Polyvinyl composite reverse osmosis membrane and preparation method thereof

Abstract

The invention relates to the technical field of reverse osmosis composite membranes, in particular to a polyvinyl composite reverse osmosis membrane and a preparation method thereof.The polyvinyl composite reverse osmosis membrane is prepared from a polyethylene film subjected to hydrophilic modification through interfacial polymerization reaction, and a modifier for hydrophilic modification of the polyethylene film is composed of 20-30 wt% of alcohol micromolecules, 0.5-2 wt% of a surfactant, 0.5-2 wt% of a hydrophilic auxiliary and 0.1-0.5 wt% of an adhesive. According to the application, the mussel enlightens the excellent adhesion effect of the biomimetic material, the biomimetic material is used for hydrophilic modification of the PE battery diaphragm, and the interaction between a hydrophilic component and a PE substrate is enhanced, so that the hydrophilic effect stability of the modified PE diaphragm is improved, meanwhile, the modification process is simplified, reagent pollution and resource consumption are reduced, and the service life of the battery diaphragm is prolonged. The development, preparation and industrial application of the PE-based composite reverse osmosis membrane are promoted.

Description

Technical Field

[0001] This invention relates to the field of reverse osmosis composite membrane technology, specifically a polyethylene-based composite reverse osmosis membrane and its preparation method. Background Technology

[0002] Reverse osmosis technology is widely used in water treatment due to its advantages such as low power consumption and high efficiency. Currently, most reverse osmosis membranes on the market are composite membranes composed of polyester nonwoven fabric, polysulfone ultrafiltration membrane, and polyamide desalination layer. The main cost component is the base membrane development, specifically the design and development of the polyester nonwoven fabric and polysulfone ultrafiltration membrane, accounting for approximately 70% of the total membrane cost. Because there are few qualified suppliers of polyester nonwoven fabric in China, it is generally imported from the United States or Japan, while the supply of polysulfone materials is basically monopolized by overseas chemical giants such as Solvay (USA) and BASF (Germany). Therefore, although domestically developed reverse osmosis membranes have generally achieved domestic production equipment, the high cost of raw materials means that they have little advantage compared to imported products. Even with large-scale lean production management, it is difficult to significantly increase profits. Therefore, finding ways to change the membrane material to achieve a disruptive cost advantage is worthy of in-depth research.

[0003] Polyethylene (PE) polymers are simple to synthesize, have large industrial production capacity, and low cost, and have been widely used in the preparation of lithium-ion battery separators in recent years, exhibiting characteristics such as ultra-thin thickness, high mechanical strength, and excellent solvent resistance. Therefore, it is considered the most promising candidate material for water treatment membrane support layers. Its ultra-thin thickness can reduce concentration polarization in TFC membranes, increase the packing density of RO membrane modules, and reduce water transport paths, thereby effectively increasing water flux. Furthermore, compared to polyester nonwoven / polysulfone ultrafiltration membranes, PE-based lithium-ion battery separators are more affordable and have a more environmentally friendly production process. If successfully used as a substitute, it will significantly reduce the manufacturing cost of reverse osmosis membranes while achieving domestic production of raw materials and green production, and will also yield reverse osmosis membranes with higher packing density, significantly enhancing product competitiveness.

[0004] Because the inherent hydrophobicity of PE membranes is detrimental to water treatment applications, various physical or chemical methods for hydrophilic modification of PE membranes have been widely reported in order to improve their hydrophilicity, optimize membrane structure, increase membrane flux, and enhance their antifouling performance, enabling long-term high-efficiency operation and reducing industrial costs. For example, patent CN115105974A discloses a reverse osmosis membrane, its preparation method, and its application. This method involves contacting a hydrophilically modified PE microporous membrane with an aqueous solution containing amine monomers to form an intermediate membrane layer, followed by contact with an oil solution containing acyl chloride monomers. After reaction and drying, a high-flux, acid-resistant reverse osmosis membrane is obtained. The prepared PE-based reverse osmosis membrane exhibits a rejection rate ≥98.5% for a 500 ppm NaCl solution at 8 bar, with a membrane flux of 4.9–5.4 L / (m²). 2*h*bar); After the reverse osmosis membrane was immersed in a mixed solution of 20wt% sulfuric acid and 5wt% hydrochloric acid for 48 hours, the rejection rate was tested to be ≥98.0%, and the membrane flux was 5.1~5.7L / (m 2 The shortcomings of this technical solution are that hydrophilic modification using only alcohol washing results in poor modification stability. While adding terephthalic acid to the aqueous solution can improve the interfacial polymerization effect of the PE membrane and enhance the structural and mechanical stability of the reverse osmosis membrane through the conjugation effect between terephthalic acid and amine monomers, it also slows down the diffusion rate of amine monomers, prolongs the polymerization process, affects the formation of the PA layer, and increases industrial energy consumption.

