High-performance bismuth vanadate pigment coated with multi-metal oxide in situ and preparation method of high-performance bismuth vanadate pigment

Abstract

The invention relates to the technical field of inorganic pigment preparation, in particular to a high-performance bismuth vanadate pigment coated with multi-metal oxide in situ and a preparation method of the high-performance bismuth vanadate pigment. The preparation method comprises the following steps: preparing a precursor: respectively preparing a bismuth-containing solution A and a vanadium-containing solution B with the concentration of 0.1-2.0 mol / L; preparing a coating agent solution, namely preparing the coating agent solution with the total concentration of 0.5-2.0 mol / L; in-situ deposition coating: mixing and reacting the bismuth-containing solution A and the vanadium-containing solution B to obtain a mixed solution C, adding the coating agent solution, controlling the total metal ion content of the coating solution to be 5-20% of the total content of vanadium and bismuth, adjusting the pH value to be 5-8, and reacting to obtain a bismuth vanadate precursor; and post-processing. The metal oxide layer is coated in situ in the BiVO4 preparation process, the composition and the structure of the coating layer are accurately regulated and controlled, and the acid and alkali resistance, the weather resistance and the like of the pigment are remarkably improved while the excellent color performance of the pigment is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of inorganic pigment preparation technology, and is particularly applicable to fields such as architectural coatings and automotive coatings that require high color stability and durability. Specifically, it relates to a high-performance bismuth vanadate pigment with in-situ coating of multi-metal oxides and its preparation method. Background Technology

[0002] Bismuth vanadate (BiVO4), a novel environmentally friendly yellow inorganic pigment, is gradually replacing traditional heavy metal pigments such as lead chromate yellow and cadmium yellow due to its excellent color, high hiding power, good weather resistance, and low toxicity. It is widely used in architectural coatings, automotive coatings, and ceramic glazes. However, different applications have stringent requirements for its properties beyond color, such as acid and alkali resistance and weather resistance, limiting its application in high-end coatings and harsh environments. For example, architectural exterior wall coatings need to withstand acid rain erosion and long-term ultraviolet radiation, requiring a color difference ΔE ≤ 2.0 after immersion in 2% hydrochloric acid and sodium hydroxide solution for 24 hours and ΔE ≤ 3.0 after 500 hours of QUV aging. Automotive original equipment paints need to withstand high-temperature baking (150~200℃) and extreme climate cycling, with a color stability requirement of ΔE ≤ 1.5. Pure monoclinic bismuth vanadate cannot meet these requirements and must be surface-modified to improve its overall performance; otherwise, fading and chalking will shorten product lifespan and increase maintenance costs.

[0003] Currently, in domestic and international research on the coating of bismuth vanadate, oxides (such as Al2O3, ZrO2, and SiO2) have become the mainstream choice due to their high chemical stability and good compatibility with pigments. For example, Chinese patent CN116023801B discloses a coating method for bismuth vanadate pigment powder. The coating method includes the following steps: preparing a bismuth vanadate slurry using anhydrous ethanol and coating the bismuth vanadate slurry onto a flat plate receiver of an electrospinning machine; preparing a coating agent sol; injecting the coating agent sol into the electrospinning machine; repeatedly electrospinning on the flat plate receiver coated with the bismuth vanadate slurry; and peeling off the electrospun material and calcining it to obtain coated bismuth vanadate powder. It can be seen that the existing coating method is mainly a post-processing step, requiring the preparation of bismuth vanadate particles before coating, which has obvious defects: the coating layer is only physically adsorbed to the substrate, and it is easy to fall off under mechanical stirring or high temperature environment, resulting in limited improvement in weather resistance; moreover, particle agglomeration easily causes uneven coating, leading to a decrease in color performance.

[0004] Therefore, there is an urgent need to develop bismuth vanadate pigment powder coating technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, a method for preparing and applying liquid-phase in-situ coated modified bismuth vanadate pigments is provided. By in-situ coating a metal oxide layer during the preparation of BiVO4, the composition and structure of the coating layer are precisely controlled, thereby significantly improving the pigment's acid and alkali resistance, weather resistance, and other properties while ensuring its excellent color performance.

[0006] To solve at least one of the above-mentioned technical problems, the present invention adopts the following technical solution: According to one aspect of the present invention, a method for preparing a high-performance bismuth vanadate pigment with in-situ coating of multi-metal oxides is provided, comprising the following steps: precursor preparation: preparing bismuth-containing solution A and vanadium-containing solution B with concentrations of 0.1~2.0 mol / L, wherein the concentrations of bismuth-containing solution A and vanadium-containing solution B are the same; coating agent solution preparation: preparing a coating agent solution with a total concentration of 0.5~2.0 mol / L; in-situ deposition coating: reacting the bismuth-containing solution A and the vanadium-containing solution B at room temperature. The mixture is reacted for 30-90 minutes to obtain a mixed solution C. The coating agent solution is added to the mixed solution C, and the total metal ion content of the coating solution is controlled to be 5%-20% of the total vanadium and bismuth content. The pH value is adjusted to 5-8. After reacting for 30-90 minutes, the mixture is filtered, washed, and dried to obtain a bismuth vanadate precursor. Post-treatment: The bismuth vanadate precursor is calcined in air at 250-500°C for 1-6 hours and then cooled to room temperature in the furnace to obtain a surface-coated and modified environmentally friendly bismuth vanadate pigment.

