Particle transport in crossflow microfiltration -: II.: Effects of particle-particle interactions

A model previously developed for the calculation of limiting fluxes for crossflow microfiltration of non-interacting particles was extended to include the effect of physico-chemical particle-particle interactions. It was shown theoretically that the effect of particle-particle interactions on the microfiltration flux can be described by a diffusion-type equation with an effective interaction-induced diffusion coefficient. The microfiltration flux for a general situation, where particle transport is caused by convection, Brownian diffusion, shear-induced diffusion, and particle-particle interactions, was then calculated by adding the diffusion coefficients, and solving the governing convective-diffusion equation numerically. Results of these calculations agreed very well with experimental fluxes measured during crossflow microfiltration of model silica particle suspensions. The influence of wall shear stress, membrane length, particle size, and particle concentration on permeate flux was very well predicted. However. the effect of particle surface potential was quantitatively underpredicted. Shear-induced diffusion seems to be the main transport mechanism governing the flux in the microfiltration of suspensions of micron-sized particles, but charge effects can increase fluxes considerably. (C) 1998 Elsevier Science Ltd. All rights reserved.