Showing papers on "Uranyl published in 2011"
TL;DR: The intriguing, visible-light photocatalytic activities of uranyl-organic compounds are potentially applicable in decomposition of organic pollutants and in water-splitting with the irradiation of solar light.
Abstract: The ability of uranium to undergo nuclear fission has been exploited primarily to manufacture nuclear weapons and to generate nuclear power. Outside of its nuclear physics, uranium also exhibits rich chemistry, and it forms various compounds with other elements. Among the uranium-bearing compounds, those with a uranium oxidation state of +6 are most common and a particular structural unit, uranyl UO(2)(2+) is usually involved in these hexavalent uranium compounds. Apart from forming solids with inorganic ions, the uranyl unit also bonds to organic molecules to generate uranyl-organic coordination materials. If appropriate reaction conditions are employed, uranyl-organic extended structures (1-D chains, 2-D layers, and 3-D frameworks) can be obtained. Research on uranyl-organic compounds with extended structures allows for the exploration of their rich structural chemistry, and such studies also point to potential applications such as in materials that could facilitate nuclear waste disposal. In this Account, we describe the structural features of uranyl-organic compounds and efforts to synthesize uranyl-organic compounds with desired structures. We address strategies to construct 3-D uranyl-organic frameworks through rational selection of organic ligands and the incorporation of heteroatoms. The UO(2)(2+) species with inactive U═O double bonds usually form bipyramidal polyhedral structures with ligands coordinated at the equatorial positions, and these polyhedra act as primary building units (PBUs) for the construction of uranyl-organic compounds. The geometry of the uranyl ions and the steric arrangements and functionalities of organic ligands can be exploited in the the design of uranyl--organic extended structures, We also focus on the investigation of the promising physicochemical properties of uranyl-organic compounds. Uranyl-organic materials with an extended structure may exhibit attractive properties, such as photoluminescence, photocatalysis, photocurrent, and photovoltaic responses. In particular, the intriguing, visible-light photocatalytic activities of uranyl-organic compounds are potentially applicable in decomposition of organic pollutants and in water-splitting with the irradiation of solar light. We ascribe the photochemical properties of uranyl-organic compounds to the electronic transitions within the U═O bonds, which may be affected by the presence of organic ligands.
353 citations
TL;DR: In this paper, the authors developed a novel magnetic adsorbent for the removal of uranyl ions using methylenediamine-modified magnetic chitosan (EMMC) complex.
135 citations
TL;DR: A series of nine complexes has been obtained from the hydrothermal reaction of uranyl nitrate with long-chain alkyldicarboxylic acids (HOOC-(CH2)n-2-COOH, denoted H2Cn) in the presence of cucurbit[6]uril (CB6), dimethylformamide (DMF), and additional alkaline-earth metal ions in some cases as discussed by the authors.
Abstract: A series of nine complexes has been obtained from the hydrothermal reaction of uranyl nitrate with long-chain alkyldicarboxylic acids (HOOC-(CH2)n–2-COOH, denoted H2Cn) in the presence of cucurbit[6]uril (CB6), dimethylformamide (DMF), which generates dimethylammonium cations in situ, and additional alkaline-earth metal ions in some cases. The crystal structures of the three complexes [H2NMe2]2[(UO2)4O2(OH)2(C8)2(CB6)]·8H2O (1), [H2NMe2]2[(UO2)4O2(OH)2(C9)2(CB6)]·5H2O (2), and [H2NMe2]2[(UO2)4O2(OH)2(C9)2(CB6)]·8H2O (3) are closely related, since all contain the same tetranuclear motif held by two μ3-oxo and two μ2-hydroxo ions, and attached to CB6 by uranyl-O-carbonyl bonds. Two-dimensional assemblies are formed in 1 and 2 and a three-dimensional framework in 3. The cucurbituril molecule is not coordinated in compounds 4–9 but is present as a structure-directing agent. The complex [H2NMe2]2[(UO2)4O2(C6)3]·CB8·8H2O (4), in which cucurbit[8]uril (CB8) comes from the initial CB6, displays a stacking of plan...
