All-water-based superhydrophobic coating with reversible wettability for oil-water separation and wastewater purification

Superhydrophobic surfaces with reversible switchable wettability have great application value in the treatment of oily wastewater. However, the advancement of switchable wettability surfaces is limited by the complexity of the manufacturing process and the excessive use of environmentally unfriendly solvents. Herein, an all-water-based reversible wettability coating was fabricated by simply spraying a water suspension consisting of N-[3-(trimethoxysilyl) propyl] ethylenediamine (AS)-, 3-(trimethoxysilyl) propyl methacrylate (KH-570)-, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS)-modified titanium dioxide (TiO 2 ) nanoparticles and cellulose . The coating possesses good adhesion with various substrates and exhibits stable mechanical and chemical stability as well as good resistance to harsh environments such as various organic solvents , strongly corrosive environments and extreme temperature environments. The coating can be switched between having superhydrophobicity (160°) and superhydrophilicity under UV irradiation and heating treatment. The coated cotton fabric can separate heavy/light oil-water mixtures and water-in-oil/oil-in-water emulsions with a high efficiency of greater than 95%. Due to the photocatalytic properties of TiO 2 , the coating can degrade soluble pollutants in water during UV irradiation, and the degradation efficiency is over 97%. This study provides a green industrial route for designing a simple, switchable wettability coating, which is expected to promote the large-scale industrial production and application of functional smart surfaces.