Kinetic and Isotherm Studies of Adsorption of Lead (II) Ion Onto Functionalized Nigeria Ahoko Kaolin

Abstract

The kinetic and thermodynamic of lead (II) adsorption onto functionalized and unfunctionalized Nigeria Ahoko kaolin was studied with the aim to investigate the sorption potential of kaolinite clay as a commercial adsorbent in removal of Pb2+ from aqueous solution. The effect of various variables namely initial concentration of Pb2+, contact time and temperature were investigated. The equilibrium data were obtained using batch experiment process only. The equilibrium data was fitted to the three isotherm model used namely: Freundlich, Langmuir and Temkin, with Temkin having the best fit than the other with coefficient of determination R2 approximately one, while the pseudo-second order best explained the kinetics of the adsorption process. Increasing initial Pb2+ concentration, increased the rate of Pb2+ adsorbed and the initial rate of sorption h for both adsorbent, also increase in temperature from 298 K to 323 K was also observed to increase the initial sorption rate h from 10.07 to 139.07 (mg/g.min) and 9.43 to 78.57 (mg/g.min) for functionalized and unfunctionalized respectively. The adsorption reaction for both adsorbent was found to be a chemically activated reaction and endothermic with activation energy E for the 1000(mg/L) of Pb2+ in solution as 1089.78 and 3424.73 (KJ/mol) for functionalized and unfunctionalized adsorbent respectively. The positive values of the enthalpy and the entropy change suggests that the endothermic nature of the adsorption and the negative values of free energy change indicate the feasibility and spontaneity nature of the adsorption process.