Rare earth metal directional impurity removal method and prepared rare earth metal

Abstract

The invention relates to the field of rare earth materials, in particular to a directional impurity removal method for rare earth metal and rare earth metal prepared thereof.The directional impurity removal method comprises the steps that tungsten disulfide powder is added into the rare earth metal to be subjected to directional impurity removal according to a preset proportion, and a first mixture is obtained; performing first heating on the first mixture in a vacuum environment to obtain a second mixture; performing second heating on the second mixture until the second mixture is evaporated and then condensed to obtain a third mixture; the third mixture is rare earth metal subjected to directional impurity removal. Tungsten disulfide is added into rare earth metal, a thermal decomposition reaction is carried out under vacuum and high temperature, tungsten and sulfur are released, sulfur makes contact with oxygen element impurities in the floating process to generate SO2 gas to be discharged out of a melt by utilizing the difference of forming energy and binding energy, tungsten is combined with impurities such as iron, nickel and silicon, directional regulation and control of the impurities are achieved, the volatile quality of the impurities is changed, and the mechanical property of the alloy is improved. The purification efficiency and the impurity removal range of the vacuum distillation technology are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of rare earth materials, and specifically to a method for directional removal of impurities from rare earth metals and the rare earth metals obtained therefrom. Background Technology

[0002] Rare earth elements have wide applications in materials science, such as in the manufacture of high-performance magnets, luminescent materials, and catalysts. Due to their high chemical reactivity, rare earth metals inevitably introduce some metallic impurities during the smelting process; these impurities can severely affect the performance of materials. Targeted impurity removal can significantly improve the purity and performance of rare earth metals and their compounds, thereby enhancing the quality and application effectiveness of related materials.

[0003] Currently, the main methods for preparing high-purity rare earth metals include vacuum distillation, zone melting, solid-state electromigration, and solid-phase external gas extraction. Zone melting can effectively remove transition metal impurities, but it has the disadvantages of long purification time and small throughput. Solid-state electromigration can remove interstitial impurities, but a single purification session can take hundreds of hours. Vacuum distillation can remove both low and high vapor pressure impurities, and it has the advantages of simple equipment, large throughput, and minimal environmental impact, leading to its widespread application. It can be used to purify all rare earth metals except La and Ce. However, vacuum distillation also has drawbacks, such as its inability to completely remove impurity elements with vapor pressures similar to or the same as those of rare earth metals, as well as oxygen impurities. Summary of the Invention

[0004] (I) Purpose of the Invention

[0005] The purpose of this invention is to provide a method for targeted impurity removal of rare earth metals, which can directionally control impurity elements and oxygen impurities similar to rare earth metals to improve the purity of rare earth metals, and the rare earth metals obtained by the method.

[0006] (II) Technical Solution

[0007] To address the above problems, this invention provides a method for directional removal of rare earth metals, comprising:

[0008] Tungsten disulfide powder is added to the rare earth metal to be directionally purified in a preset ratio to obtain a first mixture;

[0009] The first mixture is heated in a vacuum environment to obtain a second mixture;

[0010] The second mixture is heated a second time until it evaporates and then condenses to obtain a third mixture.

[0011] The third mixture is rare earth metals after directional impurity removal.

[0012] In another aspect of the present invention, preferably, the preset ratio includes:

[0013] The molar ratio of the amount of tungsten disulfide powder added to the oxygen impurity content in the rare earth metal to be directionally purified is greater than or equal to 1:1.

[0014] In another aspect of the present invention, preferably, the first heating includes:

[0015] The heating temperature of the first heating is 50 to 200°C higher than the melting point of the rare earth metal to be directionally purified;

[0016] Heat until the first mixture is completely melted and keep warm for 0.5 to 2 hours.

[0017] In another aspect of the present invention, preferably,

[0018] The heating temperature of the first heating is 50 to 100°C higher than the melting point of the rare earth metal to be directionally purified;

[0019] The vacuum range of the vacuum environment is 10. -3 ~10 -8 Pa.

