Bismuth-silver composite micro-nano material for water treatment and preparation method thereof

Abstract

The invention relates to a bismuth-silver composite micro-nano material for water treatment and a preparation method thereof, the preparation method comprises the following steps: firstly, preparing functional graphene quantum dots: preparing N-GQDs-NH2 quantum dots by using citric acid, urea and ethylenediamine as raw materials, and then introducing a phosphate group and a porphyrinyl group through covalent bonding and pi-pi accumulation to obtain the functional graphene quantum dots; mixing a bismuth source, a tungsten source and the prepared functional graphene quantum dot dispersion liquid, and performing ultrasonic treatment to obtain a precursor solution A; and dissolving a silver source and a vanadium source in water, dropwise adding into the solution A, and carrying out hydrothermal reaction. The functional graphene quantum dots are used as a bridge to prepare the Bi2WO6 / AgVO3 compound, Bi2WO6 and AgVO3 are successfully compounded to form the stable photocatalyst with the micro-nano scale, and the formed ternary compound is high in catalytic activity on printing and dyeing molecules and good in cycling stability.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology for water treatment, specifically to a bismuth-silver composite micro / nanomaterial for water treatment and its preparation method. Background Technology

[0002] AgVO3, with a band gap of approximately 2.20 eV, is a silver-based semiconductor photocatalyst with excellent visible light absorption, showing potential for degrading organic pollutants, particularly in treating dye wastewater. Its core application lies in photocatalysis, a highly efficient, green, and reusable treatment method. Recently, bismuth-based semiconductor materials have attracted considerable attention due to their unique physicochemical properties, excellent biocompatibility, and low toxicity. Their synthesis methods (e.g., hydrothermal methods) are relatively mature, and many bismuth-based semiconductors, such as BiOX, Bi2WO6, BiVO4, and Bi2MoO6, have been successfully prepared. Among them, Bi2WO6 is a typical layered perovskite semiconductor with a band gap of approximately 2.7 eV, exhibiting a stable crystal structure and good photocatalytic activity; however, its absorption range for visible light is limited, and its quantum efficiency needs improvement. Constructing a heterojunction by combining Bi2WO6 and AgVO3 can promote charge separation through band matching, potentially yielding catalytic performance superior to that of a single component. However, research on the composite of these two substances is relatively limited. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention aims to combine functional graphene quantum dots to construct a highly stable and highly catalytically active Bi2WO6 / AgVO3 composite photocatalyst on its surface.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing bismuth-silver composite micro / nanomaterials for water treatment includes the following steps: S1, Functional Graphene Quantum Dots S1-1. Nitrogen-doped and abundant surface amino groups of N-GQDs-NH2 quantum dots were prepared by dissolving citric acid, urea and ethylenediamine in water and using a microwave-assisted method. S1-2. N-GQDs-NH2 quantum dots were dispersed in PBS buffer, and then EDC and NHS were added for activation for 30 min. 2-Carboxyethylphosphonic acid was added to the reaction system, and the reaction was carried out at room temperature in the dark under nitrogen protection for 24 h. After dialyzing and freeze drying, N-GQDs-PO3 quantum dots were obtained. S1-3. N-GQDs-PO3 quantum dots were redispersed in PBS buffer to form a stable suspension. Tetracarboxyphenylporphyrin was dissolved in PBS buffer and then slowly added dropwise to the suspension. After the addition was completed, stirring was continued for 4 hours. The entire process was carried out under the protection of light and nitrogen. The product was purified by ultrafiltration to obtain functional graphene quantum dots, which were dispersed in aqueous solution and stored in the dark for later use. S2. Preparation of ternary precursor solution: Mix bismuth source, tungsten source and functional graphene quantum dot dispersion obtained in step S1, and sonicate to obtain precursor solution A. S3, Preparation of ternary complex: Dissolve silver source and vanadium source in water to obtain solution B; add solution B dropwise to solution A, adjust pH to 4.0-6.0, age at room temperature for 2 hours, then transfer to hydrothermal reactor and react at 150-180℃ for 6-12 hours; S4. Product post-processing: After the reaction is completed, the product is centrifuged, washed and dried to obtain bismuth-silver composite micro-nano materials.

[0005] Furthermore, the preparation process of the N-GQDs-NH2 quantum dots specifically involves dissolving citric acid, urea, and ethylenediamine in deionized water at a mass ratio of 2:3:1, transferring the mixture to a microwave reactor, reacting at 200°C for 10 minutes, allowing it to cool naturally, dialyzing, and freeze-drying to obtain the final product.

[0006] Furthermore, the mass ratio of N-GQDs-NH2 quantum dots to 2-carboxyethylphosphonic acid is 1:2~3; the mass ratio of N-GQDs-PO3 quantum dots to tetracarboxyphenylporphyrin is 1:0.4~0.8.

[0007] Furthermore, the bismuth source and the tungsten source are bismuth nitrate pentahydrate and sodium tungstate, respectively, with a molar ratio of 2:1.

