Pressure-resistant filtering membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of membrane preparation, and particularly relates to a pressure-resistant filtering membrane as well as a preparation method and application thereof. The pressure-resistant filtering membrane provided by the invention comprises a porous substrate, a carbon nanotube membrane layer loaded on the porous substrate and a graphene oxide membrane layer loaded on the carbon nanotube membrane layer, and the carbon nanotube membrane layer is located between the porous substrate and the graphene oxide membrane layer. According to the pressure-resistant filtering membrane provided by the invention, the carbon nano tube membrane layer forms a middle layer between the porous substrate and the graphene oxide membrane layer, and through the synergistic interaction between the carbon nano tube membrane layer and the graphene oxide membrane layer, the pressure-resistant filtering membrane has high permeability to water and high interception effect to filtered substances, and also has high pressure resistance. Particularly, the high-efficiency filtering of substances such as dye can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane preparation, and particularly relates to a pressure-resistant filtration membrane, a preparation method thereof, and an application thereof. Background Art

[0002] Membrane separation technology has unique advantages in water resource utilization and advanced treatment. High-performance separation membranes can achieve rapid and highly selective separation of target substances, which is the focus of the membrane research field. Due to its extremely thin thickness and unique interlayer channels, graphene oxide (GO) membrane has recently been regarded as one of the ideal nanofiltration membranes. However, the application of GO membranes still remains at the laboratory or pilot plant scale and has not been industrialized. The biggest difficulty is the instability of GO membranes. For example, they are prone to damage in environments with high pressure, harsh solvents, and tangential solvent flow. In addition, during the membrane separation process, there is usually an inverse relationship between the water permeability and the membrane thickness, that is, the smaller the permeability, the smaller the resistance, and the faster the material transmission speed. Therefore, reducing the thickness of GO membranes is a very effective way to improve their permeation performance, but this brings about a decrease in membrane stability, especially poor pressure resistance.

[0003] Currently, in order to improve the pressure resistance of GO membranes, there are mainly the following two methods: 1. Increase the thickness of the GO membrane to improve stability. 2. Reduce the GO membrane to reduce the interlayer spacing between GO membranes to improve the chemical structure stability of GO nanosheets. However, the GO membranes prepared by these methods often have low water permeation performance, require more material costs, and the improvement of pressure resistance is also limited. Existing GO membranes cannot have both high water permeation performance and high pressure resistance at the same time. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect that existing graphene oxide membranes cannot have both high water permeation performance and high pressure resistance at the same time, so as to provide a pressure-resistant filtration membrane, a preparation method thereof, and an application thereof.

[0005] The present invention provides a pressure-resistant filtration membrane, which includes a porous substrate, a carbon nanotube membrane layer loaded on the porous substrate, and a graphene oxide membrane layer loaded on the carbon nanotube membrane layer, and the carbon nanotube membrane layer is located between the porous substrate and the graphene oxide membrane layer.

[0006] Preferably, the total average thickness of the carbon nanotube membrane layer and the graphene oxide membrane layer is not greater than 100 nm;

[0007] Preferably, the total average thickness of the carbon nanotube membrane layer and the graphene oxide membrane layer is 40 - 100 nm;

[0008] And / or, the average thickness of the graphene oxide membrane layer is 10 - 30 nm.

[0009] The present invention provides a method for preparing a pressure-resistant filtration membrane, comprising the following steps:

[0010] 1) Depositing carbon nanotubes on a porous substrate to form a carbon nanotube film layer;

[0011] 2) Depositing graphene oxide on the carbon nanotube film layer obtained in step 1) to form a graphene oxide film layer, thereby obtaining the pressure-resistant filtration membrane.

[0012] Preferably, in step 1), the porous substrate is selected from at least one of a polyethersulfone (PES) membrane, a polyvinylidene fluoride (PVDF) membrane, and a polytetrafluoroethylene (PTFE) membrane;

[0013] and / or, the average pore diameter of the porous substrate in step 1) is 0.05 - 0.5 μm;

[0014] and / or, the carbon nanotubes in step 1) are selected from at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes;

[0015] and / or, the average sheet diameter size of the graphene oxide in step 2) is 0.7 - 30 μm;

[0016] and / or, the loading amount of the carbon nanotubes on the porous substrate in step 1) is 2 - 8 mg / m 2 ;

[0017] and / or, the loading amount of the graphene oxide on the carbon nanotube film layer in step 2) is 20 - 30 mg / m 2 。

[0018] Optionally, the diameter of the porous substrate is 100 - 300 mm;

[0019] Optionally, the diameter of the porous substrate is 180 - 250 mm.

[0020] The polyethersulfone (PES) membrane, polyvinylidene fluoride (PVDF) membrane, and polytetrafluoroethylene (PTFE) membrane of the present invention are all conventional membranes in the art and can be obtained commercially.

