Multistage composite microporous membrane electrode, preparation method thereof and water treatment and purification method

Abstract

The invention provides a multistage composite microporous membrane electrode, a preparation method thereof and a water treatment and purification method. 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 positioned on 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 [mu] m-1 mm; silicite nanocrystals are loaded on the inner walls of pore channels of the inorganic ceramic microfiltration membrane. The particle size of the silica zeolite nanocrystal is 50 to 200 nm. When the multi-stage composite microporous membrane electrode provided by the invention is used for water treatment and purification, oxygen molecules can be efficiently enriched in micropores, the conversion efficiency of hydroxyl radicals is improved, and efficient removal of refractory organic matters is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of membrane material preparation and water treatment, and particularly relates to a multi-stage composite microporous membrane electrode, a preparation method thereof and a water treatment and purification method. BACKGROUND

[0002] With the increasingly serious problem of complex pollution in water environment (such as drug residues, endocrine disruptors, microplastics), traditional heavy metals, and refractory organic matter, traditional water purification technology is facing severe challenges. Although the current mainstream membrane separation technology can achieve physical interception of pollutants, it has problems such as serious membrane pollution, insufficient selectivity, and inability to degrade pollutants, resulting in high operating energy consumption, short membrane life, and easy formation of concentrated liquid from intercepted pollutants to cause secondary pollution.

[0003] Electrocatalytic membrane technology couples membrane separation and electrochemical oxidation processes, which can in-situ generate high active radicals while intercepting pollutants, and is considered as a frontier direction in the field of water advanced treatment. However, the existing electrocatalytic membranes generally have problems such as weak interface combination between conductive substrate and catalytic layer, low electron transmission efficiency, and uneven distribution of active sites, which leads to fast catalytic efficiency decay, insufficient anti-pollution ability, and difficulty in meeting the long-term stable operation demand in complex water quality scenarios. In addition, the existing composite membrane material has insufficient precision control ability for microporous structure, which is difficult to balance the contradiction between high water permeation flux and selective enrichment of reactants and pollutants.

[0004] Currently, electrocatalytic microfiltration membranes usually use organic and inorganic membranes as substrates, and carbon-based materials, metal oxides or conductive polymers as catalytic layer carriers, which can achieve electrochemical degradation of pollutants, but still have problems such as weak interface combination of catalytic active components, easy peeling of catalytic layer during long-term operation, and loss of active sites. In addition, the existing electrocatalytic microporous membranes only use filtration to strengthen the convective mass transfer effect, ignoring the design of the internal structure of the membrane pore for selective adsorption and enrichment of electrocatalytic reactants. Especially for gas-involved advanced oxidation reactions such as electro-Fenton and ozone catalytic oxidation, the conversion process between different phase reactants leads to the fact that the existing electrocatalytic microporous membranes cannot provide a gas-liquid-solid three-phase reaction interface that is beneficial to the whole reaction process, resulting in low enrichment efficiency of microporous structure for dissolved oxygen, limited hydroxyl radical yield, and inability to achieve efficient degradation of low-concentration refractory pollutants (such as perfluorinated compounds and antibiotics). The existing improvement technologies such as introduction of noble metal doping or construction of hollow fiber structure can improve catalytic activity, but significantly increase material cost or sacrifice mechanical strength.

[0005] Therefore, developing an electrocatalytic membrane material with high catalytic activity, excellent water permeability and long-term stability has become the key to breaking the contradiction between water treatment energy consumption and efficiency. SUMMARY

[0006] To solve the above technical problems, the present application aims to provide a multi-stage composite microporous membrane electrode and a preparation method and water treatment and purification method thereof.

[0007] To achieve the above-mentioned purposes, the present application provides a multi-stage composite microporous membrane electrode, wherein the multi-stage composite microporous membrane electrode comprises an inorganic ceramic microfiltration membrane, an anode electrocatalytic active layer and a cathode electrocatalytic active layer.

[0008] The anode electrocatalytic active layer and the cathode electrocatalytic active layer are respectively located on the two side surfaces 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 μm-1 mm.

[0009] The inner wall of the pore of the inorganic ceramic microfiltration membrane is loaded with silicon zeolite nanocrystals, and the loading amount is 1-200 g / m 2 ; the particle size of the silicon zeolite nanocrystals is 50-200 nm.

