MEASUREMENT OF STREAMING CURRENT AND CALCULATION OF ZETA-POTENTIAL FOR BEDS OF WIDE-DISPERSION MICROPARTICULATE SOLIDS INTERACTING WITH WATER

If water or an aqueous solution is replaced by an organic liquid of lo w polarity and permittivity, e.g. an n-heptane-acetone 9:1 (v/v) mixtu re, a reproducible and time-independent streaming current is generated in the bed of a water-soluble solid, e.g. calcite. In the case where the residual water content in the organic liquid is sufficiently low, a reproducible and time-independent streaming current is obtained from the bed of a water-reactive solid, e.g. cement, also. Chromatographic experimental techniques and commercial instrumentation allow us both to handle dry organic liquids and to overcome experimental difficultie s caused by the polydispersion of a microparticulate solid even if dus t particles are contained in the sample. The combination of chromatogr aphic and electrokinetic measurements in one experiment enables the si multaneous observation both of streaming current changes, induced by c oncentration pulses of probes injected into the liquid stream entering the column, and of the sorption interactions of probes with the solid column packing. This represents a new approach to the investigation b oth of solid surfaces and of the processes taking place in the solid-l iquid interface. An equation for the calculation of the zeta potential from the streaming current generated in a bed of unknown geometry and characteristized by a strong overlap of electric double layers on the bed particles is proposed and briefly tested.