Catalytic ozonation of mn-alkaline earth metal / ceramic membrane and method for preparing the same

Abstract

This invention discloses a catalytic ozonation Mn-alkaline earth metal / ceramic membrane and its preparation method, relating to the field of ceramic membrane modification and preparation technology. The method includes the following steps: adding an alkaline earth metal salt to a manganese acetate solution, mixing thoroughly, then adding it dropwise to a mixed solution of a complexing agent and a binder while stirring until a transparent sol is formed, followed by aging to obtain an active component precursor; sequentially acid-washing, water-washing, alcohol-washing, and drying the ceramic membrane to obtain a pretreated ceramic membrane; uniformly coating the active component precursor onto the surface of the pretreated ceramic membrane and allowing it to stand at room temperature, then drying, calcining, and cleaning to obtain the catalytic ozonation Mn-alkaline earth metal / ceramic membrane. This invention uses manganese as the main active metal and alkaline earth metals as regulating metals to improve the activity, stability, and antifouling ability of the Mn-alkaline earth metal / ceramic membrane in the catalytic ozonation treatment of organic wastewater. This invention solves the problem of membrane fouling that easily occurs in existing ceramic membranes.

Description

Technical Field

[0001] This invention relates to the field of ceramic membrane modification and preparation technology, specifically to a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane and its preparation method. Background Technology

[0002] Membrane separation technology can simultaneously perform separation, concentration, purification, and refining functions. It boasts advantages such as high efficiency and energy saving, no secondary pollution, simple workflow, and ease of control, and is considered one of the most prominent technologies in separation science today. Especially in the field of water treatment, membrane separation technology offers advantages over other methods such as oxidation-reduction, biochemical treatment, and flocculation, including energy saving, ease of operation, and low investment.

[0003] However, membrane fouling is inevitable during the use of ceramic membranes. Membrane fouling refers to the deposition of a large number of soluble organic pollutants of varying molecular weights on or inside the membrane surface during the actual operation of the membrane filtration device. This causes a dense fouling layer to form on the membrane surface or to clog the membrane pores, resulting in a gradual decrease in ultrafiltration membrane flux and deterioration of the effluent water quality.

[0004] To mitigate membrane fouling, the following approaches can be taken to address current issues in membrane technology applications: 1. Pretreatment and combined processes: Pretreatment of the wastewater before it enters the ceramic membrane using methods such as oxidation, adsorption, and coagulation pretreatment can effectively reduce the content or form of pollutants, improving effluent quality, reducing membrane fouling, and extending membrane lifespan. However, pretreatment is time-consuming, energy-intensive, and requires significant land area and equipment, limiting its application. 2. Membrane cleaning: This generally involves physical and chemical cleaning. Physical cleaning removes fouling from the membrane surface using mechanical force. While physical cleaning shows great promise in mitigating membrane fouling, its effectiveness is limited if there is a strong interaction between the pollutants and the membrane. Chemical cleaning is the most common method. Finding suitable cleaning agents is crucial. The cleaning agent must be able to dissolve most of the surface fouling and remove it without damaging the membrane surface, thus maintaining membrane performance. In addition, the cleaning agent should be low-cost and safe; 3. Application of modified membranes: Upgrading the membrane material or changing the surface chemical properties of the ceramic membrane by using hydrophilic modification can alleviate membrane fouling from the perspective of the membrane material. This can not only give full play to the advantages of the original membrane material, but also regulate its performance through the modified components. Therefore, research on the modification of ceramic membranes has been increasing in recent years. Summary of the Invention

[0005] To develop modified ceramic membranes with better separation and antifouling properties, the present invention aims to provide a Mn-alkaline earth metal / ceramic membrane with catalytic ozonation properties and its preparation method, thereby solving the problem of membrane fouling that is prone to occur in existing ceramic membranes by coupling catalytic ozone technology.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing a catalytic ozonation Mn-alkaline earth metal / ceramic membrane is provided, comprising the following steps:

[0007] (1) Add alkaline earth metal salt to manganese acetate solution, mix evenly, then drop it into a mixed solution of complexing agent and binder, while stirring until a transparent sol is formed, and then age for 6-72 hours to obtain the active component precursor;

[0008] (2) The ceramic membrane is sequentially acid-washed, water-washed, alcohol-washed and dried to obtain a pretreated ceramic membrane. The active component precursor obtained in step (1) is uniformly coated on the surface of the pretreated ceramic membrane, and then dried, calcined and cleaned to obtain a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane.

