Lignin sulfonate-Fe3+ initiated dynamic redox reaction endows ultrafast gelation of porous hydrogel evaporator with excellent seawater desalination performance

Bio-based hydrogels have emerged as a promising and attractive platform in solar-driven interfacial evaporation (SDIE) due to their excellent biocompatibility, super absorption capacity to water, and ability to reduce water evaporation enthalpy. However, the currently reported bio-based hydrogels are generally prepared via a long-time external energy input process, thereby limiting their large-scale application. Herein, the regenerable lignin sulfonate, rich in hydrophilic sulfonate groups and light-absorbing phenolic hydroxyls, is chelated with Fe 3+ to establish a dynamic redox system. This autocatalytic system facilitates the rapid decomposition of potassium persulfate (KPS) to generate abundant free radicals for catalyzing acrylic acid polymerized into hydrogel within 3 min. The incorporation of SLS significantly improves the light absorption properties of hydrogels, along with a decrease in water evaporation enthalpy. Notably, the prepared hydrogel evaporator effectively prevents salt accumulation during the evaporation process, which maintains an evaporation rate of 2.11 kg m −2  h −1 even after 20-cycle evaporation tests. Finally, the prepared hydrogel evaporator could effectively remove pollutants and primary metal ions from wastewater to generate freshwater, and show reliability and stability for long-term desalination. This work would provide an efficient and convenient strategy for the continuous generation of freshwater using a lignin-based solar-driven interfacial evaporator.