A method for preparing nanofiltration membrane using trace monomer pre-reaction

Abstract

The present invention discloses a novel water treatment technology, specifically a nanofiltration membrane made by pre-reaction of trace monomers. The present invention is to mix a low-carbon chain alkane solvent and a high-carbon chain alkane to form a mixed organic phase solvent; then dissolve a polyacyl chloride monomer into the mixed organic phase solvent to prepare an organic solution A; then dissolve a trace reaction monomer and a chaotropic agent into another portion of the same volume of mixed organic phase solvent to prepare an organic solution B; cool, mix, and heat the organic solution A and the organic solution B respectively to prepare an organic solution C; further dissolve a polyamine monomer in water to prepare an aqueous phase solution; finally, place an ultrafiltration base membrane into the aqueous phase solution and the organic solution C, and then dry it. The advantage of the present invention is that it can effectively change the charge and hydrophilicity and hydrophobicity properties in the nanofiltration membrane structure, achieve precise control of the nanofiltration membrane performance in a wide range, and is stable, reliable, and easy to implement.

Description

Technical Field

[0001] The nanofiltration membrane separation technology involved in the present invention is a new water treatment technology, specifically refers to a nanofiltration membrane made by pre-reaction of trace monomers. Background Art

[0002] Currently, it has been widely used in the fields of industry and environmental protection. Among them, traditional treatment methods for dye wastewater (including adsorption, photodegradation and chemical degradation) have insufficient removal efficiency (especially at low dye concentrations), complex adsorbent regeneration processes and difficult disposal of toxic sludge, making it unsuitable for large-scale water treatment projects. Nanofiltration technology, as a highly efficient and sustainable process, can not only purify water but also recover and reuse dyes. Therefore, this technology has shown broad application potential in the field of dye separation in recent years.

[0003] The current mainstream nanofiltration membrane materials on the market are all dense polyamides, which have high retention rates for both dyes and inorganic salts (especially divalent salts), making selective separation of dyes and inorganic salts difficult. High inorganic salt removal significantly increases osmotic pressure and increases process energy consumption. Therefore, developing a class of loose nanofiltration membrane materials with pore sizes intermediate between those of traditional nanofiltration membranes and ultrafiltration membranes, which would offer higher permeability to water and salt ions while retaining good dye retention, holds great market potential. Currently, there are two main strategies for preparing loose nanofiltration membranes. The most effective approach is to use reactive monomers with large geometric dimensions or low reactivity to form a loose nanofiltration separation layer through interfacial polymerization. Another approach involves precisely controlling the membrane pore size by introducing nanofillers into the separation layer matrix. Despite some progress, these methods are mostly limited to the laboratory stage. A simple, reliable, and easily scalable method is urgently needed to fabricate loose nanofiltration membranes for the selective separation of dyes and salt ions.

[0004] Existing research has confirmed that by adopting the method of trace monomer pre-reaction to directionally control the density of the nanofiltration membrane separation layer, the membrane can maintain high retention capacity for dye molecules while allowing high flux of salt ions, thereby achieving effective separation of the two. This method is simple to operate, reliable in process, and has good compatibility with conventional nanofiltration membrane manufacturing processes. It is easy to scale up industrially and has important application potential. Summary of the Invention

[0005] The present invention addresses the problem that the interfacial polymerization process of nanofiltration membranes reacts quickly but is difficult to control, and provides a method based on trace monomer pre-reaction to achieve precise control of the separation performance of nanofiltration membrane materials.