[0008] Furthermore, the concentration of the functional graphene quantum dot dispersion is 1~5 mg / mL, and the mass ratio of its solute to the total mass of the bismuth source and tungsten source is 0.1~0.3:1.

[0009] Furthermore, the silver source is silver nitrate, the vanadium source is ammonium metavanadate, and the molar ratio of the silver source to the bismuth source is 0.1~0.5:1.

[0010] The second objective of this invention is to provide bismuth-silver composite micro / nanomaterials for water treatment prepared by the method described above.

[0011] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses functional graphene quantum dots as a bridge to prepare a Bi2WO6 / AgVO3 composite, successfully combining Bi2WO6 and AgVO3 to form a stable photocatalyst with micro- and nano-scale properties. The functional graphene quantum dots are first prepared using conventional techniques, resulting in N-GQDs-NH2 quantum dots with both nitrogen doping and abundant surface amino groups, providing ample reaction sites for subsequent covalent modification. Furthermore, nitrogen doping itself helps improve its conductivity. Then, through covalent bonding of phosphate groups, it enhances its conductivity against metal ions (especially Bi). 3+ Ag + It possesses stronger coordination ability and wider pH adaptability; furthermore, through π-π stacking, it is loaded with porphyrin groups, maintaining its efficient light absorption and long excited-state lifetime, providing energy for the subsequent photocatalysis of the Bi2WO6 / AgVO3 complex under visible light. The synergistic effect of phosphate and porphyrin groups guides the Bi... 3+ With WO6 2- A Bi2WO6 nanosheet main structure is formed at the quantum dot interface, while Ag + With VO3 - Nucleation occurs on the surface of quantum dots and at the edges or defect sites of Bi2WO6 nanosheets, resulting in highly dispersed AgVO3 nanoparticles. The resulting ternary complex exhibits high catalytic activity for dyeing molecules and good cycle stability. Attached Figure Description

[0012] Figure 1 This is a TEM image of functional graphene quantum dots.

[0013] Figure 2 This is the SEM image of sample 1.

[0014] Figure 3 The graph shows the change in the degradation rate of Rhodamine B over time for different samples.

[0015] Figure 4 The graph shows the degradation rate of Rhodamine B in 10 consecutive cycles of degradation experiments on different samples. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] Example 1: Preparation of functional graphene quantum dots S1, Functional Graphene Quantum Dots S1-1. Citric acid, urea, and ethylenediamine were mixed and dissolved in deionized water at a mass ratio of 2:3:1. The mixture was transferred to a microwave reactor and reacted at 200℃ for 10 min. After natural cooling, the mixture was dialyzed and freeze-dried to obtain N-GQDs-NH2 quantum dots with both nitrogen doping and abundant surface amino groups. 100 mg of N-GQDs-NH2 quantum dots were dispersed in 50 mL of deionized water for later use. S1-2. Take 30 mL of dispersion and dilute it to 100 mL with 0.1 M PBS buffer. Then add 100 mg EDC and 50 mg NHS to activate for 30 min. Add 150 mg 2-carboxyethylphosphonic acid to the reaction system and react at room temperature in the dark under nitrogen protection for 24 h. Dialyze and freeze dry to obtain N-GQDs-PO3 quantum dots. S1-3. 50 mg of N-GQDs-PO3 quantum dots were redispersed in 100 mL of 0.1 M PBS buffer to form a stable suspension. 20 mg of tetracarboxyphenylporphyrin was dissolved in 10 mL of PBS buffer and then slowly added dropwise to the suspension. After the addition was complete, stirring was continued for 4 h. The entire process was carried out under light protection and nitrogen protection. The solution was purified by ultrafiltration to obtain functional graphene quantum dots, which were dispersed in an aqueous solution (1 mg / mL) and stored in the dark for later use.

[0019] Figure 1 This is a TEM image of functional graphene quantum dots.

[0020] Example 2: Preparation method of bismuth-silver composite micro / nanomaterials 1) Preparation of ternary precursor solution: Dissolve 2 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 1 mmol of tungsten source (Na2WO4·2H2O) in 20 mL of nitric acid aqueous solution containing 1 M, stir until clear, take 15 mL of the functional graphene quantum dot dispersion (containing 15 mg of quantum dots) obtained in step S1 and mix it with the solution, sonicate at room temperature for 60 min to obtain precursor solution A; 2) Preparation of ternary complexes: Dissolve 0.3 mmol AgNO3 and 0.3 mmol NH4VO3 in 10 mL of deionized water to obtain solution B; add solution B dropwise to solution A, adjust the pH to 4.5, age at room temperature for 2 h, and then transfer to a hydrothermal reactor and react at 160 °C for 8 h. 3) Product post-processing: After the reaction was completed, the product was centrifuged, washed and dried to obtain bismuth-silver composite micro-nano materials, which were designated as sample 1.

