Robust Sustainable Interfacial Evaporators from Lignin for Wastewater Treatment

Abstract 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.