Micro-nano photocatalytic material modified cement-based material and preparation method thereof

Abstract

A cement-based material modified with micro / nano photocatalytic materials and its preparation method belong to the field of inorganic cementitious materials technology. The cement-based material modified with micro / nano photocatalytic materials consists of two parts: an aqueous dispersion of micro / nano photocatalytic materials and powder. The aqueous dispersion of micro / nano photocatalytic materials is composed of modified calcium sulfate whisker composite micro / nano photocatalyst, modified adhesive powder, sodium hydroxymethyl cellulose, and deionized water. The powder is composed of silicate cement, graded aggregates, and polycarboxylate superplasticizer powder. The cement-based material modified with micro / nano photocatalytic materials prepared by this invention has a wear resistance grade C, a bonding strength of 7.5~8.7 MPa, and NO... x The degradation efficiency was 94.9–98.1%, and the degradation efficiency of Rhodamine B was 93.6–97.7%. After 1 day of rainwater runoff, NO... x Degradation efficiency 94.2~97.5%, NO after abrasion resistance test x Degradation efficiency: 94.0-96.4%.

Description

A cement-based material modified with micro / nano photocatalytic materials and its preparation method Technical Field

[0001] This invention relates to a cement-based material modified with micro / nano photocatalytic materials and its preparation method, belonging to the field of inorganic cementitious materials technology. Background Technology

[0002] Vehicle exhaust fumes can affect people's health. Therefore, developing efficient, environmentally friendly materials that do not cause secondary pollution is key to effectively controlling air pollution.

[0003] As a commonly used engineering material, cement-based materials are gradually developing towards high performance and multifunctionality, such as thermal insulation, lightweight and high strength, and environmental friendliness. Currently, developing cement-based materials that possess excellent construction performance, mechanical properties, and durability, while also being able to photocatalytically oxidize atmospheric pollutants, is a current research hotspot. In recent years, researchers have prepared TiO2-modified cement-based materials by adding TiO2 powder to the surface or interior of cement, mortar, or concrete through spraying, impregnation, and mixing; confirming its effectiveness in reducing NO2 emissions. x It exhibits good photocatalytic degradation effects on harmful gases such as formaldehyde and toluene, as well as pollutants such as Rhodamine B, malachite green, and 3-nitrobenzenesulfonic acid. TXActive TiO2 photocatalytic cement, produced by the Italian cement company Italcement, has been applied to building surfaces. Fujita Corporation and others in Japan have developed TiO2 photocatalytic cement; spraying this cement onto roads can reduce NOx emissions from vehicle exhaust. x pollute.

[0004] However, cement-based materials with photocatalytic properties still face problems such as low catalyst utilization, low catalytic efficiency, and short-lasting catalytic function. There are two main methods for loading TiO2 nanoparticles into cement-based materials: blending and coating. Blending involves mixing TiO2 with concrete raw materials to achieve a uniform distribution of TiO2 within the concrete, and it is the simplest and most direct method. This method fully utilizes the structural advantages of concrete itself, contributing to improved photocatalytic efficiency. However, since the photocatalytic reaction occurs on the material surface, it is difficult for the internal TiO2 to contact the light source and nitrogen oxides, resulting in wasted photocatalyst. Therefore, blending is an effective but inefficient application method. Coating involves dispersing TiO2 nanoparticles in water or organic coatings, and then applying the mixture to the concrete surface to form a photocatalytic functional coating. When the dispersion is water, the bonding force between the TiO2 nanoparticles and the concrete surface is weak, and the coating is prone to cracking and peeling. Organic coatings can provide sufficient adhesion for the TiO2 loaded onto the concrete surface, but the coating encapsulates or buries most of the TiO2, leading to excessively low catalytic efficiency. Besides the issues of low photocatalyst utilization or low catalytic efficiency, the TiO2 introduced through the above two methods is prone to detachment under the wear and tear of vehicle loads, leading to NO... x The removal efficiency is reduced, and the photocatalytic function is poorly maintained.

[0005] Chinese patent CN103833285A discloses a high-strength photocatalytic cement-based composite slurry, comprising a photocatalyst composite, cement, aggregate, active admixture, polymer additives, fiber, water-reducing agent, and water. The photocatalyst composite is composed of modified rare earth elements co-doped with nitrogen (TiO2), activated carbon, and conductive filler. This patent uses a blending method to prepare the photocatalytic cement-based composite slurry. While this yields a cement-based composite slurry with good photocatalytic performance and effective pollutant degradation, it suffers from the drawback of wasted photocatalyst because the photocatalytic reaction occurs on the material surface, making it difficult for the internal TiO2 to contact the light source and nitrogen oxides.

[0006] Chinese patent CN112573882A discloses a boron-carbon-nitrogen-containing photocatalytic cement mortar and its preparation method. The photocatalytic cement mortar comprises the following raw materials by weight: 4-10 parts cement, 10-35 parts manufactured sand, 0.004-0.02 parts boron, carbon, and nitrogen, 0.005-0.014 parts nano-montmorillonite, and 2-6 parts deionized water. The preparation method includes the following steps: Step 1: preparing a film-coating solution; Step 2: applying a film to the surface of the manufactured sand; Step 3: preparing a solid mixture; Step 4: preparing a boron, carbon, and nitrogen dispersion; Step 5: preparing the photocatalytic cement mortar. This invention uses three-dimensional layered porous boron, carbon, and nitrogen as the nano-photocatalytic material for cement mortar, which can significantly improve the efficiency of pollutant degradation under visible light irradiation. By adding boron, carbon, and nitrogen separately to cement and water, the dispersibility of boron, carbon, and nitrogen in the cement mortar is improved, ensuring the effect of photocatalytic pollutant degradation. However, this patent still uses a blending method to prepare the boron, carbon, and nitrogen-containing photocatalytic cement mortar, which inevitably leads to the drawback of wasting photocatalyst.

[0007] Chinese patent CN104909633A discloses a method for preparing polymer cement mortar using TiO2 and fly ash composite photocatalytic materials, employing a sol-gel method. TiO2 was prepared by gelation and loaded onto cleaned fly ash microspheres. The resulting composite microspheres were obtained by heat treatment at 550℃. A polymer cement mortar was then prepared by mixing cement, water, sand, water-reducing agent, and the composite microspheres in a specific ratio. This invention features a simple production process. By incorporating the composite microspheres into cement as a mixing material, it solves the environmental pollution problem caused by fly ash, reduces cement energy consumption, and alters various properties of cement-based composite materials, giving traditional cement-based materials certain electrical conductivity, electromagnetic properties, and better wave absorption and mechanical properties. Its application in road materials can achieve secondary purification of vehicle exhaust emissions. However, the polymer cement mortar prepared using this patented TiO2 and fly ash composite photocatalytic material exhibits relatively low photocatalytic efficiency, reaching a maximum of only 66.5%. Furthermore, this patent also uses a mixing method, thus still incurring the drawback of wasting photocatalyst.

[0008] As can be seen from the above, the current cement-based materials with photocatalytic functions prepared based on photocatalytic materials still have significant problems such as low catalyst utilization, low catalytic efficiency, and short-lasting catalytic function. Therefore, developing cement-based materials with high photocatalytic efficiency, long-lasting catalytic function, and high catalyst utilization is of great significance for promoting the development of environmentally friendly cement-based materials, and can also play a positive role in the treatment of air pollution. Summary of the Invention

[0009] To address the shortcomings of the existing technologies, this invention provides a cement-based material modified with micro / nano photocatalytic materials and its preparation method, achieving the following objectives: to modify cement-based materials using micro / nano photocatalytic materials in order to prepare cement-based materials with high photocatalytic efficiency, long-lasting photocatalytic function, and high photocatalyst utilization.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0011] A cement-based material modified with micro-nano photocatalytic materials and its preparation method are disclosed. The cement-based material modified with micro-nano photocatalytic materials consists of two parts: an aqueous dispersion of micro-nano photocatalytic materials and powder. The aqueous dispersion of micro-nano photocatalytic materials and powder are mixed evenly at a mass ratio of 15~25:20 before use.

[0012] The specific formulation of the aqueous dispersion of the micro / nano photocatalytic material is as follows, by weight:

[0013] 100-160 parts of modified calcium sulfate whisker composite micro / nano photocatalyst

[0014] 25-65 parts of modified rubber powder

[0015] Sodium carboxymethyl cellulose 1-2.5 parts

[0016] 250-400 parts deionized water;

[0017] The specific formula of the powder is as follows, in parts by weight:

[0018] 80-180 parts of silicate cement

[0019] Graded aggregate 60~130 parts

[0020] 1-6 parts of polycarboxylate superplasticizer powder;

[0021] The graded aggregate is sea sand that meets the gradation standards, which are: 100 wt% passing through a 2.36 mm sieve, 80-90 wt% passing through a 1.18 mm sieve, and 60-75 wt% passing through a 0.6 mm sieve.

[0022] The following are further improvements to the above technical solution:

[0023] Step 1: Preparation of micro / nano photocatalysts

[0024] There are two methods for preparing micro / nano photocatalysts: silica coating and aluminum hydroxide coating.

[0025] The silica coating method is specifically operated as follows: nano-titanium dioxide, micron-sized bismuth tungstate, and deionized water are added to a high-speed dispersion vessel and stirred vigorously to form a stable suspension. Then, sodium metasilicate aqueous solution is added under low-speed stirring. The temperature is then raised and kept constant to the reaction temperature. Next, sulfuric acid aqueous solution is added to adjust the pH value of the reaction system to 10-11. After the reaction is complete, the reaction temperature is maintained and the system is allowed to stand and mature completely. Then, the system is cooled to room temperature and filtered. The filtered solid is washed and dried to obtain micro-nano photocatalysts.

[0026] The nano-titanium dioxide is anatase type with a particle size of 10~100nm;

[0027] The particle size of the micron-sized bismuth tungstate is 0.3~2μm;

[0028] The sodium metasilicate aqueous solution contains 15-25 wt% sodium metasilicate.

[0029] The mass ratio of nano-titanium dioxide, micron-sized bismuth tungstate, deionized water, and sodium metasilicate aqueous solution is 10~45:15~80:100~180:60~110;

[0030] The sulfuric acid aqueous solution contains 10-20 wt% sulfuric acid.

[0031] The high-intensity stirring has a stirring speed of 4000~8000 rpm;

[0032] The low-speed stirring has a stirring rate of 1000~2000 rpm;

[0033] The reaction temperature is 60~80℃;

[0034] After the reaction is complete, the reaction time is 6 to 10 hours;

[0035] The constant temperature standing curing process takes 1 to 2.5 hours.

[0036] The washing process involves washing the filtered solid with deionized water until the pH of the washing solution is neutral.

[0037] The drying process involves a drying temperature of 80-95℃ and a drying time of 15-20 hours.

[0038] The aluminum hydroxide coating method is specifically operated as follows: nano-titanium dioxide, micron-sized bismuth tungstate, and aluminum nitrate aqueous solution are added to a high-speed dispersion vessel, and after being vigorously stirred into a stable suspension, the temperature is raised and kept constant under vigorous stirring until the reaction temperature is reached. Then, urea is added to maintain the pH value of the reaction system at 5-6. After the reaction is complete, the temperature is lowered to room temperature and filtered. The filtered solid is washed and dried to obtain micro-nano photocatalyst.

[0039] The nano-titanium dioxide is anatase type with a particle size of 10~100nm;

[0040] The particle size of the micron-sized bismuth tungstate is 0.3~2μm;

[0041] The aluminum nitrate aqueous solution contains 20-35 wt% aluminum nitrate.

[0042] The mass ratio of nano-titanium dioxide, micron-sized bismuth tungstate, and aluminum nitrate aqueous solution is 20~60:25~70:160~280;

[0043] The high-intensity stirring has a stirring speed of 5500~9000 rpm;

[0044] The reaction temperature is 70~85℃;

[0045] After the reaction is complete, the reaction time is 4 to 7 hours;

[0046] The washing process involves washing the filtered solid with deionized water until the pH of the washing solution is neutral.

[0047] The drying process involves a drying temperature of 80-95℃ and a drying time of 15-20 hours.

[0048] Step 2: Preparation of modified calcium sulfate whisker composite micro / nano photocatalyst

[0049] After thoroughly drying the calcium sulfate whiskers, add them to a reaction vessel, then add polyethylene glycol octylphenyl ether and toluene. After vigorous stirring and uniform dispersion, heat and maintain the temperature to the reaction temperature. Under low-speed stirring, add 3-isocyanate-propyltrimethoxysilane. After sufficient reaction, a modified calcium sulfate whisker dispersion is obtained. Add the micro / nano photocatalyst obtained in step 1, polyethylene glycol octylphenyl ether, and toluene to a high-speed dispersion vessel. After high-speed uniform dispersion, a micro / nano photocatalyst dispersion is obtained. Then, add the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion. Continue to stir at a constant temperature and low speed until the reaction is complete. After cooling to room temperature, filter. After drying the filtered solid to remove residual toluene, a modified calcium sulfate whisker composite micro / nano photocatalyst is obtained.

[0050] The calcium sulfate whiskers have a length of 10~100μm and a diameter of 0.2~2μm;

[0051] The mass ratio of the calcium sulfate whiskers, polyethylene glycol octylphenyl ether, toluene, and 3-isocyanate-propyltrimethoxysilane is 80~150:2~8:190~350:8~30;

[0052] After thorough drying, the drying temperature is 100~120℃ and the drying time is 6~10 hours;

[0053] The high-intensity stirring and dispersion is carried out at a stirring rate of 1500~3000 rpm for 5~8 hours.

[0054] The reaction temperature is 55~80℃;

[0055] The low-speed stirring has a stirring rate of 600~1000 rpm;

[0056] After the reaction is complete, the reaction time is 6 to 9 hours;

[0057] The mass ratio of the micro / nano photocatalyst, polyethylene glycol octylphenyl ether, and toluene is 90~190:3~9:150~250;

[0058] The high-speed dispersion is uniform, with a dispersion rate of 6000~10000 rpm and a dispersion time of 6~9 hours;

[0059] The mass ratio of the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion is 6~12:17;

[0060] The reaction was carried out under constant temperature and low speed stirring until complete. The reaction temperature was 55~80℃, the stirring speed was 600~1000 rpm, and the reaction time was 5~10 hours.

[0061] The drying process removes residual toluene at a temperature of 60-80°C for 11-20 hours.

[0062] Step 3: Preparation of modified adhesive powder

[0063] Add the adhesive powder and deionized water to the reaction vessel, stir vigorously until uniform, then reduce the stirring speed to low, then heat and maintain the temperature to the reaction temperature. Add the water-soluble oxidant and trifluoroacetic acid, stir at low speed until the reaction is complete, then filter the material. The filtered solid is washed and dried to obtain the surface-oxidized adhesive powder. Then, use the silica coating method or aluminum hydroxide coating method described in step 1 to coat the surface-oxidized adhesive powder. Specifically, replace all the nano-titanium dioxide and micron-sized bismuth tungstate in step 1 with the surface-oxidized adhesive powder in equal amounts. Other operations are the same as in step 1 to prepare the modified adhesive powder.

[0064] The particle size of the adhesive powder is 50~200 mesh;

[0065] The water-soluble oxidant is one of hydrogen peroxide, calcium peroxide, and sodium ferrate.

[0066] The vigorous stirring and mixing is carried out at a stirring rate of 2000~5000 rpm;

[0067] The low-speed stirring has a stirring rate of 600~1200 rpm;

[0068] The reaction temperature is 50~70℃;

[0069] The low-speed stirring reaction is complete, and the reaction time is 6-11 hours;

[0070] The washing process involves washing the filtered solids with deionized water until the pH of the washing solution is neutral.

[0071] The drying process involves a drying temperature of 80-90℃ and a drying time of 10-18 hours.

[0072] Step 4: Preparation of aqueous dispersion of micro / nano photocatalytic materials

[0073] According to the specific formula of the aqueous dispersion of micro-nano photocatalytic materials by weight, firstly, deionized water and sodium hydroxymethyl cellulose are placed in a high-speed dispersion vessel and dispersed at a dispersion rate of 3500~6500 rpm to form a uniform and stable solution. Then, the dispersion rate is increased to 8000~12000 rpm, and modified calcium sulfate whisker composite micro-nano photocatalyst is added. After dispersing for 5~9 hours, modified adhesive powder is added, and dispersion is continued for 1.5~4 hours. The material is then discharged to obtain the aqueous dispersion of micro-nano photocatalytic materials.

[0074] Step 5: Preparation of powder

[0075] According to the specific formula of cement-based material powder modified by micro-nano photocatalytic materials by weight, silicate cement, graded aggregate, and polycarboxylate superplasticizer powder are put into a high-speed mixer, and the stirring speed is controlled at 130~170 rpm. After stirring and mixing for 50~80 minutes, the material is discharged to obtain cement-based material powder modified by micro-nano photocatalytic materials.