[0005] Patent CN111389240A discloses a method for preparing a polyethylene composite nanofiltration membrane. The method involves immersing a polyolefin membrane in a wetting agent for wetting treatment, removing the polyolefin membrane and removing surface residue, then immersing it in a hydrophilic modifier, removing it again to remove surface residue, and then drying it in an oven. An interfacial polymerization reaction is then carried out on the permanently hydrophilic polyolefin membrane to obtain the polyethylene composite nanofiltration membrane. The prepared nanofiltration membrane exhibits a concentration of 21.56–53.65 L / (m³) at a test pressure of 70 psi for a 2000 ppm magnesium sulfate solution. 2 The flux is *h*bar), and the desalination rate is 94.01%–98.54%. The shortcomings of this technology are that the pretreatment steps for the polyolefin film before interfacial polymerization are numerous, resulting in a lengthy production line and significant resource waste in industrial applications. Furthermore, since the hydrophilic modification technology used in this solution is glutaraldehyde crosslinking, a significant drawback is the potential for glutaraldehyde residue during processing, posing health and environmental risks. Additionally, the crosslinking ability is greatly affected by environmental factors, the crosslinking time is long, and glutaraldehyde is expensive, leading to high industrial production costs. Therefore, the industrial application of hydrophilic PE films prepared by single alcohol washing modification or glutaraldehyde crosslinking modification is hindered. However, using mussel biomimetic adhesion technology for hydrophilic modification can utilize its inherent excellent adhesion to achieve stable modification of the PE film by the hydrophilic components, and can further enhance the modification effect through chemical interactions between mussels and hydrophilic polymers. Moreover, this technology is simple, easy to control, has low reagent costs, and poses no health or environmental risks.

[0006] Thanks to the high mechanical strength, excellent solvent resistance and ultra-thin thickness of PE battery separators, they have been creatively used as support materials for reverse osmosis membranes in water treatment in recent studies, and have achieved many excellent results. However, in practical applications, the existing hydrophilic modification process still has the following problems: (1) The non-crosslinking impregnation modification process is simple and easy to operate, but the pore-expanding effect of alcohol washing is limited, and the amount of hydrophilic agent modification is insufficient, resulting in poor modification stability and unsuitability for long-term operation; (2) The crosslinking agent impregnation modification process is complicated, involves many repetitive operations, and the current crosslinking agent is inconvenient to control, has a high cost, and poses environmental hazards, which is not conducive to commercial development.

[0007] Patent CN115178113A discloses a method for preparing a polyethylene-based high-flux reverse osmosis membrane. The method involves hydrophilically modifying a PE-based membrane using polymer solutions containing small alcohol molecules (ethanol, isopropanol, glycerol) and surfactants. A polyamide reverse osmosis composite membrane is then prepared using the hydrophilized PE substrate as a support layer and m-phenylenediamine and trimesoyl chloride as the aqueous and organic phase monomers, respectively. The optimal flux for a 2000 mg / L NaCl aqueous solution at 225 psi pressure is 57.9 L / (m²). 2 *h), with an optimal rejection rate of 99.12%. However, this technical solution only uses alcohol-based small molecule solutions to expand the pores of the PE membrane and uses surfactants for hydrophilic modification, without adding crosslinking aids. This results in poor separation stability of the PE-based reverse osmosis membrane and severe flux decay under long-term operation.