[0007] According to one embodiment of the present invention, in the precursor preparation step, the bismuth-containing solution A is prepared by dissolving bismuth nitrate or bismuth oxide in nitric acid; the vanadium-containing solution B is prepared by dissolving ammonium metavanadate, vanadium pentoxide or sodium metavanadate in NaOH solution, wherein the acid and base concentrations are the same.

[0008] According to one embodiment of the present invention, the coating agent solution is a single-element coating agent solution or a multi-element coating agent solution. The single-element coating agent solution is prepared by dissolving any one of Al salt, Zr salt, Zn salt, Sn salt, La salt, and Ce salt in deionized water; the multi-element coating agent solution is prepared by dissolving two or more of Al salt, Zr salt, Zn salt, Sn salt, La salt, and Ce salt in deionized water.

[0009] According to one embodiment of the present invention, the Al salt is aluminum nitrate or aluminum chloride, the Zr salt is zirconium nitrate or zirconium oxychloride, the Zn salt is zinc nitrate or zinc sulfate, the Sn salt is tin tetrachloride or tin sulfate, the La salt is lanthanum nitrate or lanthanum chloride, and the Ce salt is cerium nitrate or cerium chloride.

[0010] According to one embodiment of the present invention, in the in-situ deposition coating step, if a multi-layer coating modified bismuth vanadate pigment is to be prepared, multiple single-element coating agent solutions are added sequentially to the mixture C, and the reaction is stirred for 10 to 30 minutes after each single-element coating agent solution is added.

[0011] According to one embodiment of the present invention, in the in-situ deposition coating step, filtration is carried out using Buchner funnel filtration, sand core funnel suction filtration, or plate and frame pressure filtration; washing is carried out using deionized water and anhydrous ethanol alternately, each for 2 to 4 times; drying is carried out using a vacuum drying oven, a forced-air drying oven, or a microwave dryer, with a drying temperature of 60 to 100°C and a drying time of 0.5 to 24 hours.

[0012] According to one embodiment of the present invention, in the in-situ deposition coating step, the pH value is adjusted by adding sodium hydroxide solution or nitric acid solution.

[0013] According to one embodiment of the present invention, in the post-processing step, calcination is carried out using a muffle furnace, tube furnace, pusher kiln or rotary kiln.

[0014] According to one embodiment of the present invention, the mass ratio and distribution of each metal oxide in the coating layer are controlled by the amount and addition order of each metal salt in the coating agent solution.

[0015] According to one aspect of the present invention, a high-performance bismuth vanadate pigment with in-situ coating of multi-metal oxides is provided, which is prepared using the method described in any of the above embodiments, wherein the pigment surface has a coating layer with a thickness of 5-20 nm.

[0016] By adopting the above technical solution, the present invention has at least one of the following advantages compared with the prior art: (1) Excellent color performance: By precisely controlling the coating process, the pigment’s acid and alkali resistance and weather resistance are improved while maintaining the original excellent color of BiVO4, with no obvious color deviation, and the pigment’s hiding power is significantly improved. (2) Strong weather resistance and corrosion resistance: The dense metal oxide coating effectively blocks ultraviolet rays and acid and alkali media, greatly improving the weather resistance and acid and alkali resistance of pigments, and solving the problem of easy fading and powdering of pure bismuth vanadate; (3) Significant coating effect: In-situ coating technology enables the coating layer to form a strong chemical bond with the BiVO4 matrix. The bonding strength is much higher than that of traditional post-treatment coating methods. The coating layer is more uniform and more stable, and can effectively protect the matrix particles for a long time. (4) Good process controllability: Single-element, multi-element mixture or multi-layer coating methods can be flexibly selected. The composition, thickness and distribution of the coating layer can be precisely controlled by adjusting the coating agent parameters to meet the requirements of pigment performance in different application scenarios. (5) The process is simple and easy to control. The preparation is mainly based on in-situ deposition at room temperature. The key parameter range is reasonable and easy to control. There are no complicated operations and conventional equipment can be used to complete the process. (6) It has good industrial adaptability. The raw materials used for coating are all common industrial chemicals with low prices. The equipment used for filtration, calcination and other processes are all conventional equipment in the industry. No customization is required. It is easy to achieve continuous and large-scale production. Moreover, the technology can be extended to the surface modification of other inorganic pigments. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to the present invention; Figure 2 The X-ray diffraction (XRD) patterns of Examples 1, 3, the blank example, and the comparative example in this invention are shown below. Figure 3 These are scanning electron microscope (SEM) images of the morphology of Example 1 in this invention. Figure 4 This is a transmission electron microscope (TEM) image of the morphology of Example 2 in this invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0020] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0021] Compared to existing processing techniques, in-situ coating simultaneously forms a coating layer during pigment formation, achieving interfacial fusion through chemical bonding. This significantly improves coating uniformity and the bonding strength between the coating and bismuth vanadate; it also reduces processing steps and significantly lowers industrial costs. However, there are few reports on in-situ coating of various metal oxides during BiVO4 preparation, and a systematic study on the relationship between coating composition and pigment color properties, weather resistance, etc., is lacking.

