阅读说明：本技术 一种磺酸基改性二氧化硅气凝胶及其制备方法和应用 (Sulfonic modified silicon dioxide aerogel and preparation method and application thereof ) 是由 邵再东 郑煜铭 于 2021-08-24 设计创作，主要内容包括：本发明涉及一种磺酸基改性二氧化硅气凝胶及其制备方法和应用,本发明以四烷氧基硅烷和巯基硅烷为共前驱体硅源,通过溶胶-凝胶共缩聚法制备巯基改性二氧化硅凝胶,在无水乙醇溶液中进行老化,湿凝胶分别在氧化剂溶液和酸溶液中进行氧化和酸化,最后通过常压干燥制得磺酸基改性二氧化硅气凝胶。本发明所述的制备方法简单,易操作,过程易控制,可连续化生产。获得的磺酸基改性二氧化硅气凝胶具有优异的物理化学特性,不仅具有高比表面积和高孔隙率,同时气凝胶表面含有丰富的磺酸基官能团。本发明所述的磺酸基改性二氧化硅气凝胶可用于空气中碱性气体的吸附,水体中有机污染物和重金属离子的吸附,还可作为一种良好的固体酸催化剂。(The invention relates to a sulfonic acid group modified silicon dioxide aerogel and a preparation method and application thereof. The preparation method is simple, easy to operate, easy to control the process and capable of realizing continuous production. The obtained sulfonic modified silicon dioxide aerogel has excellent physicochemical characteristics, high specific surface area and high porosity, and meanwhile, the surface of the aerogel contains abundant sulfonic functional groups. The sulfonic acid group modified silicon dioxide aerogel can be used for adsorbing alkaline gas in the air and organic pollutants and heavy metal ions in water and can also be used as a good solid acid catalyst.)

1. The preparation method of the sulfonic acid group modified silicon dioxide aerogel is characterized by comprising the following specific steps of:

(1) mixing mercaptosilane, tetraalkoxysilane, ethanol and water according to a certain proportion, uniformly stirring and hydrolyzing a silicon source to form silica sol;

(2) adding ammonia water into the hydrolyzed silica sol obtained in the step (1), stirring until the mixture is uniformly mixed, standing for gelation, and aging to obtain the sulfhydryl modified silica wet gel;

(3) and (3) sequentially immersing the sulfhydryl modified wet gel obtained in the step (2) in an oxidant and an acid solution, oxidizing and acidifying the sulfhydryl on the surface of the wet gel to obtain a sulfonic group, then performing water washing and ethanol solvent exchange, and finally performing normal-pressure drying to obtain the sulfonic group modified silica aerogel.

2. The method for preparing sulfonic acid group-modified silica aerogel according to claim 1, wherein the sol is prepared from tetraalkoxysilane: mercaptosilane: ethanol: water = 5: (0.5-3): (10-30): (0.9-3.6).

3. The method for preparing sulfonic acid group-modified silica aerogel according to claim 1, wherein the type of the mercaptosilane comprises one or more of (3-mercaptopropyl) trimethoxysilane, (3-mercaptopropyl) triethoxysilane, or mercaptopropylmethyldimethoxysilane.

4. The method for preparing a sulfonic acid group-modified silica aerogel according to claim 1, wherein the tetraalkoxysilane is tetraethyl orthosilicate or tetramethyl orthosilicate.

5. The method for preparing sulfonic acid group-modified silica aerogel as claimed in claim 1, wherein the aging temperature is controlled to be 25 to 60 ℃, the aging time is 20 to 36 hours, and the drying temperature under normal pressure is 80 to 120 ℃.

6. The method for preparing sulfonic acid group modified silica aerogel according to claim 1, wherein the oxidant is one or more of hydrogen peroxide, sodium hypochlorite and potassium permanganate.

7. The method for preparing sulfonic acid group-modified silica aerogel according to claim 1, wherein the acidifying agent is one or more of sulfuric acid, hydrochloric acid or nitric acid.

8. The sulfonic acid group-modified silica aerogel prepared by the method according to claim 1 to 7, wherein the sulfonic acid group-modified silica aerogel has a specific surface area of 100-1000 m²g^-1Pore diameter of 1-10 nm and pore volume of 0.1-1 cm³g^-1。

9. The sulfonic acid group-modified silica aerogel prepared by the method according to claim 1 to 7, wherein the sulfonic acid group-modified silica aerogel can be used as an environmental purification material, including adsorption of alkaline gases in the air and adsorption of organic pollutants and heavy metal ions in water, and can also be used as a good solid acid catalyst.