117 citations
TL;DR: In this article, the effects of the pH of solution, contact time, initial concentration and presence of other metals that could compete with uranium for adsorption sites were investigated in batch adaption experiments.
115 citations
TL;DR: X-ray diffraction and density functional theory analyses of uranyl organometallic complexes showed that the U-C and U=C bonds are polarized toward the nucleophilic carbon.
Abstract: Uranyl organometallic complexes featuring uranium(VI)-carbon single and double bonds have been obtained from uranyl UO(2)X(2) precursors by avoiding reduction of the metal center. X-ray diffraction and density functional theory analyses of these complexes showed that the U-C and U=C bonds are polarized toward the nucleophilic carbon.
110 citations
TL;DR: In this paper, the authors proposed a chemical model to describe the data through a fit of uranyl distribution ratios, while some other suggestions are unable to do so, and proposed to proceed via cation exchange at low initial acidities and via anion exchange at high HNO3 concentrations.
Abstract: The extraction of U(VI) by tributylphosphate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), C4-mimTf2N, has been studied as a function of TBP and HNO3 initial concentrations. Extraction measurements have been completed by UV-vis spectroscopy in order to get insights into the extraction mechanism. The proposed chemical model describes the data through a fit of uranyl distribution ratios, while some other suggestions are unable to do so. In this model, uranyl extraction is proposed to proceed via cation exchange at low initial acidities ([UO2(TBP)n]2+ versus C4-mim+ and H+) and via anion exchange at high HNO3 concentrations ([(UO2(NO3)3(TBP)m]− versus Tf2N−). By contrast to the usual TBP/dodecane organic phase, the IL system does not favor the neutral species UO2(NO3)2(TBP)2, and TBP does not extract nitric acid.
104 citations
103 citations
TL;DR: In this paper, a multisite surface complexation model without assuming exchange is based on the binding of the most dominant uranium species to aluminol and silanol edge sites of montmorillonite.
Abstract: Batch experiments were conducted to study the sorption of uranium on selected clay minerals (KGa-1b and KGa-2 reference kaolinite, SWy-2 and STx-1b reference montmorillonite, and IBECO natural bentonite) as a function of pH (4–9) and 0.001, 0.01, and 0.025 M NaCl in equilibrium with the CO2 partial pressure of the atmosphere. Uranium concentrations were kept below 100 μg L−1 to avoid precipitation of amorphous Uranium-hydroxides. Solely PTFE containers and materials were used, because experiments showed significant sorption at higher pH on glass ware. All batch experiments were performed over a period of 24 h, since kinetic experiments proved that the common 10 or 15 min are in many cases by far not sufficient to reach equilibrium. Kaolinite showed much greater uranium sorption than the other clay minerals due to the more aluminol sites available. Sorption on the poorly crystallized KGa-2 was higher than on the well-crystallized KGa-1b. Uranium sorption on STx-1b and IBECO exhibited parabolic behavior with a sorption maximum around pH 6.5. Sorption of uranium on montmorillonites showed a distinct dependency on sodium concentrations because of the effective competition between uranyl and sodium ions, whereas less significant differences in sorption were found for kaolinite. The presence of anatase as impurity in kaolinite enhanced the binding of uranyl-carbonate complexes with surface sites. The kinetic of uranium sorption behavior was primarily dependent on the clay minerals and pH. A multisite surface complexation model without assuming exchange is based on the binding of the most dominant uranium species to aluminol and silanol edge sites of montmorillonite, respectively to aluminol and titanol surface sites of kaolinite. For eight surface species, the log_k was determined from the experimental data using the parameter estimation code PEST together with PHREEQC.
