Preparation method and application of high-performance composite photocatalyst

Abstract

The invention provides a preparation method and application of a high-performance composite photocatalyst, and relates to the technical field of photocatalytic materials. The preparation method of the composite photocatalyst comprises the following steps: firstly, preparing a two-dimensional nano material g-C3N4 by using a roasting method; then preparing a nickel-doped MgAl double hydroxide by adopting a hydrothermal method; and finally, constructing the nickel-doped MgAl double hydroxide / g-C3N4 composite photocatalyst by virtue of an ultrasonic compounding method. The composite photocatalyst can effectively promote separation and transfer of photon-generated carriers of the composite photocatalyst, so that the activity of the composite photocatalyst for photocatalytic degradation of antibiotics is improved. The composite photocatalyst can degrade an organic pollutant tetracycline solution with the concentration of 10 ppm and shows excellent photocatalytic degradation performance under excitation of visible light, and the preparation method is simple, easy to operate and suitable for application and popularization.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalytic materials, and in particular to a preparation method of a high-performance composite photocatalyst and application thereof. Background Art

[0002] With the continuous development of human society and industry, mankind has made great progress and remarkable achievements in industry and medicine. However, since humans began to use fossil energy, environmental pollution has always existed. In recent years, with the rapid development of society, the abuse of antibiotics has caused environmental pollution to become more serious. Scientists have accelerated the pace of exploring ways to effectively manage environmental problems. Antibiotics are widely used in the medical field and are the most common organic pollutants. Many antibiotics cannot be fully used and are discharged into the environment. Ordinary physical degradation methods have little effect on the treatment of antibiotics. In order to solve these problems, scientists have carried out a lot of basic and applied research from various aspects, and have achieved many significant research results so far. Photocatalytic technology is one of the more prominent representatives. It can more effectively remove certain types of pollutants without producing any waste. It is an ideal treatment technology.

[0003] g-C3N4 is one of the semiconductor photocatalytic materials. This photocatalyst is easy to prepare and shows high stability during the photocatalytic reaction. It is one of the ideal materials for photocatalysis. In addition, since g-C3N4 shows excellent photocatalytic activity under visible light conditions, it has been studied by many scientists in the field of photocatalysis. However, studies have found that the lifetime of electrons and holes generated by g-C3N4 during photoexcitation is short, and the light energy utilization rate of the catalyst is not high. In order to solve this problem, researchers have used methods such as doping, sensitization and composite to improve its photocatalytic reaction efficiency. Layered double hydroxides (LDHs for short) are a class of layered materials with two-dimensional nanostructures, also known as hydrotalcite, hydrotalcite-like or anionic clays, mainly composed of positively charged sheets and interlayer anions. LDHs are suitable for a variety of occasions due to their unique structure, good biocompatibility, large specific surface area, easy crystallization and synthesis, uniform distribution of metal cations, rich surface hydroxides and high anion exchange capacity. The composition of the metal layer and the interlayer anion in LDHs is varied, which is conducive to the formation of more metal-anion combinations, providing functional diversity for LDHs. Therefore, LDHs have broad application prospects in the fields of biomedicine, energy conversion and storage, sensors, environmental protection, etc. Therefore, the present invention couples g-C3N4 with MgAl double hydroxide semiconductor materials to construct a heterostructure, which will be beneficial to improve the photocatalytic performance of g-C3N4 nanomaterials due to the special properties of the materials and the appropriate conduction band and valence band positions. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a preparation method and application of a high-performance composite photocatalyst. The composite photocatalyst firstly prepares a two-dimensional nanomaterial g-C3N4 by a calcination method; then a nickel-doped MgAl double hydroxide is prepared by a hydrothermal method; finally, a nickel-doped MgAl double hydroxide / g-C3N4 composite photocatalyst is constructed by an ultrasonic compounding method. The constructed nickel-doped MgAl double hydroxide / g-C3N4 composite photocatalyst has excellent performance in visible light photocatalytic degradation of tetracycline, and solves the problem of low photocatalytic efficiency of g-C3N4 catalytic material, especially low separation and transfer efficiency of photogenerated carriers.

[0005] To achieve the above objectives, the present invention is implemented through the following technical scheme: a method for preparing a high-performance composite photocatalyst, comprising the following process: first, preparing a two-dimensional nanomaterial g-C3N4 by a calcination method; then preparing nickel-doped MgAl double hydroxide by a hydrothermal method; finally, constructing a nickel-doped MgAl double hydroxide / g-C3N4 composite photocatalyst by an ultrasonic compounding method.

[0006] Preferably, the preparation method of the composite photocatalyst specifically comprises the following steps: Preparation of S1.g-C3N4 First, 10 g of dicyandiamide was weighed and added to a crucible with a lid, and then the crucible was placed in a muffle furnace and heated at a heating rate of 2.3 °C / min. After the temperature was finally raised to 550 °C, it was kept warm for 4 h. After the temperature in the furnace was cooled to room temperature, the material in the furnace was taken out and ground to obtain the two-dimensional material g-C3N4. S2. Preparation of Ni-doped MgAl double hydroxide photocatalyst First, 0.002 mol aluminum nitrate, 0.001 mol nickel chloride, 0.003 mol magnesium nitrate and 0.03 mol urea were added to 100 mL polytetrafluoroethylene liner, dissolved in 60 mL water, and stirred for 10 minutes; then, the liner was moved into a high-pressure reactor and reacted at 120°C for 24 hours. After the reaction was completed, the reactor was cooled to room temperature, and the reaction liquid was taken out and washed and centrifuged; finally, the product was placed in an oven at 60°C and dried overnight to obtain nickel-doped MgAl double hydroxide; S3. Preparation of composite photocatalyst Weigh 0.5 g of g-C3N4 and 0.026-0.088 g of MgAl double hydroxide and disperse them in distilled water, put the suspension into an ultrasonic device, and continue ultrasonication for 20 minutes; after ultrasonic treatment, stir the suspension continuously for another hour; then, separate, wash and dry the product to obtain a composite photocatalyst.

[0007] Preferably, the composite photocatalyst can degrade a tetracycline solution of an organic pollutant with a concentration of 10 ppm under the excitation of visible light.

[0008] Preferably, the nickel-doped MgAl double hydroxide / g-C3N4 composite photocatalyst can degrade a tetracycline solution of an organic pollutant with a concentration of 10 ppm under the excitation of visible light.

[0009] The present invention provides a method for preparing a high-performance composite photocatalyst and its application, which has the following beneficial effects: The composite photocatalyst disclosed in the present invention can effectively promote the separation and transfer of its photogenerated carriers, thereby improving its photocatalytic degradation activity of antibiotics. The composite photocatalyst can degrade a 10 ppm organic pollutant tetracycline solution, and exhibits excellent photocatalytic degradation performance under visible light excitation. The preparation method is simple, easy to operate, and suitable for popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 XRD diagrams of samples prepared in Example 1 and Example 3 to Example 7 of the present invention; Figure 2 The SEM images of the materials obtained in Examples 1 and 2, 5 and 6 of the present invention, wherein a is Example 2, b is Example 1, c is Example 5, and d is Example 6; Figure 3 This is a bar chart of tetracycline degradation of the samples prepared in Example 1 and Examples 3 to 7 of the present invention. DETAILED DESCRIPTION

[0011] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0012] An embodiment of the present invention provides a method for preparing a two-dimensional material g-C3N4, comprising the following process: weighing 10 g of dicyandiamide and adding it into a crucible with a lid, then placing the crucible in a muffle furnace, heating it at a heating rate of 2.3°C / min, finally heating to 550°C and keeping the temperature for 4 hours; after the temperature in the furnace cools to room temperature, taking out the material in the furnace and grinding it to obtain the two-dimensional material g-C3N4, the sample number is 1. Example

[0013] The embodiment of the present invention provides a method for preparing a nickel-doped MgAl double hydroxide photocatalyst, comprising the following process: adding 0.002 mol aluminum nitrate, 0.001 mol nickel chloride, 0.003 mol magnesium nitrate and 0.03 mol urea to 100 mL of a polytetrafluoroethylene liner, dissolving them in 60 mL of water, and continuously stirring for 10 minutes; then, moving the liner into a high-pressure reactor, and continuously reacting at 120° C. for 24 hours, and after the reaction is completed, waiting for the reactor to cool to room temperature, taking out the reaction solution, washing and centrifuging; finally, placing the product in an oven at 60° C., and drying overnight to obtain nickel-doped MgAl double hydroxide. Example

[0014] An embodiment of the present invention provides a method for preparing a composite photocatalyst, comprising the following process: weighing 0.5 g of g-C3N4 and 0.026 g of MgAl double hydroxide, dispersing them in distilled water, placing the suspension in an ultrasonic device, and continuously ultrasonicating for 20 minutes; after ultrasonic treatment, stirring the suspension continuously for another hour; then, separating, washing and drying the product to obtain a composite photocatalyst, sample number 2. Example

[0015] In the embodiment of the present invention, the amount of MgAl double hydroxide added in the third embodiment is changed from 0.026 g to 0.038 g, and the remaining steps are the same as those in the third embodiment. The obtained composite photocatalyst sample is numbered 3. Example

[0016] In the embodiment of the present invention, the amount of MgAl double hydroxide added in the third embodiment is changed from 0.026 g to 0.056 g, and the remaining steps are the same as those in the third embodiment. The obtained composite photocatalyst sample is numbered 4. Example

[0017] In the embodiment of the present invention, the amount of MgAl double hydroxide added in the third embodiment is changed from 0.026 g to 0.068 g, and the remaining steps are the same as those in the third embodiment. The obtained composite photocatalyst sample is numbered 5. Example

[0018] In the embodiment of the present invention, the amount of MgAl double hydroxide added in the third embodiment is changed from 0.026 g to 0.088 g, and the remaining steps are the same as those in the third embodiment. The obtained composite photocatalyst sample is numbered 6.

