A two-phase competitive separation system and separation method for separating rare earth elements neodymium and dysprosium

Abstract

This invention belongs to the field of hydrometallurgy and separation chemistry, and provides a two-phase competitive separation system and method for separating the rare earth elements neodymium and dysprosium. The method integrates an innovative liquid-liquid extraction system and a column chromatography separation process based on specific elution. Its core lies in utilizing a specially designed water-soluble bis-lactam phenanthroline derivative ligand (preferably Phen-2DIC4NH2), which exhibits specific acidity for Nd... 3+ With Dy 3+ It exhibits differentiated complexing and decomplexing capabilities. This invention not only fundamentally overcomes the dependence of traditional methods on multi-stage extraction, significantly simplifies the process flow, and reduces energy and material consumption, but also enhances the recognition ability of target ions due to the introduction of aqueous ligands, greatly improving separation selectivity. Thus, it provides a completely new technical approach for the separation of key adjacent rare earth elements such as neodymium and dysprosium, and has broad prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy and separation chemistry technology. Specifically, it relates to a two-phase competitive separation system and method for separating rare earth elements neodymium and dysprosium. Background Technology

[0002] Rare earth elements share similar electronic structures, resulting in remarkably similar physical and chemical properties. This makes the purification of single elements from mixed rare earth elements a long-standing challenge in the metallurgical and chemical industries. Neodymium (NdFeB) and dysprosium (DFP), as key strategic rare earth resources, play an irreplaceable role in permanent magnet materials (such as NdFeB magnets), clean energy technologies, advanced electronic devices, and the defense industry. With the rapid development of the global green energy transition and high-tech industries, the demand for high-purity NdFeB and DFP continues to grow, and their supply security and efficient separation technologies have become crucial factors affecting the development of downstream industries. Currently, large-scale industrial separation of rare earth elements mainly relies on solvent extraction technology. However, traditional processes are lengthy, often requiring dozens or even hundreds of extraction cascades to obtain high-purity products, resulting in significant problems such as high reagent consumption, high equipment investment, high operating costs, and the generation of large amounts of wastewater containing organic solvents. Most importantly, for adjacent heavy rare earth elements with very small ionic radii, such as neodymium (Nd) and dysprosium (Dy), traditional extractants have limited selectivity and low separation coefficients, resulting in low separation efficiency and making it difficult to economically and environmentally meet the market demand for high-purity products. Therefore, developing a new separation technology that can achieve efficient separation of Nd and Dy in fewer steps, while possessing both high selectivity and environmental friendliness, is of great practical significance for improving the comprehensive utilization level of rare earth resources in my country and ensuring the security of the industrial chain. Summary of the Invention

[0003] This invention provides a two-phase competitive separation system and method for separating rare earth elements neodymium and dysprosium.

[0004] To achieve the objective of this invention, in a first aspect, this invention provides a two-phase competitive separation system for separating rare earth elements neodymium and dysprosium, the two-phase competitive separation system comprising a first phase and a second phase in contact with each other; The first phase is a solution containing a water-soluble selective ligand, wherein the water-soluble selective ligand has a stronger complexing ability for neodymium(III) than for dysprosium(III); The second phase contains a fat-soluble extractant that has the ability to complex trivalent lanthanide rare earth elements; The two-phase competitive separation system enables the separation of neodymium and dysprosium by creating differences in their distribution behavior between the first and second phases.

[0005] Furthermore, the two-phase competitive separation system is a liquid-liquid extraction separation system, comprising: a first aqueous phase, which is a solution containing nitric acid and contains a water-soluble selective ligand; and a second organic phase, which contains a fat-soluble extractant with complexing ability for trivalent lanthanide rare earth elements.

[0006] Furthermore, the two-phase competitive separation system is a column chromatography separation system using an extraction resin containing a lipophilic extractant with complexing ability for trivalent lanthanide rare earth elements as the second stationary phase; in use, an acidic feed solution containing neodymium (III) and dysprosium (III) is mixed with the first phase and then contacted with the second stationary phase.

[0007] Furthermore, the lipid-soluble extractant is 2,2'-oxydi(N,N-dioctylacetamide), i.e., TODGA.

[0008] Furthermore, the concentration of TODGA in the second organic phase of the liquid-liquid extraction separation system is 0.05-0.2M, and it is prepared by a diluent consisting of n-dodecane and n-octanol in a volume ratio of 8:1 to 20:1.

