Facile Preparation of Hydrophobic Melamine Sponges using Naturally Derived Urushiol for Efficient Oil/Water Separation

In this work, hydrophobic sponges for highly efficient oil/water separation and oil absorption were fabricated by a simple, eco-friendly, economical, and scalable dip-coating of hydrophilic melamine sponges in urushiol (a naturally occurring small compound) solution. Because of the unique catechol group and a long alkyl side chain with unsaturated double bonds, urushiol molecules easily adhered on the sponge wall surface and selfpolymerized to form a thin hydrophobic coating layer with the assistance of heat treatment. The urushiol-modified melamine sponge (UMS) displayed a water contact angle of similar to 139 degrees and a 3D highly porous structure, so it could effectively separate oil from dynamic oil/water mixtures. The separation flux of n-hexane from an n-hexane/water mixture was as high as 18,356 +/- 2200 L.m(-2).h(-1).bar(-1). It could quickly absorb various oils and common organic solvents with an absorption capacity of up to 181 g.g(-1) and had excellent recyclability. UMS also displayed robust mechanical stability, flexibility, elasticity, and thermal stability. Therefore, the facile preparation process, low cost, and superior oil separation/absorption would endow UMS with high potential when dealing with oily wastewater.