To assess the suitability of an alcohol ethoxylate surfactant for washing contaminants from soils, the sorption of the surfactant by a sandy soil was studied and the extent of washing of polychlorinated biphenyls (PCBs) from the soil was evaluated. The surfactant adsorption is described by an S-shaped isotherm, consistent with a Langmuir-type monomolecular adsorption followed by adsorption of the surfactant micelles. After only 10 washings with water, the surfactant concentration in the effluent samples decreased from as high as 10000 mg/L to less than 60 mg/L.PCBs could be effectively washed from the sand by using surfactant solutions. After 20 washings about 66, 86, and 56% of the PCBs were washed from the columns by 5000, 10000, and 20000 mg/L surfactant solutions, respectively. This is equivalent to a reduction in PCBs from 1728 mg/kg to about 614, 251, and 769 mg/kg, respectively. The mechanisms responsible for the PCB removal from the sand are presented and discussed.

Soil and ground‐water contamination by petroleum products, such as gasoline and oils, is widespread. A laboratory study was conducted to evaluate the relative suitability of 10 commercial surfactants for washing residual levels of automatic transmission fluid (ATF) from sandy material. The surfactants included at least one example for each of four main groups of commercial surfactants: (1) ethoxylated alcohols (nonionic), (2) ethoxylated nonylphenols (nonionic), (3) sulfates (anionic), and (4) sulfonates (anionic). Several properties of aqueous solutions of the surfactants (0.00001 to 5.0% v/v) were measured and used in evaluating their suitability. The extent of dispersion of soil colloids was measured as the turbidity (in formazin turbidity units, FTU) of soil/surfactant solution mixtures. The detergency of the surfactant solutions and the extent to which they solubilized the ATF were measured. The critical micelle concentration, which ranged from 0.05 to 5.0 percent, was measured and used to select the aqueous concentration of the surfactants in washing experiments. The amount of ATF removed from the sand ranged from about 23% by washing with water to more than 80% by washing with ethyoxylated alcohol surfactants. ATF was best removed from the soil by washing with a 0.5% aqueous solution of either alkoxylated alcohol ether, ethoxylated alcohol, or nonylphenol ether sulfate. An ethoxylated alcohol surfactant was selected for scale‐up laboratory and field tests because this surfactant caused low soil‐colloid dispersion and high ATF dispersion and solubilization, and was effective in washing ATF from the soil

was performed under the partial sponsorship of the U.S. EPA Risk Reduction Engineering Laboratory under Cooperative Agreement CR-813938. Although this research was funded by the U.S. EPA, it has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.

An in situ surfactant washing process was previously developed and successfully pilot‐tested at a field site contaminated with polychlorinated biphenyls (PCBs) and oils (Abdul et al., 1992). A second phase of the pilot study, conducted the following year at the same site, confirmed the technical viability of this process. The results of the phase II study surpassed the predictions of the long‐term performance of this technology based on the phase I results. Soil cores taken from the plot before the phase I and phase II studies and after the phase II study showed mass reduction and redistribution of the contaminants. A continuous column washing study using the same contaminated soil showed consistency with field results. The amounts of PCBs removed in the laboratory and field studies, respectively, are 7% and 10% after 5.7 pore volume (PV) washings (phase I) and 19% and 24% after 8 PV washings (phase II). More than 85% of the PCBs were removed from the laboratory soil column after 105 PV washings. This study supports the phase I study which indicates that the in situ surfactant washing process is a viable remediation technology for hydrophobic contaminants.

Batch experiments were carried out to investigate the adsorption of six polycyclic aromatic hydrocarbons (PAH) (naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene) by two aquifer materials. The results show that the adsorption of these PAH is adequately described by the linear isotherm model. Adsorption of naphthalene or fluorene in a mixture with other PAH was suppressed slightly compared to measurements when only one compound was in solution. Regression equations relating the slope of the linear isotherm (kd) to the coefficient of partition between octanol and water (Kow) of the compounds and the fraction of organic carbon (foe) of the material predicted the order of adsorption of the six PAH, but the predicted and measured values of Kd differ by a factor of up to four. Predictions based on the solubility of the PAH gave larger differences from the measured results and did not agree with the measured order of adsorption of these compounds. The adsorption and desorption of fluorene were found to be hysteretic.