CN109012517B - A method for preparing composite silicon-based aerogel using iron tailings as raw material - Google Patents

Abstract

The invention discloses a method for preparing composite silicon-based aerogel by using iron tailings as a raw material. Mixing, heating and stirring, filtration, the filtrate and water glass solution are mixed evenly, ion exchange is carried out through strong acid cation exchange resin, ammonia solution is dropped into the mixture after ion exchange to adjust the pH, and after a massive gel is formed, it is then immersed in the coagulation solution. After standing and aging in the gel aging solution, it is taken out to obtain a wet sol. The obtained wet sol is subjected to surface modification with a modification solution and n-hexane for solvent exchange, and then dried under normal pressure to obtain the composite silicon-based aerogel. glue. The invention uses solid wastes such as iron tailings as raw materials, has low price, mild preparation conditions, low requirements on equipment, and is easy to industrialize; the prepared composite silicon-based aerogel has a tap density of less than 0.175g/cm ³ Not more than 40nm, its porosity is more than 93%.

Description

A method for preparing composite silicon-based aerogel using iron tailings as raw material

technical field

The invention belongs to the technical field of inorganic materials, and in particular relates to a method for preparing a composite silicon-based aerogel by using iron tailings as a raw material.

Background technique

Iron tailings are wastes after beneficiation and are the main component of industrial solid wastes. There are more than 8,000 state-owned mines and more than 110,000 township collective mines in China, with nearly 5 billion tons of tailings stockpiled and an annual discharge of more than 500 million tons of tailings. At present, the comprehensive utilization rate of iron tailings in my country is very low, less than 20%, and most of them are used as building fillers. There are very few high-end products, mainly due to factors such as complex preparation process and harsh reaction conditions, which make it impossible to produce in large quantities. Lack of research on high value-added products, iron tailings cannot be effectively utilized.

The preparation of aerogel mainly consists of sol-gel process and post-processing process. The sol-gel process refers to the hydrolysis and condensation of compounds in solution to form a gel, and then the solvent is removed to form a gel. Post-treatment refers to obtaining aerogels with unique properties after a series of steps such as aging, anti-cracking, and drying after sol-gel polymerization. The initial post-processing of aerogels was supercritical drying; supercritical drying has the disadvantages of low safety factor and harsh conditions, which limit the industrialization and large-scale application of aerogel materials. Orthosilicate (TEOS) is used as a precursor for preparing silicon aerogels by atmospheric drying method to prepare aerogels, but tetraethylorthosilicate also has the disadvantage of being relatively expensive. The preparation of existing silicon-based aerogels is not only expensive for raw materials, but also has harsh drying conditions, which greatly limits its industrial production.

SUMMARY OF THE INVENTION

In view of the above-mentioned technical problems existing in the prior art, the purpose of the present invention is to provide a method for preparing composite silicon-based aerogels with iron tailings as raw materials, which has the advantages of wide raw material sources, low cost, mild preparation conditions, and easy large-scale production. Due to the advantages of large-scale production and the like, the composite silicon-based aerogel with high added value is prepared by the method of the present invention.

The method for preparing composite silicon-based aerogel using iron tailings as a raw material is characterized by comprising the following steps:

1) The iron tailings powder is mixed with sodium hydroxide particles, heated to 400~500℃ in a muffle furnace for 2~3 hours, cooled to room temperature, the cooled mixture is mixed with water, heated and stirred, and the filtrate is collected after filtration, to obtain crude silicon solution;

2) After the crude silicon solution obtained in step 1) and the water glass solution are evenly mixed, ion exchange is carried out through a strongly acidic cation exchange resin, and an aqueous ammonia solution is added dropwise to the mixed solution after ion exchange to adjust the pH to 7~7.5, and it is left to stand for a while. Form a blocky gel, then immerse it in the gel aging solution, stand at room temperature for 20-25 hours, and then remove the blocky gel from the gel aging solution to obtain a wet sol;

3) Step 2) The obtained wet sol is immersed in the modification solution and allowed to stand for 16-20 hours, and after hydrophobic modification of the gel surface, the wet sol is removed from the modification solution;

4) Step 3) The wet sol after being pulled out is immersed in n-hexane for 10-16 hours for solvent exchange, so as to replace the modified liquid remaining in the pores of the wet gel, and then the wet sol is pulled out from the n-hexane. , and drying at atmospheric pressure to obtain the composite silicon-based aerogel.

