An Ag / TiO2 multi-stage columnar array photocatalyst, its preparation method and application

Abstract

The present invention discloses an Ag / TiO2 multi-stage column array photocatalyst and a preparation method thereof, belonging to the technical field of photocatalytic composite materials. The preparation method comprises the following steps: vertically printing a TiO2 array on an alumina ceramic sheet; drying and then sintering in a muffle furnace to obtain a TiO2 column array; spin-coating a TiO2 sol on the surface of the TiO2 column array, drying, heating and cooling to room temperature, and then carrying out a first hydrothermal reaction with an aqueous hydrochloric acid solution of tetrabutyl titanate, drying and then heating and annealing to obtain a TiO2 multi-stage column array grown with TiO2 nanorods. After surface modification with 3-(triethoxysilyl)propyl succinic anhydride, it is placed in a silver nitrate solution for a second hydrothermal reaction to obtain an Ag / TiO2 multi-stage column array photocatalyst. The Ag / TiO2 multi-stage column array photocatalyst of the present invention has advantages such as good photocatalytic effect and enhanced photocatalytic effect with the increase of light intensity.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic composite materials, and relates to an Ag / TiO2 multi-stage column array photocatalyst for efficiently catalytically reducing 4-nitrophenol in water, a preparation method thereof, and an application thereof. Background Art

[0002] 4-Nitrophenol (4-NP), also known as p-nitrophenol, is a toxic industrial by-product. It has a certain solubility in water and is stable in water, making it difficult to remove by conventional methods, posing a great threat to the environment. Especially when 4-nitrophenol enters water bodies, due to its density being greater than that of water, it will sink to the bottom and continuously cause water pollution. Traditional methods for removing 4-NP include physical methods, chemical methods, biological methods, and photocatalytic degradation methods. Among them, physical methods such as grid filtration and equalization in the regulating tank are mainly used to remove suspended solids, sediments, and other impurities in wastewater, and can be used to remove 4-NP attached to suspended solids and sediments, but the effect of removing 4-NP dissolved in water is not good. Chemical methods generally involve oxidizing wastewater with oxidants (such as hydrogen peroxide, potassium permanganate, etc.) to oxidize and decompose 4-NP in water into small molecule substances, but secondary pollution may be generated during the treatment process, and the treatment cost is relatively high. Biological treatment methods use the metabolic action of microorganisms to further decompose organic matter in wastewater into carbon dioxide and water, as much as possible avoiding the problem of secondary pollution. However, the degradation efficiency of 4-NP by microorganisms is low, and the treatment cycle is long. Photocatalytic reduction is a method that uses light energy to excite a catalyst to generate active free radicals, thereby reducing organic pollutants. Currently, photocatalytic reduction is considered a promising treatment method due to its low energy consumption. However, the practical application of photocatalytic reduction in treating 4-NP is limited due to the lack of an efficient photocatalyst suitable for catalytically reducing 4-NP.

[0003] At present, semiconductor materials have become one of the common photocatalysts because they can generate photoinduced carriers under light excitation. Titanium dioxide (TiO2) is a semiconductor with a relatively narrow bandgap, which has good ultraviolet spectral response and is a relatively common photocatalyst used for 4-NP reduction. Currently, the commonly used method is to prepare nano-titanium dioxide by dissolving and hydrolyzing tetrabutyl titanate in alcohol. This nano-titanium dioxide has the advantages of large specific surface area and high photocatalytic activity. However, it usually uses a powder structure as a photocatalyst, and there is a serious agglomeration phenomenon, which may make it difficult to recover the nanoparticles in the dispersion system. In addition, the single TiO2 semiconductor material can only utilize the ultraviolet light with a short wavelength in sunlight, resulting in a low utilization rate of solar energy and low efficiency of photocatalytic reduction of 4-nitrophenol. A commonly used solution is to form a plasmonic nanoparticle / semiconductor composite material by loading plasmonic metal nanoparticles to broaden the light absorption range of the composite material and use the metal nanoparticles as the conduction center of photoinduced electrons to slow down the recombination of photoinduced electron-hole pairs in the semiconductor. Currently, the more widely used plasmonic metal nanoparticles are mainly materials such as gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), etc. Although these metal nanoparticles can all exhibit obvious surface plasmon resonance effects, not all plasmonic metal nanoparticles are suitable as photocatalysts for photocatalytic reduction of 4-NP. For example, the Pd / TiO2 composite material shows good catalytic efficiency in photocatalytic reduction of 4-NP, but due to the surface plasmon resonance effect of Pd nanoparticles not being as significant as that of Au and Ag nanoparticles, the catalytic efficiency of the Pd / TiO2 composite material photocatalyst is still limited. Summary of the Invention

