Self-Limited Accumulation of Colloids in Porous Media

Abstract

borosilicate beads (negatively charged, 63 μm average 66 diameter) randomly packed (porosity ϕ 0 ¼ 0.38) in a 67 square glass capillary (width w ¼ 1.0 mm), and we invade 68 this medium with positively charged, fluorescent, mono-69 disperse (diameter d p ¼ 1.0 μm) latex colloids. The 70 suspensions are made at constant dilute concentration C 0 ¼ 71 20 mg mL −1 in a mix of deionized water and DMSO to 72 match the refractive index of the beads [28]. This allows us 73 to visualize the particles inside the porous medium by 74 confocal microscopy. The opposite charges of the beads 75 and the particles fosters particle adsorption at the surface of 76 the beads. Particle-particle bonding may be promoted by 77 screening the interparticle repulsion (i.e., decreasing the 78 Debye length) through an increase of the ionic strength I by 79 addition of salt (sodium iodide) [29]. 80 A test consists of continuously injecting a suspension in 81 the porous medium (initially saturated with liquid) 82 and tracking the particle deposition inside the medium. 83 Except when mentioned, we impose a constant flow rate

Propagation and adsorption of nanoparticles in porous medium as traveling waves

“…It seems in fact rather reasonable to consider that a deposited particle will not easily be moved again if the flow conditions, which allowed the particle to fix onto the solid surface, do not change, as expected under steady injection. Remark that, on the contrary, some particle removal can result from a significant evolution of the pore structure due to deposits, which has led to a significant increase of the local velocity [47].…”

“…This porous medium is saturated with a fluid made of 90% of DMSO (Dimethyl sulfoxide) in distilled water, leading to a fluid of viscosity μ ≈ 3.3 mPa s and density ρ = 1090 kg m −3 . This fluid matches the refractive index of the beads and allows for internal imaging of the 3D pack with the help of confocal microscopy, a technique which proved to be relevant for the study of fluorescent particles in 3D porous media [47,53].…”

“…We focus on deposition processes leaving the porous medium unchanged, i.e., clogging or even thick deposit as compared to the pore scale, which have been considered in Refs. [46][47][48], are negligible. We show that a minimal number of ingredients may be used to describe the principles of the propagation and deposition of colloids in porous medium, and that such an approach leads a straightforward quantification of the process in simple physical terms.…”

“…These different works helped clarifying our understanding of the local phenomena but were in general not directly used for transport and deposition modeling at a macroscopic scale. Nevertheless, recent quantitative internal visualizations, with NMR (nuclear magnetic resonance) [46] and confocal microscopy [47], appeared useful to develop probabilistic models of deposits and/or clogging at a macroscopic scale and check their agreement with internal measurements.…”

Multiscale dynamics of colloidal deposition and erosion in porous media

“…While these studies provide tremendous insight into particle transport and deposition, they do not fully capture the connectivity and complexity of a 3D pore space. Recent work has extended these investigations to transparent 3D media, but only investigated single-particle behavior (29), did not investigate different colloidal chemistries (30,31), or only focused on particle deposition near the inlet of the medium (32). Furthermore, magnetic resonance imaging and X-ray microtomography yield additional insights into the spatial distribution of particles in the pore space-for example, indicating that the distribution of deposited particles is sensitive to the particle charge (33,34), size (35), and imposed flow conditions (36).…”