(295i) Multiscale Dynamics of Colloidal Transport and Deposition in Porous Media

Diverse processes—e.g. groundwater remediation, enhanced oil recovery, and drug delivery—rely on the transport of colloids in disordered, three-dimensional (3D) porous media. However, how pore-scale confinement and tortuosity alter particle transport and deposition in the medium, and how deposition in turns alters subsequent flow and transport, are poorly understood. Here, we elucidate these coupled dynamics by directly visualizing colloidal transport and deposition in transparent, 3D porous media over a broad range of length and time scales. We find that while the pore-scale distribution of deposited particles is sensitive to particle charge, their distribution throughout the entire medium is tuned by imposed pressure in unexpectedly similar ways, independent of particle charge. Specifically, at high injection pressures, we observe that particles are both deposited and eroded in the pore space continually, enabling them to deposit through the entire medium—in stark contrast to some theoretical predictions. Conversely, at low injection pressures, particle deposition is dominant, causing deposition to be localized only near the inlet of the medium. Guided by these findings, we develop a model that describes the evolution of the overall permeability of the medium over time, providing a quantitative description of how deposition in turn impacts fluid flow. Our results thus deepen our understanding of the multi-scale interactions between flowing fluid, particles, and a porous medium during colloidal transport, yielding guidelines for their use in environmental, energy, and biomedical settings.