CN105498553A - Polyvinylidene fluoride and metal-organic framework composite ultra-filtration membrane and preparation and application - Google Patents

Abstract

The invention belongs to the technical field of composite materials and discloses a polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane as well as its preparation and application. The preparation method comprises: ultrasonically dispersing MIL-100(Fe) prepared by a hydrothermal method in a solvent, adding polyvinylidene fluoride and a pore-forming agent in sequence, stirring for 12-24 hours to dissolve and blend evenly, and form a casting solution; After defoaming the casting solution, put it on the support to coat the film, and then stay in the air for 30-60s, then immerse in the coagulation bath for solvent exchange to obtain the polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane. The composite ultrafiltration membrane of the present invention improves the hydrophilicity of the ultrafiltration membrane by adding metal-organic framework material MIL-100 (Fe), improves the separation ability of the membrane, improves the anti-pollution ability of the ultrafiltration membrane, and prolongs the use of the membrane life and has good application prospects.

Description

A polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane and its preparation and application

technical field

The invention belongs to the technical field of composite materials, and in particular relates to a polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane and its preparation and application.

Background technique

Membrane technology has the characteristics of good treatment effect, excellent effluent quality, easy operation, and small impact on the environment. It overcomes the shortcomings of traditional water treatment processes and becomes the preferred technology in the field of water treatment in the 21st century. However, due to problems such as membrane fouling and membrane life, the further application of membrane technology in the field of water treatment is greatly limited.

As a widely used synthetic material for ultrafiltration membranes, polyvinylidene fluoride is an excellent high-molecular organic polymer with good heat resistance, radiation resistance, chemical stability and easy film formation. And it has good impact strength and wear resistance, oxidation resistance and radiation resistance, and is not subject to corrosion by strong oxidants such as acids and alkali metals and halogens at room temperature. But it also has certain defects. The strong hydrophobicity of PVDF ultrafiltration membrane reduces the flux of pure water, and PVDF membrane is easily polluted by protein and other pollutants, which reduces the service life of ultrafiltration membrane.

Metal-organic framework material MOFS (Metal Organic Frameworks) is a hybrid ultra-high molecular material with a regular network structure formed by organic linkers and metal cations through coordination. MOFs exhibit ultra-high specific surface area and pore volume, open pore structure, uniform pore size distribution, unsaturated metal coordination, adjustable pore structure and surface properties, and thousands of species composed of various coordination methods.

At present, the commonly used methods for ultrafiltration membrane modification at home and abroad include blending modification, chemical modification, and surface modification. However, the obtained ultrafiltration membranes have to be further improved in terms of wastewater treatment capacity and anti-pollution capacity.

Contents of the invention

In order to solve the above shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane.

Another object of the present invention is to provide a polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane prepared by the above method.

Another object of the present invention is to provide the application of the polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane in the fields of protein separation and wastewater treatment.

The object of the invention is achieved through the following technical solutions:

A preparation method of polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane, comprising the following preparation steps:

(1) Preparation of metal-organic framework material MIL-100(Fe) by hydrothermal method;

(2) Ultrasonic disperse MIL-100(Fe) in the solvent, add polyvinylidene fluoride (PVDF) and pore-forming agent in sequence, stir for 12-24 hours to dissolve and blend evenly, and form a casting solution;

(3) After degassing the configured casting solution, place it on the support to coat the film;

(4) After the support coated with the casting solution stays in the air for 30-60 seconds, it is immersed in a coagulation bath for solvent exchange to obtain a polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane.

The process of preparing the metal-organic framework material MIL-100(Fe) by the hydrothermal method is as follows: iron powder, 1,3,5-benzenetricarboxylic acid, nitric acid, hydrofluoric acid and water are added to the hydrothermal reaction kettle, and the Put it into an oven at 150° C. for 12 hours to react, and the product was washed and dried to obtain an orange-yellow solid product MIL-100(Fe).

The iron powder is a 300-mesh reduced iron powder with a purity of >99%; 1,3,5-benzenetricarboxylic acid is a white powder with a melting point of >300°C and a purity of >98%; nitric acid is a nitric acid with a mass concentration of >65%; Hydrofluoric acid is hydrofluoric acid with a mass concentration > 40%.

The washing refers to alternating washing with absolute ethanol and deionized water; the drying refers to drying in a vacuum oven at 100° C. for 12 hours.

