Preparation method and application of long-chain diamine cross-linked graphene oxide nanofiltration membrane

Abstract

The application relates to a preparation method and application of a long-chain diamine cross-linked graphene oxide nanofiltration membrane, belonging to the technical field of water treatment, and comprising the following steps: assembling graphene oxide dispersion liquid and long-chain diamine on a base film, and performing heat treatment to prepare a long-chain diamine cross-linked graphene oxide nanofiltration membrane; the spacer arm carbon number of the long-chain diamine is greater than or equal to 3. The long-chain diamine cross-linked graphene oxide nanofiltration membrane prepared by the application not only widens the application range of the covalent GO nanofiltration membrane, and improves the atomic economy by 4 orders of magnitude, but also can improve the rejection rate of common compact nanofiltration rejection objects, for example, the rejection rate of sodium sulfate can reach 97%, and the rejection rate of glucose can reach 92%.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and particularly relates to a method for preparing and applying a long-chain diamine crosslinked graphene oxide nanofiltration membrane. Background Technology

[0002] Graphene oxide (GO) possesses excellent hydrophilicity, antibacterial properties, and chlorine resistance, making it a superior surface material for nanofiltration membranes. By modifying the surface of a base membrane with GO nanosheets through a layer-by-layer stacking method and cross-linking the interlayers via covalent bonds, it is expected to produce dense nanofiltration membranes with interlayer spacing at the 1 nm level, providing material support for a wide range of practical nanofiltration processes.

[0003] In recent years, numerous crosslinking agents have been used for covalently crosslinking GO interlayers, primarily including: diamines / polyamines, boric acid, cyclodextrin and trimesoyl chloride combinations, diacids, diisocyanates, mercaptoethylamine, thiourea, dialdehyde, and trimesoyl chloride. Theoretically, effective retention can be achieved by controlling the length of the covalent crosslinking agent spacer arm to be slightly smaller than the diameter of the target molecule. However, the retention size of such nanofiltration membranes is often much larger than the diameter of the crosslinking agent, making it difficult to achieve dense nanofiltration retention of inorganic salt ions or neutral molecules with a molecular weight of 200 or slightly lower.

[0004] From the perspective of the GO layered structure construction process, the covalent cross-linking process of small molecules entering the GO interlayer often requires a significant excess of cross-linking agent. During the assembly of GO onto the base film surface, some cross-linking agent remains in the GO interlayer for cross-linking. In this process, cross-linking molecules usually enter the GO interlayer by blocking pores. On the one hand, this makes it difficult to ensure the uniformity of cross-linking molecule distribution in the interlayer, and the cross-linked interlayer structure is prone to defects. On the other hand, it results in extremely low utilization of cross-linking molecules, which deviates from the principles of green manufacturing and limits its subsequent practical production applications. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a method for preparing and applying a long-chain diamine crosslinked graphene oxide nanofiltration membrane. It is the first time that a long-chain diamine such as propylenediamine has been used to covalently crosslink graphene oxide membrane, and it solves the problem that covalently crosslinked GO membranes are difficult to achieve dense nanofiltration (effectively retaining high-valence inorganic salt ions and neutral small molecules with a molecular weight of less than 200).

[0006] To achieve the above objectives, the present invention provides a method for preparing a long-chain diamine crosslinked graphene oxide nanofiltration membrane, comprising the following steps:

[0007] A long-chain diamine crosslinked graphene oxide nanofiltration membrane was prepared by assembling a graphene oxide dispersion and a long-chain diamine onto a base membrane and then heat-treating it.

[0008] Preferably, the long-chain diamine has ≥3 carbon atoms in its spacer arms. This invention utilizes the fact that cross-linking GO with long-chain diamines having ≥3 carbon atoms in their spacer arms is a necessary condition for constructing dense nanofiltration membranes. It is the first time that long-chain diamines such as propylenediamine have been used to covalently cross-link graphene oxide membranes, and it solves the problem that covalently cross-linked GO membranes are difficult to achieve dense nanofiltration (effectively retaining high-valence inorganic salt ions and neutral small molecules with a molecular weight less than 200).

[0009] Preferably, the long-chain diamine includes one of propylenediamine, butanediamine, pentanediamine, and p-phenylenediamine.

[0010] Preferably, the graphene oxide dispersion is first prepared into a film-forming solution with a long-chain diamine, and then the film-forming solution is assembled onto the base membrane.

[0011] Preferably, the concentration of the long-chain diamine in the film-forming solution is 0.5 μg·mL. -1 Using long-chain diamines as covalent crosslinking agents, the covalent crosslinking of GO membranes with long-chain diamines represents a novel intercalation method. The resulting composite membranes not only achieve dense nanofiltration but also significantly reduce the amount of covalent crosslinking agent used, to only 12% of the GO mass, which is 0.005 wt% of the commonly used diamine crosslinking agent. This improves atom economy by four orders of magnitude and significantly reduces the amount of crosslinking molecules used, bringing promising prospects for practical production applications.

[0012] Preferably, the film-forming solution is assembled onto the base membrane using vacuum filtration, spin coating, pressure assembly, or gas-liquid interface assembly. This invention does not impose strict limitations on the method used to assemble the film-forming solution onto the base membrane, as long as the solution can be successfully assembled.

[0013] Preferably, the heat treatment temperature is 80°C and the time is 1 hour.

[0014] The base membrane in this invention is a common, structurally stable microfiltration membrane or ultrafiltration membrane substrate, such as a PES base membrane.

[0015] The application of the long-chain diamine crosslinked graphene oxide nanofiltration membrane obtained by the above preparation method in the retention of high-valence inorganic salt ions, which refer to divalent or trivalent anions, such as sulfate ions.

[0016] The application of the long-chain diamine crosslinked graphene oxide nanofiltration membrane obtained by the above preparation method in retaining neutral small molecules with a molecular weight cutoff of less than 200.

[0017] The long-chain diamine crosslinked graphene oxide nanofiltration membrane of this invention is designed to retain common dense nanofiltration targets in the field, such as inorganic divalent anions, inorganic trivalent anions, negatively charged small organic molecules, and neutral small molecules with a molecular weight of about 180, as well as sodium sulfate, magnesium sulfate, and glucose.

[0018] The long-chain diamine crosslinked graphene oxide nanofiltration membranes prepared by the above method are used in nanofiltration, reverse osmosis, forward osmosis, ultrafiltration, pervaporation, or oil-water separation.

[0019] This invention is based on the amphiphilicity of long-chain diamines. By increasing the carbon chain length, the size of the hydrophobic structure in the molecular structure is controlled, and the interaction between the diamine molecule and GO in aqueous solution is strengthened. This leads to the construction of a non-aggregating, non-pore-blocking intercalation method for GO interlayers, resulting in a long-chain diamine covalently crosslinked GO nanofiltration membrane with good interlayer density and a greener preparation process.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] (1) The concentration of long-chain diamine in the film-forming solution of this invention is only 0.5 μg·mL -1 It is 0.005 wt% of the ethylenediamine crosslinking system, which improves the atom economy by 4 orders of magnitude and effectively reduces the amount of covalent crosslinking molecules used. This provides an important guarantee for the application of such membrane materials in actual production.

[0022] (2) The long-chain diamine crosslinked graphene oxide nanofiltration membrane prepared by the present invention not only broadens the application range of covalent GO nanofiltration membrane, but also improves the rejection rate of common dense nanofiltration targets. For example, the rejection rate of sodium sulfate can reach 97% and the rejection rate of glucose can reach 92%. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 The PES-based film used in Example 2, and the M prepared in Example 2 GO-PD(0.5) M prepared in Example 3 GO-PD(20) SEM images, where (a)-(c) represent the PES base film, M GO-PD(0.5) M GO-PD(20) The SEM images are shown in (d)-(f), which are SEM images of (a)-(c) scaled down by a factor of 1.5. The scale bar in the images is 2μm.

