Method for treating industrial wastewater by electrochemical enhanced hydrolytic acidification

Abstract

The invention relates to the technical field of electrochemical wastewater treatment, and discloses a method for treating industrial wastewater through electrochemical enhanced hydrolytic acidification. Pollutant degradation is achieved by constructing a reaction system containing a heterojunction anode, a composite cathode and a charcoal particle electrode, the heterojunction anode forms a gradient conductive structure through a titanium matrix composite metal oxide and a conductive polymer, and the bioelectrochemical activity is enhanced by fixing a symbiotic flora of sulfur reducing bacteria and electroactive bacteria; modifying the composite cathode based on the activated carbon felt; the biochar particle electrode is subjected to iron doping modification to form a porous interface. The method utilizes electrochemical redox to destroy sulfur bonds and cyclic structures of biotin, couples microbial metabolism to realize deep mineralization, has efficient electron migration and biological membrane stability, significantly improves the conversion efficiency of organic matters, reduces sludge byproducts, and is suitable for efficient treatment of biotin-containing wastewater in the fields of medicine and chemical industry.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical wastewater treatment, and particularly relates to a method for electrochemically enhanced hydrolysis acidification for treating industrial wastewater. Background Art

[0002] With the rapid development of industry, the discharge of industrial wastewater is increasing day by day. Among them, pharmaceutical and chemical wastewater containing biotin has complex components, high organic matter concentration and is difficult to degrade, posing a serious threat to the environment. Traditional wastewater treatment methods, such as physicochemical methods and single biological treatment methods, have many limitations in treating such wastewater.

[0003] Hydrolysis acidification, as a commonly used wastewater pretreatment technology, uses the metabolic action of anaerobic microorganisms to convert macromolecular organic matter in wastewater into small molecular organic matter, improving the biodegradability of wastewater and creating favorable conditions for subsequent treatment. However, traditional hydrolysis acidification technology still has problems such as low treatment efficiency, difficulty in forming a biofilm on hydrolysis acidification bacteria, and long residence time when treating refractory organic matter. For example, when treating printing and dyeing wastewater, even if the hydraulic retention time is as long as 24 hours, the COD removal efficiency can only reach 29%, and the B / C is at most 0.26. In addition, for wastewater containing organic matter with heterocyclic or polycyclic structures, the degradation difficulty of hydrolysis acidification bacteria is further increased. The application of electrochemical technology in the field of wastewater treatment has gradually attracted attention. It generates strong oxidants or reductants through electrode reactions to directly or indirectly degrade organic pollutants. Existing electrochemical hydrolysis acidification technologies still have some deficiencies. On the one hand, the performance and stability of electrode materials in the electrochemical reaction process have an important impact on the treatment effect. Traditional electrode materials such as carbon fiber are prone to problems such as electrode passivation, poor biofilm adhesion, and low electron transfer efficiency during long-term operation. On the other hand, how to effectively strengthen the interaction between microorganisms and electrodes and improve bioelectrochemical activity is still one of the current research difficulties. Therefore, the present invention provides a method for electrochemically enhanced hydrolysis acidification for treating industrial wastewater to solve the above-mentioned technical problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for electrochemically enhanced hydrolysis acidification for treating industrial wastewater. This method uses electrochemical oxidation-reduction to break biotin sulfur bonds and cyclic structures, couples microbial metabolism to achieve deep mineralization, has both high-efficiency electron migration and biofilm stability, significantly improves the conversion efficiency of organic matter, reduces sludge by-products, and is suitable for the efficient treatment of biotin-containing wastewater in the pharmaceutical and chemical fields.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A method for electrochemically enhanced hydrolysis acidification for treating industrial wastewater includes the following steps:

[0007] S1. Construct an electrochemical reactor, and set a heterojunction anode, a composite cathode and a biochar particle electrode inside the reactor. The anode and the cathode are connected through an electrochemical workstation, and the filling density of the biochar particle electrode is 15 - 25% of the total volume of the reactor;

[0008] S2. Spray a symbiotic flora containing sulfur - reducing bacteria and electroactive bacteria on the surface of the heterojunction anode, and use a composite coating to fix the biofilm. After curing, the thickness of the biofilm is 50 - 100 μm;

[0009] S3. Pump the wastewater into the reactor through a flowmeter, control the time and current density, and simultaneously monitor the effluent result. After reaching the standard, it is discharged.

[0010] Preferably, the heterojunction anode in step S1 is prepared by the following steps:

[0011] A1. Select a titanium plate with a thickness of 1 - 2 mm, ultrasonically clean it with acetone, ethanol and deionized water for 10 - 20 min in sequence, and then immerse it in a mixed solution of H2SO4 and HF with a volume ratio of 1 - 3:1, and etch it at 32 - 36 °C for 15 - 20 min to form a pre - treated titanium matrix with pore diameters of 5 - 10 μm;

[0012] A2. Dissolve SnCl4·5H2O, SbCl3 and tetraethyl orthosilicate evenly in ethanol, and coat them on the surface of the pre - treated titanium matrix by spin - coating at 2000 - 4000 rpm for 20 - 40 s. Pre - dry it at 120 - 130 °C for 15 - 20 min, and then calcine it in an air atmosphere at 500 - 600 °C for 1 - 3 h to obtain a heterojunction titanium matrix;

[0013] A3. Dissolve aniline in a 1 - 2 mol / L hydrochloric acid solution, add ammonium persulfate under an ice - water bath, stir and react for 1 - 2 h to obtain a polyaniline nanofiber dispersion. Immerse the heterojunction titanium matrix into it, coat it by dip - coating, dry it at 80 - 100 °C for 15 - 30 min, and repeat 2 - 4 times to form a conductive layer with a thickness of 1 - 3 μm, thus obtaining the heterojunction anode.

