EFFECT OF ANIONS ON THERMODYNAMICS OF EXTRACTION OF Am(III) AND Eu(III) WITH OCTYL(PHENYL)-N,N-DIISOBUTYL-CARBAMOYLMETHYLPHOSPHINE OXIDE

Abstract

The extraction of Am(III) and Eu(III) by octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in xylene from aqueous media containing 1.0 M NH₄NO₃, NH₄SCN, NH₄ClO₄ or a mixture of 0.3 M NH₄NO₃ + 0.7 M NH₄ClO₄ at pH 2.70 and at the temperatures of 15, 25, 35 and 45±0.1 °C has been studied. At all the temperatures, the species extracted were ML₃ · 3CMPO (M = Am(III) or Eu(III), L = NO₃ ⁻, SCN⁻ or ClO₄ ⁻) and M(NO₃)(ClO₄)₂ · 3CMPO. The thermodynamic parameters of the extraction reactions have been evaluated using the temperature coefficient method. The −ΔG values follow the order SCN⁻ > NO₃ ⁻ + ClO₄ ⁻ > NO₃ ⁻ ≈ ClO₄ ⁻, whereas the −ΔH values an order NO₃ ⁻ + ClO₄ ⁻ > SCN⁻ > NO₃ ⁻ ≈ ClO₄ ⁻. The effect of these anions on the thermodynamic parameters have been discussed employing compensation effects and also on the basis of the energy associated with the transfer of these anions from aqueous to the extractant phase.

ACKNOWLEDGMENT

The authors thank Dr. S.B. Manohar, Head, Radiochemistry Division, Bhabha Atomic Research Centre (BARC) for his continued encouragement and keen interest in the work and to Dr. K.L. Nash, Chemistry Division, Argonne National Laboratory, Argonne, USA for his valuable suggestions and discussion during the preparation of the manuscript. One of the authors (G.S.) wishes to thank Dr. G.C. Shah, Head, Reactor Chemistry Section, Research Reactors Services Division, BARC for his encouragement.