Underwater superoleophobic mesh with transformable micro-nano structure for ultrafast oil/water separation

Abstract

Oil/water separation with superwetting mesh is an emerging method for removing oil from wastewater, but the adopted meshes at present are not reliable in practical applications due to their poor pressure-bearing capacity. A TiO2-deposited and coated mesh (TDCM) with underwater superoleophobicity and transformable micro-nano structure is reported to separate oil/water mixtures with efficiencies >99%. Due to the compactness of deposited porous TiO2 aggregates triggered by pressure, the TDCM can bear applied pressures of ≥12.6 kPa dependent on oil types and achieve ultrafast water transportation driven by retentate accumulation or other applied pressure without oil breaking through. The feature of the pressure-induced surface structure transformation will not damage the surface wettability and oil/water separation performance of the TDCM and is demonstrated effectively in mitigating the theoretical trade-off between water flux and pressure-bearing capacity. Furthermore, the TDCM has good self-cleaning performances for particulate and organic pollutants before and after surface structure transformation with the aid of oil and ultraviolet illumination. As a novel mesh for oil/water separation, the TDCM shows great potential in real applications and provides a brand-new perspective of developing advanced materials for oil removal from water in complicated situations.