The method for preparing composite silicon-based aerogel using iron tailings as a raw material is characterized in that the mesh number of the iron tailings powder is more than 100 meshes; the components of the iron tailings include SiO2, CaO, MgO , Al2O3 and Fe2O3.

The described method for preparing composite silicon-based aerogel by using iron tailings as a raw material is characterized in that in step 1), the mass ratio of iron tailings powder and sodium hydroxide particles is 1: 1.4～2.2; The ratio of the mass of the mixture after the cooling to the volume of water is 1: 3～6, the unit of mass is g, the unit of volume is mL, and the temperature of heating and stirring is 70～85 ℃.

The method for preparing composite silicon-based aerogel using iron tailings as a raw material is characterized in that in step 2), the volume ratio of crude silicon solution to water glass solution is 6-8:1.

The method for preparing composite silicon-based aerogel using iron tailings as raw material is characterized in that in step 2), the gel aging solution is a mixed solution composed of absolute ethanol and ethyl orthosilicate; In the gel aging solution, the volume ratio of absolute ethanol and ethyl orthosilicate is 8-12:1, preferably 10:1.

The method for preparing composite silicon-based aerogel using iron tailings as a raw material is characterized in that in step 4), the drying method under normal pressure is: after drying at 60-80° C. for 3-6 hours, Dry at 110~130℃ for 2~4h.

The method for preparing composite silicon-based aerogel using iron tailings as a raw material is characterized in that the tap density of the composite silicon-based aerogel obtained in step 4) is 0.162-0.175 g/cm3, The porosity is 93~95%, and the average pore size is 25~40 nm.

Compared with the prior art, the beneficial effects obtained by the present invention are:

1) The present invention uses solid wastes such as iron tailings as raw materials, with low price and wide sources. A large number of iron tailings are processed, and silicon and aluminum elements in the tailings are extracted to prepare a high value-added composite silicon-based aerogel. Environmental requirements;

2) The present invention provides a method for preparing a composite silicon-based aerogel using iron tailings as a raw material, comprising: heating the iron tailings and sodium hydroxide in a muffle furnace, and performing a direct alkali-dissolving operation; The silicon and aluminum elements are extracted and dissolved in water to make a crude silicon solution containing sodium silicate as a cheap silicon source; a small amount of water glass solution is added to the obtained crude silicon solution to supplement the silicon source and increase the silicon content in the solution. The resulting network structure is denser and stronger; the strong acid cation exchange resin can exchange Na ⁺ ions in the solution for H ⁺ to remove inorganic salts, so as to prevent the presence of a large amount of inorganic salts in the pores after gelation. The effect is that the strong acid cation exchange resin is filled into the exchange column, and the mixture of crude silicon solution and water glass solution can pass through the resin in the exchange column to complete the ion exchange, and then drop ammonia water to adjust the pH; , surface modification, solvent exchange and other operations: aging can enhance the structural strength of the bulk gel; surface modification is to attach a large number of methyl groups to the surface of the gel to change the gel from hydrophilic to hydrophobic, in order to reduce the The influence of liquid surface tension on the structure of the gel pores can also further discharge the water in the pores and maintain a good structure during the drying process. The surface hydrophobic modification can further reduce the influence of the solvent in the pores on the overall structure when drying; solvent exchange Most of the water in the pores can be replaced with n-hexane with lower surface tension; through the above process, the gel can be dried under normal pressure, avoiding the disadvantages of harsh reaction conditions and high energy consumption in supercritical drying. The composite silicon-based aerogel provided by the invention has mild preparation conditions, does not require high equipment, has low daily energy consumption, reasonably utilizes solid waste, reduces costs, and is easy to industrialize;

3) The aerogel prepared by the present invention has strong hydrophobic properties, which can effectively prevent water from entering the pores and cause the collapse of the aerogel pores during the application process.

Description of drawings

Fig. 1 is the process flow diagram of the present invention;

2 is a SEM image of the composite silicon-based aerogel prepared in Example 1 of the present invention;

3 is an FTIR analysis diagram of the composite silicon-based aerogel prepared in Example 1 of the present invention.

Detailed ways

The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

In the following examples and comparative examples, the mass percentages of iron tailings are as follows: SiO ₂ 45.43%, CaO 13.81%, MgO 13.10%, Al ₂ O ₃ 11.35%, Fe ₂ O ₃ 10.13%, the balance It is an impurity; the mass concentration of the water glass solution is 25%~27% (the water glass solution is an aqueous solution of sodium silicate).

