Reverse osmosis membrane and preparation method thereof

Abstract

The invention provides a reverse osmosis membrane and a preparation method thereof, and relates to the field of reverse osmosis membranes, the reverse osmosis membrane comprises a support layer, the support layer is a polysulfone porous membrane coated on a non-woven fabric, and a finger-shaped pore structure is formed; the polyamide separation layer is formed by carrying out interfacial polymerization on m-phenylenediamine and trimesoyl chloride, and is doped with hyperbranched polyamide and graphene oxide; according to the invention, a vertical magnetic field is introduced in the interfacial polymerization process, so that the aminated MOF is arranged along the direction of the magnetic field to form an oriented crystal structure, the defects of the polyamide layer are reduced, the desalination rate is improved, and the production cost is reduced. The oxygen-containing functional group of the graphene oxide and the amino group of the hyperbranched polyamide form a hydrogen bond to construct a hydrophilic channel, so that the contact angle of the surface of the membrane is reduced, the anti-pollution capacity is improved, and the water flux of the membrane is remarkably improved due to the formation of an oriented crystal structure and the hydrophilic channel.

Description

Technical Field

[0001] The present invention relates to the field of reverse osmosis membranes, and in particular to a reverse osmosis membrane and a method for preparing the reverse osmosis membrane. Background Art

[0002] Reverse osmosis membrane technology is a high-efficiency membrane separation technology developed in the 1960s. Its core lies in achieving precise separation of solvents and solutes through artificially synthesized polymer semipermeable membranes. This technology is widely used in seawater desalination, industrial pure water preparation, wastewater reuse, medical and pharmaceutical fields, and has become one of the key technologies to solve the global water shortage problem.

[0003] Traditional reverse osmosis membranes are mainly made of cellulose acetate or aromatic polyamide materials, and achieve desalination function through asymmetric membranes or composite membrane structures. However, with the expansion of application scenarios, traditional membrane materials face the following technical problems: the contradiction between desalination rate and water flux. Improving the desalination rate often requires sacrificing water flux, resulting in increased energy consumption, insufficient anti-pollution ability, and the membrane surface is easily contaminated by organic matter, microorganisms and inorganic salt scaling, which shortens the service life.

[0004] Therefore, it is necessary to provide a new reverse osmosis membrane and a method for preparing the reverse osmosis membrane to solve the above technical problems. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a reverse osmosis membrane and a method for preparing the reverse osmosis membrane.

[0006] The reverse osmosis membrane and reverse osmosis membrane provided by the present invention include: a support layer, wherein the support layer is a polysulfone porous membrane coated on a non-woven fabric to form a finger-like pore structure;

[0007] a polyamide separation layer, wherein the polyamide separation layer is formed by interfacial polymerization of m-phenylenediamine and trimesoyl chloride and is doped with hyperbranched polyamide and graphene oxide;

[0008] The protective layer is made of polyvinyl alcohol and is coated on the polyamide separation layer to form a thin and uniform protective film.

[0009] Furthermore, the porosity of the support layer is 60%-85%, and the average pore diameter is 0.05-0.2 μm.

[0010] Another aspect of the present invention provides a method for preparing a reverse osmosis membrane, the method comprising the following steps:

[0011] Step 1: Pre-treat the support layer by preparing an 18-25 wt% polysulfone / NMP solution, applying it to a non-woven fabric after vacuum degassing, immersing it in a pure water coagulation bath to form a finger-like pore structure, drying it at 60-80°C, and magnetizing it in a 0.8 T magnetic field for 30-60 minutes;

[0012] Step 2: Magnetic controlled interfacial polymerization: prepare aqueous solution and oily solution, immerse the support layer in the aqueous phase for 15-30 seconds, roll to remove the liquid, pour the oily phase under a vertical magnetic field, and react for 60-80 seconds. The direction of the magnetic field is perpendicular to the coating direction.

[0013] Step 3: Multi-stage heat treatment, including high temperature, medium temperature and low temperature treatment;

[0014] Step 4: Post-processing: After drying, apply polyvinyl alcohol and a protective layer, cross-link at 120°C for 10-15 minutes, and then cut into membrane sheets of effective area.

