Halloysite nanotube-based superhydrophobic foam for highly efficient oil/water separation

Oil/water separation is a worldwide concern because of the emissions of oil contaminated wastewater and increasing number of oil spill accidents in recent years. Materials with superhydrophobicity and superoleophilicity provide a new strategy to solve such problems, which allow organic solvents to pass through freely while repelling water. Herein, the porous foams with superhydrophobicity and superoleophilicity were prepared successfully through a facile low-temperature sintering method, in which the halloysite nanotubes (HNTs), polyvinylidene fluoride (PVDF) and sodium chloride were used as the raw materials. Among them, HNTs constructed the rough surface in micro-/nano-scale and sodium chloride served as the sacrifice template. The superhydrophobic surface was achieved via the synergistic effect between the rough surface and PVDF with the low surface energy. The foam showed good water repellency (water contact angle, CA: 156.0 ± 0.1°) and superoleophilic properties, which could selectively absorb organic solvents from the mixture solution with water. Moreover, the foam exhibited high separation efficiencies for a variety of oil/water mixed solutions with excellent cycling stability, which make it a promising material for practical oil/water separation.