Graphene oxide molecular filtration membrane, method for preparing same, and use thereof

Abstract

The present disclosure provides a preparation method of graphene oxide molecular filtration membrane, comprising the following steps. Under stirring, polyvinylpyrrolidone is added into a copper salt solution for mixing, and then lye and hydrogen peroxide solution are sequentially added for reaction to prepare copper peroxide nanodots. Neutral graphene oxide dispersion liquid is mixed with the copper peroxide nanodot dispersion liquid, under stirring, ferrous solution is added, and uniform mixing is performed to obtain casting solution. The casting solution is loaded on a base film through filtration, and then the intercalated copper peroxide nanodots are dissolved through acid treatment, and after water washing to neutral, graphene oxide molecular filtration membrane is obtained. The graphene oxide molecular filtration membrane prepared by the present disclosure expands the interlayer spacing and increases the charge density, so that the membrane has a nanocavity structure inside, can effectively intercept negative pollutants in water and separate molecules with similar sizes, and has excellent permeability.

Description

Technical Field

[0001] This disclosure pertains to the field of membrane separation, specifically relating to a graphene oxide molecular filtration membrane, its preparation method, and its applications. Background Technology

[0002] Membrane technology boasts a range of advantages, including low energy consumption, high efficiency, and low carbon emissions, and has been widely studied and applied in industrial and environmental separation fields in recent years. Developing membrane separation technologies based on differences in molecular chemical properties for the selective separation of molecules of similar size has the potential to replace many energy-intensive separation processes (e.g., distillation, extraction, and chromatographic separation), and is an important component in promoting a low-carbon economy and sustainable development.

[0003] Currently, most commercial membranes are polymer membranes prepared using interfacial polymerization. These membranes lack precise control over their structure and pore chemistry during preparation, making it difficult to achieve selective separation based on differences in molecular chemistry. Some novel polymer materials (e.g., copolymer micelles, ternary block copolymers) and pore functionalization strategies have been reported for preparing charge-selective separation membranes to sieve small molecules of similar sizes. While these novel polymer membranes can achieve selective molecular separation, they typically exhibit low permeability due to the limitations of the polymer materials themselves. Furthermore, some studies have attempted to use electrostatic membrane adsorption techniques to balance selectivity and permeability. However, adsorption techniques require additional chemical reagents and manipulations for membrane regeneration, making the separation process discontinuous and complex.

[0004] Graphene oxide (GO) membranes are a relatively new type of two-dimensional membrane. Nanochannels assembled from atomically thin GO sheets possess ultrafast water transport properties, and the inherent negative charge of the sheets and the tunable channel environment make them potentially suitable for separating substances of similar size but different charges. Currently, the use of GO-based membranes for separating similar-sized substances mainly focuses on ion separation, and is difficult to apply to molecular separation. This is primarily because the tightly stacked layered structure of the original GO membrane hinders the penetration of most molecules. Therefore, achieving molecular separation requires controlling the interlayer spacing of the membrane to be larger than the molecular size.

[0005] In related technologies, the main ways to increase the interlayer spacing of GO films include: (1) interlayer support, such as using organic polymers (polyethyleneimine, polyethylene glycol diamine, etc.) and metal ions (Fe). 3+ (1) Intercalation and support of GO using PACl and nanoparticles (silica, MOF, etc.); (2) Chemical stimulation, such as inducing GO channel swelling by regulating the pH value of the membrane environment and chemically stimulating the redox state of the intercalated material to achieve channel expansion; (3) Freeze-drying to expand the interlayer spacing of the membrane.

[0006] While these methods can increase the interlayer spacing of membranes to some extent, their ability to control the interlayer spacing is very limited (typically less than 1.5 nm), making it difficult to eliminate the size sieving effect of GO membranes on small molecules (molecules with a molecular weight of 300-1000 Da correspond to a size of approximately 1.2-2.5 nm). Furthermore, most methods for controlling the interlayer structure lack the ability to adjust charge density, resulting in membranes that still struggle to achieve efficient and selective separation of substances of similar sizes.

[0007] Therefore, providing a novel method for regulating the structure of GO membranes, while simultaneously optimizing the interlayer channels and charge density, is of profound significance for achieving selective separation of substances of similar molecular size and expanding the practical applications of GO membranes. Summary of the Invention

[0008] In view of this, in order to solve at least one technical problem in related technologies and other aspects, this disclosure proposes a graphene oxide molecular filtration membrane, its preparation method, and its application.

[0009] In one aspect of this disclosure, a method for preparing a graphene oxide molecular filtration membrane is provided, comprising the following steps.

[0010] Step S1: Under stirring conditions, polyvinylpyrrolidone was added to a copper salt solution and mixed. Then, an alkaline solution and a hydrogen peroxide solution were added sequentially to react. After the reaction was completed, the solution was washed and freeze-dried to obtain copper peroxide nanoparticle powder.

[0011] Step S2: Prepare graphene oxide dispersion and copper peroxide nanoparticle dispersion separately. Adjust the pH of graphene oxide dispersion to neutral and mix it with copper peroxide nanoparticle dispersion. Add ferrous solution under stirring and mix evenly to obtain casting solution.

[0012] Step S3: Load the casting solution onto the microfiltration membrane by filtration to obtain a copper peroxide nanodot intercalated graphene oxide membrane.

[0013] Step S4: Remove the intercalated copper peroxide nanodots by acid dissolution, and wash with deionized water until the pH value is neutral to obtain the graphene oxide molecular filter membrane.

