Process for preparing GO-PEI layered film in batches

Abstract

The invention relates to the technical field of two-dimensional layered membrane batch preparation, and discloses a GO-PEI layered membrane batch preparation process, which comprises: preparing a GO dispersion liquid and a PEI solution, the solvents of the GO dispersion liquid and the PEI solution being a mixture of absolute ethyl alcohol and ultrapure water; spreading the base film to obtain a flat base layer; coating the GO dispersion liquid and the PEI solution on the surface of the substrate layer at the same time by adopting a double-needle electrostatic spraying process to obtain a GO-PEI composite film; and carrying out high-temperature crosslinking modification on the GO-PEI composite membrane to obtain the GO-PEI layered membrane. Compared with the prior art, the GO-PEI layered membrane prepared by the method has better nanofiltration performance and operation stability, and a double-needle electrostatic spraying process used in the preparation process is simple to operate, wastes are easy to recycle, the automation degree is high, the production efficiency is high, and large-scale production is easy.

Description

Technical Field

[0001] The present invention relates to the technical field of batch preparation of composite membranes, and particularly to a process for batch preparation of GO-PEI layered membranes. Background Art

[0002] In the development process of modern industrial technologies, membrane separation technology has attracted many scholars' research due to its advantages of low energy consumption and convenient operation. At present, the vast majority of nanofiltration membranes in China are aqueous nanofiltration membranes. However, with the progress of industrialization, the usage amount of organic solvents in various industrial production links has shown a sharp growth trend. In such an environment, how to achieve efficient separation, recovery, and reuse of organic solvents has become a key technical problem that urgently needs to be broken through and solved at present.

[0003] As an important research direction to address this problem, organic solvent nanofiltration technology focuses on the research and development of solvent-resistant nanofiltration membranes. The main idea of the research and development is to use organic or inorganic materials to prepare nanofiltration membranes that can operate stably in various complex solvent environments. Among them, inorganic membranes exhibit significant advantages such as high temperature resistance, high mechanical strength, and strong chemical stability; while organic membranes have outstanding performance in flexibility and corrosion resistance. Based on this, if the advantages of organic and inorganic materials can be organically integrated to prepare organic-inorganic composite membranes, it is theoretically expected to make them simultaneously possess high solvent stability and excellent nanofiltration performance, thereby efficiently solving the related treatment problems of organic solvents.

[0004] In the preparation technology of two-dimensional layered membranes, the currently mainstream preparation method is vacuum filtration (VF). However, this traditional preparation method has a series of drawbacks that cannot be ignored. Firstly, the vacuum filtration process takes a long time, usually several hours to complete the suction filtration operation of the layered membrane, which to a certain extent limits the production efficiency; secondly, vacuum suction filtration uses pressure as the driving force, and during the suction filtration process, there will inevitably be a pressure difference between the edge and the center of the membrane, and this pressure difference ultimately leads to poor structural uniformity of the prepared layered membrane, affecting the performance stability of the membrane; thirdly, the size of the vacuum suction filtration tank imposes a hard limit on the size of the prepared membrane, making it extremely difficult to prepare large-area two-dimensional layered membranes with uniform and defect-free properties. For systems with mixed coagulation, it is difficult to achieve batch preparation by the spin coating method. Although the electrospray technology can effectively avoid the problem of large-area coagulation to a certain extent, up to now, there is still a lack of an effective technical means to realize the continuous production of composite membranes and efficiently prepare large-area layered membranes.

[0005] In summary, there are deficiencies and drawbacks to varying degrees in the existing organic solvent nanofiltration technology and two-dimensional layered membrane preparation technology. There is an urgent need to develop a new technical solution to achieve efficient treatment of organic solvents, break through various bottlenecks in the preparation process of two-dimensional layered membranes, and meet the urgent demand of industrial production for high-performance membrane materials. Summary of the Invention

[0006] The object of the present invention is to solve the existing technical problems and provide a process for batch preparation of GO-PEI layered membranes with high flux, high rejection rate and stable performance. By preparing a GO dispersion and a PEI solution, and using an electrostatic spraying process to simultaneously spray the GO dispersion and the PEI solution on the surface of a substrate membrane, and then subjecting it to high-temperature crosslinking modification to obtain a GO-PEI layered membrane. The GO-PEI layered membrane prepared by the present invention has excellent flux and rejection performance.

