A multistage composite microporous membrane electrode, a preparation method thereof and a water treatment and purification method

Abstract

The application provides a multistage composite microporous membrane electrode and a preparation method and water treatment and purification method thereof. The multistage composite microporous membrane electrode comprises an inorganic ceramic microfiltration membrane, an anode electrocatalytic active layer and a cathode electrocatalytic active layer; the anode electrocatalytic active layer and the cathode electrocatalytic active layer are respectively located on the two sides of the surface of the inorganic ceramic microfiltration membrane; the thickness of the inorganic ceramic microfiltration membrane is 2-6 mm, the thickness of the anode electrocatalytic active layer is 100-800 nm, and the thickness of the cathode electrocatalytic active layer is 1 micrometer-1 mm; the inner wall of the pore of the inorganic ceramic microfiltration membrane is loaded with silicon zeolite nanocrystals; and the particle size of the silicon zeolite nanocrystals is 50-200 nm. When the multistage composite microporous membrane electrode is used for water treatment and purification, oxygen molecules can be efficiently enriched in micropores, the conversion efficiency of hydroxyl radicals is improved, and the efficient removal of refractory organic matter is realized.

Description

Technical Field

[0001] This invention belongs to the field of membrane material preparation and water treatment technology, specifically relating to a multi-level composite microporous membrane electrode and its preparation method and water treatment purification method. Background Technology

[0002] With the increasing prominence of complex pollution problems in the aquatic environment, including emerging pollutants (such as drug residues, endocrine disruptors, and microplastics), traditional heavy metals, and recalcitrant organic matter, traditional water purification technologies face severe challenges. While current mainstream membrane separation technologies can physically retain pollutants, they suffer from severe membrane fouling, insufficient selectivity, and an inability to degrade pollutants. This results in high energy consumption, short membrane lifespan, and the retention of pollutants easily forming concentrates that can cause secondary pollution.

[0003] Electrocatalytic membrane technology, by coupling membrane separation and electrochemical oxidation processes, can generate highly reactive free radicals in situ while retaining pollutants, achieving efficient mineralization of pollutants and is considered a cutting-edge direction in the field of advanced water treatment. However, existing electrocatalytic membranes generally suffer from problems such as weak bonding between the conductive substrate and the catalyst layer interface, low electron transport efficiency, and uneven distribution of active sites, resulting in rapid catalytic efficiency decay and insufficient anti-fouling ability, making it difficult to meet the long-term stable operation requirements under complex water quality scenarios. In addition, existing composite membrane materials lack the ability to precisely control the microporous structure, making it difficult to balance the contradiction between high water permeability flux and selective enrichment of reactants and pollutants.

[0004] Currently, electrocatalytic microfiltration membranes typically use organic or inorganic membranes as substrates and carbon-based materials, metal oxides, or conductive polymers as catalyst layer supports. While they can achieve electrochemical degradation of pollutants, they still suffer from weak interfacial bonding between catalytically active components, leading to catalyst layer peeling and loss of active sites during long-term operation. Furthermore, existing electrocatalytic microporous membranes only utilize filtration to enhance convective mass transfer, neglecting the selective adsorption and enrichment effects of the membrane pore structure on electrocatalytic reactants. Particularly for advanced oxidation reactions involving gases, such as electro-Fenton and ozone catalytic oxidation, the transformation processes between different phases of reactants mean that existing electrocatalytic microporous membranes cannot provide a gas-solid-liquid three-phase reaction interface that is simultaneously beneficial to the entire reaction process. This results in low dissolved oxygen enrichment efficiency of the microporous structure, limited hydroxyl radical yield, and an inability to achieve efficient degradation of low-concentration recalcitrant pollutants (such as perfluorinated compounds and antibiotics). Existing improvement technologies, such as introducing noble metal doping or constructing hollow fiber structures, can improve catalytic activity but significantly increase material costs or sacrifice mechanical strength.

[0005] Therefore, developing electrocatalytic membrane materials that combine high catalytic activity, excellent water permeability, and long-term stability has become the key to overcoming the contradiction between energy consumption and efficiency in water treatment. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a multi-level composite microporous membrane electrode, its preparation method, and a water treatment and purification method.

