The first part of this project was a laboratory column study of attenuation of pollutants in municipal solid waste landfill leachate by mixtures of sand and calcium-saturated clays. K, NH4, Mg, Si, and Fe were moderately attenuated; and the heavy metals Pb, Cd, Hg, and Zn were strongly attenuated even in columns with small amounts of clay. Precipitation was the principal attenuation mechanism for the heavy metals; cation exchange was responsible for any attenuation of the other elements. The clays, in order of increasing attenuation capacity, were Kaolinite, Illite, Montmorillonite. The second part of the project involved batch studies of adsorption of Cr, Cu, Pb, Cd, Hg, and Zn by Montmorillonite and Kaolinite from water solutions and from landfill leachate. Adsorption of the cations Cr(III), Cu, Pb, Cd, Hg, and Zn increased with increasing pH; adsorption of the anions Cr(VI), As, and Se decreased with increasing pH. Above pH about 5.3 precipitation of the cations was an important mechanism while adsorption was the principal mechanism for the anions over the pH range studied. Because adsorption/mobility of any element was affected by other solutes in leachate, adsorption information on one leachate may not be directly applied to predicting adsorption of the same element at the same concentration in another leachate.

Issued Aug. 1978. Includes bibliographical references (pages 128-135). Report prepared by Illinois State Geological Survey under contract no. Contract Number: 68-03-0211.