A functional ionic liquid and its preparation method and application

Abstract

The application provides a functional ionic liquid, wherein the cation is a hydrophobic imidazolium radical, and the anion is a glycine radical with a long carbon chain. The ionic liquid has high loading capacity as an extractant, can effectively improve the removal rate of elements such as aluminum in rare earth ores, reduce the loss rate of rare earth, and has good recycling performance and separation capacity.

Description

Technical Field

[0001] This invention belongs to the field of rare earth ore impurity removal, specifically relating to a functional ionic liquid, its preparation method, and its application. Background Technology

[0002] Rare earth elements (REs) are widely used in permanent magnets, fluorescent lamps, rechargeable nickel-metal hydride batteries, and catalysts. In the 21st century, with the increasing popularity of hybrid vehicles, electric vehicles, and wind turbines, the demand for rare earths, as an indispensable component of permanent magnet materials for motors and turbines, is also increasing. Rare earth resources in mineral deposits coexist with other metals such as aluminum, iron, calcium, magnesium, and copper. Metallurgical methods are needed to separate the rare earth mixture from these impurities. Unfortunately, chemical beneficiation cannot completely remove all impurities from the target rare earth, causing significant problems for subsequent processing and affecting the final rare earth product.

[0003] Aluminum is often found as an impurity in many rare earth ores. For example, in in-situ leaching of ion-adsorption rare earth ores (IATREO), aluminum inevitably leaches along with the rare earth mixture. The collected leachate is selectively leached with ammonium bicarbonate to adjust the pH, removing most of the aluminum. After enrichment, precipitation and calcination yield a mixed oxide with a rare earth content of over 90%. Because the aluminum content in the leachate remains high, rare earth elements are prone to co-precipitation during subsequent alkali neutralization, leading to significant rare earth losses. Furthermore, it causes ammonia nitrogen pollution, eutrophication of water bodies, and severe damage to the ecosystem near the mining area. If oxalic acid is used for precipitation, water-soluble Al(C₂O₄) is easily formed. + Complexes significantly increase oxalic acid consumption and reduce aluminum precipitation. Solvent extraction, with its advantages of continuous operation, high throughput, and better separation performance, is commonly used in large-scale industrial production of rare earth elements. However, for example, P507 and naphthenic acids and their saponifications can cause severe emulsification of Al and other impurity metals such as Fe and Si after extraction, affecting subsequent processes and increasing production costs. Differences in extractant, feed system, and diluent conditions can also lead to variations in extraction mechanisms and effects, and some rare earth elements (REs) can be co-extracted with aluminum into the organic phase. Adding a certain amount of ammonia can improve the separation of aluminum and rare earth elements in a chlorination system with 25% (v / v) naphthenic acid, with almost complete removal of aluminum, but rare earth losses also exceed 15%. When the aluminum content in the feed is high, a third phase clearly appears between the two phases.

[0004] Ionic liquids (ILs) are molten salts composed of anions and cations, typically with melting points below 100°C, stored at room temperature. When functional groups are added to their anions or cations, they are called functionalized ionic liquids (FILs), which can be used as diluents or extractants for the separation and purification of substances. As diluents, compared to traditional organic diluents such as kerosene, ionic liquids are virtually non-volatile and non-flammable, avoiding solvent loss through evaporation, reducing environmental pollution, and increasing safety. They also improve extraction efficiency and selectivity. Compared to commonly used industrial organic extractants, in addition to the advantages mentioned above, ILs are widely considered a more environmentally friendly and sustainable extractant due to their structural designability and high selectivity. The desired effects and performance can be achieved by modifying and adjusting the structure of the anions and cations. Summary of the Invention

[0005] To improve the above-mentioned technical problems, the present invention provides a functional ionic liquid of Formula I, wherein the cation of the ionic liquid is a hydrophobic imidazolium radical and the anion is a glycine radical with a long carbon chain.

[0006]

[0007] Among them, R1 is selected from C 1-40 alkyl;

[0008] R2 is selected from C 1-40 Alkyl, C 1-40 Alkyl C(=O)C 1-40 Alkylene;

[0009] R3 and R4 may be the same or different, and are independently selected from H or C. 1-40 Alkyl group; and R3 and R4 are not both H.

[0010] According to an embodiment of the present invention, R1 is selected from C. 4-20 Alkyl; for example, C 4-12 Alkyl, C8 alkyl; such as n-butyl.