[0007] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0008] A process for batch preparation of GO-PEI layered membranes, comprising the following steps:

[0009] S1, prepare a GO dispersion (i.e., graphene oxide dispersion) and a PEI solution (i.e., polyethyleneimine solution), wherein the solvents of the GO dispersion and the PEI solution are both mixtures of absolute ethanol and ultrapure water;

[0010] S2, spread the substrate membrane to obtain a flat substrate layer;

[0011] S3, use a double-needle electrostatic spraying process to simultaneously coat the GO dispersion and the PEI solution on the surface of the substrate layer to obtain a GO-PEI composite membrane;

[0012] S4, subject the GO-PEI composite membrane to high-temperature crosslinking modification to obtain a GO-PEI layered membrane.

[0013] Preferably, in step S1, the volume ratio of absolute ethanol to ultrapure water is 0.5:1 to 3:1.

[0014] Preferably, in step S1, the concentration of the GO dispersion is 0.2 to 0.8 mg / mL, and the GO dispersion is obtained by taking a certain amount of GO nanosheet dispersion, diluting it with a solvent and subjecting it to ultrasonic dispersion, and then extracting it with a 20 mL syringe to two-thirds of the maximum capacity of the 20 mL syringe.

[0015] Preferably, the GO nanosheets are hydrophilic GO nanosheets, and the lateral size of the GO nanosheets is 1 to 3 μm, and the thickness is 2 to 4 nm.

[0016] Preferably, in step S1, based on the total mass of the PEI solution, the mass fraction of PEI is 0.1 - 0.4%, and the molecular weight of PEI is 300 - 600. More preferably, the PEI solution is obtained by taking a PEI initial solution with a mass fraction of PEI of 0.1 - 0.4% and filling a 20 mL syringe with the solution to two-thirds of the maximum capacity of the 20 mL syringe, where the molecular weight of PEI is 300 - 600.

[0017] Preferably, in step S2, the base film is one of a nylon film, an ultrafiltration membrane, a microfiltration membrane, a polyvinylidene fluoride (PVDF) membrane, and a polyethylene (PES) membrane.

[0018] Preferably, in step S2, the base film is wetted with the solvent to make the base film spread flat. More specifically, the base film is wetted with the solvent and then laid flat on tin foil paper, and then evenly attached to the surface of the receiver used in the double - needle electrostatic spraying process.

[0019] Preferably, in step S3, the parameters of the double - needle electrostatic spraying process are set as follows: temperature 20 - 25°C, air humidity 40 - 60%, the injection rate of the double - needle spraying of the GO dispersion liquid and the PEI solution is 1 - 4 mL / h, the spraying voltage is 7.0 - 9.5 kV, the receiving distance is 4 - 6 cm, the swinging speed is 21 - 30 mm / s, and the roller rotation speed is 200 - 400 rpm.

[0020] Preferably, in step S4, the temperature of the high - temperature cross - linking modification is 80 - 100°C, and the time is 8 - 24 h.

[0021] In the present invention, the selected GO nanosheets are rich in functional groups such as hydroxyl, carboxyl, and epoxy groups on the surface, enabling them to easily react with other chemical substances for functional modification. These abundant functional groups not only endow the GO nanosheets with good hydrophilic ability but also make the membrane prepared with the GO dispersion liquid have certain hydrophilicity. The two - dimensional membrane layer spacing of the stacked GO nanosheets is generally below 1 nm, and the nano - channels between adjacent GO nanosheets act as molecular sieves to block all solutes with a radius larger than the nano - channels. Such small channels are suitable for constructing nanofiltration membranes.

[0022] The pure GO membrane is relatively unstable in water, mainly because water molecules enter the interlayer of the GO nanosheets and destroy the π - π interaction between the nanosheets. When using molecular cross - linking, due to different charges, precipitation occurs in the solution, resulting in a small yield of pre - modified nanosheets. The electrostatic spraying technology is used to spray different substances with multiple needles respectively to avoid this phenomenon and prepare high - performance large - area composite membranes. The spraying method solves the problem that PEI molecules precipitate and cannot be cross - linked when added to the GO dispersion liquid during suction filtration.

