A method for preparing powder silica aerogel by using feldspar waste as silicon source

Abstract

The application discloses a method for preparing powder silica aerogel by taking feldspar waste as a silicon source. Feldspar waste, anhydrous sodium carbonate and sodium hydroxide are mixed with water for pre-activation, and then activated clinker is obtained by adding into a muffle furnace for low-temperature activation. The silica aerogel is prepared by using a method of pre-activation, acid leaching residue alkali dissolution (secondary silicon extraction), sol-gel method and multi-technology linkage. The activated clinker is obtained by using the method of pre-activation and low-temperature activation, and the Si component and the Na and Al components of the water-soluble residue are effectively separated by using the acid leaching method. Then, the sodium silicate solution is obtained by alkali dissolution and acid leaching of the residue, and is mixed with the water-soluble pre-desiliconization filtrate to quickly form the silica wet gel under the action of the acid catalyst. The preparation method is simple in operation, high in product added value, low in raw material and activation cost, and can be mass-produced in an industrialized manner.

Description

Technical Field

[0001] This invention belongs to the field of inorganic cementitious materials, and particularly relates to a method for preparing powdered silica aerogel using feldspar waste as a silicon source. Background Technology

[0002] Silica aerogels have attracted widespread research and application internationally in recent years due to their excellent properties such as high porosity, high specific surface area, low density, low thermal conductivity, and low dielectric constant. However, current production lines mostly use expensive chemicals such as tetraethyl orthosilicate, silica sol, and water glass as silicon sources, and the supercritical drying technology employed is complex, resulting in high equipment costs and significant risks, thus hindering the large-scale commercial production and application of aerogel materials. Therefore, finding inexpensive, efficient, and environmentally friendly raw materials has become an inevitable trend in current aerogel material research, possessing great necessity and practical significance.

[0003] Potassium and sodium feldspar contain a large amount of usable silicon. If silicon can be extracted from them to prepare porous silica aerogel materials, it can reduce the raw material cost of preparing silica aerogels and achieve effective recycling of mineral waste, which has important research significance, environmental protection significance and practical application value.

[0004] Patent CN116654946A describes a method for preparing silica aerogel using tetraethyl orthosilicate as the silicon source, water, and a eutectic solvent (ethylene glycol and organic acid) through hydrolysis. After pH adjustment with ammonia, the aerogel undergoes aging, displacement, and modification, followed by graded drying under normal pressure. The prepared silica aerogel exhibits a porosity exceeding 90% and a specific surface area as high as 1094 m². 2CN116639700A discloses a low-cost and rapid method for preparing silica aerogel. This method uses polymethyltriethoxysilane hydrolyzed with an inorganic acid as the silicon source, and ethanol, water, and sodium hydroxide as solvents. The mixture is stirred and allowed to stand for a period of time before solidification to obtain a gel. After aging and drying at normal pressure, silica aerogel is obtained. This method has low preparation cost, short preparation cycle, and significantly improved specific surface area of ​​the prepared silica aerogel. CN107128933B proposes a supercritical drying method for preparing silica aerogel thermal insulation materials. This method uses a diluted water glass solution as the silicon source. Hydrochloric acid is added to obtain a strongly acidic silica sol. After some water is evaporated from the silica sol by rotary evaporation, a low-surface-tension water-soluble polar solvent is added and mixed evenly. The pH of the solution is then adjusted using water glass solution to form a gel. After gel aging, supercritical CO2 is introduced for extraction and drying. This method greatly shortens the aerogel preparation cycle. CN108439418B discloses a method for producing nano-silica aerogel using supercritical extraction. The gel is prepared using methyl orthosilicate as the silicon source. Nano-silica aerogel is obtained through supercritical extraction of an aged and modified gel. The prepared silica aerogel exhibits low density, low thermal conductivity, high specific surface area, and high hydrophobicity. CN112408401B provides a method for preparing silica aerogel using industrial solid waste fly ash. The method involves thermally activating the material with additives at 850°C to obtain clinker, followed by acid and alkali dissolution to obtain a water glass solution. Acid catalysis is then added to obtain a gel, which is subsequently modified and dried to prepare a silica aerogel with a high specific surface area.

