Preparation method of nanorod hydrosol and application of nanorod hydrosol in concrete

Abstract

The invention discloses a preparation method of nanorod hydrosol and application of the nanorod hydrosol in concrete, the preparation method comprises the following steps: reacting a titanium compound in the presence of H2O2, a catalyst Fe3O4 and water at the temperature of 50-100 DEG C; wherein the nano-rod hydrosol is selected from a TiO2 nano-rod hydrosol or a TiO2-SiO2 composite nano-rod hydrosol, and the nano-rod hydrosol is selected from a TiO2 nano-rod hydrosol or a In the TiO2-SiO2 composite nanorod hydrosol, the content of SiO2 is 0.5 to 2 weight percent, and the content of SiO2 is 0.5 to 2 weight percent; the titanium compound is Ti (OH) 4 or Ti (OH) 4 (at) SiO2; the Ti (OH) 4 (at) SiO2 refers to that SiO2 is compounded on the surface of Ti (OH) 4 in situ. According to the invention, SiO2 is introduced into a TiO2 system, and the high specific surface area and excellent adsorbability of SiO2 are beneficial to enrichment of reactants on the surface of TiO2, so that the photocatalytic efficiency is improved; and meanwhile, the mechanical stability and interface adhesion of the coating are remarkably improved due to excellent chemical inertness and film-forming property.

Description

Technical Field

[0001] This invention belongs to the field of functional nanomaterials and concrete technology, specifically relating to a method for preparing nanorod hydrosols and their application in concrete. Background Technology

[0002] Concrete, as a core material in modern construction and bridge engineering, directly affects the aesthetics, durability, and maintenance costs of structures, especially in high-rise buildings and bridges where the long-term stability and safety of concrete are crucial. With the acceleration of urbanization, the development of self-cleaning concrete surface coatings has become a research hotspot. These coatings can effectively remove surface contaminants and degrade harmful substances in the atmosphere, extending building lifespan, reducing maintenance costs, and achieving harmonious coexistence between buildings and the environment.

[0003] Titanium dioxide (TiO2) is a typical semiconductor photocatalytic material that can generate hydroxyl radicals (•OH) and superoxide radicals (•O2) under light irradiation. - This allows for the photocatalytic oxidation and degradation of organic pollutants. However, the traditional sol-gel method for preparing highly crystalline TiO2 typically requires heat treatment at 400-600 °C, which easily leads to particle agglomeration, grain coarsening, and decreased sol stability, thereby reducing photocatalytic performance and increasing energy consumption. Furthermore, existing TiO2 coatings are prone to problems such as insufficient adhesion, cracking, or peeling during service, limiting their long-term application in the concrete field. Summary of the Invention

[0004] To improve the above-mentioned technical problems, the present invention provides a method for preparing nanorod hydrosol, the method comprising: reacting a titanium compound in the presence of H2O2, Fe3O4 and water; The nanorod hydrosol is selected from TiO2 nanorod hydrosol or TiO2-SiO2 composite nanorod hydrosol; in the TiO2-SiO2 composite nanorod hydrosol, the SiO2 content is 0.5-2 wt%. The titanium compound is Ti(OH)4 or Ti(OH)4@SiO2; Ti(OH)4@SiO2 refers to SiO2 being in situ composited on the surface of Ti(OH)4. The molar ratio of Ti to H2O2 in the titanium compound is 1:(4~15); The molar ratio of Ti to Fe3O4 in the titanium compound is (70~130):1; The reaction temperature is from 50°C to reflux temperature; The reaction time is 1 to 8 hours.

[0005] According to an embodiment of the present invention, the molar ratio of Ti to H2O2 in the titanium compound is 1:(4~15), for example 1:(8~12), for example 1:(9~11), such as 1:(9.5~10.5), such as 1:9.5, 1:9.8, 1:10, 1:10.2 or 1:10.5.

[0006] According to an embodiment of the present invention, the molar ratio of Ti to Fe3O4 in the titanium compound is (70~130):1, for example 80-120:1, with examples selected from 80:1, 90:1, 100:1, 110:1 or 120:1.

[0007] According to an embodiment of the present invention, the concentration of Fe3O4 in the reaction system is 0.2~0.5 mmol / L, for example, 0.2 mmol / L, 0.25 mmol / L, 0.3 mmol / L, 0.35 mmol / L, 0.4 mmol / L, 0.45 mmol / L or 0.5 mmol / L.

[0008] According to an embodiment of the present invention, Fe3O4 is used as a catalyst for the reaction.

[0009] According to an embodiment of the present invention, the reaction temperature is 50~100℃, for example, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, 93℃, 94℃, 95℃, 96℃, 97℃, 98℃, 99℃, or 100℃.

[0010] According to an embodiment of the present invention, the reaction time is 1 to 8 hours, for example, 1 hour, 2 hours, 4 hours, 6 hours or 8 hours.

[0011] According to an embodiment of the present invention, the reaction is carried out at atmospheric pressure.

[0012] According to an embodiment of the present invention, the length of the nanorod hydrosol is 50~100nm, and / or the diameter of the nanorod hydrosol is 5~10nm.

