MABR membrane material with pollutant and microorganism dual anchoring functional layers and preparation method of MABR membrane material

Abstract

The invention discloses an MABR membrane material with pollutant and microorganism dual anchoring functional layers and a preparation method thereof, and belongs to the field of preparation of breathable membrane materials. The method comprises the following steps: soaking membrane filaments in absolute ethyl alcohol, treating the membrane filaments for 2-20 minutes by an ultrasonic cleaning machine to remove surface impurities, and drying the cleaned membrane filaments; the preparation method comprises the following steps: preparing a carbon material dispersion liquid which takes n-hexane as a solvent and has a mass fraction of 0.4-1.2%, and ultrasonically mixing uniformly; preparing an adhesive solution which takes n-hexane as a solvent and has a mass fraction of 4-30%, adding a curing agent at the same time, and then carrying out ultrasonic treatment for 0.25-2 hours to dissolve PDMS in n-hexane; mixing the two solutions, and stirring for 0.25-2 hours by using a magnetic stirrer until the two solutions are completely mixed; packaging the two ends of the dried membrane filament or clamping the two ends of the dried membrane filament by using a water stop clamp, putting the membrane filament into the solution, and performing dip-coating on a shaking table for 0.5-2 hours; the membrane filaments are naturally dried for 5-30 min until the solvent is completely volatilized, and the membrane filaments are placed at the temperature of 50-80 DEG C to be subjected to cross-linking curing for 4-24 h. Pollutant attachment sites on the surface of the membrane material are increased, the biocompatibility of the breathable membrane is improved, and the stability of the biological membrane is improved.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of breathable membrane materials, and particularly relates to a MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms and a preparation method thereof. Background Art

[0002] A membrane aerated biofilm reactor (MABR for short) is a new type of membrane-based sewage treatment process. Based on the concept of bubbleless aeration, the oxygen mass transfer efficiency can reach 100%. Therefore, it has the advantages of low operating energy consumption and an oxygen transfer efficiency that is 2-3 times that of traditional processes. The basic principle of MABR for treating sewage is to remove organic matter, ammonia nitrogen and other substances in water through the microbial film attached to the breathable membrane, and to provide oxygen for microorganisms through internal aeration of the breathable membrane. At the same time, due to the unique counter-diffusion mass transfer mechanism and synchronous nitrification and denitrification mechanism of MABR, the ammonia nitrogen removal effect is improved. Compared with traditional processes, it is more energy-saving, consumption-reducing, quality-improving and efficiency-increasing.

[0003] The breathable membrane material is a crucial core in the MABR process. The breathable membrane materials of traditional MABR include microporous hydrophobic membranes and dense silica gel membranes. Traditional breathable membranes are all passive adsorption, with a single surface structure. Microorganisms grow passively on them and are not easily attached, and the bioaffinity of the breathable membrane material is low. Therefore, there are problems such as a long membrane hanging cycle and loose binding. In addition, pollutants in traditional MABR need to cross a relatively thick microbial membrane layer to reach the reaction zone where functional bacteria are located, and this mass transfer problem seriously restricts the biochemical reaction rate and fails to fully exert the degradation potential of microorganisms. Summary of the Invention

[0004] In view of the above problems existing in the background art, the present invention provides a MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms and a preparation method thereof, which not only improves the bioaffinity of the breathable membrane material and promotes microbial colonization, but also strengthens the adsorption and degradation of pollutants by microorganisms, releases the potential of microorganisms, and has good application prospects.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A preparation method of a MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms, the method comprising:

[0007] Step 1: Immerse the membrane filaments in absolute ethanol, and treat them with an ultrasonic cleaner for 2-20 minutes to remove surface impurities, and then dry the cleaned membrane filaments;

[0008] Step 2: Prepare a carbon material dispersion with n-hexane as the solvent and a mass fraction of 0.4%-1.2%. Ultrasonicate for 0.5-2 hours to uniformly disperse the carbon material in the n-hexane. As the solid content increases and the treatment time is extended, some carbon nanotubes will precipitate when the concentration is high. After subsequent mixing and dilution, they can be fully dispersed. Ultrasonication causes repulsion between the carbon materials, which is conducive to dispersion.

