Stability of U(VI) solid phases in the U(VI)-Ca2+-SiO2-OH system
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B. Ritherdon
Abstract
Synthetic metaschoepite was altered at 70 °C, for 30 days in silicate solutions of varying compositions to study alteration reactions and to compare experimental observations with a thermodynamic model of stability of the uranyl minerals metaschoepite ([(UO2)8O2(OH)12](H2O)10), becquerelite (Ca[(UO2)3O2(OH)3]2(H2O)8), α-uranophane (Ca[(UO2)(SiO3OH)]2(H2O)5) and soddyite ((UO2)2(SiO4)· (H2O)2). Powder X-ray diffraction analysis, scanning electron microscopy and solution chemistry were used to monitor the alteration of the initial metaschoepite. In general, the secondary phases predicted by the thermodynamic model formed. However, an unexpected mineral (a calcium uranate) was observed above pH 8. Also, within the timeframe of these experiments, U(VI) silicate phases only formed at Si concentrations much higher than the lower field boundaries for uranophane and soddyite.
© 2003 Oldenbourg Wissenschaftsverlag GmbH
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Artikel in diesem Heft
- Some rules to improve the energy resolution in alpha liquid scintillation with beta rejection
- Confidence intervals for experiments with background and small numbers of events
- Solubility product of Pu(VI) hydrous oxide
- Precipitation of crystalline neptunium dioxide from near-neutral aqueous solution
- Stability of U(VI) solid phases in the U(VI)-Ca2+-SiO2-OH system
- Synergistic extraction of Th(IV) by 2-hydroxy-1-naphthaldehyde thiosemicarbazone and neutral donors
- Production of 55Co via the 54Fe(d,n)-process and excitation functions of 54Fe(d,t)53Fe and 54Fe(d,α)52mMn reactions from threshold up to 13.8 MeV
- Potential in vivo generator for alpha-particle therapy with 212Bi: Presentation of a system to minimize escape of daughter nuclide after decay of 212Pb to 212Bi
- In vitro study of the interaction between neptunium ions and aposerumtransferrin by absorption spectrophotometry and ultrafiltration: the case of Np(V)