[0023] Therefore, the present invention combines the good film-forming property of hydrophilic GO nanosheets and the abundant functional groups of PEI molecules, and prepares a GO-PEI layered film by cooperating with the electrospray technology. The film modified by high-temperature crosslinking can stably exist in organic solvents.

[0024] The GO-PEI layered film with a large area prepared by the electrospray process parameters adopted in the present invention has uniform film properties at different positions and can be tested and operated in a solvent for a long time. Moreover, the electrospray method has a simple preparation process, can realize batch preparation of the film, and has the prospect of practical application. However, the solution and spraying parameters also have a great influence on the structure and properties of the layered film. Therefore, it is necessary to continuously improve the preparation method and material selection. The present invention provides more possibilities for realizing large-scale and high-efficiency preparation of layered films and applications in the fields of ion separation, membrane separation, etc.

[0025] The main principle of action of the present invention is:

[0026] (1) In the present invention, hydrophilic GO nanosheets and PEI polymer molecules are preferably used. The selected GO nanosheets are rich in oxygen-containing functional groups, including epoxy, hydroxyl, and carboxyl groups. The oxidation region of the GO nanosheets provides a large adjustment space for water molecules and the graphite region, and the water penetration with almost no frictional resistance. And the two-dimensional film layer spacing stacked by GO nanosheets is generally below 1 nm, and the nanochannels between adjacent GO nanosheets act as molecular sieves to block all solutes with a radius larger than the nanochannels. Such small channels are suitable for constructing nanofiltration membranes.

[0027] (2) The selected PEI molecules with a molecular weight of 300-600 have hyperbranched side chains and can provide abundant functional group sites.

[0028] (3) The GO-PEI layered film is prepared by high-temperature crosslinking reaction at 80-100 °C. Infrared test shows the stretching vibration of the amide bond HNC=O, the stretching vibration of N-H, and the stretching vibration of C-N, indicating that the prepared layered film is effectively crosslinked.

[0029] (4) The GO-PEI layered film is prepared by high-temperature crosslinking reaction at 80-100 °C. XPS test shows that the content of the C-O-C bond decreases from 35% to 25%, and a new C-N bond appears, indicating that GO and PEI are successfully crosslinked.

[0030] (5) The prepared GO-PEI layered films of 300 cm 2 , 600 cm 2 , 960 cm 2 , 2400 cm 2 have stable properties. The rejection of brilliant blue (BB-1.6 nm) reaches 99% in the water system, and the rejection of brilliant blue reaches about 85% in the methanol system, and the flux reaches 22.45 L m-2 h -1 bar -1 The cross-flow stability of the aqueous system reaches over 300 h; in the pressure cycling stability test, the methanol permeation attenuation rate is 24%, and the anti-solvent performance in the organic system is greatly improved. The swelling degree of the GO-PEI layered membrane after being immersed in dimethyl adipate solvent for four months is only 5.5%.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The GO-PEI layered membrane prepared by the present invention has better nanofiltration performance and operational stability. Moreover, the double-needle electrostatic spraying process used in the preparation process is simple in operation, the waste is easy to recycle, the automation degree is high, the production efficiency is high, and it is easy to scale up production. Description of the Drawings

[0033] Figure 1 SEM surface of the GO-PEI layered membrane obtained in Examples 1-6 of the present invention;

[0034] Figure 2 SEM cross-section of the GO-PEI layered membrane obtained in Examples 1-6 of the present invention;

[0035] Figure 3 XRD curve of the GO-PEI layered membrane obtained in Examples 1-6 of the present invention;

[0036] Figure 4 SEM surface of the membrane obtained in Comparative Examples 1-3 of the present invention;

[0037] Figure 5 SEM cross-section of the membrane obtained in Comparative Examples 1-3 of the present invention;

[0038] Figure 6 Flux and rejection diagram of the GO-PEI layered membrane obtained in Examples 1-3 of the present invention;

