Method for preparing ultra-pure niobium oxide by deeply removing silicon

Abstract

The invention provides a preparation method of ultra-pure niobium pentoxide, which is stable in process and high in efficiency, and aims to reduce the silicon content to be less than 3ppm and obtain ultra-pure niobium pentoxide through the synergistic effect of directional dissolution silicon removal and precision filtration and washing impurity removal.

Description

Technical Field

[0001] This invention belongs to the field of high-purity inorganic material preparation technology, specifically relating to a method for preparing ultra-high purity niobium pentoxide, and particularly to a deep desiliconization process through directional chemical dissolution. Background Technology

[0002] Niobium pentoxide is a key precursor for the preparation of high-tech materials such as lithium niobate crystals, optical coatings, high-purity targets and special ceramics. These applications have extremely stringent requirements for the purity of niobium pentoxide (especially silicon content), which usually needs to meet the requirements of Nb2O5 ≥ 99.998%, Si ≤ 3ppm, and good crystal structure.

[0003] Currently, the mainstream industrial process for large-scale production of high-purity Nb2O5 is the "sulfuric acid-hydrofluoric acid decomposition → solvent extraction → ammonia water neutralization" route. Although this process can effectively remove most metal impurities, the removal efficiency of silicon impurities (mainly in the form of silicon dioxide and silicates) is limited due to the complex distribution behavior of silicon in the extraction system. According to the "High Purity Niobium Pentoxide" (GB / T 36246-2018) and publicly available industry data, the typical purity of Nb2O5 products produced by this optimized process is between 99.995% and 99.998%, and the silicon content is generally in the range of 5ppm to 10ppm, which is difficult to meet the ultra-high purity requirements of cutting-edge fields such as lithium niobate thin film epitaxial substrates for photonic chips.

[0004] Therefore, developing a purification technology capable of deep and targeted removal of silicon impurities is key to overcoming existing technological bottlenecks and obtaining ultra-high purity niobium pentoxide products. Summary of the Invention

[0005] To address the technical shortcomings of incomplete removal of silicon impurities in existing high-purity niobium pentoxide preparation processes, this invention provides a stable and efficient method for preparing ultra-high-purity niobium pentoxide. This method aims to reduce the silicon content to below 3 ppm and obtain ultra-high-purity niobium pentoxide through the synergistic effect of directional dissolution to remove silicon and precision filtration and washing to remove impurities.

[0006] A method for producing ultra-high purity niobium oxide through deep silicon removal is described below: S1. Raw material pretreatment: The hydrated niobium oxide is dried, crushed and sieved.

[0007] S2. First dissolution and desiliconization: The sieved hydrated niobium oxide is mixed with deionized water to form a slurry, and a calculated amount of GR-grade organic niobium-dissolving reagent for dissolving hydrated niobium oxide is injected to dissolve and filter out silicon.

[0008] S3. Stir and heat to dissolve until the niobium liquid is clear.

[0009] S4. Precision filtration: Filter the above solution with a filter membrane to remove some insoluble silicon impurities and obtain a niobium filtrate that has undergone primary silicon removal.

[0010] S5. Neutralization and preliminary purification with ammonia: The niobium filtrate after the first desiliconization is neutralized with GR-grade ammonia to pH=9, followed by filtration, washing and drying to obtain the preliminary purified niobium material.

[0011] S6. Calcination: The dried niobium material is calcined to 600℃ in stages and held at that temperature for 1 hour.

[0012] S7. Secondary processing: The calcined niobium material is pulverized a second time and then sieved through a standard sieve; S8. Directional dissolution to remove silicon: Niobium oxide after secondary sieving is mixed with deionized water to form a slurry. Fluorine-containing reagent is added to the slurry under stirring to react and convert silicon impurities into soluble substances.

[0013] S9. Solid-liquid separation and washing: After the reaction is complete, solid-liquid separation is performed, the filter cake is collected, and the filter cake is washed with hot water until the pH of the washing solution is 5.0±0.5.

[0014] S10. Dehydration control: Dehydrate the washed filter cake.

[0015] S11. Drying and Crushing: After drying the dehydrated filter cake, crush and sieve it to obtain the intermediate product, namely high-purity hydrated niobium oxide, which can be further processed to obtain ultra-high-purity niobium pentoxide.

[0016] Furthermore, hydrated niobium oxide is dried niobium hydroxide.

[0017] Furthermore, in step S2, the resistivity of the deionized water is ≥18 MΩ·cm.

