Experiments were conducted to evaluate the effect of bauxite liquor from aluminum refining on the hydraulic conductivity of geosynthetic clay liners (GCLs) used in composite liner systems. Tests were conducted on a GCL containing conventional sodium-bentonite (Na-B) and a GCL containing a bentonite-polymer (B-P) composite. The bauxite liquor has pH 13 and an ionic strength of approximately 700 mM. Hydraulic conductivity tests were conducted in flexible-wall permeameters at an effective confining stress of 20 kPa. Before permeation, the GCL specimens were hydrated with tap water to 70% water content to mimic subgrade hydration that would occur in situ. Deionized (DI) water was also used for permeation as a control. Swell index tests were conducted on the Na-B and B-P with DI water and bauxite liquor. Hydraulic conductivity of the prehydrated Na-B GCL to bauxite liquor was approximately four orders of magnitude higher than to DI water (1.5 x 10~(-7) m/s vs. 3.4 x 10~(-11) m/s). In contrast, hydraulic conductivity of the prehydrated B-P GCL to bauxite liquor was consistently low and similar to the hydraulic conductivity to DI water (1.4 x 10~(-11) m/s vs. 1.1 x 10~(-11) m/s). The Na-B had a swell index of 25.0 mL/2.0 g in DI water and 9.0 mL/2.0 g in bauxite liquor. Similarly, the swell index of B-P was 74.5 mL/2.0 g in DI water and 17.5 mL/2.0 g in bauxite liquor. Reduction in swelling of the bentonite is the primary factor responsible for the higher hydraulic conductivity of the conventional Na-B GCL to bauxite liquor relative to DI water. Low hydraulic conductivity of the B-P GCL is attributed to polymer clogging intergranular pores controlling flow of bauxite liquor through the GCL. The findings indicate that B-P GCLs can be used as liners in containment facilities for residuals from aluminium refining, including bauxite liquor.
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