[0014] According to the embodiments of this disclosure, the concentrations of copper salt, alkali solution, and hydrogen peroxide are 0.01 mol / L, 0.02 mol / L, and 30%, respectively; the ratio of copper salt, polyvinylpyrrolidone, alkali solution, and hydrogen peroxide is 5 mL: 0.5 g: 5 mL: 0.1 mL; wherein, the amounts of polyvinylpyrrolidone, alkali solution, and hydrogen peroxide are adjusted based on the volume of the copper salt solution.

[0015] According to embodiments of this disclosure, the concentration of the graphene oxide dispersion is 2.5–10 mg / L.

[0016] According to embodiments of this disclosure, the concentration of the copper peroxide nanodot dispersion is 200–2000 mg / L.

[0017] According to embodiments of this disclosure, the volume ratio of graphene oxide dispersion to copper peroxide nanodot dispersion is 1:1.

[0018] According to embodiments of this disclosure, the pH of the neutral graphene oxide dispersion is 7-8 before mixing with the copper peroxide nanodot dispersion.

[0019] According to embodiments of this disclosure, the concentration of the ferrous solution in the casting solution is 0.05–0.5 mmol / L.

[0020] According to embodiments of this disclosure, the microfiltration membrane is an acid-resistant material with a pore size in the range of 0.11 to 0.45 μm.

[0021] According to embodiments of this disclosure, filtration includes vacuum filtration or pressure filtration, with the filtration pressure ranging from 0.2 to 2 bar.

[0022] According to embodiments of this disclosure, the mass concentration of the acid solution in the acid dissolution operation ranges from 0.05% to 2%, and the acid dissolution operation time is from 2 to 6 hours.

[0023] In another aspect of this disclosure, a graphene oxide molecular filter membrane prepared by the above method is provided, wherein the graphene oxide molecular filter membrane has a layered stacked structure with nanocavities inside the membrane.

[0024] In another aspect of this disclosure, an application of the graphene oxide molecular filtration membrane obtained by the above preparation method in the field of membrane separation is proposed, wherein the field of membrane separation includes water purification, drug separation or resource recovery.

[0025] This disclosure has the following characteristics and technical effects:

[0026] According to embodiments of this disclosure, copper peroxide nanodots are used as sacrificial templates to simultaneously control the interlayer structure and charge density of the GO film. First, the interlayer-embedded copper peroxide, after acid dissolution, expands the interlayer spacing and forms abundant cavity structures within the film. Second, the Cu produced during the decomposition of the copper peroxide nanodots... 2+The GO membrane undergoes a Fenton-like reaction with H₂O₂ to generate hydroxyl radicals, which oxidize the GO sheets, thereby enhancing the membrane's charge density. The increased interlayer spacing allows molecules to enter and forms a confined space to maximize the electrostatic interaction between molecules and the membrane, while the increased charge density further strengthens the membrane's repulsion of negatively charged molecules. Therefore, based on its charge sieving properties, the prepared membrane can effectively retain negatively charged molecules while allowing positively charged and neutral molecules of similar size to permeate rapidly, achieving efficient separation of substances of similar size. Furthermore, the abundant nanocavities provide additional mass transfer channels, significantly enhancing the membrane's permeability. The GO membrane structure control method disclosed in this paper is simple and controllable, and the prepared membrane has a wide separation range, showing great application potential in water treatment and industrial separation.

[0027] The concept and solutions to the key technical problems disclosed herein are as follows:

[0028] Precise control of pore structure and pore chemistry is crucial for achieving the separation of similar-sized substances based on differences in molecular chemistry. Designing and fabricating such functional membrane materials requires, on the one hand, functionalizing the membrane channels to achieve selective separation by leveraging the differences in the interaction forces between different solute molecules and the channels. On the other hand, the membrane pore size should be as close as possible to, and slightly larger than, the size of the solute molecules, thus forming a confined yet permissible space to enhance the interaction between all molecules and the membrane, thereby further improving separation selectivity. However, commercial polymer membranes struggle to achieve precise control of pore structure and pore chemistry.

[0029] GO membranes provide ideal charge-selective nanochannels, potentially enabling the selective separation of molecules of similar size but different charges. Studies have shown that the permeation rates of hydrated anions and cations with similar sizes differ by up to 10-fold within GO channels, and this difference can be further enhanced by modulating the charge density of the GO sheets. However, GO membranes are challenging for molecular separation, primarily because their dense stacked structure typically hinders the permeation of all molecules. Achieving selective separation of molecules of similar size requires adjusting the interlayer spacing of the GO membrane to be slightly larger than the molecular size to eliminate the size sieving effect of interlayer channels on molecules and maintain a confined space to strengthen the interaction between molecules and channels. Furthermore, structural modulation necessitates maximizing the negative charge of the membrane to further enhance charge selectivity and improve permeability, thus balancing permeability and separation factor.

[0030] Nanodots, acting as sacrificial templates, can increase the interlayer spacing of membranes and create cavities within the membrane; hydroxyl radicals generated by the Fenton reaction can oxidize GO sheets, increasing the membrane's charge density. Metal peroxide nanodots, due to their acid solubility and hydroxyl radical-providing properties, can simultaneously satisfy these processes, achieving simultaneous optimization of membrane channel structure and chemical environment. Therefore, this disclosure first synthesizes copper peroxide nanodots and uses them as interlayer sacrificial templates to target and regulate the GO membrane structure. Copper peroxide possesses the property of generating hydroxyl radicals through acid solubility. This regulation method simultaneously expands the interlayer spacing, optimizes mass transfer channels, and enhances the membrane's charge density. The prepared membrane exhibits excellent charge-selective separation performance, effectively separating molecules of similar size but different charges, and possesses ultra-high permeability. Furthermore, the membrane preparation method is simple, has a wide separation range, and has great application potential in water treatment and industrial separation. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the fabrication process of the graphene oxide molecular filtration membrane disclosed herein;

[0032] Figure 2 These are electron microscope images of the graphene oxide molecular filter membrane obtained in Example 1 of this disclosure, where a is a surface electron microscope image and b is a cross-sectional electron microscope image.

