A S-MoS2Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction and its preparation method

Abstract

The present application relates to sewage treatment technical field, specifically to a kind of for uranyl ion adsorption-electrochemical reduction S-MoS2Ni3S2@NF composite electrode material and its preparation method.The existing electrochemical uranium removal technology is needed to remove the applied voltage of hexavalent uranium ion in uranium-containing wastewater, which limits the development and application of electrochemical uranium removal technology to some extent.For the above technical problems, the present application provides a kind of for uranyl ion adsorption-electrochemical reduction S-MoS2 / Ni3S2@NF composite electrode material, S-MoS2 in the composite electrode material, compared with pure MoS2, strengthen the conversion process of U (VI) to U (IV), while the Ni of composite electrode material Ni3S2 can form chemical bond with the axial oxygen of UO2 2+ As electron transfer channel, further promote the reduction of U (VI), the synergistic effect of the two kinds of action greatly improves the reaction rate of electro-reduction U (VI), and more efficiently realizes the electro-reduction removal of U (VI) in uranium-containing wastewater in lower reduction voltage and wider pH range.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to an S-MoS2Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction and its preparation method. Background Technology

[0002] Existing uranium resource extraction and wastewater treatment technologies have many limitations: chemical precipitation requires strict pH control, easily introduces new impurities, and is ineffective in treating low-concentration uranium wastewater; ion exchange has low selectivity, is easily interfered with by other ions, has high costs for resin regeneration or replacement, and improper treatment of saturated resin can cause secondary pollution, significantly reducing its effectiveness in treating high-salt wastewater; biosorption has low adsorption capacity, is inefficient in treating high-concentration uranium wastewater, and microbial activity is easily affected by environmental factors, resulting in poor stability; photocatalytic reduction has low removal efficiency and requires additional sacrificial agents; electrochemical reduction has high reduction efficiency but high energy consumption.

[0003] Furthermore, uranium exists in water in both hexavalent (U(VI)) and tetravalent (U(IV)) forms. U(IV) readily precipitates, while U(VI) exhibits strong migration capabilities. Reducing hexavalent uranium to tetravalent uranium allows for the effective enrichment and extraction of uranium resources. Electrochemical extraction methods utilize an external electric field to drive electron transfer, inducing the electrodeposition of uranium compounds on the electrode surface. These methods offer advantages such as rapid mass transfer rates and a wide concentration adaptability range. However, existing electrochemical uranium removal technologies still suffer from drawbacks, including high applied voltages (generally exceeding 1.5 V), high energy consumption, and a relatively narrow pH range (2-4). These limitations, to some extent, restrict the large-scale development and application of electrochemical uranium removal technologies.

[0004] Therefore, developing an efficient, low-energy-consumption, and widely applicable electrochemical uranium removal technology is of great practical significance. Summary of the Invention

[0005] Problems with existing technologies: Current electrochemical uranium removal technologies require high applied voltages to remove hexavalent uranium ions from uranium-containing wastewater, which to some extent limits the development and application of electrochemical uranium removal technology. To address these technical problems, this invention provides an S-MoS2 / Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction, the preparation method of which includes the following steps: (1) Add molybdate and thiourea to deionized water and stir until a mixed solution is formed. Then transfer the mixed solution to a high-pressure reactor and perform hydrothermal reaction at 220°C. After the hydrothermal reaction is completed, cool naturally to room temperature. The obtained reaction product is washed with deionized water and ethanol aqueous solution and then vacuum dried to obtain S-MoS2. (2) S-MoS2 was added to deionized water to form an S-MoS2 solution with a mass concentration of 2.4±0.5 mg / mL. Then, thiourea was added to the S-MoS2 solution and stirred until homogeneous. The mixed solution and pretreated NF were placed in a high-pressure reactor and hydrothermally reacted at 180 °C. After the hydrothermal reaction was completed, the obtained product was washed with deionized water and ethanol aqueous solution and then placed in a clean air environment and dried naturally at room temperature to obtain the S-MoS2 / Ni3S2@NF composite electrode material. The molar ratio of Mo atoms in the molybdate to S atoms in the thiourea is <1:2.

[0006] Preferably, the molar ratio of Mo atoms in the molybdate to S atoms in the thiourea is 1:4.

[0007] Preferably, the molybdate is ammonium molybdate tetrahydrate.

[0008] Preferably, the hydrothermal reaction time in step (1) is not less than 18 h.

[0009] Preferably, the hydrothermal reaction time in step (2) is not less than 8 hours.

[0010] Preferably, in step (2), the mass ratio of S-MoS2 to thiourea in the S-MoS2 solution is 48:45.

