Water treatment system of electro-oxidation coupling four-electron oxygen reduction and application

Abstract

The present application relates to a kind of water treatment systems and applications of electrooxidation coupling four electron oxygen reduction, water treatment system includes electrolytic cell, BDD anode arranged in electrolytic cell, cathode arranged in the both sides of BDD anode, and for the oxygen of BDD anode, cathode is blown into aeration disc, using double cathode setting and the high 4eORR activity NF / P@Fe-N-C prepared as cathode, reduce cathode polarization, the bottom of reactor is provided with microporous aeration disc, provides the necessary reactant oxygen of cathode and induces forced convection.In addition, the present water treatment system is also used for electrooxidation degradation phenol, compared with prior art, the present application can improve the theoretical value of cathode potential from 0V of HER to 1.23V vs.RHE, realize 1.57V of ultra-low thermodynamic equilibrium potential, while realizing the deep treatment of refractory organic pollutants and the significant reduction of energy consumption, provide practical application value for electrooxidation system in energy-saving treatment of organic pollutants in wastewater.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and relates to a water treatment system with electro-oxidation coupled four-electron oxygen reduction and application. BACKGROUND

[0002] In the context of global energy shortage, the problem of pollution of refractory organic matter in industrial wastewater is increasingly serious, which poses a threat to resource utilization, ecological environment and human health. Exploring and developing efficient and low-energy water treatment technology has always been a key research direction in environmental pollution control. Electrochemical treatment technology is widely considered as one of the most potential water treatment solutions due to its easy operation, fast reaction, compact equipment design and environmental protection. Among them, electro-oxidation (EO) technology can generate hydroxyl radicals (·OH) with high activity and oxidation on the electrode surface, as shown in formula (1), which has shown great potential in eliminating refractory organic pollutants.

[0003] Anode (EO): H2O-e - →·OH+H + ,

[0004] Cathode (HER): 2H + +2e - →H2,

[0005] Cathode (2e ORR): O2+2e - +2H + →H2O2,

[0006] However, the current application of EO technology in treating refractory organic wastewater still faces great limitations. High energy consumption is the main obstacle to the widespread application of EO technology, ranging from several kilowatt-hours to hundreds of kilowatt-hours per kilogram of TOC. High energy consumption is mainly due to two aspects. From the perspective of thermodynamics, applying a higher input voltage is the key prerequisite for achieving effective ionization of water molecules and generating highly reactive ·OH. From the perspective of kinetics, mass transfer polarization caused by slow diffusion of reactants to the electrode surface and ohmic polarization caused by slow electrolyte migration are important factors leading to high energy consumption.

[0007] The main strategies to overcome the high energy consumption in the EO process are: 1) Using active electrodes in the EO system to reduce the overpotential of water electrolysis, which can effectively reduce the system input voltage, but due to the oxygen evolution side reaction, the Faraday efficiency and mineralization efficiency are low; 2) Using an electro-Fenton system, combining EO with the two-electron oxygen reduction reaction (2eORR) to enhance the degradation ability of organic compounds. By generating H2O2 and undergoing a Fenton-like reaction 2eORR (as shown in formula (3)), the traditional hydrogen evolution reaction (HER) on the cathode (as shown in formula (2)) can be replaced. The electro-Fenton system can increase the cathode potential and enhance the removal of organic pollutants. However, under actual operating conditions, it still has problems such as low Faraday efficiency, limited cathode stability, and severe polarization effect. Moreover, the theoretical operating potential of the electro-Fenton system is 2.12V, which is still too high. Summary of the Invention

[0008] The purpose of this invention is to provide a high-efficiency, low-energy-consumption electro-oxidation coupled four-electron oxygen reduction (4eORR) water treatment system and its application. Specifically, it provides an EO-4eORR electrolysis system that uses 4eORR as the cathode reaction to replace the traditional HER reaction, which can increase the cathode potential from 0V in HER to 1.23V vs. RHE (as shown in equations (2) and (4)). This can further push the thermodynamic equilibrium potential of the system to 1.57V, solving the problem of high energy consumption in electro-oxidation systems. A high-4eORR active nickel-supported phosphorus-doped iron-nitrogen-carbon (NF / P@Fe-NC) foam is used as the cathode to reduce cathode polarization. A microporous aeration disc is set at the bottom of the reactor to provide the necessary reactant oxygen for the cathode and induce forced convection. In addition, this invention also applies the coupled water treatment system to the electro-oxidation degradation of organic pollutants. By optimizing the electrochemical conditions and reactor design, it achieves efficient degradation of pollutants while significantly reducing energy consumption.

