An integrated electrically excited bubble flow inorganic membrane self-cleaning device and method

Abstract

The present application belongs to the field of membrane separation technology for sewage treatment, and specifically relates to an integrated electrically excited bubble flow inorganic membrane self-cleaning device and method. The inorganic membrane self-cleaning device of the present application includes a multi-layer packaged inorganic membrane element, and the inorganic membrane element is a package structure, including an inorganic membrane sheet, a positive and negative mesh electrode pair, and a macroporous substrate that are tightly attached in sequence; the mesh electrode pair is electrically connected to the positive and negative poles of an external power supply, respectively. The device and method of the present application can not only eliminate the external air pump and the air-water mixing device, streamline the process system, and realize the in-situ controllable occurrence of bubble flow in the membrane element, but also can produce hypochlorous acid (salt) in situ in the membrane element by simply adding cheap salts such as sodium chloride, reducing the dependence on external oxidizing cleaning agents, and realizing efficient in-situ self-cleaning of the inorganic membrane in the membrane element.

Description

Technical Field

[0001] The present application belongs to the field of membrane separation technology for sewage treatment, and specifically relates to an integrated electrically excited bubble flow inorganic membrane self-cleaning device and method. Background Art

[0002] Inorganic membranes (such as alumina ceramic membranes and metal filtration membranes) offer significant advantages over organic membranes in certain specialty separation applications due to their rigid structure, mechanical stability, and physicochemical stability. However, due to the high cost of inorganic membranes, careful maintenance and cleaning are required during application to extend their service life.

[0003] Inorganic membranes generally require frequent backwashing, using high-pressure flushing to remove pore blockages and the filter cake layer on the membrane surface. Among various flushing combinations, combined air-water backwashing is the most effective. This is because the gas adheres to the surface of pollutants, increasing their particle size and the impact force they experience during the flushing process, thereby rapidly removing certain organic molecules. Furthermore, air-water backwashing often has a higher flow rate, resulting in a higher flushing flux than pure water backwashing, and thus higher flushing efficiency.

[0004] However, air-water backwashing requires the pre-arrangement of relatively complex water and gas pipelines and two-phase mixing systems, which increases the complexity of the process. In addition, the air pump has low gas production control accuracy and most bubbles easily escape during the flushing process, which reduces the bubble utilization rate and increases the flushing energy consumption. Developing an in-situ bubble flow generation technology that does not rely on external gas-liquid mixing systems such as air pumps to achieve in-situ efficient cleaning of inorganic membranes is an important approach to solving the above problems. On the other hand, inorganic membranes require regular chemical washing, such as adding citric acid, hypochlorous acid and other chemicals to sterilize and clean microorganisms inside and on the surface of the membrane, and the cost of using chemicals is also relatively high. If the preparation and application of in-situ oxidants can be developed based on the in-situ bubble flow technology, the dependence on external oxidants can be greatly reduced, the economy of the system can be improved, and it is an important direction to break through the bottleneck of high-efficiency and low-cost inorganic membrane cleaning technology. Summary of the Invention

[0005] The present application provides an integrated electrically excited bubble flow inorganic membrane self-cleaning device and method to solve the problems of complex process, poor controllability and high energy consumption in the traditional inorganic membrane air-water backwash process, and at the same time solve the problems of large demand for oxidants and high cost in inorganic membrane chemical washing. The device and method of the present application can not only eliminate the external air pump and air-water mixing device, streamline the process system, and realize the in-situ controllable generation of bubble flow in the membrane element, but also can produce hypochlorous acid (salt) in situ in the membrane element by simply adding cheap salts such as sodium chloride, reducing the dependence on external oxidizing cleaning agents and realizing efficient in-situ self-cleaning of the inorganic membrane in the membrane element.

[0006] The first aspect of the present application provides an integrated electrically excited bubble flow inorganic membrane self-cleaning device, comprising a multi-layer encapsulated inorganic membrane element; the inorganic membrane element comprises an inorganic membrane sheet, a positive and negative mesh electrode pair and a macroporous substrate tightly attached to each other in sequence; the positive and negative mesh electrode pair comprises an anode mesh, a cathode mesh, and an insulating macroporous separator located between the anode mesh and the cathode mesh; the inorganic membrane element is a packaged structure, the surface where the inorganic membrane sheet and the macroporous substrate are located is exposed, and the rest of the parts are closed; the anode mesh and the cathode mesh are electrically connected to the positive and negative poles of an external power supply, respectively.

[0007] Optionally, in the inorganic membrane element, the cathode mesh is closer to the inorganic membrane sheet than the anode mesh.

[0008] Optionally, both the cathode mesh and the anode mesh are titanium meshes with pointed discharge synapses on their surfaces, and the anode mesh is loaded with ruthenium metal oxide.

