A preparation method and application of a catalytic membrane based on single-atom iron-manganese oxide

Abstract

A preparation method and application of a catalytic membrane based on single-atom iron-manganese oxide, belonging to the field of catalytic membrane water treatment. The present invention aims to solve the problems that the chromium mist inhibitor F-53B in existing chrome plating wastewater is difficult to degrade, and the degradation rate will decrease significantly when the residual PAM and F-53B coexist. Method: First, prepare a casting solution; second, drop the casting solution into the pores of a hollow ceramic membrane substrate and dry it; third, prepare an aqueous solution of potassium ferrocyanide; fourth, prepare a manganese acetylacetonate oil phase solution; fifth, immerse the coated ceramic membrane substrate in the aqueous solution of potassium ferrocyanide, drop the manganese acetylacetonate oil phase solution into the pores of the ceramic membrane substrate after aqueous phase treatment, and finally calcine. Application: It is used for the degradation of chlorinated polyfluoroalkyl ether sulfonates; or for the degradation of chlorinated polyfluoroalkyl ether sulfonates in the presence of polyacrylamide. The present invention is used for the preparation and application of a catalytic membrane based on single-atom iron-manganese oxide.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic membrane water treatment. Background Art

[0002] Chrome plating is a commonly used surface treatment technology. By depositing a thin and hard chromium layer on the metal surface, the wear resistance, aesthetics and service life of the workpiece are improved. The application of chrome plating process is very extensive, including fields such as electronics, automotive, and machinery. During the operation of the chrome plating process, electroplating power-on causes a large amount of hydrogen and oxygen to be generated at the cathode and anode respectively. When these gases rise to the liquid surface in the form of bubbles and are released into the air, they carry a large amount of chromium-containing liquid, forming a mist-like pollutant, that is, chromium mist. In order to prevent the harm of chromium mist to the human body and the environment, a chlorinated polyfluoroalkyl ether sulfonate (F-53B) is usually used as a chromium mist inhibitor to inhibit the escape of chromium mist. In addition, during the process of removing chromium from chrome plating wastewater, the chemical reduction method is often used to reduce the residual Cr 6+ to Cr 3+ and then calcium hydroxide is added to form Cr(OH)3 precipitate, and then macromolecular organic flocculants such as polyacrylamide (PAM) and polyaluminum chloride (PAC) are added to flocculate the chromium hydroxide generated during the chromium removal process. However, there are still residual chromium mist inhibitors and macromolecular organic substances such as PAM in the chrome plating wastewater after chromium removal, which cause great harm to the ecological environment and humans.

[0003] As a perfluorinated compound, F-53B has a very strong C-F bond energy and is difficult to break, and the degradation is very difficult. Conventional treatment technologies mainly include adsorption, advanced oxidation technology, etc., and the treatment efficiency is relatively low. Especially when PAM and F-53B coexist, PAM will interfere with the adsorption sites of the adsorbent or the active oxygen generated by the advanced oxidation technology to degrade F-53B, resulting in low treatment efficiency. Summary of the Invention

[0004] The present invention aims to solve the problem that the chromium mist inhibitor F-53B in the existing chrome plating wastewater is difficult to degrade, and the degradation rate will drop significantly when the residual PAM and F-53B coexist, and further provides a preparation method and application of a catalytic membrane based on single-atom iron-manganese oxide.

[0005] A preparation method of a catalytic membrane based on single-atom iron-manganese oxide is carried out according to the following steps:

[0006] First, dissolve polyvinyl alcohol in ultrapure water, add Al2O3, TiO2 and a dispersant to the polyvinyl alcohol solution, then ball mill, and finally degas under vacuum to obtain a casting solution;

[0007] Second, drop the casting solution into the pores of the hollow ceramic membrane substrate and dry it, and then repeat the dropping and drying to obtain the ceramic membrane substrate after drop coating;

[0008] III. Dissolve potassium ferricyanide in ultrapure water to obtain an aqueous potassium ferricyanide solution;

[0009] IV. Dissolve manganese acetylacetonate in n-hexane to obtain an organic phase solution of manganese acetylacetonate;

[0010] V. Immerse the coated ceramic membrane substrate in the aqueous potassium ferricyanide solution, then take it out to obtain the ceramic membrane substrate after aqueous phase treatment. Drop the organic phase solution of manganese acetylacetonate into the pores of the ceramic membrane substrate after aqueous phase treatment for interfacial synthesis reaction, and then dry it to obtain the ceramic membrane substrate after aqueous and organic phase treatment. Calcinate the ceramic membrane substrate after aqueous and organic phase treatment under nitrogen protection, and finally cool it naturally to room temperature, thus completing the preparation method of the catalytic membrane based on single-atom iron-manganese oxide.

