Method for recovering ionic liquid in melamine spinning coagulating bath through electrodialysis
Through the combination of electrodialysis and reduced pressure distillation, the problems of complexity and low purity of ionic liquid recovery in the prior art are solved, efficient and simple ionic liquid recovery is achieved, and recovery rate and purity are improved.
Patent Information
- Application Number
- CN202411348107.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-26
- Publication Date
- 2024-12-31
AI Technical Summary
In the prior art, the ionic liquid recovery method is complex and has many steps, resulting in low recovery purity, affecting the reusability of the ionic liquid, and requiring the introduction of other reagents, which increases the difficulty of recycling.
Using electrodialysis method, the melamine spinning solidification bath is filtered and electrodialyzed to separate and enrich the ionic liquid. Then, a high-purity ionic liquid is obtained by decompression distillation. There is no need to add chemical reagents during the whole process, which simplifies the equipment and operate.
It achieves high recovery rate (over 95%) and high purity (over 99%) of ionic liquids, reduces energy consumption, simplifies equipment and operations, avoids pollution, and improves the reusability of ionic liquids.
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of membrane separation, in particular to a method for recovering ionic liquid in a melamine spinning coagulation bath through electrodialysis. Background Art
[0002] Melamine fiber is a thermosetting resin fiber with a three-dimensional network cross-linked structure, which is prepared by dry-jet wet spinning process using melamine and formaldehyde as raw materials through addition, polycondensation and other reactions. It is widely used in many fields such as national defense and military industry, industrial protection, rail transportation, home and public place decoration. The synthesis of traditional melamine formaldehyde prepolymers all uses water as a solvent, and the synthesized melamine formaldehyde prepolymers have poor stability and are difficult to form fibers; the melamine formaldehyde prepolymers synthesized using the ionic liquid / water solvent system have high stability and good fiber forming properties. However, during the spinning process of dry-jet wet spinning of the melamine formaldehyde prepolymer synthesized using the ionic liquid / water solvent system, when the fiber is formed in the water coagulation bath, a part of the prepolymer will be taken away with the migration of the ionic liquid. Therefore, when the ionic liquid is recovered later, the prepolymer impurities dissolved in the ionic liquid need to be removed, which increases the difficulty of recovering the ionic liquid.
[0003] There are currently a variety of ionic liquid recovery methods. For example, Chinese patent CN 101748515A discloses a method for recovering ionic liquids, which uses filtration and impurity removal, concentration treatment, salting-out separation, and vacuum distillation to recover ionic liquids. Chinese patent CN 102371078A discloses a method for recovering ionic liquid solvents after homogeneous acylation of cellulose, which first homogeneously acylates the cellulose, then decolorizes, filters, and vacuum distills the ionic liquid waste to remove organic residues and water in the ionic liquid. Chinese patent CN 101392417A discloses a method for recovering ionic liquid solvents from cellulose spinning using a combined method, which recovers ionic liquids through filtration, cation exchange resin, nanofiltration or reverse osmosis treatment, and vacuum distillation. Chinese patent CN106149101A discloses a method for recovering ionic composite solvents for cellulose spinning, which uses filtration, multiple vacuum distillation processes, and post-adsorption treatment to recover ionic liquids. Chinese patent CN 110453312A discloses a method for recovering the spinning solvent produced by spinning cellulose fibers using ionic liquid as solvent, wherein the ionic liquid is recovered by adding a flocculant for precipitation, filtering, and then passing through anion and cation exchange resins, distillation, and reverse osmosis membrane treatment. Although the above recovery method can achieve the recovery of ionic liquid, the recovery method is complicated and has many steps; the need to introduce other reagents results in low purity of the recovered ionic liquid, and multiple cycles easily lead to reagent enrichment, which affects the reusability of the ionic liquid.
[0004] Based on this, developing an ionic liquid recovery method with high recovery rate and high purity has important economic value and significance. Summary of the invention
[0005] The purpose of the present invention is to provide a method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis in view of the deficiencies in the prior art.
[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0007] The present invention provides a method for recovering ionic liquid in a melamine spinning coagulation bath by electrodialysis, comprising the following steps:
[0008] (1) filtering the melamine spinning coagulation bath to obtain a filtrate;
[0009] (2) subjecting the filtrate to electrodialysis to obtain concentrated chamber recovered liquid and dilute chamber recovered liquid;
[0010] (3) The concentrated chamber recovery liquid is subjected to reduced pressure distillation to obtain an ionic liquid.
