WO2015087845A1

WO2015087845A1 - Method for fractional precipitation of rare metal in aqueous system utilizing coordination polymerization

Info

Publication number: WO2015087845A1
Application number: PCT/JP2014/082460
Authority: WO
Inventors: 友衣子半田; 大井　健太; 弘一成田; 幹也田中; 昭弘脇坂
Original assignee: 独立行政法人産業技術総合研究所
Priority date: 2013-12-13
Filing date: 2014-12-08
Publication date: 2015-06-18
Also published as: JP2015132016A; JP6411199B2

Abstract

The purpose of the present invention is to provide a method for selectively separating a rare metal such as indium and a rare earth, which is a substance that is usually difficult to be separated, at low cost, particularly a method for selectively separating dysprosium ions from an aqueous solution containing neodymium ions and the dysprosium ions at low cost. Rare metal ions can be separated by carrying out the selective coordination polymerization of the rare metal ions in an aqueous solution containing the rare metal ions using a water-soluble phosphoric acid diester, e.g., dibutyl phosphate ester and hydrogen=bis[2-(methacryloyloxy)ethyl] phosphate, as a coordination polymer forming agent to cause the fractional precipitation of the ions.

Description

Aqueous fractional precipitation of rare metals using coordination polymerisation

The present invention relates to an aqueous fractional precipitation method of a rare metal using coordination polymerization.

For rare metals (rare metals) that are in danger of stable supply, elements such as platinum group elements, tungsten, rare earth elements (rare earth), etc. that have extremely low reserves or production, or other resources such as indium Since only a very small amount is produced as a by-product when mining lime, there are elements that are difficult to increase in production according to demand.
In recent years, the importance of recycling rare metals from used products has been advocated as a measure to secure a stable supply of rare metals essential for advanced technologies. In particular, in recent years, the supply structure of rare earths has become fragile, and the realization of recycling is urgently required.
Separation is particularly important in the rare metal recycling process. When a rare metal is to be separated, there are two types of separation. One is separation of rare metals from base metals such as iron, and the other is mutual separation of rare metals. Among rare metals, rare earths are very similar in nature, so the latter is particularly difficult to separate.

For example, neodymium magnets mainly composed of neodymium (hereinafter sometimes referred to as “Nd”), iron, and boron are considered to be the strongest among permanent magnets, and drive motors and air conditioner compressors for hybrid vehicles. It is used for motors and the like, and it is known that the addition of a small amount of dysprosium (hereinafter sometimes referred to as “Dy”) improves the coercive force.
In recycling rare metals from such magnets, it is first necessary to remove a large amount of iron. For example, Naganawa et al. Have developed extraction reagents effective for removing iron (Non-Patent Documents 1 and 2). . Shirayama et al. Are studying separation of iron and lanthanoids by a dry method (Non-patent Document 3).
Next, separation of neodymium and dysprosium, which is a mutual separation of rare earths, is performed.

Conventionally, a solvent extraction method has been studied as a method for separating neodymium and dysprosium (Non-Patent Document 4).
This solvent extraction method is a method in which ions to be separated dissolved in an aqueous solution are selectively extracted into an organic solvent and then back-extracted again into an aqueous solution phase. This technique has been applied to many metal ion separation systems, and there are many types of extraction reagents used industrially.
However, it is effective when the target substance has a high concentration, but is not suitable for a low concentration system. In addition, it is the extraction reagent in the organic solvent that is responsible for the selectivity, so the extraction reagent can be selected according to the target, but if the properties of the metal ions are similar, such as mutual separation of rare earths, In this case, large-scale equipment, a large amount of organic solvent and energy are required.

As another example of separation of metal ions, Non-Patent Document 5 shows a result of separation of metal ions by acid leaching and solvent extraction to recover indium, which is one of rare metals, from a liquid crystal panel. In the solvent extraction, di- (2-ethylhexyl) phosphoric acid (Hdehp), tributyl phosphate (TBP), bis (2,4,4-trimethylpentyl) phosphinic acid (Cyanex272), Cyanex 923 (phosphine oxide) Is used as an extraction reagent, and separation of indium, aluminum, copper, iron, tin, and zinc is investigated using kerosene, toluene, n-octanol, and cyclohexane as organic solvents. Among them, it has been reported that the recovery of indium is excellent when Hdehp is used as an extraction reagent and kerosene is used as an organic solvent.