[0011] An application of a catalytic membrane based on single-atom iron-manganese oxide, which is used for the degradation of chlorinated polyfluoroalkyl ether sulfonates; or for the degradation of chlorinated polyfluoroalkyl ether sulfonates in the presence of polyacrylamide.

[0012] The beneficial effects of the present invention are as follows:

[0013] (1) The present invention uses a preparation method combining interfacial deposition and calcination to deposit a layer of single-atom iron-manganese oxide (FeO) 0.099 (MnO) 0.901 and a catalytic membrane with a nanoporous structure on a macroporous hollow ceramic membrane substrate. This catalytic membrane has a high porosity and a high active site distribution. In the form of crossflow filtration, the intercepted particles will be continuously removed from the surface of the ceramic membrane without remaining in the form of a filter cake, so continuous high flux can be achieved. The operation process of the present invention is simple and easy, and the required raw materials are easily available.

[0014] (2) During the preparation process of the present invention, due to the high porosity of the nanoporous structure of the catalytic membrane, the pure water flux is 260 L . m -2 . h -1 . bar -1 , so that the rejection rate of the catalytic membrane for the flocculant PAM reaches 92.1%. Compared with the traditional membrane filtration technology (the rejection rate is 70% - 80%), the rejection rate of the catalytic membrane of the present invention is increased by 20% - 30%, and the rejection effect is better.

[0015] (3) During the preparation process of the catalytic membrane of the present invention, due to the calcination causing the decomposition of the cyanide (C≡N) ligand and the volatilization of carbon and nitrogen oxide gases from the lattice water and adsorbed water in the Prussian blue-like thin film, thus forming (FeO) 0.099 (MnO) 0.901Single-atom oxide structure. Compared with traditional advanced oxidation technologies (degradation rate of 60%-70%), the confinement effect of the catalytic membrane nanopore structure and the distribution of high-active sites enable the degradation rate of the chromium mist inhibitor to reach 89.7%.

[0016] (4) The present invention proposes a short-process catalytic membrane technology for treating chromium plating wastewater, which can efficiently intercept PAM, reduce the interference of PAM on the degradation of chromium mist inhibitor, and activate persulfate (PMS) to generate active species, increasing the degradation rate of F-53B from 48.3% to 89.7%. The present invention is a high-efficiency membrane water treatment technology.

[0017] The present invention relates to a preparation method and application of a catalytic membrane based on single-atom iron-manganese oxide. Description of the Drawings

[0018] Figure 1 Schematic diagram of the formation of an iron-manganese Prussian blue analogue precursor by interfacial polymerization for the catalytic membrane in Example 1;

[0019] Figure 2 Flow chart of short-process chromium plating wastewater treatment based on the single-atom iron-manganese oxide catalytic membrane in Example 2;

[0020] Figure 3 Physical picture of the single-atom iron-manganese oxide catalytic membrane prepared in Step 5 of Example 1;

[0021] Figure 4 SEM images: (a) Ceramic membrane substrate after drop coating prepared in Step 2 of Example 1, (b) Local enlarged view of (a), (c) Single-atom iron-manganese oxide catalytic membrane prepared in Step 5 of Example 1, (d) Local enlarged view of (c);

[0022] Figure 5 XRD patterns of the single-atom iron-manganese oxide catalytic membranes prepared in Example 1 and Comparative Experiment 2;

[0023] Figure 6 Molecular structure diagram of the single-atom iron-manganese oxide catalytic membrane prepared in Step 5 of Example 1;

[0024] Figure 7 Comparison chart of the pure water flux of the single-atom iron-manganese oxide catalytic membranes prepared in Example 2 using Example 1 and Comparative Experiment 1 and the interception rate of PAM during chromium plating wastewater treatment;

[0025] Figure 8 Comparison chart of the degradation efficiency of F-53B during chromium plating wastewater treatment using the single-atom iron-manganese oxide catalytic membranes prepared in Example 2 using Example 1 and Comparative Experiment 2;

[0026] Figure 9 For Example 2 and Example 3, it is a comparison chart of the removal rates for the treatment of short - process chrome - plating wastewater using the single - atom iron - manganese oxide catalytic membrane prepared in Example 1 and for the treatment of short - process chrome - plating wastewater in Comparative Experiment 3;

[0027] Figure 10 For Example 2 and Comparative Experiment 4, it shows the influence of different concentrations of peroxymonosulfate (PMS) on the degradation efficiency of the catalytic membrane during the treatment of chrome - plating wastewater using the hollow ceramic catalytic membrane prepared in Example 1. Detailed implementation manners

[0028] Detailed implementation manner 1: A preparation method of a single - atom iron - manganese oxide catalytic membrane is as follows:

[0029] 1. Dissolve polyvinyl alcohol in ultrapure water, add Al2O3, TiO2 and a dispersant into the polyvinyl alcohol solution, then ball - mill, and finally perform vacuum degassing to obtain a casting solution;

[0030] 2. Drop the casting solution into the pores of the hollow ceramic membrane substrate and dry it, then repeat the dropping and drying to obtain a ceramic membrane substrate after drop - coating;

[0031] 3. Dissolve potassium ferricyanide in ultrapure water to obtain an aqueous potassium ferricyanide solution;

[0032] 4. Dissolve manganese acetylacetonate in n - hexane to obtain an organic manganese acetylacetonate solution;

[0033] 5. Immerse the ceramic membrane substrate after drop - coating in the aqueous potassium ferricyanide solution, then take it out to obtain a ceramic membrane substrate after aqueous - phase treatment. Drop the organic manganese acetylacetonate solution into the pores of the ceramic membrane substrate after aqueous - phase treatment for an interfacial synthesis reaction, and then dry it to obtain a ceramic membrane substrate after aqueous - phase and organic - phase treatments. Calcinate the ceramic membrane substrate after aqueous - phase and organic - phase treatments under nitrogen protection, and finally cool it naturally to room temperature, thus completing the preparation method of the single - atom iron - manganese oxide catalytic membrane.

[0034] Principle: In order to ensure the efficient treatment of chrome - plating wastewater, the present invention adopts a short - process technology based on a single - atom iron - manganese oxide catalytic membrane. By using the interfacial deposition method, an Fe - Mn Prussian blue - like thin film with a Prussian blue - like structure is constructed on the inner - surface of the pores of the ceramic membrane substrate. Its unique Fe - C≡N - Mn structure helps the uniform dispersion of Fe and Mn atoms. Calcination in a nitrogen atmosphere avoids the over - oxidation of Fe and Mn atoms. At the same time, the decomposition of the cyan (C≡N) ligand reacts with the lattice water and adsorbed water in the Prussian blue - like thin film to generate carbon and nitrogen oxide gases volatilization, and then form (FeO) 0.099 (MnO) 0.901The structure of single-atom oxides. In addition, a dense Fe-Mn-based Prussian blue film forms a nanoporous structure during the sintering process due to the phase transformation and shrinkage of the grains.

[0035] Single-atom iron-manganese oxide (FeO) 0.099 (MnO) 0.901 Electron transfer occurs between the Fe sites and PMS, activating PMS to generate the main 1 O2 and high-valence iron-oxide active substances. An oxidation reaction occurs between the active species and F-53B, and F-53B is gradually degraded and mineralized. The nanoporous structure of the film provides a guarantee for the effective interception and separation of macromolecular substances such as PAM, thereby reducing the negative impact of PAM, etc. on the degradation of F-53B. In addition, the nano-pores of the catalytic membrane limit the diffusion space of the active species in the pores, thereby strengthening the contact between the active species and F-53B and further improving the degradation efficiency of F-53B.

[0036] The catalytic membrane technology combines membrane separation and in-situ catalysis processes. It can first intercept PAM and then in-situ degrade F-53B, eliminating the negative impact of the coexistence of PAM and F-53B on the degradation of F-53B, and simultaneously achieving the efficient removal of both PAM and F-53B.

[0037] The beneficial effects of this embodiment are as follows:

[0038] (1) This embodiment uses a preparation method combining interfacial deposition and calcination to deposit a layer of single-atom iron-manganese oxide (FeO) 0.099 (MnO) 0.901 on the macroporous hollow ceramic membrane substrate, forming a catalytic membrane with a nano-pore structure. This catalytic membrane has a high porosity and a high active site distribution. In the form of cross-flow filtration, the intercepted particles will be continuously removed from the surface of the ceramic membrane and will not remain in the form of a filter cake, so continuous high flux can be achieved. The operation process of this embodiment is simple and easy, and the required raw materials are easily available.

[0039] (2) During the preparation process of this embodiment, due to the high porosity of the nano-pore structure of the catalytic membrane, the pure water flux is 260L . m -2 . h -1 . bar -1 , making the interception rate of the catalytic membrane for the flocculant PAM reach 92.1%. Compared with the traditional membrane filtration technology (interception rate of 70% - 80%), the interception rate of the catalytic membrane in this embodiment is increased by 20% - 30%, and the interception effect is better.

[0040] (3) During the preparation of the catalytic membrane in this embodiment, due to calcination, the cyanide (C≡N) ligand decomposes, and carbon and nitrogen oxide gases volatilize from the lattice water and adsorbed water in the Prussian blue-like thin film, thereby forming (FeO) 0.099 (MnO) 0.901 a single-atom oxide structure. Compared with traditional advanced oxidation technologies (with a degradation rate of 60%-70%), the confinement effect of the catalytic membrane nanopore structure and the high-activity site distribution enable the degradation rate of the chromium mist inhibitor to reach 89.7%.

