CN107626335B - A kind of bismuth series/carbon nitride composite catalyst and its preparation method and application - Google Patents

Abstract

The invention discloses a bismuth-based/carbon nitride composite catalyst and a preparation method and application thereof, including: (1) C ₃ N ₄ precursor and Bi ₂ O ₃ precursor are mixed in proportion to prepare Bi ₂ O ₃ /C ₃ N ₄ powder; (2) get the obtained Bi ₂ O ₃ /C ₃ N ₄ powder and mix it with KI according to the proportion and then disperse it in water. After mixing evenly, continue to stir while adding dilute sulfuric acid solution dropwise. Dry and grind to obtain Bi ₂ O ₃ ‑BiOI/C ₃ N ₄ powder; (3) get Bi ₂ O ₃ ‑BiOI/C ₃ N ₄ powder, disperse in methanol, irradiate with ultraviolet light under anaerobic conditions, and then Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ was obtained by centrifugation, washing, drying and grinding in sequence. In the present invention, C ₃ N ₄ is simultaneously introduced in the process of preparing Bi ₂ O ₃ to obtain Bi ₂ O ₃ /C ₃ N ₄ ; after Bi ₂ O ₃ -BiOI/C ₃ N ₄ is prepared under the etching effect of KI, it is To further broaden its visible light responsiveness, a part of Bi plasma was reduced by in-situ UV light, making it Bi@Bi ₂ O ₃ ‑BiOI/C ₃ N ₄ .

Description

A kind of bismuth series/carbon nitride composite catalyst and its preparation method and application

technical field

The invention relates to the technical field of high-efficiency visible light photocatalytic materials, in particular to a bismuth series/C ₃ N ₄ composite catalyst and a preparation method and application thereof.

Background technique

In recent years, with the continuous development and progress of science and technology, while people enjoy many conveniences, environmental pollution and energy shortages have shown a severe development trend, which has also attracted widespread attention from people from all walks of life. On the one hand, under the tide of vigorously developing science and technology and industry, the three industrial wastes (wastewater, waste gas, solid waste) are generated in the process of industrial and agricultural production and are discharged into the environment in large quantities, and migrate with the circulation of the natural environment. On the other hand, the continuous consumption of traditional non-renewable resources, such as coal and oil, makes high-quality energy more and more scarce, so the development of efficient and sustainable energy has become another hot topic. Water pollution, as one of the major problems of environmental pollution, has become one of the focuses of environmental governance. Take the waste water pollution control generated by the printing and dyeing industry and the pharmaceutical industry as an example, because there are a large number of organic pollutants in such waste water, such as chlorophenol and other organic pollutants, which will not only endanger human health, but also have a very bad impact on the ecological environment. . For this type of wastewater, scientists mainly use physical and chemical methods such as electrolysis, chemical flocculation, adsorption, membrane filtration, and reduction precipitation, but there are problems such as high residue, high cost, and secondary pollution.

Therefore, how to use energy-saving and high-efficiency methods to achieve the removal of organic pollutants in sewage has become the focus of sewage treatment technology research in recent years. Semiconductor photocatalysis technology, as a new type of advanced catalytic oxidation technology, has entered people's field of vision and developed rapidly because it can play a significant role in degrading various organic pollutants.

In the case of sunlight as the driving force, semiconductor photocatalysts can carry out catalytic reactions, such as hydrogen production, degradation of organic matter, etc. However, existing photocatalysts generally suffer from weak visible light response and low photocatalytic efficiency. Therefore, an efficient semiconductor photocatalyst with strong visible light responsiveness is very important for solving the current organic pollution in wastewater.

SUMMARY OF THE INVENTION

The invention provides a catalyst, a preparation method and application thereof. In the process of preparing Bi ₂ O ₃ , C ₃ N ₄ is simultaneously introduced to obtain Bi ₂ O ₃ /C ₃ N ₄ ; Bi ₂ O 3 /C 3 N 4 is prepared under the etching effect of KI. After O ₃ -BiOI/C ₃ N ₄ , in order to further broaden its visible light responsiveness, a part of Bi plasma was obtained by in-situ UV reduction, which became Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ .

A preparation method of a bismuth series/C ₃ N ₄ composite catalyst, comprising the following steps:

(1) The Bi ₂ O ₃ /C ₃ N ₄ powder is prepared by mixing the C ₃ N ₄ precursor and the Bi ₂ O ₃ precursor according to the ratio;

(2) get the obtained Bi ₂ O ₃ /C ₃ N ₄ powder and mix it with KI according to the proportion and then disperse it in water. After the mixing is uniform, continue to stir while adding dilute sulfuric acid solution dropwise. Obtain Bi ₂ O ₃ -BiOI/C ₃ N ₄ powder;

(3) Take Bi ₂ O ₃ -BiOI/C ₃ N ₄ powder, disperse it in methanol, irradiate with ultraviolet light under anaerobic conditions, and then successively centrifuge, wash, dry and grind to obtain Bi@Bi ₂ O ₃ - BiOI/C ₃ N ₄ .

In the present invention, C ₃ N ₄ is simultaneously introduced in the process of preparing Bi ₂ O ₃ , and on this basis, the Bi ₂ O ₃ -BiOI/C ₃ N ₄ ternary heterojunction is prepared by etching with KI, in order to further broaden its visible light Responsiveness, Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ was prepared by reduction with UV lamp.

Preferably, the Bi ₂ O ₃ precursor in step (1) is bismuth nitrate pentahydrate, and the C ₃ N ₄ precursor is melamine, dicyandiamide or urea; the C ₃ N ₄ precursor is combined with Bi ₂ O _3. The precursors are mixed with agate mortar and ground for half an hour, and then calcined in a muffle furnace at 300-700 °C for 1.5 to 2.5 hours; more preferably, semi-anaerobic calcination in a muffle furnace at 500 °C for 2 hours.

Most preferably, the C ₃ N ₄ precursor is melamine.

The present invention adopts melamine, dicyandiamide and urea as the precursors of C ₃ N ₄ respectively.

In the present invention, C ₃ N ₄ can be used as a carrier of various catalysts because of its unique structure and morphology and electronic energy band structure; Bi ₂ O ₃ is the most widely used catalyst among the bismuth series catalysts, and has the advantages of simple preparation method and variable band gap. However, Bi ₂ O ₃ itself has low visible light catalytic activity and needs to be modified by certain methods. Compared with Bi ₂ O ₃ , BiOX (X=Cl, Br, I) has a narrower band gap and thus exhibits stronger visible light activity. The band gaps of BiOCl, BiOBr and BiOI decrease in turn. Pure BiOX has Good photocatalytic performance, but pure BiOX does not have good stability, which limits its practical application. The metal plasma effect can effectively widen its visible light responsiveness, and the present invention innovatively uses ultraviolet to reduce metal plasma in one step, which is an innovative aspect of the present invention. In order to combine the advantages of the various products mentioned above, therefore, this patent is based on Bi ₂ O ₃ and C ₃ N ₄ . In the process of preparing Bi ₂ O ₃ , C ₃ N ₄ was introduced simultaneously, and on this basis, Bi ₂ O ₃ -BiOI-C ₃ N ₄ ternary heterojunction was prepared by KI etching, in order to further broaden its visible light responsiveness , Bi@Bi ₂ O ₃ -BiOI-C ₃ N ₄ was prepared by reduction with UV lamp.

Preferably, in step (1), the C ₃ N ₄ precursor and the Bi ₂ O ₃ precursor are proportioned according to the molar ratio of Bi ₂ O ₃ to C of 1:1 to 1:5. Further preferably, the molar ratio of Bi ₂ O ₃ to C is 1:1 to 1:3; most preferably, the molar ratio of Bi ₂ O ₃ to C is 1:2.

Preferably, the concentration of the dilute sulfuric acid in the step (2) is 0.8-1.2 mol/L; the dropwise addition is carried out during the reaction for 10 min, 30 min, 60 min and 100 min respectively, and the amount of each drop is Bi ₂ O ₃ /C ₃ 0.04% of the total volume of the N ₄ powder, KI and water reaction system. The addition of acid is to better promote the etching of KI, and the addition of acid at intervals is to prevent pH mutation and prevent excessive acid from affecting the catalyst.

