Preparation method of integrated electrode material and application thereof in electrochemical uranium extraction device

Abstract

This invention discloses a method for preparing an integrated electrode material and its application in an electrochemical uranium extraction device, comprising: immersing iron foam in hydrochloric acid for ultrasonic surface cleaning, removing it and then immersing it in anhydrous ethanol for ultrasonic cleaning, vacuum drying, and then placing it in a tube furnace for calcination in an air stream to obtain reddish iron foam FeO. x -IF; will FeO x -IF was immersed in a mixed solution containing 2-methylimidazole and cobalt nitrate hexahydrate at room temperature, and then calcined in a tube furnace to obtain a black integrated electrode material. This invention successfully prepared the integrated electrode material Co3O4@FeO. x -IF material exhibits excellent electrochemical uranium deposition performance, cycle stability, anti-interference ability, and deposition efficiency at different fluoride-uranium ratios in high-fluoride uranium-containing wastewater, and achieves efficient electrochemical reactions in both static and dynamic systems.

Description

Technical Field

[0001] This invention belongs to the field of electrode material preparation technology. More specifically, this invention relates to a method for preparing an integrated electrode material and its application in an electrochemical uranium extraction device. Background Technology

[0002] Nuclear energy, as a highly efficient, low-carbon, and clean energy source, plays an increasingly important role in the global energy structure transformation and the response to climate change. The proportion of nuclear power generation continues to rise, and uranium, as a key element in the nuclear fuel cycle, is directly related to the sustainable development of the nuclear energy industry. However, throughout the entire nuclear fuel cycle—including uranium mining, nuclear fuel processing, reactor operation, and spent fuel reprocessing—a large amount of uranium-containing radioactive wastewater is inevitably generated. If this uranium-containing wastewater is discharged into the environment without effective treatment, it not only causes the loss of valuable uranium resources but also poses a long-term threat to ecosystems and human health due to its radioactivity and chemical toxicity.

[0003] With the rapid development of the nuclear energy industry, the treatment of the large amounts of uranium-containing wastewater generated during the nuclear fuel cycle has become crucial. Uranium, a key strategic resource for the nuclear industry, not only wastes resources but also poses a radioactive threat to the ecological environment and public health. In production processes such as nuclear fuel element processing and spent fuel reprocessing, the widespread use of intermediate compounds such as UF4 or UF6 often results in high concentrations of fluoride ions coexisting with uranium-containing wastewater, forming complex uranyl fluoride complexes (UO2F). x This complex chemical state and high concentration of F - Competition and interference from uranium significantly reduce the efficiency of traditional adsorption and ion exchange methods when treating such wastewater, while electrochemical methods have shown excellent performance in the separation of uranium from fluorinated uranium solutions. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0005] To achieve these objectives and other advantages of the present invention, a method for preparing an integrated electrode material is provided, comprising the following steps: Step 1: Immerse the foamed iron in hydrochloric acid and ultrasonically clean its surface. Remove it and then immerse it in anhydrous ethanol for ultrasonic cleaning. After vacuum drying, place it in a tube furnace and calcine it in an air stream to obtain reddish-brown foamed iron FeO. x -IF; Step 2: Add FeO x -IF was immersed in a mixed solution containing 2-methylimidazole and cobalt nitrate hexahydrate at room temperature, and then calcined in a tube furnace to obtain a black integrated electrode material.

[0006] Preferably, in step one, the size of the foamed iron is (0.5~10) cm × (0.5~10) cm, and the concentration of hydrochloric acid is 0.1~0.5 mol / L.

[0007] Preferably, in step one, the ultrasound time is 5 to 20 minutes and the number of ultrasound sessions is 1 to 5.

[0008] Preferably, in step one, the vacuum drying temperature is 50~70℃ and the time is 8~16h.

[0009] Preferably, in step one, the calcination method is as follows: the temperature is increased to 400-500℃ at a rate of 3-7℃ / min, and calcined for 2-6 hours.

[0010] Preferably, in step one, FeO is... x -IF is modified, and the modification method is as follows: S1, FeO x -IF was added to 20-100 mL of 1,3-propanediol, followed by 1-2 mL of 3-aminopropyltriethoxysilane. The mixture was reacted at 70-90 °C with stirring at 300-600 rpm for 10-18 h. After the reaction, the mixture was filtered, washed 1-3 times each with deionized water and anhydrous ethanol, and then dried under vacuum at 70-80 °C for 4-8 h to obtain pretreated FeO. x -IF; S2. Add 2-10 mg of reduced graphene oxide and 100-500 μL of 1 wt% Nafion solution to 20-100 mL of anhydrous ethanol, sonicate for 10-30 min, and then place in pretreated FeO. x -IF, ultrasonic treatment for 1-3 h, then vacuum drying at 40-50℃ for 6-10 h to obtain modified FeO. x -IF.

[0011] Preferably, in step two, the molar volume ratio of 2-methylimidazole, cobalt nitrate hexahydrate, and deionized water in the mixed solution containing 2-methylimidazole and cobalt nitrate hexahydrate is 5~15 mmol:1~2 mmol:5~20 mL.

[0012] Preferably, in step two, the soaking time is 12 to 48 hours.

[0013] Preferably, in step two, the calcination method is as follows: the temperature is increased to 350-450℃ at a rate of 3-7℃ / min, and calcined for 1-3 hours.

[0014] The present invention also provides the application of an integrated electrode material prepared by the preparation method described above in electrochemical uranium extraction.

[0015] The present invention also provides the application of an integrated electrode material prepared by the preparation method described above in an electrochemical uranium extraction device.

[0016] The present invention has at least the following beneficial effects: (1) This invention successfully prepared an integrated electrode material Co3O4@FeO with a porous framework and a surface rich in active sites. x -IF, static and dynamic experimental results show that the material exhibits good electrochemical uranium extraction performance in simulated high-fluoride uranium-containing wastewater. Furthermore, the material demonstrates excellent performance in electrochemical uranium deposition, cycle stability, anti-interference ability, and deposition efficiency at different fluoride-to-uranium ratios in high-fluoride uranium-containing wastewater.

