Method for removing tungsten element in silicon carbide raw material and silicon carbide powder

Abstract

The invention relates to the technical field of silicon carbide, and discloses a method for removing a tungsten element in a silicon carbide raw material and silicon carbide powder. The method for removing the tungsten element in the silicon carbide raw material comprises the following steps: preparing a leaching agent; mixing a silicon carbide raw material and the leaching agent, and performing leaching reaction to obtain a solid-liquid mixture; carrying out post-treatment on the solid-liquid mixture to obtain silicon carbide powder; wherein the leaching agent comprises a strong oxidant and organic acid. According to the method, selective dissolution of tungsten impurities can be achieved under the mild condition, pollution to the environment is avoided, the requirements for environmental protection and industrial production are met, and the cost is greatly reduced.

Description

Technical Field

[0001] This application relates to the field of silicon carbide technology, specifically to a method for removing tungsten from silicon carbide raw materials and silicon carbide powder. Background Technology

[0002] Currently, silicon carbide, as a third-generation wide-bandgap semiconductor material, possesses excellent properties such as a large bandgap, high thermal conductivity, and fast electron saturation drift velocity, making it promising for applications in high-temperature, high-frequency, high-power electronic devices and optoelectronic devices. The quality of silicon carbide crystals directly affects the performance of electronic devices, and the tungsten (W) impurities in silicon carbide powder, used as a raw material for crystal growth, can severely impact semiconductor device performance. For example, it can lead to increased leakage current and decreased breakdown voltage in semiconductor devices. Therefore, tungsten removal treatment of silicon carbide powder is necessary.

[0003] Methods for removing tungsten from silicon carbide powder mainly include physical separation, chemical dissolution, and high-temperature treatment. Physical separation is suitable for scenarios where the particle size difference between tungsten impurities and silicon carbide powder is large, or where there are differences in density and magnetic properties. However, its effectiveness in removing finely dispersed or solid-solid tungsten impurities is limited. Chemical dissolution includes acid dissolution and alkali dissolution. Traditional acid dissolution often uses a mixture of nitric acid and hydrofluoric acid for tungsten removal. Although this method has high efficiency, hydrofluoric acid is highly corrosive, producing fluoride-containing wastewater that pollutes the environment, and the treatment cost is high. Alkali dissolution requires high temperatures, consumes a lot of energy, and may cause slight corrosion to the silicon carbide powder. Furthermore, high-temperature treatment is energy-intensive and requires sophisticated equipment, making it unsuitable for large-scale industrial production. Therefore, developing a new method for removing tungsten impurities from silicon carbide powder is currently one of the challenges.

[0004] Application content This application aims to at least partially address one of the technical problems in related technologies. Therefore, one objective of this application is to provide a method for removing tungsten from silicon carbide raw materials and silicon carbide powder. The method for removing tungsten from silicon carbide raw materials of this application can achieve selective dissolution of tungsten impurities under mild conditions without causing environmental pollution, meeting the needs of green environmental protection and industrial production, or significantly reducing costs.

[0005] The first aspect of this application proposes a method for removing tungsten from silicon carbide raw materials, comprising: Preparation of the leaching agent; The silicon carbide raw material and the leaching agent are mixed and leached to obtain a solid-liquid mixture. The solid-liquid mixture is then post-processed to obtain silicon carbide powder; The leaching agent comprises a strong oxidant and an organic acid. The organic acid in the leaching agent of this application can ionize hydrogen ions, providing an acidic environment; the strong oxidant exhibits strong oxidizing properties under acidic conditions, capable of oxidizing tungsten impurities (including metallic tungsten, tungsten oxides, tungstates, etc.) in silicon carbide powder into high-valence tungsten ions (W). 6+ The carboxyl group (-COOH) in the organic acid has complexing ability, which can form a stable complex with tungsten ions for subsequent removal. Furthermore, this leaching agent is recyclable, and the organic acids it contains are low-toxicity substances that readily degrade in the natural environment and do not leave long-term residues, making it environmentally friendly.

[0006] In some embodiments of this application, the leaching reaction is carried out under ultrasonic conditions. This helps to enhance the leaching reaction and further improve the tungsten removal efficiency.

[0007] In some embodiments of this application, at least one of the following conditions is satisfied: The ultrasonic power is 300W~400W; The ultrasonic frequency is 25kHz~40kHz; The leaching reaction temperature is 60℃~70℃; The leaching reaction takes 3 to 4 hours. This helps to further improve the tungsten removal efficiency.

