Selective Separation of Light and Heavy Rare Earth Elements from the Pregnant Leach Solution of Apatite Ore with D2EHPA

Abstract

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 (H 2 SO 4) 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 H 2 SO 4 and 1 M H 2 SO 4 solutions, respectively. Distribution of middle rare earth elements (MREEs) was discussed through the extraction processes in this study.

Selective recovery and separation of rare earth elements by organophosphorus modified MIL-101(Cr)

“…FTIR spectra of MIL-101-H50 and MIL-101-C50 showed no apparent loss of functional groups, suggesting that the reason for the decreased efficiency of MIL-101-H50 may be insufficient reaction time or acidity at desorption stage [83] for releasing of Er 3+ from occupied adsorption sites. Nevertheless, MIL-101-H50 and MIL-101-C50 demonstrated good chemical stability during the adsorption− desorption cycles.…”

Separation of Praseodymium and Neodymium from Heavy Rare Earth Elements Using Extractant-Impregnated Surfaces Loaded with 2-Ethylhexyl Phosphonic Acid-mono-2-ethylhexyl Ester (PC88A)

“…(12) Table 1. Schematic Representation of the Impaled, Impregnated, and Encapsulated Configurations a which can be reorganized as (13) Applying Young's equation: , eq 13 reduces to (14) Thus,…”

“…The achieved purity and removal rates are close to those for separation of HREEs from LREEs, but the extractant consumption is lower than solvent extraction. 13 The detailed comparison is presented in Table 2, and experimental data are presented in Supporting Information Table S1.…”

“…It achieved more than 90% of HREE removal, and more than 95% of HREEs remained in the raffinate. An organic to aqueous ratio of 1:3, contact time of 10 min, and shaking speed of 300 rpm were used in this study, and two stages were needed to achieve the results …”

“…An organic to aqueous ratio of 1:3, contact time of 10 min, and shaking speed of 300 rpm were used in this study, and two stages were needed to achieve the results. 13 Another alternative to solvent extraction is functional ligandbased materials that have been investigated by a few researchers. One study used a ligand-impregnated facial composite adsorbent (FCA) for thulium (Tm(III)) ion separation and adsorption in aqueous media.…”