Electrode material for radioactive wastewater treatment and preparation method thereof

Abstract

The invention relates to the technical field of radioactive wastewater treatment materials, in particular to an electrode material for radioactive wastewater treatment and a preparation method thereof.The electrode material comprises foamed nickel and a compound of a heterojunction material and an oxygen absorption material, the compound is loaded on the foamed nickel in situ, the heterojunction material is g-C3N4-CuO, and the oxygen absorption material is Pr2CuO4; the preparation method comprises the following steps: dissolving nitrates corresponding to Pr and Cu in a mixed solvent of water and ethylene glycol, adding citric acid, and adjusting the pH value to 5-6; carrying out heat treatment at 80-90 DEG C for 10-15 hours, adding g-C3N4 and urea, adjusting the pH value to 9-10, and putting foamed nickel; calcining at the temperature of 280-320 DEG C in an Ar / H2 atmosphere, and then calcining in air at the temperature of 380-450 DEG C; when the method is used for treating the low-concentration uranium-containing radioactive wastewater, the removal effect of over 50 percent can be achieved within 11 hours at the soonest, and the treatment time can be remarkably shortened.

Description

Technical Field

[0001] This invention relates to the field of materials technology for radioactive wastewater treatment, specifically to an electrode material for radioactive wastewater treatment and its preparation method. Background Technology

[0002] Electrochemical treatment of radioactive wastewater offers advantages such as low energy consumption, high degradation efficiency, and minimal secondary pollution, leading to its increasing importance in this field. For instance, loading heterojunctions onto electrodes as anode materials in electrochemical reaction systems allows for efficient photoelectrocatalytic oxidation of uranium-containing wastewater under visible light irradiation, room temperature, and air atmosphere. However, the low concentration and slow diffusion rate of uranium ions in the wastewater result in a low reaction rate. For example, the C3N4-Sn3O4-Ni electrode material requires nearly 16 hours to achieve a 50% removal rate in photoelectrocatalytic treatment of wastewater with a uranium ion concentration of 10 mg / L, which cannot meet the requirements of some applications in existing technologies for the short-term, high-efficiency removal of uranium-containing wastewater.

[0003] Therefore, this application is submitted. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides an electrode material for radioactive wastewater treatment and its preparation method, aiming to solve the problems of slow reaction rate and long time required when the prior art is used for the treatment of low-concentration uranium-containing wastewater.

[0005] On one hand, this invention proposes a method for preparing electrode materials for radioactive wastewater treatment, comprising the following steps: S1. Dissolve the corresponding nitrates of Pr and Cu in a water-ethylene glycol mixed solvent with a volume ratio of water to ethylene glycol of 1:(1-4). Then add citric acid and stir until homogeneous. Adjust the pH to 5-6. By controlling the above conditions, the metal ions are fully complexed with citric acid and there is still an excess of citric acid. S2. Heat the solution obtained in the previous step at 80-90℃ for 10-15h. During this period, the excess citric acid reacts with ethylene glycol to form a three-dimensional gel network. Then, g-C3N4 and urea are added. The three-dimensional gel network uniformly coats g-C3N4, making it uniformly dispersed in the system to avoid aggregation. Then, the pH value is slowly adjusted to 9-10. S3. Place the nickel foam in the mixture obtained in the previous step and let it stand in a vacuum and room temperature environment for 12-15 hours. During this period, the three-dimensional gel network will uniformly disperse the metal ions along with g-C3N4 in the pores and surface of the nickel foam. Then take it out and dry it. S4. The nickel foam obtained in the previous step is first calcined at 280-320℃ in an Ar / H2 atmosphere for 1.5-3h to generate Pr2CuO4 and Cu, and then calcined in air at 380-450℃ for 1.5-2h to oxidize Cu to CuO, finally obtaining a composite of Pr2CuO4 and g-C3N4-CuO.

[0006] The preparation method proposed in this invention uses citric acid as a ligand to complex metal ions before precipitation. At the same time, it uses Ar / H2 reducing atmosphere for low-temperature calcination to fix Pr2CuO4 and prevent particle agglomeration. Finally, a composite of uniformly dispersed Pr2CuO4 and g-C3N4-CuO is obtained on nickel foam.

