| Abstract
| - Particle residence time distributions in a membrane channelare interpreted to elucidate mechanisms of particletransport and colloidal fouling in membrane filtration.Acomparison of particle size distributions in the membranefeed suspensions and deposited cakes provides evidencefor selective particle transport and accumulation on membranes. These data support a previously hypothesizedminimum in particle back-transport from the membrane asa function of particle size. The back-transport ofsmallerparticles is apparently due to Brownian diffusion, whilelargermacrocolloids are controlled by an orthokinetic mechanismsuch as shear-induced diffusion. In all cases, cakespecific resistances measured in the dead-end mode werehigher than those of the corresponding feed suspensions.Also, cake specific resistances measured under acrossflow were higher than those in the dead-end mode.Further, the specific resistance of particle depositsonmembranes increased with shear rate and decreased asthe initial permeation rate increased, suggesting thatcake morphology is an important parameter in determiningpermeate flux. Thus, the effects of hydrodymamics oncake resistance needs to be established before a comprehensive model for crossflow filtration can bederived.
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