KINEMATIC INTERPRETATION ON COAGULATION MECHANISM OF HYDROPHOBIC COLLOIDS

An approach is proposed for the mechanism of Brownian motion coagulation of dilute colloidal suspensions. The coagulation rate, the time-averaged motion and the distribution density function of particles are derived analytically by applying the equation of motion to individual particles and the equation of continuity to the ensemble of particles. The expression of the coagulation rate given by Fuchs is confirmed by the present theory and the time-averaged approaching velocity of a colliding particle is expressed explicitly in terms of the interparticle potential energy. It is also found that when colliding particles are away from a given particle the Brownian motion force and the potential interaction force are equally balanced but when they are in the vicinity of the particle surface the hydrodynamic drag force is counterbalanced with the potential interaction attractive force, and that the effect of the hydrodynamic interaction between particles on the coagulation rate is significant especially in the intermediate region of electrolyte concentration between stable and unstable colloidal suspensions. © 1978 Academic Press, Inc.