[0011] According to an embodiment of the present invention, R2 is selected from C. 4-20 Alkyl C(=O)C 1-10 Alkylene; for example, C 4-12 Alkyl C(=O)C 1-8 Alkylene, C 4-8 Alkyl C(=O)C 1-3 Alkylene; such as C(CH3)3C(=O)CH2-.

[0012] According to an embodiment of the present invention, R3 and R4 may be the same or different, and are independently selected from C. 4-20 Alkyl; for example, C 4-20 Alkyl, C 6-12Alkyl, C8 alkyl; such as 2-ethylhexyl.

[0013] According to an embodiment of the present invention, the ionic liquid structure is as shown in Formula II, denoted as [DOC4mim][DEHG], the cation is 1-butyl-3-(3,3-dimethyl-2-oxobutyl)-1H-imidazol-3-onium ion radical, and the anion is bis(2-ethylhexyl)glycine radical;

[0014]

[0015] The present invention also provides a method for preparing the ionic liquid, comprising the following steps: reacting compound I-1 with compound I-2 to obtain the ionic liquid shown in formula I;

[0016]

[0017] Among them, R1, R2, R3, and R4 independently have the definitions described above; X is selected from anions, such as halide anions, such as Cl, Br, or I.

[0018] The present invention also provides the application of the ionic liquid as an extractant.

[0019] The present invention also provides the application of the ionic liquid in the removal of impurities from rare earth ores, such as for the removal of aluminum from rare earth ores.

[0020] The present invention also provides a method for removing impurities from rare earth ores, comprising contacting the ionic liquid with a rare earth ore leachate.

[0021] According to an embodiment of the present invention, a salting-out agent, such as Na2SO4, may also be added to the method;

[0022] According to an embodiment of the present invention, the pH of the rare earth ore leaching solution in the method is preferably 3-4;

[0023] According to an embodiment of the present invention, the concentration of the ionic liquid in the organic phase in the method is 30 mmol / L to 45 mmol / L, for example 35 mmol / L to 43 mmol / L, preferably 40 to 42.5 mmol / L.

[0024] According to an embodiment of the present invention, the method further includes a back-extraction step, preferably using NaOH solution for back-extraction or first using HCl solution for back-extraction and then using NaOH solution for regeneration.

[0025] Beneficial effects

[0026] This invention provides a functional ionic liquid, whose cation is a hydrophobic imidazolium radical and whose anion is a glycine radical with a long carbon chain. This ionic liquid, as an extractant, has a high loading capacity, effectively improving the removal rate of elements such as aluminum from rare earth ores, reducing the loss rate of rare earth elements, and exhibiting good recyclability and separation coefficient. Attached Figure Description

[0027] Figure 1 Infrared spectrum of DOC4mimCl.

[0028] Figure 2 Infrared spectrum of DEHG.

[0029] Figure 3 Infrared spectrum of [DOC4mim][DEHG].

[0030] Figure 4 [DOC4mim][DEHG] Load capacity curve for Al.

[0031] Figure 5 The effect of [DOC4mim][DEHG] concentration on extraction results.

[0032] Figure 6 Recycling of [DOC4mim][DEHG].

[0033] Figure 7 A comparison of the stratification phenomenon of [DOC4mim][DEHG] with that of saponified naphthenic acids and a comparison of the extraction rates of various elements.

[0034] Figure 8 Comparison of the extraction rates of RE and Al by [DOC4mim][DEHG] and saponified naphthenic acids.

[0035] Terminology Definitions and Explanations

[0036] Unless otherwise stated, the definitions of groups and terms recorded in this application specification and claims, including definitions as examples, exemplary definitions, preferred definitions, definitions recorded in tables, and definitions of specific compounds in the examples, can be arbitrarily combined and combined with each other. Such combinations and combinations of group definitions and compound structures should be understood as being within the scope of this application specification and / or claims.

[0037] Unless otherwise stated, the numerical ranges described in this specification and claims are equivalent to describing at least each specific integer value therein. For example, the numerical range "1-40" is equivalent to describing each integer value in the numerical range "1-10", namely 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and each integer value in the numerical range "11-40", namely 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40. Furthermore, when certain numerical ranges are defined as "numbers", it should be understood that they describe the two endpoints of the range, each integer within the range, and each decimal within the range. For example, "numbers from 0 to 10" should be understood as not only recording each integer of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10, but also recording at least the sum of each of these integers with 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9 respectively.

