SYNERGISTIC SELECTIVE EXTRACTION OF ACTINIDES(III) OVER LANTHANIDES FROM NITRIC ACID USING NEW AROMATIC DIORGANYLDITHIOPHOSPHINIC ACIDS AND NEUTRAL ORGANOPHOSPHORUS COMPOUNDS

ABSTRACT

New aromatic dithiophosphinic acids (R₂PSSH) with R = C₆H_5?, ClC₆H_4?, FC₆H_4? and CH₃C₆H_4? were synthesized, characterized and tested as potential separating agents for trivalent actinides over lanthanides. The extraction of Am(III), Eu(III) and other lanthanides was carried out from nitric acid medium with mixtures of R₂PSSHS and neutral organophosphorus compounds. There was no detectable extraction when R₂PSSHS were used alone as extractants for either Am(III) or Eu(III) (D_AM,EU.< 10^?3) under the experimental conditions used in this study. High separation factors (D_AM/D_EU > 20) with D_AM > 1 were achieved in the nitric acid range 0.1-1 mol/L by means of a synergistic mixture of bis(chloro-phenyl)dithiophosphinic acid + tributylphosphate (TBP), irioctylphosphine oxide (TOPO) or tributylphosphine oxide (TBPO). The high radiation resistance (up to 10⁶ Gy absorbed γ-doses) of the extractants was also demonstrated.