Application of potassium-doped nitrogen oxidation phosphorescence catalysis acidic uranium-containing wastewater

Abstract

The invention discloses application of potassium-doped nitrogen oxidation phosphorescence catalysis on acidic uranium-containing wastewater, and belongs to the technical field of photocatalytic materials. According to the application, the K-PON photocatalyst is directly put into acidic uranium-containing wastewater with the pH value of 0.5-6 and is used for reducing and removing U (VI). The K-PON is prepared by mixing and grinding phosphorus oxynitride and potassium thiocyanate according to a mass ratio of 1: (0.5-4), and calcining at 400-600 DEG C for 1-5 hours. The core advantage of the invention is that the prepared K-PON photocatalyst not only can efficiently reduce U (VI) under the illumination condition, but also has the unique memory photocatalysis characteristic, can continuously release stored electrons in a dark environment, realizes the continuous reduction of U (VI), and has a good application prospect. The problems that a traditional photocatalysis technology depends on continuous illumination and is inactivated in a strongly acidic environment are solved, and a new material and a new method are provided for efficient and all-weather treatment of the acidic uranium-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, specifically to the application of potassium-doped nitrogen-phosphorus photocatalysis in acidic uranium-containing wastewater. Background Technology

[0002] Nuclear energy, as a key mature technology for achieving zero carbon emissions, has garnered significant attention for its sustainable development. Uranium, as the primary fuel for nuclear energy, is crucial for its sustainable supply. However, the widely used acid extraction process in uranium extraction generates large quantities of acidic uranium-containing wastewater with a pH value between 0.5 and 6 (pH=1-6; Applied Geochemistry, 2023, 148: 105534.). This type of wastewater possesses both chemical toxicity and radioactivity, posing a serious threat to the ecological environment and public health. Therefore, developing efficient and novel uranium-containing wastewater treatment technologies is of significant theoretical value and urgent practical importance.

[0003] Photocatalysis technology has shown great potential in environmental remediation due to its advantages such as reaction at room temperature and pressure, high efficiency, and no secondary pollution. This technology, by reducing soluble U(VI) to insoluble U(IV), shows promising prospects in treating uranium-containing wastewater. However, its application faces two major challenges: First, under strongly acidic conditions, H⁺ competitively adsorbs with uranyl ions (UO₂²⁺) on the catalyst surface, significantly reducing the uranium extraction rate; second, catalytic activity is highly dependent on continuous light, which limits its application in the absence of light.

[0004] Phosphorus oxynitride (PON) is a novel photocatalytic material with visible light response and ease of preparation, and has been applied to the photocatalytic reduction of uranium-containing wastewater (Patent Nos. CN113307239B and CN113477267B; Lai Xing. Preparation of Phosphorus Oxide and Research on its Photocatalytic Reduction of Uranium-Containing Wastewater [D]. East China University of Technology, 2020). However, phosphorus oxynitride still suffers from drawbacks such as few active sites and high electron-hole recombination, leading to loss of photocatalytic activity under strong acid conditions, thus limiting its application in such environments.

[0005] Meanwhile, photocatalysts with "memory photocatalysis" capabilities have been developed and applied to the photocatalytic removal of organic pollutants in recent years. Memory catalysis refers to the ability of these photocatalysts to maintain their catalytic activity in the dark without the need for continuous light irradiation, thus achieving "all-weather catalytic degradation activity." For example, catalyst doping with K enables sustainable photocatalytic uranium extraction from seawater; the flexible structure of K can store the excited electrons in the photocatalyst to form free radicals for uranium(VI) reduction under light-free conditions (C. Xu, P. Ravi Anusuyadevi, C. Aymonier, R. Luque, S. Marre, Nanostructuredmaterials for photocatalysis, Chem. Soc. Rev. 48 (2019) 3868–3902). However, the catalytic activity of memory photocatalytic materials is still very low, and their application in strongly acidic uranium-containing wastewater has not yet been reported. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an application of potassium-doped nitrogen oxidation phosphorus photocatalysis in acidic uranium-containing wastewater.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An application of potassium-doped nitrogen-phosphorus photocatalysis in acidic uranium-containing wastewater involves adding K-PON to the wastewater and directly photocatalytically reducing U(VI) in the wastewater under illumination, and continuously reducing U(VI) in the wastewater through memory photocatalysis under no-light conditions.

[0008] Furthermore, by adding 0.01-0.1g of K-PON to every 100mL of uranium-containing wastewater, the U(VI) concentration of the uranium-containing wastewater is 10-150mg / L.

[0009] Furthermore, the pH range of the uranium-containing wastewater is 0.5-6.

[0010] Furthermore, the application is carried out at a temperature of 10-50°C.

