Evaluation of alternative leachate liner materials

Abstract

The purpose of this study is to evaluate alternative landfill liner materials that could be utilized in conjunction with current liners in order to improve the liner's performance by preventing the release of hazardous chemicals into the subsurface environment. Five alternative liner materials were tested in this study: granular activated carbon, lignite, compost, peat moss, and powdered activated carbon produced from cotton gin trash. Three volatile organic compounds are used in this study: Benzene, Toluene, and O-Xylene. The linear Langmuir isotherm coefficients, Qo, and b, and the linear adsorption distribution coefficient K,,.,, were determined by equilibrium studies for each chemical and material. The retardation factor, R., was calculated from the breakthrough curve data for each combination of chemical and material. The cotton gin trash dissolved in the presence of each of the solvents so no data is presented for this material. Because activated carbon sorbed all of the chemical during the isotherm testing, no data could be collected for the extraction procedure. Lignite has the highest adsorption capacity of the three remaining materials and the second highest retardation factor. Activated carbon has the highest retardation factor of each of the chemicals, as expected. The results show that the adsorption capacity and the retardation factor are more dependent on surface area and pore diameter than on the organic carbon content of the test materials. Lignite is the leading candidate after this study to be used as an additive material in liner design. However, further evaluation of these liner materials must be accomplished in order to determine which material, if any, could be added to the design of landfill liners to aid in preventing the release of hazardous chemicals into the subsurface environment and groundwater supply.