[0011] Preferably, the preparation steps of the pretreated NF are as follows: (1) Place NF in anhydrous acetone and ultrasonically clean for at least 15 min. After ultrasonic cleaning, remove NF and then rinse with alternating ethanol aqueous solution and deionized water to remove impurities attached to the surface of NF. (2) Place the NF cleaned in step (1) in hydrochloric acid and perform ultrasonic cleaning again for at least 15 min. After ultrasonic cleaning, remove the NF and rinse it alternately with ethanol aqueous solution and deionized water to remove impurities on the surface of the NF. Then place it in a clean air environment and let it dry naturally at room temperature. After drying, seal and store it for later use.

[0012] The present invention has the following beneficial effects: (1) In the process of synthesizing S-MoS2 / Ni3S2@NF composite electrode material, this invention synthesizes S-MoS2 by over-adding thiourea to build up material defects. Compared with pure MoS2, it has a better effect on removing U(VI). The over-addition of S effectively promotes electron transfer and strengthens the conversion process of U(VI) to U(IV). At the same time, Ni in Ni3S2 can react with UO2. 2+The axial oxygen forms chemical bonds and acts as an electron transport channel to further promote the reduction of U(VI). The synergistic effect of these two effects greatly improves the reaction rate of electroreduction of U(VI), enabling the S-MoS2 / Ni3S2@NF composite electrode material to electroreductively reduce uranyl ions more efficiently. (2) The process of preparing S-MoS2 / Ni3S2@NF composite electrode material in this invention is simpler than other synthesis processes. This not only reduces the difficulty and cost of operation in the production process, but also the composite electrode material obtained has higher adsorption and electrocatalytic reduction efficiency. In practical applications, it can treat uranium-containing wastewater more quickly and effectively. (3) When the S-MoS2 / Ni3S2@NF composite electrode material prepared in this invention is used for the adsorption-electrochemical reduction of U(VI) in uranium-containing wastewater, the process can be carried out under conditions of pH=4-8, and the UO2 after adsorption-electrochemical reduction is... 2+ The removal rate can reach about 80%. Compared with the existing electrochemical uranium removal technology, it has a wider applicable pH range. At the same time, the relatively low potential requirement of -0.9 V for electrochemical reduction helps to reduce energy consumption, further expanding the feasibility and applicability of the technology in practical applications, and can meet the needs of uranium-containing wastewater treatment under different water quality conditions. Attached Figure Description

[0013] Figure 1 The effect of applying 1-7 adsorption-electrochemical reduction of uranyl ions is shown in the figure.

[0014] Figure 2 The effect of applying 1, 8-11 adsorption-electrochemical reduction of uranyl ions is shown in the figure.

[0015] Figure 3 The diagram shows the effect of adsorption-electrochemical reduction of uranyl ions in applications 1, 12, and 13.

[0016] Figure 4 This is a SEM image of the S-MoS2 / Ni3S2@NF composite electrode material of the present invention, magnified 20,000 times.

[0017] Figure 5 The images show the XRD patterns of the MoS2 / Ni3S2@NF composite electrode material I and the S-MoS2 / Ni3S2@NF composite electrode material obtained in this invention.

[0018] Figure 6 The S 2p XPS spectra of MoS2 / Ni3S2@NF composite electrode materials I and S-MoS2 / Ni3S2@NF obtained in this invention are shown. Detailed Implementation

[0019] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0020] The nickel foam (NF) used in this invention was purchased from Guangjiayuan New Materials Co., Ltd. (Kunshan, China), with dimensions of 200mm × 300mm × 1.0mm and physical and chemical parameters of areal density of 320 g / m³. 2 The pore size is 110 ppi; the purity of the nickel foam is 99.9%; and the porosity is 96%. The preparation method of the pretreated NF of this invention is as follows: (1) Place NF in anhydrous acetone and ultrasonically clean for 15 minutes. After ultrasonic cleaning, remove NF and then rinse it three times with 95% ethanol aqueous solution and deionized water to remove impurities attached to the surface of NF. (2) Place the NF cleaned in step (1) in hydrochloric acid with a concentration of 1 mol / L and perform ultrasonic cleaning again for 15 min. After ultrasonic cleaning, take out the NF and rinse it three times with 95% ethanol aqueous solution and deionized water to remove impurities on the surface of the NF. Then place it in a clean air environment and let it air dry at room temperature for later use. Example 1

