An integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates, and its application method.

Abstract

This invention relates to an integrated electrochemical device and its application method for bipolar Fenton electrolysis of pollutants and synergistic nitrate-to-ammonia production. The integrated electrochemical device includes a dual-chamber electrolytic cell with a pollutant degradation chamber and a nitrate reduction chamber. The pollutant degradation chamber contains a first cathode and an anode, enabling the degradation of organic pollutants in wastewater. The nitrate reduction chamber contains a second cathode, enabling the reduction of nitrates in wastewater. This invention also provides an application of the integrated electrochemical device in wastewater treatment, comprising: placing wastewater in the nitrate reduction chamber of the integrated electrochemical device; connecting the first and second cathodes to the negative electrode and the anode to the positive electrode; applying electricity, the wastewater first undergoes nitrate reduction to produce ammonia in the nitrate reduction chamber, then flows into the pollutant degradation chamber for the degradation of organic pollutants, while simultaneously pumping new wastewater into the nitrate reduction chamber; achieving a cyclic treatment. This invention simultaneously achieves the degradation of organic pollutants in wastewater and the resource recovery of nitrates.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to an integrated electrochemical device and its application method for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates. Background Technology

[0002] The rapid development of my country's modern industry and the stringent requirements of wastewater discharge standards have posed significant challenges to industrial wastewater treatment technology. Industrial wastewater is characterized by large fluctuations in pollutant concentrations, complex and varied composition, and a high variety and concentration of toxic and recalcitrant pollutants. Unlike domestic sewage, industrial wastewater from industries such as coking, leather tanning, electroplating, textiles, and livestock farming contains high concentrations of nitrates and COD. COD is primarily composed of recalcitrant organic pollutants. Simultaneously, nitrifying bacteria in the water oxidize nitrogenous compounds and ammonia nitrogen into nitrate nitrogen, which accumulates in the water. Therefore, the presence of large amounts of recalcitrant organic pollutants and high concentrations of nitrates are common characteristics of most industrial wastewater. Industrial wastewater treatment has become a serious challenge facing the field of water pollution control and remediation. Summary of the Invention

[0003] The purpose of this invention is to provide an integrated electrochemical device and its application method for bipolar electro-Fenton degradation of pollutants and synergistic nitrate ammonia production, so as to simultaneously realize the degradation of organic pollutants in wastewater and the resource recovery of nitrate reduction for ammonia production.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] An integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates includes a dual-chamber electrolytic cell with a pollutant degradation chamber and a nitrate reduction chamber, the pollutant degradation chamber and the nitrate reduction chamber being separated by a diaphragm;

[0006] The pollutant degradation chamber is equipped with a first cathode and an anode, and the pollutant degradation chamber can degrade organic pollutants in wastewater;

[0007] The nitrate reduction chamber is equipped with a second cathode, which enables the reduction of nitrates in wastewater.

[0008] Based on the aforementioned technical means, a dual-chamber electrolytic cell is constructed by separating the pollutant degradation chamber and the nitrate reduction chamber with a diaphragm. A first cathode and anode are installed in the pollutant degradation chamber, and a second cathode is installed in the nitrate reduction chamber. This allows wastewater to first undergo nitrate reduction to produce ammonia on the surface of the second cathode in the nitrate reduction chamber. Simultaneously, the wastewater that has undergone nitrate reduction to produce ammonia enters the pollutant degradation chamber, where Fe2+ is generated at the anode. 2+ Activate the hydrogen peroxide generated in situ at the first cathode to achieve efficient and continuous production. ·OH is used to degrade organic pollutants in wastewater, thus successfully achieving both the degradation of organic pollutants and the recovery of nitrates. Simultaneously, this invention features an integrated electrochemical device with a dual-chamber electrolytic cell. The use of a dual-cathode system effectively reduces the operating potential, thereby significantly reducing the energy consumption of the system. This effectively solves the problem that existing electro-Fenton technology struggles to simultaneously achieve efficient in-situ generation and activation of H2O2 and continuous treatment of Fe. 2+ This solution addresses issues such as insufficient utilization efficiency, interference from nitrate quenching of active species in the pollutant degradation process, the generation of more toxic byproducts from intermediate pollutant products, and the difficulty in achieving simultaneous removal of pollutants and nitrates. It provides a novel solution for the simultaneous purification and resource recovery of nitrate-containing industrial wastewater.

[0009] Preferably, the first cathode is selected from a gas diffusion cathode.

[0010] Preferably, the anode is selected from at least one of iron sheet and transition metal sheet.

[0011] Preferably, the transition metal sheet includes at least cobalt, copper, and manganese.

[0012] Preferably, the second cathode is selected from at least one of carbon paper, carbon cloth, and nickel foam.

[0013] Preferably, the thickness of the iron sheet is between 0.1 mm and 1 cm.

[0014] Preferably, the diaphragm is selected from proton exchange membranes.

[0015] Preferably, the pollutant degradation chamber is also connected to an air pump via a gas pipe, through which air is introduced into the gas diffusion cathode to form a three-phase interface, thereby enhancing mass transfer and increasing the amount of H2O2 generated during the electrochemical reaction.

[0016] Preferably, both the pollutant degradation chamber and the nitrate reduction chamber are connected to peristaltic pumps. The wastewater after nitrate reduction to ammonia is pumped into the pollutant degradation chamber for degradation by the peristaltic pumps. This effectively avoids interference problems such as nitrate quenching active species or producing more toxic byproducts with intermediate products of pollutants. At the same time, new wastewater is added to the nitrate reduction chamber to achieve cyclic treatment.

[0017] Preferably, the structure of the gas diffusion cathode consists of an activated carbon substrate and a coagulated paste coated on the activated carbon substrate, wherein the coagulated paste comprises at least a conductive material and polytetrafluoroethylene.

[0018] Preferably, the carbon paper cathode is loaded with a catalyst, and the catalyst comprises at least iron(III) oxide (Fe3O4).

[0019] Preferably, the iron(III) oxide (Fe3O4) is synthesized using a two-step method of gas-phase assisted hydrothermal treatment and high-temperature copolymerization.

[0020] Experimental tests revealed that Fe3O4, synthesized through a two-step method of gas-phase assisted hydrothermal treatment and high-temperature copolymerization, has more oxygen vacancies, which facilitates the adsorption and reduction of nitrates to produce ammonia.

[0021] Preferably, the method for preparing the gas diffusion cathode includes the following steps:

[0022] A conductive material, polytetrafluoroethylene emulsion, and organic solvent are mixed to obtain a coagulated paste.

[0023] A condensed paste was coated onto an activated carbon substrate, dried, and calcined to obtain a gas diffusion cathode.

[0024] By mixing conductive materials, polytetrafluoroethylene emulsion, and organic solvents to form a coagulated paste, it is easier to hot-press it onto a substrate to form a three-phase interface. At the same time, by calcining the hot-pressed coagulated paste and the activated carbon substrate, the interface formed between the material and the substrate is effectively stabilized.

[0025] Preferably, the mass ratio of the conductive material to the polytetrafluoroethylene emulsion is between 1:1 and 5:1.

[0026] Preferably, the polytetrafluoroethylene emulsion contains 30% to 60% polytetrafluoroethylene by mass.

[0027] Preferably, the conductive material, polytetrafluoroethylene emulsion, and organic solvent are mixed using ultrasound, and the ultrasound time is between 30 min and 60 min.

[0028] Preferably, the agglomerated paste is coated onto an activated carbon substrate by hot pressing, with the hot pressing temperature between 30°C and 60°C and the hot pressing pressure between 0.5 MPa and 1.5 MPa.

[0029] Preferably, the calcination temperature is between 300℃ and 400℃, and the calcination time is between 1h and 3h.

[0030] Preferably, the conductive material is selected from at least one of conductive carbon black, acetylene black, and carbon nanotubes.

[0031] Preferably, the organic solvent is selected from anhydrous ethanol.

[0032] Preferably, the activated carbon substrate is selected from hydrophobic activated carbon cloth and / or hydrophobic carbon felt.

