Harnessing Lignin‐Derived Materials as Nature‐Based Solutions for Sustainable Water Treatment: From Structures, Functions, and Applications to Future Prospects

ABSTRACT Water treatment is critical for protecting human health, ensuring environmental sustainability, and efficiently utilizing limited freshwater resources. Effective treatment processes contribute to both the prevention of infectious diseases and the long‐term protection of ecosystems. Lignin, often considered an industrial byproduct, has emerged as a sustainable and innovative adsorbent for wastewater treatment due to its abundance, biodegradability, and nontoxicity. Its rich functional groups allow it to interact with a variety of contaminants, including heavy metals, dyes, and emerging pollutants. To further enhance removal efficiency, natural lignin is frequently modified through chemical or physical functionalization, creating materials with improved surface area, selectivity, and stability. This reflects lignin's versatility as a natural adsorbent, leading to a focus on modification strategies such as sulfonation, aminolation, and incorporation into composites or nanostructures. This review examines the applications of lignin‐based adsorbents in the removal of certain hazardous substances from water, along with recent methodological advances. Challenges such as variability in lignin structure and scalability of modified systems are also addressed. Overall, lignin offers a promising path toward cost‐effective, environmentally friendly, and effective wastewater treatment and offers future opportunities for advanced water treatment technologies.