Selective extraction of trivalent actinides from lanthanides with dithiophosphinic acids

The solvent extraction of trivalent actinides and lanthanides from aqueous 1 M NaNO3 by means of the sulfur containing acidic extractant CYANEX 301 was studied. This commercial extractant shows very interesting features for An(III)/Ln(III) separations depending on the purification of its main constituent bis(2,2,4-trimethylpentyl)dithiophosphinic acid. Efficient separations were observed with unpurified CYANEX 301 for high Ln(III) concentrations, but not for low Ln(III) concentrations. Successful purification of CYANEX 301 was performed by precipitation of the ammonium dithiophosphinate. Very high An(III)/Ln(III) separation factors (higher than 103) were obtained for micro or macro concentrations of Ln(III) at pH 3-4. (author)