A method for preparing chlorine-resistant polyesteramide nanofiltration membrane using highly active aqueous phase monomers

Abstract

The present invention discloses a method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer, the steps comprising: cutting of the base membrane; ultrasonic cleaning; membrane fixation; preparation of a polymerized aqueous phase solution; and intermittent interfacial polymerization reaction. The present invention utilizes a highly active aqueous phase monomer N2Hyd to replace the traditional piperazine monomer and introduces a certain amount of APG, which not only effectively improves the hydrophilicity of the membrane, but also forms a hydrophilic glycoside layer on the membrane surface, significantly reducing the lipophilicity of the membrane; since both N2Hyd and APG are highly active and contain multiple hydroxyl groups, the prepared polyesteramide nanofiltration membrane has better reaction activity. Ultimately, the membrane contains a large number of ester bonds and a thinner active layer, which greatly reduces the mass transfer resistance, thereby exhibiting a higher water flux, excellent desalination characteristics, and outstanding chlorine resistance. The implementation of this method not only promotes the technological advancement of membrane materials, but also provides new ideas and directions for research and application in related fields.

Description

Technical Field

[0001] The invention relates to the technical field of environmental science and engineering materials, and in particular to a method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a high-activity aqueous phase monomer. Background Art

[0002] As global water shortages continue to intensify, the application of seawater desalination technology is becoming increasingly important. Desalination not only effectively addresses freshwater shortages but also provides a reliable water source for arid regions. However, traditional desalination methods, such as multi-stage flash evaporation and reverse osmosis, still face numerous challenges in practical application, particularly in terms of membrane material performance, durability, and cost. Membrane separation technology, particularly reverse osmosis and nanofiltration membranes, has become a research hotspot in the desalination field due to its high efficiency, energy-saving, and environmentally friendly characteristics.

[0003] Currently, reverse osmosis membranes are widely used in seawater desalination, and their main raw materials are polyamide and polyester materials. However, as the membranes are used for a longer time, problems such as membrane fouling and degradation gradually become apparent, resulting in reduced membrane flux and a decrease in salt separation rate. Membrane fouling mainly comes from suspended matter, bacteria, and organic matter in the water. During the desalination process, chlorinating agents are usually added to inhibit the growth of microorganisms. Although these chlorinating agents can effectively control biological fouling, they also cause certain damage to the membrane material, affecting the long-term stability and economic efficiency of the membrane. Therefore, how to improve the chlorine resistance of the membrane material and extend the service life of the membrane is an urgent problem to be solved in current seawater desalination technology.

[0004] Polyesteramide (PA) materials have become a key area of ​​membrane material research due to their exceptional mechanical strength, thermal stability, and chemical tolerance. The molecular structure of PA imparts excellent chemical stability and superior separation performance, enabling effective filtration of dissolved salts and impurities from water. Furthermore, PA membranes exhibit excellent heat and pressure resistance, making them suitable for use in the demanding environments of seawater desalination.

[0005] However, in the prior art, there is no method for preparing a chlorine-resistant polyesteramide nanofiltration membrane with a stronger negative charge, higher hydrophilicity, larger membrane pores and a smoother surface, and better water permeability at the optimal co-soluble monomer combination concentration, while having a good Na2SO4 rejection rate and obvious Na2SO4 / NaCI separation ability.

[0006] Therefore, it is necessary to propose a method for preparing chlorine-resistant polyesteramide nanofiltration membrane using highly active aqueous phase monomers to solve the above problems. Summary of the Invention

[0007] Aiming at the application limitation problems of high pollution tendency and weak chlorine resistance of traditional nanofiltration membranes in the field of seawater desalination, the present invention proposes a method for preparing chlorine-resistant polyesteramide nanofiltration membranes using highly active aqueous phase monomers.

[0008] The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane with a highly active aqueous phase monomer comprises:

[0009] S1. Cut the PES-UF commercial base film to obtain the size and shape of the base film;

[0010] S2. Ultrasonic cleaning of the PES-UF commercial base membrane twice with an ethanol solution to remove the glycerol protective agent and impurities on the membrane surface to obtain a spare PES ultrafiltration base membrane;

[0011] S3, fixing the PES ultrafiltration base membrane cleaned in S2 on a polytetrafluoroethylene (PTFE) frame with the membrane selection layer facing upward for subsequent treatment and reaction;

[0012] S4. Mix appropriate amounts of alkyl polyglycoside (APG) and N-(2-hydroxyethyl)ethylenediamine (N2Hyd) in deionized water to form a uniform (monomer / surfactant) aqueous polymerization solution, and control its alkaline solution environment; the aqueous polymerization solution is allowed to contact the surface of the PES ultrafiltration base membrane for a certain period of time, and then the remaining solution is gently poured out. The residual liquid on the membrane surface is gently wiped with filter paper, and the membrane is evenly blown with an air pump gun and allowed to dry naturally to ensure that there is no residual liquid on the membrane surface;

[0013] S5. Gently pour a n-hexane organic phase solution containing a certain concentration of trimesoyl chloride (TMC) onto the membrane surface, and intermittently initiate an interfacial polymerization (IP) reaction to obtain the prepared polyesteramide composite nanofiltration membrane.

