High-flux anti-pollution composite nanofiltration membrane and preparation method thereof

Abstract

The invention discloses a high-flux anti-pollution composite nanofiltration membrane and a preparation method thereof. The method comprises the following steps: introducing diaminobenzoic acid as a water-phase monomer, carrying out interfacial polymerization reaction on the diaminobenzoic acid and an acyl chloride monomer to generate a polyamide layer, and then grafting polyquaternium-10 on the surface of the membrane to prepare the composite nanofiltration membrane. A loose and smooth polyamide layer is generated by utilizing the steric hindrance effect of diaminobenzoic acid, so that the membrane is endowed with relatively high flux and relatively good anti-pollution performance; in addition, the excellent hydrophilic performance of the cheap and easily available polyquaternium-10 and the hydrophilic performance of diaminobenzoic acid are utilized, so that the membrane is endowed with high flux and anti-pollution performance. The water flux recovery rate of the prepared nanofiltration membrane to bovine serum albumin reaches 97.0%, and the flux reaches 33.7 L.m <-2 >. H <-1 >, which indicates that the prepared composite nanofiltration membrane has excellent anti-pollution performance, effectively solves the negative influence and technical bottleneck brought to permeation flux in the modification process, and has large flux.

Description

Technical Field

[0001] The invention relates to a preparation method of a nanofiltration membrane, in particular to a large-flux anti-pollution composite nanofiltration membrane and a preparation method thereof. Background Art

[0002] In practical applications, a large number of inorganic, organic, and biological contaminants in water can adhere to the membrane surface, causing pore blockage. This requires increased operating pressure and increased cleaning frequency, which reduces membrane efficiency and even shortens membrane life. Therefore, the development of anti-fouling membranes is of great significance. At the same time, the process of developing anti-fouling membranes often results in a decrease in membrane flux. Improving membrane flux while developing anti-fouling membranes is particularly important.

[0003] Patent CN 108126530 A involves interfacial polymerization of polyamines and aromatic polyacyl chlorides on the surface of a polysulfone support membrane to form an aromatic polyamide layer. An anti-fouling coating liquid is applied to the aromatic polyamide layer, and the anti-fouling coating is formed after heat treatment, thereby improving the anti-fouling performance of the reverse osmosis membrane.

[0004] Patent CN 114713044 B uses a mixture of 4-sulfonamide o-aminophenol and amine monomers to prepare a nanofiltration membrane through interfacial polymerization with acyl chloride monomers, while giving the nanofiltration membrane good anti-fouling properties, with a water flux recovery rate of 94.5% for oil-water mixtures.

[0005] Patent CN111298660 B generates a large amount of hydrophilic silica spherical substances through grafting reaction on the membrane surface, thereby obtaining a highly stable anti-fouling composite nanofiltration membrane.

[0006] Therefore, the prior art lacks a nanofiltration membrane solution that can significantly increase membrane flux. Summary of the Invention

[0007] To address the problems described above, the present invention provides a high-flux, anti-pollution composite nanofiltration membrane and a method for preparing the same. This method improves both the anti-pollution performance and the membrane flux, thus providing a highly valuable research and application solution. The present invention utilizes a microporous membrane as a base membrane, performs a simple and effective activation, then uses diaminobenzoic acid as an aqueous monomer and grafts polyquaternium-10 onto the membrane surface. This steric hindrance and hydrophilic properties contribute to the high-flux, anti-pollution performance of the composite membrane.

[0008] The steps of the technical solution adopted by the present invention are as follows:

[0009] (1) Activation: Immerse the microporous membrane in an aqueous solution of sodium dodecylbenzenesulfonate, take it out and dry it after treatment to obtain an active base membrane;

[0010] (2) Preparation of primary membrane: The active base membrane is sequentially immersed in an aqueous solution of an aqueous phase monomer and a solution of an acyl chloride monomer, and then taken out and placed in a drying oven to obtain a primary membrane;

[0011] (3) Preparation of high-flux anti-pollution composite nanofiltration membrane: The primary membrane was immersed in a solution of polyquaternium-10 (hereinafter referred to as PQ-10) for treatment, then taken out and placed in a drying oven to obtain a high-flux anti-pollution composite nanofiltration membrane.

[0012] The step (1) is specifically as follows: immersing the microporous film in a sodium dodecylbenzenesulfonate aqueous solution with a mass concentration of 0.1% to 4.0% for 5 minutes to 12 hours, then taking it out and placing it in the air to dry, thereby obtaining an active base film.

