Advances in the Membrane Behavior of Bentonite-Based Barriers: Fid-Bau Portal

Advances in the Membrane Behavior of Bentonite-Based Barriers

Bohnhoff, Gretchen L. / Sample-Lord, Kristin M. / Shackelford, Charles D.

Sodium bentonite (Na-bentonite) commonly is used as a barrier or a component of a barrier to limit contaminant migration into the environment. Results of experimental research to date indicate that Na-bentonite may exhibit significant membrane behavior resulting in restricted solute migration (also known as anion exclusion) and development of chemico-osmosis, leading to reductions in both liquid and contaminant flux through the bentonite. Thus, bentonite-based engineered barriers may exhibit improved containment performance, which has motivated the development of laboratory research to further evaluate and quantify membrane behavior. The purpose of this paper is to provide a summary of recent and current advances in the ongoing evaluation of the significance of membrane behavior in bentonites, including chemically modified bentonites (e.g., dense pre-hydrated geosynthetic clay liners, multiswellable bentonite, bentonite polymer nanocomposite, HYPER-clay) and bentonite-amended clays. In addition, the development of an innovative apparatus to measure membrane behavior under unsaturated conditions is described. Recent research regarding the limiting concentrations at which membrane behavior continues to persist is summarized. Finally, recommendations for future research on the relevance of membrane behavior in practical applications are provided.