A High-Efficiency Recovery Method for Eutectic Solvents Based on Vacuum Distillation-Electrodialysis-Activated Carbon Adsorption

Abstract

This invention relates to a highly efficient method for recovering eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption, belonging to the field of chemical separation technology. The method includes the following steps: (1) heating and vacuum distilling the waste eutectic solvent to obtain a vacuum-distilled eutectic solvent; (2) subjecting the vacuum-distilled eutectic solvent to electrodialysis to obtain an electrodialyzed eutectic solvent; (3) adsorbing and filtering the electrodialyzed eutectic solvent, collecting the filtrate, and obtaining a high-purity recovered eutectic solvent. The highly efficient method for recovering eutectic solvents provided by this invention effectively avoids the entry of solvent and impurities into the condensation system caused by the "sudden boiling" phenomenon through vacuum distillation. Electrodialysis efficiently removes conductive inorganic salts and small-molecule polar impurities from the aqueous phase, improving the recovery purity of the eutectic solvent.

Description

Technical Field

[0001] This invention relates to a method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption, belonging to the field of chemical separation technology. Background Technology

[0002] Eutectic solvents (DESs) have been widely used in biomass material extraction due to their unique tunability, high thermal stability, and low volatility. As solvents, DESs can effectively dissolve various organic compounds, exhibiting particularly good performance in extracting active ingredients from plants such as polyphenols, sugars, and oils. However, during biomass extraction, DESs often react with water, inorganic salts, plant proteins, fats, and other organic matter, leading to severe solvent contamination. These contaminants are often difficult to completely remove during solvent recovery, affecting solvent purity and reuse efficiency. In particular, some difficult-to-dissolve small molecule impurities and large molecules may form stable complexes or precipitates during extraction, making solvent regeneration more complex. While traditional recovery methods can remove some impurities, they struggle to maintain high recovery rates while ensuring solvent purity, thus affecting the performance stability and reusability of DESs. Therefore, there is an urgent need to develop more efficient and economical recovery technologies to address these difficult-to-remove impurities, thereby enhancing the application value of DESs in biomass material extraction.

[0003] Existing solvent recovery technologies mainly rely on single physical or chemical separation methods, such as atmospheric or vacuum distillation, electrochemical treatment, and adsorbent purification. While simple distillation can remove some low-boiling-point impurities, it is prone to sudden boiling or decomposition of heat-sensitive components in DES mixtures with high salt content and high viscosity. Ion exchange or electrodialysis alone can remove conductive impurities but is difficult to effectively remove non-polar or large-molecule organic impurities. Activated carbon adsorption alone is often limited by mass transfer rates and adsorption saturation, making deep purification difficult. These methods each have their own focus and cannot meet the demand for high-purity, high-yield recovery of waste DES.

[0004] Therefore, there is an urgent need for a multi-stage composite recycling process that integrates vacuum distillation, electrodialysis, and activated carbon adsorption. This process involves physical fractional distillation pretreatment to remove moisture and volatile impurities, electrodialysis desalination to remove ionizable impurities and small polar molecules, and then supplementing with a high specific surface area adsorbent to deeply purify non-volatile organic impurities, thereby achieving efficient recycling and reuse of waste DESs. Summary of the Invention

[0005] To address the problems of low purity, low recovery rate, and difficulty in simultaneously removing multiple impurities in existing technologies for recovering waste eutectic solvents, this invention provides a highly efficient method for recovering eutectic solvents based on vacuum distillation, electrodialysis, and activated carbon adsorption. This method first employs a segmented vacuum distillation strategy, utilizing a temperature gradient to preferentially separate water and low-boiling-point impurities, suppressing sudden boiling and pre-concentrating the main solvent. Subsequently, the distillation residue is introduced into a multi-chamber electrodialysis unit, where inorganic salts and small-molecule polar impurities are efficiently removed under an electric field using an anion-cation exchange composite membrane. Finally, high-surface-area activated carbon adsorption deeply purifies non-volatile organic pigments and thermosensitive decomposition products. These three interconnected processes achieve high purity and high-yield recovery of waste eutectic solvents.

[0006] The technical solution of the present invention is as follows:

[0007] A method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption includes the following steps:

[0008] (1) Add the waste eutectic solvent (DESs) to the rotary evaporator, heat it to 45-55℃ at 5-80 kPa, distill under reduced pressure for 20-40 min, and continue heating to 75-85℃ after the collection rate drops to 0.8-1.2 mL / min, distill under reduced pressure for 60-180 min. When the reflux flow rate and product amount no longer change, end the reduced pressure distillation reaction to obtain the eutectic solvent after reduced pressure distillation.

[0009] (2) Transfer the eutectic solvent after vacuum distillation to an electrodialysis apparatus and perform electrodialysis at a current of 0.1~3.0A. When the conductivity of the eutectic solvent after vacuum distillation no longer changes, stop the electrodialysis reaction to obtain the eutectic solvent after electrodialysis.

[0010] (3) After adjusting the pH of the eutectic solvent after electrodialysis to 6.8~7.2, add activated carbon, shake and adsorb at 100~200 rpm for 2.5~3.5 h, filter, collect the filtrate, and obtain high-purity recovered eutectic solvent.

[0011] According to a preferred embodiment of the present invention, in step (1), the waste eutectic solvent refers to the remaining extract after extracting cellulose or chitin from biomass raw materials using a eutectic solvent.

[0012] More preferably, the biomass raw material is corn stalks, cassava residue, or shrimp shells; the eutectic solvent is composed of hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD) in a molar ratio of 1:(1~2);

[0013] More preferably, the hydrogen bond acceptor (HBA) is choline chloride (ChCl) or betaine (Bet); and the hydrogen bond donor (HBD) is urea (U), glycerol (Gly), or oxalic acid (OA).

[0014] According to a preferred embodiment of the present invention, in step (1), the rotary evaporator is composed of a round-bottom distillation flask, a condensation system and a collection flask connected in sequence.

[0015] More preferably, the round-bottom distillation flask has a capacity of 250 ml.

[0016] According to a preferred embodiment of the present invention, in step (1), the temperature is heated to 50°C at a heating rate of 4.5-5.5°C / min under 10-50 kPa, and then distilled under reduced pressure for 20-40 min. After the collection rate drops to 0.8-1.2 mL / min, the temperature is further heated to 75-85°C and distilled under reduced pressure for 60-180 min.

[0017] A further preferred method is to heat the sample to 50°C at a heating rate of 5°C / min under 40 kPa, distill it under reduced pressure for 30 min, and then continue heating to 80°C and distilling it under reduced pressure for 120 min after the collection rate drops to 1 mL / min.

[0018] According to a preferred embodiment of the present invention, in step (2), the electrodialysis device is composed of a desalination chamber, a concentration chamber and an electrode chamber connected in sequence, and the two ends of the desalination chamber and the electrode chamber are connected to a DC power supply; deionized water is added to the concentration chamber and electrolyte is added to the electrode chamber.

[0019] More preferably, the voltage of the DC power supply is 10~300V, and the electrolyte is a 0.1M NaCl solution.

[0020] According to a preferred embodiment of the present invention, in step (2), electrodialysis is performed at 1.5A, and the conductivity of the eutectic solvent after vacuum distillation is measured every 10 minutes and recorded until it no longer changes.

[0021] According to a preferred embodiment of the present invention, in step (3), pH adjustment is performed using 0.1M hydrochloric acid or 0.1M sodium hydroxide solution.

[0022] According to a preferred embodiment of the present invention, in step (3), the activated carbon has a mesh size of 40-60 mesh and a specific surface area of ​​800-1200 m². 2 / g of activated carbon, the amount added is 10~20% of the mass of the eutectic solvent after electrodialysis.

[0023] More preferably, the amount of activated carbon added is 20% of the mass of the eutectic solvent after electrodialysis.

[0024] The technical features and beneficial effects of this invention are as follows:

[0025] 1. The efficient recovery method for eutectic solvents provided by this invention firstly involves vacuum distillation of the waste eutectic solvent, combined with heating reflux and a segmented recovery strategy. This effectively avoids solvent and impurities caused by "sudden boiling" from entering the condensation system or even flowing back to the vacuum pump, resulting in recovery losses or equipment contamination. Furthermore, strict control of vacuum and temperature allows for the preferential distillation of low-boiling-point main solvents, significantly improving the recovery rate and purity of the main solvent while reducing contamination and wear on subsequent processing equipment.

[0026] 2. In the efficient recovery method for eutectic solvents provided by this invention, the eutectic solvent after vacuum distillation is introduced into an electrodialysis device employing anion and cation exchange composite membranes. Specific voltage and current densities are applied, and the conductivity of the desalination chamber is monitored every 10 minutes to assess the deionization process in real time. This step efficiently removes conductive inorganic salts and small-molecule polar impurities from the aqueous phase, significantly reducing the conductivity and increasing the purity of the recovered DESs. Simultaneously, by optimizing the current density, the recovery speed and energy consumption, membrane lifespan and selectivity are balanced, ensuring stable separation performance and economic efficiency.

[0027] 3. In the efficient recovery method for eutectic solvents provided by this invention, after the eutectic solvent is adjusted to neutral after electrodialysis, high specific surface area activated carbon is added and adsorbed under shaking. Residual organic impurities and pigments are removed through physical adsorption. This step has a significant purification capacity for non-volatile and difficult-to-treat components, further improving solvent transparency and chemical purity. Furthermore, the activated carbon is regenerable and recyclable, reducing consumption costs. This comprehensively achieves efficient, low-energy, and environmentally friendly DESs recovery and reuse.

[0028] Specific experimental methods

[0029] The present invention will be further described below with reference to specific embodiments, but is not limited thereto. Unless otherwise specified, the raw materials used in the embodiments are all conventional raw materials that can be obtained commercially; unless otherwise specified, the methods described are existing technologies.

[0030] The examples involve three different sources of waste eutectic solvents, referred to as DESs-1, DESs-2 and DESs-3, respectively.

[0031] DESs-1 was obtained as follows:

[0032] Choline chloride (ChCl) and urea (U) were mixed evenly at a molar ratio of 1:2 to obtain the eutectic solvent ChCl / U.

[0033] Then, the eutectic solvent ChCl / U was added to the corn stalk powder, and the material-to-liquid ratio was controlled at 1:10 (w / v). The mixture was stirred and extracted at 90-95℃ for 3-4 h. After extraction, the mixture was centrifuged (4000-5000 rpm, 15-20 minutes) and filtered to complete the cellulose extraction. The remaining extract was DESs-1.

[0034] DESs-2 was obtained using the following method:

[0035] Choline chloride (ChCl) and glycerol (Gly) were mixed evenly at a molar ratio of 1:2 to obtain the eutectic solvent ChCl / Gly.

[0036] Then, the eutectic solvent ChCl / Gly was added to the cassava residue powder, and the material-to-liquid ratio was controlled at 1:8 (w / v). The mixture was stirred and extracted at 85-90℃ for 2-3 hours. After extraction, the mixture was centrifuged (4000-5000 rpm, 15-20 minutes) to complete the cellulose extraction. The remaining extract was DESs-2.

[0037] DESs-3 is obtained as follows:

[0038] Betaine (Bet) and oxalic acid (OA) were mixed evenly at a molar ratio of 1:1.5 to obtain the eutectic solvent Bet / OA;

[0039] Then, the eutectic solvent Bet / OA was added to the shrimp shell powder, and the material-to-liquid ratio was controlled at 1:12 (w / v). The mixture was stirred and extracted at 70-75℃ for 4-5 h. After extraction, the mixture was centrifuged (4000-5000 rpm, 20-25 minutes) to complete the chitin extraction. The remaining extract was DESs-3.

