Mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane, its preparation method and application
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU UNIV OF TECH
- Filing Date
- 2026-04-24
- Publication Date
- 2026-07-24
Smart Images
Figure CN122441284A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ion exchange membrane preparation and resource recycling technology, specifically to a method for preparing a mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane and its application in the treatment and resource recovery of lithium battery production wastewater. Background Technology
[0002] With the rapid development of the new energy industry, environmental protection in lithium battery production and the recycling of used batteries has become a critical issue. Lithium sulfate (Li2SO4) waste liquid generated in the wet recycling process of spent lithium batteries is highly polluting due to its high lithium content, making its efficient treatment and recycling a significant concern. Electrodialysis, as a core separation method, relies on the overall quality of ion exchange membranes for its performance. However, existing commercial membranes generally suffer from bottlenecks such as poor ion selectivity, insufficient hydrophilicity, high membrane resistance, and weak antifouling ability. Single nanoparticle doping modification is prone to aggregation, leading to uneven membrane structure and rapid performance degradation, making it difficult to meet the industrial demands of treating complex waste liquids. Summary of the Invention
[0003] Objectives of the Invention: The first objective of this invention is to provide a mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane with high selectivity, low resistance, and strong stability; the second objective of this invention is to provide a mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane, its preparation method, and its application; the third objective of this invention is to provide an application of the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane.
[0004] Technical solution: The preparation method of the ion exchange membrane of the present invention includes the following steps:
[0005] (1) Add Al2O3 powder and TiO2 powder to water, mix and carry out hydrothermal reaction to obtain composite inorganic material;
[0006] (2) Add the composite inorganic material to N,N-dimethylformamide, disperse it evenly, then add polyvinylidene fluoride, stir until completely dissolved to form a casting solution, coat the casting solution onto the glass substrate, and obtain the base film after the casting solution dries;
[0007] (3) Immerse the base membrane in a sodium hydroxide-anhydrous ethanol mixture and heat the mixture to perform alkalization treatment; then add the base membrane to a mixture of benzoyl, styrene and tetrahydrofuran to carry out a grafting reaction, and the grafted membrane is obtained after the reaction is completed.
[0008] (4) The grafted membrane was immersed in 1,2-dichloromethane to swell, and then transferred to concentrated sulfuric acid for sulfonation. After the reaction, it was washed with dehydration until neutral and dried to obtain a mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane (mAl2O3-mTiO2 / PVDF-g-PSSA). High-density ordered distribution of -SO3H groups was formed on the surface of the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane and on the inner wall of the mesoporous channels, and the ion transport channels were regularized.
[0009] In step (1), mesoporous Al2O3 (mAl2O3) powder is prepared by hydrothermal method: aluminum nitrate nonahydrate and urea are added to a polyethylene glycol aqueous solution to obtain a mixed solution. The mixed solution is subjected to hydrothermal reaction under sealed conditions to obtain a precursor. The precursor is calcined at a constant temperature to obtain Al2O3 powder. In this process, the hydrothermal reaction enables mAl2O3 and mTiO2 to form Al-O-Ti covalent bonds, which inhibits particle agglomeration and improves the interfacial compatibility with the PVDF base film.
[0010] In step (1), mesoporous TiO2 (mTiO2) powder is prepared by an alcoholic thermal method: the surfactant hexadecyltrimethylammonium bromide (CTAB) is dissolved in isopropanol, mixed until completely dissolved, and then tetrabutyl titanate (TBOT) is added. Glacial acetic acid is gradually added dropwise while continuously stirring to obtain a mixed solution. The mixed solution is reacted under sealed conditions, and TiO2 powder is obtained after the reaction is completed. Preferably, the mass fraction of Al2O3 in the composite inorganic material is 10%~40%.
[0011] In step (2), the doping amount of the composite inorganic material in N,N-dimethylformamide is 0.5~2.0% of the mass of N,N-dimethylformamide. Preferably, the composite inorganic material exhibits optimal dispersibility and interfacial bonding when the doping ratio is 1.5% and the mass fraction of Al2O3 in the composite inorganic material is 30%. Furthermore, compared to existing PVDF-based single-doped ion exchange membranes, superior performance can be achieved without adding a high proportion of ion exchange resin exceeding 40%.
[0012] In step (3), after the grafting reaction is completed, the membrane is immersed in chloroform to remove excess styrene monomer and homopolymer from the surface.