[0008] In some embodiments of this application, the formulation of the leaching agent includes: The strong oxidant and the organic acid are mixed at a molar ratio of (1.4~3):1, and deionized water is added and stirred for 5 min~10 min; The strong oxidizing agent includes hydrogen peroxide; The organic acid includes at least one of citric acid, tartaric acid, and malic acid.

[0009] In some embodiments of this application, the mass ratio of the silicon carbide raw material to the leaching agent is 1:(8~10). This ensures that the amount of leaching agent is sufficient to fully coat the silicon carbide raw material and fully contact the tungsten impurities, thereby effectively removing the tungsten impurities from the silicon carbide raw material and ensuring that the tungsten removal effect meets the standards.

[0010] In some embodiments of this application, post-processing of the solid-liquid mixture includes: The solid-liquid mixture is filtered to obtain filter residue and filtrate; The filter residue is washed with water 3-5 times and then dried to obtain the silicon carbide powder. The organic acids in the filtrate are recovered. This helps to obtain silicon carbide powder with low tungsten impurity content. Simultaneously, the recovered organic acids can be recycled.

[0011] In some embodiments of this application, at least one of the following conditions is satisfied: The drying temperature is 80℃~100℃; The drying time is 1 hour to 2 hours; The vacuum degree of the drying process is -0.08MPa to 0.1MPa.

[0012] In some embodiments of this application, the recovery of organic acids from the filtrate includes: passing the filtrate through a cation exchange resin column to collect the organic acids.

[0013] In some embodiments of this application, the removal rate of tungsten in the silicon carbide raw material is ≥95%.

[0014] In a second aspect, this application provides a silicon carbide powder prepared by the aforementioned method. Detailed Implementation

[0015] The embodiments of this application are described in detail below. The embodiments described below are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0016] The first aspect of this application proposes a method for removing tungsten from silicon carbide raw materials, comprising: S10: Preparation of leaching agent.

[0017] In this step, the leaching agent includes a strong oxidant and an organic acid. The organic acid in the leaching agent of this application is a low-toxicity substance that is easily degraded in the natural environment and will not remain in the environment for a long time. Specifically, the leaching agent is obtained by thoroughly mixing the strong oxidant, the organic acid, and deionized water. The mixing method is not limited.

[0018] In some embodiments of this application, the strong oxidant and the organic acid are mixed at a molar ratio of (1.4~3):1, and deionized water is added and stirred for 5 min~10 min to obtain the leaching agent. Specifically, the molar ratio of the strong oxidant and the organic acid can be 1.4:1, 1.6:1, 1.8:1, 2.2:1, 2.51:1, 2.74:1, 2.9:1, 3.0:1, etc. The organic acid is the core component of the leaching agent. A molar ratio within the above range can maintain a stable acidic atmosphere. Combined with the oxidizing effect of the strong oxidant, it can fully promote the leaching reaction of tungsten and avoid incomplete leaching due to insufficient acid.

[0019] In some embodiments of this application, the strong oxidant includes hydrogen peroxide. The mass concentration of hydrogen peroxide is 30% to 50% (specifically, it can be 30%, 40%, 50%, etc.). Organic acids include citric acid, tartaric acid, malic acid, etc. When preparing the leaching agent, the organic acid can be provided in the form of an organic acid solution. Specifically, the organic acid and deionized water can be mixed to prepare an organic acid solution, and the mass concentration of the organic acid in the organic acid solution is 15% to 22% (specifically, it can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, etc.). Thus, the moderate concentrations of the strong oxidant and the organic acid solution allow for a milder and more controllable leaching reaction.

[0020] For example, 15g of citric acid (analytical grade) can be weighed, added to 85g of deionized water, and stirred until completely dissolved to obtain a 15% (w / w) citric acid solution. 20 mL of this citric acid solution can be measured, and 4 mL of 30% (w / w) hydrogen peroxide can be added. The mixture can be stirred for 5 minutes to obtain the leaching agent.

[0021] S20: Mix the silicon carbide raw material and the leaching agent and carry out a leaching reaction to obtain a solid-liquid mixture.

[0022] In this step, silicon carbide raw material with a high tungsten impurity content is added to the leaching agent, and leaching is carried out under ultrasonic and stirring conditions. The mass ratio of silicon carbide raw material to leaching agent is 1:(8~10). Specifically, the mass ratio of silicon carbide raw material to leaching agent can be 1:8, 1:9, 1:10, or any range between two of these. This ensures that the amount of leaching agent is sufficient to fully coat the silicon carbide raw material and fully contact the tungsten impurities, thereby effectively removing the tungsten impurities from the silicon carbide raw material and ensuring that the tungsten removal effect meets the standards.