[0020] In another aspect of the present invention, preferably, the heating temperature of the second heating is 1500-2000°C, and the heat preservation temperature of the second heating is 8-20 hours.

[0021] In another aspect of the invention, preferably, the condensation utilizes a condenser made of high-purity refractory metal material.

[0022] In another aspect of the present invention, preferably, the rare earth metal to be directionally purified includes any one of Sc, Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0023] In another aspect of the present invention, preferably, the impurity elements targeted for purification include oxygen and transition metal elements; the transition metal elements include iron, nickel, and silicon.

[0024] In another aspect of the present invention, preferably, the purity of the tungsten disulfide powder is greater than or equal to 3N.

[0025] In another aspect of the present invention, preferably, the rare earth metal prepared according to the rare earth metal directional impurity removal method described above has an oxygen impurity content of less than or equal to 100 ppm; an iron impurity content of less than or equal to 2 ppm; a nickel impurity content of less than or equal to 0.5 ppm; and a silicon impurity content of less than or equal to 1 ppm.

[0026] (III) Beneficial Effects

[0027] The above-described technical solution of the present invention has the following beneficial technical effects:

[0028] This invention involves distilling rare earth metals to be purified in a closed environment at sub-atmospheric pressure, separating impurities from the main metal to achieve purification. Tungsten disulfide is added, undergoing a thermal decomposition reaction under vacuum and high temperature, releasing tungsten and sulfur. Utilizing the difference in formation and binding energy, the sulfur, during its ascent, contacts oxygen impurities to generate SO2 gas, which is then discharged from the melt. Tungsten combines with impurities such as iron, nickel, and silicon, achieving targeted control of impurities and altering their volatility. This breaks through the purification limitations of traditional vacuum distillation technology, effectively improving the purification efficiency and impurity removal range of vacuum distillation. Attached Figure Description

[0029] Figure 1 This is an overall flowchart of one embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0031] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] In the description of this invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] A method for targeted impurity removal of rare earth metals is disclosed. Targeted impurity removal of rare earth metals refers to the process of removing specific impurities from rare earth metals. The purpose of this process is to improve the purity of rare earth metals. Impurities in rare earth metals mainly include rare earth impurities and non-rare earth impurities. Rare earth impurities primarily originate from raw materials, such as other rare earth elements. These impurities have a relatively small impact on the properties of rare earth metals, but may still require targeted impurity removal to improve purity. Non-rare earth impurities include non-metallic elements such as C, O, and N, as well as metallic elements such as iron. These impurities may originate from raw materials, preparation, or purification processes, and have a significant impact on the properties of rare earth metals. Figure 1 An overall flowchart of one embodiment of the present invention is shown, as follows: Figure 1 As shown, it includes:

[0035] Tungsten disulfide powder is added to the rare earth metal to be directionally purified in a preset ratio to obtain a first mixture; the specific contents of the rare earth metal to be directionally purified are not limited here, and it can be a light rare earth element or a heavy rare earth element. Optionally, in this embodiment, the rare earth metal to be directionally purified includes any one of Sc, Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0036] The specific impurities to be removed in this embodiment are not limited. Optionally, in this embodiment, the impurity elements to be removed include oxygen and transition metal elements; the transition metal elements include iron, nickel, and silicon. Traditional vacuum distillation utilizes the differences in melting and boiling points, saturated vapor pressures, and evaporation rates between the main metal and impurities. Distillation is performed in a closed environment below atmospheric pressure on the rare earth metal to be purified, separating the impurities from the main metal and achieving purification. This method is commonly used to improve the purity of rare earth metals. This method mainly removes metals with high saturated vapor pressures such as Ca, Mg, and Li, as well as metals with low saturated vapor pressures such as W, Mo, and Ta. However, vacuum distillation has no significant removal effect on impurity elements with saturated vapor pressures similar to those of the main metal. In this embodiment, the impurities to be removed are transition metal elements such as Fe, Ni, and Si, which are similar to rare earth metals, and the O impurity is also targeted.

