Composite separation membrane based on vertically oriented two-dimensional material interlayer and preparation method thereof

Abstract

The present application relates to a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer and a preparation method thereof. The preparation method comprises the following steps: (1) immersing a substrate in a solvent to sufficiently wet the substrate, and then immersing the substrate in deionized water to sufficiently replace the solvent; (2) preparing a vertically oriented two-dimensional material intermediate layer on the substrate; (3) sequentially contacting and removing an aqueous solution and an oil phase solution on the surface of the substrate after modification of the vertically oriented two-dimensional material intermediate layer, performing an interfacial polymerization reaction, washing the surface of the composite separation membrane with a solvent, and then transferring the composite separation membrane to an oven for heat treatment to obtain a top polymer active layer, wherein the composite separation membrane is composed of a bottom substrate, a vertically oriented two-dimensional material intermediate layer in the middle, and a top polymer active layer based on the interfacial polymerization reaction.

Description

Technical Field

[0001] The present invention belongs to the field of membrane separation technology, and in particular relates to a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer and a preparation method thereof. Background Art

[0002] Membrane separation technology has been widely used in water treatment, industrial separation, food and medicine and other fields. For membrane separation technology with high screening accuracy, thin film composite (TFC) membranes have been widely studied in terms of membrane materials and have become mainstream commercial products. The characteristic of TFC membranes is that they have a dense but thin active layer on the top (usually prepared by interfacial polymerization (IP) reaction). However, the performance of conventional TFC membranes usually has a "trade-off" effect, that is, the permeability and selectivity of the membrane are mutually restricted. As a simple and efficient method to break the limitation of the "trade-off" effect, intermediate layer technology has received widespread attention in recent years.

[0003] In terms of the type of intermediate layer, organic coatings generally have good stability and practicality. However, they often lead to a significant increase in mass transfer resistance. Since inorganic or crystalline materials have higher porosity and lower friction resistance, they are also often used to prepare intermediate layers. Among them, two-dimensional materials with large lateral dimensions have attracted much attention due to their rapid water transport effect between layers, but disordered stacked two-dimensional material intermediate layers often also have higher mass transfer resistance. In order to further enhance the mass transfer process, researchers usually use non-covalent bond-based intercalation technology to precisely adjust the interlayer spacing of two-dimensional materials. However, this strategy will potentially lead to relatively long mass transfer paths and uncertain stability when passing through the two-dimensional material layer. Hurt et al. (Nature Communications, 2021, 12, 507) used two-dimensional modified graphene oxide to prepare nearly vertically oriented nanochannel arrays, and pointed out that this robust nanofluidic device can significantly reduce the length of the fluid mass transfer path, thereby reducing the mass transfer resistance. However, this work did not combine the interfacial polymerization process to prepare a composite separation membrane, and did not explain the effect of the vertically oriented two-dimensional intermediate layer on the interfacial polymerization process. Xu et al. (ACS Applied Materials & Interfaces, 2021, 13, 33, 39819-39830) prepared a disordered stack of two-dimensional ZIF-L interlayers on a ceramic substrate by vacuum-assisted deposition. They then prepared a polymer active layer on top of the interfacial polymerization reaction to form a TFC membrane for pervaporation dehydration. However, this work did not mention the preparation of the vertically oriented two-dimensional material interlayer or the mechanism by which the type of the two-dimensional material interlayer affects the performance of the TFC membrane. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer and a preparation method thereof. The vertically oriented two-dimensional material intermediate layer has a short mass transfer path and excellent aqueous solution storage capacity, which is beneficial to reducing the mass transfer resistance and improving the cross-linking structure of the top polymer active layer by affecting the interfacial polymerization process, thereby improving the overall performance of the composite membrane.

[0005] The technical solution of the present invention is a method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer, which is special in that it includes the following steps:

[0006] (1) Immerse the substrate in the solvent to fully wet it, and then immerse it in deionized water to fully replace the solvent;

[0007] (2) preparing a vertically oriented two-dimensional material intermediate layer on the substrate;

[0008] ⑶ The substrate surface modified with the vertically oriented two-dimensional material intermediate layer is contacted with and removed from the aqueous phase solution and the oil phase solution in turn. After the interfacial polymerization reaction occurs, the surface of the composite separation membrane is rinsed with a solvent and then transferred to an oven for heat treatment to obtain a top polymer active layer. The composite separation membrane is composed of the bottom substrate, the middle vertically oriented two-dimensional material intermediate layer and the top polymer active layer based on the interfacial polymerization reaction.

