Modified Clays for Waste Containment and Pollutant Attenuation

Abstract
In this study, the use of organically modified clay to remove the high-strength organic pollutants in leachate as well as reduce its liquid flow was investigated. Various physical and chemical factors that may affect the suitability of using the modified clay in removing and retarding the movement of contaminants have been examined. These factors include the structural stability of the modified clay, soil and swelling properties, sorption capacity for nonpolar and polar organics at different pH solutions, and chemical permeants on clay permeability under different effective stresses. The uptake of eight organics (benzene, toluene, o-xylene, ethylbenzene, phenol, 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol) by organoclay BB-40 is found to be significant and increases with an increase in their hydrophobicity. The hydraulic conductivities of organoclay BB-40 under an effective stress of 70 kN/m2 (∼10 psi) are 7 × 10−9 cm/s to tap water, 1.6 × 10−8 cm/s to landfill codisposal leachate, and 1.1 × 10−7 cm/s to synthetic leachate. The experimental results suggest that the use of organoclay as a liner material would provide a barrier with the ability to effectively remove dissolved organic contaminants, and to resist the flow of leachate.