A high specific surface area silica gel, its preparation method and application

Abstract

This invention belongs to the technical field of separation and purification of effective components of natural products such as traditional Chinese medicine, specifically involving a high specific surface area silica gel, its preparation method, and its application. The preparation method includes (1) preparing a sol: first, mixing and reacting a sodium silicate solution with a sulfuric acid solution; when the reaction has proceeded to 5%-50% of the total reaction time, adding a silica gel particle regulator; continuing the reaction; (2) preparing a gel: aging, soaking in alkali, and washing with water sequentially with the obtained sol; (3) preparing silica gel: drying and activating the obtained gel. The specific surface area of ​​the prepared silica gel reaches 550-850 m². 2 The high specific surface area silica gel enhances the adsorption capacity of silica gel, enabling its application in the treatment of colloidal solutions from traditional Chinese medicine extracts, achieving efficient adsorption of the effective components of traditional Chinese medicine. Furthermore, this high specific surface area silica gel can also be used in the anti-turbidity treatment of beer, efficiently adsorbing and removing turbidity-sensitive proteins in beer that easily form protein-polyphenol complexes.

Description

Technical Field

[0001] This invention belongs to the technical field of separation and purification of effective components of natural products such as traditional Chinese medicine, specifically relating to a high specific surface area silica gel, its preparation method and application. Background Technology

[0002] With the development of my country's pharmaceutical industry, the rational development and utilization of traditional Chinese medicine (TCM) has received increasing attention, especially the widespread application of effective components of TCM, represented by artemisinin. Currently, separating and extracting effective substances from traditional Chinese medicinal materials has become a powerful means of modernizing TCM. However, the extraction of TCM produces a large amount of extract solutions rich in various anthocyanins, volatile oils, saponins, and other substances. How to efficiently separate and extract the effective components of TCM from these colloidal extract solutions has become a technical challenge.

[0003] Currently, the main methods for separating and extracting effective substances from traditional Chinese medicine extracts are physicochemical treatments, with adsorption being a common method—a typical application of colloidal chemistry. Adsorption utilizes the large specific surface area, multiple active sites, and unique pore structure of adsorbents to physically or chemically adsorb substances in the solution, thereby achieving the separation and purification of effective substances. Adsorption methods offer advantages such as low operating costs and stable operation. Commonly used colloidal adsorbents include activated carbon and silica gel.

[0004] Silica gel, also known as silica gel, is an amorphous substance mainly composed of silicon and oxygen atoms. Its primary preparation method is the sol-gel method using sodium silicate and inorganic acids as raw materials. Unlike crystalline substances such as quartz, which have silicon-oxygen tetrahedra as their basic structural units and are arranged in a highly ordered manner, silica gel contains fewer silicon-oxygen tetrahedra. More silicon and oxygen atoms are bonded in a disordered manner and arranged randomly. This results in extremely low crystallinity of silica gel, but also creates numerous lattice gaps and channels at the microscopic level. Statistics show that the inner surface formed by these channels provides more than 98% of the total surface area of ​​silica gel; therefore, the structural characteristics of the channels play a crucial role in the specific surface area of ​​silica gel. Through precise structural control of silica gel, it is hoped that highly efficient adsorbent materials with larger specific surface areas can be obtained.

[0005] Currently, the specific surface area of ​​colloidal silica gels used in the separation and purification of effective components from natural products such as traditional Chinese medicine is relatively small, ranging from only 220 to 460 m². 2 / g, a small specific surface area will result in insufficient adsorption capacity per unit mass of silica gel, which will easily lead to the loss of effective ingredients and generate more waste residue and waste liquid. Its subsequent treatment will put great economic and environmental pressure on enterprises and the environment.

[0006] Therefore, there is an urgent need to develop a new type of colloidal silica gel with a large specific surface area to achieve efficient adsorption of natural effective substances in the colloidal solution of traditional Chinese medicine. Summary of the Invention

[0007] The purpose of this invention is to address the problem of insufficient adsorption capacity per unit mass of silica gel currently used for the separation and purification of effective components from natural products such as traditional Chinese medicine. This invention provides a method for preparing silica gel with a high specific surface area, resulting in silica gel with a specific surface area of ​​550-850 m². 2 / g enhances the adsorption capacity of silica gel, enabling efficient adsorption of effective substances and other substances abundant in the extract of traditional Chinese medicine.