[0015] In a further method, the aqueous solution raw materials are selected from 3.2-3.5 wt% of m-phenylenediamine, 1-3 wt% of hyperbranched polyamide and 0.05-0.1 wt% of graphene oxide;

[0016] After selecting the raw materials, the pH is adjusted to 9.5, and 0.5-1 wt% of triethylamine is added as a catalyst.

[0017] In a further method, the oil phase solution raw material is selected from 0.15 wt% of trimesoyl chloride, dissolved in n-hexane, and 0.3 wt% of NH2-MIL-101 (Fe) with a particle size of 200 nm is added, and ultrasonic dispersion is performed for 1 hour.

[0018] In a further method, the high temperature stage is as follows: the set temperature is 80° C., the hot air speed is 800 fpm, the humidity is 70% RH, and the reaction is carried out for 2 minutes.

[0019] In a further method, the medium temperature stage is as follows: the set temperature is 60° C., the wind speed is 500 fpm, the humidity is 30% RH, and the reaction time is 5 minutes.

[0020] A further method is a low temperature stage: the temperature is set at 25° C., the reaction is carried out for 1 hour, and after natural cooling, the mixture is immersed in 5 wt % glycerol for moisturizing treatment for 12 hours.

[0021] In a further method, the post-treatment in step 4 also includes ultraviolet grafting modification with a wavelength of 254 nm and a dose of 500-2000 mJ / cm 2 .

[0022] In a further method, the interfacial polymerization reaction is carried out under nitrogen protection, and the relative humidity is controlled at 30%-70%.

[0023] Compared with related technologies, the reverse osmosis membrane and the method for preparing the reverse osmosis membrane provided by the present invention have the following beneficial effects:

[0024] 1. A perpendicular magnetic field is introduced during the interfacial polymerization process, causing the amino-modified MOF to align along the direction of the magnetic field, forming an oriented crystalline structure, reducing the defects of the polyamide layer and improving the desalination rate.

[0025] 2. The oxygen-containing functional groups of graphene oxide form hydrogen bonds with the amino groups of hyperbranched polyamide to construct hydrophilic channels, reduce the contact angle of the membrane surface, improve the anti-pollution ability, and form oriented crystal structures and hydrophilic channels, which significantly improves the water flux of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart of the reverse osmosis membrane and the method for preparing the reverse osmosis membrane provided by the present invention;

[0027] Figure 2 A flow chart of the multi-stage heat treatment provided by the present invention;

[0028] Figure 3 A flow chart of the preparation of the aqueous solution provided by the present invention;

[0029] Figure 4 This is a flow chart of the preparation of the oil phase solution provided by the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] Please refer to Figure 1 、 Figure 2 、 Figure 3 as well as Figure 4 ,in, Figure 1 A flow chart of the reverse osmosis membrane and the method for preparing the reverse osmosis membrane provided by the present invention; Figure 2 A flow chart of the multi-stage heat treatment provided by the present invention; Figure 3 A flow chart of the preparation of the aqueous solution provided by the present invention; Figure 4 This is a flow chart for preparing the oil phase solution provided by the present invention.

[0032] Example 1

[0033] In a specific implementation, the reverse osmosis membrane includes: a support layer, which is a polysulfone porous membrane coated on a non-woven fabric to form a finger-like pore structure;

[0034] A polyamide separation layer, wherein the polyamide separation layer is formed by interfacial polymerization of m-phenylenediamine and trimesoyl chloride and is doped with hyperbranched polyamide and graphene oxide;

[0035] The protective layer is made of polyvinyl alcohol and is coated on the polyamide separation layer to form a thin and uniform protective film.

[0036] Furthermore, the porosity of the support layer is 60%-85%, and the average pore size is 0.05-0.2 μm.

