Electrostatic contributions to permeate flux behavior in single bovine serum albumin ultrafiltration

A modified free-solvent based (FSB) osmotic pressure model was used to characterize the pressure-dependent permeate flux behavior of completely rejected bovine serum albumin (BSA) UF. Tangential-flow diafiltration experiments (30 kDa MWCO CRC membrane) were performed using BSA (69 kDa) at a pH range of between pH 4.7 and pH 10, and various ionic strength conditions (0.0037–0.15 M). Flux behaviors under various solution conditions were observed and analyzed. The FSB model for permeate flux characterization for UF processes using moderate ionic strength aqueous solutions was modified to include electrostatic contributions by adapting a modified film theory model. Comparison of the experimental results with the resulting modified FSB model calculations showed that the model provides good prediction and characterization of the pressure-dependent permeate flux behaviors of BSA UF when electrostatic effects are considered.