Chlorine-resistant drug desalting membrane and preparation method thereof

Abstract

The invention discloses a chlorine-resistant drug desalting membrane and a preparation method thereof, and belongs to the technical field of membrane separation. The chlorine-resistant drug desalting membrane comprises a base membrane, a polyamide separation layer formed on the surface of the base membrane, and a chlorine-resistant modified layer formed on the polyamide separation layer, the chlorine-resistant modified layer is formed by in-situ grafting reaction of polycarbodiimide and carboxyl of the polyamide separation layer. According to the invention, rich nitrogen acyl urea groups in the modified layer are used as sacrifice sites to block attack of active chlorine to the polyamide layer, so that the membrane is endowed with excellent chlorine resistance; carboxyl of the polyamide separation layer reacts with polycarbodiimide, the rejection rate of drug molecules can be increased, the separation performance is greatly improved, and the problems that an existing polyamide nanofiltration membrane is low in selectivity, poor in chlorine resistance and the like in the drug desalting process are solved.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to a chlorine-resistant drug desalination membrane and its preparation method. Background Technology

[0002] Antibiotics (such as tetracycline and doxorubicin) are commonly used clinical drugs, and their industrial production largely relies on microbial fermentation processes. During fermentation, to maintain a stable microbial metabolic environment and promote the synthesis of the target product, inorganic salts such as sodium chloride need to be added to the fermentation system. This results in a large amount of salt mixed in with the crude product after fermentation. Therefore, desalting and purification has become an indispensable and crucial step in the antibiotic production process. Traditional antibiotic desalting mainly uses resin adsorption. Although this method has a certain degree of separation selectivity, it suffers from problems such as cumbersome processes, high equipment investment, and the consumption of large amounts of organic solvents. This not only increases production costs but also easily causes environmental pollution, failing to meet the demands of modern pharmaceutical production for efficient and green processes. Therefore, there is an urgent need to develop superior desalting technologies.

[0003] Membrane separation technology, with its advantages of simple operation, continuous operation, low organic reagent consumption, and environmental friendliness, has gradually become the preferred solution in the field of antibiotic desalination. Among them, membrane composite nanofiltration membranes dominate the membrane separation market due to their high separation efficiency. Their core functional layer is a polyamide separation layer, typically prepared by interfacial polymerization of polyamines (such as piperazine) and polyacrylamide chlorides (such as trimesoyl chloride). However, existing polyamide nanofiltration membranes have significant technical defects in antibiotic desalination applications: on the one hand, insufficient separation selectivity makes it difficult to achieve efficient separation of antibiotics and inorganic salts; on the other hand, poor chlorine resistance, as the NH bonds in the polyamide molecular chain are easily attacked by active chlorine generated during sterilization or operation, leading to membrane structure damage, rapid decline in separation performance, and severely affecting membrane lifespan. To address these issues, the industry has attempted to optimize the performance of polyamide nanofiltration membranes through various modification methods. However, existing solutions still have significant limitations: some modification methods require multiple organic synthesis steps, which are complex and environmentally unfriendly; while some solutions can improve chlorine resistance or selectivity, they present a trade-off between low crosslinking efficiency and a significant decrease in membrane flux, making it difficult to simultaneously meet the comprehensive requirements of industrial applications for separation efficiency, stability, and economy. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a chlorine-resistant drug desalination membrane and its preparation method. This invention involves forming a polyamide separation layer on a base membrane, followed by an in-situ grafting reaction of polycarbodiimide with carboxyl groups on the surface and interior of the polyamide separation layer to form a chlorine-resistant modified layer, thus obtaining a chlorine-resistant drug desalination membrane. The modified layer of this invention's chlorine-resistant drug desalination membrane contains abundant nitrourea groups as sacrificial sites, which can block the attack of active chlorine on the polyamide layer, thereby endowing the membrane with excellent chlorine resistance. Simultaneously, it improves the drug molecule rejection rate and significantly enhances separation performance, solving the problems of low selectivity and poor chlorine resistance in existing polyamide nanofiltration membranes during drug desalination.

