High-flux polyurea acid-resistant nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention discloses a high-flux polyurea acid-resistant nanofiltration membrane as well as a preparation method and application thereof. The preparation method mainly comprises the following steps: (1) preparing an aqueous phase solution of an amine-containing monomer and a catalyst; (2) soaking the base membrane into the aqueous phase solution for a certain time, taking out the base membrane, and removing redundant aqueous phase; (3) preparing an isocyanate organic phase solution; (4) soaking the base membrane in the step (2) into the organic phase solution in the step (3), and reacting for a certain time; and (5) heating the obtained composite membrane for a period of time to obtain the high-flux polyurea acid-resistant nanofiltration membrane. The prepared polyurea nanofiltration membrane has excellent acid resistance and relatively high permeation flux.

Description

Technical Field

[0001] This invention belongs to the field of water treatment membrane technology, specifically relating to a high-flux polyurea acid-resistant nanofiltration membrane, its preparation method, and its application. Background Technology

[0002] Industries such as electroplating, metallurgy, and titanium dioxide production generate large amounts of acidic wastewater annually. Compared to traditional wastewater treatment processes like extraction, crystallization, and evaporation, nanofiltration membrane separation technology offers advantages such as low energy consumption and ease of scalability, demonstrating significant application potential in acidic wastewater treatment. However, traditional nanofiltration membranes are primarily composed of polyamide materials, which are prone to hydrolysis at low pH levels and exhibit poor acid resistance, affecting the long-term lifespan of the membrane material.

[0003] Wang et al. (RSC advances, 2019, 9(4): 2042-2054.) prepared a polysulfonamide nanofiltration membrane with a flux of 68.2 L / m³ by reacting 1,3-benzenesulfonyl chloride and polyacrylamide. -2 h -1 MPa -1 The rejection rate for magnesium chloride was 92.4%, and it exhibited good acid resistance. He et al. (Journal of Materials Science, 2019, 54(1): 886-900.) prepared an acid-resistant nanofiltration membrane by reacting 1,4,7,10-tetraazacyclododecane and 2,4,6-tris(sulfonyl chloride)phenol, with a permeation flux of 13.98 L m. -2 h -1 MPa -1 The copper sulfate rejection rate was 78%. However, the permeation flux of the aforementioned acid-resistant nanofiltration membranes was low, making it difficult to meet the treatment needs of large quantities of acidic wastewater in industry.

[0004] Patents CN 113509839A and CN 115970521A provide a method for preparing a polyurea-based acid-resistant nanofiltration membrane, which obtains a polyurea separation layer through interfacial polymerization of polyamines and polyisocyanates. However, the water flux of the nanofiltration membranes in both patents still has the potential to be further improved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-flux polyurea acid-resistant nanofiltration membrane, which is obtained by reacting isocyanate monomers with amines that have a three-dimensional structure.

[0006] To achieve the above objectives, the technical solution of the present invention includes the following:

[0007] One objective of this invention is to provide a method for preparing a high-flux polyurea acid-resistant nanofiltration membrane, comprising the following steps:

[0008] (1) Prepare an aqueous solution with an amine monomer concentration of 0.05wt%-3wt% and a catalyst concentration of 0.01wt%-0.5wt%;

[0009] (2) Immerse the base membrane in the aqueous solution of (1) for 2-30 minutes, remove the base membrane and remove excess water droplets;

[0010] (3) Prepare an organic phase solution with an isocyanate concentration of 0.05wt%-0.2wt%;

[0011] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 2-30 min;

[0012] (5) Place the composite membrane obtained above into an oven and heat it at 50-80℃ for 5-20 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0013] Specifically, the catalyst in step (1) is one or more of 4-dimethylaminopyridine, pyrazine, 2,6-dimethylpyridine and triethylamine.

[0014] The amine monomer in step (1) is one or a mixture of several of 1,4,7,10-tetraazacyclododecane, 1,3-diaminoadamantane, and polyethyleneimine, preferably a mixture of amine monomers (1,4,7,10-tetraazacyclododecane and / or 1,3-diaminoadamantane) and polyethyleneimine having a spatially distorted structure.

[0015] The base film described in step (2) is selected from one or more of polysulfone, polyethersulfone, or polyacrylonitrile.

