Photocatalyst water-based paint and preparation method thereof

Abstract

The present invention relates to a kind of photocatalytic water-based paint and preparation method thereof, belong to the technical field of coatings. In the modified TiO2 of the photocatalytic water-based paint of the present invention, TiO2 is modified with Ce, and the visible light absorption performance of TiO2 is significantly improved. Secondly, Ce-modified TiO2 is coated with N-(3-dimethylaminopropyl) methacrylamide, which can significantly reduce the van der Waals attraction between TiO2 and make it uniformly dispersed in the coating. In addition, after N-(3-dimethylaminopropyl) methacrylamide is coated on the surface of Ce-modified TiO2, poly-N-(3-dimethylaminopropyl) methacrylamide is formed, which alleviates the problem that Ce-modified TiO2 is difficult to directly contact with formaldehyde due to coating. Finally, N-(3-dimethylaminopropyl) methacrylamide introduces N element into TiO2, widening the visible light absorption range of TiO2.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a photocatalyst water-based coating and a preparation method thereof. Background Art

[0002] TiO2 is an important photocatalyst material that can catalytically degrade organic pollutants such as formaldehyde and toluene under ultraviolet light. It also has the advantages of being antibacterial, non-toxic, and acid- and alkali-resistant. However, TiO2, as a photocatalyst, only exhibits good photocatalytic activity under ultraviolet light and cannot utilize approximately 96% of visible light. This severely limits its use as a key photocatalyst material in everyday life. Summary of the Invention

[0003] The first object of the present invention is to provide a photocatalytic water-based paint that can exert a photocatalytic effect under visible light.

[0004] The second object of the present invention is to provide a method for preparing the above-mentioned water-based coating.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A photocatalyst water-based paint comprises photocatalyst material-modified TiO2, wherein the modified TiO2 is prepared by the following operations:

[0007] Preparation of Ce-modified TiO2: Mixing anhydrous ethanol and a cerium nitrate aqueous solution to obtain a mixed solution; mixing the mixed solution with titanium tetrachloride, heating the mixture for reaction, and cooling the mixture after the reaction to obtain Ce-modified TiO2;

[0008] Pretreatment: Cerium-modified TiO2 is crushed into powder and then ultrasonically dispersed in ethanol to prepare a 5-10 wt% TiO2 suspension; N-(3-dimethylaminopropyl)methacrylamide is dissolved in ethanol to obtain an 8-12 wt% mixed solution;

[0009] Coating reaction: Mix the TiO2 suspension prepared in the pretreatment with the mixed solution, then add the catalyst ammonium persulfate or azobisisobutyronitrile and the surfactant sodium lauryl sulfate, mix well, heat and react, and irradiate with ultraviolet light after the reaction is completed;

[0010] Post-processing: After the UV lamp irradiation is completed, the product is centrifuged and dried to obtain modified TiO2.

[0011] As a preferred embodiment of the present invention, in the preparation of Ce-modified TiO2, the concentration of the cerium nitrate aqueous solution is 0.5 to 1.5 mol / L.

[0012] As a preferred embodiment of the present invention, in the preparation of Ce-modified TiO2, the temperature of the heating reaction is 130-180°C, and the time of the heating reaction is 6-10 hours.

[0013] As a preferred embodiment of the present invention, in the preparation of Ce-modified TiO2, the molar ratio of cerium nitrate to titanium tetrachloride is 1-5%.

[0014] As a preferred embodiment of the present invention, in the coating reaction, the mass ratio of TiO2 to N-(3-dimethylaminopropyl)methacrylamide is controlled to be 1:50-60.

[0015] As a preferred embodiment of the present invention, in the coating reaction, the temperature-raising reaction is specifically carried out at 60-80° C. for 1.5-3.5 hours.

[0016] As a preferred embodiment of the present invention, in the coating reaction, the ultraviolet light irradiation is specifically performed with a light intensity of 2 to 4 mW / cm 2 Irradiate with ultraviolet light for 20 to 30 minutes.

[0017] As a preferred embodiment of the present invention, in the coating reaction, the mass of the catalyst is 0.1-1% of the mass of TiO2, and the mass of the surfactant is 0.5-1% of the mass of TiO2.

[0018] As a preferred embodiment of the present invention, the following components in parts by weight are included:

[0019]

[0020]

[0021] The preparation method of the above-mentioned photocatalyst water-based paint includes the following operations: quantitatively weighing water, cellulose, dispersant, and wetting agent and stirring them evenly, then adding modified TiO2 and pigment for dispersion and grinding, adding BASF pure acrylic emulsion, and then adding defoamer and thickener after uniform dispersion, mixing evenly, to prepare the photocatalyst water-based paint.

