Preparation and application of a GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane with self-cleaning ability

Abstract

The application belongs to the field of graphene oxide-based nanofiltration membrane sewage treatment, and particularly relates to preparation and application of a GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane with self-cleaning capability. The application realizes dynamic adjustment of membrane layer spacing and synergistic effect of self-cleaning function by integrating temperature response material PNIPAM and photocatalytic material ZnO. The membrane has a significantly improved water flux at a critical temperature of 32 DEG C, a rejection rate of more than 90% for various dyes and inorganic salts, and a pollutant degradation recovery rate of up to 98.88% under ultraviolet light. The composite nanofiltration membrane has high efficient separation, intelligent control and environmental protection characteristics, and is significantly superior to a traditional GO membrane in terms of rejection performance, antifouling property and applicability, thereby providing an efficient, intelligent and low maintenance cost solution for industrial wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of graphene oxide-based nanofiltration membrane wastewater treatment, specifically relating to the preparation and application of a GO-ZnO / PNIPAM temperature-responsive nanofiltration membrane with self-cleaning capabilities. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Graphene oxide (GO) has attracted considerable attention in water purification research due to its high specific surface area and abundant chemical functional groups (epoxy, hydroxyl, carboxyl, and carbonyl groups, etc.) in its two-dimensional nanosheet structure. However, the application efficiency of traditional graphene oxide-based nanofiltration membranes is limited by problems such as fixed interlayer spacing, easy surface fouling, and poor water permeability and retention.

[0004] In existing technologies, single GO membranes lack dynamic pore size adjustment capabilities, and membrane fouling leads to high cleaning costs. Although fouling can be mitigated through physical cleaning, chemical solvents, blending modification, and surface modification, these methods still suffer from drawbacks such as high energy consumption and complex processes. While photocatalysis is environmentally friendly, the integration effect of photocatalytic materials with membranes is limited, failing to simultaneously achieve efficient retention and self-cleaning functions. Furthermore, the hydrophilic and hydrophobic static properties of traditional membrane materials restrict their adaptability to different temperature environments. Therefore, there is an urgent need for a composite nanofiltration membrane that combines intelligent response and self-cleaning capabilities. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method for preparing and applying a temperature-responsive GO-ZnO / PNIPAM nanofiltration membrane with self-cleaning capabilities. This invention introduces a temperature-responsive polyisopropylacrylamide (PNIPAM) polymer, combined with the photocatalytic and mechanical enhancement properties of GO-ZnO, to propose a novel ternary composite nanofiltration membrane that achieves adjustable water flux, multiple antifouling mechanisms, and a synergistic effect of photocatalytic self-cleaning.

[0006] Specifically, the present invention provides the following technical solution:

[0007] A first aspect of the present invention provides a GO-ZnO / PNIPAM temperature-responsive nanofiltration membrane with self-cleaning capability, the GO-ZnO / PNIPAM temperature-responsive nanofiltration membrane comprising:

[0008] A layered matrix composed of graphene oxide nanosheets;

[0009] A graphene oxide-zinc oxide composite material uniformly embedded between the graphene oxide layers;

[0010] polyisopropyl acrylamide temperature response polymer distributed between and on the graphene oxide layers;

[0011] The graphene oxide-zinc oxide composite material is obtained by in-situ crystal growth of zinc oxide nanorods and graphene oxide; the mass ratio of the zinc oxide and the graphene oxide is 10:1 to 13:1.

[0012] The volume ratio of the polyisopropyl acrylamide and the graphene oxide-zinc oxide composite material is 1:3 to 3:1.

[0013] Preferably, the mass ratio of the zinc oxide nanorods and the graphene oxide is 13:1; and the volume ratio of the polyisopropyl acrylamide and the graphene oxide-zinc oxide composite material is 2:1. If the ratio is too high (such as 1:4), the PNIPAM is excessive, which may block the channels between the GO layers; if the ratio is too low (such as 5:1 or 4:1), the PNIPAM is insufficient, the temperature response is weak, and the photocatalytic components are few, which affects the self-cleaning ability.

[0014] Preferably, the zinc oxide nanorods have a length of 50 to 200 nm and a diameter of 10 to 30 nm, and are uniformly dispersed between the graphene oxide layers by physical intercalation.

[0015] Preferably, the graphene oxide composite nanofiltration membrane has a surface roughness Ra of less than or equal to 42 and a profile height quadratic mean Rq of less than or equal to 51.6.

[0016] Preferably, when the critical solution temperature of the polyisopropyl acrylamide is less than 32°C, the water contact angle of the graphene oxide composite nanofiltration membrane is 34.13 to 64.35, and the water flux is 20.87 to 24.47 ; when the temperature is higher than 32°C, the water contact angle is 40.28 to 82.43°, and the water flux is 48.61 to 55.18 .

[0017] Preferably, the graphene oxide composite nanofiltration membrane has a rejection rate of rhodamine B, congo red, methylene blue and Evans blue of greater than or equal to 81%, and a rejection rate of sodium nitrite of 74.69% to 77.82%.

[0018] Preferably, after the graphene oxide composite nanofiltration membrane is subjected to photocatalytic self-cleaning treatment, the highest recovery rate of the water flux is 56.17% to 98.88%.

[0019] In a second aspect, the application provides a preparation method of the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane with self-cleaning ability, which comprises the following steps:

[0020] S1, mixing the zinc chloride solution and the graphene oxide solution after ultrasonic exfoliation, adding the sodium hydroxide solution dropwise after ultrasonic treatment, and performing a standing reaction, to obtain a graphene oxide-zinc oxide (GO-ZnO) composite material through filtering, washing and drying;

[0021] S2, mixing the N-isopropyl acrylamide monomer, the azobisisobutyronitrile initiator and the benzene solution, performing a water bath reflux reaction, dissolving the reflux product in acetone after removing benzene by evaporation, and then precipitating the polymer by adding n-hexane to obtain a poly-N-isopropyl acrylamide temperature-responsive polymer (PNIPAM);

[0022] S3, dispersing the graphene oxide-zinc oxide composite material in the graphene oxide solution, performing ultrasonic treatment and then standing for heat preservation to obtain a physically intercalated GO-ZnO solution, and then mixing the solution with the poly-N-isopropyl acrylamide temperature-responsive polymer solution to form a composite film precursor liquid through ultrasonic treatment, and finally drying the composite film precursor liquid by suction filtration to form a film.