[0025] Figure 2 The images show the characterization of the GO interlayer structure of the composite membrane prepared in Examples 7 and 8, where (a) is the XRD pattern of the membrane prepared under different PD and GO mass ratios in dry and wet states, and (b) is the relationship between the interlayer spacing of different membranes in dry and wet states and the PD and GO mass ratios.

[0026] Figure 3 M prepared in Example 4GO (m PD / m GO 0) M prepared in Example 3 GO-PD(0.5) (m PD / m GO 0.12), M prepared in Example 3 GO-PD(2) (m PD / m GO 0.48), M prepared in Example 3 GO-PD(20) (m PD / m GO 4.8) XPS plots, where (a) is the XPS plot and (b) is the N plot. 1s / O 1s Ratio chart;

[0027] Figure 4 M was prepared in Example 4 GO The composite membrane and the M prepared in Example 3 GO-PD The nanofiltration performance test results of the composite membrane, where M GO-PD Composite membranes include: M GO-PD(2) M GO-PD(5) M GO-PD(10) M GO-PD(20) M GO-PD(50) and M GO-PD(100) ;

[0028] Figure 5 M was prepared in Example 4 GO The composite membrane and the M prepared in Example 3 GO-PD The nanofiltration performance test results of the composite membrane, where M GO-PD Composite membranes include: M GO-PD(0.11) M GO-PD(0.21) M GO-PD(0.5) M GO-PD(1) and M GO-PD(2) ;

[0029] Figure 6 M was prepared in Example 5 GO-PD The nanofiltration performance test results of the composite membrane, where the GO mass was 30, 36, 42, 48 and 54 μg respectively;

[0030] Figure 7 M was prepared in Example 6 GO-二胺 The nanofiltration performance test results of the composite membrane, in which the diamines are: ethylenediamine, propylenediamine, butanediamine, pentanediamine and p-phenylenediamine;

[0031] Figure 8 M was prepared in Example 2 GO-PD Nanofiltration performance test results of composite membranes with different permeate solutions, including: glucose (C6H4O) 12O6), sodium sulfate (Na2SO4), magnesium sulfate (MgSO4), sodium chloride (NaCl), and magnesium chloride (MgCl2). Detailed Implementation

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0034] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0035] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0036] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0037] In this embodiment of the invention, room temperature refers to 25±2℃.

[0038] In an embodiment of the present invention, for ease of labeling, the composite film without diamine crosslinking is labeled as M. GO The composite film crosslinked with propylenediamine (PD) is labeled as M. GO-PD The concentration of PD in the solution is denoted as M. GO-PD(浓度) PD concentration is measured in μg·mL -1 The general formula for diamine cross-linked composite membranes is M GO-二胺 .

[0039] Example 1

[0040] The specific steps for preparing graphene oxide (GO) and GO standard solution are as follows:

[0041] A mixture of 240 mL concentrated sulfuric acid / concentrated phosphoric acid (volume ratio 5:1), 5.0 g of graphene solid, and 25.0 g of potassium permanganate solid were added to a 500 mL round-bottom flask. The mixture was reacted at 40 °C for 6 hours. The reaction solution was then poured into a beaker, cooled to room temperature, and poured onto 400 g of ice to mix thoroughly. 20 mL of hydrogen peroxide was then added dropwise. After centrifugation for 4 hours (4000 rpm), the mixture was... -1 Discard the supernatant and collect the GO solid. Use 1 mol·L⁻¹ -1 The solid was washed eight times with HCl solution and collected. It was then washed five times with RO water and collected again. The washed solid was dispersed in 200 mL of RO water and filtered through a PVDF membrane with a pore size of 0.45 μm. The resulting filter cake was vacuum dried at room temperature to obtain graphene oxide (GO).

[0042] Weigh the graphene oxide prepared above and disperse it in deionized water. Sonicate at room temperature for 5 minutes to promote uniform dispersion, thereby obtaining a concentration of 0.6 mg·mL⁻¹. -1 GO standard solution (solution A, GO-ss, 0.6 mg·mL) -1 ).