[0033] By using hydrophobic activated carbon cloth as the activated carbon substrate, a three-phase (gas phase, solid phase and liquid phase) interface is formed in the gas diffusion cathode, which effectively promotes interfacial mass transfer and thus enhances the generation of H2O2.

[0034] Preferably, the size of the hydrophobic activated carbon cloth is 1×1cm. 2 ~5×5cm 2 between.

[0035] Preferably, the method for preparing the carbon paper cathode includes the following steps:

[0036] Iron salt and dicyandiamide were placed in a reaction flask, then the reaction flask was placed in a reaction vessel, and water was added between the reaction vessel and the reaction flask. A gas-phase assisted hydrothermal reaction was then carried out to obtain a solid.

[0037] The solid was calcined to achieve high-temperature copolymerization, yielding the iron(III) oxide (Fe3O4);

[0038] The Fe3O4 oxide, organic solvent, and binder are mixed, coated onto carbon paper, and dried to obtain a carbon paper cathode.

[0039] Preferably, the mass ratio of the iron salt to dicyandiamide is 0.1:1 to 1:1.

[0040] Preferably, the iron salt is selected from at least one of ferric chloride, ferric chloride hexahydrate (FeCl3·6H2O), ferric sulfate, and ferric nitrate.

[0041] Preferably, the temperature of the gas-phase assisted hydrothermal reaction is between 160°C and 200°C, and the time of the gas-phase assisted hydrothermal reaction is between 6 hours and 18 hours.

[0042] By properly controlling the temperature of the gas-phase assisted hydrothermal reaction, it is beneficial to the formation of metal precursors.

[0043] Preferably, the calcination temperature is between 400℃ and 600℃, and the calcination time is between 2h and 6h.

[0044] By rationally controlling the calcination temperature, the content of oxygen vacancies was effectively controlled, which is beneficial for the electrocatalytic reduction of nitrates.

[0045] Preferably, the volume ratio of the organic solvent to the adhesive is 5:1 to 10:1.

[0046] Preferably, the organic solvent is selected from ethanol.

[0047] Preferably, the adhesive is selected from a perfluorosulfonic acid polymer solution (nafion).

[0048] Preferably, the carbon paper is selected from hydrophilic carbon paper.

[0049] Preferably, the size of the hydrophilic carbon paper is 1×1cm. 2 ~5×5cm 2 between.

[0050] Preferably, the water is deionized water.

[0051] Preferably, the Fe3O4, organic solvent and binder are mixed using ultrasound, and the ultrasound time is between 30 min and 120 min.

[0052] Preferably, the calcination is carried out by programmed heating at a rate of 2.5°C / min.

[0053] The present invention also provides an application method for an integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic nitrate ammonia production as described in the present invention, wherein the integrated electrochemical device is used for wastewater treatment;

[0054] The integrated electrochemical device can degrade organic pollutants in wastewater and reduce nitrates in wastewater to produce ammonia.

[0055] Preferably, the wastewater is industrial wastewater from the coking, leather making, electroplating, textile and livestock farming industries.

[0056] Studies have shown that advanced oxidation technologies (AORs) are highly effective in treating recalcitrant organic pollutants. These technologies utilize the generation of highly oxidizing free radicals to attack large organic molecules, causing them to undergo ring-opening and breakage, ultimately mineralizing them into CO2, water, and inorganic ions. This has garnered widespread attention from researchers and engineers. AORs mainly include chemical oxidation, photochemical oxidation, critical water oxidation, wet air oxidation, and ferrate processes. Among these, electrochemical AORs, represented by the electro-Fenton process, offer milder reaction conditions, simpler operation, relatively lower cost, and wider applicability, showing promising prospects in wastewater treatment. However, current systems rely on the addition of Fe... 2+ This increased costs and the excessive Fe 2+ Nitrates may be oxidized at the anode, reducing their utilization rate. Furthermore, the electro-Fenton system only focuses on the degradation of organic pollutants, neglecting the hazards of inorganic pollutants, primarily nitrates, in actual wastewater. The presence of nitrates not only damages aquatic ecosystems but can also be absorbed by the human body and converted into nitrites, harming human health. Although nitrates are a hazard in wastewater, they are also a potential resource. Existing research has explored the reduction of nitrates to the high-value product ammonia through biocatalysis, photocatalysis, or electrocatalysis for recovery. Among these methods, electrocatalysis has gained favor due to its advantages such as renewable electricity, high efficiency, no need for chemical reagents, mild reaction conditions, environmental friendliness, and modularity.

[0057] Therefore, through extensive research and long-term experiments, this application has developed a system for the simultaneous degradation of organic pollutants and the reduction of nitrates to produce ammonia. This system not only achieves wastewater purification and resource recovery, but also realizes key cost reduction and efficiency improvement in actual wastewater treatment processes.

[0058] Preferably, the application method includes the following steps:

[0059] Wastewater is placed in the nitrate reduction chamber of the integrated electrochemical device described in this invention;

[0060] Connect the first and second cathodes to the negative electrode and the anode to the positive electrode;

[0061] When energized, the wastewater is first treated in the nitrate reduction chamber by the second cathode to reduce nitrates and produce ammonia. Then, the nitrate-removed wastewater is placed in the pollutant degradation chamber, where hydrogen peroxide is generated in situ at the first cathode and Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals to degrade organic pollutants in wastewater, while new wastewater is pumped into the nitrate reduction chamber to reduce nitrates and produce ammonia; thus achieving a cyclical treatment.

[0062] Based on the above technical means, the integrated electrochemical device with a dual-chamber electrolytic cell of the present invention is used to treat wastewater. Without the need for external addition of iron ions and H2O2, highly selective nitrate reduction to ammonia is achieved in the nitrate reduction chamber using the second cathode. Simultaneously, in another pollutant degradation chamber separated by a proton exchange membrane, the hydrogen peroxide generated in situ at the first cathode is used to generate Fe in situ at the anode. 2+ The activation process efficiently generates strong oxidizing free radicals, thereby effectively degrading organic pollutants in wastewater. The two chambers work together to achieve wastewater purification and resource recovery.

[0063] Preferably, the wastewater is wastewater containing nitrates and organic pollutants.

[0064] Preferably, the organic pollutant includes at least one of naproxen, tetracycline, methyl orange, and rhodamine B.

[0065] Preferably, the voltage applied is between -0.8V and 2.0V.

[0066] By rationally controlling the voltage applied, the occurrence of side reactions such as hydrogen evolution at the cathode was reduced, while the anode Fe was regulated. 2+ The appropriate precipitation rate.

[0067] Preferably, the application method includes the following steps:

[0068] Wastewater is placed in the nitrate reduction chamber of the integrated electrochemical device described in this invention;

[0069] Connect the first and second cathodes to the negative electrode and the anode to the positive electrode;

[0070] When energized, wastewater is first treated in the nitrate reduction chamber by the second cathode to reduce nitrates and produce ammonia. Then, a peristaltic pump pumps the nitrate-removed wastewater into the pollutant degradation chamber, where hydrogen peroxide is generated in situ at the first cathode and Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals to degrade organic pollutants in wastewater. At the same time, new wastewater is pumped into the nitrate reduction chamber to carry out the nitrate reduction reaction and produce ammonia; thus achieving a cycle treatment.

[0071] In the initial wastewater treatment, the integrated electrochemical device can be filled with a solution containing 50 mM Na2SO4 in the pollutant degradation chamber to ensure the smooth progress of the electrochemical reaction.

[0072] The wastewater treatment system of the integrated electrochemical device with a dual-chamber electrolytic cell of the present invention not only reduces the cost of external Fenton reagent addition, but also prevents Fe from being added during continuous treatment. 2+ The invention addresses the issue of insufficient utilization efficiency. Furthermore, within the nitrate reduction chamber, nitrate undergoes a reduction reaction on the surface of a preferred Fe3O4-supported carbon paper cathode, efficiently producing ammonia. The separate treatment in the two chambers resolves the interference problems caused by nitrate competing for active species and generating toxic byproducts during pollutant degradation, achieving simultaneous pollutant degradation and nitrate reduction for ammonia production. Simultaneously, the integrated electrochemical device with a dual-chamber electrolytic cell of this invention effectively reduces the operating potential through the use of a dual-cathode system, thereby significantly reducing the energy consumption of the system.

