Defective sodium titanate nanotube and use thereof

Abstract

The application belongs to the technical field of water treatment, and particularly relates to a defective sodium titanate nanotube and application thereof. The defective sodium titanate nanotube is prepared by taking titanium dioxide and a sodium hydroxide or alkaline sodium salt solution as raw materials, and then introducing oxygen vacancy defects by one-step thermal reduction in a reducing gas atmosphere. The defective sodium titanate nanotube is loaded on a support film material to obtain a defective sodium titanate nanotube catalytic film. The defective sodium titanate nanotube in the catalytic film presents a one-dimensional hollow tubular structure, and can maintain a higher permeation flux. Meanwhile, the surface of the defective sodium titanate nanotube is rich in oxygen vacancy defects, which is conducive to providing more catalytic active sites and enhancing the mass transfer efficiency of ozone and the interfacial reaction activity. Therefore, the catalytic film can efficiently degrade refractory organic pollutants in wastewater, especially ozone-inert organic pollutants, achieves the integration of catalyst separation and pollutant degradation, and provides an efficient solution for water treatment.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology. More specifically, it relates to a defective sodium titanate nanotube and its applications. Background Technology

[0002] Numerous organic chemicals used in human production and daily life, such as industrial solvents, pesticides, dyes, pharmaceuticals, and organic matter in domestic sewage, are frequently detected in water bodies and persist for extended periods. These pollutants have poor biodegradability, resulting in low removal rates with conventional treatment processes. Ozone oxidation, due to its strong oxidizing properties (E...),... 0 With advantages such as high concentration (2.07 V), no secondary pollution, and ease of operation, ozone oxidation is widely used for the degradation of organic compounds in wastewater. However, ozone oxidation alone can only react rapidly with electron-rich organic compounds (such as phenols and amines), while reacting extremely slowly with ozone-inert organic pollutants such as ibuprofen and atrazine. Its direct oxidation efficiency is insufficient, which seriously limits its application in the treatment of recalcitrant wastewater.

[0003] To overcome the aforementioned shortcomings, heterogeneous catalytic ozone oxidation technology has emerged. This technology introduces a solid catalyst to promote ozone decomposition, generating non-selective reactive oxygen species (such as hydroxyl radicals ·OH and singlet oxygen). 1 O2 (and other organic pollutants) can efficiently degrade various ozone-inert organic pollutants, and currently, powdered heterogeneous catalysts are the most widely developed. However, the current mainstream powdered heterogeneous catalysts still face severe challenges in practical applications: difficulty in solid-liquid separation after the reaction, serious catalyst loss, and easy agglomeration and deactivation of active components make it difficult to meet the engineering requirements of continuous flow processing. How to achieve efficient separation, recovery, and reuse of catalysts has become a key bottleneck restricting the industrial application of catalytic ozone oxidation technology.

[0004] Constructing catalytic membrane reactors by loading catalysts onto membrane substrates is an effective strategy for solving the separation and recovery challenges. However, such catalytic membranes still have significant drawbacks in the actual removal of organic pollutants from water: firstly, the intrinsic activity of the catalytic membrane layer is insufficient, making it difficult to activate ozone, resulting in low degradation efficiency and incomplete mineralization of ozone-inert pollutants; secondly, its water permeation flux is low, leading to excessively high filtration resistance in water, which affects the overall catalytic efficiency.

[0005] Therefore, developing a catalytic membrane with both high ozone catalytic activity and high permeation flux has become a key problem that urgently needs to be solved in this field, and is of great significance for promoting the degradation of organic pollutants (especially ozone-inert organic pollutants). Summary of the Invention

[0006] This invention addresses the problems of insufficient catalytic activity, difficulty in solid-liquid separation after reaction, and inability to meet the requirements of continuous flow treatment engineering of existing heterogeneous catalysts used for ozone catalytic oxidation reaction in water treatment, as well as the problems of insufficient catalytic activity, low water permeation flux, and low overall catalytic efficiency of current catalytic membranes. The invention aims to provide a defective sodium titanate nanotube catalytic membrane.

[0007] A second objective of this invention is to provide the application of the defective sodium titanate nanotube catalytic membrane in ozone catalytic oxidation.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution: This invention provides a defective sodium titanate nanotube catalytic membrane, which is prepared by the following steps: S1: Titanium dioxide is dispersed in sodium hydroxide or alkaline sodium salt solution and subjected to hydrothermal reaction at 120~160 ℃. After post-treatment, sodium titanate nanotube precursor is obtained. S2: The sodium titanate nanotube precursor obtained in step S1 is placed in a reducing gas atmosphere and calcined at 450~550℃ to obtain defective sodium titanate nanotubes. S3: Disperse the defective sodium titanate nanotubes obtained in step S2 in water to obtain a dispersion; use a fluoropolymer separation membrane as a filter membrane to filter the dispersion, the defective sodium titanate nanotubes form a catalytic membrane layer with a thickness of 60~80 μm, and the fluoropolymer separation membrane forms a supporting membrane layer, to obtain a catalytic membrane layer-supporting membrane layer, and after drying, obtain the defective sodium titanate nanotube catalytic membrane; The fluoropolymer separation membrane has a pore size of 0.1~0.5 μm.

