Smart TFC membrane for simulated textile wastewater concentration at elevated temperature enabled by thermal-responsive microgels

Substrate modification is advantageous to ameliorate the internal concentration polarization (ICP) phenomenon encountered by most thin-film composite (TFC) membrane in forward osmosis (FO) process, therefore promoting FO implementation to a large extent. Optimization of the intrinsic parameters of substrate (e.g. porosity and tortuosity) can generally be achieved by incorporating hydrophilic or pore-containing materials into the dope solution before the substrate fabrication. In this work, polyvinylidene fluoride (PVDF) substrate with embedded thermal-response poly (N-isopropyl acrylamide) (PNIPAM) microgels is employed for the construction of TFC-FO membrane, where the reversible shrinkage of PNIPAM microgels brings about a lower tortuosity and a higher porosity of the substrate at higher operation temperature, thereby mitigating the ICP impact of the TFC-FO membranes significantly. Effects of PNIPAM content on the properties of the substrates and the resultant polyamide (PA) layer, as well as the corresponding performance of the TFC-FO membranes were comprehensively investigated. The benchmarking shows that, TFC membrane with PNIPAM-modified substrate exhibits remarkably improved water flux of 40.2 L·m −2 ·h −1 and a reduced reverse salt flux of 10.1 g·m −2 ·h −1 , with DI water as feed (50 °C) and 1 M NaCl as draw solution (ambient temperature), which suggests its great potential for treating feed solution with relatively high temperature in the practical applications, for instance, the dyestuff wastewater enrichment.