Utilization of organoclay amended bentonite for hydraulic barrier applications under adverse electrolyte environment

Abstract

Inorganic ions such as sodium and calcium are often found in industrial leachates, municipal solid waste leachates and deep geological repositories, which can significantly impact the geotechnical properties of hydraulic barrier materials. Researchers have suggested the utilization of organoclays as landfill liner amendments, especially when the liner is in contact with organic contaminants. This study focuses on the impact of inorganic salts (NaCl and CaCl2) on the geotechnical properties, such as consistency limits, swelling, and hydraulic conductivity of organoclay-amended bentonite (BOC) liners. Different concentrations of salt solutions (0, 0.1 N and 1 N) were selected for the execution of Atterberg limits, free swell tests, and oedometer tests. The surface charge characteristics of bentonite and organoclay were attained with the aid of zeta potential measurements. The variation in the surface topographies of soil samples at different electrolyte conditions was analyzed with the help of scanning electron microscope images. The addition of organoclays significantly reduced bentonite's swelling characteristics and liquid limit due to the unique hydrophobic and organophilic attributes of organoclay but increased the hydraulic conductivity. However, the influence of inorganic salts on the geotechnical parameters of organoclay-amended bentonites showed less variance than that of bentonite. Also, no soil samples exceeded the limiting hydraulic conductivity criteria required for landfill liners, i.e. 1 × 10−9 m/s. Hence, organoclay-amended bentonites could potentially be utilized for hydraulic barrier applications even in an electrolytic environment without compromising the hydraulic conductivity criteria.