EXTRACTION OF AMERICIUM AND LANTHANIDES BY DIALKYLDITHIOPHOSPHINIC ACID AND F-F ABSORPTION-SPECTRA OF THE EXTRACTION COMPLEXES

A dialkyldithiophosphinic acid, HBTMPDTP (R2PSSH, R: trimethylpentyl g roup), has been found to be an effective extractant for separating tri valent americium from lanthanides in nitrate solution. A simple six-st age extraction process can separate >99.99% Am from fission product la nthanides and >99% lanthanides from Am. The f-f absorption spectra of Am3+ and Nd3+ extracted into HBTMPDTP were measured. Red shift of the spectra of sulfur coordinated complexes is obvious. Intensity of hyper sensitive absorption peaks increases drastically and some splittings o ccur. Absorption spectra of different inner coordination configuration s were calculated and compared with experimental ones. The most probab le inner coordination configuration of Am- and Nd-HBTMPDTP extraction complexes are both 8-sulfur coordinated cubic symmetries. (C) 1998 Els evier Science S.A.