Nanoporous polyethersulfone (PES) membrane with enhanced flux applied in forward osmosis process

► The commercial PA and CTA membranes were evaluated in FO mode. ► The properties of the FO membrane that enhance its performance were discovered. ► A nanoporous PES membrane was developed. ► The structure of the PES membrane attributed to the high flux. A forward osmosis (FO) membrane process uses the natural phenomenon of osmosis, which occurs when two solutions of differing concentration are placed on opposite sides of a semipermeable membrane. Therefore, osmotic pressure is highly influenced by the properties of the semipermeable membrane in an FO membrane process. In this study, the properties of commercial polyamide (PA) and cellulose triacetate (CTA) membranes were analyzed, and the water flux and reverse solute flux were evaluated in FO mode. The major properties of an FO membrane that enhance its performance are its thickness, hydrophilicity, and structure. This work developed a high-performance polyethersulfone (PES) membrane for FO membrane process applications. The PES membrane consists of an active layer formed atop a support layer that includes a backing filled with polymer. The water flux was maximized by forming a loose finger-like structure and generating nano-sized pores to increase porosity. The reverse solute flux was minimized by maintaining the thickness of the support layer including the backing. The performance of the PES membrane was compared with that of commercial HTI-CTA membrane. The properties of the PES membrane attributed to the high water flux and low reverse solute flux.