Chlorine-resistant nanofiltration membrane with polyamide-polyester interpenetrating network structure and application of chlorine-resistant nanofiltration membrane

Abstract

The invention discloses a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure, which comprises a base membrane and an active layer formed on the upper surface of the base membrane, and is characterized in that the active layer comprises a polyamide network layer and a polyester network layer, and the two network layers are interpenetrated and crosslinked on the molecular scale to form a stable and compact interpenetrating polymer structure; the polyamide network layer is formed by reacting a water-phase solution mainly composed of aromatic polyfunctional amine with an oil-phase solution mainly composed of aromatic polyfunctional acyl halide on a water-oil interface, and the polyester network layer is formed by carrying out esterification reaction on a post-treatment solution mainly composed of phenolic monomers and residual acyl chloride. According to the prepared nanofiltration membrane, on the basis of keeping high separation selectivity, the water flux and the oxidation resistance of the membrane body structure are remarkably improved, the nanofiltration membrane is particularly suitable for the field of healthy drinking water purification, and a new way is opened up for designing the application of the efficient nanofiltration membrane in water treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanofiltration membranes, and particularly relates to a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure and its application. Background Art

[0002] With the increasing emphasis on the quality of healthy life by the public, the safety of residential drinking water has received wide attention. Especially in urban water supply systems, due to problems such as aging pipe networks and mixed water sources, trace amounts of harmful substances such as organic pollutants, heavy metal ions, antibiotics, and pesticide metabolites may remain in tap water, posing a potential threat to human health. Therefore, the development of high-performance membrane separation materials for the purification of healthy drinking water has become an important direction for the development of water treatment technologies.

[0003] As a medium-pressure membrane material between ultrafiltration membranes and reverse osmosis membranes, nanofiltration membranes have both moderate selectivity and low operating energy consumption, and are widely used in scenarios such as drinking water purification, functional beverage processing, pretreatment of pharmaceutical water, and rural safe drinking water projects. Traditional polyamide-based nanofiltration membranes have become the mainstream materials due to their strong reaction activity and mature processes. However, there are a large number of nucleophilic sites in the polyamide membrane structure, which are extremely easy to undergo chain-breaking reactions with free chlorine, resulting in the degradation of the membrane structure and seriously affecting its service life. At the same time, when traditional PA membranes improve selectivity, the problem of decreasing water flux often occurs, and it is difficult to balance the two.

[0004] In addition, the easy fouling property of the membrane surface also limits its stability and economy during long-term operation, especially under complex raw water conditions containing organic matter and microorganisms. Therefore, the development of a new nanofiltration membrane structure that simultaneously has high water flux, excellent selectivity, strong chlorine resistance, and anti-fouling ability has become an important research topic in the current membrane separation field. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure and its preparation method to solve the problems of insufficient water flux, poor chlorine resistance, and low long-term operation stability existing in existing polyamide nanofiltration membranes. The prepared nanofiltration membrane significantly improves the water flux and the oxidation resistance of the membrane structure while maintaining high separation selectivity, and is particularly suitable for the field of healthy drinking water purification, and also opens up a new way for the application of designing efficient nanofiltration membranes in water treatment.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: A chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure, comprising a base membrane and an active layer formed on the upper surface of the base membrane. The active layer includes a polyamide network layer and a polyester network layer. The two types of network layers interpenetrate and crosslink at the molecular scale to form a stable and dense interpenetrating polymer structure. The polyamide network layer is formed by the reaction of an aqueous solution mainly composed of aromatic polyfunctional amines and an oil-phase solution mainly composed of aromatic polyfunctional acyl halides at the water-oil interface. The polyester network layer is formed by the esterification reaction of a post-treatment solution mainly composed of phenolic monomers with residual acyl chloride.

[0007] Further, the mass concentration of the aromatic polyfunctional amine in the aqueous solution is 0.2-0.5%.

[0008] Further, the oil-phase solution also contains the aliphatic alkane solvent n-hexane, and the mass concentration of the aromatic polyfunctional acyl halide in the oil-phase solution is 0.1%.

[0009] Further, in the post-treatment solution, the mass concentration of the phenolic monomer is 0.5-1%.

[0010] Further, the aromatic polyfunctional amine is piperazine.

[0011] Further, the aromatic polyfunctional acyl halide is trimesoyl chloride.

[0012] Further, the phenolic monomer compound is any one of phloroglucinol, pyrogallol, and trimellitic acid.

[0013] A preparation method of a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure, comprising the following steps: (1) Preparation of the aqueous solution: Add the aromatic polyfunctional amine to water, stir well, and then add sodium hydroxide to adjust the pH value of the solution to 7-9 to obtain an aqueous solution. (2) Preparation of the oil-phase solution: Add the aromatic polyfunctional acyl halide to a solution containing the aliphatic alkane solvent n-hexane, and stir until completely dissolved to obtain an oil-phase solution. (3) Preparation of the post-treatment solution: Dissolve the phenolic monomer in a mixed solution of ethanol and water in equal proportions, and fully dissolve it at 40°C while maintaining the pH of the solution at 8-9 to obtain the post-treatment solution. (3) Product Preparation: First, dip the non-woven base membrane coated with polyethersulfone into the aqueous solution and keep it for 2 minutes. Then, use an air-compressed air knife to remove the excess aqueous solution on the membrane surface until it dries; next, dip the non-woven base membrane into the oil-phase solution and keep it for 30 seconds. After dipping the membrane sheet into the post-treatment solution, keep the treatment temperature at 40 °C and treat it for 10 minutes. Then, put the membrane into an oven at 60 °C and heat it for 5 minutes; after taking out the heat-treated membrane from the oven, soak it in pure water, and then carry out cleaning and drying to finally obtain a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure.

[0014] Advantages: The present invention adopts a two-stage interfacial polymerization method. First, a basic polyamide layer is formed by reacting piperazine (PIP) with trimesoyl chloride (TMC). Then, phloroglucinol (PG) is introduced to further carry out an esterification reaction with the residual acyl chloride groups to form a dense polyester network, and finally a highly cross-linked interpenetrating polymer structure is constructed. This structure combines the high selectivity of the polyamide membrane and the chemical resistance of the polyester membrane, significantly improving the overall stability, water flux and antioxidant capacity of the membrane. Especially in a chlorine-containing environment, it shows excellent structural retention performance, is suitable for scenarios with high requirements for water quality safety and operation reliability in a healthy water system, and has broad application prospects and promotion value.

[0015] For a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure prepared by the present invention, using 1000 ppm NaCl, MgCl2, MgSO4 and Na2SO4 salt solutions, at a pH value of 7.0 - 7.5, a temperature of 25 °C, and a test pressure of 4 bar, the desalination rates reach 62.48%, 76.55%, 96.37% and 98.97% respectively, the removal rate of dissolved organic matter reaches 91.47% - 93.51%, and the water flux is 28 - 35 L m⁻² h⁻¹ bar⁻¹. Description of the Drawings

[0016] Figure 1 is a preparation flow chart of a chlorine-resistant nanofiltration membrane based on a polyamide-polyester interpenetrating network structure.

[0017] Figure 2 is the filtration effect diagram of the nanofiltration membrane in Application Example 1 for surface water and the filtration effect diagram after soaking in sodium hypochlorite solution. Detailed Embodiments To further illustrate the present invention, specific embodiments are provided below. It should be clear that these embodiments are only used to help understand the present invention and do not constitute a limitation on the scope of the present invention. In addition, it should be understood that after learning the content of the present invention, those skilled in the art can make various improvements or adjustments, and these changes should also be regarded as within the protection scope of the present invention.

[0019] Before introducing the specific embodiments of the present invention, it should be clear that the protection scope of the present invention is not limited to the specific implementation embodiments described below. At the same time, the terms used in the present invention are for the convenience of describing specific embodiments and are not used to limit the scope of the invention. Unless otherwise defined, all technical terms in the present invention should be interpreted according to the common understanding of those skilled in the art in this technical field. For the experimental methods not specifically listed in the examples, they should generally be operated under conventional conditions or the recommended conditions of the equipment manufacturer. In addition to the specific methods, equipment and materials used in the examples, the implementation of the present invention can also be achieved by using existing technical solutions similar or equivalent to those described in the examples for methods, equipment and materials.

