Improving the separation performance of the forward osmosis membrane based on the etched microstructure of the supporting layer

The physical and chemical characteristics of the porous supporting layer play a key role in the separation efficiency and concentration polarization of the forward osmosis (FO) membranes. In this paper, the modified polyvinylidene fluoride (PVDF) porous membranes with high porosity and large amounts of surface membrane pores were prepared with zinc oxide (ZnO) nanoparticles as the template, and used as the supporting layer of the FO membrane. The modified FO membranes showed enhanced water permeability and separation selectivity. The increased water flux was based on the increase of the effective membrane area, and the decreased τ/ε (tortuosity factor/porosity) value obviously alleviated the concentration polarization phenomenon based on the optimization of the flow channel. The etching of the porous microstructure could reduce the limit of the supporting layer on the separation performance of the FO membrane, and provide a simple method to improve the separation efficiency of the thin film composite (TFC)-type FO membranes.