[0005] The technical solution of the present invention is as follows: The first aspect of this invention protects a chlorine-resistant desalination membrane, the chlorine-resistant desalination membrane comprising a base membrane, a polyamide separation layer formed on the surface of the base membrane, and a chlorine-resistant modified layer formed on the polyamide separation layer; The chlorine-resistant modified layer is formed by in-situ grafting of carboxyl groups of polycarbodiimide with the carboxyl groups of the polyamide separation layer.

[0006] Preferably, the base membrane is a porous base membrane with a molecular weight cutoff of 10,000 to 60,000 Daltons.

[0007] Preferably, the base membrane includes at least one of polyacrylonitrile ultrafiltration membrane, polyethersulfone ultrafiltration membrane, and polysulfone ultrafiltration membrane.

[0008] Preferably, the polyamide separation layer is obtained by interfacial polymerization of polyamines and polyacrylamide chlorides on the porous base membrane; The polyamine includes at least one of piperazine, m-phenylenediamine, and p-phenylenediamine; The polyacrylic chloride includes at least one of pyromellitic trichloroisocyanurate, isophthaloyl chloride, and terephthaloyl chloride; The thickness of the polyamide separation layer is 50~200nm.

[0009] Preferably, the thickness of the chlorine-resistant modified layer is 10~200 nm.

[0010] A second aspect of this invention protects a method for preparing the chlorine-resistant desalination membrane described in the first aspect above, comprising the following steps: S1: Preparation of polyamide composite membrane The polyamine was dissolved in water to obtain an aqueous solution; Polyacyl chlorides are dissolved in a solvent to obtain an organic phase solution; The base membrane was immersed in an aqueous solution and then removed to remove excess solution from the surface. It was then placed in an organic solution to carry out an interfacial polymerization reaction. Subsequently, excess solution was removed from the membrane surface, and the membrane was heat-treated to obtain a polyamide composite membrane. S2: The polyamide composite membrane prepared in step S1 is placed in an aqueous solution of polycarbodiimide for reaction, and a chlorine-resistant modified layer is grafted onto the surface in situ. Then, heat treatment is performed to obtain a chlorine-resistant drug desalination membrane.

[0011] Preferably, in step S1, the mass concentration of the polyamine in the aqueous solution is 0.1-3%. In the organic phase solution, the mass concentration of the polyacrylamide chloride is 0.05~0.5%, preferably 0.05~0.3%.

[0012] Preferably, the immersion time is 5 to 15 minutes; The time for the interfacial polymerization reaction is 0.5~3 min; The heat treatment temperature is 30~80℃, and the heat treatment time is 3min~3h.

[0013] Preferably, in step S2, the mass concentration of the polycarbodiimide aqueous solution is 0.5-3%, and the pH value is 3-10; The reaction temperature is 30~90℃, and the reaction time is 10~60min; The heat treatment temperature is 30~90℃, and the heat treatment time is 3~60min.

[0014] The third aspect of this invention protects the application of a chlorine-resistant desalting membrane as described in the first aspect above, or a chlorine-resistant drug desalting membrane prepared by the preparation method described in the second aspect above, wherein the chlorine-resistant desalting membrane is used for the separation of drugs and salts; Preferably, the drug includes antibiotics.

[0015] The beneficial technical effects of this invention are as follows: This invention obtains a chlorine-resistant desalination membrane by forming a polyamide separation layer on a base membrane, and further forming a chlorine-resistant modified layer through an in-situ grafting reaction of polycarbodiimide with carboxyl groups on the surface and inside of the polyamide separation layer. The polycarbodiimide has multiple carbodiimide structures, which can react with the carboxyl groups on the surface and inside of the polyamide separation layer to produce secondary crosslinking, thereby reducing the pore size of the separation layer and improving the antibiotic rejection rate and antibiotic / salt selectivity of the nanofiltration membrane. Simultaneously, the drug desalination membrane provided by this invention has a rough surface structure, which can increase the effective filtration area and improve the membrane's permeate flux. The chlorine-resistant modified layer contains abundant N-acylurea structures, which can act as sacrificial groups to react with active chlorine, improving the membrane's chlorine resistance.

[0016] The preparation method of the drug desalination membrane of the present invention is simple in process and environmentally friendly. Attached Figure Description

[0017] Figure 1The infrared spectrum of the chlorine-resistant drug desalination membrane prepared in Example 2 of this invention.

[0018] Figure 2 The image shows a scanning electron microscope (SEM) image of the chlorine-resistant drug desalination membrane prepared in Example 2 of this invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the embodiments.

