CN105903359A - Chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane and preparation method thereof - Google Patents

Abstract

The invention provides a chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane and a preparation method thereof. Firstly, chitosan is used for covalent functionalization of graphene oxide to prepare chitosan-graphene oxide; the chitosan-graphene oxide is dispersed in an organic solvent in an ultrasonic mode, then polyvinylidene fluoride and a pore-foaming agent are added and stirred at certain temperature to be evenly dissolved to obtain a membrane casting solution, water serves as a coagulating bath, and the chitosan-graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane is prepared through the immerged phase-inversion process. The chitosan-graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane prepared through the method improves dispersibility of graphene oxide in a membrane matrix, and compared with a graphene oxide/polyvinylidene fluoride ultrafiltration membrane, hydrophilicity, water flux, antifouling property and other aspects are greatly improved.

Description

A chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane and its preparation method

technical field

The invention belongs to the technical field of ultrafiltration membrane separation, and in particular relates to a chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane and a preparation method thereof.

Background technique

Polyvinylidene fluoride is widely used in the preparation of ultrafiltration membranes because of its good film-forming properties, such as good mechanical properties, high temperature resistance, and chemical resistance. However, since polyvinylidene fluoride itself is a hydrophobic polymer, the prepared polyvinylidene fluoride ultrafiltration membrane has poor hydrophilicity, resulting in low water flux, and pollutants are easily adsorbed and deposited on the membrane surface or membrane during the filtration process. Pores, the separation performance of the membrane is greatly reduced, which seriously restricts the application of ultrafiltration membranes in industry.

Improving the hydrophilicity of polyvinylidene fluoride ultrafiltration membranes to enhance the separation performance and anti-fouling performance of the membranes is currently a research hotspot in the field of ultrafiltration membrane separation. Blending modification is to directly mix the modifier into the casting solution to prepare the hybrid membrane. Because of its simple operation and wide application range, it is the most common membrane modification method. In recent years, graphene oxide has been widely used to modify polyvinylidene fluoride ultrafiltration membranes due to its rich hydrophilic groups, such as carboxyl, hydroxyl and epoxy groups. Graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membranes were prepared by adding graphene oxide directly into the casting solution by blending modification. Compared with the pure polyvinylidene fluoride ultrafiltration membrane, the prepared graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane has significantly improved membrane properties such as hydrophilicity, water flux and anti-fouling. However, due to the π-π conjugation between graphene oxide sheets, graphene oxide is particularly easy to aggregate, resulting in severe uneven dispersion of graphene oxide in the polyvinylidene fluoride film matrix, mostly in an aggregated state, which makes graphite oxide Alkenes are severely constrained to improve the hydrophilicity of polyvinylidene fluoride ultrafiltration membranes.

Contents of the invention

The purpose of the present invention is to improve the dispersibility of graphene oxide in the polyvinylidene fluoride ultrafiltration membrane matrix, to fully exert the strong hydrophilicity of graphene oxide, and to improve the performance of graphene oxide/polyvinylidene fluoride ultrafiltration membrane, Provided are a chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane and a preparation method thereof. The preparation method is simple, and the prepared hybrid ultrafiltration membrane has excellent performance.

To achieve the above object, the present invention adopts the following technical solutions:

A chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane, by weight percentage, the raw materials of the ultrafiltration membrane include polyvinylidene fluoride 16-20%, porogen 0.3-5%, organic solvent 78-82% and chitosan-graphene oxide; wherein, the weight of chitosan-graphene oxide is 0.2-2% of the weight of polyvinylidene fluoride.

A further improvement of the present invention is that the polyvinylidene fluoride is pre-dried in a vacuum oven at 110° C. for 10-15 hours before use.

The further improvement of the present invention is that the porogen is one of polyvinylpyrrolidone, polyethylene glycol and polyvinyl alcohol.

A further improvement of the present invention is that the organic solvent is one of dimethylformamide, dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.

