Asymmetric Aerogel Membranes with Ultrafast Water Permeation for the Separation of Oil-in-Water Emulsion

Abstract

Owing to highly porous and low density attributes, aerogels have been actively utilized in catalysis and adsorption processes, but their great potential in filtration requires exploitation. In this study, an asymmetric aerogel membrane is fabricated via one-pot hydrothermal reaction induced self-crosslinking of poly(vinyl alcohol) (PVA), which exhibits ultra-fast permeation for separation of oil-in-water emulsion. Meanwhile, carbon nanotubes (CNT) were added to improve the mechanical strength of the aerogel membranes. The self-crosslinking of PVA forms the supporting layer, and the exchange of water and vapor at the interface of PVA solution and air generates the separating layer as well as abundant hydroxyl groups on membrane surface. The density, porosity, pore size and wettability of aerogel membrane can be tuned by PVA concentration. Owing to high porosity (>95%) and suitable pore size (<85nm), aerogel membrane exhibits high rejection (99.0%) for surfactant-stabilized oil-in-water emulsion with ultra-high permeation flux of 135.5*103 Lm-2h-1bar-1 under gravity-driven flow, which is 2 orders of magnitude higher than commercial filtration membranes with similar rejection. Meanwhile, the aerogel membrane exhibits super-hydrophilicity, super-oleophobicity underwater, and excellent antifouling properties for various surfactant-stabilized oil-in-water emulsions, as indicated by that the flux recovery ratio maintains more than 93% after five cycles of filtration experiment. The findings in this study may offer a novel idea to fabricate high throughput filtration membranes.