A core-shell structured photocatalyst and a preparation method and application thereof

Abstract

The application belongs to the technical field of photocatalysts, and discloses a core-shell structure photocatalyst and a preparation method and application thereof.The core-shell structure photocatalyst has fluorosilane modified TiO2 molecular sieve as a shell, has nano Cu+ rare earth metal as an active center, and has sepiolite as a base material of the nano Cu+ rare earth metal, and exhibits excellent purification efficiency on volatile organic compounds under natural light or indoor illumination; meanwhile, the core-shell material can realize efficient killing of common microorganisms such as escherichia coli, bacillus subtilis and staphylococcus aureus, and provides strong support for comprehensive purification and protection of indoor environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photocatalysts, in particular to a core-shell structure photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] With the rapid progress of building technology and the continuous optimization of living environment, people pay more and more attention to indoor air quality. However, in the pursuit of aesthetics and functionality, modern buildings inevitably introduce many potential pollution sources, such as volatile organic compounds (VOCs) released by widely used synthetic decorative materials, inhalable particulate matter accumulated in the air conditioning system cycle, and microbial pollution such as bacteria and viruses caused by electronic device operation and indoor human activity. The above pollution factors are mixed, which seriously threatens the indoor air quality and directly affects the health of the occupants.

[0003] At present, there are many kinds of air purification materials and processes. Each material or process tries to solve the problem of indoor air quality in its unique way, but one material or process is often difficult to handle complex air pollutants, and has limitations such as single function, low resource utilization efficiency, and unstable long-term purification effect. For example, activated carbon is favored due to its strong adsorption capacity, but its limited adsorption capacity and easy saturation characteristics cause the purification efficiency to decrease significantly after a long time of use, and even may cause secondary pollution due to improper handling after adsorption saturation; TiO2 as a typical photocatalytic material can effectively decompose organic pollutants under ultraviolet light, but its wide band gap limits its absorption capacity for visible light, resulting in a significant reduction in photocatalytic efficiency under natural light or indoor lighting conditions, making it difficult to meet the demand for all-weather and efficient purification. In view of the diversity and complexity of indoor air pollution sources, a single material is obviously difficult to meet the growing purification needs. SUMMARY

[0004] The purpose of the present application is to provide a core-shell structure photocatalyst and a preparation method and application thereof, which solves the problem that a single air purification material cannot meet the purification needs.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0006] The present application provides a preparation method of a core-shell structure photocatalyst, comprising the following steps:

[0007] (1) calcining sepiolite;

[0008] (2) mixing the calcined sepiolite obtained in step (1), a surfactant, water, a copper source and a rare earth metal source, carrying out a hydrothermal reaction, and drying to obtain sepiolite adsorbed with nano CuO-rare earth metal oxides;

[0009] (3) mixing the sepiolite adsorbed with nano CuO-rare earth metal oxide and the fluorosilane modified mesoporous TiO2 molecular sieve with water to coat the sepiolite adsorbed with nano CuO-rare earth metal oxide to obtain a core-shell material of fluorosilane modified TiO2 molecular sieve coated sepiolite adsorbed with nano CuO+ rare earth metal oxide;

[0010] (4) calcining the core-shell material of fluorosilane modified TiO2 molecular sieve coated sepiolite adsorbed with nano CuO+ rare earth metal oxide under a protective atmosphere to obtain a core-shell structured photocatalyst.

[0011] Preferably, in the preparation method, the temperature of the calcination in step (1) is 300-400℃, and the time is 2-5h.

[0012] Preferably, in the preparation method, in step (2), the surfactant is a mixture of cetyltrimethylammonium bromide and polyvinylpyrrolidone, the copper source is copper acetate or copper chloride, and the rare earth metal source is cerium nitrate, neodymium nitrate or yttrium nitrate; the mass ratio of the calcined sepiolite, the surfactant, the copper source and the rare earth metal source is 1:0.1-0.4:0.8-1.5:0.4-0.8; and the mass ratio of the cetyltrimethylammonium bromide to the polyvinylpyrrolidone is 1-2:1-2.

