Catalyst for photo-assisted activation of PMS to efficiently degrade ciprofloxacin and preparation method of catalyst

Abstract

The invention discloses a catalyst for photo-assisted activation of peroxymonosulfate (PMS) to efficiently degrade ciprofloxacin hydrochloride and a preparation method of the catalyst, and the catalyst is a nano flaky Co-C3N4 catalyst prepared by taking soluble cobalt salt, urea and melamine as raw materials through hydrothermal reaction and high-temperature roasting. The preparation method disclosed by the invention is simple and good in repeatability, and the obtained catalyst shows an excellent degradation effect in degrading ciprofloxacin by photo-assisted activation of PMS.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a Co-C3N4 photocatalyst for efficiently degrading ciprofloxacin hydrochloride by photo-assisted activation of PMS and a preparation method thereof. Background Art

[0002] Antibiotics are a class of drugs for treating bacterial infections, which can kill bacteria or inhibit their growth. Although they play an extremely important role in the field of medical treatment, with the entry of antibiotics into surface water, without timely and effective treatment, they may enter the human body through drinking water or food and accumulate continuously. Eventually, the human body will gradually develop drug resistance, greatly reducing their therapeutic effect. In severe cases, it may even have an inestimable negative impact on human health. Therefore, how to solve such pollution has become an extremely urgent topic.

[0003] Currently, advanced oxidation technology is one of the mainstream technologies for treating antibiotic-containing sewage, including photocatalytic oxidation technology, persulfate oxidation technology, wet oxidation technology, ozone oxidation technology, Fenton oxidation technology, supercritical water oxidation technology, etc. Among them, photocatalytic oxidation technology driven by clean energy solar energy has become a research hotspot, especially its characteristic of being easily synergistically oxidized with other treatment technologies is particularly remarkable. In particular, the technology of photocatalytic synergy with peroxymonosulfate has good potential. Summary of the Invention

[0004] The purpose of the present invention is to provide a catalyst for efficiently degrading ciprofloxacin hydrochloride by photo-assisted activation of PMS and a preparation method thereof. The preparation method is simple, has good repeatability, and the obtained catalyst shows excellent catalytic activity in the photo-assisted activation of PMS to degrade ciprofloxacin.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: One of the purposes of the present invention is to protect a preparation method of a Co-C3N4 photocatalyst, which includes the following steps: 1) Thoroughly stir and mix soluble cobalt salt, urea, and melamine in deionized water, and then carry out a hydrothermal reaction; 2) After the hydrothermal reaction is completed, collect the bottom red product, wash it multiple times, and dry it to obtain a precursor; 3) Place the obtained precursor in a tubular furnace for high-temperature calcination to obtain a yellow Co-C3N4 catalyst.

[0006] Further, the soluble cobalt salt in step 1) is one or more of cobalt acetate, cobalt nitrate, cobalt chloride, or cobalt sulfate.

[0007] Furthermore, the molar ratio of urea, melamine and soluble cobalt salt used in step 1) is 95:34:(0.01~3).

[0008] Furthermore, the temperature of the hydrothermal reaction in step 1) is 120-200°C, and the time is 12-32 h.

[0009] Furthermore, in step 2), deionized water and anhydrous ethanol are used as washing liquids respectively.

[0010] Furthermore, the washing method adopted in step 2) is filtration washing or centrifugal washing.

[0011] Furthermore, the high temperature calcination in step 3) is carried out in an atmosphere of one or more gases selected from argon, helium or nitrogen, with a calcination temperature of 500-600° C. and a calcination time of 60-360 min.

[0012] The second purpose of the present invention is to protect the Co-C3N4 photocatalyst prepared by the method.

[0013] The third purpose of the present invention is to protect the application of the Co-C3N4 photocatalyst in the photo-assisted activation of PMS for efficient degradation of ciprofloxacin hydrochloride.

[0014] Furthermore, the application method is to add the Co-C3N4 photocatalyst to a pollutant solution containing ciprofloxacin hydrochloride, fully mix and adsorb it, then add PMS, and then carry out an oxidative degradation reaction under light to achieve efficient degradation of ciprofloxacin hydrochloride.

[0015] Furthermore, the dosage of Co-C3N4 photocatalyst in the pollutant solution was about 0.375 g / L.

[0016] Furthermore, the dosage of PMS in the pollutant solution is about 0.1 g / L.

[0017] Furthermore, the light intensity during illumination is 100 mW / cm 2 .

[0018] C3N4 is an inorganic semiconductor photocatalyst that has emerged in recent years. It has excellent chemical stability and thermal stability, is non-toxic and harmless, has high catalytic performance, a simple synthesis method, and readily available and cheap raw materials. After the present invention uses it to load metal cobalt, the recombination efficiency of photogenerated electrons and holes can be reduced, and the catalytic activity can be significantly improved. By introducing it into the field of light-assisted activation of PMS, the degradation ability of antibiotics can be further improved.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses two common and inexpensive raw materials, urea and melamine, as the precursors of C3N4, and prepares the catalyst by a simple hydrothermal calcination method, which has simple operation and good repeatability; (2) The catalyst prepared by the present invention is nanosheet-shaped, has a high specific surface area, can expose more adsorption and activation sites, and at the same time, the catalyst has a moderate band gap, which can broaden the absorption spectrum of sunlight; (3) The catalyst provided by the present invention can synergistically activate PMS with sunlight as the energy under normal temperature and pressure conditions, so that ciprofloxacin hydrochloride can be completely degraded, and at the same time, the dosage of PMS is reduced, the utilization rate of PMS is improved, and excellent catalytic activity is demonstrated. Description of the Drawings

[0020] Figure 1 XRD patterns of the catalysts prepared in Examples 1-4 and Comparative Example 1.

[0021] Figure 2 Fourier transform infrared spectroscopy (FT-IR) patterns of the catalysts prepared in Examples 1-4 and Comparative Example 1.

[0022] Figure 3 TEM image of the catalyst prepared in Example 3.

[0023] Figure 4 HAADF and mapping images of Co, C, and N of the catalyst prepared in Example 3.

[0024] Figure 5 N2 adsorption-desorption isotherms of the catalysts prepared in Example 3 and Comparative Example 1.

[0025] Figure 6 Pore size distribution curves of the catalysts prepared in Example 3 and Comparative Example 1.

[0026] Figure 7 Performance comparison diagrams of the photocatalytic degradation of ciprofloxacin hydrochloride by the catalysts prepared in Examples 1-4 and Comparative Examples 1-3.

[0027] Figure 8 Performance comparison diagrams of the degradation of ciprofloxacin hydrochloride assisted by PMS under dark conditions by the catalysts prepared in Examples 1-4 and Comparative Examples 1-3.

[0028] Figure 9 Performance comparison diagrams of the photo-assisted activation of PMS for the degradation of ciprofloxacin hydrochloride by the catalysts prepared in Examples 1-4 and Comparative Examples 1-3.

[0029] Figure 10 Performance comparison diagrams of the photo-assisted activation of PMS for the degradation of ciprofloxacin hydrochloride using the catalyst prepared in Example 3 at different PMS dosages. Detailed implementation mode

[0030] A Co-C3N4 photocatalyst, the preparation of which comprises the following steps: 1) Mix urea, melamine and soluble cobalt salt in a molar ratio of 95:34:(0.01~3) in deionized water and stir well; 2) Transfer the mixed solution obtained in step 1) into the polytetrafluoroethylene inner liner of a hydrothermal reactor, and then transfer it into an oven, and carry out hydrothermal reaction at 120~200 °C for 12~32 h; 3) After the hydrothermal reaction is completed, pour out the upper layer solution, collect the bottom red product, wash it several times, and dry it to obtain a precursor; 4) Place the obtained precursor in a tubular furnace, and calcine it at a high temperature of 500~600 °C for 60~360 min in an atmosphere of one or more of argon, helium or nitrogen to obtain a yellow Co-C3N4 catalyst.

[0031] Among them, the soluble cobalt salt in step 1) is one or more of cobalt acetate, cobalt nitrate, cobalt chloride or cobalt sulfate.

[0032] In step 3), deionized water and absolute ethanol are used as washing liquids respectively. The washing method adopted is filtration washing or centrifugal washing.

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the following will describe the specific implementation mode of the present invention in detail with reference to the drawings. The following content is only an example and illustration of the inventive concept. Those skilled in the art can make various modifications or supplements to the described specific implementation cases, or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

[0034] The beneficial effects of the present invention are illustrated by the following specific examples.

[0035] Example 1 1) Mix 0.00045 mol of cobalt chloride hexahydrate, 0.095 mol of urea and 0.034 mol of melamine in 50 mL of deionized water, and stir for at least 30 min; 2) Transfer the mixed solution obtained in step 1) into the polytetrafluoroethylene inner liner of a hydrothermal reactor, and then transfer it into an oven, and react at 180 °C for 24 h; 3) Pour out the upper layer solution of the product after hydrothermal reaction, collect the bottom red product, wash it centrifugally 3 times with deionized water and absolute ethanol respectively, and then dry it in vacuum at 60 °C to obtain a precursor; 4) Place the precursor obtained in step 3) in a tubular furnace. Under a nitrogen atmosphere, heat it to 550 °C at a rate of 2.3 °C / min and hold for 120 min to obtain a yellow Co-C3N4 catalyst with a cobalt loading of 6%.

[0036] Example 2 In step 1), the dosage of cobalt chloride hexahydrate is 0.00089 mol, and other operations are the same as in Example 1, obtaining a Co-C3N4 catalyst with a loading of 12%.

[0037] Example 3 In step 1), the dosage of cobalt chloride hexahydrate is 0.00112 mol, and other operations are the same as in Example 1, obtaining a Co-C3N4 catalyst with a loading of 15%.

[0038] Example 4 In step 1), the dosage of cobalt chloride hexahydrate is 0.00134 mol, and other operations are the same as in Example 1, obtaining a Co-C3N4 catalyst with a loading of 18%.

[0039] Control Example 1 In step 1), the dosage of cobalt chloride hexahydrate is 0 mol, and other operations are the same as in Example 1, obtaining a C3N4 catalyst.

[0040] Control Example 2 Change the 0.00045 mol of cobalt chloride hexahydrate added in step 1) to 0.00112 mol of anhydrous ferric chloride, and other operations are the same as in Example 1, obtaining an Fe-C3N4 catalyst with a loading of 15%.

[0041] Control Example 3 Change the 0.00045 mol of cobalt chloride hexahydrate added in step 1) to 0.00112 mol of manganese chloride tetrahydrate, and other operations are the same as in Example 1, obtaining a Mn-C3N4 catalyst with a manganese loading of 15%.

[0042] Figure 1 XRD patterns of the catalysts prepared in Examples 1-4 and Control Example 1. It can be seen from the figure that the intensity of the (002) crystal plane characteristic peak (27.3°) of C3N4 decreases with the increase of the Co loading, and at the same time, characteristic peaks of Co appear at 44.2°, 51.52° and 75.84°, indicating that metal Co has been successfully loaded.

[0043] Figure 2 Fourier transform infrared spectroscopy (FT-IR) patterns of the catalysts prepared in Examples 1-4 and Control Example 1. It can be seen from the figure that except for Example 4, at 810 cm -1The peak at [x] cm -1 shows the stretching vibration peak of the C-N heterocycle in the range of 1242 - 1633 cm -1 and the characteristic peaks of terminal amino groups and surface-adsorbed hydroxyl groups in the range of 3000 - 3750 cm. This unit is caused by the incompletely polymerized structure on the surface or the interaction with water molecules.

[0044] Figure 3 Figure [x] is the TEM image of the catalyst prepared in Example 3. It can be seen from the figure that it is mainly composed of stacked nanosheets.

[0045] Figure 4 Figure [x] is the HAADF and mapping images of Co, C, and N of the catalyst prepared in Example 3. As can be seen from the figure, the distribution of each element is relatively uniform.

[0046] Figure 5 Figure [x] is the nitrogen adsorption - desorption isotherm of the catalysts prepared in Example 3 and Comparative Example 1. It can be seen from the figure that both Example 3 and Comparative Example 1 show a classic type - IV H3 hysteresis loop, indicating that they both have mesoporous structures.

[0047] Figure 6 Figure [x] is the pore size distribution diagram of the catalysts prepared in Example 3 and Comparative Example 1. It can be seen from the figure that the pore sizes of Example 3 and Comparative Example 1 are mainly distributed in the range of 0 - 2 nm. At the same time, the specific surface area of Example 3 is larger than that of Comparative Example 1, which is beneficial for increasing the catalytic active sites and can further improve its catalytic activity.

[0048] Performance Test The activities of the catalysts prepared in the examples and comparative examples were evaluated through experiments on photocatalytic degradation of ciprofloxacin hydrochloride assisted by PMS under dark conditions and photocatalytic activation of PMS for degradation of ciprofloxacin hydrochloride. The specific operation is as follows: Prepare a 40 mL ciprofloxacin hydrochloride solution with a concentration of 20 mg / L (the pH of the solution is defaulted to the initial value unless otherwise specified); The light source used in the experiment is a xenon lamp with an AM1.5G filter as the simulated sunlight (the light intensity is 100 mW / cm 2); For the experiment of photocatalytic degradation of ciprofloxacin hydrochloride, a certain amount of catalyst was added to the prepared ciprofloxacin hydrochloride solution, ultrasonicated for 15 min, and then magnetically stirred for 30 min until the adsorption-desorption equilibrium was reached. After that, the light source was turned on and the reaction was carried out at room temperature for 25 min, and sampling was started after the light source was turned on. The difference between the experimental procedure of assisting PMS to degrade ciprofloxacin hydrochloride under dark conditions and the photocatalytic degradation of ciprofloxacin hydrochloride is that after the adsorption-desorption equilibrium is reached, the light is not turned on, and an appropriate amount of PMS is directly added to start timing. The difference between the experimental procedure of photocatalytic activation of PMS to degrade ciprofloxacin hydrochloride and the photocatalytic degradation of ciprofloxacin hydrochloride is that an appropriate amount of PMS is added to start timing after the light source is turned on. Unless otherwise specified, the dosage of the catalyst is 0.375 g / L and the dosage of PMS is 0.1 g / L. The sampling times are 0, 3, 6, 9, 12, 15, 18, 25 min. Each time, 1 mL of the water sample was transferred into 1 mL of methanol solution and mixed evenly, filtered through a 0.22 μm water-based filter, and then transferred into a liquid-phase vial for testing.

