Sustainable polysaccharide-based adsorbents for PFAS removal: Mechanisms, functional engineering, and future directions.

Per- and polyfluoroalkyl substances (PFAS), often described as "forever chemicals," continue to challenge water treatment technologies because of their exceptional chemical stability, tendency to accumulate in the environment, and resistance to conventional remediation processes. In recent years, naturally derived polysaccharides, such as cellulose, chitosan, starch, alginate, and cyclodextrins, have gained increasing attention as sustainable materials for PFAS removal. Beyond their environmental compatibility, these materials offer structural flexibility that allows PFAS to be captured through a combination of electrostatic attraction, hydrophobic interactions, hydrogen bonding, and physical entrapment within porous or cross-linked networks. This review brings together current understanding of how polysaccharide chemistry, material architecture, and targeted modification strategies influence PFAS adsorption behavior. Rather than emphasizing adsorption capacity alone, the discussion focuses on the interplay between adsorption mechanisms, PFAS molecular characteristics, and water matrix effects. Recent advances in chemical functionalization and hybrid polysaccharide-based materials are highlighted for their ability to improve selectivity, adsorption kinetics, and regeneration performance, particularly for short-chain PFAS that remain difficult to remove. Finally, key challenges related to competing contaminants, regeneration efficiency, and scalability are discussed, along with emerging design considerations for translating polysaccharide-based adsorbents from laboratory studies to practical water treatment applications.