Adduct formation constant in the synergic extraction of several rare earth elements with acetylacetone and 1,10-phenanthroline in nonpolar organic solvents

The synergic extraction of La(III), Nd(III), Sm(III), Tb(III) and Lu(III) with 0.1M acetylacetone (Hacac) and 1,10-phenanthroline (phen) in benzene was studied. The adduct formation constant, βsub(s), for RE(acac)sub(3) (phen) in benzene was determined. The βsub(s) decreases with increasing atomic number of RE(III). The βsub(s) in different organic solvents can be predicted in connection with the activity coefficients of the solutes, and the validity of this prediction is confirmed by good agreement with the experimental values of βsub(s) in carbon tetrachloride and heptane. (author)