An aminated graphene oxide-based bipolar film and its preparation method

Abstract

This invention discloses an aminated graphene oxide-based bipolar membrane and its preparation method, belonging to the field of bipolar membrane technology. The bipolar membrane is composed of a sulfonated polyphenylene sulfone cation layer, an aminated graphene oxide interlayer, and a quaternized polyphenylene ether anion layer stacked sequentially. This invention utilizes the aminated graphene oxide as the interlayer, taking advantage of its two-dimensional sheet-like morphology, abundant catalytic groups, and cross-linking effect to achieve a bipolar membrane with low water dissociation voltage, good interlayer compatibility, and structural stability. When applied to electrodialysis, it improves alkali concentration and current efficiency compared to commercially available membranes, while reducing energy consumption, showing promising application prospects in acid and alkali preparation, resource recovery, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of ion exchange membrane technology, specifically relating to an aminated graphene oxide-based bipolar membrane and its preparation method. Background Technology

[0002] Bipolar membrane electrodialysis, as a highly efficient and energy-saving membrane separation technology, has been widely used in fields such as green acid and alkali preparation, resource recycling, and purification of pharmaceutical intermediates due to its advantages of low energy consumption and high separation efficiency. The bipolar membrane is the core component of bipolar membrane electrodialysis technology; it is a "sandwich" structure composite ion exchange membrane composed of a cation exchange layer, an intermediate layer, and an anion exchange layer. Under the action of a reverse electric field, water molecules diffused into the intermediate layer undergo catalytic dissociation into hydrogen ions and hydroxide ions. These ions then migrate through the cation exchange layer and the anion exchange layer to the bulk solutions on both sides of the bipolar membrane, respectively, completing the directional ion transport.

[0003] Studies have shown that introducing catalytically active materials into the interlayer of bipolar membranes can effectively enhance the interfacial electric field strength and catalyze the dissociation reaction of water molecules, which is a key means to reduce the water dissociation voltage of bipolar membranes. Maintaining the long-term stability of the structure and performance of the catalytically active materials in the interlayer is a necessary prerequisite for ensuring the continuous and efficient operation of the bipolar membrane. Therefore, the research and modification of water dissociation catalysts in the interlayer of bipolar membranes has become a research hotspot in this field.

[0004] Previous studies have shown that graphene oxide (GO) is a highly efficient bipolar film interlayer water dissociation catalyst due to its excellent catalytic performance. In 2014, McDonald et al. reported a bipolar film with a mixture of ionomer and graphene oxide as the interlayer. ACS Appl. [2014, 6(16), 13790-13797], the prepared bipolar membrane exhibited a low water dissociation overpotential; in 2025, Fen Luo et al. developed a bipolar membrane based on 4-tertiary amine calixarene-modified graphene oxide as the intermediate layer [ Energy Environ. Sci [2025, 18(2), 728-737], the exposure of active sites and the electric field strength inside the intermediate layer of modified graphene oxide are significantly improved, the water dissociation kinetics are accelerated, and the overpotential of bipolar membrane water dissociation is further reduced.

[0005] Currently, the role of graphene oxide in reducing the overpotential of water dissociation in the intermediate layer of bipolar membranes has been widely recognized. However, existing technologies only focus on optimizing the catalytic performance of graphene oxide. Key issues such as how to balance the interfacial compatibility between different layers of the bipolar membrane and further improve the current efficiency of bipolar membrane electrodialysis have not been studied in depth. As a result, existing graphene oxide-based bipolar membranes still have defects such as easy delamination between layers and poor overall electrodialysis performance, which limits their industrial application. Summary of the Invention

[0006] This invention provides an aminated graphene oxide-based bipolar membrane and its preparation method, aiming to solve the problems of low water dissociation efficiency, poor interlayer interface compatibility, and low current efficiency in the electrodialysis process of existing bipolar membranes, and to obtain a bipolar membrane product with excellent water dissociation performance, tight and stable interlayer bonding, and good overall electrodialysis performance.

[0007] To achieve its objectives, the present invention employs the following technical solution:

[0008] The present invention first provides an aminated graphene oxide-based bipolar membrane, which is a layered composite structure comprising a cation membrane layer, an intermediate layer and an anion membrane layer stacked sequentially; wherein the cation membrane layer is prepared by sulfonated polyphenyl sulfone, the anion membrane layer is prepared by quaternized polyphenylene ether, and the intermediate layer is an aminated graphene oxide thin film layer.

