FLUX DECLINE IN PROTEIN MICROFILTRATION - INFLUENCE OF OPERATIVE PARAMETERS

The flux decline, is studied in typical experiments with dead-end micr ofiltration of BSA solutions (1, 3, 5 and 10 g/L) through Cyclopore tr ack-etched polycarbonate membranes (nominal pore size 0.1 mu m) at sev eral pH values and two ionic strengths. Results have been analyzed in terms of the common blocking laws and correlated with the operation pa rameters. Variations of pressure, concentration, pH, and ionic strengt h have shown great influence on the kinetics of protein deposition. In any case, the process of membrane fouling can be divided in two steps , clearly separated in all the experiments: a rapid initial internal b locking, strongly dependent on operation parameters, and a final stage of external blocking with lower sensitivity of the flux behavior on o peration conditions. Finally, the amount of adsorbed protein and its i nfluence on pore size distribution have been analyzed by desorption wi th a SDS-solution and by an extended bubble point method. These result s show that the initial internal pore blocking can be attributed to pr otein adsorption while the long-time fouling should be caused mainly b y solute-solute interactions. (C) 1997 Academic Press.