Filter membrane as well as preparation method and application thereof

Abstract

The invention discloses a filter membrane as well as a preparation method and application thereof. The filter membrane comprises a base membrane and a functional layer, the base membrane is provided with membrane holes, and the functional layer is of a cross-linked net structure formed by further cross-linking amido bonds formed by carboxyl groups of a main body material which is graphene oxide or a carbon nano tube with carboxyl groups; the cross-linked net-shaped structure is arranged in membrane holes and on the upper surface of the base membrane; amido groups are distributed on the functional layer. The filter membrane provided by the invention has relatively high flow rate and heavy metal ion adsorption capacity at the same time.

Description

Technical Field

[0001] The present invention specifically relates to a filter membrane, a preparation method thereof, and an application thereof. Background Art

[0002] Heavy metal ions seriously affect human health. How to efficiently remove heavy metal ions is crucial. Traditional heavy metal removal methods such as activated carbon adsorption can remove most impurities in water, but have poor removal ability for some substances with strong chargeability, such as heavy metal ions, and have the problem of low adsorption life. The reverse osmosis membrane filtration method can remove heavy metals, but has problems such as high operating pressure, low flow rate, and low efficiency. Summary of the Invention

[0003] The present invention mainly aims to overcome the defect that it is difficult to combine the removal ability of heavy metal ions and the filtration efficiency in the prior art, and provides a filter membrane, a preparation method thereof, and an application thereof. The filter membrane provided by the present invention has a relatively high flow rate and the adsorption ability of heavy metal ions.

[0004] The present invention provides a filter membrane, which comprises a base membrane and a functional layer. The base membrane has membrane pores. The functional layer is a cross-linked network structure formed by using graphene oxide and / or carboxyl-functionalized carbon nanotubes as the main materials and further cross-linking through amide bonds formed by the carboxyl groups of the main materials. The cross-linked network structure is disposed in and on the upper surface of the membrane pores of the base membrane. The functional layer is distributed with amino groups.

[0005] In the present invention, the amide bond is derived from the reaction products of amino groups and carboxyl groups, and amino groups and acyl chlorides.

[0006] Among them, the source of the amino group can be a conventional amine substance in the art, preferably a polyamine, such as at least one of chitosan, N-carboxymethyl chitosan, ethylenediamine, polyethyleneimine, polyallylamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyvinylimidazole, piperazine, p-aminobenzene, m-aminobenzene, and polyvinylpyrrolidone. The function of the amino group is to cross-link through a cross-linking agent to fix graphene oxide and / or carboxyl-functionalized carbon nanotubes, so that the active ingredients are not easily lost, and at the same time, heavy metal ions can be removed.

[0007] Among them, the source of the acyl chloride can be a polyacyl chloride, such as at least one of trimesoyl chloride, isophthaloyl chloride, adipoyl chloride, and terephthaloyl chloride.

[0008] In the present invention, there is a certain physical interaction force between the functional layer and the base membrane. The presence of hydrophilic groups in the functional layer is beneficial to improving the hydrophilicity of the filter membrane, thereby increasing the water flux.

[0009] In the present invention, the base membrane can be a conventional microfiltration membrane in the art.

[0010] In the present invention, the material of the base film can be a conventional polymer in the art, such as at least one of polysulfone, polyethersulfone, polyacrylonitrile, sulfonated polysulfone and polyvinylidene fluoride.

[0011] In the present invention, the filter membrane is an ultrafiltration membrane.

[0012] In the present invention, the flow rate of the filter membrane can be 200 - 500 L·m -2 ·h -1 ·bar -1 .

[0013] In the present invention, the main body material can be the graphene oxide and carbon nanotubes with carboxyl groups, and the mass ratio of the graphene oxide to the carbon nanotubes with carboxyl groups is 1:(0.1 - 5), such as 1:1.

[0014] In some preferred embodiments, the main body material only includes graphene oxide.

