Physicochemical modification of chitosan adsorbent: A perspective

Abstract

Chitosan is a low-cost natural adsorbent. Its derivatives from chemical and physical modification processes possess superior properties for wide applications to meet the growing demands. The chemical modification includes replacement reactions, chain elongation and depolymerization, while the physical modification is to obtain polymeric forms such as powders, nanoparticles and gels. This paper is aimed to highlight the present trends in chitosan preparation and modification, the enhancement in adsorptive properties and the remarks into future directions. The mechanisms involved in adsorption by chitosan derivatives and how the spent adsorbent can be regenerated were also discussed. Meanwhile, for the adsorption of heavy metals from wastewater, chitosan modified with activated carbon showed a better adsorption capacity of 90.90 mg g-1 for Cr(VI) and 50.50 mg g-1 for Cd(II), and for dye adsorption, chitosan modified with activated neem leave showed better adsorption capacity of 90.8 mg g-1 for methylene blue, and for phenol removal, chitosan modified with salicylaldehyde and ß-cyclodextrin polymer showed better adsorption capacity of 179.73 mg g-1.