[0008] Patent CN116078160A discloses a polyethylene-based solvent- and acid / alkali-resistant reverse osmosis membrane and its preparation method. The reverse osmosis membrane comprises a three-layer composite structure consisting of a polyethylene-based membrane, a polyamide layer, and a PVA layer. The PE membrane, prepared by melt wet molding, is hydrophilically modified in a polymer solution containing hydroxyl groups. After washing and wetting with pure water, a PES-type polymer is coated on its surface. It is then sequentially immersed in an aqueous solution of aromatic polyamines and an oil solution of aromatic acyl chlorides. Finally, it is treated with glycerol immersion and then wetted in a PVA solution containing glutaraldehyde. After drying, the PE-based solvent- and acid / alkali-resistant reverse osmosis membrane is obtained. After immersion in 5% hydrochloric acid solution for 5 hours, the prepared reverse osmosis membrane exhibits a maximum flux of 26.6 gfd to 2000 ppm NaCl solution at an operating pressure of 1 MPa, with a desalination rate of 98.1%, demonstrating excellent solvent and acid / alkali resistance. However, the modification steps of this technical solution are relatively complicated, and the hydrophilic modification of PE base film is relatively simple. At the same time, PES-type polymers are coated, and PVA and glutaraldehyde are introduced after interfacial polymerization. The process involves many steps, consumes a lot of raw materials, and has a high production cost, which is not conducive to industrial promotion.

[0009] To address the problems in current PE battery separator substrate composite reverse osmosis membrane preparation technologies, such as poor hydrophilic stability, cumbersome modification steps, and significant environmental risks associated with modifying reagents, it is necessary to find a method that can improve the stability of the hydrophilic effect of modified PE separators, while simplifying the modification process, reducing reagent pollution and resource consumption, and promoting the development, preparation, and industrial application of PE-based composite reverse osmosis membranes. Summary of the Invention

[0010] In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a method for preparing a polyethylene-based composite reverse osmosis membrane.

[0011] A method for preparing a polyethylene-based composite reverse osmosis membrane specifically includes the following steps:

[0012] (1) Mix m-phenylenediamine and sodium hydroxide and dissolve them in deionized water to obtain an aqueous solution; then weigh an appropriate amount of pyromellitic chloride and dissolve it in n-hexane to prepare an oil solution.

[0013] (2) Immerse the dried hydrophilic polyethylene membrane in an aqueous solution until the membrane surface is fully wetted. Then remove the membrane and blow dry the surface moisture. Then immerse it in an oil solution to react and remove it. Wash it with deionized water and then dry it in an oven to obtain a polyethylene composite reverse osmosis membrane.

[0014] Furthermore, the concentration of intermediate-phenylenediamine in the aqueous solution is 1.0–4.0 wt%.

[0015] Furthermore, the concentration of sodium hydroxide in the aqueous solution is 0.01–0.05 wt%.

[0016] Furthermore, the concentration of pyromellitic acid chloride in the oil phase solution is 0.1–0.2 wt%.

[0017] Furthermore, the hydrophilic polyethylene-based film is prepared by interfacial polymerization of a hydrophilically modified polyethylene film. The modifier used for hydrophilic modification of the polyethylene film comprises 20-30 wt% alcohol small molecules, 0.5-2 wt% surfactant, 0.5-2 wt% hydrophilic additive, and 0.1-0.5 wt% adhesive. Preferably, the alcohol small molecules are one or more organic alcohol aqueous solutions such as ethanol, isopropanol, and glycerol, combined in any proportion. Preferably, the surfactant is one or more surfactants such as sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty alcohol ether sulfate, and alkyl alcohol ether phosphate, combined in any proportion. Preferably, the hydrophilic additive is one or more synthetic or natural hydrophilic polymers such as polyethyleneimine, polyvinyl alcohol, sodium alginate, hyaluronic acid, and ε-polylysine, combined in any proportion. Preferably, the adhesive is one or more of the following biomimetic substances with inherent viscosity: dopamine and its derivatives, catechol and its derivatives, tannic acid and its derivatives, thiolated chitosan, etc., in any proportion.

[0018] The above-mentioned hydrophilic polyethylene film (HPE) is prepared through the following steps:

[0019] (1) Dissolve the selected alcohol molecules, surfactants, hydrophilic additives and adhesives in deionized water in proportion and stir evenly to obtain a hydrophilic modifier;

[0020] (2) Immerse the clean polyethylene film, washed and dried with pure water, in a hydrophilic modifier. After thorough immersion, remove the film, rinse it with deionized water, and then dry it in an oven to obtain a permanently hydrophilic polyethylene film.

[0021] The polyethylene-based composite reverse osmosis membrane prepared by the above method and its application in the field of reverse osmosis filtration. Preferably, the application is to use the obtained polyethylene-based composite reverse osmosis membrane to prepare reverse osmosis membrane elements.

[0022] A reverse osmosis membrane element is prepared using a polyethylene-based composite reverse osmosis membrane obtained by the above preparation method as raw material.