[0017] (2) In a static experimental system, this invention determined that the small electrode spacing of the cubic electrolytic cell was the optimal reaction condition by comparing different electrode spacings in two basic electrolytic cell configurations. This condition effectively shortens the ion mass transfer path and provides favorable electric field distribution and reaction conditions for electrochemical uranium deposition.

[0018] (3) In a dynamic experimental system, this invention systematically investigated the effect of flow rate on uranium deposition performance and established 10 mL / min as the optimal flow rate. At this flow rate, the uranium removal rate reached 96.29% after 8 hours of reaction, and the residual uranium concentration in the electrolyzer was uniformly distributed, achieving a highly efficient electrochemical reaction under dynamic conditions. Furthermore, under flowing conditions, the uranium removal performance of multi-stage series treatment and single-stage treatment was compared, clarifying the key role of multi-stage scale-up treatment of uranium-containing wastewater.

[0019] (4) The present invention also provides FeO x -IF modification method, through 3-aminopropyltriethoxysilane on FeO x -IF surface modification with amino groups is performed as a pretreatment, followed by aminated FeO x -IF is immersed in a mixture containing reduced graphene oxide and Nafion and subjected to ultrasound. Through the polar interactions of amino groups and the binding and immobilizing effect of Nafion, the reduced graphene oxide is uniformly adsorbed and coated onto FeO. x -IF surface, to prepare modified FeO x -IF. Modified FeO x -IF combines amino active sites with the highly conductive structure of reduced graphene oxide. The introduction of reduced graphene oxide increases the specific surface area and functional groups, thereby enhancing the interfacial binding force and enriching the active sites, which is beneficial for subsequent loading of metal oxides.

[0020] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0021] Figure 1 FeO prepared for Comparative Example 1 of the present invention (a, d) x SEM images of Co3O4-IF prepared in Comparative Example 2; (b, e) SEM images of Co3O4-IF prepared in Comparative Example 2; (c, f) SEM images of Co3O4@FeO prepared in Example 1. x -IF SEM plot; Figure 2 The FeO of this invention x -IF, Co3O4-IF, and Co3O4@FeO x - IF's XRD plot; Figure 3 The FeO of this invention x -IF, Co3O4-IF, Co3O4@FeO x -IF and Co3O4@A / rGO-FeO prepared in Examples 2-3 x -IF、Co3O4@A-FeO x - IF electrochemical removal efficiency of uranium under static conditions; Figure 4 The present invention is Co3O4@FeO x -Graph of uranium removal efficiency of IF coexisting with different interfering ions; Figure 5 This invention relates to Co3O4@FeO x -IF uranium removal efficiency diagram at different U / F; Figure 6 This invention relates to Co3O4@FeO x -IF electrochemical removal efficiency plot for different initial U concentrations; Figure 7 This is a schematic diagram of the test points inside the cubic electrolytic cell and the cuboid electrolytic cell of the present invention; Figure 8 This is a performance diagram showing the spacing between the electrodes within the cubic electrolytic cell of this invention; Figure 9 This is a pH diagram showing the spacing between the electrodes in the cubic electrolytic cell of the present invention. Figure 10 This is a performance diagram showing the spacing between the electrodes within the cuboid electrolytic cell of the present invention; Figure 11 This is a pH diagram showing the spacing between electrodes within the cuboid electrolytic cell of the present invention. Figure 12 This is a local residual uranium content diagram under the condition of a 2cm electrode spacing in the cubic electrolytic cell of the present invention; Figure 13 This is a local residual uranium content diagram under the condition of a 2cm electrode spacing in the cuboid electrolytic cell of the present invention; Figure 14The diagram shows the electrochemical uranium deposition performance of four reactors with different inlet and outlet structures according to the present invention. Figure 15 This is a simplified schematic diagram of the flow-through reactor of the present invention; Figure 16 The present invention is Co3O4@FeO x -IF graph showing uranium removal efficiency under different flow rates; Figure 17 The FeO of this invention x -IF, Co3O4-IF, and Co3O4@FeO x -IF diagram of uranium removal efficiency under dynamic conditions; Figure 18 The present invention is Co3O4@FeO x -IF diagram showing the residual amount of uranium deposited at the inlet, outlet, and middle of the reactor under different flow rates; Figure 19 This is a diagram showing the pH test points inside the electrolytic cell and at the cathode and anode, as per the present invention. Figure 20 The pH values ​​for (a) 5 mL / min, (b) 10 mL / min, and (c) 20 mL / min are shown in the diagram. Figure 21 The diagram shows (a) the uranium removal efficiency of each stage in the three-stage series electrochemical uranium extraction reactor of the present invention; and (b) the pH of each stage in the three-stage series electrochemical uranium extraction reactor. Figure 22 The diagram shows (a) the uranium removal efficiency in a single electrochemical uranium extraction reactor and (b) the pH value in a single electrochemical uranium extraction reactor. Figure 23 The following images are from the present invention: (a) XRD pattern of the product after reaction; (b) XPS spectrum of the product after reaction; (c) O 1s spectrum of the product after reaction; (d) SEM image of the product after reaction; (e) TEM image of the product after reaction; (f) EDS mapping image of the product after reaction. Figure 24 The FeO of this invention x -IF, Co3O4-IF, Co3O4@FeO x -IF power consumption graph; Figure 25 This invention relates to Co3O4@FeO x -Power consumption plot for different flow rate gradients in IF. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0023] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0024] Example 1 A method for preparing an integrated electrode material includes the following steps: Step 1: Immerse 1cm × 2cm pieces of foamed iron in 0.2 mol / L hydrochloric acid and sonicate for 10 minutes to clean the surface. Remove and then immerse in anhydrous ethanol for ultrasonic cleaning three times, each time for 10 minutes. After vacuum drying at 60℃ for 12 hours, place in a tube furnace and calcine at 450℃ for 3 hours in an air stream at a rate of 5℃ / min to obtain reddish-brown foamed iron FeO. x -IF; Step 2: Add FeO x -IF was immersed in 10 mL of a mixed solution containing 0.8211 g of 2-methylimidazole and 0.5806 g of cobalt nitrate hexahydrate for 24 h at room temperature, and then calcined in a tube furnace at a rate of 5 °C / min to 400 °C for 2 h to obtain a black integrated electrode material, denoted as Co3O4@FeO. x -IF.

