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Journal ArticleDOI

Monovalent cations in structures of the meta-autunite group

01 Aug 2004-Canadian Mineralogist (Mineralogical Association of Canada)-Vol. 42, Iss: 4, pp 973-996
TL;DR: In this article, the structural roles of the interlayer cations in determining the symmetries and hydration states observed are discussed, and the smallest monovalent cation, Li, occurs in tetra- hedral coordination between fourfold squares of hydrogen-bonded H2O groups.
Abstract: Compounds of the meta-autunite group containing monovalent cations (Li, Na, K, Rb, Cs, Ag, Tl) have been synthesized by diffusion in gels or by hydrothermal methods, and their crystal structures determined. Single-crystal X-ray-diffraction intensity data were collected at room temperature using MoKradiation and a CCD-based area detector. These compounds contain the autunite-type sheet with composition ((UO2)(XO4)) - , X = P or As, which involves the sharing of equatorial vertices of uranyl square bipyramids with tetrahedra. The interlayer region contains cations and H2O groups, and the sheets are linked by hydrogen bonding and through bonds from the interlayer cations to oxygen atoms of the sheets. The structural roles of the interlayer cations in determining the symmetries and hydration states observed are discussed. The smallest monovalent cation, Li, occurs in tetra- hedral coordination between fourfold squares of hydrogen-bonded H2O groups. Despite a wide range in ionic radius, Na, K, Rb, Ag and Tl randomly substitute for H2O groups in the interlayer, in the same fashion as their ammonium and oxonium analogues. The large Cs cation adopts independent crystallographic sites in the interlayer. The size difference between Cs and the other monovalent cations probably prevents their direct substitution, and may limit the extent of solid solution. With the exception of
Citations
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Journal ArticleDOI
TL;DR: Burns et al. as discussed by the authors presented a structure hierarchy of hexavalent uranium (U 6+ ) compounds, with the first two being those of Burns et al., which considered 180 and 368 structures, respectively.
Abstract: Over the past four decades, the number of inorganic oxide and oxy-salt phases containing stoichiometric quantities of hexavalent uranium has increased exponentially from a few dozen to well over 700, and these structures have become well-known for their remarkable compositional diversity and topological variability. Considering the entirety of these compounds ( i . e ., crystal structures, conditions of synthesis, and geological occurrences) offers significant insight into the behavior of uranium in the solid state and in the nascent (typically aqueous) fluids. The structure hierarchy approach adopted here aims specifically to facilitate the recognition of useful patterns in the crystal-chemical behavior of hexavalent uranium (U 6+ ). This work represents the third attempt at a structure hierarchy of U 6+ compounds, with the first two being those of Burns et al . (1996) and Burns (2005), which considered 180 and 368 structures, respectively. The current work is expanded to include the structures of 727 known, well-refined synthetic compounds (610) and minerals (117) that contain stoichiometric quantities of U 6+ . As in the previous works, structures are systematically ordered on the basis of topological similarity, as defined predominantly by the polymerization of high-valence cations. The updated breakdown is as follows: (1) isolated polyhedra (24 compounds/0 minerals); (2) finite clusters (70 compounds/10 minerals); (3) infinite chains (94 compounds/15 minerals); (4) infinite sheets (353 compounds/79 minerals); and (5) frameworks (186 compounds/13 minerals). Within each of these major categories, structures are sub-divided on the basis of increasing connectivity of uranium (nearly always uranyl) polyhedra. In addition to elucidating common trends in U 6+ crystal chemistry, this structure hierarchy will serve as a comprehensive introduction for those not yet fluent in the domain of uranium mineralogy and inorganic, synthetic uranium chemistry.

133 citations


Additional excerpts

  • ...…(37) Appleman & Evans (1965); (38) Piret et al. (1980); (39) Borene & Cesbron (1970); (40) Dickens et al. (1992); (411) Gasperin (1987d); (42) Locock et al. (2004c); (43) Wallwork et al. (2006); (44) Rivenet et al. (2007); (45) Burciaga-Valencia et al. (2010); (46) Krivovichev & Burns…...