[0006] To achieve the above object, the technical solution of the present invention is as follows: a nanofiltration preparation method based on trace monomer pre-reaction, comprising the following steps:

[0007] A nanofiltration preparation method based on trace monomer pre-reaction, characterized by comprising the following steps:

[0008] (1) mixing 1% to 10% by weight of a low-carbon paraffin solvent and a high-carbon paraffin to form a mixed organic phase solvent, wherein the low-carbon paraffin is one of pentane, hexane, cyclohexane, or heptane, and the high-carbon paraffin is Isopar G;

[0009] (2) dissolving the polyacyl chloride monomer into the above-mentioned mixed organic phase solvent to prepare an organic solution A; then dissolving a trace amount of reaction monomer and a chaotropic agent into another portion of the same volume of mixed organic phase solvent to prepare an organic solution B; cooling the organic solution A and the organic solution B to 0-10°C respectively, mixing the two and heating them to 38-48°C to prepare an organic solution C; in the prepared organic solution C, the mass percentage concentration of the polyacyl chloride monomer is 0.1-0.5%, and the mass percentage concentration of the trace reaction monomer is 0.1-0.5%. The mass percentage concentration is 0.01-0.05%, and the mass percentage concentration of the dissolving agent is 0.005-0.025%; the polyacyl chloride is one of succinyl chloride, diphenyl diacetyl chloride, 4,4'-oxybis(benzoyl chloride), or trimesoyl chloride; the trace reactive monomer is one of p-aminobenzaldehyde, phenoxyethylamine, p-aminobenzenesulfonic acid, or N-methylpiperazine; and the dissolving agent is one of lauryl alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether, Tween 80, or Span 80;

[0010] Dissolving a polyamine monomer in water to prepare an aqueous phase solution with a mass percentage concentration of 0.2% to 2%, wherein the polyamine monomer is one of m-phenylenediamine, ethylenediamine, 1,4-cyclohexanediamine, or piperazine;

[0011] (3) Place the ultrafiltration base membrane in the aqueous solution for 1-5 minutes, take it out and hang it vertically in the air to dry for 1-8 minutes, and wipe off the excess aqueous solution with a paper towel;

[0012] (4) Place the ultrafiltration base membrane treated in step (3) in the organic solution C for 1-5 minutes, take it out and heat-treat it in an oven at 80-120°C for 5-20 minutes.

[0013] Preferably, in the above-mentioned nanofiltration preparation method based on trace monomer pre-reaction, the ultrafiltration base membrane is selected to have a molecular weight cutoff of 30,000-80,000. The ultrafiltration base membrane is first immersed in a 30% isopropanol aqueous solution for cleaning for 12 hours, and then rinsed with clean water for standby use. The material of the ultrafiltration base membrane is one of polyacrylonitrile, polysulfone, polyethersulfone, or polyvinylidene fluoride.

[0014] Preferably, in the above-mentioned nanofiltration preparation method based on trace monomer pre-reaction, the ultrafiltration base membrane has a molecular weight cut-off of 40,000-60,000.

[0015] Preferably, in the above nanofiltration preparation method based on trace monomer pre-reaction, the mass concentration of the polyamine monomer in the aqueous phase solution is 0.6%-1.5%.

[0016] Preferably, the concentration of the low-carbon chain alkane solvent in the mixed organic phase solvent in step (1) of the nanofiltration preparation method based on the pre-reaction of trace monomers is 2%-5%.

[0017] Preferably, in the above nanofiltration preparation method based on trace monomer pre-reaction, the cooling temperature of the organic solution B in step (2) is controlled to be 4-8°C.

[0018] Preferably, in the above nanofiltration preparation method based on trace monomer pre-reaction, the temperature of the organic solution C in step (2) is controlled at 40-45°C.

[0019] Preferably, in the organic solution C of step (2) in the above-mentioned nanofiltration preparation method based on trace monomer pre-reaction, the mass percentage concentration of the polyacyl chloride monomer is 0.2-0.4%; the concentration of the trace reaction monomer is controlled at 0.02-0.04%; and the concentration of the solubilizing agent is controlled at 0.01-0.02%.

[0020] Preferably, in the above-mentioned nanofiltration preparation method based on trace monomer pre-reaction, the aqueous solution treatment time in step (3) is 2-5 minutes.

[0021] Preferably, in the above-mentioned nanofiltration preparation method based on trace monomer pre-reaction, the treatment time of the organic phase solution in step (4) is 2-3 minutes; the heat treatment temperature is 90°C-100°C, and the heat treatment time is 10-15 minutes.