[0073] Preferably, the first cathode and the second cathode are connected to the negative electrode of the electrochemical workstation, and the anode is connected to the positive electrode of the electrochemical workstation.

[0074] The main chemical reactions occurring in the dual-chamber electrolytic cell of this invention are as follows:

[0075] Anode: Fe is produced through electrolysis. 2+ The specific reaction formula is:

[0076] Fe 0 →Fe 2+ +2e - (1)

[0077] The first cathode, i.e., the gas diffusion cathode, produces hydrogen peroxide through oxygen reduction and then electrolyzes Fe at the anode. 2+ Under the activation effect, hydroxyl radicals are efficiently generated. The specific reaction formula is as follows:

[0078] O2 + 2H + +2e -→H2O2 (2)

[0079] Fe 2+ +H₂O₂→Fe 3+ +OH - + · OH (3)

[0080] Fe 3+ +e - →Fe 2+ (4)

[0081] The second cathode, namely the carbon paper cathode, reduces nitrates to ammonia through the combined action of direct electroreduction by electrons transferred on the cathode surface and indirect electroreduction by atomic hydrogen generated from water electrolysis. The specific reaction formula is as follows:

[0082] NO3 - +H₂O + 2e - →NO2 - +2OH - (5)

[0083] NO2 - +6H2O+6e - →NH4 + +8OH - (6)

[0084] 2H2O+2e - →2H*+2OH - (7)

[0085] 3NO3 - +H*→NO2 - +NH4 + +N2+H2O (8)

[0086] 3NO2 - +H*→NH4 + +N2+H2O (9).

[0087] The electrochemical treatment method provided by this invention is not limited by concentration and can efficiently treat wastewater containing different pollutants and different nitrate concentrations.

[0088] The beneficial effects of this invention are:

[0089] 1) The integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic nitrate ammonia production of the present invention comprises a dual-chamber electrolytic cell with a diaphragm separating the pollutant degradation chamber and the nitrate reduction chamber. A first cathode and an anode are located in the pollutant degradation chamber, and a second cathode is located in the nitrate reduction chamber. This allows wastewater to first undergo nitrate reduction to produce ammonia on the surface of the second cathode in the nitrate reduction chamber. Simultaneously, the wastewater that has undergone nitrate reduction to produce ammonia enters the pollutant degradation chamber, where Fe2+ is generated at the anode.2+ Activate the hydrogen peroxide generated in situ at the first cathode to achieve efficient and continuous production. · OH is used to degrade organic pollutants in wastewater, thus successfully achieving both the degradation of organic pollutants and the recovery of nitrates. Simultaneously, the integrated electrochemical device with a dual-chamber electrolytic cell of this invention, through the use of a dual-cathode system, effectively reduces the operating potential, thereby significantly reducing the energy consumption of the system. This effectively solves the problem that existing electro-Fenton technology struggles to simultaneously achieve efficient in-situ generation and activation of H2O2 and continuous treatment of Fe... 2+ This paper addresses issues such as insufficient utilization efficiency, interference from nitrate quenching of active species in the pollutant degradation process, and the generation of more toxic byproducts from intermediate pollutant products. It also addresses the difficulty in achieving simultaneous removal of pollutants and nitrates, and proposes a novel solution for the treatment of nitrate-containing industrial wastewater that simultaneously purifies wastewater and recovers resources.

[0090] 2) The application method of the integrated electrochemical device for bipolar Fenton degradation of pollutants and synergistic nitrate ammonia production according to the present invention: The integrated electrochemical device with a dual-chamber electrolytic cell of the present invention is used to treat wastewater. Without the need for external addition of iron ions and H2O2, highly selective nitrate reduction to ammonia production is achieved in the nitrate reduction chamber using the second cathode. Simultaneously, in the other pollutant degradation chamber separated by the proton exchange membrane, the hydrogen peroxide generated in situ at the first cathode generates Fe in situ at the anode. 2+ The activation process efficiently generates strong oxidizing free radicals, thereby effectively degrading organic pollutants in wastewater. The two chambers work together to achieve wastewater purification and resource recovery. At the same time, the integrated electrochemical device with a dual-chamber electrolytic cell of this invention effectively reduces the operating potential by using a dual-cathode system, thereby effectively reducing the energy consumption of the system. It also has the advantages of simple operation, low cost and no secondary pollution, making it more valuable for industrial production and having potential application value in the field of wastewater treatment technology. Attached Figure Description

[0091] Figure 1 This is a schematic diagram of the integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates according to the present invention.

[0092] Figure 2 The graph shows the degradation performance of nitrates and organic pollutants.

[0093] Figure 3 The graph shows the changes in pollutant degradation over time in single-chamber and double-chamber electrolytic cells.

[0094] Figure 4 A comparison chart of the removal rates of naproxen and nitrate;

[0095] Among them, 1-second cathode; 2-diaphragm; 3-anode; 4-first cathode; 5-air pump; 6-peristaltic pump; 7-electrochemical workstation. Detailed Implementation

[0096] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0097] The present invention aims to disclose an integrated electrochemical device and its application method for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates, so as to simultaneously achieve the degradation of organic pollutants in wastewater and the resource recovery of nitrates.

[0098] Among them, such as Figure 1 As shown, the integrated electrochemical device for bipolar Fenton degradation of pollutants and synergistic ammonia production from nitrates includes a dual-chamber electrolytic cell with a pollutant degradation chamber and a nitrate reduction chamber, which are separated by a diaphragm 2.

[0099] The pollutant degradation chamber is equipped with a first cathode 4 and an anode 3, and the pollutant degradation chamber can degrade organic pollutants in wastewater;

[0100] The nitrate reduction chamber is equipped with a second cathode 1, which enables the reduction of nitrates in wastewater.

[0101] A dual-chamber electrolytic cell is constructed by separating the pollutant degradation chamber and the nitrate reduction chamber using a diaphragm. A first cathode and anode are located in the pollutant degradation chamber, and a second cathode is located in the nitrate reduction chamber. This allows the Fe produced at the anode in the pollutant degradation chamber to... 2+ Activate the hydrogen peroxide generated in situ at the first cathode to achieve efficient and continuous production. · OH is used to degrade organic pollutants in wastewater, while simultaneously reducing nitrates to ammonia on the surface of the second cathode in the nitrate reduction chamber. This successfully achieves both the degradation of organic pollutants and the resource recovery of nitrates. Furthermore, the integrated electrochemical device with a dual-chamber electrolytic cell of this invention effectively reduces the operating potential through the use of a dual-cathode system, thereby significantly reducing the energy consumption of the system. This effectively solves the problem that existing electro-Fenton technology struggles to simultaneously achieve efficient in-situ generation and activation of H2O2 and continuous processing of Fe. 2+This solution addresses issues such as insufficient utilization efficiency; interference from nitrate quenching of active species in the pollutant degradation process, leading to more toxic byproducts from intermediate pollutant products; and the difficulty in achieving simultaneous removal of pollutants and nitrates. It aims to provide a novel solution for the simultaneous purification and resource recovery of nitrate-containing industrial wastewater.

[0102] In some embodiments, the first cathode 4 is selected from a gas diffusion cathode.

[0103] In some embodiments, the anode 3 is selected from at least one of iron sheet and transition metal sheet.

[0104] For example, transition metal sheets include cobalt, copper, and manganese.

[0105] In some embodiments, the second cathode 1 is selected from at least one of carbon paper, carbon cloth, and nickel foam.

[0106] In some embodiments, the thickness of the iron sheet is between 0.1 mm and 1 cm.

[0107] In some embodiments, the diaphragm 2 is selected from a proton exchange membrane.

[0108] In some embodiments, the pollutant degradation chamber is also connected to an air pump 5 via an air pipe. The air pump introduces air into the gas diffusion cathode to form a three-phase interface, thereby enhancing mass transfer and increasing the amount of H2O2 generated during the electrochemical reaction.

[0109] In some embodiments, both the pollutant degradation chamber and the nitrate reduction chamber are connected to a peristaltic pump 6. The wastewater after nitrate reduction to produce ammonia is pumped into the pollutant degradation chamber for degradation by the peristaltic pump 6. This effectively avoids interference problems such as nitrate quenching active species or producing more toxic byproducts with intermediate products of pollutants. At the same time, new wastewater is added to the nitrate reduction chamber to achieve cyclic treatment.

