Modified ceramic membrane and preparation method and application thereof

Abstract

The application belongs to the technical field of water treatment, and particularly relates to a modified ceramic membrane and a preparation method and application thereof. The application provides a modified ceramic membrane, which comprises a ceramic membrane, the ceramic membrane comprises a support layer and a separation layer, metal oxides are embedded in the pore structure of the support layer, and the separation layer is loaded with a layered double metal oxide. In the application, the layered double metal oxide has abundant active sites and good catalytic activity performance on persulfate; the surface and internal pore structure of the modified ceramic membrane provided by the application both contain catalysts, the contact area and contact reaction time between the catalysts, persulfate and organic pollutants are increased, the catalytic oxidation efficiency is improved, the reinforced removal of organic matters is realized, and membrane pollution is significantly slowed down.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a modified ceramic membrane, its preparation method, and its application. Background Technology

[0002] Although ceramic membrane ultrafiltration technology has been widely applied in drinking water treatment and secondary effluent reuse in wastewater treatment plants, it faces significant bottlenecks: poor removal efficiency for organic matter and ceramic membrane fouling caused by natural organic matter (NOM). Combining catalytic ceramic membranes with advanced oxidation processes can simultaneously achieve organic matter removal and NOM membrane fouling control during filtration. Sulfate radical-based advanced oxidation technology can serve as an alternative to hydroxyl radicals, exhibiting good selectivity for organic pollutants; furthermore, due to its higher redox potential and longer half-life, it demonstrates stronger activity in degrading organic pollutants. Therefore, conducting research on persulfate activation of catalytic ceramic membranes and constructing an integrated in-situ coupled system of persulfate advanced oxidation / catalytic ceramic membrane ultrafiltration is an effective way to simultaneously enhance organic matter removal and NOM membrane fouling control in water purification.

[0003] Ensuring the activation efficiency of persulfate is crucial for constructing an in-situ coupled system of persulfate advanced oxidation / ceramic membrane ultrafiltration. Currently, the preparation of catalytic ceramic membranes typically involves loading the catalyst onto the membrane surface. During filtration, the contact time between the catalyst layer and persulfate is short, making it difficult to guarantee activation efficiency. Patent CN201810746333.7 proposes an improved scheme by embedding active catalytic materials mixed with the ceramic membrane support layer. However, the active catalytic materials need to be sintered at high temperatures (1000℃~1300℃) together with the support layer aggregate. Furthermore, after sintering, the active catalytic materials are largely covered by the support layer aggregate, significantly reducing their activation capacity for persulfate. Therefore, the low catalytic oxidation efficiency of existing catalytic ceramic membranes is a major problem in the current field of catalytic ceramic membrane water purification. Summary of the Invention

[0004] In view of this, the present invention provides a modified ceramic membrane, its preparation method and application. The modified ceramic membrane provided by the present invention has a higher activation efficiency for persulfate, and can achieve efficient removal of organic matter and simultaneous efficient control of membrane fouling.

[0005] To address the aforementioned technical problems, the present invention provides a modified ceramic membrane, comprising a support layer and a separation layer, wherein the support layer has a porous structure in which metal oxides are embedded, and the separation layer is loaded with a layered bimetallic oxide.

[0006] Preferably, the ceramic membrane has an average pore size of 200–600 nm.

[0007] Preferably, the metal oxide includes cobalt oxide, manganese oxide, or copper oxide;

[0008] The mass ratio of the metal oxide to the ceramic film is 0.1 to 0.6:100.

[0009] Preferably, the layered bimetallic oxide is a layered bimetallic oxide composed of a divalent metal and a trivalent metal;

[0010] The mass ratio of the layered bimetallic oxide to the ceramic film is 1 to 5:100.

