Barrier performance of geosynthetic clay liners to copper (II) chloride solutions

Abstract

Three needle-punched geosynthetic clay liners (GCLs) which had been manufactured with sodium (Na+) bentonite (Na-GCL) and polymerised sodium bentonites (PLS-GCL-1 and PLS-GCL-2) were permeated with 50 and 100 mM copper (II) chloride (CuCl2) solutions. The hydraulic conductivity of Na-GCL to 50 mM copper (II) chloride gradually increased to 7·7 × 10−9 m/s. In contrast, PLS-GCL-1 and PLS-GCL-2 had hydraulic conductivities of 1·5 × 10−11 and 4·2 × 10−11 m/s to 50 mM copper (II) chloride solution, respectively. Dissolution of polymers and precipitation of copper (II) (Cu2+) ions are two reasons for the low hydraulic conductivity. Metal fittings were replaced with plastic fittings, and hydraulic conductivity tests have been conducted with both solutions. The hydraulic conductivities were still low and were equal to 7·2 × 10−11 and 6·2 × 10−11 m/s with 50 and 100 mM copper (II) chloride solutions, respectively. Chemical analyses showed that cation replacements took place between bentonites and copper (II) ions. The effluents were abundant in monovalent and divalent cations which had been released from bentonites. In contrast, a considerable amount of copper (II) ions was detected in the effluents, indicating the start of the breakthrough tendency of GCLs to copper (II) ions.