Composite photocatalytic material with (Bi2+ / Bi3 +)-VO-VN synergistic regulation effect and preparation method thereof

Abstract

The invention discloses a preparation method of a composite photocatalytic material with a (Bi < 2 + > / Bi < 3 + >)-VO-VN synergistic regulation effect. The preparation method comprises the following steps: 1) mixing melamine, NaCl and KCl, grinding, putting into a crucible with a cover, calcining, cooling to room temperature, and grinding to obtain CN containing molten salt; step 2), a Bi12SiO20-Bi2O3 (BB) mixture and a BB photocatalyst are obtained; the method comprises the following steps: mixing CN of molten salt with deionized water, adjusting the pH value of the solution with dilute nitric acid, and stirring to form a suspension A; mixing a BB photocatalyst with deionized water, adjusting the pH value to form a turbid liquid B, adding a surfactant CTAC, and continuing the reaction; and dropwise adding a proper amount of the turbid liquid A into the reacted turbid liquid B to finally obtain the CBBBC series photocatalyst. According to the preparation method disclosed by the invention, by introducing a synergistic regulation strategy of the surfactant and the molten salt carbon nitride, adjustable control of Bi2 + / Bi3 + valence variation, oxygen vacancy generation and nitrogen vacancy introduction is realized, so that the performance of the photocatalytic material is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and particularly relates to a composite photocatalytic material with a (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation effect and a preparation method thereof. Background Art

[0002] Traditional bismuth-based photocatalytic materials usually face the following key problems: the recombination rate of photo-generated electrons and holes is relatively high, resulting in low quantum efficiency; poor electrical conductivity limits the migration of carriers; the adsorption capacity for organic pollutants is limited, further reducing the catalytic efficiency, etc.

[0003] To overcome the above defects, researchers have proposed various modification schemes. For example, the publication number CN109876543A improves the catalytic performance by regulating the particle size of BiOCl, and the publication number CN108765432B improves the performance by introducing a composite structure of TiO2 and Bi2O3. These studies have improved the photocatalytic performance of the materials to a certain extent, but there are still problems such as easy recombination of photo-generated electrons and holes and limited interfacial electron transport efficiency, which hinder the further improvement of the photocatalytic performance of the composite catalytic materials.

[0004] In addition, the synergistic regulation effect of surface defects (such as oxygen vacancies and nitrogen vacancies) on the photocatalytic performance is often ignored, thus failing to fully explore the performance potential of the materials. Summary of the Invention

[0005] To overcome the above problems existing in the prior art, the purpose of the present invention is to provide a composite photocatalytic material with a (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation effect and a preparation method thereof. By introducing a surfactant (active group to promote the valence change of Bi and the generation of oxygen vacancies) and a molten salt carbon nitride (to promote the generation of nitrogen vacancies) synergistic regulation strategy, the adjustable control of the valence change of Bi 2+ / Bi 3+ the generation of oxygen vacancies and the introduction of nitrogen vacancies is realized, thereby greatly improving the performance of the photocatalytic material.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A preparation method of a composite photocatalytic material with a (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation effect, comprising the following steps;

[0008] Step 1), Mix melamine, NaCl and KCl, grind them finely and load them into a crucible with a lid for calcination. After cooling to room temperature, grind to obtain CN containing molten salt;

[0009] Step 2), (1) Weigh Bi2O3 and SiO2, mix them with the composite molten salt and ball-mill using zirconia grinding balls; Obtain the Bi 12 SiO 20 -Bi2O3 (BB) mixture;

[0010] Place the BB mixture in a crucible for calcination, cool it to room temperature in the furnace, grind the powder, then alternately wash and centrifuge it with deionized water and absolute ethanol, and dry it in an oven to obtain the BB photocatalyst;

[0011] Mix the molten salt CN with deionized water, adjust the pH of the solution with dilute nitric acid, stir to form suspension A; Mix BB with deionized water, adjust the pH with dilute nitric acid and stir to form suspension B; Finally, in a water bath, gradually add a certain volume of suspension A dropwise to suspension B (volume ratio 3 - 8:1), react, and the reacted suspension is centrifuged, washed, and dried to obtain the CBBB powder; As an intermediate comparison catalyst;

