Hydraulic Conductivities and Effective Diffusion Coefficients of Geosynthetic Clay Liners with Organobentonite Amendments

Laboratory diffusion and permeability tests were performed on GCLs amended with two different types of organobentonites: benzyltriethylammonium-bentonite (BTEA-bentonite) and hexadecyltrimethylammonium-bentonite (HDTMA-bentonite) and compared to results for a GCL constructed with conventional sodium bentonite. Results from the hydraulic conductivity testing indicate the addition of both types of organobentonite results in an increase in hydraulic conductivity. Only a small increase (less than one order of magnitude) in hydraulic conductivity was observed for both types of GCLs amended with up to 20% organobentonite. At higher organobentonite contents, measured hydraulic conductivity for both types of amended GCLs increased by as much as three orders of magnitude. The effective diffusion coefficient measured for both the organobentonite-amended GCLs and the laboratory-constructed sodium bentonite GCLs were similar and ranged from 2.67 x 10^–10 to 4.17 x 10^–10 m²/sec. Considering the strong sorption capacity of organobentonites for organic contaminants, these results suggest that the ability of GCLs to retard the transport of organic contaminants can be improved by substituting 10–20% of the conventional bentonite with an organobentonite.