[0022] The main objective of this invention is to provide a method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides. This method employs a liquid-phase in-situ coating technique, allowing metal ions in the coating agent to simultaneously precipitate and adhere to the surface of the bismuth vanadate particles during the curing stage of the bismuth vanadate precursor, forming tight chemical bonds. During subsequent high-temperature calcination, these ions transform into a dense metal oxide coating layer, achieving the simultaneous formation of single-element, multi-element mixed, or multi-layer oxide coating layers with Al, Zr, Zn, Sn, La, and Ce groups during the bismuth vanadate preparation process. By controlling the pH, coating agent ratio, and reaction conditions, this technology can achieve single-element, multi-element mixed, and multi-layer coating layers while maintaining the excellent color performance of the pigment. It significantly improves acid and alkali resistance and weather resistance, solving the problem of balancing performance improvement and color retention faced by traditional processes. This provides technical support for the application of bismuth vanadate in high-end fields.

[0023] According to one aspect of the present invention, such as Figure 1 As shown, the general embodiments of the preparation method of high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides include the following steps: S100, precursor preparation: prepare bismuth-containing solution A and vanadium-containing solution B with concentrations of 0.1~2.0 mol / L, respectively. The concentrations of bismuth-containing solution A and vanadium-containing solution B are the same. S200, preparation of coating agent solution, prepare a coating agent solution with a total concentration of 0.5~2.0mol / L; S300, in-situ deposition coating, bismuth-containing solution A and vanadium-containing solution B are mixed and reacted at room temperature for 30-90 minutes to obtain mixture C. Coating agent solution is added to mixture C, and the total metal ion content of the coating solution is controlled to be 5%-20% of the total vanadium and bismuth content. The pH value is adjusted to 5-8, and after reacting for 30-90 minutes, it is filtered, washed, and dried to obtain bismuth vanadate precursor. S400, post-treatment: The bismuth vanadate precursor is calcined in air at 250~500℃ for 1~6 hours, and then cooled to room temperature in the furnace to obtain a surface-modified environmentally friendly bismuth vanadate pigment.

[0024] In step S100, bismuth-containing solution A is prepared by dissolving bismuth nitrate or bismuth oxide in nitric acid; vanadium-containing solution B is prepared by dissolving ammonium metavanadate, vanadium pentoxide, or sodium metavanadate in NaOH solution, with the same acid and alkali concentrations. The mass ratio and distribution of each metal oxide in the coating layer are controlled by the amount and order of addition of each metal salt in the coating agent solution.

[0025] In step S200, the coating agent solution is either a single-element coating agent solution or a multi-element coating agent solution. The single-element coating agent solution is prepared by dissolving any one of Al, Zr, Zn, Sn, La, and Ce salts in deionized water; the multi-element coating agent solution is prepared by dissolving two or more of Al, Zr, Zn, Sn, La, and Ce salts in deionized water. In the embodiments of this invention, a single-element coating agent solution is used to prepare the multi-layer coating, and the layers are added sequentially according to time sequence to achieve layer-by-layer coating. In addition, 1-6 mol / L sodium hydroxide solution and nitric acid solution are prepared separately for subsequent pH adjustment. Preferably, the Al salt is aluminum nitrate or aluminum chloride, the Zr salt is zirconium nitrate or zirconium oxychloride, the Zn salt is zinc nitrate or zinc sulfate, the Sn salt is tin tetrachloride or tin sulfate, the La salt is lanthanum nitrate or lanthanum chloride, and the Ce salt is cerium nitrate or cerium chloride.