[0023] The principle of leaching tungsten impurities in the leaching agent is as follows: organic acid solutions can ionize to produce hydrogen ions, providing an acidic environment; hydrogen peroxide has strong oxidizing properties under acidic conditions, which can oxidize tungsten impurities (including metallic tungsten, tungsten oxides, tungstates, etc.) in silicon carbide powder into high-valence tungsten ions (W). 6+ The carboxyl group (-COOH) in organic acids has complexing ability and can form stable complexes with tungsten ions for subsequent removal.

[0024] For example, when the organic acid is citric acid (C6H8O7), its ionization reaction in water is as follows: C6H8O7 C6H7O7 - + H + C6H7O7 - C6H6O7 2- + H + C6H6O72- C6H5O7 3- + H + The oxidation reaction of hydrogen peroxide under acidic conditions, taking the oxidation of metallic tungsten (W) as an example: W + 3H₂O₂ + 3H₂O + = W 6+ + 6H2O. W 6+ With C6H5O7 3- They combine to form a complex W(C6H5O7)2.

[0025] If the tungsten impurity is tungsten trioxide (WO3), although it is a high-valence tungsten oxide, its reaction with organic acids is relatively slow under acidic conditions. The presence of hydrogen peroxide can promote its complexation reaction with organic acids.

[0026] If the tungsten impurity is a tungstate (such as CaWO4), under acidic conditions, hydrogen ions will react with tungstate ions (WO4). 2- The two compounds combine to form tungstic acid (H₂WO₄), which is then further oxidized and activated by hydrogen peroxide, facilitating its complexation with organic acids. The specific reaction is: CaWO₄ + 2H₂O → CaWO₄ + 2H₂O + = Ca 2+ + H2WO4, H2WO4+ H2O2+ C6H8O7= [W (C6H5O7)] - + 2H₂O + 3H + .

[0027] In some embodiments of this application, the leaching reaction is carried out under ultrasonic conditions. The ultrasonic power during leaching is 300W~400W. Specifically, it can be 300W, 320W, 340W, 360W, 380W, 400W, etc. The ultrasonic frequency is 25kHz~40kHz. Specifically, it can be 25kHz, 30kHz, 35kHz, 40kHz, etc. The ultrasonic action can generate a large number of microbubbles in the mixed solution of silicon carbide raw material and leaching agent. These bubbles will grow rapidly, contract and burst under the action of the ultrasonic field, generating local high temperature, high pressure and strong shock waves. This phenomenon is called ultrasonic cavitation effect. The ultrasonic cavitation effect can destroy the diffusion boundary layer on the surface of silicon carbide powder, increase the contact area between the leaching agent and tungsten impurities, improve the mass transfer rate, and thus enhance the leaching reaction. At the same time, ultrasonic vibration can also keep the silicon carbide powder in a good dispersed state in the leaching agent, avoid powder agglomeration, and further improve the tungsten removal efficiency.

[0028] In some embodiments of this application, an intermittent ultrasonic method can be used (working for 5 minutes, then stopping for 1 minute). This ensures tungsten removal efficiency while reducing costs.

[0029] In some embodiments of this application, the ultrasonic temperature is 60°C to 70°C. Specifically, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, etc. These temperatures can increase the leaching reaction rate, thereby helping to shorten the leaching time. However, excessively high temperatures can cause hydrogen peroxide to decompose, reducing its oxidizing capacity; therefore, the temperature is controlled at 60-70°C.

[0030] In some embodiments of this application, the leaching time is 3 to 4 hours. Specifically, it can be 3 hours, 3.5 hours, 4 hours, etc. This basically ensures sufficient leaching.

[0031] In some embodiments of this application, the leaching step described above can be repeated multiple times. The specific number of times is not limited. For example, it can be leached once, three times, five times, seven times, etc. Thus, different numbers of cycles can be performed according to actual needs.

[0032] S30: The solid-liquid mixture is post-processed to obtain silicon carbide powder.

[0033] In this step, the solid-liquid mixture after the leaching reaction is completed is filtered to separate filter residue (silicon carbide powder after tungsten removal) and filtrate (containing tungsten complexes, excess organic acid, hydrogen peroxide, etc.). The filter residue is then washed with water and dried to obtain silicon carbide powder with low tungsten impurity content. Simultaneously, the organic acid in the filtrate is recovered and can be recycled.