102 citations
TL;DR: In this article, the UO(2)(2+) ion was extracted as cation complexes in a 1:2 ratio of UO (2) to extractant, and the extraction mechanism was deduced by the slope analysis and extraction tests.
101 citations
TL;DR: UV-visible absorption spectroscopy confirmed that uranium was only involved in the structure as uranyl forms (excluding the presence of tetravalent or pentavalent uranium) and assigning four uranyl contributions to the four types of uranyl entities in theructure, in agreement with the XRD analysis.
Abstract: An uranyl isophthalate has been hydrothermally synthesized at 200 °C for 24 h, from a mixture of uranyl nitrate, isophthalic acid, and hydrazine in water. It was characterized by single-crystal ana...
91 citations
TL;DR: The printed polymer nanospheres for uranium offers high retention capacity, is water compatible and works in the pH range of 5-7, making it ideal for possible use in decontamination of polluted natural water samples or front end effluents of nuclear power reactors.
TL;DR: This work describes the mechanisms of uranium biomineralization at acidic conditions by Bacillus sphaericus JG-7B and Sphingomonas sp.
TL;DR: It is demonstrated that time resolved and multi-parametric luminescence can be of value in ascertaining solution and structural forms of discrete uranyl(VI) complexes in non-aqueous solution.
Abstract: We describe the synthesis, solid state and solution properties of two families of uranyl(VI) complexes that are ligated by neutral monodentate and anionic bidentate PO, PNH and AsO ligands bearing pendent phenyl chromophores. The uranyl(VI) ions in these complexes possess long-lived photoluminescent LMCT 3Πu excited states, which can be exploited as a sensitive probe of electronic structure, bonding and aggregation behaviour in non-aqueous media. For a family of well defined complexes of given symmetry in trans-[UO2Cl2(L2)] (L = Ph3PO (1), Ph3AsO (2) and Ph3PNH (3)), the emission spectral profiles in CH2Cl2 are indicative of the strength of the donor atoms bound in the equatorial plane and the uranyl bond strength; the uranyl LMCT emission maxima are shifted to lower energy as the donor strength of L increases. The luminescence lifetimes in fluid solution mirror these observations (0.87–3.46 μs) and are particularly sensitive to vibrational and bimolecular deactivation. In a family of structurally well defined complexes of the related anion, tetraphenylimidodiphosphinate (TPIP), monometallic complexes, [UO2(TPIP)(thf)] (4), [UO2(TPIP)(Cy3PO)] 5), a bimetallic complex [UO2(TPIP)2]2 (6) and a previously known trimetallic complex, [UO2(TPIP)2]3 (7) can be isolated by variation of the synthetic procedure. Complex 7 differs from 6 as the central uranyl ion in 7 is orthogonally connected to the two peripheral ones viauranyl → uranium dative bonds. Each of these oligomers exhibits a characteristic optical fingerprint, where the emission maxima, the spectral shape and temporal decay profiles are unique for each structural form. Notably, excited state intermetallic quenching in the trimetallic complex 7 considerably reduces the luminescence lifetime with respect to the monometallic counterpart 5 (from 2.00 μs to 1.04 μs). This study demonstrates that time resolved and multi-parametric luminescence can be of value in ascertaining solution and structural forms of discrete uranyl(VI) complexes in non-aqueous solution.
TL;DR: In this article, 26 nanoscale clusters were synthesized using uranyl hexagonal bipyramids and they spontaneously self-assemble in aqueous solution under ambient conditions.
Abstract: Taking advantage of the bent uranyl-peroxide-uranyl interaction found in studtite, 26 nanoscale clusters have been synthesized using uranyl hexagonal bipyramids. Sixteen of these clusters are built from uranyl hexagonal bipyramids only. Eight contain pyrophosphate groups that bridge between uranyl polyhedra, and two contain oxalate groups that adopt a similar structural role. These clusters contain from 20 to 60 uranyl polyhedra and have diameters in the range ~1.5 to 3 nm. All spontaneously self-assemble in aqueous solution under ambient conditions.
