A visualization method for the polymerization and diffusion reaction process at the nanofiltration membrane interface

Abstract

The present invention provides a method for visualizing the interfacial polymerization diffusion reaction process of a nanofiltration membrane, comprising the following steps: preparing a piperazine PIP solution, a trimesoyl chloride (TMC) solution, and a dansyl chloride (DNSCL) solution of specified concentrations; and uniformly mixing the dansyl chloride (DNSCL) solution with the piperazine PIP solution. The present invention introduces a dansyl chloride fluorescent agent based on the special molecular structure of aqueous phase monomers required for nanofiltration membrane preparation to fluorescently label the PIP, thereby imparting fluorescent characteristics and observability, thereby solving the current problem of being unable to perform microscopic observation of aqueous phase monomer molecules of the nanofiltration membrane. Furthermore, based on specially processed cover glasses and slides of special specifications, a reaction interface is created for observing the interfacial polymerization reaction, thereby solving the problem of being unable to define the reaction interface of two-phase monomer substances in the nanofiltration membrane. At the same time, the positional accuracy of the observation is greatly improved, thereby preventing the reaction interface from being lost during observation.

Description

Technical Field

[0001] The present invention relates to a visualization method, in particular to a visualization method for a nanofiltration membrane interface polymerization diffusion reaction process, and belongs to the technical field of nanofiltration membrane preparation and membrane separation water treatment. Background Art

[0002] Nanofiltration membrane is a membrane separation technology between reverse osmosis membrane and ultrafiltration membrane, with a pore size range of approximately 1 nanometer to several nanometers. Nanofiltration membrane is mainly used in water treatment and liquid separation processes, and can effectively remove impurities such as certain ions, organic molecules, bacteria and viruses in water.

[0003] Nanofiltration membranes have become a cost-effective and efficient membrane separation process, effectively inhibiting small molecules and multivalent ions, and showing great promise in wastewater treatment, water softening, and purification. Interfacial polymerization, currently the mainstream method for preparing nanofiltration membranes, is widely used in the preparation of various nanofiltration membranes. The principle is to immerse the basement membrane in an aqueous solution for a certain period of time, then remove the membrane to remove excess aqueous solution, and then immerse it in an organic solution to react and obtain a polyamide nanofiltration membrane. During the interfacial polymerization reaction, aqueous phase monomers diffuse into organic phase monomers, diffuse to the interface between the two phases, and react with the organic phase monomers.

[0004] Numerous studies have shown that the diffusion rate of aqueous monomers into organic monomers and the reaction rate between the two phases are the fundamental factors affecting membrane structure (membrane thickness, cross-linking degree, membrane pore size, etc.). Therefore, in-depth research on the interaction mechanism between the two phases, clarifying the influence of the diffusion and reaction behavior of the two phase monomer molecules on the membrane's physical and chemical structure and membrane properties, and revealing the direct "mechanism-structure-performance" relationship of nanofiltration membranes prepared by interfacial polymerization reactions are of great significance for the targeted construction of nanofiltration membranes with specific structures and separation targets.

[0005] However, in order to clarify the diffusion and reaction behavior of the two-phase monomer molecules, it is necessary to observe the entire interfacial polymerization process. However, this microscopic molecular-level reaction occurring at the nanometer and sub-nanometer time and space scale is difficult to capture and monitor by conventional methods. The existing technical methods all use chemical characterization methods to indirectly characterize the diffusion and reaction behavior of the two-phase monomer molecules, and there is no technology that can directly observe them in real time. Therefore, a visualization method for the diffusion reaction process of nanofiltration membrane interface polymerization is proposed. Summary of the Invention

[0006] In view of this, the present invention provides a method for visualizing the interfacial polymerization diffusion reaction process of nanofiltration membranes. This method uses a dansyl chloride fluorescent agent to fluorescently label the aqueous phase monomer (PIP) molecules so that they have fluorescent properties. The diffusion and reaction behavior of the PIP molecules during the interfacial polymerization reaction are directly observed through a spinning disk confocal microscope, thereby achieving real-time and dynamic visualization of the interfacial polymerization reaction of the nanofiltration membrane, thereby solving or alleviating the technical problems existing in the prior art and at least providing a beneficial option.