[0018] Furthermore, in step S2, the fluorine-containing reagent is high-purity hydrofluoric acid or its diluted solution, preferably, the concentration of high-purity hydrofluoric acid is 30% to 50%.

[0019] Furthermore, in step S2, the mass concentration of the slurry is 15% to 25%, the reaction temperature is 30°C to 40°C, and the reaction time is 2 to 4 hours.

[0020] Furthermore, in step S2, the stirring speed is 300 r / min to 400 r / min.

[0021] Furthermore, in step S9, the temperature of the hot water is 45 ℃ to 55 ℃.

[0022] Furthermore, in step S10, the filtrate produced during dehydration is detected using the silicon molybdenum blue spectrophotometric method, with the absence of silicon as the intermediate control standard.

[0023] The beneficial effects of this invention are: 1. High efficiency in deep silicon removal: Innovatively utilizes GR-grade organic niobium-dissolving reagents to dissolve and filter silicon, and takes advantage of the directional dissolution properties of hydrofluoric acid on silicon impurities to convert solid silicon (30 ppm level) that is difficult to remove from the raw material into soluble fluorosilicic acid and remove it with the filtrate. Combined with subsequent precision washing, the silicon impurities in the product are stably reduced to ≤3 ppm, which solves the silicon removal bottleneck of traditional extraction processes.

[0024] 2. The process is well-connected and the purification effect is good: the steps of directional dissolution, precision filtration and hot water washing are closely linked, which not only efficiently removes the target impurity silicon, but also further removes other trace impurities that may be adsorbed in the process, thus achieving comprehensive purification of the product.

[0025] 3. High application value of the product: The ultra-high purity Nb2O5 prepared (purity ≥99.999%, Si≤3ppm) fully meets the extreme requirements of cutting-edge fields such as the preparation of high-end lithium niobate (LiNbO3) crystal thin films, high-purity sputtering targets, and high-performance solid electrolytes, expanding the application boundaries of domestic high-purity niobium compounds.

[0026] 4. Suitable for large-scale production: The method of this invention has clear steps, the main equipment is all conventional chemical equipment, the process conditions are reasonable and controllable, and it is easy to carry out technical transformation and upgrading on the basis of existing high-purity Nb2O5 production lines, and has good prospects for industrial scale-up. Detailed Implementation Example 1

[0027] (1) Raw material preparation: Take industrial grade niobium hydroxide (Nb2O5·5H2O, purity >99.9%, water content about 20%), analyze its silicon content ≤35ppm, place it in an oven and dry it at 200℃ for 6 hours to remove most of the adsorbed water and interstitial water.

[0028] (2) Crushing and sieving: Weigh 100 kg of dried material, crush it with an ultra-micro pulverizer, and then pass it through a 200-mesh standard sieve to obtain fine powder with a particle size ≤74μm.

[0029] (3) First dissolution and desiliconization: Accurately weigh 20 kg of the above fine powder and put it into a reaction tank with stirring and temperature control. Add 80 kg of deionized water with a resistivity of 18 MΩ·cm and start stirring (set the speed to 350 r / min) to make a uniform slurry with a mass concentration of 20%. According to the characteristics of the raw materials, inject the calculated amount of GR grade organic niobium dissolving reagent, heat and stir until the niobium material is completely clear. Use a 0.2 μm precision filter membrane to filter the clear liquid to remove insoluble impurities and obtain the first desiliconized niobium filtrate. Then use GR grade ammonia water to neutralize the first desiliconized niobium filtrate to pH=9, then filter, collect the material, wash it several times with deionized water, and dry it at 120℃ to obtain the preliminarily purified niobium material.

[0030] (4) Calcination and secondary treatment: The dried niobium material is placed in a calcining furnace and heated to 600°C according to the program. It is kept at the temperature for 1 hour. After cooling, the calcined product is crushed twice and sieved through a 200-mesh standard sieve to obtain powder with uniform particle size.

[0031] (5) Directional dissolution to remove silicon: Take 20 kg of the powder after the above secondary treatment and mix it with 80 kg of high-purity deionized water (resistivity ≥ 18 MΩ·cm). Prepare a slurry with a mass concentration of 20% in the reaction tank. Start stirring and set the speed to 350 r / min. Calculate based on the residual silicon content of the raw material and measure 5.2 g of GR grade high-purity hydrofluoric acid with a concentration of 40%. Add it slowly dropwise to the slurry while stirring. Maintain the temperature of the reaction system at 35±2℃ and continue stirring for 3 hours. During this process, hydrofluoric acid reacts with silicon impurities to generate soluble fluorosilicic acid.

