Preparation method for selective permeable Anti-pollution special separation membrane

Abstract

The present invention relates to the technical field of separation membranes, and particularly relates to a preparation method for a selective permeable anti-pollution special separation membrane. In the solution, a supporting membrane is used as a substrate; the material of the supporting membrane is any one of polysulfone, polyethersulfone, polyimide, polyvinylidene fluoride and polyvinyl chloride; by subjecting a water phase reaction liquid A and an oil phase reaction liquid to an interfacial polymerization reaction on the surface of the supporting membrane, a polyamide layer is generated; by means of unreacted acyl chloride groups left on the surface, a water phase reaction liquid B is then poured onto the surface of the membrane to generate a secondary interfacial polymerization reaction; and by utilizing 3-bromopropionic acid, a quaternization treatment is carried out to obtain an anti-pollution special separation membrane, which has good selective permeability on a divalent / monovalent salt, a relatively high water flux, and improved antibacterial properties.

Description

Preparation method of a selectively permeable anti-pollution special separation membrane Technical Field

[0001] The present invention relates to the technical field of separation membranes, in particular to a method for preparing a selectively permeable anti-pollution special separation membrane. Background Art

[0002] With the rapid growth of the world's population and global climate change, water pollution and shortage are becoming increasingly serious, becoming one of the most pressing issues of the 21st century. Therefore, to alleviate the pressure of water shortage, wastewater recycling and seawater desalination have become the main research and development projects of experts and scholars. Among them, membrane separation technology has become one of the most commonly used technologies due to its advantages such as low energy consumption, high separation efficiency, and simple operation.

[0003] Depending on the driving force, membrane separation technology can be divided into four categories: concentration-driven, electrically driven, temperature-driven and pressure-driven. The most critical material in membrane separation technology is the separation membrane. Common separation membranes include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes and reverse osmosis membranes. Due to its excellent properties, nanofiltration membranes have good application prospects in seawater and brackish water desalination, separation of monovalent / polyvalent salts, separation of organic matter / salts, and removal of heavy metal ions.

[0004] Nanofiltration membranes are generally prepared using interfacial polymerization technology. Conventional composite nanofiltration membranes will form polyamide composite nanofiltration membranes through interfacial polymerization on the surface of the base membrane. However, today's nanofiltration membranes have poor anti-pollution properties. At the same time, how to achieve excellent separation effects while improving the flux of the nanofiltration membrane is still one of the difficulties that need to be overcome.

[0005] Therefore, the present application discloses a method for preparing a selectively permeable anti-pollution special separation membrane to solve this technical problem.

[0006] Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing a selectively permeable anti-fouling special separation membrane to solve the problems raised in the above background technology.

[0008] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing a selectively permeable anti-fouling special separation membrane, comprising the following steps:

[0009] (1) piperazine, an acid scavenger, and a small-molecule hydroxyl-terminated hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous reaction solution A;

[0010] Mixing acyl chloride polyester and trimesoyl chloride, adding n-hexane and tetrahydrofuran, stirring evenly to obtain an oil phase reaction liquid;

[0011] Clean the support membrane, pour the aqueous reaction solution A onto the support membrane surface, fully adsorb for 2-3 minutes, remove the excess solution, and dry in the shade; then apply the oily reaction solution onto the support membrane surface, keep for 0.5-1 minute, remove the excess solution, and cross-link at 60-65°C for 5-10 minutes to obtain a base membrane;

[0012] (2) mixing 2,6-diaminopyridine, piperazine, and a macromolecular hydroxyl-terminated hyperbranched polyester, and dissolving them in deionized water to obtain an aqueous phase reaction solution B;

[0013] Take the base membrane, pour the aqueous reaction liquid B onto the surface of the base membrane, keep it for 30 to 40 seconds, remove the excess solution, heat treat it at 80 to 85°C for 5 to 8 minutes, pour 3-bromopropionic acid solution on the surface of the base membrane after cleaning, react at 25 to 30°C for 20 to 24 hours, clean and dry after the reaction is completed to obtain a separation membrane.

