A method for preparing a porous layered catalytic membrane and its application

Abstract

This invention discloses a method for preparing a porous layered catalytic membrane and its application, belonging to the field of wastewater treatment technology. Using MgCl2 as an etchant, this invention achieves mild control over the crystal structure by regulating the etching time and concentration of two-dimensional CoCo PBAs nanosheets in MgCl2 solution. This method successfully forms an in-plane porous structure while maintaining the original aspect ratio and crystal integrity of the two-dimensional nanosheets. The resulting two-dimensional nanosheets further self-assemble to form a porous layered catalytic membrane, constructing a dual mass transfer channel that works synergistically between interlayers and in-plane. During dynamic operation, the membrane flux is approximately 1.5 times higher than that of the unpored sample, and pollutant degradation maintains a consistently high rate. This method has advantages such as mild reaction conditions, good structure preservation, simple process, and high reproducibility, effectively solving the problems of structural damage and difficulties in large-scale preparation in existing etching technologies.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and more specifically relates to a method for preparing and applying a porous layered catalytic membrane. Background Technology

[0002] In recent years, various new pollutants, including pharmaceuticals and personal care products (PPCPs) and perfluoroalkyl and polyfluoroalkyl substances (PFAS), have been found to varying degrees in urban wastewater. These pollutants, once discharged into the environment, can not only disrupt the ecosystem balance but also pose a potential threat to human health. Faced with increasingly severe water pollution problems, developing efficient new pollutant removal technologies has become crucial for achieving wastewater reuse and sustainable water resource development. Membrane catalysis technology is a cutting-edge wastewater treatment technology that combines membrane separation processes with advanced oxidation, providing solutions for purifying complex water qualities. Two-dimensional (2D) self-assembled catalytic membranes are currently a research hotspot in the field of catalytic membranes. On the one hand, the forced dispersion of nanocatalysts within the two-dimensional space of the membrane avoids the aggregation and contamination problems of nanoparticles in the system. On the other hand, the operation of the catalytic membrane is a dynamic process; the input of the reaction substrate and the output of the product are a continuous and real-time alternation process before and after passing through the membrane reactor. This not only promotes sufficient contact between pollutants and the active sites of the catalyst within the membrane but also effectively avoids catalyst passivation caused by the accumulation of intermediate products on the active sites of the catalyst.

[0003] Two-dimensional self-assembled catalytic membranes are assembled from layers of nanosheets, with interlayer channels being the primary mass transfer pathway. However, overly densely stacked interlayer nanochannels restrict effective contact between active sites, leading to increased mass transfer resistance and difficulty for reactants to penetrate the internal surface, thus reducing the utilization efficiency of active sites and limiting membrane flux. To improve mass transfer performance, researchers have attempted to introduce in-plane pore structures onto two-dimensional nanosheets and optimize the porosity of the material through techniques such as reactive ion etching, thereby constructing dual mass transfer channels—interlayer and in-plane. Currently, common in-plane pore-opening methods include oxidative etching, catalytic etching, substitution etching, high-energy shock, photolithography, template assembly, decomposition, and bottom-up synthesis. Although these methods can achieve pore structure control to some extent, their processes are generally complex and the equipment expensive. Furthermore, most processes require strong acid or strong base conditions, which can easily damage the crystal integrity and layered structure of two-dimensional materials, leading to a decrease in specific surface area and pore structure collapse. In addition, these methods have poor reproducibility, hindering large-scale preparation and engineering applications. Therefore, there is an urgent need to develop a mild, simple, controllable preparation strategy with good structure preservation to achieve large-scale synthesis of porous two-dimensional catalytic membranes and to simultaneously construct interlayer and in-plane dual mass transfer channels during membrane operation, thereby improving membrane flux and catalytic efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing porous layered catalytic membranes and their applications, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of this invention is to provide a method for preparing a porous layered catalytic membrane, comprising the following steps:

[0007] Hexacyanocobaltate, polyvinylpyrrolidone, N,N-dimethylformamide, and water are mixed in a first step to obtain solution A; the cobalt salt solution and sodium citrate are dissolved in water to form solution B;

[0008] Solution B is added to solution A, followed by a second mixing and a first settling period to obtain CoCo PBAs nanosheets;

[0009] The CoCo PBAs nanosheets were placed in a magnesium chloride solution, and after a third mixing and a second settling, etched CoCo PBAs were obtained.

