Copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device and application

Abstract

This invention relates to the field of electrochemical technology, and particularly to copper-modified graphitic carbon nitride cathode catalytic materials, urea electro-oxidation devices, and their applications. Copper sulfate pentahydrate and urea are dissolved in water, and a precursor is obtained through mixing, reaction, centrifugation, and drying. The precursor is then ground and mixed with urea, followed by high-temperature calcination to obtain the copper-modified graphitic carbon nitride material. This copper-modified graphitic carbon nitride material is mixed with a perfluorosulfonic acid polymer solution and ethanol in a specific ratio, ultrasonically treated, and then uniformly coated onto a nickel foam electrode to obtain the copper-modified graphitic carbon nitride cathode catalytic material. The copper-modified graphitic carbon nitride material is used as the cathode, and a nickel-based hydroxyl oxide material is used as the anode in a urea electro-oxidation device. This invention overcomes the shortcomings of incomplete electro-oxidation of urea using traditional anodes, achieving 99.9% urea removal, no nitrite accumulation, and a nitrogen conversion rate of 97.2%, realizing rapid oxidation and denitrification of urea.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to copper-modified graphitic carbon nitride cathode catalytic materials, urea electro-oxidation devices, and their applications. Background Technology

[0002] Urea, an important nitrogen-containing compound, is widely used in agriculture as a nitrogen fertilizer, industry as a chemical raw material, and in the pharmaceutical field. However, the widespread use of urea leads to the generation of large amounts of urea wastewater, mainly originating from agricultural fertilization, chemical production, pharmaceutical industry, animal husbandry, and human domestic emissions. Direct discharge of urea wastewater can cause serious environmental pollution, leading to eutrophication of water bodies. In addition, the ammonia gas produced by urea decomposition can cause secondary pollution, endangering human health.

[0003] Currently, urea wastewater treatment methods mainly include adsorption, biodegradation, and electrocatalytic oxidation. Simple adsorption methods cannot decompose and mineralize urea, and adsorbent regeneration is difficult. Biodegradation utilizes the metabolism of microorganisms to decompose urea into N2, CO2, etc. While biological methods offer milder conditions, urea mineralization takes a long time, and the denitrification of intermediate products such as nitrates and nitrites requires additional carbon sources. Therefore, these methods are unsuitable for treating urea wastewater with high concentrations, high toxicity, and poor biodegradability.

[0004] Electro-oxidation technology degrades pollutants through redox reactions at the anode and cathode, offering advantages such as high treatment efficiency and ease of operation, and has been widely applied in the treatment of recalcitrant organic wastewater. However, the practical application of urea electro-oxidation technology still faces limitations. Commonly used precious metal anodes are expensive, and they struggle to achieve complete urea mineralization, often producing intermediate products in the form of nitrates, leading to ineffective nitrogen removal from urea wastewater. Nickel-based catalysts are inexpensive and exhibit high catalytic activity for the urea oxidation reaction (UOR). A published invention patent, "A Molybdenum-Nickel Hydroxide Catalyst, Preparation Method and Application" (202411981929.7), developed a new molybdenum-nickel hydroxyl oxide catalyst that achieves 100% urea removal. However, incomplete urea oxidation remains, with only 5% of the final urea product being N2, leaving a large amount of nitrite intermediates. This not only affects the harmless treatment and compliant discharge of urea wastewater, but the large amount of nitrite may also poison the anode, reducing or even deactivating the anode catalyst's electrocatalytic activity. Therefore, there is a need to develop new methods for denitrification of urea-containing wastewater with high urea removal rate and N2 selectivity.