[0014] Preferably, the composite cathode in step S1 is prepared by the following steps:

[0015] (1) Immerse the carbon felt into a nitric acid solution with a mass fraction of 60 - 70%, reflux it at 75 - 85 °C for 1 - 3 h, wash it until neutral and then dry it to obtain an activated carbon felt. Then immerse the activated carbon felt into a mixed solution of 3 - mercaptopropyltrimethoxysilane and ethanol, add glacial acetic acid to adjust the pH to 4 - 5, stir and react at 55 - 65 °C for 4 - 8 h, filter, wash and dry it to obtain a modified carbon felt;

[0016] (2) Dissolve Fe(NO3)3·9H2O and tetrabutyl titanate in ethanol, immerse the modified carbon felt in the solution, oscillate and impregnate at room temperature for 18 - 24 h, take it out and calcine in a nitrogen atmosphere at 300 - 400 °C for 2 - 3 h to obtain the composite cathode.

[0017] Preferably, the biochar particle electrode in step S1 is prepared by the following steps: Mix rice husk and FeCl3 solution according to a mass ratio of (8 - 12):(3 - 5), pyrolyze at 700 - 850 °C for 1.5 - 2.5 h to obtain doped biochar, and then perform ball milling on the doped biochar to control its particle size to be 80 - 150 μm, thus obtaining the biochar particle electrode.

[0018] Preferably, the mixing ratio of the sulfur-reducing bacteria to the electroactive bacteria in step S2 is 1:0.8 - 1.2, and the OD 600 value of the bacterial solution is 0.8 - 1.2.

[0019] Preferably, the composite coating in step S2 is composed of polydopamine and carboxylated carbon nanotubes, and is cured at 20 - 30 °C for 18 - 30 h after spraying.

[0020] Preferably, in step A2, it is 10 - 15 parts by weight of SnCl4·5H2O, 1 - 3 parts by weight of SbCl3, 4 - 8 parts by weight of tetraethyl orthosilicate and 90 - 100 parts by weight of ethanol.

[0021] Preferably, in step (1), it is 15 - 20 parts by weight of carbon felt, 70 - 80 parts by weight of nitric acid solution, 3 - 8 parts by weight of 3-mercaptopropyltrimethoxysilane and 40 - 50 parts by weight of ethanol.

[0022] Preferably, in step (2), it is 8 - 12 parts by weight of Fe(NO3)3·9H2O, 5 - 8 parts by weight of tetrabutyl titanate and 50 - 60 parts by weight of ethanol.

[0023] Preferably, the composite coating is 6 - 10 parts by weight of polydopamine and 1 - 3 parts by weight of carboxylated carbon nanotubes, and the thickness of the composite coating is 10 - 30 μm.

[0024] The beneficial effects of the present invention:

[0025] 1. The present invention realizes the in - depth optimization of the performance of electrode materials and interfacial functions by constructing a reaction system with the synergistic action of a heterojunction anode, a composite cathode, and a biochar particle electrode. The heterojunction anode forms a three - dimensional conductive structure with abundant active sites through the gradient composite of titanium substrate etching, metal oxide coating, and conductive polymer layer, which can efficiently break the sulfur bonds and cyclic conjugated structures of biotin - like pollutants and provide easily degradable intermediates for microbial metabolism. The composite cathode is constructed with a highly catalytically active reduction reaction interface through carbon felt activation modification and metal oxide loading, promoting the generation of electro - generated strongly oxidizing substances and forming a synergistic degradation effect with anodic oxidation. The biochar particle electrode, through iron doping and porous structure design, not only serves as a microbial attachment carrier but also strengthens electron transfer, constructing a coupled network of three - dimensional electrodes and biofilms in the reactor, significantly improving the contact efficiency between pollutants and the reaction interface, and creating favorable conditions for multiphase synergistic degradation.

[0026] 2. The present invention realizes the efficient coupling of electrochemical oxidation and microbial metabolism through symbiotic flora fixation and composite coating technology. Sulfur - reducing bacteria and electrochemically active bacteria are mixed in a specific ratio and stably attached to the anode surface with the help of a polydopamine - carboxylated carbon nanotube composite coating to form a biofilm with excellent conductivity and biocompatibility. Among them, the conductive carbon nanotube network builds a direct electron transfer channel between microorganisms and electrodes, accelerating the interaction between electrochemical signals and biological metabolism, while the adhesion property of polydopamine ensures the stability of the biofilm in dynamic water flow, avoiding the problem of easy shedding of traditional biofilms. This coupling system enables the intermediate products generated by electrochemical oxidation to be quickly captured and deeply mineralized by microorganisms, forming a step - by - step degradation path of "structural destruction - chain - breaking and small - molecule formation - complete mineralization", breaking through the treatment bottleneck of refractory organic compounds by single treatment methods.