[0013] Preferably, in the preparation method, the temperature of the hydrothermal reaction in step (2) is 60-100℃, the time is 8-24h, and the pH is 9-12.

[0014] Preferably, in the preparation method, in step (3), the mass ratio of the sepiolite adsorbed with nano CuO-rare earth metal oxide to the fluorosilane modified mesoporous TiO2 molecular sieve is 1:2-4; and the coating temperature is 150-250℃, and the time is 8-24h.

[0015] Preferably, in the preparation method, the preparation method of the fluorosilane modified mesoporous TiO2 molecular sieve in step (3) comprises the following steps:

[0016] alkali-activating the mesoporous TiO2 molecular sieve; mixing the obtained alkali-activated mesoporous TiO2 molecular sieve, fluorosilane and an organic solvent to modify to obtain a fluorosilane modified mesoporous TiO2 molecular sieve.

[0017] Preferably, in the preparation method, the temperature of the alkali-activation is 120-150℃, the pH is 9-12, and the time is 2-6h; the fluorosilane is perfluorohexyltriethoxysilane or perfluorooctyltriethoxysilane; the modification temperature is 20-40℃, the rotation speed is 400-800rpm, and the time is 12-36h.

[0018] Preferably, in the preparation method, in step (4), the temperature of the calcination is 160-240 DEG C, and the time is 8-20h.

[0019] The application further provides the core-shell structured photocatalyst prepared by the preparation method.

[0020] The application further provides an application of the core-shell structured photocatalyst in air purification.

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

[0022] (1) The fluorosilane modified TiO2 molecular sieve coated nanometer Cu+ rare earth metal-sepiolite core-shell material prepared by the application uses fluorosilane modified TiO2 molecular sieve as the "shell", which not only provides a broad specific surface area for the material, enhances the light absorption and scattering capacity, but also effectively generates electron-hole pairs under visible light irradiation through its inherent photocatalytic properties, and then initiates a series of redox reactions. Moreover, the fluorosilane modification can significantly improve the hydrophobicity of the TiO2 molecular sieve, which is conducive to improving the stability in a humid environment and maintaining the good catalytic performance of the photocatalyst.

[0023] (2) The core-shell material prepared by the application uses nanometer Cu+ rare earth metal-sepiolite as the "core", and a surfactant is added when nanometer CuO and rare earth metal oxides are prepared, which is conducive to the uniform distribution of nanometer CuO and rare earth metal oxides on the surface of sepiolite, and then, after the nanometer CuO and rare earth metal oxides are calcined and reduced, nanometer Cu+ rare earth metal is used as the active center, the uniform distribution of which promotes the separation and transmission of photo-generated carriers, and Cu and rare earth metal can produce a synergistic effect, further enhancing the photocatalytic activity.

[0024] (3) The core-shell material prepared by the application uses sepiolite as the base material of nanometer Cu+ rare earth metal, which not only provides good mechanical support and stability, but also further increases the active sites of sepiolite through its unique pore structure, which is conducive to the successful attachment of nanometer CuO and rare earth metal oxides, and then, after the nanometer CuO and rare earth metal oxides are calcined and reduced, the adsorption and diffusion of volatile organic compound gas molecules are improved, and the catalytic reaction process is accelerated.

[0025] (4) The core-shell material prepared by the application does not need to use external power or other energy input for synergistic catalysis, and completely relies on the photocatalytic effect of natural light or indoor lighting, realizes true energy saving and environmental protection, and exhibits excellent purification efficiency and long-term stability.

