Catalyst as well as preparation method and application thereof

Abstract

The invention discloses a catalyst as well as a preparation method and application thereof, relates to the technical field of water treatment, solves the defects of insufficient penetrability of visible light and ultraviolet light and poor photocatalytic effect in the existing photocatalytic technology, and fills the technical blank of a catalyst for realizing an efficient synergistic effect with laser. The preparation method comprises the following steps: mixing and stirring a zinc nitrate hexahydrate solution and a dimethylimidazole solution, centrifuging, collecting precipitate, and drying to prepare ZIF-8; zIF-8 is ground into powder, the powder is dispersed in a copper ion solution to be stirred and centrifuged, precipitates are collected and dried, and ZIF-8 / Cu is prepared; and the ZIF-8 / Cu powder is calcined to obtain the ZnO / Cu1.35O catalyst, and the catalyst has excellent photocatalytic performance, anti-interference capability and cyclic stability qualification. The method can be applied to catalytic degradation of tetracycline hydrochloride, and the degradation rate of tetracycline hydrochloride is increased by utilizing the synergistic effect of laser and the ZnO / Cu1.35O catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly relates to a catalyst, a preparation method thereof and an application thereof. Background Art

[0002] Currently, the improper discharge of agricultural wastewater has caused serious pollution to the surface water system. Among them, tetracycline hydrochloride (TC), as a widely used antibiotic drug, often remains in agricultural wastewater after being applied in fields such as agricultural breeding. When traditional sewage treatment technologies are used to treat agricultural wastewater, there are defects such as low treatment efficiency and difficulty in effectively removing pollutants such as TC in the wastewater. At the same time, using chemical agents to treat wastewater has a high risk of secondary pollution, increasing the treatment cost and environmental burden.

[0003] As an emerging sewage treatment technology, photocatalysis technology, relying on its significant advantages such as mild reaction conditions, no secondary pollution, and low energy consumption, can utilize the redox ability of photo-generated carriers to degrade organic pollutants such as TC into harmless small molecule substances. However, traditional photocatalysis technology mainly relies on ultraviolet light or visible light as the light source, and the energy utilization rate of these light sources is low, and most of the light energy cannot be fully utilized, resulting in difficulty in further improving the photocatalytic efficiency. At the same time, the cost of ultraviolet light or visible light sources is high, which limits the large-scale popularization and application of photocatalysis technology.

[0004] Laser technology, due to its characteristics such as good monochromaticity, strong coherence, concentrated energy, and excellent directivity, provides a more efficient light source choice for photocatalysis technology. However, the application of lasers in the field of water treatment is still in its infancy, and no catalyst that can efficiently cooperate with lasers has been developed. Therefore, researching and developing such catalysts, giving full play to the advantages of lasers in photocatalysis, and realizing the deep integration and efficient application of laser and photocatalysis technologies in water treatment are of great significance for promoting the wide application and effective treatment of laser-photocatalysis technology in the field of agricultural wastewater treatment. Summary of the Invention

[0005] In order to solve the problems of insufficient penetration of visible light and ultraviolet light, low photocatalytic effect in existing photocatalysis technology, and the lack of development of catalysts that can efficiently cooperate with lasers. The present invention proposes a catalyst, a preparation method thereof and an application thereof. The technical solution of the present invention is as follows: A preparation method of a catalyst, comprising the following preparation steps: Mix and stir, and then centrifuge a zinc nitrate hexahydrate solution and a dimethylimidazole solution, collect the precipitate and dry it to prepare ZIF-8; grind the ZIF-8 into powder, disperse it in a copper ion solution, stir and centrifuge, collect the precipitate and dry it to prepare ZIF-8 / Cu; calcine the ZIF-8 / Cu powder to obtain a ZnO / Cu 1.35 O catalyst; Furthermore, the mass ratio of zinc nitrate hexahydrate to dimethylimidazole is 1:1-30; Further, the copper ion solution is any one of anhydrous copper sulfate solution, copper nitrate solution or copper chloride solution; Furthermore, the stirring time is 5 h; Furthermore, the centrifugal speed was 1000 rpm, and the centrifugal time was 10 min; Furthermore, the drying time is 24 h and the drying temperature is 60 °C; Furthermore, the calcination temperature is 550 °C and the heating rate is 10 °C·min -1 The calcination time is 30 min, and the calcination atmosphere is nitrogen atmosphere.

[0006] A catalyst is prepared by the above method.

