A method for removing metal ion impurities from acetate ionic liquids

Abstract

This invention belongs to the field of ionic liquid purification technology and provides a method for removing metal ion impurities from acetate ionic liquids. The method comprises: mixing an acetate ionic liquid containing metal ion impurities with a protic solvent to obtain an ionic liquid solution; passing the ionic liquid solution through an ion exchange column for metal ion adsorption and collecting the effluent; subjecting the effluent to vacuum distillation; regenerating and recycling the used ion exchange column; and filling the ion exchange column with a chelating ion exchange resin. The removal method of this invention is mild, simple to operate, and can reduce the total metal ion impurity content in the purified acetate ionic liquid to below 100 ppm. The chelating ion exchange resin used can specifically coordinate with the complexed metal ions in the acetate ionic liquid, thereby adsorbing and removing the metal ions.

Description

Technical Field

[0001] This invention relates to the field of ionic liquid purification technology, and in particular to a method for removing metal ion impurities from acetate ionic liquids. Background Technology

[0002] Cellulose, chitosan, keratin, lignin, and other biomacromolecules possess excellent biocompatibility, biodegradability, and renewability, showing broad application prospects in biomedicine, functional materials, and sustainable energy. However, the dense crystalline regions and complex supramolecular networks formed by strong hydrogen bonds between these biomacromolecules make them difficult to dissolve in conventional aqueous and organic solvents, hindering their high-value processing and utilization. In recent years, acetate ionic liquids have emerged as novel solvents, exhibiting superior performance in the dissolution and processing of biomacromolecules. The acetate anion (OAc) in acetate ionic liquids... - Acetate ionic liquids possess strong hydrogen bond accepting capabilities, forming strong interactions with hydrogen bond donors such as hydroxyl and amino groups on biomolecular chains. This effectively disrupts the original hydrogen bond network, reduces crystallinity, and thus achieves efficient dissolution. The dissolution efficiency of acetate ionic liquids for biomolecular chains is highly dependent on the purity of the ionic liquid. Metal ion impurities can coordinate with coordination sites on biomolecular chains (such as hydroxyl oxygen, amino nitrogen, and carbonyl oxygen), hindering chain extension and solubilization, thereby reducing the dissolution rate and solubility. Furthermore, in applications such as homogeneous catalysis, extraction separation, and electrochemical energy storage, metal ion impurities can also cause problems such as decreased catalytic selectivity, abnormal partition coefficients, or narrowed electrochemical windows. Therefore, deep removal of metal ion impurities is crucial to ensuring the reliability of acetate ionic liquids in various applications.

[0003] Metal ion impurities in acetate ionic liquids mainly originate from the synthesis and recycling processes, including trace metal salt residues in potassium acetate / sodium exchangers and precursors such as halogenated alkanes and N-methylimidazoles, alkali metal and alkaline earth metal ions carried by anion exchange byproducts such as potassium / sodium halides, and accumulation from equipment corrosion or pretreatment steps. These metal ion impurities, especially lead (Pb) 2+ ), copper (Cu) 2+ ), iron (Fe) 2+ / Fe 3+ ), calcium (Ca 2+ Divalent and higher-valent metal ions are typical strong Lewis acids. They can coordinate with Lewis basic sites (such as hydroxyl oxygen, amino nitrogen, and carbonyl oxygen) on biomolecular chains to form stable complexes, and also coordinate with acetate anions to form complexes that are difficult to remove using conventional methods. This dual coordination significantly increases the solubility barrier of biomolecular chain segments, leading to decreased solubility. Simultaneously, the complexed metal ions remain in the recycled materials, severely affecting their mechanical properties, biocompatibility, and functionality.

[0004] Existing conventional separation methods are generally ineffective at removing complexed metal ion impurities, primarily because the separation principles of these methods are incompatible with the characteristics of these impurities. For example, vacuum drying separation utilizes differences in volatility but is ineffective against non-volatile metal salts; organic solvent extraction separation relies on the partition coefficient of the solute in the organic phase, while metal complexes have extremely low partition coefficients; recrystallization separation suffers from poor selectivity because metal complexes and the host ionic liquid exhibit similar solubility and crystallization behaviors. These methods are suitable for removing moisture, volatile organic compounds, or some inorganic salts, but their effectiveness in removing complexed metal ion impurities is limited.

