Journal Article10.2138/AM.2005.1568
Dehydration processes in the meta-autunite group minerals meta-autunite, metasaléeite, and metatorbernite
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TL;DR: In this article, the authors investigated dehydration processes in uranyl phosphate minerals of the meta-autunite group that consist of uranyl phosphates and interlayer cations, and water molecules.
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Abstract: We investigated dehydration processes in uranyl phosphate minerals of the meta-autunite group that consist of uranyl phosphate sheets and interlayer cations, and water molecules. Meta-autunite [Ca(UO 2 PO 4 ) 2 .6H 2 O], metasaleeite [Mg(UO 2 PO 4 ) 2 .8H 2 O], and metatorbernite [Cu(UO 2 PO 4 ) 2 .8H 2 O] were selected for our study. The change in basal spacing between two adjacent uranyl phosphate sheets with temperature was examined by temperature-controlled X-ray diffraction (XRD) analysis from room temperature (RT) to 300 °C to determine structurally distinct, dehydrated phases. Thermogravimetric and differential thermal analyses (TG/DTA) were also performed under conditions similar to those used for the XRD analysis to clarify the hydration states of the dehydrated phases. Retention of the structure of the uranyl phosphate sheets under a high vacuum, equivalent to 300 °C, was confirmed by transmission electron microscopy. Meta-autunite, metasaleeite, and metatorbernite decreased their basal spacings by losing water molecules. Comparison of the TG/DTA and XRD results indicates that the changes in basal spacings of the dehydrated phases with temperature are as follows: 8.32 A (6 H 2 O per unit formula) at RT, 7.31 (? H 2 O) and 6.68 A (? H 2 O) at 75 °C, 6.34 A (2 H 2 O) at 120 °C, and 5.81 A (1 H 2 O) at'300 °C for meta-autunite; 8.29 (8 H 2 O) and 7.73 A (? H 2 O) at RT, 6.62 A (probably, 2 H 2 O) at 40 °C, 6.54 A (2 H 2 O) at 160 °C, and 5.52 A (1 H 2 O) at 300 °C for metasaleeite; and 8.61 A (8 H 2 O) at RT, 8.07 A (4 H 2 O) at 100 °C, 6.58 A (2 H 2 O) at 200 °C, and 5.60 A (1 H 2 O) at 300 °C for metatorbernite. The dehydration processes revealed by XRD and TG/DTA under similar experimental conditions are slightly different from those obtained by previous studies. Our results clearly demonstrate the presence of previously unknown dehydrated phases of the meta-autunite group minerals with basal spacings less than 6 A that may have distinct thermodynamic properties.
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References
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TL;DR: In this article, a discussion is given concerning the transformation of curite into meta-torbernite in an acid environment and the surface conductivity is calculated from the measured zeta-potential.
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Synthesis, crystallographic data, solubility and electrokinetic properties of copper-, nickel- and cobalt˗uranylphosphate
R. Vochten,Paul Piret,André Goeminne +2 more
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TL;DR: In this paper, a discussion est consacree a la transformation en milieu acide de curite en phosphate d'uranyle de cuivre, de nickel and de cobalt.
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Crystal chemistry and microstructures of uranyl phosphates
TL;DR: In this article, the crystal chemistry and microstructures of saleeite (Mg(UO2PO4)2⋅10H2O), from Koongarra, Australia and Shinkolobwe, Congo, were examined by X-ray diffraction analysis, infrared spectroscopy (IR), scanning electron microscopy (SEM) equipped with energy dispersive Xray analysis, transmission electron microscopes (TEM) and analytical electron microscope.
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