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 H-1-NMR, FT-IR, SEM, contact angle, tensile, and water uptake analysis. Eventually, the S-PVDF-PVDF/(S-PVDF-PVDF)center dot SA(3%)/PA composite membrane was reported as the optimum membrane; its water flux and salt rejection for MgSO4 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-PVDF-PVDF 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.