Method for preparing high-purity metallic niobium by molten salt electrolysis

Abstract

This invention discloses a method for preparing high-purity metallic niobium by molten salt electrolysis, comprising: mixing niobium oxide and a carbonaceous reducing agent in a predetermined ratio, molding the resulting mixture, and sintering it at a predetermined temperature to obtain a niobium-carbon-based solid solution; using the obtained niobium-carbon-based solid solution as the anode and a graphite electrode as the cathode, forming an electrolysis system with a molten salt electrolyte, and performing electrolysis; collecting the cathode deposit to obtain high-purity metallic niobium. The method for preparing high-purity metallic niobium by molten salt electrolyte disclosed in this invention involves mixing niobium oxide and a carbonaceous reducing agent, molding the mixture, sintering it to form a soluble niobium-carbon-based solid solution anode, and then electrolyzing the niobium-carbon-based solid solution with a graphite electrode and a molten salt electrolyte to obtain high-purity metallic niobium. This preparation method has a short process flow, is easy to control, has low preparation cost, and can obtain metallic niobium with a purity of over 99.99%.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical metallurgy technology, specifically relating to a method for preparing high-purity metallic niobium by molten salt electrolysis. Background Technology

[0002] Due to its excellent physicochemical properties, such as good ductility, heat resistance, corrosion resistance, and small thermal neutron capture cross section, metallic niobium is widely used in metallurgy, aerospace, atomic energy, and superconductivity. Because of niobium's applications in metal targets and nanotechnology, high-purity metallic niobium is urgently needed in cutting-edge technology fields.

[0003] Currently, the main industrial methods for producing metallic niobium are carbothermal reduction and aluminothermal reduction. Vacuum carbothermal reduction utilizes the greater affinity of carbon for oxygen than niobium, using carbon as a reducing agent to reduce Nb₂O₅ to produce niobium bars. Its advantages include high product yield (>96%), inexpensive reducing agent, and low production cost. The carbon reduction process for niobium production includes single-stage and two-stage reduction methods. Single-stage reduction is mainly used for producing niobium powder. This method is generally carried out in a vacuum carbon tube furnace, directly reducing Nb₂O₅ with carbon to obtain metallic niobium. The two-stage reduction method involves reacting carbon and Nb₂O₅ to generate NbC, then mixing the carbonized NbC with Nb₂O₅, with Nb₂O₅ generally exceeding the theoretical amount by 1-5%. After shaping, it is reduced in a vacuum carbon tube furnace.

[0004] Thermothermal reduction often employs an external furnace method, yielding niobium-aluminum alloy melt and alumina slag. The reduction smelting reaction takes place in a container without external heating. After the reaction is complete, the container is removed, the product is taken out, and the metal and slag are separated outside the furnace. This method is fast, but the product purity is low, and the aluminum content in niobium is high.

[0005] The nitriding method for producing niobium uses niobium oxide or ferroniobium as raw materials, which first react with ammonia or nitrogen and carbon to form niobium nitride. The niobium nitride is then thermally decomposed into metallic niobium in a vacuum at a temperature of 2103–2373 K. However, this method is energy-intensive and the process is relatively complex, and it has not yet been industrialized on a large scale.

[0006] Currently, molten salt electrolysis uses niobium chloride as a raw material and alkali metal or alkaline earth metal chloride as a molten electrolyte to convert electrical energy into chemical energy, thereby extracting the metal. This method is prone to environmental pollution during chlorination and electrolysis, and the process is complex. Furthermore, niobium chloride readily undergoes disproportionation reactions in the molten salt, significantly reducing electrolysis efficiency and resulting in high energy consumption.

