 Angstrom. The lengthening of the average U-O eq distance in the presence of carbonate (or bicarbonate) suggests the formation of ternary U(VI

  5. Uranium complex recycling method of purifying uranium liquors

    International Nuclear Information System (INIS)

    Elikan, L.; Lyon, W.L.; Sundar, P.S.

    1976-01-01

    Uranium is separated from contaminating cations in an aqueous liquor containing uranyl ions. The liquor is mixed with sufficient recycled uranium complex to raise the weight ratio of uranium to said cations preferably to at least about three. The liquor is then extracted with at least enough non-interfering, water-immiscible, organic solvent to theoretically extract about all of the uranium in the liquor. The organic solvent contains a reagent which reacts with the uranyl ions to form a complex soluble in the solvent. If the aqueous liquor is acidic, the organic solvent is then scrubbed with water. The organic solvent is stripped with a solution containing at least enough ammonium carbonate to precipitate the uranium complex. A portion of the uranium complex is recycled and the remainder can be collected and calcined to produce U 3 O 8 or UO 2

  6. Uranium(VI) speciation: modelling, uncertainty and relevance to bioavailability models. Application to uranium uptake by the gills of a freshwater bivalve; Speciation de l'uranium(6), modelisation, incertitude et implication pour les modeles de biodisponibilite. Application a l'accumulation dans les branchies d'un bivalve d'eau douce

    Energy Technology Data Exchange (ETDEWEB)

    Denison, F.H

    2004-07-01

    The effects of varying solution composition on the interactions between uranium(VI) and excised gills of the freshwater bivalve Corbicula fluminea have been investigated in well defined solution media. A significant reduction in the uptake of uranium was observed on increasing the concentrations of the uranium complexing ligands citrate and carbonate. Saturation kinetics as a function of uranium concentration at a pH value of 5.0 were observed, indicating that the uptake of uranium is a facilitated process, probably involving one or several trans-membrane transport systems. A relatively small change in the uptake of uranium was found as a function of pH (factor of ca. 2), despite the extremely large changes to the solution speciation of uranium within the range of pH investigated (5.0 - 7.5). A comprehensive review of the thermodynamic data relevant to the solution composition domain employed for this study was performed. Estimates of the uncertainties for the formation constants of aqueous uranium(VI) species were integrated into a thermodynamic database. A computer program was written to predict the equilibrium distribution of uranium(VI) in simple aqueous systems, using thermodynamic parameter mean-values. The program was extended to perform Monte Carlo and Quasi Monte Carlo uncertainty analyses, incorporating the thermodynamic database uncertainty estimates, to quantitatively predict the uncertainties inherent in predicting the solution speciation of uranium. The use of thermodynamic equilibrium modelling as a tool for interpreting the bioavailability of uranium(VI) was investigated. Observed uranium(VI) uptake behaviour was interpreted as a function of the predicted changes to the solution speciation of uranium. Different steady-state or pre-equilibrium approaches to modelling uranium uptake were tested. Alternative modelling approaches were also tested, considering the potential changes to membrane transport system activity or sorption characteristics on

  7. Investigation of uranium (VI) extraction mechanisms from phosphoric and sulfuric media by {sup 31}P-NMR

    Energy Technology Data Exchange (ETDEWEB)

    Fries, B.; Marie, C.; Pacary, V.; Berthon, C.; Miguirditchian, M.; Charbonnel, M.C. [CEA, Centre de Marcoule, Nuclear Energy Divison, RadioChemistry and Processes Department - DRCP, F-30207 Bagnols-sur-Ceze (France); Mokhtari, H. [AREVA Mines, Process and Analysis Department - SEPA, F-87250 Bessines-sur-Gartempe (France)

    2016-07-01

    Phosphate rocks contain uranium (∼1000 ppm on average) and are considered as a secondary source for uranium production. Uranium extraction using DEHCNPB (butyl-1-[N,N-bis(2-ethylhexyl)carbamoyl]nonyl phosphonic acid, a bifunctional cationic extractant) has been studied to better understand mechanism differences depending on the original acidic solution (phosphoric or sulfuric). Solvent extraction batch experiments were carried out and the organic phases were probed using {sup 31}P-NMR. This technique enabled to demonstrate that phosphoric acid is poorly extracted by DEHCNPB ([H{sub 3}PO{sub 4}]{sub org} < 2 mM), using direct quantification in the organic phase by {sup 31}P-NMR spectra integration. Moreover, in the presence of uranium in the initial phosphoric acid solution, uranyl extraction by DEHCNPB competes with H{sub 3}PO{sub 4} extraction. Average stoichiometries of U(VI)-DEHCNPB complexes in organic phases were also determined using slope analysis on uranium distribution data. Uranium seems to be extracted from a phosphoric medium by two extractant molecules, whereas more than three DEHCNPB on average would be necessary to extract uranium from a sulfuric medium. Thus, uranium is extracted according to different mechanisms depending on the nature of the initial solution. (authors)

  8. Spectrophotometric determination of uranium (VI) with arsenazo III in a nitric medium

    International Nuclear Information System (INIS)

    Yamaura, Mitiko; Wada, Luciana Yukie; Ribeiro, Fernando Castilho

    2002-01-01

    Arsenazo III is an organic reagent usually used for the photometric determination of various elements, including the uranium, thorium, plutonium, barium, strontium, hafnium, bismuth and the rare earth elements. The reactions of arsenazo III with many elements are very sensitive and, consequently is not specific for any element. Arsenazo III with U(VI) gives a 1:1 coloured complex in diluted acid solution of pH 1 to 3, and in strong acid media forming 1:1, 1:2 and 1:3 species. In this work, a detailed study of the influence of pH is described. The stability of formed complex and the interference of Fe(III) ions were also studied. (author)

  9. Modification of zirconium diphosphate with salicylic acid and its effect on the uranium (Vi) sorption; Modificacion del difosfato de circonio con acido salicilico y su efecto sobre la sorcion de uranio (VI)

    Energy Technology Data Exchange (ETDEWEB)

    Almazan T, M. G.; Garcia G, N. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Simoni, E., E-mail: guadalupe.almazan@inin.gob.mx [Universidad Paris Sud, Instituto de Fisica Nuclear, Georges Clemenceau No. 15, Orsay (France)

    2014-10-15

    The surface of zirconium diphosphate (ZrP{sub 2}O{sub 7}) was modified with salicylic acid and its effect was evaluated on the uranium (Vi) sorption. The modified surface of the material was analyzed with different analytical techniques among which are included the atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. This analysis allowed showing that the salicylic acid is being held on the surface of the zirconium diphosphate. The reactivity of modified zirconium diphosphate compared with uranium (Vi) was investigated using the classical method of batch sorption. The analysis of sorption isotherms shows that the salicylic acid has an important effect in the uranium (Vi) sorption. According to the study conducted, the interaction among the uranium (Vi) and the surface of zirconium diphosphate modified with the salicylic acid most likely leads to the complexes formation of binary (U(Vi)/ZrP{sub 2}O{sub 7}) and ternary (U(Vi)/salicylate/ZrP{sub 2}O{sub 7}) surface. (Author)

  10. Comparison of U(VI) adsorption onto nanoscale zero-valent iron and red soil in the presence of U(VI)–CO_3/Ca–U(VI)–CO_3 complexes

    International Nuclear Information System (INIS)

    Zhang, Zhibin; Liu, Jun; Cao, Xiaohong; Luo, Xuanping; Hua, Rong; Liu, Yan; Yu, Xiaofeng; He, Likai

    2015-01-01

    Highlights: • NZVI can be used for adsorbing U(VI)–CO_3 complexes. • Use of NZVI is feasible for remediation of uranium-contaminated soils. • The mechanism of U(VI)–CO_3 complexes adsorbing onto NZVI has been explained. - Abstract: The influence of U(VI)–CO_3 and Ca–U(VI)–CO_3 complexes on U(VI) adsorption onto red soil and nanoscale zero-valent iron (NZVI) was investigated using batch adsorption and fixed-bed column experiments to simulate the feasibility of NZVI as the reactive medium in permeable- reactive barriers (PRB) for in situ remediation of uranium-contaminated red soils. The adsorption capacity (q_e) and distribution constant (K_d) of NZVI and red soil decreased with increasing pH, dissolved carbonate and calcium concentrations, but the q_e and K_d values of NZVI were 5–10 times higher than those of red soil. The breakthrough pore volume (PV) values increased with the decrease of pH, dissolved carbonate and calcium concentration; however, the breakthrough PV values of the PRB column filled with 5% NZVI were 2.0–3.5 times higher than the 100% red soil column. The U(VI)–CO_3 complexes adsorbed onto the surface of red soil/NZVI (≡SOH) to form SO–UO_2CO_3"− or SO–UO_2 (CO_3)_2"3"−. XPS and XRD analysis further confirmed the reduction of U(VI) to U(IV) and the formation of FeOOH on NZVI surfaces. The findings of this study are significant to the remediation of uranium-contaminated red soils and the consideration of practical U(VI) species in the natural environment.

  11. Comparison of U(VI) adsorption onto nanoscale zero-valent iron and red soil in the presence of U(VI)–CO{sub 3}/Ca–U(VI)–CO{sub 3} complexes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhibin [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Liu, Jun [State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Cao, Xiaohong, E-mail: xhcao@ecit.cn [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Luo, Xuanping [Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Hua, Rong; Liu, Yan [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Yu, Xiaofeng; He, Likai [Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); and others

    2015-12-30

    Highlights: • NZVI can be used for adsorbing U(VI)–CO{sub 3} complexes. • Use of NZVI is feasible for remediation of uranium-contaminated soils. • The mechanism of U(VI)–CO{sub 3} complexes adsorbing onto NZVI has been explained. - Abstract: The influence of U(VI)–CO{sub 3} and Ca–U(VI)–CO{sub 3} complexes on U(VI) adsorption onto red soil and nanoscale zero-valent iron (NZVI) was investigated using batch adsorption and fixed-bed column experiments to simulate the feasibility of NZVI as the reactive medium in permeable- reactive barriers (PRB) for in situ remediation of uranium-contaminated red soils. The adsorption capacity (q{sub e}) and distribution constant (K{sub d}) of NZVI and red soil decreased with increasing pH, dissolved carbonate and calcium concentrations, but the q{sub e} and K{sub d} values of NZVI were 5–10 times higher than those of red soil. The breakthrough pore volume (PV) values increased with the decrease of pH, dissolved carbonate and calcium concentration; however, the breakthrough PV values of the PRB column filled with 5% NZVI were 2.0–3.5 times higher than the 100% red soil column. The U(VI)–CO{sub 3} complexes adsorbed onto the surface of red soil/NZVI (≡SOH) to form SO–UO{sub 2}CO{sub 3}{sup −} or SO–UO{sub 2} (CO{sub 3}){sub 2}{sup 3−}. XPS and XRD analysis further confirmed the reduction of U(VI) to U(IV) and the formation of FeOOH on NZVI surfaces. The findings of this study are significant to the remediation of uranium-contaminated red soils and the consideration of practical U(VI) species in the natural environment.

  12. Potentiometric studies on quaternary complexes of dioxouranium(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Kumari, Vinod; Chaturvedi, G K [Agra Coll., (India). Chemical Laboratories

    1979-10-01

    The formation of quaternary complexes of dioxouranium(VI) with three different organic acids (OX, MALN and SA, SSA, TAR or TMA) has been inferred from the potentiometric studies. The formation constants for the resulting triligand complexes have been evaluated.

  13. Uranium complexes with macrosyclic polyethers. Synthesis and structural chemical analysis

    International Nuclear Information System (INIS)

    Elbasyouny, A.

    1983-01-01

    This dissertation reports about studies on the chemical coordination behaviour of uranium of oxidation stages IV and VI with regard to twelve different macrocyclic ligands. For the preparation of the complexes, for every system a different method has been developed. The elementary analysis of the various complexes including the uranium had been done by X-ray fluorescence analysis, and the structural characterization proceeded via vibrational, uv-vis and emission spectroscopy as well as 1 H-NMR and 13 C-spin-lattice relaxation time studies. Conformational analysis of the polyethers used allowed the structural changes in the complexes to be observed. The structural analysis of the hydrous uranium VI crown ether complexes yielded information of characteristic features of these types of complexes. The first coordination sphere of the uranyl ion with covalently bonded anion remains unchanged. As to the water content, there is a certain range. Depending upon the solvent used, the complexes have two or four H 2 O molecules per formula unit. (orig./EF) [de

  14. TREATMENT TESTS FOR EX SITU REMOVAL OF CHROMATE & NITRATE & URANIUM (VI) FROM HANFORD (100-HR-3) GROUNDWATER FINAL REPORT

    Energy Technology Data Exchange (ETDEWEB)

    BECK MA; DUNCAN JB

    1994-01-03

    This report describes batch and ion exchange column laboratory scale studies investigating ex situ methods to remove chromate (chromium [VI]), nitrate (NO{sub 3}{sup -}) and uranium (present as uranium [VI]) from contaminated Hanford site groundwaters. The technologies investigated include: chemical precipitation or coprecipitation to remove chromate and uranium; and anion exchange to remove chromate, uranium and nitrate. The technologies investigated were specified in the 100-HR-3 Groundwater Treatability Test Plan. The method suggested for future study is anion exchange.

  15. Removal of uranium(VI) from the aqueous phase by iron(II) minerals in presence of bicarbonate

    Energy Technology Data Exchange (ETDEWEB)

    Regenspurg, Simona, E-mail: regens@gfz-potsdam.de [Industrial Ecology, Royal Institute of Technology (KTH), SE 10044 Stockholm (Sweden); Schild, Dieter; Schaefer, Thorsten; Huber, Florian [Institut fuer Nukleare Entsorgung (INE), Forschungszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen (Germany); Malmstroem, Maria E. [Industrial Ecology, Royal Institute of Technology (KTH), SE 10044 Stockholm (Sweden)

    2009-09-15

    Uranium(VI) mobility in groundwater is strongly affected by sorption of mobile U(VI) species (e.g. uranyl, UO{sub 2}{sup 2+}) to mineral surfaces, precipitation of U(VI) compounds, such as schoepite (UO{sub 2}){sub 4}O(OH){sub 6}.6H{sub 2}O), and by reduction to U(IV), forming sparingly soluble phases (uraninite; UO{sub 2}). The latter pathway, in particular, would be very efficient for long-term immobilization of U. In nature, Fe(II) is an important reducing agent for U(VI) because it frequently occurs either dissolved in natural waters, sorbed to matrix minerals, or structurally bound in many minerals. Redox reactions between U(VI) and Fe(II) depend not only on the availability of Fe(II) in the environment, but also on the chemical conditions in the aqueous solution. Under natural groundwater condition U(VI) forms complexes with many anionic ligands, which strongly affect its speciation. Carbonate, in particular, is known to form stable complexes with U, raising the question, if U(VI), when complexed by carbonate, can be reduced to UO{sub 2}. The goal of this study was to find out if Fe(II) when structurally bound in a mineral (as magnetite, Fe{sub 3}O{sub 4}) or sorbed to a mineral surface (as corundum, Al{sub 2}O{sub 3}) can reduce U(VI) to U(IV) in the presence of HCO{sub 3}{sup -}. Batch experiments were conducted under anaerobic conditions to observe U removal from the aqueous phase by the two minerals depending on HCO{sub 3}{sup -} addition (1 mM), U concentration (0.01-30 {mu}M) and pH value (6-10). Immediately after the experiments, the mineral surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) to obtain information on the redox state of U bound to the solid surfaces. XPS results gave evidence that U(VI) can be reduced both by magnetite and by corundum amended with Fe(II). In the presence of HCO{sub 3}{sup -} the amount of reduced U on the mineral surfaces increased compared to carbonate-free solutions. This can be explained by the formation

  16. Further study of extraction equilibrium of uranium(VI) with dicyclohexano-18-crown-6 and its application to separating uranium and thorium

    International Nuclear Information System (INIS)

    Wang Wenji; Sun Qing; Chen Bozhong

    1987-01-01

    The extraction equilibrium of uranium(VI) from aqueous hydrochloric acid solution with dicyclohexano-18-crown-6 isomer A (Ia) and isomer B (Ib) in 1,2-dichloroethane is presented. The extracted species are found to be 1:2 (metal/crown) for Ia and 2:3 for Ib from slope analysis and direct determination of extracted complexes. The extraction equilibrium constants (Kex) were determined at 25 deg C, and were equal to 29.5 for the former and 0.208 for the latter. It is concluded that Ia has stronger coordinate ability for uranium than Ib. The method is effective and selective. The results can be used for the separation of uranium and thorium. (author)

  17. Selectivity enhancement of phosphate based functional polymeric gels towards Uranium(VI) using ion imprinting

    International Nuclear Information System (INIS)

    Chappa, Sankararao; Agarwal, Chhavi; Pandey, A.K.

    2015-01-01

    The imprinting of gel containing polymer chains of ethylene glycol methacrylate phosphate (EGMP) for U(VI) ions were carried out. The U(VI) imprinting has been carried out in pure EGMP and in EGMP: poly(ethylene glycol) methacrylate (PEGMA) = 1:9 composition. Complexation of the monomer with template (U(VI)) followed by polymerization have been used to imprint the U(VI) onto the polymer chains. The comparison of uptake studies of U(VI) and Pu(IV) at 3 M HNO 3 shows increased selectivity of U(VI) relative to Pu(IV) for both the gel compositions. The less uptake of U(VI) for imprinted EGMP:PEGMA gel relative to pure imprinted EGMP gel at tracer level can be possibly due to the requirement of two EGMP units in the vicinity for U(VI) complexation. (author)

  18. Extraction chromatographic method of uranium(VI) with high molecular mass amine (ALIQUAT - 336)

    International Nuclear Information System (INIS)

    Roy, Uday Sankar; Dutta, Keshab Kumar

    1999-01-01

    A selective method has been developed for reversed phase extraction chromatographic studies of uranium(VI) with Aliquat - 336 (liquid anion exchanger) coated on silica gel as stationary phase. Quantitative extraction of uranium has been achieved in HCl - medium from 1.25(M)-4(M). The effect of different acids with various concentrations stripping agents, flow rate on extraction and elution have been investigated. The exchange capacity of the prepared exchanger has been determined. Uranium(VI) has been separated quantitatively from Th, Ce, Zr, Pb, Ga, Hg, Fe, La, Pr, Nd, Sm and Cr from a binary mixture by controlling the extraction and elution conditions. The separation of U(VI) from ternary and quarternary mixtures of various metal ions has also been achieved. (author)

  19. Effect of calcium/silicon ratio on retention of uranium (VI) in portland cement materials

    International Nuclear Information System (INIS)

    Tan Hongbin; Li Yuxiang

    2005-01-01

    Calcium silicate hydrate (CSH) materials of varied calcium to silicon (Ca/Si) ratios were prepared by hydrothermal synthesis at 80 degree C, with calcium oxide and micro-silicon employed. These products were determined to be of gel phase by XRD. Leaching tests with 1% hydrochloric acid indicated that more Uranium (VI) was detained by CSH with lower Ca/Si ratios. Alkali-activated slag cement (with a lower Ca/Si ratio) was found to have a stronger retention capacity than Portland cement (with a higher Ca/Si ratio), at 25 degree C in 102-days leaching tests with simulated solidified forms containing Uranium (VI). The accumulative leaching fraction of Uranium (VI) for Alkali-activated slag cement solidified forms is 17.6% lower than that for Portland cement. The corresponding difference of diffusion coefficients is 40.6%. This could be correlated with the difference of Ca/Si ratios between cements of two kinds. (authors)

  20. Influence of radiolytic products on the chemistry of uranium VI in brines

    International Nuclear Information System (INIS)

    Lucchini, J-F.; Reed, D.T.; Borkowski, M.; Rafalski, A.; Conca, J.

    2004-01-01

    In the near field of a salt repository of nuclear waste, ionizing radiations can strongly affect the chemistry of concentrated saline solutions. Radiolysis can locally modify the redox conditions, speciation, solubility and mobility of the actinide compounds. In the case of uranium VI, radiolytic products can not only reduce U(VI), but also react with uranium species. The net effect on the speciation of uranyl depends on the relative kinetics of the reactions and the buildup of molecular products in brine solutions. The most important molecular products in brines are expected to be hypochlorite ion, hypochlorous acid and hydrogen peroxide. Although U(VI) is expected not to be significantly affected by radiolysis, the combined effects of the major molecular radiolytic products on the chemistry of U(VI) in brines have not been experimentally established previously. (authors)

  1. Study on the electrolytic reduction of Uranium-VI to Uranium-IV in a nitrate system

    International Nuclear Information System (INIS)

    Araujo, B.F. de; Almeida, S.G. de; Forbicini, S.; Matsuda, H.T.; Araujo, J.A. de.

    1981-05-01

    The determination of the best conditions to prepare hydrazine stabilized uranium (IV) nitrate solutions for utilization in Purex flowsheets is dealt with. Electrolytic reduction of U(VI) has been selected as the basic method, using an open electrolytic cell with titanum and platinum electrodes. The hydrazine concentration, the current density, acidity, U(VI) concentration and reduction time were the parameters studied and U(IV)/U(VI) ratio was used to evaluate the degree of reduction. From the results it could be concluded that the technique is reliable. The U(IV) solutions remains constant for at least two weeks and can be used in the chemical processing of irradiated uranium fuels. (Author) [pt

  2. Thermochemistry of uranium(VI), arsenic, and alkali metal triple oxides

    International Nuclear Information System (INIS)

    Karyakin, N.V.; Chernorukov, G.N.

    1994-01-01

    The standard enthalpies of reactions of stoichiometric mixtures of potassium dyhydrogen orthoarsenate, uranium(VI) oxide, alkali metal nitrates, and of mixtures of triple oxides with the general formula M I AsUO 6 (M I =Li, Na, K, Rb, and Cs) and potassium nitrate with aqueous solution of hydrofluoric acid were determined an an adiabatic calorimeter at 298.15 K. The standard enthalpies of formation of uranium(VI), arsenic, and alkali metal triple oxides at 298.15 K were calculated form the data obtained. 8 refs., 1 tab

  3. The determination of uranium(VI) by flow-injection analysis

    International Nuclear Information System (INIS)

    Jones, E.A.

    1985-01-01

    A method is described for the direct determination of uranium(VI) in waste waters and acid leach liquors by use of a flow-injection procedure and spectrophotometric measurement with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (bromo-PADAP). The interference effects of several commonly occurring elements were studied. The calibration curve is linear over concentrations of uranium(VI) from 0,5 to 20 mg/1, and the precision obtained on a synthetic leach liquor was 0,019 (relative standard deviation). The procedure is rapid and convenient, and up to 40 samples can be analysed in an hour

  4. Liquid-liquid extraction and separation studies of uranium(VI)

    International Nuclear Information System (INIS)

    Langade, A.D.; Shinde, V.M.

    1980-01-01

    Separation of uranium(VI) from iron(III), molybdenum(VI), vanadium(V), bismuth(III), zirconium(IV) and thorium(IV) is achieved by liquid-liquid extraction with 4-methyl-3-pentene-2-one (mesityl oxide; MeO) from sodium salicylate media (0.1M, pH 6.0). The extracted species is UO 2 (HO.C 6 H 4 COO) 2 .2MeO. A procedure for separating 50 μg of uranium from mg amounts of the other metals is described. (author)

  5. Solid phase extraction of uranium(VI) onto benzoylthiourea-anchored activated carbon

    International Nuclear Information System (INIS)

    Zhao Yongsheng; Liu Chunxia; Feng Miao; Chen Zhen; Li Shuqiong; Tian Gan; Wang Li; Huang Jingbo; Li Shoujian

    2010-01-01

    A new solid phase extractant selective for uranium(VI) based on benzoylthiourea anchored to activated carbon was developed via hydroxylation, amidation and reaction with benzoyl isothiocyanate in sequence. Fourier transform infrared spectroscopy and total element analysis proved that benzoylthiourea had been successfully grafted to the surface of the activated carbon, with a loading capacity of 1.2 mmol benzoylthiourea per gram of activated carbon. The parameters that affect the uranium(VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, adsorbent dose and temperature, have been investigated. Results have been analyzed by Langmuir and Freundlich isotherm; the former was more suitable to describe the sorption process. The maximum sorption capacity (82 mg/g) for uranium(VI) was obtained at experimental conditions. The rate constant for the uranium sorption by the as-synthesized extractant was 0.441 min -1 from the first order rate equation. Thermodynamic parameters (ΔH 0 = -46.2 kJ/mol; ΔS 0 = -98.0 J/mol K; ΔG 0 = -17.5 kJ/mol) showed the adsorption of an exothermic process and spontaneous nature, respectively. Additional studies indicated that the benzoylthiourea-anchored activated carbon (BT-AC) selectively sorbed uranyl ions in the presence of competing ions, Na + , Co 2+ , Sr 2+ , Cs + and La 3+ .

  6. Solid phase extraction of uranium(VI) onto benzoylthiourea-anchored activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Yongsheng; Liu Chunxia; Feng Miao; Chen Zhen; Li Shuqiong; Tian Gan; Wang Li; Huang Jingbo [College of Chemistry, Sichuan University, 29 Wangjiang Lu, Chengdu, 610064, Sichuan (China); Li Shoujian, E-mail: sjli000616@scu.edu.cn [College of Chemistry, Sichuan University, 29 Wangjiang Lu, Chengdu, 610064, Sichuan (China)

    2010-04-15

    A new solid phase extractant selective for uranium(VI) based on benzoylthiourea anchored to activated carbon was developed via hydroxylation, amidation and reaction with benzoyl isothiocyanate in sequence. Fourier transform infrared spectroscopy and total element analysis proved that benzoylthiourea had been successfully grafted to the surface of the activated carbon, with a loading capacity of 1.2 mmol benzoylthiourea per gram of activated carbon. The parameters that affect the uranium(VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, adsorbent dose and temperature, have been investigated. Results have been analyzed by Langmuir and Freundlich isotherm; the former was more suitable to describe the sorption process. The maximum sorption capacity (82 mg/g) for uranium(VI) was obtained at experimental conditions. The rate constant for the uranium sorption by the as-synthesized extractant was 0.441 min{sup -1} from the first order rate equation. Thermodynamic parameters ({Delta}H{sup 0} = -46.2 kJ/mol; {Delta}S{sup 0} = -98.0 J/mol K; {Delta}G{sup 0} = -17.5 kJ/mol) showed the adsorption of an exothermic process and spontaneous nature, respectively. Additional studies indicated that the benzoylthiourea-anchored activated carbon (BT-AC) selectively sorbed uranyl ions in the presence of competing ions, Na{sup +}, Co{sup 2+}, Sr{sup 2+}, Cs{sup +} and La{sup 3+}.

  7. Preparation and characterizations of new U(IV) and U(VI) complexes with carboxylate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Sbrignadello, G; Tomat, G; Battiston, G; Vigato, P A [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi

    1978-01-01

    The synthesis and characterization of some uranyl(VI) complexes containing glycolate (gly = CH/sub 2/OHCOO/sup -/) and methoxyacetate (MeOAc = CH/sub 3/OCH/sub 2/COO/sup -/) ligands with metal:ligand ratios of 1:1 and 1:2 are reported. In addition, new stable uranium(IV) complexes containing the same ligands, or the oxydiacetate (oda = /sup -/OOCCH/sub 2/OCH/sub 2/COO/sup -/) anion, have been prepared by photolysing aqueous solutions of uranyl(VI) nitrate in the presence of an excess of ligand. The possible structures of these complexes are discussed on the basis of IR results. The photoproduction mechanism of U(IV) complexes is proposed from electronic and spectrofluorimetric spectra and quantum yield data.

  8. Spectral and structural correlation for Bis (dibenzoyl methanato) dioxo uranium(VI) diphenyl sulfoxide. [UO2(DBM)2. PhSOPh

    International Nuclear Information System (INIS)

    Kannan, S.; Raj, S.S.S.; Fun, Hoong Kun

    2001-01-01

    In the complex [UO 2 (DBM) 2 . PhSOPh]. the sulfoxide ligand is bonded to uranium (VI) ion through sulfoxide oxygen atom and DBM ligands through the oxygen atoms to give a distorted pentagonal bipyramidal geometry. The structural study is in consistence with the spectral studies. (author)

  9. Influence of the temperature in the uranium (Vi) sorption in zirconium diphosphate

    International Nuclear Information System (INIS)

    Garcia G, N.; Solis, D.; Ordonez R, E.

    2012-10-01

    In the present work was evaluated the uranium (Vi) sorption at 10, 20, 30, 40 and 60 C on the zirconium diphosphate (ZrP 2 O 7 ). They were carried out kinetic and isotherms using the method by lots, these will allow to fix the sorption time (kinetic) and to explain the behavior of this sorption in different ph conditions and temperature (isotherm). The quantity of retained uranium in the surface was quantified by means of the fluorescence technique. (Author)

  10. Comparative study of uranyl(VI) and -(V) carbonato complexes in an aqueous solution.

    Science.gov (United States)

    Ikeda, Atsushi; Hennig, Christoph; Tsushima, Satoru; Takao, Koichiro; Ikeda, Yasuhisa; Scheinost, Andreas C; Bernhard, Gert

    2007-05-14

    Electrochemical, complexation, and electronic properties of uranyl(VI) and -(V) carbonato complexes in an aqueous Na2CO3 solution have been investigated to define the appropriate conditions for preparing pure uranyl(V) samples and to understand the difference in coordination character between UO22+ and UO2+. Cyclic voltammetry using three different working electrodes of platinum, gold, and glassy carbon has suggested that the electrochemical reaction of uranyl(VI) carbonate species proceeds quasi-reversibly. Electrolysis of UO22+ has been performed in Na2CO3 solutions of more than 0.8 M with a limited pH range of 11.7 < pH < 12.0 using a platinum mesh electrode. It produces a high purity of the uranyl(V) carbonate solution, which has been confirmed to be stable for at least 2 weeks in a sealed glass cuvette. Extended X-ray absorption fine structure (EXAFS) measurements revealed the structural arrangement of uranyl(VI) and -(V) tricarbonato complexes, [UO2(CO3)3]n- [n = 4 for uranyl(VI), 5 for uranyl(V)]. The bond distances of U-Oax, U-Oeq, U-C, and U-Odist are determined to be 1.81, 2.44, 2.92, and 4.17 A for the uranyl(VI) complex and 1.91, 2.50, 2.93, and 4.23 A for the uranyl(V) complex, respectively. The validity of the structural parameters obtained from EXAFS has been supported by quantum chemical calculations for the uranyl(VI) complex. The uranium LI- and LIII-edge X-ray absorption near-edge structure spectra have been interpreted in terms of electron transitions and multiple-scattering features.

  11. Syntheses of polystyrene supported chelating resin containing the Schiff base derived from salicylaldehyde and triethylene tetramine and its copper(II), nickel(II), cobalt(II), iron(III), zinc(II), cadmium(II), molybdenum(VI), zirconium(IV) and uranium(VI) complexes

    International Nuclear Information System (INIS)

    Syamal, A.; Singh, M.M.

    1998-01-01

    A new polymer-anchored chelating ligand has been synthesized by the reaction of chloromethylated polystyrene (containing 0.94 mmol of Cl per gram of resin and 1% cross-linked with divinylbenzene) and the Schiff base derived from salicylaldehyde and triethylenetetramine. A new series of polystyrene supported, Cu(II), Ni(II), Co(II), Fe(III), Zn(II), Cd(II), Zr(IV), dioxomolybdenum (VI) and dioxouranium (VI) complexes of the formulae PS-LCu, PS-LNi, PS-LCo, PS-LFeCl.DMF, PS-LZn, PS-LCd, PS-LZr(OH) 2 . DMF, PS L MoO 2 and PS-LUO 2 (where PS-LH 2 = polymer-anchored Schiff base and DMF dimethyl-formamide) have been synthesized and characterised by elemental analysis, infrared, electronic spectra and magnetic susceptibility measurements. The complexes PS-LCu, PS-LNi and PS-LCo have square planar structure, PS-LFeCl.DMF, PS-LMoO 2 and PS-LUO 2 have octahedral structure, PS L Zn and PS-LCd are tetrahedral and PS-LZr(OH) 2 .DMF is pentagonal bipyramidal. The polymer-anchored Cu(II), Co(II) and Fe(III) complexes are paramagnetic while Ni(II), Zn(II), Cd(II), Zr(IV), dioxomolybdenum(VI) and dioxouranium(VI) complexes are diamagnetic. The negative shift of the v (C=N) (azomethine) and the positive shift of v (C--O)(phenolic) are indicative of ONNO donor behaviour of the polymer-anchored Schiff base. (author)

  12. The uranium (VI) determination method in the technological products

    International Nuclear Information System (INIS)

    Fursa, L.I.; Belykevich, N.A.

    1994-01-01

    The method includes an extraction of the uranyl nitrate by solution' hexa butyl tries amide of phosphoric acid in the hexane, a reextraction of uranium by arsenazo III solution under pH 2 and following the solution' photometry. With the purpose of excluding the emulsion' formation under uranium reextraction has been added chloroform in volume ratio to hexane 1:(3.0-7.5). tabs. 2

  13. Contribution to the study of the redox couple Np(VI)/Np(V) in the presence of uranium(VI) in solutions of nitric acid and nitrous acid; Contribution a l'etude du comportement redox du couple Np(VI)/Np(V) en presence d'uranium VI dans les solutions constituees d'acide nitrique et d'acide nitreux

    Energy Technology Data Exchange (ETDEWEB)

    Arpigny, S. [CEA Marcoule, Dept. de Radiochimie et Procedes, DRP, 30 (France)

    2001-07-01

    The redox behavior of the Np(VI)/Np(V) couple was the subject of a spectrometric study of the Np(VI) reduction reaction in nitric acid solutions (4 to 5 M) containing variable concentrations (1.5 to 3.5 x 10{sup -3} M) of nitrous acid. A low nitrous acid concentration and a high nitric acid concentration were found to favor the stabilization of Np(VI). The stoichiometric coefficients of nitrous acid and nitric acid in the Np(VI) reduction reaction were determined thermodynamically, although only the reaction order with respect to HNO{sub 2} could be calculated from a kinetic analysis. Adding nitrate ions to a HNO{sub 3}/HNO{sub 2} solution enhanced the stability of neptunium at oxidation state +VI, but also increased the reduction rate. When uranium(VI) was added to the HNO{sub 3}/HNO{sub 2} solutions, the total quantity of neptunium at oxidation state +V (either free or as a Np(V)-U(VI) complex) remained practically unchanged, as did the Np(VI) reduction rate. The electrochemical behavior of the Np(VI)/Np(V) couple was investigated in a weak acidic medium by voltammetry with an ultra-micro-electrode (UME). The oxidation wave limiting current variation was a linear function of the Np(V) concentration when a gold UME was used, but not with a platinum UME; the reduction wave limiting current variation versus the Np(V) concentration was linear with either gold or platinum UMEs. The presence of the Np(V)-U(VI) complex in the neptunium solutions was characterized by a shift in the normal apparent potential of the Np(VI)/Np(V) couple toward anodic potentials consistent with the previously determined values of the complexation constants. (author)

  14. Study of uranium (VI) in carbonate solution by potentiometric titrations and ion-exchange

    International Nuclear Information System (INIS)

    Billon, A.

    1968-04-01

    The present work is devoted to the fixation of uranium (VI) on the conventional anion-exchange resin Dowex 2 X 8 in carbonate and hydrogen-carbonate media. Both media were successfully used for the recuperation of uranium (VI) from very dilute solutions. Equilibrium constant of the exchange [UO 2 (CO 3 ) 3 4+ ] S + 2 [CO 3 2- ] R ↔ [UO 2 (CO 3 ) 3 4- ] R + 2[CO 3 2- ] S is determined for carbonate concentration range 0.1 M to 0.6 M from partition curves. A markedly increase in the relative fixation of uranium results with: - increasing free carbonate concentration of the solution, - decreasing uranium concentration. A study in the same conditions of the fixation of molybdenum has made it possible to separate the latter from uranium by elution, the carbonate concentration being molar. It is suggested a possibility of separation on a larger scale, based upon molybdenum displacement by uranium in hydrogen-carbonate medium. (author) [fr

  15. Uranium extraction by complexation with siderophores

    Science.gov (United States)

    Bahamonde Castro, Cristina

    One of the major concerns of energy production is the environmental impact associated with the extraction of natural resources. Nuclear energy fuel is obtained from uranium, an abundant and naturally occurring element in the environment, but the currently used techniques for uranium extraction leave either a significant fingerprint (open pit mines) or a chemical residue that alters the pH of the environment (acid or alkali leaching). It is therefore clear that a new and greener approach to uranium extraction is needed. Bioleaching is one potential alternative. In bioleaching, complexants naturally produced from fungi or bacteria may be used to extract the uranium. In the following research, the siderophore enterobactin, which is naturally produced by bacteria to extract and solubilize iron from the environment, is evaluated to determine its potential for complexing with uranium. To determine whether enterobactin could be used for uranium extraction, its acid dissociation and its binding strength with the metal of interest must be determined. Due to the complexity of working with radioactive materials, lanthanides were used as analogs for uranium. In addition, polyprotic acids were used as structural and chemical analogs for the siderophore during method development. To evaluate the acid dissociation of enterobactin and the subsequent binding constants with lanthanides, three different analytical techniques were studied including: potentiometric titration, UltraViolet Visible (UV-Vis) spectrophotometry and Isothermal Titration Calorimetry (ITC). After evaluation of three techniques, a combination of ITC and potentiometric titrations was deemed to be the most viable way for studying the siderophore of interest. The results obtained from these studies corroborate the ideal pH range for enterobactin complexation to the lanthanide of interest and pave the way for determining the strength of complexation relative to other naturally occurring metals. Ultimately, this

  16. Retention of uranium(VI) by laumontite, a fracture-filling material of granite

    International Nuclear Information System (INIS)

    Baik, M.H.; Lee, S.Y.; Shon, W.J.

    2009-01-01

    Retention of U(VI) by laumontite, a fracture-filling material of granite as investigated by conducting dynamic and batch sorption experiments in a love-box using a granite core with a natural fracture. The hydrodynamic properties of the granite core were obtained from the elution curve of a on-sorbing tracer, Br - . The elution curve of U(VI) showed a similar behavior to Br - . This reveals that the retention of U(VI) by the fracture-filling material was not significant when migrating through the fracture at a given condition. From the dynamic sorption experiment, the retardation factor R a and the distribution coefficient K a of U(VI) were obtained as about 2.9 and 0.16 cm, respectively. The distribution coefficient K d ) of U(VI) onto laumontite obtained by conducting a batch sorption experiment resulted in a small value of 2.3±0.5 mL/g. This low K d value greed with the result of the dynamic sorption experiment. For the distribution of uranium on the granite surface investigated by an X-ray image mapping, the fracture region filled with laumontite showed a relatively lower content of uranium compared to the surrounding granite surface. Thus, the low retention of U(VI) by the fracture-filling material can be explained by following two mechanisms. One is that U(VI) exists as anionic uranyl hydroxides or uranyl carbonates at a given groundwater condition and the other is the remarkably low sorption capacity of the laumontite for U(VI). author)

  17. Spectrophotometric Microdetermination of Thorium(IV and Uranium(VI with Chrome Azurol-S in Presence of Cationic Surfactant

    Directory of Open Access Journals (Sweden)

    A. B. Upase

    2011-01-01

    Full Text Available Cationic surfactant, cetyldimethylethylammonium bromide (CDMEAB, sensitize the color reactions of Th(IV and U(VI with chrome azurol-S(CRAS. Formation of water soluble deeply colored ternary complexes of metal ions show large bathochromic shift. Same stoichiometric composition of ternary complexes with 1:2:4 molar ratio (M-CRAS-CDMEAB have been observed for both the metal ions and are responsible for enhancement in molar absorptivities and sensitivities at shifted wavelength. The ternary complexes of thorium(IV and uranium(VI exhibit absorption maxima at 640 and 620 nm with molar absorptivities 85500 and 69600 L.mol-1.cm-2 respectively. Beer’s law were obeyed in concentration range 0.12-0.185 ppm for Th(IV and 0.13-0.162 ppm for U(VI in presence of CDMEAB. Conditional formation constants and various analytical parameters have been evaluated and compared the results of binary and ternary complexes. Enhancement in the molar absorptivities in presence of CDMEAB clearly indicated the usefulness of these colored reactions for microdetermination.

  18. Thermochemistry of the complex oxides of uranium, vanadium, and alkali metals

    International Nuclear Information System (INIS)

    Karyakin, N.V.; Chernorukov, N.G.; Suleimanov, E.V.; Kharyushina, E.A.

    1992-01-01

    The standard enthalpies of the formation at T 298.15 K of complex oxides of uranium(VI), vanadium(V) and alkali metals with the general formula M 1 VUO 6 where M 1 = Na, K, Rb, and Cs, were calculated from the results of calorimetric experiments and from published data. 8 refs., 1 tab

  19. Biotransformation of uranium and transition metal citrate complexes by clostridia

    International Nuclear Information System (INIS)

    Francis, A.J.; Joshi-Tope, G.A.; Dodge, C.J.; Gillow, J.B.

    2002-01-01

    Clostridium sphenoides, which uses citric acid as its sole carbon source, metabolized equimolar Fe(III)-citrate with the degradation of citric acid and the reduction of Fe(III) to Fe(II), but not the U(VI)-citrate complex. However, in the presence of excess citric acid or added glucose it was reduced to U(IV)-citrate. In contrast, Clostridium sp., which ferments glucose but not citrate, reduced Fe(III)-citrate to Fe(II)-citrate and U(VI)-citrate to U(IV)-citrate only when supplied with glucose. These results show that complexed uranium is readily accessible as an electron acceptor despite the bacterium's inability to metabolize the organic ligand complexed to the actinide. These results also show that the metabolism of the metal-citrate complex depends upon the type of complex formed between the metal and citric acid. Fe(III) forms a bidentate complex with citric acid and was metabolized, whereas U forms a binuclear complex with citric acid and was recalcitrant. (author)

  20. In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen

    International Nuclear Information System (INIS)

    Wu, Weimin; Carley, Jack M.; Luo, Jian; Ginder-Vogel, Matthew A.; Cardenas, Erick; Leigh, Mary Beth; Hwang, Chaichi; Kelly, Shelly D.; Ruan, Chuanmin; Wu, Liyou; Van Nostrand, Joy; Gentry, Terry J.; Lowe, Kenneth Alan; Mehlhorn, Tonia L.; Carroll, Sue L.; Luo, Wensui; Fields, Matthew Wayne; Gu, Baohua; Watson, David B.; Kemner, Kenneth M.; Marsh, Terence; Tiedje, James; Zhou, Jizhong; Fendorf, Scott; Kitanidis, Peter K.; Jardine, Philip M.; Criddle, Craig

    2007-01-01

    Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 (micro)M uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agency maximum contaminant limit (MCL) for drinking water ( -1 or 0.126 (micro)M). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L -1 ) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from <0.13 to 2.0 (micro)M at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLS well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. At the completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 (micro)M. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species were Geothrix spp

  1. Kinetics of Uranium(VI) Desorption from Contaminated Sediments: Effect of Geochemical Conditions and Model Evaluation

    International Nuclear Information System (INIS)

    Liu, Chongxuan; Shi, Zhenqing; Zachara, John M.

    2009-01-01

    Stirred-flow cell experiments were performed to investigate the kinetics of uranyl (U(VI)) desorption from a contaminated sediment collected from the Hanford 300 Area at the US Department of Energy (DOE) Hanford Site, Washington. Three influent solutions of variable pH, Ca and carbonate concentrations that affected U(VI) aqueous and surface speciation were used under dynamic flow conditions to evaluate the effect of geochemical conditions on the rate of U(VI) desorption. The measured rate of U(VI) desorption varied with solution chemical composition that evolved as a result of thermodynamic and kinetic interactions between the influent solutions and sediment. The solution chemical composition that led to a lower equilibrium U(VI) sorption to the solid phase yielded a faster desorption rate. The experimental results were used to evaluate a multi-rate, surface complexation model (SCM) that has been proposed to describe U(VI) desorption kinetics in the Hanford sediment that contained complex sorbed U(VI) species in mass transfer limited domains. The model was modified and supplemented by including multi-rate, ion exchange reactions to describe the geochemical interactions between the solutions and sediment. With the same set of model parameters, the modified model reasonably well described the evolution of major ions and the rates of U(VI) desorption under variable geochemical and flow conditions, implying that the multi-rate SCM is an effective way to describe U(VI) desorption kinetics in subsurface sediments

  2. Speciation of bioaccumulated uranium(VI) by Euglena mutabilis cells obtained by laser fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Brockmann, Sina; Bernhard, Gert [Technical Univ. Dresden (Germany). Radiochemistry; Helmholtz-Zentrum Dresden-Rossendorf (HZDR) e.V., Dresden (Germany). Inst. of Resource Ecology; Arnold, Thuro [Helmholtz-Zentrum Dresden-Rossendorf (HZDR) e.V., Dresden (Germany). Inst. of Resource Ecology

    2014-07-01

    The ability of Euglena mutabilis cells - a unicellular protozoan with a flexible pellicle, which is typically found in acid mine drainage (AMD) environments - to bioaccumulate uranium under acid conditions was studied in batch sorption experiments at pH 3 and 4 using Na{sub 2}SO{sub 4} and NaClO{sub 4} as background media. It was found that axenic cultures of Euglena mutabilis Schmitz were able to bioaccumulate in 5 days 94.9 to 99.2% of uranium from a 1 x 10{sup -5} mol/L uranium solution in perchlorate medium and 95.1 to 95.9% in sodium sulfate medium, respectively. The speciation of uranium in solution and uranium bioaccumulated by Euglena mutabilis cells, were studied by laser induced fluorescence spectroscopy (LIFS). The LIFS investigations showed that the uranium speciation in the NaClO{sub 4} systems was dominated by free uranyl(VI) species and that the UO{sub 2}SO{sub 4} species was dominating in the Na{sub 2}SO{sub 4} medium. Fluorescence spectra of the bioaccumulated uranium revealed that aqueous uranium binds to carboxylic and/or (organo)phosphate groups located on the euglenid pellicle or inside the Euglena mutabilis cells. Reduced uranium immobilization rates of 0.93-1.43 mg uranium per g Euglena mutabilis biomass were observed in similar experiments, using sterile filtrated AMD waters containing, 4.4 x 10{sup -5} mol/L uranium. These lower rates were attributed to competition with other cations for available sorption sites. Additional LIFS measurements, however, showed that the speciation of the bioaccumulated uranium by the Euglena mutabilis cells was found to be identical with the uranium speciation found in the bioaccumulation experiments carried out in Na{sub 2}SO{sub 4} and NaClO{sub 4} media. The results indicate that Euglena mutabilis has the potential to immobilize aqueous uranium under acid condition and thus may be used in future as promising agent for immobilizing uranium in low pH waste water environments. (orig.)

  3. Speciation of bioaccumulated uranium(VI) by Euglena mutabilis cells obtained by laser fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Brockmann, Sina; Bernhard, Gert; Helmholtz-Zentrum Dresden-Rossendorf; Arnold, Thuro

    2014-01-01

    The ability of Euglena mutabilis cells - a unicellular protozoan with a flexible pellicle, which is typically found in acid mine drainage (AMD) environments - to bioaccumulate uranium under acid conditions was studied in batch sorption experiments at pH 3 and 4 using Na 2 SO 4 and NaClO 4 as background media. It was found that axenic cultures of Euglena mutabilis Schmitz were able to bioaccumulate in 5 days 94.9 to 99.2% of uranium from a 1 x 10 -5 mol/L uranium solution in perchlorate medium and 95.1 to 95.9% in sodium sulfate medium, respectively. The speciation of uranium in solution and uranium bioaccumulated by Euglena mutabilis cells, were studied by laser induced fluorescence spectroscopy (LIFS). The LIFS investigations showed that the uranium speciation in the NaClO 4 systems was dominated by free uranyl(VI) species and that the UO 2 SO 4 species was dominating in the Na 2 SO 4 medium. Fluorescence spectra of the bioaccumulated uranium revealed that aqueous uranium binds to carboxylic and/or (organo)phosphate groups located on the euglenid pellicle or inside the Euglena mutabilis cells. Reduced uranium immobilization rates of 0.93-1.43 mg uranium per g Euglena mutabilis biomass were observed in similar experiments, using sterile filtrated AMD waters containing, 4.4 x 10 -5 mol/L uranium. These lower rates were attributed to competition with other cations for available sorption sites. Additional LIFS measurements, however, showed that the speciation of the bioaccumulated uranium by the Euglena mutabilis cells was found to be identical with the uranium speciation found in the bioaccumulation experiments carried out in Na 2 SO 4 and NaClO 4 media. The results indicate that Euglena mutabilis has the potential to immobilize aqueous uranium under acid condition and thus may be used in future as promising agent for immobilizing uranium in low pH waste water environments. (orig.)

  4. Influence of Calcium on Microbial Reduction of Solid Phase Uranium (VI)

    International Nuclear Information System (INIS)

    Liu, Chongxuan; Jeon, Byong-Hun; Zachara, John M.; Wang, Zheming

    2007-01-01

    The effect of calcium on microbial reduction of a solid phase U(VI), sodium boltwoodite (NaUO2SiO3OH · 1.5H2O), was evaluated in a culture of a dissimilatory metal-reducing bacterium (DMRB), Shewanella oneidensis strain MR-1. Batch experiments were performed in a non-growth bicarbonate medium with lactate as electron donor at pH 7 buffered with PIPES. Calcium increased both the rate and extent of Na-boltwoodite dissolution by increasing its solubility through the formation of a ternary aqueous calcium-uranyl-carbonate species. The ternary species, however, decreased the rates of microbial reduction of aqueous U(VI). Laser-induced fluorescence spectroscopy (LIFS) and transmission electron microscopy (TEM) revealed that microbial reduction of solid phase U(VI) is a sequentially coupled process of Na-boltwoodite dissolution, U(VI) aqueous speciation, and microbial reduction of dissolved U(VI) to U(IV) that accumulated on bacterial surfaces/periplasm. The overall rates of microbial reduction of solid phase U(VI) can be described by the coupled rates of dissolution and microbial reduction that were both influenced by calcium. The results demonstrated that dissolved U(VI) concentration during microbial reduction was a complex function of solid phase U(VI) dissolution kinetics, aqueous U(VI) speciation, and microbial activity

  5. A new optical sensor for spectrophotometric determination of uranium (VI) and thorium (IV) in acidic medium

    Energy Technology Data Exchange (ETDEWEB)

    Elhefnawy, O.A. [Nuclear and Radiological Regulatory Authority (NRRA), Cairo (Egypt). Nuclear Safeguards and Physical Protection Dept.

    2017-07-01

    A spectrophotometric method was developed for U(VI) and Th(IV) determination in acidic medium by using proposed optical sensor. This sensor is base on the complexation reaction of the ionophore midodrine hydrochloride (L) with U(VI)/Th(IV) in plasticized (o-NPOE) high molecular weight (PVC). Several parameters such as effect of acidic medium, response time and sensor compositions were studied. The determination of the complexes stoichiometry was also studied using Job's method. The complexes stoichiometry were measured at the absorbance spectra 302 nm and the results were found to be 1:1 for both complexes U(VI)-L and Th(IV)-L. The complexation reaction was extremely rapid at room temperature; it takes 5, 10 min to complete the complexation reaction in U(VI) and Th(IV), respectively. Under the optimum conditions the calibration curves of U(VI)/Th(IV) determination, have good linearity at different acidic medium nitric, sulfuric, and phosphoric acids with low detection and quantification limits. The accuracy and precision studies proved that the proposed optical sensor is valid and qualified for U(VI)/Th(IV) spectrophotometric determination in different acidic medium. The selectivity of the proposed optical sensor was studied. The proposed optical sensor was applied successfully for U(VI)/Th(IV) determination in research and development (R and D) nuclear waste samples with satisfactory results. A comparative study of the proposed optical sensor with other previous spectrophotometric sensors for U(VI)/Th(IV) determination, proved the high efficiency of the proposed optical sensor, that it presents wide linear range and low detection limit. The proposed optical sensor could be applied for a quantitative determination of U(VI)/Th(IV) in acidic waste samples.

  6. A new optical sensor for spectrophotometric determination of uranium (VI) and thorium (IV) in acidic medium

    International Nuclear Information System (INIS)

    Elhefnawy, O.A.

    2017-01-01

    A spectrophotometric method was developed for U(VI) and Th(IV) determination in acidic medium by using proposed optical sensor. This sensor is base on the complexation reaction of the ionophore midodrine hydrochloride (L) with U(VI)/Th(IV) in plasticized (o-NPOE) high molecular weight (PVC). Several parameters such as effect of acidic medium, response time and sensor compositions were studied. The determination of the complexes stoichiometry was also studied using Job's method. The complexes stoichiometry were measured at the absorbance spectra 302 nm and the results were found to be 1:1 for both complexes U(VI)-L and Th(IV)-L. The complexation reaction was extremely rapid at room temperature; it takes 5, 10 min to complete the complexation reaction in U(VI) and Th(IV), respectively. Under the optimum conditions the calibration curves of U(VI)/Th(IV) determination, have good linearity at different acidic medium nitric, sulfuric, and phosphoric acids with low detection and quantification limits. The accuracy and precision studies proved that the proposed optical sensor is valid and qualified for U(VI)/Th(IV) spectrophotometric determination in different acidic medium. The selectivity of the proposed optical sensor was studied. The proposed optical sensor was applied successfully for U(VI)/Th(IV) determination in research and development (R and D) nuclear waste samples with satisfactory results. A comparative study of the proposed optical sensor with other previous spectrophotometric sensors for U(VI)/Th(IV) determination, proved the high efficiency of the proposed optical sensor, that it presents wide linear range and low detection limit. The proposed optical sensor could be applied for a quantitative determination of U(VI)/Th(IV) in acidic waste samples.

  7. Sorption of Uranium(VI and Thorium(IV by Jordanian Bentonite

    Directory of Open Access Journals (Sweden)

    Fawwaz I. Khalili

    2013-01-01

    Full Text Available Purification of raw bentonite was done to remove quartz. This includes mixing the raw bentonite with water and then centrifuge it at 750 rpm; this process is repeated until white purified bentonite is obtained. XRD, XRF, FTIR, and SEM techniques will be used for the characterization of purified bentonite. The sorption behavior of purified Jordanian bentonite towards and Th4+ metal ions in aqueous solutions was studied by batch experiment as a function of pH, contact time, temperature, and column techniques at 25.0∘C and . The highest rate of metal ions uptake was observed after 18 h of shaking, and the uptake has increased with increasing pH and reached a maximum at . Bentonite has shown high metal ion uptake capacity toward uranium(VI than thorium(IV. Sorption data were evaluated according to the pseudo- second-order reaction kinetic. Sorption isotherms were studied at temperatures 25.0∘C, 35.0∘C, and 45.0∘C. The Langmuir, Freundlich, and Dubinin-Radushkevich (D-R sorption models equations were applied and the proper constants were derived. It was found that the sorption process is enthalpy driven for uranium(VI and thorium(IV. Recovery of uranium(VI and thorium(IV ions after sorption was carried out by treatment of the loaded bentonite with different concentrations of HNO3 1.0 M, 0.5 M, 0.1 M, and 0.01 M. The best percent recovery for uranium(VI and thorium(IV was obtained when 1.0 M HNO3 was used.

  8. Synthesis of graphite intercalation compound of group VI metals and uranium hexafluorides

    International Nuclear Information System (INIS)

    Fukui, Toshihiro; Hagiwara, Rika; Ema, Keiko; Ito, Yasuhiko

    1993-01-01

    Systematic investigations were made on the synthesis of graphite intercalation compounds of group VI transition metals (W and Mo) and uranium hexafluorides. The reactions were performed by interacting liquid or gaseous metal hexafluorides with or without elemental fluorine at ambient temperature. The degree of intercalation of these metal fluorides depends on the formation enthalpy of fluorometallate anion from the original metal hexafluoride, as has been found for other intercalation reactions of metal fluorides. (author)

  9. Uranium in drinking water. A simple determination of uranium (VI) according to DIN standard 38406-17

    International Nuclear Information System (INIS)

    Haug, Sandro

    2009-01-01

    The number of reports on uranium loads in tap water and drinking water increases. Already for years, the organization Foodwatch e.V. (Berlin, Federal Republic of Germany) warns about to high concentrations of uranium in tap water. So far, only a limit value for mineral water exists in the Mineral Water Regulation which is suitable for the production of infant diet. This limit value amounts 2 microgram per litre. Temporarily, also in the policy a national limit value for uranium in drinking water is introduced. The Federal Office for Environment Protection (Dessau, FRG) designates a value of ten microgram uranium per litre of drinking water and mineral water as an approximate value. The effective control of water quality presupposes high-performance, simple and economical analysis methods. A particularly well suitable measuring technique for the determination of uranium(VI) in groundwater, raw water and drinking water is the voltammetry. In the last years, a national standard was compiled based on this measuring technique: DIN standard 38406-17

  10. U(VI) speciation and reduction in acid chloride fluids in hydrothermal conditions: from transport to deposition of uranium in unconformity-related deposits

    International Nuclear Information System (INIS)

    Dargent, Maxime

    2014-01-01

    Circulations of acidic chloride brines in the earth's crust are associated with several types of uranium deposits, particularly unconformity-related uranium (URU) deposits. The spectacular high grade combined with the large tonnage of these deposits is at the origin of the key questions concerning the geological processes responsible for U transport and precipitation. The aim of this work is to performed experimental studies of U(VI) speciation and its reduction to U(IV) subsequently precipitation to uraninite under hydrothermal condition. About uranium transport, the study of U(VI) speciation in acidic brines at high temperature is performed by Raman and XAS spectroscopy, showing the coexistence of several uranyl chloride complexes UO 2 Cl n 2-n (n = 0 - 5). From this study, complexation constants are proposed. The strong capability of chloride to complex uranyl is at the origin of the transport of U(VI) at high concentration in acidic chloride brines. Concerning uranium precipitation, the reactivity of four potential reductants under conditions relevant for URU deposits genesis is investigated: H 2 , CH 4 , Fe(II) and the C-graphite. The kinetics of reduction reaction is measured as a function of temperature, salinity, pH and concentration of reductant. H 2 , CH 4 , and the C-graphite are very efficient while Fe(II) is not able to reduce U(VI) in same conditions. The duration of the mineralizing event is controlled by (i) the U concentration in the ore-forming fluids and (ii) by the generation of gaseous reductants, and not by the reduction kinetics. These mobile and efficient gaseous reductant could be at the origin of the extremely focus and massive character of ore in URU deposits. Finally, first partition coefficients uraninite/fluid of trace elements are obtained. This last part opens-up new perspectives on (i) REE signatures interpretation for a given type of uranium deposit (ii) and reconstruction of mineralizing fluids composition. (author) [fr

  11. Stability of uranium(VI) doped CSH phases in high saline water

    Energy Technology Data Exchange (ETDEWEB)

    Wolter, Jan-Martin; Schmeide, Katja [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

    2017-06-01

    To evaluate the long-term stability of U(VI) doped calcium silicate hydrate (CSH) phases at high saline conditions, leaching experiments with NaCl, NaCl/Na{sub 2}SO{sub 4} and NaCl/NaHCO{sub 3} containing solutions were performed. Time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR) and X-ray powder diffraction (XRD) were applied to study the U(VI) binding onto the CSH phases and to get a deeper understanding of structural changes due to leaching. Results indicate that neither NaCl nor Na{sub 2}SO{sub 4} affect the structural stability of CSH phases and their retention potential for U(VI). However, carbonate containing solutions lead to a decomposition of CSH phases and thus, to a release of incorporated uranium.

