JP5905592B2 - Rare earth element separation method and separation apparatus - Google Patents

Description

  The present invention relates to a technique for separating rare earth elements, and more particularly to a method for separating rare earth elements from a composition containing a plurality of types of rare earth elements and a separation apparatus for performing the method.

  Rare earth elements exhibit unique physical properties due to their characteristic electron arrangement, and various materials and products (for example, hydrogen storage alloys, secondary batteries, optical glasses, magnets, phosphors, Used in abrasives). Without knowing that the demand for higher performance of materials and products will not stop, demand for rare earth elements is expected to increase further in the future.

  Rare earth elements have abundant reserves themselves, but their chemical properties are very similar to each other, making them difficult to separate and purify as a single element, and are therefore said to be rare elements. In addition, there is a problem (resource risk) that the supply amount and price fluctuate greatly due to the geographical uneven distribution of production areas.

  As a resource risk hedge, the development of technologies and alternative materials that reduce the use of rare earth elements while maintaining the performance of materials and products has been intensively studied. However, it seems that it will take time to put these technologies into practical use. Therefore, it is an important technique to separate and collect rare earth elements from waste materials (used materials, used products, defective products, etc.), and to recycle them.

  For example, Patent Document 1 discloses a divalent trivalent mixture in which the average valence of two or more rare earth ions is 2 or more and 3 or less by halogenating a rare earth element in a mixture containing a plurality of rare earth elements or compounds thereof. Producing a mixture containing a rare earth halide which is not dissolved in an aqueous solution or an organic solvent, and then utilizing the difference in properties between the divalent rare earth halide and the trivalent rare earth halide, There has been proposed a rare earth element separation method characterized by separating elements into at least two groups. According to Patent Document 1, it is said that the separation factor between rare earth elements can be dramatically increased, and mutual separation can be performed more efficiently than in the conventional method. Furthermore, when separating from rare earth concentrates such as phosphates, steps such as acid dissolution, filtration, precipitation removal of impurities, concentration, neutralization, and drying, which are essential for conventional wet methods, can be omitted. It is said that the cost can be greatly reduced.

  Patent Document 2 discloses a method for recovering a rare earth element from a material containing a rare earth element and an iron group element, and a rare earth element such as a rare earth magnet scrap or sludge is added to a gaseous or molten iron chloride. Select a rare earth element as a chloride from the substance by contacting a substance containing an iron group element and proceeding the chlorination reaction of the rare earth element in the substance while maintaining the metallic state of the iron group element in the substance. There has been proposed a method for recovering a rare earth element characterized by having a step of recovering automatically. According to Patent Document 2, it is possible to extract and separate only high-purity rare earth components from materials containing rare earth elements and iron group elements, such as rare earth magnet scraps or sludges, especially wastes, and thus lower cost rare earth elements. It is said that the magnet recycling law can be established.

JP 2001-303149 A Japanese Patent Laid-Open No. 2003-73754

  As mentioned above, the demand for rare earth elements is expected to increase in the future. On the other hand, in recent years, technology for separating, recovering, and recycling rare earth elements has become more important than ever due to the growing awareness of global environmental protection and the use of sustainable resources. In addition, since rare earth elements have similar chemical properties, a technique for separating specific rare earth elements from a mixture of a plurality of types of rare earth elements is particularly important.

  In the conventional separation and recovery technology, since the ratio (separation rate) for separating a specific rare earth element from a composition containing a plurality of types of rare earth elements is not necessarily large, a large number of separation processes are required to increase the degree of purification. There was a problem that the cost increased because it was necessary to repeat the operation. For this reason, there has been a strong demand for a method capable of obtaining a higher separation rate and capable of separating rare earth elements simply (ie, at low cost).

  Accordingly, an object of the present invention is to provide a method capable of easily separating a rare earth element from a composition containing a plurality of types of rare earth elements at a high separation rate, and a separation apparatus for executing the method. It is in.

(I) One aspect of the present invention is a method for separating a plurality of rare earth elements,
Producing a chloride / acid chloride mixture comprising a rare earth chloride of a first group of rare earth elements and a rare earth acid chloride of a second group of rare earth elements from a starting mixture comprising a plurality of rare earth oxides and a chlorinating agent. A selective chlorination / acidification heat treatment step of performing a heat treatment at a predetermined temperature in a non-oxidizing atmosphere;
By selectively introducing the chloride / acid chloride mixture into a solvent, the rare earth chloride is selectively dissolved in the solvent and extracted into a liquid phase, and the rare earth acid chloride is left as a solid phase. An extraction process;
Separation for separating the first group of rare earth elements and the second group of rare earth elements by solid-liquid separation of the liquid phase from which the rare earth chloride is extracted and the solid phase of the remaining rare earth acid chloride. And providing a method for separating rare earth elements.

The present invention can add the following improvements or changes to the above-described rare earth element separation method (I).
(I) The chlorinating agent is ammonium chloride, and the predetermined temperature in the selective chlorination / acidification heat treatment step is a temperature within a temperature range in which the oxide of the rare earth element of the first group becomes a chloride. And a temperature within a temperature range in which the oxide of the second group rare earth element becomes an acid chloride.
(Ii) In the starting mixture, 1 mol of the rare earth oxide is mixed with more than 6 mol and less than 15 mol of the ammonium chloride.
(Iii) The selective chlorination / acidification heat treatment step includes a step of generating a rare earth ammonium chloride salt of the first group of rare earth elements from the plurality of rare earth oxides and the ammonium chloride by a heat treatment under normal pressure. ,
Subsequently, an elementary step of generating a rare earth chloride of the first group rare earth element from the rare earth ammonium chloride salt by a heat treatment under reduced pressure is included.
(Iv) The first group rare earth elements are light rare earth elements, and the second group rare earth elements are heavy rare earth elements.
(V) The first group rare earth element is neodymium or europium, and the second group rare earth element is at least one selected from yttrium, terbium and dysprosium.

