Extraction of trivalent actinides and lanthanides by tertiary and quaternary amines from concentrated chloride solutions

Abstract

Extraction of some trivalent actinides and lanthanides from 11.9 M LiCl (pH 2.0) by some primary, secondary, tertiary and quaternary amines in xylene has been studied. Negligible extraction of the metal ions was found with primary and secondary amines whereas they are appreciably extracted with tertiary and quaternary amines, the trivalent actinides always being extracted to a greater extent. The separation factors Kd An(III)/Kd Ln(III) for several trivalent actinides with respect to Eu(III) and Tm(III) are found to be much greater when tertiary amines are used as extractants compared to when quaternary amines are used which has been ascribed to the extraction of higher chloro complexes of the metal ions by tertiary amines. Absorption spectra of Am(III) and Nd(III) extracted into the long chain amines from 11.0 M LiCl (pH 2.0) indicate that octahedral hexachloro complexes are present in the tertiary amine extracts whereas lower complexes are predominantly extracted by the quaternary amines leading to the observed lower separation factors for the trivalent actinides with reference to the lanthanides. Possible role of hydrogen bonding in the stabilization of chloro complexes extracted by tertiary amines as well as the extraction of hydrated chloro complexes by the quaternary amines are discussed.