[0007] The FFC method, proposed in 2000 by Professor Fray's team at Cambridge University, is an electro-deoxidation method using TiO2 as the cathode. It boasts advantages such as a short process and simple operation. Deng Liqin et al. successfully achieved the electro-deoxidation of Nb2O5 using the FFC method, but this method suffers from complex deoxidation processes and low electrolysis efficiency. The OS method, proposed in 2002 by Professors Ono and Suzuki of Japan, combines electrochemical electrolysis with thermal reduction of metallic calcium. This method has a simple process and high utilization efficiency of metallic calcium, but the cathode product has a high impurity content. The SOM method utilizes a solid oxygen-permeable membrane to selectively control the ions participating in the reaction, thereby achieving the purpose of electrolytic metal preparation. This method has simple raw material requirements, a short process flow, and fewer byproducts, but it has high requirements for the electrolyte, making it difficult to scale up production. Summary of the Invention

[0008] In view of this, some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, including:

[0009] Niobium oxide and carbonaceous reducing agent are mixed in a set ratio, the resulting mixture is shaped, and sintered at a set temperature to obtain a niobium-carbon-based solid solution;

[0010] Electrolysis was carried out using the obtained niobium-carbon-based solid solution as the anode and the graphite electrode as the cathode, together with the molten salt electrolyte, to form an electrolysis system.

[0011] High-purity metallic niobium was obtained by collecting the cathode deposits.

[0012] Furthermore, in some embodiments of the method for preparing high-purity metallic niobium by molten salt electrolysis, the sintering process of the mixture is carried out in a nitrogen atmosphere, and the sintered product obtained is a niobium carbon nitrogen oxygen solid solution.

[0013] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, wherein the sintering process of the mixture is carried out in an argon atmosphere, and the sintered product is a niobium carbon-oxygen solid solution.

[0014] In some embodiments, the method for preparing high-purity metallic niobium by molten salt electrolysis is disclosed, wherein the molar ratio of niobium oxide to carbonaceous reducing agent is set to 1:3 to 1:6.

[0015] Some embodiments of the method for preparing high-purity metallic niobium by molten salt electrolysis further include a pretreatment step of the molten salt electrolyte, wherein the pretreatment method includes:

[0016] Multiple molten salt electrolytes are mixed in a set ratio to obtain a molten salt electrolyte mixture;

[0017] Dry molten salt electrolyte mixture;

[0018] The molten salt electrolyte mixture is melted to obtain a eutectic salt electrolyte;

[0019] In a molten eutectic salt electrolyte, high-purity molybdenum rod electrodes and graphite rod electrodes are set up, and constant voltage electrolysis is performed to remove impurities. After electrolysis, a molten salt electrolyte for preparing high-purity metallic niobium is obtained.

[0020] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, including a step of pretreating the cathode, the pretreating method comprising:

[0021] The graphite rod electrode was immersed in nitric acid solution, then removed and cleaned.

[0022] The graphite rod electrode was immersed in an organic solvent, then removed and cleaned.

[0023] The cleaned graphite rod electrode is then heated and dried.

[0024] In some embodiments, the method for preparing high-purity metallic niobium by molten salt electrolysis is disclosed, wherein the sintering temperature for obtaining the niobium carbon-based solid solution is set to 1000–1500 °C.

[0025] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, wherein the molten salt electrolyte includes NaCl and KCl, and the molar ratio of NaCl to KCl is 0.8:1 to 1.2:1.

[0026] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, in which the mixture is ball-milled and the resulting mixture is pressurized in a mold.

[0027] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, wherein the niobium oxide is Nb2O5.

[0028] This invention discloses a method for preparing high-purity metallic niobium using molten salt electrolyte. The method involves mixing niobium oxide with a carbonaceous reducing agent, molding the mixture, and then sintering it to form a soluble niobium-carbon-based solid solution anode. The niobium-carbon-based solid solution is then used in an electrolysis system consisting of a graphite electrode and a molten salt electrolyte to obtain high-purity metallic niobium. This method features a short process flow, easy process control, low cost, and the ability to obtain metallic niobium with a purity exceeding 99.99%. Attached Figure Description

[0029] Figure 1 Scanning electron microscope images of solid solution products disclosed in some embodiments;

[0030] Figure 2 XRD patterns of solid solution products disclosed in some embodiments;

[0031] Figure 3 XRD patterns of solid solution products disclosed in some embodiments. Detailed Implementation

[0032] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in these embodiments of the invention, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in these embodiments is merely for describing particular implementations and is not intended to limit the scope of the disclosure of these embodiments.

