Photo-Fenton catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a photo-Fenton catalyst and a preparation method and application thereof. The preparation method comprises the following steps: pretreating a silicon nitride carrier with a buffer oxide etching agent to obtain a pretreated carrier; titanium nitride is loaded on the pretreated carrier for the first time by using ethanol slurry of titanium nitride, and a primary loaded carrier is obtained; secondarily loading titanium dioxide on the primary loading carrier by using ethanol slurry of titanium dioxide, and sintering to obtain a secondary loading carrier; and dipping the secondary load carrier in a ferrite solution, and drying to obtain the photo-Fenton catalyst. The photo-Fenton catalyst has a structure that silicon oxide is used as an innermost layer carrier, and TiN, TiO2 and amorphous iron species are sequentially loaded on the silicon oxide, and the photo-Fenton catalyst is good in catalytic performance, convenient to regenerate and wide in applicable working condition environment.

Description

Technical Field

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

[0002] Whether in daily life or industrial production, the demand for polymer products is increasing day by day. The production of polymer products will cause a sharp increase in the content of water-soluble organic matter in the discharged water, bringing serious environmental pollution. As a new type of 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 refractory organic sewage. Titanium dioxide (TiO2) is a typical photocatalyst. By modifying TiO2 with amorphous iron species, the light response range of TiO2 can be broadened to natural visible light, improving the utilization rate of light energy. The converted light can enhance the reduction of Fe 2+ in the Fenton oxidation process, effectively combining photocatalysis and Fenton technology. However, as a heterogeneous catalyst, powdered TiO2 faces great difficulties in the fields of light conversion, catalytic stability, and recovery convenience when treating water pollution.

[0003] Silicon nitride ceramic balls have physical properties such as high strength, wear resistance, corrosion resistance, and low density, and can be applied to the field of high-end intelligent manufacturing. However, a certain amount of defective silicon nitride ceramic balls will inevitably appear during the preparation process. For example, after the sintering process, some surface shells of the ball blanks will fall off, there will be internal and external color differences and a large number of pores in the cross section, microcracks will exist at the annulus position, and surface cracks will occur, making it impossible to carry out the production of the next process. However, the defective silicon nitride ceramic balls still have excellent physical properties, and their applications under suitable working conditions can be studied to reduce waste. Summary of the Invention

[0004] Therefore, the present invention provides a photo-Fenton catalyst, a preparation method thereof, and an application thereof. Using silicon nitride as a carrier, TiN, TiO2, and amorphous iron species are sequentially loaded thereon to obtain a photo-Fenton catalyst with good catalytic performance, convenient regeneration, and a wide range of applicable working conditions.

[0005] For this purpose, the present invention provides the following technical solutions.

[0006] The present invention provides a preparation method of a photo-Fenton catalyst, comprising the following steps: S1: Immerse the silicon nitride carrier in a buffered oxide etchant for pretreatment to obtain a pretreated carrier; S2: Prepare an ethanol slurry of titanium nitride, and immerse the pretreated carrier in the ethanol slurry of titanium nitride to obtain a once-loaded carrier; S3: Prepare an ethanol slurry of titanium dioxide. Under stirring, immerse the primary supported carrier in the ethanol slurry of titanium dioxide, and sinter to obtain a secondary supported carrier. S4: Immerse the secondary supported carrier in a ferrous salt solution, perform solid-liquid separation, and dry to obtain the photo-Fenton catalyst.

[0007] In the preparation method of the photo-Fenton catalyst provided by the present invention, typically and non-limitingly, the buffered oxide etchant (Buffered Oxide Etch, BOE) used is commercially available BOE, regardless of whether it is BOE solution 10:1 (where the volume ratio of 40 wt% ammonium fluoride aqueous solution to 49 wt% hydrofluoric acid aqueous solution is 10:1) or BOE solution 6:1 (where the volume ratio of 40 wt% ammonium fluoride aqueous solution to 49 wt% hydrofluoric acid aqueous solution is 6:1); the BOE solution has a specific etching rate and selectivity in microfabrication, can be applied to specific process requirements, and is widely used in fields such as semiconductor manufacturing and microelectromechanical system (MEMS) processing for steps such as etching microstructures and removing oxide layers; after the pretreatment is completed, it also includes the step of washing the BOE solution on the surface of the pretreated carrier, and generally rinsing with deionized water 3 times is sufficient to remove the residual BOE solution.

