High performance electrospun thin-film composite forward osmosis membrane by tailoring polyamide active layer with polydopamine interlayer for desulfulrization wastewater desalination

The relatively poor selectivity of electrospun nanofiber membrane (ENM) substrate supported thin film composite forward osmosis (eTFC-FO) membranes has hindered their applications. In this study, to overcome the high roughness and large pore size of ENM substrate, a smooth and hydrophilic polydopamine (PDA) interlayer was fabricated on a polyvinylidene fluoride (PVDF) ENM, which was found to be favourable for the formation of a thinner, more cross-linked and less defective polyamide (PA) active layer on the ENM substrate. Desalination tests proved the great effectiveness of PDA interlayer on performance improvement for the eTFC-FO membrane. A quite high water flux (43.0 LMH) and ions rejection (>97.0%) were achieved for a real desulfurization wastewater desalination tested in FO mode. The alleviated PA defects by the PDA interlayer could greatly improve the selectivity. As a comparison with PDA interlayer, PDA coating on each individual nanofiber inside the PVDF ENM substrate was also prepared for eTFC-FO membrane, which would not overcome the disadvantages of rough and large pore sized ENM substrate for PA preparation. Mechanisms of PA formation and performance improvement were detailly discussed in this work.