[0009] This invention discovers that sodium titanate nanotubes are prepared by using titanium dioxide powder and sodium hydroxide or alkaline sodium salt as raw materials, followed by a one-step thermal reduction treatment in a reducing gas atmosphere to introduce oxygen vacancy defects, resulting in defective sodium titanate nanotubes. These defective nanotubes are then used as a catalytic membrane. Due to their one-dimensional hollow tubular structure, these nanotubes exhibit higher permeation flux compared to powdered catalysts, thus possessing superior ozone catalytic oxidation performance, which is beneficial for improving water treatment efficiency in practical applications. Furthermore, compared to defective sodium titanate nanotubes obtained using a liquid-phase reduction method (immersing defective sodium titanate nanotubes in a reducing solution such as sodium borohydride solution) or defective titanium dioxide nanotubes obtained by acid replacement of sodium ions followed by calcination, the defective sodium titanate nanotubes prepared in this invention exhibit superior ozone catalytic oxidation performance, capable of efficiently degrading various organic pollutants, and also demonstrating excellent catalytic degradation performance for ozone-inert organic pollutants that are difficult to degrade, such as ibuprofen and atrazine.

[0010] Preferably, in step S1, the mass-to-volume ratio of titanium dioxide to sodium hydroxide or alkaline sodium salt solution is (3~3.5) g: 70 mL.

[0011] Preferably, in step S1, the concentration of the sodium hydroxide or alkaline sodium salt solution is 8~12 mol / L.

[0012] Preferably, in step S1, the alkaline sodium salt is selected from sodium carbonate and / or sodium bicarbonate.

[0013] Preferably, in step S1, the hydrothermal reaction takes 18 to 30 hours.

[0014] Preferably, in step S1, the post-processing includes washing, drying, and grinding.

[0015] More preferably, in step S1, the washing is to wash the precipitate with water.

[0016] More preferably, in step S1, the volume-to-mass ratio of water to titanium dioxide used for washing is 5 L: (3~3.5) g.

[0017] More preferably, in step S1, the drying is carried out at 40~80 °C.

[0018] Furthermore, in step S2, the wall thickness of the defective sodium titanate nanotube is 2~3 nm.

[0019] Furthermore, in step S2, the inner diameter of the defective sodium titanate nanotube is 5~6 nm.

[0020] Preferably, in step S2, the reducing gas atmosphere includes hydrogen and an inert atmosphere gas.

[0021] More preferably, in step S2, the volume ratio of hydrogen to inert atmosphere gas is (8~12):90.

[0022] More preferably, in step S2, the inert atmosphere gas is selected from at least one of argon, helium, and nitrogen.

[0023] Preferably, in step S2, the calcination time is 1 to 3 hours.

[0024] Preferably, in step S2, the heating rate of the calcination is 3~8 °C / min.

[0025] Preferably, in step S3, the fluoropolymer separation membrane is a polyvinylidene fluoride separation membrane or a polytetrafluoroethylene separation membrane.

[0026] Preferably, in step S3, the drying is performed at 20~30 °C.

[0027] The present invention also provides the application of the defective sodium titanate nanotube catalytic membrane in ozone catalytic oxidation to remove organic pollutants.

[0028] Furthermore, the ozone catalytic oxidation reaction is such that the catalytic film layer in the defective sodium titanate nanotube catalytic film can catalyze the generation of highly reactive hydroxyl radicals (·OH) and / or singlet oxygen from ozone. 1 Highly reactive oxygen species such as O2 are used to achieve efficient and thorough degradation of organic pollutants in water.

[0029] Furthermore, the organic pollutants include ozone-inert compounds.

[0030] Optionally, the organic pollutant includes one or more of acetaminophen, bisphenol A, sulfamethoxazole, amoxicillin, and methylene blue.

[0031] Optionally, the ozone inert compound includes ibuprofen and atrazine.

[0032] The present invention has the following beneficial effects: This invention prepares sodium titanate nanotubes using titanium dioxide and sodium hydroxide or alkaline sodium salt solution as raw materials, followed by a one-step thermal reduction in a reducing gas atmosphere to introduce oxygen vacancy defects. These defective sodium titanate nanotubes are then loaded onto a supporting membrane material to obtain a defective sodium titanate nanotube catalytic membrane. The defective sodium titanate nanotubes in this catalytic membrane exhibit a one-dimensional hollow tubular structure, maintaining a higher permeation flux. Simultaneously, their surface is rich in oxygen vacancy defects, which helps provide more catalytically active sites, enhancing ozone mass transfer efficiency and interfacial reactivity. Therefore, this catalytic membrane can efficiently degrade recalcitrant organic pollutants (especially ozone-inert organic pollutants) in wastewater, achieving integrated treatment of catalyst separation and pollutant degradation, providing a highly efficient solution for water treatment. Attached Figure Description

[0033] Figure 1 The image shows a scanning electron microscope (SEM) image of the defective sodium titanate nanotube catalytic membrane obtained in Example 1.

