Fly ash-based composite catalytic material for normal-temperature gaseous ammonia oxidation and preparation method and application thereof

Abstract

The application belongs to the technical field of catalytic materials and its application, and relates to fly ash-based composite catalytic material for normal-temperature gaseous ammonia oxidation and a preparation method and application thereof. The preparation method comprises the following steps: S1, adding fly ash into water to obtain fly ash suspension liquid; S2, mixing titanium glue and the fly ash suspension liquid, stirring and heating until the liquid is evaporated dry; then drying and grinding to obtain fine powder; S3, adding the fine powder into HF solution to react, filtering, drying, calcining and then cooling to room temperature; and finally grinding to obtain the fly ash-based composite catalytic material for normal-temperature gaseous ammonia oxidation. The fly ash-based composite catalytic material is prepared by taking fly ash and titanium glue as raw materials, has significant catalytic activity, high catalytic efficiency, and can promote the oxidation of gaseous ammonia at normal temperature and normal pressure.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic materials and their applications, and relates to a fly ash-based composite catalytic material for normal-temperature gaseous ammonia oxidation, a preparation method and an application thereof. Background Art

[0002] With the development of animal husbandry in various regions, intensive pig farming has emerged on a large scale, resulting in increasing amounts of manure discharge and a growing problem of manure odor. Manure odor primarily originates from odorous substances such as ammonia, hydrogen sulfide, indole, and skatole. Excessive odorous substances pollute the pig farm environment, which not only affects the healthy growth of pigs and the quality of pork, but also has adverse effects on the health of farmers. Therefore, to maintain a clean pig farm environment, timely manure treatment and odor elimination are necessary. This ensures a clean pig farm environment, accelerates pig growth and development, and improves pork quality.

[0003] Existing technologies mostly use microbial deodorizers, spraying, and activated carbon adsorption to deodorize pig farms. While microbial deodorizers are quick to act, they are short-lived and have poor sustained effectiveness. Spraying produces wastewater, posing an environmental risk. Activated carbon adsorption generates solid waste and fails to fundamentally address the odor problem in pig farms. Therefore, existing deodorization methods are ineffective in deodorizing pig farms.

[0004] With the continuous advancement of technology, researchers have proposed the use of photocatalytic technology for deodorization. Specifically, photocatalytic technology can oxidize ammonia into N2 or nitrates; oxidize hydrogen sulfide into sulfates; and oxidize organic odorous substances such as indole and skatole into CO2 and H2O, thereby addressing the pollution problem caused by odorous substances. However, existing photocatalysts use TiO2 as the main material. Due to the normal temperature and pressure environment in pig farms, TiO2 has poor catalytic activity and is difficult to achieve ideal catalytic effects. This results in low catalytic efficiency for odorous substances (especially ammonia), resulting in limited catalytic oxidation of odorous substances (especially ammonia) in pig farms, which cannot meet actual needs.

[0005] In view of this, how to develop catalytic materials that have efficient catalytic oxidation effects on ammonia at room temperature and pressure is a current difficulty in research and development. Summary of the Invention

[0006] In response to the technical problems pointed out in the existing background technology that the existing photocatalysts have poor catalytic activity at room temperature and normal pressure, are difficult to exert catalytic effects, and have low catalytic efficiency, the present invention provides a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation, and its preparation method and application.

[0007] The fly ash-based composite catalytic material prepared by the invention uses fly ash and titanium colloid as raw materials, has significant catalytic activity and high catalytic efficiency, and can promote the oxidation of gaseous ammonia at normal temperature and pressure.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation comprises the following steps:

[0010] S1. Add fly ash into water and stir to obtain a fly ash suspension;

[0011] S2, mixing titanium colloid and the fly ash suspension obtained in step S1, stirring and heating until the liquid evaporates to dryness; then drying and grinding to obtain a fine powder; the titanium colloid contains TiO2, and the mass ratio of the fly ash to TiO2 is (1-3):(1-2);

[0012] S3. Add the fine powder from step S2 to an HF solution for reaction, then filter, dry the obtained solid product, calcine it at a temperature of 300° C. to 700° C., and cool it to room temperature; finally grind it to obtain a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation.

[0013] It is further defined that in step S2, the heating temperature is 70°C to 85°C; the drying temperature is 90°C to 100°C, and the drying time is 10h to 15h.

[0014] It is further defined that in step S3, the reaction time is 1 hour to 2 hours; the drying temperature is 80° C. to 100° C., and the drying time is 9 hours to 12 hours.

