CN110420654A - A kind of hollow ball-type carbon nitride photocatalyst and its preparation method and application - Google Patents

Abstract

The invention belongs to photocatalyst technology field, a kind of hollow ball-type carbon nitride photocatalyst and its preparation method and application is disclosed.The photochemical catalyst is to mix ethyl alcohol, ammonium hydroxide and ultrapure water, and tetraethoxysilane is added, and keeps constant speed stirring, matches to obtain solution A；The mixed liquid B of tetraethoxysilane and n-octadecane base trimethoxy silane is added drop-wise in solution A again, is stood at room temperature, centrifugation obtained solid is calcined at 500~550 DEG C, obtains silica ball template；Silica ball template and cyanamide are mixed at 60~80 DEG C, gained mixture is calcined in nitrogen atmosphere at 500~550 DEG C, obtains powder C；Ammonium hydrogen fluoride solution is added in powder C and removes removing template, washes, is obtained after dry.Synthesis technology of the present invention is simple, and the uniform ball-type pattern of size is presented in the hollow porous photochemical catalyst of gained, has good physical and chemical stability and huge specific surface area, and catalytic performance is good, the primary condition with practical application.

Description

A kind of hollow spherical carbon nitride photocatalyst and its preparation method and application

technical field

The invention belongs to the technical field of photocatalysis, and more specifically relates to a hollow spherical carbon nitride photocatalyst and its preparation method and application.

Background technique

The pollution of aquatic environments by pharmaceuticals and personal care products (PPCPs) has received extensive attention in recent years. Due to its high chemical stability, it is difficult to remove it effectively by traditional water treatment processes. Long-term exposure to PPCPs water environment will bring harm to the ecosystem and even human health. Therefore, it is urgent to develop technologies for the efficient removal of PPCPs in water. Photocatalytic degradation technology uses sunlight as energy, has the advantages of high treatment efficiency, low cost, green and pollution-free, and provides a new way for treating wastewater and removing toxic substances in the environment.

Graphitized carbon nitride (gC ₃ N ₄ ), as a new type of metal-free polymer visible light photocatalyst, has been widely used in photocatalysis due to its moderate band gap, simple preparation method, high stability and safety. Degradation of organic pollutants. However, the bulk gC ₃ N ₄ inevitably has some disadvantages. Issues such as small specific surface area, few active sites, low visible light absorption efficiency, and high hole-electron pair recombination rate have greatly hindered its practical application.

Contents of the invention

In order to solve the deficiencies in the above-mentioned prior art, the primary purpose of the present invention is to provide a hollow spherical carbon nitride photocatalyst.

Another object of the present invention is to provide a method for preparing the above-mentioned hollow spherical carbon nitride photocatalyst. The method starts with Methods Silica spheres were prepared as a template, and then cyanamide was injected into the template, and a graphitic carbon nitride photocatalyst with a hollow porous structure was obtained by thermal polymerization and removal of the template.

Another object of the present invention is to provide the application of the above-mentioned hollow spherical carbon nitride photocatalyst.

The purpose of the present invention is achieved through the following technical solutions:

A hollow spherical carbon nitride photocatalyst, the photocatalyst is mixed with ethanol, ammonia water and ultrapure water, added tetraethoxysilane, and kept stirring at a constant speed to obtain solution A; then tetraethoxysilane Add the mixed solution B of n-octadecyltrimethoxysilane to solution A dropwise, let it stand at room temperature, and centrifuge the obtained solid to calcinate at 500-550°C to obtain a silica sphere template; mix the silica sphere template and ammonia The nitrile is mixed and stirred at 60-80°C, and the resulting mixture is calcined at 500-550°C in a nitrogen atmosphere to obtain powder C; add ammonium bifluoride solution to powder C to remove the template, wash with water, and dry to obtain.

Preferably, the volume ratio of ethanol, ammonia water, ultrapure water and tetraethoxysilane in the solution A is 75:4:10:(5-6).

Preferably, the stirring time is 1-3 hours.

Preferably, the volume ratio of tetraethoxysilane to n-octadecyltrimethoxysilane in the solution B is (5-6): (2-3).

Preferably, the volume ratio of the solution A to the solution B is (94-95): (7-9).

