A method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification

Abstract

The present invention relates to the technical field of electrochemical wastewater treatment, and discloses a method for electrochemically enhanced hydrolysis and acidification treatment of industrial wastewater. Pollutant degradation is achieved by constructing a reaction system containing a heterojunction anode, a composite cathode, and a biochar particle electrode. The heterojunction anode forms a gradient conductive structure with a titanium matrix composite metal oxide and a conductive polymer, and fixes a symbiotic flora of sulfur-reducing bacteria and electroactive bacteria to enhance bioelectrochemical activity; the composite cathode is modified based on activated carbon felt; and the biochar particle electrode is modified by iron doping to form a porous interface. This method utilizes electrochemical oxidation-reduction to destroy the sulfur bond and ring structure of biotin, couples microbial metabolism to achieve deep mineralization, and has both efficient electron migration and biofilm stability, significantly improving the conversion efficiency of organic matter and reducing sludge by-products. It is suitable for the efficient treatment of biotin-containing wastewater in the pharmaceutical and chemical fields.

Description

Technical Field

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

[0002] With the rapid development of industry, the discharge of industrial wastewater is increasing. Pharmaceutical and chemical wastewater containing biotin, for example, has complex composition, high concentrations of organic matter, and is difficult to degrade, posing a serious threat to the environment. Traditional wastewater treatment methods, such as physical and chemical methods and single biological treatment, have many limitations when treating this type of wastewater.

[0003] As a commonly used wastewater pretreatment technology, hydrolysis and acidification utilizes the metabolic activity of anaerobic microorganisms to convert large organic molecules in wastewater into small organic molecules, thereby improving the biodegradability of the wastewater and creating favorable conditions for subsequent treatment. However, traditional hydrolysis and acidification technologies still face challenges in treating difficult-to-degrade organic matter, such as low treatment efficiency, difficulty in biofilm formation by hydrolytic acidifying bacteria, and long residence times. For example, when treating printing and dyeing wastewater, even with a hydraulic retention time of up to 24 hours, the COD removal efficiency can only reach 29%, and the maximum B / C ratio reaches only 0.26. In addition, for wastewater containing heterocyclic or polycyclic organic matter, degradation by hydrolytic acidifying bacteria is even more difficult. The application of electrochemical technology in wastewater treatment is gradually gaining attention. Electrochemical technology produces strong oxidants or reducing agents through electrode reactions, directly or indirectly degrading organic pollutants. However, existing electrochemical hydrolysis and acidification technologies still have some shortcomings. On the one hand, the performance and stability of electrode materials during electrochemical reactions significantly impact treatment outcomes. 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, effectively enhancing the interaction between microorganisms and electrodes and improving bioelectrochemical activity remains a major challenge in current research. Therefore, the present invention provides a method for electrochemically enhanced hydrolysis and acidification treatment of industrial wastewater to address these technical issues. Summary of the Invention

[0004] The object of the present invention is to provide a method for electrochemically enhanced hydrolysis and acidification treatment of industrial wastewater. This method utilizes electrochemical redox to destroy the sulfur bonds and ring structures of biotin, couples microbial metabolism to achieve deep mineralization, combines efficient electron transfer with biofilm stability, significantly improves organic matter conversion efficiency, and reduces sludge by-products. The method is suitable for the efficient treatment of biotin-containing wastewater in the pharmaceutical and chemical fields.

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

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

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

[0008] S2. Spraying a symbiotic bacterial community containing sulfur-reducing bacteria and electroactive bacteria on the surface of the heterojunction anode, and using a composite coating to fix the biofilm. After solidification, the biofilm thickness is 50-100 μm;

[0009] S3. Wastewater is pumped into the reactor through a flow meter, controlling the time and current density, while monitoring the effluent results, and discharged after meeting the standards.

[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 and ultrasonically clean it with acetone, ethanol, and deionized water for 10-20 minutes. Then immerse it in a mixture of H2SO4 and HF in a volume ratio of 1-3:1 and etch it at 32-36°C for 15-20 minutes to form a pretreated titanium substrate with a pore size of 5-10 μm.

