CN115779942B - Modified fern-shaped bismuth vanadate photocatalytic nanomaterial as well as preparation method and application thereof - Google Patents

Abstract

The invention discloses a modified fern-like bismuth vanadate photocatalytic nanomaterial and its preparation method and application. The material includes a fern-like bismuth vanadate nanomaterial, and nitrogen elements and oxygen defects are introduced into the surface of the fern-like bismuth vanadate nanomaterial. . The preparation method includes: using bismuth salt and vanadium salt as raw materials, preparing fern-like bismuth vanadate nanomaterials by hydrothermal reaction under a pH value of 3-4, and conducting fern-like bismuth vanadate nanomaterials in a nitrogen atmosphere above 350°C. Calcined. The modified fern-like bismuth vanadate photocatalytic nanomaterial of the present invention has large specific surface area, many active sites, strong light absorption ability, wide photoresponse range, low photogenerated electron-hole recombination rate, good conductivity and photocatalytic activity. It is a new type of bismuth vanadate catalyst that can be widely used and has excellent performance. It can achieve rapid and complete removal of organic pollutants in wastewater when used to treat wastewater with organic pollutants. High value and good application prospects.

Description

Modified fern-like bismuth vanadate photocatalytic nanomaterials and their preparation methods and applications

Technical field

The invention belongs to the field of material technology and relates to a functional nanomaterial for treating environmental pollutants and its preparation method and application. Specifically, it relates to a modified fern-like bismuth vanadate photocatalytic nanomaterial and its preparation method and treatment water. Applications in organic pollutants in the environment.

Background technique

Due to the rapid development of industrialization and urbanization, the discharge of large amounts of industrial wastewater and domestic sewage, as well as the extensive use of chemical fertilizers and pesticides, a large amount of organic pollutants are discharged into the environment. Most of the organic matter is toxic and easy to bioaccumulate, and some organic matter is also harmful to the environment. The three effects of teratogenesis, carcinogenesis and mutagenesis pose a huge threat to human health, terrestrial and aquatic life. At present, the pollution of water environment has become an important issue related to public health, which contains at least 51 kinds of toxic organic pollutants. For example, bisphenol A (BPA) is an endocrine disruptor with estradiol-like activity. Low doses can destroy normal endocrine function and cause adverse reactions such as metabolic disorders, precocious puberty, sperm abnormalities, and cancer. According to reports, the extensive use of plastics containing bisphenol A has led to large exposures in the food chain, water and soil. What is more serious is that BPA can enter the human body through dietary and non-dietary sources, thus long-term exposure to BPA-contaminated environments , may have catastrophic consequences. Therefore, effectively removing bisphenol A and other organic pollutants in the environment is an urgent technical problem that needs to be solved at this stage.

Photocatalytic technology has been widely used to degrade organic pollutants in the water environment. Obtaining a catalyst with excellent photocatalytic performance is the key to effectively degrading organic pollutants. Bismuth vanadate (BiVO ₄ ), as a common semiconductor nanomaterial, has a suitable energy band width (2.4eV), good photochemical stability and controllable morphology, and can be used as a catalyst to degrade organic pollutants. However, , Existing BiVO ₄ materials still have shortcomings such as low carrier mobility, short diffusion distance of photogenerated holes, and serious carrier recombination, resulting in low photoelectric conversion efficiency and still unable to achieve the desired catalytic effect. in addition,. Existing BiVO ₄ materials still have the following defects: small specific surface area, few active sites, weak light absorption ability, narrow photoresponse range, high photogenerated electron-hole recombination rate, poor photocatalytic activity, poor stability, etc., which makes It is still difficult for existing BiVO ₄ materials to efficiently remove organic pollutants in the water environment. In addition, the existing methods of introducing defects still have shortcomings such as complex processes, harsh processing conditions, and high safety risks. Moreover, in the process of introducing defects, it is easy to introduce defects into the deep layers (internally), which not only easily destroys the original structure of the crystal, resulting in Its stability becomes worse, and it is not conducive to reducing the recombination rate of photogenerated electrons and holes, resulting in that its photocatalytic activity is still poor. So far, there have been no relevant reports about "fern-like BiVO ₄ materials". Therefore, a modified fern-like structure with large specific surface area, many active sites, strong light absorption capacity, wide photoresponse range, low photogenerated electron-hole recombination rate, good conductivity, high photocatalytic activity and good stability is obtained. Bismuth vanadate photocatalytic nanomaterials and the accompanying preparation methods are simple in process, easy to operate, low in cost and high in yield, which are useful for improving the removal effect of bismuth vanadate photocatalytic nanomaterials on organic pollutants in the environment and realizing environmental protection. The effective removal of organic pollutants is of great significance.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a device with large specific surface area, many active sites, strong light absorption ability, wide light response range, low photogenerated electron-hole recombination rate, and good conductivity. The modified fern-like bismuth vanadate photocatalytic nanomaterial with high photocatalytic activity and good stability also provides a modified fern-like photocatalytic nanomaterial with mild reaction conditions, safety and reliability, simple process, convenient operation, low cost and high yield. Preparation method of bismuth vanadate photocatalytic nanomaterials, and application of the modified fern-shaped bismuth vanadate photocatalytic nanomaterials in treating organic pollutant wastewater.

