Electrostatic Interactions During Surfactant Adsorption

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Some attempts to understand surfactant adsorption on the molecular level have recently been reported although the effect of electrostatic interactions between the adsorbing surface and the surfactant are still poorly understood. As a result, most current descriptions of surfactant adsorption remain empirical and thus are not predictive. This investigation uses a modification of the most recent theoretical models to predict the adsorption of singly charged surfactants as well as experimental adsorption measurements to test the results of the modeling. This project is unique in the use of the observation that surfactant adsorption can increase with increasing surface charge density of the same sign. This result may be due to changes in the configuration of the adsorbed materials brought on by electrostatic repulsions between their ionic end groups and the adsorbing surface. The changes in adsorption behavior that have been observed are quite large indicating significant changes at the molecular level. By experimenting in a region where surfactant adsorption is very sensitive to surface charge density, the greatest amount of information about electrostatic interactions is obtained in this work. Surface active materials are used in many processes today and are likely to find even wider application in the future. The impact of a better understanding of the adsorption process for surface active agents is manyfold. Current trends in chemical processing are towards micro-engineering, control of processes at the molecular level. Surfactants are one of the major means of obtaining this control. The results of this investigation could find immediate application in such fields as flotation, dispersion, separations and ceramic processing-- with future applications in microelectronics.