Hydrophilic complexes of the actinides. 2

The liquid-liquid distribution equilibria of the Am(III), Eu(III), U(IV), Th(IV) and UO22+ ions with tributyl phosphate (TBP), di-(2-ethylhexyl) phosporic acid (HDEHP) and 2-thenoyltrifluoroaceton (HTTA) have been studied at 25degC by tracer technique, pH-measurements and optical methods. The ionic strength was maintained constant by adding NaClO4, NaCl or NaNO3 while heptane and toluene were employed as diluents. The distribution equilibrium (extraction) constants are summarized in Tables 1 and 2. The acidity, the ionic strength and the ligand concentration were in each case varied systematically to ascertain the stoichiometry and kinetics of the extraction reactions. The application and usefulness of the three extraction reagents for their use in actinide complex chemistry studies are discussed in some details. (author)