A lignin carbon-based bismuth oxyhalide Z-type heterojunction composite material with regular flower-like morphology, a preparation method and applications thereof

Abstract

The application discloses a lignin carbon-based halogen bismuth oxide Z-type heterojunction composite material with regular flower-like morphology and a preparation method and application thereof. A lignin carbon-based halogen bismuth oxide Z-type heterojunction composite material BiOX / C with regular flower-like morphology, wide spectral response range, high efficiency and strong stability is synthesized by using lignin carbon with rich oxygen-containing functional groups for induction and pH regulation. Based on the flower-like morphology structure and Z-type heterojunction of the material, the separation of photo-generated carriers and holes is effectively promoted, so that the material has higher photo-reaction efficiency, and the shortcomings of traditional photocatalytic degradation of organic pollutants, such as low quantum efficiency, slow degradation rate, poor stability, easy deactivation and the like, are effectively solved. Moreover, the lignin carbon-based substrate material takes lignocellulose in agricultural waste as a carbon source, is environment-friendly and low in production cost, and has the advantages of simple synthesis method, considerable yield, mild reaction condition in the process of photocatalytic degradation of organic pollutants, simple operation and wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a lignin-based carbon halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology, its preparation method, and its application. Background Technology

[0002] In recent years, resource scarcity and environmental pollution have increasingly become critical issues threatening human survival and development. The development and utilization of new phenomena, theories, and technologies capable of safely, rapidly, with low energy consumption, and with high efficiency in degrading various pollutants have become a hot topic of continuous exploration for researchers. Due to its advantages of being green, mild, and energy-efficient, solar energy as the sole energy source for removing pollutants from water bodies has gradually become one of the most promising strategies for alleviating energy shortages and protecting the water environment. As a key step in achieving efficient water purification, the development of efficient, environmentally friendly, highly stable, and inexpensive photoresponsive materials has also become a focus of attention for scientists both now and in the future.

[0003] The mechanism of semiconductor photocatalytic degradation of organic pollutants utilizes the strong oxidizing power of holes or the reactive species generated by electrons and holes in water, such as hydroxyl radicals (·OH) and superoxide radicals (·O). 2- The photocatalytic activity of TiO2 and its secondary free radicals can undergo a series of reactions with organic pollutants in the system, including addition, substitution, and electron transfer. These free radicals break the C-C bonds and CH bonds in the organic matter, ultimately converting it into CO2 and H2O, thus degrading the organic pollutants. While traditional semiconductor photocatalysts, such as TiO2, possess advantages like high stability, non-toxicity, and low cost, their wide band gaps (e.g., 3.2 eV for anatase TiO2 and 3.0 eV for rutile TiO2) limit their practical application to a small proportion of ultraviolet light. Furthermore, the easy recombination of photogenerated electrons and holes and the tendency for nanoparticles to aggregate significantly reduce the photocatalytic activity of TiO2. Therefore, developing photocatalytic materials with broad spectral response and high catalytic activity is of great practical significance.

[0004] In recent years, a series of novel semiconductor photocatalytic materials have emerged to address these problems, including metal oxides (Ag₂O, ZnO, SnO₂, ZrO₂), vanadates (BiAlVO₇, BiVO₄), tungsticomolybdates (Bi₂MoO₆, Bi₂WO₆), and bismuth oxyhalides (BiOCl, BiOBr, BiOI). Among them, bismuth oxyhalides BiOX (X = Cl, Br, and I), composed of multiple components from the V-VI-VII main groups, possess the characteristic of [Bi₂O₂] 2+ The layered structure, with bonds intertwined with halogens, creates a structure within the BiOX crystal perpendicular to [Bi2O2]. 2+The internal electric field between the photogenerated electrons and halogens promotes the separation of photogenerated electrons and holes, resulting in excellent photocatalytic activity in BiOX semiconductors. Furthermore, the band gap of BiOX semiconductors decreases from 4.18 eV (BiOF) to 1.7 eV (BiOI) with increasing atomic number, significantly expanding the material's photocatalytic activity range. These materials show broad application prospects in the degradation of organic pollutants. However, BiOX materials also have several limitations. BiOCl has virtually no visible light response, limiting its utilization of sunlight; BiOBr has a suitable band gap, but its absorption range for visible light is narrow, requiring further tuning of the band structure; BiOI has a narrow band gap, making it easy for photogenerated carriers and holes to recombine, resulting in low photocatalytic efficiency. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problem of low photocatalytic efficiency of BiOX materials in the prior art, and to provide a lignin carbon-based halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology, its preparation method and application.

