Novel polysulfonamide composite nanofiltration membrane and preparation method thereof

Abstract

The invention discloses a novel polysulfonamide composite nanofiltration membrane and a preparation method thereof, and belongs to the technical field of membrane separation. The method comprises the following steps: preparing a 2-chloro-4, 6-amino-[1, 3, 5]-triazine (CAT) amine monomer, cleaning an ultrafiltration base membrane, immersing the ultrafiltration base membrane in a CAT aqueous solution with a concentration of 2.0-10.0 g / L, adjusting the pH value of the solution to 8-13, immersing the ultrafiltration base membrane for 1-30 min, taking out the ultrafiltration base membrane, removing excess water on the surface of the ultrafiltration base membrane, immersing the ultrafiltration base membrane in an organic solvent containing a sulfonyl chloride organic monomer with a concentration of 3.0-15.0 g / L, carrying out an interface reaction, taking out the ultrafiltration base membrane after 5-20 min, washing the ultrafiltration base membrane, and drying the ultrafiltration base membrane. And performing post-treatment for 5-55 minutes at the temperature of 35-95 DEG C to obtain the triazine ring group polysulfonamide composite nanofiltration membrane. The prepared triazine ring amino polysulfonamide composite nanofiltration membrane has good separation performance and acid-resistant stability, and shows good application prospects.

Description

Technical Field

[0001] This invention relates to a novel polysulfonamide composite nanofiltration membrane and its preparation method, specifically to a triazine cyclic polysulfonamide composite nanofiltration membrane constructed by interfacial polymerization of a triazine cyclic amine aqueous monomer and a sulfonyl chloride oil monomer, and its preparation method, belonging to the field of membrane separation technology. Background Technology

[0002] With the development of the industrial economy, large amounts of acidic wastewater are generated in fields such as metallurgy, semiconductor industry, metal processing, and new energy battery recycling. Due to their high content of metal ions and inorganic acids, the harmless treatment of acidic wastewater is difficult and costly. Nanofiltration membranes, with their nanopore size and molecular weight cutoff of 200-2000 Da, can selectively separate monovalent and polyvalent salts. They offer advantages such as low energy consumption, simple operation, high safety, and environmental friendliness, making them significant for improving acidic wastewater treatment and resource recovery.

[0003] Commercial nanofiltration membranes are primarily polyamide (PA) composite membranes prepared via interfacial polymerization, characterized by low cost and excellent separation performance. However, if PA nanofiltration membranes are exposed to strong acidic environments for extended periods, the amide bonds are prone to hydrolysis, leading to damage to the separation layer structure, reduced retention rate, and decreased separation performance. Researchers have introduced acid-resistant functional groups into interfacial polymerization to replace amide groups, thereby improving the acid resistance of the separation membrane. Polysulfonamide structures possess excellent acid and alkali resistance, thermal stability, and oxidation resistance, and have been widely used in recent years to prepare novel acid-resistant nanofiltration composite membranes. Examples include patents US683711, US6873996, US20120152839, CN102120149, CN103260731, CN 106999870, CN107126850, CN 113509839, CN11678593, CN115608176, and related literature such as Desalination, 315: 164–172 (2013), Journal of Membrane Science, 415–416:122–131 (2012), Journal of Materials Science, 54: 886–900 (2018), Chemical Engineering Research and Design, 155: 172–179 (2020), and Separation and Purification Technology, 239:116528. (2020) et al. reported on the preparation of polysulfonamide nanofiltration composite membranes by interfacial polymerization of polyamines and polysulfonyl chlorides. However, the reactivity of polysulfonyl chloride monomers is lower than that of polyacrylamide monomers. Polysulfonamide composite membranes prepared by traditional interfacial polymerization techniques have low separation performance, and there are still few commercially available acid-resistant nanofiltration membranes based on polysulfonamide structures.

[0004] Cyanuronic acid (CC) forms a conjugated structure through alternating nitrogen and carbon single and double bonds. This structure undergoes interfacial polymerization with aqueous monomers to prepare triazine-containing polymer membranes. These membranes do not contain amide groups and exhibit better acid resistance. Introducing triazine groups into acid-resistant nanofiltration membranes with polysulfonamide structures yields composite membranes with even better acid resistance, high separation performance, and long-term stable operation, showing significant application potential. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a triazine cyclic amino polysulfonamide composite nanofiltration membrane prepared from a melamine-treated aqueous monomer and a sulfonyl chloride oil monomer, and its preparation method.

