Effect of the surface conductance on electrokinetic potential measured in nonaqueous media

Abstract

The effect of the surface conductance on the ζ-potential of dispersed particles determined from their electrophoretic mobility in nonaqueous electrolyte solutions was considered. The conductivity of dilute quartz suspensions and the electrophoretic mobility of quartz particles in NaBr solutions in butanol-1 and dimethyl sulfoxide as well as in LiBr solutions in acetone at the salt concentration C= 10–5–10–2M were determined by conductometry and microelectrophoresis. The dependences of surface conductivity and ζ-potential on the electrolyte content were calculated by formulas of the Wagner and Henry theories. It was shown that, in the region of dilute solutions, ζ(log C) curves thus obtained significantly differ from corresponding functions calculated by the Smoluchowski equation. At the same time, these dependences agreed closely with the ζ(log C) dependences determined for the same systems by the streaming potential method with allowances for experimental values of the surface conductivity. Using aluminum oxide suspensions in NaBr and HBr ethanol solutions as examples, it was shown that, to obtain correct values of the ζ-potential from electrophoretic mobility of porous particles impregnated with a solution, it is necessary to allow for the bulk conductance of the particles.