Preparation and application method of mnO2@nicu LDH catalytic membrane degraded by total non-radical process

Abstract

The application relates to a catalytic membrane preparation technology, and aims to provide a preparation and application method of MnO2@NiCu LDH catalytic membrane with a full non-radical process degradation. The method comprises the following steps: the whole polysulfone membrane is immersed in ultrapure water, one side surface of the polysulfone membrane is immersed in an ethanol aqueous solution containing fluorosilane at room temperature, cross-linking polymerization is generated between the fluorosilane and the surface structure of the polysulfone membrane; the polysulfone membrane with fluorosilane on one side is obtained by taking out and cleaning with deionized water; the MnO2@NiCu LDH catalyst is uniformly dispersed in an aqueous solution, and then the catalyst is assembled on the fluorosilane side of the polysulfone membrane through suction filtration; after drying treatment, the MnO2@NiCu LDH composite membrane is obtained. The composite membrane is applied to wastewater containing quinolone antibiotics, and the non-radical process in the catalytic activation degradation process is close to 100%; under different pH conditions, the composite membrane shows strong catalytic performance and a wide adaptability range. The product has strong anti-interference ability and wide application prospect, and effectively avoids the problem of powder catalyst recovery after water treatment.

Description

Technical Field

[0001] This invention pertains to catalytic membrane preparation technology, specifically relating to a method for preparing and applying a MnO2@NiCuLDH catalytic membrane with a completely non-radical degradation process. Background Technology

[0002] Quinolone antibiotics (FQs), as an emerging pollutant, are characterized by high chemical stability, high water solubility, and poor biodegradability. Excessive use of FQs during use ultimately leads to their entry into biological ecosystems as parent compounds or incomplete metabolites, posing a serious threat to human and ecological health through the food chain. Therefore, exploring novel, efficient, and environmentally friendly antibiotic treatment technologies is of paramount importance.

[0003] Compared to physical adsorption and biodegradation methods, advanced oxidation processes (SR-AOP) exhibit stronger oxidation capabilities and higher removal efficiency for recalcitrant organic pollutants such as quinolone antibiotics. Persulfate (PMS), based on SO₄²⁻, is easier to activate, has a higher redox potential, and a richer variety of active species compared to traditional advanced oxidation processes, and has been widely studied and applied in SR-AOP systems. PMS can be activated by transition metal catalysts to generate reactive oxygen species (ROS) for wastewater treatment. Of particular note are layered bimetallic hydroxides (LDHs), which, as metal hydroxides with unique structures composed of binary or multi-metals, possess exchangeable anions between layers, tunable metal chemical composition, and abundant catalytic sites, and are often used as adsorbents and catalysts in wastewater treatment. Bimetallic activation of PMS generally involves the main metal reacting with PMS to generate active species, while the secondary metal reduces the main metal to maintain its activity. Redox reactions occur through electron transfer between the two transition metals and between the transition metal and PMS, ultimately generating free radicals. In recent years, compared with the disadvantages of PMS activation to generate free radicals, such as susceptibility to water background values, easy oxidation of halide ions to produce carcinogens, and large consumption of PMS, non-radical pathway activated PMS has become more popular.

[0004] 1 O2, as a type of reactive oxygen species, has selective oxidizing ability for organic matter. It also exhibits selectivity in oxidizing highly electrophilic and electron-rich substrates. Its mild oxidizing power and unoccupied π-ions... * Its orbital characteristics and relatively long half-life (~4 μs) mean that its degradation process of pollutants is mainly through a non-radical mechanism involving electron transfer, compared to ·OH and... It has higher compatibility in wastewater substrates and can effectively overcome the limitations of current activated PMS advanced oxidation technology in practical wastewater treatment.

[0005] To improve the non-radical pathway in the catalytic degradation of pollutants, it is necessary to generate as many free radicals as possible. 1 O2, and metal doping is a common method for modifying catalysts. Existing research shows that doping with transition metals such as cobalt, copper, and nickel generally produces ·OH and ·OH during the activation of PMS. Doping with precious metals such as gold, rhodium, and platinum primarily introduces conductive electron transfer. However, when manganese is doped to activate PMS, both radical and non-radical mechanisms may play a role. A design using NiCuLDH as a support, uniformly loaded with MnO2, achieved a completely non-radical degradation process while simultaneously doping with manganese. Results show that the active species generated by MnO2@NiCuLDH activation of PMS contain... 1 O2 accounted for 88%, O · 2 - It accounts for 11%, but during the degradation reaction, O · 2 - It will eventually transform into 1 O2 participates in the degradation of pollutants, and detection revealed that non-free radical processes account for 100% of the degradation process.

[0006] However, single powder catalysis suffers from drawbacks in practical applications, such as difficult catalyst recovery and low mass transfer efficiency. With the increasing widespread use of membrane filtration for wastewater treatment, this invention introduces a molecular bridge PFSS (fluorosilane) with functional groups similar to those found in biological organisms. The fluoroalkyl and siloxane groups in the PFSS, through hydrophobic interactions and encapsulated chemical cross-linking, are responsible for adhesion and fixation on the polymer, achieving catalyst particle assembly and fixation. This ensures the catalyst is uniformly and tightly dispersed on the membrane surface, thereby improving the stability of the catalytic membrane. Furthermore, it increases the membrane flux by increasing the surface roughness, solving the problems of poor stability and low mass transfer efficiency in catalytic membranes obtained by traditional vacuum direct filtration. The MnO2@NiCu LDH catalytic membrane prepared by this invention achieves a completely non-radical degradation process while efficiently utilizing the catalyst, thus solving the catalyst recovery problem.

[0007] However, existing research shows that when using doped transition metals (such as cobalt, copper, nickel, manganese, palladium, etc.) and precious metals (such as gold, rhodium, platinum, etc.), they are usually used in the form of powdered catalysts. However, powdered catalysts not only suffer from drawbacks such as difficult catalyst recovery and low mass transfer efficiency in heterogeneous reaction systems, but also place higher demands on catalyst adhesion capabilities as membrane filtration methods for wastewater treatment become increasingly widespread.

[0008] Therefore, it is necessary to propose new catalyst preparation and application technologies to solve the above problems. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying a MnO2@NiCu LDH catalytic membrane with a completely non-radical degradation process.

[0010] To solve the technical problem, the solution of the present invention is:

[0011] A method for preparing a MnO2@NiCu LDH catalytic membrane with a completely non-radical degradation process is provided, comprising the following steps:

[0012] (1) The polysulfone membrane was placed in ultrapure water and soaked for 12 hours before being taken out. At room temperature, one side of the polysulfone membrane was soaked in an ethanol aqueous solution containing fluorosilane for 1 to 24 hours to allow the fluorosilane to crosslink and polymerize with the surface structure of the polysulfone membrane. The membrane was then removed and washed with deionized water to obtain a polysulfone membrane with fluorosilane on one side.

[0013] (2) The MnO2@NiCu LDH catalyst was uniformly dispersed in an aqueous solution, and then the MnO2@NiCu LDH in the dispersion was assembled on the fluorosilane side of the polysulfone membrane by vacuum filtration; after drying, the MnO2@NiCu LDH composite membrane was obtained.

[0014] The MnO2@NiCu LDH catalyst was prepared by the following method:

[0015] (a) Nickel nitrate hexahydrate (Ni(NO3)2·6H2O), copper nitrate trihydrate (Cu(NO3)2·3H2O), and 2-methylimidazole (Hmim) were added sequentially to a methanol solution (MeOH) at a molar ratio of 15:1:15. The mixture was heated at 80°C for 4 hours. The product was washed sequentially with ultrapure water and methanol, and then centrifuged and dried to obtain NiCu LDH powder.

[0016] (b) Take NiCu LDH powder, manganese chloride tetrahydrate (MnCl2·4H2O) and potassium permanganate (KMnO4) in a mass ratio of 1:0.033-0.233:0.04-0.28 (more preferably 1:0.167:0.2); first disperse NiCu LDH powder and manganese chloride tetrahydrate in ultrapure water and sonicate for 1 h; then add potassium permanganate and react under magnetic stirring for 6 h; after the reaction is completed, wash the precipitate with ultrapure water, and after centrifugation, drying and grinding, obtain brown powder MnO2@NiCu LDH catalyst;

[0017] When the MnO2@NiCu LDH composite membrane is used to treat organic pollutants in water, the catalyst loaded on it can activate persulfate (PMS) and ultimately form a single active species. 1 O2 is degraded entirely through a non-radical process involving electron transfer.

[0018] As a preferred embodiment of the present invention, in step (1), the volume concentration of the ethanol aqueous solution is 30%, and the mass percentage of fluorosilane in the mixed solution is 1 to 15 wt% (more preferably 10 wt%).

[0019] As a preferred embodiment of the present invention, in step (2), the mass ratio of the MnO2@NiCu LDH catalyst in the mixed solution is controlled so that the loading amount of MnO2@NiCu LDH on the polysulfone membrane is 0.2–1.0 mg / cm³. 2 (More preferably 0.8 mg / cm) 2 ).

[0020] As a preferred embodiment of the present invention, in step (a), the centrifugation conditions are 10,000 rpm for 8 min; the drying conditions are 80 degrees Celsius for 8 h.

[0021] As a preferred embodiment of the present invention, in step (b), the centrifugation conditions are 10,000 rpm for 8 min; and the drying conditions are 80°C for 6 h.

