Showing papers on "Uranyl published in 1986"
TL;DR: It was shown that uranium accumulation exhibits a maximum at pH 4.6 that is supported by experimental data from previous investigations and proposed that metal ions are bound to phosphodiester residues present both in the cell wall and cytoplasmic fractions.
Abstract: Biosorption of uranium and lead by lyophilized cells of Streptomyces longwoodensis was examined as a function of metal concentration, pH, cell concentration, and culture age. Cells harvested from the stationary growth phase exhibited an exceptionally high capacity for uranium (0.44 g U/g dry weight) at pH 5. Calculated values of the distribution coefficient and separation factor indicated a strong preference of the cell mass for uranyl ions over lead ions. The specific uranium uptake was similar for the cell wall and the cytoplasmic fraction. Uranium uptake was associated with an increase in hydrogen ion concentration, and phosphorus analysis of whole cells indicated a simple stoichiometric ratio between uranium uptake and phosphorus content. It is proposed that metal ions are bound to phosphodiester residues present both in the cell wall and cytoplasmic fractions. Based on this model, it was shown that uranium accumulation exhibits a maximum at pH 4.6 that is supported by experimental data from previous investigations.
233 citations
TL;DR: In this article, the adsorption of uranyl species onto a well-characterized hematite sol has been studied in the presence of bicarbonate ions and it was shown that the uptake of uranium decreases abruptly with increasing solution pH.
119 citations
TL;DR: In this paper, the physicochemical characterization of uranium(VI) in seawater is described on the basis of species distribution calculations and experiments using polarography and spectrophotometry.
Abstract: The physicochemical characterization of uranium(VI) in seawater is described on the basis of species distribution calculations and experiments using polarography and spectrophotometry in artificial seawater at elevated uranium concentrations. Various dissolved uranium(VI) species are identified under different conditions of pH and carbonate concentration. Below pH 4, the hydrated uranyl ion is present in the free state (forming labile complexes). Above pH 4, a stepwise coordination of uranyl by the carbonate ion occurs. The monocarbonate complex is formed in the pH range 4-5, the bicarbonate uranyl complex between 5 and 6. Above pH 8, uranium is present predominately as the tricarbonate and to a smaller extent as a trihydroxide complex. There is satisfactory agreement between our experiments and the theoretically computed distribution of uranium(VI) in seawater based on published stability constants. The experiments done at higher concentrations are justified by theoretical distributions showing that there is no great difference in species distribution between the uranium at concentrations of 10/sup -4/ and /sup -8/ mol dm/sup -3/.
86 citations
TL;DR: Percolation of uranium mine discharge water through Ambrosia Lake, NM, soil is shown to be an effective method for lowering selenium, uranium, molybdenum, and sulfate concentrations in the mine water.
Abstract: Percolation of uranium mine discharge water through Ambrosia Lake, NM, soil is shown to be an effective method for lowering selenium, uranium, molybdenum, and sulfate concentrations in the mine water. Selenium concentrations were lowered from approx.1.6 to <0.05 mg/L by reduction of soluble selenate and selenite to insoluble selenium metal. This reaction is most likely performed by bacteria belonging to the genus Clostridium. In addition, sulfate-reducing bacteria in the soil, such as Desulfovibrio bacteria, metabolize sulfate to hydrogen sulfide, which reacts with uranyl and molybdate ions to form insoluble uranium and molybdenum species. The concentrations of sulfate, uranium, and molybdenum were reduced to less than 600, 0.1, and 0.05 mg/L, respectively. A qualitative understanding of the effects of mine water temperature, flow rate, and nutrients on metals removal is provided. The process was successfully field tested for 7 months in a soil column 1.5 m deep. 13 references, 3 figures, 4 tables.
52 citations
TL;DR: In this article, a new hydrazinium uranyl oxalate complex (N2H5)6[(UO2)2(C2O4)5]·2H2O has been prepared and characterized by chemical analysis.
50 citations
TL;DR: In this paper, a product analysis indicates that uranyl ions in the clay pillars produce a more selective catalyst than materials obtained by inserting uranyl ion in the interlamellar spacings of the clay.
Abstract: Uranyl-containing pillared clays, uranyl-exchanged clays, and zeolites have been used to photooxidize solutions of ethanol and diethyl ether. Product analysis indicates that uranyl ions in the clay pillars produce a more selective catalyst than materials obtained by inserting uranyl ion in the interlamellar spacings of the clay. Mechanisms are proposed to distinguish reactivity and selectivity differences of these photocatalysts. Incorporation of uranyl ions does not significantly affect the cracking properties of pillared clay catalysts.