[0076] Compared with the prior art, the present invention achieves the following beneficial effects:

[0077] 1. The photocatalytic nano-titanium dioxide and micron-sized bismuth tungstate used in this invention present two major problems when incorporated into cement-based materials. First, both nano-titanium dioxide and micron-sized bismuth tungstate are prone to agglomeration, especially nano-titanium dioxide, which is more likely to agglomerate due to its very large specific surface area. Therefore, ensuring that these two particles can be well and uniformly dispersed in the cement-based material matrix is ​​the key issue to be addressed. Second, due to its huge specific surface area, nano-titanium dioxide is prone to undergo hydration reaction with cement particles, which leads to the loss of its photocatalytic effect. Micron-sized bismuth tungstate also has the above-mentioned problems to some extent. To address the two prominent issues mentioned above, this invention first coats nano-titanium dioxide and micron-sized bismuth tungstate with silica or aluminum hydroxide, and then reacts them with surface-modified calcium sulfate whiskers through a surface chemical adsorption reaction. During this adsorption reaction, nano-titanium dioxide and micron-sized bismuth tungstate are uniformly adsorbed onto the surface of the surface-modified calcium sulfate whiskers. The relatively large size of the calcium sulfate whiskers facilitates uniform dispersion. Subsequently, as the calcium sulfate whiskers become uniformly dispersed, the nano-titanium dioxide and micron-sized bismuth tungstate are also well dispersed. The specific chemical reactions occurring in the above process are described in detail below: Under the dispersing action of the dispersant polyethylene glycol octylphenyl ether, the calcium sulfate whiskers are first uniformly dispersed in toluene solvent through a vigorous stirring dispersion process. Then, the hydroxyl groups on the surface of the calcium sulfate whiskers react with 3-isocyanate-propyltrimethoxysilane. After the reaction is complete, the sulfuric acid... Calcium whiskers are covered with methoxysilane functional groups and isocyanate groups. Meanwhile, the silica or aluminum hydroxide coatings on the surfaces of nano-titanium dioxide and micron-sized bismuth tungstate have a large number of active hydroxyl groups. These active hydroxyl groups react chemically with the methoxysilane functional groups and isocyanate groups on the surface of calcium sulfate whiskers. During the reaction, nano-titanium dioxide and micron-sized bismuth tungstate are driven by both chemical adsorption and chemical reaction forces, and approach and adhere to the surface of calcium sulfate whiskers in a relatively controllable and orderly manner. At the microscopic level, this process can be considered to have a certain degree of autonomous assembly behavior. In this way, nano-titanium dioxide and micron-sized bismuth tungstate are uniformly distributed on the surface of calcium sulfate whiskers by chemical bonding, and are well dispersed along with the uniform dispersion of calcium sulfate whiskers. The problem of easy agglomeration and difficulty in dispersion of nano-titanium dioxide and micron-sized bismuth tungstate is solved. After nano-titanium dioxide and micron-sized bismuth tungstate are coated with silica or aluminum hydroxide, the silica or aluminum hydroxide on the surface has very high reactivity during the subsequent hydration reaction of cement particles. The silica or aluminum hydroxide will preferentially react with cement particles in the hydration reaction, which protects the nano-titanium dioxide and micron-sized bismuth tungstate and prevents them from losing their photocatalytic properties.Furthermore, during the curing process of cement-based materials, the nano-titanium dioxide and micron-sized bismuth tungstate chemically bonded to the surface of calcium sulfate whiskers eventually undergo a chemical bonding reaction with the cement-based material. This dual chemical bonding effect (i.e., the nano-titanium dioxide and micron-sized bismuth tungstate are chemically bonded to the calcium sulfate whiskers, and the nano-titanium dioxide and micron-sized bismuth tungstate are chemically bonded to the cement matrix through surface silica or aluminum hydroxide) allows the calcium sulfate whiskers to achieve a chemical doping-like strengthening and toughening effect on the cement-based material. This effect is more pronounced than simple physical doping. Therefore, the cement-based material modified with the micro / nano photocatalytic material obtained in this invention exhibits better wear resistance, bonding strength, rain erosion resistance, and durability.

[0078] 2. The cement-based material modified with the micro / nano photocatalytic material prepared in this invention is applied to the existing concrete substrate in the form of a cement coating using a spraying process. This can improve the utilization rate of the photocatalyst, but it also has the problem of poor adhesion strength between the coating and the concrete substrate, and stress concentration at the bonding interface leading to brittle debonding. The above-mentioned addition of calcium sulfate whiskers to strengthen and toughen the coating can alleviate the problem of brittle debonding of the cement coating to a certain extent. In order to better solve the above problems, this invention introduces adhesive powder. This elastic material has a buffering effect and can effectively buffer or release the interfacial stress between the cement coating and the concrete substrate, preventing brittle debonding or even brittle cracks. However, the adhesive powder has weak surface polarity and is difficult to be uniformly dispersed in the cement-based material. Therefore, this invention first performs oxidative etching on the surface of the adhesive powder, specifically using water-soluble oxidants such as hydrogen peroxide, calcium peroxide, and sodium ferrate. At the same time, in order to enhance the etching degree and oxidation... To improve efficiency, a small amount of corrosive trifluoroacetic acid was added to promote the surface etching rate and surface oxidation reaction rate of the adhesive powder. After surface oxidation, a large number of active hydroxyl groups appeared on the surface of the adhesive powder. Then, taking advantage of the property that these active hydroxyl groups can adsorb active silica or aluminum hydroxide gel, the adhesive powder was coated with silica or aluminum hydroxide. The coated adhesive powder became more polar and could be well dispersed in cement-based materials. In addition, the silica or aluminum hydroxide coated on the surface of the adhesive powder could undergo a hydration reaction with cement particles. The adhesive powder was finally dispersed in the cement-based material matrix in a chemical bond with the cement-based material. In this way, the adhesive powder and the finally cured cement coating adhered to the surface of the cement concrete substrate as a whole. The internal stress at the interface between the cement coating and the substrate surface and the external stress from the external environment were more easily buffered and released, thereby avoiding brittle debonding or even brittle cracks.

[0079] 3. The cement-based material modified with the micro / nano photocatalytic material prepared in this invention has a wear resistance grade C, a bonding strength of 7.5~8.7 MPa, and NO... xThe degradation efficiency was 94.9–98.1%, and the degradation efficiency of Rhodamine B was 93.6–97.7%. After 1 day of rainwater runoff, NO... x Degradation efficiency 94.2~97.5%, NO after abrasion resistance test x Degradation efficiency: 94.0-96.4%. Detailed Implementation

[0080] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0081] Example 1: A method for preparing cement-based materials modified with micro / nano photocatalytic materials

[0082] Step 1: Preparation of micro / nano photocatalysts

[0083] The preparation method of micro / nano photocatalysts is silica coating method;

[0084] The silica coating method is specifically operated as follows: nano-titanium dioxide, micron-sized bismuth tungstate, and deionized water are added to a high-speed dispersion vessel and stirred vigorously to form a stable suspension. Then, sodium metasilicate aqueous solution is added under low-speed stirring. The temperature is then raised and kept constant to the reaction temperature. Next, sulfuric acid aqueous solution is added to adjust the pH of the reaction system to 10.6. After the reaction is complete, the reaction temperature is maintained and the system is allowed to stand and mature completely. Then, the system is cooled to room temperature and filtered. The filtered solid is washed and dried to obtain micro-nano photocatalysts.

[0085] The nano-titanium dioxide is anatase type with a particle size of 50 nm.

[0086] The particle size of the micron-sized bismuth tungstate is 1 μm;

[0087] The sodium metasilicate aqueous solution contains 20 wt% sodium metasilicate.

[0088] The mass ratio of nano-titanium dioxide, micron-sized bismuth tungstate, deionized water, and sodium metasilicate aqueous solution is 30:60:150:90.

[0089] The sulfuric acid aqueous solution contains 16 wt% sulfuric acid.

[0090] The powerful stirring has a stirring speed of 7000 rpm;

[0091] The low-speed stirring has a stirring rate of 1600 rpm;

[0092] The reaction temperature is 75°C;

[0093] After the reaction is complete, the reaction time is 9 hours;

[0094] The constant temperature standing curing process takes 2 hours.

[0095] The washing process involves washing the filtered solid with deionized water until the pH of the washing solution is neutral.

[0096] The drying process involves a drying temperature of 90°C and a drying time of 18 hours.

[0097] Step 2: Preparation of modified calcium sulfate whisker composite micro / nano photocatalyst

[0098] After thoroughly drying the calcium sulfate whiskers, add them to a reaction vessel, then add polyethylene glycol octylphenyl ether and toluene. After vigorous stirring and uniform dispersion, heat and maintain the temperature to the reaction temperature. Under low-speed stirring, add 3-isocyanate-propyltrimethoxysilane. After sufficient reaction, a modified calcium sulfate whisker dispersion is obtained. Add the micro / nano photocatalyst obtained in step 1, polyethylene glycol octylphenyl ether, and toluene to a high-speed dispersion vessel. After high-speed uniform dispersion, a micro / nano photocatalyst dispersion is obtained. Then, add the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion. Continue to stir at a constant temperature and low speed until the reaction is complete. After cooling to room temperature, filter. After drying the filtered solid to remove residual toluene, a modified calcium sulfate whisker composite micro / nano photocatalyst is obtained.

[0099] The calcium sulfate whiskers are 40 μm long and 1 μm in diameter;

[0100] The mass ratio of the calcium sulfate whiskers, polyethylene glycol octylphenyl ether, toluene, and 3-isocyanate-propyltrimethoxysilane is 120:5:260:15.

