CN109012517B - Method for preparing composite silicon-based aerogel by taking iron tailings as raw materials - Google Patents
Method for preparing composite silicon-based aerogel by taking iron tailings as raw materials Download PDFInfo
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Abstract
The invention discloses a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials, which comprises the following steps: mixing iron tailing powder and sodium hydroxide particles, carrying out alkali dissolution reaction at high temperature, cooling, mixing with water, heating and stirring, filtering, uniformly mixing filtrate with a water glass solution, carrying out ion exchange through a strong acid cation exchange resin, dripping an ammonia water solution into the mixed solution after the ion exchange to adjust the pH value, immersing the mixed solution into a gel aging solution after forming a blocky gel, standing and aging, taking out the blocky gel to obtain wet sol, sequentially carrying out surface modification on the wet sol through a modification solution and carrying out solvent exchange through n-hexane, and drying at normal pressure to obtain the composite silicon-based aerogel. The invention adopts solid wastes such as iron tailings and the like as raw materials, has low price, mild preparation conditions, low requirements on equipment and easy industrialization; the tap density of the prepared composite silicon-based aerogel is 0.175g/cm3Hereinafter, the average pore diameter is not more than 40nm, and the porosity thereof is 93% or more.
Description
Technical Field
The invention belongs to the technical field of inorganic materials, and particularly relates to a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials.
Background
The iron tailings are wastes after mineral separation and are the main components of industrial solid wastes. In China, more than 8000 national mines and more than 11 million village and town collective mines exist, the quantity of stockpiled tailings is nearly 50 hundred million tons, and the quantity of tailings discharged in the year is more than 5 hundred million tons. At present, the comprehensive utilization rate of iron tailings in China is low and is less than 20%, most of the iron tailings are used as building fillers, and high-end products are few, mainly because of factors such as complex preparation process and harsh reaction conditions, the iron tailings cannot be produced in large scale. In the absence of research on high value-added products, the iron tailings cannot be effectively utilized.
The preparation of aerogels consists mainly of a sol-gel process and a post-treatment process. The sol-gel process refers to the hydrolytic condensation of a compound in solution to a gum solution, followed by removal of the solvent to form a gel. The post-treatment refers to that after sol-gel polymerization, the aerogel with unique performance is obtained through a series of steps of aging, cracking prevention, drying and the like. The initial post-treatment for preparing the aerogel adopts a supercritical drying method; the supercritical drying has the defects of low safety coefficient, harsh conditions and the like, and limits the industrialization and large-scale application of the aerogel material. Tetraethoxysilane (TEOS) is used as a precursor for preparing the silicon aerogel to prepare the aerogel by adopting a normal pressure drying method, but the tetraethoxysilane also has the defect of higher price. The existing preparation of the silica-based aerogel has expensive raw materials and harsh drying conditions, and greatly limits the industrial production.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention aims to provide a method for preparing composite silicon-based aerogel by using iron tailings as raw materials, which has the advantages of wide raw material source, low cost, mild preparation conditions, easiness in large-scale production and the like, and the composite silicon-based aerogel with high added value is prepared by the method.
The method for preparing the composite silicon-based aerogel by taking the iron tailings as the raw materials is characterized by comprising the following steps of:
1) mixing iron tailing powder and sodium hydroxide particles, heating the mixture in a muffle furnace to 400-500 ℃, keeping the mixture for 2-3 hours, cooling the mixture to room temperature, mixing the cooled mixture with water, heating and stirring the mixture, filtering the mixture, and collecting filtrate to obtain a crude silicon solution;
2) uniformly mixing the crude silicon solution obtained in the step 1) with a water glass solution, carrying out ion exchange by using a strong-acid cation exchange resin, dropwise adding an ammonia solution into the mixed solution after the ion exchange to adjust the pH value to 7-7.5, standing to form blocky gel, immersing the blocky gel into a gel aging solution, standing at room temperature for 20-25 h, and taking out the blocky gel from the gel aging solution to obtain wet sol;
3) immersing the wet sol obtained in the step 2) into the modification solution, standing for 16-20 h, and fishing out the wet sol from the modification solution after hydrophobic modification of the gel surface is carried out;
4) and 3) soaking the fished wet sol into n-hexane, standing for 10-16 h for solvent exchange to replace the modification solution remaining in the wet gel pore channel, fishing the wet sol out of the n-hexane, and drying at normal pressure to obtain the composite silicon-based aerogel.
