Adsorption of mixed surfactant systems

The mechanism responsible for the existence of an adsorption maximum observed in static experiments gives rise to unusual effects attending the chromatographic movement of surfactant solutions through a porous medium. These effects are identified by studying the transport of a model system consisting of a binary surfactant mixture as it moves through a porous medium. It is shown that surfactant fractionation is likely to be more significant at low concentrations and that fractionation will be more important in the field than in laboratory models. Two other interesting features are observed: (1) the effluent concentration may in some cases exceed that of the inflow; and (2) the effect of rate-controlled transport is to introduce additional surfactant dispersion. (17 refs.) l surfactant dispersion. (17 refs.)