[0041] (4) This embodiment proposes a short-process catalytic membrane technology for treating chromium-plating wastewater, which can efficiently intercept PAM, reduce the interference of PAM on the degradation of the chromium mist inhibitor, and increase the degradation rate of F-53B from 48.3% to 89.7% by activating peroxymonosulfate (PMS) to generate reactive species. This embodiment is a high-efficiency membrane water treatment technology.

[0042] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the mass ratio of polyvinyl alcohol to ultrapure water in Step 1 is 1:(20-30); the mass ratio of polyvinyl alcohol to Al2O3 in Step 1 is 1:(50-60); the mass ratio of polyvinyl alcohol to TiO2 in Step 1 is 1:(20-30); the mass ratio of polyvinyl alcohol to the dispersant in Step 1 is 1:(15-30). Others are the same as Specific Embodiment 1.

[0043] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that the particle size of Al2O3 in Step 1 is 0.3 μm - 5 μm; the particle size of TiO2 in Step 1 is 200 nm - 300 nm. Others are the same as Specific Embodiment 1 or 2.

[0044] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that in Step 1, under the conditions of a temperature of 70°C - 80°C and a rotation speed of 100 rpm - 200 rpm, polyvinyl alcohol is dissolved in ultrapure water, Al2O3, TiO2, and the dispersant are added to the polyvinyl alcohol solution, and then ball-milled for 4 h - 5 h under the conditions of a ball-to-material mass ratio of 1:(0.2 - 0.3) and a rotation speed of 100 rpm - 200 rpm, and finally vacuum degassed for 10 min - 20 min. Others are the same as Specific Embodiments 1 to 3.

[0045] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is as follows: In Step 2, the casting solution is dropped into the pores of the hollow ceramic membrane substrate, and then dried under the condition of a temperature of 45°C to 55°C within 120 s to 180 s, and then the dropping and drying are repeated 2 to 3 times; the ratio of the dropping volume of the casting solution described in Step 2 to the inner surface area of the pores of the hollow ceramic membrane substrate is (2 - 3) μL: 2 mm 2 ; the pore diameter of the hollow ceramic membrane substrate described in Step 2 is 5 to 8 micrometers. The others are the same as those in Specific Embodiments 1 to 4.

[0046] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is as follows: In Step 3, potassium ferricyanide is added to ultrapure water, and then stirred and dissolved at a temperature of 20°C to 30°C and a rotation speed of 200 rpm to 400 rpm for 5 min to 10 min to obtain an aqueous potassium ferricyanide solution; the concentration of the aqueous potassium ferricyanide solution is 40 mM to 50 mM. The others are the same as those in Specific Embodiments 1 to 5.

[0047] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is as follows: In Step 4, manganese acetylacetonate is added to n - hexane, and then under the conditions of a temperature of 40°C to 50°C and a power of 120 W to 240 W, it is ultrasonically treated in a water bath for 20 min to 30 min to obtain a manganese acetylacetonate oil - phase solution; the concentration of the obtained manganese acetylacetonate oil - phase solution is 20 mM to 30 mM. The others are the same as those in Specific Embodiments 1 to 6.

[0048] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is as follows: In Step 5, under the condition of a shaker rotation speed of 150 rpm to 200 rpm, the coated ceramic membrane substrate is immersed in the aqueous potassium ferricyanide solution for 30 min to 60 min, and then taken out to obtain a ceramic membrane substrate after aqueous - phase treatment. The manganese acetylacetonate oil - phase solution is dropped into the pores of the ceramic membrane substrate after aqueous - phase treatment, and under the condition of a shaker rotation speed of 100 rpm to 200 rpm, an interfacial synthesis reaction is carried out for 30 min to 60 min, and then dried to obtain a ceramic membrane substrate after aqueous - phase and oil - phase treatment; the ratio of the dropping volume of the manganese acetylacetonate oil - phase solution described in Step 5 to the inner surface area of the pores of the hollow ceramic membrane substrate is (3 - 4) μL: 2 mm 2 ; the calcination in Step 5 is specifically carried out in a nitrogen atmosphere, heated to 500°C to 700°C at a rate of 5°C / min to 10°C / min, and then calcined for 1 h to 2 h under the condition of a temperature of 500°C to 700°C. The others are the same as those in Specific Embodiments 1 to 7.

[0049] Embodiment IX: An application of a single-atom iron-manganese oxide catalytic membrane, which is used for the degradation of chlorinated polyfluoroalkyl ether sulfonates; or for the degradation of chlorinated polyfluoroalkyl ether sulfonates in the presence of polyacrylamide.