(II) Another aspect of the present invention is a separation apparatus for separating a plurality of types of rare earth elements,
The separation apparatus comprises a composition supply part to be separated, a heat treatment part, an atmosphere control part, a gas treatment part, and a separation part,
The composition to be separated supply unit is connected to the heat treatment unit, prepares a starting mixture by mixing the composition to be separated and a chlorinating agent, and supplies the starting mixture to the heat treatment unit,
The heat treatment section is connected to the atmosphere control section, the gas processing section, and the separation section in addition to the composition-to-be-separated composition supply section, and the rare earth chloride of the first group of rare earth elements from the starting mixture. And a selective chlorination / acidification heat treatment to produce a chloride / acid chloride mixture comprising a rare earth oxychloride of a second group of rare earth elements,
The heat treatment is a heat treatment performed at a predetermined temperature in a non-oxidizing atmosphere controlled by the atmosphere control unit, and ammonia gas generated by the heat treatment is processed in the gas processing unit,
The gas processing unit includes a chemical reaction monitoring mechanism for monitoring a chemical reaction by the heat treatment,
The separation unit puts the chloride / acid chloride mixture into a solvent to selectively dissolve the rare earth chloride and extract it into a liquid phase, and remains with the liquid phase from which the rare earth chloride has been extracted. An apparatus for separating a rare earth element, wherein the rare earth element is a portion that separates the rare earth element of the first group and the rare earth element of the second group by solid-liquid separation of the solid phase of the rare earth acid chloride. provide.

The present invention can add the following improvements and changes to the rare earth element separation device (II).
(Vi) The chemical reaction monitoring mechanism includes an ammonia gas sensor.
(Vii) The chlorinating agent powder is ammonium chloride powder, and the predetermined temperature in the selective chlorination / acid oxidization heat treatment is a temperature within a temperature region in which the oxide of the rare earth element of the first group becomes a chloride. And the temperature in the temperature region where the oxide of the second group rare earth element becomes an acid chloride.
(Viii) In the starting mixture, 1 mol of the rare earth oxide is mixed with more than 6 mol and less than 15 mol of the ammonium chloride.
(Ix) the selective chlorination / acidification heat treatment includes an elementary reaction for generating a rare earth ammonium chloride salt of the first group rare earth element from the plurality of types of rare earth oxides and the ammonium chloride by a heat treatment under normal pressure;
Subsequently, an elementary reaction of generating a rare earth chloride of the rare earth element of the first group from the rare earth ammonium chloride salt by a heat treatment under reduced pressure,
Pressure control during the heat treatment is performed by the atmosphere control device.
(X) The first group rare earth elements are light rare earth elements, and the second group rare earth elements are heavy rare earth elements.
(Xi) The first group rare earth element is neodymium or europium, and the second group rare earth element is at least one selected from yttrium, terbium and dysprosium.

  ADVANTAGE OF THE INVENTION According to this invention, the method which can isolate | separate rare earth elements easily with a high separation rate (namely, low cost) from the composition in which multiple types of rare earth elements are mixed, and the separation apparatus for performing this method Can provide.

It is a flowchart which shows the process example of the separation method of the rare earth elements based on this invention. When the rare earth element is neodymium or dysprosium, the rare earth oxide chlorination reaction (chemical reaction formula (1)), the rare earth oxide acidification reaction (chemical reaction formula (2)), and the rare earth acid chloride chlorination reaction It is a graph which shows the relationship between the standard Gibbs energy change in (chemical reaction formula (3)), and temperature. When the rare earth element is yttrium, europium or terbium, the chlorination reaction (chemical reaction formula (1)) of the rare earth oxide, the acidification reaction of the rare earth oxide (chemical reaction formula (2)), and the rare earth acid chloride It is a graph which shows the relationship between the standard Gibbs energy change and temperature in a chlorination reaction (chemical reaction formula (3)). It is a schematic diagram which shows the structural example of the separation apparatus of the rare earth elements based on this invention.

  The present inventors aim to separate specific rare earth elements from a composition in which a plurality of types of rare earth elements are mixed at a high separation rate and easily, in particular, chemical reactions of rare earth elements (especially chloride reactions, The acidification reaction) was investigated in detail. As a result, the present inventors have found that the behavior of the chemical reaction differs depending on the type of rare earth element. And it discovered that a specific rare earth element could be isolate | separated with a high separation rate by the difference in the behavior of the chemical reaction. The present invention has been completed based on these findings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the embodiments taken up here, and can be appropriately combined and improved without departing from the technical idea of the invention.

[Separation and recovery of rare earth elements]
FIG. 1 is a flowchart showing an example of steps of a method for separating rare earth elements according to the present invention. The outline of the separation method will be described with reference to FIG. First, a plurality of rare earth oxides and a chlorinating agent are mixed to prepare a starting mixture. Next, a selective chlorination / acidification heat treatment is performed to produce a chloride / acid chloride mixture containing a first group of rare earth element chlorides and a second group of rare earth element acid chlorides from the prepared starting mixture. Do. The present invention has the greatest feature in this selective chlorination / acidification heat treatment step. The resulting chloride / acid chloride mixture is then charged into a solvent to selectively dissolve the rare earth chloride and extract into the liquid phase. Finally, the liquid phase from which the rare earth chloride is extracted and the solid phase of the remaining rare earth oxychloride are subjected to solid-liquid separation to recover the first group of rare earth elements and the second group of rare earth elements, respectively.

  Hereinafter, each process will be described in detail.

