An electrochemical process and device for sewage treatment, synergistic power generation and fuel production

Abstract

An electrochemical process and device for wastewater treatment, combined with electricity generation and fuel production, uses at least one of ruthenium-cobalt and ruthenium-copper catalysts to electrocatalyze hydrazine oxidation, nitrate reduction, and hydrogen evolution reactions. A hydrazine-nitrate cell, composed of industrial hydrazine waste and nitrate wastewater, is assembled for power generation and ammonia production. Furthermore, the generated electricity can also drive a hydrazine wastewater electrolyzer, thereby producing hydrogen.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical wastewater treatment, and in particular to an electrochemical process and reaction device capable of simultaneously treating hydrazine wastewater and nitrate wastewater and simultaneously generating electricity, ammonia and hydrogen. Background Art

[0002] In recent years, the rapid development of urbanization, agriculture, and industrialization has brought about a series of problems, such as the greenhouse effect, air pollution, and environmental pollution. The direct discharge of industrial, agricultural, and urban sewage can seriously contaminate surface water resources, leading to ecosystem imbalances. Consequently, standards for pollutant emissions are becoming increasingly stringent. Currently, pollutants in industrial, agricultural, and urban sewage primarily include organic matter, heavy metal ions, sulfur salts, nitrogen salts, and phosphorus salts. Because sewage contains many substances that are toxic and harmful to humans, animals, and plants, direct discharge of sewage not only directly endangers life on Earth but also causes immeasurable harm to the ecological environment. Traditional sewage treatment processes include enzyme catalysis, physical multiple evaporation crystallization, and chemical Fenton reactions. These treatment methods inevitably involve complex separation processes, additional energy consumption, and the use of chemical reagents, which increases sewage treatment costs. Furthermore, the pollutant removal efficiency of these traditional methods is unsatisfactory. Therefore, there is an urgent need to develop new and efficient sewage treatment technologies and processes.

[0003] In recent years, electrochemical wastewater treatment has garnered significant attention. Compared to traditional physical, chemical, and biological methods for treating wastewater, electrochemical water treatment offers advantages such as rapid reaction rates, controllable product selectivity, and high wastewater purification efficiency. However, the electrolytic cells used in this approach suffer from small capacity, high ohmic impedance, and a single wastewater treatment method. Consequently, this approach often consumes excessive electrical energy and requires the design of electrolytic cells with high liquid flow rates and specialized electrode catalysts. Therefore, this technology remains unsuitable economically and technically as a standalone wastewater treatment process. Summary of the Invention

[0004] The purpose of the present invention is to address the shortcomings of existing electrochemical technologies in sewage treatment and to provide an electrochemical process and device for sewage treatment that can synergistically generate electricity and produce fuel. The process and device can simultaneously treat hydrazine and nitrate sewage and synergistically generate electricity, ammonia and hydrogen, thereby achieving the purpose of spontaneously purifying the two waste liquids and simultaneously generating electricity and producing fuel.

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

[0006] An electrochemical process for wastewater treatment to generate electricity and fuel, comprising the following steps:

[0007] 1) Using a close-fitting membrane electrode flow reactor to construct a hydrazine-nitrate battery and a hydrazine electrolyzer;

[0008] 2) using a ruthenium-cobalt-copper-based catalyst to drive hydrazine oxidation, nitrate reduction, and hydrogen evolution reactions; the ruthenium-cobalt-copper-based catalyst is at least one of a ruthenium-cobalt-based catalyst and a ruthenium-copper-based catalyst;

[0009] 3) Highly purifying hydrazine and nitrate wastewater by mixing and stirring under the action of ruthenium cobalt copper-based catalyst, wherein the concentration range of the hydrazine and nitrate wastewater is 0.01-2000 mM.

