High-temperature-resistant composite reverse osmosis membrane and preparation method thereof

Abstract

The invention belongs to the technical field of reverse osmosis membrane materials, and particularly relates to a high-temperature-resistant composite reverse osmosis membrane and a preparation method thereof. According to the high-temperature-resistant composite reverse osmosis membrane, different polymer chains are connected by virtue of a cross-linking agent between molecular chains to construct a three-dimensional network cross-linked structure, so that the movement of the molecular chains is limited, the creep deformation and the deformation of the molecular chains at high temperature are reduced, the thermal stability and the mechanical property of the material are improved, and a final finished product can bear relatively high temperature without deformation or decomposition. The preparation method has the characteristics of easily available raw materials, simple and feasible preparation process, low operation requirement and easiness in industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of reverse osmosis membrane materials, and particularly relates to a high-temperature resistant composite reverse osmosis membrane and a preparation method thereof. Background Art

[0002] At present, in the industrial production processes such as textile printing and dyeing, petrochemical industry, electric power, and coal chemical industry, a large amount of highly polluted industrial wastewater containing organic and inorganic compounds is generated in the field of industrial wastewater treatment. This industrial wastewater is characterized by high temperature, high salinity, high chemical oxygen demand, high toxicity, complex chemical composition, and poor biodegradability.

[0003] Existing industrial wastewater treatment technologies include physical and chemical methods, biological methods, and membrane separation methods. Among them, the membrane separation method is widely used in the field of industrial wastewater treatment due to its low operating cost, no phase change, and environmental friendliness. It can realize the reuse of water resources and salt, save energy, and recycle waste.

[0004] When treating industrial wastewater based on the membrane separation method, the reverse osmosis technology is a commonly used desalination technology and is widely applied to the concentration treatment of high-salt wastewater. Among them, the existing mainstream reverse osmosis membrane materials use polyamide composite membranes, which replace the cellulose acetate separation membranes with poor chemical properties, thermal stability, compaction resistance, and easy degradation. The high-crosslinking polyamide material layer of the polyamide composite reverse osmosis membrane has certain chemical stability and durability, and the hydrophilic amide groups have comprehensive properties of certain high water production and high salt rejection rates. However, at present, the organic separation layer of the polyamide reverse osmosis membrane is not resistant to high temperatures, and the maximum operating temperature generally does not exceed 40°C under normal circumstances. Moreover, for treating wastewater with 35,000 mg / L TDS (i.e., salt concentration), due to its application being restricted by the maximum hydraulic pressure that the current reverse osmosis membrane and components can withstand, the desalination effect is poor. Based on the above technical status, currently, the polyamide reverse osmosis membrane cannot operate at higher working temperatures and higher operating pressures, and the water reuse rate is low under high-salt conditions, resulting in higher operating costs.

[0005] The patent with the publication number CN115634579 A obtains an ultrathin polyamide separation layer by sequentially pouring an aqueous solution of polyamine and an organic solution of polyacyl chloride onto a base membrane and reacting. Subsequently, an aqueous solution of polyol is poured onto the ultrathin polyamide separation layer to react to obtain a two-layer composite reverse osmosis membrane. This invention prepares a double-layer composite reverse osmosis membrane through two interfacial polymerizations, but the adhesion between the polyamide layer and the base membrane is not improved, and the reverse osmosis membrane is easily damaged during repeated high-temperature operation, and the durability of the high-temperature resistant reverse osmosis membrane cannot be improved.

[0006] The patent with the bulletin number CN113952846B prepares an amphoteric ionized polyether ether ketone base membrane through chemical synthesis and then makes an amphoteric ionized polyether ether ketone loose nanofiltration membrane. This invention prepares a high-temperature resistant nanofiltration membrane by synthesizing an amphoteric base membrane in the laboratory, and it is not easy to realize industrial production.

[0007] The patent with publication number CN110605033B obtains modified nanoparticles by soaking nanoparticles in an initiator solution, drying, and then adding them to an aqueous solution of a modified monomer for polymerization. The modified nanoparticles, polyvinylidene fluoride polymer, and pore-forming agent are then introduced into an organic solvent for dissolution, and hollow fibers are extruded to obtain membrane filaments. Subsequently, the membrane filaments are soaked in an aqueous solution of a crosslinking modifier to obtain a heat-resistant hollow fiber ultrafiltration membrane. This invention obtains a high-temperature-resistant ultrafiltration membrane by adding modified nanoparticles, but the process is relatively complex and not easy for industrial production.