[0026] (5) The core-shell material prepared by the application can realize efficient killing of common microorganisms such as Escherichia coli, Bacillus subtilis and Staphylococcus aureus, and provides strong support for the comprehensive purification and protection of indoor environment. DETAILED DESCRIPTION

[0027] The application provides a preparation method of a core-shell structure photocatalyst, comprising the following steps:

[0028] (1) calcining sepiolite;

[0029] (2) mixing the calcined sepiolite obtained in step (1), a surfactant, water, a copper source and a rare earth metal source, and performing hydrothermal reaction, drying to obtain sepiolite adsorbed with nano CuO-rare earth metal oxide;

[0030] (3) mixing the sepiolite adsorbed with nano CuO-rare earth metal oxide in step (2), fluorosilane modified mesoporous TiO2 molecular sieve and water, and performing coating to obtain a core-shell material of fluorosilane modified TiO2 molecular sieve coated nano CuO+rare earth metal oxide-sepiolite;

[0031] (4) calcining the core-shell material of fluorosilane modified TiO2 molecular sieve coated nano CuO+rare earth metal oxide-sepiolite in step (3) under a protective atmosphere to obtain a core-shell material of fluorosilane modified TiO2 molecular sieve coated nano Cu+rare earth metal-sepiolite, that is, a core-shell structure photocatalyst.

[0032] In the application, the sepiolite in step (1) preferably further comprises sequentially performing grinding and sieving before calcination.

[0033] In the application, the ball-to-material ratio of the grinding is preferably 5-10:1, further preferably 5-6:1, and more preferably 6:1; the rotation speed is preferably 1500-3000 rpm, further preferably 2000-3000 rpm, and more preferably 2500 rpm; and the time is preferably 2-8 h, further preferably 5-8 h, and more preferably 5 h.

[0034] In the application, the sieving is preferably passing through a 100-400 mesh sieve, further preferably passing through a 100-300 mesh sieve, and more preferably passing through a 200 mesh sieve.

[0035] In the application, the calcination temperature in step (1) is preferably 300-400 DEG C, further preferably 350-400 DEG C, and more preferably 380 DEG C; and the time is preferably 2-5 h, further preferably 3-5 h, and more preferably 4 h.

[0036] In the application, the surfactant in step (2) is preferably a mixture of cetyltrimethylammonium bromide and polyvinylpyrrolidone.

[0037] In the present application, the mass ratio of the cetyltrimethylammonium bromide to the polyvinylpyrrolidone is preferably 1-2:1-2, further preferably 1-2:1, and more preferably 1:1.

[0038] In the present application, the molecular weight of the polyvinylpyrrolidone is preferably 200-100,000, further preferably 400-800,000, and more preferably 600,000.

[0039] In the present application, the copper source in step (2) is preferably copper acetate or copper chloride, and further preferably copper acetate.

[0040] In the present application, the rare earth metal source in step (2) is preferably cerium nitrate, neodymium nitrate or yttrium nitrate, and further preferably cerium nitrate or yttrium nitrate, and more preferably cerium nitrate.

[0041] In the present application, the mass ratio of the calcined sepiolite, the surfactant, the copper source and the rare earth metal source in step (2) is preferably 1:0.1-0.4:0.8-1.5:0.4-0.8, further preferably 1:0.2-0.4:1-1.5:0.6-0.8, and more preferably 1:0.4:1.5:0.8.

[0042] In the present application, the ratio of the amount of the calcined sepiolite to the amount of water in step (2) is preferably 1g:30-50mL, further preferably 1g:30-40mL, and more preferably 1g:30mL.

[0043] In the present application, the temperature of the hydrothermal reaction in step (2) is preferably 60-100℃, further preferably 70-100℃, and more preferably 90℃; the time is preferably 8-24h, further preferably 12-24h, and more preferably 12h; and the pH is preferably 9-12, further preferably 10-12, and more preferably 11.

[0044] In the present application, the temperature of the drying in step (2) is preferably 50-80℃, further preferably 60-80℃, and more preferably 60℃; and the time is preferably 4-10h, further preferably 8-10h, and more preferably 8h.