[0014] In the aqueous reaction solution A, the concentration of piperazine is 0.5 wt% to 2 wt%, the concentration of the acid scavenger is 0.5 wt% to 0.6 wt%, the concentration of the small-molecule hydroxyl-terminated hyperbranched polyester is 0.5 wt% to 1.5 wt%, the concentration of trimesoyl chloride is 0.2 wt% to 0.5 wt% in the oil-phase reaction solution, the volume ratio of n-hexane to tetrahydrofuran is 9:1, and the concentration of the chlorinated polyester is 0.3 to 0.5 wt%.

[0015] In the aqueous reaction solution B, the concentration of the 2,6-diaminopyridine is 2 wt% to 4 wt%; the concentration of the piperazine is 0.5 wt% to 1.2 wt%; and the concentration of the macromolecular hydroxyl-terminated hyperbranched polyester is 0.5 wt% to 1.5 wt%.

[0016] The number average molecular weight of the small-molecule terminal hydroxyl hyperbranched polyester is 1000-4000; the number average molecular weight of the large-molecule terminal hydroxyl hyperbranched polyester is 5000-8000.

[0017] The preparation steps of the chlorinated polyester are as follows: a carboxyl-terminated hyperbranched polyester and thionyl chloride are mixed, stirred in an oil bath at 80-85°C for 10-12 hours, and after completion of the reaction, the thionyl chloride is removed by rotary evaporation to obtain the chlorinated polyester. The acid scavenger is trisodium phosphate; and the support membrane is any one of polysulfone, polyethersulfone, polyimide, polyvinylidene fluoride, and polyvinyl chloride.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This scheme uses a support membrane as a substrate, and the support membrane material is any one of polysulfone, polyethersulfone, polyimide, polyvinylidene fluoride, and polyvinyl chloride. The aqueous phase reaction liquid A and the oil phase reaction liquid undergo interfacial polymerization reaction on the surface of the support membrane to generate a polyamide layer. Then, utilizing the unreacted acyl chloride groups remaining on the surface, the aqueous phase reaction liquid B is poured onto the membrane surface to undergo a secondary interfacial polymerization reaction. The membrane is quaternized with 3-bromopropionic acid to obtain a special anti-pollution separation membrane. The separation membrane has excellent selective permeability to divalent / monovalent salts and a high water flux.

[0020] The main technical effects of this solution are:

[0021] (1) In the present application, piperazine, an acid absorber and a small molecule end-hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous phase reaction liquid A; the aqueous phase reaction liquid A is poured onto the surface of the base membrane; then, an acyl chloride polyester is introduced into the oil phase reaction liquid, the acyl chloride polyester and trimesoyl chloride are mixed, and n-hexane and tetrahydrofuran are used as solvents, and the mixture is stirred evenly to obtain an oil phase reaction liquid; the oil phase reaction liquid is poured onto the surface of the base membrane and subjected to a primary interfacial polymerization reaction with the aqueous phase reaction liquid A to form a loose polyamide layer; tetrahydrofuran is used as a cosolvent and can be miscible with water, thereby reducing the interfacial tension between the two phases, reducing the mass transfer resistance, and increasing the water flux; at the same time, due to the presence of the acyl chloride polyester, the water permeation flux of the separation membrane is increased, and the membrane has a stronger negative charge, can intercept divalent salts, reduce the interception rate of monovalent salts, and improve the selectivity for monovalent and divalent salts.

[0022] The chlorinated polyester is prepared from a carboxyl-terminated hyperbranched polyester through chlorination reaction, and can participate in the interfacial polymerization reaction of the polyamide layer.

[0023] (2) Secondary interfacial polymerization is carried out on the outside of the polyamide layer using the residual acyl chloride groups, wherein 2,6-diaminopyridine is added to the aqueous reaction liquid B and quaternized with 3-bromopropionic acid to form a surface protective layer; this structure can protect the loose polyamide layer, the pyridine ring and quaternary amine group in 2,6-diaminopyridine are both electron-withdrawing groups, and a large molecular end-hydroxyl hyperbranched polyester is also added to the aqueous reaction liquid, and the chlorine resistance of the separation membrane is improved under the effect of steric hindrance; on the other hand, the presence of the protective membrane also improves the antibacterial properties of the separation membrane, and the quaternized 2,6-diaminopyridine destroys the metabolism of cells through quaternary ammonium cations and alkyl chains, thereby inhibiting bacterial reproduction and growth.