[0009] Preferably, the preparation method of aminated modified graphene oxide is as follows: graphene oxide is ultrasonically dispersed in deionized water to obtain a graphene oxide dispersion with a concentration of 1~2 mg / mL. The obtained dispersion is transferred to a two-necked flask with a spherical condenser, and potassium hydroxide powder is added, wherein the mass ratio of potassium hydroxide to graphene oxide is 1~3:1. After magnetic stirring and mixing evenly, the temperature is raised to 60~80℃. Then, 1,3-diaminoisopropanol is added to the flask and reacted with graphene oxide at 60~80℃ for 6~10 h, wherein the volume ratio of 1,3-diaminoisopropanol to the mass ratio of graphene oxide is 1~12 μL:1 mg. After the reaction is completed, the obtained suspension is washed with deionized water and centrifuged several times until the pH of the system is neutral after washing. The washed dispersion is collected, pre-frozen, and vacuum freeze-dried to finally obtain black, fluffy aminated modified graphene oxide sheet material. Wherein: the graphene oxide mentioned can be referred to in the literature "Improved synthesis of graphene oxide with controlled oxidation degree by using different dihydrogen phosphate as intercalators" [ Chem. Phys. The sample was prepared according to the method described in "2020, 539, 110938". The preferred speed for washing and centrifuging with deionized water is 5000~10000 rpm, the preferred number of washing cycles is 2~6, and the preferred washing time is 10~40 minutes per cycle. The preferred pre-freezing temperature is -15~-5℃, and the preferred pre-freezing time is 12~24 hours. The preferred vacuum freeze-drying temperature is -50~0℃, the preferred time is ≥12 hours, and the preferred vacuum degree is <10 Pa.

[0010] The present invention also provides a method for preparing the above-mentioned aminated modified graphene oxide-based bipolar film, specifically including the following steps:

[0011] Step 1: Prepare the cation exchange solution: Add sulfonated polyphenylsulfone to an organic solvent and stir until completely dissolved to prepare the sulfonated polyphenylsulfone cation exchange solution;

[0012] Step 2, Preparation of anion membrane solution: Add quaternized polyphenylene ether to an organic solvent and stir until completely dissolved to prepare quaternized polyphenylene ether anion membrane solution;

[0013] Step 3: Prepare the intermediate layer suspension: Disperse the aminated graphene oxide in deionized water to prepare an aminated graphene oxide intermediate layer suspension.

[0014] Step 4: Prepare the bipolar membrane according to Method 1 or Method 2:

[0015] Method 1: The cation membrane solution is coated onto the substrate to form a film, and after drying, a cation membrane layer is obtained; the intermediate layer suspension is uniformly sprayed onto the surface of the cation membrane layer, and after drying, a cation membrane layer-intermediate layer composite layer is obtained; then the anion membrane solution is sprayed onto the surface of the intermediate layer, and after drying, a sandwich structure of cation membrane layer-intermediate layer-anion membrane layer is obtained, which is the bipolar membrane.

[0016] Method 2: The anion membrane solution is coated onto the substrate to form a film, and after drying, an anion membrane layer is obtained; the intermediate layer suspension is uniformly sprayed onto the surface of the anion membrane layer, and after drying, an anion membrane layer-intermediate layer composite layer is obtained; then the cation membrane solution is sprayed onto the surface of the intermediate layer, and after drying, a sandwich structure of anion membrane layer-intermediate layer-cation membrane layer is obtained, which is the bipolar membrane.

[0017] Preferably, the degree of sulfonation of the sulfonated polyphenylene sulfone is 20-50%; the degree of quaternization of the quaternized polyphenylene ether is 20-50%; the mass fraction of sulfonated polyphenylene sulfone in the cation exchange solution is 5-20%; the mass fraction of quaternized polyphenylene ether in the anion exchange solution is 5-20%; and the concentration of aminated modified graphene oxide in the intermediate layer suspension is 0.2-2 mg / mL.

[0018] Preferably, the organic solvents used to prepare the cation exchange solution and the anion exchange solution are each independently selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide, with dimethyl sulfoxide being the most preferred.

