Preparation method of blue nano tungsten oxide

Abstract

The invention relates to the technical field of material preparation, in particular to a preparation method of blue nano tungsten oxide. The invention provides a preparation method of blue nano tungsten oxide, which comprises the following steps: S1, grinding, acid leaching, oxidizing roasting and alkaline leaching tungsten-containing waste in sequence to obtain a crude sodium tungstate solution; s2, purifying the crude sodium tungstate solution to obtain a purified sodium tungstate solution; s3, diluting the purified sodium tungstate solution, adding an acid solution, and carrying out a first reaction to obtain a tungstic acid precursor solution; s4, performing a second reaction on the tungstic acid precursor solution and hydrazine hydrate to obtain a solid precipitate; and calcining the solid precipitate to obtain the blue nano tungsten oxide. The blue nano tungsten oxide is successfully prepared by the method, the raw material utilization rate is high, the yield is high, and the process is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, and particularly to a method for preparing blue nano tungsten oxide. Background Art

[0002] Tungsten-containing waste mainly comes from tungsten and its alloys, such as the production and processing of products like cemented carbide, tungsten steel, tungsten electrodes, etc. These wastes have a high tungsten content and high recycling value. However, traditional recycling methods face many challenges in practical applications.

[0003] Pyrometallurgical recycling can handle a large amount of waste, but it has extremely high energy consumption and may produce harmful gases and solid waste, causing environmental pollution. Hydrometallurgical recycling is relatively environmentally friendly, but its treatment process is complex, the recycling efficiency is often not high, and it requires a large amount of water resources and chemical reagents. As an emerging recycling technology, the microbial method has potential environmental friendliness, but its application is still in the laboratory stage and it is difficult to be applied on a large scale industrially. Therefore, developing efficient and environmentally friendly recycling technologies is a current research hotspot.

[0004] Converting tungsten-containing waste into nano tungsten oxide is an efficient recycling method. Through appropriate treatment and conversion, tungsten in the waste can be recycled, and at the same time, high-value nano tungsten oxide products can be obtained. This conversion not only realizes the recycling of resources but also reduces environmental pollution, having important economic and environmental benefits.

[0005] However, the preparation of nano tungsten oxide still faces some challenges. The control of the color and size of nano tungsten oxide is a key issue, as the color and size of nano tungsten oxide directly affect its physical and chemical properties. Different application fields have different requirements for the color and size of nano tungsten oxide, and nano tungsten oxide with different colors and sizes can be obtained by adopting different preparation methods and controlling the reaction conditions.

[0006] In view of this, this invention is specifically proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing blue nano tungsten oxide, which successfully prepares blue nano tungsten oxide, has a high raw material utilization rate, a high yield, and a simple process.

[0008] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0009] The present invention provides a method for preparing blue nano tungsten oxide, comprising the following steps:

[0010] S1. After sequentially grinding, acid leaching, oxidative roasting, and alkali leaching the tungsten-containing waste, a crude sodium tungstate solution is obtained;

[0011] S2. After purifying the crude sodium tungstate solution, a purified sodium tungstate solution is obtained;

[0012] S3. After diluting the purified sodium tungstate solution, an acid solution is added for a first reaction to obtain a tungstic acid precursor solution;

[0013] S4. A second reaction is carried out between the tungstic acid precursor solution and hydrazine hydrate to obtain a solid precipitate; after calcining the solid precipitate, the blue nano tungsten oxide is obtained.

[0014] Further, the chemical formula of the blue nano tungsten oxide is WO 2.9 ;

[0015] And / or, the particle size of the blue nano tungsten oxide is 50 - 150 nm.

[0016] Further, in step S4, the molar ratio of hydrazine hydrate to tungsten element in the tungstic acid precursor solution is 1:(3 - 5).

[0017] Further, in step S4, the second reaction includes: dropping the hydrazine hydrate into the tungstic acid precursor solution, and after a reduction reaction, the solid precipitate is obtained;

[0018] Wherein, the dropping rate of the hydrazine hydrate is 5 - 10 mL / min, the temperature of the reduction reaction is 60 - 80 °C, and the time of the reduction reaction is 0.5 - 2 h.

[0019] Further, in step S4, the calcining includes: under a protective atmosphere, heat preservation treatment is carried out at 250 - 350 °C for 1.5 - 2.5 h.