[0024] (3) In order to avoid the influence of the surface protective layer structure on the selectivity of monovalent salts and divalent salts and the water flux, a macromolecular end-hydroxyl hyperbranched polyester is added to the aqueous phase reaction liquid B, and the concentration of the macromolecular end-hydroxyl hyperbranched polyester is limited to 0.5wt% to 1.5wt%. This can ensure the retention of divalent salts. At the same time, the presence of the macromolecular end-hydroxyl hyperbranched polyester will cause the size of the aggregation pores to expand, forming straight-through channels for monovalent salt ions. Therefore, the separation membrane maintains a low monovalent salt retention rate and a high permeation flux.

[0025] (4) A small molecular weight end hydroxyl hyperbranched polyester was added to the aqueous phase reaction liquid A, and the small molecular weight end hydroxyl hyperbranched polyester was Boltorn H20, with a number average molecular weight of 1748; a large molecular weight end hydroxyl hyperbranched polyester was added to the aqueous phase reaction liquid B, and the large molecular weight end hydroxyl hyperbranched polyester was Boltorn H40, with a number average molecular weight of 7316; during the secondary interfacial polymerization of the scheme, the secondary interfacial polymerization was performed by "mixing 2,6-diaminopyridine, piperazine and a large molecular weight end hydroxyl hyperbranched polyester, dissolving them in deionized water to obtain an aqueous phase reaction liquid B", and then quaternizing the mixture with a 3-bromopropionic acid solution. Hydrophilic substances were introduced in the above steps, and the separation membrane finally obtained had excellent hydrophilicity and improved anti-fouling properties. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] In this embodiment, the model of the carboxyl-terminated hyperbranched polyester is HyPerC203, provided by Wuhan Hyperbranched Polyester Resin Technology Co., Ltd.; the small molecule hydroxyl-terminated hyperbranched polyester is BoltornH20, and the large molecule hydroxyl-terminated hyperbranched polyester is BoltornH40, both provided by Perstorp, Sweden; the support membrane is a polysulfone ultrafiltration membrane NF1, provided by Hunan Qinsen Environmental Protection Technology Co., Ltd.

[0028] Example 1: A method for preparing a selectively permeable anti-pollution special separation membrane, comprising the following steps:

[0029] (1) 2 g of carboxyl-terminated hyperbranched polyester and 50 mL of thionyl chloride were mixed and stirred in an 80°C oil bath for 12 h. After the reaction, the thionyl chloride was removed by rotary evaporation to obtain acyl chloride polyester.

[0030] Piperazine, an acid scavenger and a small-molecule terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous phase reaction liquid A; the concentration of the piperazine is 1 wt%, the acid scavenger is trisodium phosphate, and the concentration of the acid scavenger is 0.6 wt%; the concentration of the small-molecule terminal hydroxyl hyperbranched polyester is 1 wt%.

[0031] The chlorinated polyester and trimesoyl chloride are mixed, and n-hexane and tetrahydrofuran are added and stirred evenly to obtain an oil phase reaction liquid; the concentration of the trimesoyl chloride is 0.5wt%; the volume ratio of the n-hexane and tetrahydrofuran is 9:1; and the concentration of the chlorinated polyester is 0.35wt%.

[0032] The support membrane was cleaned, and the aqueous reaction liquid A was poured onto the surface of the support membrane, fully adsorbed for 2 minutes, excess aqueous reaction liquid A was removed, and the membrane was dried in the shade; then the oily reaction liquid was coated on the surface of the support membrane, kept for 1 minute, excess oily reaction liquid was removed, and cross-linked at 60°C for 10 minutes to obtain a base membrane;

[0033] (2) 2,6-diaminopyridine, piperazine and a macromolecular terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous reaction solution B; the concentration of the 2,6-diaminopyridine is 3 wt %; the concentration of the piperazine is 0.8 wt %; and the concentration of the macromolecular terminal hydroxyl hyperbranched polyester is 0.5 wt %.

