Hollow quince-shaped silica microspheres and a method for preparing the same

Abstract

The application discloses hollow plum-shaped silica microspheres and a preparation method thereof. The method comprises the following steps: (1) mixing an oily curing agent, an additive, water and a surfactant, and obtaining a white oil-in-water emulsion after emulsification; (2) stirring the emulsion at room temperature for a period of time, adding ammonia water to adjust the pH to be greater than 8, and continuously stirring at room temperature for a period of time; and (3) performing solid-liquid separation on the product, washing and drying to obtain hollow plum-shaped silica microspheres. The obtained silica microspheres are in a hollow plum shape, and the particle size is 1-10 mu m. The microemulsion method is used to prepare the hollow silica microspheres, a large amount of alkane compounds is not needed, the whole preparation process is carried out at room temperature and normal pressure, the preparation process is simple, energy consumption is low, the prepared hollow silica microspheres have a larger specific surface area and more active sites, and have a wider application prospect.

Description

Technical Field

[0001] This invention belongs to the field of hollow microsphere material technology, specifically relating to a hollow plum-shaped silica microsphere and its preparation method. Background Technology

[0002] Many substances in nature, such as cells, plant fibers, and viruses, possess unique properties due to their multi-scale, multi-level nanostructures, including hollow cavities. Artificial systems with similar structures, such as nanotubes and hollow microspheres, have become an important research direction in materials science. Among them, silica hollow microspheres are a key area of ​​development for hollow microspheres, due to their narrow particle size distribution, good dispersibility, good stability, high melting point, and large specific surface area, offering broad development prospects in fields such as biochemical engineering, medicine, optics, catalysis, and composite materials.

[0003] Currently, the main method for preparing hollow silica microspheres is the template method. However, the selection of the template is particularly important. It is also necessary to prevent the template from agglomerating and being etched during the silica coating process, and to ensure that the removal of the template does not affect the collapse or breakage of the silica. The preparation process is relatively complex and costly, which limits the application of hollow silica microspheres.

[0004] CN114409335A discloses an emulsion method for preparing hollow silica microspheres. Silica particles are added to an oil phase, and an aqueous solution containing a surfactant is added under continuous stirring. A prepolymerization reaction is carried out at a high temperature of 180-220℃, followed by centrifugation, washing, and high-temperature calcination. This method requires high-temperature holding and calcination, resulting in high energy consumption, a high risk factor, and certain safety hazards.

[0005] CN111566047A discloses a method for manufacturing hollow silica particles. Sodium silicate is added as a silicon source to an oil-in-water emulsion containing an aqueous phase, an oil phase, and a surfactant. Under alkaline conditions, sodium silicate is further added to obtain a hollow silica precursor dispersion, which is then calcined to obtain hollow silica particles. This method uses sodium silicate as the silicon source, and sodium cannot be completely removed during the entire preparation process, limiting its application in the electronics industry. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides hollow plum-shaped silica microspheres and their preparation method. The silica microspheres prepared by this invention have a large specific surface area, the preparation method is simple, and no template is required.

[0007] The technical solution of this invention is as follows:

[0008] This invention relates to a method for preparing hollow, plum-shaped silica microspheres, comprising the following steps:

[0009] (1) Mix the oily curing agent, additives, water and surfactant, and emulsify to obtain a white oil-in-water emulsion;

[0010] (2) After stirring the emulsion obtained in step (1) at room temperature for a period of time, add ammonia water to adjust the pH to >8, and continue stirring at room temperature for a period of time.

[0011] (3) The product obtained in step (2) is subjected to solid-liquid separation, washed and dried to obtain hollow plum-shaped silica microspheres.

[0012] Preferably, in step (1), the oily curing agent is an alkoxysilane condensate, the additive is an alkane compound, and the emulsifier is a nonionic surfactant.

[0013] Preferably, the mass ratio of the oil-based curing agent to water is 1:(2-10), the mass ratio of the additive to the oil-based curing agent is 1:(5-20), and the mass ratio of the surfactant to the oil-based curing agent is 1:(150-300).

[0014] Preferably, the alkoxysilane condensate is one or more of methyltrimethoxysilane condensate, tetramethoxysilane condensate, and tetraethoxysilane condensate, with a solid content of 50-70% and a viscosity of 20-30 mPa·s.

[0015] Preferably, the alkane compound is one or more of heptane, decane, cyclohexane, and n-octane.

[0016] Preferably, the nonionic surfactant is one or more of the Tween series, BRIJ-721 / 721S, and M68.

