Method for catalytic degradation of NTO wastewater by FeCuO / mpg-C3N4 catalyst in photo-Fenton

Abstract

The application discloses a method for degrading NTO wastewater by FeCuO / mpg-C3N4 bimetallic catalyst light Fenton catalysis, and a new type of heterogeneous catalyst (FeCuO / mpg-C3N4) of bimetallic oxide is prepared by depositing Fe and Cu particles on mesoporous carbon nitride (mpg-C3N4) and then low-temperature annealing in air, and is used for light Fenton catalytic degradation of NTO. Under the conditions of irradiation of visible light and addition of proper H2O2, the FeCuO / mpg-C3N4 shows significant catalytic activity and stability for degradation of NTO. Researches show that the synergistic effect of the bimetal and the light / mpg-C3N4 effectively improve the reaction rate of the iron-based catalyst. Under the irradiation of visible light, the catalyst is put into NTO wastewater solution, proper H2O2 is added, 96.4% of NTO in the aqueous solution is degraded in 30 min, and after two cycles, the catalyst still has good catalytic activity, so that the NTO industrial wastewater generated in the development, preparation, transportation and assembly of NTO explosives can be treated economically, greenly and efficiently, and green, economic and efficient treatment of NTO wastewater is realized.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment and relates to a method for preparing FeCuO / mpg-C3N4 bimetallic catalyst and its application in the photocatalytic degradation of NTO explosive wastewater. Background Technology

[0002] 3-Nitro-1,2,4-triazol-5-one (NTO) is a non-sensitive, high-energy-density compound that has attracted widespread attention in recent years, with a density as high as 1.93 g / cm³. 3 The measured explosive performance of NTO is close to that of RDX (RDX); its sensitivity is low, similar to 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), and it also possesses the characteristic of TNT (trinitrotoluene) that it only burns without exploding when exposed to fire, making it an ideal choice for high-energy-density, low-sensitivity single-element explosives. NTO is water-soluble, with a solubility of 16.6 g / L in water at 25°C, 180 times that of TNT. This means that NTO can exist in high concentrations in wastewater. NTO aqueous solutions are acidic and have a low pKa value (between 3.7 and 3.76), posing a certain degree of environmental hazard. Compared with other energetic materials, NTO has a lower LD50. 50 The concentration is relatively high, approximately 5000 mg / kg. Similar results were obtained in rat and aquatic toxicity studies. Furthermore, when the concentration of NTO aqueous solution exceeds 100 mg / kg, a color change is visually observable, contributing to environmental degradation. Therefore, treating its industrial wastewater is essential.

[0003] Currently, the main treatment method for industrial wastewater from energetic materials industries, including NTO, is adsorption using adsorbents such as activated carbon. While this method is highly efficient, it also has drawbacks. When treating large volumes of wastewater, the adsorbent quickly becomes saturated, requiring frequent replacement of the adsorption column or reaction bed. Furthermore, the need to purchase large quantities of adsorbent leads to significant costs. In addition, addressing the issue of saturated adsorbents remains a challenging problem. Therefore, finding a green, economical, and efficient way to treat this type of industrial wastewater is an urgent issue that needs to be addressed.

[0004] Advanced oxidation processes (AOPs) are an alternative wastewater treatment technology. Among AOPs, the Fenton reaction is widely used for the degradation of various organic pollutants due to its low cost, simple operation, mild reaction conditions, and high efficiency. The Fenton reaction was discovered by H.J. Fenton in 1894, who reported that H₂O₂ can be degraded by ferrous (Fe₂O₂). 2+ Salts activate the oxidation of tartaric acid. The traditionally accepted Fenton mechanism is represented by the following equation:

[0005] Fe 2+ +H₂O₂→Fe 3++·OH+OH -

[0006] Ferrous ions (Fe) 2+ The above formula decomposes hydrogen peroxide (H2O2) to generate hydroxyl radicals (·OH) responsible for the degradation of organic matter, which then oxidize pollutants. The Fenton oxidation process is a highly efficient method for treating wastewater from high-energy materials. In 1999, Laurence Le Campion et al., through monitoring... 14 The oxidative decomposition of C-labeled NTO was evaluated, and the Fenton oxidation method for treating NTO wastewater was demonstrated, confirming the high efficiency of the Fenton reaction in degrading NTO.

[0007] With further development, Fe-based catalysts have been used in heterogeneous Fenton reactions to degrade organic pollutants due to their advantages such as low cost, non-toxicity, easy separation, and reusability

[30] . Traditional Fe-based catalysts face the problems of low catalytic efficiency and large metal particles, resulting in fewer active reaction sites; at the same time, the Fe produced by the reaction 3+ To Fe 2+ The slow conversion rate and the stringent requirements of pH, temperature and other conditions limit the catalytic activity of Fe-based catalysts. Summary of the Invention

[0008] The purpose of this invention is to address the aforementioned problems by providing a method for preparing a FeCuO / mpg-C3N4 bimetallic catalyst and applying this catalyst to the removal of NTO from industrial wastewater under light irradiation. This invention uses silica microspheres as a template and designs a nanostructure for carbon nitride through three steps: mixing with a precursor, thermal polymerization, and template cleaning, thereby increasing the specific surface area and pore volume of the carbon nitride. Using chemical reduction and low-temperature annealing calcination, Fe-Cu bimetallic oxide is loaded onto the high specific surface area carbon nitride. With the assistance of hydrogen peroxide and visible light, the activity of the Fenton reaction can be effectively improved, thus efficiently performing the Fenton oxidation reaction to degrade NTO. This makes it possible to treat NTO industrial wastewater in a green, economical, and efficient manner using photo-Fenton catalysis.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] A method for preparing FeCuO / mpg-C3N4 includes the following steps:

[0011] (1) Disperse the cyanamide and Ludox HS 40 silica microsphere solution evenly by ultrasonication, and then place it in an oil pan at 90°C and stir to slowly evaporate the water;

[0012] (2) Grind the white solid obtained by evaporation into fine powder and place it in an alumina crucible; in a muffle furnace, heat the muffle furnace to 550°C and keep it at that temperature, and thermally polymerize cyanamide to obtain graphitic carbon nitride (g-C3N4); cool naturally to room temperature and grind the resulting dark yellow solid into yellow powder using a mortar and pestle.

