Preparation method of ternary rare earth co-modified bismuth vanadate material

Abstract

The invention relates to a preparation method of a ternary rare earth co-modified bismuth vanadate material. The method comprises the following steps: 1, dissolving bismuth nitrate in nitric acid to obtain a bismuth source solution; nH4VO3 with the molar weight equal to that of Bi (NO3) 3.5 H2O is added into ionized water to be completely dissolved, and a vanadium source solution is obtained; step 2, adding the vanadium source solution prepared in the step 1 into the bismuth source solution at room temperature, and continuously stirring during the period to form a turbid liquid; adjusting the pH value to 7-8 to complete the pretreatment process of the precursor solution; step 3, transferring the turbid liquid in the step 2 into a hydrothermal reaction kettle to react, centrifuging, washing, precipitating and drying to obtain a bismuth vanadate material; 4, rare earth elements are introduced into the bismuth vanadate material washed in the step 3 through a calcination method or an ion impregnation method, and the ternary rare earth co-modified bismuth vanadate material is obtained. According to the invention, the problems of low transport efficiency of bismuth vanadate photon-generated carriers and high recombination rate of electron hole pairs are effectively solved. And the visible light catalysis capability of bismuth vanadate is improved.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and in particular to a method for preparing a ternary rare earth co-modified bismuth vanadate material. Background Art

[0002] Photocatalytic technology is in line with the concept of green, low-carbon and sustainable development, and is of great significance in solving environmental pollution and alleviating energy shortages. Bismuth vanadate is an excellent photocatalytic material with excellent photon performance and good visible light response ability, and therefore has attracted much attention from researchers in the industry. Bismuth vanadate mainly has three crystal forms: monoclinic scheelite, tetragonal scheelite, and tetragonal zirconite. All three crystal forms have good photoelectrochemical properties and are non-toxic and harmless. The catalytic mechanism of bismuth vanadate includes three basic steps: the generation of photogenerated electron-hole pairs, the transition of electrons, and the surface diffusion of bismuth vanadate and the redox reaction at the surface catalytic active sites.

[0003] Pure bismuth vanadate (BVO) has a small specific surface area, a narrow band gap, and a high electron-hole recombination rate. These factors all affect its photocatalytic activity. However, its excellent response to visible light continues to drive researchers to innovate its modification methods. Consequently, numerous strategies have been developed to enhance the photocatalytic performance of BVO. Morphological design, heterostructure construction, and element doping have all been shown to improve the catalytic activity of BVO under visible light irradiation by increasing the photosensitive area, promoting electron migration, and adjusting the electronic structure. Unfortunately, while morphological design can adjust the photosensitive area and enhance light utilization, it does not alter the electronic structure, and the high electron-hole recombination rate hinders its application. Heterostructure construction can significantly enhance the photocatalytic activity of the material, but it is dependent on the type of semiconductor, and the construction of composite materials also requires consideration of the matching of the material crystal planes. This significantly increases the cost and requirements of the material construction. Element doping can modify the electronic structure and introduce impurity energy levels within the original band gap, significantly reducing the energy required for electron transitions. However, element doping can easily form electron traps in the material, which in turn become recombination sites and hinder the photocatalytic reaction. Although the element doping strategy has its problems, it is highly operational and has low technical difficulty, and is expected to be applied in actual working conditions. More importantly, multi-element synergistic modification can make up for the shortcomings of a single element and introduce additional active sites into the bismuth vanadate material. The outer electron structure of rare earth elements is [Xe]4f n 6s 2, which means that it has rich electron orbits, which is conducive to the formation of stable impurity energy levels after doping. In addition, rare earth element doping can red-shift the light absorption wavelength of the bulk material, which will provide bismuth vanadate with a wider light absorption range. In view of the advantages of the bismuth vanadate modification strategy and the feasibility of element doping, the synergistic use of the advantages brought by different elements can achieve the complementarity of material properties and enhance the photocatalytic performance of bismuth vanadate. In addition, bismuth vanadate also requires a larger specific surface area and light response range so that it has more active sites and a wider light absorption capacity. These will ensure that bismuth vanadate has improved photocatalytic efficiency. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing a ternary rare earth co-modified bismuth vanadate material. By introducing rare earth elements, impurity energy levels are introduced into the bismuth vanadate's band structure, which serves as a springboard for transitions to lower-energy electrons. This effectively reduces the recombination rate of photogenerated electrons and holes, providing a wider source of electrons for subsequent photocatalytic reactions. This effectively addresses the low transport efficiency of photogenerated carriers and the high recombination rate of electron-hole pairs in bismuth vanadate, and enhances the visible light photocatalytic ability of bismuth vanadate.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a ternary rare earth co-modified bismuth vanadate material comprises the following steps:

[0007] Step 1, preparation of bismuth source solution and vanadium source solution:

[0008] Dissolving bismuth nitrate in nitric acid to obtain a bismuth source solution; adding NH4VO3 in an amount equal to that of Bi(NO3)3·5H2O to ionized water and completely dissolving the NH4VO3 to obtain a vanadium source solution;

[0009] Step 2, precursor pretreatment:

[0010] The vanadium source solution prepared in step 1 is added to the bismuth source solution at room temperature while continuously stirring to form a suspension; the pH is adjusted to 7-8 to complete the pretreatment process of the precursor solution;

[0011] Step 3, preparation of bismuth vanadate material:

[0012] The suspension in step 2 is transferred to a hydrothermal reactor for reaction, centrifuged, washed, precipitated, and dried to obtain a bismuth vanadate material;

[0013] Step 4, rare earth ion modified bismuth vanadate material:

[0014] The bismuth vanadate material washed in step 3 is introduced with rare earth elements by calcination or ion impregnation to obtain a ternary rare earth co-modified bismuth vanadate material.

[0015] The step 1 is specifically as follows:

[0016] Using Bi(NO3)3·5H2O as a bismuth source, dissolving bismuth nitrate in nitric acid at a mass ratio of 1:(40-60) to obtain a bismuth source solution; using NH4VO3 as a vanadium source, adding NH4VO3 in an amount equal to that of Bi(NO3)3·5H2O at a mass ratio of 1:(80-100) to deionized water and completely dissolving them to obtain a vanadium source solution;

[0017] The purpose of adding equimolar amounts of NH4VO3 and Bi(NO3)3·5H2O is to make the V element and the Bi element have a stoichiometric ratio of 1:1 (Bi:V) in the chemical formula of BiVO4, ensuring that BiVO4 can be stably formed during the reaction.

[0018] The step 2 is specifically as follows:

[0019] Add the vanadium source solution prepared in step 1 to the bismuth source solution at room temperature while stirring continuously to form a suspension. Under acidic conditions, an orange-red byproduct, V2O5, will appear in the precursor solution. Therefore, adjust the solution pH to 7 using ammonia and dilute nitric acid to prevent the formation of V2O5 in the BiVO4 precursor. This completes the precursor solution pretreatment process.

[0020] The step 3 is specifically as follows:

[0021] The suspension from step 2 is transferred to a hydrothermal reactor. The hydrothermal temperature affects the reaction rate, which in turn influences the orientation of the BiVO4 crystal planes and ultimately the morphology of the bismuth vanadate. The hydrothermal time also affects the crystallinity of the BiVO4. Therefore, the hydrothermal reactor is set at a temperature of 180-220°C for 24 hours. After drying, the bismuth vanadate material is obtained.

[0022] The step 4 is specifically as follows:

[0023] The calcination method is as follows: weigh the bismuth vanadate in step 4 and place it in a crucible, and add lanthanum oxide, cerium oxide, and neodymium oxide at a molar ratio of rare earth atoms to bismuth atoms of (0.01 to 0.05):1; and ensure that the molar ratio of lanthanum: cerium: neodymium is 1:1:1; after thorough mixing, heat to 400°C in a muffle furnace at 5°C / min and keep warm for 2h; thus, a ternary rare earth co-modified bismuth vanadate material is obtained.

[0024] The ion impregnation method is implemented as follows: Weigh the bismuth vanadate from step 4 and place it in a beaker. Then, add lanthanum nitrate, cerium nitrate, and neodymium nitrate at a molar ratio of rare earth atoms to bismuth atoms of 0.01-0.05:1, ensuring a molar ratio of lanthanum:cerium:neodymium of 1:1:1. Allow to fully dissolve for 20 minutes. After drying, heat the mixture in a muffle furnace at 5°C / min to 400°C and maintain the temperature for 2 hours. This yields a ternary rare earth co-modified bismuth vanadate material.

[0025] Preferably, in step 1, the bismuth source and vanadium source are dissolved in 2 mol / L nitric acid and ultrapure water, respectively, and the ammonium metavanadate is dissolved in a water bath heated at 70-90°C. This method can significantly increase the dissolution rate of ammonium metavanadate and bismuth nitrate and reduce the experimental cycle.

[0026] Preferably, in step 2, the vanadium source solution is slowly dripped into the bismuth source solution while continuously stirring. This method allows for uniform formation of bismuth vanadate crystals and controls the reaction rate, resulting in a uniform morphology of the bismuth vanadate material during subsequent hydrothermal growth.

[0027] Preferably, in step 3, washing is performed by alternately rinsing with ethanol and deionized water and centrifuging. This method can remove unreacted materials to the greatest extent possible and ensure that the bismuth vanadate material is not affected by the unreacted materials.

[0028] Preferably, in step 4, when preparing the ternary rare earth co-modified bismuth vanadate using a calcination method, the bismuth vanadate, lanthanum oxide, cerium oxide, and neodymium oxide are placed in a mortar and ground thoroughly for 20 minutes, and finally pressed into tablets. This method can evenly mix the bismuth vanadate and rare earth oxide, partially break the chemical bonds between the rare earth oxide and the bismuth vanadate, and fully incorporate the rare earth element into the bismuth vanadate.