[0010] 1. Assembly of the membrane electrode flow reactor of the present invention:

[0011] The present invention assembles a close-fitting membrane electrode flow reactor comprising a bipolar plate, cathode current collector, diaphragm, anode current collector, and bipolar plate. The bipolar plate material of this assembly can be selected from titanium, stainless steel, graphite, or organic glass. A flow channel is provided on the bipolar plate, with liquid inlet and outlet ports at both ends. The liquid flow channel can be a fully hollow channel or a serpentine channel. The diaphragm can be a cation exchange membrane, a proton exchange membrane, an anion exchange membrane, or a glass fiber diaphragm. The liquid inlet and outlet can be made of iron or plastic with external threaded pagoda connectors or quick-connect connectors. The wires can be titanium, silver, or copper wires. A silicone gasket needs to be added between the bipolar plates. Finally, holes are opened around the two bipolar plates, and suitable plastic or stainless steel bolts and nuts are selected and tightened to secure the membrane electrode flow reactor. The cathode and anode current collectors are loaded with the ruthenium cobalt copper-based catalyst.

[0012] 2. Selection and synthesis of catalysts in the present invention:

[0013] The catalysts used to drive the hydrazine oxidation, nitrate reduction, and hydrogen evolution reactions in the present invention are oxides, hydroxides, metals, and composites thereof, primarily composed of ruthenium, cobalt, and copper. These catalysts can be grown directly on the current collector in situ or coated on the current collector by spraying and hot pressing. The current collector can be made of carbon paper, carbon felt, carbon cloth, nickel foam, cobalt foam, copper foam, iron foam, titanium foam, nickel mesh, cobalt mesh, copper mesh, iron mesh, and titanium mesh.

[0014] Take the in-situ synthesis of a ruthenium-cobalt bimetallic catalyst on a cobalt foam current collector as an example. First, a hydrothermal method is used to grow rod-shaped cobalt hydroxide structures on the cobalt foam to expand its specific surface area. Then, ruthenium trichloride is used as a raw material for cation exchange in an aqueous phase, so that the ruthenium species is loaded on the rod-shaped cobalt hydroxide. Finally, calcination is performed in a mixed atmosphere of hydrogen and inert gas to form a ruthenium-cobalt bimetallic catalyst. Urea or hexamethylenetetramine is used as a precipitant during hydrothermal treatment, the temperature is 80-160°C, and the reaction time is 4-24 hours. The ruthenium concentration during ion exchange is 0.01-1 mg mL -1The reaction time is 0.5-12 h, the reaction temperature is 0-60 ° C; the calcination temperature is 150-600 ° C, the time is 1-6 h, and the calcination atmosphere is a mixture of hydrogen and inert gas; the synthesized catalyst has a rod-like morphology, and the cobalt loading is 1-5 mg cm -2 , ruthenium loading is 0.01~1mg cm -2 .

[0015] In addition, a hydrothermal method can also be used to directly synthesize rod-shaped cobalt hydroxide powder, which is then cation exchanged with a certain amount of ruthenium trichloride in an aqueous phase to load the ruthenium species on the rod-shaped cobalt hydroxide. The powder is then calcined in a mixture of hydrogen and inert gas to form a ruthenium-cobalt bimetallic powder. Finally, the powder is mixed with a binder and dissolved in an organic solvent. After uniform dispersion, it is loaded on a carbon paper current collector by spraying and hot pressing.

[0016] The ruthenium copper-based catalyst is prepared as follows: first, a copper hydroxide precursor is prepared by electrochemical anodic oxidation or a strong oxidant wet method, then ion exchange is performed with ruthenium ions, and finally calcined under a reducing atmosphere, wherein the electrochemical anodic oxidation current density is 0.01 to 100 mA cm -2 The wet process uses an alkaline persulfate solution as a strong oxidant, with a pH of 12-15, an ammonium persulfate concentration of 0.01-1M, a temperature of 0-60°C, and a reaction time of 1-180 min. The ion exchange ruthenium concentration is 0.01-1 mg mL -1 The reaction time is 0.5-12 h, the reaction temperature is 0-60 ° C; the calcination temperature is 150-500 ° C, the time is 1-6 h, and the calcination atmosphere is a mixture of hydrogen and inert gas. The synthesized catalyst has a rod-like morphology, and the copper loading is 1-5 mg cm -2 , ruthenium loading is 0.01~1mg cm -2 .

