Reverse osmosis membrane, preparation method and application in field of seawater desalination
By performing activation crosslinking, modified crosslinking and reduction treatment on the reverse osmosis membrane, the problems of insufficient performance and poor durability of traditional seawater desalination membranes are solved, and more efficient desalination and boron deborosion performance and longer service life are achieved.
Patent Information
- Application Number
- CN202411263878.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-10
- Publication Date
- 2025-02-11
AI Technical Summary
In applications, traditional seawater desalination reverse osmosis membranes have problems such as low desalination and boron desalination, impotence to pollution and short service life.
By performing activation crosslinking treatment, modified crosslinking treatment and reduction treatment on the reverse osmosis membrane body, the desalination and boron deborosion properties of the membrane are improved and the anti-pollution performance is enhanced.
It improves the desalination and boron desalination performance of seawater reverse osmosis membrane, extends the service life of the membrane, reduces the system operating costs, and improves the anti-pollution performance.
Smart Images
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Abstract
Description
Technical Field
[0001] The present application relates to the field of reverse osmosis filtration technology, and in particular to a reverse osmosis membrane, a preparation method and its application in the field of seawater desalination. Background Art
[0002] In today's water shortage, seawater desalination technology is playing an increasingly important role in alleviating the problem of water shortage in coastal areas. Reverse osmosis membrane is the most promising and fastest-growing water treatment technology in seawater desalination. Due to the high salt content in seawater, the large differences in regional salt concentration and the proportion of various salt components, the complex water quality, and the presence of a certain concentration of boron. Traditional seawater desalination reverse osmosis membranes have problems in application such as low desalination and boron removal rates, poor pollution resistance, and short service life. The development of more durable, high-performance seawater desalination reverse osmosis membranes has always been the focus of market demand.
[0003] The most widely used desalination membrane material is aromatic polyamide reverse osmosis membrane, which is prepared by interfacial polymerization. First, a certain amount of casting liquid is coated on the non-woven fabric, and the base membrane is obtained by gel phase transformation. The base membrane is immersed in an aqueous phase containing a certain concentration of amine monomers and other additives for a certain period of time, and the excess aqueous phase on the surface is removed. Then, an organic phase containing a certain concentration of acyl chloride monomers is coated, and a reverse osmosis membrane is formed through a condensation reaction at the oil-water interface. The organic phase on the surface is dried and rinsed in various ways, coated with a certain concentration of PVA and dried again to obtain a finished desalination reverse osmosis membrane.
[0004] The desalination layer of the seawater desalination membrane prepared by conventional processes is rich in carboxyl and amino groups, the functional groups are not fully utilized, the free volume of the polymer chain is large, the deboronization rate is low, and the anti-pollution performance is poor. In addition, the coated PVA will be washed off after multiple alkaline washings, and the desalination layer can no longer be protected, resulting in a short service life of the seawater membrane and an increase in system operating costs.
[0005] In the post-treatment of traditional seawater desalination reverse osmosis membranes, the alkaline washing process hydrolyzes the acyl chloride groups on the surface of the desalination layer into carboxyl groups, and the heat treatment washes out the unreacted amine monomers in the base membrane and the lower part of the desalination layer. The modification process uses NaClO for substitution reaction to improve the performance of the membrane, or uses NaNO2 solution treatment to convert the amino groups in the desalination layer into diazo groups to improve the performance of the membrane. The coated protective layer is a single PVA component or a component cross-linked with PVA glutaraldehyde.
[0006] Among the above technologies, although post-treatment with NaClO can improve the performance of seawater desalination reverse osmosis membranes, aromatic polyamide membrane materials are not chlorine-resistant in themselves, and the long-term service life of membrane materials prepared using this process will be reduced. Although the performance of membranes post-treated with NaNO2 solution can also be improved, the aromatic diazonium salts formed are not very stable in themselves, and will gradually convert into phenols or aromatic hydrazines in the later stage, which will reduce the free volume of the molecular chain in the desalination layer and reduce the desalination rate. The converted aromatic hydrazines have azo groups and have poor tolerance to alkaline environments. Coated PVA or cross-linked PVA can keep the performance of the membrane material stable in a short period of time, but it will still be hydrolyzed or washed away after long-term use, and cannot fundamentally solve the market use pain points of seawater desalination reverse osmosis membranes. Summary of the invention
[0007] In order to solve at least one of the above technical problems, a (purpose of the invention) is developed. The present application provides a reverse osmosis membrane, a preparation method and its application in the field of seawater desalination.
[0008] On the one hand, the present application provides a reverse osmosis membrane, which is obtained by subjecting a reverse osmosis membrane body to an activation cross-linking treatment, a modification cross-linking treatment, and a reduction treatment.
