Improved performance of thin-film composite membrane with PVDF/PFSA substrate for forward osmosis process

In this work, a small amount of hydrophilic perfluorosulfonic acid (PFSA) is incorporated into the polyvinylidene fluoride (PVDF) substrate to develop the high-performance thin-film composite (TFC) membrane for forward osmosis applications. Because of the hydrophilicity and excellent compatibility with PVDF, PFSA not only significantly improves the wettability of the modified membrane substrate, but also well optimizes the pore size by changing the membrane morphology of PVDF/PFSA substrate. These two factors effectively mitigate the water transport resistance and favor the better formation of the polyamide (PA) layer during the interfacial polymerization, thus improving both the water flux and membrane selectivity of the resultant TFC membranes simultaneously. Effects of the PFSA concentration on the overall properties of the modified substrates and corresponding PVDF/PFSA TFC membranes are systematically investigated via various characterizations. Consequently, the PVDF/PFSA TFC membrane achieves a best water flux (JV) of 54.4 LMH and a reverse salt flux (JS) of 10.9 gMH in AL-DS mode, and a JV of 27.0 LMH with JS of 8.4 gMH in AL-FS mode using deionized (DI) water and 1 M NaCl aqueous solution as the feed and draw solutions respectively. This work may provide a new orientation in developing TFC membranes on the hydrophobic substrate with its intrinsic advantages maximized.