[0050] Embodiment X: The difference between this embodiment and Embodiment IX is that it uses a cross-flow filtration method to generate active species through the activation of peroxymonosulfate for degradation. Others are the same as Embodiment IX.

[0051] The following examples are used to verify the beneficial effects of the present invention:

[0052] Example 1:

[0053] A preparation method of a single-atom iron-manganese oxide catalytic membrane is carried out according to the following steps:

[0054] I. At a temperature of 75 °C and a rotation speed of 150 rpm, dissolve polyvinyl alcohol in ultrapure water, add Al2O3, TiO2 and a dispersant to the polyvinyl alcohol solution, then ball mill for 4 h under the conditions of a ball-to-material mass ratio of 1:0.25 and a rotation speed of 150 rpm, and finally perform vacuum degassing for 15 min to obtain a casting solution;

[0055] The mass ratio of the polyvinyl alcohol to the ultrapure water is 1:30; the mass ratio of the polyvinyl alcohol to the Al2O3 is 1:50; the mass ratio of the polyvinyl alcohol to the TiO2 is 1:20; the mass ratio of the polyvinyl alcohol to the dispersant is 1:20;

[0056] The molecular weight of the polyvinyl alcohol is 44.05 Mw, the degree of alcoholysis is 98.0 mol% to 99.0 mol%, and the viscosity is 54 mPa·s to 66 mPa·s; the average particle size of the Al2O3 is 0.3 μm; the average particle size of the TiO2 is 300 nm; the dispersant is dispersant DARVANC-N;

[0057] II. Drop the casting solution into the pores of the hollow ceramic membrane substrate, then dry it at a temperature of 50 °C within 150 s, and then repeat the dropping and drying 3 times to obtain the coated ceramic membrane substrate;

[0058] The ratio of the dropping volume of the casting solution to the inner surface area of the pores of the hollow ceramic membrane substrate is 3 μL:2 mm 2 ;

[0059] The hollow ceramic membrane substrate is purchased from Pingxiang Jiaheng Ceramics Co., Ltd., with a wall thickness of 2 mm, a diameter of 11 mm, a pore diameter of 7 mm, and a length of 100 mm;

[0060] III. Add potassium ferricyanide to ultrapure water, and then stir and dissolve it at a temperature of 25 °C and a rotation speed of 300 rpm for 8 min to obtain an aqueous potassium ferricyanide solution;

[0061] The concentration of the aqueous potassium ferricyanide solution is 45 mM;

[0062] IV. Add manganese acetylacetonate to n-hexane, and then perform water bath ultrasonic treatment at a temperature of 45 °C and a power of 200 W for 25 min to obtain an oily manganese acetylacetonate solution;

[0063] The concentration of the obtained oily manganese acetylacetonate solution is 25 mM;

[0064] V. Under the condition that the shaking table rotation speed is 100 rpm, immerse the coated ceramic membrane substrate in the aqueous potassium ferricyanide solution for 60 min, and then take it out to obtain the ceramic membrane substrate after aqueous phase treatment. Drop the oily manganese acetylacetonate solution into the pores of the ceramic membrane substrate after aqueous phase treatment. Under the condition that the shaking table rotation speed is 150 rpm, carry out an interfacial synthesis reaction for 45 min, and then dry it at a temperature of 60 °C for 3 h to obtain the ceramic membrane substrate after aqueous and oily phase treatment. Under a nitrogen atmosphere, heat the ceramic membrane substrate after aqueous and oily phase treatment to 600 °C at a rate of 10 °C / min, and then calcine it at a temperature of 600 °C for 2 h, and finally cool it naturally to room temperature to obtain a catalytic membrane based on single-atom iron-manganese oxide, that is, a hollow ceramic catalytic membrane;

[0065] The ratio of the dropping volume of the oily acetylacetonate solution to the inner surface area of the pores of the hollow ceramic membrane substrate is 4 μL:2 mm 2 .

[0066] Comparative Experiment 1: The difference between this comparative experiment and Example 1 is that the average particle size of the Al2O3 described in Step I is 9 μm. Others are the same as in Example 1.

[0067] Comparative Experiment 2: The difference between this comparative experiment and Example 1 is that in Step V, under a nitrogen atmosphere, heat the porous ceramic substrate after aqueous and oily phase treatment to 800 °C at a rate of 10 °C / min, and then calcine it at a temperature of 800 °C for 2 h. Others are the same as in Example 1.

