Janus structured 3D PVA/rGO hydrogel evaporator for highly efficient desalination, salt collection and oil-water separation

Abstract

The study proposed a Janus-structure PVA/rGO hydrogel solar-driven evaporation system to achieve highly efficient desalination and wastewater reuse, to alleviate the increasingly serious freshwater shortage and pollution. To further explore the evaporation potential, the evaporator was systematically optimized in terms of material composition and structural design to improve light absorption and photothermal conversion, reduce evaporation enthalpy, increase evaporation interface, facilitate vapor escape, and enhance environmental energy harvesting. Accordingly, the evaporation rate of the optimized evaporator reaches 3.71 kg m⁻² h⁻¹. The mushroom-shaped Janus structure allows for localized preferential salt crystallization and provides additional heating for sidewall evaporation, preventing salt fouling at the evaporation interface in the desalination process. The superhydrophilic-oleophobic treatment of the underwater supply channels provides efficient oil-water separation and wastewater purification during solar evaporation. In addition, the Janus-structure evaporator exhibits good work performance in acidic, alkaline and organic solutions, possesses excellent long-term operational stability and environmental adaptability, and demonstrates good economics. The work will provide new inspiration for researchers to design and fabricate high-efficiency 3D solar evaporators for desalination and wastewater purification to harvest freshwater resources.