A method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as raw material

Abstract

The present invention provides a method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material, comprising the following steps: adding tellurium dioxide to a hydrochloric acid solution to react and obtain a tellurium tetrachloride solution A; evaporating the tellurium tetrachloride solution A to 10% to 50% of the original volume to obtain a tellurium tetrachloride solution B; adding anhydrous ethanol to the tellurium tetrachloride solution B, stirring and filtering, evaporating the obtained filtrate to dryness, and obtaining tellurium tetrachloride crystals; adding the tellurium tetrachloride crystals to deionized water to form a first suspension, and performing a heat preservation reaction, and separating and obtaining a first precipitate after the heat preservation reaction ends; adjusting the pH value of the first precipitate to obtain a second precipitate; washing and calcining the second precipitate to obtain crystalline tellurium dioxide. The method for preparing crystalline tellurium dioxide of the present invention is simple, and the yield of the obtained crystalline tellurium dioxide product is high, which can reach more than 90%, and the purity reaches more than 99.999%.

Description

Technical Field

[0001] The present invention relates to the field of crystal materials, and particularly to a method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material. Background Art

[0002] Crystalline tellurium dioxide is a newly discovered elemental material with very peculiar physical properties. This material can not only be used to prepare electronic components, but also novel crystalline devices, and a series of special composite materials can be developed.

[0003] The electrical properties of crystalline tellurium dioxide are very excellent. The dielectric constant of this material is lower than that of the metals commonly used in electronics, and it has high isolation performance, which also makes it a conductive material frequently used in high-efficiency batteries. Crystalline tellurium dioxide can also be combined with various metal ions such as tin oxide and aluminum oxide to synthesize various composite materials with special properties, and it also has corrosion resistance and strong durability. The application of crystalline tellurium dioxide in the electronic field is also very extensive. It can be used to prepare capacitors, switches, transistors, and optoelectronic devices, etc. This material can also be applied to circuits to prevent damage to the circuits caused by accidental contact, which is also one of its important uses. In the paper industry, the crystals made of tellurium dioxide can be used to improve the quality of paper. Using these crystals for papermaking can significantly improve the folding strength of the paper, thereby increasing the service life of the product and the quality of the paper, and being favored by many users.

[0004] In summary, crystalline tellurium dioxide has very strong application value. Its appearance has brought changes and improvements to people's lives. How to find a method for preparing crystalline tellurium dioxide with a higher yield on the basis of existing technologies is the research direction for the preparation of crystalline tellurium dioxide. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies, provide a method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material, and solve the technical problem of low yield in the preparation of crystalline tellurium dioxide in the existing technologies.

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

[0007] In a first aspect, the present invention provides a method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material, comprising the following steps: Step 1: Adding tellurium dioxide to a hydrochloric acid solution and reacting to obtain a tellurium tetrachloride solution A; Step 2: Evaporating the tellurium tetrachloride solution A to 10% - 50% of its original volume to obtain a tellurium tetrachloride solution B; adding absolute ethanol to the tellurium tetrachloride solution B, stirring and then filtering, and evaporating the obtained filtrate to dryness to obtain tellurium tetrachloride crystals; Step 3: Adding the tellurium tetrachloride crystals to deionized water to form a first suspension, and performing a heat preservation reaction. After the heat preservation reaction ends, separating to obtain a first precipitate; Step 4: Adjusting the pH value of the first precipitate to obtain a second precipitate; Step 5: Washing and calcining the second precipitate to obtain crystalline tellurium dioxide.

[0008] Compared with the prior art, the beneficial effects of the present invention include:

[0009] The present invention uses tellurium dioxide as a raw material, adds it to a hydrochloric acid solution to prepare a tellurium tetrachloride solution, partially evaporates the obtained tellurium tetrachloride solution, adds absolute ethanol, filters and then evaporates to dryness to obtain tellurium tetrachloride crystals, and then sequentially obtains crystalline tellurium dioxide through hydrolysis, pH adjustment, washing and calcination; among them, the evaporation crystallization step effectively improves the yield of the target product; the method for preparing crystalline tellurium dioxide of the present invention is simple, the yield of the obtained crystalline tellurium dioxide product is high, reaching more than 90%, the utilization rate of raw materials is high, and the cost is effectively reduced. Description of the Drawings