[0022] Compared with the existing nanofiltration membrane preparation technology, the beneficial effects of the present invention are:

[0023] The present invention improves upon the traditional interfacial polymerization process for preparing nanofiltration membranes. By pre-reacting a mixture of trace reactive monomers and polyacyl chloride monomers, different charged and hydrophilic functional groups are introduced into the nanofiltration membrane structure, achieving controllable regulation of the polyamide nanofiltration separation layer structure and directionally controlling the separation performance of the nanofiltration membrane. Compared to the prior patent (US9895666B2) describing the addition of modified small molecules to the organic phase, this patent specifically addresses the following aspects in order to achieve fine-grained control of the nanofiltration membrane:

[0024] ① Using mixed alkane solvent as the organic phase to improve the solubility of trace polar reaction monomers;

[0025] ② Using a special non-ionic surfactant as a solubilizing agent, it not only overcomes the problem of the difficulty of dissolving trace polar reaction monomers in non-polar organic solvents, but also does not react with the polyacyl chloride monomers to interfere with the interfacial polymerization process;

[0026] ③ The organic phase solution adopts a special "low-temperature mixing-temperature pre-reaction" treatment method to reduce the initial stage rate of the pre-reaction monomer and the multi-acyl chloride monomer, prevent the pre-reaction monomer from excessively consuming the acyl chloride groups on the multi-acyl chloride monomer molecules, resulting in the acyl chloride monomer being unable to participate in the subsequent film-forming reaction and then embedded in the membrane structure.

[0027] In summary, this patent adopts the method of pre-reaction of trace pre-reaction monomers, which can effectively change the charge and hydrophilicity and hydrophobicity properties in the nanofiltration membrane structure, and realizes precise control of nanofiltration membrane performance in a wide range, which is stable, reliable and easy to implement. DETAILED DESCRIPTION

[0028] The present invention will be described in more detail below with reference to specific embodiments. However, the present invention is not limited to the following embodiments, and other embodiments in which some elements are replaced by equivalent methods are also possible.

[0029] The test method for the flux and divalent salt ion removal rate of the nanofiltration membrane of the present invention is as follows:

[0030] The prepared nanofiltration membrane was pre-pressed with an electrolyte solution of 0.2% mass concentration of MgSO4 at 0.31 MPa for half an hour to test the desalination performance and water flux of the nanofiltration membrane.

[0031] The calculation formula for water flux is as follows:

[0032]

[0033] Where A is the effective membrane area, in m 2 ; t—the time required to collect Q volume of liquid production, in h; Q—the volume of liquid production collected during time t, in L. (The flux unit in the subsequent tables is abbreviated as LMH). The calculation method for the removal performance of nanofiltration membranes for salt ions is shown in (2):

[0034]

[0035] Among them, R is the salt rejection rate of the membrane, C f - Conductivity of the stock solution, in μS / cm; C p - Conductivity of produced water, in μS / cm.

[0036] Similarly, the nanofiltration membrane was used to filter a 0.02% mass concentration Congo red dye molecule aqueous solution under similar operating conditions to determine the retention effect of the nanofiltration membrane on the dye molecules.

[0037] Example 1

[0038] 1) Using a polyacrylonitrile ultrafiltration membrane (molecular weight cut-off ≈ 30,000), immerse the membrane in a 30% isopropyl alcohol aqueous solution for 12 hours, and then rinse with clean water for later use;

[0039] 2) dissolving m-phenylenediamine in the aqueous solution to a concentration of 0.2% (mass percentage);

[0040] 3) 1% (mass percentage) of pentane and isoparaffin (trade name Isopar G) were mixed to form an organic phase solvent;

[0041] 4) First, dissolve succinyl chloride in the above-mentioned organic phase solvent (referred to as organic solution A), and then dissolve p-aminobenzaldehyde and lauryl alcohol polyoxyethylene ether in another equal volume of organic phase solvent (referred to as organic solution B). Cool organic solution A and organic solution B to 0°C respectively, slowly mix the two at low temperature and stir them thoroughly for 5 minutes, then continue stirring for 1 hour and gradually heat the solution to 38°C (referred to as organic solution C). In the final organic solution C, the concentration of succinyl chloride is 0.1% (mass percentage), the concentration of p-aminobenzaldehyde is 0.01% (mass percentage), and the concentration of lauryl alcohol polyoxyethylene ether is 0.005% (mass percentage);

[0042] 5) Place the ultrafiltration base membrane in the aqueous solution for 1 minute, then remove it from the aqueous solution and place it in the air, hang it vertically to dry for 1 minute, and wipe off the excess aqueous solution with a paper towel; then place the base membrane in the organic solution for 1 minute, remove it and heat treat it in an 80℃ oven for 5 minutes; finally, soak the membrane in pure water for testing.