[0009] Preferably, step (1) further includes the following: the substrate is made of organic material, inorganic material or organic / inorganic composite material, with a pore size of 10 to 500 nm, wherein: the organic material substrate is made of polyacrylonitrile, polyimide, polyethylene, polypropylene or polyvinyl chloride; the inorganic material substrate is made of anodized aluminum or ceramic; the solvent does not cause swelling to the substrate and can fully infiltrate the substrate, preferably isopropanol, and the solvent infiltration time is 10 to 180 minutes, and then the substrate is transferred to deionized water and soaked for 1 to 8 hours.

[0010] Preferably, step (2) further includes the following: adjusting the vertical orientation degree of the vertically oriented two-dimensional material by changing the preparation conditions of the vertically oriented two-dimensional material intermediate layer, thereby directly changing the length of the mass transfer path and affecting the subsequent interfacial polymerization reaction.

[0011] Preferably, the preparation conditions include one or more combinations of the growth time of the two-dimensional material, the deposition time of the two-dimensional material seed layer, the amount of the two-dimensional material template, and the concentration of the ligands required for the synthesis of the two-dimensional material; the adjustment of the vertical orientation degree of the vertically oriented two-dimensional material further includes: increasing the growth time of the two-dimensional material, increasing the deposition time of the two-dimensional material seed layer, increasing the amount of the two-dimensional material template, and increasing the concentration of the ligands required for the synthesis of the two-dimensional material.

[0012] Preferably: in step ⑵, the preparation method of the vertically oriented two-dimensional material intermediate layer is a combination of one or more of in-situ growth method, secondary growth method, water / solvent thermal method, atomic layer deposition, chemical vapor deposition or template method, preferably secondary growth method; the vertically oriented two-dimensional material is a combination of one or more of molybdenum disulfide, hexagonal boron nitride, zeolite imidazolate framework structure ZIF-L or transition metal carbon / nitride two-dimensional nanolayered material MXene, preferably zeolite imidazolate framework structure ZIF-L.

[0013] As a preference: the solute of the aqueous phase solution in step (3) is selected from one or more polyamines or polyol monomers of pentaerythritol, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, triethanolamine or dendritic polyamide amine; the solute of the aqueous phase solution further comprises additives, including one or more combinations of cosolvents, surfactants, high molecular polymers, monoamines or alcohol molecules and nanoparticles; the solute of the oil phase solution in step (3) is selected from trimesoyl chloride, terephthaloyl chloride, cyclohexanetriyl chloride, cyclobutanetetrayl chloride, benzene-1,3-disulfonyl chloride , benzene-1,3,5-trisulfonyl chloride or naphthalene-1,3,6-trisulfonyl chloride; the solute of the oil phase solution is selected from one or more polyacyl chloride monomers of cyclobutanetetrachloride, benzene-1,3-disulfonyl chloride, benzene-1,3,5-trisulfonyl chloride or naphthalene-1,3,6-trisulfonyl chloride; the solvent of the oil phase solution is a straight-chain alkane, an isoalkane or a mixture of multiple alkanes with a carbon chain length of 6 to 12; the solute of the oil phase solution contains oil phase additives, including one or more combinations of co-solvents or nanoparticles.

[0014] Preferably, step (3) further includes: the temperature of the heat treatment is 50 to 90°C; the heat treatment time is 2 to 30 minutes; the contact time between the substrate surface after the modification of the vertically oriented two-dimensional material intermediate layer and the aqueous solution is 1 to 30 minutes; the contact time between the substrate surface after the modification of the vertically oriented two-dimensional material intermediate layer and the oil phase solution is 20 to 900 seconds.

[0015] Another technical solution of the present invention is the composite separation membrane based on the vertically oriented two-dimensional material intermediate layer, which is special in that it is prepared according to any of the preparation methods described above.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The composite separation membrane based on the vertically oriented two-dimensional material intermediate layer described in the present invention can be applied to a variety of membrane separation processes, including but not limited to pressure osmosis process, pervaporation desalination process and forward osmosis process.