[0034] Figure 2 This is a transmission electron microscope (TEM) image of the defective sodium titanate nanotubes obtained in Example 1. Figure 2 In the image, A represents a transmission electron microscope image at a scale bar of 50 nm. Figure 2 B in the image is a transmission electron microscope image with a scale bar of 10 nm.

[0035] Figure 3X-ray diffraction (XRD) patterns of the defective sodium titanate nanotube catalytic membrane obtained in Example 1, the defective sodium titanate nanotube obtained in Example 1, the sodium titanate nanotube catalytic membrane obtained in Comparative Example 1, the titanium dioxide powder catalytic membrane obtained in Comparative Example 5, and the polyvinylidene fluoride separation membrane.

[0036] Figure 4 The electron paramagnetic resonance (EPR) spectra of the defective sodium titanate nanotubes obtained in Example 1, the sodium titanate nanotubes obtained in Comparative Example 1, and the titanium dioxide powder obtained in Comparative Example 5 are shown. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0038] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0039] The polyvinylidene fluoride separation membrane used in this invention has a pore size of 0.22 μm and was purchased from Tianjin Jinteng Experimental Equipment Co., Ltd., with product number JTMF0451.

[0040] Example 1: Preparation of defective sodium titanate nanotube catalytic membranes The defective sodium titanate nanotube catalytic membrane is prepared by the following steps: (1) Weigh 3 g of titanium dioxide and add it to 70 mL of 10 mol / L sodium hydroxide solution, and stir continuously for 30 min. Then transfer the mixture to a polytetrafluoroethylene-lined high-pressure reactor and carry out a hydrothermal reaction at 140 ℃ for 24 h. After the reaction is completed, collect the precipitate by filtration, wash it with 5 L of deionized water, and then transfer it to a 60 ℃ oven for further drying. Grind it until there are no obvious lumps to obtain the sodium titanate nanotube precursor.

[0041] (2) The sodium titanate nanotube precursor obtained in step (1) is placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a reducing gas atmosphere (hydrogen and argon with a volume ratio of 10:90). It is then calcined at 450 °C for 2 hours and cooled to room temperature (25 °C) to obtain defective sodium titanate nanotubes.

[0042] (3) Disperse the defective sodium titanate nanotubes obtained in step (2) in deionized water to obtain a dispersion; (4) Fix the polyvinylidene fluoride separation membrane onto the filter element of the vacuum filtration device to obtain a support membrane layer.

[0043] (5) Transfer the dispersion obtained in step (3) to the filtration device described in step (4) and use a vacuum pump to perform filtration so that the thickness of the catalytic film layer is 70 μm, thus obtaining the catalytic film layer-support film layer.

[0044] (6) The catalyst film layer-support film layer obtained in step (5) is dried at room temperature (25 °C) to obtain a defective sodium titanate nanotube catalyst film.

[0045] Example 2: Preparation of defective sodium titanate nanotube catalytic membranes The difference from Example 1 is that the calcination temperature in step (2) is 550 ℃, while the other step conditions are the same as in Example 1. The specific preparation process of the defective sodium titanate nanotube catalytic membrane includes the following steps: (1) Weigh 3 g of titanium dioxide and add it to 70 mL of 10 mol / L sodium hydroxide solution, and stir continuously for 30 min. Then transfer the mixture to a polytetrafluoroethylene-lined high-pressure reactor and carry out a hydrothermal reaction at 140 ℃ for 24 h. After the reaction is completed, collect the precipitate by filtration, wash it with 5 L of deionized water, and then transfer it to a 60 ℃ oven for further drying. Grind it until there are no obvious lumps to obtain the sodium titanate nanotube precursor.

[0046] (2) The sodium titanate nanotube precursor obtained in step (1) is placed in a tube furnace and heated to 550 °C at a heating rate of 5 °C / min under a reducing gas atmosphere (hydrogen and argon with a volume ratio of 10:90). It is then calcined at 550 °C for 2 hours and cooled to room temperature (25 °C) to obtain defective sodium titanate nanotubes.

[0047] (3) Disperse the defective sodium titanate nanotubes obtained in step (2) in deionized water to obtain a dispersion; (4) Fix the polyvinylidene fluoride separation membrane onto the filter element of the vacuum filtration device to obtain a support membrane layer.

[0048] (5) Transfer the dispersion obtained in step (3) to the filtration device described in step (4) and use a vacuum pump to perform filtration so that the thickness of the catalytic film layer is 70 μm, thus obtaining the catalytic film layer-support film layer.

[0049] (6) The catalyst film layer-support film layer obtained in step (5) is dried at room temperature (25 °C) to obtain a defective sodium titanate nanotube catalyst film.

