Flower-like carbon / bismuth oxyhalide photocatalytic material and preparation method and application thereof

Abstract

The application discloses a flower-shaped carbon / halogen bismuth oxide photocatalytic material and a preparation method and application thereof, and belongs to the photocatalytic field.The halogen bismuth oxide is BiOCl, BiOBr and BiOI.The flower-shaped carbon / halogen bismuth oxide photocatalytic material is prepared by a one-pot solvent thermal method with carbonized carboxylated nanocellulose dispersion liquid as a reaction solvent.The carbonized cellulose forms the flower-shaped photocatalyst as a structure directing agent, and the cellulose has the advantages of being green, economical and sustainable as a carbon source.Compared with the halogen bismuth oxide, the flower-shaped carbon / halogen bismuth oxide has a larger specific surface area, better light absorption and a higher photogenerated carrier separation efficiency.The photocatalytic material is used for 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 Cr(VI) reduction.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis, specifically to a flower-like carbon / bismuth halide (BiOCl, BiOBr, and BiOI) catalytic material for the visible light photocatalytic reduction of Cr(VI). Background Technology

[0002] Bismuth oxyhalides (BiOX, X = Cl, Br, I) are a promising photocatalytic material and have been extensively studied. Their advantages include: (1) stable physicochemical properties, low toxicity, economic efficiency, and the ability to effectively control the band gap by changing the types of halogen atoms; (2) composed of layered [Bi₂O₂]. 2+ The layered structure formed by the interleaving of bilayer halide ions is beneficial for shortening the transport distance of photogenerated carriers and promoting their transport in different directions. However, the photocatalytic performance of the monolithic structure is still limited by the rapid recombination of photogenerated carriers. Carbonaceous materials have good visible light absorption and strong conductivity. Combining carbonaceous materials with BiOX can promote the separation and transport of photogenerated carriers. However, most carbonaceous materials are currently derived from fossil fuels and the preparation process is quite demanding. Therefore, it is of great significance to adopt a green and sustainable carbon source. In addition, the conventional BiOX microstructure is a disordered layered stacked structure with a small specific surface area and poor light-trapping ability. By structurally guiding the formation of an ordered three-dimensional flower-like structure, the specific surface area can be increased and the light-trapping ability can be enhanced, which is beneficial to the photocatalytic reaction. This invention uses green, economical, sustainable and abundant cellulose as a carbon source, and carbonizes it using a mild solvothermal method. The carbonized cellulose can also serve as a structure guiding agent, thereby preparing a flower-like carbon / bismuth halide photocatalytic material.

[0003] Chromium (Cr) is a typical heavy metal pollutant in water bodies, mostly produced in industrial processes such as leather tanning, textiles, electroplating, and steel manufacturing. Cr exists primarily in two ionic states: Cr(VI) and Cr(III). Cr(VI) is classified as a Group 1 carcinogen by the World Health Organization due to its strong carcinogenic and teratogenic properties. However, Cr(III) has lower toxicity and is an essential trace metal element for the human body. Therefore, reducing Cr(VI) to Cr(III) can effectively alleviate water pollution problems. Visible light accounts for approximately 46% of sunlight; therefore, photocatalytic reduction of Cr(VI) to Cr(III) using visible light 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 efficient photocatalytic reduction of Cr(VI) under visible light and its preparation method.

[0005] The technical solution of the present invention is to provide a photocatalytic material, characterized in that: the photocatalytic material is flower-shaped carbon / bismuth halide, wherein the bismuth halide is BiOCl, BiOBr and BiOI.

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

[0007] Step 1: Place the carboxylated nanocellulose dispersion in an oven and perform a solvothermal reaction at 180-220℃ for 42-54 hours, then filter to obtain a cellulose-based carbon dispersion.

