Nanoflower-like bi2w06-based composite material containing oxygen vacancies, and preparation method and application thereof

Abstract

The application discloses a nano-flower-like Bi2WO6-based composite material rich in oxygen vacancies and a preparation method and application thereof, and belongs to the technical field of novel photocatalytic material development.The preparation method disclosed by the application is that lignin is added into a hydrothermal synthesis system of Bi2WO6 to obtain a three-dimensional nano-flower-like carbon quantum dot and Bi2WO6 composite material.Further, a simple alkali etching strategy is adopted to obtain the nano-flower-like carbon quantum dot and Bi2WO6 composite material rich in oxygen vacancies.The obtained composite material has a large specific surface area, more catalytic reaction active sites and a stable structure, and can remove 95.2% of the ciprofloxacin within 40 minutes under visible light.The preparation process of the application is simple, low in cost and environment-friendly, and provides a green and low-cost scheme for the development of high-efficiency photocatalysts and the treatment of antibiotic sewage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of developing new photocatalytic materials, and particularly relates to an oxygen vacancy-containing nano-flower-shaped Bi2WO6-based composite material and a preparation method and application thereof. BACKGROUND

[0002] Antibiotics are widely used to treat diseases suffered by humans, animals and aquaculture, and have high structural stability and are difficult to degrade by metabolic methods, and thus stably exist in the natural environment, causing serious threats to the ecological environment. Therefore, it is urgent to develop green and efficient antibiotic removal technologies. Photocatalysis as a safe, efficient and sustainable purification technology has attracted widespread attention. The core of the photocatalysis technology is to develop efficient and stable photocatalysts. Among various photocatalysts, bismuth tungstate (Bi2WO6) is a representative perovskite bismuth-based oxide, which is characterized by a unique layered structure, high stability and a suitable band gap of about 2.75 eV, which makes it suitable for use as a photocatalyst for the removal of antibiotic pollutants. However, the limited visible light utilization rate (λ≤450 nm), the rapid recombination of photo-generated carriers and the low conduction band position which cannot effectively participate in redox reactions reduce the photocatalytic activity. In order to overcome the above obstacles of Bi2WO6 photocatalysts, researchers have developed several strategies to improve the photocatalytic performance of Bi2WO6, including heterostructure construction, defect introduction, morphology control, non-metallic or metallic atom doping, loading of cocatalysts (such as noble metals Ag, Au, Pd) and the like. However, these strategies often have problems such as high energy consumption, precise equipment requirements, complicated steps, high preparation cost, complex preparation process, unstable catalyst structure and difficult to control morphology. SUMMARY

[0003] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide an oxygen vacancy-containing nano-flower-shaped Bi2WO6-based composite material and a preparation method and application thereof, so as to solve the technical problems of the current Bi2WO6-based photocatalytic material preparation process being complex, high cost and poor photocatalytic removal performance of antibiotics.

[0004] In order to achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0005] 2. The application discloses a preparation method of an oxygen vacancy-containing nano-flower-shaped Bi2WO6-based composite material, comprising the following steps:

[0006] S1: Hexadecyl trimethyl ammonium bromide is added to a Na2WO4·2H2O aqueous solution, and after stirring treatment, a mixed solution A is obtained;

[0007] S2: Bi(NO3)3·5H2O suspension is added to the mixed solution A, and after stirring, a mixed solution B is obtained;

[0008] S3: adding the lignin aqueous solution into the mixed solution B, and obtaining a mixed solution C after stirring; collecting a solid product after a hydrothermal reaction of the mixed solution C, and performing washing and drying treatment on the solid product, to obtain a nanoflower-shaped carbon quantum dot and Bi2WO6 composite material;

[0009] S4: adding the nanoflower-shaped carbon quantum dot and Bi2WO6 composite material into a NaOH solution to perform etching treatment by stirring, obtaining an etched product, and obtaining an oxygen vacancy-containing nanoflower-shaped Bi2WO6-based composite material after cleaning and drying of the etched product.