[0043] Example 2

[0044] 1) Using a polyvinylidene fluoride-based membrane (molecular weight cut-off ≈ 80,000), immerse the membrane in a 30% isopropyl alcohol aqueous solution for 12 hours, and then rinse with clean water for later use;

[0045] 2) dissolving piperazine in the aqueous solution to a concentration of 2% (mass percentage);

[0046] 3) mixing 10% (mass percentage) of heptane and isoparaffin (trade name Isopar G) to form a mixed organic phase solvent;

[0047] 4) First, dissolve trimesoyl chloride in the above-mentioned organic phase solvent (referred to as Organic Solution A), then dissolve N-methylpiperazine and Span 80 in another equal volume of organic phase solvent (referred to as Organic Solution B). Organic Solution A and Organic Solution B are cooled to 10°C, slowly mixed, and stirred thoroughly at low temperature for 10 minutes. Stirring is then continued over 1 hour while gradually warming the solution to 48°C (referred to as Organic Solution C). In the final Organic Solution C, the concentration of trimesoyl chloride is 0.5% (mass percent), the concentration of N-methylpiperazine is 0.05% (mass percent), and the concentration of Span 80 is 0.025% (mass percent).

[0048] 5) Place the ultrafiltration base membrane in the aqueous solution for 5 minutes, then remove it from the aqueous solution and place it in the air, hang it vertically to dry for 8 minutes, and wipe off the excess aqueous solution with a paper towel; then place the base membrane in the organic solution for 5 minutes, remove it and heat treat it in a 120℃ oven for 20 minutes; finally, soak the membrane in pure water for testing.

[0049] Example 3

[0050] 1) Using a polysulfone membrane (molecular weight cut-off ≈ 40,000), immerse the membrane in a 30% isopropyl alcohol solution for 12 hours, and then rinse with clean water for later use;

[0051] 2) dissolving ethylenediamine in the aqueous solution to a concentration of 0.6% (mass percentage);

[0052] 3) 2% (mass percentage) of hexane and isoparaffin (trade name Isopar G) were mixed to form a mixed organic phase solvent;

[0053] 4) First, dissolve diphenyl diacetyl chloride in the above organic phase solvent (referred to as organic solution A), and then dissolve phenoxyethylamine and nonylphenol polyoxyethylene ether in another organic phase solvent of the same volume (referred to as organic solution B).

[0054] Organic Solution A and Organic Solution B were cooled to 4°C, slowly mixed, and stirred for 7 minutes at low temperature. Stirring was then continued over 1 hour while gradually warming the solution to 40°C (referred to as Organic Solution C). The final concentration of Organic Solution C was 0.2% (by mass) of diphenyl diacetyl chloride, 0.02% (by mass) of phenoxyethylamine, and 0.01% (by mass) of nonylphenol polyoxyethylene ether.

[0055] 5) Place the ultrafiltration base membrane in the aqueous solution for 2 minutes, then remove it from the aqueous solution and place it in the air, hang it vertically to dry for 4 minutes, and wipe off the excess aqueous solution with a paper towel; then place the base membrane in the organic solution for 2 minutes, remove it and heat treat it in a 90℃ oven for 10 minutes; finally, soak the membrane in pure water for testing.