[0018] (2) The vertically oriented two-dimensional material interlayer of the present invention has a shorter mass transfer path in the mass transfer process compared with the disordered stacked two-dimensional material interlayer. Figure 1 , therefore, the mass transfer resistance can be significantly reduced, which in turn directly affects the permeability of the composite membrane.

[0019] ⑶ Compared with the original substrate, the vertically oriented two-dimensional material intermediate layer of the present invention has abundant and easily accessible interlayer spaces, so it can store more aqueous monomers participating in the interfacial polymerization reaction. Figure 2 , thereby achieving the regulation of the interfacial polymerization reaction and the cross-linking structure of the top active layer.

[0020] ⑷ The brackish water desalination performance of the composite separation membrane based on the vertically oriented two-dimensional material intermediate layer described in the present invention is better than that of the composite separation membrane based on the disordered stacked two-dimensional material intermediate layer, and the comprehensive performance of the composite membrane reaches the best when the secondary growth time is 10 minutes. Please refer to the desalination performance of Examples 1 to 3 and Control Example 1 in Table 1, which shows that the performance of the composite membrane can be optimized by regulating the structure of the vertically oriented two-dimensional material intermediate layer.

[0021] ⑸ The pervaporation desalination performance of the composite separation membrane based on the vertically oriented two-dimensional material intermediate layer described in the present invention is better than that of the composite separation membrane based on the disordered stacked two-dimensional material intermediate layer, and the comprehensive performance of the composite membrane reaches the best when the secondary growth time is 30 minutes. Please refer to the desalination performance of Examples 4 to 6 and Control Example 2 in Table 2, indicating that the performance of the composite membrane can be optimized by regulating the structure of the vertically oriented two-dimensional material intermediate layer.

[0022] ⑹ The performance of the composite separation membrane based on the vertically oriented two-dimensional material intermediate layer described in the present invention can be adjusted by changing the preparation process and conditions of the vertically oriented two-dimensional material intermediate layer, thereby adjusting the vertical orientation degree of the two-dimensional material. The change in the vertical orientation degree of the two-dimensional material will directly affect the length of the mass transfer path and the adsorption capacity for amine monomers, thereby affecting the subsequent interfacial polymerization reaction process.

[0023] ⑺The top ultra-thin polymer active layer of the composite separation membrane based on the vertically oriented two-dimensional material intermediate layer described in the present invention is prepared by an interfacial polymerization process, which is relatively mature and easy to scale up industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the mass transfer path of the middle layer of the vertically oriented two-dimensional material of the present invention and the ability of the middle layer to store aqueous solution;

[0025] Figure 2 Schematic diagram of the mass transfer path of the middle layer of traditional disordered stacked two-dimensional materials and the ability of the middle layer to store aqueous solutions;

[0026] Figure 33 is a schematic diagram of a surface scanning electron microscope (SEM) of a vertically aligned two-dimensional material intermediate layer according to Example 2 of the present invention;

[0027] Figure 4 This is a surface SEM diagram of the middle layer of the disordered stacked two-dimensional material of Control Example 1;

[0028] Figure 5 is a grazing incidence X-ray diffraction (GIXRD) pattern of the vertically aligned two-dimensional material intermediate layer of Example 1;

[0029] Figure 6 is the GIXRD pattern of the vertically aligned two-dimensional material intermediate layer of Example 2;

[0030] Figure 7 is the GIXRD pattern of the middle layer of the disordered stacked two-dimensional material of Control Example 1;

[0031] Figure 8 is a UV-visible spectrum of the m-phenylenediamine solution adsorbed by the intermediate layer of the two-dimensional material of Examples 1 to 3 and Comparative Example 1;

[0032] Figure 9 3 is a surface SEM diagram of the vertically aligned two-dimensional material intermediate layer of Example 5 of the present invention;

[0033] Figure 10 This is a surface SEM diagram of the middle layer of the disordered stacked two-dimensional material of Control Example 2;

[0034] Figure 11 is the GIXRD pattern of the vertically aligned two-dimensional material intermediate layer of Example 4;

[0035] Figure 12 is the GIXRD pattern of the vertically aligned two-dimensional material intermediate layer of Example 5;

[0036] Figure 13 This is the GIXRD pattern of the middle layer of the disordered stacked two-dimensional material of Control Example 2;