[0020] Addressing the shortcomings of existing polyamide desalination membranes, such as insufficient separation selectivity, difficulty in achieving efficient separation of antibiotics and inorganic salts, poor chlorine resistance, and short membrane lifespan, this invention provides a chlorine-resistant drug desalination membrane and its preparation method.

[0021] The first aspect of the present invention provides a chlorine-resistant desalination membrane, the chlorine-resistant desalination membrane comprising a base membrane, a polyamide separation layer formed on the surface of the base membrane, and a chlorine-resistant modified layer formed on the polyamide separation layer; The chlorine-resistant layer is formed by in-situ grafting of carboxyl groups onto the surface of the polyamide separation layer with polycarbodiimide.

[0022] It is understood that in the desalination membrane of the present invention, the polycarbodiimide has multiple carbodiimide structures, which can react with the carboxyl groups on the surface and inside of the polyamide separation layer to produce secondary crosslinking, thereby reducing the pore size of the separation layer and improving the antibiotic rejection rate and antibiotic / salt selectivity of the nanofiltration membrane. In addition, the reaction between polycarbodiimide and carboxyl groups increases the surface roughness of the membrane, increases the effective filtration area, and thus improves the permeate flux of the membrane. Furthermore, the chlorine-resistant modified layer contains abundant N-acylurea structures, which can act as sacrificial groups to react with active chlorine and improve the chlorine resistance of the membrane.

[0023] In some embodiments, the base membrane is a porous base membrane with one side being nonwoven fabric, which is conventional in the art, and has a molecular weight cutoff of 10,000 to 60,000 Daltons.

[0024] In some embodiments, the base membrane includes at least one of polyacrylonitrile ultrafiltration membrane, polyethersulfone ultrafiltration membrane, and polysulfone ultrafiltration membrane.

[0025] In some embodiments, the base film of the present invention is prepared by the following method: 16.2–64.8 g of polymer powder was dissolved in 147.6 g of DMF solvent to prepare a casting solution. The solution was stirred in an oil bath at 30–90 °C for 48 h, then allowed to stand in an oil bath at 40 °C for 24–48 h to remove bubbles. The solution was then removed and cooled to room temperature for later use. A 200 μm thick casting solution layer was scraped onto a glass plate with nonwoven fabric attached using a film scraper at a speed of 75 mm / s. The glass plate was then immersed in deionized water at 25 °C to form a film through phase inversion, yielding the base film. Finally, the base film was stored in deionized water for later use.

[0026] In some embodiments, the polymer powder includes at least one of polyacrylonitrile, polyethersulfone, and polysulfone.

[0027] In some embodiments, the polyamide separation layer is obtained by interfacial polymerization of polyamines and polyacrylamide chlorides on the non-nonwoven side of the porous base membrane. The polyamine includes at least one of piperazine, m-phenylenediamine, and p-phenylenediamine; The polyacrylic chloride includes at least one of pyromellitic trichloroisocyanurate, isophthaloyl chloride, and terephthaloyl chloride; The thickness of the polyamide separation layer is 50~200nm.

[0028] In some embodiments, the thickness of the chlorine-resistant modified layer is 50~200 nm.

[0029] Understandably, if the chlorine-resistant modified layer is too thin, it indicates that the grafting reaction has not been carried out sufficiently, and the chlorine resistance will decrease. Conversely, if the chlorine-resistant modified layer is too thick, some flux will be lost.

[0030] The polycarbodiimides used in the embodiments and comparative examples of this invention are all urethane-type polycarbodiimides.

[0031] A second aspect of this invention protects a method for preparing the chlorine-resistant desalination membrane described in the first aspect above, comprising the following steps: S1: Preparation of polyamide composite membrane The polyamine was dissolved in deionized water to obtain an aqueous solution; Polyacyl chlorides are dissolved in a solvent to obtain an organic phase solution; The base membrane was immersed in an aqueous solution and then removed, and excess solution was removed from the surface. It was then placed in an organic solution for interfacial polymerization. Subsequently, excess solution was removed from the membrane surface, and the membrane was heat-treated to obtain a polyamide composite membrane. S2: The polyamide composite membrane prepared in step S1 is placed in an aqueous solution of polycarbodiimide for reaction, and a chlorine-resistant modified layer is grafted onto the surface in situ. Then, heat treatment is performed to obtain a chlorine-resistant drug desalination membrane.