[0009] Step 3: Prepare an adhesive solution with a mass fraction of 4-30% using n-hexane as the solvent, add a curing agent, and then sonicate for 0.25-2 hours to dissolve the PDMS in the n-hexane. Similarly, the treatment time is extended as the concentration increases.

[0010] Step 4: Mix the carbon material dispersion and the binder solution in a mass ratio of 1:1, and stir using a magnetic stirrer for 0.25-2 hours until completely mixed. Rinse during mixing to maintain the original concentration as much as possible;

[0011] Step 5: Encapsulate or clamp the ends of the dried membrane filaments with water-stopping clamps, place them in the solution obtained in step 4, and then place them on a shaker for 0.5-2 hours. Encapsulating or clamping the membrane filaments with water-stopping clamps prevents the mixed solution from step 4 from entering the interior of the breathable membrane, so that it only forms an anchoring functional layer on the outside of the breathable membrane base. The dip coating method uses a shaker to ensure the dispersion of the carbon material in the solution (if left standing, the carbon material may precipitate) and the uniformity of the dip coating (the membrane filaments are uniformly exposed to the uniformly concentrated solution).

[0012] Step 6: After taking out, place the membrane filaments in a fume hood and let them dry naturally for 5 - 30 min until the solvent completely volatilizes. Then put them into an oven at 50 - 80 °C for crosslinking and curing for 4 - 24 h, and the MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms is obtained. PDMS has reactive silicon groups and forms a crosslinked polymer network through reaction with a curing agent by heating. The curing process is to connect the monomers in PDMS into longer chains by introducing a crosslinking agent (curing agent), thereby forming a stable structure. The curing agents are hydrogen-containing silicone oils such as methyltrichlorosilane, propylsilane, phenyltrichlorosilane, and platinum catalysts such as chloroplatinic acid, Karstedt catalyst (platinum complex of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane), or peroxides. When the curing agent is a peroxide, it can be heated to accelerate the chemical reaction. At high temperatures, the curing agent decomposes and releases free radicals, which are then captured by the silicon groups in the PDMS chains, thereby causing a crosslinking reaction; when the curing product is a hydrogen-containing silicone oil and a platinum catalyst, under the action of the platinum catalyst, the Si-H bond of the hydrogen-containing silicone oil crosslinks with the silicon hydroxyl group in PDMS or undergoes an addition reaction with vinyl-encapsulated PDMS, thereby achieving the curing effect; without the crosslinking and curing reaction, the combination between the breathable membrane substrate and the functional layer is only loose, not tight, and the overall functional layer covering the outside of the breathable membrane cannot be formed. In Step 5, the dual-anchoring functional layer is loaded onto the breathable membrane substrate, while in Step 6, the functional layer is further tightly combined with the breathable membrane, will not fall off easily, prolongs the service life, and enhances the effect.

[0013] Further, in Step 1, the material of the membrane filaments is a dense non-porous membrane (silicone) or a microporous hydrophobic membrane (PVDF, PTFE, PP, etc.), and the pore size is 0.08 - 0.12 microns.

[0014] Further, in Step 1, the drying temperature is 50 - 80 °C and the time is 15 - 30 min.

[0015] Further, in Step 2, the carbon material is one of carbon nanotubes, carbon fibers, or carbon black.

[0016] Further, in Step 3, the adhesive is PDMS or polymethylvinylsiloxane, and the mass ratio of the main agent of the adhesive to the curing agent is 10:1.

[0017] An MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms prepared by the above preparation method.

[0018] The beneficial effects of the present invention compared with the prior art are as follows:

[0019] (1) The microbial film formation is faster. The microbial film is not easy to fall off, and the PN / PS is higher than that of ordinary commercial membranes. The surface loading amount of the breathable membrane material is larger, reaching 90 g / m 2 . The growth effect of microorganisms is good.