[0021] The sheet diameter size of the graphene oxide of the present invention is the lateral dimension size of the graphene oxide sheet and is measured according to the enterprise standard: O / XMBD 105 - 2019.

[0022] Preferably, in step 1), a carbon nanotube dispersion is prepared, and the carbon nanotubes are deposited on the porous substrate by suction filtration to form a carbon nanotube film layer;

[0023] Optionally, before the step of depositing the carbon nanotubes on the porous substrate by suction filtration, a treatment step of wetting the porous substrate with water and then performing suction filtration is further included;

[0024] And / or, after the step of depositing carbon nanotubes on the porous substrate by suction filtration, a drying treatment step is further included.

[0025] Optionally, the drying temperature is 35 - 40 °C; the present invention does not specifically limit the drying time, and it is only necessary to achieve the drying purpose of removing moisture. For example, optionally, the drying time is more than 20 h.

[0026] Preferably, the solvent in the carbon nanotube dispersion is selected from at least one of water, methanol, and ethanol;

[0027] And / or, the mass concentration of carbon nanotubes in the carbon nanotube dispersion is 0.06 - 0.09 mg / L.

[0028] Preferably, the carbon nanotubes are deposited on the porous substrate by suction filtration through an intermittent wet forming device;

[0029] Optionally, the suction filtration pressure is 0.01 - 0.1 MPa, and the suction filtration time is not less than 5 min.

[0030] Optionally, the suction filtration pressure is 0.1 MPa;

[0031] Optionally, the suction filtration time is 5 min - 24 h.

[0032] Preferably, in step 2), a graphene oxide dispersion is prepared, and the graphene oxide is deposited on the carbon nanotube film layer of step 1) by suction filtration to form a graphene oxide film layer, thereby obtaining the pressure-resistant filtration membrane;

[0033] Optionally, before the step of depositing graphene oxide on the carbon nanotube film layer of step 1) by suction filtration, a treatment step of wetting the carbon nanotube film layer with water and then performing suction filtration is further included;

[0034] Optionally, after the step of depositing graphene oxide on the carbon nanotube film layer by suction filtration, a drying treatment step is further included.

[0035] Optionally, the drying temperature is 35 - 60 °C; the present invention does not specifically limit the drying time, and it is only necessary to achieve the drying purpose of removing moisture. For example, optionally, the drying time is more than 20 h.

[0036] Preferably, the solvent in the graphene oxide dispersion is selected from at least one of water, methanol, and ethanol;

[0037] And / or, the mass concentration of graphene oxide in the graphene oxide dispersion is 0.6 - 1.2 mg / L;

[0038] And / or, depositing graphene oxide on the carbon nanotube film layer by means of suction filtration with an intermittent wet forming device;

[0039] Optionally, the suction filtration pressure is 0.01 - 0.1 MPa, and the suction filtration time is not less than 10 min.

[0040] Optionally, the suction filtration pressure is 0.1 MPa;

[0041] Optionally, the suction filtration time is 10 min - 24 h.

[0042] The present invention provides an application of the pressure-resistant filtration membrane described above or the pressure-resistant filtration membrane prepared by the preparation method described above in the field of membrane separation technology.

[0043] The technical solution of the present invention has the following advantages:

[0044] 1. The pressure-resistant filtration membrane provided by the present invention, the pressure-resistant filtration membrane includes a porous substrate, a carbon nanotube film layer loaded on the porous substrate, and a graphene oxide film layer loaded on the carbon nanotube film layer, and the carbon nanotube film layer is located between the porous substrate and the graphene oxide film layer. The specific pressure-resistant filtration membrane of the present invention has a carbon nanotube film layer as a network layer support. This structure contains a mechanically strong and interconnected carbon nanotube network, which shows a strong π-π interaction with the supported graphene oxide layer and serves as a microscopic framework to support the graphene oxide layer, thereby enhancing the mechanical strength of the graphene oxide membrane without affecting the permeability of the filtration membrane. At the same time, placing the carbon nanotube film layer between the porous substrate and the graphene oxide film layer can play the role of a support layer. On the one hand, it reduces the suspended diameter of the graphene oxide film layer, and on the other hand, it increases the thickness and modulus of the overall membrane, effectively solving the defect that the graphene oxide film layer directly loaded on the porous substrate has unstable structure and cannot achieve the improvement of pressure resistance while ensuring permeability. The pressure-resistant filtration membrane provided by the present invention has a carbon nanotube film layer forming an intermediate layer between the porous substrate and the graphene oxide film layer. The synergistic interaction between the carbon nanotube film layer and the graphene oxide film layer makes the pressure-resistant filtration membrane have high water permeability, high retention effect on the filtrate, and at the same time also has high pressure resistance. In particular, it can achieve efficient filtration of substances such as dyes.

