ZIF-based catalytic ceramic membrane, preparation method and application of ZIF-based catalytic ceramic membrane in water treatment

Abstract

The invention discloses a ZIF-based catalytic ceramic membrane, a preparation method and application of the ZIF-based catalytic ceramic membrane in water treatment, and belongs to the technical field of environmental functional materials and membrane separation. According to the method, a bimetallic precursor solution and an organic ligand solution are adopted, ZIF crystals grow on a ceramic membrane in situ, and then the ZIF-based catalytic ceramic membrane with Co-Co metallic bond and Co-N coordination double active sites is prepared through high-temperature pyrolysis and acid pickling treatment. The prepared ZIF-based catalytic ceramic membrane has high porosity (the specific surface area is greater than or equal to 360 m < 2 > / g) and strong binding force, can stably operate for 3720 minutes or more in a continuous flow reaction, has a removal rate of up to 90% for electronic-enriched pollutants such as sulfamethoxazole and the like, and can resist water quality interference. The process is simple, active sites are controllable, and the method is suitable for high-efficiency low-consumption treatment of industrial wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental functional materials and membrane separation, and specifically relates to a ZIF-based catalytic ceramic membrane, a preparation method and application thereof in water treatment. Background Art

[0002] Although traditional heterogeneous Fenton catalysts have certain applications in the field of water treatment, there are many problems that need to be solved. They have a single active site and are difficult to efficiently catalyze multiple reaction pathways at the same time, resulting in a serious lack of synergy between free radical and non-free radical pathways, and are unable to fully realize the potential of catalytic degradation of pollutants, and have limited effects on the treatment of complex and diverse difficult-to-degrade pollutants in water.

[0003] Ceramic membranes, as a commonly used material in separation technology, stand out in water treatment with their advantages such as high mechanical strength and corrosion resistance. They can effectively intercept large particle pollutants such as suspended matter and bacteria in water. However, ordinary ceramic membranes lack catalytic function. Faced with the increasing number of difficult-to-degrade organic pollutants in water, such as complex organic molecules in pharmaceutical wastewater and dye wastewater, it is difficult to achieve efficient removal by physical interception alone, and it cannot meet the needs of deep water treatment and water purification. To make up for the shortcomings of ordinary ceramic membranes, existing studies have attempted to endow membranes with catalytic activity by loading metal oxides or carbon-based materials. However, these methods have obvious defects. The active components are unevenly dispersed on the surface of the ceramic membrane, resulting in uneven distribution of catalytic active sites, affecting the overall catalytic efficiency. Moreover, in the dynamic environment of water treatment, the binding force between the active components and the ceramic membrane is not enough to resist external forces such as water flow impact and chemical erosion, and it is easy to fall off.

[0004] Metal-organic framework (ZIF) materials have become a research hotspot in the field of materials science due to their unique structure and properties. ZIF materials have adjustable metal centers and organic ligand structures. This structural diversity enables them to precisely control the pore size, porosity and surface chemical properties of the materials through reasonable design and selection, showing excellent gas storage and separation performance and potential catalytic activity. Based on their advantages, ZIF materials are considered to be useful as high-performance catalyst precursors for the development of new catalytic materials for water treatment. However, there are still huge technical challenges in stably integrating ZIF-derived catalysts on the surface of ceramic membranes to achieve synergistic catalysis of dual active sites (such as Co-Co / Co-N). Summary of the invention

[0005] The purpose of the present invention is to solve the deficiencies of the prior art and provide a ZIF-based catalytic ceramic membrane, a preparation method and its application in water treatment. The present invention realizes the controllable construction of dual active sites, improves the catalytic performance and stability of the membrane, and is suitable for continuous flow wastewater treatment by a method for preparing a catalytic ceramic membrane through in-situ growth and pyrolysis of ZIF.