The mass percentages of MIL-100 (Fe), polyvinylidene fluoride, pore-forming agent and solvent described in step (2) are respectively MIL-100 (Fe) 0.05% to 2%, polyvinylidene fluoride 16% to 20%, 0.25% to 1% pore forming agent, and the balance is solvent.

Preferably, the solvent described in step (2) refers to N-methylpyrrolidone; the pore-forming agent refers to polyvinylpyrrolidone (PVP).

The ultrasonic dispersion described in the step (2) refers to the ultrasonic dispersion for 30-60 minutes under the condition of a frequency of 20-60 kHz.

Preferably, the configuration process of the casting solution in step (2) is carried out at a temperature of 60°C.

The defoaming described in the step (3) refers to standing in an oven at 60° C. for 48 hours to defoam.

Preferably, the support described in step (3) refers to smooth polyester non-woven fabric, carbon fiber or glass plate; the thickness of the coating film is 200-350 μm.

Preferably, the coagulation bath described in step (4) is a mixed solution with a volume ratio of deionized water and ethanol of 1:1.

A polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane is prepared by the above method.

The application of the polyvinylidene fluoride-metal organic framework composite ultrafiltration membrane in the fields of protein separation, waste water treatment and the like.

The preparation method of the present invention and the resulting product have the following advantages and beneficial effects:

(1) The polyvinylidene fluoride-metal organic framework MIL-100(Fe) composite ultrafiltration membrane prepared by the present invention is due to the addition of metal organic framework material MIL-100(Fe) with large specific surface area, strong adsorption capacity and large pore size. , improve the hydrophilicity of the ultrafiltration membrane, improve the separation ability of the membrane, improve the anti-pollution ability of the ultrafiltration membrane, and prolong the service life of the membrane;

(2) The preparation method of the present invention can efficiently control the pore structure, hydrophilicity and chargeability of the membrane by adjusting the addition of MIL-100 (Fe), the concentration of the casting solution, and the ratio of the pore-forming agent , thereby optimizing the separation performance of the membrane;

(3) The preparation method of the present invention is easy to operate, has low production cost, and is suitable for large-scale production.

detailed description

The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1

(1) Preparation of metal-organic framework MIL-100(Fe): Weigh 277.5 mg of iron powder (purity>99%, 300 mesh), 687.5 mg of 1,3,5-benzenetricarboxylic acid (melting point>300°C, purity >98% white powder) into the polytetrafluoroethylene liner, add 20mL high-purity water, then add dropwise 200μL hydrofluoric acid (35wt%) and 190μL nitric acid (65wt%) to mix well, cover and move to the inner liner After the PTFE stainless steel reaction kettle was sealed, it was placed in an electric blast constant temperature drying oven at 150°C for 12 hours. The product was washed with ethanol and high-purity water, and dried by high-speed centrifugation. The finally obtained orange-yellow solid was vacuum-dried at 100° C. for 12 h to obtain a metal-organic framework MIL-100(Fe).

(2) Configure the casting solution: add 2wt% of MIL-100(Fe) to 77wt% of N-methylpyrrolidone, ultrasonically disperse at an ultrasonic frequency of 50kHz for 30min, and then add 20wt% of the dried polyvinylidene fluoride Ethylene and 1 wt% polyvinylpyrrolidone with an average molecular weight of 5000 were added to the ultrasonicated solution, and stirred at 60°C for 12 hours to obtain a uniformly dissolved and mixed casting solution;

(3) Coating film: After the casting solution is left to defoam in a 60°C drying oven for 48 hours, the casting solution is coated on flat glass. The thickness of the coating film is controlled at 250 μm, and the coating speed is 1.2m/ min;

(4) Film formation: After the support coated with the casting solution stays in the air for 30s, it is immersed in a coagulation bath with a volume ratio of ethanol and deionized water of 1:1 for solvent exchange for 12 hours, and then taken out and placed in deionized water Soak for 3 days, change the water every 8 hours, take it out and dry it in the air to obtain a 250 μm polyvinylidene fluoride-metal organic framework MIL-100(Fe) composite ultrafiltration membrane.

