KINETIC-STUDIES OF EXTRACTION FOR A MIXTURE OF SOME EUROPIUM PHOSPHONATE COMPLEXES AND 2-BENZOYL OR 2-ANILINOPYRIDINE IN N-HEXANE

The kinetics and mechanism of solvent extraction of Eu3+ from an aqueo us phase of 0.1 M ionic strength (Na+, HClO4) at pH 3.2 and 25 degrees C by a mixture of ethylhydrogen benzyl phosphonate (HEBzP), ethylhydr ogen benzoyl phosphonate (HEBoP), and 2-benzoylpyridine (BP), or 2-ani linopyridine was studied using a stirred Lewis cell. The extraction wa s investigated over a wide range of extractant concentrations and pH. The kinetic data were treated according to the mass transfer with chem ical reaction (MTWCR) model, in which the extraction rate was shown to be controlled by a mechanism involving. diffusion of the extractant i nto the aqueous phase boundary layer followed by addition of the first ligand to the europium ion. The rate constants K-HL = 2.49 +/- 0.02 X 10(3) M-2 min(-1), K-L = 10.35 +/- 0.05 x 10(2) M-2 min(-1), and K-LS = 1.105 +/- 0.12 x 10(3) M-2 min(-1) (HL, HEBzP; S, AP). (C) 1998 Aca demic Press.