Method for enriching uranium through electrocatalysis of zero-valent iron aerogel

Abstract

The invention belongs to the technical field related to water treatment, and particularly discloses a method for electrocatalytic enrichment of uranium by using zero-valent iron aerogel, and the method comprises the following steps: slicing hydrophilic carbon paper, and treating for later use; the preparation method comprises the following steps: dissolving zero-valent iron aerogel and an adhesive in an organic solvent, and performing ultrasonic dispersion to form uniform catalyst slurry; uniformly coating the surface of pretreated carbon paper with the obtained slurry in an oxygen-free environment, drying to obtain a zero-valent iron aerogel-loaded carbon paper working electrode, forming a three-electrode system by matching the prepared working electrode with a counter electrode and a reference electrode, and performing electrochemical reduction reaction on uranium-containing water in an electrolytic tank by applying pulse voltage to obtain uranium-containing water. Uranium is enriched in the working electrode. The zero-valent iron aerogel loaded electrode with high specific surface area and excellent electron conduction performance is constructed, the low-pulse voltage electro-catalysis technology is combined, efficient, high-selectivity and low-energy-consumption enrichment of uranium in seawater is achieved, and the dual functions of resource recovery and environmental pollution control are achieved.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically a method for enriching uranium using zero-valent iron aerogel electrocatalysis. Background Technology

[0002] Uranium is the core fuel for nuclear power generation, and its stable supply is crucial for energy security. Seawater contains approximately 4.5 billion tons of uranium, far exceeding the reserves found in terrestrial uranium deposits, but the concentration is extremely low (approximately 3.3 μg / L), and it contains a large number of competing ions (such as Na+). + Mg 2+ Ca 2+ Uranium enrichment technologies, including those for uranium-containing materials (such as nitrogen, sulfur, and nitrogen), are extremely difficult to extract. Furthermore, the direct discharge of untreated uranium-containing wastewater from the nuclear industry poses a long-term radioactive threat to the ecological environment and human health. Therefore, developing efficient, economical, and environmentally friendly uranium enrichment technologies is of significant strategic importance.

[0003] Currently, uranium enrichment technologies mainly include adsorption, ion exchange, solvent extraction, and electrochemical methods. While adsorption is simple to operate, it suffers from poor material selectivity, low adsorption capacity, and difficulty in regeneration. Ion exchange is costly and highly susceptible to salinity. Solvent extraction uses toxic organic reagents, easily causing secondary pollution. Electrochemical methods are gaining attention due to their advantages such as no need for added chemical reagents, controllable reactions, and environmental friendliness; however, they still face the following challenges:

[0004] (1) Insufficient electrode material performance: Traditional electrode materials such as precious metals (Pt, Pd) are expensive and scarce; carbon-based materials have low activity; metal oxides have poor conductivity and are easily passivated. (2) Excessive operating voltage: Most electrocatalytic uranium extraction studies use a constant voltage of −0.6V ~ −1.0V (vs. RHE), which easily triggers the hydrogen evolution reaction (HER), reducing electron utilization efficiency and Faraday efficiency. (3) Poor selectivity: In high salinity or complex water bodies, coexisting ions compete with uranium for active sites, leading to a decrease in uranium enrichment efficiency. (4) High energy consumption: High-voltage operation leads to a significant increase in energy consumption, restricting its large-scale application.

[0005] Zero-valent iron (Fe) 0 Due to its strong reducing properties, low cost, and environmental friendliness, zero-valent iron (ZCE) particles have shown potential in the field of electrocatalysis. However, traditional ZCE particles have a small specific surface area, are easily oxidized, and have few active sites, thus they cannot be directly applied to electrocatalytic uranium extraction.

[0006] Therefore, developing a technology suitable for the industrial treatment of uranium-containing water has significant scientific value and application prospects. Summary of the Invention

[0007] The purpose of this invention is to provide a method for enriching uranium using zero-valent iron aerogel electrocatalysis. By constructing a zero-valent iron aerogel supported electrode with high specific surface area and excellent electronic conductivity, and combining it with low-pulse voltage electrocatalysis technology, a highly efficient, selective, and low-energy-consumption enrichment of uranium in seawater can be achieved, which also has the dual functions of resource recovery and environmental pollution control.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] A method for uranium enrichment via electrocatalysis using zero-valent iron aerogel includes the following steps:

[0010] S1. Cut hydrophilic carbon paper into slices, and sonicate them in acetone, ethanol, pure water and hydrochloric acid solutions in sequence. After rinsing with pure water, dry them in a vacuum environment for later use.