[0013] According to an embodiment of the present invention, the preparation method includes the following steps: (1) A precursor solution was prepared by mixing titanium compound Ti(OH)4 or Ti(OH)4@SiO2 with an aqueous solution of H2O2; (2) The precursor solution obtained in step (1) is mixed with Fe3O4 and heated to prepare the nanorod hydrosol.

[0014] According to an embodiment of the present invention, in step (1), the concentration of the H2O2 aqueous solution is 15-30 wt%, preferably 20-30 wt%.

[0015] According to an embodiment of the present invention, in step (1), the molar ratio of Ti to H2O2 in Ti(OH)4 is 1:(4~15), for example 1:(8~12), for example 1:(9~11), such as 1:(9.5~10.5), such as 1:9.5, 1:9.8, 1:10, 1:10.2 or 1:10.5.

[0016] According to an embodiment of the present invention, in step (1), the precursor is a titanium peroxide complex precursor. Preferably, the concentration of the titanium peroxide complex in the precursor solution is 0.01~0.05 mol / L, more preferably 0.02~0.05 mol / L.

[0017] According to an embodiment of the present invention, in step (2), the temperature of the heating reaction is 50~100℃, for example, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, 93℃, 94℃, 95℃, 96℃, 97℃, 98℃, 99℃, or 100℃.

[0018] According to an embodiment of the present invention, in step (2), the heating reaction time is 1 to 8 hours, for example 1h, 2h, 4h, 6h or 8h.

[0019] According to an embodiment of the present invention, in step (1), the method for preparing Ti(OH)4 as a titanium compound includes the following steps: under ice-water bath conditions, TiCl4 is mixed with water and ammonia is added to make the pH of the system above 10 (e.g., 10.5-13) to obtain the Ti(OH)4; preferably, after the reaction is completed, the mixture is filtered and washed until neutral to obtain Ti(OH)4 precipitate.

[0020] According to an embodiment of the present invention, in step (1), the preparation method of Ti(OH)4@SiO2 as a titanium compound includes the following steps: mixing Ti(OH)4 dispersion with silicon source solution, carrying out hydrolysis reaction under alkaline conditions, and aging the resulting mixture to generate a SiO2 layer in situ on the surface of Ti(OH)4, thereby obtaining Ti(OH)4@SiO2.

[0021] Preferably, in the preparation method of Ti(OH)4@SiO2, the Ti(OH)4 dispersion refers to an aqueous and ethanolic dispersion of Ti(OH)4. As an example, an aqueous Ti(OH)4 dispersion with a solid content of 10-30% (e.g., 10%, 17%, 20%, 25%, 28%, or 30%) can be mixed with ethanol to obtain an aqueous and ethanolic Ti(OH)4 dispersion. Preferably, the concentration of Ti(OH)4 in the dispersion is 0.005~2 g / mL, more preferably 0.01~1 g / mL, for example, 0.01 g / mL, 0.015 g / mL, 0.02 g / mL, or 0.03 g / mL.

[0022] Preferably, in the preparation method of Ti(OH)4@SiO2, the silicon source is selected from tetraethyl orthosilicate (TEOS).

[0023] Preferably, in the preparation method of Ti(OH)4@SiO2, the silicon source solution is an ethanol solution of silicon source, and the volume concentration of the silicon source solution is 1~10 vol%, preferably 3~6 vol%, for example 3.5%, 4%, 4.5%, 5%, 5.5% or 6%.

[0024] Preferably, in the method for preparing Ti(OH)4@SiO2, the ratio of the mass of TiO2 generated from Ti(OH)4 in the Ti(OH)4 dispersion to the mass of SiO2 generated from the added silicon source is 1:(0.001~0.05), more preferably 1:(0.005~0.02).

[0025] Preferably, in the preparation method of Ti(OH)4@SiO2, the alkaline condition refers to a pH of 10 or higher, for example, 10.5-11.2.

[0026] Preferably, in the preparation method of Ti(OH)4@SiO2, the hydrolysis reaction temperature is 15-35℃, for example, room temperature; and / or the hydrolysis reaction time is 2-10h.

[0027] Preferably, in the preparation method of Ti(OH)4@SiO2, the static aging temperature is 15-35℃, for example, room temperature; and / or the static aging time is 2-48h.

[0028] Preferably, the preparation method of Ti(OH)4@SiO2 further includes a post-processing step: centrifuging the aged mixture and taking the precipitate to obtain Ti(OH)4@SiO2.

[0029] According to an embodiment of the present invention, the present invention also provides a method for preparing TiO2 nanorod hydrosol, the method comprising: (S1) Ti(OH)4 was mixed with an aqueous solution of H2O2 to prepare a titanium peroxide complex (PTC) precursor solution; (S2) The titanium peroxide complex precursor solution in step (1) is mixed with Fe3O4 and heated to prepare the TiO2 nanorod hydrosol.

[0030] According to an embodiment of the present invention, in step (S1), the molar ratio of Ti to H2O2 in Ti(OH)4 is 1:(4~15), for example 1:(8~12), for example 1:(9~11), such as 1:(9.5~10.5), such as 1:9.5, 1:9.8, 1:10, 1:10.2 or 1:10.5.

