Cost-Effective, Facile Preparation of Self-Floating Hydrogel Foam for Efficient Solar-Driven Interfacial Evaporation and Wastewater Purification

Polymeric hydrogels have been identified as a highly hopeful material in solar-driven interfacial evaporation (SIE) systems for freshwater production, but high materials cost and easy scale-up have hindered their industrialization process. In this research, a cost-effective, self-floating, sponge-like hydrogel foam evaporator was developed through a straightforward and scalable foaming-cross-linking-freezing strategy. This hydrogel foam evaporator exhibits ultralightweight characteristics and robust mechanical strength while maintaining its intrinsic hydrophilicity. By employing low-cost raw materials and fabrication techniques, the production cost of the device was reduced to $3.6 per square meter, achieving a high evaporation rate and energy efficiency of approximately 85%. Furthermore, the hydrogel foam evaporator demonstrated the capability of binding heavy metals and organic contaminants, enabling efficient removal of these pollutants from contaminated water. Owing to these advantages, this simply fabricated evaporator holds substantial potential for advancing low-cost solar-driven evaporation technologies, with promising applications in potable water generation, heavy metal ion adsorption, and wastewater purification.