[0014] In a preferred embodiment of this solution, the PES-UF commercial base membrane in S1 is a polyethersulfone ultrafiltration membrane with a molecular weight cutoff (MWCO) of 30 kDa (provided by Microdyn-Nadir); the size of the base membrane obtained after cutting is 11 cm*11 cm.

[0015] In a preferred embodiment of this scheme, the concentration of the ethanol solution in S2 is 1%-5% (v / v); the ultrasonic cleaning time is 1-3 minutes each time; and the obtained spare PES ultrafiltration base membrane is stored in pure water for future use.

[0016] Furthermore, the specific steps of fixing the PES ultrafiltration base membrane on the PTFE frame in S3 are: taking out the PES ultrafiltration base membrane from the pure water, and using filter paper to dry the membrane surface until there are no obvious water droplets, and then fixing the ultrafiltration base membrane on the polytetrafluoroethylene (PTFE) frame with the membrane selection layer facing up, and drying it for 2-5 minutes. During this period, use an air pump gun to evenly blow air for 1-3 minutes to provide evenly distributed base membrane pores for the mixed water phase.

[0017] In a preferred embodiment of this scheme, the uniform aqueous polymerization solution in S4 is 0.05-0.15% (v / v) N2Hyd and 5%-15% APG aqueous solution.

[0018] Furthermore, the specific operation for controlling the alkaline solution environment is as follows: an appropriate amount of APG and N2Hyd are mixed in deionized water to form a uniform aqueous polymerization solution, during which the alkaline environment pH is tested to be in the range of 8-10.5 to prevent the deprotonation effect of subsequent side reaction products.

[0019] Furthermore, the aqueous polymer solution is brought into contact with the surface of the PES ultrafiltration base membrane for a certain period of time, such as 5-8 minutes.

[0020] Furthermore, the specific operation of gently wiping the residual liquid on the surface of the membrane with filter paper is as follows: use filter paper to dry the surface of the membrane until there are no obvious water droplets; use an air pump gun to blow it evenly with air, and let it dry naturally. The specific operation is as follows: use an air pump gun to blow it evenly with air, the operation time is 30 seconds, and re-fix the PES ultrafiltration base membrane soaked in the aqueous solution to the PTFE frame, and then let it dry naturally for 2-5 minutes.

[0021] In a preferred embodiment of this scheme, the specific operation of intermittently starting the interfacial polymerization reaction in S5 is: gently pouring an organic phase solution of n-hexane containing 0.05-0.2% (w / v) TMC onto the membrane surface for a soaking time of 20-50S to start the first step of the intermittent interfacial polymerization reaction, then pouring out the organic phase solution and rinsing twice with an n-hexane solution; after an interval of 10S, immediately inverting an organic phase solution of n-hexane containing 0.05-0.2% (w / v) TMC onto its surface for 30S to maintain a sufficient organic phase concentration to allow the remaining aqueous phase monomers to undergo the remaining reaction at the same diffusion rate, thereby achieving complete and uniform regulation characteristics, and then placing it in an oven for heat treatment for 5-10min to perform a heat-stabilized active layer to enhance its mechanical properties, and then taking it out and cooling it to room temperature to obtain the prepared polyester amide composite nanofiltration membrane, and soaking it in pure water for storage.

[0022] According to the method for preparing chlorine-resistant polyesteramide nanofiltration membrane with high-activity aqueous phase monomer, the prepared novel chlorine-resistant polyesteramide nanofiltration membrane with high-activity aqueous phase monomer is applied in the fields of seawater desalination, wastewater treatment and membrane separation technology.

[0023] The mechanism of the technical solution of the present invention:

[0024] In the preparation of polyesteramide nanofiltration membranes by interfacial polymerization of the surfactant APG and the highly active aqueous monomer N2Hyd with TMC, it is crucial to understand the chemical attraction or chemical synergy between the two in aqueous solution. This interaction can influence the reaction rate and thus facilitate the preparation of a uniform active layer.

[0025] Characteristics of surfactant alkyl polyglycoside (APG):

[0026] (1) Surfactant properties: APG is a nonionic surfactant with good wettability and foaming properties, and can reduce the surface tension of the liquid interface.

[0027] (2) Molecular structure: Its molecule contains a hydrophobic alkyl chain and a hydrophilic saccharide part. This amphiphilic structure enables APG to form micelles in the aqueous phase, which is beneficial to improving the solubility and mass transfer rate of the reactants.

[0028] Features of N2Hyd:

[0029] (1) Highly active aqueous monomer: N2Hyd has two amino groups and one hydroxyl group. Its amino group has strong nucleophilicity and can react rapidly with TMC to form a polyesteramide chain.

[0030] (2) Solubility in aqueous phase: Due to its polarity, N2Hyd has a high solubility in aqueous phase, which provides a good premise for reaction with TMC.