[0009] Cathode (4eORR): O2 + 4e - +4H + →2H2O,

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] The first aspect of the present invention provides a water treatment system for electro-oxidation coupled with four-electron oxygen reduction. The water treatment system includes an electrolytic cell, a boron-doped diamond (BDD) anode disposed in the electrolytic cell, cathodes disposed on both sides of the BDD anode, and an aeration disc for blowing oxygen into the BDD anode and cathode. By providing the necessary oxygen through forced convection and enhancing mass transfer, the system improves the mass transfer of the reactants at the anode and cathode, promotes the anode electro-oxidation and cathode four-electron oxygen reduction processes, and thereby reduces mass transfer polarization.

[0012] Furthermore, the cathode is a cathode with high four-electron oxygen reduction catalytic activity.

[0013] Furthermore, the cathode includes a cathode substrate and a catalyst layer, wherein the catalyst layer is selected from at least one of transition metal / phosphorus-doped carbon nitride, carbon nanosheets, or carbon nanotubes.

[0014] Furthermore, the cathode substrate is selected from any one of carbon felt, nickel foam, graphite felt, or carbon foam. Preferably, the cathode substrate is nickel foam.

[0015] Furthermore, the catalyst layer is P@Fe-NC, and the preparation process of P@Fe-NC includes: mixing Fe(NO3)3·9H2O with phytic acid, Zn(NO3)2·6H2O and 2-methylimidazole in a solvent, precipitating and drying to obtain a precursor, and pyrolyzing the precursor under an argon atmosphere to obtain P@Fe-NC.

[0016] Further, the molar ratio of Fe(NO3)3·9H2O, phytic acid, Zn(NO3)2·6H2O, and 2-methylimidazole is (0.1-0.2):(0.1-0.2):(8-9):(36-37). In the pyrolysis, the pyrolysis temperature is 700-900℃, and the pyrolysis time is 1-2 h. Preferably, the molar ratio of Fe(NO3)3·9H2O, phytic acid, Zn(NO3)2·6H2O, and 2-methylimidazole is 0.15:0.18:8.4:36.5, and the pyrolysis temperature is 900℃, and the pyrolysis time is 1 h. More preferably, the phytic acid is introduced into the reaction system in the form of a 50% (w / w) H2O solution.

[0017] Furthermore, the cathode preparation process includes: dispersing P@Fe-NC in a mixed solution of ethanol, water and naphthol and sonicating for 30 min (600 W, 25-28 kHz), then adding a cathode substrate for immersion and sonication to obtain a cathode substrate / P@Fe-NC, which serves as the cathode.

[0018] Further, the feed ratio of P@Fe-NC to naphthol solution is (45-55) mg:(98-110) μL. Preferably, the feed ratio of P@Fe-NC to naphthol is 50 mg:100 μL, and the mass ratio of cathode substrate to P@Fe-NC is (45-52):(50-55). Preferably, the mass ratio of cathode substrate to P@Fe-NC is 48:50. More preferably, the naphthol is introduced into the reaction system in the form of a 50% (w / w) H2O solution.

[0019] Furthermore, the BDD anode and dual cathodes are placed parallel to each other, with a distance of 1-3 cm between adjacent electrodes. Preferably, the distance between adjacent electrodes is 1 cm.

[0020] Furthermore, the BDD anode is a commercially available plate electrode. The BDD anode electrolyzes water to generate ·OH, achieving efficient degradation of pollutants.

