Antifouling graphene oxide membrane with multilevel hydrophilic structure and method of making same

Abstract

The application discloses a preparation method of an anti-pollution graphene oxide film with a multistage hydrophilic structure. The method mainly comprises the following steps: growing a phytic acid-based super-hydrophilic layer on the surface of graphene oxide nanosheets in situ; assembling the graphene oxide nanosheets with the grown phytic acid-based super-hydrophilic layer into a super-hydrophilic graphene oxide film; assembling sugar acid on the surface of the super-hydrophilic graphene oxide film through a coordination-driven bridging assembly method to form the graphene oxide film with the multistage hydrophilic structure. The method realizes controllable construction of a multistage hydrophilic structure surface with a continuous phytic acid-based coupling molecule-level dispersed sugar acid. The phytic acid layer forms a continuous hydration layer, the molecule-level distributed sugar acid forms a hydrogen bond interaction with interface water in the hydration layer through a hydroxyl group, a hydration superposition effect is formed, the cohesion strength of the hydration layer is increased, the adhesion of pollutants is extremely low, and the anti-pollution performance of the graphene oxide film is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing an anti-fouling membrane, in particular to an anti-fouling graphene oxide membrane with multi-level hydrophilic structure and a method for preparing the same. BACKGROUND

[0002] Graphene oxide (GO) has atomic thickness, ultrahigh specific surface area, high mechanical strength and chemical stability, and is widely favored in the construction of ultrafast mass transfer channels. It is considered to be a new generation of high-performance separation membrane material, and has shown considerable application prospects in the fields of gas separation, proton transfer, desalination, ion or molecular separation, etc. However, membrane fouling is a common bottleneck problem in the development of high-performance GO membranes. Although GO surface contains a large number of oxygen-containing functional groups, the uneven distribution of the groups and the inherent lipophilicity of C-H bond lead to strong interaction between GO membrane surface and pollutants. At the same time, due to the high permeation flux of GO membrane, the surface concentration polarization effect is serious, a large number of pollutants reach the membrane surface and produce non-specific interaction with the membrane surface, resulting in more serious flux decay and separation performance loss. It is urgent to develop GO membranes with excellent anti-fouling performance.

[0003] Surface hydrophilization is one of the most common means to prevent pollutants from contacting the surface and improve the surface anti-fouling performance. The basic principle is to tightly bind water molecules to the surface through electrostatic or hydrogen bonding to form a continuous hydration layer, providing a spatial and energy barrier for the contact and adhesion of pollutants. Although GO-based separation membranes have been hydrophilically modified, it is still difficult to reduce their serious flux decay (>60%) at high flux, limiting the application of GO membranes. The main reason for this phenomenon is that the interfacial water outside the hydration layer is mainly adsorbed on the surface by intermolecular forces, and the interaction force is weak, making the hydration layer unstable. After long-term exposure to a polluted environment, the contact between pollutants and the surface is caused by the destruction of the surface hydration structure, resulting in a decrease in anti-fouling performance. Therefore, constructing an anti-fouling modified layer that can form a stable hydration structure is the key to obtaining high anti-fouling performance. Phytic acid (PA) is a hydrophilic small molecule containing six phosphate groups. The hydration free energy of the phosphate group is about 47.3 kJ mol -1 , which can form a continuous hydration layer and has been widely used in surface hydrophilic modification. However, strategies and methods to improve the cohesion strength of PA-based surface hydration layer have not been reported. SUMMARY

[0004] In view of the above prior art, the present application provides an anti-fouling graphene oxide membrane with multi-level hydrophilic structure and a method for preparing the same. By sequentially assembling hydrophilic phytic acid and sugar acid on the membrane surface, a coating with multi-level hydrophilic structure is formed, the cohesion strength of the surface hydration layer is improved, and the anti-fouling performance of the GO membrane is improved.