[0019] Preferably, the drying temperature during the preparation of the cation film layer, anion film layer and intermediate layer is 40~120℃.

[0020] Preferably, the substrate is a quartz glass plate, a polytetrafluoroethylene plate, a stainless steel plate, or a polyethylene terephthalate plate.

[0021] This invention provides an aminated graphene oxide-based bipolar film and its preparation method. Compared with the prior art, it has the following advantages:

[0022] 1. The aminated graphene oxide-based bipolar membrane prepared by this invention has a lower water dissociation voltage. On one hand, the aminated graphene oxide has a two-dimensional sheet-like morphology, which facilitates the rapid migration of hydrogen and hydroxide ions generated during water dissociation out of the intermediate layer and into the cation and anion layers, effectively promoting the water dissociation reaction. On the other hand, this aminated graphene oxide has excellent hydrophilicity and its surface is rich in catalytic water dissociation active groups such as -OH, -COOH, and -NH2, which can significantly increase the active sites for water dissociation. Based on the above synergistic effect, the aminated graphene oxide-based bipolar membrane prepared by this invention has a lower water dissociation voltage at a current density of 100 mA·cm⁻¹. -2 Under the test conditions, the water dissociation voltage was as low as 1.211 V, which is 4.38% lower than that of commercially available membranes.

[0023] 2. The aminated graphene oxide-based bipolar film prepared by this invention exhibits excellent interlayer compatibility and strong structural stability. On one hand, the -OH and -NH2 groups on the surface of the aminated graphene oxide can form hydrogen bonds with the functional groups on the surfaces of the anion and cation layers, resulting in tight interlayer bonding in the "sandwich" structure of the bipolar film and making it less prone to delamination. On the other hand, the 1,3-diaminoisopropanol used for modification has a diamino structure, which can achieve cross-linking between graphene oxide sheets, effectively solving the problem of bipolar film delamination caused by increased interlayer spacing and swelling of unmodified graphene oxide in an aqueous environment. Compared with the unmodified graphene oxide-based bipolar film, the structural stability of the product of this invention is significantly improved.

[0024] 3. The aminated graphene oxide-based bipolar membrane prepared in this invention exhibits excellent performance in bipolar membrane electrodialysis systems. Benefiting from the synergistic effect of the two-dimensional sheet structure of the aminated graphene oxide and the abundant catalytic water-dissociation groups on its surface, this bipolar membrane, when applied to bipolar membrane electrodialysis, shows superior performance compared to commercially available membranes at a current density of 100 mA·cm⁻¹. -2 Under the test conditions, the alkali concentration was increased by 3.70~6.38%, the current efficiency was increased by 5.83~6.90%, and the energy consumption was reduced by 1.67~9.57%, significantly optimizing the overall performance of electrodialysis. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 XPS image of the graphene oxide sheet material prepared in the embodiments of the present invention;

[0027] Figure 2 XPS image of the aminated modified graphene oxide prepared in the embodiments of the present invention;

[0028] Figure 3 This is a schematic diagram of the apparatus for testing the electrodialysis performance of a bipolar membrane in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the apparatus for testing the current-voltage polarization curve of a bipolar film in an embodiment of the present invention;

[0030] Figure 5 This is a graph showing the acid and alkali concentrations and voltage-time curves of the bipolar membrane obtained in Example 1 of the present invention during the electrodialysis test.

[0031] Figure 6 The figures show the current-voltage curves of the bipolar films prepared in the various embodiments and comparative examples of this invention.

[0032] Figure 7 A digital photograph of the bipolar film prepared in Example 1 of this invention;

[0033] Figure 8 This is a digital photograph of the bipolar film prepared in Comparative Example 2 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention are described in detail and completely below with reference to embodiments. Obviously, the described embodiments are some preferred embodiments of this invention and are not intended to limit the invention. All other implementation methods obtained by those skilled in the art based on the embodiments disclosed in this invention without creative effort are within the protection scope of this invention.