[0020] (2)Enhanced pollutant removal effect. The ammonia nitrogen removal rate can reach over 90%, and the COD removal rate can reach over 90%.

[0021] (3)Increase the attachment sites of pollutants on the surface of the membrane material, improve the bioaffinity of the breathable membrane, and enhance the stability of the biofilm. Solve the problems of the traditional material with a smooth surface and a single structure, which cannot induce and promote the binding of microorganisms, has weak bioaffinity, and the growth cycle of the microbial film on the material surface is long, and there are problems of instability and easy shedding.

[0022] (4)Introduce functional materials (carbon nanotubes / carbon fibers / carbon black). Since carbon nanotubes have strong polar functional groups such as hydroxyl groups, and through the synergistic action of van der Waals forces, hydrogen bonds, etc., they have strong adsorption ability for ammonia nitrogen and organic substances. At the same time, a locally high-concentration environment is formed on the membrane surface to promote the growth of microorganisms, thereby playing a dual anchoring function for microorganisms and pollutants. Solve the problem that traditional materials lack the ability to enhance the degradation of pollutants by microorganisms and limit the potential of microbial degradation, and further improve the pollution removal efficiency. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the MABR membrane material of the present invention;

[0024] Figure 2 It is an electron microscope picture;

[0025] Figure 3 It is a comparison chart of the ammonia nitrogen and removal rate of the effluent (blue is Example 3, red is Comparative Example 3);

[0026] Figure 4 It is a comparison chart of the COD and removal rate of the effluent. Detailed Embodiments

[0027] The technical solutions of the present invention will be further described below in conjunction with the drawings and embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0028] The present invention uses a microporous hydrophobic membrane (PVDF / PTFE / PP) or a non-porous dense silica gel membrane with a pore size of about 0.1 micron as the breathable membrane substrate, and a functional layer is loaded on the outer layer of the breathable membrane. The medium with an anchoring function in the functional layer is carbon nanotubes (CNT) / carbon fibers / carbon black, and the binder of the functional layer is polydimethylsiloxane (PDMS) or polymethylvinylsiloxane. The electron microscope pictures are as Figure 2As shown, (a) shows that carbon nanotubes and PDMS are successfully loaded on the breathable membrane substrate, and it can be clearly seen that there are sites with anchoring functions formed by carbon nanotubes (take the red circle as an example); (b) breathable membrane substrate. The carbon nanotubes are only located in the functional layer and are cross-linked with the substrate only through the adhesive, and do not exist inside the substrate. This membrane material plays a breathable function, different from the water-permeable filter membrane.

[0029] Example 1

[0030] 1. Immerse the dense silica gel membrane filaments in absolute ethanol, ultrasonically treat for 2 min to remove surface impurities, and dry the cleaned membrane filaments.

[0031] 2. Prepare a CNT dispersion with a mass fraction of 1.2% using n-hexane as the solvent, and then ultrasonically treat for 2 h to disperse CNT in n-hexane.

[0032] 3. Prepare a PDMS solution with a mass fraction of 30% using n-hexane as the solvent, and the ratio of the main agent to the curing agent is 10:1. Then ultrasonically treat for 1 h to dissolve PDMS in n-hexane.

[0033] 4. Mix the above CNT dispersion and PDMS solution according to a mass ratio of 1:1, and use a magnetic stirrer to stir for 1 h until completely mixed. In this way, a n-hexane solution with a CNT mass fraction of 0.6% and a PDMS mass fraction of 15% is obtained.

[0034] 5. Put the dried silica gel membrane into the mixed solution and place it on a shaker for dip coating for 1 h.

[0035] 6. After taking it out, place the silica gel membrane in a fume hood to dry naturally for 10 min until the solvent completely evaporates, and put it into an oven at 80 °C for cross-linking and curing for 24 h to obtain a MABR membrane material with a dual anchoring functional layer for pollutants and microorganisms.

