Electrode material for electrocatalytic degradation of organic wastewater containing high concentration of nitrate and application thereof

Abstract

The application discloses an electrode material for electrocatalytic degradation of organic wastewater containing high-concentration nitrate and application thereof, which comprises the following steps: sequentially attaching copper salt precursor solution and tin salt precursor solution on the surface of a Ti plate to obtain a Ti / Cu-Sn multi-metal coating electrode material, and constructing an electrolytic cell by taking the electrode material as a cathode and a metal electrode as an anode, so as to simultaneously degrade NO3 ‑ and COD in the organic wastewater containing high-concentration nitrate and produce hydrogen in parallel. The preparation process of the electrode material is simple and low in cost, and the catalytic activity and stability are high. The electrolysis process can safely and mildly remove nitrate and organic matters in wastewater at the same time, and almost no secondary pollution by-products such as ammonia nitrogen and nitrite are generated. According to test, the nitrate removal rate can reach 99.72%, the COD removal rate can reach 84.61%, and the nitrogen selectivity can reach 99.83% by using the method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical wastewater treatment, and particularly relates to an electrode material for electrocatalytic degradation of organic wastewater containing high-concentration nitrate and application thereof. BACKGROUND

[0002] In the process of preparing silver powder by liquid phase reduction method in industry, industrial silver powder wastewater containing extremely high concentration of nitrate and COD is produced, which is difficult to treat and has a huge impact on the water cycle system in the ecological environment. High concentration of nitrate in drinking water is very harmful to human body. Therefore, it is of great practical significance to develop efficient and economical nitrate removal technology. At present, the treatment methods for nitrate in wastewater include biological denitrification, ion exchange, reverse osmosis, chemical catalysis and electrochemical catalysis. Among them, electrochemical catalysis has the advantages of high efficiency, high selectivity and environmental friendliness compared with other methods, but also has the disadvantages of high energy consumption and large amount of ammonia nitrogen, which need to be solved urgently.

[0003] At the same time, the current organic matter removal technologies for wastewater mainly include activated carbon adsorption, chemical adsorbent adsorption, Fenton oxidation method, Fenton-like oxidation method and the like. Among them, Fenton-like oxidation method is widely used due to its mild reaction conditions and high catalytic efficiency. The technologies mainly used in Fenton-like oxidation method include electrocatalytic oxidation, ozone catalytic oxidation and hydrogen peroxide catalytic oxidation. Among them, electrocatalytic oxidation technology is favored by researchers due to its super strong oxidizing property and catalytic stability.

[0004] However, although electrochemical technology has been reported to be used for treating organic wastewater and wastewater containing nitrate respectively, there is still a lack of research on the treatment of industrial wastewater containing both organic matter and nitrate. In addition, the traditional electrochemical denitrification method has the problems of low nitrogen selectivity, poor electrode stability and environmental pollution caused by ammonia nitrogen by-product. SUMMARY

[0005] In view of the above problems, the application provides an electrode material for electrocatalytic degradation of organic wastewater containing high-concentration nitrate and application thereof.

[0006] Specifically, the first object of the application is to provide an electrode material which is simple in preparation process, low in cost and can be applied to electrocatalytic degradation of NO3 - and COD at the same time.

[0007] The second object of the application is to provide an electrochemical method which is safe, efficient and green in removing nitrate and organic matter at the same time and can co-produce hydrogen.

[0008] To achieve the above objects, the application adopts the following technical solutions:

[0009] A cathode material for catalytic degradation of organic wastewater containing high concentration of nitrate, the preparation thereof comprises the following steps:

[0010] 1) After polishing the Ti plate with sandpaper, first put it into a 10 wt% NaOH solution to heat and remove oil, and then put it into a 10 wt% oxalic acid solution to heat and perform surface etching;

[0011] 2) Uniformly apply the copper salt precursor solution to the surface of the etched Ti plate, dry and then calcine; repeat the process 6 times, then rinse with deionized water and anhydrous ethanol and wipe the surface with filter paper to ensure that no coating falls off;

[0012] 3) Use the tin salt precursor solution to perform step 2) to prepare a Ti / Cu-Sn multi-metal coating electrode material.