TL;DR: In this paper, the recycling and reuse of uranyl salt solutions produced from the acid dissolution of spent nuclear fuels is of particular interest for reprocessing of nuclear fuels, and the ability to utilize th...
Abstract: The recycling and reuse of uranyl salt solutions produced from the acid dissolution of spent nuclear fuels is of particular interest for the reprocessing of nuclear fuels. The ability to utilize th...
TL;DR: Two uranyl nanotubules with elliptical cross sections were synthesized in high yield from complex and large oxoanions using hydrothermal reactions of uranyl salts with 1,4-benzenebisphosphonic acid and Cs(+) or Rb(+) cations in the presence of hydrofluoric acid to show high stability and exceptional ion-exchange properties toward monovalent cations.
Abstract: Two uranyl nanotubules with elliptical cross sections were synthesized in high yield from complex and large oxoanions using hydrothermal reactions of uranyl salts with 1,4-benzenebisphosphonic acid or 4,4′-biphenylenbisphosphonic acid and Cs+ or Rb+ cations in the presence of hydrofluoric acid. Disordered Cs+/Rb+ cations and solvent molecules are present within and/or between the nanotubules. Ion-exchange experiments with A2{(UO2)2F(PO3HC6H4C6H4PO3H)(PO3HC6H4C6H4PO3)}·2H2O (A = Cs+, Rb+), revealed that A+ cations can be exchanged for Ag+ ions. The uranyl phenyldiphosphonate nanotubules, Cs3.62H0.38[(UO2)4{C6H4(PO2OH)2}3{C6H4(PO3)2}F2]·nH2O, show high stability and exceptional ion-exchange properties toward monovalent cations, as demonstrated by ion-exchange studies with selected cations, Na+, K+, Tl+, and Ag+. Studies on ion-exchanged single crystal using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS) provide evidence for chemical zonation in Cs3.62H0.38[(UO2)4{C6H4(PO2OH)...
TL;DR: In this article, a series of layered uranyl diphosphonate compounds, including Me4Ubbp and Et2Me2UbbP, are shown to contain UO6F and UO7 pentagonal bipyramids within dimers.
Abstract: The hydrothermal treatment of uranyl nitrate and 1,4-benzenebisphosphonic acid with a variety of aliphatic amines (tetramethylammonium hydroxide, tetraethylammonium hydroxide, and diethyldimethylammonium hydroxide) and small quantities of hydrofluoric acid at 200 °C results in the crystallization of a series of layered uranyl diphosphonate compounds, [(CH3)4N][(UO2)3(O3PC6H4PO3H)2F(H2O)]·0.5H2O (Me4Ubbp), [(CH3CH2)4N]{(UO2)[C6H4(PO3H)(PO3H1.5)]2(H2O)} (Et4Ubbp), and [(CH3CH2)2N(CH3)2][(UO2)3(O3PC6H4PO3H)2F(H2O)] (Et2Me2Ubbp). All these new compounds have layered structures, but the structures of Me4Ubbp and Et2Me2Ubbp are similar in that they both contain UO6F and UO7 pentagonal bipyramids within dimers that are bridged by the phosphonate into a three-dimensional structure. The structure of Et4Ubbp contains a single crystallographically unique UO7 unit. The edge-sharing pentagonal bipyramids are linked into chains formulated as {(UO2)[C6H4(PO3H)(PO3H1.5)]2(H2O)}1−. The voids in these structures are filled...
TL;DR: Three uranyl phthalates have been hydrothermally synthesized (200 °C, 24 h) and characterized by means of single-crystal X-ray diffraction analysis as mentioned in this paper.
