Method for selectively removing total cyanide in acrylonitrile wastewater by electrogenerating active oxygen

Abstract

The present application belongs to the field of environmental electrocatalysis, and particularly relates to a method for selectively removing total cyanide in acrylonitrile wastewater by electrogenerating active oxygen. A large amount of acrylonitrile, succinonitrile, methyl acrylate, acrylamide and other compounds exist in acrylonitrile wastewater, and most of them will be converted into total cyanide in the traditional oxidation process, resulting in that the total cyanide in the effluent exceeds the standard. The present application innovatively selects manganese-cerium composite metal oxide as an active coating of an electrocatalytic electrode, plays a medium barrier role to selectively generate active oxygen species such as singlet oxygen with weak oxidation ability, realizes the polycondensation and phase separation of various organic nitriles on the electrode surface, and removes them in the form of gas float by means of the hydrogen-oxygen gas bubbles co-produced in the electrochemical process. The method can simultaneously remove a large amount of pollutants such as COD and ammonia nitrogen existing in acrylonitrile wastewater, avoid the problems of high energy consumption and low energy efficiency caused by over-oxidation in other oxidation technologies, and has good economy.

Description

I. Technical Field

[0001] This invention belongs to the field of environmental electrocatalysis, specifically relating to a method for selectively removing total cyanide from acrylonitrile wastewater by electrogenerating active oxygen. This invention innovatively uses a manganese-cerium composite metal oxide as the active coating of the electrocatalytic electrode, selectively generating active oxygen species such as singlet oxygen with weak oxidizing capabilities, while simultaneously removing large amounts of pollutants such as COD, total cyanide, and ammonia nitrogen present in acrylonitrile wastewater. This effectively avoids the high energy consumption and low energy efficiency problems caused by over-oxidation in other oxidation technologies, and has good economic advantages. II. Background Technology

[0002] Acrylonitrile wastewater mainly originates from the production processes of acrylonitrile, acrylic fiber, and ABS plastics. The most difficult to treat is the wastewater from the fourth-effect evaporation process in the acrylonitrile workshop. This wastewater is extremely polluted, containing toxic and harmful substances such as acrylic acid, acrylonitrile, acrolein, allyl alcohol, methyl acrylate, acetonitrile, acetone cyanohydrin, pyridine formamide, and dimethylisoazole formamide, as well as high levels of COD and ammonia nitrogen. Direct discharge without treatment would cause significant harm and impact on residents and the environment. Furthermore, the acrylonitrile, acrolein, pyridine, and cyanide in the wastewater inhibit and toxicize the activated sludge in the biological treatment system of wastewater treatment plants. Therefore, treating acrylonitrile wastewater using currently common biological methods is extremely difficult.

[0003] Various technological strategies have been employed to treat acrylonitrile wastewater, combining multi-stage treatment, high-gravity gas extraction, and ozone catalytic oxidation coupled with biological nitrification. Multi-stage treatment strategies, through integrated pretreatment, biochemical treatment, advanced treatment, and advanced oxidation, can comprehensively remove harmful substances from wastewater, ensuring stable effluent quality and partial water reuse. High-gravity gas extraction is particularly suitable for treating high-concentration acrylonitrile wastewater, efficiently recovering resources and reducing the organic load. Ozone catalytic oxidation coupled with biological nitrification improves the biodegradability of wastewater through oxidation and biochemical coupling, ensuring stable effluent compliance. Each technology has its advantages and disadvantages; the choice depends on the specific properties of the wastewater, treatment objectives, and economic and environmental considerations. Currently, there are numerous methods and case studies for treating acrylonitrile production wastewater in China. However, these methods suffer from varying degrees of problems, including high costs, poor effluent quality, and unstable operation.