45 citations
TL;DR: In this paper, the adsorption equilibrium of uranium from aqueous solutions containing tricarbonatouranate(VI) ions on a polymer bearing amidoxime groups was examined at pH 8-9.
Abstract: The adsorption equilibrium of uranium from aqueous solutions containing tricarbonatouranate(VI) ions on a polymer bearing amidoxime groups was examined at pH 8–9 It is suggested that the adsorption proceeds by ligand exchange of three carbonate ions on the central uranyl(VI) ion with two amidoxime groups, accompanied by deprotonations The uranyl(VI) complex formed with the polymer was found to be more stable than that with acetamidoxime as a ligand, suggesting that the amidoxime polymer has potential for the recovery of uranium from sea-water
44 citations
TL;DR: In this article, a tridentate ligand for salicylaldehyde-4-aminoantipyrine (SAAP) complexes with the general formula [Ln(AAP)2]-NO3)3 (where Ln = Pr, Nd, Sm, Gd, Dy or Y) was proposed.
42 citations
TL;DR: In this article, the physicochemical properties and catalytic activity of cyclic ligands derived from 2, 6-diformyl-4-chlorophenol and polyamines of the type NH2 and/or ethylenediamine were investigated.
35 citations
TL;DR: In this article, SALH2 has been synthesized from 4′,5′-diaminobenzo{15-crown-5} and salicylaldehyde.
Abstract: 4′,5′-Bis(salicylideneimino)benzo{15-crown-5} (SALH2) has been synthesized from 4′,5′-diaminobenzo{15-crown-5} and salicylaldehyde. The crystalline sodium nitrate complex of the ligand (SALH2.NaNO3.H2O) has also been isolated. As an N2O2-donor ligand, SALH2 forms 1:1 metal complexes with various metals {SAL(M)xH2O where M = UO2(VI), Cu(II), or Ni(II)}. The octahedral Co(II) complex of SALH2 is capable of binding molecular oxygen. Also prepared were the complexes which simultaneously contain both sodium and transition metal ion. 1H-n.m.r., i.r., u.v.-visible, and conductance data are presented.
32 citations
TL;DR: A series of dioxouranium(VI) complexes with 7-carboxaldehyde-8hydroxyquinoline (oxine) and with some of its Schiff bases, LH, have been prepared and characterized by elemental analyses, electronic and vibrational spectral studies as discussed by the authors.
Abstract: A series of dioxouranium(VI) complexes with 7-carboxaldehyde-8hydroxyquinoline (oxine) and with some of its Schiff bases, LH, have been prepared and characterized by elemental analyses, electronic and vibrational spectral studies. All complexes except those of the oxine have the [UO2L2] · EtOH, stoichiometry (n=0, 1, 2 or 4). The uranyl complexes of the oxine have the formula [UO2L2(LH)]. The i.r. spectra reveal all ligands to be monobasic bidentate chelating agents coordinated to the uranium(VI)via the enolized phenolic OH and aldehydic oxygen or azomethine nitrogen atom. The force constant fU-o (mdyn A) and the bond length rU-o (A) of the U-O bond are also calculated and related to the electronic properties of thep-substituents.
TL;DR: In this article, the electrochemical behavior of a series of mono-nuclear, homo-and hetero-dinuclear complexes of dioxouranium(VI), nickel(II) and copper (II) ions with acyclic and cyclic compartmental ligands, derived from the condensation of 2,6-diformyl-4-chlorophenol and polyamines of the type NH 2 (XNH, S), is reported.
TL;DR: In this paper, the crystal structure of the triniclic trinear complex was determined by X-ray crystallography from single-crystal diffractometer data, and the hexagonal dipyramid around the uranium atom contains two carboxyl ligands and two water molecules in the equatorial plane of the uranyl ion.
Abstract: The crystal structure of the complex in the title was determined by X-ray crystallography from single-crystal diffractometer data. Crystal data: UO2C10O8H4 · 2H2O, triniclic, P 1 , a = 6.355(6) A , b = 11.531(9) A , c = 5.548(5) A , α = 104.07 °, β = 109.06 °, γ = 81.85 °, M = 558.192, Z = 1, V =371.875 A 3 , dcalc = 2.49 g cm−3, R (F) = 0.106, Rw = 0.134 for 3413 independent reflections. The hexagonal dipyramid around the uranium atom contains two carboxyl ligands and two water molecules in the equatorial plane of the uranyl ion. The U—O (uranyl bond) is 1.70(2) A, 〈U—O〉 in the equatorial plane is 2.48 A, and other distances and angles are similar to those in the literature.