[0020] Further, in step S3, the dilution includes: mixing the purified sodium tungstate solution and water to obtain a diluted sodium tungstate solution;

[0021] And / or, the concentration of sodium tungstate in the diluted sodium tungstate solution is 150 - 250 g / L.

[0022] Further, in step S3, the acid solution includes at least one of hydrochloric acid solution, sulfuric acid solution and nitric acid solution;

[0023] And / or, the molar ratio of H + in the acid solution to tungsten element in the diluted sodium tungstate solution is 1:(5 - 7).

[0024] Further, in step S3, the first reaction includes: dropping the diluted sodium tungstate solution into the acid solution, and adding ethylene glycol, and after a water bath reaction, the tungstic acid precursor solution is obtained;

[0025] Among them, the volume of the ethylene glycol is 10% - 30% of the total volume of the diluted sodium tungstate solution and the acid solution; the dropping rate of the acid solution is 15 - 40 mL / min, the stirring speed of the water bath reaction is 150 - 350 rpm / min, the temperature of the water bath reaction is 35 - 80 °C, and the time of the water bath reaction is 1 - 3 h.

[0026] Further, in step S2, the purification includes: after the third reaction of the crude sodium tungstate solution and magnesium sulfate, a reaction solution is obtained; after the fourth reaction of the reaction solution and sodium sulfide, the pH of the system is adjusted to 2.5 - 3.0 to obtain the purified sodium tungstate solution.

[0027] Further, in step S2, the pH of the third reaction is 8.5 - 9.5, and the temperature is 70 - 80 °C;

[0028] And / or, the pH of the fourth reaction is 10 - 12, and the temperature is 80 - 85 °C.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. By precisely controlling the reaction conditions of sodium tungstate and acid, and using hydrazine hydrate as a reducing agent for the reduction reaction, the present invention successfully prepares blue nano tungsten oxide after calcination.

[0031] 2. In the preparation method of the blue nano tungsten oxide of the present invention, by precisely controlling the reaction conditions of sodium tungstate and acid, the precipitation rate of tungsten after the reaction of sodium tungstate and acid reaches more than 99%, thereby improving the yield.

[0032] 3. The preparation method of the blue nano tungsten oxide of the present invention uses tungsten-containing waste as a raw material, realizes the recycling of resources, significantly improves the utilization rate of raw materials, and reduces the production cost; moreover, the process is simple, the operation is convenient, and it is easy to industrialize production. Specific Embodiments

[0033] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, not all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0034] The following specifically describes a method for preparing blue nano tungsten oxide according to an embodiment of the present invention.

[0035] In some embodiments of the present invention, a method for preparing blue nano tungsten oxide is provided, including the following steps:

[0036] S1. The tungsten-containing waste is successively subjected to grinding, acid leaching, oxidative roasting, and alkali leaching to obtain a crude sodium tungstate solution.

[0037] S2. After the crude sodium tungstate solution is purified, a purified sodium tungstate solution is obtained.

[0038] S3. After the purified sodium tungstate solution is diluted, an acid solution is added for a first reaction to obtain a tungstic acid precursor solution.

[0039] S4. The tungstic acid precursor solution and hydrazine hydrate are subjected to a second reaction to obtain a solid precipitate; after the solid precipitate is calcined, blue nano tungsten oxide is obtained.

[0040] In the present invention, the recovered tungsten-containing waste is separated from metals such as cobalt and nickel in the tungsten-containing waste through grinding and atmospheric acid leaching to obtain the acid-leached tungsten-containing waste, the main component of which is tungsten carbide; the acid-leached tungsten-containing waste is subjected to oxidative roasting to oxidize tungsten carbide to tungsten oxide to obtain an oxidized material; the oxidized material is subjected to alkali leaching to further extract tungsten elements and simultaneously remove some impurities insoluble in alkali. The main component in the solution after alkali leaching is sodium tungstate, that is, the crude sodium tungstate solution; the crude sodium tungstate solution is purified to remove most of the impurities to obtain a purified sodium tungstate solution; after the purified sodium tungstate solution is diluted, an acid solution is added for reaction to obtain a tungstic acid precursor solution; hydrazine hydrate is added to the tungstic acid precursor solution for a reduction reaction. Through the reduction of hydrazine hydrate, tungsten elements are reduced to tungsten in a low valence state to form a blue nano tungsten oxide precursor; after the blue nano tungsten oxide precursor is calcined, blue nano tungsten oxide is obtained.