[0006] To address the shortcomings of the aforementioned technical problems, the present invention provides a method for preparing a lignin-carbon-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology, comprising the following steps:

[0007] S1. Dissolve the template agent and lignin together in ethylene glycol, disperse and mix them ultrasonically, and then heat and evaporate to dryness to obtain raw material A;

[0008] S2. Raw material A is heated to 500-1000℃ for 6-12 hours under nitrogen protection at a heating rate of 1-5℃ / min to obtain precursor B.

[0009] S3. Add precursor B to a strongly alkaline solution and heat to react. After the reaction is complete, wash and dry to obtain lignin carbon.

[0010] S4. Add the aqueous solution of halogen salt to the aqueous solution of bismuth salt and lignin carbon dropwise at a rate of 1 to 10 drops / second. After mixing, adjust the pH to 3 to 7 and heat to 150 to 200℃ for reaction. After the reaction is completed, centrifuge, wash, dry and grind to obtain a lignin carbon-based halogen bismuth composite material with a regular flower-like morphology.

[0011] As a further optimization of the preparation method of the lignin-carbon-based halooxybismuth Z-type heterojunction composite material with regular flower-like morphology of the present invention: the template agent in step S1 is silica microspheres and the lignin is alkali lignin.

[0012] As a further optimization of the preparation method of the lignin-carbon-based halooxybismuth Z-type heterojunction composite material with regular flower-like morphology of the present invention: the mass ratio of silica microspheres to alkali lignin is 1:1-1:10.

[0013] As a further optimization of the preparation method of the lignin carbon-based halooxybismuth Z-type heterojunction composite material with regular flower-like morphology of the present invention: the halogen salt in step S4 is a mixture of two of potassium chloride, potassium bromide and potassium iodide.

[0014] As a further optimization of the preparation method of the lignin-carbon-based bismuth halide Z-type heterojunction composite material with regular flower-like morphology of the present invention: the molar ratio of the two halogen salts is 1:1-10:1.

[0015] As a further optimization of the preparation method of the lignin-carbon-based halooxybismuth Z-type heterojunction composite material with regular flower-like morphology of the present invention: the strong alkaline solution in step S3 is sodium hydroxide solution, and the heating reaction temperature is 80℃.

[0016] As a further optimization of the preparation method of the lignin-carbon-based halooxybismuth Z-type heterojunction composite material with regular flower-like morphology of the present invention: in step S4, ammonia water is used to adjust the pH value of the solution.

[0017] The present invention also provides a lignin-based carbon halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology, which is prepared by the above method.

[0018] This invention also provides the application of a lignin-based carbon halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology in a photocatalytic degradation system of organic pollutants.

[0019] This invention offers the following advantages: Addressing the shortcomings of existing bismuth halide materials, this invention utilizes lignin carbon with abundant oxygen-containing functional groups and pH regulation to synthesize a lignin carbon-based bismuth halide Z-type heterojunction composite material, BiOX / C, with a wide spectral response range, high efficiency, and strong stability, featuring a regular flower-like morphology. The flower-like morphology and Z-type heterojunction effectively promote the separation of photogenerated carriers and holes, resulting in higher photoreaction efficiency. This effectively solves the drawbacks of traditional photocatalytic degradation materials for organic pollutants, such as low quantum efficiency, slow degradation rate, poor stability, and easy deactivation. Furthermore, this lignin carbon-based material uses lignocellulose from agricultural waste as a carbon source, making it environmentally friendly, low-cost, and easy to synthesize with a simple and feasible method and considerable yield. The photocatalytic degradation of organic pollutants occurs under mild reaction conditions and is simple to operate, showing broad application prospects. Attached Figure Description

[0020] Figure 1 BiOCl@C, BiOClx Br y SEM topography of @C;

[0021] Figure 2 (a) and (b) are the XRD patterns of BiOCl and BiOCl@C before and after the photocatalytic reaction, respectively;

[0022] Figure 3 PC, BiOCl@C and BiOCl, respectively. x Br y UV-Vis diffuse reflectance spectrum of @C;

[0023] Figure 4 For BiOCl, BiOCl@C and BiOBr x Cl y @C Photocatalytic Degradation Performance of Organic Dyes. Detailed Implementation

[0024] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0025] A method for preparing a lignin-based carbon halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology includes the following steps:

[0026] S1. Dissolve the template agent and lignin together in ethylene glycol, disperse and mix them ultrasonically, and then heat and evaporate to dryness to obtain raw material A.