Preferably, the calcination time is 4-5 hours.

Preferably, the mass ratio of the silica sphere template to the cyanamide is 1: (5-7).

The preparation method of described hollow spherical carbon nitride photocatalyst comprises the following specific steps:

S1. Mix ethanol, ammonia water and ultrapure water, add tetraethoxysilane into the solution, keep stirring at a constant speed, and prepare solution A;

S2. Add the mixed solution B of tetraethoxysilane and n-octadecyltrimethoxysilane dropwise to the solution A, let stand at room temperature, centrifuge to obtain a solid and calcinate at 500-550°C to obtain a silica spherical template;

S3. Mixing and stirring the silica spherical template, the carbon quantum dot solution and cyanamide at 60-70°C, and calcining the obtained mixture in a nitrogen atmosphere at 500-550°C to obtain powder C;

S4. Add ammonium bifluoride solution to the powder C to remove the template, wash with water, and dry at 60-80° C. to obtain a hollow spherical carbon nitride photocatalyst.

Preferably, the standing time in step S2 is 2 to 4 hours; the stirring time in step S3 is 4 to 6 hours; the number of times of washing in step S4 is 2 to 3 times; the ammonium bifluoride solution The concentration is 1~1.5mol/L.

The application of the hollow spherical carbon nitride photocatalyst in degrading indomethacin under simulated sunlight.

The above-mentioned gC ₃ N ₄ hollow spheres are used in the degradation of indomethacin under simulated sunlight. The method of application is as follows:

A 420nm filter light source configured with a 300w xenon lamp was used as a visible light source. The composite photocatalyst was placed in a quartz photolysis tube with an amount of 0.025g, and 50ml of indomethacin solution to be degraded with a concentration of 10mg/L was added. The mixed solution was irradiated under a light source for 60 min, and the concentration of remaining indomethacin in the solution was measured by liquid chromatography.

Generally, bulk gC ₃ N ₄ has the following disadvantages as a photocatalytic material: gC ₃ N ₄ has a narrow visible spectrum absorption range and low solar energy utilization. In addition, gC ₃ N ₄ has a high recombination rate of photogenerated electrons and holes during the photocatalytic process, which inhibits its photocatalytic performance. The gC ₃ N ₄ hollow spheres in the present invention have the characteristics of large surface area, which improves their ability to adsorb pollutants. In addition, the hollow structure of gC ₃ N ₄ is not only beneficial to the light absorption during the photocatalytic process, but also can effectively separate the photogenerated electrons and holes, thereby improving the catalytic ability of gC ₃ N ₄ .

Compared with the prior art, the present invention has the following beneficial effects:

1. The gC ₃ N ₄ hollow sphere photocatalyst of the present invention has a larger specific surface area than bulk gC ₃ N ₄ , can effectively adsorb pollutants, and can increase the utilization rate of gC ₃ N ₄ .

2. The gC ₃ N ₄ hollow sphere photocatalyst of the present invention has a stronger light absorption ability due to its hollow sphere structure, which broadens the absorption range of visible light, and can effectively separate photogenerated electrons and holes, and improve the gC ₃ N ₄ catalytic ability.

3. The preparation method of the present invention has low cost, environmentally friendly raw materials, safe and controllable process, high catalytic activity of the product, high application prospect and wide use space.

Description of drawings

FIG. 1 is a SEM photo of gC ₃ N ₄ hollow spheres (HCNS) in Example 1 (b) and bulk gC ₃ N ₄ in Comparative Example 1 (a).

Fig. 2 is the ultraviolet diffuse reflectance spectrum of HCNS in the embodiment 1 and the bulk phase gC in the comparative example ₁ N ₄ ;

Fig. 3 is the nitrogen adsorption-desorption curve of HCNS in embodiment 1;

FIG. 4 is a pore size distribution diagram of HCNS in Example 1. FIG.

Detailed ways

The content of the present invention will be further described below in conjunction with specific examples, but it should not be construed as a limitation of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

Example 1

The preparation of a gC ₃ N ₄ hollow sphere (HCNS) photocatalyst comprises the following specific steps:

1. Measure 4ml of ammonia water, add 75ml of ethanol and 10ml of ultrapure water into it, and after ultrasonic stirring, add 5ml of tetraethoxysilane (TEOS) into the solution, react for 1 hour, and keep stirring at a constant speed.

