High-temperature-resistant polyamide composite nanofiltration membrane for water purification and preparation method thereof

Abstract

The application discloses a kind of high-temperature-resistant polyamide composite nanofiltration membrane for water purification and preparation method thereof, and it relates to nanofiltration membrane preparation technical field.In the application, amide carbon nanotubes are loaded on porous support base film, which on the one hand stably combines the porous support base film and polyamide separation layer, and on the other hand can isolate the polyamide separation layer and the porous support base film, reduce the probability of interlayer thermal deformation, so that the high-temperature-resistant polyamide composite nanofiltration membrane is not easy to deform, prolonging its service life;The amine monomer containing benzene ring structure is used in the application, which has better high-temperature resistance than ordinary amine monomers, and further improves the high-temperature resistance in cooperation with amide carbon nanotubes;The application also provides an anti-pollution hydration layer on the surface of the polyamide separation layer, which can effectively combine water molecules, prevent pollutants from directly contacting the membrane surface without affecting the flux of the nanofiltration membrane, reduce the adsorption of pollutants, and improve the anti-pollution property of the nanofiltration membrane.

Description

Technical Field

[0001] This invention relates to the field of nanofiltration membrane preparation technology, specifically a high-temperature resistant polyamide composite nanofiltration membrane for water purification and its preparation method. Background Technology

[0002] Nanofiltration is a pressure-driven membrane separation technology that lies between reverse osmosis and ultrafiltration. It achieves separation through sieving, charge repulsion, and the Donnan effect. Nanofiltration membranes are mostly modified reverse osmosis membranes, and the materials include cellulose acetate and aromatic polyamide composite membranes. They are widely used in drinking water softening, industrial wastewater treatment, and material recovery.

[0003] Patent CN104582822A discloses an amino-siloxane flux enhancer for improving the flux of polyamide reverse osmosis membranes. However, as the flux increases, the desalination rate and antifouling performance decrease, which leads to frequent cleaning and reduces the service life of the polyamide membrane.

[0004] Therefore, we propose a high-temperature resistant polyamide composite nanofiltration membrane for water purification and its preparation method, so that the prepared polyamide composite nanofiltration membrane has high temperature resistance, high flux and anti-fouling properties. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant polyamide composite nanofiltration membrane for water purification and its preparation method, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification, comprising the following steps:

[0007] Step 1: Take the aminated carbon nanotube suspension and the porous support base membrane, place the porous support base membrane on the vacuum filter, pour the aminated carbon nanotube suspension, and then vacuum to 0.08~0.10MPa to assist deposition to obtain a porous support base membrane loaded with aminated carbon nanotubes.

[0008] Step 2: Immerse the product obtained in Step 1 in an amine monomer solution and react for 4-6 minutes. Remove excess liquid and then immerse it in a polyacrylamide chloride monomer solution for 0.5-1.5 minutes. Remove excess liquid and cure at high temperature to form a polyamide separation layer.

[0009] Step 3: Take the product obtained in Step 2, pour in a 2-4% (w / w) polyethylene glycol aqueous solution, react for 4-6 minutes, pour off the excess solution, rinse 3-5 times to form an anti-fouling hydration layer, and obtain a high-temperature resistant polyamide composite nanofiltration membrane.

[0010] Furthermore, in step 1, the porous support substrate membrane is one of polyethersulfone membrane, polyvinyl chloride membrane, polytetrafluoroethylene membrane, and polyimide membrane;

[0011] The porous support substrate membrane has a pore size of 0.001~1.0μm.

[0012] Furthermore, in step 2, the amine monomer solution is obtained by mixing amine monomers with N,N'-dimethylacetamide and deionized water in a ratio of (1~3) g:(0.4~0.6) L:(0.4~0.6) L;

[0013] In step 2, the amine monomer is one or more of 3,3'-dihydroxybenzidine, 4,4'-diaminodiphenyl sulfone, and 3,3'-dimethylbenzidine.

[0014] Furthermore, in step 2, the polyacrylamide chloride monomer solution is obtained by mixing polyacrylamide chloride monomer and n-hexane in a ratio of (1.5~2.5) g: 1 L;

[0015] In step 2, the polyacrylamide chloride monomer is one or both of pyromellitic terephthaloyl chloride and terephthaloyl chloride.

[0016] Furthermore, in step 2, the bath ratio for impregnation is 1:(8~10).