Example 2

(1) Preparation of metal-organic framework MIL-100(Fe): Weigh 277.5 mg of iron powder (purity>99%, 300 mesh), 687.5 mg of 1,3,5-benzenetricarboxylic acid (melting point>300°C, purity >98% white powder) into the polytetrafluoroethylene liner, add 20mL high-purity water, then add 200μL hydrofluoric acid (35wt%) and 190μL nitric acid (65wt%) dropwise, mix well, cover and move to a stainless steel reaction kettle After inner sealing, place in an electric blast constant temperature drying oven to react at 150°C for 12h. The product was washed with ethanol and high-purity water, and dried by high-speed centrifugation. The finally obtained orange-yellow solid was vacuum-dried at 100° C. for 12 h to obtain a metal-organic framework MIL-100(Fe).

(2) Configure the casting solution: add 0.25wt% of MIL-100 (Fe) to 83.5wt% of N-methylpyrrolidone, ultrasonically disperse at an ultrasonic frequency of 50kHz for 30min, and then add 16wt% of the dried poly Vinylidene fluoride and 0.25 wt% polyvinylpyrrolidone with an average molecular weight of 5000 were added to the solution after ultrasonication, and stirred at 60°C for 12 hours to obtain a uniformly dissolved and mixed casting solution;

(3) Coating film: After the casting solution is left to defoam in a 60°C drying oven for 48 hours, the casting solution is coated on flat glass. The thickness of the coating film is controlled at 250 μm, and the coating speed is 1.2m/ min;

(4) Film formation: After the support coated with the casting solution stays in the air for 30s, it is immersed in a coagulation bath with a volume ratio of ethanol and deionized water of 1:1 for solvent exchange for 12 hours, and then taken out and placed in deionized water Soak for 3 days, change the water every 8 hours, take it out and dry it in the air to obtain a 250 μm polyvinylidene fluoride-metal organic framework MIL-100(Fe) composite ultrafiltration membrane.

Example 3

(1) Preparation of metal-organic framework MIL-100(Fe): Weigh 277.5 mg of iron powder (purity>99%, 300 mesh), 687.5 mg of 1,3,5-benzenetricarboxylic acid (melting point>300°C, purity >98% white powder) into the polytetrafluoroethylene liner, add 20mL high-purity water, then add 200μL hydrofluoric acid (35wt%) and 190μL nitric acid (65wt%) dropwise, mix well, cover and move to a stainless steel reaction kettle After inner sealing, place in an electric blast constant temperature drying oven to react at 150°C for 12h. The product was washed with ethanol and high-purity water, and dried by high-speed centrifugation. The finally obtained orange-yellow solid was vacuum-dried at 100° C. for 12 h to obtain a metal-organic framework MIL-100(Fe).

(2) Configure the casting solution: add 1wt% of MIL-100(Fe) to 80.5wt% of N-methylpyrrolidone, ultrasonically disperse at an ultrasonic frequency of 50kHz for 30min, and then add 18wt% of the dried poly Vinyl fluoride and 0.5 wt% polyvinylpyrrolidone with an average molecular weight of 5000 were added to the ultrasonicated solution, and stirred at 60°C for 12 hours to obtain a uniformly dissolved and mixed casting solution;

(3) Coating film: After the casting solution is left to defoam in a 60°C drying oven for 48 hours, the casting solution is coated on flat glass. The thickness of the coating film is controlled at 250 μm, and the coating speed is 1.2m/ min;

(4) Film formation: After the support coated with the casting solution stays in the air for 30s, it is immersed in a coagulation bath with a volume ratio of ethanol and deionized water of 1:1 for solvent exchange for 12 hours, and then taken out and placed in deionized water Soak for 3 days, change the water every 8 hours, take it out and dry it in the air to obtain a 250 μm polyvinylidene fluoride-metal organic framework MIL-100(Fe) composite ultrafiltration membrane.

Example 4

(1) Preparation of metal-organic framework MIL-100(Fe): Weigh 277.5 mg of iron powder (purity>99%, 300 mesh), 687.5 mg of 1,3,5-benzenetricarboxylic acid (melting point>300°C, purity >98% white powder) into the polytetrafluoroethylene liner, add 20mL high-purity water, then add 200μL hydrofluoric acid (35wt%) and 190μL nitric acid (65wt%) dropwise, mix well, cover and move to a stainless steel reaction kettle After inner sealing, place in an electric blast constant temperature drying oven to react at 150°C for 12h. The product was washed with ethanol and high-purity water, and dried by high-speed centrifugation. The finally obtained orange-yellow solid was vacuum-dried at 100° C. for 12 h to obtain a metal-organic framework MIL-100(Fe).