[0016] The isocyanate mentioned in step (3) is one or more of triphenylmethane triisocyanate (CAS#2422-91-5), tetra(4-isocyanate benzene)methane (CAS#697746-87-5), and 4,4'-diisocyanate-5'-(4-isocyanate benzene) (CAS#865709-48-4).

[0017] Specifically, the structure of the triphenylmethane triisocyanate is as follows:

[0018]

[0019] Specifically, the structure of the tetra(4-isocyanate benzene)methane is as follows:

[0020]

[0021] Specifically, the structure of 4,4'-diisocyanate-5'-(4-isocyanate benzene) is shown below:

[0022]

[0023] Specifically, 4,4'-diisocyanate-5'-(4-isocyanate benzene) can be prepared by referring to the synthesis method in patent JP2022173757.

[0024] The solvent in the organic phase solution in step (3) is chlorobenzene or a chlorobenzene-benzene mixed solvent. If a chlorobenzene-benzene mixed solvent is selected, the mass ratio of the two is preferably 1:1-5:1.

[0025] A second objective of this invention is to provide a high-flux polyurea acid-resistant nanofiltration membrane prepared by the preparation method provided by this invention.

[0026] A third objective of this invention is to provide the application of the high-flux polyurea acid-resistant nanofiltration membrane described in this invention and the high-flux polyurea acid-resistant nanofiltration membrane prepared by the preparation method described in this invention in the field of water treatment, especially in acidic wastewater.

[0027] The present invention has the following beneficial effects:

[0028] This invention utilizes traditional interfacial polymerization to prepare polyurea nanofiltration membranes. By selecting isocyanate monomers and amines with spatially twisted structures, more water channels can be provided in the prepared nanofiltration membrane. Compared with existing preparation techniques, this results in a composite membrane with higher permeation flux. Furthermore, the nanofiltration membrane preparation method provided by this invention is simple to operate and has promising prospects for industrial application. Attached Figure Description

[0029] Figure 1 This refers to the rejection rate of different salts by the high-flux polyurea acid-resistant nanofiltration membrane in Example 4 of this invention. Detailed Implementation

[0030] The technical solution of the present invention will be further defined below with reference to specific embodiments, but the scope of protection is not limited to the description.

[0031] Performance testing methods and conditions:

[0032] (1) The initial separation performance of the acid-resistant nanofiltration membrane for 2 g / L magnesium chloride solution was tested under the conditions of 1.0 MPa and 25 °C.

[0033] (2) After immersing the acid-resistant nanofiltration membrane in 20wt% concentrated sulfuric acid for 30 days, its separation performance for 2g / L magnesium chloride solution was tested at 1.0MPa and 25℃; then, after immersing the acid-resistant nanofiltration membrane in 20wt% concentrated sulfuric acid for 120 days, its separation performance for 2g / L magnesium chloride solution was tested under the same conditions.

[0034] Product source:

[0035] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0036] 4,4'-diisocyanate-5'-(4-isocyanate benzene) was prepared according to Synthesis Example 2 of JP2022173757A.

[0037] Example 1

[0038] A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane includes the following steps:

[0039] (1) Prepare an aqueous solution with 1.0 wt% 1,4,7,10-tetraazacyclododecane and 0.1 wt% 4-dimethylaminopyridine;

[0040] (2) Immerse the polysulfone-based membrane in the aqueous solution of (1) for 2 minutes, remove the membrane and remove excess water droplets;

[0041] (3) Prepare a chlorobenzene solution with a triphenylmethane triisocyanate concentration of 0.10 wt%;

[0042] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 2 min;

[0043] (5) Place the composite membrane obtained above into an oven and heat it at 50°C for 5 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0044] Example 2

[0045] A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane includes the following steps:

[0046] (1) Prepare an aqueous solution with a concentration of 1.0 wt% for 1,3-diaminoadamantane and a concentration of 0.5 wt% for pyrazine;

[0047] (2) Immerse the polysulfone-based membrane in the aqueous solution of (1) for 30 min, remove the membrane and remove excess water droplets;

[0048] (3) Prepare a chlorobenzene solution with a triphenylmethane triisocyanate concentration of 0.15 wt%;

[0049] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 30 min;

[0050] (5) Place the composite membrane obtained above into an oven and heat it at 80°C for 10 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0051] Example 3

[0052] A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane includes the following steps:

[0053] (1) Prepare an aqueous solution with 0.5 wt% 1,4,7,10-tetraazacyclododecane, 2.0 wt% polyethyleneimine, 0.2 wt% pyrazine, and 0.2 wt% 2,6-dimethylpyridine.

