In this research, lime-treated montmorillonite clay is used toadsorb Zn(II) in a wide range of Zn(II) concentrations. Batch testresults show that the adsorption of Zn(II) by montmorillonite appearsto be dominated by different adsorption mechanisms. At low Zn(II)concentrations, chemisorption affects the amount of Zn(II) adsorbedby montmorillonite. When lime is added, physisorption becomesincreasingly important. At high Zn(II) concentrations, physisorptionis the dominnt mechanism for Zn(II) adsorption. Lime also enhancesthe ability of montmorillonite to adsorb Zn(II) at low initial Zn(II)concentrations, and does not significantly affect the ability ofmontomorillonite to adsorb Zn(II) at high initial Zn(II)concentrations. In chemisorption, montmorillonite provides cationexchange sites for the adsorption of Zn(II). In physisorption,montmorillonite acts as not only numcleation center to adsorb zinchydroxide-oxides but also helps to coagulate the zinchydroxide-oxides. Lime-treated clay can therefore be an effectivelyused to adsorb metals such as zinc even at very high metalconcentrations. The significance of these findings is in the designof landfill liner. A mixture of montmorillonite (bentonite) clay andlime is shown to have characteristics that would make this material asuperior landfill liner. The lime-treated clay has low hydraulicconductivity, enhanced metal removal capability, and betterresistance to penetration by sharp objects.
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