Method for improving purity of target metal

Abstract

The present invention relates to a method for improving the purity of a target metal, comprising the steps of: (S10) reacting a fluoride of a target metal with a reducing agent so as to generate a first portion comprising a fluoride of the reducing agent and a second portion comprising the residual reducing agent and the target metal; (S20) separating the first portion and the second portion; and (S30) reacting the second portion, the purity of which is to be improved, with a fluoride of an additional target metal so as to generate a third portion comprising a fluoride of the target metal and a fluoride of the reducing agent and a fourth portion comprising the target metal having increased purity.

Description

Method for improving the purity of target metal

[0001] The present invention relates to a method for improving the purity of a target metal.

[0002] With the recent rapid expansion of the hybrid and electric vehicle markets, demand for permanent magnets, a key component of these vehicles, is also increasing. Permanent magnets are a critical factor in determining the efficiency of electric motors, and those made from Nd-Fe-B (neodymium-iron-boron) alloys are among the most efficient currently available permanent magnets. However, these permanent magnets also present some drawbacks.

[0003] Permanent magnets made solely of light rare earth metals, such as neodymium (Nd) or praseodymium (Pr), suffer from a low Curie temperature. A low Curie temperature can easily lead to loss of magnetism in high-temperature environments, which may limit their use in high-temperature applications such as electric motors. Therefore, materials with a high Curie temperature are required to maintain stable magnetism even at high temperatures.

[0004] To address this, high-coercivity permanent magnets doped with heavy rare earth metals, such as dysprosium (Dy) or terbium (Tb), are primarily used. Heavy rare earth metals have higher Curie temperatures than light rare earth metals, allowing them to maintain their magnetism even at high temperatures. However, heavy rare earth metals are rarer and more expensive than light rare earth metals, a major factor driving up their production costs. This, in turn, increases the manufacturing costs of hybrid and electric vehicles.

[0005] While light rare earth metals are primarily produced through electrolysis and thermal reduction processes, heavy rare earth metals are produced exclusively through thermal reduction processes due to their high melting points. The reducing metals used in thermal reduction processes can introduce impurities into the target metal, reducing the purity of the final product. Therefore, obtaining high-purity heavy rare earth metals requires additional refining processes, which incur additional costs.

[0006] The purpose of the present invention is to provide a method for improving the purity of a target metal.

[0007] The present invention relates to a method for improving the purity of a target metal, comprising the steps of: (S10) reacting a fluoride of the target metal with a reducing agent to produce a first portion containing a fluoride of the reducing agent and a second portion containing residual reducing agent and the target metal; (S20) separating the first portion and the second portion; and (S30) reacting the second portion as a purity-improving target metal object with an additional fluoride of the target metal to produce a third portion containing a fluoride of the target metal and a fluoride of the reducing agent and a fourth portion containing the target metal with increased purity.

[0008] The method may further include a step (S40) of separating the third portion and the fourth portion; a step (S50) of reacting the third portion with an additional reducing agent to produce a fifth portion containing a fluoride of the reducing agent and a sixth portion containing the remaining reducing agent and the target metal; a step (S60) of separating the sixth portion from the fifth portion; and a step (S70) of supplying the sixth portion to the purity improvement target of the step S30.

[0009] The above target metal may include a heavy rare earth element.

[0010] The above heavy rare earth elements may include one or more of Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y.

[0011] The above target metal may include Dy.

[0012] The fluoride of the above target metal may include DyF3.

[0013] The reducing agent may include an alkaline earth metal.

[0014] The above alkaline earth metal may include calcium (Ca).

[0015] In the above step S10, the Ca can be supplied so that the number of moles of the Ca is 0.50 to 0.90 times the number of moles of F.

[0016] The above step S10 may include a step of applying heat to the fluoride of the target metal to convert it into a liquid phase before the reaction; and a step of adding the reducing agent after the liquid phase conversion.

[0017] In the above step S30, the DyF3 can be supplied so that the mole number of Ca is 0.0055 to 0.4000 times the mole number of F.

