Preparation method of nano visible light catalytic refrigerant and visible light catalytic concrete

Abstract

The application discloses a kind of nano visible light catalytic refrigerant and the preparation method of visible light catalytic concrete, first titanium isopropanol is dissolved in anhydrous ethanol, then is added dropwise to the aqueous acetic acid solution dispersed with nanocellulose fiber, after dropwise addition is completed, it is stirred uniformly at room temperature;After the temperature range is raised, reaction is completed, and after standing for a period of time, obtain nano visible light catalytic refrigerant;Gelled material;Water;Nano visible light catalytic refrigerant are configured slurry together, using unidirectional freezing technology and low-temperature slow melting technology are combined, obtain visible light catalytic concrete with radiation refrigeration performance.The application effectively improves the visible light catalytic degradation air pollutant effect of low-dosage photocatalyst modified concrete, and can improve the daytime radiation refrigeration performance of concrete slab.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of materials, and relates to a functional concrete and a preparation method thereof, in particular to a nano visible light catalytic refrigerant and a preparation method of visible light catalytic concrete. BACKGROUND

[0002] Nitrogen oxide (NO x ) is a major air pollutant produced by fossil fuel combustion, chemical manufacturing processes and nitric acid metal processing. NO x Not only causes environmental problems such as acid rain and PM2.5, but also is toxic to the human body. Even if the concentration of NO x is in the low concentration range of ppm or ppb, it will also have adverse effects on humans and the environment. NO x Reduction method assisted by high temperature can effectively remove high-concentration NO x (200-2000 ppm) in automobile exhaust and industrial manufacturing. However, these NO x reduction methods cannot effectively remove low-concentration NO x (below 1 ppm) in the human living environment. Therefore, domestic and foreign researchers have been committed to finding a method of low energy consumption and high efficiency for removing low-concentration NO x in the environment, among which photocatalytic degradation of NO x is considered to be one of the most promising methods for removing low-concentration NO x in the indoor and outdoor environment of human living room. Because cement-based materials are the most widely used and largest amount of building materials in the world today, combined with the huge surface area of buildings, cement-based materials have become an excellent carrier for photocatalytic degradation of NO x . For this reason, photocatalytic cement-based materials have emerged, among which nano photocatalyst modified cement-based materials have developed rapidly in the past 20 years. Powdered nano titanium dioxide (TiO2) has high cost performance, non-toxicity, chemical inertness under no light, size effect and other advantages, and is the most commonly used photocatalyst in photocatalytic concrete. However, there are hard agglomerations between the grains of powdered nano TiO2, and the ions in the cement-based pore solution exacerbate the secondary agglomeration of powdered nano TiO2 particles, which greatly reduces the pollutant degradation efficiency of photocatalytic concrete.

[0003] Generally speaking, the recommended dosage of powdered nano-TiO2 in photocatalytic cement-based materials in the existing reported data is about 3-5 wt.% of the cement mass. Increasing the dosage will not significantly improve the degradation efficiency of pollutants. Spraying photocatalyst on the surface of concrete is another application method, but it has the characteristics of easy wear, peeling and failure of the coating layer. Therefore, it is not within the scope of this invention. The NO conversion rate of the modified titanium dioxide photocatalytic cement hardening paste with 3% iron oxide added to the ordinary cement is less than 25% in the patent "Use of photocatalytic coating particles for decomposing air pollutants" (CN101980988A). After 8 days of standard curing, the NO conversion rate of the hardened photocatalytic cement paste is reduced to less than 8%. The current patents on photocatalytic concrete mainly focus on the effect of photocatalytic degradation of liquid-phase organic dyes, and less on the effect of degradation of gas-phase pollutants. The main reason is that the attachment methods of gas-phase and liquid-phase pollutants on the surface and pores of photocatalytic concrete are different, and the photocatalytic degradation effects are quite different. For example, the photocatalytic degradation of pollutants by the photocatalytic concrete material proposed in the patent "High-strength cement-based composite photocatalytic material and its preparation method" (CN110482963B) is described by degrading liquid-phase dyes, and there is no experimental verification of photocatalytic degradation of gas-phase pollutants. The performance characterization of photocatalytic degradation of pollutants is not involved in the effect verification of the photocatalytic concrete proposed in the patent "High-efficiency self-cleaning photocatalytic concrete and its preparation method" (CN115057673B), and the photocatalytic effect of the concrete cannot be evaluated. Based on the above performance characteristics, simply increasing the dosage of nano-TiO2 in concrete cannot effectively improve its ability to degrade air pollutants, and will increase the cost of raw materials. Therefore, improving the photocatalytic degradation of gas-phase pollutants by existing nano-TiO2 modified photocatalytic concrete is one of the urgent problems to be solved.