[0007] To achieve the above objectives, the present invention provides a multi-level composite microporous membrane electrode, wherein the multi-level composite microporous membrane electrode comprises an inorganic ceramic microfiltration membrane, an anodic electrocatalytic active layer, and a cathode electrocatalytic active layer;

[0008] The anodic electrocatalytic active layer and the cathode electrocatalytic active layer are located on both sides of the inorganic ceramic microfiltration membrane, respectively; the thickness of the inorganic ceramic microfiltration membrane is 2-6 mm, the thickness of the anodic electrocatalytic active layer is 100-800 nm, and the thickness of the cathode electrocatalytic active layer is 1 μm-1 mm.

[0009] The inner wall of the pores of the inorganic ceramic microfiltration membrane is loaded with silica zeolite nanocrystals at a loading rate of 1-200 g / m³. 2 The particle size of the silicon zeolite nanocrystals is 50-200 nm.

[0010] In this invention, the two sides of the inorganic ceramic microfiltration membrane refer to the upper and lower surfaces of the inorganic ceramic microfiltration membrane. The inorganic ceramic microfiltration membrane is sandwiched between the anodic electrocatalytic active layer and the cathode electrocatalytic active layer, forming a three-layer structure.

[0011] According to a specific embodiment of the present invention, preferably, 30%-80% of the pore size of the multi-level composite microporous membrane electrode is concentrated in the range of 1.5-4 μm, and 20%-70% is concentrated in the range of 0.1-1.2 μm. The multi-level composite microporous membrane electrode provided by the present invention allows for controlled concentration of the pore size within different ranges, thus achieving regulation of the pore size distribution and pore structure.

[0012] According to a specific embodiment of the present invention, preferably, the specific surface area of ​​the silica zeolite nanocrystals is 300-600 m². 2 / g, the surface of the silica zeolite nanocrystals contains a microporous network with a pore size of 0.55-0.65 nm, and the volume of the micropores accounts for 20%-60% of the total pore volume. The silica zeolite nanocrystals have a hydrophobic inner surface and a hydrophilic outer surface. Because the interior of the microporous structure of the silica zeolite nanocrystals is hydrophobic, while the outer surface of the silica zeolite nanocrystals and the pores of the inorganic ceramic microfiltration membrane are hydrophilic, the multi-level composite microporous membrane electrode provided by this invention has a gas-solid-liquid three-phase interface when used for filtration and degradation, which is beneficial to the efficient degradation of pollutants.

[0013] According to a specific embodiment of the present invention, preferably, the inorganic ceramic microfiltration membrane is made of α-Al2O3 microfiltration membrane and / or SiC microfiltration membrane.

[0014] In some specific embodiments, preferably, the loading of the silica zeolite nanocrystals is 1-50 g / m³. 2 .

[0015] In some specific embodiments, preferably, the thickness of the anode electrocatalytic active layer is 100-500 nm, and the thickness of the cathode electrocatalytic active layer is 1 μm-100 μm.

[0016] In some specific embodiments, preferably, the particle size of the silica zeolite nanocrystals is 50-140 nm.

[0017] According to a specific embodiment of the present invention, preferably, the material of the anode electrocatalytic active layer includes one or more of iridium oxide, ruthenium oxide, iron-nickel oxide, and manganese oxide.

[0018] According to a specific embodiment of the present invention, preferably, the material of the cathode electrocatalytic active layer is carbon nanomaterial, and the loading of carbon nanomaterial is 5-100 g / m³. 2 .

[0019] According to a specific embodiment of the present invention, preferably, the carbon nanomaterial is a carbon nanotube material doped with metal atoms, and the doping amount of metal atoms is 0.1%-5%.

[0020] According to a specific embodiment of the present invention, preferably, the metal atoms include one or more combinations of iron, nickel, cobalt, manganese, platinum, and palladium.

[0021] According to a specific embodiment of the present invention, preferably, the pore size of the cathode electrocatalytic active layer is 0.01-0.5 μm.

