A hybrid membrane for selectively transporting lithium ions and a preparation method and application thereof
The preparation of HMO/PVDF hybrid membranes solves the selectivity and stability problems of existing cation membranes, enabling rapid migration and efficient extraction of lithium ions, reducing lithium extraction costs, and making it suitable for the treatment of leachate from spent lithium batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN POLYTECHNIC UNIV
- Filing Date
- 2025-02-28
- Publication Date
- 2026-05-12
AI Technical Summary
Existing commercial cation exchange membranes have low ion selectivity, resulting in poor lithium extraction efficiency through electrodialysis. Furthermore, the cation exchange membranes in acidic ion mixtures have poor chemical stability and low reusability, which increases the cost of lithium extraction.
HMO was used as a functional filler and mixed with a PVDF matrix to prepare an HMO/PVDF hybrid membrane. A selective lithium-ion transport network was constructed by crosslinking with m-phenylenediamine for use in selective electrodialysis.
It achieves rapid migration and highly selective transport of lithium ions, improves reusability, reduces operating costs of the electrodialysis process, and is conducive to large-scale promotion.
Smart Images
Figure CN119909547B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wastewater treatment and cation exchange membrane preparation technology, and particularly to a hybrid membrane for selectively transporting lithium ions, its preparation method, and its application. Background Technology
[0002] The rapid growth of electric vehicles and large-scale energy storage have driven the manufacturing and disposal of lithium-ion batteries. It is projected that by 2030, the rapidly accumulating lithium-ion waste will reach approximately 11 million tons. Given the limited lithium resources, lithium recovery from battery waste has attracted significant interest from battery manufacturers. Selective electrodialysis, with its advantages of both separation and concentration, is considered a superior downstream process for extracting lithium ions from waste lithium-ion battery leachate. However, the low ion selectivity of commercial cation exchange membranes leads to poor lithium extraction efficiency in electrodialysis processes. Furthermore, the chemical stability of cation exchange membranes in acidic ion mixtures results in low membrane reuse rates, increasing lithium extraction costs.
[0003] To improve the performance of cation exchange membranes, the following points should be noted:
[0004] (1) Use an inert polymer matrix to ensure the acid resistance of the ion exchange membrane and increase the reusability;
[0005] (2) Add hydrophilic transport sites to reduce the migration resistance of hydrated ions and improve transport efficiency;
[0006] (3) Ensure high lithium selectivity.
[0007] To address the above challenges, using lithium-ion sieves with lithium transport sites as inorganic fillers blended into an inert polymer matrix may be an effective method to improve the selective adsorption performance of lithium ions. Currently, inorganic filler-modified polymer membranes mainly come in two structural forms. One is a bilayer structure consisting of a polymer layer and a selective layer. The polymer layer primarily provides mechanical strength as a support for the inorganic adsorbent, while the selective layer mainly provides lithium selectivity; however, filler loss is prone to occur during mass transfer. The other is a hybrid homogeneous membrane structure, where a selective inorganic molecular sieve is uniformly mixed into a polymer solution, and the polymer solution with uniformly dispersed inorganic fillers is used to prepare the hybrid membrane. This type of membrane exhibits more stable ion selectivity, but it is necessary to address the interfacial defects caused by incompatibility between the inorganic phases.
[0008] Therefore, it is necessary to provide a novel hybrid membrane structure and its preparation method to solve the above problems. Summary of the Invention
[0009] To address the shortcomings and deficiencies of existing cation exchange membranes, this invention provides a hybrid membrane for selective lithium ion transport, along with its preparation method and applications. The invention primarily involves adding HMO as a functional filler to a PVDF matrix, followed by uniform mixing to obtain an HMO / PVDF hybrid membrane. HMO provides transport sites for lithium ions, and the uniformly distributed HMO constructs a selective lithium ion transport network. Furthermore, its application in selective electrodialysis technology enables rapid lithium ion migration, allowing for the rapid extraction / separation of lithium from leachate from spent lithium batteries. The provided hybrid membrane exhibits excellent lithium selective transport capability, high reusability, and a simple preparation method, facilitating large-scale application.
[0010] The technical means employed in this invention are as follows:
[0011] A method for preparing a selective lithium-ion transport hybrid membrane involves mixing hydrophilic HMO with PVDF, coating the membrane, and then crosslinking it with m-phenylenediamine to obtain the hybrid membrane.