[0017] 3. Construction method of the hydrazine-nitrate battery in the present invention:

[0018] The present invention uses a liquid circulation method to allow hydrazine and nitrate wastewater to enter a membrane electrode flow reactor (MEF) to achieve both wastewater purification and electricity generation. First, peristaltic pumps are used to flow the hydrazine and nitrate wastewater into the anode and cathode flow channels of the MEF, respectively. The wastewater is then discharged and returned to the hydrazine and nitrate wastewater tanks, respectively, achieving a circulating flow. The anode and cathode of the MEF are then connected to an electrochemical workstation, and a specific output voltage or current is set to activate the hydrazine-nitrate battery. After a long period of flow circulation testing, the hydrazine in the wastewater is oxidized to nitrogen and the nitrate is reduced to ammonia, achieving the purification goal. Furthermore, the electricity extracted by the electrochemical workstation can be further used to power a hydrazine wastewater electrolyzer for hydrogen production. During the hydrazine-nitrate battery reaction, the nitrogen produced by hydrazine oxidation is directly discharged into the atmosphere, while the ammonia produced by nitrate reduction is subsequently separated using gas stripping technology to produce high-purity and high-concentration ammonia fuel. The hydrogen produced by the hydrazine electrolyzer can then be directly stored in a gas storage tank via a gas-liquid separator.

[0019] 4. Method for constructing the hydrazine electrolytic cell of the present invention:

[0020] The construction method of the hydrazine electrolyzer in the present invention is similar to that of the hydrazine-nitrate battery. First, a peristaltic pump is used to flow the hydrazine wastewater and potassium hydroxide solution into the anode and cathode flow channels of the membrane electrode flow reactor respectively, and then the effluent is returned to the hydrazine wastewater pool and the potassium hydroxide storage tank respectively, thereby achieving the purpose of circulating flow. Then, an electrochemical workstation is connected, and the electricity generated by the above-mentioned hydrazine-nitrate battery is input into the anode and cathode of the hydrazine electrolyzer. After a long period of flow circulation test, the hydrazine in the wastewater is oxidized into nitrogen, thereby achieving the purpose of purification; and the water in the potassium hydroxide solution will be reduced to hydrogen. The generated hydrogen can be collected by the drainage method, or directly stored in the gas storage tank using a gas-liquid separator. If there is no need to control the output power of the hydrazine-nitrate battery and the input power of the hydrazine electrolyzer, the two devices can be directly connected by wires, without the need to use an additional electrochemical workstation as an intermediate medium for energy storage and release.

[0021] 5. The method for highly purifying hydrazine and nitrate wastewater of the present invention:

[0022] In the present invention, if there is no need to collect electricity or if high purification of low-concentration residual hydrazine and nitrate wastewater is required, the two wastewaters can be directly mixed in a container, and then a catalyst is added and stirred.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] 1. The present invention utilizes the electrochemical property that the hydrazine oxidation reaction and the nitrate reduction reaction can spontaneously couple to form a primary cell to treat hydrazine and nitrate wastewater. The method is simple, environmentally friendly, and does not require additional electricity consumption, providing a new approach for the application of electrochemical technology in wastewater treatment. The membrane electrode flow reactor designed in the present invention is specifically used to collect the generated electricity and ammonia products. The generated electricity can also drive the hydrazine wastewater electrolyzer for hydrogen production. It can be seen that the method of the present invention can not only treat hydrazine and nitrate wastewater, but also produce additional electricity, ammonia and hydrogen, achieving multiple goals at one stroke and high economic benefits.

[0025] 2. The membrane electrode flow reactor device of the present invention features a compact design, small footprint, low ohmic resistance, and fast gas / liquid transmission. The reaction can be initiated simply by pouring wastewater into the anode and cathode flow channels of the device. This device can be used to assemble not only hydrazine-nitrate batteries but also hydrazine electrolyzers, thus offering broad applicability.

