Loose polyamine aqueous solution, preparation method of hollow fiber composite nanofiltration membrane and hollow fiber composite nanofiltration membrane

Abstract

In order to improve the permeability of hollow fiber nanofiltration membrane, the present invention provides a loose polyamine aqueous phase solution, a hollow fiber composite nanofiltration membrane and a preparation method thereof. A loose polyamine aqueous phase solution comprises a loosening agent and a polyamine monomer dissolved in water to form a loose polyamine aqueous phase solution. The above-mentioned loose polyamine aqueous phase solution and a polyacyl chloride organic phase solution are used to carry out an interfacial polymerization reaction on a base membrane, and then the hollow fiber composite nanofiltration membrane is prepared by two heat treatments. The loose aqueous phase solution and the preparation method of the hollow fiber composite nanofiltration provided by the present invention can prevent the hollow fiber composite nanofiltration membrane from excessively shrinking and causing a decrease in permeability, and can also expand the pore size of the hollow fiber composite nanofiltration membrane to improve its permeability. Finally, the water flux of the hollow fiber composite nanofiltration membrane can be improved without affecting the desalination rate.

Description

Technical Field

[0001] The invention relates to the field of filter membrane materials, in particular to a loose polyamine aqueous phase solution, a hollow fiber composite nanofiltration membrane preparation method and a hollow fiber composite nanofiltration membrane. Background Art

[0002] Water flux is an important performance indicator of current nanofiltration membrane technology. The current mainstream hollow fiber nanofiltration membrane has limitations in internal space design and flow channel distribution, which makes it difficult to increase its own water flux. It can only increase pressure compensation water flux through external force, but it will increase operating energy consumption. During long-term operation, it will also face the problem of irreversible attenuation of membrane performance caused by membrane pollution, increasing the cost of component replacement. Given that the current performance of hollow fiber nanofiltration membranes has reached its limit, only by making breakthroughs and innovations in membrane materials can hollow fiber nanofiltration membranes with higher processing efficiency be developed. Summary of the invention

[0003] The first object of the present invention is to provide a loose polyamine aqueous phase solution. The preparation method of the loose polyamine aqueous phase solution comprises dissolving a loosening agent and a polyamine monomer in water to prepare the loose polyamine aqueous phase solution.

[0004] As an embodiment, the loosening agent is one or more of ammonium bicarbonate, ammonium carbonate and ammonium chloride.

[0005] As an embodiment, the mass concentration fraction of the loosening agent in the loose polyamine aqueous solution is 1.00%-5.00% or 2.00%-3.00%.

[0006] As an embodiment, the mass fraction of the polyamine monomer in the aqueous solution is 0.20%-2.00% or 0.50%-2.00%.

[0007] As an embodiment, the polyamine monomer may be one or more selected from piperazine, polyethyleneimine, m-phenylenediamine and p-phenylenediamine.

[0008] The second object of the present invention is to provide a method for preparing a hollow fiber composite nanofiltration membrane, comprising the following steps: step 1, placing a base membrane in the above-mentioned loose polyamine aqueous phase solution for one soak to form a base membrane with a loose polyamine aqueous phase solution on the surface; step 2, placing the base membrane with the loose polyamine aqueous phase solution on the surface in a polyacid chloride organic phase solution for a second soak, taking it out after the second soaking, and then heat-treating it twice at a temperature lower than the decomposition temperature of the loosening agent and higher than the decomposition temperature of the loosening agent in sequence, finally obtaining a hollow fiber nanofiltration composite membrane; wherein the polyacid chloride organic phase solution is prepared by dissolving polyacid chloride monomers in an organic solvent.

[0009] As an embodiment, the polyamine monomer may be selected from one or more of piperazine, polyethyleneimine, m-phenylenediamine and p-phenylenediamine.

[0010] As an embodiment, the polyacyl chloride monomer may be selected from one or more of terephthaloyl chloride, isophthaloyl chloride, and trimesoyl chloride.