[0017] Furthermore, in step 2, the high-temperature curing process conditions are: temperature 60~70℃, time 3~5min.

[0018] Furthermore, in step 1, the amidated carbon nanotube suspension is prepared by the following process:

[0019] S1: Take carboxylated carbon nanotubes and thionyl chloride, mix them, stir evenly, heat under reflux to react, and distill to obtain acyl chloride carbon nanotubes;

[0020] S2: Acid-chlorinated carbon nanotubes and amine monomer solutions are mixed and reacted by heating in an oil bath to obtain amidated carbon nanotubes;

[0021] S3: Mix amidated carbon nanotubes and epigallocatechin gallate, and disperse by ultrasonication to form an amidated carbon nanotube suspension.

[0022] Furthermore, in S1, the mass ratio of carboxylated carbon nanotubes to thionyl chloride is 1:(5~10).

[0023] Furthermore, in S1, the process conditions for the heating and reflux reaction are: temperature 110~115℃, time 20~22h.

[0024] Furthermore, in S2, the mass ratio of acyl chloride carbon nanotubes to amine monomer solution is 1:(3~5).

[0025] Furthermore, in S2, the process conditions for the oil bath heating reaction are: temperature 55~65℃, time 4~6h.

[0026] Furthermore, in S3, the mass ratio of amidated carbon nanotubes to epigallocatechin gallate is 1:(5~7).

[0027] Furthermore, in S3, the ultrasonic dispersion process conditions are: frequency 30~50kHz, time 15~25min.

[0028] In the above technical solution, firstly, thionyl chloride is used as an acyl chloride reagent to modify carboxylated carbon nanotubes to form acyl chloride carbon nanotubes. Then, through a nucleophilic substitution reaction between the amino groups of amine monomers and acyl chloride groups, amide bonds are generated. By controlling the excess of amine monomers, amidated carbon nanotubes are obtained. These are then mixed with epigallocatechin gallate to form an amidated carbon nanotube suspension, which is deposited on a porous support membrane to obtain a porous support membrane loaded with amidated carbon nanotubes. Next, the membrane is sequentially immersed in amine monomer solutions and polyacyl chloride monomer solutions. Unreacted amino groups in the amidated carbon nanotube suspension participate in the reaction between amine monomers and polyacyl chlorides to form a polyamide separation layer. Finally, polyethylene glycol reacts with the residual acyl chloride monomers in the polyamide separation layer to form an antifouling hydration layer on the surface of the polyamide separation layer, resulting in a high-temperature resistant polyamide composite nanofiltration membrane.

[0029] Carbon nanotubes possess a regular hollow tubular structure, allowing water molecules to flow rapidly within them. The flow resistance is lower than that of nanofiltration membranes, enabling them to be loaded onto the base membrane and thus increasing the flux of the nanofiltration membrane. Simultaneously, carbon nanotubes exhibit good tensile strength, enhancing the mechanical properties of the base membrane. The amidated carbon nanotubes contain amide bonds on their surface, which, on the one hand, stably bond the porous supporting base membrane and the polyamide separation layer, and on the other hand, isolate the polyamide separation layer from the porous supporting base membrane, reducing the probability of interlayer thermal deformation. This makes the high-temperature resistant polyamide composite nanofiltration membrane less prone to deformation and extends its service life. The amine used in this invention... The monomers contain benzene ring structures, which have better high-temperature resistance compared to ordinary amine monomers. They also synergistically enhance the high-temperature resistance by merging with amidated carbon nanotubes. In addition, this invention uses polyethylene glycol to react with the residual acyl chloride and amino groups in the polyamide separation layer, grafting them onto the surface of the polyamide separation layer to form an antifouling hydration layer. Polyethylene glycol contains multiple hydroxyl groups, which can effectively bind water molecules. Its chain segments themselves can act as molecular brushes, preventing pollutants from directly contacting the membrane surface without affecting the nanofiltration membrane flux, reducing pollutant adsorption, and improving the antifouling properties of the nanofiltration membrane.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. In this invention, amidated carbon nanotubes are loaded onto a porous support base membrane. On the one hand, the porous support base membrane and the polyamide separation layer are stably combined. On the other hand, the polyamide separation layer and the porous support base membrane are isolated, reducing the probability of interlayer thermal deformation. This makes the high-temperature resistant polyamide composite nanofiltration membrane less prone to deformation and extends its service life.

