A catalyst, its preparation method and application

Abstract

A catalyst, its preparation method and application relate to the technical field of water treatment, solve the defects of insufficient visible light and ultraviolet light penetration and low photocatalytic effect in the existing photocatalytic technology, and fill the technical gap of catalysts that achieve efficient synergy with lasers. In the present invention, a zinc nitrate hexahydrate solution and a dimethylimidazole solution are mixed, stirred, centrifuged, the precipitate is collected and dried to prepare ZIF-8; ZIF-8 is ground into powder, dispersed in a copper ion solution, stirred, centrifuged, 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, which has excellent photocatalytic performance, anti-interference ability and cyclic stability. The present invention can be applied to the catalytic degradation of tetracycline hydrochloride, and the degradation rate of tetracycline hydrochloride is improved by the synergistic effect of laser and ZnO / Cu 1.35 O 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] At present, 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 a new 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, restricting 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 the 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:

[0006] A preparation method of a catalyst, comprising the following preparation steps:

[0007] Mix a zinc nitrate hexahydrate solution and a dimethylimidazole solution, stir and centrifuge, collect the precipitate and dry it to prepare ZIF-8; grind 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 ZnO / Cu1.35 O catalyst;

[0008] Further, the mass ratio of zinc nitrate hexahydrate to dimethylimidazole is 1:1 to 30;

[0009] Further, the copper ion solution is any one of anhydrous copper sulfate solution, copper nitrate solution or copper chloride solution;

[0010] Further, the stirring time is 5 h for all;

[0011] Further, the centrifugation rate is 1000 rpm for all, and the centrifugation time is 10 min for all;

[0012] Further, the drying time is 24 h for all, and the drying temperature is 60 °C for all;

[0013] Further, 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 under nitrogen atmosphere.

[0014] A catalyst is prepared by the above method.

[0015] An application of a catalyst in the field of water treatment;

[0016] Further, the catalyst is applied to catalytic degradation of tetracycline hydrochloride. The steps of the catalytic degradation are to place the ZnO / Cu 1.35 O catalyst in the test solution containing tetracycline hydrochloride, and use laser irradiation on the test solution for degradation reaction; the laser is one or a combination of two of red laser or blue laser; the light intensity of the laser is 50~300 μmol·m -2 ·s -1 .

[0017] 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 existing photocatalytic technology, fills the technical gap of the catalyst that can achieve efficient synergistic effect with laser, and the specific beneficial effects are as follows:

[0018] 1. The ZnO / Cu 1.35 O catalyst provided by the present invention has a heterojunction structure, which can effectively promote the separation of photo-generated electrons and holes, enabling more carriers to participate in the photocatalytic reaction and improving 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 enhancing the photocatalytic performance of the ZnO / Cu 1.35 O catalyst; In addition, ZnO / Cu1.35 The O catalyst has strong anti-interference ability and cyclic stability, and can be reused.

[0019] 2. ZnO / Cu 1.35 The O catalyst is prepared by loading copper ions on ZIF-8. The preparation process is simple and efficient. There are no harmful by-products in the whole preparation process, and no secondary pollution will be caused, meeting the requirements of green environmental protection. At the same time, the required raw materials are abundant and easy to obtain, and the cost is low, which is suitable for large-scale industrial production.

[0020] 3. In the present invention, a laser lamp is used to replace visible light and ultraviolet light. The laser and the ZnO / Cu 1.35 O catalyst act synergistically to generate free radicals with strong oxidation ability ( 1 O2, h + , ·O 2- ) to attack TC molecules and break the chemical bonds in TC molecules (such as C=C, C-N, C-O, etc.), gradually degrading them into small molecules and finally mineralizing them, increasing the degradation rate of TC. At the same time, the monochromaticity and high light intensity of the laser can accurately match the energy band structure of the ZnO / Cu 1.35 O catalyst, efficiently exciting electron transitions, and promoting the separation of photo-generated electrons and holes in the heterojunction of the ZnO / Cu 1.35 O catalyst, improving the utilization rate of carriers. Compared with traditional light sources, the laser lamp can be applied to waste water with different turbidities, has low power and is easy to carry. By adjusting the different light qualities, intensities and light ratios of the laser emitted by the laser lamp, the photocatalytic reaction can be accurately regulated, the reaction rate and selectivity can be improved, and the energy consumption can be reduced at the same time, making the ZnO / Cu 1.35 O catalytic system show better performance in the field of catalytic degradation of tetracycline hydrochloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a diagram of the reaction device for the synergistic catalytic degradation of TC by the laser-ZnO / Cu 1.35 O catalyst;

[0022] Figure 2 is a diagram showing the relationship between the concentration of different ZnO / Cu 1.35 O catalysts and the degradation rate of TC;

[0023] Figure 3 is a diagram showing the relationship between different laser light intensities and the degradation rate of TC;

[0024] Figure 4 is a diagram showing the relationship between different catalyst types and the degradation rate of TC;

[0025] Figure 5 is a diagram showing the relationship between different light qualities and the degradation rate of TC;

[0026] Figure 6 Relationship diagram of the influence of different cycle numbers on the TC degradation rate;

[0027] Figure 7 Relationship diagram of the influence of water depth on light intensity when the turbidity is equal to 0;

[0028] Figure 8 Relationship diagram of the influence of water depth on light intensity when the turbidity is equal to 12.5;

[0029] Figure 9 Relationship diagram of the influence of water depth on light intensity when the turbidity is equal to 25;

[0030] Figure 10 Relationship diagram of the influence of water depth on light intensity when the turbidity is equal to 50;

[0031] Figure 11 Relationship diagram of the influence of water depth on light intensity when the turbidity is equal to 100;

[0032] Figure 12 Relationship diagram of the influence of water depth on light intensity when the turbidity is equal to 200. Detailed implementation manners

[0033] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as a limitation of the present invention.

[0034] Example 1.

[0035] Dissolve 3 g of zinc nitrate hexahydrate and 4 g of dimethylimidazole in 200 mL of deionized water respectively. Subsequently, slowly pour the zinc nitrate hexahydrate solution into the dimethylimidazole solution, stir for 5 h, centrifuge at 1000 rpm for 10 min, collect the precipitate and dry it in an oven at 60 °C for 24 h to obtain the ZIF-8 sample; grind the dried ZIF-8 sample into powder, take 2 g and disperse it in 450 mL of copper sulfate anhydrous solution (the concentration of the copper sulfate anhydrous solution is 3.91 g / L), stir for 5 h and then centrifuge at 1000 rpm for 10 min, collect the precipitate and dry it in an oven at 60 °C for 24 h to obtain the ZIF-8 / Cu sample; finally, place the ZIF-8 / Cu powder in a tubular furnace, introduce nitrogen for protection, and heat it to 550 °C at a heating rate of 10 °C·min -1 and keep it at this temperature for 30 min. After calcination, the ZnO / Cu 1.35 O catalyst is obtained.

[0036] Example 2.

[0037] Put 0.0150 g of ZnO / Cu1.35 Place the ZnO / Cu₂O catalyst in a beaker, add 30 mL of 40 mg / L TC to the beaker, stir at 300 rpm, seal the surroundings of the beaker to make it light-tight, place the laser 50 cm away from the beaker, with a light intensity of 50 μmol·m -2 ·s -1 , irradiate it with a red laser for 180 min, and the TC degradation rate is 100% in all cases. As Figure 1 shown in the figure of the reaction device for the synergistic catalytic degradation of TC by the laser-ZnO / Cu₂O catalyst. 1.35

[0038] Example 3.

[0039] The difference between this example and Example 2 is that the mass of the ZnO / Cu₂O catalyst is changed to 0.0100 g, and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 73.12%. 1.35

[0040] Example 4.

[0041] The difference between this example and Example 2 is that the mass of the ZnO / Cu₂O catalyst is changed to 0.0125 g, and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 88.18%. 1.35

[0042] Example 5.

[0043] The difference between this example and Example 2 is that the mass of the ZnO / Cu₂O catalyst is changed to 0.0175 g, and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 100%. 1.35

[0044] Example 6.

[0045] The difference between this example and Example 2 is that the mass of the ZnO / Cu₂O catalyst is changed to 0.0200 g, and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 100%. 1.35

[0046] As Figure 2 shown in the figure of the effect of different ZnO / Cu₂O catalyst concentrations on the TC degradation rate in Examples 2 - 6. It can be seen from the figure that within 180 min, when the mass of the added ZnO / Cu₂O catalyst is greater than 0.0150 g, the degradation rate of TC can reach 100%, proving that the ZnO / Cu₂O catalyst provided by the present invention can achieve the complete degradation of TC within 180 min. 1.35 1.35 1.35 ​​​​​​​​

[0047] Example 7.

[0048] The difference between this example and Example 2 is that the light quality of the laser is changed to blue laser, and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 100%.

[0049] Example 8.

[0050] The difference between this example and Example 2 is that the light quality of the laser is changed to a red - blue mixed laser, and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 100%.

[0051] Example 9.

[0052] The difference between this example and Example 2 is that the light intensity of the laser is changed to 3 μmol·m -2 ·s -1 , and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 84.43%.

[0053] Example 10.

[0054] The difference between this example and Example 2 is that the light intensity of the laser is changed to 7 μmol·m -2 ·s -1 , and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 88.53%.

[0055] Example 11.

[0056] The difference between this example and Example 2 is that the light intensity of the laser is changed to 11 μmol·m -2 ·s -1 , and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 92.5%.

[0057] Example 12.