[0007] The technical solution of the embodiment of the present invention is achieved as follows: A method for visualizing the polymerization diffusion reaction process at the nanofiltration membrane interface includes the following steps:

[0008] S1, preparing piperazine PIP solution, trimesoyl chloride TMC solution and dansyl chloride DNSCL solution of specified concentrations;

[0009] S2, mixing the dansyl chloride DNSCL solution and the piperazine PIP solution, fluorescently labeling the piperazine PIP to obtain a PIP-DNSCL solution;

[0010] S3, selecting a cover glass, covering it on a glass slide after treatment, and performing an interfacial polymerization reaction between the labeled piperazine PIP and trimesoyl chloride TMC to create a reaction interface;

[0011] S4. Set the relevant parameters of the microscope, and add PIP-DNSCL solution and trimesoyl chloride (TMC) solution on both sides of the reaction interface respectively. Under the microscope, the diffusion movement of the fluorescently labeled molecules can be observed to visualize the polymerization diffusion reaction process at the nanofiltration membrane interface.

[0012] Further preferably, in said S1, the piperazine PIP solution is an aqueous solution, the solute thereof is piperazine PIP, the solvent is deionized water, and the concentration is 0.1-0.2% w / v;

[0013] The TMC solution is an organic phase solution, wherein the solute is TMC and the solvent is n-hexane, and the concentration is 0.1-0.2% w / v;

[0014] The solute of the dansyl chloride DNSCL solution is dansyl chloride DNSCL, the solvent is n-hexane, and the concentration thereof is 0.05-0.1% w / v.

[0015] Further preferably, in S2, the volume ratio of the dansyl chloride DNSCL solution to the piperazine PIP solution is 10:1, the mixing container is a centrifuge tube, and the mixing equipment is a constant temperature shaker.

[0016] Further preferably, in said S2, the mixing conditions are: temperature of 25-30°C; amplitude of 3 mm, rotation speed of 60 rpm, and time of 24-36 h.

[0017] Further preferably, the fluorescent labeling is performed by fluorescently labeling the piperazine PIP molecule with a dansyl chloride DNSCL molecule to generate PIP-DNSCL.

[0018] Further preferably, in S3, the size of the cover glass is 50×26 mm, and the thickness is 0.13-0.17 mm; the size of the slide glass is 76×26 mm, and the thickness is ≤170 μm.

[0019] Further preferably, in said S3, the processing of the cover glass is to cut it at the midline of the long side of the cover glass to divide it into two cover glasses of the same size and symmetrical appearance.

[0020] Further preferably, the reaction interface is created by covering one side of a glass slide with a cut cover glass to form a reaction interface between the cover glass and the glass slide.

[0021] Further preferably, in S4, the microscope adopts a medium-disk confocal microscope, and the specific parameters are set as follows: excitation wavelength is 405nm; emission wavelength is 520nm; magnification is 40×-100×; dwell time is 10ms-100ms; exposure time is 1ms-10ms; test temperature is 23-28°C; relative humidity is ≤70%.

[0022] Further preferably, in S4, the solution is added dropwise by using two syringes to draw 3-5 ml of the PIP-DNSCL solution and trimesoyl chloride TMC solution respectively, and dropwise adding them on both sides of the reaction interface formed by the cover glass and the slide.