[0023] Preferably, in step S1, the concentration of the graphene oxide solution after ultrasonic exfoliation is 0.2-0.3 mg / mL, the concentration of the zinc chloride solution is 0.035-0.045 M, and the concentration of the sodium hydroxide is 0.02-0.03 M.

[0024] Further preferably, the concentration of the graphene oxide solution after ultrasonic exfoliation is 0.25 mg / mL, the concentration of the zinc chloride solution is 0.04 M, and the concentration of the sodium hydroxide is 0.0267 M.

[0025] Preferably, in step S1, the ultrasonic treatment time is 20-40 min, and the standing reaction temperature is 60-90℃ and the time is 5-10 h.

[0026] Preferably, in step S2, the amount of the N-isopropyl acrylamide monomer, the azobisisobutyronitrile initiator and the benzene solution is (3-4) g:(0.05-0.06) g:(15-25) mL, preferably 4 g:0.058 g:20 mL.

[0027] Preferably, in step S2, the water bath reflux temperature is 60-70℃ and the time is 8-12 h.

[0028] Preferably, in step S3, the concentration of the graphene oxide solution is 0.2-0.3 mg / mL, preferably 0.25 mg / mL, the ultrasonic treatment time is 2.5-3.5 h, and the standing temperature is 60-70℃ and the time is 1-2 h.

[0029] Preferably, in step S3, the concentration of the polyisopropyl acrylamide temperature-responsive polymer solution is 0.2-0.3 mg / mL, preferably 0.25 mg / mL.

[0030] Preferably, in step S3, the composite film precursor solution is loaded on a cellulose acetate substrate film with a pore size of 0.2-0.25 μm by vacuum suction filtration, and then naturally air-dried to form a film.

[0031] In a third aspect of the present application, the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane with self-cleaning ability according to the first aspect is applied in industrial wastewater purification or treatment.

[0032] One or more embodiments of the present application have at least the following beneficial effects:

[0033] (1) The present application realizes the design strategy of dual-function synergy of temperature response and self-cleaning of nanofiltration membranes by introducing GO-ZnO and PNIPAM into GO nanofiltration membranes, providing an innovative solution for developing efficient and energy-saving sustainable water treatment technology.

[0034] (2) The temperature-responsive self-cleaning nanofiltration membrane designed in the present application has three core advantages: physical component response (temperature-driven), functional dynamic switching (separation / cleaning mode), and significantly prolonged service life (mechanical-chemical synergistic anti-fouling), which solves the pain points of high energy consumption, single selectivity, and frequent maintenance of traditional membrane technology, and realizes single-membrane step-by-step separation of dyes / salts and dual cleaning of "physical peeling + chemical degradation". BRIEF DESCRIPTION OF DRAWINGS

[0035] The drawings accompanying the specification of the present application serve to provide a further understanding of the present application, and the schematic embodiments of the present application and their descriptions serve to explain the present application and do not constitute an improper limitation on the present application.

[0036] Figure 1 Scanning electron microscope (SEM) image of the graphene oxide-zinc oxide / polyisopropyl acrylamide intelligent response nanofiltration membrane prepared for Example 1 of the present application;

[0037] Figure 2 X-ray photoelectron spectroscopy (XPS) image of the graphene oxide-zinc oxide / polyisopropyl acrylamide intelligent response nanofiltration membrane prepared for Example 1 of the present application;

[0038] Figure 3 Water flux test graph of the sample membrane with different proportions prepared for Example 1 of the present application at different temperatures;

[0039] Figure 4 Dye rejection test graph of the sample membrane with different proportions prepared for Example 1 of the present application;

[0040] Figure 5 Inorganic salt rejection test chart of sample membranes of different proportions prepared for the embodiments of the present application;

[0041] Figure 6 Self-cleaning water flux recovery test chart of sample membranes of different proportions prepared for the embodiments of the present application at different temperatures. DETAILED DESCRIPTION

[0042] It should be noted that the following detailed description is illustrative only and is not intended to limit the present application in any way. Other embodiments of the present application will be readily apparent to those skilled in the art from the following detailed description, in conjunction with the accompanying drawings. As used herein, the term "or" as used herein, without further qualification, is used to describe either a single item, the item apart from items in an "or" list, or a list of items derived from the "or" list mutatis mutandis. Only those limitations of significant consequence are particularly pointed out by the language in which a claim is drafted.

[0043] The protection scheme of the present application is described below through specific examples. It should be noted that these examples are only used to facilitate the understanding of those skilled in the art and should not be regarded as limiting the scope of protection of the present application. Unless otherwise specified, the reagents used in the examples can be obtained by commercial purchase.

[0044] Example 1 The present embodiment provides a graphene oxide-zinc oxide / polyisopropyl acrylamide intelligent response nanofiltration membrane and a preparation method thereof

[0045] (1) Preparation of photocatalytic composite material GO-ZnO: 50 mg of GO was dispersed in 200 mL of pure water, 33.3 mL was taken and then ultrasonically treated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL. Subsequently, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and the mixture was continuously ultrasonically treated for 30 minutes to produce a uniform solution. 0.0267 M NaOH solution was added dropwise to the solution under vigorous stirring, and the mixture was sealed in a glass bottle (60 mL), and was left to stand at 90°C for 6 h, and then naturally cooled to room temperature. Finally, the composite material was filtered, washed with distilled water and ethanol several times, and dried at 80°C for 24 hours.