[0013] The microporous membrane is one of polyvinylidene fluoride flat membrane or polyvinylidene fluoride hollow fiber membrane, polytetrafluoroethylene flat membrane or polytetrafluoroethylene hollow fiber membrane, polysulfone flat membrane or polysulfone hollow fiber membrane, polyethersulfone flat membrane or polyethersulfone hollow fiber membrane.

[0014] The step (2) is specifically as follows: immersing the active base membrane in an aqueous solution of an aqueous phase monomer with a mass concentration of 0.1% to 5.0% and staying for 5 seconds to 30 minutes, taking it out and placing it in the air to dry, and then immersing it in an organic solvent solution of an acyl chloride monomer with a mass concentration of 0.1% to 5.0% and staying for 5 seconds to 30 minutes, taking it out and placing it in a drying oven at 30 to 90° C. and staying for 1 to 30 minutes to obtain a primary membrane.

[0015] The step (3) is specifically as follows: immersing the primary membrane in an aqueous solution of polyquaternium-10 with a mass concentration of 0.01% to 1.0% for 5 seconds to 30 minutes, taking it out and placing it in a drying oven at 30 to 90° C. for 1 to 30 minutes to obtain a high-flux anti-pollution composite nanofiltration membrane.

[0016] The chemical structural formula of the polyquaternium-10 is:

[0017]

[0018] The aqueous phase monomer is 3,5-diaminobenzoic acid, and its structural formula is:

[0019]

[0020] The acyl chloride monomer is any one of trimesoyl chloride, isophthaloyl chloride, terephthaloyl chloride and phthaloyl chloride, or a mixture of the two in any proportion.

[0021] The organic solvent is any one of n-hexane, toluene, n-octane, ethyl acetate, isooctane and n-heptane.

[0022] The present invention utilizes the steric hindrance effect of diaminobenzoic acid, thereby slowing down the diffusion rate and reaction rate, thereby generating a loose and smooth polyamide layer. The loose polyamide layer gives the membrane a higher flux, and the smooth polyamide layer gives the membrane better anti-fouling performance.

[0023] Compared with the background technology, the present invention has the following beneficial effects:

[0024] Generally, in the process of improving the anti-pollution performance of nanofiltration membrane, it is inevitable to cause the decline of permeation flux. The present invention is by introducing diaminobenzoic acid as water phase monomer, itself and acyl chloride monomer generation interfacial polymerization reaction generate polyamide layer, then on the membrane surface grafting polyquaternium-10, thus prepared composite nanofiltration membrane.Utilize the steric hindrance effect of diaminobenzoic acid, diffusion rate and reaction rate are slower thus, generate loose and smooth polyamide layer thus. Loose polyamide layer gives the higher flux of film, and smooth polyamide layer gives the good anti-pollution performance of film. In addition, utilize the hydrophilic property of cheap and easy to get polyquaternium-10 excellence, and the hydrophilic property of diaminobenzoic acid, give membrane large flux and anti-pollution performance.

[0025] The water flux recovery rate of the nanofiltration membrane prepared by the present invention for bovine serum albumin reaches 97.0%, and the flux reaches 33.7 L·m -2 ·h -1 These results show that the prepared nanofiltration membrane not only has excellent anti-fouling performance, but also effectively solves the negative impact and technical bottlenecks on the permeation flux brought about by the anti-fouling modification process of the existing nanofiltration membrane, and has a large flux and high permeation flux. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to specific examples, but the present invention is not limited to the following examples.

[0027] The embodiments of the present invention are as follows:

[0028] Example 1:

[0029] (1) Activation: Immerse the polyvinylidene fluoride flat membrane in a 0.1% mass concentration sodium dodecylbenzene sulfonate aqueous solution for 12 h, remove it and air dry it to obtain an active base membrane;

[0030] (2) Preparation of primary membrane: The active base membrane was immersed in a 5.0% mass concentration 3,5-diaminobenzoic acid aqueous solution for 5 seconds, taken out and placed in air to dry, and then immersed in a 0.1% trimesoyl chloride n-hexane solution for 30 minutes, taken out, and placed in a drying oven at 90°C for 1 minute to obtain a primary membrane;

[0031] (3) Preparation of high-flux anti-pollution composite nanofiltration membrane: The nascent membrane was immersed in a 1.0% mass concentration PQ-10 solution for 5 seconds, taken out, and placed in a drying oven at 30°C for 30 minutes to obtain a high-flux anti-pollution composite nanofiltration membrane.