[0034] In some embodiments of this application, the filter residue is washed with deionized water. Each wash involves adding 3-5 times the volume of the filter residue, stirring thoroughly, and then filtering. This washing process is repeated 3-5 times until the pH of the washing solution reaches 6-7 to remove residual solution adsorbed on the surface of the filter residue. Here, filtration is the process of separating the filter residue (silicon carbide powder) from the filtrate (a solution containing tungsten complexes) using porous media (such as filter cloth or filter paper). Washing uses deionized water to rinse off soluble impurities adsorbed on the surface of the filter residue (such as residual tungsten complexes, organic acids, hydrogen peroxide, etc.), improving the purity of the silicon carbide powder. When the pH of the washing solution reaches 6-7, it indicates that the acidic substances on the surface of the filter residue have been largely removed, and washing is complete.

[0035] In some embodiments of this application, the washed filter residue is dried at a temperature of 80°C to 100°C (specifically, it can be 80°C, 85°C, 90°C, 100°C, etc.) for a time of 1 hour to 2 hours (specifically, it can be 1 hour, 1.5 hours, 2 hours, etc.). The above drying temperature and time can essentially ensure that the deionized water on the surface of the filter residue, and even the moisture inside the filter residue, is fully removed, resulting in dried silicon carbide powder.

[0036] In some embodiments of this application, the vacuum degree for drying is -0.08 MPa to 0.1 MPa. Specifically, it can be -0.08 MPa, -0.06 MPa, -0.04 MPa, -0.02 MPa, 0.1 MPa, etc. The above vacuum degree range can reduce the gas pressure in the system, significantly lower the boiling point of water, and allow the moisture on the surface and inside of the filter residue to vaporize more quickly, thus shortening the drying time.

[0037] In some embodiments of this application, the recovery of organic acids from the filtrate is achieved by passing the filtrate through a cation exchange resin column. The cation exchange resin has the ability to exchange cations and its surface contains dissociable cations (such as H+). + Na + When the filtrate passes through the resin column, the metal cations in the filtrate (such as W...) 6+ The cation exchange resin reacts with cations on the resin surface and is adsorbed onto the resin. Organic acid molecules (such as citric acid molecules), being neutral or negatively charged, do not react with the cation exchange resin, thus separating organic acids from metal ions and achieving the goal of organic acid recovery. The recovered organic acid solution contains a certain amount of organic acid; after adding appropriate amounts of organic acid and hydrogen peroxide, it can be reused, reducing both costs and wastewater discharge.

[0038] The chemical formula for the exchange reaction mentioned above can be represented as: 6R-H + W 6+ =R6-W + 6H + In this context, cation exchange resin is represented by RH (R stands for resin skeleton).

[0039] For example, when passing the filtrate through a cation exchange resin column, the flow rate of the filtrate is controlled at 1 BV / h to 2 BV / h (BV is the resin column volume). The cation exchange resin adsorbs metal ions (such as W) in the filtrate. 6+ (Potentially other metal impurities, such as ions), while the organic acid passes through the resin column into the collection container. The collected organic acid solution can be returned to the leaching agent preparation step, and after adding appropriate amounts of organic acid and hydrogen peroxide according to the new leaching agent preparation ratio, it can be used again as a leaching agent.

[0040] In some embodiments of this application, the cation exchange resin column that has adsorbed metal ions can also be regenerated. Specifically, the cation exchange resin can be eluted with dilute hydrochloric acid solution to remove the adsorbed metal ions, and the metal ions can be recovered and reused; then the resin column is rinsed sequentially with dilute sulfuric acid (H2SO4) and deionized water to obtain a regenerated cation exchange resin column.

[0041] In the above text, the reaction of elution with dilute hydrochloric acid (HCl) during resin regeneration can be represented as: R6-W + 6HCl = 6R-Cl + H6WO6 (tungstic acid); the reaction of rinsing with dilute sulfuric acid (H2SO4) can be represented as: 2R-Cl (chlorinated resin) + H2SO4 → 2R-H (restored to the initial H) + (Resin) + 2HCl. Finally, rinse with deionized water to remove the HCl from the resin surface.

[0042] In some embodiments of this application, the recovery rate of the organic acid solution is as high as 80% or more. This helps to greatly reduce costs.

[0043] In some embodiments of this application, the method for removing tungsten impurities described above is used to achieve a tungsten removal rate of ≥95% in the silicon carbide raw material.