(Mixing process)
This step is a step of preparing a starting mixture by mixing a powder in which a plurality of kinds of rare earth oxides are mixed with a powder of a chlorinating agent. As the chlorinating agent to be used, it is preferable not to leave an excess element (cation) in the rare earth compound generated in the selective chlorination / acidification heat treatment step of the next step, and for example, ammonium chloride (NH ₄ Cl) is preferable. In addition, the mixing method is not particularly limited as long as the rare earth oxide and the chlorinating agent are mixed uniformly.

  In addition, in the selective chlorination / acidification heat treatment process of the next step, in order to promote and reliably complete the chlorination / acidification reaction of the rare earth oxide, over 6 mol over 15 mol per 1 mol of the rare earth oxide. It is preferable to mix less than ammonium chloride. It is more preferable to mix 9 mol or more and 13.5 mol or less of ammonium chloride with 1 mol of rare earth oxide.

(Selective chlorination / acid heat treatment process)
This step is a step of performing a heat treatment for generating a chloride / acid chloride mixture containing a first group rare earth element chloride and a second group rare earth element acid chloride from the prepared starting mixture. The heat treatment atmosphere is preferably a non-oxidizing atmosphere (an atmosphere in which oxygen components are not substantially mixed, for example, in an inert gas (argon, nitrogen, etc.) stream or in a vacuum). The heat treatment temperature is a temperature within a temperature region where the oxide of the first group rare earth element becomes a chloride, and a temperature within a temperature region where the oxide of the rare earth element of the second group becomes an acid chloride. Is preferred.

Here, the heat treatment temperature in the selective chlorination / acidification heat treatment step will be considered. Rare earth oxide (RE ₂ O ₃₎ of rare earth chloride chloride reaction to produce (RECL ₃₎ is, (RE what is believed to be a chemical reaction such as chemical reaction formula (1) below represents a rare earth element. Less The same).
_{RE 2 O 3 + 6NH 4 Cl} → 2RECl 3 + 6NH 3 + 3H 2 O ... chemical formula (1).

The acidification reaction for producing rare earth acid chloride (REOCl) from rare earth oxide (RE ₂ O ₃ ) is considered to be a chemical reaction represented by the following chemical reaction formula (2).
_{RE 2 O 3 + 2NH 4 Cl} → 2REOCl + 2NH 3 + H 2 O ... chemical formula (2).

In addition, the chlorination reaction that generates rare earth chloride (RECl ₃ ) from rare earth acid chloride (REOCl) is considered to be a chemical reaction represented by the following chemical reaction formula (3).
_{REOCl + 2NH 4 Cl → RECl 3} + 2NH 3 + H 2 O ... chemical formula (3).

  Regarding the heat treatment temperature for generating the rare earth compound, the relationship between the standard Gibbs energy change in the chemical reaction and the temperature is helpful. FIG. 2 shows the case where the rare earth element is neodymium or dysprosium, the rare earth oxide chlorination reaction (chemical reaction formula (1)), the rare earth oxide acidification reaction (chemical reaction formula (2)), and the rare earth acidification. It is a graph which shows the relationship between the standard Gibbs energy change and temperature in the chlorination reaction (chemical reaction formula (3)) of a thing. As shown in FIG. 2, the standard Gibbs energy change decreases as the temperature increases. However, when the standard Gibbs energy change reaches a negative value, the chemical reaction can proceed continuously. Note that the standard Gibbs energy change can discuss thermodynamic stability / instability by negative / positive, but we can discuss the activation energy for starting a chemical reaction, and the chemical reaction rate. Not what you want.

In addition, in each chemical reaction, ammonia gas (NH ₃ ) and water vapor (H ₂ O) are generated as reaction products in addition to rare earth compounds, but in an argon or nitrogen stream or in a vacuum (in a reduced pressure atmosphere) By performing the heat treatment, the product gas component can be quickly discharged out of the system. As a result, the reaction can proceed without inhibiting the chlorination / acidification reaction by the reaction product gas.

More specifically, Fig. 2 shows that in the rare earth oxide chlorination reaction (chemical reaction formula (1)), neodymium oxide (Nd ₂ O ₃ ) shows a negative value of standard Gibbs energy change at about 200 ° C or higher. Dysprosium oxide (Dy ₂ O ₃ ) shows a negative standard Gibbs energy change at about 350 ° C. or higher. In other words, if the activation energy for starting the chemical reaction can be exceeded, neodymium oxide (Nd ₂ O ₃ ) is about 200 ° C or higher and dysprosium oxide (Dy ₂ O ₃ ) is about 350 ° C or higher. The chlorination reaction of formula (1) can proceed.

In the acidification reaction of the rare earth oxide (chemical reaction formula (2)), neodymium oxide (Nd ₂ O ₃ ) shows a negative standard Gibbs energy change in the calculated total temperature range (0 to 600 ° C.), Dysprosium oxide (Dy ₂ O ₃ ) shows a negative standard Gibbs energy change at about 180 ° C or higher. In other words, if the activation energy of the chemical reaction is exceeded, neodymium oxide (Nd ₂ O ₃ ) is 0 ° C or higher, dysprosium oxide (Dy ₂ O ₃ ) is about 180 ° C or higher, and the chemical reaction formula (2) The acidification reaction can proceed.

  In the rare earth oxychloride chloride reaction (chemical reaction formula (3)), neodymium oxychloride (NdOCl) shows a negative standard Gibbs energy change at about 330 ° C, and dysprosium oxychloride (DyOCl) about 420 ° C. The standard Gibbs energy change shows a negative value. In other words, if the activation energy of the chemical reaction can be exceeded, neodymium oxychloride (NdOCl) is about 330 ° C, dysprosium oxychloride (DyOCl) is about 420 ° C or higher, and the chlorination reaction of chemical reaction formula (3) proceeds. It becomes possible.

