A regenerable confined catalytic membrane and its preparation and regeneration methods

Abstract

The application discloses a renewable confined catalytic membrane and a preparation method and a regeneration method thereof, and the preparation method comprises the following steps: providing a ceramic membrane, cleaning and drying the ceramic membrane for standby; dissolving cyanuric acid and xanthine in pure water to prepare a first solution; dissolving melamine in pure water to prepare a second solution; stirring and mixing the first solution and the second solution under water bath conditions, then performing centrifugation and drying to obtain a first product; adding the first product into polytetrafluoroethylene dispersion liquid and pure water, performing ultrasonic dispersion to obtain a third solution; performing calcination on the third solution in a protective atmosphere, performing grinding after cooling to obtain a second product; loading the ceramic membrane through the third solution; performing calcination on the ceramic membrane in the protective atmosphere; dispersing the second product in ethanol, standing and precipitating, extracting supernatant, and loading the calcined ceramic membrane through the supernatant; and performing calcination on the ceramic membrane in the protective atmosphere to obtain the renewable confined catalytic membrane.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a regenerable confined catalytic membrane and its preparation and regeneration methods. Background Technology

[0002] With the acceleration of global urbanization and industrialization, water scarcity and water pollution have become core environmental problems restricting sustainable social development. According to the World Health Organization, approximately 62% of industrial wastewater and 44% of domestic sewage are discharged directly without effective treatment each year. These wastewaters contain "new pollutants" such as pharmaceuticals, personal care products, endocrine disruptors, and persistent organic pollutants (POPs), which are persistent, difficult to degrade, and pose a "three-fold" risk (mutagenic, teratogenic, and carcinogenic). Even at concentrations in the nanogram to microgram range, they can cause irreversible damage to aquatic ecosystems and human health. In 2022, my country issued the "Action Plan for the Treatment of New Pollutants," which explicitly requires deepening research and development of end-of-pipe treatment technologies, highlighting the urgent need for technological innovation to efficiently treat new pollutants.

[0003] Traditional water treatment technologies (such as biological treatment and physical sedimentation) generally have a degradation efficiency of less than 30% for new pollutants, making it difficult to meet emission standards. While chemical oxidation methods can partially degrade pollutants, they suffer from problems such as high oxidant consumption and the generation of toxic byproducts. Against this backdrop, the advanced oxidation process based on persulfate (PMS) (PMS-AOP) has emerged as a promising alternative due to its ability to generate highly reactive free radicals (such as SO42-). - •OH) has become one of the mainstream technologies for degrading recalcitrant organic compounds. However, PMS-AOP has inherent limitations: short lifetime of active species (only microseconds to milliseconds), low mass transfer efficiency, and the nanoscale metal catalyst is prone to agglomeration and loss, resulting in rapid decay of catalytic efficiency and difficulty in long-term stable operation.

[0004] To address the aforementioned issues, membrane separation technology is coupled with catalytic reactions to develop "confined catalytic membranes." These membranes immobilize the catalyst within the membrane channels, utilizing the nanoscale confinement effect to enrich pollutants and active species, accelerating reaction kinetics and simultaneously achieving "separation-degradation." However, current confined catalytic membrane technology still faces multiple bottlenecks, specifically the following shortcomings:

[0005] Firstly, there is an imbalance between the performance and stability of membrane materials. Currently, mainstream membrane substrates are divided into two categories: organic membranes and ceramic membranes. Organic membranes (such as PVDF and PES membranes) are inexpensive, but have poor chemical stability. They are prone to swelling and degradation in strong acid, strong alkali, or oxidizing environments, and have low mechanical strength. Under long-term pressure operation, they are prone to deformation, leading to a decrease in porosity. They are also difficult to degrade after disposal, easily causing secondary pollution. Furthermore, the binding force between organic membranes and catalysts is weak, causing catalysts to easily detach, which reduces catalytic activity and introduces new sources of pollution. Compared with polymer membranes, ceramic membranes have higher resistance to chemical corrosion, a wider pH range, resistance to stronger oxidation conditions, higher permeation flux, and longer service life. However, in traditional processes, the lifespan of ceramic membranes is "tied" to that of metal catalysts, and the high manufacturing cost has always been a major obstacle to their large-scale application. How to reduce costs, enhance long-term effectiveness, and fully utilize their performance advantages through innovative processes is the core issue that needs to be addressed for their large-scale application.

[0006] Secondly, the regeneration of metal catalytic membranes remains a significant challenge. Currently, most finite-domain catalytic membranes rely on metal or metal oxide catalysts such as Co, Fe, and Cu. Once these catalysts deactivate (due to carbon buildup, chemical poisoning, valence state changes, or particle sintering), they are difficult to completely remove from the ultrafiltration channels (pore size <100 nm) of ceramic membranes. High-temperature calcination can further sinter the metal particles, exacerbating deactivation; acid washing (such as with nitric acid or hydrochloric acid) can corrode the ceramic membrane substrate, damaging the pore structure. Ultimately, this leads to the expensive ceramic membrane being scrapped along with the deactivated catalyst, resulting in severe resource waste, and the potential for secondary pollution from metal leaching.

[0007] Thirdly, optimizing catalytic performance is the core challenge of catalytic membrane technology, and existing non-metallic catalyst systems have not yet overcome this bottleneck. While non-metallic catalysts, represented by graphitic carbon nitride (g-C3N4), possess natural advantages such as environmental friendliness and no heavy metal leaching, their structural design has not been specifically optimized for the nanopore confinement characteristics of ceramic membranes. Their layered crystal structure, due to strong π-π stacking, forms a dense packing, which not only limits the specific surface area but also causes a large number of catalytically active sites (such as pyridine nitrogen and graphitic nitrogen) to be encapsulated between layers, preventing effective contact with pollutants within the pores. Simultaneously, the imbalance between hydrophobicity and acidity on the g-C3N4 surface weakens its adsorption and capture capacity for polar organic pollutants, violating the fundamental principle of "reactant enrichment—efficient collision of active sites" in confined catalysis. Regarding the PMS activation mechanism, g-C3N4 mainly relies on surface defect sites to initiate the reaction, but the low defect density leads to the limited activity of active species (•OH, SO4•). - The generation efficiency is low and the lifespan is extremely short. These inherent contradictions in structure and performance, coupled with the lack of loading processes adapted to ceramic membranes, ultimately lead to limitations in catalytic efficiency, making it difficult to meet the high-efficiency and stable technical requirements of actual water purification.

[0008] In summary, existing water treatment catalytic membrane technologies suffer from four major drawbacks: high preparation costs, membrane-catalyst lifetime binding, weak catalytic performance, and high environmental risks. There is an urgent need to develop a novel confined catalytic membrane that combines high catalytic performance, convenient regeneration capabilities, and environmental friendliness in order to overcome technical bottlenecks and promote the industrial application of new pollutant treatment technologies.

[0009] The above background information is provided only to aid in understanding the concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention proposes a regenerable confined catalytic membrane and its preparation and regeneration methods, which achieve low-cost and high-efficiency recycling of the membrane substrate while efficiently removing pollutants.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention discloses a method for preparing a regenerable confined catalytic membrane, comprising the following steps:

[0013] S1: Provide a ceramic membrane, which should be cleaned and dried for later use;

[0014] S2: Dissolve cyanuric acid and xanthine in pure water to prepare the first solution; dissolve melamine in pure water to prepare the second solution;

[0015] S3: The first solution and the second solution are stirred and mixed under water bath conditions, and then centrifuged and dried to obtain the first product;

[0016] S4: Add the first product to the polytetrafluoroethylene dispersion and pure water, and after ultrasonic dispersion, obtain a third solution. Divide the third solution into two parts, one part for step S5 and the other part for step S6.

[0017] S5: The third solution is calcined in a protective atmosphere and then ground after cooling to obtain the second product;

[0018] S6: Load the ceramic membrane with the third solution;

[0019] S7: The ceramic film treated in step S6 is calcined in a protective atmosphere;

[0020] S8: Disperse the second product in ethanol, allow it to stand and precipitate, extract the supernatant, and use the supernatant to load the ceramic membrane calcined in step S7.

[0021] S9: The ceramic membrane treated in step S8 is calcined in a protective atmosphere to obtain a regenerable confined catalytic membrane.

[0022] Preferably, the molar ratio of cyanuric acid, xanthine, and melamine in step S2 is (1~10):(1~5):(5~20).

[0023] Preferably, step S3 specifically includes:

[0024] S31: The first solution and the second solution are subjected to ultrasonic treatment respectively, and then the second solution is added to the first solution and stirred for 2h to 6h under constant temperature water bath conditions of 25℃~60℃;

[0025] S32: Transfer the mixture of the first solution and the second solution to a centrifuge tube, centrifuge at 5000 rpm to 12000 rpm for 2 min to 10 min, and collect the bottom precipitate;

[0026] S33: Wash the bottom precipitate obtained in step S32 with pure water 1 to 5 times and with anhydrous ethanol 1 to 5 times. After each washing, centrifuge at 5000 rpm to 12000 rpm for 1 min to 10 min. Finally, place the precipitate in an oven at 45℃ to 70℃ and dry for more than 12 h to obtain the first product.

[0027] Preferably, step S4 specifically includes: adding (1~5)ag of the first product to (1~5)a mL of 40wt%~60wt% polytetrafluoroethylene dispersion and (2~5)a mL of pure water, and ultrasonically dispersing for 1h~5h to obtain a third solution, wherein a is a scaling factor or a reference amount.

[0028] Preferably, step S5 specifically includes: placing the third solution in a heating device, heating it from room temperature to 450°C to 650°C at a rate of 5°C / min to 15°C / min in a protective atmosphere, holding it at that temperature for 1 hour to 5 hours, and then cooling it to room temperature before grinding to obtain the second product.

[0029] Preferably, the loading of the ceramic membrane with the third solution in step S6 specifically includes: performing step A at least once to achieve a first preset loading amount on the ceramic membrane:

[0030] A: Immerse the ceramic membrane in the third solution and keep it in a vacuum environment for 5 min to 30 min. Take out the ceramic membrane and dry it at a temperature of 80℃ to 120℃ for 5 min to 30 min.

[0031] Preferably, the loading of the ceramic membrane after calcination in step S7 with the supernatant in step S8 specifically includes: performing step B at least once to achieve a second preset loading amount on the ceramic membrane:

[0032] B: Immerse the ceramic membrane in the supernatant and keep it in a vacuum environment for 5 min to 30 min. Take out the ceramic membrane and dry it at a temperature of 80℃ to 120℃ for 5 min to 30 min.

[0033] Preferably, step S7 specifically includes: placing the ceramic film treated in step S6 in a heating device, heating it from room temperature to 450°C to 650°C at a rate of 5°C / min to 15°C / min in a protective atmosphere, and holding it at that temperature for 1 hour to 5 hours.

[0034] Preferably, step S9 specifically includes: placing the ceramic membrane treated in step S8 into a heating device, filling the heating device with a protective atmosphere, and controlling the flow rate of the protective atmosphere to be 50 mL / min to 100 mL / min. After completely removing the air from the heating device, the temperature is increased from room temperature to 450°C to 650°C at a rate of 5°C / min to 15°C / min. The protective atmosphere inlet valve is then closed, and the temperature is further increased to 650°C to 750°C at a rate of 5°C / min to 15°C / min. The temperature is then maintained for 1 hour to 5 hours to obtain a regenerable confined catalytic membrane.

[0035] Preferably, the protective atmosphere is nitrogen, argon, or a mixture of ammonia and hydrogen.