[0021] (1) 1 mmol of ammonium molybdate tetrahydrate and 28 mmol of thiourea were added to 35 mL of deionized water and stirred vigorously to form a homogeneous mixed solution. The mixed solution was then placed in a stainless steel high-pressure reactor with a Teflon liner with a volume of 50 mL and kept at a constant temperature of 220 °C for 18 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction product was washed three times with water and three times with anhydrous ethanol. The obtained solid product was vacuum dried at 60 °C for 12 h to obtain S-MoS2. (2) S-MoS2 (0.048 g) was added to 20 mL of deionized water to form an S-MoS2 solution. Then, thiourea (0.045 g, 0.6 mmol) was added to the S-MoS2 solution. After stirring and mixing evenly, the mixed solution and pretreated NF were placed in a high-pressure reactor and hydrothermally reacted at 180 °C for 8 h. After the hydrothermal reaction was completed, the obtained product was washed three times with deionized water and ethanol aqueous solution, respectively, and then placed in a clean air environment and dried naturally at room temperature to obtain the S-MoS2 / Ni3S2@NF composite electrode material.

[0022] Comparative Example 1 is the same as Example 1, except that the amount of thiourea added in step (1) of Comparative Example 1 is 14 mmol. The electrode material obtained by the reaction is denoted as MoS2 / Ni3S2@NF composite electrode material I.

[0023] Comparative Example 2 MoS2 (0.048 g, analytical grade, commercially available) was added to 20 mL of deionized water to form a MoS2 solution. Then, thiourea (0.045 g) was added to the MoS2 solution and stirred until homogeneous. The mixture and pretreated NF were placed in a high-pressure reactor and hydrothermally reacted at 180 °C for 8 h. After the hydrothermal reaction was completed, the obtained product was washed three times alternately with deionized water and ethanol aqueous solution, and then placed in a clean air environment and naturally dried at room temperature to obtain MoS2 / Ni3S2@NF composite electrode material II.

[0024] Comparative Example 3 is a preprocessed NF.

[0025] Comparative Example 4 is an S-Ni3S2@NF composite electrode material, prepared by the following method: Thiourea (0.09 g, 1.2 mmol) was added to deionized water (20 mL), and the mixture was stirred for 15 minutes to obtain a thiourea solution. Then, the pretreated NF and the thiourea solution were placed together in a stainless steel high-pressure reactor with an effective volume of 50 mL and lined with polytetrafluoroethylene. The reactor was hydrothermally reacted at 180 °C for 8 h. The sample was then removed and rinsed three times alternately with deionized water and ethanol aqueous solution. Finally, the sample was placed in a clean air environment and allowed to dry naturally at room temperature to obtain the S-Ni3S2@NF composite electrode material.

[0026] Comparative Example 5 is a Ni3S2@NF composite electrode material, prepared by the following method: Thiourea (0.045 g, 0.6 mmol) was added to deionized water (20 mL), and the mixture was stirred for 15 minutes to obtain a thiourea solution. Then, the pretreated NF and the thiourea solution were placed together in a stainless steel high-pressure reactor with an effective volume of 50 mL and lined with polytetrafluoroethylene. The reactor was hydrothermally reacted at 180 °C for 8 h. The sample was then removed and rinsed three times alternately with deionized water and ethanol aqueous solution. Finally, the sample was placed in a clean air environment and allowed to dry naturally at room temperature to obtain the Ni3S2@NF composite electrode material.

[0027] Comparative Example 6 is an S-MoS2@NF composite electrode material, prepared by the following method: The S-MoS2 (0.048 g, 0.05 mmol) obtained in step (1) of Example 1 was added to deionized water (20 mL), and the mixture was stirred for 15 minutes to obtain a mixture. Then, the pretreated NF and the mixture were placed together in a stainless steel high-pressure reactor with an effective volume of 50 mL and lined with polytetrafluoroethylene. The reactor was hydrothermally reacted at 180°C for 8 h. Finally, the reactor was rinsed three times alternately with deionized water and ethanol aqueous solution, and then placed in a clean air environment and dried naturally at room temperature to obtain the S-MoS2@NF composite electrode material.

[0028] Performance testing The adsorption-electrochemical reduction performance of the electrode materials obtained in the embodiments and comparative examples of this invention was tested using a dual-electrode electrochemical system. The electrodes in both embodiments and comparative examples were cut to a size of 1 cm × 1 cm and used as cathodes in the dual-electrode system. These, along with the anode (platinum wire), electrolyte, external power supply, and electrolytic cell, constituted four different dual-electrode electrochemical systems. The electrolyte in all cases was uranyl ion-containing wastewater, and the preparation method for the uranyl ion-containing wastewater is as follows: (1) Weigh 35.5 g of anhydrous Na2SO4 powder and add it to a 500 mL volumetric flask. Then add deionized water to make up to 500 mL to obtain an aqueous solution of Na2SO4. (2) Dissolve uranyl nitrate hexahydrate (UO2(NO3)2·6H2O) in deionized water to obtain a uranium-containing mother liquor with a mass concentration of 1 g / L. Then, use Na2SO4 aqueous solution to dilute its concentration to 12 mg / L to obtain uranyl ion-containing wastewater.

