Qing Song

A Theoretical and Experimental Study of Surfactant Transport: from a Micellar Solution to a Clean Air / Water Interface Qing Song

This dissertation studies the transport dynamics of a water soluble nonionic surfactant C14E6 at the air/water interface at concentration below the critical micelle concentration (CMC) and above the CMC. A method which involves using the pendant bubble as a monolayer film balance is used to directly measure the surface tension as a function of surface concentration. The equilibrium parameters could be uniquely determined by fitting the directly measured equation of state and adsorption isotherm. Instead remarkably different equilibrium parameters for the same surfactant system fit experimental data equally well in the traditional treatment. The kinetic constants are obtained by numerically solving the transport equations for surfactant transport from aqueous solution at concentration below the critical micelles concentration. Theoretically, a model was developed to describe the surfactant transport from micellar solution for the case in which the kinetic rate of breakdown of micelles into monomers is much faster than the rates of bulk diffusion of monomers and micelles.