[0005] In order to solve the above technical problems, the application provides an anti-pollution graphene oxide film with a multi-level hydrophilic structure, wherein a phytic acid-based super-hydrophilic layer is grown in situ on a GO nanosheet to obtain a GO nanosheet with a phytic acid-based super-hydrophilic layer; then, a super-hydrophilic GO film based on phytic acid is prepared through a film forming technology; and finally, a GO film with a multi-level hydrophilic structure is assembled based on a multi-level hydrophilic structure of phytic acid coupling sugar acid.

[0006] The preparation method of the anti-pollution graphene oxide film comprises the following steps:

[0007] In step one, the phytic acid-based super-hydrophilic layer is grown in situ on the GO nanosheet: a GO / phytic acid mixed dispersion liquid with a GO mass concentration of 5-100 μg / mL and a phytic acid molar concentration of 0.1-20 mM is configured; then, a transition metal salt solution with a molar concentration of 0.1-20 mM is added to the GO / phytic acid mixed dispersion liquid, and in the obtained mixed liquid, the phytic acid is 0.075 mmol and the metal salt is 0.0375 mmol per milligram of GO; the assembly is performed in a shaking table for 5-60 min to obtain a GO nanosheet with a phytic acid-based super-hydrophilic layer, which is referred to as PA@GO nanosheet;

[0008] In step two, the super-hydrophilic GO film based on phytic acid is prepared: the PA@GO nanosheet obtained in step one is prepared into a super-hydrophilic GO film based on phytic acid through a film forming technology, which is referred to as hGO film;

[0009] In step three, a multi-level hydrophilic structure is assembled based on a multi-level hydrophilic structure of phytic acid coupling sugar acid: the hGO film obtained in step two is immersed in a transition metal salt solution with a molar concentration of 0.025-1.0 mM and assembled in a shaking table for 5-60 min; after washing, the hGO film is immersed in a sugar acid solution with a molar concentration of 0.5-5 mM and assembled in a shaking table for 5-60 min; and after washing, a GO film with a multi-level hydrophilic structure is obtained.

[0010] Further, in the preparation method, the transition metal salt is any one or a combination of two or more of silver nitrate, ferric chloride, zinc chloride, nickel chloride, calcium chloride and zirconium nitrate.

[0011] In step two, the film forming technology is selected from one of vacuum assisted self-assembly, template method, drop coating and spin coating.

[0012] In step three, the transition metal salt solution is a ferric chloride solution with a molar concentration of 0.025-0.5 mM.

[0013] In step three, the sugar acid in the sugar acid solution is any one or a combination of two or more of threose, xylose, arabinose, ribose, gluconic acid, mannose, galactose, idose and glucoheptonic acid.

[0014] Compared with the prior art, the present application has the beneficial effects that:

[0015] (1) The GO membrane with multi-level hydrophilic structure is prepared by selecting hydrophilic phytic acid and sugar acid and using a coordination bridging assembly method. The multi-level hydrophilic structure of the coating layer acts as a physical barrier to prevent pollutants from contacting the GO membrane, reduces the non-specific interaction between the two, prevents the accumulation of pollutants on the membrane surface to form a filter cake layer, improves the anti-pollution performance of the GO membrane, and realizes low flux decay rate and high flux recovery rate.

[0016] (2) The controllable construction of the multi-level hydrophilic structure surface with continuous phytic acid substrate coupled molecularly dispersed sugar acid is realized. The PA layer has excellent hydration capacity and can form a continuous hydration layer. The molecularly distributed sugar acid has rich hydroxyl groups and can interact with the interfacial water in the hydration layer through hydrogen bonds to form a hydration superposition effect, thereby increasing the cohesive strength of the hydration layer and limiting the contact and pollution of pollutants on the GO membrane surface, realizing ultra-low adhesion of pollutants.

[0017] (3) The PA layer improves the interlayer spacing of the assembled membrane and enhances the structural stability of the membrane through rigidification of the channels, effectively improving the permeation flux of the membrane and avoiding the use of intercalation agents.

