Composite doped photocatalyst and application thereof in degrading and removing methyl mercaptan

Abstract

The invention discloses a composite doped catalyst and a preparation method thereof, and an application of the composite doped catalyst in degrading and removing a harmful pollutant methyl mercaptan under an illumination condition. The composite doped catalyst is specifically a TiO2 catalyst co-doped with Si and W. The composite doped photocatalyst is immobilized on flaky fiber cotton, methyl mercaptan can be completely degraded within a short time under ultraviolet irradiation, and the composite doped photocatalyst is proved to have good stability through multiple cyclic experiments. Therefore, the composite photocatalyst can be applied to various environments in which stink and harmful pollutants need to be removed, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic removal technology, specifically relating to a composite doped photocatalyst and its preparation, as well as its application in removing malodorous pollutants such as methanethiol under light irradiation. Background Technology

[0002] Methanethiol is a typical sulfur-containing organic odorous gaseous pollutant, a gas with a smell of rotting cabbage. Its sources are widespread, mainly encompassing natural processes such as the decay of plants and animals, as well as production and municipal activities such as papermaking, petroleum refining, and wastewater treatment. Methanethiol is significantly harmful to human health, even at concentrations as low as 0.2 ppm (corresponding to a concentration of 0.3 mg / m³). 3 In environments with high concentrations of methanethiol, it can cause unbearable discomfort. Therefore, research on the efficient degradation of low-concentration methanethiol is of great significance.

[0003] The main technologies for degrading methanethiol include physical adsorption, alkaline absorption oxidation, and biological deodorization, but these traditional methods all have certain limitations. In contrast, solar photocatalysis technology for degrading gaseous pollutants has significant advantages such as mild reaction conditions, simple operation, direct utilization of solar energy, and no secondary pollution, thus attracting widespread attention from academia and industry. Among photocatalytic materials, TiO2 has become the most widely studied photocatalyst due to its high photoactivity, low cost, low toxicity, and excellent chemical and thermal stability. Modifying TiO2 by introducing composite oxides to improve its efficiency in degrading pollutants has become one of the current research hotspots in the field of photocatalysis. Summary of the Invention

[0004] The purpose of this invention is to provide a composite doped photocatalyst that has a good removal effect on the harmful pollutant methanethiol, and thus has broad practical and economic value.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A composite doped photocatalyst is prepared by adding TiO2 powder to deionized water and stirring until it is uniformly dispersed. Then, silicon source and tungsten source are added, and the suspension is heated and stirred in a water bath until it is completely dried. After vacuum drying, it is ground into powder and calcined to obtain Si-W / TiO2 composite photocatalyst.

[0006] Furthermore, the silicon source is silicon tetrachloride, tetraethyl orthosilicate, or silicon powder.

[0007] Furthermore, the tungsten source is ammonium paratungstate or ammonium metatungstate.

[0008] Furthermore, the amount of the tungsten source used is approximately 5% of the mass of the TiO2 powder.

[0009] Furthermore, the molar ratio of the silicon source to the tungsten source used is (1-4):1.

[0010] Furthermore, the water bath heating temperature is 60-80℃.

[0011] Furthermore, the vacuum drying temperature is 80-100℃, and the time is 12-24h.

[0012] Furthermore, the calcination temperature is 300-600℃, and the time is 4-8 hours.

[0013] The composite doped photocatalyst can be used to remove harmful pollutants, especially methanethiol.

[0014] Furthermore, its application method involves immobilizing the composite doped photocatalyst on sheet-like porous fiber cotton, which is then used for the efficient removal of methanethiol under light irradiation.

[0015] Furthermore, the immobilization involves mixing the composite-doped photocatalyst with titanium sol at a ratio of 1g:200mL to form a suspension, then placing it in a high-pressure spray gun and spraying at approximately 1mL / cm². 2 The amount of material is evenly sprayed onto the surface of the sheet-like porous fiber cotton. Then, the sprayed fiber cotton is placed in a muffle furnace and heated to 300-600℃ at a heating rate of 2-5℃ / min, and kept at that temperature for 6-8 hours.

[0016] Furthermore, the light source used during illumination is ultraviolet light.

[0017] The fiber cotton and photocatalyst exhibit excellent adhesion, large specific surface area, and high light transmittance. This invention, by curing a composite-doped photocatalyst onto the fiber cotton, enables the removal of harmful pollutants such as methanethiol using ultraviolet light irradiation. This invention provides mild and stable pollutant removal conditions, eliminates the need for high temperature and pressure, and utilizes low-cost curing materials for the catalyst, thus possessing broad practical and economic value.

[0018] The advantages of this invention are: 1) The composite doped photocatalyst obtained by this invention has good photocatalytic performance, which is both efficient and stable and green and pollution-free; 2) This invention can completely remove harmful methanethiol contaminants in a short time; 3) This invention uses ultraviolet light for photocatalysis, resulting in low reaction cost and simple, mild reaction conditions; 4) The catalytic material of this invention has a simple manufacturing process and is easy to operate, and has broad application prospects. Attached Figure Description

[0019] Figure 1The image shows a SEM image of the Si-W / TiO2 photocatalyst prepared in Example 1.

