Thermodynamic Model for ThO2(am) Solubility in Isosaccharinate Solutions
Extensive studies on ThO2(am) solubility were carried out as functions of a wide range of isosaccharinate concentrations (0.0002 to 0.2 mol·kg-1) at fixed pH values of about 6 and 12, and varying pH (ranging from 4.5 to 12) at fixed aqueous isosaccharinate concentrations of 0.008 mol·kg-1 or 0.08 mol·kg-1, to determine the aqueous complexes of isosaccharinate with Th(IV). The samples were equilibrated over periods ranging up to 69 days, and the data showed that, in most cases, steady-state concentrations were reached in <15 days. The data were interpreted using the SIT model, and required the inclusion of mixed hydroxy-ISA complexes of Th(IV) [Th(OH)ISA2+, Th(OH)3(ISA)- 2 , and Th(OH)4(ISA)2-2] with log10K0 = 12.5± 0.5, 4.4±0.5 and -3.2±0.5 for the reactions: ThO2(am)+ 3H+ +ISA- *Th(OH)ISA2+ + H2O ThO2(am)+ H+ +2ISA- +H2O*Th(OH)3(ISA)-2 and ThO2(am)+ 2ISA- +2H2O*Th(OH)4(ISA)2-2 respectively. Predictions based on these Th-ISA complexes agreed closely with the extensive experimental data developed in this study as well as the very limited (only at pH = 8.3) data from liquid-liquid extractions recently reported in the literature.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 973726
- Report Number(s):
- PNNL-SA-71133; KP1301020
- Journal Information:
- Journal of Solution Chemistry, Journal Name: Journal of Solution Chemistry Journal Issue: 12 Vol. 38; ISSN 0095-9782
- Country of Publication:
- United States
- Language:
- English
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