[0010] Figure 1 is the SEM image of the crystalline tellurium dioxide prepared in Example 3 of the present invention. Detailed Embodiments

[0011] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0012] A method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material according to the present invention comprises the following steps:

[0013] Step 1: Acid dissolution: Adding tellurium dioxide to a hydrochloric acid solution and reacting to obtain a tellurium tetrachloride solution A;

[0014] Step 2: Evaporation crystallization: Evaporating the tellurium tetrachloride solution A to 10% - 50% of its original volume to obtain a tellurium tetrachloride solution B; adding absolute ethanol to the tellurium tetrachloride solution B, stirring and then filtering, and evaporating the obtained filtrate to dryness to obtain tellurium tetrachloride crystals;

[0015] Step 3: Hydrolysis: Add tellurium tetrachloride crystals into deionized water to form a first suspension, and carry out a heat preservation reaction. After the heat preservation reaction ends, separate to obtain a first precipitate;

[0016] Step 4: Adjust pH: Adjust the pH value of the first precipitate to obtain a second precipitate;

[0017] Step 5: Wash and calcine: Wash and calcine the second precipitate to obtain crystalline tellurium dioxide.

[0018] Preferably, in Step 1, the mass concentration of the hydrochloric acid solution is 36% - 38%.

[0019] Preferably, in Step 1, the molar ratio of tellurium dioxide to hydrochloric acid in the hydrochloric acid solution is 1:(3.8 - 4.0), and further preferably 1:(3.85 - 3.95); Add the tellurium dioxide raw material into the hydrochloric acid solution, stir for 1 - 2 h and then filter to obtain a tellurium tetrachloride solution.

[0020] Preferably, in Step 2, evaporation and crystallization: Place the tellurium tetrachloride solution in an oil bath at 100 - 120 °C and heat for 1 - 2 h, slowly evaporate to 10% - 50% of the original volume.

[0021] Preferably, in Step 2, the volume ratio of the tellurium tetrachloride solution B to the volume of absolute ethanol is 1:2.

[0022] Preferably, in Step 2, add absolute ethanol into the tellurium tetrachloride solution B, stir for 1 - 2 h and then filter.

[0023] Preferably, in Step 2, place the filtrate in an oil bath at 100 - 120 °C and heat, slowly evaporate to dryness until white tellurium tetrachloride crystals appear.

[0024] Preferably, in Step 3, heat the deionized water to 40 - 50 °C, under the condition that the stirring speed is 200 - 400 r / min, according to the solid-liquid ratio of tellurium tetrachloride crystals to deionized water of 1 g:(50 - 100) mL, add the tellurium tetrachloride crystals into the deionized water to form a first suspension.

[0025] Preferably, in Step 3, the temperature of the heat preservation reaction is 40 - 50 °C, and the time is 1.5 - 2.5 h.

[0026] Preferably, in Step 4, adjusting the pH value specifically includes: Add the first precipitate into deionized water at 30 - 60 °C according to the solid-liquid ratio of 1 g:(3 - 4) mL, stir for 15 - 30 min to form a second suspension, then add ammonia water to the second suspension to adjust the pH value of the second suspension to 5.0 - 7.0, continue to stir and react for 15 - 45 min and then filter to obtain a second precipitate;

[0027] Preferably, in step five, the washing is carried out by washing the second precipitate with deionized water at a solid-liquid ratio of 1:(3-4) multiple times until the pH of the washing liquid > 5.0 and the conductivity < 10 μS / cm.

[0028] Preferably, in step five, the calcination is to dry the washed second precipitate at 200 °C for 2-3 h, and then calcine it in an oxygen atmosphere at 600-680 °C for 8 h with an oxygen flow rate of 1 L / min; crystalline tellurium dioxide can be obtained.