[0022] The present invention also provides a method for preparing the above-mentioned multi-level composite microporous membrane electrode, wherein the preparation method includes the following steps:

[0023] Step 1: Immerse an inorganic ceramic microfiltration membrane with an average pore size of 1-50 μm (preferably 5-20 μm) in an acidic solution for surface activation treatment. After washing and a first calcination, a pretreated inorganic ceramic microfiltration membrane is obtained.

[0024] Step 2: Tetraethyl silicate (TEOS), tetrapropylammonium hydroxide (TPAOH), deionized water and organic template agent are mixed to obtain a precursor solution; the pretreated inorganic ceramic microfiltration membrane undergoes a hydrothermal reaction with the precursor solution, followed by washing, drying and a second calcination to obtain a second calcined product; the second calcined product is an inorganic ceramic microfiltration membrane with silica zeolite nanocrystals loaded on the inner wall of the pores, forming a silica zeolite nanocrystal-ceramic composite layer;

[0025] The molar ratio of tetraethyl silicate, tetrapropylammonium hydroxide, and deionized water is 1:(0.1-0.5):(50-200), and the mass of the organic template agent accounts for 1%-10% of the total mass of the precursor solution.

[0026] Step 3: Deposit an anodic electrocatalytic active layer on one side of the surface of the second calcined product; deposit a cathodic electrocatalytic active layer on the other side of the surface of the second calcined product to obtain a multi-level composite microporous membrane electrode.

[0027] According to a specific embodiment of the present invention, preferably, the organic template agent is ethylenediamine and / or hexadecyltrimethylammonium bromide.

[0028] In some specific embodiments, preferably, the molar concentration of the acidic solution is 0.1-5M, and the acidic solution includes one or more of hydrochloric acid, nitric acid, and sulfuric acid.

[0029] In some specific embodiments, preferably, the surface activation treatment is performed at a temperature of 50-90°C for 2-6 hours, followed by rinsing with deionized water until neutral. Prior to the surface activation treatment, the inorganic ceramic microfiltration membrane can be ultrasonically cleaned to remove impurities from the surface and pores.

[0030] In this invention, the pretreated inorganic ceramic microfiltration membrane has hydroxyl active sites, which make it easier for the surface and inner wall of the pores of the inorganic ceramic microfiltration membrane to attach the precursor required for the growth of silicon zeolite nanocrystals.

[0031] According to a specific embodiment of the present invention, preferably, the temperature of the hydrothermal reaction is 80-200°C and the time of the hydrothermal reaction is 24-96 hours.

[0032] According to a specific embodiment of the present invention, preferably, the anodic electrocatalytic active layer is deposited by magnetron sputtering, wherein the parameters of the magnetron sputtering process are: sputtering power 100-500W, argon flow rate 50-150sccm, substrate temperature 200-400℃, and sputtering time 0.5-4 hours.

[0033] In some specific embodiments, preferably, the cathode electrocatalytic active layer is obtained by pressure self-assembly via filtration.

[0034] According to a specific embodiment of the present invention, preferably, the first calcination condition is calcination at 300-600°C for 1-3 hours.

[0035] According to a specific embodiment of the present invention, preferably, the second calcination condition is calcination at 400-700°C for 4-12 hours.

[0036] In some specific embodiments, preferably, the drying conditions are drying at a temperature of 80-120°C for 2-24 hours.

[0037] The present invention also provides a water treatment and purification method, which employs the above-mentioned multi-stage composite microporous membrane electrode, the water treatment and purification method comprising:

[0038] The multi-stage composite microporous membrane electrode is placed in an electrofiltration reactor, and the influent aqueous solution flows through the multi-stage composite microporous membrane electrode at a constant filtration flow rate. A voltage is applied to purify the influent aqueous solution. In this invention, a peristaltic pump is used to purify the influent aqueous solution by flowing it through the multi-stage composite microporous membrane electrode. The water treatment purification system is not aerated; it utilizes only the dissolved oxygen in the influent aqueous solution and the oxygen generated on the anode side of the multi-stage composite microporous membrane electrode to filter and purify the influent aqueous solution.

