A graphene oxide-based film and a method for preparing and using the same

Abstract

The application discloses a kind of graphene oxide-based membranes and its preparation method and application, the preparation method includes after diluting carboxylated graphene oxide dispersion liquid is dispersed in alkaline environment, so that carboxylated graphene oxide occurs deoxidation, complexation reaction obtains film-forming fluid, with microporous filter membrane as substrate, the film-forming fluid is covered on the surface of substrate to prepare graphene oxide-based membrane;The graphene oxide-based membrane prepared can be used to remove dissolved organic matter in salt lake brine.The application is free from the dependence on crosslinking agent when preparing graphene oxide-based membrane, simplifies process, is conducive to popularization, and the prepared membrane has high retention rate for dissolved organic matter;The graphene oxide-based membrane prepared by the method provided by the application is conducive to the establishment of internal efficient mass transfer channel, so that the performance of graphene oxide-based membrane is more stable.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an oxide graphene-based membrane, its preparation method, and its application. Background Technology

[0002] High-salinity wastewater is easily generated in the salt lake industry. For example, when lithium is extracted from salt lakes using extraction methods, the emulsification and dissolution of the extractant produce a large amount of high-salinity wastewater containing organic matter. Membrane separation technology has attracted much attention due to its high efficiency and energy saving advantages; however, due to the complexity and diversity of high-salinity brine systems, and the fact that most organic matter has undergone years of degradation and equilibrium in salt lakes, most organic matter has a low molecular weight. Conventional membrane treatment processes are limited by salinity and pore size requirements and cannot effectively remove it. Considering the corrosiveness of the brine system, existing technologies are difficult to achieve efficient removal. Therefore, developing separation membranes capable of treating organic matter in high-salinity solutions is of significant practical importance.

[0003] Graphene oxide (GO), as a novel two-dimensional nanomaterial, has attracted considerable attention in membrane research due to its inherent ultrathin size and excellent wettability. Abundant oxygen-containing groups exist on its edges and basal surfaces, allowing for varying degrees of modification and adjustment to suit different applications. Furthermore, the abundant oxygen-containing groups enable graphene oxide nanosheets to exhibit good dispersibility in water, which is beneficial for processing graphene oxide nanosheets into membrane materials through various methods (e.g., vacuum filtration, layer-by-layer assembly, surface coating, etc.).

[0004] Currently, some researchers construct graphene oxide films by adding crosslinking agents to the film-forming system, using covalent crosslinking to prepare the graphene oxide film. Chinese invention patent CN114618324A discloses a method for preparing a composite crosslinked graphene oxide film and its product. The method involves modifying the surface of a porous ceramic support with a 3-aminopropyltriethoxysilane ethanol solution and modifying a graphene oxide dispersion with amidothiourea and aminothiourea. Then, a film-forming process is used to prepare a composite crosslinked graphene oxide film product supported on a porous ceramic support. The obtained graphene oxide film exhibits excellent anti-swelling properties; however, this method is cumbersome and difficult to promote. Other researchers have used polyethyleneimine of different molecular weights to crosslink graphene oxide nanosheets, forming a robust three-dimensional covalent crosslinked network between the polyethyleneimine and the graphene oxide nanosheets (Separation and Purification Technology, 2022, 286:). (120459); Other researchers have enhanced the structural stability of graphene oxide-based films during aqueous phase separation by coupling graphene oxide nanosheets with silica nanoparticles and covalently crosslinking the graphene oxide nanosheets with ethylenediamine, thereby achieving efficient oil-water separation and dye removal (Carbon, 2020, 160: 88-97); still others have constructed highly hydrophilic two-dimensional sub-nanometer interlayer channels for rapid water transport through the self-assembly stacking of sulfonated carbon quantum dots and graphene oxide nanosheets. The crosslinking effect between sulfonated carbon quantum dots and graphene oxide nanosheets can produce a stable microstructure to maintain the interlayer spacing of graphene oxide and inhibit swelling (Journal of Membrane Science, 2022, 644: ). 120069.); Others have supported graphene oxide films by introducing biuret crosslinking agents and magnesium ion interlayer carriers into the interlayer structure. Biuret mainly acts on the oxidation sites in the nanochannels through the condensation reaction of amino and carboxyl groups, while magnesium ions are fixed on the graphene sites through non-covalent cation-π interactions. The synergistic effect of crosslinking and support keeps the film in a tightly filled two-dimensional structure (Journal of Membrane Science, 2023, 675: 121542).