TL;DR: In this paper, the tetragonal structures of all these product compounds are derived from HUP, and the diffuse electronic reflectance spectra of every sample show characteristic absorption bands.
Abstract: HUO2PO4•4H2O (HUP) forms a laminar intercalate with butylamine, c = 29.30(5) A, which accepts cationic metals in exchange for the n-butylammonium ions. Hydrated uranyl metal phosphates M(UO2PO4)2•nH2O (M = Mn, Co, Ni, Cu, Zn, Cd) are obtained by ionic exchange and were studied by thermal analysis and X-ray diffraction. The tetragonal structures of all these product compounds are derived from HUP. The diffuse electronic reflectance spectra of every sample show characteristic absorption bands. In the spectra of the Co, Ni, and Cu phosphates there are other bands in the 500–800 nm zone compatible with their observed aquocation transitions.
TL;DR: In this paper, the structure of the uranyl(VI) complex with the ligand 1,7,15,21-tetra-aza-4,18-dithia-11,25-dichloro 8,22-bis- meta diphenyl cyclophane-gb-7,14,21,28 has been determined by X-ray crystallography.
TL;DR: In this paper, a polymeric chain is formed between uranyl groups by sharing two of the three azide ligands, the third being coordinated only to one uranium, leading to the classical pentagonal bipyramidal configuration.
Abstract: I) (N(C2Hs)4)(UO2(N 3)3) , M,=526.34, orthorhombic, P2~2121, a = 7.768 (4), b = 12.047 (3), c=18-016(6)/~, V=1686(2)A 3, Z=4, D x= 2.073 Mg m -3, 2(Mo Ka) = 0.71073 A, # = 9.15 mm -1, F(000) = 984, T = 294 K, R = 0.031 for 1184 independent reflections (I > 3tr(/)). A polymeric chain is formed between uranyl groups by sharing two of the three azide ligands, the third being coordinated only to one uranium. The uranyl group is thus pentacoordinated in its equatorial plane, leading to the classical pentagonal bipyramidal configuration. The tetraethylammonium ions are located between poly- meric chains. (II) (N(CH3)414((UO2)a(Na)80).H20, M,= 1476.9, monoclinic, P2Jn, a=21.893 (4), b = 22.586 (4), c= 9.070 (1)A, fl= 94.31 (1) °, V= 4472 (2) A 3, Z = 4, D x = 2.194 Mg m -a, 2(Mo Kct) = 0.71073 A, /t = 10.34 mm -1, F(000) = 2728, T= 294K, R =0.041 for 2063 independent reflections (1>3o(/)). The compound contains hexanuclear anions ((UO2)6(N3)I602 )8- and tetramethylammonium cations. The anion is formed by two triangular units (three UO 2 groups with a g3- bridging O 2- bonded to the three U atoms), linked by a symmetry centre. Six g2-N~- ligands are located on the edges of such triangles while two others are bonding two triangular units; the last eight azides included in the complex anion act as unshared ligands. Each uranium atom is then seven- coordinated in a nearly perfect pentagonal bipyramidal geometry.
TL;DR: In this paper, the authors showed that the phosphonomethylation of polyethylenimine (BPEI) is very important for the uranium recovery from seawater, and that the molar ratio of the PHONOME group to amino groups affects the adsorption ability very much.
Abstract: Branched polyethylenimine (BPEI) was crosslinked by a bis-epoxide to give a resin (CL-BPEI), which was further functionalized by phosphorous acid / formaldehyde leading to phosphonomethylated CL-BPEI (PhosCL-BPEI). The latter resin has been found to recover uranium from natural seawater very efficiently but not the former resin; with column method PhosCL-BPEI recovered 85-64 % of uranium in the original seawater at SV=170–680 hr−1. The highest recovery rate obtained so far was 46.8 μg-U/g-resin/6 hr at SV=680 hr−1. PhosCL-BPEI could be used repeatedly without appreciable decrease of the efficiency. The molar ratio of phosphonomethyl group to amino groups in the resin affects the adsorption ability very much, the adequate P/N ratio being ∼0.25. Both PhosCL-BPEI and CL-BPEI showed a large adsorption capacity from an aqueous solution of uranyl ions. It is stressed, however, that the phosphonomethylation of CL-BPEI is very important for the uranium recovery from seawater.
