Protein fouling of asymmetric and composite microfiltration membranes

Although many microfiltration membranes have asymmetric or composite structures, there is little understanding of the effects of this multilayer structure on fouling. A new model was developed that explicitly accounts for fluid flow through two layers: an upper layer with noninterconnected pores and a substructure with highly interconnected pores. Initial fouling occurs by pore blockage, with a cake layer then forming over those regions covered by foulant. Model calculations are in excellent agreement with experimental data for the filtrate flux and resistance during constant-pressure filtration of bovine serum albumin. The highly interconnected pores within the support structure reduce the rate of flux decline by shunting more fluid through the open pores. The extra resistance provided by the support also reduces the relative importance of the protein deposit. The results provide important insights into the effects of pore morphology on membrane fouling.