A new ionic liquid extractant, its preparation method and impurity removal application

Abstract

The application provides an ionic liquid shown in formula (I) and a method for separating impurity aluminum ions from a transition metal solution by using the ionic liquid as an extractant. The ionic liquid extractant used in the application has good selectivity for impurity aluminum ions in a transition metal solution, and can better realize the separation of aluminum ions and transition metal ions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of separation and extraction technology, and particularly relates to an ionic liquid extractant, a preparation method thereof and a method for removing impurities. BACKGROUND

[0002] Lithium ion batteries (LIBs) have been widely used in portable electronic devices, such as mobile phones, digital cameras, notebook computers and notebook computers, due to their high energy density, good cycle life, low memory effect, low self-discharge rate and other advantages. Due to these advantages, the potential applications of LIBs have been extended to electric vehicles (EVs) and hybrid electric vehicles (HEVs). It is predicted that the consumption of LIBs will further increase in the future. Since the average service life of LIBs is 1-3 years, this growing consumption has generated a large amount of waste LIBs, which contain many toxic substances, including heavy metals such as copper, cobalt and nickel, and organic chemicals such as electrolytes and separators. Disposing of used LIBs in landfills can allow heavy metals to seep into groundwater, causing long-term environmental impact. If LIBs are burned together with general solid waste, a large amount of toxic gases, such as HF, will be generated, which will pollute the atmosphere. Some researchers have reported the potential impact of LIBs on the environment and human health. However, if the large amount of metal substances contained in waste LIBs are recycled, they can become an important secondary resource and help to solve the shortage of natural resources. Therefore, recycling of waste LIBs and electrode waste in an environmentally friendly manner has attracted widespread attention.

[0003] Although the recovery of Li is very important, according to research statistics, only about less than 1% of lithium will be recycled. To achieve the recovery of Li, wet metallurgy, pyrometallurgy, bio-metallurgy and other technologies can be used to treat waste LIBs, and these research methods have been reported in previous studies. Compared with other technologies, wet metallurgy technology provides a new way for the recovery of waste LIBs, which can not only be used to separate REEs, but also is feasible for the recovery of lithium. After leaching with acid, wet metallurgy technology can be used for separation and recovery of waste LIBs, such as common chemical precipitation method, solvent extraction method and adsorption method.

[0004] The above LIB recovery is only based on ideal conditions, that is, the feed solution they used actually contains only LIB active material, that is, only Li, Ni, Co, Mn. But the real industrial battery active material part of waste, not only contains active material (Li, Ni, Co, Mn), but also contains impurities from the current collector material and the battery shell, such as the main impurity Al(III) and the like. In each step of the battery waste recycling value chain (pretreatment, hydrometallurgical treatment, recovery, calcination and recycling process), the interaction of impurities with active battery metals will have metallurgical and electrochemical effects on the recovered battery materials. Therefore, it is necessary to study the effect of the presence of Al(III) on the recovery of various ions in LIB. SUMMARY

[0005] To improve the above technical problems, the present application provides an ionic liquid represented by formula (I):

[0006]

[0007] wherein R1, R2, R3, R4, R5 are the same or different, and are independently selected from C 1-20 alkyl.

[0008] According to an embodiment of the present application, R1 is selected from C 1-6 alkyl; such as methyl.

[0009] According to an embodiment of the present application, R2, R3, R4 are the same or different, and are independently C 6-20 alkyl; such as C 8-12 alkyl; such as n-octyl.

[0010] According to an embodiment of the present application, R5 is selected from C 6-20 alkyl; such as C 8-12 alkyl; such as n-hexyl.

[0011] According to an embodiment of the present application, the ionic liquid structure is represented by formula (II), denoted as [N 1888 ][PHOA],

[0012]

[0013] The present application also provides a preparation method of the ionic liquid, comprising the following steps: mixing compound I-1 with compound I-2 to obtain the ionic liquid represented by formula (I) after reaction;

[0014]

[0015] wherein R1, R2, R3, R4, R5 are independently defined as described above, and X is selected from halogen, such as Cl, Br or I.