[0032] (6) Solid-liquid separation and deep washing: After the reaction, the slurry is filtered to obtain a filter cake. The silica-containing filtrate is treated as waste liquid. The filter cake is transferred to a washing tank and soaked and washed with high-purity deionized water preheated to 50±2℃. The amount of water used each time is about 5 times the volume of the filter cake. The washing is repeated 5 times. After each washing, the washing liquid is separated and its pH value is measured. The pH value of the washing liquid is stable at 5.1 after the 5th washing, which meets the set requirements (pH 5.0±0.5).

[0033] (7) Dehydration control: The washed and qualified filter cake is transferred to a plate and frame filter press for dehydration. The filtrate produced by the filter press is collected and tested by the silicon molybdenum blue spectrophotometric method. If no silicon is detected, the intermediate product is deemed qualified.

[0034] (8) Drying and pulverizing: The qualified filter cake after dehydration is dried to constant weight at 120°C, then pulverized and sieved to obtain high-purity hydrated niobium oxide intermediate. The intermediate is then calcined at high temperature (e.g., 850°C) to obtain ultra-high purity niobium pentoxide product with silicon content ≤3ppm.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for deep desiliconization to produce ultra-high purity niobium oxide, characterized in that: The specific preparation method is as follows: S1. The hydrated niobium oxide is dried, crushed, and sieved; S2. Mix the sieved hydrated niobium oxide with deionized water to make a slurry, inject a calculated amount of GR-grade organic niobium-dissolving reagent to dissolve the hydrated niobium oxide, and filter to remove silicon. S3. Stir and heat to dissolve until the niobium solution is clear; S4. Filter the dissolving solution through the filter membrane to remove some insoluble silicon impurities and obtain a primary silicon-removed niobium filtrate. S5. The silica-niobium removal filtrate is neutralized to pH=9 with GR grade ammonia water, then filtered, washed, and dried. S6. Increase the temperature in stages, calcine the dried niobium material to 600℃, and hold for 1 hour; S7. The calcined niobium material is then pulverized a second time and sieved through a standard sieve; S8. Directional dissolution to remove silicon: The sieved niobium oxide is mixed with deionized water to form a slurry. A reagent is added to the slurry under stirring to react and convert silicon impurities into soluble substances. S9. Solid-liquid separation and washing: After the reaction is complete, solid-liquid separation is performed, the filter cake is collected, and the filter cake is washed with hot water until the pH of the washing solution is 5.0±0.5; S10. Dehydration control: The washed filter cake is dehydrated; S11. Drying and Crushing: After drying the dehydrated filter cake, crush and sieve it to obtain the intermediate product.

2. The method for producing ultra-high purity niobium oxide through deep desiliconization according to claim 1, characterized in that: Hydrated niobium oxide is dried niobium hydroxide, and the resistivity of deionized water in step S2 is ≥18 MΩ·cm.

3. The method for producing ultra-high purity niobium oxide through deep desiliconization according to claim 1, characterized in that: In step S5, the ammonia water in the primary silica-niobium removal filtrate is neutralized to GR grade ammonia water.

4. The method for producing ultra-high purity niobium oxide through deep desiliconization according to claim 1, characterized in that: The reagent in step S8 is high-purity hydrofluoric acid or its diluted solution.

5. The method for producing ultra-high purity niobium oxide through deep desiliconization according to claim 4, characterized in that: The concentration of high-purity hydrofluoric acid is 30% to 50%.

6. The method for producing ultra-high purity niobium oxide through deep desiliconization according to claim 1, characterized in that: The slurry obtained in step S8 has a mass concentration of 15% to 25%, a reaction temperature of 30°C to 40°C, and a reaction time of 2 to 4 hours.

7. The method for producing ultra-high purity niobium oxide through deep desiliconization according to claim 1, characterized in that: The stirring speed in step S3 is 300 r / min to 400 r / min.

8. The method for producing ultra-high purity niobium oxide through deep desiliconization according to claim 1, characterized in that: In step S9, the temperature of the hot water is 45°C to 55°C.

9. The method for producing ultra-high purity niobium oxide through deep desiliconization according to claim 1, characterized in that: In step S10, the filtrate produced during dehydration is detected using the silicon molybdenum blue spectrophotometric method, with the absence of silicon as the intermediate control standard.