[0045] 2. The pressure-resistant filtration membrane provided by the present invention, the total average thickness of the carbon nanotube film layer and the graphene oxide film layer is not greater than 100 nm; preferably, the total average thickness of the carbon nanotube film layer and the graphene oxide film layer is 40 - 100 nm; and / or, the average thickness of the graphene oxide film layer is 15 - 30 nm. The pressure-resistant filtration membrane has the characteristics of being ultra-thin, and the raw materials do not require extra treatment and have low cost.

[0046] 3. The pressure-resistant filtration membrane provided by the present invention can be prepared into a filtration membrane with a relatively large size of about 200 mm in diameter, which is applicable to various water filtration scenarios, including water purification applications in various fields such as power, textile, chemical industry, electronics, metallurgy, food, drinking water purification, industrial water treatment, biopharmaceuticals, fermentation, etc. It is particularly suitable for the filtration of dyes and food and beverages in water treatment, has a high water flux and a high rejection effect for organic dyes, and has a rejection effect of more than 90% for tea polyphenols. It can also be applied to direct current and cross-flow filtration. At the same time, the film-making cost is low, which further accelerates the application process of the graphene oxide membrane and is more conducive to industrial production.

[0047] 4. The preparation method of the pressure-resistant filtration membrane provided by the present invention includes the following steps: 1) depositing carbon nanotubes on a porous substrate to form a carbon nanotube film layer; 2) depositing graphene oxide on the carbon nanotube film layer in step 1) to form a graphene oxide film layer, thereby obtaining the pressure-resistant filtration membrane. The pressure-resistant filtration membrane obtained by the above preparation method of the present invention includes a porous substrate, a carbon nanotube film layer loaded on the porous substrate, and a graphene oxide film layer loaded on the carbon nanotube film layer. The carbon nanotube film layer is located between the porous substrate and the graphene oxide film layer, and has high permeability and high pressure resistance at the same time.

[0048] 5. The preparation method of the pressure-resistant filtration membrane provided by the present invention deposits carbon nanotubes on a porous substrate by means of suction filtration with an intermittent wet forming device; deposits graphene oxide on the carbon nanotube film layer by means of suction filtration with an intermittent wet forming device; through specific processes and equipment, the present invention rapidly prepares carbon nanotube materials and graphene oxide materials into thin film materials by means of wet forming respectively, with a fast forming speed, high efficiency, and high film forming uniformity.

[0049] 6. The preparation method of the pressure-resistant filtration membrane provided by the present invention further includes a treatment step of wetting and suction filtering the porous substrate with water before the step of depositing carbon nanotubes on the porous substrate by means of suction filtration; the present invention allows pure water to pass through the inside of the porous substrate to remove the air inside the porous substrate.

[0050] The preparation method of the pressure-resistant filtration membrane provided by the present invention further includes a drying treatment after the step of depositing carbon nanotubes on the porous substrate by means of suction filtration. Through complete drying treatment, it can be ensured that the carbon nanotube film layer will not fall off.

[0051] 7. The preparation method of the pressure-resistant filtration membrane provided by the present invention further includes a treatment step of wetting and suction filtering the carbon nanotube film layer with water before the step of depositing graphene oxide on the carbon nanotube film layer in step 1) by means of suction filtration. Through the steps of wetting and suction filtering with water, it is detected whether the carbon nanotube film layer is completely dry and the air bubbles inside the film are discharged. If the carbon nanotube film layer is not completely dry, the carbon nanotube film layer will fall off after wetting with water. Brief Description of the Drawings

[0052] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0053] Figure 1 SEM image of graphene oxide sheets used in Example 1 of the present invention;

[0054] Figure 2 SEM images of the upper surface and cross-section of the filtration membranes prepared in Comparative Example 1 and Comparative Example 3 of the present invention;

[0055] Among them, Figure (a) is the SEM image of the upper surface of the filtration membrane prepared in Comparative Example 1, (b) is the cross-sectional SEM image of the filtration membrane prepared in Comparative Example 1, Figure (c) is the SEM image of the upper surface of the filtration membrane prepared in Comparative Example 1, and (d) is the cross-sectional SEM image of the filtration membrane prepared in Comparative Example 1;

[0056] Figure 3 SEM images of the upper surface and cross-section of the filtration membrane prepared in Example 1 of the present invention;

[0057] Among them, Figure (a) is the SEM image of the upper surface of the filtration membrane prepared in Example 1, and (b) is the cross-sectional SEM image of the filtration membrane prepared in Example 1;

