Multiscale dynamics of colloidal deposition and erosion in porous media

Abstract

Diverse processes—e.g., environmental pollution, groundwater remediation, oil recovery, filtration, and drug delivery—involve the transport of colloidal particles in porous media. Using confocal microscopy, we directly visualize this process in situ and thereby identify the fundamental mechanisms by which particles are distributed throughout a medium. At high injection pressures, hydrodynamic stresses cause particles to be continually deposited on and eroded from the solid matrix—notably, forcing them to be distributed throughout the entire medium. By contrast, at low injection pressures, the relative influence of erosion is suppressed, causing particles to localize near the inlet of the medium. Unexpectedly, these macroscopic distribution behaviors depend on imposed pressure in similar ways for particles of different charges, although the pore-scale distribution of deposition is sensitive to particle charge. These results reveal how the multiscale interactions between fluid, particles, and the solid matrix control how colloids are distributed in a porous medium.

A seemingly universal particle kinetic distribution in porous media

“…For example: (1) Hydrodynamics, represented by the particle Péclet number, has a positive impact on particles deposition, as discussed in Sec. V of the SM; this effect in our analysis is qualitatively consistent with direct experimental confocal microscopy observations 58 . (2) Because the proposed function considers particle-medium interactions via the XDLVO theory, it may help to interpret the progressive attachment of particles on medium surfaces when ionic conditions intensify 59 or the enhanced deposition observed as a function of particles surface charge 58 .…”

“…(3) Our simulation results also demonstrate a descending deposition pattern along with the porous medium, as discussed in Sec. V of SM, in qualitative agreement with confocal microscopy 58 and coreflooding experiments on sand/bead packs 60 , indicating the applicability of our approach to designing experiments of particulate flows.…”

Modeling the effect of flow-induced mechanical erosion during coffee filtration

“…2. It demonstrates a unique erosion model compared with those in literatures 18,21,22,24,26,51,52 . In literatures, some erosion models assume that the erosion rate is proportional to the difference between the shear stress and the threshold stress 18,[25][26][27] ; other erosion models assume that the erosion is dependent on the local flow velocity 24,53 ; in effective models using Darcy's law it is usually assumed that the erosion rate depends on the difference between the local pressure gradient and a threshold 21,22 .…”

Modeling Multiphase Flow Within and Around Deformable Porous Materials: A Darcy-Brinkman-Biot Approach

“…Added to these spatial challenges is the fact that clogging is also a temporal process. Clogging mechanisms often don't reach a steady state: Clogs can form, redirect fluid fields, change pressure gradients, break, and form again downstream (Bizmark et al, 2020).…”

“…Confocal microscopy takes advantage of the fact that it is possible to match the refractive index of an artificial porous medium with the index of its permeating fluid phase in order to "see" through the whole solid-fluid mixture. This technique has allowed scientists to characterize particle deposition and clogging as a function of time while having a high level of control of the relevant flow variables and material characteristics (Bizmark et al, 2020;Mays et al, 2011).…”