Preparation method of electrochemical uranium extraction electrode material and electrochemical uranium extraction device

Abstract

This invention discloses a method for preparing an electrochemical uranium extraction electrode material and an electrochemical uranium extraction apparatus. The preparation method includes: continuously cleaning iron foil in an ultrasonic cleaner using acetone, ethanol, and deionized water, followed by vacuum drying; then annealing the dried iron foil in an alumina crucible in air to generate Fe. 3 O 4 foil; then Fe 3 O 4 Foil soaked in Co(NO) 3 ) 2 ·6H 2 After soaking in solution O, the Fe was dried in a vacuum dryer, and then the dried Fe was... 3 O 4 The foil was annealed in air to complete the first cobalt loading, yielding Co. 3 O 4 @Fe 3 O 4 -1, repeated loading, yielding Co 3 O 4 @Fe 3 O 4 Nanosheet array; this invention is applied to the working electrode of a three-electrode electrochemical workstation for uranium removal. This invention has the following advantages: it can greatly accelerate the capture and reduction of uranium in electrochemical uranium removal, improve the uranium extraction rate, and has excellent uranium extraction capabilities. At the same time, the manufacturing process is simple and the cost is low.

Description

A method for preparing an electrochemical uranium extraction electrode material and an electrochemical uranium extraction device Technical Field

[0001] This invention belongs to the field of uranium-containing wastewater treatment, specifically relating to a method for preparing an electrochemical uranium extraction electrode material and an electrochemical uranium extraction device. Background Technology

[0002] With the development of the nuclear industry, an increasing amount of radioactive wastewater will inevitably be generated and discharged into the environment, causing water and soil pollution and posing potential safety threats to the ecological environment and human health. Traditional soil remediation methods have many drawbacks, including generating secondary waste, having unsatisfactory purification effects, and consuming excessive energy. Therefore, finding an efficient, inexpensive, and environmentally friendly technology to replace traditional materials and processes is an urgent problem to be solved by the nuclear energy industry.

[0003] In existing technologies, the main methods for extracting uranium from uranium-containing wastewater are membrane treatment and ion exchange. These methods can extract most of the uranium from the wastewater, but some uranium is still difficult to extract, resulting in low uranium recovery rates and failure to meet wastewater discharge standards.

[0004] Currently, electrochemical catalytic extraction technology has been applied to the extraction of uranium from wastewater. It is characterized by high efficiency, environmental friendliness, and low energy consumption. Patent CN105280261A discloses a method for the electroreduction precipitation of uranium in uranium-containing wastewater. This method adjusts the pH of the uranium-containing wastewater to 2-4 using sulfuric acid or sodium hydroxide, depending on the wastewater's properties. Then, using metallic iron as the anode and graphite as the cathode, electroreduction is performed using a DC power supply. By controlling process parameters, iron ions are converted to iron(III) oxide (Fe3O4), and hexavalent uranium is reduced to tetravalent uranium. The uranium and iron(III) oxide co-precipitate, thus achieving the purpose of removing uranium from the wastewater. However, the poor charge transfer efficiency between the aqueous electrolyte and uranyl ions results in a very low efficiency in reducing hexavalent uranium to tetravalent uranium. Furthermore, under low pH conditions, the activity of uranyl ions in the wastewater is high, causing the generated tetravalent uranium to oxidize back to hexavalent uranium, further reducing the efficiency of uranium-containing wastewater treatment. Summary of the Invention

[0005] 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.

[0006] To achieve these objectives and other advantages according to the present invention, a method for preparing an electrochemical uranium extraction electrode material is provided, comprising the following steps:

[0007] Step 1: Clean the iron foil in an ultrasonic cleaner;

[0008] Step 2: Place the cleaned iron foil into a vacuum dryer to dry it. After drying, place the iron foil into an alumina crucible and anneal it in air to generate Fe3O4 foil.

[0009] Step 3: Immerse the Fe3O4 foil obtained in Step 2 in Co(NO3)2·6H2O solution. After immersion, dry it in a vacuum dryer. Then anneal the dried Fe3O4 foil in air to complete the first cobalt loading and obtain Co3O4@Fe3O4-1.

[0010] Step 4: Repeat step 3 with the Co3O4@Fe3O4-1 obtained in step 3 to obtain Co3O4@Fe3O4-2. After repeating step 3 multiple times, a Co3O4@Fe3O4 nanosheet array is obtained, which is the electrochemical electrode uranium extraction material.