[0010] In the present application, the two side surfaces of the inorganic ceramic microfiltration membrane refer to the upper surface and the lower surface of the inorganic ceramic microfiltration membrane, and the inorganic ceramic microfiltration membrane is sandwiched between the anode electrocatalytic active layer and the cathode electrocatalytic active layer to form a three-layer structure.

[0011] According to a specific embodiment of the present application, preferably, 30%-80% of the pore size of the multi-stage composite microporous membrane electrode is concentratedly distributed in 1.5-4 μm, and 20%-70% is concentratedly distributed in 0.1-1.2 μm. The pore size of the multi-stage composite microporous membrane electrode provided by the present application can be controlled to be concentratedly distributed in different ranges, realizing the regulation of the pore size distribution and the pore structure.

[0012] According to a specific embodiment of the present application, preferably, the specific surface area of the silicon zeolite nanocrystals is 300-600 m 2 / g, the surface of the silicon 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 silicon zeolite nanocrystals have a hydrophobic inner surface and a hydrophilic outer surface. Since the interior of the microporous structure of the silicon zeolite nanocrystals is hydrophobic, and the outer surface of the silicon zeolite nanocrystals and the pore of the inorganic ceramic microfiltration membrane are hydrophilic, the multi-stage composite microporous membrane electrode provided by the present application 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 application, preferably, the material of the inorganic ceramic microfiltration membrane is an α-Al2O3 microfiltration membrane and / or a SiC microfiltration membrane.

[0014] In some embodiments, preferably, the loading amount of the silicon zeolite nanocrystals is 1-50 g / m 2 .

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

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

[0017] According to some embodiments of the present application, preferably, the material of the anode electrocatalytically active layer comprises one or a combination of two or more of iridium oxide, ruthenium oxide, iron-nickel oxide, and manganese oxide.

[0018] According to some embodiments of the present application, preferably, the material of the cathode electrocatalytically active layer is a carbon nanomaterial, and the loading amount of the carbon nanomaterial is 5-100 g / m 2 .

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

[0020] According to some embodiments of the present application, preferably, the metal atoms comprise one or a combination of two or more of iron, nickel, cobalt, manganese, platinum, and palladium.

[0021] According to some embodiments of the present application, preferably, the pore size of the cathode electrocatalytically active layer is 0.01-0.5 μm.

[0022] The present application also provides a preparation method of the multi-stage composite microporous membrane electrode.

[0023] Step one: immerse an inorganic ceramic microfiltration membrane with an average pore size of 1-50 μm (preferably 5-20 μm) into an acid solution for surface activation treatment, and after washing and first calcination, obtain a pretreated inorganic ceramic microfiltration membrane;

[0024] Step two: mix tetraethyl orthosilicate (TEOS), tetrapropylammonium hydroxide (TPAOH), deionized water, and an organic template to obtain a precursor solution; subject the pretreated inorganic ceramic microfiltration membrane to hydrothermal reaction with the precursor solution, and then after washing, drying, and second calcination, obtain a second calcination product; the second calcination product is an inorganic ceramic microfiltration membrane with silicon zeolite nanocrystals loaded on the inner wall of the pore channel, forming a silicon zeolite nanocrystal-ceramic composite layer;

[0025] The molar ratio of tetraethyl silicate, tetrapropyl ammonium 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 three: depositing an anode electrocatalytic active layer on one side surface of the second calcination product and depositing a cathode electrocatalytic active layer on the other side surface of the second calcination product to obtain a multi-stage composite microporous membrane electrode.

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

[0028] In some specific embodiments, preferably, the molar concentration of the acid solution is 0.1-5M, and the acid solution comprises one or a combination of two 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℃ for 2-6 hours, and after the treatment, the inorganic ceramic microfiltration membrane is washed with deionized water until neutral. Before the surface activation treatment, the inorganic ceramic microfiltration membrane can be ultrasonically cleaned to remove impurities on the surface and in the pores.

[0030] In the present application, the pretreated inorganic ceramic microfiltration membrane has hydroxyl active sites, and the surface and the inner wall of the pores of the inorganic ceramic microfiltration membrane are more easily attached to the precursor required for the growth of siliceous zeolite nanocrystals by means of the hydroxyl active sites.