[0022] This invention further provides an application method for the MnO2@NiCu LDH composite membrane prepared by the aforementioned method. The method is characterized in that the MnO2@NiCu LDH composite membrane is used for percolation filtration of sewage or wastewater, wherein the dosage of persulfate in the sewage or wastewater is 0.05–0.10 mmol / L. During the percolation filtration process, the catalyst loaded on the surface of the composite membrane can activate the persulfate to generate active species. 1 O2 and O · 2 - The latter further transformed into 1 O2; by 1 O2 degrades organic pollutants in water, and the non-free radical process that activates persulfate accounts for 100% of the degradation process.

[0023] As a preferred embodiment of the present invention, the organic pollutant is a quinolone antibiotic, specifically any one or more of the following: ciprofloxacin, levofloxacin, fleroxacin, pefloxacin, lomefloxacin, and enoxacin.

[0024] Description of the invention principle:

[0025] 1. This invention innovatively proposes to modify NiCu LDH using MnO2 doping. During the loading process, Mn... 2+ Part of the Cu in the NiCu LDH support 2+Reduction generates abundant oxygen vacancies in some crystal structure defects, transforming the activation pathway of PMS from a radical-dominated pathway to a completely non-radical pathway. This improves degradation efficiency while solving problems such as the short duration of free radicals, the easy generation of secondary free radicals, and the influence of water body interference factors in the traditional free radical activation process.

[0026] The uniformly loaded MnO2 on the NiCu LDH support surface provides the catalyst with stronger acid resistance, solving the problem of easy deactivation of most metal catalysts under acidic conditions. Simultaneously, the coupling technology combining advanced oxidation techniques with membrane separation not only maintains high membrane flux but also improves the catalyst's mass transfer efficiency and enables catalyst recovery.

[0027] 2. Manganese oxides possess advantages such as environmental friendliness, low cost, and diverse valence states, making them more promising for applications. Through long-term research by the inventors' team, it has been found that the active species produced by MnO2@NiCu LDH activation of PMS contain… 1 O2 accounted for 88%. It accounts for 11%, but during the degradation reaction process It will eventually transform into 1 O2 participates in the degradation of pollutants, therefore it can be considered that non-free radical processes account for 100% of the degradation process.

[0028] Specifically, the catalyst supported on the surface of the MnO2@NiCu LDH catalytic film activates persulfate production. 1 O2 is used to degrade organic pollutants; Cu doping increases oxygen defects on the Ni LDH surface, thereby increasing the proportion of non-radical components; at the same time, during the growth of MnO2 on the NiCuLDH surface, some Cu doping enters MnO2, further enriching the oxygen defects of the catalyst, which greatly enhances the non-radical pathway during catalytic activation, and the non-radical process accounts for 100% of the degradation process. 1 O2 exhibits a longer half-life, higher electrophilicity, and selective and mild oxidizing power for electron-rich substrates compared to other reactive species. In catalytic degradation reactions, it performs better than hydroxyl radicals (·OH) and sulfate radicals. The base has a stronger ability to resist environmental disturbances.

[0029] 3. Existing catalyst attachment methods typically employ vacuum filtration to deposit MnO2@NiCu LDH onto organic membrane products. However, this approach suffers from weak interactions between the material and the organic membrane, resulting in poor membrane stability and low mass transfer efficiency, leading to suboptimal degradation. This invention introduces PFSS (fluorosilane) molecular bridges with functional groups similar to those found in biological organisms. The fluoroalkyl and siloxane groups in PFSS, through hydrophobic interactions and encapsulated chemical cross-linking, are responsible for adhesion and fixation on the polymer. Furthermore, vacuum filtration is used to assemble and fix the catalyst particles through the strong chemical coordination of PFSS sulfonamides. This not only ensures uniform and tight dispersion of MnO2@NiCu LDH on the membrane surface, improving membrane stability, but also increases membrane flux by increasing surface roughness. Therefore, the MnO2@NiCu LDH catalytic membrane of this invention not only effectively exposes more active sites of MnO2@NiCu LDH but also exhibits high flux and stability, and can efficiently remove quinolone antibiotics from water entirely via non-free pathways.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. This invention introduces a surfactant (fluorosilane, PFSS) to connect organic membranes and inorganic materials, and the catalytic membrane has a high permeation flux.

[0032] 2. The MnO2@NiCu LDH composite membrane prepared by this invention is beneficial to improving the mass transfer efficiency of reactants. Experimental verification shows that the degradation efficiency of levofloxacin by the MnO2@NiCu LDH composite membrane during permeation filtration can reach up to 97.7%, which is much higher than the degradation efficiency of ordinary MnO2@NiCu LDH powder (76.2%).