[0027] The template agent can be silica microspheres, and the lignin can be alkali lignin. The mass ratio of silica microspheres to alkali lignin is 1:1 to 1:10.

[0028] S2. Raw material A is heated to 500-1000℃ for 6-12 hours under nitrogen protection at a heating rate of 1-5℃ / min to obtain precursor B.

[0029] S3. Precursor B is added to a strongly alkaline solution and heated to react. After the reaction is complete, it is washed and dried to obtain lignin carbon.

[0030] The strongly alkaline solution is a sodium hydroxide solution, and the reaction temperature is 80℃.

[0031] S4. Add the aqueous solution of halogen salt to the aqueous solution of bismuth salt and lignin carbon dropwise at a rate of 1 to 10 drops / second. After mixing, adjust the pH (ammonia water) to 3 to 7, and heat to 150 to 200℃ for reaction. After the reaction is completed, centrifuge, wash, dry and grind to obtain a lignin carbon-based halogen bismuth composite material with a regular flower-like morphology.

[0032] The halogen salt is a mixture of two of potassium chloride, potassium bromide, and potassium iodide, with a molar ratio of 1:1 to 10:1.

[0033] <Example 1>

[0034] 5g of silica microspheres and 5g of alkali lignin were added to 50ml of ethylene glycol and ultrasonically mixed for 30min. The mixture was then continuously stirred and heated to dryness. Under nitrogen protection, the temperature was increased to 800℃ at 5℃ / min and calcined for 12h to obtain a lignin-based carbon precursor. The precursor was added to 50ml of concentrated sodium hydroxide solution and stirred at 80℃ for 6h. After centrifugation and washing until neutral, the mixture was dried and ground to obtain lignin-based carbon, which was then sealed and stored.

[0035] 6 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.047 g of lignin carbon were added to 30 mL of deionized water and stirred for 30 min to prepare solution A. 6 mmol of potassium chloride (KCl) was added to 30 mL of deionized water and stirred for 30 min to prepare solution B. After stirring, solution B was poured into a separatory funnel and added dropwise to solution A at a rate of 5 drops / second. The mixture was stirred until homogeneous, and the pH was adjusted to 3 with ammonia. Stirring continued for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 200 °C for 12 h. After natural cooling, the mixture was centrifuged at 10000 r / min and dried at 80 °C for 12 h. After cooling to room temperature and grinding, 3% BiOCl@C lignin carbon-based bismuth oxyhalide material was obtained and stored in a sealed container.

[0036] Figure 1 The SEM images shown in the figure depict the composite material prepared in Example 1. As can be seen from the figures, all products exhibit numerous well-defined flower-like structures with diameters ranging from 3 to 5 μm. High-magnification SEM images reveal the fine structure of the flower-like surface of this catalyst, which is composed of nanosheets tightly bound together to form the flower-like structure.

[0037] <Example 2>

[0038] 5g of silica microspheres and 5g of alkali lignin were added to 50ml of ethylene glycol and ultrasonically mixed for 30min. The mixture was then continuously stirred and heated to dryness. Under nitrogen protection, the temperature was increased to 800℃ at 5℃ / min and calcined for 12h to obtain a lignin-based carbon precursor. The precursor was added to 50ml of concentrated sodium hydroxide solution and stirred at 80℃ for 6h. After centrifugation and washing until neutral, the mixture was dried and ground to obtain lignin-based carbon, which was then sealed and stored.

[0039] 6 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.047 g of lignin carbon were added to 30 mL of deionized water and stirred for 30 min to prepare solution A. 3 mmol of potassium bromide (KBr) and 3 mmol of potassium chloride (KCl) were added to 30 mL of deionized water and stirred for 30 min to prepare solution B. After stirring, solution B was poured into a separatory funnel and added dropwise to solution A at a rate of 2 drops / second. The mixture was stirred until homogeneous, and the pH was adjusted to 3 with ammonia. Stirring continued for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 200 °C for 12 h. After natural cooling, the mixture was centrifuged at 10000 r / min and dried at 80 °C for 12 h. After cooling to room temperature and grinding, a lignin carbon-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology (3% BiOCl) was obtained. 0.5 Br 0.5 @C, seal and store.

