Preparation method of iron-doped tungsten trioxide composite electrode and application thereof in treatment of uranium wastewater

Abstract

The application provides a preparation method of an iron-doped tungsten trioxide composite electrode and application of the iron-doped tungsten trioxide composite electrode in treatment of uranium wastewater, and belongs to the technical field of electrochemical wastewater treatment. The application takes foamed copper as a three-dimensional conductive framework, is favorable for improving electron transmission efficiency and mass transfer performance, in-situ grows an iron-doped tungsten trioxide active layer on the surface of the foamed copper through a hydrothermal method, and avoids problems of large interface contact resistance and easy peeling of the active layer caused by the traditional powder electrode relying on a binder for fixation. The application dopes WO3 with iron elements, can effectively regulate local electron structure of WO3, and thus enhances adsorption activation and reduction removal capacity of U(VI). The preparation method provided by the application is simple in operation and low in cost, the obtained composite electrode has good conductivity and interface bonding state, can promote interface reaction of U(VI) on the electrode surface under the action of an applied bias, realizes effective removal and fixation of U(VI) in uranium-containing wastewater, and is suitable for further popularization and application.

Description

Technical Field

[0001] This invention relates to the field of electrochemical wastewater treatment technology, specifically to a method for preparing an iron-doped tungsten trioxide composite electrode and its application in uranium wastewater treatment. Background Technology

[0002] With the continuous development of nuclear energy development, uranium mining, nuclear fuel cycle, and related industrial activities, the problem of uranium-containing wastewater discharge has become increasingly prominent. Hexavalent uranium (U(VI)) in water bodies typically exists as uranyl ions (UO2). 2+ Uranium exists in forms such as VI and VII, exhibiting high solubility and strong mobility, easily spreading in groundwater and surface water, posing potential hazards to the ecological environment and human health. In contrast, tetravalent uranium (U(IV)) has low solubility and is more easily fixed in the form of precipitation. Therefore, reducing U(VI) to U(IV) is an important way to achieve uranium pollution control and resource recovery.

[0003] Existing technologies for treating uranium-containing wastewater mainly include chemical precipitation, adsorption, ion exchange, photocatalysis, and electrochemical reduction. Among these, electrochemical reduction has advantages such as controllable reaction conditions, no need for additional chemical reducing agents, and ease of in-situ remediation and uranium resource recovery, making it a promising candidate for treating low-concentration uranium-containing wastewater.

[0004] Tungsten trioxide (WO3) exhibits good chemical stability and has potential applications in electrochemical wastewater treatment. However, existing WO3-based electrodes still suffer from insufficient conductivity, limited interfacial active sites, and low U(VI) reduction efficiency, which restricts their further application. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing an iron-doped tungsten trioxide composite electrode and its application in uranium wastewater treatment. The iron-doped tungsten trioxide composite electrode prepared by this invention has good conductivity, interfacial bonding state, and abundant interfacial active sites, which can achieve efficient reduction and stable fixation of U(VI) in uranium wastewater treatment.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing an iron-doped tungsten trioxide composite electrode, comprising the following steps: A precursor solution is obtained by mixing tungsten source, iron source, glucose, dopamine, ascorbic acid and water. The copper foam was placed in the precursor solution and subjected to a hydrothermal reaction. The copper foam composite material after the hydrothermal reaction was taken out and subjected to heat treatment to obtain an iron-doped tungsten trioxide composite electrode.

[0007] Preferably, the tungsten source includes sodium tungstate, and the iron source includes one or more of ferric nitrate, ferric sulfate, ferric chloride, and ferric citrate. The mass of Fe in the iron source is 1 to 9% of the mass of the tungsten source.

[0008] Preferably, the mass ratio of glucose, dopamine, and ascorbic acid is (0.1~0.6):(0.1~0.4):(0.05~0.2). The mass ratio of the tungsten source to glucose is (0.4~2):(0.2~0.6).

[0009] Preferably, the pore size of the copper foam is 10~150 ppi, the porosity is 60~99%, and the thickness of the copper foam is 0.1~5 mm.

