The ζ-potential of glass surface in contact with aqueous solutions

In this paper, the streaming potential technique is utilized to measure the zeta-potential of glass surface in contact with a variety of aqueous solutions. A flow cell made of a parallel-plate microchannel is devised to conduct the streaming potential measurements. Particular efforts are made to characterize the well-recognized effect of surface conductance and to determine its role in the electrokinetic phenomenon. Instead of determining the zeta-potential directly from the classical streaming potential equation, an alternative strategy is employed to determine the zeta-potential and the surface conductivity lambda(s) at the glass-water interfaces simultaneously from the streaming potential equation in which the surface conductance is accounted for. A series of measured streaming potential data for the parallel-plate microchannels of different gaps is acquired and used to fit the streaming potential equation. This method is then applied to study the effects of surface conductance, pH values, ionic features, concentrations of two electrolytes, and two ionic surfactants on the measured zeta-potential at the solid-liquid interfaces. (C) 2000 Academic Press.