In order to solve the above technical problems, the present invention adopts the following technical solutions.

A modified fern-like bismuth vanadate photocatalytic nanomaterial includes a fern-like bismuth vanadate nanomaterial, and nitrogen elements and oxygen defects are introduced on the surface of the fern-like bismuth vanadate nanomaterial.

The above-mentioned modified fern-like bismuth vanadate photocatalytic nanomaterial is further improved. The modified fern-like bismuth vanadate photocatalytic nanomaterial is prepared by calcining the fern-like bismuth vanadate nanomaterial in a nitrogen atmosphere; The fern-like bismuth vanadate nanomaterial is prepared by using bismuth salt and vanadium salt as raw materials and hydrothermal treatment under a pH value of 3 to 4; the fern-like bismuth vanadate nanomaterial has bismuth vanadate distributed on its surface. Nanoparticles.

As a technical concept, the present invention also proposes a preparation method of modified fern-like bismuth vanadate photocatalytic nanomaterials, which includes the following steps:

S1. Dissolve the bismuth salt in water, add the vanadium salt, and stir to obtain a mixed solution;

S2. Adjust the pH value of the mixed solution to 3 to 4, and perform a hydrothermal reaction to obtain fern-like bismuth vanadate nanomaterials;

S3. Under a nitrogen atmosphere, heat the fern-like bismuth vanadate nanomaterial obtained in step S2 to above 350°C for calcination to obtain a modified fern-like bismuth vanadate photocatalytic nanomaterial.

The above preparation method is further improved. In step S3, the calcination temperature is 350°C to 650°C.

The above preparation method is further improved. In step S3, the calcination temperature is 400°C to 600°C.

The above preparation method is further improved. In step S1, the mass fraction of the bismuth salt in the mixed solution is 1.25 mg/mL ~ 1.5 mg/mL, and the mass fraction of the vanadium salt is 1.5 mg/mL ~ 2.5 mg/mL; The bismuth salt is bismuth nitrate pentahydrate; the vanadium salt is sodium orthovanadate; the stirring time is 5 to 10 minutes.

The above preparation method is further improved. In step S2, glacial acetic acid is used to adjust the pH value of the mixed solution; the temperature of the hydrothermal reaction is 110°C to 200°C; and the hydrothermal reaction time is 10h to 12h.

The above preparation method is further improved. In step S3, the calcination time is 2h to 3h; the modified fern-like bismuth vanadate photocatalytic nanomaterials include fern-like bismuth vanadate nanomaterials, and the fern-like vanadium Nitrogen and oxygen defects are introduced on the surface of bismuth acid nanomaterials.

As a technical concept, the present invention also provides the above-mentioned modified fern-like bismuth vanadate photocatalytic nanomaterial or the modified fern-like bismuth vanadate photocatalytic nanomaterial prepared by the above-mentioned preparation method for treating organic pollution. Application in wastewater.

The above application is further improved, and the application includes the following steps: mixing the modified fern-shaped bismuth vanadate photocatalytic nanomaterials with organic pollutant wastewater, stirring, and performing a photocatalytic reaction to complete the treatment of organic pollutants in the wastewater. ; The amount of the modified fern-like bismuth vanadate photocatalytic nanomaterial added is 0.5g to 1.5g of the modified fern-like bismuth vanadate photocatalytic nanomaterial per liter of organic pollutant wastewater.

The above application is further improved, the organic pollutant in the organic pollutant wastewater is at least one of bisphenol A, bisphenol B, and bisphenol F; the initial concentration of the organic pollutant in the organic pollutant wastewater is 20mg/L.

The above application can be further improved in that the stirring time is 30 minutes; the photocatalytic reaction time is 60 minutes.