[0032] In some embodiments, in step S1, the mass concentration of the polyamine in the aqueous solution is 0.1-3%, including but not limited to 0.1%, 0.5%, 1%, 2%, and 3%.

[0033] In the organic phase solution, the mass concentration of the polyacrylamide chloride is 0.05~0.5%, preferably 0.05~0.3%, including but not limited to 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, and 0.3%.

[0034] In some embodiments, the solvent includes at least one of n-hexane, cyclohexane, n-heptane, and isoheptane.

[0035] In some embodiments, the immersion time is 5 to 15 minutes, including but not limited to 5 minutes, 10 minutes, and 15 minutes.

[0036] The time for the interfacial polymerization reaction is 0.5 to 3 minutes; including but not limited to 0.5 minutes, 1 minute, 2 minutes, and 3 minutes.

[0037] The heat treatment temperature is 30~80℃, including but not limited to 30℃, 40℃, 50℃, 60℃, 70℃, and 80℃, and the heat treatment time is 3min~3h, including but not limited to 3min, 5min, 30min, 1h, 2h, and 3h.

[0038] In some embodiments, in step S2, the mass concentration of the polycarbodiimide aqueous solution is 0.5-3%, including but not limited to 0.5%, 1%, 2%, and 3%, and the pH value is 3-10, including but not limited to 3, 5, 7, and 10. The reaction temperature is 30~90℃, including but not limited to 30℃, 40℃, 50℃, 60℃, 70℃, and 90℃, and the reaction time is 10~60min, including but not limited to 10min, 30min, and 60min.

[0039] The heat treatment temperature is 30~90℃, including but not limited to 30℃, 40℃, 50℃, 60℃, 70℃, and 90℃, and the heat treatment time is 3~60min, including but not limited to 3min, 4min, 5min, 10min, 30min, and 60min.

[0040] The third aspect of this invention protects the application of a chlorine-resistant desalting membrane as described in the first aspect above, or a chlorine-resistant drug desalting membrane prepared by the preparation method described in the second aspect above, wherein the chlorine-resistant desalting membrane is used for the separation of drugs and salts; In some embodiments, the drug includes antibiotics.

[0041] The present invention will be further described below through examples and comparative examples.

[0042] Example 1 A novel chlorine-resistant drug desalination membrane is prepared by the following steps: A 0.1% aqueous solution was prepared by dissolving piperazine in deionized water.

[0043] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.1%.

[0044] Preparation of polyacrylonitrile-based membrane: 32.4 g of polyacrylonitrile polymer powder was dissolved in 147.6 g of DMF solvent to prepare an 18 wt% casting solution. The solution was stirred in an oil bath at 70 °C for 48 h, then allowed to stand in an oil bath at 40 °C for 24 h to remove bubbles. The solution was then removed and cooled to room temperature for later use. A 200 μm thick casting solution layer was scraped onto a glass plate with nonwoven fabric attached using a film scraper at a speed of 75 mm / s. The glass plate was then immersed in deionized water at 25 °C to form a membrane through phase inversion, yielding a polyacrylonitrile-based membrane with a molecular weight cutoff of approximately 10,000–60,000 Daltons. Finally, the membrane was stored in deionized water for later use.

[0045] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 10 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 1 minute. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 minutes to obtain a polyamide composite membrane.

[0046] Prepare a 3.0% (pH 7.0) aqueous solution of polycarbodiimide: Dissolve the polycarbodiimide in deionized water, then adjust the pH to 7.0 with a dilute hydrochloric acid solution.

[0047] The prepared polyamide composite membrane was placed in a 3.0% (w / w) aqueous solution of polycarbodiimide at pH 7.0 and reacted at 60°C for 30 min, followed by heat treatment at 60°C for 5 min to obtain a chlorine-resistant drug desalination membrane. The modified layer of the prepared drug desalination membrane had a thickness of 18 nm, and the polyamide layer had a thickness of 69 nm.

[0048] Example 2 A novel chlorine-resistant drug desalination membrane is prepared by the following steps: A 0.1% aqueous solution was prepared by dissolving piperazine in deionized water.

