Facile Preparation of Superhydrophobic-Superoleophilic Isotactic Polypropylene Microporous Membranes with High-Aspect-Ratio Surface for Nano-Scale Water-in-Oil Emulsion Separation

Abstract

For preparing superhydrophobic-superoleophilic anisotropic polypropylene (iPP) microporous membranes, a modified method namely introduced a facile peeling procedure to a synergistic operation of micromolding and thermally induced phase separation (TIPS) was developed. This method mainly involves semi-gelation process of liquid membrane, peeling procedure and further gelation process in water bath. During peeling, the aspect ratio of the micron-scale structure on the membrane surface was effectively stretched, which in combination with the submicron-scale structure generated by TIPS process achieved a superhydrophobic-superoleophilic iPP membrane with high-aspect-ratio surface. The membranes prepared under optimum conditions displayed a water contact angle of 157°, a low sliding angle of 3.2° and an oil droplet spread time of 0.24 s. The iPP membrane could be used for the separation of nano-scale water-in-oil emulsions, experimental results showed oil fluxes of up to 1230 L·m-2·h-1 at 0.09 MPa and water contents as low as 44 ppm in the infiltrated oil. Moreover, the prepared membrane exhibited excellent separation efficiency, anti-oil fouling and recyclability. Such a facile method will serve as an alternative for the preparation of superhydrophobic-superoleophilic polymer microporous membranes with both low cost and high throughput.

Keywords: iPP membrane, Peeling procedure, Superhydrophobic-superoleophilic, Thermally induced phase separation (TIPS), oil-water separation