Preparation method and application of foamy copper-based integrated electrode for electrochemically separating uranium

Abstract

The invention discloses a preparation method and application of a foamy copper-based integrated electrode for electrochemically separating uranium. The preparation method comprises the following steps: pretreating foamy copper; preparing Cu (OH) 2 / CF by using sodium hydroxide, ammonium persulfate and pretreated foamy copper as raw materials; cuP3 / CF is prepared through high-temperature calcination in a tubular furnace, the CuP3 / CF is immersed in a hydrogen peroxide solution for a period of time and washed with deionized water for multiple times, POx-CuP3 / CF is obtained, and the foamy copper-based integrated electrode for electrochemical uranium separation is obtained. According to the method, the foamy copper-based integrated electrode with Cu-P-O sites is successfully synthesized in a mode of combining high-temperature phosphorization and H2O2 oxidation, the foamy copper-based integrated electrode is applied to electrochemical separation of uranium in a strongly acidic fluorine-containing uranium-containing system, efficient separation of uranium is achieved, and an acid-resistant uranium product is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical fields of electrode material preparation and wastewater treatment. More specifically, the present invention relates to a preparation method and application of a foam copper-based integrated electrode for electrochemical separation of uranium. Background Art

[0002] Fluoride-containing uranium wastewater is a typical pollutant generated during nuclear fuel cycle, uranium mining, and nuclear waste treatment. Uranium (U) exists in the form of uranyl fluoride (such as UO2 2+ ) etc., and has high radioactivity, chemical toxicity, and environmental persistence. Traditional treatment methods (such as chemical precipitation, ion exchange, solvent extraction, etc.) have problems such as low efficiency, high risk of secondary pollution, and difficulty in treating high-salt complex systems. Electrochemical separation technology has become a research hotspot due to its advantages of high efficiency, low energy consumption, and environmental friendliness. Nanoscale electrode sheets, due to their high specific surface area, excellent electrical conductivity, and adjustable active sites, have become the core materials for improving electrochemical separation performance.

[0003] When using nanosheet electrode materials to efficiently separate uranium in a strongly acidic fluoride-containing and uranium-containing wastewater system at pH = 2 - 3, when the acidity is further increased, even low-sized reduced uranium oxides will be dissolved in the solution. For example, when pH = 1, U(IV) cannot exist in the form of uranium dioxide, but exists as stable free ions. Therefore, a new method is needed to achieve efficient separation of uranium. Summary of the Invention

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

[0005] To achieve these objects and other advantages according to the present invention, a preparation method of a foam copper-based integrated electrode for electrochemical separation of uranium is provided, including the following steps:

[0006] Step 1: Pretreat the foam copper;

[0007] Step 2: Use sodium hydroxide, ammonium persulfate, and the pretreated foam copper as raw materials to prepare Cu(OH)2 / CF;

[0008] Step 3: Calcinate at high temperature in a tubular furnace to prepare CuP3 / CF, immerse CuP3 / CF in hydrogen peroxide solution for a period of time, and rinse with deionized water multiple times to obtain PO x -CuP3 / CF, that is, the foam copper-based integrated electrode is obtained.

[0009] Preferably, in the first step, the specific method for pretreating the copper foam includes: cutting the copper foam into blocks with dimensions of 1 cm × 2 cm × 0.2 cm, ultrasonically treating it with acetone, 0.5 M dilute hydrochloric acid, ethanol, and deionized water for 10 - 20 min respectively, and then drying it in a vacuum oven at 50 - 70 °C for later use.

[0010] Preferably, in the second step, the specific method for preparing Cu(OH)2 / CF includes: dissolving sodium hydroxide in deionized water, stirring until completely dissolved, adding ammonium persulfate to the sodium hydroxide solution, stirring until completely dissolved, immersing the pretreated copper foam into the above mixed solution, and maintaining for 20 - 30 min; then rinsing it several times with deionized water to wash away the excess impurity ions, and drying it in a vacuum drying oven at 50 - 70 °C to obtain Cu(OH)2 / CF.

[0011] Preferably, the dosage ratio of sodium hydroxide, deionized water, and ammonium persulfate is 3.0 - 3.5 g:30 mL:0.9 - 1.0 g.

[0012] Preferably, in the third step, the specific method for preparing CuP3 / CF by high-temperature calcination in a tube furnace includes: preparing two small porcelain boats, adding sodium hypophosphite to one of the small porcelain boats and placing it upstream in the tube furnace; loading Cu(OH)2 / CF into the other small porcelain boat and placing it downstream in the tube furnace; heating and calcining at a certain heating rate to obtain CuP3 / CF.

[0013] Preferably, the dosage ratio of sodium hypophosphite to ammonium persulfate in the second step is 0.3:0.9 - 1.0.

[0014] Preferably, the calcination temperature is 300 - 400 °C, the calcination time is 2 - 3 h, and the heating rate is 2 °C / min.

[0015] Preferably, in the third step, the concentration of the hydrogen peroxide solution is 1 - 3 wt%, and the immersion time of CuP3 / CF in the hydrogen peroxide solution is 10 - 30 min.

[0016] The application of a copper foam-based integrated electrode, where the copper foam-based integrated electrode is applied to electrochemically separate uranium in a strong acid fluorine-containing system.

[0017] Preferably, the simulation method for applying the copper foam-based integrated electrode to electrochemically separate uranium in a strong acid fluorine-containing system includes: using the copper foam-based integrated electrode as the working electrode, Ag / AgCl as the reference electrode, and a platinum wire as the counter electrode, respectively using UO2(NO3)2·6H2O and KF·2H2O as the uranium source and fluorine source to dissolve in deionized water to prepare a fluorine-containing and uranium-containing solution, and conducting an electrochemical separation experiment.