[0020] The present invention uses a self-made porous polyethersulfone support membrane, which is first immersed in an aqueous phase solution and then in an oil phase solution. After post-treatment, the monomer reacts with the residual acyl chloride to form an esterification reaction, further forming a polyester network. The two types of networks interpenetrate and crosslink at the molecular scale to form a stable and dense interpenetrating polymer structure. The prepared composite nanofiltration membrane has high water flux, controllable desalination rate, excellent chlorine resistance and good anti-fouling performance. The membrane exhibits excellent separation performance under ultra-low pressure driving, while maintaining a long service life and stability. The polyamide–polyester composite structure of the membrane enhances its chemical stability, especially its tolerance in a chlorine-containing environment, making it suitable for multiple fields such as drinking water purification, the food industry, pharmaceutical water treatment, and industrial wastewater reuse, with broad application prospects and significant economic value.

[0021] Example 1 The nanofiltration membrane was prepared by the interfacial polymerization method. First, the polyethersulfone support membrane was immersed in a 20% isopropanol solution for 5 minutes to remove any protective chemicals. Subsequently, the pretreated polyethersulfone support membrane was thoroughly rinsed with deionized water and then immersed in an aqueous solution of 0.2 wt% piperazine and 0.2 wt% sodium hydroxide for 3 minutes. Subsequently, the excess solution on the surface was blown dry using an air knife. Next, the organic phase solution (30 mL, 0.1 wt% trimesoyl chloride dissolved in n-hexane) was poured onto the PES support membrane and allowed to stand for 40 seconds to form a separation layer. Finally, the prepared nanofiltration membrane was heat-treated in an oven at 60 °C for 5 minutes.

[0022] The performance of the prepared nanofiltration membrane was tested. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L); the water flux was 9.35 m -2 h -1 bar -1, the rejection rates of NaCl, MgCl2, MgSO4, and Na2SO4 are 23.45%, 51.28%, 90.51%, and 95.79% respectively. The rejection rate of dissolved organic matter is 76.34%. The rejection rate of the membrane is calculated using the following formula:

[0023] where C p (mg L -1 ) represents the permeate concentration, and C f (mg L -1 ) represents the feed concentration; Example 2 The difference between this Example 2 and Example 1 is that the concentration of PIP is set to 0.5 wt%.

[0024] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L); the water flux was 8.34 m -2 h -1 bar -1 , the rejection rates of NaCl, MgCl2, MgSO4, and Na2SO4 are 33.84%, 58.18%, 92.43%, and 95.83% respectively. The rejection rate of dissolved organic matter is 78.17%.

[0025] Example 3 The difference between this Example 3 and Example 1 is that a post-treatment step was added and phloroglucinol solution with a concentration of 0.5 wt% was used.

[0026] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L); the water flux was 17.97 m -2 h -1 bar -1 , the rejection rates of NaCl, MgCl2, MgSO4, and Na2SO4 are 56.23%, 63.27%, 94.12%, and 95.93% respectively. The rejection rate of dissolved organic matter is 79.34%.

[0027] Example 4 The difference between Example 4 and Example 1 is that a post-treatment step is added and a phloroglucinol solution with a concentration of 1.0 wt% is used.

[0028] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L); the water flux was 27.86 m -2 h -1 bar -1 , the NaCl rejection rate was 62.58%, the MgCl2 rejection rate was 76.55%, the MgSO4 rejection rate was 96.37%, and the Na2SO4 rejection rate was 98.97%. The rejection rate of dissolved organic matter was 93.51%.

[0029] Example 5 The difference between Example 5 and Example 1 is that a post-treatment step is added and a pyrogallol solution with a concentration of 0.5 wt% is used.

[0030] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L); the water flux was 15.32 m -2 h -1 bar -1 , the NaCl rejection rate was 59.12%, the MgCl2 rejection rate was 64.87%, the MgSO4 rejection rate was 91.33%, and the Na2SO4 rejection rate was 94.37%. The rejection rate of dissolved organic matter was 80.85%.

[0031] Example 6 The difference between Example 6 and Example 1 is that a post-treatment step is added and a pyrogallol solution with a concentration of 1.0 wt% is used.

