A Fe / g-C3N4 modified cathode-deposited microbial fuel cell and its application in self-driven photoelectro-Fenton degradation of tetracycline

Abstract

The present invention discloses an Fe / g-C3N4-modified cathode-deposited microbial fuel cell and its application in self-driven photoelectro-Fenton degradation of tetracycline, belonging to the technical field of water pollution treatment. The Fe / g-C3N4-modified cathode-deposited microbial fuel cell includes: a reactor, in which a cathode region and an anode region are provided. The cathode region includes water and an Fe / g-C3N4-modified carbon felt cathode fixed on the water surface. The anode region includes a water sediment matrix and a carbon felt anode buried in the water sediment matrix. The Fe / g-C3N4-modified carbon felt cathode and the carbon felt anode form a closed circuit by connecting an external resistor. Compared with other technologies, the present invention can achieve efficient photoelectric synergistic degradation of tetracycline without external energy and H2O2 under natural light, with a simple structure, low construction and operation costs, and easy management and maintenance.

Description

Technical Field

[0001] The present invention relates to an Fe / g-C3N4 modified cathode deposition type microbial fuel cell and its application in self-driven photoelectro-Fenton degradation of tetracycline, belonging to the technical field of water pollution control. Background Art

[0002] As broad-spectrum antibacterial drugs, tetracycline antibiotics are widely used in the medical, livestock, and aquaculture fields in China. However, the problem of their environmental residues is becoming increasingly serious. Tetracycline in the environment mainly migrates and diffuses through the discharge of medical wastewater, excreta from farms, and application in the environment. Existing monitoring data show that the detected concentrations of tetracycline in water bodies and soils in some areas have exceeded the ecological safety threshold of 0.5 mg / L, resulting in problems such as ecological toxicity and the spread of resistance genes.

[0003] Currently, the methods for removing tetracycline antibiotics mainly include physical adsorption, chemical oxidation, and biodegradation. However, compared with other types of wastewater, the composition of antibiotic wastewater is relatively complex and highly toxic, and the traditional single-process treatment method cannot achieve good treatment effects, highlighting the urgency of developing efficient and low-carbon advanced treatment technologies. Summary of the Invention

[0004] In view of the above technical problems, the present invention provides an Fe / g-C3N4 modified cathode deposition type microbial fuel cell and its application in self-driven photoelectro-Fenton degradation of tetracycline.

[0005] The technical solution adopted by the present invention to achieve the technical purpose is as follows:

[0006] The present invention provides an Fe / g-C3N4 modified cathode deposition type microbial fuel cell, comprising: a reactor, in which a cathode region and an anode region are provided. The cathode region includes water and an Fe / g-C3N4 modified carbon felt cathode fixed on the water surface. The anode region includes a water sediment matrix and a carbon felt anode buried in the water sediment matrix. The Fe / g-C3N4 modified carbon felt cathode and the carbon felt anode form a closed circuit by connecting an external resistor.

[0007] Preferably, the height ratio of the cathode region to the anode region is 0.9~1.1.

[0008] Preferably, the water sediment matrix includes sea sand and quartz sand, and the carbon felt anode is buried in the quartz sand 5~10 cm away from the bottom of the reactor in the anode region.

[0009] More preferably, the particle size of the sea sand is 0.1~0.3 cm, and the laying thickness is 2~4 cm; the particle size of the quartz sand is 0.2~0.5 cm, and the laying thickness is 8~16 cm.

[0010] Preferably, the reactor is a cylinder made of acrylic organic glass, with a diameter of 20 - 30 cm and a height of 25 - 45 cm, and is provided with a water inlet hole, a water outlet hole, and a sampling hole.

[0011] Preferably, the Fe / g-C3N4 modified carbon felt cathode has a length of 5 - 8 cm, a width of 5 - 8 cm, a thickness of 0.2 - 0.4 cm, and the loading amount of Fe / g-C3N4 is 4 - 8 mg / cm 2 ; the carbon felt anode has a length of 5 - 8 cm, a width of 5 - 8 cm, and a thickness of 0.2 - 0.4 cm.

[0012] Preferably, the Fe / g-C3N4 modified carbon felt cathode and the carbon felt anode are connected by a titanium wire to an external resistor.

