A nonwoven supported polyvinylidene fluoride water treatment membrane and method of making the same

Abstract

The application discloses a non-woven fabric supported polyvinylidene fluoride water treatment membrane and a preparation method thereof, and belongs to the technical field of membrane material preparation. The preparation method comprises the following steps: using hydrophobic nanomaterial acetylene black as a blending modifier, polyvinylidene fluoride as a main membrane material, dissolving in a polar organic solvent to prepare casting solution; using non-woven fabric as a support body, uniformly coating the casting solution, and preparing the non-woven fabric supported polyvinylidene fluoride water treatment membrane through phase inversion, cleaning, soaking and air drying. The polyvinylidene fluoride water treatment membrane and the preparation method thereof have the advantages that the oxidation resistance and the hydrophobic effect of acetylene black are utilized to enhance the tolerance and service life of the polyvinylidene fluoride water treatment membrane in sodium hypochlorite aqueous solution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of film material preparation, and particularly relates to a non-woven fabric supported polyvinylidene fluoride water treatment film and a preparation method thereof. BACKGROUND

[0002] The polyvinylidene fluoride material has good chemical stability and can be used to prepare a water treatment film through a phase inversion method. The polyvinylidene fluoride water treatment film is a microfiltration membrane or an ultrafiltration membrane, which can retain microorganisms and solid suspensions in water and has excellent separation performance. However, the mechanical strength of the polyvinylidene fluoride membrane itself is poor, and a permeable material such as non-woven fabric or polyester braided tube is usually used to enhance the tensile resistance and prevent the breakage. The polyester braided tube can be used as a lining to prepare a polyvinylidene fluoride hollow fiber membrane or a tubular membrane, and the non-woven fabric can be used as a support to prepare a polyvinylidene fluoride flat membrane.

[0003] The most widely used polyvinylidene fluoride water treatment film is a membrane bioreactor (MBR), which is used for municipal and enterprise sewage treatment. In a high-load MBR sewage treatment system, the polyvinylidene fluoride water treatment film needs to withstand a certain hydraulic pressure and needs to be frequently backwashed and cleaned with chemicals. The backwashing under a large water pressure or multiple backwashings can cause the separation between the polyvinylidene fluoride water treatment film and the support, resulting in the so-called peeling phenomenon and reducing the performance of the water treatment film. In the MBR system, a large amount of biomass and microorganisms are adsorbed on the membrane, blocking the membrane pores and reducing the permeation flux of the membrane, so the polyvinylidene fluoride water treatment film needs to be cleaned with chemicals, especially sodium hypochlorite sterilizing agent. Sodium hypochlorite has oxidizing ability, and the polyvinylidene fluoride water treatment film is cleaned with a high-concentration sodium hypochlorite aqueous solution or repeatedly cleaned with a sodium hypochlorite aqueous solution, which causes the oxidation and rupture of the polyvinylidene fluoride membrane and reduces the service life of the water treatment film. It has become a common concern and an urgent technical problem to be solved in the industry to further improve the bonding force between the polyvinylidene fluoride water treatment film and the support and to improve the oxidation resistance of the polyvinylidene fluoride water treatment film. SUMMARY

[0004] The present application aims to provide a non-woven fabric supported polyvinylidene fluoride water treatment film and a preparation method thereof. The use of acetylene black as a blending modifier enhances the resistance of the polyvinylidene fluoride water treatment film to sodium hypochlorite aqueous solution through the antioxidant property of acetylene black. The use of acetylene black improves the bonding force between the polyvinylidene fluoride water treatment film and the support material through the hydrophobic effect of acetylene black, prevents the peeling phenomenon of the polyvinylidene fluoride water treatment film in long-term use, and prolongs the service life of the non-woven fabric supported polyvinylidene fluoride water treatment film.

[0005] To achieve the above-mentioned purpose, the present application provides a preparation method of a non-woven fabric supported polyvinylidene fluoride water treatment film, which comprises the following steps:

[0006] S1, preparing a casting solution;

[0007] S2, coating the casting solution on a non-woven fabric and performing phase inversion by a phase inversion method;

[0008] S3, washing, soaking and air-drying the membrane obtained by phase inversion to obtain a non-woven fabric supported polyvinylidene fluoride water treatment membrane.

