A nitrogen-triacetamide extractant for separating praseodymium and neodymium, its preparation method and application

Abstract

The structural formula of the nitrogen-triacetamide extractant for separating praseodymium and neodymium disclosed in this invention is as follows: This invention also discloses a method for preparing the above-mentioned nitrogen-triacetamide extractant and its applications. The extractant molecule disclosed in this invention has good lipid solubility and low steric hindrance. It not only has high extraction selectivity, excellent extraction kinetics and acid resistance, but also does not require saponification before use, nor does it require the addition of water-soluble complexing agents or co-extractants during use. This avoids the potential threat to the ecological environment and human health posed by the large amount of ammonia nitrogen wastewater generated by saponification treatment. Furthermore, it simplifies the extraction system, expands the acidity range, reduces extraction costs, and is simple, mature, easy to control, and suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the technical field of extractants for separating and purifying light rare earth elements, as well as their preparation and applications. Specifically, it relates to a nitrogen-triacetamide extractant for separating praseodymium and neodymium, its preparation method, and its application. Background Technology

[0002] Light rare earth elements praseodymium (Pr) and neodymium (Nd) are widely used in metallurgy, petrochemicals, functional materials, and glass ceramics due to their unique physicochemical properties. With the development of these fields, the demand for high-purity rare earth Pr and Nd in domestic and international markets is increasing, leading to widespread attention on the separation of Pr / Nd. However, the very similar physicochemical properties of Pr and Nd make Pr / Nd separation quite challenging. Solvent extraction is the most important method for extracting and separating rare earth elements due to its advantages such as good selectivity, fast kinetics, simple equipment, convenient operation, ease of continuous and automated processing, and applicability to both trace element separation and industrial-scale separation. Among these methods, acidic phosphorus extractants P204 (di-(2-ethylhexyl)phosphoric acid) and P507 (2-ethylhexylphosphonic acid mono(2-ethylhexyl) ester) are widely used in rare earth extraction processes. P204 and P507 extract rare earth ions mainly through a cation exchange mechanism, extracting rare earth ions from the aqueous phase into the organic phase, i.e., the H+ of the extractant... + Separation occurs through ion exchange between ions and rare earth cations. However, during the extraction process, H₂O₄ and P₅O₇ release H₂. + Ions can reduce the separation efficiency of Pr and Nd. Therefore, P204 and P507 need to be saponified before extraction. However, studies have shown that the separation coefficient (β) of saponified P204 and P507 for Pr and Nd is not optimal. Nd / Pr The β value is only about 1.3 to 1.5. Clearly, the β value of the extractant... Nd / Pr Lower concentrations will undoubtedly lead to an increase in the number of extraction stages required for Pr / Nd separation, thereby increasing separation costs. Furthermore, saponification treatment generates large amounts of ammonia nitrogen wastewater, posing a potential threat to the ecological environment and human health.

[0003] To improve the β-value of extractants P204 and P507 Nd / Pr To avoid the generation of ammonia nitrogen wastewater, two main methods were employed. One method involved adding water-soluble complexing agents such as tartaric acid, lactic acid, citric acid, and acetic acid to the aqueous phase. For example, when the tartaric acid concentration was 0.4 mol / L and the pH of the aqueous solution was 2.5, the β-type of P2O4... Nd / PrThe value can be increased to 1.85. Although the separation effect of Pr and Nd can be improved, the low concentration of rare earth ions remaining in the raffinate after extraction is difficult to recover after binding with the complexing agent, and the residue of the complexing agent in the water will also cause environmental problems. Secondly, co-extractants such as P350 (dimethylheptyl methylphosphonate), TBP (tributyl phosphate), and TOA (tri-n-octylamine) can be added to the organic phase for the separation of Pr / Nd. For example, when P350 is added to the P204 extraction system, at a pH of 2.85 in the aqueous phase, the β... Nd / Pr The value can be increased to 1.45. Although the addition of a co-extractant can appropriately increase β... Nd / Pr However, this also presents problems such as complex separation systems and high costs. Therefore, there is a need to develop novel extractants and extraction systems with higher separation capabilities for Pr / Nd. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the extraction and separation of praseodymium and neodymium using existing extractants. It first provides an asymmetric structure nitrogen-triacetamide extractant for separating praseodymium and neodymium, which can be used to selectively extract and separate praseodymium and neodymium elements from a mixed solution of praseodymium and neodymium rapidly and efficiently.