[0037] Figure 14 It is the ultraviolet-visible spectrum of the m-phenylenediamine solution adsorbed by the intermediate layer of the two-dimensional materials of Examples 4 to 6 and Comparative Example 2. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the embodiments:

[0039] Example 1 to Example 3:

[0040] A method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer for brackish water desalination, comprising the following steps:

[0041] (1.1) Immersing an organic material substrate in isopropyl alcohol for 10 to 180 minutes, including 10 minutes, 40 minutes, 90 minutes, 135 minutes, 180 minutes, and 10 to 40 minutes, 40 minutes to 90 minutes, 90 minutes to 135 minutes, 135 minutes to 180 minutes, 10 minutes to 85 minutes, and 85 minutes to 180 minutes; the organic material substrate is preferably polyethylene, and the pore size is 100 nm to 200 nm, including 100 nm, 150 nm, 200 nm, 100 to 150 nm, and 150 to 200 nm, and then transferring the substrate to deionized water and soaking for 1 to 8 hours;

[0042] (1.2) A vertically oriented two-dimensional material intermediate layer is prepared on an organic material substrate by a secondary growth method. The two-dimensional material is preferably ZIF-L. Specifically, the preparation steps are as follows:

[0043] (1.2.1) preparing a zinc nitrate aqueous solution and a dimethylimidazole aqueous solution, wherein the solute molar ratio of the zinc nitrate aqueous solution to the dimethylimidazole aqueous solution must be 1:8;

[0044] (1.2.2) Premix the prepared zinc nitrate aqueous solution and dimethylimidazole aqueous solution in a volume ratio of 1:2 and quickly pour the mixture onto the substrate surface to form a seed layer. The deposition time is 5 to 30 minutes, preferably 10 minutes. After the deposition is completed, remove any remaining liquid from the surface.

[0045] (1.2.3) Premix the prepared zinc nitrate aqueous solution and dimethylimidazole aqueous solution in a volume ratio of 1:1 and quickly pour the mixture onto the substrate surface to achieve secondary growth. The deposition time is 5 min to 30 min, including 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, and 5 min to 10 min, 10 min to 15 min, 15 min to 20 min, 20 min to 25 min, and 25 min to 30 min. After the deposition is completed, remove the residual liquid on the surface.

[0046] (1.3) The top polymer active layer is prepared by an interfacial polymerization process. Specifically, the surface of the substrate modified with the vertically oriented two-dimensional material intermediate layer is sequentially exposed to and removed from the aqueous solution and the oil phase solution. After the interfacial polymerization reaction occurs, the membrane surface is rinsed with a solvent and then transferred to an oven for heat treatment.

[0047] The solute of the aqueous solution is one or more polyamine or polyol monomers such as piperazine, m-phenylenediamine, p-phenylenediamine, pentaerythritol, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, triethanolamine or dendritic polyamidoamine, preferably m-phenylenediamine;

[0048] The solute of the aqueous solution may further comprise additives, including one or more combinations of cosolvents, surfactants, high molecular polymers, monoamines or alcohol molecules and nanoparticles, preferably sodium lauryl sulfate;

[0049] The solute of the oil phase solution is one or more polyacyl chloride monomers selected from trimesoyl chloride, terephthaloyl chloride, cyclohexanetrichloride, cyclobutanetetrachloride, benzene-1,3-disulfonyl chloride, benzene-1,3,5-trisulfonyl chloride or naphthalene-1,3,6-trisulfonyl chloride, preferably trimesoyl chloride;

[0050] The solvent of the oil phase solution is a straight-chain alkane or isoalkane or a mixture of multiple types with a carbon chain length of 6 to 12, preferably n-hexane;

[0051] The contact time between the substrate surface modified with the vertically oriented two-dimensional material intermediate layer and the aqueous phase solution is 2 to 30 minutes, including 2 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, and 2 to 10 minutes, 10 to 15 minutes, 15 to 20 minutes, 20 to 25 minutes, 25 to 20 minutes; the contact time between the substrate surface modified with the vertically oriented two-dimensional material intermediate layer and the oil phase solution is 20 to 900 seconds, preferably 1 minute; including 20 seconds, 50 seconds, 100 seconds, 150 seconds, 200 seconds, 250 seconds, 300 seconds, 300 seconds, 400 seconds, 500 seconds, 600 seconds, 700 seconds, 800 seconds, 900 seconds, 1000 seconds, 1500 seconds, 2000 seconds, 2500 seconds, 3000 seconds, 4000 seconds, 5000 seconds, 6000 seconds, 7000 seconds, 8000 seconds, 9 ...8000 seconds, 50s, 400s, 450s, 500s, 550s, 600s, 650s, 700s, 7500s, 800s, 850s, 900s, 20-100s, 100-150s, 150-200s, 200-250s, 250-300s, 300-350s, 350-400s, 400-450s, 450-500s, 500-550s, 550-600s, 600-650s, 6500-700s, 700-750s, 750-800s, 800-850s, 850-900s;