The method for preparing the composite silicon-based aerogel by taking the iron tailings as the raw materials is characterized in that the mesh number of iron tailing powder is more than 100 meshes; the components of the iron tailings comprise SiO2, CaO, MgO, Al2O3 and Fe2O 3.
The method for preparing the composite silicon-based aerogel by taking the iron tailings as the raw materials is characterized in that in the step 1), the mass ratio of iron tailing powder to sodium hydroxide particles is 1: 1.4-2.2; the ratio of the mass of the cooled mixture to the volume of water is 1: 3-6, the unit of the mass is g, the unit of the volume is mL, and the heating and stirring temperature is 70-85 ℃.
The method for preparing the composite silicon-based aerogel by taking the iron tailings as the raw materials is characterized in that in the step 2), the volume ratio of the crude silicon solution to the water glass solution is 6-8: 1.
the method for preparing the composite silicon-based aerogel by taking the iron tailings as the raw materials is characterized in that in the step 2), the gel aging liquid is a mixed liquid composed of absolute ethyl alcohol and ethyl orthosilicate; in the gel aging liquid, the volume ratio of absolute ethyl alcohol to ethyl orthosilicate is 8-12: 1, preferably 10: 1.
the method for preparing the composite silicon-based aerogel by taking the iron tailings as the raw materials is characterized in that in the step 4), the normal-pressure drying method comprises the following steps: drying the mixture at the temperature of 60-80 ℃ for 3-6 h, and then drying the mixture at the temperature of 110-130 ℃ for 2-4 h.
The method for preparing the composite silicon-based aerogel by using the iron tailings as the raw materials is characterized in that the tap density of the composite silicon-based aerogel prepared in the step 4) is 0.162-0.175 g/cm3, the porosity is 93-95%, and the average pore diameter is 25-40 nm.
Compared with the prior art, the invention has the following beneficial effects:
1) the invention adopts solid wastes such as iron tailings and the like as raw materials, and has low price and wide source. A large amount of iron tailings are treated, silicon and aluminum elements in the tailings are extracted to prepare the composite silicon-based aerogel with high added value, so that the influence on the environment is reduced, the recovery utilization rate of the tailings is improved, and the requirement of environmental protection is met;
2) the invention provides a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials, which comprises the following steps: heating the iron tailings and sodium hydroxide in a muffle furnace, performing direct alkali dissolution operation, extracting silicon and aluminum elements in the iron tailings, and dissolving the extracted silicon and aluminum elements in water to prepare a crude silicon solution containing sodium silicate as a cheap silicon source; adding a small amount of water glass solution into the obtained crude silicon solution to supplement a silicon source, and increasing the silicon content in the solution, so that the formed network structure is denser and has higher strength; the strong acid cation exchange resin can remove Na in the solution+Ion exchange to H+Removing inorganic salt to prevent the influence of inorganic salt in a pore passage after gelation on the effect of normal pressure drying, filling strong acid cation exchange resin into an exchange column, completing ion exchange of a mixed solution of a crude silicon solution and a water glass solution in the exchange column through the resin, and then dropping ammonia water to adjust the pH; aging, surface modification, solvent exchange and the like are carried out on the massive gel: aging may enhance the structural strength of the block gel; the surface modification is to make a great deal of methyl attached to the surface of the gel to change the hydrophilicity of the gel into hydrophobicity, in order to reduce the influence of the surface tension of the liquid on the pore structure of the gel during drying, the water in the pore can be further discharged, a good structure is kept during drying, and the influence on the overall structure during the drying of the solvent in the pore is further reduced through the surface hydrophobic modification; most of water in the pore channels can be replaced by n-hexane with smaller surface tension through solvent exchange; through the process, the gel can be dried under normal pressure, and the defects of harsh reaction conditions, high energy consumption and the like in supercritical drying are avoided. The composite silicon-based aerogel provided by the invention has the advantages of mild preparation conditions, low requirements on equipment, low daily energy consumption, reasonable utilization of solid wastes, cost reduction and easiness in industrialization;
3) the aerogel prepared by the method has stronger hydrophobic property, and can effectively prevent water from entering the pore channels to cause the collapse of the pore channels of the aerogel in the application process.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is an SEM image of a composite silica-based aerogel prepared in example 1 of the present invention;
FIG. 3 is a FTIR analysis chart of the composite silica-based aerogel prepared in example 1 of the present invention.
Detailed Description
The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.