[0036] Secondly, the present invention discloses a regenerable confined catalytic membrane, which is prepared by the method for preparing a regenerable confined catalytic membrane described in the first aspect.

[0037] Thirdly, the present invention discloses a method for regenerating a regenerable confined catalytic membrane, used to regenerate the deactivated regenerable confined catalytic membrane described in the second aspect, comprising the following steps:

[0038] After rinsing the deactivated regenerable confined catalytic membrane described in the second aspect with water, it is placed in a heating device and heated from room temperature to 450°C to 650°C in an air atmosphere at a rate of 5°C / min to 15°C / min, and kept at that temperature for 1 hour to 5 hours. After natural cooling, a ceramic membrane is obtained. Steps S2 to S9 in the first aspect are then performed to obtain the regenerable confined catalytic membrane.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows: The regenerable confined catalytic membrane and its preparation and regeneration methods proposed in the present invention, wherein the supported non-metallic catalyst is supported on the ceramic membrane through the synergy of "F doping and imidazole structure modification" and through "two-step calcination", so that the high-performance non-metallic catalyst with unique ultrathin nanosheet structure and multiple active sites (pyrrole nitrogen + nitrogen vacancy + F doping) can be supported on the ceramic membrane. This not only can efficiently remove pollutants, but also achieves the separation of the lifetime of the ceramic membrane substrate and the catalyst, so that the expensive ceramic membrane substrate can be regenerated multiple times, significantly reducing the cost of use and environmental risks throughout the entire life cycle. Thus, it solves the core problem of existing confined catalytic membranes that cause the entire membrane module to be scrapped due to catalyst deactivation, resulting in high costs and environmental risks.

[0040] Furthermore, the regenerative confined catalytic membrane and its preparation method of the present invention can produce a regenerative confined catalytic membrane with the following effects:

[0041] (1) Complete regenerability: The ceramic membrane substrate is completely regenerated through a one-step calcination method. After the catalyst is deactivated, it can be completely removed from the ceramic membrane, avoiding the problem of the ceramic membrane substrate being scrapped along with the deactivated catalyst, and solving the problem of high cost of waste membrane treatment and secondary pollution.

[0042] (2) Environmentally friendly: Non-metallic catalyst, which avoids the problem of metal catalyst ion dissolution and reduces environmental risks.

[0043] (3) Cost-effectiveness: The use of low-cost microfiltration ceramic membranes as the substrate and the construction of ultrafiltration membrane layers through nanoscale catalysts significantly reduces the cost of confined catalytic membranes. Since the ceramic membrane substrate and the catalyst achieve separation of lifespan, they can be reused multiple times, significantly reducing long-term operating costs.

[0044] (4) High filtration performance: flux up to 3673 L / m 2 / h / bar~4305.2 L / m 2 / h / bar, far exceeding that of traditional confined membranes.

[0045] (5) Broad-spectrum applicability: Under the conditions of PMS oxidant addition, it can achieve a removal rate of nearly 100% for a variety of new pollutants such as sulfamethoxazole, bisphenol A, and ofloxacin.

[0046] (6) Long-term stability: It can still maintain nearly 100% degradation of sulfamethoxazole even after long-term operation (374 hours).

[0047] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0048] Figure 1This is a flowchart of the preparation method of the regenerable confined catalytic membrane disclosed in a preferred embodiment of the present invention;

[0049] Figure 2a These are low-magnification SEM images of the surface of a pure ceramic substrate film characterized by scanning electron microscopy.

[0050] Figure 2b This is a high-magnification SEM image of the surface of a pure ceramic substrate film characterized by scanning electron microscopy;

[0051] Figure 2c These are cross-sectional SEM images of a pure ceramic substrate film characterized by scanning electron microscopy.

[0052] Figure 2d The image shows a low-magnification SEM image of the surface of the regenerable confined catalytic membrane obtained by scanning electron microscopy in a specific embodiment of the present invention.

[0053] Figure 2e This is a high-magnification SEM image of the surface of the regenerable confined catalytic membrane obtained by scanning electron microscopy in a specific embodiment of the present invention.

[0054] Figure 2f The image shows a cross-sectional SEM image of the regenerable confined catalytic membrane obtained by scanning electron microscopy in a specific embodiment of the present invention.

[0055] Figure 3a This is a schematic diagram illustrating the PMS utilization rate analysis of the regenerable confined catalytic membrane prepared according to a specific embodiment of the present invention under different fluxes;

[0056] Figure 3b This is a schematic diagram showing the degradation test results of sulfamethoxazole (SFX) by the regenerable confined catalytic membrane prepared in a specific embodiment of the present invention at different flux levels;

[0057] Figure 4 This is a schematic diagram illustrating the effect of a regenerable confined catalytic membrane prepared according to a specific embodiment of the present invention on treating simulated wastewater containing sulfamethoxazole.

[0058] Figure 5a This is an operational test of the regenerable confined catalytic membrane prepared according to a specific embodiment of the present invention under different PMS dosages and different pH conditions;

[0059] Figure 5b The regenerable confined catalytic membrane prepared in a specific embodiment of the present invention is effective against humic acid and common anions (Cl). - NO3 - H2PO4 - SO4 2- HCO3 - Anti-interference experiment;

[0060] Figure 6a This is a schematic diagram of the structure of the regenerable confined catalytic membrane (MPX@CM) prepared according to a specific embodiment of the present invention, which is used to perform a broad-spectrum degradation test on different single pollutants.

[0061] Figure 6b This is a schematic diagram of the structure of the renewable confined catalytic membrane (MPX@CM) prepared in a specific embodiment of the present invention, which is used to conduct broad-spectrum degradation tests on different single pollutants in three real water bodies: pure water, tap water, and lake water.

[0062] Figure 7 This is a schematic diagram illustrating the process of preparing and regenerating the regenerable confined catalytic membrane obtained in a specific embodiment of the present invention; Detailed Implementation

[0063] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0064] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be used for both fixing and circuit / signal connectivity.