[0110] In some embodiments, the structure of the gas diffusion cathode consists of an activated carbon substrate and a coagulated paste coated on the activated carbon substrate, wherein the coagulated paste comprises at least a conductive material and polytetrafluoroethylene.

[0111] In some embodiments, a catalyst is supported on the carbon paper cathode, and the catalyst comprises at least iron(Fe3O4) oxide.

[0112] In some embodiments, in order to give iron(III) oxide (Fe3O4) more oxygen vacancies to help nitrate adsorption and reduction to produce ammonia, iron(III) oxide (Fe3O4) is synthesized by a two-step method of gas-phase assisted hydrothermal treatment and high-temperature copolymerization.

[0113] In some embodiments, the method for preparing a gas diffusion cathode includes the following steps:

[0114] Conductive material, polytetrafluoroethylene emulsion and organic solvent are mixed. To facilitate the subsequent formation of a three-phase interface, the mixture is ultrasonically treated to obtain a coagulated paste.

[0115] A condensed paste was coated onto an activated carbon substrate, dried, and calcined to obtain a gas diffusion cathode.

[0116] In some embodiments, the mass ratio of the conductive material to the polytetrafluoroethylene emulsion is between 1:1 and 5:1.

[0117] In some embodiments, the polytetrafluoroethylene emulsion contains 30% to 60% by mass.

[0118] In some embodiments, the conductive material, polytetrafluoroethylene emulsion, and organic solvent are mixed using ultrasound for a duration between 30 and 60 minutes.

[0119] In some embodiments, the agglomerated paste is coated onto an activated carbon substrate by hot pressing, with the hot pressing temperature between 30°C and 60°C and the hot pressing pressure between 0.5 MPa and 1.5 MPa.

[0120] In some embodiments, in order to stabilize the interface formed between the material and the substrate as much as possible, the calcination temperature is controlled between 300°C and 400°C, and the calcination time is between 1 hour and 3 hours.

[0121] In some embodiments, the conductive material is selected from at least one of conductive carbon black, acetylene black, and carbon nanotubes. This can be understood as the conductive material being selected from conductive carbon black, acetylene black, or carbon nanotubes, or it can be a mixture of conductive carbon black and acetylene black, a mixture of conductive carbon black and carbon nanotubes, or a mixture of acetylene black and carbon nanotubes, or even a mixture of all three.

[0122] For example, the organic solvent is selected from anhydrous ethanol.

[0123] For example, in order to ensure that the fabricated gas diffusion cathode forms a three-phase (gas phase, solid phase and liquid phase) interface to promote interfacial mass transfer and thereby enhance the generation of H2O2, the activated carbon substrate is selected from hydrophobic activated carbon cloth.

[0124] For example, the size of the hydrophobic activated carbon cloth is 1×1cm. 2 ~5×5cm 2 between.

[0125] In some embodiments, the method for preparing the carbon paper cathode includes the following steps:

[0126] Iron salt and dicyandiamide were placed in a reaction flask, then the reaction flask was placed in a reaction vessel, and water was added between the reaction vessel and the reaction flask. A gas-phase assisted hydrothermal reaction was then carried out to obtain a solid.

[0127] The solid was calcined to obtain the iron(III) oxide (Fe3O4);

[0128] The Fe3O4 oxide, organic solvent, and binder are mixed, coated onto carbon paper, and dried to obtain a carbon paper cathode.

[0129] In some embodiments, the mass ratio of iron salt to dicyandiamide is 0.1:1 to 1:1.

[0130] For example, the iron salt is selected from at least one of ferric chloride, ferric chloride hexahydrate (FeCl3·6H2O), ferric sulfate, and ferric nitrate.

[0131] In some embodiments, the temperature of the gas-phase assisted hydrothermal reaction is between 160°C and 200°C, and the time of the gas-phase assisted hydrothermal reaction is between 6h and 18h.

[0132] In some embodiments, in order to control the oxygen vacancy content to facilitate electrocatalytic nitrate reduction, the calcination temperature is controlled between 400°C and 600°C, and the calcination time is controlled between 2h and 6h.

[0133] In some embodiments, the volume ratio of organic solvent to adhesive is 5:1 to 10:1.

[0134] For example, the organic solvent is selected from ethanol.

[0135] For example, the adhesive is selected from perfluorosulfonic acid polymer solutions (nafion).

[0136] For example, the carbon paper is selected from hydrophilic carbon paper.

[0137] For example, the size of the hydrophilic carbon paper is 1×1cm. 2 ~5×5cm 2 between.

[0138] For example, the water is deionized water.

[0139] In some embodiments, the iron(III) oxide (Fe3O4), organic solvent and adhesive are mixed by ultrasonication for a time between 30 min and 120 min.

[0140] For example, the calcination is carried out by programmed heating at a rate of 2.5°C / min.

[0141] The above-mentioned integrated electrochemical device for bipolar Fenton degradation of pollutants and synergistic ammonia production from nitrates is described in its application method, and the integrated electrochemical device is used for wastewater treatment.

[0142] Integrated electrochemical devices can degrade organic pollutants in wastewater and reduce nitrates in wastewater to produce ammonia.

[0143] For example, wastewater refers to industrial wastewater from industries such as coking, leather making, electroplating, textiles, and livestock and poultry farming.

[0144] The method for using the above-mentioned integrated electrochemical device for wastewater treatment includes the following steps:

[0145] Wastewater was placed in a dual-chamber electrolytic cell of the aforementioned integrated electrochemical device for bipolar Fenton degradation of pollutants and synergistic ammonia production from nitrates.

[0146] Connect the first cathode 4 and the second cathode 1 to the negative electrode, and connect the anode 3 to the positive electrode;

[0147] When electricity is applied, hydrogen peroxide is generated in situ at the first cathode, and Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals, which degrade organic pollutants in wastewater. At the same time, nitrates undergo a reduction reaction on the surface of the second cathode to produce ammonia.

[0148] In some embodiments, the wastewater is wastewater containing nitrates and organic pollutants.

[0149] For example, organic pollutants include at least one of naproxen, tetracycline, methyl orange, and rhodamine B.

[0150] In some embodiments, in order to effectively reduce the occurrence of side reactions such as hydrogen evolution at the cathode, and at the same time regulate the Fe content at the anode... 2+ To achieve an appropriate precipitation rate, the voltage is controlled to be between -0.8V and 2.0V.

[0151] The integrated electrochemical device with a dual-chamber electrolytic cell of the present invention treats wastewater without the need for external addition of iron ions and H2O2. In the pollutant degradation chamber, hydrogen peroxide generated in situ at the first cathode is used to generate Fe in situ at the anode. 2 + Under the activation of the proton exchange membrane, strong oxidizing free radicals are generated efficiently, thereby effectively degrading organic pollutants in wastewater. At the same time, another nitrate reduction chamber separated by the proton exchange membrane uses a second cathode to achieve highly selective nitrate reduction to produce ammonia. The two chambers work together to achieve wastewater purification and resource recovery.

[0152] The wastewater treatment system of the integrated electrochemical device with a dual-chamber electrolytic cell of the present invention not only reduces the cost of external Fenton reagent addition, but also prevents Fe from being added during continuous treatment.2+ The invention addresses the issue of insufficient utilization efficiency. Furthermore, within the nitrate reduction chamber, nitrate undergoes a reduction reaction on the surface of a preferred Fe3O4-supported carbon paper cathode, efficiently producing ammonia. The separate treatment in the two chambers resolves the interference problems caused by nitrate competing for active species and generating toxic byproducts during pollutant degradation, achieving simultaneous pollutant degradation and nitrate reduction for ammonia production. Simultaneously, the integrated electrochemical device with a dual-chamber electrolytic cell of this invention effectively reduces the operating potential through the use of a dual-cathode system, thereby significantly reducing the energy consumption of the system.

[0153] For example, the first cathode 1 and the second cathode 4 are connected to the negative electrode of the electrochemical workstation 7, and the anode 3 is connected to the positive electrode of the electrochemical workstation 7.

