High-performance thin-film composite forward osmosis membrane fabricated on low-cost PVB/PVC substrate
A series of low-cost poly(vinyl butyral) (PVB)/poly(vinyl chloride) (PVC) blended substrates were fabricated for the preparation of thin-film composite (TFC) forward osmosis (FO) membranes. The effect of PVB blend ratio on the substrate and TFC membrane was investigated. The results showed that the properties of the substrates were significantly improved and that the selective layer became looser, rougher, and less crosslinked after the introduction of PVB. The water permeability was initially improved when the PVB blend ratio increased from 0% to 30%. However, the NaCl rejection was rapidly declined with a further increase in the blend ratio, which should be ascribed to a decrease in the crosslinked degree of the PA selective layer. Meanwhile, the calculated results shows the value of structure parameter is sharply decreased to 186 μm for TFC30 from 2680 μm for TFC0. The results demonstrated that a PVB blend ratio of 30% should be the optimal ratio for fabrication of the substrate for the TFC membrane showing satisfactory FO performance: a high water flux of 29.37/49.85 L m−2 h−1 (FO/PRO mode) and a low specific salt flux of 0.11/0.10 g L−1 (FO/PRO mode) using 1 M NaCl as the draw solution and DI water as feed solution.