[0039] According to a specific embodiment of the present invention, preferably, the dissolved oxygen concentration of the influent aqueous solution is 8-9 mg / L. When the multi-stage composite microporous membrane electrode provided by the present invention is used for water treatment and purification, no additional aeration is required; the naturally dissolved oxygen concentration in the influent aqueous solution at room temperature and pressure is sufficient to meet the requirements.

[0040] According to a specific embodiment of the present invention, preferably, the concentration of pollutants in the influent aqueous solution is 0.1-10 mg / L. The water treatment and purification method provided by the present invention is applicable to the degradation of any organic matter, and is particularly useful for purifying recalcitrant organic matter, including antibiotics (e.g., tetracycline), endocrine disruptors, perfluorinated compounds, etc.

[0041] According to a specific embodiment of the present invention, preferably, the filtration flow rate is 1-20 mL·min. -1 The applied voltage is 1.0-3.0V. In this invention, the water treatment and purification process is continuous, with a hydraulic retention time of 0.01-3.6s. By adjusting the filtration flow rate and extending the hydraulic retention time, the removal effect can be improved.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] (1) In the multi-level composite microporous membrane electrode provided by the present invention, there are in-situ grown silica zeolite nanocrystals on the inner wall of the pores of the inorganic ceramic microfiltration membrane. The in-situ grown silica zeolite nanocrystals have strong interfacial bonding with the membrane material, which makes the multi-level composite microporous membrane electrode have high mechanical strength and good long-term operation stability. It provides a multi-level composite microporous membrane electrode that is simple to operate, green, environmentally friendly, economical and efficient for electrofiltration to remove refractory organic matter in water.

[0044] (2) When the multi-level composite microporous membrane electrode provided by this invention is used for water treatment and purification, the silica zeolite nanocrystals have a hydrophobic inner surface and a hydrophilic outer surface, enabling the multi-level composite microporous membrane electrode to selectively enrich dissolved oxygen in the aqueous solution within the micropores and enrich oxygen generated by the anodic electrocatalytic reaction. This eliminates the external aeration cost in traditional electrocatalytic reactions, saves energy, and significantly improves the conversion efficiency of hydroxyl radicals. This invention combines the directional convective mass transfer effect of membrane filtration with the cathodic reduction to hydroxyl radicals, achieving efficient and rapid removal of recalcitrant organic matter.

[0045] (3) The method for preparing the multi-level composite microporous membrane electrode provided by this invention achieves oxygen enrichment and concentration by in-situ growing silica zeolite nanocrystals with hydrophobic inner surfaces and hydrophilic outer surfaces on the inner wall of the pores of an inorganic ceramic microfiltration membrane. This improves the problem of low free radical conversion efficiency under the limitation of low dissolved oxygen concentration at the cathode. Furthermore, by adjusting the synthesis conditions of the hydrothermal reaction, the size and loading of the silica zeolite nanocrystals grown on the pore walls can be controlled, resulting in a controllable pore size distribution and pore structure for the multi-level composite microporous membrane electrode, with a wide adjustable range of membrane flux. Simultaneously, by constructing a hydrophobic micropore-hydrophilic outer surface heterostructure, this invention achieves selective enrichment of oxygen molecules while maintaining high water permeability, providing a new approach for efficient and low-power catalytic deep water purification technology. Attached Figure Description

[0046] Figure 1 Electron microscopy images of silica zeolite nanocrystals of different sizes prepared in Examples 1-2.

[0047] Figure 2 The pore size distribution diagram is shown for the multi-level composite microporous membrane electrode prepared in Example 1.

[0048] Figure 3 This is a schematic diagram of the molecular structure and microporous network configuration of the silica zeolite nanocrystals in water in Example 1.

[0049] Figure 4 This is a kinetic simulation diagram of the enrichment of oxygen molecules in water by silica zeolite nanocrystals in Example 1.