[0018] The above step S40 may include a step of converting the third part and the fourth part from a liquid state to a solid state; and a step of physically separating the third part and the fourth part in a solid state.

[0019] In the above S50 step, the Ca can be supplied so that the number of moles of the Ca is 0.50 to 0.90 times the number of moles of F of DyF3.

[0020] The above S50 step may further include a step of applying heat to the third portion to convert it into a liquid phase before the reaction; and a step of adding the additional reducing agent after the liquid phase conversion.

[0021] In the above steps S10, S30 and S50, each of the reactions can be performed at 1000°C to 2000°C for 1 to 5 hours.

[0022] It may be characterized in that the above steps S30 to S70 are repeatedly performed at least N (N is an integer) times.

[0023] Through the above repetition, the purity of the high-purity target metal can be characterized as being 99.95 to 99.99%.

[0024] According to the present invention, a method for improving the purity of a target metal is provided.

[0025] Figure 1 is a flowchart showing a method for improving the purity of a target metal according to one embodiment of the present invention.

[0026] Figure 2 is a diagram illustrating a method for improving the purity of a target metal according to one embodiment of the present invention.

[0027] Figure 3 shows the fluoride of the reducing agent produced in the experimental example.

[0028] Figure 4 shows the fluoride of the target metal and the fluoride of the reducing agent and the target metal generated in the experimental example.

[0029] Figure 5 shows the high-purity target metal produced in an experimental example.

[0030] Hereinafter, a method for improving the purity of a target metal according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the positional relationship between each component is explained, in principle, based on the drawings. Furthermore, the drawings may simplify the structure of the invention for convenience of explanation or, if necessary, exaggerate it. Therefore, the present invention is not limited to this, and it is obvious that various devices can be added, modified, or omitted.

[0031] Hereinafter, a method for improving the purity of a target metal will be described, primarily using dysprosium (Dy) as an example. However, the present invention is not limited thereto and can be applied to heavy rare earth elements other than Dy. Here, heavy rare earth elements include Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0032] The fluoride of the target metal may be a fluoride of a heavy rare earth element, and may be selected from, for example, EuF3, GdF3, DyF3, TbF3, HoF3, ErF3, TmF3, YbF3, LuF3 and YF3, but the following description will be given as an example using DyF3.

[0033] The reducing agent may be any alkaline earth metal, but calcium (Ca) is preferably used.

[0034] The reducing agent's fluoride contains CaF2, and at least some of the calcium (Ca) used as the reducing agent is converted to CaF2.

[0035] Hereinafter, a method for improving the purity of a target metal according to an embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a flowchart illustrating a method for improving the purity of a target metal according to an embodiment of the present invention.

[0036] Referring to Figure 1, first, a fluoride of a target metal and a reducing agent are reacted in the reaction space of a reactor to produce a first portion containing a fluoride of the reducing agent and a second portion containing the remaining reducing agent and the target metal. (S10)

[0037] The reaction temperature of step S10 can be selected from, for example, temperatures of 1000 to 2000°C, 1150 to 1950°C, 1200 to 1900°C, 1250 to 1850°C, 1300 to 1800°C, 1350 to 1750°C, 1400 to 1700°C or 1450 to 1650°C, and the reaction time can be 1 to 5 hours or 2 to 4 hours.

[0038] The reaction yields a first liquid portion containing the fluoride (CaF2) of the reducing agent and a second liquid portion containing the remaining reducing agent and the target metal.

[0039] In step S10, Ca can be added so that the mole number of calcium (Ca) in the fluoride (CaF2) of the reducing agent is 0.50 to 0.90 times, 0.60 to 0.80 times, or 0.65 to 0.75 times the mole number of F. Here, Ca is supplied in excess so that DyF3 is completely reduced to Dy through a reduction reaction with Ca.

[0040] In another embodiment, the fluoride of the target metal (DyF3) may be first introduced into the reaction space, heated to convert it into a liquid phase, and then a reducing agent (Ca) may be introduced.

