Kinetics, equilibrium, and thermodynamic studies on adsorption of methylene blue by carbonized plant leaf powder

Abstract

Carbon synthesized from plant leaf powder was employed for the adsorption of methylene blue from aqueous effluent. Effects of pH (2, 4, 6, 8, and 9), dye concentration (50, 100, 150, and 200 mg/dm3), adsorbent dosage (0.5, 1.0, 1.5, and 2.0 g/dm3), and temperature (303, 313, and 323 K) were studied. The process followed pseudo-second-order kinetics. Equilibrium data was examined with Langmuir and Freundlich isotherm models and Langmuir model was found to be the best fitting model with high R 2 and low chi 2 values. Langmuir monolayer adsorption capacity of the adsorbent was found to be 61.22 mg/g. From the thermodynamic analysis, ΔH, ΔG, and ΔS values for the adsorption of MB onto the plant leaf carbon were found out. From the values of free energy change, the process was found out to be feasible process. From the magnitude of ΔH, the process was found to be endothermic physisorption. © 2013 V. Gunasekar and V. Ponnusami.