[0065] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0067] like Figure 1 As shown, a preferred embodiment of the present invention discloses a method for preparing a regenerable confined catalytic membrane, comprising the following steps:

[0068] S1: Provide a ceramic membrane, which should be cleaned and dried for later use;

[0069] S2: Dissolve cyanuric acid and xanthine in pure water to prepare the first solution; dissolve melamine in pure water to prepare the second solution;

[0070] The molar ratio of cyanuric acid, xanthine, and melamine is (1~10):(1~5):(5~20).

[0071] S3: The first solution and the second solution are stirred and mixed under water bath conditions, then centrifuged and dried to obtain the first product;

[0072] Step S3 specifically includes:

[0073] S31: The first solution and the second solution are subjected to ultrasonic treatment respectively, and then the second solution is added to the first solution and stirred for 2h to 6h under constant temperature water bath conditions of 25℃~60℃.

[0074] S32: Transfer the mixture of the first solution and the second solution to a centrifuge tube, centrifuge at 5000 rpm to 12000 rpm for 2 min to 10 min, and collect the bottom precipitate;

[0075] S33: Wash the bottom precipitate obtained in step S32 with pure water 1 to 5 times and with anhydrous ethanol 1 to 5 times. After each washing, centrifuge at 5000 rpm to 12000 rpm for 1 min to 10 min. Finally, place the precipitate in an oven at 45℃ to 70℃ and dry for more than 12 h to obtain the first product.

[0076] The first product is a cyanuric acid-melamine supramolecular complex formed by self-assembly through hydrogen bonding, and it encapsulates xanthine molecules.

[0077] S4: Add the first product to the polytetrafluoroethylene dispersion and pure water, and after ultrasonic dispersion, obtain the third solution. Divide the third solution into two parts, one part for step S5 and the other part for step S6.

[0078] In this process, (1~5)ag of the first product is added to (1~5)a mL of 40wt%~60wt% polytetrafluoroethylene dispersion and (2~5)a mL of pure water, and ultrasonically dispersed for 1h~5h to obtain the third solution. Here, a is a scaling factor or reference amount, which is only used to characterize the ratio of the first product to polytetrafluoroethylene and pure water in this step.

[0079] S5: The third solution is calcined in a protective atmosphere and then ground after cooling to obtain the second product;

[0080] The third solution is placed in a heating device and heated to 450℃~650℃ from room temperature at a rate of 5℃ / min~15℃ / min under a protective atmosphere, held at this temperature for 1h~5h, and then naturally cooled to room temperature before grinding to obtain the second product. The protective atmosphere is nitrogen, argon, or a mixture of ammonia and hydrogen.

[0081] The second product is a fluorine-doped graphite-phase carbon nitride material with pyrrole nitrogen-rich defect sites.

[0082] S6: Loading the ceramic membrane with a third solution;

[0083] Specifically, loading the ceramic membrane with the third solution includes performing step A at least once to achieve a first preset loading amount on the ceramic membrane:

[0084] A: Immerse the ceramic membrane in the third solution and keep it in a vacuum environment for 5 to 30 minutes. Remove the ceramic membrane and dry it at a temperature of 80°C to 120°C for 5 to 30 minutes.

[0085] The first preset loading amount is, for example, an increase in the weight of the ceramic membrane of 5~15 mg / cm³. 2 Alternatively, the slurry can be uniformly loaded onto the surface of the ceramic membrane until there is no dripping.

[0086] S7: The ceramic film treated in step S6 is calcined in a protective atmosphere;

[0087] In this process, the ceramic film treated in step S6 is placed in a heating device and heated from room temperature to 450℃~650℃ at a rate of 5℃ / min~15℃ / min in a protective atmosphere, and held at that temperature for 1h~5h. The protective atmosphere is nitrogen, argon, or a mixture of ammonia and hydrogen.

[0088] S8: Disperse the second product in ethanol, let it stand to precipitate, extract the supernatant, and use the supernatant to load the ceramic membrane calcined in step S7.

[0089] Specifically, loading the ceramic membrane calcined in step S7 with the supernatant includes performing step B at least once to achieve a second preset loading amount on the ceramic membrane:

[0090] B: Immerse the ceramic membrane in the supernatant and keep it in a vacuum environment for 5 min to 30 min. Remove the ceramic membrane and dry it at a temperature of 80℃ to 120℃ for 5 min to 30 min.

[0091] The second preset loading amount is, for example, an increase in the weight of the ceramic membrane of 5~15 mg / cm³. 2 Alternatively, the slurry can be uniformly loaded onto the surface of the ceramic membrane until there is no dripping.

[0092] S9: The ceramic membrane treated in step S8 is calcined in a protective atmosphere to obtain a regenerable confined catalytic membrane.

[0093] In this process, the ceramic membrane processed in step S8 is placed in a heating device, and a protective atmosphere is introduced into the heating device at a flow rate of 50 mL / min to 100 mL / min. After completely removing the air from the heating device, the temperature is increased from room temperature to 450°C to 650°C at a rate of 5°C / min to 15°C / min. The protective atmosphere inlet valve is then closed, and the temperature is further increased to 650°C to 750°C at a rate of 5°C / min to 15°C / min. The temperature is then maintained for 1 hour to 5 hours to obtain a regenerable confined catalytic membrane. The protective atmosphere is nitrogen, argon, or a mixture of ammonia and hydrogen.

[0094] Another preferred embodiment of the present invention discloses a regenerable confined catalytic membrane, which is prepared by the regenerable confined catalytic membrane preparation method of the above preferred embodiment.

