Poplar derived carbon / bismuth oxybromide photocatalytic material as well as preparation method and application thereof

Abstract

The invention discloses a poplar derived carbon / bismuth oxybromide photocatalytic material as well as a preparation method and application thereof, and belongs to the field of photocatalysis. The flower-like poplar derived carbon / bismuth oxybromide photocatalytic material is prepared in one pot through a solvothermal method by taking a poplar derived carbon dispersion liquid as a reaction solvent. The poplar derived carbon serves as a structure-directing agent to form the flower-shaped photocatalyst, and poplar serving as a carbon source has the advantages of being environmentally friendly, economical and sustainable. Compared with bismuth oxybromide, the poplar derived carbon / bismuth oxybromide has the advantages of large specific surface area, good light absorption and high photon-generated carrier separation efficiency. The photocatalytic material is used for photocatalytic reduction of Cr (VI) under visible light, has the advantages of simple preparation method and high visible light catalytic activity, and provides an economic, green and sustainable way for reduction of Cr (VI).

Description

Technical Field

[0001] The invention relates to the field of photocatalysis, and in particular to an application of a poplar-derived carbon / bismuth oxybromide catalytic material for visible light photocatalytic reduction of Cr(VI). Background Art

[0002] Bismuth oxybromide (BiOBr) is a promising photocatalytic material that has been widely studied. Its advantages are: (1) stable physical and chemical properties, low toxicity, economical and narrow band gap; (2) composed of layered [Bi2O2] 2+ The double-layer Br ions are interlaced to form a lamellar structure, which is beneficial to shorten the transmission distance of photogenerated carriers and promote the transmission of carriers in different directions. However, the photocatalytic performance of the monomer structure is still limited by the rapid recombination of photogenerated carriers. Carbonaceous materials have good visible light absorption ability and strong conductivity. The composite of carbonaceous materials and BiOBr can promote the separation and transmission of photogenerated carriers. However, most of the carbonaceous materials currently come from fossil energy and the preparation process is relatively harsh. It is of great significance to use a green and sustainable carbon source. Poplar is a high-yield tree species with a wide planting range and fast growth rate. Therefore, it is rich in resources and has strong renewable capacity. Using poplar powder as a carbon source is very consistent with the concept of green sustainability. In addition, the conventional BiOBr micromorphology is a disordered lamellar stacking structure with a small specific surface area and poor light capture ability. The formation of a three-dimensional flower-like structure through structural guidance can increase the specific surface area and enhance the capture of light, which is conducive to the photocatalytic reaction. The present invention adopts green, economical, sustainable and abundant poplar wood powder as a carbon source, carbonizes it by a mild solvent thermal method, and the derived carbon can also serve as a structure directing agent, thereby preparing a flower-shaped poplar wood derived carbon / bismuth oxybromide photocatalytic material.

[0003] Chromium (Cr) is a typical heavy metal water pollutant, mostly produced in industrial production processes such as leather tanning, textiles, electroplating and steel manufacturing. Cr mainly exists in two ionic states: Cr(VI) and Cr(III). Cr(VI) is listed as a Class I carcinogen by the World Health Organization due to its strong carcinogenicity and teratogenicity. However, Cr(III) is less toxic and is an essential trace metal element for the human body. Therefore, reducing Cr(VI) to Cr(III) can effectively alleviate the problem of water pollution. Visible light accounts for about 46% of sunlight. Reducing Cr(VI) to Cr(III) through visible light photocatalysis is a green and sustainable technology, which is of great significance for promoting the application of photocatalysis in environmental remediation. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a catalytic material capable of efficiently photocatalytically reducing Cr(VI) under visible light and a preparation method thereof.

[0005] The technical solution of the present invention is to provide a photocatalytic material, characterized in that the photocatalytic material is poplar-derived carbon / bismuth oxybromide.