[0046] (2) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropyl acrylamide monomer was weighed into a 100 mL three-necked flask, 1% of the mass of the monomer was added to the initiator azobisisobutyronitrile (AIBN) (0.058 g), and 20 mL of benzene was added, and the mixture was refluxed in a nitrogen atmosphere at 65°C in a constant temperature water bath for 10 h. The refluxed product was evaporated by heating in a constant temperature water bath at 90°C to remove benzene, and then dissolved in 50 mL of acetone, and then added dropwise into n-hexane. After the reaction was completed, the mixture was filtered and dried in vacuum at 30°C for 48 h to obtain white solid poly-N-isopropyl acrylamide.

[0047] (3) Preparation of GO-ZnO / PNIPAM temperature-responsive nanofiltration membrane: 25 mg of the prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and sonicated for 3 h. Then, it was placed in a 65℃ incubator for 1.5 h to obtain a physically intercalated GO-ZnO solution. A 0.25 mg / mL PNIPAM solution was prepared. The GO-ZnO solution and PNIPAM solution were mixed at a volume ratio of 2:1 to obtain 6 mL of composite membrane precursor solution, which was sonicated for 1 h. The precursor solution was filtered onto a 0.22 μm cellulose acetate substrate membrane using a vacuum filtration device at a pressure of 1 bar. After filtration, the membrane was naturally dried to form the final membrane.

[0048] like Figure 1 The image shown is a scanning electron microscope (SEM) image of the graphene oxide-zinc oxide / polyisopropylacrylamide smart responsive nanofiltration membrane prepared in this embodiment. As can be seen from the image, the membrane surface has many undulations and wrinkles, providing transport channels for the rapid passage of water molecules.

[0049] like Figure 1 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the graphene oxide-zinc oxide / polyisopropylacrylamide smart responsive nanofiltration membrane prepared in this embodiment. The image shows... , and The peaks, their positions and intensity ratios, can be used to determine the state of zinc oxide; the O1s and C1s peaks indicate the presence of oxygen and carbon elements in the sample, which can be used to determine the presence of graphene oxide; the appearance of the N1s peak indicates the presence of nitrogen in the sample. The nitrogen originates from PNIPAM (poly-N-isopropylacrylamide). The figure shows Zn-O bonds, C-C bonds, C-H bonds, C-O bonds, C=O bonds, and N-C bonds, illustrating the GO-ZnO / PNIPAM composite structure.

[0050] Example 2 This embodiment provides a graphene oxide-zinc oxide / polyisopropylacrylamide smart responsive nanofiltration membrane and its preparation method.

[0051] (1) Preparation of photocatalytic composite material GO-ZnO: 50 mg of GO was dispersed in 200 mL of pure water, and 33.3 mL was taken and ultrasonically treated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL. Then, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and the mixture was continuously ultrasonically treated for 30 minutes to produce a uniform solution. A 0.0267 M NaOH solution was added dropwise to the solution under vigorous stirring, and the mixture was sealed in a glass bottle (60 mL), and was left to stand at 90°C for 6 hours, and then was naturally cooled to room temperature. Finally, the composite material was filtered, washed with distilled water and ethanol for several times, and dried at 80°C for 24 hours, to obtain the product.

[0052] (2) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropyl acrylamide monomer was weighed into a 100 mL three-necked bottle, and 1% of the mass of the monomer, i.e. 0.058 g of initiator azobisisobutyronitrile (AIBN) and 20 mL of benzene were added, and the mixture was refluxed in a constant-temperature water bath at 65°C for 10 hours under nitrogen protection. The refluxed product was evaporated by using a constant-temperature water bath at 90°C to remove benzene, and was dissolved in 50 mL of acetone, and then was added dropwise into n-hexane. After the reaction was completed, the product was filtered and dried at 30°C under vacuum for 48 hours, to obtain white solid of poly-N-isopropyl acrylamide.

[0053] (3) Preparation of GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane: 25 mg of prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and ultrasonically treated for 3 hours, and then was placed in a constant-temperature oven at 65°C for 1.5 hours to obtain a physically intercalated GO-ZnO solution. A 0.25 mg / mL PNIPAM solution was prepared, and the GO-ZnO solution and the PNIPAM solution were mixed in a volume ratio of 3:1 to obtain 6 mL of a composite membrane precursor solution, which was ultrasonically treated for 1 hour. The precursor solution was filtered onto a cellulose acetate substrate membrane with a pore size of 0.22 μm by using a vacuum filtration device under a pressure of 1 bar, and was naturally air-dried to form a membrane after the filtration was completed.

[0054] Example 3 The embodiment provides a graphene oxide-zinc oxide / polyisopropyl acrylamide intelligent response nanofiltration membrane and a preparation method thereof

[0055] (1) Preparation of photocatalytic composite material GO-ZnO: 50 mg of GO was dispersed in 200 mL of pure water, and 33.3 mL was taken and then ultrasonically treated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL. Subsequently, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and the mixture was continuously ultrasonically treated for 30 minutes to produce a uniform solution. A 0.0267 M NaOH solution was added dropwise to the solution under vigorous stirring, and the mixture was sealed in a glass bottle (60 mL), and was left to stand at 90°C for 6 hours, and then was naturally cooled to room temperature. Finally, the composite material was filtered, washed with distilled water and ethanol for several times, and dried at 80°C for 24 hours, to obtain the product.

[0056] (2) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropyl acrylamide monomer was weighed into a 100 mL three-necked bottle, and 1% of the mass of the monomer, i.e. 0.058 g of initiator azobisisobutyronitrile (AIBN) and 20 mL of benzene were added, and the mixture was refluxed in a constant-temperature water bath at 65°C for 10 hours under nitrogen protection. The refluxed product was evaporated by using a constant-temperature water bath at 90°C to remove benzene, and was then dissolved in 50 mL of acetone, and was added dropwise into n-hexane. After the reaction was completed, the product was filtered and dried at 30°C under vacuum for 48 hours, to obtain white solid of poly-N-isopropyl acrylamide.