[0020] Figure 2 The image shows the XRD pattern of the Si-W / TiO2 photocatalyst prepared in Example 1.

[0021] Figure 3 The image shows the DRS diagram of the Si-W / TiO2 photocatalyst prepared in Example 1.

[0022] Figure 4 The image shows the BET plot of the Si-W / TiO2 photocatalyst prepared in Example 1.

[0023] Figure 5 The graph shows a comparison of the degradation effects of photocatalysts prepared at different calcination temperatures in Examples 1-4 on 6 ppm methanethiol.

[0024] Figure 6 The graph shows a comparison of the degradation effects of photocatalysts prepared in Examples 1, 5-7 with different silicon-tungsten molar ratios on 6 ppm methanethiol.

[0025] Figure 7 This is a comparison chart showing the degradation effect of the photocatalysts prepared in Example 1 and the comparative example on 6 ppm methanethiol. Detailed Implementation

[0026] A composite doped photocatalyst, the preparation of which includes the following steps: 1) Preparation of TiO2: TiO2 was prepared by sol-gel method using organic titanium source as precursor, and then ground to obtain TiO2 powder; 2) Preparation of composite photocatalyst: The obtained TiO2 powder was added to deionized water and stirred until uniformly dispersed. Then, silicon source and tungsten source were added (the molar ratio of the two was 1-4:1, and the amount of tungsten source was 5% of the mass of TiO2 powder). The mixture was stirred under water bath heating at 60-80℃ until the suspension was completely dry. Then, it was placed under vacuum drying at 80-100℃ for 12-24h. After being ground into powder, it was calcined at 300-600℃ for 4-8h (heating rate was 2-10℃ / min) to obtain Si-W / TiO2 composite photocatalyst.

[0027] The organic titanium source is isopropyl titanate. The silicon source is silicon tetrachloride, tetraethyl orthosilicate, or silicon powder. The tungsten source is ammonium paratungstate or ammonium metatungstate.

[0028] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0030] Example 1 The specific steps for preparing a composite-doped photocatalyst are as follows: (1) First, 20 mL of anhydrous ethanol and 1 mL of isopropyl titanate were mixed to obtain solution A; 8 mL of deionized water, 9 mL of anhydrous ethanol and 3 mL of glacial acetic acid were stirred and mixed to obtain solution B. Solution B was cooled to 0 °C under stirring, and then solution A was slowly added dropwise. Stirring was continued until a sol was formed. Stirring was continued for 12 h. The resulting gel was then vacuum dried overnight at 80 °C. The dried sample was then ground to obtain TiO2 powder. (2) Weigh 1g of the TiO2 powder prepared above and add it to deionized water. Stir it evenly in a magnetic stirrer, and then add 0.055g of (NH4). 10 H2(W2O7)6 and 0.1099g SiCl4 (Si / W=3) were mixed and heated and stirred in a water bath until the suspension was completely dried. The suspension was then vacuum dried overnight and ground into powder. The powder was then calcined in a muffle furnace at 500℃ for 4h (heating rate 2℃ / min) to prepare the Si-W / TiO2 composite doped photocatalyst.

[0031] The obtained Si-W / TiO2 composite doped photocatalyst was tested by SEM, and the results are shown in the figure. Figure 1 .Depend on Figure 1 As can be seen, the obtained composite doped catalyst consists of irregular spherical particles.

[0032] The obtained Si-W / TiO2 composite doped photocatalyst was subjected to XRD analysis, and the results are shown in the figure. Figure 2 . Figure 2 The results show that TiO2 in the Si-W / TiO2 composite doped photocatalyst is mainly anatase phase with a small proportion of rutile phase, indicating that the photocatalyst has the best degradation effect under a certain crystal phase ratio.

[0033] DRS tests were performed on the obtained Si-W / TiO2 composite doped photocatalyst, and the results are shown in the figure. Figure 3 .Depend on Figure 3 It is evident that the Si-W / TiO2 composite doped photocatalyst mainly absorbs in the ultraviolet region, and the absorption peak is strong. Therefore, using an ultraviolet lamp as the light source for degradation can achieve the best results.

[0034] The obtained Si-W / TiO2 composite doped photocatalyst was subjected to BET testing, and the results are shown in the figure. Figure 4 .Depend on Figure 4This indicates that the obtained Si-W / TiO2 composite doped photocatalyst is mainly mesoporous with abundant pores and a large specific surface area, which means that it has more surface active sites and thus has stronger pollutant adsorption and activation performance.

[0035] Example 2 Change the calcination temperature in step (2) to 400℃, and perform the other operations as in Example 1.

[0036] Example 3 Change the calcination temperature in step (2) to 500℃, and perform the other operations as in Example 1.

[0037] Example 4 Change the calcination temperature in step (2) to 600℃, and perform the other operations as in Example 1.

[0038] Example 5 Add 0.055g of (NH4) in step (2). 10 H2(W2O7)6 and 0.366g SiCl4 (Si / W=1), other operations are the same as in Example 1.

[0039] Example 6 Add 0.055g of (NH4) in step (2). 10 H2(W2O7)6 and 0.0733g SiCl4 (Si / W=2), other operations are the same as in Example 1.