[0021] Furthermore, the anode size is 1cm × 2cm, and the cathode size is (1-3)cm × (1-2)cm. Preferably, the cathode size is 1.5cm × 1cm.

[0022] A second aspect of the present invention provides an application of the water treatment system based on the electro-oxidation coupled four-electron oxygen reduction described in the first aspect, wherein the water treatment system is used to degrade organic pollutants.

[0023] Further, the organic pollutant includes at least one of phenols, heterocyclic compounds, benzene ring compounds, pharmaceutical compounds, and pesticide compounds. Preferably, the organic pollutant is a phenol. More preferably, the organic pollutant is phenol.

[0024] Furthermore, the degradation conditions for the organic pollutants include: a BDD anode current density of 5-25 mA / cm². 2 The oxygen aeration rate is 30-70 mL / min; the electrolyte is 0.1 mol / L potassium hydroxide, and the pH value is controlled between 11.0 and 13.0. Preferably, the BDD anode current density is 5 mA / cm². 2 The oxygen aeration rate was 70 mL / min, and the pH value was 12.

[0025] A dual-cathode bottom microporous aeration reactor employing electro-oxidation coupled with four-electron oxygen reduction (BERR) degrades organic pollutants. The reactor comprises a single-chamber cylindrical shell, a DC regulated power supply, and vertically placed BDD anode and cathode within the shell. An air inlet and microporous aeration disc are also located at the bottom of the shell. The BDD anode is connected to the positive terminal of the DC regulated power supply, while the cathode is connected to the negative terminal. During operation, the sum of the current values ​​of the two cathodes must equal the current applied to the anode surface. By applying DC current and adjusting the anode current, this invention effectively degrades organic pollutants, demonstrating significant advantages in both degradation efficiency and energy consumption.

[0026] This invention provides a highly efficient and low-energy-consumption water treatment system by coupling EO and 4eORR. EO technology can generate highly active and oxidizing ·OH on the electrode surface, showing great potential in eliminating recalcitrant organic pollutants. Combining EO with 4eORR to enhance the degradation capacity of organic compounds and using 4eORR instead of the traditional HER can reduce the thermodynamic potential of the electro-oxidation system to 1.57V. The dual-cathode setup maximizes the utilization of the electrode surface area and improves the spatiotemporal yield of reactant conversion. Under constant current input conditions, it can reduce cathode polarization, thereby reducing the external input voltage of the system and reducing energy consumption.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) This invention provides a novel low-energy water treatment system with electro-oxidation coupled with four-electron oxygen reduction. The cathode reaction is replaced by four-electron oxygen reduction, which replaces the hydrogen evolution reaction in the traditional electro-oxidation system. This can increase the cathode potential from 0V to 1.23V vs. RHE, achieving an ultra-low thermodynamic equilibrium potential of 1.57V, thus solving the problem of high energy consumption in electro-oxidation systems.

[0029] 2) This invention provides a dual-cathode bottom microporous aeration disc reactor for electro-oxidation coupled with four-electron oxygen reduction. The microporous aeration disc provides the necessary oxygen for the cathode reaction and enhances mass transfer through forced convection, thereby promoting the anodic electro-oxidation and cathode four-electron oxygen reduction processes. The dual-cathode setup can maximize the utilization of the electrode surface area and improve the spatiotemporal yield of reactant conversion. Under constant current input conditions, it can weaken cathode polarization and thus reduce the external input voltage of the system.

[0030] 3) By optimizing the electro-oxidation process, this invention can simultaneously achieve deep treatment of recalcitrant organic pollutants and a significant reduction in energy consumption. The system design takes into account ease of operation and cost-effectiveness, and is suitable for the field of wastewater treatment.

[0031] 4) This invention provides new theoretical insights and practical application value for the energy-saving treatment of organic pollutants in wastewater by electro-oxidation systems, and has important environmental significance and market potential. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the dual-cathode bottom microporous aeration reactor structure of the present invention;

[0033] The markings in the diagram are as follows: 1-DC regulated power supply, 2-BDD anode, 3-NF / P@Fe-NC cathode, 4-microporous aeration disc, 5-air inlet, 6-single-chamber cylindrical shell.

