Chitosan-based adsorbents for wastewater treatment: A comprehensive review

Chitosan has emerged as a promising biopolymer for developing eco-friendly adsorbents for wastewater treatment contaminated by different compounds, such as heavy metals, pharmaceutical compounds, pesticides, and synthetic dyes. Despite its biocompatibility and biodegradability, the application of pristine chitosan in adsorption systems is limited by its low surface area, poor thermal and mechanical stability, and high solubility under acidic conditions. This comprehensive review analyzes recent advances in chitosan's chemical and physical modification to enhance its physicochemical, morphological, and adsorption performance. The role of crosslinking agents, nanocomposite synthesis, and the incorporation of magnetic particles in improving the material's textural characteristics, selectivity, and regeneration potential was highlighted. The novelty of this work lies in its evaluation of how these structural modifications can influence the adsorption mechanisms and performance in different classes of contaminants under varying experimental conditions. Furthermore, this review highlighted the importance of structural-functional correlations, including surface area, pore distribution, crystallinity, and thermal stability, in optimizing adsorbents' adsorption capacity and reusability. The study also provides critical insights into the effects of pH, temperature, ionic strength, and competitive adsorption in multicomponent systems, furnishing valuable details about the design of high-performance and sustainable chitosan-based adsorbents.