[0004] Additionally, nano-TiO2 modified concrete needs to absorb ultraviolet light photon energy with a certain radiation power to exhibit the effect of photocatalytic degradation of gaseous pollutants. This characteristic is not conducive to the popularization and application of photocatalytic concrete in residential buildings. By screening and surface modification of photocatalysts, visible light catalysts with ultraviolet-visible light catalytic effect can be obtained, which can enable photocatalytic concrete to degrade pollutants under visible light. In the literature “Atmospheric NOx removal: Study of cement mortars with iron-and vanadium-doped TiO2 as visible light–sensitive photocatalysts” (Construction and Building Materials 149 (2017) 257-271), the NO degradation rate of the mortar mixed with 2.5% ultraviolet-visible light catalyst (V-TiO2) under simulated sunlight conditions is about 15.5%, and the NO degradation rate of the mortar mixed with 0.5% ultraviolet-visible light catalyst under simulated sunlight conditions is about 13.9%. In the literature “The effect of TiO2@CoAl-LDH nanosphere on early hydration of cement and its photocatalytic depollution performance under UV–visible light” (Construction and Building Materials 319 (2022) 126227), it is reported that the NO degradation rate of the mortar mixed with 1% ultraviolet-visible light catalyst (TiO2@CoAl-LDH) of cement under simulated sunlight conditions is 12.3%, the NO degradation rate of the mortar mixed with 4% ultraviolet-visible light catalyst (TiO2@CoAl-LDH) of cement under simulated sunlight conditions is 58.3%, and the NO degradation rate of the mortar mixed with 4% photocatalyst (TiO2) of cement under simulated sunlight conditions is 24.1%. At the same time, the synthesis conditions of visible light catalysts are harsh and not suitable for large-scale production. For example, the ultraviolet-visible light catalyst (V-TiO2) in the above literature is prepared by spray combustion and thermal decomposition process, which requires precise instruments and higher energy consumption auxiliary process. The preparation of ultraviolet-visible light catalyst (TiO2@CoAl-LDH) requires a high-temperature and high-pressure reaction kettle at 180°C for 48 hours, which has a certain risk of explosion during the process, and has higher requirements for the environmental parameters and safety facilities of the production plant. x x x

[0005] ​​​Therefore, for the TiO2-based visible light catalyst modified concrete, a relatively high dosage is still needed to obtain a relatively ideal NO x degradation efficiency. However, the cost of the visible light catalyst in the existing reports is much higher than that of the TiO2 photocatalyst, so its application in concrete is very limited. Therefore, how to improve the photocatalytic effect of the low-cost and low-photocatalyst dosage photocatalytic concrete on the gaseous pollutants in the ultraviolet-visible light band is still a problem to be solved. SUMMARY

[0006] In view of the technical problems of the existing photocatalytic concrete, the application provides a nano visible light catalyst and a preparation method of visible light catalyst concrete.

[0007] In view of the technical problems of high cost and harsh synthesis conditions of the visible light catalyst, the application proposes to prepare the TiO2-based visible light catalyst at a reaction temperature slightly higher than room temperature (35-85 0C), which has a simple production process and low energy consumption. In view of the technical difficulty of low photocatalytic efficiency of the concrete with low dosage of visible light catalyst on gaseous pollutants, the application starts from the aspects of material and microstructure design, improves the catalytic activity of the catalyst and the micro-pore structure in the hardened concrete, and comprehensively improves the efficiency of the visible light catalytic degradation of nitrogen oxides in the concrete, and gives the concrete slab a passive radiation refrigeration effect.

[0008] From the perspective of material design, the application proposes to use the radial morphology structure characteristics of the nanocellulose fiber material to modify the surface of the nano TiO2 hydrosol particles by using the low-cost nanocellulose fiber, and to prepare a high-dispersity nano visible light catalyst. This can effectively improve the visible light reaction activity of the nano TiO2 hydrosol and significantly improve the viscosity and thixotropy of the fresh paste.

