Extraction of americium and lanthanides by dialkyldithiophosphinic acid and f-f absorption spectra of the extraction complexes

A dialkyldithiophosphinic acid, HBTMPDTP (R2PSSH, R: trimethylpentyl group), has been found to be an effective extractant for separating trivalent americium from lanthanides in nitrate solution. A simple six-stage extraction process can separate >99.99% Am from fission product lanthanides 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 hypersensitive absorption peaks increases drastically and some splittings occur. Absorption spectra of different inner coordination configurations were calculated and compared with experimental ones. The most probable inner coordination configuration of Am- and Nd-HBTMPDTP extraction complexes are both 8-sulfur coordinated cubic symmetries. (C) 1998 Elsevier Science S.A.