[0005] As can be seen from the above, current production lines mostly use expensive chemicals such as tetraethyl orthosilicate, silica sol, and water glass as silicon sources. Furthermore, the supercritical drying technology employed is complex, resulting in high equipment costs and significant risks. Additionally, the high activation temperatures required for preparing aerogels from waste materials also hinder the large-scale commercial production and application of aerogel materials due to cost issues. Therefore, finding inexpensive, efficient, and environmentally friendly raw materials has become an inevitable trend in current aerogel material research, possessing significant necessity and practical importance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing powdered silica aerogel using feldspar waste as a silicon source. This invention provides a method for producing silica aerogel that reduces production costs, increases equipment lifespan, improves the extraction rate of silicon from waste, and is safe and environmentally friendly.

[0007] The mineral waste (mainly potassium, sodium feldspar, and quartz) contained a large amount of usable silicon. Extracting silicon from it to prepare porous silica aerogel materials can reduce the raw material cost of silica aerogel preparation and achieve effective recycling of mineral waste. At the same time, the present invention uses an atmospheric pressure drying method instead of a complex supercritical drying method, which reduces the cost of aerogel preparation and improves the safety of the generation process. Therefore, it has important research significance, environmental protection significance and practical application value.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing powdered silica aerogel using feldspar waste as a silicon source includes the following steps:

[0010] (1) Feldspar waste, anhydrous sodium carbonate and sodium hydroxide mixed alkali and water were pre-activated and then placed in a muffle furnace for low-temperature activation to obtain activated clinker. The activated clinker was then dispersed in water and filtered to obtain the first filter residue and the first filtrate.

[0011] (2) After adding excess acid solution to the first filter residue, filter to obtain acid-soluble residue, wash with water and dry to obtain the second filter residue;

[0012] (3) Add sodium hydroxide solution to the second filter residue for alkaline dissolution, and separate to obtain the third filtrate and the third filter residue;

[0013] (4) Mix the first filtrate and the third filtrate, add an acid solution to make it gel, and then age it to obtain a wet gel; use a modifier to hydrophobically modify the broken wet gel, and finally dry it under normal pressure to prepare powdered silica aerogel.

[0014] Preferably, in step (1), the mass ratio of anhydrous sodium carbonate to sodium hydroxide is 1:1.2.

[0015] Preferably, in step (1), the mass ratio of feldspar waste to alkali mixture is 5:4.

[0016] Preferably, in step (1), the pre-activated solid-liquid ratio is 1g / 2mL.

[0017] Preferably, in step (1), the particle size of the ground feldspar waste is 180 mesh or larger.

[0018] Preferably, in step (1), the pre-activation temperature is 80°C and the time is 120 min.

[0019] Preferably, in step (1), the low-temperature activation temperature is 200℃ and the time is 120min.

[0020] Preferably, in step (1), the solid-liquid ratio of activated clinker to water is 1g / 4-5mL.

[0021] Preferably, in step (1), the activated clinker is dispersed in water at a temperature of 80-90°C and stirred at a constant temperature for 60-90 minutes after dispersion.

[0022] Preferably, in step (2), the acid solution is one of acetic acid, sulfuric acid, and nitric acid.

[0023] Preferably, in step (2), the mass ratio of the first filter residue to the acid solution is 1 g / 10 mL.

[0024] Preferably, in step (2), the concentration of the acid solution is 4 mol / L.

[0025] Preferably, in step (3), the solid-liquid ratio of the second filter residue and the sodium hydroxide solution is 1g / 20-25mL.

[0026] Preferably, in step (3), the concentration of the sodium hydroxide solution is 1-2 mol / L and the temperature is 60℃.

[0027] Preferably, in step (3), the stirring rate for alkali dissolution is 400-500 r / min and the time is 60 min.

[0028] Preferably, in step (4), the acid solution is one of acetic acid, nitric acid, or sulfuric acid; the modifier is one of trimethylchlorosilane or hexamethyldisilazane; and the alcohol solution is one of methanol or propanol.