[0037] Example 2

[0038] In the specific implementation process, Figures 1-4 As shown, a method for preparing a reverse osmosis membrane comprises the following steps:

[0039] Step 1: Pretreatment of the support layer: prepare an 18 wt% polysulfone / NMP solution, apply it to the non-woven fabric after vacuum degassing, immerse it in a pure water coagulation bath to form a finger-like pore structure, dry it at 60°C, and magnetize it in a 0.8 T magnetic field for 30 minutes;

[0040] Step 2: Magnetic controlled interfacial polymerization: prepare aqueous and oily phase solutions, immerse the support layer in the aqueous phase for 15 seconds, roll to remove the liquid, and pour the oily phase under a vertical magnetic field for 60 seconds. The direction of the magnetic field is perpendicular to the coating direction.

[0041] Step 3: Multi-stage heat treatment, including high temperature, medium temperature and low temperature treatment;

[0042] Step 4: Post-processing: After drying, apply polyvinyl alcohol and a protective layer, cross-link at 120° C. for 10 minutes, and then cut into membrane sheets of effective area.

[0043] For further methods, see Figure 3 As shown, the raw materials of the aqueous solution are 3.2 wt% m-phenylenediamine, 1 wt% hyperbranched polyamide and 0.05 wt% graphene oxide;

[0044] After selecting the raw materials, the pH was adjusted to 9.5, and 0.5 wt % of triethylamine was added as a catalyst.

[0045] Optional, reference Figure 4 As shown, the raw material of the oil phase solution is 0.15 wt% of trimesoyl chloride, which is dissolved in n-hexane, and 0.3 wt% of NH2-MIL-101 (Fe) with a particle size of 200 nm is added, and ultrasonic dispersion is performed for 1 hour.

[0046] Optional, high temperature stage: set temperature 80°C, hot air speed 800fpm, humidity 70%RH, and react for 2 minutes.

[0047] Optional, medium temperature stage: set temperature to 60°C, wind speed to 500 fpm, humidity to 30% RH, and react for 5 minutes.

[0048] Optional, low temperature stage: set the temperature to 25°C, react for 1 hour, cool naturally, and then immerse in 5wt% glycerol for moisturizing treatment for 12 hours.

[0049] Optionally, the post-treatment in step 4 also includes ultraviolet grafting modification with a wavelength of 254 nm and a dose of 500 mJ / cm 2 .

[0050] Optionally, the interfacial polymerization reaction is carried out under nitrogen protection, and the relative humidity is controlled at 30%-70%.

[0051] Example 3

[0052] In the specific implementation process, Figure 1 As shown, a method for preparing a reverse osmosis membrane comprises the following steps:

[0053] Step 1: Pretreatment of the support layer: prepare a 20 wt% polysulfone / NMP solution, apply it to the non-woven fabric after vacuum degassing, immerse it in a pure water coagulation bath to form a finger-like pore structure, dry it at 70°C, and magnetize it in a 0.8 T magnetic field for 40 minutes;

[0054] Step 2: Magnetic controlled interfacial polymerization: prepare aqueous and oily phase solutions, immerse the support layer in the aqueous phase for 20 seconds, roll to remove the liquid, and pour the oily phase under a vertical magnetic field for 70 seconds. The direction of the magnetic field is perpendicular to the coating direction.

[0055] Step 3: Multi-stage heat treatment, including high temperature, medium temperature and low temperature treatment;

[0056] Step 4: Post-treatment: After drying, apply polyvinyl alcohol and a protective layer, cross-link at 120° C. for 15 minutes, and then cut into membrane sheets of effective area.

[0057] In a further method, the aqueous solution raw materials are selected from 3.3 wt% m-phenylenediamine, 2 wt% hyperbranched polyamide and 0.08 wt% graphene oxide;

[0058] After selecting the raw materials, the pH was adjusted to 9.5, and 0.7 wt % of triethylamine was added as a catalyst.

[0059] Optionally, the oil phase solution raw material is 0.15 wt% of trimesoyl chloride, dissolved in n-hexane, and 0.3 wt% of NH2-MIL-101(Fe) with a particle size of 200 nm is added, and ultrasonic dispersion is performed for 1 hour.

[0060] Optional, high temperature stage: set temperature 80°C, hot air speed 800fpm, humidity 70%RH, and react for 2 minutes.

[0061] Optional, medium temperature stage: set temperature to 60°C, wind speed to 500 fpm, humidity to 30% RH, and react for 5 minutes.

