Adsorption and Hydraulic Conductivity Studies on Bentonites in the Presence of Zinc

Abstract

Clay liners are commonly used in landfills to avoid the contaminant migration from the waste to the groundwater and the surrounding environment. Bentonite contains montmorillonite mineral that offers favourable properties such as low hydraulic conductivity, high adsorption capacity, high cation exchange capacity and capacity to retard the percolation of pollutant through sorption. However, properties of bentonite can be affected due to the presence of various heavy metals in the leachate. The present investigation was conducted to examine the change in hydraulic conductivity and sorption capacity of bentonites in the presence of zinc (Zn2+). Two different bentonites with different swelling, chemical and mineralogical composition were exposed to a series of consolidation test and batch study to examine the hydraulic conductivity and metal adsorption capacity for the geoenvironmental application. Langmuir and Freundlich models were used in order to understand the adsorption mechanism. Tests were performed at a various concentration of Zn2+ ranges from 100 to 1000 mg/L at room temperature and pH 5. The results indicate that with the increase in metal concentration hydraulic conductivity increases. Bentonite with a higher swelling capacity shows higher removal percentage and sorption capacity in comparison to bentonite of lower swelling capacity. The isotherm study predicts that equilibrium data obtained from the study fitted well with the Langmuir model. The study will assist the designer and engineer for opting bentonite type in the various geoenvironmental application.