  12. Kinetic and equilibrium study of uranium(VI) adsorption by Bacillus licheniformis

    International Nuclear Information System (INIS)

    Zheng-ji Yi; University of Science and Technology Beijing, Beijing; Jun Yao

    2012-01-01

    Uranium pollution is a severe problem worldwide. Biosorption has been proposed as one of the most promising technologies for the removal of uranyl cations. Here we report on the adsorption behavior of uranium(VI) [U(VI)] on Bacillus licheniformis biomass to explore the potentiality of its application in uranium contamination control. The adsorption equilibrium, adsorption kinetics, and effects of temperature, pH and initial biosorbent dosage on the adsorption equilibrium were investigated in detail through batch experiments. The adsorption process is pronouncedly affected by the solution pH and the optimum pH range should be 4.5-5.0.Temperature range from 25 to 45 deg C has a certain effect on the rate of biosorption, but little effect on the equilibrium adsorption capacity. The U(VI) percentage removal increased concurrently with increasing biomass dosage, whereas the adsorption capacity decreased. The process follows the Langmuir isotherm model. The adsorption kinetics data were fitted very well by the pseudo-first-order rate model. Finally, the calculation results of thermodynamic constant (ΔG a = 9.98 kJ/mol) reveal that the adsorption process can be identified as a spontaneous chemical process. The present results suggest that B. licheniformis has considerable potential for the removal of uranyl from aqueous solution. (author)

  13. Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal.

    Science.gov (United States)

    Bots, Pieter; Morris, Katherine; Hibberd, Rosemary; Law, Gareth T W; Mosselmans, J Frederick W; Brown, Andy P; Doutch, James; Smith, Andrew J; Shaw, Samuel

    2014-12-09

    The favored pathway for disposal of higher activity radioactive wastes is via deep geological disposal. Many geological disposal facility designs include cement in their engineering design. Over the long term, interaction of groundwater with the cement and waste will form a plume of a hyperalkaline leachate (pH 10-13), and the behavior of radionuclides needs to be constrained under these extreme conditions to minimize the environmental hazard from the wastes. For uranium, a key component of many radioactive wastes, thermodynamic modeling predicts that, at high pH, U(VI) solubility will be very low (nM or lower) and controlled by equilibrium with solid phase alkali and alkaline-earth uranates. However, the formation of U(VI) colloids could potentially enhance the mobility of U(VI) under these conditions, and characterizing the potential for formation and medium-term stability of U(VI) colloids is important in underpinning our understanding of U behavior in waste disposal. Reflecting this, we applied conventional geochemical and microscopy techniques combined with synchrotron based in situ and ex situ X-ray techniques (small-angle X-ray scattering and X-ray adsorption spectroscopy (XAS)) to characterize colloidal U(VI) nanoparticles in a synthetic cement leachate (pH > 13) containing 4.2-252 μM U(VI). The results show that in cement leachates with 42 μM U(VI), colloids formed within hours and remained stable for several years. The colloids consisted of 1.5-1.8 nm nanoparticles with a proportion forming 20-60 nm aggregates. Using XAS and electron microscopy, we were able to determine that the colloidal nanoparticles had a clarkeite (sodium-uranate)-type crystallographic structure. The presented results have clear and hitherto unrecognized implications for the mobility of U(VI) in cementitious environments, in particular those associated with the geological disposal of nuclear waste.

  14. Oxo-group-14-element bond formation in binuclear uranium(V) pacman complexes

    International Nuclear Information System (INIS)

    Jones, Guy M.; Arnold, Polly L.; Love, Jason B.

    2013-01-01

    Simple and versatile routes to the functionalization of uranyl-derived U"V-oxo groups are presented. The oxo-lithiated, binuclear uranium(V)-oxo complexes [{(py)_3LiOUO}_2(L)] and [{(py)_3LiOUO}(OUOSiMe_3)(L)] were prepared by the direct combination of the uranyl(VI) silylamide ''ate'' complex [Li(py)_2][(OUO)(N'')_3](N''=N(SiMe_3)_2) with the polypyrrolic macrocycle H_4L or the mononuclear uranyl (VI) Pacman complex [UO_2(py)(H_2L)], respectively. These oxo-metalated complexes display distinct U-O single and multiple bonding patterns and an axial/equatorial arrangement of oxo ligands. Their ready availability allows the direct functionalization of the uranyl oxo group leading to the binuclear uranium(V) oxo-stannylated complexes [{(R_3Sn)OUO}_2(L)] (R=nBu, Ph), which represent rare examples of mixed uranium/tin complexes. Also, uranium-oxo-group exchange occurred in reactions with [TiCl(OiPr)_3] to form U-O-C bonds [{(py)_3LiOUO}(OUOiPr)(L)] and [(iPrOUO)_2(L)]. Overall, these represent the first family of uranium(V) complexes that are oxo-functionalised by Group 14 elements. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Impact of the uranium (VI) speciation in mineralised urines on its extraction by calix[6]arene bearing hydroxamic groups used in chromatography columns.

    Science.gov (United States)

    Baghdadi, S; Bouvier-Capely, C; Ritt, A; Peroux, A; Fevrier, L; Rebiere, F; Agarande, M; Cote, G

    2015-11-01

    Actinides determination in urine samples is part of the analyses performed to monitor internal contamination in case of an accident or a terrorist attack involving nuclear matter. Mineralisation is the first step of any of these analyses. It aims at reducing the sample volume and at destroying all organic compounds present. The mineralisation protocol is usually based on a wet ashing step, followed by actinides co-precipitation and a furnace ashing step, before redissolution and the quantification of the actinides by the appropriate techniques. Amongst the existing methods to perform the actinides co-precipitation, alkali-earth (typically calcium) precipitation is widely used. In the present work, the extraction of uranium(VI), plutonium(IV) and americium(III) from the redissolution solutions (called "mineralised urines") on calix[6]arene columns bearing hydroxamic groups was investigated as such an extraction is a necessary step before their determination by ICP-MS or alpha spectrometry. Difficulties were encountered in the transfer of uranium(VI) from raw to mineralised urines, with yield of transfer ranging between 0% and 85%, compared to about 90% for Pu and Am, depending on the starting raw urines. To understand the origin of such a difficulty, the speciation of uranium (VI) in mineralised urines was investigated by computer simulation using the MEDUSA software and the associated HYDRA database, compiled with recently published data. These calculations showed that the presence of phosphates in the "mineralised urines" leads to the formation of strong uranyl-phosphate complexes (such as UO2HPO4) which compete with the uranium (VI) extraction by the calix[6]arene bearing hydroxamic groups. The extraction constant of uranium (VI) by calix[6]arene bearing hydroxamic groups was determined in a 0.04 mol L(-1) sodium nitrate solution (logK=4.86±0.03) and implemented in an extraction model taking into account the speciation in the aqueous phase. This model allowed to

  16. Solvent extraction of uranium (VI) by Amberlite Lsub(A-1)

    International Nuclear Information System (INIS)

    Kim, S.S.

    1977-01-01

    The effects of uranium, amine and sulfuric acid concentrate, and temperature on the extraction of uranium(VI) from acidic sulphate solutions by Amberlite Lsub(A-1) in benzene was studied. The extraction of sulfuric acid by Amberlite Lsub(A-1) in benzene was also examined. It was found that 92 to 98 percent extraction was obtained for a uranyl sulphate solution of 5g/1 concentrate containing of 0.2M to 0.3M sulfuric acid, a Amberlite Lsub(A-1) of 5 to 10 percent (weight) in benzene, at a temperature of less than 20 0 C. The mechanism of uranium extraction was discussed on the basis of the resluts obtained. (author)

  17. Spectroscopic Studies on Complex Formation of U(VI)-thiosalicylate

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Wan Sik; Cho, Hye Ryun; Park, Kyoung Kyun; Jung, Euo Chang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-05-15

    The dynamic interaction between radionuclides and organic ligands is largely dependent on the composition of functional groups in a ligand chemical structure. Therefore, the structural mimics of natural ligands possessing specific functional groups, such as hydroxy, phenol, carboxyl, thiol and amine groups, have been studied to understand their influence on the migration of radionuclides including actinide species under geological groundwater conditions. In previous studies, we demonstrated that the fraction of hydrolyzed U(VI) species occurring in weak acidic solutions (pH {approx}4.5) is significantly influenced by the presence of salicylate (Sal) ligand due to the simultaneous participation of both phenol and carboxyl groups in the formation of U(VI)-complexes. Thiosalicylic acid (TSalH{sub 2}) is a good model compound for studying the effects of both carboxyl and thiol (-SH) groups. The fraction of di-anionic ligand form (TSal{sup 2-}) is higher at near neutral pH due to the lower pKa ({approx} 8) of the thiol group than the case of salicylic acid (pKa, {approx}13 for salicylic -OH), despite the structural similarity. In addition, the redox capability of the thiol group is expected to influence the reducible radiouclides and the chemical structures of natural ligands by creating cross-linkage (-S-S-) upon oxidation. The goal of the present study is to investigate aqueous U(VI)-TSal complexation equilibrium via laser-based spectroscopic techniques including time resolved laser-induced fluorescence spectroscopy (TRLFS). In this preliminary work, we report the results of spectroscopic studies using conventional UVVis absorbance and fluorescence (FL) measurement methods. The photo-stability of U(VI)-TSal complex or ligand itself upon exposure to a series of laser pulses is estimated by monitoring the change in their absorption bands. Additionally, TSal FL-quenching effect by U(VI) ions is discussed in comparison with that of Sal FL-quenching

  18. Ligand influences on properties of uranium coordination complexes. Structure, reactivity, and spectroscopy

    International Nuclear Information System (INIS)

    Kosog, Boris

    2012-01-01

    In this thesis several different aspects of uranium chemistry are presented. It was shown that terminal uranium(V) oxo and imido complexes [(( R ArO) 3 tacn)U V (O)] and [(( R ArO) 3 tacn)U V (NSiMe 3 )] (R = t Bu, Ad) can be oxidized by silver(I) hexafluoro-antimonate to the uranium(VI) oxo and imido complexes [(( R ArO) 3 tacn)U VI (O)]SbF 6 and [(( R ArO) 3 tacn)U VI (NSiMe 3 )]SbF 6 . While for the t Bu-derivative of the oxo complex an equatorial coordination is observed due to stabilization by the inverse trans-influence, normal axial coordination is observed for the Ad-derivative and both imido complexes. The inverse trans-influence was thus proven to be a key factor for the coordination mode of a terminal ligand on high valent uranium complexes. L III XANES was shown to be a great tool for the determination of oxidation states of uranium complexes. Therefore, a series of uranium complexes in all stable oxidation states for uranium, +III to +VI was prepared, and their spectra analyzed. All compounds bear only O-donor ligands in addition to the chlating trisaryloxide-tacn-ligand. A separation of 1.5 to 3 eV in the white line energy is observed between the different oxidation states. This series can be used as reference for compounds, where oxidation state assignment is not obvious, such as a ketyl radical complex [(( t-Bu Ar)O 3 tacn)U(O-C( t-Bu Ph) 2 .- )]. For this complex, the oxidation state of +IV could be assigned. Moreover, a series of isostructural uranium(IV) complexes was prepared. The influence of different ligands according to the spectrochemical series on the electronic and magnetic properties could be shown using UV/vis/NIR spectroscopy and variable temperature SQUID measurements. Calculations of uranium L III XANES spectra show a variation in the shape of the spectra and thus high resolution PFY-XANES would be a great tool to determine the electronic influence of these different axial ligands. Using the single N-anchored ligand system, the first

  19. New insights into uranium (VI) sol-gel processing

    International Nuclear Information System (INIS)

    King, C.M.; Thompson, M.C.; Buchanan, B.R.; King, R.B.; Garber, A.R.

    1990-01-01

    Nuclear Magnetic Resonance (NMR) investigations on the Oak Ridge National Laboratory process for sol-gel synthesis of microspherical nuclear fuel (UO 2 ), has been extremely useful in sorting out the chemical mechanism in the sol-gel steps. 13 C, 15 N, and 1 H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C 6 H 12 N 4 ) has revealed near quantitative stability of this adamantane-like compound in the sol-gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. 17 O NMR of uranyl (UO 2 ++ ) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, [(UO 2 ) 3 (μ 3 -O)(μ 2 -OH) 3 ] + , induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results will be presented to illustrate that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH + is occluded as an ''intercalation'' cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH 4 ) 2 [(UO 2 ) 8 O 4 (OH) 10 ] · 8H 2 O. This compound is the precursor to sintered UO 2 ceramic fuel. 23 refs., 10 figs

  20. Laser enhanced reductions of uranium(VI) ion in aqueous phosphoric acid solutions

    International Nuclear Information System (INIS)

    Park, Y.Y.; Harada, M.; Tomiyasu, H.; Ikeda, Y.; Takashima, Y.

    1991-01-01

    Photochemical reactions of U(VI) ions with inorganic anions (I - , Br - , Cl - , NCS - ) and organic compounds (1-hexene, cyclohexene, pyridine) in phosphoric acid were studied for the purpose of finding an efficient method of adjusting the oxidation states of uranium ions in nuclear fuel reprocessing. The formation of U(IV) was observed in the photoreactions with I - , Br - and NCS - , but not with Cl - . The yield of U(VI) increased in the order, Br - - - . This order was the same as the quenching rate constants of the excited U(VI) ions with these anions, and the reverse of their standard redox potentials. The rates of the formation of U(IV) in the presence of Br - were measured spectrophotometrically. It was found that the rate equation was first order in both [U(VI)] and [Br - ]. The results were reasonably interpreted by a series of reaction processes involving U(V) and Br radical. With organic molecules, 1-hexene, cyclohexene, and pyridine, the formation of U(IV) were observed. The yield of U(IV) increased in the order pyridine < 1-hexene < cyclohexene. This order is the reverse of their vertical ionization potentials, suggesting an electron transfer mechanism between these organic molecules and excited U(VI). (author)

  1. Gravimetric determination of uranium(VI) and thorium(IV) with substituted pyrazolones

    International Nuclear Information System (INIS)

    Arora, H.C.; Rao, G.N.

    1981-01-01

    4-Acylpyrazolones like 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), 1-phenyl-3-methyl-4-p-nitrobenzoyl-5-pyrazolone (PMNP) and 1-phenyl-3-methyl-4-(3,5 dinitrobenzoyl)-5-pyrazolone (PMDP) have been synthesized and developed as gravimetric reagents for the determination of U(VI) and Th(IV). Uranium(VI) is almost quantitatively precipitated with PMBP, PMNP, and PMDP at pH 2.20, 1.85 and 1.70 respectively. The pH values for the complete precipitation of thorium(IV) with PMBP, PMNP and PMDP are 2.90, 2.75 and 2.50 respectively. PMBP has proved to be an efficient ligand for gravimetric determination of U(VI) by direct weighing method after drying at 100 +- 10 deg C. The percentage relative error varies from 0.4 to 1.6 in the determination of U(VI) by this method. The effect of a number of interfering ions on the precipitation of U(VI) by PMBP has been reported. (author)

  2. Synthesis, structure and properties of oxo- and dioxochloride complexes of molybdenum(VI) and tungsten(VI) with 8-oxyquinoline

    International Nuclear Information System (INIS)

    Abramenko, V.L.; Sergienko, V.S.; Egorova, O.A.

    2005-01-01

    Complexes of oxo- and dioxochlorides of molybdenum(VI) and tungsten(VI) with 8-oxyquinoline of molecular and intracomplex type are synthesized and studied by the method of IR spectroscopy. The complexes have octahedral structure. It is proposed that 8-oxyquinoline in molecular complexes is coordinated by central atom through nitrogen atom of heterocycle, but in intracomplex compounds - through heterocyclic nitrogen atom and oxygen atom of deprotonated OH-group. Thermal stability of the complexes is studied [ru

  3. Cordilleran metamorphic core complexes and their uranium favorability

    International Nuclear Information System (INIS)

    Coney, P.J.; Reynolds, S.J.

    1980-11-01

    The objective of this report is to provide a descriptive body of knowledge on Cordilleran metamorphic core complexes including their lithologic and structural characteristics, their distribution within the Cordillera, and their evolutionary history and tectonic setting. The occurrence of uranium in the context of possibility for uranium concentration is also examined. This volume contains appendices of the following: annotated bibliography of Cordilleran metamorphic core complexes; annotated bibliography of the uranium favorability of Cordilleran metamorphic core complexes; uranium occurrences in the Cordilleran metamorphic core complex belt; and geology, uranium favorability, uranium occurrences and tectonic maps of individual Cordilleran metamorphic core complexes; and locations, lithologic descriptions, petrographic information and analytical data for geochemical samples

  4. Microbial reduction of uranium(VI) in sediments of different lithologies collected from Sellafield

    International Nuclear Information System (INIS)

    Newsome, Laura; Morris, Katherine; Trivedi, Divyesh; Atherton, Nick; Lloyd, Jonathan R.

    2014-01-01

    Highlights: • U(VI) (aq) mobility can be controlled by stimulating biogeochemical interactions. • Indigenous microbes in varied sediments reduced U(VI) to insoluble U(IV). • Sediment cell numbers and amount of bioavailable Fe(III) could limit this process. - Abstract: The presence of uranium in groundwater at nuclear sites can be controlled by microbial processes. Here we describe the results from stimulating microbial reduction of U(VI) in sediment samples obtained from a nuclear-licensed site in the UK. A variety of different lithology sediments were selected to represent the heterogeneity of the subsurface at a site underlain by glacial outwash deposits and sandstone. The natural sediment microbial communities were stimulated via the addition of an acetate/lactate electron donor mix and were monitored for changes in geochemistry and molecular ecology. Most sediments facilitated the removal of 12 ppm U(VI) during the onset of Fe(III)-reducing conditions; this was reflected by an increase in the proportion of known Fe(III)- and U(VI)-reducing species. However U(VI) remained in solution in two sediments and Fe(III)-reducing conditions did not develop. Sequential extractions, addition of an Fe(III)-enrichment culture and most probable number enumerations revealed that a lack of bioavailable iron or low cell numbers of Fe(III)-reducing bacteria may be responsible. These results highlight the potential for stimulation of microbial U(VI)-reduction to be used as a bioremediation strategy at UK nuclear sites, and they emphasise the importance of both site-specific and borehole-specific investigations to be completed prior to implementation

  5. Liquid-liquid extraction of uranium(VI) using Cyanex 272 in toluene from sodium salicylate medium

    International Nuclear Information System (INIS)

    Madane, Namdev S.; Nikam, Gurunath H.; Jadhav, Deepali V.; Mohite, Baburao S.

    2011-01-01

    Liquid-liquid extraction of U(VI) from sodium salicylate media using Cyanex 272 in toluene has been carried out. Uranium(VI) was quantitatively extracted from 1 x 10 -3 M sodium salicylate with 5 x 10 -4 M Cyanex 272 in toluene. It was stripped quantitatively from the organic phase with 1M HCl and determined spectrophotometrically with arsenazo(III) at 660 nm. The effect of concentrations of sodium salicylate, extractant, diluents, metal ion and strippants have been studied. Separation of uranium(VI) from other elements was achieved from binary as well as from multicomponent mixtures. The method was extended to determination of uranium(VI) in geological samples. The method is simple, rapid and selective with good reproducibility (approximately ± 2%). (author)

  6. Complex formation between glutamic acid and molybdenum (VI)

    International Nuclear Information System (INIS)

    Gharib, Farrokh; Khorrami, S.A.; Sharifi, Sasan

    1997-01-01

    Equilibria of the reaction of molybdenum (VI) with L-glutamic acid have been studied in aqueous solution in the pH range 2.5 to 9.5, using spectrophotometric and optical rotation methods at constant ionic strength (0.15 mol dm -3 sodium perchlorate) and temperature 25 ± 0.1 degC. Our studies have shown that glutamic acid forms a mononuclear complex with Mo(VI) of the type MoO 3 L 2- at pH 5.5. The stability constant of this complexation and the dissociation constants of L-glutamic acid have been determined. (author). 17 refs., 2 figs., 4 tabs

  7. Study on selective separation of uranium(VI) by new N,N-dialkyl carboxy-amides

    International Nuclear Information System (INIS)

    Suzuki, Shinichi; Sugo, Yumi; Kimura, Takaumi; Yaita, Tsuyoshi

    2007-01-01

    -amides and group separation of Pu-Np linear alkyl type N,N-di-alkyl carboxy-amide for FBR and LWR spent fuel treatment. Since the branched alkyl type N,N-di-alkyl carboxy-amides have the steric hindrance on the complexation with metal cations, branched alkyl type N,N-di-alkyl carboxy-amides can be used to separate An(VI) from An(IV). On the other hand, linear type N,N-di-alkyl carboxy-amides have potential for alternative extractant for tri-butyl phosphate(TBP) because linear type N,N-di-alkyl-amide can extract An(VI) and An(IV). In our previous research work, we have proposed N,N-di-(2- ethyl)hexyl-(2,2-dimethyl)-propanamide (D2EHDMPA) as a candidate extractant for uranium selective separation in FBR spent fuel treatments. However D2EHDMPA was able to separate uranium(VI) from plutonium(IV) and neptunium(VI), D2EHDMPA showed poor U(VI) loading capacity in organic phase. For the purpose of improvement of U(VI) loading capacity in organic phase, nineteenth kinds of New N,N-di-alkyl-amides: N,N-di-hexyl-(3,3-dimethyl)butanamide (DHDMBA), N,N-di-oxyl-(3,3-dimethyl)butanamide (DODMBA), N,N-di-hexyl-(2,2-dimethyl)propanamide (DHDMPA) N,N-di-octyl-(2,2-dimethyl)propanamide (DODMPA), N,N-di-octyl-(2-ethyl)butanamide (DO2EBA), N,N-di-hexyl-(2-ethyl)butanamide (DH2EBA), N-benzyl-N-R 1 -(2-ethyl)hexanamide (R 1 :- C 4 H 9 , -C 6 H 13 , -C 8 H 17 , N-cyclohexyl-N-R 1 -(2- ethyl)hexanamide (R 1 :-C 4 H 9 , -C 6 H 13 , -C 8 H 17 ), N-phenyl- N-R 1 -(2-ethyl)hexanamide (R 1 :-C 3 H 9 , -C 4 H 9 , -C 5 H 11 , - C 6 H 13 , -C 8 H 17 , N-(2-ethyl)hexyl-N-Phenyl-octanamide, N-Benzyl- N-Phenyl-(2-ethyl)hexanamide are synthesized. In this paper, our experimental results of new N,N-dialkyl carboxy-amides extraction property of U(VI)/Pu(IV), extraction of macro amount of U(VI), and gamma-ray radiolysis will be summarized. Solvent extraction of U(VI) and Pu (IV) by nineteenth kinds of new N,N-di-alkyl carboxy-amides, macro amount of U(VI) extraction and radiolysis of four compounds were carried

  8. Interactions of quercetin-uranium complexes with biomembranes and DNA

    Energy Technology Data Exchange (ETDEWEB)

    Attia, Enas Mohammed Hassan

    2014-07-21

    Uranium decontamination gains a great importance with the spread of nuclear waste in both soil and water systems across the planet. All known remediation methods of uranium can be exclusively based either on synthetic materials with high adsorbent power and known physical chemistry or life organisms by which the uranium eventually accumulated inside their tissues. In the present thesis, it was attempted to design a rational approach for uranyl removal primarily from waters using the reducing potential of quercetin, which is a plant-derived small organic molecules, along with its photochemical activities. Such approach, which is neither a fully synthetic nor an organism-based approach, was chosen here to avoid disadvantages with both traditional strategies. Here, complexation experiments were designed to assess the use of uranyl-quercetin complexes for the photoreduction of water-soluble U(VI) to insoluble U(IV) by comparing absorption properties of uranyl-quercetin complexes in acetone, water, and hydrophobic bilayer lipid vesicles. The UV-vis data show that uranyl quercetin complex can form in both hydrophobic and hydrophilic environments. In both cases the B-ring band in quercetin structure becomes reduced, red shifted and a pronounced absorption arises in the 400-500 nm range. Such data suggests that U(VI) binds at the 3-OH and 4-carbonyl of ring C of quercetin. Interestingly, the results of UV-Vis spectroscopy part hint at a crucial role of a stable or transiently ionized hydroxyl for the efficient uranyl-dependent photodegradation of quercetin. FTIR spectroscopy absorption changes further demonstrates that the UV-vis-spectroscopic changes are indeed accompanied by changes in the chemical structure of the complex as expected for a uranyl-dependent photodegradation. IR data thus suggest that U(VI) becomes reduced by the photoreaction, rather than merely changing its coordination shell. The frequency shifts in the C=C and C=O absorption range on the other hand

  9. Interactions of quercetin-uranium complexes with biomembranes and DNA

    International Nuclear Information System (INIS)

    Attia, Enas Mohammed Hassan

    2014-01-01

    Uranium decontamination gains a great importance with the spread of nuclear waste in both soil and water systems across the planet. All known remediation methods of uranium can be exclusively based either on synthetic materials with high adsorbent power and known physical chemistry or life organisms by which the uranium eventually accumulated inside their tissues. In the present thesis, it was attempted to design a rational approach for uranyl removal primarily from waters using the reducing potential of quercetin, which is a plant-derived small organic molecules, along with its photochemical activities. Such approach, which is neither a fully synthetic nor an organism-based approach, was chosen here to avoid disadvantages with both traditional strategies. Here, complexation experiments were designed to assess the use of uranyl-quercetin complexes for the photoreduction of water-soluble U(VI) to insoluble U(IV) by comparing absorption properties of uranyl-quercetin complexes in acetone, water, and hydrophobic bilayer lipid vesicles. The UV-vis data show that uranyl quercetin complex can form in both hydrophobic and hydrophilic environments. In both cases the B-ring band in quercetin structure becomes reduced, red shifted and a pronounced absorption arises in the 400-500 nm range. Such data suggests that U(VI) binds at the 3-OH and 4-carbonyl of ring C of quercetin. Interestingly, the results of UV-Vis spectroscopy part hint at a crucial role of a stable or transiently ionized hydroxyl for the efficient uranyl-dependent photodegradation of quercetin. FTIR spectroscopy absorption changes further demonstrates that the UV-vis-spectroscopic changes are indeed accompanied by changes in the chemical structure of the complex as expected for a uranyl-dependent photodegradation. IR data thus suggest that U(VI) becomes reduced by the photoreaction, rather than merely changing its coordination shell. The frequency shifts in the C=C and C=O absorption range on the other hand

  10. Complex formation in the system uranium(VI) - alpha-substituted carboxylic acids studied by TRLFS. Pt. I. Glycolic and alpha-hydroxyisobutyric acid at pH 2

    International Nuclear Information System (INIS)

    Moll, H.; Geipel, G.; Bernhard, G.; Fanghaenel, Th.; Grenthe, I.

    2002-01-01

    We observed a very strong quenching of the U(VI) fluorescence in these systems that can be quantitatively described by the Stern-Volmer equation. The following stability constants were determined: a) for the glycolate system log β 1:1 = 2.52±0.20, b) for the α-hydroxyisobutyrate system log β 1:1 = 3.40±0.21. (orig.)

  11. Solvent extraction of uranium(VI) and thorium(IV) from nitrate media by carboxylic acid amides

    International Nuclear Information System (INIS)

    Preston, J.S.; Preez, A.C. du

    1995-01-01

    A series of nineteen N-alkyl carboxylic acid amides (R.CO.NHR') has been prepared, in which the alkyl groups R and R' have been varied in order to introduce different degrees of steric complexity into the compounds. A smaller number of N,N-dialkyl amides (R.CO.NR 2 ') and non-substituted amides (R.CO.NH 2 ) has also been prepared for comparison purposes. These amides were characterized by measurement of their boiling points, melting points, refractive indices and densities. The solvent extraction of uranium(VI) and thorium(IV) from sodium nitrate media by solutions of the amides in toluene was studied. Increasing steric bulk of the alkyl groups R and R' was found to cause a marked decrease in the extraction of thorium, with a much smaller effect on the extraction of uranium, thus considerably enhancing the separation between these metals. Vapour pressure osmometry studies indicate that the N-alkyl amides are self-associated in toluene solution, with aggregation numbers up to about 2.5 for 0.6 M solutions at 35 degree C. In contrast, the N,N-dialkyl amides behave as monomers under these conditions. The distribution ratios for the extraction of uranium and thorium show second- and third-order dependences, respectively, on the extractant concentration for both the N-alkyl and N,N-dialkyl amides. 15 refs., 8 figs., 8 tabs

  12. Mixed-ligand complexes of dioxouranium(VI)

    International Nuclear Information System (INIS)

    Ahuja, Renu; Dwivedi, K.

    1995-01-01

    A number of mixed ligand complexes of UO 2 2+ ion have been studied with aminopolycarboxylic acids, such as ethylenediaminetetraacetic acid with coordination number (CN) = 6, nitrilotriacetic acid with CN = 4 and iminodiacetic acid with CN = 3. Ethyleneglycol-bis-2-aminoethylether tetraacetic acid (EGTA) is an octadentate aminopolycarboxylic acid and forms stable binary complexes with many metal ions at low pH. In this paper the results obtained for the study of 1:1:1 UO 2 VI -EGTA-aspartic acid/glutamic acid systems are studied. (author). 7 refs., 1 fig., 1 tab

  13. Uranium

    International Nuclear Information System (INIS)

    Hamdoun, N.A.

    2007-01-01

    The article includes a historical preface about uranium, discovery of portability of sequential fission of uranium, uranium existence, basic raw materials, secondary raw materials, uranium's physical and chemical properties, uranium extraction, nuclear fuel cycle, logistics and estimation of the amount of uranium reserves, producing countries of concentrated uranium oxides and percentage of the world's total production, civilian and military uses of uranium. The use of depleted uranium in the Gulf War, the Balkans and Iraq has caused political and environmental effects which are complex, raising problems and questions about the effects that nuclear compounds left on human health and environment.

  14. Catechol functionalized aminopropyl silica gel: synthesis, characterization and preconcentrative separation of uranium(VI) from thorium(IV)

    International Nuclear Information System (INIS)

    Metilda, P.; Mary Gladis, J.; Prasada Rao, T.P.

    2005-01-01

    A novel solid phase extractant is prepared by chemically immobilizing catechol with diazotized aminopropyl silica gel. The resulting catechol functionalized silica gel (CASG) was characterized by FTIR, and microanalysis and was used for selective enrichment of uranium(VI) from other inorganic ions. The optimum pH range for maximum sorption of uranium(VI) and thorium(IV) was found to be in the range 3.5-6.0. The above actinides were eluted with 10 cm 3 of 1.0 mol dm -3 HCl and determined by using an Arsenazo III spectrophotometric procedure. The calibration graph was rectilinear over the uranium(VI) concentration in the range 2-100 μg dm -3 with a relative standard deviation of 2.15% (for 25 μg of uranium(VI) present in 1.0 dm 3 of sample). The validation of the developed preconcentration procedure was carried out by analyzing marine sediment (MESS-3, NRC, Canada) and soil (IAEA soil-7, Austria) reference materials. The developed preconcentration method enables a simple instruments like a spectrophotometer gave comparable values of uranium(VI) to that of standard inductively coupled plasma-mass spectrometric values during the analysis of real soil and sediment samples. (orig.)

  15. Catechol functionalized aminopropyl silica gel: synthesis, characterization and preconcentrative separation of uranium(VI) from thorium(IV)

    Energy Technology Data Exchange (ETDEWEB)

    Metilda, P.; Mary Gladis, J.; Prasada Rao, T.P. [Regional Research Lab. (CSIR), Trivandrum (India)

    2005-07-01

    A novel solid phase extractant is prepared by chemically immobilizing catechol with diazotized aminopropyl silica gel. The resulting catechol functionalized silica gel (CASG) was characterized by FTIR, and microanalysis and was used for selective enrichment of uranium(VI) from other inorganic ions. The optimum pH range for maximum sorption of uranium(VI) and thorium(IV) was found to be in the range 3.5-6.0. The above actinides were eluted with 10 cm{sup 3} of 1.0 mol dm{sup -3} HCl and determined by using an Arsenazo III spectrophotometric procedure. The calibration graph was rectilinear over the uranium(VI) concentration in the range 2-100 {mu}g dm{sup -3} with a relative standard deviation of 2.15% (for 25 {mu}g of uranium(VI) present in 1.0 dm{sup 3} of sample). The validation of the developed preconcentration procedure was carried out by analyzing marine sediment (MESS-3, NRC, Canada) and soil (IAEA soil-7, Austria) reference materials. The developed preconcentration method enables a simple instruments like a spectrophotometer gave comparable values of uranium(VI) to that of standard inductively coupled plasma-mass spectrometric values during the analysis of real soil and sediment samples. (orig.)

  16. Terminal uranium(V/VI) nitride activation of carbon dioxide and carbon disulfide. Factors governing diverse and well-defined cleavage and redox reactions

    International Nuclear Information System (INIS)

    Cleaves, Peter A.; Gardner, Benedict M.; Liddle, Stephen T.; Kefalidis, Christos E.; Maron, Laurent; Tuna, Floriana; McInnes, Eric J.L.; Lewis, William

    2017-01-01

    The reactivity of terminal uranium(V/VI) nitrides with CE 2 (E=O, S) is presented. Well-defined C=E cleavage followed by zero-, one-, and two-electron redox events is observed. The uranium(V) nitride [U(Tren TIPS )(N)][K(B15C5) 2 ] (1, Tren TIPS =N(CH 2 CH 2 NSiiPr 3 ) 3 ; B15C5=benzo-15-crown-5) reacts with CO 2 to give [U(Tren TIPS )(O)(NCO)][K(B15C5) 2 ] (3), whereas the uranium(VI) nitride [U(Tren TIPS )(N)] (2) reacts with CO 2 to give isolable [U(Tren TIPS )(O)(NCO)] (4); complex 4 rapidly decomposes to known [U(Tren TIPS )(O)] (5) with concomitant formation of N 2 and CO proposed, with the latter trapped as a vanadocene adduct. In contrast, 1 reacts with CS 2 to give [U(Tren TIPS )(κ 2 -CS 3 )][K(B15C5) 2 ] (6), 2, and [K(B15C5) 2 ][NCS] (7), whereas 2 reacts with CS 2 to give [U(Tren TIPS )(NCS)] (8) and ''S'', with the latter trapped as Ph 3 PS. Calculated reaction profiles reveal outer-sphere reactivity for uranium(V) but inner-sphere mechanisms for uranium(VI); despite the wide divergence of products the initial activation of CE 2 follows mechanistically related pathways, providing insight into the factors of uranium oxidation state, chalcogen, and NCE groups that govern the subsequent divergent redox reactions that include common one-electron reactions and a less-common two-electron redox event. Caution, we suggest, is warranted when utilising CS 2 as a reactivity surrogate for CO 2 . (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains

    International Nuclear Information System (INIS)

    Pan, Xiaohong; Chen, Zhi; Chen, Fanbing; Cheng, Yangjian; Lin, Zhang; Guan, Xiong

    2015-01-01

    Highlights: • Indigenous B. thuringiensis exhibited highly accumulation ability to U(VI) in the absence of additional nutrients. • The amorphous uranium compound would transformed into crystalline nano-uramphite by B. thuringiensis. • The chemical nature of formed U-species were monitored. • The cell-free extracts of B. thuringiensis had better uranium-immobilization ability than its cell debris. • Provided the understanding of the uranium transformation mechanism. - Abstract: The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains was investigated in the present work. Our data showed that the bacteria isolated from uranium mine possessed highly accumulation ability to U(VI), and the maximum accumulation capacity was around 400 mg U/g biomass (dry weight). X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analyzes indicated that the U(VI) was adsorbed on the bacterial surface firstly through coordinating with phosphate, −CH 2 and amide groups, and then needle-like amorphous uranium compounds were formed. With the extension of time, the extracellular crystalline substances were disappeared, but some particles were appeared in the intracellular region, and these particles were characterized as tetragonal-uramphite. Moreover, the disrupted experiment indicated that the cell-free extracts had better uranium-immobilization ability than cell debris. Our findings provided the understanding of the uranium transformation process from amorphous uranium to crystalline uramphite, which would be useful in the regulation of uranium immobilization process

  18. The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Xiaohong; Chen, Zhi [Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian–Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002 (China); Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Chen, Fanbing [Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian–Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002 (China); Cheng, Yangjian [Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Lin, Zhang, E-mail: zlin@fjirsm.ac.cn [Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); School of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); Guan, Xiong, E-mail: guanxfafu@126.com [Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian–Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002 (China)

    2015-10-30

    Highlights: • Indigenous B. thuringiensis exhibited highly accumulation ability to U(VI) in the absence of additional nutrients. • The amorphous uranium compound would transformed into crystalline nano-uramphite by B. thuringiensis. • The chemical nature of formed U-species were monitored. • The cell-free extracts of B. thuringiensis had better uranium-immobilization ability than its cell debris. • Provided the understanding of the uranium transformation mechanism. - Abstract: The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains was investigated in the present work. Our data showed that the bacteria isolated from uranium mine possessed highly accumulation ability to U(VI), and the maximum accumulation capacity was around 400 mg U/g biomass (dry weight). X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analyzes indicated that the U(VI) was adsorbed on the bacterial surface firstly through coordinating with phosphate, −CH{sub 2} and amide groups, and then needle-like amorphous uranium compounds were formed. With the extension of time, the extracellular crystalline substances were disappeared, but some particles were appeared in the intracellular region, and these particles were characterized as tetragonal-uramphite. Moreover, the disrupted experiment indicated that the cell-free extracts had better uranium-immobilization ability than cell debris. Our findings provided the understanding of the uranium transformation process from amorphous uranium to crystalline uramphite, which would be useful in the regulation of uranium immobilization process.

  19. Uranium(VI) coordination polymers with pyromellitate ligand: Unique 1D channel structures and diverse fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yingjie, E-mail: yzx@ansto.gov.au [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Bhadbhade, Mohan [Mark Wainwright Analytical Centre, University of New South Wales, Kensington, NSW 2052 (Australia); Karatchevtseva, Inna [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Price, Jason R. [Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168 (Australia); Liu, Hao [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology Sydney, PO Box 123, Broadway, Sydney, NSW 2007 (Australia); Zhang, Zhaoming; Kong, Linggen [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Čejka, Jiří [Department of Mineralogy, National Museum, Václavské náměstí, 68, Prague 1, 115 79-CZ (Czech Republic); Lu, Kim; Lumpkin, Gregory R. [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia)

    2015-03-15

    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 (~4.5 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.

  20. Solvent extraction of uranium(VI) with benzoylacetanilide and its nitro derivatives

    International Nuclear Information System (INIS)

    Mukherjee, Gautam Kumar; Das, Jyotirmoy

    1984-01-01

    The extraction behaviour of uranium(VI) chelates of benzoylacetanilide and four of its mononitro derivatives, viz., benzoyl-o-nitroacetanilide, benzoyl-m-nitroacetanilide, benzoyl-p-nitro-acetanilide and p-nitrobenzoylacetanilide from aqueous solution into carbon tetrachloride has been studied. The extractions have also been carried out in the presence of pyridine, α-picoline, β-picoline and γ-picoline. The extraction constants, and the two phase formation constants of the chelates and adducts have been determined. The effects of the nitro substituent in benzoylacetanilide and formation of syngergistic adducts have been discussed. (author)

  1. Effect of porosity and surface chemistry on the adsorption-desorption of uranium(VI) from aqueous solution and groundwater

    International Nuclear Information System (INIS)

    Yakout, S.M.

    2016-01-01

    Rice straw-based biochars modified with different chemical regents were used as an adsorbent for uranium(VI). Effect of pyrolysis temperature and nature of modifying agent's as well as surface chemistry, surface charge, and pore structure on U(VI) removal was investigated. Amount and nature of the surface groups has, in general, more influence than its porosity on U(VI) adsorption. The adsorption was maximum for the initial pH of 5.5. Rice straw derived biochars had comparable U(VI) adsorption as compared to other adsorbents. The U(VI) removal was 90 % from groundwater. NaHCO 3 was found to be the most efficient desorbent eluent for U(VI). (author)

  2. Effect of flavin compounds on uranium(VI) reduction- kinetic study using electrochemical methods with UV-vis spectroscopy

    International Nuclear Information System (INIS)

    Yamasaki, Shinya; Tanaka, Kazuya; Kozai, Naofumi; Ohnuki, Toshihiko

    2017-01-01

    The reduction of uranium hexavalent (U(VI)) to tetravalent (U(IV)) is an important reaction because of the change in its mobility in the natural environment. Although the flavin mononucleotide (FMN) has acted as an electron shuttle for the U(VI) reduction in vivo system, which is called an electron mediator, only the rate constant for the electron transfer from FMN to U(VI) has been determined. This study examined the rate constant for the U(VI) reduction process by three flavin analogues (riboflavin, flavin mononucleotide, flavin adenine dinucleotide) to elucidate their substituent group effect on the U(VI) reduction rate by electrochemical methods. The formation of the U(IV) was monitored by UV-vis spectrometry at 660 nm during the constant potential electrolysis of the U(VI) solution in the presence of the mediator. The cyclic voltammograms indicated that the three flavin analogues behaved as electron mediator to reduce U(VI). The logarithmic rate constant for the U(VI) reduction was related to the standard redox potential of the mediators. This linear relationship indicated that the redox-active group of the mediator and the substituent group of the mediator dominate capability of the U(VI) reduction and its rate, respectively. The apparent reduction potential of U(VI) increased about 0.2 V in the presence of the mediators, which strongly suggests that the biological electron mediator makes the U(VI) reduction possible even under more oxidative conditions. - Highlights: • The rate constant for the U(VI) reduction by flavin analogues was determined. • The flavins showed a mediator effect on the U(VI) reduction. • The logarithmic rate constants for the U(VI) reduction was proportional to redox potential of the mediator. • The presence of the mediator increased about 0.2 V apparent redox potential of U(VI) to U(IV).

  3. Synthesis and evaluation of complexing and extracting properties of diamides for the U(VI)/Pu(IV) partitioning

    International Nuclear Information System (INIS)

    Wahu, S.

    2012-01-01

    This work concerns the synthesis and evaluation of new diamides for co-extraction of U(VI) and Pu(IV) from spent nuclear fuels in concentrated nitric acid medium and the subsequent selective back-extraction of Pu(IV) at lower nitric acidity. Thus, three diamides series, namely R 2 NOC(CH 2 ) n CONR 2 , RR'NOC(CH 2 ) n CONRR' and R 2 NOC(CH 2 CHR')CONR 2 (series 1, 2 and 3, respectively) were synthesized and studied in the expectation to establish a structure-activity relationship regarding the extraction properties of such compounds towards actinides. Extraction tests showed that these diamides can effectively and selectively extract U(VI) and Pu(IV) from Am(III) at high acidity. In addition, it was found that the selective back-extraction of Pu(IV) from U(VI) can be achieved, as expected, merely by changing the acidity, when the nitrogen atoms of these diamides are substituted by branched alkyl chains. The mode of coordination of actinides by the above diamides has also been studied through the use of short chain diamides model compounds, allowing the crystallization of the actinide complexes and, thus, their characterization by X-ray diffraction. EXAFS investigation suggested that the uranium coordination sphere in the complexes formed with long chain diamides and extracted into the organic phase is identical to the one observed in U(VI) complexes obtained with short chain diamides model compounds. However, the stoichiometry of model complexes is 1:1, UO 2 (NO 3 ) 2 TEDA, whereas extracted U(VI) complexes exhibit 1:2 stoichiometry, UO 2 (NO 3 ) 2 (TEHDA) 2 . Finally, Th (IV) complexes were also prepared and characterized and further compared to U(VI) complexes. (author) [fr

  4. EXAFS investigation of uranium(6) complexes formed at Acidithiobacillus ferro oxidans types

    International Nuclear Information System (INIS)

    Merroun, M.; Reich, T.; Hennig, Ch.; Selenska-Pobell, S.

    2002-01-01

    Mining activities have brought excessive amounts of uranium into the environment. In uranium deposits a number of acidophilic chemo-litho-autotrophic bacteria have been identified which are able to oxidize sulphide minerals, elemental sulphur, ferrous iron and also (in the presence of uranium mineral) U(IV). In particular, the interaction of one representative of the group Acidithiobacillus ferro oxidans (new designation of Thiobacillus ferro oxidans) with uranium has been investigated. Uranium(VI) complex formations at the surfaces of Acidithiobacillus ferro oxidans were studied using uranium L III -edge extended X-ray absorption fine structure (EXAFS) spectroscopy. In all samples uranium is co-ordinated by two axial oxygen atoms (O ax ) at a distance of 1.77-1.78 angstrom. The average distance between uranium and the equatorial oxygen atoms (O eq ) is 2.35 angstrom. The co-ordination number for O eq is 5-6. In comparison to the uranium crystal structure data, the U-O eq distance indicates a co-ordination number of the equatorial oxygen of 5. Within the experimental error, there are no differences in the U-O bond distances between samples from the three types of A. ferro oxidans investigated. The fit to the EXAFS data of samples measured as wet pastes gave the same results as for dried samples. No significant structural differences were observed for the uranium complexes formed by the eco-types of A. ferro oxidans. However, the EXAFS spectra do indicate a formation of uranium complexes which are different from those formed by Bacilli where the bond length of 2.28 angstrom indicates a co-ordination number of 4 for the equatorial oxygen atoms. (authors)

  5. Kinetics and equilibrium modeling of uranium(VI) sorption by bituminous shale from aqueous solution

    International Nuclear Information System (INIS)

    Ortaboy, Sinem; Atun, Gülten

    2014-01-01

    Highlights: • Oil shales are sedimentary rocks containing a polymeric matter in a mineral matrix. • Sorption potential of bituminous shale (BS) for uranium recovery was investigated. • U(VI) sorption increased with decreasing pH and increasing temperature. • Kinetic data were analyzed based on single and two resistance diffusion models. • The results fit well to the McKay equation assuming film and intraparticle diffusion. - Abstract: Sorption of U(VI) onto a bituminous shale (BS) from a nuclear power plant project site in Black Sea region was investigated for potential risk assessment when it releases into the environment with contaminated ground and surface water. The sorption characteristics of the BS for U(VI) recovery were evaluated as a function of contact time, adsorbent dosage, initial concentration, pH and temperature. Kinetic results fit better with pseudo-second-order model rather than pseudo-first-order. The possibility of diffusion process was analyzed based on Weber–Morris intra-particle diffusion model. The McKay equation assuming film- and intraparticle diffusion better predicted the data than the Vermeulen approximation presuming surface diffusion. Equilibrium sorption data were modeled according to the Langmuir, Dubinin–Radushkevich (D–R) and Freundlich isotherm equations. Sorption capacity increased from 0.10 to 0.15 mmol g −1 in 298–318 K temperature range. FT-IR analysis and pH dependent sorption studies conducted in hydroxide and carbonate media revealed that U(VI) species were sorbed in uranyl and its hydroxo forms on the BS. Desorption studies showed that U(VI) leaching with Black Sea water was negligible from the loaded BS. The activation parameters (E a , ΔH ∗ and ΔG ∗ ) estimated from diffusion coefficients indicated the presence of an energy barrier in the sorption system. However, thermodynamic functions derived from sorption equilibrium constants showed that overall sorption process was spontaneous in nature

  6. Macrocyclic ligands for uranium complexation

    International Nuclear Information System (INIS)

    Potts, K.T.

    1991-04-01

    A highly preorganized 24-macrocycle containing biuret, thiobiuret and pyridine subunits has been prepared by high dilution ring-closure procedures. Intermediate products to this macrocycle have been utilized to extend this synthetic route to include further representatives where solubility and stability will be influenced by substituent variation. A 1:1 complex has been formed from uranyl acetate and a quinquepyridine derivative, this representing a new type of ligand for the uranyl ion. A very convenient synthetic procedure that will allow the incorporation of these macrocycles into polymeric systems has been developed for the introduction of a vinyl substituent into the 4-position of the pyridine ring. Using triflate, vinyltributyltin and Pd 0 chemistry, this procedure should make a variety of substituted 4-vinylpyridines available for the first time. 3 refs

  7. Ligand Influences on Properties of Uranium Coordination Complexes - Structure, Reactivity, and Spectroscopy

    OpenAIRE

    Kosog, Boris

    2012-01-01

    In this thesis several different aspects of uranium chemistry are presented. It was shown that terminal uranium(V) oxo and imido complexes [((RArO)3tacn)UV(O)] and [((RArO)3tacn)UV(NSiMe3)] (R = t Bu, Ad) can be oxidized by silver(I) hexafluoro-antimonate to the uranium(VI) oxo and imido complexes [((RArO)3tacn)UVI(O)]SbF6 and [((RArO)3tacn)UVI(NSiMe3)]SbF6. While for the t Bu-derivative of the oxo complex an equatorial coordination is observed due to stabilization by the inverse trans-influe...

  8. Extraction of uranium(VI) by emulsion liquid membrane containing 5,8-diethyl-7-hydroxy-6-dodecanone oxime

    International Nuclear Information System (INIS)

    Akiba, Kenichi; Takahashi, Toshihiko; Kanno, Takuji

    1984-01-01

    Extraction of uranium(VI) by a liquid surfactant membrane has been studied. The stability of water-in-oil (w/o) emulsion dispersed in the continuous aqueous phase increased with an increase in surfactant concentrations and in the fraction of the organic phase in emulsion globules. Uranium(VI) in dilute acid solutions was extracted into (w/o) emulsions containing 5,8-diethyl-7-hydroxy-6-dodecanone oxime (LIX 63) as a mobile carrier and its concentration decreased according to [U]sub(t)=[U]sub(o)exp(-ksub(obsd)t). The apparent rate constants (ksub(obsd)) increased with an increase in carrier concentrations and in external pH values, while they were slightly dependent on the stripping acid concentrations. Uranium was transported and concentrated into the internal aqueous droplets. The final concentration of uranium in the external aqueous phase dropped to about 10 -3 of its initial value. (author)

  9. Influence of the temperature in the uranium (Vi) sorption in zirconium diphosphate; Influencia de la temperatura en la sorcion de uranio (VI) en difosfato de circonio

    Energy Technology Data Exchange (ETDEWEB)

    Garcia G, N.; Solis, D. [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Paseo Colon y Paseo Tollocan, 50120 Toluca, Estado de Mexico (Mexico); Ordonez R, E., E-mail: nidgg@yahoo.com.mx [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2012-10-15

    In the present work was evaluated the uranium (Vi) sorption at 10, 20, 30, 40 and 60 C on the zirconium diphosphate (ZrP{sub 2}O{sub 7}). They were carried out kinetic and isotherms using the method by lots, these will allow to fix the sorption time (kinetic) and to explain the behavior of this sorption in different ph conditions and temperature (isotherm). The quantity of retained uranium in the surface was quantified by means of the fluorescence technique. (Author)

  10. Determination of submicromolar amounts of uranium(VI) by compleximetric titration with pyridine-2,6-dicarboxylic acid

    International Nuclear Information System (INIS)

    Marsh, S.F.; Betts, M.R.; Rein, J.E.

    1980-01-01

    Uranium(VI) is selectively determined by a compleximetric titration with pyridine-2,6-dicarboxylic acid, using arsenazo-I indicator and hexamethylenetetramine buffer at pH 4.9. Cyclohexanediaminetetraacetic acid and diethylenetriaminepentaacetic acid provide masking of interfering metal ions. A probe colorimeter apparatus is recommended for end-point detection. The relative standard deviation is 0.6% for 0.17-0.76 μmol of uranium. (Auth.)

  11. Determination of submicromolar amounts of uranium(VI) by compleximetric titration with pyridine-2,6-dicarboxylic acid

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, S F; Betts, M R; Rein, J E [Los Alamos Scientific Lab., NM (USA)

    1980-10-01

    Uranium(VI) is selectively determined by a compleximetric titration with pyridine-2,6-dicarboxylic acid, using arsenazo-I indicator and hexamethylenetetramine buffer at pH 4.9. Cyclohexanediaminetetraacetic acid and diethylenetriaminepentaacetic acid provide masking of interfering metal ions. A probe colorimeter apparatus is recommended for end-point detection. The relative standard deviation is 0.6% for 0.17-0.76 ..mu..mol of uranium.

  12. A modelling exercise on the importance of ternary alkaline earth carbonate species of uranium(VI) in the inorganic speciation of natural waters

    International Nuclear Information System (INIS)

    Vercouter, Thomas; Reiller, Pascal E.; Ansoborlo, Eric; Février, Laureline; Gilbin, Rodolphe; Lomenech, Claire; Philippini, Violaine

    2015-01-01

    Highlights: • The U(VI) speciation in natural waters has been modelled through a modelling exercise. • The results evidence the importance of alkaline earth U(VI) carbonate complexes. • Possible solubility-controlling phases were reported and discussed. • The differences were related to the choice and reliability of thermodynamic data. • Databases need to be improved for reliable U(VI) speciation calculations. - Abstract: Predictive modelling of uranium speciation in natural waters can be achieved using equilibrium thermodynamic data and adequate speciation software. The reliability of such calculations is highly dependent on the equilibrium reactions that are considered as entry data, and the values chosen for the equilibrium constants. The working group “Speciation” of the CETAMA (Analytical methods establishment committee of the French Atomic Energy commission, CEA) has organized a modelling exercise, including four participants, in order to compare modellers’ selections of data and test thermodynamic data bases regarding the calculation of U(VI) inorganic speciation. Six different compositions of model waters were chosen so that to check the importance of ternary alkaline earth carbonate species of U(VI) on the aqueous speciation, and the possible uranium solid phases as solubility-limiting phases. The comparison of the results from the participants suggests (i) that it would be highly valuable for end-users to review thermodynamic constants of ternary carbonate species of U(VI) in a consistent way and implement them in available speciation data bases, and (ii) stresses the necessary care when using data bases to avoid biases and possible erroneous calculations

  13. Spectroscopic investigations on sorption of uranium onto suspended bentonite. Effects of pH, ionic strength and complexing anions

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Parveen Kumar; Pathak, Priyanath; Mohapatra, Manoj; Mohapatra, Prasanta Kumar [Bhabha Atomic Research Centre, Mumbai (India). Radiochemistry Div.; Yadav, Ashok Kumar; Jha, Sambhunath; Bhattacharyya, Dibyendu [Bhabha Atomic Research Centre, Mumbai (India). Atomic and Molecular Physics Div.

    2015-06-01

    Batch sorption experiments were carried out under aerobic conditions to understand the sorption behavior of U(VI) onto bentonite clay under varying pH (2-8) and ionic strength (I = 0.01 - 1 M (NaClO{sub 4})) conditions. The influences of different complexing anions (1 x 10{sup -4} M) such as oxalic acid (ox), carbonate (CO{sub 3}{sup 2-}), citric acid (cit), and humic acid (HA, 10 mg/L) on the sorption behavior were also investigated. The sorption of U(VI) increased with increasing pH up to pH 6 beyond which a decrease was attributed to the formation of anionic carbonate species. Marginal influence of the change in the ionic strength of the medium on the sorption profile of uranium suggested inner-sphere complexation onto the bentonite surface. The presence of humic acid showed interesting sorption profile with varying pH. Initially, there was an enhancement in the sorption with increased pH followed by a plateau and finally a decrease thereafter due to the formation of aqueous U(VI)-humate complexes. Spectroscopic studies such as UV spectrophotometry, luminescence and extended X-ray absorption fine structure (EXAFS) measurements were also performed to understand the changes in aqueous speciation of U(VI) ion. The luminescence yields of different aqueous U(VI) species followed the order: U(VI){sub Hydroxy} > U(VI){sub HumicAcid} > U(VI){sub carbonate} > U(VI){sub citrate}. The lower luminescence yield of U(VI)carbonate complex can be attributed to the strong dynamic quenching by carbonate at room temperature. The U(VI) samples shows two distinct life-time suggesting the presence of the different luminescent U(VI) species. Similar trend was observed for U(VI)-bentonite suspension in presence/absence of the complexing ligands. There was luminescence quenching for the sorbed U(VI) due to surface complexation. These observations were further supported by spectrophotometric measurements. EXAFS spectra of U(VI) samples were recorded in luminescence mode at the U L{sub 3

  14. Kinetic and equilibrium characterization of uranium(VI) adsorption onto carboxylate-functionalized poly(hydroxyethylmethacrylate)-grafted lignocellulosics.

    Science.gov (United States)

    Anirudhan, T S; Divya, L; Suchithra, P S

    2009-01-01

    This study investigated the feasibility of using a new adsorbent prepared from coconut coir pith, CP (a coir industry-based lignocellulosic residue), for the removal of uranium [U(VI)] from aqueous solutions. The adsorbent (PGCP-COOH) having a carboxylate functional group at the chain end was synthesized by grafting poly(hydroxyethylmethacrylate) onto CP using potassium peroxydisulphate-sodium thiosulphite as a redox initiator and in the presence of N,N'-methylenebisacrylamide as a crosslinking agent. IR spectroscopy results confirm the graft copolymer formation and carboxylate functionalization. XRD studies confirm the decrease of crystallinity in PGCP-COOH compared to CP, and it favors the protrusion of the functional group into the aqueous medium. The thermal stability of the samples was studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was determined using potentiometric titration. The ability of PGCP-COOH to remove U(VI) from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed at the pH range 4.0-6.0. Maximum removal of 99.2% was observed for an initial concentration of 25mg/L at pH 6.0 and an adsorbent dose of 2g/L. Equilibrium was achieved in approximately 3h. The experimental kinetic data were analyzed using a first-order kinetic model. The temperature dependence indicates an endothermic process. U(VI) adsorption was found to decrease with an increase in ionic strength due to the formation of outer-sphere surface complexes on PGCP-COOH. Equilibrium data were best modeled by the Langmuir isotherm. The thermodynamic parameters such as DeltaG(0), DeltaH(0) and DeltaS(0) were derived to predict the nature of adsorption. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC-50, with carboxylate functionality for comparison. Utility of the adsorbent was tested by removing U(VI) from simulated nuclear industry wastewater

  15. Interaction of uranium(VI) towards glutathione. An example to study different functional groups in one molecule

    International Nuclear Information System (INIS)

    Frost, L.; Geipel, G.; Viehweger, K.; Bernhard, G.