[0012] (2) Weigh Bi2O3 and SiO2, mix them with the composite molten salt and ball-mill using zirconia grinding balls; Obtain the Bi 12 SiO 20 -Bi2O3 (BB) mixture;

[0013] Place the BB mixture in a crucible for calcination, cool it to room temperature in the furnace, grind the powder, then alternately wash and centrifuge it with deionized water and absolute ethanol, and dry it in an oven to obtain the BB photocatalyst;

[0014] Mix the molten salt CN with deionized water, adjust the pH of the solution with dilute nitric acid, stir to form suspension A;

[0015] After mixing the BB photocatalyst with deionized water, adjust the pH and react to form suspension B; Add a certain amount of surfactant CTAC and continue to react;

[0016] Subsequently, gradually add an appropriate amount of suspension A dropwise to suspension B, and the reacted suspension is washed, centrifuged, and dried multiple times to finally obtain the CBBBC series of photocatalysts.

[0017] Step 1) is specifically as follows: Prepare molten salt CN: Weigh 5 g to 7 g of melamine, 4 g to 6 g of NaCl, and 6 g to 7 g of KCl, mix them, grind them finely, and then put them into a crucible with a lid; Under the condition that the heating rate is 8 °C / min to 12 °C / min, calcine at a temperature of 500 °C to 700 °C, keep warm for 3 h to 5 h, and after cooling to room temperature, grind to obtain CN containing molten salt, which is used as one of the basic complexes of the subsequent CBBB composite photocatalyst. Make the molten salt carbon nitride crystallize and the microscopic morphology thin, which is convenient for its subsequent composite.

[0018] In step 2), prepare CN-Bi as the intermediate comparison catalyst 12 SO 20 -Bi2O3-BiOCl (CBBB) photocatalyst:

[0019] (1) Prepare BB: Use K2CO3 and KCl as the composite molten salt, weigh 9 g to 12 g of K2CO3 and 8 g to 11 g of KCl according to the molar ratio of the eutectic point, accounting for 35% to 45% of the total mass of the raw materials (K2CO3 and KCl composite molten salt);

[0020] Weigh Bi2O3 and SiO2 in a molar ratio of 4:1 to 8:1, mix them with the composite molten salt, and then ball-mill for 4 h to 6 h using zirconia grinding balls with diameters of 0.3 cm to 0.7 cm and 0.8 to 1.2 cm;

[0021] (2) Weigh 4 g to 6 g of the ball-milled mixture and place it in a crucible. After calcining at a temperature of 670 °C to 700 °C for 0.3 h to 0.7 h, cool it to room temperature with the furnace. After grinding the powder, wash and centrifuge it alternately 2 to 4 times with deionized water and absolute ethanol, and dry it in an oven at 70 °C to 75 °C for 10 h to 14 h to obtain the BB photocatalyst;

[0022] (3) Prepare the CBBB catalyst: Mix 0.8 g to 1.2 g of molten salt carbon nitride with 20 mL to 30 mL of deionized water, adjust the pH of the solution to about 1.8 to 2.2 with dilute nitric acid, and stir for 0.8 h to 1.2 h to form suspension A; Mix 0.2 g to 0.3 g of BB with 25 mL to 35 mL of deionized water, adjust the pH to 1 to 2 with dilute nitric acid, and stir for 25 to 35 min to form suspension B; Finally, in a water bath at 30 to 35 °C, slowly add a certain volume of suspension A dropwise to suspension B, react for 25 min to 35 min, and the reacted suspension is centrifuged, washed, and dried to obtain the CBBB powder. Different ratios affect the microscopic size and morphology of the final CBBC photocatalyst.