[0032] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L); the water flux was 17.41 m -2 h-1 bar -1 The rejection rates for NaCl, MgCl2, MgSO4, and Na2SO4 were 63.96%, 68.46%, 93.11%, and 96.35% respectively. The rejection rate for dissolved organic matter was 86.33%.

[0033] Example 7 The difference between this Example 7 and Example 1 is that a post-treatment step was added and a phloroglucinol solution with a concentration of 0.5 wt% was used.

[0034] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. A membrane filtration experiment was conducted on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L) at an operating pressure of 4 bar and a temperature of 25°C; the water flux was 13.87 m -2 h -1 bar -1 , the rejection rates for NaCl, MgCl2, MgSO4, and Na2SO4 were 52.87%, 60.88%, 91.28%, and 95.33% respectively. The rejection rate for dissolved organic matter was 81.66%.

[0035] Example 8 The difference between this Example 8 and Example 1 is that a post-treatment step was added and a phloroglucinol solution with a concentration of 1.0 wt% was used.

[0036] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. A membrane filtration experiment was conducted on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L) at an operating pressure of 4 bar and a temperature of 25°C; the water flux was 23.57 m -2 h -1 bar -1 , the rejection rates for NaCl, MgCl2, MgSO4, and Na2SO4 were 62.44%, 70.34%, 95.33%, and 96.32% respectively. The rejection rate for dissolved organic matter was 91.21%.

[0037] Example 9 The difference between this Example 9 and Example 2 is that a post-treatment step was added and a phloroglucinol solution with a concentration of 0.5 wt% was used.

[0038] Performance tests were conducted on the prepared nanofiltration membranes, and the results are as follows: Performance tests were conducted on the prepared nanofiltration membranes. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L); the water flux was 18.37 m -2 h -1 bar -1 , the rejection rate of NaCl was 59.43%, the rejection rate of MgCl2 was 66.27%, the rejection rate of MgSO4 was 95.32%, and the rejection rate of Na2SO4 was 96.43%. The rejection rate of dissolved organic matter was 81.24%.

[0039] Example 10 The difference between this Example 10 and Example 2 is that a post-treatment step was added and a phloroglucinol solution with a concentration of 1.0 wt% was used.

[0040] Performance tests were conducted on the prepared nanofiltration membranes, and the results are as follows: Performance tests were conducted on the prepared nanofiltration membranes. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L); the water flux was 35.13 m -2 h -1 bar -1 , the rejection rate of NaCl was 62.17%, the rejection rate of MgCl2 was 76.24%, the rejection rate of MgSO4 was 96.32%, and the rejection rate of Na2SO4 was 98.43%. The rejection rate of dissolved organic matter was 93.10%.

[0041] Example 11 The difference between this Example 11 and Example 2 is that a post-treatment step was added and a pyrogallol solution with a concentration of 0.5 wt% was used.

[0042] Performance tests were conducted on the prepared nanofiltration membranes, and the results are as follows: Performance tests were conducted on the prepared nanofiltration membranes. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L); the water flux was 16.12 m -2 h -1 bar -1, the rejection rates of NaCl, MgCl2, MgSO4, and Na2SO4 are 60.32%, 65.37%, 92.37%, and 95.17% respectively. The rejection rate of dissolved organic matter is 83.95%.

[0043] Example 12 The difference between this Example 12 and Example 2 is that a post-treatment step is added and pyrogallol solution with a concentration of 1.0 wt% is used.

[0044] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L); the water flux was 19.21 m -2 h -1 bar -1 , the rejection rates of NaCl, MgCl2, MgSO4, and Na2SO4 are 65.06%, 69.16%, 93.71%, and 96.95% respectively. The rejection rate of dissolved organic matter is 90.13%.

[0045] Example 13 The difference between this Example 13 and Example 2 is that a post-treatment step is added and trimellitic acid solution with a concentration of 0.5 wt% is used.

[0046] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The performance of the prepared nanofiltration membrane was tested. At an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L); the water flux was 15.47 m -2 h -1 bar -1 , the rejection rates of NaCl, MgCl2, MgSO4, and Na2SO4 are 58.27%, 64.58%, 93.08%, and 97.83% respectively. The rejection rate of dissolved organic matter is 89.63%.

