Determination of Cationic and Anionic Surfactant Concentrations in Soil

Recently, surfactants have been given serious consideration with respect to their potential use in environmental remediation. Proposed in situ clean-up efforts focus on utilizing surfactants to solubilize/emulsify organic contaminants or to desorb heavy metals. Anionic surfactants are the type most likely to be used for removal of organics, whereas cationic surfactants may have application for displacement and mobilization of heavy metals. Research within this field often requires determination of anionic and cationic surfactant concentrations in soil. This paper details a study through which simple and effective extraction procedures were established for use in conjunction with two different surfactant chemical analysis methods. Surfactant extraction is accomplished in two steps. First, a sodium chloride solution is used to reduce electrostatic soil/surfactant attractions and precipitation, and second, acetone is added to minimize hydrophobic adsorption. The extractant solution was diluted, followed by colorimetric chemical analysis using a spectrophotometer. The extraction effectiveness of these procedures was found to be near 100% for both cationic and anionic surfactants.