[0029] Preferably, in step (4), the aging method is as follows: add deionized water to the wet gel, the water covers the wet gel, and age it in a water bath at 45℃~60℃; the aging time is 1~2h.

[0030] Preferably, in step (4), the broken wet gel is hydrophobically modified by a modifier, wherein the volume ratio of alcohol solution, modifier and acid solution is 1:(0.1~1):(0.1~1); the total volume ratio of alcohol solution, modifier and acid solution to gel is (1~10:1); and the concentration of acid solution is 6~12 mol / L.

[0031] Preferably, in step (4), an acid solution is added to make it gel, and the concentration of the acid solution is 1 to 5 mol / L.

[0032] Compared with the prior art, the beneficial effects of the present invention include:

[0033] (1) The method for preparing silica aerogel using feldspar waste proposed in this invention uses inexpensive mineral solid waste as raw material to replace expensive organosilicon alkoxides, which not only solves the problem of high cost of silica aerogel preparation, but also improves the high-value utilization rate of mineral waste.

[0034] (2) The present invention extracts and separates the silica components contained in the waste by pre-activation with mixed alkali and low-temperature activation, followed by water-soluble preliminary extraction and acid leaching residue alkali-soluble secondary extraction; specifically, silica aerogel is prepared by a multi-technology linkage method of pre-desiliconization treatment of clinker (water-soluble primary silica extraction), acid leaching residue alkali-soluble (secondary silica extraction), and sol-gel method.

[0035] (3) This paper makes full use of the silicon-containing components of feldspar waste and activates the feldspar waste through a two-step activation method, which greatly reduces the temperature of direct activation by alkali fusion. At the same time, the silicon extraction rate of this method can reach 95%.

[0036] (4) The present invention uses a water-soluble method to pre-desiliconize activated clinker. The water-soluble step leaches out some silicon elements, which avoids the problem of low silicon leaching rate caused by excessive silicon component concentration increasing solution viscosity during direct acid leaching. It also avoids the problem of low final silicon extraction rate caused by excessive silicon elements dissolving into acid filtrate during acid leaching and the problem of difficulty in removing impurities caused by direct acid leaching.

[0037] (5) The present invention uses acid leaching to effectively separate the Si component and Na and Al components of the water-soluble residue. Then, the acid-leached residue is dissolved in alkali to obtain sodium silicate solution, which is mixed with water-soluble pre-desiliconized filtrate and rapidly forms silica wet gel under acid catalysis. This preparation method is simple to operate, has high product added value, low raw material cost, and can be industrialized on a large scale.

[0038] (5) The silica aerogel prepared by this invention can achieve a specific surface area of ​​up to 940.2 m². 2 / g, pore size ranges from 12 to 25 nm, and pore volume can reach up to 5.18 cm³. 3 / g. The prepared aerogel is a typical high specific surface area mesoporous material, and its quality also exceeds that of most commercially available silica aerogels. Attached Figure Description

[0039] Figure 1 This is a flowchart illustrating the preparation process of the silica aerogel described in this invention.

[0040] Figure 2 This is the XRD pattern of feldspar mineral waste.

[0041] Figure 3 The XRD diffraction patterns are those of the activated clinker described in Examples 1 to 5. 5:2, 5:3, 5:4, 5:5 and 5:6 are the mass ratios of feldspar mineral waste to mixed alkali in different examples.

[0042] Figure 4 The images shown are actual pictures of the wet gels obtained in Examples 6 and 7, where the image on the left corresponds to Example 6 and the image on the right corresponds to Example 7.

[0043] Figure 5 This is a photograph of the aerogel prepared in Example 7.

[0044] Figure 6 The images shown are scanning electron microscope (SEM) images of the silica aerogel prepared in Example 7, where the left image is magnified to 20k and the right image is magnified to 50k.

[0045] Figure 7 The graphs show the N2 adsorption and desorption and pore size distribution of the silica aerogel prepared in Example 7. The graph on the left is the N2 adsorption and desorption graph, and the graph on the right is the pore size distribution graph. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0047] The feldspar mineral waste described in this embodiment originates from tailings waste generated during mining operations. The XRD pattern of the feldspar mineral waste is shown below. Figure 2 ,Depend on Figure 2 The main phases of the waste are potassium, sodium feldspar and quartz.