[0015] It is further defined that in step S3, the heating rate of the calcination process is 5°C / min; and the concentration of the HF solution is 0.5 mol / L to 1 mol / L.

[0016] The fly ash-based composite catalytic material is prepared by utilizing the method for preparing the fly ash-based composite catalytic material for normal-temperature gaseous ammonia oxidation.

[0017] It is further defined that, after XRD measurement, characteristic peaks of anatase TiO2 were detected at 25.7°, 37.5°, 38.4°, 39.2°, 48.8°, 54.8° and 55.9° of the fly ash-based composite catalytic material; characteristic peaks of rutile TiO2 were detected at 27.4°, 36.1°, 39.2°, 41.2°, 44.1°, 54.3° and 56.6°; the fly ash-based composite catalytic material has a twin phase structure of anatase TiO2 and rutile TiO2.

[0018] It is further defined that in the fly ash-based composite catalytic material, the optimal ratio of anatase TiO2 to rutile TiO2 is 9:1.

[0019] It is further defined that the fly ash-based composite catalytic material has a minimum band gap value of 2.87 eV and a maximum flat band potential of -0.43 V.

[0020] The fly ash-based composite catalytic material is used as a photocatalyst in the oxidation of gaseous ammonia at room temperature.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The fly ash-based composite catalytic material prepared by the present invention uses fly ash and titanium colloid as raw materials. It has significant catalytic activity and high catalytic efficiency at room temperature and pressure. It can improve the oxidation effect of gaseous ammonia when used in the oxidation of gaseous ammonia at room temperature.

[0023] 2. The present invention first mixes, heats and grinds fly ash and titanium colloid, and then treats and calcines them with HF to allow the fly ash and titanium colloid to be synergistically compounded to obtain a fly ash-based composite catalytic material. The synergistic effect of the raw materials allows the simultaneous presence of both anatase and rutile crystal phases of TiO2 in the fly ash-based composite catalytic material, ensuring that the fly ash-based composite catalytic material has excellent catalytic performance and promotes the oxidation of gaseous ammonia.

[0024] 3. The present invention has found through research that fly ash-based composite catalytic materials have significant photochemical properties, adsorption properties and repeatability, and can greatly improve the oxidation efficiency of ammonia at room temperature and pressure.

[0025] 4. The present invention uses fly ash and titanium colloid for compounding. The addition of fly ash not only improves the catalyst performance of the overall composite catalytic material, but also uses industrial solid waste fly ash as a matrix to achieve the purpose of treating waste with waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 XRD patterns of materials prepared in Example 1, Comparative Example 1 and Comparative Example 2;

[0027] Figure 2 This is an SEM image of the fly ash-based composite catalytic material prepared in Comparative Example 1;

[0028] Figure 3 This is an SEM image of the catalytic material prepared in Comparative Example 2;

[0029] Figure 4 This is a SEM image of the fly ash-based composite catalytic material prepared in Example 1;

[0030] Figure 5 This is a diagram showing the effects of ammonia oxidation of materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0031] Figure 6 The UV-Vis DRS graphs of the examples and comparative examples are shown;

[0032] Figure 7 Band gap diagrams of examples and comparative examples;

[0033] Figure 8 The photoluminescence spectra of the materials of the embodiment and the comparative example are shown;

[0034] Figure 9 Mott-Schottky test results of fly ash-based composite catalytic materials prepared in different embodiments;

[0035] Figure 10 Transient photocurrent response results of fly ash-based composite catalytic materials prepared in different embodiments;

[0036] Figure 11 Electrochemical impedance spectroscopy of materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0037] Figure 12 This is the repeatability test result of the fly ash-based composite catalytic material of Example 1;

[0038] Figure 13 This is a map of species produced on the surface of the fly ash-based composite catalytic material after catalytic reaction in Example 1. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will now be further described with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following implementations.

[0040] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0041] Technologies, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies, methods, and equipment should be considered part of the specification.

[0042] It should also be understood that the specific embodiments described above are only used to explain the present invention, and the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the scope of protection of the present invention / invention.

[0043] The present invention provides a method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation, comprising the following steps:

[0044] S1. Dissolve fly ash in water and stir to obtain a fly ash suspension;

[0045] S2. Mix the titanium colloid and the fly ash suspension obtained in step S1, stir and heat until the liquid evaporates to dryness; then dry and grind to obtain a fine powder.