[0009] Optionally, the activated crosslinking treatment uses an activated crosslinking agent, and the activated crosslinking agent is prepared from the following components in percentage by mass:
[0010] Component a: 92-98.5 wt%;
[0011] Component b: 0.05-0.5wt%;
[0012] Component c: 0.5-3.8 wt%;
[0013] Component a is at least one of benzene, toluene, ethylbenzene, xylene, chlorobenzene, dichlorobenzene and styrene;
[0014] Component b is at least one of dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), 4-N,N-dimethylpyridine (DMAP), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI), and 1-hydroxybenzotriazole (HOBt);
[0015] Component c is at least one of a fatty amine containing an unsaturated bond, an aliphatic alkane containing an amino group, an aromatic amine, and an amino ether. More preferably, component c is at least one of 1,7-diaminoheptane and its isomers, 1,8-diaminooctane and its isomers.
[0016] Optionally, the temperature of the activated cross-linking agent is 35-65°C.
[0017] Optionally, the modified cross-linking treatment uses a modified cross-linking agent, and the modified cross-linking agent is prepared from the following components in percentage by mass:
[0018] Component a: 97-99.5wt%;
[0019] Component d: 0.5-5wt%;
[0020] Component e: 0.05-0.5wt%;
[0021] Component a is at least one of benzene, toluene, ethylbenzene, xylene, chlorobenzene, dichlorobenzene and styrene;
[0022] Component d is at least one of carbonyldiimidazole, 2-phenylbenzimidazole, hexaaryldiimidazole, diimidazole benzene, 2,2-diimidazole methane, and N,N-thiocarbonyldiimidazole;
[0023] Component e is at least one of O-(7-azabenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate (HATU), 6-chlorobenzotriazole-1,1,3,3-tetramethyluronium hexafluorophosphate (HCTU), benzotriazole-N,N,N,N-tetramethyluronium hexafluorophosphate (HBTU), O-benzotriazole-N,N,N,N-tetramethyluronium tetrafluoroborate (TBTU), and 2-succinimidyl-1,1,3,3-tetramethyluronium tetrafluoroborate (TSTU);
[0024] Optionally, the temperature of the modified cross-linking agent is 65-95°C.
[0025] Optionally, the reduction treatment uses a reducing agent, and the reducing agent is prepared from the following components in percentage by mass:
[0026] Component f: 1-5 wt%;
[0027] Tetrahydrofuran: 95-98wt%;
[0028] The mass ratio of boron chloride is: 0.5-2wt%;
[0029] Component f is at least one of sodium hydride, potassium hydride, lithium aluminum hydride, magnesium dihydride, and calcium hydride.
[0030] Optionally, the temperature of the reducing agent is 10-25°C.
[0031] In a second aspect, the present application provides a method for preparing the above-mentioned reverse osmosis membrane, comprising the following steps:
[0032] S1. Preparation of reverse osmosis membrane
[0033] After a certain amount of aqueous solution is coated on the surface of the base membrane, excess aqueous phase droplets on the surface are removed by a pressure roller and an air knife; then an organic phase solution is coated, and after a certain reaction time, excess organic phase on the surface is dried in an oven to obtain a primary reverse osmosis membrane; sodium carbonate solution is sprayed on the surface of the primary reverse osmosis membrane, and then it is washed with pure water, and excess pure water on the surface is removed by an air knife to obtain a reverse osmosis membrane body;
[0034] S2. Activation and cross-linking treatment
[0035] The activated cross-linking agent is coated on the surface of the reverse osmosis membrane body, and after reacting for 5 minutes, the excess solution on the surface is dried in an oven. Then the membrane is washed in high-temperature deionized water at 70°C for 6 minutes to wash out the excess water-phase amine monomer in the membrane, and the excess water on the surface is removed with an air knife;
[0036] S3, modified cross-linking treatment
[0037] A modified cross-linking agent is coated on the surface of the membrane after activation cross-linking and high-temperature cleaning. After the reaction is completed, an air knife is used to remove excess solution on the surface.
[0038] S4. Restore Process
[0039] A reducing agent is coated on the surface of the membrane, the reaction time is 3 minutes, and excess tetrahydrofuran on the surface is removed with an air knife; the membrane is immersed in a sodium bisulfite solution with a concentration of 0.2% to 3% for 3 to 6 minutes, and after the excess sodium bisulfite solution on the surface is removed with an air knife, the membrane is dried in an oven at 70° C. for 2 minutes to obtain a finished reverse osmosis membrane.
[0040] Optionally, the oven drying temperature in S2 is 100-130° C., and the drying time is 3.5-8 min.
[0041] Optionally, in S3, the reaction time after coating the modified cross-linking agent is 3 to 6 minutes;
[0042] And / or, in S4, the membrane is immersed in the sodium bisulfite solution for 2.5 to 4.5 minutes.
[0043] In a third aspect, the present application provides the application of the above-mentioned reverse osmosis membrane in the field of seawater desalination.
