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

Abstract

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 (FeIII) 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 (7092Lm−2h−1bar−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 15min and the underwater superoleophobicity was well maintained even after rigorous long-term washing operation. More importantly, both the remaining solutions of TA and FeIII 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.