[0010] Further, in S1, the Na2WO4·2H2O aqueous solution is obtained by stirring and mixing Na2WO4·2H2O and water; the amount ratio of the Na2WO4·2H2O and water is (0.75-1.5) mmol: 30 mL; and the stirring time is 30-60 min.

[0011] Further, in S1, the amount ratio of the cetyltrimethylammonium bromide and the Na2WO4·2H2O aqueous solution is (0.05-0.1) g: 30 mL.

[0012] Further, in S2, the Bi(NO3)3·5H2O suspension is obtained by adding Bi(NO3)3·5H2O into water and performing ultrasonic treatment; the amount ratio of the Bi(NO3)3·5H2O and water is (1.5-3.0) mmol: 30 L; and the ultrasonic treatment time is 30-60 min.

[0013] Further, in S3, the lignin aqueous solution is prepared by stirring and mixing lignin and water, adjusting the pH of the mixture to be acidic by using HNO3, and obtaining the lignin aqueous solution; the amount ratio of the lignin and water is (5.3-31.5) g: 20 mL; and the stirring time is 0.5-2.0 h.

[0014] Further, in S3, the molar ratio of Na2WO4·2H2O and Bi(NO3)3·5H2O in the mixed solution C is 1:2; and the amount ratio of the lignin aqueous solution and the mixed solution B is 20 mL: 60 mL.

[0015] Further, in S3, the stirring time is 1 h; the hydrothermal reaction temperature is 150-170℃, and the hydrothermal reaction time is 24 h.

[0016] Further, in S4, the etching treatment temperature is 50 DEG C; the NaOH solution concentration is 0.1-0.3 mol / L; the nano-flower-like carbon quantum dot and Bi2WO6 composite material and NaOH solution dosage ratio is (0.1-0.2) g: 50 mL; and the stirring time is 1-2 h.

[0017] The application further discloses the oxygen-vacancy-containing nano-flower-like Bi2WO6-based composite material prepared by the preparation method.

[0018] The application further discloses application of the oxygen-vacancy-containing nano-flower-like Bi2WO6-based composite material, and the oxygen-vacancy-containing nano-flower-like Bi2WO6-based composite material is used as a catalytic material in a process of removing antibiotic pollutants in a water environment by a photocatalytic reaction.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] The application discloses a preparation method of an oxygen-vacancy-containing nano-flower-like Bi2WO6-based composite material, lignin is added into a hydrothermal reaction system of Bi2WO6, and a nano-flower-like carbon quantum dot and Bi2WO6 composite material can be obtained in one step; subsequently, an oxygen-vacancy-containing nano-flower-like Bi2WO6-based composite material rich in oxygen vacancies can be obtained by further adopting a simple alkali etching strategy.

[0021] The application further discloses the oxygen-vacancy-containing nano-flower-like Bi2WO6-based composite material prepared by the preparation method, and compared with existing semiconductor photocatalysts. The application first modifies Bi2WO6 by using lignin, and the composite material has low cost and small secondary pollution; the obtained composite material has a three-dimensional nano-flower petal structure and rich surface oxygen vacancies, the unique structure makes the composite material have a larger specific surface area (42.29 g / m 2 ), exposes more surface catalytic reaction active sites, can increase the absorption range and utilization rate of sunlight of the material. Secondly, the composite materials are combined by chemical bonds, which is beneficial to rapid separation and transmission of photo-generated charges in the photocatalytic reaction process, and improves the stability of the composite material.

[0022] The application further discloses application of the nanoflower-like Bi2WO6-based composite material containing oxygen vacancies as a high-efficiency photocatalyst. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 SEM photos of the nanoflower-like Bi2WO6 nanomaterial, the nanoflower-like carbon quantum dot and Bi2WO6 composite material and the nanoflower-like carbon quantum dot and Bi2WO6 composite material rich in oxygen vacancies prepared by the application;

[0024] Wherein, a is the nanoflower-like Bi2WO6 nanomaterial under 500nm scale; d is the nanoflower-like Bi2WO6 nanomaterial under 100nm scale; c is the nanoflower-like Bi2WO6-based composite material containing oxygen vacancies under 400nm scale; f is the nanoflower-like Bi2WO6-based composite material containing oxygen vacancies under 100nm scale; b is the nanoflower-like carbon quantum dot and Bi2WO6 composite material under 400nm scale; e is the nanoflower-like carbon quantum dot and Bi2WO6 composite material under 100nm scale.

