Simply Prepared, Wood‐Based Solar Evaporators for Highly Effective Oily Wastewater Purification

Oily wastewater has been causing serious water environment pollution and greatly affecting the safety of drinking water. Compared with superwettable oil‐water separation membrane technology, solar‐driven evaporators based on specific wettability can effectively remove not only oil but also ions, dyes, and other substances from wastewater. We report a longitudinally cut, porous, and wood‐based evaporator that exhibits superhydrophilic and underwater superoleophobic properties. By collaborating hydrophilic and oleophobic wettability, high porosity and the structural anisotropy of wood, the solar evaporators effectively remove different oils from oily emulsions. Separation efficiency of surfactant‐containing crude oil‐in‐water, peanut oil‐in‐water, silicone oil‐in‐water, diesel oil‐in‐water, and n‐dodecane‐in‐water emulsions can reach up to 99.57%, 99.1%, 99.86%, 99.75%, and 99.28%, respectively. The rate of evaporation increased by 1.83 times to 1.63 kg m −2 h −1 compared with the radially‐cut wood‐based evaporator. Meanwhile, it is also capable of purifying heavy metal ions, dyes, and acid‐base solution. This easily prepared and accessible solar evaporator provides a viable idea for obtaining pure water from oily wastewater treatment.