[0013] More preferably, the diameter of the titanium wire is 0.1 - 0.2 cm, and the resistance value of the external resistor is 100 - 2000 Ω.

[0014] Preferably, a data collector is also connected to the closed circuit.

[0015] The present invention also provides the application of any one of the above Fe / g-C3N4 modified cathode deposition type microbial fuel cells in the self-driven photoelectro-Fenton reaction for degrading tetracycline.

[0016] The present invention realizes the coupling of a deposition type microbial fuel cell (SMFC) and a photoelectro-Fenton (PEF) technology. By integrating bioelectrochemistry, photocatalysis, and electrochemical oxidation mechanisms, an efficient and sustainable pollution treatment and energy recovery system is formed. Its core advantages are as follows: 1) Energy self-sufficiency and in-situ pollutant removal; 2) Enhanced Fe 3+ / Fe 2+ cycle and free radical generation; 3) Economy and environmental friendliness; 4) System stability and multi-functional remediation potential. Among them, the Fe / g-C3N4 composite photocatalytic material of the modified carbon felt cathode has extremely strong photocatalytic performance. The doping of Fe not only expands the visible light absorption range of g-C3N4, but also enhances the separation efficiency of photogenerated electron-hole pairs. In addition, the Fe / g-C3N4 composite photocatalytic material has a relatively wide pH application range (pH 3 - 9), overcoming the drawback that traditional iron-based materials can only work under acidic conditions (pH 3 - 4).

[0017] Compared with other technologies, the present invention can achieve photoelectric synergistic and efficient degradation of tetracycline under natural light without the need for external energy and H2O2. It has a simple structure, low construction and operation costs, and is easy to manage and maintain. When the Fe / g-C3N4 modified carbon felt cathode is exposed to sufficient light, the sedimentation-type microbial fuel cell of the present invention is used to treat simulated wastewater containing 5-20 mg / L of tetracycline. The degradation rate reaches more than 99% within 3-4 days, the maximum output voltage reaches 752 mV, and the maximum power density reaches 30.42 mW / m 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the Fe / g-C3N4-modified cathode deposition-type microbial fuel cell based on the present invention, in which: 1, reactor, 2, tetracycline simulated wastewater, 3, sea sand, 4, quartz sand, 5, Fe / g-C3N4-modified carbon felt cathode, 6, titanium wire, 7, carbon felt anode, 8, external resistor, 9, copper wire, 10, data collector, 11, light.

[0019] Figure 2 The photocatalytic performance test results of the Fe / g-C3N4 composite photocatalytic material in Example 1 are as follows: Figure 2 (a) is the UV-visible diffuse reflectance spectrum (UV), Figure 2 (b) is the degradation rate of tetracycline by Fe / g-C3N4 photocatalytic degradation at different pH. Figure 2 (c) in the figure is the electron paramagnetic resonance (EPR) spectrum.

[0020] Figure 3 The results of the self-driven cathode electro-Fenton reaction in the dark to degrade tetracycline simulated wastewater using the Fe / g-C3N4 modified cathode deposition type microbial fuel cell in Example 1 are as follows: Figure 3 (a) is the cyclic voltammetry (CV) curve at different pH. Figure 3 (b) is the degradation rate of tetracycline by SMFC electro-Fenton degradation. Figure 3 (c) in the figure is the electron paramagnetic resonance (EPR) spectrum.

[0021] Figure 4 The results of the self-driven cathode electro-Fenton reaction in the Fe / g-C3N4 modified cathode deposition type microbial fuel cell under light conditions in Example 2 to degrade tetracycline simulated wastewater are shown. Figure 4 (a) is the UV-visible diffuse reflectance spectrum (UV), Figure 4 (b) is the cyclic voltammetry (CV) curve under dark / light conditions. Figure 4 (c) in the figure is the photoresponse current (it) diagram.

