Specific ion effects on surrogate compatibility indices of bentonite for hydraulic barrier applications

Abstract

Bentonites are extensively used in waste containment facilities for controlling the migration of contaminants. The performance assessment of these facilities requires study on long-term hydraulic behaviour of proposed barrier material in the presence of different salts. Liquid limit water content and equilibrium sediment volume (ESV) of clays in the presence of different salt electrolytes are recognised to be the surrogate compatibility indices for understanding the long-term hydraulic behaviour of bentonites. The present paper provided a detailed analysis of influencing parameters on the behaviour of potential clay barrier through these two surrogate compatibility tests. The influence of different pore-fluid parameters, such as electrolyte concentration and specific ion effects on the behaviour of Indian bentonite was presented. The controlling mechanism of these two indices in the presence of different pore-fluid parameters was brought out. A relationship was obtained between the liquid limit water content and ESV data from the present study and the literature studies on different clays. Similarly, a good correlation was found between these indices and equilibrium hydraulic conductivity in the presence of different salt concentrations and different hydrated cation radii.