[0032] 2. In this invention, the amine monomers used contain benzene ring structures, which have better high-temperature resistance than ordinary amine monomers. In conjunction with amidation of carbon nanotubes, the high-temperature resistance is further improved.

[0033] 3. In this invention, a polyethylene glycol antifouling hydration layer is also provided on the surface of the polyamide separation layer, which can effectively bind water molecules and prevent pollutants from directly contacting the membrane surface without affecting the nanofiltration membrane flux, thereby reducing the adsorption of pollutants and improving the antifouling properties of the nanofiltration membrane. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the following specific implementation,

[0036] The porous supporting substrate membrane is a polyethersulfone membrane with a pore size of 0.22 μm;

[0037] The amine monomer is 3,3'-dihydroxybenzidine;

[0038] The polyacryl chloride monomer is pyromellitic trimethylol chloride;

[0039] Polyethylene glycol, average molecular weight 400;

[0040] Carboxylated carbon nanotubes, with a diameter of 1~2 nm and a length of 0.5~2 μm;

[0041] Preparation of piperazine solution: Piperazine, sodium dodecylbenzenesulfonate, and water are mixed and stirred evenly at a mass ratio of 0.5:0.1:100.

[0042] Example 1: A method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification, comprising the following steps:

[0043] (1) Preparation of amidated carbon nanotube suspension:

[0044] S1: Carboxylated carbon nanotubes and thionyl chloride are mixed, stirred evenly, heated under reflux, and distilled to obtain acyl chloride carbon nanotubes; S2: Acyl chloride carbon nanotubes and amine monomer solution are mixed and heated in an oil bath to obtain amidated carbon nanotubes; S3: Amidated carbon nanotubes and epigallocatechin gallate are mixed and ultrasonically dispersed to form an amidated carbon nanotube suspension; In S1, the mass ratio of carboxylated carbon nanotubes to thionyl chloride is 1:10; The reflux reaction conditions in S1 are: temperature 115℃, time 22h; In S2, the mass ratio of acyl chloride carbon nanotubes to amine monomer solution is 1:5; The oil bath reaction conditions in S2 are: temperature 65℃, time 6h; In S3, the mass ratio of amidated carbon nanotubes to epigallocatechin gallate is 1:7; The ultrasonic dispersion conditions in S3 are: frequency 50kHz, time 25min.

[0045] (2) Preparation of high-temperature resistant polyamide composite nanofiltration membrane:

[0046] Step 1: Take the amidated carbon nanotube suspension and the porous support membrane, place the porous support membrane on a vacuum filter, pour out the amidated carbon nanotube suspension, and then apply a vacuum to 0.10 MPa to assist deposition, obtaining a porous support membrane loaded with amidated carbon nanotubes; Step 2: Immerse the product obtained in Step 1 in an amine monomer solution, react for 6 min, remove excess liquid, then immerse in a polyacrylamide chloride monomer solution and react for 1.5 min, remove excess liquid, and cure at high temperature to form a polyamide separation layer; Step 3: Take the product obtained in Step 2, pour out a mass fraction of... A 4% polyethylene glycol aqueous solution was reacted for 6 minutes, excess solution was discarded, and the membrane was rinsed 5 times to form an antifouling hydration layer, thus obtaining a high-temperature resistant polyamide composite nanofiltration membrane. In step 2, the amine monomer solution was obtained by mixing amine monomers with N,N'-dimethylacetamide and deionized water in a ratio of 3g:0.6L:0.6L. In step 2, the polyacrylamide chloride monomer solution was obtained by mixing polyacrylamide chloride with n-hexane in a ratio of 2.5g:1L. In step 3, the impregnation bath ratio was 1:10. In step 2, the high-temperature curing process conditions were: temperature 70℃, time 5 minutes.

[0047] Example 2: A method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification, comprising the following steps:

[0048] (1) Preparation of amidated carbon nanotube suspension:

[0049] S1: Carboxylated carbon nanotubes and thionyl chloride are mixed, stirred evenly, heated under reflux, and distilled to obtain acyl chloride carbon nanotubes; S2: Acyl chloride carbon nanotubes and amine monomer solution are mixed and heated in an oil bath to obtain amidated carbon nanotubes; S3: Amidated carbon nanotubes and epigallocatechin gallate are mixed and ultrasonically dispersed to form an amidated carbon nanotube suspension; In S1, the mass ratio of carboxylated carbon nanotubes to thionyl chloride is 1:8; The reflux reaction conditions in S1 are: temperature 112℃, time 21h; In S2, the mass ratio of acyl chloride carbon nanotubes to amine monomer solution is 1:4; The oil bath reaction conditions in S2 are: temperature 60℃, time 5h; In S3, the mass ratio of amidated carbon nanotubes to epigallocatechin gallate is 1:6; The ultrasonic dispersion conditions in S3 are: frequency 40kHz, time 20min.