[0004] Electrocatalytic oxidation water treatment technology is a technique that uses an electric current-driven electrochemical reaction to degrade and remove organic pollutants from wastewater. Its principle is to apply a voltage to electrodes, causing pollutants in the wastewater to undergo an oxidation-reduction reaction on the electrode surface, thereby converting them into harmless substances. Electrocatalytic oxidation technology shows significant advantages in treating acrylonitrile wastewater. It can efficiently degrade recalcitrant organic compounds such as acrylonitrile, converting them into low-toxicity or non-toxic substances. Furthermore, this process is usually carried out at ambient temperature and pressure, making it simple and easy to control. However, electrocatalytic oxidation technology also has some potential drawbacks. In particular, improper control during the treatment process can lead to over-oxidation, resulting in an increase in the total cyanide content in the wastewater. For example, acrylic acid, acrylonitrile, acrolein, allyl alcohol, methyl acrylate, acetonitrile, and acetone cyanohydrin can all be converted into cyanide ions or thiocyanate ions during electrolysis, causing the total cyanide in the effluent to increase rather than decrease. This places higher demands on subsequent treatment and discharge. Therefore, when using electrocatalytic oxidation technology to treat acrylonitrile wastewater, it is necessary to reasonably control mild oxidation conditions and selectivity to ensure treatment effectiveness while avoiding the generation of highly toxic inorganic cyanides.

[0005] Analyzing the current problems in the electrocatalytic oxidation treatment of acrylonitrile wastewater, there is an urgent need to develop an electrocatalytic method capable of simultaneously treating organic nitrile compounds and cyanide ions in the wastewater, while also preventing the organic nitrile compounds from converting into inorganic cyanide ions. This electrocatalytic method requires the core electrode material in the electrocatalytic process to selectively generate weakly oxidizing species, promoting the selective conversion of organic nitrile compounds rather than oxidative decomposition. Improving the selectivity of the electrocatalytic process can significantly improve the treatment efficiency of acrylonitrile wastewater, reduce maintenance costs, and enhance the economic benefits of the project. Simultaneously, it also contributes to improving environmental quality, protecting human health, and promoting sustainable social development. III. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art, aiming to provide a method for selectively removing total cyanide from acrylonitrile wastewater using electro-generated active oxygen. This method employs a manganese-cerium composite metal oxide as the active coating of the electrocatalytic electrode, selectively generating active oxygen species such as singlet oxygen with weak oxidizing capabilities. Simultaneously, it removes large amounts of pollutants such as COD, total cyanide, and ammonia nitrogen present in acrylonitrile wastewater. This effectively avoids the high energy consumption and low energy efficiency problems caused by over-oxidation in other oxidation technologies, demonstrating good economic efficiency.

[0007] The selectivity of electrocatalytic electrodes is primarily achieved through precise control of electrode materials, surface morphology and structure, electrode potential, and surface and interface atomic engineering. Choosing appropriate electrode materials, such as metals, carbon materials, and semiconductors, can influence the catalytic activity of the electrode for specific reactions. Simultaneously, controlling the surface morphology and structure of the electrode, such as by synthesizing electrode materials with specific morphologies and structures, can increase the active surface area and improve reaction efficiency. Furthermore, precise control of the electrode potential can alter the charge state and reactivity of the catalyst surface, thereby affecting the selectivity of the electrocatalytic reaction. Finally, surface and interface atomic engineering enhances the selectivity of electrocatalytic reactions by introducing catalytically active sites and accelerating kinetic processes, or by creating new physical and chemical properties on material surfaces and interfaces. These techniques can be used individually or in combination to meet the selectivity requirements of different reaction systems.

[0008] Nitrogen-boron-doped graphene, as a cutting-edge inorganic low-dimensional nanomaterial, has demonstrated significant effects in the field of electrocatalysis, particularly in adjusting electrocatalytic activity and selectivity. Nitrogen doping effectively increases the active sites for catalytic reactions by altering the electronic structure of graphene, thus significantly enhancing its electrocatalytic activity. For example, nitrogen-doped graphene exhibits excellent performance in promoting the selective oxidation of ethylbenzene and aromatic alcohols, an advantage confirmed in numerous studies. On the other hand, although boron has relatively weak chemical activity, its unique electron transfer mechanism provides new active sites for graphene, enabling boron-doped graphene to exhibit unique selectivity in certain specific reactions. More notably, nitrogen-boron co-doped graphene can achieve fine-tuning of electrocatalytic activity and selectivity by precisely controlling the ratio and doping method of nitrogen and boron. A study by Professor Zheng Gengfeng of Fudan University and Professor Ma Jianmin's team at Hunan University found that at a boron atom doping level of 6.2%, the NH3 yield of boron-doped graphene reached 9.8 μg·h⁻¹. -1 ·cm -2 The Faraday efficiency reached 10.8%, demonstrating its high efficiency and selectivity in the electrocatalytic nitrogen reduction reaction. These studies not only reveal the enormous potential of nitrogen-boron-doped graphene in the field of electrocatalysis, but also provide new directions for research and application in this field.