[0032] The prepared membrane was subjected to cross-flow filtration test at 25°C and 0.4 MPa, and the water flux recovery rate (FRR) of bovine serum albumin (BSA) solution was 96.8%. The flux of MgSO4 was 33.3 L·m -2 ·h -1 .

[0033] Example 2:

[0034] (1) Activation: Immerse the polytetrafluoroethylene flat membrane in a 4.0% mass concentration sodium dodecylbenzenesulfonate aqueous solution for 5 minutes, remove and air dry to obtain an active base membrane;

[0035] (2) Preparation of primary membrane: The active base membrane was immersed in a 0.1% mass concentration of 3,5-diaminobenzoic acid aqueous solution for 30 minutes, taken out and placed in air to dry, and then immersed in a 5.0% isophthaloyl chloride n-octane solution for 5 seconds, taken out, and placed in a drying oven at 30°C for 30 minutes to obtain a primary membrane;

[0036] (3) Preparation of high-flux anti-pollution composite nanofiltration membrane: The nascent membrane was immersed in a 0.01% mass concentration of PQ-10 solution for 30 minutes, taken out, and placed in a drying oven at 90°C for 1 minute to obtain a high-flux anti-pollution composite nanofiltration membrane.

[0037] The prepared membrane was subjected to cross-flow filtration test at 25°C and 0.4 MPa, and the water flux recovery rate (FRR) of bovine serum albumin (BSA) solution was 97.0%. The flux of MgSO4 was 33.7 L·m -2 ·h -1 .

[0038] Example 3:

[0039] (1) Activation: Immerse the polytetrafluoroethylene hollow fiber membrane in a 2.0% mass concentration sodium dodecylbenzene sulfonate aqueous solution for 8 h, remove it and air dry it to obtain an active base membrane;

[0040] (2) Preparation of primary membrane: The active base membrane was immersed in a 3.0% mass concentration 3,5-diaminobenzoic acid aqueous solution for 10 min, taken out and placed in air to dry, and then immersed in a 2.0% trimesoyl chloride toluene solution for 15 min, taken out, and placed in a drying oven at 50°C for 20 min to obtain a primary membrane;

[0041] (3) Preparation of high-flux anti-pollution composite nanofiltration membrane: The nascent membrane was immersed in a 0.2% mass concentration of PQ-10 solution for 15 minutes, taken out, and placed in a drying oven at 60°C for 20 minutes to obtain a high-flux anti-pollution composite nanofiltration membrane.

[0042] The prepared membrane was subjected to cross-flow filtration test at 25°C and 0.4 MPa, and the water flux recovery rate (FRR) of bovine serum albumin (BSA) solution was 96.7%. The flux of MgSO4 was 33.5 L·m -2 ·h -1 .

[0043] Example 4:

[0044] (1) Activation: Immerse the polytetrafluoroethylene flat membrane in a 3.0% mass concentration sodium dodecylbenzenesulfonate aqueous solution for 4 h, remove it and air dry it to obtain an active base membrane;

[0045] (2) Preparation of primary membrane: The active base membrane was immersed in a 1.5% mass concentration 3,5-diaminobenzoic acid aqueous solution for 2 h, taken out and placed in air to dry, and then immersed in a 3.5% hexane solution of trimesoyl chloride and isophthaloyl chloride (mass ratio of 1:2) for 10 min, taken out, and placed in a drying oven at 70°C for 8 min to obtain a primary membrane;

[0046] (3) Preparation of high-flux anti-pollution composite nanofiltration membrane: The nascent membrane was immersed in a 0.5% mass concentration PQ-10 solution for 10 minutes, taken out, and placed in a drying oven at 60°C for 25 minutes to obtain a high-flux anti-pollution composite nanofiltration membrane.

[0047] The prepared membrane was subjected to cross-flow filtration test at 25°C and 0.4 MPa, and the water flux recovery rate (FRR) of bovine serum albumin (BSA) solution was 97.0%. The flux of MgSO4 was 33.6 L·m -2 ·h -1 .