[0044] In summary, the present invention includes at least one of the following beneficial technical effects:
[0045] 1. The reverse osmosis membrane prepared in the present application is activated by a cross-linking agent to activate the surface carboxyl groups, and the principle of azeotropic thermal reaction is used to promote the cross-linking bridging effect between the amino groups of the activated cross-linking agent amine substances and the carboxyl groups on the surface of the desalination layer, thereby removing excess water from the reaction and promoting the overall reaction to move to the right, thereby reducing the content of carboxyl groups on the surface of the desalination layer, increasing the cross-linking degree of the desalination layer, and enhancing the desalination and deboronization performance of the seawater desalination reverse osmosis membrane;
[0046] 2. The reverse osmosis membrane prepared in the present application is modified with a cross-linking agent, and an imidazole substance is used as an acylating agent to react the unreacted amino groups in the desalination layer in an organic solvent to form urea. On the one hand, the amino groups at different positions can be combined by the acylating agent, and at the same time, the hydrogen bond forming ability of urea is stronger, and the free volume of the polymer chain in the desalination layer is controlled within a smaller range, thereby enhancing the compactness of the bottom of the desalination layer;
[0047] 3. The reducing agent provided in the present application can reduce the unreacted carboxyl groups on the surface of the desalting layer during the activation and cross-linking process, and reduce the carboxyl groups to alcoholic hydroxyl groups, thereby ensuring the necessary hydrophilicity while further reducing the charge on the membrane surface and improving the anti-pollution performance. The reverse osmosis membrane prepared by the technical solution of the present application still has high performance as a whole even without a protective coating; the anti-pollution property of the reverse osmosis membrane prepared by the technical solution of the application is enhanced, while ensuring the necessary hydrophilicity of the membrane. DETAILED DESCRIPTION
[0048] The present application provides a reverse osmosis membrane, which is obtained by subjecting a reverse osmosis membrane body to activation cross-linking treatment, modified cross-linking treatment and reduction treatment.
[0049] The present application provides a method for preparing the above-mentioned reverse osmosis membrane, comprising the following steps:
[0050] S1. Preparation of reverse osmosis membrane
[0051] After a certain amount of aqueous solution is coated on the surface of the base membrane, excess aqueous phase droplets on the surface are removed by a pressure roller and an air knife; then an organic phase solution is coated, and after a certain reaction time, excess organic phase on the surface is dried in an oven to obtain a primary reverse osmosis membrane; sodium carbonate solution is sprayed on the surface of the primary reverse osmosis membrane, and then it is washed with pure water, and excess pure water on the surface is removed by an air knife to obtain a reverse osmosis membrane body;
[0052] S2. Activation and cross-linking treatment
[0053] The activated cross-linking agent is coated on the surface of the reverse osmosis membrane body, and after reacting for 5 minutes, the excess solution on the surface is dried in an oven. Then the membrane is washed in high-temperature deionized water at 70°C for 6 minutes to wash out the excess water-phase amine monomer in the membrane, and the excess water on the surface is removed with an air knife;
[0054] S3, modified cross-linking treatment
[0055] A modified cross-linking agent is coated on the surface of the membrane after activation cross-linking and high-temperature cleaning. After the reaction is completed, an air knife is used to remove excess solution on the surface.
[0056] S4. Restore Process
[0057] A reducing agent is coated on the surface of the membrane, the reaction time is 3 minutes, and excess tetrahydrofuran on the surface is removed with an air knife; the membrane is immersed in a sodium bisulfite solution with a concentration of 0.2% to 3% for 3 to 6 minutes, and after the excess sodium bisulfite solution on the surface is removed with an air knife, the membrane is dried in an oven at 70° C. for 2 minutes to obtain a finished reverse osmosis membrane.
[0058] The present application provides the application of the above reverse osmosis membrane in the field of seawater desalination.
[0059] Desalination reverse osmosis membranes can be used in various fields such as desalination and zero-emission; the water treatment environment is complex. When used for drinking water in desalination, the insufficient boron removal rate due to the small size of boric acid molecules and their uncharged characteristics has always been a pain point in the market. In order to achieve standard boron removal, secondary treatment is required, which greatly increases the operating cost of the system. When used in fields such as zero-emission, chemical cleaning is frequent, the amide bonds on the membrane surface are easily hydrolyzed, resulting in performance degradation and poor recovery of membrane element cleaning.
[0060] Therefore, the inventors have improved the reverse osmosis membrane prepared in the prior art. According to the present invention, the activated crosslinking and modified crosslinking of the post-treatment can significantly improve the crosslinking degree of the desalination layer of the seawater desalination reverse osmosis membrane, enhance the pore size screening effect of the desalination layer, and make the desalination layer more resistant to physical and chemical damage.
[0061] At present, anti-pollution performance has always been the focus of market attention. The surface of conventional seawater desalination reverse osmosis membranes is rich in carboxyl groups, and it is necessary to improve the anti-pollution performance of membrane products through anti-pollution coatings. The present invention directly starts with the modification of the desalination layer, improves the cross-linking degree, and changes the charge distribution on the membrane surface, making the negative charge on the membrane surface lower, reducing the adsorption of cations on the membrane surface, and being more resistant to chemical cleaning. The anti-pollution performance has obvious advantages over similar products.
[0062] Long-term performance stability and reduced operating costs are the direction pursued by the market, especially high-pressure membrane products. The reverse osmosis membrane prepared by the technical solution of this application has activated cross-linking to improve the cross-linking degree on the surface of the membrane desalination layer, and modified cross-linking also improves the internal cross-linking. The two processes can greatly improve the long-term operating stability of membrane products. The high-cross-linked desalination layer has greatly enhanced tolerance to different water qualities, thereby increasing its service life.
[0063] The present application is further described in detail below with reference to the embodiments.
[0064] In the following examples / comparative examples of the present application, the main components involved, unless otherwise specified, were purchased from commercially available products.
[0065] Preparation Example 1
[0066] This preparation example is used to prepare a reverse osmosis membrane body, which is prepared by the following preparation method:
[0067] After heating N,N-dimethylformamide to 70° C., polysulfone and lithium chloride are added and stirred for more than 12 hours to obtain a casting solution; the casting solution contains 15.5% polysulfone, 0.1% lithium chloride and 84.4% solvent.
[0068] The casting solution after degassing and standing for 8 hours is evenly coated on the non-woven fabric, and then subjected to deionized water gel phase transformation at 15°C, deionized water washing at 25°C, and deionized water curing at 70°C to obtain the reverse osmosis membrane base membrane.
[0069] An aqueous solution containing 2.5% to 5% of m-phenylenediamine monomer and 2% to 4% of sodium camphorsulfonate is coated on the surface of the reverse osmosis membrane base film, and after 30 seconds, excess water phase on the surface is removed by a pressure roller and an air knife, and an IsoparG solution containing 0.15% to 0.45% of trimesoyl chloride is coated. After reacting for 30 seconds, excess organic phase on the membrane surface is dried in an oven to obtain a primary reverse osmosis membrane.
[0070] A 0.5% sodium carbonate solution was sprayed on the surface of the primary reverse osmosis membrane, and after contacting for 30 seconds, it was rinsed with deionized water, and excess deionized water on the surface was removed with an air knife to obtain the reverse osmosis membrane body.
[0071] Preparation Examples 2 to 6 are used to prepare an activated crosslinking agent, and the details are as follows.
[0072] Preparation Example 2
[0073] This preparation example is used to prepare an activated crosslinking agent. Toluene, dicyclohexylcarbodiimide, and 1,7-diaminoheptane are prepared in a mass ratio of 95:0.05:4.5 to prepare the activated crosslinking agent, and the temperature is kept constant at 60±2°C.
[0074] Preparation Example 3
[0075] This preparation example is used to prepare an activated crosslinking agent, wherein toluene, dicyclohexylcarbodiimide, and 1,7-diaminoheptane are prepared in a mass ratio of 95:0.05:4.5 to prepare the activated crosslinking agent, and the temperature is kept constant at 35±2° C. Compared with Preparation Example 2, the temperature of the activated crosslinking agent is lowered in this preparation example.
[0076] Preparation Example 4
[0077] This preparation example is used to prepare an activated crosslinking agent, and toluene, dicyclohexylcarbodiimide, and 1,7-diaminoheptane are prepared in a mass ratio of 92:0.04:7.6 to prepare an activated crosslinking agent, and the temperature is kept constant at 60±2° C. Compared with Preparation Example 2, the proportions of the components in this preparation example are adjusted.
[0078] Preparation Example 5
[0079] This preparation example is used to prepare an activated crosslinking agent, and toluene and 1,7-diaminoheptane are prepared in a mass ratio of 95:4.5 to prepare an activated crosslinking agent, and the temperature is kept constant at 60±2°C. Compared with Preparation Example 2, dicyclohexylcarbodiimide is not added in this preparation example; the mass ratio of toluene and 1,7-diaminoheptane remains unchanged.
[0080] Preparation Example 6
[0081] This preparation example is used to prepare an activated crosslinking agent, and toluene and dicyclohexylcarbodiimide are prepared into an activated crosslinking agent in a mass ratio of 92:0.04, and the temperature is kept constant at 60±2°C. Compared with Preparation Example 2, this preparation example does not add 1,7-diaminoheptane; the mass ratio of toluene and dicyclohexylcarbodiimide remains unchanged.
[0082] Preparation Examples 7 to 11 are used to prepare a modified crosslinking agent, as follows.
[0083] Preparation Example 7
[0084] This preparation example is used to prepare a modified crosslinking agent. Toluene, carbonyl diimidazole, and benzotriazole-N,N,N,N-tetramethyluronium hexafluorophosphate are prepared in a mass ratio of 97:2.8:0.2 to prepare the modified crosslinking agent, and the temperature is kept constant at 70±2°C.