[0101] After thorough drying, the drying temperature is 110℃ and the drying time is 7 hours;

[0102] The high-intensity stirring and dispersion is carried out at a stirring rate of 1800 rpm for 7 hours.

[0103] The reaction temperature is 65°C;

[0104] The low-speed stirring has a stirring rate of 900 rpm;

[0105] After the reaction is complete, the reaction time is 7 hours;

[0106] The mass ratio of the micro / nano photocatalyst, polyethylene glycol octylphenyl ether, and toluene is 130:7:190;

[0107] The high-speed dispersion is uniform, with a dispersion rate of 9000 rpm and a dispersion time of 7 hours;

[0108] The mass ratio of the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion is 11:17.

[0109] The reaction was carried out under constant temperature and low speed stirring until complete. The reaction temperature was 65℃, the stirring speed was 900 rpm, and the reaction time was 8 hours.

[0110] The drying process removes residual toluene at a temperature of 75°C for 17 hours.

[0111] Step 3: Preparation of modified adhesive powder

[0112] Add the adhesive powder and deionized water to the reaction vessel, stir vigorously until uniform, then reduce the stirring speed to low, then heat and maintain the temperature to the reaction temperature. Add the water-soluble oxidant and trifluoroacetic acid, stir at low speed until the reaction is complete, then filter the material. The filtered solid is washed and dried to obtain the surface-oxidized adhesive powder. Then, use the silica coating method described in step 1 to coat the surface-oxidized adhesive powder. Specifically, replace all 30 parts of nano titanium dioxide and 60 parts of micron-sized bismuth tungstate in step 1 with 90 parts of surface-oxidized adhesive powder. Other operations are the same as in step 1 to prepare the modified adhesive powder.

[0113] The particle size of the adhesive powder is 100 mesh;

[0114] The water-soluble oxidant is hydrogen peroxide;

[0115] The vigorous stirring and mixing is carried out at a stirring rate of 4000 rpm;

[0116] The low-speed stirring has a stirring rate of 1000 rpm;

[0117] The reaction temperature is 65°C;

[0118] The low-speed stirring reaction was completed within 7 hours.

[0119] The washing process involves washing the filtered solids with deionized water until the pH of the washing solution is neutral.

[0120] The drying process was carried out at a temperature of 88°C for 14 hours.

[0121] Step 4: Preparation of aqueous dispersion of micro / nano photocatalytic materials

[0122] The specific formulation of the aqueous dispersion of the micro / nano photocatalytic material is as follows, by weight:

[0123] 150 parts of modified calcium sulfate whisker composite micro / nano photocatalyst

[0124] 50 parts of modified rubber powder

[0125] 2 parts sodium hydroxymethyl cellulose

[0126] 300 parts deionized water;

[0127] According to the specific formula of the aqueous dispersion of micro-nano photocatalytic materials by weight, deionized water and sodium hydroxymethyl cellulose are first placed in a high-speed dispersion vessel and dispersed at a dispersion rate of 5500 rpm to form a uniform and stable solution. Then, the dispersion rate is increased to 9000 rpm, and modified calcium sulfate whisker composite micro-nano photocatalyst is added. After dispersing for 8 hours, modified adhesive powder is added, and dispersion is continued for 3 hours. The material is then discharged to obtain the aqueous dispersion of micro-nano photocatalytic materials.

[0128] Step 5: Preparation of powder

[0129] The specific formula of the powder is as follows, in parts by weight:

[0130] 110 parts of silicate cement

[0131] 80 parts of graded aggregate

[0132] 4 parts of polycarboxylate superplasticizer powder;

[0133] The graded aggregate is sea sand that meets the gradation standard, which is: 100 wt% passing through a 2.36 mm sieve, 84 wt% passing through a 1.18 mm sieve, and 70 wt% passing through a 0.6 mm sieve.

[0134] According to the specific formula of cement-based material powder modified by micro-nano photocatalytic materials by weight, silicate cement, graded aggregate, and polycarboxylate superplasticizer powder are put into a high-speed mixer, the stirring speed is controlled at 150 rpm, and the mixture is stirred for 70 minutes before being discharged to obtain cement-based material powder modified by micro-nano photocatalytic materials.

[0135] Example 2: A method for preparing cement-based materials modified with micro / nano photocatalytic materials

[0136] Step 1: Preparation of micro / nano photocatalysts

[0137] The preparation method of micro / nano photocatalysts is silica coating method;

[0138] The silica coating method is specifically operated as follows: nano-titanium dioxide, micron-sized bismuth tungstate, and deionized water are added to a high-speed dispersion vessel and stirred vigorously to form a stable suspension. Then, sodium metasilicate aqueous solution is added under low-speed stirring. The temperature is then raised and kept constant to the reaction temperature. Next, sulfuric acid aqueous solution is added to adjust the pH of the reaction system to 10. After the reaction is complete, the reaction temperature is maintained and the system is allowed to stand and mature completely. Then, the system is cooled to room temperature and filtered. The filtered solid is washed and dried to obtain micro-nano photocatalysts.

[0139] The nano-titanium dioxide is anatase type with a particle size of 10 nm.

[0140] The micron-sized bismuth tungstate has a particle size of 0.3 μm;

[0141] The sodium metasilicate aqueous solution contains 15 wt% sodium metasilicate.

[0142] The mass ratio of nano-titanium dioxide, micron-sized bismuth tungstate, deionized water, and sodium metasilicate aqueous solution is 10:15:100:60.

[0143] The sulfuric acid aqueous solution contains 10 wt% sulfuric acid.

[0144] The powerful stirring has a stirring speed of 4000 rpm;

[0145] The low-speed stirring has a stirring rate of 1000 rpm;

[0146] The reaction temperature is 60°C;

[0147] After the reaction is complete, the reaction time is 6 hours;

[0148] The constant temperature static curing process takes 1 hour.

[0149] The washing process involves washing the filtered solid with deionized water until the pH of the washing solution is neutral.

[0150] The drying process involves a drying temperature of 80°C and a drying time of 15 hours.

[0151] Step 2: Preparation of modified calcium sulfate whisker composite micro / nano photocatalyst

[0152] After thoroughly drying the calcium sulfate whiskers, add them to a reaction vessel, then add polyethylene glycol octylphenyl ether and toluene. After vigorous stirring and uniform dispersion, heat and maintain the temperature to the reaction temperature. Under low-speed stirring, add 3-isocyanate-propyltrimethoxysilane. After sufficient reaction, a modified calcium sulfate whisker dispersion is obtained. Add the micro / nano photocatalyst obtained in step 1, polyethylene glycol octylphenyl ether, and toluene to a high-speed dispersion vessel. After high-speed uniform dispersion, a micro / nano photocatalyst dispersion is obtained. Then, add the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion. Continue to stir at a constant temperature and low speed until the reaction is complete. After cooling to room temperature, filter. After drying the filtered solid to remove residual toluene, a modified calcium sulfate whisker composite micro / nano photocatalyst is obtained.

[0153] The calcium sulfate whiskers are 10 μm long and 0.2 μm in diameter;

[0154] The mass ratio of the calcium sulfate whiskers, polyethylene glycol octylphenyl ether, toluene, and 3-isocyanate-propyltrimethoxysilane is 80:2:190:8;

[0155] After thorough drying, the drying temperature is 100℃ and the drying time is 6 hours;

[0156] The high-intensity stirring and dispersion is carried out at a stirring rate of 1500 rpm for 5 hours.

[0157] The reaction temperature is 55°C;

[0158] The low-speed stirring has a stirring rate of 600 rpm;

[0159] After the reaction is complete, the reaction time is 6 hours;

[0160] The mass ratio of the micro / nano photocatalyst, polyethylene glycol octylphenyl ether, and toluene is 90:3:150.

[0161] The high-speed dispersion is uniform, with a dispersion rate of 6000 rpm and a dispersion time of 6 hours;

[0162] The mass ratio of the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion is 6:17.

[0163] The reaction was carried out under constant temperature and low speed stirring until complete. The reaction temperature was 55℃, the stirring speed was 600 rpm, and the reaction time was 5 hours.

[0164] The drying process removes residual toluene at a temperature of 60°C for 11 hours.

[0165] Step 3: Preparation of modified adhesive powder

[0166] Add the adhesive powder and deionized water to the reaction vessel, stir vigorously until uniform, then reduce the stirring speed to low, then heat and maintain the temperature to the reaction temperature. Add the water-soluble oxidant and trifluoroacetic acid, stir at low speed until the reaction is complete, then filter the material. The filtered solid is washed and dried to obtain the surface-oxidized adhesive powder. Then, use the silica coating method described in step 1 to coat the surface-oxidized adhesive powder. Specifically, replace all 10 parts of nano titanium dioxide and 15 parts of micron-sized bismuth tungstate in step 1 with 25 parts of surface-oxidized adhesive powder. Other operations are the same as in step 1 to prepare the modified adhesive powder.