[0011] The present invention also provides a method for preparing the modified ceramic membrane described in the above technical solution, comprising the following steps:

[0012] A soluble metal salt, a first dispersant, and a first organic solvent are mixed to obtain an embedded solution;

[0013] A layered bimetallic hydroxide, a second dispersant, and a second organic solvent are mixed to obtain a loaded solution;

[0014] The embedded solution is first vacuum filtered using a ceramic membrane as a filter membrane, and then first calcined to obtain a ceramic membrane with embedded metal oxides.

[0015] The loaded solution is subjected to a second vacuum filtration using the ceramic membrane with embedded metal oxide as a filter membrane, followed by a second calcination to obtain the modified ceramic membrane.

[0016] Preferably, the first dispersant and the second dispersant are independently polyethylene glycol or hydroxypropyl methylcellulose;

[0017] The mass concentration of the first dispersant in the embedded solution is 2-6 g / L, and the mass concentration of the second dispersant in the loaded solution is 2-6 g / L.

[0018] The molecular weight of the polyethylene glycol is 1000-8000 Da.

[0019] Preferably, the temperatures of the first and second calcinations are independently 450–550°C, the heating rate to the required temperature for the first or second calcination is independently 4–6°C / min, and the holding time for the first or second calcination is independently 3–5h.

[0020] Preferably, the vacuum levels of the first vacuum filter and the second vacuum filter are independently 0.08 to 0.1 MPa;

[0021] The first vacuum filtration time is 10–60 min;

[0022] The second vacuum filtration time is 20 to 30 minutes.

[0023] Preferably, the soluble metal salt is cobalt nitrate, copper nitrate, or manganese nitrate;

[0024] The mass concentration of the soluble metal salt in the embedded solution is 10–30 g / L.

[0025] The present invention also provides the application of the modified ceramic membrane described in the above technical solution or the modified ceramic membrane prepared by the preparation method described in the above technical solution in water treatment.

[0026] This invention provides a modified ceramic membrane, comprising a support layer and a separation layer. The support layer has a porous structure in which metal oxides are embedded, and the separation layer is loaded with a layered bimetallic oxide. In this invention, the layered bimetallic oxide has abundant active sites and exhibits good catalytic activity against persulfate. The modified ceramic membrane provided by this invention contains catalysts in both its surface and internal pore structure, increasing the contact area and reaction time between the catalyst, persulfate, and organic pollutants, thereby improving catalytic oxidation efficiency, achieving enhanced removal of organic matter, and significantly mitigating membrane fouling. Attached Figure Description

[0027] Figure 1 Diagram of a submersible membrane module vacuum filtration device;

[0028] Figure 2 CoAl prepared in Example 1 30 Planar microstructure of @AM-Co30;

[0029] Figure 3 CoAl prepared in Example 1 30 Microscopic morphology of the cross section of @AM-Co30. Detailed Implementation

[0030] This invention provides a modified ceramic membrane, comprising a ceramic membrane including a support layer and a separation layer. The support layer has a pore structure in which a metal oxide is embedded, and the separation layer is loaded with a layered bimetallic oxide. In this invention, the average pore size of the ceramic membrane is preferably 200–600 nm, more preferably 200–400 nm. In this invention, the metal oxide preferably includes cobalt oxide, manganese oxide, or copper oxide, more preferably cobalt oxide. In this invention, the mass ratio of the metal oxide to the ceramic membrane is preferably 0.1–0.6:100, more preferably 0.3–0.6:100. In this invention, the layered bimetallic oxide is preferably a composite layered bimetallic oxide of a divalent and a trivalent metal; the layered bimetallic oxide preferably includes CoAl layered bimetallic oxide (CoAl-LMO), CuAl layered bimetallic oxide (CuAl-LMO), or MnAl layered bimetallic oxide (MnAl-LMO), more preferably CoAl layered bimetallic oxide. In this invention, the mass ratio of the layered bimetallic oxide to the ceramic film is preferably 1 to 5:100, and more preferably 3 to 5:100.