As another method for separating metal ions, there is an “ion exchange method”.
This method is a method in which a target substance is separated by selectively desorbing after adsorbing metal ions to a porous polymer. In ordinary ion exchange resins and the like, there is no great difference in the interaction between the exchanger itself and the rare earth, and separation is performed by using a complexing agent having selectivity for the rare earth in the desorption process. In addition, with a chelate resin in which a highly selective chelating agent is bound to a specific metal ion, the separation process is simplified, but an organic solvent is required for the synthesis of the chelate resin, and the synthesis process is complicated. is there.

As another separation method, an “impregnation resin method” can also be mentioned.
In this method, a solvent extraction reagent is used by being immersed in a porous polymer. The metal ion separation mechanism is the same as the solvent extraction method described above, but is excellent in that no organic solvent is used. However, since only the liquid is infiltrated, deterioration due to the liquid starting to dissolve from the polymer is a problem.

Furthermore, as another separation method, “precipitation separation method” may be mentioned.
Aisin Seiki has announced technology to extract neodymium, dysprosium, etc. from used magnets using inosinic acid contained in skipjack soup (Non-Patent Documents 6 and 7), which is cheaper and safer than conventional methods. It can be said that it is a feature. According to this method, when 90 grams of inosinic acid per liter is mixed with 40 grams of neodymium chloride solution per liter, 95% or more of neodymium can be recovered as a precipitate, and there is a certain target for stable procurement of dysprosium. Has been. However, data on the mutual separation of neodymium and dysprosium is not shown.

In Non-Patent Document 8, neodymium, praseodymium, and erbium are 62% di (2-ethylhexyl) phosphoric acid (HA) and 37% mono- (2-etylhexyl) phosphoric acid (H ₂ A ′). It has been found that when the mixture is mixed in an acetone solution, only a precipitate is formed with HA, while lanthanum is precipitated only by complexing with H ₂ A ′. And as a result of trying to separate them from a mixed solution of lanthanum and neodymium using this, for example, in a system in which lanthanum and neodymium are mixed at 1: 1, neodymium is 19.8% and lanthanum is 0.7% precipitated. . The results of separation of praseodymium and erbium are not described, but are reported to be worse than the neodymium-lanthanum system. However, there is no description about neodymium ions and dysprosium ions.

In view of the current situation, the present inventors have examined a method for selectively separating rare earths, particularly neodymium and dysprosium, which are very difficult to separate, and extracting them with high selectivity to the rare earths. Di-2-ethylhexyl phosphate (Hdehp) (liquid) (DF Peppard, GW Mason, JL Maier, and WJ Driscoll, J., known as a reagent). Inorg.Nucl.Chem. 1957,4,334-343.) (See the following formula) was obtained as a coordinating polymer forming agent.

The coordination polymer is a polymer type complex formed by crosslinking an organic ligand with a metal ion, and is a material group that has been attracting attention in recent years.
The present inventors have found that metal (M) and Hdehp are coordinated and polymerized with ethanol or an ethanol-water mixed solvent to form [M (dehp) ₃ ] _n and precipitate (the above non-reactions). Patent documents (9, 10)).

As a result of further studies, the present inventors have found that Hdehp reacts with rare earth to form a coordination polymer, and that this reaction rate varies depending on the type of ion and the composition ratio of the mixed solvent. The fractionation precipitation method which can isolate | separate neodymium ion and dysprosium ion selectively and low-cost using this reaction was proposed (patent document 1, nonpatent literature 11).
FIG. 10 is a diagram for explaining the coordination polymerization of Hdehp. In the figure, C represents the coordination polymer [M (dehp) ₃ ] _n (M is a rare earth metal) when Hdehp reacts with a rare earth metal ion. Ion) is formed.
The Hdehp shown in A in the figure is said to form a dimer in a non-polar solvent. As shown in B, in the conventional solvent extraction system, three Hdehp dimers are present. A 1: 6 complex is formed with a trivalent rare earth metal ion.

Japanese Patent Application No. 2013-214843

As a result of further studies by the present inventors, the method of Patent Document 1 described above uses a hydrophilic organic solvent such as ethanol or a mixed solvent of a hydrophilic organic solvent such as ethanol and water, but considers the actual process. Then, it was found that it is difficult to use repeatedly, and it is preferable to perform fractional precipitation with a single solvent consisting of only water rather than a mixed solution.

The present invention has been made in view of the current situation, and a method of selectively separating low-cost rare metals that are difficult to separate using only water as a solvent and the rare metals after separation are recovered. It is intended to provide a method.