[0023] The method for visualizing the interfacial polymerization and diffusion reaction process of a nanofiltration membrane according to the present invention is described in detail as follows (the temperature not specified below is performed at room temperature):

[0024] S11, taking a certain amount of piperazine PIP and deionized water, and preparing an aqueous solution with a mass percentage of 0.1% w / v to 0.2% w / v;

[0025] S12, taking a certain amount of trimesoyl chloride (TMC) and n-hexane, and preparing an organic phase solution with a mass percentage of 0.1% w / v to 0.2% w / v;

[0026] S13, taking a certain amount of dansyl chloride DNSCL and n-hexane, preparing a dansyl chloride solution with a mass percentage of 0.05% w / v to 0.1% w / v;

[0027] S21. Mix the prepared aqueous solution and sulfonyl chloride solution in a centrifuge tube at a volume ratio of 10:1, and place the mixture in a constant temperature shaker with an amplitude of 3 mm and a speed of 60 rpm at 25-30°C for 24-36 hours.

[0028] S22. After the mixing and shaking is completed, the supernatant is taken and the mixed aqueous solution is observed under ultraviolet light at a wavelength of 365 nm to determine whether there is fluorescence brightness to confirm that piperazine PIP is successfully labeled;

[0029] S31. Select a cover glass with a size of 50×26 mm and a thickness of 0.15 mm, and use a glass cutter to cut the cover glass at the center line of the long side to cut it into a cover glass with a size of 25×26 mm for subsequent use;

[0030] S32. Select a glass slide with a size of 76×26 mm and a thickness of 150 μm, and place the cut cover glass in the middle of the slide for subsequent use.

[0031] S41. Set the spinning disk confocal microscope to an excitation wavelength of 405 nm, an emission wavelength of 520 nm, a magnification of 40×-100×, a dwell time of 10 ms-100 ms, and an exposure time of 24-36 ms.

[0032] S42. Turn on the spinning disk confocal microscope, place the prepared cover glass-slide under the microscope, and adjust the lens to the created reaction interface;

[0033] S43. Use two syringes to draw 3-5 ml of fluorescently labeled piperazine PIP solution and TMC solution respectively, and add them dropwise on both sides of the reaction interface formed by the coverslip and the slide. After adding, use a microscope to observe the diffusion movement of fluorescently labeled piperazine PIP molecules and the interfacial reaction in real time.

[0034] The embodiment of the present invention adopts the above technical solution, which has the following advantages:

[0035] 1. Based on the special molecular structure of the aqueous phase monomers required for nanofiltration membrane preparation, the present invention introduces a dansyl chloride fluorescent agent to fluorescently label PIP, giving it fluorescent properties and observable properties, thus solving the current problem of being unable to microscopically observe the aqueous phase monomer molecules of nanofiltration membranes.

[0036] 2. The present invention is based on special specifications of cover glass and slide glass. After special treatment, a reaction interface is created for observing interfacial polymerization reactions, which solves the problem that the reaction interface of the two-phase monomer substances in the nanofiltration membrane cannot be defined. At the same time, it also greatly improves the accuracy of the observation position and prevents the reaction interface from being lost during observation.

[0037] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application 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 application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0039] Figure 1 This is a schematic diagram of the reaction between piperazine PIP and dansyl chloride DNSCL in the present invention;

[0040] Figure 2 Schematic diagram of the reaction interface between the cover glass and the slide glass of the present invention;

[0041] Figure 3 Schematic diagram of the dropwise addition positions of the PIP-DNSCL solution and the trimesoyl chloride TMC solution of the present invention;

[0042] Figure 4 The fluorescence effect and FT-IR test image of the PIP-DNSCL solution in Example 3 of the present invention;

[0043] Figure 5 This is a distribution change diagram of PIP-DNSCL and trimesoyl chloride TMC on both sides of the reaction interface in Example 3 of the present invention;

[0044] Figure 6 This is a comparison diagram of piperazine PIP after irradiation in the comparative example of the present invention;

[0045] Figure 7 This is a distribution change diagram of piperazine PIP and trimesoyl chloride TMC on both sides of the reaction interface in the comparative example of the present invention. DETAILED DESCRIPTION

[0046] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0047] It should be noted that the terms "first," "second," "symmetrical," and "array" are used solely for descriptive and positional purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the technical features being referred to. Therefore, limitations on features such as "first" and "symmetrical" may explicitly or implicitly include one or more of these features. Similarly, when features are not limited in quantity using words such as "two" or "three," it should be noted that these features also explicitly or implicitly include one or more of these features.

