Efficient Purification and Production of Rare Earth Metals from Bastnasite Ore: Beneficiation, Leaching, Solvent Extraction, and Metallothermic Reduction Approaches
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Date
2024-10-30
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Türkiye Enerji, Nükleer ve Maden Araştırma Kurumu (TENMAK)
Abstract
Rare earth elements (REE) are one of the indispensable raw materials of modern technologies and are used in many critical applications such as magnetic materials, catalysts and batteries. The economic and efficient recovery of REE from ores is of great importance to reduce global supply risks [1,2] This study investigates the production of high purity rare earth metals by physical pre-benefication, leaching, solvent extraction and metallothermic reduction steps applied in the process of recovery of rare earth elements from bastnasite ore containing rare earth elements. Bastnasite occurs naturally with fluorite, barite, calcite, quartz, hematite and some silicates. Various methods, mainly gravity separation, magnetic separation, flotation and electrical separation, can be used to extract these gangue minerals [3]. In the present study, bastnasite ore was subjected to crushing-grinding-sieving processes and pre-enrichment process was carried out. The direct leaching and roasting methods were applied to the screened ore and the pre-beneficatio ore sample with a particle size of -45 µm was then subjected to mineral acid leaching with and without roasting. The effects of roasting temperature, roasting type, acid type, acid concentration on the leaching efficiency of the pre-enriched ore concentrate were investigated. Solvent extraction parameters were investigated for the purification and selective recovery of REEs from the REE loaded solution obtained. In the following stage of the study, we focused on the production of high purity rare earth metals from rare earth oxides purified by solvent extraction by metallothermic method. The metallothermic process is based on a reduction reaction, usually using reactive metals such as Ca or Mg. In this study, neodymium metal (Nd) production by metallothermic reduction method using neodymium oxide (Nd₂O₃) obtained after solvent extraction process with 95%-97% Nd content is discussed. Mg was selected as the reactive metal. The reduction reaction was carried out in vacuum under high temperature conditions (800-1000°C). As a result of metallothermic reduction, high purity neodymium sponge was obtained.