[0033] 3. The MnO2@NiCu LDH composite membrane prepared in this invention is applied to wastewater containing quinolone antibiotics. Cu doping increases the oxygen vacancies on the Ni LDH surface, thereby increasing the proportion of non-radical components during PMS activation. Simultaneously, during the growth of MnO2 on the NiCu LDH surface, some Cu doping enters the MnO2, further enriching the oxygen vacancies of the catalyst, resulting in a significant increase in the non-radical pathway during catalytic activation, with the non-radical degradation process approaching 100%. Due to the high stability, long lifetime, high selectivity, and mild oxidizing ability of non-radical components, the MnO2@NiCu LDH composite membrane exhibits strong catalytic performance and a wide range of adaptability under different pH conditions.

[0034] 4. The MnO2@NiCu LDH composite membrane prepared by this invention has strong anti-interference ability and broad application prospects when applied to actual wastewater treatment.

[0035] 5. This invention effectively avoids the problem of recovering powdered catalysts after water treatment, and its technical feasibility is significantly improved.

[0036] 6. The catalytic membrane prepared by this invention improves the mineralization of pollutants, reduces the leaching of metal ions during the catalytic process, and avoids the problem of secondary pollution. Attached Figure Description

[0037] Figure 1 This is a SEM image of the MnO2@NiCu LDH catalytic membrane in Example 1.

[0038] Figure 2 To verify the effect of the catalytic membrane on LEV catalytic degradation under different pH conditions in Experiment 1.

[0039] Figure 3 To verify the degradation effect of MnO2@NiCu LDH catalytic membrane and MnO2@NiCu LDH catalyst on levofloxacin in water in Experiment 2.

[0040] Figure 4 To verify the effect of the catalytic membrane on the catalytic degradation of LEV in the presence of different quenchers in Experiment 3.

[0041] Figure 5 To verify the EPR spectra of different active substances in Experiment 3.

[0042] Figure 6 To verify the proportion of different active substances in Experiment 3. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to embodiments. However, it should be understood that the following embodiments are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto.

[0044] The preparation and application method of the MnO2@NiCu LDH catalytic membrane with a completely non-radical degradation process as described in this invention includes the following steps:

[0045] (1) The polysulfone membrane is placed in ultrapure water and soaked for 12 hours. Then it is taken out. At room temperature, one side of the polysulfone membrane is soaked in an ethanol aqueous solution containing fluorosilane for 1 to 24 hours to allow the fluorosilane to crosslink and polymerize with the surface structure of the polysulfone membrane. The membrane is taken out and washed with deionized water to obtain a polysulfone membrane with fluorosilane on one side. The volume concentration of the ethanol aqueous solution is 30%, and the mass percentage of fluorosilane in the mixed solution is 1 to 15 wt% (more preferably 10 wt%).

[0046] (2) The MnO2@NiCu LDH catalyst was uniformly dispersed in an aqueous solution, and then the MnO2@NiCu LDH in the dispersion was assembled onto the fluorosilane side of the polysulfone membrane by vacuum filtration; after drying, the MnO2@NiCu LDH composite membrane was obtained; the loading of MnO2@NiCu LDH on the polysulfone membrane was 0.2–1.0 mg / cm³. 2 .

[0047] The MnO2@NiCu LDH catalyst used in the assembly was prepared by the following method:

[0048] (a) Nickel nitrate hexahydrate (Ni(NO3)2·6H2O), copper nitrate trihydrate (Cu(NO3)2·3H2O), and 2-methylimidazole (Hmim) were added sequentially to a methanol solution (MeOH) at a molar ratio of 15:1:15. The mixture was heated at 80°C for 4 hours. The product was washed sequentially with ultrapure water and methanol, and then centrifuged and dried to obtain NiCu LDH powder. The centrifugation conditions were 10,000 rpm for 8 minutes and 80°C for 8 hours.

[0049] (b) NiCu LDH powder, manganese chloride tetrahydrate (MnCl2·4H2O), and potassium permanganate (KMnO4) were prepared at a mass ratio of 1:0.033–0.233:0.04–0.28 (more preferably 1:0.167:0.2). NiCu LDH powder and manganese chloride tetrahydrate were first dispersed in ultrapure water and sonicated for 1 hour. Then, potassium permanganate was added, and the reaction was carried out under magnetic stirring for 6 hours. After the reaction, the precipitate was washed with ultrapure water, and after centrifugation, drying, and grinding, a brownish-red powdery MnO2@NiCu LDH catalyst was obtained. The centrifugation conditions were 10,000 rpm for 8 minutes; the drying conditions were 80°C for 6 hours.

[0050] The method of applying this MnO2@NiCu LDH composite membrane is to use it for the percolation filtration of sewage or wastewater. During this process, the catalyst loaded on the surface of the composite membrane can activate persulfate (PMS) to generate active species. 1 O2 and The latter further transformed into 1 O2; by 1 O2 degrades organic pollutants in water, with 100% of the degradation occurring via non-radical mechanisms that activate PMS. As an example, the organic pollutants are quinolone antibiotics, such as ciprofloxacin, levofloxacin, fleroxacin, pefloxacin, lomefloxacin, and enoxacin.