[0038] Term "C" 1-40 "Alkyl" should be understood as referring to a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 40 carbon atoms. For example, "C 4-20 "Alkyl" refers to straight-chain and branched alkyl groups having 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms. 4-12 "Alkyl" refers to straight-chain and branched alkyl groups having 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms, such as butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, 2-ethylhexyl, 2-ethylheptyl, 2-ethyloctyl, 2-ethylnonyl, 2-ethyldecyl, etc., or their isomers. "C" 1-6 "Alkyl" refers to straight-chain and branched alkyl groups having 1, 2, 3, 4, 5, or 6 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, or 1,2-dimethylbutyl, or their isomers. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0040] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0041] Example 1

[0042] 1. Preparation of the cationic moiety

[0043] 100 mmol of N-butylimidazole and 120 mmol of 1-chloropinazone were dissolved in 120 mL of ethanol and heated to 70 °C under microwave conditions of 500 W for 2 h. The ethanol was evaporated under vacuum, and the mixture was washed with petroleum ether to give 25.7 g of 1-butyl-3-(3,3-dimethyl-2-oxobutyl)-imidazolium-3-chloride (DOC4mimCl), with a yield of 99%.

[0044] Characterization results:

[0045] 1 H NMR (500MHz, DMSO, ppm): δ7.87(t,J=1.8Hz,1H),7.72(t,J=1.8Hz,1H),5.71(s,2H),4.26(t,J=7 .1Hz,2H),1.78(dq,J=9.2,7.2Hz,2H),1.26(h,J=7.4Hz,2H),1.20(s,9H),0.91(t,J=7.4Hz,3H).

[0046] IR (cm) -1 ):1720(C=O),1564,1169(imidazolium ring stretching vibration).

[0047] 2. Preparation of the anionic moiety

[0048] 100 mmol of bromoacetic acid was dissolved in 60 mL of ethanol solution, and 200 mmol of potassium hydroxide solid was added. Then, an ethanol solution containing 50 mmol of di(2-ethylhexyl)amine was added dropwise to the flask while stirring, and the reaction was carried out at 70 °C for 12 hours. After the reaction was complete, the solvent was evaporated under vacuum and dissolved in chloroform. The solution was washed several times with distilled water, and the organic phase was dried over anhydrous sodium sulfate. The chloroform was then evaporated under vacuum to give a pale yellow liquid: bis(2-ethylhexyl)glycine (DEHG), in 84% yield.

[0049] Characterization results:

[0050] 1 H NMR (500MHz, DMSO, ppm): δ3.66(d,J=68.8Hz,1H),2.57(d,J=6.5Hz,1H),2.39(dd ,J=7.0,2.3Hz,1H),1.50(q,J=6.1Hz,1H),1.40–1.19(m,8H),0.90–0.79(m,6H).

[0051] IR (cm) -1 ):1755(C=O).

[0052] 3. Preparation of ionic liquids

[0053] 50 mmol of DEHG was weighed and dissolved in 60 ml of ethanol containing 55 mmol of sodium hydroxide. The mixture was heated to 50 °C, and then 50 ml of ethanol containing 50 mmol of DOC4mimCl was added dropwise to the flask, and the reaction was continued for 6 h. After the solvent was evaporated, 100 ml of dichloromethane was added to dissolve the product, resulting in the precipitation of a large amount of inorganic salt. The product was washed with deionized water, and finally, after evaporation, a dark red liquid was obtained. The product was 1-butyl-3-(3,3-dimethyl-2-oxobutyl)-imidazolium-3-bis(2-ethylhexyl)glycine onium salt, abbreviated as [DOC4mim][DEHG], with a yield of 68%. Its density and viscosity were measured to be 0.884 g / ml and 37.5 mPa / s, respectively.

[0054] Characterization results:

[0055] 1 H NMR (500MHz, DMSO, ppm): δ9.31(d,J=20.9Hz,1H),7.82(t,J=1.7Hz,1H),7.64(d,J=2.0Hz,1H),5.66–5.61(m,2H),4.24(t,J=7.1Hz,2H),3.95(t,J=7. 1Hz,2H),2.94(d,J=12.5Hz,2H),2.38(dd,J=8.9,6.0Hz,4H),1.84–1.74(m ,2H),1.67(tt,J=7.4,6.6Hz,2H),1.37–1.14(m,25H),0.96–0.76(m,15H).