[0029] When using the ion impregnation method to prepare ternary rare earth co-modified bismuth vanadate, bismuth vanadate, lanthanum nitrate, cerium nitrate, and neodymium nitrate are added and dissolved, and then ultrasonicated for 20 minutes; this can more fully disperse the bismuth vanadate and allow the rare earth nitrate to be fully adsorbed on the surface of the bismuth vanadate, thereby more evenly doping the rare earth element into the bismuth vanadate.

[0030] The surface of the ternary rare earth co-modified bismuth vanadate material exhibits irregular short rods; this structure facilitates the rapid transfer of electrons between the rod-like structures to the surface to participate in the photocatalytic reaction; in addition, after the introduction of rare earth elements, the light absorption capacity of the ternary rare earth co-modified bismuth vanadate in the range of 500-800nm ​​is significantly enhanced, and the absorbance is significantly improved. The electron-hole recombination rate of the ternary rare earth co-modified bismuth vanadate is significantly reduced. These results all indicate that the rare earth elements have been successfully introduced, and the ternary co-modified bismuth vanadate thus achieves the excitation and migration of low-energy electrons. The impurity energy levels introduced by rare earth doping act as a transit station, allowing the low-energy electrons that jump here to further migrate to the energy band position of bismuth vanadate to participate in the photocatalytic reaction. At the same time, the impurity energy levels can also prevent electrons from falling back and recombination with holes. Therefore, the ternary co-modified bismuth vanadate has enhanced photocatalytic performance.

[0031] Ternary rare earth co-modified bismuth vanadate materials are used in water purification and photocatalytic hydrogen production. Compared to pure bismuth vanadate, their efficiency is approximately 45% higher, with over 90% degradation of dye wastewater. Furthermore, they can produce hydrogen from photocatalytic water splitting using methanol as a sacrificial agent. Their enhanced light absorption range and narrowed energy band make ternary co-modified bismuth vanadate suitable for a wider range of applications.

[0032] Beneficial effects of the present invention:

[0033] 1. The present invention significantly improves the photocatalytic performance and stability of bismuth vanadate through the synergistic doping of ternary rare earth elements, thereby significantly improving its degradation efficiency of organic pollutants under visible light irradiation.

[0034] 2. The ternary rare earth modified BiVO4 material obtained in the present invention has excellent light absorption performance in the visible light range and is suitable for the fields of photocatalysis and photoelectrochemistry.

[0035] 3. The ternary rare earth modified BiVO4 material obtained by the present invention has stable chemical properties and good photocatalytic performance, and has broad application prospects in the fields of environmental pollution control.

[0036] 4. The preparation method of the present invention is simple, easy to operate, does not require harsh conditions such as high temperature and high pressure, and is suitable for laboratory and industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the present invention.

[0038] Figure 2 This is the SEM image of the ternary rare earth co-modified bismuth vanadate material.

[0039] Figure 3 This is the extrapolated energy band spectrum of ternary rare earth co-modified bismuth vanadate material and BiVO4.

[0040] Figure 4This is the ultraviolet diffuse reflectance spectrum of ternary rare earth co-modified bismuth vanadate material and BiVO4.

[0041] Figure 5 This is the XPS graph of ternary rare earth co-modified bismuth vanadate material and BiVO4.

[0042] Figure 6 PL spectra of ternary rare earth co-modified bismuth vanadate material and BiVO4.

[0043] Figure 7 Photocatalytic degradation kinetic curves of ternary rare earth co-modified bismuth vanadate material and BiVO4.

[0044] Figure 8 This is the degradation curve of methylene blue by ternary rare earth co-modified bismuth vanadate material and BiVO4. DETAILED DESCRIPTION

[0045] The present invention will be described in further detail below with reference to the accompanying drawings.

[0046] In order to further understand the implementation method of the present invention, the specific embodiments of the present invention are further described in detail herein. It should also be noted that the following detailed descriptions are all examples, the purpose of which is to provide further explanation of the present invention. Unless otherwise specified, the technical and scientific terms used herein are the same as those generally understood by those skilled in the art to which the present invention belongs. It should be noted that the terms used here are only used to describe specific implementation methods, and are not intended to limit the implementation methods according to the examples of the present invention. The examples given below are only part of the present invention, not all. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention.