[0068] Figure 1 It is a schematic diagram of the formation of an iron-manganese Prussian blue analogue precursor through interfacial polymerization of the catalytic membrane in Example 1. An iron-manganese Prussian blue analogue thin film that closely adheres to the inner side of the hollow ceramic membrane is formed through an interfacial polymerization reaction between the aqueous potassium ferricyanide solution and the oily manganese acetylacetonate solution. A Fe-Mn Prussian blue-like thin film with a Prussian blue-like structure is constructed on the surface of the ceramic membrane substrate by means of interfacial deposition. Its unique Fe-C≡N-Mn structure helps the uniform dispersion of Fe and Mn atoms.

[0069] Figure 3 It is a physical diagram of the single-atom iron-manganese oxide catalytic membrane prepared in Step 5 of Example 1. A layer of single-atom iron-manganese oxide catalytic layer is deposited on the inner side of the hollow ceramic membrane, and the catalytic layer activates persulfate (PMS) to degrade F-53B through the advanced oxidation process.

[0070] Figure 4 It is an SEM image. (a) is the ceramic membrane substrate after drop coating prepared in Step 2 of Example 1, (b) is a partial enlarged view of (a), (c) is the single-atom iron-manganese oxide catalytic membrane prepared in Step 5 of Example 1, and (d) is a partial enlarged view of (c). It can be seen from Figures (a) and (b) that the hollow ceramic membrane substrate has a nanoporous structure with a high porosity. It can be seen from Figures (c) and (d) that the dense Fe-Mn-based Prussian blue thin film forms a nanoporous structure during the sintering process due to the phase transformation and shrinkage of the grains.

[0071] Figure 5 It is an XRD pattern of the single-atom iron-manganese oxide catalytic membrane prepared in Example 1 and Comparative Experiment 2. It can be seen from the figure that when calcined at 600 °C and 800 °C respectively, the catalytic membrane precursors both obtain (FeO) 0.099 (MnO) 0.901 . However, compared with 600 °C, the material obtained by calcination at 800 °C has a higher intensity of carbides and nitrides, while the intensity of (FeO) 0.099 (MnO) 0.901 is relatively low. Therefore, it can be known that the material obtained by firing at 600 °C has better performance.

[0072] Figure 6 It is a molecular structure diagram of the single-atom iron-manganese oxide catalytic membrane prepared in Step 5 of Example 1. It can be seen from the figure that iron atoms are connected to oxygen atoms, iron atoms are isolated, and manganese atoms surround the iron atoms. The ratio of the number of iron atoms to the number of manganese atoms is 1:9. This structure can maximize the utilization efficiency of iron atom catalytic sites.

[0073] Example 2, in combination with Figure 2 Specific description:

[0074] Use the single-atom iron-manganese oxide catalytic membranes prepared in Example 1 and Comparative Experiments 1 to 2 to treat short-process chrome plating wastewater, and the specific steps are as follows:

[0075] ① Dissolve the chromium mist inhibitor (F-53B) in ultrapure water and stir for 24 h to obtain the chromium mist inhibitor mother liquor with a concentration of 50 mg / L; dissolve polyacrylamide (MW molecular weight: 15 million - 18 million) in ultrapure water and stir to obtain the polyacrylamide mother liquor with a concentration of 1 g / L;

[0076] ② Dilute the mother liquor of the chromium mist inhibitor, and then add the mother liquor of polyacrylamide to obtain the water sample to be treated. The concentration of the chromium mist inhibitor in the water sample to be treated is 0.1 mg / L, and the concentration of polyacrylamide is 10 mg / L. Load the water sample to be treated into the water tank, and persulfate (PMS) is added to the water supply tank through a dosing pump so that the concentration of PMS in the water sample to be treated is 1 mM. When operating, turn on the lift pump to lift the water sample to be treated into the membrane device equipped with a single-atom iron-manganese oxide catalytic membrane. Cross-flow filtration is carried out under the conditions of a flow rate of 2 m / s and a transmembrane pressure difference of 0.2 MPa. After passing through the membrane device, a part of the concentrated water in the pipeline direction is discharged, and another part enters the water supply tank for recycling. The water passing through the membrane perpendicular to the pipeline direction in the membrane device is the effluent. The effluent is collected by the collection tank, and the membrane flux data is output by the output device. After the cross-flow filtration is completed, the membrane is backwashed with backwash water from the backwash water tank through the pipeline by the backwash pump.

[0077] Example 3: The difference between this example and Example 2 is that the short-process chrome plating wastewater treatment is carried out using the single-atom iron-manganese oxide catalytic membrane prepared in Example 1, and the addition of polyacrylamide is cancelled in step ②. Others are the same as Example 2.