[0048] Example 5:

[0049] (1) Activation: Immerse the polyvinylidene fluoride hollow fiber membrane in a 3.0% mass concentration sodium dodecylbenzenesulfonate aqueous solution for 6 h, remove it and air dry it to obtain an active base membrane;

[0050] (2) Preparation of primary membrane: The active base membrane was immersed in a 2.5% mass concentration of 3,5-diaminobenzoic acid aqueous solution for 7 h, taken out and placed in air to dry, and then immersed in a 2.5% n-octane solution of trimesoyl chloride and terephthaloyl chloride (mass ratio of 3:1) for 10 min, taken out, and placed in a drying oven at 45°C for 15 min to obtain a primary membrane;

[0051] (3) Preparation of high-flux anti-pollution composite nanofiltration membrane: The nascent membrane was immersed in a 0.3% mass concentration PQ-10 solution for 8 minutes, taken out, and placed in a drying oven at 55°C for 18 minutes to obtain a high-flux anti-pollution composite nanofiltration membrane.

[0052] The prepared membrane was subjected to cross-flow filtration test at 25°C and 0.4 MPa, and the water flux recovery rate (FRR) of bovine serum albumin (BSA) solution was 96.9%. The flux of MgSO4 was 33.2 L·m -2 ·h -1 .

[0053] Example 6:

[0054] (1) Activation: Immerse the polyvinylidene fluoride flat membrane in a 2.0% mass concentration sodium dodecylbenzene sulfonate aqueous solution for 6 h, remove it and air dry it to obtain an active base membrane;

[0055] (2) Preparation of primary membrane: The active base membrane was immersed in a 4.5% mass concentration of 3,5-diaminobenzoic acid aqueous solution for 18 minutes, taken out and placed in air to dry, and then immersed in a 4.5% trimesoyl chloride n-hexane solution for 18 minutes, taken out, and placed in a drying oven at 60°C for 20 minutes to obtain a primary membrane;

[0056] (3) Preparation of high-flux anti-pollution composite nanofiltration membrane: The nascent membrane was immersed in a 0.15% mass concentration of PQ-10 solution for 8 minutes, taken out, and placed in a drying oven at 50°C for 10 minutes to obtain a high-flux anti-pollution composite nanofiltration membrane.

[0057] The prepared membrane was subjected to cross-flow filtration test at 25°C and 0.4 MPa, and the water flux recovery rate (FRR) of bovine serum albumin (BSA) solution was 97.0%. The flux of MgSO4 was 33.6 L·m -2 ·h -1 .

[0058] Comparative Example 1:

[0059] (1) Activation: Immerse the polyvinylidene fluoride flat membrane in a 2.0% mass concentration sodium dodecylbenzene sulfonate aqueous solution for 6 h, remove it and air dry it to obtain an active base membrane;

[0060] The resulting active base membrane is not a nanofiltration membrane. When used to separate salt solutions like MgSO₄, it is completely unable to separate them from pure water. In other words, when tested using a cross-flow filtration device, the concentration of MgSO₄ and other salts in the solution barely changes before and after the test. In short, the active base membrane at this point does not meet the separation requirements of a nanofiltration membrane and cannot be used to separate salt solutions like MgSO₄.

[0061] Comparative Example 2:

[0062] (1) Activation: Immerse the polyvinylidene fluoride flat membrane in a 2.0% mass concentration sodium dodecylbenzene sulfonate aqueous solution for 6 h, remove it and air dry it to obtain an active base membrane;

[0063] (2) Preparation of control membrane: The active base membrane was immersed in a 4.0% mass concentration of p-phenylenediamine aqueous solution for 10 min, removed and placed in air to dry, and then immersed in a 4.0% trimesoyl chloride n-hexane solution for 18 min, removed and placed in a drying oven at 60°C for 20 min to obtain a control membrane;

[0064] At 25°C and 0.4 MPa, the control membrane was subjected to cross-flow filtration test, and the water flux recovery rate (FRR) of bovine serum albumin (BSA) solution was 83.3%. The flux of MgSO4 was 6.7 L·m -2 ·h -1 .