[0011] Preferably, the mass of the ionic liquid in the concentrated chamber recovery liquid in step (2) is 70-90% of the mass of the ionic liquid in the melamine spinning coagulation bath; the dilute chamber recovery liquid is subjected to electrodialysis treatment again, and the concentrated chamber recovery liquid obtained by the two electrodialysis treatments is subjected to reduced pressure distillation to obtain the ionic liquid.
[0012] Preferably, the mass concentration of the ionic liquid in the melamine spinning coagulation bath is 2-10%.
[0013] Preferably, the ionic liquid comprises one or more of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium dimethyl phosphate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-methyl-1,5-diazabicyclo[4.3.0]-5-nonene trimethyl phosphate and 1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonene triethyl phosphate.
[0014] Preferably, the filtration accuracy in step (1) is 5 to 65 μm.
[0015] Preferably, the voltage of the electrodialysis treatment is 40 to 80 V, the current of the electrodialysis treatment is 0.5 to 3.0 A, and the time of each electrodialysis treatment is 1 to 5 hours.
[0016] Preferably, in the electrodialysis treatment of step (2), the initial solution in the dilute chamber is the filtrate, the initial solution in the concentrated chamber is water, and the solution in the cathode chamber is an ionic liquid aqueous solution, wherein the mass concentration of the ionic liquid in the ionic liquid aqueous solution is the same as the mass concentration of the ionic liquid in the melamine spinning coagulation bath.
[0017] Preferably, the volume ratio of the dilute chamber initial solution, the concentrated chamber initial solution and the cathode chamber solution is 1-3:1:0.2-1.
[0018] Preferably, the dilute chamber recovered liquid is subjected to electrodialysis treatment again, wherein the dilute chamber initial solution is the dilute chamber recovered liquid, the concentrated chamber initial solution is water, and the cathode chamber solution is an ionic liquid aqueous solution, wherein the mass concentration of the ionic liquid in the ionic liquid aqueous solution is the same as the mass concentration of the ionic liquid in the dilute chamber recovered liquid; the volume ratio of the dilute chamber initial solution, the concentrated chamber initial solution and the cathode chamber solution is 1-3:1:0.2-1.
[0019] Preferably, the vacuum degree of the reduced pressure distillation is 2 to 30 kPa, the temperature of the reduced pressure distillation is 80 to 120° C., and the time of the reduced pressure distillation is 5 to 15 hours.
[0020] Beneficial effects of the present invention:
[0021] The invention utilizes the working principle of electrodialysis, and under the action of an electric field, the anions and cations of the ionic liquid in the melamine spinning coagulation bath are enriched in the electrodialysis concentration chamber through the anion-cation membrane, and the organic impurities in the melamine spinning coagulation bath are intercepted at the same time, so as to achieve the purpose of removing the organic impurities in the melamine spinning coagulation bath. The method of the invention has low energy consumption, simple equipment, and easy operation. No chemical reagent needs to be added during the treatment process, there is no phase change, no pollution, and the separation efficiency is high. The recovery rate of the ionic liquid can reach more than 95%, and the purity can reach more than 99%. DETAILED DESCRIPTION
[0022] The present invention provides a method for recovering ionic liquid in a melamine spinning coagulation bath by electrodialysis, comprising the following steps:
[0023] (1) filtering the melamine spinning coagulation bath to obtain a filtrate;
[0024] (2) subjecting the filtrate to electrodialysis to obtain concentrated chamber recovered liquid and dilute chamber recovered liquid;
[0025] (3) The concentrated chamber recovery liquid is subjected to reduced pressure distillation to obtain an ionic liquid.
[0026] In the present invention, the mass of the ionic liquid in the concentrated chamber recovery liquid in step (2) is preferably 70-90% of the mass of the ionic liquid in the melamine spinning coagulation bath, further preferably 75-88%, and more preferably 82-86%; the dilute chamber recovery liquid is preferably subjected to electrodialysis treatment again, and the concentrated chamber recovery liquid obtained by the two electrodialysis treatments is subjected to reduced pressure distillation to obtain the ionic liquid.
