Method for extracting metal from transformer oil by ionic liquid and recycling

Abstract

The application provides a method for extracting metal in transformer oil by using ionic liquid and recycling the ionic liquid. Some functional groups in the ionic liquid, including halogen, hydroxyl, sulfide, urea and thiourea, can form complexes with metal ions in the transformer oil. Thus, the metal ions are extracted from the transformer oil into the ionic liquid, and the metal impurities in the transformer oil are removed. The ionic liquid is used to extract the metal in the transformer oil, so that the metal substances in the oil are reduced, and the insulation performance of the transformer oil is improved. After the metal impurities in the oil are removed, the long-term and safe operation of the transformer is ensured. After the used ionic liquid is treated by the steps of rough filtration, cation exchange resin treatment, reduced pressure distillation and evaporation crystallization, the ionic liquid can be recycled. Compared with other methods, the recovery conditions of the above steps are economical and efficient, and organic reagents are not needed, so that the application of the ionic liquid in the power system is provided.

Description

Technical Field

[0001] This invention relates to the field of extracting metals from transformer oil, and more specifically, to a method for extracting metals from transformer oil using ionic liquids and recycling them. Background Technology

[0002] Transformers occupy an irreplaceable core position in power systems, and their stable operation highly depends on transformer oil as a crucial insulation and cooling medium. The quality of transformer oil directly affects the safe and efficient operation of transformers. However, during the continuous and long-term operation of transformers, various factors can cause metallic impurities such as copper and iron to dissolve into the oil. The accumulation of these impurities not only weakens the insulation performance of transformer oil but also accelerates the aging process of the oil-paper insulation system. In extreme cases, this may induce transformer failures and endanger the stability of the entire power system. Therefore, exploring an efficient and feasible technology to remove metallic impurities from transformer oil is of extremely urgent practical significance.

[0003] Currently, widely used solutions in the industry, such as adsorption and filtration, while effective in removing metallic impurities, generally face challenges such as low removal efficiency, cumbersome operation procedures, and high economic costs. Therefore, finding more advanced, economical, and easy-to-operate methods has become a key issue urgently needing to be addressed in this field. Existing research shows that ionic liquids possess unique physicochemical properties, such as extremely low vapor pressure, good thermal stability, wide liquid range, good solubility, and excellent adjustable acidity, leading to their widespread application. Compared with other chemical, physicochemical, and biochemical methods for metal extraction, ionic liquids offer significant advantages, enabling simple operation, no secondary pollution, and high extraction efficiency. Furthermore, ionic liquids can be recycled, making them a worthwhile treatment method to promote. Removing metallic impurities from transformer oil helps improve the operational reliability and safety of transformers, extends their service life, and provides new ideas and methods for the application of ionic liquids in the power industry. Therefore, we propose a method for extracting metals from transformer oil using ionic liquids and their recycling. Summary of the Invention

[0004] The purpose of this invention is to address the problems identified in the existing background technology. To achieve the above-mentioned objective, this invention provides the following technical solution: a method for recycling metals extracted from transformer oil using ionic liquids, comprising the following steps:

[0005] Step 1: Take 16-30 mL of the actual operating transformer oil sample and put it into a beaker;

[0006] Step 2: Add 2-4 mL of imidazole ionic liquid, pyridine ionic liquid, pyrrole ionic liquid, or tetraalkylammonium ionic liquid to the transformer oil sample in the beaker; the volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:15.

[0007] Step 3: Add the ionic liquid to the transformer oil sample, and stir the mixture with a stirrer at a temperature of 40-60℃ for 10-30 minutes and a speed of 500-2000 rpm.

[0008] Step 4: When mixing the ionic liquid with the transformer oil sample, nitrogen gas (N2) is introduced to prevent the metal from being reduced; the gas flow rate is 5-30 mL / min and the gas introduction time is 5-60 min.

[0009] Step 5: Use a mechanical shaker to further promote mixing at a frequency of 50-100Hz for 15-30 minutes; then use centrifugation to separate the layers at a speed of 3000-5000 r / min for 5-20 minutes.

