Anti-pollution self-cleaning intelligent filter screen membrane and application

Abstract

The invention provides an anti-pollution self-cleaning intelligent filter screen membrane and application, and relates to the technical field of copper screen filter membranes. According to the anti-pollution self-cleaning intelligent filter screen membrane, a copper mesh is subjected to laser etching and then subjected to two-step electrodeposition in a copper sulfate electrolyte to obtain the super-hydrophobic intelligent filter screen membrane, the copper mesh membrane is converted to be super-hydrophilic through external voltage, the membrane is endowed with high anti-pollution capacity, and the membrane is used for efficiently removing algae when a water body is eutrophicated; when the membrane is seriously polluted, the membrane is converted into a super-hydrophobic state through heating, has a self-cleaning function and is used for cleaning and maintaining the membrane; reversible conversion of super-hydrophobicity and super-hydrophilicity of the copper net film can be achieved based on electric / thermal response.

Description

Technical Field

[0001] The present application belongs to the field of filter membrane technology, and in particular relates to an anti-pollution and self-cleaning intelligent filter membrane and its application. Background Art

[0002] In recent years, the problem of eutrophication has become increasingly serious. Annual algae outbreaks in various watersheds pose a severe challenge to traditional water treatment processes. Microalgae not only impact coagulation, sedimentation, and filtration processes but also increase water treatment costs: algae interfere with coagulation and increase chemical dosage. Operational efficiency decreases: algae clogs filter media, shortening filter cycle times. Structural corrosion increases: algae metabolites accelerate equipment aging. Water quality risks increase: organic matter released by algae forms disinfection byproducts, threatening drinking water safety.

[0003] Traditional algae removal technologies, such as flotation, are highly effective but costly, requiring integration with other processes when algae concentrations are high. Chemical algaecide methods rapidly kill algae but are prone to producing harmful byproducts (such as trihalomethanes) and potentially releasing algal toxins, which can cause secondary pollution. Activated carbon adsorption effectively absorbs algal toxins and can reduce water odors. However, activated carbon easily saturates, requiring frequent replacement or regeneration, increasing operating costs and posing a risk of secondary pollution. These traditional algae removal methods all have limitations in terms of efficiency, cost, and environmental friendliness. Microporous filter membranes rely on physical size screening, offering a high retention rate for algae without causing secondary pollution. However, microporous filters present challenges such as easy contamination and difficulty in cleaning during use, which require urgent attention.

[0004] Learning from nature and imitating certain aspects of biological functions is a "shortcut" to achieve functional design of materials. Cells use cell membranes to achieve specific substance transfer and anti-fouling functions. Despite the presence of proteins, carbohydrates, inorganic salts and metabolic products in the surrounding environment, the cell membrane can still prevent the uncontrollable adhesion of exogenous substances and maintain its own cleaning function. This is due to its super-hydrophilic high repulsive surface energy to resist pollution. On the other hand, the self-cleaning ability of lotus leaves comes from its super-hydrophobic low surface energy waxy layer. Water droplets on this type of surface are spherical and easy to roll, thereby carrying away pollutants such as sludge and dust. Therefore, if a microporous filter membrane with a "super-hydrophilic / super-hydrophobic" reversible switching function can be designed, it is expected to achieve both anti-fouling and membrane cleaning and self-cleaning functions in the process of membrane filtration of microalgae.

[0005] Some materials can change their surface profile or chemical composition in response to environmental stimuli such as pH, light, electricity, and heat, reversibly switching their wettability from "friendly to sparing" (i.e., wettability). These materials are known as smart responsive materials. Copper-based materials are widely used in sterilization and water purification due to their low cost, electrical conductivity, and catalytic properties.

[0006] The prior art discloses a method for constructing a biomimetic super-hydrophobic film on the surface of a copper substrate by electrolyzing organic matter. The method comprises the following steps: a copper foil is used as a cathode, a Pt sheet electrode is used as an anode, and an aqueous solution containing an organic carbon source, a conductive salt, and metal nanoparticles is used as an electrolyte. Electrolysis is performed using a constant voltage electrolysis method until a silver-carbon composite film is collected at the cathode. The treated copper foil is immersed in a n-hexane mixture of stearic acid and dicyclohexylcarbodiimide for 10-30 hours, and then rinsed with n-hexane to form a super-hydrophobic copper foil. Only a super-hydrophobic material is obtained, but no consideration is given to achieving super-hydrophilic conversion.