In the following examples and comparative examples, the iron tailings comprise the following components in percentage by mass: SiO2245.43%、CaO13.81%、MgO 13.10%、Al2O311.35%、Fe2O310.13 percent, and the balance being impurities; the mass concentration of the water glass solution is 25-27% (the water glass solution is sodium silicate solution).
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 an exchange column, the mixed solution flows into the exchange column, ion exchange is carried out through the strong acid cation exchange resin, and the pH of the mixed solution is adjusted by ammonia water solution after the mixed solution flows out of the exchange column.
Example 1:
a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials comprises the following steps:
1) crushing iron tailings, namely taking iron tailings powder with the mesh number of more than 100 meshes and sodium hydroxide particles according to the mass ratio of 1: 1.4, heating the mixture to 400 ℃ in a muffle furnace, keeping the mixture for 2 hours for alkali dissolution reaction, cooling the mixture to room temperature, and mixing the mixture with water according to a solid-to-liquid ratio of 1: 3 (namely mixing the whole mixture of the cooled iron tailings and sodium hydroxide with water, wherein the unit of solid-to-liquid ratio is g/mL, the same below, heating and stirring the mixture at 70 ℃ for 20 hours, filtering the mixture, and collecting filtrate to obtain a crude silicon solution;
2) uniformly mixing the crude silicon solution obtained in the step 1) with a water glass solution according to the volume ratio of 6: 1 (adding the water glass solution to supplement a silicon source), carrying out ion exchange by using D-62 macroporous strong-acid styrene cation exchange resin, dropwise adding 0.5mol/L ammonia water solution into the mixed solution after ion exchange to adjust the pH value to 7, standing to form blocky gel, immersing the blocky gel into a gel aging solution (the gel aging solution is the mixed solution of absolute ethyl alcohol and ethyl orthosilicate according to the volume ratio of 8: 1), standing at room temperature for 20 hours, and taking out the blocky gel from the gel aging solution to obtain wet sol;
3) immersing the wet sol obtained in the step 2) into a modification solution, standing for 16h (the modification solution is a mixed solution formed by n-hexane and trimethylchlorosilane in a volume ratio of 8: 1), and fishing out the wet sol from the modification solution after hydrophobic modification of the gel surface;
4) and 3) soaking the fished wet gel in n-hexane, standing for 10h for solvent exchange to replace the residual modification solution in the pore channel of the wet gel, then fishing out the wet sol from the n-hexane, and drying at normal pressure (drying at 60 ℃ for 3h, and then drying at 110 ℃ for 2 h) to obtain the composite silicon-based aerogel.
Scanning Electron Microscope (SEM) analysis and characterization were performed on the composite silicon-based aerogel prepared in this example, and the results are shown in fig. 2; as can be seen from FIG. 2, the aerogel is formed by connecting a plurality of nanometer-sized particles, has uniform particle size distribution, and belongs to a typical three-dimensional reticular nano-porous structure.
Fourier infrared (FTIR) analysis and characterization are performed on the composite silica-based aerogel prepared in the embodiment, and the result is shown in fig. 3; as can be seen from FIG. 3, at a wave number of 2925 cm-1Is of Si-CH3The stretching vibration peak of (1); at 1094 cm-1The strong and broad peak is the Si-O-Si oscillation peak. As can be seen from the above figures, the aerogel is a three-dimensional network structure composed of a large amount of Si-O-Si, and has many methyl groups present for hydrophobic effect.
The silica aerogel prepared in example 1 had a silicon recovery of 62%. (the silicon recovery rate is the ratio of the silicon content in the prepared silicon dioxide aerogel and the iron tailing raw material).