[0056] IR (cm) -1 ):1722(C=O),1569,1173(imidazolium ring stretching vibration).

[0057] Example 2

[0058] Extraction method using the ionic liquid [DOC4mim][DEHG] prepared in Example 1 as the extractant:

[0059] Kerosene was used as the diluent for all extraction and back-extraction experiments. The extractant diluted with the diluent served as the organic phase, with the organic phase to water ratio always at 1. The mixtures were brought into contact at room temperature (25°C) and shaken for 30 min to reach equilibrium. The organic phase contained 10% by volume isooctyl alcohol as a phase modifier. After extraction, the mixture was centrifuged at 3000 rpm for 2 min for rapid phase separation. The elemental composition of the aqueous phase was determined by ICP-OES, while the elemental composition of the organic phase was calculated using mass conservation. Extraction efficiency (E), back-extraction efficiency (S), partition ratio (D), and separation coefficient (β) were calculated using the following equations:

[0060]

[0061]

[0062]

[0063]

[0064] Where M f and M r M represents the metal concentration in the feed solution and the raffinate, respectively. s D1 and D2 represent the concentration of the metal in the aqueous phase when the stripping stage reaches equilibrium. D1 and D2 are the distribution ratios of the two components during a single extraction process.

[0065] Test Example 1

[0066] 1. Load test of aluminum

[0067] The loading of the extractant is obtained by contacting the organic phase with multiple equal volumes of fresh feed solution for extraction, such as... Figure 4 As shown, the extraction efficiency approaches zero after five repeated extractions, indicating that Al in the aqueous phase... 3+ The concentration remained almost constant, indicating that the solvent loading was essentially saturated. Each extraction of Al into the organic phase... 3+ The cumulative calculation yielded a saturated loading of 425.4 mg / L for 0.5 mol / L [DOC4mim][DEHG]. (Extractant concentration = 0.5 mol / L, [Al...) 3+ ]=0.01mol / L, pH=3.0, Na2SO4=0mol / L)

[0068] 2. Extraction Study of Magnesium Sulfate Leachate from Ion-Adsorption Rare Earth Minerals

[0069] In this invention, magnesium sulfate, an ion-adsorption type rare earth ore sourced from Dingnan, Jiangxi Province, China, was selected for leaching. The content of various metals in the leachate was measured using ICP-OES (Table 1), and the pH value of the leachate was found to be 4.0. In this invention, the performance of the extractant under different conditions was investigated using metal ions with relatively high content (>2.0 mg / L).

[0070] Table 1. Metal element content in magnesium sulfate leaching solution of ion-adsorption type rare earth ore (pH=4.0)

[0071]

[0072]

[0073] 2.1 Effect of Salting-out Agent

[0074] The effect of Na₂SO₄ concentration (0–0.5 mol / L) on aluminum removal and rare earth loss reduction of [DOC₄mim][DEHG] from the leachate was investigated by varying the amount of Na₂SO₄ added to the feed solution. With increasing Na₂SO₄ concentration, the extraction rates of both aluminum and rare earth decreased to varying degrees. When the concentration was 0.5 mol / L, compared to a Na₂SO₄ concentration of 0, the aluminum extraction rate decreased by 3%, while the rare earth extraction rate decreased by 4.8 percentage points, with an average loss rate of only 2.8%. At this concentration, the separation coefficient reached a maximum of 555, the aluminum removal rate was 94.1%, and the rare earth recovery rate was 97.2%. (Extractant concentration = 0.04 mol / L, aqueous phase is the leachate in Table 1)

[0075] 2.2 Effect of initial pH in aqueous phase

[0076] In this invention, H₂SO₄ solution was used to adjust the pH of the aqueous phase to investigate the effect of acidity on extraction. The pH range was (1-4). Extraction essentially did not occur when the acidity was high (pH = 1-2.5). The extraction efficiency increased rapidly in the pH range of 3-4, at which point a significant separation of aluminum and rare earth elements was observed. (Extractant concentration = 0.04 mol / L, aqueous phase is the leachate in Table 1)