TL;DR: In this article, the radiolytic reduction of uranyl ions in degassed sulphuric acid solutions containing various organic solutes was studied, and it was shown that while ĊOOH, CO2−, and α-hydroxy-alkyl radicals reduced...
Abstract: The radiolytic reduction of uranyl ions in degassed sulphuric acid solutions containing various organic solutes was studied. It was shown that while ĊOOH, CO2−, and α-hydroxy-alkyl radicals reduced...
TL;DR: In this paper, the authors investigated the transfer flux of uranyl nitrate across a supported liquid membrane using tributyl phosphate as mobile carrier, and evaluated the separate interfacial resistances.
TL;DR: In this paper, the macrocyclic tris(dithiocarbamates) was used to obtain a triphasic (successive three-step) equilibrium with three different equilibrium constants.
Abstract: Equilibria and rates of ligand-exchange reactions between uranyl tricarbonate and dithiocarbamates and between uranyl tris-(dithiocarbamates) and carbonate were studied under a variety of conditions. The dithiocarbamates used were acyclic diethyl-dithiocarbamate and macrocyclic tris(dithiocarbamate). The acyclic ligand showed a triphasic (successive three-step) equilibrium with three different equilibrium constants while the macrocyclic ligand showed a clear monophasic (one-step) equilibrium with a much larger stability constant for the dithiocarbamate-uranyl complex. The macrocyclic ligand showed the S/sub N/2-type ligand-exchange rate in the forward as well as reverse process, while the first step of the acyclic ligand-exchange reaction proceeded via the S/sub N/1-type mechanism. This kinetic macrocyclic effect on molecularity is interpreted as the result of a unique topological requirement of uranyl complexation. The macrocyclic ligand also exhibited a clear protection effect, leading to the large stability constant. 19 references, 10 figures, 2 tables.
TL;DR: In this article, the reaction of one mole of acetylacetone with two moles of 4-phenylthiosemicarbazide yields the unusual Schiff base, MeC( =N-NHCSNHPh)CH2C(=NNHCSNHPH)Me.
Abstract: Reaction of one mole of acetylacetone with two moles of 4-phenylthiosemicarbazide yields the unusual Schiff base, MeC(=N-NHCSNHPh)CH2C(=NNHCSNHPh)Me. APT = H2L) acetylacetone bis(4-phenylthiosemicarbazone). The complexes of CoII, NiII, CuII, ZnII and UVIO2 have been prepared and characterized by analytical, i.r., electronic spectral and magnetic measurements. The CoII, NiII and CuII complexes have been assigned square-planar stereochemistry on the basis of magnetic and spectroscopic studies. The ligand is a neutral or dibasic quadridentate SNNS donor as revealed by i.r. spectral studies.
TL;DR: Some uranyl complexes of benzoylhydrazine (BH), sali-cyloylnhydrazine (MSH), and isonic-cycloylhexine (ISH) of the type UO2 LX2°nH2O (where L = BH, MSH and ISH, X = NO3, CH3COO−, SCN−, Cl− and n = 0,1 or 2) have been prepared and characterized by analytical data, decomposition temperature, molar conductance and infrared spectral measurements down to
Abstract: Some uranyl complexes of benzoylhydrazine (BH), sali-cyloylhydrazine (MSH) and isonicotinoylhydrazine (ISH) of the type UO2 LX2°nH2O (where L = BH, MSH and ISH, X = NO3, CH3COO−, SCN−, Cl− and n = 0,1 or 2) have been prepared and characterized by analytical data, decomposition temperature, molar conductance and infrared spectral measurements down to 200 cm−1. The molar conductance data in DMF indicate that all the completes are ionic in this solvent. The infrared spectral data indicate that the BH and MSH coordinate as neutral bi-dentate ligands through the -NH2 and >C=O groups and ISH coordinates as a neutral tridentate ligand through the -NH2, >C=O and the ring nitrogen. The nitrate and acetate groups function as a bidentate chelating ligand and thiocyanate and chloride groups as a terminal ligand.