[0006] A triazine cyclic amino polysulfonamide composite nanofiltration membrane and its preparation method mainly include the following steps:

[0007] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0008] Disperse the weighed cyanuric chloride (CC) in an organic solvent and stir thoroughly in an ice-water bath to dissolve it. Then, introduce ammonia gas with a molar ratio of 1:1 to 6:1 with CC and carry out the substitution reaction under ice bath conditions. After 0.2 to 2.0 hours, raise the temperature to 20 to 80°C and introduce ammonia gas with the same molar ratio again. Maintain the temperature and continue the reaction for 1 to 12 hours. After the reaction is completed, remove the solvent and wash thoroughly. Dry the product under vacuum to obtain 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) as a white solid.

[0009] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0010] After ultrasonically cleaning the ultrafiltration membrane in pure water, it is immersed in the aqueous solution of CAT synthesized in step (1) at a concentration of 2.0-10.0 g / L. The pH of the solution is adjusted to 8-13. After immersion for 1-30 minutes, the membrane is removed, excess water is removed from the membrane surface, and then it is immersed in an organic solvent containing sulfonyl chloride organic monomer at a concentration of 3.0-15.0 g / L for interfacial reaction. After 5-20 minutes, the membrane is removed and placed in an oven for post-treatment at 35-95℃ for 5-55 minutes to obtain the triazine cyclic polysulfonamide composite nanofiltration membrane.

[0011] Furthermore, the ultrafiltration base membrane is a polymer sheet membrane with a molecular weight cutoff of 10-100 kD, including but not limited to polysulfone (PSf), polyethersulfone (PES), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), and cellulose acetate (CA). Before use, it is ultrasonically cleaned in deionized water for 30 minutes. Polysulfone and polyether ether ketone ultrafiltration membranes are preferred.

[0012] Furthermore, the sulfonyl chloride organic monomer is an aromatic ring organic compound containing a polysulfonyl chloride group, including but not limited to one or more of 1,3-benzene disulfonyl chloride, 1,3,5-benzene trisulfonyl chloride, 1,3-naphthalene disulfonyl chloride, 1,3,6-naphthalene trisulfonyl chloride, 1,4-di(2,6-diamino)-3,3'-diphenylnaphthalene disulfonyl chloride, and 1,5-di(2-anisamino)-3,3'-anthracene disulfonyl chloride;

[0013] Furthermore, the organic solvent is an organic compound with a dielectric constant of 2 to 12, such as one or more of the following: n-hexane, cyclohexane, n-heptane, Isopar-H, Isopar-G, acetonitrile, dichloromethane, chloroform, dimethyl sulfoxide, N-methylpyrrolidone, xylene, and tetrahydrofuran.

[0014] The polysulfonamide composite nanofiltration membrane obtained in this invention is used for nanofiltration of metal ions under acidic conditions, wherein the metal ions include one or more of La, Na, Mg, etc. Furthermore, the acidic conditions have a pH value of less than or equal to 2.

[0015] This invention synthesizes a 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer by nucleophilic substitution of cyanuric chloride with ammonia. CAT is then used as the aqueous monomer in an interfacial polymerization reaction with a sulfonyl chloride oil monomer on the surface of an ultrafiltration membrane to prepare a triazine cyclic polysulfonamide composite nanofiltration membrane. Due to the smaller bond angles and greater steric hindrance of the formed sulfonamide structure, the transient structure exhibits resonance under acid nucleophilic attack, resulting in a polysulfonamide composite membrane with superior acid resistance compared to polyamide membranes. Furthermore, the conjugated structure formed by alternating single and double bonds between carbon and nitrogen atoms in the triazine ring introduced into the composite membrane also contributes to its excellent acid resistance. Therefore, the introduction of a triazine ring structure into the polyamide acid-resistant membrane process in this invention further enhances the membrane's acid resistance. The triazine cyclic polysulfonamide composite nanofiltration membrane prepared in Example 5 was used for nanofiltration separation of a 1000 ppm lanthanum sulfate (La2(SO4)3) aqueous solution at pH 2. The results showed that under room temperature operating conditions, the composite membrane retained 97.3% of La2(SO4)3. After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the retention rate of La2(SO4)3 decreased to 95.7%, a decrease of only 1.6%. Immersion in strong acid for several days had little impact on the separation performance, with only a small decrease. In comparison, a triazine cyclic polyamide comparative composite membrane prepared under the same conditions had a retention rate of 91.0% for La2(SO4)3 solutions of the same pH and concentration. After immersing the membrane in a 15% sulfuric acid solution for 14 days, the retention rate of La2(SO4)3 decreased to 69.1%, a decrease of 24%. Furthermore, [the following text is missing from the original extract]. Figure 3 Scanning electron microscopy (SEM) images showed that the surface morphology of the composite membrane remained essentially unchanged before and after acid treatment. This indicates that the triazine cyclic amino polysulfonamide composite nanofiltration membrane prepared by this invention has good acid resistance. The technique provided by this invention is simple to operate, requires no special reagents, and the excellent separation performance and acid resistance of the prepared triazine cyclic amino polysulfonamide composite nanofiltration membrane show promising application prospects. Attached Figure Description