[0006] The specific technical solution adopted by the present invention is as follows:

[0007] In the first aspect, the present invention provides a method for preparing a ZIF-based catalytic ceramic membrane, and the specific steps are as follows:

[0008] S1: Dissolve cobalt salt and zinc salt in an organic solvent to obtain a precursor solution; transfer the precursor solution and the organic ligand solution to the surface of the cleaned ceramic membrane alternately for multiple times, so that the precursor solution and the organic ligand solution are in full contact; place the ceramic membrane in a sealed container and let it stand still, so that ZIF crystals grow in-situ on the surface and in the pores of the ceramic membrane;

[0009] S2: Place the standing ceramic membrane under an inert atmosphere for high-temperature pyrolysis, so that the ZIF crystals grown in-situ on the ceramic membrane are converted into metal / nitrogen-doped carbon composite catalysts; the product after high-temperature pyrolysis is pickled with acid to remove loose particles, and then washed to neutral and dried to obtain a ZIF-based catalytic ceramic membrane.

[0010] Preferably, in step S1, the molar ratio of cobalt ions to zinc ions in the precursor solution is 1:(0.5 - 2).

[0011] Preferably, the organic solvent is methanol, ethanol, n-propanol, isopropanol or N,N-dimethylformamide; the cobalt salt is cobalt nitrate, cobalt chloride, cobalt acetate, cobalt formate, cobalt citrate or cobalt oxalate; the zinc salt is zinc nitrate, zinc acetate, zinc acetate dihydrate, zinc chloride or zinc sulfate.

[0012] Preferably, the organic ligand solution is a methanol solution of 2-methylimidazole; the molar ratio of 2-methylimidazole to the sum of cobalt ions and zinc ions in the precursor solution in the organic ligand solution is (4 - 8):1.

[0013] Preferably, the precursor solution and the organic ligand solution are transferred to the surface of the cleaned ceramic membrane by means of impregnation, coating, spin coating or high-pressure filtration.

[0014] Preferably, the specific process of the high-temperature pyrolysis is as follows: under a nitrogen atmosphere, heat up at a heating rate of 2 - 5 °C / min to 600 - 800 °C and keep it warm for 2 - 4 hours; the pickling process is as follows: soak the product after high-temperature pyrolysis in 0.5 - 1.0 mol / L hydrochloric acid for 30 - 60 minutes.

[0015] Preferably, the ceramic membrane is a titanium suboxide, alumina, zirconia or silica ceramic membrane; the pore diameter of the ceramic membrane is less than 1 μm.

[0016] In the second aspect, the present invention provides a ZIF-based catalytic ceramic membrane obtained by using the preparation method described in the first aspect.

[0017] In a third aspect, the present invention provides an application of a ZIF-based catalytic ceramic membrane for removing organic pollutants in water. The ZIF-based catalytic ceramic membrane obtained by the preparation method described in the first aspect is vertically placed in the wastewater to be treated containing organic pollutants, and an oxidant is added to the wastewater to be treated. The wastewater to be treated flows through the ZIF-based catalytic ceramic membrane under the action of an external force. The active sites on the ZIF-based catalytic ceramic membrane catalyze the oxidant to generate active oxidation substances, enabling the active oxidation substances to come into full contact with the organic pollutants in the wastewater to be treated, thereby achieving the removal of organic pollutants.

[0018] Preferably, the organic pollutants include sulfamethoxazole, carbamazepine, naproxen, methyl orange, atrazine; the oxidant is peroxymonosulfate, and the addition amount of peroxymonosulfate is 0.1 - 0.3 g / L.

[0019] The present invention has the following beneficial effects compared with the prior art:

[0020] (1) The innovation of the preparation method provided by the present invention is mainly reflected in the in-situ growth strategy and pore functionalization. The in-situ growth strategy enables the ZIF crystals to directly nucleate on the surface of the ceramic substrate membrane, greatly enhancing the binding strength between the catalyst and the substrate and effectively avoiding the problem of shedding of the active components. Pore functionalization, through the mesoporous carbon structure formed by pyrolysis, while improving the mass transfer efficiency, retains the microporous filtration function of the ceramic membrane.