[0016] According to the embodiments of the present application, the reaction can be carried out under the action of a base, such as lithium hydroxide, sodium hydroxide, potassium hydroxide.

[0017] According to the embodiments of the present application, the reaction can be carried out under the action of a solvent, which can be an alcohol solvent, such as methanol, ethanol, isopropanol.

[0018] According to the embodiments of the present application, the preparation method can be mixing compound I-2 with the base in a solvent to obtain saponified compound I-2, and then adding a solution of compound I-1 to obtain the ionic liquid shown in formula (I).

[0019] The present application also provides the use of the ionic liquid as an extractant.

[0020] The present application also provides an ionic liquid extractant, comprising the ionic liquid shown in formula (I) and a diluent.

[0021] According to the embodiments of the present application, the diluent is selected from at least one of kerosene, toluene, hexane, and n-heptane.

[0022] According to the embodiments of the present application, the ionic liquid extractant has a pKa value of 3-10, such as 2, 2.5, 3, 4, 4.2, 4.4, 4.42, 4.44, 4.46, 4.48, 4.5, 4.6, 4.8, 5, 6, 7, 8, 9, or 10.

[0023] According to the embodiments of the present application, in the ionic liquid extractant, the concentration of the ionic liquid shown in formula (I) is 0.01-0.07 mol / L.

[0024] The present application also provides the use of the ionic liquid for removing aluminum from a transition metal feed solution, such as for removing aluminum from a leaching solution of a waste battery, such as a waste lithium battery.

[0025] According to the embodiments of the present application, the feed solution comprises at least one of Al 3+ , Li + , Ni 2+ , Co 2+ , and Mn 2+ .

[0026] The present application also provides a method for removing aluminum, comprising contacting the ionic liquid with the transition metal feed solution.

[0027] According to the embodiments of the present application, the contacting is extraction.

[0028] The present invention also provides an extraction method, specifically a method for extracting impurity aluminum ions from a transition metal solution, the extraction method comprising the following steps:

[0029] The transition metal feed solution (aqueous phase) and the ionic liquid extractant (organic phase) are mixed and extracted. The extracted mixed solution is then separated to obtain an organic phase extraction layer loaded with aluminum ions and an aqueous phase extraction layer containing transition metal ions.

[0030] According to an embodiment of the present invention, in the transition metal molten metal, Al 3+ The concentration is less than or equal to 0.04 mol / L, for example, 0.014 mol / L.

[0031] According to an embodiment of the present invention, the pH value of the transition metal solution is 1 to 5, exemplarily 2, 2.5, 3, or 4.

[0032] According to an embodiment of the present invention, the mixed extraction includes: mixing the transition metal feed solution and the ionic liquid extractant, shaking, and then separating the phases by centrifugation. Specifically, the shaking time is 30 min to 60 min, for example, 40 min to 50 min.

[0033] According to an embodiment of the present invention, the volume ratio of the transition metal solution to the ionic liquid extractant is 1:3 to 3:1, for example, 1:3, 1:2, 1:1, 2:1 or 3:1.

[0034] According to an embodiment of the present invention, the temperature of the mixed extraction is 20-60°C, for example 25-50°C, and exemplaryly 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 60°C or 70°C.

[0035] According to an embodiment of the present invention, the concentration ratio of aluminum ions in the organic phase extraction layer and the aqueous phase extraction layer is greater than or equal to 3:1, for example, 3:1 to 5:1, or even 3:1 to 4:1.

[0036] According to an embodiment of the present invention, the extraction method further includes a step of back-extracting the organic phase extraction layer with a back-extraction solution, wherein Al 3+ Removed from the organic phase extraction layer.

[0037] According to an embodiment of the present invention, the back-extraction includes: back-extracting the organic phase extraction layer using a back-extraction solution, optionally, the back-extraction is performed 1 to 2 times.

[0038] According to an embodiment of the present invention, the back-extraction solution is a low-concentration inorganic acid, such as dilute sulfuric acid. Exemplarily, in the back-extraction solution, H... + The concentration is 0.4–0.8 mol / L, for example, 0.6 mol / L.

[0039] According to an embodiment of the present invention, the back-extraction time is 10 min to 60 min, for example, 20 min.