[0009] Optionally, the cathode mesh and the anode mesh are obtained by the following preparation method: the titanium mesh is subjected to acid leaching, followed by pulse discharge anodization and constant voltage DC electrode reduction, followed by cleaning and drying, and then high temperature roasting and annealing.

[0010] Optionally, the acid leaching treatment is: placing the titanium mesh in a 10-20% by mass hydrochloric acid solution, keeping it at a constant temperature of 50-90° C. for 10-60 minutes, and then adjusting the pH of the solution to 5-6.5 to obtain the acid-leached titanium mesh.

[0011] Optionally, the pulse discharge anodic oxidation and constant voltage DC electrode reduction method includes:

[0012] Pulse discharge anodization: Use the acid-leached titanium mesh as the anode and another titanium sheet as the cathode. Set the electrode spacing to 0.3-10 cm, the voltage to 10-220 V, the DC pulse frequency to 10-100 Hz, and use a mixed solution of 0.3-1.2 mol / L sulfuric acid, 0.02-0.1 mol / L ammonium fluoride, and 0.2-1 mol / L perchloric acid as the electrolyte. Perform pulse anodization on the titanium mesh for 1-18 hours.

[0013] Constant voltage DC electrode reduction: Reverse the positive and negative poles, set the voltage to 50-200V, turn off the pulse, and continue the reaction under DC constant voltage for 1-10 hours.

[0014] Optionally, for the preparation of the anode mesh, after the cleaning and drying steps, the cleaned and dried anode mesh is placed in a ruthenium precursor solution for immersion and drying, and the immersion and drying steps are repeated 2-5 times, followed by high-temperature calcination and annealing to obtain an anode mesh loaded with ruthenium metal oxide.

[0015] Optionally, the ruthenium-containing precursor solution is a 10-30 g / L ruthenium chloride solution, and each impregnation and drying step is: impregnation for 10-60 minutes, and then standing and drying in an 80°C oven after taking out; the high-temperature calcination treatment is: placing in a 400-800°C oven for 0.5-3 hours.

[0016] The second aspect of the present application provides a method for sewage treatment using the above-mentioned inorganic membrane self-cleaning device, comprising: placing the inorganic membrane self-cleaning device in a sewage reactor, and connecting it to a pump system for water intake and backwashing, and a dosing system for adding chemicals, so that the sewage passes through the inorganic membrane, the positive and negative mesh electrode pairs, and the macroporous substrate in sequence and is filtered and purified.

[0017] The third aspect of the present application provides a method for membrane self-cleaning using the above-mentioned inorganic membrane self-cleaning device, comprising: when backwashing the inorganic membrane element, applying a 10-30V DC voltage to the positive and negative mesh electrode pairs through an external power supply, so that electrolysis inside the inorganic membrane element excites a large number of bubbles and impacts the inorganic membrane with the water flow.

[0018] Optionally, when backwashing the inorganic membrane, a salt solution containing chloride ions is added to the flushing water to electrolyze the inorganic membrane element to generate hypochlorous acid, which is then cleaned by the water flow.

[0019] Compared with the prior art, the integrated electrically excited bubble flow inorganic membrane self-cleaning device and method of the present application has the following beneficial effects:

[0020] The multi-layer encapsulated inorganic membrane element proposed in this application integrates the diaphragm, electrode pair, and macroporous substrate into a single unit, offering high integration, ease of use, and simple disassembly, making it easy to disassemble for cleaning and component replacement. During backwashing, energizing the electrodes within the membrane element converts pure water flushing into bubble flow backwashing, enhancing flushing kinetic energy and improving membrane cleaning efficiency. This device does not require an external air pump or oxidation, and is characterized by high integration and simple operation.

[0021] Furthermore, the mesh electrode fabrication method of this application differs from conventional methods by employing pulsed discharge anodic oxidation and constant voltage DC conductive reduction. This method, without the need for a stenciling process, can in situ generate a certain number of synaptic structures on the titanium mesh surface while maintaining the conductivity of the titanium surface. The generated synaptic structures are susceptible to rapid hydrolysis by tip discharge, and their conductivity helps reduce the material's surface impedance, improve current efficiency, and facilitate the electrolysis of a large number of bubbles.

[0022] In addition, the anode mesh of the present application is also loaded with ruthenium metal oxide. When the membrane element needs to be sterilized by drug washing, a certain concentration of chloride ion solution is added to the backwash water. After passing through the electrode area of ​​the membrane element, the chloride ions are converted into hypochlorous acid in the anode mesh, which has an oxidative sterilization function. The bubble flow is combined to form a bubble cleaning liquid to clean the microorganisms / organic pollution inside and on the surface of the membrane without relying on an external air pump and an oxidizing cleaning agent. In particular, when a solution containing chloride salts is used as backwash water, a small amount or no chloride solution can be added, and the chloride ions in the flushing water can be directly used to generate hypochlorite in situ in the membrane element. The bubble generation rate and the concentration of hypochlorous acid can be achieved by simply adjusting the current / voltage time. The operation of the entire inorganic membrane air-water backwash process is simple and the process is controllable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 This is a schematic diagram of the internal disassembled structure of the membrane element of an embodiment of the present application;