[0040] The above DESs-1, DESs-2 and DESs-3 all contain the target product, residual moisture, inorganic ions and high molecular impurities.

[0041] Example 1

[0042] A method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption includes the following steps:

[0043] (1) Put 100 mL of DESs-1 into a 250 mL round bottom distillation flask, connect the rotary evaporator, condenser and collection bottle, and start the cooling water circulation; then adjust the vacuum degree to 20 kPa, heat from room temperature to 50 °C at a rate of 5 °C / min, and distill under reduced pressure for 30 min to distill off the low boiling point impurities in DESs-1. After the collection rate drops to below 1 mL / min, continue heating to 80 °C and distill under reduced pressure for 120 min to distill off the high boiling point impurities in DESs-1. Monitor the vacuum degree and temperature in real time during the entire heating process to prevent sudden boiling; when the reflux flow rate and the reflux product in the collection bottle tend to be stable and no longer change, end the reduced pressure distillation reaction to obtain the eutectic solvent after reduced pressure distillation.

[0044] (2) Transfer the eutectic solvent after vacuum distillation to the desalination chamber of the electrodialysis apparatus. At the same time, add an equal volume of deionized water to the concentration chamber and inject an equal volume of 0.1M NaCl solution into the electrode chamber. Then, set the DC power supply to 50V and the output current to 0.5A. Perform electrodialysis under these conditions. During the electrodialysis process, take 2mL of the eutectic solvent after vacuum distillation in the desalination chamber every 10min, measure its conductivity and record it. When the conductivity of the eutectic solvent after vacuum distillation no longer changes, stop the electrodialysis reaction and obtain the eutectic solvent after electrodialysis.

[0045] (3) After adjusting the pH of the eutectic solvent after electrodialysis to 7.0 with 0.1M hydrochloric acid or 0.1M sodium hydroxide solution, add 50-mesh solution with a specific surface area of ​​1000 m². 2 / g of activated carbon was added at an amount equal to 10% of the mass of the eutectic solvent after electrodialysis. The mixture was shaken and adsorbed at 150 rpm for 3 hours. After the adsorption was completed, the mixture was transferred to a Buchner funnel to separate the activated carbon and collect the filtrate to obtain a high-purity recovered eutectic solvent.

[0046] Example 2

[0047] A method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption is described in Example 1, except that the waste DESs in step (1) is DESs-2, and the other steps and conditions are the same as in Example 1.

[0048] Example 3

[0049] A method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption is described in Example 1, except that the waste DESs in step (1) is DESs-3, and the other steps and conditions are the same as in Example 1.

[0050] Example 4

[0051] A method for efficient recovery of eutectic solvent based on vacuum distillation-electrodialysis-activated carbon adsorption is described in Example 3, except that in step (1), heating and vacuum distillation are performed at 30 kPa, and other steps and conditions are the same as in Example 3.

[0052] Example 5

[0053] A method for efficient recovery of eutectic solvent based on vacuum distillation-electrodialysis-activated carbon adsorption is described in Example 3, except that in step (1), heating and vacuum distillation are performed at 40 kPa, and other steps and conditions are the same as in Example 3.

[0054] Example 6

[0055] A method for efficient recovery of eutectic solvent based on vacuum distillation-electrodialysis-activated carbon adsorption is described in Example 5, except that in step (2), the DC power supply is set to 100V and the output current is 1A, and the other steps and conditions are the same as in Example 5.

[0056] Example 7

[0057] A method for efficient recovery of eutectic solvent based on vacuum distillation-electrodialysis-activated carbon adsorption is described in Example 5, except that in step (2), the DC power supply is set to 150V and the output current is 1.5A. Other steps and conditions are the same as in Example 5.