[0040] <Example 3>

[0041] 5g of silica microspheres and 25g of alkali lignin were added to 50ml of ethylene glycol and ultrasonically mixed for 30min. The mixture was then continuously stirred and heated to dryness. Under nitrogen protection, the temperature was increased to 1000℃ at 2℃ / min and calcined for 6h to obtain a lignin-based carbon precursor. The precursor was added to 50ml of concentrated sodium hydroxide solution and stirred at 80℃ for 6h. After centrifugation and washing until neutral, the mixture was dried and ground to obtain lignin-based carbon, which was then sealed and stored.

[0042] 6 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.047 g of lignin carbon were added to 30 mL of deionized water and stirred for 30 min to prepare solution A. 3 mmol of potassium bromide (KBr) and 3 mmol of potassium iodide (KI) were added to 30 mL of deionized water and stirred for 30 min to prepare solution B. After stirring, solution B was poured into a separatory funnel and added dropwise to solution A at a rate of 10 drops / second. The mixture was stirred until homogeneous, and the pH was adjusted to 3 with ammonia water. Stirring continued for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 150 °C for 12 h. After natural cooling, the mixture was centrifuged at 10000 r / min and dried at 80 °C for 12 h. After cooling to room temperature and grinding, a lignin carbon-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology (3% BiOBr) was obtained. 0.5 I 0.5 @C, seal and store.

[0043] <Example 4>

[0044] 5g of silica microspheres and 50g of alkali lignin were added to 50ml of ethylene glycol and ultrasonically mixed for 30min. The mixture was then continuously stirred and heated to dryness. Under nitrogen protection, the temperature was increased to 500℃ at 1℃ / min and calcined for 8h to obtain a lignin-based carbon precursor. The precursor was added to 50ml of concentrated sodium hydroxide solution and stirred at 80℃ for 6h. After centrifugation and washing until neutral, the carbon was dried and ground to obtain lignin-based carbon, which was then sealed and stored.

[0045] 6 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.047 g of lignin carbon were added to 30 mL of deionized water and stirred for 30 min to prepare solution A. 3 mmol of potassium chloride (KCl) and 3 mmol of potassium iodide (KI) were added to 30 mL of deionized water and stirred for 30 min to prepare solution B. After stirring, solution B was poured into a separatory funnel and added dropwise to solution A at a rate of 10 drops / second. The mixture was stirred until homogeneous, and the pH was adjusted to 3 with ammonia water. Stirring continued for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 180 °C for 10 h. After natural cooling, the mixture was centrifuged at 10000 r / min and dried at 80 °C for 12 h. After cooling to room temperature and grinding, a lignin carbon-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology (3% BiOCl) was obtained. 0.5 I 0.5 @C, seal and store.

[0046] <Comparative Example 1>

[0047] 5g of silica microspheres and 5g of alkali lignin were added to 50ml of ethylene glycol and ultrasonically mixed for 30min. The mixture was then continuously stirred and heated to dryness. Under nitrogen protection, the temperature was increased to 800℃ at 30℃ / min and calcined for 12h to obtain a lignin-based carbon precursor. The precursor was added to 50ml of concentrated sodium hydroxide solution and stirred at 80℃ for 6h. After centrifugation and washing until neutral, the carbon was dried and ground to obtain lignin-based carbon, which was then sealed and stored.

[0048] 6 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.047 g of lignin carbon were added to 30 mL of deionized water and stirred for 30 min to prepare solution A. 3 mmol of potassium bromide (KBr) and 3 mmol of potassium chloride (KCl) were added to 30 mL of deionized water and stirred for 30 min to prepare solution B. After stirring, solution B was poured into a separatory funnel and added dropwise to solution A at a rate of 2 drops / second. The mixture was stirred until homogeneous, and the pH was adjusted to 3 with ammonia. Stirring continued for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 200 °C for 12 h. After natural cooling, the mixture was centrifuged at 10000 r / min and dried at 80 °C for 12 h. After cooling to room temperature and grinding, a lignin carbon-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology (3% BiOCl) was obtained. 0.5 Br 0.5 @C, seal and store.

