Self-sustained webs of polyvinylidene fluoride electrospun nanofibers at different electrospinning times:1.Desalination by direct contactmembrane distillation

Self-sustained electrospun nanofibrous membranes (ENMs) were prepared using the polymer poly-vinylidenefluoride (PVDF) and applied for desalination by direct contact membrane distillation(DCMD).Different electrospinning times were considered to prepare the PVDFENMs of differentthicknesses ranging from 144.4 to 1529.3 mm. A systematic experimental study on the effects ofmembrane thickness on the DCMD performance is carried out for the first time.The surface and cross-section of the ENMs were studied by scanning electronmicroscopy and the mean size of the fiberstogether with its distribution was determined. The water contact angle,the inter-fiber space,the voidvolume fraction and the liquid entry pressure of water inside the inter-fiberspace were determined bydifferent characterization techniques. It was observed an enhancement of the thickness and the liquidentry pressure of water with the increase of electrospinning time,a decrease of the mean size of theinter-fiberspace,whereas no significant changes were observed for the diameter of the electrospunfibers(1.0–1.3 mm), the void volume fraction (0.85–0.93) and the water contact angle(137.4–141.11).The size of the inter-fiberspace is not uniform throughout the thickness of the ENMs.The effects of theENMs thickness on the DCMD performance was studied for different feed temperatures and sodiumchloride feed aqueous solutions with concentrations up to 60g/L,which is about two times greater thana typical seawater concentration.The permeate flux of the ENMs is lower for longer electrospinningtime and the obtained permeate fluxes in this study are higher than those reported so far forPVDF ENMs.