[0010] Preferably, before the hydrothermal reaction, the foamed copper is further subjected to pretreatment, which includes ultrasonic cleaning and acid pickling activation performed sequentially. The activating solution used for pickling and activation is a dilute nitric acid solution, and the pickling and activation time is 5~30 min.

[0011] Preferably, the temperature of the hydrothermal reaction is 80~200℃, and the holding time is 6~18 h; The heat treatment temperature is 60~300℃, and the holding time is 1~3h.

[0012] The present invention provides an iron-doped tungsten trioxide composite electrode prepared by the above preparation method, comprising a copper foam substrate and an iron-doped tungsten trioxide active layer grown in situ on the surface of the copper foam substrate.

[0013] This invention provides the application of the above-mentioned iron-doped tungsten trioxide composite electrode in uranium wastewater treatment.

[0014] Preferably, the method of application includes the following steps: An iron-doped tungsten trioxide composite electrode was placed in uranium-containing wastewater and used as the cathode. An electrochemical reduction reaction was carried out under an applied bias voltage to remove hexavalent uranium from the wastewater.

[0015] Preferably, the operating potential of the cathode is 0 to -2.0V; The pH value of the uranium-containing wastewater is 2 to 7.

[0016] This invention provides a method for preparing an iron-doped tungsten trioxide (Fe-WO3) composite electrode, comprising the following steps: mixing a tungsten source, an iron source, glucose, dopamine, ascorbic acid, and water to obtain a precursor solution; placing copper foam in the precursor solution and performing a hydrothermal reaction; removing the hydrothermally reacted copper foam composite material and performing heat treatment to obtain the iron-doped tungsten trioxide (Fe-WO3) composite electrode. This invention uses copper foam as a three-dimensional conductive framework, which is beneficial for improving electron transport efficiency and mass transfer performance. Copper foam, as a three-dimensional conductive substrate, provides continuous electron transport channels and a large reaction interface, which is beneficial for the uniform loading of Fe-WO3 and the exposure of active sites. Fe-WO3, as a functional active layer, can enhance the adsorption and enrichment of U(VI) and its electrochemical reduction capability. The close combination of these two components reduces interfacial charge transport resistance, accelerates electron transfer from copper foam to the Fe-WO3 surface, thereby promoting the reduction and deposition of U(VI) on the electrode surface and improving the removal rate and efficiency. This invention utilizes a hydrothermal method to grow an iron-doped tungsten trioxide active layer in situ on the surface of WO3, avoiding the problems of high interfacial contact resistance and easy detachment of the active layer caused by the reliance on binders in traditional powder electrodes. By doping WO3 with iron, this invention effectively modulates its local electronic structure, thereby enhancing the adsorption, activation, reduction, and removal capabilities of U(VI). The hydrothermal growth is assisted by glucose, dopamine, and ascorbic acid. Glucose regulates crystal growth and improves material dispersibility; dopamine facilitates metal ion complexation and enhances the adhesion between the active layer and the copper foam; ascorbic acid, as a mild reducing agent, regulates the reaction environment and promotes the formation of defects or oxygen vacancies. The synergistic effect of these three agents facilitates the construction of a stable and highly active Fe-WO3 / copper foam composite electrode.

[0017] The preparation method provided by this invention is simple to operate and low in cost. The resulting composite electrode has good conductivity and interfacial bonding, and can promote the interfacial reaction of U(VI) on the electrode surface under an applied bias voltage, thereby achieving effective removal and fixation of U(VI) in uranium-containing wastewater, making it suitable for further application. The results of the examples show that the composite electrode obtained by this invention exhibits good U(VI) removal capacity over a wide range of initial uranium concentrations, with a removal rate >90%, demonstrating good applicability. Attached Figure Description

[0018] Figure 1 The XRD pattern of the 5wt% Fe-doped WO3 composite electrode prepared in Example 3; Figure 2 The image shows a SEM image of 5 wt% iron-doped tungsten trioxide obtained in Example 3. Figure 3 The effect of samples prepared at different hydrothermal temperatures on the U(VI) removal rate is shown in the figure. Figure 4 The graph shows the removal effect of U(VI) on samples with different Fe contents; Figure 5 The graph shows the removal effect of U(VI) under different initial pH conditions; Figure 6 The image shows the removal effect of U(VI) under different applied bias voltage conditions. Detailed Implementation

[0019] This invention provides a method for preparing an iron-doped tungsten trioxide composite electrode, comprising the following steps: A precursor solution is obtained by mixing tungsten source, iron source, glucose, dopamine, ascorbic acid and water. The copper foam was placed in the precursor solution and subjected to a hydrothermal reaction. The copper foam composite material after the hydrothermal reaction was taken out and subjected to heat treatment to obtain an iron-doped tungsten trioxide composite electrode.