[0004] The object of the present invention is to provide an Ag / TiO2 multi-stage column array photocatalyst for highly efficient catalytic reduction of 4-nitrophenol in water, its preparation method and application. The Ag / TiO2 multi-stage column array photocatalyst described in the present invention can be applied to catalytic reduction of 4-nitrophenol in water, and has the advantages of good photocatalytic effect, recyclability, and the enhancement of photocatalytic effect with the increase of light intensity.

[0005] The technical solution provided by the present invention is as follows:

[0006] A preparation method of an Ag / TiO2 multi-stage column array photocatalyst, comprising the following steps:

[0007] Mix TiO2 powder with a polyethylene glycol-polypropylene glycol copolymer, and vertically print a TiO2 array on an alumina ceramic sheet; after the printed TiO2 array is naturally dried, sinter it in a muffle furnace to obtain a TiO2 column array;

[0008] A mixture of titanium diisopropoxide bis(acetylacetonate) and n-butanol was spin-coated on the surface of the TiO2 column array. After drying, it was heated and cooled to room temperature. Then it was placed in an aqueous mixed solution of tetrabutyl titanate and hydrochloric acid for the first hydrothermal reaction. After drying, it was heated and annealed to obtain a TiO2 hierarchical column array with TiO2 nanorods grown on it.

[0009] The TiO2 hierarchical column array with TiO2 nanorods grown on it was immersed in an ethanol solution of 3-(triethoxysilyl)propyl succinic anhydride for modification. After being rinsed clean, it was placed in an aqueous silver nitrate solution for the second hydrothermal reaction to obtain an Ag / TiO2 hierarchical column array photocatalyst.

[0010] Furthermore, the TiO2 powder includes TiO2 powder with a particle size of 20 - 30 nm and TiO2 powder with a particle size of 180 - 220 nm, and the mass ratio of the TiO2 powder with a particle size of 20 - 30 nm to the TiO2 powder with a particle size of 180 - 220 nm is 1:3 - 5.

[0011] Furthermore, the sintering temperature is 800 - 1000 °C, the sintering time is 3 - 5 h, and the heating rate is 4 - 6 °C / min.

[0012] Furthermore, the temperature of the first hydrothermal reaction is 150 - 170 °C, and the reaction time is 40 - 80 min.

[0013] Furthermore, the temperature of the second hydrothermal reaction is 80 - 120 °C, and the reaction time is 16 - 20 h.

[0014] Furthermore, the volume ratio of titanium diisopropoxide bis(acetylacetonate) to n-butanol is 3 - 4:6 - 7.

[0015] The present invention also provides an Ag / TiO2 hierarchical column array photocatalyst prepared by the above preparation method.

[0016] The present invention also provides the application of the above Ag / TiO2 hierarchical column array photocatalyst in treating organic wastewater pollution.

[0017] The present invention also provides the application of the above Ag / TiO2 hierarchical column array photocatalyst in treating 4-NP pollution in organic wastewater.

[0018] Furthermore, the light intensity of photocatalysis is greater than 50 mW / cm 2 .

[0019] Furthermore, the concentration of 4-NP is greater than 10 mM.