[0009] Based on the above technical solution, the present invention can be further improved as follows:

[0010] Furthermore, in step (1), the mass ratio of alkaline earth metal salt to manganese acetate is 0.5-3:1, the molar ratio of alkaline earth metal salt to complexing agent is 1:1-1.5, and the mass ratio of alkaline earth metal salt to binder is 1:0.01-0.1.

[0011] Furthermore, in step (1), the mass ratio of alkaline earth metal salt to manganese acetate is 2:1.

[0012] Furthermore, in step (1), the concentration of the manganese acetate solution is 0.8-1.2 mol / L.

[0013] Furthermore, in step (1), the concentration of the manganese acetate solution is 1 mol / L.

[0014] Furthermore, in step (1), the concentration of the complexing agent and binder mixed solution is 2.8-3.2 mol / L.

[0015] Furthermore, in step (1), the concentration of the complexing agent and binder mixture solution is 3 mol / L.

[0016] Furthermore, in step (1), the alkaline earth metal salt is magnesium nitrate, calcium nitrate or barium nitrate, the binder is carboxymethyl cellulose, polyvinyl alcohol or polyvinylpyrrolidone, and the complexing agent is citric acid, gluconic acid or ethylenediaminetetraacetic acid.

[0017] Furthermore, in step (1), the alkaline earth metal salt is magnesium nitrate.

[0018] Furthermore, in step (1), the adhesive is polyvinylpyrrolidone.

[0019] Furthermore, in step (1), the complexing agent is citric acid.

[0020] Furthermore, in step (1), stirring is carried out at 40-100℃ and 800-1500r / min.

[0021] Furthermore, in step (1), stirring is performed at 70°C and 1000 r / min.

[0022] Furthermore, in step (1), the product is aged at room temperature for 12-48 hours.

[0023] Furthermore, in step (1), the product is aged at room temperature for 36 hours.

[0024] Furthermore, in step (2), acid washing is performed using a 0.8-1.2 mol / L nitric acid solution.

[0025] Furthermore, in step (2), acid washing is performed using a 1 mol / L nitric acid solution.

[0026] Furthermore, in step (2), the pickling process lasts for 10-15 hours.

[0027] Furthermore, in step (2), anhydrous ethanol is used for alcohol washing for 10-15 hours.

[0028] Furthermore, in step (2), the product is dried at 70-90°C.

[0029] Furthermore, in step (2), the ratio of the mass of the ceramic membrane to the total mass of the alkaline earth metal salt and manganese acetate is 10:1.

[0030] Furthermore, in step (2), a spin coater is used for coating, with a spin coater speed of 200-1000 r / min.

[0031] Furthermore, the coating time is 1-5 minutes, and the coating is applied 1-6 times.

[0032] Furthermore, apply the coating 2-6 times.

[0033] Furthermore, the coating is applied twice.

[0034] Furthermore, in step (2), the product is dried at 80-120℃ for 10-15 hours to complete the drying process.

[0035] Furthermore, in step (2), the calcination is carried out at 450-850℃ in an air atmosphere for 2-5 hours.

[0036] Furthermore, in step (2), the sample is calcined at 650°C in an air atmosphere for 2-5 hours.

[0037] Furthermore, in step (2), anhydrous ethanol or deionized water is used for cleaning.

[0038] The present invention also provides a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane prepared by the above method.

