Membrane pore blocking during cake formation in constant pressure and constant flux dead-end microfiltration of very dilute colloids

Dead-end microfiltration experiments of very dilute colloids of polystylene latex (PSL) were conducted under constant flux and constant pressure conditions using the track-etched polycarbonate membranes. The pressure rising behaviors in constant flux filtration were examined under different filtration rate and solid mass fraction conditions, and the flux decline behaviors in constant pressure filtration were examined under different pressure and solid mass fraction conditions. The combined filtration model in which the pore blocking of membrane and the cake formation on the membrane surface took place simultaneously has been developed in order to evaluate the filtration behaviors. In the model, it was assumed that all the particles rejected by the membrane contributed the cake resistance and that a part of them also served as the pore blocking resistance by reaching and completely sealing the open pores in the membrane. The intermediate blocking law was employed in the model in order to describe the pore clogging behavior of the membrane, and the model also assumed that a part of membrane pores remained open eventually. The calculations based on the model revealed the existence of the negative slope in the characteristic filtration curve based on the classical blocking filtration law, as observed in the initial period of filtration experiments. The model developed well described the pressure rising behaviors in constant flux filtration and the flux decline behaviors in constant pressure filtration.