[0035] The aminated modified graphene oxide used in the following examples was prepared according to the following steps:

[0036] Preparation of graphene oxide: First, add 200 mL of 98% concentrated sulfuric acid and 60 mL of 75% concentrated phosphoric acid to the reaction vessel and stir until homogeneous; then, weigh 5 g of graphite powder and add it to the reaction vessel, and slowly add 30 g of potassium permanganate powder over 1 hour, heat and stir, set the temperature to 40℃, and the reaction time to 3 hours. After the reaction was complete, heating was stopped, and the reaction solution was stirred continuously and allowed to cool. The cooled reaction solution was added dropwise to 800 mL of a 0.5% hydrogen peroxide aqueous solution at a rate of approximately 6 drops / minute. After the addition was complete, the resulting solution was allowed to stand for one day, the supernatant was removed, and the lower suspension was collected. The collected suspension was washed with a 5% hydrochloric acid solution by centrifugation at 8000 rpm for 30 minutes each time, and this washing was repeated 4 times. The acid-washed suspension was then washed with deionized water at 5000 rpm for 30 minutes each time, and this washing was repeated 6 times until the pH of the supernatant was close to neutral. The collected graphene oxide dispersion was pre-frozen at -10°C for 12–24 hours, and then freeze-dried under vacuum at -50°C and a vacuum of <10 Pa for 2 days to obtain dark green, fluffy graphene oxide. Its XPS image is shown below. Figure 1 As shown, unmodified graphene oxide has a large number of epoxy groups and carboxyl groups. These groups will cause graphene oxide to delaminate in an aqueous environment through steric repulsion and electrostatic repulsion effects, respectively, ultimately leading to the macroscopic delamination of the bipolar film.

[0037] Preparation of aminated modified graphene oxide: 20 mg of graphene oxide was ultrasonically dispersed in 20 mL of deionized water to obtain a graphene oxide dispersion of 1 mg / mL. The dispersion was then transferred to a two-necked flask equipped with a spherical condenser, and 40 mg of potassium hydroxide was added. After magnetic stirring and mixing, the mixture was heated to 60 °C. Subsequently, 240 μL (corresponding to Examples 1 and 2) or 60 μL (corresponding to Example 3) of 1,3-diaminoisopropanol was added to the flask, and the mixture was reacted with the graphene oxide for 6 hours. After the reaction, the resulting suspension was washed with deionized water by centrifugation at 8000 rpm for 30 minutes each time. The washing was repeated 4 times until the pH of the supernatant after centrifugation was approximately 7. The washed dispersion was collected and pre-frozen at -10 °C for 12 hours. Then, the dispersion was freeze-dried under vacuum at -25 °C and a vacuum degree <10. Pa, vacuum freeze-drying time of 18 hours, yielded black, fluffy, aminated modified graphene oxide; its characteristic XPS image is shown below. Figure 2As shown (corresponding to a sample with 240 μL of 1,3-diaminoisopropanol), the number of epoxy and carboxyl groups decreased significantly after modification, the interlayer repulsion was weakened, and CN and NC=O bonds were widely generated in graphene oxide. Diaminohydroxypropane played its interlayer bridging role, making the modified graphene oxide less prone to delamination in water and well maintaining the mechanical strength of the bipolar film.

[0038] Example 1

[0039] This embodiment discloses a method for preparing an aminated graphene oxide-based bipolar film, the specific steps of which are as follows:

[0040] S1. Preparation of cation exchange solution: Weigh 10 g of sulfonated polyphenylsulfone with a sulfonation degree of 30%, add it to 70 g of N-methylpyrrolidone, stir until completely dissolved, and prepare a sulfonated polyphenylsulfone cation exchange solution with a mass fraction of 12.5%.

[0041] S2. Preparation of anion membrane solution: Weigh 5 g of quaternized polyphenylene ether with a degree of quaternization of 20%, add it to 95 g of dimethyl sulfoxide, stir until completely dissolved, and prepare anion membrane solution with a mass fraction of 5% quaternized polyphenylene ether.

[0042] S3. Preparation of intermediate layer suspension: Weigh 20 mg of the aforementioned aminated modified graphene oxide and disperse it in 20 mL of deionized water to prepare an aminated modified graphene oxide intermediate layer suspension with a concentration of 1 mg / mL.