[0008] The patent with publication number CN107362702B prepares a mixed matrix original membrane by formulating a membrane-forming solution with graphene oxide, metal alkoxide, acetic acid, polymer, and organic solvent and then preparing the membrane. It can maintain the pore structure and high permeation separation performance of the mixed matrix original membrane, and also has solvent resistance and heat resistance. This invention adds modified nanoparticles and graphene oxide to the base membrane, but the nanoparticles are basically solid materials and the graphene oxide is in sheet form, which cannot provide porous water channels and cannot effectively promote interfacial polymerization reactions to improve the high-temperature resistance of the polyamide layer. Moreover, its material cost is high and it is not easy to realize industrial production. Summary of the Invention

[0009] In view of the deficiencies of the prior art, the present invention provides a high-temperature-resistant composite reverse osmosis membrane and its preparation method for achieving technical purposes.

[0010] Specifically, it is achieved through the following technical solutions:

[0011] The first object of the present invention is to provide: A high-temperature-resistant composite reverse osmosis membrane, which is prepared by adding a membrane strengthening liquid during the preparation process, thereby introducing an intermolecular crosslinking agent containing an organic compound with multiple acrylate groups during the reaction, and a Michael addition reaction occurs between the amino group and the acrylate during the interfacial polymerization process. The reaction formula can be simply expressed as follows: R-NH 2 +CH 2 =CH-COR'→R-NH-CH 2 -CH 2 -COR'

[0012] The preparation principle is that the membrane strengthening liquid contains multiple acrylate groups, and each molecule can react with multiple amino groups. As the reaction progresses, different polymer chains are interconnected through the molecules in the intermolecular crosslinking agent to form a three-dimensional network crosslinked structure. This crosslinked structure restricts the movement of molecular chains, reduces the creep and deformation of molecular chains at high temperatures, improves the thermal stability and mechanical properties of the material, and enables it to withstand higher temperatures without deformation or decomposition.

[0013] The second object of the present invention is to provide:

[0014] A method for preparing a high-temperature resistant composite reverse osmosis membrane, comprising the following steps:

[0015] (1) Preparation of the base membrane

[0016] Immerse the base membrane material in the casting solution, and after the immersion precipitation phase inversion reaction, a base membrane is made by slit coating;

[0017] (2) Treatment with polyamine

[0018] Immerse the base membrane prepared in step (1) in the polyamine solution for soaking, and then take it out;

[0019] (3) Treatment with organic phase

[0020] After the surface of the membrane obtained in step (2) is dried, immerse it in the membrane strengthening solution for Michael addition reaction;

[0021] (4) Heat treatment

[0022] After the treatment in step (3) is completed, take out the membrane, rinse it with pure water in sequence, and then perform heat treatment at 40 - 100 °C to obtain the high-temperature resistant composite reverse osmosis membrane.

[0023] The base membrane material is one or more of polysulfone, polyethersulfone, polyacrylonitrile, polyimide, and polyvinylidene fluoride; the casting solution is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. Further preferably, the casting solution is N-methylpyrrolidone.

[0024] The thickness of the base membrane is 2 - 8 mil; further preferably 4 - 6 mil.

[0025] The components of the polyamine solution include water, m-phenylenediamine, and an acid acceptor; the mass concentration of m-phenylenediamine in the polyamine solution is 0.1 - 10%, and the mass concentration of the acid acceptor is 0.001 - 10%; the acid acceptor is sodium hydroxide.

[0026] Further preferably, the mass concentration of m-phenylenediamine in the polyamine solution is 1 - 5%; the mass concentration of the acid acceptor in the polyamine solution is 0.01 - 1%.

[0027] The membrane strengthening solution is composed of benzoyl trichloride, an intermolecular crosslinking agent, and an organic solvent. The intermolecular crosslinking agent is an organic compound containing polyacrylate groups, and the organic compound containing polyacrylate groups is trimethylolpropane triacrylate or pentaerythritol tetraacrylate; preferably pentaerythritol tetraacrylate.

