ABSTRACT
The influence of natural clay's bentonite proportion on Pb2+ sorption capacity was investigated using response surface methodology (RSM), kinetics and equilibrium studies. Experiments were conducted at different initial pH (3–7), bentonite to clay ratio (0–100%), initial Pb2+ ions concentration (20–120 mg/L) and sorbent dosage (0.2–1 g). Under the RSM study, data obtained from 27 experiments undertaken were found to fitted second-order polynomial model (R2 = 0.998 and R2-predicted = 0.994). Analysis of variance showed that the Pb2+ sorption capacity was influenced according to the order; initial concentration> mass of adsorbent > initial pH > bentonite proportion. Optimal operating conditions were obtained at initial pH 5, 0.2 g sorbent dosage, 30% bentonite to clay ratio and 100 mg/L Pb2+ ion concentration. Regardless of the bentonite proportion, Pb2+ sorption kinetics followed pseudo-second-order associated with intra-particle diffusion. The sorption isotherm for the clay which was described by Freundlich yielded higher adsorption capacity (25 mg/g) while that of the bentonite was described by Langmuir model with lower maximum sorption capacity of 15 mg/g. These results suggest that sorption of the Pb2+ ions was not likely to significantly impact on the removal of Pb2+ ions during electrokinetic remediation process of clay having different proportion of bentonite.
Acknowledgments
The authors thank the University of Dammam (UoD) and the Environmental Engineering Department of the University, Saudi Arabia, for providing the resources and facilities used in conducting this research work. The authors also thank to Mr. Mukarram and Mr. Ehab for the invaluable help they rendered for the analytical technique measurements.