[0029] Application 1 At room temperature, the S-MoS2 / Ni3S2@NF composite electrode material obtained in Example 1 was used as the cathode of the dual-electrode system. 50 mL of electrolyte was taken, and the pH of the electrolyte was adjusted to 6 using a pH adjuster (hydrochloric acid or sodium hydroxide aqueous solution). The electrolyte was magnetically stirred at 2 r / s for 45 min, and then an external power supply was applied with a voltage of -0.9 V for electrochemical reduction for 45 min. The electrolyte was then filtered to collect the solid precipitate.

[0030] Application 2 is the same as Application 1, except that the voltage in Application 2 is -0.8 V.

[0031] Application 3 is the same as Application 1, except that the voltage in Application 3 is -1.0 V.

[0032] Application 4 is the same as Application 1, except that Application 4 uses a sodium hydroxide aqueous solution with a mass concentration of 0.1 mol / L to adjust the pH of the electrolyte to 7.

[0033] Application 5 is the same as Application 1, except that Application 5 uses 0.1 mol / L hydrochloric acid to adjust the pH of the electrolyte to 4.

[0034] Application 6 is the same as Application 1, except that Application 6 uses 0.1 mol / L hydrochloric acid to adjust the pH of the electrolyte to 5.

[0035] Application 7 is the same as Application 1, except that Application 7 uses a sodium hydroxide aqueous solution with a mass concentration of 0.1 mol / L to adjust the pH of the electrolyte to 8.

[0036] Application 8 is the same as Application 1, except that in Application 8, the MoS2 / Ni3S2@NF composite electrode material I obtained in Comparative Example 1 is used to replace the S-MoS2 / Ni3S2@NF composite electrode material in Application 1.

[0037] Application 9 is the same as Application 1, except that in Application 9, the MoS2 / Ni3S2@NF composite electrode material II obtained in Comparative Example 2 is used to replace the S-MoS2 / Ni3S2@NF composite electrode material in Application 1.

[0038] Application 10 is the same as Application 1, except that in Application 10, the pretreated NF of Comparative Example 3 is used to replace the S-MoS2 / Ni3S2@NF composite electrode material in Application 1.

[0039] Application 11 is the same as Application 1, except that the S-Ni3S2@NF composite electrode material obtained in Comparative Example 4 is used in Application 11 to replace the S-MoS2 / Ni3S2@NF composite electrode material in Application 1.

[0040] Application 12 is the same as Application 1, except that the Ni3S2@NF composite electrode material obtained in Comparative Example 5 is used in Application 12 to replace the Ni3S2@NF composite electrode material in Application 1.

[0041] Application 13 is the same as Application 1, except that the S-MoS2@NF composite electrode material obtained in Comparative Example 6 is used in Application 13 to replace the Ni3S2@NF composite electrode material in Application 1.

[0042] The removal efficiency of the dual-electrode systems obtained in Applications 1 and 8-13 for U(VI) in the electrolyte is shown in the attached instruction manual. Figure 1 As shown. The formula for calculating the removal rate is as follows: , In the above formula, C0 represents the initial concentration of hexavalent uranyl ions in the electrolyte, C t This represents the concentration of hexavalent uranyl ions in the electrolyte at time t, where t is in minutes and C is in mg / L.

[0043] Test results show that the S-MoS2 / Ni3S2@NF composite electrode material obtained in Example 1 has a significantly better removal effect on U(VI) ions than MoS2 / Ni3S2@NF composite electrode material I, MoS2 / Ni3S2@NF composite electrode material II, and pretreated NF. Specific test results are shown in Table 1. Table 1 , Applications 1 and 4-7 show the effects of adsorption on the electrochemical reduction of uranyl ions as per the instruction manual. Figure 2As shown in the figure. The test results show that the S-MoS2 / Ni3S2@NF electrocatalytic material has the best adsorption and reduction effect at pH=6, and the removal rate of U(VI) ions can reach 85% under acidic conditions; the removal rate of U(VI) ions can also reach 78% under alkaline conditions, with a wide pH adaptability range.

[0044] The effect of application 1-3 on the adsorption and electrochemical reduction of uranyl ions is shown in the attached instruction manual. Figure 3 As shown in the figure. Test results show that the optimal applied voltage in the S-MoS2 / Ni3S2@NF composite electrode material is -0.9 V, which is economical and energy-saving.