[0013] (3) Add the yellow powder obtained in step (2) to the ammonium fluoride aqueous solution, stir evenly to obtain a suspension, filter the filter cake obtained after filtration, wash it with sodium carbonate aqueous solution until neutral, and then wash it with water and ethanol in sequence.

[0014] (4) Place the filter cake from step (3) in an oven and dry it under vacuum at 60°C. Then grind the filter cake into powder to obtain mpg-C3N4.

[0015] (5) Add the mpg-C3N4 obtained in step (4) to an aqueous solution of FeCl3 and CuCl2 and disperse it evenly by ultrasonication; add sodium borohydride (NaBH4) solution dropwise to reduce the Fe on mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained; the mixture was stirred at room temperature until the reaction was complete, filtered, collected, washed with water, dried in an oven, and ground into powder to obtain FeCu / mpg-C3N4 powder;

[0016] (6) The FeCu / mpg-C3N4 powder from step (5) was heated to 350°C in a muffle furnace and held for annealing. After natural cooling to room temperature, the resulting yellow-green solid was ground into powder using a mortar and pestle, and FeCuO / mpg-C3N4 was finally synthesized.

[0017] The heat preservation time in step (2) is 3 to 5 hours; the heating rate in step (2) is 2 to 2.5 °C / min.

[0018] In step (3), the concentration of the ammonium fluoride aqueous solution is 4-6 mol / L, and the concentration of the sodium carbonate aqueous solution is 0.005-0.01 mol / L.

[0019] In step (4), the mass of mpg-C3N4 is 0.8-1.2g, the amount of FeCl3 is 0-1mmol, and the amount of CuCl2 is 0-1mmol. The amounts of mpg-C3N4, FeCl3, and CuCl2 can be adjusted according to the actual required loading rate and iron-copper ratio. The amount of sodium borohydride aqueous solution is 40-60mL, and the concentration is 4mg / mL.

[0020] A method for photo-Fenton catalytic degradation of NTO wastewater using FeCuO / mpg-C3N4 catalyst was employed. An aqueous NTO solution, FeCuO / mpg-C3N4 catalyst, and a magnetic stirrer were sequentially added to a reactor, denoted as the solution system. Cooling water was used to maintain a constant temperature, and the system was stirred for a period until physical adsorption equilibrium was reached. Subsequently, the system was exposed to visible light, and simultaneously, a 30% hydrogen peroxide (H2O2) solution with a volume ratio of 0.005–0.05 to the solution system was added, allowing for photo-Fenton catalytic degradation of NTO in the aqueous solution.

[0021] The concentration of the FeCuO / mpg-C3N4 catalyst in the solution system is above 1 mg / mL.

[0022] The volume ratio of the added 30% hydrogen peroxide (H2O2) solution to the solution system is 0.005 to 0.05;

[0023] The "stirring period" refers to stirring for more than 30 minutes.

[0024] The constant temperature is between 10 and 30°C.

[0025] The preparation method of the FeCuO / mpg-C3N4 catalyst includes the following steps:

[0026] (1) Disperse the cyanamide and Ludox HS 40 silica microsphere solution evenly by ultrasonication, and then place it in an oil pan at 90°C and stir to slowly evaporate the water;

[0027] (2) Grind the white solid obtained by evaporation into fine powder and place it in an alumina crucible; in a muffle furnace, heat the muffle furnace to 550℃ at a heating rate of 2-2.5℃ / min and keep it at that temperature for 3-5 hours, and thermally polymerize cyanamide to obtain graphitic carbon nitride (g-C3N4); cool naturally to room temperature and grind the obtained dark yellow solid into yellow powder using a mortar and pestle;

[0028] (3) Add the yellow powder obtained in step (2) to the ammonium fluoride aqueous solution, stir evenly to obtain a suspension, filter the filter cake obtained after filtration, wash it with sodium carbonate aqueous solution until neutral, and then wash it with water and ethanol in sequence; the concentration of the ammonium fluoride aqueous solution is 4-6 mol / L, and the concentration of the sodium carbonate aqueous solution is 0.005-0.01 mol / L.

[0029] (4) Place the filter cake from step (3) in an oven and dry it under vacuum at 60°C. Then grind the filter cake into powder to obtain mpg-C3N4.

[0030] (5) Add the mpg-C3N4 obtained in step (4) to an aqueous solution of FeCl3 and CuCl2 and disperse it evenly by ultrasonication; add sodium borohydride (NaBH4) solution dropwise to reduce the Fe on mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained; the reaction was stirred at room temperature until complete, filtered, collected, washed with water, dried in an oven, and ground into powder to obtain FeCu / mpg-C3N4 powder; wherein the mass of mpg-C3N4 was 0.8-1.2 g, the amount of FeCl3 was 0-1 mmol, and the amount of CuCl2 was 0-1 mmol; the amounts of mpg-C3N4, FeCl3, and CuCl2 could be adjusted according to the actual required loading rate and iron-copper ratio; the amount of sodium borohydride aqueous solution was 40-60 mL, and the concentration was 4 mg / mL.