[0095] Another preferred embodiment of the present invention discloses a method for regenerating a regenerable confined catalytic membrane, used to regenerate the deactivated regenerable confined catalytic membrane of the above preferred embodiment, comprising the following steps: rinsing the deactivated regenerable confined catalytic membrane of the above preferred embodiment with water, placing it in a heating device, heating it from room temperature to 450°C to 650°C in an air atmosphere at a rate of 5°C / min to 15°C / min, holding it at that temperature for 1 hour to 5 hours, and obtaining a ceramic membrane after natural cooling, and continuing to perform steps S2 to S9 of the above preferred embodiment to obtain a regenerable confined catalytic membrane.

[0096] The following detailed description of the preparation and regeneration methods of the regenerable confined catalytic membrane disclosed in the preferred embodiments of the present invention is provided with reference to specific examples.

[0097] First, this specific embodiment discloses the construction process of a regenerable confined catalytic membrane (MPX@CM), wherein M in MPX refers to melamine and cyanuric acid, P refers to polytetrafluoroethylene (PTFE), X refers to xanthine, and MPX refers to a non-metallic catalyst prepared from the above raw materials.

[0098] This specific embodiment uses a low-cost micron-pore ceramic membrane as a substrate. The catalyst is uniformly filled within the membrane pores through "vacuum-assisted loading + secondary calcination," while simultaneously constructing an ultrafiltration-grade separation layer. The specific steps are as follows:

[0099] A1: Select an Al2O3 ceramic membrane (base membrane pore size 1μm~2μm, porosity 45%~65%) and cut it to the required size; immerse it in distilled water and ultrasonically clean it multiple times (1000W~2000W) until no obvious floating dust is dissolved; dry it at 40℃~80℃ for 10h~24h and set aside.

[0100] A2: Melamine (1 mmol–10 mmol), xanthine (1 mmol–5 mmol), and melamine (5 mmol–20 mmol) were selected as carbon and nitrogen sources, and a 40 wt%–60 wt% polytetrafluoroethylene (PTFE) dispersion was used as the fuel source; ultrapure water was used as the solvent. Melamine and xanthine were co-dissolved in 50 mL–100 mL of ultrapure water and magnetically stirred for 20–60 min until completely dissolved to obtain the first solution. Melamine was separately dissolved in 50 mL–100 mL of ultrapure water and stirred for 20–60 min to obtain the second solution.

[0101] A3: The first and second solutions were ultrasonically treated (1000W~2000W) for 20-60 minutes to ensure sufficient dispersion of the precursors. The second solution was slowly poured into the first solution, and the mixture was vigorously stirred (800 rpm) in a constant temperature water bath at 25℃~60℃ for 2-6 hours to form stable supramolecular aggregates through hydrogen bonding between cyanuric acid and melamine. The mixture was transferred to centrifuge tubes and centrifuged at 5000-12000 rpm for 2-10 minutes, collecting the bottom precipitate. A cyclical washing process of "1-5 times with ultrapure water + 1-5 times with anhydrous ethanol" was adopted, with centrifugation after each washing (10000 rpm, 1-10 minutes). Finally, the precipitate was dried in a 60℃ oven for 12 hours to obtain the first sample.

[0102] A4: Take 1g~5g of the first sample, add 2mL~5mL of ultrapure water and 1mL~5mL of 40wt%~60wt% PTFE solution, and ultrasonically disperse (power 1000W~2000W) for 1h~5h to obtain the third solution. Divide the obtained third solution into two parts; transfer one part of the third solution to an alumina crucible, seal it with aluminum foil, and place it in a tube furnace. Use 99.99% pure nitrogen as a protective atmosphere, and raise the temperature from room temperature to 450℃~650℃ at a heating rate of 5℃ / min~15℃ / min, and hold it for 1h~5h (at this temperature, PTFE pyrolyzes to produce HF, realizing in-situ doping of F, and xanthine promotes the conversion of pyridine nitrogen to pyrrole nitrogen; at the same time, the supramolecular precursor condenses into g-C3N4); after naturally cooling to room temperature, grind to obtain the second sample.

[0103] A5: Using a vacuum loading system (including a membrane impregnation container, vacuum tank, and vacuum pump, with an adjustable vacuum range of -0.15 MPa to -0.05 MPa), place the dried ceramic membrane into the membrane impregnation container and pour in the other part of the third solution prepared in step A4; start the vacuum pump and maintain the system vacuum at -0.15 MPa to -0.05 MPa for 5 to 30 minutes (using negative pressure to force the slurry deep into the membrane pores); remove the ceramic membrane and place it in a forced-air drying oven at 80℃ to 120℃ for 5 to 30 minutes, and repeat the "impregnation-vacuuming-drying" cycle until the required loading is achieved.

[0104] A6: Place the loaded ceramic membrane in a tube furnace, use 99.99% pure nitrogen as a protective atmosphere, and heat it from room temperature to 450℃~650℃ at a heating rate of 5℃ / min~15℃ / min, hold it at this temperature for 1h~5h, and perform a single calcination.

[0105] A7: Disperse the second sample obtained in step A4 in ethanol at a solid-liquid ratio of 1:(10~50) (mass ratio), and ultrasonically disperse (1000W~2000W, 60min) for 1h~6h. Then let it stand to precipitate for 1h~12h. Take a portion of the supernatant to avoid particles that are too large and block the membrane pores, and to ensure uniform concentration during the loading process.

[0106] A8: Use a vacuum loading system (including a membrane impregnation container, vacuum tank, and vacuum pump, with an adjustable vacuum range of -0.15MPa to -0.05MPa); immerse the pretreated ceramic membrane from step A6 into the supernatant slurry of the second sample, which was fully dispersed in step A7, ensuring complete immersion; start the vacuum pump and maintain the system vacuum at -0.15MPa to -0.05MPa for 5 to 30 minutes (using negative pressure to force the slurry deep into the membrane pores); remove the ceramic membrane and place it in a forced-air drying oven at 80℃ to 120℃ for 5 to 30 minutes (within this temperature range, the ethanol in the membrane pores is rapidly flashed out, and the ethanol expands rapidly during evaporation and quickly leaves the pores, creating a momentary negative pressure in the local pores of the membrane to enhance the loading); repeat the "impregnation-vacuuming-drying" cycle until the desired loading is achieved.

