Synthesis and characterization of uranium (VI) chloride flourides

Uranium (VI) chloride fluorides were synthesized by the reaction of liquid HCl and solid UF₆ between −80 and −114°C. These dark red compounds are unstable above −40 to −60°C. The simplest formulas derived from compositional analysis are UF₅Cl and UF₄Cl₂.     

Sorption of uranium(VI) from aqueous solution onto magnesium silicate hollow spheres

The sorption of uranium(VI) from aqueous solutions was investigated using synthesized magnesium silicate hollow spheres as a novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, contact time and initial U(VI) concentrations on uranium sorption efficiency. The desorbing of U(VI) and the effect of coexisting ions were also investigated. Kinetic studies showed that the sorption followed a pseudo-second-order kinetic model. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 25–400 mg/L. The maximum uranium sorption capacity onto magnesium silicate hollow spheres was estimated to be about 107 mg/g under the experimental conditions. Desorption of uranium was achieved using inorganic acid as the desorbing agent. The practical utility of magnesium silicate hollow spheres for U(VI) uptake was investigated with high salt concentration of intercrystalline brine. This work suggests that magnesium silicate hollow spheres can be used as a highly efficient adsorbent for removal of uranium from aqueous solutions.     

Microdetermination of uranium (VI)

Summary A new method has been evolved for the separation and estimation of UO₂ ²⁺ from Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺, Ga³⁺, In³⁺, Tl³⁺, La³⁺, Ti⁴⁺, Zr⁴⁺ and Th⁴⁺ with the sodium salt of benzilic acid as precipitating and chelating agent andn-butanol as solvent for solvent extraction. All these cations except UO₂ ²⁺ are precipitated by benzilic acid; UO₂ ²⁺ forms a deep yellow complex extractable byn-butanol. The uranium can be determined in the organic phase spectrophotometrically at 430 nm. The pH range over which the separation can be carried out is 2.6–4.0. Few anions and cations interfere.

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Zusammenfassung Eine neue Methode der Trennung und Bestimmung von UO₂ ²⁺ neben Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺, Ga³⁺, In³⁺, Tl²⁺, La³⁺, Ti⁴⁺, Zr⁴⁺ und Th⁴⁺ wurde ausgearbeitet. Das Natriumsalz der Benzilsäure dient als Färbungs- und Komplexbildungsmittel und n-Butanol zur Extraktion. Alle angeführten Kationen mit Ausnahme von UO₂ ²⁺ werden von Benzilsäure gefällt; UO^{2 2+} bildet einen tiefgelben, mit n-Butanol extrahierbaren Komplex und kann in der organischen Phase spektrophotometrisch bei 430 nm bestimmt werden. Die Trennung kann bei pH 2,6 bis 4,0 durchgeführt werden. Nur wenige Anionen und Kationen stören.

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Résumé On développe une nouvelle méthode pour la séparation et l'évaluation de UO₂ ²⁺ dans Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺, Ga³⁺, In³⁺, Tl³⁺, La³⁺, Ti⁴⁺, Zr⁴⁺ et Th⁴⁺, par le sel de sodium de l'acide benzilique comme agent précipitant et chélatant et le N-butanol comme solvant pour l'extraction par solvant. Tous ces cations, sauf UO₂ ²⁺, précipitent par l'acide benzilique; UO₂ ²⁺ forme un complexe jaune intense que l'on peut extraire par le N-butanol. On peut doser l'uranium en phase organique par spectrophotométrie à 430 nm. La séparation peut s'effectuer dans le domaine de pH de 2,6 à 4,0. Peu d'anions et de cations interfèrent.

     

Structural and spectroscopic characterization of plutonyl(VI) nitrate under acidic conditions

The plutonyl(VI) dinitrate complex [PuO(2)(NO(3))(2)(H(2)O)(2)]·H(2)O (1) has been structurally characterized by single-crystal X-ray diffraction and spectroscopically characterized by solid-state vis-NIR and Raman spectroscopies. Aqueous solution spectroscopic studies indicate only weak plutonyl(VI) nitrate complexation, with the mononitrate complex dominating and negligible dinitrate formation, even in concentrated nitric acid.     

Synthesis and characterization of peroxo complexes of uranium(VI) with aroylhydrazone ligands

The uranium(VI) peroxo complexes containing aroylhydrazones ligands having composition [UO(O₂)L-L(NO₃)₂]·H₂O (where L-L = Benzoic acid[1-(Furan-2-yl)methylene] hydrazide, Benzoic acid[(thiophene-2-yl)methylene] hydrazide, Benzoic acid[1-(thiophene-2-yl)ethylidene] hydrazide, Benzoic acid(phenylmethylene) hydrazide, Benzoic acid[1-(anisol-3-yl)methylene] hydrazide and Benzoic acid[(p-chlorobenzyl)methylene] hydrazide are reported. The complexes were characterized by various physico-chemical techniques, viz. elemental analysis, molar conductivity, magnetic susceptibility measurements, infra red, electronic, mass spectral and TGA/DTA studies. These studies revealed that complexes are non-electrolytes and diamagnetic in nature. The ligands are bound to metal in a bidentate mode. Thermal analysis results provide conclusive evidence for the presence of water molecules in the complexes. Mass spectra confirm the molecular mass of the complexes. Antifungal activity of complexes revealed enhanced activity of complexes as compared to the corresponding ligands.     