[0031] According to an embodiment of the present invention, in step (S2), the concentration of the titanium peroxide complex in the titanium peroxide complex precursor solution is 0.01~0.05 mol / L, preferably 0.02~0.05 mol / L.

[0032] According to an embodiment of the present invention, in step (S2), the concentration of Fe3O4 in the titanium peroxide complex precursor solution is 0.2~0.5 mmol / L, for example, 0.2 mmol / L, 0.25 mmol / L, 0.3 mmol / L, 0.35 mmol / L, 0.4 mmol / L, 0.45 mmol / L or 0.5 mmol / L.

[0033] According to an embodiment of the present invention, in step (S2), the temperature of the heating reaction is 50~100°C, for example 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, and the heating reaction time is 1-8h, for example 1h, 2h, 4h, 6h or 8h.

[0034] According to an embodiment of the present invention, in step (S2), the length of the TiO2 nanorod hydrosol is 50-100 nm and the diameter is 5-10 nm.

[0035] According to an embodiment of the present invention, a method for preparing a TiO2-SiO2 composite sol includes: (K1) The Ti(OH)4 dispersion was mixed with the silicon source solution and hydrolyzed under alkaline conditions. The resulting mixture was then allowed to stand and age to generate a SiO2 layer in situ on the Ti(OH)4 surface, thus obtaining Ti(OH)4@SiO2. (K2) TiO2-SiO2 composite sol was prepared by mixing Ti(OH)4@SiO2 with H2O2 aqueous solution and Fe3O4.

[0036] According to an embodiment of the present invention, in step (K2), the molar ratio of Ti to H2O2 in Ti(OH)4@SiO2 is 1:(4~15), for example 1:(8~12), for example 1:(9~11), such as 1:(9.5~10.5), such as 1:9.5, 1:9.8, 1:10, 1:10.2 or 1:10.5.

[0037] According to an embodiment of the present invention, in step (K2), the molar ratio of Ti to Fe3O4 in Ti(OH)4@SiO2 is (70~130):1, preferably 80-120:1, and examples are selected from 80:1, 90:1, 100:1, 110:1 or 120:1.

[0038] According to an embodiment of the present invention, in step (K2), the reaction is carried out in water, wherein the concentration of titanium ions in Ti(OH)4@SiO2 in water is 0.01-0.06 mol / L, preferably 0.02-0.04 mol / L.

[0039] According to an embodiment of the present invention, in step (K2), the reaction temperature is 80-100°C and the reaction time is 1-6 hours, for example, 1 hour, 2 hours, 4 hours, 6 hours or 8 hours.

[0040] According to an embodiment of the present invention, in step (K2), the SiO2 content in the TiO2-SiO2 composite sol is 0.5-2wt%, for example, 0.5wt%, 1wt%, 1.5wt% or 2wt%.

[0041] The present invention also provides nanorod hydrosols prepared by the above method, wherein the nanorod hydrosols include TiO2 nanorod hydrosols and / or TiO2-SiO2 composite sols.

[0042] According to an embodiment of the present invention, the TiO2-SiO2 composite sol has the following properties: Figure 12 The shown is a rod-shaped structure.

[0043] The present invention also provides the application of the above-mentioned nanorod hydrosol in concrete, preferably, TiO2 nanorod hydrosol and / or TiO2-SiO2 composite sol are used in concrete.

[0044] The present invention also provides a photocatalytic coating for concrete surface, characterized in that the above-mentioned TiO2 nanorod hydrosol and / or TiO2-SiO2 composite sol are coated on the surface of concrete, for example, by spraying or other methods.

[0045] Preferably, the coating amount of the TiO2-SiO2 composite sol is 5-25 mL / m. 2 Preferably 8-20 mL / m2 .

[0046] Beneficial effects The inventors discovered that introducing SiO2 into the TiO2 system, with its high specific surface area and excellent adsorption properties, helps to enrich reactants on the TiO2 surface, thereby improving photocatalytic efficiency. Simultaneously, its excellent chemical inertness and film-forming properties significantly improve the mechanical stability and interfacial adhesion of the coating. Furthermore, the low refractive index of SiO2 increases the light transmittance of the composite material, allowing more light energy to enter the catalytic layer, further enhancing photocatalysis and self-cleaning effects. Through the composite design of TiO2 and SiO2, durability, hydrophilicity, and mechanical properties can be simultaneously improved while maintaining the photocatalytic activity of TiO2.

[0047] Specifically, the advantages of the present invention include the following aspects: (1) In the preparation of the TiO2 nanorod hydrosol of the present invention, Fe3O4 is used as a Fenton-like catalyst, and its surface Fe 2+ / Fe 3+ The cyclic reaction with the peroxytitanium complex (PTC) promotes the breaking of Ti-OO bonds and induces the condensation of Ti-O-Ti bonds, generating hydroxyl radicals (•OH) and peroxy radicals (•OOH), which promotes the directional crystallization of TiO2 along the (101) crystal plane at low temperature (50-100 ℃) to form a nanorod structure, significantly reducing energy consumption and avoiding particle agglomeration and crystal phase transformation caused by high-temperature calcination, thus achieving green and low-energy preparation; and the nanorods have high crystallinity.