[0018] To improve the separation efficiency of uranium by the foam copper-based integrated electrode (Cu-P-O / CF), the CuP3 / CF obtained in Step 3 was successively doped with sulfur and nitrogen to obtain sulfur- and nitrogen-doped CuP3 / CF. The sulfur- and nitrogen-doped CuP3 / CF was immersed in a 1% hydrogen peroxide solution for 20 min. After the reaction, it was rinsed several times with deionized water to obtain sulfur- and nitrogen-codoped PO x -CuP3 / CF; wherein, the specific method for doping CuP3 / CF with sulfur and nitrogen is as follows:

[0019] Put CuP3 / CF into a high-pressure reaction kettle with a polytetrafluoroethylene liner, add thiourea solution as the sulfur source and ethanol / water mixture solvent as the solvent; carry out hydrothermal reaction at 180 - 220 °C for 3 - 12 h, and after cooling, wash and dry to obtain sulfur-doped CuP3 / CF. Among them, the dosage ratio of thiourea solution, ethanol / water mixed solvent to sodium hydroxide in Step 2 is 10 - 20 mL:100 - 300 mL:3.0 - 3.5 g. The volume ratio of ethanol to water in the ethanol / water mixed solvent is 1:1;

[0020] Mix the sulfur-doped CuP3 / CF with urea, evacuate to below 1.2×10 -3 Pa, introduce Ar, and heat it to 500 - 800 °C at a heating rate of 5 °C / min in an Ar atmosphere, keep it warm for 2 - 6 h, and after cooling to room temperature, obtain sulfur- and nitrogen-doped CuP3 / CF. Among them, the dosage ratio of urea to thiourea solution is 1.0 - 3.0 g:10 - 20 mL.

[0021] The present invention has at least the following beneficial effects: The present invention combines high-temperature phosphating and H2O2 oxidation to successfully synthesize a foam copper-based integrated electrode (Cu-P-O / CF) with Cu-P-O sites, and applies it to a strongly acidic fluorine- and uranium-containing system, realizing the efficient separation of uranium and obtaining an acid-resistant uranium product. In the simulated strongly acidic fluorine- and uranium-containing wastewater, the PO x -Cu3P / CF integrated electrode achieved a uranium separation efficiency of 97.4% within 105 min, which is higher than that of the Cu3P / CF integrated electrode (81.3%) and CF (58.0%), and obtained a uranium product (K2UF6) 1.333 (a special form of UF4·2KF).

[0022] After 10 extraction-desorption cycles, the uranium removal efficiency of the PO x -Cu3P / CF integrated electrode was still as high as 95%. The electrochemical extraction of uranium by the POx-Cu3P / CF integrated electrode is not affected by the fluorine-uranium ratio, interfering ions, and the initial uranium concentration, and the removal efficiency can reach more than 95%.

[0023] The feasibility was verified in real strongly acidic fluorine-containing and uranium-containing wastewater, and the removal efficiency of uranium in the real wastewater can still reach 96.3%.

[0024] The present invention sequentially performs sulfur doping and nitrogen doping on the obtained CuP3 / CF, which provides more electrochemical active sites for CuP3 / CF and improves the PO x -The electrolyte wettability of the Cu3P / CF integrated electrode improves the PO x -Cu3P / CF integrated electrode for the separation and extraction efficiency of uranium in fluorine-containing uranium wastewater. Among them, the sulfur doping of the present invention is carried out by high-temperature hydrothermal method, and the nitrogen doping is carried out by vacuum high-temperature calcination method, and the sulfur doping is carried out first, and then the nitrogen doping is carried out. The hydrothermal method generates a sulfur-doped carbon layer on the surface of CuP3 / CF, and the subsequent high-temperature calcination and nitrogen doping method forms a stable CSC bond. Such a doping method and doping order reduce the free -SH, S 2- The introduction of reduced states such as amino-NH2 and pyrrole-N, high-temperature calcination allows nitrogen to be embedded in the nitrogen skeleton, reducing the amount of subsequent substances that react with hydrogen peroxide and increasing the PO x -Sulfur and nitrogen doping loading in Cu3P / CF integrated electrode.

[0025] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The foam copper (CF), Cu(OH)2 / CF, CuP3 / CF and PO prepared in Example 1 x -CuP3 / CF sample physical picture;

[0027] Figure 2 The CuP3 / CF and PO prepared in Example 1 x -SEM image of the integrated electrode of CuP3 / CF;

[0028] Figure 3 PO prepared in Example 1 x -HRTEM image, TEM and EDS spectrum of CuP3 / CF integrated electrode;

[0029] Figure 4 The foam copper (CF), CuP3 / CF and PO prepared in Example 1 x -XRD pattern of CuP3 / CF integrated electrode;

[0030] Figure 5 The CuP3 / CF and PO prepared in Example 1 xP 2p XPS spectrum of the integrated CuP3 / CF electrode;

[0031] Figure 6 CuP3 / CF and PO prepared in Example 1 x Cu 2p XPS spectrum of the integrated CuP3 / CF electrode;

[0032] Figure 7 CuP3 / CF and PO prepared in Example 1 x FTIR spectrum of the integrated CuP3 / CF electrode;

[0033] Figure 8 CuP3 / CF and PO prepared in Example 1 x LSV test chart of the integrated CuP3 / CF electrode;

[0034] Figure 9 PO prepared in Example 1 x Uranium removal efficiency of the integrated CuP3 / CF electrode at -0.8 to -1.4 V potential;

[0035] Figure 10 CF, CuP3 / CF and PO prepared in Example 1 x Electrochemical uranium extraction efficiency of the integrated CuP3 / CF electrode;

