Fully waste-based solar evaporator in interfacial solar-driven seawater desalination

The scarcity of freshwater resources and the increasing demand for sustainable water treatment technologies have prompted the development of interfacial solar-driven seawater desalination (ISSD). However, designing stable solar evaporators to alleviate freshwater scarcity and reduce environmental stress remains a significant challenge. This study presents a solar evaporator from waste materials to address these challenges. The device comprises a photothermal membrane (CLPM) made from cattail leaf-based fibers (CLF) and cattail leaf-based carbon (CLC) with a simple crosslinking method using sodium alginate and CaCl2, a waste humidifier filter (WHF), and discarded packaging foam. The CLPM exhibits approximately 96 % solar absorption, achieving an evaporation rate of 1.38 kg m-2 h-1 when treating groundwater and 1.22 kg m-2 h-1 when desalinating a 3.5 wt % NaCl solution. The desalination performance of CLPM can be stable for 6 h due to the sufficient water provided by the WHF with vertical water conductivity channels. The desalination performance of CLPM can be restored by washing off the accumulated salts in a 3.5 wt % NaCl solution or by self-cleaning overnight, as verified by indoor and outdoor cycling experiments. 1 m2 of CLPM can produce approximately 5.3 kg of freshwater during the daytime, sufficient to meet two adults' daily water consumption needs. This waste-derived solar evaporator promotes the efficient utilization of waste materials and offers a sustainable solution to address freshwater scarcity while reducing environmental impact.