A bottom-up etched graphene oxide composite nanofiltration membrane and application thereof
By employing bottom-up etching technology for graphene oxide composite nanofiltration membranes, the problem of difficult interlayer channel control in graphene oxide membranes has been solved, resulting in high-flux, high-selectivity, and high-stability graphene oxide composite membranes suitable for the treatment of dyeing and printing wastewater and brackish water.
Patent Information
- Application Number
- CN202611192814.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-07
- Publication Date
- 2026-11-03
AI Technical Summary
Existing graphene oxide films have small interlayer channels that are difficult to control precisely, resulting in low water flux, easy swelling leading to decreased selectivity, and insufficient long-term stability. Existing preparation methods are unable to construct uniform and controllable nanopores.
A bottom-up etching method was used to prepare a VD-MOF composite membrane via vapor deposition. An oxidant was added to an aqueous solution of graphene oxide for etching to form a graphene oxide composite nanofiltration membrane, thereby controlling the nanopore size and enhancing the membrane structure stability.
The graphene oxide composite membrane achieves high throughput, high selectivity, and high stability, making it suitable for the treatment of dyeing and printing wastewater and the remediation of brackish water, thus improving water treatment efficiency.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane materials technology, and in particular to a bottom-up selectively etched graphene oxide composite membrane and its applications in areas such as dyeing and printing wastewater treatment and brackish water remediation. Background Technology
[0002] With the acceleration of industrialization, water pollution has become increasingly severe, especially industrial wastewater containing dyes, heavy metal ions, and recalcitrant organic matter, posing a serious threat to the environment and human health. Membrane separation technology, particularly nanofiltration, has shown great application potential in water treatment due to its advantages such as high efficiency, energy saving, and ease of operation. Traditional polymer nanofiltration membranes have limitations in selectivity, flux, and antifouling performance, making it difficult to simultaneously achieve high flux and high rejection rate. Graphene oxide, as a two-dimensional nanomaterial, is considered an ideal building block for constructing high-performance separation membranes due to its abundant oxygen-containing functional groups on its sheets, excellent mechanical strength, ultrathin two-dimensional nanochannels, and functionalizable surface properties. Layered membranes formed by stacking graphene oxide sheets can have interlayer spacing that serves as nanochannels for molecular or ion transport, enabling precise sieving of substances of different sizes. However, existing graphene oxide membranes still face some key challenges: (1) The interlayer channel size of pure graphene oxide membranes is small and difficult to control precisely, which usually results in low water flux; (2) The swelling phenomenon of graphene oxide sheets in aqueous solution will increase the interlayer spacing, leading to a decrease in separation selectivity and insufficient long-term stability; (3) Existing preparation methods (such as simple vacuum filtration, spin coating, etc.) are difficult to accurately construct graphene oxide separation layers with uniform and controllable nanopores on a macroscopic scale.
