A membrane chromatography filter for removing charged ions from liquids and its preparation method.

Abstract

This invention belongs to the field of wet electronic chemical purification, specifically relating to a membrane chromatography filter membrane for removing charged ions from liquids and its preparation method, including the following steps: S1, preparing casting solutions: preparing positively charged layer casting solutions, neutral layer casting solutions, and negatively charged layer casting solutions separately; S2, using a three-layer die to sequentially extrude the positively charged layer casting solutions, neutral layer casting solutions, and negatively charged layer casting solutions onto a polyester film; S3, exposing the casting solutions under set temperature, humidity, and airflow conditions to allow for initial phase separation; S4, immersing the coated film in a pure water coagulation bath to complete phase separation and solidification; S5, rinsing, drying, and then winding to obtain the membrane chromatography filter membrane. By designing a special three-layer composite structure with a "positively charged layer-neutral layer-negative layer," the filter membrane can simultaneously adsorb anions and cations in the solution during a single filtration process, overcoming the limitation of traditional single-charge membranes that can only remove one type of ion, thus improving purification efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wet electronic chemical purification, specifically relating to a membrane chromatography filter membrane for removing charged ions from liquids and its preparation method. Background Technology

[0002] In the electronics industry, especially in high-end manufacturing sectors such as semiconductors, display panels, and photovoltaics, the purity requirements for the chemicals used are extremely stringent. Even trace amounts of metal or inorganic ions in these chemicals can lead to product defects, performance degradation, or reduced yield. Therefore, developing efficient and reliable ion removal technologies has become one of the key issues in this field.

[0003] Currently, common ion removal methods mainly include ion exchange resin methods and distillation / rectification methods. While ion exchange resin methods are widely used, they suffer from drawbacks such as high operating pressure, low throughput, and slow processing speed. Furthermore, the resin regeneration process is complex, increasing operating costs and time. Distillation / rectification methods, although effective in separating impurities, are energy-intensive and require complex equipment, making them unsuitable for continuous, large-scale processing, especially for removing trace amounts of ions from high-purity chemicals.

[0004] Membrane chromatography, as a highly efficient separation technique, was initially mainly used for the separation and purification of biological macromolecules (such as proteins and nucleic acids). It combines the advantages of membrane filtration and chromatographic adsorption, offering high throughput, ease of operation, and easy scale-up. However, its application in the removal of inorganic ions has not been fully explored. Traditional single-charged membrane materials typically adsorb only one type of ion, making it difficult to simultaneously and efficiently remove both anions and cations from solution, thus limiting its applicability in the purification of electronic chemicals.

[0005] Furthermore, existing membrane materials have limitations in terms of structural design and functional integration. Most membrane products only have a single function (such as filtration or adsorption), making it difficult to efficiently remove ions while simultaneously filtering particulate impurities, resulting in complex processes and increased equipment investment.

[0006] Therefore, there is an urgent need in this field for a membrane chromatography technology that can simultaneously and efficiently remove anions and cations, has a filtration function, and is suitable for the processing of high-purity chemicals in the electronics industry. Summary of the Invention

[0007] To address the problems mentioned in the background art, this invention proposes a membrane chromatography filter membrane for removing charged ions from liquids and its preparation method. By designing a special three-layer composite structure with a "positively charged layer-neutral layer-negatively charged layer", the filter membrane can simultaneously adsorb anions and cations in the solution during a single filtration process, overcoming the limitation of traditional single-charge membranes that can only remove one type of ion and improving purification efficiency.

[0008] The technical solution adopted by this invention to solve its technical problem is: to provide a method for preparing a membrane chromatography filter membrane for removing charged ions from liquids, comprising the following steps:

[0009] S1. Preparation of casting solutions: Prepare positive charge layer casting solution, neutral charge layer casting solution and negative charge layer casting solution respectively. The positive charge layer casting solution is prepared by adding a positive charge modifier to the casting solution. The negative charge layer casting solution is prepared by adding a negative charge modifier to the casting solution. The neutral charge layer casting solution is an unmodified casting solution.

[0010] S2. Using a three-layer die head, the positively charged layer casting solution, the neutral layer casting solution, and the negatively charged layer casting solution are simultaneously extruded and coated onto a polyester film.

