Chitosan-based carbonaceous adsorbent for wastewater treatment applications

Chitosan-based adsorbents have drawn considerable attention due to their effective removal of hazardous pollutants, such as heavy metal ions, microplastics, and organic pollutants, including phenols, dyes, fertilizers, pesticides, herbicides, and pharmaceuticals. However, the practical application of chitosan is limited by its relatively low adsorption capacity, poor mechanical properties, and susceptibility to dissolution in acidic solutions. Therefore, chitosan is commonly modified using different techniques, including chemical and physical approaches, or combined with other adsorbent materials to enhance its structural stability and adsorption properties. Chitosan has been integrated with various materials, including natural polymers (e.g., cellulose, chitin/chitosan, starch, alginate), clay minerals (e.g., perlite and montmorillonite), inorganic materials (e.g., zeolite, metal oxides, and metal-organic frameworks), and carbonaceous materials (e.g., graphene oxide, activated carbon, biochar, and carbon nanotubes). Among these, carbonaceous materials are promising materials, due to their high surface area, porosity, and stability, which significantly improve the mechanical properties, thermal stability, and electrical properties, as well as adsorption capacity. This review focuses on chitosan-based carbonaceous composite materials as adsorbents and covers several aspects, including their synthesis methods, structural and surface characteristics, mechanical properties, and adsorption performance as well as their applications in wastewater treatment, particularly for the removal heavy metals, dyes, organic pollutants (such as oil, fertilizers, antibiotics, and pharmaceuticals), nuclear wastes, and pathogenic microoganisms.