[0025] Example 2 A method for preparing an integrated electrode material includes the following steps: Step 1: Immerse 1cm × 2cm pieces of foamed iron in 0.2 mol / L hydrochloric acid and sonicate for 10 minutes to clean the surface. Remove and then immerse in anhydrous ethanol for ultrasonic cleaning three times, each time for 10 minutes. After vacuum drying at 60℃ for 12 hours, place in a tube furnace and calcine at 450℃ for 3 hours in an air stream at a rate of 5℃ / min to obtain reddish-brown foamed iron FeO. x -IF, will FeO x -IF is modified, and the modification method is as follows: S1, FeO x -IF was added to 30 mL of 1,3-propanediol, followed by 1.5 mL of 3-aminopropyltriethoxysilane. The mixture was reacted at 80 °C with stirring at 400 rpm for 14 h. After the reaction was complete, the mixture was filtered, washed twice each with deionized water and anhydrous ethanol, and dried under vacuum at 80 °C for 5 h to obtain pretreated FeO. x -IF; S2. Add 3 mg of reduced graphene oxide and 200 μL of 1 wt% Nafion solution to 30 mL of anhydrous ethanol, sonicate for 20 min, and then place in pretreated FeO. x -IF, ultrasonic treatment for 1 h, then vacuum drying at 50℃ for 8 h, to obtain modified FeOx -IF; Step 2: Modify FeO x -IF was immersed in 10 mL of a mixed solution containing 0.8211 g of 2-methylimidazole and 0.5806 g of cobalt nitrate hexahydrate for 24 h at room temperature, and then calcined in a tube furnace at a rate of 5 °C / min to 400 °C for 2 h to obtain a black integrated electrode material, denoted as Co3O4@A / rGO-FeO. x -IF.

[0026] Example 3 A method for preparing an integrated electrode material includes the following steps: Step 1: Immerse 1cm × 2cm pieces of foamed iron in 0.2 mol / L hydrochloric acid and sonicate for 10 minutes to clean the surface. Remove and then immerse in anhydrous ethanol for ultrasonic cleaning three times, each time for 10 minutes. After vacuum drying at 60℃ for 12 hours, place in a tube furnace and calcine at 450℃ for 3 hours in an air stream at a rate of 5℃ / min to obtain reddish-brown foamed iron FeO. x -IF, will FeO x -IF is modified, and the modification method is: FeO x -IF was added to 30 mL of 1,3-propanediol, and 1.5 mL of 3-aminopropyltriethoxysilane was added. The mixture was reacted at 80 °C and 400 r / min with stirring for 14 h. After the reaction was completed, the mixture was filtered, washed twice with deionized water and twice with anhydrous ethanol, and dried under vacuum at 80 °C for 5 h to obtain modified FeO. x -IF; Step 2: Modify FeO x -IF was immersed in 10 mL of a mixed solution containing 0.8211 g of 2-methylimidazole and 0.5806 g of cobalt nitrate hexahydrate for 24 h at room temperature, and then calcined in a tube furnace at a rate of 5 °C / min to 400 °C for 2 h to obtain a black integrated electrode material, denoted as Co3O4@A-FeO. x -IF.

[0027] Comparative Example 1 A method for preparing an electrode material includes the following steps: Foamed iron cut into 1cm × 2cm pieces was immersed in 0.2 mol / L hydrochloric acid and ultrasonically cleaned for 10 minutes. After removal, it was immersed in anhydrous ethanol and ultrasonically cleaned three times, each time for 10 minutes. After vacuum drying at 60℃ for 12 hours, it was placed in a tube furnace and calcined at 450℃ for 3 hours in an air stream at a rate of 5℃ / min to obtain a reddish electrode material, denoted as FeO. x -IF.

[0028] Comparative Example 2 A method for preparing an electrode material includes the following steps: The foamed iron, cut into 1cm×2cm pieces, was immersed in 0.2 mol / L hydrochloric acid and ultrasonically cleaned for 10 min. After removal, it was immersed in anhydrous ethanol and ultrasonically cleaned three times, each time for 10 min. After vacuum drying at 60℃ for 12 h, it was immersed in 10 mL of a mixed solution containing 0.8211 g of 2-methylimidazole and 0.5806 g of cobalt nitrate hexahydrate at room temperature for 24 h. Then, it was heated to 400℃ in a tube furnace at a rate of 5℃ / min and calcined for 3 h to obtain a black electrode material, denoted as Co3O4-IF.

[0029] Figure 1 FeO prepared for Comparative Example 1 of the present invention (a, d) x SEM images of Co3O4-IF prepared in Comparative Example 2; (b, e) SEM images of Co3O4-IF prepared in Comparative Example 2; (c, f) SEM images of Co3O4@FeO prepared in Example 1. x -IF SEM image. To investigate the microstructure of the electrode materials and establish the structure-property relationship of electrochemical performance, scanning electron microscopy (SEM) was used to analyze the Co3O4@FeO prepared in Example 1 and Comparative Examples 1-2. x -IF, FeO x The morphology and structure of three electrode materials, namely -IF, Co3O4-IF, were characterized, and the results are as follows: Figure 1 As shown in (af). Figure 1 (ac) shows the morphology of the three electrode materials at a scale of 200 μm. The morphology exhibits a three-dimensional network structure, which provides channels for electron transport and provides sufficient attachment sites for the load. Figure 1 (df) shows the surface microstructure of the electrode under different conditions at a 2 μm scale. FeO x -IF is obtained by air sintering pretreated iron foam, and its surface has no Co3O4 particles; while Co3O4-IF, due to the introduction of Co and O elements, has better particle dispersion and exposes more active edges; the material Co3O4@FeO x -IF exhibits a unique nanosheet array structure. This unique morphology is expected to provide abundant active sites in electrochemical reactions and shorten ion transport paths, thus providing a structural basis for efficient electrochemical uranium extraction. The following research and applications of FeO... x -IF, Co3O4-IF, Co3O4@FeO x -IF were prepared in Comparative Examples 1-2 and Example 1.

