Permeability and solute sorption of unamended and polymer-enhanced geosynthetic clay liners

Polymer treatment is an increasingly adopted approach to mitigate the impact of aggressive liquids on the hydraulic performance of geosynthetic clay liners (GCLs). Dense prehydrated (DPH) GCLs are particular products that combine polymer treatment, prehydration and densification to improve the overall containment performance. This study investigated the saturated hydraulic conductivity, k, and heavy-metal retention in a conventional GCL and a DPH GCL. Both materials were permeated first with water and then with a synthetic solution containing zinc (Zn), copper (Cu) and lead (Pb), also with the purpose of extending a previous study where a solution of the same solutes at higher concentrations had been used. The k of the conventional GCL increased by one order of magnitude with respect to that of water upon permeation with the synthetic solution. The solutes were partly retained, and the increase in k was associated with the breakthrough of solutes. Upon permeation with the same solution, the k of the DPH GCL decreased by a factor of 1.6 with respect to that of water. No significant breakthrough of metals was observed, despite the considerably longer test duration. Under the adopted testing conditions, owing to polymer amendment and densification, the hydraulic performance and solute retention properties of the DPH GCLs were superior to those of the conventional GCL.