Cationic membrane as well as preparation method and application thereof

Abstract

The invention provides a cationic membrane as well as a preparation method and application thereof. The preparation method of the cationic membrane comprises the following steps: S1, prepolymerization: dissolving a first unsaturated monomer containing a halogen group, a second unsaturated monomer and an initiator in an organic solvent, and carrying out polymerization reaction after dissolving to obtain a membrane casting solution; s2, curing: coating a supporting base material with the membrane casting solution, and curing to form a membrane; s3, functional modification: transferring a membrane into a sulfate solution for soaking after the membrane is completely cured to form a membrane, and fully reacting to obtain a functional modified cationic membrane; the molar ratio of the first unsaturated monomer to the second unsaturated monomer is 1: (0.03-0.10). According to the preparation method provided by the invention, the use of dangerous chemicals such as concentrated sulfuric acid and chlorosulfonic acid in the traditional functional modification step is avoided, green production of the high-performance cationic membrane is realized, accurate regulation and control of the thickness of the cationic membrane are also realized, and the application of the cationic membrane in the salt concentration test of electrodialysis has good application prospects. And higher current efficiency and lower unit energy consumption are obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and specifically comprises a cationic membrane and a preparation method and application thereof. Background Art

[0002] With the continuous advancement of industrialization and scientific and technological progress, ion exchange membranes are increasingly being used in energy, environmental protection, chemical engineering, and other fields. Cationic membranes, as a key branch of ion exchange membranes, play a key role in electrodialysis, fuel cells, water electrolysis for hydrogen production, heavy metal recovery, and wastewater treatment due to their unique ion-selective permeability. The performance of cationic membranes directly impacts the efficiency and stability of related equipment, making the optimization and innovation of their preparation technologies a research hotspot.

[0003] In the current production of cationic membranes, concentrated sulfuric acid or chlorosulfonic acid is used to carry out sulfonation reaction to achieve functional modification of groups. For example, CN1104556A discloses a cationic exchange membrane and its preparation method, in which slurry is prepared using styrene, a cross-linking agent aromatic diene compound, a softening enhancer and an initiator, and then the membrane is prepared and sulfonated with concentrated sulfuric acid to obtain a cationic exchange membrane. However, the concentrated sulfuric acid or chlorosulfonic acid commonly used in the sulfonation process are both highly dangerous, such as dehydration and corrosiveness, and the large amount of acidic wastewater also produced has a certain degree of impact on the environment. Therefore, developing a method for preparing a cationic membrane with high efficiency, low cost and green sustainability has important scientific significance and application value. Summary of the Invention

[0004] To address the aforementioned issues with the existing technology, the first objective of the present invention is to provide a method for preparing a cationic membrane. By optimizing material selection and introducing unsaturated monomers containing benzyl chloride groups during the cationic membrane preparation process, the use of strong acids such as concentrated sulfuric acid and chlorosulfonic acid during functionalization is avoided, enabling the green production of high-performance cationic membranes and supporting technological advancements in related fields.

[0005] The second object of the present invention is to provide a cationic membrane prepared by the above-mentioned preparation method.

[0006] The third object of the present invention is to provide an application of the cationic membrane described above in electrodialysis.

[0007] To achieve the above first object, the technical solution adopted by the present invention includes:

[0008] The present invention discloses a method for preparing a cationic membrane, comprising the following steps:

[0009] S1, prepolymerization: dissolving the first unsaturated monomer containing a halogen group, the second unsaturated monomer and an initiator in an organic solvent, and performing a polymerization reaction after dissolution to obtain a casting solution;

[0010] S2, solidification: coating the casting solution on the supporting substrate and solidifying it into a film;

[0011] S3. Functional modification: After the membrane is completely solidified, the membrane is transferred to a sulfate solution. After sufficient reaction, a functionally modified cationic membrane is obtained.

[0012] The molar ratio of the first unsaturated monomer to the second unsaturated monomer is 1:0.03 to 0.10; for example, the molar ratio of the first unsaturated monomer to the second unsaturated monomer may be 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.10, etc.

