Polymer Treatment of Bentonite Clay for Contaminant Resistant Barriers

The hydraulic conductivity of clay significantly increases when permeated with high concentrations of inorganic solutions due to changes in clay chemistry and fabric. Chemical amendment of clays using soluble polymeric compounds creates a clay-polymer fabric that can be engineered to provide an attractive alternative for containment systems. The amended material can be made to resist different classes of chemical contaminants and span a broad range of engineering properties. In the present study, polymer treated clays are prepared by sorbing polymers to the surface of commercial sodium bentonite. Three classes of polymers: cationic, anionic and nonionic, are used in the study. All the polymers are water-soluble polyacrylamides in granular form. Basic engineering properties of the polymer-treated clay are investigated through a series of liquid limit and swell index tests. Mixing procedures are discussed, and compared to industrial processes used to synthesize contaminant resistant clays. Permeability tests are performed to evaluate the performance when permeated with highly concentrated salt solutions. The void ratio, initial wetting conditions, and polymer type are found to have a significant effect on the hydraulic conductivity.