Comprehensive Studies on Methylene Blue Adsorption onto Na-bentonite Clay and its Kinetics, Isotherm and Thermodynamics

Abstract

The main objective of this study was to study adsorption of methylene blue (MB) onto Na-bentonite as adsorbent. Firstly, effects of operating factors including initial MB concentration (100-700 mg/L), pH (2-10), temperature (35-55°C), and contact time (0-240 minutes) on performance of adsorption were studied. It was found that these factors had significant effects on both adsorption capacity and percent removal. The adsorption reached equilibrium in a short period of time. Secondly, kinetic and isotherm and thermodynamic studies were investigated. The results revealed that pseudo-first, pseudo-second order and Langmuir models were able to match experimental data using non-linear curve fitting technique. Also, thermodynamic studies indicated that the process under study was spontaneous and endothermic reaction. Finally, a surrogate model was developed to investigate the combined effects of operating factors and examine the optimal operating condition. The optimal result from model prediction was found at initial concentration of 634 mg/L, temperature of 55°C, and pH of 10 and was in good agreement with experimental data indicating applicability of the surrogate model.