Example 2:
a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials comprises the following steps:
1) crushing iron tailings, namely taking iron tailings powder with the mesh number of more than 100 meshes and sodium hydroxide particles according to the mass ratio of 1: 2.2, mixing, heating to 500 ℃ in a muffle furnace, keeping for 3h for alkali dissolution reaction, cooling to room temperature, and mixing with water according to a solid-to-liquid ratio of 1: 6, mixing (the unit of the solid-liquid ratio is g/mL), heating and stirring at 85 ℃ for 24 hours, filtering, and collecting filtrate to obtain a crude silicon solution;
2) uniformly mixing the crude silicon solution obtained in the step 1) with a water glass solution according to a volume ratio of 8:1 (adding the water glass solution to supplement a silicon source), carrying out ion exchange by using D-62 macroporous strong-acid styrene cation exchange resin, dropwise adding 0.5mol/L ammonia water solution into the mixed solution after ion exchange to adjust the pH value to 7.5, standing to form blocky gel, immersing the blocky gel into a gel aging solution (the gel aging solution is a mixed solution of absolute ethyl alcohol and ethyl orthosilicate according to a volume ratio of 12: 1), standing at room temperature for 25 hours, and fishing out the blocky gel from the gel aging solution to obtain wet sol;
3) immersing the wet sol obtained in the step 2) into a modification solution, standing for 20h (the modification solution is a mixed solution formed by n-hexane and trimethylchlorosilane in a volume ratio of 12: 1), and fishing out the wet sol from the modification solution after hydrophobic modification of the gel surface;
4) and 3) soaking the fished wet gel in n-hexane, standing for 16h for solvent exchange to replace the residual modifying solution in the pore channel of the wet gel, then fishing out the wet sol from the n-hexane, and drying at normal pressure (drying at 80 ℃ for 6h, and then drying at 130 ℃ for 4 h) to obtain the composite silicon-based aerogel.
Example 3:
a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials comprises the following steps:
1) crushing iron tailings, namely taking iron tailings powder with the mesh number of more than 100 meshes and sodium hydroxide particles according to the mass ratio of 1: 1.8, heating the mixture to 450 ℃ in a muffle furnace, keeping the mixture for 2.5 hours for alkali dissolution reaction, cooling the mixture to room temperature, and mixing the mixture with water according to a solid-to-liquid ratio of 1: 5, mixing (the unit of the solid-liquid ratio is g/mL), heating and stirring at 80 ℃ for 23 hours, filtering, and collecting filtrate to obtain a crude silicon solution;
2) uniformly mixing the crude silicon solution obtained in the step 1) with a water glass solution according to the volume ratio of 7: 1 (adding the water glass solution to supplement a silicon source), carrying out ion exchange by using D-62 macroporous strong-acid styrene cation exchange resin, dropwise adding 0.4mol/L ammonia water solution into the mixed solution after ion exchange to adjust the pH value to 7.5, standing to form blocky gel, immersing the blocky gel into a gel aging solution (the gel aging solution is the mixed solution of absolute ethyl alcohol and ethyl orthosilicate according to the volume ratio of 10: 1), standing at room temperature for 24 hours, and fishing out the blocky gel from the gel aging solution to obtain wet sol;
3) immersing the wet sol obtained in the step 2) into a modification solution, standing for 18h (the modification solution is a mixed solution formed by n-hexane and trimethylchlorosilane in a volume ratio of 10: 1), and fishing out the wet sol from the modification solution after hydrophobic modification of the gel surface;
4) and 3) soaking the fished wet gel in n-hexane, standing for 12h for solvent exchange to replace the residual modification solution in the pore channel of the wet gel, then fishing out the wet sol from the n-hexane, and drying at normal pressure (drying at 70 ℃ for 5h, and then drying at 120 ℃ for 3 h) to obtain the composite silicon-based aerogel.
Example 4:
a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials comprises the following steps:
1) crushing iron tailings, namely taking iron tailings powder with the mesh number of more than 100 meshes and sodium hydroxide particles according to the mass ratio of 1: 2, heating the mixture to 480 ℃ in a muffle furnace, keeping the mixture for 2 hours for alkali dissolution reaction, cooling the mixture to room temperature, and mixing the mixture with water according to a solid-to-liquid ratio of 1: 6, mixing (the unit of the solid-liquid ratio is g/mL), heating and stirring at 85 ℃ for 24 hours, filtering, and collecting filtrate to obtain a crude silicon solution;
2) uniformly mixing the crude silicon solution obtained in the step 1) with a water glass solution according to the volume ratio of 6: 1 (adding the water glass solution as a silicon source supplement), carrying out ion exchange by using D-62 macroporous strong-acid styrene cation exchange resin, dropwise adding 0.5mol/L ammonia water solution into the mixed solution after ion exchange to adjust the pH value to 7, standing to form blocky gel, immersing the blocky gel into a gel aging solution (the gel aging solution is the mixed solution of absolute ethyl alcohol and ethyl orthosilicate according to the volume ratio of 11: 1), standing at room temperature for 22h, and fishing out the blocky gel from the gel aging solution to obtain wet sol;
3) immersing the wet sol obtained in the step 2) into a modification solution, standing for 20h (the modification solution is a mixed solution formed by n-hexane and trimethylchlorosilane in a volume ratio of 11: 1), and fishing out the wet sol from the modification solution after hydrophobic modification of the gel surface;
4) and 3) soaking the fished wet gel in n-hexane, standing for 13h for solvent exchange to replace the residual modifying solution in the pore channel of the wet gel, then fishing out the wet sol from the n-hexane, and drying at normal pressure (drying at 75 ℃ for 5h, and then drying at 125 ℃ for 4 h) to obtain the composite silicon-based aerogel.