(2) Configure the casting solution: add 0.75wt% of MIL-100(Fe) to 82wt% of N-methylpyrrolidone, ultrasonically disperse at an ultrasonic frequency of 50kHz for 30min, and then add 17wt% of the dried poly Vinyl fluoride and 0.25 wt% polyvinylpyrrolidone with an average molecular weight of 5000 were added to the solution after ultrasonication, and stirred at 60°C for 12 hours to obtain a uniformly dissolved and mixed casting solution;

(3) Coating film: After the casting solution is left to defoam in a 60°C drying oven for 48 hours, the casting solution is coated on flat glass. The thickness of the coating film is controlled at 250 μm, and the coating speed is 1.2m/ min;

(4) Film formation: After the support coated with the casting solution stays in the air for 30s, it is immersed in a coagulation bath with a volume ratio of ethanol and deionized water of 1:1 for solvent exchange for 12 hours, and then taken out and placed in deionized water Soak for 3 days, change the water every 8 hours, take it out and dry it in the air to obtain a 250 μm polyvinylidene fluoride-metal organic framework MIL-100(Fe) composite ultrafiltration membrane.

Example 5

(1) Preparation of metal-organic framework MIL-100(Fe): Weigh 277.5 mg of iron powder (purity>99%, 300 mesh), 687.5 mg of 1,3,5-benzenetricarboxylic acid (melting point>300°C, purity >98% white powder) into the polytetrafluoroethylene liner, add 20mL high-purity water, then add 200μL hydrofluoric acid (35wt%) and 190μL nitric acid (65wt%) dropwise, mix well, cover and move to a stainless steel reaction kettle After inner sealing, place in an electric blast constant temperature drying oven to react at 150°C for 12h. The product was washed with ethanol and high-purity water, and dried by high-speed centrifugation. The finally obtained orange-yellow solid was vacuum-dried at 100° C. for 12 h to obtain a metal-organic framework MIL-100(Fe).

(2) Configure the casting solution: add 0.5wt% of MIL-100(Fe) to 82.25wt% of N-methylpyrrolidone, ultrasonically disperse for 30min at an ultrasonic frequency of 50kHz, and then add 17wt% of the dried poly Vinylidene fluoride and 0.25 wt% polyvinylpyrrolidone with an average molecular weight of 5000 were added to the solution after ultrasonication, and stirred at 60°C for 12 hours to obtain a uniformly dissolved and mixed casting solution;

(3) Coating film: After the casting solution is left to defoam in a 60°C drying oven for 48 hours, the casting solution is coated on flat glass. The thickness of the coating film is controlled at 250 μm, and the coating speed is 1.2m/ min;

(4) Film formation: After the support coated with the casting solution stays in the air for 30s, it is immersed in a coagulation bath with a volume ratio of ethanol and deionized water of 1:1 for solvent exchange for 12 hours, and then taken out and placed in deionized water Soak for 3 days, change the water every 8 hours, take it out and dry it in the air to obtain a 250 μm polyvinylidene fluoride-metal organic framework MIL-100(Fe) composite ultrafiltration membrane.

The polyvinylidene fluoride-metal organic framework MIL-100 (Fe) composite ultrafiltration membrane that above embodiment makes is carried out performance test:

1. Determination of water flux

After placing the prepared composite ultrafiltration membrane in deionized water for a period of time, cut out a circular membrane with a diameter of 7.5 cm, put it into a YL-300 ultrafiltration cup, and pre-compress it under a pressure of 0.1 MPa for 40 minutes until the water passes through. After the amount is basically stable, it is then measured under a pressure of 0.1MPa.

2. Determination of anti-pollution performance

(1) Pre-compress the prepared membrane for 40 minutes at a pressure of 0.1 MPa until the water flux is basically stable, then measure the pure water flux;

(2) Get 250mL of 1g/L bovine serum albumin solution and import it into the ultrafiltration cup to filter;

(3) Turn over the modified membrane after filtering, and filter and rinse with an appropriate amount of deionized water;

(4) Turn over the modified membrane again, measure the flux of pure water and record the data.

