A photo-Fenton catalyst and its preparation method and application

Abstract

The present invention belongs to the field of catalyst technology and specifically relates to a photo-Fenton catalyst, its preparation method, and application. The preparation method comprises: pre-treating a silicon nitride support with a buffered oxide etchant to obtain a pre-treated support; loading the pre-treated support with titanium nitride using an ethanol slurry of titanium nitride to obtain a primary loaded support; loading the primary loaded support with titanium dioxide using an ethanol slurry of titanium dioxide, sintering the support, and immersing the secondary loaded support in a ferrous salt solution, followed by drying to obtain a photo-Fenton catalyst. The photo-Fenton catalyst has a structure in which silicon oxide serves as the innermost layer support, on which TiN, TiO2, and an amorphous iron species are sequentially loaded. It exhibits excellent catalytic performance, is easily regenerated, and is applicable to a wide range of working environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a photo-Fenton catalyst and a preparation method and application thereof. Background Art

[0002] Whether in daily life or industrial production, the demand for polymer products is increasing. The production of polymer products will cause a sharp increase in the content of water-soluble organic matter in the discharged water, causing serious environmental pollution. As a new advanced oxidation technology, photo-Fenton has the characteristics of being green, efficient and stable, and can provide an effective solution for the effective treatment of difficult-to-degrade organic wastewater. Titanium dioxide (TiO2) is a typical photocatalyst. Modifying TiO2 with amorphous iron species can broaden the light response range of TiO2 to natural light and visible light, thereby improving the utilization rate of light energy. The converted light can enhance the Fe 2+ The reduction of TiO2 effectively combines photocatalysis and Fenton technology. However, powdered TiO2, as a heterogeneous catalyst, faces great difficulties in treating water pollution in terms of light conversion, catalytic stability, and convenient recycling.

[0003] Silicon nitride ceramic balls possess high strength, wear resistance, corrosion resistance, and low density, making them suitable for high-end intelligent manufacturing applications. However, a certain amount of defects are unavoidable during the manufacturing process. For example, after sintering, the ball embryo may exhibit partial surface shell shedding, internal and external color differences in cross-section, numerous pores, microcracks in the annular zone, and surface cracking, making it impossible to proceed to the next production step. However, these defective silicon nitride ceramic balls still possess excellent physical properties, and their application under appropriate working conditions can be studied to reduce waste. Summary of the Invention

[0004] Therefore, the present invention provides a photo-Fenton catalyst and its preparation method and application, using silicon nitride as a carrier, on which TiN, TiO2 and amorphous iron species are loaded in sequence to obtain a photo-Fenton catalyst with good catalytic performance, convenient regeneration and applicability to a wide range of working conditions.

[0005] To this end, the present invention provides the following technical solutions.

[0006] The present invention provides a method for preparing a photo-Fenton catalyst, comprising the following steps:

[0007] S1: immersing the silicon nitride carrier in a buffered oxide etchant for pretreatment to obtain a pretreated carrier;

[0008] S2: preparing an ethanol slurry of titanium nitride, and immersing the pretreated support in the ethanol slurry of titanium nitride to obtain a primary loaded support;

[0009] S3: preparing an ethanol slurry of titanium dioxide, immersing the primary support in the ethanol slurry of titanium dioxide under stirring, and sintering to obtain a secondary support;

[0010] S4: immersing the secondary load carrier in a ferrous salt solution, performing solid-liquid separation, and drying to obtain the photo-Fenton catalyst.

[0011] In the preparation method of the photo-Fenton catalyst provided by the present invention, the buffered oxide etchant (BOE) used is typically, but not limited to, commercially available BOE, and is either a 10:1 BOE solution (comprising a 10:1 volume ratio of 40 wt% ammonium fluoride aqueous solution to a 49 wt% hydrofluoric acid aqueous solution) or a 6:1 BOE solution (comprising a 6:1 volume ratio of 40 wt% ammonium fluoride aqueous solution to a 49 wt% hydrofluoric acid aqueous solution). BOE solutions exhibit specific etching rates and selectivity in microfabrication, adaptable to specific process requirements, and are widely used in semiconductor manufacturing, microelectromechanical systems (MEMS) processing, and other fields for etching microstructures and removing oxide layers. After the pretreatment is completed, the method further includes rinsing the BOE solution from the surface of the pretreated support. Generally, three rinses with deionized water are sufficient to remove all residual BOE solution.

[0012] Optionally, in S3, the sintering temperature is 400-800° C. and the sintering time is 40-70 min.

[0013] Optionally, in S3, the sintering method includes spark plasma sintering.

[0014] Optionally, in S4, the immersion time is 30-60 min and the temperature is 60-80° C. This temperature is more suitable for the growth of amorphous iron species and can make the amorphous iron species grown in situ on the surface of the secondary support carrier more solid.

