Tea waste biochar hydrogel evaporator with high salt − resistance for highly efficient solar interfacial evaporation

Solar-driven interfacial evaporation (SDIE) is considered to be one of the most promising strategies to solve the global freshwater shortage. However, the high cost of photothermal materials, the complex manufacturing process of evaporators, and low water evaporation rates and evaporation efficiency limit their practical application. In this study, a biochar-deduced porous hydrogel (TBC-PH) based on tea waste as a raw material was prepared as an efficient solar-driven interfacial evaporator using a simple cross-linking foaming method. The evaporator exhibits good light absorption, hydrophilicity and excellent salt resistance for efficient solar evaporation. Its interconnected porous structure enhances capillary action and enables rapid water transport while effectively preventing salt crystallization. Under one solar intensity, the water evaporation rate of 3.268 kg m −2 h −1 and the solar-to-vapor conversion efficiency of 95.14 % were achieved. Besides, TBC-PH exhibits obvious purification effect on seawater and organic dye wastewater. The evaporator’s utilization of waste biomass is not only simple and economical, but also advances the practical application of waste management while addressing water scarcity, highlighting its potential as an efficient and sustainable solution for SDIE applications.