[0041] In the present invention, blue nano tungsten oxide is successfully prepared after calcination by precisely controlling the reaction of sodium tungstate with acid and using hydrazine hydrate as a reducing agent for the reduction reaction.

[0042] In the method for preparing blue nano tungsten oxide of the present invention, by precisely controlling the reaction conditions of sodium tungstate with acid, the precipitation rate of tungsten after the reaction of sodium tungstate with acid reaches more than 99%, and the yield is improved under high concentration and high precipitation rate.

[0043] The method for preparing blue nano tungsten oxide of the present invention uses tungsten-containing waste as a raw material, realizes the reuse of resources, significantly improves the utilization rate of raw materials, and reduces the production cost.

[0044] The method for preparing blue nano tungsten oxide of the present invention has a simple process, is easy to operate, and is easy to industrialize.

[0045] In some embodiments of the present invention, the chemical formula of blue nano tungsten oxide is WO 2.9 ; the particle size of the blue nano oxide is 50 - 150 nm.

[0046] In some embodiments of the present invention, in step S4, the molar ratio of hydrazine hydrate to tungsten element in the tungstic acid precursor solution is 1:(3 - 5); typically but not limited to, for example, the molar ratio of hydrazine hydrate to tungsten element in the tungstic acid precursor solution can be 1:3, 1:4, 1:5 or the range values composed of any two of them.

[0047] In some embodiments of the present invention, in step S4, the second reaction includes: dropping hydrazine hydrate into the tungstic acid precursor solution, and after a reduction reaction, obtaining a solid precipitate;

[0048] wherein, the dropping rate of hydrazine hydrate is 5 - 10 mL / min, the temperature of the reduction reaction is 60 - 80 °C, and the time of the reduction reaction is 0.5 - 2 h; typically but not limited to, for example, the dropping rate of hydrazine hydrate can be 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min or the range values composed of any two of them; the temperature of the reduction reaction can be 60 °C, 65 °C, 70 °C, 75 °C, 80 °C or the range values composed of any two of them; the time of the reduction reaction can be 0.5 h, 1 h, 2 h or the range values composed of any two of them.

[0049] Adding a certain amount of hydrazine hydrate to the tungstic acid precursor solution, under the above reaction conditions, can enable hydrazine hydrate to fully carry out a reduction reaction with the tungstic acid precursor. Through the reduction effect of hydrazine hydrate, the tungsten element is reduced to a low-valence tungsten, forming a blue nano tungsten oxide precursor.

[0050] In some embodiments of the present invention, in step S4, the calcination includes: under a protective atmosphere, heat preservation treatment at 250 - 350 °C for 1.5 - 2.5 h; typically but not limited to, for example, the calcination temperature can be 250 °C, 280 °C, 300 °C, 320 °C, 350 °C or the range values composed of any two of them; preferably, the calcination time is 2 h; the protective atmosphere includes nitrogen (N2).

[0051] In some embodiments of the present invention, before step S4, it further includes: washing and drying the solid precipitate in sequence; preferably, the washing liquid for washing is a mixed solution of ethanol and water; the drying temperature is 60 - 80 °C.

[0052] The reduction reaction is carried out on the hydrazine hydrate and tungstic acid precursor solution. After filtration, a solid precipitate is obtained; the solid precipitate is washed with an aqueous solution of ethanol until neutral, dried, and then calcined in an N2 atmosphere at 250 - 350 °C to obtain blue nano tungsten oxide.

[0053] In some embodiments of the present invention, in step S3, dilution includes: mixing the purified sodium tungstate solution and water to obtain a diluted sodium tungstate solution.

[0054] In some embodiments of the present invention, in step S3, the concentration of sodium tungstate in the diluted sodium tungstate solution is 150 - 250 g / L; typically but not restrictively, for example, the concentration of sodium tungstate in the diluted sodium tungstate solution can be 150 g / L, 200 g / L, 250 g / L or a range value composed of any two of them.

[0055] In some embodiments of the present invention, in step S3, the acid solution includes at least one of hydrochloric acid solution, sulfuric acid solution and nitric acid solution; preferably, the concentrations of the hydrochloric acid solution and the nitric acid solution are each independently 2 - 5 mol / L; the concentration of the sulfuric acid solution is 1 - 2.5 mol / L.

[0056] In some embodiments of the present invention, in step S3, H in the acid solution + and the molar ratio of tungsten element in the diluted sodium tungstate solution is 1:(5 - 7); preferably 1:6.