[0015] Optionally, in S4, the mass ratio of the ferrous salt solution to the secondary load carrier is 2-3:1.

[0016] Optionally, in S4, the mass concentration of the ferrous salt solution is 3% to 6%.

[0017] Optionally, in S4, the drying temperature is 60-80° C. and the drying time is 5-8 hours.

[0018] Optionally, in S4, the ferrous salt solution includes at least one of ferrous chloride solution and ferrous sulfate solution.

[0019] Optionally, in S1, the pretreatment time is ≥4h.

[0020] Optionally, in S2, in the titanium nitride ethanol slurry, the solid-liquid volume ratio of titanium nitride to ethanol is 1:1~1.5.

[0021] Optionally, in S2, the mass ratio of the titanium nitride ethanol slurry to the pretreated carrier is 2-3:1.

[0022] Optionally, in S2, the titanium nitride is immersed in an ethanol slurry and the ethanol is evaporated.

[0023] Optionally, in S2, the impregnation includes using at least one of stirring and brushing methods to uniformly load the titanium nitride onto the silicon nitride carrier.

[0024] Optionally, in S1, the pretreatment time is 4 to 10 hours.

[0025] Optionally, in S3, in the titanium dioxide ethanol slurry, the solid-liquid volume ratio of titanium dioxide to ethanol is 1:1~1.5.

[0026] Optionally, in S3, the mass ratio of the ethanol slurry of titanium dioxide to the primary load carrier is 2-3:1.

[0027] Optionally, in S3, the titanium dioxide is immersed in an ethanol slurry and the ethanol is evaporated.

[0028] Optionally, in S3, the impregnation includes using at least one of stirring and brushing methods to uniformly load the titanium dioxide onto the primary loading carrier.

[0029] Optionally, the silicon nitride carrier includes silicon nitride ceramic balls.

[0030] Optionally, in S2, the step of preparing the ethanol slurry of titanium nitride includes: mixing titanium nitride with ethanol, and ball milling at 200-400 r / min for 1.5-6 hours to obtain the ethanol slurry of titanium nitride.

[0031] Optionally, in S3, the step of preparing the ethanol slurry of titanium dioxide includes: mixing titanium dioxide and ethanol, and ball milling at 200-400 r / min for 1.5-6 hours to obtain the ethanol slurry of titanium dioxide.

[0032] In the preparation method of the photo-Fenton catalyst provided by the present invention, typically but not limitedly, the titanium nitride and titanium dioxide used can be purchased or homemade, but the purity must be ≥99.9%; the purity and photocatalytic performance of affordable products among commercially available products cannot be guaranteed, and the prices of products with guaranteed purity are relatively high. Therefore, it is preferred to prepare high-purity titanium nitride and titanium dioxide by yourself for use.

[0033] Optionally, the size of the silicon nitride carrier is 4-15 mm.

[0034] Optionally, the silicon nitride ceramic balls include defective silicon nitride ceramic balls. Typically, but not limitedly, defective silicon nitride ceramic balls have surface shell shedding, internal and external color difference in the cross section, a large number of pores, microcracks in the annular position, surface cracking, etc., and cannot be used for further processing and production of ball embryos.

[0035] Optionally, the preparation of the titanium nitride comprises the following steps: adding ammonia water to an organic titanium source, adjusting the pH to 2.8-4.5, stirring to a gel state, drying to obtain titanium dioxide, and nitriding in a nitrogen atmosphere to obtain the titanium nitride.

[0036] Optionally, the preparation of titanium dioxide comprises the following steps: adding ammonia water to an organic titanium source, adjusting the pH to 2.8-4.5, stirring, standing until the mixture is in a gel state, and drying to obtain titanium dioxide.

[0037] Typically, but not limited to, the stirring method includes magnetic stirring at a rate of 200 to 800 r / min; in the preparation steps of titanium nitride and titanium dioxide, the steps of washing and drying the obtained titanium nitride and titanium dioxide are also included to reduce system errors.

[0038] Optionally, during the preparation of titanium nitride, the drying temperature is 60-80° C. and the drying time is 6-10 hours.

[0039] Optionally, during the preparation of titanium nitride, the nitriding temperature is 800-1200° C., and the time is 4-6 hours.

[0040] Optionally, in the preparation process of titanium nitride, before adding ammonia water, the step of stirring the organic titanium source for 10 to 20 minutes is also included.

[0041] Optionally, during the preparation of titanium dioxide, the stirring time is 10 to 20 minutes.

[0042] Optionally, during the preparation of titanium dioxide, the drying temperature is 60-80° C. and the drying time is 4-6 hours.