[0008] Step 2: Mix Bi(NO3)3·5H2O with an aqueous acetic acid solution to obtain a homogeneous solution A;

[0009] Step 3: Mix potassium halide with the cellulose-based carbon dispersion obtained in Step 1 to obtain a homogeneous solution B;

[0010] Step 4: Mix solution A and solution B and then perform a solvothermal reaction at 140-180℃ in an oven for 10-14 hours to obtain the photocatalytic material.

[0011] Specifically, in step 1, the carboxylated nanocellulose dispersion is placed in an oven and subjected to a solvothermal reaction at 200°C for 48 hours, and then filtered to obtain a cellulose-based carbon dispersion.

[0012] Step 2: Mix Bi(NO3)3·5H2O with an aqueous acetic acid solution to obtain a homogeneous solution A;

[0013] Step 3: Mix potassium halide with the cellulose-based carbon dispersion obtained in Step 1 to obtain a homogeneous solution B;

[0014] Step 4: Mix solution A and solution B and then perform a solvothermal reaction at 160°C in an oven for 12 hours to obtain the photocatalytic material.

[0015] In the above technical solution, the volume of the carboxylated nanocellulose dispersion in step 1 is 60 mL, the solid content is 6 wt%, and the cellulose diameter is about 4-10 nm and the length is about 200 nm.

[0016] In the above technical solution, the volume of the acetic acid aqueous solution in step 2 is 40 mL, and the mass ratio is 10 wt%.

[0017] In the above technical solution, the potassium halide in step 3 is KCl, KBr, or KI;

[0018] In the above technical solution, the molar ratio of Bi(NO3)3·5H2O to potassium halide in steps 2 and 3 is 1:1;

[0019] In the above technical solution, the volume of the cellulose-based char dispersion in step 3 is 40 mL;

[0020] This invention also provides the application of the above-mentioned photocatalytic material in the photocatalytic reduction of Cr(VI) under visible light.

[0021] Compared with the prior art, the present invention has the following advantages after adopting the above solution:

[0022] Flower-shaped carbon / bismuth halide photocatalyst was prepared in a one-pot solvothermal process using a carbonized carboxylated nanocellulose dispersion as the reaction solvent. Carbonized cellulose acts as a structure directing agent, forming the aforementioned flower-shaped photocatalyst. Furthermore, cellulose as a carbon source offers advantages such as being green, economical, and sustainable. Compared to bismuth halide, flower-shaped carbon / bismuth halide has a larger specific surface area, better light absorption, and higher photogenerated carrier separation efficiency, ultimately improving the catalytic activity of the photocatalyst and enabling its application in the photocatalytic reduction of Cr(VI) under visible light. Among the flower-shaped photocatalysts provided by this invention, the carbon / BiOBr exhibits the best catalytic performance, achieving a Cr(VI) reduction rate of 98% after 30 minutes of visible light irradiation. Attached Figure Description

[0023] Figure 1 X-ray diffraction (XRD) patterns of flower-like carbon / bismuth halide, cellulose-based carbon, BiOCl, BiOBr and BiOI prepared in Examples 1-3 (Example 1: carbon / BiOCl; Example 2: carbon / BiOBr; Example 3: carbon / BiOI);

[0024] Figure 2 The images are scanning electron microscope (SEM) images of the flower-like carbon / bismuth halide materials prepared in Examples 1-3, respectively.

[0025] Figure 3 The graph shows the performance of the flower-like carbon / bismuth halide materials prepared in Examples 1-3, as well as cellulose-based carbon, BiOCl, BiOBr and BiOI, in the photocatalytic reduction of Cr(VI) under visible light. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments:

[0027] Example 1

[0028] 60 mL of carboxylated cellulose nanoparticle dispersion was placed in a 100 mL high-pressure reactor and maintained at 200 °C for 48 h. After cooling to room temperature, the dispersion was filtered through a 0.22 μm filter membrane to obtain a cellulose-based carbon dispersion. 0.605 g of Bi(NO3)3·5H2O was dissolved in 40 mL of acetic acid aqueous solution (10 wt%) to obtain solution A. Simultaneously, 0.095 g of KCl was dissolved in 40 mL of the cellulose-based carbon dispersion to obtain solution B. Solution B was then added dropwise to solution A, and after stirring for 30 min, the mixture was transferred to a 150 mL high-pressure reactor and maintained at 160 °C for 12 h. 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 °C. Flower-like carbon / BiOCl material was obtained.