[0154] The main chemical reactions that occur in the dual-chamber electrolytic cell are as follows:

[0155] Anode: Fe is produced through electrolysis. 2+ The specific reaction formula is:

[0156] Fe 0 →Fe 2+ +2e - (1)

[0157] The first cathode, i.e., the gas diffusion cathode, produces hydrogen peroxide through oxygen reduction and then electrolyzes Fe at the anode. 2+ Under the action of [something], hydroxyl radicals are efficiently generated through activation. The specific reaction formula is as follows:

[0158] O2 + 2H + +2e - →H2O2 (2)

[0159] Fe 2+ +H₂O₂→Fe 3+ +OH - + · OH (3)

[0160] Fe 3+ +e - →Fe 2+ (4)

[0161] The second cathode, namely the carbon paper cathode, reduces nitrates to ammonia through the combined action of direct electroreduction by electrons transferred on the cathode surface and indirect electroreduction by atomic hydrogen generated from water electrolysis. The specific reaction formula is as follows:

[0162] NO3 - +H₂O + 2e - →NO2 - +2OH - (5)

[0163] NO2 - +6H2O+6e - →NH4 + +8OH - (6)

[0164] 2H2O+2e - →2H*+2OH - (7)

[0165] 3NO3 - +H*→NO2 - +NH4 + +N2+H2O (8)

[0166] 3NO2 - +H*→NH4 + +N2+H2O (9).

[0167] The above-mentioned electrochemical treatment method is not limited by concentration and can efficiently treat wastewater containing different pollutants and different nitrate concentrations.

[0168] Example 1

[0169] like Figure 1 As shown, an integrated electrochemical device for bipolar Fenton degradation of pollutants and synergistic ammonia production from nitrates includes a dual-chamber electrolytic cell with a pollutant degradation chamber and a nitrate reduction chamber, which are separated by a diaphragm 2.

[0170] The pollutant degradation chamber is equipped with a first cathode 4 and an anode 3, and the pollutant degradation chamber can degrade organic pollutants in wastewater;

[0171] The nitrate reduction chamber is equipped with a second cathode 1, which enables the reduction of nitrates in wastewater.

[0172] In this embodiment, the first cathode 4 is a gas diffusion cathode composed of an activated carbon substrate and a condensed paste coated on the activated carbon substrate, and the anode 3 is a commercial iron sheet with a thickness of 0.1 mm; the second cathode 1 is a carbon paper cathode loaded with a catalyst.

[0173] The pollutant degradation chamber is also connected to an air pump 5 via an air pipe. Air is introduced into the pollutant degradation chamber through the air pump 5 to enhance mass transfer and increase the amount of H2O2 generated during the electrochemical reaction.

[0174] Both the pollutant degradation chamber and the nitrate reduction chamber are connected to peristaltic pumps 6. The wastewater after nitrate reduction to produce ammonia is pumped into the pollutant degradation chamber for degradation by the peristaltic pumps 6. This avoids interference problems such as nitrate quenching active species or producing more toxic byproducts with intermediate products of pollutants. At the same time, new wastewater is added to the nitrate reduction chamber to achieve recycling treatment.

[0175] The first cathode 4 and the second cathode 1 are connected to the negative electrode of the electrochemical workstation 7, and the anode 3 is connected to the positive electrode of the electrochemical workstation 7.

[0176] The method for preparing the gas diffusion cathode includes the following steps:

[0177] S1. Add 0.1g of conductive carbon black and 0.35mL of polytetrafluoroethylene emulsion to 10mL of anhydrous ethanol and mix. After mixing, sonicate for 30 minutes to make the solution uniformly mixed and form a coagulated paste.

[0178] S2. Using a hot press at a temperature of 50℃ and a pressure of 0.5MPa, the agglomerated paste is uniformly rolled onto a hydrophobic activated carbon cloth substrate, then dried in an oven, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours to obtain a gas diffusion cathode.

[0179] The method for preparing a carbon paper cathode includes the following steps:

[0180] Among them, iron(III) oxide (Fe3O4) is synthesized by a two-step method of gas-phase assisted hydrothermal treatment and high-temperature copolymerization;

[0181] S1. Place 1g of dicyandiamide and 1mmol of ferric chloride hexahydrate (FeCl3·6H2O) in a 20mL glass bottle, then transfer the glass bottle to a 100mL polytetrafluoroethylene-lined reactor, and add 10mL of deionized water to the gap between the glass bottle and the polytetrafluoroethylene liner. Then heat at 200℃ for 10 hours, and let it cool naturally to room temperature. Separate the solid and liquid to obtain a solid substance.

[0182] S2. The solid material was placed in a muffle furnace and heated to 550°C at a heating rate of 2.5°C / min. It was calcined for 4 hours, cooled to room temperature, and the product was ground to obtain iron(Fe3O4).

[0183] S3. Weigh 8 mg of iron(III) oxide (Fe3O4), add 180 μL of ethanol and 20 μL of perfluorosulfonic acid polymer solution (Nafion), mix, sonicate for 1 h, and then drop-coat to a 2×2 cm layer. 2 Dry the carbon paper to obtain a carbon paper cathode, which is then ready for use.

[0184] Example 2

[0185] An application method for an integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates includes the following steps:

[0186] The wastewater in question is simulated wastewater, with each 50 mL of simulated wastewater containing 50 mM Na2SO4 and 50 ppm NO3. - -N and 10ppm naproxen;

[0187] S1. Place 50 mL of simulated wastewater in the nitrate reduction chamber of the integrated electrochemical device in Example 1, and at the same time add 50 mL of a solution containing 50 mM Na2SO4 to the pollutant degradation chamber.

[0188] S2. Connect the gas diffusion cathode and carbon paper cathode to the negative electrode of the electrochemical workstation, connect the anode to the positive electrode of the electrochemical workstation, and control the distance between the gas diffusion cathode and the anode to about 2 cm. Then turn on the air pump and introduce air at a flow rate of 1 L / min.

[0189] S3. Turn on the electrochemical workstation and set the voltage to -1.6V so that the simulated wastewater undergoes a reduction reaction to produce ammonia in the nitrate reduction chamber.

[0190] Nitrate reduction to produce ammonia involves removing nitrates for 3 hours. Then, a peristaltic pump is used to pump the simulated wastewater in the nitrate reduction chamber into the pollutant degradation chamber. At the same time, new simulated wastewater is added to the nitrate reduction chamber for recycling.

[0191] In the nitrate reduction chamber, nitrates undergo a reduction reaction on the surface of the carbon paper cathode, producing ammonia. Simultaneously, in the pollutant degradation chamber, hydrogen peroxide is generated in situ at the gas diffusion cathode under the influence of oxygen in the air, while Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals, which degrade organic pollutants in wastewater.

[0192] At regular intervals, 1 mL of sample was taken from the reaction solution in the pollutant degradation chamber and nitrate reduction chamber, filtered through a 0.22 μm filter membrane, and then the nitrate nitrogen in the sample was determined by the HJ / T 346—2007 method, the nitrite nitrogen by the naphthylethylenediamine hydrochloride method, and the ammonia nitrogen by the Nessler's reagent method; the concentration of residual naproxen in the sample was determined by high performance liquid chromatography.

[0193] Example 3

[0194] An application method for an integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates includes the following steps:

[0195] The wastewater in question is simulated wastewater, with each 50 mL of simulated wastewater containing 50 mM Na2SO4 and 50 ppm NO3. - -N and 10ppm tetracycline;

[0196] S1. Place 50 mL of simulated wastewater in the nitrate reduction chamber of the integrated electrochemical device in Example 1, and at the same time add 50 mL of a solution containing 50 mM Na2SO4 to the pollutant degradation chamber.

[0197] S2. Connect the gas diffusion cathode and carbon paper cathode to the negative electrode of the electrochemical workstation, connect the anode to the positive electrode of the electrochemical workstation, and control the distance between the gas diffusion cathode and the anode to about 2 cm. Then turn on the air pump and introduce air at a flow rate of 1 L / min.

[0198] S3. Turn on the electrochemical workstation and set the voltage to -1.6V so that the simulated wastewater undergoes a reduction reaction to produce ammonia in the nitrate reduction chamber.