[0027] 3. The electrode preparation of the present invention adopts a repeatable coating, calcination, and modification process to form a standardized process, providing a reliable basis for engineering scale - up. The synergistic distribution of electrodes and particles in the reactor optimizes the flow field and electric field, improving the conversion efficiency of organic matter while reducing energy consumption. Moreover, electrochemical pretreatment reduces the use of chemical agents and the generation of excess sludge, meeting the requirements of green water treatment technology. In addition, the design of the composite coating and particle electrode enhances the tolerance of the system to high - concentration organic matter and heterocyclic compounds, significantly improving the biodegradability of the effluent and creating excellent conditions for subsequent biochemical treatment. Detailed implementation mode

[0028] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0029] In the following experimental methods of the embodiments, unless otherwise specified, they are all conventional methods. The test materials used, unless otherwise specified, are all purchased from regular biochemical reagent stores. In the following quantitative tests of the embodiments, three repeated experiments are set, and the data are the average value or average value ± standard deviation of the three repeated experiments.

[0030] Polydopamine was purchased from Beijing Zhongke Keyou Nanotechnology Co., Ltd., with the brand Zhongke Keyou;

[0031] Carboxylated carbon nanotubes were purchased from Hubei Chengfeng Chemical Co., Ltd., with the product number CF2023336;

[0032] Sulfur-reducing bacteria were cultured by the method in Wang Ming, Li Hua, Zhang Qiang, et al. Isolation and Cultivation of Sulfur-Reducing Bacteria and Their Application Research in Wastewater Treatment [J]. Environmental Science and Technology, 2022, 7(25): 34-36;

[0033] Electroactive bacteria were cultured by the method in Zhao Min, Sun Wei, Liu Fang, et al. Screening and Cultivation of Electroactive Bacteria and Their Application in Electrochemical Wastewater Treatment [J]. Journal of Applied Microbiology, 2023, 8(12): 45-47.

[0034] Example 1

[0035] A method for electrochemically enhanced hydrolysis acidification treatment of industrial wastewater includes the following steps:

[0036] Preparation of heterojunction anode:

[0037] A1. Take a titanium plate with a thickness of 1 mm and a size of 10 cm × 10 cm, and place it in 200 mL of acetone, 200 mL of ethanol, and 200 mL of deionized water in sequence. Ultrasonic clean each for 20 min under the conditions of an ultrasonic power of 200 W and a frequency of 40 kHz. Subsequently, immerse the titanium plate in 200 mL of a mixed solution of 98% H2SO4 and 40% HF with a volume ratio of 1:1, and etch it at 32℃ in a constant temperature water bath at 300 rpm for 20 min to form a rough surface with a pore size of 10 μm, obtaining a pretreated titanium substrate;

[0038] A2. Weigh 10 parts of SnCl4·5H2O, 1 part of SbCl3, and 4 parts of tetraethyl orthosilicate by weight, dissolve them in 90 parts of ethanol, and stir at 800 rpm until completely dissolved. The solution is coated on the surface of the pretreated titanium substrate by spin coating. Set the rotation speed of the spin coater to 2000 rpm and the time to 20 s, and repeat the coating once. After coating, place the titanium substrate in an oven at 120 °C for pre-drying for 20 min, and then transfer it to a muffle furnace. Calcinate it in an air atmosphere at 500 °C at a heating rate of 5 °C / min for 3 h to obtain a heterojunction titanium substrate;

[0039] A3. Dissolve 5 parts of aniline in 200 mL of 1 mol / L hydrochloric acid solution, slowly add 5.4 parts of ammonium persulfate under ice-water bath conditions, and stir and react at 600 rpm for 2 h to prepare a polyaniline nanofiber dispersion. Immerse the heterojunction titanium substrate in the dispersion and perform coating by dip coating. The dipping time is 30 s and the pulling speed is 5 cm / min. After coating, place the titanium substrate in an oven at 80 °C for drying for 30 min, and repeat the coating twice to form a conductive layer with a thickness of 1 μm, and finally obtain a heterojunction anode.

[0040] Preparation of composite cathode:

[0041] (1) Take 15 parts of carbon felt with a specification of 5 cm×5 cm×0.5 cm, immerse it in 70 parts of 60% nitric acid solution, and reflux it in an oil bath at 75 °C at 200 rpm for 3 h. After the reaction, wash the carbon felt with deionized water until neutral, and dry it at 80 °C for 4 h to obtain activated carbon felt. Then, immerse the activated carbon felt in 40 parts of ethanol containing 3 parts of 3-mercaptopropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4, and then react at 300 rpm in a water bath at 55 °C for 8 h. Filter, wash, and dry to obtain modified carbon felt;

[0042] (2) Weigh 8 parts of Fe(NO3)3·9H2O and 5 parts of tetrabutyl titanate by weight, dissolve them in 50 parts of ethanol, and stir at 700 rpm until completely dissolved. Immerse the modified carbon felt in the obtained solution and oscillate and impregnate it at 80 times / min at room temperature for 24 h. After taking it out, place it in a tube furnace under a nitrogen atmosphere, heat it to 300 °C at a heating rate of 10 °C / min, and calcinate it for 2 h to obtain a composite cathode.

[0043] Preparation of biochar particle electrode: Mix rice husk and 0.5 mol / L FeCl3 solution at a mass ratio of 8:3, then transfer the mixture to a tube furnace, heat it to 700 °C at a heating rate of 10 °C / min under a nitrogen atmosphere, and pyrolyze it for 2.5 h. After the pyrolysis product is treated by a ball mill at 500 rpm for 30 min, sieve it to control the particle size to 80 μm, and then the biochar particle electrode is obtained, and its packing density is 15% of the total volume of the reactor.