[0007] Therefore, the development of a filter membrane based on copper-based materials that can achieve intelligent reversible conversion of superhydrophilicity / superhydrophobicity has important research significance and application value. Summary of the Invention

[0008] In order to solve the problem that the filter membrane is easy to be polluted and difficult to clean during the algae removal process, the primary purpose of the present invention is to provide an anti-pollution and self-cleaning intelligent filter membrane. Micro-nano rough structures are created through laser etching and electrochemical deposition, and super-hydrophilic / super-hydrophobic intelligent reversible conversion is achieved based on electrical / thermal means, so that the filter membrane has both anti-pollution and self-cleaning functions, and is applied to the field of algae removal.

[0009] Another object of the present invention is to provide a method for reversible conversion of the above-mentioned anti-pollution and self-cleaning smart filter membrane from "super-hydrophilic to super-hydrophobic".

[0010] Another object of the present invention is to provide an application of the above-mentioned anti-pollution and self-cleaning intelligent filter membrane in the algae removal process.

[0011] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: The present invention provides an anti-pollution and self-cleaning intelligent filter membrane, which is prepared by the following method: S1. After pretreatment, the copper mesh is laser etched to form a grooved surface texture. S2. Two-step electrodeposition of copper mesh in copper sulfate electrolyte: The voltage of the first electrodeposition was 20–30 V; The second electrodeposition voltage is 3~5 V; The concentration of the copper sulfate electrolyte is 0.04~0.06M; S3. After heating and drying, a pollution-resistant and self-cleaning smart filter membrane is obtained, with a water contact angle greater than 150°.

[0012] The present invention proposes to use a microporous copper mesh as a base membrane, and to construct an anti-pollution and self-cleaning smart filter membrane with a micro-nano rough structure through laser etching and electrochemical deposition of copper. The prepared membrane has superhydrophobic properties (contact angle greater than 150°). The copper mesh is prepared by two-step electrodeposition. The first electrodeposition is a high negative voltage deposition to promote the cathode reaction and form a loosely bound rough structure layer. The second deposition is a low voltage deposition to further enhance the adhesion of the structure, obtain a stable hierarchical micro-nano rough structure layer, and form a surface copper oxide Cu. n O (a mixture of Cu2O and CuO). The deposited sample is heated and dried to complete the preparation process.

[0013] Preferably, the copper mesh in step S1 has a pore size of 38 μm and a thickness of 50 μm.

[0014] Preferably, the copper mesh pretreatment in step S1 includes polishing, cleaning and drying.

[0015] Preferably, the cleaning in step S1 is to clean the copper mesh with acetone, alcohol and ultrapure water in sequence to completely remove the oxide and organic residue protective layer on the surface, and the cleaned copper mesh is naturally air-dried for use.

[0016] Preferably, the spacing of the groove texture in step S1 is 0.5-2 mm.

[0017] Preferably, the diameter of the laser beam in the laser etching method in step S1 is 0.5 mm.

[0018] Preferably, the copper sulfate electrolyte in step S2 is a mixed solution of CuSO4·5H2O, Na2SO4, and H2SO4.

[0019] Preferably, the time for the first electrodeposition in step S2 is 5 to 8 minutes.

[0020] Preferably, the second electrodeposition time in step S2 is 3 to 5 minutes.

[0021] Preferably, the heating and drying conditions in step S3 are 100° C. and 60 min.

[0022] The present invention also provides a method for reversibly converting the above-mentioned anti-pollution self-cleaning smart filter membrane from "super-hydrophilic to super-hydrophobic", comprising the following steps: The anti-pollution self-cleaning smart filter membrane is reduced to a super-hydrophilic smart filter when placed in a sodium chloride solution at a voltage of 20-25V; and is converted into a super-hydrophobic smart filter when heated at 100-120°C.

[0023] The present invention realizes the copper oxide Cu deposited on the intelligent filter membrane that resists pollution and self-cleaning by applying voltage nAfter O reduction, elemental copper Cu is formed, which realizes the transformation to superhydrophilicity; under heating and drying, Cu generates superhydrophobic Cu n For treating algae-containing water, an external voltage is applied before filtration to impart superhydrophilicity to the membrane, achieving high resistance to fouling. When the membrane is severely fouled and requires cleaning, the copper mesh membrane is rendered superhydrophobic by heating and drying, enabling its self-cleaning function.

[0024] Preferably, the power reduction time is 20 to 25 minutes.

[0025] Preferably, the heating time is 50 to 60 minutes.

[0026] Preferably, the concentration of the sodium chloride solution is 1-2 mM.