[0011] In one embodiment, the polyamine monomer is polyethyleneimine (PEI), the polyacyl chloride monomer is trimesoyl chloride (TMC), and the reactants of the secondary immersion (interfacial polymerization) are as follows:

[0012]

[0013] The products of the secondary immersion (interfacial polymerization) are as follows:

[0014]

[0015] The present application introduces ammonium carbonate (bicarbonate) salts or ammonium chloride with a decomposition temperature as a loosening agent into the process of preparing nanofiltration membranes by interfacial polymerization reaction. The loosening agent does not decompose or decomposes in small amounts below the decomposition temperature. At this time, the aqueous solution on the interface of the hollow fiber composite nanofiltration membrane and the solvent in the organic phase solution are dried, and the residual loosening agent (in some embodiments, it can account for 50%-100% of the total mass of the initially added loosening agent) crystallizes and precipitates, filling or attaching to the pores of the hollow fiber composite nanofiltration membrane, preventing the hollow fiber composite nanofiltration membrane from shrinking when removing the solvent (water in the aqueous solution and the alkane solvent in the organic phase solution) so that the pore size is reduced, thereby reducing the permeability (water flux). When the loosening agent is greater than the decomposition temperature and less than the failure temperature of the membrane components (above the failure temperature of the membrane components, it will damage the hollow fiber composite nanofiltration membrane), the residual loosening agent will quickly decompose to form a large amount of gas (ammonia, carbon dioxide or hydrochloric acid gas). The large amount of gas increases the pore size of the hollow fiber composite nanofiltration membrane, thereby reducing the density of the hollow fiber composite nanofiltration membrane layer (the higher the density, the smaller the pore size, and the lower the density, the larger the pore size), further improving the permeability (water flux) of the hollow fiber composite nanofiltration membrane. The salt rejection rate of the nanofiltration membrane is related to the composition and structure of the membrane. In some embodiments, changing the density of the membrane will slightly affect the salt rejection rate of the membrane, but will significantly improve the permeability (water flux) of the membrane. In summary, the preparation method of the loose aqueous phase solution and the hollow fiber composite nanofiltration membrane in the present invention can improve the water flux of the hollow fiber composite nanofiltration membrane without affecting the salt rejection rate.

[0016] As an embodiment, in step 1, the base film is first cleaned with an alkaline solution having a pH of 8-12 before being soaked once.

[0017] Therefore, the oil-soluble impurities inside the base film can be washed out by soaking the base film in a sodium hydroxide solution with a pH of 8-12.

[0018] As an implementation mode, the soaking time in step 1 is 1-30 minutes; or 3-5 minutes.

[0019] As an implementation mode, after soaking once in step 1, the base film with the loose polyamine aqueous solution needs to be dried by hanging it vertically for 1-30 minutes or 5-10 minutes, and wiping off the excess loose polyamine aqueous solution on the base film.

[0020] As an implementation mode, in step 1, the base film material is one or more of polyamide, polyacrylonitrile, polysulfone, and polyvinylidene fluoride.

[0021] As an embodiment, in step 2, the mass fraction of the polyacyl chloride monomer in the polyacyl chloride organic phase solution is 0.10%-0.50%, or 0.15%-0.40%.

[0022] As an embodiment, the solvent of the polyacyl chloride organic phase solution is one or more of pentane, hexane, cyclohexane and heptane.

[0023] As an implementation mode, the secondary immersion time in step 2 is 1-20 minutes; or 2-5 minutes.

[0024] As an embodiment, in step 2, after the second immersion, the membrane is taken out and kept at a temperature lower than the decomposition temperature of the loosening agent for 10-60 minutes or 15-18 minutes; then kept at a temperature higher than the decomposition temperature of the loosening agent and lower than the failure temperature of the membrane components for 5-20 minutes or 6-8 minutes. Finally, the hollow fiber composite nanofiltration membrane is washed with water to obtain the hollow fiber composite nanofiltration membrane.

[0025] In some embodiments, the decomposition temperature of the bulking agent is 80-120°C, and the failure temperature of the membrane component is 140-180°C.

[0026] As an embodiment, in step 2, the two heat treatments include first keeping in a No. 1 blast drying oven at a temperature of 50-90°C for 10-20 minutes or in a No. 1 blast drying oven at a temperature of 60-80°C for 15-18 minutes; then keeping in a No. 2 blast drying oven at a temperature of 100-140°C for 5-10 minutes or in a No. 2 blast drying oven at a temperature of 120-130°C for 6-8 minutes. Finally, washing with water obtains the hollow fiber composite nanofiltration membrane.

[0027] The fourth object of the present invention is to provide a hollow fiber composite nanofiltration membrane, which is prepared by the above-mentioned method for preparing the hollow fiber composite nanofiltration membrane.

[0028] Beneficial effects of the present invention:

[0029] After the hollow fiber composite nanofiltration membrane of the present invention is formed by interfacial polymerization reaction, the loosening agent is an inert substance and can be retained on the membrane. After that, through two heat treatments, when the loosening agent is below the decomposition temperature of the loosening agent, part of the loosening agent remains in the membrane and the membrane pores, preventing the hollow fiber composite nanofiltration membrane from shrinking the membrane and the membrane pores due to desolvation, thereby causing the membrane permeability to decrease; when the temperature is higher than the decomposition temperature of the loosening agent and lower than the failure temperature of the membrane components, the residual loosening agent is accelerated to decompose and produce a large amount of gas (ammonia, carbon dioxide or hydrochloric acid gas), thereby expanding the pore size of the hollow fiber composite nanofiltration membrane and improving its permeability. In summary, the preparation method of the loose aqueous phase solution and the hollow fiber composite nanofiltration membrane in the present invention can increase the water flux of the hollow fiber composite nanofiltration membrane without affecting the salt rejection rate. DETAILED DESCRIPTION

[0030] The test method for the flux and salt rejection of the hollow fiber nanofiltration membrane of the present invention is as follows:

[0031] The prepared hollow fiber nanofiltration membrane was pre-pressed with a 0.20 mass% magnesium sulfate (MgSO4) aqueous solution at 0.31 MPa for half an hour to test the water flux and desalination performance of the hollow fiber composite nanofiltration membrane.

[0032] The calculation formula of water flux is as follows:

[0033]

[0034] Where A = πDL (A - effective membrane area, unit is m 2 ; D - average diameter (outer diameter) of membrane filaments, in m; L - effective length of membrane filaments, in m); t - time required to collect Q volume of produced liquid, in h; Q - volume of produced liquid collected within t time, in L.

[0035] The calculation method of the membrane desalination is as follows:

[0036]

[0037] 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.

[0038] The present invention is described in detail in the following specific examples, but the present invention is not limited to the following examples.

[0039] Example 1

[0040] Ammonium bicarbonate is dissolved in water to prepare an ammonium bicarbonate aqueous solution with a mass fraction of 1.00%, and then piperazine monomer is added to the ammonium bicarbonate aqueous solution to make the mass fraction of the piperazine monomer in the aqueous solution 0.20%, and finally stirred to form a loose polyamine aqueous solution.

[0041] Example 2

[0042] Dissolve ammonium carbonate in water to prepare an ammonium carbonate aqueous solution with a mass fraction of 5.00%, then add polyethyleneimine monomer to the ammonium carbonate aqueous solution to make the mass fraction of the polyethyleneimine monomer in the aqueous solution 2.00%, and finally stir to form a loose polyamine aqueous solution.

[0043] Example 3

[0044] Dissolve ammonium bicarbonate in water to prepare an ammonium bicarbonate aqueous solution with a mass fraction of 2.00%, then add meta-phenylenediamine monomer to the ammonium bicarbonate aqueous solution to make the mass fraction of the meta-phenylenediamine monomer in the aqueous solution 1.00%, and finally stir to form a loose polyamine aqueous solution.

[0045] Example 4

[0046] Dissolve ammonium carbonate in water to prepare an ammonium carbonate aqueous solution with a mass fraction of 4.00%, then add p-phenylenediamine monomer to the ammonium carbonate aqueous solution to make the mass fraction of p-phenylenediamine monomer in the aqueous solution 1.50%, and finally stir to form a loose polyamine aqueous solution.

[0047] Example 5

[0048] Ammonium bicarbonate is dissolved in water to prepare an ammonium bicarbonate aqueous solution with a mass fraction of 1.00%, and then piperazine monomer is added to the ammonium bicarbonate aqueous solution to make the mass fraction of the piperazine monomer in the aqueous solution 2.00%, and finally stirred to form a loose polyamine aqueous solution.

[0049] Example 6

[0050] Ammonium carbonate is dissolved in water to prepare an ammonium carbonate aqueous solution with a mass fraction of 1.00%, and then polyethyleneimine monomer is added to the ammonium carbonate aqueous solution to make the mass fraction of the polyethyleneimine monomer in the aqueous solution 0.80%, and finally stirred to form a loose polyamine aqueous solution.

[0051] Example 7

[0052] Ammonium bicarbonate is dissolved in water to prepare an ammonium bicarbonate aqueous solution with a mass fraction of 3.00%, and then p-phenylenediamine monomer is added to the ammonium bicarbonate aqueous solution to make the mass fraction of p-phenylenediamine monomer in the aqueous solution 0.20%, and finally stirred to form a loose polyamine aqueous solution.

[0053] Example 8 (Comparative Example 1)

[0054] A polyamide hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) is used, and the base membrane is added to a sodium hydroxide solution (pH = 8-12) for immersion. A piperazine monomer aqueous phase solution with a mass fraction of 0.20% is prepared. Then a terephthaloyl chloride organic phase solution with a mass fraction of 0.10% is prepared, wherein the solvent is pentane. The base membrane washed with alkali solution is first placed in the piperazine monomer aqueous phase solution and kept for 1 minute. Then the base membrane is taken out from the piperazine monomer aqueous phase solution and hung vertically for 1 minute. Then the base membrane is immersed in the terephthaloyl chloride organic phase solution for 1 minute, and then the base membrane is taken out from the terephthaloyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 50°C for 10 minutes, then transferred to a No. 2 blast drying oven at 100°C for 5 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0055] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 98.7%, and the water flux was 13.1L / m 2 h.

[0056] Example 9 (Comparative Example 2)

[0057] A polyacrylonitrile polyamide hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) is used, and the base membrane is added to a sodium hydroxide solution (pH = 8-12) for immersion. A polyethyleneimine aqueous phase solution with a mass fraction of 2.00% is prepared. Then a 0.50% isophthaloyl chloride organic phase solution is prepared, wherein the solvent is hexane. The base membrane washed with alkali solution is first placed in the polyethyleneimine aqueous phase solution and kept for 10 minutes. Then the base membrane is taken out from the polyethyleneimine aqueous phase solution and hung vertically for 10 minutes. Then the base membrane is immersed in the isophthaloyl chloride organic phase solution for 8 minutes, and then the base membrane is taken out from the isophthaloyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 90°C for 20 minutes, then transferred to a No. 2 blast drying oven at 140°C for 10 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0058] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 96.6%, and the water flux was 18.3L / m 2 h.

[0059] Example 10

[0060] A polyamide hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) is used, and the base membrane is added to a sodium hydroxide solution (pH = 8-12) for immersion. A loose polyamine aqueous phase solution is prepared as in Example 1. A terephthaloyl chloride organic phase solution with a mass fraction of 0.10% is prepared, wherein the solvent is pentane. The base membrane washed with alkali solution is first placed in the loose polyamine aqueous phase solution and kept for 1 minute. The base membrane is then taken out from the loose polyamine aqueous phase solution and hung vertically for 1 minute. The base membrane is then immersed in the terephthaloyl chloride organic phase solution for 1 minute, and then the base membrane is taken out from the terephthaloyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 50°C for 10 minutes, then transferred to a No. 2 blast drying oven at 100°C for 5 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0061] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 95.8%, and the water flux was 29.3L / m 2 h.