[0043] Optionally, during the preparation of titanium dioxide, before adding ammonia water, the step of stirring the organic titanium source for 10 to 20 minutes is further included.

[0044] Optionally, the organic titanium source includes at least one of tetrabutyl titanate and tetraisopropyl titanate.

[0045] The present invention also provides a photo-Fenton catalyst prepared by the above preparation method.

[0046] The present invention provides the use of the above-mentioned photo-Fenton catalyst in treating organic pollutants. Optionally, when using the above-mentioned photo-Fenton catalyst to treat organic pollutants, H2O2 is required, and the concentration of H2O2 is ≥ 2 mmol / L; further optionally, the concentration of H2O2 is 4 to 24 mmol / L; and even more optionally, the concentration of H2O2 is 16 mmol / L.

[0047] The beneficial effects of the present invention are:

[0048] The present invention provides a method for preparing a photo-Fenton catalyst, comprising the following steps: S1: immersing a silicon nitride support in a buffered oxide etchant for pretreatment to obtain a pretreated support; S2: preparing an ethanol slurry of titanium nitride and immersing the pretreated support in the titanium nitride ethanol slurry to obtain a primary loaded support; S3: preparing an ethanol slurry of titanium dioxide and immersing the primary loaded support in the titanium dioxide ethanol slurry under stirring, followed by sintering to obtain a secondary loaded support; S4: immersing the secondary loaded support in a ferrous salt solution, performing solid-liquid separation, and drying to obtain the photo-Fenton catalyst. The photo-Fenton catalyst has a structure in which silicon oxide is the innermost layer support, on which TiN, TiO2, and an amorphous iron species are sequentially loaded. The catalyst can efficiently convert solar energy, activate the Fenton system, generate a large amount of free radicals such as ·OH, and decompose organic pollutants in water into small molecules such as CO2 and H2O, exhibiting excellent catalytic performance. The photo-Fenton catalyst is also easy to regenerate and is applicable to a wide range of working environments.

[0049] Using silicon nitride as a support, and its physical properties such as high strength, wear resistance, corrosion resistance, and low density, make the resulting photo-Fenton catalyst suitable for use in a wider range of complex environments, such as waters with frequent undercurrents and eddies. Directly loading TiO2 onto a silicon nitride support results in different thermal shrinkage rates between the two ceramic phases, leading to a larger shrinkage gap after sintering and reduced bonding stability. However, sequentially loading TiN and TiO2 onto a silicon nitride support and sintering results in the formation of micro-liquid phases at each interface, allowing interfacial reactions and atomic interdiffusion to generate chemical bonds. Specifically, atoms diffuse and migrate between silicon nitride (Si and N) and titanium nitride (Ti and N), forming Ti-N and Si-N covalent bonds, respectively. Similarly, atoms diffuse between titanium dioxide (Ti and O) and titanium nitride (Ti and N), forming Ti-N and Ti-O covalent bonds. Furthermore, the thermal shrinkage differences between adjacent phases are smaller, resulting in a strong and stable bond. Pre-treating silicon nitride ceramics with a buffered oxide etchant can increase surface defects and provide more attachment sites for subsequent TiN loading.

[0050] In the preparation method of the photo-Fenton catalyst provided by the present invention, the silicon nitride ceramic balls include defective silicon nitride ceramic balls. The defective silicon nitride ceramic balls themselves have a certain amount of surface defects. After being treated with a BOE solution, the unstable areas on their surfaces will be etched away, and the surface will be smooth, with obvious pit defects and no obvious impurities. However, after the macroscopic surface defects are removed, from an atomic microscopic perspective, defects such as points, lines, and grain boundaries still exist. Ceramic defects, such as cracks, pores, and impurities, have relatively high energy and can serve as reactive active sites. During the sintering process, they will have a positive effect on the migration and diffusion of interface atoms, making the TiN load more secure. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 Schematic diagram of the structure and working principle of the photo-Fenton catalyst prepared in Example 1;

[0053] Figure 2 is the XRD pattern of TiO2 prepared in Example 3;

[0054] Figure 3 is the XRD pattern of the iron species prepared in Test Example 1;

[0055] Figure 4 is the XPS image of the iron species prepared in Test Example 1;

[0056] Figure 5 The UV diffuse reflectance curve images of TiO2 prepared in Example 3 and the finally prepared photo-Fenton catalyst obtained in the test in Test Example 1;

[0057] Figure 6 The bandgap width curve images of TiO2 prepared in Example 3 and the finally prepared photo-Fenton catalyst obtained in the test in Test Example 1;

[0058] Figure 7 These are the photoluminescence performance images of the TiO2 prepared in Example 3 and the finally prepared photo-Fenton catalyst obtained in the test in Test Example 1. DETAILED DESCRIPTION

[0059] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0060] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0061] Experimental drugs:

[0062] Defective silicon nitride ceramic balls: Defective silicon nitride ceramic balls screened out after the atmosphere sintering step are ball embryos with surface shell shedding, internal and external color difference in the cross section, a large number of pores, microcracks in the annular position, and surface cracks. The particle sizes are 5mm, 6mm, and 7mm.