[0047] The present invention provides a method for preparing a ternary rare earth co-modified bismuth vanadate material, comprising the following steps:

[0048] Step 1, preparation of bismuth source solution and vanadium source solution:

[0049] Using Bi(NO3)3·5H2O as a bismuth source, dissolving bismuth nitrate in 2 mol / L nitric acid at a mass ratio of 1:(40-60), and stirring thoroughly until completely dissolved to obtain a bismuth source solution; using NH4VO3 as a vanadium source, adding NH4VO3 in an amount equal to that of Bi(NO3)3·5H2O at a mass ratio of 1:(80-100) to ultrapure water, heating to 70°C in a constant temperature water bath and continuously stirring until completely dissolved to obtain a vanadium source solution;

[0050] Step 2, precursor pretreatment:

[0051] Slowly drip the vanadium source solution prepared in step 1 into the bismuth source solution at room temperature while stirring continuously to form a suspension. Adjust the solution pH to 7 using ammonia and dilute nitric acid to prevent the formation of V2O5 in the BiVO4 precursor. This completes the precursor solution pretreatment process.

[0052] Step 3, preparation of bismuth vanadate material:

[0053] The suspension in step 2 is transferred to a hydrothermal reactor. The hydrothermal temperature affects the reaction rate, which in turn affects the oriented growth of the BiVO4 crystal plane and ultimately affects the morphology of the bismuth vanadate. The hydrothermal time affects the crystallinity of BiVO4. Therefore, the time and temperature are set at 180-220°C for 24 hours. The bismuth vanadate material is obtained after repeated washing, centrifugation and drying with anhydrous ethanol and deionized water.

[0054] Step 4, rare earth ion modified bismuth vanadate material:

[0055] The bismuth vanadate material washed in step 3 is introduced with rare earth elements by calcination or ion impregnation. The calcination method is as follows: weigh the bismuth vanadate from step 4 and place it in a mortar. Add lanthanum oxide, cerium oxide, and neodymium oxide at a molar ratio of rare earth atoms to bismuth atoms of (0.01-0.05):1. Ensure that the molar ratio of lanthanum:cerium:neodymium is 1:1:1. After thorough grinding for 20 minutes, press the tablets and heat them in a muffle furnace at 5°C / min to 400°C and maintain the temperature for 2 hours. This results in a ternary rare earth co-modified bismuth vanadate material.

[0056] The ion impregnation method is implemented as follows: Weigh the bismuth vanadate from step 4 into a beaker and add lanthanum nitrate, cerium nitrate, and neodymium nitrate, respectively, at a rare earth atom:bismuth atom molar ratio of 0.01-0.05:1. Ensure the molar ratio of lanthanum:cerium:neodymium is 1:1:1. Dissolve thoroughly for 20 minutes, then sonicate for 20 minutes. After drying, heat in a muffle furnace at 5°C / min to 400°C and maintain for 2 hours. This yields a ternary rare earth co-modified bismuth vanadate material.

[0057] The high efficiency photocatalyst prepared by the present invention can be seen from the following aspects:

[0058] (1) Preparation process of ternary rare earth co-modified bismuth vanadate materials

[0059] like Figure 1 As shown, the preparation process for ternary rare earth co-modified bismuth vanadate involves dissolving Bi(NO₃)₃·5H₂O in 2 mol / L dilute nitric acid to obtain a bismuth source solution. An equal amount of NH₄VO₃ to the Bi(NO₃)₃·5H₂O is then added to deionized water to obtain a vanadium source solution. The bismuth source solution is slowly dripped into the vanadium source solution, and the pH of the solution is adjusted to 7. Bismuth vanadate is obtained after a hydrothermal reaction. Subsequently, calcination or ion impregnation is used to obtain the ternary rare earth co-modified bismuth vanadate.

[0060] (2) Morphology analysis of ternary rare earth co-modified bismuth vanadate materials

[0061] like Figure 2 As shown, the ternary rare earth co-modified bismuth vanadate material appears as an irregular rod-shaped aggregate, which is conducive to increasing the light absorption area and realizing electron migration.

[0062] (3) Analysis of the extrapolated energy band spectrum of ternary rare earth co-modified bismuth vanadate materials

[0063] like Figure 3 As shown, the present invention uses multi-element rare earth doping to change the band structure of BiVO4. When multi-element doping with bismuth vanadate occurs, a synergistic effect exists between different rare earth elements. This synergistic effect can improve the conduction efficiency of photogenerated electrons and holes, thereby effectively inhibiting the recombination of photogenerated electrons and holes, and enabling them to participate in the photocatalytic reaction more effectively. Figure 3 The extrapolated energy band spectra of ternary rare earth modified bismuth vanadate material and BiVO4 are given. The results show that the band gap of BiVO4 is 2.4eV, while the band gap of ternary rare earth co-modified bismuth vanadate material is 2.2eV. The reduction of the band gap can reduce the energy absorbed during electron transition, increase the transition efficiency of photogenerated carriers, and thus improve the catalytic performance of the photocatalyst.