[0057] (3) Preparation of GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane: 25 mg of prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and ultrasonically treated for 3 hours, and then was placed in a constant-temperature oven at 65°C for 1.5 hours to obtain a physically intercalated GO-ZnO solution. A 0.25 mg / mL PNIPAM solution was prepared, and the GO-ZnO solution and the PNIPAM solution were mixed in a volume ratio of 1:1 to obtain 6 mL of a composite membrane precursor solution, which was ultrasonically treated for 1 hour. The precursor solution was filtered onto a cellulose acetate substrate membrane with a pore size of 0.22 μm by using a vacuum filtration device under a pressure of 1 bar, and was naturally air-dried to form a membrane after the filtration was completed.

[0058] Example 4 The embodiment provides a graphene oxide-zinc oxide / polyisopropyl acrylamide intelligent response nanofiltration membrane and a preparation method thereof

[0059] (1) Preparation of photocatalytic composite material GO-ZnO: 50 mg of GO was dispersed in 200 mL of pure water, and 33.3 mL was taken and then ultrasonically treated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL. Subsequently, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and the mixture was continuously ultrasonically treated for 30 minutes to produce a uniform solution. A 0.0267 M NaOH solution was added dropwise to the solution under vigorous stirring, and the mixture was sealed in a glass bottle (60 mL), and was left to stand at 90°C for 6 hours, and then was naturally cooled to room temperature. Finally, the composite material was filtered, washed with distilled water and ethanol for several times, and dried at 80°C for 24 hours, to obtain the product.

[0060] (2) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropyl acrylamide monomer was weighed into a 100 mL three-necked bottle, and 1% of the mass of the monomer, i.e. 0.058 g of initiator azobisisobutyronitrile (AIBN) and 20 mL of benzene were added, and the mixture was refluxed in a nitrogen-protected constant-temperature water bath at 65°C for 10 hours. The refluxed product was evaporated by using a constant-temperature water bath at 90°C to remove benzene, and was then dissolved in 50 mL of acetone, and was added dropwise into n-hexane. After the reaction was completed, the product was filtered and dried at 30°C under vacuum for 48 hours, to obtain white solid of poly-N-isopropyl acrylamide.

[0061] (3) Preparation of GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane: 25 mg of prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and ultrasonically treated for 3 hours, and then was placed in a 65°C incubator for 1.5 hours to obtain a physically intercalated GO-ZnO solution. A 0.25 mg / mL PNIPAM solution was prepared, and the GO-ZnO solution and the PNIPAM solution were mixed in a volume ratio of 1:2 to obtain 6 mL of a composite membrane precursor solution, which was ultrasonically treated for 1 hour. The precursor solution was filtered onto a cellulose acetate substrate membrane with a pore size of 0.22 μm by using a vacuum filtration device under a pressure of 1 bar, and was naturally air-dried to form a membrane after the filtration was completed.

[0062] Example 5 The embodiment provides a graphene oxide-zinc oxide / polyisopropyl acrylamide intelligent response nanofiltration membrane and a preparation method thereof

[0063] (1) Preparation of photocatalytic composite material GO-ZnO: 50 mg of GO was dispersed in 200 mL of pure water, and 33.3 mL was taken and then ultrasonically treated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL. Subsequently, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and continuous ultrasonic treatment was performed for 30 minutes to produce a uniform solution. A 0.0267 M NaOH solution was added dropwise to the solution under vigorous stirring, and the mixture was sealed in a glass bottle (60 mL), placed at 90°C for 6 h, and then naturally cooled to room temperature. Finally, the composite material was filtered, washed with distilled water and ethanol several times, and dried at 80°C for 24 hours.

[0064] (2) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropyl acrylamide monomer was weighed into a 100 mL three-necked bottle, 1% of the mass of the monomer was added to the initiator azobisisobutyronitrile (AIBN) (0.058 g), and 20 mL of benzene was added, and refluxed in a constant temperature water bath at 65°C for 10 h under nitrogen protection. The refluxed product was evaporated by a constant temperature water bath at 90°C to remove benzene and then dissolved in 50 mL of acetone, which was then added dropwise into n-hexane. After the reaction was completed, the product was filtered and dried at 30°C under vacuum for 48 h to obtain white solid poly-N-isopropyl acrylamide.

[0065] (3) Preparation of GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane: 25 mg of prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and ultrasonically treated for 3 h, and then placed in a 65°C incubator for 1.5 h to obtain a physically intercalated GO-ZnO solution. A 0.25 mg / mL PNIPAM solution was prepared, and the GO-ZnO solution and the PNIPAM solution were mixed in a volume ratio of 1:3 to obtain 6 mL of a composite membrane precursor solution, which was ultrasonically treated for 1 h. A vacuum filtration device was used to filter the precursor solution onto a cellulose acetate substrate membrane with a pore size of 0.22 μm under a pressure of 1 bar, and the membrane was naturally dried after filtration to obtain the composite nanofiltration membrane.

[0066] Comparative Example 1 The comparative example provides a composite nanofiltration membrane and a preparation method thereof

[0067] The difference between the comparative example and Example 1 is that the comparative example does not perform step (1) of preparation, and only involves the preparation of a composite membrane of temperature-responsive polymer PNIPAM and graphene oxide solution, and the specific preparation process is as follows:

[0068] (1) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropyl acrylamide monomer was weighed into a 100 mL three-necked flask, 1% of initiator azobisisobutyronitrile (AIBN) corresponding to the mass of the monomer (0.058 g) and 20 mL of benzene were added, and the mixture was refluxed in a constant-temperature water bath at 65°C for 10 h under nitrogen protection. The refluxed product was evaporated by using a constant-temperature water bath at 90°C to remove benzene and then dissolved in 50 mL of acetone, which was then added dropwise into n-hexane. After the reaction was completed, the mixture was filtered and dried at 30°C under vacuum for 48 h to obtain white solid poly-N-isopropyl acrylamide.

