Bioinspired Janus membrane of polyacrylonitrile/poly (vinylidene fluoride)@poly (vinylidene fluoride)-methyltriethoxysilane for oil-water separation

Abstract

Currently, Janus membranes have attracted growing attention in oil-water separation due to the unique asymmetric wettability on opposite two surfaces. Nevertheless, it is still challengeable to achieve the superhydrophilicity and superhydrophobicity of the two opposite sides. Inspired by the lotus leaf and orange structure, the Janus membrane of polyacrylonitrile/poly (vinylidene fluoride)@poly (vinylidene fluoride)-methyltriethoxysilane (PAN/PVDF@PVDF-MTES) is developed by electrospinning and electrospraying technique for oil-water separation. In Janus membrane structure, each layer is physically combined, and the Janus-PAN side is superhydrophilic with water contact angle (WCA) of ∼0°, while the Janus-PVDF-MTES side is superhydrophobic with WCA of ∼170.2 ± 2.4°. These characteristics endow the membrane with outstanding separation efficiencies and good reusability. The separation mechanism is elucidated on the basis of the asymmetric wettability. The kinetics behavior of the oils in Janus membrane follows the models of pseudo-first-order and intra-particle diffusion. The oil flux of the Janus membrane is associated with the types of oil and the diffusion is not the only influence factor in oil adsorption. The application trial results indicate the potential of PAN/PVDF@PVDF-MTES membrane in the separation of the oil/water mixtures and surfactant-stabilized emulsions.