[0007] Furthermore, the nitrate of Pr is praseodymium nitrate hexahydrate, and the nitrate of Cu is copper nitrate trihydrate. The mass ratio of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 is 1:(2-2.5):(1-1.4):(0.4-0.6). Preferably, the mass ratio of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 is 1:2.2:1.1:0.5.

[0008] Furthermore, in step S2, the mass ratio of urea to copper nitrate trihydrate is (2.5-3.7):1. For example, the specific mass ratio can be 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, etc.

[0009] In this technical solution, the limited amount of urea mainly plays the following roles: (1) Urea decomposes at high temperature to generate NH3, which can help g-C3N4 to disperse more evenly; (2) When the pH value of the system is 9-10, the NH4 generated by urea hydrolysis + It can buffer OH - The concentration of Cu 2+ precipitation.

[0010] Furthermore, the nickel foam is first activated and then placed in the mixture obtained in S2. The specific activation operation is as follows: the nickel foam is immersed in nitric acid with a mass percentage of 3.5%-7.5% and ultrasonically treated for at least 15 minutes, and then rinsed with deionized water and ethanol.

[0011] Furthermore, in step S3, the ambient pressure is between -0.08 MPa and -0.1 MPa. For example, the specific ambient pressure can be -0.08 MPa, -0.09 MPa, -0.1 MPa, etc.

[0012] In this technical solution, by regulating the environmental pressure, air in the pores of the nickel foam can be effectively expelled, allowing the three-dimensional gel network to be fully filled, while avoiding deformation of the nickel foam structure due to excessive pressure.

[0013] Furthermore, in step S4, the volume percentage of H2 in Ar / H2 is 5%-10%.

[0014] On the other hand, the present invention proposes an electrode material for radioactive wastewater treatment.

[0015] Furthermore, the electrode material comprises nickel foam and a composite of a heterojunction material and an oxygen-absorbing material in situ supported on the nickel foam. The heterojunction material is g-C3N4-CuO, which dominates the reduction, and the oxygen-absorbing material is Pr2CuO4. This invention unexpectedly discovered that the synergistic effect of the two can significantly improve the reduction rate of hexavalent uranium ions, achieving the effect of removing uranium ions from uranium-containing wastewater in a short time and with high efficiency. It is speculated that Pr2CuO4 has a strong oxygen absorption capacity and high electronic conductivity, which can autonomously absorb free oxygen in wastewater and enter the interstitial positions of its crystal lattice to form lattice oxygen, eliminating competing oxygen and improving the selectivity of uranium reduction. The loading of the composite on nickel foam was 10-15 mg / cm³. 2 For example, it could be 10 mg / cm³ 2 11mg / cm 2 12mg / cm 2 13mg / cm 2 14mg / cm 2 15mg / cm 2 Within this loading range, the heterojunction material in the composite exhibits high catalytic activity, the oxygen-absorbing material demonstrates significant oxygen absorption, and the conductive network of the nickel foam remains intact. However, if the loading is below 10 mg / cm³, the results are less favorable. 2 Low active site density leads to poor catalytic activity of the complex, and low-content oxygen-absorbing materials cannot effectively perform their oxygen-absorbing function; for example, if the loading is higher than 15 mg / cm³... 2 This will cause the pores of the nickel foam to become clogged, resulting in decreased conductivity and impeded mass transfer. The loading range defined in this invention is a better choice that balances conductivity, oxygen absorption effect and catalytic activity. The heterojunction material in the composite contains 82wt%-87wt%, specifically 82wt%, 82.2wt%, 82.4wt%, 82.6wt%, 82.8wt%, 83wt%, 83.1wt%, 83.3wt%, 83.5wt%, 83.7wt%, 83.9wt%, 84wt%, 84.5wt%, 85wt%, 85.5wt%, 86wt%, 86.5wt%, 87wt%, etc. This high proportion of heterojunction material ensures that photogenerated electrons are preferentially used for the reduction of hexavalent uranium ions, rather than being consumed by oxygen absorbed by Pr2CuO4. Simultaneously, the oxygen vacancies in Pr2CuO4 and the N vacancies in g-C3N4 form charge transfer channels, reducing interfacial resistance. In g-C3N4-CuO, the mass ratio of g-C3N4 to CuO is 1:(1-1.5), specifically 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc. g-C3N4 provides photogenerated electrons, while CuO accelerates electron transfer and enhances conductivity. However, excessive CuO will cover the active sites of g-C3N4 and affect catalytic activity. When the mass ratio of the two satisfies the above relationship, the contact area between CuO and g-C3N4 is larger and will not adversely affect the active sites of g-C3N4, thus forming more effective heterojunction interfaces and higher catalytic efficiency.