[0033] Figure 3 This is a bar chart of the interlayer spacing of the membrane materials in Example 1 and Comparative Examples 1 and 2 of this disclosure;

[0034] Figure 4 These are bar charts showing the charge density of the membrane materials in Examples 1 and Comparative Examples 1 and 2 of this disclosure;

[0035] Figure 5 This is a bar chart showing the rejection rate and permeability of the membrane materials of Examples 1 and Comparative Examples 1 and 2 in this disclosure to methylene blue;

[0036] Figure 6 This is a graph showing the separation factor and permeability of the membrane materials of Examples 5 and Comparative Examples 3 and 4 in this disclosure to the mixture of Acid Red and Rhodamine B.

[0037] Figure 7 This is the ultraviolet spectrum of the mixture of acid red and tetracycline separated by the graphene oxide molecular filter membrane obtained in Example 6 of this disclosure;

[0038] Figure 8 This is the ultraviolet spectrum of the methyl orange and methylene blue mixture separated by the graphene oxide molecular filter membrane obtained in Example 7 of this disclosure. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0040] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this disclosure.

[0041] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0042] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0043] Throughout the accompanying drawings, identical elements are represented by the same or similar reference numerals. Conventional structures or configurations have been omitted where they may cause confusion in understanding this disclosure. Furthermore, the shapes, dimensions, and positional relationships of the components in the drawings do not reflect their actual size, scale, or actual positional relationships. Additionally, any reference symbols enclosed in parentheses should not be construed as limiting this disclosure.

[0044] Similarly, to simplify this disclosure and aid in understanding one or more of the various aspects of the disclosure, in the above description of exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present disclosure. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0045] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this disclosure.

[0046] Figure 1 This is a schematic diagram of the preparation process of the graphene oxide molecular filter membrane disclosed herein.

[0047] In one aspect of this disclosure, a method for preparing a graphene oxide molecular filtration membrane is provided, comprising the following steps.

[0048] Step S1: Under stirring, polyvinylpyrrolidone was added to a copper salt solution and mixed. Then, alkali solution and hydrogen peroxide solution were added sequentially to carry out the reaction. The reaction was continued for about 30 minutes under stirring. After the reaction was completed, the resulting solution was washed and freeze-dried to obtain copper peroxide nanoparticle powder.

[0049] Step S2: Prepare graphene oxide dispersion and copper peroxide nanoparticle dispersion separately. Adjust the pH of graphene oxide dispersion to neutral and mix it with copper peroxide nanoparticle dispersion. Add ferrous solution under stirring and mix evenly to obtain casting solution.

[0050] Step S3: As Figure 1 As shown, the casting solution was loaded onto a microfiltration membrane by filtration to obtain a copper peroxide nanodot intercalated graphene oxide membrane (CP / GO membrane).

[0051] Step S4: Remove the intercalated copper peroxide nanodots by acid dissolution, and wash with deionized water until the pH value is neutral to obtain the graphene oxide molecular filtration membrane (H-CP / GO membrane).

[0052] According to embodiments of this disclosure, copper peroxide nanodots are first prepared and introduced into the interlayer space during GO film assembly, followed by dissolution with acid. On one hand, the intercalation of copper peroxide nanodots and subsequent acid dissolution can increase the interlayer spacing of the film and form nanocavity structures within the film (e.g., ...). Figure 1 (As shown); On the other hand, during acid dissolution, copper peroxide nanodots undergo a Fenton-like reaction to generate hydroxyl radicals, which oxidize and etch the GO film, enhancing its charge density. Simultaneous control of film structure and charge density was achieved through a simple two-step method of copper peroxide intercalation and dissolution.

[0053] According to the embodiments of this disclosure, the concentration of the copper salt solution is 0.01 mol / L, the concentration of the alkali solution is 0.02 mol / L, and the concentration of hydrogen peroxide is 30%; the ratio of copper salt, polyvinylpyrrolidone, alkali solution, and hydrogen peroxide is 5 mL: 0.5 g: 5 mL: 0.1 mL. The amounts of polyvinylpyrrolidone, alkali solution, and hydrogen peroxide are adjusted based on the volume of the copper salt solution.

[0054] According to embodiments of this disclosure, the molecular weight of polyvinylpyrrolidone ranges from 10,000 to 30,000 Da, with 10,000 Da being preferred. The copper salt solution is preferably CuCl2·2H2O. The alkaline solution is preferably NaOH, whose function is to deprotonate hydrogen peroxide, thereby promoting its reaction with Cu. 2+ Coordination. The role of polyvinylpyrrolidone is to stabilize the formed copper peroxide nanoparticles and prevent their aggregation.

[0055] According to an embodiment of this disclosure, in step S1, the reaction lasts for approximately 30 minutes.

[0056] According to embodiments of this disclosure, the concentration of the graphene oxide dispersion is 2.5 to 10 mg / L, for example, 2.5 mg / L, 5 mg / L, 7.5 mg / L, 10 mg / L, etc.

[0057] According to embodiments of this disclosure, the concentration of the copper peroxide nanodot dispersion is 200–2000 mg / L, for example, 200 mg / L, 500 mg / L, 800 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, etc.

[0058] According to embodiments of this disclosure, the volume ratio of graphene oxide dispersion to copper peroxide nanodot dispersion is 1:1.