[0013] Further, the temperature of the heating in step 1) is 60-90 ℃, and the time is 30-180 min.

[0014] Further, the copper salt precursor solution in step 2) is specifically a copper nitrate ethanol solution, with a concentration of 0.1-2 mol / L, and a coating amount of 0.08 mL / cm 2 .

[0015] Further, the temperature of the drying in step 2) is 60-120 ℃, and the time is 10-60 min.

[0016] Further, the temperature of the calcination in step 2) is 250-850 ℃, and the time is 10-60 min.

[0017] Further, the coating amount of the tin salt precursor solution in step 3) is 0.04 mL / cm 2 ; it is mixed by heating and stirring at 60-100 ℃ for 5-45 min to make it uniform, and then cooled, wherein the concentrations of the metal tin salt, sodium hypophosphite, thiourea, complexing agent and concentrated hydrochloric acid are 0.05-2 mol / L, 0.5-3 mol / L, 0.05-1.5 mol / L, 0.01-1 mol / L and 0.1-1 mol / L, respectively.

[0018] Further, the metal tin salt is selected from one of stannous chloride, tin chloride, trimethyltin chloride and stannous sulfate.

[0019] Further, the complexing agent is selected from one of sodium citrate, ascorbic acid, sodium bicarbonate and glucose.

[0020] The electrode material can be used for electrochemical catalytic degradation of industrial silver powder wastewater and other organic wastewater containing high concentration of nitrate.

[0021] Specifically, the application method is to use the electrode material to construct an electrolytic cell as a cathode, and under the condition of containing Cl - , the electrode material is used for simultaneous degradation of NO3 - and COD in organic wastewater containing high concentration of nitrate, and hydrogen is produced.

[0022] Further, the electrolytic cell uses one of a Pt electrode, an iridium tantalum titanium electrode, a ruthenium iridium titanium electrode and a nickel plate electrode as an anode.

[0023] Further, during electrolysis, 1-12 mol / L of HCl solution is used to adjust the pH of the waste liquid to 0.5-3, and the conductivity is 15-45 mS / cm, so that the system contains Cl - .

[0024] Further, the concentration of NO3 - in the wastewater is less than or equal to 10000 mg / L, and the concentration of COD is less than or equal to 5000 mg / L.

[0025] The present application uses Ti plate as the substrate, copper nitrate solution and metal tin salt solution as the precursor solution, and produces Ti / Cu-Sn multi-metal coating electrode material by high temperature calcination method. Compared with other electrolytic wastewater denitrification electrodes, the synthesis method is simple and the production cost is low, and it also has high catalytic activity and stability, and also has high catalytic activity in the field of electrocatalytic reduction of carbon dioxide.

[0026] The present application uses Ti / Cu-Sn as the cathode and metal electrode as the anode to construct an electrolytic cell for electrolytic denitrification treatment of organic wastewater containing high concentration of nitrate, in which the chloride ion can be oxidized to nitrogen gas by oxidizing the ammonia nitrogen generated by the degradation of nitrate at the anode, and simultaneously removing nitrate at the cathode, producing hydrogen and removing organic matter at the anode. This new electrochemical denitrification method not only avoids the pollution of by-products to the environment, but also simplifies the wastewater treatment process of multiple pollution sources.

[0027] The beneficial effects of the present application are as follows:

[0028] 1) Low cost and multiple application fields of the electrode. The electrode preparation process of the present application does not need to add reagents, the power consumption is low, the materials used for the electrode are non-noble metal materials, and the electrode can be simultaneously applied in the field of electrocatalytic reduction of carbon dioxide.

[0029] 2) Simple and green method. Compared with the existing multi-effect evaporation method, biological denitrification method and other methods, the present application uses electrochemical catalytic method for degradation, which does not need additional energy consumption process, does not produce secondary pollutants, and the facility device is more simple.