[0011] S3. Expose the casting solution to set temperature, humidity and air flow rate conditions to allow for initial phase separation;

[0012] S4. Immerse the coated film in a pure water coagulation bath to complete phase separation and curing.

[0013] S5. After rinsing and drying, the membrane is wound up to obtain a membrane chromatography filter membrane; wherein, in S1, the casting solution contains a polymer, a hydrophilic polymer, a charge modifier, a solvent and a non-solvent.

[0014] The composition of the casting solution is as follows: polymer 10-15%, hydrophilic polymer 0-2%, solvent 20-80%, and non-solvent 18-70%.

[0015] Furthermore, in S1, the positively charged modifier includes polyquaternary ammonium salt, polydiallyldimethylammonium chloride, poly(methacryloyloxyethyltrimethylammonium chloride), or polyethyleneimine, with a content of 0.5-5%.

[0016] Furthermore, in S1, the negative charge modifier includes sulfonated polyethersulfone, polyacrylic acid, polymethacrylic acid, polymaleic anhydride, sodium polystyrene sulfonate, or polyphosphate, with a content of 0.5-5%.

[0017] Furthermore, the polymer includes polyethersulfone or nylon-6.

[0018] Furthermore, the hydrophilic polymer includes polyvinylpyrrolidone K90 or polyvinylpyrrolidone K30.

[0019] Furthermore, the solvent includes N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, formic acid, or acetic acid;

[0020] Non-solvents include water, ethanol, ethylene glycol, glycerol, triethylene glycol, or polyethylene glycol.

[0021] Furthermore, in S3, the temperature is set to 20-25℃; the humidity to 80-90%; and the air velocity to 0.8-1.2m / s.

[0022] A membrane chromatography filter membrane for removing charged ions from liquids, the filter membrane having a three-layer composite structure, comprising a positively charged layer, a neutral layer, and a negatively charged layer arranged sequentially; the neutral layer is located between the positively charged layer and the negatively charged layer, serving to support and isolate the positively charged layer and the negatively charged layer; the overall thickness of the filter membrane is 120-250 μm, wherein the thicknesses of the positively charged layer and the negatively charged layer are 50-100 μm, and the thickness of the neutral layer is 20-50 μm.

[0023] The application of membrane chromatography filter membranes in removing charged ions from liquids, specifically the adsorption and removal of trace metal or inorganic ions from chemicals used in the electronics industry.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) This invention designs a special three-layer composite structure with a “positive charge layer-neutral layer-negative charge layer”, which enables the filter membrane to adsorb anions and cations in the solution simultaneously in a single filtration process, thus solving the limitation of traditional single charge membranes that can only remove one type of ion and improving purification efficiency.

[0026] (2) The membrane chromatography technology used in this invention is based on pressure-driven filtration, which has a higher permeation flux, lower operating pressure, and faster processing speed compared with traditional ion exchange resins. At the same time, compared with thermal separation technologies such as distillation / rectification, its energy consumption is significantly reduced, which is more in line with the production requirements of energy conservation and environmental protection.

[0027] (3) The neutral layer of the filter membrane described in this invention not only serves to support and isolate the positive and negative charge layers and prevent charge interference, but its microporous structure can also effectively trap insoluble particulate impurities in the liquid, realizing the integration of the two functions of "adsorbing ions" and "filtering particles" in the same membrane unit, simplifying the purification process and equipment.

[0028] (4) This invention is designed to meet the stringent requirements for the removal of trace ions in chemicals in the electronics industry. It has an excellent ion removal rate and is suitable for the preparation of ultrapure water, ultrapure reagents, etc., to ensure the product yield of high-end electronic manufacturing.

[0029] (5) The present invention can achieve precise control and firm bonding of the three-layer structure through the three-layer die co-extrusion process. The process has good repeatability and is suitable for continuous production, which provides a guarantee for large-scale industrial application. Attached Figure Description

[0030] Figure 1 The images show the results of methylene blue staining in Examples 1 and 6.

[0031] Figure 2 The staining results of carmine in Examples 1 and 6 are shown in the figure.