[0046] The titanium colloid contains TiO2, and the mass ratio of fly ash to TiO2 is (1-3):(1-2). Exemplarily, the mass ratio of fly ash to TiO2 is 1:1, 1:2, 2:1, 3:1 or 3:2.

[0047] It should be noted that titanium colloid is a commercially available product; during implementation, the added volume of titanium colloid is calculated by reverse calculation based on the mass of TiO2 contained in the purchased titanium colloid and the mass ratio of fly ash to TiO2.

[0048] In step S2, the heating temperature is 70°C to 85°C; the drying temperature is 90°C to 100°C, and the drying time is 10 hours to 15 hours.

[0049] S3. Add the fine powder from step S2 to an HF solution for reaction, then filter, dry the obtained solid product, calcine it at a temperature of 300° C. to 700° C., and cool it to room temperature; finally grind it to obtain a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation.

[0050] In the present invention, the reaction time is 1 h to 2 h; the drying temperature is 80° C. to 100° C., and the drying time is 9 h to 12 h.

[0051] In the present invention, the heating rate during the calcination process is 5°C / min, the concentration of the HF solution is 0.5 mol / L to 1 mol / L, and the calcination temperature is 300°C, 400°C, 500°C, 600°C, or 700°C.

[0052] The fly ash-based composite catalytic material prepared by the present invention using the above-mentioned method for preparing fly ash-based composite catalytic materials for room-temperature gaseous ammonia oxidation has a twin-phase structure of anatase TiO2 and rutile TiO2 and has excellent catalytic activity; at the same time, the minimum band gap value is 2.87eV, the maximum flat band potential is -0.43V, it has significant photochemical properties, can establish a fast electron transmission channel at the interface, and the charge transfer is more efficient, which can greatly improve the oxidation efficiency of ammonia at room temperature and pressure.

[0053] The present invention also provides an application of a fly ash-based composite catalytic material as a photocatalyst in the oxidation of gaseous ammonia at room temperature.

[0054] The technical solution provided by the present invention is described in detail below with several implementations and the performance of the fly ash-based composite catalytic material prepared is studied through testing.

[0055] It should be noted that, in the following examples, unless otherwise specified, the chemicals and reagents used are commercially available products commonly used in the art.

[0056] It should be noted that, in the following examples, unless otherwise specified, the operations used are conventional operations; for example, unless otherwise specified, the operation temperature is room temperature operation. Unless otherwise specified, the test method is the standard test method available in the art.

[0057] It should be noted that, in the following examples, unless otherwise specified, the TiO2 mass contained in the titanium glue purchased is: 3g of TiO2 per 100mL of titanium glue, and the fly ash-based composite catalytic material is prepared based on this example.

[0058] Example 1

[0059] The preparation method of the fly ash-based composite catalytic material for gaseous ammonia oxidation at room temperature provided in this embodiment comprises the following steps:

[0060] S1, weigh 18g of fly ash into a beaker, and add 100mL of deionized water into the beaker; then stir for 1h to obtain a fly ash suspension.

[0061] S2, mix 300mL of titanium glue with the fly ash suspension, stir and heat at 80℃ until the liquid is evaporated; then dry at 100℃ for 12h, take out the mortar and grind until fine powder is obtained.

[0062] In this step, the mass ratio of fly ash to TiO2 is 2:1, the mass of fly ash in the fly ash suspension is 18g, and the mass of TiO2 is 9g; therefore, the volume of titanium glue is calculated to be 300mL, containing 3g of TiO2 per 100mL of titanium glue.

[0063] S3, add the fine powder into a 0.5mol / L HF solution and react for 1h, then filter, and dry the obtained solid product in an 80℃ oven for 12h; then put it into a muffle furnace, heat at a rate of 5℃ / min to 500℃ and keep for 6h, then cool to room temperature; finally, grind to obtain a fly ash-based composite catalytic material, marked as ACT (2:1).

[0064] Example 2

[0065] The preparation method of the fly ash-based composite catalytic material for gaseous ammonia oxidation at room temperature provided in this embodiment comprises the following steps:

[0066] S1, weigh 18g of fly ash into a beaker, and add 100mL of deionized water into the beaker; then stir for 1h to obtain a fly ash suspension;

[0067] S2. Measure 600 mL of titanium colloid and fly ash suspension, mix them, stir and heat at 80°C until the liquid evaporates; then dry them at 100°C for 12 h, take out and grind them in a mortar until a fine powder is obtained.