[0057] In some embodiments of the present invention, in step S3, the first reaction includes: dropping the diluted sodium tungstate solution into the acid solution, adding ethylene glycol, and after carrying out a water bath reaction, a tungstic acid precursor solution is obtained.

[0058] In some embodiments of the present invention, in step S3, the volume of ethylene glycol is 10% - 30% of the total volume of the diluted sodium tungstate solution and the acid solution; typically but not restrictively, for example, the volume of ethylene glycol is 10%, 20%, 30% of the total volume of the diluted sodium tungstate solution and the acid solution or a range value composed of any two of them.

[0059] A certain amount of ethylene glycol is added to the system of the reaction between sodium tungstate and the acid. Ethylene glycol is added as a dispersant in the system of the reaction between the acid solution and the sodium tungstate solution, which can improve the dispersibility and stability of the product.

[0060] In some embodiments of the present invention, in step S3, the dropping rate of the acid solution is 15-40 mL / min, the stirring rate of the water bath reaction is 150-350 rpm / min, the temperature of the water bath reaction is 35-80 °C, and the time of the water bath reaction is 1-3 h; typically but not restrictively, for example, the dropping rate of the acid solution can be 15 mL / min, 20 mL / min, 25 mL / min, 30 mL / min, 35 mL / min, 40 mL / min or a range value composed of any two of them; the stirring rate of the water bath reaction can be 150 rpm / min, 200 rpm / min, 250 rpm / min, 300 rpm / min, 350 rpm / min or a range value composed of any two of them; the temperature of the water bath reaction can be 35 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C or a range value composed of any two of them; the time of the water bath reaction can be 1 h, 2 h, 3 h or a range value composed of any two of them. Reacting the purified sodium tungstate solution, ethylene glycol and the acid solution, by controlling the raw material dosage, feeding rate, stirring rate, reaction temperature and reaction time, a tungsten acid precursor can be obtained; the precipitation rate of tungsten after the reaction of sodium tungstate and the acid can reach more than 99%, and the yield is improved at high concentration and high precipitation rate.

[0061] In some embodiments of the present invention, in step S2, the purification includes: after the third reaction of the crude sodium tungstate solution and magnesium sulfate, a reaction solution is obtained; after the fourth reaction of the reaction solution and sodium sulfide, the pH of the system is adjusted to 2.5-3.0 to obtain the purified sodium tungstate solution.

[0062] Magnesium sulfate and sodium sulfide can remove impurities such as Si, P, Mo, etc. in the crude sodium tungstate solution, improve the purity of the sodium tungstate solution, and provide high-quality raw materials for subsequent steps; among them, after adding magnesium sulfate for reaction and filtering, a sodium tungstate solution removing Si and P is obtained; then adding sodium sulfide for reaction and adjusting the pH, molybdenum precipitates in the form of molybdenum trisulfide, and the purified sodium tungstate solution is obtained after filtration.

[0063] In some embodiments of the present invention, in step S2, the pH of the third reaction is 8.5-9.5, and the temperature is 70-80 °C.

[0064] In some embodiments of the present invention, in step S2, the pH of the fourth reaction is 10-12, and the temperature is 80-85 °C.

[0065] In some embodiments of the present invention, in step S2, the purification includes: heating the crude sodium tungstate solution to 70 - 80 °C, adjusting the pH of the solution to 8.5 - 9.5 with dilute sulfuric acid or dilute hydrochloric acid under stirring conditions, then adding a magnesium sulfate solution and continuously stirring for 0.5 - 1.5 h. The volume of the magnesium sulfate solution is 4% - 10% of the volume of the crude sodium tungstate solution. After filtration, a preliminarily purified crude sodium tungstate solution is obtained; preferably, the concentration of the magnesium sulfate solution is 25% - 35%.

[0066] React with sodium sulfide to the preliminarily purified crude sodium tungstate solution. The dosage of sodium sulfide is 1.1 - 1.4 times the theoretical amount. Control the reaction temperature at 80 - 85 °C, the pH of the reaction system at 10 - 12, and the reaction time at 1.5 - 2 h; after the reaction, adjust the pH to 2.5 - 3.0 with dilute sulfuric acid, and after filtration, a purified sodium tungstate solution is obtained; the theoretical dosage of sodium sulfide refers to the theoretical dosage required for the reaction between sodium sulfide and molybdenum ions; preferably, add an alkali to control the pH of the reaction system at 10 - 12.

[0067] In some embodiments of the present invention, in step S1, the grinding includes: ball - milling the tungsten - containing waste to obtain a slurry; preferably, the rotation speed of the ball - milling is 300 - 450 r / min, and the ball - milling time is 2 - 4 h.

[0068] The tungsten - containing waste mainly comes from the production and processing processes of tungsten and its alloys, such as cemented carbide, tungsten steel, tungsten electrodes, etc.

[0069] Perform ball - milling treatment on the tungsten - containing waste, and refine it into a slurry by mechanical force. The purpose is to increase the specific surface area of the tungsten - containing waste, making it easier to react with the subsequent treatment liquid, thereby improving the leaching rate.

[0070] In some embodiments of the present invention, in step S1, the acid leaching includes: mixing the slurry and a hydrochloric acid solution and then performing leaching. After filtration, an acid - leached tungsten - containing waste (mainly tungsten carbide) is obtained; preferably, the acid leaching uses a hydrochloric acid solution with a mass concentration of 10% - 20%; the pH of the acid leaching is 1, the temperature of the acid leaching is 75 - 85 °C, the time of the acid leaching is 6 - 10 h, and the stirring speed of the acid leaching is 300 - 450 r / min; the acid leaching is carried out under normal pressure.

[0071] Use an appropriate amount of hydrochloric acid solution to leach the ball - milled slurry, separate valuable metals such as cobalt and nickel, and remove some impurities at the same time.

[0072] In some embodiments of the present invention, in step S1, the temperature of the oxidative roasting is 600 - 800 °C, the time of the oxidative roasting is 2 - 4 h, and the oxidative roasting is carried out in an air atmosphere.

[0073] The tungsten-containing waste after acid leaching is subjected to oxidative roasting to obtain a roasted material, in which tungsten carbide is oxidized to tungsten oxide, preparing for the subsequent alkali leaching step and improving the leaching rate and purity of tungsten.

[0074] In some embodiments of the present invention, in step S1, the alkali leaching includes: leaching with an alkali solution; preferably, the alkali solution includes a NaOH solution; the pH of the alkali leaching is 14, the concentration of the NaOH solution is 3-5 mol / L; the temperature of the alkali leaching is 85-95 °C, and the time of the alkali leaching is 1-3 h. The roasted material is leached with an alkali solution to convert the tungsten element into the form of sodium tungstate.

[0075] Example 1

[0076] The preparation method of blue nano tungsten oxide provided in this example includes the following steps:

[0077] S1. Ball-mill the tungsten-containing waste at a rotation speed of 450 rpm / min for 3 h to obtain a slurry;

[0078] Mix the slurry with a hydrochloric acid solution with a mass concentration of 20%, stir at a stirring speed of 450 rpm / min at 80 °C for 10 h, control the pH of the system to 1, and after filtration, obtain the tungsten-containing waste after acid leaching;

[0079] Under an air atmosphere, oxidatively roast the tungsten-containing waste after acid leaching at 700 °C for 3 h to obtain a roasted material;

[0080] Leach the roasted material with a NaOH solution with a concentration of 5 mol / L at 95 °C for 3 h, control the pH of the system to 14, and obtain a crude sodium tungstate solution;

[0081] S2. Heat the crude sodium tungstate solution to 80 °C, adjust the pH of the solution to 9.0 with dilute sulfuric acid under stirring conditions, then add a magnesium sulfate solution and continuously stir for 1.5 h. The dosage of the magnesium sulfate solution is 7% of the volume of the crude sodium tungstate solution. After filtration, obtain a preliminarily purified crude sodium tungstate solution;

[0082] Add sodium sulfide to the preliminarily purified crude sodium tungstate solution for reaction. The dosage of sodium sulfide is 1.4 times the theoretical amount. Control the reaction temperature to 85 °C, the pH of the reaction system to 11, and the reaction time to 2 h; after the reaction, adjust the pH to 3.0 with dilute sulfuric acid, and after filtration, obtain a purified sodium tungstate solution;

[0083] S3. Mix the purified sodium tungstate solution and water to obtain a diluted sodium tungstate solution; drop the diluted sodium tungstate solution into a hydrochloric acid solution with a concentration of 5 mol / L, and add ethylene glycol. After a water bath reaction, obtain a tungstic acid precursor solution;

[0084] Among them, the concentration of sodium tungstate in the diluted sodium tungstate solution is 200 g / L; the volume of ethylene glycol is 20% of the total volume of the diluted sodium tungstate solution and hydrochloric acid solution; the molar ratio of H + in the hydrochloric acid solution to tungsten element in the diluted sodium tungstate solution is 1:6;