[0052] The temperature of the heat treatment is 50-90°C, including 50°C, 60°C, 70°C, 80°C, 90°C, and 50°C-60°C, 60°C-70°C, 70°C-80°C, 80°C-90°C. The time of the heat treatment is 2-30min, preferably 5min, including 2min, 7min, 14min, 20min, 25min, 30min, as well as 2-5min, 6-10min, 10-15min, 15-20min, 20-25min, 25-30min.

[0053] Examples 1-3 were prepared according to the above steps to obtain composite separation membranes based on a vertically oriented two-dimensional material intermediate layer, except that the secondary growth time of the intermediate layer was 6 min, 10 min, and 15 min, respectively. The surface SEM image of the vertically oriented two-dimensional material intermediate layer of Example 2 is shown in the attached figure. Figure 3 shown.

[0054] Comparative Example 1:

[0055] The difference between Control Example 1 and Examples 1 to 3 is that the ZIF-L intermediate layer in step (1.2) is prepared by vacuum assisted deposition process, and the ZIF-L nanosheets are in a disordered stacking state, and the surface SEM image thereof is shown in the attached Figure 4 shown.

[0056] The vacuum assisted deposition process is characterized in that a ZIF-L dispersion needs to be prepared in advance and then filtered onto the substrate surface.

[0057] The preparation steps of the ZIF-L dispersion are as follows:

[0058] (2.1) Mixing the prepared aqueous solution of zinc nitrate and aqueous solution of dimethylimidazole in a volume ratio of 1:1 and stirring at room temperature for 3 h;

[0059] (2.2) The reaction solution was then centrifuged at 4500 rpm and the precipitate was washed with deionized water. This operation was repeated three times.

[0060] (2.3) Finally, the washing solution was centrifuged at 3000 rpm, and the supernatant was the desired ZIF-L dispersion.

[0061] The grazing incidence X-ray diffraction patterns of Example 1, Example 2 and Comparative Example 1 are shown in the attached figures. Figure 5 , Attachment Figure 6 and attached Figure 7 As shown in the figure, the results show that with the increase of growth time, the crystallographic preferred orientation of (020) and (112) planes of ZIF-L CPO 020 / 112 This indicates that the vertical orientation of the two-dimensional ZIF-L can be improved by increasing the growth time. In addition, the CPO of the disordered stacked two-dimensional material intermediate layer in Example 1 020 / 112 It is significantly lower than the vertically oriented two-dimensional material intermediate layer based on secondary growth, which verifies the difference in orientation between the two in SEM.

[0062] The UV-visible spectra of Examples 1 to 3 and Comparative Example 1 (the test method refers to the method disclosed in the literature (Journal of Membrane Science, 2024, 695, 122455), and the characteristic peak of m-phenylenediamine is at 294 nm) are shown in the attached figure. Figure 8As shown, the results show that with the increase of growth time, the amount of adsorbed meta-phenylenediamine in the vertically oriented two-dimensional material interlayer (positively correlated with the spectral peak intensity) increases accordingly, which indicates that the ability of the two-dimensional ZIF-L interlayer to adsorb amine monomers can be improved by increasing the growth time; in addition, the adsorption amount of meta-phenylenediamine in the disordered stacked two-dimensional material interlayer in Control Example 2 is significantly lower than that in the vertically oriented two-dimensional material interlayer based on secondary growth, highlighting the advantages of the vertically oriented two-dimensional material interlayer in adsorbing amine monomers.

[0063] Examples 1 to 3 and Comparative Example 1 were subjected to a brackish water desalination test under the following conditions: the feed liquid was a 2 g / L sodium chloride aqueous solution, the test pressure was 1.5 MPa, and the desalination performance after two hours of stable operation was shown in Table 1.

