Modulated colloidal deposition and accumulation in model porous media

Suspended colloids flowing through porous structures are subject to various events, including size-exclusion clogging [1], surface adsorption, or interactions with previously attached bodies. Current models [2,3] qualitatively describe those local mechanisms, while observations are mostly limited to break-through analysis and 2D geometries.

Here, we observe and quantify the local adsorption mechanisms on the internal surface of a 3D porous structure. We consider the accumulation of charged colloids (1µm) in model packs of silica grains and vary the intercolloidal interactions to modulate colloidal aggregation. Deposition is followed by confocal microscopy to identify the precise deposition mechanisms (grain scale) and estimate the spatiotemporal distributions of deposited particles (cm scale). We observe and model two main regimes: (i) deposition of a Langmuirian single-layer of particles due to repulsive intercolloidal interactions, and (ii) multi-layer deposits reaching a critical size (cohesion to drag equilibrium; including potential clogging), when screening those interactions. This provides new tools to predict the transport of suspensions, e.g. for soils remediation or filtration processes.

[1] Gerber, PRL 2018
[2] Elimelech, J. of Col. 1991
[3] Bradford, Env Sci Tech 2003