The strong acid cation exchange resin is D-62 macroporous strong acid styrene cation exchange resin. The strong acid cation exchange resin is filled into the exchange column, the mixed liquid flows into the exchange column, and the ion exchange is carried out through the strong acid cation exchange resin, and the mixed liquid After flowing out from the exchange column, the pH is adjusted by an aqueous ammonia solution.

Example 1:

A method for preparing composite silicon-based aerogel using iron tailings as raw material, comprising the following steps:

1) Pulverize the iron tailings, take the iron tailings powder with a mesh number of 100 or more and mix them with sodium hydroxide particles in a mass ratio of 1:1.4, and heat them in a muffle furnace to 400 °C for 2 hours for alkali dissolution reaction. After cooling to room temperature, mix with water at a solid-liquid ratio of 1:3 (that is, the overall mixture of iron tailings and sodium hydroxide after cooling is mixed with water, the following are equivalent, and the unit of solid-liquid ratio is g/mL), at Heating and stirring at 70°C for 20h, the filtrate was collected after filtration to obtain crude silicon solution;

2) Step 1) The obtained crude silicon solution is uniformly mixed with the water glass solution in a volume ratio of 6:1 (the water glass solution is added to supplement the silicon source), and ion exchange is carried out through D-62 macroporous strongly acidic styrene-based cation exchange resin , 0.5mol/L ammonia solution was added dropwise to the ion-exchanged mixed solution to adjust the pH to 7, left standing to form a massive gel, and then immersed in the gel aging solution (the gel aging solution is anhydrous). A mixture of ethanol and ethyl orthosilicate in a volume ratio of 8:1), after standing at room temperature for 20 hours, the bulk gel was removed from the gel aging solution to obtain a wet sol;

3) Step 2) The obtained wet sol was immersed in the modification solution and allowed to stand for 16 hours (the modification solution was a mixture of n-hexane and trimethylchlorosilane in a volume ratio of 8:1) to perform hydrophobic modification of the gel surface. Then, remove the wet sol from the modified liquid;

4) Step 3) The wet gel after being pulled out is immersed in n-hexane for 10 hours for solvent exchange to replace the modified liquid remaining in the pores of the wet gel. After the wet gel is pulled out from the n-hexane, Drying at normal pressure (first drying at 60° C. for 3 hours, and then drying at 110° C. for 2 hours), the composite silicon-based aerogel is obtained.

The composite silicon-based aerogel prepared in this example was characterized by scanning electron microscope (SEM), and the results are shown in Figure 2; it can be seen from Figure 2 that the aerogel is connected by many nano-scale particles. The particle size distribution is relatively uniform, which belongs to the typical three-dimensional network nanoporous structure.

The composite silicon-based aerogel prepared in this example is characterized by Fourier transform infrared (FTIR) analysis, and the results are shown in Figure 3; it can be seen from Figure 3 that at the wavenumber of 2925 cm ^-1 Si-CH ₃ The stretching vibration peak of ; the strong and broad peak at 1094 cm ^-1 is the Si-O-Si vibration peak. It can be seen from the above figure that the aerogel is a three-dimensional network structure composed of a large number of Si-O-Si, and also has a lot of hydrophobic methyl groups.

The silicon recovery rate of the silica aerogel prepared in Example 1 was 62%. (The silicon recovery is the ratio of the silicon dioxide aerogel prepared to the silicon content in the iron tailings raw material).

Example 2:

A method for preparing composite silicon-based aerogel using iron tailings as raw material, comprising the following steps:

1) The iron tailings are crushed, and the iron tailings powder with a mesh number of more than 100 meshes is mixed with sodium hydroxide particles in a mass ratio of 1:2.2, and heated to 500 °C in a muffle furnace for 3 hours for alkali dissolution reaction. After cooling to room temperature, mix with water at a solid-liquid ratio of 1:6 (the unit of solid-liquid ratio is g/mL), heat and stir at 85 °C for 24 h, filter and collect the filtrate to obtain a crude silicon solution;

2) Step 1) The obtained crude silicon solution is evenly mixed with water glass solution in a volume ratio of 8:1 (the water glass solution is added to supplement the silicon source), and ion exchange is carried out through D-62 macroporous strong acid styrene cation exchange resin , 0.5mol/L ammonia solution was added dropwise to the ion-exchanged mixed solution to adjust the pH to 7.5, left standing to form a massive gel, and then immersed in the gel aging solution (the gel aging solution is anhydrous). A mixture of ethanol and ethyl orthosilicate in a volume ratio of 12:1), left standing at room temperature for 25 hours, and the bulk gel was removed from the gel aging solution to obtain a wet sol;

3) Step 2) The obtained wet sol is immersed in the modification solution and allowed to stand for 20 hours (the modification solution is a mixed solution of n-hexane and trimethylchlorosilane in a volume ratio of 12:1) to perform hydrophobic modification of the gel surface Then, remove the wet sol from the modified liquid;

4) Step 3) The wet gel after being pulled out is immersed in n-hexane for 16 hours for solvent exchange to replace the modified liquid remaining in the pores of the wet gel. After the wet gel is pulled out from the n-hexane, Drying at normal pressure (first drying at 80° C. for 6 hours, and then drying at 130° C. for 4 hours), the composite silicon-based aerogel is obtained.

Example 3:

A method for preparing composite silicon-based aerogel using iron tailings as raw material, comprising the following steps:

1) The iron tailings are crushed, and the iron tailings powder with a mesh number of 100 or more is mixed with sodium hydroxide particles in a mass ratio of 1:1.8, and heated to 450 °C in a muffle furnace for 2.5 hours for alkali dissolution reaction. , cooled to room temperature and mixed with water at a solid-liquid ratio of 1:5 (the unit of solid-liquid ratio is g/mL), heated and stirred at 80 °C for 23 h, filtered and collected the filtrate to obtain a crude silicon solution;

2) Step 1) The obtained crude silicon solution is evenly mixed with water glass solution in a volume ratio of 7:1 (the water glass solution is added to supplement the silicon source), and ion exchange is carried out through D-62 macroporous strong acid styrene cation exchange resin , 0.4mol/L ammonia solution was added dropwise to the ion-exchanged mixed solution to adjust the pH to 7.5, left to stand to form a blocky gel, and then immersed in the gel aging solution (the gel aging solution is anhydrous). A mixed solution of ethanol and ethyl orthosilicate in a volume ratio of 10:1), left standing at room temperature for 24 hours, and the bulk gel was removed from the gel aging solution to obtain a wet sol;

3) Step 2) The obtained wet sol is immersed in the modification solution and allowed to stand for 18 hours (the modification solution is a mixed solution of n-hexane and trimethylchlorosilane in a volume ratio of 10:1) to perform hydrophobic modification of the gel surface Then, remove the wet sol from the modified liquid;

4) Step 3) The wet gel after being pulled out is immersed in n-hexane for 12 hours for solvent exchange to replace the modified liquid remaining in the pores of the wet gel. After the wet gel is pulled out from the n-hexane, Drying at normal pressure (first drying at 70° C. for 5 hours, and then drying at 120° C. for 3 hours), the composite silicon-based aerogel is obtained.

Example 4:

A method for preparing composite silicon-based aerogel using iron tailings as raw material, comprising the following steps:

1) The iron tailings are crushed, and the iron tailings powder with a mesh number of more than 100 meshes is mixed with sodium hydroxide particles in a mass ratio of 1:2, and heated to 480 °C in a muffle furnace for 2 hours for alkali dissolution reaction. After cooling to room temperature, mix with water at a solid-liquid ratio of 1:6 (the unit of solid-liquid ratio is g/mL), heat and stir at 85 °C for 24 h, filter and collect the filtrate to obtain a crude silicon solution;

2) Step 1) The obtained crude silicon solution is uniformly mixed with the water glass solution in a volume ratio of 6:1 (the water glass solution is added to supplement the silicon source), and ion exchange is carried out through D-62 macroporous strongly acidic styrene-based cation exchange resin , 0.5mol/L ammonia solution was added dropwise to the ion-exchanged mixed solution to adjust the pH to 7, left standing to form a massive gel, and then immersed in the gel aging solution (the gel aging solution is anhydrous). A mixed solution of ethanol and ethyl orthosilicate in a volume ratio of 11:1), let stand for 22 hours at room temperature, and the lumpy gel is removed from the gel aging solution to obtain a wet sol;

3) Step 2) The obtained wet sol is immersed in the modification solution and allowed to stand for 20 hours (the modification solution is a mixture of n-hexane and trimethylchlorosilane in a volume ratio of 11:1) to perform hydrophobic modification of the gel surface Then, remove the wet sol from the modified liquid;

4) Step 3) The wet gel after being pulled out is immersed in n-hexane for 13 hours for solvent exchange to replace the remaining modified liquid in the pores of the wet gel. After the wet gel is pulled out from the n-hexane, Drying at normal pressure (first drying at 75° C. for 5 hours, and then drying at 125° C. for 4 hours), the composite silicon-based aerogel is obtained.