[0008] The overall adsorption capacity of silica gel is highly dependent on its specific surface area. Therefore, increasing the specific surface area of ​​silica gel is an effective way to enhance its adsorption properties.

[0009] During the research process of this invention, it was discovered that the most critical step in the formation of the silica microstructure is the addition of sulfuric acid to a sodium silicate solution for acidification. This causes silicate ions to combine with hydrogen ions to generate orthosilicic acid, which precipitates out and then spontaneously dehydrates and condenses to form polysilicic acid aging products. The formation of polysilicic acid in this stage has a crucial impact on the pore structure and specific surface area of ​​the final silica product. However, the formation and dehydration condensation process of orthosilicic acid are often difficult to control precisely in this step, easily leading to excessively large silica particle sizes. Larger particle sizes have a significant negative impact on the specific surface area of ​​silica. The specific surface area of ​​nanomaterials is directly correlated with particle size; when the particle size is below a certain value, the specific surface area of ​​the material increases exponentially with decreasing particle size. Therefore, reducing the particle size of silica can effectively and significantly increase the specific surface area, thereby improving its adsorption capacity.

[0010] Therefore, the key to solving the problem lies in how to increase the specific surface area by controlling the reduction of particle size. Further research revealed that the particle size of silica nanoparticles produced by the reaction can be reduced and the specific surface area increased by regulating the crystal nucleation and growth.

[0011] Therefore, the present invention proposes the following inventive concept: starting from limiting crystal growth and increasing the number of crystal nuclei in the reaction system, by adding an appropriate silica particle regulator to the reaction system, the traditional reaction solution is transformed into a colloid rich in micelles. The micelles are used to limit the excessive dehydration and condensation of orthosilicic acid and subsequent particle aggregation, thereby limiting the increase in the particle size of silica nanoparticles. This allows the particle size of the silica adsorbent to be precisely adjusted within a certain range, achieving a significant increase in the specific surface area of ​​silica, and thus improving the adsorption efficiency.

[0012] The specific technical solution is as follows: A method for preparing high specific surface area silica gel includes the following steps: (1) Preparation of sol: First, mix and stir the sodium silicate solution and sulfuric acid solution to allow the reaction to proceed, adjusting the pH to 2-4. The mass fraction of the sodium silicate solution can be 2-50%, and the mass fraction of the sulfuric acid solution can be 2-70%. The stirring speed should be 60-1000 rpm.

[0013] Then, when the reaction has proceeded to 5%-50% of the total reaction time, a silica particle regulator is added. Silica gel is composed of many small particles at the microscopic level; the smaller the particles, the larger the surface area, and vice versa. The added silica particle regulator regulates the particle size of the silica gel. Each small vesicle formed by the silica particle regulator can encapsulate a small amount of orthosilicic acid molecules, thus isolating the orthosilicic acid molecules and limiting the polymerization of the material. This allows for minimal polymerization, depleting the orthosilicic acid within the vesicles and limiting the unrestricted polymerization of silica gel, thereby reducing the particle size.

[0014] Continue the reaction until it is complete, then maintain the pH at 3-4 to prepare the sol. During the process of silicate ions combining with hydrogen ions to form orthosilicic acid, adjust the pH of the system to control it at 2-4; after the reaction is complete, maintain the final pH of the system at 3-4. If the pH is too low, polymerization will be too fast; if the pH is too high, polymerization will be slow or insufficient, or even fail to initiate polymerization.

[0015] The silica gel particle regulator is one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, or dodecyltrimethylammonium bromide; the molar ratio of silica gel particle regulator to sodium silicate is 0.01-0.3:1.

[0016] (2) Preparation of gel: The sol obtained in step (1) is aged, soaked in alkali and washed with water in sequence to obtain gel.