[0068] In this step, the mass ratio of fly ash to TiO2 is 1:1. The mass of fly ash in the fly ash suspension is 18g, and the mass of TiO2 is 18g. Since each 100mL of titanium colloid contains 3g of TiO2, the volume of the titanium colloid is calculated to be 600mL.

[0069] S3. Add the fine powder to 0.5 mol / L HF solution and react for 1 hour, then filter and place the obtained solid product in an 80°C oven to dry for 12 hours; then place it in a muffle furnace, heat it to 500°C at a rate of 5°C / min, hold it for 6 hours, and then cool it to room temperature; finally grind it to obtain a fly ash-based composite catalytic material, marked as ACT (1:1).

[0070] Example 3

[0071] The method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation provided in this embodiment comprises the following steps:

[0072] S1. Weigh 9 g of fly ash and add it to a beaker. Measure 100 mL of deionized water and add it to the beaker. Then stir for 1 hour to obtain a fly ash suspension.

[0073] S2. Measure 600 mL of titanium colloid and fly ash suspension, mix them, stir and heat at 80°C until the liquid evaporates; then dry them at 100°C for 12 h, take out and grind them in a mortar until a fine powder is obtained.

[0074] In this step, the mass ratio of fly ash to TiO2 is 1:2. The mass of fly ash in the fly ash suspension is 9g, and the mass of TiO2 is 18g. Since each 100mL of titanium colloid contains 3g of TiO2, the volume of the titanium colloid is calculated to be 600mL.

[0075] S3. The fine powder was added to a 0.5 mol / L HF solution and reacted for 1 h. The solid product was then filtered and dried in an 80°C oven for 12 h. The solid product was then placed in a muffle furnace and heated to 500°C at a rate of 5°C / min and maintained for 6 h. The solid product was then cooled to room temperature. The fly ash-based composite catalytic material was finally ground and labeled as ACT (1:2).

[0076] Example 4

[0077] The method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation provided in this embodiment comprises the following steps:

[0078] S1. Weigh 54 g of fly ash and add it to a beaker. Measure 100 mL of deionized water and add it to the beaker. Then stir for 1 hour to obtain a fly ash suspension.

[0079] S2. Measure 600 mL of titanium colloid and fly ash suspension, mix them, stir and heat at 80°C until the liquid evaporates; then dry them at 100°C for 12 h, take out and grind them in a mortar until a fine powder is obtained.

[0080] In this step, the mass ratio of fly ash to TiO2 is 3:1. The mass of fly ash in the fly ash suspension is 54g, and the mass of TiO2 is 18g. Since each 100mL of titanium colloid contains 3g of TiO2, the volume of the titanium colloid is calculated to be 600mL.

[0081] S3. Add the fine powder to 0.5 mol / L HF solution and react for 1 hour, then filter and place the obtained solid product in an 80°C oven to dry for 12 hours; then place it in a muffle furnace, heat it to 500°C at a rate of 5°C / min, hold it for 6 hours, and then cool it to room temperature; finally grind it to obtain a fly ash-based composite catalytic material, marked as ACT (3:1).

[0082] Furthermore, the performance of the fly ash-based composite catalytic materials prepared in the above examples was tested. At the same time, in order to highlight the advantages of the fly ash-based composite catalytic materials of the present invention, the following control examples were designed.

[0083] Comparative Example 1

[0084] This comparative example provides a method for preparing a fly ash-based catalytic material, comprising the following steps:

[0085] S1. Weigh 20 g of fly ash and add it to a beaker. Measure 100 mL of deionized water and add it to the beaker. Stir for 1 hour to obtain a fly ash suspension.

[0086] S2. Take 20 mL of fly ash suspension, mix, stir and heat at 80°C until the liquid evaporates; then dry at 100°C for 12 hours, take out and grind in a mortar until a fine powder is obtained;

[0087] S3. The fine powder was added to a 0.5 mol / L HF solution and reacted for 1 hour, then filtered and the obtained solid product was placed in an 80°C oven and dried for 12 hours; then placed in a muffle furnace, heated to 500°C at a rate of 5°C / min and maintained for 6 hours, and then cooled to room temperature; finally, ground to obtain a fly ash-based catalytic material, recorded as ASH.