[0025] Figure 2 This is a schematic diagram of the membrane element packaging structure of an embodiment of the present application;

[0026] Figure 3 This is a schematic diagram of the membrane filtration operation state of the inorganic membrane self-cleaning device according to an embodiment of the present application;

[0027] Figure 4 This is a schematic diagram of the backwashing operation state of the inorganic membrane self-cleaning device according to an embodiment of the present application;

[0028] Figure 5 This is a schematic diagram of the dosing and backwashing operation state of the inorganic membrane self-cleaning device according to an embodiment of the present application;

[0029] Figure 6 This is a scanning electron microscope image of an electrode mesh having a tip synaptic structure in an inorganic membrane self-cleaning device according to an embodiment of the present application;

[0030] Figure 7 This is a comparison chart of the membrane flux of the inorganic membrane self-cleaning device of the comparative example of this application under different backwash conditions.

[0031] In the figure, 10-external power supply, 11-pump system, 12-dosing system, 2-inorganic membrane element, 201-exposed surface, 202-packaging shell, 21-inorganic membrane, 22-positive and negative mesh electrode pairs, 221-anode mesh, 222-insulating macroporous separator, 223-cathode mesh, 23-macroporous substrate. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is described in detail below with reference to the accompanying drawings and embodiments.

[0033] The present application provides an integrated electrically excited bubble flow inorganic membrane self-cleaning device, comprising a multi-layer encapsulated inorganic membrane element; the inorganic membrane element comprises an inorganic membrane sheet, a positive and negative mesh electrode pair, and a macroporous substrate that are tightly attached to each other in sequence; the positive and negative mesh electrode pair comprises an anode mesh, a cathode mesh, and an insulating macroporous separator located between the anode mesh and the cathode mesh; the inorganic membrane element is a packaged structure, the surface where the inorganic membrane sheet and the macroporous substrate are located is exposed, and the rest of the parts are closed; the anode mesh and the cathode mesh are electrically connected to the positive and negative poles of an external power supply, respectively.

[0034] Specifically, if Figures 1 to 5 As shown, the inorganic membrane self-cleaning device of this embodiment includes a multi-layer encapsulated inorganic membrane element 2, which is also connected to an external power supply 10, a pump system 11 for water intake and backwashing, and a dosing system 12 for adding reagents. The multi-layer encapsulated inorganic membrane element 2 comprises an inorganic membrane sheet 21, a positive and negative mesh electrode pair 22 (insulated and separated), and a macroporous substrate 23. These units are sequentially pressed together and then encapsulated to form the anode and cathode of the membrane element. After encapsulation, extended wires are provided for connection to the external power supply 10.

[0035] The cathode and anode meshes can be made of titanium mesh, serving as the anode and cathode. During conventional pure water backwashing, they electrolyze water to generate a bubble flow, transforming the pure water backwash into a bubble flow backwash within the membrane element, significantly enhancing flushing efficiency. The insulating macroporous separator, or insulating macroporous permeable barrier, can be made of plastic, polytetrafluoroethylene, or silicone, with a pore size of ≥5mm at its narrowest point and a thickness of 0.2mm-5mm. The macroporous substrate can be made of insulating plastic, polytetrafluoroethylene, or silicone, with a pore size of ≥1cm at its narrowest point and a thickness of 1mm-5mm.

[0036] The packaging of inorganic membrane elements can be done by Figure 1 and Figure 2The parallel sheet structure shown in the figure can also be packaged with a tubular sleeve structure. The specific assembly method is as follows: the inorganic diaphragm 21, the cathode mesh 223, the insulating macroporous separator 222, the anode mesh 221, and the macroporous substrate 23 are tightly compacted in sequence, and sealed to form a membrane element. During the packaging process, conductive materials such as wires are used to connect to the anode mesh and cathode mesh inside the membrane element from the outside, and the conductive materials are connected to the corresponding positive and negative electrodes of the external power supply from the outside. When the tubular sleeve structure is used for packaging, the tube can be an inorganic diaphragm, a positive and negative mesh electrode pair, and a macroporous substrate from the outside to the inside. The curved surface where the inorganic diaphragm and the macroporous substrate are located is an exposed surface, which is used for inlet and outlet water when filtering sewage. The remaining surfaces, such as the top and bottom surfaces of the sleeve, are closed. Using a method such as Figure 2 In the flat sheet packaging method shown, the exposed surface 201 is the direct contact surface for water inlet and outlet, that is, the water inlet direction and the water outlet direction are perpendicular to the surface where the inorganic membrane is located, and the packaging shell 202 surrounds the remaining four sides of the component except the two exposed surfaces to form a packaging structure.