[0023] Step 2) is specifically as follows: Prepare surfactant-modified carbon nitride Bi 12 SO 20-Bi2O3-BiOCl Composite Photocatalyst CBBBC:

[0024] (1) Preparation of BB: Use K2CO3 and KCl as composite molten salts, weigh 9 g to 12 g of K2CO3 and 8 g to 11 g of KCl according to the molar ratio of the eutectic point, accounting for 35% to 45% of the total mass of the raw materials (K2CO3 and KCl composite molten salts);

[0025] Weigh Bi2O3 and SiO2 in a molar ratio of 4:1 to 8:1, mix them with the composite molten salt, and then ball-mill them for 4 h to 6 h using zirconia grinding balls with diameters of 0.3 cm to 0.7 cm and 0.8 to 1.2 cm;

[0026] (2) Weigh 4 g to 6 g of the ball-milled mixture and place it in a crucible. Calcinate it at a temperature of 670 °C to 700 °C for 0.3 h to 0.7 h, and then cool it to room temperature with the furnace. After grinding the powder, wash and centrifuge it alternately 2 to 4 times with deionized water and absolute ethanol, and place it in an oven at 70 °C to 75 °C to dry for 10 h to 14 h to obtain the BB photocatalyst;

[0027] (3) Mix 0.8 g to 1.2 g of molten salt carbon nitride with 20 mL to 30 mL of deionized water, adjust the pH of the solution to about 1.8 to 2.2 with dilute nitric acid, and stir for 0.8 h to 1.2 h to form suspension A;

[0028] Mix 0.2 g to 0.3 g of BB with 25 mL to 35 mL of deionized water, adjust the pH to 1 to 2 with dilute nitric acid, and stir for 25 to 35 min to form suspension B; Add a certain amount of surfactant CTAC (mass ratio of 0.8:1 to 1.2:1), and continue to react for 25 min to 35 min;

[0029] Different ratios result in different Si:Bi ratios of the composite BB, which is an important factor affecting the bonding between bonds. At the same time, different ratios affect the microscopic morphology and size. (4) Subsequently, add an appropriate amount of suspension A dropwise to suspension B and react fully for 25 min to 35 min. The reacted suspension is washed, centrifuged, and dried multiple times to finally obtain the CBBBC series of photocatalysts with excellent degradation effects on different antibiotics.

[0030] In the step (2), the solution concentration of the surfactant CTAC is 0.02 mol / mL to 0.03 mol / mL.

[0031] In the preparation process of suspension B in the step (2), for the convenience of measurement and control of variables, the pH is controlled at 1 to 2, and all reactions are carried out under the water bath condition of 30 °C to 35 °C, so as to control the microscopic morphology of the catalyst to be flower-like lamellae.

[0032] The CBBBC photocatalyst provided by the present invention has excellent visible-light photocatalytic performance and can be widely applied in the fields of wastewater treatment, organic pollutant degradation, environmental remediation, etc.

[0033] A composite photocatalytic material with a synergistic regulation effect of (Bi 2+ / Bi 3+ )-V O -V N In the composite photocatalytic material, the synergistic regulation effect of Bi 2+ / Bi 3+ ions and V O -V N is such that the different oxidation states of Bi 2+ and Bi 3+ can regulate the electron migration and the activity of catalytic centers, and the presence of V O -V N helps with the electron distribution and transfer;

[0034] The change in the oxidation state of Bi 2+ / Bi 3+ can adjust the excitation energy required for the catalytic reaction by changing the electron density on the catalyst surface; the defect sites of V O -V N provide better capture and transport pathways for photo-generated electrons;

[0035] The oxygen defects of V O -V N enhance the ability to adsorb active substances, and the presence of Bi 2+ / Bi 3+ can promote the degradation of reactants and enhance the selectivity and rate of the catalytic process.