As a result of intensive studies to achieve the above-mentioned object, the present inventors have replaced water-soluble phosphate diesters such as dibutyl phosphate (hereinafter referred to as the following) instead of di-2-ethylhexyl phosphate (Hdehp). "Hdbp") or hydrogen phosphate = bis [2- (methacryloyloxy) ethyl] (hereinafter also referred to as "Hpmoe"), etc. As a result, it was found that separation of neodymium and dysprosium, which is difficult to separate, is possible. It was also found that trivalent rare metals such as indium can be selectively fractionated.
Furthermore, by further mixing an acid to adjust the acid dissociation degree of the phosphoric acid diester in the aqueous solution, the separation is improved, and as the acid to be used, it is better to separate using nitric acid than hydrochloric acid, Furthermore, it was also found that the separation is improved when the coordination polymer precipitated at high temperature is aged at high temperature and then filtered.

In addition, as a result of studying a reusable recovery method for separated and precipitated dysprosium, it is effective for reuse by converting the fractionally precipitated dysprosium coordination polymer into oxalate and carbonate and firing it. It was also found that it could be recovered as dysprosium oxide.

The present invention has been completed based on this finding, and the following inventions are provided.
[1] A method for separating rare metal by fractional precipitation from an aqueous solution containing rare metal ions,
A fractional precipitation method characterized in that a water-soluble phosphoric acid diester is used as a coordination polymer forming agent, and trivalent rare metal ions are selectively converted into a coordination polymer in an aqueous solution for fractional precipitation.
[2] The fractional precipitation method according to [1], wherein the water-soluble phosphate diester is dibutyl phosphate or hydrogen phosphate = bis [2- (methacryloyloxy) ethyl].
[3] The fractional precipitation method according to [1] or [2], wherein the trivalent rare metal is rare earth or indium.
[4] The fractional precipitation method according to [1] or [2], wherein the dysprosium ion is selectively coordinated and polymerized in an aqueous solution containing neodymium ions and dysprosium ions.
[5] The fractional precipitation method according to [4], wherein an acid is further mixed with the aqueous solution to adjust the dissociation degree of the phosphoric acid diester in the aqueous solution.
[6] The fractional precipitation method according to [4] or [5], wherein the aqueous solution is heated to less than 100 ° C.
[7] A method in which the coordination polymer of dysprosium separated and precipitated by the method according to any one of [4] to [6] is converted into oxalate or carbonate and then baked to recover it as dysprosium oxide.

According to the present invention, trivalent rare metals can be separated using only water as a solvent without requiring a multistage process using an organic solvent as in solvent extraction, and separation is particularly difficult. Neodymium and dysprosium can be separated. In addition, the method of the present invention solidifies the extraction reagent itself, and unlike the impregnating resin that supports the liquid extraction reagent, water is the only solvent required for separation, and is very inexpensive and simple. .

The figure which shows the hydrochloric acid concentration dependence of the precipitation rate in each single-component solution of Nd and Dy of Example 1. The figure which shows the hydrochloric acid concentration dependence of the precipitation rate of Nd and Dy in the mixed solution of Nd and Dy of Example 2. The figure which shows the Nadbp density | concentration dependence of the precipitation rate of Nd and Dy in the hydrochloric acid acidic mixed solution of Nd and Dy of Example 3. The figure which shows the nitric acid concentration dependence of the precipitation rate of Nd and Dy in the mixed solution of Nd and Dy of Example 4. The figure which shows the precipitation rate of Nd and Dy when the standing time in 20 degreeC in the mixed solution of Nd and Dy of Example 5 is changed. The figure which shows the precipitation rate of Nd and Dy when the standing time in 80 degreeC in the mixed solution of Nd and Dy of Example 7 is changed. The figure which shows the Nadbp density | concentration dependence of the precipitation rate of Nd and Dy in the nitric acid acidic mixed solution of Nd and Dy of Example 8. The figure which shows the precipitation rate of Nd and Dy when the nitric acid concentration is changed at 80 degreeC in the mixed solution of Nd and Dy of Example 9. SEM image of the Dy coordination polymer of Example 10 and the precipitate after the Dy coordination polymer was treated with an oxalic acid aqueous solution and a sodium hydrogen carbonate solution Powder X-ray diffraction pattern of a precipitate obtained by treating the Dy coordination polymer of Example 10 with an oxalic acid aqueous solution and a sodium hydrogen carbonate solution and calcining at 800 ° C. Diagram explaining Hdehp's coordination polymerisation

In the fractional precipitation method of the present invention, a water-soluble phosphoric acid diester is used as a coordination polymer-forming agent, and a rare metal ion is selectively converted into a coordination polymer in an aqueous solution containing a trivalent rare metal ion. It is characterized by fractional precipitation.