Preferably, the ratio of Bi ₂ O ₃ /C ₃ N ₄ powder and KI in step (2) is calculated by mixing 0.3-0.5g KI per 0.5g of Bi ₂ O ₃ /C ₃ N ₄ . Further preferably, 0.4g KI is used for etching per 0.5g Bi ₂ O ₃ /C ₃ N ₄ .

When there is less KI, less BiOI is produced, and the improvement effect on the catalyst is not obvious; more KI can improve the yield of BiOI, but the relative stability of the catalyst is not good; considering the visible light responsiveness and stability of the catalyst, the choice of 0.5g Bi ₂ O ₃ /C ₃ N ₄ etched with 0.4g KI was selected as the optimal ratio.

Preferably, the ultraviolet irradiation in step (2) is: 20-300 min under full-wavelength irradiation under an ultraviolet iodine lamp. More preferably, the irradiation is 150-200 min, most preferably 200 min.

A most preferred preparation method:

(1) isotopic introduction of C ₃ N ₄ during the preparation of Bi ₂ O ₃ :

1) Put 0.368g melamine and 4.85g bismuth nitrate pentahydrate (Bi(NO ₃ ). 5H ₂ O purity 99.0%) into an agate mortar and mix them evenly, grind them hard and finely crush them, and add 4 drops with a dropper. -5 drops of deionized water continued to grind, resulting in a sticky white paste.

2) Put it in a 50ml crucible, and then transfer it to a thermostatic blast drying oven at a constant temperature of 80°C for 3 hours to dry.

3) After being placed in a muffle furnace and calcined at a constant temperature of 500°C for 2 hours, the powder is obtained.

(2) Potassium iodide (KI) is used as the source of I element of Bi ₂ O ₃ -BiOI/C ₃ N ₄ :

1) Put 0.5g of Bi ₂ O ₃ /C ₃ N ₄ powder into a 25ml beaker respectively, weigh 0.4g of KI into the beaker, add 25ml of water, and add a rotor of appropriate size.

2) After stirring evenly on a magnetic stirrer, keep the stirring continuously on and the rotation speed unchanged, use a pipette to transfer 20 microliters of 1 mol/L concentrated H ₂ SO ₄ solution and place it in a beaker.

3) At intervals of 10min, 20min, 30min, and 40min in sequence, pipette 10 microliters of 1 mol/L concentrated H ₂ SO ₄ solution each time with a pipette and place it in a beaker.

4) After stirring for 20min, turn off the agitator, take out the rotor, transfer the solution to a 50ml centrifuge tube for centrifugation, pour off the supernatant, wash with water for 2-3 times, and place it in an oven at 80°C for 3 hours to dry.

5) After taking out the centrifuge tube, the powder was ground in an agate mortar to obtain three different carbon nitride sources Bi ₂ O ₃ -BiOI/C ₃ N ₄ .

(3) Reduction of Bi ₂ O ₃ -BiOI/C ₃ N ₄ by ultraviolet light source to generate Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ :

1) Take 0.5g of the prepared Bi ₂ O ₃ -BiOI/C ₃ N ₄ powder and put it in a 50ml photochemical reaction bottle, add a rotor, 50ml of 100% methanol, and seal with a cap.

2) Under the condition of flushing nitrogen (N ₂ ) to squeeze out the remaining air in the bottle, keep the stirrer continuously working and nitrogen continuously rushing in, and under full-wavelength illumination of ultraviolet iodine lamp for 3 hours.

3) Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ of different carbon nitride sources were prepared according to this method. After the rotor was taken out, the contents in the bottle were transferred to a centrifuge tube for centrifugation, and the methanol supernatant was recovered. After washing the sediment in the bottle several times, it was dried in an oven at a constant temperature of 30°C for 8 hours.

4) After taking out the centrifuge tube, the powder was ground in an agate mortar to obtain the optimal Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ .

The present invention also provides a bismuth series/C ₃ N ₄ composite catalyst prepared by the preparation method.

The invention also provides the application of the bismuth series/C ₃ N ₄ composite catalyst in the treatment of organic polluted wastewater. That is, a method for treating organic polluted wastewater by utilizing the bismuth series/C ₃ N ₄ composite catalyst is provided. It includes the following steps:

The bismuth series/C ₃ N ₄ composite catalyst is added into the organic polluted waste water, and the reaction is irradiated with visible light.