Comparative example 1:
a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials is compared according to the same feeding amount in example 1, and comprises the following steps:
1) crushing iron tailings, namely taking iron tailings powder with the mesh number of more than 100 meshes and sodium hydroxide particles according to the mass ratio of 1: 1.4, heating the mixture to 400 ℃ in a muffle furnace, keeping the mixture for 2 hours for alkali dissolution reaction, cooling the mixture to room temperature, and mixing the mixture with water according to a solid-to-liquid ratio of 1: 3 (namely mixing the whole mixture of the cooled iron tailings and sodium hydroxide with water, wherein the unit of solid-to-liquid ratio is g/mL, the same below, heating and stirring the mixture at 70 ℃ for 20 hours, filtering the mixture, and collecting filtrate to obtain a crude silicon solution;
2) carrying out ion exchange on the crude silicon solution obtained in the step 1) through D-62 macroporous strong-acid styrene cation exchange resin, dropwise adding 0.5mol/L ammonia water solution into the mixed solution after ion exchange to adjust the pH value to 7, standing to form blocky gel, immersing the blocky gel into gel aging solution (the gel aging solution is the mixed solution of absolute ethyl alcohol and tetraethoxysilane according to the volume ratio of 8: 1), standing at room temperature for 20 hours, and taking out the blocky gel from the gel aging solution to obtain wet sol;
3) immersing the wet sol obtained in the step 2) into a modification solution, standing for 16h (the modification solution is a mixed solution formed by n-hexane and trimethylchlorosilane in a volume ratio of 8: 1), and fishing out the wet sol from the modification solution after hydrophobic modification of the gel surface;
4) and 3) soaking the fished wet gel in n-hexane, standing for 10h for solvent exchange to replace the residual modification solution in the pore channel of the wet gel, then fishing out the wet sol from the n-hexane, and drying at normal pressure (drying at 60 ℃ for 3h, and then drying at 110 ℃ for 2 h) to obtain the composite silicon-based aerogel.
Comparative example 2:
a method for preparing composite silicon-based aerogel by taking iron tailings as raw materials is compared according to the same feeding amount in example 1, and comprises the following steps:
1) uniformly mixing deionized water and a water glass solution according to a volume ratio of 6: 1, carrying out ion exchange through D-62 macroporous strong-acid styrene cation exchange resin, dropwise adding 0.5mol/L ammonia water solution into the mixed solution after the ion exchange to adjust the pH value to 7, standing to form blocky gel, immersing the blocky gel into a gel aging solution (the gel aging solution is the mixed solution formed by absolute ethyl alcohol and tetraethoxysilane according to a volume ratio of 8: 1), standing at room temperature for 20 hours, and taking out the blocky gel from the gel aging solution to obtain wet sol;
2) immersing the wet sol obtained in the step 1) into a modification solution, standing for 16h (the modification solution is a mixed solution formed by n-hexane and trimethylchlorosilane in a volume ratio of 8: 1), and fishing out the wet sol from the modification solution after hydrophobic modification of the gel surface;
3) and 2) soaking the fished wet gel in n-hexane, standing for 10h for solvent exchange to replace the residual modification solution in the pore channel of the wet gel, then fishing out the wet sol from the n-hexane, and drying at normal pressure (drying at 60 ℃ for 3h, and then drying at 110 ℃ for 2 h) to obtain the composite silicon-based aerogel.
The composite silicon-based aerogels prepared in examples 1 to 4 and comparative examples 1 to 2 are subjected to performance tests, and the tap density, the average pore diameter and the porosity of the composite silicon-based aerogels are detected, wherein the detection results are shown in table 1; the detection standard of tap density in Table 1 is GB/T21354-.