[0054] (2) Immerse the polysulfone-based membrane in the aqueous solution of (1) for 15 minutes, remove the membrane and remove excess water droplets;

[0055] (3) Prepare a chlorobenzene-benzene solution with a triphenylmethane triisocyanate concentration of 0.15 wt% (mass ratio 1:1);

[0056] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 20 min;

[0057] (5) Place the composite membrane obtained above into an oven and heat it at 50°C for 15 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0058] Example 4

[0059] A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane includes the following steps:

[0060] (1) Prepare an aqueous solution with 0.8 wt% 1,3-diaminoadamantane, 2.0 wt% polyethyleneimine, and 0.3 wt% triethylamine;

[0061] (2) Immerse the polysulfone-based membrane in the aqueous solution of (1) for 20 min, remove the membrane and remove excess water droplets;

[0062] (3) Prepare a chlorobenzene solution with a triphenylmethane triisocyanate concentration of 0.2 wt%;

[0063] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 20 min;

[0064] (5) Place the composite membrane obtained above into an oven and heat it at 70°C for 20 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0065] The separation performance of the prepared polyurea acid-resistant nanofiltration membrane was tested: the water permeation flux was 226 L / m³. -2 h -1 MPa -1 The magnesium chloride rejection rate was 98.3%; after soaking in 20 wt% concentrated sulfuric acid for 30 days, the water permeability was 299 Lm. -2 h - 1 MPa -1The magnesium chloride rejection rate was 97.9%; after soaking in 20 wt% concentrated sulfuric acid for 120 days, the water permeability was 413 Lm. -2 h -1 MPa -1 The retention rate of magnesium chloride was 96.7%.

[0066] As attached Figure 1 As shown, the acid-resistant nanofiltration membrane prepared in this embodiment (after being soaked in 20wt% concentrated acid for 120 days) has a retention rate of over 70% for magnesium chloride, magnesium sulfate, sodium sulfate and sodium chloride.

[0067] Example 5

[0068] A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane includes the following steps:

[0069] (1) Prepare an aqueous solution with 0.5 wt% 1,4,7,10-tetraazacyclododecane, 2.0 wt% polyethyleneimine, and 0.4 wt% pyrazine.

[0070] (2) Immerse the polyethersulfone base film in the aqueous solution of (1) for 20 min, remove the base film and remove excess water droplets;

[0071] (3) Prepare a chlorobenzene-benzene solution with a tetra(4-isocyanate benzene)methane concentration of 0.10 wt% (mass ratio 1:1);

[0072] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 15 min;

[0073] (5) Place the composite membrane obtained above into an oven and heat it at 60°C for 20 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0074] Example 6

[0075] A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane includes the following steps:

[0076] (1) Prepare an aqueous solution with a concentration of 0.5 wt% for 1,3-diaminoadamantane, 2.5 wt% for polyethyleneimine, and 0.35 wt% for triethylamine;

[0077] (2) Immerse the polyethersulfone base film in the aqueous solution of (1) for 20 min, remove the base film and remove excess water droplets;

[0078] (3) Prepare a chlorobenzene-benzene organic solution with a tetra(4-isocyanate benzene)methane concentration of 0.15 wt% (mass ratio 1:1);

[0079] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 30 min;

[0080] (5) Place the composite membrane obtained above into an oven and heat it at 60°C for 20 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0081] Example 7

[0082] A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane includes the following steps:

[0083] (1) Prepare an aqueous solution with 0.4 wt% 1,4,7,10-tetraazacyclododecane, 2.0 wt% polyethyleneimine, and 0.25 wt% 2,6-dimethylpyridine;

[0084] (2) Immerse the polyacrylonitrile base film in the aqueous solution of (1) for 5 minutes, remove the base film and remove excess water droplets;

[0085] (3) Prepare a chlorobenzene-benzene solution with a concentration of 0.08 wt% of 4,4'-diisocyanate-5'-(4-isocyanate benzene) (mass ratio 1:1);

