Silicon dioxide compound as well as preparation method and application thereof

Abstract

The invention discloses a silicon dioxide compound as well as a preparation method and application thereof. The preparation method of the silicon dioxide compound comprises the following steps: reacting a silicon source, manganese salt and inorganic acid in a solvent, and calcining to obtain the silicon dioxide compound. According to the preparation method disclosed by the invention, a one-pot co-gel method is adopted, so that the manganese element participates in the reaction at the initial stage of hydrolytic polycondensation of a silicon source and is compounded at a molecular level to form a Si-O-Mn chemical bond, and the manganese element is uniformly dispersed at an atomic level in a silica gel network, is firmly combined and is not easy to lose; the catalyst is beneficial to catalytic oxidation of toluene and adsorption of heavy metals in water, and has wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, specifically to a silica composite, its preparation method, and its uses. Background Technology

[0002] Manganese oxides (such as MnO2, Mn2O3, and Mn3O4) have shown great potential in environmental catalysis, battery electrodes, and adsorbents due to their excellent redox capabilities, catalytic activity, and electrochemical performance. However, pure manganese oxides have extremely high surface energy, causing them to spontaneously aggregate into large particles like magnets. Furthermore, the dense structure or sintering of pure manganese oxides makes it difficult to achieve a high specific surface area. In addition, manganese oxides are easily dissolved and prone to structural collapse during reactions, resulting in poor stability. Therefore, these factors collectively limit their application effectiveness.

[0003] Currently, heterogeneous solid catalysts are often prepared by loading active components (such as transition metals or noble metals) onto supports with high specific surface areas (such as silica gel, molecular sieves, alumina, etc.) to improve the dispersibility and stability of manganese oxides. Commonly used methods for preparing heterogeneous solid catalysts include co-precipitation, impregnation, and co-mixing. In the precipitation method, the active component is precipitated into an insoluble precipitate using a precipitant in a solution containing the active component, and the catalytically active metal or metal oxide is uniformly dispersed and loaded onto the surface of the support to prepare a supported catalyst. The co-mixing method involves mechanically mixing the support and active component, extruding, and calcining. The impregnation method involves immersing the support in a liquid containing the active component for impregnation, followed by drying, calcination, and activation after impregnation equilibrium to obtain a metal-supported catalyst.

[0004] Silica sol, due to its high specific surface area, good dispersibility, and stability, is widely used as a nano-silica dispersion system, such as a catalyst support, coating additive, and binder. Previous studies have attempted to composite manganese with silicon-based materials through simple physical mixing or post-impregnation methods. For example, in materials prepared by impregnation, manganese species tend to agglomerate on the surface of silica sol particles and are easily detached under harsh reaction conditions (such as high temperature and liquid phase), leading to performance degradation. For instance, CN201410249742.8 discloses a catalyst, catalyst support, and preparation method for advanced wastewater treatment. This method first prepares a porous silica support, then impregnates it in an impregnation solution containing active metal components, followed by washing, drying, and high-temperature calcination to obtain the catalyst for advanced wastewater treatment, reducing COD in wastewater. However, these two methods result in problems such as uneven distribution of manganese, weak bonding with the silicon matrix, easy loss, and unsatisfactory modification effects.

[0005] Therefore, developing a silica composite with simple process, uniform manganese dispersion, strong bonding and stable performance, and its preparation method, has important practical significance and industrial value. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a silica composite, its preparation method and uses.

[0007] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0008] The first aspect of this invention protects a method for preparing a silica composite, comprising the following steps:

[0009] The silicon source, manganese salt, and inorganic acid are reacted in a solvent and then calcined to obtain the silicon dioxide composite.

[0010] In some embodiments, the silicon source is selected from one or two of tetraethyl orthosilicate (TEOS), methyl orthosilicate, and sodium silicate.

[0011] In some embodiments, the silicon source is selected from tetraethyl orthosilicate.