[0040] Example 7 Add 0.055g of (NH4) in step (2). 10 H2(W2O7)6 and 0.1466g SiCl4 (Si / W=4), other operations are the same as in Example 1.

[0041] Comparative Example 1 In step (2), only 0.055g of (NH4) is added. 10 H2(W2O7)6, and other operations are the same as in Example 1, to obtain the W / TiO2 photocatalyst.

[0042] Comparative Example 2 In step (2), only 0.1g of SiCl4 was added, and the other operations were the same as in Example 1, to obtain the Si / TiO2 photocatalyst.

[0043] Application Examples The composite doped photocatalysts prepared in the examples and comparative examples were used to remove methanethiol, a malodorous pollutant, under light irradiation. The operation was as follows: (1) Take 2g of composite doped photocatalyst and mix it with 400mL of titanium sol. Place the resulting suspension in a high-pressure spray gun and spray it evenly on the surface of sheet-like flexible porous fiber cotton (27cm×15cm). Then place the sprayed flexible porous fiber cotton in a muffle furnace and heat it to 400℃ at a rate of 2℃ / min. Keep it at the temperature for 6h to obtain the cured sheet-like fiber cotton. (2) Place the obtained cured sheet fiber cotton in a photocatalytic reactor containing an ultraviolet lamp tube. The photocatalytic reactor is placed in a sealed environment test chamber. Turn on the constant temperature and humidity function of the sealed environment test chamber to keep the temperature and humidity constant at room temperature 25℃ (±1℃) and humidity 50% (±2%). After the temperature and humidity stabilize, open the air inlet valve of the sealed environment test chamber, open the pressure reducing valve of the standard pollutant cylinder, and introduce methanethiol. After the concentration shown by the pollutant concentration detector stabilizes for 30 minutes without change (<5%), stop the introduction of methanethiol, turn on the photocatalytic reactor, and start the pollutant removal test.

[0044] (3) When the detector reading drops to zero, record the test time, turn off the photocatalytic reactor, and the pollutant removal test process ends.

[0045] Figure 5 A comparison of the effects of photocatalysts prepared at different calcination temperatures on the degradation of methanethiol. (See figure.) Figure 1 As shown, Si-W / TiO2 prepared by calcination at 500℃ exhibits the best photocatalytic degradation activity for methanethiol, completing degradation in just 87 minutes with a conversion rate of 99.9%. However, when the calcination temperature is increased to 600℃, it takes 186 minutes to complete the degradation of methanethiol.

[0046] Figure 6 A comparison of the effects of photocatalysts prepared with different silicon-tungsten molar ratios on the degradation of methanethiol. (See figure.) Figure 2 As shown, the tungsten-silicon molar ratio of 1:3 exhibits the best photocatalytic degradation activity for methanethiol, which can be degraded in 87 minutes and has a degradation conversion rate of 99.9%.

[0047] Figure 7 A comparison of the effects of photocatalysts prepared with different doping components on the degradation of methanethiol. (See figure.) Figure 3 As shown, the composite doped photocatalyst Si-W / TiO2 exhibits the best photocatalytic degradation activity for methanethiol. Under the same conditions, Si-W / TiO2 can complete the degradation in only 87 minutes, achieving a conversion rate of 99.9% for methanethiol, while W-TiO2 requires 120 minutes to complete the degradation and Si-TiO2 requires 120 minutes to achieve a conversion rate of 83.4%.

[0048] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a composite-doped photocatalyst, characterized in that: TiO2 powder was added to deionized water and stirred until it was evenly dispersed. Then, tungsten source and silicon source were added, and the suspension was heated and stirred in a water bath until it was completely dried. The powder was then ground into powder and calcined to obtain Si-W / TiO2 composite photocatalyst.

2. The method for preparing the composite doped photocatalyst according to claim 1, characterized in that: The amount of tungsten source used is 5% of the mass of TiO2 powder.

3. The method for preparing the composite doped photocatalyst according to claim 1, characterized in that: The molar ratio of silicon source to tungsten source used is (1-4):

1.

4. The method for preparing the composite doped photocatalyst according to claim 1 or 3, characterized in that: The silicon source is silicon tetrachloride, tetraethyl orthosilicate, or silicon powder.

5. The method for preparing the composite doped photocatalyst according to claim 1 or 3, characterized in that: The tungsten source is ammonium paratungstate or ammonium metatungstate.

6. The method for preparing the composite doped photocatalyst according to claim 1, characterized in that: The water bath heating temperature is 60-80℃.

7. The method for preparing the composite doped photocatalyst according to claim 1, characterized in that: The calcination temperature is 300-600℃, and the time is 4-8 hours.

8. A composite doped photocatalyst prepared by the method described in any one of claims 1-7.

9. The application of the composite doped photocatalyst as described in claim 8 in the removal of harmful pollutants, characterized in that: The composite doped photocatalyst is immobilized on sheet-like porous fiber cotton and used to efficiently remove malodorous pollutant methanethiol under light conditions.

10. The application according to claim 9, characterized in that: The light source used during illumination is ultraviolet light.

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