[0030] 3) Performance is observable and hydrogen can be co-produced. By using Ti / Cu-Sn as the cathode and a metal electrode as the anode, the chloride ions can be oxidized to nitrogen gas at the anode by oxidizing the ammonia nitrogen generated by the degradation of nitrate, and at the same time, the nitrate is removed at the cathode and hydrogen is co-produced, and the organic matter is removed at the anode. The test results show that the removal rate of nitrate can reach 99.72%, the removal rate of COD can reach 84.61%, and the nitrogen selectivity can reach 99.83%. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The conversion of nitrate and the removal rate of organic matter obtained by electrochemically catalytically degrading high-concentration nitrate-containing organic wastewater using the Ti / Cu-Sn cathode prepared in Example 1.

[0032] Figure 2 The change of the concentration and removal rate of nitrate obtained by electrochemically catalytically degrading high-concentration nitrate-containing organic wastewater with time using the Ti / Cu-Sn cathode prepared in Example 1.

[0033] Figure 3 A comparison chart of the removal rate of nitrate obtained by electrochemically catalytically degrading high-concentration nitrate-containing organic wastewater using the cathodes prepared in Example 1 and Comparative Examples 2-4. DETAILED DESCRIPTION

[0034] A cathode material for catalytically degrading high-concentration nitrate-containing organic wastewater, the preparation thereof comprising the following steps:

[0035] 1) After polishing the Ti plate with sandpaper of different grits, first put it into a 10 wt% NaOH solution, heat at 60-90°C for 30-180 min for oil removal, and then put it into a 10 wt% oxalic acid solution, heat at 60-90°C for 30-180 min for surface etching;

[0036] 2) 0.1-2 mol / L copper nitrate ethanol solution is uniformly applied to the surface of the etched Ti plate at an amount of 0.08 mL / cm 2 , dried at 60-120°C for 10-60 min, and calcined at 250-850°C for 10-60 min; repeat the process 6 times, then rinse with deionized water and anhydrous ethanol in turn and wipe the surface with filter paper to ensure that no coating falls off;

[0037] 3) mixing the metal tin salt, sodium hypophosphite, thiourea, complexing agent and concentrated hydrochloric acid (36.5 wt%) and stirring at 60-100 ℃ for 5-45 min to make the tin salt precursor solution uniform, and then cooling; the concentrations of the metal tin salt, sodium hypophosphite, thiourea, complexing agent and concentrated hydrochloric acid are 0.05-2 mol / L, 0.5-3 mol / L, 0.05-1.5 mol / L, 0.01-1 mol / L and 0.1-1 mol / L, respectively; then the tin salt precursor solution is applied in an amount of 0.04 mL / cm 2 to prepare the Ti / Cu-Sn multi-metal coating electrode material.

[0038] The metal tin salt is selected from one of stannous chloride, tin chloride, trimethyl tin chloride and stannous sulfate. The complexing agent is selected from one of sodium citrate, ascorbic acid, sodium bicarbonate and glucose.

[0039] In order to make the content of the application more convenient to understand, the technical solutions of the application will be further described below in combination with specific embodiments, but the application is not limited thereto.

[0040] The Pt anode, ruthenium-iridium-titanium anode, iridium-tantalum-titanium anode and nickel plate anode used in the examples are all purchased from Suzhou Shulai Industrial Technology Co., Ltd.