[0064] (4) Ultraviolet diffuse reflectance spectroscopy analysis of ternary rare earth co-modified bismuth vanadate materials

[0065] like Figure 4 As shown in the figure, the present invention provides the UV-visible diffuse reflectance spectra of modified and unmodified BiVO4. It can be seen that the doping of rare earth elements causes the absorption edge to gradually shift toward longer wavelengths (e.g., from 500nm to above 600nm), indicating a smaller band gap and enhanced visible light capture capability. The absorbance is increased due to more active sites or a stronger light scattering effect, that is, the ternary rare earth co-modified bismuth vanadate material successfully broadens the light response range of BiVO4, enhances the visible light absorption capacity, and significantly improves the photocatalytic performance of the BiVO4 material.

[0066] (5) XPS analysis of ternary rare earth co-modified bismuth vanadate material and BiVO4

[0067] like Figure 5 As shown, XPS was used to further analyze the chemical state and elemental composition of the prepared materials. Figure 5 (a) shows the Bi 4f XPS spectrum of BiVO4 and ternary rare earth co-modified bismuth vanadate material. It can be seen that there are two different peaks at 159.1eV and 164.4eV, which are attributed to Bi 4f respectively. 7 / 2 and Bi 4f 5 / 2 orbital, corresponding to Bi 3+Rare earth-doped BiVO4 shows two similar peaks, but they shift to higher binding energies at 159.5 eV and 164.8 eV. Figure 5 (b) shows the binding energies of 517.3 eV and 524.6 eV corresponding to V 2p 3 / 2 , V 2p 1 / 2 , which means V 5+ Compared with BiVO4, the V 2p of the modified material shifted to lower binding energies of 517.1eV and 524.4eV.

[0068] (6) Analysis of the electron-hole coincidence rate of ternary rare earth co-modified bismuth vanadate material and BiVO4

[0069] like Figure 6 As shown, the electron-hole recombination rate of the ternary co-modified bismuth vanadate is much lower than that of the comparative example BiVO4, which indicates that the impurity energy level formed by the ternary co-modified bismuth vanadate rare earth plays a full role, hindering the fall of electrons and realizing the separation of electrons and holes.

[0070] (7) Analysis of the photocatalytic degradation kinetics of ternary rare earth co-modified bismuth vanadate materials and BiVO4

[0071] like Figure 7 As shown in Figure 2, the degradation of methylene blue by ternary co-modified bismuth vanadate was completed within 120 min, while Figure 8 As shown, the change of In (initial concentration / instantaneous concentration) of the ternary rare earth co-modified bismuth vanadate material and BiVO4 with time is linear, indicating that the reaction conforms to the first-order reaction kinetics. The results show that the reaction rates of pure Example 123 and Comparative Example 123 are 0.04682, 0.02919, 0.02253, 0.00483, 0.00477, and 0.01035 min -1 The corresponding degradation rates are 99%, 98%, 96%, 81%, 45% and 44%. The ternary rare earth co-modified bismuth vanadate material prepared in Example 1 has the highest degradation rate of 99% and the largest reaction rate constant of 0.04682 min. -1 .

[0072] The following are several specific embodiments of the present invention

[0073] Example 1:

[0074] The present invention provides a method for preparing a ternary rare earth bismuth vanadate material by a calcination method, which comprises the following steps in sequence:

[0075] (1) Preparation of bismuth source solution and vanadium source solution: Weigh 0.5 g of bismuth nitrate and dissolve it in 20 g of 0.2 mol / L dilute nitric acid to obtain a bismuth source solution. Weigh 0.12 g of ammonium metavanadate (equimolar to bismuth nitrate) and dissolve it in 10 g of ultrapure water at 70°C to obtain a vanadium source solution.

[0076] (2) Precursor pretreatment: Slowly add the vanadium source solution to the bismuth source solution and stir to mix. Use ammonia water to adjust the pH of the precursor solution to 7.

[0077] (3) Preparation of bismuth vanadate material: The homogeneously mixed precursor solution from step 2 was transferred to a polytetrafluoroethylene-lined reactor and the reaction temperature was set at 180°C for 24 hours in an oven. The hydrothermal product was rinsed with anhydrous ethanol and deionized water, centrifuged (at a speed of 10,000 rad / min for 15 minutes), and dried at 60°C for 12 hours.

[0078] (4) Rare earth ion modified bismuth vanadate material: The bismuth vanadate material washed in step 3 is introduced with rare earth elements by calcination. The calcination method is as follows: weigh the bismuth vanadate in step 4 and place it in a mortar. Add lanthanum oxide at a molar ratio of lanthanum atom to bismuth atom of 0.01:1; add cerium oxide at a molar ratio of cerium atom to bismuth atom of 0.01:1; and add neodymium oxide at a molar ratio of neodymium atom to bismuth atom of 0.01:1. Ensure that the molar ratio of lanthanum: cerium: neodymium is 1:1:1. After fully grinding for 20 minutes, press the tablets, heat the tablets in a muffle furnace at 5°C / min to 400°C and keep them warm for 2 hours. The ternary rare earth co-modified bismuth vanadate material is obtained.