[0016] Preferably, the loading of the composite on the nickel foam is 12 mg / cm³. 2 The heterojunction material in the composite accounts for 85 wt%, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:1.2. The present invention has surprisingly found that when the composite on the electrode material meets the above requirements, it responds rapidly when used for the treatment of low-concentration uranium-containing radioactive wastewater, and can achieve a removal effect of more than 50% in 11 hours. Compared with the prior art, the time required to achieve the same removal effect is shortened by about 30%.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The addition of oxygen-absorbing material Pr2CuO4 creates a "locally low oxygen" microenvironment, which allows photogenerated electrons to be preferentially used for uranium reduction. At the same time, the conductivity of Pr2CuO4 enables it to act as an "electron bridge" to accelerate the carrier transport of g-C3N4-CuO. The synergistic effect with g-C3N4-CuO can provide a rapid response and significantly improve the reduction rate of hexavalent uranium ions. The resulting electrode material has a fast reaction rate and short time required when used for the treatment of low-concentration uranium-containing wastewater, which can meet the needs of some application scenarios in the prior art for short-time and efficient removal of uranium-containing wastewater.

[0018] (2) The preparation method does not involve expensive equipment or complex processes, and it has high repeatability and good prospects for large-scale production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The electrode materials obtained in Example 1 and Comparative Example 7 of this invention are used as anodes for photoelectrocatalytic treatment of wastewater with a uranium ion concentration of 10 mg / L, showing the removal rate-time curves.

[0021] Figure 2 The electrode materials obtained in Example 1, Comparative Examples 1 and 2 of this invention are used as anodes for photoelectrocatalytic treatment of wastewater with a uranium ion concentration of 10 mg / L, showing the removal rate-time curves.

[0022] Figure 3 The electrode materials obtained in Examples 1-3 of this invention are used as anodes for photoelectrocatalytic treatment of wastewater with a uranium ion concentration of 10 mg / L, showing the removal rate-time curves.

[0023] Figure 4 The electrode materials obtained in Examples 1, 4, and 5 of this invention are used as anodes for photoelectrocatalytic treatment of wastewater with a uranium ion concentration of 10 mg / L, showing the removal rate-time curves.

[0024] Figure 5 The electrode materials obtained in Examples 1, 3, and 6 of this invention are used as anodes for photoelectrocatalytic treatment of wastewater with a uranium ion concentration of 10 mg / L, showing the removal rate-time curves.

[0025] Figure 6 The images show SEM images of the electrode material and the composite obtained in Example 1 of this invention.

[0026] Figure 7 for Figure 6 The element distribution diagram within the red box in Figure B.

[0027] Figure 8 The images show the XRD patterns of the products obtained in Comparative Example 1 and Comparative Example 2 of this invention. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0029] All chemical raw materials used in the following examples and comparative examples were commercially available and from various manufacturers. In the following examples and comparative examples, g-C3N4 was commercially available and had a two-dimensional sheet-like microstructure. The nickel foam was commercially available and its main structural parameters were: pore size 100-300 μm, porosity ≥95%, size 2cm×3cm×0.1cm, and surface roughness 1-2 μm. The activation treatment of the nickel foam was as follows: the nickel foam was immersed in 5.5% nitric acid by mass and ultrasonically treated for 25 min, and then rinsed three times each with deionized water and ethanol.

[0030] Example 1 An electrode material for radioactive wastewater treatment comprises nickel foam and a composite material of a heterojunction material and an oxygen-absorbing material in situ supported on the nickel foam. The heterojunction material is g-C3N4-CuO, the oxygen-absorbing material is Pr2CuO4, and the loading of the composite material on the nickel foam is 12 mg / cm³. 2 The heterojunction material accounts for 85 wt% of the composite, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:1.2; the microstructure of this electrode material is as follows. Figure 6 As shown in Figure A, it can be seen that the surface of the nickel foam clearly shows loadings, such as... Figure 6 As shown in Figure B, the composite material exhibits a scattered, flaky, mixed-particle morphology on the surface of nickel foam. EDS analysis reveals that Pr, Cu, O, and N elements are well-dispersed (e.g., ...). Figure 7 (As shown).

