Bioinspired fabrication of ZrO2 nanocomposite PVDF membranes with underwater superoleophobicity for oil/water separation

Membrane technologies have been extensively employed to separate and purify emulsified oily wastewater. However, the long-term performance of membranes is still restricted by oil fouling and their inability to function in severe conditions. Herein, ZrO₂ nanoparticles were deposited onto the poly(vinylidene fluoride) membrane surface using γ-aminopropyl triethoxysilane (KH550) as a coupling agent, as inspired by a biomimetic coating method of polydopamine (PDA). It has been determined that the distribution density of nanoparticles can be tuned by adjusting the KH550 and ZrO₂ concentrations. After coating the PDA and ZrO₂ layers, the nanocomposite membrane exhibits a high degree of hydrophilicity, underwater superoleophobicity, and anti-oil-fouling properties. This outstanding characteristic endows the membrane with an ultrahigh permeation flux of emulsion and a rejection ratio of over 99 % for a variety of oil/water emulsions. The flux recovery of the nanocomposite membrane remains at over 91 % after thirteen cyclic filtrations of emulsions. Moreover, the excellent surface wettability and oil/water separation properties of the nanocomposite membranes can be maintained under prolonged exposure to strong acid, alkali, and salt solutions.