Author(s)

Ariuntuya Battsengel^1*, Altansukh Batnasan², Kazutoshi Haga², Atsushi Shibayama²

¹Graduate School of Engineering and Resource Science, Akita University, Akita, Japan.
²Graduate School of International Resource Sciences, Akita University, Akita, Japan.

Different separation techniques such as solvent extraction, ion exchange, and precipitation are often used for recovery of rare earth elements (REEs) from pregnant leach solutions obtained from acid leaching. Solvent extraction is generally accepted as the most appropriate commercial technology for separating REEs due to the need to be able to handle larger volumes of diluted pregnant solutions. This study focused on the development of selective separation of light and heavy REEs from the pregnant leach solution obtained from leaching of apatite ore in 1 M sulfuric acid (H2SO4) using solvent extraction. Three different commercial organophosphorus extractants (di-(2-ethylhexyl) phosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC88A) and tributyl phosphate (TBP)), and the influences of experimental parameters such as extractant concentration, organic/aqueous phase ratio, diluent type, pH, extraction time and stripping agent concentration were examined. Results showed that light REEs (LREEs) and heavy REEs (HREEs) in the pregnant leach solution were selectively separated with D2EHPA via a two-stage extraction process. In the first-stage of solvent extraction, >90% of (0.05 g/L) HREEs was extracted with 1.8 M D2EHPA in kerosene while the vast majority (>95%) of LREEs was remained in raffinate. In the second-stage, >93% (1.01 g/L) of LREEs was extracted from the raffinate with 1.8 M D2EHPA dissolved in kerosene at pH 1.6. HREEs (>95%) and LREEs (>90%) loaded with D2EHPA after the first and second-stage of extraction were stripped by 4 M H₂SO₄ and 1 M H₂SO₄ solutions, respectively. Distribution of middle rare earth elements (MREEs) was discussed through the extraction processes in this study.

Light Rare Earth Elements, Heavy Rare Earth Elements, Solvent Extraction, Di-(2-ethylhexyl) Phosphoric Acid, Stripping

Battsengel, A. , Batnasan, A. , Haga, K. and Shibayama, A. (2018) Selective Separation of Light and Heavy Rare Earth Elements from the Pregnant Leach Solution of Apatite Ore with D2EHPA. Journal of Minerals and Materials Characterization and Engineering, 6, 517-530. doi: 10.4236/jmmce.2018.65037.