Behavior of Fine Particles Present in Aqueous Solution in an Electric Field

Abstract

The behavior in an electric field of fine particles present in aqueous solution was measured in order to apply the results to the classification of fine particles. The sample particles used were spherical polystyrene particles with average diameters of 0.03, 0.1, 1.0, 4.3 and 9.6 μm. Electrophoretic mobility and zeta potential of the particles were measured based on the principle of the laser Doppler effect.
The electrophoretic mobility was found to increase with increasing pH and temperature of suspensions, and to vary with electrolyte concentration and particle size. The electrophoretic retardation effect and relaxation effect were considered to explain the behavior of fine particles in an electric field by applying the electro-kinetic theory of Wiersema et al.
The forces acting on particles in an electric field are considered to be electrical force, friction force and other forces like relaxation effect and electrophoretic retardation effect which appear in ionic behavior. We found that the particle moving velocity depends on the particle size. When the particle size is less than 1 μm, the velocity increases with increasing the particle size. On the other hand, the velocity deceases with increasing in particle size when the particle size is larger than 1 μm. These phenomena can be explained by the forces acting on the fine particles in the electric field. The behavior can be applied to classification of fine particles.