Kinetics of phenylalanine extraction and reextraction by cationic reversedmicelles using a diffusion cell

The kinetics of extraction and reextraction of phenylalanine with a reverse d micellar system consisting of TOMAC/hexanol/n-heptane was studied under d ifferent hydrodynamic conditions using a rotating diffusion cell. A mathema tical model was developed taking into account the mass transfer of the diff erent species involved, the interfacial exchange process and the hydrodynam ics of the cell. The model describes adequately the experimental concentrat ion-time data for the extraction process under different conditions of rota tion speed and TOMAC concentration. The results obtained show that the extr action process is mediated by an instantaneous interfacial reaction, being controlled by the diffusion of the reversed micelles in the organic phase. Reextraction was found to be a slower process due to the higher dynamic sta bility of the reversed micelles at high ionic strengths, which causes an in crease in the rigidity of the reversed micellar interface hindering the coa lescence/"de-coalescence" mechanism necessary for the interfacial exchange of phenylalanine. (C) 2000 Elsevier Science Ltd. All rights reserved.