[0020] Beneficial effects

[0021] Ag nanoparticles not only have a significant surface plasmon resonance effect but also have a good effect on the photocatalytic reduction of 4-NP. Therefore, loading Ag nanoparticles on a TiO2 columnar bulk support to develop a recyclable Ag / TiO2 multi-stage columnar photocatalyst is of great significance for the efficient, environmentally friendly, and low-cost removal of 4-NP in sewage. In this invention, an Ag / TiO2 multi-stage columnar array photocatalyst was constructed through 3D composite printing technology, realizing the efficient catalytic reduction of high-concentration (14.38 mM) 4-NP under light irradiation; with the increase of light intensity, the performance of Ag / TiO2 in catalyzing 4NP was significantly improved, showing a positive correlation with light intensity. Under 2.5 sunlights, using sodium borohydride as the hydrogen source for the photocatalytic reduction of 4-NP, the photocatalytic reaction time was less than 2 min, and the turnover frequency (TOF value) of the photocatalyst was as high as 721.06 min -1 , which was about 46.7 times higher than that in the dark reaction. There was an obvious synergistic effect when Ag was combined with the TiO2 support; the synergistic effect of Ag / TiO2 was enhanced with the increase of light intensity, showing a positive correlation with light intensity. The Ag / TiO2 multi-stage columnar array photocatalyst had a catalytic conversion rate of up to 90% or more in 5 recycling uses. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the preparation process of the method described in this invention;

[0023] Figure 2 is a photo of the Ag / TiO2 multi-stage columnar array photocatalyst;

[0024] Figure 3 is the SEM image of TiO2 nanorods grown on TiO2 columns and the SEM image of Ag nanoparticles loaded on TiO2 nanorods;

[0025] Figure 4 is the high-resolution image taken by HRTEM of Ag NPs successfully loaded on TiO2 nanorods and the elemental distribution images;

[0026] Figure 5 is the composition analysis of the Ag / TiO2 multi-stage columnar array photocatalyst using XRD; and the XPS spectrum of Ag element;

[0027] Figure 6 is the value of the change of 4-NP concentration with reaction time (C t / C0), its ln value, and TOF value in the photocatalytic reduction of 4-NP reaction by the Ag / TiO2 multi-stage columnar array photocatalyst under dark and 1 sun light conditions.

[0028] Figure 7Bar graph of the conversion rate of catalytic 4-NP reduction for the Ag / TiO2 multi-stage column array photocatalyst under 1 sun illumination for 1-5 cycles.

[0029] Figure 8 Values of the change in 4-NP concentration over reaction time (C t / C0), its ln value, and the TOF value for the Ag / TiO2 multi-stage column array photocatalyst in the photocatalytic reduction of 4-NP reaction under different intensities of sunlight illumination. Detailed implementation method

[0030] The present invention will be specifically described below with reference to the accompanying drawings.

[0031] Example 1

[0032] Figure 1 It is a preparation flow chart of the Ag / TiO2 multi-stage column array photocatalyst provided by the present invention. The preparation method of the Ag / TiO2 multi-stage column array photocatalyst includes the following steps:

[0033] S1: Select TiO2 powders with particle sizes of 25 nm and 200 nm, and adjust the slurry viscosity together with a 10 wt% polyethylene glycol - polypropylene glycol copolymer (F127, manufacturer: Sigma-Aldrich, USA, product number: P2443-250g, CAS: 9003-11-6). Mix them according to the mass ratio of TiO2 powder to 10 wt% F127 of 1:4. Select a printing needle with an inner diameter of 0.21 mm, and make it vertically print at a pressure of 300 - 550 Kpa. Vertically print a 10*10*1.2 mm TiO2 array on a 15*15*2 mm alumina ceramic sheet. After the printed TiO2 array is naturally dried, sinter it in a muffle furnace at 900 °C in air for 4 h with a heating rate of 5 °C / min to obtain a TiO2 column array.

