Dynamical transition from fluid to gel of colloids under simultaneous shear flow, pressure and ultrasound during cross-flow ultrafiltration
| When |
Mar 08, 2016
from 10:45 to 12:00 |
|---|---|
| Where | Centre Blaise Pascal |
| Attendees |
Frédéric Pignon |
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The dynamical phase transition from fluid to gel state of colloidal particles submitted simultaneously to shear flow, pressure and ultrasound has been investigated during ultrafiltration process assisted by ultrasound (US). Specific “cross-flow US-coupled filtration cell” has been developed to monitor in-situ the colloidal organization and sol-gel transition of colloidal dispersions near the membrane surface by in-situ time-resolved small-angle X-ray scattering [1]. Several aqueous dispersions have been studied: clays, casein micelles, starch and cellulose nanocrystals [2-4]. From the scattered intensities of colloidal particles, the structural organizations and the volume fraction evolutions as a function of the distance z from the membrane surface have been deduced for different filtration conditions. US leads to different mechanisms: i) a progressive disruption of the fouling layer (case of an open structural organization) ii) no layer disruption but with a probably shear-localization or localized particle agitation phenomena (case of a denser network of particles pertaining to an anisotropic accumulation of particles).
[1] Pignon F. et al., Langmuir, 28, 1083-1094, (2012).
[2] Y. Jin et al., J. Membr. Sci. 453, 624–635 (2014).
[3] Y. Jin et al., J. Membr. Sci. 470, 205-218 (2014).
[4] Y. Jin et al., Carbohydrate Polymers, 124, 66-76 (2015).