[0036] Figure 11 CF, CuP3 / CF and PO prepared in Example 1 x Current change during uranium removal by the integrated CuP3 / CF electrode;

[0037] Figure 12 CF, CuP3 / CF and PO prepared in Example 1 x Kinetic curve of electrochemical U(VI) separation of the CuP3 / CF electrode sheet;

[0038] Figure 13 PO prepared in Example 1 x Recycling efficiency chart of uranium extraction by the integrated CuP3 / CF electrode sheet in simulated wastewater;

[0039] Figure 14 PO under the condition of coexistence of interfering ions x Uranium extraction efficiency of the integrated CuP3 / CF electrode sheet;

[0040] Figure 15 PO prepared in Example 1 x Uranium extraction efficiency of the integrated CuP3 / CF electrode sheet at different U / F;

[0041] Figure 16The PO prepared for Example 1 x - The uranium extraction efficiency and extraction rate of the CuP3 / CF integrated electrode sheet at an initial uranium concentration of 100 - 500 mg / L;

[0042] Figure 17 For the PO after electrochemical uranium extraction x - SEM images, TEM images, HRTEM images, and EDS spectra of the CuP3 / CF integrated electrode;

[0043] Figure 18 For the PO x - XRD pattern of the CuP3 / CF integrated electrode after electrochemical uranium extraction;

[0044] Figure 19 For the PO x - FTIR spectrum of the CuP3 / CF integrated electrode after electrochemical uranium extraction;

[0045] Figure 20 For the PO x - XPS survey spectrum of the CuP3 / CF integrated electrode after electrochemical uranium extraction;

[0046] Figure 21 For the PO x - U 4f XPS spectrum of the CuP3 / CF integrated electrode after electrochemical uranium extraction;

[0047] Figure 22 For the PO x - F 1s XPS spectrum of the CuP3 / CF integrated electrode after electrochemical uranium extraction;

[0048] Figure 23 For the PO x - Analysis of the contents of uranium and potassium elements in the product after electrochemical uranium extraction by the CuP3 / CF integrated electrode;

[0049] Figure 24 For the fluoride ion concentrations before and after electrochemical uranium extraction;

[0050] Figure 25 For the composition of the real acidic uranium wastewater solution;

[0051] Figure 26 For the PO x - Uranium removal efficiency graph of the CuP3 / CF integrated electrode in 100 mL of real acidic wastewater;

[0052] Figure 27 For the PO x - I - T curve of the CuP3 / CF integrated electrode in real uranium wastewater;

[0053] Figure 28 For the PO x-Power consumption diagram of the CuP3 / CF integrated electrode in real uranium wastewater. Detailed implementation mode

[0054] The present invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it according to the description in the specification.

[0055] It should be understood that terms such as "having", "comprising" and "including" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0056] Example 1

[0057] This example provides a preparation method for a copper foam-based integrated electrode for electrochemical separation of uranium, including the following steps:

[0058] Step 1: Cut the copper foam into blocks with a width of 1 cm, a length of 2 cm, and a thickness of 0.2 cm, ultrasonically clean them with acetone, 0.5 M dilute hydrochloric acid, ethanol, and deionized water for 15 min respectively, and then put them in a vacuum oven at 60 °C for drying to obtain pretreated copper foam (CF).

[0059] Step 2: Dissolve 3.2 g of sodium hydroxide in 30 mL of deionized water, stir until completely dissolved, add 0.91 g of ammonium persulfate to the sodium hydroxide solution, stir until completely dissolved to obtain a mixed solution, immerse the pretreated copper foam in the above mixed solution, and keep it for 20 min. Then rinse it several times with deionized water to wash away the excess impurity ions on the material, and dry it in a vacuum drying oven at 60 °C to obtain Cu(OH)2 / CF.

[0060] Step 3: Prepare two small porcelain boats, add 0.3 g of sodium hypophosphite to one of them and place it upstream of the tube furnace. Load Cu(OH)2 / CF into the other small porcelain boat and place it downstream of the tube furnace. Keep it at 300 °C for 2 h, and set the heating rate to 2 °C / min. Name the obtained product CuP3 / CF. Prepare a 1% hydrogen peroxide solution, immerse CuP3 / CF in the solution, keep it for 20 min, and rinse it several times with deionized water after the reaction to obtain PO x -CuP3 / CF, that is, the copper foam-based integrated electrode is obtained.

[0061] The sample physical diagrams of the copper foam (CF), Cu(OH)2 / CF, CuP3 / CF and PO x -CuP3 / CF prepared in Example 1 are as Figure 1 shown.

[0062] Example 2

[0063] This example provides a preparation method for a copper foam-based integrated electrode for electrochemical separation of uranium, including the following steps:

[0064] Step 1: Cut the copper foam into blocks with a width of 1 cm, a length of 2 cm, and a thickness of 0.2 cm. Ultrasonically clean them with acetone, 0.5 M dilute hydrochloric acid, ethanol, and deionized water for 15 min respectively, and then put them into a vacuum oven at 60 °C for drying to obtain the pretreated copper foam (CF).

[0065] Step 2: Dissolve 3.2 g of sodium hydroxide in 30 mL of deionized water and stir until completely dissolved. Add 0.91 g of ammonium persulfate to the sodium hydroxide solution and stir until completely dissolved to obtain a mixed solution. Immerse the pretreated copper foam into the above mixed solution and keep it for 20 min. Then rinse it several times with deionized water to wash away the excess impurity ions on the material, and dry it in a vacuum drying oven at 60 °C to obtain Cu(OH)2 / CF.

