Consolidation and Compressibility Behavior of Compacted Nanoclay-Amended Bentonite Liners Inundated with Inorganic Salt Solutions

Abstract

The hazardous waste leachates from landfills and tailing disposal facilities pose a severe threat to environmental ecosystems if they infiltrate through the barrier component. Bentonite and its amendments are frequently employed as hydraulic barriers because of their low cost, environmentally sustainable nature, and peculiar impermeable properties. Even so, the interaction of the bentonite barrier with inorganic and organic chemicals significantly deteriorates the long-term performance of bentonite. Hydrophobic nanoclays are proven to have better chemical compatibility and performance, especially in organic solutions. Therefore, this study employed a mixture of bentonite and hydrophobic nanoclay (referred to as BNC) to understand its feasibility for containment applications under aggressive electrolytic conditions. BNC liners were employed to immobilize and adsorb organic and inorganic pollutants without compromising the hydraulic performance. For this experimental program, inorganic salt solutions of NaCl and CaCl2 were chosen at concentrations of 0, 0.1, and 1 N. The effect of various permeants on the compressibility and consolidation characteristics of compacted BNC liners was investigated by performing a series of oedometer tests. From the test results, it was observed that the time for 90% consolidation (t90), compression index (Cc), and coefficient of volume change (mv) of BNC decreased, but the coefficient of consolidation (cv) and yield stress (Po) increased with an increase in electrolyte concentration and valency. The Cc of BNC declined by 23.9% and 25.5%, respectively, when the permeant solution was changed from deionized (water to 1 N NaCl and CaCl2, whereas bentonite showed a significant drop of 37.4% and 39.5% for the same solutions. However, the effect of inorganic salts on these parameters was significantly less in BNC liners than in bentonite liners. In the light of these findings, this study recommends the use of nanoclay-amended bentonite liners for containment applications at high electrolytic conditions.