[0037] Preferably, in the inorganic membrane element, the cathode mesh is closer to the inorganic membrane than the anode mesh.

[0038] Specifically, if Figure 4 As shown, the cathode is on the left and the anode is on the right. The cathode mesh is closer to the inorganic membrane. During backwashing, due to the electrolysis reaction of water, the amount of hydrogen produced on the cathode mesh is greater than the amount of oxygen produced by the anode. Relatively speaking, the number of bubbles generated is also greater. The cathode is closer to the inorganic membrane, and the large number of bubbles generated can be used to backwash the inorganic membrane more quickly and without loss along with the water flow. In addition, Figure 5 As shown, the anode mesh is closer to the backwash water inlet direction. When backwashing and cleaning, the reagent reaches the anode mesh first with the backwash water, which makes it easier for the reagent to produce hypochlorous acid on the anode mesh more quickly and efficiently, and avoids the reagent being dispersed by the water flow without reacting on the anode.

[0039] Preferably, the cathode mesh and the anode mesh are both titanium meshes with sharp discharge synapses on their surfaces, and the anode mesh is loaded with ruthenium metal oxide.

[0040] Specifically, the cathode mesh and anode mesh of the embodiment of the present application use titanium mesh with a tip discharge synapse on the surface. The tip synapse structure is easy to be rapidly hydrolyzed by tip discharge and can be obtained by material science related etching process, template method and other process processing. As an advantage, the cathode mesh and anode mesh preparation method of the present application can be used to form a titanium mesh surface. Figure 6The tip synaptic structure shown in the scanning electron microscope image. Among them, the anode mesh also carries ruthenium metal oxide. In this embodiment, the ruthenium metal oxide is ruthenium oxide. In the cleaning process of the membrane, drug cleaning is an important link. By adding cleaning agents such as hypochlorous acid to the rinse water, the microorganisms on the surface of the membrane and in the pores are sterilized and removed. At the same time, the chemical oxidizing property of hypochlorous acid can also produce a certain destructive decomposition effect on organic pollutants. Therefore, the addition of hypochlorous acid (or hypochlorite) is the key to the drug cleaning of the membrane. The anode mesh embedded in the membrane element of the device of the present application is loaded with ruthenium element to form a ruthenium oxide active layer. Compared with other metal aluminum oxides, ruthenium oxide has an active component with the ability to efficiently convert chlorine into hypochlorous acid, which can achieve a good membrane cleaning effect.

[0041] The present application also provides a method for preparing the cathode mesh and the anode mesh in an inorganic membrane self-cleaning device, which mainly includes acid leaching the titanium mesh, then sequentially performing pulse discharge anodizing and constant voltage DC electrode reduction, and then cleaning and drying.

[0042] Preferably, the cleaned and dried anode mesh is immersed in a ruthenium precursor solution, dried, and the immersion and drying steps are repeated 2-5 times, followed by calcination and annealing to obtain an anode mesh loaded with ruthenium metal oxide.

[0043] The ruthenium metal oxide-loaded anode mesh, i.e., an anode mesh containing ruthenium, is based on a titanium mesh. Electrochemical pulse etching is performed on the mesh to create an uneven, concave and convex surface. The mesh is then impregnated with a ruthenium precursor solution, dried, calcined, and annealed to form an anode mesh loaded with ruthenium oxide and having discharge synapses on its surface. The cathode mesh, excluding the impregnation step, is prepared in the same manner as the anode mesh.

[0044] Specifically, the preparation process of the anode mesh includes the following steps:

[0045] Step 101: Select a titanium mesh of a certain mesh size (4-40 mesh) and pre-treat the surface of the titanium mesh by degreasing and washing. After pre-treatment, place the titanium mesh in a 10-20% hydrochloric acid solution at a constant temperature of 50-90°C for 10-60 minutes. After the solution is finished, adjust the pH of the solution to 5-6.5 and set aside. This step promotes the formation of a concave-convex structure on the mesh surface.

[0046] Step 102: Remove the titanium mesh obtained in step 101, rinse it with pure water, and dry it. Use it as the anode. Use another titanium sheet as the cathode. Pulse anodization is performed on the titanium mesh anode using a mixture of 0.3-1.2 mol / L sulfuric acid, 0.02-0.1 mol / L ammonium fluoride, and 0.2-1 mol / L perchloric acid as the electrolyte at a distance of 0.3-10 cm, a voltage of 10-220 V, and a DC pulse frequency of 10-100 Hz for 1-18 hours. This step improves the surface roughness of the mesh and forms discharge synapses.

[0047] Step 103: Reverse the positive and negative electrodes, apply a voltage of 50-200 V, turn off the pulse, and continue the reaction under a DC constant voltage for 1-10 hours. This treatment is used to remove some oxygen atoms from the titanium dioxide lattice and improve the conductivity of the titanium mesh surface.