[0063] Example 1

[0064] This embodiment provides a photo-Fenton catalyst and a preparation method thereof, comprising the following steps:

[0065] (1) Use 10:1 BOE solution to immerse the defective silicon nitride ceramic balls and pretreat them for 4 hours. Then remove the pretreated ceramic balls, wash them with deionized water three times, and dry them.

[0066] (2) Place 50 mL of tetrabutyl titanate in a magnetic stirring pot and stir at 500 r / min for 10 min. Then, add ammonia water dropwise until the pH reaches 2.8. Continue stirring until it reaches a gel state. Transfer to a vacuum drying oven and dry at 80°C for 8 h to obtain titanium dioxide powder. Grind in a mortar until the powder is uniform. Nitridize at 800°C for 4 h in a nitrogen atmosphere. Grind, wash, and dry to obtain titanium nitride powder.

[0067] (3) Place 50 mL of tetrabutyl titanate in a magnetic stirring pot and stir at 500 r / min for 10 min. Then add ammonia water until the pH reaches 2.8 and continue stirring for 10 min. Then let it stand until it gels. Transfer it to a vacuum drying oven and dry it at 80 °C for 6 h. Then grind, wash, and dry it to obtain titanium dioxide powder.

[0068] (4) Mix titanium nitride powder with ethanol and place it in a planetary ball mill at 200 r / min for 1.5 hours to prepare a titanium nitride ethanol slurry with a solid-liquid volume ratio of 1:1. Immerse the pretreated ceramic balls in the titanium nitride ethanol slurry with a mass ratio of titanium nitride ethanol slurry to pretreated ceramic balls of 2:1. Use a brush to apply the titanium nitride evenly to the pretreated ceramic balls until the ethanol is completely evaporated to obtain a primary loaded ceramic ball.

[0069] (5) Mix titanium dioxide powder with ethanol and place it in a planetary ball mill at 200 rpm for 1.5 h to prepare a titanium dioxide ethanol slurry with a solid-liquid volume ratio of 1:1. Immerse the primary loaded ceramic balls in the titanium dioxide ethanol slurry with a mass ratio of titanium dioxide ethanol slurry to primary loaded ceramic balls of 2:1. Use a brush to apply titanium dioxide evenly to the primary loaded ceramic balls until the ethanol evaporates. Spark plasma sintering is performed at 400°C for 40 min to obtain secondary loaded ceramic balls. Wash and dry them for later use.

[0070] (6) Prepare a 3 wt% FeCl2 solution and immerse the secondary loaded ceramic balls in the FeCl2 solution at 80°C for 30 min. The mass ratio of FeCl2 solution to secondary loaded ceramic balls is 3:1. Remove the ceramic balls and place them in a vacuum drying oven at 80°C for 6 h to obtain a photo-Fenton catalyst.

[0071] The structural diagram and working principle diagram of the prepared photo-Fenton catalyst are shown in Figure 1 . It can be seen that the structure of the photo-Fenton catalyst is the innermost silicon nitride carrier (corresponding to the defective silicon nitride ceramic ball in this embodiment), which is then loaded with a titanium nitride layer, a titanium dioxide layer, and an amorphous iron species layer in sequence. Ti-N and Si-N covalent bonds are formed between silicon nitride (Si and N) and titanium nitride (Ti and N); Ti-N and Ti-O covalent bonds are formed between titanium dioxide (Ti and O) and titanium nitride (Ti and N); to help the photo-Fenton catalyst have a more stable structure. After titanium dioxide receives photon energy, the electrons are excited and react with Fe in the amorphous iron species layer. 3+ The reaction yields Fe 2+ , Fe 2+ Reacts with H2O2 to produce OH and Fe 3+ , ·OH can react with pollutants to produce carbon dioxide and water, completing the decomposition of pollutants.

[0072] Example 2

[0073] This embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with Example 1, the differences are as follows: the pretreatment time in step (1) is 6 hours; in step (2), ammonia water is added dropwise until the pH is 3.4; in step (3), ammonia water is added dropwise until the pH is 3.4; in step (4), the ball milling rate when preparing the ethanol slurry of titanium nitride is 300 r / min; in step (5), the ball milling rate when preparing the ethanol slurry of titanium dioxide is 300 r / min.