[0031] Chemical synergistic mechanism:

[0032] 1. Mutual Attraction and Stability

[0033] (1) Hydrogen bond formation: The hydroxyl groups in APG can form hydrogen bonds with the amino and hydroxyl groups in N2Hyd, enhancing the interaction between the two. This hydrogen bonding can stabilize the mixture of APG and N2Hyd, slowing their diffusion in the aqueous phase and thus regulating the reaction rate.

[0034] (2) Micellar effect: When APG forms micelles, N2Hyd can be “encapsulated” in the micelles, increasing the effective concentration of N2Hyd and promoting its reaction with TMC.

[0035] 2. Dynamics Control

[0036] (1) Reaction interface characteristics: APG, as a surfactant, can reduce the interfacial tension between the aqueous phase and the organic phase, thereby affecting the rate of interfacial polymerization. The reduced interfacial tension can make N2Hyd and TMC more easily contact, increasing the probability of reaction.

[0037] (2) Reaction rate regulation: By adjusting the concentration of APG, the reaction rate can be effectively regulated, promoting the formation of a uniform active layer. For example, an appropriate amount of APG can increase the concentration of reactants at the interface, thereby accelerating the polymerization reaction; while an excessive amount of APG may dilute the reactants and slow down the reaction rate.

[0038] In summary, through the reasonable combination of APG and N2Hyd, the chemical attraction and synergistic effect of the two in the aqueous solution can be optimized. This optimization not only helps to increase the rate of interfacial polymerization reaction, but also forms a uniform active layer in the process of preparing polyesteramide nanofiltration membrane, providing a theoretical basis and practical basis for improving the performance of the membrane. Through further experimental verification, its specific reaction mechanism can be explored and provide a reference for industrial applications.

[0039] The implementation of the present invention has the following beneficial effects:

[0040] The present invention discloses a method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous monomer. The cross-linked polymer network structure of the PEA nanofiltration membrane is constructed using N-(2-hydroxyethyl)ethylenediamine (N2Hyd) as the main reactive monomer. The cross-linked polymer network structure is mainly connected by amide bonds formed by the hydrolysis reaction of hydrazine di(primary and secondary)amine groups and acyl chloride groups. The hydroxyl groups contained in the monomer also react to form ester bonds, which become part of the cross-linked network structure. This is the first time that the N2Hyd aqueous monomer has been used to prepare a polyesteramide nanofiltration membrane.

[0041] The surface active properties of APG contribute to the cleaning and regeneration of the membrane surface; during the separation process, dirt molecules are easily washed off the membrane surface, thereby reducing membrane contamination and flux attenuation; the present invention uses it and the N2Hyd water-soluble monomer as co-soluble aqueous phase polymerization monomers for the first time, combining the properties of the two to successfully prepare the target polyester amide composite nanofiltration membrane.

[0042] The polyester amide nanofiltration membrane prepared by the present invention adopts a highly active hydrazine-containing diamine reaction monomer and combines it with a polyhydroxy surfactant APG to carry out an intermittent interfacial polymerization reaction, fully maintaining the reaction intensity to form a uniform, complete and thin polyester amide active layer, reducing the mass transfer resistance, effectively increasing the water flux of the nanofiltration membrane, and enhancing its anti-pollution property.

[0043] The polyesteramide nanofiltration membrane prepared by the present invention has a stronger negative charge, higher hydrophilicity, larger membrane pores and a smoother surface, so that it has better water permeability at the optimal co-soluble monomer combination concentration, and at the same time has a good Na2SO4 rejection rate and obvious Na2SO4 / NaCI separation ability.

[0044] The polyester amide nanofiltration membrane prepared by the present invention has a significant chlorine resistance effect due to the uniform distribution of its multi-ester bond cross-linking structure, which is beneficial to alleviating the influence of chlorine oxidation and hydrolysis on the membrane, thereby increasing the service life of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 (a, b, c) are the SEM surface morphologies of the ultrafiltration base membrane (PES-UF) required for the nanofiltration membrane prepared in Examples 1-5, the polyesteramide nanofiltration membrane prepared according to the optimal ratio in Example 3, and the optimal nanofiltration membrane after soaking in sodium hypochlorite;

[0047] Figure 2 (a, b, c) are the AFM surface morphologies of the ultrafiltration base membrane (PES-UF) required for the nanofiltration membrane prepared in Examples 1-5, the polyesteramide nanofiltration membrane prepared with the optimal ratio in Example 3, and the optimal nanofiltration membrane after soaking in sodium hypochlorite.

[0048] Figure 3 The water flux and removal rate of four common salts (Na2SO4, MgSO4, NaCl, MgCl2) of the polyesteramide nanofiltration membrane prepared in Examples 1-5 were tested;

[0049] Figure 4 This is a stability test chart of the optimal polyester amide nanofiltration membrane prepared in Example 3 after being soaked in sodium hypochlorite for 24 hours. DETAILED DESCRIPTION

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0051] The method for preparing chlorine-resistant polyesteramide nanofiltration membrane with high-activity aqueous phase monomer comprises the following steps:

[0052] S1. Cut a polyethersulfone ultrafiltration membrane with a molecular weight cutoff (MWCO) of 30 kDa to obtain a square base membrane with a size of 11 cm*11 cm.

[0053] S2. Ultrasonic cleaning of the PES-UF commercial base membrane was performed twice with 1%-5% (v / v) ethanol solution, each time for 1-3 min, to remove the glycerol protective agent and impurities on the membrane surface, to obtain a spare PES ultrafiltration base membrane, which was stored in pure water for future use.

[0054] S3. Fix the PES ultrafiltration base membrane cleaned in S2 on a polytetrafluoroethylene (PTFE) frame with the membrane selection layer facing upward for subsequent processing and reaction; the specific steps are: remove the PES ultrafiltration base membrane from the pure water, and use filter paper to dry the membrane surface until there are no obvious water droplets, then fix the ultrafiltration base membrane on a polytetrafluoroethylene (PTFE) frame with the membrane selection layer facing upward, and dry it for 2-5 minutes. During this period, use an air pump gun to blow air evenly for 1-3 minutes to provide evenly distributed base membrane pores for the mixed water phase.

[0055] S4. Mix an appropriate amount of alkyl polyglycoside (APG) and N-(2-hydroxyethyl)ethylenediamine (N2Hyd) in deionized water to form a uniform (monomer / surfactant) aqueous polymerization solution, and control its alkaline solution environment; the aqueous polymerization solution is 0.05-0.15% (v / v) N2Hyd and 5%-15% APG aqueous solution; the specific operation of controlling its alkaline solution environment is: mix an appropriate amount of APG and N2Hyd in deionized water to form a uniform aqueous polymerization solution, during which the alkaline environment pH is tested to be within the range of 8-10.5 to prevent the deprotonation effect of subsequent side reaction products.

[0056] The aqueous polymerization solution is brought into contact with the surface of the PES ultrafiltration base membrane for 5-8 minutes, and then the remaining solution is gently poured out. The residual liquid on the membrane surface is gently wiped with filter paper, and it is evenly blown with an air pump gun and allowed to dry naturally to ensure that there is no residual liquid on the membrane surface; the specific operation of gently wiping the residual liquid on the membrane surface with filter paper is as follows: use filter paper to wet the membrane surface until there are no obvious water droplets; the specific operation of blowing it evenly with an air pump gun and letting it dry naturally is as follows: use an air pump gun to blow it evenly, the operation time is 30 seconds, and re-fix the PES ultrafiltration base membrane soaked in the aqueous solution to the PTFE frame, and then let it dry naturally for 2-5 minutes.

[0057] S5. Gently pour a n-hexane organic phase solution containing a certain concentration of trimesoyl chloride (TMC) onto the membrane surface, and intermittently initiate an interfacial polymerization (IP) reaction to obtain the prepared polyesteramide composite nanofiltration membrane.

[0058] The specific operation of intermittent initiation of interfacial polymerization reaction is as follows: an organic phase solution of n-hexane containing 0.05-0.2% (w / v) TMC is gently poured onto the membrane surface for 20-50 seconds to start the first step of the intermittent interfacial polymerization reaction, and then the organic phase solution is poured out and rinsed twice with an n-hexane solution; after an interval of 10 seconds, an organic phase solution of n-hexane containing 0.05-0.2% (w / v) TMC is immediately inverted on the surface for 30 seconds to maintain a sufficient organic phase concentration to allow the remaining aqueous phase monomers to undergo the remaining reaction at the same diffusion rate, thereby achieving complete and uniform regulation characteristics, and then placed in an oven for heat treatment for 5-10 minutes to perform a heat-stabilized active layer to enhance its mechanical properties, and then taken out and cooled to room temperature to obtain the prepared polyester amide composite nanofiltration membrane, and then immersed in pure water for storage.

[0059] According to the method for preparing chlorine-resistant polyesteramide nanofiltration membrane with high-activity aqueous phase monomer, the prepared novel chlorine-resistant polyesteramide nanofiltration membrane with high-activity aqueous phase monomer is applied in the fields of seawater desalination, wastewater treatment and membrane separation technology. Example 1

