Anion exchange membrane for acid recovery based on cross-linked network structure pypech / pva / pi diffusion dialysis, preparation method and application thereof
By introducing a cross-linked network structure of PyPECH/PVA/PI into an anion exchange membrane, the problem of the extreme hydrophilicity of polyvinyl alcohol limiting the treatment of acidic wastewater was solved, and the stability and diffusion performance of the membrane were improved. A green and environmentally friendly preparation method was adopted.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANHUI UNIVERSITY OF ARCHITECTURE
- Filing Date
- 2024-01-30
- Publication Date
- 2026-07-21
Smart Images
Figure CN117942789B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of anion exchange membrane preparation technology, specifically to anion exchange membrane for acid recovery via diffusion dialysis based on a cross-linked network structure (PyPECH / PVA / PI), its preparation method, and its application. Background Technology
[0002] Numerous methods exist for treating acidic wastewater, including solvent extraction, evaporation, neutralization, direct treatment, crystallization, thermal decomposition, and diffusion dialysis. Among these, diffusion dialysis has become a representative method in the field of acidic wastewater treatment due to its low cost and low energy consumption. Anion exchange membranes (AEMs), as the most important component in the diffusion dialysis process, are receiving increasing attention from the academic community. However, the extreme hydrophilicity of polyvinyl alcohol (PVA), the most common membrane material, limits its widespread application in the treatment of acidic wastewater.
[0003] In view of the above-mentioned defects, the inventors of this invention have finally obtained this invention after a long period of research and practice. Summary of the Invention
[0004] The purpose of this invention is to solve the problem that the extreme hydrophilicity of polyvinyl alcohol (PVA) limits its widespread application in the field of acidic wastewater treatment, and to provide an anion exchange membrane for diffusion dialysis acid recovery based on a cross-linked network structure, PyPECH / PVA / PI, its preparation method, and its application.
[0005] To achieve the above objectives, the invention discloses a method for preparing anion exchange membrane for diffusion dialysis acid recovery based on a cross-linked network structure of PyPECH / PVA / PI, comprising the following steps:
[0006] S1, dissolve polyvinyl alcohol (PVA), polyimide (PI) and polyepoxychloropropane (PECH) in dimethyl sulfoxide, heat to 90°C while stirring, and continue stirring for 2 hours to obtain a homogeneous mixture;
[0007] S2, the mixture obtained in step S1 is coated on glass and film is formed by evaporation;
[0008] S3, Immerse the membrane obtained in step S2 in bipyridine reagent, take it out after 8 hours, wash off the bipyridine on the membrane surface, cover both sides of the membrane with polytetrafluoroethylene membrane, and carry out crosslinking and quaternization reaction.
[0009] S4. After the reaction in step S3 is completed, the membrane is removed at room temperature, cleaned with deionized water, dried, and then heat-treated to obtain anion exchange membrane.
[0010] In step S1, the mass ratio of polyepoxychloropropane, polyvinyl alcohol, and polyimide is 0.3:1 to 1.5:1.
[0011] In step S1, the polyimide is a soluble polyimide.
[0012] In step S2, the specific conditions for film formation by evaporation are: oven temperature 80℃ and drying time 48h.
[0013] In step S3, the crosslinking and quaternization reactions are carried out at a temperature of 80°C, a pressure of 1 MPa, and a reaction time of 8 hours.
[0014] In step S4, the initial thickness of the membrane is 90μm-110μm.
[0015] In step S4, the heat treatment is as follows: the peeled film is heated from 25°C to 120°C at a rate of 10°C / h, and then cooled down by 10°C every 2 hours in the oven to 25°C, and this process is repeated three times.
[0016] This invention also discloses an anion exchange membrane for acid recovery from diffusion dialysis based on a cross-linked network structure, prepared by the above-described method, and its application in the treatment of acidic wastewater.
[0017] In ethylene-vinyl alcohol copolymer (EVOH), the number of hydroxyl groups is much smaller than that in polyvinyl alcohol (PVA), therefore its hydrophilicity is not as extreme as that of PVA. Furthermore, polyimide (PI) is a material with good stability and excellent mechanical properties; its application in membrane fabrication can improve the practical performance of the membrane.