[0047] Example 14 The difference between this Example 14 and Example 2 is that a post-treatment step is added and trimellitic acid solution with a concentration of 1.0 wt% is used.

[0048] The performance of the prepared nanofiltration membrane was tested, and the results are as follows: The prepared nanofiltration membrane was subjected to performance testing. Under an operating pressure of 4 bar and a temperature of 25 °C, a membrane filtration experiment was carried out on an aqueous solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L); the water flux was 26.57 m -2 h -1 bar -1 , the rejection rate of NaCl was 69.24%, the rejection rate of MgCl2 was 74.27%, the rejection rate of MgSO4 was 95.97%, and the rejection rate of Na2SO4 was 97.57%. The rejection rate of dissolved organic matter was 92.63%.

[0049] Table 1 shows the experimental conditions of the examples

[0050] Application Example 1 The polyamide-polyester composite nanofiltration membrane prepared in Example 10 was used to purify surface water (TOC: 6.35 mg / L, TDS: 923 mg / L, Ca 2+ : 512 mg / L, Mg 2+ : 467 mg / L) for purification testing, and a single cycle was carried out.

[0051] The specific steps are as follows: a. The surface water was pretreated with a microfiltration membrane: The surface water was filtered and pretreated using a commercial microfiltration membrane. The purpose was to remove impurities and suspended particles in the raw water to prevent clogging of the nanofiltration membrane. The operating pressure was 0.04 Mpa. The pore size of the microfiltration membrane was 0.45 μm, which was much larger than the pore size of the nanofiltration membrane and could not retain dissolved substances and ions in the water. Therefore, it would not affect the experimental data of the retention of Ca 2+ , Mg 2+ and other ions. The permeate obtained by microfiltration was used as the feed water for the nanofiltration membrane system; b. The surface water pretreated by microfiltration entered the feed water tank and was deeply filtered using the chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure prepared in the present invention under a pressure of 0.4 Mpa; The effluent of the nanofiltration membrane was collected, and the TOC and TDS of the sample solution were measured and analyzed. At the same time, an ion chromatograph was used to detect and calculate the Ca 2+ , Mg 2+ contents in the raw water and permeate. The following formula was specifically used for calculation:

[0052] Among them, R is the removal rate, C p is the mass concentration of the permeate, Cf is the mass concentration of the concentrated solution; According to Figure 2 The results show that the removal efficiency of the nanofiltration membrane for TOC is 93.51%, the removal efficiency for total dissolved solids TDS in water is 89.34%, for Ca 2+ the removal efficiency is 76.23%, for Mg 2+ the removal efficiency is 85.77%. By changing the types and concentrations of piperazine and the post-treatment solution, the performance of the nanofiltration membrane can be further optimized.

[0053] Application Example 2 The difference between this application example and Application Example 1 is that the polyamide nanofiltration membrane prepared in Example 1 is used to purify surface water (TOC: 6.35 mg / L, TDS: 923 mg / L, Ca 2+ : 512 mg / L, Mg 2+ : 467 mg / L) for purification testing, with a single cycle.

[0054] The effluent of the nanofiltration membrane is collected, and the sample solution is measured and analyzed for TOC and TDS. At the same time, an ion chromatograph is used to detect and calculate the Ca in the raw water and permeate 2+ , Mg 2+ contents. The following formula is specifically used for calculation:

[0055] Among them, R is the removal rate, C p is the mass concentration of the permeate, C f is the mass concentration of the concentrated solution; The removal efficiency of the nanofiltration membrane for TOC is 73.14%, the removal efficiency for total dissolved solids TDS in water is 64.18%, for Ca 2+ the removal efficiency is 52.71%, for Mg 2+ the removal efficiency is 58.32%.

[0056] Application Example 3 The difference between this application example and Application Example 1 is that the polyamide nanofiltration membrane prepared in Example 2 is used to purify surface water (TOC: 6.35 mg / L, TDS: 923 mg / L, Ca 2+ : 512 mg / L, Mg 2+ : 467 mg / L) for purification testing, with a single cycle.