[0022] Beneficial effects of the present invention:

[0023] In the modified TiO2 of the photocatalytic water-based paint of the present invention, Ce is used to modify TiO2, Ce does not change the crystal form of TiO2, and significantly improves the visible light absorption performance of TiO2.

[0024] Secondly, Ce-modified TiO2 was coated with N-(3-dimethylaminopropyl)methacrylamide. TiO2 has a large specific surface area and Gibbs free energy, and its thermodynamic state is unstable. When TiO2 is directly added to the coating, the particles approach each other due to van der Waals attraction, and the TiO2 changes from a dispersed state to an agglomerated state, thus affecting the final coating performance of the coating. The coating effect can significantly reduce the van der Waals attraction between TiO2, making it evenly dispersed in the coating. In addition, after N-(3-dimethylaminopropyl)methacrylamide is coated on the surface of Ce-modified TiO2, it forms poly-N-(3-dimethylaminopropyl)methacrylamide, which introduces carboxyl and tertiary amine groups. In the presence of Ce, it can partially react with formaldehyde to absorb formaldehyde. At the same time, after the reaction, the coated Ce-modified TiO2 is more exposed, alleviating the problem that Ce-modified TiO2 is difficult to directly contact with formaldehyde due to coating. Finally, N-(3-dimethylaminopropyl) methacrylamide introduces nitrogen element into TiO2, and part of the nitrogen element enters TiO2, reducing the band gap of TiO2 and thus broadening the visible light absorption range of TiO2. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with specific embodiments.

[0026] Example 1

[0027] A modified TiO2 is prepared by the following operations:

[0028] Preparation of Ce-modified TiO2: Place 3.35 L of anhydrous ethanol in a container, add 0.5 mol / L of cerium nitrate aqueous solution and mix evenly to obtain a mixed solution; add 2.65 L of titanium tetrachloride to the mixed solution while stirring until a sol-state substance is formed, react it at 130°C for 6 hours, and naturally cool it after the reaction to obtain a solid. Wash the solid three times with anhydrous ethanol, filter and dry it to obtain Ce-modified TiO2, wherein the molar ratio of cerium nitrate to titanium tetrachloride is 1%.

[0029] Pretreatment: Ce-modified TiO2 was ultrasonically dispersed in ethanol for 30 min to obtain a 5wt% TiO2 suspension; N-(3-dimethylaminopropyl)methacrylamide was dissolved in ethanol to obtain an 8wt% mixed solution.

[0030] Coating reaction: The TiO2 suspension and mixed solution prepared in the pretreatment were slowly added into a glass reactor, wherein the mass ratio of TiO2 to N-(3-dimethylaminopropyl) methacrylamide was 1:50; then the catalyst ammonium persulfate and the surfactant sodium lauryl sulfate were added, stirred evenly, and reacted at 60°C for 1.5h. After the reaction was completed, the light intensity was 2mW / cm 2The catalyst mass is 0.1% of the mass of TiO2, and the surfactant mass is 0.5% of the mass of TiO2.

[0031] Post-treatment: After the reaction is completed, the product is centrifuged and washed with ethanol three times. The washed product is dried in an oven to constant weight to obtain modified TiO2.

[0032] Example 2

[0033] A modified TiO2 is prepared by the following operations:

[0034] Preparation of Ce-modified TiO2: Place 3.35 L of anhydrous ethanol in a container, add 0.8 mol / L of cerium nitrate aqueous solution and mix evenly to obtain a mixed solution; add 2.65 L of titanium tetrachloride to the mixed solution while stirring until a sol-state substance is formed, react it at 140°C for 7 hours, and naturally cool it after the reaction to obtain a solid. Wash the solid three times with anhydrous ethanol, filter and dry it to obtain Ce-modified TiO2, wherein the molar ratio of cerium nitrate to titanium tetrachloride is 2%.

[0035] Pretreatment: Ce-modified TiO2 was ultrasonically dispersed in ethanol for 30 min to obtain a 6wt% TiO2 suspension; N-(3-dimethylaminopropyl)methacrylamide was dissolved in ethanol to obtain a 9wt% mixed solution.

