Modeling surfactant-enhanced nonaqueous-phase liquid remediation of porous media.

摘要

A mathematical model was developed to investigate the main processes associated with surfactant-enhanced non-aqueous-phase liquid (NAPL) remediation of porous media. The model couples four non-linear 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 was incorporated using surfactant concentration-dependent interfacial tensionlowering, scaled relative permeability-saturation-capillary pressure relations, and trapping number-dependent effective residual saturations for the non-wetting liquid. Sorption of surfactant is assumed to conform to a Langmuir isotherm model, whereas organic sorption was modelled using a linear isotherm with a surfactant and soil-organic content-dependent retardation coefficient. The model was used to simulate experiments in which the NAPL perchloroethylene was flushed from sand columns using differentsurfactant solutions.