[0029] Example 2:

[0030] 60 mL of carboxylated nanocellulose dispersion was placed in a 100 mL high-pressure reactor and maintained at 200 °C for 48 h. After cooling to room temperature, the dispersion was filtered through a 0.22 μm filter membrane to obtain a cellulose-based carbon dispersion. 0.605 g of Bi(NO3)3·5H2O was dissolved in 40 mL of acetic acid aqueous solution (10 wt%) to obtain solution A. Simultaneously, 0.148 g of KBr was dissolved in 40 mL of the cellulose-based carbon dispersion to obtain solution B. Solution B was then added dropwise to solution A, and after stirring for 30 min, the mixture was transferred to a 150 mL high-pressure reactor and maintained at 160 °C for 12 h. 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 °C. Flower-like carbon / BiOBr material was obtained.

[0031] Example 3:

[0032] 60 mL of carboxylated cellulose nanoparticle dispersion was placed in a 100 mL high-pressure reactor and maintained at 200 °C for 48 h. After cooling to room temperature, the dispersion was filtered through a 0.22 μm filter membrane to obtain a cellulose-based carbon dispersion. 0.605 g of Bi(NO3)3·5H2O was dissolved in 40 mL of acetic acid aqueous solution (10 wt%) to obtain solution A. Simultaneously, 0.206 g of KI was dissolved in 40 mL of the cellulose-based carbon dispersion to obtain solution B. Solution B was then added dropwise to solution A, and after stirring for 30 min, the mixture was transferred to a 150 mL high-pressure reactor and maintained at 160 °C for 12 h. 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 °C. Flower-like carbon / BiOI material was obtained.

[0033] Figure 1The XRD patterns of the flower-shaped carbon / bismuth halide prepared in Examples 1-3 are shown. It can be seen that the crystal structure of bismuth halide remains unchanged, and the carbon / bismuth halide materials prepared in Examples 1-3 contain both cellulose-based carbon and bismuth halide.

[0034] Figure 2 The images show SEM images of the flower-like carbon / bismuth halide prepared in Examples 1-3. It can be seen that the microstructures of carbon / BiOCl, carbon / BiOBr, and carbon / BiOI are all relatively regular flower-like structures.

[0035] The photocatalytic test conditions are as follows:

[0036] 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). -1 The mixed solution was first stirred in the dark for 60 minutes to reach the adsorption-desorption equilibrium of Cr(VI) by the catalyst. Then, the reaction solution was placed under a 300W xenon lamp equipped with a filter (light wavelength range: 400-780nm, light intensity: 50mW). -2 The photocatalytic reaction was carried out under [a specific environment / condition]. During the photocatalytic reaction, samples were taken at regular intervals, and the catalyst was filtered through a 0.22 μm nylon 66 filter head. The filtrate samples were collected. The Cr(VI) concentration was determined at 540 nm using a UV-Vis spectrophotometer and the diphenylcarbazide spectrophotometric method.

[0037] The results of the examples show (e.g.) Figure 3 Among the flower-like photocatalytic materials provided by the present invention, carbon / BiOBr (Example 2) exhibits the best catalytic performance, with a Cr(VI) reduction rate of 98% after 30 minutes of visible light irradiation.