[0041] Next, the first and second parts generated in step S10 are separated. (S20)

[0042] Although not shown, the first and second parts are converted from a liquid state to a solid state, and the first and second parts are physically separated in the solid state. At this time, the first and second parts may be separated by solidifying them in a mold, but this is not limited thereto.

[0043] Thereafter, the second part as the purity-improving target and the fluoride (DyF3) of the additional target metal are reacted to produce a third part containing the fluoride of the target metal and the fluoride of the reducing agent, and a fourth part containing the target metal with increased purity. (S30)

[0044] Referring to Figure 2, the second part as a purity improvement target and the fluoride of the additional target metal are introduced into the reaction space of the reactor and heat is applied to cause a reaction. Here, the reactor may be a different reactor from the S10 step.

[0045] The reaction temperature of the S30 step can be selected from, for example, temperatures of 1000 to 2000°C, 1150 to 1950°C, 1200 to 1900°C, 1250 to 1850°C, 1300 to 1800°C, 1350 to 1750°C, 1400 to 1700°C or 1450 to 1650°C, and the reaction time can be 1 to 5 hours or 2 to 4 hours.

[0046] At step S30, DyF3 can be added so that the mole number of calcium (Ca) is 0.0055 to 0.4000, 0.0060 to 0.3000, 0.0065 to 0.2500, 0.0070 to 0.2000, 0.0075 to 0.0120, or 0.20 to 0.45 times the mole number of F. Here, DyF3 is supplied in excess so that all Ca is converted to CaF2 through the reaction with DyF3.

[0047] Through the reaction, a third liquid portion containing the fluoride of the target metal and the fluoride of the reducing agent and a fourth liquid portion containing the target metal with increased purity are obtained. Here, due to the difference in density, the third portion is located at the upper part of the reaction space, and the fourth portion is located at the lower part.

[0048] Next, separate the third and fourth parts generated in step S30. (S40)

[0049] Although not shown, in step S40, the third and fourth parts are converted from a liquid state to a solid state, and the third and fourth parts are physically separated in the solid state. At this time, the third and fourth parts may be separated by solidifying in a mold, but this is not limited thereto. Here, the purity of the fourth part may be 99.95 to 99.99% or 99.96 to 99.98%.

[0050] After step S40, the third part is reacted with an additional reducing agent to produce a fifth part containing a fluoride of the reducing agent and a sixth part containing the remaining reducing agent and the target metal. (S50)

[0051] The reaction temperature of the S50 step can be selected from, for example, temperatures of 1000 to 2000°C, 1150 to 1950°C, 1200 to 1900°C, 1250 to 1850°C, 1300 to 1800°C, 1350 to 1750°C, 1400 to 1700°C or 1450 to 1650°C, and the reaction time can be 1 to 5 hours or 2 to 4 hours.

[0052] At step S50, calcium (Ca) can be added so that the number of moles is 0.50 to 0.90 times, 0.60 to 0.80 times, or 0.65 to 0.75 times the number of moles of F in DyF3. Here, Ca is supplied in excess so that DyF3 is completely reduced to Dy through a reduction reaction with Ca.

[0053] In another embodiment, the third part may be first introduced into the reaction space, heated to convert it into a liquid phase, and then a reducing agent (Ca) may be introduced.

[0054] After step S50, the sixth part is separated from the fifth part (S60), and the sixth part is supplied as a purity improvement target for step S30 (S70).

[0055] In the method for improving the purity of a target metal according to the present invention, steps S30 to S70 are repeatedly performed at least N times (N is an integer) to obtain a target metal with high purity.

[0056] Hereinafter, a method for improving the purity of a target metal according to the present invention will be described in more detail with reference to specific experimental examples and FIGS. 3 to 5. FIG. 3 shows a fluoride of a reducing agent produced in an experimental example, FIG. 4 shows a fluoride of a target metal produced in an experimental example, a fluoride of a reducing agent, and a target metal, and FIG. 5 shows a high-purity target metal produced in an experimental example. However, the following experimental examples are only a reference for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

[0057] Additionally, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this description is solely for the purpose of effectively describing specific embodiments and is not intended to limit the invention. Furthermore, unless specifically stated in the specification, units for additives represent weight percent.