[0009] Preferably, the concentration of TODGA in the second organic phase of the liquid-liquid extraction separation system is 0.1 M, and it is prepared by a diluent consisting of n-dodecane and n-octanol in a volume ratio of 9:1.

[0010] Furthermore, the water-soluble selective ligand is a water-soluble bis-lactam phenanthroline derivative ligand, Phen-2DIC4NH2, with the following structural formula: Preferably, the concentration of the water-soluble selective ligand in the first aqueous phase of the liquid-liquid extraction separation system is 20 mM.

[0011] Furthermore, the concentration of nitric acid in the aqueous phase of the liquid-liquid extraction separation system is from 0.1 M to 1.5 M, preferably 0.5 M.

[0012] Furthermore, in the liquid-liquid extraction separation system, the second organic phase and the first aqueous phase are mixed in equal volumes.

[0013] Secondly, the present invention provides the application of the two-phase competitive separation system in the separation of rare earth elements neodymium and dysprosium.

[0014] Thirdly, the present invention provides a liquid-liquid extraction method for separating rare earth elements neodymium and dysprosium, wherein the two rare earth elements are separated from a feed liquid containing neodymium(III) and dysprosium(III) using the above-mentioned liquid-liquid extraction separation system; The method includes: adding the feed solution containing neodymium (III) and dysprosium (III) to be separated into the first aqueous phase, and then contacting the second organic phase with the first aqueous phase. Under competitive extraction conditions, dysprosium (III) is preferentially extracted into the second organic phase, while neodymium (III) is retained in the first aqueous phase, thereby achieving the separation of the two rare earth elements.

[0015] Furthermore, the competitive extraction conditions are as follows: constant temperature extraction at 25 ± 1 ℃ for 10-60 minutes (preferably 30 minutes), followed by centrifugation after extraction (e.g., centrifugation at 3000 rpm for 2 minutes).

[0016] Fourthly, the present invention provides a method for separating rare earth elements neodymium and dysprosium using extraction chromatography, wherein the two rare earth elements are separated from a feed solution containing neodymium(III) and dysprosium(III) using the above-mentioned column chromatography separation system; Includes the following steps: (1) An acidic feed solution containing neodymium (III) and dysprosium (III) is loaded onto the chromatographic column so that neodymium ions and dysprosium ions are adsorbed by the stationary phase; (2) The chromatographic column is eluted with a first eluent to selectively elute neodymium, wherein the first eluent is a first acidic solution containing the water-soluble bis-lactam phenanthroline derivative ligand Phen-2DIC4NH2; (3) The chromatographic column is eluted with a second eluent to obtain dysprosium, wherein the second eluent is a second acidic solution containing the ligand Phen-2DIC4NH2, and the acidity of the second acidic solution is lower than that of the first acidic solution.

[0017] Furthermore, between steps (1) and (2), the chromatographic column is washed with a nitric acid solution containing the ligand Phen-2DIC4NH2 to remove non-rare earth impurity ions from the feed solution.

[0018] Preferably, the first eluent is a 0.1 M nitric acid solution containing 10 mM of the ligand Phen-2DIC4NH2; and the second eluent is a 0.01 M nitric acid solution containing 10 mM of the ligand Phen-2DIC4NH2.

[0019] By employing the above technical solution, the present invention has at least the following advantages and beneficial effects: (i) This invention provides a highly efficient separation method for adjacent heavy rare earth elements neodymium (Nd) and dysprosium (Dy). This method integrates an innovative liquid-liquid extraction system with a column chromatography separation process based on specific elution, forming a complete separation technology solution from principle to application.

[0020] (ii) The separation efficiency and selectivity are extremely high. The liquid-liquid extraction part obtains an ultra-high single-stage separation factor through the ligand competition mechanism, and the chromatographic part achieves complete separation of Nd / Dy through ligand-acidity synergistic regulation.

[0021] (iii) The process flow is significantly simplified and flexible. Liquid-liquid extraction reduces the number of stages, and chromatographic separation completes purification and separation in one step. The two can be used in series or independently.

[0022] (iv) It has strong resistance to interference from impurities. The chromatographic steps can effectively separate rare earth and non-rare earth impurities, making it suitable for processing complex raw materials.

[0023] (v) This invention provides a complete set of innovative, efficient and industrially scalable separation and purification solutions to solve the industrial problem of Nd and Dy separation. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the water-soluble ligand structure in a preferred embodiment of the present invention.