    2011-01-01

    Glutathione, the most abundant thiol compound of the cell, has a great binding potential towards heavy metal ions. Hence it might influence the distribution of actinides on a cellular level. The unknown strength of the interaction of uranium(VI) with glutathione at physiologically relevant pH is subject of this paper and was studied with UV-vis spectroscopy and time-resolved laserinduced fluorescence spectroscopy (TRLFS). The complex stability constant of UO 2 H 2 GS + , logβ 121 0 , was calculated to be 39.09±0.15 and 39.04±0.02 in case of UV-vis spectroscopy and TRLFS respectively. Therefore the average formation constant for UO 2 2+ +H 2 GS - = UO 2 H 2 GS + can be assigned to be log K 0 11 = 19.83±0.15. Furthermore it was demonstrated that derivatization of the ligand associated with an enhancement of the ligand's spectroscopic properties can be used for the determination of complex stability constants and to assess the coordination chemistry in more detail. Using UV-vis spectroscopy, the stability constant of the complex between UO 2 2+ and glutathione pyruvate S-conjugate, a well absorbing ligand in contrast to glutathione, was calculated to be > 39.24±0.08. Furthermore the interaction of UO 2 2+ with glutathione derivatized with the fluorescent label monobromobimane was examined with femtosecond laser fluorescence spectroscopy. Thereby the stability constant of the 1: 1 complex was determined to be > 39.35±0.02. Although the thiol group of glutathione was blocked a strong coordination was found. Thus a significant involvement of the thiol group in the coordination of U(VI) can be excluded. (orig.)

  16. Aqueous Complexation Reactions Governing the Rate and Extent of Biogeochemical U(VI) Reduction

    International Nuclear Information System (INIS)

    Scott C. Brooks; Wenming Dong; Sue Carroll; James K. Fredrickson; Kenneth M. Kemner; Shelly D. Kelly

    2006-01-01

    The proposed research will elucidate the principal biogeochemical reactions that govern the concentration, chemical speciation, and reactivity of the redox-sensitive contaminant uranium. The results will provide an improved understanding and predictive capability of the mechanisms that govern the biogeochemical reduction of uranium in subsurface environments. In addition, the work plan is designed to: (1) Generate fundamental scientific understanding on the relationship between U(VI) chemical speciation and its susceptibility to biogeochemical reduction reactions. (2) Elucidate the controls on the rate and extent of contaminant reactivity. (3) Provide new insights into the aqueous and solid speciation of U(VI)/U(IV) under representative groundwater conditions

  17. Oxo-group-14-element bond formation in binuclear uranium(V) pacman complexes

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Guy M.; Arnold, Polly L.; Love, Jason B. [EaStCHEM School of Chemistry, University of Edinburgh (United Kingdom)

    2013-07-29

    Simple and versatile routes to the functionalization of uranyl-derived U{sup V}-oxo groups are presented. The oxo-lithiated, binuclear uranium(V)-oxo complexes [{(py)_3LiOUO}{sub 2}(L)] and [{(py)_3LiOUO}(OUOSiMe{sub 3})(L)] were prepared by the direct combination of the uranyl(VI) silylamide ''ate'' complex [Li(py){sub 2}][(OUO)(N''){sub 3}](N''=N(SiMe{sub 3}){sub 2}) with the polypyrrolic macrocycle H{sub 4}L or the mononuclear uranyl (VI) Pacman complex [UO{sub 2}(py)(H{sub 2}L)], respectively. These oxo-metalated complexes display distinct U-O single and multiple bonding patterns and an axial/equatorial arrangement of oxo ligands. Their ready availability allows the direct functionalization of the uranyl oxo group leading to the binuclear uranium(V) oxo-stannylated complexes [{(R_3Sn)OUO}{sub 2}(L)] (R=nBu, Ph), which represent rare examples of mixed uranium/tin complexes. Also, uranium-oxo-group exchange occurred in reactions with [TiCl(OiPr){sub 3}] to form U-O-C bonds [{(py)_3LiOUO}(OUOiPr)(L)] and [(iPrOUO){sub 2}(L)]. Overall, these represent the first family of uranium(V) complexes that are oxo-functionalised by Group 14 elements. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Synthesis and structural characterization of nickel(II), cobalt(II), Zinc(II), manganese(II), cadmium(II) and uranium(VI) complexes of α-oximinoacetoacet-o/p-anisidide thiosemicarbazone

    International Nuclear Information System (INIS)

    Patel, P.S.; Patel, M.M.; Ray, R.M.

    1993-01-01

    A few metal complexes of α-oximinoacetoacet-o/p-anisidide thiosemicarbazones (OAOATS)/(OAPATS) with Ni(II), Co(II), Zn(II), Mn(II), Hg(II), Cd(II) and UO 2 (II) have been prepared and characterized by elemental analyses, conductivity, differential scanning calorimetry study, thermogravimetric analyses and infrared and electronic spectral measurements in conjunction with magnetic susceptibility measurements at room temperature. They have also been tested for their antimicrobial activities. (author). 24 refs., 2 tabs

  19. Density functional study of uranyl (VI) amidoxime complexes

    International Nuclear Information System (INIS)

    Chi Fang-Ting; Xiong Jie; Hu Sheng; Xia Xiu-Long; Wang Xiao-Lin; Li Peng; Gao Tao

    2012-01-01

    Uranyl (VI) amidoxime complexes are investigated using relativistic density functional theory. The equilibrium structures, bond orders, and Mulliken populations of the complexes have been systematically investigated under a generalized gradient approximation (GGA). Comparison of (acet) uranyl amidoxime complexes ([UO 2 (AO) n ] 2−n , 1 ≤ n ≤ 4) with available experimental data shows an excellent agreement. In addition, the U−O(1), U−O(3), C(1)−N(2), and C(3)−N(4) bond lengths of [UO 2 (CH 3 AO) 4 ] 2− are longer than experimental data by about 0.088, 0.05, 0.1, and 0.056 Å. The angles of N(3)−O(3)−U, O(2)−N(1)−C(1), N(3)−C(3)−N(4), N(4)−C(3)−C(4), and C(4)−C(3)−N(3) are different from each other, which is due to existing interaction between oxygen in uranyl and hydrogen in amino group. This interaction is found to be intra-molecular hydrogen bond. Studies on the bond orders, Mulliken charges, and Mulliken populations demonstrate that uranyl oxo group functions as hydrogen-bond acceptors and H atoms in ligands act as hydrogen-bond donors forming hydrogen bonds within the complex

  20. Study of uranium (VI) in carbonate solution by potentiometric titrations and ion-exchange; Etude des solutions d'uranium (VI) en milieu carbonate par titrages potentiometriques et echange d'ions

    Energy Technology Data Exchange (ETDEWEB)

    Billon, A [Commissariat a l' Energie Atomique, 92 - Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1968-04-01

    The present work is devoted to the fixation of uranium (VI) on the conventional anion-exchange resin Dowex 2 X 8 in carbonate and hydrogen-carbonate media. Both media were successfully used for the recuperation of uranium (VI) from very dilute solutions. Equilibrium constant of the exchange [UO{sub 2}(CO{sub 3}){sub 3}{sup 4+}]{sub S} + 2 [CO{sub 3}{sup 2-}]{sub R} {r_reversible} [UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}]{sub R} + 2[CO{sub 3}{sup 2-}]{sub S} is determined for carbonate concentration range 0.1 M to 0.6 M from partition curves. A markedly increase in the relative fixation of uranium results with: - increasing free carbonate concentration of the solution, - decreasing uranium concentration. A study in the same conditions of the fixation of molybdenum has made it possible to separate the latter from uranium by elution, the carbonate concentration being molar. It is suggested a possibility of separation on a larger scale, based upon molybdenum displacement by uranium in hydrogen-carbonate medium. (author) [French] Le present travail precise la fixation de l'uranium (VI) sur la resine echangeuse d'anions Dowex 2 X 8, en milieu carbonate et hydrogeno-carbonate. Nous en avons deduit que ces deux milieux sont egalement favorables a la recuperation de l'uranium a partir de solutions tres diluees. La constante d'equilibre de la reaction d'echange [UO{sub 2}(CO{sub 3}){sub 3}{sup 4+}]{sub S} + 2 [CO{sub 3}{sup 2-}]{sub R} {r_reversible} [UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}]{sub R} + 2[CO{sub 3}{sup 2-}]{sub S} a ete determinee pour le milieu carbonate 0.1 M a 0.6 M, a partir deb courbes de partage. La fixation relative de l'uranium augmente considerablement lorsque: - la concentration du carbonate libre (respectivement hydrogenocarbonate) diminue, - la concentration de l'uranium en solution diminue. Le comportement du molybdene a ete etudie en vue de la separation uranium-molybdene. L'ion fixe sur la resine est l'ion molybdate MoO{sub 4}{sup 2-}. La separation est

  1. Enhancement of uranium(VI) biosorption by chemically modified marine-derived mangrove endophytic fungus Fusarium sp. ZZF51

    International Nuclear Information System (INIS)

    Chen, F.; Tan, N.; Long, W.; Yang, S.K.; She, Z.G.; Lin, Y.C.

    2014-01-01

    Fusarium sp. ZZF51, mangrove endophytic fungus originated from South China Sea coast, was chemically modified by formaldehyde, methanol and acetic acid to enhance its affinity of uranium(VI) from waste water. The influencing factors about uranium(VI) adsorption such as contact time, solution pH, the ratio of solid/liquid (S/L) and initial uranium(VI) concentration were investigated, and the suitable adsorption isotherm and kinetic models were determined. In addition, the biosorption mechanism was also discussed by FTIR analysis. Experimental results show that the maximum biosorption capacity of formaldehyde-treated biomass for uranium(VI) at the optimized condition of pH 6.0, S/L 0.6 and equilibrium time 90 min is 318.04 mg g -1 , and those of methanol-treated and HAc-treated biomass are 311.95 and 351.67 mg g -1 at the same pH and S/L values but different equilibrium time of 60 and 90 min, respectively. Thus the maximum biosorption capacity of the three kind of modified biomass have greatly surpassed that of the raw biomass (21.42 mg g -1 ). The study of kinetic exhibits a high level of compliance with the Lagergren's pseudo-second-order kinetic models. Langumir and Freundlich models have proved to be well able to explain the sorption equilibrium with the satisfactory correlation coefficients higher than 0.96. FTIR analysis reveals that the carboxyl, amino and hydroxyl groups on the cell wall of Fusarium sp. ZZF51 play an important role in uranium(VI) biosorption process. (author)

  2. Alkaline-earth metal bicarbonates as lixiviants for uranium (VI) under CO2 sparging

    International Nuclear Information System (INIS)

    Vaziri, F.; White, D.A.

    1989-01-01

    In recent years it has become apparent that uranium is significantly soluble in solutions of alkaline-earth metal bicarbonates -particularly those of magnesium and calcium. A system has been proposed by previous authors in which milled uranium ore is leached in a medium to which an oxidizing agent, the metal hydroxide and CO 2 are added. The alkaline-earth metal hydroxides are much more readily soluble in this medium than the corresponding carbonates. Magnesium and calcium bicarbonates are quite soluble in aqueous media at neutral or nearly neutral pH. The pH determines the relative quantities of bicarbonate and carbonate ions in the system. Even if the pH is quite low, small amounts of carbonate ion are present that can complex with the uranyl ion to produce anionic uranyl complexes. Both UO 2 (CO 3 ) 2 2- and UO 2 (CO 3 ) 3 4- complexes are known and both have a very high stability constant. Despite the appearance of several patents on the use of alkaline-earth metal ions in carbonate media as uranium lixiviants, little theoretical or experimental work on the system has been published. In view of the potential of these systems for cheap, large-scale dissolution of uranium the present contribution will discuss the theory behind this method and provide some experimental data to verify the theoretical treatment. (author)

  3. Preparation, characterization, uranium (VI) biosorption models, and conditions optimization by response surface methodology (RSM) for amidoxime-functionalized marine fungus materials

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xuechun; Gao, Yang; Jiang, Min; He, Dianxiong; Liao, Sen; Hou, Dan; Yan, Xueming; Long, Wei; Wu, Yaxin; Tan, Ni [Univ. of South China, Hengyang (China). School of Chemistry and Chemical Engineering

    2017-08-01

    Amidoxime-functionalized marine fungus Fusarium sp. ZZF51 (ZGDA) was synthesized and studied to adsorb uranium (VI) from the aqueous solution. Different instrumental techniques such as FTIR, SEM, and TGA were employed for the characterization of the manufactured materials, and theirs ability of removal uranium (VI) was optimized using RSM. The experimental results showed the maximum adsorption capacity for the synthesized materials was 230.78 mg g{sup -1} at the following optimization conditions: S-L ratio 150 mg L{sup -1}, pH 5.13, uranium (VI) initial concentration 40 mg L{sup -1}, and equilibrium time 122.40 min. More than 85% of the absorbed uranium (VI) could be desorbed by 0.5 or 1.0 mol L{sup -1} HCl, and the modified mycelium could be reused at least five times. The thermodynamic experimental data of adsorption uranium (VI) could fit better with Langmuir and Freundlich isotherms models, and the pseudo-second-order model was better to interpret the kinetics process. The modified fungus materials exhibited the better sorption capacity for uranium (VI) in comparison with raw biomass should be attributed to the strong chelation of amidoxime to uranium (VI) ions.

  4. Study of uranium(VI) speciation in phosphoric acid solutions and of its recovery by solvent extraction

    International Nuclear Information System (INIS)

    Dartiguelongue, Adrien

    2014-01-01

    Because small amounts of uranium are present in phosphate rocks, wet phosphoric acids may contain up to 300 ppm of uranium(VI). Therefore, such acids are a cost-effective unconventional source of this metal. Its recovery is a challenge for metallurgical firms which must develop reliable and selective solvent extraction processes. Such processes need to know the chemical equilibria involved in the extraction process, the speciation of uranium and its thermodynamics in solution. These two last points have been investigated in this work. Firstly, the most probable species of uranium(VI) in phosphoric acid solutions have been selected thanks to a detailed review of the literature. Then, a thermodynamic model founded on an equation of state for electrolytes has been built according these hypotheses. It has been validated with speciation data coming from original ATR-IR spectroscopy measurements. Finally, the composition of the aqueous phosphoric acid solutions and the activity coefficients obtained have been combined with a chemical model of uranium(VI) extraction into an organic phase containing a synergistic mixture of bis(2-ethylhexyl)phosphoric acid (D2EHPA) and tri-n-octylphosphine oxide (TOPO) in order to represent the variation of the distribution coefficient of uranium(VI) with H 3 PO 4 concentration. This model had been previously developed at Chimie ParisTech at a given concentration of H 3 PO 4 (i.e., 5,3 mol/L), but in the present study we have tested its validity in an extended range of phosphoric acid concentrations (i.e., 1-7 mol/L) and improved it. (author)

  5. Magnetic study of solid uranium-fluorine complexes; Contribution a l'etude magnetique de composes fluores solides de l'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Dianoux, A J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-06-01

    A study of the magnetic susceptibility of uranium V fluorine complexes and of the magnetic resonance of fluorine atoms in uranium VI fluorine complexes has made it possible to put forward a structural model for these compounds for which it is impossible, because of the lack of suitable single crystals for X-ray diffraction work, to deduce the exact position of the fluorine atoms. It is shown that it is difficult to interpret the paramagnetism of uranium fluorides, because the uranium ions are in low-symmetry sites. A theoretical study of the magnetism of the U{sup V} ion in complex fluorides of the type M{sub 3}UF{sub 8} (M = NH{sub 4}, Na, Rb, Cs) leads to an interpretation based on a trigonal deformation of the eight fluorine atom structure surrounding the uranium atom. By applying a Hamiltonian spin formalism and making a systematic use of group theory, it is possible to present the susceptibility calculations very concisely. Study of the resonance and of the relaxation of the fluorine atoms in powdered uranium VI complex fluorides suggests a structural model in the case of NaUF{sub 7}. It is shown that the shape of the magnetic resonance absorption lines is strongly affected by the presence of large anisotropic chemical shifts. In the model proposed here, six fluorine atoms are linked to the uranium, atom by strongly covalent bonds in a deformed UF{sub 6} octahedral structure; the seventh fluorine atom remains ionic. The occurrence of a rotational movement of the octahedron is confirmed by a study of the longitudinal relaxation of the fluorine atoms, the activation energy being 0.46 eV. (author) [French] L'etude de la susceptibilite magnetique de complexes fluores d'uranium V et la resonance magnetique des fluors dans des complexes fluores d'uranium VI permettent de proposer un modele structural pour ces composes, ou la diffraction des rayons X, en l'absence de monocristaux convenables, est incapable de preciser la position des atomes de fluor. Nous montrons

  6. Magnetic study of solid uranium-fluorine complexes; Contribution a l'etude magnetique de composes fluores solides de l'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Dianoux, A.J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-06-01

    A study of the magnetic susceptibility of uranium V fluorine complexes and of the magnetic resonance of fluorine atoms in uranium VI fluorine complexes has made it possible to put forward a structural model for these compounds for which it is impossible, because of the lack of suitable single crystals for X-ray diffraction work, to deduce the exact position of the fluorine atoms. It is shown that it is difficult to interpret the paramagnetism of uranium fluorides, because the uranium ions are in low-symmetry sites. A theoretical study of the magnetism of the U{sup V} ion in complex fluorides of the type M{sub 3}UF{sub 8} (M = NH{sub 4}, Na, Rb, Cs) leads to an interpretation based on a trigonal deformation of the eight fluorine atom structure surrounding the uranium atom. By applying a Hamiltonian spin formalism and making a systematic use of group theory, it is possible to present the susceptibility calculations very concisely. Study of the resonance and of the relaxation of the fluorine atoms in powdered uranium VI complex fluorides suggests a structural model in the case of NaUF{sub 7}. It is shown that the shape of the magnetic resonance absorption lines is strongly affected by the presence of large anisotropic chemical shifts. In the model proposed here, six fluorine atoms are linked to the uranium, atom by strongly covalent bonds in a deformed UF{sub 6} octahedral structure; the seventh fluorine atom remains ionic. The occurrence of a rotational movement of the octahedron is confirmed by a study of the longitudinal relaxation of the fluorine atoms, the activation energy being 0.46 eV. (author) [French] L'etude de la susceptibilite magnetique de complexes fluores d'uranium V et la resonance magnetique des fluors dans des complexes fluores d'uranium VI permettent de proposer un modele structural pour ces composes, ou la diffraction des rayons X, en l'absence de monocristaux convenables, est incapable de preciser la position des atomes de

  7. Synthesis and reactivity of triscyclopentadienyl uranium (III) and (IV) complexes

    International Nuclear Information System (INIS)

    Berthet, J.C.

    1992-01-01

    The reactions of (RC 5 H 4 ) 3 U with R=trimethylsilylcyclopentadienyl or tertiobutylcyclopentadienyl are studied for the synthesis of new uranium organometallic compounds. Reactions with sodium hydride are first described uranium (III) anionic hydrides obtained are oxidized for synthesis of stable uranium (IV) organometallic hydrides. Stability of these compounds is discussed. Reactivity of these uranium (III) and (IV) hydrides are studied. Formation of new binuclear compounds with strong U-O and U-N bonds is examined and crystal structure are presented. Monocyclooctatetraenylic uranium complexes are also investigated

  8. Spectrophotometric determination of trace amount of uranium (VI) in different aqueous and organic streams of nuclear fuel processing using 2-(5-bromo-2-pyridylazo-5-diethylaminophenol)

    International Nuclear Information System (INIS)

    Das, S.K.; Kedari, C.S.; Tripathi, S.C.

    2010-01-01

    Present investigation describes the development of a spectrophotometric method for trace level determination of U(VI) encountered during the process of nuclear fuel fabrication and reprocessing industries. A chromogenic reagent, 2-(5-bromo-2-pyridylazo-5-diethylaminophenol) (Br-PADAP) is used to complex with U(VI) under optimized solution conditions. The absorption maxima of the uranyl Br-PADAP complex at 578 nm is computed to be 73540 ± 1438 for U-Br-PADAP solution containing 20% ethanol (in aqueous sample media) and 58216 ± 1208 for U-Br-PADAP solution containing 80% ethanol (for organic sample media). Employing suitable sample treatment methods, the scope of analytical method has been widened to permit accurate determination of U(VI) in the samples with variation in the relative compositions of Th(IV), Pu(IV) and Fe(III). The method is applicable to samples matrices with, acidic, alkaline highly salted media. Effect of commonly associated ionic species on the optical density of U-Br-PADAP is determined. Depending on the extent of the interfering impurities present, the method permits estimation of U(VI) either direct or after its selective extraction into tri-octyl phosphine oxide dissolved in cyclohexane. The method is precise with <5% standard error and can be used for the estimation of uranium in organic as well as in aqueous samples. The method has been validated for quantitative determination of uranium extracted in the organic phase comprising of heavy metal extractants like TBP, HDEHP, PC-88A and Aliquot 336. (author)

  9. Liquid-solid extraction of uranium (VI) with TOPO - molten naphthalene and determination by laser fluorimetry in geological samples

    International Nuclear Information System (INIS)

    Kumar, Sanjay; Krishnakumar, M.; Patwardhan, A.A.

    2007-01-01

    A simple, rapid, sensitive, cost-effective and efficient method for separation of uranium using tri-n-octylphosphine oxide (TOPO)-molten naphthalene as solid phase extractant and its determination by laser fluorimetry in geological samples (rock, soil, sediment) was developed. Under optimum conditions, using 50 mg TOPO and 100 mg naphthalene, 50 - 5000 ng of uranium in 10 ml sample solution (3% (v/v) HNO 3 ) could be extracted quantitatively. The extracted uranium was stripped using tetra sodium pyrophosphate (5% (v/v) solution, pH adjusted to 7.0 with H 3 PO 4 ) and determined by laser fluorimetry. The influence of different acid concentrations, the amount of solid phase extractant, sample volumes, different stripping reagents, their volumes and effect of foreign ions on the extraction and determination of uranium (VI) were investigated. Synthetic samples of varying concentration as regards uranium were prepared and analysed. Recoveries ranging from 90% to 105% were obtained. The method was validated by analyzing four certified reference materials namely, BL-5, DH-1a, SY-2, SY-3 and the values obtained for uranium agreed well with the certified values. The method was also applied to the determination of uranium in geological samples (rock, soil and sediment) by laser fluorimetry and the results obtained compared favorably with those obtained from the pellet fluorimetry method. Following the proposed method, determination limit for uranium was found to be 1 μg/g with RSD ± 10%. (author)

  10. Phthalocyaninato complexes of thorium, protactinium and uranium

    International Nuclear Information System (INIS)

    Beck, O.F.

    1985-01-01

    For the preparation of Bis(phthalocyaninato)-actinoid(IV) complexes, AnPc 2 , a new optimizing synthesis procedure was developed, with which it was possible to prepare spectrally pure, that is, H 2 Pc-free, ThPc 2 , UPc 2 and the isostructurally similar 231 PaPc 2 .PaPc 2 . This was verified with the help of electron spectra, which were compared to preparations which were synthesized in another manner. The corresponding perfluorinated compounds were also produced for thorium and uranium by use of tetrafluorophthalic acid nitrile instead of phthalic acid nitrile as initial product. Electron and infrared spectra show the typical bands of the non-substituted complexes. By the attempt to produce a mono(phthalocyaninato)-thorium complex with the use of ThI 4 as initial material a pyridine-extracted pure ThPcI 2 (py) 2 was obtained with a typical mono(phthalocyaninato) complex electron spectrum, an extremely moisture sensitive compound which in water or acids decomposes and produces H 2 Pc. (orig./RB) [de

  11. The sorption of uranium(VI) and neptunium(V) onto surfaces of selected metal oxides and alumosilicates studied by in situ vibrational spectroscopy

    International Nuclear Information System (INIS)

    Mueller, Katharina

    2010-05-01

    The migration behavior of actinides and other radioactive contaminants in the environment is controlled by prominent molecular phenomena such as hydrolysis and complexation reactions in aqueous solutions as well as the diffusion and sorption onto minerals present along groundwater flow paths. These reactions significantly influence the mobility and bioavailability of the metal ions in the environment, in particular at liquid-solid interfaces. Hence, for the assessment of migration processes the knowledge of the mechanisms occurring at interfaces is crucial. The required structural information can be obtained using various spectroscopic techniques. In the present study, the speciation of uranium(VI) and neptunium(V) at environmentally relevant mineral-water interfaces of oxides of titania, alumina, silica, zinc, and alumosilicates has been investigated by the application of attenuated total reflection Fouriertransform infrared (ATR FT-IR) spectroscopy. Moreover, the distribution of the hydrolysis products in micromolar aqueous solutions of U(VI) and Np(V/VI) at ambient atmosphere has been characterized for the first time, by a combination of ATR FT-IR spectroscopy, near infrared (NIR) absorption spectroscopy, and speciation modeling applying updated thermodynamic databases. From the infrared spectra, a significant change of the U(VI) speciation is derived upon lowering the U(VI) concentration from the milli- to the micromolar range, strongly suggesting the dominance of monomeric U(VI) hydrolysis products in the micromolar solutions. In contradiction to the predicted speciation, monomeric hydroxo species are already present at pH ≥ 2.5 and become dominant at pH 3. At higher pH levels (> 6), a complex speciation is evidenced including carbonate containing complexes. For the first time, spectroscopic results of Np(VI) hydrolysis reactions are provided in the submillimolar concentration range and at pH values up to 5.3, and they are comparatively discussed with U(VI

  12. Terminal uranium(V/VI) nitride activation of carbon dioxide and carbon disulfide. Factors governing diverse and well-defined cleavage and redox reactions

    Energy Technology Data Exchange (ETDEWEB)

    Cleaves, Peter A.; Gardner, Benedict M.; Liddle, Stephen T. [School of Chemistry, The University of Manchester (United Kingdom); Kefalidis, Christos E.; Maron, Laurent [LPCNO, CNRS and INSA, Universite Paul Sabatier, Toulouse (France); Tuna, Floriana; McInnes, Eric J.L. [School of Chemistry and Photon Science Institute, The University of Manchester (United Kingdom); Lewis, William [School of Chemistry, The University of Nottingham (United Kingdom)

    2017-02-24

    The reactivity of terminal uranium(V/VI) nitrides with CE{sub 2} (E=O, S) is presented. Well-defined C=E cleavage followed by zero-, one-, and two-electron redox events is observed. The uranium(V) nitride [U(Tren{sup TIPS})(N)][K(B15C5){sub 2}] (1, Tren{sup TIPS}=N(CH{sub 2}CH{sub 2}NSiiPr{sub 3}){sub 3}; B15C5=benzo-15-crown-5) reacts with CO{sub 2} to give [U(Tren{sup TIPS})(O)(NCO)][K(B15C5){sub 2}] (3), whereas the uranium(VI) nitride [U(Tren{sup TIPS})(N)] (2) reacts with CO{sub 2} to give isolable [U(Tren{sup TIPS})(O)(NCO)] (4); complex 4 rapidly decomposes to known [U(Tren{sup TIPS})(O)] (5) with concomitant formation of N{sub 2} and CO proposed, with the latter trapped as a vanadocene adduct. In contrast, 1 reacts with CS{sub 2} to give [U(Tren{sup TIPS})(κ{sup 2}-CS{sub 3})][K(B15C5){sub 2}] (6), 2, and [K(B15C5){sub 2}][NCS] (7), whereas 2 reacts with CS{sub 2} to give [U(Tren{sup TIPS})(NCS)] (8) and ''S'', with the latter trapped as Ph{sub 3}PS. Calculated reaction profiles reveal outer-sphere reactivity for uranium(V) but inner-sphere mechanisms for uranium(VI); despite the wide divergence of products the initial activation of CE{sub 2} follows mechanistically related pathways, providing insight into the factors of uranium oxidation state, chalcogen, and NCE groups that govern the subsequent divergent redox reactions that include common one-electron reactions and a less-common two-electron redox event. Caution, we suggest, is warranted when utilising CS{sub 2} as a reactivity surrogate for CO{sub 2}. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Uranium(VI) and ruthenium extraction by dialkyldithio-phosphoric acids

    International Nuclear Information System (INIS)

    Fitoussi, R.; Musikas, C.

    1980-01-01

    Oxygen donors like dialkylphosphoric acids are good extractants for actinide ions, but little is known about their sulfur homologs. Investigations of U(VI) and Ru extraction from various aqueous media are reported. This includes extraction of U(VI) from nitric, perchloric, and phosphoric acids by solutions of dialkyldithiophosphoric acids in dodecane or benzene. Extraction of U(VI) by synergistic mixtures, of which at least one of the components is a sulfur donor, has been investigated. The extracted species have been identified, and a comparison with the complexes obtained by extraction with the homologous oxygen donors is made. The sulfur-actinide bond is weaker than the oxygen-actinide one, but in some synergistic extractions the dialkyldithiophosphonates are more efficient than the oxygen donors. In addition to size effects, this behavior could be attributed to the weakness of the hydrogen bonds of the SH groups, which allows a greater variety of the ligands to enter the coordination sphere of the metal. Ruthenium, like the d-transition elements, gives strong bonds with the sulfur donors. However, its extraction from nitric acid is slow. We investigated the influence of several parameters on the distribution coefficients and found that the presence of a reagent which destroys nitrous ions is necessary to achieve quantitative extraction. The role of RuNO groups is also discussed

  14. Solvent-extraction and purification of uranium(VI) and molybdenum(VI) by tertiary amines from acid leach solutions

    International Nuclear Information System (INIS)

    La Gamma, Ana M.G.; Becquart, Elena T.; Chocron, Mauricio

    2008-01-01

    Considering international interest in the yellow-cake price, Argentina is seeking to exploit new uranium ore bodies and processing plants. A study of similar plants would suggest that solvent- extraction with Alamine 336 is considered the best method for the purification and concentration of uranium present in leaching solutions. In order to study the purification of these leach liquors, solvent-extraction tests under different conditions were performed with simulated solutions which containing molybdenum and molybdenum-uranium mixtures. Preliminary extraction tests carried out on mill acid-leaching liquors are also presented. (authors)

  15. The use of halloysite functionalized with isothiouronium salts as an organic/inorganic hybrid adsorbent for uranium(VI) ions removal.

    Science.gov (United States)

    Gładysz-Płaska, A; Majdan, M; Tarasiuk, B; Sternik, D; Grabias, E

    2018-07-15

    Elimination of U(VI) from nuclear wastes and from the underground water near the uranium mines is the serious problem. Therefore search for new sorbents for U(VI) is still a big challenge for the scientists. This paper investigates of U(VI) ions sorption on halloysite modified with the isothiouronium salts: S-dodecaneisothiouronium bromide (ligand 1), S,S'-dodecane-1,12-diylbis(isothiouronium bromide) (ligand 2), S-hexadecaneisothiouronium chloride (ligand 3), S,S'-naphthalene-1,4-diylbis(methylisothiouronium) dichloride (ligand 4), and S,S'-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) dichloride (ligand 5). It was established that halloysite modified by the ligands with four nitrogen atoms in their structure (ligand-5, 2 and 4) was characterized by higher sorption capacity compared with that modified by the ligands with two donor nitrogens (ligand-1 and 3). The maximum sorption capacity of halloysite-5 toward U(VI) was 157 mg U/g and this places the modified mineral among the most effective sorbents for U(VI) removal from wastes. As follows from ATR, XPS and thermal degradation spectra of the sorption products [R-S-C(NH)(NH 2 )] n = 1-2 (UO 2 2+ ) complexes are formed on the external surface of the halloysite whereas oligomeric hydroxy complexes (UO 2 ) 3 (OH) 5 + and (UO 2 ) 4 (OH) 7 + are present in the interior of halloysite structure and interact predominantly with aluminols. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Isolation of a star-shaped uranium(V/VI) cluster from the anaerobic photochemical reduction of uranyl(VI)

    International Nuclear Information System (INIS)

    Chatelain, Lucile; White, Sarah; Scopelliti, Rosario; Mazzanti, Marinella

    2016-01-01

    Actinide oxo clusters are an important class of compounds due to their impact on actinide migration in the environment. The photolytic reduction of uranyl(VI) has potential application in catalysis and spent nuclear fuel reprocessing, but the intermediate species involved in this reduction have not yet been elucidated. Here we show that the photolysis of partially hydrated uranyl(VI) in anaerobic conditions leads to the reduction of uranyl(VI), and to the incorporation of the resulting U V species into the stable mixed-valent star-shaped U VI /U V oxo cluster [U(UO 2 ) 5 (μ 3 -O) 5 (PhCOO) 5 (Py) 7 ]. This cluster is only the second example of a U VI /U V cluster and the first one associating uranyl groups to a non-uranyl(V) center. The U V center in 1 is stable, while the reaction of uranyl(V) iodide with potassium benzoate leads to immediate disproportionation and formation of the U 12 IV U 4 V O 24 cluster {[K(Py) 2 ] 2 [K(Py)] 2 [U 16 O 24 (PhCOO) 24 (Py) 2 ]}.

  17. Isolation of a star-shaped uranium(V/VI) cluster from the anaerobic photochemical reduction of uranyl(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Chatelain, Lucile; White, Sarah; Scopelliti, Rosario; Mazzanti, Marinella [Ecole Polytechnique Federale de Lausanne (EPFL) (Switzerland). Inst. de Sciences et Ingenierie Chimiques

    2016-11-07

    Actinide oxo clusters are an important class of compounds due to their impact on actinide migration in the environment. The photolytic reduction of uranyl(VI) has potential application in catalysis and spent nuclear fuel reprocessing, but the intermediate species involved in this reduction have not yet been elucidated. Here we show that the photolysis of partially hydrated uranyl(VI) in anaerobic conditions leads to the reduction of uranyl(VI), and to the incorporation of the resulting U{sup V} species into the stable mixed-valent star-shaped U{sup VI}/U{sup V} oxo cluster [U(UO{sub 2}){sub 5}(μ{sub 3}-O){sub 5}(PhCOO){sub 5}(Py){sub 7}]. This cluster is only the second example of a U{sup VI}/U{sup V} cluster and the first one associating uranyl groups to a non-uranyl(V) center. The U{sup V} center in 1 is stable, while the reaction of uranyl(V) iodide with potassium benzoate leads to immediate disproportionation and formation of the U{sub 12}{sup IV}U{sub 4}{sup V}O{sub 24} cluster {[K(Py)_2]_2[K(Py)]_2[U_1_6O_2_4(PhCOO)_2_4(Py)_2]}.

  18. Development of metal uranium fuel and testing of construction materials (I-VI); Part I

    International Nuclear Information System (INIS)

    Mihajlovic, A.

    1965-11-01

    This project includes the following tasks: Study of crystallisation of metal melt and beta-alpha transforms in uranium and uranium alloys; Study of the thermal treatment influence on phase transformations and texture in uranium alloys; Radiation damage of metal uranium; Project related to irradiation of metal uranium in the reactor; Development of fuel element for nuclear reactors

  19. Highly efficient extraction and selective separation of uranium (VI) from transition metals using new class of undiluted ionic liquids based on H-phosphonate anions.

    Science.gov (United States)

    Zarrougui, Ramzi; Mdimagh, Raouf; Raouafi, Nourreddine

    2018-01-15

    In this paper, we report the development of an environmental friendly process to decontaminate uranium-containing ores and nuclear wastes by using non-fluorinated ionic liquids (ILs). The main advantages of this extraction process are the absence of any organic diluent and extra extraction agents added to the organic phase. Moreover, the process is cost-effective and maybe applied as a sustainable hydrometallurgical method to recover uranium. The distribution ratio (D U ) and the extraction efficiency (%E) of uranium(VI) (UO 2 2+ ) were found to be dependent on the acidity of the aqueous phase, the extraction time, the alkyl chain length in the ILs, the concentration of the aqueous feed and molar quantity of ILs. The D U value is higher than 600 and the %E is equal to 98.6% when [HNO 3 ]=7M. The extraction reactions follows a neutral partition or ionic exchange mechanism depending on nitric acid concentration. The nature of bonding in the extracted complexes was investigated by spectroscopic techniques. The potential use of Mor 1-8 -OP for the separation of UO 2 2+ from a mixture containing transition metal ions M n+ was also examined. The UO 2 2+ ions were separated and extracted efficiently. These ILs are promising candidates for the recovery and separation of uranium. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Antagonism in the extraction of uranium(VI) by the binary mixture of PC88A and benzimidazole

    International Nuclear Information System (INIS)

    Mukherjee, A.; Kamila, S.; Chakravortty, V.

    1999-01-01

    Extraction studies of uranium(VI) by the binary mixture of PC88A and benzimidazole show an antagonistic behavior in the concentration range 10 -5 -10 -6 M of PC88A and 0.005M of benzimidazole. Antagonism is observed due to the deprotonation of PC88A by benzimidazole forming an adduct resulting in the virtual removal of PC88A from the system. (author)

  1. Synthesis of C14/Fe3O4@SiO2 and Its Performance in Removing Uranium (VI from Aqueous Solutions and Real Wastewater Using Benzamide

    Directory of Open Access Journals (Sweden)

    Zohreh Akbari Jonoosh

    2016-09-01

    Full Text Available Uranium separation and removal are important from environmental, public health, and strategic veiwpoints. Scientits have put great efforts to develop technologies for uranium removal and regeneration because of its important applications and beneficial uses. In this study, efforts have been made to synthesize a modified form of Fe3O4@SiO2 and benzamide uranium complexes that can be exploited to remove and adsorb uranium onto an adsorbent that can be recycled. In the first step, Fe3O4@SiO2 was synthesized and later modified with trimethoxysilane. The adsorbent was subsequently characterized by SEM and FTIR.  In a second step, experiments were performed to determine optimum stirring speed, contact time, ion strength, and adsorbent reusability. Finally, the performance of the adsorbent was tested in samples of real wastewater. SEM and FTIR analyses confirmed the satisfactory synthesis and modification of Fe3O4@SiO2 Nps. Statistical analyses revealed that although contact time, ion strength, and stirring speed were effective in adsorbent performance, they only led to a removal enhancement of 5% and a decrease of only 17% with increasing RPM to 250 and the enhancement of ion strength to 1.5M. The highest U(VI removal efficiency in the synthetic solution was found to be 97%, which reduced to 49% in real wastewater samples. It was concluded that the nano-composite C14/SiO2_Fe3O4 adsorbent with its magnetic core and resistant surface not only offers the possibility for easy separation of urnaium from solutions but is also reusable and is only slightly affected by changes in stirring speed or ion strength. It, therefore, has a good capability for use as a U(VI adsorbent in wastewater treatment.

  2. The existence state of uranium(VI) in portland cement matrix material immobilization body

    International Nuclear Information System (INIS)

    Tan Hongbin; Li Yuxiang

    2005-01-01

    The basis of Portland cement material reaction with uranium, the corrosion of uranium minerals in nature and the state of study on immobilization of uranium by Portland cement matrix material are introduced, and some considerations are presented. (authors)

  3. Preparation of 1-(2-pyridylazo)-2-naphthol functionalized benzophenone/naphthalene and their uses in solid phase extractive preconcentration/separation of uranium(VI)

    International Nuclear Information System (INIS)

    Preetha, C.R.; Prasada Rao, T.

    2003-01-01

    The preparation of solid reagent 1-(2-pyridylazo)-2-naphthol functionalized benzophenone/naphthalene for preconcentration/separation of uranium(VI) is described. These reagents enriches uranium(VI) quantitatively from dilute aqueous solutions in the pH range 10.5-11.0. The solid mixture consisting of the enriched metal ion along with solid phase extractant were dissolved in 2 ml of acetone and uranium(VI) content was established spectrophotometrically by using Arsenazo III procedure. Calibration graphs were rectilinear over the uranium(VI) concentration in the range 0.002-0.1 μg cm -3 . Five replicate determinations of 40 μg of uranium present in 1 dm 3 of sample solution gave a mean absorbance of 0.185 with a relative standard deviation of 1.4%. The detection limit (corresponding to 3 times the standard deviation of the blank) and the enrichment factor were found to be 2 μg dm -3 and 500 respectively. Further the possible separation of uranium(VI) from several bivalent, trivalent and tetravalent elements was also established. In addition to validating the developed method by successfully analysing marine sediment reference material (MESS-3), uranium content was established in soil, river and marine sediment samples by the developed method and compared with standard inductively coupled plasma mass spectrometry (ICP-MS) values. (orig.)

  4. Osmium(VI) complexes as a new class of potential anti-cancer agents.

    Science.gov (United States)

    Ni, Wen-Xiu; Man, Wai-Lun; Cheung, Myra Ting-Wai; Sun, Raymond Wai-Yin; Shu, Yuan-Lan; Lam, Yun-Wah; Che, Chi-Ming; Lau, Tai-Chu

    2011-02-21

    A nitridoosmium(VI) complex [Os(VI)(N)(sap)(OH(2))Cl] (H(2)sap = N-salicylidene-2-aminophenol) displays prominent in vitro and in vivo anti-cancer properties, induces S- and G2/M-phase arrest and forms a stable adduct with dianionic 5'-guanosine monophosphate.

  5. Uranium (VI) transport in saturated heterogeneous media: Influence of kaolinite and humic acid.

    Science.gov (United States)

    Chen, Chong; Zhao, Kang; Shang, Jianying; Liu, Chongxuan; Wang, Jin; Yan, Zhifeng; Liu, Kesi; Wu, Wenliang

    2018-05-07

    Natural aquifers typically exhibit a variety of structural heterogeneities. However, the effect of mineral colloids and natural organic matter on the transport behavior of uranium (U) in saturated heterogeneous media are not totally understood. In this study, heterogeneous column experiments were conducted, and the constructed columns contained a fast-flow domain (FFD) and a slow-flow domain (SFD). The effect of kaolinite, humic acid (HA), and kaolinite/HA mixture on U(VI) retention and release in saturated heterogeneous media was examined. Media heterogeneity significantly influenced U fate and transport behavior in saturated subsurface environment. The presence of kaolinite, HA, and kaolinite/HA enhanced the mobility of U in heterogeneous media, and the mobility of U was the highest in the presence of kaolinite/HA and the lowest in the presence of kaolinite. In the presence of kaolinite, there was no difference in the amount of U released from the FFD and SFD. However, in the presence of HA and kaolinite/HA, a higher amount of U was released from the FFD. The findings in this study showed that medium structure and mineral colloids, as well as natural organic matter in the aqueous phase had significant effects on U transport and fate in subsurface environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

  6. Formation of nitridotechnetium(VI) μ-oxo dimer complexes with EDTA and EDDA

    International Nuclear Information System (INIS)

    Takayama, T.; Kani, Y.; Sekine, T.; Kudo, H.; Yoshihara, K.

    1995-01-01

    Reactions of [ 99 TcNCl 4 ] - with ethylenediaminetetraacetic acid 4 (ETDA) and ethylenediamine-N,N'-diacetic acid (EDDA) in a mixture of water and acetone gave Tc VI N-EDTA and Tc VI N-EDTA complexes. The infrared spectra of both reaction products showed the existence of the Tc≡N and C=O groups. The elemental analysis indicated the 1:1 TcN-ligand ratio in the EDTA and EDDA complexes. Electrophoresis showed that the Tc VI -EDTA complex was an anionic species in a perchlorate solution. For the Tc VI N-EDDA complex, neutral and anionic species were formed, depending on the pH of the solution. Formation of the μ-oxo dimer complexes was suggested from the UV-Vis absorption spectra. (author) 11 refs.; 4 figs.; 1 tab

  7. Study of new complexes of uranium and comba radical. I.- Complexes defective in sodium carbonate; Estudio de nuevos complejos entre el uranio y el radical CDMBA. I. Complejos con defectos de carbonato sodico

    Energy Technology Data Exchange (ETDEWEB)

    Vera Palomino, J; Galiano Sedano, J A; Parellada Bellod, R; Bellido Gonzalez, A

    1975-07-01

    Some complexes formed in presence of defect of sodium carbonate with respect to the stoichiometric ratio (U): (C0{sub 3}) = 1:3 are studied. This ratio corresponds to the main complex which is responsible for the uranium extraction with CDMBAC organic solutions and from U(VI) aqueous solutions with an excess of sodium carbonate. (Author) 10 refs.

  8. Effect of anthropogenic organic complexants on the solubility of Ni, Th, U(IV) and U(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Felipe-Sotelo, M., E-mail: m.felipe-sotelo@lboro.ac.uk [Department of Chemistry, Loughborough University, LE11 3TU Loughborough, Leicestershire (United Kingdom); Edgar, M. [Department of Chemistry, Loughborough University, LE11 3TU Loughborough, Leicestershire (United Kingdom); Beattie, T. [MCM Consulting. Täfernstrasse 11, CH 5405 Baden-Dättwil (Switzerland); Warwick, P. [Enviras Ltd., LE11 3TU Loughborough, Leicestershire (United Kingdom); Evans, N.D.M.; Read, D. [Department of Chemistry, Loughborough University, LE11 3TU Loughborough, Leicestershire (United Kingdom)

    2015-12-30

    Highlights: • Citrate increases the solubility of Ni, Th and U between 3 and 4 orders of magnitude. • Theophrastite is the solubility controlling phase of Ni in 95%-saturated Ca(OH){sub 2}. • U(VI) and Ni may form Metal-citrate-OH complexes stabilised by the presence of Ca{sup 2+}. - Abstract: The influence of anthropogenic organic complexants (citrate, EDTA and DTPA from 0.005 to 0.1 M) on the solubility of nickel(II), thorium(IV) and uranium (U(IV) and U(VI)) has been studied. Experiments were carried out in 95%-saturated Ca(OH){sub 2} solutions, representing the high pH conditions anticipated in the near field of a cementitious intermediate level radioactive waste repository. Results showed that Ni(II) solubility increased by 2–4 orders of magnitude in the presence of EDTA and DTPA and from 3 to 4 orders of magnitude in the case of citrate. Citrate had the greatest effect on the solubility of Th(IV) and U(IV)/(VI). XRD and SEM analyses indicate that the precipitates are largely amorphous; only in the case of Ni(II), is there some evidence of incipient crystallinity, in the form of Ni(OH){sub 2} (theophrastite). A study of the effect of calcium suggests that U(VI) and Ni(II) may form metal-citrate-OH complexes stabilised by Ca{sup 2+}. Thermodynamic modelling underestimates the concentrations in solution in the presence of the ligands for all the elements considered here. Further investigation of the behaviour of organic ligands under hyperalkaline conditions is important because of the use of the thermodynamic constants in preparing the safety case for the geological disposal of radioactive wastes.

  9. Uranium

    International Nuclear Information System (INIS)

    Poty, B.; Cuney, M.; Bruneton, P.; Virlogeux, D.; Capus, G.

    2010-01-01

    concentration in peat bogs, deposits combined with marine phosphates, with coal and lignite, with black shales, with carbonate rocks, deposits in Precambrian quartz pebble conglomerates, basal-type deposits, deposits in sandstones (tabular, roll-type and tectono-lithologic deposits), breccia chimney filling deposits, deposits in metamorphic rocks, metasomatic deposits, deposits in intrusive rocks, deposits associated with hematite breccia complexes, deposits in granitic rocks, deposits in volcanic rocks, deposits in proterozoic discordances (Athabasca basin, Pine Creek geo-syncline); 4 - French uranium bearing areas and deposits: history of the French uranium mining industry, geological characteristics of French deposits (black shales, sandstones, granites), abroad success of French mining companies (Africa, North America, South America, Australia, Asia); 5 - exploration and exploitation; 6 - uranium economy: perspectives of uranium demand, present day production status, secondary resources, possible resources, market balances, prices and trends, future availability and nuclear perspectives. (J.S.)

  10. Unique advantages of organometallic supporting ligands for uranium complexes

    Energy Technology Data Exchange (ETDEWEB)

    Diaconescu, Paula L. [Univ. of California, Los Angeles, CA (United States); Garcia, Evan [Univ. of California, Los Angeles, CA (United States)

    2014-05-31

    The objective of our research project was to study the reactivity of uranium complexes supported by ferrocene-based ligands. In addition, this research provides training of graduate students as the next generation of actinide scientists.

  11. Unique advantages of organometallic supporting ligands for uranium complexes

    International Nuclear Information System (INIS)

    Diaconescu, Paula L.; Garcia, Evan

    2014-01-01

    The objective of our research project was to study the reactivity of uranium complexes supported by ferrocene-based ligands. In addition, this research provides training of graduate students as the next generation of actinide scientists.

  12. Study of uranium (VI) in carbonate solution by potentiometric titrations and ion-exchange; Etude des solutions d'uranium (VI) en milieu carbonate par titrages potentiometriques et echange d'ions

    Energy Technology Data Exchange (ETDEWEB)

    Billon, A. [Commissariat a l' Energie Atomique, 92 - Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1968-04-01

    The present work is devoted to the fixation of uranium (VI) on the conventional anion-exchange resin Dowex 2 X 8 in carbonate and hydrogen-carbonate media. Both media were successfully used for the recuperation of uranium (VI) from very dilute solutions. Equilibrium constant of the exchange [UO{sub 2}(CO{sub 3}){sub 3}{sup 4+}]{sub S} + 2 [CO{sub 3}{sup 2-}]{sub R} {r_reversible} [UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}]{sub R} + 2[CO{sub 3}{sup 2-}]{sub S} is determined for carbonate concentration range 0.1 M to 0.6 M from partition curves. A markedly increase in the relative fixation of uranium results with: - increasing free carbonate concentration of the solution, - decreasing uranium concentration. A study in the same conditions of the fixation of molybdenum has made it possible to separate the latter from uranium by elution, the carbonate concentration being molar. It is suggested a possibility of separation on a larger scale, based upon molybdenum displacement by uranium in hydrogen-carbonate medium. (author) [French] Le present travail precise la fixation de l'uranium (VI) sur la resine echangeuse d'anions Dowex 2 X 8, en milieu carbonate et hydrogeno-carbonate. Nous en avons deduit que ces deux milieux sont egalement favorables a la recuperation de l'uranium a partir de solutions tres diluees. La constante d'equilibre de la reaction d'echange [UO{sub 2}(CO{sub 3}){sub 3}{sup 4+}]{sub S} + 2 [CO{sub 3}{sup 2-}]{sub R} {r_reversible} [UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}]{sub R} + 2[CO{sub 3}{sup 2-}]{sub S} a ete determinee pour le milieu carbonate 0.1 M a 0.6 M, a partir deb courbes de partage. La fixation relative de l'uranium augmente considerablement lorsque: - la concentration du carbonate libre (respectivement hydrogenocarbonate) diminue, - la concentration de l'uranium en solution diminue. Le comportement du molybdene a ete etudie en vue de la separation uranium-molybdene. L'ion fixe sur la resine est l

  13. Effect of high ionic strength on the extraction of uranium(VI ions

    Directory of Open Access Journals (Sweden)

    M.K. Nazal

    2014-01-01

    Full Text Available Preparation and characterization of didodecylphosphoric acid (HDDPA as an extractant in toluene was carried. Mass spectroscopy showed that the monomer peak at 457.4 amu [M–Na+] is double that of the dimer at 891.9 amu [M–M–Na+] and the monomer molecules concentration dominate the dimer molecules in toluene. HDDPA was used as an extractant for the extraction of U(VI ion from perchlorate and nitrate media that have ionic strength (1.00, 3.00, 5.00, 7.00 M. The effect of HDDPA concentration, pcH, ionic strength of supporting electrolytes, and temperature in the range 15–45 °C on the extraction process have been studied. The stoichiometry of the extraction of U(VI ion, the free energy change (ΔG, the enthalpy change (ΔH, the entropy change (ΔS, and Kex at different ionic strength have been calculated. The formula of the complexes, which were formed has been established to be UO2(X(R2(HR2 at pcH equal 2.00 and UO2(X(R2(HR2 and UO2(X(R2 at pcH = 1.00, where (X isClO4- orNO3- and (HR2 is didodecylphosphoric acid monomer, (R2 is the deprotonated didodecylphosphoric acid, where R is the dodecyl group.

  14. Extraction of uranium (VI) from sea water using hydrous metalic oxide binded with hydrophilic polymers

    International Nuclear Information System (INIS)

    Shigetomi, Yasumasa; Kojima, Takehiro; Kamba, Hideaki

    1978-01-01

    In the past five years, many researches have been made to extract U(VI) from sea water. This is a report of the extraction of U(VI) from sea water using hydrous titanium oxide binded with hydrophilic polymers, the apparatus for the adsorption and the separation of U(VI) by means of ion exchange. (author)

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

    Science.gov (United States)

    Li, Peng; Zhun, Bao; Wang, Xuegang; Liao, PingPing; Wang, Guanghui; Wang, Lizhang; Guo, Yadan; Zhang, Weimin

    2017-12-19

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

  16. Uranium sorption to natural substrates-insights provided by isotope exchange, selective extraction and surface complexation modelling approaches

    International Nuclear Information System (INIS)

    Waite, T.D.; Payne T.E.; Davis, J.A.

    1993-01-01

    An extensive experimental program has been conducted over the last three years into the interaction of U(VI) with both single oxides and clays and complex natural substrates from the weathered zone in the vicinity of a uranium ore body in northern Australia. While iron oxides have frequently been considered to account for much of the uptake on such natural substrates, the results of laboratory open-quotes pH edgeclose quotes studies and of isotope exchange and selective extraction studies suggest that other phases must also play a significant role in controlling the partitioning of U(VI) between solid and solution phases. Supporting studies on kaolinite, the dominant clay in this system, provide insight into the most appropriate method of modelling the interaction of U(VI) with these natural substrates. The problems still remaining in adequately describing sorption of radionuclides and trace elements to complex natural substrates are discussed

  17. Adsorption of uranium(VI) from sulphate solutions using Amberlite IRA-402 resin: Equilibrium, kinetics and thermodynamics study

    International Nuclear Information System (INIS)

    Solgy, Mostafa; Taghizadeh, Majid; Ghoddocynejad, Davood

    2015-01-01

    Highlights: • Adsorption of uranium from sulphate solutions by an anion exchange resin. • The effects of pH, contact time and adsorbent dosage were investigated. • The adsorption equilibrium is well described by the Freundlich isotherm model. • The adsorption kinetics can be predicted by the pseudo second-order model. • The adsorption is a physical, spontaneous and endothermic process. - Abstract: In the present study, adsorption of uranium from sulphate solutions was evaluated using Amberlite IRA-402 resin. The variation of adsorption process was investigated in batch sorption mode. The parameters studied were pH, contact time and adsorbent dosage. Langmuir and Freundlich isotherm models were used in order to present a mathematical description of the equilibrium data at three different temperatures (25 °C, 35 °C and 45 °C). The final results confirmed that the equilibrium data tend to follow Freundlich isotherm model. The maximum adsorption capacity of Amberlite IRA-402 for uranium(VI) was evaluated to be 213 mg/g for the Langmuir model at 25 °C. The adsorption of uranium on the mentioned anion exchange resin was found to follow the pseudo-second order kinetic model, indicating that chemical adsorption was the rate limiting-step. The values of thermodynamic parameters proved that adsorption process of uranium onto Amberlite IRA-402 resin could be considered endothermic (ΔH > 0) and spontaneous (ΔG < 0)

  18. Hazelnut shell activated carbon. A potential adsorbent material for the decontamination of uranium(VI) from aqueous solutions

    International Nuclear Information System (INIS)

    Mijia Zhu; Hankui Chai; Jun Yao; China University of Geosciences; Yunpeng Chen; Zhengji Yi

    2016-01-01

    Batch experiments were conducted to study the ability of hazelnut shell activated carbon (HSAC) to remove uranium(VI) ions from aqueous solutions. The effects of various operational parameters, such as contact time (0-200 min), pH (2.0-7.0), initial U(VI) concentration (20-240 mg/L) and adsorbent dosage (4.0-50 g/L) were examined. Results showed that the adsorption process was rapid within the first 100 min and then achieved equilibrium at 140 min. The kinetics followed a pseudo-second-order rate equation, and the adsorption process was well fit with the Langmuir model. HSAC exhibited good uranium adsorption capacity (16.3 mg/g) at pH 6.0, 140 min contact time and 8.0 g/L adsorbent dosage. Furthermore, the regeneration efficiency was 96.3 % over five cycles under the optimum operational conditions. These properties revealed that HSAC can be a suitable adsorbent for the fast and convenient removal of U(VI) from contaminated water. (author)

  19. A Highly Expressed High-Molecular-Weight S-Layer Complex of Pelosinus sp. Strain UFO1 Binds Uranium

    Energy Technology Data Exchange (ETDEWEB)

    Thorgersen, Michael P. [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Lancaster, W. Andrew [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Rajeev, Lara [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Biological Systems and Engineering Division; Ge, Xiaoxuan [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Vaccaro, Brian J. [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Poole, Farris L. [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Arkin, Adam P. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Biological Systems and Engineering Division; Mukhopadhyay, Aindrila [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Biological Systems and Engineering Division; Adams, Michael W. W. [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology

    2016-12-02

    Cell suspensions of Pelosinus sp. strain UFO1 were previously shown, using spectroscopic analysis, to sequester uranium as U(IV) complexed with carboxyl and phosphoryl group ligands on proteins. The goal of our present study was to characterize the proteins involved in uranium binding. Virtually all of the uranium in UFO1 cells was associated with a heterodimeric protein, which was termed the uranium-binding complex (UBC). The UBC was composed of two S-layer domain proteins encoded by UFO1_4202 and UFO1_4203. Samples of UBC purified from the membrane fraction contained 3.3 U atoms/heterodimer, but significant amounts of phosphate were not detected. The UBC had an estimated molecular mass by gel filtration chromatography of 15 MDa, and it was proposed to contain 150 heterodimers (UFO1_4203 and UFO1_4202) and about 500 uranium atoms. The UBC was also the dominant extracellular protein, but when purified from the growth medium, it contained only 0.3 U atoms/heterodimer. The two genes encoding the UBC were among the most highly expressed genes within the UFO1 genome, and their expressions were unchanged by the presence or absence of uranium. Therefore, the UBC appears to be constitutively expressed and is the first line of defense against uranium, including by secretion into the extracellular medium. Although S-layer proteins were previously shown to bind U(VI), here we showed that U(IV) binds to S-layer proteins, we identified the proteins involved, and we quantitated the amount of uranium bound. Widespread uranium contamination from industrial sources poses hazards to human health and to the environment. Here in this paper, we identified a highly abundant uranium-binding complex (UBC) from Pelosinus sp. strain UFO1. The complex makes up the primary protein component of the S-layer of strain UFO1 and binds 3.3 atoms of U(IV) per heterodimer. Finally, while other bacteria have been shown to bind U(VI) on their S-layer, we demonstrate here an example of U(IV) bound by

  20. Tetra- and hexavalent uranium forms bidentate-mononuclear complexes with particulate organic matter in a naturally uranium-enriched peatland

    International Nuclear Information System (INIS)

    Mikutta, Christian; Langner, Peggy; Bargar, John R.; Kretzschmar, Ruben

    2016-01-01

    Peatlands frequently serve as efficient biogeochemical traps for U. Mechanisms of U immobilization in these organic matter-dominated environments may encompass the precipitation of U-bearing mineral(oid)s and the complexation of U by a vast range of (in)organic surfaces. The objective of this work was to investigate the spatial distribution and molecular binding mechanisms of U in soils of an alpine minerotrophic peatland (pH 4.7–6.6, E_h = –127 to 463 mV) using microfocused X-ray fluorescence spectrometry and bulk and microfocused U L_3-edge X-ray absorption spectroscopy. The soils contained 2.3–47.4 wt % organic C, 4.1–58.6 g/kg Fe, and up to 335 mg/kg geogenic U. Uranium was found to be heterogeneously distributed at the micrometer scale and enriched as both U(IV) and U(VI) on fibrous and woody plant debris (48 ± 10% U(IV), x̄ ± σ, n = 22). Bulk U X-ray absorption near edge structure (XANES) spectroscopy revealed that in all samples U(IV) comprised 35–68% of total U (x̄ = 50%, n = 15). Shell-fit analyses of bulk U L_3-edge extended X-ray absorption fine structure (EXAFS) spectra showed that U was coordinated to 1.3 ± 0.2 C atoms at a distance of 2.91 ± 0.01 Å (x̄ ± σ), which implies the formation of bidentate-mononuclear U(IV/VI) complexes with carboxyl groups. We neither found evidence for U shells at ~3.9 Å, indicative of mineral-associated U or multinuclear U(IV) species, nor for a substantial P/Fe coordination of U. As a result, our data indicates that U(IV/VI) complexation by natural organic matter prevents the precipitation of U minerals as well as U complexation by Fe/Mn phases at our field site, and suggests that organically complexed U(IV) is formed via reduction of organic matter-bound U(VI).

