Ml. Dietz et R. Sperline, THE EFFECT OF HIGH-SPEED STIRRING ON THE DISTRIBUTION EQUILIBRIA OF NEUTRAL METAL-CHELATES, Langmuir, 11(10), 1995, pp. 3766-3771
When a two-phase system comprising an organic solution of any of vario
us interfacially active neutral metal chelates in contact with an appr
opriate buffered aqueous phase is vigorously agitated, a reversible de
crease in the organic phase concentration of the chelate is observed.
This decrease gives rise to a shift in the pH(1/2) value of the metal
ion (i.e., the pH corresponding to 50% extraction) from that observed
in the corresponding unstirred system. The magnitude of this shift is
shown to vary with the distribution constant of the chelate, the inter
facial area generated upon stirring, and the organic solvent. In syste
ms in which a pair of extractable metal chelates differing in interfac
ial activity is present, the shifts in pH(1/2) are shown to alter the
apparent selectivity of the chelating extractant and to enhance the se
paration of the metal ions.