[0034] The basement membrane was taken and the aqueous reaction solution B was poured onto the surface of the basement membrane for 30-40 seconds. After removing the excess solution, the membrane was heat-treated at 80°C for 8 minutes. After washing, a 3-bromopropionic acid solution was poured onto the surface of the basement membrane and reacted at 25°C for 22 hours. After the reaction, the membrane was washed and dried to obtain a separation membrane. The 3-bromopropionic acid solution was composed of 30 wt% 3-bromopropionic acid and 70 wt% ethanol.

[0035] Example 2: A method for preparing a selectively permeable anti-pollution special separation membrane, comprising the following steps:

[0036] (1) 2 g of carboxyl-terminated hyperbranched polyester and 50 mL of thionyl chloride were mixed and stirred in an oil bath at 80-85° C. for 10-12 h. After the reaction was completed, the thionyl chloride was removed by rotary evaporation to obtain acyl chloride polyester.

[0037] Piperazine, an acid scavenger and a small molecule terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous phase reaction liquid A; the concentration of the piperazine is 1 wt%, the acid scavenger is trisodium phosphate, and the concentration of the acid scavenger is 0.6 wt%; the concentration of the small molecule terminal hydroxyl hyperbranched polyester is 1.1 wt%.

[0038] The chlorinated polyester and trimesoyl chloride are mixed, and n-hexane and tetrahydrofuran are added and stirred evenly to obtain an oil phase reaction liquid; the concentration of the trimesoyl chloride is 0.5wt%; the volume ratio of the n-hexane and tetrahydrofuran is 9:1; and the concentration of the chlorinated polyester is 0.35wt%.

[0039] The support membrane was cleaned, and the aqueous reaction liquid A was poured onto the surface of the support membrane, fully adsorbed for 2 minutes, and the excess aqueous reaction liquid A was removed, and the membrane was dried in the shade; then the oily reaction liquid was coated on the surface of the support membrane, kept for 1 minute, and the excess oily reaction liquid was removed, and cross-linked at 65°C for 8 minutes to obtain a base membrane;

[0040] (2) 2,6-diaminopyridine, piperazine and a macromolecular terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous reaction solution B; the concentration of the 2,6-diaminopyridine is 3 wt %; the concentration of the piperazine is 0.8 wt %; and the concentration of the macromolecular terminal hydroxyl hyperbranched polyester is 0.5 wt %.

[0041] The basement membrane was removed and the aqueous reaction solution B was poured onto the surface of the basement membrane for 30 seconds. After removing the excess solution, the membrane was heat-treated at 85°C for 7 minutes. After washing, a 3-bromopropionic acid solution was poured onto the surface of the basement membrane and reacted at 25°C for 23 hours. After the reaction, the membrane was washed and dried to obtain a separation membrane. The 3-bromopropionic acid solution consisted of 30 wt% 3-bromopropionic acid and 70 wt% ethanol.

[0042] Example 3: A method for preparing a selectively permeable anti-pollution special separation membrane, comprising the following steps:

[0043] (1) 2 g of carboxyl-terminated hyperbranched polyester and 50 mL of thionyl chloride were mixed and stirred in an oil bath at 85°C for 10 h. After the reaction, the thionyl chloride was removed by rotary evaporation to obtain acyl chloride polyester.

[0044] Piperazine, an acid scavenger and a small molecule terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous phase reaction liquid A; the concentration of the piperazine is 1 wt%, the acid scavenger is trisodium phosphate, and the concentration of the acid scavenger is 0.6 wt%; the concentration of the small molecule terminal hydroxyl hyperbranched polyester is 1.2 wt%.

[0045] The chlorinated polyester and trimesoyl chloride are mixed, and n-hexane and tetrahydrofuran are added and stirred evenly to obtain an oil phase reaction liquid; the concentration of the trimesoyl chloride is 0.5wt%; the volume ratio of the n-hexane and tetrahydrofuran is 9:1; and the concentration of the chlorinated polyester is 0.4wt%.