[0043] S4. Preparation of bipolar membrane: Measure 3 mL of cation membrane solution and pour it onto a glass substrate. Dry at 40℃ for 6 hours to obtain the cation membrane layer. Use a spray gun to uniformly spray 1.5 mL of intermediate layer suspension onto the surface of the cation membrane layer. Dry at 50℃ for 15 minutes to obtain the cation membrane layer-intermediate layer composite layer. Then use a spray gun to spray 1.5 mL of anion membrane solution onto the surface of the intermediate layer. Dry at 60℃ for 10 hours to obtain the "sandwich" structure bipolar membrane of cation membrane layer-intermediate layer-anion membrane layer. Immerse the prepared bipolar membrane in 0.3 mol / L sodium sulfate solution for later use.

[0044] The bipolar membrane prepared in this embodiment was subjected to bipolar membrane electrodialysis performance testing and current-voltage polarization curve testing. The specific test methods and results are as follows:

[0045] Bipolar membrane electrodialysis test: using methods such as Figure 3 The bipolar membrane electrodialysis stack shown comprises one anion membrane, one cation membrane, and two bipolar membranes prepared in this embodiment; the anion and cation membranes were purchased from Asahi Glass Co., Ltd., Japan, and each membrane has an effective area of ​​7.07 cm². 2 The test conditions were: current density of 50 mA / cm². 2The alkaline chamber was purged with 200 mL of 0.05 mol / L sodium hydroxide solution, the acid chamber with 200 mL of 0.05 mol / L dilute sulfuric acid, and the salt and electrode chambers with 1000 mL and 200 mL of 0.5 mol / L sodium sulfate solution, respectively. The membrane stack operated continuously and stably for 3 hours, and the solution concentrations in the alkaline and acid chambers were measured at fixed intervals.

[0046] Current-voltage polarization curve testing: using Figure 4 The test apparatus shown includes two cation exchange membranes and one bipolar membrane prepared in this embodiment; the cation exchange membranes were purchased from Asahi Glass Co., Ltd., Japan, and each membrane has an effective area of ​​1.03 cm². 2 The test conditions were as follows: 200 mL of 0.3 mol / L sodium chloride solution was introduced into the salt chamber, and 200 mL of 0.3 mol / L sodium sulfate solution was introduced into the electrode chamber; the current density was increased from 0 mA / cm². 2 Start at 10 mA / cm 2 The gradient was gradually increased to 100 mA / cm. 2 Record the voltage readings displayed on the multimeter when each current density is stable.

[0047] The electrodialysis test results of the bipolar membrane prepared in this embodiment are shown in the figure. Figure 5 And Table 1: at 50 mA / cm 2 At the specified current density, after 3 hours of continuous operation of the membrane stack, the concentration increment of the alkali chamber solution was 0.198 mol / L, and the concentration increment of the acid chamber solution was 0.145 mol / L. Based on the alkali production rate, the energy consumption of the electrodialysis process was 13.52 kWh / kg, and the current efficiency reached 99.0%. Compared with the commercially available membrane in Comparative Example 3 (energy consumption 14.95 kWh / kg, current efficiency 92.7%), the overall performance is significantly superior.

[0048] The current-voltage polarization curve test results of the bipolar film prepared in this embodiment are shown in the figure. Figure 6 At 100 mA / cm 2 At the current density, the water dissociation voltage across the bipolar membrane is 1.21 V, which is much lower than that of the bipolar membrane without an interlayer in Comparative Example 1 (20.50 V), proving that aminated graphene oxide as an interlayer can significantly reduce the water dissociation voltage of the bipolar membrane; and this voltage value is also significantly competitive with the commercially available membrane in Comparative Example 3 (1.26 V).

[0049] Digital photographs of the bipolar film in this embodiment can be found here. Figure 7 , and like Figure 8As shown in Comparative Example 2, which compares the unmodified graphene oxide-based bipolar film, the bipolar film with aminated graphene oxide as the intermediate layer exhibits tight interlayer bonding and no delamination, demonstrating excellent structural stability and interlayer compatibility.

[0050] Example 2

[0051] This embodiment discloses a method for preparing an aminated graphene oxide-based bipolar film, the specific steps of which are as follows:

[0052] S1. Preparation of cation exchange solution: Weigh 15 g of sulfonated polyphenylsulfone with a sulfonation degree of 25%, add it to 85 g of N-methylpyrrolidone, stir until completely dissolved, and prepare a sulfonated polyphenylsulfone cation exchange solution with a mass fraction of 15.0%.