[0026] 3. In the present invention, a ruthenium-cobalt bimetallic catalyst in situ grown on a cobalt foam substrate is used as an electrocatalyst to drive hydrazine oxidation, nitrate reduction and hydrogen evolution reactions. The hydrazine-nitrate battery assembled with the catalyst has a discharge current density of 100 mA cm -2 When the peak power density is 12 mW cm -2 The ammonia production rate was 0.37 mmol h -1 cm -2 The hydrazine electrolyzer only needs 0.23V cell voltage to reach 50mA cm -2 The current density and hydrogen production rate were 0.93 mmol h -1 cm -2 ; and the former can spontaneously drive the latter to produce hydrogen, with a hydrogen production rate of 0.35 mmol h -1 cm -2 .

[0027] 4. The present invention achieves high-level purification of hydrazine and nitrate wastewater by simply mixing low-concentration residual hydrazine and nitrate wastewater, then adding a catalyst and stirring. After the reaction, the concentrations of hydrazine and nitrate in the wastewater are reduced to below 1 ppm, with removal efficiencies reaching 99.98% and 99.94%, respectively, with excellent repeatability. Furthermore, this technology is simple to manufacture, with easy equipment construction and maintenance, enabling large-scale purification of hydrazine and nitrate wastewater and promising industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the assembly of the membrane electrode flow reactor.

[0029] Figure 2 Scanning electron microscopy and element distribution map of ruthenium-cobalt bimetallic catalyst.

[0030] Figure 3 Schematic diagram and performance diagram of the hydrazine-nitrate battery device.

[0031] Figure 4 Schematic diagram and performance diagram of hydrazine electrolyzer device.

[0032] Figure 5 Schematic diagram of the hydrazine electrolyzer hydrogen production device driven spontaneously by a hydrazine-nitrate battery.

[0033] Figure 6 Schematic diagram of hydrazine and nitrate high-level purification equipment and wastewater residual concentration diagram. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0035] The main components of hydrazine wastewater in the present invention are hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, and other hydrazine-containing derivatives, with the hydrazine concentration ranging from 0.01 to 2000 mM. Nitrate wastewater mainly contains inorganic nitrates, with the nitrate concentration ranging from 0.01 to 2000 mM. These wastewaters may also contain other inorganic salt impurities, such as potassium hydroxide, potassium sulfate, and sodium chloride, as well as some common organic matter, such as fats, alkanes, cellulose, and proteins.

[0036] 1. Specific assembly method of the membrane electrode flow reactor in the present invention:

[0037] First, build a hydrazine-nitrate battery membrane electrode flow reactor and prepare two blocks with a serpentine flow channel (1×1 cm 2 ) and organic glass plates (5×5cm 2 ) as bipolar plates; proton exchange membrane (1.5×1.5cm 2 ) as a separator; two pieces of in-situ grown cobalt foam (1×1cm 2 ) is directly used as the current collector and the hollow silicone gasket, conductive titanium foil, bolts and nuts and other consumables. Figure 1 As shown, first, a plexiglass plate with a serpentine flow channel and four nuts are used as a substrate (step 1), then covered with a layer of hollowed-out silicone gasket (step 2), and placed in the current collector and titanium foil conductor (step 3), then covered with a proton exchange membrane in the middle (step 4), and then covered with another layer of hollowed-out silicone gasket (step 5), then placed in the middle of the current collector and titanium foil conductor (step 6), and finally covered with another plexiglass plate (step 7), and tightened with bolts to seal (step 8).

[0038] The use of a proton exchange membrane during the assembly process of the present invention can not only prevent direct contact between the anode and cathode current collectors to avoid short circuits, but also effectively inhibit the cross-flow of nitrate wastewater and ammonia products between the anode and cathode chambers, thereby facilitating the subsequent separation and collection of ammonia.

[0039] The assembly process of the hydrazine electrolyzer membrane electrode flow reactor is the same as that of the hydrazine-nitrate battery membrane electrode flow reactor, except that the proton exchange membrane is replaced by an anion exchange membrane.