[0049] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.1%.

[0050] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0051] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 10 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 1 minute. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 minutes to obtain a polyamide composite membrane.

[0052] Prepare an aqueous solution of polycarbodiimide with a pH of 7.0 and a mass concentration of 3.0% according to the method in Example 1.

[0053] The prepared polyamide composite membrane was placed in a 3.0% (w / w) aqueous solution of polycarbodiimide at pH 7.0 and reacted at 30°C for 10 min, followed by heat treatment at 60°C for 5 min to obtain a chlorine-resistant drug desalination membrane. The modified layer of the prepared drug desalination membrane had a thickness of 13 nm, and the polyamide layer had a thickness of 79 nm.

[0054] Example 3 A novel chlorine-resistant drug desalination membrane is prepared by the following steps: A 0.1% aqueous solution was prepared by dissolving piperazine in deionized water.

[0055] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.1%.

[0056] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0057] The prepared polyacrylonitrile group was immersed in an aqueous solution for 10 min, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization reaction for 1 min. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 min to obtain a polyamide composite membrane.

[0058] Prepare a 3.0% (pH 9.0) aqueous solution of polycarbodiimide: Dissolve the polycarbodiimide in deionized water, then adjust the pH to 9.0 with sodium hydroxide solution.

[0059] The prepared polyamide composite membrane was placed in a 3.0% (pH 9.0) aqueous solution of polycarbodiimide and reacted at 30°C for 10 min, followed by heat treatment at 60°C for 3 min to obtain a chlorine-resistant drug desalination membrane. The modified layer of the prepared drug desalination membrane had a thickness of 12 nm, and the polyamide layer had a thickness of 89 nm.

[0060] Example 4 A novel drug desalination membrane is prepared by the following steps: A 0.3% aqueous solution was prepared by dissolving piperazine in deionized water.

[0061] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.1%.

[0062] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0063] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 10 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 1 minute. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 minutes to obtain a polyamide composite membrane.

[0064] Following the method in Example 3, an aqueous solution of polycarbodiimide with a pH of 9.0 and a mass concentration of 3.0% was prepared.

[0065] The prepared polyamide composite membrane was placed in a 3.0% (pH 9.0) aqueous solution of polycarbodiimide and reacted at 30°C for 10 min, followed by heat treatment at 60°C for 3 min to obtain a chlorine-resistant drug desalination membrane. The modified layer of the prepared drug desalination membrane had a thickness of 29 nm, and the polyamide layer had a thickness of 108 nm.

[0066] Example 5 A novel drug desalination membrane is prepared by the following steps: A 0.3% aqueous solution was prepared by dissolving piperazine in deionized water.

[0067] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.5%.

[0068] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0069] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 10 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 1 minute. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 minutes to obtain a polyamide composite membrane.

[0070] Prepare an aqueous solution of polycarbodiimide with a pH of 7.0 and a mass concentration of 3.0% according to the method in Example 1.

[0071] The prepared polyamide composite membrane was placed in a 3.0% (w / w) aqueous solution of polycarbodiimide at pH 9.0 and reacted at 30°C for 10 min, followed by heat treatment at 60°C for 3 min to obtain a chlorine-resistant drug desalination membrane. The modified layer of the prepared drug desalination membrane had a thickness of 31 nm, and the polyamide layer had a thickness of 124 nm.

[0072] Example 6 A novel chlorine-resistant drug desalination membrane is prepared by the following steps: A 0.2% (w / w) aqueous solution was prepared by dissolving piperazine in deionized water.

[0073] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.05%.

[0074] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0075] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 5 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 0.5 minutes. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 50°C for 3 minutes to obtain a polyamide composite membrane.

[0076] Following the method in Example 1, an aqueous solution of polycarbodiimide with a pH of 7.0 and a mass concentration of 0.5% was prepared, the difference being the mass concentration.

[0077] The prepared polyamide composite membrane was placed in a 3.0% (w / w) aqueous solution of polycarbodiimide at pH 7.0 and reacted at 30°C for 60 min, followed by heat treatment at 90°C for 5 min to obtain a chlorine-resistant drug desalination membrane. The modified layer of the prepared drug desalination membrane had a thickness of 18 nm, and the polyamide layer had a thickness of 89 nm.