[0032] Figure 3 This is an electron microscope image of the membrane chromatography filter membrane prepared in Example 1. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1:

[0035] This embodiment provides a method for preparing a membrane chromatography filter membrane for removing charged ions from liquids, the specific steps of which are as follows:

[0036] First, three casting solutions were prepared: a positively charged layer casting solution, a neutral layer casting solution, and a negatively charged layer casting solution.

[0037] The composition of the positive charge layer casting solution includes: 13% polyethersulfone, 1% hydrophilic polymer polyvinylpyrrolidone (PVP), 4% positive charge modifier polydiallyldimethylammonium chloride, 28.67% solvent N-methylpyrrolidone (NMP), and 53.33% non-solvent polyethylene glycol 400 (PEG400).

[0038] The neutral layer casting solution consists of: 12% polyethersulfone, 2% hydrophilic polymer polyvinylpyrrolidone (PVP), 30% solvent N-methylpyrrolidone (NMP), and 56% non-solvent polyethylene glycol 400 (PEG400).

[0039] The composition of the negative charge layer casting solution includes: 13% polyethersulfone, 1% hydrophilic polymer polyvinylpyrrolidone (PVP), 1% negative charge modifier sulfonated polyethersulfone, 29.72% solvent N-methylpyrrolidone (NMP), and 55.28% non-solvent polyethylene glycol 400 (PEG400).

[0040] Table 1 shows the composition of the membrane chromatography filter used in Example 1 for removing charged ions from liquids.

[0041]

[0042] Subsequently, coating was performed using a three-layer co-extrusion die. The lip gaps of the three dies were set to 0.15 mm, 0.1 mm, and 0.15 mm from top to bottom, respectively, while the feed rates for each layer were set as follows: 3 L / h for the positively charged layer, 2 L / h for the neutral layer, and 3 L / h for the negatively charged layer. The three casting solutions were extruded simultaneously to form a three-layer stacked liquid film, which was then coated onto a polyester film.

[0043] Next, the coated liquid film is exposed to an air duct with a temperature of 21°C, a humidity of 65%, and an air velocity of 1.0 m / s for 20 seconds to allow the casting liquid to undergo initial phase separation.

[0044] Then, the preliminarily phase-separated film is immersed in a pure water coagulation bath to complete the final phase separation and solidification.

[0045] Finally, the cured film is thoroughly rinsed with pure water, dried, and then wound up to obtain the membrane chromatography filter membrane. Figure 3 As shown, the filter membrane has an overall thickness of approximately 150 μm and a composite structure consisting of a positively charged layer, a neutral layer, and a negatively charged layer. It is suitable for adsorbing and removing trace metal ions or inorganic ions from chemicals in the electronics industry.

[0046] Examples 2-5:

[0047] The process conditions for Examples 2-5 are the same as those for Example 1, and their formulations are shown in Table 2.

[0048]

[0049] Example 6:

[0050] Three casting solutions were prepared according to Table 3. The lip gaps of the three-layer die heads were set to 0.2 mm, 0.1 mm, and 0.2 mm from top to bottom, respectively. Simultaneously, the feed rates of the three-layer die heads were set to 5 L / h, 3 L / h, and 5 L / h, respectively, for extrusion. After extrusion, three stacked liquid films were formed. The liquid films were then placed in an air duct at a temperature of 21℃, humidity of 85%, and air velocity of 1.0 m / s for 5 minutes to form a preliminary phase-separated structure. They were then placed in a pure water coagulation bath for final phase separation and solidification. Finally, after thorough rinsing with pure water, the films were dried and wound up to obtain a roll film.

[0051] Table 3 shows the composition of the membrane chromatography filter used in Example 6 for removing charged ions from liquids.

[0052]

[0053] like Figure 1 and Figure 2 As shown, the filter membranes prepared in Examples 1 and 6 can be stained with methylene blue, a positively charged dye, on one side and carmine, a negatively charged dye, on the other side, and do not fade after rinsing, proving that the filter membranes have positive and negative charges on both sides, respectively.

[0054] Experimental Cases 7-8:

[0055] The process conditions for Examples 2-5 are the same as those for Example 6, and their formulations are shown in Table 4.

[0056]

[0057] Table 5: Test results for Examples 1 to 8, with the following basic data:

[0058]

[0059] Table 6 shows the ion removal capacity characterization data of the membrane chromatography filters prepared in Examples 1-8.