[0005] Graphite-phase carbon nitride (g-C3N4) is a polymer semiconductor mainly composed of carbon and nitrogen, possessing high specific surface area, good electrical conductivity, and mechanical stability, and is widely used in photocatalytic degradation of organic matter. This invention prepares a copper-doped graphite-phase carbon nitride catalyst, combining anodic urea oxidation with cathode intermediate product reduction to form a synergistic electrocatalytic redox reaction between the anode and cathode. This enhances urea degradation, reduces the accumulation of urea oxidation intermediate products, and improves the efficiency of complete urea conversion to N2, thus achieving effective treatment of urea wastewater. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of intermediate product accumulation and low efficiency of urea mineralization to N2 in the current urea electro-oxidation technology, and to provide a method for preparing a copper-modified graphitic carbon nitride cathode catalyst. The cathode catalyst obtained by this method can be used as the cathode of a urea electro-oxidation device to achieve efficient reduction and degradation of nitrous acid to N2. Coupled with the molybdenum-nickel hydroxyl oxide catalyst of the anode, it can accelerate urea oxidation, reduce the poisoning effect of nitrous acid on the anode catalyst, and achieve effective mineralization of urea.

[0007] A further objective of this invention is to provide a copper-modified graphitic carbon nitride cathode catalytic material.

[0008] A further object of the present invention is to provide the application of the above-mentioned material as a cathode in a urea electro-oxidation device.

[0009] A further object of the present invention is to provide a urea electro-oxidation device.

[0010] A further objective of this invention is to provide a method for the effective mineralization and denitrification of urea.

[0011] The above-mentioned objective of this invention is achieved through the following technical solution: a method for preparing copper-modified graphite-phase carbon nitride cathode catalytic material, comprising the following steps:

[0012] S1: Copper sulfate pentahydrate and urea are dissolved in water, and the precursor is obtained by mixing reaction, centrifugation and drying;

[0013] S2: The precursor is ground and mixed with urea, and then calcined at high temperature to obtain the copper-modified graphitic carbon nitride material.

[0014] S3: The copper-modified graphitic carbon nitride material prepared in S2 is mixed with perfluorosulfonic acid polymer solution and ethanol in a certain proportion. After ultrasonic treatment, it is uniformly coated on the nickel foam electrode to obtain the copper-modified graphitic carbon nitride cathode catalyst material.

[0015] In step S1, the mass ratio of the sum of copper sulfate pentahydrate and urea to the volume of deionized water in the preparation of the precursor is (17-19) g / 100mL; in step S2, the mass ratio of the precursor to urea is 1:0-0:1, and the precursor is calcined in a muffle furnace at 520℃ for 4 hours; in step S3, the ratio of copper-modified graphitic carbon nitride material, perfluorosulfonic acid polymer solution, and ethanol is 62.5mg:1mL:4mL, the concentration of the perfluorosulfonic acid polymer solution is 5%, the ultrasonic time is 30min, and the loading mass of the copper-modified graphitic carbon nitride catalyst is 1mg / cm³. 2 .

[0016] In this invention, copper-modified graphitic carbon nitride material is prepared by adjusting the ratio of the sum of the masses of copper sulfate pentahydrate and urea to water, as well as the mass ratio of the precursor to urea. Then, the copper-modified graphitic carbon nitride material is loaded onto nickel foam in proportion to form a cathode. This material has excellent nitrite reduction performance and can be used in the nitrite reduction process generated in urea oxidation. Moreover, the preparation process is simple and the cost is low.

[0017] If the ratio of the sum of the masses of copper sulfate pentahydrate and urea to water, and the mass ratio of the precursor to urea, are too large or too small, the pore size of the prepared copper-modified graphitic carbon nitride material will change, the catalytic activity for nitrite ions will decrease, and the stability of the material will be reduced.

[0018] Preferably, the mass ratio of copper sulfate pentahydrate to urea in step S1 is 1:2.

[0019] Preferably, the mass ratio of the precursor to urea in step S2 is 1:8.

[0020] Preferably, step S3 further includes a pre-use cleaning step for the nickel foam, wherein the cleaning step is as follows: first, ultrasonicate the nickel foam with 1M hydrochloric acid for 15 minutes; then, ultrasonicate it with deionized water for 15 minutes, and finally, allow it to air dry naturally.

[0021] Preferably, the size of the nickel foam in step S3 is 2.5cm × 2.5cm.

[0022] Preferably, the average pore size of the nickel foam in step S3 is 0.1 mm, and the porosity is 97%.