[0039] The present invention has the following beneficial effects:

[0040] 1. This invention couples membrane filtration with catalytic ozonation. Ozone possesses strong oxidizing power and is green, safe, and easily separated. After modification, the metallic active components on the ceramic membrane can promote ozone decomposition, generating free radicals (·OH, ·O2) with even stronger oxidizing power. - , 1 O2, etc., further enhance the separation performance and anti-fouling ability of the modified ceramic membrane, while also solving the problem of difficult separation and recovery of traditional catalytic ozonation catalysts.

[0041] 2. This invention selects Mn as the main active component. Compared with other transition metals (Co, Ni, Cu, Fe, etc.), Mn is more likely to undergo redox cycles with multiple valence states, which can promote electron transfer in the catalytic ozonation process and enhance the interconversion between lattice oxygen (Olat) and oxygen vacancy (Ovac), thus exhibiting relatively superior catalytic ozonation activity. This invention selects alkaline earth metals as regulating metals. For the catalytic ozonation reaction, alkaline earth metals are prone to hydration reactions, which can form more hydroxyl functional groups on the surface, further enhancing catalytic activity. In addition, manganese and alkaline earth metals can easily form Mn-OM bonds, which can effectively prevent the dissolution of Mn.

[0042] 3. This invention uses manganese as the main active metal, and uses alkaline earth metals to regulate the acid-base properties of the catalyst surface and enhance the interaction between the metal and the ceramic membrane carrier. It combines oxidation pretreatment, membrane chemical cleaning, and improvement of the membrane's antifouling ability, thereby improving the activity, stability, and antifouling ability of the Mn-alkaline earth metal / ceramic membrane catalytic ozonation treatment of organic wastewater. Attached Figure Description

[0043] Figure 1 These are physical images of the samples obtained in Example 1 and Comparative Example 1;

[0044] Figure 2 The XRD characterization spectra of the ceramic films prepared in Example 1 and Comparative Example 1 are shown.

[0045] Figure 3 Dynamic water contact angle diagrams of the ceramic membranes prepared in Example 1 and Comparative Example 1;

[0046] Figure 4 Diagram of the experimental setup for evaluating the performance of ceramic membranes;

[0047] Figure 5 The flux curves for the ceramic membrane-catalyzed ozonolysis of bovine serum albumin (BSA) prepared in Examples 1, 4-5 and Comparative Example 1 are shown.

[0048] Figure 6 for Figure 5 The corresponding BSA retention rate curve;

[0049] Figure 7 The flux curves for the ceramic membrane-catalyzed ozonolysis of bovine serum albumin (BSA) prepared in Examples 1 and 6-8 are shown.

[0050] Figure 8 for Figure 7 The corresponding BSA retention rate curve;

[0051] Figure 9 The flux curves for the ceramic membrane-catalyzed ozonolysis of bovine serum albumin (BSA) prepared in Examples 1 and 9-10 are shown.

[0052] Figure 10 for Figure 9 The corresponding BSA retention rate curve;

[0053] Figure 11 The flux curves for the ceramic membrane-catalyzed ozonolysis of bovine serum albumin (BSA) prepared in Examples 1 and 11-12 are shown.

[0054] Figure 12 for Figure 11 The corresponding BSA retention rate curve;

[0055] Figure 13 The flux curves for the ceramic membrane-catalyzed ozonolysis of bovine serum albumin (BSA) prepared in Examples 1, 13-15 are shown.

[0056] Figure 14 for Figure 13 The corresponding BSA retention rate curve;

[0057] Figure 15 The flux curves for the ceramic membrane-catalyzed ozonolysis of bovine serum albumin (BSA) prepared in Examples 1 and 16-17 are shown.

[0058] Figure 16 for Figure 15 The corresponding BSA retention rate curve;

[0059] Figure 17 The flux curves for the ceramic membrane-catalyzed ozonolysis of bovine serum albumin (BSA) prepared in Examples 1 and 18-19 are shown.

