Preparation method of block copolymer / PVDF (Polyvinylidene Fluoride) blended membrane for removing methyl orange in wastewater

Abstract

The invention discloses a polymethyl methacrylate macroinitiator / polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF (Polyvinylidene Fluoride) blended membrane and application of a preparation method thereof in wastewater treatment. Belongs to the technical field of wastewater treatment adsorption material preparation. The invention discloses a high-temperature-resistant composite material which is prepared from the following raw materials: 3-(((2-cyanopropane-2-yl) oxy) (isopropyl) amino)-2, 2-dimethyl-3-phenylpropionitrile (CPDMN) synthesized in a laboratory, methyl methacrylate, methyl methacrylate, methylbenzene, n-butyl acetate, polyvinylidene fluoride and N-N dimethylacetamide. The preparation method comprises the following steps: preparing a polymethyl methacrylate macroinitiator, preparing polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate), and blending the polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) and polyvinylidene fluoride to prepare the membrane. The block copolymer product prepared through stable polymerization of the nitroxide free radicals has the advantages of being pure, free of color, simple in reaction process and the like, and the membrane prepared by blending the block copolymer product with vinylidene fluoride is good in performance and wide in application prospect.

Description

Technical Field

[0001] The invention belongs to the field of preparation of wastewater treatment adsorption materials, and discloses application of polymethyl methacrylate macromolecular initiator / polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blended membrane and preparation method thereof in wastewater treatment. Background Art

[0002] Synthetic dyes are used in a wide range of industries, including textile processing, food production and the pharmaceutical industry.

[0003] Considering the economical efficiency, membrane separation technology is usually used as a treatment method for dye wastewater, but the application of traditional membrane in direct treatment of dye-containing textile wastewater is limited, and the dye removal rate is insufficient. The polymer blended membrane can effectively remove the dye through the complexation of the dye with the high molecular weight polymer or based on the electrostatic interaction with the dye. Summary of the invention

[0004] The purpose of the present invention is to provide a polymethyl methacrylate macroinitiator / polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend membrane, a preparation method and application thereof in wastewater treatment. The preparation process is simple, and the obtained blend membrane has excellent separation performance and good reuse performance, high economic benefit and broad application prospect.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing a polymethyl methacrylate macroinitiator / polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend film comprises the following steps: (1) Preparation of 3-(((2-cyanopropane-2-yl)oxy)(isopropyl)amino)-2,2-dimethyl-3-phenylpropionitrile (CPDMN) Benzaldehyde, isopropylamine and methanol were added to a three-necked flask, and a magnetite was added. The reaction was carried out in an oil bath. After the reaction was completed, the mixture was cooled to room temperature, and sodium borohydride was added thereto in batches. After stirring for a certain period of time, the reaction of the raw materials was monitored by thin layer chromatography. The solvent was removed by rotary evaporation, the mixture was dissolved in ethyl acetate, washed with saturated brine, dried over anhydrous magnesium sulfate, and rotary evaporated to obtain compound 1; Compound 1 and sodium bicarbonate were dissolved in acetone and water, potassium peroxymonosulfonate was added in batches under ice bath condition, the mixture was stirred and filtered with acetone, washed with saturated brine, the upper organic phase was collected, dried over anhydrous magnesium sulfate, filtered and rotary evaporated, and then separated and purified by chromatography column to obtain compound 2; Compound 2, azobisisobutyronitrile and toluene were added to a single-necked flask. After the reaction was completed in an oil bath, the solvent was removed by rotary evaporation to obtain a crude product, which was separated and purified by a chromatography column to obtain a compound CPDMN product; (2) Preparation of polymethyl methacrylate macroinitiator Methyl methacrylate, alkoxyamine 3-(((2-cyanopropane-2-yl)oxy)(isopropyl)amino)-2,2-dimethyl-3-phenylpropionitrile CPDMN and toluene are placed in a reaction container, fully stirred and dissolved, vacuumed and nitrogen-filled to remove oxygen in the reaction system, reacted at 90° C. for 4 h, diluted with tetrahydrofuran solution after the reaction, precipitated in cold methanol, filtered and dried to prepare polymethyl methacrylate macroinitiator; (3) Preparation of polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer The polymethyl methacrylate macroinitiator prepared in step (1) is dissolved in n-butyl acetate, and after it is completely dissolved, dimethylaminoethyl methacrylate is added, and the mixture is stirred to be uniformly mixed. After the solution becomes clear and transparent, the reaction system is vacuumed and nitrogen is used to remove oxygen from the reaction system. The reaction is carried out at 90° C. for 4 h. After the reaction is completed, the mixture is cooled to room temperature, diluted with a dichloromethane solution, precipitated in an n-hexane solution, filtered, and dried to obtain a polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer; (4) Preparation of polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane The prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer, polyvinylidene fluoride and NN dimethylacetamide were mixed and mechanically stirred at 80 °C for 12 h. After the reaction was completed, the mixture was placed in a vacuum oven for degassing for 2 h to obtain a casting solution after the reaction. The solution was cast on a glass plate to prepare a film with a thickness of 200 μm. The film was immediately immersed in 30 °C deionized water at room temperature. After the film was formed, it was transferred to deionized water at room temperature and immersed overnight. After drying for 12-48 h, the prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane was obtained.