[0007] An application of a catalyst in the field of water treatment; Furthermore, the catalyst is used to catalyze the degradation of tetracycline hydrochloride, and the catalytic degradation step is to convert ZnO / Cu 1.35 The catalyst O is placed in a test solution containing tetracycline hydrochloride, and a laser is used to irradiate the test solution to perform a degradation reaction; the laser is a red laser or a blue laser or a combination of the two; the light intensity of the laser is 50-300 μmol·m -2 ·s -1 .

[0008] Compared with the prior art, the present invention solves the defects of insufficient visible light and ultraviolet light penetration and low photocatalytic effect in the prior art photocatalytic technology, fills the technical gap of catalysts that can achieve efficient synergy with laser, and has the following specific beneficial effects: 1. ZnO / Cu provided by the present invention 1.35 The ZnO / Cu catalyst has a heterojunction structure, which can effectively promote the separation of photogenerated electrons and holes, allowing more carriers to participate in the photocatalytic reaction and improve the photocatalytic efficiency; at the same time, the heterojunction interface can provide more active sites for the photocatalytic reaction, making it easier for reactant molecules (such as pollutant molecules) to adsorb and react on the heterojunction interface, further improving the ZnO / Cu 1.35 O catalyst photocatalytic performance; In addition, ZnO / Cu 1.35 The O catalyst has strong anti-interference ability and cyclic stability, and can be reused.

[0009] 2. ZnO / Cu 1.35The O catalyst is prepared by using ZIF-8 loaded with copper ions. The preparation process is simple and efficient. The entire preparation process has no harmful by-products and will not cause secondary pollution, which meets the requirements of green environmental protection. At the same time, the required raw materials are abundant and easy to obtain, with low cost, and are suitable for large-scale industrial production.

[0010] 3. The present invention uses laser light to replace visible light and ultraviolet light. Laser and ZnO / Cu 1.35 O catalysts work synergistically to generate free radicals with strong oxidative ability ( 1 O 2 、h + , ·O 2- ) attacks TC molecules, destroys the chemical bonds in TC molecules (such as C=C, CN, CO, etc.), and gradually degrades them into small molecules and finally mineralizes, increasing the degradation rate of TC; at the same time, the monochromaticity and high light intensity of the laser can accurately match the ZnO / Cu 1.35 O catalyst band structure, efficient excitation of electronic transition, promote ZnO / Cu 1.35 O catalyst heterojunction photogenerated electron-hole separation, improve the utilization of carriers. Compared with traditional light sources, laser lamps can be applied to wastewater with different turbidity, and have low power and are easy to carry; by adjusting the different light quality, intensity and light ratio of the laser lamp, the photocatalytic reaction can be precisely controlled to improve the reaction rate and selectivity, while reducing energy consumption, so that ZnO / Cu 1.35 The O catalytic system showed better performance in the catalytic degradation of tetracycline hydrochloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Laser-ZnO / Cu 1.35 O catalyst synergistic catalytic degradation of TC reaction device diagram; Figure 2 For different ZnO / Cu 1.35 The relationship between the concentration of O catalyst and the degradation rate of TC; Figure 3 This is the relationship diagram of the effect of different laser intensities on TC degradation rate; Figure 4 This is the relationship diagram of the effect of different catalyst types on TC degradation rate; Figure 5 This is the relationship diagram of the effect of different light qualities on TC degradation rate; Figure 6 This is the relationship diagram of the effect of different cycle numbers on TC degradation rate; Figure 7 This is the relationship diagram of the effect of water depth on light intensity when turbidity is equal to 0; Figure 8 This is the relationship diagram of the effect of water depth on light intensity when turbidity is equal to 12.5; Fig. 9 This is the relationship diagram of the effect of water depth on light intensity when turbidity is equal to 25; Fig.10 This is the relationship diagram of the effect of water depth on light intensity when the turbidity is equal to 50; Fig.11 This is the relationship diagram of the effect of water depth on light intensity when turbidity is equal to 100; Fig.12 This is a graph showing the effect of water depth on light intensity when turbidity is equal to 200. DETAILED DESCRIPTION

[0012] In order to make the technical solution of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the specification of the present invention. It should be noted that the following embodiments are only used to better understand the technical solution of the present invention and should not be understood as a limitation to the present invention.