[0012] A2. Dissolve SnCl4·5H2O, SbCl3 and ethyl orthosilicate uniformly in ethanol, apply the mixture to the surface of the pretreated titanium substrate by spin coating at 2000-4000 rpm for 20-40 seconds, pre-dry at 120-130°C for 15-20 minutes, and then calcine at 500-600°C in air atmosphere for 1-3 hours to obtain a heterojunction titanium substrate;

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

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

[0015] (1) Immersing the carbon felt in a 60-70% by mass nitric acid solution, reflux treatment at 75-85°C for 1-3 hours, washing until neutral and then drying to obtain activated carbon felt, then immersing the activated carbon felt in a mixed solution of 3-mercaptopropyltrimethoxysilane and ethanol, adding glacial acetic acid to adjust the pH to 4-5, stirring the reaction at 55-65°C for 4-8 hours, filtering, washing and drying to obtain modified carbon felt;

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

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

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

[0020] Preferably, in step A2, the components by weight include 10-15 parts of SnCl4.5H2O, 1-3 parts of SbCl3, 4-8 parts of ethyl orthosilicate and 90-100 parts of ethanol.

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

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

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

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention achieves deep optimization of electrode material performance and interface functions by constructing a reaction system in which a heterojunction anode, a composite cathode, and a biochar particle electrode work synergistically. The heterojunction anode forms a three-dimensional conductive structure with abundant active sites through titanium matrix etching, metal oxide coating, and gradient composite of a conductive polymer layer. This structure can efficiently destroy the sulfur bonds and cyclic conjugated structures of biotin-like pollutants, providing easily degradable intermediates for microbial metabolism. The composite cathode is activated and modified by carbon felt and loaded with metal oxides to construct a highly catalytically active reduction reaction interface, promote the generation of electrogenerated strong oxidizing substances, and form a synergistic degradation effect with anodic oxidation. The biochar particle electrode, through iron doping and porous structure design, serves as a microbial attachment carrier and strengthens electron transfer, constructing a three-dimensional electrode and biofilm coupling network in the reactor, significantly improving the contact efficiency between pollutants and the reaction interface, and creating favorable conditions for multi-phase synergistic degradation.

[0026] 2. The present invention achieves efficient coupling of electrochemical oxidation and microbial metabolism through the fixation of symbiotic bacteria and composite coating technology. Sulfur-reducing bacteria and electroactive 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, forming a biofilm with excellent conductivity and biocompatibility. Among them, the conductive carbon nanotube network builds a direct electron transfer channel between the microorganisms and the electrode, accelerating the interaction between electrochemical signals and biological metabolism, while the adhesion properties of polydopamine ensure 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 scission to small molecules-thorough mineralization", breaking through the bottleneck of treating difficult-to-degrade organic matter with a single treatment method.

[0027] 3. The electrode preparation of this invention utilizes a repeatable coating, calcination, and modification process, forming a standardized process that provides a reliable foundation for engineering scale-up. The coordinated distribution of electrodes and particles within the reactor optimizes the flow and electric fields, reducing energy consumption while improving organic matter conversion efficiency. Electrochemical pretreatment reduces the use of chemical agents and excess sludge generation, meeting the requirements of green water treatment technology. Furthermore, the design of the composite coating and particle electrodes enhances the system's tolerance to high concentrations of organic matter and heterocyclic compounds, significantly improving the biodegradability of the effluent and creating excellent conditions for subsequent biochemical treatment. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used are purchased from conventional biochemical reagent stores unless otherwise specified. The quantitative experiments in the following examples were all repeated three times, and the data are the average or mean ± standard deviation of the three repeated experiments.

[0030] Polydopamine was purchased from Beijing Zhongke Keyou Nanotechnology Co., Ltd. (brand: Zhongke Keyou);

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

[0032] Sulfur-reducing bacteria were cultured using the method described in Wang Ming, Li Hua, Zhang Qiang, et al. Isolation and cultivation of sulfur-reducing bacteria and their application in wastewater treatment [J]. Environmental Science and Technology, 2022, 7(25): 34-36;

[0033] The electroactive bacteria were cultured using the method described 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 treating industrial wastewater by electrochemically enhanced hydrolysis and acidification comprises the following steps:

[0036] Heterojunction anode preparation:

[0037] A1. Place a 1mm thick, 10cm x 10cm titanium plate in 200mL of acetone, 200mL of ethanol, and 200mL of deionized water, sequentially, and ultrasonically clean it for 20 minutes each at 200W and 40kHz. Then, immerse the titanium plate in 200mL of a 1:1 (volume ratio) mixture of 98% H2SO4 and 40% HF. Etch it in a 32°C water bath at 300rpm for 20 minutes to create a roughened surface with pores of 10μm in diameter, thus obtaining a pretreated titanium substrate.

[0038] A2. Weigh 10 parts SnCl4·5H2O, 1 part SbCl3, and 4 parts ethyl orthosilicate by weight, dissolve them in 90 parts ethanol, and stir at 800 rpm until completely dissolved. Apply the solution to the pretreated titanium substrate surface by spin coating, setting the spin coater speed to 2000 rpm and the coating time to 20 seconds, and repeat the coating once. After coating, pre-dry the titanium substrate in a 120°C oven for 20 minutes, then transfer it to a muffle furnace and calcine it at 500°C in an air atmosphere at a heating rate of 5°C / min for 3 hours to obtain a heterojunction titanium substrate;

[0039] A3. Dissolve 5 parts of aniline in 200 mL of a 1 mol / L hydrochloric acid solution. Slowly add 5.4 parts of ammonium persulfate in an ice-water bath and stir at 600 rpm for 2 hours to produce a polyaniline nanofiber dispersion. Immerse a heterojunction titanium substrate in the dispersion and coat it using a dip coating method. The immersion time is 30 seconds and the pull-out speed is 5 cm / min. After coating, dry the titanium substrate in an 80°C oven for 30 minutes. Repeat the coating twice to form a conductive layer with a thickness of 1 μm, thus producing the heterojunction anode.

[0040] Composite cathode preparation:

[0041] (1) Take 15 parts of carbon felt with a size of 5cm×5cm×0.5cm, immerse them in 70 parts of 60% nitric acid solution, and reflux them in an oil bath at 75℃ at 200rpm for 3h. After the reaction is completed, wash the carbon felt with deionized water until it is neutral and dry it at 80℃ for 4h 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 in a water bath at 55℃ at 300rpm for 8h, filter, wash and dry to obtain modified carbon felt;

[0042] (2) 8 parts of Fe(NO₃)₃·9H₂O and 5 parts of tetrabutyl titanate were weighed and dissolved in 50 parts of ethanol. The mixture was stirred at 700 rpm until completely dissolved. The modified carbon felt was immersed in the resulting solution and shaken at 80 times / min at room temperature for 24 h. After removal, the mixture was placed in a tube furnace under a nitrogen atmosphere and heated to 300°C at a heating rate of 10°C / min. The mixture was calcined for 2 h to obtain a composite cathode.

[0043] Preparation of biochar particle electrode: Rice husk and 0.5 mol / LFeCl3 solution were mixed in a mass ratio of 8:3. The mixture was then transferred to a tube furnace and heated to 700°C at a heating rate of 10°C / min under a nitrogen atmosphere. Pyrolysis was carried out for 2.5 h. The pyrolysis products were ball milled at 500 rpm for 30 min and sieved to control the particle size to 80 μm. The biochar particle electrode was obtained, and its filling density was 15% of the total volume of the reactor.

[0044] Reactor construction and wastewater treatment:

[0045] S1. The prepared heterojunction anode and composite cathode with an effective area of ​​10 cm × 10 cm were fixed in parallel on both sides of a 10 L reactor, and the biochar particle electrode was filled between the two electrodes. The anode and cathode were connected through an electrochemical workstation in constant current mode.

[0046] S2, take sulfur-reducing bacteria and electroactive bacteria in a volume ratio of 1:0.8, and mix the OD 600 The value was adjusted to 0.8, and then a composite coating solution consisting of 6 parts of polydopamine, 1 part of carboxylated carbon nanotubes and 20 parts of deionized water was added. After dispersion under the conditions of ultrasonic power 200W and frequency 40kHz, it was sprayed on the anode surface and cured in a constant temperature box at 20℃ for 18 hours to form a biofilm with a thickness of 50μm.