[0015] In the present invention, the thicknesses of the base film and the functional layer can be measured by observing the cross-section of the filter membrane through SEM.

[0016] In the present invention, the pore size range of the filter membrane can be 2 nm - 100 nm, such as 27.4 nm, 30.4 nm, 34.1 nm, 47.1 nm, 50.2 nm or 96.9 nm.

[0017] In the present invention, the thickness of the base film can be 2 μm - 100 μm, such as 20 μm or 25 μm.

[0018] In the present invention, the thickness of the functional layer can be 2 nm - 50 nm, preferably 10 nm - 40 nm, such as 20 nm, 24 nm, 25 nm, 32 nm or 35 nm.

[0019] In the present invention, the pore size of the base film can be 0.1 μm - 0.4 μm, such as 0.22 μm.

[0020] In the present invention, the pore size of the functional layer can be 2 nm - 100 nm, such as 50 nm.

[0021] In the present invention, the pore size is measured by the retention molecular weight test, the membrane pore size shows a log-normal distribution, and the average pore size of the membrane is analyzed by the PEG solute transport method.

[0022] The present invention also provides a preparation method of a filter membrane, which includes the following steps: depositing an amine-modified carbon source on a base film and performing a cross-linking reaction to form a functional layer, thus obtaining the filter membrane; the carbon source is graphene oxide and / or carbon nanotubes with carboxyl groups; the functional layer is distributed with amine groups.

[0023] In the present invention, the amino-modified carbon source can be obtained commercially or prepared by conventional methods in the art. The preparation method preferably includes the following steps: simply mixing an amine substance with the carbon source for reaction.

[0024] Among them, the amine substance is preferably a polyamine, such as at least one of chitosan, N-carboxymethyl chitosan, ethylenediamine, polyethyleneimine, polyallylamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyvinylimidazole, piperazine, p-aminobenzene, m-aminobenzene, and polyvinylpyrrolidone.

[0025] Among them, the amine substance reacts in the form of an amine substance solution; the solvent of the amine substance solution is preferably at least one of water, methanol aqueous solution, ethanol aqueous solution, and acetone aqueous solution; the concentration of the amine substance in the amine substance solution is preferably 0.5 wt% - 5 wt%, such as 0.5 wt%, 2 wt%, or 3 wt%.

[0026] Among them, the carbon source reacts in the form of a carbon source dispersion; the dispersant of the carbon source dispersion is preferably water; the concentration of the carbon source in the carbon source dispersion is preferably 0.1 wt% - 1 wt%, such as 0.1 wt%, 0.5 wt%, or 1 wt%.

[0027] Among them, the mass ratio of the carbon source to the amine substance can be 1:(1 - 10), such as 1:3, 1:4, or 1:5.

[0028] Among them, the reaction preferably takes place under water bath conditions.

[0029] Among them, the temperature of the reaction is preferably 50°C - 90°C, such as 50°C, 70°C, or 90°C.

[0030] Among them, the reaction time is preferably 12 h - 24 h, such as 12 h or 24 h.

[0031] Among them, after the reaction, centrifugation and washing are also carried out; the number of times of centrifugation and washing is preferably 3 times.

[0032] In the present invention, the carbon source is graphene oxide and carbon nanotubes with carboxyl groups, and the mass ratio of the graphene oxide to the carbon nanotubes with carboxyl groups is 1:(0.1 - 5), such as 1:1.

[0033] In some preferred embodiments, the carbon source is only graphene oxide.

[0034] In the present invention, the base membrane can be a microfiltration membrane commonly used in the art, such as at least one of polysulfone, polyethersulfone, polyacrylonitrile, sulfonated polysulfone, and polyvinylidene fluoride.

[0035] In the present invention, the cross-linking reaction is preferably to mix the amino-modified carbon source with a cross-linking agent.

[0036] Among them, the cross-linking agent can be a polyacyl chloride, preferably at least one of trimesoyl chloride, isophthaloyl chloride, adipoyl chloride and terephthaloyl chloride.

