Novel Dimensionally Controlled Nanopore Forming Template in Forward Osmosis Membranes

To lower the unfavorable internal concentration polarization effect in forward osmosis (FO) membranes, support layers of highly porous interconnected structures with specifically large surface-to-volume ratios are indispensable. Herein, zinc oxide (ZnO) has been introduced as a new template to manipulate the porous structure of poly(ether sulfone) (PES) support layer. The ZnO can be readily synthesized as desired in different dimensionally controlled nanostructures. The performance of the FO membrane was initially ameliorated in terms of permeability and selectivity through simple incorporation of ZnO nanostructures in the PES support layer. The PES support layer was blended with appropriate amounts of ZnO nanostructures, casted on a glass plate, and subsequently acid washed to leach out the embedded ZnO nanostructures. Different nanoporous structures were achieved when ZnO of different nanostructures was used to modify the PES support layer. The experimental results indicated that the permeability of FO membranes could be simply improved by incorporation of ZnO nanostructures in PES support layer. Higher hydrophilicity and formation of suitable internal pores were mainly responsible for such observation. Although surface hydrophilicity of the support layers was reduced after being acid washed, water permeation through the membrane was intensified due to the formation of interconnected porous structure.