[0031] (6) The FeCu / mpg-C3N4 powder from step (5) was heated to 350°C in a muffle furnace at a heating rate of 5°C / min and held at that temperature. After annealing, the powder was naturally cooled to room temperature. The resulting yellow-green solid was ground into powder using a mortar and pestle, and FeCuO / mpg-C3N4 was finally synthesized.

[0032] This invention provides an application of Fe-Cu bimetallic oxide-supported mesoporous graphitic carbon nitride as a photocatalyst for photo-Fenton degradation of NTO industrial wastewater under the combined action of light and H2O2.

[0033] Beneficial effects

[0034] (1) In this invention, FeCuO / mpg-C3N4 has a mesoporous nanostructure with a large specific surface area and pore volume, high efficiency of photogenerated electron-hole pair separation, and strong stability, which are all beneficial for photocatalysis.

[0035] (2) The preparation method of the material in this invention is simple, time-saving, energy-saving and controllable, and the raw material cost is low. It is expected to be applied on a large scale to produce highly active FeCuO / mpg-C3N4 catalyst material and has practical application value.

[0036] (3) Bimetallic compounds can effectively enhance the catalytic performance of catalysts. Iron oxide is an n-type semiconductor, and copper oxide is a p-type semiconductor. The pn junction formed by their co-supporting on mpg-C3N4 enhances the light absorption capacity of the catalyst and promotes the generation and migration of photogenerated carriers. Furthermore, iron and copper form a galvanic cell structure, and the Cu in the system... + The generated electrons can convert Fe 3+ Reduced to Fe 2+ This increases the Fenton reaction rate.

[0037] (4) The introduction of light can also improve the performance of the catalytic process. When the energy of the light irradiation exceeds the band gap, electrons will be excited from the valence band of carbon nitride to the conduction band, and the generated electrons will... 3+ Reduced to Fe 2+ This allows the Fenton reaction to occur again. Furthermore, carbon nitride, as a semiconductor, can also generate ·OH and ·O2 upon light excitation. - It is used to degrade NTO wastewater.

[0038] (5) The mesoporous graphitic carbon nitride material supported by Fe-Cu bimetallic oxide in this invention has excellent catalytic activity. After the addition of hydrogen peroxide, it can degrade more than 96.4% of NTO within 30 minutes under visible light or sunlight conditions and room temperature conditions, and still has good catalytic activity after two cycles.

[0039] (6) This application provides a green, environmentally friendly and efficient method for the treatment of industrial wastewater containing energetic materials such as NTO, and has practical application value. Attached Figure Description

[0040] In the following explanation, the samples refer to: The sample in Example 1 is FeCuO(5:5) / mpg-C3N4; the sample in Example 2 is FeCuO(5:5) / mpg-C3N4; the sample in Example 3 is FeCuO(5:5) / mpg-C3N4cycle1; the sample in Example 4 is FeCuO(5:5) / mpg-C3N4cycle2; and the sample in Example 5 is...

[0041] The sample in Example 6 was FeCuO(7:3) / mpg-C3N4, the sample in Comparative Example 1 was FeCuO(3:7) / mpg-C3N4, and the sample in Comparative Example 1 was FeO. x / mpg-C3N4, the sample in Comparative Example 2 is CuO x / mpg-C3N4, the sample in Comparative Example 3 is mpg-C3N4;

[0042] Figure 1 The components are FeCuO(5:5) / mpg-C3N4, FeCuO(5:5) / mpg-C3N4cycle1, and FeCuO(5:5).

[0043] / mpg-C3N4cycle2、FeCuO(7:3) / mpg-C3N4、FeCuO(3:7) / mpg-C3N4、FeO x / mpg-C3N4、CuO x XRD patterns of / mpg-C3N4 and mpg-C3N4;

[0044] Figure 2 SEM image of FeCuO(5:5) / mpg-C3N4;

[0045] Figure 3 TEM image of FeCuO(5:5) / mpg-C3N4;

[0046] Figure 4 HRTEM image of FeCuO(5:5) / mpg-C3N4;

[0047] Figure 5 TEM elemental mapping image of FeCuO(5:5) / mpg-C3N4;

[0048] Figure 6 is FeCuO(5:5) / mpg-C3N4, FeCuO(7:3) / mpg-C3N4, FeCuO(3:7) / mpg-C3N4, FeO x / mpg-C3N4、CuO x / mpg-C3N4, FT-IR spectra of mpg-C3N4;

[0049] Figure 7 Nitrogen adsorption-desorption curves for FeCuO(5:5) / mpg-C3N4 and mpg-C3N4;

[0050] Figure 8 BJH pore size distribution diagrams for FeCuO(5:5) / mpg-C3N4 and mpg-C3N4;

[0051] Figure 9 is FeCuO(5:5) / mpg-C3N4, mpg-C3N4, FeO x / mpg-C3N4、CuO x UV-Vis diffuse reflectance absorption spectrum of / mpg-C3N4;

[0052] Figure 10 FeCuO(5:5) / mpg-C3N4, mpg-C3N4, FeO x / mpg-C3N4、CuO x Fluorescence quantum yield parameters of / mpg-C3N4;

[0053] Figure 11 FeCuO(5:5) / mpg-C3N4, mpg-C3N4, FeO x / mpg-C3N4、CuO x EIS impedance diagram of / mpg-C3N4;

[0054] Figure 12For FeCuO(5:5) / mpg-C3N4, FeCuO(7:3) / mpg-C3N4, FeCuO(3:7) / mpg-C3N4mpg-C3N4, FeO x / mpg-C3N4、CuO x Concentration change curves of NTO degradation by photo-Fenton of / mpg-C3N4 and mpg-C3N4;

[0055] Figure 13 Concentration change curves of NTO degradation by photo-Fenton for FeCuO(5:5) / mpg-C3N4, FeCuO(5:5) / mpg-C3N4cycle1, and FeCuO(5:5) / mpg-C3N4cycle2;

[0056] Figure 14 Concentration change curves of NTO degradation by FeCuO / mpg-C3N4 under light and dark Fenton conditions;

[0057] Figure 15 FeCuO(5:5) / mpg-C3N4、FeCuO(5:5) / mpg-C3N4cycle1、FeCuO(5:5)

[0058] The first-order kinetic fitting curve of NTO degradation by Fenton using / mpg-C3N4cycle2 photocatalysis. Detailed Implementation

[0059] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. The following are only specific embodiments, but the scope of protection of the invention is not limited thereto.