[0023] The copper-modified graphitic carbon nitride cathode catalytic material was prepared by the method described above.

[0024] The application of copper-modified graphitic carbon nitride material as cathode and nickel-based hydroxyl oxide material as anode in urea electro-oxidation device.

[0025] A urea electro-oxidation device includes an anode, an anode chamber, an anion exchange membrane, a cathode chamber, and a cathode; the ion exchange membrane separates the anode chamber and the cathode chamber; the anode and cathode are made of nickel-based hydroxyl oxide and copper-modified graphitic carbon nitride, respectively; the anolyte is a urea-containing solution, and the catholyte is one or more of sulfate, acetate, bicarbonate, or phosphate solutions.

[0026] This invention constructs a urea electro-oxidation device using copper-modified graphite-phase carbon nitride material as the cathode, molybdenum-nickel hydroxide material as the anode, and an ion exchange membrane as the spacer material. The device can achieve a urea removal rate of 99.9% within 40 minutes, with virtually no accumulation of intermediate product nitrite, and a conversion efficiency of 97.2% to N2, thus achieving effective mineralization.

[0027] Preferably, the ion exchange membrane is an anion exchange membrane.

[0028] Preferably, the anolyte is a urea-containing solution with a urea concentration of 0.33 mol / L.

[0029] More preferably, the concentration of potassium hydroxide in the urea-containing solution is 1.5 mol / L.

[0030] Preferably, the catholyte is a sodium sulfate solution with a concentration of 0.3 mol / L.

[0031] Preferably, the distance between the anode and the cathode is 1-6 mm, and the ratio of the anode to cathode area is 1:1.

[0032] Preferably, the applied voltage of the urea electro-oxidation device is provided by a DC power supply.

[0033] More preferably, the DC power supply provides a current density of 50-500 mA / cm². 2 The running time is 20-40 minutes.

[0034] More preferably, the operating temperature is 25-85℃.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: The urea electro-oxidation device constructed by the present invention using copper-modified graphite phase carbon nitride cathode material, molybdenum nickel hydroxide anode material and anion exchange membrane achieves efficient degradation and mineralization of urea, eliminates the inhibitory effect of intermediate product nitrite, and improves the effect of mineralizing urea into N2. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device, and urea electro-oxidation device of the present invention.

[0037] Figure 2 This is a comparison chart of the linear sweep voltammetry (LSV) test results of copper-modified graphite-phase carbon nitride cathode catalysts prepared with different precursor-to-urea ratios in Example 1 of the present invention, copper-modified graphite-phase carbon nitride cathode catalyst, urea electro-oxidation device and application.

[0038] Figure 3 In Example 1 of the present invention, copper-modified graphitic carbon nitride cathode catalytic material, urea electro-oxidation device and application, (a) and (b) are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the copper-modified graphitic carbon nitride catalyst prepared under optimal conditions, respectively.

[0039] Figure 4 This is a graph showing the concentration changes of total nitrogen, nitrite nitrogen, and urea in the urea electro-oxidation device in Example 2 of the present invention, which describes the copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device, and its application.

[0040] Figure 5 This is a graph showing the urea removal rate and N2 selectivity results of 8 cycles in the urea electro-oxidation device in Example 2 of the present invention, which describes the copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device and its application.

[0041] Figure 6 This is an ion chromatography result of the anode and cathode chambers in the urea electro-oxidation device in Example 2 of the present invention, which describes the copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device and its application.

[0042] Figure 7 This is a gas chromatographic result of the anode and cathode chambers in the urea electro-oxidation device in Example 2 of the present invention, which describes the copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device and its application.

[0043] Figure 8 This is a graph showing the results of measuring the effect of different potassium hydroxide concentrations on urea removal rate and N2 selective mineralization in Example 3 of the present invention, which describes the copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device and its application.

[0044] Figure 9 This is a graph showing the results of measuring the effect of initial urea concentration on urea removal rate and N2 selective mineralization in Example 4 of the present invention, which describes the copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device and its application.