Technical Field

The invention relates to the technical field of environmental pollution treatment, in particular to a sulfonic modified silicon dioxide aerogel and a preparation method thereof, and the sulfonic modified silicon dioxide aerogel is applied as an environmental purification material.

Background

The silicon dioxide aerogel is a nano porous material taking air as a medium and has low density (0.003-0.35 g/cm)³) High, highSpecific surface area (600-1500 m)²The silica aerogel has wide application prospect in the fields of chemistry, thermal, acoustics, optics, electricity and the like, and in recent years, the silica aerogel is considered as a potentially excellent environment purification functional material, and shows excellent performances in the directions of adsorption, catalysis, separation and the like.

The application of the silica aerogel as a high-efficiency environment purification material requires not only the maintenance of excellent porous characteristics, but also the regulation of surface functional group characteristics. The surface of the traditional silicon dioxide aerogel skeleton is mainly silicon hydroxyl, and the silicon hydroxyl can adsorb water vapor in the air through the action of hydrogen bonds, so that the aim of dehumidifying in the air is fulfilled. However, the traditional silica aerogel has poor effect of removing other pollutants in the environment, because the acting force of the silicon hydroxyl on the surface of the traditional silica aerogel and the pollutants is weak and the selectivity is poor. Therefore, silica aerogel needs to be modified or compounded with surface functional groups to improve adsorption selectivity and binding energy to target pollutants. For example, patent publication No. CN107188188B discloses a method for preparing amino-modified silica aerogel, which grafts amino functional groups on the surface of silica aerogel skeleton, thereby significantly improving the adsorption performance of aerogel on pollutants, and the amino-modified silica aerogel can be used for capturing carbon dioxide in the air, purifying sulfur oxides, and adsorbing organic pollutants in water. Patent application publication No. CN 111253615A discloses super hydrophobic organosilicon aerogel and normal atmospheric temperature drying preparation method thereof, through carrying out surperficial super hydrophobic modification to silica-based aerogel, the silica-based aerogel that obtains has super hydrophobic oleophylic characteristic, can demonstrate good application in water oil separating. Patent application publication No. CN109133071A discloses a preparation method of organic hybrid silica aerogel, wherein a composite silane coupling agent prepared by reacting chloropropyl trimethoxy silane and aminopropyl trimethoxy silane modifies the surface of a silica aerogel skeleton, and the obtained organic hybrid silica aerogel has high extraction performance and certain application potential in the fields of environmental detection, food detection and drug analysis.

Although various methods for modifying silica aerogel are disclosed, the modification of silica aerogel is mainly focused on hydrophobic modification and amine modification, and the methods and processes for modifying other functional groups are still lack of research.

Disclosure of Invention

The invention aims to provide a method for preparing sulfonic acid group modified silica aerogel, which has simple process, easily controlled process and continuous production, has high specific surface area and high porosity and simultaneously contains abundant sulfonic acid group functional groups. Another object of the present invention is to provide use of the sulfonic acid group-modified silica aerogel as an environmental purification material.

The preparation method of the sulfonic acid group modified silicon dioxide aerogel block comprises the following steps:

(1) mixing mercaptosilane, tetraalkoxysilane, ethanol and water according to a certain proportion, stirring uniformly and hydrolyzing a silicon source to form silica sol.

In the step (1), according to the volume ratio of raw materials, the volume ratio of tetraalkoxysilane: mercaptosilane, anhydrous ethanol, water 5: (0.5-3): (10-30): (0.9-3.6), and the stirring time is controlled between 16-24 hours when the silicon source is hydrolyzed.

(2) And (2) adding ammonia water into the hydrolyzed silica sol obtained in the step (1), stirring until the mixture is uniformly mixed, standing for gelation, and aging to obtain the sulfhydryl modified silica wet gel.

In the step (2), the stirring time is 5 to 30 minutes after the ammonia water is added, and the standing time is 1 to 5 hours.

In the step (2), the aging temperature of the wet gel may be 25 to 60 ℃ and the time may be 20 to 36 hours.

(3) And (3) sequentially immersing the sulfhydryl modified wet gel obtained in the step (2) in an oxidant and an acid solution, oxidizing and acidifying the sulfhydryl on the surface of the wet gel to obtain a sulfonic group, then performing water washing and ethanol solvent exchange, and finally performing normal-pressure drying to obtain the sulfonic group modified silica aerogel.