[0088] Comparative Example 2

[0089] This comparative example provides a method for preparing a catalytic material, comprising the following steps:

[0090] S1. Measure 600 mL of titanium colloid, stir, and heat at 80°C until the liquid evaporates; then dry at 100°C for 12 h, remove from the mortar, and grind until a fine powder is obtained;

[0091] S2. Add the fine powder to 0.5 mol / L HF solution and react for 1 hour, then filter and place the obtained solid product in an 80°C oven to dry for 12 hours; then place it in a muffle furnace, heat it to 500°C at a rate of 5°C / min, hold it for 6 hours, and then cool it to room temperature; finally grind it to obtain the catalytic material, recorded as TiO2.

[0092] Comparative Example 3

[0093] The preparation method of the composite catalytic material provided in this comparative example comprises the following steps:

[0094] S1. Weigh 18 g of fly ash and add it to a beaker. Measure 100 mL of deionized water and add it to the beaker. Then stir for 1 hour to obtain a fly ash suspension.

[0095] S2. Measure 300 mL of titanium colloid and mix with the fly ash suspension, stir and heat at 80°C until the liquid evaporates; then dry at 100°C for 12 h, take out and grind in a mortar until a fine powder is obtained.

[0096] In this step, the mass ratio of fly ash to TiO2 is 2:1. The mass of fly ash in the fly ash suspension is 18g, and the mass of TiO2 is 9g. Since each 100mL of titanium colloid contains 3g of TiO2, the volume of the titanium colloid is calculated to be 300mL.

[0097] S3. Place the fine powder in a muffle furnace, heat it to 500°C at a rate of 5°C / min, hold it for 6 hours, and then cool it to room temperature; finally, grind it to obtain a composite catalytic material, which is labeled as ACT (2:1, without HF).

[0098] The performance of fly ash-based composite catalytic materials (also called catalytic materials) was tested through the following experimental studies.

[0099] Test 1, XRD

[0100] The fly ash-based composite catalytic material prepared in Example 1, the fly ash-based catalytic material in Control Example 1, the catalytic material prepared in Control Example 2, and the catalytic material prepared in Control Example 3 were used as test samples. The crystal structures of the test samples were analyzed by X-ray diffraction (XRD). The results are as follows: Figure 1 shown.

[0101] See also Figure 1Example 1 detected characteristic peaks of anatase Ti02(PDF #75-1573) at 25.7°, 37.5°, 38.4°, 39.2°, 48.8°, 54.8°, and 55.9° corresponding to (101), (103), (004), (112), (200), (105), and (211) crystal planes, and characteristic peaks at 27.4°, 36.1°, 39.2°, 41.2°, 44.1°, 54.3°, and 56.6° corresponding to (110), (101), (200), (111), (210), (211), and (220) crystal planes of rutile Ti02(PDF #99-0090). This indicates that the fly ash-based composite catalytic material exhibits a unique dual-phase structure of anatase Ti02and rutile Ti02. By calculation, the optimal ratio of anatase Ti02to rutile Ti02is 9:1; the coexistence of the two phases promotes higher-density lattice defects, promotes electron-hole separation, and enhances the adsorption and activation of surface oxygen. In addition, diffraction peaks at 17.4°, 31.8°, 34.3°, 58.3°, and 61.4° match the original fly ash, confirming that the underlying ash structure remains stable during Ti02incorporation. In addition, a decrease in peak intensity and broadening of the full width at half maximum were observed in the fly ash-based composite catalytic material of Example 1, indicating a decrease in crystallinity and the formation of nanocrystalline domains. This structural feature is generally associated with defect-mediated carrier generation, which helps to improve photocatalytic performance. Overall, these findings indicate that the fly ash-based composite catalytic material prepared by the present application successfully integrates a defect-rich interface, which plays a key role in improving photocatalytic efficiency.

[0102] Test 2, SEM

[0103] The fly ash-based composite catalytic material prepared in Example 1, the fly ash-based catalytic material of Comparative Example 1, and the fly ash-based composite catalytic material of Comparative Example 2 were used as test samples, and the morphology of each test sample at different magnifications was obtained using a scanning electron microscope (SEM), as shown in Figure 2 , Figure 3 and Figure 4 , wherein: Figure 2 SEM of Comparative Example 1 (ASH); Figure 3 SEM of Comparative Example 2 (Ti02); Figure 4 SEM of Example 1 (ACT (2:1)).