[0005] Another object of the present invention is to provide a method for preparing a nitrogen-triacetamide extractant for separating praseodymium and neodymium.

[0006] Another object of the present invention is to provide the application of the above-mentioned nitrogen-triacetamide extractant for separating praseodymium and neodymium.

[0007] The present invention provides a nitrogen-based triacetamide extractant for separating praseodymium and neodymium, the structural formula of which is as follows:

[0008]

[0009] The method for preparing the above-mentioned nitrogen-triacetamide extractant for separating praseodymium and neodymium provided by the present invention includes the following process steps and conditions:

[0010] 1) First, add imino-di(N,N-dioctyl)acetamide, potassium iodide and alkaline reagent together into an inert atmosphere reaction vessel and mix. Then, slowly inject N,N-dibutyl-2-bromoacetamide compound, which has been dissolved in acetonitrile solvent, into the mixed reactants, stir continuously and react at 60-90℃ for 2-5 hours.

[0011] 2) After the reaction is complete, remove the acetonitrile solvent and extract with ethyl acetate in a mass ratio of 10-40 to the reactant imino-bis(N,N-dioctyl)acetamide to obtain the organic phase;

[0012] 3) The organic phase was washed sequentially with citric acid solution, saturated NaHCO3 solution, and saturated NaCl solution. After washing, it was dried with anhydrous sulfate and filtered to obtain the filtrate. Finally, the filtrate was concentrated and purified to obtain N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant.

[0013] The alkaline reagent mentioned in the above methods is potassium carbonate or sodium carbonate.

[0014] The anhydrous sulfate mentioned in the above methods is anhydrous sodium sulfate or anhydrous magnesium sulfate.

[0015] The application of the above-mentioned nitrogen-triacetamide extractant for separating praseodymium and neodymium provided by the present invention is to extract and separate praseodymium and neodymium from light rare earth mineral slurries, or to separate praseodymium and neodymium from crude praseodymium and neodymium products.

[0016] The specific method for separating praseodymium and neodymium using the above-mentioned triacetamide extractant provided by this invention is as follows:

[0017] 1) Dissolve a mixture of praseodymium and neodymium in a 0.1-6.0 mol / L nitric acid solution to obtain the extraction aqueous phase;

[0018] 2) Dissolve N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide extractant in n-dodecane diluent to obtain the extracted organic phase;

[0019] 3) Mix equal volumes of the extraction aqueous phase and the extraction organic phase thoroughly at room temperature for 5-60 minutes, then centrifuge to obtain the praseodymium or neodymium organic phase and aqueous phase;

[0020] 4) Remove the aqueous phase and measure the concentrations of praseodymium and neodymium before and after aqueous phase extraction using an inductively coupled plasma optical emission spectrometer (ICP-OES). Then, calculate the concentration of praseodymium or neodymium extracted into the organic phase using the difference method. At the same time, the extraction rate, partition ratio and separation coefficient can also be calculated.

[0021] The calculation formula is as follows:

[0022] [M] org. =[M] ini. -[M] aq.

[0023] Extraction rate E% = [M] org. / [M] ini. ×100%

[0024] Distribution ratio D M =[M] org. / [M] aq

[0025] Separation coefficient β Pr / Nd =DPr / D Nd .