[0078] Example 7 A novel chlorine-resistant drug desalination membrane is prepared by the following steps: A 0.1% aqueous solution was prepared by dissolving piperazine in deionized water.

[0079] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.1%.

[0080] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0081] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 15 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 3 minutes. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 80°C for 3 minutes to obtain a polyamide composite membrane.

[0082] Following the method in Example 1, an aqueous solution of polycarbodiimide with a pH of 7.0 and a mass concentration of 1.0% was prepared, the difference being the mass concentration.

[0083] The prepared polyamide composite membrane was placed in a 3.0% (w / w) aqueous solution of polycarbodiimide at pH 7.0 and reacted at 90°C for 30 min, followed by heat treatment at 30°C for 15 min to obtain a chlorine-resistant drug desalination membrane. The modified layer of the prepared drug desalination membrane had a thickness of 18 nm, and the polyamide layer had a thickness of 79 nm.

[0084] Comparative Example 1 A drug desalination membrane, the preparation method of which includes the following steps: A 0.3% aqueous solution was prepared by dissolving piperazine in deionized water.

[0085] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.5%.

[0086] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0087] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 10 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 1 minute. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 minutes to obtain a polyamide composite membrane.

[0088] Comparative Example 2 A chlorine-resistant drug desalination membrane, the preparation method of which includes the following steps: A 0.3% aqueous solution was prepared by dissolving piperazine in deionized water.

[0089] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.5%.

[0090] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0091] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 10 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 1 minute. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 minutes to obtain a polyamide composite membrane.

[0092] Prepare an aqueous solution of N,N-dicyclohexylcarbodiimide with a pH of 9.0 and a mass concentration of 3.0%: Dissolve N,N-dicyclohexylcarbodiimide in deionized water, and then adjust the pH to 9.0 with sodium hydroxide solution.

[0093] The prepared polyamide composite membrane was placed in a 3.0% (w / w) N,N-dicyclohexylcarbodiimide solution at pH 9 and reacted at 30°C for 10 min, followed by heat treatment at 60°C for 3 min to obtain the drug desalination membrane. The modified layer thickness of the prepared drug desalination membrane was 46 nm.

[0094] Comparative Example 3 A novel drug desalination membrane is prepared by the following steps: A 0.3% aqueous solution was prepared by dissolving piperazine in deionized water.

[0095] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.5%.

[0096] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0097] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 10 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 1 minute. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 minutes to obtain a polyamide composite membrane.

[0098] Prepare a 4.0% (pH 9.0) aqueous solution of polycarbodiimide: Dissolve the polycarbodiimide in deionized water, then adjust the pH to 9.0 with sodium hydroxide solution.

[0099] The prepared polyamide composite membrane was placed in an aqueous solution of polycarbodiimide at pH 9.0 and a mass concentration of 4.0%, and reacted at 30°C for 10 min, followed by heat treatment at 60°C for 3 min to obtain a chlorine-resistant drug desalination membrane. The modified layer thickness of the prepared drug desalination membrane was 126 nm.

[0100] Comparative Example 4 A novel drug desalination membrane is prepared by the following steps: A 0.3% aqueous solution was prepared by dissolving piperazine in deionized water.

[0101] Trimethylbenzene chloride was dissolved in n-hexane to prepare an organic phase solution with a mass concentration of 0.5%.

[0102] Polyacrylonitrile-based films were prepared according to the method described in Example 1.

[0103] The prepared polyacrylonitrile-based membrane was immersed in an aqueous solution for 10 minutes, and then the excess solution on the surface was removed. It was then placed in an organic solution for interfacial polymerization for 1 minute. Subsequently, the excess solution on the membrane surface was removed, and the membrane was heat-treated at 30°C for 3 minutes to obtain a polyamide composite membrane.

[0104] Prepare a 0.1% (pH 9.0) aqueous solution of polycarbodiimide: Dissolve the polycarbodiimide in deionized water, then adjust the pH to 9.0 with sodium hydroxide solution.

[0105] The prepared polyamide composite membrane was placed in an aqueous solution of polycarbodiimide at pH 9.0 and a mass concentration of 0.1%, and reacted at 30°C for 10 min, followed by heat treatment at 60°C for 3 min to obtain a chlorine-resistant drug desalination membrane. The modified layer thickness of the prepared drug desalination membrane was 46 nm.

