Preparation method of composite photocatalyst

Abstract

The present application relates to a kind of preparation methods of composite photocatalyst, utilize metal load to inhibit photoelectron-hole recombination, and utilize RuO2 To generate hypochlorous acid by precipitation of chlorine ion in water, the characteristics of electron transfer of Pt are cooperated to speed up reaction rate, improve yield.Hypochlorous acid is used to remove nitrogen-containing nutrient substance, to control the growth of algae from source.Chlorine ion realizes circulation, reduces the use of chemical reagent in removal process and the generation of secondary pollution.In addition, the photocatalyst in the present application can realize the control and removal of algae under solar irradiation, greatly saves cost.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a method for preparing a composite photocatalyst. Background Technology

[0002] Eutrophication is a widespread problem in small rivers, lakes, landscape water bodies, and nearshore areas. Eutrophic water bodies provide the material basis for algal blooms, especially nutrients such as nitrogen and phosphorus. Furthermore, the removal and elimination of these nutrients is a long and difficult process, making algae control technology particularly important. Existing algae control and removal methods are mainly divided into three categories: physical, chemical, and biological methods. Current physical methods are costly and uneconomical, and cannot fundamentally solve the stimulating effect of nutrients on algae. Chemical methods involve adding oxidants such as sodium hypochlorite, hydrogen peroxide, and chlorine dioxide, which can easily cause secondary pollution. Biological methods involve planting aquatic plants and releasing algae-eating aquatic animals to inhibit algal growth, but these methods are time-consuming and expensive. Photocatalysis technology is favored due to its low cost and environmental friendliness, and some studies have applied it to the removal of algal blooms. However, conventional photocatalytic materials have wide band gaps, low visible light utilization, and high photogenerated electron-hole recombination rates, limiting their practical application. Furthermore, photocatalysis technology is limited by sunlight, resulting in low algae removal efficiency and its algae control effect has not yet been evaluated. Therefore, how to select a practical photocatalyst and whether its algae control effect exists have become key and challenging issues that urgently need to be addressed. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems of secondary pollution caused by the use of existing algaecides and the low algae removal efficiency of existing photocatalytic technologies, and to provide a method for preparing a composite photocatalyst.

[0004] The specific plan is as follows:

[0005] A method for preparing a composite photocatalyst includes the following steps:

[0006] Step 1: Place melamine into a ceramic crucible, heat it in a muffle furnace, and then cool it to obtain g-C3N4, which is then ground into powder.

[0007] Step 2: Dissolve RuCl3·3H2O in anhydrous ethanol, add g-C3N4 powder to the dissolved RuCl3·3H2O solution and heat and stir, then dry and sinter to obtain RuO2 / g-C3N4;

[0008] Step 3: Dissolve potassium chloroplatinate in hydrochloric acid solution, add RuO2 / g-C3N4, and irradiate with a xenon lamp under nitrogen protection. Wash and vacuum dry the resulting solution to obtain Pt / RuO2 / g-C3N4 photocatalyst.

[0009] Step four: Add the Pt / RuO2 / g-C3N4 photocatalyst described in step three to the AgNO3 solution, perform Ag deposition under xenon lamp irradiation, and then wash and vacuum dry to finally obtain the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst.

[0010] Furthermore, the heating parameters in step one are: temperature 520-600℃, time 4-6h, and heating rate 1-10℃ / min.

[0011] Furthermore, the heating temperature in step two is 50–80°C, and the stirring time is 30–60 min.

[0012] Furthermore, the sintering temperature in step two is 520–600℃, and the sintering time is 1–3 hours.

[0013] Furthermore, the irradiation time in step three is 6 to 10 hours.

[0014] Furthermore, the vacuum drying parameters in step three are: drying temperature 140℃, drying time 10-16h.

[0015] Furthermore, the lighting conditions described in step four are: xenon lamps are used, and the lighting time is 8 hours.

[0016] Furthermore, the vacuum drying parameters in step four are: drying temperature 80℃, drying time 10-16h.

[0017] A composite photocatalyst prepared by the aforementioned method.

[0018] Application of the aforementioned composite photocatalyst in algae control and / or algae removal.

[0019] Beneficial effects:

[0020] 1. This invention utilizes metal loading to suppress photogenerated electron-hole recombination and uses RuO2 to precipitate chloride ions in water to generate hypochlorous acid. This, combined with the electron-transferring properties of Pt, accelerates the reaction rate and increases the yield. Hypochlorous acid is used to remove nitrogenous nutrients, controlling algae growth at its source.

[0021] 2. Chloride ions are recycled, reducing the use of chemical reagents and the generation of secondary pollution during the removal process. Furthermore, this catalyst can control and remove algae under sunlight, significantly saving costs.

[0022] 3. Since sunlight has a certain divergence angle, based on the traditional Fresnel lens, this invention designs a new type of condenser lens and a flow-through device that can operate under sunlight, which has a wide range of applications and no secondary pollution. Attached Figure Description

[0023] To more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0024] Figure 1 This is a schematic diagram of the structure of the novel algae control and removal device based on solar photocatalysis of the present invention; in the figure: 1 is a serrated Fresnel lens; 2 is a first valve; 3 is a water flow device; 4 is a first filter device; 5 is a pump; 6 is a second filter device; 7 is a second valve.

[0025] Figure 2 The image shows the catalytic effect of the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst provided in Example 1 of this invention.

[0026] Figure 3 The image shows the catalytic effect of the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst provided in Example 2 of this invention.

[0027] Figure 4 The image shows the catalytic effect of the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst provided in Example 3 of this invention.

[0028] Figure 5 The image shows the catalytic effect of the Ag / Pt / g-C3N4 composite photocatalyst provided in Comparative Example 1 of this invention. Detailed Implementation

[0029] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.

[0030] Example 1

[0031] Preparation of Ag / Pt / RuO2 / g-C3N4 composite photocatalyst:

[0032] Step one: Melamine is placed in a ceramic crucible and kept at 520°C for 4 hours in a muffle furnace, with a heating rate of 5°C / min. After cooling at room temperature, a yellow product, g-C3N4, is obtained, which is then ground into powder for further use.

[0033] Step 2: Dissolve 0.1g RuCl3·3H2O in 50mL of anhydrous ethanol, then add 3.5g g-C3N4 powder to the solution, stir at 50℃ for 30min, dry and evaporate the resulting solution, and then sinter at 520℃ for 1h to obtain RuO2 / g-C3N4.

[0034] Step 3: Dissolve 0.5g of potassium chloroplatinate in a diluted 10% hydrochloric acid solution, then add RuO2 / g-C3N4 and irradiate with a 40W xenon lamp for 6 hours under nitrogen protection. After washing the resulting solution, dry it in a vacuum drying oven for 10 hours to obtain the Pt / RuO2 / g-C3N4 photocatalyst.

[0035] Step 4: Add 0.1g of Pt / RuO2 / g-C3N4 photocatalyst to 20mL of 0.1M AgNO3 solution, and perform Ag deposition under irradiation with a 40W xenon lamp. Wash the resulting solution three times and dry it in a vacuum drying oven for 10h to finally obtain the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst.

[0036] The catalytic effect of the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst prepared in this embodiment is as follows: Figure 2 As shown, calculate using the formula below:

[0037]

[0038] Among them, C t Ct is the ammonia nitrogen / chlorophyll concentration at time t (mg / L), and C0 is the initial ammonia nitrogen / chlorophyll concentration (mg / L).

[0039] Depend on Figure 2 (a) It can be seen that the ammonia nitrogen content was completely removed after 70 minutes of catalysis; Figure 2 (b) It can be seen that algae were completely removed after 80 minutes of catalysis. The composite photocatalyst was tested for its removal efficiency of ammonia nitrogen and algae within 90 minutes using the optimal loading ratio. The excellent performance achieved by the metal co-loading at this ratio is attributed to the synergistic effect between the three metals, which greatly increases the yield of hypochlorous acid without depleting the concentration of chloride ions in the water.

[0040] The composite photocatalyst is uniformly dispersed in the photocatalytic device under the action of water. The sunlight is significantly enhanced by the action of the Fresnel lens. Under the irradiation of sunlight, the composite photocatalyst enables the chloride ions in seawater to be efficiently converted into active chlorine substances. The active chlorine substances remove ammonia nitrogen in the water while efficiently killing algal cells, thereby achieving the control and removal of algae.

[0041] like Figure 1As shown, 1 is a sawtooth Fresnel lens; 2 is a first valve; 3 is a water flow device; 4 is a first filter device; 5 is a pump; 6 is a second filter device; and 7 is a second valve. The first valve 2 is connected to the first filter device 4; the first filter device 4 and the second filter device 6 are connected through the water flow device 3; the sawtooth Fresnel lens 1 is placed above the water flow device 3; the second filter device 6 is connected to the pump 5, and the second valve 7 is connected to the pump 5.

[0042] Eutrophic water is introduced into the flow-through device 3 through the first valve 2 for direct photocatalytic degradation. In this area, the water and catalyst are fully mixed. Considering the scattering angle of sunlight and the shortcomings of insufficient sunlight intensity with seasonal changes, a serrated Fresnel lens 1 is installed above the flow-through device 3. This device is an optimization of the traditional Fresnel lens, with the addition of a serrated arc to maximize the focusing effect of sunlight, effectively improving the removal of nitrogenous substances and the killing of algae cells. Through the combined action of photocatalyst and sunlight, ammonia nitrogen and total nitrogen in the water are removed and algae are killed. At the inlet and outlet of the flow-through device 3, a second filter device 6 is used to intercept the particles. This device consists of a nanomembrane and filter components, which can effectively intercept nano-sized particles.