[0078] Comparative experiment 3: The difference between this comparative experiment and Example 2 is that in step ②, the mother liquor of the chromium mist inhibitor is diluted, and then the mother liquor of polyacrylamide is added to obtain the water sample to be treated. The concentration of the chromium mist inhibitor in the water sample to be treated is 0.1 mg / L, and the concentration of polyacrylamide is 10 mg / L. Persulfate (PMS) is directly added as an oxidant, and the catalytic reaction is carried out for 80 min. The concentration of PMS in the water sample to be treated is 1 mM, and the use of the single-atom iron-manganese oxide catalytic membrane and the treatment device is cancelled. Others are the same as Example 2.

[0079] Comparative experiment 4: The difference between this comparative experiment and Example 2 is that in step ②, the concentration of PMS in the water sample to be treated is 0 mM, 0.25 mM, 0.5 mM, and 1.5 mM. Others are the same as Example 2.

[0080] Figure 7 It is a comparative chart of the pure water flux of the single-atom iron-manganese oxide catalytic membrane prepared in Example 1 and Comparative Experiment 1 and the rejection rate of PAM for chrome plating wastewater treatment in Example 2. As can be seen from the figure, the pure water flux of the catalytic membrane obtained by treating the ceramic membrane substrate with 0.3 μm Al2O3 is 260 L . m -2 . h -1 . bar -1The PAM rejection rate reaches 92.1%, while the PAM rejection rate of the catalytic membrane obtained by treating the ceramic membrane substrate with 9μmAl2O3 is only 50.8%.

[0081] Figure 8 The figure is a comparison chart of the degradation efficiency of F-53B in chromium plating wastewater treatment based on the single-atom iron-manganese oxide catalytic membrane prepared in Example 1 and Comparative Experiment 2. As can be seen from the figure, the degradation rate of F-53B for the catalytic membrane fired at 600°C reaches 89.7%, and the degradation rate of F-53B for the catalytic membrane fired at 800°C reaches 70.2%.

[0082] Figure 9 The removal rate comparison chart of the short-process chromium plating wastewater treatment based on the single-atom iron-manganese oxide catalytic membrane prepared in Example 1 for Example 2 and Example 3 and the short-process chromium plating wastewater treatment for comparative experiment 3 is shown. It can be seen from the figure that in comparative experiment 3, the chromium mist inhibitor coexists with PAM and no membrane filtration is performed, and the removal rate is 48.3%, and the removal rate of the chromium mist inhibitor is very low. When the hollow ceramic catalytic membrane is used in Example 2 and Example 3, the removal rates of the single chromium mist inhibitor and the coexistence of the chromium mist inhibitor and PAM are 89.4% and 89.7% respectively. It is proved here that PAM has a great influence on the degradation of F-53B when coexisting. The addition of the membrane filtration device intercepts most of the PAM by the membrane filtration, making the chromium mist inhibitor, so that the degradation is not disturbed, and the degradation rate containing PAM is not much different from the degradation rate without PAM.

[0083] Figure 10 The effects of different concentrations of permonosulfate (PMS) on the degradation efficiency of the catalytic membrane in the treatment of chromium plating wastewater using the hollow ceramic catalytic membrane prepared in Example 1 are shown in Example 2 and Comparative Experiment 4. As can be seen from the figure, when the PMS addition concentration is 0mM, 0.5mM, 1mM, and 1.5mM, the removal rates of F-53B are 9.1%, 40.1%, 55.2%, 89.7%, and 88.3%, respectively, which indicates that the most appropriate setting of the PMS dosage concentration is 1mM; when the PMS dosage is lower than 1mM, the degradation efficiency of the chromium mist inhibitor is low. When the PMS dosage increases to 1.5mM, the degradation rate of the chromium mist inhibitor is slightly lower than the effect when the dosage is 1mM, which may be due to the saturation of PMS adsorption in the catalytic reaction, so the PMS dosage concentration is set to 1mM for the most appropriate.

Claims

1. A preparation method of a catalytic membrane based on single-atom iron-manganese oxide, characterized in that It is carried out according to the following steps: First, dissolve polyvinyl alcohol in ultrapure water, add Al2O3, TiO2 and a dispersant into the polyvinyl alcohol solution, then ball mill, and finally carry out vacuum degassing to obtain a casting solution; Second, drop the casting solution into the pores of a hollow ceramic membrane substrate and dry it, then repeat the dropping and drying to obtain a ceramic membrane substrate after drop coating; Third, dissolve potassium ferricyanide in ultrapure water to obtain an aqueous potassium ferricyanide solution; Fourth, dissolve manganese acetylacetonate in n-hexane to obtain an oily manganese acetylacetonate solution; Fifth, immerse the ceramic membrane substrate after drop coating in the aqueous potassium ferricyanide solution, then take it out to obtain a ceramic membrane substrate after aqueous phase treatment, drop the oily manganese acetylacetonate solution into the pores of the ceramic membrane substrate after aqueous phase treatment for an interfacial synthesis reaction, and then dry it to obtain a ceramic membrane substrate after aqueous and oily phase treatments. Calcinate the ceramic membrane substrate after aqueous and oily phase treatments under nitrogen protection, and finally naturally cool it to room temperature, thus completing the preparation method of the single-atom iron-manganese oxide catalytic membrane.