[0033] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this invention pertain; other experimental methods and technical means not specifically noted in the embodiments of this invention refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0034] The terms “basic” and “approximately” used in this document are to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format in this document are used for convenience and brevity only, and should therefore be flexibly interpreted to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0035] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0036] To better illustrate the content of this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the invention can be practiced even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail, in order to highlight the main points of the invention.

[0037] Without conflict, the technical features disclosed in the embodiments of the present invention can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of the present invention.

[0038] In some embodiments, the method for preparing high-purity metallic niobium by molten salt electrolysis includes:

[0039] Niobium oxide and a carbonaceous reducing agent are mixed in a predetermined ratio, the resulting mixture is shaped, and sintered at a predetermined temperature to obtain a niobium-carbon-based solid solution. Niobium oxide typically refers to oxides of metallic niobium, including niobium pentoxide, niobium dioxide, and niobium monoxide. The carbonaceous reducing agent refers to a reducing agent containing carbon, primarily carbon materials such as graphite, activated carbon, and carbon fibers. During the sintering process, some of the carbonaceous reducing agent partially reduces the niobium oxide, while some of the carbonaceous reducing agent remains in the niobium-carbon-based solid solution.

[0040] Using the obtained niobium-carbon-based solid solution as the anode and a graphite electrode as the cathode, an electrolysis system is formed with a molten salt electrolyte for electrolysis. During electrolysis, the niobium-carbon-based solid solution, as the anode active material, participates in the electrochemical oxidation process. Niobium ions dissolve into the molten salt electrolyte and migrate to the cathode, where they precipitate, forming cathode precipitates. Oxygen ions combine with carbon to form carbon monoxide or carbon dioxide, which are released. The niobium-carbon-based solid solution, participating in the electrode reaction, can also be referred to as a soluble anode. Oxygen ions in the soluble anode react with the remaining carbonaceous reducing agent in the anode to form carbon oxide gas, which is released. Under the influence of the electric field, metallic niobium ions migrate from the anode region to the cathode region, precipitating on the cathode. Since no anode metal sludge is produced, the electrolysis process can be carried out continuously, improving electrolysis efficiency and reducing energy consumption.

[0041] High-purity metallic niobium was obtained by collecting the cathode deposits.

[0042] The main electrode reactions that occur during electrolysis include:

[0043] cathode Nb 4+ +4e - =Nb

[0044] Anode C 2- -4e - +O 2- =CO or C 2- -6e - +2O 2- =CO2

[0045] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, wherein the sintering process of the mixture is carried out in a nitrogen atmosphere, and the sintered product is a niobium carbon-nitrogen-oxygen solid solution. A mixture of niobium oxide and a carbonaceous reducing agent is sintered in a nitrogen atmosphere to obtain a niobium carbon-based solid solution, which is also a niobium carbon-nitrogen-oxygen solid solution.

[0046] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, in which the sintering process of the mixture is carried out in an argon atmosphere, and the obtained sintered product is a niobium carbon-oxygen solid solution. A mixture of niobium oxide and a carbonaceous reducing agent is sintered in an argon atmosphere to obtain a niobium carbon-based solid solution, which is also a niobium carbon-oxygen solid solution.

[0047] In some embodiments, the method for preparing high-purity metallic niobium by molten salt electrolysis is disclosed, wherein the molar ratio of niobium oxide to carbonaceous reducing agent is set to 1:3 to 1:6.