[0011] S2. Dissolve zero-valent iron aerogel and binder in an organic solvent and disperse them ultrasonically to form a uniform catalyst slurry;

[0012] S3. The slurry obtained in step S2 is uniformly coated onto the surface of the carbon paper pretreated in step S1 under an oxygen-free environment. The coated carbon paper is then vacuum dried to obtain a carbon paper working electrode supported by zero-valent iron aerogel.

[0013] S4. The working electrode prepared in step S3 is combined with the counter electrode and the reference electrode to form a three-electrode system. By applying a pulse voltage, an electrochemical reduction reaction is carried out on the uranium-containing water in the electrolytic cell, so that uranium is enriched in the working electrode. The electrolytic cell has a gas inlet, a liquid outlet and an electrode socket, and inert gas can be introduced. Uranium can be recovered by removing the working electrode.

[0014] Furthermore, in step S1, the concentration of hydrochloric acid solution is 0.5 mol / L, and the ultrasonic treatment time is 30~40 min.

[0015] Furthermore, in step S2, the zero-valent iron aerogel possesses a three-dimensional porous structure with a specific surface area greater than 200 m². 2 / g, with a porosity greater than 95%, and an extremely low apparent density and a lattice spacing of no more than 0.2 nm.

[0016] Furthermore, in step S2, the preparation method of the zero-valent iron aerogel is as follows:

[0017] Ferrous sulfate and sodium sulfide were simultaneously dissolved in a pure aqueous solution treated with nitrogen aeration to obtain solution A; sodium borohydride was dissolved in a pure aqueous solution treated with nitrogen aeration to obtain solution B; solution A and solution B were rapidly mixed and stirred to obtain a black colloid; the black colloid was filtered and washed to obtain the zero-valent iron aerogel.

[0018] Furthermore, in step S2, in solution A, the concentration of ferrous sulfate is 10 mmol / L and the concentration of sodium sulfide is 1 mmol / L; in solution B, the concentration of sodium borohydride is 30~50 mmol / L, and solutions A and B are mixed at a volume ratio of 9:1.

[0019] Furthermore, in step S2, the binder is a perfluorosulfonic acid polymer solution, such as 5 wt.% Nafion, and its addition amount is 0.5%~5% of the total mass of the catalyst slurry;

[0020] The organic solvent is one of ethanol and isopropanol, or a mixture of ethanol and isopropanol.

[0021] Furthermore, in step S4, the counter electrode is a platinum sheet, a graphite rod, or a carbon felt, and the reference electrode is a saturated calomel electrode, an Ag / AgCl electrode, or a reversible hydrogen electrode.

[0022] Furthermore, in step S4, an inert gas is introduced into the electrolytic cell during the electrochemical reduction reaction to maintain an oxygen-free environment inside the electrolytic cell. The inert gas introduced can be nitrogen, argon, etc.

[0023] Furthermore, in step S4, the applied pulse voltage is −0.1 V ~ −0.3 V (vs. RHE), the waveform of the pulse voltage is a square wave, the pulse-station-pulse method is used, the pulse frequency is 0.1 Hz ~ 10 Hz, and the duty cycle is 50%.

[0024] Furthermore, in step S4, before the electrochemical reduction reaction, the pH of the uranium-containing water is adjusted to 4-8 using hydrochloric acid, nitric acid, or sodium hydroxide.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) High selective enrichment: The working electrode is prepared by using zero-valent iron aerogel. The three-dimensional porous structure of zero-valent iron aerogel provides abundant active sites. Combined with the mass transfer enhancement effect of low pulse voltage, it can preferentially reduce uranyl ions and maintain excellent selectivity in high salinity or complex water bodies.

[0027] (2) Low energy consumption and high efficiency of uranium enrichment: Uranium enrichment can be achieved by using a low pulse voltage of −0.1 V ~ −0.3 V (vs. RHE), which is much lower than the traditional constant voltage mode of uranium enrichment, significantly reducing energy consumption, while suppressing hydrogen evolution reaction and improving electron utilization efficiency and Faraday efficiency.

[0028] (3) Good electrode stability: The zero-valent iron aerogel is tightly bonded to the carbon paper, has a stable structure, is not easy to fall off or oxidize, and can be recycled more than 6 times while still maintaining high catalytic activity.