[0012] Furthermore, it includes the following steps:
[0013] S1, Sulfonation of HMO: HMO was dispersed in a mixture containing ethanol, water, and ammonia solution in a certain proportion and stirred at room temperature; (3-mercaptopropyl)trimethoxysilane was added for modification; the modified HMO was purified by centrifugation with ethanol in a triple cycle and then dried in a vacuum oven; the modified HMO was co-dispersed with acetonitrile, styrene, divinylbenzene, and azobisisobutyronitrile, heated to boiling, and half of the acetonitrile was removed by distillation; the modified HMO was dried in a vacuum oven, sulfonated with concentrated sulfuric acid, and then dried in a vacuum oven to constant weight;
[0014] S2, casting: Dissolve PVDF in NMP to obtain a casting solution; stir at room temperature until all PVDF is dissolved; disperse the sulfonated HMO obtained in step S1 into the PVDF solution, stir vigorously and then sonicate; cast the resulting homogeneous solution onto a glass plate and dry in a high-temperature oven until the solvent is completely evaporated;
[0015] S3, Crosslinking: The membrane prepared in step S2 is washed multiple times with methanol until no residual solvent remains. The membrane is then transferred to a crosslinking solution for crosslinking. After crosslinking, the membrane is transferred to a hydrochloric acid solution to terminate the crosslinking. The membrane is then washed with methanol and stored in deionized water.
[0016] Further, in step S1, the mass-to-volume ratio of HMO to ethanol, water and ammonia is 1g:160ml:10ml:15ml.
[0017] Further, in step S1, the mass-to-volume ratio of (3-mercaptopropyl)trimethoxysilane added to HMO is 1 ml: 1 g, the mixture is ultrasonically treated for 50-60 minutes, and then stirred for an additional 22-24 hours.
[0018] Further, in step S1, the modified HMO is dispersed in a flask together with acetonitrile, styrene, divinylbenzene and azobisisobutyronitrile in a mass-to-volume ratio of 1g:530ml:3ml:3ml:0.1g.
[0019] Further, in step S1, the modified HMO is dried in a vacuum oven at 50°C, then sulfonated with concentrated sulfuric acid at 40°C for 3-4 hours, and then dried in a vacuum oven at 30°C to constant weight.
[0020] Further, in step S2, the PVDF concentration is 20 wt%, the stirring time at room temperature is 22-24 hours; the sulfonated HMO mass fraction is 30 wt%, the vigorous stirring time is 22-24 hours, the ultrasonic time is 1-2 hours; the drying temperature is 80℃, and the drying time is 24 hours.
[0021] Furthermore, in step S3, the crosslinking beaker contains sodium hydroxide, m-phenylenediamine, and magnesium oxide, with contents of 4.5 wt%, 18.2 wt%, and 9.1 wt%, respectively, and the crosslinking time is 24 hours, with a hydrochloric acid concentration of 1M.
[0022] The present invention also discloses a hybrid membrane for selectively transporting lithium ions, which is prepared by the above-described preparation method.
[0023] Furthermore, the hybrid membrane is an HMO / PVDF hybrid membrane with a thickness between 110 μm and 95 μm.
[0024] This invention also provides an application of a selective lithium-ion transport hybrid membrane, which is used for the extraction and separation of lithium ions in leachate from spent lithium batteries. The hybrid membrane promotes the rapid migration of lithium ions through selective electrodialysis, thereby achieving efficient extraction and separation of lithium ions from spent lithium battery leachate. Simultaneously, the membrane exhibits excellent lithium-ion selective permeability and reusability.
[0025] Compared with the prior art, the present invention has the following advantages:
[0026] 1. This invention uses HMO as a functional filler added to a PVDF matrix. HMO provides transport sites for lithium ion transport. The uniformly distributed HMO constructs a selective lithium ion transport network, which greatly improves the migration speed of hydrated lithium ions. At the same time, it is used in selective electrodialysis technology to achieve rapid migration of lithium ions, which can be used to quickly extract / separate lithium from the leachate of waste lithium batteries.
[0027] 2. The lithium transport hybrid membrane prepared by this invention maintains a high lithium selective transport capability after being crosslinked with m-phenylenediamine, and still maintains a high selectivity after 100 hours of selective electrodialysis cycle.
[0028] 3. The invention has low preparation cost, and its high selectivity and durability reduce the operating costs of the electrodialysis process, which is conducive to the large-scale promotion of membrane preparation and the corresponding electrodialysis process.
[0029] Based on the above reasons, this invention can be widely applied in the fields of wastewater treatment and cation exchange membrane preparation technology. Attached Figure Description
[0030] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 The FTIR spectrum of the sulfonated HMO prepared in Example 1 of this invention;
[0032] Figure 2 The XRD pattern of sulfonated HMO prepared in Example 1 of this invention;
[0033] Figure 3 Photograph of the sulfonated HMO / PVDF hybrid membrane prepared in Example 1 of this invention. Detailed Implementation
[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0035] Example 1
[0036] The method for preparing a selective lithium-ion transport hybrid film provided by the present invention specifically includes the following steps:
[0037] Preparation of S1 and sulfonated HMO
[0038] HMO was dispersed in a mixture of ethanol, water and ammonia solution in a mass-to-volume ratio of 1 g: 160 ml: 10 ml: 15 ml and stirred vigorously at room temperature. Then (3-mercaptopropyl)trimethoxysilane was added and stirred for 24 hours. The mass-to-volume ratio of (3-mercaptopropyl)trimethoxysilane to HMO was 1 ml: 1 g. The mixture was sonicated for 60 minutes and then stirred for an additional 24 hours.
[0039] The obtained (3-mercaptopropyl)trimethoxysilane-modified HMO was separated and purified by three-cycle centrifugation with ethanol. After purification, the (3-mercaptopropyl)trimethoxysilane-modified HMO was dried in a vacuum oven at 30°C. The modified HMO was dispersed in a vertical flask with acetonitrile, styrene, divinylbenzene, and azobisisobutyronitrile at a mass-to-volume ratio of 1 g: 530 ml: 3 ml: 3 ml: 0.1 g in a mixture. The mixture was heated and kept at boiling until half of the acetonitrile was distilled off. The modified HMO was then dried in a vacuum oven at 50°C. The dried sample was sulfonated with concentrated sulfuric acid at 40°C for 4 hours. The sulfonated HMO was then dried in a vacuum oven at 30°C until a constant weight was achieved.
[0040] The FTIR chromatogram of the obtained sulfonated HMO is shown below. Figure 1 As shown, at 630cm 1 The adsorption bands on the left and right are attributed to the Mn-O stretching vibration. 3410 cm⁻¹ 1 and 1645cm 1 The wide bands around the left and right are caused by the asymmetric stretching and bending vibrations of water molecules adsorbed by the sulfonic acid groups of SHMO (sulfonated HMO). These vibrations occur at 1149 and 1046 cm⁻¹. 1 Two broadband vibrations can be observed at this point, namely the stretching vibrations of the S=O or SO bonds of the sulfonic acid group. From Figure 2 It can be seen that sulfonated HMO exhibits strong crystalline phase characteristics, and characteristic diffraction peaks of crystal planes (111), (311), (400), and (440) can be observed.
[0041] S2, Coating
[0042] 20 wt% PVDF was dissolved in NMP to obtain a film-forming solution; the solution was stirred at room temperature for 24 hours until all PVDF was dissolved; 30 wt% sulfonated HMO was dispersed in the PVDF solution to obtain solution A, which was stirred vigorously for 24 hours, followed by sonication for 1 hour. The resulting homogeneous solution was cast onto a glass plate and dried in a high-temperature oven at 80°C for 24 hours to ensure complete solvent evaporation.
[0043] S3, crosslinking
[0044] The membrane was washed multiple times with methanol to ensure that there was no solvent residue in the pores of the membrane obtained in step S2, and then transferred to a beaker for crosslinking. The crosslinking beaker contained sodium hydroxide, m-phenylenediamine, and magnesium oxide, with contents of 4.5 wt%, 18.2 wt%, and 9.1 wt%, respectively. After 24 hours of crosslinking, the membrane was transferred to a 1M hydrochloric acid solution to terminate the crosslinking, and the hybrid membrane washed with methanol was stored in deionized water.
[0045] The surface photograph of the obtained CL-SHMO / PVDF hybrid membrane (i.e., the sample that has been simultaneously blended with sulfonated HMO and crosslinked) shows a dark, thin, dense membrane (e.g. Figure 3 (As shown).
