Tetrachloroethylene migration and remediation by surfactant-alcohol in two-dimensional saturated layered sand laboratory experiment

Abstract

Surfactant-alcohol remediation have been reviewed by many researchers as an innovative technology to remediate tetrachloroethylene (PCE) from the subsurface. However, the application of surfactant-alcohol remediation to layered sand conditions is still obscurity and its implementation is limited due to flow sensitivity to site characterization. The laboratory experiment was performed in assessing the efficiency of surfactant-alcohol remediation through two-dimensional (2-D) saturated layered sand contaminated with tetrachloroethylene (PCE) spill. The 2-D physical model consist of front clear glass for easy visualization of 2-D PCE migration and framed with aluminum material has been developed. The type of sand use is fine sand and coarse sand. The laboratory investigation of PCE remediation in 2-D saturated layered sand using three different surfactant solutions. The first solution consist of 4 % surfactant, the second solution consist of 8 % surfactant and the third solution consist of 4 % surfactant and 15 % n-butanol. The PCE migration has been captured and analyzed to evaluate the dominant mechanisms and efficiency of PCE remediation. The laboratory experimental results shows that the dominant mechanism of PCE remediation in 2-D saturated layered sand using surfactant-alcohol treatment is solubilization and mobilization mechanisms. The solubilisation mechanisms are govern by the properties of surfactant itself where the surfactant are soluble in water due to the oxygen atom that are capable in forming hydrogen bond with the water molecules. The oxygen atom in surfactant are the hydrophilic head which is water lover attach to water and the other atom with the hydrophobic tail which is water hate attach to PCE. The interfacial tension between PCE, water and sand are lod because the surfactant molecules are surround PCE. The addition of co-surfactant, n-butanol in surfactant solution help in the formation of microemulsion which increase the number of micelles thus increase the solubilisation and mobilization of PCE. The reduction of total density of the microemulsion result in the PCE migration to the upward direction following its low density compared to water density. This shows that the prevention of uncontrolled downward migration of PCE are possible. The effect of microemulsion in lowering the interfacial tension between PCE, water and sand has result in no residual PCE left at the PCE source zone. The results of this study shows that surfactant-alcohol are very efficient solution to remediate PCE in 2-D saturated layered sand.