[0058] The difference between this example and Example 2 is that the light intensity of the laser is changed to 26 μmol·m -2 ·s -1 , and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 95.2%.

[0059] Example 13.

[0060] The difference between this example and Example 2 is that the light intensity of the laser is changed to 300 μmol·m -2 ·s -1 , and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 100%.

[0061] AsFigure 3 It is a graph showing the relationship between different laser intensities and the degradation rate of TC in Example 2 and Examples 9 - 13. It can be seen from the graph that within 180 min, as the laser intensity increases, the degradation rate of TC gradually increases. This is because high light intensity enables the ZnO / Cu 1.35 O catalyst to absorb more light energy, generating more photoexcited electron - hole pairs. The surface plasmon resonance effect of the catalyst is enhanced under high light intensity, improving the photocatalytic activity.

[0062] Example 14.

[0063] The difference between this example and Example 1 is that 1 g of zinc nitrate hexahydrate and 10 g of dimethylimidazole are respectively dissolved in 200 mL of deionized water, and other experimental steps and conditions are the same as those in Example 1, to prepare the ZnO / Cu 1.35 O catalyst.

[0064] Put 0.0150 g of the ZnO / Cu 1.35 O catalyst into a beaker, add 30 mL of 40 mg / L TC to the beaker, stir at 300 rpm, seal the four sides of the beaker to be light - impermeable, place the laser 50 cm away from the beaker, with a light intensity of 50 μmol·m -2 ·s -1 , irradiate it with a red laser for 180 min, and the TC degradation rate is 94.3%.

[0065] Example 15.

[0066] The difference between this example and Example 1 is that 2 g of zinc nitrate hexahydrate and 7 g of dimethylimidazole are respectively dissolved in 200 mL of deionized water, and other experimental steps and conditions are the same as those in Example 1. Prepare the ZnO / Cu 1.35 O catalyst.

[0067] Put 0.0150 g of the ZnO / Cu 1.35 O catalyst into a beaker, add 30 mL of 40 mg / L TC to the beaker, stir at 300 rpm, seal the four sides of the beaker to be light - impermeable, place the laser 50 cm away from the beaker, with a light intensity of 50 μmol·m -2 ·s -1 , irradiate it with a red laser for 180 min, and the TC degradation rate is 97.6%.

[0068] Comparative Example 1.

[0069] The ZIF-8 powder prepared in Example 1 was placed in a tubular furnace, purged with nitrogen, heated to 550 °C at a heating rate of 10 °C·min⁻¹, held for 30 min, and ZnO was obtained after calcination.

[0070] Weigh 0.0150 g of the ZIF-8, ZnO, ZIF-8 / Cu, and ZnO / Cu 1.35 O catalysts prepared in Example 1 and Comparative Example 1, respectively, place them in beakers, add 30 mL of 40 mg / L TC to the beakers, stir at 300 rpm, seal the surroundings of the beakers to be light-tight, place the laser 50 cm away from the beakers, and the light intensity is 50 μmol·m -2 ·s -1 , irradiate it with a red laser, and the irradiation time is 180 min. As Figure 4 is the relationship diagram of the effect of ZIF-8, ZnO, ZIF-8 / Cu, and ZnO / Cu 1.35 O catalysts on the degradation rate of TC. 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 the ZnO / Cu 1.35 O catalyst has the best degradation rate. This is because a heterojunction structure is formed between ZnO and Cu 1.35 O, which promotes electron-hole separation, broadens the light absorption range, and increases the catalytic active sites, thus accelerating the photocatalytic degradation reaction.

[0071] Comparative Example 2.

[0072] The difference between this comparative example and Example 2 is that the light quality of the light is changed to visible light, and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 93.94%.

[0073] Comparative Example 3.

[0074] The difference between this comparative example and Example 2 is that the light quality of the light is changed to ultraviolet light, and other experimental steps and conditions are the same as those in Example 2. The TC degradation rate is 94.95%.

[0075] As Figure 5 is the relationship diagram of the effect of different light qualities on the degradation rate of TC. It can be seen from the figure 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 because the ZnO / Cu 1.35 O catalyst has a synergistic effect with the laser and can generate free radicals with strong oxidation ability ( 1O2, h + , ·O 2- ) to attack TC molecules, gradually degrade them into small molecules and finally mineralize them; at the same time, the monochromaticity and high light intensity of the laser can accurately match the energy band structure of the ZnO / Cu 1.35 O catalyst, efficiently excite electron transitions, and promote the separation of photo-generated electrons and holes within the heterojunction of the ZnO / Cu 1.35 O catalyst, improve the utilization rate of carriers, and thus increase the degradation rate of TC.