[0011] Furthermore, the K-PON is prepared by the following method: phosphorus oxynitride and potassium thiocyanate are thoroughly ground in a mortar, transferred to a crucible, and reacted in a tube furnace at 400-600℃ to obtain phosphorus oxynitride.

[0012] Furthermore, the preparation method of the K-PON includes the following steps: (1) Grind phosphorus oxide and potassium thiocyanate thoroughly in a mortar at a mass ratio of 1:(0.5-4); (2) Transfer the resulting mixture to a crucible and place it in a tube furnace, and react at 400-600℃ for 1-5 hours; (3) After cooling, filter, wash and dry to obtain K-PON photocatalyst.

[0013] Furthermore, in step (1), the mass ratio of nitrogen oxidizing phosphorus to potassium thiocyanate is 1:(0.5-4).

[0014] Furthermore, in step (2), the crucible is a quartz crucible.

[0015] Furthermore, in step (2), the heating rate of the reaction is 10-20 °C / min.

[0016] Furthermore, in step (3), the washing process uses anhydrous ethanol.

[0017] The beneficial effects of this invention are as follows: First, the most prominent advantage of this invention lies in its excellent adaptability to strong acid environments. Through successful potassium doping, the prepared K-PON photocatalyst can still maintain extremely high photocatalytic activity in strongly acidic uranium-containing wastewater with a pH value as low as 0.5-6. This effectively overcomes the technical bottleneck of traditional photocatalysts being easily deactivated under such harsh conditions due to competitive adsorption of hydrogen ions, solving a long-standing key problem in this field. Second, this invention introduces a unique "memory photocatalysis" performance, which is a first in this application field. The K-PON material can absorb and store photogenerated electrons during illumination. In the dark environment after the illumination stops, these stored electrons can be continuously released to reduce U(VI) in the wastewater, thereby achieving a breakthrough all-weather catalytic function of "energy storage under illumination and reaction in the dark," greatly improving the overall efficiency of the uranium extraction process and the feasibility of practical operation.

[0018] Furthermore, this K-PON catalyst exhibits highly efficient photocatalytic reduction capabilities. Experimental results show that it can achieve a removal rate of over 83.2% for high-concentration uranium solutions (e.g., 150 mg / L) after illumination. XPS analysis confirmed that the uranium mainly exists in the insoluble U(IV) form after the reaction, demonstrating that its core mechanism is highly efficient photocatalytic reduction, rather than simple physical adsorption, ensuring the stability and thoroughness of the treatment effect. Because of its ability to operate continuously in the dark, this invention greatly expands the application scenarios of photocatalysis technology, enabling its application in real-world environments with limited or unstable light conditions, such as deep wastewater, nighttime, or continuous rainy days, providing a novel solution for the practical promotion of nuclear wastewater treatment technology.

[0019] From the perspective of preparation process, this invention also has significant advantages. The preparation method of K-PON adopts a one-step molten salt reaction method, which is simple. It only requires simple grinding and mixing of phosphorus oxide and potassium thiocyanate and then direct calcination to obtain the product. It has low equipment requirements, is easy to scale up production, and has significant economic benefits and industrialization prospects. Finally, this technology is an environmentally friendly green technology. Its core is to achieve efficient extraction and safe immobilization of uranium by photocatalytically reducing toxic and soluble U(VI) to chemically stable and insoluble U(IV) precipitate. The entire process does not introduce additional harmful chemicals, fundamentally avoiding secondary pollution. It achieves the dual goals of environmental pollution control and strategic resource recovery, and has significant environmental benefits and resource value. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 The image shows the XRD pattern of the K-PON prepared in Example 1 of this invention.

[0022] Figure 2 This is a diagram of photocatalytic uranium extraction using K-PON prepared in Example 2 of the present invention.

[0023] Figure 3 This is an XPS image of the surface U after the K-PON reaction in Example 2 of the present invention.

[0024] Figure 4 This is a memory catalytic diagram of the K-PON prepared in Example 3 of the present invention.

[0025] Figure 5 This is a memory photocatalytic uranium extraction diagram of K-PON prepared in Example 4 of the present invention under a strong acid environment. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] An application of potassium-doped nitrogen-phosphorus photocatalysis in acidic uranium-containing wastewater involves using K-PON as a photocatalyst to photocatalytically reduce uranium ions in the wastewater. Specifically, K-PON is added to the acidic uranium-containing wastewater to directly photocatalytically reduce U(VI) in the wastewater.

[0028] Example 1: Phosphorus oxynitride and potassium thiocyanate were weighed at a mass ratio of 1:2 (0.4 g and 0.8 g respectively), ground thoroughly, and transferred to a crucible. The crucible was then placed in a tube furnace and held at 450°C for 3 hours. The heating rate was 15°C / min. After cooling to room temperature, the product was filtered, washed, and dried to obtain the target product K-PON. The XRD pattern of the target product is shown below. Figure 1 As shown, its peaks are consistent with those of the PON and K standard cards (PDF#80-0869 and PDF#40-0995), indicating that the prepared matrix is ​​still phosphorus oxynitride and K has been successfully doped. In summary, the sample prepared by this method is K-PON.