Preferably, the organic polluted wastewater is phenol polluted wastewater. Preferably, the dosage of the bismuth-based/C ₃ N ₄ composite catalyst is 0.8-1.2 g/L. More preferably, it is 1 g/L.

Preferably, the light intensity is 100mW/m ² to 160mW/m ² . Lighting time ~ 55 ~ 65min; more preferably light 60min. There is no need to adjust the pH value in the treatment of wastewater, and the original pH value is 5-6.

Taking phenol degradation as a model, the photocatalytic activity of the prepared catalysts was investigated. Under the irradiation of visible light, after a certain time of reaction, the residual concentration of phenol was monitored by a liquid chromatograph to determine the removal efficiency of phenol.

In the experiment, the simulated target pollutant phenol was degraded under the condition of adding light, and a 420-nanometer filter was used for filtering in the ultraviolet light source. First, 0.05 g of the prepared catalyst powder was put into 50 mL of a 5 mg/L phenol solution for adsorption for 40 min, so that the reaction substrate reached the adsorption-desorption equilibrium. Then turn on the light source, carry out the corresponding catalytic reaction, and take samples regularly (the sampling volume is about 2ml). The intensity of light (ultraviolet-visible light) added in the photocatalytic reactor was measured to be 100mW/m ² . During the catalytic oxidation degradation process of 105min, one sample was collected at 0, 15, 30, 45, 60, 75, 90, and 105min. Samples were used to determine the content of phenol at different degradation times by high performance liquid chromatography. All reactions were carried out in glass apparatus, and the target contaminants were 50 ml of 5 mg/L phenol solution.

The content of phenol in the phenol solution obtained by different sampling time was determined by high performance liquid chromatography, and the content of phenol was expressed by the peak area, and the chromatographic condition was 30% methanol solution as the mobile phase. Before injection, the sample should be centrifuged with a high-speed centrifuge to prevent the suspended matter (suspended catalyst powder) in the solution from damaging the chromatographic column.

The core of the present invention is to provide a preparation method of a bismuth series/C ₃ N ₄ composite catalyst, and apply the method to degrade organic pollutants in water, especially phenol. Bi ₂ O ₃ /C ₃ N 4 is obtained by simultaneously introducing C ₃ N ₄ in the process of preparing Bi ₂ O _{3 ;} after preparing Bi ₂ O ₃ -BiOI/C ₃ N ₄ under the etching effect of KI, in order to further broaden the With its visible light responsiveness, a part of Bi plasma is reduced by in-situ UV light, making it Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ . The catalyst has good visible light responsiveness, efficient organic degradation performance and stability.

Beneficial effects of the present invention:

(1) The prepared bismuth series/C ₃ N ₄ composite catalyst has good organic degradation ability;

(2) The catalyst has good stability;

(3) Visible light is used, and ultraviolet light is avoided;

(4) It has extremely high visible light responsiveness.

Description of drawings

Figure 1 is a columnar comparison chart of the degradation efficiency of phenol for different catalysts in Example 1 within 60 min.

2 is a bar graph showing the degradation efficiency of Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ catalysts prepared by different carbon nitride precursors in Example 2 for phenol within 60 min.

3 is a bar graph showing the ratios of 1:1 to 1:5 corresponding to different doping amounts of carbon nitride in Example 3 of the present invention, and the degradation efficiency of phenol within 60 min corresponding to the catalyst performance.

FIG. 4 is a bar graph of the degradation efficiency of phenol within 60 min of catalysts represented by different ultraviolet reduction times in Example 4 of the present invention.

Figure 5 is a bar graph of the degradation efficiency of the catalyst to phenol within 60 min under different pH conditions in Example 5 of the present invention, with the conditions of acidity, alkalinity and unadjusted pH.

6 is a bar graph of the degradation efficiency of the catalyst for phenol in 60min under five light intensities of 40mW/m ² , 70mW/m ² , 100mW/m ² , 130mW/m ² and 160mW/m ² in Example 6 of the present invention .

Detailed ways

The present invention will now be further described with reference to the accompanying drawings and specific embodiments of the description.