The present invention utilizes the fact that a phosphate diester that has been acid-dissociated in an aqueous solution reacts with trivalent rare metal ions in the aqueous solution to form a coordination polymer (solid). However, it is not necessary that all the phosphoric acid diesters in the aqueous solution are acid-dissociated.

The water-soluble phosphate diester used in the present invention preferably has a water solubility of 0.01 mol·L ⁻¹ or more, more preferably 0.05 mol·L ⁻¹ . However, a substance satisfying the above-mentioned conditions may be used for the solubility of the phosphoric diester made dissociated by mixing sodium salt or the like.
Specifically, a phosphoric acid diester having 2 to 6 carbon atoms in the alkyl chain is desirable, and if it has a hydrophilic group such as an ether or a hydroxyl group, it may be a diester having 6 or more carbon atoms, particularly preferably easily available. Commercially available water-soluble phosphoric acid diesters are used, for example:

Dibutyl phosphate represented by the following formula:

And hydrogen phosphate = bis [2- (methacryloyloxy) ethyl] and the like.

In addition to the rare earths (scandium, yttrium, and lanthanoids from lanthanum to lutetium, a total of 17 mineral species), trivalent rare metals in the present invention include indium, titanium, vanadium, chromium, manganese, cobalt, gallium, Zirconium, niobium, molybdenum, ruthenium, rhodium, antimony, tantalum, rhenium, thallium, bismuth can be mentioned.
In particular, the present invention is capable of selectively coordinating polymerizing dysprosium ions and fractionally precipitating them in an aqueous solution containing neodymium and dysprosium ions, which are difficult to separate. That is, in the method of the present invention, in the aqueous solution containing rare metal ions, particularly at least neodymium ions and dysprosium ions, the phosphate diester dissolved in water selectively forms a coordination polymer with the rare metal ions. The coordinating polymer is precipitated, and the rare metal can be separated using only water as a solvent.

In the present invention, the concentration of the water-soluble phosphoric diester in the aqueous solution is preferably 0.01 to 0.5 mol·L ⁻¹ .
In the mixed solution containing neodymium ions and dysprosium ions, the concentration of the water-soluble phosphate diester is desirably mixed so as to be approximately three times the concentration of the dysprosium ions to be separately precipitated.

In the present invention, as a method for selectively converting dysprosium ions into an aqueous solution in an aqueous solution, a water-soluble phosphate diester which is a coordination polymerizing agent in a mixed solution containing neodymium ions and dysprosium ions. The mixing method is not particularly limited.
That is, for example, as a solution containing neodymium ions and dysprosium ions, an aqueous solution in which a salt of neodymium and dysprosium is dissolved in water is used. Then, a water-soluble phosphate diester is mixed with an aqueous solution containing these neodymium ions and dysprosium ions, or an aqueous solution in which a water-soluble phosphate diester is dissolved is mixed with the aqueous solution. Mix water accordingly.
The coordination polymer thus obtained is separated by washing and filtering after, for example, standing at room temperature overnight.

Furthermore, in this invention, separation efficiency can be improved by mixing an acid with a liquid mixture and adjusting the acid dissociation degree of the phosphoric acid diester in this liquid mixture.
The acid to be mixed is not particularly limited as long as it is soluble in water. For example, nitric acid or hydrochloric acid is preferably used, and nitric acid is more preferably used.
The preferred acid concentration varies depending on the acid dissociation constant of the water-soluble phosphate diester and the type of acid, but when Na-type dibutyl phosphate is used in a nitric acid solution, the acid concentration is preferably 0.4 mol·L ⁻¹ .

The temperature at which the solution is mixed is preferably higher than 100 ° C., more preferably 50 to 80 ° C., rather than room temperature (20 ° C.). Furthermore, if the solution is allowed to stand for 3 hours or more, preferably 24 hours or more, and more preferably 72 hours or more, rather than filtering immediately after mixing the solution, the selectivity for precipitation separation is increased.