[0027] The application of the above-mentioned anti-pollution and self-cleaning intelligent filter membrane in removing algae is also within the scope of protection of the present invention.

[0028] Compared with the prior art, the present invention has the following beneficial effects: The anti-pollution and self-cleaning intelligent filter membrane provided by the present invention is prepared by laser etching and two-step electrochemical deposition, and can achieve reversible conversion between superhydrophilicity and superhydrophobicity based on electrical / thermal means; it achieves high anti-pollution performance in the algae removal process in the superhydrophilic state, and achieves the self-cleaning function of membrane cleaning in the superhydrophobic state, which is of great significance to improving the operating stability and self-cleaning ability of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a SEM image of the smart filter membrane with micro-nano rough structure prepared in Example 1; Figure 2 This is a diagram showing the algae removal efficiency of the copper mesh filter membrane according to the present invention. DETAILED DESCRIPTION

[0030] The present invention is further described below with reference to the examples. These examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. Experimental methods in the following examples where specific conditions are not specified are generally performed in accordance with conventional conditions in the art or the conditions recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from conventional markets. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection claimed in the present invention.

[0031] 1. Test indicators (1) Contact angle (°) Use clean tools (such as sharp blades) to cut a film sample of about (2cm×2cm), ensuring that the sample surface is not contaminated or damaged during the cutting process. Paste the cut sample flatly on a clean glass sheet. When pasting, ensure that the sample fits tightly to the glass sheet without bubbles or wrinkles to provide a stable test base. Use a contact angle meter, turn on the machine and preheat it to a stable working state. Place the glass sheet with the pasted sample on the instrument sample stage, adjust the sample stage XYZ axis, and use the instrument's built-in observation system to find a relatively flat cross-section area on the sample surface with no obvious defects, as the test position for applying water droplets. The equipment will automatically read and record the contact angle data. To ensure the accuracy of the test, select at least 3 different flat areas for the same sample for testing, and take the average value as the contact angle test result of the sample; (2) Copper mesh membrane flux: This is to characterize the amount of permeation of the anti-pollution self-cleaning intelligent filter membrane when it passes through the water body where algal bloom occurs in eutrophic water. The permeate quality is tested under the condition of 10cm filtration head by gravity flow. The flux calculation formula is:

[0032] Where: J -Membrane flux (L / m 2 ·h); Δ m -Time step Δ t (s) Mass of the internally filtered water sample (g); ρ - is the density of the permeate; A -Effective filtration area of ​​membrane (m 2 ); (3) Flux attenuation rate: It characterizes the anti-pollution ability of the copper mesh membrane. The initial flux of the net membrane is recorded as J 0, the flux of filtering for a certain time is J t , then the membrane flux attenuation rate at filtration time t is R =( J 0– J t ) / J 0 ； (4) Flux recovery rate: It characterizes the self-cleaning ability of the anti-pollution self-cleaning smart filter membrane. The flux of the clean membrane is J 0, the water flux after the contaminated membrane is cleaned is J c , the flux recovery rate is F = J c / J 0; (5) Algae removal rate: The algae removal rate is calculated by measuring the concentration of microalgae in the copper mesh membrane influent and permeate; Use an algae analyzer to measure the concentration of algae in the copper mesh membrane inlet and outlet water, and then calculate the removal rate (R) using the following formula:

[0033] Among them, C f and C p are the pollutant concentrations in the feed water and permeate effluent, respectively.

[0034] 2. Example / Comparative Example Experimental Methods and Test Results Example 1 S1. Substrate Film Preparation: Select a copper mesh substrate film with a pore size of 38 μm and a thickness of 50 μm, measuring 4.0 cm (length × width = 4.0 cm) by 4.0 cm. Use a grinder to create a rough, uneven surface. Clean the copper mesh with acetone, alcohol, and ultrapure water, sequentially, to thoroughly remove any surface oxides and organic residues. Allow the cleaned copper mesh to air-dry before use. Laser etching process: A laser processing system was used to create groove textures on the surface of the copper mesh, using a laser beam with a diameter of 0.5 mm and a line spacing of 0.5 mm; S2. Electrochemical deposition process: An electrodeposition solution was prepared, consisting of the following components: 0.05 M copper sulfate pentahydrate (CuSO4·5H2O), 0.05 M sodium sulfate (Na2SO4), and 0.05 M sulfuric acid (H2SO4), and the solution was uniformly mixed. The treated copper mesh is used as the cathode and the titanium plate is used as the anode for electroplating, using a two-step electrochemical deposition process. The first step of electroplating: 20V high voltage deposition for 5 minutes to induce and promote the reduction reaction at the cathode. This step forms a loosely bound rough structure on the surface of the cathode copper mesh. The second step of electroplating: 3V low voltage deposition for 3 minutes can enhance the firmness of the structure formed in the first step and obtain a stable graded rough structure layer. Membrane surface treatment and drying: The deposited sample is dried at 100°C for 60 minutes to complete the curing of the surface structure and obtain a super-hydrophobic smart filter membrane with a hierarchical micro-nano rough structure. Figure 1 This is the SEM image of the super-hydrophobic smart filter membrane.

