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Concentrated phases of colloids or nanoparticles: Solid pressure and dynamics of concentration processes

Aimar, Pierre and Bacchin, Patrice Concentrated phases of colloids or nanoparticles: Solid pressure and dynamics of concentration processes. (2010) In: Nanoscience: Colloidal and Interfacial Aspects. (Taylor & Francis Surfactant science series). Taylor & Francis (CRC Press), USA, 1-256. ISBN 978-1-42-006500-8

(Document in English)

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The behaviour of colloids concentrated at an interface is strongly affected by surface interactions occurring on the nanoscale between colloids and between the colloids and the surface. For instance, processes such as ultrafiltration, nanofiltration or reverse osmosis which are classically used to purify, eliminate and concentrate colloids or nanoparticles strongly depend on these interfacial phenomena. The level of fouling, its kinetics or even the way colloids build up (porosity, hydraulic resistance or accumulation reversibility) are driven by colloidal properties. It is therefore necessary to establish experimental and theoretical connections between colloidal properties at the local (micro) scale and the efficiency of the concentration process; this knowledge being compulsory for the control of numerous processes dealing with nanoparticles. In this chapter, our aim is to show how the concept of solid pressure can be a good vehicle to account for particle-particle interactions in the macroscopic description of separation processes like membrane filtration, sedimentation or drying. It will be shown how solid pressure (or to be more precise its variation with the volume fraction) can be related to the way a suspension resists an increase in concentration. We shall also try to illustrate in which way the change of state of the suspension, can be put in relation to the various forms of accumulation on a surface, both from a theoretical and an experimental point of view. The resistance of the dispersion to over-concentration will be defined by osmotic pressure variation and this resistance will be linked to a Péclet number relative to filtration conditions. The importance of a critical volume fraction inducing a phase transition between fluid (dispersed) and solid (condensed) phases will be underlined in order to describe the transition between accumulation phenomena of polarisation concentration and of dense layer formation. The consequence of this transition on the reversibility of accumulated layers will be discussed. The chapter will then investigate how the variation of osmotic pressure with volume fraction can explain the variety of accumulation phenomena occurring at an interface.

Item Type:Book Section
Additional Information:Thanks to Taylor & Francis Editor. The definitive version is available at http://www.routledge.com
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
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Deposited On:17 Nov 2011 08:26

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