[0059] According to embodiments of this disclosure, since the initial graphene oxide dispersion has an acidic pH, and copper peroxide nanodots decompose under acidic conditions, the pH of the graphene oxide dispersion needs to be adjusted to neutral using an alkaline solution before mixing with the copper peroxide nanodot dispersion. For example, alkaline solutions such as NaOH or KOH can be used for adjustment, resulting in a final pH range of 7–8 for the graphene oxide dispersion.

[0060] According to embodiments of this disclosure, the ferrous solution is preferably FeSO4·7H2O, and its concentration in the casting solution is 0.05–0.5 mmol / L. The amount used is based on the final volume of the mixed liquid, and can be selected as 0.05 mmol / L, 0.1 mmol / L, 0.2 mmol / L, 0.3 mmol / L, 0.4 mmol / L, 0.5 mmol / L, etc.

[0061] According to embodiments of this disclosure, ferrous ions are primarily used as crosslinking agents to pre-stabilize the GO membrane, thereby preventing damage to the membrane structure from subsequent acid treatment.

[0062] According to embodiments of this disclosure, the microfiltration membrane is an acid-resistant material with a pore size in the range of 0.11 to 0.45 μm.

[0063] According to embodiments of this disclosure, the materials of the microfiltration membrane include nylon, polyvinylidene fluoride (PVDF), polyethersulfone (PES), mixed cellulose ester (MCE), etc.

[0064] According to embodiments of this disclosure, filtration includes vacuum filtration or pressure filtration, with the filtration pressure ranging from 0.2 to 2 bar.

[0065] According to embodiments of this disclosure, the mass concentration of the acid solution in the acid dissolution operation ranges from 0.05% to 2%, and the acid dissolution operation time is from 2 to 6 hours.

[0066] In another aspect of this disclosure, a graphene oxide molecular filtration membrane prepared by the above method is provided, wherein the graphene oxide molecular filtration membrane has a layered stacked structure with intramembrane nanocavities. Electron microscopy images of the membrane surface and cross-section are provided. Figure 2 The presence of cavities and regular stacking structure are clearly shown, with the height of the nanocavities being 5–8 nm.

[0067] According to embodiments of this disclosure, the graphene oxide molecular filtration membrane proposed in this disclosure can effectively trap negatively charged molecules in water and separate molecules of similar size but different charges, and this selective separation capability has good universality.

[0068] In another aspect of this disclosure, an application of the graphene oxide molecular filtration membrane obtained by the above preparation method in the field of membrane separation is proposed, wherein the field of membrane separation includes water purification, drug separation or resource recovery.

[0069] It should be noted that the described embodiments are merely some, not all, of the embodiments disclosed herein. Other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are all within the scope of protection of this disclosure.

[0070] Example 1

[0071] Under stirring, 2.5 g of polyvinylpyrrolidone (PVP) with a molecular weight of 10000 Da was added to 25 mL of 0.01 mol / L CuCl2·2H2O solution. The resulting solution was light green. Then, 25 mL of 0.02 mol / L NaOH solution was added, and the solution turned bright blue. Adding 0.5 mL of 30% H2O2 solution turned the solution dark brown. The mixture was stirred for another 30 min to ensure complete reaction. After the reaction was complete, the resulting solution was concentrated by filtration through a 1K ultrafiltration membrane and washed several times with deionized water (DI). Finally, the solution was freeze-dried to obtain copper peroxide (CP) powder.

[0072] A 5 mg / L graphene oxide dispersion (GO dispersion) was prepared using DI, and the pH was adjusted to 7 using NaOH after ultrasonic treatment. A 1400 mg / L copper peroxide dispersion (CP dispersion) was prepared using DI and ultrasonicated to ensure uniform dispersion. 100 mL of GO dispersion and 100 mL of CP dispersion were mixed, stirred thoroughly, and then 1 mL of freshly prepared 10 mmol / L FeSO4·7H2O solution was added. After thorough mixing, the casting solution was obtained.

[0073] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate microfiltration membrane. Before use, the nylon membrane was soaked in disintegrating solution (DI) for 12 h, followed by filtration through 300 mL of DI to remove impurities. Freshly prepared casting solution was then loaded onto the nylon membrane using pressure filtration at 1 bar to obtain a CP-intercalated GO membrane (CP / GO membrane).

[0074] After loading was completed, 50 mL of 1% HCl solution was added to the filtration device while the membrane was wetted to dissolve the interlayer embedded CP nanodots. The acid dissolution process was carried out under gravity filtration conditions for 2.5 h. After acid dissolution, the residual acid was removed by filtration, and then the membrane surface was rinsed with DI. Filtration with DI was continued until the pH of the filtrate was neutral, thus obtaining the graphene oxide molecular filtration membrane (H-CP / GO membrane).

[0075] The performance of the obtained H-CP / GO membrane was tested:

[0076] At a pressure of 1 bar, the H-CP / GO membrane obtained in Example 1 exhibited a 99.1% rejection rate for 20 mg / L methylene blue (a negatively charged dye molecule) in an aqueous system, with a flux of 46.3 L / (m³). 2 h bar).

[0077] Example 2

[0078] Under stirring, 2.5 g of PVP with a molecular weight of 10000 Da was added to 25 mL of 0.01 mol / L CuCl2·2H2O solution. The resulting solution was light green. Then, 25 mL of 0.02 mol / L NaOH solution was added, and the solution turned bright blue. Adding 0.5 mL of 30% H2O2 solution turned the solution dark brown. Stirring was continued for 30 min to ensure complete reaction. After the reaction was complete, the resulting solution was concentrated by filtration through a 1K ultrafiltration membrane and washed several times with DI filtration. Finally, the solution was freeze-dried to obtain CP powder.