[0050] Example 3: Preparation of defective sodium titanate nanotube catalytic membranes The difference from Example 1 is that the mass of titanium dioxide powder is 3.5 g, while all other steps and conditions are the same as in Example 1. The specific preparation process of the defective sodium titanate nanotube catalytic membrane includes the following steps: (1) Weigh 3.5 g of titanium dioxide and add it to 70 mL of 10 mol / L sodium hydroxide solution, and stir continuously for 30 min. Then transfer the mixture to a polytetrafluoroethylene-lined high-pressure reactor and carry out a hydrothermal reaction at 140 ℃ for 24 h. After the reaction is completed, collect the precipitate by filtration, wash it with 5 L of deionized water, and then transfer it to a 60 ℃ oven for further drying. Grind it until there are no obvious lumps to obtain the sodium titanate nanotube precursor.

[0051] (2) The sodium titanate nanotube precursor obtained in step (1) is placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a reducing gas atmosphere (hydrogen and argon with a volume ratio of 10:90). It is then calcined at 450 °C for 2 hours and cooled to room temperature (25 °C) to obtain defective sodium titanate nanotubes.

[0052] (3) Disperse the defective sodium titanate nanotubes obtained in step (2) in deionized water to obtain a dispersion; (4) Fix the polyvinylidene fluoride separation membrane onto the filter element of the vacuum filtration device to obtain a support membrane layer.

[0053] (5) Transfer the dispersion obtained in step (3) to the filtration device described in step (4) and use a vacuum pump to perform filtration so that the thickness of the catalytic film layer is 70 μm, thus obtaining the catalytic film layer-support film layer.

[0054] (6) The catalyst film layer-support film layer obtained in step (5) is dried at room temperature (25 °C) to obtain a defective sodium titanate nanotube catalyst film.

[0055] Comparative Example 1: Preparation of Sodium Titanate Nanotube Catalytic Film The difference from Example 1 is that calcination is carried out in an air atmosphere, while all other steps and conditions are the same as in Example 1. The specific preparation process of the sodium titanate nanotube catalytic membrane includes the following steps: (1) Weigh 3 g of titanium dioxide and add it to 70 mL of 10 mol / L sodium hydroxide solution, and stir continuously for 30 min. Then transfer the mixture to a polytetrafluoroethylene-lined high-pressure reactor and carry out a hydrothermal reaction at 140 ℃ for 24 h. After the reaction is completed, collect the precipitate by filtration, wash it with 5 L of deionized water, and then transfer it to a 60 ℃ oven for further drying. Grind it until there are no obvious lumps to obtain the sodium titanate nanotube precursor.

[0056] (2) The sodium titanate nanotube precursor obtained in step (1) is placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min in an air atmosphere. It is then calcined at 450 °C for 2 h and cooled to room temperature (25 °C) to obtain sodium titanate nanotubes.

[0057] (3) Disperse the sodium titanate nanotubes obtained in step (2) in deionized water to obtain a dispersion; (4) Fix the polyvinylidene fluoride separation membrane onto the filter element of the vacuum filtration device to obtain a support membrane layer.

[0058] (5) Transfer the dispersion obtained in step (3) to the filtration device described in step (4) and use a vacuum pump to perform filtration so that the thickness of the catalytic film layer is 70 μm, thus obtaining the catalytic film layer-support film layer.

[0059] (6) The catalyst film layer-support film layer obtained in step (5) is dried at room temperature (25 °C) to obtain sodium titanate nanotube catalyst film.

[0060] Comparative Example 2: Preparation of Defective Sodium Titanate Nanotube Catalytic Films The difference from Example 1 is that sodium borohydride (NaBH4) is used for reduction treatment and calcination is carried out in nitrogen atmosphere. All other steps and conditions are the same as in Example 1. The specific preparation process of the defective sodium titanate nanotube catalytic membrane includes the following steps: (1) Weigh 3 g of titanium dioxide and add it to 70 mL of 10 mol / L sodium hydroxide solution, and stir continuously for 30 min. Then transfer the mixture to a polytetrafluoroethylene-lined high-pressure reactor and carry out a hydrothermal reaction at 140 ℃ for 24 h. After the reaction is completed, collect the precipitate by filtration, wash it with 5 L of deionized water, and then transfer it to a 60 ℃ oven for further drying. Grind it until there are no obvious lumps to obtain the sodium titanate nanotube precursor.

[0061] (2) The sodium titanate nanotube precursor obtained in step (1) was placed in a 0.05 M NaBH4 solution and stirred at room temperature (25℃) for 2 h. The solid product was then separated, washed, dried, and ground. Subsequently, it was placed in a tube furnace and heated to 450℃ at a heating rate of 5℃ / min under a nitrogen atmosphere. It was then calcined at 450℃ for 2 h and cooled to room temperature (25℃) to obtain defective sodium titanate nanotubes.

[0062] (3) Disperse the defective sodium titanate nanotubes obtained in step (2) in deionized water to obtain a dispersion; (4) Fix the polyvinylidene fluoride separation membrane onto the filter element of the vacuum filtration device to obtain a support membrane layer.

