Separation and solvent extraction of rare earth elements (Pr, Nd, Sm, Eu, Tb, and Er) using TBP and Cyanex 572 from a chloride medium

In this study, synergistic effect of Cyanex 572 mixed with TBP on the extraction and separation of six selected light, medium and heavy rare earth elements (REE), namely neodymium (Nd), praseodymium (Pr), samarium (Sm), europium (Eu), terbium (Tb), and erbium (Er), from the chloride medium was investigated. The results demonstrated that sole TBP is not a suitable extractant for the separation of the REEs from the chloride media. However, Cyanex 572 was identified as a suitable extractant for the separation of heavy REEs, Er, and Tb. At initial pH (pHi) of 1.5, the mixture of 25% TBP + 75% Cyanex 572 extracted about 70% and 85% of Er and Tb, respectively. The separation factor (SF) results of some couples were noteworthy: SFEr/Pr = 30.08, SFEr/Nd = 29.95, SFTb/Pr = 12.22, SFTb/Nd = 12.16, SFEr/Sm = 9.96. Furthermore, the extraction mechanism of these two heavy REEs was studied using slope analysis and Fourier transform infrared measurements (FT-IR). The results showed that Er and Tb were extracted as ErCl2R(HR)(3)TBP and TbCl2R(HR)(3)TBP complexes (presumably R and HR refers to Cyanex 572), respectively. The FT-IR spectra confirmed these obtained results qualitatively.

Automated summary

This study investigated the synergistic effect of Cyanex 572 mixed with TBP on the extraction and separation of heavy rare earth elements erbium and terbium. The results showed that the mixture of 25% TBP + 75% Cyanex 572 could extract about 70% of erbium and 85% of terbium at pH 1.5, demonstrating effective separation.