CN104801320B - Bismuthyl fluorite photochemical catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a bismuth oxyfluoride photocatalyst and a preparation method thereof. The preparation method comprises the following steps: adding glacial acetic acid into water, the volume ratio of glacial acetic acid to water is 1:2-5:1, and stirring; adding bismuth nitrate and soluble fluoride salt into the glacial acetic acid solution, and keeping the temperature at 75°C-85°C Stir in a constant temperature water bath for 20-40 minutes to dissolve the bismuth nitrate and fluoride salt to prepare a mixed solution with a bismuth nitrate concentration of 0.95mmol/30ml~1.05mmol/30ml, and the molar ratio of bismuth to fluorine is 1:1.9~ 1:2.1; add the above mixed solution into the polytetrafluoroethylene lining, 120~160°C constant temperature hydrothermal reaction for 10~13 hours, centrifuge, wash and dry to obtain bismuth oxyfluoride photocatalyst. The method is simple and easy to implement, and is easy to be popularized on a large scale, and can prepare a bismuth oxyfluoride photocatalyst with high catalytic activity, which can be used to catalyze and degrade organic pollutants.

Description

Bismuth oxyfluoride photocatalyst and preparation method thereof

technical field

The invention relates to the field of catalyst preparation, in particular to a bismuth oxyfluoride photocatalyst and a preparation method thereof.

Background technique

With the development of chemical industry, environmental pollution is becoming more and more serious. Utilizing the surface energy activation characteristics of semiconductor oxide materials under sunlight irradiation, organic pollutants can be effectively oxidized and decomposed. Compared with traditional environmental purification treatment methods, semiconductor photocatalysis technology has the advantages of mild reaction conditions, no secondary pollution, simple operation and significant degradation effect. _TiO2 is the most common and one of the most studied catalysts, but the photogenerated electron-hole pairs generated by it are easy to recombine, resulting in the inability of electrons and holes to migrate to the surface in time to participate in redox reactions, resulting in low photoconversion efficiency. . Therefore, it is very meaningful to search for new photocatalytic materials with excellent performance to obtain photocatalysts with high photocatalytic activity.

Bismuth-containing compounds have a wide range of applications, not only in the pharmaceutical industry, but also in semiconductors. Since bismuth is relatively a non-toxic green metal, in recent years, it has increasingly replaced compounds containing toxic elements such as lead, antimony, cadmium, and mercury in the preparation of photocatalysts.

Contents of the invention

The object of the present invention is to provide a kind of method for preparing bismuth oxyfluoride photocatalyst, this method is simple and easy, easy to large-scale popularization, can make the high bismuth oxyfluoride photocatalyst of catalytic activity;

Another object of the present invention is to provide three different fluorine/oxygen bismuth oxyfluoride photocatalysts with high catalytic activity;

Another object of the present invention is to provide the application of three different fluorine/oxygen bismuth oxyfluoride photocatalysts in the catalytic degradation of organic pollutants.

The above-mentioned purpose is achieved through the following technical solutions:

A method for preparing bismuth oxyfluoride photocatalyst, comprises the steps:

(1) Preparation of glacial acetic acid solution: add glacial acetic acid to water, the volume ratio of glacial acetic acid to water is 1:2~5:1, and stir;

(2) Dissolving in water bath: add bismuth nitrate and soluble fluoride salt to the glacial acetic acid solution, stir in a constant temperature water bath at 75°C~85°C for 20~40 minutes, dissolve bismuth nitrate and fluoride salt, and make bismuth nitrate with a concentration of 0.95 A mixed solution of mmol/30ml~1.05mmol/30ml, the molar ratio of bismuth to fluorine is 1:1.9~1:2.1;

(3) Hydrothermal reaction: Add the above mixed solution into the polytetrafluoroethylene lining, conduct a hydrothermal reaction at a constant temperature of 120-160°C for 10-13 hours, centrifuge, wash and dry to obtain the bismuth oxyfluoride photocatalyst.

Further, in the method for preparing bismuth oxyfluoride photocatalyst, the bismuth nitrate in step (2) is bismuth nitrate pentahydrate.

Further, in the method for preparing bismuth oxyfluoride photocatalyst, the soluble fluoride salt in step (2) is sodium fluoride or ammonium fluoride.

Further, in the method for preparing bismuth oxyfluoride photocatalyst, the constant temperature hydrothermal reaction time of step (3) is 10.5 hours, and the temperature is 150°C.