[0025] Figure 2 TEM photo of the nanoflower-like Bi2WO6-based composite material containing oxygen vacancies prepared by the application;

[0026] Wherein, a is the TEM photo under low magnification; b is the corresponding TEM photo under high magnification.

[0027] Figure 3 BET adsorption and desorption diagram of the sample prepared by the application;

[0028] Figure 4 Comparison curve of removal performance of the nanoflower-like carbon quantum dot and Bi2WO6 composite material (containing different amounts of carbon quantum dots) on ciprofloxacin prepared by the application;

[0029] Wherein, CQDs / Bi2WO6-1 in a indicates that the content of CQDs is 1%, CQDs / Bi2WO6-2 indicates that the content of CQDs is 2%, and CQDs / Bi2WO6-3 indicates that the content of CQDs is 3%; b is the fitted reaction rate corresponding to a.

[0030] Figure 5 The removal performance comparison curve of the nanoflower Bi2WO6 nanomaterial (Bi2WO6), the nanoflower carbon quantum dot and Bi2WO6 composite material (CQDs / Bi2WO6), and the nanoflower Bi2WO6-based composite material containing oxygen vacancies (CQDs / Bi2WO6-Vo) on ciprofloxacin;

[0031] Wherein: a- is the comparison curve of the removal performance of different samples on ciprofloxacin under visible light; b and c are the fitted reaction rates of a. DETAILED DESCRIPTION

[0032] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein have their usual meanings understood by those skilled in the art of the present application, and in the event of conflict, the definitions in the specification shall prevail.

[0033] Theories or mechanisms described and disclosed herein, whether correct or not, should not be used to limit the scope of the present application, i.e., the present application can be practiced without any particular theory or mechanism.

[0034] Herein, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are for the sake of brevity and convenience. Therefore, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0035] Herein, unless otherwise specified, “comprise”, “include”, “contain”, “have” or similar terms encompass the meaning of “consist of” and “consist essentially of”, for example, “A comprises a” encompasses the meaning of “A comprises a and other” and “A only comprises a”.

[0036] Herein, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as the combinations of the technical features do not conflict, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope disclosed in the specification.

[0037] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that after reading the content of the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The following examples use the apparatus and equipment that are conventional in the art. The experimental methods in the following examples, unless otherwise specified, are generally carried out according to conventional conditions, or according to the conditions recommended by the manufacturer. The following examples use various raw materials, unless otherwise specified, all use conventional commercially available products, and the specifications are conventional specifications in the art. In the specification of the application and the following examples, unless otherwise specified, "%" means weight percent, "parts" means weight parts, and the ratio means weight ratio.

[0039] Example 1

[0040] A preparation method of a nanoflower-shaped Bi2WO6-based composite material containing oxygen vacancies, comprising the following steps:

[0041] Step 1: Dissolve 1.0 mmol of Na2WO4·2H2O in 30 mL of water, and after stirring for 30 min, obtain a Na2WO4·2H2O aqueous solution; add 0.08 g of cetyltrimethylammonium bromide (CTAB) to the above aqueous solution, and after stirring for 30 min, obtain a mixed solution A;

[0042] Step 2: Add 14 mg of lignin to 20 mL of water, and after stirring for 1 h, adjust the pH to 2 with 0.5 mol / L HNO3 to obtain a lignin aqueous solution; add 2 mmol of Bi(NO3)3·5H2O to 30 mL of water, and after ultrasonic treatment for 30 min, obtain a Bi(NO3)3·5H2O suspension; add the Bi(NO3)3·5H2O suspension to the mixed solution A obtained in step 1, and after continuous stirring for 1 h, obtain a mixed solution B; add the lignin aqueous solution to the mixed solution B, and after stirring for 1 h, obtain a mixed solution C;