[0060] Example 1:

[0061] Take 5 g of cyanamide and 12.5 g of Ludox-HS 40 solution and sonicate them for 20 min in an ultrasonic machine to disperse them evenly. Then add a magnetic stir bar and place it in an oil pan at 90℃ to slowly evaporate. Grind the white solid obtained by evaporation into a fine powder without particles and place it in an alumina crucible. Place the crucible in a muffle furnace and heat the muffle furnace to 550℃ at a heating rate of 2.3℃ / min and hold it at that temperature for 4 h. After the reaction is completed, let it cool naturally to room temperature and grind the deep yellow solid obtained into a yellow powder without particles using a mortar and pestle. Add the yellow powder to 100 mL of 4 mol / L ammonium fluoride aqueous solution and stir for 48 h. Then filter the suspension. Wash the filter cake obtained with 0.01 mol / L sodium carbonate aqueous solution until neutral, then wash it three times with water and once with ethanol. Then dry it to obtain mpg-C3N4.

[0062] 1000 mg of mpg-C3N4 was added to 100 mL of water containing 0.5 mmol (81.1 mg) FeCl3 and 0.5 mmol (67.2 mg) FeCl3 and ultrasonically dispersed for 4 h. Subsequently, under magnetic stirring, 40 mL of sodium borohydride solution (4 mg / mL) was added dropwise to reduce the Fe on the mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained, and then stirred at room temperature for 8 h. The sample was collected by filtration, washed with water and ethanol, and dried under vacuum at 60 °C for 12 h. FeCu / mpg-C3N4 was heated to 350 °C in a muffle furnace at a rate of 5 °C / min and held for 2 h to finally synthesize FeCuO / mpg-C3N4.

[0063] The prepared FeCuO / mpg-C3N4 was applied to the photo-Fenton catalytic degradation of NTO wastewater.

[0064] Add 50.0 mg FeCuO / mpg-C3N4, 50.0 mL of 40 mg / L NTO aqueous solution, and a magnetic stir bar to the reactor. Connect the reactor to a condenser. Place a filter above the reactor that can remove light wavelengths below 400 nm. Adjust the distance between the 300 W xenon lamp light source and the reactor so that the power of the light is 1000 mW / cm² when it comes into contact with the aqueous phase system. 2 Stirring for 30 minutes under light-protected conditions to reach physical adsorption equilibrium. Turn on the reactor's condensate drain to maintain room temperature. Turn on the xenon lamp and add 0.2 mL of 30% H₂O₂ solution. React under light irradiation. Take 2 mL samples at 5, 10, 20, and 30 minutes of reaction time and measure the absorbance at 336 nm using a UV spectrophotometer to monitor the NTO concentration change. The degradation curve is obtained, as shown below. Figure 13 As shown; and a pseudo-first-order dynamic model was used for fitting, as follows. Figure 15 As shown in Table 2, the specific k values ​​are as follows.

[0065] Example 2:

[0066] Take 5 g of cyanamide and 12.5 g of Ludox-HS 40 solution and sonicate them for 20 min in an ultrasonic machine to disperse them evenly. Then add a magnetic stir bar and place it in an oil pan at 90℃ to slowly evaporate. Grind the white solid obtained by evaporation into a fine powder without particles and place it in an alumina crucible. Place the crucible in a muffle furnace and heat the muffle furnace to 550℃ at a heating rate of 2.3℃ / min and hold it at that temperature for 4 h. After the reaction is completed, let it cool naturally to room temperature and grind the deep yellow solid obtained into a yellow powder without particles using a mortar and pestle. Add the yellow powder to 100 mL of 4 mol / L ammonium fluoride aqueous solution and stir for 48 h. Then filter the suspension. Wash the filter cake obtained with 0.01 mol / L sodium carbonate aqueous solution until neutral, then wash it three times with water and once with ethanol. Then dry it to obtain mpg-C3N4.

[0067] 1000 mg of mpg-C3N4 was added to 100 mL of water containing 0.5 mmol (81.1 mg) FeCl3 and 0.5 mmol (67.2 mg) FeCl3 and ultrasonically dispersed for 4 h. Subsequently, under magnetic stirring, 40 mL of sodium borohydride solution (4 mg / mL) was added dropwise to reduce the Fe on the mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained, and then stirred at room temperature for 8 h. The sample was collected by filtration, washed with water and ethanol, and dried under vacuum at 60 °C for 12 h. FeCu / mpg-C3N4 was heated to 350 °C in a muffle furnace at a rate of 5 °C / min and held for 2 h to finally synthesize FeCuO / mpg-C3N4.

[0068] The prepared FeCuO / mpg-C3N4 was applied to the photo-Fenton catalytic degradation of NTO wastewater.

[0069] 50.0 mg FeCuO / mpg-C3N4, 50.0 mL of a 40 mg / L NTO aqueous solution, and a magnetic stir bar were added to the reactor. The reactor's cooling water system was connected, and the mixture was stirred for 30 min under light-protected conditions to reach physical adsorption equilibrium. The reactor's cooling water system was then turned on to maintain room temperature. 0.2 mL of 30% H2O2 solution was added, and the reaction was carried out in the dark. 2 mL samples were taken at 5, 10, 20, and 30 min of reaction time, and the absorbance of the solution at 336 nm was measured using a UV spectrophotometer to monitor the NTO concentration change. The degradation curve was obtained, as shown below. Figure 14 As shown in Table 2, a quasi-first-order dynamic model was used for fitting, and the specific k values ​​are shown in Table 2.