[0063] (5) Transfer the dispersion obtained in step (3) to the filtration device described in step (4) and use a vacuum pump to perform filtration so that the thickness of the catalytic film layer is 70 μm, thus obtaining the catalytic film layer-support film layer.

[0064] (6) The catalyst film layer-support film layer obtained in step (5) is dried at room temperature (25 °C) to obtain a defective sodium titanate nanotube catalyst film.

[0065] Comparative Example 3: Preparation of Defective Titanium Dioxide Nanotube Catalytic Films The difference from Example 1 is that in step (1), after filtering and collecting the precipitate, it is soaked in hydrochloric acid to remove sodium ions from the precipitate by acid washing, forming a protonated titanate precursor, which is then calcined in a reducing gas atmosphere (hydrogen and argon in a volume ratio of 10:90) to obtain defective titanium dioxide nanotubes rich in oxygen vacancies. The other steps are the same as in Example 1. The specific preparation process of the defective titanium dioxide nanotube catalytic film includes the following steps: (1) Weigh 3 g of titanium dioxide and add it to 70 mL of 10 mol / L sodium hydroxide solution, and stir continuously for 30 min. Then transfer the mixture to a polytetrafluoroethylene-lined high-pressure reactor and carry out a hydrothermal reaction at 140 ℃ for 24 h. After the reaction is completed, collect the precipitate by filtration, soak it in 0.2 M hydrochloric acid solution for 12 h, wash it with 5 L of deionized water, and then transfer it to a 60 ℃ oven for further drying. Grind it until there are no obvious lumps to obtain the titanium dioxide nanotube precursor.

[0066] (2) The titanium dioxide nanotube precursor obtained in step (1) is placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a reducing gas atmosphere (hydrogen and argon with a volume ratio of 10:90). It is then calcined at 450 °C for 2 hours and cooled to room temperature (25 °C) to obtain defective titanium dioxide nanotubes.

[0067] (3) Disperse the defective titanium dioxide nanotubes obtained in step (2) in deionized water to obtain a dispersion; (4) Fix the polyvinylidene fluoride separation membrane onto the filter element of the vacuum filtration device to obtain a support membrane layer.

[0068] (5) Transfer the dispersion obtained in step (3) to the filtration device described in step (4) and use a vacuum pump to perform filtration so that the thickness of the catalytic film layer is 70 μm, thus obtaining the catalytic film layer-support film layer.

[0069] (6) The catalyst film layer-support film layer obtained in step (5) is dried at room temperature (25 °C) to obtain a defective titanium dioxide nanotube catalyst film.

[0070] Comparative Example 4: Preparation of Defective Titanium Dioxide Powder Catalytic Film The difference from Example 1 is that no hydrothermal reaction was performed, but all other steps and conditions were the same as in Example 1. The specific preparation process of the defective titanium dioxide powder catalytic film includes the following steps: (1) Place 3 g of titanium dioxide in a tube furnace and heat it to 450 °C at a heating rate of 5 °C / min under a reducing gas atmosphere (hydrogen and argon with a volume ratio of 10:90). Calcinate at 450 °C for 2 h and cool to room temperature (25 °C) to obtain defective titanium dioxide powder.

[0071] (2) Disperse the defective titanium dioxide powder obtained in step (1) in deionized water to obtain a dispersion; (3) Fix the polyvinylidene fluoride separation membrane onto the filter element of the vacuum filtration device to obtain a support membrane layer.

[0072] (4) Transfer the dispersion obtained in step (2) to the filtration device described in step (3) and use a vacuum pump to perform filtration so that the thickness of the catalytic film is 70 μm, thus obtaining the catalytic film-support film.

[0073] (5) The catalyst film layer-support film layer obtained in step (4) is dried at room temperature (25 °C) to obtain a defective titanium dioxide powder catalyst film.

[0074] Comparative Example 5: Preparation of Titanium Dioxide Powder Catalytic Film The difference from Example 1 is that no hydrothermal reaction was performed, and calcination was carried out in an air atmosphere. All other steps and conditions were the same as in Example 1. The specific preparation process of the titanium dioxide powder catalytic film includes the following steps: (1) Place 3 g of titanium dioxide in a tube furnace and heat it to 450 °C at a heating rate of 5 °C / min in an air atmosphere. Calcinate at 450 °C for 2 h and cool to room temperature (25 °C) to obtain titanium dioxide powder.

[0075] (2) Disperse the titanium dioxide powder obtained in step (1) in deionized water to obtain a dispersion; (3) Fix the polyvinylidene fluoride separation membrane onto the filter element of the vacuum filtration device to obtain a support membrane layer.

[0076] (4) Transfer the dispersion obtained in step (2) to the filtration device described in step (3) and use a vacuum pump to perform filtration so that the thickness of the catalytic film is 70 μm, thus obtaining the catalytic film-support film.