[0008] Optionally, in S3, the sintering temperature is 400 - 800 °C and the time is 40 - 70 min.

[0009] Optionally, in S3, the sintering method includes spark plasma sintering.

[0010] Optionally, in S4, the impregnation 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 in-situ grown on the surface of the secondary supported carrier more firm.

[0011] Optionally, in S4, the mass ratio of the ferrous salt solution to the secondary supported carrier is 2 - 3:1.

[0012] Optionally, in S4, the mass concentration of the ferrous salt solution is 3% - 6%.

[0013] Optionally, in S4, the drying temperature is 60 - 80 °C and the time is 5 - 8 h.

[0014] Optionally, in S4, the ferrous salt solution includes at least one of ferrous chloride solution and ferrous sulfate solution.

[0015] Optionally, in S1, the pretreatment time ≥ 4 h.

[0016] Optionally, in S2, in the ethanol slurry of titanium nitride, the solid-liquid volume ratio of titanium nitride to ethanol is 1:1 to 1.5.

[0017] Optionally, in S2, the mass ratio of the ethanol slurry of titanium nitride to the pretreated carrier is 2 to 3:1.

[0018] Optionally, in S2, impregnate until the ethanol in the ethanol slurry of titanium nitride evaporates completely.

[0019] Optionally, in S2, during impregnation, at least one of stirring and brushing methods is included to uniformly load titanium nitride onto the silicon nitride carrier.

[0020] Optionally, in S1, the pretreatment time is 4 to 10 h.

[0021] Optionally, in S3, in the ethanol slurry of titanium dioxide, the solid-liquid volume ratio of titanium dioxide to ethanol is 1:1 to 1.5.

[0022] Optionally, in S3, the mass ratio of the ethanol slurry of titanium dioxide to the once-loaded carrier is 2 to 3:1.

[0023] Optionally, in S3, impregnate until the ethanol in the ethanol slurry of titanium dioxide evaporates completely.

[0024] Optionally, in S3, during impregnation, at least one of stirring and brushing methods is included to uniformly load titanium dioxide onto the once-loaded carrier.

[0025] Optionally, the silicon nitride carrier includes silicon nitride ceramic balls.

[0026] Optionally, in S2, the steps of preparing the ethanol slurry of titanium nitride include: mixing titanium nitride and ethanol, and ball-milling at 200 to 400 r / min for 1.5 to 6 h to obtain the ethanol slurry of titanium nitride.

[0027] Optionally, in S3, the steps of preparing the ethanol slurry of titanium dioxide include: mixing titanium dioxide and ethanol, and ball-milling at 200 to 400 r / min for 1.5 to 6 h to obtain the ethanol slurry of titanium dioxide.

[0028] In the preparation method of the photo-Fenton catalyst provided by the present invention, typically but not limitedly, the used titanium nitride and titanium dioxide can be purchased or self-made, but the purity needs to be ≥99.9%; in commercially available products, the purity and photocatalytic performance of inexpensive products cannot be guaranteed, and the price of guaranteed products is relatively high. Therefore, it is preferred to self-prepare high-purity titanium nitride and titanium dioxide for use.

[0029] Optionally, the size of the silicon nitride carrier is 4 to 15 mm.

[0030] Optionally, the silicon nitride ceramic balls include defective silicon nitride ceramic balls. Typically but not limited to, defective silicon nitride ceramic balls are those with surface shell peeling, internal and external color differences in the cross-section, a large number of pores, microcracks at the annulus position, surface cracking, etc., and are ball blanks that cannot be used for further processing and production.

[0031] Optionally, the preparation of titanium nitride includes the following steps: adding ammonia water to an organic titanium source, adjusting the pH to 2.8 - 4.5, stirring until it becomes a gel state, drying to obtain titanium dioxide, and nitriding in a nitrogen atmosphere to obtain the titanium nitride.

[0032] Optionally, the preparation of titanium dioxide includes the following steps: adding ammonia water to an organic titanium source, adjusting the pH to 2.8 - 4.5, stirring, standing until it becomes a gel state, and drying to obtain titanium dioxide.

