Eur. Phys. J. E 4, 59-68
Systematic study of the settling kinetics in an aggregating colloidal suspension
D. Senis, L. Gorre-Talini and C. Allain.Laboratoire FAST, Bât. 502 - Campus Universitaire, 91405 Orsay Cedex, France talini@fast.u-psud.fr
(Received 13 October 1999 and Received in final form 21 April 2000)
Abstract
We present a study of the settling of a strongly-aggregating
colloidal suspension. Using well-controlled samples, the different
settling behaviours have been systematically investigated according
to the values of the volume fraction 
of the suspension and
of the inclination angle of the cell. In a vertical cell, three
velocity regimes are observed. To describe the first and final
regimes, we propose a simple 1D model that takes into account the
microscopic structure of the gel constituted by a packing of
fractal aggregates. The second regime coincides with the opening of
fractures within the gel and its description would require a more
complex model. When the cell is inclined at an angle 
to
the vertical, new settling regimes can emerge and an enhancement of
the settling velocity can be observed as in usual macroscopic
suspensions. Using both our 1D model and arguments similar to the
ones used for macroscopic suspensions (PNK model), we propose a
description of the influence of inclination that is in good
agreement with the experimental data. We also present the various
experimental settling behaviours we have observed in a
vs.
diagram that covers the whole range of experimental
conditions.
82.70.Dd - Colloids.
47.20.Bp - Buoyancy-driven instability.
61.43.Hv - Fractals; macroscopic aggregates (including diffusion-limited aggregates).
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