Comparative Example 1:

A method for preparing composite silicon-based aerogel using iron tailings as a raw material is compared according to the same feeding amount in Example 1, comprising the following steps:

1) Pulverize the iron tailings, take the iron tailings powder with a mesh number of 100 or more and mix them with sodium hydroxide particles in a mass ratio of 1:1.4, and heat them in a muffle furnace to 400 °C for 2 hours for alkali dissolution reaction. After cooling to room temperature, mix with water at a solid-liquid ratio of 1:3 (that is, the overall mixture of iron tailings and sodium hydroxide after cooling is mixed with water, the following are equivalent, and the unit of solid-liquid ratio is g/mL), at Heating and stirring at 70°C for 20h, the filtrate was collected after filtration to obtain crude silicon solution;

2) The crude silicon solution obtained in step 1) is ion-exchanged through D-62 macroporous strongly acidic styrene-based cation-exchange resin, and 0.5 mol/L aqueous ammonia solution is added dropwise to the ion-exchanged mixed solution to adjust the pH to 7, Let stand to form a blocky gel, then immerse it in the gel aging solution (the gel aging solution is a mixture of absolute ethanol and ethyl orthosilicate in a volume ratio of 8:1), and let it stand at room temperature. After 20 hours, the bulk gel was removed from the gel aging solution to obtain a wet sol;

3) Step 2) The obtained wet sol was immersed in the modification solution and allowed to stand for 16 hours (the modification solution was a mixture of n-hexane and trimethylchlorosilane in a volume ratio of 8:1) to perform hydrophobic modification of the gel surface. Then, remove the wet sol from the modified liquid;

4) Step 3) The wet gel after being pulled out is immersed in n-hexane for 10 hours for solvent exchange to replace the modified liquid remaining in the pores of the wet gel. After the wet gel is pulled out from the n-hexane, Drying at normal pressure (first drying at 60° C. for 3 hours, and then drying at 110° C. for 2 hours), the composite silicon-based aerogel is obtained.

Comparative Example 2:

A method for preparing composite silicon-based aerogel using iron tailings as a raw material is compared according to the same feeding amount in Example 1, comprising the following steps:

1) Mix the deionized water with the water glass solution in a volume ratio of 6:1, carry out ion exchange through D-62 macroporous strong acid styrene cation exchange resin, and add 0.5mol/L dropwise to the mixed solution after ion exchange. The aqueous ammonia solution was adjusted to pH 7, left standing to form a massive gel, and then immersed in the gel aging solution (the gel aging solution is composed of absolute ethanol and ethyl orthosilicate in a volume ratio of 8:1). After standing at room temperature for 20 hours, the lumpy gel was pulled out from the gel aging solution to obtain a wet sol;

2) Step 1) The obtained wet sol was immersed in the modification solution and allowed to stand for 16 hours (the modification solution was a mixed solution of n-hexane and trimethylchlorosilane in a volume ratio of 8:1) to perform hydrophobic modification of the gel surface Then, remove the wet sol from the modified liquid;

3) Step 2) The wet gel after being pulled out is immersed in n-hexane for 10 hours for solvent exchange to replace the remaining modified liquid in the pores of the wet gel. After the wet gel is pulled out from the n-hexane, Drying at normal pressure (first drying at 60° C. for 3 hours, and then drying at 110° C. for 2 hours), the composite silicon-based aerogel is obtained.

The composite silicon-based aerogels prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were tested for their performance, and their tapped density, average pore size and porosity were tested. The test results are shown in Table 1; The testing standard for density is GB/T 21354-2008.