[0036] Coating reaction: The TiO2 suspension and mixed solution prepared in the pretreatment were slowly added into a glass reactor, wherein the mass ratio of TiO2 to N-(3-dimethylaminopropyl) methacrylamide was 1:52; then the catalyst ammonium persulfate and the surfactant sodium dodecyl sulfate were added, stirred evenly, and reacted at 65°C for 2h. After the reaction was completed, the light intensity was 2.5mW / cm 2 The catalyst mass is 0.8% of the mass of TiO2, and the surfactant mass is 0.6% of the mass of TiO2.

[0037] Post-treatment: After the reaction is completed, the product is centrifuged and washed with ethanol three times. The washed product is dried in an oven to constant weight to obtain modified TiO2.

[0038] Example 3

[0039] A modified TiO2 is prepared by the following operations:

[0040] Preparation of Ce-modified TiO2: Place 3.35 L of anhydrous ethanol in a container, add 1.0 mol / L of cerium nitrate aqueous solution and mix evenly to obtain a mixed solution; add 2.65 L of titanium tetrachloride to the mixed solution while stirring until a sol-state substance is formed, react it at 150°C for 8 hours, and naturally cool it after the reaction to obtain a solid. Wash the solid three times with anhydrous ethanol, filter and dry it to obtain Ce-modified TiO2, wherein the molar ratio of cerium nitrate to titanium tetrachloride is 3%.

[0041] Pretreatment: Ce-modified TiO2 was ultrasonically dispersed in ethanol for 30 min to obtain an 8wt% TiO2 suspension; N-(3-dimethylaminopropyl)methacrylamide was dissolved in ethanol to obtain a 10wt% mixed solution.

[0042] Coating reaction: The TiO2 suspension and mixed solution prepared in the pretreatment were slowly added into a glass reactor, wherein the mass ratio of TiO2 to N-(3-dimethylaminopropyl) methacrylamide was 1:55; then the catalyst ammonium persulfate and the surfactant sodium dodecyl sulfate were added, stirred evenly, and reacted at 70°C for 2.5h. After the reaction was completed, the light intensity was 3mW / cm 2 The catalyst mass is 0.3% of the mass of TiO2, and the surfactant mass is 0.8% of the mass of TiO2.

[0043] Post-treatment: After the reaction is completed, the product is centrifuged and washed with ethanol three times. The washed product is dried in an oven to constant weight to obtain modified TiO2.

[0044] Example 4

[0045] A modified TiO2 is prepared by the following operations:

[0046] Preparation of Ce-modified TiO2: Place 3.35 L of anhydrous ethanol in a container, add 1.2 mol / L of cerium nitrate aqueous solution and mix evenly to obtain a mixed solution; add 2.65 L of titanium tetrachloride to the mixed solution while stirring until a sol-state substance is formed, react it at 160°C for 9 hours, and naturally cool it after the reaction to obtain a solid. Wash the solid three times with anhydrous ethanol, filter and dry it to obtain Ce-modified TiO2, wherein the molar ratio of cerium nitrate to titanium tetrachloride is 4%.

[0047] Pretreatment: Ce-modified TiO2 was ultrasonically dispersed in ethanol for 30 min to obtain a 9wt% TiO2 suspension; N-(3-dimethylaminopropyl)methacrylamide was dissolved in ethanol to obtain an 11wt% mixed solution.

[0048] Coating reaction: The TiO2 suspension and mixed solution prepared in the pretreatment were slowly added into a glass reactor, wherein the mass ratio of TiO2 to N-(3-dimethylaminopropyl) methacrylamide was 1:58; then the catalyst azobisisobutyronitrile and surfactant sodium dodecyl sulfate were added, stirred evenly, and reacted at 75°C for 3h. After the reaction was completed, the light intensity was 3.5mW / cm 2 The catalyst mass is 0.5 of the mass of TiO2, and the surfactant mass is 0.9% of the mass of TiO2.

[0049] Post-treatment: After the reaction is completed, the product is centrifuged and washed with ethanol three times. The washed product is dried in an oven to constant weight to obtain modified TiO2.

[0050] Example 5

[0051] A modified TiO2 is prepared by the following operations:

[0052] Preparation of Ce-modified TiO2: Place 3.35 L of anhydrous ethanol in a container, add 1.5 mol / L of cerium nitrate aqueous solution and mix evenly to obtain a mixed solution; add 2.65 L of titanium tetrachloride to the mixed solution while stirring until a sol-state substance is formed, react it at 180°C for 10 hours, and naturally cool it after the reaction to obtain a solid. Wash the solid three times with anhydrous ethanol, filter and dry it to obtain Ce-modified TiO2, wherein the molar ratio of cerium nitrate to titanium tetrachloride is 5%.