[0023] Compared with the prior art, the technical effects of this invention are reflected in:

[0024] 1. Traditional reverse osmosis membranes are supported by a combination of polyester nonwoven fabric and polysulfone ultrafiltration membrane. Their preparation process is greatly affected by process conditions, and they are heavily reliant on imported raw materials, resulting in high production costs and low industrial profits. In contrast, this application uses inexpensive PE membranes, which have advantages such as high mechanical strength, excellent solvent resistance, and ultra-thin thickness, as the support material. PE-based composite reverse osmosis membranes are prepared through an impregnation modification process. The preparation process is simple and environmentally friendly, consumes few resources, is suitable for industrial production, and can provide higher membrane module packing density while reducing membrane manufacturing costs, significantly improving membrane performance.

[0025] 2. Although PE membranes are thin and have excellent mechanical properties, they have great application potential as support materials for reverse osmosis membranes. However, due to their poor surface hydrophilicity, which is not conducive to interfacial polymerization, their application research has been slow. To address this, this application uses hydrophilic polymers rich in hydrophilic groups as hydrophilic additives and adds small alcohol molecules and surfactants to modify the PE membrane for hydrophilicity. By utilizing the wetting effect of small alcohol molecules and the affinity effect of surfactants, hydrophilic components are introduced into the membrane surface, improving the hydrophilicity of the PE membrane and providing sufficient support for the subsequent interfacial polymerization reaction.

[0026] 3. The introduction of hydrophilic agents can effectively improve the hydrophilicity of the PE membrane surface and provide favorable support for its further interfacial polymerization reaction. However, the performance stability of the impregnation modification process is insufficient. To address this, this application uses an adhesive to synergistically modify the PE membrane. Through hydrogen bonding, chelation, electrostatic interactions, or covalent reactions between the adhesive and the PE membrane, the membrane is stably adhered to the substrate. Simultaneously, Michael addition or Schiff base reactions occur between the adhesive and the hydrophilic components, enhancing the stability of the hydrophilic coating, promoting the effective adsorption and uniform diffusion of aqueous monomers, and facilitating the continuous progress of the interfacial polymerization reaction. The resulting PE-based composite reverse osmosis membrane exhibits uniform PA layer growth, larger pore sizes, better membrane permeability and desalination capacity, and minimal performance degradation over long-term operation. Attached Figure Description

[0027] Figure 1 The surface morphology, contact angle, and roughness characteristics of the diaphragm obtained in Example 1 are characterized.

[0028] Figure 2 This is the infrared spectrum of the membrane obtained in Example 1.

[0029] Figure 3 It refers to the long-term operational stability of the diaphragm. Detailed Implementation

[0030] The technical solution of the present invention will be further defined below with reference to specific embodiments, but the scope of protection is not limited to the description made.

[0031] Example 1

[0032] (1) Weigh appropriate amounts of isopropanol (IPA, 25wt%), sodium dodecyl sulfate (SDS, 2.0wt%), polyethyleneimine (PEI, 1.0wt%), and tannic acid (TA, 0.1wt%) and dissolve them in deionized water according to the set mass fractions, and stir evenly to obtain a hydrophilic modifier;

[0033] (2) Immerse the clean PE film washed and dried with pure water in the hydrophilic modifier for 2 minutes. After fully wetting, take out the film, clean it with deionized water, and transfer it to the oven for drying to obtain the permanent hydrophilic polyethylene film HPE1.

[0034] (3) Mix m-phenylenediamine (MPD, 2.0 wt%) and sodium hydroxide (NaOH, 0.01 wt%) and dissolve them in deionized water to obtain an aqueous solution; then weigh an appropriate amount of trimesoyl chloride (TMC, 0.1 wt%) and dissolve it in n-hexane to prepare an oil solution;

[0035] (4) Immerse the prepared dry hydrophilic polyethylene membrane in an aqueous solution for 1 minute until the membrane surface is fully wetted. Then remove the membrane and carefully blow dry the surface moisture with an air gun. Then immerse it in an oil solution for 1 minute and remove it. After rinsing with deionized water, place it in an oven to dry and obtain polyethylene composite reverse osmosis membrane RO-HPE1.