[0034] Figure 2 This is a thermodynamic and kinetic diagram illustrating the energy-saving principles of this invention.

[0035] Figure 3 This is a schematic diagram of the working state of the two systems in Example 1;

[0036] The markings in the figure indicate: A-EO-4eORR dual cathode system, B-EO-HER dual cathode system.

[0037] Figure 4 This is a schematic diagram of the working state of the two systems in Example 2;

[0038] The markings in the diagram indicate: A-EO-4eORR dual-cathode system, B-EO-4eORR single-cathode system. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are based on the above-described technical solutions of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0040] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0041] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0042] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art. Unless otherwise specified, the functional components or structures are conventional components or conventional structures used in the art to achieve the corresponding functions.

[0043] Example 1:

[0044] This embodiment proposes a single-chamber reactor with a dual-cathode bottom microporous aeration disc, and employs a traditional electro-oxidation coupled HER dual-cathode system (EO-HER dual-cathode system) and an electro-oxidation coupled 4eORR dual-cathode system (EO-4eORR dual-cathode system) to degrade the organic pollutant phenol. The cathode in the traditional EO-HER dual-cathode system is HER; the cathode in the EO-4eORR dual-cathode system is 4eORR, as detailed below:

[0045] EO-4eORR dual cathode system:

[0046] The EO-4eORR dual-cathode system increases the theoretical cathode potential from 0V for HER to 1.23V vs. RHE (as shown in equations (2) and (4)), thus reducing the external input voltage of the system. This system uses a single-chamber reactor with a dual-cathode bottom microporous aeration disc to treat the pollutant phenol. Its structure is as follows: Figure 1 As shown, the device includes a DC regulated power supply 1, a BDD anode (Hunan Xinfeng Technology Co., Ltd.) 2, two NF / P@Fe-NC cathodes 3, a microporous aeration disc 4, an air inlet 5, and a single-chamber cylindrical shell 6. The BDD anode 2 is located between the two NF / P@Fe-NC cathodes 3, and the BDD anode 2 and the two NF / P@Fe-NC cathodes 3 are placed perpendicular to the bottom inside the single-chamber cylindrical shell 6. The three electrodes are placed parallel to each other, with the same distance of 1 cm between adjacent electrodes. The BDD anode 2 is connected to the positive terminal of the DC regulated power supply 1, and the two NF / P@Fe-NC cathodes 3 are connected to the negative terminal of the DC regulated power supply 1. The BDD anode 2 electrolyzes water to generate ·OH, achieving efficient degradation of pollutants, while the NF / P@Fe-NC cathodes 3 generate 4eORR. The bottom of the dual-cathode bottom microporous aeration disc single-chamber reactor is equipped with a microporous aeration disc 4 and an air inlet 5. The air inlet 5 is located at the bottom edge of the single-chamber cylindrical shell 6. The bottom microporous aeration disc 4 provides the necessary oxygen for the cathode reaction and enhances mass transfer through forced convection, thereby promoting the anodic electro-oxidation and cathode 4eORR process.

[0047] The EO-4eORR dual-cathode system uses a BDD electrode (1cm×2cm) as the anode and an NF / P@Fe-NC electrode (1.5cm×1cm) as the cathode. The preparation process of the NF / P@Fe-NC cathode 3 is as follows:

[0048] 1) Preparation of P@Fe-NC catalyst layer: A methanol solution containing 60 mg Fe(NO3)3·9H2O was mixed with 84 μL phytic acid solution, and methanol solutions containing 2.5 g Zn(NO3)2·6H2O and 3.0 g 2-methylimidazole were added. After stirring and mixing, the precipitate was dried to form a precursor. The precursor was pyrolyzed at 900℃ under an argon atmosphere for 1 h to obtain the P@Fe-NC catalyst layer.