[0060] A PEA-TFC-NF membrane was prepared on a PES ultrafiltration substrate using the IP technique at room temperature (25°C). Prior to the IP reaction, the PES-UF membrane was ultrasonically cleaned twice with 1% (v / v) ethanol solution for 1-3 minutes to remove the glycerol protective agent from the commercial ultrafiltration membrane and then stored in pure water until use. The IP reaction steps were as follows: (a) The cleaned ultrafiltration membrane was mounted on a polytetrafluoroethylene (PTFE) frame with the membrane selective layer facing upward. (b) A 0.05% (v / v) aqueous solution of N-(2-hydroxyethyl)ethylenediamine (N2Hyd) and 5% (v / v) alkyl polyglycoside (APG) co-dissolved monomers was placed in contact with the membrane surface for 5-8 minutes. (c) After the aqueous phase was decanted, the membrane surface was gently wiped clean with filter paper to remove any residual liquid and then air-dried for 2-5 minutes. (d) An organic phase containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) was gently poured onto the membrane surface to initiate intermittent interfacial polymerization (IP) for 20-50 seconds (20-50 seconds). The remaining solution was then removed and the membrane was rinsed twice with hexane, followed by a 10-second interval. The reaction was then reinitiated by inverting the organic phase solution containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) in n-hexane onto the membrane surface for 30 seconds. (e) The resulting TFC membrane was further heat-treated in a 60°C oven for 5-10 minutes (5-10 min), removed, cooled to room temperature, and then transferred to ultrapure water at 4°C, yielding a polyesteramide nanofiltration membrane prepared from a highly active aqueous monomer combined with a surfactant. Example 2

[0061] The difference between this embodiment and embodiment 1 is that the concentration of the new aqueous phase monomer and the concentration of the surfactant added are changed. The rest of the raw materials and preparation methods are the same. The specific steps are as follows:

[0062] A PEA-TFC-NF membrane was prepared on a PES ultrafiltration substrate using the IP technique at room temperature (25°C). Prior to the IP reaction, the PES-UF membrane was ultrasonically cleaned twice with a 1% (v / v) ethanol solution for 1-3 minutes to remove the glycerol protective agent from the commercial ultrafiltration membrane. The membrane was then stored in pure water until ready for use. The IP reaction steps were as follows: (a) The cleaned ultrafiltration membrane was mounted on a polytetrafluoroethylene (PTFE) frame with the membrane selective layer facing upward. (b) A 0.075% (v / v) aqueous solution of N-(2-hydroxyethyl)ethylenediamine (N2Hyd) and 7.5% (v / v) alkyl polyglycoside (APG) co-dissolved monomer was placed in contact with the base membrane surface for 5-8 minutes (5-8 min). (c) After the aqueous phase was poured out, the residual liquid on the membrane surface was gently wiped dry with filter paper and allowed to dry naturally for 2-5 minutes (2-5 min). (d) An organic phase containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) was gently poured onto the membrane surface to initiate intermittent interfacial polymerization (IP) reaction for 20-50 seconds (20-50 s). The residual solution was then removed and the membrane was rinsed twice with hexane with a rest of 10 s. Then, a 0.05-0.2% (w / v) organic phase was immediately poured onto the membrane surface. The surface of the membrane was inverted for 30 seconds to restart the reaction by adding a (w / v) solution of trimesoyl chloride (TMC) in n-hexane to the organic phase. (e) The resulting TFC membrane was further heat-treated in a 60°C oven for 5-10 minutes (5-10 min), removed, cooled to room temperature, and then transferred to ultrapure water at 4°C to obtain a polyesteramide nanofiltration membrane prepared from a highly active aqueous monomer combined with a surfactant. Example 3

[0063] The difference between Example 3 and Example 1 is that the concentration of the new aqueous phase monomer and the concentration of the surfactant added are changed. The other raw materials and preparation methods are the same. The specific steps are as follows:

[0064] A PEA-TFC-NF membrane was prepared on a PES ultrafiltration substrate using the IP technique at room temperature (25°C). Prior to the IP reaction, the PES-UF membrane was ultrasonically cleaned twice with 1% (v / v) ethanol solution for 1-3 minutes to remove the glycerol protective agent from the commercial ultrafiltration membrane and then stored in pure water until use. The IP reaction steps were as follows: (a) The cleaned ultrafiltration membrane was mounted on a polytetrafluoroethylene (PTFE) frame with the membrane selective layer facing upward. (b) A 0.1% (v / v) aqueous solution of N-(2-hydroxyethyl)ethylenediamine (N2Hyd) and 10% (v / v) alkyl polyglycoside (APG) co-dissolved monomers was placed in contact with the membrane surface for 5-8 minutes. (c) After the aqueous phase was decanted, the membrane surface was gently wiped clean with filter paper to remove any residual liquid and then air-dried for 2-5 minutes. (d) An organic phase containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) was gently poured onto the membrane surface to initiate intermittent interfacial polymerization (IP) for 20-50 seconds (20-50 seconds). The remaining solution was then removed and the membrane was rinsed twice with hexane, followed by a 10-second interval. The reaction was then reinitiated by inverting the organic phase solution containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) in n-hexane onto the membrane surface for 30 seconds. (e) The resulting TFC membrane was further heat-treated in a 60°C oven for 5-10 minutes (5-10 min), removed, cooled to room temperature, and then transferred to ultrapure water at 4°C, yielding a polyesteramide nanofiltration membrane prepared from a highly active aqueous monomer combined with a surfactant. Example 4

[0065] The difference between Example 4 and Example 1 is that the concentration of the new aqueous phase monomer and the concentration of the surfactant added are changed. The other raw materials and preparation methods are the same. The specific steps are as follows:

[0066] A PEA-TFC-NF membrane was prepared on a PES ultrafiltration substrate using the IP technique at room temperature (25°C). Prior to the IP reaction, the PES-UF membrane was ultrasonically cleaned twice with 1% (v / v) ethanol solution for 1-3 minutes to remove the glycerol protective agent from the commercial ultrafiltration membrane and then stored in pure water until use. The IP reaction steps were as follows: (a) The cleaned ultrafiltration membrane was mounted on a polytetrafluoroethylene (PTFE) frame with the membrane selective layer facing upward. (b) A 0.125% (v / v) aqueous solution of N-(2-hydroxyethyl)ethylenediamine (N2Hyd) and 12.5% ​​(v / v) alkyl polyglycoside (APG) co-dissolved monomers was placed in contact with the membrane surface for 5-8 minutes. (c) After the aqueous phase was decanted, the membrane surface was gently wiped clean with filter paper to remove any residual liquid and then air-dried for 2-5 minutes. (d) An organic phase containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) was gently poured onto the membrane surface to initiate intermittent interfacial polymerization (IP) for 20-50 seconds (20-50 seconds). The remaining solution was then removed and the membrane was rinsed twice with hexane, followed by a 10-second interval. The reaction was then reinitiated by inverting the organic phase solution containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) in n-hexane onto the membrane surface for 30 seconds. (e) The resulting TFC membrane was further heat-treated in a 60°C oven for 5-10 minutes (5-10 min), removed, cooled to room temperature, and then transferred to ultrapure water at 4°C, yielding a polyesteramide nanofiltration membrane prepared from a highly active aqueous monomer combined with a surfactant. Example 5

[0067] The difference between Example 5 and Example 1 is that the concentration of the new aqueous phase monomer and the concentration of the surfactant added are changed. The other raw materials and preparation methods are the same. The specific steps are as follows:

[0068] A PEA-TFC-NF membrane was prepared on a PES ultrafiltration substrate using the IP technique at room temperature (25°C). Prior to the IP reaction, the PES-UF membrane was ultrasonically cleaned twice with 1% (v / v) ethanol solution for 1-3 minutes to remove the glycerol protective agent from the commercial ultrafiltration membrane and then stored in pure water until use. The IP reaction steps were as follows: (a) The cleaned ultrafiltration membrane was mounted on a polytetrafluoroethylene (PTFE) frame with the membrane selective layer facing upward. (b) A 0.15% (v / v) aqueous solution of N-(2-hydroxyethyl)ethylenediamine (N2Hyd) and 15% (v / v) alkyl polyglycoside (APG) co-dissolved monomers was placed in contact with the membrane surface for 5-8 minutes. (c) After the aqueous phase was decanted, the membrane surface was gently wiped clean with filter paper to remove any residual liquid and then air-dried for 2-5 minutes. (d) An organic phase containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) was gently poured onto the membrane surface to initiate intermittent interfacial polymerization (IP) for 20-50 seconds (20-50 seconds). The remaining solution was then removed and the membrane was rinsed twice with hexane, followed by a 10-second interval. The reaction was then reinitiated by inverting the organic phase solution containing 0.05-0.2% (w / v) trimesoyl chloride (TMC) in n-hexane onto the membrane surface for 30 seconds. (e) The resulting TFC membrane was further heat-treated in a 60°C oven for 5-10 minutes (5-10 min), removed, cooled to room temperature, and then transferred to ultrapure water at 4°C, yielding a polyesteramide nanofiltration membrane prepared from a highly active aqueous monomer combined with a surfactant.

[0069] The polyester amide nanofiltration membranes prepared in Examples 1-5 above were subjected to performance tests:

[0070] 1. Scanning electron microscopy (SEM) analysis

[0071] See Figure 1 , Figure 1 (a, b, c) are the SEM surface morphologies of the ultrafiltration base membrane (PES-UF) required for the nanofiltration membranes prepared in Examples 1-5, the polyesteramide nanofiltration membrane prepared using the optimal ratio in Example 3, and the optimal nanofiltration membrane after soaking in sodium hypochlorite. Scanning electron microscopy reveals that the new monomer combined with the surfactant successfully prepared a polyesteramide nanofiltration membrane, covering the basement membrane pores and exhibiting a relatively uniform and rough surface morphology, which is conducive to improving hydrophilicity. Furthermore, the surface morphology remains relatively intact after sodium hypochlorite treatment, indicating that the polyesteramide membrane has good chlorine resistance.

[0072] 2. Atomic force microscopy (AFM) analysis

[0073] See Figure 2 , Figure 2(a, b, c) are the AFM surface morphologies of the ultrafiltration base membrane (PES-UF) required for the nanofiltration membranes prepared in Examples 1-5, the polyesteramide nanofiltration membrane prepared using the optimal ratio in Example 3, and the optimal nanofiltration membrane after soaking in sodium hypochlorite. Atomic force microscopy observations show that the polyesteramide nanofiltration membrane successfully prepared using the new monomer combined with the surfactant has a rougher surface than the ultrafiltration base membrane (PES-UF), which corresponds to the SEM image. The relatively rough surface morphology is retained after treatment with sodium hypochlorite, further confirming that the polyesteramide nanofiltration membrane prepared by this invention has chlorine resistance.