[0036] Example 2

[0037] (1) Weigh appropriate amounts of anhydrous ethanol (AE, 20wt%), sodium dodecylbenzenesulfonate (SDBS, 1.0wt%), polyvinyl alcohol (PVA, 0.5wt%), and dopamine (DA, 0.1wt%) and dissolve them in deionized water according to the set mass fractions, and stir evenly to obtain a hydrophilic modifier.

[0038] (2) Immerse the clean PE film washed and dried with pure water in the hydrophilic modifier for 2 minutes. After being fully wetted, take out the film, clean it with deionized water, and transfer it to the oven for drying to obtain the permanent hydrophilic polyethylene film HPE2.

[0039] (3) Mix m-phenylenediamine (MPD, 2.0 wt%) and sodium hydroxide (NaOH, 0.01 wt%) and dissolve them in deionized water to obtain an aqueous solution; then weigh an appropriate amount of trimesoyl chloride (TMC, 0.1 wt%) and dissolve it in n-hexane to prepare an oil solution;

[0040] (4) Immerse the prepared dry hydrophilic polyethylene membrane in an aqueous solution for 1 minute until the membrane surface is fully wetted. Then remove the membrane and carefully blow dry the surface moisture with an air gun. Then immerse it in an oil solution for 1 minute and remove it. After rinsing with deionized water, place it in an oven to dry and obtain the polyethylene composite reverse osmosis membrane RO-HPE2.

[0041] Example 3

[0042] (1) Weigh appropriate amounts of glycerol (GL, 20wt%), sodium fatty alcohol ether sulfate (AES, 1.0wt%), sodium alginate (SA, 0.5wt%), and 3,4-dihydroxyphenylpropionic acid (DHPA, 0.1wt%) and dissolve them in deionized water according to the set mass fractions, and stir evenly to obtain a hydrophilic modifier.

[0043] (2) Immerse the clean PE film washed and dried with pure water in the hydrophilic modifier for 2 minutes. After fully wetting, take out the film, clean it with deionized water, and transfer it to the oven for drying to obtain the permanent hydrophilic polyethylene film HPE3.

[0044] (3) Mix m-phenylenediamine (MPD, 3.0 wt%) and sodium hydroxide (NaOH, 0.01 wt%) and dissolve in deionized water to obtain an aqueous solution; then weigh an appropriate amount of trimesoyl chloride (TMC, 0.15 wt%) and dissolve in n-hexane to prepare an oil solution;

[0045] (4) Immerse the prepared dry hydrophilic polyethylene membrane in an aqueous solution for 1 minute until the membrane surface is fully wetted. Then remove the membrane and carefully blow dry the surface moisture with an air gun. Then immerse it in an oil solution for 1 minute and remove it. After rinsing with deionized water, place it in an oven to dry and obtain polyethylene composite reverse osmosis membrane RO-HPE3.

[0046] Example 4

[0047] (1) Weigh an appropriate amount of anhydrous ethanol and isopropanol (AE:IPA = 1:1, 20wt%), alkyl alcohol ether phosphate (AEP, 1.0wt%), hyaluronic acid (HA, 0.5wt%), and thiolated chitosan (HSCS, 0.1wt%) and dissolve them in deionized water according to the set mass fractions, and stir evenly to obtain a hydrophilic modifier;

[0048] (2) Immerse the clean PE film washed and dried with pure water in the hydrophilic modifier for 2 minutes. After fully wetting, take out the film, clean it with deionized water, and transfer it to the oven for drying to obtain the permanent hydrophilic polyethylene film HPE4.

[0049] (3) Mix m-phenylenediamine (MPD, 3.0 wt%) and sodium hydroxide (NaOH, 0.01 wt%) and dissolve in deionized water to obtain an aqueous solution; then weigh an appropriate amount of trimesoyl chloride (TMC, 0.15 wt%) and dissolve in n-hexane to prepare an oil solution;

[0050] (4) Immerse the prepared dry hydrophilic polyethylene membrane in an aqueous solution for 1 minute until the membrane surface is fully wetted. Then remove the membrane and carefully blow dry the surface moisture with an air gun. Then immerse it in an oil solution for 1 minute and remove it. After rinsing with deionized water, place it in an oven to dry to obtain polyethylene composite reverse osmosis membrane RO-HPE4.

[0051] Example 5

[0052] (1) Weigh an appropriate amount of anhydrous ethanol and glycerol (AE:GL = 1:1, 20wt%), sodium dodecylbenzenesulfonate (SDBS, 1.0wt%), polyethyleneimine (PEI, 0.5wt%), and tannic acid (DA, 0.1wt%) and dissolve them in deionized water according to the set mass fractions, and stir evenly to obtain a hydrophilic modifier.

