Polyphenolic-Chemistry-Enabled, Mechanically Robust, Flame Resistant and Superhydrophobic Membrane for Separation of Mixed Surfactant-Stabilized Emulsions.

Superhydrophobic materials hold great promise in emulsion separation, but they have inherent mechanical weakness and are ineffective to separate mixed surfactant-stabilized emulsions. Herein, we combined the adhesion ability of polyphenol-Fe3+ bis-complexes with the high mechanical strength of carbon nanotubes (CNTs) to construct a mechanically robust and superhydrophobic coating on a collagen fiber membrane (CFM). We demonstrated that both CNTs and polyphenolic complexes competed with the surfactants adsorbed onto the emulsion droplets, serving as efficient demulsifiers to various mixed surfactant-stabilized emulsions. CFM has a 3D fibrous structure and a high limiting oxygen index, which provides high flux and flame resistance. The as-prepared superhydrophobic membrane can separate diverse anionic/nonionic and cationic/nonionic surfactant-stabilized micro- and nanoemulsions under gravity, with a separation efficiency and flux up to 99.999 % and 1695 L m-2  h-1 , respectively. The membranes also retained the emulsion separation ability after sandpaper abrasion. These features demonstrate a practical technology for emulsion separation.