  1. Tetra- and Hexavalent Uranium Forms Bidentate-Mononuclear Complexes with Particulate Organic Matter in a Naturally Uranium-Enriched Peatland.

    Science.gov (United States)

    Mikutta, Christian; Langner, Peggy; Bargar, John R; Kretzschmar, Ruben

    2016-10-04

    Peatlands frequently serve as efficient biogeochemical traps for U. Mechanisms of U immobilization in these organic matter-dominated environments may encompass the precipitation of U-bearing mineral(oid)s and the complexation of U by a vast range of (in)organic surfaces. The objective of this work was to investigate the spatial distribution and molecular binding mechanisms of U in soils of an alpine minerotrophic peatland (pH 4.7-6.6, E h = -127 to 463 mV) using microfocused X-ray fluorescence spectrometry and bulk and microfocused U L 3 -edge X-ray absorption spectroscopy. The soils contained 2.3-47.4 wt % organic C, 4.1-58.6 g/kg Fe, and up to 335 mg/kg geogenic U. Uranium was found to be heterogeneously distributed at the micrometer scale and enriched as both U(IV) and U(VI) on fibrous and woody plant debris (48 ± 10% U(IV), x̅ ± σ, n = 22). Bulk U X-ray absorption near edge structure (XANES) spectroscopy revealed that in all samples U(IV) comprised 35-68% of total U (x̅ = 50%, n = 15). Shell-fit analyses of bulk U L 3 -edge extended X-ray absorption fine structure (EXAFS) spectra showed that U was coordinated to 1.3 ± 0.2 C atoms at a distance of 2.91 ± 0.01 Å (x̅ ± σ), which implies the formation of bidentate-mononuclear U(IV/VI) complexes with carboxyl groups. We neither found evidence for U shells at ∼3.9 Å, indicative of mineral-associated U or multinuclear U(IV) species, nor for a substantial P/Fe coordination of U. Our data indicates that U(IV/VI) complexation by natural organic matter prevents the precipitation of U minerals as well as U complexation by Fe/Mn phases at our field site, and suggests that organically complexed U(IV) is formed via reduction of organic matter-bound U(VI).

  2. Preparation and properties of N-Phenylbutyrohydroxamic acid and N-p-Chlorophenylbutyrohydroxamic acid and their uses as extracting agents for Chromium (VI), Molybdenum (VI), Titanium (IV) and Uranium (VI)

    Energy Technology Data Exchange (ETDEWEB)

    Abu Elnour, Sawsan Hassan [Department of Chemistry, Faculty of Science, University of Khartoum, Khartoum (Sudan)

    1993-05-01

    Two lignads, N-phenylbutyrohydroxamic acid (1), N-p-chlorophenylbutyryl chloride with {beta} phenyl-hydroylamine and N-p-chlorophenylhydroxylamine, respectively. The acids prepared were identified and characterised through their reactions with Vanadiun (V) and iron (III), their melting points, infra-red spectra and nitrogen content. The extractive properties of these acids towards the metals Cr (VI), Mo (VI), Ti (IV) and U (VI) were examined at different PH values. The percentage of maximum extraction with the two acids was found to be as follows : for Cr (VI) at PH 1, (100%) for both acids, Mo (VI) at PH 2 (33.34%) with acid (I) and (16.67%) with acid (II) and U (VI) at PH 6 (72%) with acid (I) and (76%) with acid (II). The metal: Ligand complexes ratios were determined by using the continuous variation method, the ratio of the two ligands with four metals was found to be 1:2. Finally the suitability of the two acids for spectrophotometric determination of four metals was examined.(Author) 90 refs. , 24 tabs. , 24 figs

  3. Preparation and properties of N-Phenylbutyrohydroxamic acid and N-p-Chlorophenylbutyrohydroxamic acid and their uses as extracting agents for Chromium (VI), Molybdenum (VI), Titanium (IV) and Uranium (VI)

    International Nuclear Information System (INIS)

    Abu Elnour, Sawsan Hassan

    1993-05-01

    Two lignads, N-phenylbutyrohydroxamic acid (1), N-p-chlorophenylbutyryl chloride with β phenyl-hydroylamine and N-p-chlorophenylhydroxylamine, respectively. The acids prepared were identified and characterised through their reactions with Vanadiun (V) and iron (III), their melting points, infra-red spectra and nitrogen content. The extractive properties of these acids towards the metals Cr (VI), Mo (VI), Ti (IV) and U (VI) were examined at different PH values. The percentage of maximum extraction with the two acids was found to be as follows : for Cr (VI) at PH 1, (100%) for both acids, Mo (VI) at PH 2 (33.34%) with acid (I) and (16.67%) with acid (II) and U (VI) at PH 6 (72%) with acid (I) and (76%) with acid (II). The metal: Ligand complexes ratios were determined by using the continuous variation method, the ratio of the two ligands with four metals was found to be 1:2. Finally the suitability of the two acids for spectrophotometric determination of four metals was examined.(Author)

  4. Thermodynamics of U(VI) and Eu(III) complexation by unsaturated carboxylates

    Energy Technology Data Exchange (ETDEWEB)

    Rawat, Neetika; Bhattacharyya, A. [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Tomar, B.S., E-mail: bstomar@barc.gov.in [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Ghanty, T.K. [Theoretical Chemistry Section, Bhabha Atomic Research Centre, Mumbai 400085 (India); Manchanda, V.K. [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2011-05-10

    Highlights: {yields} {Delta}H and log K determined for U(VI) and Eu(III) complexes with maleate and fumarate. {yields} log K and coordination environment of Eu(III) complexes has been studied by TRFS. {yields} Higher log K of U(VI) complexes than Eu(III) complexes is due to higher entropy. {yields} Plot of log K vs log K{sub P} suggest charge polarization in fumarate complexes. {yields} Ab initio calculations support charge polarization in fumarate complexes. - Abstract: The thermodynamic parameters ({Delta}G, {Delta}H and {Delta}S) of complexation of U(VI) and Eu(III) by unsaturated dicarboxylic acids, namely, maleic and fumaric acid, has been determined by potentiometric and microcalorimetric titrations at fixed ionic strength (I = 1.0 M) and temperature (298 K). The results show formation of 1:1 complexes by both the ligands with Eu(III). In the case of U(VI), maleate forms both 1:1 and 1:2 complexes, while only 1:1 complex was formed with fumarate. The fluorescence emission spectra of Eu(III)-dicarboxylate solutions at varying ligand to metal ratio were also used to obtain their stability constants. In addition, the fluorescence lifetimes reveal higher dehydration of Eu(III)-maleate compared to Eu(III)-fumarate which corroborates the {Delta}S values. The thermodynamic quantities suggest charge polarization effects in the case of U(VI) and Eu(III) complexes of fumarate, which is further corroborated by theoretical calculations. For the same ligand, U(VI) complexes were found to be more stable which was mainly due to higher entropy term.

  5. Solvent extraction of uranium(VI), plutonium(VI) and americium(III) with HTTA/HPMBP using mono- and bi-functional neutral donors. Synergism and thermodynamics

    International Nuclear Information System (INIS)

    Pai, S.A.; Lohithakshan, K.V.; Mithapara, P.D.; Aggarwal, S.K.

    2000-01-01

    Synergistic extraction of hexavalent uranium and plutonium as well as trivalent americium was studied in HNO 3 with thenoyl, trifluoro-acetone (HTTA)/1-phenyl, 3-methyl, 4-benzoyl pyrazolone-5 (HPMBP) in combination with neutral donors viz. DPSO, TBP, TOPO (mono-functional) and DBDECMP, DHDECMP, CMPO (bi-functional) with wide basicity range using benzene as diluent. A linear correlation was observed when the equilibrium constant log Ks for the organic phase synergistic reaction of both U(VI) and Pu(VI) with either of the chelating agents HTTA or HPMBP was plotted vs. the basicity (log Kh) of the donor (both mono- and bi-functional) indicating bi-functional donors also behave as mono-functional. This was supported by the thermodynamic data (ΔG 0 , ΔH 0 , ΔS 0 ) obtained for these systems. The organic phase adduct formation reactions were identified for the above systems from the thermodynamic data. In the Am(III) HTTA system log K s values of bi-functional donors were found to be very high and deviate from the linear plot (log K s vs. log K h ) obtained for mono-functional donors, indicating that they function as bi-functional for the Am(III)/HTTA) system studied. This was supported by high +ve ΔS 0 values obtained for this system. (author)

  6. Complex defects in the oxidation of uranium

    International Nuclear Information System (INIS)

    MacCrone, R.K.; Sankaran, S.; Shatynski, S.R.; Colmenares, C.A.

    1986-01-01

    We are reporting EPR results obtained with uranium powder samples fully oxidized in dry air, water vapor, and air/water vapor mixtures. The results reported previously are confirmed and additional paramagnetic centers, associated with chemisorbed species, have been identified. The temperature dependence of the g-value for these centers from room temperature to 10K is also reported

  7. Potentiometric titration in a low volume of solution for rapid assay of uranium. Application to quantitative electro-reduction of uranium(VI)

    International Nuclear Information System (INIS)

    Sahoo, P.; Ananthanarayanan, R.; Murali, N.; Mallika, C.; Falix Lawrence; Kamachi Mudali, U.

    2012-01-01

    A simple, inexpensive PC based potentiometric titration technique for the assay of uranium using low volumes of sample aliquot (25-100 μL) along with all reagents (total volume of solution being less than 2.5 mL) is presented. The technique involves modification of the well known Davies and Gray Method recommended for assay of uranium(VI) in nuclear materials by introducing an innovative potentiometric titration device with a mini cell developed in-house. After appropriate chemical conditioning the titration is completed within a couple of minutes with display of online titration plot showing the progress of titration. The first derivative plot generated immediately after titration provides information of end point. The main advantage of using this technique is to carry out titration with minimum volumes of sample and reagents generating minimum volume of wastes after titration. The validity of the technique was evaluated using standard certified samples. This technique was applied for assay of uranium in a typical sample collected from fuel reprocessing laboratory. Further, the present technique was deployed in investigating the optimum conditions for efficient in situ production of U(IV). The precision in the estimation of uranium is highly satisfactory (RSD less than 1.0%). (author)

  8. Spectrophotometric study of neptunium (VI) complexation by nitrate ions; Etude par spectrophotometrie de la complexation du neptunium au degre d'oxydation (VI) par les ions nitrates

    Energy Technology Data Exchange (ETDEWEB)

    Pochon, P. [CEA/VALRHO - site de Marcoule, Dept. de Recherche en Retraitement et en Vitrification (DRRV), 30 - Marcoule (France)]|[Conservatoire National des Arts et Metiers (CNAM), 75 - Paris (France)]|[Centre Regional Associe de Lyon, 69 (France)

    2000-07-01

    Neptunium(VI) complexation by nitrate ions was investigated by visible and near-infrared spectrophotometry, a technique suitable for observing the appearance and evolution of the species in solution. In the absence of reference spectra for Np(VI) nitrate- complexes, mathematical (factor analysis) tools were used to interpret the spectra. These chemo-metric techniques were first tested and validated on a simpler chemical system: Np(VI)complexation by the SiW{sub 11}O{sub 39}{sup 8-} anion. The test media used to investigate Np(VI) nitrate- complexes generally contain nitrate and perchlorate salts at high concentrations (high ionic strength). Media effects arising from the presence of cations, acidity or the perchlorate ion concentration are therefore significant, and no doubt account for the scattered values of the complexation constants published in the literature. The evolution of the neptunium spectra according to the parameters of the reaction medium illustrated these effects and allowed them to be quantified by a global 'perturbation constant'. In order to minimize the spectrum modifications due to media effects, the neptunium nitrate-complexes were studied at constant ionic strength in weak acidic media (2 mol.kg{sup -1}{sub H2O}) in the presence of sodium salts. The bulk formation constants and the spectrum of the NpO{sub 2}(NO{sub 3}){sup +} complex were determined for ionic strength values of 2.2, 4, 6 and 8 mol.kg{sup -1}{sub H2O}. The constants remained on the same order of magnitude regardless of the ionic strength; the thermodynamic constant {beta}{sub 1}{sup 0} determined from them according to specific interaction theory is thus probably of little significance. Conversely, the bulk constants can be corrected for the effects of the perchlorate ions by taking the global 'perturbation constant' into account. (author)

  9. Study of polyethyleneimine- and amidoxime-functionalized hybrid biomass of Spirulina (Arthrospira) platensis for adsorption of uranium (VI) ion.

    Science.gov (United States)

    Bayramoglu, Gulay; Akbulut, Aydin; Arica, M Yakup

    2015-11-01

    This study investigates the potential application of the polyethyleneimine- (PEI) and amidoxime-modified Spirulina (Arthrospira) platensis biomasses for the removal of uranium ion in batch mode using the native biomass as a control system. The uranium ion adsorption was also characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra, zeta potential analysis, and surface area measurement studies. The effects of pH, biomass amount, contact time, initial uranium ion concentration, and ionic strength were evaluated by using native and modified algal biomass preparations. The uranium ion removal was rapid, with more than 70% of total adsorption taking place in 40 min, and equilibrium was established within 60 min. From the experimental data, it was found that the amount of adsorption uranium ion on the algal preparations decreased in the following series: amidoxime-modified algal biomass > PEI-modified algal biomass > native algal biomass. Maximum adsorption capacities of amidoxime- and PEI-modified, and native algal biomasses were found to be 366.8, 279.5, and 194.6 mg/g, respectively, in batchwise studies. The adsorption rate of U(VI) ion by amidoxime-modified algal biomass was higher than those of the native and PEI-modified counterparts. The adsorption processes on all the algal biomass preparations followed by the Dubinin-Radushkevitch (D-R) and Temkin isotherms and pseudo-second-order kinetic models. The thermodynamic parameters were determined at four different temperatures (i.e., 15, 25, 35, and 45 °C) using the thermodynamics constant of the Temkin isotherm model. The ΔH° and ΔG° values of U(VI) ion adsorption on algal preparations show endothermic heat of adsorption; higher temperatures favor the process. The native and modified algal biomass preparations were regenerated using 10 mM HNO3. These results show that amidoxime-modified algal biomass can be a potential candidate for effective removal of U(VI) ion from

  10. Cordilleran metamorphic core complexes and their uranium favorability. Final report

    International Nuclear Information System (INIS)

    Coney, P.J.; Reynolds, S.J.

    1980-11-01

    The objective of this report is to provide a descriptive body of knowledge on Cordilleran metamorphic core complexes including their lithologic and structural characteristics, their distribution within the Cordillera, and their evolutionary history and tectonic setting. The occurrence of uranium in the context of possibility for uranium concentration is also examined. Chapter 1 is an overview of Cordilleran metamorphic core complexes which describes their physical characteristics, tectonic setting and geologic history. This overview is accompanied by a tectonic map. Chapter 2 is a discussion of the mantled gneiss dome concept. The purpose of including this work is to provide a basic history of this concept and to describe the characteristics and distribution of gneiss domes throughout the world to enable one to compare and contrast them with the metamorphic core complexes as discussed in this report. Some gneiss domes are known producers of uranium (as are also some core complexes). Chapter 3 is an examination of the effects of the core complex process on adjacent sedimentary and volcanic cover terranes. Also included is a discussion of the kinematic significance of these cover terranes as they are related to process within the cores of the complexes. Some of the cover terranes have uranium prospects in them. Chapter 4 is a detailed discussion of uranium in Cordilleran metamorphic core complexes and includes the conceptual basis for the various types of occurrences and the processes that might favor concentration of uranium. The report is supported by a 5-part Appendix. The majority of the core complexes discussed in this report either do not appear or are not recognizable on existing published geologic maps

  11. Chromatographic retention of molybdenum, titanium and uranium complexes for removal of some interferences in inductively-coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Jiang, S.-J.; Palmieri, M.D.; Fritz, J.S.; Houk, R.S.; Iowa State Univ., of Science and Technology, Ames

    1987-01-01

    Complexes of molybdenum(VI) or titanium(IV) with N-methylfurohydroxamic acid (N-MFHA) are retained on a column packed with polystyrene/divinylbenzene. At the pH values chosen, copper, zinc and cadmium are washed rapidly through the column and are detected by inductively-coupled plasma mass spectrometry without interference from metal oxide ions of titanium or molybdenum. Detection limits are 1 to 2 μg l -1 , and analyte recoveries are essentially 100%. The resin capacity for the titanium and molybdenum complexes is sufficient for several hundred injections, and the complexes can be readily washed from the column. Uranium(VI) also forms a stable complex with N-MFHA, and ionization interference caused by excess of uranium can be avoided by chromatographic removal of the uranium complex. Various other potentially interfering elements with aqueous oxidation states of +4 or higher (e.g. Sn, W, Hf or Zr) could also be separated by this technique. 33 refs.; 4 figs.; 3 tabs

  12. Quantum mechanical calculation of aqueuous uranium complexes: carbonate, phosphate, organic and biomolecular species

    Directory of Open Access Journals (Sweden)

    Jha Prashant

    2009-08-01

    Full Text Available Abstract Background Quantum mechanical calculations were performed on a variety of uranium species representing U(VI, U(V, U(IV, U-carbonates, U-phosphates, U-oxalates, U-catecholates, U-phosphodiesters, U-phosphorylated N-acetyl-glucosamine (NAG, and U-2-Keto-3-doxyoctanoate (KDO with explicit solvation by H2O molecules. These models represent major U species in natural waters and complexes on bacterial surfaces. The model results are compared to observed EXAFS, IR, Raman and NMR spectra. Results Agreement between experiment and theory is acceptable in most cases, and the reasons for discrepancies are discussed. Calculated Gibbs free energies are used to constrain which configurations are most likely to be stable under circumneutral pH conditions. Reduction of U(VI to U(IV is examined for the U-carbonate and U-catechol complexes. Conclusion Results on the potential energy differences between U(V- and U(IV-carbonate complexes suggest that the cause of slower disproportionation in this system is electrostatic repulsion between UO2 [CO3]35- ions that must approach one another to form U(VI and U(IV rather than a change in thermodynamic stability. Calculations on U-catechol species are consistent with the observation that UO22+ can oxidize catechol and form quinone-like species. In addition, outer-sphere complexation is predicted to be the most stable for U-catechol interactions based on calculated energies and comparison to 13C NMR spectra. Outer-sphere complexes (i.e., ion pairs bridged by water molecules are predicted to be comparable in Gibbs free energy to inner-sphere complexes for a model carboxylic acid. Complexation of uranyl to phosphorus-containing groups in extracellular polymeric substances is predicted to favor phosphonate groups, such as that found in phosphorylated NAG, rather than phosphodiesters, such as those in nucleic acids.

  13. Influence of Calcite and Dissolved Calcium on Uranium(VI) Sorption to a Hanford Subsurface Sediment

    International Nuclear Information System (INIS)

    Dong, Wenming; Ball, William P.; Liu, Chongxuan; Wang, Zheming; Stone, Alan T.; Bai, Jing; Zachara, John M.

    2005-01-01

    The influence of calcite and dissolved calcium on U(VI) adsorption was investigated using a calcite-containing sandy silt/clay sediment from the U. S. Department of Energy Hanford site. U(VI) adsorption to sediment, treated sediment, and sediment size fractions was studied in solutions that both had and had not been preequilibrated with calcite, at initial [U(VI)] ) 10-7-10-5 mol/L and final pH ) 6.0- 10.0. Kinetic and reversibility studies (pH 8.4) showed rapid sorption (30 min), with reasonable reversibility in the 3-day reaction time. Sorption from solutions equilibrated with calcite showed maximum U(VI) adsorption at pH 8.4 (0.1. In contrast, calcium-free systems showed the greatest adsorption at pH 6.0-7.2. At pH > 8.4, U(VI) adsorption was identical from calcium-free and calcium-containing solutions. For calcite-presaturated systems, both speciation calculations and laser-induced fluorescence spectroscopic analyses indicated that aqueous U(VI) was increasingly dominated by Ca2UO2(CO3)3 0(aq) at pH<8.4 and that formation of Ca2UO2(CO3)3 0(aq) is what suppresses U(VI) adsorption. Above pH 8.4, aqueous U(VI) speciation was dominated by UO2(CO3)3 4- in all solutions. Finally, results also showed that U(VI) adsorption was additive in regard to size fraction but not in regard to mineral mass: Carbonate minerals may have blocked U(VI) access to surfaces of higher sorption affinity

  14. Final Report - Elucidating Bioreductive Transformations within Physically Complex Media: Impact on the Fate and Transport of Uranium and Chromium

    International Nuclear Information System (INIS)

    Benner, Shawn G.; Fendorf, Scott

    2009-01-01

    In situ stabilization (inclusive of natural attenuation) of toxic metals and radionuclides is an attractive approach for remediating many contaminated DOE sites. By immobilizing toxic metals and radionuclides in place, the removal of contaminated water to the surface for treatment as well as the associated disposal costs are avoided. To enhance in situ remediaton, microbiological reductive stabilization of contaminant metals has been, and continues to be, actively explored. It is likely that surface and subsurface microbial activity can alter the redox state of toxic metals and radionuclides, either directly or indirectly, so they are rendered immobile. Furthermore, anaerobic bacterial metabolic products will help to buffer pulses of oxidation, typically from fluxes of nitrate or molecular oxygen, and thus may stabilize reduced contaminants from oxidative mobilization. Uranium and chromium are two elements of particular concern within the DOE complex that, owing to their abundance and toxicity, appear well suited for biologically mediated reductive stabilization. Subsurface microbial activity can alter the redox state of toxic metals and radionuclides, rending them immobile. Imparting an important criterion on the probability that contaminants will undergo reductive stabilization, however, is the chemical and physical heterogeneity of the media. Our research first examined microbially induced transformation of iron (hydr)oxide minerals and their impact on contaminant attenuation. We revealed that in intricate cascade of geochemical reactions is induced by microbially produced Fe(II), and that during transformation contaminants such as U(VI) can be incorporated into the structure, and a set of Fe(II) bearing solids capable of reducing Cr(VI) and stabilizing resulting Cr(III). We also note, however, that common subsurface constituents such as phosphate can modify iron oxide transformation pathways and thus impact contaminant sequestration - 'affecting both Cr and U

  15. Elucidating Bioreductive Transformations within Physically Complex Media: Impact on the Fate and Transport of Uranium and Chromium

    International Nuclear Information System (INIS)

    Fendorf, Scott; Francis, Chris; Jardine, Phil; Benner, Shawn

    2009-01-01

    In situ stabilization (inclusive of natural attenuation) of toxic metals and radionuclides is an attractive approach for remediating many contaminated DOE sites. By immobilizing toxic metals and radionuclides in place, the removal of contaminated water to the surface for treatment as well as the associated disposal costs are avoided. To enhance in situ remediaton, microbiological reductive stabilization of contaminant metals has been, and continues to be, actively explored. It is likely that surface and subsurface microbial activity can alter the redox state of toxic metals and radionuclides, either directly or indirectly, so they are rendered immobile. Furthermore, anaerobic bacterial metabolic products will help to buffer pulses of oxidation, typically from fluxes of nitrate or molecular oxygen, and thus may stabilize reduced contaminants from oxidative mobilization. Uranium and chromium are two elements of particular concern within the DOE complex that, owing to their abundance and toxicity, appear well suited for biologically mediated reductive stabilization. Subsurface microbial activity can alter the redox state of toxic metals and radionuclides, rending them immobile. Imparting an important criterion on the probability that contaminants will undergo reductive stabilization, however, is the chemical and physical heterogeneity of the media. Our research first examined microbially induced transformation of iron (hydr)oxide minerals and their impact on contaminant attenuation. We revealed that in intricate cascade of geochemical reactions is induced by microbially produced Fe(II), and that during transformation contaminants such as U(VI) can be incorporated into the structure, and a set of Fe(II) bearing solids capable of reducing Cr(VI) and stabilizing resulting Cr(III). We also note, however, that common subsurface constituents such as phosphate can modify iron oxide transformation pathways and thus impact contaminant sequestration - affecting both Cr and U

  16. Structure of some complex halides of uranium(III)

    International Nuclear Information System (INIS)

    Volkov, V.A.; Suglobova, I.G.; Chirkst, D.E.

    1987-01-01

    Polycrystals of some halide complexes of uranium(III) were obtained and investigated by x-ray diffraction. The M 2 UCl 5 compounds (M = K, Rb) are isostructural with K 2 PrCl 5 ; RbU 2 Cl 7 is of the same type as RbDy 2 Cl 7 or KDy 2 Cl 7 . The coordination number of the uranium is 7. The M 2 UBr 5 compounds (M = K-Cs) are isostructural with Cs 2 DyCl 5 , and the coordination number of the uranium is 6. Rb 2 NaUCl 6 is a 12L-hexagonal polytype, the structural analog of Cs 2 NaCrF 6 . The most characteristic coordination number of uranium in the UHal 3 -MHal systems is 8 for Hal = F, 7 for Hal = Cl, and 6 for Hal = Br

  17. Effective Uranium (VI) Sorption from Alkaline Solutions Using Bi-Functionalized Silica-Coated Magnetic Nanoparticles

    International Nuclear Information System (INIS)

    Chen, X.; He, L.; Liu, B.; Tang, Y.

    2015-01-01

    High temperature gas reactor is one of generation IV reactors that can adapt the future energy market, of which the preparation of fuel elements will produce a large amount of radioactive wastewater with uranium and high-level ammonia. Sorption treatment is one of the most important method to recover uranium from wastewater. However, there are few report on uranium sorbent that can directly be applied in wastewater with ammonia. Therefore, the development of a sorbent that can recover uranium in basic environment will greatly decrease the cost of fuel element production and the risk of radioactive pollution. In this work, ammonium-phosphonate-bifunctionalized silica-coated magnetic nanoparticles has been developed for effective sorption of uranium from alkaline media, which are not only advantaged in the uranium separation from liquid phase, but also with satisfactory adsorption rate, amount and reusability. The as-prepared sorbent is found to show a maximum uranium sorption capacity of 70.7 mg/g and a fast equilibrium time of 2 h at pH 9.5 under room temperature. Compared with the mono-functionalized (phosphonate alone and ammonium alone) particles, the combination of the bi-functionalized groups gives rise to an excellent ability to remove uranium from basic environment. The sorbent can be used as a promising solid phase candidate for highly-efficient removal of uranium from basic solution. (author)

  18. Carbon-13 NMR characterization of actinyl(VI) carbonate complexes in aqueous solution

    International Nuclear Information System (INIS)

    Clark, D.L.; Hobart, D.E.; Palmer, P.D.; Sullivan, J.C.; Stout, B.E.

    1992-01-01

    The uranyl(VI) carbonate system has been re-examined using 13 C NMR of 99.9% 13 C-enriched U VI O 2 ( 13 CO 3 ) 3 4- in millimolar concentrations. By careful control of carbonate ion concentration, we have confirmed the existence of the trimer, and observed dynamic equilibrium between the monomer and the timer. In addition, the ligand exchange reaction between free and coordinated carbonate on Pu VI O 2 ( 13 CO 3 ) 3 4- and Am VI O 2 ( 13 CO 3 ) 3 4- systems has been examined by variable temperature 13 C NMR line-broadening techniques 13 C NMR line-broadening techniques. A modified Carr-Purcell-Meiboom-Gill NMR pulse sequence was written to allow for experimental determination of ligand exchange parameters for paramagnetic actinide complexes. Preliminary Eyring analysis has provided activation parameters of ΔG double-dagger 295 = 56 kJ/M, ΔH double-dagger = 38 kJ/M, and ΔS double-dagger = -60 J/M-K for the plutonyl triscarbonate system, suggesting an associative transition state for the plutonyl (VI) carbonate complex self-exchange reaction. Experiments for determination of the activation parameters for the americium (VI) carbonate system are in progress

  19. The uranium potential of the Bushveld igneous complex

    International Nuclear Information System (INIS)

    Andreoli, M.A.G.; Hart, R.J.; Brynard, H.J.; Camisani-Calzolari, F.A.G.M.

    1987-06-01

    A review of published literature supported by field observations on the uranium potential of the Bushveld Complex indicates that this geological region may host deposits with reserves in the range of a few thousand tons U 3 O 8 . The possibility that the Bushveld Complex or its cover rocks hosts, or has ever hosted in the past, giant uranium deposits such as those of Olympic Dam, Key Lake, Jabiluka or Rossing is considered to be unlikely. The potential for volcanogenic, caldera-type deposits in the Rooiberg Felsites remains at present untested. Recommendations for research currently sponsored by the AEC at the University of Pretoria are presented

  20. A study of the direct spectrophotometric determination of uranium (VI) in trialkylamine extracts with 2-(5-bromo- 2-pyridylazo)-5-diethylaminophenol

    International Nuclear Information System (INIS)

    Lyle, S.J.; Tamizi, M.

    1979-01-01

    A straightforward spectrophotometric method is described for the determination of uranium (VI) in trialkylamine sulphate extracts in kerosene diluent; 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) is used for colour formation without resort to back extraction into an aqueous phase. The method provides good tolerance to sulphate ion and rapid colour development and appears to be free from interference when applied to extracts from uranium sulphate leach liquors. (Auth.)

  1. Organomolybdenum (VI) and lithium Organomolybdate (VI) and (V) Complexes with C,N-Chelating Aminoaryl Ligands

    NARCIS (Netherlands)

    Koten, G. van; Brandts, J.A.M.; Leur, M. de; Gossage, R.A.; Spek, A.L.

    1999-01-01

    The synthesis and characterization of new, five-coordinate molybdenum bis(imidoaryl) complexes [Mo(NAr)2(C-N)X] (Ar = C6H3i-Pr2-2,6; C-N = [C6H4(CH2NMe2)-2]-; X = Cl (1), Me (2), Et (3), Bu (4), CH2SiMe3 (5), (p-tolyl) (6), (C-N) (7)) is reported. The solid-state structure of 2 has been elucidated

  2. Adsorption equilibrium studies of uranium (VI) onto cross-linked chitosan-citric acid

    International Nuclear Information System (INIS)

    Ho Thi Yeu Ly; Nguyen Van Suc; Vo Quang Mai; Nguyen Mong Sinh

    2011-01-01

    Investigation of U(VI) adsorption by the cross- linked chitosan with citric acid was conduced by bath method. Effect of parameters such as pH, contact time, adsorbent dosage and other metal cations was determined. The maximum adsorption capacity of U(VI) at pH 4 was found to be 71.43 mg U(VI) / g cross-linked chitosan - citric acid after 300 min of contact time. The Langmuir and Freundlich isotherm models were used to describe adsorption equilibrium. The correction values, R 2 of two models were found to be 0.991 and 0.997, respectively. Therefore, it could be concluded that the adsorption equilibrium for U(VI) was followed the Langmuir and the Freundlich isotherm models. (author)

  3. Effect of silica fume on reaction products of uranium (VI) with portland cement

    International Nuclear Information System (INIS)

    Tan Hongbin; Shaanxi Univ. of Technology, Hanzhong; Li Yuxiang

    2005-01-01

    Simulation of radioactive waste of U(VI) by uranyl nitrate and the effects of different additive quantities (12%, 20%, 30%, 35%, 40%) of silica fume on the products of U(VI) with Portland cement were studied at a hydrothermal condition of 180 degree C for a duration of one week. The X-ray powder diffraction examination results showed that the calcium uranate would be transformed into uranophane when the cement contained 30% silica fume. (authors)

  4. Development of metal uranium fuel and testing of construction materials (I-VI); Part I; Razvoj metalnog goriva i ispitivanje konstrukcionih materijala (I-VI deo); I deo

    Energy Technology Data Exchange (ETDEWEB)

    Mihajlovic, A [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1965-11-15

    This project includes the following tasks: Study of crystallisation of metal melt and beta-alpha transforms in uranium and uranium alloys; Study of the thermal treatment influence on phase transformations and texture in uranium alloys; Radiation damage of metal uranium; Project related to irradiation of metal uranium in the reactor; Development of fuel element for nuclear reactors.

  5. Studies on the kinetics of uranium (VI) electro-reduction and reextraction: Pt. 2

    International Nuclear Information System (INIS)

    Tong Jihong; Ma Xuquan; Tai Derong; Sun Shiren

    1992-01-01

    The kinetics of U(VI) reextraction and U(IV) extraction in the process of U(VI) electro-reduction with the system of HNO 3 -N 2 H 5 NO 3 (H 2 O)/UO 2 (NO 3 ) 2 -HNO 3 (30% TBP-OK) is investigated with a constant interfacial area cell (Lewis cell) with cathode and anode in it. According to the experimental results and data processing, the apparent activation energy of the U(VI) reextraction process is 36.02 kJ/nol. The U(VI) reextraction rate increases when the stirring speed of two phases increases. This process is mainly diffusion controlled. For the U(VI) extraction process, the apparent activation energy is 21.13 kJ/mol. The U(IV) extraction rate also increases when the stirring speed of two phases increases. This process is mainly diffusion controlled. The lower the potential of cathode is, the higher the rates of U(VI) reextraction and U(IV) extraction are

  6. Complexation of Eu(III), Th(IV) and U(VI) by humic substances

    International Nuclear Information System (INIS)

    Moulin, V.; Reiller, P.; Dautel, C.; Plancque, G.; Laszak, I.; Moulin, C.

    1999-01-01

    Complexation of actinides by humic substances has been studied by different techniques depending on the actinide and its oxidation state. For trivalent actinide (using a rare earth element, Eu as an analogue of trivalent actinide), Time-Resolved Laser-Induced Fluorescence (TRLIF) has been retained as a method for direction speciation at low level. By varying pH and physicochemical conditions (absence of carbonate ions) and at fixed ionic strength, it is possible together to identify spectrally and temporally, all the hydroxo and carbonato complexes. This approach has also been retained for U(VI) as a model of hexavalent actinide, for which hydroxo complexes have been characterized by TRLIF (the simple carbonato complexes are not fluorescent). In the case of U(VI), titrations hy humic acids of U(VI) solutions at various pH have allowed to characterize organic complexes formed with U(VI): single complexes (UO 2 HA) and mixed complexes (UO 2 (OH) 3 HA). The impact on U(VI) speciation has then been identified. In the case of Th(IV) as a model of tetravalent actinides, a competitive method has been used to obtain data on the Th-HA system by studying the ternary system silica colloid/HA/Th at constant pH (Schubert method). Apparent interaction constants have been calculated depending on Th hydrolysis constants used. A study of the system Th/HA/silica has a function of pH and for different HA concentrations has shown the strong complexing character of humic acids towards Th in the pH range 4-9. (orig.)

  7. Separation and concentration of uranium by extraction chromatography : U(VI) - H3PO4 system

    International Nuclear Information System (INIS)

    Nobre, J.S.M.

    1981-01-01

    The feasibility of using the extraction chromatographic technique as a way to recover uranium from phosphatic rocks evaluated. The behaviour of uranium from raw phsophoric acid solutions in chromatographic systems using the mixture di(2-ethylhexyl) orthophosphoric acid (D2EHPA) - tributyl phosphate (TBP) as the stationary phase was studied. Materials as alumina, activated carbon and the macroporous resins XAD-4 and XAD-7 were used as supports for organic stationary phase. The best results were obtained with poliacrilic polymer XAD-7, due to its excellent chromatographic properties and efficient organic phase retention. Uranium was quantitatively retained by D2EHPA-TBP-XAD-7 columns from synthetic phosphoric acid solutions with typical composition of phosphatic acid liquors. The elution of uranium from this system was also studied, and the best results were obtained with phosphoric acid solutions. This chromatographic column presented a high stability, not changing their properties even after more than twenty cycles, including the conditioning, sorption, wasking and elution steps. Uranium determinations were perfpormed by indirect titration with potassium dichromate and by molecular absorption spectrophotometry with hydrogen peroxide- carbonate. A new and more sensitive method for uranium determination in phosphoric medium, which might be applied to acid liquors of phosphatic ores, was developed. An extraction-photometric method was used, with Arsenazo III (1,8-dihydroxynaphtalene-3,6-disulphonic acid-2,7-bis(azo-2)-phenylarsonic acid) as the reagent for uranium. (Author) [pt

  8. Thermodynamic properties of actinide complexes. IV. Thorium(IV)- and uranyl(VI)-malonate systems

    Energy Technology Data Exchange (ETDEWEB)

    Di Bernardo, P; Di Napoli, V; Cassol, A; Magon, L [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi

    1977-01-01

    The stability constants and the enthalpies of formation of thorium(IV)- and uranyl(VI)-malonate complexes have been determined by potentiometric and calorimetric titrations in 1.00 M solutions of Na(ClO/sub 4/) at 25/sup 0/C. All complexes formed are found to be stabilized by a large entropy gain. The values for the stability constants agree with an ionic bonding model. The malonate behaves as a bidentate ligand forming only chelate complexes.

  9. Extraction and separation studies of uranium(VI) with tris-(2-ethyl hexyl) phosphate

    International Nuclear Information System (INIS)

    Sundaramurthi, N.M.; Desai, G.S.; Shinde, V.M.

    1990-01-01

    A solvent extraction method is proposed for the extraction and separation of uranium from salicylate media using tris-(2-ethyl hexyl) phosphate dissolved in xylene as an extractant. The optimum conditions were evaluated from a critical study of pH, salicylate concentration, extractant concentration, period of equilibration and diluent. The method permits the separation of uranium from thorium, cerium, titanium, zirconium, hafnium, copper, vanadium and chromium from binary mixtures and is applicable to the analysis of uranium in synthetic samples. The method is precise, accurate, fast and selective. (author) 5 refs.; 2 tabs

  10. [UO{sub 2}Cl{sub 2}(phen){sub 2}], a simple uranium(VI) compound with a significantly bent uranyl unit (phen=1,10-phenanthroline)

    Energy Technology Data Exchange (ETDEWEB)

    Schoene, Sebastian; Radoske, Thomas; Maerz, Juliane; Stumpf, Thorsten; Patzschke, Michael; Ikeda-Ohno, Atsushi [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, Dresden (Germany)

    2017-10-04

    A simple synthesis based on UO{sub 2}Cl{sub 2}.n H{sub 2}O and 1,10-phenanthroline (phen) resulted in the formation of a new uranyl(VI) complex [UO{sub 2}Cl{sub 2}(phen){sub 2}] (1), revealing a unique dodecadeltahedron coordination geometry around the uranium center with significant bending of the robust linear arrangement of the uranyl (O-U-O) unit. Quantum chemical calculations on complex 1 indicated that the weak but distinct interactions between the uranyl oxygens and the adjacent hydrogens of phen molecules play an important role in forming the dodecadeltahedron geometry that fits to the crystal structure of 1, resulting in the bending the uranyl unit. The uranyl oxygens in 1 are anticipated to be activated as compared with those in other linear uranyl(VI) compounds. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Uranium(VI) Reduction by Nanoscale Zerovalent Iron in Anoxic Batch Systems

    International Nuclear Information System (INIS)

    Yan, Sen; Hua, Bin; Bao, Zhengyu; Yang, John; Liu, Chongxuan; Deng, Baolin

    2010-01-01

    This study investigated the influences of pH, bicarbonate, and calcium on U(VI) adsorption and reduction by synthetic nanosize zero valent iron (nano Fe 0 ) particles under an anoxic condition. The results showed that about 87.1%, 82.7% and 78.3% of U(VI) could be reduced within 96 hours in the presence of 10 mM bicarbonate at pHs 6.92, 8.03 and 9.03, respectively. The rates of U(VI) reduction and adsorption by nano Fe 0 , however, varied significantly with increasing pH and concentrations of bicarbonate and/or calcium. Solid phase analysis by X-ray photoelectron spectroscopy confirmed the formation of UO 2 and iron (hydr)oxides as a result of the redox interactions between adsorbed U(VI) and nano Fe 0 . This study highlights the potential important role of groundwater chemical composition in controlling the rates of U(VI) reductive immobilization using nano Fe 0 in subsurface environments.

  12. MODELING OF THE SOLVENT EXTRACTION EQUILIBRIUM OF URANIUM (VI SULFATE WITH ALAMINE 336

    Directory of Open Access Journals (Sweden)

    É. C. Avelar

    Full Text Available Abstract The present study investigated the solvent extraction of uranium from sulfate acid solutions using Alamine 336 as an extractant dissolved in commercial kerosene Exxsol D-100 and 5% v/v of tridecanol as a modifying agent at room temperature (25±2 ºC and an aqueous/organic volumetric ratio of unity. Experiments were carried out at typical concentration levels like those used at the uranium plant of INB (Indústrias Nucleares do Brasil, Brazil. Data fitting using the slope analysis method revealed that uranium is extracted by Alamine 336 as UO2SO4 and UO2(SO422- species, forming (R3NH+2UO2(SO422- in the organic phase; the extraction of the species UO2(SO434- seems improbable for the operating conditions investigated. The extraction of uranium is significantly reduced when the concentrations of sulfate and chloride ions in the aqueous phase are increased.

  13. Investigation of the binding of tiron to uranium(IV) and uranium(VI) found in soil

    International Nuclear Information System (INIS)

    Birnbaum, E.R.; Iams, H.D.; del Rio Garcia, M.; Ford, D.K.; Smith, P.H.; Strietelmeier, B.; Brainard, J.

    1993-01-01

    The authors are investigating the utility of a chelate-reductant system to extract uranium from 2 million yards of contaminated soil at the Fernald uranium reprocessing plant near Cincinnati, Ohio. It has been found that reduction of the uranyl contaminants using Tiron as the ligand. Of concern is whether the increased mobilization is simply a result of the higher affinity of Tiron to U(IV), or whether reduction of amorphous iron oxides contained in the soil is exposing greater amounts of uranyl ions to the ligand. It is important to establish if the latter mechanism is occurring, since a removal process which does not damage the soil is desired. Potentiometric and spectrophotometric studies of Tiron binding to soluble uranyl and U(V) salts will be presented as models to help understand the soil studies. Extraction behavior of UO 2 (OH) 2 will also be presented

  14. Polarographic behaviour and determination of uranium(VI) in alcoholic solutions from organic extraction phases

    International Nuclear Information System (INIS)

    Degueldre, C.; Taibi, K.

    1996-01-01

    The determination of U(VI) in organic extraction phases: hydrocarbon-diethyl-2-hexyl phosphoric acid-trioctylphosphine oxide and hydrocarbon-tri-n-octylamine, diluted by an alcohol has been studied by direct current polarography, as well as by differential pulse polarography (DPP). In order to optimise the analytical procedure, miscibility and conductivity studies of the mixtures hydrocarbon-alcohol (ethanol, n- and isopropanol and n- and isobutanol) were made after addition of sulphuric acid as a supporting electrolyte. In the solutions of sulphuric acid in the alcohol-extractant-hydrocarbon phases, U(VI) gives rise to well defined polarograms. Its electroreduction involves a single electron step in all cases. The DPP peak height is proportional to the U(VI) concentration between 2x10 -6 and 2x10 -3 M, and the 3σ detection limit is ca. 10 -6 M

  15. More light on the U clan. [Uranium behaviour in complex ores

    Energy Technology Data Exchange (ETDEWEB)

    De Waal, S.A. (Potchefstroom Univ. for C.H.E. (South Africa). Dept. of Geology)

    1983-07-01

    A thorough knowledge of the geochemistry of uranium is necessary for the exploration and beneficiation of this mineral. At present we lack knowledge of the behaviour of uranium minerals in complex ores. This article deals with the geochemistry of uranium, its group identity, uranium minerals and the extraction mineralogy.

  16. Reduction of neptunium(V) and uranium(VI) in bicarbonate solutions by iron(II)

    International Nuclear Information System (INIS)

    Gogolev, A.V.; Zakharova, E.V.; Rodygina, N.I.; Fedoseev, A.M.; Shilov, V.P.

    2006-01-01

    Interaction of Np(VI) and Fe(II) compounds in bicarbonate solutions is investigated. Interaction of Np(V) with Fe(II) in the presence of phthalate-ions is studied briefly. Fe(II) compounds reduce Np(V) compounds in saturated with Ar or CO 2 solutions with any bicarbonate-ion concentrations. Chemical reaction kinetics is studied. Reduction of U(VI) by Fe(II) compounds takes place in the case of diluted bicarbonate solutions. UO 2 and FeOOH are products of reaction at raised temperatures [ru

  17. Thermodynamics of U(VI) complexation by succinate at variable temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rawat, Neetika [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Tomar, B.S., E-mail: bstomar@barc.gov.in [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Manchanda, V.K. [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2011-07-15

    Research highlights: > lg {beta} and {Delta}H{sub C} for U(VI)-succinate determined at variable temperatures. > Increase in lg {beta} with temperature well explained by Born equation. > {Delta}S{sub C} plays the dominant role in variation of {Delta}G{sub C} with temperature. > {Delta}H{sub C} for U(VI)-succinate increases linearly with temperature. > {Delta}C{sub P} of U(VI)-succinate is higher than that of oxalate and malonate complexes. - Abstract: Complexation of U(VI) by succinate has been studied at various temperatures in the range of (298 to 338) K by potentiometry and isothermal titration calorimetry at constant ionic strength (1.0 M). The potentiometric titrations revealed the formation of 1:1 uranyl succinate complex in the pH range of 1.5 to 4.5. The stability constant of uranyl succinate complex was found to increase with temperature. Similar trend was observed in the case of enthalpy of complex formation. However, the increase in entropy with temperature over-compensated the increase in enthalpy, thereby favouring the complexation reaction at higher temperatures. The linear increase of enthalpy of complexation with temperature indicates constancy of the change in heat capacity during complexation. The temperature dependence of stability constant data was well explained with the help of Born equation for electrostatic interaction between the metal ion and the ligand. The data have been compared with those for uranyl complexes with malonate and oxalate to study the effect of ligand size and hydrophobicity on the temperature dependence of thermodynamic quantities.

  18. Controlled thermolysis of uranium (alkoxy)siloxy complexes: a route to polymetallic complexes of Low-Valent uranium

    Energy Technology Data Exchange (ETDEWEB)

    Camp, Clement; Pecaut, Jacques; Mazzanti, Marinella [Laboratoire de Reconnaissance Ionique et Chimie de Coordination, SCIB, UMR-E3 CEA-UJF, INAC, CEA-Grenoble (France); Kefalidis, Christos E.; Maron, Laurent [LPCNO, CNRS et INSA, UPS, Universite de Toulouse (France)

    2013-07-01

    Decomposition into higher species: Intramolecular U{sup III}-mediated homolytic C-O bond cleavage in U{sup III} (alkoxy)siloxy complexes at low temperature and subsequent reduction with KC{sub 8} led to unprecedented polymetallic complexes containing siloxy, silanediolate, and silanetriolate ligands. Such compounds may be useful precursors to uranium ceramics relevant for catalysis and the storage of spent nuclear fuel. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. C-N bond cleavage of anilines by a (salen)ruthenium(VI) nitrido complex.

    Science.gov (United States)

    Man, Wai-Lun; Xie, Jianhui; Pan, Yi; Lam, William W Y; Kwong, Hoi-Ki; Ip, Kwok-Wa; Yiu, Shek-Man; Lau, Kai-Chung; Lau, Tai-Chu

    2013-04-17

    We report experimental and computational studies of the facile oxidative C-N bond cleavage of anilines by a (salen)ruthenium(VI) nitrido complex. We provide evidence that the initial step involves nucleophilic attack of aniline at the nitrido ligand of the ruthenium complex, which is followed by proton and electron transfer to afford a (salen)ruthenium(II) diazonium intermediate. This intermediate then undergoes unimolecular decomposition to generate benzene and N2.

  20. Selective extraction of metals from acidic uranium(VI) solutions using neo-tridecano-hydroxamic acid

    International Nuclear Information System (INIS)

    Bardoncelli, F.; Grossi, G.

    1975-01-01

    According to this invention neo-alkyl-hydroxamic acids are employed as ion-exchanging agents in processes for liquid-liquid extraction with the aim of separating, purifying dissolved metals and of converting a metal salt solution into a solution of a salt of the same metal but with different anion. In particular it is an objective of this invention to provide a method whereby a molecular pure uranium solution is obtained by selective extraction from a uranium solution delivered by irradiated fuel reprocessing plants and containing plutonium, fission products and other unwanted metals, in which method neo-tridecane-hydroxamic acid is employed as ion exchanger. (Official Gazette)

  1. Nitrogen reduction and functionalization by a multimetallic uranium nitride complex

    Science.gov (United States)

    Falcone, Marta; Chatelain, Lucile; Scopelliti, Rosario; Živković, Ivica; Mazzanti, Marinella

    2017-07-01

    Molecular nitrogen (N2) is cheap and widely available, but its unreactive nature is a challenge when attempting to functionalize it under mild conditions with other widely available substrates (such as carbon monoxide, CO) to produce value-added compounds. Biological N2 fixation can do this, but the industrial Haber-Bosch process for ammonia production operates under harsh conditions (450 degrees Celsius and 300 bar), even though both processes are thought to involve multimetallic catalytic sites. And although molecular complexes capable of binding and even reducing N2 under mild conditions are known, with co-operativity between metal centres considered crucial for the N2 reduction step, the multimetallic species involved are usually not well defined, and further transformation of N2-binding complexes to achieve N-H or N-C bond formation is rare. Haber noted, before an iron-based catalyst was adopted for the industrial Haber-Bosch process, that uranium and uranium nitride materials are very effective heterogeneous catalysts for ammonia production from N2. However, few examples of uranium complexes binding N2 are known, and soluble uranium complexes capable of transforming N2 into ammonia or organonitrogen compounds have not yet been identified. Here we report the four-electron reduction of N2 under ambient conditions by a fully characterized complex with two UIII ions and three K+ centres held together by a nitride group and a flexible metalloligand framework. The addition of H2 and/or protons, or CO to the resulting complex results in the complete cleavage of N2 with concomitant N2 functionalization through N-H or N-C bond-forming reactions. These observations establish that a molecular uranium complex can promote the stoichiometric transformation of N2 into NH3 or cyanate, and that a flexible, electron-rich, multimetallic, nitride-bridged core unit is a promising starting point for the design of molecular complexes capable of cleaving and functionalizing N2 under

  2. Redox properties of biscyclopentadienyl uranium(V) imido-halide complexes: a relativistic DFT study.

    Science.gov (United States)

    Elkechai, Aziz; Kias, Farida; Talbi, Fazia; Boucekkine, Abdou

    2014-06-01

    Calculations of ionization energies (IE) and electron affinities (EA) of a series of biscyclopentadienyl imido-halide uranium(V) complexes Cp*2U(=N-2,6-(i)Pr2-C6H3)(X) with X =  F, Cl, Br, and I, related to the U(IV)/U(V) and U(V)/U(VI) redox systems, were carried out, for the first time, using density functional theory (DFT) in the framework of the relativistic zeroth order regular approximation (ZORA) coupled with the conductor-like screening model (COSMO) solvation approach. A very good linear correlation (R(2) =  0.993) was obtained, between calculated ionization energies at the ZORA/BP86/TZP level, and the experimental half-wave oxidation potentials E1/2. A similar linear correlation between the computed electron affinities and the electrochemical reduction U(IV)/U(III) potentials (R(2) =  0.996) is obtained. The importance of solvent effects and of spin-orbit coupling is definitively confirmed. The molecular orbital analysis underlines the crucial role played by the 5f orbitals of the central metal whereas the Nalewajski-Mrozek (N-M) bond indices explain well the bond distances variations following the redox processes. The IE variation of the complexes, i.e., IE(F) uranium charges and E1/2 in the reduction process of the U(V) species.

  3. Criticality analysis for mixed thorium-uranium fuel in the Angra-2 PWR reactor using KENO-VI

    Energy Technology Data Exchange (ETDEWEB)

    Wichrowski, Caio C.; Gonçalves, Isadora C.; Oliveira, Claudio L.; Vellozo, Sergio O.; Baptista, Camila O., E-mail: wichrowski@ime.eb.br, E-mail: isadora.goncalves@ime.eb.br, E-mail: d7luiz@yahoo.com.br, E-mail: vellozo@ime.eb.br, E-mail: camila.oliv.baptista@gmail.com [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Seção de Engenharia Nuclear

    2017-07-01

    The increasing energy demand associated to the current sustainability challenges have given the thorium nuclear fuel cycle renewed interest in the scientific community. Studies have focused on energy production in different reactor designs through the fission of uranium 233, the product of thorium fertilization by neutrons. In order to make it possible for near future applications a strategy based on the adaptation of current nuclear reactors for the use of thorium fuels is being considered. In this work, bearing in mind these limitations, a code was used to evaluate the effect on criticality (k{sub inf}) of the mixing of thorium and uranium in different proportions in the fuel of a PWR, the German designed Angra-2 Brazilian reactor in order to scrutinise its behaviour and determine the feasibility of an adapted ThO{sub 2}-UO{sub 2} mixed fuel cycle using current PWR technology. The analysis is performed using the KENO-VI module in the SCALE 6.1 nuclear safety analysis simulation code and the information is taken from the Angra-2 FSAR (Final Security Analysis Report). (author)

  4. Vibrational spectroscopy and structural analysis of complex uranium compounds (review)

    International Nuclear Information System (INIS)

    Umreiko, D.S.; Nikanovich, M.V.

    1985-01-01

    The paper reports on the combined application of experimental and theoretical methods of vibrational spectroscopy together with low-temperature luminescence data to determine the characteristic features of the formation and structure of complex systems, not only containing ligands directly coordinated to the CA uranium, but also associated with the extraspherical polyatomic electrically charged particles: organic cations. These include uranyl complexes and heterocyclical amines. Studied here were compounds of tetra-halouranylates with pyridine and its derivates, as well as dipyridyl, quinoline and phenanthroline. Structural schemes are also proposed for other uranyl complexes with protonated heterocyclical amines with a more complicated composition, which correctly reflect their spectroscopic properties

  5. Synthesis and reactivity of uranium (III) cyclopentadienyl complexes

    International Nuclear Information System (INIS)

    Foyentin, M.

    1987-01-01

    New uranium organometallic complexes are synthetized from the addition compound Cp U (THF). Reactions with lithium compounds, chlorides, alkynes and borohydrides. Oxidizing addition reactions are evidenced with alkyl halogenides. With a strong reducing agent, the complex Cp-UCH-Li allows the fixation and the reduction of nitrogen into ammonia. Lability of ligands bound to U (III) is evidenced, giving very reactive species and hence catalytic properties for these compounds. Catalytic hydrogenation of olefins is studied. Substitution reactions of alkyl groups of these complexes with olefins in presence or not of hydrogen or with alkyllithium are original [fr

  6. Combined use of flow cytometry and microscopy to study the interactions between the gram-negative betaproteobacterium Acidovorax facilis and uranium(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, U., E-mail: u.gerber@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden (Germany); Zirnstein, I. [Research Institute of Leather and Plastic Sheeting (FILK) gGmbH, Meissner Ring 1-5, 09599 Freiberg (Germany); Krawczyk-Bärsch, E. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden (Germany); Lünsdorf, H. [Helmholtz Centre for Infection Research, Central Facility for Microscopy, Inhoffenstr. 7, D-38124 Braunschweig (Germany); Arnold, T. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden (Germany); Merroun, M.L. [University of Granada, Department of Microbiology, Campus Fuentenueva, E-18071 Granada (Spain)

    2016-11-05

    Highlights: • Acidovorax facilis is able to remove 130 mg U/g dry biomass from solution. • Kinetically temperature-dependent uranium removal was studied. • Cell viability and metabolic activity was tested by flow cytometry. • Uranium was removed by active biosorption and passive bioaccumulation. - Abstract: The former uranium mine Königstein (Saxony, Germany) is currently in the process of remediation by means of controlled underground flooding. Nevertheless, the flooding water has to be cleaned up by a conventional wastewater treatment plant. In this study, the uranium(VI) removal and tolerance mechanisms of the gram-negative betaproteobacterium Acidovorax facilis were investigated by a multidisciplinary approach combining wet chemistry, flow cytometry, and microscopy. The kinetics of uranium removal and the corresponding mechanisms were investigated. The results showed a biphasic process of uranium removal characterized by a first phase where 95% of uranium was removed within the first 8 h followed by a second phase that reached equilibrium after 24 h. The bacterial cells displayed a total uranium removal capacity of 130 mg U/g dry biomass. The removal of uranium was also temperature-dependent, indicating that metabolic activity heavily influenced bacterial interactions with uranium. TEM analyses showed biosorption on the cell surface and intracellular accumulation of uranium. Uranium tolerance tests showed that A. facilis was able to withstand concentrations up to 0.1 mM. This work demonstrates that A. facilis is a suitable candidate for in situ bioremediation of flooding water in Königstein as well as for other contaminated waste waters.

