Robust Sustainable Interfacial Evaporators from Lignin for Wastewater Treatment

Solar-driven interfacial evaporation technology has emerged as a promising solution for heavy metal-containing wastewater treatment, owing to its environmentally friendly and sustainable energy input advantages. However, the development of low-cost, high-efficiency photothermal agents with enhanced heavy-metal ion tolerance remains a significant challenge for advancing practical solar-powered wastewater treatment. Herein, we developed a series of metal-lignin composites, through a one-pot reaction involving lignin and heavy metal-contained wastewater, which demonstrated outstanding light-harvesting efficiency and photothermal conversion properties. The resulting metal-lignin composites can be efficiently fabricated into evaporators via 3D printing technology for wastewater treatment. The optimized evaporator achieves an exceptional water evaporation rate of 2.88 kg m^{- 2} h^-1 under 1-sun irradiation while demonstrating outstanding performance in both seawater and heavy metal-containing wastewater systems. Moreover, the evaporator exhibits no significant decline in evaporation rate during continuous wastewater treatment over 7 days, highlighting its exceptional durability and long-term stability. Finally, techno-economic analysis estimates the production cost of clean water by the evaporator at 0.372 $ m^{- 3}, below the industry average and even approaching the globally reported lowest threshold for reverse osmosis desalination. This work is believed to offer valuable insights into achieving cost-effective and highly efficient solar-driven wastewater purification technologies from lignin.