[0013] In step (4), after the reaction is complete, the membrane is washed with water until it is neutral by rinsing it in small amounts multiple times.
[0014] On the other hand, the present invention provides a mesoporous Al₂O₃-TiO₂ sulfonated electrodialysis ion exchange membrane prepared by the above method. This ion exchange membrane can be used in an apparatus for separating and recovering Li⁺ and SO₄²⁻ from lithium sulfate waste liquid. The apparatus is a three-compartment double-membrane electrodialysis reactor, wherein the cation exchange membrane in this apparatus is a mesoporous Al₂O₃-TiO₂ sulfonated electrodialysis ion exchange membrane.
[0015] In practical applications, mesoporous Al₂O₃-TiO₂ sulfonated electrodialysis ion exchange membranes are assembled into a three-compartment dual-membrane electrodialysis system. A 0.55 mol / L Li₂SO₄ waste solution is used as the desalination chamber solution. Initially, a 0.1 mol / L LiOH solution is added to the cathode concentration chamber, and an initial 0.1 mol / L H₂SO₄ solution is added to the anode concentration chamber. The reaction is carried out at a constant current density of 2.5 A for 8 hours. This system can withstand interference from trace heavy metals, organic matter, and suspended solids, achieving the desalination of Li⁺ with SO₄²⁻. 2- The efficient separation and recovery of LiOH and H2SO4 solutions is achieved. The recovered LiOH and H2SO4 solutions can be directly reused in the acid dissolution and pH adjustment processes of wet recycling of waste lithium batteries, realizing a closed-loop resource system.
[0016] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: First, highly dispersed mTiO2 and mAl2O3 powders are prepared separately. Then, a composite inorganic material is constructed through a hydrothermal reaction. The steric hindrance effect of mAl2O3 effectively inhibits the aggregation of mTiO2 particles. Simultaneously, the Al-O-Ti bonds formed at the interface of the two particles construct a synergistic conductive network, significantly improving the ion transport performance of the membrane. Through a stepwise modification process of "alkalization-grafting-sulfonation," a large number of hydrophilic sulfonic acid groups (-SO3H) are introduced into the PVDF base membrane. Combined with the high specific surface area characteristics of mesoporous materials, the water contact angle of the composite membrane is reduced to 14.901°, the ion exchange capacity is increased to 2.98 mmol / g, and the membrane resistance is reduced by 79.68% compared to pure PVDF sulfonated membrane. Hydrophilicity and conductivity are simultaneously optimized. The preparation process is simple and controllable, all raw materials are readily available, and the reaction conditions are mild, making it suitable for industrial-scale production. The resulting composite membrane has a stable structure and strong anti-fouling ability. In the treatment of lithium sulfate waste liquid, Li + With SO4 2- The separation rates reached 96.7% and 85.3%, respectively, and the recovery rates were 91.4% and 79.8%, respectively. 1.4179 mol / L LiOH solution and 0.8866 mol / L H2SO4 solution were successfully recovered, realizing closed-loop resource recovery and reducing enterprise operating costs. Attached Figure Description
[0017] Figure 1 shows the SEM and EDS spectra of the composite inorganic material prepared in Example 1 of the present invention. Among them, (a), (b), and (c) are the SEM spectra of mAl2O3, mTiO2, and mAl2O3-mTiO2 catalyst, respectively, and (d) is the EDS spectra of mAl2O3-mTiO2 element.
[0018] Figure 2 shows the SEM surface morphology of the sulfonated ion exchange membrane prepared in Example 1 of the present invention and Comparative Examples 1-3. Specifically, (a) is the surface of the pure PVDF sulfonated ion exchange membrane in Comparative Example 1; (b) is the surface of the mAl2O3 / PVDF sulfonated ion exchange membrane in Comparative Example 2; (c) is the surface of the mTiO2 / PVDF sulfonated ion exchange membrane in Comparative Example 3; and (d) is the surface of the mAl2O3-mTiO2 / PVDF sulfonated ion exchange membrane in Example 1.
[0019] Figure 3 shows the XRD patterns of mAl2O3-mTiO2 catalysts with different mAl2O3 contents prepared in Examples 1-4 of this invention.
[0020] Figure 4 shows the contact angle test results of composite films with different doping ratios in Examples 1-4 of the present invention.
[0021] Figure 5 shows the IEC test results of composite films with different doping ratios in Examples 1-4 of the present invention.
