SOLID-AQUEOUS PHASE-EQUILIBRIA OF URANIUM(VI) UNDER AMBIENT CONDITIONS

Citation
G. Meinrath et al., SOLID-AQUEOUS PHASE-EQUILIBRIA OF URANIUM(VI) UNDER AMBIENT CONDITIONS, Radiochimica Acta, 75(3), 1996, pp. 159-167
Citations number
42
Categorie Soggetti
Nuclear Sciences & Tecnology","Chemistry Inorganic & Nuclear
Journal title
ISSN journal
00338230
Volume
75
Issue
3
Year of publication
1996
Pages
159 - 167
Database
ISI
SICI code
0033-8230(1996)75:3<159:SPOUUA>2.0.ZU;2-2
Abstract
The solubility of uranium(VI) is investigated in the pH range 2.8 to 4 .6 in equilibrium with 8.0% and 0.3% CO2 partial pressure and in the p H range 3.8 to 7.0 in equilibrium with 0.03% CO2 partial pressure at I = 0.1 M NaClO4 and 25 degrees C. UO2CO3(s) under 8.0% and UO3 . 2 H2O under 0.3% CO2 and 0.03% CO2 partial pressures at pH < 7 are characte rized as solubility limiting solid phases. Above pH 7, a spontaneous p hase transformation of UO3 . 2 H2O(s) in a sodium containing poorly cr ystalline material is observed. Thermodynamic solubility products lg K -sp(o) = -14.91 +/- 0.10 for UO2CO3(s) and K-s(o) = 4.68 +/- 0.14 and lg K-s(o) = 5.14+/-0.05 for UO3 . 2 H2O(s) under 0.3% and 0.03% CO2 pa rtial pressures, resp. are obtained. The evaluation of UO3 . 2 H2O(s) solubilities on basis of spectroscopic speciation by TRLFS are discuss ed and a formation constant lg K-35' = -17.14 +/- 0.13 is obtained.