The further improvement of the present invention is that the chitosan-graphene oxide has a lamellar structure with a thickness of 2-3 nm.

A preparation method of chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane, comprising the following steps:

Chitosan-graphene oxide is added in the organic solvent, after ultrasonic at room temperature, obtain chitosan-graphene oxide dispersion liquid; Add polyvinylidene fluoride and porogen to chitosan-graphene oxide dispersion liquid, Stir and dissolve evenly, let it stand for defoaming, and obtain the casting solution, and then scrape the casting solution evenly on the polyester non-woven fabric to form a casting layer on the polyester non-woven fabric, and then immediately immerse it in the coagulation bath, wait for After curing into a film, the film is peeled off, continued to be soaked in deionized water, and the remaining solvent is removed to obtain a chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane; wherein, by weight percentage, polyvinylidene fluoride The content of vinyl fluoride is 16-20%, the porogen is 0.3-5%, the organic solvent is 78-82%, and the weight of chitosan-graphene oxide is 0.2-2% of the weight of polyvinylidene fluoride.

A further improvement of the present invention is that the chitosan-graphene oxide is prepared by the following method:

dissolving chitosan in glacial acetic acid solution with a volume fraction of 1-3% to prepare chitosan glacial acetic acid solution with a mass fraction of 1-3%;

Add graphene oxide into deionized water, and ultrasonicate at room temperature for 1 hour to obtain a graphene oxide dispersion; add the graphene oxide dispersion to chitosan glacial acetic acid solution under stirring, stir at room temperature for 24 hours, and then centrifugally wash with glacial acetic acid Several times, remove unreacted chitosan, then centrifuge and wash several times with deionized water, and vacuum dry to obtain chitosan-graphene oxide; wherein, the mass ratio of graphene oxide to chitosan is 1 : 10; Gained chitosan-graphene oxide is a lamellar structure with a thickness of 2-3nm.

The further improvement of the present invention is that the ultrasonic time is 1h, the stirring temperature is 40-60°C, and the stirring time is 24-36h; the standing defoaming temperature is 40-60°C, and the standing defoaming temperature The time is 12-24h.

The further improvement of the present invention is that the coagulation bath is deionized water, and the water temperature is 20-30°C; the time for immersing in the coagulation bath is 15-20min; the porogen is polyvinylpyrrolidone, polyethylene glycol , one in polyvinyl alcohol; the organic solvent is one in dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide.

The further improvement of the present invention lies in that the thickness of the casting layer is 130-180 μm; the soaking time in deionized water is 24-48 hours.

Compared with the prior art, the present invention has the beneficial effects:

The invention ultrasonically disperses chitosan-graphene oxide in an organic solvent, then adds polyvinylidene fluoride and a porogen, stirs and dissolves at a certain temperature to obtain a casting film uniformly, uses water as a coagulation bath, and adopts immersion precipitation phase inversion Chitosan-graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane was prepared by this method. The key of the present invention is to use chitosan to covalently functionalize graphene oxide, improve the dispersion of graphene oxide in polyvinylidene fluoride membrane matrix, and further improve the performance of graphene oxide/polyvinylidene fluoride ultrafiltration membrane . The preparation method of the invention is simple, and the obtained hybrid ultrafiltration membrane has excellent performance, and preferably solves the problem of graphene oxide aggregation in the polyvinylidene fluoride membrane matrix.

Compared with the polyvinylidene fluoride membrane filled with unfunctionalized graphene oxide, the membrane obtained by this method has significantly improved hydrophilicity, water flux and anti-pollution.

Further, when polyvinylpyrrolidone is used as a porogen, dimethylacetamide is used as an organic solvent, and the amount of chitosan-graphene oxide added is 0.6%, the chitosan-functionalized graphene oxide/polypyrene oxide obtained Compared with the graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane, the water contact angle of the membrane decreased from 73.9° to 64.2°; the pure water flux of the membrane decreased from 576.92L/m ² h It increased to 737.18L/m ² h; the flux recovery rate of the membrane increased from 63.89% to 69.57%, and the BSA flux decay rate of the membrane decreased from 83.29% to 79.3%.

detailed description

How to prepare the chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane and the performance of the prepared membrane will be described below in conjunction with specific examples.