[0047] S3. Industrial wastewater is pumped into the reactor at a flow rate of 0.4m³ / h, the hydraulic retention time is controlled at 12h, the current density is maintained at 2.0mA / cm², and the effluent results are monitored at the same time. It is discharged after meeting the standards.

[0048] Example 2

[0049] A method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification comprises the following steps:

[0050] Heterojunction anode preparation:

[0051] A1. Take a 1.2mm thick, 10cm x 10cm titanium plate and place it in 300mL of acetone, 300mL of ethanol, and 300mL of deionized water, sequentially. Ultrasonic cleaning is performed for 15 minutes each at 250W and 40kHz. The titanium plate is then immersed in 250mL of a 1.5:1 volume ratio of 98% H2SO4 to 40% HF. Etching is then performed in a 34°C water bath at 350rpm for 18 minutes, creating a roughened surface with pores of 8μm in diameter. This results in 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 at 850 rpm until completely dissolved. Apply the solution to the surface of the pretreated titanium substrate by spin coating, setting the spin coater speed to 3000 rpm and the coating time to 30 seconds, and repeat the coating once. After coating, pre-dry the titanium substrate in a 125°C oven for 18 minutes, then transfer it to a muffle furnace and calcine it at 550°C in an air atmosphere at a heating rate of 5°C / min for 2 hours to obtain a heterojunction titanium substrate;

[0053] A3. Dissolve 6 parts of aniline in 250 mL of a 1.5 mol / L hydrochloric acid solution. Slowly add 6.5 parts of ammonium persulfate in an ice-water bath. Stir at 650 rpm for 1.5 hours to produce a polyaniline nanofiber dispersion. Immerse a heterojunction titanium substrate in the dispersion and coat it using a dip coating method. The immersion time is 35 seconds and the pull-out speed is 5 cm / min. After coating, dry the titanium substrate in a 90°C oven for 25 minutes. Repeat the coating three times to form a 2 μm thick conductive layer, thus producing the heterojunction anode.

[0054] Composite cathode preparation:

[0055] (1) Take 18 parts of carbon felt with a size of 5cm×5cm×0.5cm, immerse them in 75 parts of 65% nitric acid solution, and reflux them in an oil bath at 80℃ at 250rpm for 2h. After the reaction is completed, the carbon felt is washed with deionized water until it is neutral and dried at 85℃ for 3h to obtain activated carbon felt. Then, the activated carbon felt is immersed in 45 parts of ethanol containing 5 parts of 3-mercaptopropyltrimethoxysilane, glacial acetic acid is added to adjust the pH to 4.5, and then reacted in a water bath at 60℃ at 350rpm for 7h, filtered, washed and dried to obtain modified carbon felt;

[0056] (2) 10 parts by weight of Fe(NO₃)₃·9H₂O and 6 parts of tetrabutyl titanate were weighed and dissolved in 55 parts of ethanol. The mixture was stirred at 750 rpm until completely dissolved. The modified carbon felt was immersed in the resulting solution and shaken at 100 times / min at room temperature for 22 h. After removal, the mixture was placed in a tube furnace under a nitrogen atmosphere and heated to 350°C at a heating rate of 10°C / min. The mixture was calcined for 2.5 h to obtain a composite cathode.

[0057] Preparation of biochar particle electrode: Rice husk and 0.5 mol / LFeCl3 solution were mixed in a mass ratio of 10:4, and then the mixture was transferred to a tube furnace and heated to 750°C at a heating rate of 10°C / min under a nitrogen atmosphere. Pyrolysis was carried out for 2 hours. The pyrolysis products were treated in a ball mill at 550 rpm for 35 minutes and sieved to control the particle size to 115 μm, thus obtaining a biochar particle electrode with a filling density of 20% of the total volume of the reactor.

[0058] Reactor construction and wastewater treatment:

[0059] S1. The prepared heterojunction anode and composite cathode with an effective area of ​​10 cm × 10 cm were fixed in parallel on both sides of a 10 L reactor, and the biochar particle electrode was filled between the two electrodes. The anode and cathode were connected through an electrochemical workstation in constant current mode.