[0048] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0049] Example 1

[0050] like Figure 1-Figure 3 As shown, an embodiment of the present invention provides a method for visualizing the polymerization diffusion reaction process at the nanofiltration membrane interface, comprising the following steps (the following steps without temperature indication are all performed at room temperature):

[0051] S111, take 0.1g piperazine PIP and 100ml deionized water to prepare an aqueous solution with a mass percentage of 0.1% w / v;

[0052] S112, take 0.1 g of trimesoyl chloride (TMC) and 100 ml of n-hexane to prepare an organic phase solution with a mass percentage of 0.1% w / v;

[0053] S113, taking 0.05 g of dansyl chloride DNSCI and 100 ml of n-hexane, prepare a 0.05% w / v dansyl chloride solution;

[0054] S121. Mix the prepared aqueous solution and sulfonyl chloride solution in a centrifuge tube at a volume ratio of 10:1, and place the mixture in a constant temperature shaker with an amplitude of 3 mm and a speed of 60 rpm at 25°C for 36 h.

[0055] S122, after the mixing and shaking is completed, the supernatant is taken and irradiated with ultraviolet light at a wavelength of 365 nm;

[0056] S131. Select a cover glass with a size of 50 × 26 mm and a thickness of 0.15 mm, and use a glass cutter to cut the cover glass at the center line of the long side to cut it into a cover glass with a size of 25 × 26 mm for subsequent use;

[0057] S132. Select a glass slide with a size of 76×26 mm and a thickness of 150 μm, and place the cut cover glass in the middle of the slide for subsequent use. Figure 2 As shown;

[0058] S141. At room temperature, set the spinning disk confocal microscope to an excitation wavelength of 405 nm, an emission wavelength of 520 nm, a magnification of 40×, a dwell time of 10 ms, and an exposure time of 1 ms.

[0059] S142. Turn on the spinning disk confocal microscope, place the prepared cover glass-slide under the microscope, and adjust the lens to the created reaction interface;

[0060] S143. Use two 5 ml syringes to draw 3 ml of fluorescently labeled PIP solution and TMC solution respectively, and add them dropwise on both sides of the reaction interface formed by the coverslip and the slide. After adding, use a microscope to observe the diffusion movement of the fluorescently labeled PIP molecules and the interfacial reaction in real time.

[0061] Example 2

[0062] like Figure 1-Figure 3 As shown, the embodiment of the present invention also provides a method for visualizing the polymerization diffusion reaction process at the nanofiltration membrane interface, comprising the following steps (the following steps without temperature indication are all performed at room temperature):

[0063] S211, take 0.2g piperazine PIP and 100ml deionized water to prepare an aqueous solution with a mass percentage of 0.2% w / v;

[0064] S212, take 0.2 g of trimesoyl chloride TMC and 100 ml of n-hexane to prepare an organic phase solution with a mass percentage of 0.2% w / v;

[0065] S213, taking 0.1 g of dansyl chloride DNSCI and 100 ml of n-hexane, prepare a 0.1% w / v dansyl chloride solution;

[0066] S221. Mix the prepared aqueous solution and sulfonyl chloride solution in a centrifuge tube at a volume ratio of 10:1, and place the mixture in a constant temperature shaker with an amplitude of 3 mm and a speed of 60 rpm at 30°C for 36 h.