[0069] (2) Preparation of GO-PNIPAM temperature intelligent response nanofiltration membrane: a 0.25 mg / mL PNIPAM solution was prepared, and a 6 mL composite membrane precursor solution was obtained by mixing GO solution and PNIPAM solution at a ratio of 1:1 and ultrasonic treatment for 1 h. The precursor solution was filtered onto a 0.22 μm cellulose acetate substrate membrane under a pressure of 1 bar using a vacuum filtration device, and the membrane was naturally dried after filtration to obtain the composite membrane.

[0070] Comparative Example 2 The comparative example provides a composite nanofiltration membrane and a preparation method thereof

[0071] The difference between the comparative example and Example 1 is that the comparative example does not involve step (2) of preparation, but only involves physical intercalation of photocatalytic composite material GO-ZnO into graphene oxide, and then the preparation of the composite membrane. The specific preparation process is as follows:

[0072] (1) Preparation of photocatalytic composite material GO-ZnO: 50 mg of GO was dispersed in 200 mL of pure water, and 33.3 mL of GO solution with a concentration of 0.25 mg / mL was prepared by ultrasonic treatment for 60 minutes. Then, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and the mixture was continuously ultrasonically treated for 30 minutes to produce a uniform solution. Under vigorous stirring, 0.0267 M NaOH solution was added dropwise to the solution, and the mixture was sealed in a glass bottle (60 mL) and left to stand at 90°C for 6 h, and then naturally cooled to room temperature. Finally, the composite material was filtered, washed with distilled water and ethanol several times, and dried at 80°C for 24 h to obtain the photocatalytic composite material.

[0073] (2) Preparation of GO-ZnO temperature-responsive nanofiltration membrane: 25 mg of the prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and sonicated for 3 h. Then, it was placed in a 65℃ incubator for 1.5 h to obtain a physically intercalated GO-ZnO solution. 6 mL of the physically intercalated GO-ZnO solution was taken as the precursor solution for the composite membrane and sonicated for 1 h. The precursor solution was filtered onto a 0.22 μm cellulose acetate substrate membrane using a vacuum filtration device at a pressure of 1 bar. After filtration, the membrane was naturally air-dried to form the final membrane.

[0074] Comparative Example 3 :

[0075] (1) Preparation of photocatalytic composite material GO-ZnO: 50 mg GO was dispersed in 200 mL of pure water, and 33.3 mL of the solution was taken and sonicated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL. Subsequently, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and the solution was sonicated continuously for 30 minutes to produce a homogeneous solution. Under vigorous stirring, 0.0267 M NaOH solution was added dropwise to the solution. The mixture was sealed in a glass bottle (60 mL), allowed to stand at 90 °C for 6 h, and then allowed to cool naturally to room temperature. Finally, the composite material was filtered, washed several times with distilled water and ethanol, and dried at 80 °C for 24 hours to obtain the final product.

[0076] (2) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropylacrylamide monomer was weighed and placed in a 100 mL three-necked flask. 1% of the monomer amount of initiator azobisisobutyronitrile (AIBN) (0.058 g) and 20 mL of benzene were added. The mixture was refluxed in a constant temperature water bath at 65 °C for 10 h under nitrogen protection. The reflux product was evaporated to remove benzene in a constant temperature water bath at 90 °C and dissolved in 50 mL of acetone. Then, it was added dropwise to n-hexane. After the reaction was completed, the mixture was filtered and dried under vacuum at 30 °C for 48 h to obtain poly(N-isopropylacrylamide) as a white solid.

[0077] (3) Preparation of GO-ZnO / PNIPAM temperature-responsive nanofiltration membrane: 25 mg of the prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and sonicated for 3 h. Then, it was placed in a 65℃ incubator for 1.5 h to obtain a physically intercalated GO-ZnO solution. A 0.25 mg / mL PNIPAM solution was prepared. The GO-ZnO solution and PNIPAM solution were mixed at a volume ratio of 1:4 to obtain 6 mL of composite membrane precursor solution, which was sonicated for 1 h. The precursor solution was filtered onto a 0.22 μm cellulose acetate substrate membrane using a vacuum filtration device at a pressure of 1 bar. After filtration, the membrane was naturally air-dried to form the final membrane.

[0078] Comparative Example 4 :

[0079] (1) Preparation of photocatalytic composite GO-ZnO: 50 mg of GO was dispersed in 200 mL of pure water, and 33.3 mL was taken and then ultrasonically treated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL. Subsequently, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and continuous ultrasonic treatment was performed for 30 minutes to produce a uniform solution. A 0.0267 M NaOH solution was added dropwise to the solution under vigorous stirring, and the mixture was sealed in a glass bottle (60 mL), and was left to stand at 90°C for 6 h, and then was naturally cooled to room temperature. Finally, the composite was filtered, washed with distilled water and ethanol several times, and dried at 80°C for 24 hours, to obtain the product.

[0080] (2) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropyl acrylamide monomer was weighed into a 100 mL three-necked bottle, and 1% of the mass of the monomer initiator azobisisobutyronitrile (AIBN) (0.058 g) and 20 mL of benzene were added, and refluxed in a constant temperature water bath at 65°C for 10 h under nitrogen protection. The refluxed product was evaporated by a constant temperature water bath at 90°C to remove benzene, and then dissolved in 50 mL of acetone, and then added dropwise into n-hexane. After the reaction was completed, the product was filtered and dried at 30°C under vacuum for 48 h to obtain white solid poly-N-isopropyl acrylamide.

[0081] (3) Preparation of GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane: 25 mg of prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and ultrasonically treated for 3 h, and then placed in a 65°C incubator for 1.5 h to obtain a physically intercalated GO-ZnO solution. A 0.25 mg / mL PNIPAM solution was prepared, and the GO-ZnO solution and the PNIPAM solution were mixed in a volume ratio of 4:1 to obtain 6 mL of a composite membrane precursor solution, which was ultrasonically treated for 1 h. A vacuum filtration device was used to filter the precursor solution onto a cellulose acetate substrate membrane with a pore size of 0.22 μm under a pressure of 1 bar, and after the filtration was completed, the membrane was naturally air-dried to obtain the product.