[0044] In some embodiments of this application, the method for removing tungsten impurities described herein can effectively reduce costs. For example, leaching 10 g of SiC raw material requires 1.5 g of citric acid, and 150 kg of citric acid is needed per ton. At 10 yuan / kg, the cost of citric acid is 1500 yuan / ton. However, the recovery rate of the organic acid solution is over 80%, and based on this 80% recovery rate, the cost can be reduced by approximately 80%.

[0045] In some embodiments of this application, the method for removing tungsten impurities described herein can effectively reduce the discharge of waste liquid.

[0046] In a second aspect, this application discloses a silicon carbide powder prepared by the aforementioned method. Consequently, the silicon carbide powder contains extremely low levels of tungsten impurities.

[0047] The method for removing tungsten from silicon carbide raw materials in this application has at least the following beneficial effects: 1. Efficiency meets standards: Tungsten removal rate is 95%~96.5%, meeting the purity requirements of high-end SiC powder; 2. Green and environmentally friendly: No fluorine pollution, organic acid recycling rate of over 80%, and significant reduction in chemical oxygen demand (COD) of waste liquid; 3. Controllable cost: The cost per ton is only 160-180 yuan, which is far lower than that of traditional and non-recycling processes. The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0048] Example 1 The method for removing tungsten from silicon carbide raw materials according to this application is as follows: Preparation of leaching agent: Take 15 g of citric acid (analytical grade), add 85 g of deionized water, stir until completely dissolved to obtain a citric acid solution with a mass concentration of 15%; (according to the volume ratio of hydrogen peroxide to organic acid solution of 1:5) measure 20 mL of the citric acid solution, add 4 mL of hydrogen peroxide with a mass concentration of 30%, stir for 5 minutes to obtain the leaching agent. Ultrasonic-assisted leaching: Weigh 10g of SiC powder with an initial tungsten content of 500 ppm, add 80 mL of leaching agent (solid-liquid ratio 1:8), stir and disperse, then transfer to an ultrasonic reaction tank. Set the ultrasonic power to 300 W and the ultrasonic frequency to 25 kHz, and use intermittent ultrasound (working for 5 min and stopping for 1 min) to stir and leach at 60 ℃ for 4 hours. Solid-liquid separation and washing: After the reaction was completed, the residue and filtrate were obtained by filtration through a 0.22 μm filter membrane. The residue was washed four times with deionized water (each time adding approximately five times the volume of the residue) until the pH of the washing solution was 6. The residue was dried at 80°C for 2 hours under a vacuum of -0.08 MPa.

[0049] Example 2 Similar to Example 1, the main difference is that the citric acid solution in the leaching agent partially uses the organic acid recovered in Example 1. Specifically, the final filtrate from Example 1 is passed through a 732 type cation exchange resin column at a flow rate of 1 BV / h, and the permeate (i.e., the organic acid solution) is collected; the test shows that the citric acid concentration in the permeate is 12%. An appropriate amount of citric acid is added until the organic acid mass concentration is 15%, and a new leaching agent is prepared according to the same hydrogen peroxide ratio. All other processes are consistent with Example 1.

[0050] Example 3 Preparation of leaching agent: Weigh 22 g of tartaric acid, add 78 g of deionized water, and stir until completely dissolved to obtain a tartaric acid solution with a mass concentration of 22%; (according to the volume ratio of hydrogen peroxide to organic acid solution of 1:3) Measure 20 mL of the tartaric acid solution, add 6.7 mL of hydrogen peroxide with a mass concentration of 30%, and stir for 10 minutes to obtain the leaching agent. Ultrasonic assisted leaching: Weigh 10 g of SiC powder with an initial tungsten content of 600 ppm, add 100 mL of leaching agent (solid-liquid ratio 1:10), and perform intermittent ultrasonic leaching at 70 °C with an ultrasonic power of 400 W and a frequency of 40 kHz for 3 hours. Solid-liquid separation and washing: After the reaction was completed, the mixture was filtered through a 0.22 μm filter membrane to obtain filter residue and filtrate. The filter residue was washed three times (each time with water equal to three times the volume of the filter residue) until the pH of the washing solution reached 7. The filter residue was dried at 100℃ for 2 hours under a vacuum of -0.08 MPa.