[0045] Figure 10 This is a graph showing the effect of temperature on the urea removal rate and N2 selective mineralization in Example 5 of the present invention, which describes the copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device and its application.

[0046] Figure 11This is a comparison chart of LSV test results of molybdenum-nickel hydroxide anode catalyst and copper-modified graphite-phase carbon nitride cathode catalyst in Example 6 of the present invention, which describes the copper-modified graphite-phase carbon nitride cathode catalyst, urea electro-oxidation device and its application.

[0047] Figure 12 This is a comparative diagram showing the effect of different membranes on the electro-oxidation of urea in Comparative Example 1, which is a comparison of the effects of copper-modified graphite phase carbon nitride cathode catalytic material, urea electro-oxidation device and its application of the present invention. Detailed Implementation

[0048] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments described herein are merely illustrative and are not intended to limit the scope of this application. Example 1:

[0049] The preparation method of the copper-modified graphite-phase carbon nitride cathode catalyst in this embodiment includes the following steps:

[0050] Preparation of copper-modified graphitic carbon nitride precursor: 5 g CuSO4·5H2O and 9.62 g urea were weighed and placed in 80 ml deionized water, and magnetically stirred at 80 °C for 1 h. The resulting pale blue precipitate was collected by centrifugation, washed, and dried. The centrifuged material was transferred to a crucible, sealed with tin foil, and placed in a muffle furnace for calcination at 350 °C for 2 h.

[0051] Preparation of copper-modified graphitic carbon nitride catalyst: According to different mass ratios of copper-modified graphitic carbon nitride precursor to urea (1:0, 1:4, 1:8, 1:12, 0:1), copper-modified graphitic carbon nitride precursor and urea were weighed, ground and mixed evenly, placed in a crucible, sealed with tin foil, and calcined at 520℃ for 4h. The obtained products were labeled as Cu / g-C3N4-0, Cu / g-C3N4-4, Cu / g-C3N4-8, Cu / g-C3N4-12, and Cu / g-C3N4, respectively.

[0052] 6.25 mg of the copper-modified graphitic carbon nitride catalyst prepared above and 0.1 mL of 5 wt% Nafion solution were dispersed in 0.4 mL of ethanol. After sonication for 30 min, the mixture was uniformly coated onto pretreated nickel foam (2.5 cm × 2.5 cm). The loading of the copper-modified graphitic carbon nitride catalyst was 1 mg / cm³. -2 Different Cu / g-C3N4-0, Cu / g-C3N4-4, Cu / g-C3N4-8, Cu / g-C3N4-12, and Cu / g-C3N4 cathodes were prepared.

[0053] A comparison of linear sweep voltammetry (LSV) results for copper-modified graphitic carbon nitride cathode catalysts prepared with different precursor-to-urea ratios is shown in the figure. Figure 2 As shown in the figure, when the mass ratio of copper-modified graphitic carbon nitride precursor to urea is 1:8, the catalytic performance of Cu / g-C3N4-8 is significantly better than that of Cu / g-C3N4-4, Cu / g-C3N4-12, and g-C3N4, but lower than that of Cu / g-C3N4-0. Stability tests show that Cu / g-C3N4-0 cannot provide stable catalysis. Therefore, Example 1 clearly shows that the optimal ratio of precursor to urea is 1:8, and the prepared copper-modified graphitic carbon nitride catalyst Cu / g-C3N4-8 has the best catalytic performance and stability. Its scanning electron microscope (SEM) and transmission electron microscope (TEM) images are shown in the figure. Figure 3 As shown in (a) and (b). Example 2:

[0054] The preparation method of the molybdenum-nickel hydroxide anolyte catalyst in this embodiment includes the following steps:

[0055] 1.0 mmol Ni(NO3)2∙6H2O, 0.50 mmol Na2MoO4, and 6.0 mmol CO(NH2)2 were dissolved in 35 mL of deionized water. Nickel foam was added to the solution and sealed in a 50 mL high-pressure reactor. After heating at 140 °C for 8 h, the product was washed with deionized water and dried. Finally, the product was subjected to electrochemical oxidation to obtain a molybdenum-nickel hydroxide anode catalyst.