[0012] In some embodiments, the manganese salt is selected from one or more of manganese nitrate, manganese acetate, and manganese sulfate.

[0013] In some embodiments, the solvent is selected from one or both of water and ethanol.

[0014] In some embodiments, the inorganic acid is selected from one or more of hydrochloric acid, nitric acid, and sulfuric acid. During the experiment, the applicant attempted to use alkaline conditions for the reaction; however, it was found that this condition resulted in the formation of manganese salt precipitates, preventing the uniform distribution of manganese in the silica sol system. Furthermore, attempts were made to use an organic acid system, but this resulted in an excessively low reaction rate and adversely affected the polymerization process of the silica sol, leading to a decrease in the uniformity of the final particle size.

[0015] In some embodiments, the reaction temperature is 40-80°C, or 40-60°C, or 80-80°C, for example, 40°C, 50°C, 60°C, 70°C, or 80°C. The reaction temperature of this invention cannot be too high or too low. If the temperature is too low, the nucleation rate will be much greater than the growth rate, resulting in a large number of ultrafine crystal nuclei with extremely small particle sizes. Simultaneously, the Brownian motion of the particles weakens, reducing the probability of collisional polymerization between crystal nuclei, making it impossible to achieve particle size uniformity through polymerization. This ultimately results in a silica sol with a wide particle size distribution and a high proportion of small particles. The large surface area and high surface energy of the small-particle silica sol lead to poor stability. The low activation energy results in slow monosilicic acid formation and low condensation efficiency, causing the nucleation and growth cycle of colloidal particles to increase exponentially, significantly reducing industrial production efficiency. If the temperature is too high, the hydrolysis reaction is completed instantaneously, generating a large amount of high-concentration monosilicic acid. The monosilicic acid rapidly condenses to form a three-dimensional network structure of silica polymer, causing the colloidal particle size to rapidly increase to the micrometer level, resulting in poor uniformity.

[0016] In some embodiments, the reaction time is 2 to 12 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours.

[0017] In some embodiments, the pH value of the reaction is 2.5 to 3.5, for example, 2.5, 3, or 3.5. This invention utilizes a weakly acidic environment to regulate the dissociation equilibrium of silicic acid and the surface charge characteristics of colloidal particles, achieving controllable condensation of monosilicic acid and stable particle dispersion. Once this pH range is exceeded, the reaction kinetics and the colloidal double-layer structure are disrupted, directly leading to uncontrolled particle size and decreased stability of the silica sol, ultimately resulting in a significant reduction in the application performance of the silica composite.

[0018] In some embodiments, the molar ratio of the silicon source to the manganese salt is 1:(0.01-0.3), or it can be 1:(0.01-0.06), or it can be 1:(0.05-0.12), or it can be 1:(0.11-0.22), or it can be 1:(0.21-0.3), for example 1:0.05, 1:0.08, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3.

[0019] In some embodiments, the molar ratio of the silicon source to the inorganic acid is 1:(0.1-5), or 1:(0.1-1.5), or 1:(1-3), or 1:(2.5-5), for example 1:1, 1:2, 1:0.5, 1:1.5, 1:3, 1:4, or 1:5.

[0020] In some embodiments, the calcination temperature can be 300~600℃, 300~450℃, or 400~600℃, for example, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, or 600℃. The silica sol framework has a negative charge, and moisture or volatile anions easily accumulate in the pores. High-temperature calcination removes impurities from the pores, thereby stabilizing the structure, active sites, and improving the stability of the silica composite.

[0021] In some embodiments, the calcination time is 2 to 6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours.

[0022] In some embodiments, the reaction is followed by aging and drying. This invention uses aging to transform poorly crystallized particles into well-crystallized nanoparticles, thereby improving the crystallinity of the silica composite.

[0023] In some embodiments, the aging time is 12 to 48 hours, for example 12 hours, 15 hours, 17 hours, 20 hours, 22 hours, 24 hours, 28 hours, 30 hours, 34 hours, 38 hours, 42 hours, 46 hours, or 48 hours.

[0024] In some embodiments, the drying temperature is 60~120℃, or it can be 60~110℃, or it can be 90~120℃, for example 60℃, 80℃, 70℃, 90℃, 100℃, 110℃, 120℃.

[0025] The second aspect of this invention protects the silica composite obtained by the preparation method described above.

[0026] In some embodiments, the manganese element has a mass fraction of 1-20 wt% based on the total mass of the silica composite.

[0027] A third aspect of this invention protects the use of the silica composite as described above in at least one of the following:

[0028] A1) as a catalyst in the catalytic oxidation of volatile organic compounds;

[0029] A2) As an adsorbent, it adsorbs heavy metals in water.

[0030] In some embodiments, the volatile organic compound is selected from one or both of toluene and formaldehyde.

[0031] In some embodiments, the heavy metal is selected from one or more of arsenic, lead, copper, nickel, and cadmium.

[0032] In some embodiments, the heavy metal is arsenic.

[0033] In some embodiments, the amount of silica composite added is at least 0.1 g / L, such as 0.5 g / L, based on the total volume of the water body.

[0034] In some embodiments, the heavy metal content is 0.1-3 g / L based on the total volume of the water body, such as 0.5 g / L.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) The preparation method of the present invention adopts a one-step co-gel method, which allows manganese ions to participate in the reaction in the early stage of silicon source hydrolysis and polycondensation, and achieves composite at the molecular level, forming Si-O-Mn chemical bonds. This makes the manganese element uniformly dispersed at the atomic level in the silica sol network, and the bond is strong and not easy to be lost.

[0037] 2) The preparation method of the present invention is simple and low in cost: the raw materials are all common chemicals, the reaction conditions are mild, and it is easy to achieve large-scale production.

[0038] 3) The preparation method of the present invention can precisely control the valence state and crystal form of manganese in the final product by adjusting the silicon-manganese ratio, reaction pH and temperature, thereby realizing its catalytic or adsorption performance and meeting the needs of different application scenarios.

[0039] 4) The silica composite of the present invention exhibits excellent low-temperature activity in the catalytic oxidation of VOCs.

[0040] 5) The silica composite of the present invention has a high saturation adsorption capacity when used for heavy metal adsorption. Attached Figure Description

[0041] Figure 1 This is a photograph of the silica composite of the present invention.

[0042] Figure 2 This is an energy dispersive spectroscopy (EDS) image of the silica composite in Example 1 of the present invention, where red represents silicon and green represents manganese.

[0043] Figure 3 XPS data for the silica composite in Example 1 of this invention. Detailed Implementation

[0044] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0045] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention; in the specification and claims of the present invention, unless otherwise expressly stated in the text, the singular forms "a", "an" and "this" include the plural forms.

[0046] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0047] Example 1

[0048] A method for preparing a silica composite includes the following steps:

[0049] 1) Mix 10 mmol of silicon source, 40 mL of ethanol and 10 mL of deionized water, add 10 mL of dilute nitric acid to adjust the pH of the solution to 3, and stir well; then add 0.5 mmol of manganese salt and stir in a 60℃ water bath for 6 h to obtain a gel.

[0050] The silicon source is tetraethyl orthosilicate, the inorganic acid is 6.3 wt% dilute nitric acid, and the manganese salt is manganese nitrate tetrahydrate. The molar ratio of silicon source, manganese salt, ethanol, and inorganic acid is 1:0.05:68.5:1.

[0051] 2) The gel obtained in step 1) was sealed and aged at room temperature for 24 hours, and then dried in an oven at 80°C for 12 hours to obtain a light brown dry gel.

[0052] 3) The light brown dry gel obtained in step 2) was calcined at 300°C for 6 hours in air to obtain the final product, denoted as Mn-SiO2-1.

[0053] In the silica composite obtained in this embodiment, the mass fraction of manganese is 4.58%.

[0054] See the actual photos of the silica composite. Figure 1 .

