Bio-inspired mineral-hydrogel hybrid coating on hydrophobic PVDF membrane boosting oil/water emulsion separation

Membrane fouling is one of the difficult challenges that restrict the efficient application of membrane separation technology in oil/water separations. Hydrogel with strong hydration capability has been considered as an ideal material for preparing anti-oil-fouling coating for membranes. Although some hydrogel-based coatings have been developed for the membrane interface hydrophilization modification, controlling the morphology of gel layers and improving the flux of hydrogel coated membranes remains a difficult matter to resolve. In this study, we elegantly designed a new mineral-hydrogel coating with nanostructures to modify hydrophobic polyvinylidene fluoride (PVDF) microfiltration membranes by an alternate quaternary soaking strategy. Compared with the merely hydrogel-coated membrane, the pure water flux of novel mineral-hydrogel coating membrane increased by 214% and the permeation increased by 127% with the oil rejection rate of 99.6% at 0.4 bar. Most importantly, the newly-built mineral-hydrogel layer on porous support possessed excellent hydrophilicity, underwater super-oleophobic properties and superior anti-oil-fouling performance, which is greatly promising in oily sewage remediation. In addition, this mineral-hydrogel coating could also be constructed on other hydrophobic substrates successfully, such as commercial melamine resin. Our facile strategy for designing and constructing synergetic mineral-hydrogel architecture may also inspire other functional coatings with nanostructures.