[0010] Step 6: Take the ion liquid phase after separation, and use filter paper for coarse filtration and 1-100nm microporous ceramic membrane to remove solid impurities at 25-40℃. Then, pass it through cation exchange resin IR-120 to remove metal impurities, and obtain the metal extracted from transformer oil by ion liquid extraction.

[0011] As a preferred technical solution of the present invention, the method further includes extracting ionic liquid, performing vacuum distillation on the treated ionic liquid phase at a pressure of 0.02-0.08 MPa and a temperature of 110-380°C, and further purifying the ionic liquid obtained by vacuum distillation by evaporation crystallization at 110-380°C to finally obtain the ionic liquid.

[0012] As a preferred technical solution of the present invention, the ionic liquid is selected from 1-octyl-3-methylimidazolium chloride ([C8mim]Cl), 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]), 1-hexylpyridine hexafluorophosphate ([HPy][PF6]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]), 4-(5-nonyl)pyridine (NPy) and 1-butyl-4-methylpyridine tetrafluoroborate ([BMP][BF4]).

[0013] As a preferred technical solution of the present invention, the ionic liquid extraction method is vacuum distillation and membrane separation, with a temperature of 25-38℃, a pore size of 3-7nm for the microporous ceramic membrane, a gas pressure of 0.02-0.06MPa, a temperature of 110-360℃, and an evaporation crystallization temperature of 110-370℃.

[0014] As a preferred technical solution of the present invention, in step 2, the volume ratio of ionic liquid and transformer oil sample is 1:8-1:12, and the stirring time is 10-25 min.

[0015] As a preferred technical solution of the present invention, step 5 involves an oscillation frequency of 60-80Hz and an oscillation time of 15-25min.

[0016] As a preferred technical solution of the present invention, in step 5, the centrifuge speed is 3000-4500 r / min and the centrifugation time is 5-15 min.

[0017] As a preferred technical solution of the present invention, the flow rate of nitrogen (N2) gas is 5-20 mL / min, and the gas flow time is 5-45 min.

[0018] As a preferred technical solution of the present invention, the stirring temperature is 40-50℃, the stirring time is 10-25min, and the stirring speed is 1000-2000rpm.

[0019] As a preferred technical solution of the present invention, the ionic liquid is re-extracted and recycled through vacuum distillation, extraction, adsorption, aqueous two-phase method and membrane separation method.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: In the solution of the present invention:

[0021] 1. Certain functional groups in ionic liquids, including halogens, hydroxyl groups, thioethers, ureas, and thioureas, can form complexes with metal ions in transformer oil. This allows for the extraction of metal ions from the transformer oil into the ionic liquid, thus removing metal impurities from the transformer oil.

[0022] 2. Ionic liquids are used to extract metals from transformer oil, reducing the amount of metallic substances in the oil and improving its insulation properties. Removing metallic impurities from the oil ensures the long-term safe operation of the transformer.

[0023] 3. After use, the ionic liquid can be recycled through coarse filtration, cation exchange resin treatment, vacuum distillation, and evaporation crystallization. Compared to other methods, the above recovery process is economical and efficient, requiring no organic reagents, and provides a new approach for the application of ionic liquids in power systems. Attached Figure Description

[0024] Figure 1 A flowchart of the method provided by the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely illustrates some embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. It should be noted that, in the absence of conflict, the embodiments and features and technical solutions in the embodiments of the present invention can be combined with each other. It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. The room temperature of the present invention refers to 25±2℃.

[0027] Example 1: Please refer to Figure 1 A method for extracting metals from transformer oil and recycling it using ionic liquids includes the following steps: Take 16-30 mL of a sample of transformer oil from actual operation and place it in a beaker. Add 2-4 mL of imidazole-based ionic liquid, pyridine-based ionic liquid, pyrrole-based ionic liquid, or tetraalkylammonium-based ionic liquid to the beaker. The volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:15. Add the ionic liquid to the transformer oil sample and stir the mixture using a stirrer at a temperature of 40-60℃ for 10-30 minutes and a stirring speed of 500-2000 rpm.