Compared with the prior art, the advantages of the present invention are:

(1) The bismuth vanadate material has small specific surface area, few active sites, weak light absorption ability, narrow photoresponse range, low carrier mobility, short diffusion distance of photogenerated holes, and photogenerated electron-hole recombination rate. High, poor photocatalytic activity, poor stability and other defects, the present invention creatively proposes a modified fern-like bismuth vanadate photocatalytic nanomaterial, including fern-like bismuth vanadate nanomaterial, the surface of fern-like bismuth vanadate nanomaterial Nitrogen and oxygen defects are introduced. Compared with other different shapes, the fern-like bismuth vanadate nanomaterial used in the present invention has the following advantages: As a nanomaterial with a unique fern bionic morphology, the fern-like bismuth vanadate nanomaterial has a larger specific surface area. , more active sites, while increasing the number of active sites, can also significantly shorten the diffusion distance of photogenerated carriers, which is beneficial to improving the separation efficiency of photogenerated carriers, and can significantly improve reaction kinetics and promote solution The target pollutants are fully contacted with the material, which is more conducive to promoting the rapid treatment of the target pollutants by the material. On this basis, in the present invention, nitrogen elements and oxygen defects are introduced on the surface of fern-like bismuth vanadate nanomaterials, which can further bring the following advantages: oxygen is introduced on the surface of fern-like bismuth vanadate nanomaterials through nitrogen doping. Defects, on the one hand, oxygen defects, as an electron donor, can increase most carrier density and provide electron traps to promote the separation of photogenerated carriers in fern-like bismuth vanadate nanomaterials, and oxygen defects can also pass through Impurity energy levels are generated near the conduction band (CB) or valence band (VB) edges to improve the electronic structure of BiVO ₄ "fern-like" nanomaterials, making the fern-like bismuth vanadate nanomaterials have higher electrical conductivity and thermal stability. This can also promote the improvement of the light absorption capacity of the material, thereby significantly improving the light energy utilization rate and photogenerated carrier separation efficiency of fern-like bismuth vanadate nanomaterials. At the same time, the doping of nitrogen can also introduce more Active sites, and more importantly, there is a synergistic promotion effect between nitrogen doping and oxygen defects, which can effectively reduce the band gap of the material, enhance the excitation of carrier conduction bands, and is beneficial to the electron transfer in redox reactions. transfer. Compared with the existing conventional bismuth vanadate photocatalytic nanomaterials, the modified fern-like bismuth vanadate photocatalytic nanomaterials of the present invention have large specific surface area, many active sites, strong light absorption capacity, wide light response range, and photogenerated electrons. - It has the advantages of low hole recombination rate, good conductivity, high photocatalytic activity, and good stability. It is a new bismuth vanadate catalyst that can be widely used and has excellent performance. When used to treat organic pollutant wastewater, it can It can achieve rapid and complete removal of organic pollutants in wastewater, has high use value and good application prospects.

(2) In view of the harsh reaction conditions, high safety risks, easy damage to the crystal structure and the resulting poor photocatalytic activity and poor stability of the bismuth vanadate nanomaterials in the preparation method, the present invention creatively provides A method for preparing modified fern-like bismuth vanadate photocatalytic nanomaterials. First, a mixed solution is prepared from bismuth salt and vanadium salt as raw materials, and then the pH value of the mixed solution is adjusted to 3 to 4 and undergoes simple hydrothermal treatment. The fern-like bismuth vanadate nanomaterials with unique fern-like bionic morphology can be prepared, and then the fern-like bismuth vanadate nanomaterials are placed in a nitrogen atmosphere and heated to above 350°C for calcination, and then the fern-like bismuth vanadate nanomaterials can be prepared. Nitrogen doping is introduced on the surface of the material and oxygen defects are generated. Not only the reaction conditions are mild, safe and reliable, but it is also easier to introduce oxygen defects to the surface of the material instead of deep (internally), thus preparing a product with excellent photocatalytic performance and good stability. Modified fern-like bismuth vanadate photocatalytic nanomaterials. At the same time, the preparation method of the present invention also has the advantages of simple process, convenient operation, low cost, high yield, etc., is suitable for large-scale preparation, and is convenient for industrial utilization.