[0029] (4) Green and environmentally friendly: No chemical reducing agents are required, there are no toxic byproducts, and the electrode materials are recyclable and regenerable, which is in line with the concept of green chemistry and sustainable development.

[0030] (5) Easy to apply in industry: The electrode preparation materials are inexpensive and the preparation method is simple, making it suitable for industrial and large-scale uranium extraction applications. Attached Figure Description

[0031] Figure 1 This is a transmission electron microscope (TEM) image of the zero-valent iron aerogel-supported carbon paper electrode prepared in Example 1 of the present invention. Figure 2 This is a schematic diagram of the low-pulse voltage uranium extraction device in Embodiment 1 of the present invention. Figure 3 This is a comparison chart of uranium removal rates under different pulse voltages in Example 1 of the present invention. Figure 4 This is a diagram illustrating the selective enrichment effect of uranium in the presence of competing ions in Example 2 of the present invention. Figure 5 This is a diagram showing the continuous use cycle performance of the electrode in Embodiment 3 of the present invention. Figure 6 This is a graph showing the effect of different pulse frequencies on uranium enrichment performance in Example 4 of the present invention. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0033] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art.

[0034] Example 1

[0035] This embodiment provides a method for uranium enrichment using zero-valent iron aerogel electrocatalysis. In this embodiment, the feasibility of this technology for uranium enrichment is primarily demonstrated through experiments. The method mainly includes the following steps:

[0036] 1. Preparation of zero-valent iron aerogel-supported carbon paper electrode

[0037] (1) Clean the 2 cm × 2 cm carbon paper with acetone, ethanol and deionized water in sequence for 15 minutes by ultrasonication, and dry it for later use; (2) Take 5 mg of zero-valent iron aerogel powder, 20 μL of 5 wt.% Nafion solution, add 980 μL of anhydrous ethanol, and ultrasonically disperse for 30 minutes to obtain a uniform catalyst slurry; (3) Use a pipette to take 500 μL of slurry and coat it evenly on both sides of the pretreated carbon paper, with a coating area of ​​about 8 cm²; (4) Place the coated carbon paper in a vacuum drying oven and dry it at 60 ℃ for 6-12 hours to obtain the working electrode.

[0038] In the above steps, the method for preparing zero-valent iron aerogel is as follows: Ferrous sulfate and sodium sulfide are simultaneously dissolved in a pure aqueous solution treated with nitrogen aeration to obtain solution A. In solution A, the concentration of ferrous sulfate is 10 mmol / L and the concentration of sodium sulfide is 1 mmol / L. Sodium borohydride is dissolved in a pure aqueous solution treated with nitrogen aeration to obtain solution B. In solution B, the concentration of sodium borohydride is 30-50 mmol / L. Solution A and solution B are rapidly mixed and stirred at a volume ratio of 9:1 to obtain a black colloid. The black colloid is then filtered and washed to obtain the zero-valent iron aerogel. For a detailed method for preparing zero-valent iron aerogel, please refer to the applicant's previously disclosed patent technology, publication number CN120349006A, titled...

[0039] The transmission electron microscope image of the zero-valent iron aerogel prepared by the above steps is shown below. Figure 1 As shown. From Figure 1 As can be seen, zero-valent iron aerogel exhibits a typical three-dimensional porous network structure with uniform particle distribution and no obvious agglomeration. This microscopic feature endows the material with high specific surface area, excellent electronic conductivity, and structural stability, providing a structural basis for efficient extraction, high selectivity, and low-energy enrichment of uranium.

[0040] 2. Construction of a low-pulse voltage uranium extraction device

[0041] like Figure 2 The diagram shown is a schematic representation of the structure of the constructed low-pulse voltage uranium extraction device. The device mainly includes:

[0042] Working electrode: The electrode prepared in step 1;

[0043] Counter electrode: Platinum sheet (1 cm × 1 cm);

[0044] Reference electrode: saturated calomel electrode;

[0045] Electrolytic cell: Sealed three-electrode reaction cell;

[0046] Pulse power supply: can output a square wave pulse of −0.1 V to −0.3 V (vs. RHE) with a frequency of 1 to 10 Hz and a duty cycle of 50%.

