THE NOVEL EXTRACTANTS, DIGLYCOLAMIDES, FOR THE EXTRACTION OF LANTHANIDES AND ACTINIDES IN HNO₃–n-DODECANE SYSTEM

Abstract

The novel extractants, six diglycolamides synthesized in our laboratory, were investigated for actinide extraction from nitric acid into n-dodecane. The dependence of the distribution coefficients of Eu(III) and Am(III) on the length of alkyl chain in the extractants was examined. Among the diglycolamides studied, N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TOOPDA) and N,N,N′,N′-tetradecyl-3-oxapentanediamide (TDOPDA) showed a sufficient solubility in n-dodecane, due to their appropriate lipophilicity modified by increasing the length of the alkyl chain attached to amidic N atoms. The distribution coefficients, D _M, of actinides obtained by TOOPDA increased with an increase in HNO₃ concentration. The number of diglycolamide molecules coordinated to the actinide ions was estimated to be three for Th(IV), U(VI), Pu(IV), and four for Am(III) and Cm(III) by slope analysis. The order of D _M for the actinides at high nitric acid concentrations is An(III), An(IV) > An(VI) > An(V) and that for lanthanides, heavier > lighter. It is concluded that TOOPDA diluted in n-dodecane can extract both actinides and lanthanides completely from aqueous HNO₃ solution.

ACKNOWLEDGMENTS

The authors gratefully acknowledge to Drs. H. Naganawa, T. Yaita, and H. Narita of Japan Atomic Energy Research Institute for helpful discussions, and Mr. H. Takeishi of Japan Atomic Energy Research Institute for the preparation of Np and Pu solutions.