A metal alloy electrode, its preparation method and application

Abstract

The present invention discloses a preparation method of a metal alloy electrode for removing nitrate nitrogen from wastewater, comprising: using a titanium metal as a substrate, electrochemically etching titanium dioxide nanotubes on the substrate to prepare formed titanium dioxide nanotubes, and electrodepositing and loading copper, nickel, tin and antimony to obtain a metal alloy electrode; the present invention also discloses a metal alloy electrode prepared by this method and its application for removing nitrate nitrogen from wastewater. The metal alloy electrode of the present invention has copper, nickel, tin and antimony with a specific ratio loaded on titanium dioxide nanotubes, which increases the reduction efficiency of the electrode for nitrate nitrogen, and has a strong removal ability for nitrate nitrogen in wastewater and a high nitrogen selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly to a metal alloy electrode, a preparation method thereof, and an application thereof. Background Art

[0002] The presence of nitrates in water can affect human health. It can not only cause blue baby syndrome in infants, but also greatly increase the probability of adults suffering from gastrointestinal cancer. For sustainable development, it is necessary to further remove nitrates during the wastewater treatment process.

[0003] Among the methods for removing nitrates, the electrocatalytic reduction technology for removing nitrate nitrogen has received increasing attention due to its advantages such as simplicity, high efficiency, easy control, and no need to introduce foreign ions. The core of the electrocatalytic reduction technology lies in the cathode material. A high-performance cathode reduction material can convert nitrate nitrogen into nitrogen with high selectivity. Therefore, it is necessary to develop electrodes with excellent performance. Among many cathode materials, copper electrodes and their alloy electrodes have relatively excellent nitrate nitrogen reduction performance and long electrode life, and thus are favored by more and more researchers.

[0004] CN108070886A discloses a preparation method and use of a bimetallic Cu-Bi electrocatalytic denitrification electrode. The method includes: (1) pretreatment of the copper substrate, (2) preparation of the plating solution, and (3) electroplating. The Cu-Bi electrocatalytic electrode prepared by this method has a certain reduction and removal ability for nitrates in water, but the reduction effect is poor. It takes about 5 hours to achieve about 80% removal of nitrate nitrogen, and most of the products are ammonia nitrogen.

[0005] CN108467091A discloses a highly catalytically active Cu-Sn-Bi electrode, a preparation method thereof, and a use thereof. The electrode is prepared by dissolving the following components in deionized water: Bi(NO3)3·5H2O, CuP2O7, SnP2O7, KCl, NaKC4H4O6·4H2O, EDTA-2Na, C7H6O6S·2H2O, K4O7P2, Na2HPO4, N(CH2COOH)3. The process used to prepare the electrode by this method can be plated at room temperature, the working conditions are easy to maintain, all are common chemical reagents, the price is low, and there is no need for secondary synthesis. The obtained electrode coating is firmly combined with the substrate, the electrode surface is uniform, has higher corrosion resistance, and good electrical conductivity. However, the plating solution formula and preparation method used are relatively complex, and during the process of degrading nitrates, the catalytic reduction efficiency and nitrogen selectivity are relatively low.

[0006] In summary, it is necessary to develop and prepare an electrode with high efficiency, easy preparation, and low cost. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention provides a metal alloy electrode, a preparation method thereof, and an application. When the metal alloy electrode of the present invention is used in wastewater treatment, it has a high nitrate nitrogen reduction efficiency and nitrogen selectivity.

[0008] In a first aspect of the present invention, a preparation method of a metal alloy electrode for removing nitrate nitrogen from wastewater is provided, including: using a titanium metal as a substrate, electrochemically etching titanium dioxide nanotubes on the substrate to prepare formed titanium dioxide nanotubes, and electrodepositing and loading copper, nickel, tin, and antimony to obtain a metal alloy electrode.

[0009] Further, the substrate is first pretreated and then titanium dioxide nanotubes are electrochemically etched on the substrate.