[0003] To overcome the aforementioned problems, researchers have explored various strategies, such as inserting nanoparticles or molecular spacers between graphene oxide layers to stabilize and regulate the interlayer spacing, or physically / chemically etching graphene sheets to introduce nanopores. However, these methods often suffer from complex processes, uneven pore size distribution, potential secondary contamination from introduced substances, or weakened membrane mechanical strength. A simple and controllable method to construct uniformly sized and tunable surface nanopores in graphene oxide separation layers, while simultaneously enhancing membrane structural stability, is crucial for achieving high-performance graphene membranes. Therefore, developing a novel composite membrane preparation technology capable of precisely controlling GO membrane pore size, simultaneously improving water flux and selectivity, and enhancing structural stability is of great significance for promoting the practical application of advanced separation membranes. This invention aims to solve the aforementioned technical problems. Summary of the Invention
[0004] The purpose of this invention is to overcome the technical shortcomings of existing graphene oxide-based separation membranes, such as small and difficult-to-control interlayer channel size, low water flux, easy swelling in aqueous environments leading to decreased selectivity, and insufficient long-term stability. Specifically, this invention provides a top-down selectively etched graphene oxide composite membrane with a controllable preparation method, stable structure, and excellent separation performance. By precisely controlling the nanopore size of the graphene oxide surface through free radical content, a unified high flux, high selectivity, and high stability are achieved, expanding its application in the field of high-efficiency water treatment.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a bottom-up etched graphene oxide composite nanofiltration membrane, prepared by the following method: A porous filter membrane and a metal-organic precursor are subjected to vapor deposition at 90-180℃ (preferably 110℃-150℃) for 2-6 hours (preferably 2-4 hours) to obtain a VD-MOF composite membrane. Graphene oxide powder is dispersed in water to obtain a graphene oxide aqueous solution. The graphene oxide aqueous solution is poured onto the surface of the VD-MOF composite membrane and subjected to vacuum filtration to form a graphene oxide layer, thus obtaining a GO / VD-MOF composite membrane. The composite membrane is immersed in an oxidant solution for etching to obtain the bottom-up graphene oxide composite nanofiltration membrane; the metal-organic precursor is ferrocene, ferric acetylacetone, zirconium dichlorocerocene, or trimethyl(methylcyclopentadienyl)platinum; the loading of the metal-organic precursor, based on the theoretical mass of the metal elements contained, is 0.05%~10% (preferably 0.5%~5%) of the mass of the porous filter membrane; the amount of graphene oxide used, based on the surface area of the porous filter membrane, is 5 μg / cm². 2 ~50μg / cm 2 (Preferred concentration: 10~20 μg / cm) 2 ).
[0006] Furthermore, the graphene oxide is dispersed in deionized water and then subjected to ultrasonic treatment to obtain the graphene oxide aqueous solution.
[0007] Furthermore, the porous filter membrane is a polyvinylidene fluoride membrane, a polytetrafluoroethylene membrane, a polyethersulfone membrane, a polyacrylonitrile membrane, or a ceramic membrane.
[0008] Furthermore, the amount of graphene oxide added to the aqueous solution of graphene oxide is 0.01~5 g / L (preferably 0.02~2 g / L) based on the volume of water.
[0009] Furthermore, the oxidant solution is a hydrogen peroxide solution or a persulfate solution (preferably a potassium persulfate solution).
[0010] Furthermore, the mass concentration of the hydrogen peroxide solution is 0.001~15%, and the concentration of the persulfate solution is 0.5mmol / L-200mmol / L.
[0011] Furthermore, the etching time is 0.5h-6h (preferably 2h-4h).
[0012] Furthermore, the thickness of the porous filter membrane is 50μm-200μm.
[0013] This invention also provides an application of a bottom-up etched graphene oxide composite nanofiltration membrane in removing dye molecules, high-valence salt ions, or small organic molecules from water. The specific application method is as follows: wastewater containing 4BS dye, Na2SO4, and NaCl is contacted with the composite membrane for filtration, causing the 4BS dye to be retained.
[0014] Compared with the prior art, the present invention has the following significant advantages: (1) The pore size is precisely adjustable and the separation performance is excellent: By controlling the etching conditions of the oxidant, uniform and controllable nanopores can be directly introduced on the surface of the graphene oxide separation layer, which effectively broadens the molecular / ion transport channels. While significantly improving the water flux, the synergistic sieving effect of nanopores and interlayer nanochannels maintains or even enhances the high rejection rate of the membrane for dye molecules, high-valence salt ions and small organic molecules, achieving a balance between high flux and high selectivity. Moreover, the preparation method is controllable and efficient. The free radical etching reaction is carried out under visible light or no light conditions, with low energy consumption.