  From the results of FIG. 2, it can be seen that the thermodynamically stable temperature varies greatly depending on the type of rare earth element and the type of chemical reaction. From this fact, it is possible to coexist the chlorination reaction and the acidification reaction by utilizing the difference in temperature that is thermodynamically stable.

For example, when trying to produce a chloride / acid chloride mixture from a mixture of neodymium oxide (Nd ₂ O ₃ ) and dysprosium oxide (Dy ₂ O ₃ ), to produce neodymium chloride (NdCl ₃ ) It is considered that a heat treatment temperature of at least 200 ° C. is necessary. On the other hand, in order to suppress the formation of dysprosium chloride (DyCl ₃ ) and keep dysprosium oxychloride (DyOCl) stable, it is considered that a heat treatment temperature of less than 420 ° C. is preferable.

  Next, other rare earth elements will be described.

  FIG. 3 shows a case where a rare earth element is yttrium, europium, or terbium, and a rare earth oxide chlorination reaction (chemical reaction formula (1)), a rare earth oxide acidification reaction (chemical reaction formula (2)), It is a graph which shows the relationship between the standard Gibbs energy change and temperature in the chlorination reaction (chemical reaction formula (3)) of an acid chloride. As shown in FIG. 3, as in FIG. 2, the standard Gibbs energy change decreases with increasing temperature, and the chemical reaction can proceed continuously when the standard Gibbs energy change reaches a negative value. become.

Looking more specifically at FIG. 3, in the chlorination reaction of the rare earth oxide (chemical reaction formula (1)), yttrium oxide (Y ₂ O ₃ ) is about 350 ° C. or higher, and europium oxide (Eu ₂ O ₃ ) is Above about 250 ° C., terbium oxide (Tb ₂ O ₃ ) shows a negative value of standard Gibbs energy change at about 330 ° C. or more. In other words, if the activation energy of the chemical reaction is exceeded, the chlorination reaction of the chemical reaction formula (1) can proceed at those temperatures or higher.

In the rare earth oxide acidification reaction (chemical reaction formula (2)), yttrium oxide (Y ₂ O ₃ ) is about 220 ° C or higher, europium oxide (Eu ₂ O ₃ ) is about 70 ° C or higher, and terbium oxide. (Tb ₂ O ₃ ) shows a negative value of the standard Gibbs energy change at about 200 ° C. or higher. In other words, if the activation energy of the chemical reaction is exceeded, the acidification reaction of the chemical reaction formula (2) can proceed at those temperatures or higher.

  In the rare earth acid chloride chloride reaction (chemical reaction formula (3)), yttrium oxychloride (YOCl) is about 380 ° C or higher, europium oxychloride (EuOCl) is about 350 ° C or higher, terbium oxychloride (TbOCl) Shows a negative value of standard Gibbs energy change at about 370 ° C or higher. In other words, if the activation energy of the chemical reaction is exceeded, the chlorination reaction of the chemical reaction formula (3) can proceed at those temperatures or higher.

For example, when trying to produce a chloride / acid chloride mixture from a mixture of yttrium oxide (Y ₂ O ₃ ) and europium oxide (Eu ₂ O ₃ ), to produce europium chloride (EuCl ₃ ) It is considered that a heat treatment temperature of at least 250 ° C. is necessary. On the other hand, in order to suppress the production of yttrium chloride (YCl ₃ ) and keep yttrium oxychloride (YOCl) stable, a heat treatment temperature of less than 350 ° C. is considered preferable.

In addition, when an attempt is made to produce a chloride / acid chloride mixture from a mixture of europium oxide (Eu ₂ O ₃ ) and terbium oxide (Tb ₂ O ₃ ), it is possible to produce 250 europium chloride (EuCl ₃ ). A heat treatment temperature of not lower than 330 ° C. is considered preferable in order to suppress the formation of terbium chloride (TbCl ₃ ) and keep terbium oxychloride (TbOCl) stable.

  When the results of FIGS. 2 and 3 are arranged, the temperature at which the chlorination reaction of the chemical reaction formula (1) occurs in a light rare earth element such as neodymium or europium (an element whose atomic number is smaller than gadolinium (Gd) in lanthanides) is It is found that the temperature is about 100 ° C. lower than the temperature at which the chlorination reaction of the chemical reaction formula (1) in yttrium and heavy rare earth elements such as dysprosium and terbium (elements having an atomic number of gadolinium (Gd) or higher among lanthanides) occurs. . Also, heavy rare earth elements and yttrium acid chlorides are stable in the temperature range from the temperature at which light rare earth oxides generate chloride to the time at which heavy rare earth elements and yttrium oxides generate chloride. I understand that. That is, the temperature is within a temperature range in which the standard Gibbs energy change of the chlorination reaction of oxides of light rare earth elements (defined as first group rare earth elements) is negative, and heavy rare earth elements and yttrium (second group) The rare earth oxide chlorination reaction and the acidification reaction can coexist by heat treatment at a temperature within the temperature range in which the standard Gibbs energy change of the chlorination reaction of the oxide of the .

  The chlorination reaction of the oxide of the first group of rare earth elements will be described in more detail.

The chlorination reaction of the chemical reaction formula (1) can be divided into the following two elementary reactions. In the first stage elementary reaction, a rare earth ammonium chloride salt is produced by heat treatment in an inert gas stream at normal pressure. An example of this reaction is chemical reaction formula (4) (see, for example, Meyer, et. Al., Mat. Res. Bull. 17 (1982) 1447-1455).
RE ₂ O ₃ + 12NH ₄ Cl → 2 (NH ₄ ) ₂ RECl ₅ + 6NH ₃ + 3H ₂ O Chemical reaction formula (4).