[0011] Preferably, in step one, the iron foil is continuously cleaned in an ultrasonic cleaner with acetone, ethanol, and deionized water. The ultrasonic cleaning frequency is 40-80 kHz, the ultrasonic cleaning time with acetone is 5-10 min, the ultrasonic cleaning time with ethanol is 5-10 min, and the ultrasonic cleaning time with deionized water is 5-10 min.

[0012] Preferably, in step two, the drying temperature is 90–130°C, the drying time is 10–20 min, the annealing temperature is 480–550°C, the annealing time is 2–8 h, and the heating rate is 1–5°C / min.

[0013] Preferably, before step three, the Fe3O4 foil in step two undergoes a carbon loading pretreatment, the method of which is as follows:

[0014] S21. Mix xylose and urea in a mass ratio of 100:1 to 10 and place them in a container. Stir at 100 to 220°C for 10 to 60 minutes to completely dissolve the xylose and urea. Then add Fe3O4 foil, the mass of which is 5 to 8 times the total mass of xylose and urea. Stir the mixture evenly.

[0015] S22. Heat-treat the mixture in S21 at 120-250°C for 8-48 hours to dehydrate and carbonize the xylose to obtain a dark brown solid. This heat treatment process can be carried out at atmospheric pressure or in a closed reactor.

[0016] S23. The dark brown solid obtained in S22 is heat-treated at 250-1100℃ for 2-24 hours under a nitrogen atmosphere to obtain porous carbon-supported Fe3O4 material.

[0017] Preferably, in step three, the concentration of the Co(NO3)2·6H2O solution is 0.05–0.2 mol / L, and the soaking time is 10–20 h.

[0018] Preferably, in step three, the drying temperature is 90–130°C, the drying time is 10–20 min, the annealing temperature is 320–370°C, the annealing time is 30–60 min, and the heating rate is 5–12.5°C / min.

[0019] The application of an electrochemical uranium extraction electrode material includes the following steps:

[0020] S1. The Co3O4@Fe3O4 nanosheet array and carbon black obtained in step four are added to anhydrous ethanol, and Nafion solution is added at the same time. The mixture is sonicated until the solute is evenly distributed to obtain a mixed solution. The mixed solution is evenly coated on a 1×2cm carbon felt. After the ethanol evaporates, the coating is continued until the mixed solution is exhausted to obtain a sample of Co3O4@Fe3O4 nanosheet array uniformly loaded on carbon felt. This sample is used as the working electrode in the three-electrode system of the electrochemical workstation. The counter electrode in the three-electrode system is a platinum wire electrode, and the reference electrode is an Ag / AgCl electrode.

[0021] S2. Simulated fluorine- and uranium-containing wastewater is added to a three-electrode electrolytic cell as an electrolyte, and uranium is removed from the simulated fluorine- and uranium-containing wastewater using a potential of -1.2 to 0 V / s Ag / AgCl.

[0022] Preferably, the mass ratio of the Co3O4@Fe3O4 nanosheet array to carbon black is 5:2-4; the concentration of the Nafion solution is 5wt%; and the mass-to-volume ratio of the Co3O4@Fe3O4 nanosheet array, anhydrous ethanol, and Nafion solution is 5mg:1-3mL:30-40μL.

[0023] Preferably, the simulated fluoride- and uranium-containing wastewater in S2 is a 0.5M sodium sulfate solution with a uranium concentration of 45–55 mg / L and a fluoride concentration of 0.5–1 g / L.

[0024] Preferably, the uranium extraction rate of the fluorine-containing and uranium-containing wastewater is calculated using the following formula:

[0025] Extraction rate = (C0 - C) t ) / C0×100%

[0026] Where C0 is the initial uranium concentration, C t This represents the uranium concentration after a certain period of time.

[0027] An electrochemical uranium extraction device using electrochemical uranium extraction electrode material as the electrode includes:

[0028] Base;

[0029] An electrode power supply is fixedly mounted at one end of the base;

[0030] An electrolytic cell is fixedly installed on the right side of the electrode power source. Multiple electrolytic cells are fixedly installed on the electrolytic cell. An electrolytic cell cover is detachably installed on the electrolytic cell. A dual electrode is installed inside the electrolytic cell. The dual electrode is a working electrode and a counter electrode.

[0031] A peristaltic pump is fixedly installed on the right side of the electrolytic cell. A feed solenoid valve and a discharge solenoid valve are detachably connected to the peristaltic pump, and the peristaltic pump is connected to the electrolytic cell.