[0009] Preferably, the specific steps of S1 are as follows: weighing acetylene black, polyvinylidene fluoride and a pore former, dissolving them in a polar organic solvent, stirring at room temperature, and then standing to remove bubbles to obtain a casting solution.

[0010] Preferably, the mass fraction of acetylene black in the casting solution is 0.5-10%;

[0011] The mass fraction of polyvinylidene fluoride in the casting solution is 10-20%;

[0012] The mass fraction of the pore former in the casting solution is 0.5-10%.

[0013] Preferably, the particle size of acetylene black is less than 1.0 μm.

[0014] Preferably, the pore former is one of polyethylene glycol and polyvinylpyrrolidone;

[0015] The polar organic solvent is one of acetone, dimethylformamide, dimethylacetamide and methylpyrrolidone.

[0016] Preferably, the stirring time is 3-6 h and the bubble removal time is 3-6 h.

[0017] Preferably, in S2, the thickness of the coating casting solution is 50-200 μm.

[0018] Preferably, the specific steps of S3 are as follows: washing the membrane obtained by phase inversion with deionized water to remove organic solvents and pore formers, then soaking in a glycerol aqueous solution, and air-drying to obtain a non-woven fabric supported polyvinylidene fluoride water treatment membrane.

[0019] Preferably, the mass fraction of glycerol in the glycerol aqueous solution is 20-30%.

[0020] The application provides a non-woven fabric supported polyvinylidene fluoride water treatment membrane prepared by the above-mentioned preparation method.

[0021] Therefore, the non-woven fabric supported polyvinylidene fluoride water treatment membrane and the preparation method thereof have the following beneficial effects:

[0022] (1) Acetylene black as a blending modifier, its antioxidant performance enhances the resistance of non-woven fabric supported polyvinylidene fluoride water treatment membrane in sodium hypochlorite aqueous solution;

[0023] (2) Acetylene black as a blending modifier, its hydrophobic effect improves the binding force between polyvinylidene fluoride water treatment membrane and support material, prevents the peeling phenomenon of polyvinylidene fluoride water treatment membrane in long-term use, and prolongs the service life of non-woven fabric supported polyvinylidene fluoride water treatment membrane.

[0024] The technical solutions of the present application are further described below by means of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the physical map of one embodiment of the non-woven fabric supported polyvinylidene fluoride water treatment membrane and its preparation method of the present application. DETAILED DESCRIPTION

[0026] The technical solutions of the present application are further described below by means of drawings and examples.

[0027] Unless otherwise defined, the technical terms or scientific terms used in the present application shall be understood as the usual meaning understood by those skilled in the art to which the present application belongs.

[0028] Example 1

[0029] A non-woven fabric supported polyvinylidene fluoride water treatment membrane, its preparation method comprises the following steps:

[0030] S1, weigh 3.0 g of acetylene black, 15.0 g of polyvinylidene fluoride and 3.0 g of polyethylene glycol, dissolve them in 79.0 mL of dimethylformamide, stir at room temperature for 5 h, make them uniformly dissolved, then stand for 5 h to remove bubbles, obtain casting solution.

[0031] Among them, acetylene black is a blending modifier, which is aggregated by nano-sized carbon particles. The size of these carbon particles is in the nanometer range, which gives acetylene black a larger specific surface area. When interacting with other substances, acetylene black has more contact sites. Acetylene black is composed of carbon-carbon bond basic skeleton structure, which presents strong hydrophobic performance. Preferably, the particle size of acetylene black is less than 1.0 μm, the specific surface area is greater than 100 m 2 / g of acetylene black commodity.

[0032] Polyvinylidene fluoride as the main membrane material, polyethylene glycol as the pore former, which is a hydrophilic polymer material, dimethylformamide as a polar solvent.

[0033] S2, use a doctor blade to uniformly coat the casting solution on the polyester non-woven fabric, the thickness of the coating casting solution is 100 μm, and phase inversion is carried out by phase inversion method, which is prior art.

[0034] S3, the phase inversion obtained film is washed with deionized water to remove organic solvents and porogen, then immersed in glycerol aqueous solution, the mass fraction of glycerol in glycerol aqueous solution is 25%, after drying, a non-woven fabric supported polyvinylidene fluoride water treatment membrane is obtained, as shown in Figure 1 .

[0035] Example 2

[0036] Example 2 is different from example 1 in that the polyvinylidene fluoride is 14.0 g and the dimethylformamide is 80.0 mL.