Further, in the method for preparing bismuth oxyfluoride photocatalyst, the constant temperature hydrothermal reaction time of step (3) is 11.5 hours, and the temperature is 150°C.

Further, in the method for preparing bismuth oxyfluoride photocatalyst, the constant temperature hydrothermal reaction time of step (3) is 12.5 hours, and the temperature is 150°C.

After hydrothermal reaction at 150° C. for 10.5 hours, Bi ₇ O ₅ F ₁₁ bismuth oxyfluoride photocatalyst can be prepared according to the above method for preparing bismuth oxyfluoride photocatalyst.

After hydrothermal reaction at 150°C for 11.5 hours, BiO 0.51 F 1.98 BiO _0.51 F _1.98 bismuth oxyfluoride photocatalyst can be prepared according to the above method for preparing bismuth oxyfluoride photocatalyst.

After hydrothermal reaction at 150°C for 12.5 hours, BiO _0.67 F _1.66 bismuth oxyfluoride photocatalyst can be prepared according to the above method for preparing bismuth oxyfluoride photocatalyst.

Application of the above three different fluorine/oxygen bismuth oxyfluoride photocatalysts in the catalytic degradation of organic pollutants.

Beneficial effects of the present invention:

1. The method for preparing the bismuth oxyfluoride photocatalyst provided by the present invention is simple and easy to be popularized on a large scale, and can produce a bismuth oxyfluoride photocatalyst with high catalytic activity.

2. The three different fluorine/oxygen bismuth oxyfluoride photocatalysts provided by the present invention can all exist stably, have good morphology and high catalytic activity, and can efficiently degrade rhodamine B (RhB) in wastewater solution and methylene blue in methylene blue solution (MB).

Description of drawings

Figure 1: UV diffuse reflectance diagrams of three kinds of bismuth oxyfluoride photocatalysts prepared in implementation 1-3;

Fig. 2: The degradation ability curves of three kinds of bismuth oxyfluoride photocatalysts prepared by implementing 1-3 to RhB and MB;

Figure 3: Comparison of Bi ₇ O ₅ F ₁₁ prepared in Implementation 1 with the standard card JCPDS: 50-0003;

Figure 4: Comparison of BiO _0.67 F _1.66 prepared in Implementation 3 with the standard card JCPDS:24-0146;

Figure 5: Comparison of BiO _0.51 F _1.98 prepared in Implementation 2 with the standard card JCPDS:24-0147.

detailed description

The technical solutions of the present invention will be described in detail below in conjunction with specific embodiments.

Example 1: Preparation of Bi ₇ O ₅ F ₁₁ bismuth oxyfluoride photocatalyst

(1) Preparation of glacial acetic acid solution: add 30ml of glacial acetic acid to 30ml of water, that is, mix glacial acetic acid and water at a volume ratio of 1:1, and stir;

(2) Dissolving in a water bath: take 30ml of glacial acetic acid solution, add 0.4851g (1mmol) of bismuth nitrate pentahydrate and 0.0840g (2mmol) of sodium fluoride, stir in a constant temperature water bath at 80°C for 30 minutes, and dissolve the bismuth nitrate and sodium fluoride to obtain mixture;

(3) Hydrothermal reaction: Add the above mixed solution into the polytetrafluoroethylene lining, conduct a hydrothermal reaction at a constant temperature of 150°C for 10.5 hours, centrifuge at 3000 rpm for 3 minutes, wash with distilled water and absolute ethanol in turn, and dry at 60°C for 4 hours , namely Bi ₇ O ₅ F ₁₁ bismuth oxyfluoride photocatalyst.

It can be seen from Figure 1 that the catalyst has ultraviolet absorption and ultraviolet photocatalytic activity. It can be seen from Figure 3 that the prepared catalyst is pure and has a high degree of crystallinity. Sodium fluoride can be replaced by ammonium fluoride, the amount added is 0.0741g (2mmol).

Embodiment 2: Preparation of BiO _0.51 F _1.98 bismuth oxyfluoride photocatalyst

(1) Preparation of glacial acetic acid solution: add 30ml of glacial acetic acid to 30ml of water, that is, mix glacial acetic acid and water at a volume ratio of 1:1, and stir;

(2) Dissolving in a water bath: take 30ml of glacial acetic acid solution, add 0.4851g (1mmol) of bismuth nitrate pentahydrate and 0.0840g (2mmol) of sodium fluoride, stir in a constant temperature water bath at 80°C for 30 minutes, and dissolve the bismuth nitrate and sodium fluoride to obtain mixture;

(3) Hydrothermal reaction: Add the above mixed solution into the polytetrafluoroethylene lining, conduct a hydrothermal reaction at a constant temperature of 150°C for 11.5 hours, centrifuge at 3000 rpm for 3 minutes, wash with distilled water and absolute ethanol in turn, and dry at 60°C for 4 hours , namely BiO _0.51 F _1.98 bismuth oxyfluoride photocatalyst.