[0106] Test example: (1) Membrane structure characterization The drug desalting membrane prepared in Example 2 of this invention was subjected to infrared spectroscopy, and the results are as follows: Figure 1 As shown in the figure. It can be seen from the figure that the range is 3500~3300 cm. -1 The characteristic peak at 1625 cm⁻¹ is attributed to the stretching vibrations of the OH and NH groups in the polyamide. -1 The characteristic peak at 1720 cm⁻¹ is attributed to the stretching vibration of C=O; -1 The characteristic peak is attributed to the stretching vibration of N-acylurea generated by the reaction of polycarbodiimide and carboxyl groups, 2113 cm⁻¹. -1 The characteristic peaks are attributed to unreacted N=C=N stretching vibrations on polycarbodiimide. This indicates the formation of a polyamide separation layer and a chlorine-resistant modified layer of polycarbodiimide on the polyacrylonitrile-based film.

[0107] Figure 2 The image shown is a scanning electron microscope image of the surface of the drug desalination membrane prepared in Example 2. After the reaction of polycarbodiimide with the carboxyl groups on the surface of the polyamide composite membrane, a dense and rough surface morphology is formed. (2) Desalination performance of drugs The permeation flux and antibiotic / salt selectivity of the membranes prepared in the embodiments and comparative examples of this invention were determined. The specific methods are as follows: The permeation flux and selectivity of the drug desalination membranes in the embodiments and comparative examples of this invention were tested using a cross-flow membrane performance evaluation instrument at a test temperature of 25°C.

[0108] First, the nanofiltration membranes prepared in the examples or comparative examples were pre-pressed at a pressure of 0.6 MPa for 30 min using deionized water as feed. Then, the deionized water was replaced with a pre-prepared mixed solution of tetracycline hydrochloride and 1 g / L NaCl. In the mixed solution, the concentration of tetracycline hydrochloride was 0.05 g / L and the concentration of NaCl was 1 g / L. Then, the pressure was adjusted to 0.5 MPa and the membrane was run stably for 30 min. A certain volume of permeate was taken and the permeation time was recorded. The permeation flux was calculated using formula (1).

[0109] (1); In equation (1), F Permeation flux, per unit ; V Volume of permeate, in liters (L); SThe filtration area of ​​the membrane, in meters (m²). 2 ; t The time required to measure a certain volume of permeate, expressed in hours (h).

[0110] The concentrations of the permeate and feed solution were measured by sampling. The selectivity of tetracycline hydrochloride / NaCl was calculated according to formula (2). The concentrations of tetracycline hydrochloride and NaCl were tested by a UV-Vis spectrophotometer and a conductivity meter.

[0111] (2); (3); In equation (2), S represents the selectivity of tetracycline hydrochloride / NaCl; R s and R a The rejection rates are NaCl and tetracycline hydrochloride, respectively, in units.

[0112] In equation (3), R is the retention rate; C p and C f The values ​​are the concentrations of the permeate and feed solution, respectively, in g / L.

[0113] The test results are shown in Table 1.

[0114] Table 1: Performance tests of desalination membranes prepared in the examples and comparative examples

[0115] As shown in Table 1, the examples exhibit superior permeation flux and antibiotic / salt selectivity. Comparative Example 1, lacking the chlorine-resistant modification of polycarbodiimide, resulted in a membrane with poor tetracycline hydrochloride / NaCl selectivity and a relatively lower permeation flux. Comparative Example 2, using N,N-dicyclohexylcarbodiimide instead of polycarbodiimide, also significantly reduced the performance of the resulting membrane. Comparative Examples 3 and 4, by altering the concentration of polycarbodiimide, both resulted in decreased permeation flux and tetracycline hydrochloride / NaCl selectivity.

[0116] (3) Chlorine resistance test The membranes of each embodiment and comparative example were immersed in 1000 ppm NaClO solution at room temperature and allowed to stand for 8 hours. After careful removal and thorough rinsing with deionized water, they were installed in a cross-flow filtration device. Using 50 mg / L tetracycline hydrochloride solution as the feed solution, the permeate flux and tetracycline hydrochloride rejection rate of the membranes were tested at 0.5 MPa. Simultaneously, the permeate flux of the membranes of each embodiment and comparative example without immersion in NaClO solution was measured to evaluate the chlorine resistance of the nanofiltration membranes. The results are shown in Table 2.