[0074] Example 3

[0075] The present embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with embodiment 1, the differences are as follows: the pretreatment time in step (1) is 6 hours; in step (2), ammonia water is added dropwise until the pH is 3.4, and the nitriding temperature is 1000°C; in step (3), ammonia water is added dropwise until the pH is 3.4; in step (4), when preparing the ethanol slurry of titanium nitride, the ball milling is performed at 300 r / min for 2 hours; in step (5), when preparing the ethanol slurry of titanium dioxide, the ball milling is performed at 300 r / min for 4 hours, the ethanol slurry of titanium dioxide is divided into two parts, the primary loaded ceramic balls are impregnated twice, the spark plasma sintering temperature is 600°C, and the time is 60 minutes; in step (6), the concentration of the FeCl2 solution is 5wt%.

[0076] Example 4

[0077] The present embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with embodiment 1, the differences are as follows: the pretreatment time in step (1) is 8 hours; in step (2), ammonia water is added dropwise until the pH is 4, and the nitriding temperature is 1000°C; in step (3), ammonia water is added dropwise until the pH is 4; in step (4), when preparing the ethanol slurry of titanium nitride, the ball milling is performed at 300 r / min for 2.5 hours; in step (5), when preparing the ethanol slurry of titanium dioxide, the ball milling is performed at 300 r / min for 4 hours, the ethanol slurry of titanium dioxide is divided into two parts, the primary loaded ceramic balls are impregnated twice, the spark plasma sintering temperature is 600°C, and the time is 60 minutes; in step (6), the concentration of the FeCl2 solution is 5wt%.

[0078] Example 5

[0079] The present embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with embodiment 1, the difference is that: the pretreatment time in step (1) is 10 hours; in step (2), ammonia water is added dropwise until the pH is 4, and the nitriding temperature is 1200°C; in step (3), ammonia water is added dropwise until the pH is 4; in step (4), when preparing the ethanol slurry of titanium nitride, the ball milling is performed at 400 r / min for 2.5 hours; in step (5), when preparing the ethanol slurry of titanium dioxide, the ball milling is performed at 400 r / min for 6 hours, the ethanol slurry of titanium dioxide is divided into 3 parts, the primary loaded ceramic ball is impregnated 3 times, the spark plasma sintering temperature is 600°C, and the time is 60 minutes; in step (6), the concentration of the FeCl2 solution is 7wt%.

[0080] Example 6

[0081] The present embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with Example 1, the differences are as follows: the pretreatment time in step (1) is 6 h; in step (2), ammonia water is added dropwise until the pH is 3.4, and the nitriding temperature is 1000°C; in step (3), ammonia water is added dropwise until the pH is 3.4; in step (4), when preparing the ethanol slurry of titanium nitride, the ball milling is performed at 400 r / min for 2 h; in step (5), when preparing the ethanol slurry of titanium dioxide, the ball milling is performed at 400 r / min for 4 h, the ethanol slurry of titanium dioxide is divided into two parts, the primary loaded ceramic balls are impregnated three times, the spark plasma sintering temperature is 600°C, and the time is 60 min; in step (6), the concentration of the FeCl2 solution is 7 wt%.

[0082] Comparative Example 1

[0083] This comparative example provides a photo-Fenton catalyst and a preparation method thereof. The difference from Example 3 is that steps (2) and (4) are not performed, and in step (5), the pretreated ceramic balls are directly immersed in the ethanol slurry of titanium dioxide, and the ball milling is performed at 400 r / min for 4 h when preparing the ethanol slurry of titanium dioxide in step (5).

[0084] Test Example 1

[0085] (1) Take the TiO2 prepared in Example 3 and perform XRD characterization. Figure 2 ,from Figure 2 It can be seen from the figure that the prepared TiO2 is a pure phase according to XRD characterization.

[0086] A 5 wt% FeCl2 solution was prepared, stirred at 80°C for 6.5 h, and filtered to obtain an iron species similar to the iron species attached to the outer layer of the photo-Fenton catalyst obtained in Example 3. XRD characterization was performed on it. Figure 3 The results show that there is no sharp characteristic peak, indicating that the crystallinity is poor, that is, it is amorphous. According to the characteristic peak retrieval, the main component of the iron species is FeOOH.

[0087] (2) The Fe 2p of the iron species prepared in (1) was tested by XPS (X-ray photoelectron spectroscopy), see Figure 4 , according to the characteristic peaks, there is Fe 2+ 、Fe 3+ and satellite peaks, which are characteristic peaks of FeOOH, confirm the above XRD test conclusions.