[0041] Example 1

[0042] (1) The Ti plate (5 cm x 5 cm) is polished with sandpaper of different grits, and then is placed in 10 wt% NaOH solution and 10 wt% oxalic acid solution, respectively, and is heated in a water bath at 60-90 ℃ for 30 min, and then is taken out for standby;

[0043] (2) A certain amount of copper nitrate trihydrate is dissolved in ethanol to prepare a 2 mol / L copper nitrate precursor solution; a certain amount of metal tin salt, sodium hypophosphite, thiourea, complexing agent sodium citrate and concentrated hydrochloric acid (36.5 wt%) are placed in a magnetic stirrer and heated to 60 ℃, stirred for 10 min, and then the solution is cooled to room temperature and left to stand, to obtain a metal tin salt precursor solution, wherein the content of each component is: 0.05 mol / L stannous chloride, 0.5 mol / L sodium hypophosphite, 0.05 mol / L thiourea, 0.01 mol / L sodium citrate and 0.1 mol / L concentrated hydrochloric acid;

[0044] (3) 8 mL of the prepared copper nitrate precursor solution was evenly applied to the surface of the Ti plate, which was then placed in an oven at 120 °C for 10 min and then in a box-type electric furnace at 650 °C for 15 min. This process was repeated 6 times, after which the Ti plate was placed in a box-type electric furnace at 650 °C for 1 h. After being taken out, the Ti plate was washed with deionized water and anhydrous ethanol and the surface was wiped with filter paper to ensure that no coating fell off. Then, the precursor solution was replaced with 4 mL of the prepared metal tin salt precursor solution, and the above process was repeated. Finally, a Ti / Cu-Sn cathode was obtained;

[0045] (4) A certain amount of 12 mol / L HCl solution was added to 200 mL of high-concentration nitrate-organic wastewater (NO3 - -N = 10000 mg / L, COD = 5000 mg / L, NH4 + -N = 1000 mg / L) to adjust the pH value and conductivity to 0.5 and 45 mS / cm, respectively. The wastewater, the prepared Ti / Cu-Sn cathode, the Pt anode, and the rotor were then placed in a single-chamber electrolytic cell. The positive electrode of the direct current power supply was connected to the anode plate, and the negative electrode was connected to the cathode plate. After adjusting the electrode plate spacing to 4 mm, the magnetic stirrer speed was set to 650 rpm, the direct current power supply was turned on, and the current density was set to 25 mA / cm 2 After 10 h, the nitrate and COD in the waste liquid were detected (the nitrate detection method refers to "GB / T 6912.1-2006", and the COD detection method refers to "HJ / T 399-2007"). The results showed that the nitrate removal rate was 99.72%, the COD removal rate was 84.61%, and the nitrogen selectivity was 99.83%.

[0046] Example 2

[0047] (1) The Ti plate (5 cm x 5 cm) was polished with sandpaper of different grits, and then was placed in 10 wt% NaOH solution and 10 wt% oxalic acid solution, respectively, and was heated in a water bath at 60-90 °C for 180 min. After being taken out, it was ready for use;

[0048] (2) A certain amount of copper nitrate trihydrate was dissolved in ethanol to prepare a 1 mol / L copper nitrate precursor solution. A certain amount of metal tin salt, sodium hypophosphite, thiourea, complexing agent ascorbic acid, and concentrated hydrochloric acid (36.5 wt%) were placed in a magnetic stirrer and heated and stirred. After the solution cooled to room temperature, it was left to stand, and a metal tin salt precursor solution was obtained, which contained 2 mol / L tin chloride, 3 mol / L sodium hypophosphite, 1.5 mol / L thiourea, 1 mol / L ascorbic acid, and 1 mol / L concentrated hydrochloric acid;

[0049] (3) 8 mL of the prepared copper nitrate precursor solution was evenly applied to the surface of the Ti plate, which was then placed in an oven at 90 °C for 15 min and then in a box-type electric furnace at 250 °C for 10 min. This process was repeated 6 times, after which the Ti plate was placed in the 250 °C box-type electric furnace for 1 h. After being taken out, the Ti plate was washed with deionized water and anhydrous ethanol and the surface was wiped with filter paper to ensure that no coating fell off. Then the precursor solution was replaced with 4 mL of the prepared metal tin salt precursor solution, and the above process was repeated. Finally, a Ti / Cu-Sn cathode was obtained;