[0051] In practical applications, this MnO2@NiCu LDH composite membrane can be installed at the effluent outlet of existing secondary sedimentation tanks, in tubular ultrafiltration membrane equipment, or fabricated into stackable membrane modules. These devices or products can then be used for wastewater treatment in medical wastewater, aquaculture, and domestic sewage.

[0052] The implementation process of the present invention will be described below through several specific embodiments.

[0053] Part One: Embodiments of the Invention

[0054] Example 1

[0055] (1) Preparation of MnO2@NiCu LDH

[0056] Ni(NO3)2·6H2O, Cu(NO3)2·3H2O, and Hmim were added sequentially to MeOH to achieve a mixture concentration of 0.33 mol / L for Ni(NO3)2·6H2O, 0.022 mol / L for Cu(NO3)2·3H2O, and 0.33 mol / L for Hmim. After heating at 80 °C for 4 h, the product was washed with ultrapure water and methanol, centrifuged, and dried at 80 °C for 8 h to obtain NiCu LDH powder. The NiCu LDH powder was dispersed in ultrapure water, and MnCl2·4H2O was added and ultrasonically treated for 1 h to achieve uniform dispersion. Then, KMnO4 was slowly added, and the mixture was vigorously stirred on a magnetic stirrer for 6 h. The concentrations of NiCu LDH, MnCl2·4H2O, and KMnO4 in the mixture were 6 g / L, 1 g / L, and 1.2 g / L, respectively. After the reaction was completed, the precipitate was washed with ultrapure water and centrifuged, dried at 80℃ for 6 hours, and ground to obtain MnO2@NiCu LDH powders with different manganese dioxide loads.

[0057] (2) Preparation of MnO2@NiCu LDH catalytic membrane

[0058] Using a 50000Da polysulfone (PSf) flat-sheet ultrafiltration membrane manufactured by Zhongke Ruiyang Membrane Technology (Beijing) Co., Ltd. as the base membrane, the membrane was cut to a suitable size and fixed in a custom mold. Before use, it was soaked in ultrapure water for 12 hours. PFSS was dissolved in a 30% (v / v) ethanol-water solution to prepare a PFSS solution, where the mass percentage of PFSS in the mixed solution was 10 wt%. This solution was quickly poured into the mold, ensuring that one side of the membrane was in contact with the PFSS solution, and reacted at room temperature for 2 hours. The membrane was then removed and rinsed with ultrapure water to remove unreacted PFSS. MnO2@NiCu LDH was then ultrasonically dispersed in 30 ml of aqueous solution, with the MnO2@NiCu LDH loading at 0.8 mg / cm³. 2 Calculations were performed; the MnO2@NiCu LDH dispersion was deposited onto a PFSS-treated flat sheet membrane using a vacuum filtration device and dried in an oven at 40°C to obtain the MnO2@NiCu LDH catalytic membrane.

[0059] Figure 1 This is a scanning electron microscope (SEM) image of the MnO2@NiCu LDH catalytic film. Figure 1 Images (ac) show the surface views of the PSf-based film, the PSf-based film with PFSS adhered to it, and the MnO2@NiCu LDH catalytic film, respectively. The PSf support layer and the PSf layer are clearly visible in the images, with the cross-sectional morphology of the membrane pores clearly displayed within the PSf layer. This highlights the hierarchical structure of the film and the pore formation within the PSf layer. Figure 1 In (a), it can be observed that the pores of the PSf-based membrane are uniformly distributed on the membrane surface. Figure 1 In (b), it can be observed that PFSS particles are uniformly deposited on the PSf substrate, indicating the effective deposition of PFSS on the PSf surface, which provides a basis for the subsequent attachment of the MnO2@NiCuLDH layer. Furthermore, Figure 1 (c) shows that MnO2@NiCu LDH was successfully and uniformly loaded onto the membrane surface, proving the successful synthesis of the MnO2@NiCu LDH catalytic membrane. Figure 1 (df) are cross-sectional views of the PSf-based film, the PSf-based film with PFSS adhered to it, and the MnO2@NiCu LDH catalytic film, respectively. By comparison... Figure 1 (de) It can be seen that adding PFSS adhesive did not change the internal structure of the membrane pores. Figure 1 (f) Measurements showed that the catalyst thickness was approximately 44.7 μm, and the MnO2@NiCu LDH layer was tightly attached to the PFSS layer.

[0060] (3) The catalytic oxidation performance of the MnO2@NiCu LDH catalytic membrane was evaluated by the degree of degradation of levofloxacin in water.

[0061] The pre-prepared 5 mg / L levofloxacin (LEV) aqueous solution was placed on a magnetic stirrer, and persulfate (PMS) was added in different amounts to make the concentrations in the aqueous solution 0.01, 0.03, 0.05, 0.08, and 0.10 mmol / L, respectively. The corresponding systems were labeled as 1T, 2T, 3T, 4T, and 5T.