[0079] A GO dispersion with a concentration of 5 mg / L was prepared using DI, and the pH was adjusted to 7 using NaOH after sonication. A CP dispersion with a concentration of 200 mg / L was prepared using DI and sonicated to ensure uniform dispersion. 100 mL of GO dispersion and 100 mL of CP dispersion were mixed, stirred thoroughly, and then 1 mL of freshly prepared 10 mmol / L FeSO4·7H2O solution was added. After mixing thoroughly, the casting solution was obtained.

[0080] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate microfiltration membrane. Before use, the nylon membrane was soaked in disintegrating solution (DI) for 12 h, followed by filtration through 300 mL of DI to remove impurities. Freshly prepared casting solution was then loaded onto the nylon membrane using pressure filtration at 1 bar to obtain the CP / GO membrane.

[0081] After loading was completed, 50 mL of 1% HCl solution was added to the filtration device while the membrane was wetted to dissolve the interlayer embedded CP nanodots. The acid dissolution process was carried out under gravity filtration conditions for 2.5 h. After acid dissolution, the residual acid was removed by filtration, and then the membrane surface was rinsed with DI. Filtration with DI was continued until the pH of the filtrate was neutral to obtain the H-CP / GO membrane.

[0082] The performance of the obtained H-CP / GO membrane was tested:

[0083] At a pressure of 1 bar, the H-CP / GO membrane obtained in Example 2 exhibited a 99.8% rejection rate for 20 mg / L methylene blue in an aqueous system, with a flux of 23.4 L / (m²). 2 h bar).

[0084] Example 3

[0085] Under stirring, 2.5 g of PVP with a molecular weight of 10000 Da was added to 25 mL of 0.01 mol / L CuCl2·2H2O solution. The resulting solution was light green. Then, 25 mL of 0.02 mol / L NaOH solution was added, and the solution turned bright blue. Adding 0.5 mL of 30% H2O2 solution turned the solution dark brown. Stirring was continued for 30 min to ensure complete reaction. After the reaction was complete, the resulting solution was concentrated by filtration through a 1K ultrafiltration membrane and washed several times with DI filtration. Finally, the solution was freeze-dried to obtain CP powder.

[0086] A GO dispersion with a concentration of 5 mg / L was prepared using DI, and the pH was adjusted to 7 using NaOH after sonication. A CP dispersion with a concentration of 800 mg / L was prepared using DI and sonicated to ensure uniform dispersion. 100 mL of GO dispersion and 100 mL of CP dispersion were mixed and stirred thoroughly. Then, 1 mL of freshly prepared 10 mmol / L FeSO4·7H2O solution was added and mixed thoroughly to obtain the casting solution.

[0087] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate microfiltration membrane. Before use, the nylon membrane was soaked in disintegrating solution (DI) for 12 h, followed by filtration through 300 mL of DI to remove impurities. Freshly prepared casting solution was then loaded onto the nylon membrane using pressure filtration at 1 bar to obtain the CP / GO membrane.

[0088] After loading was completed, 50 mL of 1% HCl solution was added to the filtration device while the membrane was wetted to dissolve the interlayer embedded CP nanodots. The acid dissolution process was carried out under gravity filtration conditions for 2.5 h. After acid dissolution, the residual acid was removed by filtration, and then the membrane surface was rinsed with DI. Filtration with DI was continued until the pH of the filtrate was neutral to obtain the H-CP / GO membrane.

[0089] The performance of the obtained H-CP / GO membrane was tested:

[0090] At a pressure of 1 bar, the H-CP / GO membrane obtained in Example 3 exhibited a 99.8% rejection rate for 20 mg / L methylene blue in an aqueous system, with a flux of 33.7 L / (m³). 2 h bar).

[0091] Example 4

[0092] Under stirring, 2.5 g of PVP with a molecular weight of 10000 Da was added to 25 mL of 0.01 mol / L CuCl2·2H2O solution. The resulting solution was light green. Then, 25 mL of 0.02 mol / L NaOH solution was added, and the solution turned bright blue. Adding 0.5 mL of 30% H2O2 solution turned the solution dark brown. Stirring was continued for 30 min to ensure complete reaction. After the reaction was complete, the resulting solution was concentrated by filtration through a 1K ultrafiltration membrane and washed several times with DI filtration. Finally, the solution was freeze-dried to obtain CP powder.

[0093] A GO dispersion with a concentration of 2.5 mg / L was prepared using DI, and the pH was adjusted to 7 using NaOH after sonication. A CP dispersion with a concentration of 200 mg / L was prepared using DI and sonicated to ensure uniform dispersion. 100 mL of GO dispersion and 100 mL of CP dispersion were mixed, stirred thoroughly, and then 1 mL of freshly prepared 10 mmol / L FeSO4·7H2O solution was added. After mixing thoroughly, the casting solution was obtained.

[0094] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate microfiltration membrane. Before use, the nylon membrane was soaked in disintegrating solution (DI) for 12 h, followed by filtration through 300 mL of DI to remove impurities. Freshly prepared casting solution was then loaded onto the nylon membrane using pressure filtration at 1 bar to obtain the CP / GO membrane.

[0095] After loading was completed, 50 mL of 1% HCl solution was added to the filtration device while the membrane was wetted to dissolve the interlayer embedded CP nanodots. The acid dissolution process was carried out under gravity filtration conditions for 2.5 h. After acid dissolution, the residual acid was removed by filtration, and then the membrane surface was rinsed with DI. Filtration with DI was continued until the pH of the filtrate was neutral to obtain the H-CP / GO membrane.