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Journal ArticleDOI
TL;DR: This Critical Review reviews the origin and chemical and rheological complexity of radioactive waste at the U.S. Department of Energy Hanford Site and indicates that boehmite dissolves much more slowly than predicted given surface normalized rates.
Abstract: This Critical Review reviews the origin and chemical and rheological complexity of radioactive waste at the U.S. Department of Energy Hanford Site. The waste, stored in underground tanks, was generated via three distinct processes over decades of plutonium extraction operations. Although close records were kept of original waste disposition, tank-to-tank transfers and conditions that impede equilibrium complicate our understanding of the chemistry, phase composition, and rheology of the waste. Tank waste slurries comprise particles and aggregates from nano to micro scales, with varying densities, morphologies, heterogeneous compositions, and complicated responses to flow regimes and process conditions. Further, remnant or changing radiation fields may affect the stability and rheology of the waste. These conditions pose challenges for transport through conduits or pipes to treatment plants for vitrification. Additionally, recalcitrant boehmite degrades glass quality and the high aluminum content must be r...

107 citations

Journal ArticleDOI
TL;DR: Very high concentrations of uranium (up to 4000 ppm) were found in a natural soil in the Dischma valley, an alpine region in the Grisons canton in Switzerland as discussed by the authors.

103 citations

Journal ArticleDOI
TL;DR: The molecular-scale immobilization mechanisms of uranium uptake in the presence of phosphate and goethite were examined by extended X-ray absorption fine structure (EXAFS) spectroscopy and revealed that the precipitated U(VI) had a structure consistent with the meta-autunite group of solids.
Abstract: The molecular-scale immobilization mechanisms of uranium uptake in the presence of phosphate and goethite were examined by extended X-ray absorption fine structure (EXAFS) spectroscopy. Wet chemistry data from U(VI)-equilibrated goethite suspensions at pH 4–7 in the presence of ∼100 μM total phosphate indicated changes in U(VI) uptake mechanisms from adsorption to precipitation with increasing total uranium concentrations and with increasing pH. EXAFS analysis revealed that the precipitated U(VI) had a structure consistent with the meta-autunite group of solids. The adsorbed U(VI), in the absence of phosphate at pH 4–7, formed bidentate edge-sharing, ≡Fe(OH)2UO2, and bidentate corner-sharing, (≡FeOH)2UO2, surface complexes with respective U–Fe coordination distances of ∼3.45 and ∼4.3 A. In the presence of phosphate and goethite, the relative amounts of precipitated and adsorbed U(VI) were quantified using linear combinations of the EXAFS spectra of precipitated U(VI) and phosphate-free adsorbed U(VI). A U...

96 citations

Journal ArticleDOI
TL;DR: This review article provides a thorough discussion of the vibrational modes for U(IV), U(V), and U(VI) and applications of infrared absorption and Raman scattering spectroscopies in the identification and detection of both naturally occurring and synthetic uranium species in solid and solution states.

88 citations

References
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Journal ArticleDOI
TL;DR: The effective ionic radii of Shannon & Prewitt [Acta Cryst. (1969), B25, 925-945] are revised to include more unusual oxidation states and coordinations as mentioned in this paper.
Abstract: The effective ionic radii of Shannon & Prewitt [Acta Cryst. (1969), B25, 925-945] are revised to include more unusual oxidation states and coordinations. Revisions are based on new structural data, empirical bond strength-bond length relationships, and plots of (1) radii vs volume, (2) radii vs coordination number, and (3) radii vs oxidation state. Factors which affect radii additivity are polyhedral distortion, partial occupancy of cation sites, covalence, and metallic character. Mean Nb5+-O and Mo6+-O octahedral distances are linearly dependent on distortion. A decrease in cation occupancy increases mean Li+-O, Na+-O, and Ag+-O distances in a predictable manner. Covalence strongly shortens Fe2+-X, Co2+-X, Ni2+-X, Mn2+-X, Cu+-X, Ag+-X, and M-H- bonds as the electronegativity of X or M decreases. Smaller effects are seen for Zn2+-X, Cd2+-X, In2+-X, pb2+-X, and TI+-X. Bonds with delocalized electrons and therefore metallic character, e.g. Sm-S, V-S, and Re-O, are significantly shorter than similar bonds with localized electrons.

