Semipermeable membrane behavior of geosynthetic clay liners

Abstract

Abstract The focus of this paper is on providing an overview of the results of the nearly 20 years of research related to the discovery, examination, and potential benefits of semipermeable membrane behavior of bentonite-based geosynthetic clay liners (GCLs) commonly used as barriers or components of barriers in a variety of hydraulic and chemical containment applications, such as water and chemical retention ponds, tailings and coal ash impoundments, and solid waste landfills. First, the concept of solute restriction underlying semipermeable membrane behavior and the development of a solute-restriction or membrane efficiency coefficient (ω) and chemico-osmosis (q π) are described. Second, previously measured values of ω are presented for clays and GCLs for the purpose of illustrating the physical and chemical factors affecting ω. Third, the potential benefits of both ω and q π in terms of hydraulic and chemical containment applications are illustrated, and the relative importance of ω versus q π is described. Finally, some of the remaining issues related to the semipermeable membrane behavior of GCLs, such as the uniqueness of the measured ω and the persistence of ω at high salt concentrations, are discussed.