[0050] Figure 5 The images show surface electron microscope (SEM) images of both sides of the multi-level composite microporous membrane electrode prepared in Example 1 and the elemental distribution diagram of the cross-section of the multi-level composite microporous membrane electrode.

[0051] Figure 6 The graph shows a comparison of the removal rates of pollutants by the multi-level composite microporous membrane electrodes prepared in Examples 1-2 and Comparative Example 1 when used for electrofiltration degradation.

[0052] Figure 7 The results of stability tests on the pollutant removal rate of the multi-level composite microporous membrane electrodes prepared for Example 1 and Comparative Example 1 after long-term continuous operation.

[0053] Figure 8 This is a comparison chart showing the dissolved oxygen concentration in the effluent after water treatment and purification using the multi-stage composite microporous membrane electrodes prepared in Examples 1-2 and Comparative Example 1. Detailed Implementation

[0054] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0055] Example 1

[0056] This embodiment provides a method for preparing a multi-level composite microporous membrane electrode, the specific steps of which are as follows:

[0057] (1) Pretreatment of inorganic ceramic microfiltration membrane:

[0058] An inorganic ceramic microfiltration membrane (α-Al2O3 microfiltration membrane) with an average pore size of 5 μm and a thickness of 2.5 mm was ultrasonicated in pure water for 30 min to remove impurities from the surface and pores. Then, it was dried in an oven at 60 °C for 2 hours. The cleaned ceramic membrane was then immersed in an acidic solution for surface activation treatment. The acidic solution was 0.5 M nitric acid at a treatment temperature of 50 °C for 2 hours. After treatment, it was rinsed with deionized water until neutral and then calcined at 300 °C for 2 hours to obtain a pretreated inorganic ceramic microfiltration membrane.

[0059] (2) In-situ growth of silica zeolite nanocrystals:

[0060] Tetraethyl silicate (TEOS), tetrapropylammonium hydroxide (TPAOH), deionized water, and an organic template agent were mixed to obtain a precursor solution, wherein the molar ratio of TEOS:TPAOH:H2O was 1:0.3:50, and the organic template agent was ethylenediamine, which accounted for 2% of the total mass of the precursor solution. The pretreated inorganic ceramic microfiltration membrane was placed in a closed reaction vessel, and the precursor solution was injected. The reaction was carried out hydrothermally at 90°C for 24 hours. After the reaction, the substrate was separated by centrifugation or vacuum filtration, washed with deionized water, dried at 80°C for 2 hours, and then calcined at 500°C for 6 hours to remove the template agent, thus obtaining a second calcined product. The second calcined product is an inorganic ceramic microfiltration membrane with silica zeolite nanocrystals loaded on the inner wall of the pores, forming a silica zeolite nanocrystal-ceramic composite layer.

[0061] The silicon zeolite nanocrystals have a particle size of 50-70 nm and a loading of 1 g / m³. 2 Specific surface area is 436 m² 2 / g, the surface of the silica zeolite nanocrystals contains a microporous network with a pore size of 0.55-0.65nm, and the volume of the micropores accounts for 30% of the total pore volume.

[0062] (3) Composite anode electrocatalytic active layer and cathode electrocatalytic active layer:

[0063] An IrOx anodic electrocatalytic active layer was deposited on one side of the silicon zeolite nanocrystal-ceramic composite layer using a magnetron sputtering process. Then, 25 mg of uniformly dispersed iron single-atom carbon nanotube suspension was filtered through pressure self-assembly to form a cathode electrocatalytic active layer on the other side of the silicon zeolite nanocrystal-ceramic composite layer, thus obtaining a multi-level composite microporous membrane electrode.

[0064] The specific parameters of the magnetron sputtering process are as follows: sputtering power 100W, argon flow rate 60sccm, substrate temperature 200℃, sputtering time 0.5 hours, anode electrocatalytic active layer thickness of 200nm, cathode electrocatalytic active layer thickness of 20μm, pore size of 0.05μm, and iron single-atom carbon nanotube loading of 10g / m 2 The doping level of iron single atoms is 1.6%.