[0048] (2) In the preparation of TiO2 nanorod hydrosol of the present invention, Fe3O4 catalyzes and induces TiO2 to grow in a directional manner along the (101) crystal plane to form a nanorod structure with a length of 50-100 nm and a diameter of 5-10 nm, which significantly improves its specific surface area and photocatalytic reaction activity.

[0049] (3) In the TiO2-SiO2 composite sol of the present invention, SiO2 is in situ composited on the TiO2 surface to form a Ti-O-Si bonded structure, which improves the interfacial bonding force and mechanical strength of the TiO2-SiO2 coating on the concrete surface, while improving acid resistance and rainwater erosion resistance. (4) The TiO2-SiO2 coating prepared by the TiO2-SiO2 composite sol of the present invention can efficiently degrade organic pollutants such as methylene blue (MB) under visible light or ultraviolet light irradiation, and exhibits excellent self-cleaning ability. (5) The TiO2-SiO2 composite sol method of the present invention adopts an aqueous phase system throughout the process, without the need for organic solvents or high-temperature sintering. The process is simple and energy consumption is low, making it suitable for industrial scale-up and on-site construction. It has good prospects for promotion and application. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the preparation process of the nanorod hydrosol of the present invention; Figure 2 TEM images of the product prepared in Comparative Example 1 without the addition of a catalyst and the TiO2 nanorod hydrosols prepared in Examples 1-5; Figure 3 HRTEM images of the product prepared in Comparative Example 1 without the addition of catalyst and the TiO2 nanorod hydrosols prepared in Examples 1-5; Figure 4 The XRD patterns are those of the product prepared in Comparative Example 1 without the addition of a catalyst and the TiO2 nanorod hydrosols prepared in Examples 1-5. Figure 5 A schematic diagram of the Fenton reaction mechanism for the formation of TiO2 nanorod hydrosols by the catalytic decomposition of PTC by Fe3O4; Figure 6 a represents the UV-Vis spectra of pure titanium dioxide and TiO2 nanorod hydrosols from Examples 2 and 5; Figure 6 b is a graph showing the methylene blue (MB) degradation results of the product prepared without catalyst in Comparative Example 1 and the TiO2 nanorod hydrosol in Examples 1-5; Figure 7 The contact angle variation of TiO2-SiO2 coatings with different SiO2 contents; Figure 8 Comparison of color changes of the TiO2 coating in Application Example 1 and the TiO2-SiO2 coating in Application Examples 2-5 on the concrete surface during MB degradation; Figure 9 The color change of the degradation MB after the TiO2-1% SiO2 coating on the concrete surface was peeled off with tape in Application Example 3; Figure 10 The color change of MB after the TiO2-SiO2 coating of Application Example 3 was subjected to water impact for different times after degradation. Figure 11 The color change of the TiO2-SiO2 coating on the concrete surface after acid corrosion in Application Example 3 is shown. Figure 12 The images are TEM images of the TiO2-SiO2 composite sol in Example 6 at different magnifications. Detailed Implementation

[0051] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0052] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0053] Unless otherwise stated, the reaction pressure in the following examples is atmospheric pressure.

[0054] I. Research on TiO2 nanorod hydrosols Example 1: Preparation of TiO2 nanorod hydrosol with Fe3O4 as catalyst (S0) Under ice-water bath conditions, 100 mL of TiCl4 (99%) was diluted in 1000 mL of deionized water, and 5% ammonia solution was slowly added dropwise to adjust the pH to alkaline, resulting in the formation of a white Ti(OH)4 precipitate. The precipitate was filtered using a Buchner funnel and washed with deionized water until neutral.

[0055] (S1) Dissolve 20.22 ml (solid content is 5.16%) Ti(OH)4 in 30% H2O2 solution, control the Ti:H2O2 molar ratio to be 1:10, and dilute to prepare 0.03 mol / L PTC precursor solution.

[0056] (S2) Take the PTC (peroxytitanium complex) precursor solution into a three-necked flask, add Fe3O4 catalyst to a concentration of 0.3 mmol / L, and reflux at 100℃ for 2 hours to obtain TiO2 nanorod hydrosol.

[0057] Examples 2-5: Preparation of TiO2 nanorod hydrosols using Fe3O4 as a catalyst Examples 2-5 are carried out with reference to Example 1, except that the following conditions are different from those in Example 1:

[0058] Comparative Example 1: Preparation of TiO2 nanorod hydrosol without Fe3O4 catalysis The difference between Comparative Example 1 and Example 1 is that in step (S2), no Fe3O4 catalyst was added, and the mixture was refluxed at 100°C for 8 hours.

[0059] Test Example 1: Study on the Catalytic Mechanism of Fe3O4 To investigate the regulatory effect of Fe3O4 on the crystallinity and morphology of TiO2 nanorod hydrosols in Examples 1-5, we compared the microstructure of TiO2 with and without Fe3O4 catalysis. Figure 2 As shown in Figure a, without the addition of Fe3O4, TiO2 appears as spherical nanoparticles. Figure 2 a), while after the addition of Fe3O4, TiO2 gradually transforms into a nanorod structure ( Figure 2 b–f).

