Template-Assisted Fabrication of Thin-Film Composite Forward-Osmosis Membrane with Controllable Internal Concentration Polarization

The internal concentration polarization (ICP) of solutes in the porous substrate layer may reduce the water flux of a forward-osmosis, (PO} membrane. Here we,present an efficient design by using a novel silica template strategy to address this ICP issue. In particular, a thin-film composite(TFC) FO membrane was prepared by incorporating silica nanoparticles (SiNPs) into the poly(ether sulfone) (PES) support layer, followed by the removal of the as-encapsulated SiNPs by hydrofluoric add (HF) etching, leading to the formation of a highly porous and interconnected-pore structure of the support layer. Such porous structure favors the salt back diffusion in the substrate layer, leading to an improved net osmotic pressure across the selective layer. In addition, the HF treatment also contributes to a more hydrophilic top polyamide layer, further improving the performance of the membrane. The effects of the silica template on the morphology and properties of the as-designed TFC FO membrane are systematically investigated, and two major contributors for the enhanced water flux of the membrane have also, been identified. The materials and strategy developed in this study will be of potential for the fabrication of high-quality FO membranes.