[0036] Advantages of the present invention:

[0037] The innovation of the present invention lies in promoting the valence change of Bi 2+ / Bi 3+ and the formation of nitrogen and oxygen vacancies through the synergistic effect among multiple materials, constructing a composite photocatalytic material with the synergistic regulation characteristics of (Bi 2+ / Bi 3+ )-V O -V N thereby significantly improving the photocatalytic performance. Promote electron transfer through the CTA + group in the surfactant to regulate the valence change balance of Bi (Bi 2+ -e - →Bi 3+) and promotes the generation of oxygen vacancies, playing a key role in the variable valence process of Bi element. By regulating the microtopography of the material, a nanosheet structure with appropriate thickness is formed. However, the introduction of CTAC is not conducive to the generation of bismuth oxyhalide and the stability of the original heterogeneous bismuth-based heterojunction.

[0038] By introducing acid-treated molten salt carbon nitride (CN), stable nitrogen vacancies (V N ) are induced to generate on the surface of the bismuth-based material, further enhancing the electron transfer ability and the stability of the heterojunction interface. The surface positive charges in CN can synergistically interact with the bismuth-based material, regulating the formation of a stable BiOCl crystal phase and assisting in constructing the heterogeneous Bi 12 SO 20 -Bi2O3-BiOCl, significantly improving the electron separation efficiency between interfaces and the stability of the heterojunction. It effectively avoids the potential adverse effects of surfactants on the stability of bismuth-based heterogeneous junctions, promoting [V O Bi 2+ + defects and the formation of V N through the spontaneous synergistic effect between materials, realizing the regulation of Bi 2+ / Bi 3+ valence change and Vo, V N . Thus, the separation efficiency of photogenerated electrons is improved, the lifetime of electron-hole pairs is prolonged, and the electronic bandgap of the material is optimized. This innovative design enables the composite photocatalytic material of the present invention to exhibit excellent photocatalytic performance in the degradation of various organic pollutants, while possessing extremely high stability and recyclability.

[0039] Compared with the prior art, the method of the present invention has the advantages of simple process, strong controllability, and environmental friendliness, providing a new technical solution for the wide application of efficient and stable photocatalytic materials in the field of environmental pollution treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is the photocatalytic performance diagram (under full light conditions) of CBBB and CBBBC prepared in the present invention.

[0041] Figure 2 is the photocatalytic performance diagram of CBBB and CBBBC prepared in the present invention.

[0042] Figure 3 (a) is the TEM diagram, Figure 3 (b) is the HRTEM diagram. DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention will be further described in detail below with reference to the accompanying drawings.

[0044] Example 1

[0045] (1) Weigh 6 g of melamine, 5 g of NaCl, and 6.5 g of KCl. After mixing them, grind the mixture and put it into a crucible with a lid. Calcinate it at 670 °C for 4 h under the condition that the heating rate is 10 °C / min. After cooling to room temperature, grind it to obtain CN powder containing molten salt;

[0046] (2) Weigh 10 g of K2CO3 and 9 g of KCl (accounting for 40% of the total mass of raw materials). Weigh Bi2O3 and SiO2 according to a molar ratio of 6:1. After mixing them with the composite molten salt, add zirconia grinding balls with diameters of 0.5 cm and 1 cm and ball-mill for 5 h;

[0047] (3) Weigh 5 g of the ball-milled mixture and put it into a crucible. Calcinate it at 685 °C for 0.5 h and then cool it to room temperature in the furnace. The obtained powder is washed alternately with deionized water and absolute ethanol by centrifugation 3 times and then dried in an oven at 70 °C for 12 h to obtain BB powder;

[0048] (4) Mix 1 g of molten salt CN with 25 mL of deionized water, adjust the pH of the solution to 2 with dilute nitric acid, and stir for 1 h to form suspension A; mix 0.25 g of BB with 30 mL of deionized water, adjust the pH to 1.5 with dilute nitric acid, and stir for 30 min to form suspension B; finally, at a water bath temperature of 30 °C, slowly add suspension A dropwise to suspension B, react for 30 min, centrifuge, wash, and dry to obtain CBBB powder;

[0049] (5) When preparing suspension B, after mixing BB with deionized water and adjusting the pH to 1.5, react for 30 min, then add CTAC (mass ratio of 1:1), and continue to stir for 30 min;

[0050] (6) Slowly add suspension A dropwise to suspension B, fully react for 30 min, centrifuge, wash, and dry to finally obtain the CBBBC photocatalyst.