[0046] The support membrane was cleaned, and the aqueous reaction liquid A was poured onto the surface of the support membrane, fully adsorbed for 2 minutes, excess aqueous reaction liquid A was removed, and the membrane was dried in the shade; then the oily reaction liquid was coated on the surface of the support membrane, kept for 1 minute, excess oily reaction liquid was removed, and cross-linked at 65°C for 5 minutes to obtain a base membrane;

[0047] (2) 2,6-diaminopyridine, piperazine and a macromolecular terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous reaction solution B; the concentration of the 2,6-diaminopyridine is 3 wt %; the concentration of the piperazine is 0.8 wt %; and the concentration of the macromolecular terminal hydroxyl hyperbranched polyester is 0.6 wt %.

[0048] The basement membrane was removed and the aqueous reaction solution B was poured onto the surface of the basement membrane for 30 seconds. After removing the excess solution, the membrane was heat-treated at 85°C for 5 minutes. After washing, a 3-bromopropionic acid solution was poured onto the surface of the basement membrane and reacted at 30°C for 20 hours. After the reaction, the membrane was washed and dried to obtain a separation membrane. The 3-bromopropionic acid solution consisted of 30 wt% 3-bromopropionic acid and 70 wt% ethanol.

[0049] Comparative Example 1: Example 3 was used as the control group. In Comparative Example 1, 2,6-diaminopyridine was not introduced into the aqueous reaction solution B, and 3-bromopropionic acid solution treatment was not performed. The remaining steps remained unchanged.

[0050] A method for preparing a selectively permeable anti-pollution special separation membrane comprises the following steps:

[0051] (1) 2 g of carboxyl-terminated hyperbranched polyester and 50 mL of thionyl chloride were mixed and stirred in an oil bath at 85°C for 10 h. After the reaction, the thionyl chloride was removed by rotary evaporation to obtain acyl chloride polyester.

[0052] Piperazine, an acid scavenger and a small molecule terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous phase reaction liquid A; the concentration of the piperazine is 1 wt%, the acid scavenger is trisodium phosphate, and the concentration of the acid scavenger is 0.6 wt%; the concentration of the small molecule terminal hydroxyl hyperbranched polyester is 1.2 wt%.

[0053] The chlorinated polyester and trimesoyl chloride are mixed, and n-hexane and tetrahydrofuran are added and stirred evenly to obtain an oil phase reaction liquid; the concentration of the trimesoyl chloride is 0.5wt%; the volume ratio of the n-hexane and tetrahydrofuran is 9:1; and the concentration of the chlorinated polyester is 0.4wt%.

[0054] The support membrane was cleaned, and the aqueous reaction liquid A was poured onto the surface of the support membrane, fully adsorbed for 2 minutes, excess aqueous reaction liquid A was removed, and the membrane was dried in the shade; then the oily reaction liquid was coated on the surface of the support membrane, kept for 1 minute, excess oily reaction liquid was removed, and cross-linked at 65°C for 5 minutes to obtain a base membrane;

[0055] (2) Piperazine and a macromolecular terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous reaction solution B; the concentration of the piperazine is 0.8 wt %; the concentration of the macromolecular terminal hydroxyl hyperbranched polyester is 0.6 wt %.

[0056] The base membrane was taken, and the aqueous reaction solution B was poured onto the surface of the base membrane and kept for 30 seconds. After removing the excess solution, the base membrane was heat-treated at 85°C for 5 minutes, washed and dried to obtain a separation membrane.

[0057] Comparative Example 2: Example 3 was used as the control group. In Comparative Example 2, the proportion of the aqueous phase reaction solution B was adjusted, and the macromolecular terminal hydroxyl hyperbranched polyester was not introduced. The remaining steps remained unchanged.

[0058] A method for preparing a selectively permeable anti-pollution special separation membrane comprises the following steps:

[0059] (1) 2 g of carboxyl-terminated hyperbranched polyester and 50 mL of thionyl chloride were mixed and stirred in an oil bath at 85°C for 10 h. After the reaction, the thionyl chloride was removed by rotary evaporation to obtain acyl chloride polyester.

[0060] Piperazine, an acid scavenger and a small molecule terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous phase reaction liquid A; the concentration of the piperazine is 1 wt%, the acid scavenger is trisodium phosphate, and the concentration of the acid scavenger is 0.6 wt%; the concentration of the small molecule terminal hydroxyl hyperbranched polyester is 1.2 wt%.