[0058] Example 8

[0059] A method for efficient recovery of eutectic solvent based on vacuum distillation-electrodialysis-activated carbon adsorption is described in Example 7, except that in step (3), the amount of activated carbon added is 15% of the mass of the eutectic solvent after electrodialysis, and the other steps and conditions are the same as in Example 7.

[0060] Example 9

[0061] A method for efficient recovery of eutectic solvent based on vacuum distillation-electrodialysis-activated carbon adsorption is described in Example 7, except that in step (3), the amount of activated carbon added is 20% of the mass of the eutectic solvent after electrodialysis, and the other steps and conditions are the same as in Example 7.

[0062] Comparative Example 1

[0063] A method for recovering a eutectic solvent, comprising the following steps:

[0064] 100 mL of DESs-3 was placed into a 250 mL round-bottom distillation flask, and the rotary evaporator, condenser, and collection flask were connected. Cooling water circulation was started. The vacuum degree was then adjusted to 40 kPa, and the temperature was first heated from room temperature to 50 °C at a rate of 5 °C / min. The mixture was then distilled under reduced pressure for 30 min to remove low-boiling impurities from DESs-1. After the collection rate dropped to below 1 mL / min, the temperature was further increased to 80 °C, and the mixture was then distilled under reduced pressure for 120 min to remove high-boiling impurities from DESs-1. The vacuum degree and temperature were monitored in real time throughout the heating process to prevent sudden boiling. When the reflux flow rate and the reflux product in the collection flask became stable and no longer changed, the reduced pressure distillation reaction was stopped to obtain the recovered eutectic solvent.

[0065] Comparative Example 2

[0066] A method for recovering a eutectic solvent, comprising the following steps:

[0067] 100 mL of DESs-3 was added to the desalination chamber of the electrodialysis apparatus, while an equal volume of deionized water was added to the concentration chamber, and an equal volume of 0.1 M NaCl solution was injected into the electrode chamber. The DC power supply was then set to 50 V and the output current to 1.5 A. Electrodialysis was performed under these conditions. During the electrodialysis process, 2 mL of the eutectic solvent after vacuum distillation was taken from the desalination chamber every 10 min, and its conductivity was measured and recorded. When the conductivity of the eutectic solvent after vacuum distillation no longer changed, the electrodialysis reaction was stopped, and the recovered eutectic solvent was obtained.

[0068] Comparative Example 3

[0069] A method for recovering a eutectic solvent, comprising the following steps:

[0070] After adjusting the pH of 100 mL of DESs-3 to 7.0 using 0.1 M hydrochloric acid or 0.1 M sodium hydroxide solution, add 50 mesh sodium hydroxide solution with a specific surface area of ​​1000 m². 2 / g of activated carbon was added at an amount equal to 20% of the mass of the eutectic solvent after electrodialysis. The mixture was shaken and adsorbed at 150 rpm for 3 hours. After the adsorption was completed, the mixture was transferred to a Buchner funnel to separate the activated carbon and collect the filtrate to obtain the recovered eutectic solvent.

[0071] Experimental Example

[0072] The purity and yield of the eutectic solvents recovered in Examples 1-9 and Comparative Examples 1-3 were determined, and the results are shown in Table 1.

[0073] Table 1

[0074]

[0075] As shown in Table 1, the purity and yield of the eutectic solvent recovered in Examples 1-9 of this invention are significantly higher than those in Comparative Examples 1-3. In particular, in Example 9, the purity of the recovered eutectic solvent reached 98%, which is 1.96 times that of Comparative Example 3, and the yield reached 93 wt%, which is 2.06 times that of Comparative Example 3.

[0076] A more detailed analysis follows: the waste eutectic solvents DES-1 (ChCl / U), DES-2 (ChCl / Gly), and DES-3 (Bet / OA) in each embodiment differ in chemical structure and intermolecular hydrogen bond network. Among them, the betaine / oxalic acid system in DES-3, due to the presence of dicarboxyl groups in oxalic acid, can form stronger hydrogen bond aggregates with betaine. Therefore, it is easier to volatilize small molecule impurities during vacuum distillation, resulting in lower content of macromolecules, organic pigments, and other impurities in the residual liquid. Consequently, the purity (77%) and yield (72%) of the recovered DESs are superior to those of DES-1 (72% / 65%) and DES-2 (74% / 68%).

