Adsorption of Diethylenetriamine from Water by Activated Carbon: Kinetics, Isotherms and Thermodynamics

ABSTRACT The discharge of diethylenetriamine (DETA) into aqueous environment poses a threat to public health and environment. Therefore, it is imperative to take effective measures to remove DETA from water. The elimination of DETA from water may be realized via the way of adsorption with activated carbon. In this paper, the adsorption of DETA from water by activated carbon originated from coconut shell has been explored in batchwise operation. The effects of stirring speed, temperature, pH, DETA concentration, carbon dosage and particle size on DETA adsorption have been determined by experiment. The adsorption results exhibit that the DETA adsorption rate increases with its concentration in the aqueous solution and temperature. However, the amount of DETA adsorbed on the carbon at equilibrium decreases slightly with temperature. The DETA adsorbed increases with pH changing from 8 to 11 and remains constant if pH rising over 11. The kinetic study shows that DETA adsorption on the activated carbon is in good agreement with the pseudo-second-order kinetic model with a correlation coefficient of 0.999. The DETA removal from the solution increases with the carbon dosage. The Langmuir equilibrium isotherm model has been found to provide a better fitting of the adsorption data than the Freundlich equilibrium isotherm model with a maximum adsorption of 90.50 mg g−1. The thermodynamic parameters evaluated from the experiments are ΔS 14.49 J∙mol−1∙K−1, ΔH −11.32 kJ mol−1 and ΔG changing from −15.71 from −16.15 kJ mol−1with the temperature rising from 30°C to 60°C. The thermodynamic study suggests the exothermic and spontaneous natures of DETA sorption on activated carbon.