[0076] Cyclic stability test:

[0077] The ZnO / Cu 1.35 O catalyst prepared in Example 1 was subjected to a cyclic degradation experiment, carried out according to the steps of Example 2. After the first degradation, the ZnO / Cu 1.35 O catalyst was separated by centrifugation, washed three times with deionized water and methanol, dried and used for the next degradation, for a total of 4 cycles. As Figure 6 shown, after 4 cycles, the degradation rate of TC gradually decreased from 100% to 80.87%, but still remained above 80%, indicating that the ZnO / Cu 1.35 O catalyst has good stability and recyclability. This excellent cyclic performance is mainly attributed to the formation of the ZnO and Cu 1.35 O heterojunction, which significantly improves the visible light absorption performance and promotes the separation and transport of photo-generated electrons and holes. As the number of cycles increases, the decrease in the degradation rate may be due to partial mass loss of the ZnO / Cu 1.35 O catalyst during the recycling process; at the same time, the by-products and pollutants generated from the degradation of TC occupy the pores of the ZnO / Cu 1.35 O catalyst, resulting in a decrease in its adsorption capacity; in addition, frequent rinsing and cleaning may also cause deterioration of the surface active catalytic sites of the ZnO / Cu 1.35 O catalyst.

[0078] Penetration test:

[0079] The ZnO / Cu 1.35 O catalyst prepared in Example 1 was placed in sewage with turbidities of 0, 12.5, 25, 50, 100, and 200 respectively. For each turbidity, three groups of sewage were set up. Red laser, blue laser, and visible light were used to irradiate them at a position 16 cm away from the sewage. A spectrometer was used to measure the light intensities of different light qualities respectively. After measuring three data for each group, the average value was taken. The following table shows the experimental results of the penetration test. From the content in the table, it can be seen that as the turbidity increases, the light intensities of all three light qualities show a decaying characteristic, but the light intensities of the red laser and the blue laser are both greater than that of the visible light, revealing the high-efficiency penetration performance of the laser in a complex water quality environment.

[0080]

[0081] As Figures 7 - 12 is the relationship diagram of the influence of water depth on light intensity at different turbidities. When the turbidity is between 0 and 50, the light intensities of the red laser and the blue laser gradually increase with the increase of water depth, while the light intensity of visible light is less than that of the laser. And when the turbidity is 50, its light intensity gradually shows a downward trend with the increase of water depth, further verifying the high-efficiency penetration performance of the laser and its potential in the field of sewage treatment.

[0082] The present invention utilizes the heterojunction structure of the ZnO / Cu 1.35 O catalyst to improve the photocatalytic performance, anti-interference ability and cyclic stability of the ZnO / Cu 1.35 O catalyst, and it can be reused; the preparation process is simple and efficient, meeting the requirements of green environmental protection and suitable for large-scale industrial production. The present invention utilizes the synergistic effect of laser and ZnO / Cu 1.35 O catalyst to generate free radicals with strong oxidation ability ( 1 O2, h + , ·O 2- ) to attack TC molecules and break the chemical bonds in TC molecules (such as C=C, C-N, C-O, etc.), gradually degrading them into small molecules and finally mineralizing them, increasing the degradation rate of TC; by adjusting the different light qualities, intensities and light ratios of the laser emitted by the laser lamp, the photocatalytic reaction is precisely regulated, the reaction rate and selectivity are improved, and the energy consumption is reduced at the same time, making the ZnO / Cu 1.35 O catalytic system show better performance in the field of catalytic degradation of tetracycline hydrochloride.

[0083] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0084] 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 obvious to those skilled in the art, and the general principles defined herein can 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 these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Application of a catalyst, characterized in that, Applied in the field of water treatment, including catalytic degradation of tetracycline hydrochloride; the steps of the catalytic degradation are to place the ZnO / Cu 1.35 O catalyst in the test solution containing tetracycline hydrochloride, and use laser irradiation on the test solution for the degradation reaction; the laser is one or a combination of two of red laser or blue laser; the light intensity of the laser is 50~300 μmol·m -2 ·s -1 ; The ZnO / Cu 1.35 O catalyst is prepared by the following preparation method: 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 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; Calcinate the ZIF-8 / Cu powder to obtain the ZnO / Cu 1.35 O catalyst; 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 under nitrogen atmosphere.

2. The application of the catalyst according to claim 1, characterized in that The mass ratio of the zinc nitrate hexahydrate to the dimethylimidazole is 1:1 to 30.

3. The use of the catalyst according to claim 1, wherein The copper ion solution is any one of an anhydrous copper sulfate solution, a copper nitrate solution, or a copper chloride solution.

4. Use of the catalyst according to claim 1, characterized in that, The stirring time is 5 h in each case.

5. The use of the catalyst according to claim 1, wherein The centrifugation rate is 1000 rpm in each case, and the centrifugation time is 10 min in each case.

6. The application of the catalyst according to claim 1, characterized in that, The drying time is 24 h in each case, and the drying temperature is 60 °C in each case.

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