[0006] In step (2), the molar ratio of 3-(((2-cyanopropane-2-yl)oxy)(isopropyl)amino)-2,2-dimethyl-3-phenylpropionitrile to methyl methacrylate is 1:100 to 1:150, and the reaction time is 3 h to 5 h; In step (3), the molar ratio of polymethyl methacrylate macroinitiator to dimethylaminoethyl methacrylate is 1:50-1:400, and the reaction time is 2 h-6 h; In step (4), the mass ratio of polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer to polyvinylidene fluoride is 1:9 to 2:3.

[0007] Application of the prepared polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend membrane in dye wastewater treatment.

[0008] The beneficial effects of the present invention are: polymethyl methacrylate macromolecular initiator and polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer are prepared by nitroxide free radical stable polymerization method, the preparation process is simple, the product is pure, and the prepared polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / polyvinylidene fluoride blended membrane has the hydrophilic function of block copolymer, high dye adsorption efficiency, and strong reusability. It has significant economic benefits in actual wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is the FT-IR graph of the polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / polyvinylidene fluoride blend film prepared in the present invention.

[0010] Figure 2 This is a SEM image of the polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / polyvinylidene fluoride blend film prepared in the present invention.

[0011] Figure 3 Comparative pictures of the polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / polyvinylidene fluoride blend membrane with different segment lengths prepared in the present invention before and after the adsorption of methyl orange at different addition contents.

[0012] Figure 4 The invention discloses a reaction mechanism for preparing the polymethyl methacrylate macroinitiator.

[0013] Figure 5 The present invention discloses a reaction mechanism for preparing the polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer.

[0014] Figure 6-8 Prepare NMR characterization images for CPDMN. DETAILED DESCRIPTION

[0015] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0016] Example 1 (1) Preparation of CPDMN Synthesis of compound 1: 5.0 g (47 mmol) benzaldehyde, 2.78 g (47 mmol) isopropylamine, and 60 mL methanol were added to a 250 mL three-necked flask, and a magnetic bar was added. The reaction was refluxed in a 65 °C oil bath for 8 h. After the reaction was completed, it was cooled to room temperature, and 2.83 g (75 mmol) sodium borohydride was added to the solution in multiple portions. After stirring for 2 h, the reaction of the raw materials was monitored by thin layer chromatography, and the methanol solvent and the unreacted isopropylamine were removed by rotary evaporator. The crude product was dissolved in ethyl acetate, and the solution was washed three times with saturated brine in a separatory funnel, dried over anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain 6.56 g of a light yellow viscous liquid product.

[0017] Synthesis of compound 2: 6.56 g of compound 1 and 13.12 g of sodium bicarbonate were dissolved in 22 mL of acetone and water, and 24.1 g of Oxone was added to the reaction system in batches under ice bath conditions and stirred for 2 h. The mixture solution was filtered with acetone and then washed with saturated brine three times. The upper organic phase was collected, dried with anhydrous magnesium sulfate, and filtered with a sand core funnel. The resulting solution was evaporated with a rotary evaporator to remove the solvent to obtain a light yellow viscous liquid, which was purified by chromatography column (V 石油醚 :V 乙酸乙酯 =7:1) After separation and purification, 4.82 g of light yellow liquid compound 2 was obtained.