The preparation method of bismuth series/C ₃ N ₄ composite catalyst comprises the following steps:

(1) Preparation of Bi ₂ O ₃ /C ₃ N ₄

The catalyst adopts melamine, dicyandiamide and urea as the precursors of C ₃ N ₄ respectively. In order to exclude the influence of the doping amount of carbon nitride (C ₃ N ₄ ) on the catalyst performance (the molar ratio of the fixed element Bi and C, the initial ratio is set to 1:2, that is, Bi:C=1:2), five The ratio of species is 1:1 to 1:5. The specific method is as follows (take 1:2 as an example):

₁ ) Put 0.526g urea (urea) and 4.85g bismuth nitrate pentahydrate (Bi(NO ₃ . -5 drops of deionized water continued to grind, resulting in a sticky white paste.

2) After mixing 0.368g melamine and 4.85g bismuth nitrate pentahydrate (Bi(NO ₃ .5H ₂ O purity 99.0%) in an agate mortar, repeat step 1.

3) Put 0.368 g of Dicyandiamide and 4.85 g of bismuth nitrate pentahydrate (Bi(NO ₃ ). 5H ₂ O purity 99.0%) in an agate mortar and mix uniformly, and repeat step 1.

4) The above three kinds of mixtures were placed in 50ml crucibles, and then transferred to a thermostatic blast drying oven at a constant temperature of 80°C for 3 hours for drying.

5) The three products after drying are respectively placed in a muffle furnace and calcined at a constant temperature of 500° C. for 2 hours to obtain powders.

6) The obtained powders were placed in 50ml centrifuge tubes, ultrasonically washed with distilled water, and centrifuged, and repeated 3 times. After pouring out the supernatant, place it in a hot constant temperature blast drying oven at a constant temperature of 80°C for 3 hours to dry, take it out, and grind it in an agate mortar to obtain Bi ₂ O ₃ /C ₃ with three different carbon nitride sources. N ₄ . They are respectively recorded as u-type Bi ₂ O ₃ /C ₃ N ₄ (urea), m-type Bi ₂ O ₃ /C ₃ N ₄ (melamine), and d-type Bi ₂ O ₃ /C ₃ N ₄ (dicyandiamide).

(2) Preparation of Bi ₂ O ₃ -BiOI/C ₃ N ₄

Potassium iodide (KI) was used as the source of I element for _{Bi2O3 - BiOI} /C3N4 _. The specific operation plan is as follows:

1) Put 0.5g of Bi ₂ O ₃ /C ₃ N ₄ powder into a 25ml beaker respectively, weigh 0.4g of KI into the beaker, add 25ml of water, and add a rotor of appropriate size.

2) After stirring evenly on a magnetic stirrer, keep the stirring continuously on and the rotation speed unchanged, use a pipette to transfer 20 microliters of 1 mol/L concentrated H ₂ SO ₄ solution and place it in a beaker.

3) Add dropwise at 10min, 30min, 60min and 100min, pipet 10 microliters of 1 mol/L concentrated H ₂ SO ₄ solution each time with a pipette and place it in a beaker.

4) After stirring for 20min, turn off the agitator, take out the rotor, transfer the solution to a 50ml centrifuge tube for centrifugation, pour off the supernatant, wash with water for 2-3 times, and place it in an oven at 80°C for 3 hours to dry.

5) After taking out the centrifuge tube, the powder was ground in an agate mortar to obtain three different carbon nitride sources Bi ₂ O ₃ -BiOI/C ₃ N ₄ .

Denoted as u-type Bi ₂ O ₃ -BiOI/C ₃ N ₄ (urea), m-type Bi ₂ O ₃ -BiOI/C ₃ N ₄ (melamine), d-type Bi ₂ O ₃ -BiOI/C ₃ N ₄ (dicyandiamide).

(3) Preparation of Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄

Bi ₂ O ₃ -BiOI/C ₃ N ₄ was reduced by ultraviolet light source to generate Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ . The specific operations are as follows:

1) Take 0.5g of the prepared Bi ₂ O ₃ -BiOI/C ₃ N ₄ powder and put it in a 50ml photochemical reaction bottle, add a rotor, 50ml of 100% methanol, and seal with a cap.

