An Additional Insight into the Correlation between the Distribution Ratios and the Aqueous Acidity of the TODGA System

Abstract

Extraction of Eu(III) and Am(III) from HNO₃ into the organic solvents using N,N,N′,N′‐tetraoctyl‐diglycolamide (TODGA) was investigated in order to study the detailed extraction reaction. The chemical species: 1:2 for metal:TODGA complex is present in polar diluents. On the other hand, the metal complexes need three or more TODGA molecules to remain stable in non‐polar diluents. The HNO₃ concentration dependence on the distribution ratio suggests that HNO₃ participates in the metal extraction. Infrared spectra indicate that the carbonyl oxygen coordinates with Eu(III), and luminescence lifetimes suggest that there are no water molecules in the inner coordination sphere of the extracted Eu‐complex.

Keywords:

• Eu(III)
• Am(III)
• solvent
• extraction
• TODGA
• separation

Acknowledgments

The authors would like to deeply thank Dr. A. Kirishima of the Japan Atomic Energy Agency for the determination of the successive formation constants, Dr. Y. Kitatuji of the Japan Atomic Energy Agency for the determination of hydration number and Mr. A. Ikeda and Ms. Y. Sugo of the Japan Atomic Energy Agency for the discussions of the results of IR and UV spectroscopy, and Dr. H. Suzuki of the Japan Atomic Energy Agency for the valuable information on solvent extraction.