Consolidation of concentrated dispersions of nano- and microparticles determined by analytical centrifugation - PSA 2005

Particulate Systems Analysis 2005 21 - 23rd September PSA 2005

Stratford upon Avon, UK

Consolidation of concentrated dispersions of nano- and microparticles determined by analytical centrifugation

D. Lerche, T. Sobisch

L.U.M. GmbH, Rudower Chaussee 29 (OWZ) 12489 Berlin, Germany info@lum-gmbh.de, www.lum-gmbh.com

ABSTRACT:

The consolidation behaviour of suspensions was experimentally analysed by means of a multisample analytical photocentrifuge. Experiments were conducted covering a broad range of volume concentrations and centrifugal accelerations. The obtained material functions allow to simulate batch sedimentation, filtration and consolidation. For only hydrodynamically interacting particles the separation velocity decreases with the volume concentration. The so-called hindered settling rate may be fitted to a power law. Interacting particle systems above the gelpoint have to be described by the compressive yield stress. The compressive properties of stable and flocculated dispersions can be easily determined by multisample analytical centrifugation for rapid classification and tailoring of dispersion properties.

Keywords: analytical centrifugation, consolidation, particle interaction, flocculation

1 Introduction

Separation of a dispersed phase from a fluid is extremely important from both theoretical and industrial viewpoints. Sedimentation and consolidation phenomena are crucial in decanter operation as well as in cake filtration and membrane filtration. It was comprehensively elaborated that these processes may be described by a unified theory of solid-liquid separation of non-interacting as well as flocculated suspensions (Landmann 1994; Garrido 2000). However, this mathematical description requires the knowledge of the characteristic material parameter of the dispersions as function of the volume concentration. Until now the prediction of these parameter is not possible. Their broad variation range for different dispersions requires efficient analytical tools.

In this paper the experimental setup of a multisample analytical centrifuge for determination of the characteristic material properties related to the sedimentation and consolidation behaviour of dispersions is described. Accompanied by a brief description of the theory the potential of analytical centrifugation is demonstrated for dispersions of non-interacting rigid and deformable particles and for flocculated systems as well.