[0022] Figure 5 The detection results of using the Fe / g-C3N4 modified cathode deposition type microbial fuel cell in Example 2 for the self-driven cathode electro-Fenton reaction to degrade tetracycline simulated wastewater under light conditions Figure 5 In (a) is the degradation rate diagram of tetracycline degraded by SMFC photoelectro-Fenton Figure 5 In (b) is the electron paramagnetic resonance spectroscopy (EPR) diagram [[ID=)16]]Figure 5 In (c) is the output voltage diagram of SMFC Figure 5 In (d) are the power density and polarization curve diagrams of SMFC Specific implementation manners

[0023] The present invention will be described in detail below in conjunction with specific implementation manners. The following specific examples are helpful for those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0024] The structure of the Fe / g-C3N4 modified cathode deposition type microbial fuel cell of the present invention is as Figure 1 shown, mainly including: a reactor 1, in which a cathode area and an anode area are provided. The cathode area includes a water body (tetracycline simulated wastewater 2 in the following examples) and a Fe / g-C3N4 modified carbon felt cathode 5 fixed on the water surface of the water body. The anode area includes a water body sediment matrix (sea sand 3 and quartz sand 4 in the following examples) and a carbon felt anode 7 buried in the water body sediment matrix. The Fe / g-C3N4 modified carbon felt cathode 5 and the carbon felt anode 7 form a closed circuit by connecting an external resistor 8, and a data collector 10 is connected to the closed circuit through a copper wire 9.

[0025] Preferably, the reactor 1 is a cylinder made of acrylic organic glass, with a diameter of 20 - 30 cm and a height of 25 - 45 cm, provided with a water inlet hole, a water outlet hole, and a sampling hole; the particle size of the sea sand 3 is 0.1 - 0.3 cm, and the laying thickness is 2 - 4 cm; the particle size of the quartz sand 4 is 0.2 - 0.5 cm, and the laying thickness is 8 - 16 cm; the height ratio of the cathode area to the anode area is 0.9 - 1.1; the length of the Fe / g-C3N4 modified carbon felt cathode 5 is 5 - 8 cm, the width is ς - 8 cm, and the thickness is 0.2 - 0.4 cm, and the loading amount of Fe / g-C3N4 is 4 - 8 mg / cm 2 ; the length of the carbon felt anode 7 is 5 - 8 cm, the width is 5 - 8 cm, and the thickness is 0.2 - 0.4 cm, buried in the quartz sand 4 in the anode area at a distance of 5 - 10 cm from the bottom of the reactor 1; the diameter of the titanium wire 6 is 0.1 - 0.2 cm, and the resistance value of the external resistor 8 is 100 - 2000 Ω.

[0026] The method for degrading tetracycline by self-driven photoelectro-Fenton reaction using Fe / g-C3N4 modified cathode deposition-type microbial fuel cell in the present invention includes: (1) constructing a deposition-type microbial fuel cell system: the anode area is arranged in the water sediment matrix layer, including a carbon felt anode buried in a mixed matrix of quartz sand and sea sand; the cathode area is arranged on the water surface layer, including an Fe / g-C3N4 modified carbon felt cathode fixed on the water surface; the carbon felt anode and the Fe / g-C3N4 modified carbon felt cathode form a closed circuit through an external resistor; (2) starting the bioelectrochemical process: electroactive microorganisms are enriched on the anode surface to form an electroactive biofilm, and the chemical energy of sediment organic matter is converted into electrons through anaerobic metabolism. The electrons are transferred to the anode surface through the extracellular electron transfer pathway, and further migrate to the Fe / g-C3N4 modified carbon felt cathode at the water surface through the external circuit to form a closed circuit; (3) driving the cathode photoelectro-Fenton synergistic reaction: electrons are transferred from the anode to the cathode through the external circuit, taking oxygen (O2) and Fe³⁺ as electron acceptors to generate H2O2 and Fe 2+ (O2 + 2H + + 2e - → H2O2, Fe 3+ + e - → Fe 2+ ), the generated H2O2 and Fe 2+ generate strongly oxidizing hydroxyl radicals (•OH) through the Fenton reaction and regenerate Fe 3+ (Fe 2+ + H2O2 → Fe 3+ + •OH + OH - ); meanwhile, electrons and holes are generated in the cathode Fe / g-C3N4 under light excitation. The photogenerated electrons generate H2O2 by reducing dissolved oxygen (O2 + 2H + + 2e - → H2O2) and accelerate the reduction regeneration of Fe 3+ (Fe 3+ + e - → Fe 2+ ), and the valence band holes generate hydroxyl radicals (•OH) by oxidizing water molecules / hydroxyl ions (H2O / OH - + h + → •OH) or directly oxidize organic pollutants; (4) through the continuous coupling effect of steps (2)-(3), efficient degradation of tetracycline is achieved.