[0040] According to an embodiment of the present invention, after the organic phase extraction layer is back-extracted, a recovered ionic liquid extractant is obtained, which can be recycled and reused.

[0041] Beneficial effects

[0042] This invention provides an ionic liquid of formula (I) as an extractant for extracting aluminum ions (Al) impurities in transition metal solutions. 3+ It has good selectivity and can achieve AI well. 3+ Separation of transition metal ions. The extractant described in this invention has very low water solubility, resulting in minimal loss during extraction; no emulsification occurs during extraction, and the interface between the two phases is clear; the acid concentration used during back-extraction is low, making it environmentally friendly; and the recovered extractant can be recycled and reused. Attached Figure Description

[0043] Figure 1 Fourier transform infrared spectroscopy analysis;

[0044] Figure 2 For extracting Al 3+ The relationship between concentration and distribution ratio;

[0045] Figure 3 This is a graph showing the change in the extraction efficiency (E) of the organic extraction layer with temperature.

[0046] Terminology Definitions and Explanations

[0047] 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.

[0048] 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.

[0049] 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 1-20 "Alkyl" refers to straight-chain and branched alkyl groups having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms. 6-12 "Alkyl" refers to straight-chain and branched alkyl groups having 6, 7, 8, 9, 10, 11, or 12 carbon atoms, such as hexyl (e.g., n-hexyl), heptyl (e.g., n-heptyl), octyl (e.g., n-octyl), nonyl (e.g., n-nonyl), decyl (e.g., n-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

[0050] 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.

[0051] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0052] In this invention, the feed solution is composed of active materials (including Li, Co, Ni, and Mn) and Al. Specifically, [N] was synthesized. 1888 [PHOA] ionic liquids, utilizing liquid-liquid extraction technology, by altering [N] 1888 The concentration of [PHOA], the pH value of the initial solution, the extraction reaction time, the temperature, and the type of diluent were used to systematically study the [N] content. 1888 [PHOA] is effective in removing Al impurities from feed solutions (Li, Co, Ni, Mn). After removing Al impurities, back-extraction is performed using H2SO4, and the regenerated IL can be recycled.

[0053] Extraction rate (E) and extraction partition ratio (D) can intuitively show the extraction capacity of the extractant. D represents the ratio of metal ions in the aqueous phase and the organic phase after extraction, and E is the ratio of metal ion concentrations in the aqueous phase before and after extraction. The separation factor (β) is an important indicator of the separation effect. In this invention, the concentrations of all metal ions were determined by ICP.

[0054] Preparation Example 1 [N] 1888 Preparation of [PHOA]

[0055]

[0056] The ionic liquid of this invention is prepared by a combination of ion exchange and neutralization reactions. A certain amount of 4-hexyloxybenzoic acid (PHOA) is dissolved in methanol with a stir bar. Then, an equal amount of sodium hydroxide is added and dissolved by heating and stirring. After about 20 minutes, a certain amount of trioctylmethylammonium bromide ([N... 1888 Cl, n PHOA :n [N1888]Cl =1:1) dissolved in methanol. [N] was stirred at room temperature to allow [N] to dissolve. 1888Cl solution was gradually added dropwise to a fully saponified 4-hexyloxybenzoic acid solution. The mixture was stirred at 50°C for 6 hours until the reaction was complete. The methanol in the post-reaction solution was completely distilled off, dissolved in petroleum ether, and washed several times with deionized water. After adding anhydrous Na₂SO₄ to the treated organic phase, the petroleum ether was removed by rotary evaporation. The product was then dried in a vacuum drying oven at 70°C for 12 hours to obtain the target ionic liquid [N]. 1888 ][PHOA].