[0037] The specific content of the tungsten disulfide powder is not limited here. Optionally, in this embodiment, the purity of the tungsten disulfide powder is greater than or equal to 3N. High-purity tungsten disulfide powder itself contains very few impurities, so when mixed with rare earth metals, no additional impurities are introduced, thereby improving the efficiency and effect of impurity removal and helping to reduce the complexity and cost of subsequent purification steps. The particle size of the tungsten disulfide powder is also not limited here. Tungsten disulfide powder with smaller particle size has a larger specific surface area and a larger contact area with rare earth metals, thereby improving the reaction efficiency.

[0038] The specific content of the preset ratio is not limited here. It can be the molar ratio of rare earth metal to tungsten disulfide in the rare earth metal to be targeted for impurity removal, or the mass ratio of the two, etc. Optionally, in this embodiment, the preset ratio includes: the molar ratio of the amount of tungsten disulfide powder added to the oxygen impurity content in the rare earth metal to be targeted for impurity removal is greater than or equal to 1:1. The oxygen impurity content in the rare earth metal can be determined by chemical analysis: the oxygen impurity content is determined by chemical reaction, the rare earth metal sample is reacted with a specific chemical reagent, and the oxygen impurity content is calculated based on the degree of reaction or the amount of product; instrumental analysis: the oxygen impurity content is determined by using professional analytical instruments, for example, an oxygen-nitrogen analyzer can be used to directly measure the oxygen content in rare earth metals, which is usually more accurate and faster; spectroscopic analysis: such as atomic absorption spectrometry (AAS), atomic emission spectrometry (ICP-AES), etc., can quantitatively analyze the content by measuring the absorption or emission spectrum of a specific element, which is also applicable to the determination of oxygen impurities.

[0039] The first mixture is heated in a vacuum environment to obtain a second mixture. The reactor vessel for the first heating is not limited; optionally, it can be a common vacuum resistance furnace such as a vacuum tantalum furnace or a vacuum carbon tube furnace, mainly composed of a vacuum pump, heating element, high-frequency power supply, and control cabinet. Optionally, in this embodiment, a vacuum tantalum furnace is used for the first heating. After the first mixture is placed in the vacuum tantalum furnace, the furnace body is evacuated to a vacuum environment, and the heating power supply is turned on. A large current is generated by the high-frequency power supply and passes through the heating element to heat the first mixture. Heating in a vacuum environment effectively prevents the components in the mixture from reacting with oxygen in the air, which is especially important for easily oxidized rare earth metals. Vacuum treatment ensures that the purity and quality of the material will not decrease due to oxidation during the heating process. The vacuum environment can greatly reduce impurities that may be introduced during heating, such as dust, water vapor, and other gaseous contaminants, helping to maintain the purity of the mixture and reducing potential problems in subsequent processing.

[0040] The specific content of the vacuum environment is not limited here. Optionally, in this embodiment, the vacuum range of the vacuum environment is 10. -3 ~10 -8 Pa;

[0041] The specific content of the first heating is not limited here. Optionally, in this embodiment, the heating temperature of the first heating is 50-200°C higher than the melting point of the rare earth metal to be directionally purified; the first mixture is heated until it is completely melted and held at that temperature for 0.5-2 hours; setting the heating temperature within the range of 50-200°C higher than the melting point of the rare earth metal can ensure that the rare earth metal is completely melted. The first heating condition helps the rare earth metal to form a liquid state, thereby improving the separation efficiency between impurities and metal, because the fluidity of the liquid metal helps the diffusion and aggregation of impurities, which is convenient for subsequent purification operations. Heating the first mixture until it is completely melted and holding it at that temperature for 0.5-2 hours can not only ensure that the components in the mixture are fully mixed and reach a thermal equilibrium state, which helps to homogenize the mixture and make the subsequent purification process more uniform and effective; it can also cause the added WS2 to undergo a thermal decomposition reaction. The generated S and W react fully with impurity elements such as O, Fe, Ni, and Si. The generated SO2 gas is discharged from the melt and then discharged by the vacuum system. W forms residues with Fe, Ni, and Si and remains in the crucible.