[0030] Figure 2 The FeO of this inventionx -IF, Co3O4-IF, and Co3O4@FeO x -IF XRD pattern. To investigate the crystal structure and phase composition of the prepared electrode material, X-ray diffraction (XRD) was used to analyze FeO. x -IF, Co3O4-IF and Co3O4@FeO x Three nanoarray electrode materials were characterized, and the results are as follows: Figure 2-6 As shown. For FeO x The -IF sample exhibited a series of characteristic diffraction peaks at 24.1°, 33.2°, 35.6°, 40.9°, 49.5°, 54.1°, 62.4°, and 64.0°, which highly matched those of Fe2O3 (PDF#89-0599). Similarly, the diffraction peaks of the Co3O4-IF sample at 31.2°, 36.8°, 44.8°, 59.3°, and 65.2° corresponded to the standard card of Co3O4 (PDF#43-1003), demonstrating the successful growth of the Co3O4 phase. It is noteworthy that Co3O4@FeO... x The XRD pattern of the -IF composite electrode simultaneously contains characteristic peaks of both phases mentioned above. Specifically, the diffraction peaks at 24.1°, 33.2°, 35.6°, 40.9°, 49.5°, 54.1°, 62.4°, and 64.0° correspond to the Fe₂O₃ phase, while the diffraction peaks at 31.2°, 36.8°, 44.8°, 59.3°, and 65.2° correspond to the Co₃O₄ phase. This result directly confirms the Co₃O₄@FeO₂ composite electrode. x -IF composite material is composed of two phases: Fe2O3 and Co3O4. Because air-calcined iron foam produces both +2 and +3 valence states, the material obtained in this invention is named in the form of 'x'. Spectroscopic characterization confirmed the phase composition as Fe2O3. To ensure consistency in material naming, the material name in this invention is uniformly designated as FeO. x .

[0031] Further observation revealed that the diffraction peak positions of the two phases in the composite did not show a significant shift compared to the pure phase sample, and no other impurity phase peaks were detected. This indicates that the introduction of Co3O4 during in-situ growth did not disrupt the original lattice structure of Fe2O3. XRD analysis confirmed the successful growth of the Fe2O3 and Co3O4 active phases on the foamed iron substrate, and further verified the Co3O4@FeO x - Coexistence of two phases in the IF composite electrode.

[0032] To systematically evaluate the electrochemical uranium extraction performance of the prepared electrode material in complex fluorine- and uranium-containing systems, this study employed a dual-electrode system, using the prepared FeO...x -IF, Co3O4-IF and Co3O4@FeO x -IF is the working electrode (cathode), NiO x -NF was used as the counter electrode (anode), and a constant-current electrochemical experiment was conducted under static conditions. The initial experimental conditions were set as follows: uranium concentration 500 mg / L and fluoride ion concentration 30 g / L. All simulated uranium wastewater was prepared by dissolving deionized water in UO2(NO3)2·6H2O and KF·2H2O as uranium and fluoride sources, respectively, to form fluoride-containing uranium solutions. The concentration of uranium in the extracted solution was determined by colorimetry and ICP technology, with arsene(III) as the colorimetric reagent. The formula for the uranium(VI) removal rate during the electrochemical process is as follows: in, c o Indicates the initial uranium concentration. c t This indicates the concentration of uranium in the electrochemical process.

[0033] NiO x The preparation method of -NF is as follows: Nickel foam is cut into 1cm × 2cm pieces, soaked in acetone for 24 hours, then ultrasonically cleaned three times with anhydrous ethanol for 10 minutes each time. After vacuum drying at 60℃ for 12 hours, it is placed in a tube furnace and heated to 400℃ at a rate of 5℃ / min in an air stream, and calcined for 2 hours to obtain NiO. x -NF. This material will be used as the anode in electrochemical experiments. Because air-calcined nickel foam produces both +2 and +3 valence states, the material obtained in this invention is named in the form of x. To ensure consistency in material naming, the material name in this invention is uniformly referred to as NiO. x .

[0034] Figure 3 The FeO of this invention x -IF, Co3O4-IF, Co3O4@FeO x -IF and Co3O4@A / rGO-FeO prepared in Examples 2-3 x -IF、Co3O4@A-FeO x - Graph of electrochemical removal efficiency of uranium by IF under static conditions. Results are as follows. Figure 3 As shown, during the reaction process, Co3O4@FeO x -IF consistently maintained a superior uranium removal rate. When the reaction proceeded for 8 hours, the Co3O4@FeO... x -IF achieved a uranium removal rate of 90.86%. For Co3O4-IF and FeO... xThe removal rates of FeO and IF were 80.37% and 69.66%, respectively. Performance curves show that in high-fluoride uranium-containing wastewater, FeO... x Both -IF and Co3O4-IF electrode materials have limited ability to capture uranyl ions, while Co3O4@FeO x -IF exhibits superior electrochemical uranium extraction performance under static conditions. Combined with material characterization and spectroscopic analysis, the main reason for this is that the calcination of its substrate material provides more oxygen vacancies, and the in-situ grown Co3O4 nanoparticles provide more active sites. Co3O4@A / rGO-FeO x -IF and Co3O4@A-FeO x -IF compared to Co3O4@FeO x -IF exhibits faster capture rate of uranyl ions and higher uranium removal rate, possibly due to FeO. x -IF, after being aminated and loaded with reduced graphene oxide, has increased specific surface area and functional groups, enhancing interfacial bonding and increasing active sites, thus improving its ability to remove uranium compared to FeO alone. x -IF is more effective when hydroxylated.