[0013] It is precisely because the more active first unsaturated monomer containing a halogen group is introduced during the prepolymerization process that there is no need to introduce highly dehydrating and corrosive concentrated sulfuric acid or chlorosulfonic acid when functionalizing the membrane. The functional modification of the membrane can be completed by simply immersing the membrane in a sulfate solution (such as sodium sulfate) and heating the reaction, which is safer.

[0014] Furthermore, the first unsaturated monomer includes but is not limited to one of p-vinylbenzyl chloride, m-vinylbenzyl chloride, p-chlorostyrene, m-chlorostyrene, p-bromostyrene and m-bromostyrene;

[0015] The second unsaturated monomer includes, but is not limited to, o-divinylbenzene and / or p-divinylbenzene.

[0016] Furthermore, the initiator includes but is not limited to one or more of dibenzoyl peroxide, dodecyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, diisopropyl peroxydicarbonate, diethylhexyl peroxydicarbonate, azobisisobutyronitrile, azobisisoheptylonitrile, and tetraethylthiuram;

[0017] The organic solvent includes, but is not limited to, one or more of tetrahydrofuran, N-methylpyrrolidone, and N,N-dimethylformamide.

[0018] Further, the molar ratio of the first unsaturated monomer to the initiator is 1:0.002 to 0.05; illustratively, the molar ratio of the first unsaturated monomer to the initiator can be 1:0.002, 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, 1:0.035, 1:0.04, 1:0.045, 1:0.05, etc.

[0019] Furthermore, the molar ratio of the first unsaturated monomer to the organic solvent is 1:0.5-5; illustratively, the molar ratio of the first unsaturated monomer to the organic solvent is 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, etc.

[0020] Furthermore, the polymerization reaction temperature is 40 to 70° C., and the polymerization reaction time is 1 to 4 hours.

[0021] Furthermore, the supporting substrate includes but is not limited to one of non-woven fabric, polypropylene mesh, polyvinyl chloride mesh, nylon mesh, polyester mesh, polyetheretherketone mesh, polyethylene film, and polypropylene film, and its thickness is 0.05 to 0.3 mm.

[0022] Furthermore, the curing reaction temperature is 70 to 100° C., and the curing reaction time is 12 to 24 hours.

[0023] Further, the concentration of the sulfate solution is 10 to 100 g / L;

[0024] The reaction temperature of step S3 is 40-60° C., and the reaction time is 5-18 hours.

[0025] To achieve the above second purpose, the technical solutions adopted by the present invention include:

[0026] The present invention discloses a cationic membrane prepared by the above-mentioned preparation method.

[0027] To achieve the third objective, the present invention employs the following technical solutions:

[0028] The present invention discloses an application of the cationic membrane described above in electrodialysis.

[0029] Beneficial effects of the present invention:

[0030] The present invention develops a highly efficient, low-cost, green and sustainable method for preparing cationic membranes. In this preparation method, a casting solution obtained by polymerizing a first unsaturated monomer containing a halogen group with another unsaturated monomer is selected. This method can eliminate the need to introduce hazardous chemicals such as concentrated sulfuric acid and chlorosulfonic acid when functionally modifying the membrane. Instead, the functional modification can be completed using only mild sulfates, thereby achieving green production of high-performance cationic membranes. Furthermore, the thickness of the cationic membrane can be precisely controlled by changing the concentration ratio of the solution. This method is applied to salt concentration tests in electrodialysis to achieve higher current efficiency and lower unit energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] Figure 1The process flow chart in Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0033] To more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. It should be understood that the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] In addition, unless otherwise specified, the raw materials used in the present invention can be obtained commercially, and any range recorded in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0035] Example 1

[0036] This example provides a method for preparing a cationic membrane. See the process flow chart for Figure 1 , the specific steps are as follows:

[0037] S1. Preparation of prepolymer solution: dissolving p-vinylbenzyl chloride, p-divinylbenzene, and azobisisobutyronitrile (AIBN) in NMP at a molar ratio of 1:0.05:0.005:1, and stirring thoroughly.