[0020] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0021] This invention mixes a tungsten source, an iron source, glucose, dopamine, ascorbic acid, and water to obtain a precursor solution. In this invention, the tungsten source preferably includes sodium tungstate, and the iron source preferably includes one or more of ferric nitrate, ferric sulfate, ferric chloride, and ferric citrate, more preferably ferric nitrate nonahydrate. In this invention, the mass of Fe in the iron source is preferably 1-9% of the mass of the tungsten source, more preferably 3-7%, and even more preferably 5%. In this invention, the mass ratio of glucose, dopamine, and ascorbic acid is preferably (0.1-0.6):(0.1-0.4):(0.05-0.2), more preferably (0.2-0.5):(0.2-0.3):(0.1-0.15), and even more preferably 0.43:0.3:0.1.

[0022] In this invention, the preferred mass ratio of the tungsten source to glucose is (0.4~2):(0.2~0.6), more preferably (0.5~1.5):(0.3~0.5), and even more preferably 1.2:0.43. In this invention, the water is preferably deionized water, and the preferred mass-to-volume ratio of the tungsten source to water is 0.4~1.2 g:80 mL, more preferably 0.6~1 g:80 mL. This invention does not have special requirements for the mixing method; any mixing method well known to those skilled in the art can be used, such as stirring.

[0023] After obtaining the precursor solution, copper foam is placed in the precursor solution for a hydrothermal reaction. The resulting copper foam composite material is then removed and heat-treated to obtain an iron-doped tungsten trioxide composite electrode. In this invention, the pore size of the copper foam is preferably 10-150 ppi, more preferably 30-130 ppi, and even more preferably 50-100 ppi; the porosity is preferably 60-99%, more preferably 70-95%, and even more preferably 80-90%; the thickness of the copper foam is preferably 0.1-5 mm, more preferably 1.5 mm. Before the hydrothermal reaction, this invention preferably includes a pretreatment of the copper foam, which includes sequential ultrasonic cleaning and acid washing activation. In this invention, the cleaning reagents used for ultrasonic cleaning are preferably acetone, anhydrous ethanol, and deionized water, respectively; the ultrasonic cleaning power is preferably 100-300 W, more preferably 200 W; and the ultrasonic cleaning time for each cleaning reagent is preferably 10 min. In this invention, the activating solution used for acid pickling and activation is a dilute nitric acid solution, preferably with a mass fraction of 5%, and the acid pickling and activation time is 10 minutes. After acid pickling and activation, the present invention preferably performs water washing and drying, and the drying temperature is preferably 60°C.

[0024] In this invention, the hydrothermal reaction is preferably carried out in a hydrothermal reactor, the temperature of the hydrothermal reaction is preferably 80~200℃, more preferably 150~200℃, and the holding time is preferably 6~18 h, more preferably 8~15 h, and even more preferably 10~12 h. During the hydrothermal reaction, an iron-doped tungsten trioxide active layer grows in situ on the surface of the copper foam substrate.

[0025] After the hydrothermal reaction, the present invention preferably cools the resulting hydrothermal reaction solution to room temperature, removes the foamed copper, and washes and dries it. In the present invention, the washing reagent used is preferably anhydrous ethanol and water, the drying temperature is preferably 60°C, and the drying time is preferably 2 hours.

[0026] Following the hydrothermal reaction, the present invention performs heat treatment on the resulting copper foam composite material. The preferred atmosphere for heat treatment is air, the preferred temperature is 60-300°C, more preferably 100-200°C, the preferred holding time is 1-3 hours, more preferably 2 hours, and the preferred heating rate to the heat treatment temperature is 10°C / min. Through this heat treatment, the present invention promotes the dehydration, solidification, and crystallization stabilization of the iron-doped tungsten trioxide active layer, enhances the interfacial bonding between the active layer and the copper foam substrate, and removes residual organic matter, thereby improving electrode stability and reactivity.