[0077] (5) The catalyst film layer-support film layer obtained in step (4) is dried at room temperature (25 °C) to obtain titanium dioxide powder catalyst film.

[0078] Experimental Example 1: Structural Characterization 1. Scanning electron microscope (SEM) The morphology of the defective sodium titanate nanotube catalytic films obtained in the examples was characterized using scanning electron microscopy (SEM). Since the SEM results of the catalytic films obtained in Examples 2 and 3 have similar morphological characteristics to those in Example 1, this invention only uses the data from Example 1 for representation. Figure 1 As shown, the surface of the polymer separation membrane is stacked with defective sodium titanate nanotubes with uniform morphology.

[0079] 2. Transmission electron microscope (TEM) The morphology of the defective sodium titanate nanotubes obtained in the examples was characterized using transmission electron microscopy (TEM). Since the TEM test results of the defective sodium titanate nanotubes obtained in Examples 2 and 3 have similar morphological characteristics to those in Example 1, this invention only uses the data from the defective sodium titanate nanotubes of Example 1 for representative demonstration. Figure 2 A in Figure 2 As shown in B, the defective sodium titanate nanotubes have a one-dimensional hollow tubular structure. The nanotubes are roughly parallel and open at the ends, exhibiting a hollow structure. The tube wall thickness is 2.64 nm and the inner diameter is 5.36 nm.

[0080] 3. X-ray diffraction (XRD) X-ray diffraction experiments were performed on the defective sodium titanate nanotubes and the defective sodium titanate nanotube catalytic membrane obtained in Example 1, the sodium titanate nanotube catalytic membrane obtained in Comparative Example 1, the titanium dioxide powder catalytic membrane obtained in Comparative Example 5, and the polyvinylidene fluoride separation membrane. The results are as follows: Figure 3 As shown.

[0081] The XRD pattern of the defective sodium titanate nanotube catalytic membrane prepared in Example 1 showed both peaks characteristic of the polyvinylidene fluoride separation membrane and those characteristic of sodium titanate nanotubes. Diffraction peaks observed at diffraction angles (2θ) of approximately 10.10°, 24.34°, 28.32°, and 48.36° were attributed to the (001), (201), (111), and (020) crystal planes, respectively, all consistent with the standard card for sodium titanate (JCPDS #31-1329). The reflection peak near 10° is typical evidence of the nanotube structure, corresponding to reflection from the (001) crystal plane. The XRD pattern of the defective sodium titanate nanotubes prepared in Example 1 also exhibited the aforementioned characteristic peaks of sodium titanate nanotubes. However, the catalytic membrane of Comparative Example 5, which did not undergo hydrothermal treatment during preparation, did not show the (001) reflection characteristic peaks attributed to nanotubes in its XRD pattern.

[0082] 4. Electron paramagnetic resonance spectroscopy (EPR) Electron paramagnetic resonance (EPR) experiments were performed on the defective sodium titanate nanotubes prepared in Example 1, the sodium titanate nanotubes prepared in Comparative Example 1, and the titanium dioxide powder prepared in Comparative Example 5. The content of surface defects in different samples was determined by the EPR signal intensity at g=2.00, which is attributed to single electrons trapped by surface oxygen vacancies (OVs). The results are as follows: Figure 4 As shown, the signal intensity of the defective sodium titanate nanotubes prepared in Example 1 is significantly stronger than that of the sodium titanate nanotubes prepared in Comparative Example 1, while no obvious oxygen vacancy signal was found in the titanium dioxide powder prepared in Comparative Example 5.

[0083] In summary, the defective sodium titanate nanotubes prepared in the embodiments of the present invention have a one-dimensional hollow tubular structure, which is beneficial for maintaining a higher permeation flux as a catalytic membrane layer; and their surface has abundant oxygen vacancy defects, which is beneficial for providing more catalytic active sites, enhancing the mass transfer efficiency of ozone and the interfacial reaction activity, thereby efficiently removing organic pollutants with different structures and properties.

[0084] Experimental Example 2: Evaluation of Permeability Flux The permeation flux of the catalytic membranes obtained in Examples 1 to 3 and Comparative Example 5 was evaluated.

[0085] 1. Experimental Methods The obtained catalytic membrane was installed in the ozone catalytic membrane module. 50.0 mL of deionized water was delivered to the membrane module and circulated through the catalytic membrane layer (upstream) and the support membrane layer (downstream) in sequence. The peristaltic pump speed was adjusted and the transmembrane pressure difference of the membrane module at different pump speeds was monitored using a pressure gauge.

[0086] 2. Experimental Results The defective sodium titanate nanotubes obtained in Examples 1-3 have similar structures; only the results of Example 1 are shown here. After installing the defective sodium titanate nanotube catalytic membrane obtained in Example 1, the permeation flux reached 7100 LMH / bar; after installing the titanium dioxide powder catalytic membrane obtained in Comparative Example 5 as a catalyst, the permeation flux was only 3600 LMH / bar. This indicates that the nanotubes with a one-dimensional hollow tubular structure used in the embodiments of the present invention, compared to powder structures, can significantly reduce fluid resistance during the filtration process, thereby maintaining a higher permeation flux.