[0077] Under the same current and carbon dosage, as the vacuum level increased from 20 kPa (Example 3) to 30 kPa (Example 4) and then to 40 kPa (Example 5), the absolute pressure within the system gradually decreased. This significantly amplified the boiling point differences between the main DES component and water, low-boiling-point byproducts, and high-boiling-point impurities, allowing for clearer fractional distillation within the temperature range of 50–80 °C. Although some impurities were removed at 20 kPa, a small amount of non-volatile components still refluxed with the solvent. At 30 kPa, low-boiling-point substances volatilized more thoroughly. When the vacuum was further increased to 40 kPa, the larger gas-pressure difference accelerated the mass transfer rate, minimizing impurity residue. Therefore, the purity and yield of the recovered DESs gradually increased.

[0078] Under the same vacuum level and carbon dosage, a higher current results in a faster ion migration rate through the membrane per unit time, thus more thoroughly removing residual inorganic salts and polar impurities from waste DESs components. When the current is increased from 0.5A (Example 5) to 1.0A (Example 6), the transmembrane electric field strength in the electrodialysis device increases, causing the ion migration rate on the cation-anion exchange composite membrane per unit time to rapidly increase from its previous low level, thus reducing residual Cl... - Polar small molecule impurities are more thoroughly transported to the concentration chamber. Simultaneously, due to the shortened processing time, the thermal or electrochemical degradation loss of the DESs components under the electric field is reduced, thus increasing the purity from 85% to 90% and the yield from 79% to 82%. Further increasing the current to 1.5A (Example 7) further amplifies the ion migration flux, causing the ion concentration in the desalination chamber to drop to extremely low levels in an even shorter time. This, coupled with more efficient removal of polar impurities and a faster mass transfer process, ultimately achieves a purity of 94% and a yield of 86%.

[0079] Under the same vacuum and current intensity, activated carbon removes the last remaining high molecular weight pigments and trace organic impurities through physical adsorption and electrostatic action. As the amount of activated carbon used increased from 10 wt% (Example 7) to 15 wt% (Example 8) and 20 wt% (Example 9), respectively, the purity increased from 94% to 96% and 98%, respectively, and the yield increased from 86% to 90% and 93%.

[0080] Under the same vacuum and current intensity, as the activated carbon dosage increased from 10 wt% (Example 7) to 15 wt% (Example 8) and 20 wt% (Example 9), the surface sites and pore capacity available for impurity adsorption in the system increased proportionally, thereby enhancing the physical adsorption and electrostatic induced adsorption of residual high molecular weight pigments, trace amounts of oils, and other organic polar impurities. Specifically, when the carbon dosage increased from 10 wt% to 15 wt%, the total surface area and pore volume of the activated carbon increased, further improving the adsorption efficiency of pigments and macromolecular pollutants, resulting in a DESs purity increase from 94% to 96% and a yield increase from 86% to 90%. When the carbon dosage continued to increase to 20 wt%, the adsorbent surface area continued to increase, and the pore network's ability to capture even smaller impurities was further enhanced, ultimately achieving a purity of 98% and a yield increase to 93%.

[0081] In contrast, single vacuum distillation (Comparative Example 1) can only remove some low-boiling or high-boiling impurities by relying on boiling point differences, but it cannot remove residual inorganic ions and polar molecules, resulting in a final product containing a large amount of water and salts, with a purity of only 59% and a yield of only 53%. Single electrodialysis (Comparative Example 2) can effectively remove inorganic salts and small-molecule polar impurities from the solution, but it cannot effectively eliminate high-molecular-weight pigments, oils, and non-polar impurities. Furthermore, prolonged electric field action can cause electrochemical decomposition of some DES components, resulting in a DESs purity of only 60% and a yield of 56%. Single activated carbon adsorption (Comparative Example 3) can adsorb large-molecule and pigment impurities, but it has no effect on removing ionic and small-molecule impurities. At the same time, a small amount of solvent is retained by the activated carbon during the adsorption process, resulting in a purity of only 50% and a yield of 45%.