[0021] (2) The ZIF-based catalytic ceramic membrane prepared by the above method has the following advantages:

[0022] a) High-efficiency catalysis: The Co-Co / Co-N dual active sites can synergistically activate peroxymonosulfate (PMS), and the removal rate of electron-rich pollutants such as sulfamethoxazole is as high as 90%;

[0023] b) Stable operation: After 3720 minutes of continuous flow reaction, the performance decay of the ZIF-based catalytic ceramic membrane is less than 10%, and the Co dissolution amount is less than 0.2 ppm;

[0024] c) Strong anti-interference ability: Whether in a wide pH value range (4 - 8) or in the presence of interfering substances such as humic acid, phage, and bovine serum albumin, it can maintain good organic pollutant removal performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a scanning electron microscope image of the surface of the ZIF-based catalytic ceramic membrane prepared in Example 1, where (a) is at a resolution of 500 nm and (b) is at a resolution of 1 μm;

[0026] Figure 2Scanning electron microscope images of the surfaces of different catalytic ceramic membranes prepared in Comparative Examples 1-4, where (a) is the ZIF-67-based catalytic ceramic membrane prepared in Comparative Example 1, and (b) is the ZIF-Co 0.75 Zn 0.25 catalytic ceramic membrane, (c) is the ZIF-Co 0.25 Zn 0.75 catalytic ceramic membrane prepared in Comparative Example 3, and (d) is the ZIF-8-based catalytic ceramic membrane prepared in Comparative Example 4;

[0027] Figure 3 Schematic diagram of the reaction device;

[0028] Figure 4 Experimental results of sulfamethoxazole (SMX) removal in Example 2;

[0029] Figure 5 Results of anti-interference verification in Example 3;

[0030] Figure 6 Experimental results of different organic pollutant removal in Example 4. Detailed implementation manners

[0031] The present invention will be further described and explained below in conjunction with the accompanying drawings and specific implementation manners. The technical features of each implementation manner in the present invention can be combined correspondingly without conflict.

[0032] Example 1

[0033] In this example, a ZIF-based catalytic ceramic membrane was prepared, and the specific preparation method is as follows:

[0034] (1) Prepare the precursor solution

[0035] Weigh 1.09 g of Co(NO3)2·6H2O and 1.12 g of Zn(NO3)2·6H2O respectively, and dissolve them in 40 mL of methanol to obtain the precursor solution. The molar ratio of cobalt ions to zinc ions in the precursor solution is 1:1.

[0036] (2) Prepare the organic ligand solution

[0037] Weigh 2.65 g of 2-methylimidazole and dissolve it in 40 mL of methanol to obtain the organic ligand solution. The molar ratio of 2-methylimidazole in the organic ligand solution to the sum of cobalt ions and zinc ions in the precursor solution is 4:1.

[0038] (3) Clean the ceramic membrane

[0039] Select a titanium suboxide ceramic membrane with a pore size of 500 nm. First, ultrasonically clean it with ethanol for 10 - 20 minutes, then ultrasonically clean it with deionized water for 10 - 20 minutes, and finally dry it in a vacuum drying oven at 60 °C for 2 hours to obtain a cleaned ceramic membrane for standby.

[0040] (4)In-situ growth of ZIF crystals

[0041] Immerse the cleaned ceramic membrane alternately in the above-mentioned precursor solution and organic ligand solution for 5 - 10 minutes each time, so that the precursor solution and organic ligand solution on the ceramic membrane are in full contact. Subsequently, place the ceramic membrane in a sealed container at 25 °C and let it stand for 2 hours to enable the in-situ growth of ZIF crystals on the surface and in the pores of the ceramic membrane, wash away the excess compounds with methanol and dry.

[0042] (5)High-temperature pyrolysis reaction

[0043] Place the standing ceramic membrane in a nitrogen atmosphere and pyrolyze it at 600 °C for 2 hours with a heating rate of 2 - 5 °C / min. High-temperature pyrolysis converts the in-situ grown ZIF crystals on the ceramic membrane into a metal / nitrogen-doped carbon composite catalyst. Immerse the product after high-temperature pyrolysis in 0.5 mol / L hydrochloric acid for 60 minutes, remove the loose particles by pickling, and then wash it to neutrality and dry to obtain a ZIF-based catalytic ceramic membrane (ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane).

[0044] It should be noted that the precursor solution and organic ligand solution can also be transferred to the surface of the cleaned ceramic membrane by means such as coating, spin coating, or high-pressure filtration. In addition to using titanium suboxide materials, the ceramic membrane can also use alumina, zirconia, or silica ceramic membranes.