[0010] The etched CoCo PBAs were dispersed in water and self-assembled into a membrane to obtain the porous layered catalytic membrane.

[0011] This invention utilizes polyvinylpyrrolidone (PVP) as a soft template and stabilizer to inhibit crystal aggregation and promote the formation of two-dimensional structures. Sodium citrate, as a complexing agent and morphology modifier, regulates the metal ion release rate and controls the crystal nucleation and growth process, thereby obtaining a more uniform and stable nanosheet structure. Adding solution B to solution A results in slower nucleation, more uniform morphology, and is more conducive to nanosheet formation.

[0012] Preferably, the hexacyanocobalaminate comprises potassium hexacyanocobalamin(III) and / or sodium hexacyanocobalamin(III).

[0013] Preferably, the ratio of hexacyanocobalaminate, polyvinylpyrrolidone, N,N-dimethylformamide and water is 0.4~4 mmol:0.2~2 g:50~500 mL:10~100 mL.

[0014] Preferably, the cobalt salt in the cobalt salt solution includes one or more of cobalt sulfate, cobalt nitrate, and cobalt chloride; the ratio of cobalt salt, sodium citrate, and water in the cobalt salt solution is 2 mmol:2 mmol:50 mL; and the molar ratio of the hexacyanocobalamate to cobalt in the cobalt salt solution is 1:1.

[0015] Preferably, the temperature of the second mixing is 0~4℃ and the time is 24h; the temperature of the first settling is 20~30℃ and the time is 10h.

[0016] Preferably, the concentration of the magnesium chloride solution is 0.1 mol / L.

[0017] Preferably, the third mixing time is 4 hours; the second settling time is 2 hours.

[0018] Preferably, the self-assembly is achieved by a gas pressure filtration device at a pressure of 0.3 bar.

[0019] The second technical solution of the present invention is to provide a porous layered catalytic membrane prepared by the above preparation method.

[0020] The third technical solution of the present invention is to provide the application of the above-mentioned porous layered catalytic membrane in wastewater treatment.

[0021] In the field of two-dimensional self-assembled catalytic membrane research, existing techniques for introducing in-plane porous structures into nanosheets typically employ redox etching or ion bombardment etching under strong acid or strong alkali environments. However, these etching processes are harsh and demanding, easily disrupting the crystal integrity and layered structure of the two-dimensional nanosheets. This leads to a decrease in the specific surface area of ​​the material, structural collapse, or loss of active sites, thereby affecting catalytic performance and membrane stability. Furthermore, these methods are complex and have poor reproducibility, hindering large-scale preparation and engineering applications.

[0022] To address the aforementioned problems, this invention proposes a rapid preparation method for porous two-dimensional Prussian blue analogues (2DPBAs) based on mild salt etching. This invention uses MgCl2 as the etchant and achieves mild control over the crystal structure by adjusting the etching time and concentration of the two-dimensional CoCo PBAs nanosheets in the MgCl2 solution. This method can successfully form an in-plane porous structure while maintaining the original aspect ratio and crystal integrity of the two-dimensional nanosheets. The resulting two-dimensional nanosheets further self-assemble to form a porous layered catalytic film, constructing a dual mass transfer channel that synergizes between interlayer and in-plane layers. The key to achieving the above-mentioned technical effects of this invention lies in:

[0023] (1) Introduction of MgCl2 as a mild etching agent: In this invention, magnesium chloride (MgCl2) is used as the etching agent. 2+ Infiltration leads to Co 2+ Localized dilution of concentration disrupts the original Co concentration. 2+ / [Co(CN)6] 3- Coordination equilibrium was achieved to enable gentle etching of two-dimensional CoCoPBAs nanosheets. This process was carried out in an environment free of strong acids and bases, avoiding structural collapse and lattice damage common in traditional etching processes. Even after pore opening, the two-dimensional nanosheet structure maintained a large aspect ratio (approximately 1000), providing a theoretical basis for the subsequent ordered assembly of film layers.