[0017] Preferably, in step (2), after stirring the emulsion at room temperature for 0.5-1h, ammonia is added to adjust the pH to >8, and stirring is continued at room temperature for 3-4h, wherein the pH is preferably between 9 and 11.

[0018] Preferably, in step (3), the solid-liquid separation method is one or more of centrifugation, pressure filtration, and vacuum filtration, the washing method is water washing, and the drying temperature is 70-100℃.

[0019] The present invention also relates to a hollow plum-shaped silica microsphere, which is prepared by the above preparation method. The silica microsphere is hollow plum-shaped and has a particle size of 1-10 μm.

[0020] The beneficial effects of this invention are:

[0021] (1) The present invention uses the microemulsion method to prepare hollow silica microspheres, and first prepares an oil-in-water emulsion. The entire process does not require the use of a large amount of alkane compounds, thus avoiding the recycling steps of alkane compounds.

[0022] (2) The entire preparation process is carried out at room temperature and pressure. The preparation process is simple, not strict, and has low energy consumption, which is more conducive to industrial production.

[0023] (3) The hollow silica microspheres prepared in this invention are plum-shaped, and have a larger specific surface area and more active sites compared with existing hollow silica microspheres, giving them a broader application prospect. For example, these silica microspheres have good adsorption performance and can be reused in wastewater treatment; combining these silica microspheres with mesoporous silica to prepare hollow silica microspheres with a cavity structure and mesoporous shell will greatly improve their application performance, and have a high removal capacity for heavy metal ions and dye molecules in wastewater; the silica microspheres can encapsulate guest molecules inside, and their plum-shaped surface has more active sites. Modifying their shells can further expand their application potential. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0025] Figure 1 These are scanning electron microscope images of the silica microspheres from Example 1 of this invention;

[0026] Figure 2 These are scanning electron microscope images of the silica microspheres from Embodiment 2 of the present invention;

[0027] Figure 3 This is a picture of silica microspheres from Example 1 of the present invention after being stirred in water and then left to stand. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0029] The oil-based curing agents used in the following examples were self-made.

[0030] The oily curing agent used in Examples 1 and 3 was a tetramethoxysilane condensate, which was prepared as follows: tetramethoxysilane was added to water and a small amount of nitric acid and stirred thoroughly for 4 hours. Methanol was then distilled off to obtain the tetramethoxysilane condensate, i.e., the oily curing agent. The mass ratio of water to siloxane was 1:5, and the added nitric acid (mass concentration of 68%) was 0.002% of the tetramethoxysilane.

[0031] The oil-based curing agent used in Example 2 is a tetraethoxysilane condensate, which is prepared as follows: tetraethoxysilane is added to water and a small amount of nitric acid, stirred and reacted thoroughly for 3 hours, and then ethanol is distilled off to obtain the tetraethoxysilane condensate, i.e., the oil-based curing agent. The mass ratio of water to siloxane is 1:6, and the added nitric acid (mass concentration of 68%) is 0.004% of the tetraethoxysilane.

[0032] The oily curing agent used in Example 4 was a methyltrimethoxysilane condensate, which was prepared as follows: methyltrimethoxysilane was added to water and a small amount of nitric acid, stirred and reacted thoroughly for 4 hours, and then methanol was distilled off to obtain the methyltrimethoxysilane condensate, i.e., the oily curing agent. The mass ratio of water to siloxane was 1:5, and the added nitric acid (mass concentration of 68%) was 0.003% of the mass of methyltrimethoxysilane.

[0033] Example 1

[0034] The preparation is carried out according to the following steps:

[0035] Take 60g of oil-based curing agent, 3.6g of heptane, and 0.4g of Tween 80 and stir evenly. Add 420g of pure water to the solution and stir. After emulsification in a high-speed emulsifier, a white oil-in-water emulsion is obtained. After stirring the emulsion at room temperature for 0.5h, add 20g of 5% dilute ammonia water to adjust the pH of the solution to 9. Stir at room temperature for 3h under the same conditions and filter to obtain a white semi-solid material. After washing with water, pre-dry at 70℃ for 3h and then dry at 100℃ for 2h to obtain white, soft, hollow, plum-shaped silica microspheres.

[0036] Example 2

[0037] The preparation is carried out according to the following steps:

[0038] Take 50g of oil-based curing agent, 2.5g of heptane, and 0.25g of Tween 80 and stir evenly. Add 250g of pure water to the solution and stir. Emulsify the solution using a high-speed emulsifier to obtain a white oil-in-water emulsion. Stir the emulsion at room temperature for 1 hour, then add 18g of 8% dilute ammonia to adjust the pH of the solution to 10. Stir at room temperature for 4 hours under the same conditions, then filter to obtain a white semi-solid material. After washing with water, pre-dry at 70℃ for 3 hours, then dry at 100℃ for 2 hours to obtain white, soft, hollow, plum-shaped silica microspheres.