[0031] The preparation method of the above electrode material includes the following steps: S1. Dissolve praseodymium nitrate hexahydrate and copper nitrate trihydrate thoroughly in 200 mL of a water-ethylene glycol mixed solvent with a water-ethylene glycol volume ratio of 1:2. Then add citric acid and stir well to adjust the pH to 5. S2. Heat the solution obtained in the previous step at 85°C for 12 hours, then add g-C3N4 and urea, and slowly adjust the pH to 10. In steps S1 and S2, the masses of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 are 1g, 2.2g, 1.1g, and 0.5g, respectively, and the mass of urea is 6.6g. S3. Place the nickel foam in the mixture obtained in the previous step, let it stand in a vacuum and room temperature environment for 13 hours, then take it out and dry it. S4. The foamed nickel obtained in the previous step is first calcined at 300℃ in an Ar / H2 atmosphere (H2 volume percentage is 8%) for 2.5h, and then calcined in air at 420℃ for 2h.

[0032] Example 2 An electrode material for radioactive wastewater treatment comprises nickel foam and a composite material of a heterojunction material and an oxygen-absorbing material in situ supported on the nickel foam. The heterojunction material is g-C3N4-CuO, the oxygen-absorbing material is Pr2CuO4, and the loading of the composite material on the nickel foam is 12 mg / cm³. 2 The heterojunction material accounts for 85 wt% of the composite, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:1.2.

[0033] The preparation method of the above electrode material includes the following steps: S1. Dissolve praseodymium nitrate hexahydrate and copper nitrate trihydrate thoroughly in 200 mL of a water-ethylene glycol mixed solvent with a water-ethylene glycol volume ratio of 1:2. Then add citric acid and stir well to adjust the pH to 6. S2. Heat the solution obtained in the previous step at 80°C for 15 hours, then add g-C3N4 and urea, and slowly adjust the pH to 9. In steps S1 and S2, the masses of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 are 1g, 2.2g, 1.1g, and 0.5g, respectively, and the mass of urea is 8.1g. S3. Place the nickel foam in the mixture obtained in the previous step, let it stand in a vacuum and room temperature environment for 12 hours, and then take it out and dry it. S4. The foamed nickel obtained in the previous step is first calcined at 280℃ in an Ar / H2 atmosphere (H2 volume percentage is 8%) for 3 hours, and then calcined in air at 450℃ for 1.5 hours.

[0034] Example 3 An electrode material for radioactive wastewater treatment comprises nickel foam and a composite material of a heterojunction material and an oxygen-absorbing material in situ supported on the nickel foam. The heterojunction material is g-C3N4-CuO, the oxygen-absorbing material is Pr2CuO4, and the loading of the composite material on the nickel foam is 12 mg / cm³. 2 The heterojunction material accounts for 85 wt% of the composite, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:1.2.

[0035] The preparation method of the above electrode material includes the following steps: S1. Dissolve praseodymium nitrate hexahydrate and copper nitrate trihydrate thoroughly in 200 mL of a water-ethylene glycol mixed solvent with a water-ethylene glycol volume ratio of 1:2. Then add citric acid and stir well to adjust the pH to 5.5. S2. Heat the solution obtained in the previous step at 90℃ for 10 hours, then add g-C3N4 and urea, and slowly adjust the pH to 9.5. In steps S1 and S2, the masses of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 are 1g, 2.2g, 1.1g, and 0.5g, respectively, and the mass of urea is 5.5g. S3. Place the nickel foam in the mixture obtained in the previous step, let it stand in a vacuum and room temperature environment for 15 hours, then take it out and dry it. S4. The nickel foam obtained in the previous step is first calcined at 320℃ in an Ar / H2 atmosphere (H2 volume percentage is 8%) for 1.5 hours, and then calcined in air at 380℃ for 2 hours.

[0036] Example 4 Compared with Example 1, in the preparation method: in steps S1 and S2, the masses of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 are 1g, 2.5g, 1g, and 0.4g respectively, and the mass of urea is 6.3g; the rest are consistent with Example 1.

