Polyvinylidene fluoride water treatment membrane supported by non-woven fabric and preparation method of polyvinylidene fluoride water treatment membrane

Abstract

The invention 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 a hydrophobic nano material acetylene black as a blending modifier and polyvinylidene fluoride as a main body membrane material, and dissolving in a polar organic solvent to prepare a membrane casting solution; and uniformly coating the membrane casting solution on a non-woven fabric serving as a support body, and carrying out phase inversion, cleaning, soaking and airing to obtain the non-woven fabric supported polyvinylidene fluoride water treatment membrane. According to the non-woven fabric supported polyvinylidene fluoride water treatment membrane and the preparation method thereof, the endurance capacity of the polyvinylidene fluoride water treatment membrane in a sodium hypochlorite aqueous solution is enhanced and the service life of the polyvinylidene fluoride water treatment membrane in the sodium hypochlorite aqueous solution is prolonged through the oxidation resistance and hydrophobic interaction of acetylene black.

Description

Technical Field

[0001] The invention relates to the technical field of membrane material preparation, in particular to a non-woven fabric-supported polyvinylidene fluoride water treatment membrane and a preparation method thereof. Background Art

[0002] Polyvinylidene fluoride materials have good chemical stability and can be used to prepare water treatment membranes through phase inversion methods. Polyvinylidene fluoride water treatment membranes are microfiltration membranes or ultrafiltration membranes that can intercept microorganisms and suspended solids in water and have excellent separation performance. However, the mechanical strength of the polyvinylidene fluoride membrane itself is poor, and permeable materials such as non-woven fabrics and polyester braided tubes are usually used to enhance tensile and fracture resistance. Polyester braided tubes can be used as linings for the preparation of polyvinylidene fluoride hollow fiber membranes or tubular membranes, and non-woven fabrics can be used as supports for the preparation of polyvinylidene fluoride flat membranes.

[0003] The most widely used application of polyvinylidene fluoride water treatment membrane is membrane bioreactor (MBR), which is used for urban and industrial sewage treatment. In the high-load MBR sewage treatment system, the polyvinylidene fluoride water treatment membrane needs to withstand a certain hydraulic pressure and requires frequent backwashing and chemical cleaning. Backwashing with a large water pressure or multiple backwashing will cause the peeling between the polyvinylidene fluoride water treatment membrane and the support, resulting in the so-called "peeling" phenomenon, which reduces the performance of the water treatment membrane. In the MBR system, biomass and microorganisms are adsorbed on the membrane in large quantities, blocking the membrane pores and reducing the membrane's permeation flux. Therefore, the polyvinylidene fluoride water treatment membrane needs to be cleaned with chemicals, especially sodium hypochlorite disinfectant. Sodium hypochlorite has oxidizing ability. The polyvinylidene fluoride water treatment membrane is cleaned with a high concentration of sodium hypochlorite aqueous solution or repeatedly cleaned with sodium hypochlorite aqueous solution, which causes the polyvinylidene fluoride membrane to oxidize and rupture, reducing the service life of the water treatment membrane. Further improving the bonding strength between polyvinylidene fluoride water treatment and the support and improving the oxidation resistance of polyvinylidene fluoride water treatment have become technical problems that are of general concern and urgently need to be solved in the industry. Summary of the invention

[0004] The purpose of the present invention is to provide a non-woven fabric supported polyvinylidene fluoride water treatment membrane and a preparation method thereof, wherein acetylene black is used as a blending modifier, and the tolerance of the polyvinylidene fluoride water treatment membrane in a sodium hypochlorite aqueous solution is enhanced by the antioxidant property of acetylene black; the binding force between the polyvinylidene fluoride water treatment membrane and a supporting material is improved by the hydrophobic effect of acetylene black, and the polyvinylidene fluoride water treatment membrane is prevented from peeling during long-term use, thereby extending the service life of the polyvinylidene fluoride water treatment membrane supported by the non-woven fabric.

[0005] To achieve the above object, the present invention provides a method for preparing a non-woven fabric-supported polyvinylidene fluoride water treatment membrane, comprising the following steps:

[0006] S1, preparing a casting solution;

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

[0008] S3, washing, soaking and 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: 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.