[0070] Example 3:

[0071] After Example 1, the solution system was filtered and washed with deionized water, then vacuum dried in an oven at 60°C. Subsequently, 50.0 mg FeCuO / mpg-C3N4, 50.0 mL of a 40 mg / L NTO aqueous solution, and a magnetic stir bar were added to the reactor. A condenser was connected to the reactor, and a filter capable of removing light wavelengths below 400 nm was placed above the reactor. The distance between the 300 W xenon lamp light source and the reactor was adjusted so that the power of the light upon contact with the aqueous phase was 1000 mW / cm². 2 Stirring for 30 minutes under light-protected conditions to reach physical adsorption equilibrium. Turn on the reactor's condensate drain to maintain room temperature. Turn on the xenon lamp and add 0.2 mL of 30% H₂O₂ solution. React under light irradiation. Take 2 mL samples at 5, 10, 20, and 30 minutes of reaction time and measure the absorbance at 336 nm using a UV spectrophotometer to monitor the NTO concentration change. The degradation curve is obtained, as shown below. Figure 13 As shown; and a pseudo-first-order dynamic model was used for fitting, as follows. Figure 15 As shown in Table 2, the specific k values ​​are as follows.

[0072] Example 4:

[0073] After Example 3, the solution system was filtered and washed with deionized water, then vacuum dried in an oven at 60°C. Subsequently, 50.0 mg FeCuO / mpg-C3N4, 50.0 mL of a 40 mg / L NTO aqueous solution, and a magnetic stir bar were added to the reactor. The reactor's condenser was connected, and a filter capable of removing light wavelengths below 400 nm was placed above the reactor. The distance between the 300 W xenon lamp light source and the reactor was adjusted so that the light power upon contact with the aqueous phase was 1000 mW / cm². 2 Stirring for 30 minutes under light-protected conditions to reach physical adsorption equilibrium. Turn on the reactor's condensate drain to maintain room temperature. Turn on the xenon lamp and add 0.2 mL of 30% H₂O₂ solution. React under light irradiation. Take 2 mL samples at 5, 10, 20, and 30 minutes of reaction time and measure the absorbance at 336 nm using a UV spectrophotometer to monitor the NTO concentration change. The degradation curve is obtained, as shown below. Figure 13 As shown; and a pseudo-first-order dynamic model was used for fitting, as follows. Figure 15 As shown in Table 2, the specific k values ​​are as follows.

[0074] Example 5:

[0075] The preparation method and parameters of mpg-C3N4 are the same as those in Example 1.

[0076] 1000 mg of mpg-C3N4 was added to 100 mL of water containing 0.7 mmol (113.5 mg) FeCl3 and 0.3 mmol (40.3 mg) FeCl3 and ultrasonically dispersed for 4 h. Subsequently, under magnetic stirring, 40 mL of sodium borohydride solution (4 mg / mL) was added dropwise to reduce the Fe on the mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained, and then stirred at room temperature for 8 h. The sample was collected by filtration, washed with water and ethanol, and dried under vacuum at 60 °C for 12 h. FeCu / mpg-C3N4 was heated to 350 °C in a muffle furnace at a rate of 5 °C / min and held for 2 h to finally synthesize FeCuO / mpg-C3N4.

[0077] The prepared FeCuO / mpg-C3N4 was applied to the photo-Fenton catalytic degradation of NTO wastewater.

[0078] The subsequent degradation applications followed the same procedures and parameters as in Example 1. Degradation curves were shown below. Figure 12 As shown in Table 2, a quasi-first-order dynamic model was used for fitting, and the specific k values ​​are shown in Table 2.

[0079] Example 6:

[0080] The preparation method and parameters of mpg-C3N4 are the same as those in Example 1.

[0081] 1000 mg of mpg-C3N4 was added to 100 mL of water containing 0.3 mmol (48.7 mg) FeCl3 and 0.7 mmol (94.1 mg) FeCl3 and ultrasonically dispersed for 4 h. Subsequently, under magnetic stirring, 40 mL of sodium borohydride solution (4 mg / mL) was added dropwise to reduce the Fe on the mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained, and then stirred at room temperature for 8 h. The sample was collected by filtration, washed with water and ethanol, and dried under vacuum at 60 °C for 12 h. FeCu / mpg-C3N4 was heated to 350 °C in a muffle furnace at a rate of 5 °C / min and held for 2 h to finally synthesize FeCuO / mpg-C3N4.

[0082] The prepared FeCuO / mpg-C3N4 was applied to the photo-Fenton catalytic degradation of NTO wastewater.

[0083] The subsequent degradation applications followed the same procedures and parameters as in Example 1. Degradation curves were shown below. Figure 12 As shown in Table 2, a quasi-first-order dynamic model was used for fitting, and the specific k values ​​are shown in Table 2.

[0084] Comparative Example 1:

[0085] Take 5 g of cyanamide and 12.5 g of Ludox-HS 40 solution and sonicate them for 20 min in an ultrasonic machine to disperse them evenly. Then add a magnetic stir bar and place it in an oil pan at 90℃ to slowly evaporate. Grind the white solid obtained by evaporation into a fine powder without particles and place it in an alumina crucible. Place the crucible in a muffle furnace and heat the muffle furnace to 550℃ at a heating rate of 2.3℃ / min and hold it at that temperature for 4 h. After the reaction is completed, let it cool naturally to room temperature and grind the deep yellow solid obtained into a yellow powder without particles using a mortar and pestle. Add the yellow powder to 100 mL of 4 mol / L ammonium fluoride aqueous solution and stir for 48 h. Then filter the suspension. Wash the filter cake obtained with 0.01 mol / L sodium carbonate aqueous solution until neutral, then wash it three times with water and once with ethanol. Then dry it to obtain mpg-C3N4.

