Non-woven fabric for MBR flat sheet membrane and preparation method of non-woven fabric
By introducing quaternized polyethyleneimine-modified carbon nanotubes mixed with polyvinyl butyral onto MBR flat sheet membranes to form a three-dimensional network structure, the problems of insufficient tolerance and membrane fouling of MBR filter membranes are solved, the hydrophilicity and antifouling properties of the membrane are improved, the antibacterial properties of the membrane are enhanced, and the treatment efficiency is increased.
Patent Information
- Application Number
- CN202511206003.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-27
- Publication Date
- 2025-11-07
AI Technical Summary
The insufficient tolerance of MBR filter membranes and serious membrane fouling problems lead to decreased filtration performance, slowed flow rate, weakened treatment capacity, increased cleaning and replacement costs, and limit their large-scale promotion.
Quaternized polyethyleneimine was used to modify carbon nanotubes and mixed with polyvinyl butyral to form a three-dimensional network structure, which improved the hydrophilicity and antifouling properties of the membrane. The uniformity of pore size distribution and antibacterial properties of the membrane were enhanced by coating the casting solution on polypropylene nonwoven fabric.
It improves the hydrophilicity and antifouling properties of MBR flat sheet membranes, enhances the antibacterial properties of the membranes, reduces the risk of membrane fouling, and improves treatment efficiency and stability.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of membranes, and particularly relates to a non-woven fabric for MBR flat membrane and a preparation method thereof. BACKGROUND
[0002] Membrane bioreactor (MBR) is an advanced wastewater treatment method integrating membrane separation technology and biological treatment technology. It is favored in the field of wastewater treatment due to its small footprint, excellent effluent, and no need for secondary sedimentation. However, as the application demand increases, MBR puts forward higher requirements for the tolerance, anti-pollution, high water flux and high retention rate of the filter membrane. Currently, the lack of tolerance of the filter membrane and membrane fouling are particularly prominent. If not controlled in time and effectively, it will lead to a decrease in filtration performance, a decrease in flow rate, a weakening of treatment capacity, and an increase in cleaning and replacement costs, and even cause system paralysis, so that MBR cannot achieve the goal of wastewater purification, and seriously restricts its large-scale promotion.
[0003] Currently, the anti-pollution technology of MBR membrane mainly includes three methods of blending modification, chemical modification and physical modification. Blending modification adds hydrophilic polymers (PVA, PVP) or inorganic nanoparticles (TiO2, SiO2) in the membrane-forming material to improve the hydrophilicity and mechanical strength of the membrane, but it is limited by the compatibility requirements of the additives and the base material, and uneven distribution and elution problems are easy to occur, leading to performance decline or even secondary pollution.
[0004] Chemical modification modifies the membrane surface through grafting or crosslinking reaction, which can significantly enhance the hydrophilicity and anti-pollution property, but the operation is complex and the reaction conditions need to be strictly controlled, and harmful by-products may be produced by chemical reagents. Physical modification relies on radiation, heat treatment or mechanical stretching to adjust the membrane structure, which is relatively environmentally friendly, but it has high requirements for equipment, limited modification effect and difficulty in dealing with high-difficulty wastewater treatment demand. SUMMARY
[0005] The purpose of the present application is to provide a non-woven fabric for MBR flat membrane and a preparation method thereof to solve the problem of the non-woven fabric for MBR flat membrane.
[0006] The purpose of the present application can be achieved by the following technical solutions: A preparation method of a non-woven fabric for MBR flat membrane, comprising the following steps: Polyvinyl butyral, polyethylene glycol and solvent are mixed, stirred at a temperature of 20-30℃ for 24h, then quaternary ammonium polyethyleneimine modified carbon nanotubes are added for continuous stirring and dispersion, and then left to stand for defoaming to obtain a coating solution; The polypropylene non-woven fabric is soaked in the casting solution, shaken and dispersed, the excess casting solution is scraped off, placed in water at a constant temperature of 25℃ for soaking, and then taken out and air dried at room temperature to obtain a non-woven fabric for MBR flat membrane.