In order to reuse rare metals such as neodymium and dysprosium separated by the method of the present invention, it is necessary to recover them as highly versatile compounds.
For that purpose, it is desirable to form an oxide that has high solubility in water, can be converted into chlorides and nitrates, and can be converted into metal when reduced at a high temperature.
In the present invention, the separately precipitated dysprosium can be recovered as dysprosium oxide by converting it into oxalate or carbonate and baking it.
Specifically, the fractionally precipitated dysprosium is put into an aqueous solution of oxalic acid or carbonic acid or a salt of oxalic acid or carbonic acid. Since oxalic acid or carbonic acid forms a sparingly soluble salt with dysprosium, the aqueous solution contains an amount necessary for dysprosium to precipitate as a salt of oxalic acid or carbonic acid, an amount exceeding the so-called stoichiometric ratio. However, it is considered that the recovery rate is improved by increasing the concentration, and it is preferable that the amount is twice or more.
Moreover, although a solution may be left still, it is preferable to improve a collection rate by shaking a solution. Further, the reaction is preferably performed for 1 day or longer, more preferably 2 days or longer.

Hereinafter, although the precipitation separation method of this invention is demonstrated using an Example, this invention is not limited to these Examples.
In the following examples, dibutyl phosphate (hereinafter referred to as “Hdbp”) or hydrogen phosphate = bis [2- (methacryloyloxy) ethyl] (hereinafter referred to as “Hpmoe”) as the water-soluble phosphate diester. ) Was used.

[Preparation of 0.30mol·L ^-1 Nadbp aqueous solution]
Hdbp was changed to Na type using an aqueous NaOH solution so that the pH did not change before and after the reaction.
Hdbp (6.3 g) was mixed with 2.07 mL of 14.5 mol·L ⁻¹ NaOH aqueous solution to make 100 mL with water to prepare 0.30 mol·L ⁻¹ Nadbp aqueous solution.
[Preparation of 0.37mol·L ^-1 Napmoe aqueous solution]
To prevent the pH from changing before and after the reaction, HPmoe was changed to Na type using an aqueous NaOH solution.
Hpmoe 5.11 g was mixed with 1.07 mL of 14.5 mol·L ⁻¹ NaOH aqueous solution to make 50 mL with water to prepare 0.32 mol·L ⁻¹ Napmoe aqueous solution.

[Preparation of 1.0 mol·L ⁻¹ MCl ₃ and M (NO ₃ ) ₃ aqueous solution (M is Nd or Dy)]
An aqueous solution of Nd and Dy was prepared by the following two methods.
(1) Each of NdCl ₃ hexahydrate and DyCl ₃ hexahydrate was dissolved in water to prepare 1.0 mol·L ⁻¹ solution. In order to prevent salt precipitation, hydrochloric acid (HCl) was added so that the concentration was 0.25 mol·L ⁻¹ .
(2) Each of Nd (NO ₃ ) ₃ hexahydrate and Dy (NO ₃ ) ₃ hexahydrate was dissolved in water to prepare a 1.0 mol·L ⁻¹ solution. In order to prevent salt precipitation, nitric acid (HNO ₃ ) was added so as to be 0.25 mol·L ⁻¹ .

0.30mol · L ^-1 Nadbp aqueous solution of the, and with reference to 1.0mol · L ^-1 MCl ₃ aqueous solution of the (1) was mixed with 4 kinds of solutions shown in Table 1-1, in each solution 20 ° C. After allowing to stand overnight, the precipitated coordination polymer was washed and filtered, the weight was measured, and each weight was recorded.
Hereinafter, the concentration unit “mol·L ⁻¹ ” in the table may be expressed as “M”.

(Measurement of solubility product)
In order to evaluate the effectiveness of Hdbp precipitation separation, the solubility product of Nd-dbp coordination polymer ([Nd (dbp) ₃ ]) and Dy-dbp coordination polymer ([Dy (dbp) ₃ ]) It was measured.
Dbp ^- precipitation reaction between the Nd or Dy expressed in the following reaction scheme.

The conditions under which precipitation occurs are determined by the solubility product (K _sp ) determined by the following equation, and the larger the difference between K _sp (Nd) and K _sp (Dy), the more effective the fractional precipitation.

In the formula, a is the activity, γ is the activity coefficient, and c is the concentration.
Assuming γ = 1, the product of concentration can be used to evaluate the effectiveness of fractional precipitation. The product of this concentration is the apparent solubility (K ^a _sp ).

The Nd coordination polymer and the Dy coordination polymer synthesized under the conditions of Experiments No. 1-1 and 1-5 in Table 1-1 above were measured at 20 ° C. in the weight shown in Table 1-2. I put it in the water.