[0065] Example 2

[0066] This embodiment provides a method for preparing a multi-level composite microporous membrane electrode, which is prepared according to the method in Example 1, except that in step (2), the hydrothermal reaction is carried out at a temperature of 150°C for 24 hours, while the other steps and process parameters remain unchanged, and a multi-level composite microporous membrane electrode is obtained.

[0067] The size of silica zeolite nanocrystals can be controlled by changing the hydrothermal reaction conditions. In this embodiment, the particle size of the in-situ grown silica zeolite nanocrystals is 100-140 nm, and the loading of silica zeolite nanocrystals is 10 g / m³. 2 Specific surface area is 368m² 2 / g, the surface of the silica zeolite nanocrystals contains a microporous network with a pore size of 0.55-0.65nm, and the volume of the micropores accounts for 45% of the total pore volume.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing a multi-level composite microporous membrane electrode, which is prepared according to the method in Example 1, with the only difference being that: in step (1), the inorganic ceramic microfiltration membrane is not surface activated and subjected to a first calcination treatment, hydroxyl active sites are not introduced, and step (2) is omitted, and the anode electrocatalytic active layer and the cathode electrocatalytic active layer are directly composited, while the remaining steps and process parameters remain unchanged, thus obtaining a multi-level composite microporous membrane electrode.

[0070] The controllability of the in-situ growth of silica zeolite nanocrystals and the pore structure of the multi-level composite microporous membrane electrode in this invention is explored in the following details:

[0071] Figure 1 Electron microscopy images of silica zeolite nanocrystals of different sizes prepared in Examples 1 and 2, from... Figure 1 It can be seen that by controlling the growth conditions of silica zeolite, silica zeolite nanocrystals with diameters in two different ranges, 50-70 nm and 100-140 nm, can be prepared.

[0072] Figure 2 The pore size distribution diagram of the multi-level composite microporous membrane electrode prepared in Example 1 is shown below. Figure 2 As can be seen, by growing silica zeolite nanocrystals in situ within the pores of the inorganic ceramic microfiltration membrane and constructing a carbon nanotube cathode electrocatalytic active layer, the pore size of the inorganic ceramic microfiltration membrane with an original size of 5 μm was reduced. Due to the influence of the pore structure and the carbon nanotube layer, the pore size of the multi-level composite microporous membrane electrode can be controlled to be mainly concentrated at 0.55 μm (approximately 16%) and 2.1 μm (approximately 32%), thus achieving the regulation of pore size distribution and pore structure.

[0073] Figure 3 This is a schematic diagram of the molecular structure and microporous network configuration of the silica zeolite nanocrystals grown in water in Example 1, obtained through molecular dynamics simulation calculations. The gray boxes represent the outer aqueous solution background, and the central circle represents the molecular structure of the silica zeolite nanocrystals. Figure 3 As can be seen, a microporous network is distributed on the silica zeolite nanocrystals, which is formed during the self-assembly process of silica zeolite nanocrystal growth.

[0074] Figure 4 This is a kinetic simulation diagram of the enrichment of oxygen molecules in water by the silica zeolite nanocrystals grown in Example 1. Figure 4 As can be seen, under the initial conditions (0 ns), dissolved oxygen is distributed in the water. After a reaction time of 20 ns, oxygen molecules in the water can be enriched in the microporous network of silica zeolite nanocrystals.

[0075] Figure 5 The images show surface electron microscope (SEM) images of both sides of the multi-level composite microporous membrane electrode prepared in Example 1 and an elemental distribution diagram of the cross-section of the multi-level composite microporous membrane electrode. Figure 5 A and B in the diagram show the surface morphology of one side of the iridium oxide anode electrocatalytic active layer and the other side of the carbon nanotube cathode electrocatalytic active layer, respectively. Figure 5 Figure C shows the cross-sectional elemental distribution of the iridium oxide active layer and part of the silica zeolite nanocrystal-ceramic composite layer on the anode side. It can be seen that silica zeolite nanocrystals are grown in situ on the inner wall of the pores of the inorganic ceramic microfiltration membrane, and oxygen molecule enrichment is achieved.