[0060]

[0061] In summary, this invention utilizes a three-layer co-extrusion technique to prepare a membrane chromatography filter with a unique structure of "positively charged layer-neutral layer-negatively charged layer". Test data from Examples 1-8 demonstrate that this filter not only simultaneously and efficiently adsorbs and removes cations and anions from liquids, reducing the conductivity of various typical ionic solutions from hundreds of μS / cm to single digits, but also effectively filters particulate impurities. Dye staining and SEM results visually confirm the stable charged characteristics and regular three-layer microstructure on both sides of the filter membrane. This invention offers a controllable and reproducible process, providing a high-throughput, low-energy, and integrated innovative solution for addressing trace ion contamination in chemicals used in the electronics industry, and possesses promising prospects for industrial application.

[0062] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a membrane chromatography filter membrane for removing charged ions from liquids, characterized in that, Includes the following steps: S1. Preparation of casting solutions: Prepare positive charge layer casting solution, neutral charge layer casting solution and negative charge layer casting solution respectively. The positive charge layer casting solution is prepared by adding a positive charge modifier to the casting solution. The negative charge layer casting solution is prepared by adding a negative charge modifier to the casting solution. The neutral charge layer casting solution is an unmodified casting solution. S2. Using a three-layer die head, the positively charged layer casting solution, the neutral layer casting solution and the negatively charged layer casting solution are simultaneously extruded and coated onto a polyester film. S3. Expose the casting solution to set temperature, humidity and air flow rate conditions to allow for initial phase separation; S4. Immerse the coated film in a pure water coagulation bath to complete phase separation and curing. S5. After rinsing and drying, the membrane is wound up to obtain the membrane chromatography filter membrane; In S1, the casting solution contains a polymer, a hydrophilic polymer, a charge modifier, a solvent, and a non-solvent. The content of each component in the casting solution is as follows: polymer 10-15%, hydrophilic polymer 0-2%, solvent 20-80%, and non-solvent 18-70%.

2. The method for preparing a membrane chromatography filter membrane for removing charged ions from a liquid according to claim 1, characterized in that, In S1, the positively charged modifier includes polyquaternary ammonium salt, polydiallyldimethylammonium chloride, poly(methacryloyloxyethyltrimethylammonium chloride), or polyethyleneimine, with a content of 0.5-5%.

3. The method for preparing a membrane chromatography filter membrane for removing charged ions from a liquid according to claim 1, characterized in that, In S1, the negative charge modifier includes sulfonated polyethersulfone, polyacrylic acid, polymethacrylic acid, polymaleic anhydride, sodium polystyrene sulfonate or polyphosphate, with a content of 0.5-5%.

4. The method for preparing a membrane chromatography filter membrane for removing charged ions from a liquid according to claim 1, characterized in that, The polymers include polyethersulfone or nylon-6.

5. The method for preparing a membrane chromatography filter membrane for removing charged ions from a liquid according to claim 1, characterized in that, Hydrophilic polymers include polyvinylpyrrolidone K90 or polyvinylpyrrolidone K30.

6. The method for preparing a membrane chromatography filter membrane for removing charged ions from a liquid according to claim 1, characterized in that, Solvents include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, formic acid, or acetic acid; Non-solvents include water, ethanol, ethylene glycol, glycerol, triethylene glycol, or polyethylene glycol.

7. The method for preparing a membrane chromatography filter membrane for removing charged ions from a liquid according to claim 1, characterized in that, In S3, the set temperature is 20-25℃; humidity is 80-90%; and air velocity is 0.8-1.2m / s.

8. A membrane chromatography filter membrane for removing charged ions from liquids, characterized in that: The filter membrane has a three-layer composite structure, including a positively charged layer, a neutral layer and a negatively charged layer arranged sequentially. The neutral layer is located between the positive and negative charge layers and is used to support and isolate the positive and negative charge layers. The overall thickness of the filter membrane is 120-250 μm, of which the thicknesses of the positive and negative charged layers are 50-100 μm and the thickness of the neutral layer is 20-50 μm.

9. The application of the membrane chromatography filter membrane as described in claim 8 in the removal of charged ions from liquids, characterized in that, The application is to adsorb and remove trace metal or inorganic ions from chemicals in the electronics industry.

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