[0022] Figure 6 shows the effects of composite films with different doping ratios on Li in Examples 1-4 of the present invention. + and SO4 2- Separation and recovery rates.
[0023] Figure 7 is a schematic diagram of the three-compartment dual-membrane electrodialysis system used in this invention.
[0024] Figure 8 shows the surface resistance test results of composite films with different doping ratios in Examples 1-4 of the present invention.
[0025] Figure 9 shows the long-term stability test results of Embodiment 1 of the present invention. Detailed Implementation
[0026] Example 1
[0027] A method for preparing a mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane, the specific steps of which are as follows:
[0028] (1) Preparation of mTiO2 powder: Dissolve 1.5g CTAB in 40mL isopropanol and stir magnetically at room temperature until uniform; add 4mL TBOT and add 1mL glacial acetic acid dropwise at 0.1mL / min while stirring continuously. After stirring for 30min, transfer to a high-pressure reactor and react at 120℃ for 48h; after cooling, wash with anhydrous ethanol by centrifugation until no foam is present, dry under vacuum at 80℃ for 24h, and grind and sieve to obtain mTiO2 powder.
[0029] (2) Preparation of mAl2O3 powder: 10.0g PEG (molecular weight 400) was dispersed in 50mL distilled water and stirred until clear; 8g aluminum nitrate nonahydrate and 20.0g urea were added and stirred until dissolved. The mixture was transferred to a high-pressure reactor (75% filling degree) and hydrothermally reacted at 120℃ for 24h; after cooling, it was washed 4 times by centrifugation with anhydrous ethanol, dried under vacuum at 90℃ to constant weight, and ground and sieved to obtain the precursor; the precursor was heated to 900℃ at 5℃ / min in a tube furnace and calcined for 3h to obtain mAl2O3 powder.
[0030] (3) Preparation of composite inorganic materials: mix mAl2O3 powder and mTiO2 powder at a mass fraction of 30%, add deionized water, stir magnetically for 20 min, disperse ultrasonically for 1 h, transfer to high pressure reactor, react at 180℃ for 16 h, and vacuum dry at 100℃ for 24 h to obtain composite inorganic materials.
[0031] (4) Preparation of base film: Add N,N-dimethylformamide to the composite inorganic material at a doping ratio of 1.5% and disperse it by ultrasonication for 30 min; add PVDF powder (PVDF to solvent mass-volume ratio 1:10 g / mL), stir to dissolve and form casting solution, let stand to degas for 24 h; coat it with a thickness of 0.2 mm on a glass substrate, dry it at 60℃ for 4 h, and peel off the film to obtain the base film.
[0032] (5) Alkalization and grafting: The base membrane was immersed in a 0.1 mol / L sodium hydroxide-anhydrous ethanol solution and heated in a water bath at 70°C for 12 h; after washing until neutral, it was immersed in a mixture containing 0.35 g benzoyl peroxide (BPO), 40 mL styrene and 10 mL tetrahydrofuran, and reacted at 70°C for 14 h under nitrogen protection, with stirring at 130 rpm during the reaction; after the reaction, it was soaked in chloroform for 24 h to obtain the grafted membrane.
[0033] (6) Sulfonation treatment: Immerse the grafted membrane in 1,2-dichloromethane and swell at 70°C for 2 hours; transfer it to 98% concentrated sulfuric acid and sulfonate at 70°C for 8 hours; rinse it with deionized water in small amounts several times until neutral, and dry it at 60°C for 2 hours to obtain the target ion exchange membrane.
[0034] Example 2
[0035] The difference between this embodiment and embodiment 1 is that the mass fraction of mAl2O3 in step (3) is 10%, the doping ratio of the composite inorganic material is 0.5%, and the remaining steps and parameters are the same as in embodiment 1.
[0036] Example 3
[0037] The difference between this embodiment and embodiment 1 is that the mass fraction of mAl2O3 in step (3) is 20%, the doping ratio of the composite inorganic material is 1.0%, and the remaining steps and parameters are the same as in embodiment 1.
[0038] Example 4
[0039] The difference between this embodiment and embodiment 1 is that the mass fraction of mAl2O3 in step (3) is 40%, the doping ratio of the composite inorganic material is 2.0%, and the remaining steps and parameters are the same as in embodiment 1.
