Mixed\nMatrix Polytetrafluoroethylene/Polysulfone Electrospun Nanofibrous\nMembranes for Water Desalination by Membrane Distillation

Abstract

The\nelectrospinning technique was used successfully to fabricate nanofibers\nof polysulfone (PSF) in which polytetrafuoroethylene nanoparticles\n(PTFE NPs) were embedded. The size of the PTFE NPs is only 1.7 to\n3.6 times smaller than the nanofiber diameter. The transition from\nhydrophobic to superhydrophobic character of the bead-free PSF electrospun\nnanofiber mats occurred with a PTFE NPs loading in the range 12–18%\nof the PSF weight. Transmission electron microscopy images revealed\nprotruding nanosized asperities on the fiber surface due to the embedded\nPTFE NPs in the PSF matrix. For low PTFE NPs content in PSF matrix\n(<6% of the polymer weight), the PTFE NPs were arranged one by\none in a single file along the PSF nanofiber axis. The structural\ncharacteristics of the nanofibers and electrospun nanofibrous membranes\n(ENMs) were studied by means of different techniques and their relationship\nwith the PTFE NPs loading in PSF were discussed. The PSF/PTFE ENMs\nwere tested in desalination by direct contact membrane distillation\n(DCMD) and the obtained performance was discussed in terms of the\nENMs structural characteristics. Competitive permeate fluxes, as high\nas 39.5 kg/m²h, with stable low permeate electrical conductivities\n(<7.145 μS/cm) for 30 g/L NaCl aqueous solution and transmembrane\ntemperature of 60 °C were achieved without detecting any interfiber\nspace wetting.