[0076] The pollutant degradation performance of the multi-level composite microporous membrane electrodes prepared in Examples 1-2 and Comparative Example 1 is investigated below:

[0077] Electrofiltration Degradation of Pollutants Test:

[0078] Water treatment and purification were carried out using the multi-stage composite microporous membrane electrodes prepared in Examples 1-2 and Comparative Example 1, respectively. Different multi-stage composite microporous membrane electrodes were placed in electrofiltration reactors. The influent water was made to flow through the multi-stage composite microporous membrane electrodes at a constant filtration flow rate by a peristaltic pump. A voltage of 3V was applied. The system was not aerated. The influent water was filtered by only the dissolved oxygen in the influent water and the oxygen generated on the anode side of the multi-stage composite microporous membrane electrode.

[0079] The filtration flow rate was 2 mL / min. -1 The target pollutant in the influent aqueous solution is tetracycline, with a concentration of 2 mg / L. The concentration of dissolved oxygen in the influent aqueous solution is 8-9 mg / L.

[0080] The removal rate of pollutants by electrofiltration is calculated using the formula: Removal Rate = [(Influent Concentration - Effluent Concentration) / Influent Concentration] × 100%. The results are as follows: Figure 6 As shown, from Figure 6 As can be seen from the data, compared with Comparative Example 1, the multi-level composite microporous membrane electrodes prepared in Examples 1-2 have a higher pollutant removal rate. Specifically, Example 1 can reach 96%, while Comparative Example 1 is only 74%.

[0081] Furthermore, the stability of the pollutant removal rate of the multi-level composite microporous membrane electrodes prepared in Example 1 and Comparative Example 1 after long-term continuous operation was investigated, and the results are as follows: Figure 7 As shown, from Figure 7 As can be seen, after 60 hours of continuous operation, the removal rate of Comparative Example 1 decreased significantly, while the removal rate of Example 1 remained stable, indicating that the multi-level composite microporous membrane electrode provided by the present invention has excellent long-term operational stability.

[0082] In addition, to verify the oxygen enrichment capacity of the multi-level composite microporous membrane electrode, the multi-level composite microporous membrane electrodes prepared in Examples 1-2 and Comparative Example 1 were used to filter the aqueous solution. After 20 minutes of stable operation, the comparison of dissolved oxygen concentration in the effluent was shown in the following graph. Figure 8 As shown, from Figure 8 As can be seen, after filtering the influent aqueous solution using the multi-level composite microporous membrane electrode prepared in Examples 1-2, the dissolved oxygen concentration in the effluent aqueous solution is higher. In particular, the dissolved oxygen concentration in the effluent aqueous solution corresponding to Example 1 can reach 20 mg / L, indicating that the silica zeolite nanocrystal-ceramic composite layer has good oxygen enrichment performance.

Claims

1. A multi-level composite microporous membrane electrode, wherein, This multi-level composite microporous membrane electrode includes an inorganic ceramic microfiltration membrane, an anode electrocatalytic active layer, and a cathode electrocatalytic active layer; The anodic electrocatalytic active layer and the cathode electrocatalytic active layer are located on both sides of the inorganic ceramic microfiltration membrane, respectively. The inorganic ceramic microfiltration membrane has a thickness of 2-6 mm, the anode electrocatalytic active layer has a thickness of 100-800 nm, and the cathode electrocatalytic active layer has a thickness of 1 μm-1 mm. The inorganic ceramic microfiltration membrane has silica zeolite nanocrystals loaded on the inner walls of its pores at a loading rate of 1-200 g / m³. 2 ; The particle size of the silicon zeolite nanocrystals is 50-200 nm.

2. The multi-level composite microporous membrane electrode according to claim 1, wherein, The pore size of the multi-level composite microporous membrane electrode is concentrated in the range of 1.5-4 μm for 30%-80% and in the range of 0.1-1.2 μm for 20%-70%.

3. The multi-level composite microporous membrane electrode according to claim 1, wherein, The specific surface area of ​​the silicon zeolite nanocrystals is 300-600 m². 2 / g, the surface of silica zeolite nanocrystals contains a microporous network with a pore size of 0.55-0.65 nm, and the volume of the micropores accounts for 20%-60% of the total pore volume.