[0117] Table 2: Chlorine resistance test results of membranes prepared in the examples and comparative examples

[0118] As can be seen from Table 2, after After treatment with active chlorine, the chlorine-resistant membrane in the examples still exhibited a high rejection rate; the rejection rate in the comparative example was significantly reduced. Furthermore, the membrane prepared in the embodiments of the present invention showed minimal fluctuations in permeate flux before and after immersion, further demonstrating that the membrane of the embodiments of the present invention possesses excellent chlorine resistance.

[0119] It is evident that the chlorine-resistant drug desalination membrane provided by this invention exhibits superior tetracycline hydrochloride / NaCl selectivity and higher permeation flux during drug desalination; furthermore, under the same chlorine exposure intensity, the drug desalination membrane provided by this invention maintains higher drug retention performance and demonstrates better chlorine resistance.

[0120] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A chlorine-resistant desalination membrane, characterized in that, The chlorine-resistant desalination membrane includes a base membrane, a polyamide separation layer formed on the surface of the base membrane, and a chlorine-resistant modified layer formed on the polyamide separation layer; The chlorine-resistant modified layer is formed by in-situ grafting of carboxyl groups of polycarbodiimide with the carboxyl groups of the polyamide separation layer.

2. The chlorine-resistant desalination membrane according to claim 1, characterized in that, The base membrane is a porous base membrane with a molecular weight cutoff of 10,000 to 60,000 Daltons.

3. The chlorine-resistant desalination membrane according to claim 1, characterized in that, The base membrane includes at least one of polyacrylonitrile ultrafiltration membrane, polyethersulfone ultrafiltration membrane, and polysulfone ultrafiltration membrane.

4. The chlorine-resistant desalination membrane according to claim 1, characterized in that, The polyamide separation layer is obtained by interfacial polymerization of polyamines and polyacryl chlorides on the porous base membrane; The polyamine includes at least one of piperazine, m-phenylenediamine, and p-phenylenediamine; The polyacrylic chloride includes at least one of pyromellitic trichloroisocyanurate, isophthaloyl chloride, and terephthaloyl chloride; The thickness of the polyamide separation layer is 50~200nm.

5. The chlorine-resistant desalination membrane according to claim 1, characterized in that, The thickness of the chlorine-resistant modified layer is 10~200nm.

6. A method for preparing the chlorine-resistant desalination membrane according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Preparation of polyamide composite film The polyamine was dissolved in water to obtain an aqueous solution; Polyacyl chlorides are dissolved in a solvent to obtain an organic phase solution; After immersing the base film in an aqueous solution, remove it and remove excess solution from the surface; The membrane is then placed in an organic phase solution for interfacial polymerization; subsequently, excess solution is removed from the membrane surface, followed by heat treatment to obtain a polyamide composite membrane. S2: The polyamide composite membrane prepared in step S1 is placed in an aqueous solution of polycarbodiimide for reaction, and a chlorine-resistant modified layer is grafted onto the surface in situ. Then, heat treatment is performed to obtain a chlorine-resistant drug desalination membrane.

7. The preparation method according to claim 6, characterized in that, In step S1, the mass concentration of the polyamine in the aqueous solution is 0.1~3.0%; In the organic phase solution, the mass concentration of the polyacrylamide chloride is 0.05~0.5%.

8. The preparation method according to claim 6, characterized in that, The immersion time is 5-15 minutes; The time for the interfacial polymerization reaction is 0.5~3 min; The heat treatment temperature is 30~80℃, and the heat treatment time is 3min~3h.

9. The preparation method according to claim 6, characterized in that, In step S2, the mass concentration of the polycarbodiimide aqueous solution is 0.5-3%, and the pH value is 3-10; The reaction temperature is 30~90℃, and the reaction time is 10~60min; The heat treatment temperature is 30~90℃, and the heat treatment time is 3~60min.

10. The application of a chlorine-resistant desalination membrane according to any one of claims 1-5, or a chlorine-resistant drug desalination membrane prepared by the preparation method according to any one of claims 6-9, characterized in that, The chlorine-resistant desalination membrane is used for the separation of drugs and salts; Preferably, the drug includes antibiotics.

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