[0028] The organic solvent is one or more of cyclohexane, n-hexane, and ISOPAR series isoparaffins.

[0029] The mass concentration of benzoyl trichloride in the membrane strengthening liquid is 0.01-10%, and the mass concentration of the organic compound containing polyacrylate groups is 0.001-1%.

[0030] Further preferably, the mass concentration of benzoyl trichloride in the membrane strengthening liquid is 0.01-5%; the mass concentration of the organic compound containing polyacrylate groups in the membrane strengthening liquid is 0.01-0.5%.

[0031] Further preferably, the temperature of the heat treatment is 60-90°C, and the time is 5 minutes.

[0032] Beneficial effects

[0033] A high-temperature resistant composite reverse osmosis membrane protected by the present invention adds a membrane strengthening liquid during the preparation process of the reverse osmosis membrane. The principle of the membrane strengthening liquid is to introduce an intermolecular chain crosslinking agent in an organic solution, and a Michael addition reaction occurs between amino groups and acrylates during the interfacial polymerization process. This reverse osmosis membrane has the following beneficial effects:

[0034] 1. The addition of the membrane strengthening liquid enables different polymer chains to be interconnected through the intermolecular chain crosslinking agent, forming a three-dimensional network crosslinked structure that restricts the movement of molecular chains, reduces the creep and deformation of molecular chains at high temperatures, improves the thermal stability and mechanical properties of the material, and enables the final product to withstand higher temperatures without deformation or decomposition.

[0035] 2. The polyamide layer can undergo a neutralization reaction with the by-product hydrogen chloride, improving the crosslinking degree of the polyamide layer, thereby enhancing the high-temperature resistance of the polyamide layer.

[0036] 3. The raw materials for preparing the membrane strengthening liquid are easily obtained, the industrial production cost is low, and the use of the membrane strengthening liquid does not require major modifications to the preparation process, making it easy to improve the existing technology.

[0037] 4. The materials used to prepare the reverse osmosis membrane are easily obtained, the operations required for preparing the reverse osmosis membrane are simple, and it is easy for industrial production. Specific embodiments

[0038] The following further details the specific embodiments of the present invention, but the present invention is not limited to these embodiments. Any improvement or substitution based on the basic spirit of this embodiment still falls within the scope protected by the claims of the present invention.

[0039] Comparative example 1

[0040] (1) Preparation of the base membrane

[0041] Using polysulfone as the solute and N-methylpyrrolidone as the solvent, a casting solution with a polysulfone content of 20% was prepared. After the polysulfone was completely dissolved, it was left to stand for defoaming at room temperature. After defoaming was completed, phase separation was carried out in a coagulation bath at 20°C, and a base film with a thickness of 5 mil was scraped. After scraping, the base film was placed in pure water for standby.

[0042] (2) Polyamine treatment

[0043] The above-mentioned base film was soaked on one side in an aqueous solution containing 2% m-phenylenediamine and 0.02% sodium hydroxide for 1 minute. After soaking, the film surface was dried.

[0044] (3) Organic phase treatment

[0045] The film after polyamine treatment was soaked in cyclohexane containing 0.1% benzoyl trichloride for 30 seconds, and then taken out after soaking.

[0046] (4) Heat treatment

[0047] After the organic phase treatment was completed, the resulting film after the reaction was rinsed with pure water, and then the film after pure water rinsing was heat-treated at a temperature of 70°C for 5 minutes to obtain a composite reverse osmosis membrane.

[0048] In the preparation method of the reverse osmosis membrane in Example 1, an organic compound containing a polyacrylate group was not added.

[0049] Example 1

[0050] (1) Base film preparation

[0051] Using polysulfone as the solute and N-methylpyrrolidone as the solvent, a casting solution with a polysulfone content of 20% was prepared. After the polysulfone was completely dissolved, it was left to stand for defoaming at room temperature. After defoaming was completed, phase separation was carried out in a coagulation bath at 20°C, and a base film with a thickness of 5 mil was scraped. After scraping, the base film was placed in pure water for standby.

[0052] (2) Polyamine treatment

[0053] The above-mentioned base film was soaked on one side in an aqueous solution containing 2% m-phenylenediamine and 0.02% sodium hydroxide for 1 minute. After soaking, the film surface was dried.