[0010] Further, the process of electrochemically etching titanium dioxide nanotubes on the substrate is as follows: using the substrate as the anode and a platinum sheet as the cathode, and using a mixed solution of sodium fluoride, ethylene glycol, and water as the electrolyte solution. The electrolysis conditions are as follows: voltage 20 - 50V, temperature 40 - 70°C, time 40 - 200 min. In the electrolyte solution, the volume ratio of ethylene glycol to water is 90 - 96:4 - 10, and the mass concentration of sodium fluoride is 1% - 4%.

[0011] Further, the process of preparing formed titanium dioxide nanotubes is as follows: roasting the electrochemically etched titanium dioxide nanotubes to obtain formed titanium dioxide nanotubes. The roasting temperature is 400 - 700°C, and the roasting time is 30 - 180 min.

[0012] Further, when electrodepositing and loading copper, nickel, tin, and antimony, the preparation process of the electrodeposition solution is as follows: dissolving copper salt, nickel salt, tin salt, and antimony salt in an acid, then adding boric acid, adding deionized water, and ultrasonicating for 10 - 30 min to mix evenly to obtain an electrodeposition solution. In the electrodeposition solution, the molar concentration of boric acid is 0.1 - 0.5 mol / L. Further, the acid includes at least one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and acetic acid. There are no special limitations on the concentration and dosage of the acid, as long as the copper salt, nickel salt, tin salt, and antimony salt can be dissolved.

[0013] Further, the copper salt, nickel salt, tin salt, and antimony salt are soluble salts, including at least one of chlorides, nitrates, sulfates, phosphates, and acetates.

[0014] Further, in the copper salt, nickel salt, tin salt, and antimony salt, the molar ratio of copper, nickel, tin, and antimony is (1 - 10):(1 - 5):(1 - 5):1, preferably (1 - 6):(1 - 3):(1 - 3):1.

[0015] Further, the process of electrodepositing copper, nickel, tin, and antimony is as follows: Using the substrate containing the formed titanium dioxide nanotubes as the cathode, electrodeposition is carried out in the electrodeposition solution. The conditions for electrodeposition are: the current density is 2 - 30 mA / cm 2 , the electrodeposition time is 10 - 120 min. After the electrodeposition is completed, the electrode is washed and dried to obtain a metal alloy electrode.

[0016] The second aspect of the present invention provides a metal alloy electrode prepared by the above method.

[0017] The third aspect of the present invention provides the application of the above metal alloy electrode in the removal of nitrate nitrogen from wastewater.

[0018] Further, an electrolyte is added to the wastewater. Using the metal alloy electrode of the present invention as the cathode and a platinum electrode as the anode, the nitrate nitrogen in the wastewater is removed by electrocatalytic reduction.

[0019] Further, the initial content of nitrate nitrogen in the wastewater is 50 - 500 mg / L.

[0020] Further, the conditions for electrocatalytic reduction are as follows: the current density is 40 - 100 mA / cm 2 , the temperature is 20 - 80 °C, and the time is 0.5 - 2 h.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The inventors have found through a large number of studies that the metal alloy electrode with copper, nickel, tin, and antimony loaded on titanium dioxide nanotubes in a specific ratio has a strong ability to remove nitrate nitrogen from wastewater and has a high nitrogen selectivity.

[0023] (2) The present invention uses titanium dioxide nanotubes for the loading of the metal alloy. The titanium dioxide nanotubes endow the metal alloy electrode with a high specific surface area, so that more copper, nickel, tin, and antimony can be loaded per unit area, further providing more reactive sites for the electrode, that is, it can cooperate better with each metal, thereby increasing the reduction efficiency of the electrode for nitrate nitrogen. Description of the Drawings

[0024] Figure 1 It is the electron microscope image of the titanium dioxide nanotubes prepared in Example 1;

[0025] Figure 2 It is the electron microscope image of the metal alloy electrode prepared in Example 1. Detailed Embodiments

[0026] The method of the present invention will be further described in detail below by way of examples. The examples are implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples.