[0047] 3. Uranium extraction experiment under low pulse voltage

[0048] Uranium-containing simulated seawater (uranium concentration 40 mg / L, supporting electrolyte 1 M NaCl, pH = 5.0) was added to the electrolytic cell. Argon gas was purged for 30 minutes to remove oxygen. A pulsed voltage of −0.3 V (vs. RHE) at a frequency of 10 Hz and a duty cycle of 50% was applied. After 24 hours of reaction, the uranium removal rate reached over 97.5%, and the uranium extraction yield reached over 780 mg / g without reaching the maximum adsorption capacity.

[0049] Comparative Example 1: The difference between this comparative example and step 3 is that the pulse input voltage is adjusted to −0.2 V (vs. RHE).

[0050] Comparative Example 2: The difference between this comparative example and step 3 is that the pulse input voltage is adjusted to −0.1 V (vs. RHE).

[0051] Comparative Example 3: The difference between this comparative example and step 3 is that no additional voltage is applied.

[0052] In step 3 of Example 1 and Comparative Examples 1-3, uranium was reduced and enriched using zero-valent iron aerogel as the working electrode under electrocatalytic and physicochemical conditions, with the uranium removal rate and extraction amount as follows: Figure 3 As shown in the figure. The results show that efficient reduction and enrichment of uranyl ions can be achieved by applying a low pulse voltage, while it is difficult to achieve efficient reduction and enrichment of uranyl ions without applying an additional voltage.

[0053] Example 2: Selective Experiment

[0054] This embodiment differs from Embodiment 1 in that: uranium-containing simulated seawater (uranium concentration 40 mg / L, supporting electrolyte 1 M NaCl, pH = 5.0) is added to the electrolytic cell. Argon gas is passed through for 30 minutes to remove oxygen, and then... 2+ Na + K + In a competitive ion system (1 g / L each), a pulse voltage of −0.2 V (vs. RHE) with a frequency of 10 Hz and a duty cycle of 50% was applied, and the reaction was carried out for 24 hours.

[0055] Example 2: Using zero-valent iron aerogel as the working electrode, under conditions of uranium-added seawater and high competing ion concentration, its selective reduction and extraction performance for uranium is as follows: Figure 4As shown in the figure. The results indicate that in the low-pulse voltage electrocatalytic reduction system with zero-valent iron aerogel as the working electrode, highly selective adsorption and reduction of uranium can be achieved under the condition of a large number of competing ions, with a selective enrichment rate of uranium exceeding 95%.

[0056] Example 3: Electrode Recycling Performance

[0057] The electrode prepared in Example 1 was subjected to a pulse voltage of −0.2 V (vs. RHE) with a pulse frequency of 10 Hz and a duty cycle of 50% in seawater with an external uranium concentration of 20 mg / L. The electrode was used continuously for 6 cycles, with each reaction lasting 24 hours.

[0058] Example 3: Under low pulse voltage conditions, the continuous current cycling performance of the zero-valent iron aerogel electrode is as follows: Figure 5 As shown in the figure. The results indicate that the low-pulse voltage electrocatalytic reduction system using zero-valent iron aerogel as the working electrode can maintain a removal rate of over 98% for hexavalent uranium within 6 consecutive cycles, while the extraction yield is close to 200 mg / g and has not reached the maximum extraction capacity. This performance demonstrates that using zero-valent iron aerogel as the working electrode has good stability and reusability. The electrocatalyst of this invention has good practical application prospects for uranium enrichment in seawater or nuclear wastewater.

[0059] Example 4: Effect of different pulse frequencies on uranium enrichment performance

[0060] The difference from Example 1 is that uranium-containing seawater (uranium concentration 40 mg / L, supporting electrolyte 1 M NaCl, pH=5.0) was added to the electrolytic cell. Argon gas was purged for 30 minutes to remove oxygen. A pulse voltage of −0.2 V (vs. RHE) with a frequency of 1 Hz and a duty cycle of 50% was applied, and the working electrode was removed to measure the uranium adsorption capacity after 24 hours of reaction.

[0061] Comparative Example 4: The difference between this comparative example and Example 4 is that the pulse frequency is adjusted to 5 Hz.

[0062] Comparative Example 5: The difference between this comparative example and Example 4 is that the pulse frequency is adjusted to 10 Hz.