[0026] In step S300, while bismuth-containing solution A and vanadium-containing solution B react at room temperature to generate bismuth vanadate, a coating agent solution is simultaneously added and deposited, allowing the coating layer to form a growth-type bond with the bismuth vanadate matrix. Compared to traditional post-coating processes, this results in stronger bonding and more uniform coating. Specifically, if preparing a multi-layer coated bismuth vanadate pigment, multiple single-element coating agent solutions are added sequentially to the mixture C, with each solution stirred for 10-30 minutes after addition. In embodiments of this invention, filtration is performed using a Buchner funnel, sand core funnel, or plate and frame filter press; washing is performed alternately with deionized water and anhydrous ethanol, 2-4 times each; drying is performed using a vacuum drying oven, forced-air drying oven, or microwave dryer at a temperature of 60-100°C for 0.5-24 hours. Further, the pH value can be adjusted by adding sodium hydroxide solution or nitric acid solution. Preferably, changing the single-element coating agent solution to a multi-element coating agent solution yields a multi-element mixed coated bismuth vanadate precursor. Similarly, multiple single-element coating agent solutions are slowly added dropwise to the mixture C in sequence. After each single-element coating agent solution is added, the mixture is stirred and reacted for 10 to 30 minutes. Finally, a multi-layer coated bismuth vanadate precursor can be obtained.

[0027] In step S400, calcination is carried out using a muffle furnace, tube furnace, pusher kiln or rotary kiln. Different equipment is used in the examples to verify the applicability of the process.

[0028] According to another aspect of the present invention, the present invention also provides a high-performance bismuth vanadate pigment with in-situ coating of multi-metal oxides prepared by the above method. In an embodiment of the present invention, the pigment surface has a coating layer with a thickness of 5-20 nm, the specific thickness of which can be controlled by the concentration and amount of the coating agent solution.

[0029] The following are specific embodiments of the preparation method of high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to the present invention.

[0030] Example 1: Al2O3 single-element coating of BiVO4 pigment, with a coating thickness of ~10 nm. S100, prepare a bismuth precursor solution by dissolving Bi(NO3)3·5H2O in nitric acid, stirring until homogeneous, and cooling to room temperature to obtain a 1.0 mol / L bismuth-containing solution A (50 mL), with a nitric acid concentration of 3.0 mol / L; dissolve NH4VO3 in NaOH, stir until homogeneous, and cool to room temperature to obtain a 1.0 mol / L vanadium-containing solution B (50 mL), with a NaOH concentration of 3.0 mol / L. S200, coating agent solution preparation: Dissolve Al(NO3)3·9H2O in deionized water, stir well, and obtain 10 mL of 0.8 mol / L aluminum nitrate solution, so that the molar content of Al ions is 8% of the total vanadium-bismuth content; S300, in-situ deposition coating: The bismuth-containing solution A and vanadium-containing solution B prepared in step S100 are mixed evenly at room temperature, stirred and reacted for 60 minutes; under vigorous stirring, aluminum nitrate solution is slowly added dropwise to adjust the pH value to 6.0; then stirring and reacting is continued for 60 minutes; the resulting liquid mixture is then filtered through a Buchner funnel, washed three times alternately with deionized water and anhydrous ethanol, and dried in a forced-air drying oven at 60°C for 24 hours to obtain the precursor.

[0031] S400, post-processing: The precursor is placed in a muffle furnace and calcined at 400°C for 2 hours in air atmosphere, and then cooled to room temperature with the furnace to obtain an Al2O3-coated BiVO4 pigment with a coating thickness of ~10 nm.

[0032] Example 2: ZnO single-element coating of BiVO4 pigment, with a coating thickness of ~5nm S100, prepare a bismuth precursor solution by dissolving Bi(NO3)3·5H2O in nitric acid, stirring until homogeneous, and cooling to room temperature to obtain a 1.0 mol / L bismuth-containing solution A (50 mL), with a nitric acid concentration of 3.0 mol / L; dissolve NH4VO3 in NaOH, stir until homogeneous, and cool to room temperature to obtain a 1.0 mol / L vanadium-containing solution B (50 mL), with a NaOH concentration of 3.0 mol / L. S200, coating agent solution preparation: Dissolve ZnSO4·7H2O in deionized water, stir well, and obtain 10 mL of 0.5 mol / L zinc sulfate solution, so that the molar content of Zn ions is 5% of the total vanadium-bismuth content; S300, in-situ deposition coating: The bismuth-containing solution A and vanadium-containing solution B prepared in step S100 are mixed evenly at room temperature, stirred and reacted for 30 minutes; under vigorous stirring, zinc sulfate solution is slowly added dropwise to adjust the pH value to 5.0; then stirring and reacting is continued for 30 minutes; the resulting liquid mixture is then filtered using a sintered glass funnel, washed twice alternately with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 70°C for 12 hours to obtain the precursor.

[0033] S400, post-processing: The precursor is placed in a tube furnace and calcined at 350°C for 4 hours in an air atmosphere, and then cooled to room temperature with the furnace to obtain a ZnO-coated BiVO4 pigment with a coating thickness of ~5nm.