[0048] Some embodiments of the method for preparing high-purity metallic niobium by molten salt electrolysis further include a pretreatment step of the molten salt electrolyte, wherein the pretreatment method includes:

[0049] Multiple molten salt electrolytes are mixed in a set ratio to obtain a molten salt electrolyte mixture;

[0050] Dry molten salt electrolyte mixture;

[0051] The molten salt electrolyte mixture is melted to obtain a eutectic salt electrolyte;

[0052] In a molten eutectic salt electrolyte, high-purity molybdenum rod electrodes and graphite rod electrodes are set up, and constant voltage electrolysis is performed to remove impurities. After electrolysis, a molten salt electrolyte for preparing high-purity metallic niobium is obtained.

[0053] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, including a step of pretreating the cathode, the pretreating method comprising:

[0054] The graphite rod electrode was immersed in nitric acid solution, then removed and cleaned.

[0055] The graphite rod electrode was immersed in an organic solvent, then removed and cleaned.

[0056] The cleaned graphite rod electrode is then heated and dried.

[0057] In some embodiments, the method for preparing high-purity metallic niobium by molten salt electrolysis is disclosed, wherein the sintering temperature for obtaining the niobium carbon-based solid solution is set to 1000–1500 °C.

[0058] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, wherein the molten salt electrolyte includes NaCl and KCl, and the molar ratio of NaCl to KCl is 0.8:1 to 1.2:1.

[0059] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, in which the mixture is ball-milled and the resulting mixture is pressurized in a mold.

[0060] Some embodiments disclose a method for preparing high-purity metallic niobium by molten salt electrolysis, wherein the niobium oxide is Nb₂O₅. The following embodiments further illustrate the technical details.

[0061] Preparation of niobium-carbon-based solid solutions from niobium oxides and carbonaceous reducing agents

[0062] Niobium pentoxide (Nb₂O₅) and graphite were thoroughly mixed at a molar ratio of 1:3 to 1:6, and then sintered at 1200℃ to 1600℃ under an argon atmosphere for 2 to 12 hours with an argon flow rate of 20 to 100 mL / min to obtain a soluble anodic niobium carbon-oxygen solid solution.

[0063] Niobium pentoxide (Nb₂O₅) and graphite were thoroughly mixed at a molar ratio of 1:3 to 1:6, and then sintered at 1200℃ to 1600℃ under a nitrogen atmosphere for 2 to 12 hours with a nitrogen flow rate of 20 to 100 mL / min to obtain a soluble anodic niobium carbon oxygen nitrogen solid solution.

[0064] Niobium pentoxide reacts with carbon to form a niobium carbon-oxygen solid solution. This niobium carbon-oxygen solid solution has a complete crystal lattice structure, with no carbon or oxygen vacancies. The reaction formula is as follows:

[0065] Nb₂O₅ + (4x + 3)C → 2NbC x O 1-x +(2x+3)CO………… (a)

[0066] Or Nb₂O₅ + 7C → 2NbC + 5CO…………(b)

[0067] In order to obtain NbC with different carbon and oxygen contents x O y Solid solution; if the reaction proceeds according to reaction formula (a), the theoretical molar ratio of Nb2O5 and C is generally set to 1:3, 1:4, 1:5, or 1:6; if the reaction proceeds according to reaction formula (b), the product is NbC. Thermodynamic calculations show that the reaction temperature is above 962℃, so the initial temperature is selected between 1000℃ and 1500℃.

[0068] In some embodiments, niobium pentoxide (Nb₂O₅) and graphite were thoroughly mixed at molar ratios of 1:3, 1:4, 1:5, and 1:6, and then sintered at 1500°C under an argon atmosphere for 8 hours with an argon flow rate of 20 mL / min to obtain four niobium carbon-oxygen solid solutions.

[0069] Scanning electron microscope (SEM) images of the four solid solution products at ratios of 1:3, 1:4, 1:5, and 1:6 are shown below. Figure 1 As shown, the XRD pattern is as follows Figure 2 As shown, the carbon, oxygen, and niobium atom contents in each solid solution product were analyzed, and the results are listed in Table 1.

[0070] Table 1. Carbon, oxygen, and niobium atomic content in solid solution products.

[0071]

[0072]

[0073] The detection areas listed in Table 1 correspond to the numerical points in the scanning electron microscope images.

