Abstract
Among the naturally occurring polysaccharides, chitosan is the second-most abundant polysaccharide. It is obtained from chitin through a process known as deacetylation. It is biodegradable, biocompatible, and non-toxic, which made it suitable for various environmental applications. In the present review, the structure, properties, and characteristics of chitosan were discussed. In addition, the modified forms of chitosan (including cross-linked, nanoparticles, functionalized, and grafted forms of chitosan) were enumerated. The applications of these modified forms of chitosan in the adsorption of organic pollutants (such as antibiotics, dyes, pesticides, microplastics, polyaromatic hydrocarbons, parabens, and polychlorobiphenyls) are comprehensively reviewed. Furthermore, the mechanism of adsorption, adsorption isotherm (Langmuir and Freundlich), and the kinetic models are highlighted. Finally, the economic viability assessment and environmental impact of processing tons of shrimp shells into chitosan annually were discussed.