The selective extraction of low-concentration light rare earth ions(LREs) by 1,7-diaza-15-crown-5 ether(2N15C5) from complex ammonium sulfate solutions containing multiple impurity ions was studied, which provides a new method for efficient separation of Ln³⁺ from the tail liquid wastewater discharged from in-suit leaching of ion-adsorbed rare earth ores. Liquid–liquid extraction experiments showed that impurity ions affect the extraction distribution of LREs via inducing the formation of rare earth ammonium sulfate compound salts, and the single-stage extraction coefficients of LREs were 2.20 for aluminum (Al) and 7.80 for iron (Fe) under the condition of pH 1.5 ± 0.5 and [SO₄²⁻]_T/∑[Ln³⁺] < 10. Multistage counter-current extraction can further enhance the selective extraction of light rare earth ions with β_LREs/Al = 21.41 and β_LREs/Fe = 23.33 from the tail liquid wastewater. Density functional theory calculations indicated that steric hindrance caused by size compatibility and electron density-based weak interactions affect the coordination between 2N15C5 and different cations.

Graphical Abstract

中文翻译：

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利用配位能力从高浓度硫酸铵体系中选择性回收低浓度轻稀土离子

研究了1,7-二氮杂-15-冠-5醚(2N15C5)从含有多种杂质离子的复杂硫酸铵溶液中选择性萃取低浓度轻稀土离子(LRE)，为高效分离提供了新方法离子吸附型稀土矿浸出尾液废水中Ln ^{3+的含量。}液-液萃取实验表明，杂质离子通过诱导稀土硫酸铵复合盐的形成影响LREs的萃取分布，铝（Al）的LREs单级萃取系数为2.20，铁（Fe）的LREs单级萃取系数为7.80。在pH 1.5 ± 0.5、[SO ₄ ²⁻ ] _T /Σ[Ln ³⁺ ] < 10条件下，多级逆流萃取可进一步增强轻稀土离子的选择性萃取，β _LREs/Al  = 21.41， 尾液废水中β _{LREs/Fe = 23.33。}密度泛函理论计算表明，尺寸相容性和基于电子密度的弱相互作用引起的空间位阻影响2N15C5与不同阳离子之间的配位。

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