One-step rapid co-deposition of oxidant induced mussel-polyphenol coating on PVDF substrate for separating oily water

Inspired by mussels and plant polyphenols, surface-coated membranes for oil-in-water emulsion separation have attracted extensive attention recently. Here, a one-step rapid co-deposition strategy was proposed to fabricate membranes for separating oily water by oxidation reaction of tannic acid and polydopamine. The polyphenol cross-linked network was formed and quickly co-deposited on the surface of polyvinylidene difluoride (PVDF) membrane. The developed hydrophilic membrane was able to efficiently separate different oil-in-water emulsions. FTIR-ATR, XPS and SEM characterization methods were used to investigate the chemical composition and surface morphology of the modified membranes. Water contact angle, underwater oil contact angle, emulsion permeability, and oil rejection were measured. The experimental results showed that the permeability of pure water and the isooctane-in-water emulsion using PVDF-0.1/0.4/0.2 membrane were 15,713 L∙m −2 ∙h −1 ∙bar −1 and 14,552 L∙m −2 ∙h −1 ∙bar −1 , respectively. The oil rejection reached 99.3%. After five cycles, the initial permeability and the oil rejection were 12,849 L∙m −2 ∙h −1 ∙bar −1 and 98.6%, respectively. The developed PVDF-0.1/0.4/0.2 membrane still maintained excellent underwater oleophobicity after being treated in acid, base and salt solutions for 30 days. Furthermore, the time for membrane fabrication was shortened to only 1 h. The proposed membrane modification strategy would have potential application prospects in the efficient separation of oily wastewater.