[0058] [Experimental Example]

[0059] Table 1 below shows the amount and production of the target metal fluoride (DyF3), reducing agent (Ca), and target metal (Dy) and reducing agent fluoride (CaF2) produced through the reaction used in each step.

[0060] Usage GenerationDyF3(g)Ca(g)Dy(g)Dy(g)CaF2(g)S10200.076.7-126.9105.8S30200.0-126.9106.7200.3S50200.376.7-125.3105.5Additional S30200.0-125.3105.4201.0

[0061] The target metal fluoride DyF3 powder was prepared by synthesis from the target metal oxide Dy2O3 (purity 99.5%), and the reducing agent Ca (purity 98%) was purchased and used.

[0062] First, 200.0 g (0.9 mol) of DyF3 powder and 76.7 g (1.9 mol) of Ca were added to the reaction vessel, and a reduction reaction was performed at 1500°C for 2 hours to produce the target metal Dy in liquid form and the fluoride CaF2 of the reducing agent in liquid form. (S10)

[0063] Afterwards, the liquid target metal Dy and the liquid reducing agent fluoride CaF2 generated through the reaction were solidified in a mold and separated. The recovered Dy and CaF2 amounts were confirmed to be 126.9 g and 105.8 g, respectively.

[0064] Next, 126.9 g (0.8 mol) of Dy as a primary purity improvement target and 200.0 g (0.9 mol) of additional target metal fluoride DyF3 were reacted in a reaction vessel at a temperature of 1500°C for 2 hours to produce target metal fluoride DyF3, which was partially mixed with liquid Dy and liquid reducing agent fluoride CaF2. (S30)

[0065] Afterwards, the liquid DyF3-CaF2 containing the fluoride of the target metal and the fluoride of the reducing agent generated through the reaction and the target metal Dy with high purity were solidified in a mold and separated. The primary Dy with high purity recovered through separation was confirmed to be 106.7 g and DyF3-CaF2 was confirmed to be 200.3 g.

[0066] Next, 200.3 g (approximately 0.9 mol) of DyF3-CaF2 containing the fluoride of the target metal and the fluoride of the reducing agent generated through S40 and 76.7 g (1.9 mol) of Ca were added to the reaction vessel, and a reduction reaction was performed at a temperature of 1500°C for 2 hours to produce liquid Dy and liquid fluoride of the reducing agent CaF2. (S50)

[0067] Afterwards, the liquid target metal Dy and the liquid reducing agent fluoride CaF2 generated through the reaction were solidified in a mold and separated. The recovered Dy and CaF2 were confirmed to be 125.3 g and 105.5 g, respectively.

[0068] Dy 125.3 g (0.8 mol) as a secondary purity improvement target generated through S60 and 200.0 g (0.9 mol) of DyF3 powder, a fluoride of the target metal, were reacted at 1500°C for 2 hours to produce a liquid DyF3-CaF2 containing liquid Dy, fluoride of the target metal, and fluoride of a reducing agent. (Additional S30)

[0069] Afterwards, the liquid DyF3-CaF2 containing Dy, the fluoride of the target metal, and the fluoride of the reducing agent generated through the reaction was solidified in a mold and separated, and the recovered secondary purity target metal Dy was confirmed to be 106.7 g and DyF3-CaF2 was confirmed to be 201.0 g.

[0070] [Experimental Results]: Impurity content of the target metal

[0071] The Ca content of Dy recovered by each step was analyzed by ICP-OES, and the results are shown in Table 2 below.

[0072] Ca content S100.790wt.% S300.024wt.% S500.742wt.% Additional S300.021wt.%

[0073] As described in Table 2, the Ca content of Dy according to S10 is 0.790 wt.%, and the Ca content of Dy with increased purity according to S30 is confirmed to be 0.024 wt.%.

