Sulfonated silica nanofiber aerogel and method of making same

Abstract

The application provides sulfonated silica nanofiber aerogel and a preparation method thereof, and belongs to the technical field of silica nanofiber aerogel.The modified silica nanofiber dispersion liquid is obtained by grafting a silane coupling agent on the surface of the silica nanofiber membrane fiber, then the end group is modified into a sulfonic acid group to obtain the sulfonated silica nanofiber aerogel.The sulfonated silica nanofiber aerogel has good fiber structure, good compression resilience and breaking strength, superhydrophilicity, and high adsorption performance on positive heavy metal ions.

Description

Technical Field

[0001] This invention relates to the field of silica nanofiber aerogel technology, and more particularly to a sulfonated silica nanofiber aerogel and its preparation method. Background Technology

[0002] Silica nanofiber aerogel is a novel material with a nanoporous structure, hailed as the lightest solid material. It possesses significant advantages in sound insulation, thermal insulation, fire retardancy, filtration, drug delivery, catalysts and catalyst supports, and fuel cells, demonstrating immense application value. A particularly attractive characteristic of silica nanofiber aerogel is the abundance of silanol groups on its surface, which can covalently bind various organic molecules. These so-called organic-inorganic hybrid materials have recently attracted increasing research interest. Currently, sulfonated aerogels are mostly carbon-based aerogels prepared with fuming sulfuric acid, and the preparation technology is relatively mature. Sulfonation modification of silicon-based materials mainly involves the preparation of vertical mesoporous silica membranes and silica nanoparticles. The preparation of silica nanofiber aerogels through sulfonation has not yet been reported. Summary of the Invention

[0003] The purpose of this invention is to provide a sulfonated silica nanofiber aerogel and its preparation method, so as to solve the above-mentioned technical problems.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing sulfonated silica nanofiber aerogel, comprising the following steps:

[0006] 1) Break the silica nanofiber membrane into silica nanofibers;

[0007] 2) Silica nanofibers were dispersed in water, and then mercaptosilane coupling agent was added and heated to obtain a mercapto reaction dispersion.

[0008] 3) An oxidant was added to the mercapto reaction dispersion to carry out a sulfonation reaction. Tert-butanol was added to the reaction solution for dispersion, and then freeze-drying was performed to obtain sulfonated silica nanofiber aerogel.

[0009] Furthermore, the mercaptosilane coupling agent comprises γ-mercaptopropyltrimethoxysilane coupling agent, the mass ratio of the silica nanofibers to the mercaptosilane coupling agent is 5-15:1, and the mass ratio of the silica nanofibers to water is 1:60-100.

[0010] Furthermore, in step 2), the temperature of the heating reaction is 25–30°C, and the heating reaction time is 30–60 min.

[0011] Furthermore, in step 2), the dispersion is carried out under stirring, with a stirring speed of 1000-2000 rpm and a stirring time of 15-30 min.

[0012] Furthermore, the silica nanofibers are silica nanofibers directly electrospun from silica gel, aluminum-doped silica nanofibers, MoS2-doped silica nanofibers, or alkyl silane-doped silica nanofibers.

[0013] Furthermore, the oxidant comprises hydrogen peroxide at a mass concentration of 20-40%, and the mass ratio of the oxidant to the mercaptosilane coupling agent is 1:0.01-0.05.

[0014] Furthermore, the mass ratio of tert-butanol to water is 1:4 to 10.

[0015] Furthermore, the sulfonation reaction takes 1 to 2 hours, and the dispersion takes 15 to 30 minutes.

[0016] Furthermore, the silica nanofiber membrane is broken into 1cm×1cm fragments.

[0017] The present invention also provides a sulfonated silica nanofiber aerogel.