[0018] Synthesis of CPDMN: 4.82 g of compound 2, 7.76 g of AIBN, and 50 mL of toluene were added to a 100 mL single-necked flask in sequence and reacted at 92 °C for 6 h. After the reaction, the solvent was removed by rotary evaporation to obtain a crude product, which was purified by chromatography (V 石油醚 :V 乙酸乙酯 =7:1) After separation and purification, 4.7 g of light yellow viscous liquid compound CPDMN was obtained.

[0019] (2) Preparation of polymethyl methacrylate macroinitiator Weigh 0.1 g of alkoxyamine CPDMN, 3.35 g of methyl methacrylate, and 3.45 g of toluene, stir and dissolve them fully, then evacuate and pass nitrogen to remove oxygen in the reaction system, react at 90°C for 3 h, dilute with tetrahydrofuran solution after the reaction, precipitate in cold methanol, filter, and dry to prepare polymethyl methacrylate macroinitiator; (3) Preparation of polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer Weigh 2.0 g of polymethyl methacrylate macroinitiator, 8.64 g of dimethylaminoethyl methacrylate, and 10.64 g of n-butyl acetate, stir and dissolve them fully, evacuate and pass nitrogen to remove oxygen in the reaction system, react at 90 °C for 4 h, dilute with dichloromethane solution after the reaction, precipitate in cold n-hexane, filter and dry to prepare polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer; (4) Preparation of polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend membrane Weigh 0.5 g of the prepared polymethyl methacrylate-block-poly(dimethylaminoethyl methacrylate) copolymer, 2 g of PVDF and NN dimethylacetamide, and mechanically stir at 80 °C for 12 h. After the reaction is completed, place it in a vacuum oven for degassing for 2 h to obtain the casting solution after the reaction, cast it on a glass plate to prepare a film with a thickness of 200 μm, and immediately immerse it in 30 °C deionized water at room temperature. After the film is formed, transfer it to deionized water at room temperature and soak it overnight. After drying for 12-48 h, collect it to obtain the prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane.

[0020] Example 2 Steps (2) and (3) are the same as in Example 1 Weigh 0.75 g of the prepared polymethyl methacrylate-block-poly(dimethylaminoethyl methacrylate) copolymer, 1.75 g of PVDF and NN dimethylacetamide, and mechanically stir at 80 °C for 12 h. After the reaction is completed, place it in a vacuum oven for degassing for 2 h to obtain the casting solution after the reaction, cast it on a glass plate to prepare a film with a thickness of 200 μm, and immediately immerse it in 30 °C deionized water at room temperature. After the film is formed, transfer it to deionized water at room temperature and soak it overnight. After drying for 12-48 h, collect it to obtain the prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane.

[0021] Example 3 Steps (2) and (3) are the same as in Example 1 Weigh 1 g of the prepared polymethyl methacrylate-block-poly(dimethylaminoethyl methacrylate) copolymer, 1.5 g of PVDF and NN dimethylacetamide, and mechanically stir them at 80 °C for 12 h. After the reaction is completed, place them in a vacuum oven for degassing for 2 h to obtain the casting solution after the reaction, cast it on a glass plate to prepare a film with a thickness of 200 μm, and immediately immerse it in 30 °C deionized water at room temperature. After the film is formed, transfer it to deionized water at room temperature and soak it overnight. After drying for 12-48 h, collect and obtain the prepared polymethyl methacrylate-block-poly(dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane.

[0022] Example 4 (1) Preparation of polymethyl methacrylate macroinitiator Weigh 0.1 g of alkoxyamine CPDMN, 5.02 g of methyl methacrylate, and 5.12 g of toluene, stir and dissolve them fully, then evacuate and pass nitrogen to remove oxygen in the reaction system, react at 90°C for 4 h, dilute with tetrahydrofuran solution after the reaction, precipitate in cold methanol, filter, and dry to prepare polymethyl methacrylate macroinitiator; (2) Preparation of polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer Weigh 2.0 g of polymethyl methacrylate macroinitiator, 8.98 g of dimethylaminoethyl methacrylate, and 10.64 g of n-butyl acetate, stir and dissolve them fully, evacuate and pass nitrogen to remove oxygen in the reaction system, react at 90 °C for 4 h, dilute with dichloromethane solution after the reaction, precipitate in cold n-hexane, filter and dry to prepare polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer; (3) Preparation of polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend membrane Weigh 0.5 g of the prepared polymethyl methacrylate-block-poly(dimethylaminoethyl methacrylate) copolymer, 2 g of PVDF and NN dimethylacetamide, and mechanically stir at 80 °C for 12 h. After the reaction is completed, place it in a vacuum oven for degassing for 2 h to obtain the casting solution after the reaction, cast it on a glass plate to prepare a film with a thickness of 200 μm, and immediately immerse it in 30 °C deionized water at room temperature. After the film is formed, transfer it to deionized water at room temperature and soak it overnight. After drying for 12-48 h, collect it to obtain the prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane.