[0009] Manganese-cerium composite metal oxide electrodes, with their unique electronic structure and catalytic performance, can selectively generate weakly oxidizing singlet oxygen (1O2) during electrocatalysis. This selectivity mainly stems from the synergistic effect of manganese and cerium oxides. Manganese oxides provide abundant active sites, promoting the adsorption and activation of oxygen molecules, while cerium oxides, through their electronic structure, facilitate electron transfer and oxygen molecule excitation. Compared to traditional electrocatalytic electrodes, manganese-cerium composite metal oxide electrodes exhibit high selectivity, high efficiency, and good stability in generating singlet oxygen, significantly improving the efficiency and yield of specific reactions. Furthermore, the manganese-cerium composite metal oxide coating also possesses high selective adsorption capacity for cyanides, primarily attributed to its abundant surface porosity and active sites, as well as the specific chemical interactions between manganese, cerium, and organic nitriles. These characteristics make manganese-cerium composite metal oxide electrodes a promising candidate for applications in electrocatalysis and adsorption.

[0010] In summary, the electrode plate prepared using nitrogen-boron-doped graphene and manganese-cerium composite metal oxide as the electrocatalytic active layer can generate weakly oxidizing singlet oxygen. Simultaneously, the selective adsorption characteristics between the manganese-cerium composite metal oxide and organic nitrile compounds enable selective catalytic oxidation and moderate polymerization of organic nitrile species, thus avoiding the negative effect of increased total cyanide due to peroxidation of organic nitriles. The polymerization products of organic nitriles can be removed by stripping and flotation, saving most of the oxidation energy and making this method highly technical and economical.

[0011] To achieve the above objectives, the present invention provides a method for selectively removing total cyanide from acrylonitrile wastewater using electrogenerated active oxygen, characterized in that the method comprises the following steps:

[0012] Step 1: Prepare acrylonitrile wastewater containing compounds such as acrylonitrile, succinic anhydride, methyl acrylate, acrylamide, and cyanide;

[0013] Step 2: Prepare manganese-cerium composite metal oxide coated electrode. First, select a titanium plate of appropriate area as the substrate and polish it with 20-mesh, 200-mesh and 800-mesh sandpaper respectively until smooth to remove the surface oxide layer. Then, boil it in a 10% oxalic acid aqueous solution for 30 minutes and store it in a 1% oxalic acid aqueous solution for later use.

[0014] Step 3: Mix nitrogen-boron-doped graphene, manganese nitrate, cerium nitrate, ethylene glycol, and citric acid in a mass ratio of 0.012:2:0.17:25:1.7 to form a reddish-brown viscous solution. Add an appropriate amount of nitric acid until the pH value is between 2 and 3. Let it stand at room temperature for 72 hours to achieve full aging and form a semi-solid composite metal oxide gel.

[0015] Step 4: Heat the composite metal oxide gel obtained in Step 3 in an oven at 100°C for 30 minutes to restore its fluidity. Then, introduce the composite metal oxide gel and an equal volume of ethanol into the spraying device. Under the propulsion of the airflow, form atomized droplets and spray them evenly onto the surface of the titanium plate described in Step 2.

[0016] Step 5: When the composite metal oxide gel on the surface of the titanium plate is evenly covered and reaches a visual thickness of 1 mm, stop spraying, transfer the titanium plate to an oven, dry it at 150°C for 15 minutes, then transfer it to a muffle furnace and bake it at 450°C for 10 minutes. Remove the quenching from the titanium plate and rinse it simply to wash away the carbon black and fly ash adhering to the surface and keep the surface flat.