[0055] EDS Mapping of silica composites can be found in [link to documentation]. Figure 2In the figure, a is an SEM image of the sample; b is the distribution of silicon and manganese in the field of view of figure a; c is the distribution of manganese in the field of view of figure a; and d is the distribution of silicon in the field of view of figure a.

[0056] from Figure 2 It can be seen that manganese is uniformly dispersed in the silica sol particles.

[0057] XPS of silica composites are shown below. Figure 3 .

[0058] from Figure 3 XPS analysis revealed that manganese on the surface of the silica composite exhibited a variety of valence states. Among these, Mn... 4+ It dominates, while a considerable proportion of Mn exists. 3+ And a small amount of Mn 2+ This multivalent form of manganese has unique advantages: different valence states of manganese can form a dynamic oxidation-reduction-regeneration cycle. During this cycle, manganese continuously undergoes valence changes, enabling the silica composite to continuously oxidize toluene and reduce heavy metals, demonstrating promising application potential in the field of environmental pollutant remediation.

[0059] Example 2

[0060] A method for preparing a silica composite includes the following steps:

[0061] 1) Mix 10 mmol of silicon source, 40 mL of ethanol and 10 mL of deionized water, add 10 mL of dilute nitric acid to adjust the pH of the solution to 3, and stir well; then add 0.5 mmol of manganese salt and stir in an 80℃ water bath for 4 h to obtain a gel.

[0062] The silicon source is tetraethyl orthosilicate, the catalyst is 6.3 wt% dilute nitric acid, and the manganese salt is manganese acetate.

[0063] 2) After the reaction is complete, the gel obtained in step 1) is sealed and aged at room temperature for 24 hours, and then dried in an oven at 80°C for 12 hours to obtain a light brown dry gel.

[0064] 3) The dry gel obtained in step 2) was calcined at 400°C for 3 hours in air to obtain a silica composite, denoted as Mn-SiO2-2.

[0065] In the silica composite obtained in this embodiment, the mass fraction of manganese is 4.58%.

[0066] Example 3

[0067] A method for preparing a silica composite includes the following steps:

[0068] 1) Mix 10 mmol of silicon source, 40 mL of ethanol and 10 mL of deionized water, add 10 mL of dilute nitric acid to adjust the pH of the solution to 3, and stir well; then add 0.5 mmol of manganese salt and stir in a 40℃ water bath for 12 h to obtain a gel.

[0069] The silicon source is tetraethyl orthosilicate, and the catalyst is 6.3 wt% dilute nitric acid. The manganese salt is manganese sulfate.

[0070] 2) After the reaction is complete, the gel obtained in step 1) is sealed and aged at room temperature for 24 hours, and then dried in an oven at 80°C for 12 hours to obtain a light brown dry gel.

[0071] 3) The dry gel obtained in step 2) was calcined at 600°C for 2 hours in air to obtain a silica composite, denoted as Mn-SiO2-3.

[0072] In the silica composite obtained in this embodiment, the mass fraction of manganese is 4.58%.

[0073] Example 4

[0074] The difference between this embodiment and Embodiment 1 is that: 1) the ratio of silicon source, manganese salt, ethanol and inorganic acid is different, being 1:0.08:68.5:2, while the rest are the same as in Embodiment 1. A silica composite was obtained, denoted as Mn-SiO2-4.

[0075] In the silica composite obtained in this embodiment, the mass fraction of manganese is 7.33%.

[0076] Example 5

[0077] The difference between this embodiment and Embodiment 1 is that: 1) the ratio of silicon source, manganese salt, ethanol and inorganic acid is different, being 1:0.1:68.5:2, while the rest are the same as in Embodiment 1. A silica composite was obtained, denoted as Mn-SiO2-5.

[0078] In the silica composite obtained in this embodiment, the mass fraction of manganese is 9.17%.

[0079] Example 6

[0080] The difference between this embodiment and Example 1 is that: 1) the calcination temperature is 600℃ and the time is 2h, while the rest is the same as in Example 1. A silica composite was obtained, denoted as Mn-SiO2-6.

