An ultrafiltration membrane for waste acid recovery

Abstract

This invention discloses an ultrafiltration membrane for waste acid recovery, belonging to the field of ultrafiltration membrane technology. It includes several filtration units arranged in a decreasing concentration gradient. Each filtration unit includes a concentration chamber and a dilute chamber, with an anion exchange membrane disposed between the concentration and dilute chambers. The preparation method of the anion exchange membrane includes the following steps: preparing zirconium-based metal-organic framework powder, in-situ growing carbon nanotubes, carboxylating the powder, and grafting polyethylene glycol to obtain polyethylene glycol-grafted Zr@carbon nanotubes; preparing chloromethylated polysulfone, quaternizing it, dissolving it in dimethyl sulfoxide, adding 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes, and polyvinylpyrrolidone, ultrasonically dispersing the mixture evenly, pouring it into a mold, vacuum drying, demolding, washing, and drying to obtain a cross-linked polysulfone membrane material. After ion exchange and activation, the anion exchange membrane is obtained. This improves the high conductivity, low swelling, high strength, fouling resistance, and long lifespan of the anion exchange membrane in the waste acid recovery ultrafiltration membrane.

Description

Technical Field

[0001] This invention belongs to the field of ultrafiltration membrane technology, and specifically relates to an ultrafiltration membrane device for waste acid recovery. Background Technology

[0002] The core of specialized ultrafiltration membrane equipment lies in the structure of the ultrafiltration membrane: during waste acid recovery, when waste acid and receiving liquid (tap water) are introduced into the two sides of the concentration chamber respectively, the waste acid and its salts tend to migrate towards the dilute chamber due to the concentration gradient. Since the ultrafiltration membrane has selective permeability to anions, the anions (A-) on the waste acid side migrate smoothly into the water side. Due to the requirement of electroneutrality, the cations also migrate into the water side simultaneously. The hydration radius of H+ ions is relatively small and the charge number is small, while the hydration radius of cations (M+) in metal salts is large and the charge number is large. Therefore, H+ will preferentially migrate through the membrane, while M+ is blocked, thereby achieving the separation of acid from the waste liquid.

[0003] A search revealed that document CN202210367730.X discloses an apparatus for treating high-salt desulfurization wastewater. The apparatus continuously feeds ultrafiltration-treated wastewater into an electrodialysis unit for desalination, yielding high-concentration and low-concentration salt solutions. The electrodialysis unit includes an electrodialysis chamber, a concentrate tank, and a desalination tank. The electrodialysis chamber contains opposing electrode plates, and between the electrode plates are several alternately arranged anion exchange membranes and cation exchange membranes. These membranes facilitate the electrodialysis process. The chamber is divided into alternating concentration chambers and dilute chambers. The outlet of the concentration chamber is connected to the inlet of the concentration tank, and the outlet of the dilute chamber is connected to the inlet of the dilute tank. The ultrafiltration membrane unit is connected to the inlet of the concentration chamber and the inlet of the dilute chamber via pipelines and three-way valves. In step S500, the wastewater after ultrafiltration treatment is sent to the inlet of the concentration chamber and the inlet of the dilute chamber. Prior art document CN202211007306.0 discloses an anion exchange membrane for acid recovery, which can be used to recover waste acid by diffusion dialysis.

[0004] It is evident that membrane separation technology, due to its advantages such as low energy consumption and high separation efficiency, has gradually become the core technology for waste acid recovery. Among them, ultrafiltration membrane technology can precisely retain metal ions in waste acid, achieving efficient separation of acid and impurities, and providing a feasible solution for the resource utilization of waste acid. However, existing ultrafiltration membrane devices for waste acid recovery still face many technical bottlenecks: Insufficient acid resistance and stability of membrane materials: Commercial ultrafiltration membranes mostly use polymer materials such as polysulfone, which are prone to swelling and chain segment degradation in strong acid environments. After long-term operation, the membrane pore structure collapses and the separation performance deteriorates significantly, making them unsuitable for the treatment of high-concentration waste acid. Membrane fouling is a prominent problem: During long-term operation, polysulfone membranes have poor hydrophilicity and are often modified by grafting hydrophilic groups. However, the hydrophilic groups may be degraded due to acid corrosion and shear erosion, resulting in a decrease in the hydrophilicity of the membrane surface, aggravated fouling, and a rapid decline in membrane flux. This leads to high cleaning frequency, high maintenance costs, and severely restricts the service life of the membrane.

[0005] Therefore, developing an ultrafiltration membrane for waste acid recovery that is resistant to strong acids, pollution, highly selective, and structurally optimized is of great practical significance and engineering value for improving the efficiency of waste acid resource recovery, reducing operating costs, and promoting the green recycling of industrial acidic waste liquids. Summary of the Invention

[0006] The purpose of this invention is to provide an ultrafiltration membrane for waste acid recovery, which improves the anion exchange membrane of the waste acid recovery ultrafiltration membrane by improving its high conductivity, low swelling, high strength, fouling resistance, and long service life.

[0007] The objective of this invention can be achieved through the following technical solutions: An ultrafiltration membrane device for waste acid recovery includes several filtration units arranged in a decreasing concentration gradient. Each filtration unit includes a concentration chamber and a dilute chamber, and an anion exchange membrane is disposed between the concentration chamber and the dilute chamber. The preparation method of the anion exchange membrane includes the following steps: S1. Preparation of zirconium-based metal-organic framework powder; S2. Carbon nanotubes are grown in situ on the zirconium-based metal-organic framework to obtain Zr@carbon nanotube powder. S3. Surface-treat the Zr@carbon nanotube powder to obtain carboxylated Zr@carbon nanotubes; S4. Take the carboxylated Zr@carbon nanotubes and graft them with polyethylene glycol to obtain polyethylene glycol-grafted Zr@carbon nanotubes. S5. Take the polysulfone surface modification to obtain chloromethylated polysulfone; S6. Take the chloromethylated polysulfone and quaternize it to obtain quaternized polysulfone; S7. Dissolve the quaternized polysulfone in dimethyl sulfoxide, add 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes and polyvinylpyrrolidone, disperse evenly by ultrasonication, pour into a mold, vacuum dry, demold, wash, and dry to obtain a cross-linked polysulfone membrane material. After ion exchange and activation, the anion exchange membrane is obtained.

[0008] As a preferred technical solution of the present invention, step S1 specifically includes the following steps: zirconium chloride, acetic acid and N,N-dimethylformamide are mixed, ultrasonically dispersed for 30-40 min, terephthalic acid is added, and after stirring evenly, it is transferred to a Teflon-lined reaction vessel, kept at a constant temperature of 120℃ for 24 h, cooled to room temperature, centrifuged, and the solid phase is washed and vacuum dried to obtain zirconium-based metal-organic framework powder; the ratio of zirconium chloride, acetic acid, N,N-dimethylformamide and terephthalic acid is 40-50 mg: 0.3-0.4 g: 10-20 mL: 28-32 mg.

[0009] As a preferred embodiment of the present invention, step S2 specifically includes the following steps: the zirconium-based metal-organic framework powder and melamine powder are mixed and ground evenly, and then heated to 500-550℃ at 3℃ / min and held for 1h in an argon atmosphere, then heated to 600-650℃ at 2℃ / min and held for 2h, then heated to 700℃ at 3℃ / min and held for 0.5h, and then cooled naturally to obtain Zr@carbon nanotube powder; the mass ratio of the zirconium-based metal-organic framework powder to the melamine powder is 1:2-3.

[0010] As a preferred technical solution of the present invention, step S3 specifically includes the following steps: adding the Zr@carbon nanotube powder to a mixed acid solution, stirring at room temperature for 24 hours, filtering, washing the solid phase, and vacuum drying to obtain carboxylated Zr@carbon nanotubes; the ratio of Zr@carbon nanotube powder to mixed acid solution is 1g:100mL.

[0011] As a preferred technical solution of the present invention, step S4 specifically includes the following steps: taking the carboxylated Zr@carbon nanotubes and sulfoxide, mixing them, ultrasonically dispersing for 20-40 min, heating and stirring at 65°C for 10-20 h for acylation, thoroughly washing with tetrahydrofuran, vacuum drying, adding to polyethylene glycol 400, heating and refluxing at 120°C for 10-20 h, cooling, washing, and vacuum drying to obtain polyethylene glycol grafted Zr@carbon nanotubes; the ratio of carboxylated Zr@carbon nanotubes, sulfoxide, and polyethylene glycol 400 is 1-1.2 g: 150-180 mL: 200-250 mL.

[0012] As a preferred embodiment of the present invention, step S5 specifically includes the following steps: dissolving polysulfone in 1,1-dichloroethane, adding a catalyst, stirring evenly, then adding 1,4-di(chloromethoxy)-butane dropwise, heating and refluxing at 50°C in the dark for 4-8 hours, washing, precipitating, centrifuging, and drying to obtain chloromethylated polysulfone; the mass ratio of polysulfone, 1,1-dichloroethane, catalyst, and 1,4-di(chloromethoxy)-butane is 1:10-20:0.6-0.8:0.01.

[0013] As a preferred technical solution of the present invention, step S6 specifically includes the following steps: dissolving the chloromethylated polysulfone in dimethyl sulfoxide, adding a quaternizing agent, heating and stirring at 30-40°C for 1-2 hours, then adding isopropanol for precipitation, and separating, washing and drying the precipitate to obtain quaternized polysulfone; the mass ratio of the chloromethylated polysulfone, dimethyl sulfoxide and quaternizing agent is 1:10-20:0.7-0.8.

[0014] As a preferred embodiment of the present invention, in step S7, the mass ratio of the quaternized polysulfone, dimethyl sulfoxide, 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes and polyvinylpyrrolidone is 4-5:30-40:5-7:0.05-0.12:0.04-0.05.

[0015] As a preferred technical solution of the present invention, step S7, ion exchange and activation, specifically includes the following steps: the cross-linked polysulfone membrane material is immersed in a 1 mol / L sodium hydroxide solution for 24 hours, the wet membrane is removed with tweezers, rinsed with deionized water until the washing solution is neutral, then immersed in deionized water for 24 hours, and finally vacuum dried.

[0016] The beneficial effects of this invention are: The ultrafiltration membrane for waste acid recovery disclosed in this invention utilizes polyethylene glycol (PEG) grafted Zr@carbon nanotubes embedded in a polysulfone crosslinking network. The Zr@carbon nanotube aggregation problem is solved through PEG hydrophilic dispersion modification, achieving nanoscale uniform dispersion. This constructs a synergistic anion conduction system combining Zr anion adsorption sites, a carbon nanotube ion conduction framework, and PEG hydrophilic channels. This allows for precise control of membrane water absorption and swelling rates, significantly improving anion conduction performance. Simultaneously, the rigidity enhancement of Zr@carbon nanotubes synergistically enhances the membrane's mechanical strength, dimensional stability, oxidation resistance, and chemical stability. The interface is tightly bonded and defect-free, ultimately resulting in an anion exchange membrane with high conductivity, low swelling, high strength, and long lifespan due to its antifouling properties. Detailed Implementation

[0017] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below. Example 1

[0018] An ultrafiltration membrane device for waste acid recovery includes several filtration units arranged in a decreasing concentration gradient. Each filtration unit includes a concentration chamber and a dilute chamber, and an anion exchange membrane is disposed between the concentration chamber and the dilute chamber. The method for preparing the anion exchange membrane includes the following steps: S1. Zirconium chloride, acetic acid, and N,N-dimethylformamide were mixed and ultrasonically dispersed for 30 min. Terephthalic acid was then added and stirred until homogeneous. The mixture was then transferred to a Teflon-lined reactor and kept at 120℃ for 24 h. After cooling to room temperature, the mixture was centrifuged, and the solid phase was washed and vacuum dried to obtain zirconium-based metal-organic framework powder. The ratio of zirconium chloride, acetic acid, N,N-dimethylformamide, and terephthalic acid was 40 mg: 0.3 g: 10 mL: 28 mg. S2. The zirconium-based metal-organic framework powder and melamine powder are mixed and ground evenly. Then, under an argon atmosphere, the temperature is increased to 500℃ at 3℃ / min and held for 1 hour, then increased to 600℃ at 2℃ / min and held for 2 hours, then increased to 700℃ at 3℃ / min and held for 0.5 hours, and then naturally cooled to obtain Zr@carbon nanotube powder. The mass ratio of the zirconium-based metal-organic framework powder to the melamine powder is 1:2. S3. The Zr@carbon nanotube powder is added to a mixed acid solution, stirred at room temperature for 24 hours, filtered, and the solid phase is washed and dried under vacuum to obtain carboxylated Zr@carbon nanotubes. The mixed acid solution is prepared by mixing 98% concentrated sulfuric acid and 70% concentrated nitric acid at a volume ratio of 3:1. The ratio of Zr@carbon nanotube powder to mixed acid solution is 1g:100mL. S4. Take the carboxylated Zr@carbon nanotubes and sulfoxide, add N,N-dimethylformamide, ultrasonically disperse for 20 min, heat and reflux at 65℃ for 10 h for acylation, wash thoroughly with tetrahydrofuran, vacuum dry, add to polyethylene glycol 400, heat and reflux at 120℃ for 10 h, cool to room temperature, wash thoroughly with tetrahydrofuran, vacuum dry to obtain polyethylene glycol grafted Zr@carbon nanotubes; the ratio of carboxylated Zr@carbon nanotubes, sulfoxide, N,N-dimethylformamide, and polyethylene glycol 400 is 1 g: 150 mL: 1 mL: 200 mL; S5. Dissolve polysulfone P-1700 (purchased from Shanghai Kaiyin Chemical Co., Ltd.) in 1,1-dichloroethane, add tin tetrachloride, stir evenly, then add 1,4-di(chloromethoxy)-butane dropwise, heat and reflux at 50°C in the dark for 4 hours, and then wash the mixture with 2 mol / L hydrochloric acid solution. Precipitate the product with anhydrous ethanol as a precipitant, and then centrifuge and dry to obtain chloromethylated polysulfone. The mass ratio of polysulfone P-1700, 1,1-dichloroethane, tin tetrachloride, and 1,4-di(chloromethoxy)-butane is 1:10:0.6:0.01. S6. Dissolve the chloromethylated polysulfone in dimethyl sulfoxide, add 3-dimethylamino-1-propanol, heat and stir at 30°C for 1 hour, then add isopropanol to precipitate. The precipitate is separated, washed and dried to obtain quaternized polysulfone. The mass ratio of the chloromethylated polysulfone, dimethyl sulfoxide and quaternizing agent 3-dimethylamino-1-propanol is 1:10:0.7. S7. Dissolve the quaternized polysulfone in dimethyl sulfoxide, add 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes, and polyvinylpyrrolidone, and ultrasonically disperse until uniform. Pour into a mold and dry in a vacuum drying oven at 80°C for 24 hours. Demold with distilled water, wash the film three times alternately with distilled water and anhydrous ethanol, and dry to obtain a cross-linked polysulfone membrane. Then, soak it in a 1 mol / L sodium hydroxide solution for 24 hours. Remove the wet film with tweezers, rinse with deionized water until the washing solution is neutral, soak it in deionized water for 24 hours, and vacuum dry to obtain the anion exchange membrane. The mass ratio of the quaternized polysulfone, dimethyl sulfoxide, 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes, and polyvinylpyrrolidone is 4:30:5:0.05:0.04. Example 2

[0019] An ultrafiltration membrane device for waste acid recovery includes several filtration units arranged in a decreasing concentration gradient. Each filtration unit includes a concentration chamber and a dilute chamber, and an anion exchange membrane is disposed between the concentration chamber and the dilute chamber. The method for preparing the anion exchange membrane includes the following steps: S1. Zirconium chloride, acetic acid, and N,N-dimethylformamide were mixed and ultrasonically dispersed for 35 min. Terephthalic acid was then added and stirred until homogeneous. The mixture was then transferred to a Teflon-lined reactor and kept at a constant temperature of 120℃ for 24 h. After cooling to room temperature, the mixture was centrifuged, and the solid phase was washed and vacuum dried to obtain zirconium-based metal-organic framework powder. The ratio of zirconium chloride, acetic acid, N,N-dimethylformamide, and terephthalic acid was 45 mg: 0.35 g: 15 mL: 30 mg. S2. The zirconium-based metal-organic framework powder and melamine powder are mixed and ground evenly. Then, under an argon atmosphere, the temperature is increased to 525℃ at 3℃ / min and held for 1 hour, then increased to 625℃ at 2℃ / min and held for 2 hours, then increased to 700℃ at 3℃ / min and held for 0.5 hours, and then naturally cooled to obtain Zr@carbon nanotube powder. The mass ratio of the zirconium-based metal-organic framework powder to the melamine powder is 1:2.5. S3. The Zr@carbon nanotube powder is added to a mixed acid solution, stirred at room temperature for 24 hours, filtered, and the solid phase is washed and dried under vacuum to obtain carboxylated Zr@carbon nanotubes. The mixed acid solution is prepared by mixing 98% concentrated sulfuric acid and 70% concentrated nitric acid at a volume ratio of 3:1. The ratio of Zr@carbon nanotube powder to mixed acid solution is 1g:100mL. S4. Take the carboxylated Zr@carbon nanotubes and sulfoxide, add N,N-dimethylformamide, ultrasonically disperse for 30 min, heat at 65℃ and reflux for 15 h for acylation, wash thoroughly with tetrahydrofuran and vacuum dry, add to polyethylene glycol 400, heat at 120℃ and reflux for 15 h, cool to room temperature, wash thoroughly with tetrahydrofuran and vacuum dry to obtain polyethylene glycol grafted Zr@carbon nanotubes; the ratio of carboxylated Zr@carbon nanotubes, sulfoxide, N,N-dimethylformamide and polyethylene glycol 400 is 1.1 g: 165 mL: 1.5 mL: 225 mL; S5. Dissolve polysulfone P-1700 (purchased from Shanghai Kaiyin Chemical Co., Ltd.) in 1,1-dichloroethane, add tin tetrachloride, stir evenly, then add 1,4-di(chloromethoxy)-butane dropwise, heat and reflux at 50°C in the dark for 6 hours, then wash the mixture with 2 mol / L hydrochloric acid solution, precipitate the product with anhydrous ethanol, centrifuge and dry to obtain chloromethylated polysulfone; the mass ratio of polysulfone P-1700, 1,1-dichloroethane, tin tetrachloride and 1,4-di(chloromethoxy)-butane is 1:15:0.7:0.01; S6. Dissolve the chloromethylated polysulfone in dimethyl sulfoxide, add 3-dimethylamino-1-propanol, heat and stir at 35°C for 1.5 h, then add isopropanol to precipitate. The precipitate is separated, washed and dried to obtain quaternized polysulfone. The mass ratio of the chloromethylated polysulfone, dimethyl sulfoxide and quaternizing agent 3-dimethylamino-1-propanol is 1:15:0.75. S7. Dissolve the quaternized polysulfone in dimethyl sulfoxide, add 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes, and polyvinylpyrrolidone, and ultrasonically disperse until uniform. Pour into a mold and dry in a vacuum drying oven at 80°C for 24 hours. Demold with distilled water, wash the film three times alternately with distilled water and anhydrous ethanol, and dry to obtain a cross-linked polysulfone membrane. Then, soak it in a 1 mol / L sodium hydroxide solution for 24 hours. Remove the wet film with tweezers, rinse with deionized water until the washing solution is neutral, soak it in deionized water for 24 hours, and vacuum dry to obtain the anion exchange membrane. The mass ratio of the quaternized polysulfone, dimethyl sulfoxide, 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes, and polyvinylpyrrolidone is 4.5:35:6:0.09:0.045. Example 3

[0020] An ultrafiltration membrane device for waste acid recovery includes several filtration units arranged in a decreasing concentration gradient. Each filtration unit includes a concentration chamber and a dilute chamber, and an anion exchange membrane is disposed between the concentration chamber and the dilute chamber. The method for preparing the anion exchange membrane includes the following steps: S1. Zirconium chloride, acetic acid, and N,N-dimethylformamide were mixed and ultrasonically dispersed for 40 min. Terephthalic acid was then added and stirred until homogeneous. The mixture was then transferred to a Teflon-lined reactor and kept at 120℃ for 24 h. After cooling to room temperature, the mixture was centrifuged, and the solid phase was washed and vacuum dried to obtain zirconium-based metal-organic framework powder. The ratio of zirconium chloride, acetic acid, N,N-dimethylformamide, and terephthalic acid was 50 mg: 0.4 g: 20 mL: 32 mg. S2. The zirconium-based metal-organic framework powder and melamine powder are mixed and ground evenly. Then, under an argon atmosphere, the temperature is increased to 550℃ at 3℃ / min and held for 1 hour, then increased to 650℃ at 2℃ / min and held for 2 hours, then increased to 700℃ at 3℃ / min and held for 0.5 hours, and then naturally cooled to obtain Zr@carbon nanotube powder. The mass ratio of the zirconium-based metal-organic framework powder to the melamine powder is 1:3. S3. The Zr@carbon nanotube powder is added to a mixed acid solution, stirred at room temperature for 24 hours, filtered, and the solid phase is washed and dried under vacuum to obtain carboxylated Zr@carbon nanotubes. The mixed acid solution is prepared by mixing 98% concentrated sulfuric acid and 70% concentrated nitric acid at a volume ratio of 3:1. The ratio of Zr@carbon nanotube powder to mixed acid solution is 1g:100mL. S4. Take the carboxylated Zr@carbon nanotubes and sulfoxide, add N,N-dimethylformamide, ultrasonically disperse for 40 min, heat and reflux at 65°C for 20 h for acylation, wash thoroughly with tetrahydrofuran, vacuum dry, add to polyethylene glycol 400, heat and reflux at 120°C for 20 h, cool to room temperature, wash thoroughly with tetrahydrofuran, vacuum dry, and obtain polyethylene glycol grafted Zr@carbon nanotubes; the ratio of carboxylated Zr@carbon nanotubes, sulfoxide, N,N-dimethylformamide, and polyethylene glycol 400 is 1.2 g: 180 mL: 2 mL: 250 mL; S5. Dissolve polysulfone P-1700 (purchased from Shanghai Kaiyin Chemical Co., Ltd.) in 1,1-dichloroethane, add tin tetrachloride, stir evenly, then add 1,4-di(chloromethoxy)-butane dropwise, heat and reflux at 50°C in the dark for 8 hours, and then wash the mixture with 2 mol / L hydrochloric acid solution. Precipitate the product with anhydrous ethanol as a precipitant, and obtain chloromethylated polysulfone by centrifugation and drying. The mass ratio of polysulfone P-1700, 1,1-dichloroethane, tin tetrachloride, and 1,4-di(chloromethoxy)-butane is 1:20:0.8:0.01. S6. Dissolve the chloromethylated polysulfone in dimethyl sulfoxide, add 3-dimethylamino-1-propanol, heat and stir at 40°C for 2 hours, then add isopropanol to precipitate. The precipitate is separated, washed and dried to obtain quaternized polysulfone. The mass ratio of the chloromethylated polysulfone, dimethyl sulfoxide and quaternizing agent 3-dimethylamino-1-propanol is 1:20:0.8. S7. Dissolve the quaternized polysulfone in dimethyl sulfoxide, add 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes, and polyvinylpyrrolidone, and ultrasonically disperse until uniform. Pour into a mold and dry in a vacuum drying oven at 80°C for 24 hours. Demold with distilled water, wash the film three times alternately with distilled water and anhydrous ethanol, and dry to obtain a cross-linked polysulfone membrane. Then, soak it in a 1 mol / L sodium hydroxide solution for 24 hours. Remove the wet film with tweezers, rinse with deionized water until the washing solution is neutral, soak it in deionized water for 24 hours, and vacuum dry to obtain the anion exchange membrane. The mass ratio of the quaternized polysulfone, dimethyl sulfoxide, 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes, and polyvinylpyrrolidone is 5:40:7:0.12:0.05.

[0021] Comparative Example 1 The difference from Example 2 is that the preparation method of the anion exchange membrane includes the following steps: S1. Dissolve polysulfone P-1700 (purchased from Shanghai Kaiyin Chemical Co., Ltd.) in 1,1-dichloroethane, add tin tetrachloride, stir evenly, then add 1,4-di(chloromethoxy)-butane dropwise, heat and reflux at 50°C in the dark for 6 hours, then wash the mixture with 2 mol / L hydrochloric acid solution, precipitate the product with anhydrous ethanol, centrifuge and dry to obtain chloromethylated polysulfone; the mass ratio of polysulfone P-1700, 1,1-dichloroethane, tin tetrachloride and 1,4-di(chloromethoxy)-butane is 1:15:0.7:0.01; S2. Dissolve the chloromethylated polysulfone in dimethyl sulfoxide, add 3-dimethylamino-1-propanol, heat and stir at 35°C for 1.5 h, then add isopropanol to precipitate. The precipitate is separated, washed and dried to obtain quaternized polysulfone. The mass ratio of the chloromethylated polysulfone, dimethyl sulfoxide and quaternizing agent 3-dimethylamino-1-propanol is 1:15:0.75. S3. Dissolve the quaternized polysulfone in dimethyl sulfoxide, add 1,4-dibromobutane and polyvinylpyrrolidone, ultrasonically disperse evenly, pour into a mold, dry in a vacuum drying oven at 80℃ for 24h, demold with distilled water, wash the film three times alternately with distilled water and anhydrous ethanol, dry to obtain cross-linked polysulfone membrane material, then soak in 1mol / L sodium hydroxide solution for 24h, remove the wet film with tweezers, rinse with deionized water until the washing solution is neutral, soak in deionized water for 24h, vacuum dry to obtain the anion exchange membrane; the mass ratio of the quaternized polysulfone, dimethyl sulfoxide, 1,4-dibromobutane and polyvinylpyrrolidone is 4.5:35:6:0.045.

[0022] Comparative Example 2 The difference from Example 2 is that the preparation method of the anion exchange membrane includes the following steps: S1. Zirconium chloride, acetic acid, and N,N-dimethylformamide were mixed and ultrasonically dispersed for 35 min. Terephthalic acid was then added and stirred until homogeneous. The mixture was then transferred to a Teflon-lined reactor and kept at a constant temperature of 120℃ for 24 h. After cooling to room temperature, the mixture was centrifuged, and the solid phase was washed and vacuum dried to obtain zirconium-based metal-organic framework powder. The ratio of zirconium chloride, acetic acid, N,N-dimethylformamide, and terephthalic acid was 45 mg: 0.35 g: 15 mL: 30 mg. S2. The zirconium-based metal-organic framework powder and melamine powder are mixed and ground evenly. Then, under an argon atmosphere, the temperature is increased to 525℃ at 3℃ / min and held for 1 hour, then increased to 625℃ at 2℃ / min and held for 2 hours, then increased to 700℃ at 3℃ / min and held for 0.5 hours, and then naturally cooled to obtain Zr@carbon nanotube powder. The mass ratio of the zirconium-based metal-organic framework powder to the melamine powder is 1:2.5. S3. Dissolve polysulfone P-1700 (purchased from Shanghai Kaiyin Chemical Co., Ltd.) in 1,1-dichloroethane, add tin tetrachloride, stir evenly, then add 1,4-di(chloromethoxy)-butane dropwise, heat and reflux at 50°C in the dark for 6 hours, then wash the mixture with 2 mol / L hydrochloric acid solution, precipitate the product with anhydrous ethanol, centrifuge and dry to obtain chloromethylated polysulfone; the mass ratio of polysulfone P-1700, 1,1-dichloroethane, tin tetrachloride and 1,4-di(chloromethoxy)-butane is 1:15:0.7:0.01; S4. Dissolve the chloromethylated polysulfone in dimethyl sulfoxide, add 3-dimethylamino-1-propanol, heat and stir at 35°C for 1.5 h, then add isopropanol to precipitate. The precipitate is separated, washed and dried to obtain quaternized polysulfone. The mass ratio of the chloromethylated polysulfone, dimethyl sulfoxide and quaternizing agent 3-dimethylamino-1-propanol is 1:15:0.75. S5. Dissolve the quaternized polysulfone in dimethyl sulfoxide, add 1,4-dibromobutane, Zr@carbon nanotube powder and polyvinylpyrrolidone, ultrasonically disperse evenly, pour into a mold, and dry in a vacuum drying oven at 80℃ for 24h. Demold with distilled water, wash the film three times alternately with distilled water and anhydrous ethanol, and dry to obtain a cross-linked polysulfone membrane. Then soak it in a 1mol / L sodium hydroxide solution for 24h, remove the wet film with tweezers, rinse with deionized water until the washing solution is neutral, soak in deionized water for 24h, and vacuum dry to obtain the anion exchange membrane. The mass ratio of the quaternized polysulfone, dimethyl sulfoxide, 1,4-dibromobutane, Zr@carbon nanotube powder and polyvinylpyrrolidone is 4.5:35:6:0.09:0.045.

[0023] Comparative Example 3 The difference from Example 2 is that the preparation method of the anion exchange membrane includes the following steps: S1. Commercially available multi-walled carbon nanotubes (brand: Maclean | product number: C835677 | Purity: >95%, ID: 2-5nm, OD: <8nm, Length: 10-30um) were added to a mixed acid solution and stirred at room temperature for 24 hours. The mixture was then filtered, and the solid phase was washed and dried under vacuum to obtain carboxylated carbon nanotubes. The mixed acid solution was prepared by mixing 98% concentrated sulfuric acid and 70% concentrated nitric acid at a volume ratio of 3:1. The ratio of multi-walled carbon nanotubes to the mixed acid solution was 1g:100mL. S2. Take the carboxylated carbon nanotubes and sulfonium chloride, add N,N-dimethylformamide, ultrasonically disperse for 30 min, heat and reflux at 65°C for 15 h for acylation, wash thoroughly with tetrahydrofuran, vacuum dry, add to polyethylene glycol 400, heat and reflux at 120°C for 15 h, cool to room temperature, wash thoroughly with tetrahydrofuran, vacuum dry, and obtain polyethylene glycol grafted carbon nanotubes; the ratio of carboxylated carbon nanotubes, sulfonium chloride, N,N-dimethylformamide, and polyethylene glycol 400 is 1.1 g: 165 mL: 1.5 mL: 225 mL; S3. Dissolve polysulfone P-1700 (purchased from Shanghai Kaiyin Chemical Co., Ltd.) in 1,1-dichloroethane, add tin tetrachloride, stir evenly, then add 1,4-di(chloromethoxy)-butane dropwise, heat and reflux at 50°C in the dark for 6 hours, then wash the mixture with 2 mol / L hydrochloric acid solution, precipitate the product with anhydrous ethanol, centrifuge and dry to obtain chloromethylated polysulfone; the mass ratio of polysulfone P-1700, 1,1-dichloroethane, tin tetrachloride and 1,4-di(chloromethoxy)-butane is 1:15:0.7:0.01; S4. Dissolve the chloromethylated polysulfone in dimethyl sulfoxide, add 3-dimethylamino-1-propanol, heat and stir at 35°C for 1.5 h, then add isopropanol to precipitate. The precipitate is separated, washed and dried to obtain quaternized polysulfone. The mass ratio of the chloromethylated polysulfone, dimethyl sulfoxide and quaternizing agent 3-dimethylamino-1-propanol is 1:15:0.75. S5. Dissolve the quaternized polysulfone in dimethyl sulfoxide, add 1,4-dibromobutane, polyethylene glycol-grafted carbon nanotubes, and polyvinylpyrrolidone, and ultrasonically disperse until uniform. Pour into a mold and dry in a vacuum drying oven at 80°C for 24 hours. Demold with distilled water, wash the film three times alternately with distilled water and anhydrous ethanol, and dry to obtain a cross-linked polysulfone membrane. Then, soak it in a 1 mol / L sodium hydroxide solution for 24 hours. Remove the wet film with tweezers, rinse with deionized water until the washing solution is neutral, soak it in deionized water for 24 hours, and vacuum dry to obtain the anion exchange membrane. The mass ratio of the quaternized polysulfone, dimethyl sulfoxide, 1,4-dibromobutane, polyethylene glycol-grafted carbon nanotubes, and polyvinylpyrrolidone is 4.5:35:6:0.09:0.045.

[0024] Performance testing The anion exchange membranes prepared in Examples 1-3 and Comparative Examples 1-3 were tested for ion exchange capacity, acid resistance, dimensional stability, anion selectivity, and antifouling performance. The test results are shown in Table 1 below. Table 1 The test results above show that the anion exchange membranes prepared in Examples 1-3 have high ion exchange capacity, strong acid resistance, good dimensional stability, high selectivity for acid radical anions, and excellent anti-fouling performance. Their overall performance is significantly better than that of Comparative Examples 1-3, and they are fully suitable for the harsh working conditions of waste acid recovery.

[0025] Zr@carbon nanotubes, prepared using Zr-MOF as a precursor, exhibit Zr-O coordination bonds that synergize with the carbon nanotubes, preventing degradation and detachment in strong acids and significantly enhancing the membrane's chemical stability. A chemical cross-linking network constructed with 1,4-dibromobutane inhibits membrane swelling and deformation in acidic solutions, preventing the loss of quaternary ammonium groups and maintaining conductivity retention of over 93%. The polyethylene glycol-grafted Zr@carbon nanotubes show good compatibility with the polysulfone cross-linking system, preventing inorganic phase aggregation and precipitation, and maintaining structural integrity during long-term operation. The MOF-derived porous structure of the Zr@carbon nanotubes forms... Uniform pores physically block contaminants from entering the membrane, resulting in a flux recovery rate of ≥91% after fouling. A moderate distribution of quaternary ammonium cations on the membrane surface electrostatically repels positively charged metal ions, further reducing membrane fouling. Quaternized polysulfone provides a high density of fixed positive charges, selectively attracting acid anions for efficient acid anion permeation. A cross-linked network and Zr@carbon nanotubes construct precise pores, electrostatically repelling metal cations with a metal ion rejection rate of ≥98%. Zr@carbon nanotubes penetrate the membrane, creating continuous acid anion transport channels, maintaining high conductivity while ensuring high selectivity. Comparative Example 1 (without polyethylene glycol grafted Zr@carbon nanotubes): Without the inorganic reinforcing phase, stability, conductivity, and anti-fouling properties are significantly reduced; Comparative Example 2 (ungrafted polyethylene glycol): Zr@carbon nanotubes have poor dispersion, no hydrophilic layer, and poor anti-fouling and dimensional stability; Comparative Example 3 (Ordinary carbon nanotubes): Without Zr-MOF-derived structure, its acid resistance, selectivity, and stability are weaker than those of the Examples.

[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An ultrafiltration membrane device for waste acid recovery, comprising a plurality of filtration units arranged in a decreasing concentration gradient, each filtration unit comprising a concentration chamber and a dilute chamber, wherein an anion exchange membrane is disposed between the concentration chamber and the dilute chamber, characterized in that, The method for preparing the anion exchange membrane includes the following steps: S1. Preparation of zirconium-based metal-organic framework powder; S2. Carbon nanotubes are grown in situ on the zirconium-based metal-organic framework to obtain Zr@carbon nanotube powder. S3. Surface-treat the Zr@carbon nanotube powder to obtain carboxylated Zr@carbon nanotubes; S4. Take the carboxylated Zr@carbon nanotubes and graft them with polyethylene glycol to obtain polyethylene glycol-grafted Zr@carbon nanotubes. S5. Take the polysulfone surface modification to obtain chloromethylated polysulfone; S6. Take the chloromethylated polysulfone and quaternize it to obtain quaternized polysulfone; S7. Dissolve the quaternized polysulfone in dimethyl sulfoxide, add 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes and polyvinylpyrrolidone, disperse evenly by ultrasonication, pour into a mold, vacuum dry, demold, wash, and dry to obtain a cross-linked polysulfone membrane material. After ion exchange and activation, the anion exchange membrane is obtained.

2. The ultrafiltration membrane for waste acid recovery according to claim 1, characterized in that, Step S1 specifically includes the following steps: Zirconium chloride, acetic acid, and N,N-dimethylformamide are mixed and ultrasonically dispersed for 30-40 minutes. Terephthalic acid is then added, and the mixture is stirred evenly. The mixture is then transferred to a Teflon-lined reactor and kept at a constant temperature of 120°C for 24 hours. After cooling to room temperature, the mixture is centrifuged, and the solid phase is washed and vacuum dried to obtain zirconium-based metal-organic framework powder. The ratio of zirconium chloride, acetic acid, N,N-dimethylformamide, and terephthalic acid is 40-50 mg: 0.3-0.4 g: 10-20 mL: 28-32 mg.

3. The ultrafiltration membrane for waste acid recovery according to claim 1, characterized in that, Step S2 specifically includes the following steps: take the zirconium-based metal-organic framework powder and melamine powder, mix and grind them evenly, then in an argon atmosphere, heat to 500-550℃ at 3℃ / min and hold for 1h, then heat to 600-650℃ at 2℃ / min and hold for 2h, then heat to 700℃ at 3℃ / min and hold for 0.5h, and then cool naturally to obtain Zr@carbon nanotube powder; the mass ratio of the zirconium-based metal-organic framework powder to the melamine powder is 1:2-3.

4. The ultrafiltration membrane device for waste acid recovery according to claim 1, characterized in that, Step S3 specifically includes the following steps: the Zr@carbon nanotube powder is added to a mixed acid solution, stirred at room temperature for 24 hours, filtered, the solid phase is washed and vacuum dried to obtain carboxylated Zr@carbon nanotubes; the ratio of Zr@carbon nanotube powder to mixed acid solution is 1g:100mL.

5. The ultrafiltration membrane device for waste acid recovery according to claim 1, characterized in that, Step S4 specifically includes the following steps: Take the carboxylated Zr@carbon nanotubes and sulfoxide, mix them, ultrasonically disperse them for 20-40 min, heat and stir at 65℃ for 10-20 h for acylation, wash thoroughly with tetrahydrofuran, vacuum dry them, add them to polyethylene glycol 400, heat and reflux at 120℃ for 10-20 h, cool, wash, vacuum dry them to obtain polyethylene glycol grafted Zr@carbon nanotubes; the ratio of carboxylated Zr@carbon nanotubes, sulfoxide, and polyethylene glycol 400 is 1-1.2 g: 150-180 mL: 200-250 mL.

6. The ultrafiltration membrane for waste acid recovery according to claim 1, characterized in that, Step S5 specifically includes the following steps: dissolve polysulfone in 1,1-dichloroethane, add catalyst, stir evenly, then add 1,4-di(chloromethoxy)-butane dropwise, heat and reflux at 50°C in the dark for 4-8 hours, wash, precipitate, centrifuge and dry to obtain chloromethylated polysulfone; the mass ratio of polysulfone, 1,1-dichloroethane, catalyst and 1,4-di(chloromethoxy)-butane is 1:10-20:0.6-0.8:0.

01.

7. The ultrafiltration membrane for waste acid recovery according to claim 1, characterized in that, Step S6 specifically includes the following steps: dissolving the chloromethylated polysulfone in dimethyl sulfoxide, adding a quaternizing agent, heating and stirring at 30-40℃ for 1-2 hours, then adding isopropanol for precipitation, and separating, washing and drying the precipitate to obtain quaternized polysulfone; the mass ratio of the chloromethylated polysulfone, dimethyl sulfoxide and quaternizing agent is 1:10-20:0.7-0.

8.

8. The ultrafiltration membrane for waste acid recovery according to claim 1, characterized in that, In step S7, the mass ratio of the quaternized polysulfone, dimethyl sulfoxide, 1,4-dibromobutane, polyethylene glycol-grafted Zr@carbon nanotubes, and polyvinylpyrrolidone is 4-5:30-40:5-7:0.05-0.12:0.04-0.

05.

9. The ultrafiltration membrane for waste acid recovery according to claim 1, characterized in that, Step S7, ion exchange and activation, specifically includes the following steps: the cross-linked polysulfone membrane is immersed in a 1 mol / L sodium hydroxide solution for 24 hours, the wet membrane is removed with tweezers, rinsed with deionized water until the washing solution is neutral, then immersed in deionized water for 24 hours, and finally vacuum dried.

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