[0082] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the scope of protection of the present invention. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption, characterized in that, The steps include the following: (1) Add the waste eutectic solvent to the rotary evaporator, heat it to 45-55℃ at 5-80 kPa, distill under reduced pressure for 20-40 min, and continue heating to 75-85℃ after the collection rate drops to 0.8-1.2 mL / min, distill under reduced pressure for 60-180 min. When the reflux flow rate and the amount of product no longer change, stop the reduced pressure distillation reaction to obtain the eutectic solvent after reduced pressure distillation. (2) Transfer the eutectic solvent after vacuum distillation to an electrodialysis apparatus and perform electrodialysis at a current of 0.1~3.0A. When the conductivity of the eutectic solvent after vacuum distillation no longer changes, stop the electrodialysis reaction to obtain the eutectic solvent after electrodialysis. (3) After adjusting the pH of the eutectic solvent after electrodialysis to 6.8~7.2, add activated carbon, shake and adsorb at 100~200 rpm for 2.5~3.5 h, filter, collect the filtrate, and obtain high-purity recovered eutectic solvent.

2. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 1, characterized in that, In step (1), the waste eutectic solvent refers to the remaining extract after extracting cellulose or chitin from biomass raw materials using eutectic solvent; the biomass raw materials are corn stalks, cassava residue or shrimp shells; the eutectic solvent is composed of hydrogen bond acceptors and hydrogen bond donors in a molar ratio of 1:(1~2).

3. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 2, characterized in that, The hydrogen bond acceptor is choline chloride or betaine; the hydrogen bond donor is urea, glycerol or oxalic acid.

4. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 1, characterized in that, In step (1), the rotary evaporator consists of a round-bottom distillation flask, a condensation system, and a collection flask connected in sequence.

5. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 1, characterized in that, In step (1), the temperature is increased to 50°C at a rate of 4.5-5.5°C / min under 10-50 kPa, and then distilled under reduced pressure for 20-40 min. After the collection rate drops to 0.8-1.2 mL / min, the temperature is increased to 75-85°C and then distilled under reduced pressure for 60-180 min.

6. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 5, characterized in that: At 40 kPa, the temperature was increased to 50 °C at a rate of 5 °C / min, and then distilled under reduced pressure for 30 min. After the collection rate dropped to 1 mL / min, the temperature was increased to 80 °C and then distilled under reduced pressure for 120 min.

7. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 1, characterized in that, In step (2), the electrodialysis device is composed of a desalination chamber, a concentration chamber and an electrode chamber connected in sequence, and the two ends of the desalination chamber and the electrode chamber are connected to a DC power supply; deionized water is added to the concentration chamber and electrolyte is added to the electrode chamber. The DC power supply has a voltage of 10~300V and the electrolyte is a 0.1M NaCl solution.

8. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 1, characterized in that, In step (2), electrodialysis is performed at 1.5A. The conductivity of the eutectic solvent after vacuum distillation is measured every 10 minutes and recorded until it no longer changes.

9. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 1, characterized in that, In step (3), pH adjustment is performed using 0.1M hydrochloric acid or 0.1M sodium hydroxide solution.

10. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 1, characterized in that, In step (3), the activated carbon has a mesh size of 40-60 and a specific surface area of ​​800-1200 m². 2 / g of activated carbon, the amount added is 10~20% of the mass of the eutectic solvent after electrodialysis.

11. The method for efficient recovery of eutectic solvents based on vacuum distillation-electrodialysis-activated carbon adsorption as described in claim 10, characterized in that, The amount of activated carbon added is 20% of the mass of the eutectic solvent after electrodialysis.

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