[0067] S222, after the mixing and shaking is completed, the supernatant is taken and irradiated under a UV lamp with a wavelength of 365 nm;

[0068] S231. Select a cover glass with a size of 50 × 26 mm and a thickness of 0.15 mm, and use a glass cutter to cut the cover glass at the center line of the long side to cut it into a cover glass with a size of 25 × 26 mm for subsequent use;

[0069] S232. Select a glass slide with a size of 76 × 26 mm and a thickness of 150 μm, and place the cut cover glass in the middle of the slide for subsequent use.

[0070] S241. At room temperature, set the spinning disk confocal microscope to an excitation wavelength of 405 nm, an emission wavelength of 520 nm, a magnification of 100×, a dwell time of 100 ms, and an exposure time of 10 ms.

[0071] S242. Turn on the spinning disk confocal microscope, place the prepared cover glass-slide under the microscope, and adjust the lens to the created reaction interface;

[0072] S243. Use two 5 ml syringes to draw 5 ml of fluorescently labeled PIP solution and TMC solution respectively, and add them dropwise on both sides of the reaction interface formed by the coverslip and the slide. After adding, use a microscope to observe the diffusion movement of the fluorescently labeled PIP molecules and the interfacial reaction in real time.

[0073] Example 3

[0074] like Figure 1-Figure 5 As shown, the embodiment of the present invention also provides a method for visualizing the polymerization diffusion reaction process at the nanofiltration membrane interface, comprising the following steps (the following steps without temperature indication are all performed at room temperature):

[0075] S311, take 0.15g piperazine PIP and 100ml deionized water to prepare an aqueous solution with a mass percentage of 0.15% w / v;

[0076] S312, take 0.15g of trimesoyl chloride TMC and 100ml of n-hexane to prepare an organic phase solution with a mass percentage of 0.15% w / v;

[0077] S313, take 0.075g of dansyl chloride DNSCI and 100ml of n-hexane to prepare a dansyl chloride solution with a mass percentage of 0.075% w / v;

[0078] S321. Mix the prepared aqueous solution and sulfonyl chloride solution in a centrifuge tube at a volume ratio of 10:1, and place the mixture in a constant temperature shaker with an amplitude of 3 mm and a speed of 60 rpm at 30°C for 30 h.

[0079] S322. After the mixing and shaking, the supernatant was taken and irradiated under the condition of ultraviolet light at a wavelength of 365 nm. The specific results are as follows: Figure 4 As shown in a, it can be seen that the labeled PIP (PIP-DNSCL) has fluorescence characteristics; at the same time, the FT-IR test of PIP before and after labeling is performed, and the results are as follows Figure 4As shown in Figure B, in the infrared spectrum of the labeled PIP-DNSCI, we observed that the sharp peak near 3204.1 cm-1 is attributed to the stretching vibration peak of NH in the PIP monomer, and the characteristic peak near 1329.7 cm-1 corresponds to the stretching vibration of CN in the PIP monomer; the peak at 1573.5 cm-1 is attributed to the C=C skeleton stretching vibration absorption peak of the benzene ring in DNSCI, and the peak at 790.2 cm-1 is attributed to the absorption peak of CH in DNSCI; and the stretching vibration absorption peak of O=S=O in DNSCI appears at 1052.4 cm-1; the results show that the PIP molecule has been successfully labeled as PIP-DNSCL by DNSCI;

[0080] S331. Select a cover glass with a size of 50 × 26 mm and a thickness of 0.15 mm, and use a glass cutter to cut the cover glass at the center line of the long side to cut it into a cover glass with a size of 25 × 26 mm for subsequent use;

[0081] S332. Select a glass slide with a size of 76×26 mm and a thickness of 150 μm, and place the cut cover glass in the middle of the slide for subsequent use. Figure 2 As shown;

[0082] S341. At room temperature, set the spinning disk confocal microscope to an excitation wavelength of 405 nm, an emission wavelength of 520 nm, a magnification of 100×, a dwell time of 50 ms, and an exposure time of 10 ms.

