Role and importance of surface heterogeneities in transport of particles in saturated porous media

Knowledge of particle deposition and transport in saturated porous media is of significant importance for various engineered applications and environmental concerns. Surface physical and chemical heterogeneities play a critical role in particle deposition because they can increase attachment in the primary minima of Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profile by reducing the repulsive energy barrier. We present a comprehensive review showing that surface heterogeneity can alter particle deposition through multiple additional mechanisms such as increasing attachment at secondary minima at concave locations and detachment from primary minima at nanoscale convex asperities. The pore-scale deposition mechanisms due to surface heterogeneity can cause anomalous particle retention and transport behaviors at continuum scales such as equilibrium sorption and nonmonotonic retention profiles. To accurately determine the particle transport in porous media at continuum scales requires future research: (1) improving existing techniques to accurately measure and represent surface heterogeneities and determine attachment and detachment; (2) using statistic models to characterize variations of attachment and detachment with surface heterogeneity; (3) using Lagrangian/Eulerian approach to thoroughly understand pore-scale retention mechanisms in porous media, and incorporating them into continuum equations to simulate particle transport at continuum scales.