[0081] In the silica composite obtained in this embodiment, the mass fraction of manganese is 4.58%.

[0082] Example 7

[0083] The difference between this embodiment and Example 1 is that: 1) the calcination temperature is 300℃ and the time is 6h, while the rest is the same as in Example 1. The final product obtained is denoted as Mn-SiO2-7.

[0084] In the silica composite obtained in this embodiment, the mass fraction of manganese is 4.58%.

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 1 is that no manganese nitrate tetrahydrate was added, while all other aspects were the same as in Example 1, and the final product was denoted as Mn-SiO2-1#.

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 1 is that no inorganic acid was added; it was simply a physical mixture of silicon source and manganese salt. Everything else was the same as in Example 1, and the final product was denoted as Mn-SiO2-2#.

[0089] In the silica composite obtained in this comparative example, the mass fraction of manganese is 4.58%.

[0090] Comparative Example 3

[0091] The difference between Comparative Example 3 and Example 1 is that the silicon source, water, ethanol and organic acid were first stirred in a 60°C water bath for 6 hours, and then manganese salt was added. The rest was the same as in Example 1. The final product was denoted as Mn-SiO2-3#.

[0092] Comparative Example 4

[0093] The difference between Comparative Example 4 and Example 1 is that 10 wt% ammonia water was used to replace dilute nitric acid, while the rest were the same as in Example 1. The final product was denoted as Mn-SiO2-4#.

[0094] Application Example 1

[0095] The silica composites obtained in Examples 1-7 and Comparative Examples 1-4 were subjected to toluene catalytic oxidation performance studies.

[0096] The study investigated toluene as the target pollutant in a fixed-bed reactor at a concentration of 100 ppm and a space velocity of 1000 h⁻¹. -1 The silica composite was loaded with 20g and the catalytic temperature was 120℃.

[0097] The conversion rate of toluene was detected by a handheld gas chromatograph, measuring the concentrations at the inlet and outlet. The conversion rate was calculated using the formula: E = (C1 - C0) / C0 * 100%, where C0 represents the concentration of inlet toluene and C1 represents the concentration of outlet toluene.

[0098] Service life: The time required for the activity of the silica composite to decay to 50% of its initial value during continuous operation in a fixed-bed reactor (i.e., half-life).

[0099] Table 1

[0100] Group Conversion rate (%) Service life Example 1 87.3 6h Example 2 87.1 6.2h Example 3 87.4 6.1h Example 4 95.9 20h Example 5 99.2 27h Example 6 85.4 4.5h Example 7 84.7 5h Comparative Example 1 0 0 Comparative Example 2 20.5 3.5h Comparative Example 3 41.7 4.5h Comparative Example 4 15.4 3h

[0101] Table 1 shows that pure silica sol (Comparative Example 1) showed almost no conversion of toluene. Comparative Example 2, without the addition of inorganic acid, had a conversion rate of only 20.5%. This is likely because Mn did not form a stable Si-O-Mn bond with the silica sol Si-O, but only through van der Waals forces, without chemical bonds, resulting in a weak bond, low conversion rate, and a short lifespan of only 3.5 hours. In Comparative Example 3, a stepwise method of mixing silicon source, ethanol, and organic acid, followed by the addition of manganese salt, resulted in a toluene conversion rate of 41.7% and a lifespan of only 4.5 hours. In Comparative Example 4, a silica complex formed by using alkali instead of inorganic acid showed a toluene conversion rate of 15.4% and a lifespan of only 3 hours. This is likely because the alkali caused manganese salt precipitation, preventing uniform distribution of manganese in the silica sol. The silica complexes prepared in Examples 1-7 of this invention can almost completely oxidize toluene to CO2 and H2O, with a conversion rate of over 84.7%.

[0102] Application Example 2

[0103] The silica composites obtained in Examples 1-7 and Comparative Examples 1-4 were used to adsorb heavy metals from water.