[0085] The dropping rate of the sodium tungstate solution is 35 mL / min; the stirring speed of the water bath reaction is 300 rpm / min, the temperature is 50 °C, and the time is 2 h;

[0086] S4. Drop hydrazine hydrate into the tungstic acid precursor solution for reduction reaction. After filtration, a solid precipitate is obtained; the solid precipitate is successively washed with a mixed solution of ethanol and water and dried at 80 °C, and then heat-treated at 300 °C for 2 h under a nitrogen atmosphere to obtain blue nano tungsten oxide;

[0087] Among them, the molar ratio of hydrazine hydrate to tungsten element in the tungstic acid precursor solution is 1:5; the dropping rate of hydrazine hydrate is 8 mL / min, the temperature of the reduction reaction is 80 °C, and the time is 2.0 h.

[0088] Example 2

[0089] The preparation method of blue nano tungsten oxide provided in this example includes the following steps:

[0090] S1. Ball-mill the tungsten-containing waste, with the rotation speed of 300 rpm / min and the time of 2 h to obtain a slurry;

[0091] Mix the slurry with a hydrochloric acid solution with a mass concentration of 10%, stir at 80 °C at a stirring speed of 300 rpm / min for 6 h, control the pH of the system to 1, and after filtration, obtain the acid-leached tungsten-containing waste;

[0092] Under an air atmosphere, oxidize and roast the acid-leached tungsten-containing waste at 600 °C for 2 h to obtain a roasted material;

[0093] Use a NaOH solution with a concentration of 3 mol / L to leach the roasted material at 85 °C for 1 h, control the pH of the system to 14, and obtain a crude sodium tungstate solution;

[0094] S2. Heat the crude sodium tungstate solution to 80 °C, adjust the pH of the solution to 8.5 with dilute sulfuric acid under stirring conditions, then add a magnesium sulfate solution and continue stirring for 0.5 h. The dosage of the magnesium sulfate solution is 5% of the volume of the crude sodium tungstate solution. After filtration, obtain a preliminarily purified crude sodium tungstate solution;

[0095] Sodium sulfide is added to the preliminarily purified crude sodium tungstate solution for reaction. The dosage of sodium sulfide is 1.1 times the theoretical amount. The reaction temperature is controlled at 80 °C, the pH of the reaction system is 11, and the reaction time is 1.5 h. After the reaction, the pH is adjusted to 2.5 with dilute sulfuric acid. After filtration, the purified sodium tungstate solution is obtained.

[0096] S3. The purified sodium tungstate solution and water are mixed evenly to obtain a diluted sodium tungstate solution. The diluted sodium tungstate solution is dropped into a hydrochloric acid solution with a concentration of 2 mol / L, and ethylene glycol is added. After a water bath reaction, a tungstic acid precursor solution is obtained.

[0097] Among them, the concentration of sodium tungstate in the diluted sodium tungstate solution is 150 g / L; the volume of ethylene glycol is 10% of the total volume of the diluted sodium tungstate solution and the hydrochloric acid solution; the molar ratio of H in the hydrochloric acid solution + and the tungsten element in the diluted sodium tungstate solution is 1:6.

[0098] The dropping rate of the sodium tungstate solution is 15 mL / min; the stirring speed of the water bath reaction is 150 rpm / min, the temperature is 35 °C, and the time is 1 h.

[0099] S4. Hydrazine hydrate is dropped into the tungstic acid precursor solution for a reduction reaction. After filtration, a solid precipitate is obtained. The solid precipitate is successively washed with a mixed solution of ethanol and water and dried at 60 °C. Then, under a nitrogen atmosphere, it is heat-treated at 250 °C for 2 h to obtain blue nano tungsten oxide.

[0100] Among them, the molar ratio of hydrazine hydrate to the tungsten element in the tungstic acid precursor solution is 1:3; the dropping rate of hydrazine hydrate is 5 mL / min, the temperature of the reduction reaction is 60 °C, and the time is 0.5 h.

[0101] Example 3

[0102] The preparation method of blue nano tungsten oxide provided in this example includes the following steps:

[0103] S1. The tungsten-containing waste is ball-milled at a rotation speed of 400 rpm / min for 3 h to obtain a slurry.

