Preparation of superhydrophilic/underwater superoleophobic membranes for separating oil-in-water emulsion: mechanism, progress, and perspective

The superhydrophilic/underwater superoleophobic (SUS) membrane has attracted significant attention in the separation process of oily wastewater, especially for the oil-in-water emulsions, due to high separation efficiency and remarkable antifouling performance. In this review, the related wetting mechanisms of SUS membranes, design criteria of constructing rough surface, and recent developments in materials with SUS membranes for separating oily wastewater are detailed. According to the creative design of the micro-nano scale hierarchical surface morphology of SUS membranes, various porous membranes with surface roughness, including xD (herein, x represents 0 ~ 3) micronano, are systemically analyzed. In each section, various types of membranes are also presented with design ideas, base materials, and preparation methods. Then, the high-energy rough micro-nano structures are proposed for constructing on the surface of the membrane as a more effective method for preparing SUS membranes. Finally, conclusions and perspectives for future research are provided in depth according to the existing problems in this field.