[0074] like Figure 2 The XRD results shown indicate that both NbO2 and NbC phases were present regardless of the carbon content, but the peak shapes of both phases were shifted relative to the standard card, indicating the formation of NbC. x O y After solid solution formation, the lattice parameters of the NbO2 and NbC phases changed. Figure 1 The results in Table 1, along with scanning electron microscopy and energy dispersive spectroscopy analysis, show that when the ratio is 1:5, the sample morphology is a structure of large particles attached to small particles. The Nb content of all particles is higher than the O content, indicating that a complete NbCxOy solid solution has been formed. A more preferred ratio is a molar ratio of niobium pentoxide to carbon of 1:5.

[0075] In some embodiments, niobium pentoxide (Nb₂O₅) and graphite were thoroughly mixed at a molar ratio of 1:4, and then sintered at 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, and 1500℃ under an argon atmosphere for 10 h, with the argon flow rate set at 60 mL / min, to obtain six kinds of niobium carbon-oxygen solid solutions.

[0076] XRD analysis was performed on six niobium carbon-oxygen solid solutions, and the results are as follows: Figure 3 As shown;

[0077] The results show that the XRD diffraction peaks and SEM-EDS indicate that the reaction exhibits a peak shape that is shifted from the characteristic peaks of NbC above 1300℃, suggesting that the product corresponding to this characteristic peak is NbC. x O y .

[0078] Molten salt electrolyte pretreatment

[0079] In some embodiments, in the method for preparing high-purity metallic niobium by molten salt electrolysis, the molten salt electrolyte is pretreated, and then the pretreated electrolyte is used to prepare metallic niobium by electrolysis; the following uses NaCl and KCl as examples to illustrate the process of pretreating the molten salt electrolyte;

[0080] Molten salt pretreatment includes the following steps:

[0081] (1) Mix NaCl and KCl in a molar ratio of 0.8:1 to 1.2:1, place the mixture in a clean and dry container, and dry it in a vacuum environment at 100℃ to 250℃ for 8h to 24h.

[0082] (2) Take out the mixture of NaCl and KCl, weigh it, place it in a corundum crucible, and then place the crucible in an electrolytic furnace. Heat the crucible to 300℃~400℃ and keep it at that temperature for 2~12 hours to ensure that the moisture is completely removed.

[0083] (3) Using high-purity molybdenum rods and graphite rods as working electrodes and counter electrodes respectively, they are placed in molten electrolyte for constant voltage electrolysis. When the current is stable, the electrolysis is stopped, thus completing the molten salt pretreatment and obtaining the molten salt electrolyte for preparing metallic niobium.

[0084] Pretreatment of graphite electrodes

[0085] In some embodiments, the graphite electrode, which serves as the cathode, is pretreated before being used as the anode for preparing metallic niobium. The pretreatment process for the graphite cathode includes:

[0086] (1) Soak the graphite electrode in a 30% nitric acid solution, then remove and clean it.

[0087] (2) The cleaned electrodes are degreased, then cleaned with deionized water and anhydrous ethanol, and finally placed in an oven to dry at 80℃~150℃ for 12~48h.

[0088] Example 1

[0089] In Example 1, the method for preparing high-purity metallic niobium by molten salt electrolysis includes:

[0090] (1) Niobium oxide and carbonaceous reducing agent are mixed in a set ratio, the resulting mixture is shaped and sintered at a set temperature to obtain niobium carbon-based solid solution;

[0091] Specifically, Nb₂O₅ and graphite were weighed at a molar ratio of 1:5 and placed in a ball mill jar. An equal weight of anhydrous ethanol was added to the ball mill jar as a dispersant. ZrO₂ grinding balls with a diameter of 5 mm and a ball-to-material mass ratio of 4:1 were added. The ball mill jar containing the raw materials and grinding balls was placed on a planetary ball mill for ball milling and mixing. The ball milling speed was 180 r / min, rotating forward for 1 hour, stopping for 20 minutes, then rotating in reverse for 1 hour, stopping for 20 minutes, and repeating this process. The total effective ball milling time was 24 hours. After ball milling, the mixed slurry was poured into a beaker and dried at 80℃ for 48 hours to remove ethanol, resulting in a uniformly mixed raw material. The raw material was then pressed into briquettes using a tablet press. The mold material was stainless steel, the pressure was 100 MPa, and the briquettes were round discs with a diameter of 12.5 mm. The mass of each sample was 1.2 ± 0.05 g.