[0053] S2. Preparation of anion membrane solution: Weigh 15 g of quaternized polyphenylene ether with a degree of 30% quaternization, add it to 85 g of dimethyl sulfoxide, stir until completely dissolved, and prepare anion membrane solution with a mass fraction of 15.0% quaternized polyphenylene ether.

[0054] S3. Preparation of intermediate layer suspension: Weigh 30 mg of the aforementioned aminated modified graphene oxide and disperse it in 20 mL of deionized water to prepare an aminated modified graphene oxide intermediate layer suspension with a concentration of 1.5 mg / mL.

[0055] S4. Preparation of bipolar membrane: Measure 3 mL of cation membrane solution and pour it onto a glass substrate. Dry at 70℃ for 6 hours to obtain the cation membrane layer. Use a spray gun to uniformly spray 2.0 mL of intermediate layer suspension onto the surface of the cation membrane layer. Dry at 80℃ for 15 minutes to obtain the cation membrane layer-intermediate layer composite layer. Then use a spray gun to spray 1.5 mL of anion membrane solution onto the surface of the intermediate layer. Dry at 90℃ for 10 hours to obtain the "sandwich" structure bipolar membrane of cation membrane layer-intermediate layer-anion membrane layer. Immerse the prepared bipolar membrane in 0.3 mol / L sodium sulfate solution for later use.

[0056] Following the same method as in Example 1, the bipolar membrane prepared in this example was subjected to bipolar membrane electrodialysis performance testing and current-voltage polarization curve testing. The specific results are as follows:

[0057] The electrodialysis test results of the bipolar membrane prepared in this embodiment are shown in Table 1: at 50 mA / cm 2 At the given current density, after 3 hours of continuous operation of the membrane stack, the concentration increase of the alkali chamber solution was 0.195 mol / L. Based on the alkali production rate, the energy consumption of the electrodialysis process was 14.95 kWh / kg, and the current efficiency reached 98.1%. Compared with the commercially available membrane in Comparative Example 3 (energy consumption 14.95 kWh / kg, current efficiency 92.7%), the current efficiency was significantly improved, demonstrating good performance competitiveness.

[0058] The test results of the current-voltage polarization curve of the bipolar film in this embodiment are shown below. Figure 6 At 100 mA / cm 2 At the current density, the water dissociation voltage across the bipolar membrane is 1.32 V, which is much lower than that of the bipolar membrane without an intermediate layer in Comparative Example 1 (20.50 V), demonstrating that the bipolar membrane prepared in this embodiment has excellent water dissociation catalytic performance.

[0059] Example 3

[0060] This embodiment discloses a method for preparing an aminated graphene oxide-based bipolar film, the specific steps of which are as follows:

[0061] S1. Preparation of cation exchange solution: Weigh 10 g of sulfonated polyphenylsulfone with a sulfonation degree of 40%, add it to 90 g of N-methylpyrrolidone, stir until completely dissolved, and prepare a sulfonated polyphenylsulfone cation exchange solution with a mass fraction of 10.0%.

[0062] S2. Preparation of anion membrane solution: Weigh 10 g of quaternized polyphenylene ether with a degree of quaternization of 15%, add it to 90 g of dimethyl sulfoxide, stir until completely dissolved, and prepare anion membrane solution with a mass fraction of 10.0% quaternized polyphenylene ether.

[0063] S3. Preparation of intermediate layer suspension: Weigh 14 mg of the aforementioned aminated modified graphene oxide and disperse it in 20 mL of deionized water to prepare an aminated modified graphene oxide intermediate layer suspension with a concentration of 0.7 mg / mL.

[0064] S4. Preparation of bipolar membrane: Measure 3 mL of cation membrane solution and pour it onto a glass substrate. Dry at 40℃ for 6 hours to obtain the cation membrane layer. Use a spray gun to uniformly spray 1.5 mL of intermediate layer suspension onto the surface of the cation membrane layer. Dry at 50℃ for 15 minutes to obtain the cation membrane layer-intermediate layer composite layer. Then use a spray gun to spray 1.5 mL of anion membrane solution onto the surface of the intermediate layer. Dry at 60℃ for 10 hours to obtain the "sandwich" structure bipolar membrane of cation membrane layer-intermediate layer-anion membrane layer. Immerse the prepared bipolar membrane in 0.3 mol / L sodium sulfate solution for later use.

