Mesoporous silica gel with high pore volume and high specific surface area as well as preparation method and application of mesoporous silica gel

Abstract

The invention discloses mesoporous silica gel with high pore volume and high specific surface area as well as a preparation method and application of the mesoporous silica gel, and belongs to the field of inorganic porous materials. The preparation method of the mesoporous silica gel comprises the following steps: (1) dissolving a silicon source in an ethanol solution, adjusting the pH value by using acid, adding water, stirring, and drying; and (2) dissolving the product obtained in the step (1) in isopropanol and ammonia water, mixing with an aqueous solution containing a template agent, stirring, standing, centrifugally drying and calcining. The average pore size of the mesoporous silica gel is 15-30 nm, the pore volume is 1-3 cm < 3 > / g, and the specific surface area is 600-700 m < 2 > / g. According to the method, regular pore channels are prepared on the surface of SiO2.mH2O, and the surface area of the SiO2.mH2O is greatly increased while the large pore volume is ensured.

Description

Technical Field

[0001] The invention belongs to the field of inorganic porous materials, and specifically relates to a mesoporous silica gel with high pore volume and high specific surface area, and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Silica gel is a typical high-activity adsorption material. Its rich pore structure and high specific surface area give it excellent adsorption performance and are widely used in the preparation of various gas adsorbents, catalyst carriers, environmental purification functional materials, and chromatographic column fillers. The adsorption activity of silica gel mainly depends on its pore structure and specific surface area. Therefore, the research on the synthesis method of porous and high specific surface area silica gel is very important. However, in the prior art, the prepared porous silica gel cannot achieve a large pore volume while greatly increasing its surface area. Summary of the invention

[0004] In order to solve the shortcomings of the prior art, the purpose of the present invention is to provide a mesoporous silica gel having both high pore volume and high specific surface area and a preparation method and application thereof. The present invention prepares regular pores on the surface of SiO2·mH2O and ensures a large pore volume while greatly increasing its surface area.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] In a first aspect, the present invention provides a method for preparing mesoporous silica gel having both high pore volume and high specific surface area, comprising the following steps:

[0007] (1) dissolving a silicon source in an ethanol solution, adjusting the pH with an acid, adding water, stirring, and drying;

[0008] (2) dissolving the product obtained in step (1) in isopropanol and ammonia water, mixing with an aqueous solution containing a template, stirring, standing, centrifugally drying, and calcining to obtain the product.

[0009] In one or more embodiments, in step (1), the mixing and stirring of the solution is carried out at room temperature.

[0010] In one or more embodiments, in step (1), the silicon source is tetraethyl orthosilicate (TEOS).

[0011] In one or more embodiments, in step (1), the volume ratio of the silicon source, ethanol solution and water is (15-30):(40-60):(2-6), preferably (20-30):(45-55):(3-4), and further preferably (24-26):(48-52):(3.4-3.7).

[0012] In one or more embodiments, in step (1), the acid is sulfuric acid, and the pH is adjusted to 5-6.

[0013] In one or more embodiments, in step (1), the stirring time during adding water and stirring is 0.5 to 2 hours, preferably 1 to 2 hours.

[0014] In one or more embodiments, in step (1), the drying temperature is 120-150° C., and the drying time is 2-5 hours.

[0015] In one or more embodiments, in step (2), the template is cetyltrimethylammonium bromide (CTAB).

[0016] In one or more embodiments, in step (2), the volume ratio of the silicon source, isopropanol and aqueous ammonia is (15-30):(50-70):(1-4), preferably (20-30):(55-65):(2-3), and further preferably (24-26):(58-62):(1.5-2.5).

[0017] In one or more embodiments, in step (2), the mass volume ratio of the template and water is (5-10):(50-100), preferably (7-8):(70-90).

[0018] In one or more embodiments, the mass volume ratio of the template and the silicon source is (5-10):(15-30), preferably (7-8):(20-30), and further preferably (7-8):(24-26).

[0019] In one or more embodiments, in step (2), the stirring time is 20 to 60 min, preferably 30 to 40 min, and the stirring speed is 1000 to 3000 r / min, preferably

[0020] 1500~2500r / min.

[0021] In one or more embodiments, the standing time is 6 to 10 hours, preferably 8 to 10 hours.

[0022] In one or more embodiments, the calcination temperature is 500-600° C., and the calcination time is 5-7 hours.