[0043] Example 2

[0044] Propylene diamine intercalated GO composite membrane M GO-PD(0.5) The specific steps for preparing [the substance] are as follows:

[0045] 70 μL of GO standard solution prepared in Example 1 and concentrated propylenediamine solution (1 μg·mL⁻¹) were mixed. -1 Mix 5 mL of propylenediamine (containing 5 μg) and RO water to obtain 10 mL of membrane-forming solution B (propylenediamine concentration: 0.5 μg / mL). -1 (PD to GO mass ratio is 0.12); a PES base membrane with a pore size of 0.15 μm was taken and placed on the sand core of a vacuum filtration device. The vacuum filtration device was assembled, and the membrane preparation solution B was poured into the glass sand core filtration device. The membrane preparation solution was filtered until the membrane surface was completely filtered through the membrane. The composite membrane was taken out, dried at room temperature, and placed in a forced-air drying oven at 80℃ for 1 h to obtain M. GO-PD(0.5) Composite membrane.

[0046] Example 3

[0047] M with different concentrations of propylenediamine intercalation amount GO-PD The specific steps for preparing the composite membrane are as follows:

[0048] Similar to Example 2, except for the concentration of propylenediamine, a series of MGO-PD composite membranes were prepared. The concentrations of propylenediamine were controlled at 0.11, 0.21, 1, 2, 5, 10, 20, 50, and 100 μg·mL. -1 The corresponding PD to GO mass ratios are: 0.024, 0.05, 0.24, 0.48, 1.2, 2.4, 4.8, 12, and 24.

[0049] Example 4

[0050] M, a composite membrane without diamine crosslinking GO The specific steps for preparing [the substance] are as follows:

[0051] Same as Example 2, except that the concentrated propylene diamine solution was replaced with RO water to prepare a GO composite membrane M without diamine crosslinking. GO .

[0052] Example 5

[0053] Different thicknesses M GO-PD The specific steps for preparing [the substance] are as follows:

[0054] Similar to Example 2, except for the volume of GO standard solution used, a series of MGO-PD composite membranes were prepared. The volumes (μL) of GO standard solution used were 50, 60, 80, and 90, respectively. The corresponding mass (μg) of GO consumed were 30, 36, 48, and 54, respectively.

[0055] Example 6

[0056] Other long-chain diamine intercalated GO composite membranes M GO-二胺 The specific steps for preparing [the substance] are as follows:

[0057] Same as Example 2, except that the concentrated propylene diamine solution was replaced with an aqueous solution of other long-chain diamines of the same concentration to prepare a series of M... GO-二胺 Composite membranes. The types of long-chain diamines used include: ethylenediamine (EDA), butanediamine, pentanediamine, and p-phenylenediamine.

[0058] Example 7

[0059] Same as Example 2, except that the volume of GO standard solution in the GO film-forming solution was 1 mL (0.4 mg), and the mass ratios of PD to GO were fixed at 0.024, 0.12, 0.48, and 4.8, respectively, to prepare a series of M... GO-PD Composite membrane.

[0060] Example 8

[0061] Same as Example 4, except that the volume of GO standard solution in the GO film-forming solution was 1 mL (0.4 mg), resulting in a high GO content (48.6 μg·cm³).-2 M GO Composite membrane.

[0062] The characterization of the series of membrane structures is as follows:

[0063] (1) Characterization of surface morphology

[0064] Field emission scanning electron microscopy (SEM) was used to study the PES-based film and M... GO-PD(0.5) M GO-PD(20) The surface morphology was characterized, and the morphological differences were compared on a 2μm scale.

[0065] (2) Characterization of surface chemical properties

[0066] X-ray photoelectron spectroscopy (XPS) was used to characterize the surface chemical properties of the film materials. This was specifically applied to PES-based films and M... GO / EDA M GO-EDA The surface chemical composition was characterized by monitoring the percentage content of C, O, and N elements on the surface, with a focus on comparing changes in the nitrogen-oxygen ratio.