[0009] The efficiency of photocatalytic concrete in removing gaseous pollutants is closely related to its photocatalytic activity, which is affected by the dispersion of photocatalysts (surface active sites), the generation, separation and recombination of photo-generated electrons and holes. From the perspective of microstructure design, the present application proposes that the above-mentioned nano visible light photocatalyst with high dispersity, i.e. the nano visible light photocatalytic refrigerant, can be used as a nano visible light photocatalytic refrigerant, which can effectively improve the thermal conductivity of the liquid phase in the freshly mixed paste, increase the average cooling rate and improve the pore structure of the hardened paste. Therefore, the present application uses the freeze forming technology to prepare a hardened concrete with directional micropores, which has smaller pore size and higher specific surface area, which is beneficial to the adhesion of gaseous pollutants on the surface of the photocatalytic concrete, thereby promoting the photocatalytic reaction and improving the efficiency of photocatalytic degradation of gaseous pollutants.

[0010] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0011] In one aspect, the present application provides a preparation method of a nano visible light photocatalytic refrigerant, comprising the following steps:

[0012] S1, dissolving titanium isopropoxide in anhydrous ethanol to obtain a titanium isopropoxide ethanol solution;

[0013] S2, adding the titanium isopropoxide ethanol solution dropwise into an acetic acid aqueous solution containing dispersed nano cellulose fibers, and stirring uniformly at room temperature after the addition is completed;

[0014] S3, stirring at a temperature of 35-45℃ for a period of time;

[0015] S4, after the reaction is completed, standing for a period of time to obtain a nano cellulose fiber modified TiO2 aqueous sol, i.e. a nano visible light photocatalytic refrigerant.

[0016] As a preferred solution, in step S1, the molar ratio of titanium isopropoxide to anhydrous ethanol in the titanium isopropoxide ethanol solution is 1.5-4:1.

[0017] As a preferred solution, in step S1, the titanium isopropoxide is dissolved in anhydrous ethanol, and the stirring is performed at a temperature of about 38-42℃ for 30-45min to obtain the titanium isopropoxide ethanol solution.

[0018] As a preferred solution, in step S2, the molar ratio of acetic acid to water in the acetic acid aqueous solution containing dispersed nano cellulose fibers is 0.1-0.2:1.

[0019] As a preferred solution, in step S2, the dropping speed of the titanium isopropoxide ethanol solution is 0.01-0.05mL / s.

[0020] As a preferred solution, in step S2, after the dropwise addition is completed, the mixture is stirred at room temperature for 1.5-3h to be well mixed.

[0021] As a preferred solution, in step S3, the magnetic stirring is performed at about 38-42℃ for 24-72h.

[0022] As a preferred solution, in step S4, after the reaction is completed, the standing time is 72-100h, and the standing environment is: temperature 20℃, relative humidity 60%.

[0023] As a preferred solution, in the nano-cellulose fiber modified TiO2 hydrosol, the mass ratio of nano-cellulose fiber to nano-TiO2 is 1-2:1.

[0024] As a preferred solution, the nano-cellulose fiber is a white slurry with a solid content of 3.30%-5% and a pH value of 7-9.

[0025] On the other hand, the present application provides a preparation method of visible light catalytic concrete with radiation refrigeration performance, which uses the above-mentioned nano visible light catalytic refrigerant as an additive, comprising the following steps:

[0026] (1) mixing the nano visible light catalytic refrigerant with mixing water to obtain a well-mixed mixing suspension;

[0027] (2) slowly pouring the obtained mixing suspension into the cementing material, stirring at low speed first and then at high speed to obtain a uniform slurry;

[0028] (3) loading the stirred slurry into a mold required for freeze forming, and then placing the mold on a freeze sample forming platform to perform freeze hardening, with a freeze temperature of-85℃ to-55℃;

[0029] (4) after freeze hardening, removing the mold to obtain a test block, and placing the test block in a refrigeration box for slow thawing;

[0030] (5) taking out the thawed test block and placing it in a curing box for curing, and obtaining a thermal insulation cement-based material after the curing is completed.

[0031] As a preferred solution, in step (2), the low-speed stirring speed is 100-150rpm for 30-60s, and the high-speed stirring speed is 200-400rpm for 60-120s.

[0032] As a preferred solution, in step (3), the freeze hardening time is 10-20 minutes, and the freeze time is determined according to the volume, height and mixing water amount of the test block. For general size components, 10-20 minutes is sufficient.

[0033] As a preferred scheme, in step (4), after the frozen hardening, the test block is obtained by rapid demolding, and the test block is thawed at a temperature of 4-10 DEG C for 48-72 hours.

[0034] As a preferred scheme, in step (5), the mold required for the freeze forming is made of a copper-silver alloy plate lined with a low-temperature resistant organic polymer.

[0035] As a preferred scheme, in step (5), the curing condition is curing at 20 DEG C and 95% relative humidity until the test age.