[0035] Example 2 The experimental method is the same as that of Example 1, except that the line spacing during the laser etching process in step S1 is 2 mm.

[0036] Example 3 The experimental method is the same as that of Example 1, except that in the first deposition step S2, the voltage is 25V.

[0037] Example 4 The experimental method is the same as that of Example 1, except that in the first deposition step in step S2, the deposition time is 30V.

[0038] Example 5 The experimental method is the same as that of Example 1, except that in the first deposition step S2, the deposition time is 8 minutes.

[0039] Example 6 The experimental method is the same as that of Example 1, except that the voltage in the second deposition step in step S2 is 5V.

[0040] Example 7 The experimental method is the same as that of Example 1, except that in the second deposition step in step S2, the deposition time is 5 minutes.

[0041] Comparative Example 1 The experimental method is the same as that of Example 1, except that in the first deposition step in step S2, the concentration of the copper sulfate electrolyte is 0.02M.

[0042] Comparative Example 2 The experimental method is the same as that of Example 1, except that in the first deposition step in step S2, the concentration of the copper sulfate electrolyte is 0.1 M.

[0043] Comparative Example 3 The experimental method is the same as that of Example 1, except that in the first deposition step in step S2, the deposition voltage is 10V.

[0044] Comparative Example 4 The experimental method is the same as that of Example 1, except that in the second deposition step in step S2, the deposition voltage is 1V.

[0045] Table 1 Test results of examples / comparative examples

[0046] A contact angle greater than 150° is a superhydrophobic membrane; according to Table 1, Examples 1 to 7 provide anti-pollution and self-cleaning smart filter membranes prepared under different conditions with superhydrophobic properties; while in Comparative Examples 1 to 4, since the electrolyte solution concentration, deposition voltage or deposition time are not within the implementation range, a superhydrophobic, anti-pollution and self-cleaning smart filter membrane cannot be formed.

[0047] Implementation of Experiments 1-3: Experimental Methods for Transforming Anti-Pollution and Self-Cleaning Smart Filter Membrane from Superhydrophobic to Superhydrophilic Experiment 1 The super-hydrophobic filter membrane prepared in Example 1 was transformed into a super-hydrophilic one: the prepared copper membrane was immersed in a 1 mM sodium chloride solution and a reduction voltage of 20 V was applied for 20 min.

[0048] Experiment 2 The super-hydrophobic filter membrane prepared in Example 1 was transformed into a super-hydrophilic one: the prepared copper membrane was immersed in a 1 mM sodium chloride solution and a reduction voltage of 25 V was applied for 20 min.

[0049] Experiment 3 The super-hydrophobic filter membrane prepared in Example 1 was transformed into a super-hydrophilic one: the prepared copper membrane was immersed in a 1 mM sodium chloride solution and a reduction voltage of 25 V was applied for 25 min.

[0050] 4. Experiments 4-6: Experimental Methods for Transforming Anti-Pollution and Self-Cleaning Smart Filter Membrane from Super-Hydrophilic to Super-Hydrophobic Experiment 4 The superhydrophilic filter membrane obtained in Experiment 1 was converted into superhydrophobic: the copper film sample was heated to 100°C and kept for 60 min.

[0051] Experiment 5 The super-hydrophilic filter membrane obtained in Experiment 1 was converted into super-hydrophobic: the copper film sample was heated to 120°C and kept for 60 min.

[0052] Experiment 6 The super-hydrophilic filter membrane obtained in Experiment 1 was converted into super-hydrophobic: the copper membrane sample was heated to 120°C and kept for 50 min.

[0053] V. Implementation of Experiments 1-6: Experimental Results and Analysis The initial flux, flux decay rate, flux recovery rate and algae removal rate of Example 1 for algae removal (taking linear diatoms causing eutrophication of water bodies (containing 35 μg / L) in southern China as an example) under the two conditions of superhydrophilicity (experiments 1 to 3) and superhydrophobicity (experiments 4 to 6) are shown in Tables 2 and 3.

