Preparation method of reverse osmosis membrane with anti-cation capacity and application thereof

Abstract

The application belongs to the technical field of membrane separation, and particularly relates to a preparation method of a reverse osmosis membrane with cation resistance and application thereof. The application realizes integration of TiO2 nanoparticles coupled with high molecular weight PEI in a polyamide rejection layer by coupling TiO2 with polyethylene imine to form nanoparticles (PEI-TiO2) second monomers with surface amine groups and co-reacting m-phenylenediamine with an acyl chloride monomer. The application solves the problem that the surface energy of nanoparticles is high, agglomeration occurs in the doping process, and defects are brought to the polyamide layer, and solves the problem that the electric potential of the polyamide layer is difficult to adjust, thereby causing weak cation resistance of the polyamide layer. The application provides a preparation method of a reverse osmosis membrane with cation resistance, which is simple, efficient and easy to scale up.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing a reverse osmosis membrane with anti-cation capability and its application. Background Technology

[0002] With the surge in global population and the irreversible depletion of fossil fuels, water scarcity and energy crisis have become the core contradictions restricting sustainable social development. Traditional water treatment technologies struggle to balance high desalination efficiency with low energy consumption, while membrane separation technology, due to its green and efficient characteristics, has become a key path to overcome this bottleneck.

[0003] Reverse osmosis membrane technology, as the dominant solution in the field of desalination, has become a core component for seawater desalination and reclaimed water reuse due to its high efficiency in retaining multivalent ions and small organic molecules. Currently, commercially available reverse osmosis membranes are mainly polyamide-based, which have a dense-porous composite structure constructed through interfacial polymerization. However, their permeability and retention capacity are mutually limited, and traditional interfacial polymerization cannot overcome the "trade-off" effect. At the same time, the smooth but negatively charged membrane surface easily adsorbs hydrophobic organic matter or positively charged pollutants, leading to irreversible fouling.

[0004] Patent CN104028118B describes the preparation of an amphoteric cationic polymer using free radical polymerization, followed by the preparation of an amphoteric sodium carboxymethyl cellulose complex via ionic crosslinking. This complex is then added to the aqueous monomer solution used to prepare the polyamide membrane. An interfacial polymerization method is then used to obtain a polyamide reverse osmosis membrane containing the amphoteric sodium carboxymethyl cellulose complex. The complex exhibits excellent hydrophilicity, fouling resistance, and a unique nanoparticle structure, which, while maintaining the high rejection rate of inorganic salts in the polyamide membrane, significantly improves the membrane's water permeability and resistance to contaminants.

[0005] Patent CN119819146B describes a high-retention and fouling-resistant polyamide functional layer on a porous ultrafiltration membrane by using an aromatic cationic surfactant containing two benzene rings to regulate the interfacial polymerization formulation of polyamine monomers and polyacrylamide monomers. The surface potential of the polyamide retention layer is >-20mV after testing.

[0006] Existing technical solutions show that adjusting the interfacial polymerization formulation to increase the membrane surface potential, or grafting a graft with an opposite charge to the target pollutant onto the membrane surface, can effectively improve the membrane's antifouling performance.

[0007] However, existing technologies have several drawbacks: 1. Due to the high surface energy of nanoparticles, agglomeration occurs during the doping process, resulting in defects in the polyamide layer; 2. The potential of the polyamide layer is difficult to adjust, leading to weak resistance to cations; 3. Significant changes are required to existing processes, necessitating the rebuilding of production lines and incurring high improvement costs. Summary of the Invention

[0008] To address the problems of existing technologies, such as: 1. defects introduced into the polyamide layer due to particle doping; 2. difficulty in adjusting the potential of the polyamide layer, resulting in weak resistance to cations; 3. significant changes to existing processes, requiring the reconstruction of production lines and incurring high improvement costs.

[0009] This invention provides a method for preparing a reverse osmosis membrane with anti-cation capability. This method is simple, efficient, and easy to scale up.

[0010] By coupling TiO2 with polyethyleneimine to form nanoparticles with surface amine groups (PEI-TiO2) as a second monomer, and co-reacting m-phenylenediamine with acyl chloride monomers, it is possible to integrate high-molecular-weight coupled TiO2 nanoparticles within a polyamide trapping layer. This ensures a dense, negatively charged polyamide upper layer dominated by m-phenylenediamine, while the TiO2 nanoparticles (PEI-TiO2) coupled with the cationic macromolecular polyethyleneimine, acting as a second monomer, promote the formation of a loose, positively charged lower layer, thereby creating a polyamide film with significant charge and structural heterogeneity.