[0060] S2, take sulfur-reducing bacteria and electroactive bacteria in a volume ratio of 1:1 and mix them.600 The value was adjusted to 1.0, and then a composite coating solution consisting of 8 parts of polydopamine, 2 parts of carboxylated carbon nanotubes and 25 parts of deionized water was added. After dispersion under the conditions of ultrasonic power of 250 W and frequency of 40 kHz, it was sprayed on the anode surface and cured in a constant temperature box at 25°C for 24 hours to form a biofilm with a thickness of 75 μm.

[0061] S3. Industrial wastewater is pumped into the reactor at a flow rate of 0.5m³ / h, the hydraulic retention time is controlled at 9h, the current density is maintained at 2.5mA / cm², and the effluent results are monitored at the same time. It is discharged after meeting the standards.

[0062] Example 3

[0063] A method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification comprises the following steps:

[0064] Heterojunction anode preparation:

[0065] A1. Take a 2mm thick, 10cm x 10cm titanium plate and place it in 400mL of acetone, 400mL of ethanol, and 400mL of deionized water, sequentially. Ultrasonic cleaning is performed for 20 minutes each at 300W power and 40kHz frequency. The titanium plate is then immersed in 300mL of a 3:1 volume ratio mixture of 98% H2SO4 and 40% HF. Etching is performed in a 36°C water bath at 400rpm for 20 minutes to create a roughened surface with pores of 10μm in diameter, thus 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. Apply the solution to the surface of the pretreated titanium substrate by spin coating, setting the spin coater speed to 4000 rpm and the coating time to 40 seconds, and repeat the coating once. After coating, pre-dry the titanium substrate in a 130°C oven for 20 minutes, then transfer it to a muffle furnace and calcine it at 600°C in an air atmosphere at a heating rate of 5°C / min for 3 hours to obtain a heterojunction titanium substrate;

[0067] A3. Dissolve 7 parts of aniline in 300 mL of a 2 mol / L hydrochloric acid solution. Slowly add 7.5 parts of ammonium persulfate in an ice-water bath and stir at 700 rpm for 2 hours to produce a polyaniline nanofiber dispersion. Immerse a heterojunction titanium substrate in the dispersion and coat it using a dip coating method. The immersion time is 40 seconds and the pull-out speed is 5 cm / min. After coating, dry the titanium substrate in an oven at 100°C for 30 minutes. Repeat the coating four times to form a 3 μm thick conductive layer, thus producing the heterojunction anode.

[0068] Composite cathode preparation:

[0069] (1) Take 20 parts of carbon felt with a size of 5cm×5cm×0.5cm, immerse them in 80 parts of 70% nitric acid solution, and reflux them in an oil bath at 85℃ at 300rpm for 3h. After the reaction is completed, wash the carbon felt with deionized water until it is neutral and dry it at 90℃ for 4h 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 in a water bath at 65℃ at 400rpm for 8h, filter, wash and dry to obtain modified carbon felt;

[0070] (2) 12 parts of Fe(NO₃)₃·9H₂O and 8 parts of tetrabutyl titanate were weighed and dissolved in 60 parts of ethanol. The mixture was stirred at 800 rpm until completely dissolved. The modified carbon felt was immersed in the resulting solution and shaken at 120 times / min at room temperature for 24 h. After removal, the mixture was placed in a tube furnace under a nitrogen atmosphere and heated to 400°C at a heating rate of 10°C / min. The mixture was calcined for 3 h to obtain a composite cathode.

[0071] Preparation of biochar particle electrode: Rice husk and 0.5 mol / LFeCl3 solution were mixed in a mass ratio of 12:5. The mixture was then transferred to a tube furnace and heated to 850°C at a heating rate of 10°C / min under a nitrogen atmosphere. Pyrolysis was carried out for 2.5 h. The pyrolysis products were ball milled at 600 rpm for 40 min and sieved to control the particle size to 150 μm. The biochar particle electrode was obtained, and its filling density was 25% of the total volume of the reactor.

[0072] Reactor construction and wastewater treatment:

[0073] S1. The prepared heterojunction anode and composite cathode with an effective area of ​​20 cm × 20 cm were fixed in parallel on both sides of a 50 L reactor, and the biochar particle electrode was filled between the two electrodes. The anode and cathode were connected through an electrochemical workstation in constant current mode.