[0027] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all purchased from conventional biochemical reagent stores.

[0028] In the present invention, the scanning electron microscope photographs of the samples are measured by a Philips Fei Quanta200F field emission scanning electron microscope.

[0029] In the present invention, unless otherwise clearly specified, the percentages and percentage contents are all based on mass.

[0030] Example 1

[0031] (1) Substrate pretreatment: Wash the titanium substrate successively with acetone, sulfuric acid, and deionized water, and then place it in a drying oven at 120 °C for drying.

[0032] (2) Electrochemical etching of titanium dioxide nanotubes on the substrate: Using the above titanium substrate as the anode and a platinum sheet of equal area as the cathode, electrochemical etching of titanium dioxide nanotubes is carried out in a mixed electrolyte solution of sodium fluoride, ethylene glycol, and water. Among them, the volume ratio of ethylene glycol to water is 90:10, and the mass fraction of sodium fluoride is 2%. The experimental conditions are: voltage 30V, temperature 40 °C, and time 60 min.

[0033] (3) Shaping of titanium dioxide nanotubes on the substrate: Place the oxidized titanium substrate with titanium dioxide nanotubes in a muffle furnace at 500 °C for roasting for 120 min, as Figure 1 shown, to obtain shaped titanium dioxide nanotubes.

[0034] (4) Preparation of electroplating solution: Dissolve the sulfates of copper, nickel, tin, and antimony in a molar ratio of 1:4:3:1 in 6 mL of concentrated sulfuric acid, and then add an appropriate amount of boric acid, and dissolve and mix uniformly by ultrasonic treatment. The molar concentration of boric acid is 0.2 mol / L.

[0035] (5) Preparation of the electrode by electroplating: Using the above titanium substrate containing shaped titanium dioxide nanotubes as the cathode, electroplating is carried out in the above-prepared electroplating solution to deposit copper, nickel, tin, and antimony metals on the cathode. The electroplating conditions are: current density 10 mA / cm 2 , electroplating time 30 min. After electroplating is completed, wash and dry the electrode, as Figure 2 shown.

[0036] (6) Electro-catalytic reduction for nitrate nitrogen removal: Using the electro-deposited titanium substrate electrode as the cathode and the platinum electrode as the anode, it is used for removing nitrate nitrogen from wastewater (the initial content of nitrate nitrogen is 100 mg / L, containing 20 g / L sodium sulfate). When the current density is 50 mA / cm 2 , 86.5% of nitrate nitrogen can be removed in 1 hour, and the total nitrogen removal rate is 69.5%.

[0037] Example 2

[0038] (1) Substrate pretreatment: Wash the titanium substrate successively with acetone, sulfuric acid, and deionized water, and then place it in a drying oven at 120 °C for drying.

[0039] (2) Electrochemical etching of titanium dioxide nanotubes on the substrate: Using the above-mentioned titanium substrate as the anode and an equal-area platinum sheet as the cathode, electrochemical etching of titanium dioxide nanotubes is carried out in a mixed electrolyte solution of sodium fluoride, ethylene glycol, and water. Among them, the volume ratio of ethylene glycol to water is 90:10, and the mass fraction of sodium fluoride is 2%. The experimental conditions are: voltage 30 V, temperature 40 °C, and time 60 min.

[0040] (3) Shaping of titanium dioxide nanotubes on the substrate: Place the oxidized titanium substrate with titanium dioxide nanotubes in a muffle furnace at 500 °C for roasting for 120 min to obtain shaped titanium dioxide nanotubes.

[0041] (4) Preparation of electro-deposition solution: Dissolve the sulfates of copper, nickel, tin, and antimony in a molar ratio of 4:4:3:2 in 8 mL of concentrated sulfuric acid, then add an appropriate amount of boric acid, and dissolve and mix well by ultrasonic. The molar concentration of boric acid is 0.2 mol / L.