[0025] Figure 2 The extraction distribution ratio of 14 lanthanide metal ions in the two-phase extraction system composed of Phen-2DIC2NH2 under different acidity conditions in a preferred embodiment of the present invention.

[0026] Figure 3 The extraction distribution ratio of 14 lanthanide metal ions in the two-phase extraction system composed of Phen-2DIC4NH2 under different acidity conditions in a preferred embodiment of the present invention.

[0027] Figure 4 The extraction distribution ratio of 14 lanthanide metal ions in the two-phase extraction system composed of Phen-2DIC6NH2 under different acidity conditions in a preferred embodiment of the present invention.

[0028] Figure 5 The extraction distribution ratio of 14 lanthanide metal ions in a two-phase extraction system composed of three water-soluble ligands under 0.5 M HNO3 acidity conditions is shown in the preferred embodiment of the present invention.

[0029] Figure 6 This invention provides a preferred embodiment of a two-phase extraction system composed of three water-soluble ligands, and the extraction partition ratio and corresponding separation factor of TODGA for Nd / Dy under 0.5 MHNO3 acidity conditions.

[0030] Figure 7 This is a schematic diagram comparing the Nd / Dy separation factors in a preferred embodiment of the present invention.

[0031] Figure 8 This is a diagram showing the effect of extraction chromatography separation of Nd and Dy elements in a simulated feed solution of NdFeB in a preferred embodiment of the present invention.

[0032] Figure 9 The synthetic route for the ligand compound Phen-2DIC6NH2 of this invention is shown below.

[0033] Figure 10 The ligand compound Phen-2DIC6NH2 of this invention 1 H-NMR characterization results. Detailed Implementation

[0034] This invention provides a dual strategy integrating "competitive extraction" and "ligand-selective elution chromatography" for the efficient separation and purification of Nd and Dy. The core of this invention lies in utilizing a specially designed water-soluble bis-lactam phenanthroline derivative ligand (preferably with a C4 alkoxy chain length, i.e., Phen-2DIC4NH2), which, under specific acidity, selectively elutes Nd... 3+ With Dy 3+ It demonstrates differentiated complexing and decomplexing capabilities.

[0035] In the competitive extraction section, this invention provides an innovative "ligand competition" separation strategy. The core of this strategy lies in constructing a two-phase extraction system comprising an aqueous phase and an organic phase, and introducing functional ligands with different size selectivity into each phase. Specifically, a water-soluble ligand with a strong affinity for light rare earth elements with large ionic radii is used in the aqueous phase, while a lipophilic extractant with strong complexing ability for various rare earth metal ions is used in the organic phase. When Nd is present... 3+ and Dy 3+ When the mixed liquid comes into contact with this system, the two ligands compete with the target ion for coordination, thereby transforming the small difference in ionic radius between Nd and Dy into a significant difference in their partitioning behavior between the two phases.

[0036] By precisely controlling the ligand structure, concentration, and extraction conditions (such as acidity), this system can achieve efficient and highly selective separation of Nd and Dy in a single or very few extraction steps, obtaining high-purity single rare earth products.

[0037] This invention not only fundamentally overcomes the reliance on multi-stage extraction in traditional methods, significantly simplifying the process and reducing energy and material consumption, but also enhances the recognition ability of target ions and greatly improves separation selectivity due to the introduction of aqueous ligands. Furthermore, the reagents used in this system can be designed to be more environmentally compatible, thereby reducing secondary pollution and conforming to the concepts of green chemistry and sustainable development. This invention provides a novel technical approach for the separation of key adjacent rare earth elements such as neodymium and dysprosium, and has broad prospects for industrial application.

[0038] The present invention adopts the following technical solution: In a first aspect, the present invention provides a two-phase competitive extraction separation system for separating rare earth elements neodymium and dysprosium, the system comprising: a) an aqueous phase containing neodymium and dysprosium ions to be separated, nitric acid, and a water-soluble bis-lactam phenanthroline derivative ligand; and b) an organic phase containing the lipid-soluble extractant 2,2'-oxydi(N,N-dioctylacetamide), i.e., TODGA; The water-soluble bis-lactam phenanthroline derivative ligand preferentially complexes with neodymium ions in the aqueous phase to inhibit their entry into the organic phase, while the TODGA preferentially extracts dysprosium ions in the organic phase.