Colorimetric determination of uranium(VI)

A new, very sensitive reagent is proposed for the colorimetric determination of uranium(VI), namely 1-phenyl-3-methyl-4-(3'-carboxy-4'-hydroxyphenyl-azo)-pyrazol-5-one.     

Liquid-liquid extraction of molybdenum(VI) and uranium(VI) by LIX 622

The order of extraction of Mo(VI) from 1M acid solutions by 5% (v/v) LIX 622 (HL) in benzene is HCl>HNO₃>HClO₄>H₂SO₄, and extraction decreases with increasing concentration of HCl and H₂SO₄, and increases slightly with increasing concentration of HNO₃ and HClO₄. The extracted species is shown to be MoO₂L₂ as established by IR data of organic extracts and the extracted species in the solid form. Extraction is almost quantitative at and above 10% LIX 622, and is found to be independent of [Mo(VI)] in the range of 10^–4 to 10^–3 M. The diluents CCl₄, CHCl₃ and C₆H₆ are found to be superior to solvents of high dielectric constant for extraction of Mo(VI). Extraction of uranium(VI) by 10% (v/v) LIX 622 in benzene was found to increase with increasing equilibrium pH (3.0 to 6.0), and becomes quantitative at pH 5.9. Tributyl phosphate acts as a modifier up to 2% (v/v). Thorium(IV) is almost not extracted by LIX 622 or its mixture. Separation of Mo(VI) and U(VI) is feasible.     

Syntheses, crystal structure and spectroscopic characterization of new platinum(II) dithiocarbimato complexes

The reaction of 4-iodobenzenesulfonamide or 4-fluorobenzenesulfonamide with CS₂ and KOH in dimethylformamide yielded the potassium N-R-sulfonyldithiocarbimates, K₂(RSO₂NCS₂) [R = 4-IC₆H₄ (1) and 4-FC₆H₄ (2)]. These salts reacted with K₂[PtCl₄] in water/methanol to yield complex anions bis(N-R-sulfonyldithiocarbimato)platinate(II), which were isolated as their tetrabutylammonium salts, (Bu₄N)₂[Pt(RSO₂NCS₂)₂] [R = 4-IC₆H₄ (3) and 4-FC₆H₄ (4)]. The structures of 2–4 were determined by X-ray crystallography. The Pt²⁺ in both complexes 3 and 4 lies at the inversion centre and the PtS₄ moiety has a distorted square-planar configuration. The compounds were also characterized by IR, ¹H NMR and ¹³C NMR spectroscopies, and elemental analyses. The molar conductance data are consistent with the fact that 3 and 4 are dianionic complexes.     

The synthesis, structural, and spectroscopic characterization of uranium(IV) perrhenate complexes

We report the synthesis, structural, and spectroscopic characterization of a series of uranium(IV)-perrhenato complexes. Three isostructural complexes with general formula [U(ReO4)4(L)4] (where L = tri-n-butylphosphine oxide/TBPO (2), triethyl phosphate/TEP (3), or tri-iso-butyl phosphate/TiBP (4)), have been synthesized, both through the photoreduction of ethanolic {UO2}2+ solutions and also via a novel U(IV) starting material, U(ReO4)4.5H2O (1). Compound 1 has also been used in the preparation of [U(ReO4)4(TPPO)3(CH3CN)].2CH3CN (5) and [U(ReO4)(DPPMO2)3(OH)][ReO4]2.2CH3CN (6), where TPPO represents triphenylphosphine oxide and DPPMO2 represents bis(diphenylphosphino)methane dioxide. All six complexes have been spectroscopically characterized using NMR, UV-vis-NIR, and IR techniques, with 2, 3, 5, and 6 also fully structurally characterized. The U atoms in compounds 2-6 all exhibit eight-coordinate geometry with up to four perrhenate groups in addition to three (DPPMO2 and TPPO) or four (TEP, TiBP, TBPO) coordinated organic ligands. In the case of compounds 5 and 6, the coordination of eight ligands to the U(IV) center is completed by the binding of a solvent molecule (CH3CN) and OH-, respectively. Solid-state physical analysis (elemental and thermogravimetric) and infrared spectroscopy are in agreement with the structural studies. The crystallographic data suggest that the strength of the U(IV)-O-donor ligand bonds decreases across the series R3PO > [ReO4]- > (RO)3PO. Solution-state IR and 31P NMR spectroscopy appear to be in agreement with these solid-state results.     