[0054] Table 2 Test results of super-hydrophilic copper mesh membranes in experiments 1 to 3

[0055] Table 3 Test results of super-hydrophobic copper mesh films in experiments 4 to 6

[0056] Compared to superhydrophobic smart filter membranes, superhydrophilic filters exhibit higher water yields at a 10 cm head, with an initial water flux exceeding 29,000 LMH, nearly double that of superhydrophobic smart filter membranes. Notably, superhydrophilic copper mesh exhibits superior anti-fouling capabilities, with a flux decay rate of only 5.6% to 6.9% of the initial flux after 10 minutes of filtration, compared to over 30% for superhydrophobic smart filter membranes. This is because water easily permeates the superhydrophilic copper mesh, forming a hydrated repellent layer on the surface that effectively prevents contaminants from coming into contact with the membrane. In contrast, superhydrophobic smart filter membranes have poor water permeability and, due to a lack of hydration repellent properties on their surface, cannot effectively prevent contaminants from coming into contact with the membrane surface, resulting in weaker anti-fouling capabilities. Therefore, superhydrophilic copper mesh offers potential advantages over superhydrophobic smart filter membranes for filtration and algae removal.

[0057] Although super-hydrophilic copper mesh membranes have good anti-pollution capabilities, their cleaning effectiveness is inferior to that of super-hydrophobic smart mesh membranes. As shown in Tables 2 and 3, under the same pollution conditions, the flux recovery rate of super-hydrophobic smart mesh membranes is 4–5 percentage points higher than that of super-hydrophilic membranes. This is due to the low surface interaction energy of super-hydrophobic membranes, allowing water molecules suspended on the rough surface to slide easily, thus easily carrying away pollutants, similar to the lotus leaf effect. In contrast, water molecules on the surface of super-hydrophilic copper mesh membranes are trapped in grooves and are less likely to roll. Therefore, super-hydrophobic smart mesh membranes offer potential advantages over super-hydrophilic membranes for copper mesh membrane cleaning and maintenance.

[0058] Furthermore, Tables 2 and 3 show that the copper mesh membrane achieved a removal rate of over 90% for linear diatoms. Linear diatoms are the primary algal species causing algal blooms in South China. Therefore, the intelligent mesh membrane of the present invention can effectively intercept microalgae when addressing eutrophication, thereby reducing the processing load on municipal water treatment systems and significantly ensuring the safety of discharged water quality.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An anti-pollution self-cleaning smart filter membrane, characterized in that: Prepared by the following method: S1. After pretreatment, the copper mesh is laser etched to form a grooved surface texture. S2. Two-step electrodeposition of copper mesh in copper sulfate electrolyte: The voltage of the first electrodeposition was 20–30 V; The second electrodeposition voltage is 3~5 V; The concentration of the copper sulfate electrolyte is 0.04~0.06M; S3. After heating and drying, a pollution-resistant and self-cleaning smart filter membrane is obtained, with a water contact angle greater than 150°.

2. The anti-pollution self-cleaning smart filter membrane according to claim 1, characterized in that: The spacing of the groove texture in step S1 is 0.5-2 mm.

3. The anti-pollution self-cleaning smart filter membrane according to claim 1, characterized in that: The copper sulfate electrolyte in step S2 is a mixture of CuSO4·5H2O, Na2SO4, and H2SO4.

4. The anti-pollution self-cleaning smart filter membrane according to claim 1, characterized in that: The time of the first electrodeposition in step S2 is 5 to 8 minutes.

5. The anti-pollution self-cleaning smart filter membrane according to claim 1, characterized in that: The second electrodeposition time in step S2 is 3 to 5 minutes.

6. The method for reversibly converting the anti-pollution self-cleaning smart filter membrane from super-hydrophilic to super-hydrophobic according to any one of claims 1 to 5, characterized in that: The anti-pollution self-cleaning smart filter membrane is reduced to a super-hydrophilic smart filter when placed in a sodium chloride solution at a voltage of 20-25V; and is converted into a super-hydrophobic smart filter when heated at 100-120°C.

7. The method according to claim 6, wherein The reduction time is 20-25 min.

8. The method according to claim 6, wherein The heating time is 50 to 60 minutes.

9. The method according to claim 6, wherein The concentration of the sodium chloride solution is 1-2 mM.

10. Use of the anti-pollution and self-cleaning smart filter membrane according to any one of claims 1 to 5 in an algae removal process.

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