Purification and Fractionation of Rare Earth Elements from Synthetic Pregnant Leach Solution using Solvent Extraction Approach
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Authors
Yildiz, Ilkay
Date
Type
Language
eng
Keyword
Rare Earth Elements , Solvent Extraction , Purification , Critical Metals , Impurity Removal , Cyanex 272 , Ionquest 801
Alternative Title
Abstract
The purpose of this study is to examine a two-step purification process for the separation of rare earth elements (REE) from impurities in a chloride pregnant leach solution. The first step aimed to eliminate iron impurities through the use of alkaline reagents, with the goal of recovering the lost REE through subsequent acid leaching. The second step utilized various extractants through solvent extraction to achieve selective REE extraction from cobalt.
The iron removal process yielded conclusive results, showing that Fe precipitation from the leach solution was complete at pH 4.0 through the use of 1M sodium hydroxide as the alkaline reagent. This method demonstrated the lowest REE losses in comparison to using 5 wt.% calcium hydroxide as the reagent. The REE losses that did occur with the use of sodium hydroxide were attributed to REE ion hydrolysis and lower REE chloride solubility compared to that of Ca chlorides. As a result of these findings, it was suggested that sodium hydroxide be used for the iron removal process, with the subsequent recovery of REE lost to the precipitation step achieved through acid leaching.
The results of the solvent extraction process revealed that Ionquest 801 was a more efficient extractant than Cyanex 272 for the selective separation of REE from cobalt. Specifically, at pH 3.0, Ionquest 801 displayed extraction percentages of 90% or more for all REE and achieved complete selective separation with cobalt. Cyanex 272, on the other hand, exhibited less effectiveness overall, but appropriate extraction percentages for terbium and dysprosium, 100% and 89.1% respectively. The findings from this study have significant implications for the industry's utilization of REE. Future research can center around enhancing these processes, with the intention of increasing the efficiency of REE extraction and separation.