[0056] Example 4

[0057] 1) Using a polyethersulfone membrane (molecular weight cut-off ≈ 60,000), immerse the membrane in a 30% isopropyl alcohol aqueous solution for 12 hours, and then rinse with clean water for later use;

[0058] 2) dissolving 1,4-cyclohexanediamine in the aqueous solution to a concentration of 1.5% (mass percentage);

[0059] 3) 2% (mass percentage) of cyclohexane and isoparaffin (trade name Isopar G) are mixed to form a mixed organic phase solvent;

[0060] 4) First, dissolve 4,4'-oxybis(benzoyl chloride) in the above-mentioned organic phase solvent (referred to as Organic Solution A). Then, dissolve sulfanilic acid and Tween 80 in another equal volume of organic phase solvent (referred to as Organic Solution B). Cool Organic Solution A and Organic Solution B separately to 8°C, slowly mix them at low temperature, and stir thoroughly for 8 minutes. Then, continue stirring over 1 hour while gradually warming the solution to 45°C (referred to as Organic Solution C). The final concentration of Organic Solution C is 0.4% (mass percentage) of 4,4'-oxybis(benzoyl chloride), 0.04% (mass percentage) of sulfanilic acid, and 0.02% (mass percentage) of Tween 80.

[0061] 5) Place the ultrafiltration base membrane in the aqueous solution for 3 minutes, then remove it from the aqueous solution and place it in the air, hang it vertically to dry for 6 minutes, and wipe off the excess aqueous solution with a paper towel; then place the base membrane in the organic solution for 3 minutes, remove it and heat treat it in a 100℃ oven for 15 minutes; finally, soak the membrane in pure water for testing.

[0062] Example 5

[0063] 1) Using a polyacrylonitrile-based membrane (molecular weight cut-off ≈ 50,000), immerse the membrane in a 30% isopropyl alcohol aqueous solution for 12 hours, and then rinse with clean water for later use;

[0064] 2) dissolving m-phenylenediamine in the aqueous solution to a concentration of 0.8% (mass percentage);

[0065] 3) 2% (mass percentage) of pentane and isoparaffin (trade name Isopar G) were mixed to form a mixed organic phase solvent;

[0066] 4) First, dissolve succinyl chloride in the above-mentioned organic phase solvent (referred to as organic solution A), then dissolve p-aminobenzaldehyde and lauryl alcohol polyoxyethylene ether in another equal volume of organic phase solvent (referred to as organic solution B). Organic solution A and organic solution B are cooled to 4°C, slowly mixed and stirred at low temperature for 6 minutes, and then stirred continuously over 1 hour while gradually warming the solution to 41°C (referred to as organic solution C). In the final organic solution C, the concentration of succinyl chloride is 0.2% (mass percentage), the concentration of p-aminobenzaldehyde is 0.02% (mass percentage), and the concentration of lauryl alcohol polyoxyethylene ether is 0.005-0.025% (mass percentage).

[0067] 5) Place the ultrafiltration base membrane in the aqueous solution for 2 minutes, then remove it from the aqueous solution and place it in the air, hang it vertically to dry for 2 minutes, and wipe off the excess aqueous solution with a paper towel; then place the base membrane in the organic solution for 2 minutes, remove it and heat treat it in a 90℃ oven for 10 minutes; finally, soak the membrane in pure water for testing.

[0068] Example 6

[0069] 1) Using a polysulfone membrane (molecular weight cut-off ≈ 45,000), immerse the membrane in a 30% isopropyl alcohol aqueous solution for 12 hours, and then rinse with clean water for later use;

[0070] 2) dissolving ethylenediamine in an aqueous solution to a concentration of 1.0% (mass percentage), wherein the polyamine monomer can be one of m-phenylenediamine, ethylenediamine, 1,4-cyclohexanediamine, and piperazine;

[0071] 3) Mixing 3% (mass percentage) of hexane and isoparaffin (trade name Isopar G) to form a mixed organic phase solvent;

[0072] 4) First, dissolve biphenyl diacetyl chloride in the above-mentioned organic phase solvent (referred to as organic solution A), and then dissolve phenoxyethylamine and nonylphenol polyoxyethylene ether in another equal volume of organic phase solvent (referred to as organic solution B). Organic solution A and organic solution B are cooled to 5°C, slowly mixed and stirred at low temperature for 7 minutes, and then continued to stir and gradually warm the solution to 42°C within 1 hour (referred to as organic solution C). In the final organic solution C, the concentration of biphenyl diacetyl chloride is 0.3% (mass percentage), the concentration of phenoxyethylamine is 0.03% (mass percentage), and the concentration of nonylphenol polyoxyethylene ether is 0.01% (mass percentage).

