PREVENTION OF PARTICLE DEPOSITION IN CROSS-FLOW MICROFILTRATION

The likelihood of particles depositing on the filtering membrane in cr ossflow microfiltration of dilute suspensions is investigated by calcu lating steady-state particle concentration profiles. The profiles are the result of the interaction of Brownian diffusion and hydrodynamic d rag, electrostatic and van der Waals forces. It is shown that the ulti mate equilibrium state is for particles to migrate to the filtering me mbrane. However, the electrostatic force can be so strong that particl es cannot reach the membrane in an observable period and a metastable equilibrium then results. Factors that inhibit deposition are low ioni c strength of the suspending liquid, high particle and membrane potent ials, low Hamaker constant, low trans-membrane permeation rate and liq uid viscosity, and large particle size.