[0007] Further, the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide. Both N-methyl-2-pyrrolidone and N,N-dimethylacetamide are strong polar aprotic solvents, have very good solubility to polyvinyl butyral, and can form a uniform and stable plating solution.
[0008] Further, the ratio of the polyvinyl butyral, the polyethylene glycol, the quaternary ammonium polyethylene imine modified carbon nanotube and the solvent is 15:5:0.2-0.6:79-80. The weight average molecular of the polyvinyl butyral is 9*10 4 -1.2*10 5 , the hydroxyl content is 11%-13%, and the butyraldehyde content is 88%.
[0009] Further, the molecular weight of the polyethylene glycol is 2000-20000.
[0010] The carboxylated carbon nanotube is used as raw material, modified by acyl chloride, then polyethylene imine is grafted on the carbon nanotube, and finally N-alkylation modification is carried out using halogenated hydrocarbon to convert part of the amino groups in the polyethylene imine on the carbon nanotube into quaternary ammonium salt to obtain the quaternary ammonium polyethylene imine modified carbon nanotube.
[0011] The carboxylated multi-walled carbon nanotube itself has many oxygen-containing functional groups, and has better dispersibility in the plating solution than the multi-walled carbon nanotube (not carboxylated), but due to the small particle size and high surface energy of the carbon nanotube, there are still problems of poor dispersibility or instability. In the present application, the multi-walled carbon nanotube is modified by introducing quaternary ammonium polyethylene imine on the surface of the multi-walled carbon nanotube, and the branched structure of the quaternary ammonium polyethylene imine is utilized to form mutual support between the multi-walled carbon nanotubes. The quaternary ammonium polyethylene imine is a high molecular compound with branched structure, and contains a large number of quaternary ammonium groups and amino groups and other active groups on the molecular chain. In the polyvinyl butyral solution, the quaternary ammonium polyethylene imine can interweave and entangle with the polyvinyl butyral molecules to form a relatively complex three-dimensional network structure. When the solution is formed into a film, this three-dimensional network structure will affect the pore structure of the film, making the pore size distribution of the film more uniform.
[0012] The quaternary ammonium groups contained in the molecular chain of the quaternary ammonium polyethylene imine have strong hydrophilicity. After the polyvinyl butyral is formed into a film, the quaternary ammonium groups will be distributed on the surface and inside of the film, making the film surface carry positive charges. These positive charges can produce electrostatic attraction with the negative charges in water molecules, thereby enhancing the interaction force between the film surface and water molecules and improving the hydrophilicity of the film. In addition, the branched structure of the quaternary ammonium polyethylene imine also increases the roughness of the film surface, forming more micro-nano structures, which can increase the adsorption and diffusion of water molecules on the film surface, further improving the hydrophilic performance of the film.
[0013] Further, the quaternary ammonium polyethylene imine modified carbon nanotube is prepared by the following steps: The carboxylated multi-walled carbon nanotube is dispersed in thionyl chloride and N,N-dimethylformamide, and is reacted at room temperature for 16-24 hours to obtain acyl chloride multi-walled carbon nanotube; the volume ratio of thionyl chloride and N,N-dimethylformamide is 20:1, and the usage ratio of carboxylated multi-walled carbon nanotube and thionyl chloride is 1-3g:200mL; the acyl chloride multi-walled carbon nanotube and polyethylene imine are added into N,N-dimethylformamide, triethylamine is added, and stirring is carried out at 50-60°C for 24-30 hours to obtain polyethylene imine grafted multi-walled carbon nanotube; the usage ratio of acyl chloride multi-walled carbon nanotube, polyethylene imine and triethylamine is 1g:1g:200μL; The polyethylene imine grafted multi-walled carbon nanotube is added into N,N-dimethylformamide and is dispersed by stirring, then halogenated hydrocarbon and potassium hydroxide are added, and stirring is carried out at 85-90°C for 10-12 hours; after the reaction is completed, methanol and deionized water are sequentially used for washing to obtain quaternary ammonium polyethylene imine modified carbon nanotube; the usage ratio of polyethylene imine grafted multi-walled carbon nanotube, halogenated hydrocarbon and potassium hydroxide is 1g:0.14-0.15g:0.05g.
[0014] Further, the halogenated hydrocarbon is one of 1-bromohexane and iodomethane.