[0034] S2: Take 3.5 mL of diisopropoxybis(acetylacetonate)titanium and 6.5 mL of n-butanol and put them into a beaker, and stir vigorously with a magnetic stirrer for 4 h to make them uniformly mixed to obtain a TiO2 sol as the spin coating solution. Then, fix the TiO2 column array in a spin coater, drop about 200 µL of the appropriate amount of TiO2 sol on the surface of the array, and spin coat it at a speed of 5000 rpm for 30 s. Subsequently, place it on a hot plate and dry it at 100 °C for 10 min, and then adjust the hot plate to 400 °C to keep the spin-coated TiO2 multi-stage column array at 400 °C for 1 h, and then naturally cool it to room temperature in an air atmosphere to obtain a TiO2 column array with a TiO2 thin film attached to its surface;

[0035] S3: Add 5 mL of deionized water, 5 mL of concentrated hydrochloric acid (12 mM), and 0.4 mL of tetrabutyl titanate into a 25 mL hydrothermal reactor. Then place the TiO₂ column array with a TiO₂ thin film attached to its surface into the reactor and conduct the first hydrothermal reaction at 160 °C for 1 h. After the first hydrothermal reaction is completed, wash it alternately with ethanol and water 5 times, dry it in an oven at 50 °C for half an hour, then heat it to 450 °C in a muffle furnace at a heating rate of 5 °C / min and keep it at 450 °C for 2 h, and let it cool naturally to room temperature in the muffle furnace to achieve the growth of TiO₂ nanorods on the TiO₂ column array, obtaining a TiO₂ multi-stage column array with TiO₂ nanorods grown on it.

[0036] S4: Immerse the TiO₂ multi-stage column array with TiO₂ nanorods grown on it in 2 mL of an ethanol solution of 3-(triethoxysilyl)propyl succinic anhydride with a concentration of 0.1 wt% for modification. Seal it well and place it at room temperature for 8 h, then rinse the sample 3 - 5 times with ethanol and deionized water in sequence to obtain a TiO₂ multi-stage column array with 3-(triethoxysilyl)propyl succinic anhydride modified on its surface.

[0037] S5: Add 4 mL of an aqueous silver nitrate solution with a concentration of 0.15 g / L as a precursor into a 25 mL hydrothermal reactor. Place the TiO₂ multi-stage column array with 3-(triethoxysilyl)propyl succinic anhydride modified on its surface into the reactor for the second hydrothermal reaction. The reaction temperature is 100 °C and the reaction time is 18 h to obtain an Ag / TiO₂ multi-stage column array photocatalyst loaded with Ag nanoparticles, and its optical photograph is as Figure 2 shown.

[0038] Characterize the Ag / TiO₂ multi-stage column array photocatalyst with a scanning electron microscope (SEM), as Figure 3 shown. The size of the TiO₂ nanorods is about 100 - 200 nm × 1 µm; Ag nanoparticles are successfully loaded on the TiO₂ nanorods and are evenly distributed.

[0039] Characterize the Ag / TiO₂ multi-stage column array photocatalyst with a high-resolution transmission electron microscope (HRTEM), as Figure 4 shown. The lattice spacing of the Ag NPs is about 0.233 nm, which matches the (111) crystal plane of the Ag nanocrystal. In addition, the EDS elemental mapping obtained by HRTEM shows that a large number of Ag NPs are loaded on the TiO₂ nanorods.

[0040] Analyze the composition of the Ag / TiO₂ multi-stage column array photocatalyst using an X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS), as Figure 5As shown, the XRD pattern indicates that TiO2 in the Ag / TiO2 multi-stage columnar array photocatalyst is mainly in the anatase phase. At the same time, characteristic peaks of Ag element are detected in the XRD pattern. Combining with the XPS pattern, it shows that there are two characteristic peaks in the 3d orbit of Ag, and the binding energy value of the characteristic peak corresponding to the 3d 3 / 2 orbital is 374.1 eV, and the binding energy value of the characteristic peak belonging to the 3d 5 / 2 orbital is 368.1 eV. Compared with the binding energies of 374.2 eV (3d 3 / 2 ) and 368.2 eV (3d 5 / 2 ) corresponding to the standard characteristic peaks of the 3d orbit of Ag element, the characteristic peaks of Ag element in the Ag / TiO2 sample have all undergone a negative shift. Therefore, it can be speculated that there is also a Schottky heterojunction between Ag and TiO2 and electron transfer will occur. In the Ti 2p spectrum, the two peaks located at 464.5 and 458.7 eV respectively belong to Ti 4+ in TiO2 for Ti 2p 1 / 2 and Ti 2p 3 / 2 .