[0027] This invention provides an iron-doped tungsten trioxide composite electrode prepared by the above-described method, comprising a copper foam substrate and an iron-doped tungsten trioxide active layer grown in situ on the surface of the copper foam substrate. In this invention, the thickness of the copper foam substrate is preferably 0.1–5 mm, more preferably 1–3 mm, and even more preferably 1.5 mm; the iron doping amount in the iron-doped tungsten trioxide active layer is preferably 1–9 wt%, more preferably 2–8 wt%, and even more preferably 5 wt%. In this invention, the iron-doped tungsten trioxide composite electrode has a porous structure, with a pore size preferably 3–5 nm, more preferably 3.41 nm.

[0028] This invention provides the application of the above-mentioned iron-doped tungsten trioxide composite electrode in the treatment of uranium wastewater. In this invention, the uranium in the uranium wastewater is hexavalent uranium (U(VI)).

[0029] In this invention, the method of application includes the following steps: An iron-doped tungsten trioxide composite electrode was placed in uranium-containing wastewater and used as the cathode. An electrochemical reduction reaction was carried out under an applied bias voltage to remove hexavalent uranium from the wastewater.

[0030] In this invention, the U(VI) concentration in the uranium-containing wastewater is preferably 5-300 mg / L, more preferably 20-100 mg / L, and even more preferably 20 mg / L. In this invention, the pH value of the uranium-containing wastewater is preferably 2-7, more preferably 3-6, and even more preferably 4. This invention preferably uses a 5% dilute nitric acid solution and a 1-2 mol / L sodium hydroxide solution to adjust the pH value of the uranium-containing wastewater.

[0031] In this invention, the anode of the electrochemical reaction is preferably a titanium sheet. In this invention, the operating potential of the cathode is preferably 0 to -2.0V, more preferably -0.1V. In this invention, the time of the electrochemical reduction reaction is preferably 5 to 90 min, more preferably 10 to 60 min, and even more preferably 20 to 40 min.

[0032] In this invention, the reaction process of the electrochemical reduction reaction is shown in Formula 1 and Formula 2: The electrochemical reaction process involved in this application is as follows: UO2 2+ +2e - →UO2 Formula 1; 2H₂O→O₂+4H + +4e - Equation 2.

[0033] The following detailed description, in conjunction with embodiments, illustrates the preparation method of the iron-doped tungsten trioxide composite electrode provided by the present invention and its application in uranium wastewater treatment. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1 A method for preparing an iron-doped tungsten trioxide composite electrode comprises the following steps: (a) Cut the foamed copper into 20mm×20mm×1.5mm pieces, and place them in acetone, anhydrous ethanol and deionized water for ultrasonic cleaning in sequence. The power is 150W and each cleaning lasts for 10 minutes. Then, place the foamed copper in dilute nitric acid solution for activation treatment for 10 minutes. After taking it out, wash it with deionized water and dry it at 60℃ for later use to obtain pretreated foamed copper. (ii) Dissolve 1.2g of sodium tungstate in 80mL of deionized water and stir to dissolve, to obtain mixed solution A; add ferric nitrate nonahydrate (0.087g) at a mass fraction of Fe relative to W precursor of 1wt%, and then add 0.43g of glucose, 0.3g of dopamine and 0.1g of ascorbic acid to solution A in sequence, and continue stirring to obtain a homogeneous precursor solution; (iii) The pretreated copper foam was placed in the above mixed reaction solution, transferred to a reaction vessel, heated at 200°C for 12 hours, cooled to room temperature, the sample was taken out, washed repeatedly with anhydrous ethanol and deionized water, dried at 60°C for 2 hours, and then heat-treated at 200°C for 2 hours in air atmosphere to obtain iron-doped tungsten trioxide composite electrode.