[0011] Specifically, this is achieved through the following technical solutions:

[0012] A method for preparing a reverse osmosis membrane with cation resistance, characterized in that the method includes the following steps:

[0013] (1) Synthesis of PEI-TiO2: TiO2 was ultrasonically dispersed evenly in deionized water, and then 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinamide were added and stirred for 40 min to 80 min to carry out the reaction. The reactants were then centrifuged to obtain a white solid. The obtained white solid was ultrasonically dispersed again in water and added to a polyethyleneimine solution. The mixture was stirred at room temperature for 5 to 8 h to carry out the reaction to obtain PEI-TiO2. After the reaction was completed, the reaction solution was centrifuged to obtain white PEI-TiO2 solid, which was washed with ethanol and deionized water, and then dried in an oven for later use.

[0014] (2) Preparation of aqueous solution: Add amine monomer, sodium hydroxide and PEI-TiO2 to deionized water and stir ultrasonically to obtain a white and uniform aqueous suspension;

[0015] (3) Preparation of organic phase solution: Add acyl chloride monomer to organic solvent and stir evenly to obtain organic phase solution;

[0016] (4) Interfacial polymerization to prepare reverse osmosis membrane: The polysulfone ultrafiltration membrane is immersed in the aqueous suspension obtained in step (2), and the residual water on the surface of the ultrafiltration membrane is removed after a period of time; then the polysulfone ultrafiltration membrane with the residual water removed is immersed in the organic phase solution prepared in step (3), and then allowed to stand and dry after a period of time.

[0017] (5) Post-treatment: The membrane obtained in step (4) above is placed in an oven for heat treatment to obtain a reverse osmosis membrane with anti-cation capability.

[0018] The amine monomer in step (2) is one or a combination of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, benzylenediamine, 2,4-diaminotoluene, 2,4-diaminophenol, 2,4-diaminobenzoic acid, 1,6-hexanediamine, and 1,5-diaminonaphthalene; the proportion of the amine monomer in the aqueous solution is 0.1 to 4 wt%, and the proportion of sodium hydroxide in the aqueous solution is 0.1 to 4 wt%; the nanoparticles are one or a combination of titanium dioxide, silicon dioxide, nanomolecular sieves, zinc oxide, carbon nanotubes, zeolite imidazole ester metal-organic nanoframeworks, UIO-66 and its corresponding derivatives, graphene oxide, Mxene, and other hydrophilic two-dimensional nanosheets; the proportion of nanoparticles is 0.01 to 3 wt%, and the polyethyleneimine used has a molecular weight of 300 to 600, 1200 to 1800, or 10000 to 700000.

[0019] In step (3), the organic solvent is one or more of n-decane, n-hexane, cyclohexane and n-heptane; the acyl chloride monomer is one or more of trimesoyl chloride, isophthaloyl chloride and phthaloyl chloride; the proportion of the acyl chloride monomer in the organic phase solution is 0.1 to 0.4 wt%.

[0020] In step (4), the immersion time of the polysulfone ultrafiltration membrane in the aqueous solution is 0.5 to 3 min, and the residual water on the surface is removed by air drying; the immersion time in the organic phase is 0.5 to 2 min, and the residual organic solution on the surface is removed by air drying.

[0021] Step (5) The oven temperature is 60 to 90 ℃ and the heat treatment time is 3 to 10 min.

[0022] Beneficial effects

[0023] This invention provides a method for preparing a reverse osmosis membrane with anti-cation capability and its application, the specific effects of which are:

[0024] (1) Adding PEI-TiO2 to the aqueous phase can form a TFN film with greater permeability during the interfacial reaction. Furthermore, due to the polyethyleneimine coupled on the surface of the nanoparticles, the nanoparticles form a second monomer to participate in the interfacial polymerization reaction, thereby avoiding the defects in the polyamide layer caused by the agglomeration of nanoparticles due to their high surface energy.

[0025] (2) The introduction of polyethyleneimine can effectively regulate the potential of the polyamide layer, thereby giving the polyamide layer anti-cation reverse osmosis membrane.

[0026] (3) Compared with the industrialized reverse osmosis membrane process, the present invention does not change its process and is easy to scale up. Attached Figure Description

[0027] none Detailed Implementation

[0028] 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.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0030] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0031] To better understand the technical solution of the present invention, the present invention will be further processed in conjunction with specific embodiments below, but the present invention is not limited to the following embodiments.

[0032] A highly permeable reverse osmosis membrane with cation resistance, the method comprising the following steps:

[0033] Example 1:

[0034] (1) Add 20 g of m-phenylenediamine and 11 g of NaOH to 969 g of deionized water and stir evenly at room temperature to obtain a 2 wt% m-phenylenediamine aqueous mixed solution.

[0035] (2) Add 2 g of trimesoyl chloride to 1000 g of n-hexane and stir at room temperature to obtain a 0.2 wt% trimesoyl chloride organic solution.