[0066] Step 3: Prepare two small porcelain boats. Add 0.3 g of sodium hypophosphite to one of them and place it upstream of the tube furnace. Load Cu(OH)2 / CF into the other small porcelain boat and place it downstream of the tube furnace. Keep it at 300 °C for 2 h with a heating rate of 2 °C / min. Name the obtained product CuP3 / CF.

[0067] Put CuP3 / CF into a high-pressure reactor lined with polytetrafluoroethylene. Add 20 mL of 0.2 M thiourea solution as the sulfur source and 150 mL of ethanol / water mixture solvent. Carry out hydrothermal reaction at 180 °C for 4 h. After cooling, wash and dry it to obtain sulfur-doped CuP3 / CF. The volume ratio of ethanol to water in the ethanol / water mixed solvent is 1:1.

[0068] Mix the sulfur-doped CuP3 / CF with 2.0 g of urea, evacuate to below 1.2×10 -3 Pa, introduce Ar, heat it to 500 °C at a heating rate of 5 °C / min in an Ar atmosphere, keep it for 4 h, and cool it to room temperature to obtain sulfur- and nitrogen-doped CuP3 / CF.

[0069] Prepare 1% hydrogen peroxide solution. Immerse the sulfur- and nitrogen-doped CuP3 / CF into the hydrogen peroxide solution and keep it for 20 min. After the reaction, rinse it several times with deionized water to obtain sulfur- and nitrogen-doped PO x -CuP3 / CF.

[0070] Comparative Example 1

[0071] This comparative example provides a preparation method of a copper foam-based integrated electrode for electrochemical uranium separation, including the following steps:

[0072] Step 1: Cut the copper foam into blocks with a width of 1 cm, a length of 2 cm, and a thickness of 0.2 cm. Ultrasonically clean them with acetone, 0.5 M dilute hydrochloric acid, ethanol, and deionized water for 15 min respectively, and then place them in a 60 °C vacuum oven for drying to obtain pretreated copper foam (CF).

[0073] Step 2: Dissolve 3.2 g of sodium hydroxide in 30 mL of deionized water, stir until completely dissolved, add 0.91 g of ammonium persulfate to the sodium hydroxide solution, and stir until completely dissolved to obtain a mixed solution. Immerse the pretreated copper foam into the above mixed solution and keep it for 20 min. Then rinse it several times with deionized water to wash away the excess impurity ions on the material, and dry it in a 60 °C vacuum drying oven to obtain Cu(OH)2 / CF.

[0074] Step 3: Prepare two small porcelain boats. Add 0.3 g of sodium hypophosphite to one of them and place it upstream of the tube furnace. Load Cu(OH)2 / CF into the other small porcelain boat and place it downstream of the tube furnace. Keep it at 300 °C for 2 h, and set the heating rate to 2 °C / min. Name the obtained product CuP3 / CF.

[0075] Mix CuP3 / CF with 2.0 g of urea, evacuate to below 1.2×10 -3 Pa, introduce Ar, heat it to 500 °C at a heating rate of 5 °C / min in an Ar atmosphere, keep it for 4 h, and cool it to room temperature to obtain nitrogen-doped CuP3 / CF.

[0076] Prepare 1% hydrogen peroxide solution, immerse the nitrogen-doped CuP3 / CF into the hydrogen peroxide solution and keep it for 20 min. After the reaction, rinse it several times with deionized water to obtain nitrogen-doped PO x -CuP3 / CF.

[0077] Comparative Example 2

[0078] This comparative example provides a preparation method of a copper foam-based integrated electrode for electrochemical uranium separation, including the following steps:

[0079] Step 1: Cut the copper foam into blocks with a width of 1 cm, a length of 2 cm, and a thickness of 0.2 cm. Ultrasonically clean them with acetone, 0.5 M dilute hydrochloric acid, ethanol, and deionized water for 15 min respectively, and then place them in a 60 °C vacuum oven for drying to obtain pretreated copper foam (CF).

[0080] Step 2: Dissolve 3.2 g of sodium hydroxide in 30 mL of deionized water, stir until completely dissolved, add 0.91 g of ammonium persulfate to the sodium hydroxide solution, stir until completely dissolved to obtain a mixed solution, immerse the pretreated copper foam into the above mixed solution, and keep it for 20 min. Then rinse it several times with deionized water to wash away the excess impurity ions on the material, and dry it in a vacuum drying oven at 60 °C to obtain Cu(OH)2 / CF.

[0081] Step 3: Prepare two small porcelain boats, add 0.3 g of sodium hypophosphite to one of them and place it upstream of the tube furnace. Load Cu(OH)2 / CF into the other small porcelain boat and place it downstream of the tube furnace. Keep it at 300 °C for 2 h, and set the heating rate to 2 °C / min. The obtained product is named CuP3 / CF.

[0082] Put CuP3 / CF into a high-pressure reactor lined with polytetrafluoroethylene, add 20 mL of 0.2 M thiourea solution as the sulfur source and 150 mL of ethanol / water mixture solvent as the solvent; carry out hydrothermal reaction at 180 °C for 4 h, cool it, wash and dry it to obtain sulfur-doped CuP3 / CF. The volume ratio of ethanol to water in the ethanol / water mixed solvent is 1:1.

[0083] Prepare 1% hydrogen peroxide solution, immerse the sulfur-doped CuP3 / CF into the hydrogen peroxide solution, keep it for 20 min, and rinse it several times with deionized water after the reaction to obtain sulfur-doped PO x -CuP3 / CF.