[0042] Furthermore, the heating temperature of the first heating is 50-100°C higher than the melting point of the rare earth metal to be directionally purified; reducing the upper limit of the heating temperature from 200°C above the melting point to 100°C can significantly reduce energy consumption during the heating process.

[0043] The second mixture is heated a second time until it evaporates and then condenses to obtain a third mixture. The specific details of the second heating are not limited here. After the rare earth metals are completely melted during the first heating process and held at that temperature for 0.5–2 hours, the heating power is increased, and the temperature is further raised to 1500–2000°C and held for 8–20 hours. This allows the rare earth metals to be selectively purified to evaporate and condense on a condenser. Through high-temperature evaporation and condensation, impurities in the rare earth metals can be separated more effectively, thereby improving the purity of the metals. At the high temperature of 1500–2000°C, impurity elements in the rare earth metals may have different vapor pressures; therefore, the separation of impurities can be achieved by controlling the evaporation and condensation conditions. The evaporation and condensation process ensures that most of the rare earth metals are separated from the raw materials in vapor form and then re-condensed into solids on the condenser, thus achieving efficient recovery of rare earth metals. Compared with traditional chemical purification methods, the evaporation and condensation method reduces the use of chemical reagents, thereby reducing environmental pollution. At the same time, since this method mainly relies on physical processes, energy consumption is relatively low. Optionally, in this embodiment, the condensation utilizes a condenser made of high-purity refractory metal material. Further, the high-purity refractory metal material is tantalum, and the condenser is a cylindrical condenser. Tantalum is a highly corrosion-resistant metal that remains stable in high-temperature and corrosive environments. During the evaporation and condensation of rare earth metals, the condenser can operate stably for extended periods without being affected by corrosion, thus maintaining the condensation effect and the purity of the condensate. Tantalum also has excellent thermal conductivity, which helps to quickly and effectively condense the evaporated rare earth metals during the condensation process. Efficient condensation improves production efficiency and reduces the loss of rare earth metals during condensation. Using high-purity tantalum material to make the condenser avoids introducing new impurities during condensation, thereby ensuring the high purity of the condensed rare earth metals. The cylindrical condenser provides a larger condensation area, allowing the evaporated rare earth metals to condense more evenly on the condenser surface. Furthermore, the cylindrical design also helps improve condensation efficiency because heat can be transferred from the evaporation source to the condenser surface more quickly.

[0044] The surface of the third mixture is rare earth metal after directional impurity removal. Further, after the third mixture cools, it is removed together with the condenser, and the edge tantalum sheets are removed by machining. The tantalum at the contact surface between the third mixture and the condenser is also removed. Optionally, a predetermined size, such as 0.1 mm, can be removed by machining to obtain high-purity rare earth metal after directional impurity removal.

[0045] The rare earth metal prepared according to the method for directional removal of rare earth metals as described above has an oxygen impurity content of less than or equal to 100 ppm; an iron impurity content of less than or equal to 2 ppm; a nickel impurity content of less than or equal to 0.5 ppm; and a silicon impurity content of less than or equal to 1 ppm.

[0046] In this embodiment, tungsten disulfide is added to the traditional vacuum distillation process, resulting in a thermal decomposition reaction under vacuum and high temperature, releasing W and S. Utilizing the difference in formation energy and binding energy, S comes into contact with O impurities during its ascent to generate SO2 gas, which is then discharged from the melt. W combines with impurities such as Fe, Ni, and Si, achieving targeted control of impurities and altering their volatility. This breaks through the purification limitations of traditional vacuum distillation technology, effectively improving the purification efficiency and impurity removal range of vacuum distillation. It enables the large-scale, short-process preparation of various high-purity rare earth metals.