[0104] Referring to Figure 2 , Figure 3 and Figure 4It can be seen that the fly ash-based composite catalytic material prepared in Comparative Example 1 is composed of smooth and uniform spherical particles and irregular and disordered structures composed of amorphous agglomerates, in which finer spheres are embedded in an organized manner; and the surface of the fly ash-based composite catalytic material prepared in Example 1 (ACT (2:1)) can be seen that a uniform and continuous TiO2 layer is clearly visible, covering the surface of the activated fly ash. It is worth noting that the original microstructure of Comparative Example 1 (ASH) remains intact after the modification process, which is consistent with the XRD results. However, due to the considerable shrinkage and unevenness of the Ti-based gel during drying and thermal activation, the surface of the fly ash-based composite catalytic material appears rough and uneven, with obvious irregularities and enhanced structural complexity.

[0105] Test 3, ammonia oxidation performance

[0106] The fly ash-based composite catalytic material prepared in Example 1, the fly ash-based catalytic material of Comparative Example 1, the catalytic material prepared in Comparative Example 2, and the catalytic material prepared in Comparative Example 3 were used as test samples, and the catalytic oxidation effect of each test sample on ammonia was obtained.

[0107] The test method was as follows: each fly ash-based composite catalytic material was oxidized by NH3 under ultraviolet light; ammonia gas with a concentration (40 ppm) and a flow rate (100 mL / min) was introduced into a dynamic photocatalytic experimental device by a flow gas distribution device, and a glass fiber filter film containing each test sample was placed in the photocatalytic reaction device in advance, and the concentration change of the tail end ammonia detection device was observed to calculate the catalytic oxidation efficiency. The results are shown in Table 1. Figure 5

[0108] From Figure 5 It can be seen that the fly ash-based catalytic material (ASH) prepared by only using fly ash in Comparative Example 1 has a catalytic oxidation efficiency of ammonia below 10%; the catalytic material (TiO2) of Comparative Example 2 has a catalytic oxidation efficiency of ammonia reaching 50% after 2h of catalysis; the catalytic material (ACT (2:1), without HF) of Comparative Example 3 has a catalytic oxidation efficiency of ammonia reaching only 75% after 2h of catalysis; the fly ash-based composite catalytic material (ACT (2:1)) of Example 1 has a catalytic oxidation efficiency of ammonia reaching above 80% after 90min of catalysis, and the highest can reach 90%. This shows that the fly ash and titanium gel are compounded by using the preparation method of the present application, and the fly ash and titanium gel synergistically act, greatly improving the catalytic oxidation efficiency of ammonia, and realizing efficient oxidation of gaseous ammonia.

[0109] Test 4, photochemical performance

[0110] ​The fly ash-based composite catalytic material (ACT (2:1)) prepared in Example 1, the catalytic material (TiO2) of Comparative Example 2, and the catalytic material (ACT (2:1) (without HF)) prepared in Control Example 3 were used as test samples for photochemical performance testing.

[0111] The test method is to use ultraviolet-visible diffuse reflectance absorption spectroscopy (UV-Vis DRS, TU-1901, Japan) to determine its absorption characteristics, using BaSO4 as a blank control, 0.6nm•s -1 The scanning rate was measured in the scanning range of 240~800nm. Test results Figure 6 and Figure 7 shown.

[0112] See also Figure 6 The ultraviolet-visible diffuse reflectance spectrum (UV-Vis DRS) showed that the fly ash-based composite catalytic material exhibited a significant red shift in the absorption edge compared to TiO2 and showed enhanced absorption intensity in the range of 240-800nm. Figure 7 As can be seen in the results, compared to Control Examples 2 and 3, the fly ash-based composite catalytic material exhibits an absorption edge at approximately 400nm, corresponding to a narrowed optical band gap of 2.87eV. The light absorption range extends into the visible light region, and visible light absorption performance is enhanced. This indicates that the broader light-harvesting capability of the fly ash-based composite catalytic material extends the light absorption range into the visible light region, enhancing visible light absorption performance, improving visible light responsiveness, and enabling more efficient photocatalytic activation.

[0113] Experiment 5: PL spectroscopy

[0114] In this experiment, photoluminescence (PL) spectroscopy can be used to further study the charge carrier recombination behavior of fly ash-based composite catalytic materials.

[0115] The fly ash-based composite catalytic material (ACT (2:1)) prepared in Example 1, the fly ash-based composite catalytic material (ASH) prepared in Comparative Example 1, the catalytic material (TiO2) of Comparative Example 2, and the catalytic material (ACT (2:1) (without HF)) prepared in Comparative Example 3 were used as test samples for testing.

