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 (R-2 = 0.998 and R-2-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.