[0036] The low-temperature resistant range of the organic polymer is -100 DEG C to 60 DEG C, and polytetrafluoroethylene, polysulfone, polyimide, etc.

[0037] As a preferred scheme, the visible light catalytic concrete has the following component ratio: 100 parts of cementitious material, 30-50 parts of water and 0.1-0.5 parts of nano visible light catalytic refrigerant.

[0038] As a preferred scheme, the cementitious material is portland cement; the portland cement can meet the requirement of the cementitious material, and special cementitious material is not required.

[0039] Compared with the prior art, the technical method and product provided by the application have the following beneficial effects:

[0040] (1) The raw material of the visible light catalytic concrete with the radiation refrigeration performance prepared by the application is easy to obtain, the light catalyst content is low, the performance improvement effect is good, the improved preparation process has good energy saving effect, and the cost benefit is high.

[0041] (2) The visible light catalytic concrete with the radiation refrigeration performance prepared by the application has good rheological properties, and can meet the demand of various construction modes. The functional improvement of the visible light catalytic concrete with the radiation refrigeration performance can be used for the functional improvement of the outer wall, the building fence structure and the roof, can effectively improve the air purification effect of the light catalytic building, and can reduce the indoor refrigeration energy consumption. In particular, the visible light catalytic concrete with the radiation refrigeration performance can be used for the processing of the low water-binder ratio cement-based curtain wall plate, and the application prospect is very promising.

[0042] DRAWINGS

[0043] Figure 1 The flow chart of the preparation method of the nano visible light catalytic refrigerant in the embodiment of the application is shown.

[0044] Figure 2 The schematic diagram of the radiation refrigeration performance test is shown.

[0045] Figure 3 The schematic diagram of the installation position of the temperature sensor on the light catalytic concrete plate is shown. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be described clearly and completely below. In the embodiments of the present application, nano visible light catalytic refrigerant is mixed into P.W. 52.5 white cement by two molding methods. In the condition of freeze molding, according to different ratios of nano cellulose fiber and nano TiO2, the following examples are divided; in the condition of cast molding, according to the corresponding proportions, the following comparative examples are divided. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0047] Example 1: The present application provides a preparation method of nano visible light catalytic refrigerant as follows:

[0048] S1, dissolve titanium isopropoxide in anhydrous ethanol at 40°C, stir for 30-45 min to obtain a titanium isopropoxide ethanol solution, and the molar ratio of titanium isopropoxide to anhydrous ethanol is 2.44:1;

[0049] S2, add the titanium isopropoxide ethanol solution dropwise into the acetic acid aqueous solution in which the nano cellulose fiber is dispersed, the liquid dropwise adding speed is 0.01-0.05 mL / s, after the dropwise adding is completed, stir and mix uniformly at room temperature, and the molar ratio of acetic acid to water is 0.175:1;

[0050] S3, stir at 40°C for 48 hours;

[0051] S4, after the reaction is completed, under the condition of temperature 20°C and relative humidity 60%, stand for 80 hours to obtain nano cellulose fiber modified TiO2 hydrosol (wherein the mass ratio of nano cellulose fiber to nano TiO2 is 1.0:1), namely nano visible light catalytic refrigerant.

[0052] Example 2: The present application provides a preparation method of nano visible light catalytic refrigerant as follows:

[0053] S1, dissolve titanium isopropoxide in anhydrous ethanol at 40°C, stir for 30-45 min to obtain a titanium isopropoxide ethanol solution, and the molar ratio of titanium isopropoxide to anhydrous ethanol is 2.44:1;

[0054] S2, add the titanium isopropoxide ethanol solution dropwise into the acetic acid aqueous solution in which the nano cellulose fiber is dispersed, the liquid dropwise adding speed is 0.01-0.05 mL / s, after the dropwise adding is completed, stir and mix uniformly at room temperature, and the molar ratio of acetic acid to water is 0.175:1;

[0055] S3, stir at 40°C for 48 hours;

[0056] S4, after the reaction is completed, under the condition of temperature 20℃, relative humidity 60%, standing for 80 hours, to obtain the nano cellulose fiber modified TiO2 hydrosol (the mass ratio of nano cellulose fiber and nano TiO2 is 1.5:1), namely the nano visible light catalytic refrigerant.