[0029] The main mechanism of action and advantages of the present invention:

[0030] The acid dissolution reaction in step one is a reversible reaction:

[0031] 4HCl + TeO 2 TeCl 4 + 2H 2 O

[0032] Without intervention, the reaction reaches equilibrium after a period of time. The formation of tellurium tetrachloride in the reaction equilibrium is less, and directly carrying out the hydrolysis reaction in step three will result in an unsatisfactory yield of crystalline tellurium dioxide (less than 80%). In the present invention, by evaporation crystallization in step two, heating and evaporation shift the reaction equilibrium to the positive direction. At the same time, taking advantage of the property that tellurium dioxide and its impurities are insoluble in absolute ethanol while tellurium tetrachloride is soluble in absolute ethanol, adding absolute ethanol further facilitates the shift of the reaction equilibrium to the positive direction, greatly improving the formation and purity of tellurium tetrachloride, and ultimately increasing the yield (up to over 90%) and purity (≥99.999%) of crystalline tellurium dioxide.

[0033] The following further elaborates on the present invention through specific examples.

[0034] Example 1

[0035] Step one: Acid dissolution: Add 2.82 mol of tellurium dioxide raw material to 11.00 mol of hydrochloric acid solution, stir for 1.5 h, and then filter to obtain a tellurium tetrachloride solution;

[0036] Step two: Evaporation crystallization: Place the tellurium tetrachloride solution in an oil bath at 110 °C and heat it to slowly evaporate to 50% of the original volume. Prepare materials with a volume ratio of the remaining volume after evaporation to the volume of absolute ethanol of 1:2, add absolute ethanol to the remaining volume solution, stir for 1.5 h, and then filter. Place the filtrate in an oil bath at 110 °C and heat it to slowly evaporate to dryness until white tellurium tetrachloride crystals appear;

[0037] Step 3: Hydrolysis: Heat deionized water to 45°C. Under the condition that the stirring speed is 300 r / min, add tellurium tetrachloride crystals to deionized water according to the solid-liquid ratio of tellurium tetrachloride crystals to deionized water of 1:75 to form a first suspension, and keep the reaction at 45°C for 1.5 - 2.5 h. After the heat preservation is completed, filter to obtain a first precipitate;

[0038] Step 4: Adjust pH: Add the first precipitate to deionized water at 45°C according to the solid-liquid ratio of 1:3.5, stir for 20 min to form a second suspension, then add ammonia water to the second suspension to adjust the pH of the second suspension to 6.0, continue to stir and react for a period of time, and then filter to obtain a second precipitate;

[0039] Step 5: Washing and calcination: Wash the second precipitate with deionized water multiple times according to the solid-liquid ratio of 1:3.5 until the pH of the washing solution > 5.0 and the conductivity < 10 μS / cm; Dry the washed second precipitate at 200°C for 2 h, and then calcine it at 630°C with an oxygen flow rate of 1 L / min for 8 h to obtain crystalline tellurium dioxide.

[0040] Example 2

[0041] Step 1: Acid dissolution: Add 2.82 mol of tellurium dioxide raw material to 11.00 mol of hydrochloric acid solution, stir for 1.5 h, and then filter to obtain a tellurium tetrachloride solution;

[0042] Step 2: Evaporation and crystallization: Place the tellurium tetrachloride solution in an oil bath at 110°C and heat it, slowly evaporate to 40% of the original volume. Prepare materials according to the volume ratio of the remaining volume after evaporation to anhydrous ethanol of 1:2. Add anhydrous ethanol to the remaining volume of the solution, stir for 1.5 h, and then filter. Place the filtrate in an oil bath at 110°C and heat it, slowly evaporate to dryness until white tellurium tetrachloride crystals appear;

[0043] Step 3: Hydrolysis: Heat deionized water to 45°C. Under the condition that the stirring speed is 300 r / min, add tellurium tetrachloride crystals to deionized water according to the solid-liquid ratio of tellurium tetrachloride crystals to deionized water of 1:75 to form a first suspension, and keep the reaction at 45°C for 1.5 - 2.5 h. After the heat preservation is completed, filter to obtain a first precipitate;

[0044] Step 4: Adjust pH: Add the first precipitate to deionized water at 45°C according to the solid-liquid ratio of 1:3.5, stir for 20 min to form a second suspension, then add ammonia water to the second suspension to adjust the pH of the second suspension to 6.0, continue to stir and react for a period of time, and then filter to obtain a second precipitate;

[0045] Step 5: Washing and calcination: Wash the second precipitate with deionized water multiple times according to a solid-liquid ratio of 1:3.5 until the pH of the washing solution > 5.0 and the conductivity < 10 μS / cm; dry the washed second precipitate at 200 °C for 2 h, and then calcine it at 630 °C for 8 h with an oxygen flow rate of 1 L / min to obtain crystalline tellurium dioxide.