[0026] Among them, [M] org. [M] indicates the concentration of praseodymium or neodymium in the organic phase. ini. [M] indicates the initial concentration of praseodymium or neodymium in the aqueous phase before extraction. aq. This indicates the concentration of praseodymium or neodymium in the aqueous phase after extraction.

[0027] The mixture described in the above methods is a crude product of praseodymium and neodymium or a light rare earth mineral slurry.

[0028] The preferred mixing time in the above method is 5-30 minutes.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. Because the branched chain of the nitrogen-triacetamide extractant molecule provided by this invention is composed of 4 n-octyl substituents and 2 n-butyl substituents, it has an asymmetric structure. This structure not only ensures the extractant has excellent lipophilicity, which is beneficial for extracting metal ions from the aqueous phase into the organic phase, but also has less steric hindrance compared to the branched chain with 6 n-octyl substituents, resulting in stronger extraction ability. Therefore, the separation coefficient β of this extractant is increased. Pr / Nd It can reach 4.3 or higher.

[0031] 2. Because the extraction system composed of triacetamide extractant and n-dodecane diluent provided by this invention has excellent extraction kinetics, it can achieve extraction equilibrium within 5 minutes of contact between the two phases, thus greatly shortening the extraction process time and improving extraction efficiency.

[0032] 3. Because the extraction system composed of triacetamide extractant and n-dodecane diluent provided by the present invention has excellent acid resistance stability, emulsification or third phase phenomenon can be avoided in the extraction process of praseodymium and neodymium, thereby effectively preventing the two phases from being unable to separate.

[0033] 4. Since the nitrogen triacetamide extractant provided by this invention does not require saponification treatment before use, nor does it require the addition of water-soluble complexing agents or co-extracting agents during use, it avoids the potential threat to the ecological environment and human health posed by the large amount of ammonia nitrogen wastewater generated by saponification treatment, and also makes its extraction system simple, with a wide acidity range and low extraction cost.

[0034] 5. Since the nitrogen-containing triacetamide extractant provided by this invention contains only four elements, C, H, O and N, compared with phosphorus-containing extractants, it can be completely incinerated and basically does not produce secondary solid waste, which is very environmentally friendly.

[0035] 6. Since the preparation of the triacetamide extractant provided by this invention is simple and mature, it is easy to control and carry out industrial production. Attached Figure Description

[0036] Figure 1 The synthetic route of N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide provided by the present invention is shown in the structural formula, where n-Oct is n-octyl and n-But is n-butyl.

[0037] Figure 2 The 1H NMR spectrum of N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide, the extractant provided in this invention, shows that its synthesis was successful.

[0038] Figure 3 The graphs show the separation curves of praseodymium and neodymium from crude praseodymium and neodymium products using the N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant provided by this invention under different contact time conditions. The graphs show that extraction equilibrium is reached within 5 minutes of phase contact, indicating that the N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant possesses excellent extraction kinetics.

[0039] Figure 4 The separation coefficient β of the N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide extractant provided by this invention, after separating various elements from light rare earth ore slurry, was calculated through testing. Pr / Nd The bar chart shows that the separation of praseodymium and neodymium can reach 4.3.

[0040] Figure 5 The graphs show the separation curves of praseodymium and neodymium from crude praseodymium and neodymium products using the N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant provided by this invention under different nitric acid concentrations. As can be seen from the graphs, at a nitric acid concentration of 1.0 mol / L, the separation coefficient β of the N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant is... Pr / Nd The highest, that is, the most suitable for the separation of praseodymium and neodymium.

[0041] Figure 6 Using the N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant provided in Example 1 of this invention, the N,N-diethyl-N',N',N”,N”-tetraoctylazinetriacetamide provided in the comparative example, and a commercially available azinetriacetamide extractant, praseodymium and neodymium were separated from crude praseodymium and neodymium products under different nitric acid concentrations. The separation coefficient β of the extractant was calculated by testing. Pr / NdCurve comparison graph. As can be seen from the graph, at a nitric acid concentration of 1.0 mol / L, the separation coefficient β of the N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant provided by this invention... Pr / Nd Highest. Detailed Implementation

[0042] The following embodiments are provided to further illustrate the present invention. It should be noted that the following embodiments should not be construed as limiting the scope of protection of the present invention. If those skilled in the art make some non-essential improvements and adjustments to the present invention based on the above description, they shall still fall within the scope of protection of the present invention.

