Robust and fouling-resistant ultrathin membranes for water purification tailored via semi-dissolved electrospun nanofibers

Abstract

Energy-efficient membranes with high mechanical strength and fouling resistance is highly required in the current membrane industry. In this research, a novel type of water purification membrane was fabricated using a nylon 6 nanofiber membrane as a base polymer and further mechanical processing. The electrospun nylon 6 membrane was first semi-dissolved by spraying diluted formic acid solvent, then re-casted by thermal rolling, and a very-tight ultrafiltration membrane named SP6 was obtained. Fabricated SP6 had an ultrathin thickness of 9 μm and ultimately high mechanical strength (53 MPa). Owing to the enhanced hydrophilicity and ultra-low thickness, a 59 ± 7 LMH water flux was observed for SP6. Furthermore, SP6 showed 98 ± 0.85% humic acid (H.A) and 92.13 ± 0.46% organic dye rejection. When an organic fouling study was conducted (8 h H.A. fouling tests with 30 min DI water filtration/flushing in between), SP6 had only a 20% drop, which also recovered up to 90% after 30 min of DI water filtration. After the fouling test was completed, significantly less foulant (2817 ± 1503 μm3) was observed on the surface of SP6 (on the 500*500 μm2 surface area), in line with the trend for the flux recovery. Therefore, this novel approach utilizing semi-dissolved nanofibers as fabrication material could represent a path for fabricating membranes with great longevity for practical applications.