A SIMPLE-MODEL FOR ESTIMATING SURFACE POROSITY OF CAKE IN CAKE FILTRATION OF SUBMICRON PARTICLES

A force balance model for estimating the surface porosity of cake in c ake filtrations of submicron particles is proposed. The major factors affecting particle packing, such as filtration rate, particle size, ze ta potential of particles, and electrolyte concentration, are discusse d. A most compact cake is constructed when the drag force is equal to the net interparticle force. For a given size of particles with a give n surface potential, the value of surface porosity decreases in a smal l filtration rate region but increases with filtration rate in a large filtration rate region. For particles with a low zeta potential, the surface porosity increases with the increase of particle size and the decrease of electrolyte concentration. However, this tendency will be reversed if the particles have a zeta potential higher than the critic al value. The results estimated by this study are very close to those obtained by the Brownian dynamic simulation, but minimal calculation t imes was required.