[0046] Example 3

[0047] Step 1: Acid dissolution: Add 2.82 mol of tellurium dioxide raw material to 11.00 mol of hydrochloric acid solution, stir for 1.5 h, and then filter to obtain a tellurium tetrachloride solution;

[0048] Step 2: Evaporation and crystallization: Place the tellurium tetrachloride solution in an oil bath at 110 °C and heat it to slowly evaporate to 30% of the original volume. Prepare materials according to a ratio of the remaining volume after evaporation to the volume of absolute ethanol of 1:2. Add absolute ethanol to the remaining volume of the solution, stir for 1.5 h, and then filter. Place the filtrate in an oil bath at 110 °C and heat it to slowly evaporate to dryness until white tellurium tetrachloride crystals appear;

[0049] Step 3: Hydrolysis: Heat deionized water to 45 °C. Under the condition of a stirring speed of 300 r / min, add tellurium tetrachloride crystals to deionized water according to a solid-liquid ratio of 1:75 of tellurium tetrachloride crystals to deionized water to form a first suspension, and keep it warm and react at 45 °C for 1.5 - 2.5 h. After the heat preservation is completed, filter to obtain a first precipitate;

[0050] Step 4: pH adjustment: Add the first precipitate to deionized water at 45 °C according to a solid-liquid ratio of 1:3.5, stir for 20 min to form a second suspension, and then add ammonia water to the second suspension to adjust the pH of the second suspension to 6.0. Continue to stir and react for a period of time, and then filter to obtain a second precipitate;

[0051] Step 5: Washing and calcination: Wash the second precipitate with deionized water multiple times according to a solid-liquid ratio of 1:3.5 until the pH of the washing solution > 5.0 and the conductivity < 10 μS / cm; dry the washed second precipitate at 200 °C for 2 h, and then calcine it at 630 °C for 8 h with an oxygen flow rate of 1 L / min to obtain crystalline tellurium dioxide.

[0052] The tellurium dioxide prepared by the present invention is as Figure 1 shown. It can be seen that the tellurium dioxide powder presents a crystalline structure and the crystal distribution is uniform.

[0053] Example 4

[0054] Step 1: Acid dissolution: Add 2.82 mol of tellurium dioxide raw material to 11.00 mol of hydrochloric acid solution, stir for 1.5 h, and then filter to obtain a tellurium tetrachloride solution;

[0055] Step 2: Evaporative Crystallization: Place the tellurium tetrachloride solution in an oil bath at 110°C and heat it, slowly evaporating until it reaches 20% of its original volume. Prepare materials with a volume ratio of the remaining volume after evaporation to absolute ethanol of 1:2. Add absolute ethanol to the remaining volume of the solution, stir for 1.5 h, then filter. Place the filtrate in an oil bath at 110°C and heat it, slowly evaporating to dryness until white tellurium tetrachloride crystals appear;

[0056] Step 3: Hydrolysis: Heat deionized water to 45°C. Under the condition of a stirring speed of 300 r / min, add tellurium tetrachloride crystals to the deionized water according to a solid-liquid ratio of tellurium tetrachloride crystals to deionized water of 1:75 to form a first suspension, and keep the reaction at 45°C for 1.5 - 2.5 h. After the heat preservation ends, filter to obtain a first precipitate;

[0057] Step 4: Adjust pH: Add the first precipitate to deionized water at 45°C according to a solid-liquid ratio of 1:3.5, stir for 20 min to form a second suspension, then add ammonia water to the second suspension to adjust the pH of the second suspension to 6.0. Continue to stir and react for a period of time, then filter to obtain a second precipitate;

[0058] Step 5: Washing and Calcination: Wash the second precipitate with deionized water multiple times according to a solid-liquid ratio of 1:3.5 until the pH of the washing solution > 5.0 and the conductivity < 10 μS / cm; Dry the washed second precipitate at 200°C for 2 h, and then calcine it at 630°C with an oxygen flow rate of 1 L / min for 8 h to obtain crystalline tellurium dioxide.