[0043] Example 1

[0044] N,N-dibutyl-2-bromoacetamide (2.13 g, 8.5 mmol), anhydrous K₂CO₃ (7.05 g, 51 mmol), and KI (0.28 g, 1.7 mmol) were added together into a 250 mL two-necked round-bottom flask filled with N₂ and mixed. Then, imino-bis(N,N-dioctyl)acetamide (4.93 g, 8.5 mmol), which had been pre-dissolved in 80 mL of anhydrous acetonitrile, was slowly injected into the mixture. The mixture was stirred continuously and reacted at 85 °C for 3 hours. After the reaction was complete, the acetonitrile solvent was removed, and the target product was extracted with 200 mL of ethyl acetate to obtain the organic phase. The organic phase was washed successively with 5% citric acid solution (3 × 50 mL), saturated NaHCO₃ solution (3 × 50 mL), and saturated NaCl solution (3 × 50 mL), dried over anhydrous sodium sulfate, and filtered to obtain the filtrate. Finally, the filtrate was concentrated under reduced pressure to obtain the crude product, which was then purified by silica gel column chromatography to obtain a pale yellow oily N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide (4.20 g, 66%). The 1H NMR spectrum is attached. Figure 2 .

[0045] Characterization by proton nuclear magnetic resonance (NMR): 1 H NMR(400MHz,CDCl3)δ3.64(6H,s,NCH2CON),3.22-3.28(12H,m,CONCH2CH2),1.44-1.53(12H,m,CONCH2CH2CH2),1.25-1.30(44H,m,(CH2)5CH3 andCONCH2CH2CH2CH3),0.85-0.93(18H,m,CH3).

[0046] High-resolution mass spectrometry characterization: ESI-HRMS (C 46 H 93 N4O3 +Calculated value), m / z: 749.7242 (749.7243).

[0047] The characterization results above indicate that the extractant was successfully prepared.

[0048] Example 2

[0049] N,N-dibutyl-2-bromoacetamide (2.13 g, 8.5 mmol), anhydrous Na₂CO₃ (5.41 g, 51 mmol), and KI (0.28 g, 1.7 mmol) were added together into a 250 mL two-necked round-bottom flask filled with N₂ and mixed. Then, imino-bis(N,N-dioctyl)acetamide (4.93 g, 8.5 mmol), which had been pre-dissolved in 80 mL of anhydrous acetonitrile, was slowly injected into the mixture. The mixture was stirred continuously and reacted at 60 °C for 5 hours. After the reaction was complete, the acetonitrile solvent was removed, and the target product was extracted with 200 mL of ethyl acetate to obtain the organic phase. The organic phase was washed successively with 5% citric acid solution (3 × 50 mL), saturated NaHCO₃ solution (3 × 50 mL), and saturated NaCl solution (3 × 50 mL), dried over anhydrous magnesium sulfate, and filtered to obtain the filtrate. Finally, the filtrate was concentrated under reduced pressure to obtain the crude product, which was then purified by silica gel column chromatography to obtain a pale yellow oily N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide (3.31 g, 52%).