[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 porogen 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 porogen is one of polyethylene glycol and polyvinyl pyrrolidone;

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

[0016] Preferably, the stirring time is 3-6 hours and the defoaming time is 3-6 hours.

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

[0018] Preferably, 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.

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

[0020] The present invention provides a non-woven fabric supported polyvinylidene fluoride water treatment membrane, which is prepared by adopting the above-mentioned method for preparing a non-woven fabric supported polyvinylidene fluoride water treatment membrane.

[0021] Therefore, the present invention adopts the above-mentioned non-woven fabric-supported polyvinylidene fluoride water treatment membrane and its preparation method, which has the following beneficial effects:

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

[0023] (2) Acetylene black is used as a blending modifier. Its hydrophobic effect improves the bonding force between the polyvinylidene fluoride water treatment membrane and the supporting material, preventing the polyvinylidene fluoride water treatment membrane from peeling during long-term use, and extending the service life of the polyvinylidene fluoride water treatment membrane supported by the non-woven fabric.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a physical picture of a non-woven fabric-supported polyvinylidene fluoride water treatment membrane and a preparation method thereof in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0027] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0028] Example 1

[0029] A non-woven fabric-supported polyvinylidene fluoride water treatment membrane, the preparation method of which 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 and dissolve them in 79.0 mL of dimethylformamide. Stir for 5 h at room temperature to make them dissolve evenly. Let them stand for degassing for 5 h to obtain a casting solution.

[0031] Among them, acetylene black is a blending modifier, which is composed of nano-scale 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 has a basic skeleton structure composed of carbon-carbon bonds and exhibits strong hydrophobic properties. The preferred particle size is less than 1.0 μm and the specific surface area is greater than 100 m 2 / g of acetylene black products.

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

[0033] S2. Use a scraper to evenly apply the casting solution on the polyester non-woven fabric. The thickness of the applied casting solution is 100 μm. Perform phase inversion by a phase inversion method. The phase inversion method is a prior art.

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

[0035] Example 2

[0036] The difference between Example 2 and Example 1 is that the amount of polyvinylidene fluoride is 14.0 g and the amount of dimethylformamide is 80.0 mL.

[0037] Example 3

[0038] The difference between Example 3 and Example 1 is that the amount of polyvinylidene fluoride is 14.0 g and the amount of polyethylene glycol is 4.0 g.

[0039] Example 4

[0040] The difference between Example 4 and Example 1 is that the amount of acetylene black is 2.0 g, the amount of polyvinylidene fluoride is 14.0 g, and the amount of polyethylene glycol is 4.0 g.

[0041] Example 5

[0042] The difference between Example 5 and Example 1 is that the amount of acetylene black is 4.0 g and the amount of dimethylacetamide is 78.0 mL.

[0043] Example 6

[0044] The difference between Example 6 and Example 1 is 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] The difference between Example 7 and Example 1 is 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] The difference between Example 8 and Example 1 is that the amount of polyvinylidene fluoride is 14.0 g, the amount of polyethylene glycol is 5.0 g, and the polar solvent is 78.0 mL of dimethylacetamide.

[0049] Example 9

[0050] The difference between Example 9 and Example 1 is that the amount of polyvinylidene fluoride is 14.0 g, the polar solvent is 79.0 mL of dimethylacetamide, and the thickness of the coated casting solution is 120 μm.

[0051] Example 10

[0052] The difference between Example 10 and Example 1 is that the amount of polyvinylidene fluoride is 14.0 g, the porogen is 4.0 g of polyvinyl pyrrolidone, the polar solvent is 79.0 mL of dimethylacetamide, and the thickness of the coated casting solution is 200 μm.

[0053] Comparative Example 1

[0054] S1. Weigh 14.0 g of polyvinylidene fluoride and 3.0 g of polyethylene glycol and dissolve them in 83.0 mL of dimethylacetamide. Stir at room temperature for 5 h to make them dissolve evenly. Let them stand for degassing for 5 h to obtain a casting solution.

[0055] S2. Use a scraper to evenly apply the casting solution on the polyester non-woven fabric. The thickness of the applied casting solution is 100 μm. Perform phase inversion by a phase inversion method. The phase inversion method is a prior art.

