Natural polyphenol chemistry inspired organic-inorganic composite coating decorated PVDF membrane for oil-in-water emulsions separation

With the ever-increasing discharge of industrial oily wastewater, oil-water separation has attracted widespread concern in recent years. In this work, we fabricated a tannic acid/polyvinylpyrrolidone/SiO2 composite coating decorated PVDF membrane for effective oil-in-water emulsions separation. Tannic acid and polyvinylpyrrolidone form complex through hydrogen bonding, generating stable sol after associating with SiO2, which endows the hydrophobic PVDF membrane with superhydrophilicity and underwater superoleophobicity. The rejections of the modified membrane for the emulsions were higher than 99.9 % and the 5-min fluxes reached over 690 L∙m−2 h-1. Four rounds of continuous separation exhibited that the membrane has outstanding flux recovery capability with water washing among each cycle. We envision that this natural polyphenol chemistry inspired coating process with green, low-energy, cost-effective advantages indicates great potential for practical applications.