[0018] The beneficial effects of this invention are:

[0019] This invention obtains a modified silica nanofiber dispersion by grafting a silane coupling agent onto the surface of a silica nanofiber membrane, and then modifies the end groups to sulfonate groups to obtain a sulfonated silica nanofiber aerogel. The sulfonated silica nanofiber aerogel has a better fiber structure, better compression resilience and tensile strength, and superhydrophilicity. The sulfonated silica nanofiber aerogel also exhibits high adsorption performance for positively charged heavy metal ions. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation process of sulfonated silica nanofiber aerogel in Example 3 of the present invention.

[0021] Figure 2 The infrared spectra of silica nanofiber aerogels before and after sulfonation modification in Example 1 of the present invention are shown in the following comparison (a is the infrared spectrum of silica nanofiber aerogel before modification; b is the infrared spectrum of sulfonated silica nanofiber aerogel after modification).

[0022] Figure 3These are top and side views of the sulfonated silica nanofiber aerogel in Example 1 of the present invention.

[0023] Figure 4 This is a diagram showing the contact angle and hydrophilicity of the sulfonated silica nanofiber aerogel in Example 1 of the present invention.

[0024] Figure 5 The sulfonated silica nanofiber aerogel in Example 1 of this invention is a reaction with Cu. 2+ Cr2O7 2- Adsorption rate diagram;

[0025] Figure 6 This is an electron microscope image of the sulfonated silica nanofiber aerogel in Example 1 of the present invention;

[0026] Figure 7 The images show the 60% cyclic compression curve and the force-time graph at a compression depth of 60% for the sulfonated silica nanofiber aerogel in Example 1 of this invention.

[0027] Figure 8 This is a diagram showing the average tensile strength of sulfonated silica nanofiber aerogels in an embodiment of the present invention.

[0028] Figure 9 This is a diagram illustrating the reaction process of the sulfonated silica nanofiber aerogel in this invention. Detailed Implementation

[0029] This invention provides a method for preparing sulfonated silica nanofiber aerogel, comprising the following steps:

[0030] 1) Break the silica nanofiber membrane into silica nanofibers;

[0031] 2) Silica nanofibers were dispersed in water, and then mercaptosilane coupling agent was added and heated to obtain a mercapto reaction dispersion.

[0032] 3) An oxidant was added to the mercapto reaction dispersion to carry out a sulfonation reaction. Tert-butanol was added to the reaction solution for dispersion, and then freeze-drying was performed to obtain sulfonated silica nanofiber aerogel.

[0033] In this invention, the mercaptosilane coupling agent comprises γ-mercaptopropyltrimethoxysilane coupling agent, and the mass ratio of the silica nanofibers to the mercaptosilane coupling agent is 5-15:1, preferably 8-12:1, and more preferably 10:1; the mass ratio of the silica nanofibers to water is 1:60-100, preferably 1:70-90, and more preferably 1:75-85.

[0034] In this invention, in step 2), the temperature of the heating reaction is 25-30°C, preferably 30°C; the heating reaction time is 30-60 min, preferably 40-50 min.

[0035] In this invention, in step 2), dispersion is carried out under stirring, with a stirring speed of 1000-2000 rpm, preferably 1500 rpm; and a stirring time of 15-30 min, preferably 20 min.

[0036] In this invention, the silica nanofibers are silica nanofibers directly electrospun from silica gel, aluminum-doped silica nanofibers, MoS2-doped silica nanofibers, or alkyl silane-doped silica nanofibers.

[0037] In this invention, the oxidant contains hydrogen peroxide at a mass concentration of 20-40%, preferably 30% hydrogen peroxide; the mass ratio of the oxidant to the mercaptosilane coupling agent is 1:0.01-0.05, preferably 1:0.02-0.04, and more preferably 1:0.03.

[0038] In this invention, the mass ratio of tert-butanol to water is 1:4 to 10, preferably 1:5 to 9, and more preferably 1:6 to 8.

[0039] In this invention, the temperature of the sulfonation reaction is 70-90°C, preferably 80°C; the time of the sulfonation reaction is 1-2 hours, preferably 1.5 hours; and the dispersion time is 15-30 minutes, preferably 20 minutes.