[0024] This invention successfully leverages the unique, mild, and controllable coordination interference mechanism of magnesium chloride (MgCl2) through specific two-dimensional CoCo PBAs nanosheets. The mild etching effect of MgCl2 strongly depends on the structure and chemical properties of the two-dimensional CoCo PBAs nanosheets as the specific host material. Other metal salts (such as Cu) can be used... 2+ Ni 2+ Zn 2+ Other methods for preparing nanosheets cannot form the two-dimensional nanosheet structure described in this invention, nor can they achieve the etching effect achievable by this invention.

[0025] The reason why the two-dimensional nanosheet structure described in this invention cannot be formed using other etching agents or other two-dimensional nanosheet materials is that other metal salts (such as Cu) 2+ Ni 2+ Zn 2+ ) and cyanide (CN) - It has a strong coordination tendency and strongly interacts with [Co(CN)6]. 3- Coordination, or direct interaction with Co 2+ Competition disrupts the originally ordered lattice growth. This leads to the formation of amorphous precipitates, three-dimensional bulk crystals, or other impurities, rather than well-ordered two-dimensional nanosheets. The reason why two-dimensional CoCo PBAs nanosheets can be gently etched by MgCl2 is because their specific crystal field stability energy and chemical bond strength allow Mg... 2+ "Ion exchange / perturbation" is performed without excessively damaging the framework.

[0026] Taking Cu-PBA as an example: Cu 2+ Exhibiting the Jan-Taylor effect, Cu-PBA exhibits a distorted octahedral coordination structure. Therefore, the crystal structure of Cu-PBA is inherently less stable and more brittle than that of CoCo-PBA. Even when using the same concentration of MgCl2, Cu-PBA nanosheets will dissolve or fragment due to intrinsic structural instability, rather than forming uniform pores. Its etching window (optimal etching time) will be very narrow, or even nonexistent.

[0027] Taking Ni-PBA as an example: Ni 2+ The high crystal field stabilization energy of Mg makes the Ni-PBA structure very stable and inert. 2 + Mild perturbations may not even be enough to initiate an effective etching process. This is because Ni... 2+ With CN - The coordination bonds are too strong to be broken by simple concentration dilution. More stringent conditions are required for etching, but this would destroy the two-dimensional morphology.

[0028] Taking Zn-PBA as an example: Zn 2+ Having d10 Its electronic configuration lacks crystal field stabilization energy, and its coordination geometry is a flexible tetrahedron, which is similar to Co. 2+ The octahedral structure of Zn-PBA differs from that of CoCo-PBA. The stability of Zn-PBA is drastically different from that of CoCo-PBA. Treatment with MgCl2 leads to an amorphous transformation or unpredictable reorganization of the structure, rather than the formation of an ordered porous structure.

[0029] (2) The optimal etching conditions for two-dimensional CoCo PBAs nanosheets using MgCl2 are: etching with a 0.1 mol / L MgCl2 solution. At this concentration, Mg... 2+ The exchange rate and coordination perturbation are moderate, which can ensure the uniformity and controllability of the etching process, avoid local over-etching or crystal disintegration, and thus achieve the synergistic stability of pore structure and two-dimensional morphology.

