A critical review on the stability constants of the fluoride complexes of actinides in aqueous solution and their correlation with fundamental properties of the ions

Abstract

Literature data on the stability constants of the fluoride complexes of the actinides in different oxidation states have been compiled. In order to have a reasonable inter-comparison, the stability constant ([31) values obtained in diverse ionic strength media are converted to so called thermodynamic stability constants, [3 ~ using the DAVIES equation (a modification of Debye-Huckel equation). A correlation of the [3 ~ values with the fundamental properties of the actinide ions using various models available in the literature has been attempted. Using the values of ionic radii and best available values of the stability constants of a large number of metal ions from recent compilations a comparative study of the various models or relations available in the literature has been tried. For metal ions in general, the semi-empirical relation recently developed by BROWN, SYLVA and ELLIS (BSE equation) gives the best correlation. In an attempt to accommodate the unusual trend in the stability constants of the tetravalent actinides a modification in a parameter of the BSE equation has been proposed. Good agreement between the theoretically calculated and experimentally determined values for actinides in different oxidation states is obtained in most of the cases, Further improvements in theoretical relation as well as experimental data are required for better correlation.

Method to Eliminate Fluoride Interference in the Spectrophotometric Estimation of Zirconium: Application to U–Zr Alloys

“…A critical review of the literature data on the stability constants of the fluoride complexes of various metal ions in different oxidation states has been presented by Chaudhari et al 51 Zr forms the most stable complex (log β1-8.27) with fluoride among all other elements and hence, responsible for severe interference. To suppress the effect of fluoride, the suppressing agent should be chosen in such a way that it could form quite stable complex with fluoride.…”

Evaluations of Mechanisms for Pu Uptake and Retention within Spherical Resorcinol-Formaldehyde Resin Columns

“…However, complexation of Pu by citrate at low pH is expected to be suppressed due to the weakly acidic nature of the citric acid leading to its being protonated. Table 8 of Chaudhuri et al (1999);7: Sawant et al (1990);8: Xia et al (2010) This brief overview provides information on potential Pu-complexing eluting agents to amend the 0.5 M HNO 3 solution currently used to strip and regenerate the sRF resin. The candidate eluting agents are shown in Figure 17.…”

“…Hydrofluoric acid (HF) strongly complexes with Pu in various oxidation states and is often used in combination with HNO 3 to facilitate Pu oxide dissolution (Barney 1977;Tallent 1976). The complexation behaviors of Pu(IV) and Pu(III) with fluoride have been extensively investigated and several studies report association constants obtained under different conditions and different experimental methods (Chaudhuri et al 1999). Only formation of the 1:1 PuF 3+ complex has been examined in the majority of the studies and reported values demonstrate good agreement across the tested methods.…”

Actinides in Solution: Complexation and Kinetics

“…Anionic complexes of AnO þ 2 and AnO 2þ 2 have also been studied (Ahrland and Kullberg, 1971b;Inoue and Tochiyama, 1985), and pentagonal bipyramidal UO 2 F 3À 5 forms at high fluoride concentrations (Vallet et al, 2002). Stability constants and thermodynamic parameters for the formation of the fluoro complexes of actinides in various oxidation states are summarized in (Chaudhuri et al, 1999). Stability constants for the fluoro complexes of the pentavalent actinides have been reported only for protactinium (Guillaumont, 1966;Kolarich et al, 1967) and neptunium (as assessed by Lemire et al, 2001).…”