Photocatalyst with core-shell structure as well as preparation method and application of photocatalyst

Abstract

The invention discloses a photocatalyst with a core-shell structure as well as a preparation method and application of the photocatalyst. The core of the photocatalyst is Cu0-doped titanium dioxide particles of which the surfaces are modified with ethylene glycol, and the shell is polyaniline. The photocatalyst can degrade nitrate radicals in a chlorine-containing solution under ultraviolet irradiation and has excellent activity and stability, the activity of the catalyst is not obviously reduced after circulation for 4 times, a catalytic reaction system does not need to adjust the pH value of the solution or additionally add a sacrificial agent, the operation cost is low, and the method is suitable for industrial production. The method has a wide application prospect in treatment of nitrate radicals in chlorine-containing water.

Description

Technical Field

[0001] The present invention belongs to the field of environmental functional materials, and particularly relates to a core-shell structured photocatalytic composite material, a preparation method thereof, and an application in photocatalytic degradation of nitrate in chlorine-containing water bodies. Background Art

[0002] Nitrate is a pollutant commonly present in water environments. Excessive discharge of nitrate-containing wastewater can easily cause eutrophication of water bodies, leading to a large consumption of oxygen in fresh water and the death of a large number of aquatic organisms, causing serious pollution to the environment. To reduce nitrate emissions in surface water, the standards for total nitrogen emissions from wastewater have become increasingly strict in various countries. Currently, biological methods are commonly used to treat nitrate-containing wastewater. However, industrial tailwaters have a high chloride ion content and a low organic matter content, which can easily inhibit the growth and development of microorganisms, greatly limiting the application of biological methods. Currently, the photocatalytic method can convert nitrate in chlorine-containing water bodies into nitrogen for removal, and is energy-saving and environmentally friendly, with extensive research and application value. However, in the actual application process, since the reduction of nitrate mainly occurs at metal sites, and such catalytic sites are easily corroded in chlorine-containing water bodies through chlorine coordination and the oxidation of active chlorine species, it is extremely easy to cause the passivation of active sites, thereby hindering the reaction process or reducing the selectivity of photocatalytic nitrate conversion (M. Yue, et al, ZnCr2S4: Highly effective photocatalyst converting nitrate into N2 without over-reduction under both UV and pure visible light, Sci Rep 6, 30992 (2016)). In addition, this reaction usually adjusts the pH or adds a sacrificial agent to quench active oxygen species, thereby promoting the reduction reaction. Therefore, for this system, there are usually the following problems: (1) The metal active sites are corroded and inactivated by chlorine; (2) It is necessary to adjust the pH to acidic or add a sacrificial agent, which is likely to cause secondary pollution and increase the cost.

[0003] The prior art on photocatalytic denitrification technology has a high dependence on pH or sacrificial agents, and there is little exploration of the influence of chloride ions on the catalyst and the reaction system, such as: The invention patent with the publication number CN117619374A discloses a metal-doped SrTiO3 / TiO2 photocatalytic material, its preparation method and application. In this invention, ethanolamine is first used as a solvent to prepare SrTiO3 doped with different metals by hydrothermal method, and then ethanol and glycerol are used as solvents for secondary hydrothermal preparation to obtain metal-doped SrTiO3 / TiO2. This catalyst uses formic acid as a sacrificial agent to catalytically reduce nitrate under ultraviolet light, and can achieve a degradation rate of more than 95% and an N2 selectivity of more than 95%. Although this catalyst has high activity and reduces the amount of formic acid used, in practical applications, the addition of formic acid increases the operating cost and is prone to cause secondary pollution.

[0004] The invention patent with the publication number CN108975507A discloses a method for simultaneously removing nitrite and ammonia nitrogen by a zinc ferrite-fullerene photocatalyst. In this invention, soluble zinc salt, soluble iron salt and fullerene are dissolved in deionized water and mixed evenly, then the mixed solution is adjusted to be alkaline and reacted at 180 °C for 8 h, and after drying, the zinc ferrite-fullerene photocatalyst is prepared. This catalyst can simultaneously remove nitrite and ammonia nitrogen under ultraviolet light with a removal rate greater than 90%. However, the reaction requires adjusting the pH to strong alkalinity and the reaction time is relatively long, so its practical application is limited.