[0033] Typically but not limited to, the above stirring method includes magnetic stirring, and the rate of magnetic stirring is 200 - 800 r / min; in the preparation steps of titanium nitride and titanium dioxide, it also includes the steps of washing and drying the obtained titanium nitride and titanium dioxide to reduce systematic errors.

[0034] Optionally, during the preparation of titanium nitride, the drying temperature is 60 - 80 °C and the time is 6 - 10 h.

[0035] Optionally, during the preparation of titanium nitride, the nitriding temperature is 800 - 1200 °C and the time is 4 - 6 h.

[0036] Optionally, during the preparation of titanium nitride, before adding ammonia water, it also includes the step of stirring the organic titanium source for 10 - 20 min.

[0037] Optionally, during the preparation of titanium dioxide, the stirring time is 10 - 20 min.

[0038] Optionally, during the preparation of titanium dioxide, the drying temperature is 60 - 80 °C and the time is 4 - 6 h.

[0039] Optionally, during the preparation of titanium dioxide, before adding ammonia water, it also includes the step of stirring the organic titanium source for 10 - 20 min.

[0040] Optionally, the organic titanium source includes at least one of tetrabutyl titanate and tetraisopropyl titanate.

[0041] The present invention also provides a photo-Fenton catalyst prepared by the above preparation method.

[0042] The present invention provides the application of the above-mentioned photo-Fenton catalyst in treating organic pollutants. Optionally, H2O2 is required when using the above-mentioned photo-Fenton catalyst to treat organic pollutants, and the concentration of H2O2 ≥ 2 mmol / L; further optionally, the concentration of H2O2 is 4-24 mmol / L; more preferably, the concentration of H2O2 is 16 mmol / L.

[0043] The beneficial effects of the present invention are as follows: The present invention provides a preparation method of a photo-Fenton catalyst, including the following steps: S1: Immerse a silicon nitride carrier in a buffered oxide etchant for pretreatment to obtain a pretreated carrier; S2: Prepare an ethanol slurry of titanium nitride, and immerse the pretreated carrier in the ethanol slurry of titanium nitride to obtain a once-loaded carrier; S3: Prepare an ethanol slurry of titanium dioxide, and under stirring, immerse the once-loaded carrier in the ethanol slurry of titanium dioxide and sinter to obtain a twice-loaded carrier; S4: Immerse the twice-loaded carrier in a ferrous salt solution, perform solid-liquid separation, and dry to obtain the photo-Fenton catalyst. This photo-Fenton catalyst has a structure with silicon oxide as the innermost carrier, on which TiN, TiO2, and amorphous iron species are successively loaded. It 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 molecule substances such as CO2 and H2O, with good catalytic performance; and this photo-Fenton catalyst is convenient for regeneration and can be applied to a wide range of working conditions.

[0044] Using silicon nitride as the carrier, and because silicon nitride has physical properties such as high strength, wear resistance, corrosion resistance, and low density, the prepared photo-Fenton catalyst can be applied to more working conditions with complex environments, such as water environments with more undercurrents and vortices. If only TiO2 is directly loaded on the silicon nitride carrier, the thermal shrinkage rates of the two-phase ceramics are different, which will lead to an increased shrinkage gap between the two after sintering and low bonding stability. However, after successively loading TiN and TiO2 on the silicon nitride carrier and then sintering, micro-liquids will be generated between the interfaces, interface reactions will occur, atoms will diffuse mutually, and chemical bonding forces will be generated; that is, between silicon nitride (Si and N) and titanium nitride (Ti and N), atoms will diffuse and migrate mutually, and form Ti-N and Si-N covalent bonds respectively; similarly, atoms between titanium dioxide (Ti and O) and titanium nitride (Ti and N) will also diffuse mutually to form Ti-N and Ti-O covalent bonds; and the thermal shrinkage rate differences between adjacent phases are also small, and they can be firmly and stably bonded together after forming chemical bonds. Using a buffered oxide etchant to pretreat the silicon nitride ceramic can increase the defects on its surface and provide more attachment sites for the subsequent loading of TiN.

