A smart membrane with antifouling capability and switchable oil wettability for high-efficiency oil/water emulsions separation

There are large amounts of oily wastewater produced by industrial production processes and daily life, and oily wastewater is one of the most widespread environmental issues. These effluents contain a large amount of emulsified oil/water mixtures. However, separation of stabilized oil/water emulsions is difficult and a global challenge. Oily wastewater is not only harmful to the environment but it also affects human health. Thus, development of materials that can effectively solve this problem is of great interest. Here, a smart surface with antifouling property and pH-controllable oil wettability in aqueous media is reported. The smart surface on a porous anodic aluminum oxide (PAAO) membrane (pore size < 1 µm) shows switchable superoleophilic/superoleophobic performance in different pH aqueous media. The smart surface was fabricated by modifying the PAAO membrane with the pH-responsive poly(4-vinylpyridine) and hydrophobic/oleophilic polystyrene block copolymer. The as-prepared PAAO membrane can effectively separate stabilized oil-in-water and water-in-oil emulsions by adjusting the pH of the aqueous medium (3.0 and 7.0). Furthermore, the as-prepared membrane with superior antifouling capacity and could be used at least 10 times with high separation efficiency (99.95%). The present study suggests that PAAO membranes have potential applications for separation of stabilized oil/water emulsions.