Adsorption of Hexavalent Chromium on Chitosan Beads: Sorption Isotherms and Kinetics

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Abstract
Chitosan is a biopolymer that is usually obtained in a flaked form, nonporous and partially soluble in acidic media. The low porosity of the polymer introduces diffusion constraints which are rate limiting. Modifying the structure of the chitosan is a way to improve the accessibility of the adsorption sites. In this study, the modifications were carried out by dissolving chitosan flakes in an acetic acid solution followed by precipitation in a sodium hydroxide solution to form gel beads. The study deals with the influence of several parameters (metal ion concentration, size of the beads, Chitosan conditioning) on metal ion diffusion. Both sorption isotherms and kinetics were taken into account. The use of this material allowed an adsorption capacity of 76 mg g−1 to be obtained.