[0047] Example 1-1

[0048] Weigh out the rare earth metal Sc and tungsten disulfide powder to be directionally purified according to a preset ratio. The initial purity of the rare earth metal Sc is 4N, and the purity of the tungsten disulfide powder is 3N. The preset ratio is WS2:O = 1:1. Using a vacuum tantalum sheet furnace, add the rare earth metal to be directionally purified into a crucible, spread both evenly at the bottom of the crucible, and evacuate to 10°C. -3 Pa; turn on the heating power and heat to about 50°C above the melting point of rare earth metals and hold for 2 hours; increase the heating power and heat to 1600°C and hold for 12 hours; then turn off the heating power and allow the volatiles to cool naturally to room temperature, remove them together with the condenser, remove the edge tantalum sheets, and obtain the purified high-purity rare earth metal Sc.

[0049] Examples 1-2

[0050] WS2:O = 2:1, and the other conditions are the same as in Example 1-1.

[0051] Examples 1-3

[0052] WS2:O = 1.5:1, and the other conditions are the same as in Example 1-1.

[0053] Examples 1-4

[0054] WS2:O = 3:1, and the remaining conditions are the same as in Example 1-1.

[0055] Examples 1-5

[0056] The first heating temperature is 100°C above the melting point, the second heating temperature is 1700°C, the second heating time is 20 hours, and the vacuum degree is 10. -4 The remaining conditions are the same as in Example 1-1.

[0057] Examples 1-6

[0058] The first heating temperature is 200°C above the melting point, and the first heating time is 1 hour. The second heating temperature is 2000°C, and the second heating time is 8 hours. The vacuum degree is 10. -8 The remaining conditions are the same as in Example 1-1.

[0059] Example 2-1

[0060] Weigh out the rare earth metal Ho and tungsten disulfide powder to be directionally purified according to a preset ratio. The initial purity of rare earth metal Ho is 4N1, and the purity of tungsten disulfide powder is 4N. The preset ratio is WS2:O = 2:1. In a vacuum tantalum sheet furnace, add the rare earth metal to be directionally purified into a crucible, spread both evenly at the bottom of the crucible, and evacuate to 10°C. -8 Pa; turn on the heating power and heat to about 100°C above the melting point of rare earth metals, and hold for 0.8 hours; increase the heating power and heat to 1650°C, and hold for 10 hours; then turn off the heating power and allow the volatiles to cool naturally to room temperature, remove them together with the condenser, remove the edge tantalum sheets, and obtain the purified high-purity rare earth metal Ho.

[0061] Example 2-2

[0062] WS2:O = 1.8:1, and the other conditions are the same as in Example 2-1.

[0063] Example 2-3

[0064] WS2:O = 1.2:1, and the other conditions are the same as in Example 2-1.

[0065] Examples 2-4

[0066] WS2:O = 2.5:1, and the other conditions are the same as in Example 2-1.

[0067] Examples 2-5

[0068] The first heating temperature is 50°C above the melting point, and the first heating time is 1.5 hours. The second heating temperature is 1750°C, and the second heating time is 18 hours. The vacuum degree is 10. -5 The remaining conditions are the same as in Example 2-1.

[0069] Examples 2-6

[0070] The first heating temperature is 200°C above the melting point, and the first heating time is 1.8 hours. The second heating temperature is 1850°C, and the second heating time is 16 hours. The vacuum degree is 10. -6 The remaining conditions are the same as in Example 2-1.