[0085] Preparation Example 8
[0086] This preparation example is used to prepare a modified crosslinking agent. Toluene, carbonyl diimidazole, and benzotriazole-N,N,N,N-tetramethyluronium hexafluorophosphate are prepared in a mass ratio of 97:2:1 to prepare a modified crosslinking agent, and the temperature is kept constant at 70±2° C. Compared with Preparation Example 7, the addition amount of each component is adjusted in this preparation example.
[0087] Preparation Example 9
[0088] This preparation example is used to prepare a modified crosslinking agent. Toluene, carbonyl diimidazole, and benzotriazole-N,N,N,N-tetramethyluronium hexafluorophosphate are prepared in a mass ratio of 97:2.8:0.2 to prepare a modified crosslinking agent, and the temperature is kept constant at 85±2° C. Compared with Preparation Example 7, the temperature of the modified crosslinking agent is increased in this preparation example.
[0089] Preparation Example 10
[0090] This preparation example is used to prepare a modified crosslinking agent, and toluene and benzotriazole-N,N,N,N-tetramethyluronium hexafluorophosphate are prepared in a mass ratio of 97:0.2 to prepare a modified crosslinking agent, and the temperature is kept constant at 70±2° C. Compared with Preparation Example 7, carbonyl diimidazole is not added in this preparation example, and the mass ratio of toluene and benzotriazole-N,N,N,N-tetramethyluronium hexafluorophosphate remains unchanged.
[0091] Preparation Example 11
[0092] This preparation example is used to prepare a modified crosslinking agent, and toluene and carbonyl diimidazole are prepared into a modified crosslinking agent in a mass ratio of 97:2.8, and the temperature is kept constant at 70±2° C. Compared with Preparation Example 7, benzotriazole-N,N,N,N-tetramethyluronium hexafluorophosphate is not added in this preparation example; the mass ratio of toluene and carbonyl diimidazole remains unchanged.
[0093] Preparation Examples 12 to 17 are used to prepare a reducing agent, and the details are as follows.
[0094] Preparation Example 12
[0095] This preparation example is used to prepare a reducing agent. Lithium aluminum hydride, tetrahydrofuran, and boron chloride are prepared into a reducing agent in a mass ratio of 2:97:1, and the temperature of the reducing agent is kept constant within the range of 20°C±2°C.
[0096] Preparation Example 13
[0097] This preparation example is used to prepare a reducing agent, wherein lithium aluminum hydride, tetrahydrofuran, and boron chloride are prepared into a reducing agent in a mass ratio of 4:95:1, and the temperature of the reducing agent is kept constant within the range of 20°C±2°C. Compared with Preparation Example 12, the addition ratio of lithium aluminum hydride and boron chloride is adjusted in this preparation example.
[0098] Preparation Example 14
[0099] This preparation example is used to prepare a reducing agent, wherein lithium aluminum hydride, tetrahydrofuran, and boron chloride are prepared into a reducing agent in a mass ratio of 3:97:2, and the temperature of the reducing agent is kept constant within the range of 20°C±2°C. Compared with Preparation Example 12, the addition ratio of lithium aluminum hydride and boron chloride is adjusted in this preparation example.
[0100] Preparation Example 15
[0101] This preparation example is used to prepare a reducing agent, lithium aluminum hydride, tetrahydrofuran, and boron chloride are prepared into a reducing agent in a mass ratio of 2:97:1, and the temperature of the reducing agent is kept constant within the range of 12°C ± 2°C. Compared with Preparation Example 12, the temperature of the reducing agent is lowered in this preparation example.
[0102] Preparation Example 16
[0103] This preparation example is used to prepare a reducing agent, tetrahydrofuran and boron chloride are prepared into a reducing agent in a mass ratio of 97:1, and the temperature of the reducing agent is kept constant within the range of 20°C±2°C. Compared with Preparation Example 12, lithium aluminum hydride is not added in this preparation example; the mass ratio of tetrahydrofuran and boron chloride remains unchanged.
[0104] Preparation Example 17
[0105] This preparation example is used to prepare a reducing agent, wherein lithium aluminum hydride and tetrahydrofuran are prepared into a reducing agent at a mass ratio of 2:97, and the temperature of the reducing agent is kept constant within the range of 20°C±2°C. Compared with Preparation Example 12, boron chloride is not added in this preparation example; the mass ratio of lithium aluminum hydride and tetrahydrofuran remains unchanged.
[0106] Preparation Example 18
[0107] This preparation example is used to prepare a sodium bisulfite solution, and deionized water is used to prepare a 0.5% sodium bisulfite solution.
[0108] Examples 1 to 9 are used to prepare reverse osmosis membranes, and the details are as follows.