[0038] This invention utilizes a carbonized carboxylated cellulose nanoparticle dispersion as the reaction solvent to prepare a flower-like carbon / bismuth halide photocatalyst in a one-pot solvothermal process. The carbonized cellulose acts as a structure directing agent, forming the aforementioned flower-like photocatalyst, and cellulose as a carbon source offers advantages such as being green, economical, and sustainable. Compared to bismuth halide, the flower-like carbon / bismuth halide exhibits a larger specific surface area, better light absorption, and higher photogenerated carrier separation efficiency. This photocatalyst is used for the photocatalytic reduction of Cr(VI) under visible light, offering advantages such as a simple preparation method and high visible light catalytic activity, providing an economical, green, and sustainable pathway for Cr(VI) reduction.

[0039] The above description only illustrates preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. Any equivalent structural or procedural modifications made using this specification are included within the patent protection scope of the present invention.

Claims

1. A flower-like photocatalytic material, wherein the photocatalytic material is cellulose-based carbon / bismuth halide, and the bismuth halide is BiOCl, BiOBr, or BiOI, and its preparation method includes the following steps: Step 1: Place the carboxylated nanocellulose dispersion in an oven and perform a solvothermal reaction at 180-220℃ for 42-54 hours, then filter to obtain a cellulose-based carbon dispersion. Step 2: Mix Bi(NO3)3·5H2O with an aqueous acetic acid solution to obtain a homogeneous solution A; Step 3: Mix potassium halide with the cellulose-based carbon dispersion obtained in Step 1 to obtain a homogeneous solution B; Step 4: Mix solution A and solution B and then perform a solvothermal reaction at 140-180℃ in an oven for 10-14 hours to obtain the photocatalytic material.

2. The method of claim 1, wherein the method is characterized by: Includes the following steps, Step 1: Place the carboxylated nanocellulose dispersion in an oven and perform a solvothermal reaction at 180-220℃ for 42-54 hours, then filter to obtain a cellulose-based carbon dispersion. Step 2: Mix Bi(NO3)3·5H2O with an aqueous acetic acid solution to obtain a homogeneous solution A; Step 3: Mix potassium halide with the cellulose-based carbon dispersion obtained in Step 1 to obtain a homogeneous solution B; Step 4: Mix solution A and solution B and then perform a solvothermal reaction at 140-180℃ in an oven for 10-14 hours to obtain the photocatalytic material.

3. The method for preparing the photocatalytic material according to claim 1, characterized in that: Includes the following steps, Step 1: The carboxylated nanocellulose dispersion was placed in an oven and subjected to a solvothermal reaction at 200°C for 48 hours, and then filtered to obtain a cellulose-based carbon dispersion. Step 2: Mix Bi(NO3)3·5H2O with an aqueous acetic acid solution to obtain a homogeneous solution A; Step 3: Mix potassium halide with the cellulose-based carbon dispersion obtained in Step 1 to obtain a homogeneous solution B; Step 4: Mix solution A and solution B and then perform a solvothermal reaction at 160°C in an oven for 12 hours to obtain the photocatalytic material.

4. The method for preparing the photocatalytic material according to claim 3, characterized in that: The volume of the carboxylated nanocellulose dispersion in step 1 is 60 mL, the solid content is 6 wt%, and the cellulose has a diameter of 4-10 nm and a length of 200 nm.

5. The method for preparing the photocatalytic material according to claim 3, characterized in that: The volume of the acetic acid aqueous solution in step 2 is 40 mL, and the mass ratio is 10 wt%.

6. The method for preparing the photocatalytic material according to claim 3, characterized in that: The potassium halide in step 3 is KCl, KBr, or KI.

7. The method for preparing the photocatalytic material according to claim 3, characterized in that: The molar ratio of Bi(NO3)3·5H2O to potassium halide in steps 2 and 3 is 1:

1.

8. The method for preparing the photocatalytic material according to claim 3, characterized in that: The volume of the cellulose-based carbon dispersion in step 3 is 40 mL.

9. The application of a catalyst prepared by the photocatalytic material as described in claim 1 or by the method for preparing the photocatalytic material as described in any one of claims 2-8 in the photocatalytic reduction of Cr(VI) under visible light.

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