[0039] Figure 7 Infrared analysis diagram of the GO-PEI layered membrane obtained in Example 1 of the present invention;

[0040] Figure 8 Operational stability diagram of the GO-PEI layered membrane obtained in Example 4 of the present invention;

[0041] Figure 9 Swelling degree test diagram of the GO-PEI layered membrane obtained in Example 5 of the present invention;

[0042] Figure 10 Ultraviolet analysis diagram of bovine serum albumin solution of the GO-PEI layered membrane obtained in Example 6 of the present invention. Detailed Description of the Invention

[0043] The present invention will be further described below with specific embodiments. The illustrative embodiments of the present invention and the descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0044] There are no particular restrictions on the sources of all raw materials of the present invention, and they can be purchased on the market or prepared by conventional methods well-known to those skilled in the art.

[0045] There are no particular restrictions on the purity of all raw materials of the present invention. The present invention preferably uses industrial purity or conventional purity used in the art.

[0046] For the devices used in the present invention, those without particular restrictions are all commonly used devices in the art.

[0047] The membrane area prepared in batches in the present invention is not limited to 300 cm 2 , 600 cm 2 , 960 cm 2 , 2400 cm 2 , and larger membrane areas prepared by the method of the present invention are all within the protection scope of the present invention.

[0048] Example 1

[0049] A process for batch preparation of GO-PEI layered membranes includes the following steps:

[0050] S1, Prepare a GO dispersion (i.e., graphene oxide dispersion) and a PEI solution (i.e., polyethyleneimine solution). The solvents of the GO dispersion and the PEI solution are both mixtures of absolute ethanol and ultrapure water; and the volume ratio of absolute ethanol to ultrapure water is 1:1;

[0051] Among them, the concentration of the GO dispersion is 0.4 mg / mL, and the GO dispersion is obtained by taking a certain amount of GO nanosheet dispersion, diluting it with a solvent and subjecting it to ultrasonic dispersion, and then sucking it into a 20 mL syringe to two-thirds of the maximum capacity of the 20 mL syringe. The lateral size of the GO nanosheets is 1 - 3 μm, and the thickness of the GO nanosheets is 2 - 4 nm;

[0052] The PEI solution is obtained by taking a PEI initial solution with a mass fraction of 0.1% of PEI and sucking its solution into a 20 mL syringe to two-thirds of the maximum capacity of the 20 mL syringe, and the molecular weight of PEI is 300.

[0053] S2, Wet the nylon membrane with a solvent and lay it flat on the tin foil paper, and then attach it flatly to the surface of the receiver used in the double-needle electrostatic spraying process to obtain a flat base layer;

[0054] S3. Use the double - needle electrostatic spraying process to coat the GO dispersion and the PEI solution on the surface of the base layer simultaneously, obtaining a GO - PEI composite membrane with a membrane area of 2400 cm 2 The parameters of the double - needle electrostatic spraying process are: voltage 9.5 kV, injection rate 1 mL / h, roller rotation speed 300 rpm, swing speed 30 mm / s, receiving distance 5 cm, controlling the room temperature at 22 °C and the relative humidity at 60%.

[0055] S4. Subject the GO - PEI composite membrane with a membrane area of 2400 cm 2 to high - temperature cross - linking modification at 80 °C for 24 h to obtain a GO - PEI layered membrane, and name this GO - PEI layered membrane as Membrane - 1.

[0056] Example 2

[0057] The difference from Example 1 is only that:

[0058] In step S1, the concentration of the GO dispersion is 0.8 mg / mL, the mass fraction of PEI in the initial PEI solution is 0.2%, and the volume ratio of absolute ethanol to ultrapure water is 3:2;

[0059] In step S2, wet the ultrafiltration membrane with a solvent and lay it flat on the tin foil paper, and then attach it smoothly to the surface of the receiver used in the double - needle electrostatic spraying process to obtain a flat base layer;

[0060] In step S3, obtain a GO - PEI composite membrane with a membrane area of 960 cm 2 and the parameters of the double - needle electrostatic spraying process are: voltage 8 kV, injection rate 1.5 mL / h, roller rotation speed 350 rpm, swing speed 25 mm / s, receiving distance 4 cm, controlling the room temperature at 20 °C and the relative humidity at 50%;

[0061] In step S4, subject the GO - PEI composite membrane with a membrane area of 960 cm 2 to high - temperature cross - linking modification at 100 °C for 10 h to obtain a GO - PEI layered membrane, and name this GO - PEI layered membrane as Membrane - 2.

