A promising new forward-osmosis membrane

Forward osmosis (FO) has been recognized as a valuable technology for many applications including wastewater reclamation, seawater desalination, and energy production, due to the low energy input required. The osmotic pressure gradient across a semipermeable FO membrane causes water to diffuse naturally through the membrane, leaving impurities behind. However, when water diffuses through the selective layer of the FO membrane, the draw solution at the permeate side is substantially diluted, while the back diffusion of draw solutes through the support layer works to compensate the diluted draw solutes. The compensation process is severely hindered by the tortuous, dense and thick support layers of conventional FO membranes. As a result, the competing process between dilution and back diffusion equilibrates at a transverse draw-solute concentration profile, leading to an internal concentration polarization (ICP) problem. To overcome this problem, researchers from the School of Civil and Environmental Engineering, Nanyang Technological University (Singapore; www.ntu.edu.sg) fabricated a novel nanocomposite FO membrane with a scaffold-like nanofiber layer that, the researchers claim, possesses remarkable advantages over conventional sponge-like…