[0199] Nitrate reduction to produce ammonia involves removing nitrates for 3 hours. Then, a peristaltic pump is used to pump the simulated wastewater in the nitrate reduction chamber into the pollutant degradation chamber. At the same time, new simulated wastewater is added to the nitrate reduction chamber for recycling.

[0200] In the nitrate reduction chamber, nitrates undergo a reduction reaction on the surface of the carbon paper cathode, producing ammonia. Simultaneously, in the pollutant degradation chamber, hydrogen peroxide is generated in situ at the gas diffusion cathode under the influence of oxygen in the air, while Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals, which degrade organic pollutants in wastewater.

[0201] At regular intervals, 1 mL of sample was taken from the reaction solution in the pollutant degradation chamber and nitrate reduction chamber, filtered through a 0.22 μm filter membrane, and then the nitrate nitrogen in the sample was determined by the HJ / T 346—2007 method, the nitrite nitrogen by the naphthylethylenediamine hydrochloride method, and the ammonia nitrogen by the Nessler's reagent method; the concentration of residual tetracycline in the sample was determined by high performance liquid chromatography.

[0202] Example 4

[0203] An application method for an integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates includes the following steps:

[0204] The wastewater in question is simulated wastewater, with each 50 mL of simulated wastewater containing 50 mM Na2SO4 and 50 ppm NO3. - -N and 10ppm methyl orange;

[0205] S1. Place 50 mL of simulated wastewater in the nitrate reduction chamber of the integrated electrochemical device in Example 1, and at the same time add 50 mL of a solution containing 50 mM Na2SO4 to the pollutant degradation chamber.

[0206] S2. Connect the gas diffusion cathode and carbon paper cathode to the negative electrode of the electrochemical workstation, connect the anode to the positive electrode of the electrochemical workstation, and control the distance between the gas diffusion cathode and the anode to about 2 cm. Then turn on the air pump and introduce air at a flow rate of 1 L / min.

[0207] S3. Turn on the electrochemical workstation and set the voltage to -1.6V so that the simulated wastewater undergoes a reduction reaction to produce ammonia in the nitrate reduction chamber.

[0208] Nitrate reduction to produce ammonia involves removing nitrates for 3 hours. Then, a peristaltic pump is used to pump the simulated wastewater in the nitrate reduction chamber into the pollutant degradation chamber. At the same time, new simulated wastewater is added to the nitrate reduction chamber for recycling.

[0209] In the nitrate reduction chamber, nitrates undergo a reduction reaction on the surface of the carbon paper cathode, producing ammonia. Simultaneously, in the pollutant degradation chamber, hydrogen peroxide is generated in situ at the gas diffusion cathode under the influence of oxygen in the air, while Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals, which degrade organic pollutants in wastewater.

[0210] At regular intervals, 1 mL of sample was taken from the reaction solution in the pollutant degradation chamber and nitrate reduction chamber, filtered through a 0.22 μm filter membrane, and then the nitrate nitrogen in the sample was determined by the HJ / T 346—2007 method, the nitrite nitrogen by the naphthylethylenediamine hydrochloride method, and the ammonia nitrogen by the Nessler's reagent method; the concentration of residual methyl orange in the sample was determined by high performance liquid chromatography.

[0211] Example 5

[0212] An application method for an integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates includes the following steps:

[0213] The wastewater in question is simulated wastewater, with each 50 mL of simulated wastewater containing 50 mM Na2SO4 and 50 ppm NO3. - -N and 10ppm Rhodamine B;

[0214] S1. Place 50 mL of simulated wastewater in the nitrate reduction chamber of the integrated electrochemical device in Example 1, and at the same time add 50 mL of a solution containing 50 mM Na2SO4 to the pollutant degradation chamber.

[0215] S2. Connect the gas diffusion cathode and carbon paper cathode to the negative electrode of the electrochemical workstation, connect the anode to the positive electrode of the electrochemical workstation, and control the distance between the gas diffusion cathode and the anode to about 2 cm. Then turn on the air pump and introduce air at a flow rate of 1 L / min.

[0216] S3. Turn on the electrochemical workstation and set the voltage to -1.6V so that the simulated wastewater undergoes a reduction reaction to produce ammonia in the nitrate reduction chamber.

[0217] Nitrate reduction to produce ammonia involves removing nitrates for 3 hours. Then, a peristaltic pump is used to pump the simulated wastewater in the nitrate reduction chamber into the pollutant degradation chamber. At the same time, new simulated wastewater is added to the nitrate reduction chamber for recycling.

[0218] In the nitrate reduction chamber, nitrates undergo a reduction reaction on the surface of the carbon paper cathode, producing ammonia. Simultaneously, in the pollutant degradation chamber, hydrogen peroxide is generated in situ at the gas diffusion cathode under the influence of oxygen in the air, while Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals, which degrade organic pollutants in wastewater.

[0219] At regular intervals, 1 mL of sample was taken from the reaction solution in the pollutant degradation chamber and nitrate reduction chamber, filtered through a 0.22 μm filter membrane, and then the nitrate nitrogen in the sample was determined by the HJ / T 346—2007 method, the nitrite nitrogen by the naphthylethylenediamine hydrochloride method, and the ammonia nitrogen by the Nessler's reagent method; the concentration of residual Rhodamine B in the sample was determined by high performance liquid chromatography.

[0220] Comparative Example 1

[0221] A conventional wastewater treatment method includes the following steps:

[0222] The wastewater in question is simulated wastewater, with each 50 mL of simulated wastewater containing 50 mM Na2SO4 and 50 ppm NO3. - -N and 10ppm naproxen;

[0223] S1. Place 50 mL of simulated wastewater in a single-chamber electrolytic cell. The single-chamber electrolytic cell is equipped with a gas diffusion cathode, a carbon paper cathode, and an anode. In other words, compared with the integrated electrochemical device in Example 1, the two-chamber electrolytic cell in this comparative example 1 has been changed to a single-chamber electrolytic cell, and the peristaltic pump has been reduced. The rest of the structure is the same as in Example 1.

[0224] S2. Connect the gas diffusion cathode and carbon paper cathode to the negative electrode of the electrochemical workstation, connect the anode to the positive electrode of the electrochemical workstation, and control the distance between the carbon paper cathode, gas diffusion cathode and anode to about 2 cm. Then turn on the air pump and introduce air into the gas diffusion cathode side at a flow rate of 1 L / min.

[0225] S3. Turn on the electrochemical workstation and set the voltage to -1.6V to allow the simulated wastewater to simultaneously undergo nitrate reduction to produce ammonia and pollutant degradation reactions.

[0226] In this process, nitrates undergo a reduction reaction on the surface of the carbon paper cathode, producing ammonia gas; simultaneously, hydrogen peroxide is generated in situ at the gas diffusion cathode under the influence of oxygen in the air, and Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals, which degrade organic pollutants in wastewater.

[0227] At regular intervals, 1 mL of sample was taken from the reaction solution of the single-chamber electrolytic cell, filtered through a 0.22 μm filter membrane, and then the nitrate nitrogen in the sample was determined by the HJ / T 346—2007 method, the nitrite nitrogen by the naphthylethylenediamine hydrochloride method, and the ammonia nitrogen by the Nessler's reagent method. The concentration of residual naproxen in the sample was determined by high performance liquid chromatography.

[0228] Comparative Example 2

[0229] A conventional wastewater treatment method includes the following steps:

[0230] The wastewater in question is simulated wastewater, with each 50 mL of simulated wastewater containing 50 mM Na2SO4 and 50 ppm NO3. - -N and 10ppm naproxen;

[0231] S1. Place 50 mL of simulated wastewater in the nitrate reduction chamber of the integrated electrochemical device in Example 1, and at the same time add 50 mL of a solution containing 50 mM Na2SO4 to the pollutant degradation chamber.

[0232] S2. Connect the gas diffusion cathode and carbon paper cathode to the negative electrode of the electrochemical workstation, connect the anode to the positive electrode of the electrochemical workstation, and control the distance between the gas diffusion cathode and the anode to about 2 cm. Then turn on the air pump and introduce air at a flow rate of 1 L / min.

