Clay/carbon composite aerogels for effective solar-driven water desalination and treatment

Solar-driven interfacial evaporation (SDIE) is emerging as a promising pathway to mitigate the global freshwater crisis by harnessing renewable solar energy for desalination and wastewater treatment. However, the high-cost evaporators with limited evaporation performance and complex preparation have curtailed the widespread application of SDIE technology. Here, we designed and fabricated clay/carbon composite aerogels that were easily compatible with various carbon-based photothermal materials (including multi-walled carbon nanotubes (MWCNTs), carbon black, graphite, and graphene) for effective SDIE. Clay served as the structural framework of aerogels and dispersant of photothermal materials. The black carbon-based photothermal materials increased solar absorption performance of aerogels. All of as-obtained clay/carbon composite aerogels exhibited porous monolithic structure, great hydrophilicity, high solar light absorbance, and outstanding mechanical strength. The evaporation enthalpy of water was significantly decreased in the presence of clay/carbon composite aerogels. Under 1.0 sun irradiation, the clay/MWCNT composite aerogels displayed a high evaporation rate of 2.53 kg m-2 h-1 and a photothermal conversion efficiency of 96.7 % in 3.5 wt% saline water. The clay/MWCNT composite aerogels also maintained high evaporation performance across diverse environments and over ten evaporation cycles. In addition, the clay/MWCNT composite aerogel showed excellent purification performance for seawater and dye wastewater. The purified water produced by SDIE using clay/MWCNT composite aerogel met the drinking standard of World Health Organization. These findings provided a promising strategy for developing the effective and low-cost solar driven evaporators with the broad applications in both desalination and wastewater treatment.