[0058] Figure 4 Water flux change of Example 1 of the present invention under different hydraulic pressures from 2 to 62 bar in units of L m -2 h -1 bar -1 and the corresponding rejection rate change diagram of rose bengal dye;

[0059] Figure 5 Water flux change of Example 1 of the present invention under different hydraulic pressures from 4 to 60 bar in units of L m -2 h -1 and the corresponding rejection rate change diagram of rose bengal dye;

[0060] Figure 6 Comparison diagram of the maximum water flux and pressure resistance value of Example 1 and Comparative Example 1 of the present invention under different hydraulic pressures from 0 to 62 bar in units of L m -2 h -1 Specific Embodiments

[0061] ​The following embodiments are provided to better understand the present invention further. It is not limited to the best mode described, and does not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with those of other prior arts falls within the protection scope of the present invention.

[0062] For those embodiments in which specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0063] The polyethersulfone membranes used in the embodiments and comparative examples of the present invention are purchased from Longjin Membrane Industry Co., Ltd., Nantong, Jiangsu.

[0064] Example 1

[0065] This embodiment provides a pressure-resistant filtration membrane, which includes a porous substrate, a carbon nanotube film layer loaded on the porous substrate, and a graphene oxide film layer loaded on the carbon nanotube film layer. The carbon nanotube film layer is located between the porous substrate and the graphene oxide film layer.

[0066] The total average thickness of the carbon nanotube film layer and the graphene oxide film layer is 70 nm;

[0067] The average thickness of the graphene oxide film layer is 20 nm.

[0068] This embodiment provides a preparation method of the above pressure-resistant filtration membrane, including the following steps:

[0069] 1) Prepare a single-walled carbon nanotube dispersion with a mass concentration of 0.08 mg / L of single-walled carbon nanotubes using single-walled carbon nanotubes and deionized water. Place a polyethersulfone (PES) membrane porous substrate with an average pore diameter of 0.1 μm and a diameter of 240 mm in an intermittent wet forming machine, moisten it with water and filter it by suction to discharge the air inside the porous substrate. Then deposit the single-walled carbon nanotubes on the polyethersulfone (PES) membrane porous substrate by suction filtration (suction filtration pressure is 0.1 MPa, suction filtration time is 5 min) through the intermittent wet forming machine, and dry it at 40 °C for 24 h to form a carbon nanotube film layer, and the loading amount of single-walled carbon nanotubes is 7.5 mg / m 2 ;

[0070] 2) Prepare a graphene oxide dispersion with a graphene oxide mass concentration of 0.8 mg / L using graphene oxide nanosheets with an average sheet diameter of 0.89 μm and deionized water. Wet the carbon nanotube film layer with water and perform suction filtration. Then, deposit graphene oxide on the carbon nanotube film layer obtained in step 1) by suction filtration through an intermittent wet forming device (suction filtration pressure: 0.1 MPa, suction filtration time: 10 min), and dry it at 40°C for 24 h to obtain the pressure-resistant filtration membrane (denoted as SG / C7.5). The loading amount of graphene oxide is 25 mg / m 2 。

[0071] Example 2

[0072] This example provides a pressure-resistant filtration membrane, which includes a porous substrate, a carbon nanotube film layer loaded on the porous substrate, and a graphene oxide film layer loaded on the carbon nanotube film layer. The carbon nanotube film layer is located between the porous substrate and the graphene oxide film layer.

[0073] The total average thickness of the carbon nanotube film layer and the graphene oxide film layer is 70 nm;

[0074] The average thickness of the graphene oxide film layer is 20 nm.

[0075] This example provides a preparation method of the above pressure-resistant filtration membrane, including the following steps:

[0076] 1) Prepare a single-walled carbon nanotube dispersion with a single-walled carbon nanotube mass concentration of 0.08 mg / L using single-walled carbon nanotubes and deionized water. Place a porous substrate of a polyethersulfone (PES) membrane with an average pore diameter of 0.1 μm and a diameter of 240 mm in an intermittent wet forming device, wet it with water and perform suction filtration to expel the air inside the porous substrate. Then, deposit single-walled carbon nanotubes on the porous substrate of the polyethersulfone (PES) membrane by suction filtration through an intermittent wet forming device (suction filtration pressure: 0.1 MPa, suction filtration time: 5 min), and dry it at 40°C for 24 h to form a carbon nanotube film layer. The loading amount of single-walled carbon nanotubes is 7.5 mg / m 2 ;

[0077] 2) Prepare a graphene oxide dispersion with a graphene oxide mass concentration of 0.8 mg / L using graphene oxide sheets with an average sheet diameter of 4.6 μm and deionized water. Wet the carbon nanotube film layer with water and perform suction filtration. Then, deposit graphene oxide on the carbon nanotube film layer obtained in step 1) by suction filtration through an intermittent wet forming device (suction filtration pressure: 0.1 MPa, suction filtration time: 10 min), and dry it at 40°C for 24 h to obtain the pressure-resistant filtration membrane (denoted as MG / C7.5). The loading amount of graphene oxide is 25 mg / m 2 。

[0078] Example 3

[0079] This example provides a pressure-resistant filtration membrane, which includes a porous substrate, a carbon nanotube film layer loaded on the porous substrate, and a graphene oxide film layer loaded on the carbon nanotube film layer. The carbon nanotube film layer is located between the porous substrate and the graphene oxide film layer.