[0005] While adding crosslinking agents to the film-forming system can enhance the stability of graphene oxide films and effectively alleviate the swelling problem in aqueous applications, it also increases costs and complicates the manufacturing process. Furthermore, it increases steric hindrance within the graphene oxide film, hindering the establishment of efficient mass transfer channels. Therefore, providing a simple method for preparing superhydrophilic / superoleophobic graphene oxide-based films in brine is an urgent technical problem to be solved. Summary of the Invention

[0006] This invention provides a method for preparing graphene oxide-based films and their applications, which solves the problem of complex processes caused by adding crosslinking agents in the preparation of graphene oxide-based films in the prior art.

[0007] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for preparing a graphene oxide-based film:

[0009] The method includes dispersing carboxylated graphene oxide in an alkaline environment to obtain a film-forming solution, and then covering the film-forming solution onto a substrate surface to obtain a graphene oxide-based film.

[0010] Furthermore, the preparation method of the above-mentioned graphene oxide-based film includes the following steps:

[0011] S1. Preparation of carboxylated graphene oxide dispersion.

[0012] S2. Preparation of film-forming solution: Adjust the carboxylated graphene oxide dispersion to alkaline, so that the carboxylated graphene oxide undergoes deoxygenation and complexation reactions to obtain film-forming solution;

[0013] S3. Preparation of graphene oxide-based membrane: Using a microporous filter membrane as a substrate, the film-forming solution obtained in S2 is applied to the surface of the substrate to prepare a graphene oxide-based membrane.

[0014] Furthermore, the pH of the carboxylated graphene oxide dispersion is adjusted to between 8 and 12.

[0015] Furthermore, the concentration of the carboxylated graphene oxide dispersion is between 0.02 mg / mL and 10 mg / mL.

[0016] Furthermore, an alkaline solution is added to S2 above to make the carboxylated graphene oxide dispersion alkaline.

[0017] Furthermore, the solute in the alkaline solution includes any one or a combination of two or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia.

[0018] Furthermore, the microporous filter membrane includes polyethersulfone membranes, nylon membranes, cellulose acetate membranes, ceramic membranes, etc.

[0019] Further, the film-forming solution is filtered onto the substrate to self-assemble a graphene oxide-based membrane.

[0020] Furthermore, the graphene oxide-based membrane has a retention rate of 90%-99% for dissolved organic matter in salt lake wastewater, including tributyl phosphate, sulfonated kerosene, dioctyl phosphate, methylene blue, and other organic compounds with a molecular weight greater than 200.

[0021] The application of the graphene oxide-based membrane prepared by the preparation method provided by this invention in the treatment of organic matter in salt lake wastewater.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention eliminates the dependence on crosslinking agents in the preparation of graphene oxide-based membranes, simplifies the process, facilitates its widespread application, and produces membranes with high retention rates of dissolved organic matter. The graphene oxide-based membranes prepared using the method provided by this invention exhibit superhydrophilic / superoleophobic properties under brine conditions, which is beneficial for establishing efficient internal mass transfer channels and makes the performance of the graphene oxide-based membranes more stable. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a SEM image of the graphene oxide-based film prepared in Example 1 of this invention.

[0026] Figure 2 These are the FT-IR spectra of graphene oxide films prepared at different pH values ​​according to the present invention.

[0027] Figure 3 (a) is the C1s high-resolution XPS spectrum of the PES-based film in Example 1 of the present invention. Figure 3 (b) is the O 1s high-resolution XPS spectrum of the PES-based film. Figure 3 (c) is the S 2p high-resolution XPS spectrum of the PES-based film; Figure 3 (d) is the C1s high-resolution XPS spectrum of the PES-based film-graphene oxide (GO-PES) interface in Example 1 of this invention. Figure 3 (e) is the O 1s high-resolution XPS spectrum of the PES-based film-graphene oxide (GO-PES) interface. Figure 3 (f) is the S2p high-resolution XPS spectrum of the PES-based film-graphene oxide (GO-PES) interface; Figure 3 (g) is the C 1s high-resolution XPS spectrum of the graphene oxide film (GO / PES). Figure 3 (h) is the O 1s high-resolution XPS spectrum of the graphene oxide film (GO / PES) surface. Detailed Implementation

[0028] Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0029] This invention provides a method for preparing a super-brine / brine-based superoleophobic graphene oxide film: including dispersing carboxylated graphene oxide in an alkaline environment to obtain a film-forming solution, and covering the film-forming solution onto the surface of a substrate to obtain a graphene oxide film.

