Modelling surfactant influenced PAH migration

Abstract

Within the framework of a comprehensive investigation concerning the use of surfactants to enhance the remediation of PAH contaminations in the subsurface, a multicomponent transport model was developed to study the processes (interactions) taking place when surfactants and PAH migrate through porous media as solutes. Based on a close co-operation with the laboratory investigations during model development only those processes that could be identified within laboratory experiments have been implemented in the model: (i) surfactant-micellization, (ii) surfactant sorption (formation of hemi- and admicelles), (iii) intra-particle diffusion of PAH, (iv) PAH sorption on hemi- or into admicelles, (v) solution of PAH within micelles. Furthermore, process-oriented descriptions are used to guarantee that only measurable parameters are needed as model input. In a first step column experiments with phenanthrene and the surfactant Terrasurf G50 (Danzer and Grathwohl, 1997, this issue) have been simulated by pure forward modelling in order to validate the conceptual model. Using independently measured parameters only the model is able to reproduce the breakthrough curves of both phenanthrene and Terrasurf G50 very well. Furthermore, the modelling results provide evidence that not only PAH sorption but also the sorption of surfactants may be limited by diffusion. Based upon these results a new conceptual model of the processes involved in the coupled transport of PAH and surfactants has been developed.