[0053] (2) Immerse the clean PE film washed and dried with pure water in the hydrophilic modifier for 2 minutes. After fully wetting, take out the film, clean it with deionized water, and put it into the oven to dry to obtain the permanent hydrophilic polyethylene film HPE5.

[0054] (3) Mix m-phenylenediamine (MPD, 4.0 wt%) and sodium hydroxide (NaOH, 0.01 wt%) and dissolve in deionized water to obtain an aqueous solution; then weigh an appropriate amount of trimesoyl chloride (TMC, 0.2 wt%) and dissolve in n-hexane to prepare an oil solution;

[0055] (4) Immerse the prepared dry hydrophilic polyethylene membrane in an aqueous solution for 1 minute until the membrane surface is fully wetted. Then remove the membrane and carefully blow dry the surface moisture with an air gun. Then immerse it in an oil solution for 1 minute and remove it. After rinsing with deionized water, place it in an oven to dry and obtain a polyethylene composite reverse osmosis membrane RO-HPE5.

[0056] Example 6

[0057] (1) Weigh appropriate amounts of the blended isopropanol and glycerol (IPA:GL = 1:1, 20wt%), sodium dodecyl sulfate (SDS, 1.0wt%), ε-polylysine (ε-PL, 0.5wt%), and tannic acid (DA, 0.1wt%) and dissolve them in deionized water according to the set mass fractions, and stir evenly to obtain a hydrophilic modifier;

[0058] (2) Immerse the clean PE film washed and dried with pure water in the hydrophilic modifier for 2 minutes. After fully wetting, take out the film, clean it with deionized water, and put it into the oven to dry to obtain the permanent hydrophilic polyethylene film HPE6.

[0059] (3) Mix m-phenylenediamine (MPD, 4.0 wt%) and sodium hydroxide (NaOH, 0.01 wt%) and dissolve in deionized water to obtain an aqueous solution; then weigh an appropriate amount of trimesoyl chloride (TMC, 0.2 wt%) and dissolve in n-hexane to prepare an oil solution;

[0060] (4) Immerse the prepared dry hydrophilic polyethylene membrane in an aqueous solution for 1 minute until the membrane surface is fully wetted. Then remove the membrane and carefully blow dry the surface moisture with an air gun. Then immerse it in an oil solution for 1 minute and remove it. After rinsing with deionized water, place it in an oven to dry to obtain polyethylene composite reverse osmosis membrane RO-HPE6.

[0061] Performance characterization and test results

[0062] (1) Surface morphology, contact angle and roughness of the diaphragm

[0063] The surface morphology, contact angle, and roughness of the hydrophilic polyethylene film HPE1 and the polyethylene-based composite reverse osmosis membrane RO-HPE1 prepared in Example 1 were characterized, and the results are as follows: Figure 1 As shown, both hydrophilic agent modification and interfacial polymerization can improve the surface water contact angle and roughness of the membrane, exhibiting excellent hydrophilicity. Furthermore, the PA layer on the RO-HPE1 surface grows uniformly, and the leaf structure is intact.

[0064] (2) Chemical composition analysis of the membrane

[0065] Infrared spectral characterization analysis was performed on the hydrophilic polyethylene film HPE1 and the polyethylene-based composite reverse osmosis membrane RO-HPE1 prepared in Example 1. The results are as follows: Figure 2 As shown in the figure, the prepared HPE1 and RO-HPE1 exhibit characteristic absorption peaks of the hydrophilic agent-modified component and the interfacial polymerization product, respectively, in the spectrum. This indicates that the hydrophilicization of the PE membrane was successfully achieved through impregnation modification and interfacial polymerization processes, and a cross-linked and fully aromatic PA layer was formed on the HPE carrier.

[0066] (3) Membrane desalination performance

[0067] 500 ppm NaCl and MgSO4 solutions were prepared using deionized water as feed solutions. The reverse osmosis membranes prepared in the examples were tested on a cross-flow membrane testing platform. Test conditions: operating pressure 60 psi, solution temperature 25℃, pH 6.5-7.5. The water flux and rejection rate after 30 min of membrane operation were measured, and the results are shown in Table 1.