After shaking for 45 days, a predetermined amount of supernatant was collected and weighed, and ₃ mL of 60% HNO 3 and 0.3 mL of H ₂ O ₂ were put in a PTFE container dedicated to acid decomposition and decomposed in a microwave oven (200 W). . The resulting acid solution was diluted and the concentrations of Nd or Dy and P were quantified by ICP-emission spectroscopic analysis. Table 1-3 summarizes the results.

C in the above table (P) is c (dbp ^-) by equal and to determine the apparent solubility K ^a _sp (Nd) and K ^a _sp (Dy) according to [0044]. Table 1-4 summarizes the results.
For reference, K _sp (Nd) / K _sp (Dy) of phosphate (MPO ₄ ) and oxalate (M ₂ (C ₂ O ₄ ) ₃ ) are described.

1) K _sp (Nd) / K _sp (Dy) calculated based on the solubility product described in Liu et al., Geochim. Cosmochimica Acta., 1997, 61, 1625.
2) K _sp (Nd) / K _sp (Dy) calculated based on the solubility product described in Chung et al. J. Ind. Eng. Chem., 1998, 4, 277.
* M indicates Nd or Dy

The ratio of K ^a _sp in the case of [M (dbp) _3] is larger than that in the phosphate (MPO ₄₎ and oxalate _{_{_{(M 2 (C 2 O 4}}} ) 3), utilizing the dbp It can be seen that the precipitation reaction is effective for separation of Nd and Dy.

Example 1
In this example, the dependence of the precipitation rate of Nd and Dy on the HCl concentration when a single component solution of Nd and Dy and a Nadbp solution were mixed was examined.
About 0.015 g of the precipitate obtained from each solution shown in Table 1-1 was weighed and subjected to acid decomposition using a microwave oven in the same manner as described in [0047]. The resulting acid solution was diluted and Nd or Dy and P concentrations were quantified by ICP-emission spectroscopic analysis.
The obtained P / M molar ratio, HCl concentration at the time of mixing, Nd and Dy precipitation rates calculated from the Nd or Dy concentration in the solution are summarized in Table 1-5. FIG. 1 plots the precipitation rate against the HCl concentration.

The P / M molar ratio is 3, indicating that the precipitate has a coordination polymer structure.
It can also be seen that the precipitation rate is higher for Dy than Nd, and the higher the HCl concentration, the lower the precipitation rate, but the greater the difference between the Nd precipitation rate and the Dy precipitation rate.

(Example 2)
In this example, the dependence of the precipitation rate of Nd and Dy on the HCl concentration when the mixture was precipitated as a dbp coordination polymer using a mixed solution of Nd and Dy was examined.
As shown in Table 2-1, four types of solutions were mixed, and each weight was recorded.

After allowing the solution to stand overnight, the precipitated coordination polymer was washed and filtered, and the weight was measured.
The precipitate was filtered and decomposed by the same procedure as described above.
Table 2-2 summarizes the obtained P / (Dy + Nd) molar ratio, HCl concentration at the time of solution mixing, and Nd and Dy precipitation rates calculated from the concentrations of Nd and Dy in the solution. Further, the precipitation rate against the HCl concentration is plotted in FIG.

Since the P / (Nd + Dy) molar ratio is approximately 3, it can be seen that the precipitate obtained by mixing the mixed solution of Nd and Dy and the Nadbp solution also has a coordination polymer structure.
In addition, the precipitation rate is higher for Dy than for Nd. In particular, when the HCl concentration is 5 mol·L ⁻¹ , only Dy is selectively precipitated.

Example 3
In this example, the dependence of the precipitation rate on the Nadbp concentration was examined using a mixed solution of Nd and Dy.
In Experiment No. 2-2 of Example 2, the precipitation rates of Nd and Dy were examined under the conditions where the Nadbp concentration was changed.
As shown in Table 3-1, four types of solutions were mixed and each weight was recorded.

After allowing the solution to stand overnight, the precipitated coordination polymer was washed and filtered to measure the weight, and the precipitate was filtered and decomposed in the same manner as described above.
The obtained P / (Dy + Nd) molar ratio, HCl concentration at the time of solution mixing, and Nd and Dy precipitation rates calculated from the concentrations of Nd and Dy in the solution were compared with those in Experiment No. 2-2. Sum it up in two. Moreover, the precipitation rate of Nd and Dy with respect to the Nadbp density | concentration at the time of solution mixing is plotted in FIG.

