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J Hazard Mater. 2011 Mar 15;187(1-3):164-70. doi: 10.1016/j.jhazmat.2011.01.016. Epub 2011 Jan 13.

Adsorption of food dyes acid blue 9 and food yellow 3 onto chitosan: stirring rate effect in kinetics and mechanism.

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Unit Operation Laboratory, School of Chemistry and Food, Federal University of Rio Grande - FURG, 475 Engenheiro Alfredo Huch Street, 96201-900 Rio Grande, RS, Brazil.


Adsorption of food dyes acid blue 9 and food yellow 3 onto chitosan was studied. Stirring rate influence on kinetics and mechanism was verified. Infra-red analysis was carried out before and after adsorption in order to verify the adsorption nature. Adsorption experiments were carried out in batch systems with different stirring rates (15-400 rpm). Kinetic behavior was analyzed through the pseudo-first-order, pseudo-second-order and Elovich models. Adsorption mechanism was verified according to the film diffusion model and HSDM model. Pseudo-second-order and Elovich models were satisfactory in order to represent experimental data in all stirring rates. For both dyes, adsorption occurred by film and intraparticle diffusion, and the stirring rate increase caused a decrease in film diffusion resistance. Therefore, the film diffusivity increased the adsorption capacity and, consequently, intraparticle diffusivity increased. In all stirring rates, the rate-limiting step was film diffusion. Adsorption of acid blue 9 and food yellow 3 onto chitosan occurred by chemiosorption.

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