Combined Effect of Inorganic Salts and Heavy Metals on the Engineering Behaviour of Compacted Bentonites

Abstract

The possible contamination of groundwater by the chemicals present in leachates is of serious environmental problems, which may lead to an alteration in the pore water chemistry of surrounding soil. Due to its lower permeability, bentonite is primarily applied as a liner material. This study has been performed to compare the combined influence of inorganic salts and heavy metals on two different bentonites. Two bentonites, differ markedly by their swelling ability, were investigated for change in their swelling and hydraulic behaviour due to the exposure to various combinations of inorganic and heavy metals solution. Different concentrations of NaCl and CaCl2 and heavy metals such as lead, copper, and zinc were chosen for the study. Results showed that the combined influence of salts had a significant impact on the behaviour of both the bentonites in comparison to the effect due to the individual salt solution indicating an additive effect of salt on these properties. It was also observed that the hydraulic and swelling behaviour of bentonites depends more on the quality of the bentonite at low concentrations of the permeant; whereas, for high concentrations, the quality of bentonite is dominated by the concentrations of the permeant.