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

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

[0058] Water flux:

[0059] Using a cross-flow membrane pool, the water flux of the non-woven fabric-supported polyvinylidene fluoride water treatment membrane was calculated by the following formula:

[0060]

[0061] Where: J is water flux, L / (m 2 h bar); V is the permeate volume, L; A is the membrane surface area, m 2 ; Δt is the membrane filtration running time, h; P is the operating pressure, bar.

[0062] Yeast retention rate:

[0063] A cross-flow membrane pool was used, with yeast aqueous solution as the raw liquid, and a turbidity meter was used to measure the yeast concentration. The yeast retention rate of the non-woven fabric-supported polyvinylidene fluoride water treatment membrane was calculated by the following formula:

[0064]

[0065] Where: R is the yeast retention rate, %; C p is the turbidity of the filtrate; C f is the turbidity of the raw material solution.

[0066] Adhesion:

[0067] The adhesive force between the polyvinylidene fluoride water treatment membrane and the non-woven fabric support is tested by the tape bonding and peeling method. First, cut a piece of non-woven fabric support polyvinylidene fluoride water treatment membrane of appropriate area, use tape to bond the polyvinylidene fluoride water treatment membrane, press lightly, and then pull the tape and non-woven fabric support apart. If the polyvinylidene fluoride water treatment membrane falls off the non-woven fabric, it is judged that the bonding force is unqualified. If the polyvinylidene fluoride water treatment membrane is still bonded to the non-woven fabric, it is judged that the bonding force is good.

[0068] Experimental Test 1

[0069] In Examples 1-10, the water flux of the non-woven fabric-supported polyvinylidene fluoride water treatment membrane was 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), 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 show that the polyvinylidene fluoride water treatment membranes prepared in Examples 1-10 are well bonded to the non-woven fabric support, while the comparative example 1 does not add acetylene black blending modifier, and the adhesive tape peeling test shows that the bonding strength between the polyvinylidene fluoride water treatment membrane and the non-woven fabric support is unqualified, and peeling may occur after long-term use.

[0070] Experimental Test 2

[0071] The nonwoven fabric-supported polyvinylidene fluoride water treatment membranes prepared in Examples 1-10 and Comparative Example 1 were immersed in a 2-5% sodium hypochlorite aqueous solution for 10 hours, and then their yeast retention rates were tested, and the binding strength between the polyvinylidene fluoride water treatment membranes and the nonwoven fabric support was determined. The results are shown in Table 1.

[0072] Table 1 Yeast retention rate and binding capacity test results

[0073]

[0074] In Examples 1-10 and Comparative Example 1, after immersion in 2-5% sodium hypochlorite aqueous solution for 10 hours, the yeast retention rate was 100%. However, in the tape adhesion peeling test, the polyvinylidene fluoride water treatment membrane prepared in Comparative Example 1 failed to adhere to the non-woven fabric support, and peeling may occur after long-term use.

[0075] Therefore, the present invention adopts the above-mentioned non-woven fabric-supported polyvinylidene fluoride water treatment membrane and its preparation method, uses acetylene black as a blending modifier, and enhances the tolerance of the non-woven fabric-supported polyvinylidene fluoride water treatment membrane in a sodium hypochlorite aqueous solution through the antioxidant property of acetylene black; improves the bonding force between the polyvinylidene fluoride water treatment membrane and the supporting material through the hydrophobic effect of acetylene black, prevents the polyvinylidene fluoride water treatment membrane from peeling during 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 embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

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. Wash, soak and air-dry the membrane obtained by phase inversion to obtain a polyvinylidene fluoride water treatment membrane supported by a non-woven fabric.

2. The preparation method according to claim 1, characterized in that: 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.

3. The preparation method according to claim 2, characterized in that: The mass fraction of acetylene black in the casting solution is 0.5-10%; 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%.

4. The preparation method according to claim 2, characterized in that: The particle size of acetylene black is less than 1.0 μm.

5. The preparation method according to claim 2, 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.

6. The preparation method according to claim 2, characterized in that: The stirring time is 3-6h, and the defoaming time is 3-6h.

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

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

9. The preparation method according to claim 8, characterized in that: The mass fraction of glycerol in the glycerol aqueous solution is 20-30%.

10. 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 as described in any one of claims 1 to 9.

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