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

[0032] According to a specific embodiment of the present application, preferably, the anode electrocatalytic active layer is deposited by a magnetron sputtering process, and the parameters of the magnetron sputtering process are as follows: 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.

[0034] According to a specific embodiment of the present application, preferably, the first calcination is performed at 300-600℃ for 1-3 hours.

[0035] According to a specific embodiment of the present application, preferably, the second calcination is performed at 400-700℃ for 4-12 hours.

[0036] In some embodiments, preferably, the drying condition is drying at a temperature of 80-120℃ for 2-24 hours.

[0037] The present application also provides a water treatment and purification method using the multi-stage composite microporous membrane electrode as described above, which comprises:

[0038] The multi-stage composite microporous membrane electrode is placed in an electrofiltration reactor, the influent solution is made to flow through the multi-stage composite microporous membrane electrode at a constant filtration flow rate, and a voltage is applied to achieve the purification of the influent solution. In the present application, the influent solution is made to flow through the multi-stage composite microporous membrane electrode for purification by a peristaltic pump, and the water treatment and purification system is not aerated, but only utilizes the dissolved oxygen in the influent solution and the oxygen produced on the anode side of the multi-stage composite microporous membrane electrode to filter and purify the influent solution.

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

[0040] According to a specific embodiment of the present application, preferably, the concentration of pollutants in the influent solution is 0.1-10 mg / L. The water treatment and purification method provided by the present application is suitable for the degradation of any organic matter, and can be particularly used for the purification of refractory organic matter, including antibiotics (such as tetracycline), endocrine disruptors, perfluorinated compounds, etc.

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

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] (1) The multi-stage composite microporous membrane electrode provided by the present application has in-situ grown silicon zeolite nanocrystals on the inner wall of the pore channel of the inorganic ceramic microfiltration membrane, and the interface bonding force between the in-situ grown silicon zeolite nanocrystals and the membrane material is strong, so that the multi-stage composite microporous membrane electrode has high mechanical strength and good long-period operation stability, and provides a kind of multi-stage composite microporous membrane electrode which is simple to operate, green and environmentally friendly, and economical and efficient for removing refractory organic matter in water by electrofiltration.

[0044] (2) The multi-stage composite microporous membrane electrode provided by the application can selectively enrich dissolved oxygen in the water solution in the micropores and enrich oxygen generated by anodic electrocatalytic reaction, so that the cost of external aeration in the traditional electrocatalytic reaction is eliminated, energy consumption is saved, and the conversion efficiency of hydroxyl radicals is significantly improved. The application realizes efficient and rapid removal of refractory organic matter by combining membrane filtration with directed convective mass transfer and reducing conversion into hydroxyl radicals at the cathode.

[0045] (3) The preparation method of the multi-stage composite microporous membrane electrode provided by the application realizes enrichment and concentration of oxygen molecules by in-situ growth of silicon zeolite nanocrystals with a hydrophobic inner surface and a hydrophilic outer surface on the inner wall of the pore channel of the inorganic ceramic microfiltration membrane, and can improve the low conversion efficiency of radicals under the limitation of low dissolved oxygen concentration at the cathode. In addition, by adjusting the synthesis conditions of the hydrothermal reaction, the size and loading amount of the silicon zeolite nanocrystals grown on the pore wall can be controlled, so that the multi-stage composite microporous membrane electrode has a controllable pore size distribution and pore structure, and the membrane flux can be adjusted in a wide range. At the same time, by constructing a hydrophobic micropore-hydrophilic outer surface heterostructure, the application realizes selective enrichment of oxygen molecules while maintaining high water flux, and provides a new way for efficient and low-consumption electrocatalytic deep water purification technology. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 Electron microscope images of silicon zeolite nanocrystals of different sizes prepared for Examples 1-2.

[0047] Figure 2 Pore size distribution graph of the multi-stage composite microporous membrane electrode prepared for Example 1.

[0048] Figure 3 Molecular structure and micropore network configuration diagram of the silicon zeolite nanocrystals in Example 1 in water.

[0049] Figure 4 Kinetics simulation graph of the enrichment of oxygen molecules of the silicon zeolite nanocrystals in Example 1 in water.