[0104] The slurry and a hydrochloric acid solution with a mass concentration of 15% are mixed and stirred at a stirring speed of 400 rpm / min at 80 °C for 8 h. The pH of the system is controlled at 1. After filtration, the acid-leached tungsten-containing waste is obtained.

[0105] Under an air atmosphere, the acid-leached tungsten-containing waste is oxidized and roasted at 800 °C for 4 h to obtain a roasted material.

[0106] Using a NaOH solution with a concentration of 4 mol / L, leach the calcined material at 90 °C for 2 h, control the pH of the system to 14, and obtain a crude sodium tungstate solution;

[0107] S2. Heat the crude sodium tungstate solution to 75 °C, adjust the pH of the solution to 9.0 with dilute sulfuric acid under stirring conditions, then add a magnesium sulfate solution and stir continuously for 1 h. The dosage of the magnesium sulfate solution is 10% of the volume of the crude sodium tungstate solution. After filtration, obtain a preliminarily purified crude sodium tungstate solution;

[0108] Add sodium sulfide to the preliminarily purified crude sodium tungstate solution for reaction. The dosage of sodium sulfide is 1.2 times the theoretical amount. Control the reaction temperature to 80 °C, the pH of the reaction system to 11, and the reaction time to 1.5 h; after the reaction, adjust the pH to 2.5 with dilute sulfuric acid, and after filtration, obtain a purified sodium tungstate solution;

[0109] S3. Mix the purified sodium tungstate solution and water to obtain a diluted sodium tungstate solution; drop the diluted sodium tungstate solution into a hydrochloric acid solution with a concentration of 4 mol / L, and add ethylene glycol. After a water bath reaction, obtain a tungstic acid precursor solution;

[0110] Among them, the concentration of sodium tungstate in the diluted sodium tungstate solution is 250 g / L; the volume of ethylene glycol is 30% of the total volume of the diluted sodium tungstate solution and the hydrochloric acid solution; the molar ratio of H + in the hydrochloric acid solution to the tungsten element in the diluted sodium tungstate solution is 1:6;

[0111] The dropping rate of the sodium tungstate solution is 40 mL / min; the stirring speed of the water bath reaction is 350 rpm / min, the temperature is 80 °C, and the time is 3 h;

[0112] S4. Drop hydrazine hydrate into the tungstic acid precursor solution for a reduction reaction. After filtration, obtain a solid precipitate; wash the solid precipitate successively with a mixed solution of ethanol and water and dry it at 60 °C, and then carry out heat preservation treatment at 350 °C for 2 h under a nitrogen atmosphere to obtain blue nano tungsten oxide;

[0113] Among them, the molar ratio of hydrazine hydrate to the tungsten element in the tungstic acid precursor solution is 1:4; the dropping rate of hydrazine hydrate is 10 mL / min, the temperature of the reduction reaction is 70 °C, and the time is 1.5 h.

[0114] Comparative Example 1

[0115] The preparation method of tungsten oxide provided in this comparative example refers to Example 1, and the difference is only that in step S3, the concentration of sodium tungstate in the diluted sodium tungstate solution is 100 g / L; the volume of ethylene glycol is 5% of the total volume of the diluted sodium tungstate solution and the hydrochloric acid solution; H +The molar ratio of tungsten in the diluted sodium tungstate solution is 1:3; the dropping rate of the sodium tungstate solution is 10 mL / min; the stirring rate of the water bath reaction is 100 rpm / min, the temperature is 95 °C, and the time is 1.5 h.

[0116] Comparative Example 2

[0117] The method for preparing tungsten oxide provided in this comparative example refers to Example 1, the difference is only that in step S4, no reduction reaction is carried out. After the tungstic acid precursor solution is filtered, washed with a mixed solution of ethanol and water, and dried at 80 °C, it is heat-treated at 300 °C for 2 h under a nitrogen atmosphere.

[0118] Comparative Example 3

[0119] The method for preparing tungsten oxide provided in this comparative example refers to Example 1, the difference is only that in step S4, the molar ratio of hydrazine hydrate to tungsten in the tungstic acid precursor solution is 1:5, the dropping rate of hydrazine hydrate is 2 mL / min, the temperature of the reduction reaction is 35 °C, and the time is 3 h.

[0120] Comparative Example 4

[0121] The method for preparing tungsten oxide provided in this comparative example refers to Example 1, the difference is only that in step S4, it is heat-treated at 600 °C for 2 h under a nitrogen atmosphere.