[0064] Table 1 Desalination performance of Examples 1 to 3 and Comparative Example 1

[0065]

[0066] The results show that the composite separation membrane based on the vertically oriented two-dimensional material interlayer has good operability in the membrane preparation process. The brackish water desalination performance of the composite separation membrane based on the vertically oriented two-dimensional material interlayer is better than that of the composite separation membrane based on the disordered stacked two-dimensional material interlayer. The comprehensive performance of the composite membrane reaches the best when the secondary growth time is 10 minutes, as shown in Table 1. This shows that the performance of the composite membrane can be optimized by regulating the structure of the vertically oriented two-dimensional material interlayer.

[0067] Example 4 to Example 6:

[0068] A method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer for pervaporation desalination, comprising the following steps:

[0069] (3.1) Immersing the organic material substrate in isopropyl alcohol for 10 to 180 minutes, including 10 minutes, 40 minutes, 90 minutes, 135 minutes, 180 minutes, and 10 minutes to 40 minutes, 40 minutes to 90 minutes, 90 minutes to 135 minutes, 135 minutes to 180 minutes, 10 minutes to 85 minutes, and 85 minutes to 180 minutes; the organic material substrate is preferably polyethylene with a pore size of 100 nm to 200 nm, including 100 nm, 150 nm, 200 nm, 100 to 150 nm, and 150 to 200 nm; the organic material substrate is preferably polypropylene with a pore size of 50 to 150 nm, and then transferring the substrate to deionized water and soaking for 1 to 8 hours;

[0070] (3.2) A vertically oriented two-dimensional material intermediate layer is prepared on an organic material substrate by a secondary growth method. The two-dimensional material is preferably ZIF-L. Specifically, the preparation steps are as follows:

[0071] (3.2.1) Prepare an aqueous solution of zinc nitrate and an aqueous solution of dimethylimidazole, wherein the solute molar ratio of the aqueous solution of zinc nitrate and the aqueous solution of dimethylimidazole is 1:8;

[0072] (3.2.2) Premix the prepared aqueous solution of zinc nitrate and the aqueous solution of dimethylimidazole in a volume ratio of 1:2 and quickly pour the mixture onto the substrate surface to form a seed layer. The deposition time is 10 to 60 minutes, preferably 20 minutes. After the deposition is completed, remove any residual liquid from the surface.

[0073] (3.2.3) Premix the prepared aqueous solution of zinc nitrate and the aqueous solution of dimethylimidazole in a volume ratio of 1:1 and quickly pour the mixture onto the substrate surface to achieve secondary growth. The deposition time is 10-120 minutes. After the deposition is completed, remove any remaining liquid from the surface.

[0074] (3.3) The top polymer active layer is prepared by an interfacial polymerization process. Specifically, the surface of the substrate modified with the vertically oriented two-dimensional material intermediate layer is contacted with and removed from the aqueous phase solution and the oil phase solution in sequence. After the interfacial polymerization reaction occurs, the membrane surface is rinsed with a solvent and then transferred to an oven for heat treatment.

[0075] The solute of the aqueous solution can be one or more polyamine or polyol monomers such as piperazine, m-phenylenediamine, p-phenylenediamine, pentaerythritol, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, triethanolamine or dendritic polyamidoamine, preferably piperazine.

[0076] The solute of the aqueous solution may further include additives, including one or more combinations of cosolvents, surfactants, high molecular polymers, monoamines or alcohol molecules, and nanoparticles, preferably sodium lauryl sulfate.

[0077] The solute of the oil phase solution can be one or more polyacyl chloride monomers such as trimesoyl chloride, terephthaloyl chloride, cyclohexanetrichloride, cyclobutanetetrachloride, benzene-1,3-disulfonyl chloride, benzene-1,3,5-trisulfonyl chloride or naphthalene-1,3,6-trisulfonyl chloride, preferably trimesoyl chloride.

[0078] The solvent of the oil phase solution may be a straight-chain alkane or isoalkane or a mixture of multiple types of alkane with a carbon chain length of 6 to 12, preferably n-hexane.

