Underwater superoleophobic biomaterial based on waste potato peels for simultaneous separation of oil/water mixtures and dye adsorption

Underwater superoleophilicity involves interactions between a solid surface and two immiscible liquids, viz., water and oils, in which water remains in the completely wetted and oils in the non-wetted state. Materials with underwater superoleophilicity have drawn significant interest due to their superior performance in selective separation of oil and organic solvents from an aqueous phase. However, the development of such materials with special wettability for water and oils are hindered by (1) complex fabrication process (2) long processing duration with high cost, and (3) use of environmentally unfriendly and expensive fluorochemicals to lower the surface energy. Herein, we demonstrate the use of waste potato peels (WPP) to fabricate simple, economical and eco-friendly materials with superhydrophilic (water contact angle ~ 0°) and underwater superoleophobic (oil contact angle > 150°) properties. Initially, powder of WPP was prepared and accumulated into a layer via a simple cleaning, smashing, one step inexpensive chemical treatment and stacking procedures. The developed WPP layer was efficient for the gravity-driven separation of various oil/water mixtures (including hexane, toluene, dodecylbenzene, and kerosene) and water-in-oil emulsions, with high efficiency (> 98%) in single unit operation. During the oil/water separation process, the WPP layer was also found to serve as an adsorbent material for efficient removal of various water-soluble dyes (methylene blue and rhodamine B, 50 mg L⁻¹) contaminants, simultaneously. Thus, the developed WPP layer is not only a good biomaterial for water remediation by the oil/water separation and dye adsorption simultaneously, but can also contribute in reducing environmental pollution and wastage.