[0051] The CBBBC photocatalyst obtained in this example is a cluster formed by stacking nanosheets with nanosheets. The thickness of its nanosheets is between 11.4 nm and 15.1 nm, and the degradation efficiency for RhB (15 mg / L) reaches 99.9% within 60 min.

[0052] Example 2

[0053] (1) Weigh 7 g of melamine, 14 g of NaCl, and 16 g of KCl. Grind the mixture and put it into a crucible. Calcinate it at 670 °C for 3 h under the condition that the heating rate is 10 °C / min. After cooling, grind it to obtain CN powder;

[0054] (2) Weigh 12 g of K2CO3 and 11 g of KCl (accounting for 45% of the total mass of the raw materials), weigh Bi2O3 and SiO2 in a molar ratio of 7:1, mix them with the composite molten salt, add zirconia grinding balls with diameters of 0.4 cm and 0.9 cm, and ball mill for 4 h;

[0055] (3) Weigh 6 g of the mixture and put it into a crucible, calcine at 700 °C for 0.5 h. After cooling, the powder is alternately washed and centrifuged 3 times with deionized water and ethanol, and then placed in an oven at 75 °C to dry for 14 h to obtain BB;

[0056] (4) Mix 1.2 g of molten salt CN with 20 mL of deionized water, adjust the pH of the solution to 2.2 with dilute nitric acid, and stir for 1.2 h to form suspension A; mix 0.3 g of BB with 35 mL of deionized water, adjust the pH to 1 with dilute nitric acid, and stir for 35 min to form suspension B; finally, drop suspension A into suspension B drop by drop in a 35 °C water bath, react for 35 min, centrifuge, wash, and dry to obtain CBBB powder;

[0057] (5) When preparing suspension B, after mixing BB with deionized water and adjusting the pH to 1.2, reacting for 35 min, add CTAC (mass ratio of 1.2:1), and continue to stir for 35 min;

[0058] (6) Drop suspension A into suspension B drop by drop, react fully for 35 min, centrifuge, wash, and dry to finally obtain the CBBBC photocatalyst.

[0059] The CBBBC photocatalyst obtained through this example is composed of nanoflowers formed by the interpenetration and overlapping of nanosheets with an average thickness of 15.1 nm. The entire framework is formed by the overlapping and stacking of nanosheets with an average thickness of about 14.5 nm. The edges of the nanosheets show a curled state, and the overall agglomeration state of the nanosheets is between SBBC and CN. When irradiated with visible light for 120 min, the degradation rate of a 20 mg / L TC solution reaches 93%.

[0060] Example 3

[0061] (1) Weigh 5.5 g of melamine, 4.5 g of NaCl, and 6.2 g of KCl, grind the mixture and put it into a crucible. Under the condition of a heating rate of 10 °C / min, calcine at 700 °C for 4 h, and grind after cooling to obtain CN powder;

[0062] (2) Prepare 11 g of K2CO3 and 10 g of KCl (accounting for 42% of the total mass of the raw materials), weigh Bi2O3 and SiO2 in a molar ratio of 5:1, mix them with the composite molten salt, add zirconia grinding balls with diameters of 0.6 cm and 1 cm, and ball mill for 6 h;

[0063] (3) Weigh 5 g of the mixture and put it into a crucible. Calcinate it at 690 °C for 0.6 h. After cooling, the powder is washed and centrifuged 3 times alternately with deionized water and absolute ethanol, and then placed in an oven at 72 °C for drying for 12 h to obtain BB;

[0064] (4) Prepare the CBBB catalyst: Mix 1 g of molten salt CN with 30 mL of deionized water, and adjust the pH of the solution to 2 with dilute nitric acid. Stir for 1 h to form suspension A; Mix 0.25 g of BB with 25 mL of deionized water, and adjust the pH to 1.5 with dilute nitric acid. Stir for 25 min to form suspension B; Finally, drop suspension A into suspension B drop by drop under a 32 °C water bath, react for 30 min, centrifuge, wash and dry to obtain the CBBB powder;

[0065] (5) When preparing suspension B, after mixing BB with deionized water and adjusting the pH to 1.5, react for 30 min, then add CTAC (mass ratio is 0.9:1), and continue to stir for 30 min;

[0066] (6) Drop suspension A into suspension B drop by drop, react fully for 30 min, centrifuge, wash and dry to finally obtain the CBBBC photocatalyst.