[0107] A9: Place the loaded ceramic membrane in a tube furnace, using 99.99% pure nitrogen as a protective atmosphere, and control the nitrogen flow rate at 50mL / min~100mL / min. After completely purging the air in the furnace, raise the temperature from room temperature to 450℃~750℃ at a rate of 5℃ / min~15℃ / min. When the temperature reaches 450℃~650℃, close the nitrogen inlet valve. After reaching 650℃~750℃, hold the temperature for 1h~5h and perform a second calcination to obtain the regenerable confined catalytic membrane (MPX@CM).

[0108] Then, this specific embodiment discloses the regeneration process of the regenerable confined catalytic membrane (MPX@CM); when the regenerable confined catalytic membrane (MPX@CM) is deactivated, the deactivated catalyst can be removed by "one-step calcination" to achieve the regeneration of the ceramic membrane substrate. The specific steps are as follows:

[0109] B1: Rinse the deactivated membrane with tap water for 3-5 minutes to remove contaminants and aged, loose catalyst particles adhering to the membrane surface; place the pre-cleaned membrane in a muffle furnace and heat it to 450-650°C at a rate of 5-15°C / min under air atmosphere, and hold it at this temperature for 0.5-1 hour (at this temperature, the deactivated MPX non-metallic catalyst is completely decomposed into gases such as CO2 and N2, which escape from the membrane pores, while the organic contaminants remaining in the membrane pores are oxidized and removed). After natural cooling, the ceramic membrane substrate regeneration is complete.

[0110] B2: Repeat steps A2 to A9 above on the regenerated ceramic membrane substrate to complete the catalytic membrane construction process, that is, to complete the regeneration of the regenerable confined catalytic membrane (MPX@CM) and realize the recyclable long-term water purification function.

[0111] In this specific embodiment, a regenerable confined catalytic membrane is prepared through a "secondary calcination" process. Specifically, the "secondary calcination" involves loading the catalyst onto the ceramic membrane substrate in a high-temperature tube furnace with a nitrogen atmosphere. Furthermore, this embodiment only requires a "one-step calcination" process to regenerate the regenerable confined catalytic membrane. This "one-step calcination" refers to restoring the catalytic membrane to the ceramic membrane substrate in a high-temperature muffle furnace with an oxygen atmosphere. The key to this regeneration process lies in separating the deactivated catalyst from the ceramic membrane substrate. Traditional catalytic membranes struggle to separate the expensive membrane substrate from the deactivated catalyst. When the catalytic function fails, the entire membrane module faces the problem of being scrapped, preventing long-term utilization and limiting the application of confined catalytic membranes. Therefore, the key to the regeneration process in this specific embodiment is the separation of the catalyst from the ceramic membrane substrate, and the "one-step calcination" method embodies this simple and easy-to-implement regeneration feature.

[0112] The regenerable confined catalytic membrane and its preparation and regeneration methods disclosed in the preferred embodiments of this invention have the following advantages:

[0113] (1) Renewable technology: By constructing a non-metallic confined catalytic membrane, the ceramic membrane substrate can be completely regenerated by a "one-step calcination method", which solves the problem of difficult regeneration of traditional confined catalytic membranes and is the core innovation of this invention.

[0114] (2) Catalyst molecular structure design: Based on graphitic carbon nitride catalysts, the F element enhances the negative charge and surface acidity, and the imidazole structure regulates the N type, so as to realize the integration of adsorption and catalytic functions, which is the key to catalyst performance.

[0115] (3) Membrane loading process: The catalyst slurry is uniformly pressed into the membrane pores by vacuum negative pressure and high temperature flash evaporation. Combined with a two-step calcination process, the catalyst is anchored in the ceramic membrane channel through thermal polymerization, thereby achieving effective loading of the catalyst in the ceramic membrane channel.

[0116] (4) Performance parameters: The permeability of the catalytic membrane can reach 3673 L / m 2 / h / bar~4305.2 L / m 2 With a throughput of / h / bar, the SFX removal rate is nearly 100% and the PMS utilization rate is as high as 90% within 374 hours of continuous operation, while maintaining a constant flux. These are important technical indicators of this invention.

[0117] (5) Application scenarios: Applicable to water pollution control including industrial wastewater, municipal sewage, reclaimed water and drinking water. It is particularly suitable for the efficient degradation of new pollutants in water bodies, especially for the broad-spectrum treatment of new pollutants such as pharmaceuticals and endocrine disruptors.

[0118] The performance test of the regenerable confined catalytic membrane (MPX@CM) prepared by the specific embodiments of the present invention is further explained below.

[0119] (1) Explanation of electron microscope images

[0120] The morphology and structure of the pure ceramic substrate membrane (i.e., the white membrane) and the regenerable catalytic ceramic membrane (MPX@CM) prepared in the above specific examples were characterized by scanning electron microscopy (SEM).

[0121] like Figure 2a The image shown is a low-magnification SEM image (5.00k×) of the surface of the white film (pure ceramic substrate film). It can be seen that its surface is composed of irregularly stacked blocky particles with uneven particle size (1~5 μm), sparse pore distribution and large pore size, presenting a typical ceramic film substrate morphology.

[0122] like Figure 2bThe image shown is a high-magnification SEM image (50.0k×) of the surface of the white film (pure ceramic substrate film). Further observation reveals that the surface of the white film particles is smooth and dense, with no obvious nanoscale structure, only a small number of micron-sized gaps, and a lack of catalytic active sites.

[0123] like Figure 2c The image shown is a cross-sectional SEM image (1.50k×) of the white film (pure ceramic substrate film), which shows that it has a particle stacking structure, uniform thickness, and micron-level interconnected channels without forming nano-confined spaces.

