Underwater superoleophobic membrane with hydrophobic bump and hydrophilic sublayer structure for effective oil-in-water emulsions separation

Abstract

Underwater superoleophobic membranes are competitive strategy for accomplishing efficient oil-in-water emulsions separation. However, permeating flux of water probably may be dropped with the reduction of pore size. Moreover, the plenty of oil phase may block pore canal resulting the decrease of separation performance. Herein, an underwater superoleophobic membrane with hydrophobic bump and hydrophilic sublayer structure was fabricated through spinning hexadecyltrimethoxysilane (HDTMS) modified SiO2 (H-SiO2) micro-particles on polydopamine (PDA) hydrophilized polyvinylidene fluoride (PVDF, PDP) membrane. Therefore, the sieving of hydrophilic PDP membrane sublayer and oil absorption-flotation of hydrophobic H-SiO2 bump are ongoing simultaneously in separation processes, thus effective decreasing oil fouling to break the trade-off effect between separation efficiency and permeation flux. Interestingly, the PDPS membrane not only could efficiently separate diverse emulsions involving low and high-viscosity oil/water emulsions, but also possessed excellent mechanical (200 times of bending test) and chemical (separation of oil-in-corrosive waster emulsions) stabilities. More importantly, the separation performance of PDP-H-SiO2 (PDPS) membrane with bump-sublayer structure is obviously superior to the single PDP membrane. The idea of rationally combing opposite wetting and bump-sublayer structures has certain significance towards the fabrication and development about oil/water separation materials.