Separation of Ce and La from Synthetic Chloride Leach Solution of Monazite Sand by Precipitation and Solvent Extraction
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I.
INTRODUCTION
RARE earth elements (REEs) are widely used in various types of modern electronics and green technologies, and their potential applications have increased rapidly. The sources of REEs occur in minerals such as bastnasite, monazite, xenotime, and so forth.[1,2] The separation of REEs is difficult due to their similarity in chemical properties. As a result, the separation methods available are not very selective.[3] Among several separation methods, solvent extraction is one of the most efficient ones.[4,5] Abdeltawab et al.[6] described the separation of La and Ce with PC 88A from nitrate medium using multistage continuous extraction. Morais and Ciminelli[7] proposed a process to attain high-grade La2O3 using PC 88A by continuous extraction, scrubbing, and stripping. Thakur[8] reported process parameters for the production of magnetic grade Nd2O3 using saponified PC 88A. Kim et al.[9] developed a process for the separation of Light Rare Earth Elements (LREEs) using precipitation and solvent extraction. Banda et al.[10] recently reported some results on the separation of La over Pr and Nd using saponified Cyanex 272. In addition, selective oxidation and reductions are commonly used for the separation of cerium and europium from the REEs solutions.[11,12] A synergistic mixture of extractants is often used to increase the extraction and for better selectivity; and the RAJU BANDA, Ph.D. Scholar, is with the Department of Advanced Material Science & Engineering, Institute of Rare Metal, Mokpo National University, Chonnam 534-729, Republic of Korea and also Researcher with the LS-Nikko, Ulsan, Republic of Korea. HO SEOK JEON, Principal Researcher, is with the Division of Minerals Utilization and Materials, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejon 305-350, Republic of Korea. MAN SEUNG LEE, Professor, is with the Department of Advanced Material Science & Engineering, Institute of Rare Metal, Mokpo National University. Contact e-mail: [email protected] Manuscript submitted January 17, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
application of synergistic mixtures on the extraction of REEs has already appeared in the literature.[13–17] For instance, Xiong et al.[18] demonstrated that a mixture of P507 and Cyanex 272 is effective for the separation of heavy rare earths. Tachimori and Nakamura[19] examined the synergistic extraction ability of MEHPA + DEHPA toward lanthanides from strong nitric acid solutions. By using mixture of HDEHP and PC 88A, a greater synergism for Nd and Pm was observed at 104 M HCl.[20] However, the stripping of REEs from a loaded mixture of HDEHP and HEH/EHP is easier than that from HDEHP alone.[21] In addition, a higher distribution factor of rare earths is noted with mixtures of trioctylmethylammonium salt and dialkyl-phosphinicbased extractants.[22] In our work on the recovery of REEs from monazite sand leach liquors, the initial digestion of monazite sand was performed with NaOH followed by dilute HCl leaching to dissolve the REEs. The thorium (Th) and othe
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