CN115805067A - A photocatalyst for efficiently degrading toluene and its preparation method - Google Patents

Abstract

The invention discloses a photocatalyst for efficiently degrading methylbenzene and a preparation method thereof, wherein titanium isopropoxide is used as a titanium source, titanium dioxide is prepared through hydrothermal hydrolysis, the obtained titanium dioxide is dispersed in ethylene glycol, bismuth nitrate is added, the reaction is carried out for a period of time at a certain temperature, and metal bismuth is slowly reduced on the surface of the titanium dioxide, so that Bi/TiO is obtained ₂ A photocatalyst. The preparation method disclosed by the invention is simple to operate, wide in raw material source, low in cost, green and environment-friendly, has higher inspiration on the research of non-noble metal cocatalyst, and has great practical significance in the field of industrial photocatalytic treatment of VOCs.

Description

A photocatalyst for efficiently degrading toluene and its preparation method

technical field

The invention belongs to the technical field of photocatalytic materials, and in particular relates to a photocatalyst for efficiently degrading toluene and a preparation method thereof.

Background technique

Toluene is a common volatile organic compound (VOCs), which seriously threatens human health and the ecological environment. According to the survey, long-term exposure to high concentrations of volatile organic compounds can easily lead to various diseases such as childhood sluggishness and juvenile leukemia, respiratory damage, etc. Long-term exposure to low concentrations of volatile organic compounds can also lead to various neurasthenia and cardiovascular diseases. In addition, VOCs and NO _x will undergo chemical reactions under the irradiation of sunlight to form photochemical smog and urban haze weather, which seriously affects the environment and climate. Common VOCs treatment technologies include biodegradation, plasma technology, adsorption, catalytic combustion, and photocatalysis, among which photocatalytic oxidation technology (PCO) is considered to be a treatment technology with a good research background at present. PCO can degrade harmful gases into CO ₂ and H ₂ O at normal temperature and pressure, and it has low cost, simple operation, wide application range and less secondary pollution.

Due to its good stability, non-toxic and harmless, and simple preparation methods, TiO ₂ is widely used in photocatalytic degradation. However, the degradation effect of pure TiO ₂ is average, and it needs to be modified. Among many modification methods, metal modification is a method that can effectively improve the degradation frequency of VOCs. Among them, although precious metals exhibit better performance, their industrial application is limited due to their high cost and low reserves. Therefore, exploring a non-precious metal modified TiO ₂ that can be comparable to noble metals has attracted more attention of researchers.

Contents of the invention

Aiming at the prior art, the present invention provides a Bi/ _TiO2 photocatalyst and preparation method thereof for efficiently degrading toluene, which can photocatalytically degrade trace amounts of toluene in the air under ultraviolet light, and its degradation rate and mineralization rate are high, It has good stability and is environmentally friendly. Compared with precious metals, bismuth metal has low cost and abundant reserves, and can be produced and applied on a large scale.

In order to achieve the above object, the present invention adopts the following technical solutions:

A photocatalyst for efficiently degrading toluene, the preparation method of which comprises the following steps:

1) Preparation of TiO ₂ by hydrothermal method: add a certain amount of titanium isopropoxide to sulfuric acid solution, stir well and then transfer it to a polytetrafluoroethylene reactor, react hydrothermally at a certain temperature for a period of time, and wait for it to cool to room temperature Finally, the obtained product is centrifuged, washed and dried to obtain TiO ₂ ;

2) Preparation of Bi/TiO ₂ photocatalytic material: add nitric acid solution to a certain amount of ethylene glycol to obtain a colorless and transparent solution, then add a certain amount of bismuth nitrate solution, stir at room temperature for 15 minutes, and then add a certain amount of mass step 1) The obtained TiO ₂ was stirred at room temperature for 1 hour to disperse it evenly, and then the obtained mixed solution was transferred to a reaction kettle, and hydrothermally reacted at a certain temperature for a certain period of time. After it was cooled to room temperature, the obtained precipitate was centrifuged with ethanol and water respectively. After washing and drying, a Bi/TiO ₂ photocatalyst for efficiently degrading toluene is finally obtained.

Further, the volume ratio of titanium isopropoxide to sulfuric acid solution used in step 1) is 1:50, and the concentration of the sulfuric acid solution is 2mol/L.

Further, the temperature of the hydrothermal reaction in step 1) is 160° C., and the time is 12 hours.

Further, the volume ratio of the nitric acid solution used in step 2) to ethylene glycol is 1:50, and the concentration of the nitric acid solution is 1mol/L.

Further, the amount of bismuth nitrate solution in step 2) is calculated as 0.5wt%~5wt% of Bi per 500mg of TiO ₂ , and the concentration of the bismuth nitrate solution is 3.45mg/mL.