[0050] (4) A certain amount of 10 mol / L HCl solution was added to 1000 mL of high-concentration nitrate-organic wastewater (NO3 - -N = 100 mg / L, COD = 100 mg / L, NH4 + -N = 100 mg / L) to adjust the pH value and conductivity to 1.5 and 30 mS / cm, respectively. The wastewater, the prepared Ti / Cu-Sn cathode, the iridium tantalum titanium anode, and the rotor were then placed in a single-chamber electrolytic cell. The positive electrode of the direct current power supply was connected to the anode plate, and the negative electrode was connected to the cathode plate. After adjusting the electrode plate spacing to 20 mm, the magnetic stirrer was set to a speed of 150 rpm, the direct current power supply was turned on, and the current density was set to 20 mA / cm 2 After 5 h, the nitrate and COD in the waste liquid were detected (the nitrate detection method refers to “GB / T 6912.1-2006”, and the COD detection method refers to “HJ / T 399-2007”). The results showed that the nitrate removal rate was 98.81%, the COD removal rate was 72.71%, and the nitrogen selectivity was 98.13%.

[0051] Example 3

[0052] (1) The Ti plate (5 cm x 5 cm) was polished with sandpaper of different grits, and then placed in 10 wt% NaOH solution and 10 wt% oxalic acid solution, respectively, and heated in a water bath at 60-90 °C for 120 min. After being taken out, it was ready for use.

[0053] (2) A certain amount of copper nitrate trihydrate was dissolved in ethanol to prepare a 0.1 mol / L copper nitrate precursor solution. A certain amount of metal tin salt, sodium hypophosphite, thiourea, complexing agent sodium bicarbonate, and concentrated hydrochloric acid (36.5 wt%) were placed in a magnetic stirrer and heated and stirred. After the solution cooled to room temperature, it was left to stand, and a metal tin salt precursor solution was obtained, which contained 1 mol / L trimethyltin chloride, 2 mol / L sodium hypophosphite, 1 mol / L thiourea, 0.5 mol / L sodium bicarbonate, and 0.5 mol / L concentrated hydrochloric acid.

[0054] (3) evenly spread 8 mL of the prepared copper nitrate precursor solution onto the surface of the Ti plate, place it in an oven at 60 °C and dry for 60 min, then place it in a box-type electric furnace at 850 °C and calcine for 60 min; repeat the process 6 times, then place it in a box-type electric furnace at 850 °C and calcine for 1 h, then take it out, rinse it with deionized water and anhydrous ethanol in turn, and wipe the surface with filter paper to ensure that no coating falls off; then replace the precursor solution with 4 mL of the prepared metal tin salt precursor solution and repeat the above process, and finally obtain a Ti / Cu-Sn cathode;

[0055] (4) add a certain amount of 1 mol / L HCl solution to 250 mL of high-concentration nitrate-organic wastewater (NO3 - -N = 5000 mg / L, COD = 3000 mg / L, NH4 + -N = 500 mg / L) to adjust the pH value and conductivity to 3 and 15 mS / cm, respectively; then place the wastewater, the prepared Ti / Cu-Sn cathode, the ruthenium iridium titanium anode, and the rotor into a single-chamber electrolytic cell, connect the positive electrode of the direct current power supply to the anode plate and the negative electrode to the cathode plate, adjust the distance between the electrode plates to 6 mm, set the speed of the magnetic stirrer to 450 rpm, turn on the direct current power supply, set the current density to 50 mA / cm 2 After 1 h, detect the nitrate and COD in the wastewater (the nitrate detection method refers to "GB / T 6912.1-2006", and the COD detection method refers to "HJ / T 399-2007"), and obtain a nitrate removal rate of 95.65%, a COD removal rate of 75.29%, and a nitrogen selectivity of 95.77%.

