Robust Superhydrophobic/Superoleophilic Filter Paper with TiO2 Nanoparticles for Separating Oil–Water Mixtures and Surfactant-Stabilized Water–Oil Emulsions

Superwetting materials for oil–water separation have attracted increasing research attention recently. Developing cost-effective and high-efficiency filter materials to separate oil–water mixtures and stable water–oil emulsions is challenging. Herein, the TiO2 nanoparticles were first hydrophobically modified using γ-aminopropyltriethoxysilane, and then polydimethylsiloxane was subsequently added to obtain a stable superhydrophobic coating. The superhydrophobic filter paper was obtained via roll coating. The water contact angle on the coated filter paper exceeded 152°, and the oil droplets were quickly absorbed by the coated filter paper. The superhydrophobic filter paper was used for separating various immiscible oil–water emulsions, with separation efficiencies of >99.5%. In addition, the synthesized filter paper can effectively separate various surfactant-stabilized water–oil emulsions. The separation efficiency was satisfactory even after 10 cycles. When the volume ratio of water in water–oil emulsions reached 20%, the separation efficiency exceeded 97.5%. The results indicate that the superhydrophobic/superoleophilic filter paper exhibits satisfactory oil–water separation ability and is environmentally friendly, cost effective, and easy to implement, making it suitable for continuous industrial production.