2) Under the condition of flushing nitrogen (N ₂ ) to squeeze out the remaining air in the bottle, keep the stirrer working continuously and nitrogen continuously rushing in, and under full-wavelength illumination of ultraviolet iodine lamp for 20-300 minutes.

3) Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ of different carbon nitride sources were prepared according to this method. After the rotor was taken out, the contents in the bottle were transferred to a centrifuge tube for centrifugation, and the methanol supernatant was recovered. After washing the sediment in the bottle several times, it was dried in an oven at a constant temperature of 30°C for 8 hours.

4) After taking out the centrifuge tube, the powder was ground in an agate mortar to obtain three different carbon nitride sources Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ .

They are recorded as u-type Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ (urea), m-type Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ (melamine), d-type Bi@Bi ₂ O ₃ - BiOI/C ₃ N ₄ (dicyandiamide)

Example 1

Catalysts containing five different components were selected to determine the effectiveness of each component by comparing their degradation performance. From Figure 1, it can be found that under the illumination intensity of 100mW/m ² , adding 50 mg of catalyst to 50 ml of 5 mg per liter of phenol solution shows the degradation trend of phenol over time. Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ had the best degradation effect, and phenol was completely degraded within 60 min.

Referring to Figure 1, it is found that although the degradation effect of the other four catalysts is not very good, and some are relatively poor, it can be found by comparison:

1) Comparing the degradation efficiency of g/C ₃ N ₄ and Bi ₂ O ₃ /C ₃ N ₄ , it can be found that the doping of Bi ₂ O ₃ can improve the catalytic degradation effect of the catalyst to a certain extent.

2) Comparing the degradation efficiency of Bi ₂ O ₃ -BiOI/C ₃ N ₄ and Bi ₂ O ₃ /C ₃ N ₄ , it can be found that the doping of part of BiOI can properly improve the catalytic performance.

3) Comparing Bi@Bi ₂ O ₃ -BiOI with Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ , it can be clearly found that doping with appropriate amount of carbon nitride can significantly improve the degradation efficiency of the catalyst.

Example 2

The effect of catalysts prepared with different carbon nitride precursors on the degradation performance of phenol was investigated. In the experiment, three common carbon nitride precursors were selected, namely melamine, dicyandiamide and urea; they were denoted as u-type Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ (urea), m-type Bi@ Bi ₂ O ₃ -BiOI/C ₃ N ₄ (melamine), d-type Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ (dicyandiamide).

From the degradation effect diagram (Fig. 2), it can be found that the Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ prepared by three different precursors have good degradation effect on phenol, but the m-type Bi@Bi ₂ O ₃ has a good degradation effect on phenol. -BiOI/C ₃ N ₄ (using melamine as carbon nitride precursor) has the fastest degradation rate and can completely degrade phenol. The other two prepared catalysts also showed good results.

Example 3

The effect of carbon nitride doping in the catalyst on the performance of the catalyst was investigated. According to the degradation trend of the prepared five catalysts under the same conditions, it can be seen that the doping amount of C ₃ N ₄ has a relatively large effect on the performance of the catalyst. The catalytic performance of Bi ₂ O ₃ -BiOI/C ₃ N ₄ 1:2 is the best, that is, the catalyst prepared by uniformly mixing bismuth nitrate pentahydrate and melamine in a ratio of 4.85g:0.368g.

Table 1 Configurations of different ratios of Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄

By comparing the degradation efficiencies of various ratios, it can be found that the addition of an appropriate amount of carbon nitride can effectively improve the degradation performance of the catalyst (for Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ 1:0.5, Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ 1:1, Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ 1:2 for comparison); but when the added amount exceeds a certain limit, the increase in the amount of carbon nitride will cause The performance of the catalyst decreased (for Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ 1:2, Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ 1:3, Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ 1:4 for comparison).

Example 4

In order to compare the influence of UV reduction illumination time on the performance of the catalyst, the present invention selects different illumination times of 20min, 40min, 180min and 300min under the same preparation conditions in the previous stage; The specific degradation effect is shown in Figure 4. It can be found that the catalysts have good degradation effects under the four selected light times, and the degradation efficiencies of Bi20, Bi180 and Bi300 are relatively similar.