[0049] <Comparative Example 2>

[0050] 5g of silica microspheres and 5g of alkali lignin were added to 50ml of ethylene glycol and ultrasonically mixed for 30min. The mixture was then continuously stirred and heated to dryness. Under nitrogen protection, the temperature was increased to 800℃ at 5℃ / min and calcined for 12h to obtain a lignin-based carbon precursor. The precursor was added to 50ml of concentrated sodium hydroxide solution and stirred at 80℃ for 6h. After centrifugation and washing until neutral, the mixture was dried and ground to obtain lignin-based carbon, which was then sealed and stored.

[0051] 6 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.047 g of lignin carbon were added to 30 mL of deionized water and stirred for 30 min to prepare solution A. 3 mmol of potassium bromide (KBr) and 3 mmol of potassium chloride (KCl) were added to 30 mL of deionized water and stirred for 30 min to prepare solution B. After stirring, solution B was poured into a separatory funnel and added dropwise to solution A at a rate of 20 drops / second. The mixture was stirred until homogeneous, and the pH was adjusted to 3 with ammonia water. Stirring continued for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 200 °C for 12 h. After natural cooling, the mixture was centrifuged at 10000 r / min and dried at 80 °C for 12 h. After cooling to room temperature and grinding, a lignin carbon-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology (3% BiOCl) was obtained. 0.5 Br 0.5 @C, seal and store.

[0052] <Comparative Example 3>

[0053] 5g of silica microspheres and 5g of alkali lignin were added to 50ml of ethylene glycol and ultrasonically mixed for 30min. The mixture was then continuously stirred and heated to dryness. Under nitrogen protection, the temperature was increased to 800℃ at 5℃ / min and calcined for 12h to obtain a lignin-based carbon precursor. The precursor was added to 50ml of concentrated sodium hydroxide solution and stirred at 80℃ for 6h. After centrifugation and washing until neutral, the mixture was dried and ground to obtain lignin-based carbon, which was then sealed and stored.

[0054] 6 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.047 g of lignin carbon were added to 30 mL of deionized water and stirred for 30 min to prepare solution A. 3 mmol of potassium bromide (KBr) and 3 mmol of potassium chloride (KCl) were added to 30 mL of deionized water and stirred for 30 min to prepare solution B. After stirring, solution B was poured into a separatory funnel and added dropwise to solution A at a rate of 2 drops / second. The mixture was stirred until homogeneous, and the pH was adjusted to 10. Stirring continued for 30 min. The mixture was then transferred to a hydrothermal reactor and reacted at 200 °C for 12 h. After natural cooling, the mixture was centrifuged at 10000 r / min and dried at 80 °C for 12 h. After cooling to room temperature and grinding, a lignin carbon-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology (3% BiOCl) was obtained. 0.5 Br 0.5 @C, seal and store.

[0055] <Photocatalytic performance testing>

[0056] 20 mg of BiOCl, the composite materials prepared in Examples 1 and 2, and Comparative Examples 1-3 were weighed and placed in a special quartz reactor. Under light-protected conditions, 50 ml of methylene blue MB solution and Rhodamine RhB (20 mg / L) were added respectively. At room temperature, the reactor was transferred to a 500 W xenon lamp for 3 hours of illumination, with samples taken every 20 minutes. The absorbance of each sample at the 664 nm absorption wavelength was measured using a Purkinje T6 New Century UV-Vis spectrophotometer.

[0057] Figure 2 (a) and (b) show the XRD patterns of BiOCl and 3% BiOCl@C before and after 3 h of photocatalytic degradation of MB and RhB, respectively. As shown in the figure, the crystal structure of BiOCl and 3% BiOCl@C did not change before and after the reaction, which indicates the stability of the PbFCl type structure of the bismuth halide material.

[0058] Figure 3 Bismuth oxide materials with medium halogens: 3% BiOCl@C (Example 1) and 3% BiOCl 0.5 Br 0.5In the UV-Vis diffuse reflectance spectra of sample @C (Example 2), 3% BiOCl@C and 3% BiOCl 0.5 Br 0.5 The @C sample exhibits strong light absorption across the entire visible light region. The lignin carbon material sample in the image does not show strong light absorption across the entire visible light region. Data analysis shows that the band gap of 3% BiOCl@C is Eg = 3.14 eV, and the 3% BiOCl... 0.5 Br 0.5 The bandgap of @C is Eg = 2.92 eV. The bandgap of both materials is smaller than that of BiOCl, indicating that the formation of the flower-like structure and Z-shaped heterojunction enhances the visible light response of the materials.