[0062] Embodiment 11

[0063] A polyacrylonitrile polyamide hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) is used, and the base membrane is added to a sodium hydroxide solution (pH = 8-12) for immersion. A loose polyamine aqueous phase solution as in Example 2 is configured. Then a 0.50% isophthaloyl chloride organic phase solution is configured, wherein the solvent is hexane. The base membrane washed with alkali solution is first placed in the loose polyamine aqueous phase solution and kept for 10 minutes. Then the base membrane is taken out from the loose polyamine aqueous phase solution and hung vertically for 10 minutes. Then the base membrane is immersed in the isophthaloyl chloride organic phase solution for 8 minutes, and then the base membrane is taken out from the isophthaloyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 90°C for 20 minutes, then transferred to a No. 2 blast drying oven at 140°C for 10 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0064] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 94.9%, and the water flux was 38.6L / m 2 h.

[0065] Example 12

[0066] A polysulfone hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) was used, and the base membrane was added to a sodium hydroxide solution (pH = 8-12) for immersion. A loose polyamine aqueous phase solution as in Example 3 was prepared. A trimesoyl chloride organic phase solution with a mass fraction of 0.20% was prepared, wherein the solvent was cyclohexane. The base membrane washed with alkali solution was first placed in the loose polyamine aqueous phase solution and kept for 5 minutes. The base membrane was then taken out from the loose polyamine aqueous phase solution and hung vertically for 5 minutes. The base membrane was then immersed in the trimesoyl chloride organic phase solution for 4 minutes, and then the base membrane was taken out from the trimesoyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 60°C for 15 minutes, then transferred to a No. 2 blast drying oven at 120°C for 7 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0067] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 98.1%, and the water flux was 27.8L / m 2 h.

[0068] Example 13

[0069] A polyvinylidene fluoride hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) was used, and the base membrane was added to a sodium hydroxide solution (pH = 8-12) for immersion. A loose polyamine aqueous phase solution as in Example 4 was prepared. A terephthaloyl chloride organic phase solution with a mass fraction of 0.40% was prepared, wherein the solvent was heptane. The base membrane washed with alkali solution was first placed in the loose polyamine aqueous phase solution and kept for 8 minutes. The base membrane was then taken out from the loose polyamine aqueous phase solution and hung vertically for 7 minutes. The base membrane was then immersed in the terephthaloyl chloride organic phase solution for 6 minutes, and then the base membrane was taken out from the terephthaloyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 80°C for 15 minutes, then transferred to a No. 2 blast drying oven at 130°C for 8 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0070] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 98.1%, and the water flux was 26.4L / m 2 h.

[0071] Embodiment 14

[0072] A polyvinylidene fluoride hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) is used, and the base membrane is added to a sodium hydroxide solution (pH = 8-12) for immersion. A loose polyamine aqueous phase solution is prepared as in Example 5. A terephthaloyl chloride organic phase solution with a mass fraction of 0.50% is prepared, wherein the solvent is pentane. The base membrane washed with alkali solution is first placed in the loose polyamine aqueous phase solution and kept for 10 minutes. The base membrane is then taken out from the loose polyamine aqueous phase solution and hung vertically for 1 minute. The base membrane is then immersed in the terephthaloyl chloride organic phase solution for 1 minute, and then the base membrane is taken out from the terephthaloyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 90°C for 20 minutes, then transferred to a No. 2 blast drying oven at 100°C for 5 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0073] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 95.8%, and the water flux was 33.2L / m 2 h.

[0074] Embodiment 15

[0075] A polyvinylidene fluoride hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) is used, and the base membrane is added to a sodium hydroxide solution (pH = 8-12) for immersion, and the oil-soluble impurities inside the base membrane are washed out for standby use. A loose polyamine aqueous phase solution as in Example 6 is prepared. Then a 0.30% mass fraction of isophthaloyl chloride organic phase solution is prepared, wherein the solvent is cyclohexane. The base membrane washed with alkali solution is first placed in a loose polyamine aqueous phase solution and kept for 1 minute. Then the base membrane is taken out from the loose polyamine aqueous phase solution and hung vertically for 5 minutes. Then the base membrane is immersed in a terephthaloyl chloride organic phase solution for 6 minutes, and then the base membrane is taken out from the terephthaloyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 50°C for 18 minutes, and then transferred to a No. 2 blast drying oven at 100°C for 5 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0076] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 94.6%, and the water flux was 40.3L / m 2 h.

