Thermal and radiation control of the electrical double layer properties of silica and glass

Abstract

High temperature or γ-radiation pretreatment of pyrex glass and vitreous silica has been found to change the isoelectric point of the oxide, and decrease, substantially, the magnitude of the zeta potential at any pH. The changes observed can be adequately explained in terms of a decrease in the number of surface hydroxyl groups existing on the metal oxide. Model calculations of the zeta potential as a function of the number of surface hydroxyl groups, indicate that the surface density of hydroxyl groups after pretreatment is of the order of less than one hydroxyl group per nm 2 This value is affirmed by independent contact angle measurements made on γ-irradiated quartz plates.