Transport d'ions sous l'effet d'un champ électrique en milieu poreux : applications à la séparation de terres rares par électrophorèse à focalisation

Abstract : Trivalent ions of rare earth elements have very similar properties and their difficult separation each from another is usually carried out by liquid-liquid extraction or ion exchange focalisation electrophoresis represehts an alternative route to the usual techniques. The purpose of this work consisted of the fundamental investigation of ion transport phenomena in electrophoretic processes. Focalisation electrophoresis is suitable for separation of amphoteric species such as rare earth ions, using a pH gradient in the cell and upon addition of a complexed agent e. g. EDTA. This technique relies upon the difference in isoelectrical points of the considered species, being under the form of free cation near the ano'de, and in the form of anionic complexed species doser to the cathode Rare earth species are submitted to the antagonist effects of diffusion and migration, enabling their focalisation to occur at the isoelectrial point, corresponding to nil value of their effective mobility. Following a literature survey on rare earth elements and electrophoresis processes, the document describes theoretical and experimental investigations of complexation equilibria of some rare earth elements, namely lanthanum, neodymium, praseodymium and cerium, depending on pH. Values for the isoelectrical points coulb be estimated. Transport and focalisation phenomena in view of rare earth separation, are dealt in the last chapter. Investigations were first carried out without forced circulation of the electrolyte solution and the transient behavior of the system allowed operating conditions to be design and built-up of a continuos device, more suitable to separation, and provided with 42 potential and 42 temperature sensors: the results of the preliminary runs, in form of variable profiles, are presented and discussed.
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Antonio Idivan Vieira Nunes. Transport d'ions sous l'effet d'un champ électrique en milieu poreux : applications à la séparation de terres rares par électrophorèse à focalisation. Alimentation et Nutrition. Institut National Polytechnique de Lorraine, 1999. Français. ⟨NNT : 1999INPL017N⟩. ⟨tel-01749932⟩

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