[0067] (3) Characterization of the interlayer structure of graphene oxide

[0068] X-ray diffraction (XRD) was used to characterize the interlayer structure of the graphene oxide on the surface of the composite membrane. Characterization was performed on both the dry and wet surfaces of the composite membrane. For the dry membrane, the skin layer was characterized directly. For the wet membrane, it was immersed in pure water overnight, and then the skin layer was characterized directly without drying.

[0069] The interplanar spacing d is calculated from the 2θ peaks in XRD and denoted as the interlayer spacing of graphene oxide. Characteristic 2θ peaks appearing in the 5-10° range in the XRD spectrum are marked and substituted into the Bragg formula (Formula 1) to calculate the corresponding interlayer spacing d.

[0070] 2d sinθ=λ Formula 1

[0071] The performance characteristics of the series of membrane nanofiltration devices are characterized as follows:

[0072] (1) Sieving performance of long-chain diamine cross-linked graphene oxide nanofiltration membrane on sodium sulfate aqueous solution

[0073] The nanofiltration performance of graphene oxide composite membranes was tested using a laboratory cross-flow filtration apparatus. The permeate solution was an aqueous sodium sulfate solution. Each membrane was pre-pressurized at 0.7 MPa for 2 hours, and all membrane data were obtained from parallel tests of three membranes. The nanofiltration performance of the composite membranes was compared under different membrane fabrication parameters, including the concentration of diamine, GO consumption, and type of diamine.

[0074] (2) Sieving performance of long-chain diamine cross-linked graphene oxide nanofiltration membrane for inorganic salt solutions and glucose aqueous solutions

[0075] The test method is the same as that for the sieving performance of sodium sulfate aqueous solution, the only difference being that the membrane solution is replaced with other solutions, including: magnesium sulfate, magnesium chloride, sodium chloride and glucose.

[0076] like Figure 1 As shown, compared with the propylenediamine crosslinked GO composite membrane, the composite membranes obtained under different PD film-forming solution concentrations ( Figure 1 (b) Figure 1 (c) Figure 1 (e) Figure 1 The surface structure of the middle (f) is flat and can effectively cover the micropores on the PES base film.

[0077] Figure 2 It is M GO and series M GO-PD XRD results of the membrane in dry and wet states. In the dry state, the GO interlayer spacing increases with m. PD / m GO The value increases with increasing m, indicating that PD molecules entering the GO interlayer do indeed expand the interlayer space. Under wet conditions, the interlayer spacing initially increases with m. PD / m GO The value decreases as it increases, indicating that the anti-swelling ability of GO interlayer increases with the increase of crosslinking agent when there is only a small amount of PD crosslinking. In m PD / m GO When the value reaches 0.12, the underwater interlayer spacing of the separation layer increases with m. PD / m GO The increase in value does not change the overall value significantly.

[0078] Comparison M GO and series M GO-PD Chemical composition of membrane surface ( Figure 3 It can be seen that as m PD / m GO As the value increases, the surface nitrogen-to-oxygen ratio gradually increases, and at m PD / m GO When the value is less than 0.48, this increasing trend is significant. This result indicates that by changing the m in the film-forming solution... PD / m GO The value can indeed regulate the amount of PD molecules entering the GO interlayer.

[0079] Figure 4 It is M GO and series M GO-PD Nanofiltration performance tests of the membrane for sodium sulfate showed that at lower m PD / m GO At a value of (0.48), the retention performance is optimal. Figure 5To further investigate the nanofiltration performance of the composite membrane at low PD content, the results showed m PD / m GO The value is 0.12 (PD concentration in the film-forming solution is 0.5 μg·mL). -1 The effect is best when the sodium sulfate is retained at 97%, which is far superior to existing covalently cross-linked GO membranes (such as ethylenediamine covalently cross-linked GO membranes).