[0083] S342. Turn on the spinning disk confocal microscope, place the prepared cover glass-slide under the microscope, and adjust the lens to the created reaction interface;

[0084] S343, use two 5ml syringes to draw 3-5ml of fluorescently labeled PIP solution and TMC solution respectively, and drop them on both sides of the reaction interface formed by the cover glass and the slide (the specific drop position is as follows Figure 3 After the addition, the diffusion movement of the fluorescent labeled PIP molecules and the interfacial reaction were observed in real time using a microscope;

[0085] S344、 Figure 5As shown in the figure, the diffusion movement and interfacial reaction of the fluorescently labeled PIP molecules were successfully observed. It can be clearly seen that before diffusion occurs (0ms), the distribution of PIP-DNSCL and TMC on both sides of the interface; further, with the diffusion movement of PIP molecules and the start of interfacial polymerization reaction, PIP molecules quickly diffuse and enrich at the interface (10ms) to undergo polymerization reaction with TMC molecules, and as the reaction proceeds, they gradually diffuse to the inside of the TMC side to react, eventually generating a polyamide membrane with fluorescent properties (50ms).

[0086] Comparative Example

[0087] like Figure 6-Figure 7 As shown, for the visualization of PIP and interfacial polymerization reactions without fluorescent labeling, the following steps without temperature indication were performed at room temperature:

[0088] S411, take 0.15g piperazine and 100ml deionized water to prepare an aqueous solution with a mass percentage of 0.15% w / v;

[0089] S412, take 0.15g of trimesoyl chloride and 100ml of n-hexane to prepare an organic phase solution with a mass percentage of 0.15% w / v;

[0090] S421, take a certain amount of aqueous solution, irradiate it under the condition of ultraviolet lamp with a wavelength of 365nm, and according to the results ( Figure 6 ) It can be seen that PIP molecules without fluorescent labeling do not have fluorescent properties and the ability to be observed;

[0091] S431. Select a cover glass with a size of 50 × 26 mm and a thickness of 0.15 mm, and use a glass cutter to cut the cover glass at the midline of the long side to cut it into a cover glass with a size of 25 × 26 mm for subsequent use;

[0092] S432. Select a glass slide with a size of 76×26 mm and a thickness of 150 μm, and place the cut cover glass in the middle of the slide for subsequent use. Figure 2 As shown;

[0093] S441. At room temperature, set the spinning disk confocal microscope to an excitation wavelength of 405 nm, an emission wavelength of 520 nm, a magnification of 100×, a dwell time of 50 ms, and an exposure time of 10 ms.

[0094] S442. Turn on the spinning disk confocal microscope, place the prepared cover glass-slide under the microscope, and adjust the lens to the created reaction interface;

[0095] S443. Use two 5ml syringes to draw 3-5ml of PIP solution and TMC solution respectively, and drop them on both sides of the reaction interface formed by the cover glass and the slide (the specific drop position is as follows Figure 3 As shown in the figure), after the addition, the diffusion movement of PIP molecules and the interfacial reaction were observed in real time using a microscope;

[0096] like Figure 7 As shown, the diffusion behavior of PIP molecules without fluorescent labeling and their interfacial reaction were observed. During the entire process (0ms, 10ms, 50ms), no diffusion behavior of any PIP molecules was observed, nor was any interfacial polymerization reaction observed.

[0097] In summary, comparing the observation results of Example 3 with those of the comparative example, the present invention demonstrates that the method for visualizing the interfacial polymerization diffusion reaction process of nanofiltration membranes can effectively visualize the interfacial polymerization reaction process of nanofiltration membrane monomers, enabling intuitive and real-time observation of the monomer diffusion behavior and the extent of the reaction throughout the entire process. Therefore, the present invention is highly effective in providing real-time, dynamic visualization of interfacial polymerization reactions on nanofiltration membranes.