[0036] (3) Immerse the polysulfone ultrafiltration membrane in the m-phenylenediamine solution of step (1) for 1 min, take it out and blow dry the residual water on its surface with an air knife; then immerse the ultrafiltration membrane that has been immersed in the m-phenylenediamine solution in the pyromellitic chloride solution of step (2) for 1 min, and let it stand to dry.

[0037] (4) The polyamide reverse osmosis membrane obtained in step (3) above is placed in an oven at 75 °C for heat treatment. After 5 min, it is taken out and placed in deionized water.

[0038] Example 2:

[0039] (1) Disperse 1g of TiO2 nanoparticles in deionized water with pH adjusted to 5.5, then sonicate to disperse evenly, add 100mM of 1-ethyl-3-(3-dimethylaminopropylcarbodiimide) and 50mM of N-hydroxysuccinamide and stir for 1h, centrifuge and wash, then sonicate to disperse 100mg / ml of polyethyleneimine with a molecular weight of 70000, then centrifuge, wash and dry for later use.

[0040] (2) Add 20 g of m-phenylenediamine, 11 g of triethylamine and 0.5 g of PEI-TiO2 to 968.5 g of deionized water and stir evenly at room temperature to obtain a 2 wt% aqueous mixed solution of m-phenylenediamine.

[0041] (3) Add 2 g of trimesoyl chloride to 1000 g of n-hexane and stir evenly at room temperature to obtain a 0.2 wt% trimesoyl chloride organic solution.

[0042] (4) Immerse the polysulfone ultrafiltration membrane in the m-phenylenediamine solution of step (1) for 1 min, take it out and blow dry the residual water on its surface with an air knife; then immerse the ultrafiltration membrane that has been immersed in the m-phenylenediamine solution in the pyromellitic chloride solution of step (2) for 1 min, take it out and let it stand to dry.

[0043] (5) The polyamide reverse osmosis membrane obtained in step (4) above is placed in an oven at 75 °C for heat treatment and taken out after 5 min.

[0044] Test example:

[0045] The reverse osmosis membranes obtained in Examples 1 and 2 were subjected to performance tests under the following conditions: 2000 ppm NaCl aqueous solution, operating pressure of 1.55 MPa, temperature of 25 °C, and pH of 7.0 ± 0.5. Under these conditions, the water flux and desalination rate of the membranes in Examples 1 and 2 were tested. The membrane performance of Examples 1 and 2 is shown in Table 1.

[0046] Table 1. Membrane performance of Examples 1 and 2

[0047]

[0048] The experimental results in Table 1 show that when PEI-TiO2 nanoparticles are added to the aqueous phase, the water flux of the membrane increases by 3.3 times, and the retention rate does not decrease significantly.

[0049] Example 3

[0050] The test solution was replaced with a 15 ppm aqueous solution of dodecyltrimethylammonium bromide. After continuous operation for 16 hours, the water flux and desalination rate of the membranes in Examples 1 and 2 were tested after 16 hours of cation fouling.

[0051] Table 2. Membrane performance of Examples 1 and 2 after 16 hours of cation contamination.

[0052]

[0053] The experimental results in Table 1 show that the water flux of the membrane decreased to varying degrees after adding PEI-TiO2 nanoparticles to the aqueous phase. The decrease rate in Example 1 was 25.14%, while the decrease rate in Example 2 was 60.4%, indicating that the reverse osmosis membrane has higher resistance to cation fouling after adding PEI-TiO2 nanoparticles.

[0054] Example 4

[0055] The three-dimensional TiO2 nanoparticles were replaced with three-dimensional SiO2, two-dimensional hydrotalcite-like nanosheets (ZnFe-LDH), vermiculite nanosheets, one-dimensional carbon nanotubes, and one-dimensional manganese oxide nanowires, respectively. Polyethyleneimine was coupled to the surface of the above nanomaterials using the coupling method described in Example 1 and participated in the reaction in an aqueous solution.

[0056] Table 3. Film properties of different nanomaterials added to polyamide layers

[0057]

[0058] Table 3 shows that TiO2 nanoparticles exhibit superior desalination rate and permeation flux compared to other selected analog nanomaterials. Notably, the polyamide retention layer blended with carbon nanotubes maintains good retention performance while still exhibiting high water flux, presumably due to the additional mass transfer channels provided by the carbon nanotubes.

[0059] This invention integrates high-molecular-weight PEI-coupled TiO2 nanoparticles (PEI-TiO2) with surface amine groups into a polyamide retaining layer by reacting TiO2 with polyethyleneimine to form a second monomer, and m-phenylenediamine with an acyl chloride monomer. On one hand, this ensures a dense, negatively charged polyamide upper layer dominated by m-phenylenediamine; on the other hand, the TiO2 nanoparticles (PEI-TiO2) coupled with the cationic macromolecular polyethyleneimine, acting as a second monomer, promote the formation of a loose, positively charged lower layer, thereby creating a polyamide film with significant charge and structural heterogeneity.