[0104] The concentration of As(III) in 1L of water was 1.5 mmol / L, pH=5.0, the amount of silica complex added was 0.5 g / L, and the adsorption time was 24 h. The saturated adsorption capacity of heavy metals in water is the core indicator for evaluating the performance of adsorption materials, which refers to the maximum mass of heavy metal ions that a unit mass of adsorbent can adsorb.

[0105] Formula for calculating saturated adsorption capacity:

[0106] C0 and C e These are the initial and equilibrium concentrations of As (mmol / L), respectively; V is the volume of the solution (L); M s The mass (g) of the silica composite is represented by ms = 0.5 g / L * V; M As is the relative molecular mass of arsenic (As).

[0107] The initial and equilibrium concentrations of As were determined by ICP-MS.

[0108] The results of the saturated adsorption capacity determination are shown in Table 2.

[0109] Table 2

[0110] Group Saturated adsorption capacity of As(III) Example 1 45 mg / g Example 2 46.1 mg / g Example 3 45.7mg / g Example 4 47.8 mg / g Example 5 48.6 mg / g Example 6 44.9 mg / g Example 7 45.2 mg / g Comparative Example 1 <5 mg / g Comparative Example 2 8.8 mg / g Comparative Example 3 8.4 mg / g Comparative Example 4 6.7 mg / g

[0111] Table 2 shows that pure silica sol (Comparative Example 1) hardly adsorbs heavy metals in water; Comparative Example 2, without the addition of ethanol and inorganic acid, has a saturated adsorption capacity of 8.8 mg / g for heavy metals in water; Comparative Example 3, using a stepwise method of mixing silicon source, ethanol, and organic acid before adding manganese salt, has a saturated adsorption capacity of 8.4 mg / g for heavy metals in water; Comparative Example 4, using alkali instead of inorganic acid to form a silica complex, has a saturated adsorption capacity of 6.7 mg / g for heavy metals in water. The silica complexes prepared in Examples 1-7 of this invention have a saturated adsorption capacity of over 44.9 mg / g for heavy metals in water.

[0112] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications listed herein, as well as variations in the methods and compositions of the invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. A method for preparing a silica composite, characterized in that, Includes the following steps: The silicon source, manganese salt, and inorganic acid are reacted in a solvent and then calcined to obtain the silicon dioxide composite.

2. The preparation method according to claim 1, characterized in that, The silicon source is selected from one or more of tetraethyl orthosilicate, methyl orthosilicate, and sodium silicate; And / or, the manganese salt is selected from one or more of manganese nitrate, manganese acetate, and manganese sulfate; And / or, the solvent is selected from one or both of water and ethanol; And / or, the inorganic acid is selected from one or more of hydrochloric acid, nitric acid and sulfuric acid.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the silicon source to the manganese salt is 1:(0.01-0.3). And / or, the molar ratio of the silicon source to the inorganic acid is 1:(0.1-5).

4. The preparation method according to claim 1, characterized in that, The reaction temperature is 40~80℃; And / or, the reaction time is 2 to 12 hours; And / or, the pH of the reaction is 2.5 to 3.

5.

5. The preparation method according to claim 1, characterized in that, The calcination temperature is 300~600℃; And / or, the calcination time is 2 to 6 hours.

6. The preparation method according to claim 1, characterized in that, The reaction process also includes aging and drying.

7. The preparation method according to claim 6, characterized in that, The aging time is 12-48 hours; And / or, the drying temperature is 60~120℃.

8. The silica composite obtained by the preparation method according to any one of claims 1-7.

9. The silica composite as described in claim 8, characterized in that, Based on the total mass of the silica composite, the mass fraction of manganese is 1-20 wt%.

10. Use of the silica composite of claim 9 or 10 in at least one of the following: A1) as a catalyst in the catalytic oxidation of volatile organic compounds; A2) As an adsorbent, it adsorbs heavy metals in water.

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