(3) In the preparation method of the modified fern-like bismuth vanadate photocatalytic nanomaterials of the present invention, by optimizing the calcination temperature, it is more conducive to introducing oxygen defects to the surface of the material, thereby effectively preventing oxygen defects from entering the interior of the crystal. Modified fern-like bismuth vanadate photocatalytic nanomaterials with better photocatalytic performance and better stability can be obtained. For example, compared with the calcination temperature of 350°C or 650°C, the present invention is prepared at 400°C-600°C. The fluorescence emission signal of the modified fern-like bismuth vanadate photocatalytic nanomaterial is weaker and the photocurrent signal is stronger, which shows that the modified fern-like bismuth vanadate photocatalytic nanomaterial prepared has more excellent photocatalytic performance. In particular, when the calcination temperature is lower than 350°C, it is difficult to successfully introduce the N element through N ₂ atmosphere calcination, while when it is higher than 650°C, bulk defects will be formed, which serve as the composite center of the photogenerated carrier and will lead to the catalytic activity of the catalyst. reduce.

(4) The present invention also provides an application of modified fern-like bismuth vanadate photocatalytic nanomaterials in the treatment of organic pollutant wastewater, by mixing the modified fern-like bismuth vanadate photocatalytic nanomaterials with organic pollutant wastewater. Photocatalytic reaction can achieve efficient removal of organic pollutants in wastewater. It has the advantages of simple process, operation method, low cost, high treatment efficiency, and good removal effect, which is conducive to the effective treatment of organic pollutant wastewater. Taking bisphenol A as an example, the removal rate of bisphenol A is as high as 97.16% after being treated with the modified fern-like bismuth vanadate photocatalytic nanomaterial of the present invention for 60 minutes, showing very excellent removal ability, while conventional BiVO ₄ nanosheets The removal rate of bisphenol A is only 49.51%. At the same time, when the modified fern-shaped bismuth vanadate photocatalytic nanomaterials of the present invention are used to cyclically treat bisphenol A wastewater, the removal rate of bisphenol A can still be achieved after recycling 4 times. The effective removal of bisphenol A not only has good reusability, but is also more conducive to reducing treatment costs.

Description of the drawings

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention.

Figure 1 shows the fern-like bismuth vanadate nanomaterial (a) prepared in Example 1 of the present invention, the modified fern-like bismuth vanadate photocatalytic nanomaterial (b) and the sheet-like bismuth vanadate nanomaterial prepared in Comparative Example 1. SEM image of (c), where a is "fern-like" BiVO ₄ , b is N/O _v /BiVO ₄ -450, and c is BiVO ₄ nanosheets.

Figure 2 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ), modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -450) prepared in Example 1 of the present invention. Nitrogen adsorption-desorption isotherm diagram of the sheet-like bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1.

Figure 3 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-shaped bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 UV-diffuse spectral reflectance plot.

Figure 4 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-shaped bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 Photoluminescence fluorescence spectrum.

Figure 5 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-shaped bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 Photocurrent response signal diagram.

Figure 6 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) XPS O1s spectra.

Figure 7 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) XPS N1s spectra.

Figure 8 shows the modified fern-like bismuth vanadate photocatalytic nanomaterial (N/O _v /BiVO ₄ -450) and fern-like bismuth vanadate nanomaterial ("fern-like" BiVO ₄ ) prepared in Example 2 of the present invention. , schematic diagram of the relationship between the concentration of bisphenol A and the photocatalytic time during the photodegradation process of flaky bismuth vanadate nanomaterials (BiVO ₄ nanosheets).

Figure 9 is a diagram showing the effect of recycling bisphenol A wastewater by modified fern-like bismuth vanadate photocatalytic nanomaterials in Example 3 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments of the specification, but the protection scope of the present invention will not be limited thereby. The materials and instruments used in the following examples are all commercially available.

Example 1:

A modified fern-like bismuth vanadate photocatalytic nanomaterial, which is characterized in that it includes a fern-like bismuth vanadate nanomaterial, and nitrogen elements and oxygen defects are introduced on the surface of the fern-like bismuth vanadate nanomaterial.

In this embodiment, the modified fern-like bismuth vanadate photocatalytic nanomaterial is prepared by calcining the fern-like bismuth vanadate nanomaterial in a nitrogen atmosphere, wherein the fern-like bismuth vanadate nanomaterial is made of bismuth salt and vanadium salt. It is obtained by hydrothermal treatment of raw materials at a pH value of 3 to 4.

In this embodiment, bismuth vanadate nanoparticles are distributed on the surface of the fern-like bismuth vanadate nanomaterial.