[0096] The performance of the obtained H-CP / GO membrane was tested:

[0097] At a pressure of 1 bar, the H-CP / GO membrane obtained in Example 4 exhibited a 94.9% rejection rate for 20 mg / L methylene blue in an aqueous system, with a flux of 69.3 L / (m³). 2 h bar).

[0098] Example 5

[0099] Under stirring, 2.5 g of PVP with a molecular weight of 10000 Da was added to 25 mL of 0.01 mol / L CuCl2·2H2O solution. The resulting solution was light green. Then, 25 mL of 0.02 mol / L NaOH solution was added, and the solution turned bright blue. Adding 0.5 mL of 30% H2O2 solution turned the solution dark brown. Stirring was continued for 30 min to ensure complete reaction. After the reaction was complete, the resulting solution was concentrated by filtration through a 1K ultrafiltration membrane and washed several times with DI filtration. Finally, the solution was freeze-dried to obtain CP powder.

[0100] A GO dispersion with a concentration of 5 mg / L was prepared using DI, and the pH was adjusted to 7 using NaOH after sonication. A CP dispersion with a concentration of 1400 mg / L was prepared using DI and sonicated to ensure uniform dispersion. 100 mL of GO dispersion and 100 mL of CP dispersion were mixed and stirred thoroughly. Then, 1 mL of freshly prepared 10 mmol / L FeSO4·7H2O solution was added and mixed thoroughly to obtain the casting solution.

[0101] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate microfiltration membrane. Before use, the nylon membrane was soaked in disintegrating solution (DI) for 12 h, followed by filtration through 300 mL of DI to remove impurities. Freshly prepared casting solution was then loaded onto the nylon membrane using pressure filtration at 1 bar to obtain the CP / GO membrane.

[0102] After loading was completed, 50 mL of 1% HCl solution was added to the filtration device while the membrane was wetted to dissolve the interlayer embedded CP nanodots. The acid dissolution process was carried out under gravity filtration conditions for 2.5 h. After acid dissolution, the residual acid was removed by filtration, and then the membrane surface was rinsed with DI. Filtration with DI was continued until the pH of the filtrate was neutral to obtain the H-CP / GO membrane.

[0103] The performance of the obtained H-CP / GO membrane was tested:

[0104] At a pressure of 1 bar, the H-CP / GO membrane obtained in Example 5 exhibited a separation factor of 24.0 and a flux of 46.0 L / (m³) for a mixture of Acid Red (negatively charged molecules) and Rhodamine B (neutral molecules) at a concentration of 20 mg / L in an aqueous system. 2 h bar).

[0105] Example 6

[0106] Under stirring, 2.5 g of PVP with a molecular weight of 10000 Da was added to 25 mL of 0.01 mol / L CuCl2·2H2O solution. The resulting solution was light green. Then, 25 mL of 0.02 mol / L NaOH solution was added, and the solution turned bright blue. Adding 0.5 mL of 30% H2O2 solution turned the solution dark brown. Stirring was continued for 30 min to ensure complete reaction. After the reaction was complete, the resulting solution was concentrated by filtration through a 1K ultrafiltration membrane and washed several times with DI filtration. Finally, the solution was freeze-dried to obtain CP powder.

[0107] A GO dispersion with a concentration of 5 mg / L was prepared using DI, and the pH was adjusted to 7 using NaOH after sonication. A CP dispersion with a concentration of 1400 mg / L was prepared using DI and sonicated to ensure uniform dispersion. 100 mL of GO dispersion and 100 mL of CP dispersion were mixed and stirred thoroughly. Then, 1 mL of freshly prepared 10 mmol / L FeSO4·7H2O solution was added and mixed thoroughly to obtain the casting solution.

[0108] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate microfiltration membrane. Before use, the nylon membrane was soaked in disintegrating solution (DI) for 12 h, followed by filtration through 300 mL of DI to remove impurities. Freshly prepared casting solution was then loaded onto the nylon membrane using pressure filtration at 1 bar to obtain the CP / GO membrane.

[0109] After loading was completed, 50 mL of 1% HCl solution was added to the filtration device while the membrane was wetted to dissolve the interlayer embedded CP nanodots. The acid dissolution process was carried out under gravity filtration conditions for 2.5 h. After acid dissolution, the residual acid was removed by filtration, and then the membrane surface was rinsed with DI. Filtration with DI was continued until the pH of the filtrate was neutral to obtain the H-CP / GO membrane.

[0110] The performance of the obtained H-CP / GO membrane was tested:

[0111] At a pressure of 1 bar, the H-CP / GO membrane obtained in Example 6 exhibited a separation factor of 14.5 and a flux of 41.3 L / (m³) for a mixture of acid red and tetracycline (neutral molecule) at a concentration of 20 mg / L in an aqueous system. 2 h bar).

[0112] Example 7

[0113] Under stirring, 2.5 g of PVP with a molecular weight of 10000 Da was added to 25 mL of 0.01 mol / L CuCl2·2H2O solution. The resulting solution was light green. Then, 25 mL of 0.02 mol / L NaOH solution was added, and the solution turned bright blue. Adding 0.5 mL of 30% H2O2 solution turned the solution dark brown. Stirring was continued for 30 min to ensure complete reaction. After the reaction was complete, the resulting solution was concentrated by filtration through a 1K ultrafiltration membrane and washed several times with DI filtration. Finally, the solution was freeze-dried to obtain CP powder.

