Synergistic extraction of Nd(III), Tb(III) and Lu(III) ions with a mixture of picrolonic acid and benzo-15-crown-5 in chloroform

The synergistic mixture comprising picrolonic acid (HPA) and benzo-15-crown-5 (B15C5) in chloroform has been used for the extraction of Nd3+, Tb3+ and Lu3+ as representatives of lanthanide(III) ions from pH 1-2 solutions having ionic strength of 0.1 mol l(-1) (K+/H+, Cl-). The composition of the extracted species has been determined as M(PA)(3) (.) nB15C5 where M is Nd, Tb and Lu and n = 1 or 2. The acid dissociation constant (pK(a)) has been evaluated to be 2.52 +/- 0.01. The influence of various anions and cations on the extraction of these lanthanide(III) ions has also been studied and only oxalate and thiosulphate among the anions and Cu2+, Fe3+, Zn2+ and Ni2+ among the cations have some deleterious effect. The extraction equilibrium constants have been evaluated and discussed.