SORPTION OF METHYL TERT-BUTYL ETHER (MTBE) IN CLAY-RICH MATERIALS

The U.S. Geological Survey has identified methyl tert-butyl ether (MTBE), a constituent of reformulated gasoline, as one of the most common contaminants of urban aquifers in the United States. The primary avenue of MTBE release into groundwater supplies has been by leaking underground fuel tanks. In Illinois, MTBE has been found in 26 of the 1,800 public water supplies and although detection was intermittent, levels were high enough to be offensive to users in three Illinois communities. In Mexico to improve the air quality in urban areas, MTBE has been blended in the two types of gasoline sold by the state oil company (PEMEX). So far only partial data is available about the extent of the contamination in Mexico’s groundwater supply due to limited monitoring. Early research on MTBE considered it unable to adsorb to soils and sediments. However, recent evidence indicates that about 8% of total MTBE could be adsorbed to organic material. The objective of this study is to determine if clay has the potential for sorption of MTBE due to its high specific surface area (10-700 m2/g) and potentially high organic matter (0.5 – 3.8%). The experiment consisted of sorption isotherms to glacial tills from DeKalb, Illinois and lacustrine clays from Chalco, Mexico. Experiments were performed with various concentrations of MTBE (10, 50, 100, 500 and 1000 ppb) at various temperatures (10-25 °C). Results showed a range of values of distribution coefficient (Kd, linear model). Samples of organic rich lacustrine clays had Kd values as high as 5.1657 while samples of lower organic glacial till had a value of 1.072. By contrast the samples of no organic matter sands (Ottawa sand) had a value of only 0.00001. This research is still underway and we expect that it will increase understanding of the sorption of MTBE and lay the necessary groundwork to implement the optimal remediation method for sites contaminated by MTBE.