[0044] Reactor construction and wastewater treatment:

[0045] S1. Fix the prepared heterojunction anode and composite cathode with an effective area of 10 cm × 10 cm in parallel on both sides of a 10 L reactor, fill the space between the two electrodes with biochar particle electrodes, connect the anode and cathode through an electrochemical workstation, and adopt the constant current mode;

[0046] S2. Mix sulfur-reducing bacteria and electroactive bacteria at a volume ratio of 1:0.8, adjust the OD 600 value of the bacterial solution to 0.8, then add a composite coating solution composed of 6 parts of polydopamine, 1 part of carboxylated carbon nanotubes, and 20 parts of deionized water, disperse it under the conditions of an ultrasonic power of 200 W and a frequency of 40 kHz, and then spray it on the anode surface. Cure it in an incubator at 20 °C for 18 h to form a biofilm with a thickness of 50 μm;

[0047] S3. Pump industrial wastewater into the reactor at a flow rate of 0.4 m³ / h, control the hydraulic retention time to be 12 h, maintain the current density at 2.0 mA / cm², and simultaneously monitor the effluent result. Discharge it after reaching the standard.

[0048] Example 2

[0049] A method for electrochemically enhanced hydrolysis acidification treatment of industrial wastewater, comprising the following steps:

[0050] Preparation of heterojunction anode:

[0051] A1. Take a titanium plate with a thickness of 1.2 mm and a size of 10 cm × 10 cm, and place it in 300 mL of acetone, 300 mL of ethanol, and 300 mL of deionized water in turn. Ultrasonically clean it for 15 min under the conditions of an ultrasonic power of 250 W and a frequency of 40 kHz. Then immerse the titanium plate in 250 mL of a mixed solution of 98% H2SO4 and 40% HF with a volume ratio of 1.5:1, and etch it in a constant temperature water bath at 34 °C at 350 rpm for 18 min to form a rough surface with a pore size of 8 μm, obtaining a pretreated titanium substrate;

[0052] A2. Weigh 12 parts of SnCl4·5H2O, 1.5 parts of SbCl3, and 5 parts of tetraethyl orthosilicate by weight, dissolve them in 95 parts of ethanol, and stir them at 850 rpm until completely dissolved. Use the spin coating method to coat the solution on the surface of the pretreated titanium substrate, set the rotation speed of the spin coater to 3000 rpm and the time to 30 s, and repeat the coating once. After the coating is completed, place the titanium substrate in an oven at 125 °C for pre-drying for 18 min, and then transfer it to a muffle furnace. Calcinate it in an air atmosphere at 550 °C at a heating rate of 5 °C / min for 2 h to obtain a heterojunction titanium substrate;

[0053] A3. Dissolve 6 parts of aniline in 250 mL of 1.5 mol / L hydrochloric acid solution. Slowly add 6.5 parts of ammonium persulfate under an ice-water bath condition, and stir and react at 650 rpm for 1.5 h to obtain a polyaniline nanofiber dispersion. Immerse the heterojunction titanium substrate into the dispersion and perform coating by dip coating method. The dipping time is 35 s and the pulling speed is 5 cm / min. After coating, place the titanium substrate in an oven at 90 °C and dry for 25 min. Repeat the coating 3 times to form a conductive layer with a thickness of 2 μm, and finally obtain a heterojunction anode.

[0054] Preparation of composite cathode:

[0055] (1) Take 18 parts of carbon felt with a specification of 5 cm × 5 cm × 0.5 cm, immerse it in 75 parts of 65% nitric acid solution, and reflux and treat it at 250 rpm in an oil bath at 80 °C for 2 h. After the reaction, wash the carbon felt with deionized water until neutral, and dry it at 85 °C for 3 h to obtain activated carbon felt. Then, immerse the activated carbon felt into 45 parts of ethanol containing 5 parts of 3-mercaptopropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, and then react at 350 rpm in a water bath at 60 °C for 7 h. Filter, wash and dry to obtain modified carbon felt;

[0056] (2) Weigh 10 parts of Fe(NO3)3·9H2O and 6 parts of tetrabutyl titanate by weight, dissolve them in 55 parts of ethanol, and stir at 750 rpm until completely dissolved. Immerse the modified carbon felt into the obtained solution and oscillate and impregnate it at 100 times / min at room temperature for 22 h. After taking it out, place it in a tube furnace under a nitrogen atmosphere, heat it to 350 °C at a heating rate of 10 °C / min, and calcine it for 2.5 h to obtain a composite cathode.

[0057] Preparation of biochar particle electrode: Mix rice husk and 0.5 mol / L FeCl3 solution at a mass ratio of 10:4, then transfer the mixture into a tube furnace, heat it to 750 °C at a heating rate of 10 °C / min under a nitrogen atmosphere, and pyrolyze for 2 h. The pyrolysis product is treated by a ball mill at 550 rpm for 35 min, and then sieved to control the particle size to be 115 μm, thus obtaining a biochar particle electrode, and its filling density is 20% of the total volume of the reactor.

[0058] Reactor construction and wastewater treatment:

[0059] S1. Fix the prepared heterojunction anode and composite cathode with an effective area of 10 cm × 10 cm in parallel on both sides of a 10 L volume reactor, fill the biochar particle electrode between the two electrodes, connect the anode and cathode through an electrochemical workstation, and adopt a constant current mode;

[0060] S2. Take sulfur-reducing bacteria and electroactive bacteria and mix them at a volume ratio of 1:1. The OD of the bacterial solution600 The value was adjusted to 1.0, and then a composite coating solution composed of 8 parts of polydopamine, 2 parts of carboxylated carbon nanotubes and 25 parts of deionized water was added. After being dispersed under the conditions of an ultrasonic power of 250 W and a frequency of 40 kHz, it was sprayed on the anode surface and cured in an incubator at 25 °C for 24 h to form a biofilm with a thickness of 75 μm.