[0029] Example 2: Treatment of uranium-containing wastewater using K-PON as a reducing agent Weigh 20 mg of the K-PON prepared in Example 1 and add it to 100 ml of uranium standard solution (concentration 150 mg / L), adjusting the pH to 2.0. Place the solution in a photochemical reactor and react in the dark for 40 min, followed by photocatalytic reaction under a 400 W xenon lamp. After 150 min, turn off the lamp, and collect the supernatant every 30 min. Measure the uranium concentration using the arsene III spectrophotometric method. The results are as follows: Figure 2 As shown in the figure. The results indicate that the removal rate of K-PON can reach 83.2% after 150 min of photoreaction. XPS analysis of U on the K-PON surface after the reaction is shown in the figure. Figure 3 As shown, most of them are tetravalent, indicating that the reaction is a photocatalytic reduction reaction.

[0030] Example 3: Using K-PON as a reducing agent for memory photocatalysis of uranium-containing wastewater Two 20mg samples of K-PON prepared in Example 1 were weighed. One sample was added to 10ml of deionized water and placed in a photochemical reactor. It was then photocatalytically irradiated under a 400W xenon lamp for 30min. The irradiated sample was then added to 100ml of a uranium standard solution (pH=3.0, concentration 100mg / L). The lamp was turned off, and the reaction continued for 150min. The supernatant was collected every 30min, and the uranium concentration was measured using the arsene III spectrophotometric method. The other sample of K-PON was added to 100ml of a uranium standard solution (pH=3.0, concentration 100mg / L), the pH was adjusted to 3.0, and the reaction was carried out directly in the dark. The results are as follows. Figure 4As shown, the results indicate that unilluminated K-PON reaches adsorption equilibrium after 30 minutes. Illuminated K-PON, however, exhibits excellent memory photocatalytic activity, with a removal rate reaching 81.2%, demonstrating the superior memory photocatalytic activity of K-PON.

[0031] Example 4: Weigh 25 mg of the K-PON prepared in Example 1 and add it to 100 ml of uranium standard solution (concentration 50 mg / L), adjusting the pH to 1.0. Place the solution in a photochemical reactor and react in the dark for 40 min. Then, conduct a photocatalytic reaction under a 400 W xenon lamp for 2 h. After turning off the lamp, continue the reaction for 90 min. Take the supernatant every 30 min and measure the uranium concentration using the arsene III spectrophotometric method. The results are as follows: Figure 5 As shown, the results indicate that K-PON achieves memory photocatalytic activity in a strong acid system.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An application of potassium-doped nitrogen oxidation phosphorus photocatalysis in acidic uranium-containing wastewater, characterized in that, Potassium-doped phosphorus oxide (K-PON) was added to acidic uranium-containing wastewater, and U(VI) in the wastewater was directly photocatalytically reduced under light conditions, and U(VI) in the wastewater was continuously reduced under light-free conditions through memory photocatalysis.

2. The application according to claim 1, characterized in that, Add 0.01-0.1g of K-PON to every 100mL of uranium-containing wastewater to achieve a U(VI) concentration of 10-150mg / L.

3. The application according to claim 2, characterized in that, The pH range of the uranium-containing wastewater is 0.5-6.

4. The application according to claim 1, characterized in that, The application is carried out at a temperature of 10-50°C.

5. The application according to claim 1, characterized in that, The K-PON was prepared by grinding phosphorus oxynitrate and potassium thiocyanate thoroughly in a mortar, transferring them to a crucible, and reacting them in a tube furnace at 400-600℃ to obtain K-PON.

6. The application according to claim 5, characterized in that, The preparation method of the K-PON includes the following steps: (1) Grind phosphorus oxide and potassium thiocyanate thoroughly in a mortar at a mass ratio of 1:(0.5-4); (2) Transfer the resulting mixture to a crucible and place it in a tube furnace, and react at 400-600℃ for 1-5 hours; (3) After cooling, filter, wash and dry to obtain K-PON photocatalyst.

7. The application according to claim 6, characterized in that, In step (1), the mass ratio of nitrogen oxidizing phosphorus to potassium thiocyanate is 1:(0.5-4).

8. The application according to claim 6, characterized in that, In step (2), the crucible is a quartz crucible.

9. The application according to claim 6, characterized in that, In step (2), the heating rate of the reaction is 10-20 °C / min.

10. The application according to claim 6, characterized in that, In step (3), the washing is performed using anhydrous ethanol.

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