Surface Functionalization of Polybenzimidazole Nanofiltration Membranes for Forward Osmosis

Membrane selection and operation are critical issues in design of forward osmosis (FO) processes. For example, hydrophilicity and surface negative charge can be combined with thin film composite membrane configuration to enhance both water flux and salt rejection. Recent studies by Chung et.al. indicate that polybenzimidazole (PBI) nanofiltration membranes are efficient for FO which is a ground-breaking technique as a nano-filtration membrane has been incorporated in FO for the first time. The ideal nanofiltration membranes for forward osmosis would be highly negatively charged at most pH values. Since PBI is neutrally charged at a pH of 7.0, there is a decrease in electrostatic repulsion between the membrane surface and electrolytes to be rejected which would adversely affect the separations process. Modification of the membrane surface with negatively charged hyrophylic groups can be used to enhance the FO separations and extend range of application of this membrane system.

The presentation will focus on a joint project with Dr. Chung of National University of Singapore to functionalize the surface of PBI based nanofiltration membranes with short hydrophilic charged groups. Specifically, the membrane functionalization and characterization of surface chemistry using a variety of techniques will be discussed. Preliminary studies of impact of surface functionalization on the steady state flux for pure water and electrolyte solution will be discussed.