Dual oil-resistant membranes based on metal-polyphenol networks and NiFe layered double hydroxides for sustainable oil-in-water emulsion separation

In this study, NiFe layered double hydroxides (LDHs) are embedded in metal-polyphenol networks (MPNs) composed of tannic acid and Ti to build dual oil-resistant barriers on the substrate. The prepared membrane shows 99.9 % oil removal due to the synergistic effect of the first barrier based on LDHs and the second barrier based on MPNs. It achieves an average flux of 4174 L m- 2 h-1 bar-1 in the cross-flow separation of oil-in-water emulsions containing surfactants, which is 3.9 times higher than that of the pristine PVDF. In addition, it can treat complex emulsions, removing 99.22 % of methylene blue, 92.47 % of tetracycline hydrochloride and and 89.65 % of Cr (VI) from the emulsion while removing oil. It also shows good separation performance for actual emulsified wastewater from industrial processes. This research provides a new approach to the design of oil- -water separation materials to achieve high oil resistance and continuous separation.