[0045] Instruction manual attached Figure 4 The images show SEM images of the S-MoS2 / Ni3S2@NF composite electrode material obtained in Example 1 of this invention at different magnifications. As shown in the SEM images, S-MoS2 / Ni3S2 nanosheets are uniformly distributed on the surface of nickel foam, forming a complex porous or layered wrinkled structure with aggregates resembling "flower balls," surrounded by numerous curled and wrinkled sheets. This loose structure is conducive to increasing the specific surface area and providing more active sites.

[0046] Instruction manual attached Figure 5 The figures show the XRD patterns of MoS2 / Ni3S2@NF obtained in Comparative Example 2 and S-MoS2 / Ni3S2@NF obtained in Example 1 of this invention. As shown in the figure, both composite electrodes exhibit typical MoS2 diffraction peaks, indicating that S doping has little effect on crystallinity.

[0047] Instruction manual attached Figure 6 XPS spectra of S2p in MoS2 / Ni3S2@NF obtained in Comparative Example 2 and S-MoS2 / Ni3S2@NF obtained in Example 1 of this invention; the results show that the forms and contents of S in the S-MoS2 / Ni3S2@NF material have changed significantly, with reduced S species (S2p) being present. 2- and S2 2- () increased significantly.

[0048] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An S-MoS2 / Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction, characterized in that, The preparation method includes the following steps: (1) Add molybdate and thiourea to deionized water and stir to form a mixed solution. Then transfer the mixed solution to a high-pressure reactor and perform hydrothermal reaction at 220 °C. After the hydrothermal reaction is completed, cool naturally to room temperature. The obtained reaction product is washed with deionized water and ethanol aqueous solution and then vacuum dried to obtain S-MoS2. (2) S-MoS2 was added to deionized water to form an S-MoS2 solution with a mass concentration of 2.4±0.5 mg / mL. Then, thiourea was added to the S-MoS2 solution and stirred until homogeneous. The mixed solution and pretreated NF were placed in a high-pressure reactor and hydrothermally reacted at 180 °C. After the hydrothermal reaction was completed, the obtained product was washed with deionized water and ethanol aqueous solution and then dried to obtain the S-MoS2 / Ni3S2@NF composite electrode material. The molar ratio of Mo atoms in the molybdate to S atoms in the thiourea is <1:

2.

2. The S-MoS2 / Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction according to claim 1, characterized in that, The molar ratio of Mo atoms in the molybdate to S atoms in the thiourea is 1:

4.

3. The S-MoS2 / Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction according to claim 1, characterized in that, The molybdate is ammonium molybdate tetrahydrate.

4. The S-MoS2 / Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction according to claim 1, characterized in that, The hydrothermal reaction time in step (1) shall be no less than 18 h.

5. The S-MoS2 / Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction according to claim 1, characterized in that, The hydrothermal reaction time in step (2) shall be no less than 8 hours.

6. The S-MoS2 / Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction according to claim 1, characterized in that, In step (2), the mass ratio of S-MoS2 to thiourea in the S-MoS2 solution is 48:

45.

7. The S-MoS2 / Ni3S2@NF composite electrode material for uranyl ion adsorption-electrochemical reduction according to claim 1, characterized in that, The preparation steps for pretreated NF are as follows: (1) Place NF in anhydrous acetone for ultrasonic cleaning. After ultrasonic cleaning, remove NF and then rinse it alternately with ethanol aqueous solution and deionized water to remove impurities attached to the surface of NF. (2) Place the NF cleaned in step (1) in hydrochloric acid and perform ultrasonic cleaning again. After ultrasonic cleaning, remove the NF and then rinse it with alternating ethanol aqueous solution and deionized water to remove impurities on the surface of the NF. Then dry it and seal it for later use.

8. A method for adsorption-electrochemical reduction of U(VI) in uranium-containing wastewater, characterized in that, The S-MoS2 / Ni3S2@NF composite electrode material according to any one of claims 1-7 is used as the cathode of a dual-electrode system to perform adsorption-electrochemical reduction of hexavalent uranyl ions in wastewater.

9. The method for adsorption-electrochemical reduction of U(VI) in uranium-containing wastewater according to claim 8, characterized in that, During the adsorption-electrochemical reduction process, the pH of the uranium-containing wastewater is 6.

10. The method for adsorption-electrochemical reduction of U(VI) in uranium-containing wastewater according to claim 8, characterized in that, The potential for the adsorption-electrochemical reduction is -0.9 V.

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