[0122] Test Example 1

[0123] The particle size range, purity, and precipitation rate of the tungsten oxide prepared by the methods for preparing tungsten oxide of Examples 1 to 3 and Comparative Examples 1 to 4 are recorded in Table 1.

[0124] Table 1

[0125] Precipitation rate of tungsten (%) Average particle size (nm) Purity (%) Example 1 99.99 50 99.9 Example 2 99.81 100 99.9 Example 3 99.66 150 99.9 Comparative Example 1 98.81 300 99.9 Comparative Example 2 96.37 250 99.9 Comparative Example 3 96.07 500 99.9 Comparative Example 4 96.35 400 99.9

[0126] It can be seen from Table 1 that blue nano tungsten oxide can be prepared by using the preparation methods of Examples 1 to 3; the preparation methods of Comparative Examples 1 to 4 cannot prepare blue nano tungsten oxide.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of blue tungsten oxide nanoparticles, characterized in that, It includes the following steps: S1. After the tungsten-containing waste is successively ground, acid-leached, oxidatively roasted, and alkali-leached, a crude sodium tungstate solution is obtained; S2. After the crude sodium tungstate solution is purified, a purified sodium tungstate solution is obtained; S3. After the purified sodium tungstate solution is diluted, an acid solution is added for a first reaction to obtain a tungstic acid precursor solution; S4. A second reaction is carried out between the tungstic acid precursor solution and hydrazine hydrate to obtain a solid precipitate; after the solid precipitate is calcined, the blue nano tungsten oxide is obtained.

2. The preparation method of the blue nano tungsten oxide according to claim 1, characterized in that, The chemical formula of the blue tungsten oxide nanoparticles is WO 2.9 ; And / or, the particle size of the blue nano tungsten oxide is 50 - 150 nm.

3. The preparation method of blue nano tungsten oxide according to claim 1, characterized in that, In step S4, the molar ratio of hydrazine hydrate to tungsten element in the tungstic acid precursor solution is 1:(3 - 5).

4. The preparation method of blue nano tungsten oxide according to claim 1, characterized in that, In step S4, the second reaction includes: dropping the hydrazine hydrate into the tungstic acid precursor solution, and after a reduction reaction, the solid precipitate is obtained; wherein, the dropping rate of the hydrazine hydrate is 5 - 10 mL / min, the temperature of the reduction reaction is 60 - 80 °C, and the time of the reduction reaction is 0.5 - 2 h.

5. The preparation method of blue nano tungsten oxide according to claim 1, characterized in that, In step S4, the calcination includes: under a protective atmosphere, heat preservation treatment is carried out at 250 - 350 °C for 1.5 - 2.5 h.

6. The preparation method of blue nano tungsten oxide according to claim 1, characterized in that, In step S3, the dilution includes: mixing the purified sodium tungstate solution and water evenly to obtain a diluted sodium tungstate solution; And / or, the concentration of sodium tungstate in the diluted sodium tungstate solution is 150 - 250 g / L.

7. The preparation method of the blue nano tungsten oxide according to claim 6, characterized in that, In step S3, the acid solution includes at least one of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution; and / or, H in the acid solution + and the molar ratio of tungsten element in the diluted sodium tungstate solution is 1:(5-7).

8. The preparation method of the blue nano tungsten oxide according to claim 6, characterized in that, In step S3, the first reaction includes: dropping the diluted sodium tungstate solution into the acid solution, adding ethylene glycol, and after a water bath reaction, the tungstic acid precursor solution is obtained; wherein, the volume of the ethylene glycol is 10% - 30% of the total volume of the diluted sodium tungstate solution and the acid solution; the dropping rate of the acid solution is 15 - 40 mL / min, the stirring speed of the water bath reaction is 150 - 350 rpm / min, the temperature of the water bath reaction is 35 - 80 °C, and the time of the water bath reaction is 1 - 3 h.

9. The preparation method of blue nano tungsten oxide according to claim 1, characterized in that, In step S2, the purification includes: carrying out a third reaction between the crude sodium tungstate solution and magnesium sulfate to obtain a reaction solution; after the reaction solution and sodium sulfide carry out a fourth reaction, the pH of the system is adjusted to 2.5 - 3.0 to obtain the purified sodium tungstate solution.

10. The preparation method of the blue nano tungsten oxide according to claim 9, characterized in that, In step S2, the pH of the third reaction is 8.5 - 9.5, and the temperature is 70 - 80 °C; And / or, the pH of the fourth reaction is 10 - 12, and the temperature is 80 - 85 °C.