Leaf-structure-inspired photothermal evaporator for versatile oily wastewater purification

Wastewater containing organic pollutants, such as emulsion, soluble organic sewage, oily seawater, and acid/alkali corrosive sewage, poses a grand challenge to the existing membrane separation technology for obtaining freshwater. Inspired by leaf structure, here we report a carbon felt/poly(vinyl alcohol) (PVA) solar-driven device to separate versatile oily wastewater. This evaporator exhibits superior full-spectrum solar energy absorption (88%) and steady vapor release capacity (1.3–1.4 kg m−2 h−1) under 1.0 sun irradiation. The carbon felt/PVA foam with strong underwater superoleophobicity cannot only achieve efficient separation of oil-in-water but also purify extra high oil/water ratio emulsion directly with high efficiency of 99.99%. It is noteworthy, for seawater-emulsion and water-soluble organic sewage, that the purification efficiency of carbon felt/PVA foam can exceed 99.86%. More importantly, strong acid and alkali water do not affect the operation of carbon felt/PVA foam. This work provides a feasible method to purify versatile wastewater in a harsh environment.