[0015] Further, the pore size of the polypropylene non-woven fabric is 1-10μm; and the penetration of the coating solution into the pore size of the polypropylene non-woven fabric is conducive to the uniform and stable adhesion of the coating solution on the surface of the non-woven fabric.
[0016] Further, the coating solution further comprises fluorescent powder, such as yellow-green luminescent powder; the distribution of the pollutants on the non-woven fabric for MBR flat membrane can be judged by detecting and analyzing the distribution of the fluorescent particles, and the pollutants on the non-woven fabric for MBR flat membrane can be cleaned in time.
[0017] The non-woven fabric for MBR flat membrane is prepared by the above method.
[0018] The beneficial effects of the present application are as follows: The present application provides a preparation method of non-woven fabric for MBR flat membrane; the hydrophilicity and anti-pollution of the polypropylene non-woven fabric are improved by coating the casting solution on the surface of the polypropylene non-woven fabric; the preparation method is simple; the prepared non-woven fabric for MBR flat membrane has good permeability and good antibacterial property, which is conducive to inhibiting bacterial adhesion.
[0019] In the present application, the multi-walled carbon nanotubes are modified by introducing quaternary ammonium polyethyleneimine on the surface of the multi-walled carbon nanotubes, which can interweave and entangle with polyvinyl butyral molecules to form a relatively complex three-dimensional network structure. After the casting solution is formed into a film, the three-dimensional network structure will affect the pore structure of the film, making the pore size distribution of the film more uniform. The quaternary ammonium polyethyleneimine molecules can make the surface of the film carry a positive charge, enhance the interaction between the surface of the film and water molecules, and improve the hydrophilicity of the film. In addition, the branched structure of the quaternary ammonium polyethyleneimine also increases the roughness of the film surface, forming more micro-nano structures, which can increase the adsorption and diffusion of water molecules on the film surface, further improving the hydrophilic performance of the film and improving the anti-pollution property. DETAILED DESCRIPTION
[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0021] The following is a detailed description of a non-woven fabric for MBR flat membrane and a preparation method thereof according to an embodiment of the present application.
[0022] The following will be specifically described in combination with embodiments.
[0023] Embodiment 1
[0024] The present embodiment provides a preparation method of a non-woven fabric for MBR flat membrane, comprising the following steps: Polyvinyl butyral, polyethylene glycol and a solvent are mixed, stirred at a temperature of 20-30℃ for 24h, then quaternary ammonium polyethyleneimine modified carbon nanotubes are added for continuous stirring and dispersion, and then standing and defoaming to obtain a coating solution; the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide. The amount ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethyleneimine modified carbon nanotubes and solvent is 15:5:0.2:79.8; the molecular weight of the polyethylene glycol is 2000.
[0025] The polypropylene non-woven fabric is soaked in the casting solution, shaken and dispersed, the excess casting solution is scraped off, and then placed in water at a constant temperature of 25℃ for soaking. After taking out, the non-woven fabric is dried at room temperature to obtain a non-woven fabric for MBR flat membrane. The pore size of the polypropylene non-woven fabric used is 1-10μm.
[0026] The quaternary ammonium polyethyleneimine modified carbon nanotubes are prepared by the following steps: Carboxylated multi-walled carbon nanotubes are dispersed in thionyl chloride and N,N-dimethylformamide to react for 16-24 hours at room temperature to obtain acyl chloride multi-walled carbon nanotubes; wherein the volume ratio of thionyl chloride and N,N-dimethylformamide is 20:1, and the dosage ratio of carboxylated multi-walled carbon nanotubes and thionyl chloride is 1-3 g:200 mL; the acyl chloride multi-walled carbon nanotubes and polyethyleneimine (M W 10000) are added into N,N-dimethylformamide, triethylamine is added, and the mixture is stirred to react for 24-30 hours at 50-60°C to obtain polyethyleneimine grafted multi-walled carbon nanotubes; the dosage ratio of acyl chloride multi-walled carbon nanotubes, polyethyleneimine, triethylamine and N,N-dimethylformamide is 1 g:1 g:200 μL:100 mL; The polyethyleneimine grafted multi-walled carbon nanotubes are added into N,N-dimethylformamide and stirred to disperse, then halogenated hydrocarbon and potassium hydroxide are added, and the mixture is stirred to react for 10-12 hours at 85-90°C; after the reaction, the mixture is washed with methanol and deionized water in sequence to obtain quaternary ammonium polyethyleneimine modified carbon nanotubes; the dosage ratio of polyethyleneimine grafted multi-walled carbon nanotubes, halogenated hydrocarbon and potassium hydroxide is 1 g:0.15 g:0.05 g, and the halogenated hydrocarbon is 1-bromohexane.
[0027] Example 2
[0028] The present embodiment provides a preparation method of a non-woven fabric for MBR flat membrane, which comprises the following steps: Polyvinyl butyral, polyethylene glycol and a solvent are mixed, and the mixture is stirred for 24 hours at a temperature of 20-30°C; then quaternary ammonium polyethyleneimine modified carbon nanotubes are added to continue stirring and dispersion, and the mixture is left to stand to remove bubbles to obtain a coating solution; the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide; wherein the dosage ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethyleneimine modified carbon nanotubes and the solvent is 15:5:0.4:79.6; and the molecular weight of the polyethylene glycol is 2000.
[0029] The polypropylene non-woven fabric is soaked into the casting solution, shaken to disperse, and the excess casting solution is scraped off; the polypropylene non-woven fabric is placed into water at a constant temperature of 25°C to soak, and then taken out to dry at room temperature to obtain a non-woven fabric for MBR flat membrane; the pore size of the polypropylene non-woven fabric used is 1-10 μm.
[0030] The quaternary ammonium polyethyleneimine modified carbon nanotubes are the same as those in Example 1.
[0031] Example 3
[0032] The present embodiment provides a preparation method of a non-woven fabric for MBR flat membrane, which comprises the following steps: Polyvinyl butyral, polyethylene glycol and solvent are mixed, stirred for 24h at a temperature of 20-30℃, then quaternary ammonium polyethylene imine modified carbon nanotube is added to continue stirring and dispersion, and then standing and defoaming to obtain a coating solution; the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide. The ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethylene imine modified carbon nanotube and solvent is 15:5:0.6:79.4; the molecular weight of the polyethylene glycol is 2000.
[0033] Polypropylene non-woven fabric is soaked into the casting solution, oscillation dispersed, and the excess casting solution is scraped off, then placed into water at a constant temperature of 25℃ for soaking, and taken out to dry at room temperature to obtain a non-woven fabric for MBR flat plate membrane, the pore size of the polypropylene non-woven fabric is 1-10μm.
[0034] Quaternary ammonium polyethylene imine modified carbon nanotube is the same as in Embodiment 1.
[0035] Embodiment 4
[0036] The embodiment provides a preparation method of a non-woven fabric for MBR flat plate membrane, comprising the following steps: Polyvinyl butyral, polyethylene glycol and solvent are mixed, stirred for 24h at a temperature of 20-30℃, then quaternary ammonium polyethylene imine modified carbon nanotube is added to continue stirring and dispersion, and then standing and defoaming to obtain a coating solution; the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide. The ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethylene imine modified carbon nanotube and solvent is 15:5:0.2:79.8; the molecular weight of the polyethylene glycol is 10000.
[0037] Polypropylene non-woven fabric is soaked into the casting solution, oscillation dispersed, and the excess casting solution is scraped off, then placed into water at a constant temperature of 25℃ for soaking, and taken out to dry at room temperature to obtain a non-woven fabric for MBR flat plate membrane, the pore size of the polypropylene non-woven fabric is 1-10μm.
[0038] Quaternary ammonium polyethylene imine modified carbon nanotube is the same as in Embodiment 1.
[0039] Embodiment 5
[0040] The embodiment provides a preparation method of a non-woven fabric for MBR flat plate membrane, comprising the following steps: Polyvinyl butyral, polyethylene glycol and solvent are mixed, stirred for 24h at a temperature of 20-30℃, then quaternary ammonium polyethylene imine modified carbon nanotube is added to continue stirring and dispersion, and then standing and defoaming to obtain a coating solution; the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide. The ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethylene imine modified carbon nanotube and solvent is 15:5:0.2:79.8; the molecular weight of the polyethylene glycol is 20000.
[0041] Polypropylene non-woven fabric is soaked into the casting solution, oscillation dispersed, and the excess casting solution is scraped off, then placed into water at a constant temperature of 25℃ for soaking, and taken out to dry at room temperature to obtain a non-woven fabric for MBR flat plate membrane, the pore size of the polypropylene non-woven fabric is 1-10μm.
[0042] Quaternary ammonium polyethylene imine modified carbon nanotube is the same as in Embodiment 1.
[0043] Embodiment 6
[0044] The embodiment provides a preparation method of a non-woven fabric for MBR flat plate membrane, which comprises the following steps: Polyvinyl butyral, polyethylene glycol and solvent are mixed, stirred for 24h at a temperature of 20-30℃, then quaternary ammonium polyethylene imine modified carbon nanotube is added to continue stirring and dispersion, and then standing and defoaming to obtain a coating solution; the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide. The ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethylene imine modified carbon nanotube and solvent is 15:5:0.6:79.4; the molecular weight of the polyethylene glycol is 10000.
[0045] Polypropylene non-woven fabric is soaked into the casting solution, oscillation dispersed, and the excess casting solution is scraped off, then placed into water at a constant temperature of 25℃ for soaking, and taken out to dry at room temperature to obtain a non-woven fabric for MBR flat plate membrane, the pore size of the polypropylene non-woven fabric is 1-10μm.
[0046] Quaternary ammonium polyethylene imine modified carbon nanotube is the same as in Embodiment 1.
[0047] Embodiment 7
[0048] The embodiment provides a preparation method of a non-woven fabric for MBR flat plate membrane, which comprises the following steps: Polyvinyl butyral, polyethylene glycol and solvent are mixed, stirred for 24h at a temperature of 20-30℃, then the quaternary ammonium polyethylene imine modified carbon nanotube is added to continue stirring and dispersion, and then placed to remove bubbles to obtain a coating solution; the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide. The ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethylene imine modified carbon nanotube and solvent is 15:5:0.6:79.4; the molecular weight of the polyethylene glycol is 20000.
[0049] Polypropylene non-woven fabric is soaked in the casting solution, shaken and dispersed, and the excess casting solution is scraped off. The non-woven fabric is placed in water at a constant temperature of 25℃ for soaking, and then taken out to dry at room temperature to obtain a non-woven fabric for MBR flat plate membrane. The pore size of the polypropylene non-woven fabric used is 1-10μm.
[0050] The quaternary ammonium polyethylene imine modified carbon nanotube is the same as in Example 1.
[0051] Comparative Example 1
[0052] The comparative example is different from Example 1 in that the quaternary ammonium polyethylene imine modified carbon nanotube is not added, and the rest of the raw materials and the preparation process are the same as in Example 1.
[0053] Comparative Example 2
[0054] The comparative example is different from Example 1 in that the quaternary ammonium polyethylene imine modified carbon nanotube is replaced by the carboxylated multi-walled carbon nanotube in Example 1, and the rest of the raw materials and the preparation process are the same as in Example 1.
[0055] Comparative Example 3
[0056] The comparative example is different from Example 1 in that the quaternary ammonium polyethylene imine modified carbon nanotube is replaced by the polyethylene imine grafted multi-walled carbon nanotube in Example 1, and the rest of the raw materials and the preparation process are the same as in Example 1.
[0057] Comparative Example 4
[0058] The comparative example provides a preparation method of a non-woven fabric for MBR flat plate membrane, which comprises the following steps: Polyvinyl butyral, polyethylene glycol and solvent are mixed, stirred for 24h at a temperature of 20-30℃, then the quaternary ammonium polyethylene imine modified carbon nanotube is added to continue stirring and dispersion, and then placed to remove bubbles to obtain a coating solution; the solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide. The ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethylene imine modified carbon nanotube and solvent is 15:5:2:78; the molecular weight of the polyethylene glycol is 10000.
[0059] Polypropylene non-woven fabric is soaked into casting solution, oscillation dispersion, scraping off the excess casting solution, placing in constant temperature water of 25℃, drying after taking out at room temperature to obtain a non-woven fabric for MBR flat membrane, the polypropylene non-woven fabric used has a pore size of 1-10μm.
[0060] Quaternary ammonium polyethylene imine modified carbon nanotube is the same as in example 1.
[0061] The non-woven fabric for MBR flat membrane prepared in example 1 and comparative examples 1-3 is subjected to antibacterial property test, the number of colony survival after contacting with E. coli suspension for 2h is calculated to obtain the sterilization rate; the blank control refers to the same concentration of bacterial suspension (10 6 cfu / mL) without contacting with the membrane piece, after culturing in a constant temperature incubator at 37℃ for 2h, 100μL of the bacterial suspension is mixed with 20mL of normal saline by oscillation, then 100μL of the diluted bacterial suspension is uniformly coated on LB solid culture medium, and then cultured in a constant temperature incubator at 37℃ for 12h, and the number of colonies on the culture medium is counted.
[0062] The antibacterial rate = (B-A) / B*100%; wherein B is the number of colonies of the blank control, and A is the number of colonies after contacting with the E. coli suspension for 2h.
[0063] The test results are shown in table 1 below: Table 1
[0064] According to the test results, the non-woven fabric for MBR flat membrane prepared in the application has a certain antibacterial rate, since the quaternary ammonium polyethylene imine is closely connected with the carbon nanotube, a relatively stable structure is formed, so that the carbon nanotube can maintain uniform dispersion in the polyvinylidene butyral solution for a long time, and is not prone to sedimentation or stratification. And uniformly exists on the membrane surface after film formation, plays a persistent and stable antibacterial role, has good antibacterial property, is conducive to inhibiting the survival of bacteria on the surface of the non-woven fabric for MBR flat membrane, thereby reducing the adhesion of bacteria.
[0065] The pure water flux of the non-woven fabric for MBR flat membrane prepared in examples 1-7 and comparative examples 1-4 is tested, 0.2Mpa is pre-pressed for 0.5h, and then tested at a pressure of 0.1Mpa and a temperature of 25℃: Pure water flux ( J W ): ; The pure water flux (L·m 2 ·h -1 ·bar -1 ) is calculated according to the following formula: Q The pure water flux (L / h) is calculated according to the following formula: Pbar, A effective area of the membrane (m 2 ).
[0066] The contact angle was tested by a water contact angle analyzer at 25°C.
[0067] BSA (bovine serum albumin) protein static contamination: a BSA solution phosphate buffer solution was prepared, and the MBR flat membranes prepared in Examples 1-7 and Comparative Examples 1-4 were soaked in the above solution with non-woven fabric, and then the membranes were carefully taken out, and the absorbance of the BSA solution was tested with a UV spectrophotometer, and the static adsorption amount was calculated.
[0068] Static adsorption amount: ; In the formula C 0 is the concentration of the BSA solution stock solution: C 1 is the concentration of the BSA solution after adsorption: V V is the volume of the BSA solution for testing: A A is the effective area of the membrane.
[0069] The test results are shown in Table 2 below: Table 2
[0070] The membrane flux size is mainly related to the pore size, and the water flux decreases as the pore size decreases. According to Table 2 combined with Examples 1-3, under the condition that the molecular weight of polyethylene glycol remains unchanged, increasing the amount of quaternized polyethyleneimine modified carbon nanotubes is beneficial to improve the pure water flux and hydrophilicity (reduce the water contact angle). Combined with Examples 1 and Examples 4-5, keeping the quaternized polyethyleneimine modified carbon nanotubes unchanged, increasing the molecular weight of the molecular weight of polyethylene glycol is beneficial to the improvement of the pure water flux, but as the molecular weight of polyethylene glycol continues to increase, it will lead to an increase in the casting solution viscosity, resulting in a tight entanglement of molecular chains, affecting the formation of porous structure, and further affecting the improvement of pure water flux. Combined with Examples 3, Examples 6-7 and Comparative Example 1, within a certain range, optimizing the molecular weight of polyethylene glycol and the proportion of quaternized polyethyleneimine modified carbon nanotubes can improve the pure water flux, and the reason is that the introduction of quaternized polyethyleneimine in quaternized polyethyleneimine modified carbon nanotubes can reduce the casting solution viscosity, offset the influence of high molecular weight polyethylene glycol, the phase separation rate is moderate, and a larger pore structure is formed to improve the water flux and increase the hydrophilicity.
[0071] In the embodiments 1-7, the quaternary ammonium polyethyleneimine is closely connected with the carbon nanotubes, and the quaternary ammonium polyethyleneimine and the carboxylated carbon nanotubes in the mixture can be phase-separated or unevenly distributed due to the intermolecular interaction or the change of external factors (such as temperature, stirring speed, etc.), which can result in the decrease of the stability of the solution and affect the performance of the non-woven fabric for MBR flat membrane.
[0072] It is to be noted that the relational terms herein such as first and second and the like are used solely to distinguish one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.
[0073] Although the embodiments of the present application have been shown and described, it is to be understood that for the purpose of the present application, the embodiments change, modify, replace, and vary in many ways without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.
Claims
1. A method for producing a nonwoven fabric for MBR flat sheet membranes, characterized by comprising the steps of: It comprises the following steps: Mixing polyvinyl butyral, polyethylene glycol and solvent, stirring evenly, then adding quaternary ammonium polyethyleneimine modified carbon nanotubes to continue stirring and dispersing, and then standing to remove bubbles to obtain a coating solution; Soaking the polypropylene non-woven fabric in the casting solution, oscillating and dispersing, scraping off the excess casting solution, placing in water for soaking, and taking out to dry at room temperature to obtain a non-woven fabric for MBR flat plate membrane.
2. The method for producing a nonwoven fabric for MBR flat membranes according to claim 1, characterized by, The solvent is one of N-methyl-2-pyrrolidone and N,N-dimethylacetamide.
3. The method for preparing a nonwoven fabric for an MBR flat sheet membrane according to claim 1, characterized in that, The amount ratio of polyvinyl butyral, polyethylene glycol, quaternary ammonium polyethyleneimine modified carbon nanotubes and solvent is 15:5:0.2-0.6:79.4-79.
8.
4. The method for preparing a nonwoven fabric for an MBR flat sheet membrane according to claim 1, characterized in that, The molecular weight of the polyethylene glycol is 2000-20000.
5. The method for preparing a nonwoven fabric for an MBR flat sheet membrane according to claim 1, characterized in that, The quaternary ammonium polyethyleneimine modified carbon nanotubes are prepared by the following steps:
6. The method for preparing a nonwoven fabric for an MBR flat sheet membrane according to claim 1, characterized in that, The carboxylated multi-walled carbon nanotubes are dispersed in thionyl chloride and N,N-dimethylformamide, and reacted at room temperature for 16-24 hours to obtain acyl chloride multi-walled carbon nanotubes; the acyl chloride multi-walled carbon nanotubes and polyethyleneimine are added to N,N-dimethylformamide, and triethylamine is added to stir and react at 50-60°C for 24-30 hours to obtain polyethyleneimine grafted multi-walled carbon nanotubes; The polyethyleneimine grafted multi-walled carbon nanotubes are added to N,N-dimethylformamide to stir and disperse, then halogenated hydrocarbon and potassium hydroxide are added, and the mixture is stirred and reacted at 85-90°C for 10-12 hours; after the reaction is completed, the mixture is washed with methanol and deionized water in sequence to obtain quaternary ammonium polyethyleneimine modified carbon nanotubes. The halogenated hydrocarbon is one of 1-bromohexane and iodomethane.
7. A method for preparing a nonwoven fabric for an MBR flat sheet membrane according to claim 6, characterized in that, The pore size of the polypropylene non-woven fabric is 1-10μm.
8. The method for preparing a nonwoven fabric for an MBR flat sheet membrane according to claim 1, characterized in that, The coating solution further comprises fluorescent powder.
9. The method for preparing a nonwoven fabric for an MBR flat sheet membrane according to claim 1, characterized in that, Prepared by the preparation method of any one of claims 1-9.
10. A nonwoven fabric for MBR flat membrane, characterized by comprising: