PDMS mesh with reversible super-wettability for oil/water separation

Frequently-occurring oil spills and wastewater discharge pose great threats to ecological environment and economy. Although various extreme wettability materials have been designed for separations of oil/water mixtures, most of them tend to involve toxic chemical reagents, thus resulting in second pollution to the environment. This paper develops polydimethylsiloxane (PDMS) meshes with excellent chemical stability, reversible super-wettability and good reusability for efficient gravity-driven oil/water separation. Superhydrophobic PDMS meshes can be fabricated by directly constructing microstructures via laser-textured aluminum sheet templates, and heavy oils/water mixtures can thus be separated. After treated by atmospheric-pressure plasma jet for just 2 mins, the superhydrophobic PDMS meshes become superhydrophilic-underwater-superoleophobic, and separation of light oils/water mixtures can be thereby achieved. More interestingly, the plasma-treated superhydrophilic meshes can recover to be superhydrophobic by heating under 80 °C for 20 mins. Therefore, PDMS meshes with reversible super-wettability can be efficiently prepared, and the separation efficiencies for various heavy/light oils and water mixtures are all above 96%. In addition, the prepared PDMS meshes show excellent separation ability under harsh conditions including hot water, acidic and salty conditions, having great application potential in oil/water separation field.