[0027] Example 1

[0028] I. Synthesis of Fe / g-C3N4 composite photocatalytic material and its photocatalytic degradation of tetracycline

[0029] Synthesis of Fe / g-C3N4 composite photocatalytic material: Weigh 1.0 g of FeCl3·6H2O and 5.0 g of urea according to the mass ratio of 1:5, add them to 10 mL of pure water, and ultrasonicate for 20 - 30 min until completely dissolved. Then transfer it to a narrow-mouth anaerobic bottle, wrap it with tin foil, and place it in a muffle furnace for calcination at 550 °C for 2 h (heating rate is 10 °C / min). Finally, thoroughly grind the obtained solid to obtain Fe / g-C3N4 powder.

[0030] It can be detected by ultraviolet-visible diffuse reflectance spectroscopy that Fe / g-C3N4 has very strong light absorption performance in both the ultraviolet light wavelength range (200 - 380 nm) and the visible light wavelength range (380 - 760 nm) ( Figure 2 (a) in Figure 2 ); in the photocatalytic degradation reaction system (Fe / g-C3N4 50 mg / L, tetracycline 20 mg / L, H2O2 6 mM, xenon lamp 200 W, 25 ± 5 °C) ( + (b) in Figure 2 ), the degradation rate of 20 mg / L tetracycline by Fe / g-C3N4 reached over 99% within 10 min under the condition of pH 3 - 7; under the condition of pH 9, although the photocatalytic degradation effect of Fe / g-C3N4 was inhibited by 34%, the degradation rate of tetracycline could still reach over 99% within 30 min, indicating that the Fe / g-C3N4 composite photocatalytic material has a relatively wide pH application range (pH 3 - 9). Through electron paramagnetic resonance (EPR) technology, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) captured a typical •OH signal peak with a signal peak intensity ratio of 1:2:2:1. At the same time, the h

[0031] II. Construction of Fe / g-C3N4 modified cathode deposition type microbial fuel cell and its self-driven electro-Fenton reaction for degradation of tetracycline

[0032] Carbon felt pretreatment method: Immerse the cut carbon felt electrode (length × width × thickness = 6 cm × 6 cm × 0.2 cm) in 1 M HCl solution for 24 h, take it out, rinse it with pure water until neutral, and put it in an oven at 60 °C for drying.

[0033] Acclimation of carbon felt anode: 5.0 g of paddy soil was added to 50 mL of LB liquid medium and activated for 24 h. Then, 10 mL of the activated bacterial solution was added to 100 mL of EM medium containing 30 mM ferric citrate. After purging with nitrogen to remove oxygen, it was further enriched and cultured on a shaker at a rotation speed of 120 rpm and a temperature of 30 °C for 48 h. After replenishing the enriched bacterial solution with fresh medium (keeping the nutrient concentration unchanged), a pretreated carbon felt electrode (6 cm × 6 cm × 0.2 cm) was placed back into the wide-mouth bottle, purged with nitrogen to remove oxygen, sealed, and cultured on a shaker (under the same culture conditions) so that electroactive microorganisms could rapidly enrich on the carbon felt to form an electroactive biofilm.

[0034] LB liquid medium formula: Peptone 10.0 g / L, Yeast extract 5.0 g / L, NaCl 10.0 g / L.

[0035] EM medium formula: NaHCO3 2.5 g / L, KH2PO4 0.6 g / L, NH4Cl 1.5 g / L, KCl 0.1 g / L, CH3COONa 1.36 g / L, Vitamins 1.0 mL / L, Mineral elements 2.0 mL / L.

[0036] Preparation of Fe / g-C3N4 modified carbon felt cathode: An appropriate amount of Fe / g-C3N4 powder obtained in the first step was weighed and added to 100 mL of absolute ethanol, and then 400 μL of 5% Nafion D520 solution (DuPont, USA) was added. It was ultrasonicated for 20 - 30 min to disperse it evenly. A pretreated carbon felt electrode (6 cm × 6 cm × 0.2 cm) was immersed in it. After ultrasonicating for 1.5 h, it was left standing for 30 min, taken out, washed with pure water, and dried in an oven at 60 °C. The carbon felt electrode was weighed before and after loading Fe / g-C3N4 to calculate the loading amount of Fe / g-C3N4.