[0080] The total average thickness of the carbon nanotube film layer and the graphene oxide film layer is 50 nm;

[0081] The average thickness of the graphene oxide film layer is 15 nm.

[0082] This example provides a preparation method of the above pressure-resistant filtration membrane, including the following steps:

[0083] 1) Prepare a single-walled carbon nanotube dispersion with a single-walled carbon nanotube mass concentration of 0.06 mg / L using single-walled carbon nanotubes and deionized water. Place a polytetrafluoroethylene (PTFE) membrane porous substrate with an average pore diameter of 0.3 μm and a diameter of 240 mm in an intermittent wet forming machine, wet it with water and filter it to discharge the air inside the porous substrate. Then, deposit the single-walled carbon nanotubes on the polytetrafluoroethylene (PTFE) membrane porous substrate by filtering through the intermittent wet forming machine (the filtration pressure is 0.1 MPa and the filtration time is 30 min), and dry it at 40 °C for 20 h to form a carbon nanotube film layer, and the single-walled carbon nanotube loading is 5.6 mg / m 2 ;

[0084] 2) Prepare a graphene oxide dispersion with a graphene oxide mass concentration of 1 mg / L using graphene oxide sheets with an average sheet diameter size of 10 μm and deionized water. Wet the carbon nanotube film layer with water and filter it, and then deposit the graphene oxide on the carbon nanotube film layer in step 1) by filtering through the intermittent wet forming machine (the filtration pressure is 0.1 MPa and the filtration time is 60 min), and dry it at 40 °C for 30 h to obtain the pressure-resistant filtration membrane, and the graphene oxide loading is 18.8 mg / m 2 .

[0085] Example 4

[0086] This example provides a pressure-resistant filtration membrane, which includes a porous substrate, a carbon nanotube film layer loaded on the porous substrate, and a graphene oxide film layer loaded on the carbon nanotube film layer. The carbon nanotube film layer is located between the porous substrate and the graphene oxide film layer.

[0087] The total average thickness of the carbon nanotube film layer and the graphene oxide film layer is 70 nm;

[0088] The average thickness of the graphene oxide film layer is 20 nm.

[0089] This embodiment provides a method for preparing the above-mentioned pressure-resistant filtration membrane, including the following steps:

[0090] 1) Prepare a single-walled carbon nanotube dispersion with a single-walled carbon nanotube mass concentration of 0.07 mg / L using single-walled carbon nanotubes and deionized water. Place a polyvinylidene fluoride (PVDF) membrane porous substrate with an average pore size of 0.2 μm and a diameter of 240 mm in an intermittent wet forming machine, wet it with water and perform suction filtration to discharge the air inside the porous substrate. Then, deposit the single-walled carbon nanotubes on the polyvinylidene fluoride (PVDF) membrane porous substrate by suction filtration through the intermittent wet forming machine (suction filtration pressure is 0.1 MPa, suction filtration time is 40 min), and dry it at 35 °C for 30 h to form a carbon nanotube membrane layer. The single-walled carbon nanotube loading is 7.5 mg / m 2 ;

[0091] 2) Prepare a graphene oxide dispersion with a graphene oxide mass concentration of 0.6 mg / L using graphene oxide sheets with an average sheet diameter size of 29 μm and deionized water. Wet the carbon nanotube membrane layer with water and perform suction filtration, and then deposit the graphene oxide on the carbon nanotube membrane layer obtained in step 1) by suction filtration through the intermittent wet forming machine (suction filtration pressure is 0.1 MPa, suction filtration time is 30 min), and dry it at 40 °C for 24 h to obtain the pressure-resistant filtration membrane. The loading of graphene oxide is 25 mg / m 2 。

[0092] Comparative Example 1

[0093] This comparative example provides a filtration membrane, which includes a porous substrate and a graphene oxide membrane layer loaded on the porous substrate.

[0094] The average thickness of the graphene oxide membrane layer is 20 nm.