[0057] Example 1

[0058] 1. Preparation of IL extractant: Take 0.025g of [N 1888 [PHOA] (with a pKa value of 4.48) was dissolved in 5 mL of toluene (diluent) to obtain a diluted IL extractant;

[0059] 2. Extraction: The IL extractant described in step 1 and the feed solution (the feed solution is an aqueous solution, pH=5, containing Al) are mixed together. 3+ and transition metal ions M 3+ , using [Al 3+ ] and [M 3+ ] respectively represent Al 3+ The molar concentration of transition metal ions, and the [Al] in the feed solution 3+ ] = 0.387 g / L, [Co 2+ ]=5.088g / L, [Li + ] = 3.071 g / L, [Mn 2+ ] = 5.876 g / L, [Ni 2+ The aqueous phase and organic phase were separated by a volume ratio of 1:1 (13.506 g / L) and placed in a shaking box. The mixture was shaken at 30°C for 40 min. After centrifugation, the mixture was separated into aqueous and organic phases.

[0060] 3. Back-extraction: The organic phase extraction layer from step 2 is back-extracted with 0.60 mol / L H2SO4 for 20 min to obtain an organic phase layer and an aqueous phase layer.

[0061] 4. Use the organic phase from step 3 as an extractant to repeat steps 2-3, and repeat the cycle 5 times.

[0062] After performing ICP testing on the aqueous phase extraction layer from step 2 above, it was found that the transition metal M in the aqueous phase extraction layer... 3+ The extraction rate is less than 4%, while Al 3+ The extraction rate reached 100%.

[0063] In solvent extraction, studying the extraction mechanism helps to gain a more systematic understanding of the extraction process and clarify the main influencing factors and their causes. In particular, for new extractants, it is necessary to explore the role of their functional groups in the extraction process. Although sometimes actual extraction reactions are too complex, there is a lack of conclusive evidence to elucidate the mechanism and structure of the extraction complex. The mechanism of solvent extraction of metal ions can be anion / cation exchange or ion pair formation (also known as ion association), where the target ion and inorganic anion enter the organic phase together, and the extraction complex is a complex ion pair. Solvents using this extraction method typically have a strong hydrophobic structure, which binds to inorganic anions during extraction and dissolves in the organic phase. To elucidate the specific extraction mechanism, we studied the solvent before extraction, the solvent after Al(III) extraction, and the solvent after back-extraction at 4000–800 cm⁻¹. -1 Infrared spectra within the range. After extraction, the material was completely dried by rotary evaporation, and the infrared spectra of IL(b) loaded with Al(III) were measured. Figure 1 As shown, IL ( ) before extraction Figure 1 In the infrared spectrum of (a), the stretching vibration of C=O in the -COO- functional group is 1602 cm⁻¹. -1 After extraction, IL molecules ( Figure 1 (b) The stretching vibration of C=O in (b) starts from 1602 cm. -1 It became 1598cm -1 After back-extraction is completed, IL molecules ( Figure 1 (c) The infrared spectrum shows that the stretching vibration of C=O in the functional group -COO- has recovered to 1602 cm⁻¹. -1 This indicates that the carboxyl functional group on the IL anion participates in the extraction process.

[0064] Examples 2-4

[0065] 1. Preparation of IL extractant: The IL extractants in Examples 2-4 were prepared using the following organic solvents: n-hexane, kerosene and n-heptane, respectively. The pH value of the solution was 1, and the rest was the same as in Example 1.

[0066] 2. The extraction and back-extraction steps are the same as in Example 1.

[0067] When toluene is used as a diluent, Co 2+ Li + Mn 2+ Ni 2+ Al 3+ The extraction rates were 2.79%, 10.97%, 3.99%, 2.61%, and 80.24%, respectively.

[0068] Comparing Examples 1 and 2-4, it can be seen that when toluene is used as the diluent for the IL extractant, its extraction effect is significantly better than that of extractants with hexane, kerosene, and heptane as diluents.

[0069] Example 5

[0070] 1. The IL extractant in Example 5 is the same as that in Example 1.

[0071] 2. During extraction, the extraction temperature is 25℃, and the pH values ​​of the feed solution are adjusted to 1, 2, 3, 4 and 5 respectively.

[0072] 3. The back-extraction steps are the same as in Example 1.

[0073] The experimental results show that as the pH value of the feed solution increases, Al 3+ The extraction rate increased from 80.24% to 100%, with the highest extraction rate at pH 5.

[0074] Example 6

[0075] 1. The IL extractant in Example 6 is the same as that in Example 1.