[0062] The catalytic membrane was then cut into circular pieces of a specific size and placed on a flat-panel membrane performance evaluation instrument. The permeate concentration was tested using cross-flow filtration. Every 3 minutes, 1 mL of solution was taken, filtered, and added to a 0.5 mL vial of methanol. Ultra-high performance liquid chromatography (UHPLC) was used for detection at a wavelength of λ = 293 nm. The mobile phase was acetonitrile:0.1% formic acid = 17:83; column temperature: 30℃; flow rate: 0.2 mL / min; injection volume: 5 μL for sample concentration detection. Each experiment was repeated three times to ensure accuracy.

[0063] The final degradation rates of LEV for each system after 30 minutes were measured to be 61.2%, 85.6%, 97.7%, 97.5%, and 96.9%, respectively, indicating that the catalytic membrane has a good degradation effect on LEV. The 3T group was the optimal group, achieving a degradation rate of 97.7%. Figure 3 (Lower middle curve). To maintain a good degradation effect, when using the MnO2@NiCu LDH composite membrane of the present invention to treat sewage or wastewater by permeation filtration, the preferred dosage of persulfate (PMS) is 0.05-0.10 mmol / L.

[0064] Example 2

[0065] The MnO2@NiCu LDH catalyst was prepared using the method described in step (1) of Example 1. In step (1), the mass concentrations of MnCl2·4H2O were 0.2, 0.6, 1, and 1.4 g / L, and the mass concentrations of KMnO4 were 0.24, 0.72, 1.2, and 1.68 g / L, respectively. The resulting MnO2@NiCu LDH catalysts were labeled 1C, 2C, 3C, 4C, and 5C. The prepared MnO2@NiCu LDH catalysts were subjected to degradation experiments in beakers. After 30 min, the degradation rates of LEV by the 1C, 2C, 3C, 4C, and 5C systems were 51.7%, 60.3%, 69.4%, 76.2%, and 70.1%, respectively. The optimal synthesis ratio was determined to be 4C.

[0066] Example 3

[0067] The MnO2@NiCu LDH catalytic membrane was prepared using the method described in step (2) of Example 1. The mass concentrations of the PFSS solution in step (2) were 1, 5, 8, 10, and 15 wt%, respectively, and the resulting catalytic membranes were labeled as 1W, 2W, 3W, 4W, and 5W. The prepared MnO2@NiCu LDH catalytic membranes were cut into circular shapes and subjected to flux testing using a flat-panel membrane performance testing and evaluation instrument with cross-flow filtration. At room temperature and an operating pressure of 0.4 MPa, the membranes were pre-pressurized with ultrapure water for at least 30 minutes before the test to allow the membranes to stabilize. The outflow volume of ultrapure water permeate flux was recorded within a certain operating time, and the membrane permeate flux was calculated using a formula. The test results showed that the membrane fluxes of the 1W, 2W, 3W, 4W, and 5W catalytic membranes were 340.7, 356.9, 374.5, 399.2, and 401.6 L / m³, respectively. 2 After 30 minutes of reaction, the degradation effects of the system on LEV were 88.6%, 92.2%, 94.6%, 97.7%, and 97.8%, respectively. Among them, 4W and 5W had larger water flux. Compared with 5W, 4W used less PFSS. Therefore, 4W was selected as the optimal polymerization concentration.

[0068] The MnO2@NiCu LDH catalytic membrane was prepared using the method described in step (2) of Example 1. The PFSS polymerization times in step (2) were 1, 2, 3, 8, 12, and 24 h, respectively, and the resulting catalytic membranes were labeled 1H, 2H, 3H, 4H, 5H, and 6H. The prepared MnO2@NiCu LDH catalytic membranes were cut into circular shapes and subjected to flux testing using a cross-flow filtration system in a flat-panel membrane performance testing and evaluation instrument (test conditions as shown above). The water fluxes for 1H, 2H, 3H, 4H, 5H, and 6H were 360.4, 399.2, 402.3, 410.6, 415.6, and 420.3 L / m³, respectively. 2 After 30 minutes of reaction, the LEV degradation rates were 90.3%, 97.7%, 97.3%, 98.1%, 97.4%, and 97.6% (L / m³, respectively). 2 ·h, where the degradation effect of the system remains almost unchanged after the polymerization time reaches 2h, so 2H is selected as the optimal polymerization time.

