Streaming potential of mica covered by latex particles

Adsorption of colloid latex particles on mica was correlated with streaming potential changes. Measurements were carried out using the parallel-plate channel formed by two mica sheets separated by a Teflon spacer. The coverage of particles was determined directly by an optical microscope counting. Two limiting series of experiments were performed: (i) neutral particles on negatively charged mica and (ii) positively charged particles on neutral mica. In the former case the charge of particles was neutralized by pH adjustment, whereas in the latter case the charge of mica was neutralized by adsorption of cationic surfactant (DTACl). 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. Opposite to previous 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 functions for both limiting cases. The validity of the proposed model was further checked by performing streaming potential measurements as a function of particle coverage for arbitrary charged mica and particles surfaces. The results obtained can be exploited for quantitative evaluation of deposition kinetics of colloid and bioparticles (proteins).