[0030] (3) Precise control of MgCl2 etching time: Etching time is a key parameter affecting the formation of pore structure and the maintenance of two-dimensional morphology, and 4h is the optimal control time. After etching for 4h, a multi-level pore size distribution was successfully formed on the surface of the nanosheet, the pores were uniform and still maintained an aspect ratio of about 1000 (e.g., Figure 2 As shown in the figure, this indicates that MgCl2 achieved mild and efficient in-plane pore construction during this time period. Furthermore, the chemical composition and crystal phase structure of the sample after 4 hours of etching remained consistent with the original CoCo PBAs nanosheets, indicating that the etching process did not alter the intrinsic chemical structure, and the specific surface area was increased (e.g., ...). Figure 3 As shown). In the dynamic membrane reaction system, the sample obtained after etching for 4 hours (CoCo PBAs-4) exhibited the best catalytic performance, with membrane flux increasing by approximately 1.5 times compared to the original CoCo PBAs nanosheets (as shown). Figure 4 As shown in the figure, it exhibits excellent mass transfer and reaction kinetics performance.

[0031] The present invention discloses the following technical effects:

[0032] This invention proposes a rapid preparation method for porous two-dimensional Prussian blue analogues (2D PBAs) based on mild salt etching. This method uses MgCl2 as the etchant and achieves mild control over the crystal structure by adjusting the etching time and concentration of the 2D CoCo PBAs nanosheets in the MgCl2 solution. This method successfully forms in-plane pore structures while maintaining the original aspect ratio and crystal integrity of the 2D CoCo PBAs nanosheets. The resulting 2D CoCo PBAs nanosheets further self-assemble to form a porous layered catalytic membrane, constructing a dual mass transfer channel that works synergistically between the interlayer and in-plane layers. During dynamic operation, the membrane flux is approximately 1.5 times higher than that of the non-porous sample, and the pollutant degradation rate remains consistently high (e.g., ...). Figure 4(As shown). This method has the advantages of mild reaction conditions, good structure preservation, simple process and high repeatability, and effectively solves the problems of structural damage and difficulty in large-scale preparation in existing etching technologies. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the preparation process of the porous layered catalytic membrane described in this invention;

[0034] Figure 2 SEM and AFM images of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 prepared for Example 1, wherein (a) to (c) are SEM images of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 respectively, (d) to (f) are AFM images of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 respectively, and (g) to (i) are width and thickness distribution maps of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 respectively;

[0035] Figure 3 XRD patterns (a) and N2 adsorption-desorption curves (b) of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 prepared in Example 1.

[0036] Figure 4 The dynamic water treatment performance of the two-dimensional layered membranes CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 prepared in Example 1 is compared, where (a) is the removal rate and (b) is the flux.

[0037] Figure 5 Tyndall effect diagrams of filtrates obtained at different magnesium chloride concentrations prepared in Example 2;

[0038] Figure 6 The Tyndall effect diagram is shown for the filtrate obtained under different etching agents (magnesium chloride or sodium chloride) as described in Example 3.

[0039] Figure 7 The results show the dynamic treatment performance evaluation of the CoCo PBA-4 membrane. The left figure represents the treatment results in lake water, and the right figure represents the treatment results in ultrapure water. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0046] Unless otherwise specified, all raw materials used in the following embodiments are commercially available products, and the source of commercially available products does not affect the technical effect of the present invention.

[0047] Unless otherwise specified, the room temperature involved in this invention is calculated as 25±5℃.

[0048] The specific detection process of the N2 adsorption-desorption curve involved in the following examples is as follows: 100 mg of sample was weighed and placed in a sample tube. First, it was degassed under vacuum at 100 °C for 6 h to completely remove physical adsorbates on the surface and in the pores. Then, N2 adsorption-desorption tests were performed in liquid nitrogen using a specific surface area and pore size analyzer.

[0049] The specific testing procedure for comparing the dynamic water treatment performance is as follows: 10 mg of sample was weighed and ultrasonically treated for 10 min, then filtered under nitrogen-assisted pressure into a self-made membrane chamber. A 5 ppm norfloxacin (NOR) solution was prepared, and the dynamic catalytic performance of the membrane was evaluated using a customized dead-end filtration device. Peroxymonosulfate (PMS) was introduced as an oxidant into the contaminant solution (5 ppm norfloxacin (NOR) solution). The filtrate was collected at predetermined time intervals, and the reaction was then rapidly quenched with Na2S2O3 and immediately filtered through a 0.22 μm membrane. Finally, the contaminant concentration was analyzed by high-performance liquid chromatography (HPLC). A cellulose acetate (CA) membrane (0.22 μm pore size) was set up as a blank control.