TL;DR: In this paper, the interaction between D-glucuronic acid and hydrated uranyl salts has been studied in aqueous solution and solid complexes of the type UO 2 (D- glucuronate)X·2H 2 0, where X = CI −, Br − or NO 3 −, are isolated and characterized by means of FT-IR and proton-NMR spectroscopy.
TL;DR: In this paper, the standard molar ideal gas thermodynamic functions of the singly and doubly charged uranyl, neptunyl, plutonyl and americyl ions MOn+2(n= 1 or 2) have been calculated from structural, and electronic and vibrational spectroscopic data.
Abstract: The standard molar ideal gas thermodynamic functions of the singly and doubly charged uranyl, neptunyl, plutonyl and americyl ions MOn+2(n= 1 or 2) have been calculated from structural, and electronic and vibrational spectroscopic data. Estimates have been made for values not found in the literature. The heat capacity, entropy, enthalpy and Gibbs free energy are reported over the temperature range 100–1000 K. The values for 298.15 K have been combined with the standard partial molar entropies of these ions in aqueous solutions to yield the standard molar entropies of hydration. For the hexavalent uranyl ion data are also available for the standard partial molar heat capacity of the aqueous ion and the standard molar heat of formation of the gaseous ion, so that the corresponding quantities of hydration could be calculated. The thermodynamic functions of hydration are interpreted in terms of a model for the hydrated ions.
TL;DR: In this paper, the authors reported good agreement between the values of Stern-Volmer constants for quenching of uranyl luminescence by dialkyl sulfides measured by the authors and those reported by Sandhu, et al., however, a marked difference in kinetic reactivity toward R/sub 2/S between uranyl nitrate and acetate was noted.
Abstract: This paper attempts to resolve some disagreement between work reported by the authors and that reported by Sandhu, et al. on the photochemical reduction of uranyl ion by several dialkyl sulfides. Results of studies carried out to ascertain whether the differences in data resulted from the conditions of irradiation indicated that the difference did not lie in questions of intensity, position, or bandwidth of absorbed radiation nor in the choice of uranium (IV) salt or solvent. Redetermination of quantum yields for production of U(IV) from the disulfides with those obtained during photoreduction of ethanol still yielded results that do not agree with those published by Sandhu, et al. Good agreement is reported between the values of Stern-Volmer constants for the quenching of uranyl luminescence by dialkyl sulfides measured by the authors and those reported by Sandhu, et al.; however, a marked difference in kinetic reactivity toward R/sub 2/S between uranyl nitrate and acetate was noted. 9 references, 5 figures, 5 tables.
TL;DR: In this paper, the synthesis and characterization of dioxoyranyl(VI) complexes containing 3-benzamidorhodanine and its substituted derivatives as ligands are reported.
TL;DR: Protasite, a barium-containing member of the uranyl oxide hydrate group, occurs as bright orange pseudo-hexagonal platelets associated with uraninite and uranophane on unidentified rock matrix from Shinkolobwe mine, Zaire as mentioned in this paper.
Abstract: Protasite, a new barium-containing member of the uranyl oxide hydrate group, occurs as bright orange pseudo-hexagonal platelets associated with uraninite and uranophane on unidentified rock matrix from Shinkolobwe mine, Zaire. Protasite is monoclinic, Pn with a 12.295(2), b 7.221(1), c 6.9558(8) A, β 90.40(2)°, and V 617.50(11) A3. The tabular pseudo-hexagonal crystals are flattened on {010}, 0.1 mm to 0.5 mm wide and up to 0.1 mm thick. They are biaxial negative, 2 V = 60–65°, β and γ 1.79–1.83, and X = b. Sector twinning is common. Microprobe analysis shows BaO 15.0, UO3 78.0, H2O(diff.) 7.0%. The structural formula is Ba[(UO2)3O3(OH)2]. 3H2O, Z = 2, and density(calc.) = 5.827(3) g cm−3. Complete crystal-structure analysis shows protasite to be the simplest model structure of the uranyl oxide hydrate group.
TL;DR: In this paper, it was shown that the apparent rates of the fluorescence quenching of aromatic molecules by the uranyl ion in ethanol solutions are considerably higher than the rate of diffusion.
TL;DR: In this article, the ligand 2-dimethylacetal-4-chloro-6-formylphenol, H(ALAC), prepared by boiling 2,6-diformyl- 4-chlorophenol, in methanol, was reacted with uranyl acetate to obtain the complex [UO2(alAC)2(H2O)] and was characterized by X-ray crystallography, infrared, 1H NMR and electronic spectroscopy.