[0060] Figure 18 for Figure 17 The corresponding BSA retention rate curve;

[0061] Figure 19 The stability curve of bovine serum albumin (BSA) catalytically ozonated by the ceramic membrane prepared in Example 1 is shown.

[0062] Figure 20 for Figure 19 The corresponding BSA retention rate curve. Detailed Implementation

[0063] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0064] Example 1:

[0065] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0066] (1) Add the alkaline earth metal salt magnesium nitrate to a manganese acetate solution (concentration of 1 mol / L), mix well, and then slowly drop it into a mixed solution of binder citric acid and complexing agent polyvinylpyrrolidone (concentration of 3 mol / L). At the same time, stir at 70℃ and 1000 r / min until a transparent sol is formed, and then age at room temperature for 36 h to form a gel to obtain the active component precursor; wherein, the mass ratio of alkaline earth metal salt to manganese acetate is 2:1, the molar ratio of alkaline earth metal salt to citric acid is 1:1.2, and the mass ratio of alkaline earth metal salt to polyvinylpyrrolidone is 1:0.05;

[0067] (2) The ceramic membrane was acid-washed with 1 mol / L nitric acid solution for 12 h, then washed with deionized water until neutral, and then soaked in anhydrous ethanol for 12 h. It was dried at 80 °C to obtain a pretreated ceramic membrane. The membrane was placed on the stage of a spin coater, the spin coater speed was set to 500 r / min, and the coating time was 2 min. After the spin coater was turned on, the active component precursor obtained in step (1) was uniformly coated on the surface of the pretreated ceramic membrane twice with a syringe. It was left to stand at room temperature for 18 h, then dried at 100 °C for 12 h, and calcined at 650 °C in an air atmosphere for 4 h. It was then cleaned with anhydrous ethanol or deionized water to obtain a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane (named Mn-Mg / CM).

[0068] Example 2:

[0069] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0070] (1) Add the alkaline earth metal salt magnesium nitrate to a manganese acetate solution (concentration of 1 mol / L), mix well, and then slowly drop it into a mixed solution of citric acid and polyvinylpyrrolidone (concentration of 3 mol / L). Stir at 40℃ and 800 r / min until a transparent sol is formed, and then age at room temperature for 6 h to form a gel to obtain the active component precursor; wherein, the mass ratio of alkaline earth metal salt to manganese acetate is 0.5:1, the molar ratio of alkaline earth metal salt to citric acid is 1:1, and the mass ratio of alkaline earth metal salt to polyvinylpyrrolidone is 1:0.01;

[0071] (2) The ceramic membrane was acid-washed with 0.8 mol / L nitric acid solution for 10 h, then washed with deionized water until neutral, and then soaked in anhydrous ethanol for 10 h. It was dried at 70 °C to obtain a pretreated ceramic membrane. The membrane was placed on the spin coater platform, the spin coater speed was set to 200 r / min, and the coating time was 1 min. After the spin coater was turned on, the active component precursor obtained in step (1) was uniformly coated on the surface of the pretreated ceramic membrane once with a syringe. Then it was dried at 80 °C for 15 h, calcined at 450 °C in an air atmosphere for 5 h, and cleaned with anhydrous ethanol or deionized water to obtain a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane (named Mn-Mg / CM).

[0072] Example 3:

[0073] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0074] (1) Add the alkaline earth metal salt magnesium nitrate to a manganese acetate solution (concentration of 1 mol / L), mix well, and then slowly drop it into a mixed solution of citric acid and polyvinylpyrrolidone (concentration of 3 mol / L). At the same time, stir at 100℃ and 800 r / min until a transparent sol is formed, and then age at room temperature for 72 h to form a gel to obtain the active component precursor; wherein, the mass ratio of alkaline earth metal salt to manganese acetate is 3:1, the molar ratio of alkaline earth metal salt to citric acid is 1:1.5, and the mass ratio of alkaline earth metal salt to polyvinylpyrrolidone is 1:0.1;