[0037] The obtained electrode material: the composite material had a loading capacity of 10 mg / cm³ on nickel foam, as tested. 2 The heterojunction material accounts for 87 wt% of the composite, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:1.5.

[0038] Example 5 Compared with Example 1, in steps S1 and S2, the masses of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 are 1g, 2g, 1.4g, and 0.6g respectively, and the mass of urea is 7.4g; the rest are the same as in Example 1.

[0039] The obtained electrode material: the composite material had a loading capacity of 15 mg / cm³ on nickel foam, as tested. 2 The heterojunction material accounts for 82 wt% of the composite, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:1.

[0040] Example 6 Compared with Example 1, the ambient pressure in step S3 is -0.08 MPa, while the rest are the same as in Example 1.

[0041] Example 7 Compared with Example 1, the ambient pressure in step S3 is -0.1 MPa, while the rest are the same as in Example 1.

[0042] Comparative Example 1 Compared to Example 1, praseodymium nitrate hexahydrate was not added in step S1, while all other steps remained the same as in Example 1. The XRD pattern of the obtained product is shown below. Figure 8 As shown: Compared with the XRD pattern of g-C3N4, the characteristic peaks of CuO are added between 30° and 40°, which are the diffraction peaks corresponding to the (110), (002) and (111) crystal planes of CuO in sequence, indicating that g-C3N4-CuO has been generated.

[0043] Comparative Example 2 Compared to Example 1, step S2 did not involve the addition of g-C3N4; all other steps remained the same as in Example 1. The XRD pattern of the resulting product is shown below. Figure 8 As shown: By comparing with PDF#22-0245 Pr2CuO4, the formation of Pr2CuO4 was confirmed.

[0044] Comparative Example 3 Compared with Example 1, the ambient pressure in step S3 is -0.2 MPa, while the rest is the same as in Example 1.

[0045] Comparative Example 4 Compared with Example 1, the ambient pressure in step S3 is -0.05MPa, while the rest are the same as in Example 1.

[0046] Comparative Example 5 Compared with Example 1, citric acid is not added in step S1, but all other steps are the same as in Example 1.

[0047] Comparative Example 6 Compared with Example 1, the water-ethylene glycol mixed solvent in step S1 was changed to water, while the rest remained the same as in Example 1.

[0048] Comparative Example 7 The g-C3N4-Sn3O4-Ni electrode material was prepared using existing technology. The specific procedure was as follows: 10g of urea was placed in a crucible and calcined in a muffle furnace under air atmosphere. The temperature was increased to 550℃ at a rate of 3℃ / min and held for 2 hours. The product was then ground to obtain g-C3N4. 0.4g of... g-C3N4 was mixed with 15 mL of ultrapure water and ultrasonically dispersed at 100 W for 5 min to obtain a uniformly dispersed g-C3N4 dispersion. 0.3 g of NaOH solid was dissolved in 10 mL of ultrapure water to obtain a NaOH aqueous solution. A mixed aqueous solution of 2 g SnCl2•2H2O and 7.3542 g Na3C6H5O7•2H2O was stirred on a magnetic stirrer for 24 g. Nickel foam with dimensions of 2 cm × 3 cm × 0.1 cm was added, and then the mixture was transferred to a 100 mL hydrothermal reactor and reacted at a constant temperature of 180 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature and the product was collected. It was washed three times each with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 65 °C for 24 h to obtain the g-C3N4-Sn3O4-Ni electrode material. Using the electrode materials obtained in each embodiment and comparative example as the anode and a platinum electrode as the cathode, uranium-containing wastewater with a uranium ion concentration of 10 mg / L under visible light and constant voltage photocatalytic oxidation was carried out. The light source was provided by a 10W LED lamp, the constant voltage power supply provided a voltage of 1.2V, and the temperature was 25℃±1℃. Wastewater samples were collected at 1h, 3h, 5h, 7h, 9h, 11h, 13h, 15h, 20h, 24h, 36h, and 48h using a syringe and filtered through a 0.22μm filter membrane. The uranium content was determined by ICP-MS. It should be noted that Na2SO4 was added to the uranium-containing wastewater as an electrolyte and methanol as a hole scavenger. The concentration of Na2SO4 in the uranium-containing wastewater was 0.15mol / L, and the volume ratio of methanol to uranium-containing wastewater was 1:25.