[0032] A control mechanism is located on the right side of the peristaltic pump and at the other end of the base. The control mechanism is electrically connected to the electrode power supply, the dual electrodes, the peristaltic pump, the feed solenoid valve, and the discharge solenoid valve.

[0033] The present invention includes at least the following beneficial effects: By loading Fe3O4 onto iron foil and then repeatedly loading Co3O4, a Co3O4@Fe3O4 nanosheet array is obtained, which forms a strong built-in interfacial electric field and contains abundant metal-oxygen-hydrogen bonds, which can greatly accelerate the confined capture and reduction of uranium in electrochemical uranium removal, improve the uranium extraction rate, have excellent uranium extraction capabilities, be reusable, and have a simple manufacturing process and low cost; by loading porous carbon onto Fe3O4 foil and then loading Co3O4 onto the Fe3O4 foil loaded with porous carbon, the resulting Co3O4@Fe3O4 nanosheet array has a better adsorption effect on uranium in fluorine-containing and uranium-containing wastewater, and can improve the uranium removal rate.

[0034] 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. Figure description:

[0035] Figure 1 is a top-view SEM image of the Fe3O4 foil in Comparative Example 1 of the present invention;

[0036] Figure 2 is a top-view SEM image of Co3O4@Fe3O4-4 in Example 4 of the present invention.

[0037] Figure 3 is a side view SEM image of the Fe3O4 foil in Comparative Example 1 of the present invention;

[0038] Figure 4 is a side view SEM image of Co3O4@Fe3O4-4 in Example 4 of the present invention;

[0039] Figure 5 is a TEM image of Co3O4@Fe3O4-4 in Example 4 of the present invention;

[0040] Figure 6 is a TEM image of Comparative Example 1 and Example 4 of the present invention;

[0041] Figure 7 shows the uranium removal rates of Examples 4-7 of the present invention and Comparative Example 1;

[0042] Figure 8 shows the cobalt content in the products of Examples 4-7 of the present invention;

[0043] Figure 9 shows the uranium removal rate in uranium-containing wastewater at different pH values ​​in Example 4 of the present invention;

[0044] Figure 10 shows the uranium removal rate under different voltages in Embodiment 4 of the present invention.

[0045] Figure 11 shows the Raman spectra of the products in Examples 4 to 7 of the present invention;

[0046] Figure 12 shows the uranium removal rates of Example 8 and Comparative Example 2 at different reaction times;

[0047] Figure 13 shows the ERP spectra of Comparative Example 1 and Example 4 of the present invention;

[0048] Figure 14 is a comparison chart of the uranium removal rate of Example 9 of the present invention with the uranium removal rates of Examples 4 to 7 of the present invention;

[0049] Figure 15 is a schematic diagram of the electrochemical uranium extraction device of the present invention, which uses electrochemical uranium extraction electrode material as the electrode. Detailed implementation method:

[0050] 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.

[0051] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not imply the presence or addition of one or more other elements or combinations thereof.

[0052] It should be noted that in the description of this invention, the orientations or positional relationships indicated by terms are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] Furthermore, in this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Moreover, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0055] Example 1

[0056] A method for preparing an electrochemical uranium extraction electrode material includes the following steps:

[0057] Step 1: Clean the iron foil with acetone in an ultrasonic cleaner for 5 minutes, then clean it with ethanol in an ultrasonic cleaner for 5 minutes, and finally clean it with deionized water in an ultrasonic cleaner for 5 minutes.

[0058] Step 2: Place the cleaned iron foil into a vacuum dryer and dry it at 120℃ for 15 minutes. After drying, place the iron foil into an alumina crucible and anneal it in air at 500℃ for 4 hours with a heating rate of 2℃ / min to generate Fe3O4 foil.

[0059] Step 3: Immerse 55g of the Fe3O4 foil obtained in Step 2 in 1L of 0.1mol / L Co(NO3)2·6H2O solution for 12h. After immersion, dry it in a vacuum dryer at 120℃ for 15min. Then anneal the dried Fe3O4 foil in air at 350℃ for 30min at a heating rate of 11℃ / min to complete the first cobalt loading and obtain 1-Co3O4@Fe3O4-1.

[0060] Step 4: Repeat step 3 with the 1-Co3O4@Fe3O4-1 obtained in step 3 to obtain 1-Co3O4@Fe3O4-2. Repeat step 3 3 times to obtain a 1-Co3O4@Fe3O4-4 nanosheet array.

