The Roles of Hydrophilic Nature and Sponge-Like Structure of Membrane Support Layers In the Development of Thin-Film Composite (TFC) Forward Osmosis (FO) Membranes

A new approach to fabricate thin film composite (TFC) membranes via interfacial polymerization for forward osmosis (FO) applications has revealed that it is possible to design TFC-FO membranes with fully sponge-like structure and likely anti-fouling characteristics while maintaining a high water flux. Not only does the sulphonated material in the substrate of TFC-FO membranes play the key role to create macrovoid-free structure but also induces hydrophilic properties with enhanced water fluxes. This is proven by the high water flux up to 15LMH (PRO mode) when using 3.5wt% NaCl (seawater composition) as feed solution and 2M NaCl draw solution. Despite the debates on whether TFC-FO membranes should possess a finger-like or sponge-like structure, it is proven that the degree of hydrophilicity of membrane substrates is a much stronger factor enhancing the water flux in FO tests. Furthermore, the structural parameter indicating the internal concentration polarization (ICP) can be remarkably decreased with an increase in sulphonated material content in membrane substrates.