SURFACTANT-ENHANCED SOLUBILIZATION OF RESIDUAL DODECANE IN SOIL COLUMNS .2. MATHEMATICAL-MODELING

A mathematical model is developed to describe surfactant-enhanced solu bilization of nonaqueous-phase liquids (NAPLs) in porous media. The mo del incorporates aqueous-phase transport equations for organic and sur factant components as well as a mass balance for the organic phase. Ra te-limited solubilization and surfactant sorption are represented by a linear driving force expression and a Langmuir isotherm, respectively . The model is implemented in a one-dimensional Galerkin finite elemen t simulator which idealizes the entrapped residual organic as a collec tion of spherical globules. Soil column data for the solubilization of residual dodecane by an aqueous solution of polyoxyethylene (20) sorb itan mono-oleate are used to evaluate the conceptual model. Input para meters were obtained, where possible, from independent batch experimen ts. Calibrated model simulations exhibit good agreement with measured effluent concentrations, supporting the utility of the conceptual mode ling approach. Sensitivity analyses explore the influence of surfactan t concentration and flushing strategy on NAPL recovery.