[0054] (3) Organic phase treatment

[0055] The film after polyamine treatment was soaked in a film strengthening solution containing 0.1% benzoyl trichloride and 0.01% trimethylolpropane triacrylate for 30 seconds, and then taken out after the reaction ended.

[0056] (4) Heat treatment

[0057] After the treatment of the organic phase, the obtained membrane after the completion of the reaction is rinsed with pure water, and then the membrane after pure water rinsing is heat-treated at a temperature of 70 °C for 5 minutes to obtain a composite reverse osmosis membrane.

[0058] Example 2

[0059] (1) Preparation of the base membrane

[0060] A casting solution with a polysulfone content of 20% is prepared using polysulfone as the solute and N-methylpyrrolidone as the solvent. After the polysulfone is completely dissolved, it is left to stand at room temperature for defoaming. After defoaming is completed, phase separation is carried out in a coagulation bath at 20 °C, and a base membrane with a thickness of 5 mil is scraped. After scraping, the base membrane is placed in pure water for standby.

[0061] (2) Polyamine treatment

[0062] The above base membrane is soaked on one side in an aqueous solution containing 2% m-phenylenediamine and 0.02% sodium hydroxide for 1 minute, and after soaking, the membrane surface is dried.

[0063] (3) Organic phase treatment

[0064] The membrane after polyamine treatment is soaked in a membrane strengthening solution containing 0.1% benzoyl trichloride and 0.5% trimethylolpropane triacrylate for 30 s, and after the reaction is completed, it is taken out.

[0065] (4) Heat treatment

[0066] After the treatment of the organic phase, the obtained membrane after the completion of the reaction is rinsed with pure water, and then the membrane after pure water rinsing is heat-treated at a temperature of 70 °C for 5 minutes to obtain a composite reverse osmosis membrane.

[0067] Example 3

[0068] (1) Preparation of the base membrane

[0069] A casting solution with a polysulfone content of 20% is prepared using polysulfone as the solute and N-methylpyrrolidone as the solvent. After the polysulfone is completely dissolved, it is left to stand at room temperature for defoaming. After defoaming is completed, phase separation is carried out in a coagulation bath at 20 °C, and a base membrane with a thickness of 5 mil is scraped. After scraping, the base membrane is placed in pure water for standby.

[0070] (2) Polyamine treatment

[0071] The above base membrane is soaked on one side in an aqueous solution containing 2% m-phenylenediamine and 0.02% sodium hydroxide for 1 minute, and after soaking, the membrane surface is dried.

[0072] (3) Organic phase treatment

[0073] The film treated with polyamine was immersed in a film strengthening solution containing 0.1% benzoyl trichloride and 0.01% pentaerythritol tetraacrylate for 30 s, and then taken out after the reaction ended.

[0074] (4) Heat treatment

[0075] After the organic phase treatment was completed, the obtained film after the reaction was rinsed with pure water, and then the film after pure water rinsing was heat-treated at a temperature of 70 °C for 5 minutes to obtain a composite reverse osmosis membrane.

[0076] Example 4

[0077] (1) Preparation of the base film

[0078] A casting solution with a polysulfone content of 20% was prepared using polysulfone as the solute and N-methylpyrrolidone as the solvent. After the polysulfone was completely dissolved, it was left to stand at room temperature for defoaming. After defoaming was completed, phase separation was carried out in a coagulation bath at 20 °C, and a base film with a thickness of 5 mil was scraped. After scraping, the base film was placed in pure water for later use.

[0079] (2) Polyamine treatment

[0080] The above base film was immersed on one side in an aqueous solution containing 2% m-phenylenediamine and 0.02% sodium hydroxide for 1 min, and after immersion, the film surface was dried.

[0081] (3) Organic phase treatment

[0082] The film treated with polyamine was immersed in a film strengthening solution containing 0.1% benzoyl trichloride + 0.5% pentaerythritol tetraacrylate for 30 s, and then taken out after the reaction ended.

[0083] (4) Heat treatment

[0084] After the organic phase treatment was completed, the obtained film after the reaction was rinsed with pure water, and then the film after pure water rinsing was heat-treated at a temperature of 70 °C for 5 minutes to obtain a composite reverse osmosis membrane.