[0048] Step 104: After the reaction in step 3 is completed, the titanium mesh anode is taken out, cleaned, and dried in an oven at 35-95° C. for 2-24 hours.

[0049] Step 105: Place the dried titanium mesh anode in a solution of ruthenium chloride (10-30 g / L) at a certain concentration for 10-60 minutes, remove it, and dry it in an oven at 80°C. Repeat this step 2-5 times.

[0050] Step 106: Place the titanium mesh after final drying in an oven at 400-800° C. for 0.5-3 hours and anneal. After annealing, a finished anode mesh loaded with ruthenium metal oxide is obtained.

[0051] The specific preparation process and method of the cathode mesh adopts the above steps 101, 102, 103, 104, and 106, but does not perform step 105.

[0052] This embodiment also provides a method for sewage treatment using the above-mentioned inorganic membrane self-cleaning device, wherein the inorganic membrane self-cleaning device is placed in a sewage reactor and connected to a pump system for water intake and backwashing, as well as a dosing system for adding chemicals, so that the sewage is filtered and purified by passing through the inorganic membrane, the positive and negative mesh electrode pairs, and the macroporous substrate in sequence.

[0053] This embodiment also provides a method for self-cleaning an inorganic membrane using the above-mentioned inorganic membrane self-cleaning device. When backwashing the inorganic membrane element, a 10-30V DC voltage is applied to the positive and negative mesh electrode pairs through the electrode power supply system, so that electrolysis inside the inorganic membrane element excites a large number of bubbles and impacts the inorganic membrane with the water flow.

[0054] Preferably, when backwashing the inorganic membrane element, a salt solution containing chloride ions is added to the flushing water to electrolyze the inorganic membrane element to generate hypochlorous acid, which is then used to clean the inorganic membrane along with the water flow.

[0055] Specifically, the anode mesh of the inorganic membrane self-cleaning device of this embodiment is loaded with ruthenium, forming an active ruthenium oxide layer. When powered, it can rapidly convert chloride ions in water into hypochlorite. Therefore, during the membrane element cleaning process, there's no need to add expensive hypochlorous acid. Instead, a solution such as inexpensive and readily available sodium chloride is added, which converts chloride ions into hypochlorite on the anode surface, forming a hypochlorous acid cleaning solution.

[0056] From the above sewage treatment method and membrane self-cleaning method, it can be seen that the device can be divided into three states during operation, including:

[0057] Operation state a - membrane filtration process. Figure 3 Figure 2 shows a schematic diagram of a conventional inorganic membrane filtration process using the inorganic membrane self-cleaning device of this embodiment, used to purify wastewater. The sewage is subjected to a transmembrane pressure differential applied by a pump on the side closest to the inorganic membrane. This pressure forces the water through the inorganic membrane, the positive and negative mesh electrode pairs, and the macroporous substrate before exiting. Larger molecular contaminants, such as organic matter and microorganisms, are trapped on the membrane surface or within the pores, purifying the sewage while also fouling the inorganic membrane.

[0058] Operation status b - backwash process. Figure 4 As shown, it is a schematic diagram of the process of backwashing the membrane using the inorganic membrane self-cleaning device of an embodiment of the present application; during backwashing, a DC voltage (10-30V) is applied to cause the mesh electrode to generate a large amount of charge accumulation at the synaptic point, thereby generating a rapid discharge dissociation reaction on the water molecules, stimulating a large number of bubbles inside the membrane element, and quickly converting the pure water backwash into bubble flow backwash, greatly enhancing the flushing efficiency.

[0059] Operation state c - dosing backwash process. Figure 5 As shown, based on operating state b, a salt solution containing chloride ions (such as sodium chloride solution, concentration 0.3-0.5%) is added to the backwash water inlet. The flushing water passes through the electrode reaction zone inside the membrane element. The chloride ions are excited by the anode to become hypochlorite, which has an oxidizing and sterilizing effect. Combined with the bubble flow, a high-efficiency cleaning solution is formed, realizing an ultra-high-efficiency inorganic membrane backwash process.

[0060] In summary, the integrated electrically excited bubble flow inorganic membrane self-cleaning device designed by the present invention does not work during normal filtration, and is a conventional membrane filtration system. The sewage passes through the inorganic membrane, the positive and negative mesh electrode pairs, and the macroporous substrate in sequence before being discharged. During backwashing, an external voltage is applied to cause the mesh electrode to generate a large amount of charge accumulation at the synaptic point, thereby generating a rapid discharge dissociation reaction on the water molecules. Inside the membrane element, the pure water backwash is instantly converted into a bubble flow backwash, greatly enhancing the flushing efficiency. At the same time, this device can produce hypochlorous acid in situ in the membrane element by using a ruthenium-containing anode with the assistance of an external chlorine-containing solution such as sodium chloride, and combine it with the bubble flow to form an efficient cleaning solution, thereby realizing an ultra-high-efficiency inorganic membrane backwashing process. In the inorganic membrane self-cleaning device of the present invention, both the bubble flow and hypochlorous acid can be produced in situ, and it has the characteristics of high integration, simple operation mode, and no need for external aeration and oxidant addition.