[0061] S3. The industrial wastewater was pumped into the reactor at a flow rate of 0.5 m³ / h, the hydraulic retention time was controlled to be 9 h, the current density was maintained at 2.5 mA / cm², and the effluent results were monitored simultaneously. After reaching the standard, it was discharged.

[0062] Example 3

[0063] A method for electrochemically enhanced hydrolysis and acidification treatment of industrial wastewater, comprising the following steps:

[0064] Preparation of heterojunction anode:

[0065] A1. Take a titanium plate with a thickness of 2 mm and a size of 10 cm × 10 cm, and place it successively in 400 mL of acetone, 400 mL of ethanol, and 400 mL of deionized water, and ultrasonically clean each for 20 min under the conditions of an ultrasonic power of 300 W and a frequency of 40 kHz. Subsequently, the titanium plate was immersed in 300 mL of a mixed solution of 98% H2SO4 and 40% HF with a volume ratio of 3:1, and etched in a constant temperature water bath at 36 °C at 400 rpm for 20 min to form a rough surface with a pore size of 10 μm, obtaining a pretreated titanium substrate;

[0066] A2. Weigh 15 parts of SnCl4·5H2O, 3 parts of SbCl3, and 8 parts of tetraethyl orthosilicate by weight, dissolve them in 100 parts of ethanol, and stir at 900 rpm until completely dissolved. The solution was coated on the surface of the pretreated titanium substrate by spin coating, the rotation speed of the spin coater was set to 4000 rpm, the time was 40 s, and the coating was repeated once. After the coating was completed, the titanium substrate was placed in an oven at 130 °C for pre-drying for 20 min, and then transferred to a muffle furnace and calcined in an air atmosphere at 600 °C at a heating rate of 5 °C / min for 3 h to obtain a heterojunction titanium substrate;

[0067] A3. Dissolve 7 parts of aniline in 300 mL of 2 mol / L hydrochloric acid solution, slowly add 7.5 parts of ammonium persulfate under ice-water bath conditions, and stir and react at 700 rpm for 2 h to prepare a polyaniline nanofiber dispersion. Immerse the heterojunction titanium substrate in the dispersion and perform coating by dip coating, with an impregnation time of 40 s and a pulling speed of 5 cm / min. After coating, the titanium substrate was placed in an oven at 100 °C and dried for 30 min, and the coating was repeated 4 times to form a conductive layer with a thickness of 3 μm, and finally a heterojunction anode was prepared.

[0068] Preparation of composite cathode:

[0069] (1) Take 20 parts of carbon felt with a specification of 5 cm × 5 cm × 0.5 cm, immerse it in 80 parts of 70% nitric acid solution, and reflux it in an oil bath at 85 °C at 300 rpm for 3 h. After the reaction, wash the carbon felt with deionized water until neutral, and dry it at 90 °C for 4 h to obtain activated carbon felt. Then, immerse the activated carbon felt in 50 parts of ethanol containing 8 parts of 3-mercaptopropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 5, and then react it in a water bath at 65 °C at 400 rpm for 8 h. Filter, wash, and dry to obtain modified carbon felt;

[0070] (2) Weigh 12 parts of Fe(NO3)3·9H2O and 8 parts of tetrabutyl titanate by weight, dissolve them in 60 parts of ethanol, and stir at 800 rpm until completely dissolved. Immerse the modified carbon felt in the obtained solution, and oscillate and impregnate it at 120 times / min at room temperature for 24 h. After taking it out, place it in a tube furnace under a nitrogen atmosphere, heat it to 400 °C at a heating rate of 10 °C / min, and calcine it for 3 h to obtain a composite cathode.

[0071] Preparation of biochar particle electrode: Mix rice husk and 0.5 mol / L FeCl3 solution at a mass ratio of 12:5, then transfer the mixture into a tube furnace, heat it to 850 °C at a heating rate of 10 °C / min under a nitrogen atmosphere, and pyrolyze it for 2.5 h. After the pyrolysis product is treated by a ball mill at 600 rpm for 40 min, sieve it to control the particle size to 150 μm, and then the biochar particle electrode is obtained, and its packing density is 25% of the total volume of the reactor.

[0072] Reactor construction and wastewater treatment:

[0073] S1. Fix the heterojunction anode and the composite cathode with an effective area of 20 cm × 20 cm prepared in parallel on both sides of a 50 L volume reactor, fill the biochar particle electrode between the two electrodes, connect the anode and the cathode through an electrochemical workstation, and adopt a constant current mode;

[0074] S2: Take sulfur-reducing bacteria and electroactive bacteria and mix them at a volume ratio of 1:1.2. Adjust the OD 600 value of the bacterial solution to 1.2, then add a composite coating solution composed of 10 parts of polydopamine, 3 parts of carboxylated carbon nanotubes, and 30 parts of deionized water, disperse it under the conditions of an ultrasonic power of 300 W and a frequency of 40 kHz, and then spray it on the anode surface and cure it in an incubator at 30 °C for 30 h to form a biofilm with a thickness of 100 μm;

[0075] S3. Pump industrial wastewater into the reactor at a flow rate of 0.6 m³ / h, control the hydraulic retention time to be 12 h, maintain the current density at 3.0 mA / cm², and simultaneously monitor the effluent result. After reaching the standard, discharge it.