[0062] Optional, low temperature stage: set the temperature to 25°C, react for 1 hour, cool naturally, and then immerse in 5wt% glycerol for moisturizing treatment for 12 hours.

[0063] Optionally, the post-treatment in step 4 also includes ultraviolet grafting modification with a wavelength of 254 nm and a dose of 1000 mJ / cm 2 .

[0064] Optionally, the interfacial polymerization reaction is carried out under nitrogen protection, and the relative humidity is controlled at 30%-70%.

[0065] Example 4

[0066] In the specific implementation process, Figure 1 As shown, a method for preparing a reverse osmosis membrane comprises the following steps:

[0067] Step 1: Pretreatment of the support layer: prepare a 25 wt% polysulfone / NMP solution, apply it to the non-woven fabric after vacuum degassing, immerse it in a pure water coagulation bath to form a finger-like pore structure, dry it at 80°C, and magnetize it in a 0.8 T magnetic field for 60 minutes;

[0068] Step 2: Magnetic controlled interfacial polymerization: prepare aqueous and oily phase solutions, immerse the support layer in the aqueous phase for 30 seconds, roll to remove the liquid, and pour the oily phase under a vertical magnetic field for 80 seconds. The direction of the magnetic field is perpendicular to the coating direction.

[0069] Step 3: Multi-stage heat treatment, including high temperature, medium temperature and low temperature treatment;

[0070] Step 4: Post-treatment: After drying, apply polyvinyl alcohol and a protective layer, cross-link at 120° C. for 15 minutes, and then cut into membrane sheets of effective area.

[0071] Optionally, the aqueous solution raw materials are selected from 3.5 wt% m-phenylenediamine, 3 wt% hyperbranched polyamide and 0.1 wt% graphene oxide;

[0072] After selecting the raw materials, the pH was adjusted to 9.5, and 1 wt% triethylamine was added as a catalyst.

[0073] Optionally, the oil phase solution raw material is 0.15 wt% of trimesoyl chloride, dissolved in n-hexane, and 0.3 wt% of NH2-MIL-101(Fe) with a particle size of 200 nm is added, and ultrasonic dispersion is performed for 1 hour.

[0074] Optional, high temperature stage: set temperature 80°C, hot air speed 800fpm, humidity 70%RH, and react for 2 minutes.

[0075] Optional, medium temperature stage: set temperature to 60°C, wind speed to 500 fpm, humidity to 30% RH, and react for 5 minutes.

[0076] Optional, low temperature stage: set the temperature to 25°C, react for 1 hour, cool naturally, and then immerse in 5wt% glycerol for moisturizing treatment for 12 hours.

[0077] Optionally, the post-treatment in step 4 also includes ultraviolet grafting modification with a wavelength of 254 nm and a dose of 2000 mJ / cm 2 .

[0078] Optionally, the interfacial polymerization reaction is carried out under nitrogen protection, and the relative humidity is controlled at 30%-70%.

[0079] Comparative Example 1

[0080] In the preparation method, the magnetic field treatment step of the support layer is omitted.

[0081] Comparative Example 2

[0082] In the preparation method, no hyperbranched polyamide and graphene oxide are added, and the aqueous phase contains only m-phenylenediamine (3.2 wt %), without hyperbranched polyamide (1 wt %) and graphene oxide (0.05 wt %).

[0083] Comparative Example 3

[0084] In the preparation process, the direction of the magnetic field is parallel (not perpendicular) to the coating direction when the oil phase is poured.

[0085] Comparative Example 4

[0086] In the preparation method, a single-stage heat treatment replaces a multi-stage heat treatment, and only a medium-temperature treatment of 60° C., 500 fpm, 30% RH, and 5 minutes is performed, omitting the high-temperature and low-temperature stages.

