A green starch-based aerogel prepared by enhanced microwave freeze-drying for solar interfacial evaporation

A starch-based aerogel was prepared through freeze-drying for solar interfacial evaporation (SIE). Attapulgite was used as the framework, and polydopamine-modified carbon black was used as the photothermal material. The freeze-drying process was enhanced using directional freezing to improve mass transfer and lossy material-aided microwave heating to improve heat transfer. Meanwhile, a multiphase transport model coupling mass and heat transfer equations with Maxwell’s equation was formulated and numerically solved. The enhanced freeze-drying achieved a 55.6% reduction in drying time compared with conventional freeze-drying. The simulation results showed excellent agreements between numerical and experimental drying curves. The SIE results displayed that the prepared aerogel had 1.93 kg·m−2·h−1 of evaporation rate and 94.1% of light-evaporation conversion efficiency for pure water. The aerogel maintained 96.7% of initial evaporation rate for 3.5% modeled brine after 20 cycles. This work is expected to provide a sustainable and economical approach to the desalination.