[0059] Example 5

[0060] Step 1: Acid Dissolution: Add 2.82 mol of tellurium dioxide raw material to 11.00 mol of hydrochloric acid solution, stir for 1.5 h, and then filter to obtain a tellurium tetrachloride solution;

[0061] Step 2: Evaporative Crystallization: Place the tellurium tetrachloride solution in an oil bath at 110°C and heat it, slowly evaporating until it reaches 10% of its original volume. Prepare materials with a volume ratio of the remaining volume after evaporation to absolute ethanol of 1:2. Add absolute ethanol to the remaining volume of the solution, stir for 1.5 h, then filter. Place the filtrate in an oil bath at 110°C and heat it, slowly evaporating to dryness until white tellurium tetrachloride crystals appear;

[0062] Step 3: Hydrolysis: Heat deionized water to 45°C. Under the condition of a stirring speed of 300 r / min, add tellurium tetrachloride crystals to the deionized water according to a solid-liquid ratio of tellurium tetrachloride crystals to deionized water of 1:75 to form a first suspension, and keep the reaction at 45°C for 1.5 - 2.5 h. After the heat preservation ends, filter to obtain a first precipitate;

[0063] Step 4: Adjust the pH: Add the first precipitate to deionized water at 45°C according to a solid-liquid ratio of 1:3.5, stir for 20 min to form a second suspension, then add ammonia water to the second suspension to adjust the pH of the second suspension to 6.0, continue stirring and reacting for a period of time, and then filter to obtain a second precipitate;

[0064] Step 5: Wash and calcine: Wash the second precipitate with deionized water multiple times according to a solid-liquid ratio of 1:3.5 until the pH of the washing solution > 5.0 and the conductivity < 10 μS / cm; Dry the washed second precipitate at 200°C for 2 h, and then calcine it at 630°C for 8 h with an oxygen flow rate of 1 L / min to obtain crystalline tellurium dioxide.

[0065] Example 6

[0066] Step 1: Acid dissolution: Add 2.82 mol of tellurium dioxide raw material to 11.00 mol of hydrochloric acid solution, stir for 1.5 h, and then filter to obtain a tellurium tetrachloride solution;

[0067] Step 2: Evaporation and crystallization: Heat the tellurium tetrachloride solution in an oil bath at 110°C, slowly evaporate to 30% of the original volume, prepare materials according to a ratio of the remaining volume after evaporation to the volume of absolute ethanol of 1:2, add absolute ethanol to the remaining volume of the solution, stir for 1.5 h, and then filter. Heat the filtrate in an oil bath at 110°C and slowly evaporate to dryness until white tellurium tetrachloride crystals appear;

[0068] Step 3: Hydrolysis: Heat deionized water to 45°C, under the condition of a stirring speed of 300 r / min, add tellurium tetrachloride crystals to deionized water according to a solid-liquid ratio of 1:50 of tellurium tetrachloride crystals to deionized water to form a first suspension, and keep it at 45°C for 1.5 - 2.5 h. After the heat preservation is completed, filter to obtain a first precipitate;

[0069] Step 4: Adjust the pH: Add the first precipitate to deionized water at 30°C according to a solid-liquid ratio of 1:3.5, stir for 20 min to form a second suspension, then add ammonia water to the second suspension to adjust the pH of the second suspension to 6.0, continue stirring and reacting for a period of time, and then filter to obtain a second precipitate;

[0070] Step 5: Wash and calcine: Wash the second precipitate with deionized water multiple times according to a solid-liquid ratio of 1:3.5 until the pH of the washing solution > 5.0 and the conductivity < 10 μS / cm; Dry the washed second precipitate at 200°C for 2 h, and then calcine it at 630°C for 8 h with an oxygen flow rate of 1 L / min to obtain crystalline tellurium dioxide.

