Modeling surfactant-enhanced nonaqueous-phase liquid remediation of porous media
1998
White, M. D. | Oostrom, M.
A mathematical model is developed to investigate the main processes associated with surfactant-enhanced nonaqueous-phase liquid (NAPL) remediation of porous media. The model couples four nonlinear mass balance conservation equations (i.e., water, NAPL-phase organic, aqueous-phase organic, and aqueous-phase surfactant) that incorporate aqueous- and NAPL-phase migration and transport of aqueous-phase dissolved surfactant and organics. Rate-limited solubilization of the organic into the aqueous phase is represented by a linear driving force expression and is dependent on the surfactant-enhanced equilibrium concentration. Surfactant-enhanced mobilization of the NAPL phase is incorporated using surfactant concentration-dependent interfacial tension lowering, scaled relative permeability-saturation-capillary pressure relations, and trapping number-dependent effective residual saturations for the nonwetting liquid. Sorption of surfactant is assumed to conform to a Langmuir isotherm model, whereas organic sorption is modeled using a linear isotherm with a surfactant and soil-organic content-dependent retardation coefficient. The model is used to simulate experiments described by in which the NAPL perchloroethylene was flushed from sand columns using different surfactant solutions.
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