[0049] Figure 7 It is a performance comparison chart of the photocatalytic degradation of ciprofloxacin hydrochloride by the catalysts prepared in Examples 1-4 and Comparative Examples 1-3. As can be seen from the figure, the photocatalytic activity of the catalysts prepared in the examples is generally better than that of the comparative examples, and the photocatalytic effect of the Co-C3N4 catalyst with a loading of 15% is the most excellent.

[0050] Figure 8 It is a performance comparison chart of the catalysts prepared in Examples 1-4 and Comparative Examples 1-3 assisting PMS to degrade ciprofloxacin hydrochloride under dark conditions. As can be seen from the figure, the degradation effect of the catalysts prepared in the examples assisting PMS under dark conditions is significantly better than that of the comparative examples, and the degradation effect of the Co-C3N4 catalyst with a loading of 15% assisting PMS under dark conditions is the best.

[0051] Figure 9 It is a performance comparison chart of the catalysts prepared in Examples 1-4 and Comparative Examples 1-3 photocatalytically activating PMS to degrade ciprofloxacin hydrochloride. As can be seen from the figure, the degradation effect of the catalysts prepared in the examples photocatalytically activating PMS is generally better than that of the comparative examples, and the degradation effect of the Co-C3N4 catalyst with a loading of 15% is the best.

[0052] The effect of photocatalytically activating PMS to degrade ciprofloxacin hydrochloride using the catalyst prepared in Example 3 with different dosages of PMS was further investigated, and the results are shown in Figure 10 .

[0053] As can be seen from the figure, under the condition of using the catalyst of Example 3, the dosage of PMS only needs to reach 0.1 g / L to achieve excellent degradation activity, which is lower than the conventional usage concentration of PMS in this system. This proves that the use of this catalyst can improve the utilization rate of PMS, thereby reducing the dosage of PMS.

[0054] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing a Co-C3N4 photocatalyst, characterized in that: The following steps are involved: 1) Soluble cobalt salt, urea and melamine are fully stirred and mixed in deionized water, and then subjected to hydrothermal reaction; 2) After the hydrothermal reaction is completed, the red product at the bottom is collected and washed multiple times and dried to obtain a precursor; 3) The obtained precursor is placed in a tubular furnace for high-temperature calcination to obtain a yellow Co-C3N4 catalyst.

2. The method for preparing a Co-C3N4 photocatalyst according to claim 1, characterized in that: The molar ratio of urea, melamine and soluble cobalt salt used in step 1) is 95:34:(0.01~3).

3. A method for preparing a Co-C3N4 photocatalyst according to claim 1 or 2, characterized in that: The soluble cobalt salt is one or more of cobalt acetate, cobalt nitrate, cobalt chloride or cobalt sulfate.

4. The method for preparing a Co-C3N4 photocatalyst according to claim 1, characterized in that: Step 1) The temperature of the hydrothermal reaction is 120-200°C and the time is 12-32 h.

5. The method for preparing a Co-C3N4 photocatalyst according to claim 1, characterized in that: In step 2), deionized water and anhydrous ethanol are used as washing liquids respectively.

6. The method for preparing a Co-C3N4 photocatalyst according to claim 1, characterized in that: Step 3) The high temperature calcination is carried out in an atmosphere of one or more gases selected from argon, helium or nitrogen, with a calcination temperature of 500-600° C. and a calcination time of 60-360 min.

7. A Co-C3N4 photocatalyst prepared by the method as claimed in claim 1.

8. Use of the Co-C3N4 photocatalyst as claimed in claim 7 in photo-assisted activation of PMS for efficient degradation of ciprofloxacin hydrochloride.

9. The use according to claim 8, characterized in that: The application method is to add the Co-C3N4 photocatalyst into a pollutant solution containing ciprofloxacin hydrochloride, fully mix and adsorb, then add PMS, and then carry out an oxidative degradation reaction under light to achieve efficient degradation of ciprofloxacin hydrochloride.

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