[0088] (3) Take the TiO2 prepared in Example 3 and the photo-Fenton catalyst finally prepared, and test the UV diffuse reflectance curve respectively. Figure 5 , and the corresponding calculation results are obtained, see Figure 6 It can be seen that after modifying the amorphous iron species, the light response range is extended from 437 nm to 635 nm, and the band gap is narrowed from 2.79 eV to 1.91 eV, greatly improving the efficiency of the catalyst in utilizing natural light.

[0089] (4) The TiO2 prepared in Example 3 and the photo-Fenton catalyst finally prepared were tested for their photoluminescence properties. Figure 7 The horizontal axis represents the wavelength of the excitation light, and the vertical axis represents the relative energy intensity generated by the fallback of photogenerated electrons after transition at different wavelengths. Higher intensity indicates a higher recombination rate of photogenerated electrons, lower photogenerated electron utilization, and poorer photocatalytic effect. Conversely, lower intensity indicates a higher photogenerated electron utilization rate and better photocatalytic effect. The results show that compared to secondary-loaded ceramic spheres, the recombination rate of photogenerated electrons in the photo-Fenton catalyst is significantly lower, and the improved photoelectric performance is the main reason for the increased catalytic efficiency.

[0090] Test Example 2 (Cyclic Stability Test)

[0091] Nine photo-Fenton catalysts (3 each of 5 mm, 6 mm, and 7 mm) were taken from the final products obtained in the examples and comparative examples, and placed in 1L methylene blue solution of 100 mg / L. Under natural light conditions, 30% vol hydrogen peroxide was added dropwise until the hydrogen peroxide concentration reached 16 mmol / L, and the pH was adjusted to 6.8. The catalytic performance of the photo-Fenton catalyst was monitored: 280 minutes was considered as one cycle. After one cycle was completed, the photo-Fenton catalyst was taken out and placed in a new 1L methylene blue solution of 100 mg / L for the next cycle. The value of the reduction in methylene concentration in the methylene blue solution at the completion of the first cycle was taken as the initial catalytic performance, which was calculated as 100%; the ratio of the subsequent catalytic performance was the percentage of the value of the reduction in methylene concentration in the corresponding number of cycles to the initial catalytic performance. Whenever the catalytic performance showed a significant decline (the difference from the initial catalytic performance was greater than 30%), the photo-Fenton catalyst was taken out and the preparation step (6) was repeated to achieve regeneration of the photo-Fenton catalyst, which was counted as one round of experiment. The number of cycles before the performance of the photo-Fenton catalyst showed a significant decline in each round was recorded, as well as the recovery rate of the catalytic performance after regeneration, with the initial catalytic performance as 100%, as shown in Table 1.

[0092] As can be seen from Table 1, the photo-Fenton catalyst obtained in Comparative Example 1, which was prepared without titanium nitride loading, exhibited lower cycling times and catalytic performance recovery after each regeneration cycle than those in the Examples. In contrast, the photo-Fenton catalyst prepared using the method of the present invention in the Examples exhibited excellent cycling and regeneration performance.

[0093] Table 1

[0094]

[0095] Test Example 3 (Actual Water Pollution Degradation Simulation)

[0096] Nine photo-Fenton catalysts (3 each of 5 mm, 6 mm, and 7 mm) were taken from the final products prepared in the Examples and Comparative Examples and placed in a 1L 100 mg / L methylene blue solution (the solution was placed in a 2L container). Under natural light, 30% vol hydrogen peroxide was added dropwise to the solution until the concentration reached 16 mmol / L, and the pH was adjusted to 6.8. The container was placed in a variable-speed shaker (100 rpm / min) to monitor the catalytic performance. Each cycle lasted 280 minutes. After each cycle, the photo-Fenton catalyst was removed and placed in a fresh 1L 100 mg / L methylene blue solution for the next cycle. The initial catalytic performance was calculated as 100% based on the reduction in methylene concentration in the methylene blue solution at the completion of the first cycle. The subsequent catalytic performance ratio was calculated as the percentage of the reduction in methylene concentration during the corresponding number of cycles to the initial catalytic performance. Whenever the catalytic performance showed a significant decline (the difference from the previous cycle was greater than 30%), the photo-Fenton catalyst was removed and preparation step (6) was repeated to achieve regeneration of the photo-Fenton catalyst, which was counted as one round of experiment. The number of cycles before the photo-Fenton catalyst performance showed a significant decline in each round, as well as the recovery rate of the catalytic performance after regeneration, with the initial catalytic performance as 100%, were recorded in Table 2.

[0097] The results of the actual water pollution degradation simulation are consistent with the cyclic stability test results of Test Example 2. The photo-Fenton catalyst obtained in Comparative Example 1 has poor circulation and regeneration performance, while the photo-Fenton catalyst prepared using the preparation method of the present invention in the embodiment has good circulation and regeneration performance.