[0039] Furthermore, the ligand of the water-soluble bis-lactam phenanthroline derivative is Phen-2DIC4NH2.

[0040] Secondly, the present invention provides a liquid-liquid extraction method for separating rare earth elements neodymium and dysprosium, comprising the following steps: (1) Provide a feed solution containing neodymium ions and dysprosium ions to be separated as the aqueous phase of the two-phase competitive extraction separation system for separating rare earth elements neodymium and dysprosium as described above; (2) Liquid-liquid extraction: The aqueous phase is brought into contact with the organic phase. Under the acidity conditions of the aqueous phase, the water-soluble bis-lactam phenanthroline derivative ligand in the aqueous phase preferentially complexes neodymium ions, while the TODGA in the organic phase preferentially extracts dysprosium ions. (3) Separate the aqueous phase and the organic phase to obtain an aqueous phase enriched with neodymium and an organic phase enriched with dysprosium.

[0041] Furthermore, the concentration of nitric acid in the aqueous phase is from 0.1 M to 1.5 M, preferably 0.5 M.

[0042] Furthermore, the concentration of the water-soluble bis-lactam phenanthroline derivative ligand in the aqueous phase is 20 mM.

[0043] Furthermore, the concentration of TODGA in the organic phase is 0.1 M, and it is prepared by a diluent consisting of n-dodecane and n-octanol.

[0044] Preferably, the diluent is a mixture of n-dodecane and n-octanol in a volume ratio of 9:1.

[0045] Further, the conditions for liquid-liquid extraction in step (2) are: constant temperature extraction at 25 ± 1 ℃ for 10-60 minutes (preferably 30 minutes), followed by centrifugation after extraction (e.g., centrifugation at 3000 rpm for 2 minutes).

[0046] Thirdly, the present invention provides a method for separating rare earth elements neodymium and dysprosium using extraction chromatography, comprising the following steps: 1) Provide a chromatographic column using an extraction resin containing TODGA as the stationary phase; 2) An acidic feed solution containing neodymium ions and dysprosium ions, for example, an acidic feed solution containing neodymium (III) and dysprosium (III) of a simulated NdFeB magnet solution (containing boron (III), aluminum (III), iron (II), nickel (II) and neodymium (III) and dysprosium (III) elements) is loaded onto the chromatographic column so that neodymium ions and dysprosium ions are adsorbed by the stationary phase; 3) The chromatographic column is eluted with a first eluent to selectively elute neodymium, wherein the first eluent is a first acidic solution containing a water-soluble bis-lactam phenanthroline derivative ligand; 4) The chromatographic column is eluted with a second eluent to obtain dysprosium, wherein the second eluent is a second acidic solution containing the water-soluble bis-lactam phenanthroline derivative ligand, and the acidity of the second acidic solution is lower than that of the first acidic solution.

[0047] Furthermore, between step 1) and step 2), the chromatographic column is washed with a nitric acid solution that does not contain the water-soluble bis-lactam phenanthroline derivative ligand to remove non-rare earth impurity ions from the feed solution.

[0048] Preferably, the water-soluble bis-lactam phenanthroline derivative ligand is Phen-2DIC4NH2.

[0049] Further, the first eluent is a 0.1 M nitric acid solution containing 10 mM Phen-2DIC4NH2; and the second eluent is a 0.01 M nitric acid solution containing 10 mM Phen-2DIC4NH2.

[0050] In practical applications, the liquid-liquid extraction step can serve as a highly efficient pre-enrichment and coarse separation unit, rapidly separating and enriching Nd and Dy from a large rare earth background. This step can yield a high separation factor Nd-rich aqueous phase and a Dy-rich organic phase.

[0051] The column chromatography separation step serves as the purification and final separation unit, particularly suitable for processing complex feed solutions or enriched products obtained from liquid-liquid extraction. This step can yield high-purity Nd and Dy products, respectively.

[0052] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

[0053] In this invention, a mature commercial organic phase extractant, 2,2'-oxydi(N,N-dioctylacetamide) (TODGA, CAS No.: 342794-43-8), is used as a co-extractant in the organic phase. It is prepared by dissolving TODGA in a mixed solvent consisting of 90% v / v n-dodecane and 10 v / v n-octanol, wherein the concentration of TODGA is 0.1 M. The aqueous phase contains the rare earth ions to be separated, nitric acid of varying concentrations, and a specific type of hydrophilic ligand (structure shown in Figure 1). Figure 1 The solution (shown) has a concentration of 20 mM of the ligand in the aqueous phase.

