Membrane behavior of bentonite-amended compacted clay

The performance of landfill liners can be enhanced if they exhibit a semipermeable membrane behavior, which restricts the migration of contaminants. Consequently, enhancing the membrane property of clays used for liners is becoming increasingly important. As bentonite has already proven to be an excellent additive for improving the membrane behavior of clay, the hydraulic conductivities and membrane behaviors of a locally available clay, known as Fukakusa clay, amended with different amounts of dry bentonite (5%, 10%, 15%, and 20%) were herein evaluated. The chemico-osmotic efficiency coefficient, ω, was obtained under different concentration differences of KCl solution (0.5, 1, 5, 10, and 50 mM) for specimens in rigid-wall cells. The test results show that the ω of unamended clay is very low and can be ignored unless amended with bentonite, and that hydraulic conductivity k is suitably low (1.58×10−9 m/s). Additionally, ω decreased as the KCl concentration increased, which is consistent with the theory that increasing concentration causes progressively greater shrinkage of the diffuse-double layers of the clay particles. Furthermore, the mechanisms that influence the membrane behavior are discussed from the viewpoints of the diffuse-double layer and the interparticle pore size with the assistance of SEM.