2. A mixture of 5ml TEOS and 2ml n-octadecyltrimethoxysilane was added dropwise to the mixed solution prepared above, and stood at room temperature for 2h. The solution was centrifuged to obtain a solid, which was then calcined at a high temperature of 500°C. After cooling to room temperature, grind and sieve to obtain a silica sphere template.

3. Add 5 g of cyanamide to 1 g of silica template, mix and stir, and calcinate the obtained mixture at 550° C. in a nitrogen atmosphere.

4. Add 1M ammonium bifluoride to the obtained powder to remove the template, and obtain hollow carbon nitride sphere powder gC ₃ N ₄ (HCNS).

Comparative example 1

The preparation of a bulk phase gC ₃ N ₄ photocatalyst comprises the following steps:

Add 3g of dicyandiamide and 15ml of ultrapure water into the alumina crucible, dissolve it by ultrasonic, dry at 70°C, transfer the crucible to a muffle furnace, raise the temperature to 500°C at a heating rate of 3°C/min, and bake for 3 hours. After cooling to room temperature, grind and sieve to obtain bulk gC ₃ N ₄ photocatalyst.

FIG. 1 is a SEM photo of gC ₃ N ₄ hollow spheres in Example 1 and bulk gC ₃ N ₄ in Comparative Example 1. Among them, (a) is bulk gC ₃ N ₄ , and (b) is C ₃ N ₄ hollow spheres. It can be seen from Figure 1 that the gC ₃ N ₄ hollow spheres are spherical in shape and have a larger specific surface area than the bulk gC ₃ N ₄ . Figure 2 is the ultraviolet diffuse reflectance spectrum of HCNS in this example and the bulk phase gC ₃ N ₄ in Comparative Example 1; it can be seen from Figure 2 that compared with the pure bulk phase g-C3N, the absorption edge of HCNS has a little Blue shift, which may be due to quantum effects. Fig. 3 is the nitrogen adsorption-desorption curve of HCNS in the present embodiment; As can be seen from Fig. 3, the specific surface area of HCNS is 48.1m / g, and HCNS has mesoporous structure; Fig. 4 is the HCNS in the present embodiment Pore size distribution diagram. It can be seen from Figure 4 that the mesopore diameter is about 3.52nm.

Example 2

The preparation of a gC ₃ N ₄ hollow sphere photocatalyst comprises the following specific steps:

1. Measure 4ml of ammonia water, add 75ml of ethanol and 10ml of ultrapure water to it, and after ultrasonic mixing, add 6ml of tetraethoxysilane (TEOS) into the solution, react for 1 hour, and keep stirring at a constant speed.

2. A mixture of 6ml TEOS and 3ml n-octadecyltrimethoxysilane was added dropwise to the mixed solution prepared above, and stood at room temperature for 4h. The solution was centrifuged to obtain a solid, which was then calcined at a high temperature of 550°C. After cooling to room temperature, grind and sieve to obtain a silica sphere template.

3. 7 g of cyanamide was added to 1 g of silica template, mixed and stirred, and the obtained mixture was calcined at 550° C. in a nitrogen atmosphere.

4. Add 1.5M ammonium bifluoride to the obtained powder to remove the template, and obtain hollow carbon nitride sphere powder gC ₃ N ₄ (HCNS).

Application example 1

A kind of gC ₃ N ₄ application of hollow sphere photocatalyst in indomethacin wastewater treatment, comprises the following steps:

1. Add the gC ₃ N ₄ hollow sphere photocatalyst prepared in Example 1 to the photolysis tube in an amount of 0.025 mg, indomethacin solution in an amount of 50 ml, and a concentration of 10 mg/L.

2. Place the prepared solution in a photochemical reaction apparatus for dark reaction for 30 minutes and then carry out photocatalytic reaction. The reaction time is 60 minutes. After the reaction is completed, use liquid chromatography to measure the remaining concentration C of indomethacin in the solution.

