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

Abstract The kinetics of extraction and reextraction of phenylalanine with a reversed micellar system consisting of TOMAC/hexanol/n-heptane was studied under different hydrodynamic conditions using a rotating diffusion cell. A mathematical model was developed taking into account the mass transfer of the different species involved, the interfacial exchange process and the hydrodynamics of the cell. The model describes adequately the experimental concentration–time data for the extraction process under different conditions of rotation speed and TOMAC concentration. The results obtained show that the extraction 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 stability of the reversed micelles at high ionic strengths, which causes an increase in the rigidity of the reversed micellar interface hindering the coalescence/“de-coalescence” mechanism necessary for the interfacial exchange of phenylalanine.