[0031] This invention simultaneously loads catalysts onto the surface and within the pores of a ceramic membrane, preparing an embedded-external dual-catalyst layer ceramic membrane. This increases the contact time between the membrane region and persulfate, significantly improving its activation efficiency. In this invention, the surface separation layer and the support layer pores produce a synergistic catalytic effect, achieving secondary degradation of pollutants and further enhancing the removal of organic matter in water membrane filtration and the antifouling performance of ultrafiltration membranes.

[0032] The present invention also provides a method for preparing the modified ceramic membrane described in the above technical solution, comprising the following steps:

[0033] A soluble metal salt, a first dispersant, and a first organic solvent are mixed to obtain an embedded solution;

[0034] A layered bimetallic hydroxide, a second dispersant, and a second organic solvent are mixed to obtain a loaded solution;

[0035] The embedded solution is first vacuum filtered using a ceramic membrane as a filter membrane, and then first calcined to obtain a ceramic membrane with embedded metal oxides.

[0036] The loaded solution is subjected to a second vacuum filtration using the ceramic membrane with embedded metal oxide as a filter membrane, followed by a second calcination to obtain the modified ceramic membrane.

[0037] This invention mixes a soluble metal salt, a first dispersant, and a first organic solvent to obtain an embedded solution. In this invention, the soluble metal salt is preferably cobalt nitrate, copper nitrate, or manganese nitrate, more preferably cobalt nitrate; the cobalt nitrate is preferably cobalt nitrate monohydrate. In this invention, the first dispersant is preferably polyethylene glycol or hydroxypropyl methylcellulose, more preferably polyethylene glycol. In this invention, the molecular weight of the polyethylene glycol is preferably 1000–8000 Da, more preferably 4000–6000 Da. In this invention, the first organic solvent is preferably ethanol or methanol, more preferably ethanol.

[0038] In this invention, the mass concentration of the soluble metal salt in the embedded solution is preferably 10–30 g / L, more preferably 20 g / L. In this invention, the mass concentration of the first dispersant in the embedded solution is preferably 2–6 g / L, more preferably 4 g / L.

[0039] The present invention has no special requirements for the mixing, as long as the mixing is uniform.

[0040] This invention involves mixing a layered bimetallic hydroxide, a second dispersant, and a second organic solvent to obtain a loaded solution. Preferably, the layered bimetallic hydroxide is prepared using a low-saturation co-precipitation method. In this invention, the preparation method of the layered bimetallic hydroxide preferably includes the following steps:

[0041] A mixed solution of metal salts is obtained by dissolving divalent and trivalent metal salts in water.

[0042] The metal salt mixture and the alkaline solution are mixed and then added dropwise to water to obtain an alkaline mixture.

[0043] The alkaline mixed solution is aged to obtain the layered bimetallic hydroxide.

[0044] This invention dissolves divalent and trivalent metal salts in water to obtain a mixed metal salt solution. In this invention, the divalent metal salt preferably includes cobalt, copper, or manganese salts, and more preferably cobalt salts. In this invention, the cobalt salt is preferably cobalt nitrate, cobalt chloride, or cobalt sulfate, and more preferably cobalt nitrate. In this invention, the cobalt nitrate is preferably cobalt nitrate tetrahydrate. In this invention, the trivalent metal salt preferably includes aluminum, iron, or chromium salts, and more preferably aluminum salts. In this invention, the aluminum salt is preferably aluminum nitrate, aluminum chloride, or aluminum sulfate, and more preferably aluminum nitrate. In this invention, the aluminum nitrate is preferably aluminum nitrate nonahydrate. In this invention, the molar ratio of the divalent and trivalent metal salts is preferably 1:1 to 4, and more preferably 1:3 to 4. In this invention, the water is preferably ultrapure water.

[0045] In this invention, the mass concentration of divalent metal salt in the metal salt mixed solution is preferably 0.1-0.25 g / mL, more preferably 0.15-0.25 g / mL; the mass concentration of trivalent metal salt in the metal salt mixed solution is preferably 0.06-0.1 g / mL, more preferably 0.08-0.1 g / mL.

[0046] The present invention has no special requirements for the dissolution, as long as it can be completely dissolved.