[0098] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for visualizing the polymerization diffusion reaction process at the nanofiltration membrane interface, characterized in that: The following steps are involved: S1, preparing a piperazine PIP solution with a concentration of 0.1-0.2% w / v, a trimesoyl chloride TMC solution with a concentration of 0.1-0.2% w / v, and a dansyl chloride DNSCL solution with a concentration of 0.05-0.1% w / v; S2, mixing the dansyl chloride DNSCL solution and the piperazine PIP solution, fluorescently labeling the piperazine PIP to obtain a PIP-DNSCL solution; S3, selecting a cover glass, covering it on a glass slide after treatment, and performing an interfacial polymerization reaction between the labeled piperazine PIP and trimesoyl chloride TMC to create a reaction interface; S4. Set the excitation wavelength of the microscope to 405 nm and the emission wavelength to 520 nm. Add PIP-DNSCL solution and trimesoyl chloride (TMC) solution on both sides of the reaction interface. Under the microscope, the diffusion movement of the fluorescently labeled molecules can be observed to visualize the polymerization diffusion reaction process at the nanofiltration membrane interface.

2. The method for visualizing the interfacial polymerization and diffusion reaction process of a nanofiltration membrane according to claim 1, characterized in that: In S1, the piperazine PIP solution is an aqueous solution, the solute is piperazine PIP, and the solvent is deionized water; The TMC solution is an organic phase solution, wherein the solute is TMC and the solvent is n-hexane. The solute of the dansyl chloride DNSCL solution is dansyl chloride DNSCL, and the solvent is n-hexane.

3. The method for visualizing the interfacial polymerization and diffusion reaction process of nanofiltration membranes according to claim 1, characterized in that: In the S2, the volume ratio of the dansyl chloride DNSCL solution to the piperazine PIP solution is 10:1, the mixing container is a centrifuge tube, and the mixing equipment is a constant temperature shaker.

4. The method for visualizing the interfacial polymerization and diffusion reaction process of a nanofiltration membrane according to claim 1, characterized in that: In the above-mentioned S2, the mixing conditions are as follows: temperature of 25-30° C., amplitude of 3 mm, rotation speed of 60 rpm, and time of 24-36 h.

5. The method for visualizing the interfacial polymerization and diffusion reaction process of nanofiltration membranes according to claim 1, characterized in that: The fluorescent labeling is to fluorescently label the piperazine PIP molecule by using the dansyl chloride DNSCL molecule to react and generate PIP-DNSCL.

6. The method for visualizing the interfacial polymerization and diffusion reaction process of a nanofiltration membrane according to claim 1, characterized in that: In the S3, the size of the cover glass is 50×26 mm, and the thickness is 0.13-0.17 mm; the size of the slide glass is 76×26 mm, and the thickness is ≤170 μm.

7. The method for visualizing the interfacial polymerization and diffusion reaction process of a nanofiltration membrane according to claim 1, characterized in that: In the above-mentioned S3, the cover glass is processed by cutting it at the midline of the long side of the cover glass to divide it into two cover glasses of the same size and symmetrical appearance.

8. The method for visualizing the interfacial polymerization and diffusion reaction process of nanofiltration membranes according to claim 7, characterized in that: The reaction interface is created by covering one side of the glass slide with a cut cover glass to form a reaction interface between the cover glass and the glass slide.

9. The method for visualizing the interfacial polymerization and diffusion reaction process of nanofiltration membranes according to claim 1, characterized in that: In the S4, the microscope adopts a medium-disk confocal microscope, and the specific parameters are set as follows: magnification of 40×-100×; dwell time of 10ms-100ms; exposure time of 1ms-10ms; test temperature of 23-28°C; relative humidity ≤70%.

10. The method for visualizing the interfacial polymerization and diffusion reaction process of nanofiltration membranes according to claim 1, characterized in that: In S4, the solution is added dropwise as follows: 3-5 ml of the PIP-DNSCL solution and the trimesoyl chloride TMC solution are drawn into two syringes respectively, and then added dropwise onto both sides of the reaction interface formed by the cover glass and the slide glass.

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