Abstract: Three uranyl phthalates have been hydrothermally synthesized (200 °C, 24 h) and characterized by means of single-crystal X-ray diffraction analysis. The compound UO2(H2O)(1,2-bdc)·0.32H2O (1,2-bdc = phthalate) crystallizes at low pH (0.9−1.5). Its structure is built up from pentagonal bipyramids (UO2)O4(H2O) linked to each other through the phthalate groups and defines infinite nanotubular 1D motifs delimited by six uranyl centers. The two other compounds A(UO2)3O(OH)(H2O)(1,2-bdc)2 (A = K, NH4) are formed for higher pH (1.5−3). They are isostructural and consist of the 1D connection of dinuclear units (UO2)2O4(μ2-OH)2(H2O)2 with tetranuclear units (UO2)4(μ3-O)2O12via the phthalate groups. The cationic A species are intercalated between the mixed organic−inorganic chains. Discussion of the formation of these different phases was given as a function of pH.
TL;DR: The role of the dipyridyl appears to be directly related not only to the length of the dicarboxylate with which it is paired, but also to the rigidity of the species as mentioned in this paper.
Abstract: Seven novel U(VI)-bearing compounds have been synthesized using hydrothermal conditions and characterized via single crystal X-ray diffraction. These materials are the result of systematically pairing aliphatic dicarboxylic acids and dipyridyl (1,2-bis(4-pyridyl)ethane and trans-1,2-bis(4-pyridyl)ethylene) molecules with the uranyl cation and are a conclusion to parts I and II of this study. A common factor of this family of materials is that the carboxylate group preferentially coordinates to the uranyl center, whereas the dipyridyl plays one of two roles: space filling or direct coordination uranyl cation. The role of the dipyridyl appears to be directly related not only to the length of the aliphatic dicarboxylate with which it is paired but also to the rigidity of the dipyridyl species. Further, this family of materials shows a tendency toward specific primary and secondary building units formed by the oligomerization of the uranyl cation despite the diversity suggested by other studies. This tendency...
TL;DR: In this article, the ability of a synthetic goethite nanocrystal to remove hexavalent uranium from aqueous solutions under various conditions was examined and the experimental data fitted well with the pseudo-second-order kinetics.
TL;DR: In this article, the authors performed computational and experimental studies to explore heterogeneous reduction of U 6+ by structural Fe 2+ at magnetite (Fe 3 O 4 ) surfaces.
TL;DR: Novel ammonium based hydrophobic ionic liquids (ILs) have been synthesised and characterised, and their use in the liquid-liquid extraction of uranium(VI) from an aqueous nitric acid solution using tri-n-butyl phosphate (TBP), studied.
Abstract: Novel ammonium based hydrophobic ionic liquids (ILs) have been synthesised and characterised, and their use in the liquid–liquid extraction of uranium(VI) from an aqueous nitric acid solution using tri-n-butyl phosphate (TBP), studied. On varying the nitric acid concentration, each IL was found to give markedly different results. Relatively hydrophilic ILs showed high uranium(VI) extractability at 0.01 M nitric acid solution which progressively decreased from 0.01 to 2 M HNO3 and then increased again as the nitric acid concentration was increased to 6 M. An analysis of the mechanisms involved for one such IL, pointed to cationic-exchange being the predominant route at low nitric acid concentrations whilst at high nitric acid concentrations, anionic-exchange predominated. Strongly hydrophobic ILs showed low extractability for nitric acid concentrations below 0.1 M but increasing extractability from 0.1 M to 6 M nitric acid. The predominant mechanism in this case involved the partitioning of a neutral uranyl complex. The uranyl complexes were found to be UO22+·(TBP)3 for the cationic exchange mechanism, UO2(NO3)2(TBP)2 for the neutral mechanism and UO2(NO3)3−·(TBP) for the anionic exchange mechanism.
TL;DR: The combination of contemporary computational chemistry and experimental techniques leads to a detailed understanding of structures, thermodynamics, and luminescence of actinide compounds, including those with bioligands.