[0042] (5) Preparation of the electrode by electro-deposition: Using the above-mentioned titanium substrate containing shaped titanium dioxide nanotubes as the cathode, electro-deposition is carried out in the above-prepared electro-deposition solution to deposit copper, nickel, tin, and antimony metals on the cathode. The electro-deposition conditions are: current density 10 mA / cm 2 , electro-deposition time 30 min. After electro-deposition, wash and dry the electrode.

[0043] (6) Electro-catalytic reduction for nitrate nitrogen removal: Using the electro-deposited titanium substrate electrode as the cathode and the platinum electrode as the anode, it is used for removing nitrate nitrogen from wastewater (the initial content of nitrate nitrogen is 100 mg / L, containing 20 g / L sodium sulfate). When the current density is 50 mA / cm 2 , at a temperature of 20 °C, 92.5% of nitrate nitrogen can be removed in 1 hour, and the total nitrogen removal rate is 62.3%.

[0044] Example 3

[0045] (1) Substrate pretreatment: Wash the titanium substrate successively with acetone, sulfuric acid, and deionized water, and then dry it in an oven at 120 °C.

[0046] (2) Electrochemical etching of titanium dioxide nanotubes on the substrate: Using the above titanium substrate as the anode and a platinum sheet of equal area as the cathode, electrochemically etch titanium dioxide nanotubes in a mixed electrolyte solution of sodium fluoride, ethylene glycol, and water. Among them, the volume ratio of ethylene glycol to water is 90:10, and the mass fraction of sodium fluoride is 2%. The experimental conditions are: voltage 50 V, temperature 80 °C, and time 60 min.

[0047] (3) Shaping of titanium dioxide nanotubes on the substrate: Place the oxidized titanium substrate with titanium dioxide nanotubes in a muffle furnace at 700 °C and bake for 60 min to obtain shaped titanium dioxide nanotubes.

[0048] (4) Preparation of the electrodeposition solution: Dissolve the sulfates of copper, nickel, tin, and antimony in a molar ratio of 4:4:3:2 in 15 mL of concentrated sulfuric acid, then add an appropriate amount of boric acid and dissolve and mix well by ultrasonic. The molar concentration of boric acid is 0.2 mol / L.

[0049] (5) Preparation of the electrode by electrodeposition: Using the above titanium substrate containing shaped titanium dioxide nanotubes as the cathode, perform electrodeposition in the above-prepared electrodeposition solution to deposit copper, nickel, tin, and antimony metals on the cathode. The conditions for electrodeposition are: current density 10 mA / cm 2 , electrodeposition time 30 min. After electrodeposition, wash and dry the electrode.

[0050] (6) Electro-catalytic reduction for nitrate nitrogen removal: Using the electrodeposited titanium substrate electrode as the cathode and a platinum electrode as the anode, for the removal of nitrate nitrogen in wastewater (the initial content of nitrate nitrogen is 100 mg / L, containing 20 g / L of sodium sulfate). When the current density is 50 mA / cm 2 , temperature 20 °C, 89.4% of nitrate nitrogen can be removed in 1 hour, and the total nitrogen removal rate is 57.6%.

[0051] Example 4

[0052] (1) Substrate pretreatment: Wash the titanium substrate successively with acetone, sulfuric acid, and deionized water, and then dry it in an oven at 120 °C.

[0053] (2) Electrochemical etching of titanium dioxide nanotubes on the substrate: Using the above titanium substrate as the anode and a platinum sheet of equal area as the cathode, electrochemically etch titanium dioxide nanotubes in a mixed electrolyte solution of sodium fluoride, ethylene glycol, and water. Among them, the volume ratio of ethylene glycol to water is 90:10, and the mass fraction of sodium fluoride is 2%. The experimental conditions are: voltage 30 V, temperature 40 °C, and time 60 min.