[0067] Benefiting from the action of CTAC, the CBBBC photocatalyst obtained in this example is thinned on the basis of CN, and the large surface area of the powder can promote the photocatalytic reaction as much as possible. When irradiated with visible light for 120 min, the degradation rate of a 10 mg / L CIP solution reaches 90%.

[0068] From the attached Figure 1 It can be seen that when irradiated with visible light for 60 min, the degradation rate of a 15 mg / L RhB solution by CBBBC reaches 99.9%.

[0069] From the attached Figure 2 It can be seen that when irradiated with visible light for 120 min, the degradation rate of a 20 mg / L TC solution reaches 93%.

[0070] Figure 3 a is the TEM image of CBBBC. It can be observed from it that the powder is formed by assembling nanosheets, which also confirms the microscopic morphology observed by SEM. And it can be observed from the figure that the small particles with an average size of 4.96 nm appearing on the nanosheet layer are carbon nitride particles calcined by the molten salt method. As Figure 3 As shown in b, 7 kinds of lattice fringes with different spacings are found in HRTEM. Different lattice spacings represent different crystal planes of different crystal phases ( Figure 3(b)). Among them, 0.268 nm, 0.272 nm, 0.276 nm, 0.278 nm, 0.355 nm, 0.396 nm respectively represent the Bi2O3(321) crystal plane contained in SBCN-6, Bi 12 SiO 20 (321) crystal plane, BiOCl(110) crystal plane, Bi2O3(113) crystal plane, Bi 12 SiO 20 (220) crystal plane and Bi2SiO5(400) crystal plane. In addition, the lattice fringe of 0.332 nm indicates the presence of carbon nitride in the photocatalyst. These lattices reflect the interfacial relationship between some crystal phases, C3N4 - Bi 12 SiO 20 -Bi2O3 - BiOCl - Bi2SiO5 is a possible heterostructure form in the above-prepared CBBBC composite photocatalytic material. The high-density defect distribution can be reflected by the dense appearance of defect sites, and these defect sites often present as missing oxygen atoms or local lattice distortion. The existence of defects provides additional active sites for the photocatalytic reaction, enhances the electron transport ability of the material, and thus improves the catalytic efficiency.

[0071] Mechanism and catalytic process of synergistic regulation:

[0072] In the composite photocatalytic material, the synergistic regulation effect of Bi 2+ / Bi 3+ ions and V O -V N is mainly reflected in the regulation of electronic structure, enhancement of catalytic activity and optimization of reaction path. The different oxidation states of Bi 2+ and Bi 3+ can regulate the migration of electrons and the activity of catalytic centers, while the presence of V O -V N helps the distribution and transfer of electrons, thus improving the photocatalytic efficiency: (1) Regulation of electronic structure: The change in the oxidation state of Bi 2+ / Bi 3+ can adjust the excitation energy required for the catalytic reaction by changing the electron density on the catalyst surface. Bi 2+ can provide additional electrons under light illumination, thus reducing the energy barrier of the catalytic reaction, while Bi 3+ helps the stabilization and migration of electrons. The defect sites of V O -V N provide better capture and transport paths for photogenerated electrons, further improving the reaction efficiency. (2) Optimization of catalytic reaction: The synergistic regulation effect of the composite material is not only manifested in the optimization of electronic structure, but also includes the activation of species in the catalytic reaction. V O -VN The oxygen defects can enhance the ability to adsorb active substances, while Bi 2+ / Bi 3+ can promote the degradation of reactants and enhance the selectivity and rate of the catalytic process. (3) Relationship between regulation means and regulation results: By adjusting the ratio of Bi 2+ / Bi 3+ , the defect structure and distribution of V O -V N , the electronic structure and surface properties of the material can be precisely controlled, thereby realizing the effective regulation of the photocatalytic reaction. The ratio control of Bi 2+ / Bi 3+ can adjust the electron supply and the reaction activity of the catalytic center, while the defect density and distribution of V O -V N directly affect the rate and selectivity of the catalytic reaction.