[0167] The particle size of the adhesive powder is 50 mesh;

[0168] The water-soluble oxidant is calcium peroxide;

[0169] The vigorous stirring and mixing is carried out at a stirring rate of 2000 rpm;

[0170] The low-speed stirring has a stirring rate of 600 rpm;

[0171] The reaction temperature is 50°C;

[0172] The low-speed stirring reaction was completed within 6 hours;

[0173] The washing process involves washing the filtered solids with deionized water until the pH of the washing solution is neutral.

[0174] The drying process involves a drying temperature of 80°C and a drying time of 10 hours.

[0175] Step 4: Preparation of aqueous dispersion of micro / nano photocatalytic materials

[0176] The specific formulation of the aqueous dispersion of the micro / nano photocatalytic material is as follows, by weight:

[0177] 100 parts of modified calcium sulfate whisker composite micro / nano photocatalyst

[0178] 25 parts of modified adhesive powder

[0179] 1 part sodium carboxymethyl cellulose

[0180] 250 parts deionized water;

[0181] According to the specific formula of the aqueous dispersion of micro-nano photocatalytic materials by weight, deionized water and sodium hydroxymethyl cellulose are first placed in a high-speed dispersion vessel and dispersed at a dispersion rate of 3500 rpm to form a uniform and stable solution. Then, the dispersion rate is increased to 8000 rpm, and modified calcium sulfate whisker composite micro-nano photocatalyst is added. After dispersing for 5 hours, modified adhesive powder is added, and dispersion is continued for 1.5 hours. The material is then discharged to obtain the aqueous dispersion of micro-nano photocatalytic materials.

[0182] Step 5: Preparation of powder

[0183] The specific formula of the powder is as follows, in parts by weight:

[0184] 80 parts of silicate cement

[0185] 60 parts of graded aggregate

[0186] 1 part of polycarboxylate superplasticizer powder;

[0187] The graded aggregate is sea sand that meets the gradation standard, which is: 100 wt% passing through a 2.36 mm sieve, 80 wt% passing through a 1.18 mm sieve, and 60 wt% passing through a 0.6 mm sieve.

[0188] According to the specific formula of cement-based material powder modified by micro-nano photocatalytic materials by weight, silicate cement, graded aggregate, and polycarboxylate superplasticizer powder are put into a high-speed mixer, the stirring speed is controlled at 130 rpm, and the mixture is stirred for 50 minutes before being discharged to obtain cement-based material powder modified by micro-nano photocatalytic materials.

[0189] Example 3: A method for preparing cement-based materials modified with micro / nano photocatalytic materials

[0190] Step 1: Preparation of micro / nano photocatalysts

[0191] The preparation method of micro / nano photocatalysts is silica coating method;

[0192] The silica coating method is specifically operated as follows: nano-titanium dioxide, micron-sized bismuth tungstate, and deionized water are added to a high-speed dispersion vessel and stirred vigorously to form a stable suspension. Then, sodium metasilicate aqueous solution is added under low-speed stirring. The temperature is then raised and kept constant to the reaction temperature. Next, sulfuric acid aqueous solution is added to adjust the pH value of the reaction system to 11. After the reaction is complete, the reaction temperature is maintained and the system is allowed to stand and mature completely. Then, the system is cooled to room temperature and filtered. The filtered solid is washed and dried to obtain micro-nano photocatalysts.

[0193] The nano-titanium dioxide is anatase type with a particle size of 100 nm.

[0194] The particle size of the micron-sized bismuth tungstate is 2 μm;

[0195] The sodium metasilicate aqueous solution contains 25 wt% sodium metasilicate.

[0196] The mass ratio of nano-titanium dioxide, micron-sized bismuth tungstate, deionized water, and sodium metasilicate aqueous solution is 45:80:180:110.

[0197] The sulfuric acid aqueous solution contains 20 wt% sulfuric acid.

[0198] The powerful stirring has a stirring speed of 8000 rpm;

[0199] The low-speed stirring has a stirring rate of 2000 rpm;

[0200] The reaction temperature is 80°C;

[0201] After the reaction is complete, the reaction time is 10 hours;

[0202] The constant temperature static curing process takes 2.5 hours.

[0203] The washing process involves washing the filtered solid with deionized water until the pH of the washing solution is neutral.

[0204] The drying process involves a drying temperature of 95°C and a drying time of 20 hours.

[0205] Step 2: Preparation of modified calcium sulfate whisker composite micro / nano photocatalyst

[0206] After thoroughly drying the calcium sulfate whiskers, add them to a reaction vessel, then add polyethylene glycol octylphenyl ether and toluene. After vigorous stirring and uniform dispersion, heat and maintain the temperature to the reaction temperature. Under low-speed stirring, add 3-isocyanate-propyltrimethoxysilane. After sufficient reaction, a modified calcium sulfate whisker dispersion is obtained. Add the micro / nano photocatalyst obtained in step 1, polyethylene glycol octylphenyl ether, and toluene to a high-speed dispersion vessel. After high-speed uniform dispersion, a micro / nano photocatalyst dispersion is obtained. Then, add the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion. Continue to stir at a constant temperature and low speed until the reaction is complete. After cooling to room temperature, filter. After drying the filtered solid to remove residual toluene, a modified calcium sulfate whisker composite micro / nano photocatalyst is obtained.

[0207] The calcium sulfate whiskers are 100 μm long and 2 μm in diameter;

[0208] The mass ratio of the calcium sulfate whiskers, polyethylene glycol octylphenyl ether, toluene, and 3-isocyanate-propyltrimethoxysilane is 150:8:350:30.

[0209] After thorough drying, the drying temperature is 120℃ and the drying time is 10 hours;

[0210] The high-intensity stirring and dispersion is carried out at a stirring rate of 3000 rpm for 8 hours.

[0211] The reaction temperature is 80°C;

[0212] The low-speed stirring has a stirring rate of 1000 rpm;

[0213] After the reaction is complete, the reaction time is 9 hours;

[0214] The mass ratio of the micro / nano photocatalyst, polyethylene glycol octylphenyl ether, and toluene is 190:9:250.

[0215] The high-speed dispersion is uniform, with a dispersion rate of 10,000 rpm and a dispersion time of 9 hours;

[0216] The mass ratio of the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion is 12:17.

[0217] The reaction was carried out under constant temperature and low speed stirring until complete. The reaction temperature was 80℃, the stirring speed was 1000 rpm, and the reaction time was 10 hours.

[0218] The drying process removes residual toluene at a temperature of 80°C for 20 hours.

[0219] Step 3: Preparation of modified adhesive powder

[0220] Add the adhesive powder and deionized water to the reaction vessel, stir vigorously until uniform, then reduce the stirring speed to low, then heat and maintain the temperature to the reaction temperature. Add the water-soluble oxidant and trifluoroacetic acid, stir at low speed until the reaction is complete, then filter the material. The filtered solid is washed and dried to obtain the surface-oxidized adhesive powder. Then, use the silica coating method described in step 1 to coat the surface-oxidized adhesive powder. Specifically, replace all 45 parts of nano titanium dioxide and 80 parts of micron-sized bismuth tungstate in step 1 with 125 parts of surface-oxidized adhesive powder. Other operations are the same as in step 1 to prepare the modified adhesive powder.

[0221] The particle size of the adhesive powder is 200 mesh;

[0222] The water-soluble oxidant is sodium ferrate;

[0223] The vigorous stirring and mixing is carried out at a stirring speed of 5000 rpm;

[0224] The low-speed stirring has a stirring rate of 1200 rpm;

[0225] The reaction temperature is 70°C;

[0226] The low-speed stirring reaction was completed in 11 hours;

[0227] The washing process involves washing the filtered solids with deionized water until the pH of the washing solution is neutral.

[0228] The drying process involves a drying temperature of 90°C and a drying time of 18 hours.

[0229] Step 4: Preparation of aqueous dispersion of micro / nano photocatalytic materials

[0230] The specific formulation of the aqueous dispersion of the micro / nano photocatalytic material is as follows, by weight:

[0231] 160 parts of modified calcium sulfate whisker composite micro / nano photocatalyst

[0232] 65 parts of modified adhesive powder

[0233] Sodium hydroxymethyl cellulose 2.5 parts

[0234] 400 parts of deionized water;

[0235] According to the specific formula of the aqueous dispersion of micro-nano photocatalytic materials by weight, deionized water and sodium hydroxymethyl cellulose are first placed in a high-speed dispersion vessel and dispersed at a dispersion rate of 6500 rpm to form a uniform and stable solution. Then, the dispersion rate is increased to 12000 rpm, and modified calcium sulfate whisker composite micro-nano photocatalyst is added. After dispersing for 9 hours, modified adhesive powder is added, and dispersion is continued for 4 hours. The material is then discharged to obtain the aqueous dispersion of micro-nano photocatalytic materials.