  7. Molecular interactions of Leucoagaricus naucinus with uranium(VI) and europium(III)

    Energy Technology Data Exchange (ETDEWEB)

    Wollenberg, Anne; Raff, Johannes [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biogeochemistry; Guenther, A. [Helmholtz Institute Freiberg for Resource Technology, Freiberg (Germany)

    2017-06-01

    With regard to a molecular understanding of the interaction of fungal mycelium with radionuclides and its possible application for precautionary radiation protection and bio-remediation, the binding mechanism of the radionuclide uranium and the metal europium, as surrogate for trivalent actinides, where investigated with different starting conditions by the living fungal cells of Leucoagaricus naucinus.

  8. Molecular interactions of Leucoagaricus naucinus with uranium(VI) and europium(III)

    International Nuclear Information System (INIS)

    Wollenberg, Anne; Raff, Johannes

    2017-01-01

    With regard to a molecular understanding of the interaction of fungal mycelium with radionuclides and its possible application for precautionary radiation protection and bio-remediation, the binding mechanism of the radionuclide uranium and the metal europium, as surrogate for trivalent actinides, where investigated with different starting conditions by the living fungal cells of Leucoagaricus naucinus.

  9. Selective Adsorption of Uranium (VI) on NaHCO 3 Leached ...

    African Journals Online (AJOL)

    Ion imprinted nano-magnetic composite polymers for selective removal of hexavalent uranium were prepared by a precipitation polymerization technique in the presence of γ-methacryloxypropyltrimethoxysilane (γ-MPS) coated magnetite and other pre-polymerization reagents. The synthesized magnetic polymers were then ...

  10. Determination of small amounts of nitric acid in the presence of large amounts of uranium (VI) and extraction of nitric acid into TBP solutions highly loaded with uranyl nitrate

    International Nuclear Information System (INIS)

    Kolarik, Z.; Schuler, R.

    1982-10-01

    A new method for the determination of small amounts of nitric acid in the presence of large amounts of uranium(VI) was elaborated. The method is based on the precipitation of uranium(VI) as iodate and subsequent alkalimetric titration of the acid in the supernatant. The extraction of nitric acid and uranium(VI) with 30% TBP in dodecane was studied at high loading of the organic phase with uranyl nitrate and at 25, 40 and 60 0 C. The results are compared with available published data on the extraction of nitric acid under similar conditions. (orig.) [de

  11. Spectroscopic studies on U(VI)-salicylate complex formation with multiple equilibria

    Energy Technology Data Exchange (ETDEWEB)

    Cha, W.; Cho, H.R.; Jung, E.C.; Park, K.K.; Kim, W.H.; Song, K. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of). Nuclear Chemistry Research Div.

    2012-07-01

    This study investigates multiple equilibria related to the formation of the U(VI)-salicylate complex in a pH range of 3.0-5.5 using UV-Vis absorption and fluorescence measurement techniques. The absorbance changes at the characteristic charge-transfer bands of the complex were monitored, and the results indicated the presence of multiple equilibria and the formation of both 1:1 and 1:2 (U(VI):salicylate) complexes possessing bi-dentate chelate structures. The determined step-wise formation constants (log K{sub 1:1} and log K{sub 1:2}) are as follows: 12.5 {+-} 0.1 and 11.4 {+-} 0.2 for salicylate, 11.2 {+-} 0.1 and 10.1 {+-} 0.2 for 5-sulfosalicylate, and 12.4 {+-} 0.1 and 11.4 {+-} 0.1 for 2,6-dihydroxybenzoate, respectively. The molar absorptivities of the complexes are also provided. Furthermore, time-resolved laser-induced luminescence spectra of U(VI) species demonstrate the presence of both a dynamic and static quenching process upon the addition of a salicylate ligand. Particularly for the luminescent hydroxouranyl species, a strong static quenching effect is observed. The results suggest that both the UO{sub 2}(HSal){sup +} and the U(VI)-Sal chelate complexes serve as ground-state complexes that induce static quenching. The Stern-Volmer parameters were derived based on the measured luminescent intensity and lifetime data. The static quenching constants (log K{sub S}) obtained are 3.3 {+-} 0.1, 4.9 {+-} 0.1, and 4.4 {+-} 0.1 for UO{sub 2}{sup 2+}, (UO{sub 2}){sub 2}(OH){sub 2}{sup 2+} and (UO{sub 2}){sub 3}(OH){sub 5}{sup +}, respectively. (orig.)

  12. Spectroscopic studies on U(VI)-salicylate complex formation with multiple equilibria

    International Nuclear Information System (INIS)

    Cha, W.; Cho, H.R.; Jung, E.C.; Park, K.K.; Kim, W.H.; Song, K.

    2012-01-01

    This study investigates multiple equilibria related to the formation of the U(VI)-salicylate complex in a pH range of 3.0-5.5 using UV-Vis absorption and fluorescence measurement techniques. The absorbance changes at the characteristic charge-transfer bands of the complex were monitored, and the results indicated the presence of multiple equilibria and the formation of both 1:1 and 1:2 (U(VI):salicylate) complexes possessing bi-dentate chelate structures. The determined step-wise formation constants (log K 1:1 and log K 1:2 ) are as follows: 12.5 ± 0.1 and 11.4 ± 0.2 for salicylate, 11.2 ± 0.1 and 10.1 ± 0.2 for 5-sulfosalicylate, and 12.4 ± 0.1 and 11.4 ± 0.1 for 2,6-dihydroxybenzoate, respectively. The molar absorptivities of the complexes are also provided. Furthermore, time-resolved laser-induced luminescence spectra of U(VI) species demonstrate the presence of both a dynamic and static quenching process upon the addition of a salicylate ligand. Particularly for the luminescent hydroxouranyl species, a strong static quenching effect is observed. The results suggest that both the UO 2 (HSal) + and the U(VI)-Sal chelate complexes serve as ground-state complexes that induce static quenching. The Stern-Volmer parameters were derived based on the measured luminescent intensity and lifetime data. The static quenching constants (log K S ) obtained are 3.3 ± 0.1, 4.9 ± 0.1, and 4.4 ± 0.1 for UO 2 2+ , (UO 2 ) 2 (OH) 2 2+ and (UO 2 ) 3 (OH) 5 + , respectively. (orig.)

  13. Radioactive effluents, Portsmouth Uranium Enrichment Complex, calendar year 1983

    International Nuclear Information System (INIS)

    Acox, T.A.; Klein, L.S.

    1984-03-01

    Radioactive discharges from the Portsmouth Uranium Enrichment Complex are discussed and tabulated. Tables indicate both the location of the discharge and the nuclides discharged. Routine discharges for 1983 are well below the Radioactive Concentration Guide limits specified in DOE Order 5480.1, Chapter XI. There was, however, an unplanned release in December from the X-326 Building Side Purge which exceeded the limits. 1 figure

  14. Electrode Induced Removal and Recovery of Uranium (VI) from Acidic Subsurfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gregory, Kelvin [Carnegie Mellon University

    2013-08-12

    The overarching objective of this research is to provide an improved understanding of how aqueous geochemical conditions impact the removal of U and Tc from groundwater and how engineering design may be utilized to optimize removal of these radionuclides. Experiments were designed to address the unique conditions in Area 3 of ORNL while also providing broader insight into the geochemical effectors of the removal rates and extent for U and Tc. The specific tasks of this work were to: 1) quantify the impact of common aqueous geochemical and operational conditions on the rate and extent of U removal and recovery from water, 2) investigate the removal of Tc with polarized graphite electrode, and determine the influence of geochemical and operational conditions on Tc removal and recovery, 3) determine whether U and Tc may be treated simultaneous from Area 3 groundwater, and examine the bench-scale performance of electrode-based treatment, and 4) determine the capacity of graphite electrodes for U(VI) removal and develop a mathematical, kinetic model for the removal of U(VI) from aqueous solution. Overall the body of work suggests that an electrode-based approach for the remediation of acidic subsurface environments, such as those observed in Area 3 of ORNL may be successful for the removal for both U(VI) and Tc. Carbonaceous (graphite) electrode materials are likely to be the least costly means to maximize removal rates and efficiency by maximizing the electrode surface area.

  15. Determination of free acid in highly concentrated organic and aqueous solutions of plutonium (IV) and uranium (VI) nitrate

    International Nuclear Information System (INIS)

    Wagner, J.F.; Lacour, J.L.

    1989-01-01

    Free acidity is an important parameter in the nuclear reprocessing control. The accuracy on the determination of free acidity is not really required in the nuclear reprocessing control itself but is necessary for certain types of analysis such as spectrophotometry (Pu (VI), Am (III),...), density determinations. A new titripotentiometric method for free acidity determination in concentrated U(VI) and Pu(IV) solutions is presented. This method is based on the complexing properties of dipicolinic acid (pyridine 2.6 dicarboxylic acid) and medium effect with H 2 O/DMSO mixture. This method can be used either in organic or aqueous phases with ratio /H + I/ metal ≥ 5.10 -2 and a relative standard deviation of 1%

  16. Reactivity of nitrido complexes of ruthenium(VI), osmium(VI), and manganese(V) bearing Schiff base and simple anionic ligands.

    Science.gov (United States)

    Man, Wai-Lun; Lam, William W Y; Lau, Tai-Chu

    2014-02-18

    Nitrido complexes (M≡N) may be key intermediates in chemical and biological nitrogen fixation and serve as useful reagents for nitrogenation of organic compounds. Osmium(VI) nitrido complexes bearing 2,2':6',2″-terpyridine (terpy), 2,2'-bipyridine (bpy), or hydrotris(1-pyrazolyl)borate anion (Tp) ligands are highly electrophilic: they can react with a variety of nucleophiles to generate novel osmium(IV)/(V) complexes. This Account describes our recent results studying the reactivity of nitridocomplexes of ruthenium(VI), osmium(VI), and manganese(V) that bear Schiff bases and other simple anionic ligands. We demonstrate that these nitrido complexes exhibit rich chemical reactivity. They react with various nucleophiles, activate C-H bonds, undergo N···N coupling, catalyze the oxidation of organic compounds, and show anticancer activities. Ruthenium(VI) nitrido complexes bearing Schiff base ligands, such as [Ru(VI)(N)(salchda)(CH3OH)](+) (salchda = N,N'-bis(salicylidene)o-cyclohexyldiamine dianion), are highly electrophilic. This complex reacts readily at ambient conditions with a variety of nucleophiles at rates that are much faster than similar reactions using Os(VI)≡N. This complex also carries out unique reactions, including the direct aziridination of alkenes, C-H bond activation of alkanes and C-N bond cleavage of anilines. The addition of ligands such as pyridine can enhance the reactivity of [Ru(VI)(N)(salchda)(CH3OH)](+). Therefore researchers can tune the reactivity of Ru≡N by adding a ligand L trans to nitride: L-Ru≡N. Moreover, the addition of various nucleophiles (Nu) to Ru(VI)≡N initially generate the ruthenium(IV) imido species Ru(IV)-N(Nu), a new class of hydrogen-atom transfer (HAT) reagents. Nucleophiles also readily add to coordinated Schiff base ligands in Os(VI)≡N and Ru(VI)≡N complexes. These additions are often stereospecific, suggesting that the nitrido ligand has a directing effect on the incoming nucleophile. M≡N is also

  17. Mechanism of uranium(VI) uptake by Saccharomyces cerevisiae under environmentally relevant conditions: Batch, HRTEM, and FTIR studies

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xia, E-mail: lux2009@lzu.edu.cn; Zhou, Xiao-jiao; Wang, Tie-shan, E-mail: tswang@lzu.edu.cn

    2013-11-15

    Highlights: • Equilibrium reaches very rapid within 15 min. • pH shift towards neutral indicates release of hydroxyl ions. • High ionic strength inhabits biosorption capacity. • Uptake capacity of heat-killed cells is an order of magnitude higher than live one. • Electrostatic interaction, precipitation, and complexation are the main mechanisms. -- Abstract: Biosorption is of significance for the safety evaluation of high-level nuclear wastes repositories and remediation of radioactive contamination places. Quantitive study and structural characterization of uranium uptake by both live and heat-killed Saccharomyces cerevisiae at environmentally relevant uranium concentration and with different ionic strengths were carried out. Kinetic investigation showed the equilibrium reached within 15 min. In equilibrium studies, pH shift towards neutral indicated release of hydroxyl ions. pH was the most important factor, which partly affected electrostatic interaction between uranyl ions and S. cerevisiae surface. The high ionic strength inhibited biosorption capacity, which can be explained by a competitive reaction between sodium ions and uranyl ions. Heat killing process significantly enhanced biosorption capacity, showing an order of magnitude higher than that of live cells. High resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray (EDX) showed needle-like uranium-phosphate precipitation formed on the cell walls for both live and heat-killed cells. Besides, dark-field micrographs displayed considerable similar uranium-phosphate precipitation presented outside the heat-killed cells. The phosphate released during heat-killing process. FTIR illustrated function groups hydroxyl, carboxyl, phosphate, and amino groups played important role in complexation with uranium.

  18. Synthesis and reduction of uranium(V) imido complexes with redox-active substituents

    Energy Technology Data Exchange (ETDEWEB)

    Mullane, Kimberly C.; Carroll, Patrick J.; Schelter, Eric J. [P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA (United States)

    2017-04-27

    Organic azides that contain naphthyl functional groups were used to prepare uranium(V) imido complexes U{sup V}[=NC(2-naph)Ph{sub 2}][N(SiMe{sub 3}){sub 2}]{sub 3} (2), U{sup V}[=NC(2-naph){sub 3}][N(SiMe{sub 3}){sub 2}]{sub 3} (3), and U{sup V}[=N(2-naph)][N(SiMe{sub 3}){sub 2}]{sub 3} (4), and their properties were compared with U{sup V}[=NCPh{sub 3}][N(SiMe{sub 3}){sub 2}]{sub 3} (1). The electronic structures of these compounds were investigated by solution electrochemistry studies, which revealed accessible U{sup V/VI}, U{sup IV/V}, and naphthalene{sup 0}/naphthalene{sup -1} couples. The uranium(V) naphthylimido complexes were reduced by potassium graphite to yield their uranium(IV) congeners K[U{sup IV}[=NC(2-naph)Ph{sub 2}][N(SiMe{sub 3}){sub 2}]{sub 3}] (2-K), K[U{sup IV}[=NC(2-naph){sub 3}][N(SiMe{sub 3}){sub 2}]{sub 3}] (3-K), and K[U{sup IV}[=N(2-naph)][N(SiMe{sub 3}){sub 2}]{sub 3}] (4-K). The electronic structure of the dianionic compounds were investigated by DFT calculations, and this revealed that the second reduction was ligand-based, which opens the possibility of accomplishing multi-electron redox chemistry by using a tailored multiply-bonded ligand. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Silica fume effect on retention characteristics of portland cement for uranium (VI)

    International Nuclear Information System (INIS)

    Tan Hongbin; Ma Xiaoling; Li Yuxiang

    2005-01-01

    With simulated groundwater as leachant, the retention capabilities of the portland cement, which contains different amount of silica fume, are investigated under 25 degree C and 42 days. The results indicate that silica fume can improve the retention capabilities of portland cement for uranium. When the cement contains 15% silica fume, the diffusion coefficient is 7 x 10 -3 cm 3 · -1 . It is only 5.5% of the cement without containing fume. (authors)

  20. Surface complexation modeling of U(VI) adsorption by aquifer sediments from a former mill tailings site at Rifle, Colorado

    Science.gov (United States)

    Hyun, S.P.; Fox, P.M.; Davis, J.A.; Campbell, K.M.; Hayes, K.F.; Long, P.E.

    2009-01-01

    A study of U(VI) adsorption by aquifer sediment samples from a former uranium mill tailings site at Rifle, Colorado, was conducted under oxic conditions as a function of pH, U(VI), Ca, and dissolved carbonate concentration. Batch adsorption experiments were performed using tailings site at Naturita, Colorado, indicated that possible calcite nonequilibrium of dissolved calcium concentration should be evaluated. The modeling results also illustrate the importance of the range of data used in deriving the best fit model parameters. ?? 2009 American Chemical Society.

  1. Some organodioxygen complexes of molybdenum(VI), tungsten(VI), zinc(II) and cadmium(II) containing some monodentate and multidentate ligands

    International Nuclear Information System (INIS)

    Tarafder, M.T.H.; Leo Man Lin; Grouse, Karen A.; Mariotto, Gino

    2003-08-01

    Several novel organodioxygen complexes of the type [M(O)(O 2 ) 2 L](MMo(VI), W(VI)) and [M'(O 2 )L](M'= Cd(II) and Zn(II)) have been synthesized using monodentate, bidentate and tridentate ligands, L pyridine, picolinic acid, diethylenetriamine, 1,2-phenylenediamine, triphenylphosphine oxide. These complexes were characterized by elemental analyses, conductivity measurements, infrared, Raman spectral studies. For dioxygen complexes, the v(O=O) stretches of the superoxo moities were only Raman active, because of apparent linearity of the M-O 2 moieties, giving peaks at 1020-1030 cm -1 . The complexes were all thermodynamically stable. The dioxygen complexes containing bidentate co-ligands were found to show oxygen transfer reactions to various organic and inorganic substrates. Mechanisms have been postulated. (author)

  2. Formation and uranium explorating prospect of sub-volcanic granitic complex and rich uranium ore deposit in South China

    International Nuclear Information System (INIS)

    Wang Yusheng

    1997-01-01

    The rich uranium ore deposits are all closely related to tecto-magmatism of late-magmatic cycle whether volcanic types or granitic types in south China. Volcanic type rich uranium deposit has closely relationship with sub-volcanic activity, and granitic type rich uranium deposit is also closely related to mid-fine, unequal particle small massif in late main invasion stage. Based on characteristics of magmatism, we name the rock sub-volcanic granite complex, which is a unique style and closely related to the formation of rich uranium ore deposit

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

    Science.gov (United States)

    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.

  4. Persistent U(IV) and U(VI) following in-situ recovery (ISR) mining of a sandstone uranium deposit, Wyoming, USA

    Science.gov (United States)

    Gallegos, Tanya J.; Campbell, Kate M.; Zielinski, Robert A.; Reimus, P.W.; J.T. Clay,; N. Janot,; J. J. Bargar,; Benzel, William M.

    2015-01-01

    Drill-core samples from a sandstone-hosted uranium (U) deposit in Wyoming were characterized to determine the abundance and distribution of uranium following in-situ recovery (ISR) mining with oxygen- and carbon dioxide-enriched water. Concentrations of uranium, collected from ten depth intervals, ranged from 5 to 1920 ppm. A composite sample contained 750 ppm uranium with an average oxidation state of 54% U(VI) and 46% U(IV). Scanning electron microscopy (SEM) indicated rare high uranium (∼1000 ppm U) in spatial association with P/Ca and Si/O attributed to relict uranium minerals, possibly coffinite, uraninite, and autunite, trapped within low permeability layers bypassed during ISR mining. Fission track analysis revealed lower but still elevated concentrations of U in the clay/silica matrix and organic matter (several 10 s ppm) and yet higher concentrations associated with Fe-rich/S-poor sites, likely iron oxides, on altered chlorite or euhedral pyrite surfaces (but not on framboidal pyrite). Organic C (mining, the likely sequestration of uranium within labile iron oxides following mining and sensitivity to changes in redox conditions requires careful attention during groundwater restoration.

  5. Determination of the stability constants of uranium-tetracycline complexes

    International Nuclear Information System (INIS)

    Tarenzi, L.R.; Saiki, M.

    1983-01-01

    Stability constants of complexes formed with tetracycline (TC) and uranium have been determined by solvent extraction technique. The site on the tetracycline molecule at which uranyl ion may be bound has been studied by means of potentiometric titration and spectrophotometric techniques. The complex species with 1:1 and 1:2 for UO 2 : TC ratio have been identified by conductometric titration. Solvent extraction studies have also shown that the complexes are mononuclear of the type UO 2 (TC) sub (n) (n=1,2) and that no hidroxocomplexes or negatively charged complexes have been formed. Stability constant values have been calculated by numerical weighted least square method and by graphical methods of two parameters, of the average number of ligands and of the limiting value. (Author) [pt

  6. A mixed-valent uranium phosphonate framework containing U{sup IV}, U{sup V}, and U{sup VI}

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Lanhua; Zheng, Tao; Wang, Yaxing; Diwu, Juan; Chai, Zhifang; Wang, Shuao [School for Radiological and interdisciplinary Sciences (RAD-X), Soochow University, Suzhou (China); Collaborative Innovation Center of Radiation Medicine, Jiangsu Higher Education Institutions, Suzhou (China); Bao, Songsong; Zheng, Limin [State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University (China); Zhang, Linjuan; Wang, Jianqiang [Shanghai Institute of Applied Physics and, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Chinese Academy of Sciences, Shanghai (China); Liu, Hsin-Kuan [Department of Chemistry, National Central University, Jhongli (China); Albrecht-Schmitt, Thomas E. [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL (United States)

    2016-08-16

    It is shown that U{sup V}O{sub 2}{sup +} ions can reside at U{sup VI}O{sub 2}{sup 2+} lattice sites during mild reduction and crystallization process under solvothermal conditions, yielding a complicated and rare mixed-valent uranium phosphonate compound that simultaneously contains U{sup IV}, U{sup V}, and U{sup VI}. The presence of uranium with three oxidation states was confirmed by various characterization techniques, including X-ray crystallography, X-ray photoelectron, electron paramagnetic resonance, FTIR, UV/Vis-NIR absorption, and synchrotron radiation X-ray absorption spectroscopy, and magnetism measurements. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Analytical applications of N-phenyl-n-butyro hydroxamic and N-p-tolyl-n-butyro hydroxamic acids towards chromium (VI), copper (II), iron (III) and uranium (VI)

    International Nuclear Information System (INIS)

    Elkhadir, A. Y. F.

    2001-05-01

    Two aliphatic hydroxamic acids were prepared; N-phenyl-n-butyro hydroxamic acid and N-p-tolyl-n-butyro hydroxamic acid, by the reaction of β-phenylhydroxylamine and p-tolyl hydroxylamine with n-butyryl chloride. The acids were identified by: their melting points, characteristic reactions with acidic solutions of vanadium (V) and iron (III), infrared spectroscopy, nitrogen content and molecular weight determination. The extractability of these acids towards Cr (VI), Cu (II), Fe (III) and U (VI) were investigated at different pH values and molar acid concentrations. N-phenyl-n- butyro hydroxamic acid has a maximum extraction (98.80%) for Cr (VI) at 4 M H 2 SO 4 , (83.25%) for Cu (II) at pH 6, (99.17%) for Fe (III) at pH 5 and (99.76%) at 4 M HNO 3 for U (VI) respectively. N-p-tolyl-n-butyro hydroxamic acid has a maximum extraction (98.40%) for Cr (VI)at 4 M H 2 SO 4 , (81.30%) for Cu (II) at pH 6, (92.80%) for Fe (III) at pH 5 and (99.64%) for U (VI) at 4 M HNO 3 , respectively. The ratios of the metal to ligands were determined by job method (continuous variation method) and were found to be 1:2 for Cr (VI) and U (VI). (Author)

  8. Analytical applications of N-phenyl-n-butyro hydroxamic and N-p-tolyl-n-butyro hydroxamic acids towards chromium (VI), copper (II), iron (III) and uranium (VI)

    Energy Technology Data Exchange (ETDEWEB)

    Elkhadir, A Y. F. [Department of Chemistry, Faculty of Science, University of Khartoum, Khartoum (Sudan)

    2001-05-01

    Two aliphatic hydroxamic acids were prepared; N-phenyl-n-butyro hydroxamic acid and N-p-tolyl-n-butyro hydroxamic acid, by the reaction of {beta}-phenylhydroxylamine and p-tolyl hydroxylamine with n-butyryl chloride. The acids were identified by: their melting points, characteristic reactions with acidic solutions of vanadium (V) and iron (III), infrared spectroscopy, nitrogen content and molecular weight determination. The extractability of these acids towards Cr (VI), Cu (II), Fe (III) and U (VI) were investigated at different pH values and molar acid concentrations. N-phenyl-n- butyro hydroxamic acid has a maximum extraction (98.80%) for Cr (VI) at 4 M H{sub 2}SO{sub 4}, (83.25%) for Cu (II) at pH 6, (99.17%) for Fe (III) at pH 5 and (99.76%) at 4 M HNO{sub 3} for U (VI) respectively. N-p-tolyl-n-butyro hydroxamic acid has a maximum extraction (98.40%) for Cr (VI)at 4 M H{sub 2} SO{sub 4}, (81.30%) for Cu (II) at pH 6, (92.80%) for Fe (III) at pH 5 and (99.64%) for U (VI) at 4 M HNO{sub 3}, respectively. The ratios of the metal to ligands were determined by job method (continuous variation method) and were found to be 1:2 for Cr (VI) and U (VI). (Author)

  9. Thermodynamic parameters of the complexation of uranyl(VI) by diethylenetriamine in dimethyl sulfoxide

    International Nuclear Information System (INIS)

    Cassol, A.; Bernardo, P. di; Portanova, R.; Tolazzi, M.; Tomat, G.; Zanonato, P.L.

    1993-01-01

    The changes in free energy, enthalpy, and entropy for the complex formation reactions between uranyl(VI) ion and diethylenetriamine (dien) in dimethyl sulfoxide have been determined by potentiometric and calorimetric measurements at 25 C in a medium of ionic strength 0.1 mol dm -3 . The amine forms a very stable 1:1 complex which results stabilized only by the highly favourable enthalpy change. Entropy change is negative and opposes the reaction. The comparison of the thermodynamic data concerning complexation of uranyl(VI) by charged and uncharged ligands reveals that in this case (uncharged ligand) the enthalpy contribution is mainly related to the formation of the metal-ligand bonds while the entropy term might be associated with the decrease in the translational and conformational entropy occurring in the complexation of the ligand. FTIR and calorimetric measurements have been carried out to study the effect of traces of water on the equilibria in solution. It has been found that water can interfere in the complexation reaction giving rise to the formation of a dinuclear hydroxo complex in which probably two μ 2 -OH bridges link two monomer moieties. (orig.)

  10. The removal of uranium (VI) from aqueous solutions onto activated carbon developed from grinded used tire.

    Science.gov (United States)

    Belgacem, Ahmed; Rebiai, Rachid; Hadoun, Hocine; Khemaissia, Sihem; Belmedani, Mohamed

    2014-01-01

    In this study, activated carbon was prepared from waste tire by KOH chemical activation. The pore properties including the BET surface area, pore volume, pore size distribution, and average pore diameter were characterized. BET surface area of the activated carbon was determined as 558 m(2)/g. The adsorption of uranium ions from the aqueous solution using this activated carbon has been investigated. Various physico-chemical parameters such as pH, initial metal ion concentration, and adsorbent dosage level and equilibrium contact time were studied by a batch method. The optimum pH for adsorption was found to be 3. The removal efficiency has also been determined for the adsorption system as a function of initial concentration. The experimental results were fitted to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. A comparison of best-fitting was performed using the coefficient of correlation and the Langmuir isotherm was found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of uranium ions onto waste tire activated carbon was 158.73 mg/g. The thermodynamic equilibrium constant and the Gibbs free energy were determined and results indicated the spontaneous nature of the adsorption process. Kinetics data were best described by pseudo-second-order model.

  11. Electrochemical and spectroscopic studies of uranium(IV), -(V), and -(VI) in carbonate-bicarbonate buffers

    International Nuclear Information System (INIS)

    Wester, D.W.; Sullivan, J.C.

    1980-01-01

    Recently a need for more detailed knowledge of the chemistry of actinide ions in basic media has arisen in connection with deducing their chemistry in the environment. In this work the results of polarographic, cyclic voltammetric, and spectroscopic studies of U(IV), -(V), and -(VI) in carbonate and bicarbonate media are reported. Polarographic studies were in excellent agreement with those reported previously. Cyclic voltammetric scans confirmed the irreversible reduction to U(V) in both solutions, but disproportionation of the U(V) was observed only in the bicarbonate solutions. The oxidation of U(V) in carbonate was followed spectroscopically for the first time. Reduction in bicarbonate produced U(IV), the spectrum of which is now reported and the oxidation of which was also followed spectroscopically for the first time

  12. Tetra- and hexavalent uranium forms bidentate-mononuclear complexes with particulate organic matter in a naturally uranium-enriched peatland

    DEFF Research Database (Denmark)

    Mikutta, Christian; Langner, Peggy; Bargar, John R.

    2016-01-01

    Peatlands frequently serve as efficient biogeochemical traps for U. Mechanisms of U immobilization in these organic matter-dominated environments may encompass the precipitation of U-bearing mineral(oid)s and the complexation of U by a vast range of (in)organic surfaces. The objective of this work...... of bidentate-mononuclear U(IV/VI) complexes with carboxyl groups. We neither found evidence for U shells at ∼3.9 Å, indicative of mineral-associated U or multinuclear U(IV) species, nor for a substantial P/Fe coordination of U. Our data indicates that U(IV/VI) complexation by natural organic matter prevents...... the precipitation of U minerals as well as U complexation by Fe/Mn phases at our field site, and suggests that organically complexed U(IV) is formed via reduction of organic matter-bound U(VI)....

  13. Beryllium(II), manganese(II) and uranyl(VI)-salicylamide complexes

    Energy Technology Data Exchange (ETDEWEB)

    Maurya, P L; Agarwala, B V; Dey, A K [Allahabad Univ. (India)

    1977-01-01

    The preparation, composition, general properties and i.r. absorption spectra of the solid chelates formed by salicylamide with beryllium(II), manganese(II) and uranyl(VI) are described. The complexes have been synthesized by refluxing a mixture of ethanolic solutions of the reactants (metal:ligand :: 1:2) for several hours in the presence of alkali. Attempts to isolate the complexes by the interaction of ethanolic solutions of the metal salts and the ligand in the absence of alkali did not succeed.

  14. Synthesis and characterization of dioxouranium (VI) complexes of Schiff bases derived from isatin, isovanillin and o-vanillin

    International Nuclear Information System (INIS)

    Singh, Kavita; Agarwala, B.V.; Naganagowda, G.A.

    1996-01-01

    Three Schiff bases viz. isatin semicarbazone, isovanillin thiosemicarbazone, o-vanillin para-anisidine and their dioxouranium (VI) complexes have been synthesised and characterized by elemental analysis, IR and NMR spectral studies. (author). 19 refs., 1 tab

  15. Uranium hetero-bimetallic complexes: synthesis, structure and magnetic properties

    International Nuclear Information System (INIS)

    Le Borgne, Th.

    2000-01-01

    The aim of this thesis is to synthesize molecular complexes with uranium and transition metal ions in close proximity, to determine the nature of the magnetic interaction between them. We decided to use Schiff bases as assembling ligands, which are unusual for uranium (IV). Although the simplest Schiff bases, such as H 2 Salen, lead to ligand exchange reactions, the bi-compartmental Schiff base H 4 L 6 (bis(3-hydroxy-salicylidene) - 2,2-dimethyl-propylene) allows the crystal structure determination of the complex [L 6 Cu(pyr)]U[L 6 Cu].2pyr, obtained by reaction of the metallo-ligand H 2 L 6 Cu with U(acac) 4 . In this manner, the complexes [L 6 Co(pyr)] 2 U and [L 6 Ni(pyr)] 2 U.pyr were also isolated, as well as the compounds in which the paramagnetic ions have been exchanged by the diamagnetic ions Zn II , Zr IV and Th IV ': [L 6 Zn(pyr)] 2 U, [L 6 Cu] 2 Zr and [L 6 Cu(pyr)]Th[L 6 Cu].2pyr. These complexes are the first which involve three metallic centres assembling by the means of a hexa-dentate Schiff base. The crystalline structures show, for all these complexes, the outstanding orthogonal arrangement of the two fragments L 6 M around the central atom which is in a dodecahedral environment of eight oxygen atoms of two Schiff bases. The syntheses of the isostructural complexes Cu2 II and Zn 2 U in which the uranium (IV) ion is close, in the first one, to the paramagnetic ion Cu II and, in the second one, to the diamagnetic ion Zn II , has allowed the use of the empiric method to determine the nature of the magnetic interaction between an f element and a transition metal. The comparison of the magnetic behaviour of two complexes Cu 2 U and Zn 2 U, expressed by the variation of χT vs T, reveals the ferromagnetic interaction in the heart of the triad Cu-U-Cu. The magnetic behaviour of the complexes Cu 2 Th et Cu 2 Zr which does not show any coupling between the two copper (II) ions and the weak antiferromagnetic interaction in the Ni 2 U compound, favour the

  16. Crystal and molecular structure of dichlorodioxobis (triphenylphosphine oxide)uranium(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Bombieri, G; Forsellini, E [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi; Day, J P; Azeez, W I

    1978-01-01

    The crystal structure of (UO/sub 2/Cl/sub 2/(PPh/sub 3/O)/sub 2/) has been determined from three-dimensional X-ray diffraction data. Crystals are triclinic, space group P1, with a = 10.0101(6), b = 10.2589(9), c = 9.2347(8) A, ..cap alpha.. = 110.093(6). ..beta.. = 92.129(6), and ..gamma.. = 78.384(6), and Z = 1. The structure has been solved by the heavy-atom method from counter data, and refined by least squares to a final R of 0.054. The coordination polyhedron around uranium is a distorted octahedron, with a linear uranyl group (U-O 1.764A) perpendicular to a plane in which the two chloride and two oxide ions trans to each other occupy the corners of a rectangle (U-O 2.300; U-Cl 2.645 A).

  17. Quantifying differences in the impact of variable chemistry on equilibrium Uranium(VI) adsorption properties of aquifer sediments.

    Science.gov (United States)

    Stoliker, Deborah L; Kent, Douglas B; Zachara, John M

    2011-10-15

    Uranium adsorption-desorption on sediment samples collected from the Hanford 300-Area, Richland, WA varied extensively over a range of field-relevant chemical conditions, complicating assessment of possible differences in equilibrium adsorption properties. Adsorption equilibrium was achieved in 500-1000 h although dissolved uranium concentrations increased over thousands of hours owing to changes in aqueous chemical composition driven by sediment-water reactions. A nonelectrostatic surface complexation reaction, >SOH + UO₂²⁺ + 2CO₃²⁻ = >SOUO₂(CO₃HCO₃)²⁻, provided the best fit to experimental data for each sediment sample resulting in a range of conditional equilibrium constants (logK(c)) from 21.49 to 21.76. Potential differences in uranium adsorption properties could be assessed in plots based on the generalized mass-action expressions yielding linear trends displaced vertically by differences in logK(c) values. Using this approach, logK(c) values for seven sediment samples were not significantly different. However, a significant difference in adsorption properties between one sediment sample and the fines (< 0.063 mm) of another could be demonstrated despite the fines requiring a different reaction stoichiometry. Estimates of logK(c) uncertainty were improved by capturing all data points within experimental errors. The mass-action expression plots demonstrate that applying models outside the range of conditions used in model calibration greatly increases potential errors.

  18. Investigations on the elution behaviour of TOPO complexes of uranium and thorium using supercritical fluid chromatography

    International Nuclear Information System (INIS)

    Kumar, R.; Sivaraman, N.; Srinivasan, T.G.; Vasudeva Rao, P.R.

    2004-01-01

    In summary uranium and thorium could be separated by supercritical fluid chromatography technique as their TOPO complexes. The elution profiles with pre-complexation of the metal nitrate indicate a better separation than the in-situ complexation. The technique can also be employed for the assay of uranium and thorium at low levels

  19. Vibrational spectroscopy and structural analysis of uranium complexes

    Energy Technology Data Exchange (ETDEWEB)

    Umrejko, D.S.; Nikanovich, M.V.

    1984-12-01

    On the basis of experimental and theoretical studies of vibbrational spectra for halides, sulfates, phosphates, uranyl oxalates (and uranium) as well as for more complicated complex systems, reliable spectroscopic criteria have been established for estimation of their structural features by more simple and accessible (than direct) methods. Due to coordination to a central ion of U/sup 6/(U/sup 4/) ligands a geometry variation specific for each method of addition occurs and concomitant redistribution of the force interaction in the mentioned system as well, which directly affects the variation of their frequency characteristics and vibration modes. On this ground stable indications of particular types of coordination for mono- and polyatomic groups (including bridge-type, characteristic of polymetric structures) are pointed out in the IR absorption and Raman spectra. In the investigated structures the predominant effect of coordination on the spectral properties of complexes, as compared with other factors (for example, outer-sphere binding) is established. The presence of water molecules in an interlayer space does not tell essentially on the state of polyatomic ligands with all donor atoms bound with the uranium central atom (particularly, in binary uranyl phosphates). In the presence of free oxygen atoms the H/sub 2/O effect can lead only to some shift of the maxima of separate bands and their additional weak splitting (in uranyl sulfates).

  20. Characterizing particle-scale equilibrium adsorption and kinetics of uranium(VI) desorption from U-contaminated sediments

    Science.gov (United States)

    Stoliker, Deborah L.; Liu, Chongxuan; Kent, Douglas B.; Zachara, John M.

    2013-01-01

    Rates of U(VI) release from individual dry-sieved size fractions of a field-aggregated, field-contaminated composite sediment from the seasonally saturated lower vadose zone of the Hanford 300-Area were examined in flow-through reactors to maintain quasi-constant chemical conditions. The principal source of variability in equilibrium U(VI) adsorption properties of the various size fractions was the impact of variable chemistry on adsorption. This source of variability was represented using surface complexation models (SCMs) with different stoichiometric coefficients with respect to hydrogen ion and carbonate concentrations for the different size fractions. A reactive transport model incorporating equilibrium expressions for cation exchange and calcite dissolution, along with rate expressions for aerobic respiration and silica dissolution, described the temporal evolution of solute concentrations observed during the flow-through reactor experiments. Kinetic U(VI) desorption was well described using a multirate SCM with an assumed lognormal distribution for the mass-transfer rate coefficients. The estimated mean and standard deviation of the rate coefficients were the same for all Micropore volumes, assessed using t-plots to analyze N2 desorption data, were also the same for all dry-sieved micropore volumes and mass-transfer rate properties. Pore volumes for dry-sieved size fractions exceeded values for the corresponding wet-sieved fractions. We hypothesize that repeated field wetting and drying cycles lead to the formation of aggregates and/or coatings containing (micro)pore networks which provided an additional mass-transfer resistance over that associated with individual particles. The 2–8 mm fraction exhibited a larger average and standard deviation in the distribution of mass-transfer rate coefficients, possibly caused by the abundance of microporous basaltic rock fragments.

  1. Magnetic resonance as a structural probe of a uranium (VI) sol-gel process

    International Nuclear Information System (INIS)

    King, C.M.; Thompson, M.C.; Buchanan, B.R.; King, R.B.; Garber, A.R.

    1989-01-01

    NMR investigations on the ORNL process for sol-gel synthesis of microspherical nuclear fuel (UO 2 ), has been useful in sorting out the chemical mechanism in the sol-gel steps. 13 C, 15 N, and 1 H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C 6 H l2 N 4 ) has revealed near quantitative stability of this adamantane-like compound in the sol-Gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. 17 0 NMR of uranyl (UO 2 ++ ) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, [(UO 2 ) 3 (μ 3 -O)(μ 2 -OH) 3 ] + , induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results show that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH + is occluded as an ''intercalation'' cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ ion exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH 4 ) 2 [(UO 2 ) 8 O 4 (OH) 10 ] · 8H 2 0. This compound is the precursor to sintered U0 2 ceramic fuel

  2. Kinetic analysis and modeling of oleate and ethanol stimulated uranium (VI) bio-reduction in contaminated sediments under sulfate reduction conditions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Fan, E-mail: zhangfan@itpcas.ac.cn [Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China); Wu Weimin [Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305 (United States); Parker, Jack C. [Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Mehlhorn, Tonia [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Kelly, Shelly D.; Kemner, Kenneth M. [Biosciences Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Zhang, Gengxin [Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China); Schadt, Christopher; Brooks, Scott C. [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Criddle, Craig S. [Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305 (United States); Watson, David B. [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Jardine, Philip M. [Biosystems Engineering and Soil Science Department, University of Tennessee, Knoxville, TN 37996 (United States)

    2010-11-15

    Microcosm tests with uranium contaminated sediments were performed to explore the feasibility of using oleate as a slow-release electron donor for U(VI) reduction in comparison to ethanol. Oleate degradation proceeded more slowly than ethanol with acetate produced as an intermediate for both electron donors under a range of initial sulfate concentrations. A kinetic microbial reduction model was developed and implemented to describe and compare the reduction of sulfate and U(VI) with oleate or ethanol. The reaction path model considers detailed oleate/ethanol degradation and the production and consumption of intermediates, acetate and hydrogen. Although significant assumptions are made, the model tracked the major trend of sulfate and U(VI) reduction and describes the successive production and consumption of acetate, concurrent with microbial reduction of aqueous sulfate and U(VI) species. The model results imply that the overall rate of U(VI) bioreduction is influenced by both the degradation rate of organic substrates and consumption rate of intermediate products.

  3. Kinetic analysis and modeling of oleate and ethanol stimulated uranium (VI) bio-reduction in contaminated sediments under sulfate reduction conditions

    International Nuclear Information System (INIS)

    Zhang Fan; Wu Weimin; Parker, Jack C.; Mehlhorn, Tonia; Kelly, Shelly D.; Kemner, Kenneth M.; Zhang, Gengxin; Schadt, Christopher; Brooks, Scott C.; Criddle, Craig S.; Watson, David B.; Jardine, Philip M.

    2010-01-01

    Microcosm tests with uranium contaminated sediments were performed to explore the feasibility of using oleate as a slow-release electron donor for U(VI) reduction in comparison to ethanol. Oleate degradation proceeded more slowly than ethanol with acetate produced as an intermediate for both electron donors under a range of initial sulfate concentrations. A kinetic microbial reduction model was developed and implemented to describe and compare the reduction of sulfate and U(VI) with oleate or ethanol. The reaction path model considers detailed oleate/ethanol degradation and the production and consumption of intermediates, acetate and hydrogen. Although significant assumptions are made, the model tracked the major trend of sulfate and U(VI) reduction and describes the successive production and consumption of acetate, concurrent with microbial reduction of aqueous sulfate and U(VI) species. The model results imply that the overall rate of U(VI) bioreduction is influenced by both the degradation rate of organic substrates and consumption rate of intermediate products.

  4. The effect of symmetry on the U L3 NEXAFS of octahedral coordinated uranium(vi)

    Energy Technology Data Exchange (ETDEWEB)

    Bagus, Paul S. [Department of Chemistry, University of North Texas, Denton, Texas 76203-5017, USA; Nelin, Connie J. [Consultant, Austin, Texas 78730, USA; Ilton, Eugene S. [Pacific Northwest National Laboratory, Richland, Washington 99352, USA

    2017-03-21

    We describe a detailed theoretical analysis of how distortions from ideal cubic or Oh symmetry affect the shape, in particular the width, of the U L3-edge NEXAFS for U(VI) in octahedral coordination. The full-width-half-maximum (FWHM) of the L3-edge white line decreases with increasing distortion from Oh symmetry due to the mixing of symmetry broken t2g and eg components of the excited state U(6d) orbitals. The mixing is allowed because of spin-orbit splitting of the ligand field split 6d orbitals. Especially for higher distortions, it is possible to identify a mixing between one of the t2g and one of the eg components, allowed in the double group representation when the spin-orbit interaction is taken into account. This mixing strongly reduces the ligand field splitting, which, in turn, leads to a narrowing of the U L3 white line. However, the effect of this mixing is partially offset by an increase in the covalent anti-bonding character of the highest energy spin-orbit split eg orbital. At higher distortions, mixing overwhelms the increasing anti-bonding character of this orbital which leads to an accelerated decrease in the FWHM with increasing distortion. Additional evidence for the effect of mixing of t2g and eg components is that the FWHM of the white line narrows whether the two axial U-O bond distances shorten or lengthen. Our ab initio theory uses relativistic wavefunctions for cluster models of the structures; empirical or semi-empirical parameters were not used to adjust prediction to experiment. A major advantage is that it provides a transparent approach for determining how the character and extent of the covalent mixing of the relevant U and O orbitals affect the U L3-edge white line.

  5. Uranyl(VI) and lanthanum(III) complexes with functionalized macrocyclic and macroacyclic Schiff bases

    International Nuclear Information System (INIS)

    Aguiari, A.; Brianese, N.; Tamburini, S.; Vigato, P.A.

    1995-01-01

    Acyclic Schiff bases have been prepared by [2 + 1] condensation of 2,6-diformyl-4-chlorophenol and H 2 NCH 2 [CH 2 XCH 2 ] n CH 2 NH 2 (n =3D 0 H 2 -I; X =3D NH, S, O n =3D 1 H 2 -II...H 2 -IV; X =3D 0 n =3D 2 H 2 -V; X =3D 0 n =3D 3 H 2 -VI). The related uranlyl(VI) and lanthanum (III) complexes have bee synthesized by reaction by reaction of the preformed ligands with the appropriate salt or by the template procedure, in the presence of base. No base was employed in the preparation of lanthanum (III) complexes, La(H 2 -II)(NO 3 ) 3 , La(H 2 -IV)(NO 3 ) 3 where the Schiff bases coordinate as neutral chelate ligands. These acyclic complexes have been used for further condensation, and symmetric and asymmetric cyclic complexes have been obtained by their reaction with the polyamines H 2 NCH 2 [CH 2 XCH 2 ]nCH 2 NH 2 or with 4,4'-diaminodibenzo -18-crown-6. By reaction with 4-aminobenzo-15-crown-5 or 2-amino-methyl-15-crown-5, the same acyclic complexes give rise to functionalized complexes bearing crown-ether moieties. Analogously, the acyclic ligand H 3 -IXX, prepared by condensation of 2,6 diformyl-4-chlorophenol and tris(aminoethyl)amine, forms mono and homodinuclear lanthanum (III) complexes, which may undergo further condensation when reacted with primary functionalized amines. (authors). 42 refs., 2 figs., 2 schemes, 1 tab

  6. Temperature and ionic strength influences on actinide(VI)/(V) redox potentials for carbonate limiting complexes

    International Nuclear Information System (INIS)

    Capdevila, H.; Vitorge, P.

    1998-01-01

    Actinide behaviour was studied in two limiting aqueous solutions: acidic and carbonate. Cyclic voltametry was validated with well-known U redox system. SIT was used to account for I influence. Taylor's series expansions to the second order were used to account for T influence. Redox potentials of actinide couples had previously been measured in non complexing media. The above data treatments give standard values for redox potential E 0 , for the corresponding entropy ΔS 0 , enthalpy ΔH 0 and heat capacity ΔC p 0 changes, and also for the corresponding excess values (i.e. the variation of these thermodynamic constants with ionic strength). This methodology was here used in carbonate media to measure the potential of the redox couple PuO 2 (CO 3 ) 3 4- /PuO 2 (CO 3 ) 3 5- from 5 to 70 degC and from I = 0.5 to 4.5 M in Na 2 CO 3 , NaClO 4 media. Experimental details and full results are given for Pu. Only final results are given for Np. Previous and/or published data for U and Am are discussed. E and ΔS variations with T or I were enough to be measured. The values obtained for the fitted SIT coefficients Δε, and for ΔS and ΔCp are similar for U, Np and Pu redox reactions. Using this analogy for Am missing data is discussed. β 3 V /β 3 VI formation constant ratio of the carbonate limiting complexes were deduced from the potential shift from complexing to non complexing media for the Actinide(VI)/Actinide(V) redox couples. β 3 V (U and Pu) and β 3 VI (Np) were finally proposed using published β3 VI (U and Pu) and β 3 V (Np). For Am, this data treatment was used to discuss the AmO 2 2+ / AmO 2 + redox potential

  7. Studies on 4-[N-(furfural) amino] antipyrine complexes of thorium (IV) and dioxouranium (VI)

    International Nuclear Information System (INIS)

    Agarwal, R.K.; Arora, Kishore; Dutt, Prashant

    1997-01-01

    Thorium (IV) and dioxouranium (VI) complexes of Schiff base 4-[N-(furfural) amino] antipyrine (FFAP) derived from furfural and 4-aminoantipyrine having general composition ThX 4 .nL (X = Cl - , Br - , NCS - or NO 3 - , n = 2; x = I - or ClO 4 - n = 3, L = FFAP) and UO 2 X 2. nL (X Br - , I - , NCS - ,NO 3 - or CH 3 COO - , n = 2; X = ClO 4 - n = 3, L = FFAP) have been synthesized and characterized by molecular weight, conductivity, IR spectral and thermoanalytical studies. (author)

  8. Exploring the Interaction Natures in Plutonyl (VI Complexes with Topological Analyses of Electron Density

    Directory of Open Access Journals (Sweden)

    Jiguang Du

    2016-04-01

    Full Text Available The interaction natures between Pu and different ligands in several plutonyl (VI complexes are investigated by performing topological analyses of electron density. The geometrical structures in both gaseous and aqueous phases are obtained with B3LYP functional, and are generally in agreement with available theoretical and experimental results when combined with all-electron segmented all-electron relativistic contracted (SARC basis set. The Pu– O y l bond orders show significant linear dependence on bond length and the charge of oxygen atoms in plutonyl moiety. The closed-shell interactions were identified for Pu-Ligand bonds in most complexes with quantum theory of atoms in molecules (QTAIM analyses. Meanwhile, we found that some Pu–Ligand bonds, like Pu–OH−, show weak covalent. The interactive nature of Pu–ligand bonds were revealed based on the interaction quantum atom (IQA energy decomposition approach, and our results indicate that all Pu–Ligand interactions is dominated by the electrostatic attraction interaction as expected. Meanwhile it is also important to note that the quantum mechanical exchange-correlation contributions can not be ignored. By means of the non-covalent interaction (NCI approach it has been found that some weak and repulsion interactions existed in plutonyl(VI complexes, which can not be distinguished by QTAIM, can be successfully identified.

  9. Aspartic acid complexation of Am(III) and U(VI)

    International Nuclear Information System (INIS)

    Saito, A.; Choppin, G.R.

    1984-01-01

    Stability constants of Am(III) and U(VI) with L-aspartic acid have been determined at pH 8.00 by means of the solvent extraction technique. It was found that Am(III) forms 1:1 and 1:2 complexes while U(VI) formed only the 1:1 complex under these conditions. The stability constants were: Am +3 : I = 0.10 M; log β 1 = 4.81 +- 0.03, log β 2 = 6.75 +- 0.03 I = 0.70 M; log β 1 = 4.53 +- 0.08 log β 2 = 6.65 +- 0.06 UO +2 2 : I = 0.70 M; log β 1 = 3.32 +- 0.04. Comparison of these stability constants with corresponding values of some dicarboxylate ligands suggests that at pH 8 the binding of Am +3 and UO +2 2 involves both carboxylates. In the Am-aspartate complex, the data indicate the possibility of weak interaction between the Am +3 and the amino group. (orig.)

  10. Surface complexation models for uranium adsorption in the sub-surface environment

    International Nuclear Information System (INIS)

    Payne, T.E.

    2007-01-01

    Adsorption experiments with soil component minerals under a range of conditions are being used to develop models of uranium(VI) uptake in the sub-surface environment. The results show that adsorption of U on iron oxides and clay minerals is influenced by chemical factors including the pH, partial pressure of CO 2 , and the presence of ligands such as phosphate. Surface complexation models (SCMs) can be used to simulate U adsorption on these minerals. The SCMs are based on plausible mechanistic assumptions and describe the experimental data more adequately than Kd values or sorption isotherms. It is conceptually possible to simulate U sorption data on complex natural samples by combining SCMs for individual component minerals. This approach was used to develop a SCM for U adsorption to mineral assemblages from Koongarra (Australia), and produced a reasonable description of U uptake. In order to assess the applicability of experimental data to the field situation, in-situ measurements of U distributions between solid and liquid phases were undertaken at the Koongarra U deposit. This field partitioning data showed a satisfactory agreement with laboratory sorption data obtained under comparable conditions. (author)

  11. Controlled thermolysis of uranium (alkoxy)siloxy complexes. A route to polymetallic complexes of low-valent uranium

    Energy Technology Data Exchange (ETDEWEB)

    Camp, Clement; Pecaut, Jacques; Mazzanti, Marinella [CEA-Grenoble (France). Lab. de Reconnaissance Ionique et Chimie de Coordination; Kefalidis, Christos E.; Maron, Laurent [Toulouse Univ. (France). LPCNO, CNRS et INSA, UPS

    2013-11-25

    Decomposition into higher species: Intramolecular U{sup III}-mediated homolytic C-O bond cleavage in U{sup III} (alkoxy)siloxy complexes at low temperature and subsequent reduction with KC{sub 8} led to unprecedented polymetallic complexes containing siloxy, silanediolate, and silanetriolate ligands (see example: U green, Si yellow, K blue, O red). Such compounds may be useful precursors to uranium ceramics relevant for catalysis and the storage of spent nuclear fuel. [German] Zerfall in hoehere Spezies: Die intramolekulare U{sup III}-vermittelte homolytische C-O-Spaltung in U{sup III}-(Alkoxy)siloxy-Komplexen bei tiefer Temperatur mit nachfolgender Reduktion mit KC{sub 8} fuehrte zu ungewoehnlichen Polymetallkomplexen mit Siloxy-, Silandiolat- und Silantriolatliganden (siehe Beispiel: U gruen, Si gelb, K blau, O rot). Solche Verbindungen sind nuetzliche Vorstufen von Urankeramiken, die fuer die Katalyse und fuer die Speicherung verbrauchter Kernbrennstoffe wichtig sind.

  12. Uranium mill tailings neutralization: contaminant complexation and tailings leaching studies

    International Nuclear Information System (INIS)

    Opitz, B.E.; Dodson, M.E.; Serne, R.J.

    1985-05-01

    Laboratory experiments were performed to compare the effectiveness of limestone (CaCO 3 ) and hydrated lime [Ca(OH) 2 ] for improving waste water quality through the neutralization of acidic uranium mill tailings liquor. The experiments were designed to also assess the effects of three proposed mechanisms - carbonate complexation, elevated pH, and colloidal particle adsorption - on the solubility of toxic contaminants found in a typical uranium mill waste solution. Of special interest were the effects each of these possible mechanisms had on the solution concentrations of trace metals such as Cd, Co, Mo, Zn, and U after neutralization. Results indicated that the neutralization of acidic tailings to a pH of 7.3 using hydrated lime provided the highest overall waste water quality. Both the presence of a carbonate source or elevating solution pH beyond pH = 7.3 resulted in a lowering of previously achieved water quality, while adsorption of contaminants onto colloidal particles was not found to affect the solution concentration of any constituent investigated. 24 refs., 8 figs., 19 tabs

  13. Coordination phenomena of cationic uranium(iv) complexes

    International Nuclear Information System (INIS)

    Rohwer, H.E.

    1974-12-01

    The coordination properties of the cationic uranium(IV) complexes UCl 3 + , UCl 2 2+ , UCl 3+ , and U 4+ were studied in a non-aqueous medium in the presence of perchlorate as counterion which, however, proved to coordinate to a much greater extent than expected. The strong neutral ligand, HMPA, could successively displace some of the perchlorates. An electrostatic model for the U(CIO 4 ) 4 -HMPA-acetone system compared favourably with the actual results. This emphasized the high ionic content in the bonding with actenoid cations, even with such a high charge as +4 . These conclusions are in agreement with studies 75 in which nitrate acts as counter ion. Correspondingly the uranium (IV) chemistry is characterized by the absence of typical 3d-organometallic chemistry, for example, strong bonding with CO, P(Phi) 3 etc, which strongly depends on covalent bonding. This stresses the fact that the d and f orbitals are not readily available for strong bond formation with the actenoids. 76

  14. Uranium speciation in plants

    International Nuclear Information System (INIS)

    Guenther, A.; Bernhard, G.; Geipel, G.; Reich, T.; Rossberg, A.; Nitsche, H.

    2003-01-01

    Detailed knowledge of the nature of uranium complexes formed after the uptake by plants is an essential prerequisite to describe the migration behavior of uranium in the environment. This study focuses on the determination of uranium speciation after uptake of uranium by lupine plants. For the first time, time-resolved laser-induced fluorescence spectroscopy and X-ray absorption spectroscopy were used to determine the chemical speciation of uranium in plants. Differences were detected between the uranium speciation in the initial solution (hydroponic solution and pore water of soil) and inside the lupine plants. The oxidation state of uranium did not change and remained hexavalent after it was taken up by the lupine plants. The chemical speciation of uranium was identical in the roots, shoot axis, and leaves and was independent of the uranium speciation in the uptake solution. The results indicate that the uranium is predominantly bound as uranyl(VI) phosphate to the phosphoryl groups. Dandelions and lamb's lettuce showed uranium speciation identical to lupine plants. (orig.)

  15. Bioprospecting of gum kondagogu (Cochlospermum gossypium) for bioremediation of uranium (VI) from aqueous solution and synthetic nuclear power reactor effluents

    International Nuclear Information System (INIS)

    Sashidhar, R.B.; Selvi, S. Kalaignana; Vinod, V.T.P.; Kosuri, Tanuja; Raju, D.; Karuna, R.