[0049] 2) Preparation of NF / P@Fe-NC cathode: 50 mg P@Fe-NC was dispersed in a mixed solution of 500 μL ethanol, 400 μL water and 100 μL naphthol solution (50% (w / w) H2O) and sonicated for 30 min (600 W, 25-28 kHz). Then, nickel foam was added and impregnated with ultrasonic to obtain phosphorus-doped iron-nitrogen-carbon (NF / P@Fe-NC) loaded with nickel foam.

[0050] The above-mentioned single-chamber reactor with dual cathode bottom microporous aeration disc was used to degrade the pollutant phenol. The specific degradation conditions were as follows: pollutant to be treated: phenol, total organic carbon (TOC) = 200 mg / L, potassium hydroxide concentration: 0.1 mol / L, reaction solution volume: 100 mL, BDD anode current density: 5-25 mA / cm². 2 Aeration rate: 70 mL / min, oxygen, initial pH of the phenol solution to be treated: 12.0.

[0051] EO-HER dual cathode system:

[0052] The EO-HER dual-cathode system uses a BDD electrode (1cm×2cm) as the anode and a commercial platinum (Pt) sheet electrode (1.5cm×1cm) as the cathode. Before the phenol degradation reaction, argon gas is aerated at the bottom of the reactor to remove interfering gases, and the same aeration rate (argon gas), disturbance effect and dual-cathode arrangement are maintained as in the EO-4eORR system.

[0053] The above two systems are used to treat the pollutant phenol. Figure 3 This is a schematic diagram of the working state of the two systems in Example 1, under different BDD anode current densities (5-25 mA / cm). 2 The specific results of the input voltage when the phenol TOC removal rate of the two systems reaches or approaches 95% are shown in Table 1; when the BDD anode current density is 5 mA / cm² 2 At a treatment time of 4.8 hours, the phenol TOC removal rates of both systems reached or approached 95%. At this point, the EO-4eORR dual-cathode system (cathode area 1.5 cm²) showed the best performance. 2 ) and the EO-HER dual cathode system (cathode area 1.5 cm²) 2 The specific results of the comparison of anode and cathode potentials, input voltage and energy consumption (×2) are shown in Table 2.

[0054] Table 1

[0055]

[0056] Table 2

[0057]

[0058] The results show that, as shown in Table 1, the input voltage required by the EO-4eORR system is lower than that of the EO-HER system at the same current density. Table 2 shows that, within a treatment time of 4.8 h, the traditional EO-HER dual-cathode system and the EO-4eORR dual-cathode system of this embodiment exhibit almost identical performance in terms of phenol TOC removal efficiency. This result indicates that the degradation of pollutants in the system mainly depends on the anodic electro-oxidation process. Under the condition of an anode input current of 5 mA and a reaction time of 4.8 h, the anode potential of both the EO-HER dual-cathode system and the EO-4eORR dual-cathode system rises to 2.80 V, consistent with the standard electrode potential of ·OH, as shown in Equation (1). Regarding the cathode potential, the NF / P@Fe-NC cathode used in the EO-4eORR dual-cathode system exhibits polarization from the theoretical value of 1.23 V to 0.90 V, resulting in a low overpotential of only 0.33 V. This phenomenon is attributed to the high catalytic activity of the NF / P@Fe-NC cathode, which effectively promotes the four-electron oxygen reduction reaction. In contrast, the Pt cathode used in the EO-HER dual-cathode system exhibited significant polarization, dropping from the theoretical value of 0V to -0.5V, resulting in an overpotential of 0.5V. This polarization may stem from the poisoning effect of phenol on Pt and the inherent instability of the Pt material. Further energy consumption analysis showed that the EO-4eORR dual-cathode system achieved a TOC removal rate of 95% with an energy consumption of 2.53 kWh / kg TOC, compared to 4.42 kWh / kg TOC for the EO-HER dual-cathode system, achieving a significant energy saving of 42.8%.

[0059] Example 2:

[0060] This embodiment uses an EO-4eORR single cathode system and an EO-4eORR dual cathode system to treat the pollutant phenol. The EO-4eORR dual cathode system in this embodiment is completely identical to the EO-4eORR dual cathode system in Example 1. The only difference between the EO-4eORR single cathode system and the EO-4eORR dual cathode system is that an NF / P@Fe-NC cathode 3 is provided only on the BDD anode 2 side.