[0053] Pretreatment: Ce-modified TiO2 was ultrasonically dispersed in ethanol for 30 min to obtain a 10 wt% TiO2 suspension; N-(3-dimethylaminopropyl)methacrylamide was dissolved in ethanol to obtain a 12 wt% mixed solution.

[0054] Coating reaction: The TiO2 suspension and mixed solution prepared in the pretreatment were slowly added into a glass reactor, wherein the mass ratio of TiO2 to N-(3-dimethylaminopropyl) methacrylamide was 1:60; then the catalyst azobisisobutyronitrile and surfactant sodium dodecyl sulfate were added, stirred evenly, and reacted at 80°C for 3.5h. After the reaction was completed, the light intensity was 4mW / cm 2 The catalyst mass is 1% of the mass of TiO2, and the surfactant mass is 1% of the mass of TiO2.

[0055] Post-treatment: After the reaction is completed, the product is centrifuged and washed with ethanol three times. The washed product is dried in an oven to constant weight to obtain modified TiO2.

[0056] Comparative Example 1

[0057] A modified TiO2, compared with Example 3, does not modify TiO2 with Ce, and is otherwise the same as Example 3, and is prepared by the following operations:

[0058] Pretreatment: Ultrasonic dispersion of TiO2 in ethanol for 30 minutes to obtain an 8wt% TiO2 suspension; dissolve N-(3-dimethylaminopropyl)methacrylamide in ethanol to obtain a 10wt% mixed solution.

[0059] Coating reaction: The TiO2 suspension and mixed solution prepared in the pretreatment were slowly added into a glass reactor, wherein the mass ratio of TiO2 to N-(3-dimethylaminopropyl) methacrylamide was 1:55; then the catalyst ammonium persulfate / azobisisobutyronitrile and the surfactant sodium dodecyl sulfate were added, stirred evenly, and reacted at 70°C for 2.5h. After the reaction was completed, the light intensity was 3mW / cm 2 The catalyst mass is 0.3% of the mass of TiO2, and the surfactant mass is 0.8% of the mass of TiO2.

[0060] Post-treatment: After the reaction is completed, the product is centrifuged and washed with ethanol three times. The washed product is dried in an oven to constant weight to obtain modified TiO2.

[0061] Comparative Example 2

[0062] A modified TiO2, compared with Example 3, is prepared by the following operations except that only Ce is used to modify the TiO2 and Ce-modified TiO2 is not coated. The rest of the steps are the same as those in Example 3.

[0063] Preparation of Ce-modified TiO2: Place 3.35 L of anhydrous ethanol in a container, add 1.0 mol / L of cerium nitrate aqueous solution and mix evenly to obtain a mixed solution; add 2.65 L of titanium tetrachloride to the mixed solution while stirring until a sol-state substance is formed, react it at 150°C for 8 hours, and naturally cool it after the reaction to obtain a solid. Wash the solid three times with anhydrous ethanol, filter and dry it to obtain Ce-modified TiO2, wherein the molar ratio of cerium nitrate to titanium tetrachloride is 3%.

[0064] Comparative Example 3

[0065] A modified TiO2, compared with Example 3, is prepared by the following operations, except that methyl methacrylate is used instead of N-(3-dimethylaminopropyl)methacrylamide to coat the Ce-modified TiO2, and the rest is the same as Example 3:

[0066] Preparation of Ce-modified TiO2: Place 3.35 L of anhydrous ethanol in a container, add 1.0 mol / L of cerium nitrate aqueous solution and mix evenly to obtain a mixed solution; add 2.65 L of titanium tetrachloride to the mixed solution while stirring until a sol-state substance is formed, react it at 150°C for 8 hours, and naturally cool it after the reaction to obtain a solid. Wash the solid three times with anhydrous ethanol, filter and dry it to obtain Ce-modified TiO2, wherein the molar ratio of cerium nitrate to titanium tetrachloride is 3%.

[0067] Coating Reaction: Ce-modified TiO2, sodium dodecyl sulfate, and deionized water were added to a reactor in a mass ratio of 10:0.1:100. The temperature was raised to 80°C. Sodium bisulfite and ammonium persulfate were then added sequentially, with a mass ratio of Ce-modified TiO2: sodium bisulfite: ammonium persulfate of 10:0.456:0.1. After stirring for 15 minutes, methyl methacrylate was added dropwise over 1 hour. After completion of the reaction, the emulsion was broken with saturated sodium chloride solution, filtered under reduced pressure, washed three times with distilled water, dried at 45°C to constant weight, and pulverized to obtain the modified TiO2.