In step (3), the wet gel is immersed in the oxidizing agent for 6 to 24 hours.

In the step (3), the concentration of the acid solution is 0.1-1 mol/L.

In the step (3), the temperature of the normal pressure drying is 80-120 ℃, and the drying time is 4-8 hours.

According to the preparation method of the sulfonic acid group modified silicon dioxide aerogel, mercaptosilane and a silicon source are added to react together through a copolycondensation method at a sol-gel stage, so that uniform modification of a silicon dioxide gel framework can be formed, and finally, the silicon dioxide aerogel with sulfonic acid group functional groups is prepared through oxidation acidification and normal pressure drying. The prepared sulfonic modified silicon dioxide aerogel is of a nano porous structure, the pore size distribution is relatively concentrated at 1-10 nm, and the pore volume is 0.1-1 cm³g^-1. Specific surface area of 100-1000 m²g^-1。

The sulfonic acid group modified silicon dioxide aerogel prepared by the invention has rich nano-porous structures, and meanwhile, the surface of the sulfonic acid group modified silicon dioxide aerogel contains rich sulfonic acid group functional groups. The sulfonic modified silica aerogel can be used as a high-efficiency gas adsorption material, and can selectively adsorb and remove alkaline gases in the air, such as ammonia, trimethylamine, triethylamine and the like, through acid-alkali adsorption; the adsorbent can also be used as a water body adsorption material for adsorbing organic pollutants or heavy metal ions in a water body through the actions of proton exchange, acid-base adsorption, complexation and the like; in addition, the abundant sulfonic acid groups on the surface of the silica aerogel can also provide acidic catalytic sites, thereby serving as a solid acid catalyst. The sulfonic acid group modified silicon dioxide aerogel has mild preparation conditions and simple process, and is expected to be applied as an environment purification material.

Compared with the prior art, the invention has the following outstanding advantages:

the sulfonic acid group modified silicon dioxide aerogel is prepared by adopting the copolycondensation, post-oxidation and normal-pressure drying processes, so that the advantages of large specific surface area, small aperture and high porosity of the silicon dioxide aerogel are kept, and the sulfonic acid group on the surface of the aerogel is uniform in distribution, high in content and controllable. The preparation process adopted by the invention is simple and easy to control, has low cost, avoids the blockage of the holes of the silica gel by a post-grafting method, and has the defects of slow modification reaction, uneven distribution of modified groups and difficult content control. The preparation process adopts normal pressure drying, thereby avoiding the problems of high equipment requirement and operation danger caused by high supercritical temperature and pressure. And the prepared sulfonic modified silica aerogel shows excellent performance when being used as an environment purification material.

Drawings

FIG. 1 is a photograph of a sulfonic acid group-modified silica aerogel prepared in example 1 of the present invention.

Fig. 2 is a scanning electron micrograph of the sulfonic acid group-modified silica aerogel prepared in example 1 of the present invention.

Fig. 3 is a nitrogen adsorption and desorption curve and a pore size distribution diagram of the sulfonic acid group-modified silica aerogel prepared in example 1 of the present invention.

FIG. 4 shows NH pairs of sulfonic acid group-modified silica aerogels prepared in example 1 of the present invention₃Static adsorption isotherm curve of (a).

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings.

Example 1

The volume ratio of raw materials is as follows: tetraethyl orthosilicate: (3-mercaptopropyl) trimethoxysilane: ethanol: water = 5: 2: 20: and 3, mixing 5ml of tetraethyl orthosilicate, 2ml of (3-mercaptopropyl) trimethoxysilane and 20ml of absolute ethyl alcohol, stirring, adding 3ml of water, continuously stirring to promote hydrolysis of a silicon source, adding catalyst ammonia water into the sol after 16 hours, stirring for 10 minutes, and standing the obtained silica gel for 2 hours. And then placing the wet gel in an absolute ethyl alcohol solution for aging at the aging temperature of 60 ℃ for 12 hours. And (3) after aging, adding the wet gel into a hydrogen peroxide solution, soaking for 24 hours to oxidize sulfydryl, adding 0.1mol/L sulfuric acid for acidification, washing the gel with water and replacing with ethanol after acidification, and finally drying at normal pressure for 4 hours at the drying temperature of 80 ℃ to obtain the sulfonic acid group modified silica aerogel.