[0057] Example 3: the present application provides a kind of nano visible light catalytic refrigerant preparation method as follows:

[0058] S1, titanium isopropoxide is dissolved in anhydrous ethanol at 40℃, stirring for 30-45min to obtain titanium isopropoxide ethanol solution, the molar ratio of titanium isopropoxide and anhydrous ethanol is 2.44:1;

[0059] S2, titanium isopropoxide ethanol solution is added dropwise to the aqueous acetic acid solution dispersed with nano cellulose fiber, the liquid dropwise adding speed is 0.01-0.05mL / s, after dropwise adding is completed, stirring is uniformly mixed at room temperature, the molar ratio of acetic acid and water is 0.175:1;

[0060] S3, stirring is carried out under the condition of temperature rising to 40℃ for 48 hours;

[0061] S4, after the reaction is completed, under the condition of temperature 20℃, relative humidity 60%, standing for 80 hours, to obtain the nano cellulose fiber modified TiO2 hydrosol (the mass ratio of nano cellulose fiber and nano TiO2 is 2.0:1), namely the nano visible light catalytic refrigerant.

[0062] Example 4: the present application provides a kind of nano visible light catalytic refrigerant preparation method as follows:

[0063] S1, titanium isopropoxide is dissolved in anhydrous ethanol at 40℃, stirring for 30-45min to obtain titanium isopropoxide ethanol solution, the molar ratio of titanium isopropoxide and anhydrous ethanol is 2.44:1;

[0064] S2, titanium isopropoxide ethanol solution is added dropwise to the aqueous acetic acid solution dispersed with nano cellulose fiber, the liquid dropwise adding speed is 0.01-0.05mL / s, after dropwise adding is completed, stirring is uniformly mixed at room temperature, the molar ratio of acetic acid and water is 0.175:1;

[0065] S3, stirring is carried out under the condition of temperature rising to 40℃ for 48 hours;

[0066] S4, after the reaction is completed, under the condition of temperature 20℃, relative humidity 60%, standing for 80 hours, to obtain the nano cellulose fiber modified TiO2 hydrosol (the mass ratio of nano cellulose fiber and nano TiO2 is 2.5:1), namely the nano visible light catalytic refrigerant.

[0067] Application Example 1: The application example provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W. 52.5 white cement is used as a cementitious material, and a synthesized nano visible light photocatalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by one-way freeze forming. The specific ratio is: white cement 100 parts, deionized water 40 parts, and nano visible light photocatalytic refrigerant prepared in Example 1 0.1 parts.

[0068] The preparation method of the visible light photocatalytic concrete is as follows:

[0069] (1) Mix the nano visible light photocatalytic refrigerant with the mixing water, and stir until a uniformly mixed mixing suspension is obtained;

[0070] (2) Slowly pour the mixing suspension obtained in step (1) into the cementitious material, and stir at low speed in the stirring pot for 40 s (120 revolutions / minute), and then stir at high speed for 80 s (300 revolutions / minute) to obtain a uniform slurry;

[0071] (3) Put the stirred slurry into a mold required for freeze forming, and then place the mold on a freeze sample preparation platform for freezing. The temperature of the cold platform is controlled at -60°C, and the freezing time is generally about 10 minutes. After the freeze-hardened sample is quickly demolded, it is placed in a refrigerator at about 6°C for slow thawing for 48 hours to obtain a test block.

[0072] (4) After the thawed test block is taken out, it is placed in a curing box for curing at 20°C and 95% relative humidity until the test age.

[0073] Application Example 2: The example provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W. 52.5 white cement is used as a cementitious material, and a synthesized nano visible light photocatalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by one-way freeze forming. The specific ratio is: white cement 100 parts, deionized water 40 parts, and nano visible light photocatalytic refrigerant prepared in Example 2 0.1 parts.

[0074] The preparation method of the visible light photocatalytic concrete is the same as that in Application Example 1.

[0075] Application Example 3:

[0076] The example provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W. 52.5 white cement is used as a cementitious material, and a synthesized nano visible light photocatalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by one-way freeze forming. The specific ratio is: P.W. 52.5 white cement 100 parts, deionized water 40 parts, and nano visible light photocatalytic refrigerant prepared in Example 3 0.1 parts (the mass ratio of nano cellulose fiber to nano TiO2 is 2.0:1).

[0077] The preparation method of the visible light catalytic concrete is the same as that in Example 1.

[0078] Example 4:

[0079] This example provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W. 52.5 white cement is used as a cementitious material, and a synthesized nano visible light catalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by one-way freezing molding. The specific ratio is: P.W. 52.5 white cement 100 parts, deionized water 40 parts, and nano visible light catalytic refrigerant prepared in Example 4 0.1 parts (the mass ratio of nano cellulose fiber to nano TiO2 is 2.5:1).