[0045] 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 BOE solution, the unstable regions on their surfaces will be etched away, and they will be in a state of smooth surface, obvious pit defects, and no obvious impurities. However, after the macroscopic surface defects are removed, from the atomic microscopic perspective, defects such as points, lines, and grain boundaries still exist. The positions of ceramic defects such as cracks, pores, and impurities have relatively high energy and can serve as reactive sites, which will have a positive impact on the migration and diffusion of interface atoms during the sintering process, making the TiN loading more firm. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0047] Figure 1 Schematic structural diagram and working principle schematic diagram of the photo-Fenton catalyst prepared in Example 1; Figure 2 XRD image of TiO2 prepared in Example 3; Figure 3 XRD image of the iron species prepared in Test Example 1; Figure 4 XPS image of the iron species prepared in Test Example 1; Figure 5 UV diffuse reflection curve images of TiO2 prepared in Example 3 and the finally prepared photo-Fenton catalyst tested in Test Example 1; Figure 6 Band gap curve images of TiO2 prepared in Example 3 and the finally prepared photo-Fenton catalyst tested in Test Example 1; Figure 7 Photoluminescence performance images of TiO2 prepared in Example 3 and the finally prepared photo-Fenton catalyst tested in Test Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The following embodiments are provided to better further understand the present invention. It is not limited to the best embodiment, and does not limit the content and protection scope of the present invention. Any product obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features that is the same or similar to the present invention falls within the protection scope of the present invention.

[0049] For those not specifying specific experimental procedures or conditions in the examples, operations or conditions of conventional experimental procedures described in the literature in this field can be followed. For reagents or instruments without indicating the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase.

[0050] Experimental drugs: Defective silicon nitride ceramic balls: The defective silicon nitride ceramic balls screened out after the atmosphere sintering step are ball blanks with surface shell peeling, internal and external color differences and a large number of pores in the cross-section, microcracks at the annulus position, surface cracks, etc. The particle sizes are 5mm, 6mm, and 7mm.

[0051] Example 1 This example provides a photo-Fenton catalyst and its preparation method, including the following steps: (1) Immerse the defective silicon nitride ceramic balls in a BOE solution with a ratio of 10:1 for 4 h, fish out the pretreated ceramic balls, wash them 3 times with deionized water, and dry them.

[0052] (2) Put 50 mL of tetrabutyl titanate into a magnetic stirring pot, stir at 500 r / min for 10 min, then dropwise add ammonia water until the pH is 2.8, continue stirring until it becomes a gel state, transfer it to a vacuum drying oven, dry at 80 °C for 8 h to obtain titanium dioxide powder, grind it in a mortar until the powder is uniform, nitride it at 800 °C for 4 h in a nitrogen atmosphere, then grind, wash, and dry it to obtain titanium nitride powder.

[0053] (3) Put 50 mL of tetrabutyl titanate into a magnetic stirring pot, stir at 500 r / min for 10 min, then dropwise add ammonia water until the pH is 2.8, continue stirring for 10 min, then let it stand until it becomes a gel state, transfer it to a vacuum drying oven, dry at 80 °C for 6 h, then grind, wash, and dry it to obtain titanium dioxide powder.

[0054] (4) Mix the titanium nitride powder with ethanol, put it in a planetary ball mill, ball mill at 200 r / min for 1.5 h to prepare an ethanol slurry of titanium nitride with a solid-liquid volume ratio of 1:1. Immerse the pretreated ceramic balls in the ethanol slurry of titanium nitride. The mass ratio of the ethanol slurry of titanium nitride to the pretreated ceramic balls is 2:1. Use a brush to brush and coat to uniformly load titanium nitride onto the pretreated ceramic balls until the ethanol completely volatilizes to obtain the once-loaded ceramic balls.

[0055] (5) Mix the titanium dioxide powder with ethanol, place it in a planetary ball mill, and ball mill at 200 r / min for 1.5 h to prepare an ethanol slurry of titanium dioxide with a solid-liquid volume ratio of 1:1. Immerse the primary-loaded ceramic balls in the ethanol slurry of titanium dioxide. The mass ratio of the ethanol slurry of titanium dioxide to the primary-loaded ceramic balls is 2:1. Use a brush to brush-coat to evenly load titanium dioxide onto the primary-loaded ceramic balls until the ethanol evaporates completely. Then, perform spark plasma sintering at 400 °C for 40 min to obtain secondary-loaded ceramic balls, which are washed and dried for standby.