[0030] Specifically, the preparation method includes the following steps:

[0031] S1. Preparation of carboxylated graphene oxide dispersion.

[0032] S2. Preparation of film-forming solution: Adjust the carboxylated graphene oxide dispersion to alkaline, so that the carboxylated graphene oxide undergoes deoxygenation and complexation reactions to obtain the film-forming solution;

[0033] S3. Preparation of graphene oxide-based membrane: Using a microporous filter membrane as a substrate, the film-forming solution obtained in S2 is applied to the surface of the substrate to prepare a graphene oxide-based membrane.

[0034] The carboxylated graphene oxide used in this application was purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0035] Example 1

[0036] This embodiment provides a graphene oxide-based film, specifically prepared by the following steps:

[0037] 1. Preparation of carboxylated graphene oxide dispersion

[0038] 0.1 mL of carboxylated graphene oxide (2 mg·mL⁻¹) −1 The carboxylated graphene oxide dispersion was uniformly dispersed in 10 mL of ultrapure water to obtain a diluted dispersion.

[0039] 2. Preparation of film-forming solution

[0040] Sodium hydroxide solution was added dropwise to the carboxylated graphene oxide dispersion in step 1, and the pH of the carboxylated graphene oxide dispersion was continuously tested until the pH was 10, thus obtaining the film-forming solution.

[0041] 3. Preparation of graphene oxide-based films

[0042] Using a polyethersulfone (PES) microporous membrane as a substrate, it was placed at the bottom of a bottle top filter. The film-forming solution from step 2 was vacuum filtered onto the polyethersulfone substrate using the bottle top filter. Subsequently, the GO / PES membrane was removed from the bottle top filter and dried at room temperature to form a stable GO / PES membrane.

[0043] Furthermore, the GO / PES membrane prepared in this embodiment was used for the treatment of salt lake wastewater. The GO / PES membrane prepared in this embodiment showed a 93.0% rejection rate for soluble tributyl phosphate in high-salt solutions, which greatly improved the performance of the graphene oxide-based membrane. The GO / PES membrane prepared in this embodiment can also be combined with other existing technologies for wastewater treatment.

[0044] See Figure 1 The image shown is a SEM image of the graphene oxide-based film prepared in Example 1 of this invention. This invention achieves deoxygenation reaction between graphene nanosheets by controlling the reaction conditions, thereby enabling the graphene surface to achieve superhydrophilic / superoleophobic properties under brine conditions. Furthermore, the addition of metal ions strengthens the interaction forces between graphene oxide nanosheets, which is beneficial for the establishment of efficient internal mass transfer channels, resulting in more stable performance of the graphene oxide-based film.

[0045] Example 2

[0046] This embodiment provides a graphene oxide-based film, specifically, the preparation steps are as follows:

[0047] 1. Preparation of carboxylated graphene oxide dispersion

[0048] 0.6 mL of carboxylated graphene oxide (2 mg·mL⁻¹) −1 The carboxylated graphene oxide dispersion was uniformly dispersed in 10 mL of ultrapure water to obtain a diluted dispersion.

[0049] 2. Preparation of film-forming solution

[0050] Potassium hydroxide was added dropwise to the carboxylated graphene oxide dispersion in step 1, and the pH of the carboxylated graphene oxide dispersion was continuously tested until the pH reached 11, thus obtaining the film-forming solution.

[0051] 3. Preparation of graphene oxide-based films

[0052] Using a cellulose acetate microporous membrane as a substrate, it was placed at the bottom of a bottle top filter. The film-forming solution from step 2 was vacuum filtered onto the cellulose acetate substrate using the bottle top filter. The prepared membrane was then removed from the bottle top filter and dried at room temperature to form a stable graphene membrane.