[0054] (3) Formation of titanium dioxide nanotubes on the substrate: Place the oxidized titanium substrate with titanium dioxide nanotubes in a muffle furnace at 500 °C and calcine for 120 min to obtain formed titanium dioxide nanotubes.

[0055] (4) Preparation of the electrodeposition solution: Dissolve the sulfates of copper, nickel, tin, and antimony in a molar ratio of 1:4:3:1 in 8 mL of concentrated sulfuric acid, then add an appropriate amount of boric acid and dissolve and mix well by ultrasonic treatment. The molar concentration of boric acid is 0.2 mol / L.

[0056] (5) Preparation of the electrode by electrodeposition: Use the above-mentioned titanium substrate with formed titanium dioxide nanotubes as the cathode and perform electrodeposition in the above-prepared electrodeposition solution to deposit copper, nickel, tin, and antimony metals on the cathode. The conditions for electrodeposition are: current density is 10 mA / cm 2 , the electrodeposition time is 30 min, and after electrodeposition, wash and dry the electrode.

[0057] (6) Electro-catalytic reduction for removing nitrate nitrogen: Use the electrodeposited titanium substrate electrode as the cathode and a platinum electrode as the anode to remove nitrate nitrogen from wastewater (the initial content of nitrate nitrogen is 500 mg / L, containing 20 g / L of sodium sulfate). When the current density is 50 mA / cm 2 , the temperature is 60 °C, and 76.5% of nitrate nitrogen can be removed in 1.5 hours, and the total nitrogen removal rate is 51.2%.

[0058] Example 5

[0059] (1) Substrate pretreatment: Wash the titanium substrate successively with acetone, sulfuric acid, and deionized water, and then place it in a drying oven at 120 °C for drying.

[0060] (2) Electrochemical etching of titanium dioxide nanotubes on the substrate: Use the above-mentioned titanium substrate as the anode and an equal-area platinum sheet as the cathode to electrochemically etch titanium dioxide nanotubes in a mixed electrolyte solution of sodium fluoride, ethylene glycol, and water. Among them, the volume ratio of ethylene glycol to water is 90:10, and the mass fraction of sodium fluoride is 2%. The experimental conditions are: voltage 30 V, temperature 40 °C, and time 60 min.

[0061] (3) Formation of titanium dioxide nanotubes on the substrate: Place the oxidized titanium substrate with titanium dioxide nanotubes in a muffle furnace at 500 °C and calcine for 120 min to obtain formed titanium dioxide nanotubes.

[0062] (4) Preparation of the electrodeposition solution: Dissolve the chlorides of copper, nickel, tin, and antimony in a molar ratio of 10:4:3:1 in 15 mL of concentrated sulfuric acid, then add an appropriate amount of boric acid and dissolve and mix well by ultrasonic treatment. The molar concentration of boric acid is 0.2 mol / L.

[0063] (5) Preparation of the electrode by electrodeposition: Using the titanium substrate containing the formed titanium dioxide nanotubes as the cathode, perform electrodeposition in the electrodeposition solution configured above, so that copper, nickel, tin, and antimony metals are deposited on the cathode. The conditions for electrodeposition are: the current density is 10 mA / cm 2 , the electrodeposition time is 30 min. After the electrodeposition is completed, wash and dry the electrode.

[0064] (6) Electro-catalytic reduction for nitrate nitrogen removal: Using the electrodeposited titanium substrate electrode as the cathode and the platinum electrode as the anode, for the removal of nitrate nitrogen in wastewater (the initial content of nitrate nitrogen is 500 mg / L, containing 20 g / L sodium sulfate). When the current density is 50 mA / cm 2 , at a temperature of 60 °C, 69.7% of nitrate nitrogen can be removed in 1.5 hours, and the total nitrogen removal rate is 44.6%.

[0065] Comparative Example 1

[0066] Prepare the copper-nickel-tin-antimony quaternary alloy electrode in the same method as in Example 1. The difference is that steps (2) and (3) in Example 1 are omitted, so that titanium dioxide nanotubes are not prepared on the titanium substrate.