[0046] Example 2
[0047] The method for preparing a selective lithium-ion transport hybrid film provided in this embodiment differs from that in Example 1 in that:
[0048] In step S2, 10 wt% sulfonated HMO is dispersed in the PVDF solution; in step S3, the crosslinking time is 12 hours; the remaining steps and parameters are exactly the same.
[0049] The thickness of the obtained CL-SHMO\PVDF film is 110 μm.
[0050] Example 3
[0051] Compared with Example 1, the difference is that in step S2, 20 wt% of sulfonated HMO is dispersed in the PVDF solution; in step S3, the crosslinking time is 36 hours; the remaining steps and parameters are exactly the same.
[0052] The thickness of the obtained CL-SHMO\PVDF hybrid film is 100 μm.
[0053] Example 4
[0054] Compared with Example 1, the difference is that in step S2, 40 wt% of sulfonated HMO is dispersed in the PVDF solution; in step S3, the crosslinking time is 36 hours; the remaining steps and parameters are exactly the same.
[0055] The thickness of the obtained CL-SHMO\PVDF hybrid film is 100 μm.
[0056] Example 5
[0057] Compared with Example 1, the difference is that in step S2, 50 wt% of sulfonated HMO is dispersed in the PVDF solution; in step S3, the crosslinking time is 48 hours; the remaining steps and parameters are exactly the same.
[0058] The thickness of the obtained CL-SHMO\PVDF hybrid film is 95 μm.
[0059] Comparative Example 1
[0060] Compared with Example 1, the difference is that in step S2, the concentration of SHMO in solution A is 0 wt%, and the other steps and parameters are exactly the same, resulting in a CL-PVDF hybrid membrane.
[0061] Comparative Example 2
[0062] Compared with Example 1, the difference is that in step S2, HMO that has not undergone step S1 is used in solution A, while the other steps and parameters are exactly the same, and the resulting product is a CL-HMO / PVDF hybrid membrane.
[0063] Comparative Example 3
[0064] Compared with Example 1, the difference is that in step S3, the crosslinking time in solution A is 0 hours, while the other steps and parameters are exactly the same, and the resulting membrane is an SHMO / PVDF hybrid membrane.
[0065] Experimental Example 1
[0066] This experiment investigated the effects of sulfonated HMO concentration and crosslinking time on the selective transport capability of the prepared hybrid membrane during the preparation process of the selective transport lithium ion hybrid membrane.
[0067] Experimental Methods: CL-SHMO / PVDF hybrid membranes were prepared according to the method shown in Example 1. The concentration of sulfonated HMO in step S2 and the crosslinking time in step S3 were varied, as shown in Table 1. The ion separation performance and lithium-ion transport capacity of the CL-SHMO / PVDF hybrid membranes obtained with different SHMO concentrations and crosslinking times were tested to investigate the influence of sulfonated HMO concentration and crosslinking time on the selective transport capacity of the prepared hybrid membranes. The test conditions are as follows:
[0068] Using 100 ml of a 0.2 mol / L Li₂SO₄ / NiSO₄ solution as the feed solution, the prepared CL-SHMO / PVDF hybrid membrane was assembled into a selective electrodialysis unit. After one hour of stable operation, the ion selectivity and lithium-ion flux were calculated. The Li / Ni separation factor results are shown in Table 1. + Flux is shown in Table 2
[0069] As shown, the separation factor S = ,in, Indicates the initial Li ion concentration; This indicates the Li ion concentration in the desalination chamber after stabilization. Indicates the initial Ni ion concentration; This indicates the Ni ion concentration in the desalination chamber after stabilization.
[0070] Table 1. Li / Ni separation performance data for the examples and comparative examples.
[0071]
[0072] Table 2. Lithium-ion flux test data of hybrid membranes in the examples and comparative examples.
[0073]
[0074] As can be seen from the results in Tables 1 and 2, under the same test conditions, the selective lithium-ion transport hybrid membrane prepared by this invention exhibits superior lithium selective transport performance.
[0075] Experimental Example 2
[0076] This test example uses the CL-SHMO\PVDF hybrid membrane obtained in Example 1 as an example to investigate whether it still maintains a high lithium selective transport capability after 10 repeated runs.