[0050] Example 1: Film preparation at different etching times

[0051] Dissolve 2 mmol of potassium hexacyanocobalamin(III) and 1 g of polyvinylpyrrolidone (PVP) in 50 mL of deionized water, then add 250 mL of N,N-dimethylformamide (DMF). The resulting solution is denoted as solution A.

[0052] Dissolve 2 mmol of cobalt sulfate and 2 mmol of sodium citrate in 50 mL of deionized water to form solution B;

[0053] Solution B was added to solution A and stirred continuously in an ice-water bath (0~4℃) for 24 h, followed by standing at room temperature for 10 h. After standing, the solid product was collected by centrifugation, washed with deionized water and ethanol, and dried to obtain CoCo PBAs nanosheets.

[0054] 5 mmol of magnesium chloride was dissolved in 50 mL of deionized water. 100 mg of CoCo PBAs nanosheets were placed in the magnesium chloride solution and stirred for 0 h, 4 h and 8 h respectively, and then allowed to stand for 2 h. After standing, the solid product was collected by suction filtration, washed with water and dried to obtain etched CoCo PBAs nanosheets.

[0055] 10 mg of CoCo PBAs nanosheets with different etching times were placed in 30 mL of deionized water and ultrasonically dispersed for 10 min. Two-dimensional layered membranes (with a thickness of about 50 μm) were prepared by self-assembly under a pressure of 0.3 bar using a gas pressure filtration device. These membranes were designated as CoCoPBAs-0, CoCoPBAs-4, and CoCoPBAs-8, respectively.

[0056] Figure 2SEM and AFM images of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 prepared in Example 1 are shown. (a) to (c) are SEM images of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8, respectively. (d) to (f) are AFM images of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8, respectively. (g) to (i) are width and thickness distribution maps of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8, respectively. Figure 3 XRD patterns (a) and N2 adsorption-desorption curves (b) of CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 prepared in Example 1. Figure 4 The dynamic water treatment performance of the two-dimensional layered membranes CoCo PBAs-0, CoCo PBAs-4 and CoCo PBAs-8 prepared in Example 1 is compared, where (a) is the removal rate and (b) is the flux.

[0057] Etching time is a key parameter affecting the formation of pore structure and the preservation of two-dimensional morphology; 4 hours is the optimal control time. Figure 2 As shown, at 0h of etching, only a few isolated pores exist on the surface of the nanosheets; when the etching time is extended to 4h, a multi-level pore size distribution is successfully formed on the surface of the nanosheets, with uniform pores and still maintaining an aspect ratio of approximately 1000, indicating that MgCl2 achieves mild and effective in-plane pore construction within this time period. Figure 3 As shown, after 4 hours of etching, the chemical composition and crystal phase structure of the sample remained consistent with the original CoCoPBAs-0, indicating that the etching process did not change the intrinsic chemical structure, and the specific surface area was slightly increased. When the etching time was extended to 8 hours, the two-dimensional nanosheets showed obvious fragmentation, structural collapse, and a significant decrease in aspect ratio, indicating that excessive etching would destroy the integrity of the crystal framework. Figure 2 (c) and (f)). In the dynamic membrane reaction system, the sample (CoCoPBAs-4) etched for 4 h exhibited the best catalytic performance, with membrane flux increasing by approximately 1.5 times compared to 0 h. Figure 4 It exhibits excellent mass transfer and reaction kinetics performance.

[0058] exist Figure 4 Regarding the flux, the reason why the membrane prepared by the method of this invention is inferior to the blank control group is that the blank control is a pure CA substrate membrane, which has a large pore size and low mass transfer resistance. Therefore, the water flux of the blank membrane is naturally significantly higher than that of the composite membrane loaded with nanosheets. When CoCo PBA nanosheets are filtered onto the surface of the CA membrane, a dense two-dimensional nanosheet layer is formed, which narrows the effective pores and increases the interfacial resistance, thereby reducing the overall flux.

