Method for preparing nano-silica from silicon slag and modified silica thereof

Abstract

The present application relates to C01B nanometer material technical field, more particularly, the present application provides a kind of method for preparing nanometer silicon dioxide with silicon residue and its modified silicon dioxide.The present application uses the silicon residue generated in the production of phosphate fertilizer as silicon source, wherein when the silicon residue is treated with high molecular binder, through corresponding ultrasonic atomization, high-temperature furnace, high-temperature plasma multiple processing, compared with prior art, the nanometer silicon dioxide prepared has excellent sphericity, at the same time, the present synthesis process is simple, without using a large amount of acid, alkali and inorganic substance with melting effect, avoiding the pollution of a large amount of acid, alkali to environment, further improving the purity of nanometer silicon dioxide;And the silicon residue generated in the production of phosphate fertilizer is recycled, which reduces environmental pollution and avoids the loss of a large amount of silicon resources.

Description

Technical Field

[0001] This invention relates to the field of CO1B nanomaterials technology, and more specifically, this invention provides a method for preparing nano-silica from silicon slag and its modified silica. Background Technology

[0002] Nano-silica, due to its excellent reinforcing, optical, and thickening properties, is widely used in various fields such as daily necessities, coatings, rubber, and industrial additive loading. Currently, existing technologies typically employ vapor-phase methods, sol-gel methods, and microemulsion methods to prepare silica. However, with the rapid development of industry, silica prepared using these methods still suffers from drawbacks such as poor sphericity and uneven particle size distribution, failing to meet the ever-evolving needs of industrial technology.

[0003] Researchers have discovered that using waste silicon slag as raw material to prepare silicon dioxide can greatly improve the utilization rate of silicon resources. However, in the current technology, when preparing silicon dioxide from waste silicon slag through a series of chemical reactions, a large amount of acid and alkali are required, which causes certain pollution to the environment.

[0004] Chinese invention patent CN112299423A discloses a method for preparing silicon dioxide and the silicon dioxide obtained therefrom. In this patent, silicon slag generated during the production of polycrystalline silicon is used as the silicon source. After a series of treatments, silicon dioxide with a purity of 99.995% is obtained. However, in the entire synthesis process, nitric acid and hydrofluoric acid are used to pretreat the silicon slag, which causes secondary pollution to the environment. At the same time, the sphericity of the silicon dioxide prepared by this method is not prominent.

[0005] Chinese invention patent CN108569701A discloses a method for preparing silica by cutting zirconium silicon slag. This patent focuses on solving the problems of low activity of zirconium silicon slag and low purity of silica prepared in the prior art. However, its synthesis process is complicated and has many steps, which is not conducive to large-scale use and promotion in the industrial field.

[0006] Therefore, developing a method with a simple synthesis process and excellent sphericity of the prepared silica has potential market application value. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a method for preparing nano-silica from silicon slag generated during phosphate fertilizer production, comprising the following steps:

[0008] (1) After mixing the silicon slag with the polymer additive, place it in an ultrasonic atomizer, and then introduce the carrier gas into the ultrasonic atomizer for bubbling and atomization to form an aerosol.

[0009] (2) The aerosol described in step (1) is passed through a high-temperature furnace with water vapor, and then transported to a high-temperature plasma by airflow, and then cooled to obtain the nano-silica.

[0010] As a preferred technical solution of the present invention, the silica content in the silicon slag in step (1) is 15-70% by mass.

[0011] As a preferred technical solution of the present invention, the mass ratio of silicon slag to polymer additive in step (1) is 100:(1-5).

[0012] As a more preferred technical solution of the present invention, the mass ratio of silicon slag to polymer additive in step (1) is 0.7:0.9.

[0013] As a preferred technical solution of the present invention, the carrier gas in step (1) is at least one of helium, neon, argon and nitrogen.

[0014] As a preferred technical solution of the present invention, the flow rate of the carrier gas in step (1) is 200-500 mL / min.

[0015] As a preferred technical solution of the present invention, the working conditions of the ultrasonic atomizer in step (1) are: power of 150-220W, transduction frequency of 1.5-2.5MHz, and atomization rate of 0.2-1mL / min.

[0016] As a preferred technical solution of the present invention, the polymeric additive in step (1) is a binder.

[0017] As a preferred embodiment of the present invention, the adhesive is at least one selected from polyacrylate, methylcellulose, polyurethane, polystyrene, and polyvinyl alcohol.

[0018] As a more preferred technical solution of the present invention, the binder is methylcellulose and polystyrene, and the mass ratio of methylcellulose to polystyrene is (0.2-0.8):(1.1-1.7).

[0019] As a preferred embodiment of the present invention, the mass ratio of methylcellulose to polystyrene is 0.4:1.5.

[0020] The applicant discovered that when preparing nano-silica using silica slag with a silica content of 15-70% by mass, directly subjecting the silica slag to ultrasonic atomization and high-temperature plasma treatment results in uneven particle size distribution, severely limiting the application range of silica. To solve this problem, through extensive creative thinking and effort, the applicant unexpectedly discovered that adding methylcellulose and polystyrene to the system at a mass ratio of 0.4:1.5 resulted in nano-silica with a uniform particle size distribution. This application speculates that the possible reason is that the active groups of methylcellulose and polystyrene interact with each other on the surface of the silica slag powder, introducing a certain density of benzene rings and polar groups to the surface of the silica slag powder. On the one hand, this reduces the frequency of direct collisions on the surface of the silica slag powder, preventing the silica slag powder from agglomerating and forming silica slag particles with uneven particle size distribution, effectively avoiding the phenomenon of uneven silica particle size distribution in the prepared product. On the other hand, through the adhesive effect of methylcellulose and polystyrene, the degree of agglomeration of silica slag powder is controlled, forming silica slag particles with uniform particle size distribution during ultrasonic atomization. This is beneficial for subsequent high-temperature plasma spheroidization treatment, so that the prepared nano-silica maintains excellent sphericity while also having uniform particle size, expanding its application fields in practical use.

[0021] As a preferred technical solution of the present invention, the temperature of the high-temperature furnace in step (2) is 300-350℃.

[0022] As a preferred technical solution of the present invention, the flow rate of the airflow in step (2) is 5-10 L / min.

[0023] As a preferred technical solution of the present invention, the high-temperature plasma in step (2) is a high-temperature plasma generated by alternating current.

[0024] As a preferred technical solution of the present invention, the temperature of the high-temperature plasma in step (2) is 1800-2200℃.

[0025] The applicant discovered that if ultrasonically atomized aerosol is only subjected to a high-temperature furnace and then cooled, the resulting nano-silica spheres have poor sphericity. To improve the sphericity of nano-silica, increase its filler content, and expand its industrial applications, the applicant unexpectedly discovered that when the aerosol formed by ultrasonic atomization undergoes a dual treatment process of a high-temperature furnace and high-temperature plasma, the sphericity of the prepared nano-silica is significantly improved, especially at a high-temperature plasma temperature of 2000℃, where the sphericity is optimal. The applicant speculates that this may be because the aerosol melts into droplets at 2000℃, and the droplets undergo a rapid cooling process, resulting in the optimal sphericity of the formed nano-silica. If the high-temperature plasma temperature is below 2000℃, the aerosol will not melt sufficiently, significantly reducing the utilization rate of silicon in the silicon slag; if the high-temperature plasma temperature is above 2200℃, the aerosol may sublimate, causing a loss of silicon in the silicon slag, thus failing to achieve the goal of "turning waste into treasure."

[0026] A second aspect of the present invention provides a modified nano-silica, the raw materials for which include a silane-based surface treatment agent and nano-silica prepared from silicon slag.

[0027] As a preferred embodiment of the present invention, the silane-based surface treatment agent is at least one of dichlorodimethylsilane, dichloromethylsiloxane, KH-450, KH-550, and KH560.

[0028] As a preferred embodiment of the present invention, the mass ratio of the nano-silica to the silane surface treatment agent is (1.1-1.9):(1.5-2.3).

[0029] As a more preferred technical solution of the present invention, the mass ratio of the nano-silica to the silane surface treatment agent is 1.5:2.

[0030] The method for preparing the modified nano-silica includes the following steps:

[0031] Nano-silica and silane-based surface treatment agents are added to a surface reaction furnace and reacted at 60-110℃ for 4-10 hours. After cooling to room temperature, modified nano-silica is obtained.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention uses silicon slag to prepare nano-silica, with silicon slag generated during the production of phosphate fertilizer as the silicon source. When the silicon dioxide content in the silicon slag is 31%, the nano-silica prepared by multiple treatments such as ultrasonic atomization, high-temperature furnace and high-temperature plasma has excellent sphericity. At the same time, the synthesis process is simple and does not use a large amount of acid, alkali and inorganic substances that are difficult to remove due to melting, thus avoiding the pollution of the environment by a large amount of acid and alkali, and further improving the purity of nano-silica.

[0034] 2. The nano-silica prepared by this invention using silica slag, by adding methylcellulose and polystyrene in a mass ratio of 0.4:1.5 to the system, effectively avoids the phenomenon of uneven particle size distribution of the prepared silica, which is beneficial to the subsequent high-temperature plasma spheroidization treatment. This makes the prepared nano-silica maintain excellent sphericity while also having a non-uniform particle size, thus expanding its application range in practical use.

[0035] 3. The nano-silica prepared by the present invention using silicon slag is subjected to dual treatment by ultrasonic atomization aerosol and high-temperature furnace and high-temperature plasma, which significantly improves the sphericity of the nano-silica and effectively alleviates the problem of poor sphericity of nano-silica prepared in the prior art.

[0036] 4. The nano-silica prepared by the present invention using silicon slag, by adding KH550 or dichlorodimethylsilane to the system and treating it in a surface reaction furnace, enables the nano-silica to maintain excellent sphericity while also having excellent hydrophilic or hydrophobic properties, further expanding the application prospects of nano-silica.

[0037] 5. The nano-silica prepared by the present invention using silicon slag, by strictly controlling the aerosol generation and high-temperature plasma treatment when the carrier gas flow rate is 350 mL / min and the gas flow rate is 8 L / min, the nano-silica obtained has a uniform particle size distribution and excellent sphericity, which significantly improves the flowability and filling rate of the prepared nano-silica. Attached Figure Description

[0038] Figure 1 A scanning electron microscope image of the nano-silica prepared in Example 1 with an average particle size of 200 nm.

[0039] Figure 2 A scanning electron microscope image of the nano-silica prepared in Example 1 with an average particle size of 20 nm.

[0040] Figure 3 Scanning electron microscope image of the water contact angle of the modified nano-silica prepared in Example 1;

[0041] Figure 4 Scanning electron microscope image of the water contact angle of the modified nano-silica prepared in Example 2;

[0042] Figure 5 Scanning electron microscope image of the modified nano-silica prepared in Example 2;

[0043] Figure 6 Scanning electron microscope image of nano-silica prepared for Comparative Example 1. Detailed Implementation

[0044] Example 1

[0045] Example 1 provides a method for preparing nano-silica from silicon slag, comprising the following steps:

[0046] (1) Mix the silicon slag with the polymer additive and place it in an ultrasonic atomizer. Then, introduce the carrier gas into the ultrasonic atomizer to bubble and atomize, forming an aerosol.

[0047] (2) The aerosol described in step (1) is passed through a high-temperature furnace with water vapor, and then transported to a high-temperature plasma by airflow, and then cooled to obtain the nano-silica.

[0048] The silica content of the silicon slag in step (1) is 31% by mass;

[0049] The mass ratio of silicon slag to polymer additive in step (1) is 100:4;

[0050] The carrier gas in step (1) is helium;

[0051] The flow rate of the carrier gas in step (1) is 250 mL / min;

[0052] The working conditions of the ultrasonic atomizer in step (1) are: power of 200W, transduction frequency of 2MHz, and atomization rate of 0.5mL / min;

[0053] The polymeric additives in step (1) are methylcellulose and polystyrene, with a mass ratio of methylcellulose to polystyrene of 0.4:1.5. The polystyrene was purchased from Dongguan Hongyu Plastic Technology Co., Ltd., model PH-888G; the CAS number of methylcellulose is 9004-67-5.

[0054] The airflow velocity in step (2) is 6 L / min;

[0055] The temperature of the high-temperature furnace in step (2) is 320℃;

[0056] The temperature of the high-temperature plasma in step (2) is 2000℃;

[0057] The modified nano-silica is prepared from dichlorodimethylsilane and has an average particle size of 200 nm.

[0058] The CAS number of the dichlorodimethylsilane is 75-78-5;

[0059] The mass ratio of the nano-silica to the silane surface treatment agent is 1.5:2.

[0060] The method for preparing the modified nano-silica includes the following steps:

[0061] Nano-sized silica with an average particle size of 200 nm and a silane-based surface treatment agent were added to a surface reaction furnace and reacted at 80 °C for 8 h. After cooling to room temperature, modified nano-sized silica was obtained.

[0062] The scanning electron microscope image of the nano-silica with an average particle size of 200 nm is shown below. Figure 1 ;

[0063] The scanning electron microscope image of the nano-silica with an average particle size of 20 nm is shown below. Figure 2 ;

[0064] The water contact angle scanning electron microscope image of the modified nano-silica is shown below. Figure 3 ;

[0065] Example 2

[0066] Example 2 provides a method for preparing nano-silica from silicon slag, comprising the following steps:

[0067] (1) Mix the silicon slag with the polymer additive and place it in an ultrasonic atomizer. Then, introduce the carrier gas into the ultrasonic atomizer to bubble and atomize, forming an aerosol.

[0068] (2) The aerosol described in step (1) is passed through a high-temperature furnace with water vapor, and then transported to a high-temperature plasma by airflow. After cooling, the nano-silica is obtained.

[0069] The silica content of the silicon slag in step (1) is 31% by mass;

[0070] The mass ratio of silicon slag to polymer additive in step (1) is 0.7:0.9;

[0071] The carrier gas in step (1) is helium;

[0072] The flow rate of the carrier gas in step (1) is 250 mL / min;

[0073] The working conditions of the ultrasonic atomizer in step (1) are: power of 200W, transduction frequency of 2MHz, and atomization rate of 0.5mL / min;

[0074] The polymeric additives in step (1) are methylcellulose and polystyrene, with a mass ratio of methylcellulose to polystyrene of 0.4:1.5. The polystyrene was purchased from Dongguan Hongyu Plastic Technology Co., Ltd., model PH-888G; the CAS number of methylcellulose is 9004-67-5.

[0075] The airflow velocity in step (2) is 6 L / min;

[0076] The temperature of the high-temperature furnace in step (2) is 320℃;

[0077] The temperature of the high-temperature plasma in step (2) is 2000℃;

[0078] The modified nano-silica is prepared from KH-550 nano-silica with an average particle size of 200nm.

[0079] The KH-550 was purchased from Jinan Xinglongda Chemical Co., Ltd.

[0080] The mass ratio of the nano-silica to the silane surface treatment agent is 1.5:2.

[0081] The method for preparing the modified nano-silica includes the following steps:

[0082] Nano-silica with an average particle size of 200 nm and a silane-based surface treatment agent are added to a surface reaction furnace and reacted at 80 °C for 8 h. After cooling to room temperature, modified nano-silica is obtained.

[0083] The water contact angle scanning electron microscope image of the modified nano-silica is shown below. Figure 4 ;

[0084] The scanning electron microscope image of the modified nano-silica is shown below. Figure 5 .

[0085] Comparative Example 1

[0086] Comparative Example 1 provides a method for preparing nano-silica from silicon slag, comprising the following steps:

[0087] (1) After placing the silicon slag in the ultrasonic atomizer, the carrier gas is then introduced into the ultrasonic atomizer for bubbling and atomization to form an aerosol.

[0088] (2) The aerosol described in step (1) is passed through a high-temperature furnace with water vapor, and then transported to a high-temperature plasma by airflow, and then cooled to obtain the nano-silica.

[0089] The silica content of the silicon slag in step (1) is 31% by mass;

[0090] The carrier gas in step (1) is helium;

[0091] The flow rate of the carrier gas in step (1) is 250 mL / min;

[0092] The working conditions of the ultrasonic atomizer in step (1) are: power of 200W, transduction frequency of 2MHz, and atomization rate of 0.5mL / min;

[0093] The airflow velocity in step (2) is 6 L / min;

[0094] The temperature of the high-temperature furnace in step (2) is 320℃;

[0095] The temperature of the high-temperature plasma in step (2) is 2000℃;

[0096] The scanning electron microscope image of the nano-silica is shown below. Figure 6 .

Claims

1. A method for preparing nanosilica from silicon slag, characterized by, Includes the following steps: (1) After mixing the silicon slag with the polymer additive, place it in an ultrasonic atomizer, and then pass the carrier gas into the ultrasonic atomizer for bubbling and atomization to form an aerosol. (2) The aerosol described in step (1) is passed through a high-temperature furnace with water vapor, then transported to a high-temperature plasma by airflow, and then cooled to obtain the nano-silica. The polymeric additive is a binder; The binder is methylcellulose and polystyrene, with a mass ratio of methylcellulose to polystyrene of (0.2-0.8):(1.1-1.7). The temperature of the high-temperature plasma in step (2) is 2000-2200℃.

2. The method for preparing nano-silica from silicon slag according to claim 1, characterized in that, The silica content in the silicon slag in step (1) is 15-70% by mass.

3. The method for preparing nano-silica from silicon slag according to claim 1, characterized in that, The mass ratio of silicon slag to polymer additive in step (1) is 100:(1-5).

4. The method for preparing nano-silica from silicon slag according to claim 1, characterized in that, The working conditions of the ultrasonic atomizer in step (1) are: power of 150-220W, transduction frequency of 1.5-2.5MHz, and atomization rate of 0.2-1mL / min.

5. A modified nano-silica, characterized in that, The raw materials include silane-based surface treatment agents and nano-silica obtained by the method for preparing nano-silica from silicon slag as described in any one of claims 1-4.

6. The modified nano-silica according to claim 5, characterized in that, The silane-based surface treatment agent is at least one of dichlorodimethylsilane, dichloromethylsiloxane, KH-450, KH-550, and KH560.

7. The modified nano-silica according to claim 6, characterized in that, The mass ratio of the nano-silica to the silane surface treatment agent is (1.1-1.9):(1.5-2.3).

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