[0047] After obtaining the metal salt mixed solution, the present invention mixes the metal salt mixed solution and an alkaline solution and then adds the mixture dropwise to water to obtain an alkaline mixed solution. In the present invention, the water is preferably ultrapure water or distilled water, more preferably ultrapure water. In the present invention, the alkaline substance in the alkaline solution is preferably one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate, more preferably a mixture of sodium hydroxide and sodium carbonate or a mixture of potassium hydroxide and potassium carbonate. In the present invention, when the alkaline substance is a mixture of sodium hydroxide and sodium carbonate, the molar ratio of sodium hydroxide to sodium carbonate is preferably 1–3:1, more preferably 1.7–2:1; when the alkaline substance is a mixture of potassium hydroxide and potassium carbonate, the molar ratio of potassium hydroxide to potassium carbonate is preferably 1–3:1, more preferably 1.7–2:1. In the present invention, the molar concentration of the alkaline substance in the alkaline solution is preferably 0.4–0.5 mol / L, more preferably 0.42–0.45 mol / L.

[0048] In this invention, the volume ratio of the metal salt mixed solution to the alkaline solution is preferably 1:1.8 to 2.2, and more preferably 1:2.

[0049] In this invention, the pH value of the alkaline mixed solution is preferably 8-9, more preferably 8.5. This invention does not have special requirements on the amount of water used, as long as it meets the pH value of the alkaline mixed solution.

[0050] In this invention, the dropping rate is preferably 0.5–2 mL / min, more preferably 0.5–1 mL / min. The dropping temperature is preferably 50–70°C, more preferably 60–70°C; the dropping process is preferably accompanied by stirring, preferably magnetic stirring, and the stirring speed is preferably 500–700 r / min, more preferably 600–700 r / min.

[0051] After obtaining the alkaline mixed solution, the present invention ages the alkaline mixed solution to obtain the layered bimetallic hydroxide. In the present invention, the aging temperature is preferably 75-85°C, more preferably 80-85°C; the aging time is preferably 36-60 hours, more preferably 48-55 hours.

[0052] In this invention, the aging process preferably further includes: filtering the aged system to obtain a solid; and sequentially washing and drying the solid to obtain the layered bimetallic hydroxide. This invention has specific requirements for the filtration process, which can be achieved using conventional methods in the art. In this invention, the washing is preferably done with water, and the pH of the washing solution is neutral. In this invention, the drying temperature is preferably 75–85°C, more preferably 80°C; the drying time is preferably 10–14 hours, more preferably 12 hours.

[0053] In this invention, the particle size of the layered bimetallic hydroxide is preferably 30-100 nm, more preferably 50-80 nm.

[0054] In this invention, the second dispersant is preferably polyethylene glycol or hydroxypropyl methylcellulose, more preferably polyethylene glycol, wherein the molecular weight of the polyethylene glycol is preferably 1000-8000 Da, more preferably 4000-6000 Da. In this invention, the second organic solvent is preferably ethanol or methanol, more preferably ethanol.

[0055] In this invention, the mass concentration of the layered bimetallic hydroxide in the loaded solution is preferably 0.02–0.3 g / L, more preferably 0.04–0.2 g / L. In this invention, the mass concentration of the second dispersant in the loaded solution is preferably 2–6 g / L, more preferably 4 g / L.

[0056] The present invention has no special requirements for the mixing, as long as the mixing is uniform.

[0057] After obtaining the embedded solution, the present invention performs a first vacuum filtration on the embedded solution using a ceramic membrane as a filter membrane, followed by a first calcination to obtain a ceramic membrane with embedded metal oxides. In this invention, the ceramic membrane material is preferably alumina, titanium oxide, zirconium oxide, or silicon nitride, more preferably alumina. In this invention, the ceramic membrane is preferably a hollow fiber ceramic membrane, a flat ceramic membrane, or a tubular ceramic membrane, more preferably a hollow fiber membrane.

