A method for preparing a quaternized and sulfonated polyether sulfone ultrafiltration membrane

Abstract

The application discloses a preparation method of a quaternary ammonium and sulfonated polyether sulfone ultrafiltration membrane, and the preparation method comprises the following steps: 1) sulfonating chloromethylated polyether sulfone by using chlorosulfonic acid as a sulfonating reagent to prepare sulfonated polyether sulfone; 2) preparing sulfonated and chloromethylated polyether sulfone by using 1,4-dichloromethoxy butane as a chloromethylating reagent and concentrated sulfuric acid as a solvent; 3) dissolving the sulfonated and chloromethylated polyether sulfone and a pore-forming agent in a solvent, scraping a film after preparing a casting solution; and 4) immersing the finished membrane in a trimethylamine solution by using trimethylamine as a quaternary ammonium reagent to obtain the quaternary ammonium and sulfonated polyether sulfone ultrafiltration membrane. The prepared ultrafiltration membrane has the advantages of high flux and anti-pollution due to the introduction of quaternary ammonium groups and sulfonated groups.

Description

Technical Field

[0001] This invention belongs to the field of membrane material technology, specifically relating to a method for preparing quaternized and sulfonated polyethersulfone ultrafiltration membranes. Background Technology

[0002] As a type of polymer chemical material, membranes mainly separate macromolecules through physical means, and have functions of separation, concentration, purification and desalination. At the same time, they also have obvious technical advantages: simple process, easy to scale up, high throughput, no phase change during use, good chemical stability, and are widely used in pharmaceutical products, food industry and wastewater treatment.

[0003] Currently, the main membrane materials for ultrafiltration membranes include polystyrene (PS), polyethersulfone (PES), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF). Single-component ultrafiltration membranes have certain drawbacks during use, such as poor mechanical properties and susceptibility to fouling. Therefore, finding a suitable membrane process to improve the various properties of the membrane is crucial.

[0004] Polyethersulfone (PES) is a polymer containing aromatic rings, possessing excellent mechanical properties, high thermal stability, good hydrolysis resistance, and chemical stability. Ultrafiltration membranes based on PES have seen significant development. However, single-component PES ultrafiltration membranes suffer from poor hydrophilicity, readily adsorbing organic pollutants, leading to rapid flux decline and poor flux recovery. These drawbacks limit the application of PES ultrafiltration membranes. Therefore, modification methods can be used to introduce suitable chemical groups into the membrane material for physicochemical modification, thereby improving the membrane's water flux, mechanical stability, chemical stability, and antifouling performance in practical applications. In particular, hydrophilic modification and increased surface antibacterial properties can reduce the possibility of bacterial contamination leading to polysaccharide, peptide, and protein contamination, enabling PES to meet various practical application requirements.

[0005] Adding suitable modifiers and optimizing membrane processes to give products excellent and long-lasting antibacterial properties while also having high flux has always been an important direction in ultrafiltration membrane research. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a quaternized and sulfonated polyethersulfone ultrafiltration membrane. The resulting ultrafiltration membrane has electrically charged groups grafted onto both sides of the polyethersulfone, exhibiting excellent hydrophilicity and antibacterial effects, high flux, and antifouling properties.

[0007] A method for preparing a quaternized and sulfonated polyethersulfone ultrafiltration membrane includes the following steps:

[0008] (1) Preparation of sulfonated polyethersulfone

[0009] Dry polyethersulfone (PES) was dissolved in concentrated sulfuric acid until a homogeneous solution was formed. Chlorosulfonic acid was then slowly added dropwise while stirring and controlling the reaction temperature. After the reaction was completed, the solution was poured into ice water to precipitate a white filamentous solid. The white filamentous solid was washed with deionized water until the pH was neutral. The solution was then dried to obtain sulfonated polyethersulfone (SPES).

[0010] (2) Preparation of chloromethylated SPES

[0011] Take the SPES obtained in step 1), add concentrated sulfuric acid, and stir thoroughly to dissolve the SPES completely; use 1,4-dichloromethoxybutane (BCMB) as the chloromethylating agent to carry out the chloromethylation reaction; precipitate a white filamentous solid in ice water after the reaction, wash the white filamentous solid with deionized water until the pH is neutral; dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0012] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0013] The CMSPES obtained in step 2) was dissolved in N,N-dimethylacetamide (DMAC), a pore-forming agent was added, and the solution was fully dissolved to obtain a uniform and stable casting solution. The solution was allowed to stand to remove bubbles. Then, the membrane was scraped onto a glass plate and immersed in a coagulation bath to prepare a sulfonated CMPES ultrafiltration membrane by a solvent-induced phase inversion method.