[0050] Example 3

[0051] N,N-dibutyl-2-bromoacetamide (2.13 g, 8.5 mmol), anhydrous K₂CO₃ (5.41 g, 51 mmol), and KI (0.28 g, 1.7 mmol) were added together into a 250 mL two-necked round-bottom flask filled with N₂ and mixed. Then, imino-bis(N,N-dioctyl)acetamide (4.93 g, 8.5 mmol), which had been pre-dissolved in 80 mL of anhydrous acetonitrile, was slowly injected into the mixture. The mixture was stirred continuously and reacted at 85 °C for 5 hours. After the reaction was complete, the acetonitrile solvent was removed, and the target product was extracted with 100 mL of ethyl acetate to obtain the organic phase. The organic phase was washed successively with 5% citric acid solution (3 × 50 mL), saturated NaHCO₃ solution (3 × 50 mL), and saturated NaCl solution (3 × 50 mL), dried over anhydrous sodium sulfate, and filtered to obtain the filtrate. Finally, the filtrate was concentrated under reduced pressure to obtain the crude product, which was then purified by silica gel column chromatography to obtain a pale yellow oily N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide (4.14 g, 65%).

[0052] Comparative Examples

[0053] N,N-Diethyl-2-bromoacetamide (3.56 g, 18.4 mmol), anhydrous K₂CO₃ (15.26 g, 110.4 mmol), and KI (0.611 g, 3.68 mmol) were added together into a 500 mL two-necked round-bottom flask filled with N₂ and mixed. Then, imino-bis(N,N-dioctyl)acetamide (10.65 g, 18.4 mmol), which had been pre-dissolved in 150 mL of anhydrous acetonitrile, was slowly injected into the mixture. The mixture was stirred continuously and reacted at 85 °C for 5 hours. After the reaction was complete, the acetonitrile solvent was removed, and the target product was extracted with 200 mL of ethyl acetate to obtain the organic phase. The organic phase was washed successively with 5% citric acid solution (3 × 100 mL), saturated NaHCO₃ solution (3 × 100 mL), and saturated NaCl solution (3 × 100 mL), dried over anhydrous sodium sulfate, and filtered to obtain the filtrate. Finally, the filtrate was concentrated under reduced pressure to obtain the crude product, which was then purified by silica gel column chromatography to obtain pure N,N-diethyl-N',N',N”,N”-tetraoctyltriacetamide (8.93g, 70%), which is a pale yellow oil.

[0054] Characterization by proton nuclear magnetic resonance (NMR): 1 H NMR(400MHz,CDCl3)δ3.66(6H,s,NCH2CON),3.31-3.39(4H,m,CONCH2CH3),3.23-3.27(8H,m,CONCH2CH2CH2),1.4 7-1.51(8H,m,CONCH2CH2CH2),1.26(40H,m,(CH2)5CH3),1.08-1.16(6H,2t,CONCH2CH3),0.85-0.89(12H,m,CH3).

[0055] High-resolution mass spectrometry characterization: ESI-HRMS (C 42 H 85 N4O3 + Calculated value), m / z: 693.6618 (693.6617).

[0056] The characterization results above indicate that the extractant was successfully prepared.

[0057] Application Example 1

[0058] Crude praseodymium and neodymium products were dissolved in a 1.0 mol / L nitric acid solution to obtain an aqueous extraction phase with praseodymium and neodymium concentrations of approximately 1.0 mmol / L each. A 0.10 mol / L solution of N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide extractant in n-dodecane was used as the organic extraction phase. An equal volume of the aqueous phase (1.0 mL) was placed in a 10 mL centrifuge tube and stirred at 500 rpm with a magnetic stirrer at room temperature. The concentration of the aqueous phase was measured by ICP-OES at different time points to investigate the extraction rate (E%) at different extraction times. The test results are attached. Figure 3 As shown in the figure, the extraction kinetics of praseodymium and neodymium are very rapid, reaching extraction equilibrium within 5 minutes of phase contact. This result indicates that N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide extractant possesses excellent extraction kinetics.

