Tannin-inspired superhydrophilic and underwater superoleophobic polypropylene membrane for effective oil/water emulsions separation

In this work, a novel two-pot coating process that facilely transform polypropylene (PP) microfiltration membrane hydrophobicity into superhydrophilicity and underwater superoleophobicity was reported. Tannic acid (TA) and ferric ions (Fe-III) were selected as organic ligand and inorganic cross-linker, respectively. Compared with the membrane modified by the one-pot method, the two-pot treated substrate has uniformly distributed coatings, better wettability, higher water permeability (7092 Lm(-2) h(-1) bar(-1), which is 4.5 times higher than that of the one-pot modified membrane), and excellent oil/water emulsions separation performance. This treatment only took about 15 min and the underwater superoleophobicity was well maintained even after rigorous long-term washing operation. More importantly, both the remaining solutions of TA and Fe-III could be recycled and reused easily in the next two-pot coating process. Such a rapid, green, and cost-effective modification method highlights its potential for practical application in oil/water emulsions separation. (C) 2017 Elsevier B.V. All rights reserved.