[0061] The chlorinated polyester and trimesoyl chloride are mixed, and n-hexane and tetrahydrofuran are added and stirred evenly to obtain an oil phase reaction liquid; the concentration of the trimesoyl chloride is 0.5wt%; the volume ratio of the n-hexane and tetrahydrofuran is 9:1; and the concentration of the chlorinated polyester is 0.4wt%.

[0062] The support membrane was cleaned, and the aqueous reaction liquid A was poured onto the surface of the support membrane, fully adsorbed for 2 minutes, excess aqueous reaction liquid A was removed, and the membrane was dried in the shade; then the oily reaction liquid was coated on the surface of the support membrane, kept for 1 minute, excess oily reaction liquid was removed, and cross-linked at 65°C for 5 minutes to obtain a base membrane;

[0063] (2) 2,6-diaminopyridine and piperazine were mixed and dissolved in deionized water to obtain an aqueous reaction solution B; the concentration of the 2,6-diaminopyridine was 3 wt %; the concentration of the piperazine was 0.8 wt %.

[0064] The basement membrane was removed and the aqueous reaction solution B was poured onto the surface of the basement membrane for 30 seconds. After removing the excess solution, the membrane was heat-treated at 85°C for 5 minutes. After washing, a 3-bromopropionic acid solution was poured onto the surface of the basement membrane and reacted at 30°C for 20 hours. After the reaction, the membrane was washed and dried to obtain a separation membrane. The 3-bromopropionic acid solution consisted of 30 wt% 3-bromopropionic acid and 70 wt% ethanol.

[0065] Comparative Example 3: Example 3 was used as the control group. In Comparative Example 3, no secondary interfacial polymerization was performed (the aqueous phase reaction liquid B was not poured for reaction, and the 3-bromopropionic acid solution was not introduced), and the remaining steps remained unchanged.

[0066] A method for preparing a selectively permeable anti-pollution special separation membrane comprises the following steps:

[0067] (1) 2 g of carboxyl-terminated hyperbranched polyester and 50 mL of thionyl chloride were mixed and stirred in an oil bath at 85°C for 10 h. After the reaction, the thionyl chloride was removed by rotary evaporation to obtain acyl chloride polyester.

[0068] Piperazine, an acid scavenger and a small molecule terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous phase reaction liquid A; the concentration of the piperazine is 1 wt%, the acid scavenger is trisodium phosphate, and the concentration of the acid scavenger is 0.6 wt%; the concentration of the small molecule terminal hydroxyl hyperbranched polyester is 1.2 wt%.

[0069] The chlorinated polyester and trimesoyl chloride are mixed, and n-hexane and tetrahydrofuran are added and stirred evenly to obtain an oil phase reaction liquid; the concentration of the trimesoyl chloride is 0.5wt%; the volume ratio of the n-hexane and tetrahydrofuran is 9:1; and the concentration of the chlorinated polyester is 0.4wt%.

[0070] The support membrane was cleaned, and the aqueous reaction liquid A was poured onto the surface of the support membrane, fully adsorbed for 2 minutes, excess aqueous reaction liquid A was removed, and the membrane was dried in the shade; then the oil phase reaction liquid was coated on the surface of the support membrane, kept for 1 minute, excess oil phase reaction liquid was removed, and cross-linked at 65°C for 5 minutes to obtain a separation membrane.

[0071] Comparative Example 4: Comparative Example 3 was used as the control group. In Comparative Example 4, the ratio of the oil phase reaction liquid was adjusted, the acyl chloride polyester was not introduced, and the other steps remained unchanged.

[0072] A method for preparing a selectively permeable anti-pollution special separation membrane comprises the following steps:

[0073] (1) 2 g of carboxyl-terminated hyperbranched polyester and 50 mL of thionyl chloride were mixed and stirred in an oil bath at 85°C for 10 h. After the reaction, the thionyl chloride was removed by rotary evaporation to obtain acyl chloride polyester.