Further, the temperature of the hydrothermal reaction in step 2) is 160° C., and the hydrothermal time is 24 hours.

The advantages of the present invention are:

(1) Bismuth belongs to a semimetal, and as a cocatalyst, it can effectively promote the separation of photogenerated electrons and holes, and improve the separation efficiency of photogenerated electrons. Under the irradiation of ultraviolet light, the Bi/ _TiO2 photocatalyst prepared by the invention can effectively degrade toluene gas, realize high degradation rate and high mineralization rate, and is suitable for being widely used in the field of photocatalytic degradation of VOCs.

(2) The preparation conditions of the present invention are mild, the operation is simple, the material is stable and environmentally friendly, and compared with precious metals, metal bismuth is cheap and abundant in storage, making industrial mass production possible.

Description of drawings

Fig. 1 is the XRD figure of the Bi/TiO ₂ photocatalyst that embodiment prepares.

Fig. 2 is the DRS diagram of the Bi/TiO ₂ photocatalyst prepared in the embodiment.

Fig. 3 is the SEM image of the TiO ₂ and Bi/TiO ₂ photocatalysts prepared in Example 1.

Fig. 4 is the EDS spectrum diagram of the Bi/TiO ₂ photocatalyst prepared in embodiment 1.

Fig. 5 is a schematic diagram of an experimental device for photocatalytic degradation of toluene gas.

Fig. 6 is a comparison diagram of the photocatalytic degradation of toluene by the Bi/ _TiO2 photocatalyst prepared in the embodiment.

Detailed ways

A photocatalyst for efficiently degrading toluene, the preparation method of which comprises the following steps:

1) Preparation of TiO ₂ by hydrothermal method: Add titanium isopropoxide to 2mol/L sulfuric acid solution at a volume ratio of 1:50, stir well and transfer to a polytetrafluoroethylene reactor, and react in a 160°C oven for 12 hours by hydrothermal reaction , after it is cooled to room temperature, the obtained product is centrifuged, washed and dried to obtain TiO ₂ ;

2) Preparation of Bi/TiO ₂ photocatalytic material: Add 1mol/L nitric acid solution to ethylene glycol at a volume ratio of 1:50 to obtain a colorless and transparent solution, then add a certain amount of bismuth nitrate solution, and stir at room temperature for 15 minutes. Then add a certain amount of TiO ₂ obtained in step 1), stir at room temperature for 1 hour to disperse evenly, then transfer to a reaction kettle, and conduct a hydrothermal reaction in an oven at 160°C for 24 hours. and water centrifugal washing, drying, to obtain Bi/TiO ₂ photocatalyst.

Wherein, the amount of bismuth nitrate solution in step 2) is calculated as 0.5wt%~5wt% of Bi per 500mg TiO ₂ , and the concentration of the bismuth nitrate solution is 3.45mg/mL.

In order to make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

Example 1

A photocatalyst for efficiently degrading toluene, the preparation method of which comprises the following steps:

1) Preparation of TiO ₂ by hydrothermal method: add 1.5mL titanium isopropoxide to 75mL, 2mol/L sulfuric acid solution, stir thoroughly for 30min, transfer to a polytetrafluoroethylene reactor, and react hydrothermally in an oven at 160°C for 12h , after it is cooled to room temperature, the obtained product is centrifuged, washed and dried to obtain TiO ₂ ;

2) Preparation of Bi/ _TiO2 photocatalytic material: Add 1mL, 1mol/L nitric acid solution to 50mL ethylene glycol to obtain a colorless and transparent solution, then add 1449μL, 3.45mg/mL bismuth nitrate solution, and stir at room temperature for 15min , and then add 500mg of TiO ₂ obtained in step 1), stir at room temperature for 1h to disperse evenly, then transfer to a reaction kettle, and conduct a hydrothermal reaction in a 160°C oven for 24h. Ethanol and water centrifugal washing, drying, to obtain 1% Bi/TiO ₂ photocatalyst.

Example 2

The operation was basically the same as in Example 1, except that 724.5 μL, 3.45 mg/mL bismuth nitrate solution was added to prepare a 0.5% Bi/TiO ₂ photocatalyst.

Example 3

The operation was basically the same as in Example 1, except that 4374 μL, 3.45 mg/mL bismuth nitrate solution was added to prepare a 3% Bi/TiO ₂ photocatalyst.

Example 4

The operation was basically the same as in Example 1, except that 7245 μL, 3.45 mg/mL bismuth nitrate solution was added to prepare a 5% Bi/TiO ₂ photocatalyst.

Example 5

TiO ₂ was prepared according to step 1) of Example 1.

1. Characterization method of physical properties of Bi/TiO ₂ photocatalyst: X-ray powder diffractometer (XRD) was used to analyze the material composition and structure, and ultraviolet-visible diffuse reflectometer (DRS) was used to analyze the light absorption performance of photocatalytic materials. The morphology of the product was observed by field emission scanning electron microscope (FESEM).