[0017] Step 6: Repeat steps 4 and 5 a total of 8–18 times. After the operation is completed, the titanium plate with the composite metal oxide coating is kept under hot pressing at 10 MPa and 550°C for 4 hours to achieve a stable bond between the oxide coating and the titanium substrate. After the pressure is removed, it is annealed at room temperature to obtain the manganese cerium composite metal oxide coated electrode.

[0018] Step 7: Using the manganese-cerium composite metal oxide coated electrode obtained in step 6 as the anode and the stainless steel of the same area as the cathode, keeping the distance between the anode and cathode at 2 cm, connect the two electrodes to the positive and negative terminals of the DC pulse power supply with wires respectively, immerse in the acrylonitrile wastewater described in step 1, start the power supply and aerate with carbon dioxide to impact the manganese-cerium composite metal oxide coated electrode.

[0019] Step 8: Depending on the concentration and quality of the acrylonitrile wastewater, after a period of reaction, dense yellowish-brown scum and foam gradually form on the water surface, which are oligomers of nitrile formed on the anode surface. These need to be scraped or blown away in time. When the reaction is nearing its end, the solution gradually becomes colorless and clear, and no more foam of oligomers is produced. This determines the reaction endpoint. The above water sample is then sampled and analyzed to determine the changes in water quality indicators such as COD, total cyanide, and ammonia nitrogen, so as to determine the pollutant removal efficiency and unit energy consumption.

[0020] For the above technical solution, it is further specified that the acrylonitrile wastewater mentioned in step 1 mainly comes from the production processes of acrylonitrile, acrylic fiber, and ABS plastics, wherein the concentration of organic nitrile compounds is between 100 and 3000 mg / L, and the concentration of cyanide ions is between 10 and 200 mg / L.

[0021] For the above technical solution, the operating mode of the DC pulse power supply mentioned in step 7 is constant current mode, and the current density is 3–5 mA / cm². 2 .

[0022] The advantages of this invention are:

[0023] I. Highly selective removal of total cyanide, solving the problem of excessive effluent standards.

[0024] This invention utilizes a manganese-cerium composite metal oxide as the active coating of the electrocatalytic electrode, enabling the selective generation of reactive oxygen species, such as singlet oxygen with weak oxidizing capabilities. This selective oxidation mechanism allows complex compounds in acrylonitrile wastewater, such as acrylonitrile, succinic anionyl acrylate, and acrylamide, to undergo condensation and phase separation on the electrode surface. It also efficiently converts toxic cyanide into harmless substances, significantly reducing the total cyanide content in the effluent and effectively solving the problem of excessive total cyanide levels in traditional oxidation treatment processes.

[0025] II. Achieve simultaneous removal of multiple pollutants and improve treatment efficiency.

[0026] In addition to the highly efficient removal of total cyanide, the electrocatalytic method of this invention can also simultaneously remove large amounts of pollutants such as COD and ammonia nitrogen present in acrylonitrile wastewater. Through the reaction of reactive oxygen species with these pollutants during the electrocatalytic process, the simultaneous removal of multiple pollutants is achieved, greatly improving the efficiency and effectiveness of wastewater treatment. This ability to remove multiple pollutants simultaneously gives this invention a significant advantage in treating complex wastewater.

[0027] In summary, traditional oxidation technologies often suffer from over-oxidation when treating wastewater, leading to increased energy consumption and reduced treatment efficiency. The electrocatalytic method of this invention, by selectively generating reactive oxygen species such as singlet oxygen with weak oxidizing capabilities, avoids over-oxidation, thereby reducing energy consumption. Furthermore, this invention utilizes hydrogen and oxygen bubbles co-produced during the electrochemical process to assist aeration and flushing, removing pollutants via flotation. These features make this invention more economical for treating complex wastewaters such as acrylonitrile wastewater. IV. Description of the attached drawings

[0028] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments are briefly explained below.

[0029] Figure 1 This is a scanning electron microscope image of the active layer of the manganese-cerium composite metal oxide electrocatalytic electrode prepared in Example 1 of the present invention.

[0030] Figure 2 This is an X-ray diffraction image of the active layer of the manganese-cerium composite metal oxide electrocatalytic electrode prepared in Example 1 of the present invention.

