Sodium alginate-based adsorbents for pesticide removal: Advances, mechanisms, and future perspectives

The pervasive presence of pesticides in aquatic environments poses a significant threat to both ecological and human health due to their persistence, toxicity, and bioaccumulative nature. Traditional remediation methods often face limitations in sustainability. Among alternative strategies, adsorption has emerged as a promising approach for pesticide removal because of its operational simplicity, scalability, and high selectivity. This review critically examines recent progress in the development of sodium alginate (SA)-based adsorbents for efficient remediation of pesticide-contaminated water. SA, a natural, anionic polysaccharide derived from brown seaweed, offers tunable physicochemical properties, abundant functional groups, and excellent biocompatibility, making it an attractive matrix for adsorbent design. Emphasis is placed on the molecular design, functionalization strategies, and hybridization of SA-based hydrogels with inorganic fillers (e.g., metal oxides), carbonaceous materials (e.g., biochar), and magnetic nanoparticles to enhance adsorption efficiency, specificity, and reusability. Mechanistic insights into pesticide binding through electrostatic interactions, hydrogen bonding, π-π stacking, cation exchange, and metal-ligand complexation are systematically discussed. Collectively, this work provides a holistic and mechanistically grounded framework for understanding the design principles and application potential of SA-based materials. Finally, future opportunities for developing stimuli-responsive, multifunctional, and field-deployable alginate-based systems are proposed, highlighting their role in advancing sustainable water purification technologies.