[0067] Using the copper-nickel-tin-antimony quaternary alloy electrode prepared in this comparative example as the cathode and the platinum electrode as the anode, for the removal of nitrate nitrogen in wastewater (the initial content of nitrate nitrogen is 100 mg / L, containing 20 g / L sodium sulfate). When the current density is 50 mA / cm 2 , 73.3% of nitrate nitrogen can be removed in 1 hour, and the total nitrogen removal rate is 51.7%.

[0068] Comparative Example 2

[0069] Prepare the copper-nickel quaternary alloy electrode in the same method as in Example 1. The difference is that the electrodeposition solution is only copper and nickel sulfates, without tin and antimony salts, and the ratio of copper sulfate to nickel sulfate is 1:4.

[0070] Using the copper-nickel alloy electrode prepared in this comparative example as the cathode and the platinum electrode as the anode, for the removal of nitrate nitrogen in wastewater (the initial content of nitrate nitrogen is 100 mg / L, containing 20 g / L sodium sulfate). When the current density is 50 mA / cm 2 , 77.4% of nitrate nitrogen can be removed in 1 hour, and the total nitrogen removal rate is 54.1%.

[0071] Comparative Example 3

[0072] Prepare the copper-nickel quaternary alloy electrode in the same method as in Example 1. The difference is that the electrodeposition solution is only copper, nickel, and tin sulfates, without antimony salts, and the ratio of copper sulfate to nickel sulfate to tin sulfate is 1:4:3.

[0073] Using the copper-nickel alloy electrode prepared in this comparative example as the cathode and the platinum electrode as the anode, it was used to remove nitrate nitrogen from wastewater (the initial content of nitrate nitrogen was 100 mg / L, containing 20 g / L sodium sulfate). When the current density was 50 mA / cm 2 , 71.3% of nitrate nitrogen removal could be achieved in 1 hour, and the total nitrogen removal rate was 42.2%.

[0074] Comparative Example 4

[0075] (1) Substrate pretreatment: The titanium substrate was washed successively with acetone, sulfuric acid, and deionized water, and then dried in an oven at 120 °C.

[0076] (2) Electrochemical etching of titanium dioxide nanotubes on the substrate: Using the above titanium substrate as the anode and an equal-area platinum sheet as the cathode, titanium dioxide nanotubes were electrochemically etched in a mixed electrolyte solution of sodium fluoride, ethylene glycol, and water. Among them, the volume ratio of ethylene glycol to water was 90:10, and the mass fraction of sodium fluoride was 2%. The experimental conditions were: voltage 30 V, temperature 40 °C, and time 60 min.

[0077] (3) Shaping of titanium dioxide nanotubes on the substrate: The oxidized titanium substrate with titanium dioxide nanotubes was placed in a muffle furnace at 500 °C and calcined for 120 min to obtain shaped titanium dioxide nanotubes.

[0078] (4) Preparation of the electrodeposition solution: Chlorides of copper, nickel, tin, and antimony were dissolved in 15 mL of concentrated sulfuric acid according to a molar ratio of 12:6:6:1, and then an appropriate amount of boric acid was added and dissolved and mixed evenly by ultrasonic. The molar concentration of boric acid was 0.2 mol / L.

[0079] (5) Preparation of the electrode by electrodeposition: Using the above titanium substrate containing shaped titanium dioxide nanotubes as the cathode, electrodeposition was carried out in the above-prepared electrodeposition solution to deposit copper, nickel, tin, and antimony metals on the cathode. The conditions for electrodeposition were: current density 10 mA / cm 2 , electrodeposition time 30 min. After electrodeposition, the electrode was washed and dried.