[0031] Figure 3 In Example 2 of this invention, during the selective removal of wastewater from an acrylonitrile workshop in Daqing using electrogenerated active oxygen, the COD concentration, total cyanide concentration, and ammonia nitrogen concentration changed with treatment time.

[0032] Figure 4 In Example 3 of this invention, during the selective removal of triple-effect evaporation wastewater from an ABS workshop in Lianyungang using electrogenerated active oxygen, the COD concentration, total cyanide concentration, and ammonia nitrogen concentration changed with treatment time. V. Detailed Implementation Methods

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0034] Example 1:

[0035] A method for selectively removing total cyanide from acrylonitrile wastewater using electrogenerated active oxygen specifically includes the following steps: First, preparing acrylonitrile wastewater containing compounds such as acrylonitrile, succinic anion, methyl acrylate, acrylamide, and cyanide. This acrylonitrile wastewater mainly originates from acrylonitrile, acrylic fiber, and ABS plastic production processes, wherein the concentration of organic nitrile compounds is between 100–3000 mg / L, and the concentration of cyanide ions is between 10–200 mg / L; preparing a manganese-cerium composite metal oxide coated electrode, firstly selecting a titanium plate of suitable area as a substrate. The bottom was polished smooth with 20-mesh, 200-mesh, and 800-mesh sandpaper respectively to remove the surface oxide layer. It was then boiled in a 10% oxalic acid aqueous solution for 30 minutes and stored in a 1% oxalic acid aqueous solution for later use. Nitrogen-boron-doped graphene, manganese nitrate, cerium nitrate, ethylene glycol, and citric acid were mixed evenly in a mass ratio of 0.012:2:0.17:25:1.7 to form a reddish-brown viscous solution. An appropriate amount of nitric acid was added dropwise until the pH value was between 2 and 3. The solution was allowed to stand at room temperature for 72 hours to achieve complete oxidation. The mixture is aged to form a semi-solid composite metal oxide gel. The composite metal oxide gel obtained in the above steps is heated in an oven at 100°C for 30 minutes to restore its fluidity. Then, the composite metal oxide gel and an equal volume of ethanol are introduced into a spraying device, where they are atomized into droplets under the propulsion of an airflow and uniformly sprayed onto the surface of the titanium plate obtained in the above steps. When the composite metal oxide gel evenly covers the surface of the titanium plate and reaches an estimated thickness of 1 mm, spraying is stopped, and the titanium plate is transferred to an oven and dried at 150°C for 15 minutes. After 10 minutes, the titanium plate is transferred to a muffle furnace and calcined at 450°C for 10 minutes. The quenching process is then removed, and the plate is simply rinsed to remove carbon black and fly ash, ensuring a smooth surface. This process is repeated 8–18 times. Afterward, the titanium plate coated with the composite metal oxide is calcined under hot-pressing conditions at 10 MPa and 550°C for 4 hours to achieve a stable bond between the oxide coating and the titanium substrate. After releasing the pressure, it is annealed at room temperature to obtain the manganese-cerium composite metal oxide coated electrode. Scanning electron microscope and X-ray diffraction images of the electrode are attached. Figure 1 and attached Figure 2As shown; using the manganese-cerium composite metal oxide coated electrode obtained in the above steps as the anode and a stainless steel electrode of equal area as the cathode, maintaining a distance of 2 cm between the anode and cathode, the two electrodes are connected to the positive and negative terminals of a DC pulse power supply by wires, respectively, and immersed in acrylonitrile wastewater. The power supply is started and carbon dioxide is used to aerate and impact the manganese-cerium composite metal oxide coated electrode. The DC pulse power supply operates in constant current mode with a current density of 3–5 mA / cm². 2 Depending on the concentration and quality of the acrylonitrile wastewater, after a period of reaction, dense yellowish-brown scum and foam gradually form on the water surface, which are oligomers of nitrile formed on the anode surface. These need to be scraped or blown away in time. When the reaction is nearing its end, the solution gradually becomes colorless and clear, and no more oligomer foam is produced. This determines the reaction endpoint. The above water samples are then taken and analyzed to determine the changes in water quality indicators such as COD, total cyanide, and ammonia nitrogen, so as to determine the pollutant removal efficiency and unit energy consumption.