[0014] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0015] The sulfonated CMPES ultrafiltration membrane obtained in step 3) was immersed in a 30% trimethylamine solution; then rinsed with deionized water and stored in deionized water; a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structure in the side chain was obtained.

[0016] Furthermore, the reaction temperature in step (1) is 0℃-30℃.

[0017] Furthermore, the reaction time in step (1) is more than 1 hour.

[0018] Furthermore, the temperature of the coagulation bath in step (3) is 0℃-40℃, and the coagulation bath time is controlled to be 0-5min.

[0019] Furthermore, the solvent in step (3) can be one or more of the following: dimethylformamide (DMF), dimethylacetamide (DMAC), N,N-dimethylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0020] Furthermore, the pore-forming agent in step (3) can be one or a mixture of any combination of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, ethanol, glycerol, ethylene glycol, glycerol, and acetone.

[0021] Furthermore, in step (3), the mass ratio of CMSPES, solvent, and pore-forming agent is 15%–25%, 67%–80%, and 5%–15%, respectively.

[0022] Furthermore, in step 4), the sulfonated CMPES ultrafiltration membrane is soaked in a 30% trimethylamine solution for 12 hours.

[0023] This invention first grafts negatively charged sulfonic acid groups onto a polymer, followed by the grafting of chloromethyl groups. The chloromethyl groups serve as reaction sites, allowing for the grafting of different chemical reactants (not limited to quaternary ammonium groups) to impart different properties. The ultrafiltration membrane of this invention simultaneously possesses sulfonic acid and quaternary ammonium groups. The sulfonic acid groups ensure the membrane's hydrophilicity, resulting in good water flux, while the quaternary ammonium groups provide antibacterial properties. Furthermore, the insufficient hydrophilicity of the quaternary ammonium groups is compensated for by the sulfonic acid groups, allowing the membrane to combine the advantages of both groups.

[0024] This invention prepares a polyethersulfone ultrafiltration membrane with quaternized side chains and sulfonated structures. The introduction of quaternary ammonium groups enhances the antibacterial and antifouling properties of the ultrafiltration membrane, while sulfonic acid groups compensate for the insufficient hydrophilicity of quaternary ammonium salts, enabling it to resist protein adsorption and also contributing to improved antibacterial activity. This results in an ultrafiltration membrane exhibiting both high flux and excellent antifouling properties. Reducing the amount of chlorosulfonic acid and the temperature increases the BSA rejection rate of the composite ultrafiltration membrane while maintaining a relatively stable pure water flux. Detailed Implementation

[0025] The technical solutions of the present invention will be further described below with reference to specific embodiments. However, the scope of protection of the present invention is not limited to the content described herein.

[0026] A method for preparing a quaternized and sulfonated polyethersulfone ultrafiltration membrane includes the following steps:

[0027] (1) Preparation of sulfonated polyethersulfone

[0028] A certain amount of dried polyethersulfone (PES) was dissolved in an appropriate amount of concentrated sulfuric acid in a container. After a homogeneous solution was formed, a certain amount of chlorosulfonic acid was slowly added dropwise while the reaction temperature was controlled and the mixture was stirred. After the reaction was completed, the solution was poured into rapidly stirred ice water to precipitate a white filamentous solid. The solid was washed with deionized water until neutral. After drying, sulfonated polyethersulfone (SPES) was obtained.

[0029] (2) Preparation of chloromethylated SPES

[0030] SPES was dissolved in concentrated sulfuric acid in a container by thorough stirring. A chloromethylation reaction was then carried out using 1,4-dichloromethoxybutane (BCMB) as the chloromethylating agent. A white filamentous solid precipitated from the reaction solution in ice water, which was washed with deionized water until neutral. The precipitated solid was then dried to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0031] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0032] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC), and a certain amount of pore-forming agent was added. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was scraped onto a glass plate and immersed in a coagulation bath to prepare a sulfonated CMPES ultrafiltration membrane via a solvent-induced phase inversion method.

[0033] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0034] The finished membrane was immersed in a 30% trimethylamine solution for a period of time. Afterwards, it was rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0035] The following formula is the reaction formula for the preparation of quaternized and sulfonated polyether sulfone.