[0074] S2: Mix sulfur-reducing bacteria and electroactive bacteria in a volume ratio of 1:1.2 and adjust the OD 600 The value was adjusted to 1.2, and then a composite coating solution consisting of 10 parts of polydopamine, 3 parts of carboxylated carbon nanotubes and 30 parts of deionized water was added. After dispersion under the conditions of ultrasonic power of 300 W and frequency of 40 kHz, it was sprayed on the anode surface and cured in a constant temperature box at 30°C for 30 hours to form a biofilm with a thickness of 100 μm.

[0075] S3. Industrial wastewater is pumped into the reactor at a flow rate of 0.6m³ / h. The hydraulic retention time is controlled at 12h and the current density is maintained at 3.0mA / cm². The effluent results are monitored at the same time and discharged after meeting the standards.

[0076] Example 4

[0077] A method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification comprises the following steps:

[0078] Heterojunction anode preparation:

[0079] A1. Take a 1.8mm thick, 10cm x 10cm titanium plate and place it in 350mL of acetone, 350mL of ethanol, and 350mL of deionized water, sequentially. Ultrasonic cleaning is performed for 18 minutes each at 280W of ultrasonic power and 40kHz of frequency. The titanium plate is then immersed in 280mL of a 2:1 volume ratio mixture of 98% H2SO4 and 40% HF. Etching is then performed in a 35°C water bath at 380rpm for 18 minutes, creating a roughened surface with pores of 8μm in diameter. This results in 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 at 820 rpm until completely dissolved. Apply the solution to the pretreated titanium substrate surface by spin coating, setting the spin coater speed to 3200 rpm and the coating time to 35 seconds, and repeat the coating once. After coating, pre-dry the titanium substrate in a 128°C oven for 18 minutes, then transfer it to a muffle furnace and calcine it in an air atmosphere at 580°C at a heating rate of 5°C / min for 2.5 hours 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 in an ice-water bath. Stir at 680 rpm for 1.8 hours to produce a polyaniline nanofiber dispersion. Immerse a heterojunction titanium substrate in the dispersion and coat it using a dip coating method. The immersion time is 38 seconds and the pull-out speed is 5 cm / min. After coating, dry the titanium substrate in a 95°C oven for 28 minutes. Repeat the coating three times to form a 2.5 μm thick conductive layer, thus producing the heterojunction anode.

[0082] Composite cathode preparation:

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

[0084] (2) 11 parts of Fe(NO₃)₃·9H₂O and 7 parts of tetrabutyl titanate were weighed and dissolved in 58 parts of ethanol. The mixture was stirred at 780 rpm until completely dissolved. The modified carbon felt was immersed in the resulting solution and shaken at 110 times / min at room temperature for 23 h. After removal, the mixture was placed in a tube furnace under a nitrogen atmosphere and heated to 380°C at a heating rate of 10°C / min. The mixture was calcined for 2.9 h to obtain a composite cathode.

[0085] Preparation of biochar particle electrode: Rice husk and 0.5 mol / LFeCl3 solution were mixed in a mass ratio of 11:4.5. The mixture was then transferred to a tube furnace and heated to 820°C at a heating rate of 10°C / min under a nitrogen atmosphere. Pyrolysis was carried out for 2.3 h. The pyrolysis products were ball milled at 580 rpm for 38 min and sieved to control the particle size to 130 μm. The biochar particle electrode was obtained, and its filling density was 23% of the total volume of the reactor.

[0086] Reactor construction and wastewater treatment:

[0087] S1. The prepared heterojunction anode and composite cathode with an effective area of ​​18 cm × 18 cm were fixed in parallel on both sides of a 30 L reactor, and the biochar particle electrode was filled between the two electrodes. The anode and cathode were connected through an electrochemical workstation in constant current mode.

[0088] S2, take sulfur-reducing bacteria and electroactive bacteria in a volume ratio of 1:1.1, and mix the OD of the bacterial solution. 600 The value was adjusted to 1.1, and then a composite coating solution consisting of 9 parts of polydopamine, 2.5 parts of carboxylated carbon nanotubes and 28 parts of deionized water was added. After dispersion under the conditions of ultrasonic power 280 W and frequency 40 kHz, it was sprayed on the anode surface and cured in a constant temperature box at 28 ° C for 27 hours to form a biofilm with a thickness of 90 μm.