[0236] Step 5: Preparation of powder

[0237] The specific formula of the powder is as follows, in parts by weight:

[0238] 180 parts of silicate cement

[0239] 130 parts of graded aggregate

[0240] 6 parts of polycarboxylate superplasticizer powder;

[0241] The graded aggregate is sea sand that meets the gradation standard, which is: 100 wt% passing through a 2.36 mm sieve, 90 wt% passing through a 1.18 mm sieve, and 75 wt% passing through a 0.6 mm sieve.

[0242] According to the specific formula of cement-based material powder modified by micro-nano photocatalytic materials by weight, silicate cement, graded aggregate, and polycarboxylate superplasticizer powder are put into a high-speed mixer, the stirring speed is controlled at 170 rpm, and the mixture is stirred for 80 minutes before being discharged to obtain cement-based material powder modified by micro-nano photocatalytic materials.

[0243] Example 4: A method for preparing cement-based materials modified with micro / nano photocatalytic materials

[0244] Step 1: Preparation of micro / nano photocatalysts

[0245] There are two methods for preparing micro / nano photocatalysts: aluminum hydroxide coating method;

[0246] The aluminum hydroxide coating method is specifically operated as follows: nano-titanium dioxide, micron-sized bismuth tungstate, and aluminum nitrate aqueous solution are added to a high-speed dispersion vessel, and after being vigorously stirred into a stable suspension, the temperature is raised and kept constant under vigorous stirring until the reaction temperature is reached. Then, urea is added to maintain the pH value of the reaction system at 5. After the reaction is complete, the temperature is lowered to room temperature and filtered. The filtered solid is washed and dried to obtain micro-nano photocatalyst.

[0247] The nano-titanium dioxide is anatase type with a particle size of 10 nm.

[0248] The micron-sized bismuth tungstate has a particle size of 0.3 μm;

[0249] The aluminum nitrate aqueous solution contains 20 wt% aluminum nitrate.

[0250] The mass ratio of nano-titanium dioxide, micron-sized bismuth tungstate, and aluminum nitrate aqueous solution is 20:25:160.

[0251] The powerful stirring has a stirring speed of 5500 rpm;

[0252] The reaction temperature is 70°C;

[0253] After the reaction is complete, the reaction time is 4 hours;

[0254] The washing process involves washing the filtered solid with deionized water until the pH of the washing solution is neutral.

[0255] The drying process involves a drying temperature of 80°C and a drying time of 15 hours.

[0256] Step 2 is the same as in Example 1;

[0257] Step 3: Preparation of modified adhesive powder

[0258] Add the adhesive powder and deionized water to the reaction vessel, stir vigorously until uniform, then reduce the stirring speed to low, then heat and maintain the temperature to the reaction temperature. Then add the water-soluble oxidant and trifluoroacetic acid, stir at low speed until the reaction is complete, discharge and filter. The filtered solid is washed and dried to obtain the surface-oxidized adhesive powder. Then, the surface-oxidized adhesive powder is coated with the aluminum hydroxide coating method described in step 1. Specifically, replace all 20 parts of nano titanium dioxide and 25 parts of micron-sized bismuth tungstate in step 1 with 45 parts of surface-oxidized adhesive powder. Other operations are the same as in step 1 to prepare the modified adhesive powder.

[0259] The particle size of the adhesive powder is 50 mesh;

[0260] The water-soluble oxidant is hydrogen peroxide;

[0261] The vigorous stirring and mixing is carried out at a stirring rate of 2000 rpm;

[0262] The low-speed stirring has a stirring rate of 600 rpm;

[0263] The reaction temperature is 50°C;

[0264] The low-speed stirring reaction was completed within 6 hours;

[0265] The washing process involves washing the filtered solids with deionized water until the pH of the washing solution is neutral.

[0266] The drying process involves a drying temperature of 80°C and a drying time of 10 hours.

[0267] Steps 4 and 5 are the same as in Example 1.

[0268] Example 5: A method for preparing cement-based materials modified with micro / nano photocatalytic materials

[0269] Step 1: Preparation of micro / nano photocatalysts

[0270] The preparation method of the micro / nano photocatalyst is aluminum hydroxide coating method;

[0271] The aluminum hydroxide coating method is specifically operated as follows: nano-titanium dioxide, micron-sized bismuth tungstate, and aluminum nitrate aqueous solution are added to a high-speed dispersion vessel, and after being vigorously stirred into a stable suspension, the temperature is raised and kept constant under vigorous stirring until the reaction temperature is reached. Then, urea is added to maintain the pH value of the reaction system at 6. After the reaction is complete, the temperature is lowered to room temperature and filtered. The filtered solid is washed and dried to obtain micro-nano photocatalyst.

[0272] The nano-titanium dioxide is anatase type with a particle size of 100 nm.

[0273] The particle size of the micron-sized bismuth tungstate is 2 μm;

[0274] The aluminum nitrate aqueous solution contains 35 wt% aluminum nitrate.

[0275] The mass ratio of the nano-titanium dioxide, micron-sized bismuth tungstate, and aluminum nitrate aqueous solution is 60:70:280.

[0276] The powerful stirring has a stirring speed of 9000 rpm;

[0277] The reaction temperature is 85°C;

[0278] After the reaction is complete, the reaction time is 7 hours;

[0279] The washing process involves washing the filtered solid with deionized water until the pH of the washing solution is neutral.

[0280] The drying process involves a drying temperature of 95°C and a drying time of 20 hours.

[0281] Step 2 is the same as in Example 1;

[0282] Step 3: Preparation of modified adhesive powder

[0283] Add the adhesive powder and deionized water to the reaction vessel, stir vigorously until uniform, then reduce the stirring speed to low, then heat and maintain the temperature to the reaction temperature. Add the water-soluble oxidant and trifluoroacetic acid, stir at low speed until the reaction is complete, then filter the material. The filtered solid is washed and dried to obtain the surface-oxidized adhesive powder. Then, use the aluminum hydroxide coating method described in step 1 to coat the surface-oxidized adhesive powder. Specifically, replace all 60 parts of nano titanium dioxide and 70 parts of micron-sized bismuth tungstate in step 1 with 130 parts of surface-oxidized adhesive powder. Other operations are the same as in step 1 to prepare the modified adhesive powder.

[0284] The particle size of the adhesive powder is 200 mesh;

[0285] The water-soluble oxidant is hydrogen peroxide;

[0286] The vigorous stirring and mixing is carried out at a stirring speed of 5000 rpm;

[0287] The low-speed stirring has a stirring rate of 1200 rpm;

[0288] The reaction temperature is 70°C;

[0289] The low-speed stirring reaction was completed in 11 hours;

[0290] The washing process involves washing the filtered solids with deionized water until the pH of the washing solution is neutral.

[0291] The drying process involves a drying temperature of 90°C and a drying time of 18 hours.

[0292] Steps 4 and 5 are the same as in Example 1.

[0293] Comparative Example 1: Based on Example 1, step 1, the preparation of micro / nano photocatalyst, was omitted. In step 2, the preparation of modified calcium sulfate whisker composite micro / nano photocatalyst, 130 parts of micro / nano photocatalyst were replaced with 43 parts of nano titanium dioxide and 87 parts of micron-sized bismuth tungstate in the same mass ratio of 30:60 as in step 1 of Example 1. The specific operation is as follows:

[0294] Step 1, the preparation of micro / nano photocatalysts, is not performed;

[0295] Step 2: Preparation of modified calcium sulfate whisker composite micro / nano photocatalyst

[0296] Replace 130 parts of micro / nano photocatalyst with 43 parts of nano titanium dioxide and 87 parts of micron-sized bismuth tungstate in the same mass ratio of 30:60 as in step 1 of Example 1. Other operations are the same as in step 1 of Example 1.

[0297] Steps 3, 4, and 5 are the same as in Example 1.

[0298] Comparative Example 2: Based on Example 4, step 1, the preparation of micro / nano photocatalysts, was omitted. In step 2, the preparation of modified calcium sulfate whisker composite micro / nano photocatalysts, 130 parts of micro / nano photocatalysts were replaced with 58 parts of nano titanium dioxide and 72 parts of micron-sized bismuth tungstate in the same mass ratio of nano titanium dioxide and micron-sized bismuth tungstate (20:25) as in the original step 1 of Example 4. The specific operation is as follows:

[0299] Step 1, the preparation of micro / nano photocatalysts, is not performed;

[0300] Step 2: Preparation of modified calcium sulfate whisker composite micro / nano photocatalyst

[0301] Replace 130 parts of micro / nano photocatalyst with 58 parts of nano titanium dioxide and 72 parts of micron-sized bismuth tungstate in the same mass ratio of nano titanium dioxide and micron-sized bismuth tungstate as in step 1 of Example 4. Other operations are the same as in step 1 of Example 4.