3. Calculate the removal rate N of indomethacin by gC ₃ N ₄ hollow spheres, the formula N=(C ₀ −C)*100%, where C ₀ is the initial concentration of indomethacin.

4. Use the bulk gC ₃ N ₄ prepared in Comparative Example 1 in the photolysis tube, repeat steps 1-3, and calculate the removal rate of indomethacin by the bulk gC ₃ N ₄ .

Table 2 is a table of the degradation rates of indomethacin by the gC ₃ N ₄ hollow spheres in Example 1 and the bulk phase gC ₃ N ₄ in Comparative Example by summarizing the calculated data. It can be seen from Table 2 that the removal rate of indomethacin (90.3%) of gC ₃ N ₄ hollow spheres is higher than that of bulk gC ₃ N ₄ (28.6%), and the photocatalytic efficiency is significantly improved.

Catalyst in table 2 embodiment 1 and the removal rate of indomethacin in the photocatalytic degradation of simulated sunlight in comparative example 1

catalyst Bulk phase g-C₃N₄ g-C₃N₄hollow ball Indomethacin removal rate (%) 28.6 90.3

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations and modifications made without departing from the spirit and principles of the present invention Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. A hollow spherical carbon nitride photocatalyst, is characterized in that, described photocatalyst is that ethanol, ammoniacal liquor and ultrapure water are mixed, add tetraethoxysilane, keep stirring at a constant speed, prepare solution A; The mixed solution B of tetraethoxysilane and n-octadecyltrimethoxysilane was added dropwise to solution A, left standing at room temperature, and the solid obtained by centrifugation was calcined at 500-550°C to obtain a silica spherical template; Silicon ball template and cyanamide are mixed and stirred at 60-80°C, and the resulting mixture is calcined at 500-550°C in a nitrogen atmosphere to obtain powder C; add ammonium bifluoride solution to powder C to remove the template, wash with water, and dry get. 2. The hollow spherical carbon nitride photocatalyst according to claim 1, wherein the volume ratio of ethanol, ammonia, ultrapure water and tetraethoxysilane in the solution A is 75:4:10: (5~6). 3. The hollow spherical carbon nitride photocatalyst according to claim 1, characterized in that the stirring time is 1-3 hours. 4. hollow spherical carbon nitride photocatalyst according to claim 1, is characterized in that, the volume ratio of tetraethoxysilane and n-octadecyltrimethoxysilane in the solution B is (5～6) : (2～3). 5. The hollow spherical carbon nitride photocatalyst according to claim 1, characterized in that the volume ratio of the solution A to the solution B is (94-95): (7-9). 6. The hollow spherical carbon nitride photocatalyst according to claim 1, characterized in that the calcination time is 4-5 hours. 7. The hollow spherical carbon nitride photocatalyst according to claim 1, characterized in that the mass ratio of the silica spherical template to the cyanamide is 1: (5-7). 8. according to the preparation method of hollow spherical carbon nitride photocatalyst described in any one of claim 1-7, it is characterized in that, comprise the following specific steps: S1. Mix ethanol, ammonia water and ultrapure water, add tetraethoxysilane into the solution, keep stirring at a constant speed, and prepare solution A; S2. Add the mixed solution B of tetraethoxysilane and n-octadecyltrimethoxysilane dropwise to the solution A, let stand at room temperature, centrifuge to obtain a solid and calcinate at 500-550°C to obtain a silica spherical template; S3. Mixing and stirring the silica spherical template, the carbon quantum dot solution and cyanamide at 60-70°C, and calcining the obtained mixture in a nitrogen atmosphere at 500-550°C to obtain powder C; S4. Add ammonium bifluoride solution to the powder C to remove the template, wash with water, and dry at 60-80° C. to obtain a hollow spherical carbon nitride photocatalyst. 9. The preparation method of hollow spherical carbon nitride photocatalyst according to claim 8, characterized in that, the standing time described in step S2 is 2～4h; the stirring time described in step S3 is 4～4h 6h; the number of washings in step S4 is 2-3 times; the concentration of the ammonium bifluoride solution is 0.5-1.5 mol/L. 10. Application of the hollow spherical carbon nitride photocatalyst according to any one of claims 1-7 in degrading indomethacin under simulated sunlight.