Isotherm, Kinetic and Thermodynamic Studies on the Adsorption of Cd (II) and Zn (II) ions from Aqueous Solutions onto Bottom Ash

Bottom ash is a waste material obtained from electricity generation through combustion of coal at the Mae Moh power plant in Thailand.The adsorption of Cd (II) and Zn (II) ions from aqueous solutions onto bottom ash was studied using batch experiments.The effect of pH, contact time and temperature were investigated.Adsorption isotherm data for metal ions was analyzed by the Langmuir and Freundlich isotherms.The Freundlich isotherm properly described the adsorption data for all studied temperatures.The results revealed that the adsorption kinetics followed pseudo-second-order kinetic model.Thermodynamic parameters such as Gibbs free energy change (∆G°), enthalpy change (∆H°) and entropy change (∆S°) were investigated.The calculated values showed that the adsorption process for both Cd (II) and Zn (II) ions was endothermic.