[0005] The invention patent with the publication number CN101066795A discloses a method for photocatalytic reduction of nitrate nitrogen in water using Fe 0 / TiO2. This invention prepares a nano-iron-doped titanium dioxide catalyst by chemical reduction method, and uses it to degrade nitrate with formic acid as a sacrificial agent under ultraviolet light. After 2 h of reaction, the conversion rate of nitrate is about 50%, and no nitrite is produced during the reaction process. However, the catalytic reaction activity of this system is relatively low, and formic acid is added as a sacrificial agent. Summary of the Invention

[0006] Aiming at the deficiencies that photocatalytic materials in the prior art are easily corroded by chlorine, and existing photocatalytic denitrification technologies need to add sacrificial agents or adjust the pH, the present invention provides a core-shell structured PANI / EG-Cu 0 / TiO2 photocatalyst, its preparation method and application for degrading nitrate in chlorine-containing water bodies. This photocatalyst can stably and efficiently degrade nitrate in chlorine-containing solutions without the need to additionally add sacrificial agents or adjust the initial pH of the solution.

[0007] To achieve the above object, the present application adopts the following technical solutions: A core-shell structured photocatalyst, the core of which is Cu modified with ethylene glycol on the surface 0Doped titanium dioxide particles (EGCT), and the shell is polyaniline (PANI). The photocatalyst with a core-shell structure is denoted as PEGCT. In the photocatalyst, polyaniline wraps the core to form a ternary heterojunction.

[0008] Preferably, in the photocatalyst, the molar ratio of Cu element to Ti element is (0.01~0.1):1.

[0009] Preferably, the ethylene glycol is modified on the surface of the core by forming a Ti-O bond with Ti.

[0010] This application also provides a preparation method of the above photocatalyst, including the following steps: (1) Mix a titanium precursor, hydrofluoric acid, and a copper salt in a solvent, and then react at 160~200 °C to obtain doped titanium dioxide; (2) Mix the doped titanium dioxide with ethylene glycol under solvent or solvent-free conditions, and then react at 160~200 °C to obtain the core; (3) Immerse the core in a dispersion of polyaniline and mix evenly to obtain the photocatalyst, and the solvent of the dispersion is an organic solvent.

[0011] Preferably, the titanium precursor in step (1) is tetrabutyl titanate. The copper salt in step (1) is copper nitrate.

[0012] Preferably, the solvent in step (1) or step (2) is ethanol.

[0013] Preferably, the volume ratio of the titanium precursor, the hydrofluoric acid, and the solvent in step (1) is 10:1.2:(25~35).

[0014] Preferably, the reaction time in step (1) is 1~4 h.

[0015] Preferably, the reaction in step (1) or step (2) is carried out in a reaction kettle with a polytetrafluoroethylene inner liner.

[0016] Preferably, step (1) further includes the steps of washing and drying the doped titanium dioxide after the reaction. More preferably, the washing is carried out by alternately washing with deionized water and ethanol.

[0017] Preferably, the volume ratio of the ethylene glycol to the solvent in step (2) is 1:(0~2). The solvent can be not used, that is, the volume is 0.

[0018] Preferably, the reaction time in step (2) is 4~8 h.

[0019] Preferably, the polyaniline in step (3) is prepared by the following method: It is obtained by reacting aniline and ammonium persulfate in hydrochloric acid under an ice bath. More preferably, the concentration of the hydrochloric acid is 1-2 mol·L -1 . More preferably, the temperature of the ice bath is 0-10 °C. More preferably, the reaction time is 8-10 h. More preferably, the method further includes the steps of filtering, washing, and drying after the reaction.

[0020] Preferably, the dispersion of polyaniline in step (3) is prepared by the following method: Polyaniline is added to an organic solvent and ultrasonicated to obtain it. Preferably, the ultrasonic time is 10-30 min. More preferably, in the polyaniline dispersion, the concentration of polyaniline is 0.01-0.4 mg / mL.

[0021] Preferably, the organic solvent in step (3) is N-methylpyrrolidone (NMP).

[0022] Preferably, the method of uniform mixing in step (3) is: stirring. More preferably, the stirring time is 24-26 h.

[0023] This application also provides the application of the above photocatalyst.

[0024] Preferably, the application is to degrade nitrate in a chlorine-containing water body.

[0025] The photocatalyst of the present invention provides photo-generated electrons that can reduce nitrate in an aqueous solution to ammonia nitrogen. At the same time, photo-generated holes oxidize chloride ions to generate chlorine-containing free radicals, and ammonia nitrogen is selectively oxidized by chlorine-containing free radicals to nitrogen and removed. This reaction system maintains excellent activity and stability in batch experiments (96.4 ± 3.6% nitrate removal rate and 80.3 ± 1.5% nitrogen selectivity).