[0036] Example 2:

[0037] Following the operating procedure in Example 1, an electrocatalytic reactor for treating acrylonitrile wastewater was constructed. This reactor employed parallel plate electrodes with an electrode area of ​​15 × 15 cm. 2 The system consists of five double-sided anodes and six stainless steel cathodes. The anodes and cathodes are connected in parallel to the positive and negative terminals of a DC pulse power supply, respectively. The theoretical area for the electrochemical reaction is 2250 cm². 2 The reactor has an anode-cathode distance of 2 cm, an effective reaction volume of 5.4 L, and a total reaction volume of 6 L. This reactor was used to treat wastewater from an acrylonitrile workshop in Daqing. The reactor operated under constant current (11.25 A) and cell voltage (8.75 V). During the reaction, the anode plates were continuously aerated and flushed with CO2 at a flow rate of 500 mL / min. After 5 minutes of reaction, a large amount of scum and foam were rapidly generated, and the wastewater color gradually faded. During electrolysis, the scum and foam were continuously blown away with airflow. The reaction was terminated when the wastewater became completely colorless and no more foam was produced.

[0038] Depend on Figure 3 As can be seen, the raw acrylonitrile wastewater had a COD concentration of 1250 mg / L, total cyanide of 75 mg / L, and ammonia nitrogen of 450 mg / L. After electrolytic treatment for 45 minutes, the COD concentration decreased to 353.5 mg / L, total cyanide to 0.452 mg / L, and ammonia nitrogen to 18.4 mg / L, meeting the Class II standard of the "Integrated Wastewater Discharge Standard" GB8978-1996. At this point, the energy consumption per ton of wastewater treated was 12.3 kWh / m³. 3 It has significantly lower processing costs than traditional methods.

[0039] Example 3:

[0040] Using the operating procedure in Example 1 and the electrocatalytic reactor in Example 2, the triple-effect evaporation wastewater from an ABS workshop in Lianyungang was treated. The constant current operation was used with a current of 22.5A and a cell voltage of 10.42V. During the reaction, the anode plates were continuously aerated and rinsed with CO2 at a flow rate of 1000mL / min. After the reaction started, a large amount of scum and foam were quickly generated, and the color of the wastewater gradually faded. During the electrolysis process, the scum and foam were continuously blown away with airflow. The reaction was terminated when the wastewater color became completely colorless and no more foam was generated.

[0041] Depend on Figure 4 It can be seen that the COD concentration in the raw wastewater from the triple-effect evaporation was 7750 mg / L, total cyanide was 200 mg / L, and ammonia nitrogen was 1265 mg / L. After electrolysis for 120 minutes, the COD concentration was 1240 mg / L, total cyanide was 0.987 mg / L, and ammonia nitrogen was 17 mg / L, meeting the Class III standard of the "Integrated Wastewater Discharge Standard" GB8978-1996. At this point, the energy consumption per ton of wastewater treated was 78.15 kWh / m³. 3 It has significantly lower processing costs than traditional methods.

[0042] Example 4:

[0043] Using the operating procedure in Example 1 and the electrocatalytic reactor in Example 2, wastewater from an acrylonitrile workshop in Fushun was treated. The operation was constant current, with a current of 15A and a cell voltage of 7.2V. During the reaction, the anode plates were continuously aerated and rinsed with CO2 at a flow rate of 250mL / min. After the reaction started, a large amount of scum and foam were rapidly generated, and the color of the wastewater gradually faded. During the electrolysis process, the scum and foam were continuously blown away with airflow. The reaction was terminated when the wastewater color became completely colorless and no more foam was generated.

[0044] The raw acrylonitrile wastewater had a COD concentration of 720 mg / L, total cyanide of 14.2 mg / L, and ammonia nitrogen of 65.7 mg / L. After 60 minutes of electrolytic treatment, the COD concentration decreased to 226 mg / L, total cyanide to 0.96 mg / L, and ammonia nitrogen to 17.2 mg / L, meeting the Class III standard of the Integrated Wastewater Discharge Standard GB8978-1996. The energy consumption per ton of wastewater treated at this point was 18 kWh / m³. 3 It has significantly lower processing costs than traditional methods.