[0056] (6) Prepare a 3 wt% FeCl2 solution. At 80 °C, immerse the secondary-loaded ceramic balls in the FeCl2 solution for 30 min. The mass ratio of the FeCl2 solution to the secondary-loaded ceramic balls is 3:1. Take out the ceramic balls and place them in a vacuum drying oven, and dry at 80 °C for 6 h to obtain a photo-Fenton catalyst.

[0057] The structural schematic diagram and working principle schematic 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 a silicon nitride support in the innermost layer (corresponding to the defective silicon nitride ceramic balls in this example), followed by a titanium nitride layer, a titanium dioxide layer, and an amorphous iron species layer loaded in sequence. Covalent bonding of Ti-N and Si-N will form between silicon nitride (Si and N) and titanium nitride (Ti and N); covalent bonding of Ti-N and Ti-O will form between titanium dioxide (Ti and O) and titanium nitride (Ti and N); to help the photo-Fenton catalyst have a more stable structure. After the titanium dioxide receives photon energy, electrons are excited and react with Fe in the amorphous iron species layer 3+ to obtain Fe 2+ , Fe 2+ reacts with H2O2 to obtain ·OH and Fe 3+ , and ·OH can react with pollutants to obtain carbon dioxide, water, etc., completing the decomposition of pollutants.

[0058] Example 2 This example provides a photo-Fenton catalyst and its preparation method. Compared with Example 1, the differences are as follows: in step (1), the pretreatment time is 6 h; 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 is 300 r / min when preparing the ethanol slurry of titanium nitride; in step (5), the ball milling rate is 300 r / min when preparing the ethanol slurry of titanium dioxide.

[0059] Example 3 This embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with Embodiment 1, the differences are as follows: in step (1), the pretreatment time is 6 h; in step (2), ammonia water is added dropwise until the pH is 3.4, and the nitridation 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, ball milling is carried out at 300 r / min for 2 h; in step (5), when preparing the ethanol slurry of titanium dioxide, ball milling is carried out at 300 r / min for 4 h. The ethanol slurry of titanium dioxide is evenly divided into 2 parts, and the primary-loaded ceramic balls are impregnated 2 times. The temperature of spark plasma sintering is 600 °C and the time is 60 min; in step (6), the concentration of the FeCl2 solution is 5 wt%.

[0060] Example 4 This embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with Embodiment 1, the differences are as follows: in step (1), the pretreatment time is 8 h; in step (2), ammonia water is added dropwise until the pH is 4, and the nitridation 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, ball milling is carried out at 300 r / min for 2.5 h; in step (5), when preparing the ethanol slurry of titanium dioxide, ball milling is carried out at 300 r / min for 4 h. The ethanol slurry of titanium dioxide is evenly divided into 2 parts, and the primary-loaded ceramic balls are impregnated 2 times. The temperature of spark plasma sintering is 600 °C and the time is 60 min; in step (6), the concentration of the FeCl2 solution is 5 wt%.

[0061] Example 5 This embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with Embodiment 1, the differences are as follows: in step (1), the pretreatment time is 10 h; in step (2), ammonia water is added dropwise until the pH is 4, and the nitridation 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, ball milling is carried out at 400 r / min for 2.5 h; in step (5), when preparing the ethanol slurry of titanium dioxide, ball milling is carried out at 400 r / min for 6 h. The ethanol slurry of titanium dioxide is evenly divided into 3 parts, and the primary-loaded ceramic balls are impregnated 3 times. The temperature of spark plasma sintering is 600 °C and the time is 60 min; in step (6), the concentration of the FeCl2 solution is 7 wt%.

[0062] Example 6 This embodiment provides a photo-Fenton catalyst and a preparation method thereof. Compared with Embodiment 1, the differences are as follows: in step (1), the pretreatment time is 6 h; in step (2), ammonia water is added dropwise until the pH is 3.4, and the nitridation 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, ball milling is carried out at 400 r / min for 2 h; in step (5), when preparing the ethanol slurry of titanium dioxide, ball milling is carried out at 400 r / min for 4 h. The ethanol slurry of titanium dioxide is evenly divided into two parts, and the primary load ceramic balls are impregnated 3 times. The temperature of spark plasma sintering is 600 °C and the time is 60 min; in step (6), the concentration of the FeCl2 solution is 7 wt%.