[0068] The modified TiO2 of Examples 6 to 10 and Comparative Examples 4 to 6 were prepared by the following method: water, cellulose, dispersant, and wetting agent were weighed and stirred uniformly, and then the modified TiO2 and pigment were added and dispersed and ground. BASF pure acrylic emulsion (purchased from Guangzhou Xianrenhui International Trade Co., Ltd., product model: Acronal PA237) was added for dispersion. After uniform dispersion, a defoamer and a thickener were added and mixed uniformly to prepare a photocatalytic water-based coating. The components and weight parts are shown in Table 1:

[0069] Table 1

[0070]

[0071] The following tests were performed on Examples 1 to 5 and Comparative Examples 1 to 3:

[0072] Test Example 1 Stability Test

[0073] Measure 30 mL of distilled water into a 100 mL beaker. Then weigh 0.1 g of the modified TiO2 powder prepared in Examples 1-5 and Comparative Examples 1-3, respectively, and add them to the solution. Ultrasonicate at 540 W for 5 minutes, then magnetically stir for 0.5 hours. Add 25 mL of the dispersion solution to a stoppered graduated test tube and let it rest on a laboratory bench. Observe the dispersion effect of each solution after 24 hours of rest. Pour the supernatant into a graduated cylinder and read the volume V.

[0074] Gravity sedimentation stability = (25-V) / 25. The larger the V value, the less sedimented powder, which means the more stable the dispersion. The results are shown in Table 2:

[0075] Table 2

[0076] Components Gravity sedimentation stability V / mL Example 1 24.4 Example 2 24.3 Example 3 24.7 Example 4 24.4 Example 5 24.1 Comparative Example 1 23.8 Comparative Example 2 23.1 Comparative Example 3 23.4

[0077] As can be seen from Table 2, the modified TiO2 prepared in Examples 1 to 5 all showed excellent gravity sedimentation stability in the stability test, all greater than 24. However, the gravity sedimentation stability of the modified TiO2 prepared in Comparative Examples 1 to 3 was reduced to varying degrees compared with Example 3. The modified TiO2 in Comparative Example 1 did not use Ce to modify TiO2, and its formaldehyde purification rate was not significantly reduced. The modified TiO2 in Comparative Example 2 only used Ce to modify TiO2, and did not coat the Ce-modified TiO2. Its gravity sedimentation stability was significantly reduced. It can be seen that coating the TiO2 effectively improved the gravity sedimentation stability of the modified TiO2. In the modified TiO2 in Comparative Example 3, methyl methacrylate is used instead of N-(3-dimethylaminopropyl)methacrylamide to coat the Ce-modified TiO2. Its gravity sedimentation stability is slightly improved compared with Comparative Example 2, but still decreased compared with Example 3. It can be seen that coating Ce-modified TiO2 with N-(3-dimethylaminopropyl)methacrylamide can also improve the gravity sedimentation stability of the modified TiO2.

[0078] The following tests were performed on Examples 6 to 10 and Comparative Examples 4 to 6:

[0079] Test Example 2 Formaldehyde degradation performance test

[0080] The formaldehyde degradation experiment of the coating template was conducted in accordance with the JC / T1074-2021 "Purification Performance of Indoor Air Purification Functional Coating Materials" standard. The 24-hour formaldehyde purification performance test was carried out in a homemade experimental device. The experimental device consists of a sealed glass box (with a test hole in the glass box), a UV lamp, and a fan. The fan is placed to evenly distribute the air. The light intensity is 40mW·cm -2 The coating thickness was 250 μm and the time was 24 hours. The formaldehyde purification rate was tested. The results are shown in Table 3:

[0081] Table 3

[0082] Components Formaldehyde purification rate / % Example 6 96.3 Example 7 97.8 Example 8 98.7 Example 9 98.4 Example 10 97.9 Comparative Example 4 90.7 Comparative Example 5 82.6 Comparative Example 6 91.4