[0045] In the present application, the preparation method of the fluorosilane-modified mesoporous TiO2 molecular sieve in step (3) preferably comprises the following steps:

[0046] The mesoporous TiO2 molecular sieve is subjected to alkaline activation treatment; the obtained alkaline-activated mesoporous TiO2 molecular sieve, fluorosilane and organic solvent are mixed to perform modification, thereby obtaining a fluorosilane-modified mesoporous TiO2 molecular sieve.

[0047] In the present application, the preparation method of the mesoporous TiO2 molecular sieve is not limited, and the scheme well known to those skilled in the art can be adopted.

[0048] In the present application, the temperature of the alkali activation treatment is preferably 120-150℃, further preferably 140-150℃, and more preferably 140℃; the pH is preferably 9-12, further preferably 10-12, and more preferably 11; and the time is preferably 2-6h, further preferably 3-5h, and more preferably 3h.

[0049] In the present application, the fluoroalkylsilane is preferably perfluorohexyltriethoxysilane or perfluorooctyltriethoxysilane, and further preferably perfluorooctyltriethoxysilane.

[0050] In the present application, the organic solvent is preferably ethanol or isopropanol, and further preferably ethanol.

[0051] In the present application, the mass ratio of the alkali-activated mesoporous TiO2 molecular sieve to the fluoroalkylsilane is preferably 1:0.5-2, further preferably 1:0.8-1.5, and more preferably 1:1.

[0052] In the present application, the dosage ratio of the alkali-activated mesoporous TiO2 molecular sieve to the organic solvent is preferably 1g:30-50mL, further preferably 1g:30-40mL, and more preferably 1g:30mL.

[0053] In the present application, the temperature of the modification is preferably 20-40℃, further preferably 25-40℃, and more preferably 25℃; the rotation speed is preferably 400-800rpm, further preferably 600-800rpm, and more preferably 600rpm; and the time is preferably 12-36h, further preferably 18-36h, and more preferably 24h.

[0054] In the present application, the mass ratio of the sepiolite adsorbed with nano CuO-rare earth metal oxide to the modified mesoporous TiO2 molecular sieve with fluoroalkylsilane in step (3) is preferably 1:2-4, further preferably 1:3-4, and more preferably 1:3.

[0055] In the present application, the dosage ratio of the sepiolite adsorbed with nano CuO-rare earth metal oxide to water in step (3) is preferably 1g:30-50mL, further preferably 1g:30-40mL, and more preferably 1g:30mL.

[0056] In the present application, the temperature of the coating in step (3) is preferably 150-250℃, further preferably 180-220℃, and more preferably 210℃; and the time is preferably 12-20h, further preferably 8-24h, and more preferably 12h.

[0057] In the present application, the protective atmosphere in step (4) is preferably nitrogen.

[0058] In the present application, the temperature for calcination in step (4) is preferably 160-240℃, further preferably 180-240℃, and more preferably 200℃; and the time is preferably 8-20h, further preferably 12-20h, and more preferably 15h.

[0059] The present application also provides a core-shell structured photocatalyst prepared by the preparation method.

[0060] In the present application, the mass percentage of TiO2 zeolite is preferably 65-80%, further preferably 67-75%, and more preferably 75%, based on 100% of the mass of the core-shell structured photocatalyst; the mass percentage of nano-Cu is preferably 4-12%, further preferably 4.5-8%, and more preferably 7%; the mass percentage of rare earth metal is preferably 1-5%, further preferably 1.8-3%, and more preferably 3%; and the sepiolite is the remainder.

[0061] The present application also provides an application of the core-shell structured photocatalyst in air purification.

[0062] In the present application, the method for the application is not limited, and the method well known to those skilled in the art can be used. In the embodiments of the present application, the core-shell structured photocatalyst is mixed with a binder to prepare a reticular or sheet-like composite material.