[0063] Comparative Example 1 This comparative example provides a photo-Fenton catalyst and a preparation method thereof. The difference from Embodiment 3 is that steps (2) and (4) are not carried out. In step (5), the pretreated ceramic balls are directly impregnated in the ethanol slurry of titanium dioxide, and in step (5), when preparing the ethanol slurry of titanium dioxide, ball milling is carried out at 400 r / min for 4 h.

[0064] Test Example 1 (1) Take the TiO2 prepared in Embodiment 3 for XRD characterization, as shown in Figure 2 , it can be seen from Figure 2 that the prepared TiO2 is a pure phase by XRD characterization.

[0065] Prepare a 5 wt% FeCl2 solution, stir at 80 °C for 6.5 h, and filter to obtain iron species similar to those attached to the outer layer of the photo-Fenton catalyst obtained in Embodiment 3. Perform XRD characterization on it, as shown in Figure 3 . The results show that there are no sharp characteristic peaks, indicating poor crystallinity, that is, amorphous. According to the characteristic peak retrieval, the main component of the iron species is FeOOH.

[0066] (2) Perform XPS (X-ray photoelectron spectroscopy) test on the iron species prepared in (1) for Fe 2p, as shown in Figure 4 . According to the characteristic peaks, it shows the existence of Fe 2+ , Fe 3+ and satellite peaks, which are the characteristic peaks of FeOOH, confirming the above test conclusion of XRD.

[0067] (3) Take the TiO2 prepared in Embodiment 3 and the finally prepared photo-Fenton catalyst, and test the ultraviolet diffuse reflection curves respectively, as shown in Figure 5 , and calculate the corresponding band gap curves, as shown in Figure 6It 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 reduced from 2.79 eV to 1.91 eV, greatly improving the utilization efficiency of the catalyst for natural light.

[0068] (4)The TiO2 prepared in Example 3 and the finally prepared photo-Fenton catalyst were respectively tested for photoluminescence performance, as shown in Figure 7 , where the horizontal axis represents the wavelength of the excitation light, and the vertical axis represents the relative energy intensity generated after the photo-generated electrons transition and then fall back at different wavelengths. The higher the intensity, the higher the recombination rate of the photo-generated electrons, the lower the utilization rate of the photo-generated electrons, and the worse the photocatalytic effect. On the contrary, the lower the intensity, the higher the utilization rate of the photo-generated electrons, and the better the photocatalytic effect. From the results, it can be seen that compared with the secondary-loaded ceramic balls, the recombination rate of the photo-generated electrons of the photo-Fenton catalyst is significantly reduced, and the improvement of the optoelectronic performance is the main reason for the improvement of the catalytic efficiency.

[0069] Test Example 2 (Cyclic Stability Test) 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 were respectively placed into 1 L of methylene blue solution with a concentration of 100 mg / L. Under natural light conditions, 30% vol of hydrogen peroxide was added dropwise until the hydrogen peroxide concentration reached 16 mmol / L, and the pH was adjusted to 6.8. Monitor the catalytic performance of the photo-Fenton catalyst: taking 280 min as one cycle, after completing one cycle, the photo-Fenton catalyst was taken out and placed into a new 1 L of methylene blue solution with a concentration of 100 mg / L for the next cycle. The value of the decrease in the methylene concentration in the methylene blue solution when the first cycle was completed was used as the initial catalytic performance, counted as 100%; the ratio of the subsequent catalytic performance was the percentage of the value of the decrease in the methylene concentration in the corresponding cycle to the initial catalytic performance. Whenever the catalytic performance showed a significant decrease (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 realize the regeneration of the photo-Fenton catalyst, which was counted as one round of experiment. Record the number of cycles before the performance of the photo-Fenton catalyst showed a significant decrease in each round, and the ratio of the catalytic performance recovery after regeneration with the initial catalytic performance as 100%, as shown in Table 1.

[0070] It can be seen from Table 1 that the photo-Fenton catalyst obtained in Comparative Example 1 was not loaded with titanium nitride during preparation, and its recyclable number of cycles and the ratio of the catalytic performance recovery after each round of regeneration were worse than those in the examples. The photo-Fenton catalyst prepared by using the preparation method of the present invention in the examples had good cyclic and regeneration performance.