[0087] Experiment: Performance comparison of Example 4 with Comparative Examples 1 to 4

[0088] The performance comparison table is as follows:

[0089]

[0090]

[0091] According to the above results, the magnetic field treatment of the support layer significantly improves the porosity (60%-85%) and pore size uniformity (0.05-0.2 μm), directly increases the water flux by 18.2% (Comparative Example 1 vs. Example 4), the perpendicular magnetic field of magnetron interfacial polymerization optimizes the oil / water phase reaction interface, and increases the desalination rate by 2.2% (Comparative Example 3 vs. Example 1), the addition of hyperbranched polyamide and graphene oxide increases the desalination rate by 1.4% (Comparative Example 2 vs. Example 1), and at the same time reduces the pollution index by 0.4 and extends the membrane life. The high temperature, medium temperature, and low temperature gradient treatments make the membrane structure more stable, increase the water flux by 31.8% (Comparative Example 4 vs. Example 1), and enhance the mechanical strength.

[0092] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all points of view, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes that come within the meaning and range of equivalents of the claims are intended to be included in the present invention, and any reference signs in the claims should not be construed as limiting the claims involved.

[0093] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A reverse osmosis membrane, characterized in that include: A support layer, wherein the support layer is a polysulfone porous membrane coated on a non-woven fabric to form a finger-like pore structure; a polyamide separation layer, wherein the polyamide separation layer is formed by interfacial polymerization of m-phenylenediamine and trimesoyl chloride and is doped with hyperbranched polyamide and graphene oxide; The protective layer is made of polyvinyl alcohol and is coated on the polyamide separation layer to form a thin and uniform protective film.

2. The reverse osmosis membrane according to claim 1, characterized in that The porosity of the support layer is 60%-85%, and the average pore diameter is 0.05-0.2 μm.

3. A method for preparing the reverse osmosis membrane according to claim 1 or 2, characterized in that: The method comprises the following steps: Step 1: Pre-treat the support layer by preparing an 18-25 wt% polysulfone / NMP solution, applying it to a non-woven fabric after vacuum degassing, immersing it in a pure water coagulation bath to form a finger-like pore structure, drying it at 60-80°C, and magnetizing it in a 0.8 T magnetic field for 30-60 minutes; Step 2: Magnetic controlled interfacial polymerization: prepare aqueous solution and oily solution, immerse the support layer in the aqueous phase for 15-30 seconds, roll to remove the liquid, pour the oily phase under a vertical magnetic field, and react for 60-80 seconds. The direction of the magnetic field is perpendicular to the coating direction. Step 3: Multi-stage heat treatment, including high temperature, medium temperature and low temperature treatment; Step 4: Post-processing: After drying, apply polyvinyl alcohol and a protective layer, cross-link at 120°C for 10-15 minutes, and then cut into membrane sheets of effective area.

4. The method for preparing a reverse osmosis membrane according to claim 1, wherein The aqueous solution raw materials are selected from 3.2-3.5wt% m-phenylenediamine, 1-3wt% hyperbranched polyamide and 0.05-0.1wt% graphene oxide; After selecting the raw materials, the pH is adjusted to 9.5, and 0.5-1 wt% of triethylamine is added as a catalyst.

5. The method for preparing a reverse osmosis membrane according to claim 1, wherein The raw material of the oil phase solution is 0.15 wt % of trimesoyl chloride, which is dissolved in n-hexane, and 0.3 wt % of NH2-MIL-101(Fe) with a particle size of 200 nm is added, and ultrasonic dispersion is performed for 1 hour.

6. The method for preparing a reverse osmosis membrane according to claim 1, wherein The high temperature stage: set temperature to 80° C., hot air speed to 800 fpm, humidity to 70% RH, and reaction time to 2 minutes.

7. The method for preparing a reverse osmosis membrane according to claim 1, wherein The medium temperature stage: set the temperature to 60° C., the wind speed to 500 fpm, the humidity to 30% RH, and react for 5 minutes.

8. The method for preparing a reverse osmosis membrane according to claim 1, wherein The low temperature stage: set the temperature at 25° C., react for 1 hour, and after natural cooling, immerse in 5 wt % glycerol for moisturizing treatment for 12 hours.

9. The method for preparing a reverse osmosis membrane according to claim 1, wherein Step 4 post-treatment also includes ultraviolet grafting modification with a wavelength of 254nm and a dose of 500-2000mJ / cm 2 .

10. The method for preparing a reverse osmosis membrane according to claim 1, wherein The interfacial polymerization reaction is carried out under nitrogen protection, and the relative humidity is controlled at 30%-70%.

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