[0063] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0064] Preparation Example 1

[0065] 1 mol of butyl titanate and 3 mol of triethanolamine were mixed and stirred uniformly at room temperature, and then water was added and stirred for 12h to form a homogeneous gel; after drying at 100℃, the sample was transferred to a self-pressing kettle for crystallization at 150℃ for 48h to obtain a block-shaped gel. After extraction with an ethanol solution as an extractant, the sample was calcined at 150℃ to obtain mesoporous TiO2 zeolite.

[0066] Embodiment 1

[0067] The present embodiment provides a preparation method of a core-shell structured photocatalyst, which comprises the following steps:

[0068] (1) first grinding the sepiolite at 2500 rpm for 5 h, the grinding ball-to-material ratio is 6:1, and then sieving through a 200-mesh sieve, and then calcining at 380°C for 4 h;

[0069] (2) mixing the calcined sepiolite obtained in step (1) 10 g, hexadecyl trimethyl ammonium bromide 2 g, polyvinyl pyrrolidone 2 g (molecular weight 60,000), water 300 mL, copper acetate 15 g, and cerium nitrate 8 g, adjusting the pH to 11, and then hydrothermally reacting at 90°C for 12 h, and then drying at 60°C for 8 h to obtain sepiolite adsorbed with nano CuO-CeO2;

[0070] (3) alkali-activating the mesoporous TiO2 molecular sieve obtained in Preparation Example 1 at 140°C for 3 h at pH = 11, and then modifying the obtained alkali-activated mesoporous TiO2 molecular sieve 10 g, perfluorooctyl triethoxysilane 10 g, and ethanol 300 mL at 25°C and 600 rpm for 24 h to obtain fluorosilane-modified mesoporous TiO2 molecular sieve; then mixing the sepiolite adsorbed with nano CuO-CeO2 obtained in step (2) 10 g, the fluorosilane-modified TiO2 molecular sieve 30 g, and water 300 mL, and then coating at 210°C for 12 h to obtain a core-shell material of fluorosilane-modified TiO2 molecular sieve coated nano CuO+CeO2-sepiolite;

[0071] (4) calcining the core-shell material of fluorosilane-modified TiO2 molecular sieve coated nano CuO+CeO2-sepiolite obtained in step (3) 10 g at 200°C for 15 h under nitrogen protection to obtain a core-shell material of fluorosilane-modified TiO2 molecular sieve coated nano Cu+Ce-sepiolite, i.e. a core-shell structured photocatalyst. In the photocatalyst, the TiO2 molecular sieve is 75 wt%, the nano Cu is 7 wt%, the Ce is 3 wt%, and the sepiolite is the balance.

[0072] Example 2

[0073] The present embodiment provides a preparation method of a core-shell structured photocatalyst, comprising the following steps:

[0074] (1) first grinding the sepiolite at 1500 rpm for 8 h, the grinding ball-to-material ratio is 5:1, and then sieving through a 300-mesh sieve, and then calcining at 300°C for 5 h;

[0075] (2) mixing the calcined sepiolite obtained in step (1) 10 g, hexadecyl trimethyl ammonium bromide 1 g, polyvinyl pyrrolidone 1 g (molecular weight 60,000), water 500 mL, copper chloride 12 g, and yttrium nitrate 6 g, adjusting the pH to 10, and then hydrothermally reacting at 100°C for 10 h, and then drying at 80°C for 4 h to obtain sepiolite adsorbed with nano CuO-Y2O3;

[0076] (3) The mesoporous TiO2 molecular sieve obtained in Preparation Example 1 was subjected to alkaline activation treatment at pH = 10 and 120°C for 5 h. The obtained alkaline-activated mesoporous TiO2 molecular sieve 10 g, perfluorohexyltriethoxysilane 20 g and isopropyl alcohol 300 mL were mixed at 40°C and 400 rpm for modification for 36 h to obtain fluorosilane-modified mesoporous TiO2 molecular sieve. Then, the sepiolite 10 g adsorbed with nano CuO-Y2O3 obtained in step (2), fluorosilane-modified TiO2 molecular sieve 20 g and water 300 mL were mixed to perform coating at 180°C for 15 h to obtain the core-shell material of fluorosilane-modified TiO2 molecular sieve coated nano CuO+Y2O3-sepiolite;