[0059] Figure 4 As shown, 3% BiOCl 0.5 Br 0.5 The @C (Example 2) catalyst significantly improved the degradation rate of organic dyes, with degradation rates of 96.8% and 81.3% for MB and RhB, respectively; 3% BiOCl@C (Example 1) showed a degradation rate of 83.6% for MB and 62.7% for RhB.

[0060] When lignin carbon and bromine were not added to the system, BiOCl degraded MB and RhB by 37.3% and 46.2% respectively, with no significant degradation effect.

[0061] This indicates that the combined effect of the flower-like structure and the Z-shaped heterostructure enhances the catalyst's performance, which can be attributed to the following two aspects. Firstly, the well-ordered flower-like structure of the material enables spatial separation of the BiOX nanosheets and increases the material's specific surface area, significantly improving the contact area between the BiOX material and the pollutants, thus strengthening the photocatalytic reaction. Secondly, when the two halogen salts are mixed and hydrothermally heated, BiOX is formed. n Y 1-n In this type of compound, a Z-shaped heterojunction is formed between two similar semiconductor structures, which promotes the separation of photogenerated electrons and holes and extends the visible light response of the material. The synergistic effect of these two effects enables the catalyst to achieve optimal photocatalytic performance.

[0062] The catalyst in Comparative Example 1 exhibited degradation rates of 72.6% for MB and 66.4% for RhB. The catalyst in Comparative Example 2 showed degradation rates of 78.2% for MB and 68.3% for RhB. The catalyst in Comparative Example 3 achieved degradation rates of 46.6% for MB and 62.5% for RhB.

[0063] Compared with Example 2, the degradation rates of MB and RhB by the catalysts in Comparative Examples 1-3 were all lower. This indicates that medium-temperature calcination with controlled heating rate can effectively retain the rich oxygen-containing functional groups unique to lignin. Then, by controlling the dropping rate and pH adjustment, the oxygen-containing functional groups on the lignin surface form electron-donating hydroxyl groups and electron-withdrawing halide ions that attract each other, thereby achieving spatial separation of BiOX nanosheets, forming a flower-like morphology, and increasing the energy barrier for photogenerated electron-hole recombination.

[0064] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a lignin-carbon-based halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology, characterized in that, Includes the following steps: S1. Dissolve the template agent and lignin together in ethylene glycol, disperse and mix them ultrasonically, and then heat and evaporate to dryness to obtain raw material A; S2. Raw material A is heated to 500-1000℃ for 6-12 hours under nitrogen protection at a heating rate of 1~5℃ / min to obtain precursor B. S3. Add precursor B to a strongly alkaline solution and heat to react. After the reaction is complete, wash and dry to obtain lignin carbon. S4. Add the aqueous solution of halogen salt to the aqueous solution of bismuth salt and lignin carbon dropwise at a rate of 1~10 drops / second. After mixing, adjust the pH to 3~7 and heat to 150~200℃ for reaction. After the reaction is completed, centrifuge, wash, dry and grind to obtain a lignin carbon-based halogen bismuth composite material with a regular flower-like morphology. In step S4, the halogen salt is a mixture of any two of potassium chloride, potassium bromide, and potassium iodide. In step S4, ammonia is used to adjust the pH of the solution.

2. The method for preparing a lignin-carbon-based halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology as described in claim 1, characterized in that: The template agent in step S1 is silica microspheres, and the lignin is alkali lignin.

3. The method for preparing a lignin-carbon-based halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology as described in claim 2, characterized in that: The mass ratio of silica microspheres to alkali lignin is 1:1 to 1:

10.

4. The method for preparing a lignin-carbon-based halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology as described in claim 1, characterized in that: The molar ratio of the two halide salts is 1:1 to 10:

1.

5. The method for preparing a lignin-carbon-based halooxybismuth Z-type heterojunction composite material with a regular flower-like morphology as described in claim 1, characterized in that: In step S3, the strongly alkaline solution is a sodium hydroxide solution, and the heating temperature for the reaction is 80°C.

6. A lignin-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology, prepared by the method described in any one of claims 1-5.

7. The application of the lignin-based bismuth halide Z-type heterojunction composite material with a regular flower-like morphology as described in claim 6 in the photocatalytic degradation system of organic pollutants.

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