2. The preparation method of a single-atom iron-manganese oxide catalytic membrane according to claim 1, characterized in that In step one, the mass ratio of polyvinyl alcohol to ultrapure water is 1:(20 - 30); the mass ratio of polyvinyl alcohol to Al2O3 in step one is 1:(50 - 60); the mass ratio of polyvinyl alcohol to TiO2 in step one is 1:(20 - 30); the mass ratio of polyvinyl alcohol to the dispersant in step one is 1:(15 - 30).

3. The preparation method of a single-atom iron-manganese oxide catalytic membrane according to claim 1, wherein the particle size of Al2O3 in step one is 0.3 μm - 5 μm; the particle size of TiO2 in step one is 200 nm - 300 nm.

4. A preparation method of a single-atom iron-manganese oxide catalytic film according to claim 1, characterized in that In step one, dissolve polyvinyl alcohol in ultrapure water at a temperature of 70°C - 80°C and a rotation speed of 100 rpm - 200 rpm, add Al2O3, TiO2 and a dispersant into the polyvinyl alcohol solution, then ball mill for 4 h - 5 h under the conditions of a ball-to-material mass ratio of 1:(0.2 - 0.3) and a rotation speed of 100 rpm - 200 rpm, and finally carry out vacuum degassing for 10 min - 20 min.

5. The preparation method of a single-atom iron-manganese oxide catalytic membrane according to claim 1, characterized in that In Step 2, the casting solution is dropped into the pores of the hollow ceramic membrane substrate, and then dried under the condition of a temperature of 45°C to 55°C within 120 s to 180 s, and then the dropping and drying are repeated 2 to 3 times; the ratio of the dropping volume of the casting solution described in Step 2 to the inner surface area of the pores of the hollow ceramic membrane substrate is (2 to 3) μL: 2 mm 2 ; the pore diameter of the hollow ceramic membrane substrate described in Step 2 is 5 micrometers to 8 micrometers.

6. The preparation method of a single-atom iron-manganese oxide catalytic membrane according to claim 1, characterized in that In step three, add potassium ferricyanide into ultrapure water, and then stir and dissolve it for 5 min - 10 min at a temperature of 20°C - 30°C and a rotation speed of 200 pm - 400 rpm to obtain an aqueous potassium ferricyanide solution; the concentration of the aqueous potassium ferricyanide solution is 40 mM - 50 mM.

7. A preparation method of a single-atom iron-manganese oxide catalytic membrane according to claim 1, characterized in that In step four, add manganese acetylacetonate into n-hexane, and then carry out water bath ultrasonic treatment for 20 min - 30 min at a temperature of 40°C - 50°C and a power of 120 W - 240 W to obtain an oily manganese acetylacetonate solution; the concentration of the obtained oily manganese acetylacetonate solution is 20 mM - 30 mM.

8. A preparation method of a single-atom iron-manganese oxide catalytic membrane according to claim 1, characterized in that In Step 5, under the condition that the shaker speed is 150 rpm to 200 rpm, the ceramic membrane substrate after drop coating is immersed in a potassium ferricyanide aqueous solution for 30 min to 60 min, and then taken out to obtain the ceramic membrane substrate after aqueous phase treatment. The manganese acetylacetonate oil phase solution is dropped into the pores of the ceramic membrane substrate after aqueous phase treatment, and under the condition that the shaker speed is 100 rpm to 200 rpm, the interfacial synthesis reaction is carried out for 30 min to 60 min, and then dried to obtain the ceramic membrane substrate after aqueous phase and oil phase treatment; the volume ratio of the dropped manganese acetylacetonate oil phase solution to the inner surface area of the pores of the hollow ceramic membrane substrate in Step 5 is (3 - 4) μL:2 mm 2 ; the calcination in Step 5 is specifically carried out under a nitrogen atmosphere, heated to 500 °C to 700 °C at a rate of 5 °C / min to 10 °C / min, and then calcined for 1 h to 2 h under the condition that the temperature is 500 °C to 700 °C.

9. The application of a catalytic membrane based on single-atom iron-manganese oxide prepared as claimed in claim 1, characterized in that It is used for the degradation of chlorinated polyfluoroalkyl ether sulfonates; or for the degradation of chlorinated polyfluoroalkyl ether sulfonates in the presence of polyacrylamide.

10. The application of a single-atom iron-manganese oxide catalytic membrane according to claim 9, characterized in that It uses a cross-flow filtration method to generate active species through the activation of peroxymonosulfate for degradation.

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