[0043] Pack the mixed solution C into a 100 mL hydrothermal kettle, and after hydrothermal reaction at 160℃ for 24 h, collect the obtained solid product, and then wash with pure water and ethanol for 3 times respectively, and then dry at 50℃ for 12 h to obtain a nanoflower-shaped carbon quantum dot and Bi2WO6 composite material with a mass percentage of carbon quantum dots of 2wt%;

[0044] Step 3: Add 0.1g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material to 50mL of NaOH solution with a concentration of 0.2mol / L, and perform etching treatment by stirring continuously at 50℃ for 1h to obtain the etched product. Wash the etched product with pure water 5 times, and then dry it at 50℃ for 12h to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0045] Example 2

[0046] A method for preparing an oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material includes the following steps:

[0047] Step 1: Dissolve 0.75 mmol of Na2WO4·2H2O in 30 mL of water and stir for 30 min to obtain an aqueous solution of Na2WO4·2H2O; add 0.05 g of hexadecyltrimethylammonium bromide (CTAB) to the above aqueous solution and stir for 30 min to obtain mixed solution A;

[0048] Step 2: Add 5.3 mg of lignin to 20 mL of water, stir for 0.5 h, and adjust the pH to 3 with 0.5 mol / L HNO3 to obtain an aqueous lignin solution; add 1.5 mmol of Bi(NO3)3·5H2O to 30 mL of water, sonicate for 30 min to obtain a Bi(NO3)3·5H2O suspension; add the Bi(NO3)3·5H2O suspension to mixed solution A obtained in Step 1, stir continuously for 1 h to obtain mixed solution B; add the aqueous lignin solution to mixed solution B, stir for 1 h to obtain mixed solution C;

[0049] Mixed solution C was placed in a 100 mL hydrothermal reactor and hydrothermally reacted at 150 °C for 24 h. The resulting solid product was collected and washed three times with pure water and ethanol, respectively. Then it was dried at 50 °C for 12 h to obtain a composite material of nanoflower-like carbon quantum dots and Bi2WO6 with a mass percentage of 1 wt%.

[0050] Step 3: Add 0.1g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material to 50mL of NaOH solution with a concentration of 0.2mol / L, and perform etching treatment by stirring continuously at 50℃ for 1h to obtain the etched product. Wash the etched product with pure water 5 times, and then dry it at 50℃ for 12h to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0051] Example 3

[0052] A method for preparing an oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material includes the following steps:

[0053] Step 1: Dissolve 1.5 mmol of Na2WO4·2H2O in 40 mL of water and stir for 30 min to obtain an aqueous solution of Na2WO4·2H2O; add 0.1 g of hexadecyltrimethylammonium bromide (CTAB) to the above aqueous solution and stir for 30 min to obtain mixed solution A;

[0054] Step 2: Add 31.5 mg of lignin to 20 mL of water, stir for 2 h, and adjust the pH to 1 with 0.5 mol / L HNO3 to obtain an aqueous lignin solution; add 3 mmol of Bi(NO3)3·5H2O to 40 mL of water, sonicate for 30 min to obtain a Bi(NO3)3·5H2O suspension; add the Bi(NO3)3·5H2O suspension to mixed solution A obtained in Step 1, stir continuously for 1 h to obtain mixed solution B; add the aqueous lignin solution to mixed solution B, stir for 1 h to obtain mixed solution C;

[0055] Mixed solution C was placed in a 100 mL hydrothermal reactor and hydrothermally reacted at 170 °C for 24 h. The resulting solid product was collected and washed three times with pure water and ethanol, respectively. Then it was dried at 50 °C for 12 h to obtain a composite material of nanoflower-like carbon quantum dots and Bi2WO6 with a mass percentage of 3 wt%.

[0056] Step 3: Add 0.1g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material to 50mL of NaOH solution with a concentration of 0.2mol / L, and perform etching treatment by stirring continuously at 50℃ for 1h to obtain the etched product. Wash the etched product with pure water 5 times, and then dry it at 50℃ for 12h to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0057] Example 4

[0058] Unlike Example 1, 0.15g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material were added to 50mL of NaOH solution with a concentration of 0.1mol / L and stirred continuously at 50°C for 2h.

