Dynamic electrophoresis of colloidal particles in concentrated suspensions

Abstract

This chapter discusses the particle volume fraction φ dependence of the dynamic electrophoretic mobility μ of spherical colloidal particles in a concentrated suspension as well as the colloid vibration potential (CVP) and electrokinetic sonic amplitude (ESA) in the suspension on the basis of Kuwabara's cell model. When a suspension of charged colloidal particles is irradiated with a sound wave, a macroscopic electric field is generated in the suspension. This field is called the colloid vibration potential (CVP). Inversely, when an oscillating electric field is applied to the suspension, a macroscopic sound wave, whose amplitude is called the electrokinetic sonic amplitude (ESA), is generated in the suspension. The measurement of these electroacoustic quantities is a novel technique for the electrokinetic analysis of concatenated suspensions of colloidal particles. It is known that CVP and ESA are both proportional to the dynamic electrophoretic mobility of the particles in an oscillating electric field. The obtained dynamic mobility μdepends on the frequency ωof the applied electric field and the particle volume fraction φ as well as on the reduced particle radius κα(where κis the Debye-Huckel parameter and α is the particle radius) and the zeta potential ζ. From an Onsagpr relation for concentrated suspensions it is suggested that the CVP or ESA depends much stronger on φ than predicted from the φ dependence of μ.