[0086] 1000 mg of mpg-C3N4 was added to 100 mL of water containing 1 mmol (162.2 mg) of FeCl3 and ultrasonically dispersed for 4 h. Subsequently, under magnetic stirring, 40 mL of sodium borohydride solution (4 mg / mL) was added dropwise to reduce the Fe on the mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained, and then stirred at room temperature for 8 h. The sample was collected by filtration, washed with water and ethanol, and vacuum dried at 60 °C for 12 h. Fe / mpg-C3N4 was heated to 350 °C in a muffle furnace at a rate of 5 °C / min and held for 2 h to finally synthesize FeO. x / mpg-C3N4.

[0087] The prepared FeO x / mpg-C3N4 is used for photocatalytic degradation of NTO wastewater by Fenton.

[0088] 50.0 mg FeO x A 1000 mW / cm³ solution of C3N4, 50.0 mL of a 40 mg / L NTO aqueous solution, and a magnetic stir bar are added to the reactor. A condenser is connected to the reactor. A filter that removes light wavelengths below 400 nm is placed above the reactor. The distance between the 300 W xenon lamp light source and the reactor is adjusted so that the power of the light upon contact with the aqueous phase is 1000 mW / cm². 2Stir for 30 minutes under light-protected conditions to reach physical adsorption equilibrium. Turn on the reactor's condensate drain to maintain room temperature. Turn on the xenon lamp and add 0.2 mL of 30% H₂O₂ solution. React under light irradiation. Take 2 mL samples at 5, 10, 20, and 30 minutes of reaction time and measure the absorbance at 336 nm using a UV spectrophotometer to monitor the NTO concentration change. Degradation curves are shown below. Figure 12 As shown in Table 2, a quasi-first-order dynamic model was used for fitting, and the specific k values ​​are shown in Table 2.

[0089] Comparative Example 2:

[0090] The preparation method and parameters of mpg-C3N4 are the same as those in Comparative Example 1.

[0091] 1000 mg of mpg-C3N4 was added to 100 mL of water containing 1 mmol (134.4 mg) of CuCl2 and ultrasonically dispersed for 4 h. Subsequently, under magnetic stirring, 40 mL of sodium borohydride solution (4 mg / mL) was added dropwise to reduce the Fe on the mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained, and then stirred at room temperature for 8 h. The sample was collected by filtration, washed with water and ethanol, and vacuum dried at 60 °C for 12 h. Cu / mpg-C3N4 was heated to 350 °C in a muffle furnace at a rate of 5 °C / min and held for 2 h to finally synthesize CuO. x / mpg-C3N4.

[0092] The prepared CuO x / mpg-C3N4 is used for photocatalytic degradation of NTO wastewater by Fenton.

[0093] The subsequent degradation applications followed the same procedures and parameters as Comparative Example 2. Degradation curves are shown below. Figure 12 As shown in Table 2, a quasi-first-order dynamic model was used for fitting, and the specific k values ​​are shown in Table 2.

[0094] Comparative Example 3:

[0095] The preparation method and parameters of mpg-C3N4 are the same as those in Comparative Example 1.

[0096] The prepared mpg-C3N4 was applied to the photo-Fenton catalytic degradation of NTO wastewater.

[0097] The operation and parameters for subsequent degradation applications were the same as in Comparative Example 2. The degradation curves are shown below. Figure 12 As shown in Table 2, a quasi-first-order dynamic model was used for fitting, and the specific k values ​​are shown in Table 2.

[0098] Referring to the accompanying drawings, mpg-C3N4 and FeO are described. x / mpg-C3N4、CuO x Characterization of FeCuO / mpg-C3N4 and FeCuO / mpg-C3N4. The following explanations refer to the following samples: Sample 1 in Example 1 is FeCuO(5:5) / mpg-C3N4; Sample 2 in Example 2 is FeCuO(5:5) / mpg-C3N4; Sample 3 in Example 3 is FeCuO(5:5) / mpg-C3N4cycle1; Sample 4 in Example 4 is FeCuO(5:5) / mpg-C3N4cycle2; Sample 5 in Example 5 is FeCuO(7:3) / mpg-C3N4; Sample 6 in Example 6 is FeCuO(3:7) / mpg-C3N4; and Sample 1 in Comparative Example 1 is FeO / mpg-C3N4. x / mpg-C3N4, the sample in Comparative Example 2 is CuO x / mpg-C3N4, the sample in Comparative Example 3 is mpg-C3N4;

[0099] like Figure 1 As shown in the figure, all samples exhibit significant reflections at two identical locations. The reflection at 32.1° (equivalent to 27.6° for the Cu target using Jade) is due to the interlayer stacking of the conjugated aromatic system corresponding to the graphitic carbon nitride (002) crystal plane, while the weaker reflection at 15.3° (equivalent to 13.3° for the Cu target using Jade software) is related to the structural repeating units of the carbon nitride (100) crystal plane. Almost no Cu and Fe diffraction peaks were detected, likely due to the low metal content and high dispersion on the mpg-C3N4 surface, without significant agglomeration. Furthermore, all samples showed two diffraction peaks at 27.6° and 13.3°, indicating that the introduction of Fe-Cu oxide did not alter the original crystal structure of mpg-C3N4. Changing the Fe-Cu ratio, Fe-Cu loading rate, and XRD results after one cycle did not significantly alter the samples, indicating good stability.