[0061] Example 2

[0062] A method for preparing an electrochemical uranium extraction electrode material includes the following steps:

[0063] Step 1: Clean the iron foil with acetone in an ultrasonic cleaner for 5 minutes, then clean it with ethanol in an ultrasonic cleaner for 5 minutes, and finally clean it with deionized water in an ultrasonic cleaner for 5 minutes.

[0064] Step 2: Place the cleaned iron foil into a vacuum dryer and dry it at 120℃ for 15 minutes. After drying, place the iron foil into an alumina crucible and anneal it in air at 500℃ for 4 hours with a heating rate of 2℃ / min to generate Fe3O4 foil.

[0065] Step 3: Immerse 55g of the Fe3O4 foil obtained in Step 2 in 1L of 0.15mol / L Co(NO3)2·6H2O solution for 12h. After immersion, dry it in a vacuum dryer at 120℃ for 15min. Then anneal the dried Fe3O4 foil in air at 360℃ for 35min at a heating rate of 10℃ / min to complete the first cobalt loading and obtain 2-Co3O4@Fe3O4-1.

[0066] Step 4: Repeat step 3 with the 2-Co3O4@Fe3O4-1 obtained in step 3 to obtain 2-Co3O4@Fe3O4-2. Repeat step 3 3 times to obtain a 2-Co3O4@Fe3O4-4 nanosheet array.

[0067] Example 3

[0068] A method for preparing an electrochemical uranium extraction electrode material includes the following steps:

[0069] Step 1: Clean the iron foil with acetone in an ultrasonic cleaner for 5 minutes, then clean it with ethanol in an ultrasonic cleaner for 5 minutes, and finally clean it with deionized water in an ultrasonic cleaner for 5 minutes.

[0070] Step 2: Place the cleaned iron foil into a vacuum dryer and dry it at 120℃ for 15 minutes. After drying, place the iron foil into an alumina crucible and anneal it in air at 500℃ for 4 hours with a heating rate of 2℃ / min to generate Fe3O4 foil.

[0071] Step 3: Immerse 55g of the Fe3O4 foil obtained in Step 2 in 1L of 0.2mol / L Co(NO3)2·6H2O solution for 12h. After immersion, dry it in a vacuum dryer at 120℃ for 15min. Then anneal the dried Fe3O4 foil in air at 370℃ for 40min at a heating rate of 9℃ / min to complete the first cobalt loading and obtain 3-Co3O4@Fe3O4-1.

[0072] Step 4: Repeat step 3 with the Co3O4@Fe3O4-1 obtained in step 3 to obtain 3-Co3O4@Fe3O4-2. Repeat step 3 3 times to obtain a 3-Co3O4@Fe3O4-4 nanosheet array.

[0073] Example 4

[0074] A method for preparing an electrochemical uranium extraction electrode material includes the following steps:

[0075] Step 1: Clean the iron foil with acetone in an ultrasonic cleaner for 5 minutes, then clean it with ethanol in an ultrasonic cleaner for 5 minutes, and finally clean it with deionized water in an ultrasonic cleaner for 5 minutes.

[0076] Step 2: Place the cleaned iron foil into a vacuum dryer and dry it at 120℃ for 15 minutes. After drying, place the iron foil into an alumina crucible and anneal it in air at 500℃ for 4 hours with a heating rate of 2℃ / min to generate Fe3O4 foil.

[0077] Step 3: Immerse 55g of the Fe3O4 foil obtained in Step 2 in 1L of 0.1mol / L Co(NO3)2·6H2O solution for 12h. After immersion, dry it in a vacuum dryer at 120℃ for 15min. Then anneal the dried Fe3O4 foil in air at 350℃ for 30min at a heating rate of 11℃ / min to complete the first cobalt loading and obtain Co3O4@Fe3O4-1.

[0078] Step 4: Repeat step 3 with the Co3O4@Fe3O4-1 obtained in step 3 to obtain Co3O4@Fe3O4-2. Repeat step 3 3 times to obtain the Co3O4@Fe3O4-4 nanosheet array.

[0079] Electrochemical uranium removal using the prepared Co3O4@Fe3O4-4 nanosheet array includes the following steps:

[0080] S1. Add 5 mg of the Co3O4@Fe3O4-4 nanosheet array obtained in step four and 3 mg of carbon black to 2 mL of anhydrous ethanol, and simultaneously add 35 μL of 5 wt% Nafion solution. Sonicate until the solute is evenly distributed to obtain a mixed solution. Spread the mixed solution evenly on a 1×2 cm carbon felt. After the ethanol evaporates, continue to spread until the mixed solution is exhausted to obtain a sample of Co3O4@Fe3O4-4 nanosheet array uniformly loaded on carbon felt. This sample is used as the working electrode in the three-electrode system of the electrochemical workstation (CHI 660E, China). The counter electrode in the three-electrode system is a platinum wire electrode, and the reference electrode is an Ag / AgCl electrode.