[0069] Example 4

[0070] The preparation method of the MnO2@NiCu LDH catalytic film in step (2) of Example 1 was adopted, and the loading mass of MnO2@NiCuLDH in step (2) was 0.2, 0.4, 0.6, 0.8, and 1.0 mg / cm³. 2The resulting catalytic membranes were labeled 1M, 2M, 3M, 4M, and 5M. The prepared MnO2@NiCu LDH catalytic membranes were cut into circular shapes and subjected to flux testing using a cross-flow filtration system in a flat-panel membrane performance testing and evaluation instrument (test conditions as shown in Example 3). The test results showed that the fluxes for 1M, 2M, 3M, 4M, and 5M were 283.4, 320.6, 364.3, 399.2, and 326.1 L / m³, respectively. 2 After 30 min of reaction, the LEV degradation rates of the 1M, 2M, 3M, 4M, and 5M catalytic membranes were 80.3%, 85.6%, 92.3%, 97.7%, and 96.9%, respectively. The 4M membrane was the optimal group, with an optimal loading of 0.8 mg / cm³. 2 .

[0071] Part Two: Verification Experiments for the Product of this Invention

[0072] Verification Experiment 1:

[0073] Following step (3) in Example 1, the optimally configured MnO2@NiCu LDH catalytic membrane prepared in step (2) of the example was applied to LEV solution systems with different pH values, using LEV solutions of pH = 3, 5, 7, 9, 10, 11, and 12 as feed solutions. The optimally configured MnO2@NiCu LDH composite membrane showed LEV removal rates of 93.6%, 96.6%, 98.1%, 98.8%, 100%, and 81.3% at solutions of pH = 3, 5, 7, 9, 10, and 11, respectively. The test results in different pH solution systems are as follows: Figure 2 As shown, the MnO2@NiCu LDH composite membrane prepared in this embodiment has a wide pH application range.

[0074] Verification Experiment 2:

[0075] The steps are the same as step (3) in Example 1. The optimal configuration of MnO2@NiCu LDH catalytic membrane obtained in step (2) of the example is used to treat aqueous solutions of ciprofloxacin, levofloxacin, fleroxacin, pefloxacin, lomefloxacin, and enoxacin, respectively. The optimal ratio of MnO2@NiCu LDH removes 97.8%, 97.7%, 95.9%, 99.9%, 95.3%, and 97.8% of the above pollutants, respectively. The degradation effect is excellent, which shows that the MnO2@NiCu LDH catalytic membrane system has a high efficiency in removing quinolone antibiotics.

[0076] Verification Experiment 3:

[0077] The steps are the same as step (3) in Example 1, except that the optimally configured MnO2@NiCu LDH catalytic membrane prepared in step (2) of the example is used with methanol (MeOH), tert-butyl alcohol (TBA), p-benzoquinone (p-BQ), and L-histidine as ·OH, respectively. 1 O2 quencher, resulting in Figure 4 As shown, the results indicate that the degradation effect of the system on LEV remained almost unchanged when MeOH and TBA were added. The addition of p-BQ slightly inhibited the degradation of LEV, and the addition of L-histidine significantly reduced the degradation effect. Therefore, it can be concluded that the activation of PMS by the MnO2@NiCu LDH catalytic membrane mainly relies on... 1 The activation process is mainly based on O2. EPR experiment ( Figure 5 ) and live species capture experiments ( Figure 6 This conclusion was further verified, and calculations showed that the main active species were... and 1 O2 accounts for approximately 11% and 88% respectively, and the total amount of both is close to 100%.

[0078] Part Three: Comparative Experiments with Existing Technologies

[0079] Comparative Experiment 1:

[0080] Using a method similar to step (3) in Example 1, the result is as follows: Figure 3 As shown, with the same catalyst and PMS dosage, the MnO2@NiCu LDH catalytic film achieved a degradation rate of 97.7% within 30 minutes (lower curve in the figure), while the MnO2@NiCu LDH suspension system only achieved a degradation rate of 76.2% within 30 minutes. Figure 3 (The upper curve in the middle).

[0081] Comparative Experiment 2:

[0082] Following step (3) in Example 1, the catalytic membrane prepared in step (2) of the example was applied to different actual water systems. Surface water, secondary sedimentation tank effluent, and tap water influent were used as background water, and LEV was added as the target pollutant with a concentration of 5 mg / L. The LEV removal rates of the MnO2@NiCu LDH composite membrane with the optimal synthesis ratio in the actual water systems were 94.4%, 95.9%, and 95.7%, respectively. Under these three background conditions, the degradation rates of LEV by the MnO2@NiCu LDH powder system were 42.3%, 45.2%, and 43.7%, respectively. The comparison shows that the MnO2@NiCu LDH composite membrane has an excellent ability to resist environmental disturbances through the all-non-radical pathway activation of the PMS system.