[0035] Figure 4 The present invention is Co3O4@FeO x -Graph showing the uranium removal efficiency of IF coexisting with different interfering ions. Figure 5 This invention relates to Co3O4@FeO x -IF uranium removal efficiency graph at different U / F ratios. Figure 6 This invention relates to Co3O4@FeO x -IF electrochemical removal efficiency plot for different initial U concentrations. To further evaluate Co3O4@FeO x To assess the applicability of -IF, this study systematically investigated its electrochemical uranium extraction performance under various complex conditions. Experimental results are as follows: Figure 4-6 As shown, these figures reflect the coexistence of interfering ions (U(VI): 500 mg / L, F...). - The effects of different fluorine-uranium ratios and uranium concentration gradients on deposition efficiency were studied. Considering the complex composition of actual nuclear industry wastewater, which typically contains multiple coexisting ions besides the target uranyl ion, CO32- was selected for the experiment. 2- Cl - C2O4 2- NO3 - SO4 2- NH 4+ Typical competing ions were used. Under the conditions of initial uranium concentration of 500 mg / L and fluorine concentration of 30 g / L, 1 g / L of interfering ions were introduced into the system, and the changes in uranium removal rate before and after the addition were compared. Figure 4The results show that, in the tested environment of coexisting interfering ions, Co3O4@FeO x The uranium deposition efficiency of the -IF electrode did not decrease significantly. Furthermore, the electrode maintained stable deposition performance despite variations in fluorine-to-uranium ratios and uranium concentration gradients. Based on the aforementioned fundamental experimental analysis of electrochemical uranium extraction, it is evident that Co3O4@FeO... x -IF has promising applications as an electrode material for treating uranium-containing wastewater in electrochemical systems.

[0036] The above study determined Co3O4@FeO x Based on the excellent electrochemical uranium extraction electrode material, -IF (electrolyte-internal electrode) aims to further improve the efficiency of electrochemical uranium extraction. This research focuses on the electrochemical reaction site, where the electrolytic cell, as a geometric parameter of the electrochemical uranium extraction process, directly determines the internal electrochemical reaction kinetics. Specifically, the electrode spacing indirectly controls the magnitude of current and voltage during the reaction, thus affecting the reaction process and the migration of ions in the solution. Optimizing the electrode spacing can effectively improve the efficiency of electrochemical uranium extraction and also effectively reduce energy consumption. Therefore, this invention systematically investigates the effects of different electrolytic cell configurations and electrode spacings on the electrochemical uranium extraction performance of high-fluoride uranium-containing wastewater.

[0037] Figure 7 This diagram shows the internal test points of the cubic and cuboid electrolytic cells of this invention. Two electrolytic cells with different geometric configurations were designed to compare their electrochemical uranium extraction performance. The internal dimensions of the cubic electrolytic cell are 70 mm × 70 mm × 40 mm (length × width × height), and the adjustable electrode spacing parameters are 2 cm, 3 cm, and 4 cm. The internal dimensions of the cuboid electrolytic cell are 160 mm × 30 mm × 40 mm (length × width × height), and its electrode spacing adjustment range is wider, with values ​​of 2 cm, 4 cm, and 8 cm. Both electrolytic cells employ a dual-electrode system, with the cathode being Co3O4@FeO. x -IF electrode, anode is NiO x -NF electrode. Simultaneously, to investigate the changes in the solution microenvironment during electrolysis, time gradient tests were conducted on the pH of the anode and cathode regions under different electrode spacing conditions in two electrolytic cells. The test points are shown below. Figure 7 .

[0038] Figure 8 This is a performance diagram showing the spacing between each electrode in the cubic electrolytic cell of the present invention. The performance curves for each electrode spacing in the cubic electrolytic cell are as follows: Figure 8As shown, when the electrode spacing is 2 cm, the overall removal efficiency is high, reaching 95.65% after 8 hours of reaction. When the electrode spacing is 3 cm, the overall removal efficiency is slower than that of 2 cm, with a removal rate of 91.45% after 8 hours of reaction. When the electrode spacing increases to 4 cm, the curve shows a flatter trend, with a removal rate of only 87.28% after 8 hours of reaction.

[0039] Figure 9 This is a pH diagram showing the spacing between electrodes within the cubic electrolytic cell of this invention. To further elucidate the influence mechanism of different electrolytic cell configurations on ion migration behavior and the reaction microenvironment, the pH of the anode and cathode regions under different electrode spacing conditions in two types of electrolytic cells was measured. Figure 9 It can be observed that in the cubic electrolytic cell, the pH near the anode and cathode shows a slight increasing trend under the condition of the electrode spacing. This is because a large amount of OH- is generated at the cathode due to the electrochemical reaction. - , and OH - Under the influence of the electric field, ions migrate towards the anode, leading to an increase in the pH value at the anode. This indicates that in a cubic electrolytic cell, the movement of ions affects the microenvironment. For a cuboid electrolytic cell, the effect of electrode spacing on pH exhibits a completely different pattern.

[0040] Figure 10 This is a performance diagram of the electrode spacing within the cuboid electrolytic cell of the present invention. The performance curves for each electrode spacing in the cuboid electrolytic cell are shown below. Figure 10 As shown, the removal rates after 8 h of reaction were 85.74%, 74.54%, and 58.75% for the electrode spacings (2 cm, 4 cm, and 8 cm), respectively. It can be clearly observed that the removal efficiency of electrochemical uranium extraction varies significantly with increasing electrode spacing.

[0041] Figure 11 This is a pH diagram showing the spacing between the electrodes within the cuboid electrolytic cell of this invention. (See diagram for example.) Figure 11 As shown, under different electrode spacings (2 cm, 4 cm, 8 cm), the pH change trends in the anode and cathode regions were basically consistent and did not change significantly with the change in electrode spacing. Specifically, the pH value in the cathode region remained stable at around 8 from the initial stage of the reaction to the end of the reaction, while the pH value in the anode region also showed high stability, remaining at around 5. Through the above comparison of uranium removal performance and pH, the experimental results demonstrate that the change in electrode spacing has a significant impact on uranium removal, and that a smaller electrode spacing effectively promotes the electrochemical uranium extraction reaction.