[0071] Example 7

[0072] Step 1: Acid dissolution: Add 2.82 mol of tellurium dioxide raw material into 11.00 mol of hydrochloric acid solution, stir for 2.0 h, and then filter to obtain tellurium tetrachloride solution;

[0073] Step 2: Evaporation and crystallization: Place the tellurium tetrachloride solution in an oil bath at 110 °C and heat it, slowly evaporate to 30% of the original volume. Prepare materials with the volume ratio of the remaining volume after evaporation to anhydrous ethanol being 1:2. Add anhydrous ethanol to the remaining volume solution, stir for 1.5 h, and then filter. Place the filtrate in an oil bath at 110 °C and heat it, slowly evaporate to dryness until white tellurium tetrachloride crystals appear;

[0074] Step 3: Hydrolysis: Heat deionized water to 45 °C. Under the condition that the stirring speed is 300 r / min, add tellurium tetrachloride crystals to deionized water according to the solid-liquid ratio of tellurium tetrachloride crystals to deionized water being 1:100 to form a first suspension, and keep the reaction at 45 °C for 1.5 - 2.5 h. After the heat preservation ends, filter to obtain a first precipitate;

[0075] Step 4: Adjust pH: Add the first precipitate to deionized water at 45 °C according to the solid-liquid ratio of 1:3.5, stir for 20 min to form a second suspension, then add ammonia water to the second suspension to adjust the pH of the second suspension to 6.0, continue to stir and react for a period of time, and then filter to obtain a second precipitate;

[0076] Step 5: Washing and calcination: Wash the second precipitate with deionized water multiple times according to the solid-liquid ratio of 1:3.5 until the pH of the washing solution > 5.0 and the conductivity < 10 μS / cm; Dry the washed second precipitate at 200 °C for 2 h, and then calcine it at 630 °C with an oxygen flow rate of 1 L / min for 8 h to obtain crystalline tellurium dioxide.

[0077] Statistical analysis was carried out on the relevant process conditions of the above examples and the yield of the obtained crystalline tellurium dioxide, and the results are shown in Table 1 below.

[0078] Table 1 Relevant process conditions of Examples 1 - 7 and the yield of the obtained crystalline tellurium dioxide

[0079]

[0080] Analyzing Table 1, it can be seen from Examples 1 - 5 above that under the condition that other conditions are fixed, the evaporation ratio of the tellurium tetrachloride solution in Step 2 has an obvious influence on the yield. If the tellurium tetrachloride solution evaporates too much, a large amount of black passivation substances will cover the surface of tellurium tetrachloride, resulting in insufficient crystallization; if the evaporation is too little, crystals will not precipitate from the reaction solution; within a suitable range, as the evaporation volume of the tellurium tetrachloride solution increases, the yield of crystalline tellurium dioxide increases. When the evaporation reaches 30% of the original volume, i.e., Example 3, the yield of the target product is the highest. After that, as the evaporation volume increases, the yield of crystalline tellurium dioxide decreases.

[0081] As can be seen from the above Examples 3, 6, and 7, when other conditions are fixed, the solid-liquid ratio of tellurium tetrachloride crystals to deionized water has an obvious effect on the yield. During the hydrolysis process, when the solid-liquid ratio of tellurium tetrachloride crystals to deionized water is lower than 1:100, the reaction is incomplete, resulting in waste of raw materials; when the solid-liquid ratio is higher than 1:50, the reaction rate is too fast and difficult to control, and the product is prone to agglomeration and caking. Therefore, in the present invention, the preferred solid-liquid ratio of tellurium tetrachloride crystals to deionized water is 1:(50-100).

[0082] At the same time, too high or too low temperature and pH value of deionized water will affect the yield of the product.

[0083] The impurity contents of the crystal-grade tellurium dioxide obtained in Examples 1-7 of the present invention were counted, and the results are shown in Table 2 below.

[0084] Table 2 Impurity Contents of Crystal-Grade Tellurium Dioxide Obtained in Examples 1-7

[0085]

[0086] As can be seen from Table 2, the purity of the crystal-grade tellurium dioxide obtained in the present invention reaches more than 99.999%.

[0087] Table 3 Particle Size Distribution of Examples 1-7

[0088]

[0089] As can be seen from Table 3, for the crystal-grade tellurium dioxide obtained in the present invention, D50 is less than 10 μm.

