Lignin‐based Hydrogel: Mechanism, Properties, and Applications

Hydrogels have attracted attention due to their tunable properties, which make them applicable in many fields, such as wastewater treatment, drug delivery, wound dressing, agriculture, and energy storage materials. Lignin, as the second largest abundant renewable aromatic resource, could be incorporated into the hydrogel matrix for endowing versatile functions, such as high-water absorption capability, good mechanical strength, and UV-shielding performance. This chapter focuses on the production approaches and applications of lignin-based hydrogels and the future perspective of lignin-based hydrogels. In addition, the function of lignin in lignin-based hydrogels was discussed comprehensively. Generally, the poly phenol structure of lignin enables various properties, such as anti-UV blocking, antimicrobial, and antioxidative, facilitating the application of lignin-containing hydrogels in dye and heavy metal removals, drug carrier, wound dressing, watering plants, and energy storage. Finally, the prospect for the future development of lignin-based hydrogel was elaborated.