[0059] Example 2: Preparation of films at different etching concentrations

[0060] Dissolve 2 mmol of potassium cobalt cyanate and 1 g of polyvinylpyrrolidone (PVP) in 50 mL of deionized water, then add 250 mL of N,N-dimethylformamide (DMF). The resulting solution is denoted as solution A.

[0061] Dissolve 2 mmol of cobalt sulfate and 2 mmol of sodium citrate in 50 mL of deionized water to form solution B;

[0062] Solution B was added to solution A and stirred continuously in an ice-water bath (0~4℃) for 24 h, followed by standing at room temperature for 10 h. After standing, the solid product was collected by centrifugation, washed with deionized water and ethanol, and dried to obtain CoCo PBAs nanosheets.

[0063] 5 mmol of magnesium chloride was dissolved in 50 mL of deionized water to obtain a magnesium chloride solution with a concentration of 0.1 mol / L; 2.5 mmol of magnesium chloride was dissolved in 50 mL of deionized water to obtain a magnesium chloride solution with a concentration of 0.05 mol / L; 7.5 mmol of magnesium chloride was dissolved in 50 mL of deionized water to obtain a magnesium chloride solution with a concentration of 0.15 mol / L; three 100 mg CoCo PBAs nanosheets were placed in magnesium chloride solutions of different concentrations and stirred for 4 h, then allowed to stand for 2 h; after standing, the filtrate was collected by suction filtration.

[0064] The etching behavior of CoCo-PBA nanosheets showed significant differences under different MgCl2 concentrations. Because the opened CoCo-PBA nanosheets exfoliate nanoscale fragments or secondary sheets in the liquid phase, these fragments can be stably dispersed and scatter light, causing the filtrate to exhibit a significant Tyndall effect. The strength of the Tyndall effect in the filtrate reflects the degree of etching and pore opening. Treating CoCo-PBA nanosheets with 0.10 mol / L MgCl2 for 4 h can form uniform pores within the sheets while maintaining the integrity of the overall structure. The filtrate obtained exhibits a significant Tyndall effect, indicating that nanoscale fragments can be generated and stably dispersed under this condition, which is a direct characterization of controllable pore opening (e.g., ...). Figure 5 In contrast, when the MgCl2 concentration was reduced to 0.05 mol / L, the etching effect was insufficient, and no Tyndall effect was observed in the filtrate, indicating that almost no stably dispersed fragments entered the solution. However, under the condition of 0.15 mol / L MgCl2, the etching was too strong, and the pores no longer expanded uniformly but instead formed local collapses, with large areas peeling off at once. The resulting large-sized fragments or flocs were completely retained by the filtration process, and the filtrate again did not exhibit the Tyndall effect. This indicates that 0.10 mol / L is the fundamental condition for achieving controllable pore opening.

[0065] Example 3: Magnesium chloride was replaced with sodium chloride.

[0066] Dissolve 2 mmol of potassium cobalt cyanate and 1 g of polyvinylpyrrolidone (PVP) in 50 mL of deionized water, then add 250 mL of N,N-dimethylformamide (DMF). The resulting solution is denoted as solution A.

[0067] Dissolve 2 mmol of cobalt sulfate and 2 mmol of sodium citrate in 50 mL of deionized water to form solution B;

[0068] Solution B was added to solution A and stirred continuously in an ice-water bath (0~4℃) for 24h, followed by standing at room temperature for 10h. After standing, the solid product was collected by centrifugation, washed with deionized water and ethanol, and dried to obtain CoCo PBAs nanosheets.

[0069] Dissolve 5 mmol of sodium chloride in 50 mL of deionized water to obtain a sodium chloride solution with a concentration of 0.1 mol / L. Take 100 mg of CoCo PBAs nanosheets and place them in the sodium chloride solution and stir for 4 h, then let stand for 2 h. After standing, filter and collect the filtrate.