[0040] In this invention, the silica nanofiber membrane is preferably broken into 1cm×1cm fragments.

[0041] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] 5.5g of silica nanofiber membrane directly electrospun from silica gel was cut into 1×1cm fragments to obtain pretreated silica nanofibers. The pretreated silica nanofibers were added to 460g of water and stirred at 1000rpm for 15min to obtain a dispersion. Then, 0.55g of γ-mercaptopropyltrimethoxysilane coupling agent was added, and the temperature was raised to 30℃. After stirring at this temperature for 30min, a mercapto-reactive dispersion was obtained. 30g of 30% hydrogen peroxide was added to the reaction dispersion, and the mixture was stirred at 80℃ for sulfonation for 60min. 60g of tert-butanol was added, and the mixture was stirred for 15min. The mixture was then frozen and vacuum dried to obtain a 500cm³ fragment.2 Sulfonated silica nanofiber aerogel.

[0044] Example 2

[0045] 7.0 g of silica nanofiber membrane directly electrospun from silica gel was cut into 1×1 cm fragments to obtain pretreated silica nanofibers. The pretreated silica nanofibers were added to 500 g of water and stirred at 2000 rpm for 15 min to obtain a dispersion. Then, 0.6 g of γ-mercaptopropyltrimethoxysilane coupling agent was added, and the temperature was raised to 30 °C. After stirring at this temperature for 60 min, a mercapto-reactive dispersion was obtained. 35 g of 30% hydrogen peroxide was added to the reaction dispersion, and the mixture was stirred at 80 °C for sulfonation for 90 min. 50 g of tert-butanol was added, and the mixture was stirred for 15 min. The mixture was then frozen and vacuum dried to obtain a 450 cm⁻¹ fragment. 2 Sulfonated silica nanofiber aerogel.

[0046] Example 3

[0047] 10.0 g of silica nanofiber membrane directly electrospun from silica gel was cut into 1×1 cm fragments to obtain pretreated silica nanofibers. The pretreated silica nanofibers were added to 600 g of water and stirred at 2000 rpm for 30 min to obtain a dispersion. Then, 2.0 g of γ-mercaptopropyltrimethoxysilane coupling agent was added, and the temperature was raised to 30 °C. After stirring at this temperature for 60 min, a mercapto-reactive dispersion was obtained. 40 g of 30% hydrogen peroxide was added to the reaction dispersion, and the mixture was stirred at 80 °C for sulfonation for 120 min. 60 g of tert-butanol was added and stirred for 15 min. The mixture was then frozen and vacuum dried to obtain a 580 cm⁻¹ sample. 2 Sulfonated silica nanofiber aerogel.

[0048] Example 4

[0049] Same as Example 1, except that the amount of γ-mercaptopropyltrimethoxysilane coupling agent used is 0.69g, that is, the mass ratio of silica nanofibers to silane coupling agent is 8:1.

[0050] Example 5

[0051] Same as Example 1, except that the amount of γ-mercaptopropyltrimethoxysilane coupling agent used is 0.46g, that is, the mass ratio of silica nanofibers to silane coupling agent is 12:1.

[0052] Example 6

[0053] Same as Example 1, except that the amount of γ-mercaptopropyltrimethoxysilane coupling agent used is 0.37g, that is, the mass ratio of silica nanofibers to silane coupling agent is 15:1.

[0054] Comparative Example 1

[0055] First, weigh 1.25g of silicon source, 5g of anhydrous ethanol, 120g of deionized water and 0.7g of 1% HCl. Use a magnetic stirrer to stir and hydrolyze at 80℃ for 30h to obtain silica sol. Weigh 1.5g of silica nanofiber membrane, cut it into pieces and put it into the silica sol. Add 30g of tert-butanol and use a high-speed stirrer at 1500rpm for 30min to obtain fiber dispersion. Then freeze-shape and vacuum dry to obtain silica nanofiber aerogel.