[0013] Example 1. 3 g zinc nitrate hexahydrate and 4 g dimethylimidazole were dissolved in 200 mL deionized water, respectively. Then, the zinc nitrate hexahydrate solution was slowly poured into the dimethylimidazole solution, stirred for 5 h, centrifuged at 1000 rpm for 10 min, and the precipitate was collected and dried in an oven at 60 °C for 24 h to obtain the ZIF-8 sample. The dried ZIF-8 sample was ground into powder, and 2 g was dispersed in 450 mL anhydrous copper sulfate solution (the concentration of the anhydrous copper sulfate solution was 3.91 g / L). After stirring for 5 h, the solution was centrifuged at 1000 rpm for 10 min, and the precipitate was collected and dried in an oven at 60 °C for 24 h to obtain the ZIF-8 / Cu sample. Finally, the ZIF-8 / Cu powder was placed in a tubular furnace, nitrogen was introduced, and the mixture was heated at 10 °C·min -1 The temperature was heated to 550 °C at a rate of 100 °C and kept at this temperature for 30 min. ZnO / Cu 1.35 O catalyst.

[0014] Example 2. 0.0150 g ZnO / Cu 1.35 The catalyst was placed in a beaker, 30 mL of 40 mg / L TC was added to the beaker, and the mixture was stirred at 300 rpm. The beaker was sealed on all sides to prevent light from penetrating. The laser was placed 50 cm away from the beaker with a light intensity of 50 μmol·m -2 ·s -1 , the red laser was used to irradiate them for 180 min, and the TC degradation rate was 100%. Figure 1 Laser-ZnO / Cu 1.35 Diagram of the reaction device for TC degradation using O catalyst synergistically.

[0015] Example 3. The difference between this embodiment and embodiment 2 is that the ZnO / Cu 1.35 The mass of O catalyst was 0.0100 g, and other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 73.12%.

[0016] Example 4. The difference between this embodiment and embodiment 2 is that the ZnO / Cu 1.35 The mass of O catalyst was 0.0125 g, and other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 88.18%.

[0017] Example 5. The difference between this embodiment and embodiment 2 is that the ZnO / Cu 1.35 The mass of O catalyst was 0.0175 g, and other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 100%.

[0018] Example 6. The difference between this embodiment and embodiment 2 is that the ZnO / Cu 1.35 The mass of O catalyst was 0.0200 g, and other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 100%.

[0019] like Figure 2 For different ZnO / Cu in Examples 2-6 1.35 The relationship between the concentration of O catalyst and the degradation rate of TC is shown in the figure. It can be seen that within 180 min, when ZnO / Cu 1.35 When the mass of the O catalyst is greater than 0.0150 g, the degradation rate of TC can reach 100%, which proves that the ZnO / Cu 1.35 O catalyst could achieve complete degradation of TC within 180 min.

[0020] Example 7. The difference between this embodiment and embodiment 2 is that the light quality of the laser is changed to blue laser, and the other experimental steps and conditions are the same as those of embodiment 2. The TC degradation rate is 100%.

[0021] Example 8. The difference between this embodiment and embodiment 2 is that the light quality of the laser is changed to a red-blue mixed laser, and the other experimental steps and conditions are the same as those of embodiment 2. The TC degradation rate is 100%.

[0022] Example 9. The difference between this embodiment and embodiment 2 is that the laser intensity is changed to 3 μmol·m -2 ·s-1 , other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 84.43%.

[0023] Example 10. The difference between this embodiment and embodiment 2 is that the laser intensity is changed to 7 μmol·m -2 ·s -1 , other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 88.53%.

[0024] Example 11. The difference between this embodiment and embodiment 2 is that the laser intensity is changed to 11 μmol·m -2 ·s -1 , other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 92.5%.

[0025] Example 12. The difference between this embodiment and embodiment 2 is that the laser intensity is changed to 26 μmol·m -2 ·s -1 , other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 95.2%.

[0026] Example 13. The difference between this embodiment and embodiment 2 is that the laser intensity is changed to 300 μmol·m -2 ·s -1 , other experimental steps and conditions were the same as those in Example 2. The TC degradation rate was 100%.

[0027] like Figure 3 The relationship diagram of the effect of different laser intensities on TC degradation rate in Example 2 and Examples 9-13 shows that within 180 min, as the laser intensity increases, the TC degradation rate gradually increases. This is because high light intensity can make ZnO / Cu 1.35 O catalysts absorb more light energy and generate more photogenerated electron-hole pairs. The plasmon resonance effect on the catalyst surface is enhanced under high light intensity, which improves the photocatalytic activity.

[0028] Example 14. The difference between this embodiment and embodiment 1 is that 1 g of zinc nitrate hexahydrate and 10 g of dimethylimidazole are dissolved in 200 mL of deionized water respectively, and the other experimental steps and conditions are the same as those in embodiment 1 to prepare ZnO / Cu 1.35 O catalyst.

