Kinetic and Equilibrium Modeling of Anionic Dye Adsorption on Polyaniline Emeraldine Salt: Batch and Fixed Bed Column Studies

Abstract

In this work, removal of anionic dye Eosin Yellow (EY) by polyaniline emeraldine salt (PANI-ES) from the aqueous medium was studied by using both batch and fixed-bed column mode. Before and after the dye adsorption, the adsorbents were characterized by UV-Vis, FTIR, and XRD analysis. The morphology of the adsorbent was also studied by scanning electron microscopy (SEM). The batch adsorption study was performed by varying the initial concentration of the dye and pH. The experimental results obtained were fitted to the three isotherm models namely Langmuir, Freundlich, and Temkin and the Langmuir isotherm was found to be the best fitting model with the adsorption capacity 335 mg/g. The adsorption process followed pseudo second order kinetics. The thermodynamic study was also performed and thermodynamic parameters ΔH°, ΔS°, and ΔG° were calculated. The adsorption experiments were also carried out in packed columns by varying some important factors like flow rate, bed height, pH, and the initial dye concentration. The experimental results obtained were fitted using Bohart-Adams, Yoon-Nelson, and Thomas models. Among the models studied, the highest adsorption capacity, 79.0 mg/g was calculated from Thomas model at pH 4 with 375 mg/l initial concentration, flow rate 0.3 ml/min, and bed height 1.4 cm.