Use of Chitosan with Different Deacetylation Degrees for the Adsorption of Food Dyes in a Binary System

Abstract

Chitosan with different deacetylation degrees was applied for the adsorption of food dyes (Acid Blue 9 and Food Yellow 3) in a binary aqueous system. The effects of deacetylation degree (DD) and pH on the food dyes adsorption were evaluated by response surface methodology (RSM). In the more adequate adsorption condition, the equilibrium curves were obtained under different temperatures, and the extended Langmuir model was fitted to the experimental data. RSM results showed that the best conditions for the adsorption of food dyes onto chitosan were DD of 95% and pH 2.5. Under these conditions, the adsorption capacities were 163.6 and 193.4 mg/g for Acid Blue 9 and Food Yellow 3, respectively. The total percentage removal was 90%. The equilibrium curves were of high affinity (H type) and the adsorption was favored by the temperature decrease. The extended Langmuir model presented satisfactory fit with the experimental equilibrium data. These results demonstrated that chitosan is an efficient adsorbent to remove dyes from binary systems.