[0124] like Figure 2d The image shown is a low-magnification SEM image (5.00k×) of the surface of the regenerable confined catalytic membrane (MPX@CM) prepared in a specific embodiment of the present invention. It can be seen that after loading the MPX non-metallic catalyst, the membrane surface is completely covered by a large number of nanosheet catalysts, forming a dense porous network structure, and the blocky particle morphology of the original white membrane is completely reconstructed.

[0125] like Figure 2e The image shown is a high-magnification SEM image (50.0 k×) of the surface of the regenerable confined catalytic membrane (MPX@CM) prepared in a specific embodiment of the present invention. Under high magnification, the MPX catalyst is visible as an ultrathin sheet (thickness < 50 nm), with the sheets interwoven to form abundant nanopores (pore size 20~100 nm), providing sufficient confined space for pollutant adsorption and catalytic reaction.

[0126] like Figure 2f The image shown is a cross-sectional SEM image (1.50k×) of the regenerable confined catalytic membrane (MPX@CM) prepared in a specific embodiment of the present invention. The cross-sectional thickness of the membrane did not change significantly after loading, but the layered structure of the original white membrane was filled by the nanosheet network of the MPX non-metallic catalyst, and a continuous catalytic reaction channel was formed in the pores, proving that the MPX non-metallic catalyst was uniformly and deeply loaded in the membrane pores.

[0127] (2) Degradation test and PMS utilization analysis of sulfisoxazole (SFX)

[0128] For the regenerable confined catalytic membrane (MPX@CM) prepared in a specific embodiment of the present invention, sulfamethoxazole (SFX) degradation tests and PMS utilization analysis were carried out at different fluxes. Figure 3a The results show that PMS utilization gradually decreased as flux increased from 27 LMH to 140 LMH, but remained at a high utilization level of over 80% overall; Figure 3bAs shown, SFX achieved nearly 100% removal rate as the flux increased from 24 LMH to 86 LMH. While the removal rate decreased slightly when the flux reached 156 LMH, it remained as high as 87.7%. The transmembrane pressure increased linearly with increasing flux, and the membrane's permeability performance was fitted to a value of 4305.2 L / m. 2 / h / bar, fitting coefficient R 2 =0.991, which is significantly higher than the filtration performance of ordinary confined catalytic membranes.

[0129] (3) Effect of treating simulated wastewater containing sulfamethoxazole

[0130] The regenerable confined catalytic membrane (MPX@CM) prepared in a specific embodiment of the present invention was used to treat simulated wastewater containing 5 mg / L sulfamethoxazole, with a PMS concentration of 0.5 mM and a flow rate of 40 L / m³. 2 A continuous membrane filtration experiment was conducted at a constant flux of / h, and the results are as follows: Figure 4 As shown in the figure, the regenerable confined catalytic membrane (MPX@CM) can maintain a high removal rate of nearly 100% for sulfamethoxazole within 374 h, demonstrating superior membrane filtration performance and highly efficient confined catalytic activity. The filtration performance remains stable, and the PMS utilization rate is as high as 88%~92%.

[0131] (4) Stability and anti-interference test

[0132] Stability and anti-interference tests were conducted on the regenerable confined catalytic membrane (MPX@CM) prepared in specific embodiments of the present invention, such as... Figure 5a The figures show operational tests under different PMS dosages (0 mM, 0.1 mM, 0.25 mM, 0.4 mM, 0.5 mM) and different pH conditions (original, pH 5, pH 7, pH 9). The results indicate that the excellent degradation performance of this regenerable confined catalytic membrane (MPX@CM) for SFX depends on the efficient activation of PMS, exhibiting good stability with increasing PMS dosage and over a wide pH range (especially the acidic to neutral range). Figure 5b The figure shows 5 ppm humic acid and 5 mM common anions (Cl). - NO3 - H2PO4 - SO4 2- HCO3 - In the anti-interference experiment, the membrane showed strong tolerance to these interfering substances, and the removal rate did not decrease significantly, demonstrating excellent anti-interference performance.

[0133] (5) Broad-spectrum degradation test in real water bodies

[0134] The regenerable confined catalytic membrane (MPX@CM) prepared in a specific embodiment of this invention was subjected to a broad-spectrum degradation test in real water. On one hand, broad-spectrum degradation tests were conducted on different single pollutants, including SFX, ofloxacin (OFX), acetaminophen (PRXT), bisphenol A (BPA), carbamazepine (CBZ), atrazine (ATZ), and moxifloxacin (MOX), at a concentration of 5 ppm. The results are as follows: Figure 6a As shown, the membrane exhibits high degradation efficiency for a variety of pollutants. Furthermore, degradation tests were conducted on a mixture of 7 ppm pollutants (1 ppm each) in three real water bodies: pure water, tap water, and lake water. The results are as follows: Figure 6b As shown, the membrane maintains a high degradation rate for these pollutants in different real water bodies, fully demonstrating its excellent broad-spectrum degradation performance and adaptability to real water bodies, and has the potential for industrial application.

[0135] (6) Regeneration process

[0136] The regeneration process of the regenerable confined catalytic membrane (MPX@CM) prepared in a specific embodiment of the present invention is as follows: Initially, it is a white ceramic blank membrane. After being loaded with catalyst, it turns black due to the adhesion of MPX non-metallic catalyst. When the catalytic membrane is deactivated, it is regenerated by calcination at 650°C. The deactivated MPX catalyst is completely decomposed and dissipated, and the ceramic membrane substrate is restored to its initial white color. This proves that the ceramic membrane can be regenerated by this process. Moreover, the appearance of the regenerated membrane is not significantly different from that of the original blank membrane, which directly confirms the feasibility of its regeneration and the stability of the membrane substrate.