[0059] Step 2: Collect the solid product after stirring, wash it 5 times with pure water, and then dry it at 60°C to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0060] Example 5

[0061] Unlike Example 2, 0.15g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material were added to 50mL of NaOH solution with a concentration of 0.1mol / L and stirred continuously at 50°C for 2h.

[0062] Step 2: Collect the solid product after stirring, wash it 5 times with pure water, and then dry it at 60°C to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0063] Example 6

[0064] Unlike Example 3, 0.15g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material were added to 50mL of NaOH solution with a concentration of 0.1mol / L and stirred continuously at 50°C for 2h.

[0065] Step 2: Collect the solid product after stirring, wash it 5 times with pure water, and then dry it at 60°C to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0066] Example 7

[0067] Unlike Example 1, 0.2 g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material were added to 50 mL of NaOH solution with a concentration of 0.3 mol / L and stirred continuously at 50 °C for 1.5 h.

[0068] Step 2: Collect the solid product after stirring, wash it 5 times with pure water, and then dry it at 50℃ for 12h to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0069] Example 8

[0070] Unlike Example 2, 0.2g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material were added to 50mL of NaOH solution with a concentration of 0.3mol / L and stirred continuously at 50°C for 1.5h.

[0071] Step 2: Collect the solid product after stirring, wash it 5 times with pure water, and then dry it at 50℃ for 12h to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0072] Example 9

[0073] Unlike Example 3, 0.2g of the obtained nanoflower-like carbon quantum dots and Bi2WO6 composite material were added to 50mL of NaOH solution with a concentration of 0.3mol / L and stirred continuously at 50°C for 1.5h.

[0074] Step 2: Collect the solid product after stirring, wash it 5 times with pure water, and then dry it at 50℃ for 12h to obtain the oxygen-vacant nanoflower-like Bi2WO6-based composite material.

[0075] Comparative Example 1

[0076] A method for preparing a composite material of nanoflower-like carbon quantum dots and Bi2WO6 includes the following steps:

[0077] Step 1: Dissolve 1.0 mmol of Na2WO4·2H2O in 30 mL of water and stir for 30 min to obtain an aqueous solution of Na2WO4·2H2O; add 0.08 g of hexadecyltrimethylammonium bromide (CTAB) to the above aqueous solution and stir for 30 min to obtain mixed solution A;

[0078] Step 2: Add 14 mg of lignin to 20 mL of water, stir for 1 h, and adjust the pH to 2 with 0.5 mol / L HNO3 to obtain an aqueous lignin solution; add 2 mmol of Bi(NO3)3·5H2O to 30 mL of water, sonicate for 30 min to obtain a Bi(NO3)3·5H2O suspension; add the Bi(NO3)3·5H2O suspension to mixed solution A obtained in Step 1, stir continuously for 1 h to obtain mixed solution B; add the aqueous lignin solution to mixed solution B, stir for 1 h to obtain mixed solution C;

[0079] Mixed solution C was placed in a 100 mL hydrothermal reactor and hydrothermally reacted at 160 °C for 24 h. The resulting solid product was collected and washed three times with pure water and ethanol, respectively. Then it was dried at 50 °C for 12 h to obtain a composite material of nanoflower-like carbon quantum dots and Bi2WO6 with a carbon quantum dot mass percentage of 2 wt%.

[0080] Comparative Example 2

[0081] A method for preparing a composite material of nanoflower-like carbon quantum dots and Bi2WO6 includes the following steps:

[0082] Step 1: Dissolve 0.75 mmol of Na2WO4·2H2O in 30 mL of water and stir for 30 min to obtain an aqueous solution of Na2WO4·2H2O; add 0.05 g of hexadecyltrimethylammonium bromide (CTAB) to the above aqueous solution and stir for 30 min to obtain mixed solution A;