[0068] Table 1. Membrane desalination performance

[0069]

[0070] As shown in Table 1, the test membranes prepared in each embodiment have a higher NaCl retention capacity than MgSO4. Changing the composition of the hydrophilic agent changes the RO-HPE membrane's salt ion retention capacity, but the increase or decrease is not significant, and the overall membrane flux increases only slightly.

[0071] (4) Long-term operational stability of the diaphragm

[0072] The long-term operational stability of the reverse osmosis membrane prepared in Example 1 was determined and evaluated using 500 ppm NaCl and MgSO4 solutions prepared with deionized water as feed solutions. Test conditions: operating pressure 60 psi, solution temperature 25℃, pH 6.5-7.5. The membrane was continuously operated for 12 hours, and the membrane water flux and rejection rate were recorded periodically. The results are as follows: Figure 3 As shown.

[0073] The flux and rejection rate of the polyethylene-based composite reverse osmosis membrane RO-HPE prepared in Example 1 for NaCl solution (500 ppm) at 60 Psi are shown in the figure. The RO-HPE membrane prepared in this invention exhibited a flux of 18.3 L·m⁻¹ for NaCl solution (500 ppm) after the initial 1 hour of operation. -2 ·h -1 ·bar -1 The rejection rate was 98.4%, and after 12 hours of continuous operation, the flux decreased to 16.4 L·m³. -2 ·h -1 ·bar -1 Furthermore, even with a rejection rate increased to 98.7%, it still exhibits good separation performance, thus demonstrating excellent performance stability.

[0074] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should be considered within the scope of protection of this invention.

Claims

1. A method for preparing a polyethylene-based composite reverse osmosis membrane, characterized in that, Specifically, the steps include the following: (1) Mix m-phenylenediamine and sodium hydroxide and dissolve them in deionized water to obtain an aqueous solution; then weigh an appropriate amount of pyromellitic chloride and dissolve it in n-hexane to prepare an oil solution. (2) Immerse the dried hydrophilic polyethylene membrane in an aqueous solution until the membrane surface is fully wetted. Then remove the membrane and blow dry the surface moisture. Then immerse it in an oil solution to react and remove it. Wash it with deionized water and then dry it in an oven to obtain a polyethylene composite reverse osmosis membrane.

2. The preparation method according to claim 1, characterized in that, The hydrophilic polyethylene-based film is prepared by interfacial polymerization reaction of hydrophilic modified polyethylene film. The modifier used for hydrophilic modification of polyethylene film consists of 20-30 wt% alcohol small molecules, 0.5-2 wt% surfactant, 0.5-2 wt% hydrophilic additive, and 0.1-0.5 wt% adhesive.

3. The preparation method according to claim 2, characterized in that, The alcohol molecules are one or more organic alcohol aqueous solutions such as ethanol, isopropanol, and glycerol, combined in any proportion.

4. The preparation method according to claim 2, characterized in that, The surfactant is one or more of the following surfactants in any proportion: sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium fatty alcohol ether sulfate, alkyl alcohol ether phosphate, etc.

5. The preparation method according to claim 2, characterized in that, The hydrophilic additive is one or more of synthetic or natural hydrophilic polymers such as polyethyleneimine, polyvinyl alcohol, sodium alginate, hyaluronic acid, and ε-polylysine, combined in any proportion.

6. The preparation method according to claim 2, characterized in that, The adhesive is one or more of the following biomimetic substances with inherent viscosity: dopamine and its derivatives, catechol and its derivatives, tannic acid and its derivatives, thiolated chitosan, etc., in any proportion.

7. The preparation method according to claim 1, characterized in that, The concentration of intermediate-phenylenediamine in the aqueous solution is 1.0–4.0 wt%.

8. The preparation method according to claim 1, characterized in that, The concentration of sodium hydroxide in the aqueous solution is 0.01–0.05 wt%.

9. The preparation method according to claim 1, characterized in that, The concentration of pyromellitic chlorobenzene chloride in the oil phase solution is 0.1–0.2 wt%.

10. A polyethylene-based composite reverse osmosis membrane prepared by the preparation method according to any one of claims 1-9.

11. A reverse osmosis membrane element, characterized in that, The polyethylene-based composite reverse osmosis membrane prepared by the preparation method according to any one of claims 1-9 is used for preparation.

12. The application of the polyethylene-based composite reverse osmosis membrane prepared by the preparation method according to any one of claims 1-9 in the field of reverse osmosis filtration.

Images