[0018] (4) The preparation process is simple, the preparation process is relatively short, the reaction conditions are mild and controllable, the operation is relatively convenient, it is green and environmentally friendly, and no organic solvent is used. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic diagram of the structure and anti-pollution behavior of the S-hGO membrane described in the present application;

[0020] Figure 2 is a scanning electron microscope photograph of the S-hGO membrane prepared in Example 1;

[0021] Figure 3 is a graph of the normalized flux of the S-hGO membrane prepared in Example 1 versus the anti-pollution test running time;

[0022] Figure 4 is a graph of the normalized flux of the S-hGO membrane prepared in Example 3 versus the anti-pollution test running time;

[0023] Figure 5 is a graph of the normalized flux of the S-hGO membrane prepared in Example 5 versus the anti-pollution test running time;

[0024] Figure 6 is a graph of the normalized flux of the S-hGO membrane prepared in Example 6 versus the anti-pollution test running time;

[0025] Figure 7 Figure for normalized flux of S-hGO membrane prepared in Example 7 as a function of anti-fouling test run time;

[0026] Figure 8 Figure for normalized flux of hGO membrane prepared in Comparative Example 1 as a function of anti-fouling test run time;

[0027] Figure 9 Figure for normalized flux of GO membrane prepared in Comparative Example 2 as a function of anti-fouling test run time. DETAILED DESCRIPTION

[0028] The design concept of the anti-fouling graphene oxide membrane with multi-level hydrophilic structure and the preparation method thereof is as follows: Figure 1 As shown in the figure, a coordination-driven bridging assembly method is used to assemble a superhydrophilic coating with a multi-level hydrophilic structure on the surface of a GO membrane through the hydrophilic PA and sugar acid. Among them, PA forms a continuous hydrophilic substrate, which induces water molecules to hydrate to form a dense hydration layer. The molecularly distributed sugar acid forms a hydrogen bond interaction with the interfacial water induced by the PA layer, produces a hydration superposition effect, thereby increasing the cohesive strength of the hydration layer, realizing the super-low adhesion of pollutants and strengthening the anti-fouling performance. The preparation steps mainly include in-situ growth of PA-based superhydrophilic layer on GO nanosheet; preparation of PA-based superhydrophilic GO membrane; multi-level hydrophilic structure assembly based on PA coupling sugar acid, preparation of GO membrane with multi-level hydrophilic structure. This method realizes the controllable construction of the multi-level hydrophilic structure surface with a continuous PA superhydrophilic substrate coupled with molecularly dispersed sugar acid.

[0029] The specific embodiments of the present application are given below. The specific embodiments are only used to further illustrate the present application, and do not limit the protection scope of the claims of the present application.

[0030] Example 1

[0031] The preparation of the anti-fouling GO membrane with multi-level hydrophilic structure is as follows:

[0032] Step one, in-situ growth of PA-based superhydrophilic layer on GO nanosheet: configure a GO / phytic acid mixed dispersion solution with a GO mass concentration of 16.7 μg / mL and a molar concentration of 1.25 mM (i.e. mix 25 mL of GO dispersion solution with 34.7 μL of PA solution with a mass concentration of 50%). Then, 5 ml of ferric chloride solution with a molar concentration of 3.75 mM is added to the above mixed dispersion solution, and assembled in a 25℃, 150 rpm shaker for 10 min. A GO nanosheet with a phytic acid-based superhydrophilic layer is obtained, denoted as PA@GO nanosheet;

[0033] Step two, preparation of PA-based super-hydrophilic GO film: the PA@GO nanosheets obtained in step one were used to prepare a super-hydrophilic GO film based on phytic acid by vacuum-assisted self-assembly technology, denoted as hGO film;

[0034] Step three, assembly of a multi-level hydrophilic structure based on PA-coupled sugar acid:

[0035] Metal ion assembly of the hGO film obtained in step two: 15.9 cm 2 The hGO film obtained in step two was immersed in 30 mL of a 0.125 mM iron chloride solution at 25°C with 100 rpm shaking for 10 min.