[0037] Among them, before mixing, the cross-linking agent is preferably first made into a solution; the solvent of the solution is preferably an organic solvent, more preferably at least one of n-hexane, benzene, toluene and cyclohexane; the content of the cross-linking agent in the solution is preferably 0.025 wt%-0.5 wt%, more preferably 0.05 wt%-0.5 wt%, such as 0.05 wt%, 0.1 wt%, 0.2 wt% or 0.4 wt%.

[0038] Among them, the amino-modified carbon source is preferably first dispersed in water to form an aqueous solution; the content of the amino-modified carbon source in the aqueous solution is preferably 0.1 wt%-1 wt%, such as 0.1 wt%, 0.5 wt% or 1 wt%.

[0039] Among them, the mass ratio of the cross-linking agent to the amino-modified carbon source can be 1:(1-20), such as 1:1, 1:2, 1:2.5, 1:3 or 1:20.

[0040] In the present invention, the temperature of the cross-linking reaction can be 10°C-40°C, such as 10°C, 20°C or 30°C.

[0041] In the present invention, the time of the cross-linking reaction can be 30 s-300 s, such as 60 s, 120 s or 240 s.

[0042] In the present invention, after the cross-linking reaction is completed, washing is generally carried out.

[0043] The present invention also provides a filter membrane prepared by the preparation method as described above.

[0044] The present invention also provides a filter element including the filter membrane as described above.

[0045] The present invention also provides the application of the filter membrane as described above or the filter element as described above in the field of water treatment.

[0046] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0047] The reagents and raw materials used in the present invention are all commercially available.

[0048] The positive and progressive effects of the present invention are as follows:

[0049] The filter membrane provided by the present invention has a high removal rate of heavy metal ions, and the removal effect is efficient and stable; moreover, the pressure during the removal process is low and the flow rate is large. The preparation method of the filter membrane is simple, the technological process is straightforward, and the preparation cost is low.

[0050] In some preferred embodiments, on the basis that the flow rate of the filter membrane remains at 240 L·m -2 ·h -1 ·bar -1 , the adsorption capacity for heavy metal ions can reach 68.5 mg / m 2 or more. Specific Embodiments

[0051] The present invention will be further illustrated by the following examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0052] The carbon nanotubes with carboxyl groups used in the present invention are purchased from Shenzhen Nano Port Co., Ltd., and the diameter is 20 nm - 40 nm.

[0053] Example 1

[0054] (1) Using an ultrasonic instrument, 0.1 wt% of graphene oxide was dispersed in water, and then 0.5 wt% of an aqueous solution of polyethyleneimine was added. It was heated in a water bath at 90 °C for 12 h to initiate the modification of graphene oxide. Subsequently, after three centrifugation and washing processes, amine-modified graphene oxide was obtained.

[0055] (2) 0.6 wt% of the amine-modified graphene oxide was dispersed in water, and then it was deposited on a polyethersulfone microfiltration membrane with a pore size of 0.22 μm and a thickness of 20 μm through a suction filtration device. Subsequently, a 0.2 wt% solution of trimesoyl chloride in n-hexane was poured onto the surface of the above microfiltration membrane and reacted at 30 °C for 120 s. After washing with water, a functional layer with a pore size of 34.1 nm and a thickness of 20 nm was formed on the surface of the above microfiltration membrane to obtain a filter membrane.

[0056] Example 2

[0057] (1) Using an ultrasonic instrument, 0.5 wt% of carbon nanotubes with carboxyl groups was dispersed in water, and then 2 wt% of an aqueous solution of diethylenetriamine was added. It was heated in a water bath at 70 °C for 24 h to initiate the modification of the carbon nanotubes. Subsequently, after three centrifugation and washing processes, amine-modified carbon nanotubes were obtained.