[0073] 5) Place the ultrafiltration base membrane in the aqueous solution for 3 minutes, then remove it from the aqueous solution and place it in the air, hang it vertically to dry for 4 minutes, and wipe off the excess aqueous solution with a paper towel; then place the base membrane in the organic solution for 2 minutes, remove it and send it to a 95℃ oven for heat treatment for 10 minutes; finally, soak the membrane in pure water for testing.

[0074] Example 7

[0075] 1) Using a polyethersulfone membrane (molecular weight cut-off ≈ 40,000), immerse the membrane in a 30% isopropyl alcohol aqueous solution for 12 hours, and then rinse with clean water for later use;

[0076] 2) dissolving 1,4-cyclohexanediamine in an aqueous solution to a concentration of 0.9% (mass percentage), wherein the polyamine monomer can be one of m-phenylenediamine, ethylenediamine, 1,4-cyclohexanediamine, and piperazine;

[0077] 3) 4% (mass percentage) of cyclohexane and isoparaffin (trade name Isopar G) were mixed to form a mixed organic phase solvent;

[0078] 4) First, dissolve 4,4'-oxybis(benzoyl chloride) in the above-mentioned organic phase solvent (referred to as Organic Solution A). Then, dissolve sulfanilic acid and Tween 80 in another equal volume of organic phase solvent (referred to as Organic Solution B). Cool Organic Solution A and Organic Solution B separately to 6°C, slowly mix them at low temperature, and stir thoroughly for 8 minutes. Then, continue stirring over 1 hour while gradually warming the solution to 43°C (referred to as Organic Solution C). In the final Organic Solution C, the concentration of 4,4'-oxybis(benzoyl chloride) is 0.1-0.5% (mass percentage), the concentration of sulfanilic acid is 0.04% (mass percentage), and the concentration of Tween 80 is 0.015% (mass percentage).

[0079] 5) Place the ultrafiltration base membrane in the aqueous solution for 4 minutes, then remove it from the aqueous solution and place it in the air, hang it vertically to dry for 5 minutes, and wipe off the excess aqueous solution with a paper towel; then place the base membrane in the organic solution for 3 minutes, remove it and heat treat it in a 95℃ oven for 15 minutes; finally, soak the membrane in pure water for testing.

[0080] Example 8

[0081] 1) Using a polyvinylidene fluoride-based membrane (molecular weight cut-off ≈ 60,000), immerse the membrane in a 30% isopropyl alcohol aqueous solution for 12 hours, and then rinse with clean water for later use;

[0082] 2) dissolving piperazine in an aqueous solution to a concentration of 1.4% (mass percentage), wherein the polyamine monomer can be one of m-phenylenediamine, ethylenediamine, 1,4-cyclohexanediamine, and piperazine;

[0083] 3) 5% (mass percentage) of heptane and isoparaffin (trade name Isopar G) were mixed to form a mixed organic phase solvent;

[0084] 4) First, dissolve trimesoyl chloride in the above-mentioned organic phase solvent (referred to as Organic Solution A), then dissolve N-methylpiperazine and Span 80 in another equal volume of organic phase solvent (referred to as Organic Solution B). Organic Solution A and Organic Solution B are cooled to 7°C, slowly mixed, and stirred thoroughly at low temperature for 9 minutes. Stirring is then continued over 1 hour while gradually warming the solution to 44°C (referred to as Organic Solution C). The final concentration of trimesoyl chloride in Organic Solution C is 0.4% (mass percent), N-methylpiperazine is 0.03% (mass percent), and Span 80 is 0.02% (mass percent).