[0061] The above-mentioned EO-4eORR single-cathode system and EO-4eORR dual-cathode system were used to treat the pollutant phenol. Figure 4 This is a schematic diagram of the working state of the two systems in Example 2. The specific reaction conditions are as follows: phenol as the pollutant to be treated, TOC = 200 mg / L, potassium hydroxide concentration: 0.1 mol / L, reaction solution volume: 100 mL, BDD anode current density: 5 mA / cm². 2Aeration rate: 70 mL / min; Initial pH of the phenol solution to be treated: 12.0. The EO-4eORR single-cathode system and the EO-4eORR dual-cathode system both achieved phenol TOC removal rates of 95% or higher at treatment times of 6 h and 4.8 h, respectively. At this time, the EO-4eORR single-cathode system (cathode area 1.5 cm²) achieved the highest TOC removal rate. 2 ) and the EO-4eORR dual cathode system (cathode area 1.5 cm²) 2 The specific results of the comparison of anode and cathode potentials, input voltage and energy consumption (×2) are shown in Table 3.

[0062] Table 3

[0063]

[0064] The results, as shown in Table 3, indicate that under the conditions of maintaining an aeration rate of 70 mL / min and an applied current of 5 mA, the EO-4eORR dual-cathode system of this invention exhibits a significant advantage in cathode potential. Specifically, the cathode potential of the EO-4eORR dual-cathode system reaches 0.90 V, significantly higher than the 0.25 V of the EO-4eORR single-cathode system. This phenomenon can be attributed to the fact that the EO-4eORR dual-cathode design, with its larger cathode surface area, leads to a lower actual cathode current density under constant current input conditions, effectively reducing cathode polarization and lowering the cathode overpotential. This improvement reduces the required external input voltage for the entire system to 2.00 V, a significant reduction compared to 2.68 V with a single cathode configuration. Regarding the anode, the dual-cathode system design maximizes the utilization efficiency of the anode working area, thereby increasing the spatiotemporal yield of anode pollutant conversion. Therefore, the EO-4eORR dual-cathode system also exhibits a significantly higher pollutant removal rate per unit time than the EO-4eORR single-cathode system. Quantitative analysis showed that when the TOC removal rate of phenol reached 95%, the energy consumption of the EO-4eORR dual-cathode system was 2.53 kWh / kg TOC, which is 40.2% lower than that of the EO-4eORR single-cathode system (4.23 kWh / kg TOC). This significant reduction in energy consumption not only confirms the superiority of the EO-4eORR dual-cathode system in improving the efficiency of electrochemical water treatment, but also demonstrates its potential for energy saving and emission reduction in practical applications.

[0065] Example 3:

[0066] This embodiment uses an EO-4eORR single-cathode system and an EO-4eORR dual-cathode system to treat the pollutant phenol. The EO-4eORR dual-cathode system in this embodiment is completely identical to the EO-4eORR dual-cathode system in Example 1. The only difference between the EO-4eORR single-cathode system and the EO-4eORR single-cathode system in Example 2 is that the cathode size is (3cm×1cm), that is, the area of ​​a single cathode is equal to the area of ​​the cathode in the EO-4eORR dual-cathode system.

[0067] The above-mentioned EO-4eORR single-cathode system and EO-4eORR dual-cathode system were used to treat the pollutant phenol. The specific reaction conditions were as follows: pollutant phenol, TOC = 200 mg / L, potassium hydroxide concentration: 0.1 mol / L, reaction solution volume: 100 mL, BDD anolyte current density: 5 mA / cm². 2 Aeration rate: 70 mL / min; Initial pH of the phenol solution to be treated: 12.0. The EO-4eORR single-cathode system and the EO-4eORR dual-cathode system both achieved phenol TOC removal rates of 95% or higher at treatment times of 6 h and 4.8 h, respectively. At this time, the EO-4eORR single-cathode system (cathode area 3 cm²) achieved the highest TOC removal rate. 2 ) and the EO-4eORR dual cathode system (cathode area 1.5 cm²) 2 The specific results of the comparison of anode and cathode potentials, input voltage and energy consumption (×2) are shown in Table 4.