[0081] S2. A 0.5M sodium sulfate solution with a uranium concentration of 50 mg / L and a fluorine concentration of 1 g / L was used to simulate uranium- and fluorine-containing wastewater and added to a three-electrode electrolytic cell. Uranium was removed from the simulated uranium- and fluorine-containing wastewater at a potential of -1.2V Vs Ag / AgCl for 300 min. After the reaction, the extraction rate was calculated using the following formula:

[0082] Extraction rate = (C0 - C) t ) / C0×100%

[0083] Where C0 is the initial uranium concentration, C t This represents the uranium concentration after a certain period of time.

[0084] Example 5

[0085] The difference between this embodiment and Example 4 is that step four was not performed, and 5-Co3O4@Fe3O4-1 was finally obtained. The extraction rate was calculated after the reaction was completed.

[0086] Example 6

[0087] The difference between this embodiment and embodiment 4 is that in step four, step three is repeated once for Co3O4@Fe3O4-1, and finally 6-Co3O4@Fe3O4-2 is obtained. The extraction rate is calculated after the reaction is completed.

[0088] Example 7

[0089] The difference between this embodiment and embodiment 4 is that in step four, step three is repeated five times for Co3O4@Fe3O4-1, finally obtaining 7-Co3O4@Fe3O4-6, and the extraction rate is calculated after the reaction is completed.

[0090] Example 8

[0091] The Co3O4@Fe3O4-4 obtained in Example 4 was subjected to electrochemical uranium removal for different times, and the extraction rate was calculated after the reaction was completed.

[0092] Example 9

[0093] In this embodiment, the Fe3O4 foil used in step three of Example 4 is replaced with Fe3O4 foil supported on porous carbon. All other aspects are the same as in Example 4, ultimately yielding 9-Co3O4@Fe3O4-4. The method for supporting porous carbon is as follows:

[0094] S21. Mix 100g xylose and 10g urea in a container and stir at 200℃ for 60 minutes to completely dissolve the xylose and urea. Then add 550g Fe3O4 foil and stir the mixture evenly.

[0095] S22. Place the mixture in S21 into a high-temperature reactor and heat-treat it at 120°C for 48 hours to dehydrate and carbonize the xylose to obtain a dark brown solid.

[0096] S23. The dark brown solid obtained in S22 is heat-treated at 800℃ for 4 hours under a nitrogen atmosphere to obtain a porous carbon-supported Fe3O4 foil.

[0097] Example 10

[0098] Uranium removal is performed using the electrochemical uranium removal apparatus shown in Figure 15, which includes:

[0099] Base 1;

[0100] Electrode power supply 2 is fixedly disposed at one end of the base 1;

[0101] An electrolytic cell 3 is fixedly installed on the right side of the electrode power supply 2. Multiple electrolytic cells 31 are fixedly installed on the electrolytic cell 3. An electrolytic cell cover 311 is detachably installed on the electrolytic cell 31. A double electrode 32 is installed inside the electrolytic cell 31. The double electrode 32 is a working electrode 321 and a counter electrode 322.

[0102] A peristaltic pump 4 is fixedly installed on the right side of the electrolytic cell 3. A feed solenoid valve 41 and a discharge solenoid valve 42 are detachably connected to the peristaltic pump 4. The peristaltic pump 4 is connected to the electrolytic cell 3.

[0103] The control mechanism 5 is located on the right side of the peristaltic pump 4 and at the other end of the base 1. The control mechanism 5 is electrically connected to the electrode power supply 2, the dual electrode 32, the peristaltic pump 4, the feed solenoid valve 41, and the discharge solenoid valve 42.

[0104] Working principle: The prepared Co3O4@Fe3O4 nanosheet array is used as the working electrode and the counter electrode is a platinum electrode. Fluorine- and uranium-containing wastewater is transported to the electrolytic cell 31 in the electrolytic cell 3 through the feed solenoid valve 41 and the peristaltic pump 4. The dual electrodes 32 are connected to the electrode power supply 2 as needed. The parameters are set by the control mechanism 5 to electrolyze the fluorine- and uranium-containing wastewater in the electrolytic cell 31. The electrolyzed solution is output through the discharge solenoid valve 42 via the peristaltic pump 4.