[0058] (2) Disperse 1 wt% of amine-modified graphene oxide in water, and then deposit it on a polyvinylidene fluoride microfiltration membrane with a pore size of 0.22 μm and a thickness of 25 μm through a suction filtration device. Then, pour a toluene solution of 0.4 wt% of isophthaloyl chloride onto the surface of the above microfiltration membrane and react at 20 °C for 240 s. After washing with water, a functional layer with a pore size of 27.4 nm and a thickness of 25 nm is formed on the surface of the above microfiltration membrane, thus obtaining the filter membrane.

[0059] Example 3

[0060] (1) Use an ultrasonic instrument to disperse 1 wt% of graphene oxide in water, then add 3 wt% of an aqueous solution of polyethyleneimine, and heat it at 50 °C in a water bath for 24 h to initiate the modification of graphene oxide. Subsequently, through three centrifugation and washing processes, amine-modified graphene oxide is obtained.

[0061] (2) Disperse 0.1 wt% of amine-modified graphene oxide in water, and then deposit it on a polyethersulfone microfiltration membrane with a pore size of 0.22 μm and a thickness of 20 μm through a suction filtration device. Then, pour a n-hexane solution of 0.05 wt% of trimesoyl chloride onto the surface of the above microfiltration membrane and react at 10 °C for 60 s. After washing with water, a functional layer with a pore size of 50.2 nm and a thickness of 35 nm is formed on the surface of the above microfiltration membrane, thus obtaining the filter membrane.

[0062] Example 4

[0063] (1) Use an ultrasonic instrument to disperse 0.1 wt% of graphene oxide in water, then add 0.5 wt% of an aqueous solution of polyethyleneimine, and heat it at 90 °C in a water bath for 12 h to initiate the modification of graphene oxide. Subsequently, through three centrifugation and washing processes, amine-modified graphene oxide is obtained.

[0064] (2) Disperse 0.1 wt% of amine-modified graphene oxide in water, and then deposit it on a polyethersulfone microfiltration membrane with a pore size of 0.22 μm and a thickness of 20 μm through a suction filtration device. Then, pour a n-hexane solution of 0.1 wt% of trimesoyl chloride onto the surface of the above microfiltration membrane and react at 30 °C for 120 s. After washing with water, a functional layer with a pore size of 47.1 nm and a thickness of 32 nm is formed on the surface of the above microfiltration membrane, obtaining the filter membrane.

[0065] Example 5

[0066] (1) Use an ultrasonic instrument to disperse 0.1 wt% of graphene oxide in water, then add 0.5 wt% of an aqueous solution of polyethyleneimine, and heat it at 90 °C in a water bath for 12 h to initiate the modification of graphene oxide. Subsequently, through three centrifugation and washing processes, amine-modified graphene oxide is obtained.

[0067] (2) Disperse 1 wt% of amine-modified graphene oxide in water, and then deposit it on a polyethersulfone microfiltration membrane with a pore size of 0.22 μm and a thickness of 20 μm through a suction filtration device. Subsequently, pour a n-hexane solution of 0.05 wt% of trimesoyl chloride onto the surface of the above microfiltration membrane, react at 30 °C for 120 s, wash with water, and form a functional layer with a pore size of 30.4 nm and a thickness of 32 nm on the surface of the above microfiltration membrane to obtain a filtration membrane.

[0068] Example 6

[0069] (1) Use an ultrasonic instrument to disperse 0.1 wt% of graphene oxide in water, add 0.5 wt% of an aqueous solution of polyethyleneimine, heat it in a water bath at 90 °C for 12 h to initiate the modification of graphene oxide, and then obtain amine-modified graphene oxide after three centrifugation and washing processes.

[0070] (2) Disperse 0.05 wt% of amine-modified graphene oxide in water, and then deposit it on a polyethersulfone microfiltration membrane with a pore size of 0.22 μm and a thickness of 20 μm through a suction filtration device. Subsequently, pour a n-hexane solution of 0.025 wt% of trimesoyl chloride onto the surface of the above microfiltration membrane, react at 30 °C for 120 s, wash with water, and form a functional layer with a pore size of 96.9 nm and a thickness of 35 nm on the surface of the above microfiltration membrane to obtain a filtration membrane.