[0054] Compounds Phen-2DIC2NH2 and Phen-2DIC4NH2 can be found in the literature Hong Cao, Yu Kang, Bin Li, Yaoyang Liu, Mingjie Bao, Haoyu Li, Yuan Zheng, Ludi Wang, Chaoqun Weng, Xiaoyan Tang. LiWang, and Chao Xu Amine-terminated phenanthroline diimides as aqueous masking agents for Am(III) / Eu(III) separation: an alternative ligand design strategy for water-soluble lanthanide / actinide chelating ligands. Inorg. Chem. , 2024, 63,10511-10518. Phen-2DIC6NH2 is a novel synthetic ligand; the synthetic route is as follows: Figure 9 As shown. The specific method is as follows: 4 mmol of dimethyl 1,10-phenanthroline-2,9-dicarboxylate was dissolved in a mixed solution of 20 mL chloroform and 20 mL ethanol. After stirring to dissolve, 80 mmol of hexamethylenediamine was added, followed by stirring at room temperature for 12 hours. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure. The solid residue was washed three times with diethyl ether to obtain a light yellow powder, which is the target compound Phen-2DIC6NH2. 1 H-NMR characterization such as Figure 10 As shown.

[0055] Example 1: Liquid-liquid extraction method for separating rare earth elements neodymium and dysprosium The extraction and separation method provided in this embodiment specifically includes the following steps: First, a mixture of 14 trivalent lanthanide ions (including the target ion Nd) with a total concentration of 7 mM was prepared. 3+ With Dy 3 + , and La 3+ Ce 3+ Pr 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3+ Ho 3+ Er 3+ Tm 3+ Yb 3+ Aqueous solutions of lanthanides (0.5 mM each), 20 mM specific hydrophilic ligands, and different concentrations of nitric acid (0.1 M, 0.5 M, 0.75 M, 1.0 M, 1.25 M, 1.5 M) were prepared. Then, 0.5 mL of this aqueous phase and 0.5 mL of the organic phase were placed in a 10 mL centrifuge tube and vortexed vigorously for 30 minutes in a constant temperature water bath at 25 ± 1 °C to ensure sufficient contact and extraction equilibrium. Subsequently, the mixture was centrifuged at 3000 rpm for 2 minutes to achieve clear separation of the two phases. 0.1 mL of the equilibrated aqueous sample was accurately pipetted, diluted 1000-fold with 0.1 M nitric acid solution, and the concentration of each lanthanide ion was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Based on material balance, the partition ratio of each ion between the organic and aqueous phases and the separation factor between target element pairs were calculated. Among them, the allocation ratio and separation factor, as two important separation evaluation indicators, are defined as follows: When the two-phase system reaches extraction equilibrium, the distribution ratio of metal ions (M) between the aqueous and organic phases is ( D M ) is defined as the concentration of the metal ion in the organic phase. C Org. ) and the concentration of the metal ion in the aqueous phase ( C aq. The ratio of ) to: Separation factor ( SF An / An The separation efficiency of the extraction system for two metal ions is used to evaluate the separation effect of the two metal ions, and is defined as the distribution ratio of the two metal ions ( ). D M The ratio of ) to: Experimental results show that aqueous phase acidity is a key parameter for controlling separation selectivity. The competitive extraction behavior of extraction separation systems using three different water-soluble ligands as aqueous phase masking agents for all 14 trivalent lanthanide ions (La-Lu, excluding Pm) under different nitric acid concentrations (0.1 M to 5.0 M) was systematically studied. Figures 2-4 The optimal separation window was determined. Experimental data clearly show that at an acidity of 0.5 M HNO3, the system exhibits the most ideal "reverse competition" effect: the C4 ligand in the aqueous phase exhibits a strong selective complexing ability for light and medium rare earth elements (especially La to Nd) with larger ionic radii, effectively inhibiting their migration to the organic phase; at the same time, TODGA in the organic phase maintains its inherent preferential extraction tendency for medium and heavy rare earth elements (especially Tb to Lu) with smaller ionic radii. This opposite size selectivity creates a "pull competition" at the interface, thereby transforming the small physicochemical differences between adjacent rare earth ions into huge differences in partitioning behavior. Meanwhile, the fine-tuning of the ligand structure has proven to be another key to obtaining superior performance. Under optimized 0.5 M HNO3 conditions, although all three can achieve the separation of rare earth strings, as... Figure 5 and Figure 6 As shown, the Phen-2DIC4NH2 ligand exhibits unparalleled comprehensive performance. Its unique chain length achieves an optimal balance between hydrophilicity, steric hindrance, and coordination flexibility, resulting in the highest recognition accuracy for the target ion pair (Nd / Dy). Quantitative data show that the extraction system constructed using the Phen-2DIC4NH2 ligand, after single-stage contact, yielded a calculated Nd / Dy separation factor (…). SF Dy / Nd =1780) reached a breakthrough high level, which is significantly higher than that of the C2 and C6 ligand systems (i.e., Phen-2DIC2NH2 and Phen-2DIC6NH2), and as Figure 7 A comparison with existing literature data shows that this far surpasses any advanced separation method reported to date. This extremely high single-stage separation factor means that, in practical applications, only a very small number of extraction stages are needed to obtain high-purity Nd and Dy concentrates, thus significantly simplifying the lengthy process of traditional solvent extraction from the source.

