A radial flow streaming potential apparatus for electrokinetic studies of sheet or plate materials

Abstract

A radial flow streaming potential (r.f.s.p.) apparatus, and the procedure adopted for streaming potential determination, are described. It is shown by consideration of apparatus design and by experiment that the conditions necessary for valid application of the Helmholtz-Smoluchowski equation for zeta-potential calculation are satisfied by the r.f.s.p. technique.

Zeta-potential data for fused silica discs determined by the r.f.s.p, technique are found to be in good agreement with previous studies on other forms of silica. Application of the Gouy-Chapman- Stern-Grahame double-layer theory to enable calculation of surface potential (ψ_o) shows it to be independent of salt concentration and to change by 30 mV per pH unit, both results providing verification of the soundness of the r.f.s.p. technique.