Table 2 Selection of different UV irradiation times for Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄

It can be seen from Table 2 that with the increase of illumination time, its catalytic efficiency will be improved to a certain extent, but when the reduction amount in the catalyst reaches a certain saturation value, the change of catalytic efficiency is no longer obvious.

Example 5

In order to investigate the optimal pH of the catalyst during the degradation process, three conditions were selected: the acidic condition of pH 3, the alkaline condition of pH 10, and the original pH value of 5.41 without adjustment to investigate the effect of pH value on the performance of the catalyst. influences. It can be found from Figure 5 that under the conditions of pH 3 and 10, the degradation performance of the catalyst is inhibited to a certain extent, and the inhibition effect is more obvious.

Example 6

In the experiment to investigate the effect of light intensity on catalyst performance, a radiometer was used as an instrument for measuring light intensity, and the unit was mW/m ² . During the experiment, five light intensities of 40mW/m ² , 70mW/m ² , 100mW/m ² , 130mW/m ² , and 160mW/m ² were selected. From FIG. 6 , the present invention can find the following points: 1) For you The degradation effects of 40mW/m ² , 70mW/m ² , and 100mW/m ² were compared. The results are shown in Figure 6. It can be found that when other conditions are the same, with the increase of light intensity, the degradation rate of the catalyst gradually accelerated, indicating that The light intensity has a certain effect on the degradation efficiency of the catalyst. 2) When comparing the degradation efficiencies of 100mW/m ² , 130mW/m ² and 160mW/m ² as the control group, the present invention finds that the degradation efficiency of the catalyst has almost no obvious change, which shows that when the light intensity exceeds a certain At the limit, the effect of light on catalyst efficiency will no longer be a major factor.

The above is only a specific example of the implementation of the patent of the present invention, but the technical features of the patent of the present invention are not limited to this. within the scope of the patent.

Claims (5)

1. A bismuth system/C ₃ N ₄ composite catalyst, characterized in that the preparation method comprises the steps: (1) Bi ₂ O ₃ /C ₃ N ₄ powder was prepared by mixing melamine and bismuth nitrate pentahydrate in a mass ratio of 0.368:4.85; melamine was mixed with bismuth nitrate pentahydrate, ground in an agate mortar for 20 to 40 minutes, and then placed in a 500 ℃ semi-anaerobic calcination in muffle furnace for 2 hours; (2) get the obtained Bi ₂ O ₃ /C ₃ N ₄ powder and mix it with KI according to the proportion and then disperse it in water. After the mixing is uniform, continue to stir while adding dilute sulfuric acid solution dropwise. Obtain Bi ₂ O ₃ -BiOI/C ₃ N ₄ powder; (3) Take Bi ₂ O ₃ -BiOI/C ₃ N ₄ powder, disperse it in methanol, and under anaerobic conditions, under full-wavelength illumination of ultraviolet iodine lamp for 20-300 min; Obtain Bi@Bi ₂ O ₃ -BiOI/C ₃ N ₄ . 2. The bismuth-based/C ₃ N ₄ composite catalyst according to claim 1, wherein the concentration of the dilute sulfuric acid in step (2) is 0.8 to 1.2 mol/L; It is 0.04% of the total volume of the reaction system of Bi ₂ O ₃ /C ₃ N ₄ powder, KI and water. 3. The bismuth-based/C ₃ N ₄ composite catalyst according to claim 1, wherein in step (2), the Bi ₂ O ₃ /C ₃ N ₄ powder and KI are proportioned by every 0.5g Bi ₂ O ₃ /C ₃ N ₄ mixed with 0.3~0.5g KI. 4. A method of utilizing the bismuth system/C ₃ N ₄ composite catalyst according to claim 1 to treat organic polluted wastewater, characterized in that, comprising the steps: The bismuth series/C ₃ N ₄ composite catalyst is added into the organic polluted wastewater, and the reaction is irradiated with visible light; the organic polluted wastewater is phenol polluted wastewater. The method according to claim ⁴ , wherein the dosage of the bismuth-based/C ₃ N ₄ composite catalyst is 0.8-1.2 ^g /L; The time is 55 to 65 minutes.

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