Aqueous Surfactant Washing of Residual Oil Contamination from Sandy Soil |
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| Authors: | Carolina C Ang Abdul S Abdul |
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| Institution: | Carolina C. Ang received a B.Sc. in chemistry from the University of Santo Tomas, Manila, Philippines, in 1964. She has been a member of the Environmental Science Department in General Motors Research Laboratories (Warren, MI 48090–9005) since 1973. She has extensive experience in analytic and atmospheric chemistry. Her research interest is in the investigation and remediation of toxic comtaminants in the environment with primary interest in surfactant washing of contaminated soils and biological processes.;Abdul S. Abdul received his Ph.D. in contaminant hydrogeology from the Institute of Ground Water Research, Department of Earth Sciences, University of Waterloo, Ontario, Canada, in 1985. He has been a member of the Environmental Science Department in General Motors Research Laboratories (Warren, MI 48090–9005) since 1985, where he is now research manager of the Groundwater Decontamination Section. His major interests include the movement of immiscible fluids and reactive solutes through hydrogeologic materials, and the development of technologies based on physical, chemical, and biological processes to clean up contaminated soil and ground water systems. |
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| Abstract: | A laboratory study was conducted to determine the efficiency of different aqueous concentrations of an alcohol ethoxylate surfactant in washing residual levels of an oil automatic transmission fluid (ATF)] from sandy soil. Five glass columns packed with the soil were prepared in a manner that simulated conditions leading to residual saturation in an actual oil leak. Each of four columns was washed continuously with 28 pore volumes of solution by pumping either 0.0 percent (water), 0.5 percent, 1.0 percent, or 2.0 percent aqueous surfactant solutions through the columns. The fifth column was washed intermittently with 28 pore volumes of a 1.0 percent surfactant solution. Water washed only 25.5 percent of the ATF from the column soil, while the 0.5 percent, 1 percent, and 2 percent surfactant solutions washed 55 percent, 60 percent, and 72.8 percent of the ATF, respectively. The distribution of the ATF remaining in the column after washing showed that the ATF removed by water was mainly from the outlet side of the column, while the ATF removed by the 2.0 percent surfactant solution was mainly from the inlet side of the column. This observation indicated that different mechanisms were involved; namely, the displacement of oil through the soil-pore space, the dispersion of oil due to reduced surface tension, and the solubilization of oil by surfactant micelles. In the case of water, the displacement of oil was the main washing mechanism, while all three mechanisms were operative during surfactant washing. ATF dispersion and solubilization were improved at higher surfactant concentrations. The column that was washed intermittently to pulse ATF from dead end pores did not show a significant improvement over the column that was continuously washed with the same 1.0 percent surfactant solution. The results show promising potential for application in the field and will be further investigated in a two-dimensional model aquifer. |
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