[0060] Figure 3 The product prepared in Comparative Example 1 without the addition of a catalyst ( Figure 3 a) and the TiO2 nanorod hydrosols prepared in Examples 1-5 ( Figure 3 HRTEM images of b~f). Figure 3 As shown, the interplanar spacing of the nanorods in Examples 1-5 is 0.35 nm and 0.19 nm, respectively, corresponding to the (101) and (200) crystal planes of anatase TiO2, indicating that Fe3O4 induced the directional growth of TiO2, while Comparative Example 1 did not have directional growth.

[0061] Figure 4 The product prepared in Comparative Example 1 without the addition of a catalyst (i.e. Figure 4 TiO2 (-100℃-8h) and TiO2 nanorod hydrosols prepared in Examples 1-5 (i.e. Figure 4 The XRD patterns of TiO2-Fe3O4 (100℃-1h, 2h, 4h, 8h, and 50℃-8h) show that all samples are pure anatase phase, and the addition of Fe3O4 did not introduce any impurity peaks, indicating that it only participates in the reaction as a catalyst.

[0062] Figure 5 The present invention relates to a catalytic mechanism of Fe3O4 based on the Fenton reaction in TiO2 nanorod hydrosols. Under acidic conditions, Fe in Fe3O4... 3+ Reduced to Fe 2+ The latter reacts with H2O2 to generate ·OH free radicals, which promote the breaking of peroxy bonds in PTC and accelerate the nucleation and crystallization of TiO2. This reaction follows a free radical chain mechanism and can rapidly complete the crystallization process of TiO2 at low temperatures.

[0063] Test Example 2: Evaluation of Photocatalytic Performance The photocatalytic performance of TiO2 nanorod hydrosols was evaluated using UV-Vis spectroscopy and methylene blue (MB) degradation experiments. Figure 6 a represents pure titanium dioxide and the TiO2 nanorod hydrosol from Examples 2 and 5. Figure 6 In example a, the UV-Vis spectra of Fe3O4 at 100℃ correspond to Example 5, and Fe3O4 at 50℃ correspond to Example 2. Figure 6As shown in Figure a, TiO2 prepared by Fe3O4 catalysis exhibits significantly enhanced absorption in the visible light region, with the sample reacting at 100℃ showing the strongest absorption.

[0064] Figure 6 b is the product prepared in Comparative Example 1 without the addition of a catalyst (i.e. Figure 6 The results of the methylene blue (MB) degradation experiments of the TiO2 nanorod hydrosols in Examples 1-5 (100-8h) are shown in Figure b. The specific experimental procedure is as follows: The product prepared without catalyst in Comparative Example 1 and the TiO2 nanorod hydrosols in Examples 1-5 were coated onto the surface of a glass substrate, forming a TiO2 thin film coating. The coated glass substrates were then immersed in 30 mL of a solution with a concentration of 3×10⁻⁶ methylene blue (MB). -5 The sample was immersed in a mol / L MB solution and adsorbed in the dark for 15 h. The change in absorbance of the MB solution before and after adsorption was measured to evaluate the amount of contaminants adsorbed on the TiO2 film. Furthermore, the absorbance of the MB solution was measured every 20 min to determine whether the sample had reached adsorption-desorption equilibrium (the difference between two consecutive absorbance readings ≤ 0.01). Subsequently, the sample after 15 h of adsorption was transferred to 30 ml of a 1×10⁻⁶ mol / L MB solution. -5 In a mol / L MB solution, adsorption continued in the dark until adsorption-desorption was achieved. The sample was then placed in a 2 mW / cm² solution. 2 A photocatalytic reaction experiment was conducted at a distance of 5 cm from the light source under a UV lamp with high intensity. The absorbance of the MB solution after photocatalysis was measured and recorded every 20 minutes, and the absorbance change was recorded over two consecutive hours. The results are as follows: Figure 6 As shown in b. Figure 6 b shows that the sample exhibited the highest degradation rate of MB under 365 nm UV light, exceeding 90% within 2 hours. This indicates that Fe3O4 not only modulates the morphology of TiO2 but also enhances its photocatalytic activity.

[0065] II. Study on SiO2-TiO2 composite nanorod hydrosols Example 6: Preparation of SiO2-TiO2 composite nanorod hydrosol (SiO2 content 1wt%) (K1) First, prepare the TEOS stock solution: Add 9.5 mL of 99.5 wt% ethanol to a small beaker, followed by 0.5 mL of tetraethyl orthosilicate (TEOS), and gently shake to mix, obtaining a 5 vol% TEOS-ethanol solution. When using, accurately measure 0.536 mL of this stock solution (this volume is equivalent to 26.75 μL of pure TEOS, which includes 0.508 mL of ethanol) using a pipette to obtain the TEOS solution.

[0066] Next, a Ti(OH)4 dispersion was prepared: approximately 70 mL of pure ethanol was added to a 200 mL beaker, a magnetic stir bar was placed inside, and the mixture was stirred at 400-600 rpm. Then, 6.0555 g of a Ti(OH)4 aqueous dispersion with a solid content of 17.2% was slowly added. The mixture was stirred continuously for 2 hours, followed by ultrasonic treatment for 20 minutes, and then stirred for another 2 hours to ensure uniform dispersion of Ti(OH)4 in the aqueous and alcohol phases, resulting in a Ti(OH)4 dispersion with a theoretically generated TiO2 mass of 0.72 g.