[0006] The present invention also provides a method for preparing the above-mentioned photocatalytic material, comprising the following steps:

[0007] Step 1, mixing poplar wood powder with deionized water, stirring and ultrasonicating for more than 3 hours to form a poplar wood powder dispersion;

[0008] Step 2, placing the poplar wood powder dispersion in an oven for a solvothermal reaction at 180-220° C. for 42-54 hours, and filtering to obtain a poplar wood derived carbon dispersion;

[0009] Step 3, mixing Bi(NO3)3·5H2O with an acetic acid aqueous solution to obtain a uniform solution A;

[0010] Step 4, mixing potassium bromide with the poplar wood derived carbon dispersion obtained in step 1 to obtain a uniform solution B;

[0011] Step 5, after mixing solution A and solution B, perform a solvent thermal reaction in an oven at 140-180° C. for 10-14 hours to obtain a photocatalytic material.

[0012] Specifically, step 1, mixing poplar wood powder with deionized water, stirring and ultrasonicating for 3 hours to form a poplar wood powder dispersion;

[0013] Step 2, placing the poplar wood powder dispersion in an oven for a solvothermal reaction at 200° C. for 48 hours, and filtering to obtain a poplar wood derived carbon dispersion;

[0014] Step 3, mixing Bi(NO3)3·5H2O with an acetic acid aqueous solution to obtain a uniform solution A;

[0015] Step 4, mixing potassium bromide with the poplar wood derived carbon dispersion obtained in step 2 to obtain a uniform solution B;

[0016] Step 5, after mixing solution A and solution B, perform solvothermal reaction in an oven at 160° C. for 12 h to obtain a photocatalytic material.

[0017] In the above technical solution, the poplar wood powder in step 1 is 60 mesh;

[0018] In the above technical solution, the volume of the acetic acid aqueous solution in step 3 is 40 mL, and the mass ratio is 10 wt%;

[0019] In the above technical solution, the molar ratio of Bi(NO3)3·5H2O and potassium bromide in steps 3 and 4 is 1:1;

[0020] In the above technical solution, the volume of the poplar wood derived carbon dispersion in step 4 is 40 mL;

[0021] The present invention also provides the application of the photocatalytic material in photocatalytic reduction of Cr(VI) under visible light.

[0022] Compared with the prior art, the present invention has the following advantages after adopting the above scheme:

[0023] Flower-shaped poplar-derived carbon / bismuth oxybromide photocatalytic materials were prepared in one pot by solvothermal method using poplar-derived carbon dispersion as reaction solvent. Poplar-derived carbon was used as a structure directing agent to form the above-mentioned flower-shaped photocatalyst, and poplar as a carbon source has the advantages of being green, economical and sustainable. Compared with bismuth oxybromide, poplar-derived carbon / bismuth oxybromide has a larger specific surface area, good light absorption and high efficiency of photogenerated carrier separation, which ultimately improves the catalytic activity of the photocatalyst and can be applied to photocatalytic Cr(VI) reduction under visible light; in the photocatalytic material provided by the present invention, when the amount of poplar powder is 0.9g, the obtained poplar-derived carbon / bismuth oxybromide catalyst has the best performance, and after 30 minutes of visible light irradiation, the reduction rate of Cr(VI) is 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 X-ray diffraction (XRD) patterns of poplar wood derived carbon / bismuth oxybromide, poplar wood derived carbon and BiOBr prepared in Examples 1-3;

[0025] Figure 2 The scanning electron microscope (SEM) images of the flower-shaped poplar-derived carbon / bismuth oxybromide materials prepared in Examples 1-3 are respectively;

[0026] Figure 3 Performance diagram of the photocatalytic reduction of Cr(VI) under visible light of the poplar wood-derived carbon / bismuth oxybromide materials, poplar wood-derived carbon and BiOBr prepared in Examples 1-3. DETAILED DESCRIPTION

[0027] The present invention will be further described below with regard to specific embodiments:

[0028] Example 1

[0029] 0.3g of poplar wood powder was added to 59.7g of deionized water, stirred and ultrasonicated for 3h, and then the poplar wood powder dispersion was placed in a 100mL autoclave and kept at 200℃ for 48h. After cooling to room temperature, the poplar wood derived carbon dispersion was filtered through a 0.22μm filter membrane. 0.403g of Bi(NO3)3·5H2O was dissolved in 40mL of acetic acid aqueous solution (10wt%) to obtain solution A. At the same time, 0.099g of KBr was dissolved in 40mL of poplar wood derived carbon dispersion to obtain solution B. Then, solution B was added dropwise to solution A, stirred for 30min, and then transferred to a 150mL autoclave and kept at 160℃ for 12h. After cooling to room temperature, the sample was centrifuged, and the solid precipitate was washed with deionized water and ethanol and placed in an oven at 80℃ for drying. Poplar wood derived carbon / bismuth oxybromide material was obtained.

[0030] Embodiment 2:

[0031] 0.9g of poplar wood powder was added to 59.7g of deionized water, stirred and ultrasonicated for 3h, and then the poplar wood powder dispersion was placed in a 100mL autoclave and kept at 200℃ for 48h. After cooling to room temperature, the poplar wood derived carbon dispersion was filtered through a 0.22μm filter membrane. 0.403g of Bi(NO3)3·5H2O was dissolved in 40mL of acetic acid aqueous solution (10wt%) to obtain solution A. At the same time, 0.099g of KBr was dissolved in 40mL of poplar wood derived carbon dispersion to obtain solution B. Then, solution B was added dropwise to solution A, stirred for 30min, and then transferred to a 150mL autoclave and kept at 160℃ for 12h. After cooling to room temperature, the sample was centrifuged, and the solid precipitate was washed with deionized water and ethanol and then dried in an oven at 80℃. Poplar wood derived carbon / bismuth oxybromide material was obtained.

[0032] Embodiment 3:

[0033] 1.5g of poplar wood powder was added to 59.7g of deionized water, stirred and ultrasonicated for 3h, and then the poplar wood powder dispersion was placed in a 100mL autoclave and kept at 200℃ for 48h. After cooling to room temperature, the poplar wood-derived carbon dispersion was filtered through a 0.22μm filter membrane. 0.403g of Bi(NO3)3·5H2O was dissolved in 40mL of acetic acid aqueous solution (10wt%) to obtain solution A. At the same time, 0.099g of KBr was dissolved in 40mL of poplar wood-derived carbon dispersion to obtain solution B. Solution B was then added dropwise to solution A, stirred for 30min, and then transferred to a 150mL autoclave and kept at 160℃ for 12h. After cooling to room temperature, the sample was centrifuged, and the solid precipitate was washed with deionized water and ethanol and then dried in an oven at 80℃. Poplar wood-derived carbon / bismuth oxybromide material was obtained.

[0034] Figure 1This is the XRD diagram of the poplar-derived carbon / bismuth oxybromide prepared in Example 1-3; it can be seen that the crystal structure of bismuth oxybromide remains unchanged, and the poplar-derived carbon / bismuth oxybromide materials prepared in Example 1-3 contain both poplar-derived carbon and bismuth oxybromide.

[0035] Figure 2 The SEM images of the poplar-derived carbon / bismuth oxybromide prepared in Examples 1-3 show that the microstructures of the prepared poplar-derived carbon / bismuth oxybromide materials are all flower-like structures.

[0036] The photocatalytic test condition parameters are:

[0037] Photocatalytic reduction of Cr(VI) test: 40 mg of catalyst powder was dispersed in 40 mL of Cr(VI) aqueous solution (20 mg·L -1 The mixed solution was stirred in a dark environment for 60 min to achieve the adsorption-desorption equilibrium of the catalyst on Cr(VI), and then the reaction solution was placed in a 300W xenon lamp equipped with a filter (light wavelength range: 400-780nm, light intensity: 50mW·cm -2 ) to carry out the photocatalytic reaction. During the photocatalytic reaction, samples were taken at regular intervals, the catalyst was filtered through a 0.22 μm nylon 66 filter head, and the filtrate samples were collected. The Cr(VI) concentration was measured at 540 nm using a diphenylcarbazide photometric method using an ultraviolet-visible spectrophotometer.