[0075] (2) The ceramic membrane was acid-washed with 1.2 mol / L nitric acid solution for 15 h, then washed with deionized water until neutral, and then soaked in anhydrous ethanol for 15 h. It was dried at 90 °C to obtain a pretreated ceramic membrane. The membrane was placed on the stage of a spin coater, the spin coater speed was set to 1000 r / min, and the coating time was 5 min. After the spin coater was turned on, the active component precursor obtained in step (1) was uniformly coated on the surface of the pretreated ceramic membrane 6 times with a syringe. Then it was dried at 110 °C for 10 h, calcined at 850 °C in an air atmosphere for 2 h, and cleaned with anhydrous ethanol or deionized water to obtain a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane (named Mn-Mg / CM).

[0076] Examples 4-5:

[0077] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0078] In step (1), the alkaline earth metal salts are barium nitrate and calcium nitrate, and the rest are the same as in Example 1, to prepare catalytic ozonolysis Mn-alkaline earth metal / ceramic membranes (named Mn-Ba / CM and Mn-Ca / CM, respectively).

[0079] Examples 6-8:

[0080] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0081] In step (1), the mass ratios of alkaline earth metal salt and manganese acetate are 1:2, 1:1, and 3:1, respectively, and the rest is the same as in Example 1, to prepare catalytic ozonolysis Mn-alkaline earth metal / ceramic membranes (named 2Mn-1Mg / CM, 1Mn-1Mg / CM, and 1Mn-3Mg / CM, respectively).

[0082] Examples 9-10:

[0083] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0084] In step (1), the binders are carboxymethyl cellulose and polyvinyl alcohol, respectively, and the rest are the same as in Example 1, to prepare a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane.

[0085] Examples 11-12:

[0086] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0087] In step (1), the complexing agents are gluconic acid and ethylenediaminetetraacetic acid, respectively, and the rest are the same as in Example 1, to prepare a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane.

[0088] Examples 13-15:

[0089] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0090] In step (1), the aging times were 12h, 24h, and 48h, respectively, and the rest were the same as in Example 1, to obtain catalytic ozonolysis Mn-alkaline earth metal / ceramic membranes (named 12Mn-Mg / CM, 24Mn-Mg / CM, and 48Mn-Mg / CM, respectively).

[0091] Examples 16-17:

[0092] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0093] In step (2), the active component precursor obtained in step (1) was uniformly coated onto the surface of the pretreated ceramic membrane 4 and 6 times with a syringe, and the rest was the same as in Example 1, to obtain catalytic ozonolysis Mn-alkaline earth metal / ceramic membranes (named 4Mn-Mg / CM and 6Mn-Mg / CM, respectively).

[0094] Examples 18-19:

[0095] A catalytic ozonation method for a Mn-alkaline earth metal / ceramic membrane includes the following steps:

[0096] In step (2), the films were calcined at 450°C, 850°C and in air atmosphere, respectively, and the rest was the same as in Example 1, to obtain catalytic ozonolysis Mn-alkaline earth metal / ceramic films (named Mn-Mg / CM450 and Mn-Mg / CM850, respectively).

[0097] Comparative Example 1:

[0098] A ceramic membrane is prepared by the following steps: the pretreated ceramic membrane obtained in step (2) is named CM.

[0099] Test case

[0100] I. Physical images of the ceramic membranes prepared in Example 1 and Comparative Example 1 are shown below. Figure 1 .

[0101] Depend on Figure 1 It can be seen that black spots appear on the surface of the modified ceramic film, which may be manganese oxide formed on the surface. Magnesium oxide is white. Because the loading ratio of magnesium oxide is higher, the main body of the modified ceramic film is still white. The actual picture can macroscopically prove the successful loading of the metal elements manganese and magnesium.

[0102] II. The ceramic films prepared in Example 1 and Comparative Example 1 were characterized by XRD, and the results are shown in the figure. Figure 2.