[0085] 5) Place the ultrafiltration base membrane in the aqueous solution for 5 minutes, then remove it from the aqueous solution and place it in the air, hang it vertically to dry for 6 minutes, and wipe off the excess aqueous solution with a paper towel; then place the base membrane in the organic solution for 3 minutes, remove it and heat treat it in a 100℃ oven for 15 minutes; finally, soak the membrane in pure water for testing.

[0086]

[0087]

[0088]

[0089]

Claims

1. A nanofiltration preparation method based on trace monomer pre-reaction, characterized in that The steps include: (1) mixing 1% to 10% by weight of a low-carbon paraffin solvent and a high-carbon paraffin to form a mixed organic phase solvent, wherein the low-carbon paraffin is one of pentane, hexane, cyclohexane, or heptane, and the high-carbon paraffin is Isopar G; (2) dissolving the polyacyl chloride monomer into the above-mentioned mixed organic phase solvent to prepare an organic solution A; then dissolving a trace amount of reaction monomer and a chaotropic agent into another portion of the same volume of mixed organic phase solvent to prepare an organic solution B; cooling the organic solution A and the organic solution B to 0-10°C respectively, mixing the two and heating them to 38-48°C to prepare an organic solution C; in the prepared organic solution C, the mass percentage concentration of the polyacyl chloride monomer is 0.1-0.5%, and the mass percentage concentration of the trace reaction monomer is 0.1-0.5%. The mass percentage concentration is 0.01-0.05%, and the mass percentage concentration of the dissolving agent is 0.005-0.025%; the polyacyl chloride is one of succinyl chloride, diphenyl diacetyl chloride, 4,4'-oxybis(benzoyl chloride), or trimesoyl chloride; the trace reactive monomer is one of p-aminobenzaldehyde, phenoxyethylamine, p-aminobenzenesulfonic acid, or N-methylpiperazine; and the dissolving agent is one of lauryl alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether, Tween 80, or Span 80; Dissolving a polyamine monomer in water to prepare an aqueous phase solution with a mass percentage concentration of 0.2% to 2%, wherein the polyamine monomer is one of m-phenylenediamine, ethylenediamine, 1,4-cyclohexanediamine, or piperazine; (3) Place the ultrafiltration base membrane in the aqueous solution for 1-5 minutes, take it out and hang it vertically in the air to dry for 1-8 minutes, and wipe off the excess aqueous solution with a paper towel; (4) Place the ultrafiltration base membrane treated in step (3) in the organic solution C for 1-5 minutes, take it out and heat-treat it in an oven at 80-120°C for 5-20 minutes; 2. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 1, characterized in that: The ultrafiltration base membrane has a molecular weight cutoff of 30,000-80,000. The ultrafiltration base membrane is first immersed in a 30% isopropyl alcohol aqueous solution for cleaning for 12 hours, and then rinsed with clean water for use. The material of the ultrafiltration base membrane is one of polyacrylonitrile, polysulfone, polyethersulfone, or polyvinylidene fluoride.

3. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 2, characterized in that: The ultrafiltration base membrane has a molecular weight cut-off of 40,000-60,000.

4. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 1, characterized in that: The mass concentration of the polyamine monomer in the aqueous phase solution is 0.6%-1.5%.

5. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 1, characterized in that: The concentration of the low-carbon chain alkane solvent in the mixed organic phase solvent of step (1) is 2%-5%.

6. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 1, characterized in that: The cooling temperature of the organic solution B in step (2) is controlled to be 4-8°C.

7. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 1, characterized in that: In step (2), the temperature of the organic solution C is controlled to be 40-45°C.

8. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 1, characterized in that: In the organic solution C of step (2), the mass percentage concentration of the polyacyl chloride monomer is 0.2-0.4%; the concentration of the trace reaction monomer is controlled at 0.02-0.04%; and the concentration of the solubilizing agent is controlled at 0.01-0.02%.

9. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 1, characterized in that: The aqueous solution treatment time in step (3) is 2-5 minutes.

10. The nanofiltration preparation method based on trace monomer pre-reaction according to claim 1, characterized in that: The treatment time of the organic phase solution in step (4) is 2-3 minutes; the heat treatment temperature is 90°C-100°C, and the heat treatment time is 10-15 minutes.

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