Biosorption of basic dyes onto <i>Azolla filiculoides</i>: equilibrium and kinetic modeling

Abstract

Abstract The biosorption of basic dyes, rhodamine B (RMB) and methylene blue (MB), using Azolla filiculoides was investigated in a batch reactor and in a fixed‐bed column. Biosorption isotherms revealed that pH 5 was the optimum condition for maximum biosorption of both basic dyes. Sorption isotherm data were fitted with Langmuir, Freundlich, Redlich–Peterson and Sips models. A maximum uptake of 166.7 and 91.8 mg/g was observed for MB and RMB, respectively, according to the Langmuir model. It was observed from the kinetic data that the biosorption process using A. filiculoides followed pseudo‐second order kinetics. The ability of A. filiculoides to biosorb MB in a packed column was investigated, as well. Experiments conducted at different bed heights (15–25 cm) revealed that decrease in bed height resulted in inferior biosorption performance. At 25 cm, the A. filiculoides bed was capable of providing breakthrough at 76.2 h, with column uptake and removal efficiency of 80.2 mg/g and 84.9%, respectively. The Thomas model was successfully used to analyze the experimental data and the model parameters were evaluated. Copyright © 2008 Curtin University of Technology and John Wiley &amp; Sons, Ltd.