[0116] The test method is: Atomic luminescence spectroscopy (PL, F-7000, Hitachi High-Technologies Corporation) was used to measure the electron-hole recombination situation, with an operating voltage of 250V, an excitation wavelength of 300nm, a starting wavelength of 900nm, a bandwidth of 3.5nm, and a scanning speed of 1500nm / min in the range of 200~900nm. Test results Figure 8 shown.

[0117] from Figure 8It can be seen that all the tested samples showed obvious PL emission, which may be due to the rapid recombination of photogenerated electron-hole pairs; however, compared with TiO2, ASH and ACT (2:1) (without HF), the electron-hole recombination rate of the fly ash-based composite catalytic material prepared in Example 1 was significantly reduced, indicating that there was a favorable interfacial charge redistribution between the fly ash and TiO2 components, and the electron-hole recombination rate was significantly suppressed after the composite, and the charge separation efficiency was enhanced; thereby significantly enhancing the catalytic performance of the fly ash-based composite catalytic material prepared in Example 1 in the catalytic oxidation process.

[0118] Test 6: Mott-Schottky test

[0119] The fly ash-based composite catalytic materials prepared in Examples 1, 2, 3 and 4, and the catalytic material prepared in Control Example 3 (ACT (2:1) (without HF)) were tested for photoelectric properties to determine the flat band potential (Efb).

[0120] The Mott-Schottky (MS) test was carried out in a three-electrode system using the PGSTAT 204 electrochemical workstation of Metrohm China Ltd. The experimental process is: using a saturated calomel electrode as the reference electrode, Pt as the counter electrode, and the electrolyte is a 0.5 mol / L NaSO4 aqueous solution. Among them, the working electrode preparation process is as follows: This study uses 20mm×20mm FTO conductive glass to prepare the working electrode. 5mg of photocatalyst and 80μL, 5wt% Nafion solution were ultrasonically dispersed in 1mL of ethanol solution, and then 100μL of the mixed solution was evenly drop-coated on the FTO conductive glass. After it is naturally air-dried, it can be used as a working electrode. The Mott-Schottky (MS) measurement results are shown as follows: Figure 9 shown.

[0121] See also Figure 9 It can be seen that the MS curve slopes of the fly ash-based composite catalytic materials of the four examples are positive; thus, all fly ash-based composite catalytic materials exhibit typical n-type semiconductor characteristics. Furthermore, compared to the flat band potential of the catalytic material prepared in Control Example 3, which is -0.48 V, the flat band potentials of the fly ash-based composite catalytic materials prepared in Examples 1, 2, 3, and 4 are -0.43 V, -0.47 V, -0.50 V, and -0.46 V, respectively. This indicates that when the mass ratio of fly ash to TiO2 is 2:1, the prepared fly ash-based composite catalytic materials have superior catalytic oxidation performance.

[0122] Test 7: Transient photocurrent response test

[0123] The effective carrier separation performance in the fly ash-based composite catalytic material was further verified by transient photocurrent response (TPC) measurements.

[0124] The fly ash-based composite catalytic materials prepared in Examples 1, 2, 3 and 4, and the catalytic material prepared in Control Example 3 (ACT (2:1) (without HF)) were used as test objects.

[0125] The transient photocurrent response method is to examine the generation and migration of charge carriers under light conditions through the transient photocurrent-time curve (It). Detection conditions: constant potential 0.05V, 20s intermittent light exposure, the current difference between darkness and light is the transient photocurrent, the results are as follows Figure 10 shown.

[0126] from Figure 10 It can be seen that the order of the photocurrent signals of the fly ash-based composite catalytic materials is: ACT (2:1) > ACT (3:1) > ACT (1:1) > ACT (1:2). In other words, the photocurrent signals of the fly ash-based composite catalytic material of Example 1 are all higher than those of Examples 2, 3, and 4, exhibiting the highest photocurrent density, indicating a stronger charge separation capability. This reflects that under illumination, the fly ash-based composite catalytic material of Example 1 can more efficiently generate, separate, and migrate photogenerated carriers.

[0127] Test 8: Electrochemical impedance spectroscopy

[0128] In this experiment, the interfacial charge transfer ability of fly ash-based composite catalytic materials was analyzed by electrochemical impedance spectroscopy.