[0083] As can be seen from Table 3, the photocatalytic water-based coatings prepared in Examples 6 to 10 all showed excellent formaldehyde purification rates in the 24h formaldehyde purification rate test, all greater than 96%. However, the formaldehyde purification rates of the photocatalytic water-based coatings prepared in Comparative Examples 4 to 6 were reduced to varying degrees compared to Example 8. The modified TiO2 in Comparative Example 4 did not use Ce to modify TiO2, and its formaldehyde purification rate was significantly reduced. It can be seen that Ce modification effectively improved the formaldehyde purification rate of the water-based coating. The modified TiO2 in Comparative Example 5 only used Ce to modify TiO2, and did not coat the Ce-modified TiO2. Its formaldehyde purification rate was also significantly reduced. It can be seen that coating the TiO2 effectively improved the formaldehyde purification rate of the water-based coating. In the modified TiO2 in Comparative Example 6, methyl methacrylate is used instead of N-(3-dimethylaminopropyl) methacrylamide to coat the Ce-modified TiO2, and its formaldehyde purification rate is slightly improved compared with Comparative Example 5 but still significantly decreased compared with Example 8. It can be seen that coating Ce-modified TiO2 with N-(3-dimethylaminopropyl) methacrylamide can also improve the formaldehyde purification rate of photocatalyst water-based coatings.

[0084] The above is only an embodiment of the present invention and does not limit the scope of patent protection. Those skilled in the art can make non-substantial changes or substitutions based on the present invention and still fall within the scope of patent protection.

Claims

1. A photocatalyst water-based paint, characterized in that: Contains photocatalyst material modified TiO2, wherein the modified TiO2 is prepared by the following operations: Preparation of Ce-modified TiO2: Mixing anhydrous ethanol and a cerium nitrate aqueous solution to obtain a mixed solution; mixing the mixed solution with titanium tetrachloride, heating the mixture to react, and cooling the mixture after the reaction to obtain Ce-modified TiO2; wherein the heating reaction temperature is 130-180° C. and the heating reaction time is 6-10 hours; Pretreatment: Cerium-modified TiO2 was crushed into powder and then ultrasonically dispersed in ethanol to prepare a 5-10 wt% TiO2 suspension; N-(3-dimethylaminopropyl)methacrylamide was dissolved in ethanol to obtain an 8-12 wt% mixed solution; Coating reaction: Mix the TiO2 suspension prepared in the pretreatment with the mixed solution, then add the catalyst ammonium persulfate or azobisisobutyronitrile and the surfactant sodium lauryl sulfate, mix well, heat the reaction, and irradiate with ultraviolet light after the reaction is completed. The temperature reaction is specifically 60-80°C for 1.5-3.5 hours; Post-processing: After the UV lamp irradiation is completed, the product is centrifuged and dried to obtain modified TiO2.

2. The photocatalyst water-based paint according to claim 1, characterized in that: In the preparation of Ce-modified TiO2, the concentration of the cerium nitrate aqueous solution is 0.5-1.5 mol / L.

3. The photocatalyst water-based paint according to claim 1, characterized in that: In the preparation of Ce-modified TiO2, the molar ratio of cerium nitrate to titanium tetrachloride is 1-5%.

4. The photocatalyst water-based paint according to claim 1, characterized in that: During the coating reaction, the mass ratio of TiO2 to N-(3-dimethylaminopropyl)methacrylamide is controlled to be 1:50-60.

5. The photocatalyst water-based paint according to claim 1, characterized in that: During the coating reaction, the UV lamp is irradiated with a light intensity of 2-4 mW / cm 2 Irradiate with ultraviolet light for 20 to 30 minutes.

6. The photocatalyst water-based paint according to claim 1, characterized in that: In the coating reaction, the mass of the catalyst is 0.1-1% of the mass of TiO2, and the mass of the surfactant is 0.5-1% of the mass of TiO2.

7. The photocatalyst water-based paint according to claim 1, characterized in that: Contains the following components in parts by weight: 30-50 parts of water, 0.1-0.5 parts of cellulose, 1-2 parts of dispersant, 0.1-2 parts of wetting agent, 3-12 parts of modified TiO2, 10-20 parts of pigment, 20-30 parts of BASF pure acrylic emulsion, 0.1-0.4 parts of defoaming agent, 1-3 parts of thickener.

8. The method for preparing the photocatalytic water-based coating according to claim 7, characterized in that: The method comprises the following steps: quantitatively weighing water, cellulose, a dispersant, and a wetting agent, stirring the mixture evenly, adding modified TiO2 and pigment for dispersion and grinding, adding BASF pure acrylic emulsion, dispersing the mixture evenly, adding a defoamer and a thickener, and mixing the mixture evenly to prepare a photocatalyst water-based coating.

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