[0059] Application Example 2

[0060] A light rare earth ore solution with a nitric acid concentration of 1.0 mol / L was used as the aqueous extraction phase; a dodecane solution of 0.10 mol / L N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide extractant was used as the organic extraction phase. Equal volumes of the organic and aqueous phases (1.0 mL) were then placed in 10 mL centrifuge tubes and stirred at 500 rpm for 30 min at room temperature using a magnetic stirrer. The two phases were then separated, and the concentrations of light rare earth elements lanthanum (La), cerium (Ce), praseodymium, and neodymium in the aqueous phase before and after extraction were determined using ICP-OES. The test results are shown in the appendix. Figure 4 As shown in the figure, under 1.0 mol / L nitric acid conditions, N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide extractant can effectively separate praseodymium and neodymium, with a separation coefficient β. Pr / Nd The value is as high as 4.3.

[0061] Application Example 3

[0062] Crude praseodymium and neodymium products were dissolved separately in nitric acid solutions with concentrations ranging from 0.1 to 6.0 mol / L, yielding extraction aqueous phases with praseodymium and neodymium concentrations of approximately 1.0 mmol / L each. A solution of 0.10 mol / L N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide extractant in n-dodecane was used as the extraction organic phase. Equal volumes of the organic phase and the aqueous phase (1.0 mL) were placed in 10 mL centrifuge tubes and stirred at 500 rpm for 30 min at room temperature using a magnetic stirrer. The two phases were then separated, and the concentrations of praseodymium and neodymium in the aqueous phases before and after extraction were determined using ICP-OES. The experimental results are shown in the appendix. Figure 5As shown in the figure, under 1.0 mol / L nitric acid conditions, the separation coefficient β of the N,N-dibutyl-N',N',N”,N”-tetraoctylazine triacetamide extractant is... Pr / Nd It is the highest and most suitable for the separation of praseodymium and neodymium.

[0063] Application Comparative Example 1

[0064] A light rare earth ore solution with a nitric acid concentration of 1.0 mol / L was used as the extraction aqueous phase; N,N-diethyl-N',N',N”,N”-tetraoctylazinetriacetamide (L) prepared in the comparative example was used. I N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide (L) prepared in Example 1 of this invention II ) and commercially available N,N,N',N',N”,N”-hexoctylazinetriacetamide (L III The extractant was dissolved in n-dodecane to obtain an organic phase with a concentration of 0.10 mol / L. Equal volumes of the organic phase and aqueous phase (1.0 mL) were placed in 10 mL centrifuge tubes and stirred at 500 rpm for 30 min at room temperature using a magnetic stirrer. The two phases were then separated, and the concentrations of light rare earth elements lanthanum (La), cerium (Ce), praseodymium, and neodymium in the aqueous phase before and after extraction were determined by ICP-OES. The results are shown in Table 1. Table 1 shows that, compared with the other two extractants, the N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant (L... II The separation coefficient β) Pr / Nd The value is the highest, and the separation effect of praseodymium and neodymium is the best.

[0065] Table 1 Separation coefficient β of light rare earth elements extracted with triacetamide extractant M / Nd

[0066]