[0035] Examples 2-5 The difference between Examples 2-5 and Example 1 is that the mass fraction of Fe relative to the W precursor in step (ii) is 3wt% (Example 2), 5wt% (Example 3), 7wt% (Example 4) and 9wt% (Example 5), respectively. The remaining steps are the same as in Example 1 and will not be repeated here.

[0036] The 5wt% Fe-doped WO3 composite electrode prepared in Example 3 was characterized by X-ray diffraction, and the results are shown in the figure. Figure 1 .Depend on Figure 1 It can be seen that the sample has the main characteristic diffraction peaks of WO3, indicating that the obtained product forms a tungsten trioxide main crystalline phase; at the same time, Fe is also introduced into the electrode, indicating that the obtained product forms Fe-doped tungsten trioxide. The results show that the method of the present invention can form an iron-doped tungsten trioxide active layer on the surface of a copper foam substrate.

[0037] The SEM image of 5 wt% iron-doped tungsten trioxide obtained in Example 3 is shown below. Figure 2 As shown, by Figure 2It can be seen that the Fe-WO3 active material forms a sheet-like or layered interlaced structure composed of stacked nanosheets and particles, which can provide more exposed reactive sites, facilitating the adsorption of U(VI) on the electrode surface. Simultaneously, the open three-dimensional porous structure promotes electrolyte penetration and mass transfer, shortens ion diffusion paths, and helps improve interfacial electron transport efficiency. Therefore, the 5 wt% Fe-WO3 / copper foam composite electrode provides favorable conditions for the efficient electrochemical removal of U(VI) structurally.

[0038] Examples 6-8 The difference between Examples 6-8 and Example 1 is that the hydrothermal reaction temperatures in step (iii) are 80℃ (Example 6), 120℃ (Example 7), and 160℃ (Example 8), respectively. The remaining steps are the same as in Example 1 and will not be repeated here.

[0039] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that ferric nitrate nonahydrate is not added in step (ii). The remaining steps are the same as in Example 1 and will not be repeated here.

[0040] Comparative Examples 2-4 Compared with Example 1, the amounts of glucose, dopamine, and ascorbic acid were modified to 0g, 0.1g, 0.2g (Comparative Example 2), 0.6g, 0g, 0.1g (Comparative Example 3), 0.6g, 0.1g, and 0g (Comparative Example 4). The remaining steps were the same as in Example 1 and will not be repeated here.

[0041] Comparative Examples 5-7 Compared with Example 1, the dosages of glucose, dopamine, and ascorbic acid were modified to 1.2g, 0.6g, 0.3g (Comparative Example 5), 1.5g, 0.7g, 0.4g (Comparative Example 6), 0.43g, 0.5g, and 0.3g (Comparative Example 7), respectively. The remaining steps were the same as in Example 1 and will not be repeated here.

[0042] Test Example 1 The electrodes obtained in Examples 1, 6-8 were used to treat uranium (VI)-containing wastewater with a hexavalent uranium solution concentration of 20 mg / L and a pH of 5. Electrochemical treatment systems were constructed using the aforementioned electrodes as cathodes and titanium sheets as anodes, and a -0.1V external bias voltage was applied to initiate the reaction. The U(VI) removal performance was then tested.

[0043] After the experiment, the residual concentration of U(VI) in the solution was measured using a UV spectrophotometer, and the removal rate was calculated. The results are recorded in Table 1, and plotted accordingly. Figure 3 .

[0044] Table 1. Removal rate of U(VI) solution by samples prepared at different hydrothermal temperatures

[0045] From Table 1 and Figure 3 It can be seen that the removal capacity of the samples for U(VI) increases with increasing hydrothermal temperature, with the samples prepared at 200℃ showing the best performance. This indicates that a suitable hydrothermal temperature is conducive to the formation of an active layer on the surface of the copper foam, thereby improving the U(VI) removal capacity.

[0046] Test Example 2 Following the method described in Test Example 1, the U(VI) removal performance of samples with different Fe contents prepared in Comparative Example 1 and Examples 1-5 was tested. The concentration of U(VI) in the solution was measured at regular intervals during the test, and the results are recorded in Table 2. Based on these results, a plot was drawn. Figure 4 .