[0080] (6) Electro-catalytic reduction for removing nitrate nitrogen: Using the electrodeposited titanium substrate electrode as the cathode and the platinum electrode as the anode, it was used to remove nitrate nitrogen from wastewater (the initial content of nitrate nitrogen was 500 mg / L, containing 20 g / L sodium sulfate). When the current density was 50 mA / cm 2 , temperature 60 °C, 58.1% of nitrate nitrogen removal could be achieved in 1.5 hours, and the total nitrogen removal rate was 36.7%.

[0081] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A preparation method of a metal alloy electrode for removing nitrate nitrogen from wastewater, characterized in that Using titanium metal as the substrate, titanium dioxide nanotubes are electrochemically etched on the substrate to prepare formed titanium dioxide nanotubes, and copper, nickel, tin and antimony are electrodeposited and loaded to obtain a metal alloy electrode; the preparation process of the electrodeposition solution is as follows: copper salt, nickel salt, tin salt and antimony salt are dissolved in acid, then boric acid is added, deionized water is added, and ultrasonic mixing is carried out for 10 - 30 min to obtain the electrodeposition solution. In the electrodeposition solution, the molar concentration of boric acid is 0.1 - 0.5 mol / L; in the copper salt, nickel salt, tin salt and antimony salt, the molar ratio of copper, nickel, tin and antimony is (1 - 6):(1 - 3):(1 - 3):

1.

2. The preparation method of the metal alloy electrode according to claim 1, characterized in that, The substrate is first pretreated, and then titanium dioxide nanotubes are electrochemically etched on the substrate.

3. The method for preparing the metal alloy electrode according to claim 2, characterized in that, The process of electrochemically etching the titanium dioxide nanotubes on the substrate is as follows: using the substrate as the anode and a platinum sheet as the cathode, and using a mixed solution of sodium fluoride, ethylene glycol and water as the electrolyte solution, the electrolysis conditions are: voltage 20 - 50 V, temperature 40 - 70 °C, time 40 - 200 min, the volume ratio of ethylene glycol to water is 90 - 96:4 - 10, and the mass concentration of sodium fluoride is 1% - 4%.

4. The method for preparing a metal alloy electrode according to claim 3, wherein, The process of preparing the formed titanium dioxide nanotubes is as follows: the electrochemically etched titanium dioxide nanotubes are calcined to obtain the formed titanium dioxide nanotubes, the calcination temperature is 400 - 700 °C, and the calcination time is 30 - 180 min.

5. The preparation method of the metal alloy electrode according to claim 1, characterized in that, The copper salt, nickel salt, tin salt and antimony salt are soluble salts, and each is independently selected from at least one of chloride salts, nitrate salts, sulfate salts, phosphate salts and acetate salts.

6. The method for preparing the metal alloy electrode according to claim 1, wherein, The acid includes at least one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and acetic acid.

7. The preparation method of the metal alloy electrode according to claim 1, characterized in that, The process of electro-depositing the copper, nickel, tin and antimony is as follows: using the substrate containing the formed titanium dioxide nanotubes as the cathode, electro-depositing in the electro-deposition solution, and the conditions of the electro-deposition are: the current density is 2~30 mA / cm 2 , the electro-deposition time is 10~120 min. After the electro-deposition is completed, the electrode is washed and dried to obtain the metal alloy electrode.

8. A metal alloy electrode is prepared by using the preparation method according to any one of claims 1 - 7.

9. Use of the metal alloy electrode according to claim 8 in the removal of nitrate nitrogen from wastewater.

10. The application according to claim 9, wherein An electrolyte is added to the wastewater, and the metal alloy electrode is used as the cathode and a platinum electrode is used as the anode, and the nitrate nitrogen in the wastewater is removed by electrocatalytic reduction.

11. The application according to claim 9 or 10, characterized in that, The initial content of nitrate nitrogen in the wastewater is 50 - 500 mg / L.

12. The application according to claim 10, characterized in that, The conditions for the electrocatalytic reduction are as follows: the current density is 40 - 100 mA / cm 2 , the temperature is 20 - 80 °C, and the time is 0.5 - 2 h.

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