In the following examples, polyvinylidene fluoride was purchased from Solvay Co., Ltd. of the United States, and the model was Solvay-1015; graphene oxide was purchased from Nanjing Pioneer Nano Technology Co., Ltd.

Example 1

1) take 3g chitosan and be dissolved in 147g volume fraction and be made into the chitosan glacial acetic acid solution that mass fraction is 2% in the glacial acetic acid solution of 2%, then add 0.3g graphene oxide to deionized water, under room temperature Ultrasound for 1h to obtain a uniform graphene oxide dispersion;

Slowly add the graphene oxide dispersion into the chitosan glacial acetic acid solution dropwise while stirring, stir at room temperature for 24 hours, and wash several times with glacial acetic acid after the reaction to remove unreacted chitosan sugar, and then centrifuged and washed several times with deionized water, and vacuum-dried at 60° C. for 24 hours to prepare chitosan-graphene oxide, which is a nanocomposite.

2) Prepare 30 g of casting solution: weigh 0.036 g of chitosan-graphene oxide, add 23.064 g of dimethylacetamide, and ultrasonicate for 1 hour at room temperature to obtain a uniform chitosan-graphene oxide dispersion;

Weigh 6g of polyvinylidene fluoride in sequence (dried in vacuum at 110°C for 12h before use), add 0.9g of polyvinylpyrrolidone (molecular weight 58000g/mol) into the above chitosan-graphene oxide dispersion, and stir at 60°C for 24h , and then stand at a constant temperature at 60 ° C for 12 hours to obtain the casting solution, and then scrape the casting solution evenly on the polyester non-woven fabric with a scraper to form a cast layer, the thickness of the cast layer is 150 ± 10 μm, Then immediately put it into deionized water at 25°C, peel off the film from the glass plate after 15 minutes, and continue soaking in deionized water for 48 hours to completely remove the residual solvent, and obtain chitosan functionalized graphene oxide/polyvinylidene fluoride Ethylene hybrid ultrafiltration membrane.

Comparative example 1

The difference from Example 1 is that non-functionalized graphene oxide is added to the casting solution. The specific operation is as follows: prepare 30 g of casting liquid, weigh 0.036 g of graphene oxide, add 23.064 g of dimethylacetamide, and ultrasonicate for 1 h at room temperature to obtain a uniform dispersion of graphene oxide; successively weigh 6 g of polyvinylidene fluoride ( Vacuum drying at 110°C for 12h), 0.9g of polyvinylpyrrolidone (molecular weight: 58000g/mol) was added to the above graphene oxide dispersion, stirred at 60°C for 24h, then left at a constant temperature of 60°C for defoaming for 12h, scraped evenly on the Form a casting layer on polyester non-woven fabric, the thickness of the casting layer is 150±10μm, then immediately put it into deionized water at 25°C, peel off the film from the glass plate after 15min, and continue soaking in deionized water for 48h, The residual solvent was completely removed to prepare a graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane.

Comparative example 2

The difference with Example 1 is that no chitosan-graphene oxide is added in the casting solution. The specific operation is as follows: Prepare 30g of casting solution, weigh 6g of polyvinylidene fluoride (dried in vacuum at 110°C for 12h before use), add 0.9g of polyvinylpyrrolidone (molecular weight: 58000g/mol) into 23.1g of dimethylacetamide , Stir at 60°C for 24 hours, then stand at 60°C for 12 hours, scrape evenly on the polyester non-woven fabric with a scraper to form a cast layer, the thickness of the cast layer is 150±10μm, and then put it in 25°C immediately After 15 minutes, the membrane was peeled off from the glass plate, and then soaked in deionized water for 48 hours to completely remove the residual solvent and obtain a pure polyvinylidene fluoride ultrafiltration membrane.

