Preparation method of g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr (VI)

Abstract

The invention relates to the technical field of composite materials, and particularly discloses a preparation method of a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr (VI), and the preparation method comprises the following steps: mixing and grinding a hydrothermally synthesized plate-shaped TS-1 molecular sieve and amide small molecules, and directly calcining in air to obtain a molecular sieve composite photocatalyst g-C3N4-TS-1 with uniform load and clear morphology, the composite material shows relatively high photocatalytic activity. The molecular sieve composite material can be effectively synthesized under the joint participation of the amide organic matter and the molecular sieve, the synthesis process is simple, and the cost is relatively low; the obtained g-C3N4-TS-1 composite material contains relatively dispersed graphite carbon nitride and forms a heterojunction, so that the band gap of the molecular sieve is changed, the light absorption range of the molecular sieve is widened, and the problems that a molecular sieve photocatalytic material is complex to prepare and relatively low in activity under visible light are solved; the photocatalyst can be used for photodegradation of common heavy metal ion pollutants Cr (VI) in the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to a preparation method of g-C 3 N 4 -TS-1 heterojunction and photocatalytic degradation of Cr(VI). Background Art

[0002] Under the drive of solar energy, semiconductor photocatalysts generate photoexcited electrons and reactive oxygen free radicals at room temperature, and can reduce highly toxic Cr(VI) to low-toxic Cr(III). Among them, semiconductor heterojunctions maintain the high redox performance of photoexcited charges, enhance the interfacial electron transfer ability, and can improve the photocatalytic activity.

[0003] At present, people often use metal-organic framework materials (MOF) and covalent organic materials (COF) in porous materials to construct heterojunction photocatalysts. However, the raw materials required in their synthesis process are expensive, and the synthesis process is relatively cumbersome, which greatly increases the manufacturing cost of the catalyst. For molecular sieves, which also belong to porous materials, they have the advantages of low cost and simple synthesis, and are widely used in various important industrial catalysis. However, under the action of external field strengthening (such as light, electricity, magnetism, etc.), there are few relevant studies on high-performance molecular sieve catalytic materials. In the research of photocatalytic systems, there is still great room for development in the study of molecular sieve heterojunctions.

[0004] So far, several applications of titanium silicate molecular sieves in photocatalysis have been proposed. For example, improving the framework titanium species to improve the photocatalytic activity of pure TS-1 molecular sieves, but they often require a relatively strong light source (500w mercury lamp) to excite, and the required energy is strong. The ultraviolet region used is only a small part of the solar spectrum, and solar energy cannot be fully utilized. In the existing literature, there has been the use of melamine additives to compound graphitic carbon nitride (g-C 3 N 4 ) to degrade antibiotics, but their synthesis methods are relatively complex. It is necessary to first dissolve the molecular sieve and organic molecules together, evaporate the solvent and then calcine. However, the obtained material has uneven polymerization degree of graphitic carbon nitride, resulting in uneven distribution on the molecular sieve, and the controllability needs to be further improved.

[0005] In view of this, the purpose of the present invention is to provide a preparation method of g-C 3 N 4 -TS-1 heterojunction and photocatalytic degradation of Cr(VI). Summary of the Invention

[0006] The purpose of the present invention is to provide a g-C 3 N 4Preparation method of g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI) to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A preparation method of g-C3 3 N4 4 -TS-1 heterojunction and photocatalytic degradation of Cr(VI), including:

[0009] Under the condition of a mixed solvent, molecular sieve TS-1 with a plate-like morphology is prepared by a hydrothermal synthesis method;

[0010] Mix the molecular sieve with organic amide small molecules, and after grinding evenly, a molecular sieve amide mixture is obtained;

[0011] The molecular sieve amide mixture is calcined in air, and after the calcination is completed, it is washed, centrifuged, and dried, and finally a highly active molecular sieve composite photocatalyst g-C3 3 N4 4 -TS-1 is obtained;

[0012] The highly active molecular sieve composite photocatalyst g-C3 3 N4 4 -TS-1 is used to degrade the heavy metal ion Cr(VI) in an aqueous solution under visible light irradiation.