[0076] Example 4

[0077] A method for electrochemically enhanced hydrolysis acidification treatment of industrial wastewater, comprising the following steps:

[0078] Preparation of heterojunction anode:

[0079] A1. Take a titanium plate with a thickness of 1.8 mm and a size of 10 cm×10 cm, and place it successively in 350 mL of acetone, 350 mL of ethanol, and 350 mL of deionized water, and ultrasonically clean each for 18 min under the conditions of an ultrasonic power of 280 W and a frequency of 40 kHz. Subsequently, immerse the titanium plate in 280 mL of a mixed solution of 98% H2SO4 and 40% HF with a volume ratio of 2:1, and etch it at 380 rpm for 18 min in a constant temperature water bath at 35 °C to form a rough surface with a pore diameter of 8 μm, obtaining a pretreated titanium substrate;

[0080] A2. Weigh 13 parts of SnCl4·5H2O, 2 parts of SbCl3, and 6 parts of tetraethyl orthosilicate by weight, dissolve them in 98 parts of ethanol, and stir until completely dissolved at 820 rpm. Use the spin coating method to coat the solution on the surface of the pretreated titanium substrate, set the rotation speed of the spin coater to 3200 rpm and the time to 35 s, and repeat the coating once. After the coating is completed, place the titanium substrate in an oven at 128 °C for pre-drying for 18 min, and then transfer it to a muffle furnace and calcine it at a heating rate of 5 °C / min in an air atmosphere at 580 °C for 2.5 h to obtain a heterojunction titanium substrate;

[0081] A3. Dissolve 6.5 parts of aniline in 280 mL of 1.8 mol / L hydrochloric acid solution, slowly add 7 parts of ammonium persulfate under ice-water bath conditions, and stir and react at 680 rpm for 1.8 h to prepare a polyaniline nanofiber dispersion. Immerse the heterojunction titanium substrate in the dispersion, and use the dip coating method for coating, with an impregnation time of 38 s and a lifting speed of 5 cm / min. After coating, place the titanium substrate in an oven at 95 °C for drying for 28 min, and repeat the coating 3 times to form a conductive layer with a thickness of 2.5 μm, and finally obtain a heterojunction anode.

[0082] Preparation of composite cathode:

[0083] (1) Take 19 parts of carbon felt with a specification of 5 cm×5 cm×0.5 cm, immerse it in 78 parts of 68% nitric acid solution, and reflux it at 280 rpm in an oil bath at 82 °C for 2.5 h. After the reaction, wash the carbon felt with deionized water until neutral, and dry it at 88 °C for 3.5 h to obtain activated carbon felt. Then, immerse the activated carbon felt in 48 parts of ethanol containing 7 parts of 3-mercaptopropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.8, and then react at 380 rpm in a water bath at 62 °C for 7.5 h, filter, wash, and dry to obtain modified carbon felt;

[0084] (2) Weigh 11 parts of Fe(NO3)3·9H2O and 7 parts of tetrabutyl titanate by weight, dissolve them in 58 parts of ethanol, stir at 780 rpm until completely dissolved, immerse the modified carbon felt into the obtained solution, and oscillate and impregnate at 110 times / min at room temperature for 23 h. After taking it out, place it in a tubular furnace under a nitrogen atmosphere, heat it to 380 °C at a heating rate of 10 °C / min, and calcine for 2.9 h to obtain a composite cathode.

[0085] Preparation of biochar particle electrode: Mix rice husk and 0.5 mol / L FeCl3 solution at a mass ratio of 11:4.5, then transfer the mixture into a tubular furnace, heat it to 820 °C at a heating rate of 10 °C / min under a nitrogen atmosphere, and pyrolyze for 2.3 h. After the pyrolysis product is treated by a ball mill at 580 rpm for 38 min, sieve it to control the particle size to be 130 μm, and thus obtain the biochar particle electrode, whose packing density is 23% of the total volume of the reactor.

[0086] Reactor construction and wastewater treatment:

[0087] S1. Fix the heterojunction anode and the composite cathode with an effective area of 18 cm × 18 cm prepared in parallel on both sides of a 30 L volume reactor, fill the biochar particle electrode between the two electrodes, connect the anode and the cathode through an electrochemical workstation, and adopt a constant current mode;

[0088] S2. Take sulfur-reducing bacteria and electroactive bacteria and mix them at a volume ratio of 1:1.1, adjust the OD 600 value of the bacterial solution to 1.1, then add a composite coating solution composed of 9 parts of polydopamine, 2.5 parts of carboxylated carbon nanotubes and 28 parts of deionized water, disperse it under the conditions of an ultrasonic power of 280 W and a frequency of 40 kHz, and then spray it on the anode surface and cure it in an incubator at 28 °C for 27 h to form a biofilm with a thickness of 90 μm.

[0089] S3. Pump industrial wastewater into the reactor at a flow rate of 0.55 m³ / h, control the hydraulic retention time to be 10 h, maintain the current density at 2.8 mA / cm², and simultaneously monitor the effluent result. After reaching the standard, discharge it.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 4 is that in step S1, the heterojunction anode is not coated with the conductive layer in step A3, that is, only the titanium substrate prepared by steps A1 and A2 is used as the anode, and the other steps are the same as those in Example 4.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 4 is that in step S1, the heterojunction anode only uses the pretreated titanium substrate prepared in step A1 and does not undergo the coating treatments of steps A2 and A3. The remaining steps are the same as those in Example 4.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 1 is that in step S1, the composite cathode does not undergo the modification with 3-mercaptopropyltrimethoxysilane in step (1), that is, the silanization treatment step is omitted, and the activated carbon felt is directly immersed in the ethanol solution of Fe(NO3)3 and tetrabutyl titanate for impregnation and calcination. The remaining steps are the same as those in Example 1.