[0074] Piperazine, an acid scavenger and a small molecule terminal hydroxyl hyperbranched polyester are mixed and dissolved in deionized water to obtain an aqueous phase reaction liquid A; the concentration of the piperazine is 1 wt%, the acid scavenger is trisodium phosphate, and the concentration of the acid scavenger is 0.6 wt%; the concentration of the small molecule terminal hydroxyl hyperbranched polyester is 1.2 wt%.

[0075] Trimesoyl chloride, n-hexane and tetrahydrofuran are mixed and stirred evenly to obtain an oil phase reaction liquid; the concentration of the trimesoyl chloride is 0.5 wt %; and the volume ratio of the n-hexane to tetrahydrofuran is 9:1.

[0076] The support membrane was cleaned, and the aqueous reaction liquid A was poured onto the surface of the support membrane, fully adsorbed for 2 minutes, excess aqueous reaction liquid A was removed, and the membrane was dried in the shade; then the oil phase reaction liquid was coated on the surface of the support membrane, kept for 1 minute, excess oil phase reaction liquid was removed, and cross-linked at 65°C for 5 minutes to obtain a separation membrane.

[0077] Detection experiment:

[0078] Test 1: Take the separation membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 4 and test the antibacterial properties of the separation membranes. The specific steps are: a bacterial suspension of Escherichia coli (concentration of 1×10 6 cfu / mL, the inoculum size was 6×10 7 pcs / m 2 ) were evenly dispersed on the test surface of the separation membrane, and a glass slide was placed on the membrane surface to ensure that the bacterial solution was evenly dispersed and non-volatile. The culture was sealed in a sterile culture dish and cultured for 1 to 2 hours at a temperature of 37°C. The surface antibacterial properties of the separation membrane were tested, and the bactericidal performance was characterized by the cell death rate.

[0079] Test 2: Take the separation membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 4 and test the water flux and salt rejection of the separation membranes. The specific steps are as follows: After the separation membranes are rinsed with pure water, place them in a 25 cm 2 The test was carried out in a test cell with pre-pressure for 1 hour and then testing. The operating pressure was 0.8 MPa and the feed temperature was 25°C. The test raw liquid was a single salt solution of Na2SO4 or NaCl, with a concentration of 1000ppm. The water flux and salt retention rate in the 1000ppm Na2SO4 single salt solution were recorded.

[0080] Test 3: Take the separation membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 4 and test the hydrophilicity of the separation membranes: test the water contact angle on the surface of the separation membrane; the test water droplet is 3 μL, and the average value is taken at 10 test locations.

[0081] Test 4: Take the separation membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 4 and test the chlorine resistance of the separation membranes: prepare a sodium hypochlorite solution (concentration of 2500 ppm, hydrochloric acid adjusted to pH 4), place the separation membrane in the sodium hypochlorite solution and soak for 1 hour, take it out and wash it, soak it in deionized water for 48 hours, and repeat Test 2. Record the water flux and Na2SO4 retention rate of the separation membrane in a 1000 ppm Na2SO4 single salt solution, and calculate the performance retention rate before and after the chlorine resistance test.

[0082] Conclusion: (1) 2,6-diaminopyridine was added to the aqueous phase reaction liquid B and quaternized with 3-bromopropionic acid. This step can introduce antibacterial groups and improve the antibacterial properties of the separation membrane. Therefore, when the quaternization treatment with 2,6-diaminopyridine was not introduced in the scheme, the antibacterial property decreased.

[0083] (2) The addition of a macromolecular end-hydroxy hyperbranched polyester to the aqueous reaction liquid B increases the retention rate of divalent salts while forming straight-through channels for monovalent salt ions. Therefore, when the macromolecular end-hydroxy hyperbranched polyester is not introduced into the scheme, the water flux will decrease, the divalent retention rate will decrease slightly, and the monovalent retention rate will increase.

[0084] (3) Secondary interfacial polymerization was performed on the outside of the polyamide layer using the residual acyl chloride groups, wherein 2,6-diaminopyridine was added to the aqueous reaction liquid B and quaternized with 3-bromopropionic acid to form a surface protective layer. The presence of the protective layer can improve the chlorine resistance of the separation membrane. Therefore, when the protective layer is not introduced in the scheme, the chlorine resistance will be greatly reduced.