[0071] Example 3-1

[0072] The rare earth metal Pr and tungsten disulfide powder to be directionally purified are weighed according to a preset ratio. The initial purity of the rare earth metal Pr is 3N8, and the purity of the tungsten disulfide powder is 3N8. The preset ratio is WS2:O = 1.5:1. Using a vacuum tantalum sheet furnace, the rare earth metal to be directionally purified is added to a crucible, and both are spread evenly at the bottom of the crucible. The furnace is then evacuated to 10°C.-5 Pa; turn on the heating power and heat to about 200°C above the melting point of rare earth metals, and hold for 0.8 hours; increase the heating power and heat to 1900°C, and hold for 8 hours; then turn off the heating power and allow the volatiles to cool naturally to room temperature, remove them together with the condenser, remove the edge tantalum sheets, and obtain the purified high-purity rare earth metal Pr.

[0073] Example 3-2

[0074] WS2:O = 1.3:1, and the other conditions are the same as in Example 3-1.

[0075] Example 3-3

[0076] WS2:O = 2.6:1, and the other conditions are the same as in Example 3-1.

[0077] Examples 3-4

[0078] WS2:O = 3.5:1, and the other conditions are the same as in Example 3-1.

[0079] Examples 3-5

[0080] The first heating temperature is 80°C above the melting point, and the first heating time is 1.2 hours. The second heating temperature is 1850°C, and the second heating time is 13 hours. The vacuum degree is 10. -6 The remaining conditions are the same as in Example 3-1.

[0081] Examples 3-6

[0082] The first heating temperature is 180°C above the melting point, and the first heating time is 1.6 hours. The second heating temperature is 1950°C, and the second heating time is 17 hours. The vacuum degree is 10. -3 The remaining conditions are the same as in Example 3-1.

[0083] Example 4-1

[0084] The rare earth metal Nd and tungsten disulfide powder to be directionally purified are weighed according to a preset ratio. The initial purity of the rare earth metal Nd is 4N, and the purity of the tungsten disulfide powder is 4N. The preset ratio is WS2:O = 2.3:1. Using a vacuum tantalum sheet furnace, the rare earth metal to be directionally purified is added to a crucible, and both are spread evenly at the bottom of the crucible. The furnace is then evacuated to 10°C. -6 Pa; turn on the heating power and heat to about 160°C above the melting point of rare earth metals, and hold for 0.7 hours; increase the heating power and heat to 1600°C and hold for 14 hours; then turn off the heating power and allow the volatiles to cool naturally to room temperature, remove them together with the condenser, remove the edge tantalum sheets, and obtain the purified high-purity rare earth metal Nd.

[0085] Example 4-2

[0086] The initial purity of rare earth metal Nd was 4N1, and the other conditions were the same as in Example 4-1.

[0087] Example 4-3

[0088] The initial purity of rare earth metal Nd was 3N8, and the other conditions were the same as in Example 4-1.

[0089] Example 5-1

[0090] The rare earth metal Yb and tungsten disulfide powder to be directionally purified were weighed according to a preset ratio. The initial purity of the rare earth metal Yb was 3N9, and the purity of the tungsten disulfide powder was 4N1. The preset ratio was WS2:O = 2.6:1. Using a vacuum tantalum sheet furnace, the rare earth metal to be directionally purified was added to a crucible, and both were spread evenly at the bottom of the crucible. The furnace was then evacuated to 10°C. -4 Pa; turn on the heating power and heat to about 120°C above the melting point of rare earth metals, and hold for 1.5 hours; increase the heating power and heat to 1500°C, and hold for 16 hours; then turn off the heating power and allow the volatiles to cool naturally to room temperature, remove them together with the condenser, remove the edge tantalum sheets, and obtain the purified high-purity rare earth metal Yb.

[0091] Example 5-2

[0092] The initial purity of rare earth metal Yb was 3N6, and the other conditions were the same as in Example 5-1.

[0093] Example 5-3

[0094] The initial purity of rare earth metal Yb was 4N, and the other conditions were the same as in Example 5-1.