The hydrophilicity of the prepared membrane was measured with a water contact angle measuring instrument, and the water flux, flux recovery rate and flux decay rate of the membrane were measured with a dead-end stirred tank filter device. The results are shown in Table 1.

Table 1 Performance comparison of three different membranes

It can be seen from Table 1 that the hydrophilicity, water flux and anti-pollution properties of polyvinylidene fluoride ultrafiltration membranes added with chitosan functionalized graphene oxide are compared with those of polyvinylidene fluoride ultrafiltration membranes directly filled with graphene oxide. Filter membranes are significantly enhanced.

Example 2

1) The preparation of the chitosan-graphene oxide nanocomposite is exactly the same as in Example 1.

2) The difference with embodiment 1 is that the amount of chitosan-graphene oxide added in the casting solution is different. The specific operation is as follows: prepare 30 g of casting solution, weigh 0.018 g of chitosan-graphene oxide, add 23.082 g of dimethylacetamide, and ultrasonicate for 1 hour at room temperature to obtain a uniform chitosan-graphene oxide dispersion;

Sequentially weigh 6g of polyvinylidene fluoride (110°C vacuum drying for 12h), add 0.9g of polyvinylpyrrolidone (molecular weight 58000g/mol) into the above chitosan-graphene oxide dispersion, stir at 60°C for 24h, and then Stand at a constant temperature at 60°C for 12 hours for defoaming, scrape evenly on the polyester non-woven fabric with a scraper to form a casting layer, the thickness of the casting layer is 150±10μm, and then immediately put it into deionized water at 25°C, after 15 minutes The membrane was peeled off from the glass plate and immersed in deionized water for 48 hours to completely remove the residual solvent, and a chitosan-functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane was prepared.

The prepared membrane has a water contact angle of 71.35°, a water flux of 673.08L/m ² h, a flux recovery rate of 66.53%, and a flux decay rate of 82.04%. Compared with Example 1, it can be seen that the content of chitosan-graphene oxide has an influence on the film performance. Chitosan-graphene oxide is added in the organic solvent, after ultrasonic at room temperature, obtain chitosan-graphene oxide dispersion liquid; Add polyvinylidene fluoride and porogen to chitosan-graphene oxide dispersion liquid, Stir and dissolve evenly, let it stand for defoaming, and obtain the casting solution, and then scrape the casting solution evenly on the polyester non-woven fabric to form a casting layer on the polyester non-woven fabric, and then immediately immerse it in the coagulation bath, wait for After curing to form a film, the film was peeled off, continued to soak in deionized water, and the residual solvent was removed to obtain a chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane.

Example 3

1) Preparation of chitosan-graphene oxide:

Dissolving chitosan in a 1% glacial acetic acid solution by volume fraction is prepared into a 3% chitosan glacial acetic acid solution by mass fraction;

Add graphene oxide into deionized water, and ultrasonicate at room temperature for 1 hour to obtain a graphene oxide dispersion; add the graphene oxide dispersion to chitosan glacial acetic acid solution under stirring, stir at room temperature for 24 hours, and then centrifugally wash with glacial acetic acid Several times, remove unreacted chitosan, then centrifuge and wash several times with deionized water, and vacuum dry to obtain chitosan-graphene oxide; wherein, the mass ratio of graphene oxide to chitosan is 1 : 10; Gained chitosan-graphene oxide is a lamellar structure with a thickness of 2-3nm.

