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Filtration de dispersions agrégées de silice colloïdale : structure, consolidation et perméabilité de dépôts.

Abstract : In water treatment processes, the separation of colloid particles from the liquid by filtration is a crucial step for the global operation to be effective. A pre-treatment step is generally required for particles to be agglomerated before the liquid is further extracted, leaving aggregates at the membrane surface in a growing porous cake. An important issue lies in the fact that the cake may collapse in response to the applied pressure, resulting in a lost of initial porosity and decrease in permeability. The aim of this study was to investigate cake restructuration mechanism(s) through an experimental multi-scaling approach for a better understanding and tailored-control of cake properties.
For this purpose, dispersions of spherical monodisperse silica colloids (Ludox HS and Klebosol PHN) were aggregated by adding polycation 7+ named Al13 or divalent cation Ca2+. Structural and mechanical features of filtration cakes were investigated through non invasive physical techniques such as Small Angles Neutrons Scattering and Transmission Electronic Microscopy. Investigations have permitted to describe cake collapse through a general compression mechanism mainly controlled by the strength of interparticle bonds within the flocs. Impact of floc features on cake filtration properties has been investigated and we have been able to show that cake compressibility and permeability primarily result from the breakage resistance of interparticle bonds rather than flocs initial fractal properties.
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Submitted on : Friday, September 19, 2008 - 3:45:46 PM
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J.B. Madeline. Filtration de dispersions agrégées de silice colloïdale : structure, consolidation et perméabilité de dépôts.. Sciences de l'ingénieur [physics]. Université Paul Sabatier - Toulouse III, 2005. Français. ⟨tel-00323124⟩

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