[0079] The degradation efficiency of methylene blue by the prepared ternary rare earth co-modified BiVO4 reached 99% (120min), which was about 45% higher than that of the unmodified material ( Figure 7 )

[0080] Example 2:

[0081] (1) Preparation of bismuth source solution and vanadium source solution: Weigh 0.5 g of bismuth nitrate and dissolve it in 25 g of 0.2 mol / L dilute nitric acid to obtain a bismuth source solution. Weigh 0.12 g of ammonium metavanadate (equimolar to bismuth nitrate) and dissolve it in 15 g of deionized water at 70°C to obtain a vanadium source solution.

[0082] (2) Precursor pretreatment: Slowly add the vanadium source solution to the bismuth source solution and stir to mix. Use ammonia water to adjust the pH of the precursor solution to 7.

[0083] (3) Preparation of bismuth vanadate material: The homogeneously mixed precursor solution from step 2 was transferred to a polytetrafluoroethylene-lined reactor. The reaction temperature was set at 200°C in an oven for 24 hours. The hydrothermal product was rinsed with anhydrous ethanol and deionized water, centrifuged (at a speed of 10,000 rad / min for 15 minutes), and dried at 60°C for 12 hours.

[0084] (4) Rare earth ion modified bismuth vanadate material: The bismuth vanadate material washed in step 3 is introduced with rare earth elements by calcination. The calcination method is as follows: weigh the bismuth vanadate in step 4 and place it in a mortar. Add lanthanum oxide at a molar ratio of lanthanum atom to bismuth atom of 0.03:1; add cerium oxide at a molar ratio of cerium atom to bismuth atom of 0.03:1; and add neodymium oxide at a molar ratio of neodymium atom to bismuth atom of 0.03:1. Ensure that the molar ratio of lanthanum: cerium: neodymium is 1:1:1. After fully grinding for 20 minutes, press the tablets, heat the tablets in a muffle furnace at 5°C / min to 400°C and keep them warm for 2 hours. The ternary rare earth co-modified bismuth vanadate material is obtained.

[0085] The degradation efficiency of methylene blue by the prepared ternary rare earth co-modified BiVO4 is 98%.

[0086] (120min), such as Figure 7 .

[0087] Example 3:

[0088] (1) Preparation of bismuth source solution and vanadium source solution: Weigh 0.5 g of bismuth nitrate and dissolve it in 30 g of 0.2 mol / L dilute nitric acid to obtain a bismuth source solution. Weigh 0.12 g of ammonium metavanadate (equimolar to bismuth nitrate) and dissolve it in 20 g of ultrapure water at 70°C to obtain a vanadium source solution.

[0089] (2) Precursor pretreatment: Slowly add the vanadium source solution to the bismuth source solution and stir to mix. Use ammonia water to adjust the pH of the precursor solution to 7.

[0090] (3) Preparation of bismuth vanadate material: The homogeneously mixed precursor solution from step 2 was transferred to a polytetrafluoroethylene-lined reactor and the reaction temperature was set at 220°C for 24 hours in an oven. The hydrothermal product was rinsed with anhydrous ethanol and deionized water, centrifuged (at a speed of 10,000 rad / min for 15 minutes), and dried at 60°C for 12 hours.

[0091] (4) Rare earth ion modified bismuth vanadate material: Weigh the bismuth vanadate prepared in step 4 and place it in a beaker. Add lanthanum nitrate at a molar ratio of 0.05:1 between lanthanum atoms and bismuth atoms; add cerium nitrate at a molar ratio of 0.05:1 between cerium atoms and bismuth atoms; and add neodymium nitrate at a molar ratio of 0.05:1 between neodymium atoms and bismuth atoms. Ensure that the molar ratio of lanthanum:cerium:neodymium is 1:1:1. Dissolve the mixture in 2 mol / L nitric acid for 20 minutes, ultrasonicate it for 20 minutes, dry it, and heat it in a muffle furnace at 5°C / min to 400°C and keep it warm for 2 hours. This will yield a ternary rare earth co-modified bismuth vanadate material.

[0092] The degradation efficiency of methylene blue by the prepared ternary rare earth co-modified BiVO4 is 90%.

[0093] (120min), such as Figure 7 .

[0094] Comparative Example 1

[0095] The method in Example 1 is used, and no rare earth element is introduced after the bismuth vanadate material is prepared. The specific operation steps are as follows:

[0096] (1) Preparation of bismuth source solution and vanadium source solution: Weigh 0.5 g of bismuth nitrate and dissolve it in 20 g of 0.2 mol / L dilute nitric acid to obtain a bismuth source solution. Weigh 0.12 g of ammonium metavanadate (equimolar to bismuth nitrate) and dissolve it in 10 g of ultrapure water at 70°C to obtain a vanadium source solution.

[0097] (2) Precursor pretreatment: Slowly add the vanadium source solution to the bismuth source solution and stir to mix. Use ammonia water to adjust the pH of the precursor solution to 7.