[0056] The urea electro-oxidation device has an effective area of ​​6.25 cm². 2 A molybdenum-nickel hydroxide electrode was used as the anode, and the Cu / g-C3N4-8 catalyst preferred in Example 1 was used as the cathode. An anion exchange membrane (AEM8040) was used to separate the anode and cathode compartments. The effective liquid volume of both the anode and cathode compartments was 0.625 mL, and the distance between the electrodes was 1 cm. Urea oxidation electrolysis was carried out in an intermittent flow mode. A 15 mL solution containing 0.33 mol / L urea + 1.5 mol / L KOH was stored in a tank, and the solution was pumped at a rate of 8.0 mL / min using a peristaltic pump. -1 A continuous flow rate was pumped into the anode chamber. Simultaneously, 15 mL of 0.3 M Na₂SO₄ solution was circulated to the cathode chamber. A power supply (IT6720, ITECH Electronics Co., Ltd., China) was used at 300 mA cm⁻¹. -2 The performance of urea oxidation electrolysis was investigated under constant current. The above operation was repeated to carry out the cyclic reaction.

[0057] The concentration changes of total nitrogen, nitrite nitrogen, and urea in the urea electro-oxidation unit are as follows: Figure 4As shown, under the synergistic effect of anode and cathode, the urea removal rate can reach 99.9% after 40 minutes of electrocatalytic reaction, and the byproduct NO2 generated at the anode is reduced. - It almost completely removes nitrogen, with a total nitrogen removal rate of up to 97.2% and a N2 selectivity of up to 97.2%.

[0058] The results of four-cycle experiments in the urea electro-oxidation unit, showing the urea removal rate and N2 selectivity, are shown in the figure below. Figure 5 As shown, the removal rate of urea in the first treatment was 950.4 gm. –2 h –1 The urea removal rate did not change significantly in the first 7 cycles, and remained at 911.2 gm in the 8th cycle. –2 h –1 The N2 selectivity was 93.6%, indicating that the urea electro-oxidation unit performed well. The ion chromatography results of the anode and cathode chambers in the urea electro-oxidation unit are as follows: Figure 6 As shown, the main byproduct of anodic electro-oxidation of urea is NO2. - Under the catalytic action of a copper-modified graphitic carbon nitride cathode, the byproduct NO2 is produced. - It was almost completely electroreduced to N2. The gas chromatographic results of the anode and cathode chambers in the urea electro-oxidation device are shown in the figure below. Figure 7 As shown, the byproducts of anodic electro-oxidation of urea are electroreduced to N2 under cathode-assisted directional induction, instead of N2O or other gaseous NO. x . Example 3:

[0059] The difference from Example 2 is that the initial concentration of potassium hydroxide is different. At 300 mA cm⁻¹ -2 The performance of the urea electro-oxidation device under different KOH concentrations (1, 1.5, 2 and 3 mol / L) was investigated under constant current.

[0060] The results of the determination of the effect of different potassium hydroxide concentrations on urea removal rate and N2 selective mineralization are as follows: Figure 8 As shown, the urea removal rate gradually increases with increasing KOH concentration, reaching a maximum of 1376.2 gm³ when the KOH concentration is 3 mol / L. –2 h –1 The N2 selectivity was 83%. However, the N2 selectivity gradually decreased, mainly because of the OH... - With NO2 - Competition on the anion exchange membrane. Therefore, Example 3 clarifies that the optimal concentration of potassium hydroxide in the anolyte of the urea oxidation unit is 1.5 mol / L. Example 4:

[0061] The difference from Example 2 is that the initial urea concentration is different. At 300 mA cm⁻¹ -2 The performance of the urea electro-oxidation device for urea removal was investigated under constant current conditions at different urea concentrations (0.1, 0.2, 0.33, 0.5 and 1 mol / L).