[0048] Example 1

[0049] A method for preparing powdered silica aerogel using feldspar mineral waste as a silicon source, comprising the following steps:

[0050] (1) Feldspar mineral waste and mixed alkali (anhydrous sodium carbonate and sodium hydroxide in a mass ratio of 1:1.2) were mixed at a mass ratio of 5:2. After mixing, water was added at a solid-liquid ratio of 1g / 2mL. After mixing evenly, the mixture was pre-activated at 80℃ for 120min. Then, the pre-activated product was activated at a low temperature of 250℃ for 180min. The activated clinker was then ground to 180 mesh for later use.

[0051] (2) Take the activated calcined material after grinding in step (1) and mix it with deionized water at a ratio of 1g / 4mL. Stir at 80℃ for 90min at a stirring rate of 400r / min. After dissolving in water, filter to obtain the first filtrate and the first filter residue for later use.

[0052] (3) Add a sulfuric acid solution with a concentration of 4 mol / L to the first filter residue obtained in step (2) at a ratio of 1 g / 10 mL. Stir at room temperature for 60 min and then filter to obtain acid-soluble residue. Wash the acid-soluble residue with water and dry it to obtain the second filter residue for later use.

[0053] (4) Add the second filter residue obtained in step (3) to a sodium hydroxide solution for alkali dissolution for 60 min. The concentration of sodium hydroxide is 1.5 mol / L, the temperature is 60℃, the solid-liquid ratio is 1 g / 20 mL, and the stirring rate is 500 r / min. After alkali dissolution, the third filtrate is obtained and set aside.

[0054] (5) Mix the first filtrate from step (2) with the third filtrate from step (4), and add sulfuric acid with a concentration of 2 mol / L to the mixed solution to make it gel. Add deionized water to the wet gel, and let the water cover the wet gel. Aging is carried out in a water bath at 45°C for 2 hours.

[0055] (6) Physically break the aged wet gel, and add the broken gel, methanol, trimethylchlorosilane and sulfuric acid (6mol / L) in a volume ratio of 1:4:2:0.5 into a beaker. Stir in a water bath at a constant temperature of 60℃ for 60 minutes. The stirring speed is 600r / min.

[0056] (7) The gel obtained by vacuum filtration was dried at 60℃ and normal pressure for 24h to obtain hydrophobic silica aerogel.

[0057] Example 2

[0058] Based on Example 1, the step of "mixing mineral waste and alkali in a mass ratio of 5:2" is modified to "mixing mineral waste and alkali in a mass ratio of 5:3", while the other steps remain unchanged.

[0059] Example 3

[0060] Based on Example 1, the step of "mixing mineral waste and alkali at a mass ratio of 5:2" is modified to "mixing mineral waste and alkali at a mass ratio of 5:4", while the other steps remain unchanged.

[0061] Example 4

[0062] Based on Example 1, the phrase "mineral waste and alkali mixed at a mass ratio of 5:2" is modified to "mineral waste and alkali mixed at a mass ratio of 5:5", while the other steps remain unchanged.

[0063] Example 5

[0064] Based on Example 1, the step of "mixing mineral waste and alkali in a mass ratio of 5:2" is modified to "mixing mineral waste and alkali in a mass ratio of 5:6", while the other steps remain unchanged.

[0065] Figure 3 The XRD diffraction patterns of the activated clinker described in Examples 1-5 are shown below. Figure 3It can be seen that when the mass ratio of feldspar waste to alkali (ore-alkali ratio) is 5:2-3, the clinker still contains unactivated potassium and sodium feldspar. When the ore-alkali ratio is greater than or equal to 5:4, the potassium and sodium feldspar in the clinker can be fully activated, transforming into sodium silicate and nepheline, which provides favorable conditions for improving the silica extraction rate of the waste. Of course, the silica extraction rate is not only affected by the ore-alkali ratio, but also by the activation time and activation temperature. An orthogonal experiment based on the ore-alkali ratio, activation time, and activation temperature is presented here, and the results are shown in Table 1 below.