[0070] After treatment with 0.1 mol / L sodium chloride solution for 4 hours, the results showed that ( Figure 6 The filtrate obtained from sodium chloride treatment showed only a very weak Tyndall effect, indicating that only a small number of limited fragments or secondary structures of the nanosheets entered the solution, and the etching effect was very slight. In contrast, under the same conditions, the filtrate of the sample treated with 0.1 mol / L MgCl2 showed a significant Tyndall effect, indicating that Mg... 2+ It can induce significant and controllable etching behavior. The comparative results clearly reveal the effectiveness and criticality of MgCl2 in the pore-opening process of this invention, which cannot be replaced by other monovalent salts (such as NaCl).

[0071] To verify the treatment capacity of the obtained membrane material in a real aquatic environment, 200 mL of lake water was used as simulated actual wastewater for testing. First, the lake water was pre-filtered through a 0.22 μm aqueous filter membrane to remove suspended particles and large impurities, preventing membrane clogging. Then, the pre-treated lake water was prepared as a 5 ppm NOR (norfloxacin) simulated wastewater solution, and the dynamic treatment performance of the CoCo PBA-4 membrane was evaluated at an operating pressure of 0.4 bar. The results are as follows: Figure 7 As shown.

[0072] Experimental results showed that the NOR removal rate of CoCo PBA-4 remained at 100% throughout the entire operation, demonstrating excellent and stable catalytic degradation performance. Meanwhile, its steady-state flux was only slightly lower than that under ultrapure water conditions. This was mainly attributed to a slight increase in membrane resistance caused by residual trace organic matter or colloidal impurities in the lake water, but it did not significantly affect the overall treatment performance.

[0073] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0074] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a porous layered catalytic membrane, characterized by, The method comprises the following steps: a cobalt hexacyanide salt, polyvinylpyrrolidone, N,N-dimethylformamide and water are mixed to obtain solution A; a cobalt salt solution and sodium citrate are dissolved in water to form solution B; solution B is added to solution A, and second mixing and first standing are performed to obtain CoCo PBAs nanosheets; the CoCo PBAs nanosheets are placed in a magnesium chloride solution, third mixing and second standing are performed to obtain etched CoCo PBAs; the etched CoCo PBAs are dispersed in water to form a film through self-assembly to obtain the porous layered catalytic film; the concentration of the magnesium chloride solution is 0.1 mol / L; the third mixing is performed for 4 h, and the second standing is performed for 2 h.

2. The production method according to claim 1, characterized by, The cobalt hexacyanide salt comprises potassium cobalt(III) hexacyanide and / or sodium cobalt(III) hexacyanide.

3. The preparation method according to claim 1, characterized in that, The use amount ratio of the cobalt hexacyanide salt, polyvinylpyrrolidone, N,N-dimethylformamide and water is 0.4-4 mmol:0.2-2 g:50-500 mL:10-100 mL.

4. The production method according to claim 1, characterized by, The cobalt salt in the cobalt salt solution comprises one or more of cobalt sulfate, cobalt nitrate and cobalt chloride; the use amount ratio of the cobalt salt in the cobalt salt solution, sodium citrate and water is 2 mmol:2 mmol:50 mL; and the molar ratio of the cobalt hexacyanide salt and the cobalt in the cobalt salt solution is 1:

1.

5. The method of claim 1, wherein, The second mixing is performed at a temperature of 0-4 ℃ for 24 h; and the first standing is performed at a temperature of 20-30 ℃ for 10 h.

6. The method of claim 1, wherein, The self-assembly is achieved by a gas pressure filtration device under a pressure of 0.3 bar.

7. A porous layered catalytic membrane, characterized by, The porous layered catalytic film is prepared by the preparation method in any one of claims 1-6.

8. Use of a porous layered catalytic membrane, characterized in that, The application is the application of the porous layered catalytic film in claim 7 to wastewater treatment.

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