[0063] In Examples 4 and 4-5, zero-valent iron aerogel was used as the working electrode. Under low pulse voltage conditions, uranium was reduced and enriched using different pulse frequencies. The results are as follows: Figure 6 As shown in the figure. The results show that by applying a low pulse voltage, zero-valent iron aerogel can achieve efficient reduction and enrichment of uranyl ions at different pulse frequencies.

Claims

1. A method for uranium enrichment via electrocatalysis using zero-valent iron aerogel, characterized in that, Includes the following steps: S1. Cut hydrophilic carbon paper into slices, and sonicate them in acetone, ethanol, pure water and hydrochloric acid solutions in sequence. After rinsing with pure water, dry them in a vacuum environment for later use. S2. Dissolve zero-valent iron aerogel and binder in an organic solvent and disperse them ultrasonically to form a uniform catalyst slurry; S3. The slurry obtained in step S2 is uniformly coated onto the surface of the carbon paper pretreated in step S1 under an oxygen-free environment. The coated carbon paper is then vacuum dried to obtain a carbon paper working electrode supported by zero-valent iron aerogel. S4. The working electrode prepared in step S3 is combined with the counter electrode and the reference electrode to form a three-electrode system. By applying a pulse voltage, the uranium-containing water in the electrolytic cell is electrochemically reduced to enrich the uranium in the working electrode.

2. The method for uranium enrichment using zero-valent iron aerogel electrocatalysis according to claim 1, characterized in that, In step S1, the concentration of hydrochloric acid solution is 0.5 mol / L, and the ultrasonic treatment time is 30~40 min.

3. The method for uranium enrichment using zero-valent iron aerogel electrocatalysis according to claim 1, characterized in that, In step S2, the zero-valent iron aerogel possesses a three-dimensional porous structure with a specific surface area greater than that of iron aerogel. 200 m 2 / g, with a porosity greater than 95% and a lattice spacing not exceeding 0.2 nm.

4. The method for uranium enrichment using zero-valent iron aerogel electrocatalysis according to claim 3, characterized in that, In step S2, the zero-valent iron aerogel is prepared as follows: Ferrous sulfate and sodium sulfide were simultaneously dissolved in a pure aqueous solution treated with nitrogen aeration to obtain solution A; sodium borohydride was dissolved in a pure aqueous solution treated with nitrogen aeration to obtain solution B; solution A and solution B were rapidly mixed and stirred to obtain a black colloid; the black colloid was filtered and washed to obtain the zero-valent iron aerogel.

5. The method for uranium enrichment using zero-valent iron aerogel electrocatalysis according to claim 4, characterized in that, In step S2, in solution A, the concentration of ferrous sulfate is 10 mmol / L and the concentration of sodium sulfide is 1 mmol / L; in solution B, the concentration of sodium borohydride is 30~50 mmol / L. Solutions A and B are mixed at a volume ratio of 9:

1.

6. The method for uranium enrichment using zero-valent iron aerogel electrocatalysis according to claim 1, characterized in that, In step S2, the binder is a perfluorosulfonic acid polymer solution, and its addition amount is 0.5% to 5% of the total mass of the catalyst slurry; The organic solvent is one of ethanol and isopropanol, or a mixture of ethanol and isopropanol.

7. The method for uranium enrichment by electrocatalysis using zero-valent iron aerogel according to claim 1, characterized in that, In step S4, the counter electrode is a platinum sheet, a graphite rod, or a carbon felt, and the reference electrode is a saturated calomel electrode, an Ag / AgCl electrode, or a reversible hydrogen electrode.

8. The method for uranium enrichment by electrocatalysis using zero-valent iron aerogel according to claim 1, characterized in that, In step S4, during the electrochemical reduction reaction, an inert gas is introduced into the electrolytic cell at a flow rate of 100~200 mL / min, and the deoxygenation time is ≥ 30 min. The gas is continuously introduced during the reaction to maintain an oxygen-free environment in the electrolytic cell.

9. The method for uranium enrichment by electrocatalysis using zero-valent iron aerogel according to claim 1, characterized in that, In step S4, the applied pulse voltage is −0.1 V ~ −0.3 V (vs. RHE), the waveform of the pulse voltage is a square wave, the pulse-station-pulse method is used, the pulse frequency is 0.1 Hz ~ 10 Hz, and the duty cycle is 50%.

10. The method for uranium enrichment by electrocatalysis using zero-valent iron aerogel according to claim 1, characterized in that, In step S4, before the electrochemical reduction reaction, the pH of the uranium-containing water is adjusted to 4-8.

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