Tannin-Based Spontaneous Adhesion Superhydrophilic Coatings for Efficient Oil-in-Water Emulsion Separation and Dye Removal

It is significant to explore green, convenient, and widelyapplicable superhydrophilic coatings. This study proposes a strategy of usingcovalent cross-linking of tannic acid and tetrabutyl titanate to prepare asuperhydrophilic coating, which can be simply applied on the porous substratesurface by vacuumfiltration and immersion without additional binders. Thesurfaces modified by coatings get intriguing superhydrophilicity and underwatersuperoleophobicity due to the synergistic effect of the high roughness andhydrophilic polyphenols. A permeationflux of up to 5663.57 L m-2h-1bar-1with afiltrate total organic carbon content of only 41.95 ppm is obtained under0.1 bar. The modified membranes also exhibit efficient purification of dyesolutions and mixed wastewaters, with absorbance reductions of up to 99.4%. Inaddition, stability tests prove the coatings to be acid- and alkali-resistant as wellas mechanically robust. The surface modification method developed in thiswork can be easily extended to various materials for industrial wastewatertreatment