The hydrogen-atom locations in the α and β forms of uranyl hydroxide

Taylor, J. C.; Hurst, H.J.

doi:10.1107/s0567740871005259

Cited by 39 publications

(34 citation statements)

References 3 publications

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“…Other yellow phases with the general chemical composition UO 3 •nH 2 O (0.75 < n < 2) are for example ␣-and ␤-[UO 2 (OH) 2 ] (Taylor & Hurst 1971) and dehydrated schoepite (Finch et al 1998). Those compounds can be synthesized in acidic solution at temperatures above 80°C (Finch et al 1998).…”

Section: Resultsmentioning

confidence: 99%

Crystal Growth of Schoepite on the (104) Surface of Calcite

Schindler

Putnis

2004

The Canadian Mineralogist

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12 , cristallise suite à une interaction de solutions uranylées acides ou basiques avec la calcite. Ces solutions uranylées possèdent une concentration de (UO 2 ) 2+ entre 1.5 et 50 mmol L -1 , et une valeur initiale de pH de 2.5, 4.5 ou 10.0. Un examen des cristaux avec le microscope à force atomique (AFM) révèle les morphologies distinctes des cristaux de schoepite formés sur la surface (104) de la calcite. Les cristaux formés au cours des expériences in situ avec une solution de nitrate uranylée (pH initial = 2.5) ont une morphologie en plaquettes, et leur face proéminente (001) est définie par des arêtes [210]. Les cristaux formés au cours des expériences in situ avec une solution d'acétate uranylée (pH initial = 4.5) semblent plus trappus, avec des faces rectangulaires (001) de piètre qualité. Un examen des surfaces de calcite suite à une interaction avec une solution légèrement acide pour trois jours (pH final entre 5.5 et 6.5) montre des cristaux en plaquettes assymétriques avec des faces (001) proéminentes définies par les arêtes [100], [010], [120], et [110]. Des expériences avec des solutions basiques après trois semaines (pH final entre 7.5 et 8.0) révèlent de gros cristaux rectangulaires de schoepite, dans lesquels la face (001) est surtout définie par les arêtes [100] et [010]. Les épaisseurs différentes des cristaux de schoepite dans les expériences in situ seraient dues aux taux de croissance différents des faces S et F des solutions ayant des indices de saturation différents par rapport à la schoepite. La présence d'arêtes sur la face (001) des cristaux de schoepite dépendrait des paramètres structuraux des chaînes de polyèdres parallèles aux arêtes et au pH de la solution.(Traduit par la Rédaction)

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Section: Resultsmentioning

confidence: 99%

Crystal Growth of Schoepite on the (104) Surface of Calcite

Schindler

Putnis

2004

The Canadian Mineralogist

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“…Data reduction and analysis were performed using ifeffit and feffit softwares (Newville et al, 1995;Newville, 2001). Phase and amplitude were generated by the feff 8.1 code (Ankudinov and Rehr, 2000), for the model compounds a-UO 2 (OH) 2 (Taylor and Hurst, 1971) and soddyite (UO 2 ) 2 SiO 4 AE2H 2 O (Demartin et al, 1992), in which Si atoms were replaced by Al atoms (Sylwester et al, 2000). All fitting operations were performed to Fourier transform (FT) spectra in R-space between 0.9 and 4.0 Å .…”

Section: Xafs Measurementsmentioning

confidence: 99%

Uranyl sorption species at low coverage on Al-hydroxide: TRLFS and XAFS studies

Froideval

Nero

Gaillard

et al. 2006

Geochimica et Cosmochimica Acta

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International audienceDetailed understanding of the respective roles of solution and surface parameters on the reactions at uranyl solution/Al-(hydr)oxide interfaces is crucial to model accurately the behaviour of U in nature. We report studies on the effects of the initial aqueous uranyl speciation in moderately acidic solutions, e.g. of mononuclear, polynuclear uranyl species and/or (potential) U(VI) colloids, on the sorption of U by large surface areas of amorphous Al-hydroxide. Investigations by Extended X-ray Absorption Fine Structure (EXAFS) and Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS) reveal similar U coordination environments on Al-hydroxide for low to moderate U loadings of sorption samples obtained at pH 4–5, independently of the presence of mononuclear or polynuclear aqueous species, or of the potential instability of initial solutions favoring true U-colloids formation. EXAFS data can be interpreted in terms of a dimeric, bidentate, inner-sphere uranyl surface complex as an average of the U surface structures. TRLFS data, however, provide valuable insights into the complex U surface speciation. They indicate multiple uranyl surface species under moderately acidic conditions, as predominant mononuclear and/or dinuclear, inner-sphere surface complexes and as additional minor species having U atoms in a uranyl (hydr)oxide-like coordination environment. The additional species probably occur as surface polymers and/or as adsorbed true U colloids, depending on the aqueous U concentration level (1–100 μM). These results are of importance because they suggest that Al-hydroxide surface characteristics strongly control uranyl surface species in moderately acidic systems

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“…and NpO2 + interactions were derived from FEFF7.2 single or multiple scattering paths (SS or MS) calculated for the model compound α-UO2(OH)2 [9]. Microsoft EXCEL™ was used to perform principal component analysis (PCA) on the spectra using standard methodology [10].…”

Section: +mentioning

confidence: 99%

The partitioning of uranium and neptunium onto hydrothermally altered concrete

Zhao¹,

Allen²,

Sylwester³

et al. 2000

Radiochimica Acta

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SummaryPartition coefficients (K d ) of U(VI) and Np(V) on untreated and hydrothermally altered concrete were measured in 0.01 M NaCl and 0.01 M NaHCO 3 solutions as functions of concentration of the radionuclides, pH, and time. The partition coefficients for both U(VI) and Np(V) on hydrothermally altered concrete are significantly lower than those on untreated concrete. The partition of both U(VI) and Np(V) are pH dependent, although the pH dependence does not necessarily reflect precipitation of U and Np-bearing phases. Both sorption and precipitation appear to control partitioning of U to concrete; sorption alone appears to control partition of Np to concrete.The presence of 0.01 M carbonate species in solution decreases K d of U(VI) for both treated and untreated concrete to a similar value of ~500 mL/g indicating a significant impact on U(VI) sorption. However, the presence of carbonate only reduced the K d of Np(V) by one order of magnitude or less. Our results also show that significant amounts of uranium and neptunium in aqueous phase are associated with suspended colloids. In most cases, the colloid-associated uranium and neptunium are the predominant species in the liquid phase. X-ray absorption spectroscopy * Authors to whom correspondence should be addressed.analysis of U/concrete mixtures at different pHs and times indicate that uranyl ions are partitioned as monomeric species on untreated concrete, but oligomeric species on hydrothermally altered concrete. Similar analysis of Np/concrete mixtures shows that about half of the partitioned Np(V) is reduced to Np(IV) over a period of 6 months.

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The hydrogen-atom locations in the α and β forms of uranyl hydroxide

Cited by 39 publications

References 3 publications

Crystal Growth of Schoepite on the (104) Surface of Calcite

Crystal Growth of Schoepite on the (104) Surface of Calcite

Uranyl sorption species at low coverage on Al-hydroxide: TRLFS and XAFS studies

The partitioning of uranium and neptunium onto hydrothermally altered concrete

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