[0034] Example 3: La2O3 single-element coating of BiVO4 pigment, with a coating thickness of ~20nm S100, prepare a bismuth precursor solution by dissolving Bi(NO3)3·5H2O in nitric acid, stirring until homogeneous, and cooling to room temperature to obtain a 1.0 mol / L bismuth-containing solution A (50 mL), with a nitric acid concentration of 3.0 mol / L; dissolve NH4VO3 in NaOH, stir until homogeneous, and cool to room temperature to obtain a 1.0 mol / L vanadium-containing solution B (50 mL), with a NaOH concentration of 3.0 mol / L. S200, coating agent solution preparation: Dissolve La(NO3)3·6H2O in deionized water and stir until homogeneous to obtain 10 mL of 2.0 mol / L lanthanum nitrate solution, so that the molar content of La ions is 20% of the total vanadium-bismuth content; S300, in-situ deposition coating: The bismuth-containing solution A and vanadium-containing solution B prepared in step S100 are mixed evenly at room temperature, stirred and reacted for 60 minutes; under vigorous stirring, lanthanum nitrate solution is slowly added dropwise to adjust the pH value to 8.0; then stirring and reacting is continued for 90 minutes; the resulting liquid mixture is then filtered through a Buchner funnel, washed four times alternately with deionized water and anhydrous ethanol, and dried at 90°C for 0.5 hours using a microwave dryer to obtain the precursor.

[0035] S400, post-processing: The precursor is placed in a rotary kiln and calcined at 500°C for 1 hour in air atmosphere, and then cooled to room temperature with the furnace to obtain a La2O3-coated BiVO4 pigment with a coating thickness of ~20nm.

[0036] Example 4: Al2O3 / ZrO2 binary mixed coating layer of BiVO4 pigment, coating layer thickness ~12nm S100, prepare a bismuth precursor solution by dissolving Bi(NO3)3·5H2O in nitric acid, stirring until homogeneous, and cooling to room temperature to obtain a 1.0 mol / L bismuth-containing solution A (50 mL), with a nitric acid concentration of 3.0 mol / L; dissolve NH4VO3 in NaOH, stir until homogeneous, and cool to room temperature to obtain a 1.0 mol / L vanadium-containing solution B (50 mL), with a NaOH concentration of 3.0 mol / L. S200, coating agent solution preparation: Dissolve ZrOCl2·8H2O and Al(NO3)3·9H2O (molar ratio of 1:3) in deionized water, stir evenly to obtain 12 mL of mixed coating agent solution with a total metal ion concentration of 1.0 mol / L, so that the total molar content of Al / Zr is 12% of the total vanadium-bismuth content; S300, in-situ deposition coating: The bismuth-containing solution A and vanadium-containing solution B prepared in step S100 are mixed evenly at room temperature, stirred and reacted for 60 minutes; under vigorous stirring, the mixed coating agent solution is slowly added dropwise to adjust the pH value to 6.0; then stirring and reacting is continued for 60 minutes; the resulting liquid mixture is then filtered by plate and frame filter press, washed three times alternately with deionized water and anhydrous ethanol, and dried in a forced-air drying oven at 80°C for 6 hours to obtain the precursor.

[0037] S400, post-processing: The precursor is placed in a tube furnace and calcined at 450°C for 2 hours in an air atmosphere, and then cooled to room temperature with the furnace to obtain an Al2O3 / ZrO2 binary mixed coating layer BiVO4 pigment with a coating layer thickness of ~12nm.

[0038] Example 5: A La2O3 / CeO2 binary mixed coating layer of BiVO4 pigment, with a coating thickness of ~15nm. S100, prepare a bismuth precursor solution by dissolving Bi(NO3)3·5H2O in nitric acid, stirring until homogeneous, and cooling to room temperature to obtain a 1.0 mol / L bismuth-containing solution A (50 mL), with a nitric acid concentration of 3.0 mol / L; dissolve NH4VO3 in NaOH, stir until homogeneous, and cool to room temperature to obtain a 1.0 mol / L vanadium-containing solution B (50 mL), with a NaOH concentration of 3.0 mol / L. S200, coating agent solution preparation: Dissolve La(NO3)3·6H2O and Ce(NO3)3·6H2O (molar ratio of 1:1) in deionized water, stir evenly, and obtain 10 mL of mixed coating agent solution with a total metal ion concentration of 1.5 mol / L, so that the total molar content of La / Ce is 15% of the total vanadium-bismuth content; S300, in-situ deposition coating: The bismuth-containing solution A and vanadium-containing solution B prepared in step S100 are mixed evenly at room temperature, stirred and reacted for 75 minutes; under vigorous stirring, the mixed coating agent solution is slowly added dropwise to adjust the pH value to 7.5; then stirring and reacting is continued for 50 minutes; the resulting liquid mixture is then filtered by plate and frame filter press, washed three times alternately with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 85°C for 3 hours to obtain the precursor.