[0083] Step 2: Add 5.3 mg of lignin to 20 mL of water, stir for 1 h, and adjust the pH to 3 with 0.5 mol / L HNO3 to obtain an aqueous lignin solution; add 1.5 mmol of Bi(NO3)3·5H2O to 30 mL of water, sonicate for 30 min to obtain a Bi(NO3)3·5H2O suspension; add the Bi(NO3)3·5H2O suspension to mixed solution A obtained in Step 1, stir continuously for 1 h to obtain mixed solution B; add the aqueous lignin solution to mixed solution B, stir for 1 h to obtain mixed solution C;

[0084] Mixed solution C was placed in a 100 mL hydrothermal reactor and hydrothermally reacted at 150 °C for 24 h. The resulting solid product was collected and washed three times with pure water and ethanol, respectively. Then it was dried at 50 °C for 12 h to obtain a composite material of nanoflower-like carbon quantum dots and Bi2WO6 with a mass percentage of 1 wt%.

[0085] Comparative Example 3

[0086] A method for preparing a composite material of nanoflower-like carbon quantum dots and Bi2WO6 includes the following steps:

[0087] Step 1: Dissolve 1.5 mmol of Na2WO4·2H2O in 40 mL of water and stir for 30 min to obtain an aqueous solution of Na2WO4·2H2O; add 0.1 g of hexadecyltrimethylammonium bromide (CTAB) to the above aqueous solution and stir for 30 min to obtain mixed solution A;

[0088] Step 2: Add 31.5 mg of lignin to 20 mL of water, stir for 1 h, and adjust the pH to 1 with 0.5 mol / L HNO3 to obtain an aqueous lignin solution; add 3 mmol of Bi(NO3)3·5H2O to 40 mL of water, sonicate for 30 min to obtain a Bi(NO3)3·5H2O suspension; add the Bi(NO3)3·5H2O suspension to mixed solution A obtained in Step 1, stir continuously for 1 h to obtain mixed solution B; add the aqueous lignin solution to mixed solution B, stir for 1 h to obtain mixed solution C;

[0089] Mixed solution C was placed in a 100 mL hydrothermal reactor and hydrothermally reacted at 170 °C for 24 h. The resulting solid product was collected and washed three times with pure water and ethanol, respectively. Then it was dried at 50 °C for 12 h to obtain a composite material of nanoflower-like carbon quantum dots and Bi2WO6 with a carbon quantum dot mass percentage of 3 wt%.

[0090] Comparative Example 4

[0091] Unlike Comparative Example 1, no lignin was added in this example. The rest of the process was the same as in Example 1, and pure nanoflower-like Bi2WO6 nanomaterials were finally obtained.

[0092] Comparative Example 5

[0093] Unlike Comparative Example 2, no lignin was added in this example. The rest of the process was the same as in Example 2, and pure nanoflower-like Bi2WO6 nanomaterials were finally obtained.

[0094] Comparative Example 6

[0095] Unlike Comparative Example 3, no lignin was added in this example. The rest of the process was the same as in Example 3, and pure nanoflower-like Bi2WO6 nanomaterials were finally obtained.

[0096] Application Examples

[0097] The application of the products obtained in the comparative examples and embodiments—bismuth tungstate nanomaterials with nano-flower-like structures (Bi2WO6), bismuth tungstate nanomaterials with nano-flower-like structures (CQDs / Bi2WO6), and bismuth tungstate nanomaterials with oxygen vacancies (CQDs / Bi2WO6-Vo)—in removing antibiotics includes the following steps:

[0098] Step 1: The composite materials prepared in each example and comparative example were added to a 20 mg / L ciprofloxacin solution, and the catalyst concentration was 0.3 g / L. The mixture was stirred continuously for 30 min in the dark until adsorption equilibrium was reached.

[0099] Step 2: Then, under visible light (420-780nm) irradiation, the sample was irradiated at 5min, 10min, 20min, 30min and 40min respectively. The catalyst was then filtered out with a 0.22um filter to obtain the degraded ciprofloxacin solution.