[0086] (4) Immerse the base film of (2) in the organic phase solution of (3) and react for 10 min;

[0087] (5) Place the composite membrane obtained above into an oven and heat it at 60°C for 15 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0088] Example 8

[0089] A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane includes the following steps:

[0090] (1) Prepare an aqueous solution with 0.8 wt% 1,3-diaminoadamantane, 2.0 wt% polyethyleneimine, 0.2 wt% triethylamine, and 0.15 wt% 4,dimethylaminopyridine;

[0091] (2) Immerse the polyacrylonitrile base film in the aqueous solution of (1) for 5 minutes, remove the base film and remove excess water droplets;

[0092] (3) Prepare a chlorobenzene-benzene (mass ratio 1:1) solution with a 4,4'-diisocyanate-5'-(4-isocyanate benzene) concentration of 0.08 wt%;

[0093] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 30 min;

[0094] (5) Place the composite membrane obtained above into an oven and heat it at 70°C for 15 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

[0095] Comparative Example (Comparative Example 4)

[0096] A method for preparing a polyurea acid-resistant nanofiltration membrane includes the following steps:

[0097] (1) Prepare an aqueous solution with a polyethyleneimine concentration of 2.8 wt% and a triethylamine concentration of 0.3 wt%;

[0098] (2) Immerse the polysulfone-based membrane in the aqueous solution of (1) for 20 min, remove the membrane and remove excess water droplets;

[0099] (3) Prepare a chlorobenzene solution with a concentration of 0.2 wt% for isophthalic diisocyanate;

[0100] (4) Immerse the base film from (2) in the organic phase solution from (3) and react for 20 min;

[0101] (5) Place the composite membrane obtained above into an oven and heat it at 70°C for 20 minutes to obtain a polyurea acid-resistant nanofiltration membrane.

[0102] The separation performance test results of the polyurea acid-resistant nanofiltration membranes prepared in the examples and comparative examples are shown in the table below.

[0103]

Claims

1. A method for preparing a high-flux polyurea acid-resistant nanofiltration membrane, characterized in that, It includes the following specific steps: (1) Prepare aqueous solutions of amine monomer and catalyst, and prepare organic solutions of isocyanate; (2) Immerse the base membrane in the aqueous solution for a certain period of time, then remove the base membrane and remove the excess aqueous phase; (3) Immerse the base membrane in an organic phase solution for a certain period of time; (4) The composite membrane obtained above is heated to obtain a high-flux polyurea acid-resistant nanofiltration membrane; The isocyanate is one or more of triphenylmethane triisocyanate, tetra(4-isocyanate benzene)methane, and 4,4'-diisocyanate-5'-(4-isocyanate benzene).

2. The preparation method according to claim 1, characterized in that, The amine monomer is one or more selected from 1,4,7,10-tetraazacyclododecane, 1,3-diaminoadamantane, and polyethyleneimine; preferably, the concentration of the amine monomer is 0.05-3 wt%.

3. The preparation method according to claim 1, characterized in that, The catalyst is one or more of 4-dimethylaminopyridine, pyrazine, 2,6-dimethylpyridine and triethylamine; preferably, the concentration of the catalyst is 0.01-0.5 wt%.

4. The preparation method according to claim 1, characterized in that, The solvent for the organic phase solution is chlorobenzene or a chlorobenzene-benzene mixture, preferably a chlorobenzene-benzene mixture, with a mass ratio of 1:1 to 5:

1.

5. The preparation method according to claim 1, characterized in that, The concentration of the isocyanate in the organic phase solution is 0.05wt%-0.2wt%.

6. The preparation method according to claim 1, characterized in that, The base membrane is immersed in aqueous solution and organic solution for 2-30 minutes each.

7. The preparation method according to claim 1, characterized in that, The composite membrane in step (4) is heated at 50-80℃ for 5-20 minutes to obtain a high-flux polyurea acid-resistant nanofiltration membrane.

8. The high-flux polyurea acid-resistant nanofiltration membrane prepared by the preparation method according to any one of claims 1-7.

9. The application of the high-flux polyurea acid-resistant nanofiltration membrane as described in claim 8 in the field of wastewater treatment.

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