A method for treating wastewater after textile printing and dyeing

Abstract

The present invention provides a method for treating wastewater after textile printing and dyeing, which comprises the following steps: after the printing and dyeing wastewater is pretreated by a grid and flotation, it enters a micro-nano bubble enhanced coagulation reactor, and after a mixing reaction, it is precipitated and separated; the coagulation sedimentation effluent enters an electrocatalytic-ozone coupled oxidation system, and is electrocatalytically oxidized under the action of a titanium-based boron-doped diamond electrode, while ozone is introduced for reaction; the electrocatalytic-ozone oxidation effluent enters a bioenzyme enhanced degradation system, laccase and peroxidase are added to an anaerobic granular sludge reactor, and oxidoreductase and hydrolase are added to a membrane bioreactor; the membrane bioreactor effluent enters a multifunctional enzyme immobilized photocatalytic self-repairing membrane system; the clean water after treatment by the multifunctional enzyme immobilized photocatalytic self-repairing membrane system is returned to the production line as recycled water. The present invention achieves efficient removal of new pollutants in printing and dyeing wastewater and long-term stable operation of the membrane.

Description

Technical Field

[0001] The invention relates to a wastewater treatment method, in particular to a method for treating wastewater after textile printing and dyeing, and belongs to the technical field of wastewater treatment. Background Art

[0002] Printing and dyeing wastewater is characterized by large water volumes, high levels of organic pollutants, deep chroma, high alkalinity, and significant variability in water quality. In recent years, with the advancement of printing and dyeing technology, an increasing number of new dyes, auxiliaries, and chemicals have been used in the printing and dyeing process, such as brominated flame retardants, perfluorinated compound finishes, nano-scale dyes, and antimicrobial finishes. These new pollutants are difficult to effectively remove using traditional biological treatment processes.

[0003] Traditional printing and dyeing wastewater treatment processes typically employ a combination of physical, chemical, and biological treatment methods, ultimately achieving advanced wastewater treatment and reuse through membrane separation technology. However, these treatment processes face significant challenges in addressing emerging pollutants.

[0004] First, emerging pollutants possess unique physical and chemical properties, such as strong hydrophobicity, stable molecular structure, and specialized functional groups, which result in low degradation efficiency in conventional biological treatment processes. For example, the removal rate of brominated flame retardants in conventional activated sludge systems is typically less than 30%, and antimicrobial finishing agents are not only difficult to degrade but may also inhibit the normal functioning of biological systems.

[0005] Secondly, due to their unique structures and properties, these new pollutants interact strongly with membrane materials, leading to serious membrane fouling problems. For example, the hydrophobic groups and conjugated structures in new azo dye molecules make them more susceptible to adsorption on membrane surfaces; the surface activity of perfluorinated compounds causes them to form a difficult-to-remove fouling layer at the membrane interface; and antimicrobial finishing agents may inhibit the normal metabolism of biofilm on the membrane surface, leading to abnormal biofouling. These unique membrane fouling mechanisms render traditional membrane cleaning methods ineffective.

[0006] Third, to deal with new pollutants, stronger oxidation treatments or frequent membrane cleaning are often required. Although these measures can improve treatment efficiency in the short term, they will accelerate the deterioration of membrane materials and significantly shorten the membrane life.

[0007] Among the above problems, the difficulty in treating new pollutants leads to serious membrane pollution and shortened membrane life, forming a vicious cycle, which ultimately leads to poor treatment of textile printing and dyeing wastewater containing new pollutants. Summary of the Invention

[0008] Based on the above background, the purpose of the present invention is to provide a method for treating wastewater after textile printing and dyeing, which is based on a multifunctional enzyme-immobilized photocatalytic self-repairing membrane and a targeted treatment process to achieve efficient removal of new pollutants in printing and dyeing wastewater and long-term stable operation of the membrane, overcoming the problems of serious membrane pollution, short membrane life and low removal efficiency of new difficult-to-degrade pollutants in the prior art. This method achieves efficient removal of new pollutants and long-term stable operation of membrane performance through specially designed membrane materials and targeted treatment processes.

[0009] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0010] A method for treating wastewater after textile printing and dyeing, the method comprising the following steps:

[0011] After being pre-treated by screens and flotation, the printing and dyeing wastewater enters the micro-nano bubble enhanced coagulation reactor, where composite modified biochar adsorbent and bio-based flocculant are added. After mixed reaction, precipitation and separation are carried out.

[0012] The coagulation effluent enters the electrocatalytic-ozone coupled oxidation system, where it undergoes electrocatalytic oxidation under the action of titanium-based boron-doped diamond electrodes, while ozone is introduced for reaction.

[0013] The effluent from electrocatalytic-ozonation oxidation enters the bio-enzyme enhanced degradation system, which includes an anaerobic granular sludge reactor and a membrane bioreactor. Laccase and peroxidase are added to the anaerobic granular sludge reactor, and oxidoreductase and hydrolase are added to the membrane bioreactor.

[0014] The effluent from the membrane bioreactor enters the multifunctional enzyme-immobilized photocatalytic self-repairing membrane system, which includes a base membrane made of modified polyethersulfone, and a bio-enzyme immobilization layer, a photocatalytic layer, and a self-repairing hydrogel layer constructed on the surface of the base membrane. The clean water treated by the multifunctional enzyme-immobilized photocatalytic self-repairing membrane system is returned to the production line as recycled water.

[0015] During the operation of the multifunctional enzyme immobilized photocatalytic self-repairing membrane system, when the membrane is seriously polluted, the membrane regeneration treatment program is started, and low-temperature pure water backwashing, photocatalytic oxidation degradation treatment and enzymatic reaction activity recovery treatment are carried out in sequence.

[0016] Preferably, the composite modified biochar adsorbent is obtained by carbonizing agricultural waste at 400-600°C, functionalizing it with aminodiacetic acid and loading it with Fe3O4 nanoparticles; the bio-based flocculant is composed of xanthan gum, modified chitosan and polyglutamic acid in a mass ratio of 3:2:1, and the total dosage is 0.05%-0.15% of the wastewater mass.

[0017] Preferably, in the electrocatalytic-ozone coupled oxidation system, the electrodes use titanium-based boron-doped diamond electrodes as anodes and stainless steel as cathodes, and the current density is 10-30 mA / cm 2 The ozone dosage is 30-60 mg / L, 5-15 mmol / L of persulfate activator is added to the electrocatalytic-ozone coupled oxidation system, the reaction pH is controlled in the range of 5.5-6.5, and the reaction temperature is controlled in the range of 25-35°C.

[0018] Preferably, in the bio-enzyme enhanced degradation system, the dosage of laccase in the anaerobic granular sludge reactor is 50-100 U / L, and the dosage of peroxidase is 20-50 U / L; the dosage of oxidoreductase in the membrane bioreactor is 30-80 U / L, and the dosage of hydrolase is 50-120 U / L.

[0019] Preferably, the multifunctional enzyme immobilized photocatalytic self-repairing film is prepared by the following steps:

[0020] The porous base membrane was prepared using polyethersulfone as the substrate by non-solvent induced phase separation method.

[0021] Laccase, peroxidase and oxidoreductase were immobilized on the surface of the basement membrane by chitosan-glutaraldehyde cross-linking method to form an enzyme immobilization layer;

[0022] The photocatalytic layer of Ag / ZnO / g-C3N4 ternary composite nanomaterials was constructed on the surface of the enzyme immobilization layer by in situ growth method.

[0023] A self-healing hydrogel layer composed of thermosensitive poly (N-isopropylacrylamide) / polydopamine copolymer was constructed on the membrane surface.

[0024] Preferably, in the photocatalytic layer, the mass ratio of Ag / ZnO / g-C3N4 ternary composite nanomaterial is 1:10:5, the diameter of ZnO nanorods is 50-100nm, the length is 1-2μm, the average particle size of Ag nanoparticles is 5-10nm, and the thickness of the g-C3N4 layer is 20-50nm.

[0025] Preferably, the thickness of the self-healing hydrogel layer is 10-30 μm, and the mass ratio of the temperature-sensitive poly (N-isopropylacrylamide) to polydopamine is 4:1.

[0026] Preferably, the membrane regeneration process comprises the following steps:

[0027] Use pure water at a temperature of 20-25°C to backwash for 5-10 minutes to expand the self-healing hydrogel layer and release the adsorbed pollutants;

[0028] A weak acidic solution with a pH value of 4.5-5.5 is introduced, and the photocatalytic system is turned on for photocatalytic oxidation degradation for 15-30 minutes;

[0029] A solution containing enzymatic reaction cofactors is introduced to promote the recovery of enzyme activity and the degradation of residues on the membrane surface. The enzymatic reaction cofactors include ABTS, H2O2 and MnSO4. The treatment time is 20-40 minutes.

[0030] Preferably, the enzymatic reaction auxiliary factors include ABTS with a concentration of 0.5-2.0 mmol / L, H2O2 with a concentration of 1.0-5.0 mmol / L, and MnSO4 with a concentration of 0.1-0.5 mmol / L, and the pH value of the solution is maintained in the range of 4.5-5.5.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention provides a method for treating wastewater after textile printing and dyeing, which organically combines bio-enzyme immobilization technology, photocatalytic technology and self-repairing materials to form a new composite membrane system that can actively decompose membrane pollutants, self-repair and maintain high performance for a long time. The specific catalytic degradation of bio-enzymes, the oxidation of active oxygen free radicals generated by photocatalysis and the controllable release of pollutants by the self-repairing hydrogel layer form a multiple synergistic degradation mechanism, which has a good degradation effect on new difficult-to-degrade pollutants in printing and dyeing wastewater, such as brominated flame retardants, antibacterial finishing agents, azo dyes, etc.; the present invention designs a complete membrane regeneration treatment procedure, which can achieve in-situ recovery of membrane performance without disassembling the membrane components, significantly extending the membrane service life and reducing operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0034] Figure 1 This is a flow chart of the method for treating printing and dyeing wastewater based on the multifunctional enzyme immobilized photocatalytic self-repairing membrane of the present invention;

[0035] Figure 2 This is a schematic diagram of the pollutant degradation mechanism of the multifunctional enzyme-immobilized photocatalytic self-repairing membrane and the membrane regeneration treatment procedure. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any form of modification and / or change made to the present invention will fall within the scope of protection of the present invention.

[0037] In the present invention, unless otherwise specified, all parts and percentages are by weight. The equipment and raw materials used are commercially available or commonly used in the art. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art. The components or equipment in the following embodiments, unless otherwise specified, are all universal standard parts or components known to those skilled in the art. Their structures and principles are known to those skilled in the art through technical manuals or routine experimental methods.

[0038] The following detailed description of the embodiments of the present invention is made in conjunction with the accompanying drawings. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, one or more embodiments may be implemented by those skilled in the art without these specific details.

[0039] The embodiment of the present invention discloses a method for treating wastewater after textile printing and dyeing, which comprises the following steps:

[0040] After being pre-treated by screens and flotation, the printing and dyeing wastewater enters the micro-nano bubble enhanced coagulation reactor, where composite modified biochar adsorbent and bio-based flocculant are added. After mixing and reacting for 15-30 minutes, precipitation and separation are carried out.

[0041] The coagulation effluent enters the electrocatalytic-ozone coupled oxidation system, where it undergoes electrocatalytic oxidation under the action of titanium-based boron-doped diamond electrodes while ozone is introduced for a reaction of 20-40 minutes.

[0042] The effluent from electrocatalytic-ozonation oxidation enters the bio-enzyme enhanced degradation system, which consists of an anaerobic granular sludge reactor and a membrane bioreactor. Appropriate amounts of laccase and peroxidase are added to the anaerobic granular sludge reactor, and appropriate amounts of oxidoreductase and hydrolase are added to the membrane bioreactor.

[0043] The effluent from the membrane bioreactor enters the multifunctional enzyme-immobilized photocatalytic self-repairing membrane system, the structure of which includes a porous base membrane prepared by a phase separation method using modified polyethersulfone (PES) as the base membrane, and a functional layer with a layered structure constructed on the surface of the base membrane by an in situ growth method, including a biological enzyme immobilization layer, a photocatalytic layer, and a self-repairing hydrogel layer. The biological enzyme immobilization layer immobilizes various biological enzymes such as laccase, peroxidase, and oxidoreductase by chitosan-glutaraldehyde cross-linking method. The photocatalytic layer is composed of Ag / ZnO / g-C3N4 ternary composite nanomaterials, which produce reactive oxygen species through visible light excitation. The self-repairing hydrogel layer is composed of a thermosensitive poly (N-isopropylacrylamide) / polydopamine (PNIPAM / PDA) copolymer, which has temperature-responsive self-repairing properties.

[0044] The clean water treated by the multifunctional enzyme-immobilized photocatalytic self-repairing membrane is returned to the production line as recycled water.

[0045] During the operation of the membrane system, when the membrane is seriously polluted, start the membrane regeneration process:

[0046] First, backwash with low-temperature (20-25°C) pure water for 5-10 minutes to activate the self-repairing hydrogel layer to release adsorbed pollutants;

[0047] Then, a weakly acidic solution with a pH adjusted value (pH = 4.5-5.5) was introduced, and the photocatalytic system was turned on to perform photocatalytic oxidation degradation for 15-30 minutes;

[0048] Finally, a solution containing enzyme reaction cofactors is passed through to promote the recovery of enzyme activity and the degradation of residues on the membrane surface for 20-40 minutes.

[0049] The membrane flux after treatment recovered to more than 90% of the original flux.

[0050] The process of the treatment method of textile printing and dyeing wastewater is as follows: Figure 1 shown.

[0051] The composite modified biochar adsorbent is obtained by carbonizing agricultural waste (e.g., straw and / or rice husk) at 400-600 °C, functionalizing it with aminodiacetic acid, and loading it with Fe3O4 nanoparticles. The specific surface area is greater than 800 m 2 / g, and the adsorption capacity for new dyes and auxiliaries is greater than 150mg / g.

[0052] The bio-based flocculant is composed of xanthan gum, modified chitosan and polyglutamic acid in a mass ratio of 3:2:1, and the total dosage is 0.05%-0.15% of the wastewater mass.

[0053] In the electrocatalytic-ozone coupled oxidation system, the electrodes use titanium-based boron-doped diamond electrodes as anodes and stainless steel as cathodes, with a current density of 10-30 mA / cm 2 The ozone dosage is 30-60 mg / L, 5-15 mmol / L of persulfate activator is added to the system, the reaction pH is controlled in the range of 5.5-6.5, and the reaction temperature is controlled in the range of 25-35°C.

[0054] The preparation method of the enzyme preparation added to the bio-enzyme enhanced degradation system is as follows:

[0055] Highly efficient degradation strains were isolated and screened from the collected dye wastewater treatment sludge, including Trametes versicolor (producing laccase), Phanerochaete chrysosporium (producing peroxidase), Bacillus subtilis (producing oxidoreductase), and Aspergillus niger (producing hydrolase).

[0056] The isolated strain was cultured in an optimized medium for 3-7 days and the fermentation broth was collected;

[0057] Crude enzyme preparations were obtained by ammonium sulfate precipitation, dialysis, and purification by ion exchange chromatography;

[0058] The enzyme preparation is mixed with polyethylene glycol, sodium alginate and glycerol to prepare an enzyme protective agent to extend the stable period of enzyme activity;

[0059] The dosage of laccase in the anaerobic granular sludge reactor is 50-100 U / L, and the dosage of peroxidase is 20-50 U / L; the dosage of oxidoreductase in the membrane bioreactor is 30-80 U / L, and the dosage of hydrolase is 50-120 U / L.

[0060] The preparation method of the multifunctional enzyme immobilized photocatalytic self-repairing film comprises the following steps:

[0061] A 15-20 wt% casting solution is prepared using polyethersulfone as a base material, N,N-dimethylacetamide as a solvent, and polyvinylpyrrolidone as a pore-forming agent;

[0062] The casting solution is evenly coated on the non-woven fabric support, pre-evaporated in an environment of 50-70°C for 30-60s, and then immersed in a mixed coagulation bath (water / ethanol = 7:3, temperature 0-5°C) for phase inversion to form a base film;

[0063] The basement membrane was soaked in a 1 wt % chitosan solution (pH = 5.0) for 12 h and then cross-linked with a 2.5 wt % glutaraldehyde solution for 4 h to form an enzyme immobilization support layer;

[0064] The treated basement membrane was immersed in a mixed solution of laccase (300-500 U / g membrane), peroxidase (100-200 U / g membrane) and oxidoreductase (150-250 U / g membrane) for 4-8 hours and kept at 4°C for 12 hours to complete enzyme immobilization;

[0065] An Ag / ZnO / g-C3N4 composite photocatalytic layer was grown on the surface of the enzyme immobilization layer using an in situ growth method: a ZnO seed layer was first deposited on the membrane surface, followed by the hydrothermal growth of ZnO nanorod arrays. Finally, Ag nanoparticles were loaded by photoreduction and coated with a g-C3N4 layer by an impregnation-thermal polymerization method.

[0066] Finally, the membrane was immersed in a solution containing N-isopropylacrylamide monomer (8 wt%), methacrylic acid (2 wt%), N,N'-methylenebisacrylamide crosslinker (0.5 wt%), dopamine (1 wt%), and ammonium persulfate initiator (0.1 wt%), and reacted at 60 ° C for 4 h under nitrogen protection to form a PNIPAM / PDA self-healing hydrogel layer;

[0067] The prepared composite membrane was washed in deionized water for 24 h and stored in phosphate buffer (pH = 7.0) at 4°C for later use.

[0068] The mass ratio of the Ag / ZnO / g-C3N4 ternary composite nanomaterials in the photocatalytic layer is 1:10:5, the ZnO nanorods have a diameter of 50-100nm and a length of 1-2μm, the average particle size of the Ag nanoparticles is 5-10nm, and the thickness of the g-C3N4 layer is 20-50nm. The photocatalytic reaction uses a visible light source with a wavelength range of 420-530nm and a light intensity of 5-20mW / cm 2 , turn on the photocatalytic system once every 8-12 hours of operation, each time for 30-60 minutes.

[0069] The thickness of the self-healing hydrogel layer is 10-30 μm, the PNIPAM / PDA mass ratio is 4:1, and the temperature responsiveness of the hydrogel layer is: when the temperature is lower than 32°C, the hydrogel layer absorbs water and expands, which is conducive to the release of pollutants; when the temperature is higher than 32°C, the hydrogel layer shrinks, which is conducive to the improvement of membrane flux; dopamine provides free radical scavenging ability and synergistic self-healing function in the hydrogel network.

[0070] The membrane regeneration process automatically initiates every 200-400 hours of operation and can be manually initiated when the membrane flux drops below 60% of its initial value. Enzymatic cofactors used during membrane regeneration include: ABTS at a concentration of 0.5-2.0 mmol / L, H₂O₂ at a concentration of 1.0-5.0 mmol / L, and MnSO₄ at a concentration of 0.1-0.5 mmol / L. The pH is maintained within the range of 4.5-5.5.

[0071] The pollutant degradation mechanism of the multifunctional enzyme immobilized photocatalytic self-repairing membrane and the membrane regeneration treatment process are as follows Figure 2 shown.

[0072] Taking the wastewater treatment of a printing enterprise as an example, the main characteristics of its printing and dyeing wastewater are: pH 8.5-9.8, COD 950-1250mg / L, chroma 280-350 times, BOD5220-280mg / L, SS180-220mg / L, and it contains difficult-to-degrade pollutants such as azo dyes, brominated flame retardants and antibacterial finishing agents.

[0073] The wastewater treatment process is as follows:

[0074] After passing through a 5mm screen to remove large particles, the wastewater enters a flotation tank, where PAC and PAM are added in a 3:1 mass ratio. After suspended solids are removed by flotation, the wastewater enters a micro-nano bubble enhanced coagulation reactor. In this reactor, a composite modified biochar adsorbent (0.08% of the wastewater mass) made from corn straw, carbonized at 500°C and functionalized with aminodiacetic acid and loaded with Fe₃O₄ nanoparticles, is added. A bio-based flocculant (0.1% of the wastewater mass) consisting of xanthan gum, modified chitosan, and polyglutamic acid in a 3:2:1 mass ratio is also added. Mixing and reaction are enhanced by micro-nano bubbles (average diameter 15 μm) for 20 minutes before entering a sedimentation tank for separation.

[0075] The coagulation effluent enters the electrocatalytic-ozone coupled oxidation system, which uses a titanium-based boron-doped diamond electrode as the anode and stainless steel as the cathode. The electrode spacing is 2 cm and the current density is 20 mA / cm 2 Ozone was introduced simultaneously at a dosage of 45 mg / L, and sodium persulfate was added as an activator at a concentration of 10 mmol / L. During the reaction, the pH was controlled at 6.0, the temperature was 30°C, and the reaction time was 30 minutes. This process effectively degrades azo dyes and antimicrobial finishing agents in printing wastewater, achieving a COD removal rate exceeding 50% and a chroma removal rate exceeding 70%.

[0076] After the pH value of the electrocatalytic-ozonation effluent is adjusted to 7.0, it enters the bio-enzyme enhanced degradation system. It first enters an upflow anaerobic granular sludge reactor, into which laccase (80 U / L) produced by Trametes versicolor and peroxidase (30 U / L) produced by Phanerochaete chrysosporium, isolated, screened and cultured from dye wastewater treatment sludge, are added. The anaerobic granular sludge reactor has a HRT of 8 hours. The effluent enters a membrane bioreactor, into which an oxidoreductase (50 U / L) produced by Bacillus subtilis and a hydrolase (80 U / L) produced by Aspergillus niger are added. The membrane bioreactor has an HRT of 6 hours and an MLSS of 5000 mg / L. This system has a highly efficient degradation capacity for specific pollutants such as brominated flame retardants in wastewater, further increasing COD removal by 40% and chroma removal by 25%.

[0077] The effluent from the membrane bioreactor enters the multifunctional enzyme immobilized photocatalytic self-repairing membrane system for deep treatment. The preparation process of the membrane system is as follows:

[0078] The casting solution was prepared by using 18 wt% polyethersulfone as a base material, N,N-dimethylacetamide as a solvent, and adding 5 wt% polyvinylpyrrolidone as a pore-forming agent.

[0079] The casting solution was evenly coated on a non-woven fabric support with a thickness of 200 μm. After pre-evaporation at 60°C for 45 seconds, it was immersed in a water / ethanol (7:3) coagulation bath at 3°C ​​for phase inversion for 3 minutes to form a base film.

[0080] The basement membrane was soaked in a 1 wt% chitosan solution (pH = 5.0) for 12 h, cross-linked with a 2.5 wt% glutaraldehyde solution for 4 h, and then thoroughly washed to form an enzyme immobilization support layer;

[0081] The treated basement membrane was immersed in a mixed solution (phosphate buffer, pH = 6.0) of laccase (400 U / g membrane), peroxidase (150 U / g membrane), and oxidoreductase (200 U / g membrane) for 6 h and kept at 4°C for 12 h to complete enzyme immobilization;

[0082] An Ag / ZnO / g-C3N4 composite photocatalytic layer was constructed on the surface of the enzyme immobilization layer by an in situ growth method: the membrane surface was first immersed in a 0.05 mol / L Zn(CH3COO)2 solution for 2 hours, dried, and then heat-treated at 350°C for 1 hour to form a ZnO seed layer; the membrane was then immersed in a hydrothermal reaction solution containing 0.025 mol / L Zn(NO3)2 and 0.025 mol / L hexamethylenetetramine and reacted at 90°C for 5 hours to grow ZnO nanorod arrays; the membrane was then immersed in a 0.01 mol / L AgNO3 solution for 30 minutes and reduced under ultraviolet light for 2 hours to form Ag nanoparticles; finally, a g-C3N4 layer was prepared by immersing in a melamine solution, drying, and thermally polymerizing at 550°C. The mass ratio of Ag / ZnO / g-C3N4 was 1:10:5.

[0083] The membrane was immersed in a solution containing N-isopropylacrylamide monomer (8 wt%), methacrylic acid (2 wt%), N,N'-methylenebisacrylamide (0.5 wt%), dopamine (1 wt%), and ammonium persulfate (0.1 wt%), and nitrogen was passed through the solution at 60 ° C for 4 h to form a PNIPAM / PDA self-healing hydrogel layer with a thickness of about 20 μm.

[0084] The prepared composite membrane was washed in deionized water for 24 h and stored in phosphate buffer (pH = 7.0) at 4°C for later use.

[0085] The multifunctional enzyme immobilized photocatalytic self-repairing membrane system adopts a flat membrane module with a membrane area of ​​20m 2 The membrane assembly integrates an LED light source array with a wavelength of 470nm and a light intensity of 10mW / cm 2 The system operating parameters are: membrane flux of 25-30LMH, transmembrane pressure difference of 0.05-0.15MPa, and the photocatalytic system is turned on once every 8 hours for 45 minutes each time. At the same time, a temperature control system is set to reduce the temperature to 25°C when pollution is serious to promote the expansion of the hydrogel layer and release pollutants.

[0086] The water produced by the membrane system is returned to the production line as recycled water. Its water quality indicators are: COD <25mg / L, chroma <8 times, turbidity <0.5NTU, brominated flame retardant removal rate >98%, antibacterial finishing agent removal rate >96%, and azo dye removal rate >99%.

[0087] After the membrane system has been running for 300 hours, or when the membrane flux drops to 65% of the initial value, the membrane regeneration process is started:

[0088] First, pure water at 22°C was introduced for backwashing for 8 minutes to activate the hydrogel layer to expand and release the adsorbed pollutants;

[0089] Then, a citric acid solution (0.5 wt %) with a pH of 5.0 was introduced, and the photocatalytic system was turned on to perform photocatalytic oxidation treatment for 25 min.

[0090] Finally, a solution containing ABTS (1.0 mmol / L), H2O2 (3.0 mmol / L), and MnSO4 (0.3 mmol / L) was introduced at pH 5.0 to promote the recovery of enzyme activity and the degradation of residual pollutants for 30 min.

[0091] After the regeneration process is completed, the membrane flux recovers to more than 90% of the initial value and can continue to operate normally.

[0092] Performance evaluation results show that compared with traditional ultrafiltration-reverse osmosis membrane systems, the membrane fouling rate is reduced by 73%, the frequency of chemical cleaning can be reduced from once a week to once a month, saving chemical agents, reducing energy consumption and treatment costs, and the system water reuse rate reaches 86%.

[0093] It can be seen from the above examples that the textile printing and dyeing wastewater treatment method based on the multifunctional enzyme immobilized photocatalytic self-repairing membrane provided by the present invention shows excellent treatment effect and stability for textile printing and dyeing wastewater, especially wastewater containing new difficult-to-degrade pollutants, and effectively solves the problems of severe membrane pollution, short membrane life and low removal efficiency of new pollutants.

[0094] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for treating wastewater after textile printing and dyeing, characterized in that: The method comprises the following steps: After being pre-treated by screens and flotation, the printing and dyeing wastewater enters the micro-nano bubble enhanced coagulation reactor, where composite modified biochar adsorbent and bio-based flocculant are added. After mixed reaction, precipitation and separation are carried out. The coagulation effluent enters the electrocatalytic-ozone coupled oxidation system, where it undergoes electrocatalytic oxidation under the action of titanium-based boron-doped diamond electrodes, while ozone is introduced for reaction. The effluent from electrocatalytic-ozonation oxidation enters the bio-enzyme enhanced degradation system, which includes an anaerobic granular sludge reactor and a membrane bioreactor. Laccase and peroxidase are added to the anaerobic granular sludge reactor, and oxidoreductase and hydrolase are added to the membrane bioreactor. The effluent from the membrane bioreactor enters the multifunctional enzyme-immobilized photocatalytic self-repairing membrane system, which includes a base membrane made of modified polyethersulfone, and a bio-enzyme immobilization layer, a photocatalytic layer, and a self-repairing hydrogel layer constructed on the surface of the base membrane. The clean water treated by the multifunctional enzyme-immobilized photocatalytic self-repairing membrane system is returned to the production line as recycled water. During the operation of the multifunctional enzyme immobilized photocatalytic self-repairing membrane system, when the membrane is seriously polluted, the membrane regeneration process is started, and low-temperature pure water backwashing, photocatalytic oxidation degradation treatment and enzymatic reaction activity recovery treatment are carried out in sequence; The multifunctional enzyme immobilized photocatalytic self-repairing film is prepared by the following steps: The porous base membrane was prepared using polyethersulfone as the substrate by non-solvent induced phase separation method. Laccase, peroxidase and oxidoreductase were immobilized on the surface of the basement membrane by chitosan-glutaraldehyde cross-linking method to form an enzyme immobilization layer; The photocatalytic layer of Ag / ZnO / g-C3N4 ternary composite nanomaterials was constructed on the surface of the enzyme immobilization layer by in situ growth method. A self-healing hydrogel layer composed of a thermoresponsive poly (N-isopropylacrylamide) / polydopamine copolymer was constructed on the membrane surface; The membrane regeneration process comprises the following steps: Use pure water at a temperature of 20-25°C to backwash for 5-10 minutes to expand the self-healing hydrogel layer and release the adsorbed pollutants; A weak acidic solution with a pH value of 4.5-5.5 is introduced, and the photocatalytic system is turned on for photocatalytic oxidation degradation for 15-30 minutes; A solution containing enzymatic reaction cofactors is introduced to promote the recovery of enzyme activity and the degradation of residues on the membrane surface. The enzymatic reaction cofactors include ABTS, H2O2 and MnSO4. The treatment time is 20-40 minutes.

2. The method for treating wastewater after textile printing and dyeing according to claim 1, wherein: The composite modified biochar adsorbent is obtained by carbonizing agricultural waste at 400-600°C, functionalizing it with aminodiacetic acid, and loading it with Fe3O4 nanoparticles; the bio-based flocculant is composed of xanthan gum, modified chitosan, and polyglutamic acid in a mass ratio of 3:2:1, and the total dosage is 0.05%-0.15% of the wastewater mass.

3. The method for treating wastewater after textile printing and dyeing according to claim 1, wherein: In the electrocatalytic-ozone coupled oxidation system, the electrodes use titanium-based boron-doped diamond electrodes as anodes and stainless steel as cathodes, with a current density of 10-30 mA / cm 2 The ozone dosage is 30-60 mg / L, 5-15 mmol / L of persulfate activator is added to the electrocatalytic-ozone coupled oxidation system, the reaction pH is controlled in the range of 5.5-6.5, and the reaction temperature is controlled in the range of 25-35°C.

4. The method for treating wastewater after textile printing and dyeing according to claim 1, wherein: In the bioenzyme enhanced degradation system, the dosage of laccase in the anaerobic granular sludge reactor is 50-100 U / L, and the dosage of peroxidase is 20-50 U / L; the dosage of oxidoreductase in the membrane bioreactor is 30-80 U / L, and the dosage of hydrolase is 50-120 U / L.

5. The method for treating wastewater after textile printing and dyeing according to claim 1, wherein: In the photocatalytic layer, the mass ratio of Ag / ZnO / g-C3N4 ternary composite nanomaterial is 1:10:5, the diameter of ZnO nanorods is 50-100nm, the length is 1-2μm, the average particle size of Ag nanoparticles is 5-10nm, and the thickness of the g-C3N4 layer is 20-50nm.

6. The method for treating wastewater after textile printing and dyeing according to claim 1, wherein: The thickness of the self-repairing hydrogel layer is 10-30 μm, and the mass ratio of the temperature-sensitive poly (N-isopropylacrylamide) to polydopamine is 4:

1.

7. The method for treating wastewater after textile printing and dyeing according to claim 1, wherein: The enzymatic reaction auxiliary factors include ABTS with a concentration of 0.5-2.0 mmol / L, H2O2 with a concentration of 1.0-5.0 mmol / L, and MnSO4 with a concentration of 0.1-0.5 mmol / L, and the pH value of the solution is maintained in the range of 4.5-5.5.

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