[0100] Step 3: The concentration of ciprofloxacin solution was determined at 272 nm using a Shimadzu high-performance liquid chromatography (HPLC) system. The degradation rate of ciprofloxacin by the materials obtained in each example and comparative example was calculated. The HPLC test conditions were as follows: the mobile phase consisted of methanol (30%) and 1‰ formic acid in deionized water (70%), and the flow rate was 1.0 mL / min. -1 Each analysis involved injecting 10 μL of sample using an autosampler, while maintaining the column temperature at 40°C.

[0101] from Figure 1 The SEM images show that pure Bi₂WO₆ (a, b) exhibits a nanoflower-like morphology, composed of nanosheets with a thickness of 22 nm. Further introduction of lignin-derived carbon quantum dots results in carbon quantum dot-Bi₂WO₆ composites (b, e) that also retain a nanoflower-like structure. Further alkali etching to introduce oxygen vacancies yields oxygen-vacancy-rich carbon quantum dot-Bi₂WO₆ composites (c, f) that also maintain a nanoflower-like structure, with the nanoflowers composed of 22 nm nanosheets and containing numerous porous structures. This three-dimensional nanoflower-like structure exposes more active sites, and the multiple reflections of sunlight through the pores of the petals increase the absorption rate of sunlight.

[0102] Figure 2The images show TEM images of the oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material prepared in this invention. Figure (a) shows that the sample morphology is mainly composed of stacked nanosheets. Figure (b), a high-magnification TEM image, clearly shows small particles of about 5 nm on the surface of the nanosheets. As indicated by the white arrow, these are lignin-derived hydrothermal carbon quantum dots loaded on the surface of the Bi2WO6 nanosheets.

[0103] Figure 3 The attached figure shows the BET adsorption-desorption of the sample prepared in this invention. It can be seen that the specific surface area of ​​the nano-flower-like Bi2WO6 gradually increases with the introduction of carbon quantum dots and oxygen vacancies. This indicates that the prepared composite material of oxygen-vacancy-rich nano-flower-like carbon quantum dots and Bi2WO6 has a large specific surface area (42.29 g / m²). 2 This allows for the exposure of more surface active sites, promoting the photocatalytic degradation of antibiotics.

[0104] Figure 4 The graph shows a comparison of the ciprofloxacin removal performance of the nanoflower-like carbon quantum dots prepared in this invention and the Bi2WO6 composite material (containing different amounts of carbon quantum dots). It can be seen that the composite material with 2% carbon quantum dots loaded on the Bi2WO6 nanoflower surface exhibits the best degradation performance for ciprofloxacin, removing 82.5% of the ciprofloxacin within 40 minutes, with a rate constant of 0.04266 min. -1 It is 2.33 times that of pure Bi2WO6. This indicates that introducing an appropriate amount of lignin-derived carbon quantum dots onto the surface of Bi2WO6 nanoflowers can significantly improve their photocatalytic performance in removing antibiotics.

[0105] Figure 5 The graph shows a comparison of the ciprofloxacin removal performance of the nanoflower bismuth tungstate nanomaterial (Bi2WO6), the nanoflower-shaped carbon quantum dots and bismuth tungstate composite material (CQDs / Bi2WO6), and the oxygen-vacancy-containing nanoflower-shaped Bi2WO6-based composite material (CQDs / Bi2WO6-Vo) prepared in this invention. It can be seen that after introducing oxygen vacancies into the nanoflower-shaped carbon quantum dots and bismuth tungstate composite material (CQDs / Bi2WO6) through alkaline etching, the oxygen-vacancy-containing nanoflower-shaped carbon quantum dots and bismuth tungstate composite material (CQDs / Bi2WO6-Vo) exhibits the best degradation performance for ciprofloxacin, degrading 95.2% of ciprofloxacin within 40 min, with a rate constant of 0.06279 min. -1 It is 3.42 times that of pure Bi2WO6.

[0106] Ciprofloxacin is a class of recalcitrant quinolone antibiotics. This invention evaluated the practical application effect of oxygen-vacancy-containing nanoflower-shaped carbon quantum dots and Bi2WO6 composite materials by removing ciprofloxacin, proving that the oxygen-vacancy-containing nanoflower-shaped carbon quantum dots and Bi2WO6 composite materials are a highly efficient photocatalyst and can be extended to the removal of other pollutants.