[0043] Example 2

[0044] Preparation of Ag / Pt / RuO2 / g-C3N4 composite photocatalyst:

[0045] Step one: Place melamine in a ceramic crucible and maintain it at 560°C for 5 hours in a muffle furnace, with a heating rate of 5°C / min. After cooling at room temperature, a yellow product, g-C3N4, is obtained, which is then ground into powder for further use.

[0046] Step 2: Dissolve 0.1g RuCl3·3H2O in 50mL of anhydrous ethanol, add 3.5g g-C3N4 powder to the solution, stir at 60℃ for 40min, dry and evaporate the resulting solution, and then sinter at 540℃ for 2h to obtain RuO2 / g-C3N4.

[0047] Step 3: Dissolve 0.2g of potassium chloroplatinate in a diluted 10% hydrochloric acid solution, then add RuO2 / g-C3N4 and irradiate with a 40W xenon lamp for 8 hours under nitrogen protection. After washing the resulting solution, dry it in a vacuum drying oven for 14 hours to obtain the Pt / RuO2 / g-C3N4 photocatalyst.

[0048] Step 4: Add 0.1g of Pt / RuO2 / g-C3N4 photocatalyst to 20mL of 0.1M AgNO3 solution, and perform Ag deposition under xenon lamp irradiation. Wash the resulting solution three times and dry it in a vacuum drying oven for 14h to finally obtain the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst.

[0049] The catalytic effect of the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst prepared in this embodiment is as follows: Figure 3 As shown, the calculation method is the same as in Example 1. (From...) Figure 3 (a) It can be seen that the ammonia nitrogen content was completely removed after 90 min of catalysis; from Figure 3 (b) It can be seen that algae were not completely removed after 90 min of catalysis. This composite photocatalyst altered the potassium chloroplatinate content, further reducing the Pt loading. The effect of Pt loading on ammonia nitrogen and algae killing was investigated here. It can be concluded that reducing the Pt loading simultaneously decreased both ammonia nitrogen removal and algae killing.

[0050] Using the apparatus in Example 1, eutrophic water is introduced into the photocatalytic degradation zone 3 of the photocatalytic reactor for direct photocatalytic degradation. The combined action of the photocatalyst and sunlight removes ammonia nitrogen and total nitrogen from the water and kills algae.

[0051] Example 3

[0052] Preparation of Ag / Pt / RuO2 / g-C3N4 composite photocatalyst:

[0053] Step one: Melamine is placed in a ceramic crucible and kept at 600℃ for 6 hours in a muffle furnace, with a heating rate of 5℃ / min. After cooling at room temperature, a yellow product, g-C3N4, is obtained, which is then ground into powder for further use.

[0054] Step 2: Dissolve 0.1g RuCl3·3H2O in 50mL of anhydrous ethanol, add 3.5g g-C3N4 powder to the solution, stir at 60℃ for 40min, dry and evaporate the resulting solution, and then sinter at 600℃ for 3h to obtain RuO2 / g-C3N4.

[0055] Step 3: Dissolve 0.5g of potassium chloroplatinate in a diluted 10% hydrochloric acid solution, then add RuO2 / g-C3N4 and irradiate with a xenon lamp for 10h under nitrogen protection. After washing the resulting solution, dry it in a vacuum drying oven for 16h to obtain the Pt / RuO2 / g-C3N4 photocatalyst.

[0056] Step 4: Add 0.1g of Pt / RuO2 / g-C3N4 photocatalyst to 20mL of 0.5M AgNO3 solution, and perform Ag deposition under irradiation with a 40W xenon lamp. Wash the resulting solution three times and dry it in a vacuum drying oven for 16h to finally obtain the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst.

[0057] The catalytic effect of the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst prepared in this embodiment is as follows: Figure 4 As shown, the calculation method is the same as in Example 1. (From...) Figure 4 (a) It can be seen that the ammonia nitrogen content was completely removed after 70 minutes of catalysis; Figure 4 (b) It can be seen that algae were completely removed after 60 min of catalysis. The composite photocatalyst increased the Ag loading, and the effect of Ag loading on ammonia nitrogen removal and algae killing was investigated. The ammonia nitrogen removal effect did not change significantly, while the algae killing effect was significantly improved, which confirms the excellent effect of Ag as a natural algaecide in the device within the composite catalyst.

[0058] Using the apparatus in Example 1, eutrophic water is introduced into the photocatalytic degradation zone 3 of the photocatalytic reactor for direct photocatalytic degradation. The combined action of the photocatalyst and sunlight removes ammonia nitrogen and total nitrogen from the water and kills algae.