When the Nadbp concentration is in the range of 0.03 to 0.12 mol·L ⁻¹ , the precipitation rate of Nd slightly increases and the precipitation rate of Dy greatly increases as the Nadbp concentration increases. High Nadbp concentration increases Dy recovery but increases Nd content. On the other hand, when the Nadbp concentration is low, the Dy recovery rate is lowered, but the Nd content rate can be lowered. Therefore, it can be seen that the Nadbp concentration is preferably about three times the Dy concentration in order to reduce the Nd content and increase the Dy recovery rate.

Example 4
In this example, the dependence of the precipitation rate of Nd and Dy on the HNO ₃ concentration in the case of precipitation as a dbp coordination polymer using a mixed solution of Nd and Dy was examined.
As shown in Table 4-1, four types of solutions were mixed and each solution was allowed to stand at 20 ° C. overnight (24 h), and then the precipitated coordination polymer was washed and filtered to measure the weight. Recorded.

The precipitate was filtered and decomposed by the same procedure as described above.
P / (Dy + Nd) molar ratio obtained, HNO ₃ concentration at the time of solution mixing, precipitation rate of Nd and Dy calculated from Nd and Dy concentration in solution, Dy in precipitate calculated from composition analysis of precipitate The / Nd molar ratio is summarized in Table 4-2. Moreover, the precipitation rate of Nd and Dy with respect to the HNO ₃ density | concentration at the time of solution mixing is plotted in FIG.

Since P / (Nd + Dy) is approximately 3, it can be seen that the precipitate obtained in the HNO ₃ solution also has a coordination polymer structure.
Moreover, the precipitation rate is higher for Dy than for Nd, and especially when the HNO ₃ concentration at the time of mixing the solution is 0.40 mol·L ⁻¹ , the precipitation rate of Nd is low and Dy selectively precipitates. .

(Example 5)
In this example, the precipitation rates of Nd and Dy when the time until filtration in Experiment No. 4-5 of Example 4 was changed were examined.
After mixing the solution under the same conditions as in Experiment No. 4-5, the solution was allowed to stand at 20 ° C. as shown in Table 5-1.

The precipitated coordination polymer was washed and filtered to measure the weight, and the precipitate was filtered and decomposed in the same manner as described above.
Table 5 shows the obtained P / (Dy + Nd) molar ratio, the precipitation rate of Nd and Dy calculated from Nd and Dy concentrations in the solution, and the Dy / Nd molar ratio in the precipitate calculated from the composition analysis of the precipitate. Sum it up in two. Moreover, the change of the precipitation rate with respect to the solution standing time at 20 ° C. is plotted in FIG.

The longer the standing time, the lower the precipitation rate of Nd and the higher the precipitation rate of Dy. Therefore, it can be seen that the longer the standing time, the more selectively Dy is precipitated.

(Example 6)
In this example, when a mixed solution of Nd and Dy is used to precipitate as a dbp coordination polymer in an HNO ₃ acidic solution, the effect of shaking the solution before filtration and the temperature of the solution are increased. The effect was examined.
The solution was mixed under the same conditions as in Experiment No. 4-5 in Example 4 above, and the solution was processed as shown in Table 6-1.

The precipitated coordination polymer was washed and filtered to measure the weight, and the precipitate was filtered and decomposed in the same procedure as described above.
The obtained P / (Dy + Nd) molar ratio, the Nd and Dy precipitation rates calculated from the Nd and Dy concentrations in the solution, and the Dy / Nd molar ratio in the precipitate calculated from the composition analysis of the precipitate are shown in Table 6- Sum it up in two.

The Nd precipitation rate is lower and the Dy precipitation rate is higher when shaken than when the solution is allowed to stand at 20 ° C. In addition, the precipitation rate of Nd is lower and the precipitation rate of Dy is higher when the solution is allowed to stand at 80 ° C. than when the solution is shaken at 20 ° C.

(Example 7)
In this example, in Experiment No. 6-3 of Example 6, the precipitation rates of Nd and Dy when the solution standing time was changed were examined.
The solution was mixed under the same conditions as in Experiment No. 6-3, and the solution was treated as shown in Table 7-1.