[0129] The fly ash-based composite catalytic material (ACT (2:1)) prepared in Example 1, the fly ash-based composite catalytic material (ASH) prepared in Comparative Example 1, the catalytic material (TiO2) of Comparative Example 2, and the catalytic material (ACT (2:1) (without HF)) prepared in Comparative Example 3 were used as test samples for testing.

[0130] The electrochemical impedance spectroscopy test was carried out in the dark at a frequency range of 10 -1 ~10 5 HZ, constant potential 0.05V, the results are as follows Figure 11 shown.

[0131] from Figure 11 It can be seen from the electrochemical impedance spectrum that compared with ASH, TiO2 and Control Example 3, the fly ash-based composite catalytic material prepared in Example 1 has a smaller radius and the lowest charge transfer resistance, indicating that a fast electron transmission channel is established at the interface of the fly ash-based composite catalytic material and the charge transfer is more efficient.

[0132] Test 9: Repeatability

[0133] The fly ash-based composite catalytic material prepared in Example 1 was used as a test sample to conduct a stability performance test.

[0134] The test method is: after completing one oxidation performance test according to the method of test 3, repeat the test with the same catalyst sample amount and the same test method. Figure 12 As shown in the figure, it can be seen that after the catalyst was used three times, its catalytic performance still maintained above 70%. This shows that the fly ash-based composite catalytic material has good repeatability and stability.

[0135] Experiment 10: Species generated on the surface after reaction

[0136] The fly ash-based composite catalytic material prepared in Example 1 was used as a test sample for testing.

[0137] After the catalytic oxidation reaction of ammonia is completed, 100 mg of the catalytically oxidized test sample (catalyst) is placed in a 10 mL centrifuge tube and deionized water is added; the supernatant is collected by centrifugation for anion analysis. Figure 13 shown.

[0138] See also Figure 13 It can be seen that the supernatant showed a prominent strong peak at about 13 minutes, which is consistent with the NO3 - The peak positions of anions are consistent, which indicates that the supernatant contains NO3 - ; It further explains that ammonia is adsorbed and oxidized by the catalyst (fly ash-based composite catalytic material).

[0139] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation, characterized in that: The following steps are involved: S1. Add fly ash into water and stir to obtain a fly ash suspension; S2, mixing titanium colloid and the fly ash suspension obtained in step S1, stirring and heating until the liquid evaporates to dryness; then drying and grinding to obtain a fine powder; the titanium colloid contains TiO2, and the mass ratio of the fly ash to TiO2 is (1-3):(1-2); S3. Add the fine powder from step S2 to an HF solution for reaction, then filter, dry the obtained solid product, calcine it at a temperature of 300° C. to 700° C., and cool it to room temperature; finally grind it to obtain a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation.

2. The method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation according to claim 1, characterized in that: In step S2, the heating temperature is 70° C. to 85° C.; the drying temperature is 90° C. to 100° C.; and the drying time is 10 hours to 15 hours.

3. The method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation according to claim 1, characterized in that: In step S3, the reaction time is 1 h to 2 h; the drying temperature is 80° C. to 100° C., and the drying time is 9 h to 12 h.

4. The method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation according to claim 1, characterized in that: In step S3, the heating rate of the calcination process is 5°C / min; the concentration of the HF solution is 0.5 mol / L to 1 mol / L.

5. A fly ash-based composite catalytic material prepared by the method for preparing a fly ash-based composite catalytic material for room-temperature gaseous ammonia oxidation according to claim 1.

6. The fly ash-based composite catalytic material according to claim 5, characterized in that: The fly ash-based composite catalytic material was determined by XRD, and characteristic peaks of anatase TiO2 were detected at 25.7°, 37.5°, 38.4°, 39.2°, 48.8°, 54.8° and 55.9°; characteristic peaks of rutile TiO2 were detected at 27.4°, 36.1°, 39.2°, 41.2°, 44.1°, 54.3° and 56.6°; the fly ash-based composite catalytic material has a twin-phase structure of anatase TiO2 and rutile TiO2.

7. The fly ash-based composite catalytic material according to claim 6, characterized in that: In the fly ash-based composite catalytic material, the optimal ratio of anatase TiO2 to rutile TiO2 is 9:

1.

8. The fly ash-based composite catalytic material according to claim 5, characterized in that: The fly ash-based composite catalytic material has a minimum band gap value of 2.87 eV and a maximum flat band potential of -0.43 V.

9. Use of the fly ash-based composite catalytic material according to claim 5 as a photocatalyst in promoting the oxidation of gaseous ammonia at room temperature.

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