[0045] Figure 1 This is the scanning electron microscope image of the surface of the ZIF-based catalytic ceramic membrane prepared in this example. According to Figure 1 it can be seen that the catalytic ceramic membrane has a high porosity and a specific surface area of more than 360 m 2 / g. The high porosity of the ZIF-based catalytic ceramic membrane forms three-dimensional interconnected pores, which can significantly reduce the mass transfer resistance of pollutant molecules and oxidants. Moreover, the solid-liquid-gas interface formed in the pores can accelerate the activation process of the oxidant, such as promoting the generation of sulfate radicals (SO4 — ·) or singlet oxygen ( 1 O2), thereby promoting the oxidation reaction of pollutants. In addition, the pore structure of the ZIF-based catalytic ceramic membrane enables the active sites such as Co-Co and Co-N to be evenly distributed, effectively preventing their agglomeration. In terms of buffering the pH fluctuation of the buffer solution, its porous structure neutralizes H + or OH —, so as to adapt to a relatively wide pH range (pH = 4 - 8).

[0046] Comparative Example 1

[0047] In this comparative example, a ZIF-67-based catalytic ceramic membrane was prepared. The specific preparation method is as follows:

[0048] Weigh 2.18 g of Co(NO3)2·6H2O and dissolve it in 40 mL of methanol to obtain a precursor solution. Weigh 2.65 g of 2-methylimidazole and dissolve it in 40 mL of methanol to obtain an organic ligand solution.

[0049] Select the same cleaned titanium suboxide ceramic membrane as in Example 1, and alternately immerse it in the above-mentioned precursor solution and organic ligand solution for 5 - 10 minutes each time, so that the precursor solution and organic ligand solution on the ceramic membrane are in full contact. Subsequently, place the ceramic membrane in a sealed container at 25°C and let it stand for 2 hours, wash away the excess compounds with methanol and dry.

[0050] Place the standing ceramic membrane in a nitrogen atmosphere and pyrolyze it at 600°C for 2 hours, with a heating rate of 2 - 5°C / min. Immerse the product after high-temperature pyrolysis in 0.5 mol / L hydrochloric acid for 60 minutes, remove the loose particles by pickling, and then wash it to neutral and dry to obtain the ZIF-67-based catalytic ceramic membrane.

[0051] Comparative Example 2

[0052] In this comparative example, a ZIF-based catalytic ceramic membrane with different metal ratios was prepared. The specific preparation method is as follows:

[0053] Weigh 1.64 g of Co(NO3)2·6H2O and 0.56 g of Zn(NO3)2·6H2O respectively, and dissolve them in 40 mL of methanol to obtain a precursor solution. The molar ratio of cobalt ions to zinc ions in the precursor solution is 3:1. Weigh 2.65 g of 2-methylimidazole and dissolve it in 40 mL of methanol to obtain an organic ligand solution.

[0054] Select the same cleaned titanium suboxide ceramic membrane as in Example 1, and alternately immerse it in the above-mentioned precursor solution and organic ligand solution for 5 - 10 minutes each time, so that the precursor solution and organic ligand solution on the ceramic membrane are in full contact. Subsequently, place the ceramic membrane in a sealed container at 25°C and let it stand for 2 hours, wash away the excess compounds with methanol and dry.

[0055] Place the standing ceramic membrane in a nitrogen atmosphere and pyrolyze it at 600°C for 2 hours, with a heating rate of 2 - 5°C / min. Immerse the product after high-temperature pyrolysis in 0.5 mol / L hydrochloric acid for 60 minutes, remove the loose particles by pickling, and then wash it to neutral and dry to obtain ZIF-Co 0.75 Zn0.25 Catalytic ceramic membrane

[0056] Comparative Example 3

[0057] In this comparative example, a ZIF-based catalytic ceramic membrane with different metal ratios was prepared. The specific preparation method is as follows:

[0058] Weigh 0.55 g of Co(NO3)2·6H2O and 1.67 g of Zn(NO3)2·6H2O respectively, and dissolve them in 40 mL of methanol to obtain a precursor solution. The molar ratio of cobalt ions to zinc ions in the precursor solution is 1:3. Weigh 2.65 g of 2-methylimidazole and dissolve it in 40 mL of methanol to obtain an organic ligand solution.