[0056] Example 4

[0057] (1) polish the Ti plate (5 cm x 5 cm) with sandpaper of different grits, then place it in 10 wt% NaOH solution and 10 wt% oxalic acid solution in turn, heat it in a water bath at 60-90 °C for 120 min, and then take it out for use;

[0058] (2) weigh a certain amount of copper nitrate trihydrate into ethanol to prepare a 1 mol / L copper nitrate trihydrate precursor solution; weigh a certain amount of metal tin salt, sodium hypophosphite, thiourea, complexing agent glucose, and concentrated hydrochloric acid (36.5 wt%) into a magnetic stirrer and heat and stir, then let the solution cool to room temperature and stand to obtain a metal tin salt precursor solution, wherein the content of each component is: 1 mol / L stannous sulfate, 1 mol / L sodium hypophosphite, 1.25 mol / L thiourea, 0.5 mol / L glucose, and 0.5 mol / L concentrated hydrochloric acid.

[0059] (3) evenly spread 8 mL of the prepared copper nitrate precursor solution onto the surface of the Ti plate, place it in a 95 °C oven to dry for 15 min, then place it in a 650 °C box-type electric furnace for calcination for 15 min; repeat the process 6 times, then place it in a 650 °C box-type electric furnace for calcination for 1 h, then take it out and rinse it with deionized water and anhydrous ethanol in turn, and wipe the surface with filter paper to ensure that there is no coating falling off; then replace the precursor solution with 4 mL of the prepared metal tin salt precursor solution for spreading and repeating the above process, and finally obtain a Ti / Cu-Sn cathode;

[0060] (4) add a certain amount of 6 mol / L HCl solution to 450 mL of high-concentration nitrate-organic wastewater (NO3 - -N = 2000 mg / L, COD = 500 mg / L, NH4 + -N = 250 mg / L) to adjust the pH value and conductivity to 1.5 and 25 mS / cm, respectively; then place the wastewater, the prepared Ti / Cu-Sn cathode, the nickel plate anode and the rotor into a single-chamber electrolytic cell, connect the positive electrode of the direct current power supply to the anode plate and the negative electrode to the cathode plate, adjust the distance between the electrode plates to 6 mm, set the speed of the magnetic stirrer to 500 rpm, turn on the direct current power supply, set the current density to 5 mA / cm 2 After 3 h, detect the nitrate and COD in the waste liquid (the detection method of nitrate refers to “GB / T 6912.1-2006”, and the detection method of COD refers to “HJ / T 399-2007”), and obtain the removal rates of nitrate and COD of 96.61% and 70.34%, respectively, and the nitrogen selectivity of 96.02%.

[0061] Example 5

[0062] To further verify the feasibility of the Ti / Cu-Sn electrode in the field of electrocatalytic reduction of carbon dioxide, the Ti / Cu-Sn electrode prepared in Example 1 was used for the experiment of electrocatalytic reduction of carbon dioxide. The experiment was carried out using a Chenhua CHI-1140C electrochemical workstation, which was connected to an H-type electrolytic cell of a three-electrode system. The working electrode, reference electrode and counter electrode used were Ti / Cu-Sn (5×5 cm 2 ), Ag / AgCl electrode and Pt electrode (3×3 cm 2 ), respectively. The cathode and anode chambers of the H-type electrolytic cell were separated by a Nafion-117 ion exchange membrane, and the electrolyte was 0.5 M KHCO3. The gas flow rate was 20 sccm, and the reaction was carried out at -1.0 V vs. RHE potential for 90 min. The Faraday efficiencies of the products were: HCOOH = 30.45%, H2 = 52.29%, and CO = 16.44%.