[0059] Comparative Example 1

[0060] Preparation of Ag / Pt / g-C3N4 composite photocatalyst:

[0061] Step one: Melamine is placed in a ceramic crucible and kept at 520°C for 4 hours in a muffle furnace, with a heating rate of 5°C / min. After cooling at room temperature, a yellow product, g-C3N4, is obtained, which is then ground into powder for further use.

[0062] Step 2: Dissolve 0.5g of potassium chloroplatinate in a diluted 10% hydrochloric acid solution, then add g-C3N4 and irradiate with a xenon lamp for 6 hours under nitrogen protection. After washing the resulting solution, dry it in a vacuum drying oven for 10 hours to obtain the Pt / g-C3N4 photocatalyst.

[0063] Step 3: Add 0.1g of Pt / g-C3N4 photocatalyst to 20mL of 0.1M AgNO3 solution, and perform Ag deposition under irradiation with a 40W xenon lamp. Wash the resulting solution three times and dry it in a vacuum drying oven for 10h to finally obtain the Ag / Pt / g-C3N4 composite photocatalyst.

[0064] The catalytic effect of the Ag / Pt / g-C3N4 composite photocatalyst prepared in this comparative example is as follows: Figure 5As shown, the calculation method is the same as in Example 1. (From...) Figure 5 (a) It can be seen that after 90 min of catalysis, the ammonia nitrogen content was only reduced by 0.6; from Figure 5 (b) It can be seen that after 90 min of catalysis, the algae content was only reduced by 0.5%.

[0065] The effects of single-metal Pt loading on ammonia nitrogen removal and algae control were investigated in this composite photocatalyst. Pt loading not only improved the transfer of photogenerated electrons and holes, but also, due to its chlorine evolution properties, it could convert chloride ions in seawater into active chlorine substances to a certain extent, thus achieving ammonia nitrogen removal and algae control. However, the yield of active chlorine substances was far less than that of RuO2 and Pt simultaneously. Therefore, the effect of single loading was far inferior to that of co-composite loading.

[0066] Using the apparatus in Example 1, eutrophic water is introduced into the photocatalytic degradation zone 3 of the photocatalytic reactor for direct photocatalytic degradation. The combined action of the photocatalyst and sunlight removes ammonia nitrogen and total nitrogen from the water and kills algae.

[0067] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0068] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0069] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a composite photocatalyst, characterized in that: Includes the following steps: Step 1: Place melamine into a ceramic crucible, heat it in a muffle furnace, and then cool it to obtain g-C3N4, which is then ground into powder. Step 2: Dissolve RuCl3·3H2O in anhydrous ethanol, add g-C3N4 powder to the dissolved RuCl3·3H2O solution and heat and stir, then dry and sinter to obtain RuO2 / g-C3N4; Step 3: Dissolve potassium chloroplatinate in hydrochloric acid solution, add RuO2 / g-C3N4, and irradiate with a xenon lamp under nitrogen protection. Wash and vacuum dry the resulting solution to obtain Pt / RuO2 / g-C3N4 photocatalyst. Step four: Add the Pt / RuO2 / g-C3N4 photocatalyst described in step three to the AgNO3 solution, perform Ag deposition under xenon lamp irradiation, and then wash and vacuum dry to finally obtain the Ag / Pt / RuO2 / g-C3N4 composite photocatalyst.

2. The method for preparing a composite photocatalyst according to claim 1, characterized in that: The heating parameters in step one are: temperature 520-600℃, time 4-6h, and heating rate 1-10℃ / min.

3. The method for preparing a composite photocatalyst according to claim 1, characterized in that: The heating temperature in step two is 50–80°C, and the stirring time is 30–60 min.

4. The method for preparing a composite photocatalyst according to claim 1, characterized in that: The sintering temperature in step two is 520–600℃, and the sintering time is 1–3 hours.

5. The method for preparing a composite photocatalyst according to claim 1, characterized in that: The irradiation time in step three is 6 to 10 hours.

6. The method for preparing a composite photocatalyst according to claim 1, characterized in that: The vacuum drying parameters in step three are: drying temperature 140℃, drying time 10-16h.

7. The method for preparing a composite photocatalyst according to claim 1, characterized in that: The lighting conditions described in step four are: xenon lamps are used, and the lighting time is 8 hours.

8. The method for preparing a composite photocatalyst according to claim 1, characterized in that: The vacuum drying parameters in step four are: drying temperature 80℃, drying time 10-16h.

9. A composite photocatalyst prepared by the method of any one of claims 1-8.

10. The application of the composite photocatalyst as described in claim 9 in algae control and / or algae removal.

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