[0084] The scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to systematically analyze each sample electrode in Example 1. The SEM characterization results ( Figure 2 ) show that the surface of the CuP3 / CF integrated electrode ( Figure 2 a) in it) is composed of a cluster structure composed of nanoparticles, while after oxidation treatment with low-concentration H2O2, the surface of the PO x -CuP3 / CF integrated electrode ( Figure 2 b) in it) forms an open network structure. This unique morphology significantly increases the specific surface area of the material and is beneficial to enhancing its binding ability with uranyl fluoride. The lattice analysis of the PO x -CuP3 / CF integrated electrode was carried out by high-resolution transmission electron microscope (HRTEM) (as shown in Figure 3 a), and the lattice plane spacing of 0.2 nm was observed, corresponding to the (300) crystal plane of CuP3. In addition, the energy-dispersive X-ray spectroscopy (EDS) element distribution map shows that the three elements of Cu, P, and O are evenly distributed on the surface of the PO x -CuP3 / CF integrated electrode ( Figure 3As shown in b), it further confirms the uniformity and structural consistency of the material.

[0085] X-ray diffraction (XRD) technology was used for its systematic characterization. The XRD pattern is as Figure 4 shown. The strong diffraction peaks observed at 43.31°, 50.45°, and 74.12° respectively correspond to the (111), (200), and (220) crystal planes of metallic Cu (PDF#85-1326), and these peaks originate from the copper foam substrate. In addition, the diffraction peaks detected at 35.85°, 38.90°, 41.38°, 44.87°, 45.96°, 47.07°, 53.25°, and 66.18° can be attributed to the (112), (022), (211), (300), (113), (122), (104), and (124) crystal planes of Cu3P (PDF#74-1067). The above analysis results indicate that the Cu3P phase was successfully synthesized on the copper foam substrate in Example 1. It should be noted that by comparing the XRD patterns before and after H2O2 oxidation, it was found that the phase structure of Cu3P did not change significantly, indicating that the oxidation treatment did not change the crystal structure of Cu3P.

[0086] X-ray photoelectron spectroscopy (XPS) technology was used for the systematic characterization of its elemental composition and chemical valence state changes. As Figure 5 shown, the characteristic peaks at 130.0 eV and 134.2 eV in the P 2p XPS spectrum respectively correspond to the P-Cu bond of Cu3P and the P-O bond of surface free PO4 3- . Cu3P / CF is for adsorbed PO4 3- , and the P coordination is saturated. While for PO x -Cu3P / CF, the P-O moves towards the lower binding energy direction, indicating the presence of the structure of PO x (X < 4), and this structure has unsaturated coordinated P atoms that can capture F to form monofluorophosphoric acid, difluorophosphoric acid, etc. In the Cu 2p XPS spectrum, the characteristic peaks at 933.4 eV and 953.2 eV can be attributed to Cu + 2p 3 / 2 and Cu + 2p 1 / 2 in Cu3P, while the characteristic peaks at 935.2 eV and 955.2 eV respectively correspond to Cu 2+ 2p 3 / 2 and Cu 2+ 2p 1 / 2 ( Figure 6 ). The analysis results show that the Cu in the Cu3P / CF integrated electrode mainly exists in the form of Cu + , and after H2O2 oxidation, part of the Cu + is oxidized to This valence state transformation is beneficial to the binding of phosphate radical PO x .

[0087] The surface functional groups of Cu3P / CF and PO x -Cu3P / CF integrated electrodes were analyzed by Fourier transform infrared spectroscopy (FTIR). As Figure 7 shown, the absorption peaks at 3419 cm -1 and 1630 cm -1 are attributed to the O-H bond vibration of adsorbed water on the material surface, while the absorption peaks at 1088 cm -1 and 1216 cm -1 correspond to the stretching vibrations of P-O bond and P=O bond respectively. The analysis results show that both Cu3P / CF and PO x -Cu3P / CF integrated electrodes exhibit characteristic absorption peaks of phosphate radical, and the phosphate signal intensity of PO x -Cu3P / CF is significantly enhanced. This result further confirms the successful introduction of bound PO x . In summary, the Cu-P-O / CF integrated electrode with bound phosphate was successfully synthesized in Example 1.

[0088] The electrochemically uranium extraction performance of the Cu-P-O / CF integrated electrode was studied using a three-electrode system of an electrochemical workstation. In this experiment, the CF, CuP3 / CF and Cu-P-O / CF integrated electrodes were used as the working electrode, the platinum wire electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. First, to understand the uranium separation ability of the materials, the linear sweep voltammetry (LSV) curves of CuP3 / CF and PO - -CuP3 / CF integrated electrodes were tested in a 50 mL fluorine-containing and uranium-containing solution (c0(U) = 100 mg / L, c(F x ) = 4 g / L, pH = 1). The results are as Figure 8 shown. The reduction potentials of CuP3 / CF and PO x -CuP3 / CF integrated electrodes for uranium are -0.6 V and -0.4 V respectively. The PO x -CuP3 / CF integrated electrode has a lower reduction potential, indicating that in the acidic fluorine-containing and uranium-containing solution, the PO x -CuP3 / CF integrated electrode is more likely to reduce hexavalent uranium to low-valent uranium.

[0089] Using the PO x -CuP3 / CF electrode as the working electrode, the platinum wire electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. In a 50 mL fluorine-containing and uranium-containing solution (c0(U) = 100 mg / L, c(F -) = 4 g / L, pH = 1), the uranium removal efficiency of the PO x -CuP3 / CF electrode was tested at -0.8 V, -1.0 V, -1.2 V and -1.4 V potentials. The results are as Figure 9 shown. After 105 min of electrochemically extracting uranium, the uranium removal efficiencies at -0.8 V to -1.4 V potentials were 71.13%, 85.55%, 97.4% and 95.24% respectively. At -0.8 V to -1.2 V voltages, the greater the voltage, the significantly higher the efficiency of electrochemically extracting uranium. However, when the voltage was further increased to -1.4 V, the uranium removal efficiency showed a downward trend, which might be due to the strong hydrogen evolution phenomenon in the acidic environment competing with the uranium reduction reaction. Therefore, -1.2 V was selected as the optimal potential for electrochemically extracting uranium in simulated acidic uranium wastewater.