[0067] The pH was then adjusted and TEOS was introduced: 3.2 mL of 25 wt% ammonia solution was slowly added dropwise to the Ti(OH)4 dispersion system at a rate of about 5 s / drop, while stirring. After mixing evenly, the mixture was allowed to stand and stir for about 5 min, and the pH of the system was measured to be 10.5-11.2. Then, 0.536 mL of 5 vol% TEOS-ethanol solution was added dropwise to the system at a rate of about 1 min / drop. Next, the reaction and aging process is carried out: after the aforementioned components are added dropwise, the timer is started, and the reaction is stirred for 8 hours. During this period, a watch glass or sealing film should be used to cover the container to reduce solvent evaporation. After stirring is stopped, the system is allowed to stand and age for 24 hours. This process can be carried out at 30°C to promote the cross-linking of the Si-O-Si network, making the formed SiO2 shell more compact.

[0068] Finally, separation and washing were performed: the aged slurry was aliquoted into centrifuge tubes and centrifuged at 8000 rpm for 10 minutes, discarding the supernatant. The precipitate was then resuspended in ethanol and centrifuged (8000 rpm, 10 minutes), repeating this process twice. The precipitate was then resuspended in deionized water and centrifuged (8000 rpm, 20 minutes), repeating this process three times to thoroughly remove impurities, yielding Ti(OH)4@SiO2. The Ti(OH)4@SiO2 refers to SiO2 in situ composited on the surface of Ti(OH)4, corresponding to a theoretical mass of 0.0072 g of SiO2 generated.

[0069] (K2) Weigh 4.265 g (solid content 13.83%) of Ti(OH)4@SiO2 solid into a 200 mL beaker. Add H2O2 according to a Ti:H2O2 molar ratio of 1:10, and then add 50 mL of deionized water. Stir with a magnetic stir bar for 1 h to obtain a clear orange-yellow solution. Transfer the obtained solution to a 500 mL three-necked flask, add 0.017 g of Fe3O4, and then add 182 mL of deionized water to make up the final solution. 4+The concentration of Fe3O4 was 0.3 mmol / L, and the reflux condenser was set up. A magnetic stirrer was turned on, and the reaction temperature was set to 100℃. Timing was started when reflux liquid was generated. After 2 hours of reaction, heating and stirring were stopped, and the mixture was allowed to cool to room temperature to obtain TiO2-SiO2 composite nanorod hydrosol, in which the SiO2 content was 1 wt%, denoted as TiO2-1% SiO2 sol.

[0070] The SiO2 content is calculated as follows: TEOS volume: V(TEOS) = 0.536mL × 0.05 = 0.02675mL TEOS mass: m(TEOS) = 0.02675mL × 0.933g / mL ≈ 0.02496g.

[0071] n (TEOS) = (0.02496 / 208.31) mol n(TEOS) = n(Si) = n(SiO2), and the molar mass of SiO2 is 60.08 g / mol. m(SiO2) = n (SiO2)×60.08g / mol=(0.02496 / 208.31)×60.08=0.0072g The mass ratio of SiO2 to TiO2 is: 0.0072g ÷ 0.72g × 100% = 1% Examples 7-9: Preparation of SiO2-TiO2 composite nanorod hydrosols (SiO2 content: 0.5wt%, 1.5wt%, 2wt%) Examples 7-9 are performed with reference to Example 6, except that the amount of 5% TEOS-ethanol solution added in step (K1) of Example 6 is adjusted as follows, so that the SiO2 content in the TiO2-SiO2 composite sol is 0.5wt%, 1.5wt%, and 2wt%, respectively, and is denoted as TiO2-0.5% SiO2 sol, TiO2-1.5% SiO2 sol, and TiO2-2% SiO2 sol:

[0072] Comparative Example 2: Preparation of TiO2 sol without Fe3O4 catalysis The difference between Comparative Example 2 and Example 6 is that no 5% TEOS-ethanol solution was added in Comparative Example 2, and the TiO2 sol was prepared by Fe3O4 catalysis.

[0073] Application Examples 1-5 The TiO2 sol of Comparative Example 2 and the TiO2-SiO2 composite sols of Examples 7, 6, 8 and 9 (i.e., SiO2 contents of 0, 0.5 wt%, 1 wt%, 1.5 wt%, and 2 wt%, respectively) were applied using a spraying technique at a rate of 10 mL / m 2 The coating is applied to the surface of C30 / C40 concrete test blocks to form a TiO2 coating and a TiO2-SiO2 coating.

[0074] Test Example 3: Coating Performance Evaluation The performance of the coatings in Application Examples 1-5 was evaluated using contact angle testing and MB degradation experiments. The test results are as follows: Figure 7 and Figure 8 As shown.

