Optimisation d'une méthode d'extraction acide des éléments de terres rares (ÉTR) dans les résidus de bauxite
|Abstract:||The rare earth elements (REE) are minerals presents in a growing number of new technologies. The REE are composed of 16 elements. They are the lanthanides (elements 57 to 71 from periodic table) with the scandium and yttrium. Despite their names, these elements are not so rare. However, they are scattered throughout the earth crust and found in small quantities. Unfortunately, the production of the REE using ores such as monazite has significant environmental impacts since it is producing large quantities of wastes which some are radioactive. New alternative sources are now considered to minimize the environmental impact on the REE exploitation. Among the resources, the mining residues from the production of alumina (bauxite residues or red mud) are an interesting option. The red mud from the Bayer’s process contain mainly iron and alumina but also some thorium, uranium and REE. The objective of this work is to develop an acid based leaching method to perform the selective extraction of REE while minimizing the solubilisation extraction of matrix elements of the bauxite residues (BR). First, a complete digestion of the BR was done to determine the concentration of the constituting elements. Then, leaching experiments with diluted acids (hydrochloric, nitric and sulfuric) were done at different pH, temperatures and heating times. The REE and the radioactive elements were analysed by ICP-MS/MS whereas the matrix elements were analysed by ICP-OES. To simplify the investigation of the various solubilisation conditions, a statistical method was used e.g. the factorial design. This method enables the study of several parameters simultaneously and identifies the interconnectivity of the parameters. During the leaching investigation, a suitable percentage of REE were extracted over the other constituents of the matrix. After that, a liquid-liquid extraction with a diglycolamide ligand and a co-precipitation were done the separate the REE from the co-leached constituents of the matrix.|
|Document Type:||Mémoire de maîtrise|
|Open Access Date:||3 July 2018|
|Collection:||Thèses et mémoires|
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