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Soft Matter and Biological Physics
Eur. Phys. J. E 2, 31-38

Settling in aggregating colloidal suspension: Analysis of cell inclination influence

D. Senis - L. Gorre-Talini - C. Allain

Laboratoire FAST, Bât. 502 - Campus Universitaire, 91405 Orsay Cedex, France
talini@fast.u-psud.fr

Received 13 July 1999

Abstract
We present the study of the settling of a colloidal gel in a cell tilted at an angle $\alpha$. In suspensions of non-colloidal particles, the inclination of the sedimentation cell leads to a large enhancement of the settling velocity known as "Boycott effect'' well described by the PNK model. We show that the specific mechanical properties of a colloidal gel can give way to kinetics of settling very different from usual suspensions which can no longer be described using a simple PNK model. In particular, we study the influence of the very voluminous sediment generally formed in such systems. We thus propose a complete description of the kinetics of a settling colloidal gel according to its volume fraction and to the cell inclination angle. In the experimental section, the predicted settling regimes are compared to experimental results obtained with calcium carbonate suspensions. The agreement between theoretical expressions and experiments is good which shows that our results are relevant to most experimental studies of tenuous colloidal gels.

PACS
82.70.Dd Colloids - 47.20.Bp Buoyancy-driven instability


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