[0058] In this invention, the first vacuum filtration method is preferably suction filtration or pressure filtration, more preferably suction filtration. In this invention, the vacuum degree of the first vacuum filtration is preferably 0.08–0.1 MPa, more preferably 0.09–0.1 MPa. In this invention, the first vacuum filtration time is preferably 10–60 min, more preferably 20–50 min. Under the above-defined vacuum conditions, the loading of metal oxides in the modified ceramic membrane is preferably controlled by controlling the first vacuum filtration time. The filtration time and the loading of metal oxides are positively linearly correlated, as shown in Equation 1: y = 0.1xEquation 1, where y is the loading (mg) and x is the filtration time (min). In this invention, the ceramic membrane is preferably assembled into an immersion module under external pressure during the first vacuum filtration. Specifically, the immersion module consists of several ceramic membranes, one end of which is sealed with AB glue, and the other end connected to a filtration pipeline. The assembled immersion module is immersed in a container holding an embedded solution. A pressure gauge is installed on the filtration pipeline to display the filtration pressure. A gear pump is activated to achieve circulating filtration. A schematic diagram of the immersion module filtration device, using a hollow fiber ceramic membrane as an example, is shown below. Figure 1 As shown, after sealing one end of two parallel hollow fiber ceramic membranes with AB glue, the other end is connected to a filtration pipeline to obtain an immersion membrane module; the assembled immersion membrane module is immersed in a container containing an embedded solution, and a gear pump is turned on to achieve circulating filtration.

[0059] In this invention, the first step before calcination preferably includes: sequentially washing and drying the membrane after the first vacuum filtration. In this invention, the washing is preferably done with water, and the number of water washes is preferably 2 to 4 times, more preferably 3 times. In this invention, the drying temperature is preferably 50 to 70°C, more preferably 60 to 70°C; the drying time is preferably 5 to 7 hours, more preferably 5 to 6 hours.

[0060] In this invention, the temperature of the first calcination is preferably 450-550°C, more preferably 480-500°C; the heating rate to the temperature required for the first calcination is preferably 4-6°C / min, more preferably 5°C / min; and the holding time of the first calcination is preferably 3-5 hours, more preferably 4 hours.

[0061] In this invention, the product after the first calcination is preferably cooled to room temperature, preferably 20–35°C, more preferably 25–30°C. This invention does not have special requirements for the cooling method, as long as the desired temperature is achieved. In this invention, the first calcination converts soluble metal salts into metal oxides.

[0062] After obtaining the loaded solution and the ceramic membrane with embedded metal oxides, the present invention uses the ceramic membrane with embedded metal oxides as a filter membrane to perform a second vacuum filtration on the loaded solution, followed by a second calcination to obtain the modified ceramic membrane. In the present invention, the second vacuum filtration method is preferably suction filtration or pressure filtration, more preferably suction filtration. In the present invention, the vacuum degree of the second vacuum filtration is preferably 0.08–0.1 MPa, more preferably 0.09–0.1 MPa. In the present invention, the second vacuum filtration time is preferably 20–30 min, more preferably 30 min. Under the above-defined vacuum degree and second vacuum filtration time conditions, the present invention preferably controls the loading amount of layered bimetallic oxides on the surface of the modified ceramic membrane by controlling the concentration of the loaded solution used for the second vacuum filtration. During the second vacuum filtration, the ceramic membrane with embedded metal oxides adopts an immersion module external pressure mode; the immersion module external pressure mode is preferably consistent with the immersion module external pressure mode of the first vacuum filtration, and will not be elaborated here.

[0063] In this invention, the process before the second calcination preferably includes drying the second vacuum-filtered membrane. In this invention, the drying temperature is preferably 70–90°C, more preferably 80–90°C; the drying time is preferably 6–10 hours, more preferably 8–9 hours.