[0105] Comparative Example 1

[0106] A method for preparing an electrochemical uranium extraction electrode material includes the following steps:

[0107] Step 1: Clean the iron foil with acetone in an ultrasonic cleaner for 5 minutes, then clean it with ethanol in an ultrasonic cleaner for 5 minutes, and finally clean it with deionized water in an ultrasonic cleaner for 5 minutes.

[0108] Step 2: Place the cleaned iron foil into a vacuum dryer and dry it at 120℃ for 15 minutes. After drying, place the iron foil into an alumina crucible and anneal it in air at 500℃ for 4 hours with a heating rate of 2℃ / min to generate Fe3O4 foil.

[0109] Electrochemical uranium removal using the prepared Fe3O4 foil includes the following steps:

[0110] S1. Add 5 mg of Fe3O4 foil obtained in step four and 3 mg of carbon black to 2 mL of anhydrous ethanol, and simultaneously add 35 μL of 5 wt% Nafion solution. Sonicate until the solute is evenly distributed to obtain a mixed solution. Spread the mixed solution evenly on a 1×2 cm carbon felt. After the ethanol evaporates, continue to spread until the mixed solution is exhausted to obtain a sample of Fe3O4 foil uniformly loaded on carbon felt. This sample is used as the working electrode in the three-electrode system of the electrochemical workstation (CHI 660E, China). The counter electrode in the three-electrode system is a platinum wire electrode, and the reference electrode is an Ag / AgCl electrode.

[0111] S2. A 0.5M sodium sulfate solution with a uranium concentration of 50 mg / L and a fluorine concentration of 1 g / L was used to simulate uranium- and fluorine-containing wastewater and added to a three-electrode electrolytic cell. Uranium was removed from the simulated uranium- and fluorine-containing wastewater at a potential of -1.2V Vs Ag / AgCl for 300 min. After the reaction, the extraction rate was calculated using the following formula:

[0112] Extraction rate = (C0 - C) t ) / C0×100%

[0113] Where C0 is the initial uranium concentration, C t This represents the uranium concentration after a certain period of time.

[0114] Comparative Example 2

[0115] Electrochemical uranium removal experiments were conducted on the Fe3O4 foil obtained in Comparative Example 1 for different durations.

[0116] As can be seen from Figures 1 and 3, Fe3O4 nanosheets with an average thickness of 20 nm are uniformly arranged on the surface of Fe foil, and the Fe3O4 nanosheets have a distinct layered structure.

[0117] As can be seen from Figures 2 and 4, as the Fe3O4 foil was immersed in cobalt nitrate solution and then annealed, and this step was repeated, Co3O4 nanoparticles were uniformly loaded on the surface of the Fe3O4 nanoarray. With the increase of loading times, the cobalt content increased significantly, and the Fe3O4 nanosheet array was completely covered by the annealed Co3O4 nanoparticles.

[0118] As can be seen from Figure 5, iron, oxygen, and cobalt elements are uniformly distributed on the Co3O4@Fe3O4-4 nanosheet array.

[0119] As can be seen from Figures 6a and 6b, the (012) plane of ferric oxide and the (222) plane of magnetite have significant interplanar spacings of 0.368 nm and 0.242 nm, respectively. Figure 6c shows that with the introduction of Co3O4, a large number of nanoparticles are uniformly loaded on the Fe3O4 nanosheets. Figure 6c shows two distinct lattice fringes with interplanar spacings of 0.296 nm and 0.243 nm, respectively, corresponding to the (220) crystal plane of magnetite and the (311) crystal plane of Co3O4. This indicates that there is a significant heterojunction between Fe3O4 and Co3O4, which is beneficial for electron transfer during uranium extraction.

[0120] As shown in Figure 7, the uranium extraction efficiency of the original Fe3O4 was relatively low at 79.05%. With the introduction of Co3O4, the uranium extraction efficiencies of Co3O4@Fe3O4 in fluorine- and uranium-containing wastewater were 93.32% (5-Co3O4@Fe3O4-1), 97.12% (6-Co3O4@Fe3O4-2), 97.95% (Co3O4@Fe3O4-4), and 97.68% (7-Co3O4@Fe3O4-6), respectively. The increased uranium extraction efficiency is attributed to the enrichment of active sites in the nanosheet array structure and the faster charge transfer rate between Co3O4 and Fe3O4.

