Removal of Malachite Green From Aqueous Solution by Elephant Dung Activated Carbon : Kinetic, Thermodynamic and Isotherm Studies

摘要

Low cost activated carbon prepared from elephant dung by acid treatment, was used as an eco-friendly adsorbent for the removal of the textile dye malachite green from an aqueous solution. The kinetic and thermodynamic parameters of the dye adsorption were investigated with a batch system by changing various experimental conditions, like dye concentration, contact time, temperature and pH with optimum dosage of the adsorbent (100 mg). The equilibrium time was found to be 180 min for 40 mg/L, 150 min for 30 mg/L, 120 min for 20 mg/L and 90 min for 10 mg/L dye solutions. The adsorption kinetics was found to be best represented by Pseudo second order kinetic model. The mechanism of adsorption process was determined from the intraparticle diffusion model. The percentage removal of the dye was increased with increase in temperature. The isothermal data followed Langmuir model. The thermodynamic parameters, like Gibb's free energy change (AG), entropy change (AS) and enthalpy change (AH) were calculated which indicated that malachite green adsorption process was endothermic and spontaneous. The maximum uptake of the dye had taken place at pH 7.