Attenuation of contaminants in landfill leachate by lateritic soil enhanced with bentonite

Abstract

ABSTRACT The current research was carried out to evaluate improvement in the attenuative capacity of lateritic soil for landfill leachate contaminants as a result of bentonite addition. Laboratory batch adsorption test was performed using lateritic soil treated with 0%, 2.5%, 5%, 7.5% and 10% bentonite by dry weight of soil with Pb2+ and K+ ions as selected contaminants in the landfill leachate. The experimental data were analysed by both the linear and Freundlich isotherms. In this study, the untreated lateritic soil achieved about 85% and 81% removal efficiencies for K+ and Pb2+ species, respectively, while 90% and 97% removal efficiencies were achieved by lateritic soil mixed with 10% bentonite. Maximum Pb2+ adsorption capacities for soil mixtures with 0%, 2.5%, 5%, 7.5% and 10% bentonite were 1.48, 1.51, 1.55, 1.58 and 1.6 mg/g, respectively, leading to Kd values ranging from 30.04 to 77.72 mL/g, while the adsorption capacities calculated for K+ ranged from 797.68 to 907.82 mg/g with corresponding Kf values of 59.7–206.54. Correlation coefficients indicate that the adsorption data for Pb2+ were adequately described by the linear model while the adsorption equilibrium data for K+ ion fitted well to the Freundlich isotherm model. Overall, the soil mixture with higher bentonite contents produced enhanced adsorption capacities for both Pb2+ and K+ ions.