[0016] Figure 1The reaction structures are as follows: (a) is the synthesis reaction of 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) in this invention, and (b) is the equation for the interfacial polymerization reaction of CAT with 1,3,6-naphthalenetrisulfonyl chloride.

[0017] Figure 2 The separation performance of triazine cyclopolysulfonamide composite nanofiltration membranes prepared in different embodiments of the present invention for different inorganic salts.

[0018] Figure 3 Scanning electron microscope (SEM) images of (a) the polysulfone-based membrane of Example 5, (b) the composite nanofiltration membrane prepared, and (c) the nanofiltration membrane prepared in Example 5 after immersion in 15% sulfuric acid solution for 14 days. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. It should be understood that these embodiments are merely illustrative and not restrictive; their purpose is to provide a better understanding of the content of the present invention.

[0020] Comparative Example

[0021] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0022] The weighed cyanuric chloride (CC) was dispersed in anhydrous acetonitrile and dissolved by stirring in an ice-water bath. Pure ammonia gas with a molar ratio of 3:1 to CC was introduced, and the substitution reaction was carried out under ice bath conditions. After 0.8 hours, the temperature was raised to 35°C, and ammonia gas with the same molar ratio was introduced again. The temperature was maintained and the reaction was continued for 3.5 hours. The reaction was then terminated, the solvent was removed and the product was thoroughly washed, and the product was dried under vacuum to obtain 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) as a white solid.

[0023] (2) Preparation of triazine cyclic polyamide composite membrane

[0024] After ultrasonically cleaning a polysulfone ultrafiltration membrane of appropriate size in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 3.0 g / L. The pH of the solution is adjusted to 10. After immersion for 3 minutes, it is taken out and excess water on the membrane surface is removed. Then it is immersed in a hexane solution of 5.0 g / L trimesoyl chloride (TMC) for interfacial reaction. After 10 minutes, it is taken out and placed in an oven for post-treatment at 60℃ for 15 minutes to obtain the triazine cyclic polyamide composite nanofiltration membrane.

[0025] The prepared triazine cyclic polyamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration device. The feed solution was an aqueous solution of lanthanum sulfate (La2(SO4)3) with a pH of 2 and a concentration of 1000 ppm. The test pressure was 0.4 MPa. The results showed that, under room temperature conditions, the prepared composite nanofiltration membrane had a La2(SO4)3 rejection rate of 91.0% and a permeate flux of 32.4 L·m -2 ·h -1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the La2(SO4)3 rejection rate decreased to 69.1%, and the permeation flux was 58.1 L·m. -2 ·h -1 ·bar -1 .

[0026] Example 1

[0027] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0028] The weighed cyanuric chloride (CC) was dispersed in anhydrous acetonitrile and dissolved by stirring in an ice-water bath. Pure ammonia gas with a molar ratio of 1:1 to CC was introduced, and the substitution reaction was carried out under ice bath conditions. After 2.0 hours, the temperature was raised to 80°C, and ammonia gas with the same molar ratio was introduced again. The temperature was maintained and the reaction was continued for 1 hour. The reaction was then terminated, the solvent was removed and the product was thoroughly washed, and the product was dried under vacuum to obtain 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) as a white solid.

[0029] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0030] After ultrasonically cleaning a polysulfone ultrafiltration membrane of appropriate size in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 2.0 g / L. The pH of the solution is adjusted to 8. After immersion for 30 minutes, it is taken out and excess water on the membrane surface is removed. Then it is immersed in a heptane solution of 1,3-naphthalenedisulfonyl chloride with a concentration of 3.0 g / L for interfacial reaction. After 20 minutes, it is taken out and placed in an oven for post-treatment at 95°C for 5 minutes to obtain the triazine cyclopolysulfonamide composite nanofiltration membrane.

