Hot pressing of electrospun membrane composite and its influence on separation performance on thin film composite nanofiltration membrane

Abstract

The primary objective of this paper was to investigate the influence of hot pressing on electrospun nanofibrous membrane (ENM) properties and subsequently the separation of salt after interfacial polymerization was carried out on the surface of ENM. Polyacrylonitrile solution was electrospun on a Hollytex backing material and this composite layer was subsequently subjected to hot pressing at 87 °C at pressures of 0.14, 0.28 or 0.41 MPa. The bubble-point of the hot pressed ENM significantly reduced with increasing pressure. Overlapping fibers fused at 0.28 MPa and over fusing occurred at 0.41 MPa hence accounting for the drastic decrease in bubble-point. In addition, the thickness of the ENM layer decreased with applied pressure as it compressed the ENM layer. A decrease in bubble-point resulted in a drastic decrease in pure water flux. Interfacial polymerization was carried out on the surface of ENM. The interfacial polymerized control was not able to withstand higher pressures. However, with treatment of 0.14 MPa onwards, the composite membrane was resilient at higher pressure and there wasn't a drastic difference in the average separation of the interfacially polymerized ENM. When compared to NF90, ENM-1 and ENM-2 had fluxes more than 3 folds. However the rejection was compromised by 8–12%.