[0062] Example 3

[0063] The difference from Example 1 is only that:

[0064] In step S1, the concentration of the GO dispersion is 0.267 mg / mL, the mass fraction of PEI in the initial PEI solution is 0.3%, and the volume ratio of absolute ethanol to ultrapure water is 0.5:1;

[0065] In step S2, the microfiltration membrane is wetted with a solvent and then laid flat on the tin foil paper, and then evenly attached to the surface of the receiver used in the double - needle electrostatic spraying process to obtain a flat base layer;

[0066] In step S3, a GO - PEI composite membrane with a membrane area of 600 cm 2 is obtained, and the parameters of the double - needle electrostatic spraying process are: voltage 7.5 kV, injection rate 2 mL / h, roller rotation speed 250 rpm, swing speed 21 mm / s, receiving distance 6 cm, room temperature is controlled at 25 °C, and relative humidity is 40%;

[0067] In step S4, the GO - PEI composite membrane with a membrane area of 600 cm 2 is subjected to high - temperature cross - linking modification at 100 °C for 12 h to obtain a GO - PEI layered membrane, and this GO - PEI layered membrane is named membrane - 3.

[0068] Example 4

[0069] The difference from Example 1 is only that:

[0070] In step S1, the molecular weight of PEI is 600;

[0071] In step S2, the polyvinylidene fluoride (PVDF) membrane is wetted with a solvent and then laid flat on the tin foil paper, and then evenly attached to the surface of the receiver used in the double - needle electrostatic spraying process to obtain a flat base layer;

[0072] In step S3, a GO - PEI composite membrane with a membrane area of 300 cm 2 is obtained, and the parameters of the double - needle electrostatic spraying process are: voltage 9 kV, injection rate 1 mL / h, roller rotation speed 300 rpm, swing speed 30 mm / s, receiving distance 4 cm, room temperature is controlled at 22 °C, and relative humidity is 50%;

[0073] In step S4, the GO - PEI composite membrane with a membrane area of 300 cm 2 is subjected to high - temperature cross - linking modification at 80 °C for 20 h to obtain a GO - PEI layered membrane, and this GO - PEI layered membrane is named membrane - 4.

[0074] Example 5

[0075] The difference from Example 1 is only that:

[0076] In step S1, the concentration of the GO dispersion is 0.8 mg / mL, the mass fraction of PEI in the initial PEI solution is 0.2%, and the molecular weight of PEI is 600;

[0077] In step S2, the polyethylene (PES) membrane is wetted with a solvent and then laid flat on the tin foil paper, and then evenly attached to the surface of the receiver used in the double - needle electrostatic spraying process to obtain a flat base layer;

[0078] In step S3, a GO - PEI composite membrane with an area of 600 cm 2 is obtained, and the parameters of the double - needle electrostatic spraying process are: voltage 9.5 kV, injection rate 1.2 mL / h, roller rotation speed 300 rpm, swing speed 22 mm / s, receiving distance 5 cm, controlling the room temperature at 20 °C and the relative humidity at 55%;

[0079] In step S4, the GO - PEI composite membrane with an area of 600 cm 2 is subjected to high - temperature cross - linking modification according to the temperature and time parameters in Example 1 to obtain a GO - PEI layered membrane, and the obtained GO - PEI layered membrane is named Membrane - 5.

[0080] Example 6

[0081] The difference from Example 1 is only that:

[0082] In step S1, the concentration of the GO dispersion is 0.6 mg / mL, and the volume ratio of absolute ethanol to ultrapure water is 2:1;

[0083] In step S3, a GO - PEI composite membrane with an area of 300 cm 2 is obtained, and the parameters of the double - needle electrostatic spraying process are: voltage 9 kV, injection rate 1.5 mL / h, roller rotation speed 320 rpm, swing speed 25 mm / s, receiving distance 4 cm, controlling the room temperature at 20 °C and the relative humidity at 60%;

[0084] In step S4, the GO - PEI composite membrane with an area of 300 cm 2 is subjected to high - temperature cross - linking modification at 100 °C for 12 h to obtain a GO - PEI layered membrane, and this GO - PEI layered membrane is named Membrane - 6.