[0071] Example 7

[0072] (1) Use an ultrasonic instrument to disperse a mixture of 0.1 wt% of graphene oxide and carboxyl-functionalized carbon nanotubes in water, where the mass ratio of graphene oxide to carboxyl-functionalized carbon nanotubes is 1:1; add 0.5 wt% of an aqueous solution of polyethyleneimine, heat it in a water bath at 90 °C for 12 h to initiate the modification of the substances, and then obtain a mixture of amine-modified graphene oxide and amine-modified carbon nanotubes after three centrifugation and washing processes.

[0073] (2) Disperse 1 wt% of the mixture of amine-modified graphene oxide and amine-modified carbon nanotubes in water, and then deposit it on a polyethersulfone microfiltration membrane with a pore size of 0.22 μm and a thickness of 20 μm through a suction filtration device. Subsequently, pour a n-hexane solution of 0.05 wt% of trimesoyl chloride onto the surface of the above microfiltration membrane, react at 30 °C for 120 s, wash with water, and form a functional layer with a pore size of 29.6 nm and a thickness of 24 nm on the surface of the above microfiltration membrane to obtain a filtration membrane.

[0074] Comparative Example 1

[0075] (1) Use an ultrasonic instrument to disperse 0.1 wt% of graphene oxide in water, then add 0.5 wt% of polyethyleneimine aqueous solution, heat it in a water bath at 90 °C for 12 h to initiate the modification of graphene oxide, and then obtain amino-modified graphene oxide through three centrifugation and washing processes.

[0076] (2) Disperse 0.6 wt% of amino-modified graphene oxide in water, and then deposit it on a 0.22 μm polyethersulfone microfiltration membrane through a suction filtration device to obtain the final filter membrane.

[0077] Compared with Example 1, Comparative Example 1 lacks the acyl chloride cross-linking process, which will cause the deposited amino-modified graphene oxide to be easily lost and unable to be fixed on the surface of the filter membrane for a long time, so the heavy metal performance decreases.

[0078] Comparative Example 2

[0079] (1) Use an ultrasonic instrument to disperse 0.1 wt% of graphene oxide in water, then add 0.5 wt% of polyethyleneimine aqueous solution, heat it in a water bath at 90 °C for 12 h to initiate the modification of graphene oxide, and then obtain amino-modified graphene oxide through three centrifugation and washing processes.

[0080] (2) Disperse 0.6 wt% of amino-modified graphene oxide and 0.35 wt% of m-phenylenediamine in water. The mass ratio of amino-modified graphene oxide to m-phenylenediamine is 6:3.5. Then pour it on a 0.22 μm polyethersulfone microfiltration membrane, let it stay for 2 min, scrape off the remaining solution, and then pour a 0.2 wt% solution of trimesoyl chloride in n-hexane on the surface of the above microfiltration membrane, react at 30 °C for 120 s, and wash with water to obtain a reverse osmosis membrane.

[0081] Comparative Example 3

[0082] (1) Use an ultrasonic instrument to disperse 0.1 wt% of graphene oxide in water, then add 0.5 wt% of polyethyleneimine aqueous solution, heat it in a water bath at 90 °C for 12 h to initiate the modification of graphene oxide, and then obtain amino-modified graphene oxide through three centrifugation and washing processes.

[0083] (2) Prepare a casting solution by mixing 20 wt% of polyethersulfone, 5 wt% of polyvinylpyrrolidone, 5 wt% of polyethylene glycol PEG600, 0.6 wt% of amino-modified graphene oxide, and 69.4 wt% of dimethylacetamide, and prepare a flat filter membrane after scraping.

[0084] (2) Pour a 0.2 wt% solution of trimesoyl chloride in n-hexane on the surface of the above filter membrane, react at 30 °C for 120 s, and wash with water to obtain the final filter membrane.