[0037] Construction of sedimentary microbial fuel cell (SMFC) reactor: In a dark environment, in the reactor (diameter 20 cm, height 25 cm), there was a cathode region (height 10 cm) composed of tetracycline simulated wastewater (5 - 40 mg / L) and an anode region composed of sea sand (height 2 cm) and quartz sand (height 8 cm); the Fe / g-C3N4 modified carbon felt cathode (loading amount 6 mg / cm 2 ) was fixed on the liquid surface of the cathode region, and the carbon felt anode was buried in the quartz sand matrix 5 cm away from the bottom of the reactor in the anode region. The two were connected by a titanium wire with an external resistor (1000 Ω); the data collector was connected to the circuit of the reactor through a copper wire.

[0038] The cyclic voltammetry detection results show that the Fe / g-C3N4 modified cathode carbon felt has significant redox peaks in acidic and neutral environments (pH 3 - 7) ( Figure 3 (a) in

[0039] ); while in the weak alkaline environment (pH 7 - 9), although its electrochemical performance is inhibited, it still has redox peaks of a certain intensity, indicating that the Fe / g-C3N4 modified carbon felt cathode has a wide pH adaptability. Figure 3 Figure 3 + Using the Fe / g-C3N4 modified cathode deposition type microbial fuel cell, the tetracycline simulated wastewater (5 - 40 mg / L) was degraded by the self-driven cathode electro-Fenton reaction under dark conditions. The results show that the degradation rate of this system for tetracycline at a lower concentration (5 - 20 mg / L) reached over 99% within 8 - 10 days, and the degradation rate for tetracycline at a higher concentration (40 mg / L) reached over 99% within 14 days ( Figure 3 (b) in

[0040] Example 2

[0041] Construction of Fe / g-C3N4 Modified Cathode Deposition Type Microbial Fuel Cell and Its Self-Driven Photoelectro-Fenton Reaction for Degrading Tetracycline

[0042] Carbon felt pretreatment method: the same as in Example 1.

[0043] Domestication of the carbon felt anode: the same as in Example 1.

[0044] Preparation of Fe / g-C3N4 modified carbon felt cathode: the same as in Example 1.

[0045] Assembly of the SMFC reactor: Under sunlight irradiation, in the reactor (diameter 20 cm, height 25 cm), a cathode area (height 10 cm) composed of tetracycline simulated wastewater (5 - 40 mg / L) and an anode area composed of sea sand (height 2 cm) and quartz sand (height 8 cm) are set; the Fe / g-C3N4 modified carbon felt cathode (loading amount 6 mg / cm 2 ) is fixed on the liquid surface of the cathode area, the carbon felt anode is buried in the quartz sand matrix 5 cm away from the bottom of the reactor in the anode area, and the two are connected by a titanium wire with an external resistance (1000 Ω); the data collector is connected to the circuit of the reactor through a copper wire.

[0046] It can be detected by ultraviolet-visible diffuse reflectance spectroscopy that the light absorption performance of the carbon felt cathode modified with Fe / g-C3N4 has been improved by 22% - 31% in the ultraviolet light wavelength range (200 - 380 nm) and by 31% - 77% in the visible light wavelength range (380 - 760 nm) ( Figure 4 (a) in Figure 4 ); in cyclic voltammetry detection, the Fe / g-C3N4 modified carbon felt cathode exhibits significant redox peaks under dark conditions, and the height of the redox peaks is further increased by 31% under light conditions ( Figure 4 (b) in

[0047] The Fe / g-C3N4 modified cathode deposition type microbial fuel cell of the present invention degrades tetracycline by self-driven photoelectro-Fenton reaction, and shows a very high degradation effect when degrading tetracycline simulated wastewater at a lower concentration (5 - 20 mg / L) (the degradation rate reaches more than 99% in 3 - 4 days) ( Figure 5 (a) in Figure 5 When degrading 5 mg / L of tetracycline simulated wastewater, the SMFC obtains a maximum output voltage of 752 mV ( 2 ( Figure 5 (d) in + ); when degrading tetracycline simulated wastewater at a higher concentration (40 mg / L), the SMFC can still operate stably, and the output voltage is only inhibited by 16% - 38% in the early stage of the operation cycle, and the maximum power density is weakened by 20%. The degradation rate of tetracycline reaches more than 99% within 6 days; through electron paramagnetic resonance (EPR) technology, a typical •OH signal peak with a signal peak intensity ratio of 1 : 2 : 2 : 1 is captured by DMPO in the photoelectro-Fenton system, and the intensity ratio of the triplet peaks captured by TEMPO h Figure 5 It should be noted that there seems to be a small error in your original text where "[[ID=)16]]" is likely a typo. I've translated it as "Figure 5" as it's the most logical assumption based on the pattern, but you may want to double-check the original if this is incorrect. (b) in