[0114] A GO dispersion with a concentration of 5 mg / L was prepared using DI, and the pH was adjusted to 7 using NaOH after sonication. A CP dispersion with a concentration of 1400 mg / L was prepared using DI and sonicated to ensure uniform dispersion. 100 mL of GO dispersion and 100 mL of CP dispersion were mixed and stirred thoroughly. Then, 1 mL of freshly prepared 10 mmol / L FeSO4·7H2O solution was added and mixed thoroughly to obtain the casting solution.

[0115] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate microfiltration membrane. Before use, the nylon membrane was soaked in disintegrating solution (DI) for 12 h, followed by filtration through 300 mL of DI to remove impurities. Freshly prepared casting solution was then loaded onto the nylon membrane using pressure filtration at 1 bar to obtain the CP / GO membrane.

[0116] After loading was completed, 50 mL of 1% HCl solution was added to the filtration device while the membrane was wetted to dissolve the interlayer embedded CP nanodots. The acid dissolution process was carried out under gravity filtration conditions for 2.5 h. After acid dissolution, the residual acid was removed by filtration, and then the membrane surface was rinsed with DI. Filtration with DI was continued until the pH of the filtrate was neutral to obtain the H-CP / GO membrane.

[0117] The performance of the obtained H-CP / GO membrane was tested:

[0118] At a pressure of 1 bar, the H-CP / GO membrane obtained in Example 7 exhibited a separation factor of 5.7 and a flux of 29.8 L / (m³) for a mixture of methyl orange (negatively charged molecules) and methylene blue (positively charged molecules) at a concentration of 20 mg / L in an aqueous system. 2 h bar).

[0119] Comparative Example 1

[0120] A GO dispersion with a concentration of 5 mg / L was prepared using DI and then sonicated to ensure uniform dispersion.

[0121] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate. The membrane was soaked in DI for 12 h before use, and then filtered through 300 mL of DI to remove impurities from the membrane.

[0122] 100 mL of GO casting solution was loaded onto the substrate membrane under pressure of 1 bar by pressure filtration, and the GO membrane was obtained after drying for 12 h.

[0123] The performance of the obtained GO membrane was tested:

[0124] At a pressure of 1 bar, the GO membrane obtained in Comparative Example 1 exhibited a 99.4% rejection rate for 20 mg / L methylene blue in an aqueous system, with a flux of 3.3 L / (m²). 2 h bar).

[0125] Comparative Example 2

[0126] In Comparative Example 2, the preparation of CP nanodots and the formulation of GO-doped CP casting solution were the same as in Example 1.

[0127] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate. The membrane was soaked in DI for 12 h before use, and then filtered through 300 mL of DI to remove impurities from the membrane.

[0128] The casting solution was loaded onto the base membrane at a pressure of 1 bar by pressure filtration.

[0129] The performance of the obtained membrane material was tested:

[0130] At a pressure of 1 bar, the membrane obtained in Comparative Example 2 exhibited a 99.5% rejection rate for 20 mg / L methylene blue in an aqueous system, with a flux of 23.5 L / (m²). 2 h bar).

[0131] Comparative Example 3

[0132] A GO dispersion with a concentration of 5 mg / L was prepared using DI and then sonicated to ensure uniform dispersion.

[0133] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate. The membrane was soaked in DI for 12 h before use, and then filtered through 300 mL of DI to remove impurities from the membrane.

[0134] 100 mL of GO casting solution was loaded onto the substrate membrane under pressure of 1 bar by pressure filtration, and the GO membrane was obtained after drying for 12 h.

[0135] The performance of the obtained GO membrane was tested:

[0136] At a pressure of 1 bar, the GO membrane obtained in Comparative Example 3 had a separation factor of 12.4 and a flux of 2.9 L / (m³) for a mixture of Acid Red and Rhodamine B at a concentration of 20 mg / L in the aqueous system. 2 h bar).

[0137] Comparative Example 4

[0138] The preparation of CP nanodots and the formulation of GO-doped CP casting solution were the same as in Example 1.

[0139] A commercial nylon membrane with a pore size of 0.22 μm was used as the substrate. The membrane was soaked in DI for 12 h before use, and then filtered through 300 mL of DI to remove impurities from the membrane.

[0140] The casting solution was loaded onto the base membrane at a pressure of 1 bar by pressure filtration.

[0141] The performance of the obtained membrane material was tested:

[0142] At a pressure of 1 bar, the membrane obtained in Comparative Example 4 had a separation factor of 1.5 and a flux of 20.4 L / (m³) for a mixture of Acid Red and Rhodamine B at a concentration of 20 mg / L in the aqueous system. 2 h bar).

[0143] The morphology of the graphene oxide molecular filtration membrane prepared in Example 1, a representative example, was analyzed, and its structure is as follows: Figure 2 As shown, nanocavities are formed inside the membrane, which maintains a regular two-dimensional stacked configuration even after CP intercalation and acid dissolution treatment. These nanocavities provide additional water flow channels, thereby improving membrane permeability. The two-dimensional stacked configuration ensures excellent membrane sieving performance.

[0144] The interlayer spacing of the films prepared in representative Examples 1 and Comparative Examples 1 and 2 was analyzed, such as... Figure 3 As shown. Compared with the pure GO membrane (interlayer spacing: 0.84 nm), the H-CP / GO membrane prepared in Example 1 of this disclosure has a significantly increased interlayer spacing (1.61 nm), which allows for molecular permeation and charge-selective separation.

[0145] The charge density of films prepared in representative Examples 1 and Comparative Examples 1 and 2 was analyzed, such as... Figure 4 As shown. Compared with pure GO membrane, the H-CP / GO membrane prepared in Example 1 of this disclosure has a higher charge density due to the oxidative etching of the GO sheets by hydroxyl radicals generated by CP decomposition, thus enhancing the charge sieving ability of the membrane.