[0085] (4) Introducing acyl chloride polyester into the oil phase reaction liquid. The presence of acyl chloride polyester can increase the water permeation flux of the separation membrane. When acyl chloride polyester is not introduced, the divalent salt rejection rate of the scheme will decrease, and the selectivity of monovalent salt and divalent salt will decrease.

[0086] This solution prepares a special anti-pollution separation membrane, which has excellent selective permeability for divalent / monovalent salts, high water flux, and excellent anti-pollution performance.

[0087] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a selectively permeable anti-pollution special separation membrane, characterized in that: The following steps are involved: (1) mixing piperazine, an acid scavenger and a small molecular weight hydroxyl-terminated hyperbranched polyester, and dissolving them in deionized water to obtain an aqueous phase reaction solution A; The chlorinated polyester and trimesoyl chloride are mixed, and n-hexane and tetrahydrofuran are added, and stirred evenly to obtain an oil phase reaction liquid; The support membrane is cleaned, and the aqueous reaction solution A is poured onto the surface of the support membrane, fully adsorbed for 2 to 3 minutes, excess solution is removed, and the membrane is dried in the shade; then the oil phase reaction solution is coated onto the surface of the support membrane, kept for 0.5 to 1 minute, excess solution is removed, and cross-linked at 60 to 65° C. for 5 to 10 minutes to obtain a base membrane; (2) mixing 2,6-diaminopyridine, piperazine and a macromolecular terminal hydroxyl hyperbranched polyester, and dissolving them in deionized water to obtain an aqueous phase reaction solution B; Take the base membrane, pour the aqueous reaction liquid B onto the surface of the base membrane, keep it for 30-40 seconds, remove the excess solution, heat treat it at 80-85℃ for 5-8min, pour 3-bromopropionic acid solution on the surface of the base membrane after cleaning, react at 25-30℃ for 20-24h, clean and dry it after the reaction to obtain a separation membrane.

2. The method for preparing a selectively permeable anti-pollution special separation membrane according to claim 1, characterized in that: In the aqueous reaction liquid A, the concentration of piperazine is 0.5wt% to 2wt%, the concentration of the acid scavenger is 0.5wt% to 0.6wt%; and the concentration of the small molecule terminal hydroxyl hyperbranched polyester is 0.5wt% to 1.5wt%.

3. The method for preparing a selectively permeable anti-pollution special separation membrane according to claim 1, characterized in that: In the oil phase reaction liquid, the concentration of trimesoyl chloride is 0.2wt%-0.5wt%; the volume ratio of n-hexane to tetrahydrofuran is 9:1; and the concentration of chlorinated polyester is 0.3-0.5wt%.

4. The method for preparing a selectively permeable anti-pollution special separation membrane according to claim 1, characterized in that: In the aqueous reaction liquid B, the concentration of the 2,6-diaminopyridine is 2wt% to 4wt%; the concentration of the piperazine is 0.5wt% to 1.2wt%; and the concentration of the macromolecular terminal hydroxyl hyperbranched polyester is 0.5wt% to 1.5wt%.

5. The method for preparing a selectively permeable anti-pollution special separation membrane according to claim 1, characterized in that: The number average molecular weight of the small molecular terminal hydroxyl hyperbranched polyester is 1000-4000; the number average molecular weight of the large molecular terminal hydroxyl hyperbranched polyester is 5000-8000.

6. The method for preparing a selectively permeable anti-pollution special separation membrane according to claim 1, characterized in that: The preparation steps of the chlorinated polyester are as follows: mixing the carboxyl-terminated hyperbranched polyester and thionyl chloride, stirring and reacting in an oil bath at 80-85° C. for 10-12 hours, and removing the thionyl chloride by rotary evaporation after the reaction to obtain the chlorinated polyester.

7. The method for preparing a selectively permeable anti-pollution special separation membrane according to claim 1, characterized in that: The acid absorber is trisodium phosphate; the support membrane is any one of polysulfone, polyethersulfone, polyimide, polyvinylidene fluoride and polyvinyl chloride.

8. A special separation membrane prepared according to the method for preparing a selectively permeable anti-pollution special separation membrane according to claim 1.

Images