[0087] Experimental Example 3: Evaluation of Ozone Catalytic Degradation Effect In current research, the classification of ozonation reactivity of compounds is mainly based on their second-order reaction rate constant (k, in Mn) for direct reaction with ozone molecules. -1 s -1 The range of k is usually considered to be greater than 10. 4 M -1 s -1Compounds with a reaction rate of k<15 are classified as ozone-active compounds (see Hollender Juliane, Zimmermann Saskia G, Koepke Stephan, et al. Elimination of Organic Micropollutants in a Municipal Wastewater Treatment Plant Upgraded with a Full-Scale Post-Ozonation Followed by Sand Filtration. [J] Environmental science & technology. Volume 43, Issue 20. 2009. PP 7862-9), compounds with a reaction rate of k<15 are classified as ozone-inert compounds (see Yang Guo, Erzhuo Zhao, Jun Wang, et al. Comparison of emerging contaminant abatement by conventional ozonation, catalytic ozonation, O3 / H2O2 and electro-peroxone processes. [J] Journal of Hazardous Materials. Volume 389, Issue. 2020. PP 121829), and compounds with reaction rates between the two are called moderately ozone-active compounds.

[0088] The second-order reaction rate constant (k) of ibuprofen with ozone (O3) is approximately 9.6 M. -1 s -1 Ibuprofen (IBU) is a typical ozone-inert compound (see Huber MM, Canonica S, Park GY, von Gunten U. Oxidation of pharmaceuticals during ozonation and advanced oxidation processes.[J] EnvironSci Technol. 2003 Mar 1;37(5):1016-24.). Therefore, this experiment uses Ibuprofen (IBU) as the subject to evaluate the ozone catalytic degradation effect of the catalytic membranes obtained in Examples 1 to 3 and Comparative Examples 1 to 5.

[0089] 1. Experimental Methods The catalytic membranes prepared in Examples 1-3 and Comparative Examples 1-5 were installed in an ozone catalytic membrane module. 50.0 mL of wastewater with an ibuprofen concentration of 5.0 mg / L was transported to the membrane module and circulated through the catalytic membrane layer (upstream) and the support membrane layer (downstream). Ozone with a concentration of 1.0 mg / L was continuously bubbled into the water using an ozone generator at a flow rate of 200 mL / min. The concentration of gaseous ozone was continuously monitored using an online ozone analyzer. The ozone that did not participate in the reaction at the membrane module outlet was quenched with a 2% (w / v) potassium iodide solution. Samples were taken periodically. After the ozone in the solution was stripped with N2, the concentration of ibuprofen in the filtrate was immediately tested by high performance liquid chromatography (HPLC). Each set of data was repeated three times and the average value was taken.

[0090] 2. Experimental Results The results are shown in Table 1.

[0091] Table 1. Experimental results evaluating the effect of ozone catalytic degradation of ibuprofen.

[0092] Note: The same letter indicates no significant difference, while different letters indicate a significant difference.

[0093] As shown in Table 1, the defective sodium titanate nanotube catalytic membranes obtained in Examples 1-3 have significantly higher pollutant removal capabilities compared to the catalytic membranes obtained in Comparative Examples 1-5, with a removal rate of ≥85.7% for ibuprofen in water. The analysis is as follows: The defective sodium titanate nanotubes obtained in Examples 1 to 3 have a one-dimensional hollow tubular structure, a large specific surface area, and abundant oxygen vacancy defect active sites. The overall material exhibits strong Lewis basicity, while the active intermediate in the ozone catalytic reaction is Lewis acidic. The material provided by this invention can more effectively capture these acidic species, thereby significantly improving the ozone catalytic oxidation activity.

[0094] Comparative Example 1 was calcined only in air, which could not form oxygen vacancy defect active sites, and therefore its catalytic activity was significantly lower than that of the catalytic films prepared in Examples 1 to 3.

[0095] Comparative Example 2 used borohydride as a reducing agent to prepare oxygen vacancies, but its ozone catalytic degradation activity for ibuprofen was significantly lower than that of Examples 1-3. This indicates that the borohydride reduction method is not suitable for preparing oxygen vacancies on the surface of sodium titanate nanotubes.

[0096] Although the titanium dioxide nanotubes prepared in Comparative Example 3 have oxygen vacancy defects, their ozone catalytic degradation activity for ibuprofen is significantly lower than that in Examples 1 to 3.

[0097] The defective titanium dioxide powder catalytic membrane prepared in Comparative Example 4 lacks a one-dimensional hollow structure of nanotubes, resulting in insufficient permeation flux; the titanium dioxide powder catalytic membrane prepared in Comparative Example 5 also lacks a one-dimensional hollow structure and oxygen vacancies; therefore, both exhibit low ozone catalytic activity.