[0027] In the present invention, the mass concentration of the ionic liquid in the melamine spinning coagulation bath is preferably 2 to 10%, more preferably 3.5 to 8%, and even more preferably 4.5 to 7.5%.
[0028] In the present invention, the ionic liquid preferably comprises one or more of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium dimethyl phosphate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-methyl-1,5-diazabicyclo[4.3.0]-5-nonene trimethyl phosphate and 1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonene triethyl phosphate.
[0029] In the present invention, the filtration accuracy of step (1) is preferably 5 to 65 μm, more preferably 45 to 60 μm, and more preferably 50 to 55 μm. The filtration step can remove insoluble impurities in the melamine spinning coagulation bath, such as the rubber particles dripping during the spinning process, the waste silk during the molding process, and other visible impurities.
[0030] In the present invention, the voltage of the electrodialysis treatment is preferably 40 to 80 V, more preferably 50 to 75 V, and more preferably 60 to 65 V; the current of the electrodialysis treatment is preferably 0.5 to 3.0 A, more preferably 1.8 to 2.5 A, and more preferably 2 to 2.2 A; the time of each electrodialysis treatment is preferably 1 to 5 h, more preferably 1.5 to 3 h, and more preferably 2 to 2.5 h. The electrodialysis treatment can separate the ionic liquid in the melamine spinning coagulation bath from the soluble organic impurities, and the soluble organic impurities include melamine, paraformaldehyde, hydroxymethyl melamine, melamine formaldehyde dimer, melamine formaldehyde polymer, etc.
[0031] In the present invention, in the electrodialysis treatment of step (2), the initial solution of the dilute chamber is preferably a filtrate, the initial solution of the concentrated chamber is preferably water, and the cathode chamber solution is preferably an ionic liquid aqueous solution. The mass concentration of the ionic liquid in the ionic liquid aqueous solution is preferably the same as the mass concentration of the ionic liquid in the melamine spinning coagulation bath.
[0032] In the present invention, the volume ratio of the dilute chamber initial solution, the concentrated chamber initial solution and the cathode chamber solution is preferably 1-3:1:0.2-1, more preferably 1.5-2.5:1:0.5-0.8, and more preferably 2:1:0.6.
[0033] In the present invention, when the dilute chamber recovered liquid is subjected to electrodialysis treatment again, the dilute chamber initial solution is preferably the dilute chamber recovered liquid, the concentrated chamber initial solution is preferably water, and the cathode chamber solution is preferably an ionic liquid aqueous solution. The mass concentration of the ionic liquid in the ionic liquid aqueous solution is preferably the same as the mass concentration of the ionic liquid in the dilute chamber recovered liquid; the volume ratio of the dilute chamber initial solution, the concentrated chamber initial solution and the cathode chamber solution is preferably 1-3:1:0.2-1, further preferably 1.5-2.5:1:0.5-0.8, and more preferably 2:1:0.6.
[0034] In the present invention, the vacuum degree of the reduced pressure distillation is preferably 2 to 30 kPa, more preferably 5 to 25 kPa, and more preferably 10 to 20 kPa; the temperature of the reduced pressure distillation is preferably 80 to 120°C, more preferably 90 to 110°C, and more preferably 95 to 100°C; the time of the reduced pressure distillation is preferably 5 to 15 h, more preferably 7.5 to 12.5 h, and more preferably 8 to 10 h.
[0035] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.
[0036] Example 1
[0037] A melamine spinning coagulation bath containing 4.5% ionic liquid (1-allyl-3-methylimidazolium chloride) was passed through a filter with an accuracy of 60 μm to remove visible impurities such as rubber particles and waste fibers to obtain a filtrate.
[0038] 30L of filtrate was added to the dilute chamber of the electrodialysis device, 15L of water was added to the concentrate chamber of the electrodialysis device, 9L of 4.5% mass concentration of 1-allyl-3-methylimidazolium chloride aqueous solution was used as the cathode solution, and electrodialysis was carried out at 50V and 2.0A for 2h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid. The conductivity of the dilute chamber recovery liquid reached 1045μs / cm, and the conductivity of the concentrate chamber recovery liquid reached 11785μs / cm. The mass of the ionic liquid in the concentrate chamber recovery liquid reached 85% of the mass of the ionic liquid in the melamine spinning coagulation bath.
