Pore-scale simulations of colloidal transport and retention in porous media

Non-aqueous liquids (NAPLs) are water-immiscible pollutants that can disperse and release significant amounts of toxic compounds into underground water resources. Numerous methods have been developed to remove these pollutants from aquifers, but NAPL droplets remain trapped by capillary forces in the porous matrix even after depollution. The aim of our research is to explore the potential of colloids (e.g. nanoparticles, bacteria) to remobilize immiscible pollutant droplets. Our final objective is to develop a multiphase model at the pore scale that includes colloidal interactions with the solid phase, the aqueous phase, and the NAPL. Euler-Lagrange models allow an accurate description of colloidal particle interactions (e.g. transport and retention) but remains very time- and resource-intensive. In this work, we are developing Euler-Euler approaches based on OpenFOAM's multiphaseEuler module to represent particles as a dispersed phase in water. The use of this model in the context of the remediation of polluted porous media is currently under development. Our package includes new viscosity models and plastic behavior, as well as poromechanic properties to account for the compressibility threshold of clogged particles. Aggregation forces in between particles and between particles and grains are also considered. To this end, we are using DLVO theory, which characterizes the forces exerted between two charged surfaces separated by a liquid. We present preliminary results such as : i) comparisons with Euler-Lagrange simulations for very diluted suspension, ii) response to fluid stresses and its compressibility, and iii) study of the impact of particle aggregation in the context of porous media.