[0146] Dye rejection tests were performed on the membranes prepared in Example 1 and Comparative Examples 1 and 2, and the results are as follows: Figure 5 As shown. The H-CP / GO membrane prepared in Example 1 of this disclosure has a methylene blue rejection rate of 99.1% and a permeability of 46.3 L / (m). 2 h bar). In contrast, the membrane prepared in the comparative example, with a similar retention rate, exhibited permeability of only 3.3 (pure GO membrane) and 23.5 L / (m²). 2 h bar)(CP / GO membrane). Clearly, the graphene oxide molecular filtration membrane prepared in Example 1 of this disclosure has a better trade-off between permeability and retention rate.

[0147] The selective separation performance of the H-CP / GO membrane prepared in this disclosure for substances of similar size was tested and compared with that of pure GO membrane and CP / GO membrane (Example 5 and Comparative Examples 3 and 4). The results are as follows: Figure 6 As shown. The H-CP / GO membrane prepared in this disclosure achieves a separation factor of 24.0 for a mixture of negatively charged acid red and neutral rhodamine B, both with molecular weights close to 500 Da, and a permeability of 46.0 L / (m²). 2 (h bar). The separation factor is approximately twice that of a pure GO membrane and 16 times that of a CP / GO membrane. The permeability is approximately 16 times that of a pure GO membrane and twice that of a CP / GO membrane. Therefore, the graphene oxide molecular filtration membrane prepared in this disclosure can more accurately and rapidly separate substances of similar size but different charges.

[0148] The separation performance of the H-CP / GO membrane prepared in this disclosure for a mixture of acid red and tetracycline, and a mixture of methyl orange and methylene blue was tested (Examples 6 and 7). The UV spectral results are as follows: Figure 7 , 8 As shown, where, Figure 7 The dot plot in the filtrate is the UV spectrum of pure tetracycline. Figure 8 The dot plot in the filtrate is the UV spectrum of a pure methylene blue solution. After filtering the mixed solution using the H-CP / GO membrane proposed in this disclosure, the characteristic peaks of negatively charged substances in the filtrate disappeared, while only the characteristic peaks of neutral or positively charged substances were retained, indicating that the selective separation behavior of the H-CP / GO membrane is universal.

[0149] In summary, based on the membrane separation performance data from Examples 1-7 and Comparative Examples 1-4 of this disclosure, the H-CP / GO membrane proposed in this disclosure achieves highly efficient and selective separation of molecules of similar size but different charges, and this selective separation performance has good versatility. Furthermore, the H-CP / GO membrane can effectively retain negatively charged pollutants in water and exhibits ultra-high permeability. These excellent properties make it a potential candidate for applications in water purification, drug separation, and resource recovery.

[0150] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for preparing a graphene oxide molecular filtration membrane, comprising: Under stirring conditions, polyvinylpyrrolidone was added to a copper salt solution and mixed. Then, an alkaline solution and a hydrogen peroxide solution were added sequentially to carry out the reaction. After the reaction was completed, the solution was washed and freeze-dried to obtain copper peroxide nanoparticle powder. Graphene oxide dispersion and copper peroxide nanoparticle dispersion were prepared separately. The pH of the graphene oxide dispersion was adjusted to neutral and then mixed with the copper peroxide nanoparticle dispersion. Ferrous solution was added under stirring and mixed evenly to obtain casting solution. The casting solution was loaded onto a microfiltration membrane by filtration to obtain a copper peroxide nanodot intercalated graphene oxide membrane. The intercalated copper peroxide nanodots were removed by acid dissolution, and the membrane was washed with deionized water until neutral to obtain a graphene oxide molecular filter membrane. The concentration of the graphene oxide dispersion is 2.5–10 mg / L; The concentration of the copper peroxide nanodot dispersion is 200–2000 mg / L; The volume ratio of the graphene oxide dispersion to the copper peroxide nanodot dispersion is 1:

1.

2. The preparation method according to claim 1, wherein, The concentration of the copper salt solution is 0.01 mol / L, the concentration of the alkali solution is 0.02 mol / L, and the concentration of the hydrogen peroxide is 30%. The ratio of the volume of the copper salt solution, the polyvinylpyrrolidone, the alkali solution, and the hydrogen peroxide is 5 mL: 0.5 g: 5 mL: 0.1 mL. The volumes of the polyvinylpyrrolidone, the alkali solution, and the hydrogen peroxide are adjusted based on the volume of the copper salt solution.

3. According to the preparation method of claim 1, the pH of the neutral graphene oxide dispersion is 7-8 before mixing with the copper peroxide nanodot dispersion.

4. The preparation method according to claim 1, wherein, The concentration of the ferrous solution in the casting solution is 0.05–0.5 mmol / L.

5. The preparation method according to claim 1, wherein, The microfiltration membrane is an acid-resistant material with a pore size in the range of 0.11 to 0.45 μm.

6. The preparation method according to claim 1, wherein, The filtration includes vacuum filtration or pressure filtration, and the pressure range of the filtration is 0.2 to 2 bar.

7. The preparation method according to claim 1, wherein, The mass concentration of the acid solution in the acid dissolution operation ranges from 0.05% to 2%, and the acid dissolution operation time is 2 to 6 hours.

8. A graphene oxide molecular filtration membrane obtained by the preparation method according to any one of claims 1 to 7, wherein, The structure of the graphene oxide molecular filter membrane is a layered stacked structure with nanocavities inside the membrane.

9. The application of a graphene oxide molecular filtration membrane prepared by any one of claims 1 to 7 in the field of membrane separation, wherein, The membrane separation field includes water purification, drug separation, or resource recovery.

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