[0026] Preferably, in the application, the nitrate is derived from nitrate.

[0027] Preferably, in the application, the concentration of the nitrate is 50-100 mg·L -1 .

[0028] Preferably, in the application, the dosage of the photocatalyst is 0.5-1 g·L -1 .

[0029] Preferably, in the application, the chlorine in the chlorine-containing water body is chloride ion, and the concentration of the chloride ion is 10-100 mM.

[0030] The beneficial effects of the present invention are as follows: (1) The photocatalyst of the present invention does not require additional addition of a sacrificial agent and has a wide pH adaptation range for the initial solution (pH 4-7).

[0031] (2) The photocatalyst of the present invention can efficiently degrade nitrate to nitrogen in chlorine-containing water bodies. Under ultraviolet light irradiation, the photocatalytic material reduces nitrate to ammonia nitrogen, and oxidizes chloride ions to generate chlorine-containing free radicals. The ammonia nitrogen is selectively oxidized to nitrogen by the chlorine-containing free radicals and removed. This reaction path can not only selectively convert nitrate to nitrogen, but also consume the oxidizing species generated during the catalytic process, greatly enhancing the reduction reaction efficiency.

[0032] (3) The photocatalyst of the present invention can still maintain high catalytic activity in chlorine-containing water bodies and effectively inhibit the corrosion of active sites by chloride ions: PANI is easy to enrich protons, which makes the surface of the catalyst positively charged, conducive to enhancing the adsorption of nitrate in chlorine-containing solutions. Moreover, PANI can transfer electrons to metal sites to maintain the stability of copper active sites, greatly improving the activity and stability of the catalytic reaction system. Stable catalytic activity can be obtained from batch experiments: a nitrate removal rate of 96.4 ± 3.6% and a nitrogen selectivity of 80.3 ± 1.5%. This research provides new ideas for the design and construction of photocatalytic materials suitable for denitrification in chlorine-containing water bodies. Description of the Drawings

[0033] Figure 1 are the transmission electron microscopy (TEM) images of EGCT and PEGCT in Example 1 of the present invention.

[0034] Figure 2 is the energy dispersive spectroscopy (EDS) image of PEGCT in Example 1 of the present invention.

[0035] Figure 3 is the X-ray diffraction (XRD) image of PEGCT in Example 1 of the present invention.

[0036] Figure 4 is the electron paramagnetic resonance (EPR) image of PANI and PEGCT in Example 1 of the present invention.

[0037] Figure 5 is the surface zeta potential image of PEGCT in Example 1 of the present invention.

[0038] Figure 6 is the TEM image of PEGCT in Example 2 of the present invention.

[0039] Figure 7 is the TEM image of PEGCT in Example 3 of the present invention.

[0040] Figure 8 is the effect diagram of photocatalytic degradation of nitrate by PANI, EGCT, and PEGCT in Example 4 of the present invention.

[0041] Figure 9It is the product selectivity diagram of photocatalytic degradation of nitrate by PANI, EGCT, and PEGCT in Example 4 of the present invention.

[0042] Figure 10 It is the effect diagram of photocatalytic degradation of nitrate by PEGCT at different pH values in Example 5 of the present invention.

[0043] Figure 11 It is the effect diagram of cyclic photocatalytic degradation of nitrate by PEGCT in Example 6 of the present invention.

[0044] Figure 12 It is the XPS diagram of EGCT and PEGCT after degrading nitrate in Example 6 of the present invention.

[0045] Figure 13 It is the Cu concentration filtered out in the cyclic experiment in Example 6 of the present invention.

[0046] Figure 14 It is the structural schematic diagram of the photocatalyst of the present invention. Detailed implementation manners

[0047] The technical solution of the present invention will be further described below with specific examples, but the protection scope of the present invention is not limited thereto.

[0048] Example 1 (1) Dissolve 10 ml of tetrabutyl titanate and 1.2 ml of hydrofluoric acid in 30 ml of ethanol solution. Then add 0.33 g of copper nitrate to the solution. After stirring at room temperature for 10 min, transfer it into a stainless steel reaction kettle with a polytetrafluoroethylene inner liner. Place the reaction kettle in an oven and react at 180 °C for 2 h. After the reaction, let it cool naturally. Take out the sample for centrifugation, wash it alternately with deionized water and ethanol, and dry it at 80 °C to obtain doped titanium dioxide.