[0077] (4) The core-shell material of fluorosilane-modified TiO2 molecular sieve coated nano CuO+Y2O3-sepiolite obtained in step (3) was calcined at 240°C for 12 h under nitrogen protection to obtain the core-shell material of fluorosilane-modified TiO2 molecular sieve coated nano Cu+Y-sepiolite, that is, the core-shell structured photocatalyst. In the photocatalyst, TiO2 molecular sieve is 67 wt%, nano Cu is 8 wt%, Y is 2.4 wt% and sepiolite is the balance.

[0078] Example 3

[0079] The present embodiment provides a preparation method of a core-shell structured photocatalyst, comprising the following steps:

[0080] (1) The sepiolite was first ground at 3000 rpm for 2 h with a ball-to-material ratio of 10:1 and then passed through a 100-mesh sieve, followed by calcination at 350°C for 3 h;

[0081] (2) The calcined sepiolite 10 g obtained in step (1), hexadecyltrimethylammonium bromide 2 g, polyvinylpyrrolidone 1 g (molecular weight: 40,000), water 400 mL, copper acetate 10 g and neodymium nitrate 4 g were mixed to adjust the pH to 12. After hydrothermal reaction at 70°C for 24 h, drying was performed at 50°C for 10 h to obtain the sepiolite adsorbed with nano CuO-Nd2O3;

[0082] (3) The mesoporous TiO2 molecular sieve obtained in Preparation Example 1 was subjected to alkaline activation treatment at pH = 12 and 150°C for 2 h. The obtained alkaline-activated mesoporous TiO2 molecular sieve 10 g, perfluorooctyltriethoxysilane 8 g and ethanol 300 mL were mixed at 20°C and 800 rpm for modification for 18 h to obtain fluorosilane-modified mesoporous TiO2 molecular sieve. Then, the sepiolite 10 g adsorbed with nano CuO-Nd2O3 obtained in step (2), fluorosilane-modified TiO2 molecular sieve 40 g and water 500 mL were mixed to perform coating at 150°C for 20 h to obtain the core-shell material of fluorosilane-modified TiO2 molecular sieve coated nano CuO+Nd2O3-sepiolite;

[0083] (4) Under nitrogen protection, 10 g of the fluorosilane-modified TiO2 molecular sieve coated nanometer CuO+Nd2O3-sepiolite core-shell material obtained in step (3) is calcined at 180°C for 20 h to obtain a fluorosilane-modified TiO2 molecular sieve coated nanometer Cu+Nd-sepiolite core-shell material, i.e. a core-shell structured photocatalyst. In the photocatalyst, TiO2 molecular sieve is 80 wt%, nanometer Cu is 4.5 wt%, Nd is 1.8 wt%, and sepiolite is the balance.

[0084] Comparative Example 1

[0085] Comparative Example 1 differs from Example 1 in that step (1) is deleted, and in the obtained photocatalyst, TiO2 molecular sieve is 75 wt%, nanometer Cu is 1.5 wt%, Ce is 0.8 wt%, and sepiolite is the balance, and other parameter conditions are the same as in Example 1.

[0086] Comparative Example 2

[0087] Comparative Example 2 differs from Example 1 in that step (3) is deleted; and step (4) is modified as follows: 10 g of the sepiolite adsorbing nanometer CuO-CeO2 obtained in step (2) is calcined at 200°C for 15 h to obtain a nanometer Cu+Ce-sepiolite composite material, and in the obtained photocatalyst, nanometer Cu is 28 wt%, Ce is 12 wt%, and sepiolite is the balance, and other parameter conditions are the same as in Example 1.

[0088] Comparative Example 3

[0089] Comparative Example 3 differs from Example 1 in that step (4) is deleted, and in the obtained photocatalyst, TiO2 molecular sieve is 75 wt%, nanometer CuO is 9.4 wt%, CeO2 is 2.6 wt%, and sepiolite is the balance, and other parameter conditions are the same as in Example 1.