[0065] Comparative Example 3:

[0066] (1) Activation: Immerse the polyvinylidene fluoride flat membrane in a 2.0% mass concentration sodium dodecylbenzene sulfonate aqueous solution for 6 h, remove it and air dry it to obtain an active base membrane;

[0067] (2) Preparation of control membrane: The active base membrane was immersed in a 3.5% mass concentration piperazine aqueous solution for 15 min, removed and air-dried, and then immersed in a 3.5% trimesoyl chloride n-hexane solution for 20 min, removed and placed in a drying oven at 60°C for 20 min to obtain a control membrane;

[0068] At 25°C and 0.4 MPa, the cross-flow filtration test of the control membrane showed that the water flux recovery rate (FRR) of bovine serum albumin (BSA) solution was 75.1%. The flux of MgSO4 was 20.1 L·m -2 ·h -1 .

[0069] The above specific embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

[0070] The above description is only a preferred embodiment of the present invention. Therefore, any equivalent changes or modifications made according to the structure, characteristics and principles described in the scope of the patent application of the present invention are included in the scope of the patent application of the present invention.

Claims

1. A method for preparing a high-flux anti-pollution composite nanofiltration membrane, characterized in that: The steps are as follows: (1) Activation: Immerse the microporous membrane in an aqueous solution of sodium dodecylbenzenesulfonate, take it out and dry it after treatment to obtain an active base membrane; (2) Preparation of primary membrane: The active base membrane is sequentially immersed in an aqueous solution of an aqueous phase monomer and a solution of an acyl chloride monomer, and then taken out and placed in a drying oven to obtain a primary membrane; (3) Preparation of high-flux anti-pollution composite nanofiltration membrane: The primary membrane was immersed in a solution of polyquaternium-10, taken out, and placed in a drying oven to obtain a high-flux anti-pollution composite nanofiltration membrane.

2. The method for preparing a high-flux anti-pollution composite nanofiltration membrane according to claim 1, characterized in that: The step (1) is specifically as follows: immersing the microporous film in a sodium dodecylbenzenesulfonate aqueous solution with a mass concentration of 0.1% to 4.0% for 5 minutes to 12 hours, then taking it out and placing it in the air to dry, thereby obtaining an active base film.

3. The method for preparing a high-flux anti-pollution composite nanofiltration membrane according to claim 1 or 2, characterized in that: The microporous membrane is one of polyvinylidene fluoride flat membrane or polyvinylidene fluoride hollow fiber membrane, polytetrafluoroethylene flat membrane or polytetrafluoroethylene hollow fiber membrane, polysulfone flat membrane or polysulfone hollow fiber membrane, polyethersulfone flat membrane or polyethersulfone hollow fiber membrane.

4. The method for preparing a high-flux anti-pollution composite nanofiltration membrane according to claim 1, characterized in that: The step (2) is specifically as follows: immersing the active base membrane in an aqueous solution of an aqueous phase monomer with a mass concentration of 0.1% to 5.0% and staying for 5 seconds to 30 minutes, taking it out and placing it in the air to dry, and then immersing it in an organic solvent solution of an acyl chloride monomer with a mass concentration of 0.1% to 5.0% and staying for 5 seconds to 30 minutes, taking it out and placing it in a drying oven at 30 to 90° C. and staying for 1 to 30 minutes to obtain a primary membrane.

5. The method for preparing a high-flux anti-pollution composite nanofiltration membrane according to claim 1, characterized in that: The step (3) is specifically as follows: immersing the primary membrane in an aqueous solution of polyquaternium-10 with a mass concentration of 0.01% to 1.0% for 5 seconds to 30 minutes, taking it out and placing it in a drying oven at 30 to 90° C. for 1 to 30 minutes to obtain a high-flux anti-pollution composite nanofiltration membrane.

6. The method for preparing a high-flux anti-pollution composite nanofiltration membrane according to claim 5, characterized in that: The chemical structural formula of the polyquaternium-10 is:

7. The method for preparing a high-flux anti-pollution composite nanofiltration membrane according to claim 1, characterized in that: The aqueous phase monomer is 3,5-diaminobenzoic acid, and its structural formula is:

8. The method for preparing a high-flux anti-pollution composite nanofiltration membrane according to claim 1, characterized in that: The acyl chloride monomer is any one of trimesoyl chloride, isophthaloyl chloride, terephthaloyl chloride and phthaloyl chloride, or a mixture of the two in any proportion.

9. The method for preparing a high-flux anti-pollution composite nanofiltration membrane according to claim 1, characterized in that: The organic solvent is any one of n-hexane, toluene, n-octane, ethyl acetate, isooctane and n-heptane.

10. A high-flux anti-pollution composite nanofiltration membrane, characterized by: The invention is prepared by the method according to any one of claims 1 to 9.

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