The preparation method of the modified fern-like bismuth vanadate photocatalytic nanomaterial in the above embodiment includes the following steps:

(1) Dissolve 60 mg of bismuth nitrate pentahydrate in 40 mL of deionized water, stir evenly, add 100 mg of sodium orthovanadate, and stir for 10 min to obtain mixed solution A.

(2) Use glacial acetic acid to adjust the pH value of mixed solution A obtained in step (1) to 4.0 to obtain mixed solution B.

(3) Transfer the mixed solution B obtained in step (3) to the lining of the reactor, install it into the steel jacket of the hydrothermal reactor, and perform a hydrothermal reaction at 110°C for 12 hours. After the hydrothermal reaction is completed, it will naturally Lower to room temperature and vacuum dry at 45°C for 6 hours to obtain a fern-like bismuth vanadate nanomaterial, which is recorded as "fern-like" BiVO ₄ .

(4) Place the fern-like bismuth vanadate nanomaterial obtained in step (d) in a clean quartz crucible, and heat it to 450°C for 3 hours at a heating rate of 3°C/min in a nitrogen atmosphere. Nitrogen element was introduced into the bismuth vanadate nanomaterial and oxygen defects were generated to obtain a modified fern-like bismuth vanadate photocatalytic nanomaterial, recorded as N/O _v /BiVO ₄ -450.

In this example, the effects of different calcination temperatures on the properties of fern-like bismuth vanadate nanomaterials were also examined, in which the modified fern-like bismuth vanadate photocatalytic nanomaterials were calcined at temperatures of 350°C, 550°C, and 650°C. Recorded as N/O _v /BiVO ₄ -350, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650.

Comparative example 1:

A method for preparing sheet-shaped bismuth vanadate nanomaterials, including the following steps:

(1) Dissolve 60 mg of bismuth nitrate pentahydrate in 40 mL of deionized water, stir evenly, add 100 mg of sodium orthovanadate, and stir for 10 min to obtain mixed solution A.

(2) Use glacial acetic acid to adjust the pH value of mixed solution A obtained in step (1) to 6.0 to obtain mixed solution B.

(3) Transfer the mixed solution B obtained in step (3) to the lining of the reactor, install it into the steel jacket of the hydrothermal reactor, and perform a hydrothermal reaction at 110°C for 12 hours. After the hydrothermal reaction is completed, it will naturally Lower to room temperature and vacuum dry at 45°C for 6 hours to obtain sheet-like bismuth vanadate nanomaterials, which are recorded as BiVO ₄ nanosheets.

The fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ), modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -450) prepared in Example 1 and Comparative Example 1 were used. The prepared sheet-like bismuth vanadate nanomaterials (BiVO ₄ nanosheets) were analyzed by SEM, and the results are shown in Figure 1. Figure 1 shows the fern-like bismuth vanadate nanomaterial (a) prepared in Example 1 of the present invention, the modified fern-like bismuth vanadate photocatalytic nanomaterial (b) and the sheet-like bismuth vanadate nanomaterial prepared in Comparative Example 1. SEM image of (c), where a is "fern-like" BiVO ₄ , b is N/O _v /BiVO ₄ -450, and c is BiVO ₄ nanosheets. As can be seen from Figures 1a and 1b, both "fern-like" BiVO ₄ and N/O _v /BiVO ₄ -450 show a fern-like morphology with a size of 500 nm, and particles with a diameter of 10 nm are evenly distributed on the surface. This unique The bionic morphology structure will bring a larger specific surface area. At the same time, it can be seen from Figures 1a and 1b that the morphologies of "fern-like" BiVO ₄ and N/O _v /BiVO ₄ -450 are almost consistent, indicating that calcination in a nitrogen atmosphere will not destroy the special morphology of BiVO ₄ . In addition, as shown in Figure 1c, BiVO ₄ nanosheets exhibit a typical sheet structure and have a smooth surface.

The fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ), modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -450) prepared in Example 1 and Comparative Example 1 were used. The prepared sheet-like bismuth vanadate nanomaterials (BiVO ₄ nanosheets) were subjected to nitrogen adsorption and desorption tests, and the results are shown in Figure 2. Figure 2 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ), modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -450) prepared in Example 1 of the present invention. Nitrogen adsorption-desorption isotherm diagram of the sheet-like bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1. After BET calculation, "fern-like" BiVO ₄ is 11.65m ² /g, N/O _v /BiVO ₄ -450 is 20.59m ² /g, and BiVO ₄ nanosheets are 1.22m ² /g. It can be seen that compared with BiVO ₄ nanosheets, both N/O _v /BiVO ₄ -450 and "fern-shaped" BiVO ₄ have larger specific surface areas, which are beneficial to increasing the contact area between the catalyst and environmental pollutants and increasing the reaction site. point.

