Pore-scale simulation of electrokinetic remediation of organic pollutants in restructured low- permeability porous media

Abstract:

Abstract: Low permeability media causes organic contaminants, such as chlorobenzenes, remediation difficult under surface due to inability to transmit hydrostatic pressure (Qiao et al., 2018). Electrokinetic Remediation (EKR) applies extra low strength electric field to move contaminants from one electrode chamber toward the other by multiple mechanisms like electroosmosis. However, the efficiency of EKR varies either in laboratory or field applications due to various media and the corresponding difference in transport and reaction, which is not understood well. To figure out the mechanism, we establish a pore-scale numerical model for inhomogeneous charge electroosmosis including five species to consider zeta potential change on the surface of media along EKR. NPPE (Nernst-Planck-Poisson Equation) was coupled with NSE (Navier-Stokes Equation) to calculate the transport of all species. 1-pK model was proposed to consider zeta potential change with pH in pore-scale simulation to study ions transport property (Zhang and Wang, 2017). It was extended in this study to properly describe the transport behavior of organic pollutants. One in-situ soil sample was taken in a field site at Tianjin, China. FIB-SEM (Focused Ion beam- scanning electron microscope) was used to scan the sample to build 3D pore structure. The structure size is 10μm×10μm×10μm with voxel size 10nm×10nm×10nm. Some characteristic structures which can represent the features of this sample were conceptualized and then used for simulation. COMSOL Multiphysics^® was applied as the simulation platform. The phenomena of reverse electroosmosis and non-filtration were observed in our preliminary simulations.

Main Reference：

Qiao, W.J., Ye, S.J., Wu, J.C. and Zhang, M., 2018. Surfactant-Enhanced Electroosmotic Flushing in a Tricholrobenzene Contaminated Clayey Soil. Groundwater, 56(4): 673-679.

Zhang, L. and Wang, M.R., 2017. Electro-osmosis in inhomogeneously charged microporous media by pore-scale modeling. Journal of Colloid and Interface Science, 486: 219-231.