Enhancing containment performance of geosynthetic clay liner to bauxite liquor via composite polymer amendment

Polymer amended geosynthetic clay liners (GCLs) have exhibited substantial semipermeable membrane behavior in singe-species salt solution. However, very few studies have evaluated the membrane and diffusion behavior of polymer amended GCLs in multi-species leachates. This study investigated the membrane and diffusion behavior of novel composite polymer amended GCL (referred to as PHGCL) using diluted and fresh bauxite liquors as the testing liquids. The membrane efficiency coefficient (ω), effective diffusion coefficient (D*), retardation factor (R_d) of PHGCL were evaluated. Conventional (unamended) GCL was tested as control. The results revealed that PHGCL exhibited significantly higher ω ranging from 0.435 to 0.005, which was approximately 1.7–2.5 times of that for the unamended GCLs. The composite polymer amendment reduced the D* of K⁺, Ca²⁺, Na⁺, Al³⁺, and Pb²⁺ migrating through the GCLs, and the reductions were relatively limited (≤ 14.2 %). Conversely, the R_d of PHGCL was markedly elevated with the maximum increase reaching 91.6 % as compared to the unamended GCL. Comparative analysis indicated that when exposed to single-species salt solutions, multivalent cations migrating through the GCLs generally possessed higher D* than monovalent cations. However, in multi-species solutions, monovalent cations showed higher D*, as their diffusion is primarily governed by their free-solution diffusion coefficients.