[0061] Example 1

[0062] Preparation of anode mesh:

[0063] Step 1: Select a 10-mesh titanium mesh and pre-treat its surface by degreasing and washing. After pre-treatment, place the titanium mesh in a 16% hydrochloric acid solution and keep it at a constant temperature of 75°C for 30 minutes. After that, adjust the pH of the solution to 5.5 and set aside.

[0064] Step 2: Take out the titanium mesh in step 1, rinse it with pure water, dry it, and use it as the anode. Take another titanium sheet as the cathode. The electrode spacing is 2 cm, the voltage is 60 V, the DC pulse frequency is 40 Hz, and a mixed solution of sulfuric acid (0.5 mol / L), ammonium fluoride (concentration 0.05 mol / L), and perchloric acid (0.6 mol / L) is used as the electrolyte. Pulse anodization is performed on the titanium mesh anode for 8 hours. This step promotes the improvement of the surface roughness of the mesh and forms a discharge synapse at the same time.

[0065] Step 3: Reverse the positive and negative poles, set the voltage to 50V, turn off the pulse, and continue the reaction for 3 hours under DC constant voltage. This step is used to remove some oxygen atoms in the titanium dioxide lattice and improve the conductivity of the titanium mesh surface.

[0066] Step 4: Take out the titanium mesh anode after the reaction in step 3, clean it, and dry it in a 60℃ oven for 6 hours.

[0067] Step 5: Place the dried titanium mesh anode in a solution of ruthenium chloride (15 g / L) at a certain concentration for 20 minutes. Remove the anode and place it in an oven at 80°C to dry. Repeat this step three times.

[0068] Step 6: Place the finally dried titanium mesh in a 500°C oven and bake for 1.5 hours. After annealing, the finished anode mesh is obtained.

[0069] The cathode mesh is prepared according to steps 1, 2, 3, 4 and 6.

[0070] like Figure 6 As shown in FIG, a scanning electron microscope image of an electrode mesh with a sharp synaptic structure prepared according to the method of this embodiment is obtained. It can be seen from the image that the surface of the electrode mesh has an obvious sharp synaptic structure, which can produce an efficient discharge dissociation effect.

[0071] Example 2

[0072] Bubble flow backwash: During backwash, start operating state b.

[0073] Turn on the power supply and apply a DC voltage of 15V to convert the pure water flushing into bubble flow flushing.

[0074] After 30 minutes of flushing, turn off the power supply and the backwash pump in sequence, switch to operating state a, and continue the membrane filtration process.

[0075] Example 3

[0076] Dosing backwash: During backwash, start operation state c.

[0077] Sodium chloride solution (concentration 0.3%) is continuously added to the backwash water inlet, with the ratio of sodium chloride solution volume to backwash water volume = 1:5. Turn on the power supply and apply a DC voltage of 12V to convert the pure water flushing into hypochlorite bubble cleaning solution flushing.

[0078] After 30 minutes of flushing, stop adding sodium chloride solution and continue flushing with pure water bubble flow for 15 minutes. After the end, turn off the power supply and backwash pump in sequence. Switch to operating state a and continue the membrane filtration process.

[0079] Comparative Example 1

[0080] Condition 1: The inorganic membrane self-cleaning device prepared by the method of Example 1 was operated continuously for 10 hours under operating state a. Operating parameters: The inorganic membrane material is alumina ceramic membrane, the membrane pore size is 0.1 μm, and the pure water membrane flux is 160 L / (m 2 h), the primary pollutants in the wastewater were dissolved humus (1 g / L) and bacteria (turbidity 100). After 10 h of operation, the membrane flux decayed to about 17% of the pure water flux.

[0081] Condition 2: After condition 1 is completed, exit the running state a and start the backwash pump with a backwash flow rate of 160L / (m 2 h), the external power supply of the electrode remained off, and after flushing for 15 minutes, the backwash pump was turned off. The inorganic membrane flux at this time was measured to be 58% of the pure water flux.

[0082] Condition 3: After condition 1 is completed, exit operation state a and switch to operation state b, with a backwash flow rate of 160L / (m 2 h), turn on the power supply, control the output voltage to 20V, flush for 15 minutes, and then exit operation state b. The inorganic membrane flux at this time is measured to be 83% of the pure water flux.

[0083] Condition 4: After condition 1 is completed, exit operation state a and switch to operation state c, with a backwash flow rate of 160L / (m 2 ·h), continuously add sodium chloride solution (concentration 0.5%) at the inlet end of backwash water, the amount of sodium chloride solution is 32L / (m 2 h). Turn on the power supply, control the output voltage to 20V, flush for 15 minutes, and then exit operation state b. The inorganic membrane flux at this time is measured to be 89% of the pure water flux.