[0005] To obtain high-purity ionic liquids, Chinese patent CN110294712A discloses a method for preparing high-purity imidazole acetate ionic liquids, which can increase the purity to over 99%. However, the synthesis route is lengthy and uses special reagents such as perchlorate, increasing the complexity and cost of the process. Chinese patent CN120586653A uses two-stage electrodialysis to separate ionic liquids and metal salts, achieving a purity of over 98% and enabling simultaneous recovery. However, it relies on complex membrane separation equipment, which suffers from problems such as membrane fouling, limited lifespan, and high maintenance costs.

[0006] Therefore, developing a simple, cost-effective, and highly selective method for removing metal ion impurities to effectively remove complexed metal ion impurities from acetate ionic liquids is of great significance for ensuring the performance stability and application reliability of acetate ionic liquids in the dissolution and processing of biomacromolecules. Summary of the Invention

[0007] The purpose of this invention is to provide a method for removing metal ion impurities from acetate ionic liquids, addressing the shortcomings of existing technologies. The aim is to provide a mild and highly selective removal method that reduces the content of metal ion impurities without damaging the structure of the acetate ionic liquid or introducing foreign metal impurities.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for removing metal ion impurities from acetate ionic liquids, comprising the following steps: 1) Mix the acetate ionic liquid containing metal ion impurities with a protic solvent to obtain an ionic liquid solution; 2) Pass the ionic liquid solution through an ion exchange column to adsorb metal ions and collect the effluent; 3) The effluent is subjected to vacuum distillation to obtain purified acetate ionic liquid; the used ion exchange column is regenerated and recycled; The ion exchange column is filled with chelating ion exchange resin.

[0009] Preferably, the protic solvent in step 1) comprises one or more of water, methanol, anhydrous ethanol, propanol, isopropanol, and n-butanol; The volume ratio of the acetate ionic liquid to the protic solvent is 1:1 to 10.

[0010] Preferably, the metal ion impurities include one or more of lead ions, copper ions, zinc ions, iron ions, ferrous ions, and nickel ions.

[0011] Preferably, the pH value of the ionic liquid solution in step 1) is 3 to 6.

[0012] Preferably, the temperature of the ionic liquid solution in step 2) is 30~60℃, and the volume hourly space velocity of the ionic liquid solution passing through the ion exchange column is 0.5~10 BV / h.

[0013] Preferably, the cation in the acetate ionic liquid comprises one or more of 1-alkyl-3-methylimidazolium, 1-alkenyl-3-methylimidazolium, N-alkylpyridinium, and tetraalkylammonium.

[0014] Preferably, the alkyl group has an independent number of carbon atoms ranging from 1 to 8, and the alkenyl group has an independent number of carbon atoms ranging from 1 to 8.

[0015] Preferably, the functional groups of the chelating ion exchange resin are iminodiacetic acid groups, aminomethylphosphonic acid groups, or thiol groups, the resin skeleton of the chelating ion exchange resin is a styrene copolymer or an acrylic copolymer, and the particle size of the chelating ion exchange resin is 0.3~1.2 mm.

[0016] The beneficial effects of this invention are: The method of this invention is carried out under mild conditions, is simple to operate, requires no complex equipment, and can selectively remove metal ion impurities from acetate ionic liquids. The total content of metal ion impurities in the purified acetate ionic liquid can be stably controlled below 100 ppm. The acetate ionic liquid purified by this invention can significantly restore its solubility for biomacromolecules such as cellulose, chitosan, keratin, and lignin, and the solution is homogeneous and stable, facilitating subsequent processing. At the same time, the removal of metal ion impurities also helps improve the performance of acetate ionic liquids in homogeneous catalysis, extraction separation, and electrochemical energy storage applications. In addition, the chelating ion exchange resin used in this invention can be regenerated and recycled, resulting in low operating costs.