[0085] Table 1 Process Condition Settings for Examples and Comparative Examples

[0086]

[0087]

[0088] Effect Examples

[0089] 1. Flow Rate Testing Method

[0090] Under the condition of a testing temperature of 25°C and a certain external pressure, the membrane is pre-pressed for 30 minutes to reach a stable state; then, pure water is used to test the filter membrane. The test data is repeated three times and the average value is taken. The flow rate (J) of the filter membrane is calculated by the following formula:

[0091] J = V / (A × Δt × P)

[0092] where V (L) is the volume of the permeate, A (m 2 ) is the effective area of the tested filter membrane, Δt (h) is the running time, and P (bar) is the pressure in front of the membrane.

[0093] 2. Heavy Metal Adsorption Performance Testing

[0094] Using 25 ppb Cd(NO3)2, 50 ppb Pb(NO3)2, and 250 ppb Cr(NO3)3 solutions as the spiked solutions, when the concentration of heavy metal ions in the solution passing through the filter membrane reaches 20% of the original solution concentration, the test is stopped, and the test results are shown in Table 2.

[0095] 3. Removal Effect Stability

[0096] After passing the filter membranes of each example and comparative example through 2 t of spiked solution, their flow rates and heavy metal adsorption amounts are tested. The effect data is shown in Table 3. And the effect retention rate is calculated by the following method:

[0097] Effect Retention Rate = Effect after passing 2 t of spiked solution / Initial Effect, and the results are shown in Table 4.

[0098] 4. Pore Size Testing Method: In pore size testing, it is assumed that there is no steric hindrance and interaction between the solute and the membrane material. The average pore size of the membrane is defined as the average radius of polyethylene glycol with a certain molecular weight corresponding to a 50% retention rate of polyethylene glycol with that molecular weight.

[0099] Table 2 Effect Data in the Initial State

[0100]

[0101]

[0102] Table 3 Effect data after adding the standard solution for 2t

[0103]

[0104] Table 4 Effect retention rate

[0105]

[0106]

[0107] It can be seen from the data in Tables 2 - 4 that the filter membrane prepared by the present invention has a high adsorption capacity for heavy metal ions, good stability, and a high flow rate, which can effectively improve the use efficiency of the filter membrane; and it has a good effect retention rate, which can extend the service life of the filter membrane.

[0108] The difference between Comparative Example 1 and Example 1 is that no cross - linking reaction was carried out in Comparative Example 1. The data in Table 2 show that its flow rate can remain at a relatively high level, but its heavy metal adsorption ability is very poor. Combining the data in its Table 3, it can be seen that there is a large increase in the flow rate and a further decrease in the heavy metal adsorption ability. It can be known that the amine - modified carbon source is only combined with the base membrane through weak intermolecular forces and is easily lost, thus seriously affecting its ability to remove heavy metals.

[0109] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 adopted a different membrane - making method and introduced m - phenylenediamine to prepare a reverse osmosis membrane. Although this membrane introduced small - molecule m - phenylenediamine, which improved the heavy metal adsorption ability and also greatly strengthened the cross - linking process of the filter membrane, making the membrane pores smaller, with a pore size less than 2nm, even smaller than the pore size of heavy metals. That is to say, the mechanism for removing heavy metals has changed from adsorption to adsorption + interception. Therefore, the heavy metal removal ability is enhanced, but this results in a significant reduction in flux and an increase in energy consumption, which is not conducive to practical applications.

[0110] The difference between Comparative Example 3 and Example 1 is that it mixed the amine - modified carbon source with the film - forming polymer to prepare a casting solution, and then carried out cross - linking after forming the membrane by phase inversion. To a certain extent, it can overcome the defect that the flow rate and heavy metal removal ability cannot be both achieved. However, since the ultrafiltration membrane is directly obtained during the phase inversion process, and then cross - linked again, its membrane pores will become smaller further, and it may be between the ultrafiltration membrane and the nanofiltration membrane, resulting in a lower removal efficiency and a reduced flow rate; if no cross - linking is carried out subsequently, the active ingredients are easily lost, which is not conducive to the service life of the filter membrane.

