A review on decontamination of aqueous systems using chitosan-derived adsorbents

Abstract Increasing deterioration of water quality due to discharge of toxic contaminants into the aquatic systems has become a global concern that requires proper remedial measures. Research is continuously focused on developing of sustainable methods for removing these pollutants from water. Chitosan derived from chitin has been widely recognized for its versatility, biocompatibility and effectiveness in adsorbing a wide range of pollutants from water. Its amino and hydroxyl functional groups make it suitable for interaction with various pollutants. However, the challenges associated with chitosan as an adsorbent include its lack of selectivity, instability in acidic media and low mechanical strength. Cross-linking chitosan through grafting or incorporating of solid adsorbents such as carbon, metal oxide nanoparticles, metals and clay, metal organic frameworks onto chitosan has overcome this setback. As a result, cross linked chitosan, chitosan hydrogels, composites and nanocomposites have recently received much attention for sequestration of pollutants from water because they have better adsorption capabilities compared to unmodified ones. The adsorption of pollutants by chitosan based adsorbents is generally pH selective, with anions being adsorbed at low pH and cations at near neutral pH. The adsorption mechanisms include electrostatic attractions, chelation, ion exchange, π-π interactions, hydrophobic interactions, and hydrogen bonding occurring singly or simultaneously. This review highlights on the modification of chitosan based adsorbents, their potential application in the removal of pollutants from water particularly multi-pollutant aqueous systems and their regeneration efficiencies. Finally, the future prospects of these chitosan adsorbent materials are discussed and summarized.