[0098] Example 4: Evaluation of Ozone Catalytic Degradation Effect To verify that the catalytic membrane prepared in this invention possesses high-efficiency degradation activity for most organic pollutants, six compounds with significantly different reaction rates with ozone were selected as model pollutants: methylene blue (MB), acetaminophen (PCT), bisphenol A (BPA), sulfamethoxazole (SMX), amoxicillin (AMOX), and atrazine (ATZ). Among these, methylene blue, acetaminophen, and amoxicillin exhibit extremely high reaction rates with ozone and are classified as ozone-active compounds; bisphenol A and sulfamethoxazole show some reactivity with ozone and are classified as moderately reactive compounds; and atrazine exhibits extremely low reactivity with ozone and is classified as an ozone-inert compound. The catalytic membrane prepared in Example 1 was used as the subject to evaluate its ozone catalytic degradation effect on the above six compounds.

[0099] 1. Experimental Methods The defective sodium titanate nanotube catalytic membrane obtained in Example 1 was installed in an ozone catalytic membrane module. 50.0 mL of wastewater containing 50.0 mg / L of pollutants (ATZ pollutant concentration of 5.0 mg / L) was transported to the membrane module and circulated through the catalytic membrane layer (upstream) and the support membrane layer (downstream). Ozone at a concentration of 1.0 mg / L was continuously bubbled into the water using an ozone generator at a flow rate of 200 mL / min. The concentration of gaseous ozone was continuously monitored using an online ozone analyzer. The ozone that did not participate in the reaction at the membrane module outlet was quenched with a 2% (w / v) potassium iodide solution. Samples were taken periodically. After the ozone in the solution was stripped with N2, the concentration of residual pollutants in the filtrate was immediately tested by HPLC. Each set of data was repeated three times and the average value was taken.

[0100] 2. Experimental Results The degradation of pollutants in different water bodies is shown in Table 2.

[0101] Table 2 Degradation effects of different pollutants

[0102] As shown in Table 2, the degradation rate of the catalytic membrane prepared in Example 1 was ≥98.3% for ozone-active compounds (acetaminophen, amoxicillin, and methylene blue); ≥97.2% for moderately active ozone compounds (bisphenol A and sulfamethoxazole); and 86.8% for ozone-inert compounds (atrazine). These results demonstrate that the defective sodium titanate nanotube catalytic membrane prepared in this invention exhibits excellent catalytic performance in the ozone-catalyzed oxidation and degradation of various organic pollutants.

[0103] In summary, the defective sodium titanate nanotube catalytic membrane prepared by this invention exhibits excellent broad-spectrum adaptability, enabling efficient removal of organic pollutants with diverse structures and properties. This is primarily attributed to the abundant active sites provided by its oxygen-vacancy-rich nanotube structure, while the three-dimensional network structure constructed from the nanotube array enhances wastewater permeability, thereby strengthening ozone mass transfer efficiency and interfacial reactivity. Therefore, the catalytic membrane prepared by this invention has broad application prospects in the advanced treatment of complex water bodies such as industrial wastewater, groundwater, and pharmaceutical wastewater.

[0104] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. Use of a defective sodium titanate nanotube catalytic membrane for the removal of organic pollutants in catalytic ozonation reactions, characterized in that, The defective sodium titanate nanotube catalytic membrane is prepared by the following steps: S1: Titanium dioxide was dispersed in sodium hydroxide solution and subjected to hydrothermal reaction at 120~160 ℃. After post-treatment, sodium titanate nanotube precursor was obtained. S2: The sodium titanate nanotube precursor obtained in step S1 is placed in a reducing gas atmosphere and calcined at 450~550℃ to obtain defective sodium titanate nanotubes. S3: Disperse the defective sodium titanate nanotubes obtained in step S2 in water to obtain a dispersion; use a fluoropolymer separation membrane as a filter membrane to filter the dispersion, the defective sodium titanate nanotubes form a catalytic membrane layer with a thickness of 60~80 μm, and the fluoropolymer separation membrane forms a supporting membrane layer, to obtain a catalytic membrane layer-supporting membrane layer, and after drying, obtain the defective sodium titanate nanotube catalytic membrane; The fluoropolymer separation membrane has a pore size of 0.1~0.5 μm. The mass-to-volume ratio of titanium dioxide to sodium hydroxide solution is (3~3.5) g: 70 mL; The concentration of the sodium hydroxide solution is 8~12 mol / L; The organic pollutant is selected from one or more of acetaminophen, bisphenol A, sulfamethoxazole, amoxicillin, methylene blue, ibuprofen, and atrazine.

2. The use according to claim 1, characterized in that, The fluoropolymer separation membrane is a polyvinylidene fluoride separation membrane or a polytetrafluoroethylene separation membrane.

3. Use according to claim 1, characterized in that, The hydrothermal reaction takes 18-30 hours.

4. The use according to claim 1, characterized in that, The calcination time is 1 to 3 hours.

5. The use according to claim 1, characterized in that, The reducing gas atmosphere includes hydrogen and an inert atmosphere gas.

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