[0067] Application Comparative Example 2

[0068] The crude praseodymium and neodymium products were dissolved in nitric acid solutions with concentrations ranging from 0.1 to 6.0 mol / L, respectively, to obtain extraction aqueous phases with praseodymium and neodymium concentrations of approximately 1.0 mmol / L each; N,N-diethyl-N',N',N”,N”-tetraoctylazinetriacetamide (L…) prepared in the comparative example… I The N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide (L) prepared in Embodiment 1 of this invention II ) and commercially available N,N,N',N',N”,N”-hexoctylazinetriacetamide (L IIIThe extractant was dissolved in n-dodecane to obtain an organic phase with a concentration of 0.10 mol / L. Equal volumes of the organic phase and the aqueous phase (1.0 mL) were placed in 10 mL centrifuge tubes and stirred at 500 rpm for 30 min at room temperature using a magnetic stirrer. The two phases were then separated, and the concentrations of praseodymium and neodymium in the aqueous phase before and after extraction were determined by ICP-OES. The test results are shown in the appendix. Figure 6 As shown in the figure. It can be seen from the figure that, compared with the other two extractants, N,N-dibutyl-N',N',N”,N”-tetraoctylazinetriacetamide extractant (L... II The separation coefficient β) Pr / Nd The value was the highest, indicating the best separation effect between praseodymium and neodymium. Additionally, the extractant L... I A third phase appeared when the nitric acid concentration was greater than 2.0 mol / L. II Separation coefficient β of the extractant Pr / Nd Significantly higher than L III and L I This is due to the combined effects of lipid solubility and steric hindrance. Extraction performance is generally determined by the steric hindrance and lipid solubility of the extractant. II Spatial steric hindrance less than L III Therefore L II Extraction performance is better than L III L II Although the spatial steric hindrance is slightly greater than L I However, L II Its fat solubility is higher than that of L I At this point, the extractant with higher fat solubility has the advantage. Therefore, L II Extraction performance is better than L III and L I .

Claims

1. A method for preparing a nitrogen-triacetamide extractant for separating praseodymium and neodymium, wherein the process steps and conditions are as follows: 1) First, imino-di( N , N (-Dioctyl)acetamide, potassium iodide, and a basic reagent are added together into an inert atmosphere reaction vessel and mixed. Then, a solution pre-dissolved in acetonitrile solvent is added. N , N The dibutyl-2-bromoacetamide compound was slowly injected into the mixed reactants, and the mixture was stirred continuously and reacted at 60–90 °C for 2–5 hours. 2) After the reaction is complete, remove the acetonitrile solvent and add the reactant imino-di( N , N Extraction with ethyl acetate at a mass ratio of 10–40 for dioctyl)acetamide yielded an organic phase; 3) The organic phase is washed successively with citric acid solution, saturated NaHCO3 solution, and saturated NaCl solution. After washing, it is dried with anhydrous sulfate, filtered to obtain the filtrate, and finally concentrated and purified to obtain the final product. N , N -Dibutyl- N' , N' , N'' , N'' -Tetraoctyl aziridine triacetamide extractant, its structural formula is as follows: .

2. The method for preparing the triacetamide extractant for separating praseodymium and neodymium according to claim 1, wherein the alkaline reagent in the method is potassium carbonate or sodium carbonate.

3. The method for preparing the nitrogen-triacetamide extractant for separating praseodymium and neodymium according to claim 1 or 2, wherein the anhydrous sulfate in the method is anhydrous sodium sulfate or anhydrous magnesium sulfate.

4. An application of the extractant obtained by the preparation method of the nitrogen-triacetamide extractant for separating praseodymium and neodymium according to claim 1, wherein the application is to use the extractant to extract and separate praseodymium and neodymium from light rare earth mineral slurry, or to separate praseodymium and neodymium from crude products of praseodymium and neodymium.

5. The application of the extractant obtained by the method for preparing the nitrogen-triacetamide extractant for separating praseodymium and neodymium according to claim 4, wherein the specific method for application is as follows: 1) Dissolve a mixture of praseodymium and neodymium in a 0.1–6.0 mol / L nitric acid solution to obtain the extraction aqueous phase; 2) N , N -Dibutyl- N' , N' , N'' , N'' -Tetraoctyltriacetamide extractant was dissolved in n-dodecane diluent to obtain the extracted organic phase; 3) Mix equal volumes of the extraction aqueous phase and the extraction organic phase thoroughly at room temperature for 5–60 minutes, then centrifuge to obtain the praseodymium or neodymium organic phase and aqueous phase; 4) Remove the aqueous phase and measure the concentrations of praseodymium and neodymium before and after aqueous phase extraction using an inductively coupled plasma atomic emission spectrometer. Then, calculate the concentration of praseodymium or neodymium extracted into the organic phase using the difference method. At the same time, the extraction rate, partition ratio and separation coefficient can also be calculated.

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