Chitosan-based hybrid materials for adsorptive removal of dyes and underlying interaction mechanisms

Environmental pollution by dyes molecules has become a subject of intensive research in recent years due to their hazardous effects on human health, organisms, and animals. Effective treatment and removal of dye molecules from the environmental matrices and water sources are of supreme concern. The deployment of cheap, safe, green, sustainable, and eco-friendly materials to remove these pollutants from water is the main challenge during the last decades. Chitosan and its derivatives/composites, as a cheap, easily available, and environmentally friendly sorbent, have attracted increasing attention for the removal of dye molecules. This review article focuses on the application of chitosan and chitosan-based smart adsorbents for the removal of dyes. Recent methods for the preparation of chitosan-based composites and their application in the removal of dyes are discussed. Moreover, the possible mechanisms for the interaction of chitosan and chitosan-based adsorbents with dyes molecules were evaluated. Finally, future prospects of using chitosan as an adsorbent for the removal of dye molecules are directed. (c) 2021 Published by Elsevier B.V. 1. Introduction 400 2. Chitosan 401 3. Adsorption mechanisms 401 3.1. Ion-exchange 401 3.2. Complexation 402 3.3. Coordination/chelation 402 3.4. Electrostatic interactions 403 3.5. Acid-base interactions 403 3.6. Hydrogen bonding 403 3.7. Hydrophobic interactions 404 4. Chitosan-based adsorbents for removal of dyes molecules 404 4.1. Chitosan-based composite adsorbents for removal of dyes molecules 405