[0100] like Figure 2 As shown, the morphology of FeCuO(5:5) / mpg-C3N4 is not a layered stacked structure like that of blocky graphitic carbon nitride, but rather a relatively uniform porous structure.

[0101] like Figure 3 , 4As shown in Figure 5, the FeCuO(5:5) / mpg-C3N4 surface exhibits a distinct near-circular porous structure, with spherical FeCuO particles uniformly dispersed on the surface without significant agglomeration. Size measurements of over 50 particles revealed that the average particle size of the metal oxides in the catalyst ranged from 3 to 9 nm, with the main particle size being 5 to 7 nm and an average particle size of 6.45 nm. The particle size distribution is shown in Figure 5. Figure 4 As shown. To further investigate the presence of FeCuO in the catalyst, TEM-EDS spectra were used to determine the elemental distribution in the catalyst, confirming the presence of five elements: C, N, O, Fe, and Cu in FeCuO(5:5) / mpg-C3N4. The uniform dispersion of Fe, Cu, and O on the support indicates the successful preparation of Fe-Cu bimetallic oxide-supported mesoporous carbon nitride.

[0102] like Figure 6 As shown, the functional groups of the samples were studied using FT-IR, and all samples were within the range of 810 cm⁻¹. -1 A clear absorption peak was generated at 1210, which is caused by the stretching vibration of the triazine unit. All samples showed an absorption peak at 1210. -1 ~1700cm -1 The presence of similar absorption bands in the range is related to the stretching vibrations of CN, CN heterocycles, and C-NH-C. Meanwhile, at 3000... -1 ~3500cm -1 The large absorption bands in the range are attributed to the stretching vibrations of water or residual NH or OH groups of amino groups that did not participate in thermal condensation in the samples. The infrared spectra of the four samples are basically consistent, all retaining the typical basic unit structure of g-C3N4, indicating that the addition of metal oxides did not change the original chemical structure of mpg-C3N4, which is consistent with the XRD results.

[0103] Table 1. Specific surface area, pore volume, and average pore diameter of mpg-C3N4 and FeCuO(5:5) / mpg-C3N4

[0104]

[0105] like Figure 7 and 8 As shown, hysteresis loops were generated on the adsorption-desorption curves of mpg-C3N4 and FeCuO(5:5) / mpg-C3N4, which are type IV isotherms with mesoporous structure characteristics. The pore size inside mpg-C3N4 and FeCuO(5:5) / mpg-C3N4 is mainly distributed around 12 nm, which is similar to the size of nano-silica microspheres. This proves that the pores did not collapse after template removal and have good mechanical stability, and also proves that the mesoporous structure was successfully preserved.

[0106] As shown in Table 1, compared with mpg-C3N4, FeCuO(5:5) / mpg-C3N4 has a smaller specific surface area because some Fe-Cu oxide particles are deposited on the inner pore surface, which reduces the pore volume and pore size of mpg-C3N4.

[0107] like Figure 9 As shown, after loading a light-absorbing metal oxide onto mpg-C3N4, FeO x / mpg-C3N4、CuO x Both / mpg-C3N4 and FeCuO(5:5) / mpg-C3N4 showed a certain degree of red shift at their absorption edges, increasing the absorption range in the visible light region; in addition, the light absorption capacity of the loaded samples was enhanced to a certain extent, among which

[0108] The Fe-Cu bimetallic oxide-supported sample exhibits greater absorption capacity because the introduction of iron and copper constructs a heterojunction, enabling the catalyst to be excited by lower-energy, broader-wavelength light, which is beneficial for the utilization of solar energy and improves photocatalytic efficiency.

[0109] like Figure 10 As shown, mpg-C3N4, FeO x / mpg-C3N4、CuO x The quantum yields of / mpg-C3N4 and FeCuO(5:5) / mpg-C3N4 were 2.2%, 1.5%, and 1.2%, respectively, indicating that the loading and co-loading of iron and copper metal oxides can effectively suppress the recombination of photogenerated carriers and promote their separation and migration capabilities.

[0110] like Figure 11 As shown, the AC impedance Nyquist plots (EIS) of the four catalyst samples are displayed. The impedance curves of all samples exhibit a similar trend, with smaller arc radii corresponding to better photoelectric properties. Under visible light irradiation, FeO... x / mpg-C3N4、CuO x The arc radii of / mpg-C3N4 and FeCuO(5:5) / mpg-C3N4 are much smaller than those of mpg-C3N4, with FeCuO(5:5) / mpg-C3N4 having the smallest arc radius. This confirms that iron and copper oxides can promote charge transport on the catalyst surface, and the synergistic effect of iron and copper can further enhance the photoelectric performance of the catalyst.

[0111] The diagrams illustrate FeCuO(5:5) / mpg-C3N4, FeCuO(5:5) / mpg-C3N4cycle1, FeCuO(5:5) / mpg-C3N4cycle2, FeCuO(7:3) / mpg-C3N4, FeCuO(3:7) / mpg-C3N4, and FeO. x / mpg-C3N4、CuO x / mpg-C3N4 and mpg-C3N4 are used for the photo-Fenton catalytic degradation of NTO.

[0112] like Figure 12 As shown, after adding 0.2 ml of H2O2 and irradiating with light for 30 min, the following parameters were observed: FeCuO(5:5) / mpg-C3N4, FeCuO(7:3) / mpg-C3N4, FeCuO(3:7) / mpg-C3N4, and FeO... x / mpg-C3N4、CuO x / mpg-C3N4 and mpg-C3N4 degraded and removed 96.4%, 94.9%, 90.1%, 86.9%, 92.9%, and 78.0% of NTO from the solution, respectively, demonstrating the enhancement of catalytic performance by Fe-Cu bimetallic catalysts.