[0109] Example 1
[0110] In this embodiment, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1, including the following steps:
[0111] S1. Coat the activated crosslinking agent prepared in Preparation Example 2 on the surface of the reverse osmosis membrane body, react for 5 minutes, and then dry the excess toluene solution on the surface in an oven at 110°C for 3 minutes. Then wash the membrane in high-temperature deionized water at 70°C for 6 minutes to wash out the excess water-phase amine monomer in the membrane, and remove the excess water on the surface with an air knife;
[0112] S2, coating the modified cross-linking agent prepared in Preparation Example 7 on the surface of the membrane after activation cross-linking and high-temperature cleaning, reacting for 5 minutes, and removing the excess toluene solution on the surface with an air knife;
[0113] S3. Coat the reducing agent prepared in Preparation Example 12 on the surface of the membrane, react for 3 minutes, and remove excess tetrahydrofuran on the surface with an air knife; then immerse the membrane in the sodium bisulfite solution prepared in Preparation Example 18 for 3 minutes, remove excess sodium bisulfite solution on the surface with an air knife, and dry in an oven at 70° C. for 2 minutes to obtain a finished seawater desalination reverse osmosis membrane.
[0114] Example 2
[0115] In this embodiment, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the activated cross-linking agent involved in this embodiment is the activated cross-linking agent prepared in Preparation Example 3.
[0116] Example 3
[0117] This embodiment prepares a reverse osmosis membrane by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the activated cross-linking agent involved in this embodiment is the activated cross-linking agent prepared in Preparation Example 4.
[0118] Example 4
[0119] In this embodiment, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the temperature of the oven in this embodiment is set to 120°C, which is 10°C higher than the temperature of the oven in Example 1 of 110°C.
[0120] Example 5
[0121] This example prepares a reverse osmosis membrane by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the modified cross-linking agent in this example is the modified cross-linking agent prepared in Preparation Example 8.
[0122] Example 6
[0123] This example prepares a reverse osmosis membrane by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the modified cross-linking agent in this example is the modified cross-linking agent prepared in Preparation Example 9.
[0124] Example 7
[0125] In this embodiment, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the reducing agent in this embodiment is the reducing agent prepared in Preparation Example 13.
[0126] Example 8
[0127] In this embodiment, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the reducing agent in this embodiment is the reducing agent prepared in Preparation Example 14.
[0128] Example 9
[0129] In this embodiment, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the reducing agent in this embodiment is the reducing agent prepared in Preparation Example 15.
[0130] Comparative Example 1
[0131] This comparative example is also based on the reverse osmosis membrane body prepared in Preparation Example 1 to prepare a reverse osmosis membrane, comprising the following steps:
[0132] The desalination reverse osmosis membrane body was cleaned in high-temperature deionized water at 70°C for 6 minutes to wash out the excess aqueous amine monomer in the membrane, and the excess water on the surface was removed with an air knife;
[0133] The seawater desalination reverse osmosis membrane after high temperature cleaning was placed in the sodium bisulfite solution prepared in Preparation Example 18 for 3 minutes, and the excess sodium bisulfite solution on the surface was removed with an air knife, and then dried in an oven at 70° C. for 2 minutes to obtain a finished seawater desalination reverse osmosis membrane.
[0134] Comparative Example 2
[0135] This comparative example prepares a reverse osmosis membrane by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the activated cross-linking agent involved in this comparative example is the activated cross-linking agent prepared in Preparation Example 5.
[0136] Comparative Example 3
[0137] In this comparative example, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the activated cross-linking agent involved in this comparative example is the activated cross-linking agent prepared in Preparation Example 6.
[0138] Comparative Example 4
[0139] In this comparative example, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the modified cross-linking agent involved in this comparative example is the modified cross-linking agent prepared in Preparation Example 10.
[0140] Comparative Example 5
[0141] In this comparative example, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the modified cross-linking agent involved in this comparative example is the modified cross-linking agent prepared in Preparation Example 11.
[0142] Comparative Example 6
[0143] In this comparative example, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the reducing agent involved in this comparative example is the reducing agent prepared in Preparation Example 16.
[0144] Comparative Example 7
[0145] In this comparative example, a reverse osmosis membrane is prepared by modifying the reverse osmosis membrane body prepared in Preparation Example 1. The difference from Example 1 is that the reducing agent involved in this comparative example is the reducing agent prepared in Preparation Example 17.
[0146] The reverse osmosis membranes prepared in the above Examples 1 to 9 and Comparative Examples 1 to 7 were tested for membrane performance. The testing method is as follows: under the conditions of 32000ppm sodium chloride and 5ppm boron as test solution, an applied pressure of 5.51MPa, an aqueous solution temperature of 25°C, and a pH of 7.5 to 8, the membrane flux, desalination rate and boron removal rate of the seawater desalination membrane obtained by testing are shown in Table 1.
[0147] Table 1
[0148]
[0149] As can be seen from Table 1, the performance of the membrane after activated crosslinking and modified crosslinking is significantly improved compared with that in Comparative Example 1, and the boron removal of the activated crosslinked membrane is more significantly improved, indicating that the process provided by the present invention improves the performance of the seawater desalination reverse osmosis membrane, and also shows that the density of the desalination layer is indeed improved by activated crosslinking and modified crosslinking.