[0090] Among them, the PO x -CuP3 / CF prepared in Example 1, the sulfur and nitrogen-doped PO x -CuP3 / CF prepared in Example 2, and the integrated electrodes of Comparative Example 1 and Comparative Example 2, after 105 min of electrochemically extracting uranium, the uranium removal efficiencies at -0.8 V to -1.4 V potentials are shown in Table 1:

[0091] Table 1 Comparison of uranium removal rates of Cu-P-O / CF integrated electrodes in Example 1 and Example 2

[0092]

[0093]

[0094] As can be seen from the above table, after 105 min of electrochemically extracting uranium, the uranium removal efficiency of the sulfur and nitrogen-doped PO x -CuP3 / CF prepared in Example 2 was higher than that in Example 1 at each potential, and all reached over 94%.

[0095] At a potential of -1.2 V, the electrochemically extracting uranium efficiencies of the CF, CuP3 / CF and PO x -CuP3 / CF integrated electrodes were compared. The results are as Figure 10 shown. The removal efficiencies of the CF, CuP3 / CF and PO x -CuP3 / CF integrated electrodes were 58.0%, 81.3% and 97.4% respectively. The results showed that the PO x -CuP3 / CF integrated electrode had the highest uranium removal efficiency. In the constant voltage mode, the i-t changes of the CF, CuP3 / CF and PO x -CuP3 / CF integrated electrodes during the electrochemically extracting uranium process are as Figure 11As shown. During the reaction, there is always such a relationship: I(PO x -CuP3 / CF) > I(CuP3 / CF) > I(CF). This order of current magnitude is completely consistent with the trend of uranium removal efficiency. This phenomenon may be related to the number of active sites on the electrode surface: PO x -CuP3 / CF electrode exposes the most active sites due to its surface modification, followed by CuP3 / CF, and the unmodified CF electrode has the fewest active sites. The above results fully demonstrate the significant advantage of the PO x -CuP3 / CF composite electrode in uranium extraction.

[0096] The first-order kinetic model was used to study the kinetic process of electrochemical reduction of U(VI) by CF, CuP3 / CF, and PO x -CuP3 / CF integrated electrodes. The results are as Figure 12 shown in Table 2. The rate constants of CF, CuP3 / CF, and PO x -CuP3 / CF integrated electrodes are 9.89×10 -3 min -1 , 1.69×10 -2 min -1 , and 3.83×10 -2 min -1 respectively. It can be found that the rate constant of the PO x -CuP3 / CF integrated electrode is significantly higher than that of the other two electrocatalysts.

[0097] Table 2 Kinetic data of U(VI) separation for CF, CuP3 / CF, and PO x -CuP3 / CF integrated electrode sheets

[0098] Sample <![CDATA[k(min -1 )]]> <![CDATA[R 2 <!-- 7 -->]]> CF <![CDATA[9.89×10 -3 > 0.954 <![CDATA[CuP3 / CF]]> <![CDATA[1.69×10 -2 > 0.997 <![CDATA[PO x -CuP3 / CF]]> <![CDATA[3.83×10 -2 > 0.994

[0099] As Figure 13 shown, after 10 extraction-desorption processes, the uranium removal rate is still as high as 95%, indicating that the PO x -CuP3 / CF integrated electrode has excellent cycle stability in the electrochemical uranium extraction process. In real nuclear wastewater, there are often a large number of interfering ions. To explore their influence on uranium separation, the present invention evaluated the electrochemical uranium removal efficiency of several acidic uranium solutions with single-ion coexistence. In an acidic uranium-containing fluoride solution (c0(U) = 100 mg / L, c(F - ) = 4 g / L, pH = 1), C2O4 2- , NO3 - , Cl - (2 g / L), and Ni 2+ , Cu 2+, Fe 3+ , Cr 3+ , Mg 2+ (20 mg / L), the voltage was set at -1.2 V. The results are as Figure 14 shown, the removal efficiency of uranium by the PO x -CuP3 / CF integrated electrode was above 95%, indicating that the PO x -CuP3 / CF integrated electrode had excellent anti-interference ability, and its influence on the electrochemical separation of uranium could be ignored. In addition, as Figure 15 shown, even when the F:U ratio reached 300:1, the removal efficiency of uranium by the PO x -CuP3 / CF integrated electrode could still reach above 95.2%.

[0100] The fluoride ion concentration was maintained at 4 g / L, and the removal efficiency at uranium concentrations of 100 - 500 mg / L was tested respectively. The results are as Figure 16 shown. After electrochemical extraction for a period of time, the removal efficiency of uranium could reach above 95%. According to the time required for the uranium removal efficiency to reach above 95%, the uranium extraction rate of the PO x -CuP3 / CF integrated electrode in uranium solutions with different initial concentrations was calculated. The results showed that the electrochemical uranium extraction rate increased with the increase of uranium concentration. This might be due to the increase of current efficiency with the increase of uranium concentration.