[0057] The effluent of the nanofiltration membrane is collected, and the sample solution is measured and analyzed for TOC and TDS. At the same time, an ion chromatograph is used to detect and calculate the Ca in the raw water and permeate 2+ , Mg2+ Content. The specific calculation is carried out using the following formula:

[0058] Wherein, R is the removal rate, C p is the mass concentration of the permeate, C f is the mass concentration of the concentrate; The removal efficiency of the nanofiltration membrane for TOC is 78.34%, the removal efficiency for total dissolved solids TDS in water is 69.78%, the removal efficiency for Ca 2+ is 55.31%, and the removal efficiency for Mg 2+ is 62.81%.

[0059] Application Example 4 The difference between this application example and Application Example 1 is that the polyamide-polyester composite nanofiltration membrane prepared in Example 4 is used to purify surface water (TOC: 6.35 mg / L, TDS: 923 mg / L, Ca 2+ : 512 mg / L, Mg 2+ : 467 mg / L) for a single-cycle purification test.

[0060] The effluent of the nanofiltration membrane is collected, and the TOC and TDS of the sample solution are measured and analyzed. At the same time, an ion chromatograph is used to detect and calculate the Ca 2+ , Mg 2+ contents in the raw water and the permeate. The specific calculation is carried out using the following formula:

[0061] Wherein, R is the removal rate, C p is the mass concentration of the permeate, C f is the mass concentration of the concentrate; The removal efficiency of the nanofiltration membrane for TOC is 84.84%, the removal efficiency for total dissolved solids TDS in water is 76.48%, the removal efficiency for Ca 2+ is 59.81%, and the removal efficiency for Mg 2+ is 68.37%.

[0062] Application Example 5 The difference between this application example and Application Example 1 is that the polyamide-polyester composite nanofiltration membrane prepared in Example 6 is used to purify surface water (TOC: 6.35 mg / L, TDS: 923 mg / L, Ca 2+ : 512 mg / L, Mg 2+: The purification test was carried out at 467 mg / L for a single cycle.

[0063] The permeate of the nanofiltration membrane was collected, and the TOC and TDS of the sample solution were measured and analyzed. At the same time, an ion chromatograph was used to detect and calculate the Ca in the raw water and permeate 2+ , Mg 2+ contents. The following formula was specifically used for calculation:

[0064] Among them, R is the removal rate, C p is the mass concentration of the permeate, C f is the mass concentration of the concentrate; The removal efficiency of the nanofiltration membrane for TOC was 86.44%, the removal efficiency for total dissolved solids TDS in water was 79.14%, the removal efficiency for Ca 2+ was 62.76%, and the removal efficiency for Mg 2+ was 70.86%.

[0065] Application Example 6 The difference between this application example and Application Example 1 is that the polyamide-polyester composite nanofiltration membrane prepared in Example 8 was used to purify surface water (TOC: 6.35 mg / L, TDS: 923 mg / L, Ca 2+ : 512 mg / L, Mg 2+ : 467 mg / L) for a purification test, and a single cycle was carried out.

[0066] The permeate of the nanofiltration membrane was collected, and the TOC and TDS of the sample solution were measured and analyzed. At the same time, an ion chromatograph was used to detect and calculate the Ca in the raw water and permeate 2+ , Mg 2+ contents. The following formula was specifically used for calculation:

[0067] Among them, R is the removal rate, C p is the mass concentration of the permeate, C f is the mass concentration of the concentrate; The removal efficiency of the nanofiltration membrane for TOC was 90.34%, the removal efficiency for total dissolved solids TDS in water was 88.31%, the removal efficiency for Ca 2+ was 68.31%, and the removal efficiency for Mg 2+ was 72.91%.

[0068] Application Example 7 The difference between this application example and Application Example 1 is that the polyamide-polyester composite nanofiltration membrane prepared in Example 12 is used to purify surface water (TOC: 6.35 mg / L, TDS: 923 mg / L, Ca 2+ : 512 mg / L, Mg 2+ : 467 mg / L), and a single cycle is carried out.

[0069] The effluent of the nanofiltration membrane is collected, and the TOC and TDS of the sample solution are measured and analyzed. At the same time, an ion chromatograph is used to detect and calculate the Ca 2+ and Mg 2+ contents in the raw water and permeate. The following formula is specifically used for calculation:

[0070] Among them, R is the removal rate, C p is the mass concentration of the permeate, C f is the mass concentration of the concentrate; The removal efficiency of the nanofiltration membrane for TOC is 90.45%, the removal efficiency for total dissolved solids TDS in water is 85.13%, the removal efficiency for Ca 2+ is 62.75%, and the removal efficiency for Mg 2+ is 75.83%.

[0071] Application Example 8 The difference between this application example and Application Example 1 is that the polyamide-polyester composite nanofiltration membrane prepared in Example 14 is used to purify surface water (TOC: 6.35 mg / L, TDS: 923 mg / L, Ca 2+ : 512 mg / L, Mg 2+ : 467 mg / L), and a single cycle is carried out.

[0072] The effluent of the nanofiltration membrane is collected, and the TOC and TDS of the sample solution are measured and analyzed. At the same time, an ion chromatograph is used to detect and calculate the Ca 2+ and Mg 2+ contents in the raw water and permeate. The following formula is specifically used for calculation:

[0073] Among them, R is the removal rate, C p is the mass concentration of the permeate, C f is the mass concentration of the concentrate; The removal efficiency of the nanofiltration membrane for TOC is 88.41%, the removal efficiency for total dissolved solids (TDS) in water is 86.73%, and the removal efficiency for Ca 2+ is 67.22%, and the removal efficiency for Mg 2+ is 77.53%.

[0074] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure, comprising a base membrane and an active layer formed on the upper surface of the base membrane, characterized in that: The active layer includes a polyamide network layer and a polyester network layer. The two types of network layers interpenetrate and crosslink at the molecular scale to form a stable and dense interpenetrating polymer structure. The polyamide network layer is formed by the reaction of an aqueous solution mainly composed of aromatic polyfunctional amines and an oil-phase solution mainly composed of aromatic polyfunctional acyl halides at the water-oil interface. The polyester network layer is formed by the esterification reaction of a post-treatment solution mainly composed of phenolic monomers with residual acyl chloride.

2. The chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure according to claim 1, characterized in that: The mass concentration of aromatic polyfunctional amines in the aqueous solution is 0.2 - 0.5%.

3. The chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure according to claim 1, characterized in that: The oil-phase solution also contains the aliphatic alkane solvent n-hexane, and the mass concentration of aromatic polyfunctional acyl halides in the oil-phase solution is 0.1%.

4. The chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure according to claim 1, characterized in that: In the post-treatment solution, the mass concentration of phenolic monomers is 0.5 - 1%.

5. The chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure according to claim 2, characterized in that: The aromatic polyfunctional amine is piperazine.

6. The chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure according to claim 3, characterized in that: The aromatic polyfunctional acyl halide is trimesoyl chloride.

7. A chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure according to claim 4, characterized in that: The phenolic monomer compound is any one of phloroglucinol, pyrogallol, and trimellitic acid.

8. The preparation method of a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure as described in claims 1-7, characterized in that, It includes the following steps: (1) Preparation of the aqueous solution: Add aromatic polyfunctional amines to water, stir well, and then add sodium hydroxide to adjust the pH value of the solution to 7 - 9 to obtain an aqueous solution. (2) Preparation of the oil-phase solution: Add aromatic polyfunctional acyl halides to a solution containing the aliphatic alkane solvent n-hexane, stir well until completely dissolved to obtain an oil-phase solution. (3) Preparation of the post-treatment solution: Dissolve phenolic monomers in a mixed solution of ethanol and water in equal proportions, fully dissolve at 40°C, and keep the solution pH at 8 - 9 to obtain the post-treatment solution. (3) Product preparation: First, immerse a non-woven fabric base film coated with polyethersulfone in the aqueous solution for 2 minutes. Then, use an air compression air knife to remove the excess aqueous solution on the film surface until it is dry. Next, immerse the non-woven fabric base film in the oil-phase solution for 30 seconds, then immerse the film in the post-treatment solution and keep the treatment temperature at 40°C for 10 minutes. Then, place the film in an oven at 60°C and heat for 5 minutes. After taking out the heat-treated film from the oven, soak it in pure water, and then carry out cleaning and drying to finally obtain a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure.

9. Application of a chlorine-resistant nanofiltration membrane with a polyamide-polyester interpenetrating network structure as described in claims 1 - 7 in water purification.

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