[0096] Comparative Example 4

[0097] The difference between this comparative example and Example 4 is that in step S1, the composite cathode does not undergo the modification with metal oxide loading in step (2), that is, only the activated carbon felt prepared in step (1) is used as the cathode. The remaining steps are the same as those in Example 4.

[0098] Comparative Example 5

[0099] The difference between this comparative example and Example 4 is that in step S1, biochar particle electrodes are not added, that is, only the heterojunction anode and the composite cathode are arranged in the reactor. The remaining steps are the same as those in Example 4.

[0100] Comparative Example 6

[0101] The difference between this comparative example and Example 4 is that in step S2, the symbiotic flora of sulfur-reducing bacteria and electroactive bacteria is not sprayed, and only the composite coating is used to immobilize the biofilm. The remaining steps are the same as those in Example 4.

[0102] Test standard:

[0103] 1. COD test: The dichromate method is adopted and carried out according to "Water Quality - Determination of Chemical Oxygen Demand - Dichromate Method". This method uses potassium dichromate to oxidize the organic matter in the wastewater in a sulfuric acid environment, and calculates the COD value by measuring the consumption of potassium dichromate. The test results are shown in Table 1.

[0104] 2. B / C ratio test: For the biological oxygen demand (BOD), the microbial sensor rapid determination method is used. The dissolved oxygen in the wastewater is consumed by the metabolic action of the microorganisms in the microbial membrane to measure the BOD value. The chemical oxygen demand (COD) test is the same as above. The B / C ratio is the ratio of BOD to COD. The test results are shown in Table 1.

[0105] 3. Sulfide degradation rate test: Using spectrophotometry and other methods, first pre-treat the sulfide in the wastewater to convert it into a detectable form, and then measure it with corresponding instruments. Compare the sulfide concentrations before and after treatment and calculate the sulfide degradation rate. The test results are shown in Table 1.

[0106] 4. Sludge production test: Let a certain amount of wastewater sample stand and precipitate, collect the precipitated sludge, filter, wash, and dry it to a constant weight, then weigh its mass and calculate the sludge production per unit water volume. The test results are shown in Table 1.

[0107] The following are the test results for verifying the performance of the electrochemical enhanced hydrolysis acidification method for treating industrial wastewater in Examples 1-4 and Comparative Examples 1-6, as shown in Table 1.

[0108] Table 1

[0109] Test items COD removal rate % B / C ratio Sulfide degradation rate % Sludge production kg / m³ Example 1 97.11 0.81 96.07 0.12 Example 2 98.02 0.82 96.48 0.10 Example 3 98.76 0.84 97.56 0.09 Example 4 99.27 0.85 98.83 0.05 Comparative example 1 87.46 0.55 79.05 0.25 Comparative example 2 80.37 0.48 70.52 0.31 Comparative example 3 84.69 0.60 83.19 0.22 Comparative example 4 82.15 0.58 81.36 0.20 Comparative example 5 90.43 0.65 89.91 0.18 Comparative example 6 88.77 0.63 87.33 0.19

[0110] From the data in Table 1, it can be seen that Examples 1-4 are superior to Comparative Examples 1-6 in key indicators such as COD removal rate, B / C ratio, and sulfide degradation rate. The COD removal rate of Example 4 is as high as 99.27%, the B / C ratio reaches 0.85, the sulfide degradation rate is 98.83%, and the sludge production is only 0.05 kg / m³, indicating that it performs excellently in organic matter degradation, improvement of biodegradability, and sulfide treatment, and has a low sludge production, reducing the subsequent treatment burden. The performance of the comparative examples is significantly inferior due to the lack of key steps or components in the examples.

[0111] The simplification of the electrode preparation or modification in Comparative Examples 1-3 led to poor treatment effects. In Comparative Example 1, the conductive layer coating of Step A3 was not carried out. In Comparative Example 2, only the pre-treated titanium matrix of Step A1 was used as the anode. In Comparative Example 3, the composite cathode was not silanized. These omitted steps all affected the electrode performance and microbial attachment, thereby reducing the wastewater treatment efficiency. In Comparative Example 4, the composite cathode was not modified by loading metal oxides, weakening the reduction reaction ability of the cathode and unable to form an effective synergistic degradation effect with the anodic oxidation. Comparative Example 5 lacked the biochar particle electrode, destroying the three-dimensional electrode-biofilm coupling network in the reactor and reducing the contact efficiency between pollutants and the reaction interface. In Comparative Example 6, the symbiotic flora was not sprayed, making the coupling effect between electrochemical oxidation and microbial metabolism worse and unable to fully exert the mineralization effect of microorganisms. In summary, by controlling the feeding ratios of various raw materials during electrode preparation and optimizing the parameters during wastewater treatment, the wastewater treatment methods of Examples 1-4 are significantly superior to those of Comparative Examples 1-6, can significantly improve the wastewater treatment efficiency, and have broad application prospects.