[0013] Preferably, the organic small molecule is one or more of urea, acetamide, thioacetamide, and propionamide.

[0014] Preferably, the plate-like molecular sieve mixed solvent is one or more of water and methanol, water and ethanol, water and isopropanol, and water and benzyl alcohol; among them, the molar ratio of water to alcohols is: 1:(0.1 - 0.5).

[0015] Preferably, the mass ratio of the two amide molecules to the molecular sieve in the molecular sieve amide mixture is 1:(0 - 10):(0.1 - 1).

[0016] Preferably, the temperature of the hydrothermal synthesis of the plate-like molecular sieve is preferably 40 - 180 °C, and the time is preferably 2 - 50 h; the temperature for removing the template agent is 550 - 600 °C, and the time is 6 - 24 h;

[0017] Preferably, the molecular sieve and the organic amide are mixed at room temperature, and the grinding time is 0 - 1 h; the calcination temperature of the composite material is 550 - 600 °C, and the time is 1 - 12 h.

[0018] Preferably, the visible light source is one or more of a 500W mercury lamp, a 500W xenon lamp, a 300W xenon lamp, and a 100W LED lamp; the concentration of Cr(VI) is 10-160 mg / L.

[0019] Another aspect of the present invention lies in a method for preparing a g-C 3 N 4 -TS-1 heterojunction and photocatalytic degradation of Cr(VI).

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The method provided by the present invention can simply and rapidly synthesize a molecular sieve heterojunction in the presence of a small molecule organic amide. The obtained g-C 3 N 4 -TS-1 composite material contains both relatively dispersed graphitic carbon nitride and a heterojunction structure, which is beneficial to solving the limitation problem of low photocatalytic activity of the molecular sieve under visible light, effectively improving the degradation rate of the heavy metal pollutant hexavalent chromium, improving the degradation rate and the stability of the catalyst. The composite material forms a heterojunction, which not only enhances the light absorption range but also slows down the recombination rate of photoelectron-hole pairs, enhancing the photocatalytic performance. The synthesized molecular sieve catalyst has high catalytic activity in the reaction of degrading harmful metal ions under the strengthening of an external field. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the powder X-ray diffraction pattern and the structural simulation XRD pattern of the TS-1 molecular sieve composite materials prepared in Examples 1-5 of the present invention, Comparative Example TS-1, and Comparative Example g-C 3 N 4 ;

[0023] Figure 2 It is the infrared spectrum of the TS-1 molecular sieve composite materials prepared in Examples 1-5 of the present invention, Comparative Example TS-1, and Comparative Example g-C 3 N 4 ;

[0024] Figure 3 It is the transmission electron microscope photograph of the molecular sieve composite material g-C 3 N 4 -TS-1-0.5 prepared in Example 1 of the present invention;

[0025] Figure 4 It is the ultraviolet-visible spectrum of the TS-1 molecular sieve composite materials prepared in Examples 1-5 of the present invention, Comparative Example TS-1, and Comparative Example g-C 3 N 4 ;

[0026] Figure 5 Photodegradation performance results of hexavalent chromium for the present invention;

[0027] Figure 6 Simulated electron flow diagram of the present invention, demonstrating the electron transfer process in the heterojunction. Specific embodiments

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Example 1:

[0030] A preparation method of g-C 3 N 4 -TS-1 heterojunction. Under magnetic stirring conditions, 4.067 g of tetrapropylammonium hydroxide solution (TPAOH 25 wt%) was dissolved in 5.208 g of tetraethyl orthosilicate, and stirred for 4 h. Then, 0.142 g of a clear solution of tetrabutyl titanate dispersed in 1.728 g of ethanol was added and stirring was continued for 2 h to obtain a sol mixture. The sol mixture was transferred into a stainless-steel autoclave lined with polytetrafluoroethylene, and the autoclave was placed in an oven at 180 °C for hydrothermal crystallization reaction for 48 h under the pressure naturally generated in the autoclave. After the crystallization was completed, the autoclave was taken out and naturally cooled to room temperature. The solid product was separated by centrifugation, washed repeatedly with deionized water until neutral, dried at 80 °C, and then calcined in an air atmosphere at 550 °C to remove the template agent to obtain TS-1. 1 g of thioacetamide, 4 g of urea, and 0.5 g of the obtained TS-1 were ground together, and after being made uniform, they were placed in a crucible and calcined in a muffle furnace at 600 °C for 3 h (heating rate: 5 °C / min). After the calcination was completed, it was washed with water and ethanol, centrifuged, and dried, and named g-C 3 N 4 -TS-1-0.5. The molar ratio of each component of silica, titanium dioxide, tetrapropylammonium hydroxide, water, and ethanol in the sol mixture in the reaction system was 1:0.0167:0.2:6.8:1.5. The mass ratio of each component of thioacetamide, urea, and TS-1 molecular sieve in the system before calcination was 1:4:0.5.