[0042] Figure 12This image shows the local residual uranium content within the cubic electrolytic cell of this invention under a 2 cm electrode spacing condition. Building upon previous studies that have confirmed the significant impact of electrode spacing on electrochemical uranium extraction performance, this invention further explores the mechanism by which electrolytic cell configuration affects overall reaction uniformity and mass transfer efficiency. The local residual uranium concentration of two electrolytic cell configurations under a 2 cm electrode spacing condition is analyzed, and the data at each point is shown below. Figure 7 As shown. Figure 12 The changes in local uranium concentration at three sampling points (P1, P2, and P3) in a cubic electrolytic cell over time are shown. The figures reveal that the uranium concentration at all three points exhibits a continuous decreasing trend throughout the reaction, and the overall trend is relatively consistent. This result indicates that, under cubic configuration conditions, the electrochemical reaction demonstrates good spatial homogeneity in its impact on the solution within the cell. During the electrochemical reaction driven by an electric field, the mass transfer conditions within the entire reaction region are relatively uniform.

[0043] Figure 13 This is a local residual uranium content diagram under the condition of a 2 cm electrode spacing in the cuboid electrolytic cell of the present invention. The local uranium concentration at three points in the cuboid electrolytic cell shows a significant concentration gradient difference, such as... Figure 13 As shown, point P2, located in the central region of the anode and cathode, exhibits a faster uranium removal rate, while the uranium concentration at points P1 and P3, located on either side of the tank, decreases extremely slowly, with a much smaller change than at point P2. This is mainly because the rectangular electrolytic cell is relatively long and narrow, and the electric field may decay significantly and rapidly along its length. However, its influence is primarily limited to the area near the electrodes, having a relatively limited effect on the solutions at the more distant ends of the tank. This localization of the reaction's influence effectively makes regions P1 and P3 mass transfer-restricted, where uranyl ions cannot effectively participate in the electrode reaction, thus reducing the overall removal efficiency.

[0044] Figure 14 This diagram shows the electrochemical uranium deposition performance of four reactors with different inlet and outlet structures according to the present invention. In the static electrochemical performance study, the present invention determined that a 2 cm distance between the cubic electrolyzer and the electrode is more conducive to the overall efficiency of electrochemical uranium extraction. To further optimize the electrochemical uranium extraction process parameters, a systematic study of electrochemical uranium extraction under dynamic conditions will be conducted. First, the electrochemical performance of different inlet and outlet structures of the electrolyzer (bottom inlet / bottom outlet, bottom inlet / top outlet, top inlet / bottom outlet, and top inlet / top outlet) was investigated, and their performance curves are shown below. Figure 14 As shown in the figure. Experimental data indicate that the uranium removal rate of bottom-in reactors is generally better than that of top-in reactors, with the bottom-in, top-out reactor exhibiting the best performance. The data shows that this method has significant advantages in promoting uniform solution flow and enhancing mass transfer.

[0045] Figure 15This is a simplified schematic diagram of the flow-through reactor of the present invention. Based on the above, subsequent dynamic studies will employ a bottom-in, top-out electrolytic cell with dimensions of 70 mm × 70 mm × 45 mm. The solution inlet is located at the bottom left, and the outlet is located at the bottom right, 42 mm from the bottom. Solution circulation is achieved via a peristaltic pump connected to an external hose. The simplified diagram of this device is shown below. Figure 15 As shown.

[0046] Figure 16 The present invention is Co3O4@FeO x -IF graph showing uranium removal efficiency under different flow rates. To investigate the influence of dynamic conditions on the electrochemical uranium extraction process, this invention systematically examined the uranium deposition performance at different flow rates (5, 10, 20 mL / min). Experimental results show that at a flow rate of 5 mL / min, after 8 h of reaction, the uranium removal efficiency was only 81.54%, and the performance curve showed significant fluctuations. The main reason for this is that the low flow rate led to uneven distribution of uranyl ions in the solution, limiting the smooth progress of the reaction. When the flow rate was 10 mL / min, the uranium deposition performance was significantly improved. The deposition efficiency reached 63.51% in the initial stage of the reaction (2 h), increased to 90% after 6 h, and reached 96.29% after 8 h. The performance curve shows that the uranium removal efficiency under this condition was very rapid in the early stage of the reaction, and then tended to level off. This indicates that the movement conditions of uranyl ions were optimized under this flow rate, enabling them to rapidly participate in the electrochemical reaction, thereby accelerating uranium deposition. At a flow rate of 20 mL / min, the performance curve also showed good efficiency. However, compared to the flow rate of 10 mL / min, the removal rate at each time point was much lower. This indicates that although a high flow rate promotes the movement of uranyl ions, it results in a short residence time at the working electrode, making it difficult for uranyl ions to fully participate in the electrochemical reaction, thereby weakening the overall uranium deposition efficiency.

[0047] Figure 17 The FeO of this invention x -IF, Co3O4-IF, and Co3O4@FeO x -Graph of uranium removal efficiency under dynamic conditions. The electrochemical performance of the three electrode materials mentioned above was also compared under dynamic conditions. Co3O4@FeO x -IF also showed superior performance compared to other materials, reaching 95.91% in 6 hours, while the other two materials required 8 hours to reach over 90%.

[0048] Figure 18 The present invention is Co3O4@FeO x-IF residual uranium deposition at the inlet, outlet, and middle of the reactor under different flow rates. Under dynamic conditions, this invention measured the local uranium concentration at the electrolyzer inlet, outlet, and middle of the electrode. The effect of flow rate on the overall distribution of uranyl in the space and the electrochemical reaction was then analyzed. Experimental results (e.g.) Figure 18 As shown in the figure, under a flow rate of 10 mL / min, the local uranium concentration at various points inside the electrolyzer showed a significant decreasing trend. Notably, the residual uranium concentration at the outlet changed most rapidly, while the concentration change trend in the middle of the electrode was slightly slower, and the trend at the inlet was even slower. This indicates that uranyl ions in the solution continuously accumulate towards the cathode with the flow, accompanied by electrochemical reactions. The uranium concentration in the middle continuously decreases, the uranium concentration at the outlet decreases significantly, while the uranium concentration at the inlet decreases with reaction time. This demonstrates that the applied flow field has a positive promoting effect on the overall electrochemical process within the electrolyzer.