[0056] Example 2: A method for separating rare earth elements neodymium and dysprosium using extraction chromatography To address the challenges of directly purifying Nd / Dy from complex matrices (such as leachate from permanent magnet waste) or performing final purification of liquid-liquid extraction enrichment products, this embodiment further provides an innovative extraction chromatography method. This method uses commercially available TODGA extraction resin (Eichrom DN-B25-5) as the stationary phase, and the core of the elution strategy is also the aforementioned Phen-2DIC4NH2 ligand. The specific process steps are as follows: First, pack the TODGA resin into the chromatographic column (column bed height 5-7 cm). Dissolve the simulated feed solution (simulating NdFeB magnet) containing Nd, Dy and other typical impurity ions (such as B, Al, Fe, Ni) in 3.0 M HNO3 and load the sample.

[0057] After sample loading, washing was first performed using nitric acid solutions of decreasing concentrations (e.g., 30 mL each of 3.0 M, 2.5 M, 2.0 M, 1.5 M, 1.0 M, and 0.1 M HNO3). The experimental results clearly show that non-rare earth impurity ions such as B, Al, Fe, and Ni were completely eluted early in this process, and Nd and Dy were undetectable in the collected solution. Nd and Dy, however, were strongly adsorbed by the TODGA resin and were not washed away even with nitric acid as low as 0.1 M. This demonstrates that acidity changes alone cannot separate the two, creating a clean background for subsequent specific elution.

[0058] The key turning point in the separation process is the introduction of Phen-2DIC4NH2 ligand solution as an eluent.

[0059] First, elution was performed using a 10 mM Phen-2DIC4NH2 ligand solution dissolved in 0.1 M HNO3. Under these conditions, the Phen-2DIC4NH2 ligand, due to its affinity for Nd... 3+ Stronger affinity, enabling it to effectively compete for Nd on TODGA resin. 3 + This forms a water-soluble complex and elutes it. For example... Figure 8 As shown in the elution curves, Nd was efficiently and with high purity recovered from the fraction collected in this stage, while Dy was almost completely retained on the column, achieving the first-step separation. Subsequently, the eluent was replaced with a 10 mM C4 ligand solution dissolved in 0.01 M HNO3. Lowering the acidity enhanced the electron-donating ability of the nitrogen and oxygen donor atoms in the C4 ligand, significantly improving the electron-donating ability of Dy with its smaller ionic radius. 3+ The complexation strength, thereby enabling the firmly retained Dy 3+ The elution process was fully competitive and followed by elution. Through these two steps of "intelligent" elution based on the same ligand but different acidities, complete and high-purity separation of Nd and Dy was finally achieved, with a recovery rate close to quantitation.

[0060] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A two-phase competitive separation system for separating rare earth elements neodymium and dysprosium, characterized in that, The two-phase competitive separation system includes a first phase and a second phase that are in contact with each other; The first phase is a solution containing a water-soluble selective ligand, wherein the water-soluble selective ligand has a stronger complexing ability for neodymium(III) than for dysprosium(III); The second phase contains a fat-soluble extractant that has the ability to complex trivalent lanthanide rare earth elements; The two-phase competitive separation system enables the separation of neodymium and dysprosium by creating differences in their distribution behavior between the first and second phases.

