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. rresponding 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. d 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.