TIPS-co-NIPS method to prepare PES substrate with enhanced permeability for TFC-FO membrane

A thermally induced phase separation followed by non-solvent induced phase separation (TIPS-co-NIPS) was used to prepare polyethersulfone (PES) substrate with reduced internal concentration polarization (ICP) for thin film composite forward osmosis (TFC-FO) membrane. Using polyethylene glycol (PEG) as the additive, impacts of TIPS process on substrate properties, TFC layers and FO performances were investigated. The results revealed that the substrate prepared by TIPS-co-NIPS method with 10 s cooling time showed a fully finger-like structure, enhanced permeation performance and better surface hydrophilicity. As a result, the corresponding TFC-FO membrane exhibited 44% lower structural parameter than the TFC-FO membrane based on NIPS substrate (684 µm versus 380 µm), high water fluxes up to 32.9/20.4 LMH and reverse salt fluxes of 14.1/8.2 gMH in the PRO/FO mode using 1 M NaCl as the draw against DI-water feed. Therefore, the proposed TIPS-co-NIPS method utilizing PEG as the additive may be considered as a feasible approach to regulate substrate structure and property for TFC-FO membrane.