Oil/water separation membranes with a fluorine island structure for stable high flux

Abstract

Stable high flux is a big challenge for oil/water separation membranes due to the adhesivity and spreadability of oil droplets. Membranes with hydrophilic modification usually have high basic flux, but suffer from a serious flux decline. Membranes with synergic hydrophilic and low-surface-energy (LSE) modification show a remarkably relieved flux decline, but at the expense of low basic flux. The LSE domains on membrane surfaces promote oil fouling release but hinder water permeation. In order to relieve the adverse side effects of LSE domains, this study focuses on the distribution of hydrophilic and LSE domains on membrane surfaces. Membranes with a fluorine island structure are prepared, in which LSE domains are discrete in sub-microscaled distribution, while hydrophilic domains are consecutive in a wide area. The diameters of oil droplets are much larger than those of water molecules; therefore, water molecules quickly permeate at consecutive hydrophilic domains, and oil droplets are still released by discrete LSE domains. The stable flux of the membranes is improved from 280 to 770 Lm⁻² h⁻¹ bar⁻¹ just by the manipulation of domain distribution.