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Minerva Biotecnologica 2014 September;26(3):165-74


language: English

Adsorption of hexavalent chromium by chitosans with different molecular weights

Behnam S. 1, Karimi K. 1, 2, Zamani A. 1, Mehrabani-Zeinabad A. 1

1 Department of Chemical Engineering, Isfahan University of Technology, Isfahan, Iran; 2 Industrial Biotechnology Group, Institute of Biotechnology and Bioengineering, Isfahan University of Technology, Isfahan, Iran


AIM: This paper aimed to compare the ability of different molecular weight chitosans (low, medium, and high) for Cr(VI) removal from aqueous solutions and to study the effects of different parameters on chromium removal.
METHODS: Effects of different parameters, i.e., pH, temperature, time, chitosan amount, initial chromium concentration, and presence of other ions, on Cr(VI) adsorption were investigated. pH, chitosan amount, and initial Cr(VI) concentration varied in the ranges of 3.0-5.5, 200-3000 mg l-1, and 5-25 mg l-1, respectively. Analysis of variance was performed to study the effect of molecular weight on biosorption capacity.
RESULTS: The most influencing parameter was pH, while temperature did not considerably affect the adsorption capacity of chitosans. Adsorption capacities of chitosans was decreased with increasing pH, and their highest values were observed at pH 3. Among pseudo-first order, pseudo-second order, and Elovich models for describing the kinetics data, Ho’s pseudo-second order model was the best. An intra- particle diffusion based model was evaluated to study the mechanism of chromium biosorption. The controlling step was the film diffusion. Langmuir equation could successfully model the isotherm data. Presence of bi- or multi-metal ions decreased the adsorption of chromium ions.
CONCLUSION: Low, medium, and high molecular weight chitosans were effective in Cr(VI) removal from aqueous solutions. Chitosan molecular weight did not significantly affect the adsorption capacity; however, maximum adsorption capacity predicted for chitosans was the highest (185.6 mg g-1) and the lowest (142.3 mg g-1) for low and high molecular weight chitosans, respectively.

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