[0103] Depend on Figure 2 The diffraction peaks of CM are 27.5°, 32.1°, 35.3°, 44.2°, and 58.0°; the diffraction peaks of Mg-Mn / CM are 26.2°, 27.5°, 32.1°, 35.2°, 42.5°, 52.8°, and 58.1°. The positions and relative intensities of the typical characteristic peaks match those of the standard spectra, thus confirming that the modified material coated on the ceramic film is the target product. XRD results indicate successful loading of the metal elements manganese and magnesium.

[0104] III. Dynamic water contact angle testing was performed on the ceramic membranes prepared in Example 1 and Comparative Example 1. The results are shown in [the table below]. Figure 3 .

[0105] Depend on Figure 3 It can be seen that the droplets of CM completely disappeared in 6.7s, while Mg-Mn / CM only took 1.3s. The shorter the time required, the stronger the hydrophilicity of the material surface. The results of dynamic water contact angle show that the hydrophilicity of the modified ceramic membrane is significantly improved. The stronger the hydrophilicity, the stronger the antifouling ability of the ceramic membrane.

[0106] IV. Effect Evaluation

[0107] The prepared modified ceramic membrane was used in a high-pressure flat sheet membrane filtration device (see...). Figure 4 The effect was evaluated using the following method: at room temperature, with the main pump speed at 40 rpm and the membrane inlet pressure at 0.1 MPa, an ozone generator with a speed of 5 L / min was used. A catalytic ozonation Mn-alkaline earth metal / ceramic membrane was used for catalytic ozonation to treat bovine serum albumin with an initial concentration of 1.0 g / L. The system was operated in dead-end circulation filtration mode, and the permeate was continuously sampled to detect the permeate volume and the bovine serum albumin concentration.

[0108] 1. The ceramic membranes prepared in Examples 1, 4-5, and Comparative Example 1 were evaluated using a high-pressure flat-panel membrane filtration device. The results are shown in the figure. Figure 5-6 .

[0109] Depend on Figure 5-6 It can be seen that, under the same amount of alkaline earth metal, the ceramic membrane modified with magnesium nitrate as the regulating component has stronger activity, higher retention rate and stronger anti-fouling ability than the ceramic membrane modified with other alkaline earth metals as the regulating component. Its retention rate of bovine serum albumin is as high as 99.9%, and the flux of the modified ceramic membrane decreases by only 16.4% during the filtration process.

[0110] 2. The modified ceramic membranes obtained in Examples 1 and 6-8 were evaluated using a high-pressure flat-panel membrane filtration device. The results are shown in [the table below]. Figure 7-8 .

[0111] Depend on Figure 7-8 It can be seen that when the loading ratio is 2:1, 1Mn-2Mg / CM exhibits the strongest catalytic activity, the highest rejection rate, and the strongest antifouling ability. This is likely due to the formation of spinel-structured MgMn2O4, which possesses even stronger catalytic activity. The rejection rate of 1Mn-2Mg / CM reaches 99.9% with increasing time, and its flux remains at 83.6% after 46 minutes of filtration, indicating that 1Mn-2Mg / CM has strong antifouling ability.

[0112] 3. The modified ceramic membranes prepared in Examples 1 and 9-10 were evaluated using a high-pressure flat-panel membrane filtration device. The results are shown in [the table below]. Figure 9-10 .

[0113] Depend on Figure 9-10 It can be seen that the filtration flux (83.6%) and retention efficiency (99.9%) of the material using polyvinylpyrrolidone as a binder are superior to the other two. This may be because polyvinylpyrrolidone itself has a pore-forming effect, which can form a microporous structure, thus increasing the filtration flux. In addition, polyvinylpyrrolidone can improve the hydrophilicity of the material by forming a hydrophilic film and increasing the surface energy of the material, making it easier to adsorb water and interact with water molecules, thereby improving the filtration flux and retention efficiency.