[0039] S400, post-processing: The precursor is placed in a muffle furnace and calcined at 450°C for 2 hours in air atmosphere, and then cooled to room temperature with the furnace to obtain a La2O3 / CeO2 binary mixed coating layer BiVO4 pigment with a coating layer thickness of ~15nm.

[0040] Example 6: BiVO4 pigment with Al2O3 / ZrO2 bilayer coating, coating thickness ~18nm S100, prepare a bismuth precursor solution by dissolving Bi(NO3)3·5H2O in nitric acid, stirring until homogeneous, and cooling to room temperature to obtain a 1.0 mol / L bismuth-containing solution A (50 mL), with a nitric acid concentration of 3.0 mol / L; dissolve NH4VO3 in NaOH, stir until homogeneous, and cool to room temperature to obtain a 1.0 mol / L vanadium-containing solution B (50 mL), with a NaOH concentration of 3.0 mol / L. S200, coating agent solution preparation: Al(NO3)3·9H2O and ZrOCl2·8H2O are dissolved in deionized water and stirred evenly to obtain 10 mL of 1.0 mol / L aluminum nitrate solution and 10 mL of 1.0 mol / L zirconium oxychloride solution, so that the total molar content of Al / Zr is 20% of the total content of vanadium and bismuth; S300, in-situ deposition coating: The bismuth-containing solution A and vanadium-containing solution B prepared in step S100 are mixed evenly at room temperature, stirred and reacted for 60 minutes; under vigorous stirring, aluminum nitrate solution is slowly added dropwise to adjust the pH to 6.0, and then stirring and reacting is continued for 20 minutes; then zirconium oxychloride solution is slowly added dropwise to adjust the pH to 5.5, and then stirring and reacting is continued for 30 minutes; the resulting liquid mixture is then filtered using a sintered glass funnel, washed three times alternately with deionized water and anhydrous ethanol, and dried in a forced-air drying oven at 70°C for 12 hours to obtain the precursor.

[0041] S400, post-processing: The precursor is placed in a pusher kiln and calcined at 500°C for 2 hours in air atmosphere, and then cooled to room temperature with the furnace to obtain an Al2O3 / ZrO2 double-layer coated BiVO4 pigment with a coating thickness of ~18nm.

[0042] Example 7: BiVO4 pigment with Al2O3 / ZrO2 / SnO2 three-layer coating, coating thickness ~16nm S100, prepare a bismuth precursor solution by dissolving Bi(NO3)3·5H2O in nitric acid, stirring until homogeneous, and cooling to room temperature to obtain a 1.0 mol / L bismuth-containing solution A (50 mL), with a nitric acid concentration of 3.0 mol / L; dissolve NH4VO3 in NaOH, stir until homogeneous, and cool to room temperature to obtain a 1.0 mol / L vanadium-containing solution B (50 mL), with a NaOH concentration of 3.0 mol / L. S200, coating agent solution preparation: Al(NO3)3·9H2O, ZrOCl2·8H2O and SnCl4 were dissolved in deionized water and stirred evenly to obtain 18 mL of 1.0 mol / L aluminum nitrate solution, 9 mL of 1.0 mol / L zirconium oxychloride solution and 9 mL of 1.0 mol / L tin tetrachloride solution, so that the total molar content of Al / Zr / Sn is 18% of the total vanadium-bismuth content; S300, in-situ deposition coating: The bismuth-containing solution A and vanadium-containing solution B prepared in step S100 are mixed evenly at room temperature, stirred and reacted for 60 minutes; under vigorous stirring, aluminum nitrate solution is slowly added dropwise to adjust the pH to 6.0, and then stirring and reacting is continued for 20 minutes; then zirconium oxychloride solution is slowly added dropwise to adjust the pH to 5.5, and then stirring and reacting is continued for 15 minutes; then tin tetrachloride solution is slowly added dropwise to adjust the pH to 5.0, and then stirring and reacting is continued for 25 minutes; the resulting liquid mixture is then filtered through a Buchner funnel, washed three times alternately with deionized water and anhydrous ethanol, and dried at 100°C for 0.5 hours using a microwave dryer to obtain the precursor.

[0043] S400, post-processing: The precursor is placed in a rotary kiln and calcined at 500°C for 3 hours in air atmosphere, and then cooled to room temperature in the furnace to obtain a BiVO4 pigment with a three-layer coating of Al2O3 / ZrO2 / SnO2 and a coating thickness of ~16nm.