Fig. 1 is the XRD diagram of the Bi/TiO ₂ photocatalyst prepared in the embodiment, which proves that the present invention successfully prepares the titanium dioxide photocatalyst supported by metal bismuth.

Fig. 2 is the DRS diagram of the Bi/TiO ₂ photocatalyst prepared in the example, which shows that metal bismuth modification can enhance the light absorption of the catalyst.

Figure 3 is the SEM image of the _TiO2 and Bi/ _TiO2 photocatalysts prepared in Example 1. It can be seen from the figure that there is no obvious change in the morphology of the two due to the small content of the supported metal Bi.

Figure 4 is the EDS energy spectrum of the Bi/ _TiO2 photocatalyst prepared in Example 1. It can be seen from this figure that there are Ti, O and a very small amount of Bi elements in the material, which further proves the successful loading of metal bismuth.

2. The photocatalytic performance of Bi/TiO ₂ photocatalyst was tested by degrading toluene gas under ultraviolet light irradiation. The experimental device diagram is shown in Figure 5, which consists of a quartz glass tube, four ultraviolet lamps (254nm), a flow meter, and a cylinder of toluene gas (300ppm, air as a mixed gas) connected. During the test, 100mg of catalyst mixed with 0.75g of silica (60-80 mesh) was put into a quartz reaction tube, and the flow rate of toluene was set to 10 mL/min, and the humidity was 80%RH. Sweep to control the temperature. Before lighting, balance in the dark for 10 hours, and then turn on the UV lamp for corresponding tests. Toluene and generated carbon dioxide were sampled and analyzed every 1 h by online chromatography, and the results are shown in Figure 6.

It can be seen from Figure 6 that when titanium dioxide photocatalysts loaded with different proportions of metal bismuth are used for toluene degradation, 1wt%Bi/ _TiO2 performs best, and its toluene degradation rate can reach 80%. When the bismuth loading exceeds 1%, with The photocatalytic degradation efficiency of toluene decreased gradually with the increase of the loading amount. It can be seen that the effective photocatalytic degradation of toluene gas can be achieved when the appropriate metal bismuth supports titanium dioxide.

The above descriptions are only 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 (7)

1. A preparation method of a photocatalyst for efficiently degrading toluene is characterized by comprising the following steps: the method comprises the following steps:

1) Hydrothermal method for preparing TiO ₂ : adding a certain amount of titanium isopropoxide into a sulfuric acid solution, fully stirring, transferring into a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction for a period of time at a certain temperature, cooling to room temperature, centrifuging, washing and drying the obtained product to obtain TiO ₂ ；

2）Bi/TiO ₂ Preparation of photocatalytic material: adding a nitric acid solution into a certain amount of ethylene glycol to obtain a colorless transparent solution, then adding a certain amount of bismuth nitrate solution, stirring for 15min at room temperature, and then adding a certain amount of TiO obtained in the step 1) ₂ Stirring at room temperature for 1 hr to disperse uniformly, transferring the obtained mixed solution into a reaction kettle, performing hydrothermal reaction at certain temperature for certain time, cooling to room temperature, and respectively adding ethanol and ethanol into the obtained precipitateCentrifugally washing and drying the water to finally obtain Bi/TiO for efficiently degrading the toluene ₂ A photocatalyst.

2. The method for preparing the photocatalyst for efficiently degrading toluene according to claim 1, wherein the photocatalyst comprises: the volume ratio of the titanium isopropoxide used in the step 1) to the sulfuric acid solution is 1.

3. The method for preparing the photocatalyst for efficiently degrading toluene according to claim 1, wherein the photocatalyst comprises: the temperature of the hydrothermal reaction in the step 1) is 160 ℃, and the time is 12h.

4. The method for preparing the photocatalyst for efficiently degrading toluene according to claim 1, wherein the photocatalyst comprises: the volume ratio of the nitric acid solution to the ethylene glycol used in the step 2) is 1.

5. The method for preparing the photocatalyst for efficiently degrading toluene according to claim 1, wherein the photocatalyst comprises: the dosage of the bismuth nitrate solution in the step 2) is that every 500mg of TiO ₂ The amount of Bi is 0.5-5 wt%, and the concentration of the bismuth nitrate solution is 3.45mg/mL.

6. The method for preparing the photocatalyst for efficiently degrading toluene according to claim 1, wherein the photocatalyst comprises: the temperature of the hydrothermal reaction in the step 2) is 160 ℃, and the hydrothermal time is 24h.

7. Bi/TiO prepared by the method of any one of claims 1 to 6 for efficiently degrading toluene ₂ A photocatalyst.

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