[0060] This invention addresses, to some extent, the problems in existing technologies where the high surface energy of nanoparticles leads to agglomeration during doping, resulting in defects in the polyamide layer. It also solves the problem of weak cationic resistance in the polyamide layer due to the difficulty in adjusting its potential. This invention requires minimal changes to existing processes and has low improvement costs.

[0061] This invention provides a method for preparing a reverse osmosis membrane with anti-cation capability. This method is simple, efficient, and easy to scale up.

[0062] While preferred embodiments of the present invention have been disclosed above, they are not intended to limit the invention. Any researcher in the art can modify and alter the research scheme of the present invention using the design parameters and content of the disclosed embodiments without departing from the spirit and scope of the invention. Therefore, any simple modifications, parameter changes, and alterations made to the above embodiments based on the research essence of the present invention, without departing from the content of the present invention, fall within the protection scope of the present invention.

Claims

1. A method for preparing a reverse osmosis membrane with cation resistance, characterized in that, The method includes the following steps: (1) Synthesis of PEI-TiO2: TiO2 was ultrasonically dispersed evenly in deionized water, and then 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinamide were added and stirred for 40 min to 80 min to carry out the reaction. The reactants were then centrifuged to obtain a white solid. The obtained white solid was ultrasonically dispersed again in water and added to a polyethyleneimine solution. The mixture was stirred at room temperature for 5 to 8 h to carry out the reaction to obtain PEI-TiO2. After the reaction was completed, the reaction solution was centrifuged to obtain white PEI-TiO2 solid, which was washed with ethanol and deionized water, and then dried in an oven for later use. (2) Preparation of aqueous solution: Add amine monomer, sodium hydroxide and PEI-TiO2 to deionized water and stir ultrasonically to obtain a white and uniform aqueous suspension; (3) Preparation of organic phase solution: Add acyl chloride monomer to organic solvent and stir evenly to obtain organic phase solution; (4) Interfacial polymerization to prepare reverse osmosis membrane: The polysulfone ultrafiltration membrane is immersed in the aqueous suspension obtained in step (2), and the residual water on the surface of the ultrafiltration membrane is removed after a period of time; then the polysulfone ultrafiltration membrane with the residual water removed is immersed in the organic phase solution prepared in step (3), and then allowed to stand and dry after a period of time. (5) Post-treatment: The membrane obtained in step (4) above is placed in an oven for heat treatment to obtain a reverse osmosis membrane with anti-cation capability; The amine monomer in step (2) is one or a combination of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, benzylenediamine, 2,4-diaminotoluene, 2,4-diaminophenol, 2,4-diaminobenzoic acid, 1,6-hexanediamine, and 1,5-diaminonaphthalene; the proportion of the amine monomer in the aqueous solution is 0.1 to 4 wt%, and the proportion of sodium hydroxide in the aqueous solution is 0.1 to 4 wt%; the polyethyleneimine used has a molecular weight of 300 to 600 Da, 1200 to 1800 Da, or 10000 to 700000 Da. The acyl chloride monomer in step (3) is one or more of pyromellitic chloride, isophthalic chloride and phthalic chloride; the proportion of the acyl chloride monomer in the organic phase solution is 0.1 to 0.4 wt.

2. The method for preparing a reverse osmosis membrane with anti-cation capability as described in claim 1, characterized in that, In step (3), the organic solvent is one or more of n-decane, n-hexane, cyclohexane, and n-heptane.

3. The method for preparing a reverse osmosis membrane with anti-cation capability as described in claim 1, characterized in that, In step (4), the immersion time of the polysulfone ultrafiltration membrane in the aqueous solution is 0.5 to 3 min, and the residual water on the surface is removed by air drying; the immersion time in the organic phase is 0.5 to 2 min, and the residual organic solution on the surface is removed by air drying.

4. The method for preparing a reverse osmosis membrane with anti-cation capability as described in claim 1, characterized in that, Step (5) The oven temperature is 60 to 90 ℃ and the heat treatment time is 3 to 10 min.

5. A method for preparing a reverse osmosis membrane with anti-cation capability as described in any one of claims 1 to 4, characterized in that, The reverse osmosis membrane prepared by the method has applications in water conservation and reuse in circulating cooling water systems, wastewater treatment in metal processing and electroplating, preparation of ultrapure water in the electronics industry, and water treatment in pharmaceutical and food processing.

6. A method for preparing a reverse osmosis membrane with anti-cation capability as described in any one of claims 1 to 4, characterized in that, The reverse osmosis membrane prepared by the method is used in the treatment and resource utilization of high-salt wastewater and the treatment of high-hardness water.

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