[0041] Example 2

[0042] The steps of the Ag / TiO2 multi-stage columnar array photocatalyst for catalytic reduction of 4-NP in water are as follows:

[0043] Prepare a 14.38 mM aqueous solution of 4-NP (the highest concentration of photocatalytic reduction of 4-NP reported so far) as the reactant, and take 4 mL of the 4-NP solution as the single reaction solution in each experiment. Before the experiment, weigh 0.4 g of sodium borohydride (NaBH4) powder and add it to the 4-NP solution, and continuously stir to dissolve it quickly. When the NaBH4 powder is completely dissolved, absorb 80 μL of the reaction solution and dilute it 50 times with deionized water. Measure the absorption spectrum of the reaction solution by ultraviolet-visible spectrophotometer and record the absorbance C0 at λ = 400 nm of the solution. Then, put the Ag / TiO2 multi-stage columnar array photocatalyst into the mixed solution, and under dark conditions and 1 sunlight (100 mW / cm 2 ) illumination conditions, at 0.5 min, 1 min, 2 min, 3 min, 5 min, 7 min, 12 min, 17 min of the reaction, each time absorb 80 μL of the reaction solution, dilute it 50 times with deionized water, measure its absorption spectrum and record the absorbance C t at λ = 400 nm of the solution, and characterize the concentration change of 4-NP in the solution by the change of absorbance. In the experiment, all catalytic reduction reactions were carried out at room temperature and no stirring was required during the reaction process.

[0044] Performance evaluation criteria: Turnover frequency (TOF), which is the catalytic efficiency of the 4-NP catalytic reduction reaction. Generally speaking, TOF is an important parameter for evaluating the catalytic performance of metal-based heterogeneous catalysts, and the TOF value is positively correlated with the catalytic activity of the catalyst. In this example, TOF refers to the number of catalytic cycles per unit time, that is, the molar amount of 4-NP reduced by each mole of Ag nanoparticles per minute.

[0045] Figure 6 Values of the change in the concentration of 4-NP over reaction time (C t / C0), its ln value, and the TOF value for the Ag / TiO2 hierarchical cylinder array photocatalyst in the photocatalytic reduction of 4-NP reaction under light and dark conditions, respectively. The TOF value of the Ag / TiO2 hierarchical cylinder array photocatalyst for the catalytic reduction of 4-NP under one sun illumination reaches 168.66 min -1 , which is a 1092% increase compared to the TOF value under dark conditions.

[0046] Example 3

[0047] The procedure for the cyclic test of the Ag / TiO2 hierarchical cylinder array photocatalyst for the catalytic reduction of 4-NP in water is as follows:

[0048] Take 4 mL of a 4-NP aqueous solution with a concentration of 14.38 mM (C0) as the reactant, add 0.4 g of NaBH4 powder to it, and continuously stir to dissolve it quickly. After the NaBH4 powder is completely dissolved, pipette 80 μL of the reaction solution and dilute it 50 times with deionized water. Measure the absorption spectrum of the reaction solution by a UV-visible spectrophotometer and record the absorbance of the solution at λ = 400 nm. Then, place the Ag / TiO2 hierarchical cylinder array photocatalyst into the mixed solution. Under the condition of 1 sun illumination, at 2 min of the reaction, pipette 80 μL of the reaction solution, dilute it 50 times with deionized water, measure its absorption spectrum and record the absorbance of the solution at λ = 400 nm. Characterize the change in the concentration of 4-NP (C t ) in the solution by the change in absorbance, and use C t / C0 as the conversion rate of the catalytic reduction of 4-NP. After the reaction is completed, take out the Ag / TiO2 hierarchical cylinder array photocatalyst, rinse it 3 - 5 times with ethanol and water in turn, and place it on a 400 o °C heating plate for 60 min to dry. Repeat the above reaction test operation 4 times in the experiment, and record the C t / C0 values for a total of 5 cyclic tests. As Figure 7 shown, the results indicate that the Ag / TiO2 hierarchical cylinder array photocatalyst has a catalytic conversion rate of over 90% in 5 recycling uses.