In the second stage elementary reaction, it is considered that ammonium chloride present in the rare earth ammonium chloride salt and unreacted ammonium chloride in the starting mixture are removed to produce rare earth chloride (RECl ₃ ). An example of this reaction is chemical reaction formula (5) (see, for example, Meyer, et. Al., Mat. Res. Bull. 17 (1982) 1447-1455). The second stage elementary reaction is preferably performed in a reduced-pressure atmosphere (for example, a reduced-pressure atmosphere using a rotary pump or the like). This is because vaporization / decomposition of ammonium chloride tends to proceed in a reduced pressure atmosphere. Moreover, vaporization and decomposition | disassembly of ammonium chloride can be accelerated | stimulated by heating to 350 degreeC or more.
(NH ₄ ) ₂ RECl ₅ → RECl ₃ + 2NH ₃ + 2HCl ... Chemical reaction formula (5).

(Selective extraction process)
In this step, the obtained chloride / acid chloride mixture is put into a solvent, the rare earth chloride is selectively extracted into the liquid phase, and the rare earth acid chloride remains as a solid phase. This process utilizes the difference between the high solubility of rare earth chlorides and the low solubility (slight solubility) of rare earth acid chlorides.

  As the solvent, for example, pure water, lower alcohol, or a mixture thereof can be preferably used. As the lower alcohol, it is particularly preferable to use methanol or ethanol. Since these solvents have a small adverse effect on the environment and the human body, they contribute to improvement in workability and simplification of work facilities (that is, cost reduction).

  It is preferable to stir using a stirrer, a stirring blade, ultrasonic vibration, etc. according to the input amount of the chloride / acid chloride mixture and the amount of solvent. Moreover, extraction to a solvent can be accelerated | stimulated by heating at the time of stirring. However, since the amount of solvent decreases when the heating temperature becomes higher than the boiling point of the solvent, the heating temperature is preferably equal to or lower than the boiling point of the solvent. In addition, when heating a solvent, in order to suppress volatilization of a solvent, it is preferable to seal a dissolution tank.

(Separation process)
This step is a step of separating the first group of rare earth elements and the second group of rare earth elements by performing a solid-liquid separation process on the solution obtained above. Although there is no special limitation in the method of a solid-liquid separation process, For example, filtration can be utilized.

(Recovery process)
This step is a step of recovering the first group of rare earth elements and the second group of rare earth elements from the liquid phase and solid phase separated by solid-liquid separation. The liquid phase containing the rare earth chloride can be recovered as a rare earth chloride powder, for example, by spraying in a heated atmosphere using a spray dryer. In addition, after adjusting the pH of the rare earth chloride solution, a precipitant (for example, ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), ammonium hydrogen carbonate (NH ₄ HCO ₃ ), sodium carbonate (Na ₂ CO ₃₎ ), Sodium bicarbonate (NaHCO ₃ ), oxalic acid ((COOH) ₂ ), sodium oxalate ((COONa) ₂ ), sodium hydroxide (NaOH), etc.) Can be generated. The precipitate is filtered and dried, and then roasted at about 900 ° C. in the atmosphere, whereby the first group rare earth elements can be recovered as oxides.

A solid phase composed of a rare earth acid chloride can be recovered as a rare earth acid chloride powder by drying it. Moreover, after dissolving with an acid (dilute hydrochloric acid, dilute nitric acid, etc.) to produce a hydrate, and adjusting the pH of the hydrate, a precipitating agent (for example, (NH ₄ ) ₂ CO ₃ , NH ₄ HCO ₃ , Na ₂ CO ₃ , NaHCO ₃ , (COOH) ₂ , (COONa) ₂ , NaOH, etc.) can be added to form a hardly soluble rare earth precipitate. After filtering and drying the precipitate, the second group of rare earth elements can be recovered as oxides by roasting at about 900 ° C. in the atmosphere.

  By repeatedly performing the separation and recovery method according to the present invention, the separation rate between the first group of rare earth elements and the second group of rare earth elements can be further improved. Moreover, you may apply another known wet-separation method with respect to the liquid phase produced | generated by the above-mentioned selective extraction process.

  As described above, by applying the separation and recovery method according to the present invention to materials containing multiple types of rare earth elements and waste products, the first group of rare earth elements and the first group can be easily combined with a high separation rate. Two groups of rare earth elements can be separated and recovered.

[Rare earth element separation and recovery equipment]
FIG. 4 is a schematic diagram showing a configuration example of a rare earth element separation device according to the present invention. As shown in FIG. 4, the rare earth element separation apparatus 100 according to the present invention includes a composition supply unit 10 to be separated, a heat treatment unit 20, an atmosphere control unit 30, a gas treatment unit 40, and a separation unit 50. .

  The composition-to-be-separated composition supply unit 10 is connected to the heat treatment unit 20 and is a part that supplies the starting mixture obtained by performing the above-described mixing process to the heat treatment unit 20. Specifically, a composition container 11 to be separated that contains powder mixed with a plurality of types of rare earth oxides, an ammonium chloride container 12 that contains ammonium chloride powder, a raw material powder mixing device 13, and a starting mixture supply device 14 And have.

  The heat treatment unit 20 is connected to the atmosphere control unit 30, the gas processing unit 40, and the separation unit 50 in addition to the composition supply unit 10 to be separated, and performs the above-described selective chlorination / acidification heat treatment step. It is. Specifically, it has a heater 21 and a core tube 22. Furthermore, a mechanism (for example, a core tube rotation mechanism (not shown)) for stirring the material to be heat-treated is provided so that the chemical reaction in the selective chlorination / acidification heat treatment step proceeds smoothly. preferable.