[0080] The preparation method of the visible light catalytic concrete is the same as that in Example 1.

[0081] Application Comparative Example 1:

[0082] This comparative example provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W. 52.5 white cement is used as a cementitious material, and a synthesized nano visible light catalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by pouring molding. The specific ratio is: white cement 100 parts, deionized water 40 parts, and nano visible light catalytic refrigerant prepared in Example 1 0.1 parts (the mass ratio of nano cellulose fiber to nano TiO2 is 1.0:1).

[0083] The preparation of the visible light catalytic concrete adopts pouring molding.

[0084] Application Comparative Example 2:

[0085] This comparative example provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W. 52.5 white cement is used as a cementitious material, and a synthesized nano visible light catalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by pouring molding. The specific ratio is: white cement 100 parts, deionized water 40 parts, and nano visible light catalytic refrigerant prepared in Example 2 0.1 parts (the mass ratio of nano cellulose fiber to nano TiO2 is 1.5:1).

[0086] The preparation of the visible light catalytic concrete adopts pouring molding.

[0087] Application Comparative Example 3:

[0088] The comparative example 3 provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W.52.5 white cement is used as a cementitious material, and the synthetic nano visible light photocatalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by pouring molding. The specific ratio is as follows: 100 parts of white cement, 40 parts of deionized water, and 0.1 part of the nano visible light photocatalytic refrigerant prepared in the example 3 (the mass ratio of nano cellulose fiber to nano TiO2 is 2.0:1).

[0089] The preparation of the visible light photocatalytic concrete adopts pouring molding.

[0090] The comparative example 4:

[0091] The comparative example 3 provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W.52.5 white cement is used as a cementitious material, and the synthetic nano visible light photocatalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by pouring molding. The specific ratio is as follows: 100 parts of white cement, 40 parts of deionized water, and 0.1 part of the nano visible light photocatalytic refrigerant prepared in the example 3 (the mass ratio of nano cellulose fiber to nano TiO2 is 2.0:1).

[0092] The preparation of the visible light photocatalytic concrete adopts pouring molding.

[0093] The comparative example 5:

[0094] The comparative example 3 provides a nano-modified photocatalytic concrete with radiation refrigeration performance. P.W.52.5 white cement is used as a cementitious material, and the synthetic nano visible light photocatalytic refrigerant is used as an additive to prepare the nano-modified photocatalytic concrete by pouring molding. The specific ratio is as follows: 100 parts of white cement, 40 parts of deionized water, and 0.1 part of the nano visible light photocatalytic refrigerant prepared in the example 3 (the mass ratio of nano cellulose fiber to nano TiO2 is 2.0:1).

[0095] The comparative example 6:

[0096] This comparative example provides a concrete prepared by casting, using PW52.5 white cement as the binder. The specific mix ratio is: 100 parts PW52.5 white cement and 40 parts deionized water. 100 parts of white cement powder are placed in a mixing bowl and stirred at low speed. Simultaneously, 40 parts of deionized water are slowly poured into the mixing bowl. The mixture is stirred at low speed for 30 seconds, then at high speed for 60 seconds, until a homogeneous paste is obtained. The paste is then poured into a mold, covered with plastic wrap, and removed from the mold after one day. The mold is then placed in a curing chamber and cured for 28 days at 20°C and 95% relative humidity to obtain the concrete prepared by casting.

[0097] The nano-modified photocatalytic concretes prepared in the examples and comparative examples were subjected to radiation cooling performance tests, photocatalytic performance tests, and rheological performance tests, respectively. The test methods and results are as follows:

[0098] The radiation cooling performance test method involves fabricating a photocatalytic concrete slab measuring 200mm in length, 100mm in width, and 10mm in thickness from the aforementioned concrete. A house model (110x190x45mm) is then prepared, and the photocatalytic concrete slab is placed on top of the house model. Temperature recorders are installed on the upper and lower surfaces of the photocatalytic concrete slab and at the bottom of the house model. A simulated solar light source is placed above the photocatalytic concrete slab. A 24-channel temperature recorder is used to record the temperature change of the concrete surface under simulated sunlight exposure for 60 minutes (the wavelength range of the simulated sunlight source is 320-780nm). The specific test method is as follows: Figure 2 As shown, the temperature recorder channels are all located at the center of the house model and the photocatalytic concrete slab. Figure 3 Its daytime radiative cooling performance was quantitatively characterized by changes in ambient temperature, and the test results are shown in Table 2.