[0101] To reveal the mechanism of electrochemical separation of uranium by the PO x -CuP3 / CF integrated electrode, the electrochemical separation products were characterized and analyzed. First, the morphology and structure of the uranium products were studied by electron microscopy. The SEM results of the PO x -CuP3 / CF integrated electrode are as Figure 17 shown in a of Figure 17 . There were particle depositions on the electrode surface, which might be uranium species. The TEM results are as Figure 17 shown in b of Figure 17 , showing particles consistent with the SEM results. The lattice analysis of the uranium products after electrochemical uranium extraction was carried out by HRTEM technology. The results are as Figure 17 shown in c of Figure 17 . The lattice fringes appearing at a spacing of 0.20 nm belonged to the (300) crystal plane of Cu3P, and the lattice fringes appearing at a spacing of 0.34 nm belonged to the (111) crystal plane of (K2UF6) 1.333 . In addition, to further clarify the elemental composition of the deposits, through EDS energy spectrum analysis, it was found that the U, F, and K elements were evenly distributed in the products after uranium extraction ( Figure 17 shown in d of Figure 17 ), indicating that uranium products composed of U, F, and K three elements were formed on the surface of the PO x -CuP3 / CF integrated electrode after electrochemical uranium extraction.

[0102] To clarify the PO x - The types of uranium products generated by the CuP3 / CF integrated electrode during the electrochemical uranium extraction process were analyzed by X-ray diffraction (XRD) for the electrode slices after uranium extraction. As Figure 18 shown, a series of strong diffraction peaks were observed at 25.93°, 30.03°, 42.98°, 50.89° and 53.33° in the XRD pattern, and these peaks corresponded to the (111), (200), (220), (222) crystal planes of (K2UF6) 1.333 (a special form of UF4·2KF, PDF#75-2017). In addition, the diffraction peaks appearing at 29.58°, 36.44°, 42.33°, 61.40° and 73.56° could be attributed to the (111), (200), (220), (311) crystal planes of Cu2O (PDF#78-2076). At the same time, the diffraction peaks detected at 35.85°, 38.90°, 41.38°, 44.87° and 45.96° matched the (112), (022), (211), (300), (113) crystal planes of Cu3P (PDF#74-1067). In addition, the strong diffraction peaks observed at 43.31°, 50.45° and 74.12° were attributed to the substrate foam copper (CF). Based on the XRD analysis results, it can be confirmed that during the electrochemical uranium extraction process, in addition to the substrate CF and Cu3P, a new phase (K2UF6) 1.333 and Cu2O were formed. To further verify the chemical structure of the reaction products, Fourier transform infrared spectroscopy (FTIR) analysis was carried out on the products after uranium extraction. As Figure 19 shown, PO x - A significant infrared absorption peak appeared at 623.8 cm-1 in the products after uranium extraction of the CuP3 / CF integrated electrode, and this peak could be attributed to the characteristic vibration mode of the U-F bond in (K2UF6) 1.333 . This result was mutually confirmed with the XRD analysis, further verifying the formation of (K2UF6) 1.333 . In summary, the XRD and FTIR analyses jointly revealed the main products and their structural characteristics generated by the PO x - CuP3 / CF integrated electrode during the electrochemical uranium extraction process.

[0103] The surface elemental composition and chemical valence states of (K2UF6) 1.333 were systematically analyzed by X-ray photoelectron spectroscopy (XPS) technology. Figure 20 Shows the PO before and after uranium extraction x- XPS survey spectrum of the CuP3 / CF integrated electrode shows that significant K, U, and F characteristic signals appear within the binding energy range after uranium extraction, and its elemental composition is highly consistent with the results of energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Further analysis of the U 4f XPS spectrum reveals that the binding energy peaks at 380.6 eV and 391.4 eV correspond to U 4f 7 / 2 and U 4f 5 / 2 orbitals ( Figure 21 ), while the peaks at 382.0 eV and 392.8 eV are attributed to the corresponding orbitals of U(VI). This indicates that uranium mainly exists in the tetravalent state in the post-reaction uranium product (K2UF6) 1.333 , confirming that the PO x -CuP3 / CF integrated electrode successfully reduces hexavalent uranium to tetravalent uranium and forms a stable solid crystal. In addition, an obvious characteristic peak is observed at 685.2 eV in the F 1s XPS spectrum ( Figure 22 ), which can be attributed to the contribution of the F-U bond in (K2UF6) 1.333 , further verifying the formation of (K2UF6) 1.333 .

[0104] To quantify the elemental composition of the product, inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the contents of alkali metal K and heavy metal U ( Figure 23 ). The results show that the experimentally determined values of K and U in (K2UF6) 1.333 are 16.2% and 83.8% respectively, showing a certain deviation from the theoretical calculated values (K: 24.6%, U: 75.4%). The proportion of uranium in the experimental value is slightly higher than the theoretical value, which may be due to the presence of a small amount of adsorbed UO2F x species remaining in the product. In addition, ion chromatography analysis technology was used to test the change in the concentration of fluoride ions in the solution before and after electrochemically extracting uranium. After 105 min of the electrochemically extracting uranium process, the concentration of fluoride ions in the solution decreased by 0.49 g / L ( Figure 24 ). In summary, the results of XPS, ICP-MS, and ion chromatography analysis jointly confirm the high efficiency of the PO x -CuP3 / CF integrated electrode in the uranium separation process and its promoting effect on the formation of (K2UF6) 1.333 .