[0050] (2) Preparation of high-temperature resistant polyamide composite nanofiltration membrane:

[0051] Step 1: Take the amidated carbon nanotube suspension and the porous support membrane, place the porous support membrane on a vacuum filter, pour out the amidated carbon nanotube suspension, and then apply a vacuum to 0.09 MPa to assist deposition, obtaining a porous support membrane loaded with amidated carbon nanotubes; Step 2: Immerse the product obtained in Step 1 in an amine monomer solution, react for 5 min, remove excess liquid, then immerse in a polyacrylamide chloride monomer solution and react for 1.0 min, remove excess liquid, and cure at high temperature to form a polyamide separation layer; Step 3: Take the product obtained in Step 2, pour out the mass fraction A 3% polyethylene glycol aqueous solution was reacted for 5 minutes, excess solution was discarded, and the membrane was rinsed 4 times to form an antifouling hydration layer, thus obtaining a high-temperature resistant polyamide composite nanofiltration membrane. In step 2, the amine monomer solution was obtained by mixing amine monomers with N,N'-dimethylacetamide and deionized water in a ratio of 2g:0.5L:0.5L. In step 2, the polyacrylamide chloride monomer solution was obtained by mixing polyacrylamide chloride with n-hexane in a ratio of 2.0g:1L. In step 2, the impregnation bath ratio was 1:9. In step 3, the high-temperature curing process conditions were: temperature 65℃, time 4 minutes.

[0052] Example 3: A method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification, comprising the following steps:

[0053] (1) Preparation of amidated carbon nanotube suspension:

[0054] S1: Carboxylated carbon nanotubes and thionyl chloride are mixed, stirred evenly, heated under reflux, and distilled to obtain acyl chloride carbon nanotubes; S2: Acyl chloride carbon nanotubes and amine monomer solution are mixed and heated in an oil bath to obtain amidated carbon nanotubes; S3: Amidated carbon nanotubes and epigallocatechin gallate are mixed and ultrasonically dispersed to form an amidated carbon nanotube suspension; In S1, the mass ratio of carboxylated carbon nanotubes to thionyl chloride is 1:5; The reflux reaction conditions in S1 are: temperature 110℃, time 20h; In S2, the mass ratio of acyl chloride carbon nanotubes to amine monomer solution is 1:3; The oil bath reaction conditions in S2 are: temperature 55℃, time 4h; In S3, the mass ratio of amidated carbon nanotubes to epigallocatechin gallate is 1:5; The ultrasonic dispersion conditions in S3 are: frequency 30kHz, time 15min.

[0055] (2) Preparation of high-temperature resistant polyamide composite nanofiltration membrane:

[0056] Step 1: Take the amidated carbon nanotube suspension and the porous support membrane, place the porous support membrane on a vacuum filter, pour out the amidated carbon nanotube suspension, and then apply a vacuum to 0.08 MPa to assist deposition, obtaining a porous support membrane loaded with amidated carbon nanotubes; Step 2: Immerse the product obtained in Step 1 in an amine monomer solution, react for 4 min, remove excess liquid, then immerse in a polyacrylamide chloride monomer solution and react for 0.5 min, remove excess liquid, and cure at high temperature to form a polyamide separation layer; Step 3: Take the product obtained in Step 2, pour out the mass fraction A 2% polyethylene glycol aqueous solution was reacted for 4 minutes, excess solution was discarded, and the membrane was rinsed 3 times to form an anti-fouling hydration layer, thus obtaining a high-temperature resistant polyamide composite nanofiltration membrane. In step 2, the amine monomer solution was obtained by mixing amine monomers with N,N'-dimethylacetamide and deionized water in a ratio of 1g:0.4L:0.4L. In step 2, the polyacrylamide chloride monomer solution was obtained by mixing polyacrylamide chloride with n-hexane in a ratio of 1.5g:1L. In step 2, the impregnation bath ratio was 1:8. In step 2, the high-temperature curing process conditions were: temperature 60℃, time 3 minutes.