[0137] The background section of this invention may include background information about the problems or circumstances surrounding the invention, rather than a description of prior art by others. Therefore, the content included in the background section is not an admission of prior art by the applicant.

[0138] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate different embodiments or examples and features of different embodiments or examples described in this specification without contradiction. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope defined by the appended claims.

Claims

1. A method for preparing a regenerable confined catalytic membrane, characterized in that, The method comprises the following steps: S1: providing a ceramic membrane, cleaning and drying for standby; S2: dissolving cyanuric acid and xanthine in pure water to prepare a first solution; dissolving melamine in pure water to prepare a second solution; S3: stirring and mixing the first solution and the second solution under water bath conditions, then centrifuging and drying to obtain a first product of a cyanuric acid-melamine supramolecular complex self-assembled by hydrogen bonding and encapsulating xanthine molecules; S4: adding the first product to a polytetrafluoroethylene dispersion liquid and pure water, and obtaining a third solution after ultrasonic dispersion; the third solution is divided into two parts, one part is used in step S5, and the other part is used in step S6; S5: calcining the third solution in a protective atmosphere, and grinding after cooling to obtain a second product of a fluorine-doped graphite-like carbon nitride material with pyrrole nitrogen defect sites; S6: loading the ceramic membrane with the third solution; S7: calcining the ceramic membrane treated in step S6 in a protective atmosphere; S8: dispersing the second product in ethanol, precipitating after standing, extracting the supernatant, and loading the ceramic membrane calcined in step S7 with the supernatant; S9: calcining the ceramic membrane treated in step S8 in a protective atmosphere to obtain a renewable confined catalytic membrane, wherein the non-metallic catalyst of the renewable confined catalytic membrane has a synergistic effect of "F doping and imidazole structure modification", has an ultrathin nanosheet structure and multiple active sites including pyrrole nitrogen, nitrogen vacancy and F doping.

2. The method of claim 1, wherein The molar ratio of cyanuric acid, xanthine and melamine in step S2 is (1-10):(1-5):(5-20).

3. The method of claim 1, wherein the regeneratively confined catalytic membrane is prepared by the steps of: Step S3 specifically includes: S31: ultrasonic treatment of the first solution and the second solution, then adding the second solution to the first solution, and stirring in a constant temperature water bath at 25-60°C for 2-6h; S32: transferring the mixture of the first solution and the second solution to a centrifuge tube, centrifuging at a speed of 5000-12000rpm for 2-10min, and collecting the bottom precipitate; S33: washing the bottom precipitate obtained in step S32 with pure water 1-5 times and anhydrous ethanol 1-5 times, centrifuging at a speed of 5000-12000rpm for 1-10min after each washing, and finally drying the obtained precipitate in an oven at 45-70°C for more than 12h to obtain the first product.

4. The method of claim 1, wherein Step S4 specifically includes: adding (1-5)a g of the first product to (1-5)a mL of a 40wt%-60wt% polytetrafluoroethylene dispersion liquid and (2-5)a mL of pure water, and ultrasonic dispersing for 1-5h to obtain a third solution, wherein a is a scaling factor or a reference amount.

5. The method for preparing the regenerable confined catalytic membrane according to claim 1, characterized in that, The step S5 specifically comprises: placing the third solution in a heating device, heating from room temperature to 450-650 ℃ at a rate of 5-15 ℃ / min in a protective atmosphere, and keeping the temperature for 1-5 h, and then grinding after cooling to room temperature to obtain a second product.

6. The method of claim 1, wherein the renewable confined catalytic membrane is prepared by the steps of: The step S6 of loading the ceramic membrane with the third solution specifically comprises: performing the following step A at least once to reach a first preset loading amount on the ceramic membrane: A: immersing the ceramic membrane in the third solution, and placing it in a vacuum environment for 5-30 min, taking out the ceramic membrane, and drying it at a temperature of 80-120 ℃ for 5-30 min; The step S8 of loading the ceramic membrane with the supernatant after calcination in the step S7 specifically comprises: performing the following step B at least once to reach a second preset loading amount on the ceramic membrane: B: immersing the ceramic membrane in the supernatant, and placing it in a vacuum environment for 5-30 min, taking out the ceramic membrane, and drying it at a temperature of 80-120 ℃ for 5-30 min.

7. The method for preparing the regenerable confined catalytic membrane according to claim 1, characterized in that, The step S7 specifically comprises: placing the ceramic membrane treated in the step S6 in a heating device, heating from room temperature to 450-650 ℃ at a rate of 5-15 ℃ / min in a protective atmosphere, and keeping the temperature for 1-5 h.

8. The method for preparing the regenerable confined catalytic membrane according to claim 1, characterized in that, The step S9 specifically comprises: placing the ceramic membrane treated in the step S8 in a heating device, filling the heating device with a protective atmosphere, and controlling the flow rate of the protective atmosphere to be 50-100 mL / min, heating from room temperature to 450-650 ℃ at a rate of 5-15 ℃ / min after completely removing the air in the heating device, closing the protective atmosphere inlet valve, and continuing to heat to 650-750 ℃ at a rate of 5-15 ℃ / min, keeping the temperature for 1-5 h to obtain a renewable confined catalytic membrane.

9. A regenerable confined catalytic membrane characterized by, The renewable confined catalytic membrane is prepared by the method of any one of claims 1-8.

10. A method of regenerating a regenerable confined catalytic membrane, characterized in that, The method for regenerating the renewable confined catalytic membrane of claim 9 after deactivation comprises the following steps: After washing the deactivated renewable confined catalytic membrane of claim 9 with water, placing it in a heating device, heating from room temperature to 450-650 ℃ at a rate of 5-15 ℃ / min in an air atmosphere, keeping the temperature for 1-5 h, and obtaining a ceramic membrane after natural cooling, and continuing to perform the steps S2-S9 in any one of claims 1-8 to obtain a renewable confined catalytic membrane.

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