[0083] Comparative Experiment 3:

[0084] Following step (3) in Example 1, the MnO2@NiCu LDH prepared under the optimal conditions in step (2) of Example 1 was applied to the ion leaching of levofloxacin solution using MnO2@NiCu LDH powder and MnO2@NiCu LDH catalytic membrane. With the same MnO2@NiCu LDH and PMS, the ion leaching of Ni in the MnO2@NiCu LDH catalytic membrane was 0.133 mg / L, the ion leaching of Cu was 0.057 mg / L, and the ion leaching of Mn was 0.001 mg / L. All three metal ion leaching concentrations were lower than the maximum daily allowable discharge concentration specified in the "Integrated Wastewater Discharge Standard" (GB8798-1996). Furthermore, the MnO2@NiCu... In the LDH suspension system, the leaching concentrations of Ni ions were 0.431 mg / L, Cu ions were 0.193 mg / L, and Mn ions were 0.003 mg / L. Although these concentrations meet the "Integrated Wastewater Discharge Standard" (GB8798-1996), they are all higher than those of the MnO2@NiCu LDH catalytic membrane. The MnO2@NiCu LDH composite membrane prepared in this embodiment can effectively prevent the leaching of metal ions.

[0085] As can be seen from the above embodiments, the MnO2@NiCu LDH composite membrane obtained by the present invention ensures the catalytic membrane has excellent stability while maintaining high water flux and excellent antifouling performance. The MnO2@NiCuLDH catalyst in this catalytic membrane is uniformly dispersed and fully exposes more active sites, effectively activating PMS and achieving almost 100% efflux. 1 O2 is the dominant non-radical pathway, thereby achieving the oxidative degradation of quinolone antibiotics in wastewater, overcoming the shortcomings of existing technologies.

Claims

1. A method for preparing a MnO2@NiCu LDH catalytic membrane with a completely non-radical degradation process, characterized in that, Includes the following steps: (1) The polysulfone membrane was placed in ultrapure water and soaked for 12 hours before being taken out. At room temperature, one side of the polysulfone membrane was soaked in an ethanol aqueous solution containing fluorosilane for 1 to 24 hours to allow the fluorosilane to crosslink and polymerize with the surface structure of the polysulfone membrane. The membrane was then removed and washed with deionized water to obtain a polysulfone membrane with fluorosilane on one side. (2) The MnO2@NiCu LDH catalyst was uniformly dispersed in an aqueous solution, and then the MnO2@NiCu LDH in the dispersion was assembled on the fluorosilane side of the polysulfone membrane by vacuum filtration; after drying, the MnO2@NiCu LDH composite membrane was obtained. The MnO2@NiCu LDH catalyst was prepared by the following method: (a) Nickel nitrate hexahydrate, copper nitrate trihydrate and 2-methylimidazole were added to a methanol solution in a molar ratio of 15:1:

15. The solution was heated at 80°C for 4 hours. The product was washed with ultrapure water and methanol in sequence, and then centrifuged and dried to obtain NiCu LDH powder. (b) Take NiCu LDH powder, manganese chloride tetrahydrate and potassium permanganate in a mass ratio of 1:0.033-0.233:0.04-0.28; first disperse NiCu LDH powder and manganese chloride tetrahydrate in ultrapure water and sonicate for 1 h; then add potassium permanganate and react for 6 h under magnetic stirring; after the reaction is completed, wash the precipitate with ultrapure water, and after centrifugation, drying and grinding, obtain brown powder MnO2@NiCu LDH catalyst; When the MnO2@NiCu LDH composite membrane is used to treat organic pollutants in water, the catalyst loaded on it can activate persulfate and ultimately form a single active species. 1 O2 is degraded entirely through a non-radical process involving electron transfer.

2. The method according to claim 1, characterized in that, In step (1), the volume concentration of the ethanol aqueous solution is 30%, and the mass percentage of fluorosilane in the mixed solution is 1-15 wt%.

3. The method according to claim 1, characterized in that, In step (2), the mass ratio of the MnO2@NiCu LDH catalyst in the mixed solution is controlled so that the loading of MnO2@NiCu LDH on the polysulfone membrane is 0.2–1.0 mg / cm³. 2 .

4. The method according to claim 1, characterized in that, In step (a), the centrifugation conditions are 10,000 rpm for 8 min; the drying conditions are 80 degrees Celsius for 8 h.

5. The method according to claim 1, characterized in that, In step (b), the centrifugation conditions are 10,000 rpm for 8 min; the drying conditions are 80°C for 6 h.

6. A method for applying the MnO2@NiCu LDH composite film prepared by the method according to any one of claims 1 to 5, characterized in that, The MnO2@NiCu LDH composite membrane was used for percolation filtration of wastewater or sewage, with a persulfate dosage of 0.05–0.10 mmol / L. During percolation filtration, the catalyst loaded on the surface of the composite membrane could activate the persulfate to generate active species. 1 O2 and O · 2 - The latter further transformed into 1 O2; by 1 O2 degrades organic pollutants in water, and the non-free radical mechanism that activates persulfate accounts for 100% of the degradation process.

7. The method according to claim 6, characterized in that, The organic pollutant is a quinolone antibiotic, specifically any one or more of the following: ciprofloxacin, levofloxacin, fleroxacin, pefloxacin, lomefloxacin, and enoxacin.

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