[0039] 30L of dilute chamber recovery liquid was added to the dilute chamber of the electrodialysis device, 15L of water was added to the concentrate chamber of the electrodialysis device, 9L of 1-allyl-3-methylimidazolium chloride aqueous solution was used as the cathode solution (the mass concentration of ionic liquid in the 1-allyl-3-methylimidazolium chloride aqueous solution was the same as the mass concentration of ionic liquid in the dilute chamber recovery liquid), and electrodialysis was performed again at 50V and 2.0A for 2h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid.
[0040] The concentrated chamber recovery liquid obtained by two electrodialysis treatments was distilled under reduced pressure at 25 kPa and 120° C. for 8 h to obtain the ionic liquid 1-allyl-3-methylimidazolium chloride.
[0041] In this embodiment, the total recovery rate of the ionic liquid 1-allyl-3-methylimidazolium chloride is 95.5%, and the purity is 99.5%.
[0042] Example 2
[0043] A melamine spinning coagulation bath containing 5% ionic liquid (1-butyl-3-methylimidazolium chloride) was passed through a filter with an accuracy of 60 μm to remove visible impurities such as rubber particles and waste fibers to obtain a filtrate.
[0044] 30L of filtrate was added to the dilute chamber of the electrodialysis device, 15L of water was added to the concentrate chamber of the electrodialysis device, 9L of 5% mass concentration of 1-butyl-3-methylimidazolium chloride aqueous solution was used as the cathode solution, and electrodialysis was carried out at 60V and 2.5A for 2h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid. The conductivity of the dilute chamber recovery liquid reached 1245μs / cm, and the conductivity of the concentrate chamber recovery liquid reached 12315μs / cm. The mass of the ionic liquid in the concentrate chamber recovery liquid reached 88% of the mass of the ionic liquid in the melamine spinning coagulation bath.
[0045] 30L of dilute chamber recovery liquid was added to the dilute chamber of the electrodialysis device, 15L of water was added to the concentrate chamber of the electrodialysis device, 9L of 1-butyl-3-methylimidazolium chloride aqueous solution was used as the cathode solution (the mass concentration of ionic liquid in the 1-butyl-3-methylimidazolium chloride aqueous solution was the same as the mass concentration of ionic liquid in the dilute chamber recovery liquid), and electrodialysis was performed again at 60V and 2.5A for 2h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid.
[0046] The concentrated chamber recovery liquid obtained by two electrodialysis treatments was distilled under reduced pressure at 20 kPa and 110° C. for 7.5 h to obtain the ionic liquid 1-butyl-3-methylimidazolium chloride.
[0047] In this embodiment, the total recovery rate of the ionic liquid 1-butyl-3-methylimidazolium chloride is 95.8%, and the purity is 99.4%.
[0048] Example 3
[0049] A melamine spinning coagulation bath containing 3.5% ionic liquid (1-ethyl-3-methylimidazole dimethyl phosphate) was passed through a filter with an accuracy of 50 μm to remove visible impurities such as rubber particles and waste fibers to obtain a filtrate.
[0050] 20L of filtrate was added to the dilute chamber of the electrodialysis device, 10L of water was added to the concentrate chamber of the electrodialysis device, 8L of 3.5% 1-ethyl-3-methylimidazole dimethyl phosphate aqueous solution was used as the cathode solution, and electrodialysis was performed at 65V and 1.8A for 1.5h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid. The conductivity of the dilute chamber recovery liquid reached 452μs / cm, and the conductivity of the concentrate chamber recovery liquid reached 10128μs / cm. The mass of the ionic liquid in the concentrate chamber recovery liquid reached 85% of the mass of the ionic liquid in the melamine spinning coagulation bath.
[0051] 20L of dilute chamber recovery liquid was added to the dilute chamber of the electrodialysis device, 10L of water was added to the concentrate chamber of the electrodialysis device, 8L of 1-ethyl-3-methylimidazole dimethyl phosphate salt aqueous solution was used as the cathode solution (the mass concentration of ionic liquid in the 1-ethyl-3-methylimidazole dimethyl phosphate salt aqueous solution was the same as the mass concentration of ionic liquid in the dilute chamber recovery liquid), and electrodialysis was performed again at 65V and 1.8A for 1.5h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid.
[0052] The concentrated chamber recovery liquid obtained by two electrodialysis treatments was distilled under reduced pressure at 15 kPa and 100° C. for 10 h to obtain the ionic liquid 1-ethyl-3-methylimidazole dimethyl phosphate.