[0053] Furthermore, the graphene-based membrane prepared in this embodiment was used for the treatment of salt lake wastewater. The graphene-based membrane prepared in this embodiment showed a 95.6% rejection rate for soluble sulfonated kerosene in concentrated salt solutions, which greatly improved the performance of the graphene oxide-based membrane. The graphene-based membrane prepared in this embodiment can also be combined with other existing technologies for wastewater treatment.

[0054] Example 3

[0055] This embodiment provides a method for preparing a graphene oxide-based film. Specifically, the preparation steps are as follows:

[0056] 1. Preparation of carboxylated graphene oxide dispersion

[0057] 0.9 mL of carboxylated graphene oxide (2 mg·mL⁻¹) −1 The carboxylated graphene oxide dispersion was uniformly dispersed in 10 mL of ultrapure water to obtain a carboxylated graphene oxide dispersion.

[0058] 2. Preparation of film-forming solution

[0059] Lithium hydroxide was added dropwise to the carboxylated graphene oxide dispersion in step 1, and the pH of the carboxylated graphene oxide dispersion was continuously tested until the pH reached 10, thus obtaining the film-forming solution.

[0060] 3. Preparation of graphene oxide-based films

[0061] Using a nylon microporous membrane as a substrate, it was placed at the bottom of a bottle top filter. The film-forming solution from step 2 was vacuum filtered onto the nylon substrate using the bottle top filter. The membrane was then removed from the bottle top filter and dried at room temperature to form a stable graphene-based membrane.

[0062] Furthermore, the graphene-based membrane prepared in this embodiment was used for the treatment of salt lake wastewater. The graphene-based membrane prepared in this embodiment showed a 96.5% rejection rate for soluble dioctyl phosphate in concentrated salt solutions, which greatly improved the performance of the graphene oxide-based membrane. The graphene-based membrane prepared in this embodiment can also be combined with other existing technologies for wastewater treatment.

[0063] Example 4

[0064] This embodiment provides a graphene oxide-based film, specifically, the preparation steps are as follows:

[0065] 1. Preparation of carboxylated graphene oxide dispersion

[0066] 1.2 mL of carboxylated graphene oxide (2 mg·mL⁻¹) −1 The carboxylated graphene oxide dispersion was uniformly dispersed in 10 mL of ultrapure water to obtain a diluted dispersion.

[0067] 2. Preparation of film-forming solution

[0068] Sodium hydroxide was added dropwise to the carboxylated graphene oxide dispersion in step 1, and the pH of the carboxylated graphene oxide dispersion was continuously tested until the pH reached 12, thus obtaining the film-forming solution.

[0069] 3. Preparation of graphene oxide-based films

[0070] Using a ceramic microporous membrane as a substrate, it is placed at the bottom of a bottle top filter. The film-forming solution from step 2 is vacuum filtered onto the ceramic microporous membrane substrate using the bottle top filter. The membrane is then removed from the bottle top filter and dried at room temperature to form a stable graphene-based membrane.

[0071] Furthermore, the graphene-based membrane prepared in this embodiment was used for the treatment of salt lake wastewater. The graphene-based membrane prepared in this embodiment showed a 99% rejection rate for methylene blue, which greatly improved the performance of the graphene oxide-based membrane. The graphene-based membrane prepared in this embodiment can also be combined with other existing technologies for wastewater treatment.

[0072] Example 5

[0073] This embodiment provides a graphene oxide-based film, specifically prepared by the following steps:

[0074] 1. Preparation of carboxylated graphene oxide dispersion

[0075] 2.0 mL of carboxylated graphene oxide (2 mg·mL⁻¹) −1 The carboxylated graphene oxide dispersion was uniformly dispersed in 10 mL of ultrapure water to obtain a diluted dispersion.

[0076] 2. Preparation of film-forming solution

[0077] Lithium hydroxide was added dropwise to the carboxylated graphene oxide dispersion in step 1, and the pH of the carboxylated graphene oxide dispersion was continuously tested until the pH reached 9, thus obtaining the film-forming solution.