  The atmosphere control unit 30 is a part that controls the atmosphere during the heat treatment in the selective chlorination / acidification heat treatment step. Specifically, the vacuum evacuation device 31 and the gas supply device 32 are provided, and a non-oxidizing atmosphere under normal pressure and a non-oxidizing atmosphere under reduced pressure are controlled in the selective chlorination / acidification heat treatment step. There is no particular limitation on the vacuum exhaust device 31, and for example, a rotary pump can be suitably used.

  The gas treatment unit 40 is a part for detoxifying the ammonia gas and hydrogen chloride gas generated by the selective chlorination / acidification heat treatment. There is no particular limitation on the method of detoxification treatment, and a conventional method can be used.

  In addition to the ammonia treatment device 42 and the hydrogen chloride treatment device 43, the gas treatment unit 40 has a chemical reaction monitoring mechanism (for example, an ammonia gas sensor 41). By detecting the concentration of the gas generated by the chemical reaction by the ammonia gas sensor 41 and monitoring the average gas concentration per unit time (gas concentration change rate), the progress of the chemical reaction in the heat treatment can be observed. For example, when the target chemical reaction is almost completed, the concentration of the generated gas can be detected from a sharp drop. As a result, the progress of the chemical reaction for each operation batch can be stabilized, the heat treatment time can be optimized, and efficient separation and recovery can be achieved. The chemical reaction monitoring mechanism is not limited to the gas sensor, and may be a mechanism that detects a change in the weight of the object to be heat treated, for example.

  The separation unit 50 is a part that performs the above-described selective extraction step and separation step. Specifically, it has a solvent container 51 that contains the solvent used in the selective extraction step, a dissolution tank 52 that performs selective extraction / solid-liquid separation processing, and an extraction liquid container 53 that contains the extracted liquid phase components. . The extraction liquid stored in the extraction liquid container 53 and the solid phase component remaining in the dissolution tank 52 proceed to the recovery step described above, respectively.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to these examples.

An experiment was conducted to separate rare earth elements from a mixture of rare earth oxides. As starting materials for rare earth oxides, neodymium oxide powder (Nd ₂ O ₃ , manufactured by High Purity Chemical Laboratory Co., Ltd., product number: NDO01PB) and dysprosium oxide powder (Dy ₂ O ₃ , High Purity Chemical Research Laboratory) Manufactured, product number: DYO01PB). As the chlorinating agent, ammonium chloride powder (NH ₄ Cl, manufactured by Wako Pure Chemical Industries, Ltd., product number: 017-02995) was used.

Experiment 1: Examination of heat treatment temperature in selective chlorination / acidification heat treatment step First, a mixed powder was prepared in which Nd ₂ O ₃ powder and Dy ₂ O ₃ powder were mixed so that the mass ratio was “7/1”. . Next, the mixed powder is mixed with NH ₄ Cl twice the chemical equivalent shown in the chemical reaction formula (1) (12 mol of ammonium chloride with respect to 1 mol of rare earth oxide) to obtain a starting mixture. Prepared (mixing step).

  These starting mixtures were heated for 4 hours at various temperatures (200 ° C., 250 ° C., 300 ° C., 350 ° C., 400 ° C., 500 ° C.) in an argon gas stream. A two-stage heat treatment was performed in which the interior was evacuated by a rotary pump and heated at 400 ° C. for 2 hours (selective chlorination / acidification heat treatment step). Thereby, six types of samples (sample Nos. 1 to 6) were obtained.

  A part of the powder after the selective chlorination / acidification heat treatment step was collected, and the crystal phase was identified by powder X-ray diffraction (XRD) measurement. The sample powder was packed in an airtight sample holder in a glow box in an argon atmosphere, and the airtight sample holder was measured. A wide-angle X-ray diffractometer (manufactured by Rigaku Corporation, model: RU200B) was used as the measuring device. The measurement conditions were Cu-Kα ray as X-ray, X-ray output 50 kV × 150 mA, scanning range 2θ = 5 to 70 deg, and scanning speed 1.0 deg / min. ICDD (International Center for Diffraction Data), which is a collection of X-ray diffraction standard data, was used to identify the detected diffraction peaks. The results are shown in Tables 1 and 2.

Table 1 shows the identification results of the crystalline phase of the powder obtained in the selective chlorination / acidification heat treatment step. As shown in Table 1, for neodymium compounds, neodymium acid chloride (NdOCl) was detected when the heat treatment temperature at the first stage was 200 ° C. In the case of 250 ° C., neodymium acid chloride (NdOCl) and neodymium chloride (NdCl ₃ ) were detected. At temperatures above 300 ° C., only neodymium chloride (NdCl ₃ ) was detected. That is, when the heat treatment temperature in the first stage is set to 300 ° C. or higher, neodymium oxide (Nd ₂ O ₃ ) is completely salified.

On the other hand, regarding the dysprosium compound, unreacted dysprosium oxide (Dy ₂ O ₃ ) and dysprosium chloride (DyCl ₃ ) were detected when the first-stage heat treatment temperatures were 200 ° C. and 250 ° C. In the case of 300 to 500 ° C., dysprosium acid chloride (DyOCl) and dysprosium chloride (DyCl ₃ ) were detected. As chloride, some hydrates were also detected. From the above results, it was confirmed that NdCl ₃ and DyOCl were formed simultaneously when the first-stage heat treatment temperature was 300 to 500 ° C.

Table 2 shows the XRD peak intensity ratio (REOCl / RECl ₃ ) between the detected rare earth acid chloride (REOCl) and the rare earth chloride (RECl ₃ ). Here, the peak intensity ratio was calculated using the peak intensity values of the (102) plane of DyOCl, the (001) plane of DyCl ₃ , the (102) plane of NdOCl, and the (201) plane of NdCl ₃ .