[0037] Example 3

[0038] Example 3 is different from example 1 in that the polyvinylidene fluoride is 14.0 g and the polyethylene glycol is 4.0 g.

[0039] Example 4

[0040] Example 4 is different from example 1 in that the acetylene black is 2.0 g, the polyvinylidene fluoride is 14.0 g, and the polyethylene glycol is 4.0 g.

[0041] Example 5

[0042] Example 5 is different from example 1 in that the acetylene black is 4.0 g and the dimethylacetamide is 78.0 mL.

[0043] Example 6

[0044] Example 6 is different from example 1 in that the acetylene black is 5.0 g, the polyvinylidene fluoride is 14.0 g, and the polar solvent is 78.0 mL of acetone.

[0045] Example 7

[0046] Example 7 is different from example 1 in that the acetylene black is 6.0 g, the polyvinylidene fluoride is 14.0 g, and the polar solvent is 77.0 mL of dimethylacetamide.

[0047] Example 8

[0048] Example 8 is different from example 1 in that the polyvinylidene fluoride is 14.0 g, the polyethylene glycol is 5.0 g, and the polar solvent is 78.0 mL of dimethylacetamide.

[0049] Example 9

[0050] Example 9 is different from example 1 in that the polyvinylidene fluoride is 14.0 g, the polar solvent is 79.0 mL of dimethylacetamide, and the thickness of the casting solution is 120 μm.

[0051] Example 10

[0052] Example 10 is different from Example 1 in that the polyvinylidene fluoride is 14.0 g, the porogen is 4.0 g of polyvinylpyrrolidone, the polar solvent is 79.0 mL of dimethylacetamide, and the thickness of the coating casting solution is 200 μm.

[0053] Comparative Example 1

[0054] S1, 14.0 g of polyvinylidene fluoride and 3.0 g of polyethylene glycol were weighed and dissolved in 83.0 mL of dimethylacetamide, stirred at room temperature for 5 h to make them uniformly dissolved, and then left to stand for 5 h to degas, to obtain a casting solution.

[0055] S2, the casting solution was uniformly coated on a polyester non-woven fabric using a doctor blade, the thickness of the coating casting solution was 100 μm, and phase inversion was performed by a phase inversion method which is a prior art.

[0056] S3, the membrane obtained by phase inversion was sufficiently washed with deionized water to remove organic solvents and porogens, and then immersed in a glycerol aqueous solution in which the mass fraction of glycerol was 25%, and after air-drying, a non-woven fabric-supported polyvinylidene fluoride water treatment membrane was obtained.

[0057] Comparative Example 1 is different from Example 1 in that acetylene black is not used as a blending modifier, the polyvinylidene fluoride is 14.0 g, and the polar solvent is 83.0 mL of dimethylacetamide.

[0058] Water flux:

[0059] A cross-flow membrane cell was used, and the water flux of the non-woven fabric-supported polyvinylidene fluoride water treatment membrane was calculated by the following formula:

[0060]

[0061] In the formula, J is the water flux, L / (m 2 h bar); V is the permeation volume, L; A is the membrane surface area, m 2 ; Δt is the membrane filtration operation time, h; and P is the operating pressure, bar.

[0062] Yeast retention rate:

[0063] A cross-flow membrane cell was used, and the yeast aqueous solution was used as the raw material liquid, the turbidimeter was used to measure the yeast concentration, and the yeast retention rate of the non-woven fabric-supported polyvinylidene fluoride water treatment membrane was calculated by the following formula:

[0064]

[0065] In the formula, R is the yeast retention rate, %; C p is the turbidity of the permeate; and C f is the turbidity of the raw material liquid.

[0066] Adhesion:

[0067] The adhesion between the polyvinylidene fluoride water treatment membrane and the non-woven fabric support was tested by the adhesive tape peeling method. First, a piece of non-woven fabric supported polyvinylidene fluoride water treatment membrane with a suitable area was cut, the polyvinylidene fluoride water treatment membrane was adhered to the non-woven fabric support with adhesive tape, and then the adhesive tape and the non-woven fabric support were pulled apart. If the polyvinylidene fluoride water treatment membrane fell off the non-woven fabric, it was judged that the adhesion was unqualified. If the polyvinylidene fluoride water treatment membrane was still adhered to the non-woven fabric, it was judged that the adhesion was good.

