Superhydrophobic-superoleophilic biochar-based foam for high-efficiency and repeatable oil-water separation

Highlights: • Ball-milled biochar was applied for the hydrophobic modification of foam (MF). • The superhydrophobic-superoleophilic BMBC@MF displayed excellent oil absorption capacities. • BMBC@MF could maintain high hydrophobicity and adsorption stability in a wide pH range. • BM biochar was loaded on the surface of MF through functional groups. • BMBC@MF exhibited superior pressure resistance and recyclability in the cleanup of oil pollutants. Leakage accidents occurring during oil production and transportation are currently one of the most serious environmental problems worldwide. Developing efficient and environmentally friendly oil-water separation methods is the key to solve this problem. In this work, a facile method to fabricate a high-performance oil absorbent through the loading of ball-milled biochar (BMBC) and octadecylamine on the skeleton of melamine foam (MF) is reported. The resulting ball-milled biochar-based MF (BMBC@MF) displayed a complex three-dimensional porous structure. The BM biochar on the surface of BMBC@MF forms nano/μm-scale folds, which reduced the surface energy of BMBC@MF after grafted octadecylamine. These structures resulted in the conversion of the hydrophilic surface of MF to hydrophobic surface. These characteristics made the modified foam an excellent oil absorbent with a high oil absorption capacity (43–155 times its own weight) and extraordinary recyclability. Furthermore, the BMBC@MF could maintain high hydrophobicity and adsorption stability in a wide pH range (from 1 to 11). More importantly, BM biochar is a cheap and readily available material to make BMBC@MF possible for large-scale production. Therefore, this work provides an effective way for low-cost, environmentally friendly, and large-scale production of superhydrophobic adsorbents for oil-water separation.