Impregnated Membranes for Water Purification Using Forward Osmosis

The wide use of forward osmosis (FO) for water purification has been restrained by the lack of membranes with high water flux. Current FO membranes consist of a thick microporous support and a paper layer, which creates internal concentration polarization and presents major resistance for water transport across such membranes. This study investigates novel FO membranes consisting of a thin porous structure fully impregnated with a hydrophilic polymer. The elimination of the open-pore structures in these impregnated membranes (IMs) avoids the internal concentration polarization. More specifically, IMs consisting of hydrophilic cross-linked poly(ethylene glycol) diacrylate (PEGDA) in a porous hydrophobic Solupor support were prepared and thoroughly characterized for water and salt transport properties using a dead-end filtration system, salt kinetic desorption experiments, and an FO system. The IMs showed performance ratios (defined as the water permeance in FO mode to that in the dead-end filtration system) 50% higher than those of state-of-the-art commercial FO membranes, demonstrating the promise of the use of IMs to mitigate internal concentration polarization. This work provides a new route to the design of FO membranes with potentially high performances.