The solubility of PuO2(am) was determined in the aqueous Na+-H+-OH--Cl--H2O-ethylenediaminetetraacetate system as a function of pH (1 to 13.5), ethylenediaminetetraacetate (EDTA) concentrations (0.00001 to 0.093 M), and time to obtain reliable values of Pu-EDTA complexes important in the pH range that corresponds to environmental conditions. The aqueous Pu oxidation states were determined using a combination of techniques involving laser photoacoustic and x-ray absorption near edge spectroscopy and solvent extraction. The equilibrium/steady-state Pu(IV) concentrations were reached within a few days. The aqueous Pu(IV) concentrations in equilibrium with PuO2(am) at fixed concentrations of EDTA (0.0001 or 0.001 M) as a function of pH, at fixed pH (~9), and as a function of EDTA were interpreted using a the Pitzer ion-interaction model. The model was developed based on a segment of the experimental data and was validated against extensive data not used in developing the model. The log K0 values for the formation of PuOHEDTA-, Pu(OH)2EDTA-2, and Pu(OH)3EDTA-3 according to the generalized reaction Pu4+ + xOH- +EDTA4+ = Pu(OH)xEDTA-x were determined to be 36.39, 44.74, and 49.64, respectively.
Revised: January 17, 2011 |
Published: April 24, 2001
Citation
Rai D., H. Bolton, D.A. Moore, N.J. Hess, and G.R. Choppin. 2001.Thermodynamic Model for the Solubility of PuO2(am) in the Aqueous Na+-H+-OH--Cl--H2O- ehtylenediaminetetraacetate System.Radiochimica Acta 89.PNNL-SA-32162.