[0114] 4. The modified ceramic membranes prepared in Examples 1 and 11-12 were evaluated using a high-pressure flat-panel membrane filtration device. The results are shown in [the table below]. Figure 11-12 .

[0115] Depend on Figure 11-12 It can be seen that when citric acid is used as a complexing agent, the filtration flux (83.6%) and retention efficiency (99.9%) are second only to those using ethylenediaminetetraacetic acid (84.1% and 99.9%, respectively). However, ethylenediaminetetraacetic acid is expensive, has strict pH requirements, and is environmentally unfriendly, posing a risk of environmental pollution. Gluconic acid, on the other hand, has weak complexing ability and poor solubility, resulting in poor performance of the modified ceramic membrane. Citric acid, however, has strong complexing ability, is inexpensive and readily available, and is environmentally friendly.

[0116] 5. The modified ceramic membranes prepared in Examples 1 and 13-15 were evaluated using a high-pressure flat-panel membrane filtration device. The results are shown in [the table below]. Figure 13-14 .

[0117] Depend on Figure 13-14It is known that an aging time of 36 hours results in the strongest activity, highest retention rate, and strongest antifouling ability. If the aging time is too short, the transformation from sol to gel is not complete, resulting in high water content. Excessive water evaporation in the subsequent process leads to cracks in the membrane layer, affecting the filtration performance of the modified membrane. On the other hand, if the aging time is too long, the gel viscosity is higher, resulting in uneven spreading on the membrane surface and weakened adhesion to the substrate membrane surface, thus weakening the stability of the modified membrane. The 12Mn-Mg / CM membrane can achieve a retention rate of 91% in the initial stage of filtration, which can reach 99.9% with increasing filtration time, while its membrane flux decreases by only 17.1%, demonstrating excellent retention and antifouling performance.

[0118] 6. The modified ceramic membranes prepared in Examples 1 and 16-17 were evaluated using a high-pressure flat-panel membrane filtration device. The results are shown in [the table below]. Figure 15-16 .

[0119] Depend on Figure 15-16 It is known that the more coating times, the higher the retention rate of the modified membrane. This is because as the number of coating times increases, the membrane thickness also increases, resulting in a longer hydraulic residence time of the filtrate through the membrane. However, the membrane flux gradually decreases. Therefore, the number of coating times can be adjusted according to specific experimental needs. Since BSA has a large molecular weight, two coatings are sufficient to meet the requirements, so two coatings were subsequently chosen. The retention rate of 2Mn-Mg / CM reaches 91% in the initial stage of filtration and can reach 99.9% with increasing filtration time, while its membrane flux decreases by only 17.1%, demonstrating excellent retention and antifouling performance.

[0120] 7. The modified ceramic membranes prepared in Examples 1 and 18-19 were evaluated using a high-pressure flat-panel membrane filtration device. The results are shown in [the table below]. Figure 17-18 .

[0121] Depend on Figure 17-18 It is evident that calcination temperature significantly impacts the performance of the modified membrane. This is likely because calcination temperature alters the crystal structure of the active components. At 450-650℃, the main crystal structures produced are γ-MnO2 and active magnesium oxide. As the temperature increases, the γ-crystal gradually transforms into the α-crystal, and the active magnesium oxide gradually converts into light magnesium oxide. The α-crystal exhibits excellent thermal stability. Therefore, the calcination temperature can be adjusted according to specific requirements. Since the reaction occurs at room temperature, a calcination temperature of 650℃ was chosen. The Mn-Mg / CM650 membrane achieves a rejection rate of 91% in the initial stage of filtration, reaching 99.9% with increasing filtration time, while its membrane flux decreases by only 17.1%, demonstrating excellent rejection and antifouling performance.