[0036] Sugar acid assembly of the washed film: the washed film was immersed in 30 mL of a 2 mM aldaric acid solution at 25°C with 100 rpm shaking for 10 min; after washing, a GO film with a multi-level hydrophilic structure was obtained, denoted as S-hGO film. Figure 2 is a scanning electron microscope image of the S-hGO film

[0037] Tests showed that the initial water contact angle of the S-hGO film prepared in Example 1 was 8.8°, and the carbon tetrachloride contact angle under water was 162.1°. The anti-fouling performance test was performed on the film using a hexadecane emulsion with a concentration of 1000 ppm, and the flux decay rate of the film was 8.0%. After cleaning, the flux recovery rate of the film was 98.7%. Figure 3 is a plot of the normalized flux of the S-hGO film prepared in Example 1 versus anti-fouling test running time.

[0038] Example 2

[0039] Preparation of an anti-fouling GO film with a multi-level hydrophilic structure, the preparation process is basically the same as that of Example 1, except that in step three of the sugar acid assembly, the type of sugar acid is changed from aldaric acid to threonic acid, and an S-hGO film is prepared.

[0040] Tests showed that the initial water contact angle of the S-hGO film prepared in Example 2 was 8.4°, and the carbon tetrachloride contact angle under water was 156.8°. The anti-fouling performance test was performed on the film using a hexadecane emulsion with a concentration of 1000 ppm, and the flux decay rate of the film was 15.6%. After cleaning, the flux recovery rate of the film was 93.0%.

[0041] Example 3

[0042] Preparation of an anti-fouling GO film with a multi-level hydrophilic structure, the preparation process is basically the same as that of Example 1, except that in step three of the sugar acid assembly, the type of sugar acid is changed from aldaric acid to gluconic acid, and an S-hGO film is prepared.

[0043] The S-hGO membrane prepared in Example 3 was tested to have an initial water contact angle of 9.2° and a water-submerged carbon tetrachloride contact angle of 160.0°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux attenuation rate of the membrane was 13.0%. After cleaning, the flux recovery rate of the membrane was 94.7%. Figure 4 The graph of the normalized flux of the S-hGO membrane prepared in Example 3 as a function of the anti-fouling test running time is shown in FIG. 3.

[0044] Example 4

[0045] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the same procedure as in Example 1, except that in the sugar acid assembly of step three, the type of sugar acid was changed from arabonic acid to gluheptonic acid, and an S-hGO membrane was prepared.

[0046] The S-hGO membrane prepared in Example 4 was tested to have an initial water contact angle of 10.0° and a water-submerged carbon tetrachloride contact angle of 159.1°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux attenuation rate of the membrane was 18.9%. After cleaning, the flux recovery rate of the membrane was 94.3%.

[0047] Example 5

[0048] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the same procedure as in Example 1, except that in the metal ion assembly of step three, the concentration of the ferric chloride solution was changed from 0.125 mM to 0.025 mM, and an S-hGO membrane was prepared.

[0049] The S-hGO membrane prepared in Example 5 was tested to have an initial water contact angle of 8.4° and a water-submerged carbon tetrachloride contact angle of 156.8°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux attenuation rate of the membrane was 15.4%. After cleaning, the flux recovery rate of the membrane was 92.5%. Figure 5 The graph of the normalized flux of the S-hGO membrane prepared in Example 5 as a function of the anti-fouling test running time is shown in FIG. 4.

[0050] Example 6

[0051] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the same procedure as in Example 1, except that in the metal ion assembly of step three, the concentration of the ferric chloride solution was changed from 0.125 mM to 0.225 mM, and an S-hGO membrane was prepared.

[0052] The S-hGO membrane prepared in Example 6 was tested to have an initial water contact angle of 10.2° and a sub-water carbon tetrachloride contact angle of 156.6°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux decay rate of the membrane was 10.1%. After cleaning, the flux recovery rate of the membrane was 94.6%. Figure 6 The graph of the normalized flux of the S-hGO membrane prepared in Example 6 as a function of the anti-fouling test running time is shown in FIG. 6.