As shown in Table 2, with respect to neodymium, the value of “NdOCl / NdCl ₃ ” decreased as the first-stage heat treatment temperature increased, and the NdOCl phase was not detected at 300 ° C. or higher. As for dysprosium, the value of “DyOCl / DyCl ₃ ” became the largest at the first heat treatment temperature of 350 ° C., and the value of “DyOCl / DyCl ₃ ” decreased at higher temperatures. This is considered that the chlorination reaction by the chemical reaction formula (3) has progressed. From this result, it was confirmed that there exists a temperature range in which neodymium chloride (NdCl ₃ ) and dysprosium chloride (DyOCl) are simultaneously stable.

Experiment 2: Examination of mixing ratio of ammonium chloride in the starting mixture
Mix NH ₄ Cl in various ratios with Nd ₂ O ₃ powder or Dy ₂ O ₃ powder (4.5 mol, 6 mol, 9 mol, 13.5 mol, 15 mol of ammonium chloride per mol of rare earth oxide) Mixed) and subjected to a selective chlorination / acidification heat treatment. As a result, six types of samples (Sample Nos. 7 to 12) were obtained. The crystal phase was identified by XRD measurement for the obtained powder. As the heat treatment conditions (heat treatment temperature in the first stage), 300 ° C. and 350 ° C. in which NdCl ₃ and DyOCl can coexist are selected. The XRD measurement conditions are the same as in Experiment 1. The results are shown in Table 3.

Table 3 is a table showing the NH ₄ Cl mixing amount with respect to the rare earth oxide, the heat treatment temperature of the selective chlorination / acidification heat treatment step, and the identification result of the crystal phase of the obtained powder. As shown in Table 3, at a heat treatment temperature of 300 ° C., when the mixed amount of NH ₄ Cl was 6 mol or less with respect to 1 mol of Nd ₂ O ₃ , NdOCl was detected and an NdCl ₃ single phase was not obtained. However, when the NH ₄ Cl mixing amount was 9 mol, it became an NdCl ₃ single phase. In addition, when the amount of NH ₄ Cl mixed was 15 mol with respect to 1 mol of Dy ₂ O ₃ , DyOCl was not detected but a single DyCl ₃ phase was detected.

When the mixed amount of NH ₄ Cl was 15 mol with respect to 1 mol of Dy ₂ O _{3 at a} heat treatment temperature of 350 ° C., a DyCl ₃ single phase was detected as in the case of the heat treatment temperature of 300 ° C. On the other hand, when the mixed amount of NH ₄ Cl was 13.5 mol, DyOCl was detected as the main phase. From these results, in order to co-generate NdCl ₃ and DyOCl, the amount of NH ₄ Cl mixed with 1 mol of rare earth oxide is preferably more than 6 mol and less than 15 mol, more preferably 9 mol or more and 13.5 mol or less. It was confirmed.

Experiment 3: Separation experiment of neodymium and dysprosium First, a starting mixture was prepared in the same manner as in Experiment 1. Next, a selective chlorination / acidification heat treatment step was performed. The heat treatment conditions were as follows: heat treatment was held at 300 ° C. for 4 hours in an Ar gas flow and then held at 400 ° C. for 2 hours while being evacuated by a rotary pump. The obtained chloride / acid chloride mixed powder was subjected to a selective extraction step, and the solution was filtered and solid-liquid separated as a separation step.

  Composition analysis was performed on the separated solid phase by X-ray fluorescence analysis. A measurement sample was press-molded using a molding binder (boric acid powder) and subjected to measurement. A fluorescent X-ray analyzer (manufactured by Rigaku Corporation, model: ZSX Primus II) was used as the measuring device. The measurement conditions were as follows: Rh-Kα ray was used as X-ray, X-ray output was 3 kW, and analysis diameter was 20 mm. The quantitative value obtained in this analysis was calculated by the fundamental parameter method (FP method). The results are shown in Table 4.

Also, the Dy separation rate (Dy separation) obtained by substituting the Dy mass concentration (denoted [Dy]) and Nd mass concentration (denoted [Nd]) obtained by X-ray fluorescence analysis into the following formula (1) Rate) was calculated. The results are also shown in Table 4.
Dy separation rate (%) = 100 x {[Dy] / ([Dy] + [Nd])} ... Formula (1)

As shown in Table 4, when an Nd / Dy separation experiment was performed by the rare earth element separation method according to the present invention, a Dy separation rate three times higher than the initial Dy mixing rate was achieved. That is, it was demonstrated that the rare earth element separation method according to the present invention can be separated at a high separation rate in one cycle. Furthermore, it can be said that the separation method of the present invention is a very simple process (that is, low cost) because it requires less incidental work and facilities.

  As described above, according to the present invention, rare earth elements (for example, yttrium, terbium, neodymium, europium, dysprosium, etc.) can be separated with high precision from waste materials and products using rare earth elements. Elements can be regenerated as raw materials. As a result, it can contribute to effective utilization of resources and stable securing of rare earth materials.

  Note that the above-described embodiments and examples have been specifically described in order to help understanding of the present invention, and the present invention is not limited to having all the configurations described. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, a part of the configuration of each embodiment can be deleted, replaced with another configuration, or added with another configuration.

  DESCRIPTION OF SYMBOLS 100 ... Separation / recovery apparatus, 10 ... Separation composition supply part, 11 ... Composition container to be separated, 12 ... Ammonium chloride container, 13 ... Raw material powder mixing apparatus, 14 ... Starting mixture supply apparatus, 20 ... Heat treatment part, 21 ... Heater, 22 ... Core tube, 30 ... Atmosphere control unit, 31 ... Vacuum exhaust device, 32 ... Gas supply device, 40 ... Gas treatment unit, 41 ... Ammonia gas sensor, 42 ... Ammonia treatment device, 43 ... Hydrogen chloride treatment device, 50 ... Separation part, 51 ... Solvent container, 52 ... Dissolution tank, 53 ... Extraction liquid container.

