Electrospun PTFE nanofibrous composite membranes featuring a fiber network structure for organic solvent nanofiltration (OSN)

The practical implementation of organic solvent nanofiltration (OSN) was still hindered by the drawback of substrate swelling and dissolution in organic solvents. As the substrate of nanofiltration membranes, polytetrafluoroethylene (PTFE) had gained increasing attention due to its stable chemical characteristics. However, it was difficult to construct functional nanofiltration layers on the surface of PTFE due to its hydrophobicity induced by its intrinsic low surface energy, resulting into poor adhesion between substrate and functional layer. In this study, a polydopamine (PDA)-PA/PTFE composite nanofiltration membrane with a three-layer was fabricated by utilizing the poly (tetrafluoroethylene-hexafluoropropylene) (FEP) resins as the pore structure regulator of the PTFE substrate with fiber network structure, and PDA as the surface modifier of the PTFE substrate. The resultant composite nanofiltration membrane exhibited a notable rejection rate of 96.26 % for Rose Bengal (RB), and a long-term stable ethanol permeance of 2.28 (L·m⁻²·h⁻¹·bar⁻¹). After continuous filtration for 48 h, soaking in polar organic solvents (DMF) for 20 days, and circulating experiments exhibiting excellent solvent resistance and long-term stability. These results provided a useful strategy for the application of PTFE nanofiber substrates in the OSN field.