    2015-01-01

    An ecofriendly green chemistry method using a natural biopolymer, Gum Kondagogu (GK) for the removal of U (VI) from aqueous, simulated nuclear effluents was studied. The adsorption characteristic of GK towards U (VI) from aqueous solution was studied at varied pH, contact time, adsorbent dose, initial U (VI) concentration and temperature using UV–Visible spectroscopy and ICP-MS. Maximum adsorption was seen at pH 4, 0.1% GK with 60 min contact time at room temperature. The GK- U (VI) composite was characterized by FT-IR, zeta potential, TEM and SEM-EDAX. The Langmuir isotherm was found to be 487 mg of U (VI) g −1 of GK. The adsorption capacity and (%) of U (VI) was found to be 490 ± 5.4 mg g −1 and 98.5%. Moreover adsorption of U (VI) by GK was not influenced by other cations present in the simulated effluents. The adsorbed U (VI) was efficiently stripped from composite using 1 M HCl. - Highlights: • An eco-friendly method for removal of U (VI) from simulated nuclear effluents by Gum Kondagogu. • The Langmuir and Freundlich isotherm indicated favourable adsorption. • The adsorption (%) of U (VI) by GK was found to be 98.5%. • Desorption studies on biosorbed metal ions showed that HCl was a good eluent

  16. U uranium. Suppl. Vol. D3

    International Nuclear Information System (INIS)

    Haug, H.O.

    1982-01-01

    This volume of the uranium series of the Gmelin handbook deals with the anion exchange of uranium. Compounds of the valence states of III, IV, V and VI of uranium in halide, nitrate, sulfate, phosphate, and carbonate media as well as in media containing organic complexing agents are treated. The literature cited covers the period from about 1947 to the end of 1980. (RB) [de

  17. Uranium

    International Nuclear Information System (INIS)

    Cuney, M.; Pagel, M.; Leroy, J.

    1992-01-01

    First, this book presents the physico-chemical properties of Uranium and the consequences which can be deduced from the study of numerous geological process. The authors describe natural distribution of Uranium at different scales and on different supports, and main Uranium minerals. A great place in the book is assigned to description and classification of uranium deposits. The book gives also notions on prospection and exploitation of uranium deposits. Historical aspects of Uranium economical development (Uranium resources, production, supply and demand, operating costs) are given in the last chapter. 7 refs., 17 figs

  18. Bis-phosphonate sequestering agents. Synthesis and preliminary evaluation for in vitro and in vivo uranium(VI) chelation

    Energy Technology Data Exchange (ETDEWEB)

    Sawicki, M.; Lecercle, D.; Taran, F. [CEA Saclay, IBiTecS, Serv Chim Bioorgan et Marquage, F-91191 Gif Sur Yvette (France); Grillon, G.; Le Gall, B.; Serandour, A.L.; Poncy, J.L. [CEA, DSV, DRR, Lab Radiotoxicol, F-91680 Bruyeres Le Chatel (France); Bailly, T.; Burgada, R.; Lecouvey, M.; Challeix, V. [CNRS, Lab Chim Struct Biomol, UMR 7033, F-93017 Bobigny (France); Leydier, A.; Pellet-Rostaing, S. [Univ Lyon 1, ICBMS, UMR 5246, Lab Catalyse et Synth Organ, F-69622 Villeurbanne (France); Ansoborlo, E. [CEA, DEN, DRCP, CETAMA, VRH Marcoule, F-30207 Bagnols Sur Ceze (France)

    2008-07-01

    A library of bis-phosphonate-based ligands was prepared using solution-phase parallel synthesis and tested for its uranium-binding properties. With the help of a screening method, based on a chromo-phoric complex displacement procedure, 23 dipodal and tripodal chelates bearing bis-phosphonate chelating functions were found to display very high affinity for the uranyl ion and were selected for evaluation of their in vivo uranyl-removal efficacy. Among them, 11 ligands induced a huge modification of the uranyl biodistribution by deviating the metal from kidney and bones to liver. Among the other ligands, the most potent was the dipodal bis-phosphonate 3C which reduced the retention of uranyl and increased its excretion by around 10% of the injected metal. (authors)

  19. Spectroscopic properties and antimicrobial activity of dioxomolybdenum(VI complexes with heterocyclic S,S’-ligands

    Directory of Open Access Journals (Sweden)

    Sovilj Sofija P.

    2012-01-01

    Full Text Available Five new dioxomolybdenum(VI complexes of the general formula[MoO2(Rdtc2], 1-5, where Rdtc-refer to piperidine- (Pipdtc, 4-morpholine-(Morphdtc, 4-thiomorpholine-(Timdtc, piperazine- (Pzdtc or Nmethylpiperazine- (N-Mepzdtc dithiocarbamates, respectively, have been prepared. Elemental analysis, conductometric measurements, electronic, IR and NMR spectroscopy have been employed to characterize them. Complexes 1-5 contain a cis-MoO2 group and are of an octahedral geometry. Two dithiocarbamato ions join as bidentates with both the sulphur atoms to the molybdenum atom. The presence of different heteroatom in the piperidinо moiety influences the v(C----N and v(C----S vibrations, which decrease in the order of the complexes with: Pipdtc > N-Mepipdtc > Morphdtc > Pzdtc > Timdtc ligands. On the basis of spectral data, molecular structures of complexes 1-5 were optimized on semiempirical molecular-orbital level, and the geometries, as obtained from calculations, described. Antimicrobial activity was tested against nine different laboratory control strains of bacteria and two strains of yeast Candida albicans. All tested strains were sensitive. Complexes bearing heteroatom in position 4 of piperidine moiety are significantly more potent against bacteria tested comparing to corresponding ligands.

  20. Synthesis of xanthate functionalized silica gel and its application for the preconcentration and separation of uranium(VI) from inorganic components

    International Nuclear Information System (INIS)

    Gopi Krishna, P.; Naidu, G.R.K.; Rao, K.S.

    2005-01-01

    A new chelating solid extractant prepared by the chemical immobilization of xanthate on silica gel was characterized by Fourier transform infra red spectrometry (FTIR), thermogravimetric analysis (TGA) and microanalysis and used for the preconcentration and separation of uranyl ion prior to its determination by Arsenazo-III. The effect of pH, weight of the solid extractant, volume of the aqueous phase and the interference of neutral electrolytes, cations and anions on the determination of uranium, have been studied in detail to optimize the conditions for trace determination of uranium(VI). The accuracy of the developed procedure was tested by analyzing marine sediment (MESS-3) and soil (IAEA-SOIL-7) reference materials. The results obtained on analysis of soil and sediment samples are comparable to standard ICP-MS values. (author)

  1. Reactivity of uranium(IV) bridged chalcogenido complexes UIV–E–UIV (E = S, Se) with elemental sulfur and selenium: synthesis of polychalcogenido-bridged uranium complexes

    OpenAIRE

    Franke, Sebastian M.; Heinemann, Frank W.; Meyer, Karsten

    2014-01-01

    We report the syntheses, electronic properties, and molecular structures of a series of polychalcogenido-bridged dinuclear uranium species. These complexes are supported by the sterically encumbering but highly flexible, single N-anchored tris(aryloxide) chelator (AdArO)3N3−. Reaction of an appropriate uranium precursor, either the U(III) starting material, [((AdArO)3N)U(DME)], or the dinuclear mono-chalcogenido-bridged uranium(IV/IV) compounds [{((AdArO)3N)U(DME)}2(μ-E)] (E = S, Se), with el...

  2. Phosphorus-modified poly(styrene-co-divinylbenzene)–PAMAM chelating resin for the adsorption of uranium(VI) in aqueous

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qiong [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Liu, Yaochi, E-mail: liuyaochi72@163.com [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Wang, Chunzhi [Baling Company, China Petroleum and Chemical Corporation (China); Cheng, Jiashun [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)

    2013-12-15

    Highlights: • A series of phosphorus-modified poly(styrene-co-divinylbenzene)–PAMAM chelating resins were synthesized. • The materials were commercially available and economic. • The new resins were high effective and selective adsorbents. • U(VI) adsorption is fitted with pseudo-second-order equation and Langmuir model. • The new resins can be regenerated. -- Abstract: Polyamidoamine (PAMAM) modified poly(styrene-co-divinylbenzene) absorbents carrying phosphorus functional groups (PS-PAMAM-PPA) were prepared and used as adsorbents for the adsorption of uranium(VI) from aqueous solution. Different generations of PAMAM were used for obtaining different chelating resins, PS-PPA, PS-1.0G PAMAM-PPA, PS-2.0G PAMAM-PPA, PS-3.0G PAMAM-PPA and PS-4.0G PAMAM-PPA. The synthesized resins were characterized by FTIR and XPS. The effects of many physio-chemical properties on metal ion adsorption to adsorbent phase, such as solution pH, kinetic studies, initial uranium concentration, temperature, were investigated using batch method. The results showed that the maximum adsorption capacity (99.89 mg/g) was observed at the pH 5.0 and 25 °C with initial U(VI) concentration 100 mg/L and adsorbent dose 1 g/L. PS-1.0G PAMAM-PPA had the largest adsorption capacity for U(VI) compared with other prepared adsorbents. The adsorption kinetics of U(VI) onto PS-1.0G PAMAM-PPA followed the mechanism of the pseudo-second-order equation, indicating that the chemical adsorption was a rate-limiting step. The calculated thermodynamic parameters (ΔG, ΔH, ΔS) stated that the adsorption of U(VI) onto PS-1.0G PAMAM-PPA were spontaneous, endothermic and feasible. The adsorption isotherms obeyed the Langmuir isotherm models. The desorption studies showed that PS-1.0G PAMAM-PPA could be used repeatedly and adsorption and desorption percentage did not have any noticeable loss after 27 cycles in a fixed bed.

  3. Studies on bis(halogeno) dioxomolybdenum(VI)-bipyridine complexes: synthesis and catalytic activity.

    Science.gov (United States)

    Günyar, Alev; Zhou, Ming-Dong; Drees, Markus; Baxter, Paul N W; Bassioni, Ghada; Herdtweck, Eberhardt; Kühn, Fritz E

    2009-10-28

    Dioxomolybdenum(VI) complexes with the general formula [MoO2Cl2L2] (L2=3,3'-dimethyl-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, 6,6'-dimethyl-2,2'-bipyridine, 4,4'-dibromo-2,2'-bipyridine, 5,5'-dibromo-2,2'-bipyridine, 5,5'-diamino-2,2'-bipyridine; 5,5'-dinitro-2,2'-bipyridine; 5,5'-di-ethoxycarbonyl-2,2'-bipyridine; 6-phenyl-2,2'-bipyridine; 2,2':6',2''-terpyridine) have been prepared and characterised. [MoO2Cl2(5,5'-di-ethoxycarbonyl-2,2'-bipyridine)] has been examined by single crystal X-ray analysis. The complexes were applied as homogenous catalysts for the epoxidation of cyclooctene with tert-butyl hydroperoxide (TBHP) as oxidising agent. The new compounds show an overall high activity and are highly selective catalysts in the epoxidation of cyclooctene. The stability of the complexes and differences in the catalytic activity can be clearly attributed to electronic contributions of the functional groups on bipyridine ligands and to steric restrictions. DFT calculations have assisted in a better understanding of the stability of the complexes and are in agreement with experiment. The influence of the terminal oxo ligands and the Lewis base ligands on the Mo center keep the compounds on quite a stable level of electron density.

  4. Complex structure of type VI peptidoglycan muramidase effector and a cognate immunity protein

    International Nuclear Information System (INIS)

    Wang, Tianyu; Ding, Jinjing; Zhang, Ying; Wang, Da-Cheng; Liu, Wei

    2013-01-01

    The structure of the Tse3–Tsi3 complex associated with the bacterial type VI secretion system of P. aeruginosa has been solved and refined at 1.9 Å resolution. The structural basis of the recognition of the muramidase effector and its inactivation by its cognate immunity protein is revealed. The type VI secretion system (T6SS) is a bacterial protein-export machine that is capable of delivering virulence effectors between Gram-negative bacteria. The T6SS of Pseudomonas aeruginosa transports two lytic enzymes, Tse1 and Tse3, to degrade cell-wall peptidoglycan in the periplasm of rival bacteria that are competing for niches via amidase and muramidase activities, respectively. Two cognate immunity proteins, Tsi1 and Tsi3, are produced by the bacterium to inactivate the two antibacterial effectors, thereby protecting its siblings from self-intoxication. Recently, Tse1–Tsi1 has been structurally characterized. Here, the structure of the Tse3–Tsi3 complex is reported at 1.9 Å resolution. The results reveal that Tse3 contains a C-terminal catalytic domain that adopts a soluble lytic transglycosylase (SLT) fold in which three calcium-binding sites were surprisingly observed close to the catalytic Glu residue. The electrostatic properties of the substrate-binding groove are also distinctive from those of known structures with a similar fold. All of these features imply that a unique catalytic mechanism is utilized by Tse3 in cleaving glycosidic bonds. Tsi3 comprises a single domain showing a β-sandwich architecture that is reminiscent of the immunoglobulin fold. Three loops of Tsi3 insert deeply into the groove of Tse3 and completely occlude its active site, which forms the structural basis of Tse3 inactivation. This work is the first crystallographic report describing the three-dimensional structure of the Tse3–Tsi3 effector–immunity pair

  5. Complex structure of type VI peptidoglycan muramidase effector and a cognate immunity protein

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tianyu [Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Ding, Jinjing; Zhang, Ying; Wang, Da-Cheng, E-mail: dcwang@ibp.ac.cn [Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China); Liu, Wei, E-mail: dcwang@ibp.ac.cn [The Third Military Medical University, Chongqing 400038 (China); Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China)

    2013-10-01

    The structure of the Tse3–Tsi3 complex associated with the bacterial type VI secretion system of P. aeruginosa has been solved and refined at 1.9 Å resolution. The structural basis of the recognition of the muramidase effector and its inactivation by its cognate immunity protein is revealed. The type VI secretion system (T6SS) is a bacterial protein-export machine that is capable of delivering virulence effectors between Gram-negative bacteria. The T6SS of Pseudomonas aeruginosa transports two lytic enzymes, Tse1 and Tse3, to degrade cell-wall peptidoglycan in the periplasm of rival bacteria that are competing for niches via amidase and muramidase activities, respectively. Two cognate immunity proteins, Tsi1 and Tsi3, are produced by the bacterium to inactivate the two antibacterial effectors, thereby protecting its siblings from self-intoxication. Recently, Tse1–Tsi1 has been structurally characterized. Here, the structure of the Tse3–Tsi3 complex is reported at 1.9 Å resolution. The results reveal that Tse3 contains a C-terminal catalytic domain that adopts a soluble lytic transglycosylase (SLT) fold in which three calcium-binding sites were surprisingly observed close to the catalytic Glu residue. The electrostatic properties of the substrate-binding groove are also distinctive from those of known structures with a similar fold. All of these features imply that a unique catalytic mechanism is utilized by Tse3 in cleaving glycosidic bonds. Tsi3 comprises a single domain showing a β-sandwich architecture that is reminiscent of the immunoglobulin fold. Three loops of Tsi3 insert deeply into the groove of Tse3 and completely occlude its active site, which forms the structural basis of Tse3 inactivation. This work is the first crystallographic report describing the three-dimensional structure of the Tse3–Tsi3 effector–immunity pair.

  6. Bioprospecting of gum kondagogu (Cochlospermum gossypium) for bioremediation of uranium (VI) from aqueous solution and synthetic nuclear power reactor effluents.

    Science.gov (United States)

    Sashidhar, R B; Selvi, S Kalaignana; Vinod, V T P; Kosuri, Tanuja; Raju, D; Karuna, R

    2015-10-01

    An ecofriendly green chemistry method using a natural biopolymer, Gum Kondagogu (GK) for the removal of U (VI) from aqueous, simulated nuclear effluents was studied. The adsorption characteristic of GK towards U (VI) from aqueous solution was studied at varied pH, contact time, adsorbent dose, initial U (VI) concentration and temperature using UV-Visible spectroscopy and ICP-MS. Maximum adsorption was seen at pH 4, 0.1% GK with 60 min contact time at room temperature. The GK- U (VI) composite was characterized by FT-IR, zeta potential, TEM and SEM-EDAX. The Langmuir isotherm was found to be 487 mg of U (VI) g(-1) of GK. The adsorption capacity and (%) of U (VI) was found to be 490 ± 5.4 mg g(-1) and 98.5%. Moreover adsorption of U (VI) by GK was not influenced by other cations present in the simulated effluents. The adsorbed U (VI) was efficiently stripped from composite using 1 M HCl. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Trivalent metallocene chemistry of some uranium, titanium, and zirconium complexes

    International Nuclear Information System (INIS)

    Lukens, W.W. Jr.

    1995-05-01

    Dicyclopentadienyluranium halide dimers have been prepared and their solution behavior examined. These molecules exist as dimers in solution, and the halide ligands undergo rapid site exchange on the NMR timescale above 50 C. Analogous dicyclopentadienyluranium hydroxide dimers have also been prepared; they oxidatively eliminate hydrogen to give the corresponding oxide dimers. Mechanism of this reaction is consistent with αmigration of one of the hydroxide hydrogen atoms to a uranium center followed by elimination of hydrogen. Ground state of [(Me 3 Si) 2 C 5 H 3 ] 3 M M = Nd, U and their base adducts has been examined by variable temperature magnetic susceptibility and EPR spectroscopy. The ground state is found to be 4 I 9/2 with a crystal field state consisting largely of J z = 1/2 lowest, in agreement with previous studies on tris-cyclopentadienylneodymium complexes. The zirconium metallocene Cp 3 Zr has been prepared, characterized crystallographically, and its reactivity studied. Its chemical behavior is controlled by presence of an electron in the non-bonding, d z 2 orbital which prevents formation of base adducts Of Cp 3 Zr, but allows Cp 3 Zr to abstract atoms from other molecules. Electonic and EPR spectra of Cp* 2 TiX complexes, where Cp* is Me 5 C 5 and X is a monodentate, anionic ligand such as halide, have been studied. A π-bonding spectrochemical series is developed, and trends in π-bonding ability are found similar to those in other inorganic complexes. The β-agostic interactions in Cp* 2 TiN(Me)Ph have been examined using variable temperature EPR spectroscopy, and the enthalpy/entropy of the interaction determined. In Cp* 2 TiEt, enthalpy of the β-agostic interaction is -1.9 kcal/mol. The titanocene anion, Cp* 2 TiLi(TMEDA) (TMEDA is N,N,N',N'-tetramethylethylenediamine), has been prepared and its structure determined

  8. Single-molecule magnetism in a single-ion triamidoamine uranium(V) terminal mono-oxo complex

    International Nuclear Information System (INIS)

    King, David M.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T.; Tuna, Floriana; McInnes, Eric J.L.

    2013-01-01

    Straightforward oxidation of a triamidoamine uranium(III) complex with trimethyl-N-oxide affords a uranium(V) terminal mono-oxo complex which is the first clear-cut example of a uranium(V) single-molecule magnet (SMM). This monometallic complex unambiguously shows that a strongly axially ligated and thus anisotropic ligand field can be used to overcome the limited magnetic anisotropy of uranium(V). [de

  9. Uranium

    International Nuclear Information System (INIS)

    Anon.

    1984-01-01

    The article briefly discusses the Australian government policy and the attitude of political party factions towards the mining and exporting of the uranium resources in Australia. Australia has a third of the Western World's low-cost uranium resources

  10. Uranium

    International Nuclear Information System (INIS)

    Mackay, G.A.

    1978-01-01

    The author discusses the contribution made by various energy sources in the production of electricity. Estimates are made of the future nuclear contribution, the future demand for uranium and future sales of Australian uranium. Nuclear power growth in the United States, Japan and Western Europe is discussed. The present status of the six major Australian uranium deposits (Ranger, Jabiluka, Nabarlek, Koongarra, Yeelerrie and Beverley) is given. Australian legislation relevant to the uranium mining industry is also outlined

  11. Uranium

    International Nuclear Information System (INIS)

    1982-01-01

    The development, prospecting, research, processing and marketing of South Africa's uranium industry and the national policies surrounding this industry form the headlines of this work. The geology of South Africa's uranium occurences and their positions, the processes used in the extraction of South Africa's uranium and the utilisation of uranium for power production as represented by the Koeberg nuclear power station near Cape Town are included in this publication

  12. Uranium

    International Nuclear Information System (INIS)

    Stewart, E.D.J.

    1974-01-01

    A discussion is given of uranium as an energy source in The Australian economy. Figures and predictions are presented on the world supply-demand position and also figures are given on the added value that can be achieved by the processing of uranium. Conclusions are drawn about Australia's future policy with regard to uranium (R.L.)

  13. Uranium

    International Nuclear Information System (INIS)

    Toens, P.D.

    1981-03-01

    The geological setting of uranium resources in the world can be divided in two basic categories of resources and are defined as reasonably assured resources, estimated additional resources and speculative resources. Tables are given to illustrate these definitions. The increasing world production of uranium despite the cutback in the nuclear industry and the uranium requirements of the future concluded these lecture notes

  14. Catalytic properties and dynamic behaviour of uranium complexes

    International Nuclear Information System (INIS)

    Le Marechal, J.F.

    1986-01-01

    The catalytic properties of organometallic uranium III and IV compounds in solution as well as reaction mechanisms are studied. The structure in solution of CpUCl 3 L 2 (L=THF, HMPA, OPPh 3 , OP(OR) 3 ) is investigated. When L=HMPA, the complex exists in two isomers in equilibrium with the L ligands either in trans or mer-cis configuration. The isomerization (Ea=92 kJ mol -1 ) as well as the bimolecular exchange with an outer sphere ligand L are observable in 1 H and 31 P NMR, and quantified with the spin saturation transfer technique in several solvents and at different temperatures between 230 and 330 K. This property is extended to other ligands. The compound U(AlH 4 ) 3 is synthetized. This compound catalyses the hydroalumination of olefins by LiAlH 4 with a very good anti-Markovnikov regioselectivity. A simple mechanism for this reaction is suggested. The reactions of the organoaluminates products with several reactants (D 2 O, I 2 , CH 2 O, Allyl-Br...) has been shown to be a powerful synthetic tool. Some specific alkenes and alkynes exhibit an interesting behaviour as dimerization or β-alkyl elimination which is easily interpreted by our mechanism [fr

  15. Environmental Survey preliminary report, Portsmouth Uranium Enrichment Complex, Piketon, Ohio

    International Nuclear Information System (INIS)

    1987-08-01

    This report presents the preliminary findings from the first phase of the Environmental Survey of the United States Department of Energy (DOE) Portsmouth Uranium Enrichment Complex (PUEC), conducted August 4 through August 15, 1986. The Survey is being conducted by an interdisciplinary team of environmental specialists, led and managed by the Office of Environment, Safety and Health's Office of Environmental Audit. Team specialists are being supplied by a private contractor. The objective of the Survey is to identify environmental problems and areas of environmental regulation. It is being performed in accordance with the DOE Environmental Survey Manual. This phase of the Survey involves the review of existing site environmental data, observations of the operations performed at PUEC, and interviews with site personnel. The Survey team developed a Sampling and Analysis Plan to assist in further assessing certain of the environmental problems identified during its on-site activities. The Sampling and Analysis Plan will be executed by Argonne National Laboratory. When completed, the results will be incorporated into the PUEC Environmental Survey Interim Report. The Interim Report will reflect the final determinations of the PUEC Survey. 55 refs., 22 figs., 21 tabs

  16. Absorption spectra analysis of hydrated uranium(III) complex chlorides

    Science.gov (United States)

    Karbowiak, M.; Gajek, Z.; Drożdżyński, J.

    2000-11-01

    Absorption spectra of powdered samples of hydrated uranium(III) complex chlorides of the formulas NH 4UCl 4 · 4H 2O and CsUCl 4 · 3H 2O have been recorded at 4.2 K in the 4000-26 000 cm -1 range. The analysis of the spectra enabled the determination of crystal-field parameters and assignment of 83 and 77 crystal-field levels for the tetrahydrate and trihydrate, respectively. The energies of the levels were computed by applying a simplified angular overlap model as well as a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions. Ab initio calculations have enabled the application of a simplified parameterization and the determination of the starting values of the AOM parameters. The received results have proved that the AOM approach can quite well predict both the structure of the ground multiplet and the positions of the crystal-field levels in the 17 000-25 000 cm -1 range, usually obscured by strong f-d bands.

  17. The Effect of pH and Time on the Extractability and Speciation of Uranium(VI) Sorbed to SiO2

    International Nuclear Information System (INIS)

    Ilton, Eugene S.; Wang, Zheming; Boily, Jean F.; Qafoku, Odeta; Rosso, Kevin M.; Smith, Steven C.

    2012-01-01

    The effect of pH and contact time on uranium extractability from quartz surfaces was investigated using either acidic or carbonate (CARB) extraction solutions, time-delayed spikes of different U isotopes (i.e., 238U and 233U), and liquid helium temperature time-resolved laser-induced fluorescence spectroscopy (LHeT TRLFS). Quartz powders were reacted with 238U(VI) bearing solutions that were equilibrated with atmospheric CO2 at pH 6, 7, and 8. After a 42 day equilibration period with 238U(VI), the suspensions were spiked with 233U(VI) and reacted for an additional 7 days. Sorbed U was then extracted with either dilute nitric acid or CARB. For the CARB extraction there was a systematic decrease in extraction efficiency for both isotopes from pH 6 to 8. This was mimicked by less desorption of 238U, after the 233U spike, from pH 6 to 8. Further, the efficiency of 233U extraction was consistently greater than that of 238U, indicating a strong temporal component to the strength of U association with the surface that was accentuated with increasing pH. LHeT TRLFS revealed a strong correlation between carbonate extraction efficiency and differences in sorbed U speciation as a function of pH. In contrast, the acid extraction was consistently more efficient than the CARB extraction, with a smaller dependence on both pH and aging time. Collectively, the observations show that aging and pH are critical factors in determining the form and strength of uranium-silica interactions.

  18. Dioxouranium (VI) nitrate complexes of some schiff bases derived from furfural and 2-acetylfuran with certain amino compounds

    International Nuclear Information System (INIS)

    Sobhanadevi, G.; Indrasenan, P.

    1989-01-01

    Dioxouranium(VI) nitrate complexes with 10 schiff bases obtained by the condensation of furfural and 2-acetylfuran with isonicotinoylhydrazine, benzoylhydrazine, salicyloylhydrazine, anthranilic acid, and 4-aminoantipyrine have been synthesized and characterized on the basis of IR spectra, conductance, magnetic, elemental analyses and molecular weight data. (author). 1 tab., 10 refs

  19. Uranium exploration target selection for proterozoic iron oxide/breccia complex type deposits in India

    International Nuclear Information System (INIS)

    Dwivedy, K.K.; Sinha, K.K.

    1997-01-01

    Multimetal iron oxide/breccia complex (IOBC) type deposits exemplified by Olympic Dam in Australia, fall under low grade, large tonnage deposits. A multidisciplinary integrated exploration programme consisting of airborne surveys, ground geological surveys, geophysical and geochemical investigations and exploratory drilling, supported adequately by the state of the art analytical facilities, data processing using various software and digital image processing has shown moderate success in the identification of target areas for this type of deposits in the Proterozoic terrains of India. Intracratonic, anorogenic, continental rift to continental margin environment have been identified in a very wide spectrum of rock associations. The genesis and evolution of such associations during the Middle Proterozoic period have been reviewed and applied for target selection in the (i) Son-Narmada rift valley zone; (ii) areas covered by Dongargarh Supergroup of rocks in Madhya Pradesh; (iii) areas exposing ferruginous breccia in the western part of the Singhbhum Shear Zone (SSZ) around Lotapahar; (iv) Siang Group of rocks in Arunachal Pradesh; (v) Crystalline rocks of Garo Hills around Anek; and (vi) Chhotanagpur Gneissic complex in the Bahia-Ulatutoli tract of Ranchi Plateau. Of theses six areas, the Son-Narmada rift area appears to be the most promising area for IOBC type deposits. Considering occurrences of the uranium anomalies near Meraraich, Kundabhati, Naktu and Kudar and positive favourability criteria observed in a wide variety of rocks spatially related to the rifts and shears, certain sectors in Son-Narmada rift zone have been identified as promising for intense subsurface exploration. 20 refs, 4 figs, 1 tab

  20. Preparation of Ca-alginate coated nZVI core shell beads for uranium (VI) removal from aqueous solution

    International Nuclear Information System (INIS)

    Shuhong Hu; Xiaoyan Lin; Yahui Zhang; Meiling Shi

    2017-01-01

    In this study, the core-shell nanoscale zero-valent iron (nZVI)@Alg-Ca beads were synthesized by coaxial electronic injection method for removal of U (VI) from aqueous solution, and characterized by SEM, EDX and XPS. The results showed that the pseudo-second-order models and the Langmuir isotherm model fitted well with the data obtained. The removal mechanism may include both physical adsorption of U (VI) on the surface or inside of core-shell nZVI@Alg-Ca beads and subsequent reduction of U (VI) to U (IV). Therefore, the core-shell nZVI@Alg-Ca beads would have an application prospect in effective removal of U (VI) contamination from aqueous solution. (author)

  1. Solubility and sorption characteristics of uranium(VI) associated with rock samples and brines/groundwaters from WIPP and NTS

    International Nuclear Information System (INIS)

    Dosch, R.G.

    1981-01-01

    Solubility measurements for U(VI) in WIPP-related brines/groundwaters were made using initial U(VI) concentrations in the range of 1 to 50 μg/ml. Distribution coefficients (Kd) for U(VI) were determined for Culebra and Magenta dolomites using four different brine/groundwater compositions and for argillaceous shale and hornfels samples from the Eleana and Calico Hills Formation on NTS using a groundwater simulant typical of that area. The Kd's were evaluated as functions of: (1) U(VI) concentration (1.4 x 10 -4 to 1.4 μg/ml); (2) solution volume-to-rock mass ratios used in the measurements (5 to 100 ml/g), and for WIPP material only; (3) water composition (0 to 100% brine in groundwater); and (4) sample location in the Culebra and Magenta dolomite members of the Rustler Formation. The results indicate that if groundwater intrudes into a repository and leaches a waste form, significant concentrations of dissolved or colloidal U(VI) could be maintained in the liquid phase. Should these solutions enter an aquifer system, there are reasonable sets of conditions which could lead to subsequent migration of U(VI) away from the repository site

  2. The crystal chemistry of novel thorium and uranium compounds with oxo-anions from group VI of periodic table (S, Se, Te, Cr, Mo and W)

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Bin

    2016-01-26

    This dissertation focus on the synthesis, phase studies and physicochemical properties of novel thorium and uranium compounds with the Group VI (S, Se, Te, Cr, Mo, W) of the Periodic Table. All the studied compounds are listed in Table 2.2 from the page 15. I subdivided all the newly synthesized compounds into several chapters according to their structural and topological differences. First, for thorium molybdates and tungstates, almost all of these compounds are based on corner-sharing of ThO{sub x} (x = 6, 8 and 9) and MoO{sub 4} or WO{sub x} (x = 4, 5, 6) polyhedra. Interestingly, all these compounds can be seen as derived from a pure thorium molybdate compound (ThMo{sub 2}O{sub 8}) which was isolated from high-temperature solid-state synthesis method. Therefore, the polymorphs of this most basic ThMo{sub 2}O{sub 8} compound is firstly introduced (see Chapter 3.1 from page 18). The thermodynamic, electronic and vibrational properties of all investigated ThMo{sub 2}O{sub 8} polymorphs were studied using ab initio calculations. Then, two subfamilies of thorium molybdates, that is, rubidium thorium molybdate and cesium thorium molybdate and their thermal and vibrational behaviors were discussed in details in Chapter 4.1 from page 37 and Chapter 4.2 from page 50, respectively. Moreover, some new insights about the complexity of thorium tungstates were also discussed (Chapter 4.3 from page 59). Some novel thorium molybdate and chromate compounds synthesized from aqueous condition are discussed in Chapter 5 from page 71. In the Chapter 8.2.4, the stereochemistry for thorium and uranium compounds are introduced, especially thorium selinites and uranyl tellurites (see Chapter 6.1 from page 82), thorium tellurites (Chapter 6.2 from page 93), and uranyl tellurites (Chapter 6.3 from page 99 for sodium uranyl tellurium and Chapter 6.4 from page 110 for potassium uranyl tellurium, respectively). In the actinide tellurium systems, additional MoO{sub 3}/WO{sub 3} were also

  3. Surface complexation modeling of U(VI) sorption on GMZ bentonite in the presence of fulvic acid

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jie [Lanzhou Univ. (China). Radiochemistry Laboratory; Ministry of Industry and Information Technology, Guangzhou (China). The 5th Electronics Research Inst.; Luo, Daojun [Ministry of Industry and Information Technology, Guangzhou (China). The 5th Electronics Research Inst.; Qiao, Yahua; Wang, Liang; Zhang, Chunming [Ministry of Environmental Protection, Beijing (China). Nuclear and Radiation Safety Center; Wu, Wangsuo [Lanzhou Univ. (China). Radiochemistry Laboratory; Ye, Yuanlv [Ministry of Environmental Protection, Beijing (China). Nuclear and Radiation Safety Center; Lanzhou Univ. (China). Radiochemistry Laboratory

    2017-03-01

    In this work, experiments and modeling for the interactions between uranyl ion and GMZ bentonite in the presence of fulvic acid are presented. The results demonstrated that FA is strongly bound to GMZ bentonite, and these molecules have a very large effect on the U(VI) sorption. The results also demonstrated that U(VI) sorption to GMZ bentonite in the presence and absence of sorbed FA can be well predicted by combining SHM and DLM. According to the model calculations, the nature of the interactions between FA with U(VI) at GMZ bentonite surface is mainly surface complex. The first attempt to simulate clay interaction with humus by the SHM model.

  4. Seroprevalence of antibodies to Venezuelan equine encephalitis complex (subtypes IAB and VI in humans from General Belgrano Island, Formosa, Argentina

    Directory of Open Access Journals (Sweden)

    Cámara Alicia

    2003-01-01

    Full Text Available This work presents the results of the detection of antibodies (immunoglobulin G for subtypes I and VI of VEE viruses complex (Togaviridae family in people from the General Belgrano island, Formosa province (Argentina. The prevalence of neutralizing (NT antibodies for subtype VI was from 30% to 70% and the prevalence of antibodies inhibitory of hemagglutination (HI was of 0% in the first and second inquiry respectively. For the subtype IAB the prevalence of NT antibodies was from 13% to 3.6%, similar to the prevalence total for both subtypes. HI antibodies were not detected in any inquiries for any subtype. It was observed that both subtypes circulate simultaneously, while subtype VI remains constant with some peaks, subtype I was found in low level.

  5. Radium removal from Canadian uranium mining effluents by a radium-selective ion exchange complexer

    International Nuclear Information System (INIS)

    1984-07-01

    A laboratory test program was initiated by the Department of Energy, Mines and Resources as part of the National Uranium Tailings Program to investigate the applicability of a radium-selective ion exchange complexer for removing radium from Canadian uranium mining effluents. The ion exchange complexer was shown to be efficient in removing radium from contaminated water of uranium mining operations, with the ultimate loading capacity of the resin on one type of water treated being determined as approximately 1,600 Bq/cm 3 of new resin. The results showed that the resin was effective in removing radium but not any other contaminants

  6. Separation and concentration of uranium by extraction chromatography : U(VI) - H/sub 3/PO/sub 4/ system

    Energy Technology Data Exchange (ETDEWEB)

    Nobre, J S.M.

    1981-01-01

    The feasibility of using the extraction chromatographic technique as a way to recover uranium from phosphatic rocks is evaluated. The behaviour of uranium from raw phsophoric acid solutions in chromatographic systems using the mixture di(2-ethylhexyl) orthophosphoric acid (D2EHPA) - tributyl phosphate (TBP) as the stationary phase was studied. Materials as alumina, activated carbon and the macroporous resins XAD-4 and XAD-7 were used as supports for organic stationary phase. The best results were obtained with poliacrilic polymer XAD-7, due to its excellent chromatographic properties and efficient organic phase retention. Uranium was quantitatively retained by D2EHPA-TBP-XAD-7 columns from synthetic phosphoric acid solutions with typical composition of phosphatic acid liquors. The elution of uranium from this system was also studied, and the best results were obtained with phosphoric acid solutions. This chromatographic column presented a high stability, not changing their properties even after more than twenty cycles, including the conditioning, sorption, washing and elution steps. Uranium determinations were perfpormed by indirect titration with potassium dichromate and by molecular absorption spectrophotometry with hydrogen peroxide- carbonate. A new and more sensitive method for uranium determination in phosphoric medium, which might be applied to acid liquors of phosphatic ores, was developed. An extraction-photometric method was used, with Arsenazo III (1,8-dihydroxynaphtalene-3,6-disulphonic acid-2,7-bis(azo-2)-phenylarsonic acid) as the reagent for uranium.

  7. Study of the temperature influence during the uranium (Vi) sorption on surface of ZrP2O7 in presence of oxalic and salicylic acid

    International Nuclear Information System (INIS)

    Garcia G, N.

    2013-01-01

    This work studies the effect of temperature on the uranium (Vi) sorption onto zirconium diphosphate in the presence of organic acids (oxalic and salicylic acids). Zirconium diphosphate was synthesized by a chemical condensation reaction and characterized using several analytical techniques, in order to check its purity. This point is very important because the presence of any impurities or secondary phases may interfere with the hydration and sorption process. Prior to the sorption experiments, three batches of zirconium diphosphate were pre-equilibrated with NaClO 4 , oxalic acid or salicylic acid solutions. The hydrated solids were washed and dried and then again characterized in order to study the interactions between organic acids and zirconium diphosphate surface. Uranium sorption onto zirconium diphosphate (pre-equilibrated with NaClO 4 , oxalic acid and salicylic acid solutions) was investigated as a function of ph, organic acid and temperature (20, 40 y 60 grades C). Thermodynamic parameters for the sorption reactions (enthalpy change, entropy change and Gibbs free energy change) were determined from temperature dependence of distribution coefficient by using the Vant Hoff equation. Solids characterization after hydration shows that exist an interaction between organic acids and ZrP 2 O 7 . This fact was confirmed with the microcalorimetry study, the reaction heat for hydration of zirconium diphosphate in NaClO 4 solution was exothermic (-269.59 mJ) and for hydration of zirconium diphosphate in oxalic acid solution was endothermic (53.64 mJ). The experimental results showed important differences in the sorption mechanisms for the reaction of Uranium with ZrP 2 O 7 in the presence and absence of organic acids. For the zirconium diphosphate hydrated with oxalic acid, the sorption percentage was 50% from lowest ph values. For the zirconium diphosphate hydrated with salicylic acid, the initial concentration of uranium was 6 x 10 -4 M and a percentage of 10% was

  8. U(VI) complexation with selected flavonoids investigated by absorption and emission spectroscopy at light acidic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, Alix; Geipel, Gerhard [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biogeochemistry

    2017-06-01

    Flavonoids are secondary plant compounds and have important properties. Beside their antioxidant activity and effects as enzyme inhibitors, they can bind metals ions. The possible release of flavonoids from the root into the soil can affect the migration of radionuclides in the biological and geological environment. In this work, the complexation behavior of selected flavonols and a flavonol glycoside towards U(VI) were spectroscopically investigated and the corresponding complex stability constants were determined.

  9. U(VI) complexation with selected flavonoids investigated by absorption and emission spectroscopy at light acidic conditions

    International Nuclear Information System (INIS)

    Guenther, Alix; Geipel, Gerhard

    2017-01-01

    Flavonoids are secondary plant compounds and have important properties. Beside their antioxidant activity and effects as enzyme inhibitors, they can bind metals ions. The possible release of flavonoids from the root into the soil can affect the migration of radionuclides in the biological and geological environment. In this work, the complexation behavior of selected flavonols and a flavonol glycoside towards U(VI) were spectroscopically investigated and the corresponding complex stability constants were determined.

  10. ALTERATION OF U(VI)-PHASES UNDER OXIDIZING CONDITIONS

    Energy Technology Data Exchange (ETDEWEB)

    A.P. Deditius; S. Utsunomiya; R.C. Ewing

    2006-02-21

    Uranium-(VI) phases are the primary alteration products of the UO{sub 2} in spent nuclear fuel and the UO{sub 2+x}, in natural uranium deposits. The U(VI)-phases generally form sheet structures of edge-sharing UO{sub 2}{sup 2+} polyhedra. The complexity of these structures offers numerous possibilities for coupled-substitutions of trace metals and radionuclides. The incorporation of radionuclides into U(VI)-structures provides a potential barrier to their release and transport in a geologic repository that experiences oxidizing conditions. In this study, we have used natural samples of UO{sub 2+x}, to study the U(VI)-phases that form during alteration and to determine the fate of the associated trace elements.

  11. ALTERATION OF U(VI)-PHASES UNDER OXIDIZING CONDITIONS

    International Nuclear Information System (INIS)

    A.P. Deditius; S. Utsunomiya; R.C. Ewing

    2006-01-01

    Uranium-(VI) phases are the primary alteration products of the UO 2 in spent nuclear fuel and the UO 2+x , in natural uranium deposits. The U(VI)-phases generally form sheet structures of edge-sharing UO 2 2+ polyhedra. The complexity of these structures offers numerous possibilities for coupled-substitutions of trace metals and radionuclides. The incorporation of radionuclides into U(VI)-structures provides a potential barrier to their release and transport in a geologic repository that experiences oxidizing conditions. In this study, we have used natural samples of UO 2+x , to study the U(VI)-phases that form during alteration and to determine the fate of the associated trace elements

  12. Trivalent metallocene chemistry of some uranium, titanium, and zirconium complexes

    Energy Technology Data Exchange (ETDEWEB)

    Lukens, Jr., Wayne Wendell [Univ. of California, Berkeley, CA (United States)

    1995-05-01

    Dicyclopentadienyluranium halide dimers have been prepared and their solution behavior examined. These molecules exist as dimers in solution, and the halide ligands undergo rapid site exchange on the NMR timescale above 50 C. Analogous dicyclopentadienyluranium hydroxide dimers have also been prepared; they oxidatively eliminate hydrogen to give the corresponding oxide dimers. Mechanism of this reaction is consistent with αmigration of one of the hydroxide hydrogen atoms to a uranium center followed by elimination of hydrogen. Ground state of [(Me3Si)2C5H3]3M M = Nd, U and their base adducts has been examined by variable temperature magnetic susceptibility and EPR spectroscopy. The ground state is found to be 4I9/2 with a crystal field state consisting largely of Jz = 1/2 lowest, in agreement with previous studies on tris-cyclopentadienylneodymium complexes. The zirconium metallocene Cp3Zr has been prepared, characterized crystallographically, and its reactivity studied. Its chemical behavior is controlled by presence of an electron in the non-bonding, dz2 orbital which prevents formation of base adducts Of Cp3Zr, but allows Cp3Zr to abstract atoms from other molecules. Electonic and EPR spectra of Cp*2TiX complexes, where Cp* is Me5C5 and X is a monodentate, anionic ligand such as halide, have been studied. A π-bonding spectrochemical series is developed, and trends in π-bonding ability are found similar to those in other inorganic complexes. The β-agostic interactions in Cp*2TiN(Me)Ph have been examined using variable temperature EPR spectroscopy, and the enthalpy/entropy of the interaction determined. In Cp*2TiEt, enthalpy of the β-agostic interaction is -1.9 kcal/mol. The titanocene anion, Cp*2TiLi(TMEDA) (TMEDA is N,N,N`,N`-tetramethylethylenediamine), has been

  13. Irradiated uranium reprocessing, Final report - I-IV, Part I; Prerada ozracenog urana, Zavrsni izvestaj- I-VI, I Deo

    Energy Technology Data Exchange (ETDEWEB)

    Gal, I [Institute of Nuclear Sciences Boris Kidric, Laboratorija za visoku aktivnost, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    This volume of the final report describes the construction and functioning of the cell for dissolving the irradiated uranium. Annexes of this report describe the parts of the cell as follows: description of the metal frame, grid and stainless steel plate; container for irradiated uranium; small opening of the cell; vessel for dissolving; device for opening the cover; device for sampling of the radioactive solution, inner and outer parts; pneumatic taps.

  14. The Rorschach in gynecological suffering: representations and complexes of the VI table

    Directory of Open Access Journals (Sweden)

    Salvatore Settineri

    2015-09-01

    Full Text Available Background. The literature shows that women with gynecological problems have psychosomatic alteration in the body image perception and sexual distress. To our knowledge, these issues have so far been analyzed separately and rarely through a projective methods. Aim. The aim of this study is to analyze the role of body image and its relative weakness in gynecological pathology, through the Rorschach projective method. Method. The observation group consists of 66 women with an average age of 49 ± 17 year, belonging to the clinic of the University Hospital Vulvologia and Colpocitologia "Gaetano Martino" of Messina. For the evalutation was used Rorschach, according to the clinical method, in order to explore the representations of the subject's inner world. Results. The responses to the Rorschach cards show a prevalence of anatomical and sexual content, devitalized animals and object, in particular to the table VI. We observed in women a complex regarding generativity that reveals a fragmentation of body image representation and of the sexual imaginative function of the inner world. Conclusions. The sexual suffering in gynecology is a dimension that influences the symptomathology in the extent to which the psychological aspects profoundly affect bodily perceptions, weakening the self-image and altering the course of the disease.   Keywords: body image, sexuality, Rorschach, psychosomatic gynecology.

  15. Studies on some mixed ligand complexes of UO2(VI) in solution

    International Nuclear Information System (INIS)

    Katkar, V.S.; Munshi, K.N.

    1987-01-01

    Potentiometric studies on some mixed ligand complexes of UO 2 (VI) with ethylenediamine N,N' diacetic acid as primary ligand and succinic acid, malic acid, maleic acid, fumaric acid, malonic acid, adipic acid, itaconic acid, phthalic acid and mandelic acid as secondary ligands have been carried out employing modified form of Irving-Rossotti's pH titration technique. The study was carried out at three different temperatures, viz. 5deg, 25deg and 45degC and at fixed ionic strength of 0.2M KNO 3 . Thermodynamic parameters, e.g. ΔG, ΔH and ΔS have been evaluated and further ΔG and ΔH values have been separated into their electrostatic components, ΔGe and ΔHe and cratic components, ΔGsub(c) and ΔHsub(c). The effect of change in dielectric constant and change in ionic strength of the medium have also been investigated. The sequence of stability constants has been correlated with the properties of secondary ligands. (author). 21 refs., 5 tabs

  16. Cyclopentadienyl molybdenum(II/VI) N-heterocyclic carbene complexes: Synthesis, structure, and reactivity under oxidative conditions

    KAUST Repository

    Li, Shenyu

    2010-04-26

    A series of N-heterocyclic carbene (NHC) complexes CpMo(CO) 2(NHC)X (NHC = IMe = 1,3-dimethylimidazol-2-ylidene, X = Br, 1; NHC = 1,3-dipropylimidazol-2-ylidene, X = Br, 2; NHC = IMes = 1,3-bis(2,4,6- trimethylphenyl)imidazol-2-ylidene, X = Br, 3; NHC = IBz = 1,3-dibenzylimidazol- 2-ylidene, X = Br, 4a, and X = Cl, 4b; NHC = 1-methyl-3-propylimidazol-2- ylidene, X = Br, 5) and [CpMo(CO)2(IMes)(CH3CN)][BF 4] (6) have been synthesized and fully characterized. The stability of metal-NHC ligand bonds in these compounds under oxidative conditions has been investigated. The thermally stable Mo(VI) dioxo NHC complex [CpMoO 2(IMes)][BF4] (9) has been isolated by the oxidation of the ionic complex 6 by TBHP (tert-butyl hydrogen peroxide). Complex 6 can be applied as a very active (TOFs up to 3400 h-1) and selective olefin epoxidation catalyst. While under oxidative conditions (in the presence of TBHP), compounds 1-5 decompose into imidazolium bromide and imidazolium polyoxomolybdate. The formation of polyoxomolybdate as oxidation products had not been observed in a similar epoxidation catalyzed by Mo(II) and Mo(VI) complexes. DFT studies suggest that the presence of Br- destabilizes the CpMo(VI) oxo NHC carbene species, consistent with the experimental observations. © 2010 American Chemical Society.

  17. Evaluation of the uranium potential of the Bushveld Complex

    International Nuclear Information System (INIS)

    Cheney, E.S.

    1986-04-01

    The poor quality of the airborne radiometric surveys and the lack of exploration geochemical data in the public domain prevent a satisfactory assessment of the uranium potential of the Bushveld area. Undue reliance must be placed upon fitting models of uranium ore deposits to the geology of the Bushveld area. Although the Bushveld granites have an unusually high background of uranium (20 to 40 ppm), they probably only host small vein-type deposits. The vein at the Albert Silver mine should be investigated as a type example to determine if it is only economic in the narrow interval of supergene enrichment. The Rooiberg Group has considerable potential for caldera-related deposits and for uranium-bearing sulphide deposits (including Olympic Dam-type deposits) in sedimentary interbeds. The Loskop Formation appears to be correlative with the Glentig and lower Swaershoek Formations of the Waterberg area. The Waterberg Group is the logical host to investigate for giant uncomformity/vein-type uranium deposits like those in Canada and Australia. Because the Waterberg consists of four uncomformity-bounded sequences, it is rarely more than 3 km thick; all of the sequences could be younger than 1770 Ma

  18. Synthesis and insertion chemistry of mixed tether uranium metallocene complexes

    Energy Technology Data Exchange (ETDEWEB)

    Siladke, Nathan A.; LeDuc, Jennifer; Ziller, Joseph W.; Evans, William J. [Department of Chemistry, University of California, Irvine, CA (United States)

    2012-11-12

    The synthesis of mixed tethered alkyl uranium metallocenes has been investigated by examining the reactivity of the bis(tethered alkyl) metallocene [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC){sub 2}U] (1) with substrates that react with only one of the U-C linkages. The effect of these mixed tether coordination environments on the reactivity of the remaining U-C bond has been studied by using CO insertion chemistry. One equivalent of azidoadamantane (AdN{sub 3}) reacts with 1 to yield the mixed tethered alkyl triazenido complex [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC)U(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}-CH{sub 2}NNN-Ad-κ{sup 2}N{sup 1,3})]. Similarly, a single equivalent of CS{sub 2} reacts with 1 to form the mixed tethered alkyl dithiocarboxylate complex [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC)U(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}- CH{sub 2}C(S){sub 2}-κ{sup 2}S,S{sup '})], a reaction that constitutes the first example of CS{sub 2} insertion into a U{sup 4+}-C bond. Complex 1 reacts with one equivalent of pyridine N-oxide by C-H bond activation of the pyridine ring to form a mixed tethered alkyl cyclometalated pyridine N-oxide complex [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC)(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 3})U(C{sub 6}H{sub 4}NO-κ{sup 2} C,O)]. The remaining (η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC){sup 2-} ligand in each of these mixed tethered species show reactivity towards CO and tethered enolate ligands form by insertion. Subsequent rearrangement have been identified in [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 3})U(C{sub 5}H{sub 4}NO-κ{sup 2}C,O)(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}C(=CH{sub 2})O- κO)] and [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}NNN-Ad-κ{sup 2}N{sup 1,3})U(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}C(=CH{sub 2})O-κO)]. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Temperature Dependence of Uranium and Vanadium Adsorption on Amidoxime-Based Adsorbents in Natural Seawater

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Li-Jung [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; Gill, Gary A. [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; Tsouris, Costas [Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Rao, Linfeng [Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720 USA; Pan, Horng-Bin [Department of Chemistry, University of Idaho, Moscow ID 83844 USA; Wai, Chien M. [Department of Chemistry, University of Idaho, Moscow ID 83844 USA; Janke, Christopher J. [Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Strivens, Jonathan E. [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; Wood, Jordana R. [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; Schlafer, Nicholas [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Sequim WA 98382 USA; D' Alessandro, Evan K. [Rosensteil School of Marine and Atmospheric Chemistry, University of Miami, Miami FL 33149 USA

    2018-01-16

    The apparent enthalpy and entropy of the complexation of uranium (VI) and vanadium (V) with amidoxime ligands grafted onto polyethylene fiber was determined using time series measurements of adsorption capacities in natural seawater at three different temperatures. The complexation of uranium was highly endothermic, while the complexation of vanadium showed minimal temperature sensitivity. Amidoxime-based polymeric adsorbents exhibit significantly increased uranium adsorption capacities and selectivity in warmer waters.

  20. Aqueous complexation reactions governing the rate and extent of biogeochemical U(VI) reduction

    International Nuclear Information System (INIS)

    Kemner, K.M.; Kelly, S.D.; Brooks, Scott C.; Dong, Wenming; Carroll, Sue; Fredrickson, James K.

    2006-01-01

    The proposed research will elucidate the principal biogeochemical reactions that govern the concentration, chemical speciation, and reactivity of the redox-sensitive contaminant uranium. The results will provide an improved understanding and predictive capability of the mechanisms that govern the biogeochemical reduction of uranium in subsurface environments

  1. Communication: Relativistic Fock-space coupled cluster study of small building blocks of larger uranium complexes

    International Nuclear Information System (INIS)

    Tecmer, Paweł; Visscher, Lucas; Severo Pereira Gomes, André; Knecht, Stefan

    2014-01-01

    We present a study of the electronic structure of the [UO 2 ] + , [UO 2 ] 2 + , [UO 2 ] 3 + , NUO, [NUO] + , [NUO] 2 + , [NUN] − , NUN, and [NUN] + molecules with the intermediate Hamiltonian Fock-space coupled cluster method. The accuracy of mean-field approaches based on the eXact-2-Component Hamiltonian to incorporate spin–orbit coupling and Gaunt interactions are compared to results obtained with the Dirac–Coulomb Hamiltonian. Furthermore, we assess the reliability of calculations employing approximate density functionals in describing electronic spectra and quantities useful in rationalizing Uranium (VI) species reactivity (hardness, electronegativity, and electrophilicity)

  2. Communication: Relativistic Fock-space coupled cluster study of small building blocks of larger uranium complexes

    Science.gov (United States)

    Tecmer, Paweł; Severo Pereira Gomes, André; Knecht, Stefan; Visscher, Lucas

    2014-07-01

    We present a study of the electronic structure of the [UO2]+, [UO2]2 +, [UO2]3 +, NUO, [NUO]+, [NUO]2 +, [NUN]-, NUN, and [NUN]+ molecules with the intermediate Hamiltonian Fock-space coupled cluster method. The accuracy of mean-field approaches based on the eXact-2-Component Hamiltonian to incorporate spin-orbit coupling and Gaunt interactions are compared to results obtained with the Dirac-Coulomb Hamiltonian. Furthermore, we assess the reliability of calculations employing approximate density functionals in describing electronic spectra and quantities useful in rationalizing Uranium (VI) species reactivity (hardness, electronegativity, and electrophilicity).

  3. Uranium (VI) Sorption and Transport in Unsaturated, Subsurface Hanford Site Sediments - Effect of Moisture Content and Sediment Texture: Final Report for Subtask 2b

    International Nuclear Information System (INIS)

    Gamerdinger, A.P.; Resch, C.T.; Kaplan, D.I.

    1998-01-01

    A series of experiments were conducted in fiscal year 1998 at the Pacific Northwest National Laboratory as part of the Immobilized Low-Activity Waste-Performance Assessment. These experiments evaluated the sorption and transport of uranium, U(VI), under conditions of partial moisture saturation that are relevant to arid region burial sites and vadose-zone far-field conditions at the Hanford Site. The focus was on measuring breakthrough curves (from which distribution coefficient [K d ] values can be calculated) for U(W) in three Hanford Site sediments that represent different texture classes in two unsaturated moisture conditions. Previous research showed that K d values measured during transport in unsaturated sediments varied with moisture saturation

  4. Uranium

    International Nuclear Information System (INIS)

    Whillans, R.T.

    1981-01-01

    Events in the Canadian uranium industry during 1980 are reviewed. Mine and mill expansions and exploration activity are described, as well as changes in governmental policy. Although demand for uranium is weak at the moment, the industry feels optimistic about the future. (LL)

  5. Oxidation of ascorbic acid by a (salen)ruthenium(VI) nitrido complex in aqueous solution.

    Science.gov (United States)

    Wang, Qian; Man, Wai-Lun; Lam, William W Y; Lau, Tai-Chu

    2014-12-25

    The oxidation of ascorbic acid (H2A) by [Ru(VI)(N)(L)(MeOH)](+) in aqueous acidic solutions has the following stoichiometry: 2[Ru(VI)(N)] + 3H2A → 2[Ru(III)(NH2-HA)](+) + A. Mechanisms involving HAT/N-rebound at low pH (≤2) and nucleophilic attack at the nitride at high pH (≥5) are proposed.

  6. Removal of uranium (VI) from aqueous systems by nanoscale zero-valent iron particles suspended in carboxy-methyl cellulose

    Energy Technology Data Exchange (ETDEWEB)

    Popescu, Ioana-Carmen, E-mail: ioana.popescu@icpmrr.ro [R and D National Institute for Metals and Radioactive Resources – ICPMRR Bucharest B-dul Carol I No. 70, Sector 2, 202917 Bucharest (Romania); Filip, Petru [C. D. Nenitescu Institute of Organic Chemistry, Splaiul Independentei 202B, Sector 6, 71141 Bucharest (Romania); Humelnicu, Doina, E-mail: doinah@uaic.ro [Al.I. Cuza University of Iasi, The Faculty of Chemistry, Bd. Carol-I No. 11, Iasi 700506 (Romania); Humelnicu, Ionel [Al.I. Cuza University of Iasi, The Faculty of Chemistry, Bd. Carol-I No. 11, Iasi 700506 (Romania); Scott, Thomas Bligh; Crane, Richard Andrew [Interface Analysis Centre, University of Bristol, 121 St. Michael’s Hill, Bristol BS2 8BS (United Kingdom)

    2013-11-15

    Carboxy-methyl-cellulose (CMC), a common “delivery vehicle” for the subsurface deployment of iron nanoparticles (INP) has been tested in the current work for the removal of aqueous uranium from synthetic water samples. A comparison of the removal of aqueous uranium from solutions using carboxy-methyl-cellulose with and without iron nanoparticles (CMC–INP and CMC, respectively) was tested over a 48 h reaction period. Analysis of liquid samples using spectrophotometry determined a maximum sorption capacity of uranium, Q{sub max}, of 185.18 mg/g and 322.58 mg/g for CMC and CMC–INP respectively, providing strong evidence of an independent aqueous uranium removal ability exhibited by CMC. The results point out that CMC provides an additional capacity for aqueous uranium removal. Further tests are required to determine whether similar behaviour will be observed for other aqueous contaminant species and if the presence of CMC within a INP slurry inhibits or aids the reactivity, reductive capacity and affinity of INP for aqueous contaminant removal.