[0098] (3) Preparation of bismuth vanadate material: The homogeneously mixed precursor solution from step 2 was transferred to a polytetrafluoroethylene-lined reactor. The reaction temperature was set at 180°C in an oven for 24 hours. The hydrothermal product was rinsed with anhydrous ethanol and deionized water, centrifuged (at a speed of 10,000 rad / min for 15 minutes), and dried at 60°C for 12 hours.

[0099] (4) Calcination of bismuth vanadate material without introducing rare earth ions: Weigh the bismuth vanadate obtained in step 4 and place it in a mortar. Grind it thoroughly for 20 minutes, then press it into tablets. Heat the mixture in a muffle furnace at a rate of 5°C / min to 400°C and maintain the temperature for 2 hours. This yields the bismuth vanadate material.

[0100] The performance of the prepared rare earth-free BiVO4 material is significantly reduced compared with that of Example 1. After 120 minutes of illumination, the pollutant degradation is about 25%, and the photocatalytic activity is low. Figure 7 .

[0101] Comparative Example 2

[0102] (1) Preparation of bismuth source solution and vanadium source solution: Weigh 0.5 g of bismuth nitrate and dissolve it in 25 g of 0.2 mol / L dilute nitric acid to obtain a bismuth source solution. Weigh 0.12 g of ammonium metavanadate (equimolar to bismuth nitrate) and dissolve it in 15 g of ultrapure water at 70°C to obtain a vanadium source solution.

[0103] (2) Precursor pretreatment: Slowly add the vanadium source solution to the bismuth source solution and stir to mix. Use ammonia water to adjust the pH of the precursor solution to 7.

[0104] (3) Preparation of bismuth vanadate material: The homogeneously mixed precursor solution from step 2 was transferred to a polytetrafluoroethylene-lined reactor. The reaction temperature was set at 200°C in an oven for 24 hours. The hydrothermal product was rinsed with anhydrous ethanol, centrifuged (at a speed of 10,000 rad / min for 15 minutes), and dried at 60°C for 12 hours.

[0105] (4) Calcination of bismuth vanadate material without introducing rare earth ions: Weigh the bismuth vanadate obtained in step 4 and place it in a mortar. Grind it thoroughly for 20 minutes, then press it into tablets. Heat the mixture in a muffle furnace at a rate of 5°C / min to 400°C and maintain the temperature for 2 hours. This yields the bismuth vanadate material.

[0106] The performance of the prepared rare earth-free BiVO4 material is significantly reduced compared with Example 2. After 1 hour of illumination, the pollutant degradation is about 25%, which is basically the same as the performance of Comparative Example 1, and the photocatalytic activity is low. Figure 7 .

[0107] Comparative Example 3

[0108] (1) Preparation of bismuth source solution and vanadium source solution: Weigh 0.5 g of bismuth nitrate and dissolve it in 30 g of 0.2 mol / L dilute nitric acid to obtain a bismuth source solution. Weigh 0.12 g of ammonium metavanadate (equimolar to bismuth nitrate) and dissolve it in 20 g of ultrapure water at 70°C to obtain a vanadium source solution.

[0109] (2) Precursor pretreatment: Slowly add the vanadium source solution to the bismuth source solution and stir to mix. Use ammonia water to adjust the pH of the precursor solution to 7.

[0110] (3) Preparation of bismuth vanadate material: The homogeneously mixed precursor solution from step 2 was transferred to a polytetrafluoroethylene-lined reactor. The reaction temperature was set at 220°C in an oven for 24 hours. The hydrothermal product was rinsed with anhydrous ethanol and deionized water, centrifuged (at a speed of 10,000 rad / min for 15 minutes), and dried at 60°C for 12 hours.

[0111] (4) Modification of bismuth vanadate material without rare earth ion introduction: Weigh the bismuth vanadate prepared in step 4 and place it in a beaker. Stir the mixture in 2 mol / L nitric acid for 20 min and ultrasonicate for 20 min. After drying, heat the mixture in a muffle furnace at a rate of 5°C / min to 400°C and maintain the temperature for 2 h. This yields the bismuth vanadate material.

[0112] The performance of the prepared material is improved compared with that of comparative examples 1 and 2. The degradation rate of pollutants after 60 minutes of illumination is 60%. Figure 7 .

[0113] Table 1 Photocatalyst pollutant removal performance

[0114]

[0115] The above description is only for illustrative purposes. It is understood that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A method for preparing a ternary rare earth co-modified bismuth vanadate material, characterized in that: The following steps are included: Step 1: dissolving bismuth nitrate in nitric acid to obtain a bismuth source solution; adding NH4VO3 in an amount equal to that of Bi(NO3)3·5H2O to ionized water and completely dissolving the NH4VO3 to obtain a vanadium source solution; Step 2: adding the vanadium source solution prepared in step 1 to the bismuth source solution at room temperature while continuously stirring to form a suspension; adjusting the pH to 7-8; Step 3, transferring the suspension in step 2 to a hydrothermal reactor for reaction, centrifuging, washing the precipitate, and drying to obtain a bismuth vanadate material; Step 4: introducing rare earth elements into the bismuth vanadate material washed in step 3 by calcination or ion impregnation to obtain a ternary rare earth co-modified bismuth vanadate material.

