A multifunctional biomass-derived three-dimensional solar evaporator constructed from wasted herbal medical slag for efficient steam generation and water purification.

Solar-driven desalination and wastewater purification represent sustainable approaches for clean freshwater production. However, process scalability is limited by insufficient sterilization, complicated fabrication procedures, and poor mechanical stability. In this study, a multi-functional hydrogel-supported solar (MHS) evaporator is proposed that incorporates carbonized Chinese herbal medicine residues in a sodium alginate (SA) gel matrix fabricated using a scalable and cost-effective procedure. The MHS evaporator achieved a water evaporation rate of 2.69 kg m-2 h-1 with an efficiency of 97.7% under one-sun irradiation, demonstrating superior sterilization performance and mechanical durability. Furthermore, the MHS delivers effective seawater desalination and wastewater purification, reducing ionic contaminants by three orders of magnitude while achieving greater than 99% removal of organic pollutants and heavy metals. The purified water exhibits enhanced purity, with greater than 99% elimination of pathogens (E. coli and S. aureus), ensuring viable control of biological contamination during the desalination process. In addition, the MHS evaporator maintained consistent and stable performance over a 30-day period. By incorporating superior sterilization, salt resistance, efficient photothermal conversion, and a high degree of mechanical strength in a scalable design, the MHS evaporator represents a highly promising solution to address freshwater scarcity in resource-limited environments.