  7. Kinetics and mechanisms of the oxidation of iodide and bromide in aqueous solutions by a trans-dioxoruthenium(VI) complex.

    Science.gov (United States)

    Lam, William W Y; Man, Wai-Lun; Wang, Yi-Ning; Lau, Tai-Chu

    2008-08-04

    The kinetics and mechanisms of the oxidation of I (-) and Br (-) by trans-[Ru (VI)(N 2O 2)(O) 2] (2+) have been investigated in aqueous solutions. The reactions have the following stoichiometry: trans-[Ru (VI)(N 2O 2)(O) 2] (2+) + 3X (-) + 2H (+) --> trans-[Ru (IV)(N 2O 2)(O)(OH 2)] (2+) + X 3 (-) (X = Br, I). In the oxidation of I (-) the I 3 (-)is produced in two distinct phases. The first phase produces 45% of I 3 (-) with the rate law d[I 3 (-)]/dt = ( k a + k b[H (+)])[Ru (VI)][I (-)]. The remaining I 3 (-) is produced in the second phase which is much slower, and it follows first-order kinetics but the rate constant is independent of [I (-)], [H (+)], and ionic strength. In the proposed mechanism the first phase involves formation of a charge-transfer complex between Ru (VI) and I (-), which then undergoes a parallel acid-catalyzed oxygen atom transfer to produce [Ru (IV)(N 2O 2)(O)(OHI)] (2+), and a one electron transfer to give [Ru (V)(N 2O 2)(O)(OH)] (2+) and I (*). [Ru (V)(N 2O 2)(O)(OH)] (2+) is a stronger oxidant than [Ru (VI)(N 2O 2)(O) 2] (2+) and will rapidly oxidize another I (-) to I (*). In the second phase the [Ru (IV)(N 2O 2)(O)(OHI)] (2+) undergoes rate-limiting aquation to produce HOI which reacts rapidly with I (-) to produce I 2. In the oxidation of Br (-) the rate law is -d[Ru (VI)]/d t = {( k a2 + k b2[H (+)]) + ( k a3 + k b3[H (+)]) [Br (-)]}[Ru (VI)][Br (-)]. At 298.0 K and I = 0.1 M, k a2 = (2.03 +/- 0.03) x 10 (-2) M (-1) s (-1), k b2 = (1.50 +/- 0.07) x 10 (-1) M (-2) s (-1), k a3 = (7.22 +/- 2.19) x 10 (-1) M (-2) s (-1) and k b3 = (4.85 +/- 0.04) x 10 (2) M (-3) s (-1). The proposed mechanism involves initial oxygen atom transfer from trans-[Ru (VI)(N 2O 2)(O) 2] (2+) to Br (-) to give trans-[Ru (IV)(N 2O 2)(O)(OBr)] (+), which then undergoes parallel aquation and oxidation of Br (-), and both reactions are acid-catalyzed.

  8. Irradiated uranium reprocessing, Final report I-VI, Part VI - Separation of uranium, plutonium and fission products from HNO3 solution on the zirconium phosphate (part I), Adsorption equilibrium and kinetics

    International Nuclear Information System (INIS)

    Gal, I.; Ruvarac, A.

    1961-12-01

    Separation of uranium, plutonium and long-lived fission products was investigated on a inorganic ion exchanger. Zirconium phospate was chosen for this purpose because its ion exchanger properties were well known. This report deals with the study of equilibrium and kinetics of the adsorption

  9. Syntheses and catalytic oxotransfer activities of oxo molybdenum(vi) complexes of a new aminoalcohol phenolate ligand.

    Science.gov (United States)

    Hossain, M K; Haukka, M; Sillanpää, R; Hrovat, D A; Richmond, M G; Nordlander, E; Lehtonen, A

    2017-05-30

    The new aminoalcohol phenol 2,4-di-tert-butyl-6-(((2-hydroxy-2-phenylethyl)amino)methyl)phenol (H2L) was prepared by a facile solvent-free synthesis and used as a tridentate ligand for new cis-dioxomolybdenum(vi)(L) complexes. In the presence of a coordinating solvent (DMSO, MeOH, pyridine), the complexes crystallise as monomeric solvent adducts while in the absence of such molecules, a trimer with asymmetric Mo[double bond, length as m-dash]O→Mo bridges crystallises. The complexes can catalyse epoxidation of cis-cyclooctene and sulfoxidation of methyl-p-tolylsulfide, using tert-butyl hydroperoxide as oxidant.

  10. Electrospinning synthesis of porous Al{sub 2}O{sub 3} nanofibers by pluronic P123 triblock copolymer surfactant and properties of uranium (VI)-sorption

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Bo [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Department of Applied Chemistry Engineering, Jilin Vocational College of Industry and Technology, Jilin 132013 (China); Institute of Petrochemistry Heilongjiang Academy of Sciences, Harbin 150001 (China); Fan, Meiqing [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Department of Applied Chemistry Engineering, Jilin Vocational College of Industry and Technology, Jilin 132013 (China); Tan, Lichao [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Li, Rumin, E-mail: lirumin@hrbeu.edu.cn [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Song, Dalei; Liu, Qi [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Wang, Jun, E-mail: zhqw1888@sohu.com [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China); Institute of Advanced Marine Materials, Harbin Engineering University, Harbin 150001 (China); Zhang, Bin [Institute of Petrochemistry Heilongjiang Academy of Sciences, Harbin 150001 (China); Jing, Xiaoyan [The Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin 150001 (China)

    2016-07-01

    Porous Alumina (Al{sub 2}O{sub 3}) nanofibers were prepared by electrospinning process using pluronic P123 triblock copolymer surfactant as template. The characterizations of the adsorbent were investigated by X-ray diffraction (XRD) fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption–desorption. The obtained nanofibers were used as adsorbents for the removal of Uranium (VI). The maximum adsorption occurred at pH 5, the equilibrium adsorption amount was about 87 mg/g, and the equilibrium time was 6.0 h. A pseudo-second order model could best describe adsorption kinetics. The adsorption equilibrium data fit Freundlich adsorption isotherm equation well. Thermodynamic parameters such as standard enthalpy (ΔH{sup 0}), standard entropy (ΔS{sup 0}), standard free energy (ΔG{sup 0}) and activation energy (E{sub a}) were calculated. The results predict an endothermic nature of adsorption and a spontaneous process. - Highlights: • The porous Al{sub 2}O{sub 3} nanofibers were used for U(VI)-sorption for the first time. • The adsorption process was endothermic and spontaneous. • The maximum adsorption capacity was 87 mg g{sup −1} at 25 °C.

  11. Sorption of Uranium(VI) and Thorium(IV) ions from aqueous solutions by nano particle of ion exchanger SnO2

    International Nuclear Information System (INIS)

    Nilchi, A.; Rasouli Garmarodi, S.; Shariati Dehaghan, T.

    2012-01-01

    Due to the extensive use of nuclear energy and its replacement for fossil fuels in recent decades, the radioactive waste production has increased enormously. The vast majority of the radioactive wastes products, are in the liquid form and consequently their treatment is of great importance. In this paper, tin oxide with nano-structure has been synthesized as an absorbent by the homogenous sedimentation method in the presence of urea, so as to adsorb uranium(VI) and thorium(IV) ions. The results obtained from the XRD, Scanning Electron Microscopy and nitrogen adsorption/ desorption analyses on the tin oxide sample showed the cassiterite structure with an average particle size of 30 nanometer and a specific surface area of 27.5 m 2 /g. The distribution coefficients of uranium and thorium were studied by means of batch method. The effects of different variables such as pH and time of contact between the exchanger and solution were investigated and the optimum conditions for sorption of these ions were determined.

  12. Computer modelling of the chemical speciation of caesium, uranium(VI) and neptunium(V) in human duodenal fluids under fasting conditions

    International Nuclear Information System (INIS)

    Jones, P.W.; Taylor, D.M.; Webb, L.M.; Williams, D.R.

    2002-01-01

    A model simulating the human duodenal contents under physiologically realistic, fasting conditions was developed using the joint expert speciation system (JESS) computer program and database and used to investigate the chemical speciation of caesium, uranium(VI) and neptunium(V). Over the pH range 5.0-9.0, and the concentration range 5x10 -15 -5x10 -5 mol dm -3 , caesium was predicted to occur predominantly as the absorbable free monovalent cation Cs + (∼95%) with species such as CsHPO 4 - and CsCl representing the remainder. The presence or absence of sulphate at 2.1x10 -3 mol dm -3 did not influence the predicted speciation. Uranium was predicted to be present entirely as a soluble, highly charged species, both in the absence and in the presence of sulphate. Between pH 5.0 and ∼6.5 the UO 2 H 2 (PO 4 ) 2 2- predominated, above this pH carbonate species, either UO 2 (CO 3 ) 4 6- or, possibly, UO 2 (CO 3 ) 5 8- . At pH 8.0, and in the presence of sulphate, neptunium(V) was predicted to exist solely as the tetrasulphate species, whilst in the absence of sulphate, an array of negatively charged soluble carbonate species predominated. Studies over the pH range 5.0-9.0 predicted the formation of a spectrum of negatively charged carbonate and phosphate species, ∼40% of the total neptunium was predicted to be present as the electrically net-neutral species NpO 2 HCO 3 at pH6.0, ∼20% at pH 7.0, ∼10% at pH 7.5 and ∼1% at pH 8.0. The observed speciation patterns of uranium and neptunium did not change over the concentration range 5x10 -15 -5x10 -5 mol dm -3 and no solid species were predicted to occur under the conditions simulated. Whether the predicted electrically net-neutral neptunium species or the uranium pentacarbonate species do actually occur under true physiological conditions remains to be established. The observed speciation patterns for caesium and uranium are consistent with the observed absorption of these elements by humans; however, the

  13. Irradiated uranium reprocessing, Final report I-VI, Part VI - Separation of uranium, plutonium and fission products from HNO{sub 3} solution on the zirconium phosphate (part I), Adsorption equilibrium and kinetics; Prerada ozracenog urana. Zavrani izvestaj - I-VI, VI Deo - Odvajanje urana, plutonijuma i fisionih produkata iz rastvora HNO{sub 3} na cirkonijum fosfatu (deo I.), Ravnoteza i kinetika adsorpcije

    Energy Technology Data Exchange (ETDEWEB)

    Gal, I; Ruvarac, A [Institute of Nuclear Sciences Boris Kidric, Odeljenje za eksploataciju nuklearnog goriva, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    Separation of uranium, plutonium and long-lived fission products was investigated on a inorganic ion exchanger. Zirconium phospate was chosen for this purpose because its ion exchanger properties were well known. This report deals with the study of equilibrium and kinetics of the adsorption.

  14. Radiological risk assessment of U(nat) in the ground water around Jaduguda uranium mining complex

    International Nuclear Information System (INIS)

    Sethy, N.K.; Jha, V.N.; Shukla, A.K.; Tripathi, R.M.; Puranik, V.D.

    2010-01-01

    Uranium is present naturally in earth crust and hence at trace level in ground water, sea water, building materials etc. Naturally occurring radionuclide originating from industrial activities, metal mining and waste depository may contribute to the nearby ground water by radionuclide migration. Ground water ecosystem surrounding the uranium processing facility at Jaduguda has been studied for natural uranium distribution. In the present study, the drinking water sources at various distance zone (with in 1.6 km, 1.6-5 km and > 5km) covering all directions around the waste depository (tailings pond) have been investigated for uranium content. Evaluation of intake, ingestion dose and subsequent risk for population residing around the tailings pond has been carried out. Annual intake of uranium through drinking water for members of public residing around the uranium complex is found to be in the range of 41.8 - 44.4 Bq.y -1 . The intake and ingestion dose is appreciably low ( -1 ) which is far below the WHO recommended level of 100 Sv.y -1 . The life time radiological risk due to uranium natural in drinking water is insignificant and found to be of the order of 10 -6 . (author)

  15. Novel complexes of molybdenum (VI) and oxovanadium (IV) with cycloheptanecarbohydroxamic acid (CPHA) and their therapeutic effect on some microorganisms

    International Nuclear Information System (INIS)

    Aliyu, A.O.

    2012-01-01

    Cycloheptanecarbohydroxamic acid (CPHA) was synthesized, characterized and their pka determined spectrophotometrically as 9.70 at 25 deg. C and in buffers of 0.1 mol/dm-) ionic strength (J). The spectroscopic investigation of its reaction with Mo (VI) and VO (IV) in aqueous solution revealed the sole formation of 1:6 and 1:2 complexes at equilibrium. The isolated complexes were characterized by elemental analysis, molar conductance, magnetic moments, IR and electronic spectra studies. The magnetic and Spectra studies of the isolated complexes indicate coordination via oxygen atom of the hydroxamate group. The interactions of both the ligand and its isolated complexes with some microorganisms have been studied. Both the ligand and its complexes show significant sensitivity towards the microbes and also, the related complexes can enhance antibacterial activity. (author)

  16. Synthesis and characterization of a homogeneous and silica supported homoleptic cationic tungsten(vi) methyl complex: application in olefin metathesis

    KAUST Repository

    Dey, Raju

    2016-08-19

    A method for the synthesis of a homogeneous cationic tungsten(VI)penta-methyl complex [(WMe5)(+)(C6F5)(3)BMe-] from neutral tungstenhexamethyl (WMe6) and a silica supported cationic tungstentetramethyl complex [( Si-O-)WMe4+ (C6F5)(3)BMe-] from a neutral silica supported tungstenpentamethyl complex [( Si-O-)WMe5] is described. In both cases a direct demethylation using the B(C6F5)(3) reagent was used. The aforesaid complexes were characterized by liquid or solid state NMR spectroscopy. Interestingly, the homogeneous cationic complex [(WMe5)(+)(C6F5)(3)BMe-] shows moderate activity whereas the supported cationic complex [( Si-O-)WMe4+(C6F5)(3)BMe-] exhibits good activity in olefin metathesis reactions.

  17. Synthesis and characterization of a homogeneous and silica supported homoleptic cationic tungsten(vi) methyl complex: application in olefin metathesis

    KAUST Repository

    Dey, Raju; Samantaray, Manoja; Poater, Albert; Hamieh, Ali Imad Ali; Kavitake, Santosh Giridhar; Abou-Hamad, Edy; Callens, Emmanuel; Emwas, Abdul-Hamid M.; Cavallo, Luigi; Basset, Jean-Marie

    2016-01-01

    A method for the synthesis of a homogeneous cationic tungsten(VI)penta-methyl complex [(WMe5)(+)(C6F5)(3)BMe-] from neutral tungstenhexamethyl (WMe6) and a silica supported cationic tungstentetramethyl complex [( Si-O-)WMe4+ (C6F5)(3)BMe-] from a neutral silica supported tungstenpentamethyl complex [( Si-O-)WMe5] is described. In both cases a direct demethylation using the B(C6F5)(3) reagent was used. The aforesaid complexes were characterized by liquid or solid state NMR spectroscopy. Interestingly, the homogeneous cationic complex [(WMe5)(+)(C6F5)(3)BMe-] shows moderate activity whereas the supported cationic complex [( Si-O-)WMe4+(C6F5)(3)BMe-] exhibits good activity in olefin metathesis reactions.

  18. Uranium

    Energy Technology Data Exchange (ETDEWEB)

    Williams, R M

    1976-01-01

    Evidence of expanding markets, improved prices and the short supply of uranium became abundantly clear in 1975, providing the much needed impetus for widespread activity in all phases of uranium operations. Exploration activity that had been at low levels in recent years in Canada was evident in most provinces as well as the Northwest Territories. All producers were in the process of expanding their uranium-producing facilities. Canada's Atomic Energy Control Board (AECB) by year-end had authorized the export of over 73,000 tons of U/sub 3/0/sub 8/ all since September 1974, when the federal government announced its new uranium export guidelines. World production, which had been in the order of 25,000 tons of U/sub 3/0/sub 8/ annually, was expected to reach about 28,000 tons in 1975, principally from increased output in the United States.

  19. Titration of uranium trace amounts in waters environment

    International Nuclear Information System (INIS)

    Larabi-Gruet, N.; Ithurbide, A.; Poulesquen, A.; Beaucaire, C.; Peulon, S.; Chausse, A.

    2007-01-01

    In the framework of studies concerning the uranium migration in soils and rocks, it seems necessary to quantify the uranium(VI) dissolved in solution. In the environmental conditions, the uranium(VI) is present at trace amounts. The most adapted method to this study and easy to carry out is the Adsorptive Stripping Voltammetry. By addition of a compound (ligand) with a reducing and strong complexing power, the uranium(VI) present in solution is reduced into a U(VI)-ligand complex. This specie is then oxidized and adsorbed on the mercury droplet where an electrolytic pre-concentration of the element to determine the quantity of is carried out. At last, a cathodic re-dissolution of the specie adsorbed in the U(IV)-ligand complex is carried out. The chosen analytical method is the differential impulsional voltammetry. With this method, it is possible to quantify low electro-active species quantities (sensitivity ∼25 ppt (10 -10 mol.L -1 ) for the uranium). This titration method in solution has been optimized, at first, in a non complexing medium. Then, the uranium in solution has been titrated in media whose composition has been progressively complexed (additions of CO 3 2- , SO 4 2- , Cl - ..) for being at last representative of the environmental interstitial waters. At last, this study has been carried out too by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) in order to compare the analysis sensitivity of these two detection methods. (O.M.)

  20. Uranium in 50 years? - Deeper, lower grade and more metallurgically complex? - 5312

    International Nuclear Information System (INIS)

    Polak, C.

    2015-01-01

    The economic exploitation of uranium deposits in the next 50 years will benefit from advances in mining and processing technology. The 'easiness' to find uranium deposits are a relic of the past. Exploration will need to make use of new technologies to help find blind or deep deposits. These issues are already being addressed by the uranium industry. Another issue will be to obtain social and environmental acceptation of the industry. To summarize the uranium mining industry is faced with 3 main challenges that are not necessarily mutually exclusive: deeper deposits, lower grades and chemically complex ores. The deposits of the next half of 21. century are likely to face at least one but potentially a combination of two or three of these challenges

  1. Synthesis, characterisation and chemical reactivity of some new binuclear dioxouranium(VI) complexes derived from organic diazo compounds (Preprint No. CT-33)

    International Nuclear Information System (INIS)

    Pujar, M.A.; Pirgonde, B.R.

    1988-02-01

    A new series of binuclear dioxouranium(VI) complexes of polydentatate diazo compounds have been synthesised and characterised adequately by analysis, physio-chemical techniques and reactivity of these complexes. The location of bonding site of ligands, stability of complexes and status of U-O bond and probable structures of these complexes have been discussed. (author). 10 refs

  2. Single-molecule magnetism in a single-ion triamidoamine uranium(V) terminal mono-oxo complex

    Energy Technology Data Exchange (ETDEWEB)

    King, David M.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T. [School of Chemistry, University of Nottingham (United Kingdom); Tuna, Floriana; McInnes, Eric J.L. [School of Chemistry and Photon Science Institute, University of Manchester (United Kingdom)

    2013-04-26

    Straightforward oxidation of a triamidoamine uranium(III) complex with trimethyl-N-oxide affords a uranium(V) terminal mono-oxo complex which is the first clear-cut example of a uranium(V) single-molecule magnet (SMM). This monometallic complex unambiguously shows that a strongly axially ligated and thus anisotropic ligand field can be used to overcome the limited magnetic anisotropy of uranium(V). (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Single-molecule magnetism in a single-ion triamidoamine uranium(V) terminal mono-oxo complex

    International Nuclear Information System (INIS)

    King, David M.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T.; Tuna, Floriana; McInnes, Eric J.L.

    2013-01-01

    Straightforward oxidation of a triamidoamine uranium(III) complex with trimethyl-N-oxide affords a uranium(V) terminal mono-oxo complex which is the first clear-cut example of a uranium(V) single-molecule magnet (SMM). This monometallic complex unambiguously shows that a strongly axially ligated and thus anisotropic ligand field can be used to overcome the limited magnetic anisotropy of uranium(V). (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Ultraviolet-B radiation mobilizes uranium from uranium-dissolved organic carbon complexes in aquatic systems, demonstrated by asymmetrical flow field-flow fractionation.

    Science.gov (United States)

    Nehete, Sachin Vilas; Christensen, Terje; Salbu, Brit; Teien, Hans-Christian

    2017-05-05

    Humic substances have a tendency to form complexes with metal ions in aquatic medium, impacting the metal mobility, decreasing bioavailability and toxicity. Ultraviolet-B (UV-B) radiation exposure degrades the humic substance, changes their molecular weight distribution and their metal binding capacity in aquatic medium. In this study, we experimented the effect of UV-B radiation on the uranium complexed with fulvic acids and humic acids in a soft water system at different pH, uranium concentrations and radiant exposure. The concentration and distribution of uranium in a complexed form were investigated by asymmetrical flow field-flow fractionation coupled to multi detection technique (AsFlFFF-UV-ICP-MS). The major concentration of uranium present in complexes was primarily associated with average and higher molecular weight fulvic and humic acids components. The concentration of uranium in a complexed form increased with increasing fulvic and humic acid concentrations as well as pH of the solution. The higher molecular weight fraction of uranium was degraded due to the UV-B exposure, transforming about 50% of the uranium-dissolved organic carbon complexes into low molecular weight uranium species in complex form with organic ligands and/or free form. The result also suggests AsFlFFF-UV-ICP-MS to be an important separation and detection technique for understanding the interaction of radionuclides with dissolved organic matter, tracking size distribution changes during degradation of organic complexes for understanding mobility, bioavailability and ecosystem transfer of radionuclides as well as metals. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Uranium

    International Nuclear Information System (INIS)

    Perkin, D.J.

    1982-01-01

    Developments in the Australian uranium industry during 1980 are reviewed. Mine production increased markedly to 1841 t U 3 O 8 because of output from the new concentrator at Nabarlek and 1131 t of U 3 O 8 were exported at a nominal value of $37.19/lb. Several new contracts were signed for the sale of yellowcake from Ranger and Nabarlek Mines. Other developments include the decision by the joint venturers in the Olympic Dam Project to sink an exploration shaft and the release of an environmental impact statement for the Honeymoon deposit. Uranium exploration expenditure increased in 1980 and additions were made to Australia's demonstrated economic uranium resources. A world review is included

  6. Uranium

    International Nuclear Information System (INIS)

    Gabelman, J.W.; Chenoweth, W.L.; Ingerson, E.

    1981-01-01

    The uranium production industry is well into its third recession during the nuclear era (since 1945). Exploration is drastically curtailed, and many staffs are being reduced. Historical market price production trends are discussed. A total of 3.07 million acres of land was acquired for exploration; drastic decrease. Surface drilling footage was reduced sharply; an estimated 250 drill rigs were used by the uranium industry during 1980. Land acquisition costs increased 8%. The domestic reserve changes are detailed by cause: exploration, re-evaluation, or production. Two significant discoveries of deposits were made in Mohave County, Arizona. Uranium production during 1980 was 21,850 short tons U 3 O 8 ; an increase of 17% from 1979. Domestic and foreign exploration highlights were given. Major producing areas for the US are San Juan basin, Wyoming basins, Texas coastal plain, Paradox basin, northeastern Washington, Henry Mountains, Utah, central Colorado, and the McDermitt caldera in Nevada and Oregon. 3 figures, 8 tables

  7. Environmental significance of copper, lead, manganese, uranium and zinc speciation in the event of contaminated waters release from the Ranger Uranium Mining Complex

    International Nuclear Information System (INIS)

    Noller, B.N.; Currey, N.A.

    1983-01-01

    The likely impact of the accidental release of tailings dam water during the dry season at the Ranger Uranium Mining Complex was examined. A speciation scheme utilising sizing by filtration and ion-exchange with Chelex 100 has given an insight into the likely partitioning of zinc, copper, lead, manganese and uranium following the addition of tailings dam water to samples from waterbodies in the vicinity of the uranium mining/milling complex. The speciation findings are discussed in terms of likely toxic effects on fish

  8. The Y-12 National Security Complex Foreign Research Reactor Uranium Supply Production

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, T. [Nuclear Technology and Nonproliferation Programs, B and W Y-12, L.L.C., Y-12 National Security Complex, Oak Ridge, Tennessee (United States); Keller, A.P. [Disposition and Supply Programs, B and W Y-12, L.L.C., Y-12 National Security Complex, Oak Ridge, Tennessee (United States)

    2011-07-01

    The Foreign Research Reactor (FRR) Uranium Supply Program at the Y-12 National Security Complex supports the nonproliferation objectives of the National Nuclear Security Administration (NNSA) HEU Disposition, the Reduced Enrichment Research and Test Reactors (RERTR), and the United States (U.S.) FRR Spent Nuclear Fuel (SNF) Acceptance Programs. The FRR Supply Program supports the important U.S. government nuclear nonproliferation commitment to serve as a reliable and cost-effective uranium supplier for those foreign research reactors that are converting or have converted to Low-Enriched Uranium (LEU) fuel under the RERTR Program. The NNSA Y-12 Site Office maintains the prime contracts with foreign government agencies for the supply of LEU for their research reactors. The LEU is produced by down blending Highly Enriched Uranium (HEU) that has been declared surplus to the U.S. national defense needs. The down blending and sale of the LEU supports the Surplus HEU Disposition Program Record of Decision to make the HEU non-weapons usable and to recover the economic value of the uranium to the extent feasible. In addition to uranium metal feedstock for fuel fabrication, Y-12 can produce LEU in different forms to support new fuel development or target fabrication for medical isotope production. With production improvements and efficient delivery preparations, Y-12 continues to successfully support the global research reactor community. (author)

  9. Study of aqueous complexes of uranium (IV) in an acid medium by nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Kiener, C.; Folcher, G.; Rigny, P.; Virlet, J.

    1976-01-01

    The hydration of tetravalent uranium in acid solutions has been studied by proton magnetic resonance. Longitudinal and transversal relaxation rates of water are reported as a function of temperature, acidity, and added ions. The relaxation rates observed in perchloric solutions at high temperature are governed by the exchange process of water molecules between the inner coordination sphere of uranium(IV) and the bulk water. The bound proton's lifetime lies between 10 ms and 1 s. At pH > 0, the exchange rate depends upon acidity according to a simple expression. At high concentrations of diamagnetic ions the exchange rate depends linearly upon water activity. At low temperature, the proton relaxation rates are dominated by an outer sphere effect and the electronic relaxation time of uranium(IV) is found to be about 10 -13 s. No signal is observed from protons of the water molecules in the first sphere, firmly bound to uranium(IV), which undergo rapid relaxation. The chemical shift of the proton absorption signal in hydrochloric solutions arise from tightly bound water molecules in paramagnetic interaction with uranium(IV) in a second sphere, and in fast exchange with the bulk water. Above a chlorine concentration of 6 M, the monochloro complex of uranium(IV) contributes to the chemical shift. (author)

  10. Investigations on uranium sorption on bentonite and montmorillonite, respectively, and uranium in environmental samples; Untersuchungen zur Uransorption an Bentonit bzw. Montmorillonit sowie von Uran in Umweltproben

    Energy Technology Data Exchange (ETDEWEB)

    Azeroual, Mohamed

    2010-09-22

    The geotechnical barrier is an important component of a geological repository and consists of compacted bentonite surrounding radioactive waste containers. Its most important functions are, to retard the radionuclide migration into the biosphere and to prevent groundwater contact with containers. lt is therefore of central importance to investigate the bentonite material on its capacity to sorb radionuclides under near-natural chemical and physical conditions. The purpose of this work was to study the adsorption of uranium(VI) on bentonit and on montmorillonite-standards at high uranium concentrations. Thereby, a special account was given to the calcium-uranyl-carbonate complexation, which leads to the formation of very stable and mobile uncharged Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} complex. Results of batch experiments showed that the dicalcium-uranyl-tricarbonate complexation lowers the uranium(VI) sorption on natural clay (bentonite) by a factor of up to 3. After 21 days of contact time, about 40 % and 20 % of the initial uranium(VI)concentration were sorbed on Na-bentonite and ea-bentonite, respectively, from a solution with Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} dominating the uranium(VI) speciation. On the contrary, about 55 % of the initial uranium(VI)-concentration were sorbed on thes clays from the solution, in which (UO{sub 2}){sub 2}CO{sub 3}(OH){sub 3}{sup -} complex dominated the uranium(VI) speciation. Thus uranium(VI) sorption is more strongly influenced by the solution composition than by bentonite type. Na-bentonite should be used instead of ea-bentonite as a geotechnical barrier, since calcium-uranyl-carbonate complexation may be a realistic scenario. Further SEM-EDX and HREM-EDX studies showed that uranium(VI) sorption occurred predominantly on montmorillonite, which is the main component of bentonite. Uranium(VI) sorption on bentonite's accessory Minerals (pyrite, calcite, mica, and feldspar) was not observed. Investigation of uranium(VI

  11. Uranium Phases in Contaminated Sediments Below Hanford's U Tank Farm

    International Nuclear Information System (INIS)

    Um, Wooyong; Wang, Zheming; Serne, R. Jeffrey; Williams, Benjamin D.; Brown, Christopher F.; Dodge, Cleveland J.; Francis, Arokiasamy J.

    2009-01-01

    Macroscopic and spectroscopic investigations (XAFS, XRF and TRLIF) on Hanford contaminated vadose zone sediments from the U-tank farm showed that U(VI) exists as different surface phases as a function of depth below ground surface (bgs). Dominant U(VI) silicate precipitates (boltwoodite and uranophane) were present in shallow-depth sediments (15-16 m bgs). In the intermediate depth sediments (20-25 m bgs), adsorbed U(VI) phases dominated but small amounts of surface precipitates consisting of polynuclear U(VI) surface complex were also identified. The deep depth sediments (> 28 m bgs) showed no signs of contact with tank wastes containing Hanford-derived U(VI), but natural uranium solid phases were observed. Most of the U(VI) was preferentially associated with the silt and clay size fractions and showed strong correlation with Ca, especially for the precipitated U(VI) silicate phase in the shallow depth sediments. Because U(VI) silicate precipitates dominate the U(VI) phases in the shallow depth sediments, macroscopic (bi)carbonate leaching should result in U(VI) releases from both desorption and dissolution processes. Having several different U(VI) surface phases in the Hanford contaminated sediments indicates that the U(VI) release mechanism could be complicated and that detailed characterization of the sediments would be needed to estimate U(VI) fate and transport in vadose zone

  12. General synthesis of (salen)ruthenium(III) complexes via N...N coupling of (salen)ruthenium(VI) nitrides.

    Science.gov (United States)

    Man, Wai-Lun; Kwong, Hoi-Ki; Lam, William W Y; Xiang, Jing; Wong, Tsz-Wing; Lam, Wing-Hong; Wong, Wing-Tak; Peng, Shie-Ming; Lau, Tai-Chu

    2008-07-07

    Reaction of [Ru (VI)(N)(L (1))(MeOH)] (+) (L (1) = N, N'-bis(salicylidene)- o-cyclohexylenediamine dianion) with excess pyridine in CH 3CN produces [Ru (III)(L (1))(py) 2] (+) and N 2. The proposed mechanism involves initial equilibrium formation of [Ru (VI)(N)(L (1))(py)] (+), which undergoes rapid N...N coupling to produce [(py)(L (1))Ru (III) N N-Ru (III)(L (1))(py)] (2+); this is followed by pyridine substituion to give the final product. This ligand-induced N...N coupling of Ru (VI)N is utilized in the preparation of a series of new ruthenium(III) salen complexes, [Ru (III)(L)(X) 2] (+/-) (L = salen ligand; X = H 2O, 1-MeIm, py, Me 2SO, PhNH 2, ( t )BuNH 2, Cl (-) or CN (-)). The structures of [Ru (III)(L (1))(NH 2Ph) 2](PF 6) ( 6), K[Ru (III)(L (1))(CN) 2] ( 9), [Ru (III)(L (2))(NCCH 3) 2][Au (I)(CN) 2] ( 11) (L (2) = N, N'-bis(salicylidene)- o-phenylenediamine dianion) and [N ( n )Bu 4][Ru (III)(L (3))Cl 2] ( 12) (L (3) = N, N'-bis(salicylidene)ethylenediamine dianion) have been determined by X-ray crystallography.

  13. Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO3 (-) and SO3 (2-) in Aqueous Solution.

    Science.gov (United States)

    Wang, Qian; Zhao, Hong Yan; Man, Wai-Lun; Lam, William W Y; Lau, Kai-Chung; Lau, Tai-Chu

    2016-07-25

    The kinetics and mechanism of the reaction of S(IV) (SO3 (2-) +HSO3 (-) ) with a ruthenium(VI) nitrido complex, [(L)Ru(VI) (N)(OH2 )](+) (Ru(VI) N, L=N,N'-bis(salicylidene)-o-cyclohexyldiamine dianion), in aqueous acidic solutions are reported. The kinetic results are consistent with parallel pathways involving oxidation of HSO3 (-) and SO3 (2-) by Ru(VI) N. A deuterium isotope effect of 4.7 is observed in the HSO3 (-) pathway. Based on experimental results and DFT calculations the proposed mechanism involves concerted N-S bond formation (partial N-atom transfer) between Ru(VI) N and HSO3 (-) and H(+) transfer from HSO3 (-) to a H2 O molecule. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Separation of uranium(VI) by liquid-solid extraction with tri-n-octylphosphine oxide diluted with naphthalene

    International Nuclear Information System (INIS)

    Shigetomi, Y.; Kojima, T.; Kamba, H.; Yamamoto, Y.

    1980-01-01

    Liquid-liquid distribution with tri-n-octylphosphine oxide (TOPO) and molten naphthalene has been investigated for the extraction of 20 metals from nitric acid and hydrochloric acid solutions. Uranium is quantitatively extracted from 1 M nitric acid or hydrochloric acid by using 100 mg of TOPO and 200 mg of naphthalene and shaking for 5 min at 80 0 C, and separated from transition metals, alkaline earth metals and rare earth metals (except scandium). Addition of naphthalene increases the extraction efficiency. (Auth.)

  15. Geobacter daltonii sp. nov., an Fe(III)- and uranium(VI)-reducing bacterium isolated from a shallow subsurface exposed to mixed heavy metal and hydrocarbon contamination.

    Science.gov (United States)

    Prakash, Om; Gihring, Thomas M; Dalton, Dava D; Chin, Kuk-Jeong; Green, Stefan J; Akob, Denise M; Wanger, Greg; Kostka, Joel E

    2010-03-01

    An Fe(III)- and uranium(VI)-reducing bacterium, designated strain FRC-32(T), was isolated from a contaminated subsurface of the USA Department of Energy Oak Ridge Field Research Center (ORFRC) in Oak Ridge, Tennessee, where the sediments are exposed to mixed waste contamination of radionuclides and hydrocarbons. Analyses of both 16S rRNA gene and the Geobacteraceae-specific citrate synthase (gltA) mRNA gene sequences retrieved from ORFRC sediments indicated that this strain was abundant and active in ORFRC subsurface sediments undergoing uranium(VI) bioremediation. The organism belonged to the subsurface clade of the genus Geobacter and shared 92-98 % 16S rRNA gene and 75-81 % rpoB gene sequence similarities with other recognized species of the genus. In comparison to its closest relative, Geobacter uraniireducens Rf4(T), according to 16S rRNA gene sequence similarity, strain FRC-32(T) showed a DNA-DNA relatedness value of 21 %. Cells of strain FRC-32(T) were Gram-negative, non-spore-forming, curved rods, 1.0-1.5 microm long and 0.3-0.5 microm in diameter; the cells formed pink colonies in a semisolid cultivation medium, a characteristic feature of the genus Geobacter. The isolate was an obligate anaerobe, had temperature and pH optima for growth at 30 degrees C and pH 6.7-7.3, respectively, and could tolerate up to 0.7 % NaCl although growth was better in the absence of NaCl. Similar to other members of the Geobacter group, strain FRC-32(T) conserved energy for growth from the respiration of Fe(III)-oxyhydroxide coupled with the oxidation of acetate. Strain FRC-32(T) was metabolically versatile and, unlike its closest relative, G. uraniireducens, was capable of utilizing formate, butyrate and butanol as electron donors and soluble ferric iron (as ferric citrate) and elemental sulfur as electron acceptors. Growth on aromatic compounds including benzoate and toluene was predicted from preliminary genomic analyses and was confirmed through successive transfer with

  16. Dissolution of uranium oxide TBP-HNO3 complex

    International Nuclear Information System (INIS)

    Mizuno, Mineo; Kosaka, Yuji; Mori, Yukihide; Shimada, Takashi

    2002-12-01

    As a head end process for the pulverization of the spent fuel, the mechanical method (the shredder method) and the pyro-chemical method (oxidisation heat-treatment) have been examined. UO 2 is a main ingredient of Uranium oxide powder by the mechanical method, and U 3 O 8 is that by the pyro-chemical method. Moreover, the particle size of the pulverized powder depend on the conditions of the pulverizing process. As it was considered that the difference of dissolution rates of samples was caused by the difference of sample chemical forms and dissolution temperature, parametric surveys on chemical form and particle size of powder and dissolution temperature were carried out, and the following results were obtained. 1) The remarkable difference of dissolution rate between U 3 O 8 powder (average particle size 3.7 μm) and UO 2 powder (average particle size 2.4 μm) which have comparatively similar particle size was not observed. 2) It was confirmed that the dissolution rate became lower according to the particle size increase (average particle size 2.4 μm-1 mm). And it was considered that dissolution rate had strong dependency on particle size, according to the results that the powder with 1 mm particle size did not dissolute completely after 5 hours test. 3) The temperature dependency of the dissolution rate was confirmed by dissolution test with UO 2 powder (average particle size 2.4 μm-1 mm). The higher dissolution rate was obtained in the higher dissolution temperature, and 11 kcal/mol was obtained as activation energy of dissolution. 4) In the dissolution test of UO 2 powder, the nitric acid concentration started to change earlier than that of U 3 O 8 powder and concentration change range became larger compared with that in the dissolution test of U 3 O 8 powder. It was considered that those differences were caused by difference in mole ratio of Uranium and nitric acid which are consumed in the dissolution reaction (3:7 for U 3 O 8 , 3:8 for UO 2 ). 5) In case

  17. Comparison of numerical and physico-chemical models for on-line spectrophotometric control of uranium

    International Nuclear Information System (INIS)

    Corriou, J.P.; Boisde, G.

    1986-04-01

    In view of on-line spectrophotometric control of fuel reprocessing streams, a physico-chemical model able to predict uranium and nitric acid concentrations in an uranyl nitrate-nitric acid system has been searched. Thus the influences of the following parameters: uranium, nitrate, hydrogen ion concentrations, ionic strength, on the equilibria of complexation of uranium (VI) nitrate have been evaluated. Extinction coefficients for the uranium mononitrate and uranium dinitrate complexes are given between 410 and 440 nm. The apparent equilibrium constants are determined as a function of the ionic strength. The limitations of this predictive model are emphasized and comparisons with numerical models are discussed. (16 refs)

  18. Potential Aquifer Vulnerability in Regions Down-Gradient from Uranium In Situ Recovery (ISR) Sites

    Science.gov (United States)

    Sandstone-hosted roll-front uranium ore deposits originate when U(VI) dissolved in groundwater is reduced and precipitated as insoluble U(IV) minerals. Groundwater redox geochemistry, aqueous complexation, and solute migration are instrumental in leaching uranium from source rock...

  19. Uranium

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    Recent decisions by the Australian Government will ensure a significant expansion of the uranium industry. Development at Roxby Downs may proceed and Ranger may fulfil two new contracts but the decision specifies that apart from Roxby Downs, no new mines should be approved. The ACTU maintains an anti-uranium policy but reaction to the decision from the trade union movement has been muted. The Australian Science and Technology Council (ASTEC) has been asked by the Government to conduct an inquiry into a number of issues relating to Australia's role in the nuclear fuel cycle. The inquiry will examine in particular Australia's nuclear safeguards arrangements and the adequacy of existing waste management technology. In two additional decisions the Government has dissociated itself from a study into the feasibility of establishing an enrichment operation and has abolished the Uranium Advisory Council. Although Australian reserves account for 20% of the total in the Western World, Australia accounts for a relatively minor proportion of the world's uranium production

  20. Uranium

    International Nuclear Information System (INIS)

    Anon.

    1981-01-01

    The French Government has decided to freeze a substantial part of its nuclear power programme. Work has been halted on 18 reactors. This power programme is discussed, as well as the effect it has on the supply of uranium by South Africa

  1. Diazoalkane reduction for the synthesis of uranium hydrazonido complexes

    Energy Technology Data Exchange (ETDEWEB)

    Matson, Ellen M.; Fanwick, Phillip E.; Bart, Suzanne C. [Department of Chemistry, Purdue University, West Lafayette, IN (United States)

    2012-11-15

    The reactivity of the uranium(III) alkyl Tp*{sub 2}UCH{sub 2}Ph (1) toward diazoalkanes is reported. Addition of 1 equiv. N{sub 2}CPh{sub 2} produces 0.5 equiv. bibenzyl, along with Tp*{sub 2}U(N{sub 2}CPh{sub 2}) (2). This species is dynamic in solution at room temperature and rapidly interconverts between the η{sup 1}- and η{sup 2} isomers as determined by variable-temperature {sup 1}H NMR spectroscopy. X-ray crystallographic analysis at low temperature shows exclusively the η{sup 2} isomer, which features a short U-N multiple bond analogous to an imido species. The η{sup 1} isomer reacts quantitatively with aldehydes and ketones through multiple bond metathesis to produce Tp*{sub 2}U(O) and the corresponding ketazine. Treatment of 1 with N{sub 2}CHSiMe{sub 3} generates 0.5 equiv. bibenzyl and the η{sup 1} isomer Tp*{sub 2}U(N{sub 2}CHSiMe{sub 3}) (3). This species is unstable over the course of hours, and there is no spectroscopic evidence for the η{sup 2} isomer. Tp*{sub 2}U(η{sup 1}-N{sub 2}CHSiMe{sub 3}) can be trapped by addition of phenylacetylene by a [2+2] cycloaddition to afford the uranium(IV) metallacycle Tp*{sub 2}U[(N-N = CHSiMe{sub 3})CHCPh] (4). Crystallographic data for 4 are presented. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Synthesis of uranium and thorium dioxides by Complex Sol-Gel Processes (CSGP). Synthesis of uranium oxides by Complex Sol-Gel Processes (CSGP)

    International Nuclear Information System (INIS)

    Deptula, A.; Brykala, M.; Lada, W.; Olczak, T.; Wawszczak, D.; Chmielewski, A.G.; Modolo, G.; Daniels, H.

    2010-01-01

    In the Institute of Nuclear Chemistry and Technology (INCT), a new method of synthesis of uranium and thorium dioxides by original variant of sol-gel method - Complex Sol-Gel Process (CSGP), has been elaborated. The main modification step is the formation of nitrate-ascorbate sols from components alkalized by aqueous ammonia. Those sols were gelled into: - irregularly agglomerates by evaporation of water; - medium sized microspheres (diameter <150) by IChTJ variant of sol-gel processes by water extraction from drops of emulsion sols in 2-ethylhexanol-1 by this solvent. Uranium dioxide was obtained by a reduction of gels with hydrogen at temperatures >700 deg. C, while thorium dioxide by a simple calcination in the air atmosphere. (authors)

  3. Behavior of copper (II )and uranium ( VI) in precipitation chromatography in the system anion exchange resin - hexacyanoferrate (II )

    International Nuclear Information System (INIS)

    Seneda, Jose Antonio

    1997-01-01

    In this work it is shown the efficiency of precipitation chromatography for separation and concentration of metallic elements by using a strong anionic-exchange resin saturated with hexacyanoferrate (II). Metallic cations, like Cu (II) and U (VI), are retained from highly diluted solutions and enriched into the resin, in the form of the correspondent insoluble hexacyanoferrate (II), precipitated inside the resin, which permitted the visual observation of a chromatographic zone on the top of the column. It will be discussed the conditions of sorption and elution of the cations uptake by the resin. This system permits the enrichment of the above mentioned cations onto the resin and offers the possibility of interesting separations as well. (author)

  4. Oxygen atom transfer from a trans-dioxoruthenium(VI) complex to nitric oxide.

    Science.gov (United States)

    Man, Wai-Lun; Lam, William W Y; Ng, Siu-Mui; Tsang, Wenny Y K; Lau, Tai-Chu

    2012-01-02

    In aqueous acidic solutions trans-[Ru(VI)(L)(O)(2)](2+) (L=1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane) is rapidly reduced by excess NO to give trans-[Ru(L)(NO)(OH)](2+). When ≤1 mol equiv NO is used, the intermediate Ru(IV) species, trans-[Ru(IV)(L)(O)(OH(2))](2+), can be detected. The reaction of [Ru(VI)(L)(O)(2)](2+) with NO is first order with respect to [Ru(VI)] and [NO], k(2)=(4.13±0.21)×10(1) M(-1) s(-1) at 298.0 K. ΔH(≠) and ΔS(≠) are (12.0±0.3) kcal mol(-1) and -(11±1) cal mol(-1) K(-1), respectively. In CH(3)CN, ΔH(≠) and ΔS(≠) have the same values as in H(2)O; this suggests that the mechanism is the same in both solvents. In CH(3)CN, the reaction of [Ru(VI)(L)(O)(2)](2+) with NO produces a blue-green species with λ(max) at approximately 650 nm, which is characteristic of N(2)O(3). N(2)O(3) is formed by coupling of NO(2) with excess NO; it is relatively stable in CH(3)CN, but undergoes rapid hydrolysis in H(2)O. A mechanism that involves oxygen atom transfer from [Ru(VI)(L)(O)(2)](2+) to NO to produce NO(2) is proposed. The kinetics of the reaction of [Ru(IV)(L)(O)(OH(2))](2+) with NO has also been investigated. In this case, the data are consistent with initial one-electron O(-) transfer from Ru(IV) to NO to produce the nitrito species [Ru(III)(L)(ONO)(OH(2))](2+) (k(2)>10(6) M(-1) s(-1)), followed by a reaction with another molecule of NO to give [Ru(L)(NO)(OH)](2+) and NO(2)(-) (k(2)=54.7 M(-1) s(-1)). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinghao [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Cheng, Cheng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xiao, Chengjian, E-mail: xiaocj@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Shao, Dadong, E-mail: shaodadong@126.com [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, Zimu, E-mail: xzm@mail.ustc.edu.cn [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Wang, Jiaquan; Hu, Shuheng [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Li, Xiaolong; Wang, Weijuan [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2017-07-31

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH < 6.5 because of the strong complexation, and inhibits U(VI) adsorption at pH > 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  6. Simultaneous precipitation of carbonato complexes of uranium and plutonium with cationic surfactants

    International Nuclear Information System (INIS)

    Heckmann, K.; Strnad, J.; Huber, K.

    1992-01-01

    The proposed method allows to separate Uranium, Thorium and Cerium from carbonate solutions and the further processing of these metals to mixed oxides. The separation can be divided into three steps: 1. Precipitation of the metals with a 10-fold surplus of carbonate and a 5-fold surplus of a cationic surfactant. 2. Thermal decomposition of the precipitates in air at 600 C. 3. Reduction of U(VI) to U(IV) with CO at 500 C. Mixed oxides in any ratio are formed in this way. This is possible due to the coprecipitation of both metals. Comparing the standard potentials it is clear that Ce(IV) is more easily reduced that Pu(IV). Therefore, the chance on the formation of U/Pu mixed oxides by this method is quite good. (orig.) [de

  7. Public communication on times of environmental crisis. The opening of San Rafael 's uranium complex

    International Nuclear Information System (INIS)

    Calvino, Carlos; Cisneros, Martin

    2008-01-01

    Full text: Argentina has had a lot of cultural changes in the last few years. An environmental movement has gathered and is trying to stop the opening of the Sierra Pintada uranium complex, near the city of San Rafael, in the south of Mendoza province. Since 2005, several 'groundless information' have been published in the local media about the dangers of this re-opening. These news exaggerate the properties of radon gas, claiming that it will reach San Rafael city (20 miles from the complex), rising radiological risk among the population, etc. This scene shows a 'non-real' picture of the regulatory activities that the Nuclear Regulatory Authority (ARN), a government agency that regulates nuclear facilities in Argentina, is really and systematically accomplishing. In this situation, the board of Directors of ARN decided to entrust a full analysis of the environmental issue in the area. The Office of Press and Communication implemented a local communication plan, using a Strategic and Systemic tool kit. The period to be analyzed is from second semester 2005 to February 2007. A little bit of history: the San Rafael Complex started in September 20 of 1979. It belongs to the National Commission of Atomic Energy (CNEA), a government agency. Until its temporary suspension in 1995 for international market reasons (uranium price was U$S 10 / pound), almost 2 million tons of uranium were processed. Besides its temporary suspension, the ARN has been constantly monitoring this particular former complex. In the year 2001, CNEA notices that the uranium price starts to rise and entrust National Technology University, Avellaneda Branch, to accomplish an Environmental Impact Report, according to the argentine law 25.585. Due especially to the rising of uranium price, (actually, the uranium price is approximately U$S 200) the national government determined to restart the extraction of the mineral again. By the year 2004, with the results of the Environmental Impact report, CNEA

  8. Spectrophotometric determination of trace uranium in phosphate ore samples from kurum and uro areas, Nuba mountains, Sudan

    International Nuclear Information System (INIS)

    Mohamed, A. A.; Ali, A. H.; Altayeb, M. A. H.

    2004-01-01

    A method was proposed for the spectrophotometric determination of uranium content in phosphate ores. the method is based on the use of nitrogen (v) acid for leaching the rock, and treatment with ammonium carbonate solution, whereby uranium (Vi) is kept in solution as its carbonate complex. The ion-exchange technique was used for the recovery of uranium. Uranium was determined spectrophotometrically by measurement of the absorbance of the yellow uranium (Vi)-8-hydroxyquinolate complex at λ 425 nm. The procedure was used for the determination of trace uranium content in 30 phosphate ore samples collected from Kurun and Uro areas in Nuba mountains in Sudan. X-ray fluorescence technique was employed for the assessment of the method used. The spectrophotometric method results show a high similarity with those obtained by XRF technique. This agreement indicates that the procedure proposed here has been successfully applied for the determination of uranium in phosphate ores. (Author)

  9. Distribution of radium and chemical toxins in the environment of a uranium complex

    International Nuclear Information System (INIS)

    Markose, P.M.; Eapen, K.P.; Venkataraman, S.; Kamath, P.R.

    1978-01-01

    The discharge of waste effluents from mining and milling of uranium ore brings into the aquatic environment radioactive pollutants and chemical toxins. The radioactive element of primary concern is radium and the nonactive pollutants are manganese, chlorides, sulphates and water hardness. In the Uranium Complex, Bihar (India), the low grade ore is mined and processed for recovery of uranium. The waste slurries from the process are neutralised and discharged into the tailings pond(TP) where the solids settle and the effluents flow out into a natural stream, Jurianala. The TP effluent mixes with mine water and floor washings from the mill in the canal on its down stream course to the river, R. Subarnarekha. This study was conducted to assess the total pollution from the liquid discharges in the environment and the impact of discharge on water quality. The results of the study of movement of pollutants in the biosphere and laboratory investigations on containment are presented. (author)

  10. Extraction of uranium from sea water by means of fibrous complex adsorbents

    International Nuclear Information System (INIS)

    Miyamatsu, Tokuhisa; Oguchi, Noboru; Kanchiku, Yoshihiko; Aoyagi, Takanobu

    1982-01-01

    Fibrous complex adsorbents for uranium extraction from sea water were prepared by introducing titanic acid or basic zinc carbonate as effective constituents into fibrous ion exchangers. A fibrous chelate type adsorbent was also tested. Among the adsorbents examined, the following ones demonstrated excellent properties for the recovery of uranium from sea water. a) A fibrous, weakly acidic cation exchanger was treated with titanyl sulfate in aqueous sulfuric acid solution, which was followed by neutralization to afford a fibrous adsorbent containing titanic acid (QC-1f(Ti)). The adsorption capacity for uranium in sea water was estimated by extrapolation to be 50μg-U/g-Ad or 1170 μg-U/g-Ti. b) A fibrous, strongly acidic cation exchanger was treated in a similar way to afford another type of fibrous adsorbent with titanic acid incorporated (QCS-Ti). The adsorption capacity was estimated by extrapolation to be 20-30 μg-U/g-Ad. (author)

  11. Formation of Aqueous MgUO2(CO3)32- Complex and Uranium Anion Exchange Mechanism onto an Exchange Resin

    International Nuclear Information System (INIS)

    Dong, Wenming; Brooks, Scott C

    2008-01-01

    The formation of and stability constants for aqueous Mg-UO2-CO3 complexes were determined using an anion exchange method. Magnesium concentration was varied (up to 20 mmol/L) at constant ionic strength (I = 0.101, 0.202, 0.304, 0.406, and 0.509 mol/kg NaNO3), pH = 8.1, total [U(VI)] = 10.4 mol/L under equilibrium with atmospheric CO2. The results indicate that only the MgUO2(CO3)32- complex is formed. The cumulative formation constant extrapolated to zero ionic strength is similar regardless of the activity correction convention used: log = 25.8 b 0.5 using Davies equation and = 25.02 b 0.08 using specific ion interaction theory (SIT). Uranium sorption onto the exchange resin decreased in the presence of Mg putatively due to the formation of MgUO2(CO3)32- that had a lower affinity for the resin than UO2(CO3)34-. Uranium sorption results are consistent with an equivalent anion exchange reaction between NO3- and UO2(CO3)34- species to retain charge neutrality regardless of Mg concentration. No Mg was associated with the anion exchange resin indicating that the MgUO2(CO3)32- complex did not sorb

  12. Study on the interaction of U(VI) species with natural organic matters in KURT groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Euo Chang; Baik, Min Hoon; Cho, Hye Ryun; Kim, Hee Kyung; Cha, Wansik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-06-15

    The interaction of U(VI) (hexavalent uranium) species with natural organic matter (NOM) in KURT (KAERI Underground Research Tunnel) groundwater is investigated using a laser spectroscopic technique. The luminescence spectra of the NOM are observed in the ultraviolet and blue wavelength regions by irradiating a laser beam at 266 nm in groundwater. The luminescence spectra of U(VI) species in groundwater containing uranium concentrations of 0.034-0.788 mg·L-1 are measured in the green-colored wavelength region. The luminescence characteristics (peak wavelengths and lifetime) of U(VI) in the groundwater agree well with those of Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3}(aq) in a standard solution prepared in a laboratory. The luminescence intensities of U(VI) in the groundwater are weaker than those of Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3}(aq) in the standard solution at the same uranium concentrations. The luminescence intensities of Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3}(aq) in the standard solution mixed with the groundwater are also weaker than those of Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3}(aq) in the standard solution at the same uranium concentrations. These results can be ascribed to calcium-U(VI)-carbonate species interacting with NOM and forming non-radiative U(VI) complexes in groundwater.

  13. Electrocatalytic and simultaneous determination of isoproterenol, uric acid and folic acid at molybdenum (VI) complex-carbon nanotube paste electrode

    International Nuclear Information System (INIS)

    Beitollahi, Hadi; Sheikhshoaie, Iran

    2011-01-01

    Highlights: → A molybdenum (VI) complex-carbon nanotube paste electrode have been fabricated. → This electrode reduced the oxidation potential of isoproterenol by about 175 mV. → It resolved the voltammetric waves of isoproterenol, uric acid and folic acid. - Abstract: This paper describes the development, electrochemical characterization and utilization of a novel modified molybdenum (VI) complex-carbon nanotube paste electrode for the electrocatalytic determination of isoproterenol (IP). The electrochemical profile of the proposed modified electrode was analyzed by cyclic voltammetry (CV) that showed a shift of the oxidation peak potential of IP at 175 mV to less positive value, compared with an unmodified carbon paste electrode. Differential pulse voltammetry (DPV) in 0.1 M phosphate buffer solution (PBS) at pH 7.0 was performed to determine IP in the range from 0.7 to 600.0 μM, with a detection limit of 35.0 nM. Then the modified electrode was used to determine IP in an excess of uric acid (UA) and folic acid (FA) by DPV. Finally, this method was used for the determination of IP in some real samples.

  14. Magnetic-superexchange interactions of uranium(IV) chloride-addition complexes with amides, 2

    International Nuclear Information System (INIS)

    Miyake, Chie; Hinatsu, Yukio; Imoto, Shosuke

    1983-01-01

    The magnetic susceptibilities of five cyclic amide (lactam)-addition complexes of uranium(IV) chloride were measured between room temperature and 2 K. Magnetic-exchange interaction was found only for N-methyl-substituted amide complexes, and a dimer structure was assumed for them on the basis of their chemical properties. Treating interdimer interaction with a molecular-field approximation, the magnetic susceptibilities were calculated to be in good agreement with the experimental results in the temperature region of the maxima in chi sub(A). The transmission of antiparallel spin coupling via the π orbitals of the bridging amide ligands is proposed to explain the strong intradimer superexchange interaction for the uranium(IV) chloride-amide complexes with the magnetic-susceptibility maximum. (author)

  15. CATALYTIC WAVE OF CHLORATE IONS IN THE PREZENCE OF THE MOLYBDENUM (VI - 2,3-DIHYDROXYBENZALDEHYDE COMPLEX

    Directory of Open Access Journals (Sweden)

    Ludmila Kiriyak

    2010-12-01

    Full Text Available The polarographic catalytic current in acid solutions of Mo(VI, 2,3-dihydroxybenzaldehyde (2,3-DHBA and chlorate ions has been investigated. The scheme of reactions taking place in the solutions and on the electrode has been elaborated. The increase of the catalytic current is explained by the formation of the active intermediate complex [Mo(V×2,3-DHBA (ClO3-]. The rate constant of formation for the active intermediate complex K = 2.5 × 106 mol-1 × dm3 × s-1, the activation energy of reaction Ea=14.0 kcal×mol-1 and the activation entropy ∆Sa¹= -28.3 e.u. have also been determined.

  16. Preparations and crystal structures of 8 coordinate uranyl(VI) complexes having macrocyclic ligands derived from pyrroledicarboxialdehydes and diamines

    International Nuclear Information System (INIS)

    Komagine, J.; Takeda, M.; Takahashi, M.