[0023] In a second aspect, the present invention provides a mesoporous silica gel having both high pore volume and high specific surface area, which is obtained by the above-mentioned preparation method.

[0024] The average pore size of the mesoporous silica gel is 15 to 30 nm, and the pore volume is 1 to 3 cm 3 / g, specific surface area is 600~700m 2 / g; the particle size of the mesoporous silica microspheres is 7-12μm.

[0025] In a third aspect, the present invention provides the use of the above-mentioned mesoporous silica gel having both high pore volume and high specific surface area as an adsorbent; preferably, the use of the mesoporous silica gel for dye adsorption.

[0026] In one or more embodiments, when dyes are adsorbed, the specific adsorption method is: adding the above-mentioned mesoporous silica gel with both high pore volume and high specific surface area as an adsorbent to the water to be treated. Preferably, the adsorption time is 1-5 minutes, preferably 2-4 minutes.

[0027] One or some of the above technical solutions have the following advantages or beneficial effects:

[0028] (1) The silica gel prepared by the traditional method cannot have a large specific surface area while maintaining a large pore volume. The preparation method provided by the present invention greatly increases its surface area while maintaining a certain pore volume through the modification of its surface morphology. The average pore diameter of the mesoporous silica gel is 15-30nm, and the pore volume is 1-3cm 3 / g, specific surface area is 600~700m 2 / g.

[0029] (2) The method provided by the present invention has simple process and mild conditions. No hydrothermal method or other processes are required before calcination, and only mixing and stirring are required.

[0030] (3) When the mesoporous silica gel having both high pore volume and high specific surface area obtained by the preparation method of the present invention is used as an adsorbent for dye adsorption, especially for adsorption of Rhodamine B solution, a high adsorption efficiency is achieved in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] Figure 1 This is a SEM morphology image of the mesoporous silica gel prepared in Example 1 of the present invention; wherein the magnifications of (a) and (b) are 18k and 5k, respectively;

[0033] Figure 2This is the XRD pattern of the mesoporous silica gel prepared in Example 1 of the present invention;

[0034] Figure 3 The isotherm diagram and pore size distribution diagram of the mesoporous silica gel prepared in Example 1 of the present invention; wherein (a) is the isotherm diagram, and (b) is the pore size distribution diagram;

[0035] Figure 4 It is a comparison chart of the adsorption effect of Rhodamine B solution at different adsorbent dosages in Application Example 1 of the present invention; wherein, (a) is without adding adsorbent, (b) is adding 0.5g of adsorbent, (c) is adding 1.0g of adsorbent, and (d) is adding 1.5g of adsorbent. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0037] Example 1

[0038] (1) Add 25 mL of TEOS (tetraethyl orthosilicate) and 50 mL of ethanol to a 150 mL beaker at 25°C, then add a certain amount of sulfuric acid to adjust the pH to 5, and then add 3.5 mL of water and stir for 1 hour. Then put the obtained sample into a vacuum drying oven at 140°C for 3 hours to remove volatile substances.

[0039] (2) Add 60 mL of isopropanol and 2 mL of ammonia water to the sample obtained in step (1), and dissolve 7.6 g of CTAB (hexadecyltrimethylammonium bromide) in 80 mL of water, mix together, stir at 1500 r / min for 30 min, and then let stand for 8 h. Finally, centrifuge and dry. The obtained precipitate is placed in a muffle furnace and calcined at 550° C. for 6 h to obtain the final product.

[0040] Depend on Figure 1 It can be seen that the prepared mesoporous silica has abundant pores on the surface, which is beneficial to improve its adsorption performance. The particle size of the mesoporous silica microspheres is 9 μm. The surface pores of SiO2·mH2O are uniformly prepared in a pore volume of 1.743726 cm 3 / g, greatly improving its specific surface area, reaching 670.6041m 2 / g.

[0041] Depend on Figure 2 From the XRD spectrum, we can see that there is a broad peak at around 23°, which is caused by the typical indeterminate structure of SiO2.

[0042] The obtained porous silica gel was subjected to nitrogen adsorption experiment. Figure 3 It can be seen that Figure 3(a) The isotherm is a typical type IV isotherm, which is consistent with the characteristics of N2 adsorption on mesoporous silica gel; in addition, when P / P0≥0.5, the isotherm rises rapidly, indicating that N2 undergoes capillary condensation in the pores and an obvious adsorption hysteresis occurs. The resulting hysteresis loop belongs to type A hysteresis loop according to DeBoer's classification method. Figure 3 (b) The measured pore size distribution diagram shows that the average pore size is 20 nm, proving that it is a mesoporous material.