[0113] like Figure 13 As shown, the catalytic reaction rate decreased slightly after one and two cycles, but it could still degrade 94.7% and 93.8% of NTO, respectively, after 30 min, indicating that the catalyst has good cyclicity.

[0114] like Figure 14 As shown, illumination significantly improves the efficiency of the Fenton reaction; after adding illumination, the efficiency is improved within 30 minutes.

[0115] The removal rate of NTO increased from 76.6% to 96.4%, indicating that the introduction of light can also improve the performance of the catalytic process.

[0116] The first-order kinetic constants for the catalytic degradation of NTO by the above samples are shown in the table below:

[0117] Table 2 First-order kinetic constants for each embodiment

[0118]

[0119] The photocatalytic degradation of NTO by FeCuO / mpg-C3N4 using Fenton is more efficient than that by mpg-C3N4, and exhibits good cyclicity, indicating that this method can synthesize high-performance carbon nitride photocatalytic materials. The photocatalytic degradation of NTO by Fe-Cu bimetallic oxide-supported mesoporous carbon nitride is more efficient than that by FeO. x / mpg-C3N4 and CuO x / mpg-C3N4 exhibited a synergistic effect of Fe-Cu bimetallic supported catalysis, promoting the generation and migration of photogenerated carriers. The introduction of light also effectively improved catalytic performance; when the energy of the light irradiation exceeded the band gap, electrons were excited from the valence band to the conduction band of carbon nitride, and the generated electrons carried Fe... 3+ Reduced to Fe 2 + This allows the Fenton reaction to occur again. Simultaneously, carbon nitride can also photocatalytically degrade NTO through its own generated free radicals, thus enhancing the degradation capacity.

[0120] The photocatalytic degradation of NTO wastewater by mesoporous graphitic carbon nitride supported by Fe-Cu bimetallic oxide exhibits relatively high efficiency. The degradation of NTO can be achieved by adding a small amount of H2O2 under light irradiation. At the same time, the catalyst has the characteristics of simple preparation, low cost, good stability, non-toxicity, and recyclability. This method is green, energy-saving, and economical. In the future, it is expected to replace the current adsorption treatment method for treating wastewater containing energetic materials such as NTO.

[0121] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for photocatalytic degradation of NTO wastewater using FeCuO / mpg-C3N4 catalyst and Fenton catalyst, characterized in that: NTO aqueous solution, FeCuO / mpg-C3N4 catalyst, and magnetic stir bar were sequentially added to the reactor, denoted as the solution system. The system was kept at a constant temperature using condensate and stirred for a period of time until physical adsorption equilibrium was reached. Subsequently, the system was exposed to visible light, and 30% hydrogen peroxide solution with a volume ratio of 0.005 to 0.05 of the solution system was added simultaneously for photo-Fenton catalytic degradation of NTO in the aqueous solution. The preparation method of the FeCuO / mpg-C3N4 catalyst includes the following steps: The cyanamide and Ludox HS 40 silica microsphere solution were ultrasonically dispersed evenly, and then placed in an oil pan at 90°C and stirred to slowly evaporate the water. The white solid obtained from evaporation is ground into a fine powder and placed in an alumina crucible. In a muffle furnace, the temperature of the muffle furnace is raised to 550°C and held. The cyanamide is thermally polymerized to obtain graphitic carbon nitride. After naturally cooling to room temperature, the resulting dark yellow solid is ground into a yellow powder using a mortar and pestle. The yellow powder obtained in step (2) was added to an ammonium fluoride aqueous solution and stirred until a suspension was obtained. The filter cake obtained after filtration was washed with sodium carbonate aqueous solution until neutral, and then washed with water and ethanol in sequence. The filter cake from step (3) was placed in an oven and vacuum dried at 60°C. The filter cake was then ground into powder to obtain mpg-C3N4. The mpg-C3N4 obtained in step (4) was added to an aqueous solution of FeCl3 and CuCl2 and ultrasonically dispersed until uniform; sodium borohydride (NaBH4) solution was added dropwise to reduce the Fe on the mpg-C3N4. 3+ and Cu 2+ Fe-Cu alloy was obtained; the mixture was stirred at room temperature until the reaction was complete, filtered, collected, washed with water, dried in an oven, and ground into powder to obtain FeCu / mpg-C3N4 powder; The FeCu / mpg-C3N4 powder from step (5) was heated to 350°C in a muffle furnace and held at that temperature for annealing. After natural cooling to room temperature, the resulting yellow-green solid was ground into powder using a mortar and pestle, and FeCuO / mpg-C3N4 was finally synthesized.

2. The method as described in claim 1, characterized in that: The concentration of the FeCuO / mpg-C3N4 catalyst in the solution system is above 1 mg / mL.

3. The method as described in claim 1, characterized in that: The "stirring period" refers to stirring for more than 30 minutes.

4. The method as described in claim 1, characterized in that: The constant temperature is between 10 and 30°C.

5. The method as described in claim 1, characterized in that: The heat preservation time in step (2) is 3 to 5 hours; the heating rate in step (2) is 2 to 2.5 °C / min.

6. The method as described in claim 1, characterized in that: In step (3), the concentration of the ammonium fluoride aqueous solution is 4~6 mol / L, and the concentration of the sodium carbonate aqueous solution is 0.005~0.01 mol / L.

7. The method as described in claim 1, characterized in that: In step (4), the mass of mpg-C3N4 is 0.8~1.2g, the amount of FeCl3 is 0~1mmol, the amount of CuCl2 is 0~1mmol, and the amount of sodium borohydride aqueous solution is 40~60mL with a concentration of 4mg / mL.

8. The method as described in claim 1, characterized in that: The heating rate in step (6) is 5℃ / min.

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