[0085] Comparative Example 1

[0086] According to the process in Example 1, the voltage parameter in step S3 is changed to 6 kV, the injection rate is changed to 5 mL / h, and the other conditions remain unchanged. The finally obtained membrane is named Membrane - 7.

[0087] Comparative Example 2

[0088] According to the process in Example 2, the spraying distance in step S3 is changed to 10 cm, and the controlled room temperature is changed to 30 °C, and the other conditions remain unchanged. The finally obtained membrane is named Membrane - 8.

[0089] Comparative Example 3

[0090] According to the process in Example 6, change the concentration of the GO dispersion liquid in step S1 to 1.0 mg / mL, change the mass fraction of PEI in the initial PEI solution to 0.6%, keep the other conditions unchanged, and name the finally obtained membrane as Membrane-9.

[0091] Compare the GO-PEI layered membranes prepared in Examples 1-6.

[0092] As Figure 1 shown, it is the SEM surface of the GO-PEI layered membranes obtained in Examples 1-6 of the present invention.

[0093] From Figure 1 it can be seen that the surfaces of the GO-PEI layered membranes obtained in Examples 1-6 are complete and defect-free. The present invention can achieve fine control of the membrane surface under different conditions, control the surface roughness of the membrane, and further regulate the hydrophilicity and hydrophobicity of the membrane.

[0094] As Figure 2 shown, it is the SEM cross-section of the GO-PEI layered membranes obtained in Examples 1-6 of the present invention, and the cross-section thicknesses are 80, 111, 60, 102, 88, and 82 nm in sequence.

[0095] As Figure 3 shown, it is the XRD curve graph of the GO-PEI layered membranes obtained in Examples 1-6 of the present invention;

[0096] In the XRD pattern, peaks corresponding to GO appear within the diffraction angle range of about 10°. The layer spacing is calculated using Bragg's law. The layer spacings of Membrane-1, Membrane-2, Membrane-3, Membrane-4, Membrane-5, and Membrane-6 are 0.873 nm, 0.821 nm, 0.784 nm, 0.827 nm, 0.825 nm, and 0.867 nm respectively.

[0097] As Figure 4 shown, it is the SEM surface of the membranes obtained in Comparative Examples 1-3 of the present invention. The SEM surface of Membrane-7 has more defects. When working under an out-of-range voltage, an effective membrane layer cannot be formed, and at the same time, the injection rate is too fast to effectively stack and form a layered structure; most of the SEM surface defects of Membrane-8 are incomplete coating due to the limitation of the effective spraying distance; nanosheets appear on the SEM surface of Membrane-9. When the dosage of nanosheets is too high, a stacked structure cannot be formed.

[0098] As Figure 5As shown, the SEM cross-section of the membranes obtained in Comparative Examples 1-3 of the present invention is presented. For membranes -7, -8, and -9, no continuous stacked structure was formed, and there were excessive wrinkled structures. After performance testing, effective retention of dye molecules and bovine serum albumin could not be achieved, so the performance of the membranes such as swelling stability, permeation flux, and retention rate will not be mentioned further.

[0099] As Figure 6 shown, the flux and retention graphs of the GO-PEI layered membranes of Examples 1-3 of the present invention are presented.

[0100] When the spraying experiment was carried out under the optimal conditions, the methanol permeation performance of the membrane reached 33 L m -2 h -1 bar -1 , and the retention rate of brilliant blue was over 90%.