3. Performance test results

(1) The pure water average flux of the polyvinylidene fluoride-metal organic framework MIL-100 (Fe) composite ultrafiltration membrane obtained in the above examples is 140L/m ² h, which is basically similar to the PVDF ultrafiltration membrane;

(2) The average retention rate of the bovine serum albumin of 1g/L of polyvinylidene fluoride-metal organic framework MIL-100 (Fe) composite ultrafiltration membrane obtained in above embodiment reaches 96%, is higher than the average retention rate of PVDF ultrafiltration membrane rate of 85%.

From the above results, it can be shown that the composite ultrafiltration membrane of the present invention significantly improves the anti-fouling ability and the retention ability of pollutants of the PVDF ultrafiltration membrane through the addition of metal organic framework MIL-100 (Fe).

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. a preparation method for Kynoar-metallic organic framework composite hyperfiltration membrane, is characterized in that, comprises following preparation process:

(1) hydro-thermal method prepares metal-organic framework materials MIL-100 (Fe);

(2) by MIL-100 (Fe) ultrasonic disperse in solvent, successively Kynoar, pore former are added, stir 12 ~ 24h dissolve evenly blended, formed casting solution;

(3) by after the casting solution deaeration that configures, be placed on supporter and carry out film;

(4), after the supporter scribbling casting solution being stopped 30 ~ 60s in atmosphere, immerse in coagulating bath and carry out exchange of solvent, obtain Kynoar-metallic organic framework composite hyperfiltration membrane.

2. the preparation method of a kind of Kynoar-metallic organic framework composite hyperfiltration membrane according to claim 1, it is characterized in that: the process that described hydro-thermal method prepares metal-organic framework materials MIL-100 (Fe) is as follows: by iron powder, 1,3,5-benzenetricarboxylic acid, nitric acid, hydrofluoric acid and water join in hydrothermal reaction kettle, put into 150 DEG C of baking ovens and react 12h, after product washing drying, obtain crocus solid product MIL-100 (Fe).

3. the preparation method of a kind of Kynoar-metallic organic framework composite hyperfiltration membrane according to claim 2, is characterized in that: described iron powder is purity > 99%, particle diameter is 300 object reduced iron powders; Described 1,3,5-benzenetricarboxylic acid is fusing point > 300 DEG C, the white powder of purity > 98%; Described nitric acid is the nitric acid of mass concentration > 65%; Described hydrofluoric acid is the hydrofluoric acid of mass concentration > 40%; Described washing refers to absolute ethyl alcohol and deionized water alternately washing; Described drying refers to 100 DEG C of dry 12h in vacuum drying chamber.

4. the preparation method of a kind of Kynoar-metallic organic framework composite hyperfiltration membrane according to claim 1, it is characterized in that: the mass percentage of MIL-100 (Fe), Kynoar, pore former and the solvent described in step (2) is respectively MIL-100 (Fe) 0.05 ~ 2%, Kynoar 16% ~ 20%, pore former 0.25% ~ 1%, and surplus is solvent.

5. the preparation method of a kind of Kynoar-metallic organic framework composite hyperfiltration membrane according to claim 1, is characterized in that: the solvent described in step (2) refers to 1-METHYLPYRROLIDONE; Described pore former refers to polyvinylpyrrolidone.

6. the preparation method of a kind of Kynoar-metallic organic framework composite hyperfiltration membrane according to claim 1, is characterized in that: the ultrasonic disperse described in step (2) refers to ultrasonic disperse 30 ~ 60min under frequency is the condition of 20 ~ 60kHz; The layoutprocedure of described casting solution is carried out under temperature 60 C condition.

7. the preparation method of a kind of Kynoar-metallic organic framework composite hyperfiltration membrane according to claim 1, is characterized in that: the deaeration described in step (3) refers to standing 48h deaeration in 60 DEG C of baking ovens; Described supporter refers to level and smooth polyester non-woven fabric, carbon fiber or glass plate; Described coating thickness is 200 ~ 350 μm.

8. the preparation method of a kind of Kynoar-metallic organic framework composite hyperfiltration membrane according to claim 1, is characterized in that: the coagulating bath described in step (4) is the volume ratio of deionized water and ethanol is the mixed solution of 1:1.

9. Kynoar-metallic organic framework composite hyperfiltration membrane, is prepared by the method described in any one of claim 1 ~ 8.

10. the Kynoar according to claim 9-application of metallic organic framework composite hyperfiltration membrane in Separation of Proteins, field of waste water treatment.