[0040] Comparative Example 1
[0041] This comparative example uses a pure PVDF sulfonated membrane, and the preparation steps are as follows:
[0042] PVDF powder was added to N,N-dimethylformamide (mass-volume ratio 1:10 g / mL), stirred and dissolved to form a casting solution, and allowed to stand for 24 hours to remove bubbles; it was then coated onto a glass substrate with a thickness of 0.2 mm, dried at 60°C for 4 hours, and the film was peeled off to obtain a pure PVDF base film; the subsequent alkalization, grafting, and sulfonation treatment steps were the same as in Example 1 to obtain a pure PVDF sulfonated film.
[0043] Comparative Example 2
[0044] This comparative example is a single-doped mAl2O3 / PVDF sulfonated ion exchange membrane, and the preparation steps are as follows:
[0045] The difference between this comparative example and Example 1 is that only 0.5g of mAl2O3 powder is added as a dopant in step (3) (no mTiO2 powder). The remaining steps and parameters are the same as in Example 1, and an mAl2O3 / PVDF sulfonated ion exchange membrane is obtained.
[0046] Comparative Example 3
[0047] This comparative example is a single-doped mTiO2 / PVDF sulfonated ion exchange membrane, and the preparation steps are as follows:
[0048] The difference between this comparative example and Example 1 is that only 0.5g of mTiO2 powder is added as a dopant in step (3) (without mAl2O3 powder). The remaining steps and parameters are the same as in Example 1, and an mTiO2 / PVDF sulfonated ion exchange membrane is obtained.
[0049] Performance testing
[0050] The membrane materials prepared in Examples 1-4 and Comparative Examples 1-3 were characterized in structure and tested in performance. The test methods are as follows:
[0051] Structural characterization: The crystal structure of the composite inorganic material was characterized by XRD, the surface morphology of the membrane was observed by SEM, and the water contact angle was measured by a contact angle meter.
[0052] Performance testing: The ion exchange capacity of the membrane was determined using the ion exchange capacity (IEC) test method; the surface resistance of the membrane was measured using a membrane resistance meter; the membrane was assembled into a three-compartment dual-membrane electrodialysis system, using 0.55 mol / L Li₂SO₄ solution as the desalination chamber solution, and reacted for 8 h at a constant current density of 2.5 A. The reaction of Li⁺ with SO₄²⁻ was monitored by online chromatography. 2- Concentration was used to calculate the separation rate and recovery rate; the antifouling performance of the membrane material was characterized by measuring the amount of BSA solution adsorbed per unit area of the composite membrane.
[0053] Test Results
[0054] Structural characterization results: XRD images show ( Figure 3 The composite inorganic materials in Examples 1-4 all exhibited characteristic peaks of the mTiO2 anatase phase (2θ=26.34°, etc.) and the γ-Al2O3 characteristic peak of mAl2O3 (2θ=67.03°), with no impurity peaks, confirming successful composite formation. With increasing mAl2O3 mass fraction, the mTiO2 characteristic peak shifted to higher angles, indicating grain refinement. SEM and EDS images showed that mAl2O3 effectively suppressed mTiO2 agglomeration, and Al, Ti, and O elements were uniformly distributed. Figure 2 shows that the film surface of Example 1 was smooth and the particles were uniformly dispersed, while the surface of Comparative Example 1 was dense and non-porous, and Comparative Example 3 showed obvious agglomeration. Contact angle tests showed (… Figure 4 In Example 1, the water contact angle of the membrane was 14.901°, which was much lower than that of Comparative Example 1 (104.979°), indicating a significant improvement in hydrophilicity.
[0055] Performance test results: such as Figure 5As shown, the IEC value of Example 1 reached 2.98 mmol / g, which was 74.26% higher than that of Comparative Example 1 (1.71 mmol / g), and 46.79% and 51.27% higher than that of Comparative Example 2 (2.03 mmol / g) and Comparative Example 3 (1.97 mmol / g), respectively; the IEC values of Examples 2-4 were all superior to those of the comparative examples; Figure 6 As shown, Example 1 achieved separation rates of 96.7% and 85.3% for Li⁺ and SO₄²⁻, respectively, with recoveries of 91.4% and 79.8%, both optimal. Examples 2-4 and all comparative examples showed lower performance than Example 1, with Comparative Example 1 exhibiting a Li⁺ separation rate of only 55.2% and a recovery rate of 51.3%, a significant difference. Figure 8 As shown, the membrane resistance of Example 1 is reduced by 79.68% compared to the pure PVDF sulfonated membrane. Figure 9 As can be seen, the membrane assembly in Example 2, when used in a three-compartment dual-membrane electrodialysis system, maintained a Li+ separation efficiency of ≥87% after 48 hours of continuous operation. The membrane assembly in Example 2, when used in a three-compartment dual-membrane electrodialysis system, successfully recovered 1.4179 mol / L LiOH solution and 0.8866 mol / L H2SO4 solution, achieving closed-loop resource recovery.
