The influence of the membrane zeta potential on the critical flux for crossflow microfiltration of particle suspensions

It was investigated how the value of zeta potential of microfiltration membranes influenced the critical flux while filtering a suspension of silica particles. Ceramic membranes of three different materials were used and measurements were performed at two different values of pH for each material corresponding to two different values of zeta potential for each material. It was found that neither the zeta potential of the membrane nor the zeta potential of the particles influenced the observed critical flux. The critical flux increased linearly with the wall shear stress and decreased with increasing particle concentration. Expressions were obtained for the critical flux based on two different particle transport mechanisms: particle rolling (torque-balance model) and shear-induced diffusion. It was found that neither of the expressions could explain experimental critical fluxes adequately. (C) 1999 Elsevier Science B.V. All rights reserved.