[0092] The pressed sample was placed in an alumina crucible and sintered in a high-temperature sintering furnace at a heating rate of 3–10 °C / min to 1400 °C for 4 h. The protective gas was argon with a flow rate of 50 mL / min, thus obtaining a niobium carbon-oxygen solid solution (NbC). x O y .

[0093] In some embodiments, nitrogen is used as the protective gas at a flow rate of 50 mL / min. The mixture is sintered in a high-temperature sintering furnace at a heating rate of 3–10 °C / min to 1400 °C for 4 hours to obtain a carbon-oxygen-nitrogen solid solution NbC. x O y N z .

[0094] The solid solution obtained after sintering is used as a soluble anode. It is tied to an electrode rod to test its conductivity. The multimeter is set to the shortest range, and the red and black probes are connected to the two ends of the soluble anode to test its conductivity. The conductivity of the soluble anode meets the standard for soluble anodes.

[0095] In this example, Nb₂O₅ is used as the niobium oxide. As an optional embodiment, other niobium oxides with different valence states can be used. In this example, graphite is used as the carbonaceous reducing agent. As an optional embodiment, other forms of carbonaceous reducing agents, such as carbon black, can be used. Typically, in ball milling, the mixing method, milling time, briquette size, and pressure can be adjusted according to actual production needs.

[0096] (2) Molten salt pretreatment

[0097] After mixing NaCl and KCl in a molar ratio of 1:1, place them in a clean, dry container and dry them at 150°C for 8 hours in a vacuum environment.

[0098] The mixture of NaCl and KCl was taken out and placed in a tube furnace and kept at 300°C for 12 hours. Then the temperature was raised to 750°C. During this process, the mixture of NaCl and KCl melted to form molten salt.

[0099] High-purity molybdenum rods and graphite rods were used as working and counter electrodes, respectively. Constant voltage electrolysis was performed in the molten salt. When the current stabilized, it was considered that water and redox-active impurities in the molten salt had been basically removed, and electrochemical testing could be performed. Electrolysis was then stopped, thus completing the molten salt pretreatment and obtaining the molten salt for the preparation of high-purity metallic niobium.

[0100] (3) Cathode pretreatment

[0101] First, immerse the graphite electrode in a 30% nitric acid solution, then remove and clean it.

[0102] The cleaned electrodes were then degreased, rinsed with deionized water and anhydrous ethanol, and finally placed in an oven to dry at 150°C for 48 hours.

[0103] (4) Electrolysis

[0104] The soluble anode and graphite rod counter electrode were inserted into the pretreated molten salt, and controlled voltage electrolytic deposition was performed using an external power supply at a voltage of 2.9V for 6 hours.

[0105] During electrolysis, under the influence of an electric field, the oxygen ions in the oxides in the soluble anode combine with carbon to form carbon monoxide or carbon dioxide, which are then discharged. Meanwhile, the niobium ions enter the molten salt electrolyte and precipitate on the cathode substrate, forming a deposit to obtain high-purity niobium.

[0106] The electrolysis process takes place in a sealed reactor, which is continuously purged with argon gas for atmosphere protection.

[0107] While the reaction is underway, the curve of current change over time during electrolysis is recorded.