[0056] Table 1 Protein adsorption on different PVDF composite membranes
[0057]
[0058] Table 1 shows that the supported mAl2O3-mTiO2 inorganic composite material can enhance the hydrophilicity of PVDF membranes. (PVDF-g: the material obtained after alkalization of PVDF; PVDF-g-ps refers to the material after alkalization and grafting with styrene tetrahydrofuran (BPO); PVDF-g-pssa refers to the membrane after alkalization and grafting and sulfonation with concentrated sulfuric acid.)
[0059] The above test results show that the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane prepared in this invention achieves synergistic optimization of hydrophilicity, ion selectivity and conductivity through gradient doping and stepwise modification processes. It exhibits excellent separation and recovery performance in lithium sulfate waste liquid treatment and has broad industrial application prospects.
Claims
1. A method for preparing a mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane, characterized in that, Includes the following steps: (1) Add Al2O3 powder and TiO2 powder to water, mix and carry out hydrothermal reaction to obtain composite inorganic material; (2) Add the composite inorganic material to N,N-dimethylformamide, disperse it evenly, then add polyvinylidene fluoride, stir until completely dissolved to form a casting solution, coat the casting solution onto the glass substrate, and obtain the base film after the casting solution dries; (3) Immerse the base membrane in a sodium hydroxide-anhydrous ethanol mixture and heat the mixture to perform alkalization treatment; then add the base membrane to a mixture of benzoyl, styrene and tetrahydrofuran to carry out a grafting reaction, and the grafted membrane is obtained after the reaction is completed. (4) The grafted membrane was immersed in 1,2-dichloromethane to swell, and then transferred to concentrated sulfuric acid for sulfonation reaction. After the reaction was completed, it was washed with dewatered water until neutral and dried to obtain a mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane.
2. The method for preparing the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane according to claim 1, characterized in that, In step (1), the Al2O3 powder is prepared by adding aluminum nitrate nonahydrate and urea to a polyethylene glycol aqueous solution to obtain a mixed solution. The mixed solution is subjected to a hydrothermal reaction under sealed conditions to obtain a precursor. The precursor is then calcined at a constant temperature to obtain Al2O3 powder.
3. The method for preparing the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane according to claim 1, characterized in that, In step (1), the TiO2 powder is prepared by dissolving the surfactant hexadecyltrimethylammonium bromide in isopropanol, mixing it evenly until it is completely dissolved, adding tetrabutyl titanate, and gradually adding glacial acetic acid while stirring continuously to obtain a mixed solution. The mixed solution is reacted under sealed conditions, and TiO2 powder is obtained after the reaction is completed.
4. The method for preparing the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane according to claim 1, characterized in that, In step (1), the mass fraction of Al2O3 in the composite inorganic material is 10%~40%.
5. The method for preparing the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane according to claim 1, characterized in that, In step (2), the amount of composite inorganic material doped in N,N-dimethylformamide is 0.5 to 2.0% of the mass of N,N-dimethylformamide.
6. The method for preparing the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane according to claim 1, characterized in that, In step (3), after the grafting reaction is completed, the membrane is immersed in chloroform to remove excess styrene monomer and homopolymer from the surface.
7. The method for preparing the mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane according to claim 1, characterized in that, In step (4), after the reaction is complete, the membrane is washed with water until it is neutral by rinsing it in small amounts multiple times.
8. A mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane prepared by the method according to any one of claims 1-7.
9. The use of the ion exchange membrane of claim 8 in the preparation of an apparatus for separating and recovering Li⁺ and SO₄²⁻ from lithium sulfate waste liquid.
10. The application according to claim 9, characterized in that, The device is a three-compartment double-membrane electrodialysis reactor, wherein the cation exchange membrane in the device is a mesoporous Al2O3-TiO2 sulfonated electrodialysis ion exchange membrane.