[0098] Table 2

[0099]

[0100] Test Example 4 (Catalytic Performance Test)

[0101] Three batches of photo-Fenton catalysts were taken from the final products prepared in the Examples and Comparative Examples, each containing nine catalysts (three each of 5 mm, 6 mm, and 7 mm). These catalysts were placed in 1L of a 100 mg / L methylene blue solution, 1L of a 100 mg / L methylene orange solution, and 1L of a 100 mg / L rhodamine B solution, respectively. Under natural light, 30% vol hydrogen peroxide was added dropwise to a hydrogen peroxide concentration of 16 mmol / L. The pH of each solution was adjusted to 6.8. Samples were taken every 10 minutes (5 mL of the supernatant was centrifuged at 800 rpm for 3 minutes, the same below). Concentrations were measured using a UV-visible spectrophotometer. The time required for complete degradation of methylene blue, methylene orange, and rhodamine B was recorded in Table 3.

[0102] Table 3

[0103]

[0104] Test Example 5 (pH Test)

[0105] Nine photo-Fenton catalysts (3 each of 5 mm, 6 mm, and 7 mm) were taken from each of the final products prepared in the Examples and Comparative Examples and placed in a 1L solution of 100 mg / L methylene blue. Under natural light, 30% vol hydrogen peroxide was added dropwise to the solution until the hydrogen peroxide concentration reached 16 mmol / L. Six methylene blue solutions were prepared for each final product prepared in the Examples and Comparative Examples, and the pH values were adjusted to 2.2, 3.3, 4.4, 6.8, 9, and 11, respectively. The pH was adjusted using either a dilute hydrochloric acid solution at pH 1 or a NaOH solution at pH 13. Samples were taken every 10 minutes, and the concentration was measured using a UV-visible spectrophotometer. The time required for complete degradation of the methylene blue was recorded in Table 4.

[0106] It can be seen that the photo-Fenton catalysts prepared in the embodiments of the present invention can achieve complete degradation of methylene blue under acidic, alkaline and neutral conditions, and are applicable to a wide range of working conditions.

[0107] Table 4

[0108]

[0109] Test Example 6 (Hydrogen Peroxide Concentration Test)

[0110] Nine photo-Fenton catalysts (3 each of 5 mm, 6 mm, and 7 mm) were taken from each of the final products prepared in the Examples and Comparative Examples and placed in a 100 mg / L / L methylene blue solution. Catalysis was carried out under natural light, and the pH was adjusted to 6.8. Six methylene blue solutions were prepared for each final product prepared in the Examples and Comparative Examples. 30% vol hydrogen peroxide was added dropwise or not to hydrogen peroxide concentrations of 0 mmol / L, 4 mmol / L, 8 mmol / L, 16 mmol / L, 24 mmol / L, and 30 mmol / L, respectively. Samples were taken every 10 minutes, and the concentration was measured using a UV-visible spectrophotometer. The time required for complete degradation of the methylene blue was recorded in Table 5.

[0111] As can be seen from Table 5, the time required for complete degradation of methylene blue gradually decreases with increasing hydrogen peroxide concentration. Taking Example 1 as an example, at a hydrogen peroxide concentration of 24 mmol / L, the time required for complete degradation is 180 minutes, while at a concentration of 30 mmol / L, the time required for complete degradation is 170 minutes. Once the hydrogen peroxide concentration reaches a certain value, its effect on shortening degradation time becomes less pronounced. Taking into account the cost of hydrogen peroxide usage, its hazardous properties, and degradation time, 16 mmol / L can be determined to be the optimal hydrogen peroxide concentration.

[0112] Table 5

[0113]

[0114] It can be found from the data in the above test examples that the performance of the photo-Fenton catalyst obtained in different embodiments is also different. The pH during the preparation of titanium dioxide will affect the performance of titanium dioxide and thus the final catalytic performance of the photo-Fenton catalyst. The titanium dioxide obtained when the pH is 3.4 in Examples 3 and 6 is the best, and its catalytic performance is better than that of other embodiments. The preparation of the slurry will affect the coating effect of the material. The ball milling speed in Example 1 is the lowest, and the slurry grinding is not sufficient as in other embodiments, and its final catalytic effect is poor. The sintering temperature and duration will also affect the bonding strength of titanium nitride and titanium dioxide, and thus affect the cyclic stability of the photo-Fenton catalyst. For example, in Example 2, due to the low sintering temperature and short time, although the titanium dioxide preparation pH is better and the slurry preparation conditions are also better, the catalytic performance is worse than that of Examples 3 to 6. The loading concentration and duration of the amorphous iron substance affect the modification of titanium dioxide and also affect the final photo-Fenton performance of the catalyst.