[0049] (2) Take 0.2 g of doped titanium dioxide and add it to a reaction kettle with a polytetrafluoroethylene inner liner. Add 30 ml of ethylene glycol and 30 ml of ethanol. After stirring for 10 min, place it in an oven at 180 °C for hydrothermal reaction for 6 h. After the reaction, let it cool naturally. Take out the sample for centrifugation, wash it with ethanol, and then dry it under vacuum at 80 °C to obtain EGCT.

[0050] (3) Dissolve aniline and ammonium persulfate in hydrochloric acid at a molar ratio of 1:1 and stir with an ice bath for 8 h. Then filter the solution to obtain the product. Wash the product with a large amount of pure water until the pH of the supernatant is close to neutral, and dry it under vacuum at 80 °C to obtain PANI.

[0051] (4)Take 10 mg of the prepared PANI and disperse it in 50 ml of N-methylpyrrolidone under ultrasonic action. Then add 200 mg of EGCT to the dispersion and stir for 24 h. Take out the sample for centrifugation, wash it with ethanol, and dry it in vacuum at 80 °C to obtain PEGCT.

[0052] (5)Result analysis: Perform structural characterization on the obtained EGCT and PEGCT above, and the results are as follows: Perform TEM characterization on the obtained EGCT and PEGCT powders above, and the results are as Figure 1 shown. PANI was successfully loaded onto the surface of EGCT. Perform EDS characterization on the obtained PEGCT powder above, and the results are as Figure 2 shown. The C and N elements in PANI are evenly distributed on the surface of the catalyst, further proving the loading of PANI on EGCT. Perform XRD characterization on the obtained PEGCT powder above, and the results are as Figure 3 shown. Characteristic peaks of TiO2 and Cu 0 can be clearly observed in the PEGCT material. The above results prove the ternary heterostructure of PEGCT.

[0053] Perform EPR characterization on the obtained PANI and PEGCT above, and the results are as Figure 4 shown. The signal obtained by placing PANI in pure water and stirring it in the dark (PANI / Dark) is the free electron peak of PANI. Place PANI in an aqueous solution containing 50 mM chloride ions and perform ultraviolet light irradiation (PANI / UV / Cl - ), and peaks of hydroxyl radicals and chlorine radicals are generated. The generation of chlorine radicals can be attributed to the oxidation of chloride ions by photo-generated holes in PANI. This radical can convert the intermediate ammonia nitrogen obtained by reducing nitrate to nitrogen, thereby improving the nitrogen selectivity in the product. Place PEGCT in an aqueous solution containing 50 mM chloride ions and perform ultraviolet light irradiation (PEGCT / UV / Cl - ), and the signal of chloride ions is also generated, indicating that PEGCT can oxidize chloride ions to chlorine radicals under ultraviolet light to improve the nitrogen selectivity in the product. The ethylene glycol radicals generated in the PEGCT / UV / Cl - environment are attributed to the oxidation of surface-adsorbed ethylene glycol during the synthesis process. This radical helps to remove the chlorine adsorbed on the Cu surface and enhance the stability of the catalyst.

[0054] Perform surface zeta potential characterization on the obtained PEGCT above, as Figure 5As shown in the figure, when no chloride ions were added, the isoelectric point of the catalyst PEGCT was at pH 6.1. When the pH was lower than 6.1, the surface potential was positive, and it could still maintain a positively charged surface in a solution containing 50 mM chloride ions. This was mainly attributed to the enrichment effect of N-containing functional groups inside PANI on protons. Since TiO2 would undergo ionization when dissolved in water and PANI itself had abundant protons, after the catalyst was added to the solution, the initial solution pH was adjusted to about 4.5. At this value, the catalyst surface was always positively charged. This was conducive to enhancing the enrichment of nitrate in the chloride-containing solution and accelerating the reduction and transformation of nitrate.

[0055] Table 1 Changes in solution pH before and after adding the catalyst

[0056] Initial pH of the solution pH of the solution after adding the catalyst 4.01 4.48 5.03 4.55 6.07 4.74 6.80 4.43 Example 2 (1) Dissolve 10 ml of tetrabutyl titanate and 1.2 ml of hydrofluoric acid in 35 ml of ethanol solution. Then add 0.55 g of copper nitrate to the solution. After stirring at room temperature for 10 min, transfer it to a stainless-steel reaction kettle with a polytetrafluoroethylene inner liner. Place the reaction kettle in an oven and react at 200 °C for 4 h. After the reaction, let it cool naturally. Take out the sample for centrifugation, wash it alternately with deionized water and ethanol, and dry it at 80 °C to obtain doped titanium dioxide.