[0076] 2. During extraction, adjust the extraction temperature to 30℃, 40℃, 50℃, 60℃ and 70℃ respectively.

[0077] 3. The back-extraction steps are the same as in Example 1.

[0078] Figure 3 The graph shows the change in extraction efficiency (E) of the organic extraction layer with extraction temperature. A comparison of the extraction results from Examples 1 and 6 shows that extraction temperature also affects the extraction efficiency. When the extraction temperature is 30°C, Al... 3+ and M 3+ The separation effect is the best.

[0079] 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. An ionic liquid of formula (I): in, R1 is selected from C 1-6 alkyl; R2, R3, and R4 may be the same or different, and C is independent of each other. 6-20 alkyl; R5 is selected from C 6-20 alkyl.

2. The ionic liquid according to claim 1, characterized in that, R1 is a methyl group; And / or, R2, R3, R4 may be the same or different, and C may be independent of each other. 8-12 alkyl; And / or, R5 is selected from C 8-12 alkyl.

3. The ionic liquid according to claim 1, characterized in that, R2, R3, and R4 are octyl groups; And / or, R5 is a hexyl group.

4. The ionic liquid according to claim 1, characterized in that, The structure of the ionic liquid is shown in formula (II).

5. A method for preparing the ionic liquid according to any one of claims 1-4, comprising the following steps: mixing compound I-1 and compound I-2 and reacting them to obtain the ionic liquid shown in formula (I); in, R1, R2, R3, R4, and R5 each have the definition of any one of claims 1-3, and X is selected from halogens; And / or, the reaction is carried out under the action of a base, wherein the base is selected from lithium hydroxide, sodium hydroxide, and potassium hydroxide; And / or, the reaction is carried out in the presence of a solvent selected from alcohol solvents.

6. The preparation method according to claim 5, characterized in that, X is selected from Cl, Br, or I; And / or, the solvent is selected from methanol, ethanol, and isopropanol.

7. The preparation method according to claim 5, characterized in that, The preparation method involves mixing compound I-2 with the alkali in a solvent to obtain saponified compound I-2, and then adding a solution of compound I-1 to obtain the ionic liquid shown in formula (I).

8. The use of the ionic liquid according to any one of claims 1-4 as an extractant.

9. An ionic liquid extractant, comprising the ionic liquid according to any one of claims 1-4 and a diluent; And / or, the diluent is selected from at least one of kerosene, toluene, hexane, and n-heptane; And / or, the pKa value of the ionic liquid extractant is 3 to 10; And / or, in the ionic liquid extractant, the concentration of the ionic liquid is 0.01 to 0.07 mol / L.

10. A method for extracting impurity aluminum ions from a transition metal molten metal, the extraction method comprising the following steps: The transition metal feed solution and the ionic liquid extractant of claim 9 are mixed and extracted. The extracted mixed solution is then subjected to phase separation to obtain an organic phase extraction layer loaded with aluminum ions and an aqueous phase extraction layer containing transition metal ions.

11. The method according to claim 10, characterized in that, In the transition metal molten material, Al 3+ The concentration is less than or equal to 0.04 mol / L; And / or, the pH value of the transition metal solution is 1 to 5.

12. The method according to claim 10, characterized in that, In the transition metal molten material, Al 3+ The concentration was 0.014 mol / L.

13. The method according to claim 10, characterized in that, The volume ratio of the transition metal solution to the ionic liquid extractant is 1:3 to 3:1; And / or, the concentration ratio of aluminum ions in the organic phase extraction layer and the aqueous phase extraction layer is greater than or equal to 3:

1.

14. The method according to claim 13, characterized in that, The concentration ratio of aluminum ions in the organic phase extraction layer and the aqueous phase extraction layer is 3:1 to 5:

1.

15. The method according to claim 10, characterized in that, The method further includes back-extraction, which includes: back-extracting the organic phase extraction layer using a back-extraction solution; And / or, the back-extraction solution is an inorganic acid; in the back-extraction solution, H + The concentration is 0.4–0.8 mol / L.

16. The method according to claim 15, characterized in that, The inorganic acid is dilute sulfuric acid; And / or, in the back-extraction solution, H + The concentration is 0.6 mol / L.

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