[0031] The prepared triazine cyclophenyl polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The feed solution was a 1000 ppm lanthanum sulfate (La2(SO4)3) aqueous solution with a pH of 2, and the test pressure was 0.4 MPa. The results showed that, under room temperature conditions, the prepared composite nanofiltration membrane had a rejection rate of 93.1% for 1000 ppm La2(SO4)3 aqueous solution and a permeate flux of 27.6 L·m -2 ·h-1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the La2(SO4)3 rejection rate was 90.4%, and the permeation flux was 29.7 L·m. -2 ·h -1 ·bar -1 .

[0032] Example 2

[0033] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0034] The weighed cyanuric chloride (CC) was dispersed in anhydrous acetonitrile and dissolved by stirring in an ice-water bath. Pure ammonia gas with a molar ratio of 6:1 to CC was introduced, and the substitution reaction was carried out under ice bath conditions. After 0.2 hours, the temperature was raised to 20°C, and ammonia gas with the same molar ratio was introduced again. The temperature was maintained and the reaction was continued for 12 hours. The reaction was then terminated, the solvent was removed and the product was thoroughly washed, and the product was dried under vacuum to obtain 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) as a white solid.

[0035] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0036] After ultrasonically cleaning a polysulfone ultrafiltration membrane of appropriate size in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 10.0 g / L. The pH of the solution is adjusted to 13. After immersion for 1 minute, it is taken out and excess water on the membrane surface is removed. Then it is immersed in a heptane solution of 1,3-naphthalenedisulfonyl chloride with a concentration of 15.0 g / L for interfacial reaction. After 5 minutes, it is taken out and placed in an oven for post-treatment at 35°C for 55 minutes to obtain the triazine cyclopolysulfonamide composite nanofiltration membrane.

[0037] The prepared triazine cyclophenyl polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The feed solution was a 1000 ppm lanthanum sulfate (La2(SO4)3) aqueous solution with a pH of 2, and the test pressure was 0.4 MPa. The results showed that, under room temperature conditions, the prepared composite nanofiltration membrane had a rejection rate of 96.8% for 1000 ppm La2(SO4)3 aqueous solution and a permeate flux of 21.0 L·m -2 ·h -1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the La2(SO4)3 rejection rate was 92.1%, and the permeation flux was 25.6 L·m. -2 ·h -1 ·bar -1 .

[0038] Example 3

[0039] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0040] The weighed cyanuric chloride (CC) was dispersed in anhydrous acetonitrile and dissolved by stirring in an ice-water bath. Pure ammonia gas with a molar ratio of 4:1 to CC was introduced, and the substitution reaction was carried out under ice bath conditions. After 1.0 hour, the temperature was raised to 35°C, and ammonia gas with the same molar ratio was introduced again. The temperature was maintained and the reaction was continued for 5 hours. The reaction was then terminated, the solvent was removed and the product was thoroughly washed, and the product was dried under vacuum to obtain 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) as a white solid.

[0041] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0042] After ultrasonically cleaning a polysulfone ultrafiltration membrane of appropriate size in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 3.0 g / L. The pH of the solution is adjusted to 10. After immersion for 3 minutes, it is taken out and excess water on the membrane surface is removed. Then it is immersed in a heptane solution of 1,3-naphthalenedisulfonyl chloride with a concentration of 5.0 g / L for interfacial reaction. After 8 minutes, it is taken out and placed in an oven for post-treatment at 40°C for 20 minutes to obtain the triazine cyclopolysulfonamide composite nanofiltration membrane.

[0043] The prepared triazine cyclophenyl polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The feed solutions were lanthanum sulfate (La2(SO4)3) or sodium sulfate (Na2SO4) aqueous solution with a pH of 2 and a concentration of 1000 ppm, respectively, and the test pressure was 0.4 MPa. The results showed that, under room temperature conditions, the prepared composite nanofiltration membrane had a La2(SO4)3 rejection rate of 99.5% and a permeate flux of 21.7 L·m3. -2 ·h -1 ·bar -1 The rejection rate for Na2SO4 was 45.4%, and the permeation flux was 20.7 L·m. -2 ·h -1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the La2(SO4)3 rejection rate was 97.9%, and the permeation flux was 18.1 L·m. -2 ·h -1 ·bar -1 The Na₂SO₄ rejection rate was 41.2%, and the permeation flux was 22.6 L·m⁻². -2 ·h -1 ·bar -1 .

