Adsorption thermodynamic and kinetic studies of Cr(VI) by chitosan flake modified with citric acid via crosslinking with glutaraldehyde

Abstract

In this study, the sorption of Cr(VI) from aqueous solution onto the cross-linked chitosan grafting with citric acid (C-Gch) was investigated in a bath system. The optimum conditions for the adsorption were found to be pH 1 and 720 min of contact time. The maximum adsorption capacity of Cr(VI) at pH 1 was found to be 32 mg Cr(VI) /g C-Gch after 720 min of contact time.  Adsorption kinetic data were tested using pseudo-first order and pseudo-second order. The obtained results confirmed that the adsorption process of Cr(VI) followed the pseudo-second kinetic model. It was shown that the adsorption process is presumably a chemisorption. Thermodynamic parameters including changes in the standard free energy (∆G), enthalpy (∆H) and entropy (∆S) were also calculated.

Keywords. Cr(VI), modified chitosan, citric acid, adsorption thermodynamic.