[0064] In this invention, the temperature of the second calcination is preferably 450–550°C, more preferably 480–500°C; the heating rate to the required temperature for the second calcination is preferably 4–6°C / min, more preferably 5°C / min; and the holding time for the second calcination is preferably 3–5 h, more preferably 4 h. This invention, through the second calcination, enables the formation of layered bimetallic oxides (LMO) from layered bimetallic hydroxides.

[0065] The preparation method provided by this invention is simple and easy to operate. This invention loads the catalyst precursor into the pores of a ceramic membrane and then calcines it to fully expose the active sites of the catalyst, which is beneficial for the activation of persulfate. Simultaneously, this invention employs vacuum filtration technology to easily and firmly load the catalyst into the pores of the separation layer and support layer on the surface of the ceramic membrane. The combined effect of the two catalysts further enhances the membrane catalytic activity. The catalyst loading in this invention leads to a smaller pore size in the membrane separation layer, improving membrane separation efficiency. By loading the catalyst into the pores of the ceramic membrane support layer and the surface separation layer, this invention can significantly improve the stability and catalytic efficiency of the catalytic ceramic membrane, achieving efficient removal of organic matter and control of membrane fouling.

[0066] The present invention uses a vacuum filtration method to load the catalyst, which improves the dispersibility and stability of the catalyst. The preparation method is simple, easy to operate, low in cost, and short in cycle, and can be widely promoted and applied, showing good application prospects.

[0067] This invention also provides the application of the modified ceramic membrane described in the above-described technical solutions or the modified ceramic membrane prepared by the preparation method described in the above-described technical solutions in water treatment. In this invention, the modified ceramic membrane is preferably used as an ultrafiltration membrane for water treatment. This invention preferably uses the modified ceramic membrane in combination with persulfate. In the field of water treatment, the modified ceramic membrane is preferably combined with persulfate for the removal of organic matter and the control of membrane fouling in water membrane filtration.

[0068] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0069] Example 1

[0070] Step 1: Dissolve 4.365 g (0.02 mol) Co(NO3)2·4H2O and 1.875 g (0.005 mol) Al(NO3)3·9H2O in 20 mL of ultrapure water to obtain a mixed metal salt solution; dissolve 680 mg (17 mmol) NaOH and 1060 mg (10 mmol) Na2CO3 in 40 mL of ultrapure water to obtain an alkaline solution; add the mixed metal salt solution and the alkaline solution dropwise to 250 mL of ultrapure water at 70 °C (with magnetic stirring at 600 r / min) at a dropping rate of 0.8 mL / min to obtain an alkaline mixed solution with a pH of 8.5; age the alkaline mixed solution at 80 °C for 48 h and then filter to obtain a solid; wash the solid until the washing liquid is neutral and then dry it at 80 °C for 12 h to obtain CoAl layered bimetallic hydroxide with an average particle size of 60 nm;

[0071] Step 2: Dissolve 1g of polyethylene glycol (4000Da) in 250mL of ethanol (stirring at 60℃ for 20min), then add 5g of Co(NO3)2·H2O to obtain a red intercalation solution; utilize... Figure 1 The immersion module shown uses an alumina ceramic hollow fiber membrane (AM) with an average pore size of 400 nm as the filter membrane. The embedded solution is vacuum filtered under a vacuum pressure of 0.1 MPa to filter Co(NO3)2 particles into the membrane pores of the support layer of the alumina ceramic hollow fiber membrane. The filtration time is 30 min. The membrane after filtration is washed three times with ultrapure water, dried at 60 °C for 6 h, and then calcined at 500 °C for 4 h to obtain a ceramic membrane with embedded cobalt oxide, denoted as AM-Co30.

[0072] Step 3: Disperse 30 mg of CoAl layered bimetallic hydroxide in 250 mL of anhydrous ethanol solution containing 1 g of polyethylene glycol (4000 Da) to obtain a loaded solution; utilize Figure 1The submerged module shown uses AM-Co30 as the filter membrane to vacuum filter 250 mL of loaded solution under a vacuum pressure of 0.1 MPa for 30 min. After filtration, the membrane is dried at 80 °C for 8 h and then calcined in a muffle furnace at 500 °C for 4 h to obtain a modified ceramic membrane, denoted as CoAl. 30 @AM-Co30.