[0111] From the data of Examples 3, 4 and 6, it can be seen that since the concentration of the amine-modified carbon source is relatively low during the deposition process, it will affect the amount deposited in the base film to a certain extent, thereby affecting its heavy metal ion removal ability; in the present invention, the amine group has three functions, binding to the carboxyl group of the carbon source to fix the carbon source; ② crosslinking with the crosslinking agent to form a functional layer, and adsorbing heavy metal ions. It has been found through research that the multiple functions of the amine group can be achieved by increasing the concentration of the amine-modified carbon source or decreasing the concentration of the acyl chloride to make the two reach an ideal state.

[0112] From the effect data of Examples 5 and 7, it can be seen that the type of carbon source will also affect the adsorption ability of heavy metal ions; compared with only using graphene oxide as the carbon source and using both graphene oxide and carbon nanotubes with carboxyl groups as the carbon source, the removal effect of heavy metal ions has been improved to varying degrees.

[0113] The specific embodiments described above have further elaborated on the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A filter membrane, characterized in that, It includes a base film and a functional layer. The base film has membrane pores, and the functional layer is a cross-linked network structure formed by taking graphene oxide and / or carboxyl-functionalized carbon nanotubes as the main materials and further cross-linking through amide bonds formed by the carboxyl groups of the main materials. The cross-linked network structure is disposed in and on the upper surface of the membrane pores of the base film. The functional layer is distributed with amino groups.

2. The filter membrane according to claim 1, wherein, The amide bond is derived from the reaction products of amino groups with carboxyl groups and amino groups with acyl chlorides. Among them, the source of the amino group is preferably a polyamine, such as at least one of chitosan, N-carboxymethyl chitosan, ethylenediamine, polyethyleneimine, polyallylamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyvinylimidazole, piperazine, p-aminobenzene, m-aminobenzene, and polyvinylpyrrolidone. Among them, the source of the acyl chloride is preferably a polyacyl chloride, such as at least one of trimesoyl chloride, isophthaloyl chloride, adipoyl chloride, and terephthaloyl chloride. And / or, the main materials are the graphene oxide and carboxyl-functionalized carbon nanotubes, and the mass ratio of the graphene oxide to the carboxyl-functionalized carbon nanotubes is 1:(0.1-5), such as 1:

1. And / or, the thickness of the base film is 2 μm - 100 μm, such as 20 μm or 25 μm. And / or, the thickness of the functional layer is 2 nm - 50 nm, preferably 10 nm - 40 nm, such as 20 nm, 24 nm, 25 nm, 32 nm, or 35 nm. And / or, the pore diameter of the base film is 0.1 μm - 0.4 μm, such as 0.22 μm. And / or, the pore diameter of the functional layer is 2 nm - 100 nm, such as 50 nm. And / or, the material of the base film is at least one of polysulfone, polyethersulfone, polyacrylonitrile, sulfonated polysulfone, and polyvinylidene fluoride. And / or, the pore diameter range of the filter membrane is 2 nm - 100 nm, such as 27.4 nm, 30.4 nm, 34.1 nm, 47.1 nm, 50.2 nm, or 96.9 nm.

3. A method for preparing a filter membrane, characterized in that, It includes the following steps: depositing an amino-group modified carbon source on the base film and performing a cross-linking reaction to form a functional layer, thus obtaining the filter membrane. The carbon source is graphene oxide and / or carboxyl-functionalized carbon nanotubes. The functional layer is distributed with amino groups.