[0080] Figure 6 It is a series of M with different GO contents GO-PD Nanofiltration performance of the membrane for sodium sulfate was tested, and the results showed that at 42 μg GO (3.4 μg·cm⁻¹), the filtration efficiency was [not specified]. -2 At this consumption level, nanofiltration performance is already optimal.

[0081] Figure 7 M under different diamine crosslinking GO-二胺 Nanofiltration performance of membranes for sodium sulfate. Results showed that the composite membrane crosslinked with propylenediamine exhibited the best retention performance. Generally, diamines with 3 or more carbon atoms in the spacer arm showed excellent overall nanofiltration performance, exceeding 95%, while the composite membrane crosslinked with the shortest chain, ethylenediamine, showed the lowest retention performance. This may be because the carbon chain of ethylenediamine is too short, and its molecules are too hydrophilic, making it difficult to assemble on the GO surface. It mainly enters the GO interlayer in the form of pore blockage during the filtration process of the membrane preparation solution. Under these and low concentrations of diamine membrane preparation solution, it is difficult to retain the membrane in the interlayer through pore blockage during filtration, resulting in a very low degree of crosslinking in the prepared composite membrane.

[0082] Figure 8 It is M GO-二胺(0.5) Different membrane retention targets (glucose (C6H) 12 Nanofiltration performance under the conditions of O6), sodium sulfate (Na2SO4), magnesium sulfate (MgSO4), sodium chloride (NaCl), and magnesium chloride (MgCl2). The results showed that the composite membrane achieved a 92% rejection rate for neutral glucose, indicating that the membrane pore size reached a dense nanofiltration level. Overall, the composite membrane exhibited a higher rejection rate for divalent anions in inorganic salts, suggesting that the surface charge of the membrane played a role in the rejection process; the Donnan effect is one of the principles of membrane sieving. The composite membrane's rejection rate for neutral glucose was significantly higher than that for monovalent inorganic salt sodium chloride, indicating that pore size sieving also played a significant role. In summary, the M2 nanofiltration membrane prepared under the optimal conditions in this invention... GO-二胺(0.5) The membrane nanofiltration sieving process combines two mechanisms: pore size sieving and the Dornan effect.

[0083] By characterizing the membrane surface morphology, surface chemical properties, interlayer size, and nanofiltration performance, the types of covalently cross-linked diamine molecules, the diamine concentration in the membrane preparation solution, and the GO consumption parameters were optimized, resulting in the preparation of a membrane with a sodium sulfate rejection rate of 97% and a glucose rejection rate of 92%. GO-PD(0.5)Nanofiltration membrane. This not only produced the most densely structured covalently cross-linked GO nanofiltration membrane, broadening the application range of covalent GO nanofiltration membranes, but also effectively reduced the amount of covalently cross-linked molecules used, providing a more solid foundation for the practical nanofiltration applications of this type of membrane.

[0084] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. The application of a long-chain diamine cross-linked graphene oxide nanofiltration membrane in retaining high-valence inorganic salt ions and neutral small molecules with a molecular weight of less than 200, characterized in that, The method for preparing the long-chain diamine crosslinked graphene oxide nanofiltration membrane includes the following steps: first, a graphene oxide dispersion and a long-chain diamine are prepared into a membrane-forming solution, then the membrane-forming solution is assembled onto a base membrane, and heat-treated to obtain a long-chain diamine crosslinked graphene oxide nanofiltration membrane. The high-valence inorganic salt ions and neutral small molecules with a molecular weight of less than 200 are glucose, sodium sulfate and magnesium sulfate; The long-chain diamine includes one of propylenediamine, butanediamine, pentanediamine, and p-phenylenediamine; The concentration of the long-chain diamine in the film-forming solution was 0.5 µg∙mL. -1 The amount of long-chain diamine used in the film-forming solution is 12% of the mass of graphene oxide.

2. The application according to claim 1, characterized in that, The film-forming solution is assembled onto the base membrane using vacuum filtration, spin coating, pressure assembly, or gas-liquid interface assembly methods.

3. The application according to claim 1, characterized in that, The heat treatment temperature was 80℃ and the time was 1 hour.

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