[0057] (2) Take 0.2 g of the doped titanium dioxide and add it to a reaction kettle with a polytetrafluoroethylene inner liner. Add 30 ml of ethylene glycol and 60 mL of ethanol. After stirring for 10 min, place it in an oven at 200 °C for hydrothermal reaction for 8 h. After the reaction, let it cool naturally. Take out the sample for centrifugation, wash it with ethanol, and then dry it under vacuum at 80 °C to obtain EGCT.

[0058] (3) Dissolve aniline and ammonium persulfate in hydrochloric acid at a molar ratio of 1:1 and stir with an ice bath for 10 h. Then filter the solution to obtain the product. Wash the product with a large amount of pure water until the pH of the supernatant is close to neutral, and dry it under vacuum at 80 °C to obtain PANI.

[0059] (4) Take 20 mg of the prepared PANI and disperse it in 50 ml of N-methylpyrrolidone under ultrasonic action. Then add 100 mg of EGCT to the dispersion and stir for 26 h. Take out the sample for centrifugation, wash it with ethanol, and then dry it under vacuum at 80 °C to obtain PEGCT.

[0060] (5) Result analysis: Perform structural characterization on the obtained PEGCT above, and the results are as follows: Perform TEM characterization on the obtained PEGCT powder, and the results are as Figure 6 shown, PANI was successfully loaded onto the surface of EGCT.

[0061] Example 3 (1)Dissolve 10 ml of tetrabutyl titanate and 1.2 ml of hydrofluoric acid in 25 ml of ethanol solution. Then add 0.055 g of copper nitrate to the solution. After stirring at room temperature for 10 min, transfer it into a stainless-steel reactor with a polytetrafluoroethylene inner liner. Place the reactor in an oven and react at 160 °C for 1 h. After the reaction, cool it naturally, take out the sample for centrifugation, wash it alternately with deionized water and ethanol, and dry it at 80 °C to obtain doped titanium dioxide.

[0062] (2)Take 0.2 g of the doped titanium dioxide and add it to a reactor with a polytetrafluoroethylene inner liner. Add 30 ml of ethylene glycol, stir for 10 min, then place it in an oven at 160 °C for hydrothermal reaction for 4 h. After the reaction, cool it naturally, take out the sample for centrifugation, wash it with ethanol, and then dry it under vacuum at 80 °C to obtain EGCT.

[0063] (3)Dissolve aniline and ammonium persulfate in hydrochloric acid at a molar ratio of 1:1 and stir with an ice bath for 10 h. Then filter the solution to obtain the product, wash the product with a large amount of pure water until the pH of the supernatant is close to neutral, and dry it under vacuum at 80 °C to obtain PANI.

[0064] (4)Take 0.5 mg of the prepared PANI and disperse it in 50 ml of N-methylpyrrolidone under ultrasonic action. Then add 100 mg of EGCT to the dispersion and stir for 25 h. Take out the sample for centrifugation, wash it with ethanol, and then dry it under vacuum at 80 °C to obtain PEGCT.

[0065] (5)Result analysis: Characterize the structure of the obtained PEGCT above, and the results are as follows: Characterize the obtained PEGCT powder by TEM, and the results are as Figure 7 shown. PANI was successfully loaded onto the surface of EGCT.

[0066] Example 4 This example provides the application of the photocatalyst prepared in Example 1 in photocatalytic degradation of nitrate in a chlorine-containing solution. Among them, the photocatalyst includes PEGCT, EGCT and PANI, and no sacrificial agent is added during the whole catalytic process. (1) Respectively use water as a solvent to add 0.5 g·L -1 of the PEGCT, EGCT and PANI prepared in Example 1, and add 50 mM chloride ions and 50 mg·L -1 nitrate respectively.

[0067] (2) After dark stirring for 30 min, place it under ultraviolet light for reaction for 2 h. Sample at regular intervals and measure the concentrations of nitrate, nitrite, and ammonium.

[0068] (3) Calculate the nitrate removal rate and the selectivity of nitrogen-containing products.

[0069] (4) Result analysis: As Figure 8 shown, compared with PANI and EGCT, PEGCT has the highest degradation efficiency and nitrogen selectivity. This indicates that the composite structure PEGCT of PANI and EGCT can efficiently convert nitrate into nitrogen for removal. Figure 9

[0070] Example 5 This example provides the application of PEGCT prepared in Example 1 in photocatalytic degradation of nitrate in a chlorine-containing solution under different pH conditions.