[0044] Example 4

[0045] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0046] The weighed cyanuric chloride (CC) was dispersed in dimethyl sulfoxide and dissolved by stirring in an ice-water bath. Pure ammonia gas with a molar ratio of 2:1 to CC was introduced, and the substitution reaction was carried out under ice bath conditions. After 1.5 hours, the temperature was raised to 40°C, and ammonia gas with the same molar ratio was introduced again. The temperature was maintained and the reaction was continued for 6 hours. The reaction was then terminated, the solvent was removed and the product was thoroughly washed, and the product was dried under vacuum to obtain 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) as a white solid.

[0047] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0048] After ultrasonically cleaning a polyether ether ketone ultrafiltration membrane of appropriate size in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 4.0 g / L. The pH of the solution is adjusted to 10. After immersion for 3 minutes, it is taken out and excess water on the membrane surface is removed. Then it is immersed in a tetrahydrofuran solution of 1,4-bis(2,6-diamino)-3,3'-diphenylnaphthalene disulfonyl chloride with a concentration of 6.0 g / L for interfacial reaction. After 8 minutes, it is taken out and placed in an oven for post-treatment at 40°C for 20 minutes to obtain the triazine cyclic polysulfonamide composite nanofiltration membrane.

[0049] The prepared triazine cyclophenyl polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The feed solutions were either lanthanum sulfate (La2(SO4)3) at pH 2 and a concentration of 1000 ppm, or sodium sulfate (Na2SO4) aqueous solution, and the test pressure was 0.4 MPa. The results showed that, at room temperature, the prepared composite nanofiltration membrane had a La2(SO4)3 rejection rate of 99.8% and a permeate flux of 14.8 L·m3. -2 ·h -1 ·bar -1 The rejection rate for Na2SO4 was 91.5%, and the permeation flux was 16.5 L·m. -2 ·h -1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the La2(SO4)3 rejection rate was 90.3%, and the permeation flux was 17.4 L·m. -2 ·h -1 ·bar -1 bar -1 The Na₂SO₄ rejection rate was 90.2%, and the permeation flux was 173.5 L·m⁻². -2 ·h -1 ·bar -1 .

[0050] Example 5

[0051] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0052] The weighed cyanuric chloride (CC) was dispersed in N-methylpyrrolidone and dissolved by stirring in an ice-water bath. Pure ammonia gas with a molar ratio of 3:1 to CC was introduced, and the substitution reaction was carried out under ice bath conditions. After 0.8 hours, the temperature was raised to 35°C, and ammonia gas with the same molar ratio was introduced again. The temperature was maintained and the reaction was continued for 3.5 hours. The reaction was then terminated, the solvent was removed and the product was thoroughly washed, and the product was dried under vacuum to obtain 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) as a white solid.

[0053] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0054] After ultrasonically cleaning a cellulose acetate ultrafiltration membrane of appropriate size in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 3.0 g / L. The pH of the solution is adjusted to 10. After immersion for 3 minutes, it is taken out and excess water on the membrane surface is removed. Then it is immersed in a hexane solution of 1,3,6-naphthalenetrisulfonyl chloride with a concentration of 5.0 g / L for interfacial reaction. After 10 minutes, it is taken out and placed in an oven for post-treatment at 60℃ for 15 minutes to obtain the triazine cyclopolysulfonamide composite nanofiltration membrane.

[0055] The prepared triazine cyclophenyl polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The feed solutions were either lanthanum sulfate (La2(SO4)3) at pH 2 and a concentration of 1000 ppm, or sodium sulfate (Na2SO4) aqueous solution, and the test pressure was 0.4 MPa. The results showed that at room temperature, the composite membrane had a La2(SO4)3 rejection rate of 97.3% and a permeate flux of 20.8 L·m3. -2 ·h -1 ·bar -1 The rejection rate for Na2SO4 was 79.5%, and the permeation flux was 22.5 L·m. -2 ·h -1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the La2(SO4)3 rejection rate was 95.7%, and the permeation flux was 21.5 L·m. -2 ·h -1 ·bar -1 The Na₂SO₄ rejection rate was 79.5%, and the permeation flux was 23.6 L·m⁻². -2 ·h -1 ·bar -1 .

