Carnauba Wax‐Assisted Preparation of Eco‐Friendly Aerogels by the Ambient Pressure Drying Method and their Applications for Photothermal Evaporation and Dye Wastewater Treatment

Abstract In this study, a new, eco‐friendly, and efficient method to prepare aerogels using nonchemically cross‐linked agar gels is described. This new process could eventually facilitate the rapid, continuous, and large‐scale production of porous and lightweight materials, as it does not require freeze‐drying, supercritical drying, or environmentally harmful crosslinking chemicals. The reported preparation process relies entirely on targeted freezing, solvent exchange, and the ambient pressure drying of agar gels. The obtained results revealed that biomass aerogels with good shapes can be obtained by simple directional freezing and that the introduction of carnauba wax solutes can maintain a highly porous structure throughout the process. The directionally grown anisotropic gels with excellent void space, anisotropic thermal conductivity, and excellent mechanical compression properties demonstrate immense potential for water treatment, controlled release of active compounds, thermal insulation, and catalysis. PDA‐loaded aerogels exhibit excellent performance for photothermal evaporation and dye wastewater treatment, with high evaporation rates and photothermal efficiencies of 2.83 kg m −2 h −1 and 92.27%, respectively, and a dye removal efficiency of 94.5%. Hence, these aerogels demonstrate immense potential for applications in water treatment.