[0056] Figure 1 The flowchart for preparing sulfonated silica nanofiber aerogel is as follows: silica nanofibers directly electrospun from silica gel are cut into fragments of a certain size, water is added and the mixture is broken up and stirred at high speed to obtain a dispersion. γ-mercaptopropyltrimethoxysilane coupling agent is added to the dispersion as both a modifier and a binder to obtain a mercapto reaction dispersion. Then, hydrogen peroxide is added to oxidize the mercaptopropyl groups to generate sulfonic acid groups. Tert-butanol is added and stirred to disperse the mixture. The mixture is then frozen and vacuum dried to obtain the sulfonated silica nanofiber aerogel material.

[0057] Figure 2 The images show an infrared comparison of silica nanofiber aerogels before and after sulfonation modification. Figure 2 (a) is the infrared spectrum of silica nanofiber aerogel (Comparative Example 1); Figure 2 (b) is the infrared spectrum of sulfonated silica nanofiber aerogel (Example 1).

[0058] At 1085cm -1 and 1090cm -1 The largest absorption peak appears at 788 cm⁻¹, which is due to the antisymmetric stretching vibration of the Si-O-Si bonds in the nano-silica before and after modification. -1 It is a symmetrical stretching vibration of the Si-O-Si bond; 460 cm⁻¹ -1 The vibrations are due to the bending of Si-O-Si bonds, indicating that the basic structure of the silica nanofiber aerogel remained unchanged before and after modification. At 3500 cm⁻¹ -1 The peak at 2830 cm⁻¹ is the vibrational peak of the silanol group. -1 The absorption peak appearing at 1364 cm⁻¹ is the CH stretching vibration absorption peak, which is due to the incomplete hydrolysis of -SiOCH₂CH₃ on the silica nanofibers. -1The presence of a characteristic peak of sulfonic acid groups indicates that the silica nanofiber aerogel has been successfully grafted with sulfonic acid groups. This peak is a characteristic peak of S=O in -SO3H.

[0059] Figure 3 The images show the top and side views of the sulfonated silica nanofiber aerogel. The prepared sulfonated silica nanofiber aerogel material has a diameter of 120 mm, a height of 30 mm, and a volume of 339.12 cm³. 2 A cylindrical shape.

[0060] Figure 4 The image shows the contact angle of the sulfonated silica nanofiber aerogel. During the test, 12 μL of deionized water was dropped onto the sulfonated silica nanofiber aerogel. Multiple measurements showed that the sulfonated silica nanofiber aerogel samples all exhibited superhydrophilicity. The dynamic capture images show the water droplet about to fall and 0.03 seconds later; the water droplet was completely absorbed in less than 0.03 seconds.

[0061] Figure 5 This indicates that sulfonated silica nanofiber aerogels are effective against Cu. 2+ The ions exhibit a certain adsorption effect, with an adsorption rate of 96.18%. This indicates that the sulfonic acid groups have a strong affinity for positively charged heavy metal ions such as Cu. 2+ It exhibits good adsorption properties, particularly for negatively valenced Cr2O7. 2- There was almost no adsorption, with an adsorption rate of 20.7%. By comparison, it can be seen that sulfonated silica nanofiber aerogel has good adsorption performance for positively charged heavy metals.

[0062] Figure 6 It can be seen that the silica fibers in the sulfonated silica nanofiber aerogel are segmented. This is because the fibers are broken up during high-speed stirring, and there are spherical particles on the fibers, which are sulfonic acid groups grafted onto the surface of the silica nanofibers.

[0063] Figure 7 Sulfonated silica nanofiber aerogels were cut into rectangles of 50mm×50mm×30mm and compressed to a depth of 60%. After 20 cycles of compression and rebound, the aerogels showed good rebound under compression cycles, with a height collapse of only 1mm after 20 cycles (collapse ratio of approximately 3%).

