Superwetting Porous Materials for Wastewater Treatment: from Immiscible Oil/Water Mixture to Emulsion Separation

Recently, large quantities of oily wastewater discharged from our daily life and industries have caused serious environmental problems. In addition, frequent oil spill accidents occurred all over the world have also lead to a waste of precious resources. Oil/water separation has become a worldwide challenge for us to overcome. Nowadays, superwetting materials have attracted considerable attention. Among them, porous materials with special wettability are more popular since this kind of materials is easy to fabricate, cost saving and time saving. Moreover, by combining the design of special wettability with the proper pore size, the porous materials could achieve the separation of sundry oil/water mixtures including immiscible oil/water mixtures and stabilized emulsions. In this review, we summarized two types of superwetting porous materials for immiscible oil/water mixtures separation and emulsion separation: water blocking porous materials with superhydrophobic/superoleophilic wettability and oil blocking porous materials with superhydrophilic/underwater superoleophobic wettability. In each type, we introduce the mechanism, fabricating process, effects of oily wastewater treatment and the representative works in detail. Moreover, the smart controllable superwetting porous materials and the wastewater treatment of other pollutants are also introduced briefly. Two types of superwetting porous materials for oil/water separation and emulsion separation are summarized in this review: water blocking porous materials with superhydrophobic/superoleophilic wettability and oil blocking porous materials with superhydrophilic/underwater superoleophobic wettability. Through combining the special wettability with proper porous substrates, these superwetting materials are able to achieve both the immiscible oil/water separation and emulsion separation. The design, fabricating process, effects of oily wastewater treatment and the representative works are introduced in detail.