[0066] Table 1. Overview of Orthogonal Experiment Parameters

[0067] N0. Temperature (°C) mineral alkali ratio Time (h) Activation rate (%) 1 150 5:2 2 18.2 2 150 5:3 2.5 25.4 3 150 5:4 3 38 4 200 5:2 2.5 24 5 200 5:3 3 88.3 6 200 5:4 2 94 7 250 5:2 3 32 8 250 5:3 2 94 9 250 5:4 2.5 99.9 k1 27.2 24.7 68.7 blank k2 68.8 69.2 49.8 k3 75.3 77.3 52.8 R 48.1 52.6 18.9

[0068] Where k1, k2, k3 are the average activation rates under these conditions, and R is the range.

[0069] Activation rate = (m mineral powder - m alkali-soluble slag) / m mineral powder, where m is mass.

[0070] Based on orthogonal experiments, the following conclusions were drawn:

[0071] (1) Temperature and alkali-to-ore ratio have a significant impact on the activation rate of feldspar waste, while time has a smaller impact on the activation rate.

[0072] (2) Select low-temperature activation conditions: activation temperature 200℃; ore-alkali mass ratio 5:4; activation time 2h.

[0073] Example 6

[0074] A method for preparing powdered silica aerogel using feldspar waste as a silicon source, comprising the following steps:

[0075] (1) Feldspar mineral waste and mixed alkali (anhydrous sodium carbonate and sodium hydroxide in a mass ratio of 1:1.2) were mixed at a mass ratio of 5:4. After mixing, water was added at a solid-liquid ratio of 1g / 2mL. After mixing evenly, the mixture was pre-activated at 80℃ for 120min. Then, the pre-activated product was activated at a low temperature of 200℃ for 120min. The activated clinker was then ground to 180 mesh for later use.

[0076] (2) Take the activated calcined material after grinding in step (1) and mix it with deionized water at a ratio of 1g / 4mL. Stir at 80℃ for 90min at a stirring rate of 400r / min. After dissolving in water, filter to obtain the first filtrate and the first filter residue for later use.

[0077] (3) Add a sulfuric acid solution with a concentration of 4 mol / L to the first filter residue obtained in step (2) at a ratio of 1 g / 10 ml. Stir at room temperature for 60 min and then filter to obtain acid-soluble residue. Wash the acid-soluble residue with water and dry it to obtain the second filter residue for later use.

[0078] (4) Add the second filter residue obtained in step (3) to a sodium hydroxide solution for alkali dissolution for 60 min. The concentration of sodium hydroxide is 1.5 mol / L, the temperature is 60℃, the solid-liquid ratio is 1 g / 20 mL, and the stirring rate is 500 r / min. After alkali dissolution, the third filtrate is obtained and set aside.

[0079] (5) Mix the first filtrate from step (2) with the third filtrate from step (4), and add sulfuric acid with a concentration of 2 mol / L to the mixed solution to make it gel. Add deionized water to the wet gel, and let the water cover the wet gel. Aging is carried out in a water bath at 45°C for 1 to 2 hours.

[0080] (6) Physically break the aged wet gel, and add the broken gel, methanol, trimethylchlorosilane and sulfuric acid (6mol / L) in a volume ratio of 1:4:2:0.5 into a beaker. Stir in a water bath at a constant temperature of 60℃ for 60 minutes. The stirring speed is 600r / min.

[0081] (7) The gel obtained by vacuum filtration was dried at 60℃ and normal pressure for 24h to obtain hydrophobic silica aerogel.

[0082] Example 7

[0083] A method for preparing powdered silica aerogel using feldspar waste as a silicon source, comprising the following steps:

[0084] (1) Feldspar mineral waste and mixed alkali (anhydrous sodium carbonate and sodium hydroxide in a mass ratio of 1:1.2) were mixed at a mass ratio of 5:4. After mixing, water was added at a solid-liquid ratio of 1g / 2mL. After mixing evenly, the mixture was pre-activated at 80℃ for 120min. Then, the pre-activated product was activated at a low temperature of 200℃ for 120min. The activated clinker was then ground to 180 mesh for later use.

[0085] (2) Take the activated calcined material after grinding in step (1) and mix it with deionized water at a ratio of 1g / 4mL. Stir at 80℃ for 90min at a stirring rate of 400 / min. After dissolving in water, filter to obtain the first filtrate and the first filter residue for later use.

[0086] (3) The first filter residue obtained in step (2) is added to a sulfuric acid solution with a concentration of 4 mol / L at a ratio of 1 g / 10 ml. After stirring at room temperature for 60 min, the residue is filtered to obtain an acid-soluble residue. The acid-soluble residue is washed with water and dried to obtain a second filter residue for later use.

[0087] (4) Add the second filter residue obtained in step (3) to a sodium hydroxide solution for alkali dissolution for 60 min. The concentration of sodium hydroxide is 1.5 mol / L, the temperature is 60℃, the solid-liquid ratio is 1 g / 20 mL, and the stirring rate is 500 r / min. After alkali dissolution, the third filtrate is obtained and set aside.

[0088] (5) Mix the first filtrate from step (2) with the third filtrate from step (4), and add sulfuric acid with a concentration of 4 mol / L to the mixed solution to make it gel. Add deionized water to the wet gel, and let the water cover the wet gel. Aging is carried out in a water bath at 45°C for 1 to 2 hours.

[0089] (6) Physically break the aged wet gel, and add the broken gel, methanol, trimethylchlorosilane and sulfuric acid (6mol / L) in a volume ratio of 1:4:2:0.5 into a beaker. Stir in a water bath at a constant temperature of 60℃ for 60 minutes. The stirring speed is 600r / min.

[0090] (7) The gel obtained by vacuum filtration was dried at 60℃ and normal pressure for 24h to obtain hydrophobic silica aerogel.

[0091] Figure 4 The images show the wet gels obtained in Examples 6 and 7. Comparing the gels obtained in Examples 6 and 7, it was found that the gel obtained using 4 mol / L sulfuric acid as a catalyst for sol-gel formation had a denser structure than the gel obtained using 2 mol / L sulfuric acid, and the modified gel also exhibited superior performance. This may be due to the higher density of silica molecules per unit volume, resulting in better hydrolysis and condensation, and a more robust three-dimensional network structure formed by the gel. The performance indicators of the silica aerogels prepared in Examples 6 and 7 are shown in Table 2.

[0092] Table 2. Summary of performance indicators of the gels prepared in Examples 6 and 7

[0093] sample Example 6 Example 7 Specific surface area <![CDATA[641.8m 2 / g]]> <![CDATA[940.2m 2 / g]]> aperture 18~30nm 12~25nm Pore ​​volume <![CDATA[3.48cm 3 / g]]> <![CDATA[5.18cm 3 / g]]>

[0094] Figure 5 The image shows the aerogel prepared in Example 7 of this invention. Figure 5 It can be seen that the prepared silica aerogel is light blue, which is consistent with the characteristics of silica aerogel.

[0095] The silica aerogel prepared using this method (Example 7) was subjected to full-pore testing using an ASAP2020 instrument, and its specific surface area reached as high as 940.2 m². 2 / g, pore size mostly 12-25nm, pore volume also reaches 5.18cm3 / g, scanning electron microscope image of aerogel (see Figure 6 The prepared silica aerogel exhibits a clear three-dimensional network structure. The N2 adsorption-desorption curves of the aerogel are shown in [reference needed]. Figure 7 It can be seen that its isotherm is a type IV adsorption isotherm. The hysteresis loop and pore size distribution diagram in the isotherm indicate that the aerogel is a mesoporous material, and its relatively wide hysteresis loop also indicates that the sample has a high adsorption capacity.

[0096] In the silica aerogels prepared according to the embodiments of the present invention, the best-performing example can increase the silica extraction rate from mineral waste to 95% (corresponding to the activation rate in Table 1); and the prepared aerogels have good overall performance, with a maximum specific surface area of ​​940.2 m². 2 / g, pore size is mostly 12-25nm, and pore volume can reach up to 5.18cm. 3 / g, which is a typical high specific surface area mesoporous material, exceeds the quality level of silica aerogels prepared using conventional raw materials.

[0097] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing powdered silica aerogel using feldspar waste as a silicon source, characterized in that, Includes the following steps: (1) Feldspar waste, anhydrous sodium carbonate and sodium hydroxide mixed alkali and water were pre-activated and then placed in a muffle furnace for low-temperature activation to obtain activated clinker. The activated clinker was then dispersed in water and filtered to obtain the first filter residue and the first filtrate. The mass ratio of feldspar waste to alkali in step (1) is 5:4; The pre-activation temperature in step (1) is 60~80℃; the low-temperature activation temperature is 200~250℃; The pre-activation time in step (1) is 120~180 min; the low-temperature activation time is 120~180 min; (2) After adding excess acid solution to the first filter residue, filter to obtain acid-soluble residue, wash with water and dry to obtain the second filter residue; (3) Sodium hydroxide solution was added to the second filter residue for alkaline dissolution, and the third filtrate and the third filter residue were separated. (4) Mix the first filtrate with the third filtrate, add acid solution to make it gel, and age to obtain a wet gel; Hydrophobic modification can be achieved by using a modifier, followed by drying under normal pressure.

2. The method for preparing powdered silica aerogel using feldspar waste as a silicon source according to claim 1, characterized in that, The mass ratio of anhydrous sodium carbonate to sodium hydroxide in step (1) is 1:1~2; The solid-liquid ratio for pre-activation in step (1) is 1 g / 2~3 mL; The solid-liquid ratio of the activated clinker and water in step (1) is 1g / 2~5mL.

3. The method for preparing powdered silica aerogel using feldspar waste as a silicon source according to claim 1 or 2, characterized in that, In step (1), the activated clinker is dispersed in water at a temperature of 60-90°C and stirred at a constant temperature for 60-120 minutes.

4. The method of claim 1 or 2, wherein the powder silica aerogel is prepared using feldspar waste as a silicon source. The acid solution in step (2) is one of acetic acid, citric acid, nitric acid and sulfuric acid; the acid solution in step (4) is one of acetic acid, citric acid, nitric acid and sulfuric acid.

5. The method for preparing powdered silica aerogel using feldspar waste as a silicon source according to claim 4, characterized in that, In step (2), the solid-liquid ratio of the first filter residue and the acid solution is 1g / 10~15mL; The concentration of the sodium hydroxide solution in step (3) is 1~2 mol / L, and the temperature is 60~80℃.

6. The method for preparing powdered silica aerogel using feldspar waste as a silicon source according to claim 5, characterized in that, In step (3), the solid-liquid ratio of the second filter residue and the sodium hydroxide solution is 1g / 20~30mL; The stirring rate for the alkali dissolution in step (3) is 200~500 r / min, and the time is 60~120 min.

7. The method of claim 6, wherein the powder silica aerogel is prepared using feldspar waste as a silicon source. The aging method in step (4) is as follows: add deionized water to the wet gel, the water covers the wet gel, and age it in a water bath at 40℃~80℃; the aging time is 1~2h.

8. The method of claim 1 or 2, wherein the powder silica aerogel is prepared using feldspar waste as a silicon source. The method of hydrophobic modification of the gel by the modifier in step (4) is as follows: the broken gel, alcohol solvent, modifier and acid solution are added to a beaker in a water bath at a certain volume ratio and stirred for 30 to 120 minutes at a constant temperature of 50 to 80°C. The volume ratio of alcohol solution, modifier and acid solution is 1:0.1 to 1:0.1 to 1, and the total volume ratio of alcohol solution, modifier and acid solution to gel is 1 to 10:

1.

9. The method of claim 8, wherein the feldspar waste is used as a source of silicon to prepare the powder silica aerogel. The alcohol solution is one of methanol, propanol, isopropanol, and butanol; the modifier is one of trimethylchlorosilane, hexamethyldisilazane, and vinyltriethoxysilane. The drying temperature in step (4) is 60~80℃ and the time is 12~24h.

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