[0036]

[0037] The chemical formulas of the prepared quaternized and sulfonated polyether sulfones are as follows:

[0038]

[0039] Example 1

[0040] (1) Preparation of sulfonated polyethersulfone

[0041] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 8mL of chlorosulfonic acid to initiate a sulfonation reaction, controlling the reaction temperature at 10℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0042] (2) Preparation of chloromethylated SPES

[0043] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask, stirring thoroughly until the SPES is completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) dropwise to initiate the chloromethylation reaction. Control the reaction temperature at 10°C and stir uniformly for 1 hour. Then, slowly add ice water to precipitate a white precipitate, which is washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0044] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0045] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC) and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 18%:76%:6%.

[0046] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0047] The finished membrane was immersed in a 30% trimethylamine solution for 12 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0048] Example 2

[0049] (1) Preparation of sulfonated polyethersulfone

[0050] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 6.4mL of chlorosulfonic acid to initiate a sulfonation reaction, controlling the reaction temperature at 10℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0051] (2) Preparation of chloromethylated SPES

[0052] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask, stirring thoroughly until the SPES is completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) dropwise to initiate the chloromethylation reaction. Control the reaction temperature at 10°C and stir uniformly for 1 hour. Then, slowly add ice water to precipitate a white precipitate, which is washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0053] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0054] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC) and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 18%:76%:6%.

[0055] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0056] The finished membrane was immersed in a 30% trimethylamine solution for 12 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0057] Example 3

[0058] (1) Preparation of sulfonated polyethersulfone

[0059] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 3.2mL of chlorosulfonic acid to initiate a sulfonation reaction, controlling the reaction temperature at 10℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0060] (2) Preparation of chloromethylated SPES

[0061] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask, stirring thoroughly until the SPES is completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) dropwise to initiate the chloromethylation reaction. Control the reaction temperature at 10°C and stir uniformly for 1 hour. Then, slowly add ice water to precipitate a white precipitate, which is washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0062] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0063] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC) and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 18%:76%:6%.

[0064] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0065] The finished membrane was immersed in a 30% trimethylamine solution for 12 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0066] Example 4

[0067] (1) Preparation of sulfonated polyethersulfone

[0068] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 8mL of chlorosulfonic acid to initiate the sulfonation reaction, controlling the reaction temperature at 0℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0069] (2) Preparation of chloromethylated SPES

[0070] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask, stirring thoroughly until the SPES is completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) dropwise to initiate the chloromethylation reaction. Control the reaction temperature at 10°C and stir uniformly for 1 hour. Then, slowly add ice water to precipitate a white precipitate, which is washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0071] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0072] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 16%:75%:9%.

[0073] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0074] The finished membrane was immersed in a 30% trimethylamine solution for 12 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0075] Example 5

[0076] (1) Preparation of sulfonated polyethersulfone

[0077] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 6.4mL of chlorosulfonic acid to initiate a sulfonation reaction, controlling the reaction temperature at 0℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0078] (2) Preparation of chloromethylated SPES

[0079] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask with thorough stirring until completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) to initiate the chloromethylation reaction at 10°C. After stirring the mixture uniformly for 1 hour, slowly add ice water to precipitate a white precipitate, which is then washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0080] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0081] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 16%:75%:9%.

[0082] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0083] The finished membrane was immersed in a 30% trimethylamine solution for 12 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0084] Example 6

[0085] (1) Preparation of sulfonated polyethersulfone

[0086] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 3.2mL of chlorosulfonic acid to initiate the sulfonation reaction, controlling the reaction temperature at 0℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0087] (2) Preparation of chloromethylated SPES

[0088] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask, stirring thoroughly until the SPES is completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) dropwise to initiate the chloromethylation reaction. Control the reaction temperature at 10°C and stir uniformly for 1 hour. Then, slowly add ice water to precipitate a white precipitate, which is washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0089] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0090] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 16%:75%:9%.

[0091] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0092] The finished membrane was immersed in a 30% trimethylamine solution for 12 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0093] Example 7

[0094] (1) Preparation of sulfonated polyethersulfone

[0095] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 6.4mL of chlorosulfonic acid to initiate a sulfonation reaction, controlling the reaction temperature at 10℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0096] (2) Preparation of chloromethylated SPES

[0097] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask, stirring thoroughly until the SPES is completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) dropwise to initiate the chloromethylation reaction. Control the reaction temperature at 10°C and stir uniformly for 1 hour. Then, slowly add ice water to precipitate a white precipitate, which is washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0098] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0099] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 20%:75%:5%.

