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Suspensions of particles interacting with porous matrices : transport, deposition and accumulation.

Abstract : From the separation of products on industrial filters to the propagation of pollutants in soils or the transmission of micro-organisms in biological tissues, the transport of particles through porous matrices is ubiquitous. Particle-matrix interactions involve crucial deposition mechanisms, often studied by numerical simulations, global measurements or reduced (1D or 2D) systems. By making adapted 3D porous media (transparent random packings of spheres), and taking advantage of original internal observations (MRI, confocal microscopy), we have been able to directly visualize and analyze the whole range of transport and deposition dynamics at the global and local scales. Varying in turns the particles size (tens of nanometers to tens of microns), long-range interactions (electrostatic or magnetic) and shape (from unique spheres to clusters), all deposition regimes are finally mapped according to three key parameters: particle confinement (particle/pore size ratio), particle-surface affinity, and inter-particle aggregation ability.Two examples highlight the diversity of these regimes. First, we show that non-colloidal particles of sufficient size tend to clog pores by accumulating in pore size clusters, which ultimately constitute regions avoided by the flow. A critical cluster concentration (percolation) corresponds to a system saturation, i.e. caking. Further insights on the impact of the particle shape on the clogging dynamics are also proposed. On another side, for non-clogging colloidal particles, we show that particle accumulation is a self-limited mechanism, towards a deposited fraction associated with a balance between the colloidal cohesive energy and the local flow (drag energy varying with evolving porosity).In the end, the classification of the main deposition regimes combined with simple predictive models allows an application of these results to a broad range of systems.
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Gaétan Gerber. Suspensions of particles interacting with porous matrices : transport, deposition and accumulation.. Environmental Engineering. Université Paris-Est, 2019. English. ⟨NNT : 2019PESC1036⟩. ⟨tel-02884255⟩

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