[0071] (1) Adjust the initial solution pH to 4.01, 5.03, 6.07, and 6.8 respectively. Add 0.5 g / L of the photocatalyst PEGCT prepared in Example 1, 50 mM chloride ions, and 50 mg / L nitrate respectively.

[0072] (2) After dark stirring for 30 min, place it under ultraviolet light for reaction for 2 h. Sample at regular intervals and measure the concentrations of nitrate, nitrite, and ammonium.

[0073] (3) Calculate the nitrate removal rate and the selectivity of nitrogen-containing products.

[0074] As Figure 10 shown, the pH of the initial solution has little effect on the photocatalytic reduction activity of nitrate, which can be basically ignored. Moreover, it can maintain a relatively high catalytic activity.

[0075] Example 6 This example provides the application of PEGCT prepared in Example 1 in cyclic photocatalytic degradation of nitrate in a chlorine-containing solution.

[0076] (1) Using water as a solvent, add 0.5 g / L of the catalyst PEGCT and EGCT prepared in Example 1, 50 mM chloride ions, and 50 mg / L nitrate respectively.

[0077] (2) After dark stirring for 30 min, place it under ultraviolet light for reaction for 2 h. Sample at regular intervals and measure the concentrations of nitrate, nitrite, and ammonium.

[0078] (3) Calculate the nitrate removal rate and the selectivity of nitrogen-containing products.

[0079] After each experiment, the catalyst was placed in ethylene glycol and stirred for drying, and then the next cycle was started.

[0080] (5)Result analysis: As Figure 11 shown, in the cyclic experiment, PEGCT has excellent stability compared to EGCT.

[0081] In this example, the valence states of the Cu active sites of the respective catalysts after the cyclic experiments of EGCT and PEGCT were tested, as well as the leaching of Cu, to analyze the stability of the catalysts. As Figure 12 compared with Figure 13 shown, the valence state of Cu in PEGCT is mainly the low-valence Cu 0 , and the leaching concentration of Cu is relatively small compared to EGCT. This indicates that PEGCT has better stability than EGCT, which is attributed to the protective effect of PANI loading on the Cu active sites.

[0082] In summary, the photocatalytic material PEGCT prepared by the present invention greatly enhances the activity and stability of the catalyst for degrading nitrate in the chlorine-containing solution. In multiple cyclic experiments, the removal rate of nitrate can be stabilized at 96.4 ± 3.6%, and the nitrogen selectivity remains at 80.3 ± 1.5%. In addition, this reaction system does not require the additional addition of sacrificial agents or the adjustment of the initial solution pH, and has broad application prospects for treating nitrate in chlorine-containing water bodies.

Claims

1. A photocatalyst with a core-shell structure, characterized in that, The core is Cu doped with titanium dioxide particles whose surface is modified with ethylene glycol, and the shell is polyaniline. 0 ​ 2. The photocatalyst according to claim 1, characterized in that, In the photocatalyst, the molar ratio of Cu element to Ti element is (0.01~0.1):

1.

3. The preparation method of the photocatalyst according to any one of claims 1-2, characterized in that, It includes the following steps: (1) Mix a titanium precursor, hydrofluoric acid and a copper salt in a solvent, and then react at 160~200 °C to obtain doped titanium dioxide; (2) Mix the doped titanium dioxide with ethylene glycol under solvent-containing or solvent-free conditions, and then react at 160~200 °C to obtain the core; (3) Immerse the core in a dispersion of polyaniline and mix evenly to obtain the photocatalyst, and the solvent of the dispersion is an organic solvent.

4. The preparation method according to claim 3, characterized in that, In step (1), the volume ratio of the titanium precursor, the hydrofluoric acid and the solvent is 10:1.2:(25~35).

5. The preparation method according to claim 3, characterized in that, In step (2), the volume ratio of the ethylene glycol to the solvent is 1:(0~2).

6. The preparation method according to claim 3, characterized in that, In step (3), the polyaniline is prepared by the following method: Aniline and ammonium persulfate are reacted in an ice bath in hydrochloric acid to obtain it.

7. The preparation method according to claim 3, characterized in that, In step (3), the organic solvent is N-methylpyrrolidone (NMP).

8. Use of the photocatalyst according to any one of claims 1-2, characterized in that, The application is to degrade nitrate in a chlorine-containing water body.

9. The application according to claim 8, wherein The concentration of the nitrate radical is 50~100 mg·L -1 .

10. The application according to claim 8, wherein The chlorine in the chlorine-containing water body is chloride ion, and the concentration of the chloride ion is 10~100 mM.

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