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
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