[0100] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0101] The finished membrane was immersed in a 30% trimethylamine solution for 2 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0102] Example 8

[0103] (1) Preparation of sulfonated polyethersulfone

[0104] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 6.4mL of chlorosulfonic acid to initiate a sulfonation reaction, controlling the reaction temperature at 10℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0105] (2) Preparation of chloromethylated SPES

[0106] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask, stirring thoroughly until the SPES is completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) dropwise to initiate the chloromethylation reaction. Control the reaction temperature at 10°C and stir uniformly for 1 hour. Then, slowly add ice water to precipitate a white precipitate, which is washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0107] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0108] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 20%:75%:5%.

[0109] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0110] The finished membrane was immersed in a 30% trimethylamine solution for 4 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0111] Example 9

[0112] (1) Preparation of sulfonated polyethersulfone

[0113] Weigh 10g of dried PES, add 50mL of 94% sulfuric acid, and place the mixture in a 250mL three-necked flask. Stir to dissolve (800rpm) until a homogeneous solution is formed. Slowly add 6.4mL of chlorosulfonic acid to initiate a sulfonation reaction, controlling the reaction temperature at 10℃. After reacting for 2 hours, slowly add ice water to precipitate a white precipitate. Wash the solid with deionized water until neutral. Dry to obtain sulfonated polyether sulfone (SPES).

[0114] (2) Preparation of chloromethylated SPES

[0115] Weigh SPES and dissolve it in 50 ml of concentrated sulfuric acid (94%) in a three-necked flask, stirring thoroughly until the SPES is completely dissolved. Slowly add 8 ml of 1,4-dichloromethoxybutane (BCMB) dropwise to initiate the chloromethylation reaction. Control the reaction temperature at 10°C and stir uniformly for 1 hour. Then, slowly add ice water to precipitate a white precipitate, which is washed with deionized water until neutral. Dry to obtain chloromethylated and sulfonated polyethersulfone (CMSPES).

[0116] (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes

[0117] The obtained CMSPES was dissolved in N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was added simultaneously. After complete dissolution, a homogeneous and stable casting solution was prepared and allowed to stand to remove bubbles. Subsequently, the membrane was coated onto a glass plate and immersed in a coagulation bath to prepare chloromethylated and sulfonated polyethersulfone ultrafiltration membranes via a solvent-inducible phase inversion method. The mass ratio of CMSPES, N,N-dimethylacetamide (DMAC), and polyethylene glycol (PEG) was 20%:75%:5%.

[0118] (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes

[0119] The finished membrane was immersed in a 30% trimethylamine solution for 8 hours. It was then rinsed thoroughly with deionized water and stored in deionized water. This yielded a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structures in its side chains.

[0120] Comparative Example 1

[0121] Take 10g of polyethersulfone, 45g of N,N-dimethylacetamide, and 5g of polyethylene glycol. Stir in a water bath at 60℃ for 3 hours until the polyethersulfone is fully dissolved. After complete degassing, scrape the membrane to obtain a polyethersulfone ultrafiltration membrane.

[0122] The ultrafiltration membranes prepared in Comparative Example 1 and Examples 1-9 were stored in water, and the rejection rate of 1000 mg / L bovine serum albumin (BSA) and the pure water flux of the membranes were tested at 0.4 MPa. Using *E. coli* as an indicator bacterium, the filtrate from the prepared membranes was cultured, and the number of *E. coli* in the filtrate was calculated using the plate count method, and the antibacterial rate was also calculated. The final results are shown in Table 1 below.

[0123] Table 1

[0124]

[0125] As shown in the table above, the antibacterial rate of quaternized and sulfonated polyethersulfone ultrafiltration membranes is higher than that of pure PES membranes, indicating that quaternized and sulfonated polyethersulfone ultrafiltration membranes have better antifouling performance. The introduction of quaternary ammonium groups can improve the membrane's antifouling performance, and the reduction of chlorosulfonic acid content and temperature can increase the BSA rejection rate of the composite ultrafiltration membrane while maintaining a relatively stable pure water flux.