[0029] 0.0150 g ZnO / Cu 1.35The catalyst was placed in a beaker, 30 mL of 40 mg / L TC was added to the beaker, and the mixture was stirred at 300 rpm. The beaker was sealed on all sides to prevent light from penetrating. The laser was placed 50 cm away from the beaker with a light intensity of 50 μmol·m -2 ·s -1 The red laser was used for 180 min irradiation and the TC degradation rate was 94.3%.

[0030] Example 15. The difference between this embodiment and embodiment 1 is that 2 g of zinc nitrate hexahydrate and 7 g of dimethylimidazole are dissolved in 200 mL of deionized water respectively, and the other experimental steps and conditions are the same as those in embodiment 1. 1.35 O catalyst.

[0031] 0.0150 g ZnO / Cu 1.35 The catalyst was placed in a beaker, 30 mL of 40 mg / L TC was added to the beaker, and the mixture was stirred at 300 rpm. The beaker was sealed on all sides to prevent light from penetrating. The laser was placed 50 cm away from the beaker with a light intensity of 50 μmol·m -2 ·s -1 The red laser was used for 180 min irradiation, and the TC degradation rate was 97.6%.

[0032] Comparative Example 1. The ZIF-8 powder prepared in Example 1 was placed in a tubular furnace, nitrogen was introduced for protection, and the mixture was heated to 550 °C at a heating rate of 10 °C min⁻¹, and kept at this temperature for 30 min. ZnO was obtained after calcination.

[0033] Weigh 0.0150 g of ZIF-8, ZnO, ZIF-8 / Cu and ZnO / Cu prepared in Example 1 and Comparative Example 1. 1.35 O catalyst were placed in beakers, 30 mL of 40 mg / L TC was added to the beakers, and the mixture was stirred at 300 rpm. The beakers were sealed on all sides to prevent light from penetrating. The laser was placed 50 cm away from the beakers with a light intensity of 50 μmol·m -2 ·s -1 , and irradiated it with red laser for 180 min. Figure 4 For ZIF-8, ZnO, ZIF-8 / Cu and ZnO / Cu 1.35 The relationship diagram of the effect of O catalyst on TC degradation rate. It can be seen from the figure that when the degradation time is 180 min, the degradation rate of ZIF-8 / Cu is better than that of ZIF-8 and ZnO, and ZnO / Cu 1.35O catalyst has the best degradation rate, which is due to the 1.35 O forms a heterojunction structure, which promotes electron-hole separation, broadens the light absorption range, and increases the catalytic active sites, thereby accelerating the photocatalytic degradation reaction.

[0034] Comparative Example 2. The difference between this comparative example and Example 2 is that the light quality is changed to visible light, and the other experimental steps and conditions are the same as those of Example 2. The TC degradation rate is 93.94%.

[0035] Comparative Example 3. The difference between this comparative example and Example 2 is that the light quality is changed to ultraviolet light, and the other experimental steps and conditions are the same as those of Example 2. The TC degradation rate is 94.95%.

[0036] like Figure 5 FIG. 1 is a graph showing the effect of different light qualities on TC degradation rate. It can be seen from the graph that within 180 min, the TC degradation rates of Example 2, Example 7 and Example 8 using red laser (R), blue laser (B) and red-blue mixed laser (R / B) can all reach 100%, while the TC degradation rates of Comparative Example 2 and Comparative Example 3 using visible light (W) and ultraviolet light (UV) are only 94%. This is mainly due to the ZnO / Cu 1.35 O catalyst has a synergistic effect with laser to generate free radicals with strong oxidative ability ( 1 O 2 、h + , ·O 2- ) to attack TC molecules, causing them to gradually degrade into small molecules and eventually mineralize; at the same time, the monochromaticity and high light intensity of the laser can accurately match the ZnO / Cu 1.35 O catalyst band structure, efficient excitation of electronic transition, promote ZnO / Cu 1.35 The photogenerated electron-hole separation in the O-catalyst heterojunction improves the utilization of carriers and thus increases the degradation rate of TC.

[0037] Cyclic stability test: The ZnO / Cu prepared in Example 1 1.35 O catalyst was subjected to a cyclic degradation experiment according to the steps of Example 2. After the first degradation, ZnO / Cu 1.35 O catalyst, and washed it with deionized water and methanol three times, and then dried for the next degradation, for a total of 4 cycles. Figure 6 As shown in the figure, after 4 cycles, the TC degradation rate gradually decreased from 100% to 80.87%, but still remained above 80%, indicating that ZnO / Cu 1.35 O catalyst has good stability and recyclability. This excellent cycling performance is mainly attributed to the ZnO and Cu1.35 The formation of ZnO / Cu heterojunction significantly improves the visible light absorption performance and promotes the separation and transmission of photogenerated electrons and holes. The decrease in degradation rate with the increase in the number of cycles may be due to the 1.35 The catalyst loses some mass during the recycling process; at the same time, the byproducts and pollutants produced by the degradation of TC occupy the ZnO / Cu 1.35 O catalyst pores, resulting in a decrease in its adsorption capacity; in addition, frequent flushing and cleaning may also cause ZnO / Cu 1.35 O The active catalytic sites on the catalyst surface deteriorate.