[0017] The purification mechanism of this invention is based on the specific coordination between chelating ion exchange resins and metal ion impurities. Acetate ionic liquids containing metal ion impurities are characterized by high ionic strength, low dielectric constant, and high viscosity. In this medium, high-concentration acetate anions form stable complexed anions or neutral complexes with metal ions. The extremely low activity of the metal ions constitutes the main obstacle to chelation coordination. These complexed anions or neutral complexes can stably act in acetate ionic liquids containing different cations such as imidazolium, pyridinium, and quaternary ammonium salts, with minimal influence from the structure of the organic cations in the ionic liquid. This invention, by selecting resins with specific chelating functional groups and combining them with synergistic methods such as protonated solvent dilution, pH control, and fixed-bed dynamic operation, can break the metal-acetate complexation equilibrium, achieving selective migration of metal ions from the bulk phase of the ionic liquid to the resin solid phase. Detailed Implementation

[0018] This invention provides a method for removing metal ion impurities from acetate ionic liquids, comprising the following steps: 1) Mix the acetate ionic liquid containing metal ion impurities with a protic solvent to obtain an ionic liquid solution; 2) Pass the ionic liquid solution through an ion exchange column to adsorb metal ions and collect the effluent; 3) The effluent is subjected to vacuum distillation to obtain purified acetate ionic liquid; the used ion exchange column is regenerated and recycled; The ion exchange column is filled with chelating ion exchange resin.

[0019] In this invention, the protic solvent in step 1) preferably includes one or more of water, methanol, anhydrous ethanol, propanol, isopropanol and n-butanol; The volume ratio of the acetate ionic liquid to the protic solvent is preferably 1:1 to 10, specifically 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0020] In this invention, the metal ion impurities preferably include one or more of lead ions, copper ions, zinc ions, iron ions, ferrous ions, and nickel ions.

[0021] In this invention, the pH value of the ionic liquid solution in step 1) is preferably 3 to 6, specifically 3, 3.5, 4, 4.5, 5, 5.5, or 6.

[0022] In this invention, the pH value of the ionic liquid solution in step 1) is preferably adjusted by acetic acid, and the concentration of the acetic acid is preferably 0.5~1.5 mol / L, more preferably 1 mol / L.

[0023] In this invention, the temperature of the ionic liquid solution in step 2) is preferably 30~60℃, specifically 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, or 60℃; the volume hourly space velocity (VHSV) of the ionic liquid solution passing through the ion exchange column is preferably 0.5~10 BV / h, specifically 0.5 BV / h, 1 BV / h, 2 BV / h, 3 BV / h, 4 BV / h, 5 BV / h, 6 BV / h, 7 BV / h, 8 BV / h, 9 BV / h, or 10 BV / h.

[0024] In this invention, the chelating ion exchange resin is preferably pretreated before being packed into the ion exchange column; The pretreatment preferably includes first rinsing with water, then transformation and activation with inorganic acid, and finally washing with water.

[0025] In this invention, the cation in the acetate ionic liquid preferably comprises one or more of 1-alkyl-3-methylimidazolium, 1-alkenyl-3-methylimidazolium, N-alkylpyridinium, and tetraalkylammonium.

[0026] In this invention, the number of carbon atoms in the alkyl group is preferably any integer from 1 to 8, specifically 1, 2, 3, 4, 5, 6, 7, 8; the number of carbon atoms in the alkenyl group is preferably any integer from 1 to 8, specifically 1, 2, 3, 4, 5, 6, 7, 8.

[0027] In this invention, the functional groups of the chelating ion exchange resin are preferably iminodiacetic acid groups, aminomethylphosphonic acid groups, or thiol groups, the resin skeleton of the chelating ion exchange resin is preferably a styrene copolymer or an acrylic copolymer, and the particle size of the chelating ion exchange resin is preferably 0.3~1.2 mm, more preferably 0.5~1 mm, and even more preferably 0.6~0.8 mm.

[0028] In this invention, after the vacuum distillation in step 3), vacuum drying is preferably performed to obtain the purified acetate ionic liquid. Vacuum distillation removes the protic solvent, and vacuum drying removes residual moisture.

