Chemico-Osmotic Efficiency of a Geosynthetic Clay Liner

Abstract

Chemico-osmotic efficiency coefficients, ω, are determined from measured differential pressures across specimens of a geosynthetic clay liner (GCL) containing granular bentonite in response to applied differences in potassium chloride (KCl) concentrations under no-flow conditions. The results show that the GCL acts as a semipermeable membrane with ω values at steady state, ωss, ranging from 0.08 to 0.69 for KCl concentration differences ranging from 0.0039 to 0.047 M. The chemico-osmotic efficiency of the GCL decreases with increasing porosity and increasing KCl concentration. The decrease in ωss with increasing porosity is consistent with an increase in pore size reflected by an increase in measured hydraulic conductivity. The decrease in ωss with increasing KCl concentration is consistent with compression of the diffuse double layers surrounding the clay particles, and is reflected by a time-dependent decrease in the induced differential pressure as well as an increase in the hydraulic conductivity of the specimen. The results of this study are potentially significant with respect to the evaluation of the hydraulic and contaminant transport performance of GCLs used in waste containment applications.