[0044] Blank example: Uncoated BiVO4 pigment 1. Preparation of bismuth precursor solution: Dissolve Bi(NO3)3·5H2O in nitric acid, stir well, and cool to room temperature to obtain 50 mL of 1.0 mol / L bismuth-containing solution A, with a nitric acid concentration of 3.0 mol / L; Dissolve NH4VO3 in NaOH, stir well, and cool to room temperature to obtain 50 mL of 1.0 mol / L vanadium-containing solution B, with a NaOH concentration of 3.0 mol / L; 2. Liquid phase reaction: The bismuth-containing solution A and vanadium-containing solution B prepared in step S100 are mixed evenly at room temperature, stirred and reacted for 60 minutes; then the resulting liquid mixture is filtered through a Buchner funnel, washed three times alternately with deionized water and anhydrous ethanol, and dried in a forced-air drying oven at 60°C for 24 hours to obtain the precursor.

[0045] 3. Post-processing: The precursor was placed in a muffle furnace and calcined at 400°C for 2 hours in air atmosphere, and then cooled to room temperature with the furnace to obtain uncoated BiVO4 pigment.

[0046] Comparative example: A certain imported bismuth vanadate pigment product for coatings.

[0047] For Example 1 7. Performance tests were conducted on the bismuth vanadate products in the blank and comparative examples.

[0048] Specifically, Example 1 7. The main performance indicators of the bismuth vanadate products in the blank example and comparative example are as follows: (1) Color performance test: The CIELAB color space parameters of the pigment are measured using a colorimeter, and the test method is the scraper method; (2) Acid and alkali resistance test: The pigment is immersed in 2% hydrochloric acid and 2% sodium hydroxide solution for 24 hours respectively, and the color difference ΔE before and after immersion is measured; (3) Weather resistance test: The pigment is subjected to accelerated aging test using a QUV aging test chamber, the aging time is 500 hours, and the color difference ΔE before and after aging is measured. The test results are shown in Table 1.

[0049] Table 1. Results of Color Performance and Durability Tests

[0050] In Table 1, L represents luminance, with 0-100 representing black to white; a represents red-green, with positive values ​​indicating red and negative values ​​indicating green; b represents yellow-blue, with positive values ​​indicating yellow and negative values ​​indicating blue. △E represents the total color difference; the larger the △E, the greater the color difference. When △E is between 0 and 1.5, the color difference is practically indistinguishable to the naked eye (△E < 1 is completely indistinguishable); when △E > 1.5, a noticeable color difference is visible to the naked eye. Table 1 shows the following three differences: First, the color performance parameters of the coated BiVO4 pigment are close to those of pure BiVO4, and the color difference gradually decreases with the increase of coating elements, indicating that the coating process of the present invention has little impact on the color performance of the pigment; in addition, the hiding power of the coated material is significantly improved.

[0051] Secondly, the acid and alkali resistance test results showed that the acid and alkali resistance of the pigments was significantly improved with the increase of coating elements; among them, the color difference ΔE of the pigments in acid and alkali solutions of Examples 3-7 was less than 1.5, which showed excellent acid and alkali resistance.

[0052] Finally, the weather resistance test results showed that the weather resistance of the coated BiVO4 pigment was significantly better than that of pure BiVO4; among them, the color difference ΔE of the pigments in Examples 3-7 was ≤1.5 after 500 hours of QUV aging, which was significantly lower than the 3.8 of the blank example and slightly better than the imported bismuth vanadate pigment product for coatings in the comparative example.

[0053] This is because during the in-situ coating process, the coating layer and the BiVO4 matrix are formed simultaneously, and the two are bonded by chemical bonds, resulting in strong adhesion. In contrast, traditional post-processing coating is performed after the BiVO4 particles have formed, and the coating layer is mainly bonded to the matrix by physical adsorption, resulting in weaker adhesion and easy detachment during use.

[0054] Figure 2 These are the X-ray diffraction (XRD) patterns of Examples 1, 3, the blank example, and the comparative example in this invention. From... Figure 2 It can be seen that the XRD patterns of Example 1, Example 3, blank example and comparative example are similar, and no other additional diffraction peaks appear, indicating that the monoclinic crystal system structure is still maintained and the introduction of the coating layer has not changed its crystal structure.

[0055] Figure 3 These are scanning electron microscope (SEM) images of the morphology of Example 1 in this invention. From... Figure 3 It can be seen that the average particle size of the BiVO4 pigment in the Al2O3 coating layer in Example 1 is about 200 nm, and the particles are uniformly dispersed and have a dense structure.

[0056] Figure 4 These are transmission electron microscope (TEM) images of the morphology of Example 2 in this invention. From... Figure 4 It can be seen that the bismuth vanadate pigment in Example 2 has an average particle size of 150 nm, with particles exhibiting a near-spherical or polyhedral morphology, smooth surfaces, and uniform particle size distribution. This indicates that after modification using in-situ coating technology, the particles are more tightly bonded, the coating layer is uniform, and there are no island-like coatings, which should improve properties such as weather resistance and provide a microscopic basis for performance optimization.