[0056] Example 6

[0057] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0058] The CAT monomer was synthesized directly using the synthesis method described in Example 5.

[0059] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0060] After ultrasonically cleaning a polyvinylidene fluoride ultrafiltration membrane of appropriate size in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 3.5 g / L. The pH of the solution is adjusted to 9. After immersion for 15 minutes, it is taken out and excess water on the membrane surface is removed. Then it is immersed in Isopar-G solution of 1,5-bis(2-anisamino)-3,3'-anthracene disulfonyl chloride with a concentration of 5.5 g / L for interfacial reaction. After 16 minutes, it is taken out and placed in an oven for post-treatment at 65°C for 25 minutes to obtain the triazine cyclic polysulfonamide composite nanofiltration membrane.

[0061] The prepared triazine cyclophenyl polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The feed solutions were either lanthanum sulfate (La₂(SO₄)₃) at pH 2 and a concentration of 1000 ppm, or sodium sulfate (Na₂SO₄) aqueous solution, and the test pressure was 0.4 MPa. The results showed that, at room temperature, the composite membrane had a La₂(SO₄)₃ rejection rate of 99.1% and a permeate flux of 17.1 L·m⁻¹. -2 ·h -1 ·bar -1 The rejection rate for Na2SO4 was 84.5%, and the permeation flux was 19.2 L·m. -2 ·h -1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the rejection rate of La2(SO4)3 was 94.8%, and the permeation flux was 19.9 L·m. -2 ·h -1 ·bar -1 The rejection rate for Na2SO4 was 78.0%, and the permeation flux was 21.4 L·m. -2 ·h -1 ·bar -1 .

[0062] Example 7

[0063] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0064] The CAT monomer was synthesized directly using the synthesis method described in Example 3.

[0065] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0066] After ultrasonically cleaning a suitable-sized polyacrylonitrile ultrafiltration membrane in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 6.5 g / L. The pH of the solution is adjusted to 11.5. After immersion for 12 minutes, the membrane is removed, excess water is removed from the membrane surface, and then it is immersed in a dichloromethane solution of 1,3,5-benzenetrisulfonyl chloride with a concentration of 8.5 g / L for interfacial reaction. After 14 minutes, the membrane is removed and placed in an oven for post-treatment at 75°C for 12 minutes to obtain the triazine cyclic polysulfonamide composite nanofiltration membrane.

[0067] The prepared triazine cyclophenyl polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The feed solutions were sodium sulfate (Na₂SO₄) or magnesium chloride (MgCl₂) aqueous solutions with a pH of 2 and a concentration of 1000 ppm, respectively. The test pressure was 0.4 MPa. The results showed that, at room temperature, the composite membrane had a Na₂SO₄ rejection rate of 99.5% and a permeate flux of 6.2 L·m⁻¹. -2 ·h -1 ·bar -1 The MgCl2 rejection rate was 83%, and the permeation flux was 70.2 L·m⁻¹. -2 ·h -1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the rejection rate of Na₂SO₄ was 97.8%, and the permeation flux was 7.6 L·m⁻¹. -2 ·h -1 ·bar -1 The MgCl2 rejection rate was 79.8%, and the permeation flux was 8.6 L·m⁻². -2 ·h -1 ·bar -1 .

[0068] Example 8

[0069] (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer

[0070] The CAT monomer was synthesized directly using the synthesis method of Example 3.

[0071] (2) Preparation of triazine cyclic amine polyamide composite membrane

[0072] After ultrasonically cleaning a polyethersulfone ultrafiltration membrane of appropriate size in clean water, it is immersed in the CAT solution synthesized in step (1) with a concentration of 8.5 g / L. The pH of the solution is adjusted to 12.5. After immersion for 22 minutes, it is taken out and excess water on the membrane surface is removed. Then it is immersed in a chloroform solution of 1,3-naphthalenedisulfonyl chloride with a concentration of 10.5 g / L for interfacial reaction. After 26 minutes, it is taken out and placed in an oven for post-treatment at 55°C for 25 minutes to obtain the triazine cyclopolysulfonamide composite nanofiltration membrane.