[0084] Comparative Example 2

[0085] Condition 1: The inorganic membrane self-cleaning device was operated continuously for 10 hours in operating state a. Operating parameters: The inorganic membrane material was alumina ceramic membrane, the membrane pore size was 0.1 μm, and the pure water membrane flux was 160 L / (m 2 h), the primary pollutants in the wastewater were dissolved humus (1 g / L) and bacteria (turbidity 100). After 10 h of operation, the membrane flux decayed to about 17% of the pure water flux.

[0086] Condition 2: After condition 1 is completed, exit operation state a and switch to operation state c. The cathode and anode screens use ordinary titanium screens (10 mesh) available on the market. Backwash flow rate is 160L / (m 2 ·h), continuously add sodium chloride solution (concentration 0.5%) at the backwash water inlet end, the amount of sodium chloride solution is 32L / (m 2 h). Turn on the power supply, control the output voltage to 20V, flush for 15 minutes, and then exit operation state c. The inorganic membrane flux at this time is measured to be 64% of the pure water flux.

[0087] Condition 3: After condition 1 is completed, exit operation state a and switch to operation state c. The anode and cathode meshes use titanium mesh with sharp synapses (obtained according to the preparation method of this application, without ruthenium loading, 10 mesh). Backwash flow rate 160L / (m 2 ·h), continuously add sodium chloride solution (concentration 0.5%) at the inlet end of backwash water, the amount of sodium chloride solution is 32L / (m 2 h). Turn on the power supply, control the output voltage to 20V, flush for 15 minutes, and then exit operation state c. The inorganic membrane flux at this time is measured and is 70% of the pure water flux.

[0088] Condition 4: After condition 1 is completed, exit operation state a and switch to operation state c. The anode is a titanium mesh with a pointed synapse loaded with ruthenium (obtained according to the preparation method of this application, 10 mesh), and the cathode is a titanium mesh with a pointed synapse (10 mesh). Backwash flow rate 160L / (m 2 ·h), continuously add sodium chloride solution (concentration 0.5%) at the inlet end of backwash water, the amount of sodium chloride solution is 32L / (m 2 h). Turn on the power supply, control the output voltage to 20V, flush for 15 minutes, and then exit operation state c. The inorganic membrane flux at this time is measured and is 90% of the pure water flux.

[0089] For the convenience of comparison and explanation, the operating parameters under various experimental conditions in Comparative Examples 1 and 2, and the corresponding membrane cleaning effects are summarized as follows:

[0090]

[0091] As can be seen from the table, the inorganic membrane self-cleaning device of the embodiment of the present application adopted in each condition of Comparative Example 1 has pointed synapses in both the anode and cathode nets. In addition, the anode net is also loaded with ruthenium metal oxide, and the anode and cathode nets are obtained by processing using the preparation method of the present application. Condition 1 of Comparative Example 1 corresponds to the state of the sewage treatment membrane during filtration. After completion, the membrane flux is 17% of the pure water flux. It can be seen that after the sewage is subjected to membrane filtration treatment, membrane contamination is generated on the membrane while purifying the sewage, and the inorganic membrane needs to be cleaned. Conditions 2-4 of Comparative Example 1 correspond to traditional water flow backwashing, the electrically excited bubble flow backwashing of the present application, and the bubble flow dosing backwashing, respectively. Figure 7 As shown, the cleaning effects on the inorganic membrane under the above three conditions are different, and conditions 3 and 4 achieve better membrane cleaning effects than condition 2. It can be seen that the inorganic membrane self-cleaning device and membrane self-cleaning method of the present application can achieve good membrane self-cleaning effects.

[0092] Under each condition in Comparative Example 2, the materials of the electrode mesh used in the device are different. Condition 1 of Comparative Example 2, also known as Condition 1 of Comparative Example 1, is the membrane filtration state when the inorganic membrane self-cleaning device of the present application is used to treat sewage; Conditions 2-4 of Comparative Example 2 correspond to different materials of electrode meshes, including conventional electrode meshes (commercially available titanium mesh), titanium meshes with pointed synapses (cathode), titanium meshes with pointed synapses and loaded with ruthenium elements (anode) and titanium meshes with pointed synapses (cathode). Electrode meshes of different materials are used in the inorganic membrane self-cleaning device of the present application, and the cleaning effects on the inorganic membrane are also different. For the titanium mesh electrodes of Conditions 3 and 4, the electrode mesh preparation method of the present application is used to obtain the pointed synapse structure and the loaded ruthenium element, and electrolysis is carried out during backwashing to stimulate bubble flow and hypochlorous acid, thereby realizing inorganic membrane self-cleaning. By comparison, it can be seen that the membrane flux of Conditions 3 and 4 is significantly improved compared to the commercially available ordinary titanium mesh of Condition 2. It can be seen that the cleaning of the membrane using the device and method of the present application has achieved better results.