Abstract: Comprehensive computational modeling of coordination structures, thermodynamic stabilities, and luminescence spectra of uranyl-glycine-water complexes [UO2(Gly)naqm]2+ (Gly = glycine, aq = H2O, n = 0−2, m = 0−5) in aqueous solution has been carried out using relativistic density functional approaches. The solvent is approximated by a dielectric continuum model and additional explicit water molecules. Detailed pictures are obtained by synergic combination of experimental and theoretical data. The optimal equatorial coordination numbers of uranyl are determined to be five. The energies of several complex conformations are competitively close to each other. In non-basic solution the most probable complex forms are those with two water ligands replaced by the bidentate carboxyl groups of zwitterionic glycine. The N,O-chelation in non-basic solution is neither entropically nor enthalpically favored. The symmetric and antisymmetric stretch vibrations of the nearly linear O−U−O unit determine the luminescence fe...
TL;DR: In this article, the UO22+ moiety is coordinated by five additional donor atoms resulting in a pentagonal bipyramidal coordination environment, which is the case for all these compounds.
Abstract: The hydrothermal reactions of either uranyl nitrate or uranium trioxide with 4-carboxyphenylphosphonic acid and HF/CsOH in the presence of Cs+ or Ba2+ cations result in the formation of Cs2{(UO2)2(PO3HC6H4CO2H)3(PO3C6H4CO2H)F} (CsUcpp-1), Cs4{(UO2)6(PO3C6H4CO2H)8}(H2O)7 (CsUcpp-2), Ba{(UO2)2(PO3C6H4CO2H)2F2}(H2O)2 (BaUcpp-1), and Cs3{(UO2)(O3PC6H4CO2)}3(H2O)3·4H2O (CsUcpp-3). All these compounds contain the UO22+ moiety coordinated by five additional donor atoms resulting in a pentagonal bipyramidal coordination environment. CsUcpp-1, CsUcpp-2, and BaUcpp-1 were isolated at low pH, whereas CsUcpp-3 was synthesized at high pH giving rise to complete elimination of protonation of phosphonic and carboxylic acid moieties. The pH of the reaction is playing a vital role in the formation of the pillared structures in which the carboxylate and phosphonate moieties are coordinated to uranium center in CsUcpp-3, while in the other three compounds, the carboxylate moiety coordinate exclusively to the Cs+ or Ba2+ cat...
TL;DR: In this article, the reaction of uranyl nitrate with cucurbit[6]uril (CB6) under hydrothermal conditions and in the presence of alkali metal ion nitrates has been investigated.
Abstract: The reaction of uranyl nitrate with cucurbit[6]uril (CB6) under hydrothermal conditions and in the presence of alkali metal ion nitrates has been investigated. Two complexes with Na+ have been obtained, [Na3(CB6)(H2O)8][(UO2)2(OH)2(NO3)4]·NO3·2H2O (1) and [Na1.5(CB6)(H2O)4][(UO2)6O2(OH)6(HCOO)3.5(H2O)]·8H2O (2), which differ by the presence in the latter of formate ions due to the hydrolysis of the dimethylformamide cosolvent. Both 1 and 2 display columnar, cationic Na+–CB6 complexes, with independent, anionic dinuclear (1) or one-dimensional polymeric (2) uranyl complexes. The molecular species [(UO2)3K3O1.5(OH)3(HCOO)3(CB6)3(H2O)6(DMF)3]·3H2O (3) is an original arrangement in which three K+ ions assemble three CB6 molecules around a trigonal axis and are themselves bound to the terminal oxo groups of a μ3-oxo-centered uranyl trinuclear unit. Only in the case of the cesium-containing complex [(UO2)2Cs2(OH)3(CB6)(H2O)4][(UO2)2Cs2(OH)3(NO3)2(CB6)(H2O)2][(UO2)2(OH)2(NO3)4]·2NO3·10H2O (4) is uranyl coordinat...