[0122] V. Stability

[0123] The stability of the modified ceramic membrane prepared in Example 1 was evaluated using a high-pressure flat-plate membrane filtration device. The specific method was as follows: at room temperature, with a main pump speed of 40 rpm and a membrane inlet pressure of 0.1 MPa, an ozone generator with a flow rate of 5 L / min was used. A catalytic ozonation Mn-alkaline earth metal / ceramic membrane was employed for catalytic ozonation to treat bovine serum albumin (BSA) with an initial concentration of 1.0 g / L. The filtration was run in dead-end circulation mode, and permeate samples were continuously taken. The permeate volume and BSA concentration were measured. After filtration, the process was repeated four times under the same experimental conditions. The results are shown in [Figure 1]. Figures 19-20 .

[0124] Depend on Figures 19-20 It can be seen that after four cycles, the rejection rate of Mn-Mg / CM650 decreased from 91.4% in the initial stage of filtration to 77.5%, and from 99.9% to 96.4% in the later stage; the membrane flux decreased from 85% to 65%. In contrast, the rejection rate of the unmodified membrane filtration was only 60% and the membrane flux was only 15% in one pass. Therefore, the catalytic performance, rejection performance, and antifouling ability of Mn-alkaline earth metal / CM were significantly improved.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the preparation of catalytic ozonation Mn-alkaline earth metal / ceramic membranes, characterized by, Includes the following steps: (1) Add alkaline earth metal salt to manganese acetate solution, mix evenly, then drop it into a mixed solution of complexing agent and binder, while stirring until a transparent sol is formed, and then age for 6-72 hours to obtain the active component precursor; (2) The ceramic membrane is sequentially acid-washed, water-washed, alcohol-washed and dried to obtain a pretreated ceramic membrane. The active component precursor obtained in step (1) is uniformly coated on the surface of the pretreated ceramic membrane, left to stand for 6-24 hours, and then dried, calcined and cleaned to obtain a catalytic ozonolysis Mn-alkaline earth metal / ceramic membrane. In step (1), the alkaline earth metal salt is magnesium nitrate, calcium nitrate or barium nitrate, the binder is carboxymethyl cellulose or polyvinylpyrrolidone, and the complexing agent is citric acid, gluconic acid or ethylenediaminetetraacetic acid.

2. The method for preparing a catalytic ozonation Mn-alkaline earth metal / ceramic membrane according to claim 1, characterized in that, In step (1), the mass ratio of alkaline earth metal salt to manganese acetate is 0.5-3:1, the molar ratio of alkaline earth metal salt to complexing agent is 1:1-1.5, and the mass ratio of alkaline earth metal salt to binder is 1:0.01-0.

1.

3. The method for preparing a catalytic ozonation Mn-alkaline earth metal / ceramic membrane according to claim 1, characterized in that, In step (1), stirring is carried out at 40-100℃ and 800-1500r / min.

4. The method for preparing a catalytic ozonation Mn-alkaline earth metal / ceramic membrane according to claim 1, characterized in that, In step (2), acid washing is performed using a 0.8-1.2 mol / L nitric acid solution.

5. The method for preparing a catalytic ozonation Mn-alkaline earth metal / ceramic membrane according to claim 1, characterized in that, In step (2), the ratio of the mass of the ceramic membrane to the total mass of the alkaline earth metal salt and manganese acetate is 10:

1.

6. The method for preparing a catalytic ozonation Mn-alkaline earth metal / ceramic membrane according to claim 1, characterized in that, In step (2), a spin coater is used for coating, with a spin coater speed of 200-1000 r / min.

7. The method for preparing a catalytic ozonation Mn-alkaline earth metal / ceramic membrane according to claim 1, characterized in that, In step (2), the product is dried at 80-120℃ for 10-15 hours to complete the drying process.

8. The process for the preparation of catalytic ozonation Mn-alkaline earth metal / ceramic membranes according to claim 1, characterized in that, In step (2), calcination is carried out at 450-850℃ in an air atmosphere for 2-5 hours.

9. The catalytic ozonation Mn-alkaline earth metal / ceramic membrane prepared by the method according to any one of claims 1-8.

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