[0047] Table 2. Removal effect of samples with different Fe contents on U(VI)

[0048] From Table 2 and Figure 4 It can be seen that samples with different Fe contents all exhibit a certain removal ability for U(VI), with the 5wt% Fe-doped sample showing better removal performance, while the undoped sample showed relatively lower removal performance. The results indicate that appropriate Fe doping is beneficial to improving the electrode's U(VI) removal performance; when the Fe content is too low, the regulatory effect is not significant; and when the Fe content is too high (9wt%), the uranium removal effect decreases slightly.

[0049] Test Example 3 Following the method of Test Example 1, the removal rates of U(VI) solution by the electrodes obtained in Comparative Examples 2-7 with different amounts of glucose, dopamine, and ascorbic acid are shown in Table 3.

[0050] Table 3. Removal rate of U(VI) solution by electrode pair under different amounts of glucose, dopamine, and ascorbic acid.

[0051] Table 3 shows that the ratio of the three additives has a certain impact on the uranium removal efficiency. This indicates that excessive additives may affect the exposure of active sites or the electrode structure, thereby reducing the uranium removal rate.

[0052] Example 9 A method for applying an iron-doped tungsten trioxide composite electrode in the treatment of uranium-containing wastewater comprises the following steps: (i) An electrochemical treatment system was constructed by using the 5wt% Fe-doped tungsten trioxide composite electrode prepared in Example 3 as the cathode and the titanium sheet as the anode. (ii) Add wastewater containing U(VI) to the reactor, wherein the concentration of U(VI) in the uranium wastewater is 20 mg / L; (iii) Adjust the initial pH of the reduction reaction to 2 using 5% dilute nitric acid; (iv) Apply an external bias voltage of -0.1V to carry out the reaction.

[0053] Examples 10-14 The difference between Examples 10-14 and Example 9 is that the initial pH of the reduction reaction in step (iii) is 3 (Example 10), 4 (Example 11), 5 (Example 12), 6 (Example 13) and 7 (Example 14), respectively. The remaining steps are the same as in Example 9 and will not be repeated here.

[0054] U(VI) removal performance tests were conducted on Examples 9-14 under different initial pH conditions. The concentration of U(VI) in the solution was measured at regular intervals during the tests, and the results are recorded in Table 4. Based on these results, a plot was drawn. Figure 5 .

[0055] Table 4. Removal efficiency of U(VI) under different initial pH conditions

[0056] From Table 4 and Figure 5 It can be seen that as the initial pH of the solution increases, the removal efficiency of U(VI) generally shows a trend of first increasing and then decreasing. This indicates that suitable pH conditions are more conducive to the interfacial enrichment and electrochemical reduction of U(VI) on the electrode surface; when pH=2 (too low), the interfacial reaction is easily affected by proton competition; when pH=6 or 7 (too high), it may affect the existing form of uranyl ions and their mass transfer and reaction process on the electrode surface. In summary, the sample with an initial pH of 4 has the best U(VI) removal effect.

[0057] Example 15 A method for applying an iron-doped tungsten trioxide composite electrode in the treatment of uranium-containing wastewater comprises the following steps: (i) An electrochemical treatment system was constructed by using the 5wt% Fe-doped tungsten trioxide composite electrode prepared in Example 3 as the cathode and the titanium sheet as the anode. (ii) Add wastewater containing U(VI) to the reactor, wherein the concentration of U(VI) in the uranium wastewater is 20 mg / L; (iii) Adjust the initial pH of the reduction reaction to 4; (iv) Apply an external bias voltage of -0.1V to carry out the reaction.

[0058] Examples 16-18 The difference between Examples 16-18 and Example 15 is that the applied bias voltages in step (iv) are -0.5 V (Example 16), -1.0 V (Example 17), and -2.0 V (Example 18), respectively. The remaining steps are the same as in Example 15 and will not be repeated here.

[0059] Comparative Example 8 The difference between Comparative Example 8 and Example 15 is that no external bias voltage is applied in step (iv), that is, the external bias voltage is 0V. The remaining steps are the same as in Example 15, and will not be repeated here.