[0038] Penetration testing: The ZnO / Cu prepared in Example 1 1.35 O catalyst was placed in sewage with turbidity of 0, 12.5, 25, 50, 100, and 200 respectively. Three groups of sewage with the same turbidity were set up, and red laser, blue laser and visible light were used to irradiate the sewage at a distance of 16 cm. The light intensity of different light qualities was measured by a spectrometer. After measuring three data in each group, the average value was taken. The following table shows the experimental results of the penetration test. It can be seen from the table that with the increase of turbidity, the light intensity of the three light qualities all showed attenuation characteristics, but the light intensity of the red laser and the blue laser was greater than that of the visible light, which revealed the high efficiency of laser penetration in complex water quality environments.

[0039] like Figure 7-12 This is a graph showing the effect of water depth on light intensity under different turbidity levels. When the turbidity is between 0 and 50, the light intensity of the red laser and the blue laser gradually increases with the increase of water depth, while the light intensity of visible light is less than that of the laser. When the turbidity is 50, the light intensity gradually decreases with the increase of water depth, further verifying the high-efficiency penetration performance of the laser and its potential for application in sewage treatment.

[0040] The present invention utilizes ZnO / Cu 1.35 O catalyst heterojunction structure, which improves the ZnO / Cu 1.35 The photocatalytic performance, anti-interference ability and cyclic stability of the catalyst are qualitative and can be reused; the preparation process is simple and efficient, meets the requirements of green environmental protection, and is suitable for large-scale industrial production. 1.35 O catalysts work synergistically to generate free radicals with strong oxidative ability ( 1 O 2 、h + , ·O 2-) attacks TC molecules, destroys the chemical bonds in TC molecules (such as C=C, CN, CO, etc.), gradually degrades them into small molecules and finally mineralizes, increasing the degradation rate of TC; by adjusting the different light quality, intensity and light ratio of the laser lamp, the photocatalytic reaction can be precisely controlled to improve the reaction rate and selectivity, while reducing energy consumption, so that ZnO / Cu 1.35 The O catalytic system showed better performance in the catalytic degradation of tetracycline hydrochloride.

[0041] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0042] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a catalyst, characterized in that: The method comprises the following preparation steps: The zinc nitrate hexahydrate solution and the dimethyl imidazole solution are mixed, stirred, and centrifuged, and the precipitate is collected and dried to prepare ZIF-8; the ZIF-8 is ground into powder, dispersed in a copper ion solution, stirred, and centrifuged, and the precipitate is collected and dried to prepare ZIF-8 / Cu; the ZIF-8 / Cu powder is calcined to obtain ZnO / Cu 1.35 O catalyst.

2. The method for preparing a catalyst according to claim 1, characterized in that: The mass ratio of the zinc nitrate hexahydrate to dimethylimidazole is 1:1-30.

3. The method for preparing the catalyst according to claim 1, characterized in that: The copper ion solution is any one of anhydrous copper sulfate solution, copper nitrate solution or copper chloride solution.

4. The method for preparing the catalyst according to claim 1, characterized in that: The stirring time was 5 h.

5. The method for preparing the catalyst according to claim 1, characterized in that: The centrifugal speed was 1000 rpm, and the centrifugal time was 10 min.

6. The method for preparing a catalyst according to claim 1, characterized in that: The drying time was 24 h and the drying temperature was 60 °C.

7. The method for preparing a catalyst according to claim 1, characterized in that: The calcination temperature is 550 °C and the heating rate is 10 °C·min -1 The calcination time is 30 min, and the calcination atmosphere is nitrogen atmosphere.

8. A catalyst, characterized in that Prepared according to any one of claims 1 to 7.

9. Use of the catalyst as claimed in claim 8, characterized in that: Used in water treatment field.

10. Use of the catalyst according to claim 9, characterized in that: It is applied to catalytic degradation of tetracycline hydrochloride, wherein the catalytic degradation step is to convert ZnO / Cu 1.35 The catalyst O is placed in a test solution containing tetracycline hydrochloride, and a laser is used to irradiate the test solution to perform a degradation reaction; the laser is a red laser or a blue laser or a combination of the two; the light intensity of the laser is 50-300 μmol·m -2 ·s -1 .

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