Synthesis and characterization of phosphorylated Aspergillus niger for effective adsorption of uranium(VI)

The adsorption characteristics of phosphorylated Aspergillus niger (AN-P) for uranium(VI) were studied in this work. The AN-P was successfully prepared by the reaction of Aspergillus niger with phosphorus pentoxide in ice-bath under the catalysis of methanesulphonic acid. AN-P was characterized by FT-IR and SEM–EDS. The effects of pH, contact time, initial U(VI) ions concentration, adsorbent dosage and temperature on the adsorption of U(VI) by AN-P were investigated. The isotherm and kinetic data were accurately described by the Langmuir and pseudo-second-order models, respectively. The calculated thermodynamic parameters indicated that the adsorption of U(VI) by AN-P was an spontaneous and endothermic process. This indicated that the AN-P composite is a promising adsorbent for efficient removal of U(VI) from radioactive wastewater.

     

Syntheses and vibrational spectra of xenon(VI) fluorogallate,xenon(VI) fluoroaluminate and xenon(VI) fluoroindate

Liquid xenon difluoride at 140°C does not react with aluminium, gallium, and indium trifluorides, neither does liquid xenon hexafluoride at 60°C. Therefore the reactions between the corresponding hydrazinium fluorometalates (N₂H₆AlF₅, N₂H₆GaF₅ and N₂H₅InF₄) and XeF₂ and XeF₆ were carried out. N₂H₆AlF₅, N₂H₆GaF₅ and N₂H₅InF₄ react with XeF₂ at 60°C (at 25°C in the case of indium) yielding only the corresponding trifluorides, while the reaction with XeF₆ proceeds at room temperature (at - 25°C in the case of indium) yielding XeF₆.2AlF₃, XeF₆.GaF₃ and xenon(VI) fluoroindate(III) contaminated with indium trifluoride. Spectroscopic evidence suggests that these compounds are salts of the XeF⁺₅ cation squashed between polymeric anions of the type (M₂F₇)^x-_x or (MF₄)^x-_x.     

Thermal behaviour of uranium(VI) complexes

The solid-state syntheses of complexes of uranyl acetate dihydrate andN-phenylthiourea have been attempted by heating various stoichiometric mixtures of the reactants directly in a DSC and in a TA apparatus. Both the DSC and the TG results indicate that only the 1∶1 adduct is formed, independently of the molar ratios of the reactants. It appears that the reaction is complete only with a large excess ofN-phenylthiourea, in agreement with IR data.     

Interaction of uranium(VI) with lipopolysaccharide

Bacteria have a great influence on the migration behaviour of heavy metals in the environment. Lipopolysaccharides form the main part of the outer membrane of Gram-negative bacteria. We investigated the interaction of the uranyl cation (UO2(2+)) with lipopolysaccharide (LPS) from Pseudomonas aeruginosa by using potentiometric titration and time-resolved laser-induced fluorescence spectroscopy (TRLFS) over a wide pH and concentration range. Generally, LPS consists of a high density of different functionalities for metal binding such as carboxyl, phosphoryl, amino and hydroxyl groups. The dissociation constants and corresponding site densities of these functional groups were determined using potentiometric titration. The combination of both methods, potentiometry and TRLFS, show that at an excess of LPS uranyl phosphoryl coordination dominates, whereas at a slight deficit on LPS compared to uranyl, carboxyl groups also become important for uranyl coordination. The stability constants of one uranyl carboxyl complex and three different uranyl phosphoryl complexes and the luminescence properties of the phosphoryl complexes are reported.     

Identification and characterization of resistate minerals containing uranium and thorium

A set of natural matrix Standard Reference Materials were developed by the National Bureau of Standards for analytical methods evaluation. These materials were analyzed using a KF fusion procedure and an acid dissolution procedure. The latter method yielded radioactive concentrations that were 15–20% lower then that of the former. This was thought to be due to a fraction of the sample, “resistates,” that did not dissolve during the dissolution. In this study, HF dissolutions were conducted on NIST natural matrix SRMs, in which ~0.08% of total sample mass remained after dissolution. The acid resistant residual materials were concentrated, then dissolved using a LiBO₂ fusion procedure and were found to contain a considerable fraction of the uranium and thorium.     

Synthesis and characterization of peroxo complexes of uranium(VI) with some Mannich base ligands

Abstract  

Uranium(VI) peroxo complexes of composition [UO(O₂)L–L(NO₃)₂], where L–L are the Mannich base ligands morpholinobenzyl urea, piperidinobenzyl urea, morpholinobenzyl thiourea, piperidinobenzyl thiourea, morpholinomethyl thiourea, piperidinomethyl thiourea, or morpholinomethyl urea, are reported. The synthesized complexes were characterized by use of a variety of physicochemical techniques, viz. elemental analysis, molar conductivity, magnetic susceptibility measurements, IR, electronic, mass, ¹H NMR, and ¹³C NMR spectroscopy, and TGA/DTA studies. These studies revealed that the complexes are both non-electrolytic and diamagnetic in nature. The ligands are bound to the metal in a bidentate mode through carbonyl oxygen or thiocarbonyl sulfur and the ring nitrogen. Mass spectra confirm the molecular mass of the complexes. The antifungal activity of the complexes is greater than that of the corresponding free ligands.