[0031] Example 2:

[0032] Prepare the TS-1 molecular sieve composite material according to the method of Example 1, named g-C 3 N 4-TS-1-0.2. The difference from Example 1 is that the mass of TS-1 is 0.2 g, and the mass ratio of each component thioacetamide, urea, and TS-1 molecular sieve in the system before calcination is 1:4:0.2.

[0033] Example 3:

[0034] Prepare the TS-1 molecular sieve composite material according to the method of Example 1, named g-C 3 N 4 -TS-1-0.35. The difference from Example 1 is that the mass of TS-1 is 0.35 g, and the mass ratio of each component thioacetamide, urea, and TS-1 molecular sieve in the system before calcination is 1:4:0.35.

[0035] Example 4:

[0036] Prepare the TS-1 molecular sieve composite material according to the method of Example 1, named g-C 3 N 4 -TS-1-0.7. The difference from Example 1 is that the mass of TS-1 is 0.7 g, and the mass ratio of each component thioacetamide, urea, and TS-1 molecular sieve in the system before calcination is 1:4:0.7.

[0037] Example 5:

[0038] Prepare the TS-1 molecular sieve composite material according to the method of Example 1, named g-C 3 N 4 -TS-1-1. The difference from Example 1 is that the mass of TS-1 is 1 g, and the mass ratio of each component thioacetamide, urea, and TS-1 molecular sieve in the system before calcination is 1:4:1.

[0039] Comparative Example 1:

[0040] Under magnetic stirring conditions, dissolve 4.067 g of tetrapropylammonium hydroxide solution (TPAOH 25 wt%) in 5.208 g of tetraethyl orthosilicate, stir for 4 h, then add a clear solution of 0.142 g of tetrabutyl titanate dispersed in 1.728 g of ethanol and continue to stir for 2 h to obtain a sol mixture. Transfer the sol mixture into a stainless steel autoclave lined with polytetrafluoroethylene, place the autoclave in an oven at 180 °C, and carry out a hydrothermal crystallization reaction for 48 h under the pressure naturally generated in the autoclave. After the crystallization is completed, take out the autoclave and let it cool naturally to room temperature. The solid product is separated by centrifugation, washed repeatedly with deionized water until neutral, dried at 80 °C, and then calcined in an air atmosphere at 550 °C to remove the template agent to obtain TS-1.

[0041] Comparative Example 2:

[0042] Grind 1 g of thioacetamide and 4 g of urea together, and after homogenization, place them in a crucible and calcine at 600 °C in a muffle furnace for 3 h to obtain g-C 3 N 4 。

[0043] Application Example 1:

[0044] For the g-C 3 N 4 -TS-1-0.5 sample (high-activity TS-1 molecular sieve composite material) and the TS-1 sample obtained in Comparative Example 1, conduct photocatalytic degradation of Cr(VI) performance tests as catalysts. Add 0.01 g of the catalyst, 10 mL of potassium dichromate solution (100 mg / L), 0.007 g of disodium ethylenediaminetetraacetate, and 10 μL of sulfuric acid solution (4 mol / L) into a 25 mL glass vial, stir in the dark for 30 min to achieve adsorption-desorption equilibrium, and then carry out the reaction under a 300 W xenon lamp equipped with a 420 nm filter, and react for 5 minutes at a continuous magnetic stirring rate. Collect aliquots of the Cr(VI) solution at specific intervals (1 min). The solution is filtered through a 0.22 μm membrane to remove the photocatalyst, and the resulting solution is analyzed by an ultraviolet-visible absorption spectrometer (Shimadzu UV-2550, Shimadzu Corporation, Japan).