[0040] 2. Synthesis of the Ruthenium-Cobalt Bimetallic Catalyst of the Present Invention:

[0041] In this paper, a ruthenium-cobalt bimetallic catalyst grown in situ on a cobalt foam current collector is used as an example. The specific synthesis scheme is as follows: First, prepare a 0.05M cobalt chloride and 0.25M urea solution and stir evenly. Then, take 30mL of this solution and place it in a polytetrafluoroethylene-lined reactor, and place a 2×4cm 2 The foamed cobalt was placed in a stainless steel container with a lid on it. It was placed in a blast oven and the hydrothermal reaction temperature was set to 90°C for 10 hours. After the hydrothermal reaction was completed and cooled, the foamed cobalt substrate was removed and rinsed clean. Rod-shaped cobalt hydroxide was successfully grown in situ on the foamed cobalt substrate. The foamed cobalt was then vertically immersed in 60 mL of RuCl3 solution (0.05 mg mL -1 ) and stirred the solution at room temperature until a precipitate formed. The cobalt foam was then removed, rinsed, and dried. Finally, the solution was calcined in a tube furnace at 250°C for 3 hours in a 5% H2 / Ar mixture. After the reaction, a ruthenium-cobalt bimetallic catalyst grown in situ on the cobalt foam substrate was obtained. Its scanning electron micrograph and elemental distribution map are shown in Figure 2. Figure 2 shown.

[0042] In addition to ruthenium-cobalt catalysts, ruthenium-copper catalysts also have the same efficacy. Ruthenium-copper bimetallic catalysts can be synthesized directly in situ on a copper foam current collector. The specific scheme is as follows: the copper foam is placed in an alkaline ammonium persulfate solution to form a rod-shaped copper hydroxide structure, thereby expanding its specific surface area. Then, cation exchange is carried out in an aqueous phase using ruthenium trichloride as a raw material to load the ruthenium species onto the rod-shaped copper hydroxide. Finally, the ruthenium-copper bimetallic catalyst is calcined in a mixture of hydrogen and inert gas to form the ruthenium-copper bimetallic catalyst.

[0043] 3. Construction of the hydrazine-nitrate battery device in the present invention:

[0044] The present invention adopts the liquid circulation flow method to make hydrazine and nitrate wastewater enter the membrane electrode flow reactor. The specific method is as follows: Figure 3As shown in a, a peristaltic pump and silicone tube were used to connect the anode flow channel of the hydrazine-nitrate battery membrane electrode flow reactor to the hydrazine wastewater pool, and the cathode flow channel was connected to the nitrate wastewater pool in the same way. The concentration of hydrazine and nitrate wastewater was 0.1 M, and the flow rate was controlled at 150 mL min -1 Then the anode and cathode titanium wires of the battery were connected to the electrochemical workstation for testing. The testing method used was the chronopotentiometry to draw the polarization curve and power density curve. Figure 3 As shown in b, when the output current density is 100 mA cm -2 The battery can reach a maximum power of 12mW cm -2 The peak power density of Figure 3 As shown in Figure c, chronopotentiometry shows that the battery can operate continuously and stably for 20 h. The slow decrease in output voltage during this period can be attributed to the rapid consumption of hydrazine and nitrate in the wastewater. Therefore, the battery performance can be restored by simply replenishing hydrazine and nitrate. The average ammonia yield during this period is 0.37 mmol h -1 cm -2 The generated ammonia water can be combined with gas stripping technology to produce high-purity and high-concentration ammonia solution.

[0045] 4. Construction of the hydrazine-nitrate battery device in the present invention:

[0046] The present invention adopts the liquid circulation flow method to make the hydrazine wastewater and potassium hydroxide solution enter the membrane electrode flow reactor. The specific method is as follows: Figure 4 As shown in a, a peristaltic pump and silicone tube are used to connect the anode flow channel of the hydrazine electrolyzer membrane electrode flow reactor and the hydrazine wastewater tank, and the cathode flow channel and the potassium hydroxide storage tank are connected in the same way. The concentration of hydrazine wastewater is 0.1M, the concentration of potassium hydroxide solution is 1M, and the flow rate is controlled at 150mL min -1 Then the anode and cathode titanium wires of the electrolytic cell were connected to the electrochemical workstation for testing. The testing method used was the chronopotentiometry to draw the polarization curve. Figure 4 b and Figure 4 As shown in c, the electrolytic cell only needs 0.23V cell voltage to reach 50mA cm -2 The current density can be stably operated for at least 20 h, with a hydrogen production rate of 0.93 mmol h -1 cm -2 .