[0063] Comparative Example 1

[0064] In order to verify the effect of chloride ion on oxidation of ammonia nitrogen, in this comparative example, no HCl solution was added in advance before electrolytic denitrification, and specifically, 200 mL of high-concentration nitrate-organic wastewater (NO3 - -N = 10000 mg / L, COD = 5000 mg / L, NH4 + -N = 1000 mg / L) was added with a certain amount of 1 mol / L sulfuric acid solution to adjust the pH value and conductivity to 0.5 and 45 mS / cm, respectively; the rest of the electrolysis conditions were the same as in Example 1. After 10 h, the nitrate and COD in the waste liquid were detected (the nitrate detection method referred to GB / T 6912.1-2006, and the COD detection method referred to HJ / T 399-2007), and the removal rate of nitrate was 90.76%, the removal rate of COD was 65.41%, and the nitrogen selectivity was 5.35%. It can be seen that Cl - ions can convert the generated ammonia nitrogen into nitrogen gas during electrolysis, so that the presence thereof greatly improves the nitrogen selectivity, while not affecting the removal effect of nitrate and COD.

[0065] Comparative Example 2

[0066] In order to verify the effect of Sn coating on the performance of electrolytic denitrification, in this comparative example, only the Ti plate was subjected to Cu coating synthesis treatment, and the specific operation steps were consistent with those of Example 2. Then a certain amount of 10 mol / L HCl solution was added to 1000 mL of high-concentration nitrate-organic wastewater (NO3 - -N = 100 mg / L, COD = 100 mg / L, NH4 + -N = 100 mg / L) to adjust the pH value and conductivity to 1.5 and 30 mS / cm, respectively. Then the wastewater, the prepared Ti / Cu cathode, the iridium tantalum titanium anode, and the rotor were placed in a single-chamber electrolytic cell, the positive electrode of the direct current power supply was connected to the anode plate, the negative electrode was connected to the cathode plate, the distance between the electrode plates was adjusted to 20 mm, the magnetic stirrer was set to a speed of 150 rpm, the direct current power supply was turned on, the current density was set to 20 mA / cm 2After starting the reaction, the nitrate and COD in the waste liquid were detected after 5 h (the detection method of nitrate refers to GB / T 6912.1-2006, and the detection method of COD refers to HJ / T 399-2007). The final nitrate removal rate was 54.36%, the COD removal rate was 71.88%, and the nitrogen selectivity was 95.23%. It can be seen that the nitrate removal rate of the Ti / Cu coating electrode is significantly lower than that of the Ti / Cu-Sn used in Example 2, which proves that the Cu / Sn bimetallic coating has a unique performance effect on electrolytic denitrification.

[0067] Comparative Example 3

[0068] In order to verify the influence of the Cu coating on the performance of electrolytic denitrification, in this comparative example, only the Ti plate was subjected to the synthesis treatment of Sn coating, and the specific operation steps were consistent with those of Example 3. Then a certain amount of 1 mol / L HCl solution was added to 250 mL high-concentration nitrate-organic wastewater (NO3 - -N=5000 mg / L, COD=3000 mg / L, NH4 + -N=500 mg / L) to adjust the pH value and conductivity to 3 and 15 mS / cm, respectively. Then the wastewater, the prepared Ti / Cu-Sn cathode, the ruthenium iridium titanium anode and the rotor were placed in a single-chamber electrolytic cell. The positive electrode of the direct current power supply was connected to the anode plate, and the negative electrode was connected to the cathode plate. After adjusting the electrode plate spacing to 6 mm, the magnetic stirrer speed was set to 450 rpm, the direct current power supply was turned on, the current density was set to 50 mA / cm 2 After starting the reaction, the nitrate and COD in the waste liquid were detected after 5 h (the detection method of nitrate refers to GB / T 6912.1-2006, and the detection method of COD refers to HJ / T 399-2007). The final nitrate removal rate was 54.36%, the COD removal rate was 71.88%, and the nitrogen selectivity was 95.23%. It can be seen that the nitrate removal rate of the Ti / Cu coating electrode is significantly lower than that of the Ti / Cu-Sn used in Example 2, which proves that the Cu / Sn bimetallic coating has a unique performance effect on electrolytic denitrification.