For the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials prepared in Example 1 (N/O _v /BiVO ₄ -350, N/O _v / BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-shaped bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 were subjected to UV-diffusion. Spectral reflectance analysis, the results are shown in Figure 3. Figure 3 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-like bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 UV-diffuse spectral reflectance plot. As can be seen from Figure 3, the light absorption capacity of "fern-like" BiVO ₄ is improved to a certain extent compared to BiVO ₄ nanosheets; modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N/ The visible light absorption edge of O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) has a certain red shift relative to the simple "fern-like" BiVO ₄ , and with As the calcination temperature increases, the absorption of N/O _v /BiVO ₄ -x is slightly enhanced in the range <500 nm. It can be seen that the "fern-shaped" BiVO ₄ has better light absorption capacity than the lamellar BiVO _4. At the same time, the introduction of nitrogen elements and oxygen defects can further improve the "fern-shaped" BiVO ₄ . The light response range is more conducive to improving the light energy utilization rate of the material.

For the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials prepared in Example 1 (N/O _v /BiVO ₄ -350, N/O _v / BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-shaped bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 for photoluminescence fluorescence Spectral analysis and photocurrent response signal analysis, the results are shown in Figures 4 and 5. Figure 4 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-like bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 Photoluminescence fluorescence spectrum. Figure 5 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-shaped bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 Photocurrent response signal diagram. Fluorescence luminescence is caused by the recombination of photogenerated carriers, which can reflect the separation, transfer and migration rules of carriers. Fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ), modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N/O _v /BiVO ₄ -450, N/ O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the steady-state fluorescence emission spectrum (λ _ex 365nm) of the sheet-shaped bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1, As shown in Figure 4, the fluorescence intensity of BiVO ₄ nanosheets is significantly higher than that of "fern-shaped" BiVO ₄ , indicating that the carrier loading rate of the former is much higher than that of the latter. However, modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N/O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) are lower than those of "fern-like" BiVO ₄ , and show a trend of first decreasing and then increasing as the calcination temperature increases, indicating that the recombination of photoelectron-hole pairs first decreases and then increases. The photocurrent response signal shown in Figure 5 also has the same characteristics, and the photocurrent signal of N/O _v /BiVO ₄ -450 is stronger than that of N/O _v /BiVO ₄ -550 and N/O _v /BiVO ₄ -650. It can be seen that the N doping degree of the modified fern-like bismuth vanadate photocatalytic nanomaterials deepens as the calcination temperature increases, resulting in the generation of more bulk oxygen defects. When the bulk oxygen defects increase, it acts as The recombination center of the photogenerated carrier will also lead to a reduction in the catalytic activity of the catalyst. Therefore, relatively speaking, calcination at 400°C-600°C is more conducive to introducing surface oxygen defects on the surface of the material. The surface oxygen defects can serve as carrier traps and adsorption sites for active substances, thereby more effectively inhibiting photogeneration. The recombination of electrons and holes is consistent with the results in Figures 4 and 5, that is, the fluorescence emission signal becomes weaker and the photocurrent signal is enhanced. In particular, when the calcination temperature is 450°C, the modified fern produced The bismuth vanadate photocatalytic nanomaterial has a more appropriate oxygen defect surface and exhibits very excellent photocatalytic performance.

For the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials prepared in Example 1 (N/O _v /BiVO ₄ -350, N/O _v / BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) and the sheet-like bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1 were subjected to XPS analysis. The results are shown in Figures 6 and 7.

Figure 6 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) XPS O1s spectra. In Figure 6, the characteristic peaks of O1s can be divided into three types: O _L , O _V and O _A , which respectively represent lattice oxygen (O _L ), oxygen defect area (O _v ), and oxygen chemically absorbed from water (O O _A ). It can be seen from Figure 6 and Table 1 that as the calcination temperature increases, the peak area of Ov continues to increase, which indicates the increase in defective state oxygen.

Table 1 consists of fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N/O _v /BiVO ₄ -450 , N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) Peak areas of O _L , O _v and O _c calculated from high-resolution XPS peaks

Figure 7 shows the fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -350, N /O _v /BiVO ₄ -450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) XPS N1s spectra. It can be seen from Figure 7 and Table 2 that as the calcination temperature increases, the nitrogen content on the surface of the modified fern-like bismuth vanadate photocatalytic nanomaterials also increases.

