Thermodynamic modeling of trivalent Am, Cm and Eu-citrate complexation in concentrated NaClO4media

Abstract

AbstractThe dissociation constants of citric acid (Cit), and the stability constants of Am3+, Cm3+and Eu3+with Cit were determined as a function of ionic strength (NaClO4) using potentiometric titration and an extraction technique, respectively. The results have shown the presence of both 1:1 and 1:2 complexes under the experimental conditions. A thermodynamic model was constructed to predict the apparent stability constants at different ionic strengths by applying the Pitzer ionic interaction parametersβ(0),β(1), and Cφwhich were obtained to fit the experimental data. Thermodynamic stability constants of M(Cit) and M(Cit)23-(where M = Am3+, Cm3+or Eu3+) were calculated to belog β0101 = 9.91 ± 0.10,log β0102 = 14.47 ± 0.14for Am3+,log β0101 = 9.53 ± 0.16,log β0102 = 14.46 ± 0.16for Cm3+andlog β0101 = 9.82 ± 0.14,log β0102 = 13.31 ± 0.12for Eu3+as obtained by extrapolation to zero ionic strength.