[0150] The overall performance of Example 2 and Example 4 is better than other conditions. This is because in the process of activated cross-linking, the degree of cross-linking depends largely on the content of 1,7-diaminoheptane in the toluene solvent and the temperature of the cross-linking reaction. The higher the content of 1,7-diaminoheptane, the greater the probability of bridging the carboxyl groups on the surface of the desalting layer to form amide bonds during the reaction. The higher the reaction temperature, on the one hand, can promote the reaction between the amino group and the carboxyl group. At the same time, similar to the principle of azeotropic distillation, the water generated during the reaction can be evaporated faster during the reaction at a higher temperature, which is more conducive to the cross-linking reaction moving to the right.
[0151] The data of Examples 5 and 6 show that the degree of modified cross-linking reaction depends largely on the content of carbonyldiimidazole in the modified cross-linking agent. Since the amino group is below the desalting layer, it is more difficult to connect different amino groups on the desalting layer by bridging with imidazole than by cross-linking on the surface of the desalting layer. Therefore, the improvement of the deboronization rate by modified cross-linking is lower than that by activated cross-linking.
[0152] The change of reducing agent in Examples 7 to 9 has no obvious effect on improving the overall deboronization, and the flux is slightly reduced. This is because during the reduction reaction, the carboxyl hydroxyl group is reduced to alcohol hydroxyl group, and the surface charge changes to a certain extent, but the degree of cross-linking does not change significantly. The deboronization rate is not affected by the surface charge of the desalination layer, so the reduction process does not affect the overall deboronization, and is more reflected in the anti-pollution performance of the membrane.
[0153] The seawater desalination reverse osmosis membranes prepared in Examples 1 to 9 and Comparative Examples 1 to 7 were immersed in a sodium hydroxide solution at 25°C and pH=13 for 120 hours, and then the membrane performance was tested to compare the alkali resistance of the membrane and investigate the service life of the membrane: under the conditions of 32000ppm sodium chloride and 5ppm boron as the test solution, an applied pressure of 5.51MPa, an aqueous solution temperature of 25°C, and a pH of 7.5 to 8, the membrane flux, desalination rate and boron removal rate of the seawater desalination membrane were tested. The results are shown in Table 2.
[0154] Table 2
[0155]
[0156] It can be seen from Table 2 that the alkali resistance of the membrane with the cross-linking process is significantly improved compared with the alkali resistance of the membrane in Comparative Example 1. After 120 hours of alkali resistance, the desalination rate of the membrane in some embodiments can still reach more than 99.80%, and the deboronization rate is also more than 90%. The desalination rate of the membrane without the cross-linking process is reduced to 99.50% after 120 hours of alkali resistance, and the deboronization rate is also reduced to 82.4%. This fully illustrates the advantage of the seawater desalination reverse osmosis membrane provided by the patent of the present invention in alkali resistance. In the face of alkali cleaning conditions often used in industrial applications, the service life of the membrane element will also be longer.
[0157] The seawater desalination reverse osmosis membranes prepared in Examples 1 to 9 and Comparative Examples 1 to 7 were continuously operated at 800psi for 240h in a mixed solution of pH=7.5-8 and containing 50mg / L humic acid, 20mg / L sodium silicate, 2mg / L aluminum chloride, and 50mg / L sodium sulfate to simulate the pollution resistance of seawater membranes and test the performance of the components. Then, they were rinsed with a sodium hydroxide solution of pH=12 for 3h, a hydrochloric acid solution of pH=2% for 3h, and a pure water solution for 0.5h. The data of the membrane tested at 800psi, pH=7.5-8, and 25°C are shown in Table 3:
[0158] Table 3
[0159]
[0160] It can be seen from Table 3 that without changing the component process of the reducing agent, the performance differences of Examples 1 to 9 in terms of anti-pollution performance and cleaning recovery are not large, and the overall anti-pollution effect is the same. By increasing the content of metal hydride in the reducing agent, the flux change of the membrane is smaller, and the desalination rate can maintain a more stable state. It shows that the reduction of carboxyl hydroxyl groups by the reducing agent in this patent enhances the anti-pollution performance of the membrane surface. The membrane in Comparative Example 1, which does not use cross-linking and reduction processes, has the greatest change in overall performance, especially the difference in flux. And the metal hydride as the main component in the reducing agent has the greatest impact on the anti-pollution performance, which can be confirmed by the data of Comparative Example 6. Changes in the content of additives such as boron chloride will also affect the anti-pollution performance. This is because the addition of a certain amount of boron chloride can control the entire reduction reaction within a better range, and direct reduction without additives will lead to some other side reactions.
[0161] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.
Claims
1. A reverse osmosis membrane, characterized in that: The reverse osmosis membrane is obtained by subjecting the reverse osmosis membrane body to activation cross-linking treatment, modification cross-linking treatment and reduction treatment.