[0085] Table 1 Comparison of the high-temperature resistance performance results of the reverse osmosis membranes prepared in each example and comparative example

[0086] Test conditions: Pressure 150 psi, test solution is 2000 ppm sodium chloride solution

[0087]

[0088]

[0089] As can be seen from Table 1, the reverse osmosis membrane prepared by the present invention by adding an organic compound with a multi-acrylate group can improve the initial desalination rate and significantly reduce the attenuation of the desalination rate. However, the desalination attenuation rate of the reverse osmosis membrane prepared without adding the organic compound with a multi-acrylate group increases significantly. Therefore, the reverse osmosis membrane prepared by adding the organic compound with a multi-acrylate group has stronger stability during long-term operation under high-temperature conditions and has excellent durability and high-temperature resistance.

[0090] Although the present invention has been disclosed with the selected preferred embodiments as above, it is not intended to limit the present invention. Any researcher in the art can make changes and modifications to the research scheme of the present invention by using the design parameters and content in the above-mentioned disclosed embodiments without departing from the spirit and scope of the present invention. Therefore, any simple modifications, parameter changes and decorations made to the above embodiments according to the research essence of the present invention without departing from the content of the present invention scheme all fall within the protection scope of the present invention scheme.

Claims

1. A high temperature resistant composite reverse osmosis membrane, characterized in that: The high temperature resistant composite reverse osmosis membrane is obtained through four steps of base membrane preparation, polyamine treatment, organic phase treatment and heat treatment; the organic phase treatment is to soak the base membrane treated with polyamine in a membrane strengthening liquid; the membrane strengthening liquid is composed of benzyl chloride, a molecular chain crosslinking agent and an organic solvent, and the molecular chain crosslinking agent is an organic compound containing multiple acrylate groups.

2. A high temperature resistant composite reverse osmosis membrane according to claim 1, characterized in that: The organic compound containing multiple acrylate groups is trimethylolpropane triacrylate or pentaerythritol tetraacrylate.

3. A high temperature resistant composite reverse osmosis membrane according to claim 1, characterized in that: The organic solvent is one or more of cyclohexane, n-hexane, and ISOPAR series isoalkanes.

4. A high temperature resistant composite reverse osmosis membrane according to claim 1, characterized in that: The mass concentration of benzyl chloride in the membrane strengthening solution is 0.01-10%, and the mass concentration of the organic compound containing multiple acrylate groups is 0.001-1%.

5. A high temperature resistant composite reverse osmosis membrane as claimed in claim 3, characterized in that: The mass concentration of the trimesoyl chloride is 0.01-5%; the mass concentration of the organic compound containing multiple acrylate groups is 0.01-0.5%.

6. A method for preparing a high temperature resistant composite reverse osmosis membrane according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Basement membrane preparation The base film material is immersed in the casting liquid, and after the immersion precipitation phase conversion reaction, the base film is formed by slit coating; (2) Polyamine treatment The base film prepared in step (1) is immersed in the polyamine solution and then taken out; (3) Organic phase treatment After the surface of the membrane obtained in step (2) is dried, it is immersed in a membrane strengthening solution to perform a Michael addition reaction; (4) Heat treatment After the treatment in step (3) is completed, the membrane is taken out, rinsed with pure water, and heat treated at 40-100° C. to obtain a high-temperature resistant composite reverse osmosis membrane.

7. A method for preparing a high temperature resistant composite reverse osmosis membrane as claimed in claim 6, characterized in that: The base film material is one or more of polysulfone, polyethersulfone, polyacrylonitrile, polyimide, and polyvinylidene fluoride; the casting liquid is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

8. A method for preparing a high temperature resistant composite reverse osmosis membrane as claimed in claim 6, characterized in that: The base film has a thickness of 2 to 8 mil.

9. A method for preparing a high temperature resistant composite reverse osmosis membrane as claimed in claim 6, characterized in that: The components of the polyamine solution include water, m-phenylenediamine and an acid acceptor; the mass concentration of m-phenylenediamine in the polyamine solution is 0.1-10%, and the mass concentration of the acid acceptor is 0.001-10%; the acid acceptor is sodium hydroxide.

10. A method for preparing a high temperature resistant composite reverse osmosis membrane according to claim 6, characterized in that: The temperature of the heat treatment is 60-90°C.

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