Organoclay with Soil-Bentonite Admixture as Waste Containment Barriers

Organoclays, clays modified by cationic surfactants, for engineering applications have recently drawn great attention because of their high organic removal capacity. In this study, the potential use of organoclays with soil-bentonite admixtures as waste containment barriers is investigated by experimental tests such as batch equilibrium sorption studies, compaction tests, and hydraulic conductivity tests. Sorption isotherms of total organic carbon (TOC), a gross organic term, by five different types of soil admixtures are nonlinear. The soil specimen with more organoclays exhibits higher organic sorption capacity and a larger retardation factor. The specimens with 20% by dry weight of bentonite have higher optimum water content and plasticity. With the addition of bentonite in the soil material consisting of completely decomposed volcanic rock (CDV) (natural soils) and organoclays, the hydraulic conductivity to leachate decreases from about 10-7 to 10-8 cm/s. This indicates that the presence of bentonite in the admixtures is important in reducing hydraulic conductivity.