TL;DR: The dynamic precipitation characteristics of UO(4) in different solution conditions were characterized by measuring changes in the absorbance of the precipitation solution and by monitoring the change of particle size in a circulating particle size analyzer.
TL;DR: Novel crown-shaped clusters built from 32 uranyl peroxide polyhedra self-assemble and crystallize within 15 min after combining uranyl nitrate, ammonium hydroxide, and hydrogen peroxide in aqueous solution under ambient conditions.
Abstract: Clusters built from 32 uranyl peroxide polyhedra self-assemble and crystallize within 15 min after combining uranyl nitrate, ammonium hydroxide, and hydrogen peroxide in aqueous solution under ambient conditions. These novel crown-shaped clusters are remarkable in that they form so quickly, have extraordinarily low aqueous solubility, form with at least two distinct peroxide to hydroxyl ratios, and form in very high yield. The clusters, which have outer diameters of 23 A, topologically consist of eight pentagons and four hexagons. Their rapid formation and low solubility in aqueous systems may be useful properties at various stages in an advanced nuclear energy system.
TL;DR: In this article, a three-dimensional network of tetragonal bipyramidal U(VI) centers is constructed from the UO22+ moiety coordinated by four additional oxygen donor atoms from the phosphonate moiety, resulting in a tetragonal bipyramid geometry.
Abstract: The hydrothermal reactions of uranyl nitrate with diethyl(2-ethoxycarbonylphenyl)phosphonate, 3-carboxyphenylphosphonic acid, or diethyl(3-ethoxycarbonylphenyl)phosphonate with HF result in the formation of [Cu(H2O)]2Cu(H2O)2[(UO2)(PO3C6H4CO2H)(PO3C6H4CO2)]2 (UCuCPPE-1) and [H3O]2[Cu(H2O)]2[(UO2)3(PO3C6H4CO2)4]·3H2O (UCuCPPE-2). UCuCPPE-1 is constructed from the UO22+ moiety coordinated by four additional oxygen donor atoms from the phosphonate moiety, resulting in a tetragonal bipyramidal geometry. The phosphonate groups span between the uranyl cations to create chains that are in turn linked into sheets by square planar and square pyramidal Cu(II) units. The phenyl groups separate the sheets from one another. The structure of UCuCPPE-2 consists of a three-dimensional network of tetragonal bipyramidal and pentagonal bipyramidal U(VI) centers. These units form chains that the phosphonate groups link into sheets. The sheets are then joined together by square pyramidal CuO5 units to create the three-dimensi...
TL;DR: Analysis of the signal widths, persistence of the apparent exclusion rule between IR and Raman spectra of the uranyl species stretching modes, and interpretation of the absorption UV-visible spectra allow discussion of the chemistry, structures, and polynuclearity of uranyl(VI) species.
Abstract: In the field of actinide aqueous chemistry, this work aims to resolve some controversy about uranyl(VI) hydroxide species present in basic aqueous solutions. We revisit the Raman, IR, and UV−visible spectra with two new approaches. First, Raman, IR and UV data were recorded systematically from aqueous solutions with the noncomplexing electrolyte (C2H5)4NNO3 at 25 °C and 0.1 MPa ([Utotal] = 0.005−0.105 M) in H2O and D2O over a wide range of −log mH(D)+ between 2.92 and 14.50. Second, vibrational spectra (IR and Raman) of basic solutions in H2O and D2O were analyzed using the Bayesian Positive Source Separation method to estimate pure spectra of individual species. In D2O solutions, the new spectroscopic data showed the occurrence of the same species as those in H2O. As observed for the wavenumber of the symmetric stretching mode, the wavenumber characteristic of the O═U═O antisymmetric stretching mode decreases as the number of OH(D)− ligands increases. These kinds of data, completed by (1) analysis of the...
TL;DR: In this article, density functional investigations of kaolinite edge surfaces and uranyl adsorption thereon were carried out using periodic slab models, and the results indicated that a set of uranyl complexes may coexist on edge surfaces.