[0099] The photocatalytic performance testing method involves testing gaseous pollutants (typically represented by nitrogen oxides, a major component of automobile exhaust) with nitrogen oxides (NOx). x The modified concrete was selected as the target pollutant, and its air purification performance was quantitatively characterized by the efficiency of photocatalytic degradation of gaseous and solid pollutants. The test was conducted in a self-made reactor designed according to standard ISO 22197-1. The parameters of the test system were as follows: wavelength range of simulated sunlight source: 320-780 nm; irradiance of the test surface: 10 ± 0.05 W / m². 2 The NO concentration at the pollution source was 5 ppm, the pollutant flow rate and the air flow rate were 0.06 L / min and 2.94 L / min respectively, the total gas flow rate was 3.0 L / min, and the relative humidity in the reaction vessel was 50 ± 1%. The test results are shown in Table 1.

[0100] The rheological property test method is to use a soft solid rheometer (RSX SST, AMETEK Brookfield, USA) and a 40 mm x 20 mm type paddle rotor test to determine the effect of different types of modified photocatalysts on the early fluidity of cement-based materials. During the test, the shear rate is kept at 100 s -1 , the shear rate is 0 s -1 , the shear rate is kept at 0 s -1 , the shear rate is kept at 0 s -1 , the shear rate is kept at 0 s -1 , the shear rate is kept at 0 s -1 . The rheological properties of the cement paste are characterized by the thixotropic loop area.

[0101] Table 1 Degradation rate of gaseous pollutants of each group of photocatalytic concrete plates under the action of simulated sunlight radiation

[0102]

[0103]

[0104] [1] M. Perez-Nicolás, I. Navarro-Blasco, J. M. Fernandez, J. I. Alvarez, Atmospheric NOx removal: Study of cement mortars with iron- and vanadium-doped TiO2 as visible light-sensitive photocatalysts, Constr. Build. Mater. 149 (2017) 257-271. https: / / doi.org / 10.1016 / j.conbuildmat.2017.05.132.

[0105] Document [2] J. Xu, H. Yang, Z. Yang, M. Huang, Y. Zhang, C. Yang, The effect of TiO2@CoAl-LDH nanosphere on early hydration of cement and its photocatalytic depollution performance under UV-visible light, Constr. Build. Mater. 319 (2022) 126227. https: / / doi.org / 10.1016 / j.conbuildmat.2021.126227.

[0106] From Table 1, the degradation rates of NO of the four application examples are much higher than those of the four application comparative examples. The degradation rate of NO of application example 1 is 12.5%, which is 173.6% higher than that of application comparative example 1. The degradation rate of NO of application example 2 is 9.6%, which is 2374.9% higher than that of application comparative example 2. The degradation rate of NO of application example 3 is 11.4%, which is 6658.8% higher than that of application comparative example 3. The degradation rate of NO of application example 4 is 6.2%, which is 498.8% higher than that of application comparative example 4. Compared with the degradation rates of NO of the modified concrete with 1% visible light catalyst reported in documents [1, 2], the degradation rates of NO of the visible light catalytic concrete with 0.1% visible light catalyst prepared in the present application are comparable. Therefore, the above results show that the preparation process of freeze molding can greatly improve the efficiency of photocatalytic degradation of nitrogen oxides of concrete with low catalyst content, and can effectively improve the utilization rate of photocatalyst in concrete. x x

[0107] Table 2 Radiative cooling performance indicators of each group of photocatalytic concrete

[0108]

[0109]

[0110] Note: In Table 2, CH01 and CH08 are the temperature recorder readings of the lower surface and the upper surface of the photocatalytic concrete plate in the corresponding group of the house model, respectively. The temperature difference between CH01 and CH08 is the maximum temperature difference between the upper and lower surfaces of the photocatalytic concrete plate within 60 minutes of simulated sunlight.

[0111] ​​As shown in Table 2, the highest temperature on the upper surface of the photocatalytic concrete slabs in the four application examples does not exceed 34.3℃, and the highest temperature on the lower surface of the concrete slabs does not exceed 28℃ within 1h of simulated sunlight irradiation. In the application comparative examples 1-4, the temperature on the upper surface of the photocatalytic concrete slabs is close to or exceeds 34.5℃, and the highest temperature on the lower surface of the concrete slabs is in the range of 28-30℃. This directly shows that, compared with the cast molding, the photocatalytic concrete slabs formed by the freeze molding play a good role in radiation cooling.