[0062] The results of the determination of the effect of initial urea concentration on urea removal rate and N2 selective mineralization in the electro-oxidation unit are as follows: Figure 9 As shown, the urea removal rate is highest when the initial urea concentration is 0.5 mol / L, reaching 1195.7 gm. –2 h –1 The N2 selectivity was 98.1%. When the urea concentration was less than 0.5 mol / L, the urea removal rate increased significantly. When the urea concentration exceeded 0.5 mol / L, the urea removal rate showed a decreasing trend, indicating that the UOR process shifted from a diffusion-controlled process to a surface reaction-controlled process.

[0063] Therefore, Example 4 clearly shows that the optimal urea concentration in the anolyte of the urea electro-oxidation device is 0.5 mol / L. Considering that the concentration of urea in human urine is 0.33 mol / L, and Example 2 used a 0.33 mol / L urea solution, the test results of which are close to actual urea wastewater. Therefore, the urea concentration can be further optimized to 0.33 mol / L. Example 5:

[0064] The difference from Example 2 is that the reaction temperature is different. At 300 mA cm⁻¹ -2 The effect of different reaction temperatures (25, 45, 65 and 85 °C) on the urea removal performance was investigated under constant current.

[0065] The effects of temperature on the urea removal rate and N2 selective mineralization in the urea electro-oxidation unit are shown in the following results. Figure 10 As shown, the removal rate of urea and the selectivity of N2 gradually increase with increasing temperature. The removal rate of urea is highest at 85℃, reaching 1504.3 gm³. –2 h –1 The N2 selectivity is 99.6%. This is because increasing the temperature increases the activation energy, the diffusion rate of molecules, and the collision frequency. Example 6:

[0066] The electrocatalytic activity of nickel molybdenum hydroxide was evaluated in 1.5 mol / L KOH and 0.33 mol / L urea solutions, and the electrocatalytic activity of copper-modified graphitic carbon nitride was evaluated in 0.3 mol / L Na₂SO₄ and 0.05 mol / L NaNO₂ solutions. The nickel molybdenum hydroxide or copper-modified graphitic carbon nitride electrodes prepared in Example 1 were used as working electrodes, each with a geometric area of ​​1.0 cm × 1.0 cm. A Hg / HgO (1 M KOH) electrode was used as the reference electrode, and a graphite rod as the counter electrode. Linear sweep voltammetry (LSV) was performed at 5 mV s. -1 Performed at the scan rate.

[0067] LSV test results for molybdenum-nickel hydroxide anolyte catalyst and copper-modified graphite-phase carbon nitride cathode catalyst, for example... Figure 11 As shown, based on linear sweep voltammetry (LSV) and a reversible hydrogen electrode (V... RHE In comparison, the molybdenum-nickel hydroxide anolyte catalyst achieves industrial-level 100 mA cm⁻¹ at low potentials of 1.47 V and 1.75 V, respectively. -2 and 300mA cm -2 Its urea electro-oxidation activity is excellent. The copper-modified graphitic carbon nitride cathode catalyst achieves -50 mA cm⁻¹ at low potentials of -0.92 V and -1.24 V, respectively. -2 and -100mA cm -2 Its NO2 - It exhibits excellent electroreduction activity.

[0068] Comparative Example

[0069] The difference from Example 2 is the use of an ion exchange membrane. At 300 mA cm⁻¹ -2 The effect of anion and cation exchange membranes on the urea degradation performance in a urea electro-oxidation device was investigated under constant current.

[0070] The effects of different diaphragms on the electro-oxidation effect of urea electro-oxidation devices, for example... Figure 12 As shown, a cation exchange membrane separates the anode and cathode compartments. Byproducts generated during anodic electro-oxidation cannot be electro-reduced at the cathode through the membrane, thus inhibiting the urea electro-oxidation performance of the anode and leading to a significant decrease in urea conversion rate. At 40 min, the conversion rate was only 59.7%.

[0071] Therefore, Example 7 clearly shows that the anion exchange membrane in the urea electro-oxidation device is the optimal ion exchange membrane.

