Enhanced Trichloroethene Desorption from Long-Term Contaminated Soil Using Triton X-100 and pH Increases

Laboratory batch and column experiments were conducted to study the effect of relatively low concentrations of Triton X-100 and pH increases on trichloroethene (TCE) desorption from field-contaminated soil to water. TCE desorption from the contaminated soil could not be described by a model that assumes a localized equilibrium between the aqueous- and sorbed-phase concentrations of TCE. A kinetic desorption model, the multi-site model with a γ-distribution of rate constants, was used to interpret the data and to determine the mass-transfer coefficients. In both batch and column experiments, the multi-site model performed well in simulating TCE desorption. In laboratory batch and column experiments, the addition of Triton X-100 (at concentrations close to critical micelle concentration) to the soil-water system increased the rate of TCE desorption from the soil at early times, although only by a small amount. Similar results were obtained by increasing the solution pH from 7 to 10. In experiments with Triton X-100, the mean mass-transfer coefficient increased by 11.2% in batch tests and 16.5% in column tests relative to experiments without Triton X-100. The mean mass-transfer coefficient increase caused by increasing pH from 7 to 10 was 53% in batch tests and 7% in column tests.