[0029] In this invention, the temperature of the vacuum distillation in step 3) is preferably 50~80℃, specifically 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, or 80℃; the pressure of the vacuum distillation is preferably -0.1~-0.095MPa, more preferably -0.099~-0.096MPa, and even more preferably -0.098~-0.097MPa; the time of the vacuum distillation is preferably 1~4h, more preferably 2~3h, and even more preferably 2.5h. The vacuum drying temperature is preferably 60~80℃, more preferably 65~75℃, and even more preferably 70℃; the vacuum drying time is preferably 12~36h, more preferably 18~30h, and even more preferably 24h.

[0030] In this invention, the regeneration in step 3) is preferably carried out using an acid solution.

[0031] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] The functional group of the chelating ion exchange resin is iminodiacetic acid, and the resin backbone is a macroporous styrene copolymer backbone with a particle size of 0.6 mm. It was purchased from Lanxess (Lewatit® MonoPlus TP 208). The pretreatment process of the chelating ion exchange resin is as follows: the chelating ion exchange resin is washed with deionized water until the effluent is clear, then it is activated with 2% hydrochloric acid, and then washed with deionized water again. 500 mL of the pretreated chelating ion exchange resin is wet-packed into an ion exchange column to form a uniform fixed bed adsorption layer.

[0034] The acetate ionic liquid containing metal ion impurities was 1-butyl-3-methylimidazolium acetate ([Bmim]OAc). Inductively coupled plasma mass spectrometry (ICP-MS) determined the total metal ion impurity content to be 10250 ppm, with the metal ion impurity being Cu²⁺. + Pb² + Fe² + / Fe³ + Ni² + and Zn² + .

[0035] An acetate ionic liquid containing metal ion impurities was mixed with anhydrous ethanol at a volume ratio of 1:5, and the pH was adjusted to 4.5 with 1 mol / L acetic acid to obtain an ionic liquid solution. The ionic liquid solution was heated to 40°C and then passed through an ion exchange column packed with chelating ion exchange resin at a volume hourly space velocity (VHSV) of 10 BV / h to adsorb metal ions, and the eluent was collected. The eluent was filtered, and the filtrate was distilled under reduced pressure at 60°C and -0.098 MPa for 1 h, and then dried in a vacuum drying oven at 70°C for 24 h to obtain the purified acetate ionic liquid.

[0036] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 25 ppm.

[0037] Example 2

[0038] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities is 1-ethyl-3-methylimidazolium acetate ([Emim]OAc). Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the total content of metal ion impurities, which was 10540 ppm. The metal ion impurities were Cu²⁺. + Pb² + Fe² + / Fe³ + Ni² + and Zn² + .

[0039] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 12 ppm.

[0040] Example 3

[0041] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities is N-butylpyridine acetate, and the total content of metal ion impurities in it, as detected by inductively coupled plasma mass spectrometry (ICP-MS), is 10650 ppm, with the metal ion impurity being Cu²⁺. + Pb² + Fe² + / Fe³ + Ni² + and Zn² + .

[0042] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 100 ppm.

[0043] Example 4

[0044] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities and anhydrous ethanol were mixed at a volume ratio of 1:5, and then the pH was adjusted to 6.0 with 1 mol / L acetic acid to obtain the ionic liquid solution.

[0045] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 15 ppm.

[0046] Example 5

[0047] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities and anhydrous ethanol were mixed at a volume ratio of 1:5, and then the pH was adjusted to 3.0 with 1 mol / L acetic acid to obtain the ionic liquid solution.

[0048] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 50 ppm.

[0049] Example 6

[0050] The difference from Example 1 is that the ionic liquid solution is heated to 60°C and then passed through an ion exchange column packed with chelating ion exchange resin at a volume hourly space velocity of 10 BV / h to adsorb metal ions and collect the effluent.

[0051] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 20 ppm.

[0052] Example 7

[0053] The difference from Example 1 is that the metal ions are adsorbed and the effluent is collected by passing the ion exchange column packed with chelating ion exchange resin at a volume hourly space velocity of 0.5 BV / h.

[0054] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 2 ppm.

[0055] Example 8

[0056] The difference from Example 1 is that the metal ions are adsorbed and the effluent is collected by passing the ion exchange column packed with chelating ion exchange resin at a volume hourly space velocity of 5 BV / h.

[0057] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 5 ppm.

[0058] Example 9

[0059] The difference from Example 1 is that the functional group of the chelating ion exchange resin is aminomethylphosphonic acid, the resin backbone is a macroporous styrene-divinylbenzene copolymer backbone, the particle size is 0.6 mm, and it was purchased from Lanxess (Lewatit® MonoPlus TP 260). The pretreatment process of the chelating ion exchange resin is as follows: the chelating ion exchange resin is washed with deionized water until the effluent is clear, then it is activated with 3% nitric acid, and then washed with deionized water again. 500 mL of the pretreated chelating ion exchange resin is wet-packed into an ion exchange column to form a uniform fixed bed adsorption layer.

[0060] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 70 ppm.

[0061] Example 10

[0062] The difference from Example 1 is that the functional group of the chelating ion exchange resin is a thiol group, the resin backbone is a macroporous styrene-divinylbenzene copolymer backbone with a particle size of 0.6 mm, purchased from DuPont (AmberSep™ GT 74). The pretreatment process of the chelating ion exchange resin is as follows: the chelating ion exchange resin is rinsed with deionized water until the effluent is clear, then it is activated with 2% hydrochloric acid, and then washed with deionized water again. 500 mL of the pretreated chelating ion exchange resin is wet-packed into an ion exchange column to form a uniform fixed bed adsorption layer.

[0063] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 40 ppm.

[0064] Example 11

[0065] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities and deionized water were mixed at a volume ratio of 1:5, and then the pH value was adjusted to 4.5 with 1 mol / L acetic acid to obtain the ionic liquid solution.

[0066] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 5 ppm.

[0067] Example 12

[0068] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities and methanol were mixed at a volume ratio of 1:5, and then the pH was adjusted to 4.5 with 1 mol / L acetic acid to obtain the ionic liquid solution.

[0069] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 8 ppm.

[0070] Example 13

[0071] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities and isopropanol were mixed at a volume ratio of 1:5, and then the pH was adjusted to 4.5 with 1 mol / L acetic acid to obtain the ionic liquid solution.

[0072] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 35 ppm.

[0073] Example 14

[0074] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities is 1-allyl-3-methylimidazolium acetate ([Amim]OAc), and the total content of metal ion impurities in it, as determined by ICP-MS, is 10600 ppm, with the metal ion impurity being Cu²⁺. + Pb² + Fe² + / Fe³ + Ni² + and Zn² + .

[0075] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 28 ppm.

[0076] Example 15

[0077] The difference from Example 1 is that the acetate ionic liquid containing metal ion impurities is tetraethylammonium acetate, and the total content of metal ion impurities in it, as determined by inductively coupled plasma mass spectrometry (ICP-MS), is 10100 ppm, with the metal ion impurity being Cu²⁺. + Pb² + Fe² + / Fe³ + Ni² + and Zn² + .

[0078] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 90 ppm.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that the chelating ion exchange resin is replaced with a strong acid cation exchange resin (functional group is sulfonic acid group, resin skeleton is styrene copolymer, purchased from DuPont AmberLite™ IRC120), and the pretreatment and filling of the strong acid cation exchange resin are the same as in Example 1.

[0081] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 1020 ppm.

[0082] Comparative Example 2

[0083] The difference from Example 1 is that the chelating ion exchange resin is replaced with a weakly acidic carboxylic acid cation exchange resin (functional group is carboxyl, resin backbone is acrylic copolymer, particle size is 0.6 mm, purchased from Lanxess Lewatit® CNP 80), and the pretreatment and filling of the weakly acidic carboxylic acid cation exchange resin are the same as in Example 1.