[0065] Following the same method as in Example 1, the bipolar membrane prepared in this example was subjected to bipolar membrane electrodialysis performance testing and current-voltage polarization curve testing. The specific results are as follows:

[0066] The electrodialysis test results of the bipolar membrane prepared in this embodiment are shown in Table 1: at 50 mA / cm 2At the given current density, after 3 hours of continuous operation of the membrane stack, the concentration increase of the alkali solution in the alkali chamber was 0.20 mol / L. Based on the alkali production, the energy consumption of the electrodialysis process was 14.70 kWh / kg, and the current efficiency reached 99.1%. Compared with the commercially available membrane in Comparative Example 3 (energy consumption 14.95 kWh / kg, current efficiency 92.7%), the energy consumption was lower and the current efficiency was higher, demonstrating significant performance advantages.

[0067] The current-voltage polarization curve test results of the bipolar film prepared in this embodiment are shown in the figure. Figure 6 At 100 mA / cm 2 At the current density, the water dissociation voltage across the bipolar membrane is 1.64 V, which is much lower than that of the bipolar membrane without an intermediate layer in Comparative Example 1 (20.50 V), demonstrating that the bipolar membrane prepared in this embodiment has excellent water dissociation catalytic performance.

[0068] Comparative Example 1

[0069] This comparative example provides a bipolar membrane without an intermediate layer, which is composed of a cation membrane layer and an anion membrane layer stacked sequentially. The cation membrane layer is prepared from sulfonated polyphenylsulfone, and the anion membrane layer is prepared from quaternized polyphenylene ether. The specific preparation steps are as follows:

[0070] S1. Preparation of cation exchange solution: The same preparation process as in Example 1 is used;

[0071] S2. Preparation of analgesic solution: The same preparation process as in Example 1 is used;

[0072] S3. Preparation of bipolar membrane: Measure 3 mL of cation membrane solution and pour it onto a glass substrate. Dry at 60°C for 6 hours to obtain the cation membrane layer. Then, spray 1.5 mL of anion membrane solution onto the surface of the cation membrane layer with a spray gun and dry at 60°C for 10 hours to obtain a bipolar membrane with a cation membrane layer-anion membrane layer structure. Immerse the obtained bipolar membrane in 0.3 mol / L sodium sulfate solution for later use.

[0073] The test results of the current-voltage polarization curves of the bipolar film prepared in this comparative example are shown in the figure. Figure 6 .

[0074] Comparative Example 2

[0075] This comparative example prepared a bipolar membrane using the same method as in Example 1, the only difference being that in step S3, unaminated graphene oxide was used to prepare the intermediate layer suspension. A digital photograph of the bipolar membrane obtained in this comparative example is shown below. Figure 8 As shown.

[0076] Comparative Example 3

[0077] This comparative example uses a commercially available bipolar membrane, specifically the SSBP-1 type bipolar membrane produced by Hebei Sens Environmental Protection Technology Co., Ltd.

[0078] The current-voltage polarization curve test results of the bipolar film used in this comparative example are shown in [reference needed]. Figure 6 The results of the bipolar membrane electrodialysis test are shown in Table 1.

[0079] Table 1 shows the final alkali concentration, current efficiency, and energy consumption data obtained from the bipolar membrane electrodialysis tests of Examples 1 and Comparative Example 3.

[0080]

[0081] In summary, this invention constructs a composite structure by using aminated modified graphene oxide as the intermediate layer of a bipolar membrane, combined with a sulfonated polyphenylene sulfone cation membrane layer and a quaternized polyphenylene ether anion membrane layer. This structure utilizes the two-dimensional sheet-like morphology and abundant catalytic groups of aminated modified graphene oxide to reduce the water dissociation voltage of the bipolar membrane. Furthermore, the hydrogen bonding and sheet crosslinking effects of the modified groups solve the problems of poor interlayer compatibility and easy delamination in traditional graphene oxide-based bipolar membranes, significantly improving the stability of the membrane structure. Simultaneously, when applied to electrodialysis systems, this bipolar membrane exhibits higher alkali production concentration and current efficiency compared to commercially available membranes, with significantly reduced energy consumption. Its excellent overall performance makes it a promising candidate for applications in acid and alkali preparation, resource recovery, and other fields.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An aminated graphene oxide-based bipolar membrane, wherein the bipolar membrane has a layered composite structure comprising a cation membrane layer, an intermediate layer, and an anion membrane layer stacked sequentially, characterized in that: The cation membrane layer is prepared from sulfonated polyphenylsulfone, the anion membrane layer is prepared from quaternized polyphenylene ether, and the intermediate layer is an aminated modified graphene oxide film layer.