[0045] The results of the photocatalytic degradation of Cr(VI) performance are shown in Figure 5 ,from Figure 5 It can be seen that compared with the TS-1 and g-C 3 N 4 samples, the g-C 3 N 4 -TS-1-0.5 sample exhibits higher photocatalytic activity, and the degradation efficiency reaches 100% in 5 min.

[0046] From the above experiments and other additional experimental data and simulation calculation results, the simulated electron flow diagram as shown in Figure 6 is obtained. In the heterojunction structure, electrons flow from the TS-1 molecular sieve to g-C 3 N 4 。

[0047] As can be seen from the above, the method provided by the present invention can effectively synthesize a heterojunction in the presence of a small molecule organic amide, and the obtained g-C 3 N 4The -TS-1 composite material contains relatively dispersed graphitic carbon nitride and a heterojunction structure at the same time, which is beneficial to solving the problem of low photocatalytic activity of molecular sieves under visible light, can effectively improve the degradation rate of the pollutant hexavalent chromium, improve the degradation rate and the stability of the catalyst. The composite material forms a heterojunction, which not only enhances the light absorption range, but also slows down the recombination rate of photoelectron-hole pairs, enhancing the photocatalytic performance. The synthesized catalyst has high catalytic activity in the photocatalytic degradation of harmful metal ions and antibiotics.

[0048] Another aspect of the present invention lies in a preparation method of a g-C 3 N 4 -TS-1 heterojunction and its application in photocatalytic degradation of Cr(VI), which further provides more possibilities for the preparation of high-performance molecular sieve catalytic materials.

[0049] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not have to be directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0050] In the attached drawings of the disclosed embodiments of the present invention, only the structures related to the disclosed embodiments are involved, and other structures can refer to the general design. Without conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

[0051] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI), characterized in that: include: The plate-like molecular sieve TS-1 was prepared by hydrothermal synthesis under mixed solvent conditions. The molecular sieve is mixed with the organic amide small molecule, and the mixture is ground evenly to obtain a molecular sieve amide mixture; The molecular sieve amide mixture is calcined in air, and after calcination, it is washed, centrifuged, and dried to finally obtain a highly active molecular sieve composite photocatalyst g-C3N4-TS-1; The highly active molecular sieve composite photocatalyst g-C3N4-TS-1 was used to degrade heavy metal ions Cr(VI) in aqueous solution under visible light irradiation.

2. The method for preparing a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI) according to claim 1, characterized in that: The organic amide small molecule is one or more of urea, acetamide, thioacetamide and propionamide.

3. The method for preparing a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI) according to claim 1, characterized in that: The mixed solvent used in the preparation of the plate-like molecular sieve is one or more of water and methanol, water and ethanol, water and isopropanol, and water and benzyl alcohol; wherein the molar ratio of water to alcohol is 1:0.1-0.

5.

4. The method for preparing a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI) according to claim 1, characterized in that: The mass ratio of the two amide molecules to the molecular sieve in the molecular sieve amide mixture is 1:0-10:0.1-1.

5. The method for preparing a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI) according to claim 1, characterized in that: The temperature for hydrothermal synthesis of the plate-like molecular sieve is preferably 40-180° C., and the time is preferably 2-50 hours; the temperature for removing the template is 550-600° C., and the time is 6-24 hours.

6. The method for preparing a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI) according to claim 1, characterized in that: The molecular sieve and the organic amide are mixed at room temperature and the grinding time is 0 to 1 hour; the composite material is calcined at a temperature of 550 to 600° C. and the time is 1 to 12 hours.

7. The method for preparing a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI) according to claim 1, characterized in that: The visible light source is one or more of a 500W mercury lamp, a 500W xenon lamp, a 300W xenon lamp and a 100W LED lamp.

8. The method for preparing a g-C3N4-TS-1 heterojunction and photocatalytic degradation of Cr(VI) according to claim 1, characterized in that: The concentration of Cr(VI) is 10-160 mg / L.

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