[0018] Polyimide (PI) and polyvinyl alcohol (PVA) are jointly introduced into the membrane preparation process. These two substances have similar structures and properties and exhibit good compatibility. Two different network structures are formed in the membrane structure through cross-linking. These two network structures, which are respectively cross-linked with polyimide (PI) and polyepoxychloropropane and polyvinyl alcohol (PVA), also undergo cross-linking with each other. The intertwining of these different network structures greatly enhances the stability of the membrane structure. It also significantly limits the excessive swelling of polyvinyl alcohol (PVA) in water, ensuring the dimensional stability of the membrane. A slight degree of phase separation exists between the different components, which also improves the diffusion dialysis performance of the membrane.
[0019] Because polyepoxychloropropane (PECH) contains chloromethyl groups on its side chains, and these chloromethyl groups react with the tertiary amines in the polyimide, the use of carcinogenic chloromethylating agents (such as chloromethyl ether) can be avoided during the quaternization process. Therefore, using quaternized polyepoxychloropropane to provide ion exchange sites for anion exchange membranes is a simple, safe, and environmentally friendly preparation method. Quaternized polyepoxychloropropane (PyPECH) was successfully prepared through the quaternization reaction of bipyridine with polyepoxychloropropane (PECH), and a crosslinking reaction also occurred.
[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0021] 1. This invention uses polyimide (PI) and polyvinyl alcohol (PVA) together to prepare anion exchange membranes. The two have similar structures and can be dissolved in the same organic solvent, which greatly reduces the complexity of the preparation process. Furthermore, there will be slight phase separation between different components, which has a positive impact on improving the diffusion dialysis performance of the membrane.
[0022] 2. Two different network structures were constructed in the membrane, which were respectively composed of polyimide (PI), polyvinyl alcohol (PVA) and polyepoxychloropropane (PECH) and bipyridine crosslinked together. These two network structures intertwined and wrapped around each other, and crosslinked with each other, which greatly increased the stability of the membrane structure, improved the mechanical properties and stability of the membrane, and limited the swelling of the membrane, thus ensuring the dimensional stability of the membrane in practical applications.
[0023] 3. The polyepoxychloropropane (PECH) used has chloromethyl groups on its side chains, which avoids the use of carcinogenic chloromethylating agents (such as chloromethyl ether) during the quaternization process. Therefore, using quaternized polyepoxychloropropane (PyPECH) to provide ion exchange sites for anion exchange membranes is a simple, safe, and environmentally friendly preparation method. The prepared quaternized polyepoxychloropropane (PyPECH) is a linear polymer that penetrates into the stable network structure constructed from polyimide (PI) and polyvinyl alcohol (PVA) and is firmly fixed within it.
[0024] 4. This invention uses polyimide (PI), polyvinyl alcohol (PVA), and polyepoxychloropropane (PECH), polymer materials with excellent chemical stability, and adopts a green, environmentally friendly, simple, and efficient preparation method. It avoids the chloromethylation process in the traditional preparation of anion exchange membranes, and the prepared membrane product has potential application prospects. Attached Figure Description
[0025] Figure 1Scanning electron microscope images of the prepared anion exchange membranes: A: Example 1, B: Example 2, C: Example 3, D: Example 4, E: Example 5;
[0026] Figure 2 Transmission electron microscope images of the prepared anion exchange membranes: A: Example 1, B: Example 2, C: Example 3, D: Example 4, E: Example 5;
[0027] Figure 3 Infrared spectra of the prepared anion exchange membranes: A: Example 1, B: Example 2, C: Example 3, D: Example 4, E: Example 5;
[0028] Figure 4 Thermogravimetric analysis diagrams of the prepared anion exchange membranes: A: Example 1, B: Example 2, C: Example 3, D: Example 4, E: Example 5. Detailed Implementation
[0029] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.
[0030] The components and their contents in Examples 1-5 are shown in Table 1:
[0031] Table 1. Components and their contents in Examples 1-5
[0032] Polyepoxychloropropane (PECH) 0.15g 0.3g 0.45g 0.6g 0.75g Polyvinyl alcohol (PVA) 0.25g 0.25g 0.25g 0.25g 0.25g Polyimide (PI) 0.25g 0.25g 0.25g 0.25g 0.25g Dimethyl sulfoxide (DMSO) 50mL 50mL 50mL 50mL 50mL
[0033] Example 1
[0034] (1) Accurately weigh 0.15g of polyepoxychloropropane (PECH), 0.25g of polyvinyl alcohol (PVA), and 0.25g of polyimide (PI), and dissolve them in 50mL of dimethyl sulfoxide (DMSO) by stirring at 90℃ for 2h.