[0071] Table 1

[0072] Test Example 3 (Simulation of Actual Water Pollution Degradation) Take 9 photo-Fenton catalysts (3 of 5 mm, 3 of 6 mm, and 3 of 7 mm each) from the final products obtained in the examples and comparative examples, and place them separately into 1 L of methylene blue solution at 100 mg / L (the solution is placed in a 2 L container). Under natural light conditions, add 30% vol hydrogen peroxide dropwise until the hydrogen peroxide concentration reaches 16 mmol / L, and adjust the pH to 6.8. Place the container in a variable-speed shaker (100 rpm / min) and monitor the catalytic situation. Take 280 min as one cycle. After completing one cycle, take out the photo-Fenton catalyst and put it into a new 1 L of methylene blue solution at 100 mg / L for the next cycle. When the first cycle is completed, take the value of the decrease in the concentration of methylene in the methylene blue solution as the initial catalytic performance, which is counted as 100%; the ratio of the subsequent catalytic performance is the percentage of the value of the decrease in the methylene concentration in the corresponding cycle to the initial catalytic performance. Whenever the catalytic performance shows a significant decline (the difference from the catalytic performance of the previous cycle is greater than 30%), take out the photo-Fenton catalyst and repeat the preparation step (6) to regenerate the photo-Fenton catalyst, and this is counted as one round of experiments. Record the number of cycles before the catalytic performance of the photo-Fenton catalyst shows a significant decline in each round, and the ratio of the catalytic performance recovery after regeneration with the initial catalytic performance as 100%, as shown in Table 2.

[0073] 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 cyclic and regeneration performance, while the photo-Fenton catalyst prepared by the preparation method of the present invention in the examples has good cyclic and regeneration performance.

[0074] Table 2

[0075] Test Example 4 (Catalytic Performance Test) Take 3 batches of photo-Fenton catalysts from the final products obtained in the examples and comparative examples. Each batch contains 9 catalysts (3 of 5 mm, 3 of 6 mm, and 3 of 7 mm each), and place them separately into 1 L of methylene blue solution at 100 mg / L, 1 L of methyl orange solution at 100 mg / L, and 1 L of rhodamine B solution at 100 mg / L. Under natural light conditions, add 30% vol hydrogen peroxide dropwise until the hydrogen peroxide concentration reaches 16 mmol / L, and adjust the pH to 6.8 in all cases. Take samples every 10 min (take 5 mL of the supernatant and centrifuge at 800 r / min for 3 min to obtain the sample, the same below), and use an ultraviolet-visible spectrophotometer to measure the concentration. The time required for the complete degradation of methylene blue, methyl orange, and rhodamine B is counted in Table 3.

[0076] Table 3

[0077] Test Example 5 (pH Test) Take 9 photo-Fenton catalysts (3 of 5 mm, 3 of 6 mm, and 3 of 7 mm each) from the final products obtained in the examples and comparative examples, and place them separately into 1 L of methylene blue solution with a concentration of 100 mg / L. Under natural light conditions, add 30% vol hydrogen peroxide dropwise until the hydrogen peroxide concentration reaches 16 mmol / L. Prepare 6 groups of corresponding methylene blue solutions for each final product obtained in the examples and comparative examples, and adjust their pH values to 2.2, 3.3, 4.4, 6.8, 9, and 11 respectively. The reagents used to adjust the pH are dilute hydrochloric acid solution with a pH of 1 or NaOH solution with a pH of 13. Take samples every 10 min, and use an ultraviolet-visible spectrophotometer to measure the concentration. Record the time required for complete degradation of methylene blue in Table 4.

[0078] It can be seen that all the photo-Fenton catalysts prepared in the examples of the present invention can achieve complete degradation of methylene blue under acidic, alkaline, and neutral conditions, and can be applied to a wide range of working conditions.