[0074] 3. Water flux and desalination test

[0075] See Figure 3 , Figure 3 The water flux and removal efficiency of four common salts of the polyesteramide nanofiltration membrane prepared in Example 15 were tested. The water flux of the polyesteramide nanofiltration membrane prepared in Example 15 was tested using cross-flow filtration at a pressure of 5 bar. To achieve stable pure water permeability, each membrane was pre-pressurized with deionized water at 5 bar for at least 30 minutes. To minimize variability, each measurement was repeated three times, and the average value was used as the final result. The water flux was calculated using the formula F = J / A*t (F = membrane flux; J = sample volume; A = membrane effective area; t = time). Simultaneously, the nanofiltration membrane prepared in Example 15 was tested for salt removal using the same method at a pressure of 4 bar with 1 g / L Na2SO4, MgSO4, NaCl, and MgCl2 salt solutions. The conductivity of the salt solutions before and after filtration was measured using a conductivity meter. The salt removal efficiency was determined by the ratio of the difference between the before and after filtration and the influent conductivity. The results were measured three times and averaged. The results are shown in Table 1.

[0076] Table 1 Water flux test results and desalination test results

[0077]

[0078] From Table 1 and Figure 3 The results show that compared with the commercially available NF270 nanofiltration membrane with better performance, the optimal polyester amide nanofiltration membrane prepared by Example 3 of the present invention has a greater water flux than NF270 and retains a higher Na2SO4 removal rate. In comparison, the polyester amide nanofiltration membrane prepared by the present invention has better monovalent / divalent salt separation performance. It can be seen that the new polyester amide nanofiltration membrane prepared by combining the new monomer and surfactant of the technical solution of the present invention has the advantages of high flux, high separation performance and simple operation. In order to further demonstrate its advantages, the present invention conducted a chlorine resistance test.

[0079] 4. Chlorine resistance test

[0080] The optimal polyester amide nanofiltration membrane prepared in Example 3 was immersed in a sodium hypochlorite solution (pH 8, available chlorine content 2000 ppm) for 24 hours and sealed in the dark. The performance test was then carried out for 120 hours. The ratio of water flux to initial water flux and sodium sulfate (Na2SO4) removal rate were used to determine the physical and chemical stability of the polyester amide nanofiltration membrane prepared in the present invention. Figure 4 , Figure 4 The figure below shows the chlorine resistance test. The results show that the optimal polyesteramide nanofiltration membrane lost less than 10% of sodium sulfate after immersion in sodium hypochlorite solution for 24 hours and maintained stability for 120 hours of continuous operation, confirming its chlorine resistance.

[0081] This invention provides a method and application for preparing chlorine-resistant polyesteramide nanofiltration membranes using a novel highly active aqueous monomer combined with a surfactant. This method aims to address the application limitations of conventional nanofiltration membranes in seawater desalination, such as their high fouling tendency and weak chlorine resistance. By employing N-(2-hydroxyethyl)ethylenediamine (N2Hyd), a highly active water-soluble monomer with hydrazine-like diamine groups and hydroxyl groups, and a designated natural surfactant, alkyl polyglycoside (APG), as a co-polymerization monomer, the chlorine-resistant polyesteramide nanofiltration membrane is prepared via intermittent interfacial polymerization (IP). The selective co-polymerization enhances the membrane material's chlorine resistance, facilitating surface cleaning and regeneration. During the separation process, contaminants are easily washed off the membrane surface, reducing membrane fouling and flux attenuation. The introduction of the N2Hyd / APG co-polymerization aqueous solution containing the novel polyhydroxy monomer and the designated surfactant enhances the integrity and stability of the polyesteramide structure due to the highly reactive structure of the hydrazine-like diamine and the excessive exposure of the specific hydroxyl functional groups. This results in a uniform distribution of ester bonds within the cross-linked structure, thereby improving the membrane's chlorine resistance. In addition, an intermittent interfacial polymerization reaction is proposed in the polymerization reaction. Through the intermittent control process of "reaction-short pause-reaction" in a short period of time, the reaction intensity is rationally maintained, which helps to control the uniformity of the active layer and the problem of large differences in diffusion rates during formation. This new polyester amide membrane can not only maintain good separation performance in a chlorinated environment due to its rich ester bonds and activated special cross-linked polymerization structure, but also effectively reduce the risk of membrane contamination. The membrane preparation process has been optimized to ensure that the pore size distribution of the membrane is uniform and the membrane layer is dense, thereby improving the water flux and salt retention rate, and greatly improving the stability and economy of the membrane in the seawater desalination process. With the continuous development of seawater desalination technology, the market demand for high-performance membrane materials will continue to grow. The polyester amide membrane of the present invention can be widely used in seawater desalination, wastewater treatment and other membrane separation technology fields, providing a feasible technical path for solving the problem of water resource shortage. This membrane material not only improves the economy and practicality of seawater desalination technology, but also lays the foundation for the further development of membrane separation technology. In the future, with the continuous advancement of technology and the expansion of applications, polyesteramide nanofiltration membranes are expected to play a greater role in seawater desalination and other related fields, providing new solutions for the sustainable use of global water resources.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer, characterized in that: The following steps are involved: S1. Cut the PES-UF commercial base film to obtain the size and shape of the base film; S2. Ultrasonic cleaning of the PES-UF commercial base membrane twice with an ethanol solution to remove the glycerol protective agent and impurities on the membrane surface to obtain a spare PES ultrafiltration base membrane; S3, fixing the PES ultrafiltration base membrane cleaned in S2 on the PTFE frame with the membrane selection layer facing upward for subsequent processing and reaction; S4, mixing an appropriate amount of alkyl glycoside and N-(2-hydroxyethyl)ethylenediamine in deionized water to form a uniform aqueous polymerization solution, and controlling the solution environment to be alkaline; The aqueous polymerization solution was allowed to contact the surface of the PES ultrafiltration base membrane for a certain period of time, and then the remaining solution was gently poured out. The residual liquid on the membrane surface was gently wiped with filter paper, and the membrane was evenly blown with an air pump gun and allowed to dry naturally to ensure that there was no residual liquid on the membrane surface. S5. Gently pour a n-hexane organic phase solution containing a certain concentration of TMC onto the membrane surface, and intermittently initiate an interfacial polymerization reaction to obtain the prepared polyesteramide composite nanofiltration membrane.