[0095] This comparative example provides a method for preparing the above-mentioned filtration membrane, including the following steps:

[0096] 1) Prepare a graphene oxide dispersion with a graphene oxide mass concentration of 0.8 mg / L using graphene oxide nanosheets with an average sheet diameter size of 0.89 μm and deionized water. Place a polyethersulfone (PES) membrane porous substrate with an average pore size of 0.1 μm and a diameter of 240 mm in an intermittent wet forming machine, wet it with water and perform suction filtration to discharge the air inside the porous substrate. Then, deposit the graphene oxide on the polyethersulfone (PES) membrane porous substrate by suction filtration through the intermittent wet forming machine (suction filtration pressure is 0.1 MPa, suction filtration time is 10 min), and dry it at 40 °C for 24 h to obtain the filtration membrane (denoted as SG). The loading of graphene oxide is 25 mg / m 2 。

[0097] Comparative Example 2

[0098] This comparative example provides a filter membrane, which includes a porous substrate and a graphene oxide film layer loaded on the porous substrate.

[0099] The average thickness of the graphene oxide film layer is 20 nm.

[0100] This comparative example provides a preparation method of the above filter membrane, including the following steps:

[0101] 1) Prepare a graphene oxide dispersion with a graphene oxide mass concentration of 0.8 mg / L using graphene oxide nanosheets with an average sheet diameter of 4.6 μm and deionized water. Place a polyethersulfone (PES) membrane porous substrate with an average pore diameter of 0.1 μm and a diameter of 240 mm in an intermittent wet forming machine, wet it with water and filter it to discharge the air inside the porous substrate. Then deposit graphene oxide on the polyethersulfone (PES) membrane porous substrate by filtering through the intermittent wet forming machine (the filtering pressure is 0.1 MPa and the filtering time is 10 min), and dry it at 40°C for 24 h to obtain the filter membrane. The loading amount of graphene oxide is 25 mg / m 2 。

[0102] Comparative Example 3

[0103] This comparative example provides a filter membrane, which includes a porous substrate and a carbon nanotube film layer loaded on the porous substrate.

[0104] The average thickness of the carbon nanotube film layer is 50 nm.

[0105] This example provides a preparation method of the above filter membrane, including the following steps:

[0106] 1) Prepare a single-walled carbon nanotube dispersion with a single-walled carbon nanotube mass concentration of 0.08 mg / L using single-walled carbon nanotubes and deionized water. Place a polyethersulfone (PES) membrane porous substrate with an average pore diameter of 0.1 μm and a diameter of 240 mm in an intermittent wet forming machine, wet it with water and filter it to discharge the air inside the porous substrate. Then deposit single-walled carbon nanotubes on the polyethersulfone (PES) membrane porous substrate by filtering through the intermittent wet forming machine (the filtering pressure is 0.1 MPa and the filtering time is 5 min), and dry it at 40°C for 24 h to form a carbon nanotube film layer. The loading amount of single-walled carbon nanotubes is 7.5 mg / m 2 , and obtain the filter membrane.

[0107] Comparative Example 4

[0108] This comparative example provides a filtration membrane, which includes a porous substrate, a graphene oxide film layer loaded on the porous substrate, and a carbon nanotube film layer loaded on the graphene oxide film layer. The graphene oxide film layer is located between the porous substrate and the carbon nanotube film layer.

[0109] The total average thickness of the carbon nanotube film layer and the graphene oxide film layer is 70 nm;

[0110] The average thickness of the graphene oxide film layer is 20 nm.

[0111] This example provides a preparation method of the above filtration membrane, including the following steps:

[0112] 1) Prepare a graphene oxide dispersion with a graphene oxide mass concentration of 0.8 mg / L using graphene oxide nanosheets with an average sheet diameter of 0.89 μm and deionized water. Place a polyethersulfone (PES) membrane porous substrate with an average pore diameter of 0.1 μm and a diameter of 240 mm in an intermittent wet forming machine, wet it with water and filter it to discharge the air inside the porous substrate. Then, deposit graphene oxide on the polyethersulfone (PES) membrane porous substrate by filtration through the intermittent wet forming machine (filtration pressure is 0.1 MPa, filtration time is 10 min), and dry it at 40 °C for 24 h to form a graphene oxide film layer. The loading amount of graphene oxide is 25 mg / m 2 ;

[0113] 2) Prepare a single-walled carbon nanotube dispersion with a single-walled carbon nanotube mass concentration of 0.08 mg / L using single-walled carbon nanotubes and deionized water. Wet and filter the carbon nanotube film layer, and then deposit single-walled carbon nanotubes on the graphene oxide film layer obtained in step 1) by filtration through the intermittent wet forming machine (filtration pressure is 0.1 MPa, filtration time is 5 min), and dry it at 40 °C for 24 h to form a carbon nanotube film layer. The loading amount of single-walled carbon nanotubes is 7.5 mg / m 2 , obtaining the pressure-resistant filtration membrane.