[0115] 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 readily appreciate that other variations or modifications based on the above descriptions are possible. 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 photo-Fenton catalyst, characterized in that: The steps include: S1: immersing the silicon nitride carrier in a buffered oxide etchant for pretreatment to obtain a pretreated carrier; The silicon nitride carrier is a silicon nitride ceramic ball; S2: preparing an ethanol slurry of titanium nitride, and immersing the pretreated support in the ethanol slurry of titanium nitride to obtain a primary loaded support; S3: preparing an ethanol slurry of titanium dioxide, immersing the primary support in the ethanol slurry of titanium dioxide under stirring, and sintering to obtain a secondary support; The sintering temperature is 400~800℃ and the sintering time is 40~70min; The sintering method is spark plasma sintering; S4: immersing the secondary load carrier in a ferrous salt solution, performing solid-liquid separation, and drying to obtain the photo-Fenton catalyst.

2. The preparation method according to claim 1, characterized in that In said S4, the immersion time is 30-60 min and the temperature is 60-80° C.; And / or, in S4, the mass ratio of the ferrous salt solution to the secondary load carrier is 2-3:1; And / or, in S4, the mass concentration of the ferrous salt solution is 3% to 6%; And / or, in said S4, the drying temperature is 60-80° C. and the drying time is 5-8 hours; And / or, in S4, the ferrous salt solution includes at least one of ferrous chloride solution and ferrous sulfate solution; And / or, in S1, the pretreatment time is ≥4h.

3. The preparation method according to claim 2, characterized in that In S2, in the titanium nitride ethanol slurry, the solid-liquid volume ratio of titanium nitride to ethanol is 1:1-1.5; And / or, in S2, the mass ratio of the titanium nitride ethanol slurry to the pretreated support is 2-3:1; and / or, in S2, immersing the titanium nitride in the ethanol slurry until the ethanol is evaporated; And / or, in S2, the impregnation includes using at least one of stirring and brushing methods to uniformly load the titanium nitride onto the silicon nitride carrier; And / or, in S1, the pretreatment time is 4 to 10 hours.

4. The preparation method according to claim 1, characterized in that In S3, in the titanium dioxide ethanol slurry, the solid-liquid volume ratio of titanium dioxide to ethanol is 1:1-1.5; And / or, in S3, the mass ratio of the ethanol slurry of titanium dioxide to the primary support is 2-3:1; and / or, in S3, immersing the titanium dioxide in an ethanol slurry and evaporating the ethanol; And / or, in S3, the impregnation includes using at least one of stirring and brushing methods to uniformly load the titanium dioxide onto the primary loading carrier.

5. The preparation method according to claim 4, characterized in that In S2, the step of preparing the titanium nitride ethanol slurry comprises: mixing titanium nitride with ethanol, and ball milling at 200-400 r / min for 1.5-6 hours to obtain the titanium nitride ethanol slurry; And / or, in said S3, the step of preparing the ethanol slurry of titanium dioxide comprises: mixing titanium dioxide with ethanol, and ball milling at 200-400 r / min for 1.5-6 hours to obtain the ethanol slurry of titanium dioxide; And / or, the size of the silicon nitride carrier is 4 to 15 mm; And / or, the silicon nitride ceramic ball includes a defective silicon nitride ceramic ball.

6. The preparation method according to claim 5, characterized in that The preparation of the titanium nitride comprises the following steps: adding ammonia water to an organic titanium source, adjusting the pH to 2.8-4.5, stirring until a gel state is formed, drying to obtain titanium dioxide, and nitriding in a nitrogen atmosphere to obtain the titanium nitride; And / or, the preparation of titanium dioxide comprises the following steps: adding ammonia water to an organic titanium source, adjusting the pH to 2.8-4.5, stirring, standing until the mixture is in a gel state, and drying to obtain titanium dioxide.

7. The preparation method according to claim 6, characterized in that During the preparation of titanium nitride, the drying temperature is 60-80°C and the drying time is 6-10 hours; and / or, in the preparation process of titanium nitride, the nitriding temperature is 800-1200° C. and the time is 4-6 hours; And / or, in the preparation process of titanium nitride, before adding ammonia water, the step of stirring the organic titanium source for 10 to 20 minutes is also included; And / or, during the preparation of titanium dioxide, the stirring time is 10 to 20 minutes; and / or, during the preparation of titanium dioxide, the drying temperature is 60-80° C. and the drying time is 4-6 hours; And / or, in the preparation process of titanium dioxide, before adding ammonia water, the organic titanium source is further stirred for 10 to 20 minutes; And / or, the organic titanium source includes at least one of tetrabutyl titanate and tetraisopropyl titanate.

8. A photo-Fenton catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the photo-Fenton catalyst according to claim 8 in treating organic pollutants.

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