[0233] S3. Without turning on the electrochemical workstation, the simulated wastewater undergoes a reduction reaction to produce ammonia in the nitrate reduction chamber first.

[0234] Nitrate reduction to produce ammonia involves removing nitrates for 3 hours. Then, a peristaltic pump is used to pump the simulated wastewater in the nitrate reduction chamber into the pollutant degradation chamber. At the same time, new simulated wastewater is added to the nitrate reduction chamber for recycling.

[0235] In the nitrate reduction chamber, nitrates undergo a reduction reaction on the surface of the carbon paper cathode, producing ammonia. Simultaneously, in the pollutant degradation chamber, hydrogen peroxide is generated in situ at the gas diffusion cathode under the influence of oxygen in the air, while Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals, which degrade organic pollutants in wastewater.

[0236] At regular intervals, 1 mL of sample was taken from the reaction solution in the pollutant degradation chamber and nitrate reduction chamber, filtered through a 0.22 μm filter membrane, and then the nitrate nitrogen in the sample was determined by the HJ / T 346—2007 method, the nitrite nitrogen by the naphthylethylenediamine hydrochloride method, and the ammonia nitrogen by the Nessler's reagent method; the concentration of residual naproxen in the sample was determined by high performance liquid chromatography.

[0237] Comparative Example 3

[0238] A nitrate-free wastewater treatment method includes the following steps:

[0239] The wastewater is simulated wastewater, and each 50 mL of simulated wastewater contains 50 mM Na2SO4 and 10 ppm naproxen;

[0240] S1. Place 50 mL of simulated wastewater in the nitrate reduction chamber of the integrated electrochemical device in Example 1, and at the same time add 50 mL of a solution containing 50 mM Na2SO4 to the pollutant degradation chamber.

[0241] S2. Connect the gas diffusion cathode and carbon paper cathode to the negative electrode of the electrochemical workstation, connect the anode to the positive electrode of the electrochemical workstation, and control the distance between the gas diffusion cathode and the anode to about 2 cm. Then turn on the air pump and introduce air at a flow rate of 1 L / min.

[0242] S3. Turn on the electrochemical workstation and set the voltage to -1.6V. The simulated wastewater will first react in the nitrate reduction chamber. Then, the simulated wastewater in the nitrate reduction chamber will be pumped into the pollutant degradation chamber by a peristaltic pump. At the same time, new simulated wastewater will be added to the nitrate reduction chamber for recycling.

[0243] In the pollutant degradation chamber, the gas diffusion cathode generates hydrogen peroxide in situ under the influence of oxygen in the air, while the anode generates Fe. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals, which degrade organic pollutants in wastewater.

[0244] At regular intervals, 1 mL of sample was taken from the reaction solution in the pollutant degradation chamber and nitrate reduction chamber, filtered through a 0.22 μm filter membrane, and then the nitrate nitrogen in the sample was determined by the HJ / T 346—2007 method, the nitrite nitrogen by the naphthylethylenediamine hydrochloride method, and the ammonia nitrogen by the Nessler's reagent method; the concentration of residual naproxen in the sample was determined by high performance liquid chromatography.

[0245] Detection and Analysis

[0246] 1) High-performance liquid chromatography detection

[0247] The specific operation was as follows: a Chromcore C18 5μm (4.6mm × 250mm) column (35℃) was used, connected to an SC6000 detector selected at λ = 230nm. The mobile phase was CH3OH / H2O = 70 / 30 (v / v) (0.010M KH2PO4). The removal rates of organic pollutants in Examples 2 to 5 are as follows. Figure 2 As shown, the removal rates of organic pollutants in Example 2 and Control Example 1 are compared. Figure 3 As shown, the removal rates of organic pollutants in Example 2, Control Example 2, and Control Example 3 are compared. Figure 4 As shown.

[0248] As can be seen from the results in Figure 2, after the wastewater in Examples 2 to 5 was treated by the integrated electrochemical device in Example 1, the degradation rate of each organic pollutant reached 100%, thus proving that the integrated electrochemical device of the present invention can achieve efficient degradation of organic pollutants in wastewater.

[0249] from Figure 3 Analysis shows that after the wastewater in Example 2 was treated by the integrated electrochemical device in Example 1, and the wastewater in Control Example 1 was treated by the single-chamber electrochemical device, the degradation rate of naproxen in Example 2 reached 100% in only 30 minutes. In contrast, the degradation rate in Control Example 1 was 74.2%, and it took 120 minutes for the degradation rate of naproxen in Control Example 1 to reach 100%. This indicates that using a single-chamber electrolytic cell to treat wastewater containing 50 mM Na₂SO₄ and 50 ppm NO₃⁻ is effective. - When simulated wastewater containing -N and 10ppm naproxen was used, the presence of nitrates interfered with naproxen removal. However, the staged circulation treatment using a dual-chamber electrolyzer effectively avoided the interference of nitrates on naproxen removal. This demonstrated that the integrated electrochemical device using a dual-chamber electrolyzer could degrade naproxen and reduce nitrates to produce ammonia at the optimal rate, with a nitrate removal rate of 92.1% and an ammonia nitrogen selectivity of up to 90%.

[0250] from Figure 4 Analysis shows that, compared with the wastewater treatment without voltage application in Control Example 2, the integrated electrochemical device using a dual-chamber electrolytic cell in Example 2 can achieve efficient degradation of organic pollutants in wastewater under a certain voltage. The removal effect and efficiency are far superior to those of Control Example 3 without voltage application. At the same time, the removal rate results of Example 2 and Control Example 3 show that...

[0251] 2) Determination of nitrate, nitrite and ammonia nitrogen

[0252] The concentrations of residual nitrate, nitrite, and ammonia nitrogen in the samples taken last from Examples 2 to 5, as well as Control Examples 2 and 3, were determined using the HJ / T 346—2007 national standard method. The results are as follows: Figure 2 As shown and Figure 4 As shown.

[0253] from Figure 2 Analysis showed that in Example 2, the nitrate removal rate of the wastewater reached 92.1% within 3 hours, with ammonia nitrogen selectivity reaching a maximum of 90%; in Example 3, the nitrate removal rate of the wastewater reached 90.81% within 3 hours, with ammonia nitrogen selectivity reaching a maximum of 89.86%; in Example 4, the nitrate removal rate of the wastewater reached 88.56% within 3 hours, with ammonia nitrogen selectivity reaching a maximum of 87.52%; and in Example 5, the nitrate removal rate of the wastewater reached 89.85% within 3 hours, with ammonia nitrogen selectivity reaching a maximum of 86.91%. Combined with the detection results of high-performance liquid chromatography, this effectively demonstrated that various types of wastewater effectively achieved simultaneous and efficient degradation of pollutants and nitrate reduction to ammonia production in the integrated electrochemical device of the dual-chamber electrolytic cell in Example 1, and overcame the influence of nitrate on the degradation process of organic pollutants.

[0254] from Figure 4 Analysis shows that, compared with the wastewater treatment without voltage application in Control Example 2, the integrated electrochemical device using a dual-chamber electrolytic cell in Example 2 can efficiently reduce nitrates in wastewater to ammonia under a certain voltage. Combined with the detection results of high performance liquid chromatography, it is effectively proved that various wastewaters can effectively achieve simultaneous high-efficiency degradation of pollutants and reduction of nitrates to ammonia in the integrated electrochemical device using a dual-chamber electrolytic cell in Example 1. The removal effect and efficiency are far superior to those of the control examples.