[0073] The CoAl prepared in Example 1 was examined using a scanning electron microscope. 30 The planar microstructure of @AM-Co30 was examined to obtain a planar SEM image, as shown below. Figure 2 As shown. The CoAl prepared in Example 1 was analyzed using scanning electron microscopy and X-ray energy dispersive spectroscopy. 30 The cross-sectional microstructure of @AM-Co30 was examined, and SEM and EDS-mapping images of the cross-section were obtained, as shown below. Figure 3 As shown, the left image is a cross-sectional SEM image, and the right image is the corresponding EDX-mapping element mapping image.

[0074] Depend on Figure 2 and Figure 3 It can be seen that the metal oxides are successfully and uniformly dispersed on the membrane surface and in the membrane pores.

[0075] Example 2

[0076] The modified ceramic membrane was prepared according to the method of Example 1, except that the vacuum filtration time in step 2 was 10 min.

[0077] Example 3

[0078] The modified ceramic membrane was prepared according to the method of Example 1, except that the vacuum filtration time in step 2 was 20 min.

[0079] Example 4

[0080] The modified ceramic membrane was prepared according to the method of Example 1, except that the vacuum filtration time in step 2 was 60 min.

[0081] Example 5

[0082] The modified ceramic membrane was prepared according to the method of Example 1, except that in step 3, the loading solution was prepared by dispersing 10 mg of CoAl layered bimetallic hydroxide in 250 mL of anhydrous ethanol solution containing 1 g of polyethylene glycol (4000 Da).

[0083] Example 6

[0084] The modified ceramic membrane was prepared according to the method of Example 1, except that in step 3, the loading solution was prepared by dispersing 50 mg of CoAl layered bimetallic hydroxide in 250 mL of anhydrous ethanol solution containing 1 g of polyethylene glycol (4000 Da).

[0085] Comparative Example 1

[0086] 1 g of polyethylene glycol (4000 Da) was dissolved in 250 mL of ethanol solution and stirred at 60 °C for 20 min. Then, 5 g of Co(NO3)2·H2O was added to obtain a red intercalation solution. Co(NO3)2 particles were filtered into the pores of an AM membrane under a vacuum pressure of 0.1 MPa for 30 min. The membrane surface was then washed with ultrapure water and dried at 60 °C for 6 h. Finally, the membrane was calcined at 500 °C for 4 h to obtain a modified film, denoted as AM-Co30.

[0087] Comparative Example 2

[0088] After preparing CoAl layered bimetallic hydroxide according to the method of Example 1, it was calcined at 500°C for 4 hours to obtain CoAl layered bimetallic oxide (CoAl-LMO);

[0089] 30 mg of CoAl-LMO was dispersed in 250 mL of anhydrous ethanol solution containing 1 g of polyethylene glycol (4000 Da). The solution was filtered under vacuum at 0.1 MPa for 30 min onto AM, then dried in an oven at 80 °C for 8 h. Finally, it was calcined in a muffle furnace at 500 °C for 4 h to obtain the modified film, denoted as CoAl. 30 @AM.

[0090] The loading of cobalt oxide and CoAl layered bimetallic oxides in the modified ceramic films prepared in Examples 1-6 and Comparative Examples 1-2 was determined by weighing method, and the results are listed in Table 1.

[0091] The modified ceramic membranes prepared in Examples 1-6 and Comparative Examples 1-2 were used to conduct filtration experiments on actual surface water of the Beiyun River in Tianjin under a cross-flow filtration device at 0.2 MPa. The persulfate (PMS) dosage was 1.0 mmol / L. The results of membrane specific flux and total organic carbon (TOC) removal rate in leachate after filtration for 30 min are listed in Table 1.