[0017] (3) Preparation of silica gel: The gel obtained in step (2) is dried and activated to obtain the silica gel.

[0018] In the preparation method described in this invention, the silica particle regulator is added when the reaction has proceeded to 5%-50% of the total reaction time, which can form a large number of tiny micelles in the solution. The small amount of orthosilicic acid solution encapsulated by the micelles is isolated from the outside, limiting the condensation of orthosilicic acid molecules or particle aggregation within the micelles, thus preventing the unlimited epitaxial growth of silica particles. The orthosilicic acid concentration inside the micelles is limited, and once the condensation substrate is exhausted, the particles will be unable to continue growing, thereby achieving the purpose of reducing the silica particle size and increasing the specific surface area.

[0019] In the present invention, the method for preparing high specific surface area silica gel includes step (1) in which sodium silicate solution and sulfuric acid solution are mixed at 20-40°C.

[0020] In the preparation method of high specific surface area silica gel in this invention, the aging temperature in step (2) is 60-80℃ and the time is 0.5-2h.

[0021] In this invention, the method for preparing high specific surface area silica gel includes step (2) of soaking in NaOH solution for 10-15 minutes. The mass fraction of the NaOH solution can be 2-50 wt%.

[0022] In the preparation method of high specific surface area silica gel in this invention, the water washing in step (2) is carried out with distilled water.

[0023] In this invention, the high specific surface area silica gel preparation method includes a drying temperature of 60-120℃ and a drying time of 3-24h in step (3). The drying method can be selected from the following two options: one is vacuum drying at 60℃; the other is forced-air drying at 120℃. If the product quantity is large or the water content is high, forced-air drying followed by vacuum drying should be used first. If the quantity is small or the product is relatively dry, vacuum drying can be performed directly.

[0024] In the present invention, the high specific surface area silica gel preparation method, in step (3), the activation is carried out by calcination, the calcination temperature is 400-500℃, and the calcination time is 3-4h.

[0025] A high specific surface area silica gel, prepared by the above-described method for preparing high specific surface area silica gel; the specific surface area of ​​this silica gel is 550-850 m². 2 / g, with a particle size of 4-8nm and a pore size of 2-5nm.

[0026] The aforementioned high specific surface area silica gel can be used for the separation and purification of effective components from natural products such as traditional Chinese medicine, and can efficiently adsorb the effective substances rich in the colloidal solution of traditional Chinese medicine extract.

[0027] In addition, the aforementioned high specific surface area silica gel can also be used for anti-turbidity treatment of beer, which can efficiently adsorb and remove turbidity-sensitive proteins in beer that are prone to producing protein-polyphenol complexes.

[0028] The beneficial effects of this invention are as follows: The preparation method of this invention transforms the traditional reaction solution into a micelle-rich colloid by adding an appropriate silica particle regulator to the reaction system. The micelles limit the excessive dehydration and condensation of orthosilicic acid and subsequent particle aggregation, thereby limiting the increase in the particle size of silica nanoparticles. This allows the particle size of the silica adsorbent to be precisely adjusted within a certain range, achieving a significant increase in the specific surface area of ​​silica, and thus improving adsorption efficiency. Currently, the typical specific surface area of ​​commercially available silica is only 220-460 m². 2 / g; and the specific surface area of ​​the silica gel prepared by the method described in this invention can reach 550-850m². 2Based on this estimate, if the same adsorption capacity is achieved, the silica gel prepared by the method described in this invention can reduce the amount of silica gel used by at least 20% compared to existing silica gels.

[0029] In summary, the preparation method described in this invention optimizes and controls the silica gel preparation process, enabling precise adjustment of the pore size of the silica gel adsorbent within a certain range, thereby significantly increasing the specific surface area of ​​the silica gel. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of the high specific surface area silica gel described in this invention. Detailed Implementation

[0031] The technical solution of the present invention will be described in detail below.