[0090] Comparative Example 4

[0091] Comparative Example 4 differs from Example 1 in that cerium nitrate in step (2) is deleted, and in the obtained photocatalyst, TiO2 molecular sieve is 75 wt%, nanometer Cu is 8 wt%, and sepiolite is the balance, and other parameter conditions are the same as in Example 1.

[0092] Comparative Example 5

[0093] Comparative Example 5 differs from Example 1 in that copper acetate in step (2) is deleted, and in the obtained photocatalyst, TiO2 molecular sieve is 75 wt%, Ce is 4 wt%, and sepiolite is the balance, and other parameter conditions are the same as in Example 1.

[0094] Application Examples 1-3 and Comparative Application Examples 1-5

[0095] The photocatalyst prepared in Examples 1-3 and Comparative Examples 1-5 was mixed with a binder in a mass ratio of 9:1 to prepare a sheet-shaped composite material.

[0096] Test Example 1

[0097] 1 g of the sheet-shaped composite material obtained in Application Examples 1-3 and Comparative Application Examples 1-5 was placed in a dark reactor, and a mixed gas of formaldehyde-toluene-xylene was injected into the reactor to adjust the initial concentration of VOCs to 1000 ppm. When adsorption-desorption equilibrium was reached in the dark, a catalytic reaction test was performed under visible light. During the reaction, about 1 mL of the gas mixture was taken out at intervals of 10 min, and the contents of formaldehyde-toluene-xylene and carbon dioxide in the gas were analyzed using GC2030 and GC1690 gas chromatographs, respectively, to calculate the elimination rate of formaldehyde-toluene-xylene. When the elimination rate was substantially constant, the elimination rate and the loss time were recorded, and the results are shown in Table 1.

[0098] Table 1. Results of Test Example 1

[0099]

[0100] As can be seen from Table 1, in the case where the sepiolite was not calcined, the shell of the mesoporous TiO2 molecular sieve was not modified with fluorosilane, CuO+CeO2 was not reduced, or Cu / Ce was deleted, the elimination rate of the mixed gas of formaldehyde-toluene-xylene was significantly reduced in Comparative Application Examples 1-5, among which the elimination rate of Comparative Application Example 2 decreased the most and the elimination time was the longest, indicating that the comparative examples could not achieve rapid and effective removal of VOCs after deleting some process operations or raw materials, and could not meet the purification needs of people for air purification materials. The results of Comparative Application Examples 4-5 verified that a synergistic catalytic effect would be produced between Cu and rare earth elements, and both were indispensable. The core-shell structured photocatalyst prepared in Examples 1-3 of the present application had excellent purification efficiency and elimination rate for VOCs under visible light, fully exerted the synergistic catalytic effect of Cu and rare earth metals, and the elimination rate was more than 85%, which could more quickly and completely eliminate VOCs with complex components.

[0101] Test Example 2

[0102] E. coli, B. subtilis, and S. aureus were activated in LB nutrient broth for 24 h, and the resulting bacterial liquid was diluted to obtain a final concentration of 10 6Three kinds of bacteria suspensions were prepared with 1 g of the sheet-shaped composite materials obtained in Application Examples 1 to 3 and Comparative Application Examples 1 to 5, respectively. After being diffused in a refrigerator at 4℃ for 24 h and then incubated at 37℃ for 24 h, the diameters of the bacteriostatic circles were measured. The results are shown in Table 2.

