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March 9, 2023
Defense 09 mars 2023 à 14h00
Address of the defense : LiPhy, 140 rue de la Physique, 38402 Saint-Martin-d'Hères.
M Gauthier Meyer will present his thesis "Physico-chemical characterisation of aqueous biphasic systems for the recycling of metallic ions"
The need to recycle metal ions, which are omnipresent in many industrial applications such as batteries or microelectronics, is leading to an intense search for non-polluting chemical processes. For liquid-liquid extraction purposes, Acidic Aqueous Biphasic Systems (AcABS) present a promising alternative. In this thesis, we characterised the physico-chemical properties of ABS composed of an ionic liquid, tributyltetradecylphosphonium chloride, and strong acids. Phase separation is promoted by adding salt or acid to the solution and increasing the temperature. The separation mechanisms could be understood from the structural organisation of the solution and the precise titration of the ionic species: the solution is characterised by the formation of spherical micelles, whose electrostatic repulsion is more or less shielded by the presence of charges in solution and/or by their adsorption on the surface of the micelles with the increase in temperature. The interface between the two aqueous phases has a very low surface tension and spreads over more than 60 Angstrom, showing that the ionic liquid does not form a monolayer at the interface like a surfactant.
The last surprising point of these systems is the particularly slow separation kinetics. Using simple models derived from the Cahn-Hilliard equation, we were able to predict the characteristic time of phase separation, which is dominated by gravity forces on the droplets from one phase to the other and depends on viscosity and surface tension.
Finally, the migration of metal ions in the solutions can be studied thanks to the experimental set-up and analysis of the results developed in the course of this work, allowing the characterisation of the diffusion processes of metal ions in each of the phases and across the interface.
Emmanuelle DUBOIS (Phenix, Jussieu-Paris) et Damien BOURGEOIS (ICSM, Marcoule), rapporteurs.
Présidente (putative) : Elisabeth CHARLAIX (LiPhy, Grenoble)