[0032] Example 1 The specific steps for preparing the high specific surface area silica gel are as follows: (1) Preparation of sol: First, a sodium silicate solution with a mass percentage of 20 wt% and a sulfuric acid solution with a mass percentage of 30 wt% are mixed at 20°C and stirred at 100 r / min to carry out the reaction, and the pH value is adjusted to 3.

[0033] Then, when the reaction has proceeded for 1 hour (which is 20% of the total reaction time), hexadecyltrimethylammonium bromide, a silica gel particle regulator, is added; wherein the molar ratio of hexadecyltrimethylammonium bromide to sodium silicate is 0.1:1.

[0034] Continue the reaction until the total reaction time is 5 hours. Once the reaction is complete, maintain the pH value at 4 to prepare the sol.

[0035] (2) Preparation of gel: The sol obtained in step (1) is aged at 60°C for 2 hours, then soaked in a 20wt% NaOH aqueous solution for 15 minutes, and finally the filter is washed three times with distilled water to obtain the gel.

[0036] (3) Preparation of silica gel: After drying the gel obtained in step (2) at 60°C for 24 hours, it is placed in a muffle furnace at 500°C for high-temperature activation for 3 hours to obtain the silica gel.

[0037] from Figure 1 As can be seen, the obtained silica gel is composed of nanoscale particles, and each particle is composed of agglomerates of even smaller nanoparticles. Therefore, the obtained silica gel has a small particle size.

[0038] Example 2 The specific steps for preparing the high specific surface area silica gel are as follows: (1) Preparation of sol: First, a sodium silicate solution with a mass percentage of 20 wt% and a sulfuric acid solution with a mass percentage of 30 wt% are mixed at 30°C and stirred at 100 r / min to carry out the reaction, and the pH value is adjusted to 2.

[0039] Then, when the reaction has proceeded for 15 minutes (which is 5% of the total reaction time), hexadecyltrimethylammonium chloride, a silica gel particle regulator, is added; wherein the molar ratio of hexadecyltrimethylammonium chloride to sodium silicate is 0.3:1.

[0040] Continue the reaction until the total reaction time is 5 hours. Once the reaction is complete, maintain the pH at 3 to prepare the sol.

[0041] (2) Preparation of gel: The sol obtained in step (1) is aged at 70°C for 1.5 h, then soaked in 40 wt% NaOH solution for 10 min, and finally the filter is washed three times with distilled water to obtain the gel.

[0042] (3) Preparation of silica gel: After drying the gel obtained in step (2) at 80°C for 12 hours, it is placed in a muffle furnace at 400°C for high-temperature activation for 4 hours to obtain the silica gel.

[0043] Example 3 The specific steps for preparing the high specific surface area silica gel are as follows: (1) Preparation of sol: First, a sodium silicate solution with a mass percentage of 20 wt% and a sulfuric acid solution with a mass percentage of 30 wt% are mixed at 40°C and stirred at 100 r / min to carry out the reaction, and the pH value is adjusted to 3.

[0044] Then, when the reaction has proceeded for 2.5 hours (which is 50% of the total reaction time), dodecyltrimethylammonium bromide, a silica gel particle regulator, is added; wherein the molar ratio of dodecyltrimethylammonium bromide to sodium silicate is 0.05:1.

[0045] Continue the reaction until the total reaction time is 5 hours. Once the reaction is complete, maintain the pH value at 4 to prepare the sol.

[0046] (2) Preparation of gel: The sol obtained in step (1) is aged at 80°C for 0.5 h, then soaked in 20 wt% NaOH solution for 15 min, and finally the filter is washed three times with distilled water to obtain the gel.

[0047] (3) Preparation of silica gel: After drying the gel obtained in step (2) at 120°C for 3 hours, it is placed in a muffle furnace at 500°C for high-temperature activation for 3.5 hours to obtain the silica gel.

[0048] Example 4 The difference from Example 1 is that the silica gel particle control agent used in this example is dodecyltrimethylammonium bromide.

[0049] The others are the same as in Example 1.

[0050] Comparative Example 1 The difference from Example 1 is that the silica gel particle control agent used in this comparative example is dodecyltrimethylammonium chloride.

[0051] The others are the same as in Example 1.

[0052] Comparative Example 2 The difference from Example 1 is that the silica gel particle control agent used in this comparative example is octadecyltrimethylammonium bromide.

[0053] The others are the same as in Example 1.

[0054] The performance indicators of the silicone obtained by the preparation methods of each embodiment and comparative example are detailed in Table 1.

[0055] Table 1 Test Indicators for Various Silicone Components

[0056] The following experimental examples illustrate the effects of the timing and dosage of silica gel particle control agents on silica gel.

[0057] Experimental Example 1 I. Experimental Objective: To investigate the effect of the timing of adding silica gel particle regulator on various properties of silica gel.

[0058] II. Experimental Methods: Following the preparation method steps described in Example 1, the single variable was set as the proportion of the reaction proceeding to the total reaction time when the silica gel particle regulator cetyltrimethylammonium bromide was added in step (1), which were 4%, 5%, 10%, 20%, 30%, 40%, 50%, and 55%, respectively. Other steps and conditions were the same as in Example 1.

[0059] III. Experimental Results: See Table 2 for details.

[0060] Table 2 Test Indicators for Various Silicone Components

[0061] Experiment Example 2 I. Experimental Objective: To investigate the effect of the dosage of silica gel particle regulator on various properties of silica gel.

[0062] II. Experimental Methods: Following the preparation method described in Example 1, the single variable was set as the molar ratio of hexadecyltrimethylammonium bromide to sodium silicate in step (1) as 0.002:1, 0.01:1, 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, and 0.5:1, respectively. All other steps and conditions were the same as in Example 1.

[0063] III. Experimental Results: See Table 3 for details.

[0064] Table 3 Test Indicators for Various Silicone Components

[0065] Therefore, it is evident that the timing and amount of silica particle control agent added have a significant impact on various indicators of silica.

Claims

1. A method for preparing high specific surface area silica gel, characterized in that, Includes the following steps: (1) Preparation of sol: First, the raw material sodium silicate solution and sulfuric acid solution are mixed and stirred to carry out the reaction, and the pH value is adjusted to 2-4. Then, when the reaction has proceeded to 5%-50% of the total reaction time, add silica gel particle regulator; Continue the reaction until it is complete, then maintain the pH at 3-4 to prepare the sol. The silica gel particle regulator is one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, or dodecyltrimethylammonium bromide. The molar ratio of the silica gel particle regulator to sodium silicate is 0.01-0.3:1; (2) Preparation of gel: The sol obtained in step (1) is aged, soaked in alkali and washed with water in sequence to obtain gel; (3) Preparation of silica gel: The gel obtained in step (2) is dried and activated to obtain the silica gel. The specific surface area of ​​this silicone is 550-850 m². 2 / g, with a particle size of 4-5.9nm and a pore size of 2-3.6nm.

2. The method for preparing high specific surface area silica gel according to claim 1, characterized in that, In step (1), the sodium silicate solution and sulfuric acid solution are mixed at 20-40°C.

3. The method for preparing high specific surface area silica gel according to claim 1, characterized in that, In step (2), the aging temperature is 60-80℃ and the time is 0.5-2h.

4. The method for preparing high specific surface area silica gel according to claim 1, characterized in that, In step (2), the alkaline soaking is performed by soaking in NaOH solution for 10-15 minutes.

5. The method for preparing high specific surface area silica gel according to claim 1, characterized in that, In step (2), the water washing is done with distilled water.

6. The method for preparing high specific surface area silica gel according to claim 1, characterized in that, The drying temperature in step (3) is 60-120℃ and the time is 3-24h.

7. The method for preparing high specific surface area silica gel according to claim 1, characterized in that, In step (3), the activation is carried out by calcination, with a calcination temperature of 400-500℃ and a calcination time of 3-4h.

8. A high specific surface area silicone, characterized in that, The silica gel is prepared by the preparation method according to any one of claims 1-7; the specific surface area of ​​the silica gel is 550-850 m². 2 / g, with a particle size of 4-5.9nm and a pore size of 2-3.6nm.

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