[0077] 2.3 Effect of [DOC4mim][DEHG] concentration

[0078] The effect of extractant dosage is directly reflected in the extraction and separation effects. Changing the concentration of [DOC4mim][DEHG] within the range of 30 mmol / L to 45 mmol / L, for example... Figure 5As shown, more Al is transferred to the organic phase with increasing concentration. However, the extractant becomes excessive after 40 mmol / L, leading to greater rare earth losses. The optimal concentration range should be between 40 and 42.5 mmol / L, within which aluminum impurities are removed while the loss of rare earths is not excessive. (Extractant concentration = 30 mmol / L to 45 mmol, aqueous phase is the leachate in Table 1)

[0079] 2.4 Back-extraction and recycling

[0080] This invention uses a dilute sodium hydroxide solution for back-extraction and recycling experiments. After the extraction stage, a suitable concentration of NaOH aqueous solution is added to disrupt the extractant. The generated Al(OH)3 colloid is eluted into the water, thereby achieving complete back-extraction of the loaded aluminum into the aqueous phase. Subsequently, the extractant anions and cations recombine to achieve regeneration. The performance of the second extraction after back-extraction with 0.1 mol / L HCl solution followed by regeneration with 0.07 mol / L NaOH solution was compared with that after direct back-extraction and regeneration with 0.07 mol / L NaOH solution. Both methods achieve near-complete back-extraction and exhibit similar performance. Figure 6 As shown, the separation effect remained stable after 5 cycles, indicating that [DOC4mim][DEHG] has excellent recyclability. (Extractant concentration = 0.04 mol / L, aqueous phase is the leachate in Table 1)

[0081] Table 2 Comparison of different back-extraction-circulation methods

[0082]

[0083] 2.5 Comparison with saponified naphthenic acid

[0084] This invention uses saponified naphthenic acids (S-NA) for comparison in the same system (kerosene-isooctyl alcohol). For example... Figure 7 In the process, observation of the two-phase interface revealed that the interface phenomenon of [DOC4mim][DEHG] was significantly better, with no third phase generated in the middle. For example... Figure 8 As shown, in terms of impurity removal efficiency, the aluminum removal rate reached over 95%, while calcium and magnesium were not extracted. However, S-NA had an average rare earth loss rate of 19.3% and a separation coefficient of 244; [DOC4mim][DEHG] had an average rare earth loss rate of 3.9%, with 96.1% of the rare earth recovered, and a separation coefficient of 599. This indicates that [DOC4mim][DEHG] has a higher rare earth recovery rate than S-NA, even with almost complete aluminum removal. (Extractant concentration = 0.04 mol / L, aqueous phase is the leachate in Table 1, naphthenic acid saponification degree is 50%).

[0085] The embodiments of the technical solution of the present invention have been described above by way of example. It should be understood that the protection scope of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the protection scope of the claims of this application.

Claims

1. A functional ionic liquid represented by Formula I: in, R1 is selected from C 4-8 alkyl; R2 is C(CH3)3C(=O)CH2-; R3 and R4 are both 2-ethylhexyl.

2. The ionic liquid according to claim 1, characterized in that, R1 is n-butyl.

3. The ionic liquid according to claim 1, characterized in that, The structure of the ionic liquid is shown in Formula II and is denoted as [DOC4mim][DEHG]; 4. A method for preparing the ionic liquid according to any one of claims 1-3, comprising the following steps: reacting compound I-1 with compound I-2 to obtain the ionic liquid represented by formula I; in, R1, R2, R3, and R4 each have the definition as described in any one of claims 1-3; X is selected from halide anions.

5. The preparation method according to claim 4, characterized in that, The halogen is selected from Cl, Br or I.

6. The use of the ionic liquid according to any one of claims 1-3 as an extractant.

7. The application of the ionic liquid according to any one of claims 1-3 in the removal of impurities from rare earth ores.

8. The application of the ionic liquid according to any one of claims 1-3 in the removal of aluminum from rare earth ores.

9. A method for removing impurities from rare earth ores, comprising contacting the ionic liquid according to any one of claims 1-3 with a rare earth ore leachate; And / or, a salting-out agent is also added to the method; And / or, the pH of the rare earth ore leaching solution in the method is 3-4; And / or, in the method, the concentration of the ionic liquid in the organic phase is 30 mmol / L to 45 mmol / L; And / or, the method further includes a back-extraction step: back-extraction using NaOH solution or first back-extraction using HCl solution followed by regeneration using NaOH solution.

10. The method according to claim 9, characterized in that, The salting-out agent is Na2SO4; And / or, in the method, the concentration of the ionic liquid in the organic phase is 35 mmol / L to 43 mmol / L.

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