[0073] Relationship between the size of the composite photocatalytic material and the interaction mechanism

[0074] The ultrathin nanosheet structure of the material can provide a larger specific surface area and more surface active sites, which is conducive to the efficient contact between photo-generated electrons and reactants. The size and morphology of the material (such as nanosheets, nanoparticles, etc.) directly affect its photocatalytic performance. Nanostructures with smaller sizes usually have better light absorption and electron transport properties, which can improve the catalytic efficiency. In terms of the reaction mechanism, the size and morphology of the material affect the reaction path and rate of the catalytic reaction. The ultrathin nanosheet structure not only provides a large surface area, but also regulates the distribution of photo-generated carriers through its high-density defect sites, further enhancing the catalytic activity.

[0075] The present invention provides a (Bi 2+ / Bi 3+ )-V O -V N synergistically regulated composite photocatalytic material and its preparation method. Through the synergistic effect of Bi valence change, oxygen vacancies and nitrogen vacancies, combined with the functional regulation of surfactants, the present invention significantly solves the problems of high photo-generated electron-hole recombination rate, poor conductivity and insufficient adsorption capacity in traditional photocatalysts. Cetyltrimethylammonium bromide (CTAC) is used to modify the bismuth-based composite material, and carbon nitride (CN) is introduced to construct a heterojunction, thereby optimizing the microstructure of the material, improving the electron transport efficiency, and enhancing the adsorption capacity for pollutants. Specifically, CTAC regulates the balance of Bi 2+ / Bi 3+ and promotes the generation of oxygen vacancies. Acting synergistically with the nitrogen vacancies introduced by molten salt carbon nitride, the interaction between these valence changes and defects effectively improves the separation efficiency of photo-generated electrons.

[0076] The materials prepared by the present invention have an ultrathin nanosheet structure and a high-density defect distribution, which enhance the separation efficiency of photo-generated electrons and holes and broaden the visible light response range. Experimental verification shows that the materials exhibit a degradation efficiency of over 90% when degrading organic pollutants (such as rhodamine B, ciprofloxacin, and tetracycline), and have excellent recyclability. This method has a simple process and controllable structure, providing a new technical path for the development of highly efficient and stable photocatalytic materials.

Claims

1. A preparation method of a composite photocatalytic material with (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation effect, characterized in that, It includes the following steps; Step 1), mix melamine, NaCl and KCl, grind them finely and load them into a crucible with a lid for calcination. After cooling to room temperature, grind to obtain CN containing molten salt; Step 2), weigh Bi2O3 and SiO2, mix them with the composite molten salt and ball mill using zirconia grinding balls; obtain Bi 12 SiO 20 -Bi2O3 (BB) mixture; Place the BB mixture in a crucible for calcination, cool it to room temperature with the furnace, grind the powder, then wash and centrifuge it alternately with deionized water and absolute ethanol, and dry it in an oven to obtain the BB photocatalyst; Mix the CN of molten salt with deionized water, adjust the pH of the solution with dilute nitric acid, and stir to form suspension A; After mixing the BB photocatalyst with deionized water, adjust the pH with dilute nitric acid and react to form suspension B, add the surfactant CTAC, and continue the reaction; Subsequently, add an appropriate amount of suspension A dropwise to suspension B after the reaction. The suspension after the reaction is washed, centrifuged and dried multiple times to finally obtain the CBBBC series photocatalysts.