[0302] Steps 3, 4, and 5 are the same as in Example 1.

[0303] Comparative Example 3: Based on Example 1, step 2, the preparation of modified calcium sulfate whisker composite micro / nano photocatalyst, was omitted. In step 4, the preparation of the aqueous dispersion of micro / nano photocatalyst material, according to the original step 2 of Example 1, the mass ratio of micro / nano photocatalyst dispersion to modified calcium sulfate whisker dispersion was 11:17, the mass percentage of micro / nano photocatalyst in the micro / nano photocatalyst dispersion was approximately 0.4, and the mass percentage of calcium sulfate whiskers in the modified calcium sulfate whisker dispersion was approximately 0.3. The calculated mass ratio of micro / nano photocatalyst to calcium sulfate whiskers was approximately 4.4:5.1 (the calculation process is (11×0.4)÷(17×0.3)). 150 parts of modified calcium sulfate whisker composite micro / nano photocatalyst were replaced by 69 parts of micro / nano photocatalyst and 81 parts of calcium sulfate whiskers in an equal mass ratio of 4.4:5.1. The specific operation is as follows:

[0304] Step 1 is the same as in Example 1;

[0305] Step 2, preparation of modified calcium sulfate whisker composite micro / nano photocatalyst, is not performed;

[0306] Step 3 is the same as in Example 1;

[0307] Step 4: Preparation of aqueous dispersion of micro / nano photocatalytic materials

[0308] According to step 2 of Example 1, the mass ratio of micro-nano photocatalyst dispersion to modified calcium sulfate whisker dispersion is 11:17. The mass percentage of micro-nano photocatalyst in the micro-nano photocatalyst dispersion is about 0.4, and the mass percentage of calcium sulfate whiskers in the modified calcium sulfate whisker dispersion is about 0.3. The mass ratio of micro-nano photocatalyst to calcium sulfate whiskers is calculated to be about 4.4:5.1 (the calculation process is (11×0.4)÷(17×0.3)). 150 parts of modified calcium sulfate whisker composite micro-nano photocatalyst are replaced with 69 parts of micro-nano photocatalyst and 81 parts of calcium sulfate whiskers in an equal mass ratio of 4.4:5.1. Other operations are the same as in Example 1.

[0309] Step 5 is the same as in Example 1.

[0310] Comparative Example 4: Based on Example 1, step 3, the preparation of modified adhesive powder, was omitted. In step 4, the preparation of the aqueous dispersion of micro / nano photocatalytic material, 50 parts of modified adhesive powder were replaced with 50 parts of adhesive powder. The specific operation is as follows:

[0311] Steps 1 and 2 are the same as in Example 1;

[0312] Step 3, preparation of modified adhesive powder, is not performed;

[0313] Step 4: Preparation of aqueous dispersion of micro / nano photocatalytic materials

[0314] Replace 50 parts of modified adhesive powder with 50 parts of adhesive powder, and perform the other operations as in Example 1;

[0315] The particle size of the adhesive powder is 100 mesh;

[0316] Step 5 is the same as in Example 1.

[0317] Comparative Example 5: Based on Example 4, step 3, the preparation of modified adhesive powder, was omitted. In step 4, the preparation of the aqueous dispersion of micro / nano photocatalytic material, 50 parts of modified adhesive powder were replaced with 50 parts of adhesive powder. The specific operation is as follows:

[0318] Steps 1 and 2 are the same as in Example 1;

[0319] Step 3, preparation of modified adhesive powder, is not performed;

[0320] Step 4: Preparation of aqueous dispersion of micro / nano photocatalytic materials

[0321] Replace 50 parts of modified adhesive powder with 50 parts of adhesive powder, and perform the other operations as in Example 4;

[0322] The particle size of the adhesive powder is 50 mesh;

[0323] Step 5 is the same as in Example 1.

[0324] Performance testing:

[0325] For the cement-based materials modified with micro / nano photocatalytic materials obtained in Examples 1, 2, 3, 4, 5 and Comparative Examples 1, 2, 3, 4, 5, i.e., aqueous dispersions and powders of micro / nano photocatalytic materials, the powder was added to the aqueous dispersion of micro / nano photocatalytic materials at a mass ratio of 1:1. While adding the powder, the mixture was stirred thoroughly with an electric mixer. After the powder was completely added, stirring continued for 3-5 minutes to obtain a uniform and stable slurry. The slurry was then evenly sprayed onto the surface of the cement substrate using a spraying machine. The wet film thickness was controlled to be approximately 5 mm. Before spraying, the surface of the cement substrate underwent appropriate surface treatment to ensure it was clean and free of oil, adhesives, dust, and other contaminants. Larger defects or pits on the surface of the cement substrate should be repaired beforehand, and any protrusions should be smoothed and cleaned with water. After spraying, the resulting wet film was allowed to cure naturally. During the curing period, strong winds, direct sunlight, vibration, or scratches were avoided for up to 24 hours. After complete curing for 24 hours, corresponding sample blocks were cut, and test specimens were prepared according to the corresponding test standards and tested for the following indicators:

[0326] 1. Abrasion resistance: According to "JC / T 906-2023 Cement-based abrasion-resistant materials for concrete floors",

[0327] The abrasion resistance of the cement-based coating after curing was tested. The abrasion resistance was divided into three levels: A, B, and C. The abrasion resistance from high to low was C>B>A.

[0328] 2. Adhesion Strength: The adhesion strength of the coating is tested using a tensile tester, utilizing epoxy...

[0329] The resin fixes the cured cement-based material coating to the circular pull ring. After multiple pulls, a loading rate of 0.08 mm / min is applied until the interface is damaged. The final result is the average value.

[0330] 3. Degradation of NO x Test: Place the sample to be tested into a standard reactor (reactor specifications are from ISO / DIS).

[0331] In the fabrication process (using standard 22197-1), the light intensity on the sample surface was adjusted to 100 mW / cm² by adjusting the distance between the 300W xenon lamp light source and the reactor. 2 By adjusting the flow rates of dry air, humid air, and NO gas, the total flow rate of the mixed gas was made to 0.6 L / min. -1 The relative humidity was 50±2%, and the NO gas concentration was 1000ppm±50ppb. The sampling and analysis system consisted of NO... x It consists of an analyzer and a computer for data acquisition. The target gas enters the NO2 directly after passing through the reactor. x Analyzer, NO x The analyzer monitors the concentrations of NO and NO2 in the target gas in real time using the photoluminescence principle;

[0332] 4. Rhodamine B Degradation Test: Add 1 ml of Rhodamine B solution (1 mmol / L) dropwise evenly.

[0333] Apply the light to the surface of a cylindrical sample (20 mm in diameter and 20 mm in height). Place the sample under a 300 W xenon lamp, with the light passing through an ultraviolet cutoff filter (λ ≥ 420 nm), controlling the light intensity on the sample surface to be 100 mW / cm². 2 After 1 hour of illumination, the color change on the sample surface was compared to evaluate the efficiency of the sample in degrading Rhodamine B.

[0334] 5. Rainwater erosion durability test: Degradation of NO... x After the test, the sample was rinsed under a water flow of 600 ml / min for 1 day, and then the NO degradation was tested again. x Ability;

[0335] 6. Test on the effect of wear on photocatalytic efficiency: Samples before and after the wear resistance test were subjected to NO degradation under the same conditions. x Test and evaluate the impact of mechanical wear on photocatalytic efficiency;

[0336] The test results for the above indicators are shown in Table 1:

[0337] Table 1

[0338]