[0035] (2) The prepared uniform mixture was coated on glass, placed in an 80°C oven, dried for 48 hours, and then formed into a film by evaporation.
[0036] (3) The prepared membrane was immersed in bipyridine reagent and removed after 8 hours. The bipyridine on the membrane surface was washed off. Both sides of the membrane were covered with polytetrafluoroethylene membrane and kept at 80°C and 1 MPa pressure using a plate heater for crosslinking and quaternization reaction for 8 hours.
[0037] (4) After completion, the membrane was removed from the oven at room temperature and cleaned with deionized water. After drying, it was heated to 120°C in an oven, and then the temperature was lowered by 10°C to 25°C every 2 hours. This process was repeated three times to prepare the anion exchange membrane. The process involves not only thermal cross-linking but also molecular rearrangement.
[0038] Example 2
[0039] (1) Accurately weigh 0.3g of polyepoxychloropropane (PECH), 0.25g of polyvinyl alcohol (PVA), and 0.25g of polyimide (PI), and dissolve them in 50mL of dimethyl sulfoxide (DMSO) by stirring at 90℃ for 2h.
[0040] (2) The prepared uniform mixture was coated on glass, placed in an 80°C oven, dried for 48 hours, and then formed into a film by evaporation.
[0041] (3) The prepared membrane was immersed in bipyridine reagent and removed after 8 hours. The bipyridine on the membrane surface was washed off. Both sides of the membrane were covered with polytetrafluoroethylene membrane and kept at 80°C and 1 MPa pressure using a plate heater for crosslinking and quaternization reaction for 8 hours.
[0042] (4) After completion, the membrane was removed from the oven at room temperature and cleaned with deionized water. After drying, it was heated to 120°C in an oven, and then the temperature was lowered by 10°C to 25°C every 2 hours. This process was repeated three times to prepare the anion exchange membrane. The process involves not only thermal cross-linking but also molecular rearrangement.
[0043] Example 3
[0044] (1) Accurately weigh 0.45g of polyepoxychloropropane (PECH), 0.25g of polyvinyl alcohol (PVA), and 0.25g of polyimide (PI), and dissolve them in 50mL of dimethyl sulfoxide (DMSO) by stirring at 90℃ for 2h.
[0045] (2) The prepared uniform mixture was coated on glass, placed in an 80°C oven, dried for 48 hours, and then formed into a film by evaporation.
[0046] (3) The prepared membrane was immersed in bipyridine reagent and removed after 8 hours. The bipyridine on the membrane surface was washed off. Both sides of the membrane were covered with polytetrafluoroethylene membrane and kept at 80°C and 1 MPa pressure using a plate heater for crosslinking and quaternization reaction for 8 hours.
[0047] (4) After completion, the membrane was removed from the oven at room temperature and cleaned with deionized water. After drying, it was heated to 120°C in an oven, and then the temperature was lowered by 10°C to 25°C every 2 hours. This process was repeated three times to prepare the anion exchange membrane. The process involves not only thermal cross-linking but also molecular rearrangement.
[0048] Example 4
[0049] (1) Accurately weigh 0.6g of polyepoxychloropropane (PECH), 0.25g of polyvinyl alcohol (PVA), and 0.25g of polyimide (PI), and dissolve them in 50mL of dimethyl sulfoxide (DMSO) by stirring at 90℃ for 2h.
[0050] (2) The prepared uniform mixture was coated on glass, placed in an 80°C oven, dried for 48 hours, and then formed into a film by evaporation.
[0051] (3) The prepared membrane was immersed in bipyridine reagent and removed after 8 hours. The bipyridine on the membrane surface was washed off. Both sides of the membrane were covered with polytetrafluoroethylene membrane and kept at 80°C and 1 MPa pressure using a plate heater for crosslinking and quaternization reaction for 8 hours.
[0052] (4) After completion, the membrane was removed from the oven at room temperature and cleaned with deionized water. After drying, it was heated to 120°C in an oven, and then the temperature was lowered by 10°C to 25°C every 2 hours. This process was repeated three times to prepare the anion exchange membrane. The process involves not only thermal cross-linking but also molecular rearrangement.
[0053] Example 5
[0054] (1) Accurately weigh 0.75g of polyepoxychloropropane (PECH), 0.25g of polyvinyl alcohol (PVA), and 0.25g of polyimide (PI), and dissolve them in 50mL of dimethyl sulfoxide (DMSO) by stirring at 90℃ for 2h.
[0055] (2) The prepared uniform mixture was coated on glass, placed in an 80°C oven, dried for 48 hours, and then formed into a film by evaporation.
[0056] (3) The prepared membrane was immersed in bipyridine reagent and removed after 8 hours. The bipyridine on the membrane surface was washed off. Both sides of the membrane were covered with polytetrafluoroethylene membrane and kept at 80°C and 1 MPa pressure using a plate heater for crosslinking and quaternization reaction for 8 hours.
[0057] (4) After completion, the membrane was removed from the oven at room temperature and cleaned with deionized water. After drying, it was heated to 120°C in an oven, and then the temperature was lowered by 10°C to 25°C every 2 hours. This process was repeated three times to prepare the anion exchange membrane. The process involves not only thermal cross-linking but also molecular rearrangement.
[0058] The five membranes obtained in Examples 1 to 5 were subjected to diffusion dialysis experiments, and the data results are shown in Table 2.
[0059] Table 2 shows the diffusion dialysis test results of the five membranes obtained in Examples 1-5.
[0060]
[0061] The water absorption rate and linear expansion rate of the five membranes obtained in Examples 1-5 were tested, and the data results are shown in Table 3:
[0062] Table 3 shows the experimental test results of water absorption rate and linear expansion rate of the five types of membranes obtained in Examples 1-5.
[0063] Water absorption rate 45％ 62％ 82％ 100％ 135％ linear expansion rate 10％ 11.6％ 13.5％ 15％ 18％ Ion exchange capacity (mmol / g) 0.7 0.95 1.2 1.5 1.7
[0064] Tensile strength and elongation at break were tested on the five types of films obtained in Examples 1-5. The data results are shown in Table 4.
[0065] Table 4 shows the experimental test results of tensile strength and elongation at break of the five types of membranes obtained in Examples 1-5.
[0066] Tensile properties (MPa) 53.2 49.8 43.4 39.1 37.2 Elongation at break 65.2％ 77.5％ 110.7％ 140.4％ 163.4％
[0067] The five membranes obtained in Examples 1-5 were characterized as follows: The surface morphology of anion exchange membranes with different contents of quaternized polyepoxychloropropane (PyPECH) was analyzed using scanning electron microscopy (SEM), see [see details]. Figure 1 As can be seen from the figure, the membrane surface is uniform and dense, with no cracks or pores observed, indicating good compatibility between different components. Furthermore, phase separation of anion exchange membranes with different contents of quaternized polyepoxychloropropane (PyPECH) was performed using transmission electron microscopy (TEM), see [Figure number missing]. Figure 2 A slight phase separation was observed in the membrane with increasing quaternized polyepoxychloropropane (PyPECH) content, which has a positive impact on improving the membrane's diffusion dialysis acid recovery capacity. Figure 1 and Figure 2 It can be seen that as the PECH content increases, phase separation increases, which is conducive to the formation of ion channels, facilitates the passage of ions, and improves the ion throughput.
[0068] The prepared anion exchange membrane was analyzed using infrared spectroscopy. (See figure) Figure 3 3450-3200cm -1 The characteristic peaks within this range correspond to the hydroxyl groups (-OH) in polyvinyl alcohol (PVA). 3000-2800 cm⁻¹ -1 The characteristic peaks within this range are due to the stretching vibrations of the CH bonds in polyepoxychloropropane (PECH). 1440 cm⁻¹ -1 The characteristic peaks at 1150-1050 cm⁻¹ are due to the bending vibrations of asymmetric and symmetric C-H bonds in polyepoxychloropropane (PECH). -1 The characteristic peaks correspond to Si-OC, Si-O-Si, and COC bonds on the film, which are formed by PVA self-crosslinking. (1640 cm⁻¹) -1 The characteristic peak at [location] is caused by the quaternized pyridine ring. Infrared spectroscopy results indicate that the synthesized PyPECH indeed penetrates into the network structure constructed from self-crosslinked polyvinyl alcohol (PVA), PI, and PECH. Figure 3It can be seen that the peaks at 3200-3450 are for hydroxyl and NH bonds, the peaks at 2800-3000 are for -CH2, and the peak at 1440 is for quaternary ammonium groups, proving that the prepared anion exchange membrane is successful.
[0069] The prepared anion exchange membrane was subjected to thermogravimetric analysis using a thermogravimetric analyzer, such as... Figure 4 As shown in the TGA curves, the weight loss process of the membrane sample can be divided into four stages: the first stage, with a temperature range of 150-200℃, corresponds to the evaporation of bound water in the membrane matrix; the second stage, with a temperature range of 250-320℃, corresponds to the degradation of pyridine groups; the third stage, with a temperature range of 320-420℃, corresponds to the decomposition of unreacted chloromethyl groups and the aliphatic backbone of PECH; and the fourth stage, with a temperature range of 420-600℃, corresponds to the mass loss caused by the main chain breakage and decomposition of PVA and PI. Figure 4 It can be seen that the thermal decomposition temperature of the membrane AE is greater than 248 degrees (the temperature at which 5% weight loss occurs), indicating that it has good thermal temperature properties.
[0070] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.
Claims
1. A method for preparing anion exchange membrane for acid recovery via diffusion dialysis based on a cross-linked network structure of PyPECH / PVA / PI, characterized in that, Includes the following steps: S1, dissolve polyvinyl alcohol, polyimide and polyepoxychloropropane in dimethyl sulfoxide, heat to 90°C while stirring, and continue stirring for 2 hours to obtain a homogeneous mixture; S2, the mixture obtained in step S1 is coated on glass and film is formed by evaporation; S3, Immerse the membrane obtained in step S2 in bipyridine reagent, take it out after 8 hours, wash off the bipyridine on the membrane surface, cover both sides of the membrane with polytetrafluoroethylene membrane, and carry out crosslinking and quaternization reaction. S4. After the reaction in step S3 is completed, the membrane is removed at room temperature, cleaned with deionized water, dried, and then heat-treated to obtain anion exchange membrane.
2. The method for preparing anion exchange membrane for acid recovery via diffusion dialysis based on a cross-linked network structure as described in claim 1, characterized in that, In step S1, the mass ratio of polyepoxychloropropane, polyvinyl alcohol, and polyimide is 0.3:1 to 1.5:
1.
3. The method for preparing anion exchange membrane for acid recovery via diffusion dialysis based on a cross-linked network structure as described in claim 1, characterized in that, In step S1, the polyimide is a soluble polyimide.
4. The method for preparing anion exchange membrane for acid recovery via diffusion dialysis based on a cross-linked network structure as described in claim 1, characterized in that, In step S2, the specific conditions for film formation by evaporation are: oven temperature 80℃ and drying time 48h.
5. The method for preparing anion exchange membrane for acid recovery via diffusion dialysis based on a cross-linked network structure as described in claim 1, characterized in that, In step S3, the crosslinking and quaternization reactions are carried out at a temperature of 80°C, a pressure of 1 MPa, and a reaction time of 8 hours.
6. The method for preparing anion exchange membrane for acid recovery via diffusion dialysis based on a cross-linked network structure as described in claim 1, characterized in that, In step S4, the initial thickness of the membrane is 90μm-110μm.
7. The method for preparing anion exchange membrane for acid recovery via diffusion dialysis based on a cross-linked network structure as described in claim 1, characterized in that, In step S4, the heat treatment is as follows: the peeled film is heated from 25°C to 120°C at a rate of 10°C / h, and then cooled down by 10°C every 2 hours in the oven to 25°C, and this process is repeated three times.
8. An anion exchange membrane for acid recovery from diffusion dialysis based on a cross-linked network structure, prepared by the preparation method according to any one of claims 1 to 7.
9. The application of the PyPECH / PVA / PI diffusion dialysis acid recovery anion exchange membrane based on a cross-linked network structure as described in claim 8 in the treatment of acidic wastewater by diffusion dialysis.