Gelatin-tannic acid coating for high flux oil-water separation

Special wettability material with super-hydrophilicity/underwater super-oleophobicity is one of the best materials for treating oily wastewater, developing an urgent demand for simple, green, low cost, and efficient in practical application. Both gelatin and tannic acid are natural and low-cost renewable resources. In this study, gelatin-tannic acid coating(FOGE-TA) that can be applied to different substrates was prepared by a simple and green dip-coating method using the film-forming properties of gelatin as well as the hydrophobic interactions and hydrogen-bonding interaction between gelatin and tannic acid. The coating can be applied to different substrates such as glass, PP melt-blown nonwoven fabric, copper mesh, and stainless steel mesh. After dipping FOGE-TA, the underwater oil contact angle of the mesh surface all reach over 150 °, and the water contact angle is 0 °. Among them, the prepared gelatin-tannic acid-coated stainless steel mesh(FOGE-TA-4 L-SSM) has a high water flux of over 1.74 × 105 L∙m-2∙h-1 and separation efficiency of over 99.0% for oil/water separation. Due to its excellent oil repellency only needs to be soaked and rinsed with deionized water when the flux decays to continue the oil-water separation. After 90 separations, the water flux and separation efficiency did not significantly decrease. In addition, the FOGE-TA-SSM has good stability in salt solutions and an acidic environment, making it an ideal material for solving oil-water separation problems.