[0082] Comparative Example 5 :

[0083] (1) Preparation of photocatalytic composite material GO-ZnO: 50 mg of GO was dispersed in 200 mL of pure water, and 33.3 mL was taken and then ultrasonically treated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL. Subsequently, 33.34 mL of 0.04 M ZnCl2 was added dropwise to the GO solution, and continuous ultrasonic treatment was performed for 30 minutes to produce a uniform solution. A 0.0267 M NaOH solution was added dropwise to the solution under vigorous stirring, and the mixture was sealed in a glass bottle (60 mL), placed at 90°C for 6 h, and then naturally cooled to room temperature. Finally, the composite material was filtered, washed with distilled water and ethanol several times, and dried at 80°C for 24 hours, thereby obtaining the product.

[0084] (2) Preparation of temperature-responsive polymer PNIPAM: 4 g of N-isopropyl acrylamide monomer was weighed into a 100 mL three-necked bottle, 1% of the mass of the monomer was added as an initiator, azobisisobutyronitrile (AIBN) (0.058 g), and 20 mL of benzene was added, and refluxed in a constant temperature water bath at 65°C for 10 h under nitrogen protection. The refluxed product was evaporated by a constant temperature water bath at 90°C to remove benzene and then dissolved in 50 mL of acetone, which was then added dropwise into n-hexane. After the reaction was completed, the product was filtered and dried at 30°C under vacuum for 48 h to obtain white solid poly-N-isopropyl acrylamide.

[0085] (3) Preparation of GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane: 25 mg of prepared GO-ZnO was dispersed in 100 mL of 0.25 mg / mL GO solution and ultrasonically treated for 3 h, and then placed in a 65°C incubator for 1.5 h to obtain a physically intercalated GO-ZnO solution. A 0.25 mg / mL PNIPAM solution was prepared, and the GO-ZnO solution and the PNIPAM solution were mixed at a volume ratio of 5:1 to obtain 6 mL of a composite membrane precursor solution, which was ultrasonically treated for 1 h. A vacuum filtration device was used to filter the precursor solution onto a cellulose acetate substrate membrane with a pore size of 0.22 μm under a pressure of 1 bar, and the membrane was naturally air-dried after filtration to obtain the product.

[0086] Comparative Example 6 :

[0087] 50 mg of GO was dispersed in 200 mL of pure water, and then ultrasonically treated for 60 minutes to prepare a GO solution with a concentration of 0.25 mg / mL, and 6 mL was taken and ultrasonically treated for 1 h. A vacuum filtration device was used to filter the precursor solution onto a cellulose acetate substrate membrane with a pore size of 0.22 μm under a pressure of 1 bar, and the membrane was naturally air-dried after filtration to obtain the product.

[0088] Experimental Example 1 In this experimental example, the contact angles of the graphene oxide, the composite nanofiltration membranes prepared in Examples 1-5 and Comparative Examples 1-6 were measured

[0089] The contact angle test shows that the composite nanofiltration membrane prepared by the embodiment of the application exhibits more hydrophilic properties at a temperature lower than the critical solution temperature of polyisopropyl acrylamide (32°C); at a temperature higher than the critical solution temperature of polyisopropyl acrylamide, the surface wettability of the nanofiltration membrane changes to the hydrophobic direction, and the specific values are shown in Table 1:

[0090] Table 1

[0091]

[0092] According to the data analysis in Table 1, the hydrophilic performance of the filtration film prepared in Example 1 of the application is the most superior, and can realize temperature response, so as to realize the change of the surface contact angle to the change of the water flux. Although Examples 2-5 have a change in the contact angle, the performance is poor. Comparative Examples 1-6 have no change in the contact angle.

[0093] Experimental Example 1 In this test example, the water flux of the composite nanofiltration membrane prepared in Examples 1-5 and Comparative Examples 1-6 is tested

[0094] The water flux of the membrane is tested by drawing deionized water under a vacuum environment of 1 bar. The permeability J of pure water is determined by the formula J=V / (A×t×P).

[0095] The results are shown in Table 2. Figure 3 As can be seen from the water flux test pictures of the nanofiltration membrane at different temperatures, the water flux of the nanofiltration membrane increases with the increase of the temperature, which is due to the fact that the molecular chain of the temperature-responsive material polyisopropyl acrylamide shrinks with the increase of the temperature, resulting in a larger gap, and the specific values are shown in Table 2:

[0096] Table 2

[0097]

[0098] According to the data analysis in Table 2, the water flux performance of the filtration film prepared in Example 1 of the application is the most superior, and although Examples 2-5 have a trend of change in the water flux with the temperature, the water flux performance is poor, which is due to the fact that when the volume ratio of the GO-ZnO solution and the PNIPAM solution in Example 1 is 2:1, the shrinkage of the molecular chain of the PNIPAM and the cooperative effect of the GO layer spacing are the best, so as to realize efficient dynamic flux adjustment.

[0099] Comparative Example 1 has poor water flux performance and no obvious change in water flux due to temperature response, which is likely due to the fact that the PNIPAM molecules are fixed firmly and cannot change their molecular chains under temperature response, thus failing to change the water flux; Comparative Example 2 has water flux performance similar to that of Comparative Example 1 and no temperature response function; Comparative Example 6 has poor water flux performance and no temperature response change.

[0100] Comparative Example 3 has the worst water flux performance and cannot achieve efficient nanofiltration, which is due to the fact that when GO-ZnO is excessive, the zinc oxide nanorods (50-200 nm) are excessively accumulated between the GO layers to form a dense and rigid skeleton, which makes it difficult for the PNIPAM molecules to be fully embedded between the layers and fail to dynamically adjust the channel size through chain contraction / elongation, and the nanorods occupy the transmission path of water molecules, thus increasing the mass transfer resistance.