[0101] Figure 7 This is the infrared analysis graph of the GO-PEI layered membrane obtained in Example 1 of the present invention;

[0102] At 80 °C, for the cross-linking test at different times, the -OH peak of GO at 3300 cm -1 in the infrared spectrum also exists in the GO-PEI layered membrane, while the stretching vibration of the carbonyl group (1718 cm -1 ) weakens in the GO-PEI layered membrane, and three new peaks appear at 1637 cm -1 , 1541 cm -1 and 1411 cm -1 respectively, which are attributed to the stretching vibration of the amide bond HNC=O, the stretching vibration of N-H, and the stretching vibration of C-N.

[0103] Figure 8 This is the operational stability graph of the GO-PEI layered membrane obtained in Example 4 of the present invention;

[0104] In the continuous 60-h test, the water permeation flux of membrane -4 decreased in the first 15 h of the test, and the retention rate of brilliant blue dye increased. This is because under the operating pressure, the membrane layers were gradually compacted, resulting in a decrease in the layer spacing. In the subsequent time, both the permeation flux and the retention rate remained stable, which also proves that membrane -4 can maintain stability for a long time.

[0105] Figure 9 This is the swelling degree test graph of the GO-PEI layered membrane obtained in Example 5 of the present invention;

[0106] The test found that the GO-PEI layered membrane could remain stable for 240 days in the swelling tests in dimethyl adipate, n-hexane, and methanol.

[0107] Figure 10UV analysis diagram of bovine serum albumin solution of the GO-PEI layered film obtained in Example 6 of the present invention;

[0108] The retention of the GO-PEI layered film on the bovine serum albumin solution was tested, and it was calculated by the absorbance ratio of the ultraviolet spectrophotometer that the primary retention rate of the film was greater than 90%.

[0109] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A process for batch preparation of GO-PEI layered films, characterized in that: It includes the following steps: S1. Prepare a GO dispersion and a PEI solution. The solvents of the GO dispersion and the PEI solution are both mixtures of absolute ethanol and ultrapure water; S2. Spread the base film to obtain a flat base layer; S3. Simultaneously coat the GO dispersion and the PEI solution on the surface of the base layer by using a double - needle electrostatic spraying process to obtain a GO - PEI composite film; S4. Subject the GO - PEI composite film to high - temperature cross - linking modification to obtain a GO - PEI layered film.

2. The process for batch preparation of GO-PEI layered film according to claim 1, characterized in that: In step S1, the volume ratio of absolute ethanol to ultrapure water is 0.5:1 to 3:

1.

3. A process for batch preparation of GO-PEI layered film according to claim 1, characterized in that: In step S1, the concentration of the GO dispersion is 0.2 - 0.8 mg / mL, which is prepared by diluting and ultrasonically dispersing a GO nanosheet dispersion.

4. A process for batch preparation of GO-PEI layered film according to claim 3, characterized in that: The GO nanosheets used are hydrophilic GO nanosheets, and the lateral size of the GO nanosheets is 1 - 3 μm, and the thickness is 2 - 4 nm.

5. A process for batch preparation of GO-PEI layered film according to claim 1, characterized in that: In step S1, based on the total mass of the PEI solution, the mass fraction of PEI is 0.1 - 0.4%, and the molecular weight of PEI is 300 - 600.

6. A process for batch preparation of GO-PEI layered film according to claim 1, characterized in that: In step S2, the base film is one of a nylon film, an ultrafiltration membrane, a microfiltration membrane, a polyvinylidene fluoride (PVDF) membrane, and a polyethylene (PES) membrane.

7. A process for batch preparation of GO-PEI layered films according to claim 1, characterized in that: In step S2, the base film is wetted with the solvent to make the base film spread flat.

8. A process for batch preparation of GO-PEI layered film according to claim 1, characterized in that: In step S3, the parameter settings of the double - needle electrostatic spraying process are: temperature 20 - 25°C, air humidity 40 - 60%, the injection rate of the double - needle spraying of the GO dispersion and the PEI solution is 1 - 4 mL / h, the spraying voltage is 7.0 - 9.5 kV, the receiving distance is 4 - 6 cm, the swing speed is 21 - 30 mm / s, and the roller rotation speed is 200 - 400 rpm.

9. A process for batch preparation of GO-PEI layered film according to claim 1, characterized in that: In step S4, the temperature of the high - temperature cross - linking modification is 80 - 100°C, and the time is 8 - 24 h.

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