[0073] The prepared triazine cyclophenyl polysulfonamide composite nanofiltration membrane was tested for nanofiltration performance in a cross-flow nanofiltration unit. The feed solutions were sodium sulfate (Na₂SO₄) or magnesium chloride (MgCl₂) aqueous solutions with a pH of 2 and a concentration of 1000 ppm, respectively. The test pressure was 0.4 MPa. The results showed that, at room temperature, the rejection rate for Na₂SO₄ was 91.9%, and the permeate flux was 8.0 L·m⁻¹. -2 ·h -1 ·bar -1 The MgCl2 rejection rate was 88.6%, and the permeation flux was 8.2 L·m⁻². -2 ·h -1 ·bar -1 After immersing the composite membrane in a 15% sulfuric acid solution for 14 days, the rejection rate of Na₂SO₄ was 89.7%, and the permeation flux was 9.2 L·m⁻¹. -2 ·h -1 ·bar -1 The MgCl2 rejection rate was 83.5%, and the permeation flux was 9.9 L·m⁻². -2 ·h -1 ··bar -1 .

Claims

1. A method for preparing a triazine cyclic amino polysulfonamide composite nanofiltration membrane, characterized in that, Includes the following steps: (1) Synthesis of 2-chloro-4,6-amino-[1,3,5]-triazine (CAT)amine monomer Disperse the weighed cyanuric chloride (CC) in an organic solvent and stir thoroughly in an ice-water bath to dissolve it. Then, introduce ammonia gas with a molar ratio of 1:1 to 6:1 with CC and carry out the substitution reaction under ice bath conditions. After 0.2 to 2.0 hours, raise the temperature to 20 to 80°C and introduce ammonia gas with the same molar ratio again. Maintain the temperature and continue the reaction for 1 to 12 hours. After the reaction is completed, remove the solvent and wash thoroughly. Dry the product under vacuum to obtain 2-chloro-4,6-amino-[1,3,5]-triazineamine (CAT) as a white solid. (2) Preparation of triazine cyclic amine polyamide composite membrane After ultrasonically cleaning the ultrafiltration base membrane in pure water, it is immersed in the aqueous solution of CAT synthesized in step (1) for 1 to 30 minutes. After immersion, the membrane is removed, excess water is removed from the membrane surface, and then it is immersed in an organic solvent containing sulfonyl chloride organic monomers to carry out interfacial reaction. After 5 to 20 minutes, it is removed and placed in an oven for post-treatment at 35 to 95°C for 5 to 55 minutes to obtain the triazine cyclic polysulfonamide composite nanofiltration membrane.

2. The method according to claim 1, characterized in that, The aqueous solution of CAT has a concentration of 2.0-10.0 g / L and a pH value of 8-13.

3. The method according to claim 1, characterized in that, The concentration of sulfonyl chloride organic monomers in organic solvents is 3.0-15.0 g / L.

4. The method according to claim 1, characterized in that, The ultrafiltration membrane is a polymer sheet membrane with a molecular weight cutoff of 10-100kD, including but not limited to polysulfone (PSf), polyethersulfone (PES), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), and cellulose acetate (CA). It is ultrasonically cleaned in deionized water for 30 minutes before use. Polysulfone and polyether ether ketone ultrafiltration membranes are preferred.

5. The method according to claim 1, characterized in that, The sulfonyl chloride organic monomer is an aromatic ring organic compound containing a polysulfonyl chloride group, including but not limited to one or more of 1,3-benzene disulfonyl chloride, 1,3,5-benzene trisulfonyl chloride, 1,3-naphthalene disulfonyl chloride, 1,3,6-naphthalene trisulfonyl chloride, 1,4-bis(2,6-diamino)-3,3'-diphenylnaphthalene disulfonyl chloride, and 1,5-bis(2-anisamino)-3,3'-anthracene disulfonyl chloride.

6. The method according to claim 1, characterized in that, The organic solvent is an organic compound with a dielectric constant of 2 to 12, such as one or more of the following: n-hexane, cyclohexane, n-heptane, Isopar-H, Isopar-G, acetonitrile, dichloromethane, chloroform, dimethyl sulfoxide, N-methylpyrrolidone, xylene, and tetrahydrofuran.

7. The composite nanofiltration membrane prepared according to any one of claims 1-6.

8. The application of the composite nanofiltration membrane prepared according to any one of claims 1-6 for nanofiltration of metal ions under acidic conditions.

9. The application according to claim 8, wherein the metal ion comprises one or more of La, Na, Mg, etc.

10. The application according to claim 8, wherein the acidic condition pH value is less than or equal to 2.

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