Example 2

The volume ratio of raw materials is as follows: tetraethyl orthosilicate: (3-mercaptopropyl) triethoxysilane: ethanol: water = 5: 1: 15: 3.6, 5ml of tetraethyl orthosilicate, 1ml of (3-mercaptopropyl) triethoxysilane and 15ml of absolute ethanol are mixed and stirred, 3.6ml of water is added, stirring is continued to promote hydrolysis of a silicon source, 20 hours later, catalyst ammonia water is added into the sol, stirring is carried out for 20 minutes, and then the obtained silica gel is kept stand for 5 hours. And then placing the wet gel into an absolute ethyl alcohol solution for aging, wherein the aging temperature is 60 ℃, and the aging time is 24 hours. And (3) after aging, adding the wet gel into a sodium hypochlorite solution, soaking for 24 hours to oxidize sulfydryl, adding 1mol/L hydrochloric acid for acidification, washing the gel with water and replacing the gel with ethanol after acidification, and finally drying the gel at normal pressure for 4 hours at the drying temperature of 80 ℃ to obtain the sulfonic acid group modified silica aerogel.

Example 3

The volume ratio of raw materials is as follows: tetraethyl orthosilicate: mercaptopropyl methyldimethoxysilane: ethanol: water = 5: 2: 30: 1.8, 5ml of tetraethyl orthosilicate, 2ml of mercaptopropyl-methyldimethoxysilane and 30ml of absolute ethyl alcohol are mixed and stirred, 1.8ml of water is added, stirring is continued to promote hydrolysis of a silicon source, after 24 hours, catalyst ammonia water is added into the sol, stirring is carried out for 10 minutes, and then the obtained silica gel is allowed to stand for 1 hour. And then placing the wet gel in an absolute ethyl alcohol solution for aging, wherein the aging temperature is 50 ℃, and the aging time is 36 hours. And (3) after aging, adding the wet gel into a hydrogen peroxide solution, soaking for 24 hours to oxidize sulfydryl, adding 0.1mol/L sulfuric acid for acidification, washing the gel with water and replacing with ethanol after acidification, and finally drying at normal pressure for 6 hours at the drying temperature of 120 ℃ to obtain the sulfonic acid group modified silica aerogel.

Example 4

The volume ratio of raw materials is as follows: tetraethyl orthosilicate: (3-mercaptopropyl) trimethoxysilane: ethanol: water = 5: 3: 10: 2.7, 5ml of tetraethyl orthosilicate, 3ml of (3-mercaptopropyl) trimethoxysilane and 10ml of absolute ethyl alcohol are mixed and stirred, 2.7ml of water is added, stirring is continued to promote hydrolysis of a silicon source, catalyst ammonia water is added into the sol after 24 hours, stirring is carried out for 30 minutes, and then the obtained silica gel is kept stand for 5 hours. And then placing the wet gel in an absolute ethyl alcohol solution for aging, wherein the aging temperature is 35 ℃, and the aging time is 36 hours. And (3) after aging, adding the wet gel into a sodium hypochlorite solution, soaking for 6 hours to oxidize sulfydryl, adding 0.5mol/L sulfuric acid for acidification, washing the gel with water and replacing with ethanol after acidification, and finally drying at normal pressure for 8 hours at the drying temperature of 100 ℃ to obtain the sulfonic acid group modified silica aerogel.

Example 5

The volume ratio of raw materials is as follows: tetramethyl orthosilicate: (3-mercaptopropyl) triethoxysilane: ethanol: water = 5: 1: 25: 0.9, 5ml of tetramethyl orthosilicate, 1ml of (3-mercaptopropyl) triethoxysilane and 25ml of absolute ethyl alcohol are mixed and stirred, 0.9ml of water is added, stirring is continued to promote hydrolysis of a silicon source, 20 hours later, catalyst ammonia water is added into the sol, stirring is carried out for 10 minutes, and then the obtained silica gel is kept stand for 4 hours. And then placing the wet gel into an absolute ethyl alcohol solution for aging, wherein the aging temperature is 55 ℃, and the aging time is 24 hours. And (3) after aging, adding the wet gel into a hydrogen peroxide solution, soaking for 24 hours to oxidize sulfydryl, adding 1mol/L sulfuric acid for acidification, washing the gel with water and replacing the gel with ethanol after acidification, and finally drying the gel at normal pressure for 8 hours at the drying temperature of 80 ℃ to obtain the sulfonic acid group modified silica aerogel.