2. The aminated graphene oxide-based bipolar membrane according to claim 1, characterized in that: The degree of sulfonation of the sulfonated polyphenyl sulfone is 20-50%; the degree of quaternization of the quaternized polyphenylene ether is 20-50%.

3. The aminated graphene oxide-based bipolar film according to claim 1, characterized in that, The preparation method of aminated modified graphene oxide is as follows: Graphene oxide is ultrasonically dispersed in deionized water to obtain a graphene oxide dispersion with a concentration of 1~2 mg / mL. The obtained dispersion is transferred to a two-necked flask equipped with a spherical condenser, and potassium hydroxide powder is added, wherein the mass ratio of potassium hydroxide to graphene oxide is 1~3:

1. After magnetic stirring and uniform mixing, the temperature is raised to 60~80℃. Then, 1,3-diaminoisopropanol is added to the flask and reacted with graphene oxide at 60~80℃ for 6~10 h, wherein the volume ratio of 1,3-diaminoisopropanol to the mass ratio of graphene oxide is 10~15 μL:1 mg. After the reaction is completed, the obtained suspension is washed with deionized water and centrifuged several times until the pH of the system is neutral after washing. The washed dispersion is collected, pre-frozen, and vacuum freeze-dried to finally obtain aminated modified graphene oxide sheet material.

4. A method for preparing the aminated modified graphene oxide-based bipolar film according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Add sulfonated polyphenylsulfone to an organic solvent and stir until completely dissolved to prepare a sulfonated polyphenylsulfone cation exchange solution; Step 2: Add quaternized polyphenylene ether to an organic solvent and stir until completely dissolved to prepare quaternized polyphenylene ether anion membrane solution; Step 3: Disperse the aminated modified graphene oxide in deionized water to prepare an aminated modified graphene oxide intermediate layer suspension. Step 4: Prepare the bipolar membrane according to Method 1 or Method 2: Method 1: The cation membrane solution is coated onto the substrate to form a film, and after drying, a cation membrane layer is obtained; the intermediate layer suspension is uniformly sprayed onto the surface of the cation membrane layer, and after drying, a cation membrane layer-intermediate layer composite layer is obtained; then the anion membrane solution is sprayed onto the surface of the intermediate layer, and after drying, a sandwich structure of cation membrane layer-intermediate layer-anion membrane layer is obtained, which is the bipolar membrane. Method 2: The anion membrane solution is coated onto the substrate to form a film, and after drying, an anion membrane layer is obtained; the intermediate layer suspension is uniformly sprayed onto the surface of the anion membrane layer, and after drying, an anion membrane layer-intermediate layer composite layer is obtained; then the cation membrane solution is sprayed onto the surface of the intermediate layer, and after drying, a sandwich structure of anion membrane layer-intermediate layer-cation membrane layer is obtained, which is the bipolar membrane.

5. The preparation method according to claim 4, characterized in that: The cation exchange solution contains 5-20% sulfonated polyphenylsulfone by mass; the anion exchange solution contains 5-20% quaternized polyphenylene ether by mass; and the intermediate layer suspension contains 0.2-2 g / L aminated modified graphene oxide.

6. The preparation method according to claim 4, characterized in that: The organic solvents used to prepare the cation and anion membrane solutions are each independently selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide.

7. The preparation method according to claim 4, characterized in that: The drying temperature during the preparation of the cation film layer, anion film layer and intermediate layer is 40~120℃.

8. The preparation method according to claim 4, characterized in that: The substrate is a quartz glass plate, a polytetrafluoroethylene plate, a stainless steel plate, or a polyethylene terephthalate plate.

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