[0084] The content of metal ion impurities in the purified acetate ionic liquid was detected by ICP-MS, and the results showed that the total content of metal ion impurities was 1560 ppm.

[0085] Verification of regeneration and recycling of used ion exchange columns.

[0086] Experiment 1

[0087] The ion exchange column used in Example 1 was regenerated by passing hydrochloric acid with a mass concentration of 4% through the ion exchange column at a volume hourly space velocity of 2 BV / h. The total amount of hydrochloric acid used was 5 times that of the chelating ion exchange resin.

[0088] The regenerated ion exchange column was regenerated four times, and the content of metal ion impurities in the purified acetate ion liquid was detected by ICP-MS to calculate the removal rate. The results showed that the removal rate of metal ion impurities remained above 92.5%.

[0089] Experiment 2

[0090] The ion exchange column used in Example 9 was regenerated, and the specific operation was the same as in Experiment 1.

[0091] The regenerated ion exchange column was regenerated four times, and the content of metal ion impurities in the purified acetate ion liquid was detected by ICP-MS to calculate the removal rate. The results showed that the removal rate of metal ion impurities exceeded 90%.

[0092] Experiment 3

[0093] The ion exchange column used in Example 10 was regenerated, and the specific operation was the same as in Experiment 1.

[0094] The regenerated ion exchange column was regenerated four times, and the content of metal ion impurities in the purified acetate ion liquid was detected by ICP-MS to calculate the removal rate. The results showed that the removal rate of metal ion impurities remained above 88.5%.

[0095] As can be seen from the above embodiments, the present invention provides a method for removing metal ion impurities from acetate ionic liquids. After the acetate ionic liquid is mixed with a protic solvent, it is passed through an ion exchange column packed with chelating ion exchange resin for metal ion adsorption. The conditions are mild and the operation is simple. The total metal ion impurity content in the purified acetate ionic liquid can be reduced to below 100 ppm. The chelating ion exchange resin used can specifically coordinate with the complexed metal ions in the acetate ionic liquid, thereby adsorbing and removing the metal ions.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for removing metal ion impurities from acetate ionic liquids, characterized in that, It includes the following steps: 1) Mix the acetate ionic liquid containing metal ion impurities with a protic solvent to obtain an ionic liquid solution; 2) Pass the ionic liquid solution through an ion exchange column to adsorb metal ions and collect the effluent; 3) The effluent is subjected to vacuum distillation to obtain purified acetate ionic liquid; the used ion exchange column is regenerated and recycled; The ion exchange column is filled with chelating ion exchange resin.

2. The removal method according to claim 1, characterized in that, Step 1) The protic solvent includes one or more of water, methanol, anhydrous ethanol, propanol, isopropanol and n-butanol; The volume ratio of the acetate ionic liquid to the protic solvent is 1:1 to 10.

3. The removal method according to claim 1 or 2, characterized in that, The metal ion impurities include one or more of lead ions, copper ions, zinc ions, iron ions, ferrous ions, and nickel ions.

4. The removal method according to claim 3, characterized in that, Step 1) The pH value of the ionic liquid solution is 3~6.

5. The removal method according to claim 4, characterized in that, Step 2) The temperature of the ionic liquid solution is 30~60℃, and the volume hourly space velocity of the ionic liquid solution passing through the ion exchange column is 0.5~10 BV / h.

6. The removal method according to claim 4 or 5, characterized in that, The cation in the acetate ionic liquid comprises one or more of 1-alkyl-3-methylimidazolium, 1-alkenyl-3-methylimidazolium, N-alkylpyridinium, and tetraalkylammonium.

7. The removal method according to claim 6, characterized in that, The alkyl group has an independent number of carbon atoms ranging from 1 to 8, and the alkenyl group has an independent number of carbon atoms ranging from 1 to 8.

8. The removal method according to claim 7, characterized in that, The functional groups of the chelating ion exchange resin are iminodiacetic acid, aminomethylphosphonic acid, or thiol groups. The resin skeleton of the chelating ion exchange resin is a styrene copolymer or an acrylic copolymer. The particle size of the chelating ion exchange resin is 0.3~1.2 mm.