[0043] Comparative Example 1 Preparation by hydrothermal method:

[0044] At room temperature, 25 mL of TEOS, 50 mL of ethanol and 3.5 mL of water were mixed to obtain solution a, 2 mL of ammonia water, 7.6 g of CTAB and 80 mL of water were mixed to obtain solution b, solution a and solution b were mixed to obtain a mixed solution, stirred at 1500 r / min for 30 min, then heated to 120°C and stirred for 6 h; taken out for centrifugation, repeatedly washed with ethanol and deionized water, and then dried in an oven at 70°C, and finally the dried powder was calcined at 550°C for 6 h to obtain porous nano-silica microspheres.

[0045] The pore size of the porous nano-silica microspheres obtained was 3.51 nm and the pore volume was 0.82 cm 3 / g, specific surface area is 408.1m 2 / g.

[0046] Therefore, the nano-silica microspheres prepared by hydrothermal method using CTAB as template and TEOS as silicon source in Comparative Example 1 did not achieve the effect of maintaining a large pore volume while taking into account a large specific surface area.

[0047] Comparative Example 2

[0048] The difference from Example 1 is that no acid is added but only alkali is added. Specifically:

[0049] Add 60 mL of isopropanol and 2 mL of ammonia water, then add 7.6 g of CTAB (hexadecyltrimethylammonium bromide and 80 mL of water, and stir the mixed solution at 1500 r / min for 30 min. Then add 25 mL of TEOS (tetraethyl orthosilicate), mix well, stir at room temperature for 1 h, and let stand for 8 h. Finally, centrifuge and dry, and calcine it at 550 ° C for 6 h to obtain porous silica powder.

[0050] The porous silica particles obtained in this comparative example agglomerated in large quantities, mainly because there are a large number of hydroxyl groups on the surface of porous silica, which easily form hydrogen bonds with hydroxyl groups on other particles, resulting in agglomeration. The average pore size of the porous silica powder finally obtained is 1.51nm, and the pore volume is 0.512cm 3 / g, specific surface area is 452.3m 2 / g.

[0051] Obviously, the preparation of silica materials with higher pore volume and higher specific surface area cannot be achieved only in an alkaline environment.

[0052] Comparative Example 3

[0053] The difference from Example 1 is that the template agent CTAB is replaced by DMF (N,N-dimethylformamide).

[0054] (1) Add 25 mL of TEOS (tetraethyl orthosilicate) and 50 mL of ethanol to a 150 mL beaker at 25°C, then add a certain amount of sulfuric acid to adjust the pH to 5, and then add 3.5 mL of water and stir for 1 hour. Then put the obtained sample into a vacuum drying oven at 140°C for 3 hours to remove volatile substances.

[0055] (2) Add 60 mL of isopropanol and 2 mL of ammonia water to the sample obtained in step (1), and dissolve 7.6 g of DMF in 80 mL of water, mix together, stir at 1500 r / min for 30 min, and then let stand for 8 h. Finally, centrifuge and dry. The obtained precipitate is placed in a muffle furnace and calcined at 550° C. for 6 h to obtain the final product.

[0056] The pore size of the porous silica microspheres obtained in this comparative example is mainly distributed between 10-12 nm, and the pore volume is 0.65 cm 3 / g, specific surface area is 501.2m 2 / g.

[0057] Comparative Example 4

[0058] Compared with Example 1, no alkali is added. Specifically comprising:

[0059] (1) Add 25 mL of TEOS (tetraethyl orthosilicate) and 50 mL of ethanol to a 150 mL beaker at 25°C, then add a certain amount of sulfuric acid to adjust the pH to 5, and then add 3.5 mL of water and stir for 1 hour. Then put the obtained sample into a vacuum drying oven at 140°C for 3 hours to remove volatile substances.

[0060] (2) The sample obtained in step (1) was mixed with 7.6 g of CTAB (hexadecyltrimethylammonium bromide) and 80 mL of water, stirred at 1500 r / min for 30 min, and then allowed to stand for 8 h. Finally, the mixture was centrifuged and dried. The obtained precipitate was placed in a muffle furnace and calcined at 550° C. for 6 h to obtain the final product.

