Interaction of Cationic Polymer-Treated Geosynthetic Clay Liners with Various Saline Solutions

Geosynthetic clay liner (GCL) is a lining material that is used in waste containment facilities with its low hydraulic conductivity and barrier capability. In this study, %0.5, %1 and %2 cationic polymer by mass was added respectively to the bentonite component of the GCLs and triaxial hydraulic conductivity and free swell tests were performed on the GCLs that were permeated with 0.1 M KCl, 0.5 M KCl and 0.1 M MgCl2 saline solutions respectively in order to evaluate the hydraulic performance of the GCL. As a result, %0.5 cationic polymer in 0.1 M KCl solution and %1 cationic polymer in 0.5 M KCl and 0.1 M MgCl2 solutions improved the hydraulic performance of the GCL by causing almost 0.13, 0.18 and 0.08 times decrease in hydraulic conductivity respectively. However, additional polymer treatment resulted in either no change or increase in hydraulic conductivity. Furthermore, swell index of the GCL increased by adding up to an amount of %2 cationic polymer to the GCL. The effect of adding cationic polymer to the GCL on hydraulic conductivity and swell index was related to the electrostatic forces among polymer-bentonite-saline solution and diffuse double layer respectively. Increasing the concentration and valence of the cation in the saline solutions resulted in both increase in hydraulic conductivity and decrease in swell index. According to the test results, the cationic polymer improved the hydraulic properties of the GCL and resulted in a satisfactory hydraulic performance in saline solutions.