A novel multilayer thin-film membrane with high durability: preparation, characterization, performance investigation

A highly durable thin film composite membrane was fabricated using composite nanofibers including sulfonated polyvinylidene fluoride and polyvinylidene fluoride (S-PVDF-PVDF) as a supporting layer, electrosprayed sodium alginate (SA) among the S-PVDF-PVDF nanofibers as a mid-layer, and a thin film polyamide (PA) as a top layer. To prepare the mid-layer of SA, three weight percentages (0.25, 1.5, and 3%) were used. The chemical structure, morphology, and properties of the membranes were characterized using 1 H-NMR, FT-IR, SEM, contact angle, tensile, and water uptake analysis. Eventually, the S-PVDFPVDF/(S-PVDF-PVDF)SA(3%)/PA composite membrane was reported as the optimum membrane; its water flux and salt rejection for MgSO 4 were 4.29 L m 2 h −1 and 84%, respectively. This membrane, in addition to the high water flux compared to the S-PVDF-PVDF membrane, and salt rejection at the same level, had higher strength and durability (36.82 MPa) compared to the S-PVDFPVDF membrane (22.10 MPa). Also, the mid-layer of the membrane increased the durability and stability of the thin film layer and made it possible to use the membrane repeatedly. The main aim of this research is the improvement of the performance in desalination of polyamide (PA) thin film composite nanofiltration membranes by modification of nanofibrous polyvinylidene fluoride as a support layer.