[0101] Comparative Examples 4 and 5 have certain temperature response effect, but the water flux data is poor, which is due to the fact that when PNIPAM is excessive, the polymer molecular chains are excessively filled between the GO layers and on the surface, which causes the interlayer channels to be blocked by the polymer and the polymers to be intertwined with each other, thus failing to effectively expand the pore size at high temperature and affecting the water flux.

[0102] Experimental Example 2 In this test example, the composite nanofiltration membranes prepared in Examples 1-5 and Comparative Examples 1-6 were tested for membrane rejection performance.

[0103] (1) A 20 ppm organic dye molecule solution was used to test the membrane rejection performance. According to the Beer-Lambert law, the concentration of the dye solution is proportional to its UV-visible absorption rate. The permeate was collected and analyzed using UV-vis absorption spectroscopy (PerkinElmer, Lambda 750 S, USA) to calculate the rejection performance, and the rejection rate (R) was determined by the formula R = (1-C P / C f ) x 100%.

[0104] (2) In order to verify that the GO-ZnO-PNIPAM nanofiltration membrane has inorganic salt rejection capability, a 0.75 mg / mL sodium nitrite solution was used to test the rejection performance. According to the Beer-Lambert law, the concentration of the dye solution is proportional to its UV-visible absorption rate. The permeate was collected and analyzed using UV-vis absorption spectroscopy (PerkinElmer, Lambda 750 S, USA) to calculate the rejection performance, and the rejection rate (R) was determined by the formula R = (1-CP / Cf) x 100%.

[0105] The specific test data are shown in Table 3.

[0106] Table 3

[0107]

[0108] The results are shown in Table 3 and Figure 4 The dye rejection test pictures of the nanofiltration membranes with different proportions are shown in Table 3 and

[0109] The dye rejection performance of Comparative Examples 1 and 2 is relatively poor, and cannot effectively reject dyes; the dye rejection of Comparative Example 6 is poor, and only part of the dyes can meet the nanofiltration standard;

[0110] Comparative Example 3 has poor dye rejection and has certain dye rejection capacity, but cannot meet the nanofiltration membrane standard, which is due to the excessive GO-ZnO that is not effectively dispersed by PNIPAM, leading to aggregation of ZnO nanorods, thereby reducing the effective catalytic site and affecting the photocatalytic efficiency;

[0111] Comparative Examples 4 and 5 have very poor dye rejection and cannot meet the nanofiltration membrane standard, which is due to the excessive PNIPAM covering the active adsorption sites (such as oxygen-containing functional groups and ZnO catalytic sites) of GO-ZnO, thereby causing the dye rejection rate to drop sharply, and the polymer blockage leads to uneven distribution of membrane pores and loss of molecular sieving selectivity.

[0112] Therefore, Comparative Examples 1, 2, 3, 4, and 5 cannot achieve temperature response function and effective rejection of dye molecules.

[0113] The results are shown in Table 3 and Figure 5 The inorganic salt rejection test pictures of the nanofiltration membranes with different proportions are shown in Table 3 and

[0114] Experimental Example 3 In this test example, the self-cleaning performance of the composite nanofiltration membranes prepared in Examples 1 to 5 and Comparative Examples 1 to 6 was tested

[0115] The water flux was tested after vacuum filtration of 20 ppm of RB, CR, MB, EB, MO dyes at 1 bar pressure for 30 minutes, and then the nanofiltration membrane was placed under a UV lamp with a wavelength of 385 nm for 1 hour before testing the water flux, and the self-cleaning performance of the membrane was analyzed by the recovery rate of water flux. The recovery rate was determined by the formula FRR=J C / J O × 100%, and the specific test data are shown in Tables 4-6 (Tables 4-6 are tested at 25, 32, 35°C, respectively):

[0116] Table 4

[0117]

[0118] Table 5

[0119]

[0120] Table 6

[0121]

[0122] The results are shown in Tables 4-6 and Figure 6 The self-cleaning water flux recovery test pictures of the nanofiltration membranes with different proportions at different temperatures show that the highest water flux recovery rate is 91.06%, 89.34%, 98.88%, 74.61%, and 56.17%. With the increase of the environmental temperature and the proportion of the photocatalytic component GO-ZnO, all the recovery rates show an upward trend.

[0123] The nanofiltration membrane prepared in Example 1 has the best self-cleaning performance, and Examples 2-5 have better self-cleaning performance. Comparative Examples 1 and 2 have the worst self-cleaning performance, cannot achieve degradation of pollutants, and cannot extend the service life of the membrane. Among them, Comparative Example 1 does not introduce GO-ZnO composite material, and the membrane lacks photocatalytic active sites (ZnO), so it cannot produce active oxygen free radicals under UV light irradiation, and the pollutants cannot be degraded; Comparative Example 2 has GO-ZnO to provide photocatalytic ability, but lacks the physical peeling synergy of PNIPAM, so that the pollutants cannot be detached from the catalytic sites after being attached;

[0124] Comparative Example 3 has poor self-cleaning performance, and the determination of the self-cleaning ability is poor. The insufficient content of PNIPAM leads to discontinuous molecular chain network, which cannot drive the dynamic change of the interlayer distance, and the excessive ZnO nanorods will excessively accumulate between the GO layers, causing the ZnO nanorods to block the mass transfer path and the ZnO aggregation to reduce the effective catalytic area;

[0125] Comparative Examples 4 and 5 have slightly decreased self-cleaning performance, which is due to the excessive PNIPAM wrapping the ZnO nanorods, hindering the penetration of UV light and the contact of pollutants with the catalytic sites, and the self-cleaning recovery rate is the lowest.

[0126] The above descriptions are only the preferred embodiments of the present application, not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the scope of the present application.