51,997 citations


"Monovalent cations in structures of..." refers background in this paper

  • ...13, 15), which in turn are a function of the large size of the Cs cation: [9]Cs+ 1.78 Å (Shannon 1976)....

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  • ...…are isostructural with their chemically corresponding arsenates, but this is not true of the Rb members (effective ionic radius [7]Rb+ 1.56 Å, Shannon 1976) of the meta-autunite group; RbUP adopts the P4/ncc structure type, whereas its chemical analogue RbUAs crystallizes in P4/n, with the…...

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  • ...O bonds, ~2.5 Å, on the basis of ionic radii (Shannon 1976)....

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  • ...O bonds, ~2.6 Å, on the basis of ionic radii (Shannon 1976)....

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  • ...Lithium is the smallest cation, with effective ionic radius: [4]Li+ 0.59 Å (Shannon 1976) and occurs at an interstitial site in between the squares of hydrogenbonded H2O molecules (Fig....

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Book
01 Jan 1999
TL;DR: Cotton and Wilkinson's Advanced Inorganic Chemistry (AIC) as discussed by the authors is one of the most widely used inorganic chemistry books and has been used for more than a quarter century.
Abstract: For more than a quarter century, Cotton and Wilkinson's Advanced Inorganic Chemistry has been the source that students and professional chemists have turned to for the background needed to understand current research literature in inorganic chemistry and aspects of organometallic chemistry. Like its predecessors, this updated Sixth Edition is organized around the periodic table of elements and provides a systematic treatment of the chemistry of all chemical elements and their compounds. It incorporates important recent developments with an emphasis on advances in the interpretation of structure, bonding, and reactivity.From the reviews of the Fifth Edition:* "The first place to go when seeking general information about the chemistry of a particular element, especially when up-to-date, authoritative information is desired." -Journal of the American Chemical Society.* "Every student with a serious interest in inorganic chemistry should have [this book]." -Journal of Chemical Education.* "A mine of information . . . an invaluable guide." -Nature.* "The standard by which all other inorganic chemistry books are judged."-Nouveau Journal de Chimie.* "A masterly overview of the chemistry of the elements."-The Times of London Higher Education Supplement.* "A bonanza of information on important results and developments which could otherwise easily be overlooked in the general deluge of publications." -Angewandte Chemie.

12,231 citations

Journal ArticleDOI

8,158 citations


"Monovalent cations in structures of..." refers methods in this paper

  • ...…sums at the non-H cation sites for the twelve compounds are in Table 14, and were calculated using the parameters of Burns et al. (1997) for sixfoldcoordinated U6+, Brown & Altermatt (1985) for P5+, As5+, Li, Na, K, Rb, Ag and Cs, and R0 = 1.927 Å, B = 0.50 Å for Tl (Locock & Burns 2003b)....

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  • ...The long interatomic distances lead to low bond-valence sums for Ag (Table 14) using conventional bond-valence parameters (Brown & Altermatt 1985)....

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  • ...Bond-valence sums at the non-H cation sites for the twelve compounds are in Table 14, and were calculated using the parameters of Burns et al. (1997) for sixfoldcoordinated U6+, Brown & Altermatt (1985) for P5+, As5+, Li, Na, K, Rb, Ag and Cs, and R0 = 1.927 Å, B = 0.50 Å for Tl (Locock & Burns 2003b)....

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Book
13 Mar 1997
TL;DR: In this paper, the authors discuss the properties of strong and moderate hydrogen bonds in biological molecules and include inclusion of inclusion compounds in the graph set theory of graph set theories, which is used in this paper.
Abstract: 1. Brief History 2. Nature and Properties 3. Strong Hydrogen Bonds 4. Moderate Hydrogen Bonds 5. Weak Hydrogen Bonds 6. Cooperativity, Patterns, Graph Set Theory, Liquid Crystals 7. Disorder, Proton Transfer, Isotope Effect, Ferroelectrics, Transitions 8. Water, Water Dimers, Ices, Hydrates 9. Inclusion Compounds 10. Hydrogen Bonding in Biological Molecules 11. Methods

4,461 citations


"Monovalent cations in structures of..." refers background in this paper

  • ...However, the four shortest distances in each case are reasonable separation distances for oxygen atoms involved in hydrogen bonding (Jeffrey 1997)....

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