[0077] Example 16

[0078] A polyacrylonitrile hollow fiber ultrafiltration base membrane (molecular weight cutoff ≈ 30000-50000) is used, and the base membrane is added to a sodium hydroxide solution (pH = 8-12) for immersion, and the oil-soluble impurities inside the base membrane are washed out for standby use. A loose polyamine aqueous phase solution as in Example 7 is configured. Then a trimesoyl chloride organic phase solution with a mass fraction of 0.10% is configured, wherein the solvent is heptane. The base membrane washed with alkali solution is first placed in a loose polyamine aqueous phase solution and kept for 4 minutes. Then the base membrane is taken out from the loose polyamine aqueous phase solution and hung vertically for 7 minutes. Then the base membrane is immersed in a terephthaloyl chloride organic phase solution for 6 minutes, and then the base membrane is taken out from the terephthaloyl chloride organic phase solution, first placed in a No. 1 blast drying oven at 80°C for 20 minutes, and then transferred to a No. 2 blast drying oven at 140°C for 4 minutes, and finally washed with water to obtain a hollow fiber composite nanofiltration membrane.

[0079] At 25°C and 0.31MPa pressure, the separation performance of the membrane was tested with a 0.20% mass fraction magnesium sulfate (MgSO4) aqueous solution as the test water sample. The results are as follows: the desalination rate of the nanofiltration membrane was 97.1%, and the water flux was 27.3L / m 2 h.

[0080] Among them, Examples 1-7 are the preparation process and method of loose polyamine aqueous phase solution; Examples 8-16 are the preparation and test results of hollow fiber composite nanofiltration membrane, and the test results are shown in Table 1.

[0081] Table 1. Effect of bulking agent on the performance of hollow fiber composite nanofiltration membrane

[0082]

[0083] The above descriptions are only some specific embodiments of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a hollow fiber composite nanofiltration membrane, characterized in that: Dissolving a loosening agent and a polyamine monomer in water to prepare a loose polyamine aqueous phase solution; Step 1, soaking the base film in the loose polyamine aqueous solution once to form a base film with the loose polyamine aqueous solution on the surface; Step 2, placing the base membrane with the loose polyamine aqueous solution on the surface in a polyacyl chloride organic solution for a second soak, taking it out after the second soak, and then heat-treating it twice at a temperature lower than the decomposition temperature of the loosening agent and at a temperature higher than the decomposition temperature of the loosening agent, to finally obtain a hollow fiber composite nanofiltration membrane; The loosening agent is one or more of ammonium bicarbonate, ammonium carbonate and ammonium chloride; The mass fraction of the loosening agent in the loose polyamine aqueous solution is 1.00%-5.00%; The mass fraction of the polyamine monomer in the loose polyamine aqueous solution is 0.20%-2.00%; The polyamine monomer is one or more of piperazine, polyethyleneimine, m-phenylenediamine and p-phenylenediamine; The polyacyl chloride organic phase solution is prepared by dissolving polyacyl chloride monomers in an organic solvent; In the step 2, the mass fraction of the polyacyl chloride monomer in the polyacyl chloride organic phase solution is 0.10%-0.50%; the polyacyl chloride monomer is one or more of terephthaloyl chloride, isophthaloyl chloride and trimesoyl chloride.

2. The method for preparing a hollow fiber composite nanofiltration membrane according to claim 1, characterized in that: In the step 1, the base film material is one or more of polyamide, polyacrylonitrile, polysulfone and polyvinylidene fluoride.

3. The method for preparing a hollow fiber composite nanofiltration membrane according to claim 1, characterized in that: The solvent of the polyacid chloride organic phase solution is one or more of pentane, hexane, cyclohexane and heptane.

4. A hollow fiber composite nanofiltration membrane, characterized in that: The method is described in any one of claims 1 to 3.

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