[0047] 5. The method for producing hydrogen by driving a hydrazine electrolyzer device using a hydrazine-nitrate battery in the present invention:

[0048] like Figure 5As shown, in the present invention, only two hydrazine-nitrate batteries need to be connected in series through a wire, and then the anode of the battery is connected to the cathode of the anion exchange membrane hydrazine electrolyzer, and the cathode of the battery is connected to the anode of the anion exchange membrane hydrazine electrolyzer to achieve spontaneous hydrogen production. The hydrogen production rate is 0.35 mmol cm -1 h -1 .

[0049] 6. The method for highly purifying hydrazine and nitrate wastewater of the present invention:

[0050] like Figure 6 As shown in Figure a, in the present invention, only the residual / low concentration hydrazine and nitrate waste liquid need to be mixed in the same container, and then a catalyst is added to achieve high purification of hydrazine and nitrate wastewater. Figure 6 As shown in Figure b, by adjusting the ratio of hydrazine and nitrate wastewater concentrations, the concentration of one of them can be reduced to below 1ppm. For example, when the concentrations of hydrazine and nitrate are 40 and 10mM respectively, and after one day of treatment, only 0.26 and 0.36ppm of hydrazine and nitrate remain in the solution after the reaction, respectively, with removal efficiencies as high as 99.98% and 99.94%. In addition, after the reaction is completed, the content of the byproduct nitrite in the solution is only 0.07ppm. Finally, it is worth noting that Figure 6 As shown in Figure c, the catalyst can be reused at least 8 times, the residual hydrazine and (nitrite) salts are always lower than 1.1 ppm, and the removal efficiency is still maintained above 99%.

[0051] The principles of the present invention are as follows:

[0052] The standard electrode potential of the hydrazine oxidation reaction is -1.16 vs. the standard hydrogen electrode (SHE), and the anode reaction equation is: N2H4-4e - +4OH - →N2+4H2O; the standard electrode potential of nitrate reduction reaction is -0.12V vs.SHE, the cathode reaction equation is: NO3 - +8e - +7H2O→NH3·H2O+9OH - . Therefore, these two cathode and anode reactions are coupled to form a spontaneous hydrazine-nitrate primary cell, the discharge voltage of which can reach up to 1.04V. The nitrogen produced at the anode of the cell can be directly discharged into the atmosphere, while the ammonia produced at the cathode can be recycled and reused as a product of high economic value through gas stripping technology. Since the system can generate additional electricity, the hydrazine-nitrate battery assembled by it can spontaneously drive the hydrazine wastewater electrolyzer, in which the nitrogen produced at the anode is directly discharged into the atmosphere, while the hydrogen produced at the cathode with high economic value can be directly collected and reused.

Claims

1. An electrochemical process for wastewater treatment to generate electricity and fuel, characterized in that The following steps are involved: 1) Using a close-fitting membrane electrode flow reactor to construct a hydrazine-nitrate battery and a hydrazine electrolyzer; 2) using a ruthenium-cobalt-copper-based catalyst to drive hydrazine oxidation, nitrate reduction, and hydrogen evolution reactions; the ruthenium-cobalt-copper-based catalyst is at least one of a ruthenium-cobalt-based catalyst and a ruthenium-copper-based catalyst; The construction of the hydrazine-nitrate battery includes: using a peristaltic pump to flow hydrazine wastewater into the anode flow channel of a membrane electrode flow reactor, and flowing nitrate wastewater into the cathode flow channel of the membrane electrode flow reactor, and then returning the hydrazine wastewater discharged from the anode flow channel and the nitrate wastewater discharged from the cathode flow channel to the hydrazine and nitrate wastewater tanks respectively, thereby achieving a circulating flow; The construction of the hydrazine electrolyzer includes: using a peristaltic pump to flow hydrazine wastewater into the anode flow channel of a membrane electrode flow reactor, and flowing potassium hydroxide solution into the cathode flow channel of the membrane electrode flow reactor, and then returning the hydrazine wastewater discharged from the anode flow channel and the potassium hydroxide solution discharged from the cathode flow channel to the hydrazine wastewater pool and the potassium hydroxide storage tank respectively, thereby achieving a circulating flow; The electricity generated by the hydrazine-nitrate battery is input into the cathode and anode of the hydrazine electrolyzer. After flow circulation, the hydrazine in the sewage is oxidized into nitrogen, the nitrate is reduced into ammonia water, and the water in the potassium hydroxide solution is reduced into hydrogen.

