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Theses

Flottation de l'argile pour la décontamination radioactive des terres

Abstract : After a nuclear accident like Fukushima, the radioactive cesium 137 is transported from the atmosphere to the soil by rain water. Clays are mineral species which are naturally present in soils. These micrometric minerals (1- 100 µm) are very efficient and selective adsorbents for Cs ions. The objective of this PhD thesis is to look at the feasibility of a process called flotation to selectively extract these contaminated clay particles and to reduce the volume of soil to store. Flotation consists in separating minerals according to their surface properties. The most hydrophobic particles are collected by air bubbles and are transported up to the froth whereas the hydrophilic particles remain in the suspension. Cationic surfactants are employed to selectively adsorb on clays surface and increase its hydrophobicity. It was chosen to focus on systems containing illite clay and an ammonium bromide cationic surfactant called TTAB. The properties of illite and TTAB suspensions were determined (particle size, zeta potential, adsorption isotherm of TTAB, turbidity, rheology). Then, foaming ability, stability and drainage properties of these suspensions were looked at by using a lab scale instrumented column. It was shown that clay particles have a stabilizing effect on the froth. Moreover, selectivity for the smallest clay particle size fraction (3 µm) in foams was observed. The 2nd part of the work consisted in performing flotation experiments on illite clay and TTAB suspension with a new “mini” pilot flotation column in continuous mode. The influence of TTAB concentration, air flow and illite clay concentration and granulometry on foam drainage properties and extraction yields was determined. From this study, two transport parameters were dissociated and extracted: the true flotation rate constant and the drainage coefficient. Finally, they were used to perform a scale-up study of an industrial flotation unit.
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https://tel.archives-ouvertes.fr/tel-01866704
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Submitted on : Monday, September 3, 2018 - 3:39:35 PM
Last modification on : Monday, July 20, 2020 - 9:30:03 AM
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  • HAL Id : tel-01866704, version 1

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STAR | CNRS | LGP2 | CEA | DEN | UGA

Citation

Julie Chapelain. Flottation de l'argile pour la décontamination radioactive des terres. Chimie organique. Université Grenoble Alpes, 2016. Français. ⟨NNT : 2016GREAI106⟩. ⟨tel-01866704⟩

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