2) chitosan-graphene oxide is added in the organic solvent, after ultrasonic 1h at room temperature, obtain chitosan-graphene oxide dispersion liquid; Add polyvinylidene fluoride (using Vacuum drying at 110°C for 15h) and porogen, stirring at 40°C for 36h, then standing at 40°C for degassing for 24h to obtain the casting solution, and then scraping the casting solution evenly on the polyester non-woven fabric , form a casting layer on the polyester non-woven fabric, and then immediately immerse it in a deionized water coagulation bath at 20°C for 20 minutes. After the film is cured, peel off the film and continue to soak in deionized water for 24 hours to remove the residual solvent. A chitosan functionalized graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane was obtained. Wherein, by weight percentage, the total amount of polyvinylidene fluoride and chitosan-graphene oxide is 17.7%, the weight of chitosan-graphene oxide is 0.2% of the weight of polyvinylidene fluoride, and the porogen is 0.3%. , the organic solvent is 82%. The porogen is polyethylene glycol; the organic solvent is N-methylpyrrolidone; and the thickness of the casting layer is 130-180 μm.

Example 4

1) Preparation of chitosan-graphene oxide:

Dissolving chitosan in 3% glacial acetic acid solution by volume fraction is prepared into 1% chitosan glacial acetic acid solution by mass fraction;

Add graphene oxide into deionized water, and ultrasonicate at room temperature for 1 hour to obtain a graphene oxide dispersion; add the graphene oxide dispersion to chitosan glacial acetic acid solution under stirring, stir at room temperature for 24 hours, and then centrifugally wash with glacial acetic acid Several times, remove unreacted chitosan, then centrifuge and wash several times with deionized water, and vacuum dry to obtain chitosan-graphene oxide; wherein, the mass ratio of graphene oxide to chitosan is 1 : 10; Gained chitosan-graphene oxide is a lamellar structure with a thickness of 2-3nm.

2) Chitosan-graphene oxide is added in the organic solvent, after ultrasonic 1h at room temperature, obtain chitosan-graphene oxide dispersion liquid; Add polyvinylidene fluoride and Pore agent, stirred at 50°C for 30h, and then stood at 50°C for degassing for 20h to obtain a casting solution, and then scraped the casting solution evenly on the polyester non-woven fabric to form a flow on the polyester non-woven fabric layer extension, and then immediately immersed in a deionized water coagulation bath at 30°C for 15 minutes. After the film was solidified, the film was peeled off and continued to be soaked in deionized water for 24 hours to remove the residual solvent to obtain chitosan functionalized graphene oxide/ Polyvinylidene fluoride hybrid ultrafiltration membrane. Wherein, by weight percentage, the total amount of polyvinylidene fluoride and chitosan-graphene oxide is 17%, the weight of chitosan-graphene oxide is 2% of the weight of polyvinylidene fluoride, and the porogen is 5%. , the organic solvent is 78%, and the chitosan-graphene oxide weight is 0.2-2% of the polyvinylidene fluoride weight. The porogen is polyvinyl alcohol; the organic solvent is dimethyl sulfoxide; and the thickness of the casting layer is 130-180 μm.

In order to solve the problem that graphene oxide is easily aggregated in the polyvinylidene fluoride membrane matrix, which limits the membrane's hydrophilicity, water flux and anti-pollution properties, the present invention first uses chitosan to covalently function graphene oxide. Chitosan-graphene oxide was chemically prepared; then chitosan-graphene oxide was ultrasonically dispersed in an organic solvent, and polyvinylidene fluoride and porogen were added and stirred and dissolved at a certain temperature to obtain a casting solution. Water was used as coagulation bath, and chitosan-graphene oxide/polyvinylidene fluoride hybrid ultrafiltration membrane was prepared by immersion precipitation phase inversion method. The chitosan-graphene oxide/polyvinylidene fluoride ultrafiltration membrane prepared by the present invention improves the dispersion of graphene oxide in the membrane matrix and is comparable to graphite oxide in terms of hydrophilicity, water flux and anti-pollution performance. Compared with ethylene/polyvinylidene fluoride ultrafiltration membrane, it has a greater improvement.

Claims (10)

1. chitosan functional graphene oxide/Kynoar hybrid membranes, it is characterised in that by weight percentage, The raw material of ultrafilter membrane includes Kynoar 16-20%, porogen 0.3-5%, organic solvent 78-82% and chitosan-graphite oxide Alkene；Wherein, chitosan-graphene oxide weight is the 0.2-2% of Kynoar weight.

