Geo‐environmental characteristics of modified and ordinary bentonitic soils exposed to MTBE

Abstract

Methyl tertiary‐butyl ether (MTBE) is the most common oxygenated fuel additive used to increase the octane rating and enhance the combustion efficiency of gasoline. This product is characterized as a harmful compound by the US EPA and has been shown to be a health threatening contaminant for human beings. The most contingent route for MTBE to enter the environment is its leaking from underground storage tanks (USTs). To avoid soil and groundwater contaminations because of leaking of MTBE, we investigated the performance of both modified and ordinary bentonite clays as liner systems at USTs sites in this study. Modified bentonites are synthesized by changing the original metallic cations in the structure of bentonite particles, thus converting the bentonite from hydrophilic to organophilic nature. In this research both modified and ordinary bentonites were investigated to evaluate MTBE adsorption efficiencies. As permeability is a major parameter in measuring contaminants flow in soils, tests were conducted to measure the permeability characteristic of bentonites. X‐ray diffraction (XRD) analyses were also carried out to evaluate the adsorption of MTBE to bentonites. The results indicated that basal spacing of modified bentonite particles was increased from 28.64 to 42.32 Å, thus showing MTBE adsorption to the soil. In terms of permeability tests, modified bentonites showed much lower permeability values compared to ordinary bentonites (1.9 order of magnitude reduction) when exposed to MTBE. Modified clays are a viable option for use as liner system material at MTBE contaminated sites.