[0053] Example 7

[0054] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the same procedure as in Example 1, except that in the metal ion assembly of step three, the concentration of the ferric chloride solution was changed from 0.125 mM to 0.325 mM, and an S-hGO membrane was prepared.

[0055] The S-hGO membrane prepared in Example 7 was tested to have an initial water contact angle of 11.3° and a sub-water carbon tetrachloride contact angle of 155.3°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux decay rate of the membrane was 16.6%. After cleaning, the flux recovery rate of the membrane was 93.3%. Figure 7 The graph of the normalized flux of the S-hGO membrane prepared in Example 7 as a function of the anti-fouling test running time is shown in FIG. 7.

[0056] Example 8

[0057] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the same procedure as in Example 1, except that in the metal ion assembly of step three, the concentration of the ferric chloride solution was changed from 0.125 mM to 0.5 mM, and an S-hGO membrane was prepared.

[0058] The S-hGO membrane prepared in Example 8 was tested to have an initial water contact angle of 13.9° and a sub-water carbon tetrachloride contact angle of 152.8°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux decay rate of the membrane was 19.6%. After cleaning, the flux recovery rate of the membrane was 91.7%.

[0059] Example 9

[0060] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the same procedure as in Example 1, except that in the metal ion assembly of step three, the concentration of the ferric chloride solution was changed from 0.125 mM to 1 mM, and an S-hGO membrane was prepared.

[0061] The S-hGO membrane prepared in Example 9 was tested to have an initial water contact angle of 14.3° and a carbon tetrachloride contact angle under water of 151.6°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux attenuation rate of the membrane was 29.4%. After cleaning, the flux recovery rate of the membrane was 89.7%.

[0062] Example 10

[0063] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the process of Example 1, except that in step three, the metal ion assembly process was performed at a frequency of 50 rpm instead of 100 rpm, and the assembly time was 30 min instead of 10 min. In the sugar acid assembly process, the type of sugar acid was changed from arabonic acid to gluconic acid, the frequency was changed from 100 rpm to 50 rpm, and the assembly time was changed from 10 min to 30 min, and the S-hGO membrane was prepared.

[0064] The S-hGO membrane prepared in Example 10 was tested to have an initial water contact angle of 9.3° and a carbon tetrachloride contact angle under water of 159.7°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux attenuation rate of the membrane was 13.4%. After cleaning, the flux recovery rate of the membrane was 94.8%.

[0065] Example 11

[0066] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the process of Example 1, except that in step three, the type of metal salt solution was changed from ferric chloride to calcium chloride in the metal ion assembly process, the frequency was changed from 100 rpm to 150 rpm, and the assembly time was changed from 10 min to 60 min. In the sugar acid assembly process, the frequency was changed from 100 rpm to 150 rpm, and the assembly time was changed from 10 min to 60 min, and the S-hGO membrane was prepared.

[0067] The S-hGO membrane prepared in Example 11 was tested to have an initial water contact angle of 8.9° and a carbon tetrachloride contact angle under water of 161.7°. The anti-fouling performance test was performed on the membrane using a hexadecane emulsion with a concentration of 1000 ppm, and the flux attenuation rate of the membrane was 8.5%. After cleaning, the flux recovery rate of the membrane was 98.5%.

[0068] Example 12

[0069] The anti-fouling GO membrane with a multi-level hydrophilic structure was prepared according to the process of Example 1, except that in step three, the concentration of the sugar acid solution was changed from 2 mM to 0.5 mM in the sugar acid assembly, and the S-hGO membrane was prepared.

[0070] The S-hGO membrane prepared in Example 12 was tested and found to have an initial water contact angle of 8.5° and an underwater carbon tetrachloride contact angle of 162.0°. The membrane's antifouling performance was tested using a 1000 ppm hexadecane emulsion; the flux decline rate was 8.3%, and after cleaning, the flux recovery rate was 98.5%.

