The effect of surfactants on Marangoni convection in the isobutanol/water system

In this paper the effect of Marangoni convection on mass transfer for the partially miscible isobutanol/water system is analysed. Comparisons are made between the predictions for interfacial stability and mass transfer fluxes, and the experimental results obtained for the transfer of isobutanol into water when the water phase is pure, and when it is "contaminated" with surfactants. The interfaces have been visualised with the aid of a Schlieren optical system and concentration profiles obtained with a Mach-Zehnder interferometer. The presence in the system of the ionic surfactants investigated has been found to increase further the Marangoni convection observed in the clean system and to enhance the initial mass transfer fluxes. However, interfacial convection is suppressed with the addition of the non-ionic surfactant studied and a reduction in the mass transfer fluxes is measured.