[0095] Example 6

[0096] The rare earth metal Gd and tungsten disulfide powder to be directionally purified were weighed according to a preset ratio. The initial purity of rare earth metal Gd was 3N8, and the purity of tungsten disulfide powder was 4N. The preset ratio was WS2:O = 3:1. Using a vacuum tantalum sheet furnace, the rare earth metal to be directionally purified was added to a crucible, and both were spread evenly at the bottom of the crucible. The furnace was then evacuated to a vacuum of 7×10⁻⁶. -6 Pa; turn on the heating power and heat to about 80°C above the melting point of rare earth metals and hold for 1.6 hours; increase the heating power and heat to 1800°C and hold for 15 hours; then turn off the heating power and allow the volatiles to cool naturally to room temperature, remove them together with the condenser, remove the edge tantalum sheets, and obtain the purified high-purity rare earth metal Gd.

[0097] Example 7

[0098] The initial purity of rare earth metal Y is 4N, and the other conditions are shown in Table 1.

[0099] Example 8

[0100] The initial purity of rare earth metal Sm is 4N1, and the other conditions are shown in Table 1.

[0101] Example 9

[0102] The initial purity of rare earth metal Eu was 4N, and the other conditions are shown in Table 1.

[0103] Example 10

[0104] The initial purity of rare earth metal Tb was 3N8, and the other conditions are shown in Table 1.

[0105] Example 11

[0106] The initial purity of rare earth metal Dy was 4N1, and the other conditions are shown in Table 1.

[0107] Example 12

[0108] The initial purity of rare earth metal Er was 3N9, and the other conditions are shown in Table 1.

[0109] Example 13

[0110] The initial purity of rare earth metal Tm is 4N1, and the other conditions are shown in Table 1.

[0111] Example 14

[0112] The initial purity of rare earth metal Lu was 4N, and the other conditions are shown in Table 1.

[0113] The metals after directional purification in Examples 1-1 to 14 were sampled and analyzed by glow discharge mass spectrometry (GDMS). The corresponding impurity contents in the rare earth metals of Examples 1-1 to 14 are shown in Table 1 below. Table 1 shows the purity and impurity content of the rare earth metals before and after directional purification in Examples 1-1 to 14.

[0114] Table 1. Purity and impurity content of rare earth metals before and after directional purification in Examples 1-1 to 14

[0115]

[0116]

[0117] As shown in Table 1, the comparisons of Examples 1-1 to 1-4, Examples 2-1 to 2-4, and Examples 3-1 to 3-4 show that as the amount of tungsten disulfide added increases, the content of impurities such as O, Fe, Ni, and Si in the rare earth metal after directional purification gradually decreases. However, the decrease is less than the change in the ratio of tungsten disulfide to oxygen. Therefore, when the molar ratio of the amount of tungsten disulfide powder added to the oxygen impurity content in the rare earth metal to be directionally purified is greater than or equal to 1:1, the content of impurities such as O, Fe, Ni, and Si is low, and the oxygen impurity content after directional purification of the rare earth metal is less than or equal to 100 ppm; the iron impurity content is less than or equal to 2 ppm; the nickel impurity content is less than or equal to 0.5 ppm; and the silicon impurity content is less than or equal to 1 ppm.

[0118] Comparing Examples 1-1 with Examples 1-5 and 1-6, Examples 2-1 with Examples 2-5 and 2-6, and Examples 3-1 with Examples 3-5 and 3-6, it can be seen that with the same amount of tungsten disulfide powder added, the purity of rare earth metals after directional impurity removal under different experimental conditions within the scope of this invention is improved. Moreover, the oxygen impurity content after directional impurity removal of rare earth metals is less than or equal to 100 ppm; the iron impurity content is less than or equal to 2 ppm; the nickel impurity content is less than or equal to 0.5 ppm; and the silicon impurity content is less than or equal to 1 ppm.

[0119] Comparing Examples 4-1 to 4-3 and Examples 5-1 to 5-3, rare earth metals of different purities undergoing directional impurity removal, under the same experimental conditions, exhibited almost identical purity after directional impurity removal. Furthermore, the oxygen impurity content of the rare earth metals after directional impurity removal was less than or equal to 100 ppm; the iron impurity content was less than or equal to 2 ppm; the nickel impurity content was less than or equal to 0.5 ppm; and the silicon impurity content was less than or equal to 1 ppm.