[0114] Test example

[0115] Perform SEM scanning electron microscopy on the graphene oxide nanosheets used in Example 1, and the obtained SEM image is as Figure 1 shown; perform SEM scanning electron microscopy on the filtration membranes prepared in Example 1, Comparative Example 1, and Comparative Example 3. The upper surface SEM image of the filtration membrane prepared in Comparative Example 1 is as shown in Figure 2 Figure (a) in it, and the cross-sectional SEM image is as shown in Figure 2 Figure (b) in it; the upper surface SEM image of the filtration membrane prepared in Comparative Example 3 is as shown in Figure 2 Figure (c) in it, and the cross-sectional SEM image is as shown in Figure 2as shown in Figure (d) therein; the SEM image of the upper surface of the filtration membrane prepared in Example 1 is as shown in Figure 3 Figure (a) therein, and the cross-sectional SEM image is as shown in Figure 3 Figure (b) therein.

[0116] The filtration membranes prepared in Examples 1-4 and Comparative Examples 1-4 were respectively subjected to filtration tests for Rose Bengal dye (RB) with a mass concentration of 20 mg / L through a cross-flow filtration device under a hydraulic pressure environment of room temperature and 0-62 bar. The solvent in the Rose Bengal dye was water. Record the maximum water flux in L m -2 h -1 at different hydraulic pressures from 0 to 60 bar, and the rejection rate of the Rose Bengal dye corresponding to the maximum water flux. The test results of the maximum water flux and the rejection rate of the Rose Bengal dye are shown in Table 1. Among them, for Example 1, the water flux in L m -2 h -1 bar -1 at different hydraulic pressures from 2 to 62 bar, the change in the water flux (the permeation amount of solvent water) and the corresponding change in the rejection rate of the Rose Bengal dye are as shown in Figure 4 Figure shown. For Example 1, the change in the water flux in L m -2 h -1 at different hydraulic pressures from 4 to 60 bar and the corresponding change in the rejection rate of the Rose Bengal dye are as shown in Figure 5 Figure shown; when the water flux of the filtration membrane suddenly increases (the maximum water flux in L m -2 h -1 suddenly increases by more than 2 times) at a certain pressure, and the rejection rate suddenly drops by 50%, it indicates that the filtration membrane is damaged at this time. Record the previous test pressure as the pressure resistance value. The test results of the pressure resistance value are shown in Table 1. The comparison chart of the maximum water flux and the pressure resistance value of Example 1 (SG / C7.5) and Comparative Example 1 (SG) in L m -2 h -1 at different hydraulic pressures from 0 to 62 bar is as shown in Figure 6 Figure shown.

[0117] Table 1

[0118] <![CDATA[Proof pressure value P m (bar)]]> <![CDATA[Maximum water flux (L m -2 h -1 )]]> Retention rate (%) Example 1 60 966 99.6 Example 2 ＞60 810 99.5 Comparative Example 1 20 490 98.2 Comparative Example 2 24 146 98.5 Comparative Example 3 - - 0

[0119] Note: >60 means that the filtration membrane did not show damage during the hydraulic pressure test at 62 bar.

[0120] The filtration membrane prepared in Comparative Example 3 has no filtration effect. During the filtration test, the Rose Bengal dye directly passes through, and pressure treatment cannot be achieved. There is no pressure resistance value, and its maximum water flux has no practical comparison significance.

[0121] In Comparative Example 4, graphene oxide was first loaded on the substrate material, and the graphene oxide would agglomerate. Then, carbon nanotubes were filtered by suction, and the carbon nanotube film layer could not be formed evenly, so the filtration membrane could not be prepared and relevant tests could not be carried out.

[0122] As can be seen from Figure 4 , for the pressure-resistant filtration membrane in Example 1, the rejection rate for RB dye was higher than 99% under the pressure of 0 - 60 bar, and the permeation performance was stable. When the pressure was further increased to 62 bar, the rejection rate of the pressure-resistant filtration membrane in Example 1 for RB dye decreased sharply, and the permeation performance (water flux) increased sharply, indicating that the membrane was damaged at this time. Therefore, the pressure resistance of the pressure-resistant filtration membrane prepared by the present invention (P m ) can reach 60 bar.

[0123] As can be seen from Figure 5 , the maximum water flux of the pressure-resistant filtration membrane in Example 1 can reach up to 966 L m -2 h -1 , while ensuring a dye rejection effect of more than 99%.

