Ultrahigh flux of polydopamine-coated PVDF membranes quenched in air via thermally induced phase separation for oil/water emulsion separation

Poly(vinylidene fluoride) (PVDF) membranes are prepared via thermally induced phase separation (TIPS) method with cold air as quenching air (PVDFT-air), and surface-modified by polydopamine. The morphologies, surface chemistry, pore size, porosity, mechanical properties, separation performance in oil/water emulsion separation and antifouling ability of the prepared PVDF membranes were studied in detail. Compared with the PVDF membranes prepared by traditional TIPS method with cold water as quenching bath (PVDFT-water), the PVDFT-air membranes are not only more environmental friendly and energy saving, but also show ultrahigh permeation flux without sacrificing oil rejections and improve mechanical strength. After being modified by polydopamine, the rich hydrophilic groups in dopamine endow the PVDFT-air membranes with excellent hydrophilic and underwater oleophobicity. The optimal membrane sample (M-3) shows a permeation flux of 3855.6 L·m−2·h−1·bar−1 for pure water and the ones above 2600 L·m−2·h−1·bar−1 for oil/water emulsions accompanied with above 98.5% oil rejections for three oil/water emulsions (n-hexane, toluene and petroleum ether). The results demonstrate that novel PVDF microfiltration membranes with ultrahigh permeation flux and oil rejection are prepared for oil/water emulsion separations.