[0049] At a flow rate of 5 mL / min, although the overall concentration decreased synchronously, the residual uranium concentration at each point changed very slowly, far lower than at 10 mL / min. This indicates that at this flow rate, the driving force of the flow field on uranyl ions is insufficient, making it difficult to maintain efficient uranium deposition. At a flow rate of 20 mL / min, a similar situation to that at 10 mL / min was observed, with the residual uranium concentration at the outlet significantly lower than at the middle and inlet. This suggests that this flow rate exerts an excessively strong driving force on the movement of ions in the solution, preventing uranyl ions from effectively participating in the electrochemical reaction. Furthermore, the overall uranium concentration was relatively high, leading to a slow change in the residual uranium concentration at the middle and inlet.

[0050] Figure 19 This diagram shows the pH test points inside the electrolytic cell and at the cathode and anode, as per the present invention. Under dynamic conditions, in addition to measuring the local uranium concentration at the electrolytic cell inlet, outlet, and middle of the electrodes, the present invention also measured the pH inside the electrolytic cell and at the cathode and anode. The test points are shown below. Figure 19 .

[0051] Figure 20 The pH graphs for (a) 5 mL / min, (b) 10 mL / min, and (c) 20 mL / min are for this invention. Figure 20It can be clearly observed that under the three different flow rates, the pH at points P3, P4, and the cathode continuously increases, while the pH at points P1, P2, and the anode shows significant differences. This is because flow rate significantly affects the overall electrochemical reaction. At a flow rate of 10 mL / min, the pH at points P1 and P2 shows a stable increasing trend, while the pH at the anode shows a continuous increasing trend. This pH change proves that ion movement and electrochemical reaction are in equilibrium at this flow rate, maintaining efficient uranium deposition throughout the electrolytic cell. At a flow rate of 5 mL / min, the pH at the anode and points P1 and P2 both show a continuous increasing trend. This phenomenon indicates that OH- produced at the cathode at this flow rate... - The OH groups, transported to the anolyte region by the flow, failed to effectively combine with uranyl to form the target product, hindering the efficient electrochemical reaction. At a flow rate of 20 mL / min, the pH values ​​at the anolyte region and points P1 and P2 rapidly increased in the initial stage of the reaction, a phenomenon directly reflecting the low OH concentration at this flow rate. - The uranium ions are rapidly transported to various areas within the electrolytic cell, but the excessively fast flow rate is not conducive to the participation of uranium ions in the reaction, resulting in slow uranium deposition efficiency.

[0052] Figure 21 This invention presents (a) a uranium removal efficiency diagram for each stage of the three-stage series electrochemical uranium extraction reactor; and (b) a pH diagram for each stage of the three-stage series electrochemical uranium extraction reactor. To further investigate the performance differences between flow-type electrochemical uranium extraction reactors, this invention compared the uranium removal efficiency and solution pH changes (pH test point at the middle of the electrode) of a multi-stage reactor with those of a single-stage reactor under simulated uranium-containing wastewater conditions of the same volume. Figure 21 As can be seen, the multi-stage reactor consists of three electrolyzers, Cell1, Cell2, and Cell3, connected in series. During continuous operation, each unit exhibits excellent uranium extraction performance, with uranium extraction efficiencies of 89.74%, 93.63%, and 91.69% for Cell1, Cell2, and Cell3, respectively. Furthermore, the pH change trends of the solutions within the three electrolyzers are remarkably similar. Figure 21 (b) The pH gradually increased from a neutral state to a weakly alkaline state (pH≈10), which also conforms to the aforementioned flow dynamics pH change. Combined with the removal rate and pH analysis, the reaction environment inside the multi-stage reactor is stable and controllable, providing suitable chemical conditions for the efficient deposition of uranium.

[0053] Figure 22 The figures show (a) the uranium removal efficiency in a single electrochemical uranium extraction reactor and (b) the pH value in a single electrochemical uranium extraction reactor. For a single-stage reactor, the performance curves and pH changes are as follows: Figure 22As shown, during the 24-hour reaction process, the uranium extraction efficiency only slowly increased to 37.89%, far lower than the removal efficiency of the multi-stage reactor. Simultaneously, the pH change within the single-stage electrolyzer increased significantly in the early stages of the reaction, then leveled off, while the overall pH of the external storage tank remained largely unchanged. This is because the electrochemical reaction in the single-stage reactor needs to continuously process unreacted uranyl ions. As the reaction progresses, a large amount of precipitated products accumulate beneath the electrode material, thus affecting the sufficient contact between subsequent uranyl ions and the electrode surface. Based on the above analysis, multi-stage electrochemical treatment of uranium-containing wastewater demonstrates significant advantages and plays a crucial role in the process design of multi-stage electrochemical reaction structures.

[0054] Figure 23 The images show (a) the XRD pattern of the product after reaction; (b) the XPS spectrum of the product after reaction; (c) the O 1s spectrum of the product after reaction; (d) the SEM image of the product after reaction; (e) the TEM image of the product after reaction; and (f) the EDS mapping image of the product after reaction. The products of electrochemical uranium deposition on simulated nuclear wastewater were analyzed. To ensure the chemical spectra of the uranium extraction products, the products after electrochemical treatment were systematically characterized. X-ray diffraction (XRD) patterns (…) Figure 23 a) The product exhibits a series of characteristic diffraction peaks at 13.4°, 26.1°, 27.0°, 31.5°, 41.3°, 45.5°, 47.8°, 53.8°, and 56.4°, which perfectly match the standard card (PDF#37-0637) for K₂U₂O₇, indicating that the main component of the electrochemical product is K₂U₂O₇. Further analysis of the elemental composition and chemical state of the product was performed using X-ray photoelectron spectroscopy (XPS). The U₄f spectrum (…) Figure 23 In b), the two characteristic peaks of U(V) are located at 381.0 eV (4f) respectively. 7 / 2 ) and 394.6 eV (4f 5 / 2 The two characteristic peaks of U(VI) are located at 383.8 eV (4f), respectively. 7 / 2 ) and 391.9 eV (4f 5 / 2 This indicates that some U(VI) was reduced to U(V) during the electrochemical extraction process. Furthermore, the O 1S spectrum ( Figure 23 c) Three main peaks were observed, which can be attributed to different oxygen species. Specifically, the peak at 530.3 eV corresponds to lattice oxygen (OL), the peak at 532.4 eV corresponds to oxygen vacancies (OV), and the peak at 533.7 eV corresponds to surface-adsorbed oxygen (OS). Compared with before the reaction, the OS component was significantly enhanced, which is attributed to the Co3O4@FeO process during electrochemical reaction. xThe -OH groups generated in situ on the surface of -IF further promote the complexation and precipitation of U(VI). Scanning electron microscopy (SEM) images show that the product exhibits a typical nanosheet stacked structure. Figure 23 d). High-resolution transmission electron microscopy (HRTEM) images ( Figure 23 e) Further details reveal clear lattice fringes, with interplanar spacings of 0.304 nm and 0.329 nm corresponding to the {012} and {002} planes of K₂U₂O₇, respectively. Elemental distribution diagram ( Figure 23 f) This confirms that the three elements K, O, and U are evenly distributed in the product, which directly reflects the successful extraction of uranium products.