[0049] Example 4

[0050] Ag / TiO₂ multi-stage column array photocatalyst, and additionally provide three catalysts, namely TiO₂ multi-stage column array photocatalyst, Ag / TiO₂ column array photocatalyst, and Pd / TiO₂ multi-stage column array photocatalyst, for comparative experiments.

[0051] The preparation process of the Ag / TiO₂ multi-stage column array photocatalyst is prepared according to S1-S5 in Example 1.

[0052] The preparation process of the TiO₂ multi-stage column array photocatalyst is prepared according to S1-S4 in Example 1.

[0053] The preparation process of the Ag / TiO₂ column array photocatalyst: TiO₂ column array is obtained by preparing according to S1 in Example 1. The TiO₂ multi-stage column array is immersed in 2 mL of an ethanol solution of 3-(triethoxysilyl)propyl succinic anhydride with a concentration of 0.1 wt%. Then, it is sealed and placed at room temperature for 8 h, and the sample is rinsed 3-5 times with ethanol and deionized water in sequence to obtain a TiO₂ column array with 3-(triethoxysilyl)propyl succinic anhydride modified on its surface. Subsequently, 4 mL of an aqueous silver nitrate solution with a concentration of 0.15 g / L is added as a precursor in a 25 mL hydrothermal reaction kettle, and the TiO₂ column array with 3-(triethoxysilyl)propyl succinic anhydride modified on its surface is placed in the reaction kettle for hydrothermal reaction. The reaction temperature is 100 °C, and the reaction time is 18 h to obtain an Ag / TiO₂ column array photocatalyst loaded with Ag nanoparticles.

[0054] The preparation process of the Pd / TiO₂ multi-stage column array photocatalyst: The TiO₂ multi-stage column array with 3-(triethoxysilyl)propyl succinic anhydride modified on its surface is obtained by preparing according to S1-S4 in Example 1. Subsequently, 4 mL of an aqueous palladium chloride (PdCl₂) solution with a concentration of 0.15 g / L is added as a precursor in a 25 mL hydrothermal reaction kettle, and the TiO₂ column array with 3-(triethoxysilyl)propyl succinic anhydride modified on its surface is placed in the reaction kettle for hydrothermal reaction. The reaction temperature is 100 °C, and the reaction time is 18 h to obtain a Pd / TiO₂ multi-stage column array photocatalyst loaded with Pd nanoparticles.

[0055] Take 4 portions of 4 mL of 4-NP aqueous solution with a concentration of 14.38 mM (C0) as reactants, add 0.4 g of NaBH4 powder to each of them, and continuously stir to dissolve it quickly. After the NaBH4 powder is completely dissolved, aspirate 80 μL of the reaction solution from each, and dilute it 50 times with deionized water. Measure the absorption spectrum of the reaction solution using an ultraviolet-visible spectrophotometer and record the absorbance of the solution at λ = 400 nm. Then, place the Ag / TiO2 multi-stage column array photocatalyst, TiO2 multi-stage column array photocatalyst, Ag / TiO2 column array photocatalyst, and Pd / TiO2 multi-stage column array photocatalyst into 4 portions of 4 mL of the mixed solution respectively. Under dark conditions and 1 sunlight illumination condition, aspirate 80 μL of the reaction solution at 0.5 min, 1 min, 2 min, 3 min, 5 min, 7 min, 12 min, and 17 min each time, dilute it 50 times with deionized water, measure its absorption spectrum, and record the absorbance C of the solution at λ = 400 nm t , and characterize the change in the concentration of 4-NP in the solution by the change in absorbance. In the experiment, all catalytic reduction reactions were carried out at room temperature, and no stirring was required during the reaction process. The specific experimental conditions and catalytic effects are shown in Table 1