[0023] Example 5 Wherein steps (1) and (2) are the same as those in Example 4; Step (3) Preparation of polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend film Weigh 0.75 g of the prepared polymethyl methacrylate-block-poly(dimethylaminoethyl methacrylate) copolymer, 1.75 g of PVDF and NN dimethylacetamide, and mechanically stir at 80 °C for 12 h. After the reaction is completed, place it in a vacuum oven for degassing for 2 h to obtain the casting solution after the reaction, cast it on a glass plate to prepare a film with a thickness of 200 μm, and immediately immerse it in 30 °C deionized water at room temperature. After the film is formed, transfer it to deionized water at room temperature and soak it overnight. After drying for 12-48 h, collect it to obtain the prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane.

[0024] Example 6 Steps (1) and (2) are the same as those in Example 4; Step (3) Preparation of polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend film Weigh 1 g of the prepared polymethyl methacrylate-block-poly(dimethylaminoethyl methacrylate) copolymer, 1.5 g of PVDF and NN dimethylacetamide, and mechanically stir at 80 °C for 12 h. After the reaction is completed, place it in a vacuum oven for degassing for 2 h to obtain the casting solution after the reaction, cast it on a glass plate to prepare a film with a thickness of 200 μm, and immediately immerse it in 30 °C deionized water at room temperature. After the film is formed, transfer it to deionized water at room temperature and soak it overnight. After drying for 12-48 h, collect it to obtain the prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane.

[0025] The physical picture and SEM picture of the blend film are as follows: Figure 1 , Figure 2 As shown, the pure PVDF membrane has a dense structure. After adding the copolymer, a porous structure appears on the membrane surface, proving that the modification is successful.

[0026] Application Example 1 10 ml of the prepared 10 mg / L methyl orange (MO) dye solution was added into the ultrafiltration apparatus to determine the removal rate of the dye solution by the blended membrane in Example 1. The concentration of the MO solution before and after interception was determined by a visible light spectrophotometer, and the interception rate was 38%.

[0027] Application Example 2 10 ml of the prepared 10 mg / L methyl orange (MO) dye solution was added into the ultrafiltration apparatus to determine the removal rate of the dye solution by the blended membrane in Implementation 2. The concentration of the MO solution before and after interception was determined by a visible light spectrophotometer, and the interception rate was 68%.

[0028] Application Example 3 10 ml of the prepared 10 mg / L methyl orange (MO) dye solution was added into the ultrafiltration apparatus to determine the removal rate of the dye solution by the blended membrane in Implementation 3. The concentration of the MO solution before and after interception was determined by a visible light spectrophotometer, and the interception rate was 71%.

[0029] Application Example 4 10 ml of the prepared 10 mg / L methyl orange (MO) dye solution was added into the ultrafiltration apparatus to determine the removal rate of the dye solution by the blended membrane in Example 4. The concentration of the MO solution before and after interception was determined by a visible light spectrophotometer, and the interception rate was 74%.

[0030] Application Example 5 10 ml of the prepared 10 mg / L methyl orange (MO) dye solution was added into the ultrafiltration apparatus to determine the removal rate of the dye solution by the blended membrane in Example 5. The concentration of the MO solution before and after interception was determined by a visible light spectrophotometer, and the interception rate was 81%.

[0031] Application Example 6 10 ml of the prepared 10 mg / L methyl orange (MO) dye solution was added into the ultrafiltration apparatus to determine the removal rate of the dye solution by the blended membrane in Example 6. The concentration of the MO solution before and after interception was determined by a visible light spectrophotometer, and the interception rate was 90%.