[0064] Figure 8To determine the tensile strength of the aerogels, each group of aerogels was cut into rectangles measuring 1cm × 3cm for tensile testing. The average tensile strength of each group was calculated by averaging the test data. Group 1 consisted of unmodified aerogels; Group 2 had a SiO2 nanofiber membrane to γ-mercaptopropyltrimethoxysilane mass ratio of 5:1; Group 3 had a SiO2 nanofiber membrane to γ-mercaptopropyltrimethoxysilane mass ratio of 8:1; Group 4 had a SiO2 nanofiber membrane to γ-mercaptopropyltrimethoxysilane mass ratio of 10:1; Group 5 had a SiO2 nanofiber membrane to γ-mercaptopropyltrimethoxysilane mass ratio of 12:1; and Group 6 had a SiO2 nanofiber membrane to γ-mercaptopropyltrimethoxysilane mass ratio of 15:1. It can be seen that in group 4, when the mass ratio of SiO2 nanofiber membrane to γ-mercaptopropyltrimethoxysilane is 10:1, the average tensile strength of the aerogel is the highest, which is about 10 times that of the unmodified aerogel.

[0065] Figure 9 The reaction equation for the preparation of sulfonated silica nanofiber aerogel is as follows: the hydroxyl groups on the surface of silica nanofibers react to generate thiol groups, and hydrogen peroxide is used to oxidize the thiol groups to generate sulfonic acid groups.

[0066] As shown in the above embodiments, this invention provides a sulfonated silica nanofiber aerogel and its preparation method. The silica nanofibers produced by direct electrospinning with silica gel, without calcination treatment, have numerous active groups -SiOH and -SiOCH2CH3 on their surface, which is beneficial for modification. Furthermore, the fiber's breaking strength is significantly higher than that of silica nanofibers produced by polymer-based methods. The method for preparing sulfonated silica nanofiber aerogel fills a gap in the field of silica nanofiber modification using sulfonated modified aerogels and provides valuable reference for future research.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the preparation of sulfonated silica nanofiber aerogels, characterized by, Includes the following steps: 1) Break the silica nanofiber membrane into silica nanofibers; 2) Silica nanofibers were dispersed in water, and then mercaptosilane coupling agent was added and heated to obtain a mercapto reaction dispersion. 3) An oxidant was added to the mercapto reaction dispersion to carry out a sulfonation reaction. Tert-butanol was added to the reaction solution for dispersion. Then, the solution was freeze-dried to obtain sulfonated silica nanofiber aerogel. The mercaptosilane coupling agent comprises γ-mercaptopropyltrimethoxysilane coupling agent, and the mass ratio of the silica nanofibers to the mercaptosilane coupling agent is 8~12:1; In step 2), the temperature of the heating reaction is 25~30℃, and the heating reaction time is 30~60min.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the silica nanofibers to water is 1:60~100.

3. The preparation method according to claim 2, characterized in that, In step 2), the dispersion is carried out under stirring at a speed of 1000-2000 rpm for 15-30 minutes.

4. The preparation method according to claim 1, 2, or 3, characterized in that, The silica nanofibers are silica nanofibers directly electrospun from silica gel, aluminum-doped silica nanofibers, MoS2-doped silica nanofibers, or alkyl silane-doped silica nanofibers.

5. The preparation method according to claim 4, characterized in that, The oxidant contains hydrogen peroxide at a mass concentration of 20-40%, and the mass ratio of the oxidant to the mercaptosilane coupling agent is 1:0.01-0.

05.

6. The preparation method according to claim 1, characterized in that, The mass ratio of tert-butanol to water is 1:4~10.

7. The preparation method according to claim 1 or 5, characterized in that, The sulfonation reaction takes 1-2 hours, and the dispersion takes 15-30 minutes.

8. The preparation method according to claim 1, characterized in that, The silica nanofiber membrane was broken into 1cm×1cm fragments.

9. The sulfonated silica nanofiber aerogel prepared by the preparation method according to any one of claims 1 to 8.

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