[0021] <Performance Testing and Results Analysis> Structural characterization: Figure 2 The image shows the SEM image of sample 1, which reveals a regular, sheet-like flower-like structure with an average diameter of approximately 2 μm. Nanoscale AgVO3 particles are uniformly distributed on its surface and between its layers.

[0022] Photocatalytic activity: Degradation of 10 mg / L Rhodamine B (RhB) solution using a 300 W xenon lamp (λ ≥ 420 nm) as the light source.

[0023] For comparison, the effects of the amount of functional graphene quantum dots and the AgVO3 loading on catalytic performance were investigated. Samples prepared with different ratios are shown in Table 1.

[0024] Table 1 Figure 3 The figure shows the relationship between the catalytic degradation rate of Rhodamine B for different samples and time. It can be seen from the figure that sample 2 exhibits the best photocatalytic degradation performance. Excessive quantum dots may cover some semiconductor active sites or produce a light-shielding effect, leading to a decrease in activity. When the loading of AgVO3 nanoparticles is too low, the number of heterojunctions formed is insufficient, and the improvement in charge separation efficiency is limited; when the loading is too high, excessive AgVO3 nanoparticles may aggregate, blocking pores and reducing the effective reaction interface, and may also become electron-hole recombination centers. Figure 4 It was found that although excessive quantum dots lead to a decrease in catalytic activity, they have good stability; small amounts of AgVO3 nanoparticles, due to their small total amount, are fully anchored by phosphate ions and have better stability.

[0025] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A method for preparing bismuth-silver composite micro / nanomaterials for water treatment, characterized in that, Includes the following steps: S1, Functional Graphene Quantum Dots S1-1. Nitrogen-doped and abundant surface amino groups of N-GQDs-NH2 quantum dots were prepared by dissolving citric acid, urea and ethylenediamine in water and using a microwave-assisted method. S1-2. N-GQDs-NH2 quantum dots were dispersed in PBS buffer, and then EDC and NHS were added for activation for 30 min. 2-Carboxyethylphosphonic acid was added to the reaction system, and the reaction was carried out at room temperature in the dark under nitrogen protection for 24 h. After dialyzing and freeze drying, N-GQDs-PO3 quantum dots were obtained. S1-3. N-GQDs-PO3 quantum dots were redispersed in PBS buffer to form a stable suspension. Tetracarboxyphenylporphyrin was dissolved in PBS buffer and then slowly added dropwise to the suspension. After the addition was completed, stirring was continued for 4 hours. The entire process was carried out under the protection of light and nitrogen. The product was purified by ultrafiltration to obtain functional graphene quantum dots, which were dispersed in aqueous solution and stored in the dark for later use. S2. Preparation of ternary precursor solution: Mix bismuth source, tungsten source and functional graphene quantum dot dispersion obtained in step S1, and sonicate to obtain precursor solution A. S3, Preparation of ternary complex: Dissolve silver source and vanadium source in water to obtain solution B; add solution B dropwise to solution A, adjust pH to 4.0-6.0, age at room temperature for 2 hours, then transfer to hydrothermal reactor and react at 150-180℃ for 6-12 hours; S4. Product post-processing: After the reaction is completed, the product is centrifuged, washed and dried to obtain bismuth-silver composite micro-nano materials.

2. The method for preparing bismuth-silver composite micro / nanomaterials for water treatment according to claim 1, characterized in that, The preparation process of the N-GQDs-NH2 quantum dots is as follows: citric acid, urea and ethylenediamine are mixed and dissolved in deionized water at a mass ratio of 2:3:1, transferred to a microwave reactor, reacted at 200℃ for 10 min, naturally cooled, dialyzed and freeze-dried to obtain the product.

3. The method for preparing bismuth-silver composite micro / nanomaterials for water treatment according to claim 1, characterized in that, The mass ratio of N-GQDs-NH2 quantum dots to 2-carboxyethylphosphonic acid is 1:2~3; the mass ratio of N-GQDs-PO3 quantum dots to tetracarboxyphenylporphyrin is 1:0.4~0.

8.

4. The method for preparing bismuth-silver composite micro / nanomaterials for water treatment according to claim 1, characterized in that, The bismuth source and tungsten source are bismuth nitrate pentahydrate and sodium tungstate, respectively, with a molar ratio of 2:

1.

5. The method for preparing bismuth-silver composite micro / nanomaterials for water treatment according to claim 1, characterized in that, The concentration of the functional graphene quantum dot dispersion is 1~5 mg / mL, and the mass ratio of its solute to the total mass of bismuth source and tungsten source is 0.1~0.3:

1.

6. The method for preparing bismuth-silver composite micro / nanomaterials for water treatment according to claim 1, characterized in that, The silver source is silver nitrate, the vanadium source is ammonium metavanadate, and the molar ratio of the silver source to the bismuth source is 0.1~0.5:

1.

7. Bismuth-silver composite micro / nanomaterials for water treatment prepared by the method according to any one of claims 1 to 6.

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