[0049] It should be noted that the specific testing methods for the loading of the composite, the proportion of oxygen-absorbing material and heterojunction material in the composite, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO in Examples 1-5 are as follows: First, the content of g-C3N4 is tested by thermogravimetric analysis (TGA) (the specific operation is: heating to 650℃ in air at a heating rate of 10℃ / min, causing g-C3N4 to decompose and lose weight, and calculating the content of g-C3N4 based on the weight loss percentage). Then, the mass of Pr2CuO4 and CuO is tested by nitric acid dissolution-ICP (the specific testing method is: immersing the loaded nickel foam in 0.2mol / L nitric acid and sonicating for 1h to completely dissolve the composite, detecting the concentration of Pr and Cu elements in the solution by ICP, and deriving and calculating the mass of Pr2CuO4 and CuO based on the stoichiometric ratio).

[0050] like Figures 1-8As shown in the following: (1) From Figure 1 A comparison of the removal rate curves of Example 1 and Comparative Example 7 shows that: Comparative Example 7 achieves a removal rate of 50% after approximately 16 hours of reaction and 94.3% after 48 hours; while Example 1 has a faster response speed, achieving a removal rate of 52% after 11 hours and nearing completion after approximately 36 hours, significantly shortening the overall treatment time, and achieving a final removal rate of 96.2%, higher than the 94.3% of the prior art. Therefore, the electrode material proposed in this invention, when used for treating low-concentration uranium-containing wastewater, responds more rapidly than existing technologies, and is more conducive to completing the treatment of uranium-containing wastewater in a shorter time.

[0051] Furthermore, from Figure 2 A comparison of the removal rate curves of Example 1 with those of Comparative Examples 1 and 2 shows that: when the composite does not contain Pr2CuO4, the reaction rate decreases significantly during photoelectrocatalytic treatment, reaching a removal rate of 50% after approximately 15 hours and 85% after 48 hours, far lower than the 96% of Example 1; when the composite does not contain the heterojunction g-C3N4-CuO, the resulting electrode material is far inferior to Example 1 in both catalytic performance and efficiency. Clearly, the rapid response and high removal rate of the electrode material proposed in this invention when used for photoelectrocatalytic treatment of low-concentration uranium-containing wastewater are inseparable from the technological contributions of the oxygen-absorbing material Pr2CuO4 and the heterojunction g-C3N4-CuO.

[0052] (2) From Figure 3 A comparison of the removal rate curves of Examples 1, 2, and 3 shows that the product of Example 1 has slightly better performance. Electrode materials with good performance can also be obtained by preparing the materials according to the technical parameters defined in Examples 2 and 3. Under the technical conditions defined in this invention, electrode materials with good performance can be obtained.

[0053] (3) From Figure 4 A comparison of the removal rate curves in Examples 1, 4, and 5 shows that the loading amount and component proportion of the composite on nickel foam can be controlled by adjusting the mass ratio of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4. Specifically, when the mass ratio of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 is 1:2.2:1.1:0.5, the loading amount of the composite on nickel foam is 12 mg / cm³. 2 The electrode material exhibits optimal performance when the heterojunction material accounts for 85 wt% of the composite and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:1.2.

[0054] (4) The present invention also found that the citric acid and water-ethylene glycol mixed solvent involved in step S1 of the electrode material preparation method and the environmental pressure in step S3 have a significant impact on the performance of the obtained electrode material. For example Figure 5 As shown: From the removal rates of Example 1 and Comparative Examples 3 and 4 at the same reaction time, it can be seen that when the environmental pressure is higher or lower than the range defined by this invention, it is not conducive to the full filling of the three-dimensional gel network, resulting in the composite loaded on the nickel foam not reaching the optimal loading amount, thus deteriorating the catalytic performance and catalytic efficiency. From the removal rates of Example 1 and Comparative Example 5 at the same reaction time, it can be seen that when citric acid is not added, the performance of the obtained electrode material is significantly worse than that of Example 1. The reason for this is that without the addition of citric acid, the metal ions are not complexed and are prone to particle agglomeration, thus deteriorating the performance. From the removal rates of Example 1 and Comparative Example 6 at the same reaction time, it can be seen that when a water-ethylene glycol mixed solvent is not used, due to the lack of effective deposition of the three-dimensional gel network, the dispersion uniformity of metal ions and g-C3N4 on the nickel foam is poor, which also leads to performance degradation. Obviously, in the preparation method proposed in this invention, the above-mentioned technical conditions play an indispensable role in obtaining electrode materials with fast response speed and high removal efficiency.