[0079] The contact time between the substrate surface modified with the vertically oriented two-dimensional material intermediate layer and the aqueous phase solution is 1 to 30 min, including 1 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, and 1 to 10 min, 10 to 15 min, 15 to 20 min, 20 to 25 min, 25 to 20 min; the contact time between the substrate surface modified with the vertically oriented two-dimensional material intermediate layer and the oil phase solution is 20 to 900 s, preferably 1 min; including 20 s, 50 s, 100 s, 150 s, 200 s, 250 s, 300 s, 300 s, 400 s, 500 s, 1000 s, 2000 s, 2500 s, 3000 s, 4000 s, 5000 s, 6000 s, 7000 s, 8000 s, 9000 s, 10000 s, 20000 s, 30000 s, 40000 s, 50000 s, 60000 s, 70000 s, 80000 s, 90000 s, 100000 s, 200000 s, 300000 s, 400000 s, 50000 s, 60000 s, 70000 s, 80000 s, 80000 s, 90000 s, 100000 s, 50s, 400s, 450s, 500s, 550s, 600s, 650s, 700s, 7500s, 800s, 850s, 900s, 20-100s, 100-150s, 150-200s, 200-250s, 250-300s, 300-350s, 350-400s, 400-450s, 450-500s, 500-550s, 550-600s, 600-650s, 6500-700s, 700-750s, 750-800s, 800-850s, 850-900s;

[0080] The temperature of the heat treatment is 50-90°C, including 50°C, 60°C, 70°C, 80°C, 90°C, and 50°C-60°C, 60°C-70°C, 70°C-80°C, 80°C-90°C. The time of the heat treatment is 2-30min, preferably 5min, including 2min, 7min, 14min, 20min, 25min, 30min, as well as 2-5min, 6-10min, 10-15min, 15-20min, 20-25min, 25-30min.

[0081] Examples 4 to 6 were prepared according to the above steps to obtain composite separation membranes based on a vertically oriented two-dimensional material intermediate layer, except that the secondary growth time of the intermediate layer was 10 min, 30 min, and 50 min, respectively. The surface SEM image of the vertically oriented two-dimensional material intermediate layer of Example 5 is shown in the attached figure. Figure 9 shown.

[0082] Comparative Example 2:

[0083] The difference between Control Example 2 and Examples 4 to 6 is that the ZIF-L intermediate layer in step (3.2) is prepared by vacuum assisted deposition process, and the ZIF-L nanosheets are in a disordered stacking state, and the surface SEM image thereof is shown in the attached Figure 10 shown.

[0084] The vacuum assisted deposition process is the same as that of Control Example 1.

[0085] The grazing incidence X-ray diffraction patterns of Example 4, Example 5 and Comparative Example 2 are shown in the attached figures. Figure 11 , Attachment Figure 12 and attached Figure 13 As shown in the figure, the results show that with the increase of growth time, the crystallographic preferred orientation of (020) and (112) planes of ZIF-L CPO 020 / 112 This indicates that the vertical orientation of the two-dimensional ZIF-L can be improved by increasing the growth time. In addition, the CPO of the disordered stacked two-dimensional material intermediate layer in Example 2 020 / 112 It is significantly lower than the vertically oriented two-dimensional material intermediate layer based on secondary growth, which verifies the difference in orientation between the two in SEM.

[0086] The UV-visible spectra of Examples 4 to 6 and Comparative Example 2 (the test method refers to the method disclosed in the literature (Journal of Membrane Science, 2024, 695, 122455), and the characteristic peak of m-phenylenediamine is at 294 nm) are shown in the attached figure. Figure 14 As shown, the results show that with the increase of growth time, the amount of adsorbed meta-phenylenediamine in the vertically oriented two-dimensional material interlayer (positively correlated with the spectral peak intensity) increases accordingly, which indicates that the ability of the two-dimensional ZIF-L interlayer to adsorb amine monomers can be improved by increasing the growth time; in addition, the adsorption amount of meta-phenylenediamine in the disordered stacked two-dimensional material interlayer in Control Example 2 is significantly lower than that in the vertically oriented two-dimensional material interlayer based on secondary growth, highlighting the advantages of the vertically oriented two-dimensional material interlayer in adsorbing amine monomers.

[0087] The pervaporation desalination test of Examples 4 to 6 and Comparative Example 2 was carried out under the following conditions: the feed liquid was a 35 g / L sodium chloride aqueous solution, the feed liquid temperature was 70° C., and the desalination performance after two hours of stable operation was shown in Table 2.