[0112] Further analysis shows that, for the concrete slabs in the application examples 1-4 and the application comparative example 6 formed by the one-way freeze molding, the temperature difference between the upper and lower surfaces of the slabs decreases first and then increases with the increase of the ratio of the nanocellulose fibers to TiO2 in the photocatalyst. This shows that the ratio of the nanocellulose fibers to TiO2 in the nanocellulose fiber modified TiO2 photocatalyst affects the radiation cooling effect of the photocatalytic concrete slabs. When the ratio is less than or equal to 2.0, the radiation cooling effect increases with the increase of the ratio; when the ratio is greater than 2.0, the radiation cooling effect significantly decreases with the increase of the ratio. Compared with the application comparative examples 1-4 and the application comparative example 7, the temperature difference ΔT between the upper and lower surfaces of the photocatalytic concrete slabs does not change obviously with the change of the ratio of the nanocellulose fibers to TiO2 in the photocatalyst. This shows that the pure photocatalyst cannot improve the radiation cooling performance of the concrete slabs in the cast molding, i.e., the construction of the pores in the hardened concrete plays a fundamental and crucial role in the radiation cooling performance.

[0113] The above embodiments are only used to illustrate the present application, but not to limit the present application. Although the present application is described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications or equivalent replacements of the technical solutions of the present application do not deviate from the spirit and scope of the present application, and should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing visible-photocatalytic concrete with radiative cooling properties, characterized in that, Includes the following steps: The nano-visible light catalytic refrigerant was mixed with mixing water and stirred to obtain a uniformly mixed suspension for mixing. Slowly pour the obtained mixing suspension into the cementitious material, first stir at low speed, then stir at high speed to obtain a uniform slurry; The mixed slurry is poured into the mold required for cryogenic molding, and then the mold is placed on the cryogenic sample preparation platform for cryogenic hardening at a freezing temperature of -85℃ to -55℃. After freeze-hardening, the sample blocks are removed from the mold and then placed in a refrigerator to thaw slowly. After the thawed test blocks are taken out, they are placed in a curing box for curing. After curing, the thermal insulation cement-based material is obtained. The preparation method of the nano-visible photocatalytic refrigerant includes the following steps: Titanium isopropoxide is dissolved in anhydrous ethanol to obtain a titanium isopropoxide ethanol solution. The titanium isopropoxide ethanol solution was added dropwise to an aqueous acetic acid solution containing dispersed nanocellulose fibers. After the addition was completed, the mixture was stirred and mixed evenly at room temperature. The mixture is stirred and reacted at a temperature of 35℃-45℃ for a period of time. After the reaction is complete, the mixture is left to stand for a period of time to obtain nanocellulose fiber modified TiO2 hydrosol, which is a nano visible light catalytic refrigerant.

2. The method for preparing visible light catalytic concrete with radiative cooling properties according to claim 1, characterized in that, In the titanium isopropoxide ethanol solution, the molar ratio of titanium isopropoxide to anhydrous ethanol is 1.5-4:

1.

3. The method for preparing visible light-catalyzed concrete with radiative cooling properties according to claim 1, characterized in that, In an aqueous solution of acetic acid containing dispersed nanocellulose fibers, the molar ratio of acetic acid to water is 0.1-0.4:

1.

4. The method for preparing visible light-catalyzed concrete with radiative cooling properties according to claim 1, characterized in that, In the nanocellulose fiber modified TiO2 hydrosol, the mass ratio of nanocellulose fiber to nano TiO2 is 1-3:

1.

5. The method for preparing visible light photocatalytic concrete with radiative cooling properties according to claim 1, characterized in that, The reaction time is 24-72 h under the condition of heating to 35℃-50℃; the standing time is 72-240 h.

6. The method for preparing visible light-catalyzed concrete with radiative cooling properties according to claim 1, characterized in that, The hydration diameter of the obtained nanocellulose fiber-modified TiO2 hydrosol is less than 100 nanometers.

7. The method for preparing visible light photocatalytic concrete with radiative cooling properties according to claim 1, characterized in that, The low-speed mixing speed is 100-150 rpm for 30-60 seconds; the high-speed mixing speed is 200-400 rpm for 60-120 seconds.

8. The method for preparing visible light photocatalytic concrete with radiative cooling properties according to claim 1, characterized in that, The raw materials for the visible light catalytic concrete include the following components in parts by weight: 100 parts of cementitious material; 30-50 parts of water; and 0.1-0.5 parts of nano-visible light catalytic refrigerant.

9. A visible-photocatalytic concrete with radiative cooling properties, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

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