[0055] In summary, this invention, by in-situ loading a composite of g-C3N4-CuO and Pr2CuO4 onto nickel foam, and the addition of the oxygen-absorbing material Pr2CuO4, creates a "locally low-oxygen" microenvironment, allowing photogenerated electrons to preferentially reduce uranium. This synergistic effect with g-C3N4-CuO results in a significantly faster reaction rate and shorter reaction time when photoelectrocatalytically treating wastewater with a uranium ion concentration of 10 mg / L. This can meet the needs of certain application scenarios in existing technologies for the short-time, high-efficiency removal of uranium-containing wastewater.

[0056] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

Claims

1. A method for preparing an electrode material for radioactive wastewater treatment, characterized in that: The following steps are included: S1. Dissolve the corresponding nitrates of Pr and Cu in a water-ethylene glycol mixed solvent with a volume ratio of water to ethylene glycol of 1:(1-4). Then add citric acid and stir until homogeneous, and adjust the pH to 5-6. S2. Heat the solution obtained in the previous step at 80-90℃ for 10-15 hours, then add g-C3N4 and urea, and slowly adjust the pH value to 9-10. S3. Place the nickel foam in the mixture obtained in the previous step, let it stand in a vacuum and room temperature environment for 12-15 hours, then take it out and dry it. S4. The nickel foam obtained in the previous step is first calcined at 280-320℃ in an Ar / H2 atmosphere for 1.5-3 hours, and then calcined in air at 380-450℃ for 1.5-2 hours.

2. The method for preparing electrode materials for radioactive wastewater treatment according to claim 1, characterized in that: The nitrate of Pr is praseodymium nitrate hexahydrate, and the nitrate of Cu is copper nitrate trihydrate. The mass ratio of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 is 1:(2-2.5):(1-1.4):(0.4-0.6).

3. The method for preparing electrode materials for radioactive wastewater treatment according to claim 2, characterized in that: The mass ratio of praseodymium nitrate hexahydrate, copper nitrate trihydrate, citric acid, and g-C3N4 is 1:2.2:1.1:0.

5.

4. The method for preparing electrode material for radioactive wastewater treatment according to claim 1, characterized in that: In step S2, the mass ratio of urea to copper nitrate trihydrate is (2.5-3.7):

1.

5. The method for preparing electrode material for radioactive wastewater treatment according to claim 1, characterized in that: The nickel foam is first activated and then placed in the mixture obtained in S2. The specific activation operation is as follows: the nickel foam is immersed in nitric acid with a mass percentage of 3.5%-7.5% and ultrasonically treated for at least 15 minutes, and then rinsed with deionized water and ethanol.

6. The method for preparing electrode material for radioactive wastewater treatment according to claim 1, characterized in that: In step S3, the ambient pressure is -0.08 MPa to -0.1 MPa.

7. The method for preparing electrode material for radioactive wastewater treatment according to claim 1, characterized in that: In step S4, the volume percentage of H2 in Ar / H2 is 5%-10%.

8. An electrode material for radioactive wastewater treatment prepared by the method according to any one of claims 1-7.

9. The electrode material for radioactive wastewater treatment according to claim 8, characterized in that: The composite material comprises nickel foam and a heterojunction material and an oxygen-absorbing material in situ supported on the nickel foam. The heterojunction material is g-C3N4-CuO, the oxygen-absorbing material is Pr2CuO4, and the loading of the composite material on the nickel foam is 10-15 mg / cm³. 2 The heterojunction material in the composite is 82wt%-87wt%, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:(1-1.5).

10. The electrode material for radioactive wastewater treatment according to claim 9, characterized in that: The composite was loaded at a concentration of 12 mg / cm³ onto the nickel foam. 2 The heterojunction material in the composite comprises 85 wt%, and the mass ratio of g-C3N4 to CuO in g-C3N4-CuO is 1:1.2.

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