[0059] Select the same cleaned titanium suboxide ceramic membrane as in Example 1, and alternately immerse it in the above precursor solution and organic ligand solution for 5 - 10 minutes each time, so that the precursor solution and organic ligand solution on the ceramic membrane are in full contact. Then place the ceramic membrane in a sealed container at 25°C and let it stand for 2 hours, wash away the excess compounds with methanol and dry it.

[0060] Place the standing ceramic membrane in a nitrogen atmosphere and pyrolyze it at 600°C for 2 hours, with a heating rate of 2 - 5°C / min. Immerse the product after high-temperature pyrolysis in 0.5 mol / L hydrochloric acid for 60 minutes, remove the loose particles by pickling, and then wash it to neutral and dry it to obtain ZIF-Co 0.25 Zn 0.75 Catalytic ceramic membrane

[0061] Comparative Example 4

[0062] In this comparative example, a ZIF-8-based catalytic ceramic membrane was prepared. The specific preparation method is as follows:

[0063] Weigh 2.23 g of Zn(NO3)2·6H2O and dissolve it in 40 mL of methanol to obtain a precursor solution. Weigh 2.65 g of 2-methylimidazole and dissolve it in 40 mL of methanol to obtain an organic ligand solution.

[0064] Select the same cleaned titanium suboxide ceramic membrane as in Example 1, and alternately immerse it in the above precursor solution and organic ligand solution for 5 - 10 minutes each time, so that the precursor solution and organic ligand solution on the ceramic membrane are in full contact. Then place the ceramic membrane in a sealed container at 25°C and let it stand for 2 hours, wash away the excess compounds with methanol and dry it.

[0065] The static ceramic membrane was placed under a nitrogen atmosphere and pyrolyzed at 600 °C for 2 hours, with a heating rate of 2 - 5 °C / min. The product after high-temperature pyrolysis was soaked in 0.5 mol / L hydrochloric acid for 60 minutes to remove loose particles by acid washing. Subsequently, it was washed to neutrality and dried to obtain the ZIF-8-based catalytic ceramic membrane.

[0066] Scanning electron microscope images of the surfaces of the catalytic ceramic membrane materials prepared in Comparative Examples 1 - 4 are as Figure 2 shown. According to Figure 1 (b) in Figure 2 and

[0067] Example 2

[0068] In this example, the ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane prepared in Example 1 was used for the experiment on the removal of sulfamethoxazole (SMX) in the wastewater to be treated, as follows:

[0069] Wastewater to be treated containing sulfamethoxazole (SMX) at a concentration of 0.12 g / L was prepared. As Figure 3 shown, the ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane was vertically placed in the reaction device. The above-mentioned wastewater to be treated was respectively introduced from the inlet end of the reaction device and flowed through the ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane under the action of an external peristaltic pump, and finally flowed out from the outlet end of the reaction device. The constant flow rate was set at 1.0 mL / min. After adsorption saturation, peroxymonosulfate (PMS) was added to the influent to initiate the Fenton-like reaction. The experimental results are as Figure 4 shown. The ordinate removal amount refers to the amount of SMX removed per milligram of Co on this catalytic ceramic membrane.

[0070] The experimental results show that the ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane prepared in Example 1 can stably operate for at least 3720 minutes for the removal of sulfamethoxazole, with the catalytic membrane performance decay < 10% and the Co dissolution amount < 0.2 ppm, while the removal rate of the original catalyst-free ceramic membrane is only about 30% (mainly attributed to the direct oxidation of PMS).

[0071] In terms of enhancing mass transfer efficiency, the clear crystal edges form a regular microporous / mesoporous structure, which can reduce fluid resistance and enable pollutants to quickly diffuse to the active sites. In terms of improving catalytic stability, the complete crystal structure forms a uniform carbon coating layer (such as Co@C) after pyrolysis, preventing the dissolution of metal active sites (Co-Co / Co-N) caused by edge defects, and enabling the catalytic membrane to maintain a 90% removal rate after continuous operation for 3720 minutes.

[0072] Example 3

[0073] In this example, the ZIF-Co prepared in Example 1 was used. 0.5 Zn 0.5 An anti-interference verification experiment was carried out on the catalytic ceramic membrane, as follows:

[0074] (1) Prepare the wastewater to be treated containing different interfering substances

[0075] The target organic pollutant in the wastewater to be treated is sulfamethoxazole (SMX) with a concentration of 0.12 g / L. The above wastewater to be treated was divided into 7 portions, and different concentrations of humic acid (HA), bacteriophage (LZ), or bovine serum albumin (BSA) were added to each portion as interfering substances. The wastewater to be treated containing 1, 2, 5, 10, and 20 mg / L of humic acid (HA), and the wastewater to be treated containing 10 mg / L of bacteriophage (LZ) and 10 mg / L of bovine serum albumin (BSA) were obtained. The humic acid used is a natural mineralized organic carboxylic acid polymer, derived from plant residues, and formed through coalification and biochemical processes. Its molecular weight was determined to be 2375 g / mol by gel permeation chromatography (GPC), and the molecule contains various functional groups such as carboxyl, hydroxyl, carbonyl, quinone, and methoxy groups.

[0076] (2) As Figure 3 shown, the ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane was vertically placed in the reaction device. The above wastewater to be treated was respectively flowed into from the inlet end of the reaction device, and flowed through the ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane under the action of an external peristaltic pump, and finally flowed out from the outlet end of the reaction device. 0.2 g / L of peroxymonosulfate (PMS) was added as an oxidant to each group of reactions. The active sites on the ZIF-based catalytic ceramic membrane catalyze peroxymonosulfate to generate active oxidation substances, enabling the active oxidation substances to fully contact with the sulfamethoxazole in the wastewater to be treated, and thus achieving the removal of sulfamethoxazole in the wastewater. The reaction results are as Figure 5 shown.

[0077] The experimental results show that the ZIF-Co prepared in Example 1 0.5 Zn 0.5The catalytic ceramic membrane can maintain high-efficiency removal performance of organic pollutants in the presence of different interfering substances, namely humic acid (electrically neutral), bovine serum albumin (negatively charged), and bacteriophage (positively charged). This demonstrates that the ZIF-Co prepared in Example 1 0.5 Zn 0.5 The smooth crystal surface of the catalytic ceramic membrane can inhibit membrane fouling and reduce the attachment probability of macromolecules such as humic acid, bovine serum albumin, and bacteriophage.

[0078] Example 4

[0079] In this example, the ZIF-Co prepared in Example 1 0.5 Zn 0.5 catalytic ceramic membrane was used to conduct removal experiments on different organic pollutants, as follows:

[0080] (1) Prepare wastewater to be treated containing different organic pollutants

[0081] Different organic pollutants were added to natural water bodies to obtain wastewater to be treated containing carbamazepine (CBZ), naproxen (NPX), sulfamethoxazole (SMX), methyl orange (MO), atrazine (ATZ), gefitinib (GEM), and mifepristone (PRM), respectively. The initial concentration of the pollutants was 5 mg / L.

[0082] The basic parameters of the natural water body are as follows: from a lake in Zhejiang Province, with a humic acid (HA) concentration of 2.13 mg / L, conductivity of 431 µS / cm, total nitrogen content of 10.1 mg / L, Fe 3+ concentration of 0.012 mg / L, Cl - concentration of 0.950 mg / L, and total carbon content of 31.73 mg / L.

[0083] (2) As Figure 3 shown, the ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane was vertically placed in the reaction device. The above-mentioned wastewater to be treated was respectively introduced from the inlet end of the reaction device and flowed through the ZIF-Co 0.5 Zn 0.5 catalytic ceramic membrane under the action of an external peristaltic pump, and finally flowed out from the outlet end of the reaction device. 0.2 g / L of peroxymonosulfate (PMS) was added as an oxidant to each group of reactions. The active sites on the ZIF-based catalytic ceramic membrane catalyzed the generation of reactive oxygen species from peroxymonosulfate, enabling the reactive oxygen species to fully contact the organic pollutants in the wastewater to be treated, thereby achieving the removal of organic pollutants in the wastewater. The reaction results are as Figure 6 shown.

[0084] The experimental results show that the removal rates of carbamazepine (CBZ), naproxen (NPX) and sulfamethoxazole (SMX) are relatively high, which are 22×10 -3 , 20×10 -3 and 19×10 -3 mg·min -1 respectively; this catalytic ceramic membrane also has a certain removal ability for methyl orange (MO), atrazine (ATZ), gefitinib (GEM) and mifepristone (PRM), and the removal rates are 12×10 -3 , 8×10 -3 , 5×10 -3 and 2×10 -3 mg·min -1 respectively.

[0085] The above-described embodiments are only a preferred solution of the present invention, but it is not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A preparation method of a ZIF-based catalytic ceramic membrane, characterized in that, The specific steps are as follows: S1: dissolving cobalt salt and zinc salt in an organic solvent to obtain a precursor solution; transferring the precursor solution and the organic ligand solution to the surface of the cleaned ceramic membrane alternately for multiple times, so that the precursor solution and the organic ligand solution are in full contact; placing the ceramic membrane in a closed container and allowing it to stand, so that the ZIF crystals grow in situ on the surface of the ceramic membrane and in the pores; S2: The ceramic membrane after standing is placed in an inert atmosphere for high-temperature pyrolysis, so that the ZIF crystals grown in situ on the ceramic membrane are converted into a metal / nitrogen-doped carbon composite catalyst; the product after high-temperature pyrolysis is acid-washed to remove loose particles, and then washed to neutral and dried to obtain a ZIF-based catalytic ceramic membrane.

2. The preparation method of the ZIF-based catalytic ceramic membrane according to claim 1, wherein The molar ratio of cobalt ions to zinc ions in the precursor solution in step S1 is 1:(0.5-2).

3. The preparation method of the ZIF-based catalytic ceramic membrane according to claim 1, characterized in that, The organic solvent is methanol, ethanol, n-propanol, isopropanol or N,N-dimethylformamide; the cobalt salt is cobalt nitrate, cobalt chloride, cobalt acetate, cobalt formate, cobalt citrate or cobalt oxalate; the zinc salt is zinc nitrate, zinc acetate, zinc acetate dihydrate, zinc chloride or zinc sulfate.

4. The preparation method of the ZIF-based catalytic ceramic membrane according to claim 1, characterized in that The organic ligand solution is a methanol solution of 2-methylimidazole; the molar ratio of 2-methylimidazole in the organic ligand solution to the sum of cobalt ions and zinc ions in the precursor solution is (4-8):

1.

5. The preparation method of the ZIF-based catalytic ceramic membrane according to claim 1, wherein The precursor solution and the organic ligand solution are transferred to the cleaned ceramic membrane surface by dipping, coating, suspension coating or high-pressure filtration.

6. The preparation method of the ZIF-based catalytic ceramic membrane according to claim 1, wherein The high-temperature pyrolysis process is specifically as follows: in a nitrogen atmosphere, the temperature is increased to 600-800°C at a heating rate of 2-5°C / min and kept warm for 2-4 hours; the acid washing process is as follows: the product after high-temperature pyrolysis is immersed in 0.5-1.0 mol / L hydrochloric acid for 30-60 minutes.

7. The preparation method of the ZIF-based catalytic ceramic membrane according to claim 1, wherein The ceramic membrane is made of titanium dioxide, aluminum oxide, zirconium dioxide or silicon dioxide ceramic membrane; the pore size of the ceramic membrane is less than 1 μm.

8. A ZIF-based catalytic ceramic membrane obtained by the preparation method according to any one of claims 1 to 7.

9. Application of a ZIF-based catalytic ceramic membrane in removing organic pollutants from water, characterized in that, The ZIF-based catalytic ceramic membrane obtained by any one of the preparation methods described in claims 1 to 7 is vertically placed in wastewater to be treated containing organic pollutants, and an oxidant is added to the wastewater to be treated; the wastewater to be treated flows through the ZIF-based catalytic ceramic membrane under the action of external force; the active sites on the ZIF-based catalytic ceramic membrane catalyze the oxidant to generate active oxidizing substances, so that the active oxidizing substances are in full contact with the organic pollutants in the wastewater to be treated, thereby achieving the removal of the organic pollutants.

10. The application of the ZIF-based catalytic ceramic membrane for removing organic pollutants in water according to claim 9, characterized in that, The organic pollutants include sulfamethoxazole, carbamazepine, naproxen, methyl orange, and atrazine; the oxidant is peroxymonosulfate, and the added amount of peroxymonosulfate is 0.1-0.3 g / L.

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