Simultaneous solar-driven seawater desalination and continuous oil recovery

Abstract

Oil spills and freshwater scarcity remain two worldwide challenging issues. Emerging efforts have been made either to recover oil from oil/water mixture or to extract freshwater from abundant seawater. However, almost all current devices focus on oil recovery or seawater desalination separately, which is lack of energy efficiency. Herein, we propose a design of mechanically robust, bi-functional graphene devices (BGDs), containing vertical graphene sheets decorated on inverted U-shaped graphene monoliths, to achieve simultaneous solar-driven vapor generation and continuous oil recovery from oil-contaminated seawater. Benefiting from the unique wettability design of the BGDs, water evaporates on the hydrophilic surfaces, and meanwhile oil can be spontaneously recovered through the hydrophobic/oleophilic interior channels due to siphon action. Moreover, the strong photothermal effect of vertical graphene can boost both the seawater desalination and oil recovery performance. As a result, a vapor generation rate of 2.04 kg m−2 h−1 and an oil recovery rate of 105.8 L m−2 h−1 are concurrently achieved under 1-sun irradiation. The design of bi-functional devices provides a new means to maximize the utilization of solar power and reduce the costs for multi-functional practical environmental engineering applications.