[0038] The photocatalytic reaction results of the embodiment show (such as Figure 3 ), the poplar wood derived carbon / bismuth oxybromide material provided by the present invention has a relatively good photocatalytic Cr(VI) reduction performance. Among them, the catalytic performance of Example 2 is the best, and the reduction rate of Cr(VI) is 95% after 30 minutes of visible light irradiation.

[0039] The present invention uses a poplar-derived carbon dispersion as a reaction solvent, and prepares a flower-shaped poplar-derived carbon / bismuth oxybromide photocatalytic material in one pot by a solvothermal method. Poplar-derived carbon is used as a structure directing agent to form the above-mentioned flower-shaped photocatalyst, and poplar as a carbon source has the advantages of being green, economical and sustainable. Compared with bismuth oxybromide, poplar-derived carbon / bismuth oxybromide has a larger specific surface area, good light absorption and high photogenerated carrier separation efficiency. The photocatalytic material is used for the photocatalytic reduction of Cr(VI) under visible light, has the advantages of a simple preparation method and high visible light catalytic activity, and provides an economical, green and sustainable way for the reduction of Cr(VI).

[0040] The above is only an explanation of the preferred embodiments of the present invention, which should not be construed as a limitation on the claims. Any equivalent structure or equivalent process changes made using the present invention specification are included in the patent protection scope of the present invention.

Claims

1. A photocatalytic material, characterized in that: The photocatalytic material is poplar-derived carbon / bismuth oxybromide.

2. The method for preparing a photocatalytic material according to claim 1, characterized in that: The following steps are included: Step 1, mixing poplar wood powder with deionized water, stirring and ultrasonicating for more than 3 hours to form a poplar wood powder dispersion; Step 2, placing the poplar wood powder dispersion in an oven for a solvothermal reaction at 180-220° C. for 42-54 hours, and filtering to obtain a poplar wood derived carbon dispersion; Step 3, mixing Bi(NO3)3·5H2O with an acetic acid aqueous solution to obtain a uniform solution A; Step 4, mixing potassium bromide with the poplar wood derived carbon dispersion obtained in step 1 to obtain a uniform solution B; Step 5, after mixing solution A and solution B, perform a solvent thermal reaction in an oven at 140-180° C. for 10-14 hours to obtain a photocatalytic material.

3. The method for preparing a photocatalytic material according to claim 1, characterized in that: The following steps are included: Step 1, mixing poplar wood powder with deionized water, stirring and ultrasonicating for 3 hours to form a poplar wood powder dispersion; Step 2, placing the poplar wood powder dispersion in an oven for a solvothermal reaction at 200° C. for 48 hours, and filtering to obtain a poplar wood derived carbon dispersion; Step 3, mixing Bi(N03)3·5H2O with an acetic acid aqueous solution to obtain a uniform solution A; Step 4, mixing potassium bromide with the poplar wood derived carbon dispersion obtained in step 2 to obtain a uniform solution B; Step 5, after mixing solution A and solution B, perform solvothermal reaction in an oven at 160° C. for 12 h to obtain a photocatalytic material.

4. The method for preparing a photocatalytic material according to claim 3, characterized in that: The poplar wood powder in step 1 is 60 mesh.

5. The method for preparing a photocatalytic material according to claim 3, characterized in that: The volume of the acetic acid aqueous solution in step 3 is 40 mL, and the mass ratio is 10 wt %.

6. The method for preparing a photocatalytic material according to claim 3, characterized in that: The molar ratio of Bi(NO3)3·5H2O and potassium bromide in steps 3 and 4 is 1:

1.

7. The method for preparing a photocatalytic material according to claim 3, characterized in that: The volume of the poplar wood derived carbon dispersion in step 4 was 40 mL.

8. Use of the photocatalytic material according to claim 1 or a catalyst prepared by the photocatalytic material preparation method according to any one of claims 2 to 7 in photocatalytic reduction of Cr(VI) under visible light.

Images