Extraction and Back-Extraction Behaviors of La(III), Ce(III), Pr(III), and Nd(III) Single Rare Earth and Mixed Rare Earth by TODGA.

Lina Qiu,Yang Liu,Xiaotao Yuan,Aijun Gong,Weiwei Zhang,Jiandi Li

doi:10.3390/s21248316

Lina Qiu, Yang Liu + Show 4 more

Open Access

https://doi.org/10.3390/s21248316

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Abstract

N,N,N′,N′-Tetraoctyl diglycolamide (TODGA), as a new extraction agent, is effective for its excellent performance and low environmental hazard, and it is very welcome for the rare earth separation process. In this paper, by controlling the extraction time, diluent type, acid type and its concentration, rare earth concentration, etc., the optimum extraction and back-extraction effects of TODGA on La(III), Ce(III), Pr(III), and Nd(III) and mixed rare earths were obtained. The experiment showed that 0.10 mol·L−1 TODGA had the best extraction effect on single rare earth under the conditions of using petroleum ether as diluent, 5 mol·L−1 nitric acid, 20 min extraction time, and 0.01 mol·L−1 rare earth. In the mixed rare earth extraction, the percentage concentrations of La(III), Ce(III), Pr(III), and Nd(III) could be achieved from 21.7%, 19.9%, 30.8%, and 22.2% at the initial stage to 90.5%, 37%, 51%, and 62% after extraction, respectively, by controlling the number of back-extraction cycles and the concentrations of hydrochloric acid and nitric acid in the back-extraction system. The TODGA–rare earth carrier system showed the best back-extraction effect when the hydrochloric acid concentration was 1 mol·L−1 and the back-extraction time was 20 min. At the same time, the mixed rare earth liquid system with low initial concentration was selected for extraction and separation of mixed rare earth. The separation effect was better, and the recovery rate was higher than that of mixed rare earth liquid system with a high initial concentration.

Highlights

The rare earth elements can be grouped as light rare earth elements (La, Ce, Pr, Nd) and middle and heavy rare earth elements (Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y)
According to the experimental results, it can be obtained that the extraction effect of La(III) is best with petroleum ether as the diluent of Tetraoctyl diglycolamide (TODGA) under the condition of 5 mol·L−1 nitric acid concentration
It can be obtained that the extraction effect of Ce(III) was best with petroleum ether as the diluent of TODGA under the condition of 5 mol·L−1 nitric acid

Summary

Introduction

The rare earth elements can be grouped as light rare earth elements (La, Ce, Pr, Nd) and middle and heavy rare earth elements (Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y). Effect of LREE Concentration on Separation Effect of Mixed Rare Earth TODGA containing the LREE mixture was back-extracted in three minor cycles. The LREE concentrations of the solution before and after loading, as well as the aqueous phase and organic phase after elution, we4roef 2a3ll determined, and the separation effect of elution and the single LREE recovery rate were compared. The mixed solution of hydrochloric acid and nitric acid was used to reverse extract low-concentration rare earth in the aqueous phase system.

Results and Discussion

Effects of Hydrochloric Acid Concentrations on Extraction Using TODGA

Effects of Extraction Time on Extraction Characteristics Using TODGA

Effects of Different Rare Earth Concentrations on Extraction

IR Spectrum of Organic Phase after Extraction Using TODGA