[0057] This invention has broad applicability in the surface coating of inorganic powder materials and is expected to be extended to the surface modification of pigment powders such as titanium dioxide and iron oxide red, as well as other inorganic materials. Utilizing the unique vanadium resources of Panzhihua Iron and Steel Group, this invention can prepare a series of high-performance bismuth vanadate pigments, which can be widely used in architectural coatings, automotive coatings, and ceramic glazes, yielding significant economic and social benefits.

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications or equivalent substitutions made to the present invention without departing from the spirit and scope thereof should be covered within the protection scope of the claims of the present invention.

[0059] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of the present invention is limited to these examples; within the framework of the embodiments of the present invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of the present invention should be included within the protection scope of the embodiments of the present invention.

Claims

1. A method for preparing a high-performance bismuth vanadate pigment with in-situ coating of multi-metal oxides, characterized in that, Includes the following steps: Precursor preparation: Prepare bismuth-containing solution A and vanadium-containing solution B with concentrations of 0.1~2.0 mol / L, respectively, wherein the concentrations of bismuth-containing solution A and vanadium-containing solution B are the same; Preparation of coating agent solution: Prepare a coating agent solution with a total concentration of 0.5~2.0 mol / L; In-situ deposition coating: The bismuth-containing solution A and the vanadium-containing solution B are mixed and reacted at room temperature for 30-90 minutes to obtain a mixture C. The coating agent solution is added to the mixture C, and the total metal ion content of the coating solution is controlled to be 5%-20% of the total vanadium and bismuth content. The pH value is adjusted to 5-8, and after reacting for 30-90 minutes, the mixture is filtered, washed, and dried to obtain the bismuth vanadate precursor. Post-processing: The bismuth vanadate precursor is calcined in air at 250-500°C for 1-6 hours and then cooled to room temperature in the furnace to obtain a surface-modified environmentally friendly bismuth vanadate pigment.

2. The method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to claim 1, characterized in that, In the precursor preparation steps, The bismuth-containing solution A is prepared by dissolving bismuth nitrate or bismuth oxide in nitric acid. The vanadium-containing solution B is prepared by dissolving ammonium metavanadate, vanadium pentoxide, or sodium metavanadate in NaOH solution; The concentrations of nitric acid and NaOH solution are the same.

3. The method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to claim 1, characterized in that, The coating agent solution is a single-element coating agent solution or a multi-element coating agent solution, wherein, The single-element coating agent solution is prepared by dissolving any one of Al salt, Zr salt, Zn salt, Sn salt, La salt, and Ce salt in deionized water; The multi-element coating agent solution is prepared by dissolving two or more of the following salts: Al, Zr, Zn, Sn, La, and Ce in deionized water.

4. The method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to claim 3, characterized in that, The Al salt is aluminum nitrate or aluminum chloride, the Zr salt is zirconium nitrate or zirconium oxychloride, the Zn salt is zinc nitrate or zinc sulfate, the Sn salt is tin tetrachloride or tin sulfate, the La salt is lanthanum nitrate or lanthanum chloride, and the Ce salt is cerium nitrate or cerium chloride.

5. The method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to claim 3, characterized in that, In the in-situ deposition coating step, if a multi-layer coated modified bismuth vanadate pigment is to be prepared, multiple single-element coating agent solutions are added sequentially to the mixed solution C, and the reaction is stirred for 10-30 minutes after each single-element coating agent solution is added.

6. The method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to claim 1, characterized in that, In the in-situ deposition and coating step, Filtration methods include Buchner funnel filtration, sand core funnel vacuum filtration, or plate and frame filter press filtration. Washing is performed by alternating between deionized water and anhydrous ethanol, 2-4 times each; Drying is performed using a vacuum drying oven, a forced-air drying oven, or a microwave dryer, at a temperature of 60~100℃ for 0.5~24 hours.

7. The method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to claim 1, characterized in that, In the in-situ deposition coating step, the pH value is adjusted by adding sodium hydroxide solution or nitric acid solution.

8. The method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to claim 1, characterized in that, In the post-processing steps, calcination is carried out using a muffle furnace, tube furnace, pusher kiln, or rotary kiln.

9. The method for preparing high-performance bismuth vanadate pigments with in-situ coating of multi-metal oxides according to claim 1, characterized in that, The mass ratio and distribution of each metal oxide in the coating layer are controlled by the amount and order of addition of each metal salt in the coating agent solution.

10. A high-performance bismuth vanadate pigment in which polymetallic oxides are coated in situ, characterized in that, Prepared using the method of any one of claims 1-9, the pigment surface has a coating layer with a thickness of 5-20 nm.

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