[0072] In summary, the copper-modified graphitic carbon nitride cathode catalytic material, urea electro-oxidation device, and applications of the present invention, through the detailed description of the above examples and comparative examples, demonstrate that the prepared copper-modified graphitic carbon nitride cathode catalytic material possesses excellent NO2 control properties. - The electroreduction activity, combined with the synergistic effect of the molybdenum-nickel hydroxide anolyte catalyst, allows the constructed urea electro-oxidation device to efficiently and stably remove urea under optimized process conditions (precursor to urea mass ratio of 1:8, anolyte KOH concentration of 1.5 mol / L, initial urea concentration of 0.5 mol / L, suitable temperature, and the use of anion exchange membranes). It also exhibits high N2 selectivity and good recyclability, providing a practical and feasible technical solution for the treatment of urea-containing wastewater.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing copper-modified graphitic carbon nitride cathode catalytic material, characterized in that, Includes the following steps: S1: Copper sulfate pentahydrate and urea are dissolved in water, and the precursor is obtained by mixing reaction, centrifugation and drying; S2: The precursor is ground and mixed with urea, and then calcined at high temperature to obtain the copper-modified graphitic carbon nitride material. S3: The copper-modified graphitic carbon nitride material prepared in S2 is mixed with perfluorosulfonic acid polymer solution and ethanol in a certain proportion. After ultrasonic treatment, it is uniformly coated on the nickel foam electrode to obtain the copper-modified graphitic carbon nitride cathode catalyst material. In step S1, the mass ratio of the sum of copper sulfate pentahydrate and urea to the volume of deionized water in the preparation of the precursor is (17-19) g / 100mL; in step S2, the mass ratio of the precursor to urea is 1:0-0:1, and the precursor is calcined in a muffle furnace at 520℃ for 4 hours; in step S3, the ratio of copper-modified graphitic carbon nitride material, perfluorosulfonic acid polymer solution, and ethanol is 62.5mg:1mL:4mL, the concentration of the perfluorosulfonic acid polymer solution is 5%, the ultrasonic time is 30min, and the loading mass of the copper-modified graphitic carbon nitride catalyst is 1mg / cm³. 2 .

2. The method for preparing copper-modified graphitic carbon nitride cathode catalytic material according to claim 1, characterized in that, The mass ratio of copper sulfate pentahydrate and urea in step S1 is 1:

2.

3. The method for preparing the copper-modified graphite-phase carbon nitride cathode catalytic material according to claim 1, characterized in that, The mass ratio of the precursor to urea in step S2 is 1:

8.

4. A copper-modified graphitic carbon nitride cathode catalytic material, characterized in that, The copper-modified graphitic carbon nitride cathode catalytic material as described in any one of claims 1-3 was prepared.

5. The copper-modified graphite-phase carbon nitride cathode catalytic material according to claim 4, characterized in that, The application of copper-modified graphitic carbon nitride material as cathode and nickel-based hydroxyl oxide material as anode in urea electro-oxidation device.

6. A urea electro-oxidation device, characterized in that, It includes an anode, an anode chamber, an anion exchange membrane, a cathode chamber, and a cathode; the ion exchange membrane separates the anode chamber and the cathode chamber; the materials of the anode and the cathode are nickel-based hydroxyl oxide material and copper-modified graphitic carbon nitride material, respectively; the anolyte is a solution containing urea, and the catholyte is one or more of sulfate solution, acetate solution, bicarbonate solution, or phosphate solution.

7. The urea electro-oxidation device according to claim 6, characterized in that, The urea concentration in the urea-containing solution is 0.1-1.0 mol / L, and the potassium hydroxide concentration is 1.5-3.0 mol / L.

8. The urea electro-oxidation device according to claim 6, characterized in that, The concentration of the catholyte is 0.1-0.4 mol / L.

9. The urea electro-oxidation device according to claim 6, characterized in that, The distance between the anode and cathode is 1 mm, the ratio of anode to cathode area is 1:1, and an anion exchange membrane is preferred.

10. The application of a urea electro-oxidation device, characterized in that, The current density of the urea electro-oxidation device is 50-500 mA / cm². 2 The running time is 20-40 minutes; the operating temperature is 25-85℃.

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