[0071] Example 13

[0072] The preparation process of the antifouling GO membrane with a multi-level hydrophilic structure is basically the same as that in Example 1, except that in step three, the concentration of the sugar acid solution is changed from 2 mM to 5 mM to prepare the S-hGO membrane.

[0073] The S-hGO membrane prepared in Example 13 was tested and found to have an initial water contact angle of 8.9° and an underwater carbon tetrachloride contact angle of 162.3°. The membrane's antifouling performance was tested using a 1000 ppm hexadecane emulsion; the flux decay rate was 8.1%, and after cleaning, the flux recovery rate was 98.4%.

[0074] Comparative Example 1

[0075] The hGO membrane was tested using the membrane prepared in Steps 1 and 2 of Example 1. The initial water contact angle of this membrane was 7.8°, and the underwater carbon tetrachloride contact angle was 155.9°. The membrane's antifouling performance was tested using a 1000 ppm hexadecane emulsion. The membrane's flux decline rate was 28.1%, and after cleaning, the flux recovery rate was 90.5%. Figure 8 The graph shows the normalized flux of the hGO membrane prepared in Comparative Example 1 as a function of the antifouling test run time.

[0076] Comparative Example 2

[0077] The GO membrane was tested and prepared according to the following steps: GO nanosheets were uniformly dispersed in water and the GO membrane was prepared using vacuum-assisted self-assembly technology.

[0078] The initial water contact angle of the GO membrane was tested to be 65.2°, and the underwater carbon tetrachloride contact angle was 121.4°. The membrane's antifouling performance was tested using a 1000 ppm hexadecane emulsion; the flux decline rate was 40.4%, and after cleaning, the flux recovery rate was 72.3%. Figure 9 The graph shows the normalized flux of the GO membrane prepared in Comparative Example 2 as a function of the antifouling test run time.

[0079] Table 1 Test data of embodiments and comparative examples of the present invention

[0080]

[0081] According to the preparation conditions of all the above examples and comparative examples and Table 1 and Figures 1 to 9 It can be concluded that the water contact angle of the S-hGO membrane loaded with sugar acid is slightly increased compared with the water contact angle of the hGO membrane. This is because the hydroxyl density of sugar acid is less than PA, and the hydrophilic group of sugar acid is arranged on the surface of the membrane through Figure 3 and Figure 8 It can be concluded that the flux decay rate of the S-hGO membrane with a multi-level hydrophilic structure prepared by the application is greatly reduced compared with the hGO membrane with a single hydrophilic structure, and the flux recovery rate is significantly improved. Through Figure 3 and Figure 9 It can be concluded that the flux decay rate of the S-hGO membrane prepared by the application is reduced by about 80% and the flux recovery rate is increased by nearly 1.4 times compared with the GO membrane of Comparative Example 2 before modification (65.2°) due to the improvement of hydrophilicity and hydration ability. Through Figure 3 and Figures 5 to 7 It can be concluded that increasing the concentration of Fe 3+ solution, the water contact angle of the S-hGO membrane gradually increases, the underwater oil contact angle first increases and then decreases, the flux decay rate of the membrane first decreases and then increases, and the flux recovery rate first increases and then decreases. When the concentration of the Fe 3+ solution is too large, the density of the sugar acid molecules loaded on the surface of the membrane is too large, and water molecules are difficult to enter the interchain, so that the hydration ability of the membrane surface decreases, and the anti-pollution performance of the membrane decreases. The concentration of the Fe 3+ solution is too large, the flux decay rate of the membrane is >30%, and the flux recovery rate is <85%. Increasing the chain length of the sugar acid molecules, the water contact angle of the S-hGO membrane gradually increases, the underwater oil contact angle first increases and then decreases, the flux decay rate of the membrane first decreases and then increases, and the flux recovery rate first increases and then decreases. Increasing the assembly time of the sugar acid on the surface, the oscillation frequency and the type of metal ions assembled has little effect on the surface performance of the membrane.

