Separation of liquid mixtures, especially organic liquid mixtures, is widely used in industrial processes but still faces challenges with respect to separation in a high-efficiency, low-energy mode. In this work, we report a flexible wettability-tunable nanofibrous membrane composed of a high-performance fluoro-polymer as the matrix and fluorosilane as a surface energy regulator that can be successfully applied in immiscible organic liquid mixture separation. The separation is achieved by tuning the surface energy of a membrane to a value between the surface tensions of two organic liquids. Moreover, for use in different mixed liquid systems, we programmatically designed nanofibrous membranes with the proper surface energy that could intercept the relatively high surface tension liquid and allow the low surface tension liquid to pass through. These membranes are expected to become a competitive candidate for complex organic chemical product separation, resource recycling, and environmental protection.
INTRODUCTIONLiquid mixtures of solvents or reactants are ubiquitously applied in processes in the petrochemical, textile printing, food and medical industries. These complex liquid mixtures often must be separated after reaction for the purpose of product purification, resource recycling or harmless discharge. 1 Traditional liquid separation methods such as distillation and separation have exposed many drawbacks, including high-energy consumption, low flux and low efficiency, that dramatically increase the separation time and cost. 2 Therefore, challenges remain for the development of separation processes of organic liquid mixtures that are efficient, allow high throughput and conserve energy. Among various separation approaches, the membrane separation technique has been extensively proven as a high throughput and energy-efficient choice. [3][4][5] Over the past decade, various membranes with special wettability properties have been successfully prepared and have exhibited excellent performance in oil/water separation. The mechanisms of membrane separation are based on exact opposite wettabilities toward oil and water, including superhydrophobic/superoleophilic membranes 3,5-8 or superhydrophilic/superoleophobic membranes. 9-15 For example, superhydrophobic/oleophilic membranes have been prepared from various materials, including metals, polymers or even clothes and filter papers, that could intercept water and allow oil to pass through. [16][17][18][19][20] In addition, researchers have gained inspiration from oil-contaminantfree fish skin to fabricate oil-repellent hydrogel membranes that could separate oil from water. 21,22 Although significant progress has been achieved for membrane-based oil/water separation in the last few years, development of separation membranes for organic liquids is still highly limited because organic liquids usually possess a relatively lower surface tension than water. The difficulty in separation of organic liquid mixtures has increased because it is more difficult to build a super...