[0124] As can be seen from Figure 6 , the maximum water flux of the filtration membrane in Comparative Example 1 can reach up to 490 L m -2 h -1 , and at the same time, the pressure resistance P m can reach 20 bar, which is much lower than the pressure resistance P m＝ of 60 bar in Example 1. The P m in Example 1 is increased to 3 times that of Comparative Example 1, and the water flux is increased by nearly 2 times. This is because the pressure-resistant filtration membrane prepared by the present invention has a structure of a graphene oxide layer supported by a CNT network layer. This structure contains a CNT network with strong mechanical properties and interconnected connections, and it shows a strong π-π interaction with the supported GO layer, acting as a microscopic framework to support the GO layer, thereby enhancing the mechanical strength of the GO membrane. During the high-pressure filtration process, this structure can maintain the integrity of the membrane.

[0125] Obviously, the above embodiments are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A pressure-resistant filtration membrane, characterized in that: The pressure-resistant filtration membrane comprises a porous substrate, a carbon nanotube membrane layer supported on the porous substrate, and a graphene oxide membrane layer supported on the carbon nanotube membrane layer, wherein the carbon nanotube membrane layer is located between the porous substrate and the graphene oxide membrane layer.

2. The pressure-resistant filtration membrane according to claim 1, characterized in that: The total average thickness of the carbon nanotube film layer and the graphene oxide film layer is no more than 100 nm; Preferably, the total average thickness of the carbon nanotube film layer and the graphene oxide film layer is 40-100 nm; And / or, the average thickness of the graphene oxide film layer is 10-30 nm.

3. A method for preparing a pressure-resistant filtration membrane, characterized in that: The following steps are involved: 1) depositing carbon nanotubes on a porous substrate to form a carbon nanotube film layer; 2) Depositing graphene oxide on the carbon nanotube film layer of step 1) to form a graphene oxide film layer to obtain the pressure-resistant filtration membrane.

4. The method for preparing the pressure-resistant filtration membrane according to claim 3, characterized in that: The porous substrate in step 1) is selected from at least one of a polyethersulfone membrane, a polyvinylidene fluoride membrane, and a polytetrafluoroethylene membrane; And / or, the average pore size of the porous substrate in step 1) is 0.05-0.5 μm; And / or, the carbon nanotubes in step 1) are selected from at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes; And / or, the average sheet size of the graphene oxide in step 2) is 0.7-30 μm; And / or, the loading amount of the carbon nanotubes on the porous substrate in step 1) is 2-8 mg / m 2 ; And / or, the loading amount of graphene oxide on the carbon nanotube film layer in step 2) is 20-30 mg / m 2 .

5. The method for preparing the pressure-resistant filtration membrane according to claim 3 or 4, characterized in that: In step 1), a carbon nanotube dispersion is prepared, and the carbon nanotubes are deposited on a porous substrate by suction filtration to form a carbon nanotube film layer; Optionally, before the step of depositing the carbon nanotubes on the porous substrate by suction filtration, the method further includes wetting the porous substrate with water and suction filtration; And / or, after the step of depositing the carbon nanotubes on the porous substrate by suction filtration, a drying step is also included.

6. The method for preparing the pressure-resistant filtration membrane according to claim 5, characterized in that: The solvent in the carbon nanotube dispersion is selected from at least one of water, methanol and ethanol; And / or, the mass concentration of carbon nanotubes in the carbon nanotube dispersion is 0.06-0.09 mg / L.

7. The method for preparing the pressure-resistant filtration membrane according to claim 5 or 6, characterized in that: Depositing carbon nanotubes on a porous substrate by filtration in an intermittent wet forming device; Optionally, the filtration pressure is 0.01-0.1 MPa, and the filtration time is not less than 5 min.

8. The method for preparing a pressure-resistant filtration membrane according to any one of claims 3 to 7, characterized in that: In step 2), a graphene oxide dispersion is prepared, and the graphene oxide is deposited on the carbon nanotube film layer of step 1) by suction filtration to form a graphene oxide film layer, thereby obtaining the pressure-resistant filtration membrane; Optionally, before the step of depositing graphene oxide on the carbon nanotube film layer in step 1) by suction filtration, the step of wetting the carbon nanotube film layer with water and suction filtration is also included; Optionally, after the step of depositing graphene oxide on the carbon nanotube film layer by suction filtration, a drying step is also included.

9. The method for preparing the pressure-resistant filtration membrane according to claim 8, characterized in that: The solvent in the graphene oxide dispersion is selected from at least one of water, methanol and ethanol; and / or, the mass concentration of graphene oxide in the graphene oxide dispersion is 0.6-1.2 mg / L; and / or, depositing graphene oxide on the carbon nanotube film layer by means of suction filtration in an intermittent wet forming device; Optionally, the filtration pressure is 0.01-0.1 MPa, and the filtration time is not less than 10 min.

10. Use of the pressure-resistant filtration membrane according to claim 1 or 2 or the pressure-resistant filtration membrane prepared by the preparation method according to any one of claims 3 to 9 in the field of membrane separation technology.

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