[0075] in, Figure 7 In the diagram, the contact angles are represented as follows, in the order shown: Initial glass substrate contact angle (i.e., original); glass slide (i.e.) Figure 7 The surface of the glass substrate was coated with the contact angle (i.e., TiO2) of the TiO2 sol generated by Fe3O4 catalysis in Comparative Example 2. The glass slide surface was coated with a TiO2-0.5% SiO2 sol with a contact angle of 0.5% SiO2. The glass slide surface was coated with TiO2-1% SiO2 sol (i.e., 1% SiO2). The glass slide surface was coated with a TiO2-1.5% SiO2 sol with a contact angle of 1.5% SiO2. The glass slide surface was coated with a TiO2-2%SiO2 sol contact angle (i.e., 2% SiO2). The surface of the concrete substrate was coated with the contact angle (i.e., TiO2) of the TiO2 sol generated by Fe3O4 catalysis in Comparative Example 2. The surface of the concrete substrate was coated with a TiO2-1% SiO2 sol (i.e., 1% SiO2). The surface of the concrete substrate was coated with a TiO2-2% SiO2 sol (i.e., 2% SiO2).

[0076] Figure 7 The results showed that the TiO2-1%SiO2 coating surface had a water contact angle of less than 10°, exhibiting superhydrophilicity.

[0077] Figure 8This image shows a comparison of the color changes of the TiO2 coating in Application Example 1 and the TiO2-SiO2 coating in Application Examples 2-5 during the degradation of methylene blue (MB) on concrete surfaces. The specific test procedure was as follows: a 0.03 mmol / L MB solution was drop-coated onto the surfaces of the TiO2 coating in Application Example 1 and the TiO2-SiO2 coating in Application Examples 2-5, and then irradiated with ultraviolet light (25W) sequentially for 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min. After 15 minutes of ultraviolet irradiation, the MB was completely degraded, and the color disappeared. Figure 8 In Chinese, "concrete" refers to a concrete surface without any coating that has been exposed to ultraviolet light.

[0078] Peel resistance test: The surface of the concrete with a TiO2-SiO2 coating containing 1% SiO2 content in Case 3 was subjected to different numbers of tape peelings (1, 3, 7, 11 and 17 times respectively). Then, a 0.03 mmol / L MB solution was dropped onto the TiO2-SiO2 coating surface and irradiated with ultraviolet light for 5 min, 10 min, 15 min, 20 min, 25 min and 30 min respectively to carry out photocatalytic degradation test.

[0079] Figure 9 The image shows the color change of MB (dimethylbenzene) after the TiO2-1%SiO2 coating in Example 3 was peeled off from the concrete surface following tape removal. Figure 9 As shown, after 30 minutes of UV irradiation, the color retention of MB increased with the number of peelings, but even after 17 peelings, it still retained a certain photocatalytic performance.

[0080] Water impact resistance test: Water impact tests were conducted on concrete surfaces with a TiO2-SiO2 coating containing 1% SiO2 at a flow rate of 3 m / s for different durations (2 h and 6 h, respectively). The specific test procedure was as follows: the TiO2-SiO2 coating surface of Application Example 3 was subjected to water impact at a flow rate of 3 m / s for 2 h or 6 h. After the impact, a 0.03 mmol / L MB solution was dropped onto the TiO2-SiO2 coating surface, and the surface was irradiated with ultraviolet light (25 W) for 5 min, 10 min, 15 min, 20 min, 25 min and 30 min in sequence to carry out photocatalytic degradation tests.

[0081] Figure 10 The color change of MB after water impact at different times is shown for the TiO2-SiO2 coating in Application Example 3. Figure 10 As shown, after 6 hours, the TiO2-SiO2 coating still retained good photocatalytic performance within 30 minutes, and after 2 hours of light irradiation, the degradation rate was still over 90%.

[0082] Acid corrosion resistance test: The specific method is as follows: Concrete with a TiO2-SiO2 coating containing 1% SiO2, corresponding to Example 3, was immersed in acidic solutions with pH=2 and 4 for 2, 6, and 24 hours, respectively. After immersion, a 0.03 mmol / L MB solution was drop-coated onto the TiO2-SiO2 coating surface, and photocatalytic degradation experiments were conducted by sequentially irradiating the surface with ultraviolet light for 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min. The test results are as follows: Figure 11 As shown. Figure 11 The color change of the degradation MB of the TiO2-SiO2 coating on the concrete surface after acid corrosion in Example 3 shows that after 24 hours of corrosion in an acidic solution with pH=4, more than 90% of the degradation efficiency was retained within 30 minutes. After 24 hours of corrosion in an acidic solution with pH=2, the degradation remained good within 30 minutes.

[0083] The above results indicate that after incorporating 1% SiO2 onto the TiO2 surface, the TiO2-SiO2 composite sol improves the adhesion between the film and the concrete substrate and increases its durability while maintaining good photocatalytic performance.

[0084] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the claims of this application.