[0051] Example 4 Preparation of leaching agent: Weigh 18 g of malic acid, add 82 g of deionized water, and stir until completely dissolved to obtain a malic acid solution with a mass concentration of 18%; (at a volume ratio of hydrogen peroxide to organic acid solution of 1:5) add 20 mL of 30% hydrogen peroxide to the above malic acid solution, stir for 7 minutes, and obtain the leaching agent. Ultrasonic-assisted leaching: Weigh 10 g of SiC powder with an initial tungsten content of 400 ppm, add 90 mL of leaching agent (solid-liquid ratio 1:9), set the ultrasonic power to 350 W and the ultrasonic frequency to 30 kHz, and leach at 65 ℃ for 3.5 hours. Solid-liquid separation and washing: After the reaction was completed, the residue and filtrate were obtained by filtration through a 0.22 μm filter membrane. The residue was washed four times with deionized water (each time adding approximately five times the volume of the residue) until the pH of the washing solution was 6. The residue was dried at 80°C for 2 hours under a vacuum of -0.08 MPa.

[0052] Example 5 Same as Example 1, the main difference being that there is no ultrasonic assistance during leaching; The specific leaching conditions were: constant temperature stirring at 60 ℃ for 4 hours.

[0053] Comparative Example 1 Same as Example 1, the main difference being that the leachate does not contain hydrogen peroxide.

[0054] Detection methods Tungsten content: Tested using inductively coupled plasma mass spectrometry (ICP-MS).

[0055] Test results Table 1 shows the tungsten removal rates of Examples 1-5 and Comparative Example 1. It can be seen that the method for removing tungsten from silicon carbide raw materials according to this application can effectively remove more than 95% of tungsten impurities. Specifically, the tungsten removal rate of Comparative Example 1 is only 64%, a sharp drop of 31% compared to Example 1. This is because the lack of hydrogen peroxide prevents metallic tungsten and low-valent tungsten oxides (such as WO2) from being oxidized into W2, which can complex with organic acids. 6+ It can only dissolve a small amount of high-valence WO3, proving that the oxidizing power of strong oxidants is a prerequisite for achieving efficient tungsten removal; Example 2 (using recycled organic acid) showed the same tungsten removal rate as Example 1, indicating that the recycled organic acid also has stable performance and does not affect the removal of tungsten. Example 5 showed a tungsten removal rate of 95%, which was slightly lower than that of Example 1. The key issue was that without the ultrasonic cavitation effect, the diffusion boundary layer formed on the surface of the SiC raw material could not be destroyed, the leaching agent did not have sufficient contact with the finely dispersed tungsten impurities, and the reaction rate decreased. This indicates that ultrasonic assistance can improve the tungsten removal efficiency.

[0056] Table 1

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for removing tungsten from silicon carbide raw materials, characterized in that, include: Preparation of the leaching agent; The silicon carbide raw material and the leaching agent are mixed and leached to obtain a solid-liquid mixture. The solid-liquid mixture is then post-processed to obtain silicon carbide powder; The leaching agent includes a strong oxidizing agent and an organic acid.

2. The method according to claim 1, characterized in that, The leaching reaction is carried out under ultrasonic conditions.

3. The method according to claim 2, characterized in that, At least one of the following conditions must be met: The ultrasonic power is 300W~400W; The ultrasonic frequency is 25kHz~40kHz; The leaching reaction temperature is 60℃~70℃; The leaching reaction takes 3 to 4 hours.

4. The method according to claim 1, characterized in that, The leaching agent comprises: The strong oxidant and the organic acid solution are mixed at a molar ratio of (1.4~3):1, and then added to deionized water and stirred for 5 min~10 min. The strong oxidizing agent includes hydrogen peroxide; The organic acid includes at least one of citric acid, tartaric acid, and malic acid.

5. The method according to claim 1, characterized in that, The mass ratio of the silicon carbide raw material to the leaching agent is 1:(8~10).

6. The method according to claim 1, characterized in that, Post-processing of the solid-liquid mixture includes: The solid-liquid mixture is filtered to obtain filter residue and filtrate; The filter residue is washed with water 3-5 times and then dried to obtain the silicon carbide powder. The organic acids in the filtrate are recovered.

7. The method according to claim 6, characterized in that, At least one of the following conditions must be met: The drying temperature is 80℃~100℃; The drying time is 1 hour to 2 hours; The vacuum degree of the drying process is -0.08MPa to 0.1MPa.

8. The method according to claim 6, characterized in that, The step of recovering organic acids from the filtrate includes passing the filtrate through a cation exchange resin column to collect the organic acids.

9. The method according to claim 1, characterized in that, The removal rate of tungsten in the silicon carbide raw material is ≥95%.

10. A silicon carbide powder, characterized in that, It is prepared by the method described in any one of claims 1 to 9.

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