2. The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer according to claim 1, characterized in that: The PES-UF commercial base membrane in S1 is a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 30 kDa; the size of the base membrane obtained after cutting is 11 cm*11 cm.

3. The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer according to claim 1, characterized in that: The concentration of the ethanol solution in S2 is 1%-5% v / v; the ultrasonic cleaning time is 1-3 minutes each time; and the obtained spare PES ultrafiltration base membrane is stored in pure water for future use.

4. The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer according to claim 3, characterized in that: The specific steps of fixing the PES ultrafiltration base membrane on the PTFE frame in S3 are: taking out the PES ultrafiltration base membrane from pure water, and using filter paper to dry the membrane surface until there are no obvious water droplets, then fixing the ultrafiltration base membrane on the polytetrafluoroethylene PTFE frame with the membrane selection layer facing up, and drying it for 2-5 minutes. During this period, use an air pump gun to evenly blow air for 1-3 minutes to provide evenly distributed base membrane pores for the mixed water phase.

5. The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer according to claim 1, characterized in that: The uniform aqueous polymerization solution in S4 is 0.05-0.15% v / v of N-(2-hydroxyethyl)ethylenediamine and 5%-15% of an alkyl glycoside aqueous solution.

6. The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer according to claim 5, characterized in that: The specific operation of controlling the alkaline solution environment is as follows: an appropriate amount of alkyl glycoside and N-(2-hydroxyethyl)ethylenediamine are mixed in deionized water to form a uniform aqueous polymerization solution. During this period, the alkaline environment pH is tested to be in the range of 8-10.5 to prevent the deprotonation effect of subsequent side reaction products.

7. The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer according to claim 6, characterized in that: The aqueous polymer solution is brought into contact with the surface of the PES ultrafiltration base membrane for a certain period of time, 5-8 minutes.

8. The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer according to claim 7, characterized in that: The specific operation of gently wiping the residual liquid on the membrane surface with filter paper is as follows: use filter paper to dry the membrane surface until there are no obvious water droplets; use an air pump gun to blow it evenly with air, and let it dry naturally. The specific operation is as follows: use an air pump gun to blow it evenly with air, the operation time is 30 seconds, and re-fix the PES ultrafiltration base membrane soaked in aqueous solution to the PTFE frame, and then let it dry naturally for 2-5 minutes.

9. The method for preparing a chlorine-resistant polyesteramide nanofiltration membrane using a highly active aqueous phase monomer according to claim 1, characterized in that: The specific operation of the intermittent initiation of the interfacial polymerization reaction in S5 is as follows: gently pouring an organic phase solution of n-hexane containing 0.05-0.2% w / v TMC onto the membrane surface for a soaking time of 20-50S to start the first step of the intermittent interfacial polymerization reaction, then pouring out the organic phase solution and rinsing twice with an n-hexane solution; after an interval of 10S, immediately inverting the organic phase solution of n-hexane containing 0.05-0.2% w / v TMC onto the surface for 30S to maintain a sufficient organic phase concentration to allow the remaining aqueous phase monomers to undergo the remaining reaction at the same diffusion rate, thereby achieving complete and uniform regulation characteristics, and then placing the membrane in an oven for heat treatment for 5-10min to perform a heat-stabilized active layer to enhance its mechanical properties, and then taking it out and cooling it to room temperature to obtain the prepared polyester amide composite nanofiltration membrane, and soaking it in pure water for storage.

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