Colloidal particles at solid-liquid interfaces: Mechanisms of desorption kinetics

We study the sorption of colloids on equally charged surfaces. Our focus is on the time scale from hours to weeks, where adsorption is not an irreversible process but interplays with (spontaneous) desorption. Using model calculations, we show how the desorption kinetics is influenced by readsorption, a potential barrier, a secondary potential minimum, local variation of the potential, and bond aging. In the experimental part we present results of in situ observation of the sorption kinetics of polystyrene latex particles onto a glass surface. Combining the evanescent field method with video microscopy, we were able to identify the particle arrival and departure times individually and therefrom determine the adhesion time distribution function. The nonexponentiality of this function can be explained by a gamma distribution of the potential depth at the binding sites as well as by logarithmic bond aging. (C) 1998 Academic Press.