Lignocellulose-based hydrogels for environmental remediation: Structure-function relationships, adsorption mechanism, and pathways towards sustainable water treatment

Lignocellulosic biomass has emerged as a promising platform for developing sustainable hydrogel adsorbents for water treatment applications. Owing to their three-dimensional network structures, tunable surface chemistry, and high swelling capacity, lignocellulosic hydrogels represent viable alternatives to conventional adsorbents. This review critically examines how biomass composition, cross-linking strategies, and hydrogel network architectures influence the structure–property relationships governing the adsorption of organic and inorganic pollutants from water. Particular emphasis is placed on physical, chemical, and hybrid cross-linking approaches, as well as the effects of processing conditions on the mechanical properties, sustainability, and functional group accessibility of hydrogels. In addition, the adsorption mechanisms of lignocellulosic hydrogels are systematically discussed, including ion exchange, surface complexation, hydrogen bonding, hydrophobic interactions, and π–π stacking interactions enabled by lignin incorporation. Reported adsorption capacities range from moderate (∼50 mg g⁻¹) to exceptionally high (>3000 mg g⁻¹), depending on functionalization and operating conditions. Overall, chemically and hybrid cross-linked hydrogels generally outperform physically cross-linked systems, while lignocellulose-based hydrogels provide enhanced mechanical strength and tunable functionality. Moreover, hydrogels from lignocellulose possess immense potential to design functional high-performance adsorbents via tailored surface engineering. The results indicate the increasing significance of hydrogels from lignocellulosic sources due to their scalability, eco-friendliness, and tunability for next-generation wastewater treatment technologies.