Nouvelles approches pour la séparation des actinides dans les gisements de terres rares

Authors: Whitty-Léveillé, Laurence
Advisor: Larivière, DominicReynier, Nicolas
Abstract: Recently, the recovery of rare earth elements (REEs) from a variety of resources has gained interest in the mining industry. As naturally occurring actinides and REEs share similar chemical properties, the separation of those two groups of elements is often a concern in the rare earth industry to mitigate radioactive contamination of facilities and workers. Separating naturally occurring actinides from REEs poses interesting chemical challenges. Actinides and lanthanides are often co-dissolved in hydrometallurgical processes, potentially resulting in radioactive contamination of extraction cycle. Recent developments in solid-liquid extraction techniques, including solid-phase extraction (SPE), have demonstrated superior performances with higher enrichment factors, faster phase separation in the absence of emulsion, and better recoveries than liquid-liquid methods for isolating actinides. The goal of this thesis is to develop new extraction techniques for the efficient extraction of actinides from rare earths-bearing ores and leachates. The first project optimizes a sequential leaching procedure with Na2CO3/NaHCO3 and HCl for the rapid and selective dissolution of REEs and actinides through experimental design. Optimization emphases on the main operational parameters which are time, temperature and concentration, various types of minerals (REE composites and ores), maximum leaching yield, and minimization of gangue metal dissolution like Fe, Si, and Ca. The second project focusses on a new type of extraction procedure for the removal of uranium from rare earth leachates by combining a magnetic solid-phase support and a Schiff base ligand. We synthesized and characterized three Schiff base ligands (CH3Salen, H2Salophen and MeOSalophen) and the magnetic MeOSalophen Schiff base shown a high selectivity towards U(VI) over several metals in a real rare earth leaching solution. Finally, the last projects concern the design and development of functionalized solid supports (i.e. silica and core-shell nanoparticles) using tethered MeOSalophen Schiff base ligand for uranium extraction. Different grafting approached were evaluated (one-side or two-side tethering) and a fast extraction kinetic was obtained, as well as a high degree of reusability in the conditions tested.
Document Type: Thèse de doctorat
Issue Date: 2019
Open Access Date: 12 September 2019
Grantor: Université Laval
Collection:Thèses et mémoires

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