Wettability of porous materials is crucial for the separation of emulsified oil/water mixtures. Herein, high hydrophobicity of polyvinylidene fluoride (PVDF) membrane has been facilely transformed to high hydrophilicity and underwater superoleophobicity via single-step coating of plant-derived epigallocatechin gallate (EGCG) and silver ion (Ag⁺) in aqueous solution. EGCG can chelate with Ag⁺ and in-situ reduced it into Ag nanoparticle, meanwhile Ag/EGCG composite was adhered on membrane surface due to the high surface binding affinity of EGCG. The hydrophilic EGCG and formed micro/nanostructure together improved membrane hydrophilicity and oleophobicity. The optimally Ag/EGCG modified PVDF membrane possesses high permeate flux (e.g. 735 L/(m²h) for diesel-in-water emulsion, while it is zero for pristine PVDF membrane) under a low operation pressure of 0.5 bar and high oil rejections in the treatment of surfactant-stabilized oil-in-water emulsions consisting of micro/nano scale droplets. In addition, the membrane exhibits excellent antifouling property with a flux recovery ratio of 98.1% and satisfactory reusability in a 5-cycle test. Moreover, the membrane possessed desired stability during long-term rinsing test and Ag leaching test. This work would offer new insights into surface hydrophilic manipulation of porous membrane towards practical oil emulsion purification.

多孔材料的润湿性对于乳化油/水混合物的分离至关重要。在本文中，聚偏二氟乙烯（PVDF）膜的高疏水性已经通过将植物来源的表没食子儿茶素没食子酸酯（EGCG）和银离子（Ag ⁺）一步涂覆在水溶液中而轻松地转变为高亲水性和水下超疏油性。EGCG可与Ag ⁺螯合并原位还原成Ag纳米颗粒，同时由于EGCG的高表面结合亲和力，使Ag / EGCG复合物粘附在膜表面。亲水性EGCG和形成的微/纳米结构一起改善了膜的亲水性和疏油性。最佳的Ag / EGCG改性PVDF膜具有高渗透通量（例如735 L /（m ²h）对于水包柴油乳化液，而对于原始PVDF膜则为零）在0.5 bar的低操作压力和高拒油率下，用于处理由微米/纳米级组成的表面活性剂稳定的水包油乳化液飞沫。此外，该膜还具有优异的防污性能，通量回收率为98.1％，在5个循环的测试中具有令人满意的可重复使用性。而且，该膜在长期漂洗试验和Ag浸出试验中具有所需的稳定性。这项工作将为多孔膜的表面亲水处理提供实用的油乳液纯化提供新的见解。