[0108] (5) Post-processing of niobium metal products

[0109] The cathode with deposited products was removed from the molten salt electrolyte and cooled. It was then cooled under the protection of high-purity argon gas and washed twice with deionized water and anhydrous ethanol to remove the molten salt adhering to the cathode. The cathode was then separated from the remaining cathode deposits by ultrasonic vibration. Finally, the remaining cathode deposits were washed three times with deionized water and anhydrous ethanol, and the precipitate was collected. The precipitate was placed in a vacuum drying oven and dried to obtain high-purity metallic niobium.

[0110] This invention discloses a method for preparing high-purity metallic niobium using molten salt electrolyte. The method involves mixing niobium oxide with a carbonaceous reducing agent, molding the mixture, and then sintering it to form a soluble niobium-carbon-based solid solution anode. The niobium-carbon-based solid solution is then used in an electrolysis system consisting of a graphite electrode and a molten salt electrolyte to obtain high-purity metallic niobium. This method features a short process flow, easy process control, low cost, and the ability to obtain metallic niobium with a purity exceeding 99.99%.

[0111] The technical solutions and technical details disclosed in the embodiments of this invention are merely illustrative of the inventive concept of this invention and do not constitute a limitation on the technical solutions of the embodiments of this invention. Any conventional changes, substitutions, or combinations made to the technical details disclosed in the embodiments of this invention have the same inventive concept as this invention and are within the protection scope of the claims of this invention.

Claims

1. A method for preparing high-purity metallic niobium by molten salt electrolysis, characterized in that, include: Niobium oxide and carbonaceous reducing agent are mixed in a set ratio, the resulting mixture is shaped, and sintered at a set temperature to obtain a niobium-carbon-based solid solution; wherein, the molar ratio of niobium oxide to carbonaceous reducing agent is set to 1:5; and the sintering temperature is set to 1300-1500℃. Using the obtained niobium-carbon-based solid solution as the anode and a graphite electrode as the cathode, an electrolysis system was formed with a molten salt electrolyte for controlled voltage electrolysis. The molten salt electrolyte consisted of NaCl and KCl, with a molar ratio of NaCl to KCl of 0.8:1 to 1.2:

1. The electrolysis voltage was 2.9V, and the electrolysis time was 6h. The cathode deposit was collected to obtain high-purity metallic niobium with a purity of over 99.99%. The molten salt electrolyte undergoes pretreatment, which includes: mixing multiple molten salt electrolytes in a set ratio to obtain a molten salt electrolyte mixture; drying the molten salt electrolyte mixture in a vacuum environment at 100–150°C for 8–24 hours; placing the molten salt electrolyte mixture in a corundum crucible, then placing the crucible in an electrolytic furnace, heating it to 300–400°C and holding it at that temperature for 2–12 hours to remove moisture; melting the molten salt electrolyte mixture to obtain a eutectic salt electrolyte; setting high-purity molybdenum rod electrodes and graphite rod electrodes in the molten eutectic salt electrolyte, and performing constant voltage electrolysis to remove impurities; after electrolysis, a molten salt electrolyte for preparing high-purity metallic niobium is obtained. The cathode is pretreated by means of: immersing the graphite rod electrode in a 30% nitric acid solution, removing and cleaning it; degreasing the graphite rod electrode, and then cleaning it with deionized water and anhydrous ethanol; and drying the cleaned graphite rod electrode in an oven at 80-150°C for 12-48 hours.

2. The method for preparing high-purity metallic niobium by molten salt electrolysis according to claim 1, characterized in that, The sintering process of the mixture is carried out in a nitrogen atmosphere, and the sintered product is a niobium carbon nitrogen oxygen solid solution.

3. The method for preparing high-purity metallic niobium by molten salt electrolysis according to claim 1, characterized in that, The sintering process of the mixture is carried out in an argon atmosphere, and the sintered product is a niobium carbon-oxygen solid solution.

4. The method for preparing high-purity metallic niobium using molten salt electrolyte according to claim 1, characterized in that, The mixture is ball-milled, and the resulting mixture is then pressed into shape in a mold.

5. The method for preparing high-purity metallic niobium using molten salt electrolyte according to claim 1, characterized in that, The niobium oxide is Nb2O5.

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