Visualization of filtration phenomena of a suspended solution including O/W emulsion or solid particle and membrane separation properties of the solution

The filtration phenomena of O/W emulsion, baker's yeast suspension and PMMA particle suspension were studied using microfiltration membranes. The effect of the relationship between membrane pore size, operating pressure and particle types on filtration performance-was investigated. The permeation flow of various suspensions was directly visualized using a microchannel cell and a microscope video system. The emulsion particles broke through the microchannel with increasing operating pressure because of their compressibility, even though they could not permeate at low pressures. Baker's yeast and PMMA particles deposited at the entrance of the microchannel and plugged the channel. These particles were no longer permeable through the microchannel in spite of an increase in the pressure. These behaviors of various particles dependent on the pressure were also recognized with filtration experiments using ceramic microfiltration membranes. In the filtration of emulsion, the optimum membrane pore size was about 0.2 mu m for obtaining a complete rejection of emulsion and a high permeate flux. The specific resistance of the cake layer of various particles was also calculated with the cake filtration model. The specific resistance of the emulsion was 500-3000 times greater than that of other particles and similar to the high specific resistance of a protein (ovalbumin) gel layer. The emulsion resistance increased correspondingly to the increase in the operating pressure. It was also necessary for the emulsion to be filtered at low pressures for complete rejection and higher flux. (C) 1999 Elsevier Science Ltd. All rights reserved.