[0068] Table 4

[0069]

[0070] The results, as shown in Table 4, indicate that the phenol TOC removal rates of the two systems in this embodiment remained almost unchanged compared to Example 2 at treatment times of 6 h and 4.8 h, further demonstrating that the dual-cathode system has a higher pollutant removal rate than the single-cathode system. When the phenol TOC removal rates of the two systems were almost equal (reaching 95% or higher), the cathode potential of the EO-4eORR dual-cathode system was 0.90 V, higher than the 0.76 V of the EO-4eORR single-cathode system. This may be because the arrangement of the dual cathodes weakens the cathode polarization phenomenon, effectively reducing cathode polarization and lowering the cathode overpotential while ensuring a relative balance between the anode and cathode areas. This further illustrates the energy-saving and emission-reduction potential of the EO-4eORR dual-cathode system proposed in this invention in practical applications.

[0071] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A water treatment system with electro-oxidation coupled to four-electron oxygen reduction, characterized in that, The water treatment system includes an electrolytic cell, a BDD anode located within the electrolytic cell, cathodes located on both sides of the BDD anode, and aeration discs for introducing oxygen into the BDD anode and cathode. The cathode includes a cathode substrate and a catalyst layer, wherein the catalyst layer is P@Fe-NC, and the preparation process of P@Fe-NC includes: mixing Fe(NO3)3·9H2O with phytic acid, Zn(NO3)2·6H2O and 2-methylimidazole in a solvent, precipitating and drying to obtain a precursor, and pyrolyzing the precursor under an argon atmosphere to obtain P@Fe-NC; The molar ratio of Fe(NO3)3·9H2O, phytic acid, Zn(NO3)2·6H2O and 2-methylimidazole is (0.1-0.2):(0.1-0.2):(8-9):(36-37). In the pyrolysis, the pyrolysis temperature is 700-900℃ and the pyrolysis time is 1-2 h.

2. The water treatment system with electro-oxidation coupled to four-electron oxygen reduction according to claim 1, characterized in that, The cathode substrate is selected from one of carbon felt, nickel foam, graphite felt, or carbon foam.

3. The water treatment system with electro-oxidation coupled to four-electron oxygen reduction according to claim 1, characterized in that, The cathode preparation process includes: dispersing P@Fe-NC in a mixed solution of ethanol, water and naphthol and sonicating, then adding a cathode substrate for impregnation and sonication to obtain a cathode substrate / P@Fe-NC, which serves as the cathode.

4. The water treatment system with electro-oxidation coupled to four-electron oxygen reduction according to claim 3, characterized in that, The feeding ratio of P@Fe-NC to naphthol is (45-55) mg: (98-110) μL, and the mass ratio of the cathode substrate to P@Fe-NC is (45-52):(50-55).

5. The water treatment system with electro-oxidation coupled to four-electron oxygen reduction according to claim 1, characterized in that, The BDD anode and dual cathodes are placed in parallel opposite directions, with a distance of 1-3 cm between adjacent electrodes.

6. An application of a water treatment system based on the electro-oxidation coupled four-electron oxygen reduction system as described in any one of claims 1-5, characterized in that, The water treatment system described is used to degrade organic pollutants.

7. The application of the water treatment system with electro-oxidation coupled to four-electron oxygen reduction according to claim 6, characterized in that, The organic pollutants include at least one of phenolic compounds and heterocyclic compounds.

8. The application of the water treatment system with electro-oxidation coupled to four-electron oxygen reduction according to claim 6, characterized in that, Degradation conditions include: BDD anodic current density of 5-25 mA / cm². 2 The oxygen aeration rate is 30-70 mL / min; the electrolyte is 0.1 mol / L potassium hydroxide, and the pH value is controlled between 11.0 and 13.0.

Images