[0078] 3. Preparation of graphene oxide-based films

[0079] Using a polyethersulfone microporous membrane as a substrate, it was placed at the bottom of a bottle top filter. The film-forming solution from step 2 was vacuum filtered onto the polyethersulfone substrate using the bottle top filter. Subsequently, the GO / PES membrane was removed from the bottle top filter and dried at room temperature to form a stable GO / PES membrane.

[0080] Furthermore, the graphene-based membrane prepared in this embodiment was used for the treatment of salt lake wastewater. The graphene-based membrane prepared in this embodiment had a TBP rejection rate of 91%. The graphene-based membrane prepared in this embodiment can also be combined with other existing technologies for wastewater treatment.

[0081] Example 6

[0082] This embodiment provides a graphene oxide-based film, specifically, the preparation steps are as follows:

[0083] 1. Preparation of carboxylated graphene oxide film-forming solution

[0084] To carboxylated graphene oxide (10 mg·mL) −1 Ammonia water was added dropwise to the mixture, and the pH of the carboxylated graphene oxide dispersion was continuously tested until the pH reached 8, thus obtaining the film-forming solution.

[0085] 2. Preparation of graphene oxide-based films

[0086] Using a polyethersulfone microporous membrane as a substrate, it was placed at the bottom of a bottle top filter. The film-forming solution from step 1 was vacuum filtered onto the polyethersulfone substrate using the bottle top filter for vacuum-assisted self-assembly. Subsequently, the GO / PES membrane was removed from the bottle top filter and dried at room temperature to form a stable GO / PES membrane.

[0087] Furthermore, the graphene-based membrane prepared in this embodiment was used for the treatment of salt lake wastewater. The graphene-based membrane prepared in this embodiment had a rejection rate of 90% for TBP and sulfonated kerosene. The graphene-based membrane prepared in this embodiment can also be combined with other existing technologies for wastewater treatment.

[0088] Comparative Example 1

[0089] The only difference between Comparative Example 1 and Example 1 is that the pH was adjusted to 14 to obtain a film-forming solution, and a graphene oxide-based film was prepared.

[0090] The graphene oxide-based membrane prepared in Comparative Example 1 had a 10% rejection rate for soluble tributyl phosphate in high-salt solutions.

[0091] Comparative Example 2

[0092] The only difference between Comparative Example 2 and Example 1 is that the pH was adjusted to 6 to obtain a film-forming solution, and a graphene oxide-based film was prepared.

[0093] The graphene oxide-based membrane prepared in Comparative Example 2 had a 40% rejection rate for soluble tributyl phosphate in high-salt solutions.

[0094] In summary, dispersing carboxylated graphene oxide in an alkaline environment to prepare a film-forming solution allows for deoxygenation and complexation reactions of the carboxylated graphene oxide. Applying this solution to a substrate surface results in a graphene oxide-based film that facilitates the establishment of efficient internal mass transfer channels, leading to more stable performance. Furthermore, the separation and mechanical properties of the graphene oxide-based film are enhanced through the condensation of oxygen-containing functional groups and the non-covalent interactions between metal ions and graphene oxide. It should be noted that vacuum-assisted self-assembly is an existing film-forming technology; other techniques that can achieve similar results are also possible.

[0095] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. Application of graphene oxide-based membranes in the treatment of salt lake wastewater, wherein the preparation method of the graphene oxide-based membrane includes the following steps: S1. Prepare a carboxylated graphene oxide dispersion, wherein the concentration of the carboxylated graphene oxide dispersion is between 0.02 mg / mL and 10 mg / mL; S2. Preparation of film-forming solution: Add alkaline solution to adjust the pH of the carboxylated graphene oxide dispersion to between 8 and 12, so that the carboxylated graphene oxide undergoes deoxygenation and complexation reaction to obtain film-forming solution. The solute in the alkaline solution is selected from any one or a combination of two or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia water. S3. Preparation of graphene oxide-based membrane: Using a microporous filter membrane as a substrate, the film-forming solution obtained in S2 is applied to the surface of the substrate to prepare a graphene oxide-based membrane. The microporous filter membrane is selected from any one of polyethersulfone membrane, nylon membrane, cellulose acetate membrane, and ceramic membrane. The graphene oxide-based membrane has a retention rate of 90%-99% for dissolved organic matter in salt lake wastewater, and the molecular weight of the dissolved organic matter is greater than 200.

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