[0079] Table 4

[0080] Test Example 6 (Hydrogen Peroxide Concentration Test) Take 9 photo-Fenton catalysts (3 of 5 mm, 3 of 6 mm, and 3 of 7 mm each) from the final products obtained in the examples and comparative examples, and place them separately into 1 L of methylene blue solution with a concentration of 100 mg / L. Carry out catalysis under natural light conditions and adjust the pH to 6.8. Among them, prepare 6 groups of corresponding methylene blue solutions for each final product obtained in the examples and comparative examples, and add or do not add 30% vol hydrogen peroxide dropwise until the hydrogen peroxide concentration reaches 0 mmol / L, 4 mmol / L, 8 mmol / L, 16 mmol / L, 24 mmol / L, and 30 mmol / L respectively. Take samples every 10 min, and use an ultraviolet-visible spectrophotometer to measure the concentration. Record the time required for complete degradation of methylene blue in Table 5.

[0081] It can be seen from Table 5 that as the hydrogen peroxide concentration increases, the time required for complete degradation of methylene blue gradually decreases. Taking Example 1 as an example, when the hydrogen peroxide concentration is 24 mmol / L, the time required for complete degradation is 180 min, while when the concentration is 30 mmol / L, the time required for complete degradation is 170 min. Therefore, when the hydrogen peroxide concentration increases to a certain value, the effect of shortening the degradation time is not obvious. Considering the cost of hydrogen peroxide consumption, the hazardous nature of hydrogen peroxide, and the degradation time comprehensively, it can be judged that 16 mmol / L is the optimal concentration of hydrogen peroxide consumption.

[0082] Table 5

[0083] It can also be found from the data in the above test examples that the performance of the photo-Fenton catalysts obtained in different embodiments is also different. The pH during the preparation of titanium dioxide affects the performance of titanium dioxide and thus the final catalytic performance of the photo-Fenton catalyst. The titanium dioxide prepared at pH 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. In Example 1, the rotation speed of ball milling is the lowest, and the slurry is not ground as fully as in other embodiments, resulting in a relatively poor final catalytic effect. The sintering temperature and duration also affect the bonding strength between titanium nitride and titanium dioxide, and further affect the cyclic stability of the photo-Fenton catalyst. For example, in Example 2, although the pH of titanium dioxide preparation is good and the slurry preparation conditions are also good, the catalytic performance is worse than that of Examples 3 to 6 because the sintering temperature is low and the time is short. 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.

[0084] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. The obvious changes or modifications derived therefrom are still within the protection scope 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; S2: preparing an ethanol slurry of titanium nitride, and immersing the pretreated carrier in the ethanol slurry of titanium nitride to obtain a primary loaded carrier; S3: preparing an ethanol slurry of titanium dioxide, immersing the primary load carrier in the ethanol slurry of titanium dioxide under stirring, and sintering to obtain a secondary load carrier; S4: immersing the secondary load carrier in a ferrous salt solution, separating the solid from the liquid, and drying to obtain the photo-Fenton catalyst.

2. The preparation method according to claim 1, characterized in that: In S3, the sintering temperature is 400-800°C and the sintering time is 40-70 minutes; And / or, in S3, the sintering method includes spark plasma sintering.

3. The preparation method according to claim 1, characterized in that: In 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 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 a ferrous chloride solution and a ferrous sulfate solution; And / or, in S1, the pretreatment time is ≥ 4h.

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

5. The preparation method according to claim 1, characterized in that: In S3, in the ethanol slurry of titanium dioxide, 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 load carrier is 2-3:1; And / or, in S3, the titanium dioxide is immersed in an ethanol slurry and the ethanol is evaporated; 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; And / or, the silicon nitride carrier includes silicon nitride ceramic balls.

6. The preparation method according to claim 5, characterized in that: In S2, the step of preparing the ethanol slurry of titanium nitride comprises: 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; And / or, in S3, the step of preparing the ethanol slurry of titanium dioxide comprises: 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; 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.

7. The preparation method according to claim 6, 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 obtained, 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 to a gel state, and drying to obtain titanium dioxide.

8. The preparation method according to claim 7, characterized in that: In the preparation process of titanium nitride, the drying temperature is 60~80℃ and the drying time is 6~10h; 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 step of stirring the organic titanium source for 10 to 20 minutes is also included; And / or, the organic titanium source includes at least one of tetrabutyl titanate and tetraisopropyl titanate.

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

10. Use of the photo-Fenton catalyst as claimed in claim 9 in treating organic pollutants.

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