Effect of cation exchange on surfactant-enhanced solubilization of trichloroethene

The objective of this study was to develop the single-well push–pull test as a diagnostic tool for assessing the potential for cation exchange to adversely affect the phase behavior of sodium Ž . dihexyl sulfosuccinate surfactant Aerosol MA 80-I and its solubilization of trichloroethene Ž . TCE in the subsurface. Laboratory push–pull tests were conducted on a model natural aquifer sediment collected from a TCE-contaminated field site and a test solution consisting of 36,800 Ž . Ž . Ž mgrl 3.7 wt.% sulfosuccinate, 100,000 mgrl 10 wt.% isopropanol, and 3200 mgrl 0.32 . wt.% KBr. Laboratory experiments were designed to simulate conditions occurring during single-well, Apush–pullB tests. In batch experiments conducted in the presence of excess TCE, the test solution gave a Winsor Type I system with an enhanced aqueous TCE solubility of 26,700 mgrl and a solution density of 1.000 grcm. The sulfosuccinate surfactant was transported conservatively in sediment packs containing no TCE. However, increasing concentrations of Ca and Mg resulting from cation exchange caused the TCE solubilization potential of the injected surfactant to exceed values predicted from the solubilization isotherm. Sulfosuccinate surfactant transport was strongly retarded in sediment packs containing 5 vol.% residual TCE because cation exchange resulted in the formation of a Winsor Type II system, which resulted in the partitioning of the sulfosuccinate surfactant into the residual TCE phase. Conservative sulfosuccinate transport was observed in a separate sediment pack containing 5 vol.% residual TCE when a 130 meqrl Na pre-flush was used to reduce quantities of Ca and Mg in the sediment pack prior to ) Corresponding author. Tel.: q1-503-737-2265; fax: q1-541-737-0497. Ž . E-mail address: [email protected] J.A. Field . 0169-7722r00r$ see front matter q2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-7722 00 00115-7 ( ) J.A. Field et al.rJournal of Contaminant Hydrology 46 2000 131–149 132 sulfosuccinate injection. The results of this study emphasize the importance of cation exchange on the performance of surfactant-enhanced TCE solubilization and demonstrate the utility of the push–pull test for predicting the potentially deleterious effects of cation exchange on surfactant phase behavior in the presence of residual TCE. q 2000 Elsevier Science B.V. All rights reserved.