[0121] As can be seen from Figures 8 and 11, the cobalt content in the Co3O4@Fe3O4 nanosheet array increases significantly with the increase of the number of times step three is repeated, i.e., the increase of cobalt loading.

[0122] As shown in Figure 9, for Co3O4@Fe3O4-4, the uranium removal capacity of uranium-containing wastewater shows a continuous upward trend with the increase of pH value, reaching a maximum at pH 5-6. When the pH exceeds 6, the uranium removal capacity decreases significantly. The above results are because the species of uranium are relatively sensitive to pH changes. Therefore, at the increased pH level, the uranium extraction rate decreases due to the electrostatic repulsion between the cathode and the negatively charged uranium species. This repulsion slows down the migration of uranium species to the Co3O4@Fe3O4-4 electrode, resulting in a decrease in the uranium extraction rate.

[0123] As shown in Figure 10, the electric field force increases with the increase of the absolute value of the voltage, which leads to an increase in the rate of uranium adsorption at the negative electrode. The uranium extraction rate of Co3O4@Fe3O4-4 is the highest (>95%) after reacting at a low voltage of -1.2V for 300 min. The removal capacity of Co3O4@Fe3O4-4 at 0V is 51.10%, indicating the presence of physical adsorption. The results show that Co3O4@Fe3O4-4 has great energy-saving potential in the uranium extraction process.

[0124] As shown in Figure 12, the uranium extraction efficiency of Fe3O4 reached 60.98% and 75.04% within 240 min and 300 min, respectively. After loading cobalt to obtain Co3O4@Fe3O4-4, the uranium extraction efficiency of Co3O4@Fe3O4-4 reached 87.82% and 97.08% within 240 min and 300 min, respectively, and the extraction rate gradually stabilized after 300 min.

[0125] As shown in Figure 13, the ESR spectrum of Co3O4@Fe3O4-4 shows a significant strong signal g=2.003, which further confirms that there are abundant oxygen vacancy defects in Co3O4@Fe3O4-4, which is conducive to the formation of a large number of metal-oxygen-hydrogen bonds, thereby improving the selective capture of uranium.

[0126] As can be seen from Figure 14, the uranium removal rate of the 9-Co3O4@Fe3O4-4 nanosheet array obtained by loading Fe3O4 foil with porous carbon and then loading Co3O4 is higher than that of the Co3O4@Fe3O4 nanosheet array obtained by loading Co3O4 with Fe3O4 foil.

[0127] In summary, loading cobalt onto Fe3O4 foil to obtain a Co3O4@Fe3O4 nanosheet array, which can be used as a working electrode for electrochemical uranium removal, can effectively improve the uranium removal rate. Furthermore, this Co3O4@Fe3O4 nanosheet array is highly reusable and exhibits a high uranium removal rate at suitable temperatures. By loading porous carbon onto Fe3O4 foil and then loading Co3O4 onto the carbon-loaded Fe3O4 foil, the resulting Co3O4@Fe3O4 nanosheet array has a better adsorption effect on uranium in fluorine- and uranium-containing wastewater, thus improving the uranium removal rate.

[0128] 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 electrochemical uranium extraction electrode material, characterized in that, Includes the following steps: Step 1: Clean the iron foil in an ultrasonic cleaner. Step 2: Dry the cleaned iron foil in a vacuum dryer. After drying, place the iron foil in an alumina crucible and anneal it in air to generate Fe3O4 foil. Perform carbon loading pretreatment on the Fe3O4 foil: S21: Mix xylose and urea in a container at a mass ratio of 100:1~10. Stir at 100~220℃ for 10~60 minutes to completely dissolve the xylose and urea. Then add Fe3O4 foil, with a mass of 5~8 times the total mass of xylose and urea. Stir the mixture thoroughly. S22: Heat-treat the mixture from S21 at 120~250℃ for 8~48 hours to dehydrate and carbonize the xylose, obtaining a dark brown solid. This heat treatment process is carried out in an atmospheric pressure or closed reactor. S23: Heat-treat the dark brown solid obtained in S22 at 250~1100℃ under a nitrogen atmosphere. Heat treatment at ℃ for 2~24 h yields porous carbon-supported Fe3O4 material; Step 3: Immerse the porous carbon-supported Fe3O4 material obtained in Step 2 in Co(NO3)2·6H2O solution. After immersion, dry in a vacuum dryer, and then anneal the dried porous carbon-supported Fe3O4 material in air to complete the first cobalt loading, obtaining Co3O4@Fe3O4-1; wherein, the concentration of Co(NO3)2·6H2O solution is 0.05~0.2mol / L, and during immersion... The drying time is 10-20 h, the drying temperature is 90-130℃, the drying time is 10-20 min, the annealing temperature is 320-370℃, the annealing time is 30-60 min, and the heating rate is 5-12.5℃ / min; Step 4: Repeat step 3 on the Co3O4@Fe3O4-1 obtained in step 3 to obtain Co3O4@Fe3O4-2. After repeating step 3 multiple times, the Co3O4@Fe3O4 nanosheet array is obtained, which is the electrochemical uranium extraction electrode material.