[0082] The obtained membrane has a continuous PA substrate and a molecularly dispersed sugar acid microregion, and realizes the controllable construction of the multi-level hydrophilic structure on the surface of the membrane. Among them, the phytic acid layer forms a continuous hydration layer, the molecularly distributed sugar acid interacts with the interfacial water in the hydration layer through hydrogen bonds, produces a hydration superposition effect, thereby increasing the cohesive strength of the hydration layer, realizing the ultra-low adhesion of pollutants, and effectively improving the anti-pollution performance of the GO membrane. Compared with Comparative Example 1 with only a PA substrate, the underwater oil contact angle of the obtained membrane is greatly improved, the contact area of the pollutants on the surface is greatly reduced, the pollutants are immediately separated from the membrane surface under the action of hydraulic shear, and the formation of the filter cake layer is prevented, thereby improving the anti-pollution performance.

[0083] Although the present application has been described with reference to the accompanying drawings, the present application is not limited to the above described specific embodiments, and the above described specific embodiments are merely illustrative, but not restrictive, and many changes can be made by those skilled in the art without departing from the spirit of the present application, and these all belong to the protection of the present application.

Claims

1. A fouling-resistant graphene oxide membrane with a multi-level hydrophilic structure, characterized in that, GO nanosheets with phytic acid-based superhydrophilic layers were obtained by in-situ growth of GO nanosheets. Then, a phytic acid-based superhydrophilic GO membrane was prepared by film-forming technology. Finally, a GO membrane with a multi-level hydrophilic structure was assembled based on the phytic acid coupled sugar acid multi-level hydrophilic structure.

2. A method for preparing the antifouling graphene oxide film as described in claim 1, characterized in that, The method includes the following steps: Step 1: In-situ growth of a phytic acid-based superhydrophilic layer on GO nanosheets: Prepare a GO / phytic acid mixed dispersion with a GO mass concentration of 5–100 μg / mL and a phytic acid molar concentration of 0.1–20 mM; then, add a transition metal salt solution with a molar concentration of 0.1–20 mM to the above GO / phytic acid mixed dispersion. In the resulting mixture, per milligram of GO, the phytic acid content is 0.075 mmol and the metal salt content is 0.0375 mmol; assemble in a shaker for 5–60 min to obtain GO nanosheets with a phytic acid-based superhydrophilic layer, abbreviated as PA@GO nanosheets; Step 2, Preparation of superhydrophilic GO membrane based on phytic acid: The PA@GO nanosheets obtained in Step 1 are used to prepare a superhydrophilic GO membrane based on phytic acid, referred to as hGO membrane; Step 3, assembly based on the multi-level hydrophilic structure of phytic acid coupled with glycoacid: The hGO membrane obtained in Step 2 is immersed in a transition metal salt solution with a molar concentration of 0.025~1.0 mM and assembled in a shaker for 5~60 min; after washing, it is immersed in a glycoacid solution with a molar concentration of 0.5~5 mM and assembled in a shaker for 5~60 min; after washing, a GO membrane with a multi-level hydrophilic structure is obtained.

3. The preparation method according to claim 2, characterized in that, The transition metal salt is any one or a combination of two or more of silver nitrate, ferric chloride, zinc chloride, nickel chloride, calcium chloride, and zirconium nitrate.

4. The preparation method according to claim 3, characterized in that, In step three, the transition metal salt solution is a ferric chloride solution with a molar concentration of 0.025~0.5 mM.

5. The preparation method according to claim 2, characterized in that, In step three, the sugar acid in the sugar acid solution is any one or a combination of two or more of the following: threonic acid, xylitol, arabinoic acid, ribonucleic acid, gluconic acid, mannitol, galactonic acid, iduronic acid, and glucoheponic acid.

6. The preparation method according to claim 2, characterized in that, In step two, the film-forming technology is selected from one of vacuum-assisted self-assembly, template method, drop coating and spin coating.

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