EFFECTS OF SOLUTION PROPERTIES ON POLARIZATION REDEVELOPMENT AND FLUX IN PRESSURE PULSED ULTRAFILTRATION

The effect of transmembrane pressure pulsing on concentration polarization resistance was recently presented [Rodgers and Sparks, J. Membrane Sci., 68 (1992) 149]. It was determined that pulsing could moderately reduce the polarization resistance when the system was operated at laminar crossflow shear rates. It is postulated that the primary gain in permeate flux was attributed to an introduction of the redevelopment phase in the average polarization resistance that was caused by slight but significant membrane motion during the pulsing. If this postulate is correct, then solution property variations that may effect the potential range of polarization resistance as it redevelops or the redevelopment time, should alter the potential for pulsing to enhance permeate flux. Thus, this study addressed the effects of solution properties on the polarization resistance range, redevelopment time and the average flux that come about due to transmembrane pressure pulsed ultrafiltration. Variations in BSA initial concentration, solution pH and ionic strength were studied. It was determined that changes in feed concentration caused the most significant difference in flux enhancement due to pulsing. This is primarily attributed to a limited available flux range during the redevelopment phase of the polarization layer. The variation in redevelopment time as a result of solution property changes was insignificant. The average flux and impact of pulsing were increased as pH increased for 1% solutions but was less significant for higher concentrations. Ionic strength variations had negligible effect on enhanced permeate flux due to pulsing.