2. The method for preparing the electrochemical uranium extraction electrode material according to claim 1, characterized in that, In step one, the iron foil is continuously cleaned in an ultrasonic cleaner with acetone, ethanol, and deionized water. The ultrasonic cleaning frequency is 40-80kHz, the ultrasonic cleaning time with acetone is 5-10 minutes, the ultrasonic cleaning time with ethanol is 5-10 minutes, and the ultrasonic cleaning time with deionized water is 5-10 minutes.

3. The method for preparing the electrochemical uranium extraction electrode material according to claim 1, characterized in that, In step two, the drying temperature is 90~130℃, the drying time is 10~20min, the annealing temperature is 480~550℃, the annealing time is 2~8h, and the heating rate is 1~5℃ / min.

4. The application of an electrochemical uranium extraction electrode material prepared by the preparation method according to any one of claims 1 to 3, comprising the following steps: S1. The Co3O4@Fe3O4 nanosheet array and carbon black obtained in step four are added to anhydrous ethanol, and Nafion solution is added at the same time. The mixture is sonicated until the solute is evenly distributed to obtain a mixed solution. The mixed solution is evenly spread on a 1×2cm carbon felt. After the ethanol evaporates, the mixture is continued to be spread until the mixed solution is exhausted to obtain a sample of Co3O4@Fe3O4 nanosheet array uniformly loaded on carbon felt. This sample is used as the working electrode in the three-electrode system of the electrochemical workstation. The counter electrode in the three-electrode system is a platinum wire electrode, and the reference electrode is an Ag / AgCl electrode. S2. Simulated fluorine-containing and uranium-containing wastewater is added to the electrolytic cell of the three-electrode system as electrolyte. Uranium is removed from the simulated fluorine-containing and uranium-containing wastewater using a potential of -1.2~0V (vs·Ag / AgCl).

5. The application according to claim 4, characterized in that, The mass ratio of Co3O4@Fe3O4 nanosheet array to carbon black in S1 is 5:2~4; the concentration of Nafion solution is 5 wt%; the mass-volume ratio of Co3O4@Fe3O4 nanosheet array, anhydrous ethanol and Nafion solution is 5 mg:1~3 mL:30~40 μL.

6. The application according to claim 4, characterized in that, The simulated fluorine- and uranium-containing wastewater in S2 is a 0.5M sodium sulfate solution with a uranium concentration of 45-55 mg / L and a fluorine concentration of 0.5-1 g / L.

7. The application according to claim 4, characterized in that, The uranium extraction rate of the fluorine-containing and uranium-containing wastewater is calculated using the following formula: Extraction rate = (C0 - C) / (C0 - C) t ) / C0×100% where C0 is the initial uranium concentration, C t This represents the uranium concentration after a certain period of time.

8. An electrochemical uranium extraction apparatus using an electrochemical uranium extraction electrode material prepared by any one of claims 1 to 3 as an electrode, comprising: Base; An electrode power supply is fixedly mounted at one end of the base; An electrolytic cell is fixedly disposed to the right of the electrode power supply. Multiple electrolytic cells are fixedly disposed on the electrolytic cell, and each electrolytic cell is detachably covered. A dual electrode, consisting of a working electrode and a counter electrode, is disposed within each electrolytic cell. A prepared Co3O4@Fe3O4 nanosheet array is used as the working electrode, and a platinum electrode is used as the counter electrode. A peristaltic pump is fixedly disposed to the right of the electrolytic cell, and a feed solenoid valve and a discharge solenoid valve are detachably connected to the pump. The peristaltic pump is connected to the electrolytic cell. A control mechanism is disposed to the right of the peristaltic pump, located at the other end of the base. The control mechanism is electrically connected to the electrode power supply, the dual electrodes, the peristaltic pump, the feed solenoid valve, and the discharge solenoid valve.

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