[0055] Figure 24 The FeO of this invention x -IF, Co3O4-IF, Co3O4@FeO x -Power consumption diagram of IF. In the experiments of this invention, the voltage was recorded once per hour at a constant current of 60 mA for 8 hours. Due to the continuous change in voltage, the total energy consumption was calculated by integrating the instantaneous power over time. The formula used is as follows: in E Indicates total energy consumption. I This represents a constant current (0.060 A). V(t) It is the voltage that varies with time, measured hourly. Since the voltage data is collected in discrete one-hour intervals, the integral is numerically approximated using the trapezoidal rule.

[0056] here, V i Indicates that at time i The voltage value h is given, and ∆t = 1h. The integral value is multiplied by the current to obtain the energy consumption in watt-hours.

[0057] Based on energy consumption calculations, the prepared electrode materials exhibit significant performance differences in the electrochemical reactor. For example... Figure 24 As shown, FeO x -IF, Co3O4-IF, Co3O4@FeO x The energy consumption of -IF is 1.33, 1.32, and 1.18 kW·h, respectively. Among them, Co3O4@FeO x -IF consumes significantly less energy than the other two single-component materials, demonstrating its potential advantage as a composite electrode in reducing system operating costs. This result can be attributed to the combination of Co3O4 and FeO. xThe synergistic effect between them, and the regulation of the electronic structure of their interface may promote the electrochemical reaction kinetics, thereby improving the electrocatalytic efficiency and reducing energy consumption.

[0058] Figure 25 This invention relates to Co3O4@FeO x - IF power consumption plots at different flow rate gradients. Further investigation into the effect of flow rate on energy consumption revealed energy consumption values ​​of 1.24, 1.18, and 1.26 kW·h at flow rate gradients of 5, 10, and 20 mL / min, respectively. This shows that the system exhibits the lowest energy consumption and optimal energy economy at a flow rate of 10 mL / min. Too low a flow rate limits reactant mass transfer, potentially leading to incomplete reactions at the electrode surface; too high a flow rate may result in incomplete electrochemical reactions, reducing energy utilization efficiency. Therefore, a flow rate of 10 mL / min achieves a good match between reactant mass transfer and reaction kinetics, helping to minimize energy consumption while ensuring treatment effectiveness.

[0059] In summary, Co3O4@FeO x -IF achieved the lowest system energy consumption (1.18 kW·h) at a flow rate of 10 mL / min, which shows that the goal of high efficiency and low energy consumption can be effectively achieved through the synergistic optimization of electrode material structure design and process parameters, providing a new approach for engineering applications.

[0060] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing an integrated electrode material, characterized in that, Includes the following steps: Step 1: Immerse the foamed iron in hydrochloric acid and ultrasonically clean its surface. Remove it and then immerse it in anhydrous ethanol for ultrasonic cleaning. After vacuum drying, place it in a tube furnace and calcine it in an air stream to obtain reddish-brown foamed iron FeO. x -IF; Step 2: Add FeO x -IF was immersed in a mixed solution containing 2-methylimidazole and cobalt nitrate hexahydrate at room temperature, and then calcined in a tube furnace to obtain a black integrated electrode material.

2. The method for preparing the integrated electrode material as described in claim 1, characterized in that, In step one, the size of the foamed iron is (0.5~10)cm×(0.5~10)cm, and the concentration of hydrochloric acid is 0.1~0.5 mol / L.

3. The method for preparing the integrated electrode material as described in claim 1, characterized in that, In step one, the ultrasound time is 5 to 20 minutes, and the number of ultrasound sessions is 1 to 5.

4. The method for preparing the integrated electrode material as described in claim 1, characterized in that, In step one, the vacuum drying temperature is 50~70℃ and the time is 8~16h.

5. The method for preparing the integrated electrode material as described in claim 1, characterized in that, In step one, the calcination method is as follows: the temperature is increased to 400-500℃ at a rate of 3-7℃ / min, and calcined for 2-6 hours.

6. The method for preparing the integrated electrode material as described in claim 1, characterized in that, In step two, the molar volume ratio of 2-methylimidazole, cobalt nitrate hexahydrate, and deionized water in the mixed solution containing 2-methylimidazole and cobalt nitrate hexahydrate is 5~15 mmol:1~2 mmol:5~20 mL.

7. The method for preparing the integrated electrode material as described in claim 1, characterized in that, In step two, the soaking time is 12-48 hours.

8. The method for preparing the integrated electrode material as described in claim 1, characterized in that, In step two, the calcination method is as follows: the temperature is increased to 350-450℃ at a rate of 3-7℃ / min, and calcined for 1-3 hours.

9. The application of an integrated electrode material prepared by the preparation method according to any one of claims 1-8 in electrochemical uranium extraction.

10. The application of an integrated electrode material prepared by the preparation method according to any one of claims 1-8 in an electrochemical uranium extraction device.

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