[0036] Control Example 1

[0037] Use a commercial silica gel membrane as the control group, and run the reactor together with the MABR membrane material with a dual anchoring functional layer for pollutants and microorganisms prepared in Example 1 for 1 month. After one month, take out the membrane filaments and rinse the two groups of membranes with water flow. Conclusion: The experimental group has stronger resistance to water flow impact, indicating that the microbial membrane in the experimental group is more stable and more tightly combined.

[0038] Example 2

[0039] 1. Immerse the dense silica gel membrane filaments in absolute ethanol, ultrasonically treat for 5 min to remove surface impurities, and dry the cleaned membrane filaments.

[0040] 2. Prepare a CNT dispersion with a mass fraction of 0.4% using n-hexane as the solvent, and then ultrasonically treat for 30 min to disperse CNT in n-hexane.

[0041] 3. Prepare a PDMS solution with a mass fraction of 4% using n - hexane as the solvent. The ratio of the main agent to the curing agent is 10:1. Then, ultrasonicate for 20 min to dissolve PDMS in n - hexane.

[0042] 4. Mix the above CNT dispersion with the PDMS solution and stir with a magnetic stirrer for 20 min until completely mixed. Thus, a n - hexane solution with a CNT mass fraction of 0.2% and a PDMS mass fraction of 2% is obtained.

[0043] 5. Place the dried silica gel membrane into the mixed solution and dip - coat it on a shaker for 2 h.

[0044] 6. After taking it out, place the silica gel membrane in a fume hood and let it dry naturally for 10 min until the solvent completely evaporates. Then put it into an oven at 80 °C for cross - linking and curing for 4 h to obtain the MABR membrane material with a double - anchoring functional layer for pollutants and microorganisms.

[0045] Control Example 2

[0046] Use a commercial silica gel membrane as the control group and run the reactor together with the MABR membrane material with a double - anchoring functional layer for pollutants and microorganisms prepared in Example 2 for 2 months. When the biofilm growth enters the stable period, take samples to detect the bio - loading and PN / PS on the surfaces of the two groups of membranes. Conclusion: The bio - loading on the membrane surface in Example 2 reaches 90 g / m 2 , and the bio - loading on the membrane surface in Control Example 2 is 43 g / m 2 . The PN / PS in Example 2 is higher than that in Control Example 2.

[0047] Example 3

[0048] 1. Immerse the microporous hydrophobic membrane filaments made of polyvinylidene fluoride (PVDF) in absolute ethanol and ultrasonicate for 5 min to remove surface impurities, and then dry the cleaned membrane filaments.

[0049] 2. Prepare a carbon black dispersion with a mass fraction of 0.8% using n - hexane as the solvent, and then ultrasonicate for 30 min to disperse carbon black in n - hexane.

[0050] 3. Prepare a PDMS solution with a mass fraction of 4% using n - hexane as the solvent. The ratio of the main agent to the curing agent is 10:1. Then, ultrasonicate for 20 min to dissolve PDMS in n - hexane.

[0051] 4. Mix the above carbon black dispersion with the PDMS solution and stir with a magnetic stirrer for 20 min until completely mixed. Thus, a n - hexane solution with a carbon black mass fraction of 0.4% and a PDMS mass fraction of 2% is obtained.

[0052] 5. Place the dried PVDF membrane in the mixed solution and place it on a shaker for dip coating for 1 h.

[0053] 6. After taking it out, place the membrane filaments in a fume hood to dry naturally for 10 min until the solvent completely evaporates, and then put it into an oven at 80 °C for crosslinking and curing for 8 h to obtain the MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms.

[0054] Comparative Example 3

[0055] Use a commercial silicone membrane as the control group and operate the reactor together with the MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms prepared in Example 3 for 3 months. After 3 months, sample once every 2 days to detect and compare the ammonia nitrogen in the effluent and the removal rate of the two groups for 14 days (the results are shown in Figure 3 ). The influent ammonia nitrogen is 50 mg / L. The results show that the ammonia nitrogen removal effect of Example 3 is significantly better than that of Comparative Example 3 and the effect is stable.

[0056] Example 4

[0057] 1. Immerse the membrane filaments of the microporous hydrophobic membrane made of polytetrafluoroethylene (PTFE) in absolute ethanol, sonicate for 5 min to remove surface impurities, and dry the cleaned membrane filaments.

[0058] 2. Prepare a carbon fiber dispersion with a mass fraction of 0.4% using n-hexane as the solvent, and then sonicate for 30 min to disperse the carbon fibers in n-hexane;

[0059] 3. Prepare a PDMS solution with a mass fraction of 4% using n-hexane as the solvent, and the ratio of the main agent to the curing agent is 10:1. Then sonicate for 20 min to dissolve the PDMS in n-hexane.

[0060] 4. Mix the above carbon fiber dispersion and PDMS solution, and use a magnetic stirrer to stir for 20 min until completely mixed. In this way, a n-hexane solution with a carbon fiber mass fraction of 0.2% and a PDMS mass fraction of 2% is obtained.

[0061] 5. Place the dried PVDF membrane in the mixed solution and place it on a shaker for dip coating for 2 h.

[0062] 6. After taking it out, place the membrane filaments in a fume hood to dry naturally for 10 min until the solvent completely evaporates, and then put it into an oven at 80 °C for crosslinking and curing for 8 h to obtain the MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms.

[0063] Comparative Example 4

[0064] The commercial silicone membrane was used as the control group, and the reactor was operated for 3 months together with the MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms prepared in Example 4. After 3 months, samples were taken every 2 days to detect and compare the effluent COD and removal rate of the two groups for 14 days (the results are shown in Figure 4 ). The influent COD was 300 mg / L. The results showed that the COD removal effect of Example 4 was significantly better than that of Comparative Example 4, and the effect was stable.

Claims

1. A preparation method of an MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms, characterized in that: The method is as follows: Step 1: Immerse the membrane filaments in absolute ethanol and treat them with an ultrasonic cleaner for 2 - 20 min to remove surface impurities, and then dry the cleaned membrane filaments; Step 2: Prepare a carbon material dispersion with n - hexane as the solvent and a mass fraction of 0.4% - 1.2%, and ultrasonicate for 0.5 - 2 h to uniformly disperse the carbon material in n - hexane; Step 3: Prepare an adhesive solution with n - hexane as the solvent and a mass fraction of 4 - 30%, and add a curing agent at the same time. Then ultrasonicate for 0.25 - 2 h to dissolve PDMS in n - hexane; Step 4: Mix the carbon material dispersion and the adhesive solution according to a mass ratio of 1:1, and use a magnetic stirrer to stir for 0.25 - 2 h until completely mixed; Step 5: Seal the two ends of the dried membrane filaments or clamp them with a stop - water clip, put them into the solution obtained in Step 4, and then place them on a shaker for dip - coating for 0.5 - 2 h; Step 6: After taking out, let the membrane filaments dry naturally for 5 - 30 min until the solvent completely volatilizes, and then put them into an oven at 50 - 80 °C for cross - linking and curing for 4 - 24 h to obtain the MABR membrane material with a double - anchoring functional layer for pollutants and microorganisms.

2. The preparation method of a MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms according to claim 1, characterized in that: In Step 1, the material of the membrane filaments is a dense non - porous membrane (silica gel) or a microporous hydrophobic membrane (PVDF, PTFE, PP, etc.), and the pore size is 0.08 - 0.12 microns.

3. The preparation method of a MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms according to claim 1, characterized in that: In Step 1, the drying temperature is 50 - 80 °C and the time is 15 - 30 min.

4. The preparation method of an MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms according to claim 1, wherein: In Step 2, the carbon material is one of carbon nanotubes, carbon fibers or carbon black.

5. The preparation method of an MABR membrane material with a dual-anchoring functional layer for pollutants and microorganisms according to claim 1, characterized in that: In Step 3, the adhesive is PDMS or polymethylvinylsiloxane, and the mass ratio of the main adhesive agent to the curing agent is 10:

1.

6. An MABR membrane material with a double - anchoring functional layer for pollutants and microorganisms prepared by the preparation method according to any one of claims 1 - 5.

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