[0048] By integrating bioelectrochemistry, photocatalysis, and electrochemical oxidation mechanisms, the present invention has formed an efficient and sustainable technology for pollution treatment and energy recovery. Compared with other technologies, it does not require external energy and H2O2, has a simple structure, low construction and operation costs, and is easy to manage and maintain. The coupling of SMFC and photoelectro-Fenton technology has increased the degradation efficiency by 1.3 to 1.7 times compared to the coupling of SMFC with only electro-Fenton technology when treating tetracycline simulated wastewater with the same concentration. The potential of the present invention in the fields of environmental remediation and green energy has been significantly demonstrated, and it has significant practical environmental application potential. Future research can focus on the development of an intelligent regulation system to further improve the environmental adaptability and comprehensive benefits of the system.

[0049] Obviously, the above embodiments of the present invention are merely examples for more clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is impossible to enumerate all the implementation methods here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. Application of Fe / g-C3N4 modified cathode deposition type microbial fuel cell in self-driven photoelectro-Fenton reaction for degradation of tetracycline, characterized in that, The described Fe / g-C3N4 modified cathode deposition type microbial fuel cell includes: a reactor, in which a cathode area and an anode area are provided. The cathode area includes water and a Fe / g-C3N4 modified carbon felt cathode fixed on the water surface. The anode area includes a water sediment matrix and a carbon felt anode buried in the water sediment matrix. The Fe / g-C3N4 modified carbon felt cathode and the carbon felt anode form a closed circuit by connecting an external resistor. The Fe / g-C3N4 composite photocatalytic material for modifying the carbon felt cathode is synthesized by the following method: Weigh 1.0 g of FeCl3·6H2O and 5.0 g of urea according to a mass ratio of 1:5, add them to 10 mL of pure water and ultrasonicate for 20 - 30 min until completely dissolved, then transfer to a narrow-mouth anaerobic bottle, wrap it with tin foil, put it into a muffle furnace and calcine at 550 °C for 2 h, and finally grind the obtained solid thoroughly to obtain Fe / g-C3N4 powder.

2. The application according to claim 1, wherein The height ratio of the cathode area to the anode area is 0.9 - 1.

1.

3. The application according to claim 1, characterized in that, The water sediment matrix includes sea sand and quartz sand, and the carbon felt anode is buried in the quartz sand 5 - 10 cm away from the bottom of the reactor in the anode area.

4. The application according to claim 3, characterized in that, The particle size of the sea sand is 0.1 - 0.3 cm, and the laying thickness is 2 - 4 cm; the particle size of the quartz sand is 0.2 - 0.5 cm, and the laying thickness is 8 - 16 cm.

5. The application according to claim 1, wherein The reactor is a cylinder made of acrylic organic glass, with a diameter of 20 - 30 cm and a height of 25 - 45 cm, and is provided with a water inlet hole, a water outlet hole, and a sampling hole.

6. The application according to claim 1, wherein The length of the Fe / g-C3N4 modified carbon felt cathode is 5-8 cm, the width is 5-8 cm, the thickness is 0.2-0.4 cm, and the loading amount of Fe / g-C3N4 is 4-8 mg / cm 2 ; The length of the carbon felt anode is 5-8 cm, the width is 5-8 cm, and the thickness is 0.2-0.4 cm.

7. The application according to claim 1, wherein The Fe / g-C3N4 modified carbon felt cathode and the carbon felt anode are connected to an external resistor through a titanium wire.

8. The application according to claim 7, wherein The diameter of the titanium wire is 0.1 - 0.2 cm, and the resistance value of the external resistor is 100 - 2000 Ω.

9. The application according to claim 1, characterized in that, A data collector is also connected to the closed circuit.

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