2. The preparation method of a composite photocatalytic material with a (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation effect, characterized in that The specific content of step 1) is as follows: prepare molten salt CN: weigh 5 g to 7 g of melamine, 4 g to 6 g of NaCl and 6 g to 7 g of KCl, mix and grind them finely, then load them into a crucible with a lid, and under the condition that the heating rate is 8 °C / min to 12 °C / min, calcine at a temperature of 500 °C to 700 °C for 3 h to 5 h. After cooling to room temperature, grind to obtain CN containing molten salt.

3. The preparation method of a composite photocatalytic material having a synergistic regulation effect of (Bi 2+ / Bi 3+ )-V O -V N , characterized in that The specific content of step 2) is as follows: (1) Prepare BB: Use K2CO3 and KCl as the composite molten salt, weigh 9 g to 12 g of K2CO3 and 8 g to 11 g of KCl according to the molar ratio of the eutectic point, accounting for 35% to 45% of the total mass of the raw materials (K2CO3 and KCl composite molten salt); Weigh Bi2O3 and SiO2 in a molar ratio of 4:1 to 8:1, mix them with the composite molten salt, and ball-mill them with zirconia grinding balls with diameters of 0.3 cm to 0.7 cm and 0.8 to 1.2 cm for 4 h to 6 h; (2) Weigh 4 g to 6 g of the ball-milled mixture and place it in a crucible. After calcining at a temperature of 670 °C to 700 °C for 0.3 h to 0.7 h, cool it to room temperature with the furnace. Grind the powder, then wash and centrifuge it alternately with deionized water and absolute ethanol 2 to 4 times, and dry it in an oven at 70 °C to 75 °C for 10 h to 14 h to obtain the BB photocatalyst; (3) Mix 0.8 g to 1.2 g of molten salt carbon nitride with 20 mL to 30 mL of deionized water, adjust the pH of the solution to about 1.8 to 2.2 with dilute nitric acid, and stir for 0.8 h to 1.2 h to form suspension A; Mix 0.2 g to 0.3 g of the BB photocatalyst with 25 mL to 35 mL of deionized water, adjust the pH with dilute nitric acid, stir for 25 to 35 min to form suspension B; add the surfactant CTAC, and continue the reaction for 25 min to 35 min; (4) Subsequently, add an appropriate amount of suspension A dropwise to suspension B, and react fully for 25 min to 35 min. The suspension after the reaction is washed, centrifuged and dried multiple times to finally obtain the CBBBC series photocatalysts with excellent degradation effects on different antibiotics.

4. The preparation method of a composite photocatalytic material with a (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation effect, characterized in that In (3) of the step 2), the solution concentration of the surfactant CTAC is 0.02 mol / mL to 0.03 mol / mL; The mass ratio of the BB photocatalyst to the surfactant CTAC is 0.8:1 to 1.2:

1.

5. A method for preparing a composite photocatalytic material having a (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation effect, characterized in that In (3) of the step 2), during the preparation of the suspension B, the pH is controlled at 1 to 2, and all reactions are carried out under the water bath condition of 30 °C to 35 °C.

6. A composite photocatalytic material with a (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation effect, characterized in that, In the composite photocatalytic material, Bi 2+ / Bi 3+ ions and V O -V N synergistic regulation effect, Bi 2+ and Bi 3+ with different oxidation states can regulate the electron migration and the activity of catalytic centers, and V O -V N is used for the distribution and transfer of electrons; Bi 2+ / Bi 3+ The change in the oxidation state of can adjust the excitation energy required for the catalytic reaction by changing the electron density on the catalyst surface; V O -V N The defect sites of provide a capture and transport pathway for photogenerated electrons; V O -V N The ability of oxygen defects to enhance the adsorption of active substances, Bi 2+ / Bi 3 can promote the degradation of reactants and enhance the selectivity and rate of the catalytic process.

7. An application of a composite photocatalytic material with (Bi 2+ / Bi 3+ )-V O -V N synergistic regulation, characterized in that, The composite photocatalytic material is applied to the fields of wastewater treatment, organic pollutant degradation and environmental remediation.

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