Claims

1. A GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane with self-cleaning ability, characterized in that, The GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane comprises the following components: a layered matrix of graphene oxide nanosheets; a graphene oxide-zinc oxide composite material uniformly embedded between the graphene oxide layers; a poly-N-isopropyl acrylamide temperature response polymer distributed between the graphene oxide layers and on the surface of the graphene oxide; the graphene oxide-zinc oxide composite material is obtained by in-situ crystal growth of zinc oxide nanorods and graphene oxide; the mass ratio of the zinc oxide nanorods to the graphene oxide is 10:1 to 13:1; the volume ratio of the poly-N-isopropyl acrylamide to the graphene oxide-zinc oxide composite material is 1:3 to 3:

1. 2.The GO-ZnO / PNIPAM temperature-intelligent responding nanofiltration membrane of claim 1, wherein, the mass ratio of the zinc oxide nanorods to the graphene oxide is 13:1; the volume ratio of the poly-N-isopropyl acrylamide to the graphene oxide-zinc oxide composite material is 2:

1. 3.The GO-ZnO / PNIPAM temperature-intelligent responding nanofiltration membrane of claim 2, wherein, the length of the zinc oxide nanorods is 50 to 200 nm, the diameter is 10 to 30 nm, and the zinc oxide nanorods are uniformly dispersed between the graphene oxide layers by physical intercalation. 4.The GO-ZnO / PNIPAM temperature-intelligent responding nanofiltration membrane of claim 1, wherein, the surface roughness Ra of the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane is less than or equal to 42, and the profile height quadratic mean Rq is less than or equal to 51.

6. 5.The GO-ZnO / PNIPAM temperature-intelligent responding nanofiltration membrane of claim 1, wherein, The water contact angle of the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane is 34.13-64.35, and the water flux is 20.87-24.47 when the temperature is lower than the critical solution temperature 32°C of polyisopropyl acrylamide ; when the temperature is higher than 32°C, the water contact angle is 40.28-82.43°, and the water flux is 48.61-55.18 . 6.The GO-ZnO / PNIPAM temperature-intelligent responding nanofiltration membrane of claim 1, wherein, the rejection rates of the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane to rhodamine B, congo red, methylene blue and Evans blue are all greater than or equal to 81%, and the rejection rate of the nanofiltration membrane to sodium nitrite is 74.69% to 77.82%.

7. The GO-ZnO / PNIPAM temperature-intelligent nanofiltration membrane according to claim 1, wherein, after the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane is subjected to ultraviolet light catalytic self-cleaning treatment, the highest recovery rate of the water flux is 56.17% to 98.88%.

8. A method for preparing the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane with self-cleaning ability according to any one of claims 1-7, characterized in that, comprises the following steps: S1, mixing a zinc chloride solution and an ultrasonic exfoliated graphene oxide solution, adding a sodium hydroxide solution dropwise after ultrasonic treatment, and then standing for reaction, followed by filtration, washing and drying to obtain a graphene oxide-zinc oxide composite material; S2, mixing N-isopropyl acrylamide monomers, azobisisobutyronitrile initiator and benzene solution, and then performing water bath reflux reaction, evaporating benzene from the reflux product, dissolving the product in acetone, and then dropping the solution into n-hexane to precipitate the polymer to obtain a poly-N-isopropyl acrylamide temperature response polymer; S3, dispersing the graphene oxide-zinc oxide composite material in a graphene oxide solution, ultrasonic treatment, and then standing for heat preservation to obtain a physically intercalated GO-ZnO solution, then mixing the solution with a poly-N-isopropyl acrylamide temperature response polymer solution, ultrasonic treatment to form a composite membrane precursor solution, and finally performing suction filtration and drying to form a membrane.

9. The production method according to claim 8, wherein in step S1, the concentration of the ultrasonic exfoliated graphene oxide solution is 0.2 to 0.3 mg / mL, the concentration of the zinc chloride solution is 0.035 to 0.045 M, and the concentration of the sodium hydroxide solution is 0.02 to 0.03 M.

10. The production method according to claim 8, wherein in step S1, the ultrasonic treatment time is 20 to 40 min; the standing reaction temperature is 60 to 90℃, and the standing reaction time is 5 to 10 h.

11. The production method according to claim 8, wherein in step S2, the amount ratio of the N-isopropyl acrylamide monomers, azobisisobutyronitrile initiator and benzene solution is (3 to 4) g:(0.05 to 0.06) g:(15 to 25) mL.

12. The production method according to claim 11, wherein In step S2, the N-isopropyl acrylamide monomer, azobisisobutyronitrile initiator and benzene solution are used in a ratio of 4 g:0.058 g:20 mL.

13. The production method according to claim 8, wherein The water bath reflux temperature is 60-70°C, and the time is 8-12 hours.

14. The production method according to claim 8, wherein In step S3, the concentration of the graphene oxide solution is 0.2-0.3 mg / mL; the ultrasonic treatment time is 2.5-3.5 h, and the temperature of the incubation and standing is 60-70°C, and the time is 1-2 h.

15. The production method according to claim 14, wherein In step S3, the concentration of the graphene oxide solution is 0.25 mg / mL.

16. The production method according to claim 8, wherein In step S3, the concentration of the polyisopropyl acrylamide temperature-responsive polymer solution is 0.2-0.3 mg / mL.

17. The production method according to claim 16, wherein In step S3, the concentration of the polyisopropyl acrylamide temperature-responsive polymer solution is 0.25 mg / mL.

18. The production method according to claim 8, wherein In step S3, the composite film precursor solution is loaded on a cellulose acetate substrate film with a pore size of 0.2-0.25 μm by vacuum filtration, and then naturally air-dried to form a film.

19. The use of the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane with self-cleaning ability according to any one of claims 1-7 in industrial wastewater treatment.

20. The use of the GO-ZnO / PNIPAM temperature intelligent response nanofiltration membrane with self-cleaning ability according to any one of claims 1-7 in industrial wastewater purification.

Images