[0061] The pore size of the porous silica gel material obtained in this comparative example is between 3 and 4 nm, and the pore volume is 0.41 cm 3 / g, specific surface area is 598.2m 2 / g.

[0062] Obviously, the preparation of silica materials with higher pore volume and higher specific surface area cannot be achieved only in an acid environment.

[0063] Application Example 1

[0064] A 20 mg / L RhB solution was prepared, and 10 mL of the solution was taken into a reagent bottle, to which 0.5 g, 1.0 g, and 1.5 g of the mesoporous silica gel prepared in Example 1 were added respectively. After stirring for 3 minutes, the absorbance at an absorption wavelength of 554 nm was measured with a UV spectrophotometer, and the removal rate was calculated using the absorbance change of Rhodamine B.

[0065] When no mesoporous silica gel was added, the absorbance of the RhB solution was 0.633; when the amount of mesoporous silica gel added was 0.5 g, the absorbance of the RhB solution was 0.110, and the dye removal rate was 82.6%; when the amount of mesoporous silica gel added was 1.0 g, the absorbance of the RhB solution was 0.088, and the dye removal rate was 86.1%; when the amount of mesoporous silica gel added was 1.5 g, the absorbance of the RhB solution was 0.010, and the dye removal rate was 98.4%.

[0066] Therefore, when the mesoporous silica gel with high pore volume and high specific surface area prepared by the present invention is used as an adsorbent for dye adsorption, a high adsorption effect can be achieved in a short time.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing mesoporous silica gel with both high pore volume and high specific surface area, characterized in that: The following steps are involved: (1) dissolving a silicon source in an ethanol solution, adjusting the pH with an acid, adding water, stirring, and drying; (2) The product obtained in step (1) is dissolved in isopropanol and aqueous ammonia, mixed with an aqueous solution of hexadecyltrimethylammonium bromide, stirred, allowed to stand, centrifugally dried, and calcined to obtain a product.

2. The preparation method according to claim 1, characterized in that: The silicon source is tetraethyl orthosilicate; Preferably, the volume ratio of the silicon source, the ethanol solution and water is (15-30):(40-60):(2-6), preferably (20-30):(45-55):(3-4).

3. The preparation method according to claim 1, characterized in that: In step (1), the acid is sulfuric acid, and the pH is adjusted to 5-6; Preferably, in step (1), the stirring time during adding water and stirring is 0.5 to 2 hours, preferably 1 to 2 hours; Preferably, in step (1), the drying temperature is 120-150° C. and the drying time is 2-5 hours.

4. The preparation method according to claim 1, characterized in that: In step (2), the template agent is hexadecyltrimethylammonium bromide; Preferably, the volume ratio of the silicon source, isopropanol and aqueous ammonia is (15-30):(50-70):(1-4), preferably (20-30):(55-65):(2-3); Preferably, in step (2), the mass volume ratio of the template agent to water is (5-10):(50-100), preferably (7-8):(70-90); Preferably, the mass volume ratio of the template agent to the silicon source is (5-10):(15-30), preferably (7-8):(20-30).

5. The preparation method according to claim 1, characterized in that: In step (2), the stirring time is 20 to 60 min, preferably 30 to 40 min, and the stirring speed is 1000 to 3000 r / min, preferably 1500 to 2500 r / min; Preferably, the standing time is 6 to 10 hours, preferably 8 to 10 hours.

6. The preparation method according to claim 1, characterized in that: The calcination temperature is 500-600°C, and the calcination time is 5-7h.

7. A mesoporous silica gel having both high pore volume and high specific surface area, obtained by the preparation method according to any one of claims 1 to 6.

8. The mesoporous silica gel having both high pore volume and high specific surface area according to claim 7, characterized in that: The average pore size of the mesoporous silica gel is 15 to 30 nm, and the pore volume is 1 to 3 cm 3 / g, specific surface area is 600~700m 2 / g.

9. Use of the mesoporous silica gel having both high pore volume and high specific surface area as claimed in claim 7 or 8 as an adsorbent; preferably, use for dye adsorption.

10. The use according to claim 9, characterized in that: When dyes are adsorbed, the specific adsorption method is: adding the mesoporous silica gel having both high pore volume and high specific surface area as claimed in claim 7 or 8 as an adsorbent into the water to be treated.

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