It can be seen from Figure 1 that the catalyst has ultraviolet absorption and has ultraviolet photocatalytic activity. It can be seen from Figure 5 that the prepared catalyst is pure and has a high degree of crystallinity. Sodium fluoride can be replaced by ammonium fluoride, the addition amount is 0.0741g (2mmol).

Embodiment 3: Preparation of BiO _0.67 F _1.66 bismuth oxyfluoride photocatalyst

(1) Preparation of glacial acetic acid solution: add 30ml of glacial acetic acid to 30ml of water, that is, mix glacial acetic acid and water at a volume ratio of 1:1, and stir;

(2) Dissolving in a water bath: take 30ml of glacial acetic acid solution, add 0.4851g (1mmol) of bismuth nitrate pentahydrate and 0.0840g (2mmol) of sodium fluoride, stir in a constant temperature water bath at 80°C for 30 minutes, and dissolve the bismuth nitrate and sodium fluoride to obtain mixture;

(3) Hydrothermal reaction: Add the above mixed solution into the polytetrafluoroethylene lining, conduct a hydrothermal reaction at a constant temperature of 150°C for 12.5 hours, centrifuge at 3000 rpm for 3 minutes, wash with distilled water and absolute ethanol in turn, and dry at 60°C for 4 hours , that is, BiO _0.67 F _1.66 bismuth oxyfluoride photocatalyst.

It can be seen from Figure 1 that the catalyst has ultraviolet absorption and has ultraviolet photocatalytic activity. It can be concluded from Figure 4 that the prepared catalyst is pure and has a high degree of crystallinity. Sodium fluoride can be replaced by ammonium fluoride, the addition amount is 0.0741g (2mmol).

Example 4: Preparation of Bi ₇ O ₅ F ₁₁ bismuth oxyfluoride photocatalyst

(1) Preparation of glacial acetic acid solution: add 40ml of glacial acetic acid to 20ml of water, that is, mix glacial acetic acid and water at a volume ratio of 1:2, and stir;

(2) Dissolving in a water bath: Take 30ml of glacial acetic acid solution, add 0.4608g (0.95mmol) of bismuth nitrate pentahydrate and 0.0758g (1.805mmol) of sodium fluoride, and stir in a constant temperature water bath at 75°C for 40 minutes to make the bismuth nitrate and sodium fluoride Dissolving to obtain a mixed solution;

(3) Hydrothermal reaction: Add the above mixed solution into the polytetrafluoroethylene lining, conduct a hydrothermal reaction at a constant temperature of 120°C for 13 hours, centrifuge at 3000 rpm for 3 minutes, wash with distilled water and absolute ethanol in turn, and dry at 60°C for 4 hours , namely Bi ₇ O ₅ F ₁₁ bismuth oxyfluoride photocatalyst.

The composition of the prepared catalyst was consistent with that of Example 1, and its physical properties and catalytic activity were similar.

Example 5: Preparation of Bi ₇ O ₅ F ₁₁ bismuth oxyfluoride photocatalyst

(1) Preparation of glacial acetic acid solution: add 10ml of glacial acetic acid to 50ml of water, that is, mix glacial acetic acid and water at a volume ratio of 5:1, and stir;

(2) Dissolving in water bath: Take 30ml of glacial acetic acid solution, add 0.5094g (1.05mmol) of bismuth nitrate pentahydrate and 0.0926g (2.205mmol) of sodium fluoride, and stir for 20 minutes in a constant temperature water bath at 85°C to make bismuth nitrate and sodium fluoride Dissolving to obtain a mixed solution;

(3) Hydrothermal reaction: Add the above mixed solution into the polytetrafluoroethylene lining, conduct a hydrothermal reaction at a constant temperature of 160°C for 10 hours, centrifuge at 3000 rpm for 3 minutes, wash with distilled water and absolute ethanol in turn, and dry at 60°C for 4 hours , namely Bi ₇ O ₅ F ₁₁ bismuth oxyfluoride photocatalyst.