[0339] As can be seen from the data in Table 1, the wear resistance of Examples 1-5 all reached the highest grade C, and the bonding strength was also above 7.5 MPa. x The degradation efficiency was above 94.9%, and the degradation efficiency of Rhodamine B was above 93.6%. After 1 day of rainwater washing and abrasion resistance testing, NO... x The reduction in degradation efficiency is negligible, indicating that the cement-based material modified with micro / nano photocatalytic materials prepared in this invention possesses excellent characteristics of high photocatalytic efficiency and long-lasting photocatalytic function. Furthermore, the cement-based material modified with micro / nano photocatalytic materials prepared in this invention is obtained through a spraying process, resulting in high utilization efficiency of the photocatalyst. Comparative Examples 1 and 2, based on Examples 1 and 4 respectively, omitted step 1 and the preparation of the micro / nano photocatalyst; that is, the nano-titanium dioxide and micron-sized bismuth tungstate were not coated with silica or aluminum hydroxide. The wear resistance of Comparative Examples 1 and 2 decreased to grade B, and the bonding strength also decreased to 5.4 MPa and 4.9 MPa, respectively. x The degradation efficiency and Rhodamine B degradation efficiency decreased drastically. After 1 day of rainwater washing and abrasion resistance testing, NO... xThe degradation efficiency was also significantly reduced, indicating that the lack of silica or aluminum hydroxide coating on nano-titanium dioxide and micron-sized bismuth tungstate significantly negatively impacted the uniform dispersion of these two fine powders within the cement-based material. Uneven dispersion led to particle agglomeration, severely reducing the photocatalytic performance of the cement-based material. Simultaneously, wear resistance, bonding strength, and rain erosion resistance were also greatly negatively affected. In Comparative Example 3, calcium sulfate whiskers were not modified or combined with micro / nano photocatalysts. The wear resistance and bonding strength of Comparative Example 3 were reduced to the lowest values ​​among all examples and comparative examples, while NO... x The degradation efficiency of both Rhodamine B and NO2 was significantly reduced, and NO2 levels decreased after rainwater washing and abrasion tests. x The degradation efficiency also decreased drastically, indicating that surface modification of calcium sulfate whiskers and composite with micro / nano photocatalysts can comprehensively improve the wear resistance, bonding strength, photocatalytic performance, and rain erosion resistance of cement-based materials, thus significantly improving their durability. In Comparative Examples 4 and 5, the adhesive powder was not surface modified; that is, it was not surface oxidized, nor coated with silica or aluminum hydroxide. The wear resistance of these two comparative examples dropped to Grade A, and the bonding strength decreased significantly. Meanwhile, NO... x The degradation efficiency of NO and Rhodamine B also decreased significantly, and rainwater runoff and abrasion resistance tests showed a substantial reduction. x The negative impact of degradation efficiency is also very large, which indicates that the surface oxidation of the adhesive powder and the treatment of silica or aluminum hydroxide coating can enhance the compatibility between the adhesive powder and the cement matrix, promote the uniform distribution of the adhesive powder in the cement matrix and the bonding force between the adhesive powder and cement particles, thereby improving the toughening effect of the adhesive powder on cement-based materials and reducing the possibility of brittle debonding between the cement-based materials modified by micro-nano photocatalytic materials and the substrate surface.

[0340] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cement-based material modified with micro / nano photocatalytic materials, characterized in that: The cement-based material modified with micro / nano photocatalytic material consists of two parts: an aqueous dispersion of micro / nano photocatalytic material and powder. The aqueous dispersion and powder are mixed evenly at a mass ratio of 15-25:20 before use. The powder consists of silicate cement, graded aggregate, and polycarboxylate superplasticizer powder. The aqueous dispersion of micro / nano photocatalytic material consists of modified calcium sulfate whisker composite micro / nano photocatalyst, modified adhesive powder, sodium hydroxymethyl cellulose, and deionized water. The modified calcium sulfate whisker composite micro / nano photocatalyst is prepared by: thoroughly drying calcium sulfate whiskers, adding them to a reaction vessel, then adding polyethylene glycol octylphenyl ether and toluene, vigorously stirring to disperse evenly, raising the temperature and maintaining it at the reaction temperature, and stirring at low speed. Add 3-isocyanate-propyltrimethoxysilane and react fully to obtain a modified calcium sulfate whisker dispersion. Then, add the micro / nano photocatalyst, polyethylene glycol octylphenyl ether, and toluene to a high-speed dispersion vessel and disperse evenly at high speed to obtain a micro / nano photocatalyst dispersion. Next, add the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion and continue to react at a constant temperature and low speed until complete. After cooling to room temperature, filter, and dry the filtered solid to remove residual toluene to obtain the modified calcium sulfate whisker composite micro / nano photocatalyst. The micro / nano photocatalyst can be prepared by two methods: silica coating and aluminum hydroxide coating. The silica coating method specifically involves: adding nano-titanium dioxide, micron-sized bismuth tungstate, and deionized... Water is added to a high-speed dispersion vessel and vigorously stirred to form a stable suspension. Then, sodium metasilicate aqueous solution is added under low-speed stirring. The temperature is then raised and held at the reaction temperature. Next, sulfuric acid aqueous solution is added to adjust the pH of the reaction system to 10-11. After the reaction is complete, the system is kept at the reaction temperature and allowed to stand for complete maturation. The mixture is then cooled to room temperature and filtered. The filtered solid is washed and dried to obtain the micro / nano photocatalyst. The aluminum hydroxide coating method specifically involves adding nano-titanium dioxide, micron-sized bismuth tungstate, and aluminum nitrate aqueous solution to a high-speed dispersion vessel and vigorously stirring to form a stable suspension. The temperature is then raised and held at the reaction temperature while maintaining vigorous stirring. Urea is then added, and the pH of the reaction system is maintained at 5-6. After the reaction is complete, the mixture is cooled to room temperature. The solid obtained by filtration is washed and dried to obtain micro-nano photocatalysts. The modified adhesive powder is prepared by adding adhesive powder and deionized water into a reaction vessel, stirring vigorously until uniform, then reducing the stirring speed to low, then heating and maintaining the temperature to the reaction temperature, then adding water-soluble oxidant and trifluoroacetic acid, stirring at low speed until the reaction is complete, then discharging and filtering, the solid obtained by washing and drying to obtain surface-oxidized adhesive powder, and then coating the surface-oxidized adhesive powder with the above-mentioned silica coating method or aluminum hydroxide coating method. Specifically, the nano-titanium dioxide and micron-sized bismuth tungstate in the above-mentioned silica coating method or aluminum hydroxide coating method are all replaced with the surface-oxidized adhesive powder in equal amounts, while other operations remain unchanged, to obtain the modified adhesive powder. The aqueous dispersion of the micro / nano photocatalytic material comprises, by weight, 100-160 parts of modified calcium sulfate whisker composite micro / nano photocatalyst, 25-65 parts of modified adhesive powder, 1-2.5 parts of sodium hydroxymethyl cellulose, and 250-400 parts of deionized water; the powder comprises, by weight, 80-180 parts of silicate cement, 60-130 parts of graded aggregate, and 1-6 parts of polycarboxylate superplasticizer powder.

2. The cement-based material modified with micro / nano photocatalytic materials according to claim 1, characterized in that: The calcium sulfate whiskers have a length of 10-100 μm and a diameter of 0.2-2 μm; the mass ratio of the calcium sulfate whiskers, polyethylene glycol octylphenyl ether, toluene, and 3-isocyanate-propyltrimethoxysilane is 80-150:2-8:190-350:8-30; the mass ratio of the micro / nano photocatalyst, polyethylene glycol octylphenyl ether, and toluene is 90-190:3-9:150-250; and the mass ratio of the micro / nano photocatalyst dispersion to the modified calcium sulfate whisker dispersion is 6-12:

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3. The cement-based material modified with micro / nano photocatalytic materials according to claim 1, characterized in that: The nano-titanium dioxide is anatase type with a particle size of 10-100 nm; the micron-sized bismuth tungstate has a particle size of 0.3-2 μm; the sodium metasilicate aqueous solution has a sodium metasilicate mass fraction of 15-25 wt%; the mass ratio of nano-titanium dioxide, micron-sized bismuth tungstate, deionized water, and sodium metasilicate aqueous solution is 10-45:15-80:100-180:60-110; the sulfuric acid aqueous solution has a sulfuric acid mass fraction of 10-20 wt%.

4. The cement-based material modified with micro / nano photocatalytic materials according to claim 1, characterized in that: In the aluminum nitrate aqueous solution, the mass fraction of aluminum nitrate is 20~35wt%; the mass ratio of nano-titanium dioxide, micron-sized bismuth tungstate, and aluminum nitrate aqueous solution is 20~60:25~70:160~280.

5. The cement-based material modified with micro / nano photocatalytic materials according to claim 1, characterized in that: The particle size of the adhesive powder is 50-200 mesh; the water-soluble oxidant is one of hydrogen peroxide, calcium peroxide, and sodium ferrate.

6. The method for preparing cement-based materials modified with micro / nano photocatalytic materials according to claim 1, characterized in that: The preparation method of the aqueous dispersion of micro-nano photocatalytic materials in the cement-based material modified by the micro-nano photocatalytic materials is as follows: According to the composition of the aqueous dispersion of micro-nano photocatalytic materials by weight, firstly, deionized water and sodium hydroxymethyl cellulose are placed in a high-speed dispersion vessel and dispersed at a dispersion rate of 3500~6500 rpm to form a uniform and stable solution. Then, the dispersion rate is increased to 8000~12000 rpm, and modified calcium sulfate whisker composite micro-nano photocatalyst is added. After dispersing for 5~9 hours, modified adhesive powder is added, and dispersion is continued for 1.5~4 hours. The material is then discharged to obtain the aqueous dispersion of micro-nano photocatalytic materials. The preparation method of the powder is as follows: According to the composition of the cement-based material powder modified by micro-nano photocatalytic materials by weight, silicate cement, graded aggregate, and polycarboxylate superplasticizer powder are placed in a high-speed mixer. The stirring speed is controlled at 130~170 rpm, and the mixture is stirred and mixed for 50~80 minutes before being discharged to obtain the cement-based material powder modified by micro-nano photocatalytic materials.

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