[0126] Different sulfonation reaction times correspond to different degrees of reaction, i.e., different degrees of sulfonation. The amount of sulfonating reagent also affects the degree of sulfonation. This invention can change the degree of PES sulfonation by controlling the reaction temperature and the amount of sulfonating reagent, thereby altering the degree of chloromethylation of PES. During the quaternization process after film formation, the degree of quaternization is also changed. Therefore, the hydrophilicity and antibacterial properties of the membrane can be easily controlled by varying the temperature and the amount of sulfonating reagent to meet specific requirements.

[0127] In summary, the technical solution of this invention is used to prepare polyethersulfone ultrafiltration membranes with quaternized side chains and sulfonated structures. The introduction of quaternary ammonium groups enhances the antibacterial effect of the ultrafiltration membrane, while sulfonic acid groups can compensate for the insufficient hydrophilicity of quaternary ammonium salts, enabling them to resist protein adsorption and also contributing to improved antibacterial activity. This results in ultrafiltration membranes possessing both high flux and excellent antifouling properties.

[0128] The above description is merely an embodiment of the invention's technical content. Any changes or modifications made by those skilled in the art using this invention are within the scope of the patent claims of this invention, and are not limited to those disclosed in the embodiments.

Claims

1. A method for preparing a quaternized and sulfonated polyethersulfone ultrafiltration membrane, characterized in that, The preparation method includes the following steps: (1) Preparation of sulfonated polyethersulfone Dry polyethersulfone (PES) was dissolved in concentrated sulfuric acid and stirred into a homogeneous solution. Chlorosulfonic acid was then slowly added dropwise while stirring and controlling the reaction temperature. After the reaction was completed, the solution was poured into ice water to precipitate a white filamentous solid. The white filamentous solid was then washed with deionized water until the pH was neutral. Drying yields sulfonated polyether sulfone SPES; (2) Preparation of chloromethylated SPES Take the SPES obtained in step 1), add concentrated sulfuric acid, and stir thoroughly until the SPES is completely dissolved; use 1,4-dichloromethoxybutane BCMB as a chloromethylating agent to carry out a chloromethylation reaction; precipitate a white filamentous solid in ice water after the reaction, wash the white filamentous solid with deionized water until pH neutral; dry to obtain chloromethylated and sulfonated polyethersulfone CMSPES; (3) Preparation of chloromethylated and sulfonated polyethersulfone ultrafiltration membranes The CMSPES obtained in step 2) was dissolved in a solvent, a pore-forming agent was added, and a uniform and stable casting solution was obtained after complete dissolution. The solution was then allowed to stand to remove bubbles. Subsequently, the membrane was scraped onto a glass plate and immersed in a coagulation bath to prepare a sulfonated CMPES ultrafiltration membrane by a non-solvent-induced phase inversion method. (4) Preparation of quaternized and sulfonated polyethersulfone ultrafiltration membranes The sulfonated CMPES ultrafiltration membrane obtained in step 3) was immersed in a 30% trimethylamine solution; rinsed with deionized water and stored in deionized water; a polyethersulfone ultrafiltration membrane with quaternary ammonium groups and sulfonated structure in the side chain was obtained. The solvent in step (3) is one or more of the following: dimethylformamide (DMF), dimethylacetamide (DMAC), N,N-dimethylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO). The pore-forming agent in step (3) is one or a mixture of any combination of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, glycerin, ethylene glycol, glycerol, and acetone. The ratio of chlorosulfonic acid to 1,4-dichloromethoxybutane is 3.2 ml: 8 ml or 6.4 ml: 8 ml.

2. The method for preparing the quaternized and sulfonated polyethersulfone ultrafiltration membrane according to claim 1, characterized in that, The reaction temperature in step (1) is controlled between 0°C and 30°C.

3. The method for preparing quaternized and sulfonated polyethersulfone ultrafiltration membranes according to claim 1, characterized in that, The reaction time in step (1) is at least 1 hour.

4. The method for preparing the quaternized and sulfonated polyethersulfone ultrafiltration membrane according to claim 1, characterized in that, In step (3), the temperature of the coagulation bath is 0℃-40℃, and the coagulation time is controlled to be 0-5min.

5. The method for preparing the quaternized and sulfonated polyethersulfone ultrafiltration membrane according to claim 1, characterized in that, The mass ratio of CMSPES, solvent, and porogen in step (3) is 15%–25%, 67%–80%, and 5%–15%, respectively.

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