4. The preparation method of the filter membrane according to claim 3, characterized in that, The preparation method of the amino-group modified carbon source includes the following steps: mixing an amine substance with the carbon source and reacting them. Preferably, the mass ratio of the carbon source to the amine substance is 1:(1-10), such as 1:3, 1:4, or 1:

5. Preferably, the amine substance is a polyamine, such as at least one of chitosan, N-carboxymethyl chitosan, ethylenediamine, polyethyleneimine, polyallylamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyvinylimidazole, piperazine, p-aminobenzene, m-aminobenzene, and polyvinylpyrrolidone. Preferably, the amine substance reacts in the form of an amine substance solution; the solvent of the amine substance solution is preferably at least one of water, methanol aqueous solution, ethanol aqueous solution, and acetone aqueous solution; the concentration of the amine substance in the amine substance solution is preferably 0.5 wt% - 5 wt%, such as 0.5 wt%, 2 wt%, or 3 wt%; Preferably, the carbon source reacts in the form of a carbon source dispersion; the dispersant of the carbon source dispersion is preferably water; the concentration of the carbon source in the carbon source dispersion is preferably 0.1 wt% - 1 wt%, such as 0.1 wt%, 0.5 wt%, or 1 wt%; Preferably, the carbon source is graphene oxide and carbon nanotubes with carboxyl groups, and the mass ratio of the graphene oxide to the carbon nanotubes with carboxyl groups is 1:(0.1 - 5), such as 1:1; Preferably, the reaction is carried out under water bath conditions; Preferably, the temperature of the reaction is 50°C - 90°C, such as 50°C, 70°C, or 90°C; Preferably, the time of the reaction is 12 h - 24 h, such as 12 h or 24 h; Preferably, after the reaction, centrifugation and washing are also carried out; the number of times of centrifugation and washing is preferably 3 times.

5. The method for preparing the filter membrane according to claim 3, wherein, The cross-linking reaction is to mix the amino-modified carbon source with a cross-linking agent; Preferably, the cross-linking agent is a polyacyl chloride, such as at least one of trimesoyl chloride, isophthaloyl chloride, adipoyl chloride, and terephthaloyl chloride; Preferably, the cross-linking agent reacts in the form of a cross-linking agent solution; the solvent of the cross-linking agent solution is preferably an organic solvent, more preferably at least one of n-hexane, benzene, toluene, and cyclohexane; the content of the cross-linking agent in the cross-linking agent solution is preferably 0.025 wt% - 0.5 wt%, more preferably 0.05 wt% - 0.5 wt%, such as 0.05 wt%, 0.1 wt%, 0.2 wt%, or 0.4 wt%; Preferably, the amino-modified carbon source reacts in the form of an amino-modified carbon source dispersion; the solvent of the amino-modified carbon source dispersion is preferably water; the content of the amino-modified carbon source in the amino-modified carbon source dispersion is preferably 0.1 wt% - 1 wt%, such as 0.1 wt%, 0.5 wt%, or 1 wt%; Preferably, the mass ratio of the cross-linking agent to the amino-modified carbon source is 1:(1 - 20), such as 1:1, 1:2, 1:2.5, 1:3, or 1:

20.

6. The method for preparing the filter membrane according to claim 3, wherein, The temperature of the cross-linking reaction is 10°C - 40°C, such as 10°C, 20°C, or 30°C; And / or, the time of the cross-linking reaction is 30 s - 300 s, such as 60 s, 120 s, or 240 s; And / or, after the cross-linking reaction, a washing operation is also carried out.

7. The method for preparing the filter membrane according to claim 3, characterized in that, The base film is a microfiltration membrane; And / or, the material of the base film is at least one of polysulfone, polyethersulfone, polyacrylonitrile, sulfonated polysulfone, and polyvinylidene fluoride.

8. A filter membrane, characterized in that, It is prepared by the preparation method as described in any one of claims 3 - 7.

9. A filter element, characterized in that, It includes the filter membrane as described in any one of claims 1, 2, and 8.

10. Use of the filter membrane according to any one of claims 1, 2 and 8 or the filter element according to claim 9 in the field of water treatment.

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