To evaluate the potential of clay minerals for attenuating the various chemical constituents of landfill leachate, leachate was passed through laboratory columns that contained various mixtures of calcium-saturated clays and washed quartz sand. Leachates were run through the columns for periods of up to 10 months, during which time effluents were periodically collected and analyzed for 16 chemical constituents. Chloride, Na, and water-soluble organic compounds (COD) were poorly attenuated by passage through the clay columns; K, NH4, Mg, Si, and Fe were moderately attenuated; and heavy metals such as Pb, Cd, Hg, and Zn were strongly attenuated by even small amounts of clay. Concentrations of Ca, B, and Mn in the column effluents increased markedly over the original leachate concentrations. Of the three clays used in the study, montmorillonite had the highest attenuation capability, followed by illite and then kaolinite. Attenuation was a function of the CEC of the clay mineral, the initial exchangeable cations on the clay, the chemical composition of the leachate, and the pH of the leachate.
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Attenuation of pollutants in municipal landfill leachate by passage through clay