2. The method for preparing a ternary rare earth co-modified bismuth vanadate material according to claim 1, wherein: The step 1 is specifically as follows: Bismuth nitrate is dissolved in nitric acid at a mass ratio of 1: (40-60) to obtain a bismuth source solution; NH4VO3 is used as a vanadium source, and an equal molar amount of NH4VO3 to Bi(NO3)3·5H2O is added into ionized water at a mass ratio of 1: (80-100) and completely dissolved to obtain a vanadium source solution.

3. The method for preparing a ternary rare earth co-modified bismuth vanadate material according to claim 2, characterized in that: In the step 1, the bismuth source and the vanadium source are dissolved in 2 mol / L nitric acid and ultrapure water respectively, and the ammonium metavanadate is heated in a water bath at 70-90° C. when being dissolved.

4. The method for preparing a ternary rare earth co-modified bismuth vanadate material according to claim 1, wherein: The step 2 is specifically as follows: The vanadium source solution prepared in step 1 is added to the bismuth source solution at room temperature while continuously stirring to form a suspension.

5. The method for preparing a ternary rare earth co-modified bismuth vanadate material according to claim 1, characterized in that: The step 3 is specifically as follows: The time and temperature in the hydrothermal reactor were set at 180-220° C. for 24 hours, and the bismuth vanadate material was obtained after drying; The tubes were rinsed alternately with ethanol and deionized water and centrifuged.

6. The method for preparing a ternary rare earth co-modified bismuth vanadate material according to claim 1, characterized in that: The step 4 is specifically as follows: The calcination method is as follows: weigh the bismuth vanadate in step 4 and place it in a crucible, and add lanthanum oxide, cerium oxide, and neodymium oxide at a molar ratio of rare earth atoms to bismuth atoms of (0.01 to 0.05):1; and ensure that the molar ratio of lanthanum: cerium: neodymium is 1:1:1; after thorough mixing, heat to 400°C in a muffle furnace at 5°C / min and keep warm for 2h; thus, a ternary rare earth co-modified bismuth vanadate material is obtained.

7. The method for preparing a ternary rare earth co-modified bismuth vanadate material according to claim 1, characterized in that: The ion impregnation method is implemented as follows: weigh the bismuth vanadate prepared in step 4 and place it in a beaker, and add lanthanum nitrate, cerium nitrate, and neodymium nitrate at a molar ratio of rare earth atoms to bismuth atoms of (0.01 to 0.05):1; And ensure that the molar ratio of lanthanum:cerium:neodymium is 1:1:1; fully dissolve for 20 minutes, dry, and then heat to 400°C in a muffle furnace at 5°C / min and keep warm for 2 hours; thus, a ternary rare earth co-modified bismuth vanadate material is obtained.

8. The method for preparing a ternary rare earth co-modified bismuth vanadate material according to claim 1, characterized in that: In step 4, when preparing the ternary rare earth co-modified bismuth vanadate by a calcination method, bismuth vanadate, lanthanum oxide, cerium oxide, and neodymium oxide are placed in a mortar and ground for 20 minutes, and finally pressed into tablets; When the ternary rare earth co-modified bismuth vanadate is prepared by the ion impregnation method, bismuth vanadate, lanthanum nitrate, cerium nitrate and neodymium nitrate are added and dissolved, and then ultrasonicated for 20 minutes.

9. The ternary rare earth co-modified bismuth vanadate material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The surface of the ternary rare earth co-modified bismuth vanadate material exhibits irregular short rods. The short rod-like structure facilitates the rapid transfer of electrons between the rods to the surface to participate in the photocatalytic reaction. After the introduction of rare earth elements, the light absorption capacity of the ternary rare earth co-modified bismuth vanadate in the range of 500-800nm ​​is significantly enhanced, the absorbance is significantly improved, and the electron-hole recombination rate of the ternary rare earth co-modified bismuth vanadate is significantly reduced. Ternary co-modified bismuth vanadate realizes the excitation and migration of low-energy electrons. The impurity energy levels introduced by rare earth doping act as a transit station, allowing the low-energy electrons that jump here to further migrate to the energy band position of bismuth vanadate to participate in the photocatalytic reaction. At the same time, the impurity energy levels can also prevent electrons from falling back and recombining with holes. The ternary co-modified bismuth vanadate has enhanced photocatalytic performance.

10. Application of the ternary rare earth co-modified bismuth vanadate material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: Ternary rare earth co-modified bismuth vanadate materials are used in water purification and photolysis of water to produce hydrogen.

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