The Effect of Surfactants on the Sorption Partition Coefficients of Naphthalene on Aquifer Soils

The efficiency of removing organic contaminants from groundwater aquifers by the pump and treat process 1s adversely affected by the retardation of the contaminant's mobility due to adsorption onto aquifer material. The use of surfactants 1n conjunction with the pump and treat process has the potential for improving contaminant mobility by solubilizing the adsorbed contaminant. An experimental program was conducted to screen various types of commercially available nonionic and anionic surfactants for solubilizing adsorbed naphthalene from one type of aquifer soil. Two additional types of aquifer soils were obtained, and the surfactant mixture, Tween 20 and Aerosol AY-65, selected during the screening process was used at various concentrations for equilibrium desorption studies to quantify surfactant effects on naphthalene desorption. Equilibrium desorption studies showed that a 0.125 percent surfactant solution decreased the partition coefficient 65 percent compared with water alone for one soil type, while greater surfactant concentrations resulted 1n less effective mobilization. However, the same surfactant mixture markedly increased the partition coefficient when used with another soil type, and had negligible effects for the third soil type. It was shown that the clay mineralogy significantly influenced the effect of the surfactant solution.