PROTEIN FOULING OF TRACK-ETCHED POLYCARBONATE MICROFILTRATION MEMBRANES

Bovine serum albumin (BSA) solutions of 0.1 g/liter and 1.0 g/liter we re filtered through 0.05 mum and 0.2 mum polycarbonate microfiltration membranes using a stir cell. Total resistance versus time and permeat e concentration versus time curves and scanning electron micrographs w ere generated. From these, together with comparing the results to inte rnal and external fouling models, several different fouling mechanisms are hypothesized. For 0.1 g/liter concentration and 0.2 mum pore diam eter, the fouling occurs at the mouths of the pores, slowly closing of f pore entrance areas while allowing complete transmission of the prot ein for a period of time. Eventually, the pores become so constricted that protein transmission decreases and a layer of rejected protein fo rms on the external membrane surface. For 0.1 g/liter concentration an d 0.05 mum pore diameter, fouling immediately closes off pores, and pe rmeate concentration decreases quickly. For 1.0 g/liter concentration and 0.2 mum pore diameter, the fouling allows for nearly complete tran smission of proteins for the entire length of the experiment, unlike t he more dilute case of 0.1 g/liter. Since the diameters of BSA molecul es are more than an order of magnitude smaller than the pore radii, it is believed that the proteins form aggregates which accumulate on or just below the top surface of the membrane, depending on their size re lative to the pore openings. (C) 1994 Academic Press, Inc.