2. The electrochemical process for wastewater treatment, combined with electricity generation and fuel production according to claim 1, characterized in that: The method also includes highly purifying hydrazine and nitrate wastewater by mixing and stirring under the action of ruthenium cobalt copper-based catalyst, wherein the concentration range of the hydrazine and nitrate wastewater is 0.01-2000 mM.

3. The electrochemical process for wastewater treatment, combined with electricity generation and fuel production according to claim 1, characterized in that: The membrane electrode flow reactor includes a bipolar plate-cathode current collector-diaphragm-anode current collector-bipolar plate arranged in sequence; a flow channel is provided on the bipolar plate, and the two ends of the flow channel are liquid inlet and outlet; the cathode current collector and the anode current collector are loaded with the ruthenium cobalt copper-based catalyst.

4. The electrochemical process for wastewater treatment combined with power generation and fuel production as claimed in claim 3, characterized in that: The bipolar plate is selected from titanium plate, stainless steel plate, graphite plate or organic glass plate; the flow channel is a serpentine channel or a fully hollow channel; the inlet and outlet are selected from external threaded pagoda connectors or quick-plug connectors made of iron or plastic material; the diaphragm is a proton exchange membrane, anion exchange membrane, cation exchange membrane or glass fiber diaphragm.

5. The electrochemical process for wastewater treatment combined with power generation and fuel production as claimed in claim 3, characterized in that: The ruthenium cobalt copper-based catalyst is directly grown in situ on the current collector, or covered on the current collector by spraying and hot pressing; the current collector is selected from carbon paper, carbon felt, carbon cloth, foam nickel, foam cobalt, foam copper, foam iron, foam titanium, nickel mesh, cobalt mesh, copper mesh, iron mesh or titanium mesh.

6. The electrochemical process for wastewater treatment, combined with electricity generation and fuel production according to claim 1, characterized in that: The ruthenium-cobalt-based catalyst is prepared as follows: first, a cobalt hydroxide precursor is synthesized by a hydrothermal method, followed by ion exchange with ruthenium ions, and finally calcined under a reducing atmosphere. During the hydrothermal process, urea or hexamethylenetetramine is used as a precipitant, the temperature is 80-160°C, and the time is 4-24 hours. The ruthenium concentration during the ion exchange is 0.01-1 mg mL -1 The reaction time is 0.5-12 h, the reaction temperature is 0-60 °C; the calcination temperature is 150-600 °C, the time is 1-6 h, and the calcination atmosphere is a mixture of hydrogen and inert gas; the synthesized catalyst has a rod-like morphology, and the cobalt loading is 1-5 mg cm -2 , ruthenium loading is 0.01~1mg cm -2 .

7. The electrochemical process for wastewater treatment, combined with electricity generation and fuel production according to claim 1, characterized in that: The ruthenium-copper-based catalyst is prepared as follows: first, a copper hydroxide precursor is prepared by electrochemical anodic oxidation or a strong oxidant wet method, then ion exchange is performed with ruthenium ions, and finally calcined under a reducing atmosphere, wherein the electrochemical anodic oxidation current density is 0.01 to 100 mA cm -2 The wet reaction uses an alkaline persulfate solution as a strong oxidant, the reaction pH is 12-15, the ammonium persulfate concentration is 0.01-1 M, the reaction temperature is 0-60 °C, and the reaction time is 1-180 min; the ruthenium concentration during ion exchange is 0.01-1 mg mL -1 The reaction time is 0.5-12 h, the reaction temperature is 0-60 °C; the calcination temperature is 150-500 °C, the time is 1-6 h, and the calcination atmosphere is a mixture of hydrogen and inert gas; the synthesized catalyst has a rod-like morphology, and the copper loading is 1-5 mg cm -2 , ruthenium loading is 0.01-1 mg cm -2 .

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