Mass transfer characterization in forward and back extractions of lysozyme by AOT-isooctane reverse micelles across a flat liquid-liquid interface

Abstract

The mass transfer rates in lysozyme extraction between an aqueous KCl solution and an bis(2-ethyl)sodium sulfosuccinate (AOT)-isooctane reversed micellar solution were investigated using a stirred cell with a flat liquid-liquid interface. The forward extraction rates from 0.1 kmol m −3 KCl solution of pH 6.5 to a reversed micellar phase are controlled by the diffusion in the aqueous film and the solubilization at the interface. The solubilizing rate constant, k fs, increases from 3.57 × 10 −5 to 1.43 × 10 −4 m s −1 in proportion to AOT concentration of 0.05 to 0.2 kmol m −3. For the back extraction of lysozyme from the reversed micellar phase to an aqueous solution of higher KCl concentration, the rate-determining step is the release process at the interface. The releasing rate constant, k bd, decreases with an increase of AOT concentration and is also two orders smaller than the k fs values. The back extraction rates are therefore very slow compared to the forward extraction rates.