Rational Design of Biomass-Derived Composite Aerogels for Solar-Driven Seawater Desalination and Sewage Treatment

To combat the water crisis, on-site reclamation of freshwater from seawater and sewage is urgently desired, in which solar-driven interfacial evaporation has been recognized as an emerging strategy. However, potentially costly fabrication, salt accumulation, and contaminant influence still hinder the real-world application of solar–thermal evaporators. Herein, a biomass-derived composite aerogel is constructed through the Schiff base reaction of chitosan and polyethylenimine and freeze assembly and further loaded with CuS/rGO nanoheterostructures via a spray stacking strategy. Because of the reverse transport of vertical-channel arrays, the lower part enables excellent salt-resistant properties during long-term desalination in parallel to upward water supply. The upper part promotes the thermal localization by controlling the spatial distribution of CuS/rGO, providing high solar spectrum absorption for efficient water evaporation. Notably, the composite aerogel exhibits great superiority in sewage treatment benefiting from its adsorption and photocatalytic capabilities, thus harvesting freshwater resources that meet drinking water standards. The rational design of this cost-effective evaporator may inspire new paradigms for boosting the combination of solar–thermal utilization and freshwater access.