Table 2: Photocatalytic photocatalytic nanomaterials composed of fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) and modified fern-like bismuth vanadate nanomaterials (N/O _v /BiVO ₄ -350, N/O _v /BiVO ₄ - 450, N/O _v /BiVO ₄ -550, N/O _v /BiVO ₄ -650) Peak area of nitrogen characteristic peak calculated from high-resolution XPS peak

Material Characteristic peak area N/O _v /BiVO ₄ -350 2159.16 N/O _v /BiVO ₄ -450 2599.13 N/O _v /BiVO ₄ -550 3355.31 N/O _v /BiVO ₄ -650 3414.60

Example 2

The application of a modified fern-like bismuth vanadate photocatalytic nanomaterial in the treatment of organic pollutant wastewater, specifically using the modified fern-like bismuth vanadate photocatalytic nanomaterial to treat bisphenol A wastewater, including the following steps:

(1) Weigh 50 mg of the modified fern-like bismuth vanadate photocatalytic nanomaterial (N/O _v /BiVO ₄ -450) prepared in Example 1, and add it to 50 mL in a light-proof environment with an initial concentration of 20 mg/ L of bisphenol A wastewater was adsorbed under stirring for 30 minutes and then placed in a photocatalytic reaction device.

(2) Use a 300W xenon lamp to conduct a photocatalytic reaction for 60 minutes to complete the treatment of bisphenol A in wastewater.

During the treatment process, measure the absorbance value of the reaction solution at 271nm wavelength at time t, and combine it with the standard curve to get the concentration C of bisphenol A at time t. Calculate the modification according to the formula D = (C ₀ -C)/C ₀ ×100%. The removal rate D of bisphenol A by the fern-like bismuth vanadate photocatalytic nanomaterial (N/O _v /BiVO ₄ -450), where C ₀ is the initial concentration of bisphenol A, and the removal rate of bisphenol A is shown in Figure 1 Show.

In addition, weigh 50 mg of the fern-like bismuth vanadate nanomaterial ("fern-like" BiVO ₄ ) prepared in Example 1 and the sheet-like bismuth vanadate nanomaterial (BiVO ₄ nanosheet) prepared in Comparative Example 1, respectively. According to The above operation steps treat bisphenol A wastewater, and their removal rate results for bisphenol A in wastewater are shown in Figure 1.

Figure 1 shows the modified fern-like bismuth vanadate photocatalytic nanomaterial (N/O _v /BiVO ₄ -450) and fern-like bismuth vanadate nanomaterial ("fern-like" BiVO ₄ ) prepared in Example 2 of the present invention. , schematic diagram of the relationship between the concentration of bisphenol A and the photocatalytic time during the photodegradation process of flaky bismuth vanadate nanomaterials (BiVO ₄ nanosheets). As can be seen from Figure 1, the modified fern-like bismuth vanadate photocatalytic nanomaterial (N/O _v /BiVO ₄ -450) has a removal rate of 97.16% of bisphenol A after photocatalytic treatment for 60 minutes, while the "fern-like" BiVO The removal rate of bisphenol A by ₄ was 71.47% and the removal rate of bisphenol A by BiVO ₄ nanosheets was 49.51%. It can be seen that compared with BiVO ₄ nanosheets, modified fern-like bismuth vanadate photocatalytic nanomaterials (N/O _v /BiVO ₄ -450) and fern-like bismuth vanadate nanomaterials ("fern-like" BiVO ₄ ) have Higher photocatalytic activity, and the photocatalytic activity of the modified fern-like bismuth vanadate photocatalytic nanomaterial (N/O _v /BiVO ₄ -450) is significantly higher than that of "fern-like" BiVO ₄ .

Example 3

The application of a modified fern-like bismuth vanadate photocatalytic nanomaterial in the treatment of organic pollutant wastewater, specifically using the modified fern-like bismuth vanadate photocatalytic nanomaterial to repeatedly treat bisphenol A wastewater, including the following steps:

The modified fern-like bismuth vanadate photocatalytic nanomaterials after the reaction in Example 2 were centrifuged and collected, then washed with a large amount of water and ethanol, and dried in an oven at 45°C for 10 hours to obtain regenerated modified fern-like vanadium. Bismuth acid vanadate photocatalytic nanomaterial; according to the treatment method in Example 1, use the regenerated modified fern-like bismuth vanadate photocatalytic nanomaterial to repeatedly treat the bisphenol A solution for a total of 4 times.