[0015] (2) Broad application prospects: The prepared porous graphene oxide composite nanofiltration membrane is particularly suitable for the deep treatment and resource recovery of wastewater containing dyes, high-valent salts and small molecule organic pollutants, and has broad application potential in the water treatment field of printing and dyeing, pharmaceuticals, fine chemicals and other industries. Attached Figure Description
[0016] Figure 1 Example 1: TEM images of the graphene oxide composite film: (a) Transmission of the surface graphene before etching; (b) Transmission of the surface graphene after etching. Detailed Implementation
[0017] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, the embodiments described below are only some embodiments of the present invention, not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.
[0018] Example 1
[0019] (1) A flat porous polyvinylidene fluoride (PVDF) filter membrane from Haining Yibo Filter Material Factory was used. The membrane pore size was 0.22 μm, the membrane diameter was 50 mm, and the weight of a single membrane was 0.15 g. The graphene oxide dispersant used was deionized water. 500 ml of deionized water and 1 g of graphene oxide powder were mixed and ultrasonically mixed to obtain the graphene oxide aqueous solution concentration for later use. (2) Two polyvinylidene fluoride porous filter membranes and 0.5 mmol ferrocene were added to a hydrothermal reactor and placed in an oven at 120°C for 2 hours. After the reaction was completed, the hydrothermal reactor was removed and placed on the experimental table to cool naturally to room temperature. Ethanol was added for ultrasonic cleaning to remove excess metal organic matter on the surface of the base membrane, and PVDF / Fe(C5H5)2 membrane was obtained. (3) Take 50 μl of the prepared graphene oxide aqueous solution and add it to 500 ml of deionized water for ultrasonic dispersion for 10 min. First, lay a single PVDF / Fe(C5H5)2 membrane on the support layer of the sand core filtration device and seal the edges with a silicone sealing ring. Slowly pour the ultrasonic graphene oxide aqueous solution into the filtration funnel, turn on the circulating water vacuum pump, and precisely control the system vacuum degree to -0.1 MPa by adjusting the tail gas vent valve. Assemble it on the surface of the PVDF / Fe(C5H5)2 membrane by the above filtration deposition method, and then dry it to obtain a PVDF / Fe(C2H5)2 / GO composite membrane. (4) Combine PVDF / Fe(C5H5)2 / GO The composite membrane was placed in a beaker, and 50 ml of 1 μl / ml hydrogen peroxide (30%) was added as an oxidant. The membrane was soaked for 30 min, and then washed and dried to obtain a porous PVDF / Fe(C5H5)2 / PGO composite membrane.
[0020] Example 2
[0021] Except for the following technical features, the other technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the porous base membrane in step (1) is a polytetrafluoroethylene (PTFE) membrane; Example 3 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, in step (2), iron acetylacetone is deposited on the porous base film; Example 4 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, in step (2), trimethyl (methylcyclopentadienyl)platinum is deposited on the porous base film; Example 5 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the oven temperature in step (2) is 90°C; Example 6 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the oven temperature in step (2) is 150°C; Example 7 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the oven drying time in step (2) is 4 hours; Example 8 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the oven drying time in step (2) is 6 hours; Example 9 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the oxidant in step (4) is a 1.5 mmol / L potassium persulfate aqueous solution; Example 10 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the hydrogen peroxide concentration in step (4) is 5 μl / ml; Example 11 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the hydrogen peroxide concentration in step (4) is 10 μl / ml; Example 12 Except for the following technical features, the technical features in this embodiment are the same as those in Embodiment I: In this embodiment, the soaking time in step (4) is 1 hour; Comparative Example 1 The difference from Example 1 is that steps (2) and (4) are no longer performed. Comparative Example 2 The difference from Example 1 is that step (2) is no longer performed. The composite membranes prepared in Examples 1-12 and the composite membranes prepared in Comparative Examples 1-2 were subjected to flux tests and dye rejection tests.