[0056] Table 1:

[0057]

[0058] The results show that only the Ag / TiO2 multi-stage column array photocatalyst achieved a photocatalytic reaction time (conversion rate of 90%) for reducing 4-NP of less than 2 min under 1 sunlight irradiation. The TiO2 multi-stage column array photocatalyst did not achieve 90% conversion of 4-NP within 2 h under both dark and light conditions, indicating that Ag nanoparticles play a key role in the photocatalytic reduction reaction of 4-NP

[0059] Example 5

[0060] Light intensity dependence experiment

[0061] To further confirm the high catalytic activity of the Ag / TiO2 multi-stage column array photocatalyst under high light intensity, a catalytic experiment under different light intensity irradiations was carried out according to the catalytic reduction reaction steps of 4-NP in water in Example 2. The results are as Figure 8 shown. As the light intensity increases, the photocatalytic efficiency of the Ag / TiO2 multi-stage column array photocatalyst increases with the increase of light intensity, showing a positive correlation with the light intensity. Under 2.5 sunlights, the TOF value is as high as 721.06 min -1 , breaking through the limitation that the efficiency of traditional semiconductor-based catalysts is negatively correlated with light intensity

Claims

1. A method for preparing a Ag / TiO2 multi-level column array photocatalyst, characterized in that: The following steps are involved: TiO2 powder is mixed with polyethylene glycol-polypropylene glycol copolymer, and a TiO2 array is vertically printed on an alumina ceramic sheet; the printed TiO2 array is naturally dried and then sintered in a muffle furnace to obtain a TiO2 column array; the sintering temperature is 800-1000°C, the sintering time is 3-5h, and the heating rate is 4-6°C / min; A mixture of diisopropoxy diacetylacetonate titanium and n-butanol is spin-coated on the surface of the TiO2 column array, and then dried, heated and cooled to room temperature, and then placed in a mixed aqueous solution of tetrabutyl titanate and hydrochloric acid for a first hydrothermal reaction, and then dried, heated and annealed to obtain a TiO2 multi-level column array with TiO2 nanorods grown thereon; the temperature of the first hydrothermal reaction is 150-170°C, and the reaction time is 40-80 minutes; The TiO2 multilevel column array grown with TiO2 nanorods was modified by immersing it in an ethanol solution of 3-(triethoxysilyl)propylsuccinic anhydride, and then rinsed and placed in a silver nitrate aqueous solution for a second hydrothermal reaction to obtain an Ag / TiO2 multilevel column array photocatalyst; the temperature of the second hydrothermal reaction was 80~120℃, and the reaction time was 16~20h.

2. The method for preparing the Ag / TiO2 multi-level pillar array photocatalyst according to claim 1, characterized in that: The TiO2 powder includes TiO2 powder with a particle size of 20-30 nm and TiO2 powder with a particle size of 180-220 nm, and the mass ratio of the TiO2 powder with a particle size of 20-30 nm to the TiO2 powder with a particle size of 180-220 nm is 1:3-5.

3. The method for preparing the Ag / TiO2 multi-level column array photocatalyst according to claim 1, characterized in that: The volume ratio of diisopropoxy diacetylacetonate titanium to n-butanol is 3-4:6-7.

4. An Ag / TiO2 multi-level column array photocatalyst, characterized in that: Prepared by the preparation method according to any one of claims 1 to 3.

5. Use of the Ag / TiO2 multi-level column array photocatalyst as claimed in claim 4 in treating organic wastewater pollution.

6. Use of the Ag / TiO2 multi-level column array photocatalyst according to claim 4 in the photocatalytic reduction of 4-nitrophenol in water.

7. The use according to claim 6, characterized in that: The photocatalytic light intensity is greater than 50mW / cm 2 .

Images