[0039] Example 3

[0040] The preparation is carried out according to the following steps:

[0041] Take 60g of oil-based curing agent, 4g of heptane, and 0.24g of Tween 80 and stir evenly. Add 300g of pure water to the solution and stir. Emulsify the solution using a high-speed emulsifier to obtain a white oil-in-water emulsion. Stir the emulsion at room temperature for 0.5h, then add 10g of 10% dilute ammonia to adjust the pH of the solution to 10. Stir at room temperature for 3h under the same conditions, then filter to obtain a white semi-solid material. After washing with water, pre-dry at 70℃ for 3h, then dry at 100℃ for 2h to obtain white, soft, hollow, plum-shaped silica microspheres.

[0042] Example 4

[0043] The preparation is carried out according to the following steps:

[0044] Take 80g of oil-based curing agent, 8g of heptane, and 0.2g of Tween 80 and stir them evenly. Add 720g of pure water to the solution and stir. After emulsification in a high-speed emulsifier, a white oil-in-water emulsion is obtained. After stirring the emulsion at room temperature for 1 hour, add 20g of 10% dilute ammonia water to adjust the pH of the solution to 9. Stir at room temperature for 4 hours under the same conditions and then filter to obtain a white semi-solid material. After washing with water, pre-dry at 70℃ for 3 hours and then dry at 100℃ for 2 hours to obtain white, soft, hollow, plum-shaped silica microspheres.

[0045] Figure 1 and Figure 2 The images show SEM images of hollow plum-shaped silica microspheres at different magnifications. As can be seen from the images, the silica microspheres prepared in this invention have a rough surface with many wrinkles, resembling plums, compared to generally smooth and round silica microspheres. Compared to smooth silica microspheres of the same particle size, these plum-shaped silica microspheres have a larger specific surface area, more active adsorption sites, and are more conducive to the adsorption of active substances.

[0046] The hollow plum-shaped silica microspheres prepared in Example 1 and the smooth hollow silica microspheres of the same particle size were subjected to hydrophobic modification. The effect of adding 1% silane coupling agent to the plum-shaped silica microspheres was equivalent to the effect of adding 1.5% silane coupling agent to the smooth silica microspheres. That is, under the same conditions, the plum-shaped morphology provides relatively more and easier-to-modify active sites, which greatly reduces the amount of modifier used and saves costs.

[0047] Figure 3The image shows silica microspheres after being stirred in water and left to stand. As can be seen from the image, the silica microspheres float quietly on the water surface and do not sink to the bottom, indicating that the silica microspheres have good porosity.

[0048] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for producing hollow prune-shaped silica microspheres, characterized by, The silica microspheres are hollow plum-shaped with a particle size of 1-10 μm. Their preparation method includes the following steps: (1) Mix the oily curing agent, additives, water and surfactant, and emulsify to obtain a white oil-in-water emulsion; The oily curing agent is one or more of methyltrimethoxysilane condensate, tetramethoxysilane condensate and tetraethoxysilane condensate, and the oily curing agent has a solid content of 50-70% and a viscosity of 20-30 mPa·s. The additive is one or more of heptane, decane, cyclohexane, and n-octane; The surfactant is one or more of the Tween series, BRIJ-721 / 721S, and M68; (2) After stirring the emulsion obtained in step (1) at room temperature for a period of time, add ammonia water to adjust the pH to >8, and continue stirring at room temperature for a period of time; (3) The product obtained in step (2) is subjected to solid-liquid separation, washed and dried to obtain hollow plum-shaped silica microspheres.

2. The production method according to claim 1, characterized by, The mass ratio of the oily curing agent to water is 1:(2-10), the mass ratio of the additive to the oily curing agent is 1:(5-20), and the mass ratio of the surfactant to the oily curing agent is 1:(150-300).

3. The preparation method according to claim 1, characterized in that, In step (2), after stirring the emulsion at room temperature for 0.5-1h, ammonia water is added to adjust the pH to >8, and stirring is continued at room temperature for 3-4h.

4. The preparation method according to claim 1, characterized in that, In step (3), the solid-liquid separation method is one or more of centrifugation, pressure filtration, and vacuum filtration, and the washing method is water washing; the drying temperature is 70-100℃.

5. A hollow, plum-shaped silica microsphere, characterized in that, The silica microspheres prepared by the preparation method according to any one of claims 1-4 are hollow plum-shaped and have a particle size of 1-10 μm.

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