[0022] (1) Measure the pure water flux of the composite membrane
[0023] First, pour deionized water into the water tank to be treated. Then, place the membrane into the device. After turning on the device, adjust the pressure to 0.1 MPa and the flow rate to 50 L / h. Record the time required to collect 2 mL of pure water. Calculate the pure water flux of the membrane using the following formula:
[0024] V represents the volume of liquid collected within a certain time period, which is 2 mL here; P represents the operating pressure; and S is the membrane filtration area, which is 7.065 cm² here. 2 t represents the time taken to collect a certain volume of pure water.
[0025] (2) Measure the dye rejection rate of the composite membrane
[0026] Direct acid-resistant red 4BX (molecular weight 790.69) dye was selected as the organic pollutant in the water. After collecting the permeate, the absorbance at the corresponding maximum absorption wavelength was measured using a UV spectrophotometer. The rejection rate of the composite membrane was calculated using the following formula:
[0027] A0 is the absorbance of the original solution, and A1 is the absorbance of the transmitted liquid at the corresponding maximum absorption wavelength: 4BX is 495nm.
[0028] (3) Measure the salt rejection rate of the composite membrane.
[0029] Where C p and C f These represent the concentrations of the solute in the permeate and the solute in the feed solution (mg / L), respectively. For solute measurement, the salt concentration (NaCl, Na2SO4) was measured using a conductivity meter. When the salt concentration in the solution was too high, the original solution was diluted a certain factor before measuring the conductivity meter.
[0030] Table 1
Claims
1. A bottom-up etched graphene oxide composite nanofiltration membrane, characterized in that, Prepared by the following method: A porous filter membrane and a metal-organic precursor are subjected to vapor deposition at 90-180℃ for 2-6 hours to obtain a VD-MOF composite membrane. Graphene oxide powder is dispersed in water to obtain a graphene oxide aqueous solution. The graphene oxide aqueous solution is poured onto the surface of the VD-MOF composite membrane and subjected to vacuum filtration to form a graphene oxide layer, resulting in a GO / VD-MOF composite membrane. The GO / VD-MOF composite membrane is then immersed in an oxidant solution for etching to obtain the bottom-up graphene oxide composite nanofiltration membrane. The metal-organic precursor is ferrocene, ferric acetylacetone, zirconium dichlorocerocene, or trimethyl(methylcyclopentadienyl)platinum. The loading amount of the metal-organic precursor, based on the theoretical mass of the metal elements contained, is 0.05%~10% of the mass of the porous filter membrane. The amount of graphene oxide used, based on the surface area of the porous filter membrane, is 5 μg / cm². 2 ~50μg / cm 2 .
2. The bottom-up etched graphene oxide composite nanofiltration membrane as described in claim 1, characterized in that, The graphene oxide powder is dispersed in deionized water and then ultrasonically treated to obtain the graphene oxide aqueous solution.
3. The bottom-up etched graphene oxide composite nanofiltration membrane as described in claim 1, characterized in that, The porous filter membrane is a polyvinylidene fluoride membrane, a polytetrafluoroethylene membrane, a polyethersulfone membrane, a polyacrylonitrile membrane, or a ceramic membrane.
4. The bottom-up etched graphene oxide composite nanofiltration membrane as described in claim 1, characterized in that, The amount of graphene oxide added to the aqueous solution of graphene oxide is 0.01~5 g / L based on the volume of water.
5. The bottom-up etched graphene oxide composite nanofiltration membrane as described in claim 1, characterized in that, The oxidant solution is a hydrogen peroxide solution or a persulfate solution.
6. The bottom-up etched graphene oxide composite film as described in claim 5, characterized in that, The hydrogen peroxide solution has a mass concentration of 0.001-15%, and the persulfate solution has a concentration of 0.5 mmol / L-200 mmol / L.
7. The bottom-up etched graphene oxide composite nanofiltration membrane as described in claim 1, characterized in that, The etching time is 0.5h-6h.
8. The application of the bottom-up etched graphene oxide composite nanofiltration membrane as described in claim 1 in removing dye molecules, high-valence salt ions or small organic molecules from water.