[0090] Analyzing the above content, it can be seen that the evaporation ratio of tellurium tetrachloride solution, the solid-liquid ratio of tellurium tetrachloride crystals to deionized water, the temperature of deionized water, and the pH value are the key factors for controlling this reaction; through experimental verification, the present invention can control the yield of tellurium dioxide by reasonably controlling factors such as the evaporation ratio, solid-liquid ratio, temperature of deionized water, and pH value during the preparation of crystal-grade tellurium dioxide. The yield of the prepared crystal tellurium dioxide is ≥78%, and the highest can reach 90.11%; the present invention has a high utilization rate of raw materials and further reduces costs.

[0091] The present invention provides a method for efficiently preparing crystal-grade tellurium dioxide using tellurium dioxide as a raw material. By controlling conditions such as the evaporation ratio, solid-liquid ratio, temperature of deionized water, and pH value, the problem of the preparation yield of crystal-grade tellurium dioxide is effectively solved, and a crystal-grade tellurium dioxide product is efficiently prepared.

[0092] The specific embodiments of the present invention described above do not constitute a limitation to the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material, characterized in that: The following steps are involved: Step 1: adding tellurium dioxide into a hydrochloric acid solution to react and prepare a tellurium tetrachloride solution A; Step 2: Evaporate tellurium tetrachloride solution A to 10% to 50% of the original volume to obtain tellurium tetrachloride solution B; add anhydrous ethanol to tellurium tetrachloride solution B, stir and filter, evaporate the obtained filtrate to dryness, and obtain tellurium tetrachloride crystals; The volume ratio of tellurium tetrachloride solution B to anhydrous ethanol is 1:2; Step 3: heating the deionized water to 40-50° C., adding the tellurium tetrachloride crystals to the deionized water at a solid-liquid ratio of 1 g to (50-100) mL of tellurium tetrachloride crystals to deionized water to form a first suspension, and performing a heat preservation reaction. After the heat preservation reaction is completed, separating and obtaining a first precipitate; Step 4: The pH value of the first precipitate is adjusted to obtain a second precipitate; Step 5: The second precipitate is washed and calcined to obtain crystalline tellurium dioxide with a D50 of less than 10 μm.

2. The method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material according to claim 1, characterized in that: In step 1, the molar ratio of tellurium dioxide to hydrochloric acid in the hydrochloric acid solution is 1:(3.8-4.0); the tellurium dioxide raw material is added to the hydrochloric acid solution, stirred for 1-2 hours, and then filtered to obtain a tellurium tetrachloride solution.

3. The method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material according to claim 1, characterized in that: In step 2, evaporation crystallization: the tellurium tetrachloride solution is placed in an oil bath at 100-120° C. and heated, and slowly evaporated to 10%-50% of the original volume.

4. The method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material according to claim 1, characterized in that: In step 2, anhydrous ethanol is added to tellurium tetrachloride solution B, stirred for 1 to 2 hours and then filtered.

5. The method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material according to claim 1, characterized in that: In step 2, the filtrate is heated in an oil bath at 100-120° C. and slowly evaporated to dryness until white tellurium tetrachloride crystals appear.

6. The method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material according to claim 1, characterized in that: In step 3, the temperature of the heat preservation reaction is 40-50° C. and the time is 1.5-2.5 hours.

7. The method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material according to claim 1, characterized in that: In step 4, adjusting the pH value specifically includes: adding the first precipitate to deionized water at 30-60° C. at a solid-liquid ratio of 1 g: (3-4) mL, stirring for 15-30 minutes to form a second suspension, then adding ammonia water to the second suspension to adjust the pH value of the second suspension to 5.0-7.0, continuing to stir the reaction for 15-45 minutes and then filtering to obtain a second precipitate.

8. The method for efficiently preparing crystalline tellurium dioxide using tellurium dioxide as a raw material according to claim 1, characterized in that: In step five, washing is to wash the second precipitate with deionized water for multiple times at a solid-liquid ratio of 1:(3-4) until the pH of the washing liquid is greater than 5.0 and the conductivity is less than 10um / cm; calcination is to dry the washed second precipitate at 200°C for 2-3h, and then calcine it at 600-680°C with oxygen for 8h, with an oxygen flow rate of 1L / min.

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