[0069] Comparative Example 4

[0070] In order to verify the influence of the Cu-Sn coating on the performance of electrolytic denitrification, in this comparative example, only the Ti plate was subjected to sandpaper polishing treatment, and then electrolytic treatment was carried out according to Example 4. The final nitrate removal rate was 4.84%, the COD removal rate was 68.42%, and the nitrogen selectivity was 97.11%. It can be seen that the pure Ti electrode without coating can hardly remove nitrate.

[0071] From the above comparative examples, it can be seen that the pure Ti electrode without coating or the electrode with only one metal coating of Cu or Sn cannot achieve good electrolytic denitrogenation effect, which proves that the Cu / Sn bimetallic coating has unique performance effect on electrolytic denitrogenation.

[0072] The above description is merely preferred embodiments of the present application, and any changes and modifications made by those skilled in the art within the scope of the present application should be covered by the present application.

Claims

1. The application of an electrode material in the electrochemical catalytic degradation of organic wastewater containing high concentrations of nitrates, characterized in that, An electrolytic cell is constructed using electrode materials as the cathode, in an environment containing Cl... - Under certain conditions, it was used to treat NO3 in organic wastewater containing high concentrations of nitrates. - Simultaneous degradation of COD and co-production of hydrogen; The preparation of the electrode material includes the following steps: 1) After polishing the Ti plate with sandpaper, first heat it in a 10 wt% NaOH solution to remove oil, and then heat it in a 10 wt% oxalic acid solution for surface etching. 2) Apply the copper salt precursor solution evenly to the etched Ti plate surface, dry it, and then calcine it. Repeat this process 6 times, then rinse it with deionized water and anhydrous ethanol in sequence, and wipe the surface with filter paper to ensure that no coating peels off. 3) The tin salt precursor solution is evenly coated onto the surface of the material treated in step 2), dried, and then calcined. After repeating this process 6 times, the material is rinsed with deionized water and anhydrous ethanol in sequence, and the surface is wiped with filter paper to ensure that no coating falls off, thus preparing the Ti / Cu-Sn multi-metal coated electrode material.

2. The application according to claim 1, characterized in that, The electrolytic cell uses one of the following as the anode: Pt electrode, iridium-tantalum-titanium electrode, ruthenium-iridium-titanium electrode, or nickel plate electrode.

3. The application according to claim 1, characterized in that, Before electrolysis, the pH of the waste liquid is adjusted to 0.5-3 with 1-12 mol / L HCl solution, and the conductivity is 15-45 mS / cm.

4. The application according to claim 1, characterized in that, NO3 in the wastewater - Concentration ≤10000 mg / L, COD concentration ≤5000 mg / L.

5. The application according to claim 1, characterized in that, The heating temperature in step 1) is 60~90 ℃ and the time is 30~180 min.

6. The application according to claim 1, characterized in that, The copper salt precursor solution mentioned in step 2) is specifically an ethanol solution of copper nitrate with a concentration of 0.1~2 mol / L and an application rate of 0.08 mL / cm. 2 .

7. The application according to claim 1, characterized in that, The tin salt precursor solution described in step 3) is prepared by mixing metallic tin salt, sodium hypophosphite, thiourea, a complexing agent, and concentrated hydrochloric acid, heating and stirring at 60-100 °C for 5-45 min until homogeneous, and then cooling. The concentrations of metallic tin salt, sodium hypophosphite, thiourea, the complexing agent, and concentrated hydrochloric acid are 0.05-2 mol / L, 0.5-3 mol / L, 0.05-1.5 mol / L, 0.01-1 mol / L, and 0.1-1 mol / L, respectively. The application rate of the tin salt precursor solution is 0.04 mL / cm². 2 .

8. The application according to claim 7, characterized in that, The tin salt is selected from one of stannous chloride, stannous chloride, trimethylstannous chloride, and stannous sulfate; the complexing agent is selected from one of sodium citrate, ascorbic acid, sodium bicarbonate, and glucose.

9. The application according to claim 1, characterized in that, The drying temperature is 60~120 ℃ and the time is 10~60 min; the calcination temperature is 250~850 ℃ and the time is 10~60 min.

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