[0053] In this embodiment, the total recovery rate of the ionic liquid 1-ethyl-3-methylimidazole dimethyl phosphate salt is 96.25%, and the purity is 99.2%.
[0054] Example 4
[0055] A melamine spinning coagulation bath containing 5% ionic liquid (1-ethyl-3-methylimidazolium acetate) was passed through a filter with an accuracy of 65 μm to remove visible impurities such as rubber particles and waste fibers to obtain a filtrate.
[0056] 40L of filtrate was added into the dilute chamber of the electrodialysis device, 20L of water was added into the concentrate chamber of the electrodialysis device, 20L of 5% mass concentration of 1-ethyl-3-methylimidazole acetate aqueous solution was used as the cathode solution, and electrodialysis was carried out at 60V and 2.2A for 3h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid. The conductivity of the dilute chamber recovery liquid reached 623μs / cm, and the conductivity of the concentrate chamber recovery liquid reached 11128μs / cm. The mass of the ionic liquid in the concentrate chamber recovery liquid reached 82% of the mass of the ionic liquid in the melamine spinning coagulation bath.
[0057] 40L of dilute chamber recovered liquid was added to the dilute chamber of the electrodialysis device, 20L of water was added to the concentrate chamber of the electrodialysis device, 20L of 1-ethyl-3-methylimidazolium acetate aqueous solution was used as the cathode solution (the mass concentration of ionic liquid in the 1-ethyl-3-methylimidazolium acetate aqueous solution was the same as the mass concentration of ionic liquid in the dilute chamber recovered liquid), and electrodialysis was performed again at 60V and 2.2A for 3h to obtain dilute chamber recovered liquid and concentrate chamber recovered liquid.
[0058] The concentrated chamber recovery liquid obtained by two electrodialysis treatments was distilled under reduced pressure at 8 kPa and 90° C. for 12.5 h to obtain the ionic liquid 1-ethyl-3-methylimidazolium acetate.
[0059] In this embodiment, the total recovery rate of the ionic liquid 1-ethyl-3-methylimidazolium acetate is 95.14%, and the purity is 99.3%.
[0060] Example 5
[0061] A melamine spinning coagulation bath containing an ionic liquid (1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonenyl triethyl phosphate) with a mass concentration of 7.5% was passed through a filter with an accuracy of 55 μm to remove visible impurities such as rubber particles and waste fibers to obtain a filtrate.
[0062] 50L of filtrate was added to the dilute chamber of the electrodialysis device, 25L of water was added to the concentrate chamber of the electrodialysis device, 5L of 7.5% 1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonene phosphate triethyl aqueous solution was used as the cathode solution, and electrodialysis was performed at 75V and 2.0A for 2.5h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid. The conductivity of the dilute chamber recovery liquid reached 1523μs / cm, and the conductivity of the concentrate chamber recovery liquid reached 13452μs / cm. The mass of the ionic liquid in the concentrate chamber recovery liquid reached 75% of the mass of the ionic liquid in the melamine spinning coagulation bath.
[0063] 50 L of dilute chamber recovery liquid was added to the dilute chamber of the electrodialysis device, 25 L of water was added to the concentrate chamber of the electrodialysis device, and 5 L of 1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonenyl triethyl phosphate aqueous solution was used as the cathode solution (the mass concentration of ionic liquid in the 1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonenyl triethyl phosphate aqueous solution was the same as the mass concentration of ionic liquid in the dilute chamber recovery liquid), and electrodialysis was performed again at 75 V and 2.0 A for 2.5 h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid.
[0064] The concentrated chamber recovery liquid obtained by two electrodialysis treatments was distilled under reduced pressure at 10 kPa and 95° C. for 5 h to obtain the ionic liquid 1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonenyl triethyl phosphate.
[0065] In this embodiment, the total recovery rate of the ionic liquid 1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonenyl triethyl phosphate is 95%, and the purity is 99.6%.
[0066] Example 6
[0067] A melamine spinning coagulation bath containing 8% ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate) was passed through a filter with an accuracy of 45 μm to remove visible impurities such as rubber particles and waste fibers to obtain a filtrate.
