Isotherm, kinetic and thermodynamic studies on the adsorption behaviour of textile dyes onto chitosan

The present study was established to analyse the capability of Malachite Green (MG), Reactive Red (RR) and Direct Yellow (DY) dyes adsorption onto chitosan synthesized from prawn shells. The effect of process parameters such as adsorbent dosage, pH, contact time, temperature and initial concentration on dye adsorption were studied on the performance of dye removal. Chitosan was characterized by FTIR, SEM and BET analysis. The results showed that as the amount of the adsorbent was increased the percentage of dye removal increased correspondingly. Maximum dye removal was observed at pH 3. The isotherms such as Langmuir, Freundlich and Temkin and Redlich-Peterson were examined and the appropriate model was identified. The adsorption capacities of the synthesized chitosan was 166 mg/g for dye MG, 1250 mg/g for dye RR and 250 mg/g for dye DY. Dynamic adsorption studies show that the adsorption reaction was well represented by the pseudo-second-order kinetic process with intra particle diffusion being one of the rate limiting step. The thermodynamic study revealed that the adsorption of dyes on chitosan was feasible, spontaneous and exothermic process. Results indicated that the synthesized chitosan was shown to be a promising adsorbent for the removal of dyes from aqueous solutions. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.