Table 1 performance parameter table of composite silicon-based aerogel
| Grouping | Tap density | Average pore diameter | Porosity of the material |
| 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 | Few holes | 79% |
| Comparative example 2 | 0.322g/cm3 | Few holes | 86% |
As can be seen from Table 1, the aerogel product produced in comparative example 1 has a higher density and a lower porosity. The reason is that the water glass solution is not added in the comparative example 1, when 0.5mol/L ammonia water solution is slowly dripped to adjust the pH gel, no whole block of gel is generated, only a small amount of soft flocculent small blocks are generated, and a firm skeleton structure is not formed in the gel process, so that the pore canal is collapsed due to the fact that the firm skeleton structure cannot bear the pulling of the surface tension of the liquid in the drying process; in comparative example 2, the crude silicon solution is not added, and the dilution ratio of the water glass is too high, so that only gel with soft and single-thin framework is formed, and the framework collapses in the drying process to reduce the volume shrinkage porosity, which proves that more silicon elements are extracted in the alkali dissolution reaction of the iron tailing powder, and the crude silicon solution and a small amount of water glass solution are necessary to be mixed.
The results of the embodiments 1 to 4 of the invention prove that the iron tailings are recycled by the method defined by the invention, and the tap density of the prepared composite silicon-based aerogel is 0.175g/cm3Hereinafter, the average pore diameter is not more than 40nm, and the porosity thereof is 93% or more.
The description is given for the sole purpose of illustrating embodiments of the inventive concept and should not be taken as limiting the scope of the invention to the particular forms set forth in the embodiments, but rather as being limited only to the equivalents thereof as may be contemplated by those skilled in the art based on the teachings herein.
Claims (6)
1. A method for preparing composite silicon-based aerogel by taking iron tailings as raw materials is characterized by comprising the following steps:
1) mixing iron tailing powder and sodium hydroxide particles in a mass ratio of 1: 1.4-2.2, heating the mixture in a muffle furnace to 400-500 ℃ for 2-3 h, cooling the mixture to room temperature, mixing the cooled mixture with water, heating and stirring the mixture, filtering the mixture, and collecting filtrate to obtain a crude silicon solution; wherein the mesh number of the iron tailing powder is more than 100 meshes, and the iron tailing comprises the following components in percentage by mass: SiO2245.43%、CaO 13.81%、MgO 13.10%、Al2O311.35%、Fe2O310.13 percent, and the balance being impurities;
2) uniformly mixing the crude silicon solution obtained in the step 1) with a water glass solution, carrying out ion exchange by using a strong-acid cation exchange resin, dropwise adding an ammonia solution into the mixed solution after the ion exchange to adjust the pH value to 7-7.5, standing to form blocky gel, immersing the blocky gel into a gel aging solution, standing at room temperature for 20-25 h, and taking out the blocky gel from the gel aging solution to obtain wet sol; wherein the volume ratio of the crude silicon solution to the water glass solution is 6-8: 1;
3) immersing the wet sol obtained in the step 2) into the modification solution, standing for 16-20 h, and fishing out the wet sol from the modification solution after hydrophobic modification of the gel surface is carried out;
4) and 3) soaking the fished wet sol into n-hexane, standing for 10-16 h for solvent exchange to replace the modification solution remaining in the wet gel pore channel, fishing the wet sol out of the n-hexane, and drying at normal pressure to obtain the composite silicon-based aerogel.
2. The method for preparing the composite type silicon-based aerogel by using the iron tailings as raw materials according to claim 1, wherein in the step 1), the ratio of the mass of the cooled mixture to the volume of water is 1: 3-6, the unit of the mass is g, the unit of the volume is mL, and the heating and stirring temperature is 70-85 ℃.
3. The method for preparing the composite silicon-based aerogel by using the iron tailings as the raw material according to claim 1, wherein in the step 2), the gel aging solution is a mixed solution composed of absolute ethyl alcohol and ethyl orthosilicate; in the gel aging liquid, the volume ratio of absolute ethyl alcohol to ethyl orthosilicate is 8-12: 1.
4. the method for preparing the composite silicon-based aerogel by using the iron tailings as raw materials according to claim 3, wherein the volume ratio of the absolute ethyl alcohol to the tetraethoxysilane is 10: 1.
5. the method for preparing the composite silicon-based aerogel by using the iron tailings as the raw material according to claim 1, wherein in the step 4), the method for drying under normal pressure comprises the following steps: drying the mixture at the temperature of 60-80 ℃ for 3-6 h, and then drying the mixture at the temperature of 110-130 ℃ for 2-4 h.
6. The method for preparing the composite silicon-based aerogel by using the iron tailings as the raw materials according to claim 1, wherein the tap density of the composite silicon-based aerogel prepared in the step 4) is 0.162-0.175 g/cm3The porosity is 93-95%, and the average pore diameter is 25-40 nm.
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