Adsorption Property of Pb(II) by the Laterite-Bentonite Mixture Used as Waste Landfill Liner

To assess the potential use of laterite-bentonite mixture as waste landfill liner, a range of batch tests were conducted to study the influence of contact time, solid to solution ratio, pH, ion strength, and temperature on Pb(II) adsorption. The experimental results showed that the uptake of Pb(II) by laterite-bentonite mixture increases with the increase of contact time and the adsorption equilibrium can be reached within 30 minutes. This process can be delineated well using a pseudo-second-order kinetics equation. Besides, with the increase of solid to solution ratio (s/w) and pH, Pb(II) will be adsorbed more by the laterite-bentonite mixture. However, the uptake of Pb(II) will decrease when ion strength rises in the solution and this is due to the competitive adsorption and cation exchange between different cations. When conducting the batch test at 298 K and 323 K, respectively, the experiment results showed significant growth when temperature increases because the adsorption process is an endothermic reaction. This influence of temperate can be described better by the Langmuir isotherm model than that by the Freundlich isotherm model. In each experiment condition, the uptake of Pb(II) increases with the increasing of bentonite content, indicating a good improvement in the effect of bentonite on laterite used as landfill liner.

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