Flux decay in protein microfiltration through charged membranes as a function of pH

The influence of pH and electrostatic interactions on the fouling mechanism during protein dead-end microfiltration (MF) has been investigated for two charged membranes. Polyethersulfone negatively charged membranes (ICE-450) and positively charged ones (SB-6407) have been used, both manufactured by Pall Co.The corresponding electrical properties of both the membranes have been investigated as a function of pH by streaming potential measurements; confirming the respective sign of their surface charges and the absence of any isoelectric point.BSA and Lysozyme solutions at different pH values (3.0, 5.0, 7.0, 8.5 and 10.0) were microfiltered through the membranes at a constant applied pressure. Results have been analysed in terms of usual blocking filtration laws and substantial changes in the fouling behaviour have been observed as a function of the solution pH. In these conditions, fouling behaviour is determined by protein charge rather than membrane charge.