[0093] The present application has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present application. Those skilled in the art will appreciate that, without departing from the spirit and scope of the present application, various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present application, all of which fall within the scope of the present application. The scope of protection of the present application shall be determined by the appended claims.

Claims

1. An integrated electrically excited bubble flow inorganic membrane self-cleaning device, characterized in that: The invention comprises a multi-layer encapsulated inorganic membrane element; the inorganic membrane element comprises an inorganic membrane sheet, a positive and negative mesh electrode pair, and a macroporous substrate, which are tightly attached in the direction of sewage inflow; the positive and negative mesh electrode pair comprises an anode mesh, a cathode mesh, and an insulating macroporous separator located between the anode mesh and the cathode mesh; the inorganic membrane element has an encapsulated structure, with the inorganic membrane sheet and the macroporous substrate surface exposed and the remaining portion sealed; the anode mesh and the cathode mesh are electrically connected to the positive and negative electrodes of an external power supply, respectively; in the inorganic membrane element, the cathode mesh is closer to the inorganic membrane sheet than the anode mesh; both the cathode mesh and the anode mesh are titanium meshes with sharp discharge synapses on their surfaces, and the anode mesh is loaded with ruthenium metal oxide; The inorganic membrane element is connected to a pump system for water inlet and backwashing, and a dosing system for adding a chemical; the chemical is a salt solution containing chloride ions.

2. The inorganic membrane self-cleaning device according to claim 1, characterized in that: The cathode mesh and the anode mesh are both obtained according to the following preparation method: The titanium mesh is acid-leached, and then pulse discharge anodizing and constant voltage DC electrode reduction are performed in sequence, followed by cleaning and drying, and then high-temperature roasting and annealing.

3. The inorganic membrane self-cleaning device according to claim 2, characterized in that: The acid leaching treatment comprises placing the titanium mesh in a hydrochloric acid solution with a mass fraction of 10-20%, keeping the solution at a constant temperature of 50-90° C. for 10-60 minutes, and then adjusting the pH of the solution to 5-6.5 to obtain the acid-leached titanium mesh.

4. The inorganic membrane self-cleaning device according to claim 2, characterized in that: The pulse discharge anodic oxidation and constant voltage DC electrode reduction method comprises: Pulse discharge anodization: Use the acid-leached titanium mesh as the anode and another titanium sheet as the cathode. Set the electrode spacing to 0.3-10 cm, the voltage to 10-220 V, the DC pulse frequency to 10-100 Hz, and use a mixed solution of 0.3-1.2 mol / L sulfuric acid, 0.02-0.1 mol / L ammonium fluoride, and 0.2-1 mol / L perchloric acid as the electrolyte. Perform pulse anodization on the titanium mesh for 1-18 hours. Constant voltage DC electrode reduction: Reverse the positive and negative poles, set the voltage to 50-200V, turn off the pulse, and continue the reaction under DC constant voltage for 1-10 hours.

5. The inorganic membrane self-cleaning device according to claim 2, characterized in that: For the preparation of the anode mesh, after the cleaning and drying steps, the cleaned and dried anode mesh is placed in a ruthenium precursor solution for immersion and drying, and the immersion and drying steps are repeated 2-5 times. It is then subjected to high-temperature calcination and annealing to obtain an anode mesh loaded with ruthenium metal oxide.

6. The inorganic membrane self-cleaning device according to claim 5, characterized in that: The ruthenium-containing precursor solution is a 10-30 g / L ruthenium chloride solution. The dipping and drying steps are as follows: dipping for 10-60 minutes, then drying in an oven at 80°C. The high temperature calcination treatment is: placing in a 400-800° C. oven and calcining for 0.5-3 hours.

7. A method for treating sewage using the inorganic membrane self-cleaning device according to any one of claims 1 to 6, characterized in that: The inorganic membrane self-cleaning device is placed in the sewage reactor and connected to a pump system for water inlet and backwashing, as well as a dosing system for adding chemicals, so that the sewage is filtered and purified by passing through the inorganic membrane, positive and negative mesh electrode pairs, and macroporous substrate in sequence.

8. A method for membrane self-cleaning using the inorganic membrane self-cleaning device according to any one of claims 1 to 6, characterized in that: When backwashing the inorganic membrane element, a 10-30V DC voltage is applied to the positive and negative mesh electrode pairs through an external power supply, so that electrolysis inside the inorganic membrane element stimulates a large number of bubbles and impacts the inorganic membrane with the water flow.

9. The method for membrane self-cleaning according to claim 8, characterized in that: Adding salt solution containing chloride ions into the flushing water causes electrolysis inside the inorganic membrane element to produce hypochlorous acid which then flows with the water to clean the inorganic membrane.

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