[0089] S3. Industrial wastewater is pumped into the reactor at a flow rate of 0.55m³ / h. The hydraulic retention time is controlled at 10h and the current density is maintained at 2.8mA / cm². The effluent results are monitored at the same time and discharged after meeting the standards.

[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 in steps A1 and A2 is used as the anode, and the remaining steps are the same as in Example 4.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 4 is that the heterojunction anode in step S1 only uses the pretreated titanium substrate prepared in step A1, and the coating treatment in steps A2 and A3 is not performed. The remaining steps are the same as 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 is not modified with 3-mercaptopropyltrimethoxysilane in step (1), that is, the silanization step is omitted, and the activated carbon felt is directly immersed in an ethanol solution of Fe(NO3)3 and tetrabutyl titanate for immersion and calcination. The remaining steps are the same as 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 is not subjected to the metal oxide loading modification in step (2), that is, only the activated carbon felt prepared in step (1) is used as the cathode, and the remaining steps are the same as in Example 4.

[0098] Comparative Example 5

[0099] The difference between this comparative example and Example 4 is that no biochar particle electrode is added in step S1, that is, only a heterojunction anode and a composite cathode are set in the reactor, and the remaining steps are the same as in Example 4.

[0100] Comparative Example 6

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

[0102] Test standard:

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

[0104] 2. B / C ratio test: The biological oxygen demand (BOD) is measured using a rapid microbial sensor method. The metabolic activity of microorganisms in the microbial membrane consumes the dissolved oxygen in the wastewater, thereby determining 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, the sulfide in the wastewater is first pretreated and converted into a detectable form. It is then measured using appropriate instruments. The concentrations of sulfide before and after treatment are compared, and the sulfide degradation rate is calculated. The test results are shown in Table 1.

[0106] 4. Sludge production test: A certain amount of wastewater sample was allowed to settle, and the settled sludge was collected. After filtering, washing, and drying to a constant weight, its mass was weighed. The amount of sludge produced per unit water volume was calculated. The test results are shown in Table 1.

[0107] The following are test results for verifying the performance of the electrochemical enhanced hydrolysis and 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] As can be seen from the data in Table 1, Examples 1-4 outperformed 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 was as high as 99.27%, the B / C ratio reached 0.85, the sulfide degradation rate was 98.83%, and the sludge production was only 0.05 kg / m³, indicating that it performed well in terms of organic matter degradation, biodegradability improvement, and sulfide treatment, and the low sludge production reduced the burden of subsequent processing. However, the comparative example was significantly inferior in performance due to the lack of key steps or components in the examples.

[0111] The simplification of electrode preparation or modification in Comparative Examples 1-3 resulted in poor treatment effects. Comparative Example 1 did not perform the conductive layer coating of step A3, Comparative Example 2 only used the pretreated titanium substrate of step A1 as the anode, and Comparative Example 3 did not perform silanization treatment on the composite cathode. These omitted steps affected the electrode performance and microbial attachment, thereby reducing the wastewater treatment efficiency. Comparative Example 4 did not perform metal oxide loading and modification on the composite cathode, which weakened the reduction reaction ability of the cathode and could not form an effective synergistic degradation effect with anodic oxidation. Comparative Example 5 lacked a biochar particle electrode, which destroyed the three-dimensional electrode-biofilm coupling network in the reactor and reduced the contact efficiency between the pollutants and the reaction interface. Comparative Example 6 did not spray the symbiotic bacteria, which reduced the coupling effect of electrochemical oxidation and microbial metabolism and could not fully exert the mineralization effect of the microorganisms. In summary, by controlling the feed ratio of each raw material during electrode preparation and optimizing the parameters during wastewater treatment, the wastewater treatment method of Examples 1-4 is significantly better than Comparative Examples 1-6, can significantly improve wastewater treatment efficiency, and has broad application prospects.

[0112] Throughout the specification, references to terms such as "embodiment" or "various embodiments" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or preparation example are included in at least one embodiment or preparation example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or preparation example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or preparation examples.