4. The multi-level composite microporous membrane electrode according to claim 1, wherein, The inorganic ceramic microfiltration membrane is made of α-Al2O3 microfiltration membrane and / or SiC microfiltration membrane.

5. The multi-level composite microporous membrane electrode according to claim 1, wherein, The material of the anode electrocatalytic active layer includes one or more of iridium oxide, ruthenium oxide, iron-nickel oxide, and manganese oxide.

6. The multi-level composite microporous membrane electrode according to claim 1, wherein, The cathode electrocatalytic active layer is made of carbon nanomaterials, with a carbon nanomaterial loading of 5-100 g / m². 2 .

7. The multi-level composite microporous membrane electrode according to claim 6, wherein, The carbon nanomaterial is a carbon nanotube material doped with metal atoms, and the doping amount of metal atoms is 0.1%-5%.

8. The multi-level composite microporous membrane electrode according to claim 7, wherein, The metal atoms include one or more of the following: iron, nickel, cobalt, manganese, platinum, and palladium.

9. The multi-level composite microporous membrane electrode according to claim 1 or 6, wherein, The pore size of the cathode electrocatalytic active layer is 0.01-0.5 μm.

10. The method for preparing the multi-level composite microporous membrane electrode according to any one of claims 1-9, wherein, The preparation method includes the following steps: Step 1: Immerse an inorganic ceramic microfiltration membrane with an average pore size of 1-50 μm in an acidic solution for surface activation treatment. After washing and first calcination, a pretreated inorganic ceramic microfiltration membrane is obtained. Step 2: Tetraethyl silicate, tetrapropylammonium hydroxide, deionized water and organic template agent are mixed to obtain a precursor solution; the pretreated inorganic ceramic microfiltration membrane is subjected to a hydrothermal reaction with the precursor solution, and then washed, dried and calcined a second time to obtain a second calcined product; The molar ratio of tetraethyl silicate, tetrapropylammonium hydroxide, and deionized water is 1:(0.1-0.5):(50-200), and the organic template agent accounts for 1%-10% of the total mass of the precursor solution. Step 3: Deposit an anodic electrocatalytic active layer on one side of the surface of the second calcined product; deposit a cathodic electrocatalytic active layer on the other side of the surface of the second calcined product to obtain a multi-level composite microporous membrane electrode.

11. The preparation method according to claim 10, wherein, The organic template agent is ethylenediamine and / or hexadecyltrimethylammonium bromide.

12. The preparation method according to claim 10, wherein, The hydrothermal reaction temperature is 80-200℃, and the hydrothermal reaction time is 24-96 hours.

13. The preparation method according to claim 10, wherein, The anodic electrocatalytic active layer is deposited by magnetron sputtering, with the following parameters: sputtering power 100-500 W, argon flow rate 50-150 sccm, substrate temperature 200-400℃, and sputtering time 0.5-4 hours.

14. The preparation method according to claim 10, wherein, The first calcination condition is calcination at 300-600℃ for 1-3 hours; And / or, the second calcination conditions are calcination at 400-700°C for 4-12 hours.

15. A water treatment and purification method, wherein the method is performed using the multi-stage composite microporous membrane electrode as described in any one of claims 1-9, the water treatment and purification method comprising: The multi-stage composite microporous membrane electrode is placed in an electrofiltration reactor, and the influent aqueous solution flows through the multi-stage composite microporous membrane electrode at a constant filtration flow rate. Voltage is applied to achieve purification of the influent aqueous solution.

16. The water treatment and purification method according to claim 15, wherein, The dissolved oxygen concentration in the influent aqueous solution is 8-9 mg / L.

17. The water treatment and purification method according to claim 15, wherein, The concentration of pollutants in the influent aqueous solution is 0.1-10 mg / L.

18. The water treatment and purification method according to claim 15, wherein, The filtration flow rate is 1-20 mL / min. -1 The applied voltage is 1.0-3.0 V.

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