[0068] 50L of filtrate was added to the dilute chamber of the electrodialysis device, 25L of water was added to the concentrate chamber of the electrodialysis device, and 12.5L of 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution with a mass concentration of 8% was used as the cathode solution. Electrodialysis was carried out at 75V and 2.0A for 3 hours to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid. The conductivity of the dilute chamber recovery liquid reached 1856μs / cm, and the conductivity of the concentrate chamber recovery liquid reached 15487μs / cm. The mass of the ionic liquid in the concentrate chamber recovery liquid reached 86% of the mass of the ionic liquid in the melamine spinning coagulation bath.
[0069] 50 L of dilute chamber recovery liquid was added to the dilute chamber of the electrodialysis device, 25 L of water was added to the concentrate chamber of the electrodialysis device, 12.5 L of 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution was used as the cathode solution (the mass concentration of ionic liquid in the 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous solution was the same as the mass concentration of ionic liquid in the dilute chamber recovery liquid), and electrodialysis was performed again at 75 V and 2.0 A for 3 h to obtain dilute chamber recovery liquid and concentrate chamber recovery liquid.
[0070] The concentrated chamber recovery liquid obtained by two electrodialysis treatments was distilled under reduced pressure at 5 kPa and 80° C. for 15 h to obtain the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate.
[0071] In this embodiment, the total recovery rate of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate is 96.08%, and the purity is 99.8%.
[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for recovering ionic liquid in a melamine spinning coagulation bath by electrodialysis, characterized in that: The following steps are included: (1) filtering the melamine spinning coagulation bath to obtain a filtrate; (2) subjecting the filtrate to electrodialysis to obtain concentrated chamber recovered liquid and dilute chamber recovered liquid; (3) The concentrated chamber recovery liquid is subjected to reduced pressure distillation to obtain an ionic liquid.
2. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 1, characterized in that: The mass of the ionic liquid in the concentrated chamber recovery liquid in step (2) is 70-90% of the mass of the ionic liquid in the melamine spinning coagulation bath; the dilute chamber recovery liquid is subjected to electrodialysis treatment again, and the concentrated chamber recovery liquid obtained by the two electrodialysis treatments is subjected to reduced pressure distillation to obtain the ionic liquid.
3. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 1 or 2, characterized in that: The mass concentration of the ionic liquid in the melamine spinning coagulation bath is 2-10%.
4. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 3, characterized in that: The ionic liquid comprises one or more of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium dimethyl phosphate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-methyl-1,5-diazabicyclo[4.3.0]-5-nonene trimethyl phosphate and 1-ethyl-1,5-diazabicyclo[4.3.0]-5-nonene triethyl phosphate.
5. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 4, characterized in that: The filtration accuracy in step (1) is 5 to 65 μm.
6. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 5, characterized in that: The voltage of the electrodialysis treatment is 40 to 80 V, the current of the electrodialysis treatment is 0.5 to 3.0 A, and the time of each electrodialysis treatment is 1 to 5 hours.
7. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 1, characterized in that: In the electrodialysis treatment of step (2), the initial solution of the dilute chamber is the filtrate, the initial solution of the concentrated chamber is water, and the solution of the cathode chamber is an ionic liquid aqueous solution. The mass concentration of the ionic liquid in the ionic liquid aqueous solution is the same as the mass concentration of the ionic liquid in the melamine spinning coagulation bath.
8. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 7, characterized in that: The volume ratio of the initial solution of the dilute chamber, the initial solution of the concentrated chamber and the solution of the cathode chamber is 1-3:1:0.2-1.
9. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 2, characterized in that: The dilute chamber recovered liquid is subjected to electrodialysis treatment again, wherein the dilute chamber initial solution is the dilute chamber recovered liquid, the concentrated chamber initial solution is water, and the cathode chamber solution is an ionic liquid aqueous solution, wherein the mass concentration of the ionic liquid in the ionic liquid aqueous solution is the same as the mass concentration of the ionic liquid in the dilute chamber recovered liquid; the volume ratio of the dilute chamber initial solution, the concentrated chamber initial solution and the cathode chamber solution is 1-3:1:0.2-1.
10. The method for recovering ionic liquid in melamine spinning coagulation bath by electrodialysis according to claim 8 or 9, characterized in that: The vacuum degree of the reduced pressure distillation is 2-30 kPa, the temperature of the reduced pressure distillation is 80-120° C., and the time of the reduced pressure distillation is 5-15 hours.