[0103] Table 2. Results of Test Example 2

[0104]

[0105] As can be seen from Table 2, the bacteriostatic effect of Comparative Application Example 1 is obviously deteriorated due to the significant decrease of the loadings of Cu and rare earth elements caused by the uncalcined sepiolite. After the mesoporous TiO2 molecular sieve shell is removed, the bacteriostatic effect of Comparative Application Example 2 is slightly better than that of the core-shell structured photocatalysts of Application Examples 1 to 3 due to the significant increase of the copper content. In the case of no reduction of CuO and no Ce removal, the Cu content does not decrease, so the bacteriostatic effects of Comparative Application Examples 3 to 4 are not much different from that of Application Example. In the case of no Cu, the bacteriostatic effect of Comparative Application Example 5 is significantly deteriorated. The core-shell structured photocatalysts prepared in Application Examples 1 to 3 can efficiently kill common microorganisms such as Escherichia coli, Bacillus subtilis and Staphylococcus aureus, and can realize the comprehensive purification and protection of indoor environment.

[0106] The above only describes the preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the scope of the present application.

Claims

1. A method for preparing a core-shell structured photocatalyst, characterized in that, Includes the following steps: (1) Roast the sepiolite; (2) The calcined sepiolite, surfactant, water, copper source and rare earth metal source obtained in step (1) are mixed, and a hydrothermal reaction is carried out. After drying, sepiolite with adsorption of nano-CuO-rare earth metal oxide is obtained. (3) The sepiolite adsorbed with nano-CuO-rare earth metal oxides and the fluorosilane-modified mesoporous TiO2 molecular sieve described in step (2) are mixed with water and coated to obtain a core-shell material of nano-CuO+rare earth metal oxide-sepiolite coated with fluorosilane-modified TiO2 molecular sieve. (4) Under a protective atmosphere, the fluorosilane-modified TiO2 molecular sieve coated with nano-CuO + rare earth metal oxide-sepiolite core-shell material described in step (3) is calcined to obtain a core-shell structured photocatalyst. In step (2), the rare earth metal source is cerium nitrate, neodymium nitrate, or yttrium nitrate.

2. The preparation method according to claim 1, characterized in that, The roasting temperature in step (1) is 300~400℃ and the time is 2~5h.

3. The preparation method according to claim 1, characterized in that, In step (2), the surfactant is a mixture of hexadecyltrimethylammonium bromide and polyvinylpyrrolidone, and the copper source is copper acetate or copper chloride; the mass ratio of the calcined sepiolite, the surfactant, the copper source and the rare earth metal source is 1:0.1~0.4:0.8~1.5:0.4~0.8; the mass ratio of the hexadecyltrimethylammonium bromide to the polyvinylpyrrolidone is 1~2:1~2.

4. The preparation method according to claim 1 or 3, characterized in that, The hydrothermal reaction in step (2) is carried out at a temperature of 60~100℃ for 8~24h and at a pH of 9~12.

5. The preparation method according to claim 2, characterized in that, In step (3), the mass ratio of the sepiolite adsorbing nano-CuO-rare earth metal oxides to the fluorosilane-modified mesoporous TiO2 molecular sieve is 1:2~4; the coating temperature is 150~250℃ and the time is 8~24h.

6. The preparation method according to claim 1 or 5, characterized in that, The preparation method of the fluorosilane-modified mesoporous TiO2 molecular sieve in step (3) includes the following steps: Mesoporous TiO2 molecular sieves were activated with alkali; the resulting alkali-activated mesoporous TiO2 molecular sieves, fluorosilanes, and organic solvents were mixed and modified to obtain fluorosilane-modified mesoporous TiO2 molecular sieves.

7. The preparation method according to claim 6, characterized in that, The alkaline activation treatment is performed at a temperature of 120-150℃, a pH of 9-12, and a time of 2-6 hours; the fluorosilane is perfluorohexyltriethoxysilane or perfluorooctyltriethoxysilane; the modification is performed at a temperature of 20-40℃, a rotation speed of 400-800 rpm, and a time of 12-36 hours.

8. The preparation method according to claim 1, characterized in that, In step (4), the calcination temperature is 160~240℃ and the time is 8~20h.

9. A core-shell structured photocatalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the core-shell structured photocatalyst of claim 9 in air purification.

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