[0077] Test method: Using the operating parameters and influent solution from Example 1, the separation factor and lithium flux were monitored every 10 hours. The 100-hour continuous lithium-ion selective transport is shown in Table 3.
[0078] Table 3. Test data of the hybrid membrane in Example 1 for continuous lithium-ion selective transport over 100 hours.
[0079]
[0080] As can be seen from the results in Table 3, the CL-SHMO\PVDF hybrid membrane obtained in this invention still maintains a high selective lithium-ion transport capability after 100 hours of continuous operation.
[0081] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a selective lithium-ion transport hybrid film, characterized in that, The hybrid membrane was obtained by mixing hydrophilic HMO with PVDF, coating the membrane, and then crosslinking it with m-phenylenediamine. Includes the following steps: S1, Sulfonation of HMO: HMO was dispersed in a mixture containing ethanol, water, and ammonia solution in a certain proportion and stirred at room temperature; (3-mercaptopropyl)trimethoxysilane was added to modify HMO; the modified HMO was purified by centrifugation with ethanol in a triple cycle and then dried in a vacuum oven; the modified HMO was co-dispersed with acetonitrile, styrene, divinylbenzene, and azobisisobutyronitrile, heated to boiling, and half of the acetonitrile was removed by distillation; the modified HMO was dried in a vacuum oven and then sulfonated with concentrated sulfuric acid, and the sulfonated HMO was dried in a vacuum oven to constant weight; S2, casting: Dissolve PVDF in NMP to obtain a casting solution; stir at room temperature until all PVDF is dissolved; disperse the sulfonated HMO obtained in step S1 into the PVDF solution, stir vigorously and then sonicate; cast the resulting homogeneous solution onto a glass plate and dry in a high-temperature oven until the solvent is completely evaporated; S3, Crosslinking: The membrane is washed multiple times with methanol to ensure that there is no residual solvent in the pores of the membrane prepared in step S2. Then the membrane is transferred to a beaker for crosslinking. The crosslinking beaker contains sodium hydroxide, m-phenylenediamine and magnesium oxide. After crosslinking, the membrane is transferred to hydrochloric acid solution to terminate the crosslinking. The membrane is washed with methanol and the resulting hybrid membrane is stored in deionized water.
2. The preparation method according to claim 1, characterized in that, In step S1, the mass-to-volume ratio of HMO to ethanol, water, and ammonia is 1g:160ml:10ml:15ml.
3. The preparation method according to claim 2, characterized in that, In step S1, the volume-to-mass ratio of (3-mercaptopropyl)trimethoxysilane added to HMO is 1 ml: 1 g.
4. The preparation method according to claim 3, characterized in that, In step S1, the modified HMO is dispersed in a flask with acetonitrile, styrene, divinylbenzene and azobisisobutyronitrile in a mass-to-volume ratio of 1g:530ml:3ml:3ml:0.1g. After drying the modified HMO in a vacuum oven at 50°C, it is sulfonated with concentrated sulfuric acid at 40°C for 3-4 hours, and then dried in a vacuum oven at 30°C to constant weight.
5. The preparation method according to claim 1, characterized in that, In step S2, the PVDF concentration is 20 wt%, the stirring time at room temperature is 22-24 hours, the sulfonated HMO mass fraction is 30 wt%, the vigorous stirring time is 22-24 hours, the ultrasonic time is 1-2 hours, the drying temperature is 80℃, and the drying time is 24 hours.
6. The preparation method according to claim 1, characterized in that, In step S3, the crosslinking beaker contains sodium hydroxide, m-phenylenediamine, and magnesium oxide, with contents of 4.5 wt%, 18.2 wt%, and 9.1 wt%, respectively. The crosslinking time is 24 hours, and the hydrochloric acid concentration is 1M.
7. A hybrid membrane for selectively transporting lithium ions, characterized in that, The hybrid membrane is prepared by the preparation method described in any one of claims 1-6.
8. The hybrid membrane for selectively transporting lithium ions according to claim 7, characterized in that, The thickness of the hybrid membrane is between 110 μm and 95 μm.
9. An application of the selective lithium-ion transport hybrid membrane as described in claim 8, characterized in that, The hybrid membrane is used for the extraction and separation of lithium ions in the leachate of spent lithium batteries.