[0120] Comparing Example 6 and Comparative Example 1, and comparing Example 13 and Comparative Example 2, when the molar ratio of the amount of tungsten disulfide powder added to the oxygen impurity content in the rare earth metal to be directionally purified is less than 1:1, the content of impurities such as O, Fe, Ni, and Si in the rare earth metal after directional purification is higher.

[0121] As can be seen from Examples 1-1 to 14, all 14 rare earth metals of the present invention can be directionally purified by the directional purification method of the present invention, and the oxygen impurity content after directional purification is less than or equal to 100 ppm; the iron impurity content is less than or equal to 2 ppm; the nickel impurity content is less than or equal to 0.5 ppm; and the silicon impurity content is less than or equal to 1 ppm.

[0122] In summary, the method for targeted impurity removal of rare earth metals of the present invention involves adding high-purity tungsten disulfide powder, which thermally decomposes into S and W under high temperature and vacuum conditions. These S and W then combine with impurities such as O, Fe, Ni, and Si in the rare earth metal, respectively, altering the volatility of the impurity elements. After purification by vacuum distillation, high-purity rare earth metals are obtained. Compared with traditional vacuum distillation methods, the present invention can remove impurity elements that cannot be removed by traditional methods. The purity of the purified rare earth metal can reach 4N4. Furthermore, this method has a short purification time, simple equipment, and a short process, making it suitable for large-scale preparation of high-purity rare earth metals.

[0123] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

[0124] The present invention has been described above with reference to embodiments thereof. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

[0125] Although embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to the embodiments of the present invention without departing from the spirit and scope of the invention.

[0126] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for directional removal of rare earth metals, characterized in that, include: Tungsten disulfide powder is added to the rare earth metal to be directionally purified in a preset ratio to obtain a first mixture; The first mixture is heated in a vacuum environment to obtain a second mixture; The second mixture is heated a second time until it evaporates and then condenses to obtain a third mixture. The third mixture is rare earth metals after directional impurity removal.

2. The method according to claim 1, characterized in that, The preset ratio includes: the molar ratio of the amount of tungsten disulfide powder added to the oxygen impurity content in the rare earth metal to be directionally purified is greater than or equal to 1:

1.

3. The method according to claim 1, characterized in that, The first heating includes: The heating temperature of the first heating is 50 to 200°C higher than the melting point of the rare earth metal to be directionally purified; Heat until the first mixture is completely melted and keep warm for 0.5 to 2 hours.

4. The method according to claim 3, characterized in that, The heating temperature of the first heating is 50 to 100°C higher than the melting point of the rare earth metal to be directionally purified; The vacuum range of the vacuum environment is 10. -3 ~10 -8 Pa.

5. The method according to claim 1, characterized in that, The heating temperature of the second heating is 1500-2000℃, and the heat preservation temperature of the second heating is 8-20 hours.

6. The method according to claim 1, characterized in that, The condensation utilizes a condenser made of high-purity refractory metal material.

7. The method according to claim 1, characterized in that, The rare earth metals to be targeted for impurity removal include any one of the following rare earth metals: Sc, Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

8. The method according to claim 1, characterized in that, The impurity elements targeted for purification include oxygen and transition metal elements; the transition metal elements include iron, nickel, and silicon.

9. The method according to claim 1, characterized in that, The purity of the tungsten disulfide powder is greater than or equal to 3N.

10. The rare earth metal prepared by the method for directional purification of rare earth metals according to any one of claims 1-9, characterized in that, The rare earth metals have an oxygen impurity content of less than or equal to 100 ppm; an iron impurity content of less than or equal to 2 ppm; a nickel impurity content of less than or equal to 0.5 ppm; and a silicon impurity content of less than or equal to 1 ppm.

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