[0074] In addition, it can be confirmed that the Ca content of Dy according to S50 is 0.742 wt.% and the Ca content of Dy with increased purity according to additional S30 is 0.021 wt.%.

[0075] That is, when Dy manufactured through thermal reduction of calcium is reacted with DyF3, it can be seen that the Ca content decreases, and the used DyF3 can be recycled to manufacture Dy again and increase its purity.

[0076] Above, one embodiment of the present invention has been described, but a person having ordinary skill in the art will be able to modify and change the present invention in various ways by adding, changing, deleting or adding components, etc., within the scope that does not depart from the spirit of the present invention described in the claims, and this is also included within the scope of the rights of the present invention.

Claims

1. In a method for improving the purity of a target metal, A step (S10) of reacting the fluoride of the target metal with a reducing agent to produce a first portion containing the fluoride of the reducing agent and a second portion containing the remaining reducing agent and the target metal; A step (S20) of separating the first part and the second part; and A method for improving the purity of a target metal, comprising a step (S30) of reacting the second part as a purity improvement target and an additional target metal fluoride to produce a third part containing the target metal fluoride and a reducing agent fluoride and a fourth part containing the target metal with increased purity.

2. In paragraph 1, Step of separating the third part and the fourth part (S40); A step (S50) of reacting the third portion with an additional reducing agent to produce a fifth portion containing a fluoride of the reducing agent and a sixth portion containing the remaining reducing agent and the target metal; A step (S60) of separating the sixth part from the fifth part; and A method for improving the purity of a target metal, further comprising a step (S70) of supplying the sixth part to the purity improvement target of the step S30.

3. In paragraph 2, The above target metal is a method for improving the purity of a target metal containing a heavy rare earth element.

4. In paragraph 3, A method for improving the purity of a target metal, wherein the above-mentioned heavy rare earth elements include at least one of Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y.

5. In paragraph 4, The above target metal is a method for improving the purity of a target metal including Dy.

6. In paragraph 5, A method for improving the purity of a target metal, wherein the fluoride of the target metal includes DyF3.

7. In paragraph 6, The above reducing agent is a method for improving the purity of a target metal including an alkaline earth metal.

8. In paragraph 7, The above alkaline earth metal is a method for improving the purity of a target metal containing calcium (Ca).

9. In paragraph 8, In the above step S10, A method for improving the purity of a target metal by supplying Ca such that the mole number of Ca is 0.50 to 0.90 times the mole number of F.

10. In paragraph 9, The above S10 step, A step of converting the fluoride of the target metal into a liquid phase by applying heat before the above reaction; and A method for improving the purity of a target metal, comprising the step of adding a reducing agent after the liquid conversion.

11. In paragraph 9, In the above S30 step, A method for improving the purity of a target metal by supplying DyF3 so that the mole number of Ca is 0.0055 to 0.4000 times the mole number of F.

12. In paragraph 11, The above S40 step is, A step of converting the third and fourth parts from a liquid state to a solid state; and A method for improving the purity of a target metal, comprising a step of physically separating the third part and the fourth part in a solid state.

13. In paragraph 11, In the above S50 step, A method for improving the purity of a target metal by supplying Ca so that the mole number of Ca is 0.50 to 0.90 times the mole number of F of DyF3.

14. In paragraph 13, The above S50 step is, A step of applying heat to the third part before the above reaction to convert it into a liquid phase; and A method for improving the purity of a target metal, further comprising a step of adding an additional reducing agent after the liquid conversion.

15. In paragraph 14, In the above steps S10, S30 and S50, Each of the above reactions is, A method for improving the purity of a target metal, which is performed at 1000°C to 2000°C for 1 to 5 hours.

16. In paragraph 15, A method for improving the purity of a target metal, characterized in that steps S30 to S70 are repeated at least N times (N is an integer).

17. In paragraph 16, A method for improving the purity of a target metal, characterized in that the purity of the high-purity target metal becomes 99.95 to 99.99% through the above repetition.

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