Tunicate-inspired polyvinylidene fluoride (PVDF) membrane with a robust nanoarmor for corrosive emulsion separation

Bioinspired multifunctional polyphenols coatings have been widely applied in the field of oily sewage treatment. However, shortcomings, such as lengthy reaction times and poor stability, hinder large-scale applications of these coatings. Herein, a tunicate-inspired polyphenol-mediated ultrafast biomimetic mineralization strategy was proposed to ingeniously integrate prominent oil resistance, excellent chemical stability, and satisfactory durability in combination with the construction of robust nanoarmors on polyvinylidene fluoride (PVDF) membranes. Poly-gallic acid (PGA) adhesive coatings and TiO 2 nanoparticles are uniformly integrated to construct nanoarmors via stable coordination interactions between titanium and carboxylate groups and the chelation of metal ions and polyphenols. The presence of nanoarmors not only reinforced the stability of the PGA adhesive coatings but also created a reliable oil-repellent barrier on the PVDF membrane surface with almost no oil adhesion (able to resist crude oil pollution). The innermost PGA adhesive coatings strongly adhered to the PVDF membrane substrates and functioned as a “primer” layer for biomimetic mineralization. The outermost TiO 2 nanoparticles can form a firm hydration layer, endowing the PVDF membranes with excellent oil resistance even under harsh corrosive environments (1 M HCl, 1 M NaOH, and 2 M NaCl). In addition to neutral emulsions, the as-prepared membrane can also separate oil-in-corrosive water emulsions, including salty, acidic (pH = 1), and alkaline (pH = 13) sewage, with a permeate flux higher than 3200 L m −2  h −1  bar −1 and an oil rejection ratio above 99.1 %. Therefore, tunicate-inspired PVDF membranes have broad application prospects in resource recycling and aquatic environment protection.