[0105] As can be seen above, the Cu-P-O / CF integrated electrode has excellent electrochemical uranium separation performance in simulated acidic uranium-containing and fluoride-containing solutions. To further verify its potential in practical applications, the uranium separation performance of the Cu-P-O / CF integrated electrode for real acidic uranium-containing and fluoride-containing wastewater was systematically evaluated. The real wastewater used in this study contained 0.4 g / L U, 4 g / L F - , 2 g / L NO3 - and 2 g / L NH4 + . The peak mass concentration of metal cations was 0.02 g / L, and the solution pH was 1( Figure 25 ). In the electrochemical uranium separation experiment of 100 mL of real wastewater, a two-electrode system was used, and the working voltage was set at -5 V. Among them, the Cu-P-O / CF integrated electrode was used as the working electrode, and the platinum wire electrode was used as the counter electrode. The experimental results showed that after 180 min of electrochemical extraction, the removal rate of uranium by the Cu-P-O / CF integrated electrode was as high as 96.3%( Figure 26 ). In addition, the deposition of gray-green uranium products was observed on the electrode surface after electrochemical uranium extraction. To evaluate the economic feasibility of the Cu-P-O / CF integrated electrode in practical applications, a quantitative analysis of the power consumption during the electrochemical uranium extraction process was carried out. As Figure 27 and Figure 28 shown, the current was stably maintained at about 60 mA during the experiment. According to the electric energy calculation formula: electric energy (W) = voltage (U) * current (I) * time (t), it was calculated that the electric energy consumed for each treatment of 100 mL of this acidic uranium-containing and fluoride-containing wastewater was 1.13 W·h. This result confirmed that the Cu-P-O / CF integrated electrode had low energy consumption while achieving efficient uranium separation, providing an important economic basis for its application in practical wastewater treatment.

[0106] The equipment quantities and treatment scales described here are used to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be apparent to those skilled in the art.

[0107] Although the embodiments of the present invention have been disclosed above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional 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 the illustrated and described examples here.

Claims

1. A preparation method of a copper foam-based integrated electrode for electrochemical uranium separation, characterized in that, It includes the following steps: Step 1: Pretreat the copper foam; Step 2: Use sodium hydroxide, ammonium persulfate, and the pretreated copper foam as raw materials to prepare Cu(OH)2 / CF; Step 3: Prepare CuP3 / CF by high-temperature calcination in a tubular furnace. Immerse CuP3 / CF in a hydrogen peroxide solution for a period of time and rinse it with deionized water multiple times to obtain PO x -CuP3 / CF, that is, the integrated copper foam-based electrode is obtained.

2. The preparation method of the copper foam-based integrated electrode for electrochemical uranium separation according to claim 1, characterized in that, In the above Step 1, the specific method for pretreating the copper foam includes: cutting the copper foam into blocks of 1 cm×2 cm×0.2 cm, ultrasonically treating them with acetone, 0.5 M dilute hydrochloric acid, ethanol, and deionized water for 10 - 20 min respectively, and then drying them in a vacuum oven at 50 - 70 °C for later use.

3. The preparation method of the copper foam-based integrated electrode for electrochemical uranium separation according to claim 1, characterized in that, In the above Step 2, the specific method for preparing Cu(OH)2 / CF includes: dissolving sodium hydroxide in deionized water, stirring until completely dissolved, adding ammonium persulfate to the sodium hydroxide solution, stirring until completely dissolved to obtain a mixed solution, immersing the pretreated copper foam in the mixed solution for 20 - 30 min; then repeatedly rinsing with deionized water several times to wash away the excess impurity ions, and drying in a vacuum drying oven at 50 - 70 °C to obtain Cu(OH)2 / CF.

4. The preparation method of the copper foam-based integrated electrode for electrochemical uranium separation according to claim 3, characterized in that The dosage ratio of sodium hydroxide, deionized water, and ammonium persulfate is 3.0 - 3.5 g:30 mL:0.9 - 1.0 g.

5. The preparation method of the copper foam-based integrated electrode for electrochemical uranium separation according to claim 1, characterized in that, In the above Step 3, the specific method for preparing CuP3 / CF by high-temperature calcination in a tubular furnace includes: preparing two small porcelain boats, adding sodium hypophosphite to one of the small porcelain boats and placing it upstream in the tubular furnace; loading Cu(OH)2 / CF into the other small porcelain boat and placing it downstream in the tubular furnace; calcining at a certain heating rate to obtain CuP3 / CF.

6. The preparation method of the copper foam-based integrated electrode for electrochemical uranium separation according to claim 5, characterized in that, The dosage ratio of sodium hypophosphite to ammonium persulfate in Step 2 is 0.3:0.9 - 1.

0.

7. The preparation method of the copper foam-based integrated electrode for electrochemical uranium separation according to claim 5, characterized in that, The calcination temperature is 300 - 400 °C, the calcination time is 2 - 3 h, and the heating rate is 2 °C / min.

8. The preparation method of the copper foam-based integrated electrode for electrochemical uranium separation according to claim 1, characterized in that, In the above Step 3, the concentration of the hydrogen peroxide solution is 1 - 3 wt%, and the immersion time of CuP3 / CF in the hydrogen peroxide solution is 10 - 30 min.

9. Application of a copper foam-based integrated electrode for electrochemical uranium separation, wherein the copper foam-based integrated electrode is prepared by the preparation method of the copper foam-based integrated electrode for electrochemical uranium separation according to any one of claims 1-8, characterized in that The copper foam-based integrated electrode is applied to the electrochemical separation of uranium in a strong acid fluorine-containing system.

10. The application of the copper foam-based integrated electrode according to claim 9, characterized in that, The simulation method for applying the copper foam-based integrated electrode to the electrochemical separation of uranium in a strong acid fluorine-containing system includes: using the copper foam-based integrated electrode as the working electrode, Ag / AgCl as the reference electrode, and a platinum wire as the counter electrode, respectively dissolving UO2(NO3)2·6H2O and KF·2H2O as the uranium source and the fluorine source in deionized water to prepare a fluorine-containing and uranium-containing solution, and conducting an electrochemical separation experiment.

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