[0092] Table 1. Performance of the modified ceramic membranes prepared in Examples 1-6 and Comparative Examples 1-2

[0093]

[0094] As can be seen from the results in Table 1, the membrane specific flux values ​​of Comparative Examples 1 and 2 at the end of filtration were 0.4944 and 0.6316, respectively. In contrast, the membrane specific flux values ​​of Examples 1 to 6 were significantly improved. At the same time, the TOC removal rates in the membrane permeate of Comparative Examples 1 and 2 were 47.16% and 58.35%, respectively. The TOC removal rates in the membrane permeate of Examples 1 to 6 were also significantly improved. This indicates that the embedded-external dual-catalyst ceramic membrane provided by the present invention further improves the PMS activation rate compared with the single-catalyst ceramic membrane, achieving efficient removal of organic matter and mitigation of membrane fouling.

[0095] In addition, the metal leaching amount in the percolation water of the membrane filtration system was tested, and the results are shown in Table 1. The Co ion leaching amount in the percolation water of Example 1 was 0.211 mg / L, which is much lower than 0.340 mg / L in Comparative Example 1 and 0.567 mg / L in Comparative Example 2, indicating that the embedded-external dual-catalyst layer ceramic membrane is more stable than the single-catalyst layer ceramic membrane.

[0096] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a modified ceramic membrane, characterized in that, Includes the following steps: A soluble metal salt, a first dispersant, and a first organic solvent are mixed to obtain an embedded solution; A layered bimetallic hydroxide, a second dispersant, and a second organic solvent are mixed to obtain a loaded solution; The embedded solution is first vacuum filtered using a ceramic membrane as a filter membrane, and then first calcined to obtain a ceramic membrane with embedded metal oxides. The loaded solution is subjected to a second vacuum filtration using the ceramic membrane with embedded metal oxide as a filter membrane, followed by a second calcination to obtain the modified ceramic membrane; The temperatures of the first and second calcinations are independently 450~550℃; The first vacuum filtration time is 30 minutes; The mass concentration of the soluble metal salt in the embedded solution is 10~30 g / L; In the first vacuum filtration, the ceramic membrane is assembled into an immersion module under external pressure. The immersion membrane module consists of several ceramic membranes, one end of which is sealed with AB glue, and the other end is connected to a filtration pipeline. The assembled immersion membrane module is immersed in a container containing an embedded solution. The gear pump is turned on to achieve circulating filtration. The modified ceramic membrane includes a ceramic membrane, which includes a support layer and a separation layer. The support layer has a porous structure in which metal oxides are embedded, and the separation layer is loaded with layered bimetallic oxides. The mass ratio of the metal oxide to the ceramic film is 0.3:100; The ceramic membrane has an average pore size of 200~600nm; The metal oxide includes cobalt oxide, manganese oxide, or copper oxide; The layered bimetallic oxide is a composite of divalent and trivalent metals; The layered bimetallic oxide includes CoAl layered bimetallic oxide, CuAl layered bimetallic oxide, or MnAl layered bimetallic oxide.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the layered bimetallic oxide to the ceramic film is 1~5:

100.

3. The preparation method according to claim 1, characterized in that, The first and second dispersants are independently polyethylene glycol or hydroxypropyl methylcellulose; The mass concentration of the first dispersant in the embedded solution is 2~6 g / L, and the mass concentration of the second dispersant in the loaded solution is 2~6 g / L; The molecular weight of the polyethylene glycol is 1000~8000 Da.

4. The preparation method according to claim 1, characterized in that, The heating rate to the temperature required for the first or second calcination is independently 4~6℃ / min, and the holding time for the first or second calcination is independently 3~5h.

5. The preparation method according to claim 1, characterized in that, The vacuum levels of the first and second vacuum filters are independently 0.08~0.1 MPa; The second vacuum filtration time is 20~30 minutes.

6. The preparation method according to claim 1, characterized in that, The soluble metal salt is cobalt nitrate, copper nitrate, or manganese nitrate.

7. The application of the modified ceramic membrane prepared by the preparation method according to any one of claims 1 to 6 in water treatment.

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