Influence of adsorbed particles on streaming potential of mica

Zeta potential of natural mica covered by polystyrene and melamine latex particles, was determined by the streaming potential method. Measurements were carried out using the parallel-plate channel formed by two mica sheets separated by a teflon spacer. The dependence of streaming potential on surface coverage (reaching 0.45) was determined at pH 5.3, when the particles were positively charged and at pH 7.8, when the melamine particles became neutral. The coverage was determined directly by optical microscope counting procedure. It was found that the negative streaming potential for bare mica Es was significantly increased by the presence of adsorbed particles. The experimental data were interpreted in terms of a theoretical model postulating that the streaming potential change was due to flow damping over the interface and by charge transport from the double-layer surrounding adsorbed particles. In contrast to earlier approaches, no assumption of the slip (shear) plane shift upon particle adsorption was made. The experimental data allowed one to determine empirically the universal correction function, which can be exploited for quantitative measurements of bioparticle adsorption kinetics via the streaming potential method.