[0060] U(VI) removal performance of Comparative Example 8 and Examples 15-18 was tested under different applied bias voltages. The concentration of U(VI) in the solution was measured at regular intervals during the test, and the results are recorded in Table 5. Based on these results, a graph was plotted. Figure 6 .

[0061] Table 5. Removal effect of U(VI) under different applied bias voltages

[0062] From Table 5 and Figure 6 It can be seen that the electron supply capacity of the electrode surface and the reduction rate of U(VI) change significantly with the change of the applied bias voltage. Under suitable bias voltage conditions, the composite electrode has a better removal effect on U(VI); when the bias voltage is too low, the electron driving force is insufficient, making it difficult to fully promote the reduction of U(VI); when the bias voltage is too high, side reactions may be triggered, which is not conducive to the overall reaction efficiency of the system. In summary, the sample under the condition of -1.0V shows better uranium removal performance.

[0063] Example 19 A method for applying an iron-doped tungsten trioxide composite electrode in the treatment of uranium-containing wastewater comprises the following steps: (i) An electrochemical treatment system was constructed by using the 5wt% Fe-doped tungsten trioxide composite electrode prepared in Example 3 as the cathode and the titanium sheet as the anode. (ii) Add wastewater containing U(VI) to the reactor, wherein the concentration of U(VI) in the uranium wastewater is 5 mg / L, 10 mg / L, 30 mg / L, 50 mg / L, 100 mg / L, 200 mg / L and 300 mg / L respectively; (iii) Adjust the initial pH of the reduction reaction to 4; (iv) Apply an external bias voltage of -1.0V to carry out the reaction.

[0064] The results showed that the removal rate of U(VI) remained stable at over 90% under different concentration conditions, indicating that the composite electrode of the present invention exhibited good U(VI) removal capability over a wide range of initial uranium concentrations, demonstrating the good applicability of the composite electrode of the present invention.

[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an iron-doped tungsten trioxide composite electrode, characterized in that, Includes the following steps: A precursor solution is obtained by mixing tungsten source, iron source, glucose, dopamine, ascorbic acid and water. The copper foam was placed in the precursor solution and subjected to a hydrothermal reaction. The copper foam composite material after the hydrothermal reaction was taken out and subjected to heat treatment to obtain an iron-doped tungsten trioxide composite electrode.

2. The preparation method according to claim 1, characterized in that, The tungsten source includes sodium tungstate, and the iron source includes one or more of ferric nitrate, ferric sulfate, ferric chloride, and ferric citrate. The mass of Fe in the iron source is 1 to 9% of the mass of the tungsten source.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of glucose, dopamine, and ascorbic acid is (0.1~0.6):(0.1~0.4):(0.05~0.2). The mass ratio of the tungsten source to glucose is (0.4~2):(0.2~0.6).

4. The preparation method according to claim 1, characterized in that, The copper foam has a pore size of 10~150 ppi and a porosity of 60~99%; the copper foam has a thickness of 0.1~5 mm.

5. The preparation method according to claim 1 or 4, characterized in that, Before the hydrothermal reaction, the foamed copper is pretreated, which includes ultrasonic cleaning and acid pickling activation performed sequentially. The activation solution used for acid pickling activation is a dilute nitric acid solution, and the acid pickling activation time is 5-30 min.

6. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature is 80~200℃, and the holding time is 6~18 h; The heat treatment temperature is 60~300℃, and the holding time is 1~3h.

7. The iron-doped tungsten trioxide composite electrode prepared by the preparation method according to any one of claims 1 to 6, characterized in that, It includes a copper foam substrate and an iron-doped tungsten trioxide active layer grown in situ on the surface of the copper foam substrate.

8. The application of the iron-doped tungsten trioxide composite electrode according to claim 7 in uranium wastewater treatment.

9. The application according to claim 8, characterized in that, The method of the application includes the following steps: An iron-doped tungsten trioxide composite electrode was placed in uranium-containing wastewater and used as the cathode. An electrochemical reduction reaction was carried out under an applied bias voltage to remove hexavalent uranium from the wastewater.

10. The application according to claim 9, characterized in that, The operating potential of the cathode is 0 to -2.0V; The pH value of the uranium-containing wastewater is 2 to 7.

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