[0255] In summary, the integrated electrochemical device for bipolar Fenton degradation of pollutants and synergistic nitrate ammonia production of the present invention utilizes a dual-chamber electrolytic cell with a diaphragm separating the pollutant degradation chamber and the nitrate reduction chamber. A first cathode and anode are located in the pollutant degradation chamber, and a second cathode is located in the nitrate reduction chamber. This allows wastewater to first undergo nitrate reduction to produce ammonia on the surface of the second cathode in the nitrate reduction chamber. Simultaneously, the wastewater that has undergone nitrate reduction to produce ammonia enters the anode in the pollutant degradation chamber, where Fe is generated. 2+ Activate the hydrogen peroxide generated in situ at the first cathode to achieve efficient and continuous production. ·OH, thereby successfully achieving the degradation of organic pollutants in wastewater and the simultaneous recovery of nitrates. Simultaneously, the integrated electrochemical device with a dual-chamber electrolytic cell of this invention, through the use of a dual-cathode system, effectively reduces the operating potential, thus significantly reducing the energy consumption of the system. This effectively solves the problem that existing electro-Fenton technology struggles to simultaneously achieve efficient in-situ generation and activation of H2O2 and continuous processing of Fe. 2+ This solution addresses the problem of insufficient utilization efficiency. By using a peristaltic pump to pump the wastewater after nitrate removal in the nitrate reduction chamber into the pollutant degradation chamber for further treatment, it avoids interference issues such as nitrate quenching of active species in the pollutant degradation process and the generation of more toxic byproducts from intermediate pollutant products. It also addresses the difficulty in achieving simultaneous removal of pollutants and nitrates, providing a novel solution for the treatment of nitrate-containing industrial wastewater that combines simultaneous wastewater purification and resource recovery.

[0256] The application method of the integrated electrochemical device for bipolar Fenton degradation of pollutants and synergistic ammonia production from nitrates according to the present invention involves treating wastewater using the integrated electrochemical device with a dual-chamber electrolytic cell of the present invention. Under conditions where no external addition of iron ions and H2O2 is required, the device utilizes hydrogen peroxide generated in situ at the first cathode in the pollutant degradation chamber to generate Fe in situ at the anode. 2+ Under the activation of the proton exchange membrane, strong oxidizing free radicals are generated efficiently, thereby effectively degrading organic pollutants in wastewater. At the same time, another nitrate reduction chamber separated by the proton exchange membrane uses a second cathode to achieve highly selective nitrate reduction to produce ammonia. The two chambers work together to achieve wastewater purification and resource recovery.

[0257] The wastewater treatment system of the integrated electrochemical device with a dual-chamber electrolytic cell of the present invention not only reduces the cost of external Fenton reagent addition, but also prevents Fe from being added during continuous treatment. 2+ The invention addresses the issue of insufficient utilization efficiency. Furthermore, within the nitrate reduction chamber, nitrate undergoes a reduction reaction on the surface of a preferred Fe3O4-supported carbon paper cathode, efficiently producing ammonia. The separate, simultaneous treatment in the two chambers resolves the interference issues caused by nitrate competing for active species during pollutant degradation and generating toxic byproducts, achieving simultaneous pollutant degradation and nitrate reduction for ammonia production. Simultaneously, the integrated electrochemical device with a dual-chamber electrolytic cell of this invention effectively reduces the operating potential by employing a dual-cathode system, thereby significantly reducing the energy consumption of the system. It also boasts advantages such as simple operation, low cost, and no secondary pollution, making it more valuable for industrial production and possessing potential application value in the field of wastewater treatment technology.

[0258] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. An integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates, characterized in that, The invention includes a dual-chamber electrolytic cell having a pollutant degradation chamber and a nitrate reduction chamber, the pollutant degradation chamber and the nitrate reduction chamber being separated by a proton exchange membrane; The pollutant degradation chamber is equipped with a first cathode and an anode, and the pollutant degradation chamber can degrade organic pollutants in wastewater; The nitrate reduction chamber is equipped with a second cathode, and the nitrate reduction chamber can reduce nitrates in wastewater; The first cathode is selected from a gas diffusion cathode; The anode is selected from iron sheets; The second cathode is selected from carbon paper; The structure of the gas diffusion cathode consists of an activated carbon substrate and a coagulated paste coated on the activated carbon substrate. The coagulated paste is composed of at least a conductive material and polytetrafluoroethylene. A catalyst is supported on the carbon paper cathode, and the catalyst consists of at least iron(Fe3O4) oxide. The iron(III) oxide (Fe3O4) was synthesized using a two-step method involving gas-phase assisted hydrothermal treatment and high-temperature copolymerization.

2. The integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates as described in claim 1, characterized in that, The method for preparing the gas diffusion cathode includes the following steps: A conductive material, polytetrafluoroethylene emulsion, and organic solvent are mixed to obtain a coagulated paste. A condensed paste was coated onto an activated carbon substrate, dried, and calcined to obtain a gas diffusion cathode.

3. The integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates as described in claim 2, characterized in that, The mass ratio of the conductive material to the polytetrafluoroethylene emulsion is between 1:1 and 5:

1. The polytetrafluoroethylene emulsion contains 30% to 60% polytetrafluoroethylene by mass. The conductive material, polytetrafluoroethylene emulsion, and organic solvent were mixed using ultrasound for a time between 30 and 60 minutes. The condensed paste was coated onto an activated carbon substrate using a hot-pressing method. The hot-pressing temperature was between 30°C and 60°C, and the hot-pressing pressure was between 0.5 MPa and 1.5 MPa. The calcination temperature is between 300℃ and 400℃, and the calcination time is between 1 h and 3 h.

4. The integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates as described in claim 2, characterized in that, The conductive material is selected from at least one of conductive carbon black, acetylene black and carbon nanotubes. The organic solvent is selected from anhydrous ethanol; The activated carbon substrate is selected from hydrophobic activated carbon cloth and / or hydrophobic carbon felt.

5. The integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates as described in claim 1, characterized in that, The method for preparing the carbon paper cathode includes the following steps: Iron salt and dicyandiamide were placed in a reaction flask, then the reaction flask was placed in a reaction vessel, and water was added between the reaction vessel and the reaction flask. A gas-phase assisted hydrothermal reaction was then carried out to obtain a solid. The solid was calcined to achieve high-temperature copolymerization, yielding the iron(III) oxide (Fe3O4). The Fe3O4 oxide, organic solvent, and binder are mixed, coated onto carbon paper, and dried to obtain a carbon paper cathode loaded with a catalyst.

6. The integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates as described in claim 5, characterized in that, The mass ratio of the iron salt to dicyandiamide is 0.1:1 to 1:1; The iron salt is selected from at least one of ferric chloride, ferric chloride hexahydrate (FeCl3·6H2O), ferric sulfate, and ferric nitrate; The temperature of the gas-phase assisted hydrothermal reaction is between 160℃ and 200℃, and the time of the gas-phase assisted hydrothermal reaction is between 6h and 18h. The calcination temperature is between 400℃ and 600℃, and the calcination time is between 2 h and 6 h. The volume ratio of the organic solvent to the adhesive is 5:1 to 10:1; The organic solvent is selected from ethanol; The adhesive is selected from perfluorosulfonic acid polymer solution (nafion). The carbon paper is selected from hydrophilic carbon paper; The Fe3O4, organic solvent, and binder are mixed using ultrasound, with the ultrasound time ranging from 30 min to 120 min.

7. A method for applying the integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates as described in any one of claims 1 to 6, characterized in that, The integrated electrochemical device is used for wastewater treatment; The integrated electrochemical device can degrade organic pollutants in wastewater and reduce nitrates in wastewater to produce ammonia. The wastewater refers to industrial wastewater from the coking, leather making, electroplating, textile, and livestock and poultry farming industries.

8. A method for applying the integrated electrochemical device for bipolar electro-Fenton degradation of pollutants and synergistic ammonia production from nitrates as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Wastewater is placed in the nitrate reduction chamber of an integrated electrochemical device that uses bipolar Fenton electrochemical degradation of pollutants and synergistic nitrate-to-ammonia production; Connect the first and second cathodes to the negative electrode and the anode to the positive electrode; When energized, the wastewater is first treated in the nitrate reduction chamber by the second cathode to reduce nitrates and produce ammonia. Then, the nitrate-removed wastewater is placed in the pollutant degradation chamber, where hydrogen peroxide is generated in situ at the first cathode and Fe is generated at the anode. 2+ Fe 2+ Activated hydrogen peroxide generates hydroxyl radicals to degrade organic pollutants in wastewater. Simultaneously, new wastewater is pumped into the nitrate reduction chamber to reduce nitrates and produce ammonia, thus achieving a cyclical treatment. The wastewater contains nitrates and organic pollutants. The voltage applied is between -0.8 V and 2.0 V.

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