Thin film composite forward osmosis membranes based on thermally treated PAN hydrophilized PVDF electrospun nanofiber substrates for improved performance

The aim of this study was to explore the impact of thermally rolled polyvinylidene fluoride/polyacrylonitrile (PVDF/PAN) electrospun nanofibers (ESNF) as substrates to produce thin-film composite (TFC) forward osmosis (FO) membranes with better characteristics. Different loadings of PAN (0–10 wt%) were used to prepare PVDF/PAN ESNF substrates, and their surface morphology and structural properties were systematically studied. Before the deposition of the polyamide layer by interfacial polymerization, the ESNF substrates were subjected to continuous thermal rolling pretreatment to improve their mechanical stability. The water flux of 33.3 L/m²h and 42.3 L/m²h was achieved for the TFC-10 membrane with 10 wt% PAN blended PVDF ENSF substrate under FO and PRO modes, which was ~191% and ~188% higher than that of the TFC-0 membrane under FO and PRO orientations, respectively, using DI water as feed and 1 M NaCl as the draw solution. Moreover, the TFC-10 FO membrane showed improved selectivity, as indicated by the decrease in specific salt flux values (from 0.33 g/L of TFC-0–0.23 g/L for TFC-10), and a smaller structural parameter (221 µm) than the TFC-0 membrane, indicating that the influence of ICP can be reduced by the addition of PAN into PVDF ESNF substrate.