[0088] Table 2 Desalination performance of Examples 4 to 6 and Comparative Example 2

[0089]

[0090] The results show that the pervaporation desalination performance of the composite separation membrane based on the vertically oriented two-dimensional material intermediate layer is better than that of the composite separation membrane based on the disordered stacked two-dimensional material intermediate layer, and the comprehensive performance of the composite membrane reaches the best when the secondary growth time is 30 min, as shown in Table 2, indicating that the performance of the composite membrane can be optimized by regulating the structure of the vertically oriented two-dimensional material intermediate layer.

[0091] The above descriptions are merely preferred embodiments of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention shall fall within the scope of the claims of the present invention.

Claims

1. A method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer, characterized in that: The following steps are involved: (1) Immerse the substrate in a solvent to fully wet it, and then immerse it in deionized water to fully replace the solvent; the substrate is selected from polyethylene or polypropylene; the solvent does not cause swelling to the substrate and can fully infiltrate the substrate; (2) Preparing a vertically oriented two-dimensional material intermediate layer on the substrate; the preparation method of the vertically oriented two-dimensional material intermediate layer in step (2) is a secondary growth method; the vertically oriented two-dimensional material is a zeolite imidazolate framework structure ZIF-L; ⑶ The substrate surface modified with the vertically oriented two-dimensional material intermediate layer is contacted with and removed from the aqueous phase solution and the oil phase solution in turn. After the interfacial polymerization reaction occurs, the surface of the composite separation membrane is rinsed with a solvent and then transferred to an oven for heat treatment to obtain a top polymer active layer. The composite separation membrane is composed of the bottom substrate, the middle vertically oriented two-dimensional material intermediate layer and the top polymer active layer based on the interfacial polymerization reaction.

2. The method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer according to claim 1, characterized in that: The step (1) further comprises the following: The substrate pore size is 10 to 500 nm; The solvent is isopropyl alcohol, and the immersion time of the solvent is 10 to 180 minutes. Then, the substrate is transferred to deionized water and immersed for 1 to 8 hours.

3. The method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer according to claim 1, characterized in that: The step (2) further includes the following: adjusting the vertical orientation degree of the vertically oriented two-dimensional material by changing the preparation conditions of the vertically oriented two-dimensional material intermediate layer, thereby directly changing the length of the mass transfer path and affecting the subsequent interfacial polymerization reaction.

4. The method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer according to claim 3, characterized in that: The preparation conditions include one or more combinations of two-dimensional material growth time and two-dimensional material seed layer deposition time; The adjustment of the vertical orientation degree of the vertically oriented two-dimensional material further includes: increasing the growth time of the two-dimensional material, increasing the deposition time of the two-dimensional material seed layer, or a combination thereof.

5. The method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer according to claim 1, characterized in that: The solute of the aqueous solution in step (3) is selected from one or more polyamine or polyol monomers of pentaerythritol, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, triethanolamine or dendritic polyamide amine; the solute of the aqueous solution further contains additives, including one or more combinations of cosolvents, surfactants, high molecular polymers, monoamines or alcohol molecules, and nanoparticles; the solute of the oil phase solution in step (3) is selected from one or more polyacyl chloride monomers of trimesoyl chloride, terephthaloyl chloride, cyclohexanetrichloride, cyclobutanetetrachloride, benzene-1,3-disulfonyl chloride, benzene-1,3,5-trisulfonyl chloride or naphthalene-1,3,6-trisulfonyl chloride; the solvent of the oil phase solution is a straight-chain alkane, an isoalkane or a mixture of multiple alkanes with a carbon chain length of 6 to 12; the solute of the oil phase solution contains oil phase additives, including one or more combinations of cosolvents or nanoparticles.

6. The method for preparing a composite separation membrane based on a vertically oriented two-dimensional material intermediate layer according to claim 1, characterized in that: The step (3) further includes: the temperature of the heat treatment is 50 to 90°C; the heat treatment time is 2 to 30 minutes; the contact time between the substrate surface after the vertically oriented two-dimensional material intermediate layer is modified and the aqueous solution is 1 to 30 minutes; the contact time between the substrate surface after the vertically oriented two-dimensional material intermediate layer is modified and the oil phase solution is 20 to 900 seconds.

7. A composite separation membrane based on a vertically oriented two-dimensional material intermediate layer, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 6.

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