[0028] When mixing the ionic liquid with the transformer oil sample, nitrogen gas (N2) is introduced to prevent the metal from being reduced. The gas flow rate is 5-30 mL / min, and the aeration time is 5-60 min. A mechanical shaker is used to further promote mixing at a frequency of 50-100 Hz for 15-30 min. Centrifugation is then performed to separate the layers at a speed of 3000-5000 rpm for 5-20 min.

[0029] Ionic liquids can be re-extracted and recycled using methods such as vacuum distillation, extraction, adsorption, aqueous two-phase separation, and membrane separation. The separated ionic liquid phase is then subjected to coarse filtration with filter paper and a 1-100 nm microporous ceramic membrane at 25-40℃ to remove solid impurities, followed by filtration through IR-120 cation exchange resin to remove metallic impurities. The treated ionic liquid phase is then subjected to vacuum distillation at a pressure of 0.02-0.08 MPa and a temperature of 110-380℃.

[0030] The ionic liquid obtained by vacuum distillation is further purified by evaporation crystallization at 110-380℃ to obtain the final ionic liquid. The above extraction and separation steps are repeated for the obtained ionic liquid.

[0031] Preferably, the volume ratio of ionic liquid to transformer oil sample is 1:8-1:12, and the stirring time is 10-25 min.

[0032] Preferably, the oscillation frequency is 60-80Hz and the oscillation time is 15-25min.

[0033] Preferably, the centrifuge speed is 3000-4500 r / min and the centrifugation time is 5-15 min.

[0034] Preferably, the flow rate of nitrogen (N2) gas is 5-20 mL / min, and the gas flow time is 5-45 min.

[0035] Preferably, the stirring temperature is 40-50℃, the stirring time is 10-25min, and the stirring speed is 1000-2000rpm.

[0036] Preferably, the ionic liquid is selected from 1-octyl-3-methylimidazolium chloride ([C8 mim]Cl), 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]), 1-hexylpyridine hexafluorophosphate ([HPy][PF6]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]), 4-(5-nonyl)pyridine (NPy) and 1-butyl-4-methylpyridine tetrafluoroborate ([BMP][BF4]).

[0037] Preferably, the ionic liquid extraction method is vacuum distillation and membrane separation, with a temperature of 25-38℃, a pore size of 3-7nm for the microporous ceramic membrane, a gas pressure of 0.02-0.06MPa, a temperature of 110-360℃, and an evaporation crystallization temperature of 110-370℃.

[0038] The procedure for extracting metallic copper with ionic liquids and for the recovery and recycling of ionic liquids is as follows: Taking the extraction of metallic copper from transformer oil samples as an example, 16 mL of transformer oil sample is measured and placed in a beaker. Then, 2 mL of 1-octyl-3-methylimidazolium chloride ([C8 mim]Cl) is added to the transformer oil sample in the beaker. The volume ratio of ionic liquid to transformer oil sample is 1:8. The mixture is stirred using a stirrer to ensure thorough mixing of the ionic liquid and transformer oil sample. The stirring temperature is 45℃, the stirring time is 10 min, and the stirring speed is 1000 rpm. To prevent the metal from being reduced when mixing the ionic liquid with the transformer oil sample, nitrogen gas (N2) is introduced at a flow rate of 10 mL / min for 25 min. The mixture is then shaken using a mechanical shaker at a frequency of 75 Hz for 20 min. Centrifugation is then performed to separate the layers at a speed of 3000 r / min for 5 min. The separated ionic liquid phase was subjected to coarse filtration and a 4 nm microporous ceramic membrane at 30°C to remove solid impurities, followed by ion exchange resin IR-120 to remove metallic impurities. The treated ionic liquid phase was then subjected to vacuum distillation at 0.04 MPa and 130°C. The resulting ionic liquid was further purified by evaporation crystallization at 130°C to obtain the final ionic liquid. The extraction and separation steps were repeated for this final ionic liquid. The control group did not undergo the ionic liquid addition process.

[0039] Determination of copper content and performance of ionic liquid recycling:

[0040] After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 60.1%. The oil can be effectively recycled eight times, with copper content decreasing by 58.1%, 59.7%, 60.2%, 59.4%, 59.8%, 60.3%, 58.7%, and 57.9%, respectively.

[0041] Example 2: Operation process of extracting metallic copper with ionic liquid and recycling and reusing ionic liquid:

[0042] Taking the extraction of metallic copper from transformer oil samples as an example, 18 mL of transformer oil sample was measured and placed in a beaker. Then, 2 mL of 1-hexylpyridine hexafluorophosphate ([HPy][PF6]) was added to the transformer oil sample in the beaker. The volume ratio of the ionic liquid to the transformer oil sample was 1:9. The mixture was stirred using a stirrer to ensure thorough mixing of the ionic liquid and the transformer oil sample. The stirring temperature was 40℃, the stirring time was 15 min, and the stirring speed was 1200 rpm. To prevent the metal from being reduced during the mixing of the ionic liquid and the transformer oil sample, nitrogen gas (N2) was introduced at a flow rate of 12 mL / min for 30 min. The mixture was then shaken using a mechanical vibrator at a frequency of 80 Hz for 15 min. Centrifugation was performed to separate the phases, with a centrifugation speed of 3000 r / min and a centrifugation time of 5 min. The separated ionic liquid phase was then subjected to coarse filtration and a 3 nm microporous ceramic membrane at 25℃ to remove solid impurities, followed by ion exchange resin IR-120 to remove metallic impurities. The treated ionic liquid phase was then subjected to vacuum distillation at 0.02 MPa and 230 °C. The ionic liquid obtained from vacuum distillation was further purified by evaporation crystallization at 230 °C to obtain the final ionic liquid. The extraction and separation steps described above were repeated for the obtained ionic liquid. The control group did not undergo the addition of ionic liquid.

[0043] Determination of copper content and performance of ionic liquid recycling:

[0044] After extraction, the transformer oil phase was analyzed. Compared with the control group, the copper content decreased by 33.7%. It can be effectively recycled five times, with copper content decreasing by 31.8%, 32.4%, 30.7%, 33.4%, and 31.6% respectively.

[0045] Example 3: Procedure for Extracting Metallic Copper from Ionic Liquids: Taking the extraction of metallic copper from transformer oil samples as an example, 20 mL of transformer oil sample was measured and placed in a beaker. Then, 2 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) was added to the transformer oil sample in the beaker. The volume ratio of ionic liquid to transformer oil sample was 1:10. The mixture was stirred using a stirrer to ensure thorough mixing of the ionic liquid and transformer oil sample. The stirring temperature was 50°C, the stirring time was 15 min, and the stirring speed was 1400 rpm. To prevent metal reduction during the mixing of the ionic liquid and transformer oil sample, nitrogen gas (N2) was introduced at a flow rate of 16 mL / min for 25 min. The mixture was then shaken using a mechanical vibrator at a frequency of 60 Hz for 15 min. Centrifugation was then performed to separate the layers at a speed of 4000 rpm for 15 min. The separated ionic liquid phase was subjected to coarse filtration and a 5 nm microporous ceramic membrane at 30°C to remove solid impurities, followed by ion exchange resin IR-120 to remove metallic impurities. The treated ionic liquid phase was then subjected to vacuum distillation at 0.04 MPa and 360°C. The resulting ionic liquid was further purified by evaporation crystallization at 360°C to obtain the final ionic liquid. The extraction and separation steps were repeated for this final ionic liquid. The control group did not undergo the ionic liquid addition process.

[0046] Determination of copper content and performance of ionic liquid recycling:

[0047] After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 36.8%. The solution can be effectively recycled six times, with copper content decreasing by 34.3%, 36.5%, 36.7%, 35.8%, 34.7%, and 35.3%, respectively.

[0048] Example 4: Procedure for Extracting Metallic Copper from Ionic Liquids: Taking the extraction of metallic copper from transformer oil samples as an example, 28 mL of transformer oil sample was measured and placed in a beaker. Then, 2 mL of 4-(5-nonyl)pyridine (NPy) was added to the transformer oil sample in the beaker. The volume ratio of ionic liquid to transformer oil sample was 1:14. The mixture was stirred using a stirrer to ensure thorough mixing of the ionic liquid and transformer oil sample. The stirring temperature was 55℃, the stirring time was 15 min, and the stirring speed was 1600 rpm. To prevent the metal from being reduced during the mixing of the ionic liquid and the transformer oil sample, nitrogen gas (N2) was introduced at a flow rate of 18 mL / min for 30 min. The mixture was then shaken using a mechanical vibrator at a frequency of 80 Hz for 15 min. Centrifugation was then performed to separate the layers at a speed of 4000 rpm for 15 min. The separated ionic liquid phase was subjected to coarse filtration and a 6 nm microporous ceramic membrane at 35°C to remove solid impurities, followed by ion exchange resin IR-120 to remove metallic impurities. The treated ionic liquid phase was then subjected to vacuum distillation at 0.06 MPa and 280°C. The resulting ionic liquid was further purified by evaporation crystallization at 280°C to obtain the final ionic liquid. The extraction and separation steps were repeated for this final ionic liquid. The control group did not undergo the ionic liquid addition process.

[0049] Determination of Copper Content and Performance of Ionic Liquid Recycling: After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 44.5%. It can be effectively recycled 7 times, with copper content decreasing by 42.8%, 43.7%, 43.1%, 44.2%, 41.2%, 40.6%, and 43.3%, respectively.

[0050] Example 5: The procedure for extracting metallic copper from a transformer oil sample using ionic liquids is as follows: 30 mL of transformer oil sample is measured and placed in a beaker. Then, 2 mL of 1-butyl-4-methylpyridine tetrafluoroborate ([BMP][BF4]) is added to the transformer oil sample in the beaker. The volume ratio of ionic liquid to transformer oil sample is 1:15. The mixture is stirred using a stirrer to ensure thorough mixing of the ionic liquid and transformer oil sample. The stirring temperature is 60°C, the stirring time is 25 min, and the stirring speed is 2000 rpm. To prevent metal reduction during the mixing of the ionic liquid and transformer oil sample, nitrogen gas (N2) is introduced at a flow rate of 30 mL / min for 45 min. The mixture is then shaken using a mechanical vibrator at a frequency of 90 Hz for 15 min. Centrifugation is then performed to separate the layers at a speed of 4500 rpm for 20 min. The separated ionic liquid phase was subjected to coarse filtration and a 7 nm microporous ceramic membrane at 35°C to remove solid impurities, followed by ion exchange resin IR-120 to remove metallic impurities. The treated ionic liquid phase was then subjected to vacuum distillation at 0.08 MPa and 150°C. The resulting ionic liquid was further purified by evaporation crystallization at 150°C to obtain the final ionic liquid. The extraction and separation steps were repeated for this final ionic liquid. The control group did not undergo the ionic liquid addition process.

[0051] Copper content and ionic liquid recycling performance:

[0052] After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 29.6%. The oil can be effectively recycled four times, with copper content decreasing by 27.1%, 28.2%, 28.4%, and 26.3% respectively.

[0053] Example 6: Same as Example 2, except that the centrifugation speed is set to 4500 r / min.

[0054] After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 18.7%. The oil can be effectively recycled three times, with copper content decreasing by 16.2%, 17.3%, and 16.4% respectively.

[0055] Example 7: Same as Example 5, except that the oscillation time is 30 minutes.

[0056] After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 16.3%. The oil can be effectively recycled twice, with the copper content decreasing by 15.7% and 16.1% respectively.

[0057] Comparative Example 1:

[0058] The extraction of metallic copper from transformer oil was the same as in Example 1, except that nitrogen (N2) was not introduced.

[0059] (2) Copper content and ionic liquid recycling performance:

[0060] After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 12.8%. This is attributed to the accelerated oxidation of copper in the transformer oil due to the lack of N2 introduction, resulting in premature aging of the transformer oil and consequently lower efficiency in copper extraction. The oil can be effectively recycled three times, with copper content decreasing by 10.3%, 12.5%, and 10.7%, respectively.

[0061] Comparative Example 2:

[0062] The extraction of metallic copper from transformer oil is the same as in Example 4, except that the shaking and mixing step is omitted.

[0063] (2) Copper content and ionic liquid recycling performance:

[0064] After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 31.9%. The oil can be effectively recycled five times, with copper content decreasing by 27.3%, 30.8%, 29.6%, 28.1%, and 30.5% respectively.

[0065] Comparative Example 3:

[0066] The extraction of metallic copper from transformer oil was the same as in Example 3, except that 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]) was used.

[0067] (2) Copper content and ionic liquid recycling performance:

[0068] After extraction, the transformer oil phase was analyzed. The copper content in the oil was determined using an oil analysis spectrometer. Compared with the control group, the copper content decreased by 22.7%. The oil can be effectively recycled four times, with copper content decreasing by 22.4%, 20.6%, 20.3%, and 21.5% respectively.

[0069] As can be seen from the above embodiments and comparative examples, the present invention has a high metal extraction efficiency under experimental conditions, which improves the insulation performance of transformer oil to a certain extent, provides a guarantee for the safe and stable operation of transformers, and the recycling of ionic liquids provides a new approach for the application of ionic liquids in the field of transformers.

[0070] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for recycling metals extracted from transformer oil using ionic liquids, characterized in that, Includes the following steps: Step 1: Take 16-30 mL of the actual operating transformer oil sample and put it into a beaker; Step 2: Add 2-4 mL of ionic liquid to the transformer oil sample in the beaker. The ionic liquid is selected from one of the following: imidazole ionic liquid, pyridine ionic liquid, pyrrole ionic liquid, and tetraalkylammonium ionic liquid. The volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:

15. Step 3: Add the ionic liquid to the transformer oil sample, and stir the mixture with a stirrer at a temperature of 40-60℃ for 10-30 minutes and a speed of 500-2000 rpm. Step 4: When mixing the ionic liquid with the transformer oil sample, nitrogen gas is introduced to prevent the metal from being reduced. The gas flow rate is 5-30 mL / min, and the ventilation time is 5-60 min; Step 5: Use a mechanical shaker to further promote mixing at a frequency of 50-100Hz for 15-30 minutes; then use centrifugation to separate the layers at a speed of 3000-5000 r / min for 5-20 minutes. Step 6: Take the ion liquid phase after separation, and use filter paper for coarse filtration and 1-100nm microporous ceramic membrane to remove solid impurities at 25-40℃. Then, use cation exchange resin IR-120 to remove other metal impurities in the filtrate to obtain copper extracted from the transformer by ion liquid extraction. It also includes the extraction of ionic liquids, which involves vacuum distillation of the treated ionic liquid phase at a pressure of 0.02-0.08 MPa and a temperature of 110-380℃, followed by further purification of the ionic liquid obtained by vacuum distillation by evaporation crystallization at 110-380℃, to finally obtain the ionic liquid. The ionic liquid is selected from one of the following: 1-octyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium hexafluorophosphate, 1-hexylpyridine hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 4-(5-nonyl)pyridine (NPy), and 1-butyl-4-methylpyridine tetrafluoroborate.

2. The method for recycling metals extracted from transformer oil using ionic liquids according to claim 1, characterized in that, The extraction method for ionic liquids is vacuum distillation, with a pressure of 0.02-0.06 MPa and a temperature of 110-360℃. The evaporation and crystallization temperature is 110-370℃.

3. The method for recycling metals extracted from transformer oil using ionic liquids according to claim 2, characterized in that, Step 2: The volume ratio of ionic liquid to transformer oil sample is 1:8-1:12, and the stirring time is 10-25 min.

4. The method for recycling metals extracted from transformer oil using ionic liquids according to claim 3, characterized in that, Step 5: The oscillation frequency is 60-80Hz, and the oscillation time is 15-25min.

5. The method for recycling metals extracted from transformer oil using ionic liquids according to claim 4, characterized in that, Step 5: Centrifuge speed is 3000-4500 r / min, centrifugation time is 5-15 min.

6. The method for recycling metals extracted from transformer oil using ionic liquids according to claim 5, characterized in that, The nitrogen gas flow rate is 5-20 mL / min, and the gas flow time is 5-45 min.

7. The method for recycling metals extracted from transformer oil using ionic liquids according to claim 6, characterized in that, The stirring temperature is 40-50℃, the stirring time is 10-25 minutes, and the stirring speed is 1000-2000 rpm.

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