2. The reverse osmosis membrane according to claim 1, characterized in that The activated crosslinking treatment uses an activated crosslinking agent, which is prepared from the following components in percentage by mass: Component a: 92~98.5wt%; Component b: 0.05~0.5 wt %; Component c: 0.5~3.8 wt %; Component a is at least one of benzene, toluene, ethylbenzene, xylene, chlorobenzene, dichlorobenzene and styrene; Component b is at least one of dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), 4-N,N-dimethylpyridine (DMAP), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI), and 1-hydroxybenzotriazole (HOBt); Component c is at least one of a fatty amine containing an unsaturated bond, an aliphatic alkane containing an amino group, an aromatic amine, and an amino ether. More preferably, component c is at least one of 1,7-diaminoheptane and its isomers, 1,8-diaminooctane and its isomers.
3. The reverse osmosis membrane according to claim 2, characterized in that The temperature of the activated cross-linking agent is 35-65°C.
4. The reverse osmosis membrane according to claim 1, characterized in that The modified crosslinking treatment uses a modified crosslinking agent, and the modified crosslinking agent is prepared from the following components in percentage by mass: Component a: 97~99.5wt%; Component d: 0.5~5 wt %; Component e: 0.05~0.5 wt %; Component a is at least one of benzene, toluene, ethylbenzene, xylene, chlorobenzene, dichlorobenzene and styrene; Component d is at least one of carbonyldiimidazole, 2-phenylbenzimidazole, hexaaryldiimidazole, diimidazole benzene, 2,2-diimidazole methane, and N,N-thiocarbonyldiimidazole; Component e is at least one of O-(7-azabenzotriazole)-N,N,N,N-tetramethyluronium hexafluorophosphate (HATU), 6-chlorobenzotriazole-1,1,3,3-tetramethyluronium hexafluorophosphate (HCTU), benzotriazole-N,N,N,N-tetramethyluronium hexafluorophosphate (HBTU), O-benzotriazole-N,N,N,N-tetramethyluronium tetrafluoroborate (TBTU), and 2-succinimidyl-1,1,3,3-tetramethyluronium tetrafluoroborate (TSTU).
5. The reverse osmosis membrane according to claim 4, characterized in that The temperature of the modified cross-linking agent is 65-95°C.
6. The reverse osmosis membrane according to claim 1, characterized in that The reduction treatment uses a reducing agent, which is prepared from the following components in percentage by mass: Component f: 1~5 wt%; Tetrahydrofuran: 95~98 wt%; The mass ratio of boron chloride is: 0.5~2 wt%; Component f is at least one of sodium hydride, potassium hydride, lithium aluminum hydride, magnesium dihydride, and calcium hydride.
7. The reverse osmosis membrane according to claim 6, characterized in that The temperature of the reducing agent is 10-25°C.
8. A method for preparing a reverse osmosis membrane according to claim 1, characterized in that: The following steps are involved: S1. Preparation of reverse osmosis membrane After a certain amount of aqueous solution is coated on the surface of the base membrane, excess aqueous phase droplets on the surface are removed by a pressure roller and an air knife; then an organic phase solution is coated, and after a certain reaction time, excess organic phase on the surface is dried in an oven to obtain a primary reverse osmosis membrane; sodium carbonate solution is sprayed on the surface of the primary reverse osmosis membrane, and then it is washed with pure water, and excess pure water on the surface is removed by an air knife to obtain a reverse osmosis membrane body; S2. Activation and cross-linking treatment The activated cross-linking agent is coated on the surface of the reverse osmosis membrane body, and after reacting for 5 minutes, the excess solution on the surface is dried in an oven; then the membrane is washed in high-temperature deionized water at 70°C for 6 minutes to wash out the excess water-phase amine monomer in the membrane, and the excess water on the surface is removed with an air knife; S3, modified cross-linking treatment A modified cross-linking agent is coated on the surface of the membrane after activation cross-linking and high-temperature cleaning. After the reaction is completed, an air knife is used to remove excess solution on the surface. S4. Restore Process A reducing agent is coated on the surface of the membrane, the reaction time is 3 minutes, and excess tetrahydrofuran on the surface is removed with an air knife; the membrane is immersed in a sodium bisulfite solution with a concentration of 0.2% to 3% for 3 to 6 minutes, and excess sodium bisulfite solution on the surface is removed with an air knife, and then dried in an oven at 70°C for 2 minutes to obtain a finished reverse osmosis membrane.
9. The preparation method according to claim 8, characterized in that: The oven drying temperature in S2 is 100-130° C., and the drying time is 3.5-8 min.
10. The preparation method according to claim 8, characterized in that: In S3, the reaction time after coating the modified cross-linking agent is 3 to 6 minutes; And / or, in S4, the membrane is immersed in the sodium bisulfite solution for 2.5 to 4.5 minutes.
11. Use of the reverse osmosis membrane according to claim 1 in the field of seawater desalination.