[0113] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification, characterized in that: The following steps are involved: S1. Construct an electrochemical reactor, set up a heterojunction anode, a composite cathode and a biochar particle electrode inside the reactor, and connect the anode and cathode through an electrochemical workstation. The filling density of the biochar particle electrode is 15-25% of the total volume of the reactor; S2. Spraying a symbiotic bacterial community containing sulfur-reducing bacteria on the surface of the heterojunction anode, and using a composite coating to fix the biofilm. After solidification, the biofilm thickness is 50-100 μm; S3. Wastewater is pumped into the reactor through a flow meter, controlling the time and current density, while monitoring the effluent results, and discharged after meeting the standards; Wherein, the heterojunction anode in step S1 is prepared by the following steps: A1. Select a titanium plate with a thickness of 1-2 mm and ultrasonically clean it with acetone, ethanol, and deionized water for 10-20 minutes. Then immerse it in a mixture of H2SO4 and HF in a volume ratio of 1-3:1 and etch it at 32-36°C for 15-20 minutes to form a pretreated titanium substrate with a pore size of 5-10 μm. A2. Dissolve SnCl4•5H2O, SbCl3 and ethyl orthosilicate uniformly in ethanol, apply the mixture to the surface of the pretreated titanium substrate by spin coating at 2000-4000 rpm for 20-40 seconds, pre-dry at 120-130°C for 15-20 minutes, and then calcine at 500-600°C in air atmosphere for 1-3 hours to obtain a heterojunction titanium substrate; A3. Dissolve aniline in 1-2 mol / L hydrochloric acid solution, add ammonium persulfate in an ice-water bath, and stir the reaction for 1-2 hours to obtain a polyaniline nanofiber dispersion. Immerse the heterojunction titanium substrate in the dispersion and coat it by dip coating. Dry at 80-100°C for 15-30 minutes, and repeat 2-4 times to form a conductive layer with a thickness of 1-3 μm to obtain a heterojunction anode.

2. The method according to claim 1, characterized in that In step S1, the composite cathode is prepared by the following steps: (1) Immersing the carbon felt in a 60-70% by mass nitric acid solution, reflux treatment at 75-85°C for 1-3 hours, washing until neutral and then drying to obtain activated carbon felt, then immersing the activated carbon felt in a mixed solution of 3-mercaptopropyltrimethoxysilane and ethanol, adding glacial acetic acid to adjust the pH to 4-5, stirring the reaction at 55-65°C for 4-8 hours, filtering, washing and drying to obtain modified carbon felt; (2) Dissolve Fe(NO3)3•9H2O and tetrabutyl titanate in ethanol, immerse the modified carbon felt in the solution, shake and immerse at room temperature for 18-24 hours, take it out and calcine it at 300-400℃ in a nitrogen atmosphere for 2-3 hours to obtain a composite cathode.

3. The method according to claim 1, characterized in that In step S1, the biochar particle electrode is prepared by the following steps: rice husk and FeCl3 solution are mixed in a mass ratio of (8-12): (3-5), pyrolyzed at 700-850°C for 1.5-2.5 hours to prepare doped biochar, and then the doped biochar is ball-milled to control its particle size to 80-150 μm, thereby obtaining a biochar particle electrode.

4. The method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification according to claim 1, characterized in that: The symbiotic bacteria in step S2 are composed of sulfur-reducing bacteria and electroactive bacteria in a mixing ratio of 1:0.8-1.2, and the bacterial solution OD 600 The value is 0.8-1.

2.

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

6. The method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification according to claim 1, characterized in that: In step A2, the components by weight include 10-15 parts of SnCl4•5H2O, 1-3 parts of SbCl3, 4-8 parts of ethyl orthosilicate and 90-100 parts of ethanol.

7. The method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification according to claim 2, characterized in that: In step (1), the components include, by weight, 15-20 parts of carbon felt, 70-80 parts of nitric acid solution, 3-8 parts of 3-mercaptopropyltrimethoxysilane and 40-50 parts of ethanol.

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

9. The method for treating industrial wastewater by electrochemically enhanced hydrolysis and acidification according to claim 5, characterized in that: The amount of polydopamine and carboxylated carbon nanotubes is 6-10 parts by weight, and the thickness of the composite coating is 10-30 μm.