Electrospun\nSuperhydrophobic Organic/Inorganic Composite\nNanofibrous Membranes for Membrane Distillation

Abstract

Electrospun\nsuperhydrophobic organic/inorganic composite nanofibrous\nmembranes exhibiting excellent direct contact membrane distillation\n(DCMD) performance were fabricated by a facile route combining the\nhydrophobization of silica nanoparticles (SiO₂ NPs) and\ncolloid electrospinning of the hydrophobic silica/poly­(vinylidene\nfluoride) (PVDF) matrix. Benefiting from the utilization of SiO₂ NPs with three different particle sizes, the electrospun\nnanofibrous membranes (ENMs) were endowed with three different delicate\nnanofiber morphologies and fiber diameter distribution, high porosity,\nand superhydrophobic property, which resulted in excellent waterproofing\nand breathability. Significantly, structural attributes analyses have\nindicated the major contributing role of fiber diameter distribution\non determining the augment of permeate vapor flux through regulating\nmean flow pore size (MFP). Meanwhile, the extremely high liquid entry\npressure of water (LEPw, 2.40 ± 0.10 bar), robust nanofiber morphology\nof PVDF immobilized SiO₂ NPs, remarkable mechanical properties,\nthermal stability, and corrosion resistance endowed the as-prepared\nmembranes with prominent desalination capability and stability for\nlong-term MD process. The resultant choreographed PVDF/silica ENMs\nwith optimized MFP presented an outstanding permeate vapor flux of\n41.1 kg/(m²·h) and stable low permeate conductivity\n(∼2.45 μs/cm) (3.5 wt % NaCl salt feed; Δ<i>T</i> = 40 °C) over a DCMD test period of 24 h without\nmembrane pores wetting detected. This result was better than those\nof typical commercial PVDF membranes and PVDF and modified PVDF ENMs\nreported so far, suggesting them as promising alternatives for MD\napplications.