[0045] The specific embodiments described above are only used to illustrate the spirit of the present invention. The scope of protection of the present invention is not limited thereto. For those skilled in the art, other embodiments can be easily made by means of changes, substitutions or modifications based on the technical content disclosed in this specification. All such other embodiments should be covered within the scope of protection of the present invention.

Claims

1. A method for selectively removing total cyanide from acrylonitrile wastewater by electrogenerating active oxygen, characterized in that, The method includes the following steps: Step 1: Prepare acrylonitrile wastewater containing acrylonitrile, succinic anhydride, methyl acrylate, acrylamide, and cyanide; Step 2: Prepare manganese-cerium composite metal oxide coated electrode. First, select a titanium plate of appropriate area as the substrate and polish it with 20-mesh, 200-mesh and 800-mesh sandpaper respectively until smooth to remove the surface oxide layer. Then, boil it in a 10% oxalic acid aqueous solution for 30 minutes and store it in a 1% oxalic acid aqueous solution for later use. Step 3: Mix nitrogen-boron-doped graphene, manganese nitrate, cerium nitrate, ethylene glycol, and citric acid in a mass ratio of 0.012:2:0.17:25:1.7 to form a reddish-brown viscous solution. Add an appropriate amount of nitric acid until the pH value is between 2 and 3. Let it stand at room temperature for 72 hours to achieve full aging and form a semi-solid composite metal oxide gel. Step 4: Heat the composite metal oxide gel obtained in Step 3 in an oven at 100°C for 30 minutes to restore its fluidity. Then, introduce the composite metal oxide gel and an equal volume of ethanol into the spraying device. Under the propulsion of the airflow, form atomized droplets and spray them evenly onto the surface of the titanium plate described in Step 2. Step 5: When the composite metal oxide gel on the surface of the titanium plate is evenly covered and reaches a visual thickness of 1 mm, stop spraying, transfer the titanium plate to an oven, dry it at 150°C for 15 minutes, then transfer it to a muffle furnace and bake it at 450°C for 10 minutes. Remove the titanium plate from the quenching process and rinse it simply to wash away the carbon black and fly ash adhering to the surface and keep the surface flat. Step 6: Repeat steps 4 and 5 a total of 8–18 times. After the operation is completed, the titanium plate with the composite metal oxide coating is kept under hot pressing at 10 MPa and 550°C for 4 hours to achieve a stable bond between the oxide coating and the titanium substrate. After the pressure is removed, it is annealed at room temperature to obtain the manganese cerium composite metal oxide coated electrode. Step 7: Using the manganese-cerium composite metal oxide coated electrode obtained in step 6 as the anode and the stainless steel of the same area as the cathode, keeping the distance between the anode and cathode at 2 cm, connect the two electrodes to the positive and negative terminals of the DC pulse power supply with wires respectively, immerse in the acrylonitrile wastewater described in step 1, start the power supply and aerate with carbon dioxide to impact the manganese-cerium composite metal oxide coated electrode. Step 8: Depending on the concentration and quality of the acrylonitrile wastewater, after a period of reaction, dense yellowish-brown scum and foam gradually form on the water surface. These are oligomers of nitrile formed on the anode surface. They need to be scraped or blown away in time. When the reaction is nearing its end, the solution gradually becomes colorless and clear, and no more oligomer foam is produced. This determines the reaction endpoint. The resulting water sample is then taken and analyzed to determine the changes in COD, total cyanide, and ammonia nitrogen in the water, in order to determine the pollutant removal efficiency and unit energy consumption.

2. The method for selectively removing total cyanide from acrylonitrile wastewater by electrogenerating active oxygen as described in claim 1, characterized in that, The acrylonitrile wastewater mentioned in step 1 mainly comes from the production processes of acrylonitrile, acrylic fiber, and ABS plastics, with the concentration of organic nitrile compounds ranging from 100 to 3000 mg / L and the concentration of cyanide ions ranging from 10 to 200 mg / L.

3. The method for selectively removing total cyanide from acrylonitrile wastewater by electrogenerating active oxygen as described in claim 1, characterized in that, The DC pulse power supply described in step 7 operates in constant current mode with a current density of 3–5 mA / cm². 2 .

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