[0050] Figure 5 Surface electron microscope images of both sides of the multi-stage composite microporous membrane electrode prepared for Example 1 and element distribution graph of the cross section of the multi-stage composite microporous membrane electrode.

[0051] Figure 6 Comparison graph of removal rates of pollutants by the multi-stage composite microporous membrane electrode prepared for Examples 1-2 and Comparative Example 1 for electrofiltration degradation.

[0052] Figure 7 Stability test results of the removal rates of pollutants by the multi-stage composite microporous membrane electrode prepared for Examples 1 and Comparative Example 1 after long-period continuous operation.

[0053] Figure 8 The comparison chart of the dissolved oxygen concentration in the effluent solution after water treatment and purification of the multistage composite microporous membrane electrode prepared by using Examples 1-2 and Comparative Example 1. DETAILED DESCRIPTION

[0054] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application are described in detail below, but it should not be understood as limiting the scope of the present application.

[0055] Example 1

[0056] The present embodiment provides a preparation method of a multistage composite microporous membrane electrode, and the specific steps are as follows:

[0057] (1) Inorganic ceramic microfiltration membrane pretreatment:

[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 is ultrasonically treated in pure water for 30 min to remove impurities on the surface and in the pores, and then dried in an oven at 60℃ for 2 hours; the cleaned ceramic membrane is immersed in an acidic solution for surface activation treatment, the acidic solution is 0.5M nitric acid, the treatment temperature is 50℃, and the treatment time is 2 hours; after the treatment, the ceramic membrane is washed with deionized water until it is neutral, and then first calcined at 300℃ for 2 hours to obtain a pretreated inorganic ceramic microfiltration membrane.

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

[0060] Silicon tetraethoxide (TEOS), tetrapropylammonium hydroxide (TPAOH), deionized water and an organic template are mixed to obtain a precursor solution, wherein the molar ratio of TEOS:TPAOH:H2O is 1:0.3:50, and the organic template is ethylenediamine, which accounts for 2% of the total mass of the precursor solution; the pretreated inorganic ceramic microfiltration membrane is placed in a sealed reaction kettle, and the precursor solution is injected, and hydrothermal reaction is carried out at 90℃ for 24 hours; after the reaction, the substrate is separated by centrifugation or suction filtration, washed with deionized water and dried at 80℃ for 2 hours, and then second calcined at 500℃ for 6 hours to remove the template to obtain a second calcination product; the second calcination product is an inorganic ceramic microfiltration membrane with silicalite nanocrystals loaded on the inner wall of the pores, forming a silicalite nanocrystal-ceramic composite layer.

[0061] The particle size of the silicalite nanocrystals is 50-70 nm, and the loading amount of the silicalite nanocrystals is 1g / m 2 The specific surface area is 436m 2 / g, the surface of the silicalite nanocrystal contains a microporous network with a pore size of 0.55-0.65 nm, and the volume of the micropores accounts for 30% of the total pore volume.

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

[0063] The IrOx anode electrocatalytic active layer is deposited on one side surface of the silicalite nanocrystal-ceramic composite layer by a magnetron sputtering process, and then 25 mg of uniformly dispersed iron monatomic carbon nanotube suspension is suction-filtered on the other side surface of the silicalite nanocrystal-ceramic composite layer by a pressure self-assembly method to form the cathode electrocatalytic active layer, thereby obtaining the multi-stage composite microporous membrane electrode.

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

[0065] Example 2

[0066] The example provides a preparation method of a multi-stage composite microporous membrane electrode, which is prepared according to the method in Example 1, with the difference being that in step (2), the hydrothermal reaction is carried out at a temperature of 150 ℃ for 24 hours, and the remaining steps and process parameters remain unchanged, thereby obtaining the multi-stage composite microporous membrane electrode.

[0067] The size of the silicalite nanocrystal can be adjusted by changing the hydrothermal reaction conditions. In this example, the particle size of the in-situ grown silicalite nanocrystal is 100-140 nm, the loading amount of the silicalite nanocrystal is 10 g / m 2 , the specific surface area is 368 m 2 / g, and the surface of the silicalite nanocrystal contains a microporous network with a pore size of 0.55-0.65 nm, and the volume of the micropores accounts for 45% of the total pore volume.

