Highly Efficient, Salt-Resistant, and Chemically Durable Solar Evaporator for the Purification of Industrial High-Salinity Wastewater

Abstract

Solar interfacial evaporation is a promising technology for producing clean freshwater from brine or wastewater with a minimal carbon footprint. However, its application is limited by its poor salt and oil resistance and chemical durability. In this work, a superhydrophobic/superhydrophilic solar interfacial evaporator (SS-SIE) comprising a superhydrophobic top coated with carbon nanotubes is designed for absorbing light, a superhydrophilic bottom for pumping water, and resisting insoluble organic matter. Owing to this unique structure, salt deposition is confined to the superhydrophilic part, thereby ensuring the long-term stability of the SS-SIE for sustained (>100 h) solar evaporation in saturated brine, which is record-breaking for salt-resistant solar evaporators. Moreover, the chemical durability and oil resistance of the SS-SIE are demonstrated. With these excellent properties, the SS-SIE enables stable evaporation in industrial high-salinity wastewater characterized by strong alkalinity, high salinity, and high organic content under 1 sun irradiation over 7 days. Notably, purified water can be directly used for cultivating plants without causing any toxic effects on their growth. Therefore, SS-SIE provides an alternative, environmentally friendly, and efficient pathway for purifying industrial high-salinity wastewater and broadening the range of solar evaporation applications.