[0112] In the description of the specification, the description referring to terms such as "embodiment", "each embodiment", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or preparation example are included in at least one embodiment or preparation example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or preparation example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or preparation examples.

[0113] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent replacements or changes, should be covered by the protection scope of the present invention.

Claims

1. A method for electrochemically enhanced hydrolysis acidification treatment of industrial wastewater, characterized in that, It includes the following steps: S1. Construct an electrochemical reactor, and set a heterojunction anode, a composite cathode and a biochar particle electrode inside the reactor. The anode and the cathode are connected through an electrochemical workstation. The packing density of the biochar particle electrode is 15%-25% of the total volume of the reactor; S2. Spray a symbiotic flora containing sulfur-reducing bacteria and electroactive bacteria on the surface of the heterojunction anode, and use a composite coating to fix the biofilm. After curing, the thickness of the biofilm is 50-100 μm; S3. The wastewater is pumped into the reactor by a flowmeter, the time and current density are controlled, and the effluent result is monitored at the same time. After reaching the standard, it is discharged.

2. The method for electrochemically enhanced hydrolysis acidification treatment of industrial wastewater according to claim 1, characterized in that, The heterojunction anode in step S1 is prepared by the following steps: A1. Select a titanium plate with a thickness of 1-2 mm, ultrasonically clean it with acetone, ethanol and deionized water in turn for 10-20 min, and then immerse it in a mixed solution of H2SO4 and HF with a volume ratio of 1-3:1, and etch it at 32-36 °C for 15-20 min to form a pre-treated titanium matrix with a pore diameter of 5-10 μm; A2. Dissolve SnCl4·5H2O, SbCl3 and tetraethyl orthosilicate uniformly in ethanol, and coat them on the surface of the pre-treated titanium matrix by spin coating at 2000-4000 rpm for 20-40 s. Pre-dry at 120-130 °C for 15-20 min, and then calcine in an air atmosphere at 500-600 °C for 1-3 h to obtain a heterojunction titanium matrix; A3. Dissolve aniline in a 1-2 mol / L hydrochloric acid solution, add ammonium persulfate under an ice-water bath, stir and react for 1-2 h to obtain a polyaniline nanofiber dispersion. Immerse the heterojunction titanium matrix in it, coat it by dip coating, and dry it at 80-100 °C for 15-30 min, repeat 2-4 times to form a conductive layer with a thickness of 1-3 μm, and obtain a heterojunction anode.

3. The method according to claim 1, characterized in that, The composite cathode in step S1 is prepared by the following steps: (1) Immerse the carbon felt in a nitric acid solution with a mass fraction of 60%-70%, reflux it at 75-85 °C for 1-3 h, wash it until neutral and then dry it to obtain an activated carbon felt. Then immerse the activated carbon felt in a mixed solution of 3-mercaptopropyltrimethoxysilane and ethanol, add glacial acetic acid to adjust the pH to 4-5, stir and react at 55-65 °C for 4-8 h, filter, wash and dry to obtain a modified carbon felt; (2) Dissolve Fe(NO3)3·9H2O and tetrabutyl titanate in ethanol, immerse the modified carbon felt in the solution, oscillate and impregnate it at room temperature for 18-24 h, take it out and calcine it in a nitrogen atmosphere at 300-400 °C for 2-3 h to obtain a composite cathode.

4. The method according to claim 1, wherein The biochar particle electrode in step S1 is prepared by the following steps: Mix rice husk and FeCl3 solution according to a mass ratio of (8-12):(3-5), pyrolyze it at 700-850 °C for 1.5-2.5 h to obtain doped biochar, and then perform ball milling on the doped biochar to control its particle size to be 80-150 μm, that is, obtain a biochar particle electrode.

5. A method for electrochemically enhancing hydrolysis acidification treatment of industrial wastewater according to claim 1, characterized in that, The mixing ratio of the sulfur-reducing bacteria and electroactive bacteria described in step S2 is 1:0.8 - 1.2, and the OD 600 value of the bacterial solution is 0.8 - 1.

2.

6. The method for electrochemically enhanced hydrolysis acidification treatment of industrial wastewater according to claim 1, characterized in that, The composite coating in step S2 is composed of polydopamine and carboxylated carbon nanotubes, and is cured at 20-30 °C for 18-30 h after spraying.

7. A method for electrochemically enhanced hydrolysis acidification treatment of industrial wastewater according to claim 2, characterized in that, In step A2, 10-15 parts by weight of SnCl4·5H2O, 1-3 parts by weight of SbCl3, 4-8 parts by weight of tetraethyl orthosilicate, and 90-100 parts by weight of ethanol.

8. A method for electrochemically enhancing hydrolysis acidification to treat industrial wastewater according to claim 3, characterized in that, In step (1), 15-20 parts by weight of carbon felt, 70-80 parts by weight of nitric acid solution, 3-8 parts by weight of 3-mercaptopropyltrimethoxysilane, and 40-50 parts by weight of ethanol.

9. The method for electrochemically enhancing hydrolysis acidification to treat industrial wastewater according to claim 3, characterized in that, In step (2), 8-12 parts by weight of Fe(NO3)3·9H2O, 5-8 parts by weight of tetrabutyl titanate, and 50-60 parts by weight of ethanol.

10. A method for electrochemically enhancing hydrolysis acidification to treat industrial wastewater according to claim 6, characterized in that, 6-10 parts by weight of polydopamine and 1-3 parts by weight of carboxylated carbon nanotubes, and the thickness of the composite coating is 10-30 μm.