[0019] Figure 1The XRD diagrams of the samples prepared in Example 1 and Example 3 to Example 7 show that the composite photocatalyst exhibits characteristic diffraction peaks of double hydroxide and g-C3N4, and a characteristic diffraction peak can be observed at 2θ=27.4°, which is a typical interplanar stacked graphite layered structure belonging to g-C3N4 material. Compared with the pure g-C3N4 material, the composite photocatalyst also shows the characteristic diffraction peak of double hydroxide, indicating that the present invention successfully prepares the nickel-doped MgAl double hydroxide / g-C3N4 composite photocatalyst.

[0020] Figure 2 These are SEM images of the materials obtained in Examples 1 and 2, Examples 5 and 6, wherein a is the MgAl double hydroxide obtained in Example 2, b is the g-C3N4 obtained in Example 1, c is the sample 4 obtained in Example 5, and d is the sample 5 obtained in Example 6. It can be observed that the MgAl double hydroxide is a two-dimensional layered structure. Figure 2 c and d are the morphologies after the two semiconductors are combined. It can be observed that MgAl double hydroxide is perfectly composited with g-C3N4.

[0021] Take 40 mg of samples No. 1-6 and add them to 80 ml of 10 ppm tetracycline solution. Stir the solution and dark adsorb for 60 minutes to ensure the adsorption / desorption balance of the catalyst. After the dark adsorption is completed, turn on the visible light source for irradiation. After a certain period of time, take 4 ml of the reaction solution and centrifuge it. Then take the supernatant and test it on a UV-visible spectrophotometer. The experimental results are shown in Figure 3 .

[0022] Figure 3 The tetracycline degradation bar graphs of the samples prepared in Example 1 and Example 3 to Example 7 show that the sample No. 4 has the highest photocatalytic activity for tetracycline degradation, and after 90 minutes of activity testing, its degradation rate can reach 73.4%. Its photocatalytic activity is much higher than that of the pure g-C3N4 sample, indicating that the heterogeneous structure of the prepared composite photocatalyst is conducive to the photocatalytic reaction, and it is an excellent photocatalyst for tetracycline degradation.

[0023] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance composite photocatalyst, characterized in that: The process includes the following steps: firstly, a two-dimensional nanomaterial g-C3N4 is prepared by a calcination method; then, nickel-doped MgAl double hydroxide is prepared by a hydrothermal method; and finally, a nickel-doped MgAl double hydroxide / g-C3N4 composite photocatalyst is constructed by an ultrasonic compounding method.

2. The method for preparing a high-performance composite photocatalyst according to claim 1, characterized in that: The specific steps include: Preparation of S1.g-C3N4 First, 10 g of dicyandiamide was weighed and added to a crucible with a lid, and then the crucible was placed in a muffle furnace and heated at a heating rate of 2.3 °C / min. After the temperature was finally raised to 550 °C, it was kept warm for 4 h. After the temperature in the furnace was cooled to room temperature, the material in the furnace was taken out and ground to obtain the two-dimensional material g-C3N4. S2. Preparation of Ni-doped MgAl double hydroxide photocatalyst First, 0.002 mol aluminum nitrate, 0.001 mol nickel chloride, 0.003 mol magnesium nitrate and 0.03 mol urea were added to 100 mL polytetrafluoroethylene liner, dissolved in 60 mL water, and stirred for 10 minutes; then, the liner was moved into a high-pressure reactor and reacted at 120°C for 24 hours. After the reaction was completed, the reactor was cooled to room temperature, and the reaction liquid was taken out and washed and centrifuged; finally, the product was placed in an oven at 60°C and dried overnight to obtain nickel-doped MgAl double hydroxide; S3. Preparation of composite photocatalyst Weigh 0.5 g of g-C3N4 and 0.026-0.088 g of MgAl double hydroxide and disperse them in distilled water. Place the suspension in an ultrasonic device and continue ultrasonication for 20 minutes. After the ultrasonic treatment, the suspension was continuously stirred for another hour; subsequently, the product was separated, washed and dried to obtain a composite photocatalyst.

3. The composite photocatalyst prepared according to the preparation method according to any one of claims 1-2.

4. Use of the composite photocatalyst according to claim 3 in degradation of organic pollutants under visible light.

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