Solvent Extraction of Lanthanides(III) in the Presence of the Acetate Ion Acting as a Complexing Agent Using Mixtures of Cyanex 272 and Caprylic Acid in Hexane

Vera V Belova,Yulia A Zakhodyaeva,Yulia V Tsareva,Andrey A Voshkin,Vladimir K Ivanov

doi:10.3390/pr9122222

Abstract

A new extraction system containing a mixture of Cyanex 272 and caprylic acid is proposed for the extraction and separation of lanthanides(III). It was shown that this system possesses a high level of extraction ability and capacity. The extraction of lanthanides(III) from chloride-acetate and nitrate-acetate media was investigated on an example of La(III). The composition of the extracted species was confirmed, based on the analysis of lanthanum(III) extraction isotherms. In the case of acetic-acetate aqueous solutions, a decrease in lanthanum(III) extraction efficiency was observed, due to the decreasing equilibrium pH of the aqueous phase in accordance with the cation-exchange mechanism. The composition of the synergistic mixture of Cyanex 272-caprylic acid established demonstrates highly efficient separation of rare-earth metal ions.

Highlights

Rare earth elements (REE) find their application in many fields of advanced materials science and industry as they demonstrate a variety of promising and unique properties [1,2,3,4,5].The separation of lanthanides is a challenging goal, due to their similar chemical and physical behavior
Preliminary experiments indicated that the extraction of La(III) from chloride-acetate solutions with a 0.015 mol/L Cyanex 272 solution in hexane was accompanied by the formation of insoluble products
This paper has described how a new extraction system containing mixtures of Cyanex

Summary

Introduction

Rare earth elements (REE) find their application in many fields of advanced materials science and industry as they demonstrate a variety of promising and unique properties (for example, luminescent, electronic, magnetic, and catalytic properties) [1,2,3,4,5].The separation of lanthanides is a challenging goal, due to their similar chemical and physical behavior. There have been a growing number of studies on the recovery and separation of lanthanides using a variety of methods, among which special attention has been paid to liquid-liquid extraction [6,7,8,9,10,11]. Liquid-liquid extraction is the most common large-scale separation method, which is usually carried out as a continuous, multi-stage process of extraction and separation of REE from aqueous solutions using an organic solvation agent (extractant) that forms complexes with REE ions. Rare earth metals are stripped from the REE-enriched organic phase by putting it in contact with an aqueous solution with which ions have a greater affinity. Due to the very small behavioral difference between lanthanides, the extraction-stripping process should be repeated multiple times to achieve satisfactory separation. Extractants of various classes have recently been used for REE extraction and separation, for example, organophosphorus cation-exchange extractants [12,13,14,15], neutral extractants (e.g., TBP, trialkylphosphine oxides) [16,17,18,19], binary extractants and ionic liquids [20,21,22,23,24,25,26]

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Conclusion