    2006-01-01

    Six 8-coordinate uranyl(VI) complexes with macrocyclic Schiff base ligands derived from 2,6-pyrroledicarboxialdehyde and diamines are prepared and the crystal structures for two of them are determined focusing on the relation between the size of the ligands and U-N bond distances. No difference in average uranyl bond distances and bond angles are observed between [UO 2 (bipytn)](a) and [UO 2 (bipydmtn)](b). U-N bonds of these complexes are, however, not equal; the U-N(pyrrole) bonds [2.45(a), 2.44(b) A] are much shorter than the U-N(imine) bonds [2.67(a), 2.67(b) A]. (author)

  17. Theoretical modeling of the uranium 4f XPS for U(VI) and U(IV) oxides

    Energy Technology Data Exchange (ETDEWEB)

    Bagus, Paul S. [Department of Chemistry, University of North Texas, Denton, Texas 76203-5017 (United States); Nelin, Connie J. [Consulting and Services, 6008 Maury' s Trail, Austin, Texas 78730 (United States); Ilton, Eugene S. [Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2013-12-28

    A rigorous study is presented of the physical processes related to X-Ray photoelectron spectroscopy, XPS, in the 4f level of U oxides, which, as well as being of physical interest in themselves, are representative of XPS in heavy metal oxides. In particular, we present compelling evidence for a new view of the screening of core-holes that extends prior understandings. Our analysis of the screening focuses on the covalent mixing of high lying U and O orbitals as opposed to the, more common, use of orbitals that are nominally pure U or pure O. It is shown that this covalent mixing is quite different for the initial and final, core-hole, configurations and that this difference is directly related to the XPS satellite intensity. Furthermore, we show that the high-lying U d orbitals as well as the U(5f) orbital may both contribute to the core-hole screening, in contrast with previous work that has only considered screening through the U(5f) shell. The role of modifying the U-O interaction by changing the U-O distance has been investigated and an unexpected correlation between U-O distance and XPS satellite intensity has been discovered. The role of flourite and octahedral crystal structures for U(IV) oxides has been examined and relationships established between XPS features and the covalent interactions in the different structures. The physical views of XPS satellites as arising from shake processes or as arising from ligand to metal charge transfers are contrasted; our analysis provides strong support that shake processes give a more fundamental physical understanding than charge transfer. Our theoretical studies are based on rigorous, strictly ab initio determinations of the electronic structure of embedded cluster models of U oxides with formal U(VI) and U(IV) oxidation states. Our results provide a foundation that makes it possible to establish quantitative relationships between features of the XPS spectra and materials properties.

  18. Theoretical modeling of the uranium 4f XPS for U(VI) and U(IV) oxides

    Science.gov (United States)

    Bagus, Paul S.; Nelin, Connie J.; Ilton, Eugene S.

    2013-12-01

    A rigorous study is presented of the physical processes related to X-Ray photoelectron spectroscopy, XPS, in the 4f level of U oxides, which, as well as being of physical interest in themselves, are representative of XPS in heavy metal oxides. In particular, we present compelling evidence for a new view of the screening of core-holes that extends prior understandings. Our analysis of the screening focuses on the covalent mixing of high lying U and O orbitals as opposed to the, more common, use of orbitals that are nominally pure U or pure O. It is shown that this covalent mixing is quite different for the initial and final, core-hole, configurations and that this difference is directly related to the XPS satellite intensity. Furthermore, we show that the high-lying U d orbitals as well as the U(5f) orbital may both contribute to the core-hole screening, in contrast with previous work that has only considered screening through the U(5f) shell. The role of modifying the U-O interaction by changing the U-O distance has been investigated and an unexpected correlation between U-O distance and XPS satellite intensity has been discovered. The role of flourite and octahedral crystal structures for U(IV) oxides has been examined and relationships established between XPS features and the covalent interactions in the different structures. The physical views of XPS satellites as arising from shake processes or as arising from ligand to metal charge transfers are contrasted; our analysis provides strong support that shake processes give a more fundamental physical understanding than charge transfer. Our theoretical studies are based on rigorous, strictly ab initio determinations of the electronic structure of embedded cluster models of U oxides with formal U(VI) and U(IV) oxidation states. Our results provide a foundation that makes it possible to establish quantitative relationships between features of the XPS spectra and materials properties.

  19. Determination of molybdenum in uranium by differential pulse polarography

    International Nuclear Information System (INIS)

    Purwanto, A.; Iswani, G.S.

    1996-01-01

    The separation an determination of Mo (VI) in uranium dioxid (UO 2 ) samples by polarography method were studied. The determination of Mo(VI) was based on electrochemistry reduction of molybdenum (VI) quinolinolate complex (Mo VI O 2 Q 2 ). To decrease the matrix influence, this complex was extracted into chloroform. After chloroform phase was evaporate at room temperature, residues were dissolved with N,N-Dimethyl formamide (DMF). Potential wave reduction of Mo(VI) at -0,48 volt versus Ag/AgCl/KCl saturated in supporting electrolyte buffer acetate 1 M (1M CH 3 COOH-1M CH 3 COONH 4 ). Extraction was done in 0.3 M H 2 SO 4 media at optimum pH of 2.0 and 4 % oxine in 0.5 M H 2 SO 4 was used as complex compound. Extraction two times with 10 ml chloroform for 5 minutes each ratio of organic water was 1:5. This method was used to determine Mo (VI) in concentration range of 4.8 -12 μg in the presence of 200 mg uranium. It was found recovery of Mo (VI) was 95%. Mo (VI) contents in UO 2 samples determined by standard addition was 5.26±0.41 μg/g. (author)

  20. Differential pulse cathodic stripping voltammetric determination of uranium with arsenazo-III at the hanging mercury dropping electrode

    Energy Technology Data Exchange (ETDEWEB)

    Kadi, M.W.; El-Shahawi, M.S. [Chemistry Dept., King Abdulaziz Univ., Jeddah (Saudi Arabia)

    2009-07-01

    An accurate, inexpensive and less laborious controlled adsorptive accumulation of uranium(VI)-arsenazo-III on a hanging mercury drop electrode (HMDE) has been developed for uranium(VI) determination. The method is based upon the collection of uranium(VI)-arsenazo-III complex at pH 5-6 at the HMDE and subsequent direct stripping measurement of the element in the nanomolar concentration level. The cathodic peak current (i{sub p,c}) of the adsorbed complex ions of uranium(VI) was measured at -0.35 V vs. Ag/AgCl reference electrode by differential pulse cathodic stripping voltammetry (DP-CSV), proceeded by an accumulation period of 150s2.5 in Britton-Robinson buffer of pH 5. The plot of the resulting i{sub p,c} vs. uranium(VI) concentration was linear in the range 2.1 x 10{sup -9} to 9.60 x 10{sup -7} mol L{sup -1} uranium(VI) and tended to level off at above 9.6 x 10{sup -7} mol L{sup -1}. The limits of detection and quantification of uranium(VI) were found to be 4.7 x 10{sup -10} and 1.5 x 10{sup -9} mol L{sup -1}, respectively. A relative standard deviation of {+-}2.39% (n = 5) at 8.5 x 10{sup -7} mol L{sup -1} uranium(VI) was obtained. The method was validated by comparing the results with that obtained by ICP-MS method with RSD less than {+-}3.3%. The method was applied successfully for the analysis of uranium in certified reference material (IAEA soil-7), and in phosphate fertilizers. (orig.)

  1. Determination of traces of uranium in sea water after separation by froth flotation

    International Nuclear Information System (INIS)

    Sekine, K.

    1975-01-01

    Uranium in sea water is separated by froth flotation of the uranium (VI)-Arsenazo III-Zephiramine ion-adduct and then determined by neutron activation or spectrophotometric method using the uranium(IV)-Arsenazo III complex. Results of the analysis of Pacific coastal samples by the two methods are in good agreement; an average value of 3.0μg U/per liter was obtained. (author)

  2. Foreign research reactor uranium supply program: The Y-12 national security complex process

    International Nuclear Information System (INIS)

    Nelson, T.; Eddy, B.G.

    2010-01-01

    The Foreign Research Reactor (FRR) Uranium Supply Program at the Y-12 National Security Complex supports the nonproliferation objectives of the HEU Disposition Program, the Reduced Enrichment Research and Test Reactors (RERTR) Program, and the United States FRR Spent Nuclear Fuel (SNF) Acceptance Program. The Y-12 National Nuclear Security Administration (NNSA) Y-12 Site Office maintains the prime contracts with foreign governments for the supply of Low-Enriched Uranium (LEU) for their research reactors. The LEU is produced by down blending Highly Enriched Uranium (HEU) that has been declared surplus to the U.S. national defense needs. The down blending and sale of the LEU supports the Surplus HEU Disposition Program Record of Decision to make the HEU non-weapons usable and to recover the economic value of the uranium to the extent feasible. This program supports the important U.S. government and nuclear nonproliferation commitment to serve as a reliable and cost-effective uranium supplier for those foreign research reactors that are converting or have converted to LEU fuel under the guidance of the NNSA RERTR Program. In conjunction with the FRR SNF Acceptance Program which supports the global nonproliferation efforts to disposition U.S.-origin HEU, the Y-12 FRR Uranium Supply Program can provide the LEU for the replacement fuel fabrication. In addition to feedstock for fuel fabrication, Y-12 supplies LEU for target fabrication for medical isotope production. The Y-12 process uses supply forecasting tools, production improvements and efficient delivery preparations to successfully support the global research reactor community

  3. Uranium mineralization in the ring complex of Taperuaba, CE, Brazil

    International Nuclear Information System (INIS)

    Haddad, R.C.

    1981-01-01

    The study of the uraniferous deposit in the Northeast has been increased in last year, because of the discovery of many anomalies containing phosphate uraniferous mineralization. The anomalies in vila de Taperuaba at Ceara were examined. The petrografic, structural and geochemical study of the Taperuaba Ring complex, is made, in an attempt to estabilish the ore genesis and its probable controls. (L.H.L.L.) [pt

  4. The uranium potential of the Bushveld Complex, South Africa

    International Nuclear Information System (INIS)

    Simpson, P.R.

    1986-04-01

    This paper presents a summary on much of the existing geochemical data on the siliceous components of the Bushveld Complex (i.e., the felsites, granophyres and granites) with a view to establishing the U potential of the district. Although very few U analyses are actually available, sophisticated normalised data plots are utilized to estimate the probable U contents of the rock types. The members of the siliceous suite exhibit a gradual chemical evolution through time and illustrates that the most evolved members of the suite probably contained the highest primary U contents. It is emphasized that most known Bushveld Sn and F occurrences, with which U is likely to be associated, and most of the recognized radiometric anomalies in the complex, are concentrated along major lineaments. In this respect the Murchison and Franspoort directions are considered to be particularly important. In conclusion the argument follows that the potential for undiscovered hydrothermal U ores in the Bushveld Complex is high, and that five factors will probably control the location of such deposits. These factors include: 1. Sn, F and LIL-enriched source granite; 2. High post-emplacement heat production to promote the development of post-emplacement mineralizing systems; 3. A tectonically unstable source region with major fracture zones; 4. Suitable trap environments in the granites and their country rocks; 5. A source of fluids from aquifers in the granite aureole

  5. Electrochemical reactions of uranyl(VI) complexes in aqueous solution, non-aqueous solvents, and ionic liquids

    International Nuclear Information System (INIS)

    Ikeda, Yasuhisa

    2006-01-01

    Author's recent experimental results on the chemistry of U(V) in aqueous solution, non-aqueous solvents, and ionic solvents by cyclic voltametry are described. The U(V) was produced by electrochemical reduction of uranyl U(VI) ions or complexes such as carbonates, DMF(N, N-dimethylformamide), DMSO(dimethylsulfoxide), acetylacetonato, and other organic polydental ligands. The produced U(V) complexes were studied by spectrophotometry using optical-transmission thin-layer electrode. The U(V) complexes in non-aqueous solvents were found to be rather stable, they undergo ligand-dissociation reaction but not disproportionation reaction. The structure and electronic spectra as well as IR spectra of the complexes were studied. The present method was further developed to study the behavior of U(V) complexes in ionic liquids as molten salts, e.g., alkaline metals chlorides. Thus, the present research contributes to understanding the chemistry of 5fl system. Application to such nuclear technology as spent fuel reprocessing is discussed. (S. Ohno)

  6. Studies on Ternary Complex Formation of U(VI)-salicylate by Using Time-resolved Fluorescence Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Wan Sik; Cho, H. R.; Park, K. K.; Kim, W. H.; Jung, E. C. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-05-15

    Organic ligands containing carboxylic and phenolic functional groups naturally occur in groundwater environment, particularly in forms of polyelectrolytes such as humic and fulvic acids, from microbial degradation of biomass, e.g., plant and animal tissues. These ligands play important roles in dissolution and migration of actinide radionuclide species since they can form stable ternary actinide complexes with common inorganic ions like hydroxides and carbonates. Therefore, model ternary complexes of lanthanides and actinides have been targets of studies to understand their chemical behaviors under near-neutral pH groundwater conditions. Previous model carboxylic ligands include phthalates, maleic acids, or alpha- substituted carboxylic acids. However, majority of previous studies investigated binary systems or used potentiometric titration method that requires high ligand concentration in mM levels. Recently, highly sensitive time-resolved laserinduced fluorescence spectroscopy (TRLFS) has been used to investigate lower concentration (e.g., a few {mu}M levels) reactions of binary complexes between of ligands and metal ions. This technique provides information regarding electronic structures and complexation constants as well as fluorescence quenching mechanism. In the present study, we studied the U(VI)-OH-salicylate (SA) ternary complex formation at higher pH (> 4) via TRLF spectrum and UV-Vis absorbance measurement. Preliminary studies show that the fluorescence (FL) intensity of hydroxouranyl species at pH 4.5 decreases as SA concentration elevates in aqueous solution. Fluorescence quenching mechanism by SA is suggested based on FL intensity (I) and lifetime (tau) measurement via TRLFS

  7. Probing uranyl(VI) speciation in the presence of amidoxime ligands using electrospray ionization mass spectrometry.

    Science.gov (United States)

    Mustapha, Adetayo M; Pasilis, Sofie P

    2013-10-15

    Extraction processes using poly(acrylamidoxime) resins are being developed to extract uranium from seawater. The main complexing agents in these resins are thought to be 2,6-dihydroxyiminopiperidine (DHIP) and N(1),N(5)-dihydroxypentanediimidamide (DHPD), which form strong complexes with uranyl(VI) at the pH of seawater. It is important to understand uranyl(VI) speciation in the presence of these and similar amidoxime ligands to understand factors affecting uranyl(VI) adsorption to the poly(acrylamidoxime) resins. Experiments were carried out in positive ion mode on a quadrupole ion trap mass spectrometer equipped with an electrospray ionization source. The ligands investigated were DHIP, DHPD, and N(1),N(2)-dihydroxyethanediimidamide (DHED). DHED and DHPD differ only in the number of carbons separating the oxime groups. The effects on the mass spectra of changes in uranyl(VI):ligand ratio, pH, and ligand type were examined. DHIP binds uranyl(VI) more effectively than DHPD or DHED in the pH range investigated, forming ions derived from solution-phase species with uranyl(VI):DHIP stoichiometries of 1:1, 1:2, and 2:3. The 2:3 uranyl(VI):DHIP complex appears to be a previously undescribed solution species. Ions related to uranyl(VI):DHPD complexes were detected in very low abundance. DHED is a more effective complexing agent for uranyl(VI) than DHPD, forming ions having uranyl(VI):DHED stoichiometries of 1:1, 1:2, 1:3, and 2:3. This study presents a first look at the solution chemistry of uranyl(VI)-amidoxime complexes using electrospray ionization mass spectrometry. The appearance of previously undescribed solution species suggests that the uranyl-amidoxime system is a rich and relatively complex one, requiring a more in-depth investigation. Copyright © 2013 John Wiley & Sons, Ltd.

  8. The local structure of U(VI)-ferri-hydrite sorption complexes revisited: EXAFS spectroscopy and Monte-Carlo simulations

    International Nuclear Information System (INIS)

    Rossberg, A.; Ulrich, K.U.; Scheinost, A.C.

    2005-01-01

    Full text of publication follows: EXAFS analysis of actinyl sorption complexes is a complicated task due to the presence of overlapping shells, structural disorder and the presence of multiple scattering paths due to the specific actinyl structure. Hence often controversial interpretations arise from conventional shell fitting. A typical example is the proposed formation of ternary uranyl carbonato surface complexes on ferri-hydrite, where a peak at ∼2.4 Angstrom in the Fourier transform is explained by backscattering carbon atoms at 2.86-2.94 Angstrom. While such ternary carbonate complexes have been confirmed by complementary techniques like FTIR and electrophoretic mobility measurements, the EXAFS peak shows even up in those uranyl ferri-hydrite systems, where great care has been taken to keep the system carbonate-free, rendering an EXAFS fit with carbon meaningless. To overcome this common problem of EXAFS shell fitting, we developed a new analysis approach based on Monte-Carlo simulations coupled to theoretical EXAFS modeling using FEFF. Here, the position of the uranyl atom is first refined in relation to a given ferri-hydrite surface structure. In a second step, the whole complex structure is refined to allow for e.g. surface relaxation effects. Using this approach, a match to the experimental EXAFS spectra of U(VI) ferri-hydrite complexes without carbonate could be achieved. The local structure indicates a mononuclear bidentate (edge-sharing) surface complex, which was identified for the first time by EXAFS spectroscopy. Further fits were performed to elucidate the influence of carbonate and other anions on the structure of the surface complex. The results demonstrate the potential of the Monte-Carlo approach for determining the structure of actinyl surface complexes. (authors)

  9. Uranium

    International Nuclear Information System (INIS)

    Battey, G.C.; McKay, A.D.

    1988-01-01

    Production for 1986 was 4899 t U 3 O 8 (4154 t U), 30% greater than in 1985, mainly because of a 39% increase in production at Ranger. Exports for 1986 were 4166 t U 3 O 8 at an average f.o.b. unit value of $40.57/lb U 3 O 8 . Private exploration expenditure for uranium in Australia during the 1985-86 fiscal year was $50.2 million. Plans were announced to increase the nominal capacity of the processing plant at Ranger from 3000 t/year U 3 O 8 to 4500 t and later to 6000 t/year. Construction and initial mine development at Olympic Dam began in March. Production is planned for mid 1988 at an annual rate of 2000 t U 3 O 8 , 30 000 t Cu, and 90 000 oz (2800 kg) Au. The first long-term sales agreement was concluded in September 1986. At the Manyingee deposit, testing of the alkaline solution mining method was completed, and the treatment plant was dismantled. Spot market prices (in US$/lb U 3 O 8 ) quoted by Nuexco were generally stable. From January-October the exchange value fluctuated from US$17.00-US$17.25; for November and December it was US$16.75. Australia's Reasonably Assured Resources of uranium recoverable at less than US$80/kg U at December 1986 were estimated as 462 000 t U, 3000 t U less than in 1985. This represents 30% of the total low-cost RAR in the WOCA (World Outside the Centrally Planned Economy Areas) countries. Australia also has 257 000 t U in the low-cost Estimated Additional Resources Category I, 29% of the WOCA countries' total resources in this category

  10. Effects of solution pH and complexing reagents on uranium and thorium desorption under saturated equilibrium conditions

    International Nuclear Information System (INIS)

    Wang, Yug-Yea; Yu, C.

    1992-01-01

    Three contaminated bulk surface soils were used for investigating the effect of solution pH and complexing reagents on uranium and thorium desorption. At a low solution pH, the major chemical species of uranium and thorium, uranyl UO 2 +2 , thorium dihydroxide Th(OH) 2 +2 , and thorium hydroxide Th(OH) +3 , tend to form complexes with acetates in the solution phase, which increases the fractions of uranium and thorium desorbed into this phase. At a high solution pH, important uranium and thorium species such as uranyl tricarbonate complex UO 2 (CO) 33 -4 and thorium tetrahydroxide complex Th(OH) 4 tend to resist complexation with acetates. The presence of complexing reagents in solution can release radionuclides such as uranium and/or thorium from the soil to the solution by forming soluble complexes. Sodium bicarbonate (NaHCO 3 ) and diethylenetriaminepentaacetic acid (DTPA) are strong complex formers that released 38% to 62% of total uranium activity and 78% to 86% of total thorium activity, respectively, from the soil samples investigated. Solutions of 0.1 molar sodium nitrate (NaNO 3 ) and 0.1 molar sodium sulfate (Na 2 SO 4 ) were not effective complex formers with uranium and thorium under the experimental conditions. Fractions of uranium and thorium desorbed by 0.15g/200ml humic acid ranged from 4.62% to 6.17% and 1.59% to 7.09%, respectively. This work demonstrates the importance of a knowledge of solution chemistry in investigating the desorption of radionuclides

  11. Development of complex electrokinetic decontamination method for soil contaminated with uranium

    International Nuclear Information System (INIS)

    Kim, Gye-Nam; Kim, Seung-Soo; Park, Hye-Min; Kim, Wan-Suk; Moon, Jei-Kwon; Hyeon, Jay-Hyeok

    2012-01-01

    520L complex electrokinetic soil decontamination equipment was manufactured to clean up uranium contaminated soils from Korean nuclear facilities. To remove uranium at more than 95% from the radioactive soil through soil washing and electrokinetic technology, decontamination experiments were carried out. To reduce the generation of large quantities of metal oxides in cathode, a pH controller is used to control the pH of the electrolyte waste solution between 0.5 and 1 for the formation of UO 2+ . More than 80% metal oxides were removed through pre-washing, an electrolyte waste solution was circulated by a pump, and a metal oxide separator filtered the metal oxide particles. 80–85% of the uranium was removed from the soil by soil washing as part of the pre-treatment. When the initial uranium concentration of the soil was 21.7 Bq/g, the required electrokinetic decontamination time was 25 days. When the initial concentration of 238 U in the soil was higher, a longer decontamination time was needed, but the removal rate of 238 U from the soil was higher.

  12. Radiological and environmental safety aspects of uranium fuel fabrication plants at Nuclear Fuel Complex, Hyderabad

    International Nuclear Information System (INIS)

    Viswanathan, S.; Surya Rao, B.; Lakshmanan, A.R.; Krishna Rao, T.

    1991-01-01

    Nuclear Fuel Complex, Hyderabad manufactures uranium dioxide fuel assemblies for PHWRs and BWRs operating in India. Starting materials are magnesium diuranate received from UCIL, Jaduguda and imported UF. Both of these are converted to UO 2 pellets by identical chemical processes and mechanical compacting. Since the uranium handled here is free of daughter product activities, external radiation is not a problem. Inhalation of airborne U compounds is one of the main source of exposure. Engineered protective measures like enclosures around U bearing powder handling equipment and local exhausts reduce worker's exposure. Installation of pre-filters, wet rotoclones and electrostatic precipitators in the ventillation system reduces the release of U into the environment. The criticality hazard in handling slightly enriched uranium is very low due to the built-in control based on geometry and inventory. Where airborne uranium is significant, workers are provided with protective respirators. The workers are regularly monitored for external exposure and also for internal exposure. The environmental releases from the NFC facility is well controlled. Soil, water and air from the NFC environment are routinely collected and analysed for all the possible pollutants. The paper describes the Health Physics experience during the last five years on occupational exposures and on environmental surveillance which reveals the high quality of safety observed in our nuclear fuel fabricating installations. (author). 4 refs., 6 tabs

  13. Reactions of uranium (III) and (IV) compounds with ketones, nitriles and acid chlorides. Towards a use of uranium complexes in organic synthesis

    International Nuclear Information System (INIS)

    Adam, Raymond

    1993-01-01

    In this research thesis, the author shows that various organic molecules can be interestingly transformed into uranium complexes with degrees of oxidation of +3 or +4. In a first part, the author describes reactions of carbonyl compounds with the UCl 4 -Na(Hg) reducing system. Then, he addresses reductions of ketones, nitriles and acid chlorides by a uranium (III) complex: Cp 3 U(THF). The third part reports a detailed study of the reduction of ketones by U(BH 4 ) 4 [fr

  14. Agpaitic nepheline syenites from the Ilimaussaq Complex, south Greenland; an important new uranium ore type (v.2)

    International Nuclear Information System (INIS)

    Mair, J.L.; Bunn, S.

    2010-01-01

    The Ilimaussaq Intrusive Complex in south Greenland is a layered alkaline igneous body that is predominantly comprised of agpaitic nepheline syenites. The Complex is now recognized as containing vast resources of uranium in polymetallic ores that are also strongly enriched in rare earth elements (REEs) and zinc. Uranium and REEs are dominantly hosted in phosphate minerals with a minor proportion hosted in zirconium silicate minerals. Equivalent ores are yet to be mined for uranium anywhere in the world; however, studies are well advanced in confirming a process route to economically extract uranium. The Ilimaussaq Complex is considered the world's type-locality for agpaitic rocks. Formation of the complex is attributed to four successive pulses of magma. The first produced an augite syenite, which now forms a marginal shell. This was followed by intrusion of a sheet of peralkaline granite. The third and fourth stages make up the bulk of the intrusion and are peralkaline to hyper-agpaitic in composition. The third batch of magma differentiated to produce pulaskite, foyaite and naujaite. Stage four produced the kakortokites and lujavrites, which are the units of particular economic significance. Kakortokites are strongly enriched in zirconium, niobium and tantalum, whereas the lujavrites are strongly enriched in uranium, rare earth elements, fluorine and zinc. Lujavrites are vertically zoned with arfvedonsite (black) lujavrites grading downward into aegerine (green) lujavrites. The upper most portions of the black lujavrites contain uranium concentrations of greater than 450 ppm, which decreases downward over 200 - 300m toward green lujavrites where uranium concentrations rarely exceeds 200 ppm. Resources defined to date in accordance with the Australian JORC code include 192 million lb. of U_3O_8 at 350 ppm within an overall resource of 282 million lb. of uranium oxide at a grade of 280 ppm. With scope for several other similar sized resources within complex, the

  15. Thermodynamic properties of actinide complexes. Part 5: Uranyl(VI)-thioglycolate system; thorium(IV)-glycolate and -thioglycolate systems

    Energy Technology Data Exchange (ETDEWEB)

    di Bernardo, P; Roncari, E; Mazzi, U; Bettella, F [Padua Univ. (Italy). Istituto di Chimica Generale ed Inorganica; Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi); Magon, L [Ferrara Univ. (Italy). Istituto Chimico

    1978-04-01

    The changes in free energy, enthalpy and entropy for the formation of uranyl(VI)-thioglycolate, thorium(IV)-glycolate and -thioglycolate complexes have been determined. The changes in free energy were calculated from the stability constants obtained from a potentiometric determination of the concentration of free hydrogen ion, using a glass or quinhydrone electrode. The enthalpy values were measured calorimetrically. The measurements were performed at 25.0/sup 0/C in an aqueous sodium perchlorate medium with the total sodium concentration equal to 100 M. A comparison of the magnitude of the enthalpy and entropy changes for the various systems gives additional support of the view that the thioglycolate acts as a monodentate ligand while the glycolate forms chelate rings.

  16. 'Pincer' dicarbene complexes of some early transition metals and uranium.

    Science.gov (United States)

    Pugh, David; Wright, Joseph A; Freeman, Sandra; Danopoulos, Andreas A

    2006-02-14

    The complexes [(C-N-C)MX(n)(thf)(m)] with the 'pincer' 2,6-bis(imidazolylidene)pyridine, (C-N-C) = 2,6-bis(arylimidazol-2-ylidene)pyridine, aryl = 2,6-Pr(i)2C6H3, M = V, X = Cl, n = 2, m = 1 1a; M = Cr, X = Cl, n = 2, m = 0, 2a, X = Br, 2b; M = Mn, X = Br, n = 2, m = 0, 3; M = Nb, X = Cl, n = 3, m = 0, 4; and M = U, X = Cl, n = 4, m = 0, 5, were synthesised by (a) substitution of labile tmed (1a), thf (2a, 3, 5) or dme (4) by free (C-N-C) or by (b) reaction of the bisimidazolium salt (CH-N-CH)Br2 with {Cr[N(SiMe3)2]2(thf)2} followed by amine elimination (2b). Attempted alkylation of 1a, 2, 3a and 4 with Grignard or alkyl lithiums gave intractable mixtures, and in one case [reaction of 1a with (mesityl)MgBr] resulted in exchange of Cl by Br (1b). Oxidation of 1a or [(C-N-C)VCl3] with 4-methylmorpholine N-oxide afforded the trans-V(C-N-C)(=O)Cl2, 6, which by reaction with AgBF4 in MeCN gave trans-[V(C-N-C)(=O)(MeCN)2][BF4]2, 7. Reaction of 1a with p-tolyl azide gave trans-V(C-N-C)(=N-p-tolyl)Cl2 8. The complex trans-Ti(C-N-C)(=NBu(t))Cl2, 9, was prepared by substitution of the pyridine ligands in Ti(NBu(t))Cl2(py)3 by C-N-C.

  17. Effect of pH, ionic strength and humic acid on the sorption of uranium(VI) to attapulgite

    Energy Technology Data Exchange (ETDEWEB)

    Niu Zhiwei [Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, Gansu (China); Fan Qiaohui [Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, Gansu (China)], E-mail: fanqiaohui@gmail.com; Wang Wenhua; Xu Junzheng [Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, Gansu (China); Chen Lei [School of Chemical Engineering, Shandong University of Technology, 255049 Zibo, Shandong (China); Wu Wangsuo [Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, Gansu (China)], E-mail: wuws@lzu.edu.cn

    2009-09-15

    Attapulgite was investigated to remove UO{sub 2}{sup 2+} from aqueous solutions because of its strong sorption capacity. Herein, the attapulgite sample was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) and acid-base titration in detail. Sorption of UO{sub 2}{sup 2+} on attapulgite was strongly dependent on pH values and ionic strength. The presence of humic acid enhanced the sorption of UO{sub 2}{sup 2+} on attapulgite obviously because of the strong complexation of humic acid (HA) with UO{sub 2}{sup 2+} on attapulgite surface. Sorption of UO{sub 2}{sup 2+} on attapulgite was mainly dominated by ion-exchange or outer-sphere complexation at low pH values, and by inner-sphere complexation at high pH values. The results indicated that attapulgite was a suitable material for the preconcentration and solidification of UO{sub 2}{sup 2+} from large volume of solutions because of its negative surface charge and large surface areas.

  18. Magnetic properties and electronic structure of neptunyl(VI) complexes: wavefunctions, orbitals, and crystal-field models

    Energy Technology Data Exchange (ETDEWEB)

    Gendron, Frederic; Pritchard, Ben; Autschbach, Jochen [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY (United States); Paez-Hernandez, Dayan; Bolvin, Helene [Laboratoire de Physique et de Chimie Quantiques, Universite Toulouse 3 (France); Notter, Francois-Paul [Laboratoire de Chimie Quantique, Universite de Strasbourg (France)

    2014-06-23

    The electronic structure and magnetic properties of neptunyl(VI), NpO{sub 2}{sup 2+}, and two neptunyl complexes, [NpO{sub 2}(NO{sub 3}){sub 3}]{sup -} and [NpO{sub 2}Cl{sub 4}]{sup 2-}, were studied with a combination of theoretical methods: ab initio relativistic wavefunction methods and density functional theory (DFT), as well as crystal-field (CF) models with parameters extracted from the ab initio calculations. Natural orbitals for electron density and spin magnetization from wavefunctions including spin-orbit coupling were employed to analyze the connection between the electronic structure and magnetic properties, and to link the results from CF models to the ab initio data. Free complex ions and systems embedded in a crystal environment were studied. Of prime interest were the electron paramagnetic resonance g-factors and their relation to the complex geometry, ligand coordination, and nature of the nonbonding 5f orbitals. The g-factors were calculated for the ground and excited states. For [NpO{sub 2}Cl{sub 4}]{sup 2-}, a strong influence of the environment of the complex on its magnetic behavior was demonstrated. Kohn-Sham DFT with standard functionals can produce reasonable g-factors as long as the calculation converges to a solution resembling the electronic state of interest. However, this is not always straightforward. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Identification of Uranyl Surface Complexes an Ferrihydrite: Advanced EXAFS Data Analysis and CD-MUSIC Modeling

    NARCIS (Netherlands)

    Rossberg, A.; Ulrich, K.U.; Weiss, S.; Tsushima, S.; Hiemstra, T.; Scheinost, A.C.

    2009-01-01

    Previous spectroscopic research suggested that uranium(VI) adsorption to iron oxides is dominated by ternary uranyl-carbonato surface complexes across an unexpectedly wide pH range. Formation of such complexes would have a significant impact on the sorption behavior and mobility of uranium in

  20. Uranium preconcentration from seawater using adsorptive membranes

    International Nuclear Information System (INIS)

    Das, Sadananda; Pandey, A.K.; Manchanda, V.K.; Athawale, A.A.

    2009-01-01

    Uranium recovery from bio-aggressive but lean feed like seawater is a challenging problem as it requires in situ preconcentration of uranium in presence of huge excess of competing ions with fast sorption kinetics. In our laboratory, widely used amidoxime membrane (AO-membrane) was evaluated for uranium sorption under seawater conditions. This study indicated that AO-membrane was inherently slow because of the complexation chemistry involved in transfer of U(VI) from (UO 2 (CO 3 ) 3 ) 4 - to AO sites in membrane. In order to search better options, several chemical compositions of membrane were scanned for their efficacy for uranium preconcentration from seawater, and concluded that EGMP-membrane offers several advantages over AO-membrane. In this paper, the comparison of EGMP-membrane with AO-membrane for uranium sorption under seawater conditions has been reviewed. (author)

  1. New South African complex leaches gold, uranium, and sulphur from slimes

    Energy Technology Data Exchange (ETDEWEB)

    Payne, A.

    1978-01-01

    Slimes dams at various mines in the Orange Free State and the Transvaal are being re-treated to recover U, Au, and H/sub 2/SO/sub 4/. Components of the Free State Metallurgical Complex include flotation plants, a uranium plant, the President Brand plant for H/sub 2/SO/sub 4/ production from the pyrite concentrates, and a calcine leaching plant for producing gold from the calcines of the acid plant. Reasons for the complex and its operation are discussed. (DLC)

  2. Interest of uranium complexes for the mechanism study of the McMurry reaction

    International Nuclear Information System (INIS)

    Maury, O.

    1997-01-01

    The reducing coupling reactions of ketones in diols and olefins are generally carried out with titanium or samarium compounds. In this work uranium complexes have been used. They have allowed to study the chemical reaction mechanism. This thesis is divided into three parts: 1) the reduction mechanism of uranium tetrachloride by cyclic voltametry has been studied at first. It has been shown that this reduction is followed by a transfer reaction of chlorides between the reduced specie of the higher electronic density and UCl . 2) In the second part is described: the synthesis, the crystal structure, the reactivity of the chemical agents, the stereochemistry of diols and alkenes formation and the pinacolisation reaction catalysis. 3) In the last part, the limits of the McMurry reaction are given by the study of the aromatic ketones pinacolisation reaction by-products. The obtained results show that the complexes of the metals which present a high reducing and oxo-philic (Ti, Sm, U..) character react in a similar way with the carbonyl compounds. If the uranium compounds are less used than those of the titanium in the field of the organic synthesis applications, they are precious auxiliaries and excellent models for reactions mechanisms study and for the synthesis methods optimization. (O.M.)

  3. Uranium hetero-bimetallic complexes: synthesis, structure and magnetic properties; Complexes heterobimetalliques de l'uranium: synthese, structure et proprietes magnetiques

    Energy Technology Data Exchange (ETDEWEB)

    Le Borgne, Th

    2000-10-04

    The aim of this thesis is to synthesize molecular complexes with uranium and transition metal ions in close proximity, to determine the nature of the magnetic interaction between them. We decided to use Schiff bases as assembling ligands, which are unusual for uranium (IV). Although the simplest Schiff bases, such as H{sub 2}Salen, lead to ligand exchange reactions, the bi-compartmental Schiff base H{sub 4}L{sup 6} (bis(3-hydroxy-salicylidene) - 2,2-dimethyl-propylene) allows the crystal structure determination of the complex [L{sup 6}Cu(pyr)]U[L{sup 6}Cu].2pyr, obtained by reaction of the metallo-ligand H{sub 2}L{sup 6}Cu with U(acac){sub 4}. In this manner, the complexes [L{sup 6}Co(pyr)]{sub 2}U and [L{sup 6}Ni(pyr)]{sub 2}U.pyr were also isolated, as well as the compounds in which the paramagnetic ions have been exchanged by the diamagnetic ions Zn{sup II}, Zr{sup IV} and Th{sup IV}': [L{sup 6}Zn(pyr)]{sub 2}U, [L{sup 6}Cu]{sub 2}Zr and [L{sup 6}Cu(pyr)]Th[L{sup 6}Cu].2pyr. These complexes are the first which involve three metallic centres assembling by the means of a hexa-dentate Schiff base. The crystalline structures show, for all these complexes, the outstanding orthogonal arrangement of the two fragments L{sup 6}M around the central atom which is in a dodecahedral environment of eight oxygen atoms of two Schiff bases. The syntheses of the isostructural complexes Cu2{sup II} and Zn{sub 2}U in which the uranium (IV) ion is close, in the first one, to the paramagnetic ion Cu{sup II} and, in the second one, to the diamagnetic ion Zn{sup II}, has allowed the use of the empiric method to determine the nature of the magnetic interaction between an f element and a transition metal. The comparison of the magnetic behaviour of two complexes Cu{sub 2}U and Zn{sub 2}U, expressed by the variation of {chi}T vs T, reveals the ferromagnetic interaction in the heart of the triad Cu-U-Cu. The magnetic behaviour of the complexes Cu{sub 2}Th et Cu{sub 2}Zr which does not

  4. Polarographic and potentiometric studies on some binary and ternary complex systems of dioxouranium(VI)

    International Nuclear Information System (INIS)

    Janarthanam, M.; Sivasankar, B.; Rengaraj, K.; Nair, M.S.

    1995-01-01

    The relative coordinating abilities of donor sites in the potentially tridentate ligands viz., asparagine, glutamine, aspartic acid and glutamic acid towards uranyl ion have been investigated by polarographic and pH-metric techniques. The metal ion forms 1:2 complexes under polarographic conditions. However, only 1:1 complex is observed under pH-metric conditions, where 1:2 complexes do not proceed due to extensive hydrolysis of the metal ion. The relative variations of ΔE 1/2 with pH and ligand concentration supported by conductometric titration data indicate that the primary amino groups in the amino acids are not involved in coordination with uranyl ion. Further, the amide groups in asparagine and glutamine also do not participate in coordination thus rendering these ligands unidentate. In aspartic and glutamic acid complexes, seven- and eight- membered chelate rings are formed involving two terminal carboxyl groups. The mixed ligand complex equilibria of uranyl ion involving aspartic acid/glutamic acid as primary ligands (A) and maleic acid, malonic acid, succinic acid and lactic acid as secondary ligands (B) have also been studied by computer based numerical evaluation of pH titration data. The concentration profiles have indicated the favorability of the formation of ternary complexes in general as reflected in the Δlog K values. (author). 10 refs., 1 fig., 1 tab

  5. Single-molecule magnetism in a single-ion triamidoamine uranium(V) terminal mono-oxo complex

    Energy Technology Data Exchange (ETDEWEB)

    King, David M.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T. [Nottingham Univ. (United Kingdom). School of Chemistry; Tuna, Floriana; McInnes, Eric J.L. [Manchester Univ. (United Kingdom). School of Chemistry

    2013-04-26

    Straightforward oxidation of a triamidoamine uranium(III) complex with trimethyl-N-oxide affords a uranium(V) terminal mono-oxo complex which is the first clear-cut example of a uranium(V) single-molecule magnet (SMM). This monometallic complex unambiguously shows that a strongly axially ligated and thus anisotropic ligand field can be used to overcome the limited magnetic anisotropy of uranium(V). [German] Die direkte Oxidation eines Triamidoamin-Uran(III)-Komplexes mit Trimethyl-N-oxid liefert einen terminalen Uran(V)-Mono(oxo)komplex, der das erste gesicherte Beispiel eines Uran(V)-Einzelmolekuelmagnets ist. Dieser monometallische Komplex zeigt eindeutig, dass ein starkes axiales und somit anisotropes Ligandenfeld die begrenzte magnetische Anisotropie von Uran(V) beseitigen kann.

  6. Investigation and analytical application of thorium and uranium complexes with amino acids

    International Nuclear Information System (INIS)

    Korenman, I.M.; Sergeev, G.M.

    1979-01-01

    The coordination is investigated of thorium (4) and uranium (6) with aminoacids, particularly, with aspartic acid. With the latter the metals form chelates, which have a particular structure and a stationary inner sphere. A description is made of the composition, conditions of formation (gr H), and a stability of some asparaginate complexes of actinoids, the coordination methods of aspartic acid. An asparaginatometric method is proposed for a direct complexometric titration of microgram amounts of thorium in the presence of uranium, zirconium and rare earth elements with photometric indication. As metal-chromic indicators the sulfophthaleins are applied. The given procedure allows measurement of impurities of accompanying elements, viz., beryllium (up to 1%) in thorium preparations. Application of aspartic acid and arsenazo 1 indicator permits us to define Be(2) with a relative error not higher than 5% in thorium compounds, which exclude the analysis by other methods

  7. Extraction of uranium from simulated ore by the supercritical carbon dioxide fluid extraction method with nitric acid-TBP complex

    International Nuclear Information System (INIS)

    Dung, Le Thi Kim; Imai, Tomoki; Tomioka, Osamu; Nakashima, Mikio; Takahashi, Kuniaki; Meguro, Yoshihiro

    2006-01-01

    The supercritical fluid extraction (SFE) method using CO 2 as a medium with an extractant of HNO 3 -tri-n-butyl phosphate (TBP) complex was applied to extract uranium from several uranyl phosphate compounds and simulated uranium ores. An extraction method consisting of a static extraction process and a dynamic one was established, and the effects of the experimental conditions, such as pressure, temperature, and extraction time, on the extraction of uranium were ascertained. It was found that uranium could be efficiently extracted from both the uranyl phosphates and simulated ores by the SFE method using CO 2 . It was thus demonstrated that the SFE method using CO 2 is useful as a pretreatment method for the analysis of uranium in ores. (author)

  8. Factors influencing U(VI adsorption onto soil from a candidate very low level radioactive waste disposal site in China

    Directory of Open Access Journals (Sweden)

    Zuo Rui

    2016-01-01

    Full Text Available The properties of soil at disposal sites are very important for geological disposal of very low level radioactive waste in terms of U(VI. In this study, soil from a candidate very low level radioactive waste disposal site in China was evaluated for its capacity on uranium sorption. Specifically, the equilibrium time, initial concentration, soil particle, pH, temperature, and carbonate were evaluated. The results indicated that after 15-20 days of sorption, the Kd value fluctuated and stabilized at 355-360 mL/g. The adsorptive capacity of uranium was increased as the initial uranium concentration increased, while it decreased as the soil particle size increased. The pH value played an important role in the U(VI sorption onto soil, especially under alkaline conditions, and had a great effect on the sorption capacity of soil for uranium. Moreover, the presence of carbonate decreased the sorption of U(VI onto soil because of the role of the strong complexation of carbonate with U(VI in the groundwater. Overall, this study assessed the behavior of U(VI sorption onto natural soil, which would be an important factor in the geological barrier of the repository, has contribution on mastering the characteristic of the adsorption of uranium in the particular soil media for the process of very low level radioactive waste disposal.

  9. Recycled Uranium Mass Balance Project Y-12 National Security Complex Site Report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-12-01

    This report has been prepared to summarize the findings of the Y-12 National Security Complex (Y-12 Complex) Mass Balance Project and to support preparation of associated U. S. Department of Energy (DOE) site reports. The project was conducted in support of DOE efforts to assess the potential for health and environmental issues resulting from the presence of transuranic (TRU) elements and fission products in recycled uranium (RU) processed by DOE and its predecessor agencies. The United States government used uranium in fission reactors to produce plutonium and tritium for nuclear weapons production. Because uranium was considered scarce relative to demand when these operations began almost 50 years ago, the spent fuel from U.S. fission reactors was processed to recover uranium for recycling. The estimated mass balance for highly enriched RU, which is of most concern for worker exposure and is the primary focus of this project, is summarized in a table. A discrepancy in the mass balance between receipts and shipments (plus inventory and waste) reflects an inability to precisely distinguish between RU and non-RU shipments and receipts involving the Y-12 Complex and Savannah River. Shipments of fresh fuel (non-RU) and sweetener (also non-RU) were made from the Y-12 Complex to Savannah River along with RU shipments. The only way to distinguish between these RU and non-RU streams using available records is by enrichment level. Shipments of {le}90% enrichment were assumed to be RU. Shipments of >90% enrichment were assumed to be non-RU fresh fuel or sweetener. This methodology using enrichment level to distinguish between RU and non-RU results in good estimates of RU flows that are reasonably consistent with Savannah River estimates. Although this is the best available means of distinguishing RU streams, this method does leave a difference of approximately 17.3 MTU between receipts and shipments. Slightly depleted RU streams received by the Y-12 Complex from ORGDP and

  10. Synthesis and characterization of thorium(IV) and uranium(IV) complexes with Schiff bases

    Energy Technology Data Exchange (ETDEWEB)

    Radoske, Thomas; Maerz, Juliane; Kaden, Peter; Patzschke, Michael; Ikeda-Ohno, Atsushi [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Chemistry of the F-Elements

    2017-06-01

    We report herein the synthesis and characterization of several imine complexes of tetravalent thorium (Th(IV)) and uranium (U(IV)). The ligands investigated in this study are a Schiff base type, including the well-known salen ligand (H{sub 2}Le, Fig. 1). The complexation in solution was investigated by NMR measurements indicating paramagnetic effects of unpaired f-electrons of U(IV) on the ligand molecule. We also determined the solid-state molecular structures of the synthesized complexes by single crystal X-ray diffraction. The synthesized complexes show an eight-fold coordination geometry around the actinide center surrounded by two tetradentate ligands with 2N- and 2O-donor atoms.

  11. Chemistry of the uranyl group. VI. Complexes of uranyl with hexamethylphosphoramide and urea

    Energy Technology Data Exchange (ETDEWEB)

    Zarli, B; Dall' olio, G; Sindellari, L [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi

    1976-01-01

    Some uranyl complexes with hexamethylphosphoramide (HMPA) and urea were prepared and characterized. The compounds with the former ligand have the general formula UO/sub 2/X/sub 2/.HMPA (where X = (C/sub 2/H/sub 5/)/sub 2/NCSe/sub 2//sup -/, (C/sub 2/H/sub 5/)/sub 2/NCS/sub 2//sup -/ or CH/sub 3/COO/sup -/). For the acetato derivatives a dimeric acetato-bridged structure is suggested. Some properties of UO/sub 2/(NO/sub 3/)/sub 2/.2(HMPA) are also described. With the latter ligand, in addition to the complexes UO/sub 2/(NO/sub 3/)/sub 2/.2urea and (UO/sub 2/(urea)/sub 4/(H/sub 2/0))(NO/sub 3/)/sub 2/ already known, the novel complexes UO/sub 2/(pycrate)/sub 2/.4urea and (UO/sub 2/(CH/sub 3/COO)/sub 2/.urea)sub(n) (where n is probably 2) have been prepared. All attempts to obtain urea complexes of uranyl diethyldithio- or diethyldiselenocarbamate failed and only adducts of unsatisfactory stoichiometry were isolated.

  12. Synthesis, structural investigation and kinetic studies of uranyl(VI) unsymmetrical Schiff base complexes

    Czech Academy of Sciences Publication Activity Database

    Asadi, Z.; Asadi, M.; Zeinali, A.; Ranjkeshshorkaei, M.; Fejfarová, Karla; Eigner, Václav; Dušek, Michal; Dehnokhalaji, A.

    2014-01-01

    Roč. 126, č. 6 (2014), s. 1673-1683 ISSN 0974-3626 R&D Projects: GA ČR(CZ) GAP204/11/0809 Institutional support: RVO:68378271 Keywords : uranyl schiff base complexes * kinetic study * kinetics of thermal decomposition * X-ray crystallography * cyclic voltammetry Subject RIV: CA - Inorganic Chemistry Impact factor: 1.191, year: 2014

  13. The application of iterative transformation factor analysis to resolve multi-component EXAFS spectra of uranium(6) complexes with acetic acid as a function of pH

    International Nuclear Information System (INIS)

    Robberg, A.; Reich, T.

    2002-01-01

    Synchrotron-based EXAFS spectroscopy is a powerful technique to obtain structural information on radionuclide complexes in solution. Depending on the chemical conditions of the samples several radionuclide species can coexist in the solution as is often the case for environmentally related samples. All radionuclide species, which may have different near-neighbour environments, contribute to the measured EXAFS signal. In order to isolate the EXAFS spectra of the individual species (pure spectral components), it is necessary, in a first step, to measure a series of samples where their composition is changed by variation of one physico-chemical parameter (e.g. pH, concentration, etc.). For the spectral decomposition it is necessary that the EXAFS signal change as a function of the chosen physico-chemical parameter. In a second step, the series of EXAFS spectra is analysed with Eigen analysis and Iterative Transformation Factor Analysis (ITFA). As a result of the ITFA one obtains: a) for each sample the relative concentration of the structural distinguishable species and b) their corresponding pure spectral components. From the information obtained in a), one can construct a speciation diagram. The pure spectral components contain the structural information of the individual species, which can be extracted by conventional EXAFS analysis. To evaluate our ITFA algorithm for EXAFS analysis of mixtures, we prepared a series of eight solution samples of 0.05 M uranium(VI) and 1 M acetate (Ac) in the pH range of 0.1 to 4.5. From thermodynamic constants it is known that under these conditions up to four species can occur: uranyl hydrate, and the 1:1, 1:2 and 1:3 complexes of uranyl acetate. The uranium L III -edge EXAFS spectra were measured at room temperature in transmission mode at the Rossendorf Beamline (ROBL) at the ESRF. The average bond length between uranium and the equatorial oxygen atoms (O eq ) increases from 2.40 to 2.46 angstrom with increasing pH. This increase

  14. Cation-mediated conversion of the state of charge in uranium arene inverted-sandwich complexes

    Energy Technology Data Exchange (ETDEWEB)

    Camp, Clement; Mougel, Victor; Pecaut, Jacques; Mazzanti, Marinella [Laboratoire de Reconnaissance Ionique et Chimie de Coordination, SCIB, UMR-E3 CEA-UJF, INAC, CEA-Grenoble (France); Maron, Laurent [LCPNO, CNRS and INSA, UPS, Universite de Toulouse (France)

    2013-12-16

    Two new arene inverted-sandwich complexes of uranium supported by siloxide ancillary ligands [K{U(OSi(OtBu)_3)_3}{sub 2}(μ-η{sup 6}:η{sup 6}-C{sub 7}H{sub 8})] (3) and [K{sub 2}{U(OSi(OtBu)_3)_3}{sub 2}(μ-η{sup 6}:η{sup 6}-C{sub 7}H{sub 8})] (4) were synthesized by the reduction of the parent arene-bridged complex [{U(OSi(OtBu)_3)_3}{sub 2}(μ-η{sup 6}:η{sup 6}-C{sub 7}H{sub 8})] (2) with stoichiometric amounts of KC{sub 8} yielding a rare family of inverted-sandwich complexes in three states of charge. The structural data and computational studies of the electronic structure are in agreement with the presence of high-valent uranium centers bridged by a reduced tetra-anionic toluene with the best formulation being U{sup V}-(arene{sup 4-})-U{sup V}, KU{sup IV}-(arene{sup 4-})-U{sup V}, and K{sub 2}U{sup IV}-(arene{sup 4-})-U{sup IV} for complexes 2, 3, and 4 respectively. The potassium cations in complexes 3 and 4 are coordinated to the siloxide ligands both in the solid state and in solution. The addition of KOTf (OTf=triflate) to the neutral compound 2 promotes its disproportionation to yield complexes 3 and 4 (depending on the stoichiometry) and the U{sup IV} mononuclear complex [U(OSi(OtBu){sub 3}){sub 3}(OTf)(thf){sub 2}] (5). This unprecedented reactivity demonstrates the key role of potassium for the stability of these complexes. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Study on the relation between uranium content and total phosphorus in some sudanese phosphate ore samples

    International Nuclear Information System (INIS)

    Eltayeb, M. A. H.; Mohammed, A. A.

    2003-01-01

    In the present work uranium content and total phosphorus were determined in 30 phosphate ore samples collected from Kurun and Uro areas in Nuba Mountains in Sudan. Spectrophotometry technique was used for this purpose. Uranium analysis is based on the use of nitrogen (V) acid for leaching the rock, and treatment with ammonium carbonate solution, whereby uranium (Vi) is kept in solution as its carbonate complex. The ion exchange technique was used for the recovery of uranium. Uranium was eluted from the resin with 1 M hydrochloric acid. In the elute, uranium was determined spectrophotometrically by measurement of absorbance of the yellow uranium (Vi)-8-hydroxyquinolate complex at λ 400 nm. The total phosphorus was measured as (P 2 O 5 %) by treatment of the total liquor with ammonium molybdate solution. The absorbance of the blue complex was measured at λ 880 nm. The results show that a limited relation is existed between uranium content and total phosphorus in phosphate samples from kurun area, which contain 58.8 ppm uranium in average, where there are no relation is existed in phosphate samples from uro area, which contain 200 ppm uranium in average. (Author)

  16. Study on the relation between uranium content and total phosphorus in some sudanese phosphate ore samples

    International Nuclear Information System (INIS)

    Mohammed, A.A.; Eltayeb, M.A.H.

    2003-01-01

    In the present work uranium content and total phosphorous were determined in 30 phosphate ore samples collected from Kurun and Uro areas in Nuba mountains in sudan. Spectrophotometry technique was used for this purpose. Uranium analysis is based on the use of nitrogen (V) acid for leaching the rock, and treatment with ammonium carbonate solution, whereby uranium (VI) is kept in solution as its carbonate complex. The ion-exchange technique was used for the recovery of uranium. Uranium was eluted from the resin with 1 M hydrochloric acid. In the elute, uranium was determined spectrophotometrically by measurement of the absorbance of the yellow uranium (VI) - 8- hydroxyquinolate complex at λ 400 nm. The total phosphorus was measured as (P 2 O 5 %) by treatment of the leach liquor with ammonium molybdate solution. The absorbance of the blue complex was measured at λ 880 nm. The results show that a limited relation is existed between uranium content and total phosphorus in phosphate samples from Kurun area, which contain 58.8 ppm uranium in average, where there are no relation is existed in phosphate samples samples from Uro area, which contain 200 ppm uranium in average

  17. Exploration of Bernabe Montano complex of uranium deposits, New Mexico, USA

    International Nuclear Information System (INIS)

    Porter, D.A.

    1981-01-01

    The Bernabe Montano discovery is a significant eastern extension of the Grants Mineral Belt, consisting of two nearly parallel mineralized trends with a combined strike length of about 14.5 km. One deposit with approximately 10 6 lb of uranium oxide has been blocked out and several km of mineralized trend require additional delineation drilling. The mineralization exhibits many similarities to Westwater Canyon Member ore deposits in other parts of the Grants Mineral Belt; one of the most significant is the continuation of the south-easterly trend that has persisted, with some breaks, for a length of over 175 km. As with other Grants Mineral Belt deposits, the mineralization is associated with multilevel humate masses that are roughly parallel to the bedding of the Westwater Canyon Member host sandstone beds. These humate masses and the associated uranium deposits show a marked preference for the margins of the thicker, more laterally continuous, channelways. The discovery of the Bernabe Montano complex of deposits is significant for several reasons. First, it opened up exploration in the distal fan facies where many geologists thought the uranium potential was relatively low. The discovery is potentially more significant in that it demonstrates the ability of detailed subsurface geologic mapping to suggest the location of high potential geologic trends in partially explored but favourable regions where the more traditional surface geologic and radiometric techniques are no longer effective in finding new deposits. (author)

  18. Copper(II) and molybdenum(VI) complexes of a tridentate ONN donor isothiosemicarbazone: synthesis, characterization, X-ray, TGA and DFT

    Czech Academy of Sciences Publication Activity Database

    Fasihizad, A.; Akbari, A.; Ahmadi, M.; Dušek, Michal; Henriques, Margarida Isabel Sousa; Pojarová, Michaela

    2016-01-01

    Roč. 115, Sep (2016), s. 297-305 ISSN 0277-5387 R&D Projects: GA ČR(CZ) GA14-03276S; GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : isothiosemicarbazone * Copper(II) complex * molybdenum(VI) complex * crystal structure * DFT Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.926, year: 2016

  19. Indoor radon related to uranium in granitoids of the Central Bohemian plutonic complex

    International Nuclear Information System (INIS)

    Barnet, I.; Fojtikova, I.

    2004-01-01

    The study is based on the indoor radon data (one year measurements, Kodak LR 115 track etch detectors), vectorized geological maps 1:50000, vectorized coordinates of dwellings and uranium data for granitoid types of the Central Bohemian Plutonic Complex (CBPC). Using ArcGis 8.2 programme, the position of 16145 dwellings was linked to a geological database covering the CBPC (approx. 3200 km 2 ), and the type of underlying rock type was specified for each house. The resulting databases enabled us to calculate the mean EEC indoor Rn data for particular granitoid types and to study the relationship between the indoor Rn and the U concentrations. The petrogenetically variable CBPC was emplaced during Variscan orogenesis (330-350 Ma) and is among the most radioactive rock types within the Bohemian Massif. A long-term process of CBPC genesis resulted in more than 20 granitoid types, differing by their petrogenetic characteristics as well as mineralogical and chemical composition, including uranium concentration. The relation between the mean indoor radon values and uranium concentrations in particular rock types was examined. A positive regression between indoor Rn and uranium as the source of Rn soil gas clearly demonstrates how regional geology influences the indoor radon activity concentration in dwellings. The highest indoor Rn concentrations were observed in the Sedlcany granodiorite and Certovo bremeno syenite, where also the highest gamma dose rates (150-210 nGy.h -1 ) within all granitoid types in the Czech Republic were observed. The two rock types differ from other granitoids by a relatively high zircon concentration, which is the main source of U and subsequently of soil gas Rn being released from the bedrock. The lower indoor Rn values of Certovo bremeno syenite which do not correspond with the high U concentrations can be explained by a relatively low permeability of its clayey weathering crust. This feature was also observed for soil gas radon concentration

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

    Energy Technology Data Exchange (ETDEWEB)

    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.; Gupta, Manish; Chandler, Darrell P.; Murray, Christopher J.; Peacock, Aaron D.; Giloteaux, L.; 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 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.

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

    Science.gov (United States)

    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 co