2. The two-phase competitive separation system according to claim 1, characterized in that, It is a liquid-liquid extraction separation system, comprising: a first phase aqueous phase, which is a solution containing nitric acid and contains water-soluble selective ligands; and a second phase organic phase, which contains a fat-soluble extractant with complexing ability for trivalent lanthanide rare earth elements.

3. The two-phase competitive separation system according to claim 1, characterized in that, It is a column chromatography separation system that uses an extraction resin containing a fat-soluble extractant with complexing ability for trivalent lanthanide rare earth elements as the second stationary phase. In use, an acidic feed solution containing neodymium (III) and dysprosium (III) is mixed with the first phase and then contacted with the second stationary phase.

4. The two-phase competitive separation system according to any one of claims 1-3, characterized in that, The lipid-soluble extractant is 2,2'-oxydi(N,N-dioctylacetamide), i.e., TODGA; and / or, The water-soluble selective ligand is a water-soluble bis-lactam phenanthroline derivative ligand, Phen-2DIC4NH2, with the following structural formula: 。 5. The two-phase competitive separation system according to claim 4, characterized in that, The concentration of TODGA in the second organic phase of the liquid-liquid extraction separation system is 0.05-0.2 M, and it is prepared by a diluent consisting of n-dodecane and n-octanol in a volume ratio of 8:1 to 20:

1. Preferably, the concentration of TODGA in the second organic phase of the liquid-liquid extraction separation system is 0.1 M, and it is prepared by a diluent consisting of n-dodecane and n-octanol in a volume ratio of 9:

1.

6. The two-phase competitive separation system according to claim 4, characterized in that, The concentration of the water-soluble selective ligand in the first aqueous phase of the liquid-liquid extraction separation system is 20 mM; and / or, The concentration of the nitric acid is from 0.1 M to 1.5 M, preferably 0.5 M; and / or, In the liquid-liquid extraction separation system, the second organic phase and the first aqueous phase are mixed in equal volumes.

7. The application of the two-phase competitive separation system according to any one of claims 1-6 in the separation of rare earth elements neodymium and dysprosium.

8. A liquid-liquid extraction method for separating rare earth elements neodymium and dysprosium, characterized in that, Two rare earth elements, neodymium (III) and dysprosium (III), can be separated from a feed solution containing neodymium (III) and dysprosium (III) using a liquid-liquid extraction separation system in a two-phase competitive separation system as described in any one of claims 2, 4-6. The method includes: adding the feed solution containing neodymium (III) and dysprosium (III) to be separated into the first aqueous phase, and then contacting the second organic phase with the first aqueous phase. Under competitive extraction conditions, dysprosium (III) is preferentially extracted into the second organic phase, while neodymium (III) is retained in the first aqueous phase, thereby achieving the separation of the two rare earth elements. Preferably, the competitive extraction conditions are: constant temperature extraction at 25 ± 1 ℃ for 10-60 minutes with shaking, followed by centrifugation after extraction.

9. A method for separating rare earth elements neodymium and dysprosium using extraction chromatography, characterized in that, Using the column chromatography separation system in the two-phase competitive separation system according to any one of claims 3-6, two rare earth elements can be separated from a feed containing neodymium(III) and dysprosium(III); Includes the following steps: (1) The sample containing neodymium(III) and dysprosium(III) is loaded onto the chromatographic column so that neodymium ions and dysprosium ions are adsorbed by the stationary phase; (2) The chromatographic column is eluted with a first eluent to selectively elute neodymium, wherein the first eluent is a first acidic solution containing the water-soluble bis-lactam phenanthroline derivative ligand Phen-2DIC4NH2 as described in claim 4; (3) The chromatographic column is eluted with a second eluent to obtain dysprosium, wherein the second eluent is a second acidic solution containing the ligand Phen-2DIC4NH2, and the acidity of the second acidic solution is lower than that of the first acidic solution; Preferably, the first eluent is a 0.1 M nitric acid solution containing 10 mM of the ligand Phen-2DIC4NH2; and the second eluent is a 0.01 M nitric acid solution containing 10 mM of the ligand Phen-2DIC4NH2.

10. The method according to claim 9, characterized in that, Between steps (1) and (2), the column is washed with a nitric acid solution containing the ligand Phen-2DIC4NH2 to remove non-rare earth impurity ions from the feed solution.

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