Claims

1. A method for preparing a polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend film, characterized in that: The following steps are involved: (1) Preparation of 3-(((2-cyanopropane-2-yl)oxy)(isopropyl)amino)-2,2-dimethyl-3-phenylpropionitrile (CPDMN) Benzaldehyde, isopropylamine and methanol were added to a three-necked flask, and a magnetite was added. The reaction was carried out in an oil bath. After the reaction was completed, the mixture was cooled to room temperature, and sodium borohydride was added thereto in batches. After stirring for a certain period of time, the reaction of the raw materials was monitored by thin layer chromatography. The solvent was removed by rotary evaporation, the mixture was dissolved in ethyl acetate, washed with saturated brine, dried over anhydrous magnesium sulfate, and rotary evaporated to obtain compound 1; Compound 1 and sodium bicarbonate were dissolved in acetone and water, potassium peroxymonosulfonate was added in batches under ice bath condition, the mixture was stirred and filtered with acetone, washed with saturated brine, the upper organic phase was collected, dried over anhydrous magnesium sulfate, filtered and rotary evaporated, and then separated and purified by chromatography column to obtain compound 2; Compound 2, azobisisobutyronitrile and toluene were added to a single-necked flask. After the reaction was completed in an oil bath, the solvent was removed by rotary evaporation to obtain a crude product, which was separated and purified by a chromatography column to obtain a compound CPDMN product; (2) Preparation of methyl methacrylate macroinitiator Methyl methacrylate, CPDMN and toluene are placed in a reaction container, stirred and dissolved, vacuumed and nitrogen-filled to remove oxygen in the reaction system, and reacted. After the reaction, the mixture is diluted with tetrahydrofuran solution, precipitated in cold methanol, filtered and dried to prepare a polymethyl methacrylate macroinitiator. (3) Preparation of polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer The polymethyl methacrylate macroinitiator prepared in step (2) is dissolved in n-butyl acetate, and after it is completely dissolved, dimethylaminoethyl methacrylate is added, and the mixture is stirred to be uniformly mixed. After the solution becomes clear and transparent, vacuum-nitrogen is used to remove oxygen in the reaction system. After the reaction is completed, the mixture is cooled to room temperature, diluted with a dichloromethane solution, precipitated in an n-hexane solution, filtered, and dried to obtain a polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer; (4) Preparation of polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blend membrane The prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer, polyvinylidene fluoride and NN dimethylacetamide were mixed and mechanically stirred. After the reaction was completed, the mixture was placed in a vacuum oven for degassing for 2 h to obtain a casting solution after the reaction. The solution was cast on a glass plate to prepare a film with a thickness of 200 μm, and the film was immediately immersed in 30 °C deionized water at room temperature. After the film was formed, it was transferred to deionized water at room temperature and immersed overnight. After drying for 12-48 h, the prepared polymethyl methacrylate-block-poly (dimethylaminoethyl methacrylate) copolymer / PVDF blended membrane was obtained.

2. The preparation method according to claim 1, characterized in that : In step (2), the molar ratio of 3-(((2-cyanopropane-2-yl)oxy)(isopropyl)amino)-2,2-dimethyl-3-phenylpropionitrile to methyl methacrylate is 1:100 to 1:

150.

3. The preparation method according to claim 1, characterized in that : The specific reaction of step (2) is to react at 90°C for 3 h to 5 h.

4. The preparation method according to claim 1, characterized in that : In step (3), the molar ratio of polymethyl methacrylate macroinitiator to dimethylaminoethyl methacrylate is 1:50~1:

400.

5. The preparation method according to claim 1, characterized in that : The reaction conditions in step (3) are at 90°C for 2 h to 6 h.

6. The preparation method according to claim 1, characterized in that : In step (4), the mass ratio of polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer to polyvinylidene fluoride is 1:9~2:

3.

7. The preparation method according to claim 1, characterized in that : In step (4), the mechanical stirring is performed at 80°C for 12 h.

8. A polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend membrane prepared by the method according to any one of claims 1 to 7.

9. Use of the polymethyl methacrylate-block-polydimethylaminoethyl methacrylate copolymer / PVDF blend membrane as claimed in claim 8 in dye wastewater treatment.

Images