The composition of the prepared catalyst was consistent with that of Example 1, and its physical properties and catalytic activity were similar.

Embodiment 6: Degradation test of three kinds of bismuth oxyfluoride photocatalysts to RhB

Weighed 0.1 g of the three bismuth oxyfluoride photocatalysts prepared in Examples 1-3, respectively, and added 200 ml of RhB solution, and the RhB concentration was 10 mg/L. Stir in the dark for 30 minutes to make the dye reach the adsorption/desorption equilibrium on the surface of the catalyst. Then turn on the xenon light source to carry out the photocatalytic reaction under the irradiation of ultraviolet light, and the supernatant is detected by a spectrophotometer. The change of RhB concentration during the degradation process was determined according to the absorbance value at 553nm.

The degradation of RhB is shown in Figure 2, the abscissa is the light time, and the ordinate is the ratio of the RhB concentration measured after irradiation for a period of time to the initial RhB concentration. It can be seen from the figure that after 100 minutes of light irradiation, the three catalysts can catalyze the degradation of RhB60~80%, and have high photocatalytic degradation activity for RhB.

Example 7: Degradation test of MB by three kinds of bismuth oxyfluoride photocatalysts

Weighed 0.1 g of the three kinds of bismuth oxyfluoride photocatalysts prepared in Examples 1-3, respectively, and added 200 ml of MB solution, and the concentration of MB was 4.5 mg/L. Stir in the dark for 30 minutes to make the dye reach the adsorption/desorption equilibrium on the surface of the catalyst. Then turn on the xenon light source to carry out the photocatalytic reaction under the irradiation of ultraviolet light, and the supernatant is detected by a spectrophotometer. According to the absorbance value at 668nm, the change of MB concentration during the degradation process was determined.

The degradation of MB is shown in Figure 2. The abscissa is the irradiation time, and the ordinate is the ratio of the MB concentration measured after irradiation for a period of time to the initial concentration of MB. It can be seen from the figure that the adsorption amount of MB on the bismuth oxyfluoride photocatalyst reaches 10%~20% in the first 30 minutes; after 30 minutes of light irradiation, the MB in the MB dye solution is degraded by about 50%. After 60 minutes, the dye degradation rate reaches 70~80%. Thus, the bismuth oxyfluoride photocatalyst has high adsorption performance and high photocatalytic activity for MB.

Claims (4)

1. a method for preparing bismuth oxyfluoride photocatalyst is characterized in that comprising the steps: (1) Preparation of glacial acetic acid solution: add glacial acetic acid to the aqueous solution, the volume ratio of glacial acetic acid to water is 1:2～5:1, and stir; (2) Dissolving in a water bath: Add bismuth nitrate and soluble fluoride salts to the glacial acetic acid solution, stir in a constant temperature water bath at 75°C to 85°C for 20 to 40 minutes, dissolve the bismuth nitrate and fluoride salts, and make bismuth nitrate with a concentration of 0.95 The mixed solution of mmol/30ml～1.05mmol/30ml, the molar ratio of bismuth element to fluorine element is 1:1.9～1:2.1; (3) Hydrothermal reaction: add the above mixed solution into the polytetrafluoroethylene lining, conduct a hydrothermal reaction at a constant temperature of 120-160°C for 10-13 hours, centrifuge, wash and dry to obtain the bismuth oxyfluoride photocatalyst; The chemical formula of the bismuth oxyfluoride is Bi ₇ O ₅ F ₁₁ , the hydrothermal reaction time of step (3) is 10.5 hours, and the temperature is 150°C; The chemical formula of the bismuth oxyfluoride is BiO _0.51 F _1.98 , the hydrothermal reaction time of step (3) is 11.5 hours, and the temperature is 150°C; The chemical formula of the bismuth oxyfluoride is BiO _0.67 F _1.66 , the hydrothermal reaction time of step (3) is 12.5 hours, and the temperature is 150°C. 2. the method for preparing bismuth oxyfluoride photocatalyst according to claim 1 is characterized in that: in step (2), bismuth nitrate is bismuth nitrate pentahydrate. 3. the method for preparing bismuth oxyfluoride photocatalyst according to claim 1 is characterized in that: in step (2), soluble fluoride salt is sodium fluoride or ammonium fluoride. 4. The chemical formula prepared by any one of claims 1-3 is Bi ₇ O ₅ F ₁₁ or BiO _0.51 F _1.98 or BiO _0.67 F _1.66 Bismuth oxyfluoride photocatalyst used in catalytic degradation of organic pollutants.