[0068] Test Test One

[0069] In Examples 1-10, the water fluxes of the non-woven fabric supported polyvinylidene fluoride water treatment membranes were 380.6, 540.2, 622.4, 560.8, 443.0, 367.3, 285.8, 587.9, 526.9, and 480.2 L / (m 2 h bar), respectively, while the water flux of the non-woven fabric supported polyvinylidene fluoride water treatment membrane prepared in Comparative Example 1 was 728.2 L / (m 2 h bar). The adhesive tape peeling test results showed that the polyvinylidene fluoride water treatment membranes prepared in Examples 1-10 were all well adhered to the non-woven fabric support, while Comparative Example 1 did not add an acetylene black blending modifier, and the adhesive tape peeling test showed that the adhesion between the polyvinylidene fluoride water treatment membrane and the non-woven fabric support was unqualified, and peeling might occur during long-term use.

[0070] Test Test Two

[0071] The non-woven fabric supported polyvinylidene fluoride water treatment membranes prepared in Examples 1-10 and Comparative Example 1 were soaked in a 2-5% sodium hypochlorite aqueous solution for 10 h, and then their yeast interception rates were tested, and the adhesion between the polyvinylidene fluoride water treatment membrane and the non-woven fabric support was judged, and the results are shown in Table 1.

[0072] Table 1 Test Results of Yeast Interception Rate and Adhesion

[0073]

[0074] In Examples 1-10 and Comparative Example 1, the yeast interception rates were all 100% after being soaked in a 2-5% sodium hypochlorite aqueous solution for 10 h, but in the adhesive tape peeling test, the polyvinylidene fluoride water treatment membrane prepared in Comparative Example 1 was not well adhered to the non-woven fabric support, and peeling might occur during long-term use.

[0075] Therefore, the application adopts the above non-woven fabric supported polyvinylidene fluoride water treatment membrane and its preparation method, uses acetylene black as a blending modifier, enhances the tolerance of the non-woven fabric supported polyvinylidene fluoride water treatment membrane in sodium hypochlorite aqueous solution through the antioxidation of acetylene black; improves the binding force between the polyvinylidene fluoride water treatment membrane and the support material through the hydrophobic effect of acetylene black, prevents the peeling phenomenon of the polyvinylidene fluoride water treatment membrane in long-term use, and prolongs the service life of the non-woven fabric supported polyvinylidene fluoride water treatment membrane.

[0076] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application rather than limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing a non-woven fabric supported polyvinylidene fluoride water treatment membrane, characterized in that: The following steps are involved: S1, preparing a casting solution; S2, coating the casting solution on the non-woven fabric and performing phase inversion by a phase inversion method; S3, washing, soaking, and drying the membrane obtained by phase inversion to obtain a non-woven fabric-supported polyvinylidene fluoride water treatment membrane; The specific steps of S1 are: weighing acetylene black, polyvinylidene fluoride and a porogen, dissolving them in a polar organic solvent, stirring at room temperature, and then standing to degas to obtain a casting solution; The invention is characterized in that the mass fraction of acetylene black in the casting solution is 0.5-10%; the particle size of acetylene black is less than 1.0 μm; The mass fraction of polyvinylidene fluoride in the casting solution is 10-20%; The mass fraction of the porogen in the casting solution is 0.5-10%.

2. The preparation method according to claim 1, characterized in that The porogen is one of polyethylene glycol and polyvinyl pyrrolidone; The polar organic solvent is one of acetone, dimethylformamide, dimethylacetamide and methylpyrrolidone.

3. The preparation method according to claim 1, characterized in that The stirring time is 3-6 hours, and the defoaming time is 3-6 hours.

4. The preparation method according to claim 1, characterized in that In S2, the thickness of the coating casting solution is 50-200 μm.

5. The preparation method according to claim 1, characterized in that The specific steps of S3 are: washing the membrane obtained by phase inversion with deionized water to remove the organic solvent and porogen, then soaking it in a glycerol aqueous solution, and drying it to obtain a non-woven fabric supported polyvinylidene fluoride water treatment membrane.

6. The preparation method according to claim 5, characterized in that The mass fraction of glycerol in the glycerol aqueous solution is 20-30%.

7. A non-woven fabric supported polyvinylidene fluoride water treatment membrane, characterized in that: The membrane is prepared by the method for preparing a non-woven fabric-supported polyvinylidene fluoride water treatment membrane according to any one of claims 1 to 6.

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