Superhydrophilic/superoleophobic shell powder coating as a versatile platform for both oil/water and oil/oil separation

Traditional membrane-based separation methods are limited by the inability of a single membrane to separate both oil/water and oil/oil mixtures. Herein, to address this challenge, we have produced a superhydrophilic/superoleophobic shell powder coating that can be used as an advanced separation membrane for separating oil/water mixtures, emulsions, and oil/oil mixtures, when coated on a copper mesh and fabric. Utilizing its water-affinity and oil-repellency, the separation membrane can separate oil/water mixtures and emulsions with high separation efficiency. Interestingly, our separation membrane displays opposite wetting behavior between high-polar oils and low-polar oils, and utilizing this selective wetting to oils with different polarity, oil/oil mixtures separation is achieved effectively, even if the surface tension difference between two oils is as small as 2.4 mN/m. Using an ethanol-prewetting strategy, on-demand oil/water and oil/oil separation are also achieved on this separation membrane. This study is expected to present a promising approach to membrane-based separation technologies.