[0057] Comparative Example 1: Compared with Example 1, no amidation modification was performed on the carbon nanotubes, and all other conditions remained unchanged. The specific steps are as follows:

[0058] Carboxylated carbon nanotubes and epigallocatechin gallate were mixed at a mass ratio of 1:7 and ultrasonically dispersed to form a carbon nanotube suspension.

[0059] Step 1: Take a carbon nanotube suspension and a porous support membrane. Place the porous support membrane on a vacuum filtration device, pour out the carbon nanotube suspension, and then apply a vacuum to 0.10 MPa to assist deposition, obtaining a porous support membrane loaded with carbon nanotubes. Step 2: Immerse the product obtained in Step 1 in an amine monomer solution and react for 6 minutes. Remove excess liquid, then immerse it in a polyacrylamide chloride monomer solution and react for 1.5 minutes. Remove excess liquid and cure at high temperature to form a polyamide separation layer. Step 3: Take the product obtained in Step 2 and pour out a 4% (w / w) polyamide solution... Ethylene glycol aqueous solution was reacted for 6 minutes, excess solution was discarded, and the membrane was rinsed 5 times to form an anti-fouling hydration layer, thus obtaining a high-temperature resistant polyamide composite nanofiltration membrane. In step 2, the amine monomer solution was obtained by mixing amine monomers with N,N'-dimethylacetamide and deionized water in a ratio of 3g:0.6L:0.6L. In step 2, the polyacrylamide chloride monomer solution was obtained by mixing polyacrylamide chloride with n-hexane in a ratio of 2.5g:1L. In step 2, the impregnation bath ratio was 1:10. In step 2, the high-temperature curing process conditions were: temperature 70℃, time 5 minutes.

[0060] Comparative Example 2: Compared with Example 1, no anti-fouling hydration layer was provided on the surface of the polyamide separation layer, while other conditions remained unchanged. The specific steps are as follows:

[0061] (1) Preparation of amidated carbon nanotube suspension:

[0062] S1: Carboxylated carbon nanotubes and thionyl chloride are mixed, stirred evenly, heated under reflux, and distilled to obtain acyl chloride carbon nanotubes; S2: Acyl chloride carbon nanotubes and amine monomer solution are mixed and heated in an oil bath to obtain amidated carbon nanotubes; S3: Amidated carbon nanotubes and epigallocatechin gallate are mixed and ultrasonically dispersed to form an amidated carbon nanotube suspension; In S1, the mass ratio of carboxylated carbon nanotubes to thionyl chloride is 1:10; The reflux reaction conditions in S1 are: temperature 115℃, time 22h; In S2, the mass ratio of acyl chloride carbon nanotubes to amine monomer solution is 1:5; The oil bath reaction conditions in S2 are: temperature 65℃, time 6h; In S3, the mass ratio of amidated carbon nanotubes to epigallocatechin gallate is 1:7; The ultrasonic dispersion conditions in S3 are: frequency 50kHz, time 25min.

[0063] (2) Preparation of high-temperature resistant polyamide composite nanofiltration membrane:

[0064] Step 1: Take the amidated carbon nanotube suspension and the porous support membrane, place the porous support membrane on a vacuum filtration device, pour out the amidated carbon nanotube suspension, and then apply a vacuum to 0.10 MPa to assist deposition to obtain a porous support membrane loaded with amidated carbon nanotubes; Step 2: Immerse the product obtained in Step 1 in an amine monomer solution, react for 6 min, remove excess liquid, then immerse in a polyacrylamide chloride monomer solution and react for 1.5 min, remove excess liquid, and cure at high temperature to form a polyamide separation layer, thus obtaining a high-temperature resistant polyamide composite nanofiltration membrane; In Step 2, the amine monomer solution is obtained by mixing amine monomer with N,N'-dimethylacetamide and deionized water in a ratio of 3 g: 0.6 L: 0.6 L; In Step 2, the polyacrylamide chloride monomer solution is obtained by mixing polyacrylamide chloride with n-hexane in a ratio of 2.5 g: 1 L.