After 4 cycles of photocatalytic experiments, the removal rate of bisphenol A by the modified fern-like bismuth vanadate photocatalytic nanomaterials was detected. The cycle experiment results are shown in Figure 9. Figure 9 is a diagram showing the effect of recycling bisphenol A wastewater by modified fern-like bismuth vanadate photocatalytic nanomaterials in Example 3 of the present invention. As can be seen from Figure 9, in the fourth photocatalytic experiment, the photocatalytic removal rate of bisphenol A by the modified fern-like bismuth vanadate photocatalytic nanomaterials still did not significantly decrease, and the removal rate could still reach more than 90%. It shows that the modified fern-shaped bismuth vanadate photocatalytic nanomaterial of the present invention has good photocatalytic stability and good reusability, and can be widely used to treat organic pollutant wastewater.

In summary, it can be seen that the modified fern-like bismuth vanadate photocatalytic nanomaterial of the present invention has a large specific surface area, many active sites, strong light absorption capacity, wide photoresponse range, low photogenerated electron-hole recombination rate, and good conductivity. It has the advantages of high photocatalytic activity and good stability. It is a new type of bismuth vanadate catalyst that can be widely used and has excellent performance. When used to treat organic pollutant wastewater, it can achieve rapid and thorough removal of organic pollutants in wastewater. It has high use value and good application prospects, and is of great significance for effectively purifying water bodies polluted by organic waste.

The above descriptions are only preferred embodiments of the present invention and do not limit the present invention in any form. Although the present invention has been disclosed above in terms of preferred embodiments, this is not intended to limit the present invention. Any person familiar with the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical content disclosed above, or modify it to be equivalent, without departing from the spirit and technical solution of the present invention. Varied equivalent embodiments. Therefore, any simple modifications, equivalent substitutions, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims (7)

1. A method for preparing modified fern-like bismuth vanadate photocatalytic nanomaterials, which is characterized by comprising the following steps: S1. Dissolve the bismuth salt in water, add the vanadium salt, and stir to obtain a mixed solution; the bismuth salt is bismuth nitrate pentahydrate; the vanadium salt is sodium orthovanadate; S2. Use glacial acetic acid to adjust the pH value of the mixed solution to 3 to 4, and perform a hydrothermal reaction to obtain fern-like bismuth vanadate nanomaterials; S3. Under a nitrogen atmosphere, heat the fern-like bismuth vanadate nanomaterial obtained in step S2 to 350°C to 650°C for calcination to obtain a modified fern-like bismuth vanadate photocatalytic nanomaterial. 2. The preparation method according to claim 1, characterized in that in step S3, the calcination temperature is 400°C to 600°C. 3. The preparation method according to claim 1 or 2, characterized in that, in step S1, the mass fraction of the bismuth salt in the mixed solution is 1.25 mg/mL ~ 1.5 mg/mL, and the mass fraction of the vanadium salt is 1.5 mg/mL～2.5 mg/mL; the stirring time is 5 min～10 min; In step S2, the temperature of the hydrothermal reaction is 180 ℃ ~ 200 ℃; the hydrothermal reaction time is 10 h ~ 12 h; In step S3, the calcination time is 2 h to 3 h; the modified fern-like bismuth vanadate photocatalytic nanomaterials include fern-like bismuth vanadate nanomaterials, and the surface of the fern-like bismuth vanadate nanomaterials is introduced with Nitrogen and oxygen deficiencies. 4. Application of a modified fern-like bismuth vanadate photocatalytic nanomaterial prepared by the preparation method according to any one of claims 1 to 3 in the treatment of organic pollutant wastewater. 5. The application according to claim 4, characterized in that the application includes the following steps: mixing the modified fern-like bismuth vanadate photocatalytic nanomaterials with organic pollutant wastewater, stirring, performing a photocatalytic reaction, and completing the photocatalytic reaction. Treatment of organic pollutants in wastewater; the amount of the modified fern-like bismuth vanadate photocatalytic nanomaterial added is 0.5g to 1.5 g of modified fern-like bismuth vanadate photocatalytic nanomaterial per liter of organic pollutant wastewater. 6. Application according to claim 5, characterized in that, the organic pollutant in the organic pollutant wastewater is at least one of bisphenol A, bisphenol B, and bisphenol F; the organic pollutant in the wastewater The initial concentration of organic pollutants is 20 mg/L. 7. The application according to claim 5 or 6, characterized in that the stirring time is 30 min; the photocatalytic reaction time is 60 min.