A kind of chitosan functional graphene oxide/Kynoar hybrid membranes the most according to claim 1, its feature It is, described Kynoar 110 DEG C of dry 10-15h in vacuum drying oven the most in advance.

A kind of chitosan functional graphene oxide/Kynoar hybrid membranes the most according to claim 1, its feature Being, described porogen is the one in polyvinylpyrrolidone, Polyethylene Glycol, polyvinyl alcohol.

A kind of chitosan functional graphene oxide/Kynoar hybrid membranes the most according to claim 1, its feature Being, described organic solvent is in dimethylformamide, dimethyl acetylamide, N-Methyl pyrrolidone, dimethyl sulfoxide Kind.

A kind of chitosan functional graphene oxide/Kynoar hybrid membranes the most according to claim 1, its feature Being, described chitosan-graphene oxide is laminar structured, and thickness is 2-3nm.

6. the preparation method of chitosan functional graphene oxide/Kynoar hybrid membranes, it is characterised in that include Following steps:

Chitosan-graphene oxide is added in organic solvent, ultrasonic under room temperature after, obtain chitosan-graphene oxide dispersion； Adding Kynoar and porogen in chitosan-graphene oxide dispersion, stirring and dissolving is uniform, and standing and defoaming is cast Film liquid, then scrapes on polyester non-woven fabric equably by casting solution, forms cast layer, immerse the most at once on polyester non-woven fabric In coagulating bath, after film forming to be solidified, film is peeled off, continue to soak in deionized water, the solvent that abjection is remaining, obtain shell and gather Sugar functional graphene oxide/Kynoar hybrid membranes；Wherein, by weight percentage, Kynoar is 16-20%, Porogen is 0.3-5%, and organic solvent is 78-82%, and chitosan-graphene oxide weight is the 0.2-2% of Kynoar weight.

The preparation side of a kind of chitosan functional graphene oxide/Kynoar hybrid membranes the most according to claim 6 Method, it is characterised in that described chitosan-graphene oxide prepares by the following method:

Chitosan is dissolved in the glacial acetic acid solution that volume fraction is 1-3%, is configured to the chitosan glacial acetic acid of mass fraction 1-3% Solution；

Adding graphene oxide in deionized water, under room temperature, ultrasonic 1h, obtains graphene oxide dispersion；Under agitation by oxygen Functionalized graphene dispersion liquid joins in chitosan glacial acetic acid solution, uses glacial acetic acid centrifuge washing for several times, move under room temperature after stirring 24h Except unreacted chitosan, the most again with deionized water centrifuge washing the most for several times, vacuum drying, prepare chitosan-graphene oxide； Wherein, graphene oxide is 1:10 with the mass ratio of chitosan；Gained chitosan-graphene oxide is laminar structured, and thickness is 2-3nm。

The preparation side of a kind of chitosan functional graphene oxide/Kynoar hybrid membranes the most according to claim 6 Method, it is characterised in that described ultrasonic time is 1h, the temperature of stirring is 40-60 DEG C, and the time of stirring is 24-36h；Described The temperature of standing and defoaming be 40-60 DEG C, the time of standing and defoaming is 12-24h.

The preparation side of a kind of chitosan functional graphene oxide/Kynoar hybrid membranes the most according to claim 6 Method, it is characterised in that described coagulating bath is deionized water, water temperature is 20-30 DEG C；Time in described immersion coagulating bath is 15-20min；Described porogen is the one in polyvinylpyrrolidone, Polyethylene Glycol, polyvinyl alcohol；Described organic solvent is One in dimethylformamide, dimethyl acetylamide, N-Methyl pyrrolidone, dimethyl sulfoxide.

The preparation of a kind of chitosan functional graphene oxide/Kynoar hybrid membranes the most according to claim 6 Method, it is characterised in that described cast layer thickness is 130-180 μm；The described immersion time in deionized water is 24-48h.