[0065] Comparative Example 3: Compared with Example 1, the amine monomer solution was replaced with a piperazine solution, while all other conditions remained unchanged. The specific steps are as follows:

[0066] (1) Preparation of amidated carbon nanotube suspension:

[0067] S1: Carboxylated carbon nanotubes and thionyl chloride were mixed, stirred evenly, heated under reflux, and distilled to obtain acyl chloride carbon nanotubes; S2: Acyl chloride carbon nanotubes and piperazine solution were mixed and heated in an oil bath to obtain amidated carbon nanotubes; S3: Amide carbon nanotubes and epigallocatechin gallate were mixed and ultrasonically dispersed to form an amidated carbon nanotube suspension; In S1, the mass ratio of carboxylated carbon nanotubes to thionyl chloride was 1:10; The reflux reaction conditions in S1 were: temperature 115℃, time 22h; In S2, the mass ratio of acyl chloride carbon nanotubes to piperazine solution was 1:5; The oil bath reaction conditions in S2 were: temperature 65℃, time 6h; In S3, the mass ratio of amidated carbon nanotubes to epigallocatechin gallate was 1:7; The ultrasonic dispersion conditions in S3 were: frequency 50kHz, time 25min.

[0068] (2) Preparation of high-temperature resistant polyamide composite nanofiltration membrane:

[0069] Step 1: Take the amidated carbon nanotube suspension and the porous support membrane, place the porous support membrane on a vacuum filter, pour out the amidated carbon nanotube suspension, and then apply a vacuum to 0.10 MPa to assist deposition, obtaining a porous support membrane loaded with amidated carbon nanotubes; Step 2: Immerse the product obtained in Step 1 in a piperazine solution, react for 6 min, remove excess liquid, then immerse in a polyacrylamide chloride monomer solution and react for 1.5 min, remove excess liquid, and cure at high temperature to form a polyamide separation layer; Step 3: Take the product obtained in Step 2, pour out the mass fraction A 4% polyethylene glycol aqueous solution was reacted for 6 minutes, excess solution was discarded, and the membrane was rinsed 5 times to form an antifouling hydration layer, thus obtaining a high-temperature resistant polyamide composite nanofiltration membrane. In step 2, the piperazine solution was obtained by mixing piperazine with N,N'-dimethylacetamide and deionized water in a ratio of 3g:0.6L:0.6L. In step 2, the polyacrylamide chloride monomer solution was obtained by mixing polyacrylamide chloride with n-hexane in a ratio of 2.5g:1L. In step 3, the impregnation bath ratio was 1:10. In step 2, the high-temperature curing process conditions were: temperature 70℃, time 5 minutes.

[0070] Comparative Example 4: Compared with Example 1, the carbon nanotubes were not aminated, the anti-fouling hydration layer was not set on the surface of the polyamide separation layer, and the amine monomer solution was replaced with piperazine solution, while the other conditions remained unchanged.

[0071] Experiment: The high-temperature resistant polyamide composite nanofiltration membranes obtained in Examples 1-3 and Comparative Examples 1-4 were tested for various properties;

[0072] Flux and rejection rate test: The flux and rejection rate of the prepared high-temperature resistant polyamide composite nanofiltration membrane were tested at 25℃ and 85℃ through a high-temperature cross-flow filtration experiment. The feed solution was a magnesium sulfate aqueous solution with a concentration of 1g / L, and the test pressure was set to 10 bar.

[0073] flux ;

[0074] V represents the filtrate volume; A represents the filtration surface volume; t represents the filtration time; P represents the test pressure.

[0075] Retention rate ;

[0076] C p Indicates the solute concentration of the liquid; C f Indicates the solute concentration in the filtrate;

[0077] Anti-fouling test: The nanofiltration membrane was pre-pressed with a 3000 mg / L NaCl aqueous solution at 5.0 MPa for 30 min. The initial flux J0 was monitored until it stopped decreasing continuously. Then, 500 mg / L bovine serum was mixed with the NaCl aqueous solution, and the membrane was run at 5.0 MPa for another 6 h. The flux J was then measured. t The reverse osmosis membrane will be cleaned, and the flux of the cleaned membrane will be measured. rec Calculate flux recovery rate (FRR) f ;

[0078] Flux recovery rate ;

[0079]

[0080] Based on the data in the table above, the following conclusions can be drawn:

[0081] Compared to Example 1, Comparative Example 1 did not perform amidation modification on the carbon nanotubes, Comparative Example 2 did not set an antifouling hydration layer on the surface of the polyamide separation layer, and Comparative Example 3 replaced the amine monomer solution with a piperazine solution. The performance of the resulting high-temperature resistant polyamide composite nanofiltration membranes decreased to varying degrees. This is because amidation of the carbon nanotubes stabilizes the porous support membrane and the polyamide separation layer while also isolating them, reducing the probability of interlayer thermal deformation and making the high-temperature resistant polyamide composite nanofiltration membrane less prone to deformation, thus extending its service life. The polyethylene glycol in the antifouling hydration layer contains... Having multiple hydroxyl groups, it can effectively bind water molecules, preventing pollutants from directly contacting the membrane surface without affecting the nanofiltration membrane flux, reducing pollutant adsorption, and improving the antifouling performance of the nanofiltration membrane. The amine monomers used in this invention contain benzene ring structures, which have better high-temperature resistance than ordinary amine monomers. In conjunction with modified carbon nanotubes, the high-temperature resistance is further improved. In Example 4, the carbon nanotubes were not amidated, and no antifouling hydration layer was set on the surface of the polyamide separation layer. At the same time, the amine monomer solution was replaced with piperazine solution, and the performance of the resulting high-temperature resistant polyamide composite nanofiltration membrane decreased more significantly.

[0082] In summary, the modification of materials and the setting of process conditions for preparing high-temperature resistant polyamide composite nanofiltration membranes in this application can promote the improvement of their overall performance.

[0083] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification, characterized in that: Includes the following steps: Step 1: Take the aminated carbon nanotube suspension and the porous support base membrane, place the porous support base membrane on the vacuum filter, pour the aminated carbon nanotube suspension, and then vacuum to 0.08~0.10MPa to assist deposition to obtain a porous support base membrane loaded with aminated carbon nanotubes. Step 2: Immerse the product obtained in Step 1 in an amine monomer solution and react for 4-6 minutes. Remove excess liquid and then immerse it in a polyacrylamide chloride monomer solution for 0.5-1.5 minutes. Remove excess liquid and cure at high temperature to form a polyamide separation layer. Step 3: Take the product obtained in Step 2, pour in a 2-4% (w / w) polyethylene glycol aqueous solution, react for 4-6 minutes, pour off the excess solution, rinse 3-5 times to form an anti-fouling hydration layer, and obtain a high-temperature resistant polyamide composite nanofiltration membrane. In step 1, the amidated carbon nanotube suspension is prepared by the following process: S1: Take carboxylated carbon nanotubes and thionyl chloride, mix them, stir evenly, heat under reflux to react, and distill to obtain acyl chloride carbon nanotubes; S2: Acid-chlorinated carbon nanotubes and amine monomer solutions are mixed and reacted by heating in an oil bath to obtain amidated carbon nanotubes; S3: Mix amidated carbon nanotubes and epigallocatechin gallate, and disperse by ultrasonication to form an amidated carbon nanotube suspension.

2. The method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification according to claim 1, characterized in that: In step 2, the amine monomer is one or more of 3,3'-dihydroxybenzidine, 4,4'-diaminodiphenyl sulfone, and 3,3'-dimethylbenzidine; In step 2, the polyacrylamide chloride monomer is one or both of pyromellitic acid trimethylolpropionate chloride and terephthaloyl chloride.

3. The method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification according to claim 1, characterized in that: In S1, the process conditions for the heating and reflux reaction are: temperature 110~115℃, time 20~22h.

4. The method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification according to claim 1, characterized in that: In S2, the process conditions for the oil bath heating reaction are: temperature 55~65℃, time 4~6h.

5. The method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification according to claim 1, characterized in that: In S1, the mass ratio of carboxylated carbon nanotubes to thionyl chloride is 1:(5~10).

6. The method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification according to claim 1, characterized in that: In step 1, the porous support base membrane is one of polyethersulfone membrane, polyvinyl chloride membrane, polytetrafluoroethylene membrane, and polyimide membrane; The porous support substrate membrane has a pore size of 0.001~1.0μm.

7. The method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification according to claim 1, characterized in that: In step 2, the high-temperature curing process conditions are: temperature 60~70℃, time 3~5min.

8. The method for preparing a high-temperature resistant polyamide composite nanofiltration membrane for water purification according to claim 1, characterized in that: In S2, the mass ratio of acyl chloride carbon nanotubes to amine monomer solution is 1:(3~5).

9. A high-temperature resistant polyamide composite nanofiltration membrane for water purification, characterized in that: The preparation method according to any one of claims 1 to 8 is used.

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