Table 1 Performance parameters of composite silicon-based aerogels

grouping Tap density Average pore size Porosity Example 1 0.162g/cm³ 25nm 95% Example 2 0.175g/cm³ 30nm 93% Example 3 0.173g/cm³ 35nm 93% Example 4 0.166g/cm³ 40nm 94% Comparative Example 1 0.463g/cm³ less porous 79% Comparative Example 2 0.322g/cm³ less porous 86%

It can be concluded from Table 1 that the aerogel product prepared in Comparative Example 1 has a higher density and a lower porosity. This is because no water glass solution was added in Comparative Example 1. When the pH gel was adjusted by slowly adding 0.5 mol/L ammonia solution dropwise, no whole gel was produced, but only a small amount of soft flocculent pieces. There is no solid skeleton structure formed in the drying process, which leads to the collapse of the pores due to the inability to withstand the pulling of the surface tension of the liquid during the drying process; in Comparative Example 2, no crude silicon solution was added, and the dilution ratio of water glass was too high, resulting in the formation of only soft, For a gel with a thin skeleton, the collapse of the skeleton during the drying process leads to a decrease in volume shrinkage and porosity, which proves that the present invention extracts more silicon elements in the alkali-solution reaction of iron tailings powder, and shows that the crude silicon solution and a small amount of water Glass solution mixing is necessary.

The results of Examples 1 to 4 of the present invention prove that, by recycling the iron tailings by the method defined in the present invention, the tap density of the prepared composite silicon-based aerogel is less than 0.175 g/cm ³ , and the average pore size is not more than 0.175 g/cm 3 . Greater than 40nm, its porosity is more than 93%.

The content described in this specification is only an enumeration of the realization forms of the inventive concept, and the protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments, and the protection scope of the present invention is only limited to those skilled in the art according to the present invention. Equivalent technical means conceivable by the inventive concept.

Claims (6)

1. a method for preparing composite silicon-based aerogel with iron tailings as raw material, is characterized in that comprising the following steps: 1) The iron tailings powder is mixed with sodium hydroxide particles, the mass ratio of iron tailings powder and sodium hydroxide particles is 1: 1.4~2.2, heated to 400~500℃ in a muffle furnace for 2~3h, cooled To room temperature, the cooled mixture is mixed with water, heated and stirred, filtered and the filtrate is collected to obtain a crude silicon solution; wherein the mesh number of the iron tailings powder is more than 100 meshes, and the mass percentage of the components of the iron tailings is as follows: SiO ₂ 45.43%, CaO 13.81%, MgO 13.10%, Al ₂ O ₃ 11.35%, Fe ₂ O ₃ 10.13%, the balance is impurities; 2) After the crude silicon solution obtained in step 1) and the water glass solution are evenly mixed, ion exchange is carried out through a strongly acidic cation exchange resin, and an aqueous ammonia solution is added dropwise to the mixed solution after ion exchange to adjust the pH to 7~7.5, and it is left to stand for a while. A blocky gel is formed, then immersed in the gel aging solution, and after standing at room temperature for 20-25 hours, the blocky gel is pulled out from the gel aging solution to obtain a wet sol; the crude silicon solution and the water glass solution are among them. The volume ratio is 6~8:1; 3) Step 2) The obtained wet sol is immersed in the modification solution and allowed to stand for 16-20 hours, and after hydrophobic modification of the gel surface, the wet sol is removed from the modification solution; 4) Step 3) The wet sol after being pulled out is immersed in n-hexane for 10-16 hours for solvent exchange, so as to replace the modified liquid remaining in the pores of the wet gel, and then the wet sol is pulled out from the n-hexane. , and drying at atmospheric pressure to obtain the composite silicon-based aerogel. 2. A method for preparing composite silicon-based aerogel using iron tailings as a raw material according to claim 1, characterized in that in step 1), the ratio of the mass of the cooled mixture to the volume of water It is 1:3~6, the unit of mass is g, the unit of volume is mL, and the temperature of heating and stirring is 70~85℃. 3. A method for preparing composite silicon-based aerogel using iron tailings as raw material according to claim 1, characterized in that in step 2), the gel aging solution is composed of absolute ethanol and ethyl orthosilicate In the gel aging solution, the volume ratio of absolute ethanol and ethyl orthosilicate is 8-12:1. 4 . The method for preparing composite silicon-based aerogel using iron tailings as raw material according to claim 3 , wherein the volume ratio of absolute ethanol and ethyl orthosilicate is 10:1. 5 . 5 . The method for preparing composite silicon-based aerogel using iron tailings as a raw material according to claim 1 , wherein in step 4), the drying method under normal pressure is: drying at 60-80° C. 6 . After 3~6h, dry at 110~130℃ for 2~4h. 6. A method for preparing composite silicon-based aerogel using iron tailings as raw material according to claim 1, wherein the tap density of the composite silicon-based aerogel obtained in step 4) is 0.162 ~0.175g/cm ³ , the porosity is 93~95%, and the average pore size is 25~40 nm.

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