Solubility and hydrolysis of tetravalent actinides
Top Cited Papers
- 1 January 2001
- journal article
- Published by Walter de Gruyter GmbH in Radiochimica Acta
- Vol. 89 (1) , 1-16
- https://doi.org/10.1524/ract.2001.89.1.001
Abstract
The solubility and hydrolysis of Th(IV), U(IV), Np(IV), and Pu(IV) are critically reviewed and a comprehensive set of thermodynamic constants at I = 0 and 25°C is presented. The hydrolysis constants are selected preferentially from experimental studies at actinide trace concentrations, where the interference of colloid formation can be excluded. Unknown formation constants of mononuclear complexes An(OH)n4-nare estimated by applying a semi-empirical electrostatic model and an empirical correlation with the known constants of other actinide ions. Based on the known and estimated hydrolysis constants, the solubility products of An(OH)4(am) or AnO2× xH2O(am) are calculated from experimental solubility data available in the literature. The SIT is used for ionic strength corrections.The solubilities of U(IV), Np(IV), and Pu(IV) hydroxides or hydrous oxides can be calculated by accounting only for mononuclear hydrolysis species. The considerably higher solubilities of amorphous Th(IV) precipitates at pH 4(aq) are the predominant aqueous species, the solubilities of AnO2(cr) become equal to those of the amorphous solids. This indicates that the crystalline dioxides are covered by amorphous hydroxide layers.Keywords
This publication has 25 references indexed in Scilit: