Treatment method of wastewater after textile printing and dyeing

Abstract

The invention provides a textile printing and dyeing wastewater treatment method which comprises the following steps: printing and dyeing wastewater enters a micro-nano bubble enhanced coagulation reactor after being subjected to grating and air flotation pretreatment, and precipitation separation is performed after mixed reaction; allowing coagulating sedimentation effluent to enter an electro-catalysis-ozone coupling oxidation system, performing electro-catalytic oxidation under the action of a titanium-based boron-doped diamond electrode, and introducing ozone for reaction at the same time; electro-catalysis-ozone oxidation effluent enters a bio-enzyme enhanced degradation system, laccase and peroxidase are added into an anaerobic granular sludge reactor, and oxidoreductase and hydrolase are added into a membrane bioreactor; effluent of the membrane bioreactor enters a multifunctional enzyme immobilized photocatalytic self-repairing membrane system; clear water treated by the multifunctional enzyme immobilized photocatalytic self-repairing membrane system is used as reuse water to return to a production line. According to the invention, efficient removal of novel pollutants in printing and dyeing wastewater and long-term stable operation of the membrane are realized.

Description

Technical Field

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

[0002] Printing and dyeing wastewater is characterized by large water volume, high content of organic pollutants, deep color, strong alkalinity and large water quality variation. In recent years, with the development of printing and dyeing processes, more and more new dyes, auxiliaries and chemicals have been applied in the printing and dyeing process, such as brominated flame retardants, perfluorinated compound finishing agents, nano-scale dyes, antibacterial finishing agents, etc. These new pollutants are difficult to be effectively removed by traditional biological treatment processes.

[0003] Traditional printing and dyeing wastewater treatment processes usually adopt a combined method of physical-chemical-biological treatment, and finally achieve in-depth treatment and reuse of wastewater through membrane separation technology. However, these treatment processes face severe challenges when dealing with new pollutants.

[0004] Firstly, new pollutants have special physical and chemical properties, such as strong hydrophobicity, stable molecular structure and special functional groups, resulting in low degradation efficiency of conventional biological treatment processes for them. For example, the removal rate of brominated flame retardants in a conventional activated sludge system is usually less than 30%, and antibacterial finishing agents are not only difficult to be degraded, but may also inhibit the normal functions of biological systems.

[0005] Secondly, due to their special structures and properties, these new pollutants have strong interactions with membrane materials, resulting in serious membrane fouling problems. For example, the hydrophobic groups and conjugated structures in new azo dye molecules make them more likely to adsorb on the membrane surface; the surface-active properties of perfluorinated compounds lead to the formation of a pollution layer difficult to remove at the membrane interface; antibacterial finishing agents may inhibit the normal metabolism of biofilms on the membrane surface and cause abnormal biological fouling. These special membrane fouling mechanisms make the effect of traditional membrane cleaning methods poor.

[0006] Thirdly, to deal with new pollutants, stronger oxidation treatment or frequent membrane cleaning is often required. Although these measures can improve the 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 difficult treatment of new pollutants, the resulting serious membrane fouling and the shortening of membrane life form a vicious cycle, ultimately leading to poor treatment effect for textile printing and dyeing wastewater containing new pollutants. Summary of the Invention

[0008] Based on the above background, the object of the present invention is to provide a method for treating wastewater after textile printing and dyeing. Based on a multifunctional enzyme-immobilized photocatalytic self-repairing membrane and a targeted treatment process, it realizes the efficient removal of new pollutants in printing and dyeing wastewater and the long-term stable operation of the membrane, overcoming the problems of serious membrane fouling, short membrane life, and low removal efficiency of new and difficult-to-degrade pollutants in the existing technology. Through a specially designed membrane material and a targeted treatment process, it realizes the efficient removal of new pollutants and the long-term stable operation of membrane performance.

[0009] In order to achieve the above 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 the printing and dyeing wastewater is pretreated by a grille and air flotation, it enters a micro-nano bubble enhanced coagulation reactor, and a composite modified biochar adsorbent and a bio-based flocculant are added. After mixing and reacting, precipitation separation is carried out;

[0012] The effluent from coagulation and precipitation enters an electrocatalytic-ozone coupling oxidation system, where electrocatalytic oxidation is carried out under the action of a titanium-based boron-doped diamond electrode, and ozone is simultaneously introduced for reaction;

[0013] The effluent from electrocatalytic-ozone oxidation enters a 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 a multifunctional enzyme-immobilized photocatalytic self-repairing membrane system. The multifunctional enzyme-immobilized photocatalytic self-repairing membrane system includes a base membrane prepared from 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 treated clear water from 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 fouling is serious, start the membrane regeneration treatment program, and sequentially carry out low-temperature pure water backwashing, photocatalytic oxidation degradation treatment, and enzymatic reaction activity recovery treatment.

[0016] Preferably, the composite modified biochar adsorbent is obtained by carbonizing agricultural waste at 400-600 °C, followed by amino diacetic acid functionalization and Fe 3 O 4 nanoparticle loading; 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 mass of the wastewater.

[0017] Preferably, in the electrocatalytic-ozone coupling oxidation system, a titanium-based boron-doped diamond electrode is used as the anode and stainless steel is used as the cathode, 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 coupling oxidation system, the reaction pH is controlled within the range of 5.5-6.5, and the reaction temperature is controlled at 25-35 °C.

[0018] Preferably, in the biological 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-healing membrane is prepared by the following steps:

[0020] Using polyethersulfone as the substrate, a porous substrate membrane is prepared by the non-solvent induced phase separation method;

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

[0022] An Ag / ZnO / g-C 3 N 4 photocatalytic layer of ternary composite nanomaterials is constructed on the surface of the enzyme immobilization layer;

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

[0024] Preferably, in the photocatalytic layer, the mass ratio of the Ag / ZnO / g-C 3 N 4 ternary composite nanomaterials is 1:10:5, the diameter of the ZnO nanorods is 50-100 nm, the length is 1-2 μm, the average particle size of the Ag nanoparticles is 5-10 nm, and the thickness of the g-C 3 N 4 layer is 20-50 nm.

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

[0026] Preferably, the membrane regeneration treatment procedure includes the following steps:

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

[0028] Introduce a weakly acidic solution with a pH value of 4.5-5.5, and at the same time turn on the photocatalytic system for photocatalytic oxidation degradation treatment for 15-30 minutes;

[0029] Introduce a solution containing enzyme reaction cofactors to promote the recovery of enzyme activity and the degradation of residues on the membrane surface. The enzyme reaction cofactors include ABTS, H 2 O 2 and MnSO 4 , and the treatment time is 20-40 minutes.

[0030] Preferably, the enzyme reaction cofactors include ABTS with a concentration of 0.5-2.0 mmol / L, H 2 O 2 with a concentration of 1.0-5.0 mmol / L and MnSO 4 with a concentration of 0.1-0.5 mmol / L, and the pH value of the solution is maintained within the range of 4.5-5.5.

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

[0032] A method for treating textile printing and dyeing wastewater of the present invention organically combines the bio-enzyme immobilization technology, photocatalytic technology and self-healing 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-enzyme, the oxidation of reactive oxygen radicals generated by photocatalysis and the controllable pollutant release of the self-healing hydrogel layer form a multiple synergistic degradation mechanism, which has a good degradation effect on new refractory 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 realize the in-situ recovery of membrane performance without disassembling the membrane module, significantly extend the membrane service life and reduce the operation cost. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

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

[0035] Figure 2 It is a schematic diagram of the pollutant degradation mechanism and membrane regeneration treatment procedure of the multifunctional enzyme-immobilized photocatalytic self-healing membrane. Specific embodiments

[0036] The technical solutions of the present invention will be further specifically described below through specific embodiments 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 formal modification and / or change made to the present invention will fall within the protection scope of the present invention.

[0037] In the present invention, unless otherwise specified, all parts and percentages are in weight units, and the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following embodiments are conventional methods in the art unless otherwise specified. The components or equipment in the following embodiments are all general standard parts or parts known to those skilled in the art, and their structures and principles can all be learned by those skilled in the art through technical manuals or through conventional experimental methods.

[0038] The following will make a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. In the following detailed description, for the convenience of explanation, many specific details are elaborated to provide a comprehensive understanding of the embodiments of the present invention. However, one or more embodiments can also be implemented by those skilled in the art without these specific details.

[0039] The embodiments of the present invention disclose a method for treating textile printing and dyeing wastewater, which includes the following steps:

[0040] After the printing and dyeing wastewater is pretreated by a grille and air flotation, it enters a micro-nano bubble enhanced coagulation reactor, and a composite modified biochar adsorbent and a bio-based flocculant are added. After mixing and reacting for 15 - 30 minutes, precipitation separation is carried out;

[0041] The effluent from coagulation precipitation enters an electrocatalytic-ozone coupling oxidation system, where electrocatalytic oxidation is carried out under the action of a titanium-based boron-doped diamond electrode, and ozone is simultaneously introduced, and the reaction is carried out for 20 - 40 minutes;

[0042] The effluent from electrocatalytic-ozone oxidation enters a bioenzyme enhanced degradation system, which consists of an anaerobic granular sludge reactor and a membrane bioreactor. An appropriate amount of laccase and peroxidase are added to the anaerobic granular sludge reactor, and an appropriate amount of redox enzyme and hydrolase are added to the membrane bioreactor;

[0043] The effluent of the membrane bioreactor enters the multifunctional enzyme-immobilized photocatalytic self-healing membrane system. The structure of this membrane system includes a porous base membrane prepared by the phase separation method using modified polyethersulfone (PES) as the base membrane, and a functional layer with a hierarchical structure constructed on the surface of the base membrane through in-situ growth, including a bio-enzyme immobilization layer, a photocatalytic layer, and a self-healing hydrogel layer. The bio-enzyme immobilization layer immobilizes various bio-enzymes such as laccase, peroxidase, and oxidoreductase through the chitosan-glutaraldehyde cross-linking method. The photocatalytic layer is composed of an Ag / ZnO / g-C 3 N 4 ternary composite nanomaterial, which generates reactive oxygen species under visible light excitation. The self-healing hydrogel layer is composed of a thermosensitive poly(N-isopropylacrylamide) / polydopamine (PNIPAM / PDA) copolymer and has temperature-responsive self-healing properties;

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

[0045] During the operation of the membrane system, when membrane fouling is severe, start the membrane regeneration treatment procedure:

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

[0047] Then, introduce a weakly acidic solution with pH adjusted (pH = 4.5 - 5.5), and at the same time turn on the photocatalytic system for photocatalytic oxidation degradation treatment for 15 - 30 minutes;

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

[0049] The treated membrane flux is restored to more than 90% of the original flux.

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

[0051] The composite modified biochar adsorbent is obtained by carbonizing agricultural waste (such as straw and / or rice husk) at 400 - 600°C and then subjecting it to aminodiacetic acid functionalization and Fe 3 O 4 nanoparticle loading, with a specific surface area greater than 800 m 2 / g and an adsorption capacity for new dyes and auxiliaries greater than 150 mg / 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 coupling oxidation system, a titanium-based boron-doped diamond electrode is used as the anode, stainless steel is used as the cathode, 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 system, the reaction pH is controlled within the range of 5.5 - 6.5, and the reaction temperature is controlled at 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 are 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 strains are cultured in an optimized medium for 3 - 7 days, and the fermentation broth is collected;

[0057] The crude enzyme preparation is obtained by ammonium sulfate precipitation, dialysis, and ion exchange chromatography purification;

[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 membrane includes the following steps:

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

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

[0063] The base membrane is 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 base membrane is impregnated with 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 h and maintained at 4 °C for 12 h to complete enzyme immobilization;

[0065] The Ag / ZnO / g-C 3 N 4 composite photocatalytic layer is grown on the surface of the enzyme immobilization layer by an in-situ growth method: First, a ZnO seed layer is deposited on the membrane surface, then a ZnO nanorod array is grown by a hydrothermal method, and finally Ag nanoparticles are loaded by a photoreduction method, and the g-C 3 N 4 layer is coated by an impregnation-thermal polymerization method;

[0066] Finally, the membrane is 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 is washed in deionized water for 24 h and stored in a phosphate buffer solution (pH = 7.0) at 4 °C for standby.

[0068] Among them, the mass ratio of the Ag / ZnO / g-C 3 N 4 ternary composite nanomaterial in the photocatalytic layer is 1:10:5, the diameter of the ZnO nanorods is 50 - 100 nm, the length is 1 - 2 μm, the average particle size of the Ag nanoparticles is 5 - 10 nm, and the thickness of the g-C 3 N 4 layer is 20 - 50 nm. The photocatalytic reaction uses a visible light source with a wavelength range of 420 - 530 nm and a light intensity of 5 - 20 mW / cm 2 , and the photocatalytic system is turned on once every 8 - 12 hours, each time for 30 - 60 min.

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

[0070] The membrane regeneration treatment program is automatically started once every 200 - 400 hours of operation, or can also be manually started when the membrane flux drops below 60% of the initial value. The enzymatic reaction cofactors used during the membrane regeneration process include: ABTS concentration is 0.5 - 2.0 mmol / L, H 2 O 2 concentration is 1.0 - 5.0 mmol / L, MnSO 4 concentration is 0.1 - 0.5 mmol / L, and 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 program are as Figure 2 shown.

[0072] Taking the wastewater treatment of a printing enterprise as an example, the main characteristics of its printed and dyed wastewater are: pH 8.5 - 9.8, COD 950 - 1250 mg / L, chromaticity 280 - 350 times, BOD5 220 - 280 mg / L, SS 180 - 220 mg / L, containing refractory pollutants such as azo dyes, brominated flame retardants, and antibacterial finishing agents.

[0073] The wastewater treatment process is as follows:

[0074] The wastewater passes through a 5 - mm grid to remove large - particle impurities and then enters the air - flotation tank. PAC and PAM with a mass ratio of 3:1 are added. After removing suspended solids by air - flotation, it enters the micro - nano bubble - enhanced coagulation reactor. In the reactor, a composite modified biochar adsorbent loaded with amino - diacetic acid functionalized and Fe 3 O 4 nanoparticles, which is made from corn straw as raw material and carbonized at 500 °C, is added with a dosage of 0.08% of the wastewater mass; at the same time, a bio - based flocculant composed of xanthan gum, modified chitosan, and polyglutamic acid in a mass ratio of 3:2:1 is added with a dosage of 0.1% of the wastewater mass. Under the enhancement of micro - nano bubbles (average diameter 15 μm), the mixture reacts for 20 min and then enters the sedimentation tank for separation.

[0075] The coagulated and sedimented effluent enters the electro - catalytic - ozone coupling oxidation system. This system uses a titanium - based boron - doped diamond electrode as the anode and stainless steel as the cathode, with an electrode spacing of 2 cm and a current density of 20 mA / cm 2 . At the same time, ozone is introduced with a dosage of 45 mg / L, and sodium persulfate is added as an activator with a concentration of 10 mmol / L. During the reaction process, the pH is controlled at 6.0, the temperature is 30 °C, and the reaction time is 30 min. This process can effectively degrade azo dyes and antibacterial finishing agents in the printed wastewater, with a COD removal rate reaching more than 50% and a chromaticity removal rate reaching more than 70%.

[0076] After adjusting the pH value of the electrocatalytic-ozone oxidation effluent to 7.0, it enters the bio-enzyme enhanced degradation system. First, it enters the upflow anaerobic granular sludge reactor, where laccase (80 U / L) produced by Trametes versicolor isolated, screened and cultured from dye wastewater treatment sludge and peroxidase (30 U / L) produced by Phanerochaete chrysosporium are added. The HRT of the anaerobic granular sludge reactor is 8 h, and the effluent enters the membrane bioreactor, where redox enzyme (50 U / L) produced by Bacillus subtilis and hydrolase (80 U / L) produced by Aspergillus niger are added. The HRT of the membrane bioreactor is 6 h, and the MLSS is 5000 mg / L. This system has a high degradation ability for special pollutants such as brominated flame retardants in wastewater, and the COD removal rate is further increased by 40%, and the color removal rate is increased by 25%.

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

[0078] Using 18 wt% polyethersulfone as the substrate, N,N-dimethylacetamide as the solvent, and adding 5 wt% polyvinylpyrrolidone as the pore-forming agent to prepare the casting solution;

[0079] The casting solution is evenly coated on the non-woven support, with the thickness controlled at 200 μm. After pre-evaporating for 45 s in an environment at 60 °C, it is immersed in a coagulation bath of water / ethanol (7:3) at a temperature of 3 °C for 3 min for phase inversion to form the base membrane;

[0080] The base membrane is 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 washed thoroughly to form the enzyme-immobilized support layer;

[0081] The base membrane after impregnation treatment with a mixed solution (phosphate buffer solution, pH = 6.0) of laccase (400 U / g membrane), peroxidase (150 U / g membrane) and redox enzyme (200 U / g membrane) is kept at 4 °C for 12 h for 6 h to complete enzyme immobilization;

[0082] An Ag / ZnO / g-C 3 N 4 composite photocatalytic layer is constructed on the surface of the enzyme-immobilized layer by in-situ growth method: First, the membrane surface is impregnated with 0.05 mol / L Zn(CH 3 COO) 2 solution for 2 h, dried and heat-treated at 350 °C for 1 h to form the ZnO seed layer; Then the membrane is immersed in a hydrothermal reaction solution containing 0.025 mol / L Zn(NO 3 ) 2 and 0.025 mol / L hexamethylenetetramine, and ZnO nanorod arrays are grown by reacting at 90 °C for 5 h; Then in 0.01 mol / L AgNO3 Immerse it in the solution for 30 min, and reduce it under ultraviolet light irradiation for 2 h to form Ag nanoparticles; finally, prepare g-C 3 N 4 layer by impregnating with melamine solution, drying, and thermal polymerization at 550 °C. The mass ratio of Ag / ZnO / g-C 3 N 4 is 1:10:5;

[0083] Immerse the membrane 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%), introduce nitrogen protection, and react at 60 °C for 4 h to form a PNIPAM / PDA self-healing hydrogel layer with a thickness of about 20 μm;

[0084] Wash the prepared composite membrane in deionized water for 24 h and store it in a phosphate buffer solution (pH = 7.0) at 4 °C for later use.

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

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

[0087] After the membrane system operates for 300 hours, or when the membrane flux drops to 65% of the initial value, start the membrane regeneration treatment procedure:

[0088] First, backwash with pure water at 22 °C for 8 min to activate the swelling of the hydrogel layer and release the adsorbed pollutants;

[0089] Then, introduce a citric acid solution (0.5 wt%) with pH = 5.0, and at the same time turn on the photocatalytic system for photocatalytic oxidation treatment for 25 min;

[0090] Finally, introduce a solution containing ABTS (1.0 mmol / L), H 2 O 2(3.0 mmol / L) and MnSO 4 A solution of (0.3 mmol / L) with pH = 5.0 promotes the recovery of enzyme activity and the degradation of residual pollutants, and the time is 30 min;

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

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

[0093] It can be seen from the above embodiments that the textile printing and dyeing wastewater treatment method provided by the present invention based on the multifunctional enzyme - immobilized photocatalytic self - healing membrane shows excellent treatment effects and stability when treating textile printing and dyeing wastewater, especially wastewater containing new refractory pollutants, effectively solving problems such as serious membrane fouling, short membrane life, and low removal efficiency of new pollutants.

[0094] Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope 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 the grid 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, mixed and reacted, and then precipitated and separated; The coagulation precipitated water 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 the electrocatalytic-ozonation oxidation enters into 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 immobilization photocatalytic self-repairing membrane system, which includes a base membrane made of modified polyethersulfone, and a biological 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 immobilization 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 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.

2. The method for treating wastewater after textile printing and dyeing according to claim 1, characterized in that: 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, characterized in that: In the electrocatalytic-ozone coupled oxidation system, the electrode uses a titanium-based boron-doped diamond electrode as the anode and stainless steel as the cathode, 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 at 25-35°C.

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

5. The method for treating wastewater after textile printing and dyeing according to claim 1, characterized in that: The multifunctional enzyme immobilized photocatalytic self-repairing film is prepared by the following steps: Using polyethersulfone as substrate, a porous base membrane was prepared 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 thermosensitive poly (N-isopropylacrylamide) / polydopamine copolymer was constructed on the membrane surface.

6. A method for treating wastewater after textile printing and dyeing according to claim 5, characterized in that: 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.

7. The method for treating wastewater after textile printing and dyeing according to claim 5, characterized in that: The thickness of the self-repairing hydrogel layer is 10-30 μm, and the mass ratio of the temperature-sensitive poly (N-isopropylacrylamide) / polydopamine is 4:

1.

8. The method for treating wastewater after textile printing and dyeing according to claim 1, characterized in that: 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 weakly acidic solution with a pH value of 4.5-5.5 is introduced, and the photocatalytic system is turned on to perform photocatalytic oxidation degradation for 15-30 minutes; A solution containing enzyme reaction auxiliary factors is introduced to promote the recovery of enzyme activity and the degradation of residues on the membrane surface. The enzyme reaction auxiliary factors include ABTS, H2O2 and MnSO4. The treatment time is 20-40 minutes.

9. The method for treating wastewater after textile printing and dyeing according to claim 8, characterized in that: 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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