[0038] S2, prepolymerization reaction: the above prepolymer solution is heated to 45 ° C and polymerized. After 3 hours, the casting solution is obtained;

[0039] S3, coating the casting solution: the casting solution in S2 is smoothly coated on a polyvinyl chloride (PVC) mesh with a thickness of 0.15 mm using a doctor blade;

[0040] S4, film curing: transfer the polyvinyl chloride (PVC) mesh coated with the casting solution into an oven, set the oven temperature to 90°C, and keep it warm for 12 hours;

[0041] S5. Functional modification: After the membrane is completely solidified, the membrane is removed from the equipment and transferred to a sodium sulfate solution with a concentration of 100 g / L, heated to 50° C., and stirred for 6 hours to obtain a functionally modified cationic membrane.

[0042] The cationic membrane was used in combination with an anionic membrane (purchased from Shandong Tianwei Membrane Technology Co., Ltd., model TWEDA1) to assemble a 4020 electrodialysis membrane stack for salt concentration testing. The effective area of ​​the membrane is 0.05m 2The number of groups is 4. The cathode and anode are titanium plates with iridium and tantalum oxide coatings. The cathode and anode are connected in series. The electrode liquid is 5% sodium sulfate solution. The concentration of the desalination chamber and the concentration chamber is 5% sodium chloride solution. The operating current is 15A (current density 300A / m 2 ), tested at room temperature (25°C) for 1 hour. The results showed that the cationic membrane prepared according to the above scheme had a total thickness of 0.20 mm, an ion exchange capacity of 1.43 mmol / g, and a surface resistance of 3.5 Ω·cm 2 During the electrodialysis membrane component test, the current efficiency was 68.5%, the unit energy consumption was 548.41kwh / t, and the unit processing capacity was 448.57g / (m 2 ·h).

[0043] Comparative Example 1

[0044] This example provides a method for preparing a cationic membrane. See the process flow chart for Figure 1 , the specific steps are as follows:

[0045] S1. Preparation of prepolymer solution: dissolving p-vinylbenzyl chloride, p-divinylbenzene, and azobisisobutyronitrile (AIBN) in NMP at a molar ratio of 1:0.05:0.005:1, and stirring thoroughly.

[0046] S2, prepolymerization reaction: the above prepolymer solution is heated to 45 ° C and polymerized. After 3 hours, the casting solution is obtained;

[0047] S3, coating the casting solution: the casting solution in S2 is smoothly coated on a polyvinyl chloride (PVC) mesh with a thickness of 0.15 mm using a doctor blade;

[0048] S4, film curing: transfer the polyvinyl chloride (PVC) mesh coated with the casting solution into an oven, set the oven temperature to 90°C, and keep it warm for 12 hours;

[0049] S5. After taking the membrane out of the equipment, transfer it to 98% concentrated sulfuric acid, heat it to 80°C, and react for 6 hours to obtain a sulfuric acid sulfonated cationic membrane.

[0050] This method produces a large amount of sulfuric acid waste liquid, causing environmental damage.

[0051] The cationic membrane was used in combination with an anionic membrane (purchased from Shandong Tianwei Membrane Technology Co., Ltd., model TWEDA1) to assemble a 4020 electrodialysis membrane stack for salt concentration testing. The effective area of ​​the membrane is 0.05m 2The number of groups is 4. The cathode and anode are titanium plates with iridium and tantalum oxide coatings. The cathode and anode are connected in series. The electrode liquid is 5% sodium sulfate solution. The concentration of the desalination chamber and the concentration chamber is 5% sodium chloride solution. The operating current is 15A (current density 300A / m 2 ), tested at room temperature (25°C) for 1 hour. The results showed that the cationic membrane prepared according to the above scheme had a total thickness of 0.23 mm, an ion exchange capacity of 1.53 mmol / g, and a surface resistance of 3.8 Ω·cm 2 During the electrodialysis membrane module test, the current efficiency was 65.8%, the energy consumption was 591.80kwh / t, and the unit processing capacity was 430.89g / (m 2 ·h).

[0052] Example 2

[0053] This example provides a method for preparing a cationic membrane, and the specific steps are as follows:

[0054] S1. Preparation of prepolymer solution: dissolving p-vinylbenzyl chloride, p-divinylbenzene, and azobisisobutyronitrile (AIBN) in NMP in a molar ratio of 1:0.08:0.005:1, and stirring thoroughly.

[0055] S2, prepolymerization reaction: the above prepolymer solution is heated to 45 ° C and polymerized. After 3 hours, the casting solution is obtained;

[0056] S3, coating the casting solution: the casting solution in S2 is smoothly coated on a polyvinyl chloride (PVC) mesh with a thickness of 0.15 mm using a doctor blade;

[0057] S4, film curing: transfer the polyvinyl chloride (PVC) mesh coated with the casting solution into an oven, set the oven temperature to 90°C, and keep it warm for 12 hours;

[0058] S5. Functional modification: After the membrane is completely solidified, the membrane is removed from the equipment and transferred to a sodium sulfate solution with a concentration of 100 g / L, heated to 50° C., and stirred for 6 hours to obtain a functionally modified cationic membrane.

[0059] The cationic membrane was used in combination with an anionic membrane (purchased from Shandong Tianwei Membrane Technology Co., Ltd., model TWEDA1) to assemble a 4020 electrodialysis membrane stack for salt concentration testing. The effective area of ​​the membrane is 0.05m 2 The number of groups is 4. The cathode and anode are titanium plates with iridium and tantalum oxide coatings. The cathode and anode are connected in series. The electrode liquid is 5% sodium sulfate solution. The concentration of the desalination chamber and the concentration chamber is 5% sodium chloride solution. The operating current is 15A (current density 300A / m 2), tested at room temperature (25°C) for 1 hour. The results showed that the cationic membrane prepared according to the above scheme had a total thickness of 0.23 mm, an ion exchange capacity of 1.28 mmol / g, and a surface resistance of 5.4 Ω·cm 2 The electrodialysis membrane module test showed a current efficiency of 60.4%, a unit energy consumption of 659.87 kwh / t, and a unit processing capacity of 395.53 g / (m 2 ·h).

[0060] Example 3

[0061] This example provides a method for preparing a cationic membrane, and the specific steps are as follows:

[0062] S1. Preparation of prepolymer solution: dissolving p-vinylbenzyl chloride, p-divinylbenzene, and azobisisobutyronitrile (AIBN) in NMP in a molar ratio of 1:0.05:0.005:2, and stirring thoroughly.

[0063] S2, prepolymerization reaction: the above prepolymer solution is heated to 45 ° C and polymerized. After 3 hours, the casting solution is obtained;

[0064] S3, coating the casting solution: the casting solution in S2 is smoothly coated on a polyvinyl chloride (PVC) mesh with a thickness of 0.15 mm using a doctor blade;

[0065] S4, film curing: transfer the polyvinyl chloride (PVC) mesh coated with the casting solution into an oven, set the oven temperature to 90°C, and keep it warm for 12 hours;

[0066] S5. Functional modification: After the membrane is completely solidified, the membrane is removed from the equipment and transferred to a sodium sulfate solution with a concentration of 100 g / L, heated to 50° C., and stirred for 6 hours to obtain a functionally modified cationic membrane.

[0067] The cationic membrane was used in combination with an anionic membrane (purchased from Shandong Tianwei Membrane Technology Co., Ltd., model TWEDA1) to assemble a 4020 electrodialysis membrane stack for salt concentration testing. The effective area of ​​the membrane is 0.05m 2 The number of groups is 4. The cathode and anode are titanium plates with iridium and tantalum oxide coatings. The cathode and anode are connected in series. The electrode liquid is 5% sodium sulfate solution. The concentration of the desalination chamber and the concentration chamber is 5% sodium chloride solution. The operating current is 15A (current density 300A / m 2 ), tested at room temperature (25°C) for 1 hour. The results showed that the cationic membrane prepared according to the above scheme had a total thickness of 0.17 mm, an ion exchange capacity of 1.87 mmol / g, and a surface resistance of 2.6 Ω·cm 2The electrodialysis membrane module test showed a current efficiency of 63.5%, a unit energy consumption of 542.09 kwh / t, and a unit processing capacity of 415.83 g / (m 2 ·h).

[0068] Example 4

[0069] This example provides a method for preparing a cationic membrane, and the specific steps are as follows:

[0070] S1. Preparation of prepolymer solution: dissolving p-vinylbenzyl chloride, p-divinylbenzene, and azobisisobutyronitrile (AIBN) in NMP at a molar ratio of 1:0.05:0.005:1, and stirring thoroughly.

[0071] S2, prepolymerization reaction: the above prepolymer solution is heated to 45 ° C and polymerized. After 3 hours, the casting solution is obtained;

[0072] S3, coating the casting solution: the casting solution in S2 is smoothly coated on a polyethylene film with a thickness of 0.10 mm using a doctor blade;

[0073] S4, film curing: the polyethylene film coated with the casting solution is transferred to an oven, the oven temperature is set to 90°C, and the temperature is kept for 12 hours;

[0074] S5. Functional modification: After the membrane is completely solidified, the membrane is removed from the equipment and transferred to a sodium sulfate solution with a concentration of 100 g / L, heated to 50° C., and stirred for 6 hours to obtain a functionally modified cationic membrane.

[0075] The cationic membrane was used in combination with an anionic membrane (purchased from Shandong Tianwei Membrane Technology Co., Ltd., model TWEDA1) to assemble a 4020 electrodialysis membrane stack for salt concentration testing. The effective area of ​​the membrane is 0.05m 2 The number of groups is 4. The cathode and anode are titanium plates with iridium and tantalum oxide coatings. The cathode and anode are connected in series. The electrode liquid is 5% sodium sulfate solution. The concentration of the desalination chamber and the concentration chamber is 5% sodium chloride solution. The operating current is 15A (current density 300A / m 2 ), tested at room temperature (25°C) for 1 hour. The results showed that the cationic membrane prepared according to the above scheme had a total thickness of 0.15 mm, an ion exchange capacity of 1.53 mmol / g, and a surface resistance of 1.9 Ω·cm 2 The electrodialysis membrane module test showed a current efficiency of 63.5%, a unit energy consumption of 490.34 kwh / t, and a unit processing capacity of 428.27 g / (m 2 ·h).

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a cationic membrane, characterized in that: The steps include: S1, prepolymerization: dissolving the first unsaturated monomer containing a halogen group, the second unsaturated monomer and an initiator in an organic solvent, and performing a polymerization reaction after dissolution to obtain a casting solution; S2, solidification: coating the casting solution on the supporting substrate and solidifying it into a film; S3. Functional modification: After the membrane is completely solidified, the membrane is transferred to a sulfate solution. After sufficient reaction, a functionally modified cationic membrane is obtained. Wherein, the molar ratio of the first unsaturated monomer to the second unsaturated monomer is 1:0.03-0.

10.

2. The preparation method according to claim 1, characterized in that The first unsaturated monomer is selected from one of p-vinylbenzyl chloride, m-vinylbenzyl chloride, p-chlorostyrene, m-chlorostyrene, p-bromostyrene and m-bromostyrene; The second unsaturated monomer is selected from o-divinylbenzene and / or p-divinylbenzene.

3. The preparation method according to claim 1, characterized in that The initiator is selected from one or more of dibenzoyl peroxide, dodecyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate, diisopropyl peroxydicarbonate, diethylhexyl peroxydicarbonate, azobisisobutyronitrile, azobisisoheptylonitrile, and tetraethylthiuram; The organic solvent is selected from one or more of tetrahydrofuran, N-methylpyrrolidone, and N,N-dimethylformamide.

4. The preparation method according to claim 1, characterized in that The molar ratio of the first unsaturated monomer to the initiator is 1:0.002-0.

05.

5. The preparation method according to claim 1, characterized in that The polymerization reaction temperature is 40-70° C., and the polymerization reaction time is 1-4 hours.

6. The preparation method according to claim 1, characterized in that The supporting substrate is selected from one of non-woven fabrics, polypropylene mesh, polyvinyl chloride mesh, nylon mesh, polyester mesh, polyetheretherketone mesh, polyethylene film, and polypropylene film, and has a thickness of 0.05 to 0.3 mm.

7. The preparation method according to claim 1, characterized in that The temperature of the curing reaction is 70 to 100° C., and the time of the curing reaction is 12 to 24 hours.

8. The preparation method according to claim 1, characterized in that The concentration of sulfate solution is 10-100 g / L; The reaction temperature of step S3 is 40-60° C., and the reaction time is 5-18 hours.

9. A cationic membrane, characterized in that The preparation method is described in any one of claims 1 to 8.

10. Use of the cationic membrane according to claim 9 in electrodialysis.

Images