[0068] Comparative Example 1

[0069] The comparative example provides a preparation method of a multi-stage composite microporous membrane electrode, which is prepared according to the method in Example 1, with the difference being that in step (1), the inorganic ceramic microfiltration membrane is not subjected to surface activation and first calcination treatment, no hydroxyl active site is introduced, and step (2) is omitted, and the anode electrocatalytic active layer and the cathode electrocatalytic active layer are directly compounded, and the remaining steps and process parameters remain unchanged, thereby obtaining the multi-stage 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 multistage composite microporous membrane electrode prepared in Examples 1-2 and Comparative Example 1 was explored as follows:

[0077] The pollutant degradation performance of the multistage composite microporous membrane electrode prepared in Examples 1-2 and Comparative Example 1 was explored as follows:

[0078] The multistage composite microporous membrane electrodes prepared in Examples 1-2 and Comparative Example 1 were used for water treatment and purification, and different multistage composite microporous membrane electrodes were placed in an electrofiltration reactor. The influent solution flowed through the multistage composite microporous membrane electrode at a constant filtration flow rate by using a peristaltic pump. A voltage of 3 V was applied, and the system was not aerated. Only the dissolved oxygen in the influent solution and the oxygen produced on the anode side of the multistage composite microporous membrane electrode were used to filter the influent solution.

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

[0080] The removal rate of the pollutant degradation by electrofiltration was calculated according to the formula removal rate = [(influent concentration - effluent concentration) / influent concentration] x 100%. The results are shown in Figure 6 From Figure 6 it can be seen that, compared with Comparative Example 1, the multistage composite microporous membrane electrode prepared in Example 1-2 has a higher pollutant removal rate. Specifically, Example 1 can achieve a removal rate of 96%, while Comparative Example 1 only achieves a removal rate of 74%.

[0081] Further, the stability of the pollutant removal rate of the multistage composite microporous membrane electrode prepared in Example 1 and Comparative Example 1 after long-term continuous operation was explored. The results are shown in Figure 7 From Figure 7 it can be seen that, 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 multistage composite microporous membrane electrode provided by the present application has excellent long-term operation stability.

[0082] In addition, in order to verify the oxygen enrichment ability of the multistage composite microporous membrane electrode, the multistage composite microporous membrane electrodes prepared in Examples 1-2 and Comparative Example 1 were used to filter the influent solution. After 20 min of stable operation, the comparison chart of the dissolved oxygen concentration in the effluent solution is shown in Figure 8 From Figure 8 it can be seen that, after the influent solution was filtered using the multistage composite microporous membrane electrode prepared in Example 1-2, the dissolved oxygen concentration in the effluent solution was higher. Specifically, the dissolved oxygen concentration in the effluent solution corresponding to Example 1 can reach 20 mg / L, indicating that the silicon 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 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.

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 0.55-0.65nm, 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 / m³. 2 ; Preferably, the carbon nanomaterial is a carbon nanotube material doped with metal atoms, and the doping amount of metal atoms is 0.1%-5%. Preferably, the metal atoms include one or more of iron, nickel, cobalt, manganese, platinum, and palladium; Preferably, the pore size of the cathode electrocatalytic active layer is 0.01-0.5 μm.

7. The method for preparing the multi-level composite microporous membrane electrode according to any one of claims 1-6, 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 mass of 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; Preferably, the organic template agent is ethylenediamine and / or hexadecyltrimethylammonium bromide.

8. The preparation method according to claim 7, wherein, The hydrothermal reaction temperature is 80-200℃, and the hydrothermal reaction time is 24-96 hours.

9. The preparation method according to claim 7, wherein, The anodic electrocatalytic active layer is deposited by magnetron sputtering, with the following parameters: sputtering power 100-500W, argon flow rate 50-150sccm, substrate temperature 200-400℃, and sputtering time 0.5-4 hours.

10. The preparation method according to claim 7, 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.

11. A water treatment and purification method, wherein the method employs the multi-stage composite microporous membrane electrode as described in any one of claims 1-6, 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. Preferably, the dissolved oxygen concentration of the influent aqueous solution is 8-9 mg / L; Preferably, the concentration of the pollutant in the influent aqueous solution is 0.1-10 mg / L; Preferably, the filtration flow rate is 1-20 mL / min. -1 The applied voltage is 1.0-3.0V.

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