Significance of duration and amplitude in transmembrane pressure pulsed ultrafiltration of binary protein mixtures

This study examines the effects of varying the pulse amplitude and duration on permeate flux and solute throughput for a binary protein solution in crossflow transmembrane pressure pulsed ultrafiltration with semi-permeable hydrophobic membranes. Solutions of 1% BSA and 0.3% IgG in 0.15 M NaCl, with pH 7.4 were used in a crossflow ultrafiltration cell with a crossflow shear rate of 700 s(-1), pulsing frequency of 0.5 Hz, and an average operating pressure of 66 kPa was used. Polysulfone membranes with 100 000 MWCO were used throughout the study. Average pulse amplitude was varied between 60 and 27 kPa and the average pulse duration ranged between 0.13 and 0.34 s of backpressure per second of operation. The results showed that variations in pulse duration did not significantly effect permeate flux. However, mass flux of BSA was enhanced due to pulsing by as much as a factor of three. Only the case which combined reduced pulsing pressure and short duration resulted in negligible deviation in BSA concentration from the nonpulsed case results. One proposed mechanism for this is that transmembrane pressure pulsing may improve solute flux by removing lodged solute in the pores. The backward flow potentially carries the previously lodged solute out away from the pore, clearing the pore for solute transport in the next ultrafiltration cycle.