Claims

1. A method for preparing a nanorod hydrosol, characterized in that, The preparation method includes: reacting a titanium compound in the presence of H2O2, Fe3O4 and water; The nanorod hydrosol is selected from TiO2 nanorod hydrosol or TiO2-SiO2 composite nanorod hydrosol; in the TiO2-SiO2 composite nanorod hydrosol, the SiO2 content is 0.5-2 wt%. The titanium compound is Ti(OH)4 or Ti(OH)4@SiO2; Ti(OH)4@SiO2 refers to SiO2 being in situ composited on the surface of Ti(OH)4. The molar ratio of Ti to H2O2 in the titanium compound is 1:(4~15); The molar ratio of Ti to Fe3O4 in the titanium compound is (70~130):1; The reaction temperature is from 50°C to reflux temperature; The reaction time is 1 to 8 hours.

2. The method according to claim 1, characterized in that, The molar ratio of Ti to H2O2 in the titanium compound is 1:(4~15); And / or, the molar ratio of Ti to Fe3O4 in the titanium compound is (70~130):1; And / or, the concentration of Fe3O4 in the reaction system is 0.2~0.5 mmol / L; And / or, the temperature of the reaction is 50~100℃; The reaction time is 1 to 8 hours; And / or, the reaction is carried out at atmospheric pressure; And / or, the length of the nanorod hydrosol is 50~100 nm, and / or the diameter of the nanorod hydrosol is 5~10 nm.

3. The method according to claim 1, characterized in that, The preparation method includes the following steps: (1) A precursor solution was prepared by mixing titanium compound Ti(OH)4 or Ti(OH)4@SiO2 with an aqueous solution of H2O2; (2) The precursor solution obtained in step (1) is mixed with Fe3O4 and heated to prepare the nanorod hydrosol.

4. The method according to claim 3, characterized in that, In step (1), the precursor is a titanium peroxide complex precursor; And / or, in the precursor solution, the concentration of the titanium peroxide complex is 0.01~0.05 mol / L; And / or, in step (1), the preparation method of Ti(OH)4@SiO2 as a titanium compound includes the following steps: mixing Ti(OH)4 dispersion with silicon source solution, carrying out hydrolysis reaction under alkaline conditions, and aging the resulting mixture to generate SiO2 layer in situ on the Ti(OH)4 surface to obtain Ti(OH)4@SiO2.

5. The method according to claim 4, characterized in that, In the preparation method of Ti(OH)4@SiO2, the Ti(OH)4 dispersion refers to the water and ethanol dispersion of Ti(OH)4; And / or, the concentration of Ti(OH)4 in the Ti(OH)4 dispersion is 0.005~2 g / mL; And / or, in the preparation method of Ti(OH)4@SiO2, the silicon source is selected from tetraethyl orthosilicate; And / or, in the preparation method of Ti(OH)4@SiO2, the silicon source solution is an ethanol solution of silicon source, and the volume concentration of the silicon source solution is 1~10 vol%. And / or, in the method for preparing Ti(OH)4@SiO2, the ratio of the mass of TiO2 generated from Ti(OH)4 in the Ti(OH)4 dispersion to the mass of SiO2 generated from the added silicon source is 1:(0.001~0.05); And / or, in the preparation method of Ti(OH)4@SiO2, the hydrolysis reaction temperature is 15-35℃ and the hydrolysis reaction time is 2-10h; And / or, in the preparation method of Ti(OH)4@SiO2, the static aging temperature is 15-35℃, and / or the static aging time is 2-48h.

6. The method according to claim 1, characterized in that, A method for preparing TiO2 nanorod hydrosol, the method comprising: (S1) Ti(OH)4 and H2O2 aqueous solution were mixed to prepare titanium peroxide complex precursor solution; (S2) The titanium peroxide complex precursor solution in step (1) is mixed with Fe3O4 and heated to prepare the TiO2 nanorod hydrosol; And / or, in step (S2), the concentration of the titanium peroxide complex in the titanium peroxide complex precursor solution is 0.01~0.05 mol / L; And / or, in step (S2), the concentration of Fe3O4 in the titanium peroxide complex precursor solution is 0.2~0.5 mmol / L.

7. The method according to claim 1, characterized in that, A method for preparing a TiO2-SiO2 composite sol, the method comprising: (K1) The Ti(OH)4 dispersion was mixed with the silicon source solution and hydrolyzed under alkaline conditions. The resulting mixture was then allowed to stand and age to generate a SiO2 layer in situ on the Ti(OH)4 surface, thus obtaining Ti(OH)4@SiO2. (K2) TiO2-SiO2 composite sol was prepared by mixing and reacting Ti(OH)4@SiO2 with H2O2 aqueous solution and Fe3O4; And / or, in step (K2), the reaction is carried out in water, wherein the concentration of titanium ions in Ti(OH)4@SiO2 in water is 0.01-0.06 mol / L; And / or, in step (K2), the SiO2 content in the TiO2-SiO2 composite sol is 0.5-2wt%.

8. The nanorod hydrosol prepared by the method according to any one of claims 1-7, wherein the nanorod hydrosol comprises TiO2 nanorod hydrosol and / or TiO2-SiO2 composite sol.

9. The application of the nanorod hydrosol according to claim 8 in concrete, And / or, use TiO2 nanorod hydrosol and / or TiO2-SiO2 composite sol in concrete.

10. A photocatalytic coating for concrete surface, characterized in that, The TiO2 nanorod hydrosol and / or TiO2-SiO2 composite sol described in claim 8 are coated onto the surface of concrete.

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