Claims (13)

A method for separating a plurality of rare earth elements,
Producing a chloride / acid chloride mixture comprising a rare earth chloride of a first group of rare earth elements and a rare earth acid chloride of a second group of rare earth elements from a starting mixture comprising a plurality of rare earth oxides and a chlorinating agent. A selective chlorination / acidification heat treatment step of performing a heat treatment at a predetermined temperature in a non-oxidizing atmosphere;
By selectively introducing the chloride / acid chloride mixture into a solvent, the rare earth chloride is selectively dissolved in the solvent and extracted into a liquid phase, and the rare earth acid chloride is left as a solid phase. An extraction process;
Separation for separating the first group of rare earth elements and the second group of rare earth elements by solid-liquid separation of the liquid phase from which the rare earth chloride is extracted and the solid phase of the remaining rare earth acid chloride. And a rare earth element separation method. The rare earth element separation method according to claim 1,
The chlorinating agent is ammonium chloride;
The predetermined temperature in the selective chlorination / acidification heat treatment step is a temperature within a temperature region in which the oxide of the first group rare earth element becomes a chloride, and oxidation of the second group rare earth element. A method for separating a rare earth element, wherein the temperature is within a temperature range in which the product becomes an acid chloride. The method for separating rare earth elements according to claim 2,
The method for separating rare earth elements, wherein the starting mixture is mixed with 1 mol of the rare earth oxide and more than 6 mol and less than 15 mol of the ammonium chloride. In the rare earth element separation method according to claim 2 or claim 3,
The selective chlorination / acidification heat treatment step includes generating a rare earth ammonium chloride salt of the first group rare earth element from the plurality of rare earth oxides and the ammonium chloride by a heat treatment under normal pressure;
Subsequently, a rare earth element separation method comprising an elementary step of generating rare earth chlorides of the first group rare earth elements from the rare earth ammonium chloride salts by heat treatment under reduced pressure. In the rare earth element separation method according to any one of claims 1 to 4,
The method for separating rare earth elements, wherein the first group rare earth elements are light rare earth elements, and the second group rare earth elements are heavy rare earth elements. In the rare earth element separation method according to any one of claims 1 to 4,
The rare earth element of the first group is neodymium or europium;
The rare earth element separation method, wherein the second group rare earth element is at least one selected from yttrium, terbium and dysprosium. A separation device for separating a plurality of rare earth elements,
The separation apparatus comprises a composition supply part to be separated, a heat treatment part, an atmosphere control part, a gas treatment part, and a separation part,
The composition to be separated supply unit is connected to the heat treatment unit, prepares a starting mixture by mixing the composition to be separated and ammonium chloride , and supplies the starting mixture to the heat treatment unit,
The heat treatment section is connected to the atmosphere control section, the gas processing section, and the separation section in addition to the composition-to-be-separated composition supply section, and the rare earth chloride of the first group of rare earth elements from the starting mixture. And a selective chlorination / acidification heat treatment to produce a chloride / acid chloride mixture comprising a rare earth oxychloride of a second group of rare earth elements,
The selective chlorination / acidification heat treatment is a heat treatment performed at a predetermined temperature in a non-oxidizing atmosphere controlled by the atmosphere control unit, and ammonia gas generated by the heat treatment is processed in the gas processing unit. ,
The gas processing unit includes a chemical reaction monitoring mechanism for monitoring a chemical reaction by the selective chlorination / acidification heat treatment,
The separation unit puts the chloride / acid chloride mixture into a solvent to selectively dissolve the rare earth chloride and extract it into a liquid phase, and remains with the liquid phase from which the rare earth chloride has been extracted. An apparatus for separating a rare earth element, wherein the rare earth element is a portion for separating the first group of rare earth elements and the second group of rare earth elements by solid-liquid separation from the solid phase of the rare earth acid chloride. In the rare earth element separation apparatus according to claim 7,
The chemical reaction monitoring mechanism includes an ammonia gas sensor. In the rare earth element separation device according to claim 7 or 8 ,
Wherein the predetermined temperature at the previous SL selectively chloride / acid chloride heat treatment, the oxide of the first group of rare earth elements is the temperature of the temperature region where the chlorides, and oxides of rare earth elements of the second group Separation device for rare earth elements, characterized in that the temperature is within the temperature range where the product becomes an acid chloride. The rare earth element separation device according to claim 9,
The starting mixture is a rare earth element separation device, wherein 1 mol of the rare earth oxide is mixed with more than 6 mol and less than 15 mol of the ammonium chloride. In the rare earth element separation apparatus according to claim 9 or 10,
The selective chlorination / acidification heat treatment includes an elementary reaction for generating a rare earth ammonium chloride salt of the first group rare earth elements from the plurality of types of rare earth oxides and the ammonium chloride by a heat treatment under normal pressure;
Subsequently, an elementary reaction of generating a rare earth chloride of the rare earth element of the first group from the rare earth ammonium chloride salt by a heat treatment under reduced pressure,
A rare earth element separation device, wherein pressure control during the heat treatment is performed by the atmosphere control device. The rare earth element separation device according to any one of claims 7 to 11,
The rare earth element separation apparatus, wherein the rare earth element of the first group is a light rare earth element, and the rare earth element of the second group is a heavy rare earth element. The rare earth element separation device according to any one of claims 7 to 11,
The rare earth element of the first group is neodymium or europium;
The rare earth element separation apparatus, wherein the second group rare earth element is at least one selected from yttrium, terbium and dysprosium.

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