Settling in Aggregating Colloidal Suspensions
Résumé
Strongly-aggregating colloidal suspensions form gels whose stability depends on the volume fraction phi of the particles. In a given range of volume fractions, the formed gel is so fragile it collapses under its own weight. We present a study of the settling kinetics of such a colloidal gel. Systematic experiments have been performed in calcium carbonate aqueous suspensions of varying volume fractions. Different settling regimes have been observed and are successfully described using a 1D model that takes into account both the microscopic structure of the gel constituted by a packing of fractal aggregates and its specific mechanical properties. We have also varied the inclination angle alpha of the cell to the vertical direction, which can lead to the occurrence of new settling regimes. The experimental results are summarised in a alpha vs. phi diagram that covers a large range of experimental conditions. Using both our 1D model and arguments similar to the ones used for macroscopic suspensions (PNK-Ponder, Nakamura and Kuroda-model), we propose a 2D description of the influence of inclination that is in good agreement with the experimental data. The model we propose therefore enables both to interpret and predict the settling behaviours of strongly-aggregating colloidal suspensions that are involved in many industrial processes.
Domaines
Physique [physics]
Origine : Publication financée par une institution
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