[0107] This invention involves an in-situ hydrothermal reaction of lignin with a Bi2WO6 precursor solution to obtain a three-dimensional nanoflower-like carbon quantum dot-Bi2WO6 composite material. Further, oxygen vacancies are introduced into this composite material through alkaline etching, resulting in an oxygen-vacancy-rich nanoflower-like carbon quantum dot-Bi2WO6 composite material. This catalyst, powered solely by light, can degrade antibiotic pollutants into carbon dioxide, water, and non-toxic small organic molecules, providing a low-cost, efficient, green, and safe technology for environmental wastewater treatment.

[0108] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a nanoflower-like Bi2WO6-based composite material containing oxygen vacancies, characterized in that, Includes the following steps: S1: Add hexadecyltrimethylammonium bromide to an aqueous solution of Na2WO4·2H2O, stir, and then obtain mixed solution A; S2: Add Bi(NO3)3·5H2O suspension to mixed solution A, stir to obtain mixed solution B; S3: Add the lignin aqueous solution to the mixed solution B, stir to obtain mixed solution C; after the mixed solution C undergoes a hydrothermal reaction, collect the solid product after the reaction, and wash and dry the solid product to obtain a composite material of nano-flower-like carbon quantum dots and Bi2WO6. The method for preparing the lignin aqueous solution is as follows: after stirring and mixing lignin and water, the pH is adjusted to acidic using HNO3 to obtain the lignin aqueous solution; the ratio of lignin to water is (5.3~31.5) g: 20 mL; the stirring time is 0.5~2.0 h; S4: Add the nano-flower-like carbon quantum dots and Bi2WO6 composite material to NaOH solution and stir to perform etching treatment to obtain the etched product. After cleaning and drying the etched product, the oxygen-vacant nano-flower-like Bi2WO6-based composite material is obtained.

2. The method for preparing an oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material according to claim 1, characterized in that, In S1, the Na2WO4·2H2O aqueous solution is obtained by mixing Na2WO4·2H2O and water; the ratio of Na2WO4·2H2O to water is (0.75~1.5) mmol:30 mL; the stirring time is 30~60 min.

3. The method for preparing an oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material according to claim 2, characterized in that, In S1, the ratio of hexadecyltrimethylammonium bromide to Na2WO4·2H2O aqueous solution is (0.05~0.1) g: 30 mL.

4. The method for preparing an oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material according to claim 3, characterized in that, In S2, the Bi(NO3)3·5H2O suspension is obtained by adding Bi(NO3)3·5H2O to water and then sonicating it; the ratio of Bi(NO3)3·5H2O to water is (1.5~3.0) mmol:30 mL; the sonication time is 30~60 min.

5. The method for preparing an oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material according to claim 4, characterized in that, In S3, the molar ratio of Na2WO4·2H2O and Bi(NO3)3·5H2O in the mixed solution C is 1:2; the volume ratio of the lignin aqueous solution to the mixed solution B is 20 mL:60 mL.

6. The method for preparing an oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material according to claim 1, characterized in that, In S3, the stirring time is 1 h; the hydrothermal reaction temperature is 150~170 ℃, and the hydrothermal reaction time is 24 h.

7. The method for preparing an oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material according to claim 1, characterized in that, In S4, the etching temperature is 50 °C; the concentration of the NaOH solution is 0.1~0.3 mol / L; the ratio of the amount of nano-flower-like carbon quantum dots to Bi2WO6 composite material and NaOH solution is (0.1~0.2) g: 50 mL; and the stirring time is 1~2 h.

8. A nanoflower-like Bi2WO6-based composite material containing oxygen vacancies, characterized in that, The composite material with oxygen vacancies in the nanoflora-like structure of Bi2WO6 as described in any one of claims 1 to 7 was prepared.

9. The application of the oxygen-vacancy-containing nanoflower-like Bi2WO6-based composite material according to claim 8, characterized in that, The oxygen-vacant nanoflower-like Bi2WO6-based composite material serves as a catalyst for photocatalytic removal of antibiotic pollutants from the aquatic environment.

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