The precipitated coordination polymer was washed and filtered to measure the weight, and the precipitate was filtered and decomposed in the same procedure as described above.
The obtained P / (Dy + Nd) molar ratio, the Nd and Dy precipitation rates calculated from the Nd and Dy concentrations in the solution, and the Dy / Nd molar ratio in the precipitate calculated from the composition analysis of the precipitate are shown in Table 7- Sum it up in two. Moreover, the change of the precipitation rate with respect to the solution standing time at 80 ° C. is plotted in FIG.

When the mixed solution is allowed to stand at 80 ° C. for 5 minutes, Nd also precipitates, but when left for more than 24 hours, the Nd precipitation rate is zero. Therefore, it can be seen that when the mixed solution is allowed to stand at 80 ° C. for 24 hours or more, Dy can be more selectively precipitated. When left for 24 hours or 72 hours, the Dy / Nd molar ratio in the precipitate does not change much, but when left for 168 hours, the Dy / Nd ratio in the precipitate slightly increases. Therefore, it can be seen that the longer the standing time, the higher the Dy purity in the precipitate.

(Example 8)
In this example, the precipitation rate of Nd and Dy when the Nadbp concentration was changed in Experiment No. 7-2 of Example 7 was examined.
The solutions were mixed as in Table 8-1.

The mixed solution was allowed to stand at 80 ° C. for 24 hours, and then the precipitated coordination polymer was washed and filtered to measure the weight, and the precipitate was filtered and decomposed in the same procedure as described above.
The obtained P / (Dy + Nd) molar ratio, the Nd and Dy precipitation rates calculated from the Nd and Dy concentrations in the solution, and the Dy / Nd molar ratio in the precipitate calculated from the composition analysis of the precipitate are shown in Table 8- Sum it up in two. Moreover, the change of the precipitation rate with respect to the Nadbp density | concentration at the time of solution mixing is plotted in FIG.

As the Nadbp concentration increases, the precipitation rate of Nd and Dy increases. Therefore, in order to precipitate only more selective and Dy, Nadbp concentration 0.06 mol · L ^-1 when the Dy ion concentration 0.02 mol · L ^-1, i.e. equivalent of dbp forming a coordination polymer ^- a It turns out that mixing is good.

Example 9
In this example, the precipitation rates of Nd and Dy when the acid concentration in Experiment No. 7-1 in Example 7 was changed were examined.
The solutions were mixed as shown in Table 9-1.

The mixed solution was allowed to stand at 80 ° C. for 3 hours, and then the precipitated coordination polymer was washed and filtered to measure the weight, and the precipitate was filtered and decomposed in the same procedure as described above.
The obtained P / (Dy + Nd) molar ratio, Nd and Dy precipitation rates calculated from the Nd and Dy concentrations in the solution are summarized in Table 9-2. Moreover, the change of the precipitation rate with respect to the HNO ₃ density | concentration at the time of solution mixing is plotted in FIG.

As the acid concentration decreases, the precipitation rate of Nd increases. On the other hand, the precipitation rate of Dy does not change much. Therefore, in order to precipitate only Dy more selectively, it is understood that a coordination polymer is preferably formed in a 0.4 mol·L ⁻¹ HNO ₃ solution.

(Example 10)
In this example, a method for recovering fractionally precipitated Dy as a highly versatile oxide was examined.
The precipitate (Dy-dbp coordination polymer) obtained in Experiment No. 7-2 in Example 8 was placed in an oxalic acid or sodium bicarbonate solution as shown in Table 10-1.

After shaking the liquid for 2 days, the solution was filtered to collect the precipitate. The weight of the collected precipitate is summarized in Table 10-2.

FIG. 9-1 shows SEM images of the precipitate obtained in Experiment No. 7-2 in Example 8 and the precipitates obtained in 10-1-1 and 10-2-1.

From the SEM images, it can be seen that the crystal shapes of Experiment Nos. 10-1-1 and 10-2-1 are different from the precipitate obtained in Experiment No. 7-2.

The precipitates obtained in Experiment Nos. 10-1-1 and 10-2-1 were collected in the weight shown in Table 10-3, heated in an electric furnace from 25 ° C. to 800 ° C. over 1 hour, Baked at 800 ° C. for 2 hours.

The weight of the precipitate collected after cooling to room temperature is shown in Table 10-4.

Fig. 9-2 shows the powder X-ray diffraction patterns of the precipitates obtained in Experiment Nos. 10-1-2 and 10-2-2.

The powder X-ray diffraction patterns of the precipitates obtained in Experiment Nos. 10-1-2 and 10-2-2 agree with the dysprosium oxide pattern, and can be recovered as dysprosium oxide by firing at 800 ° C. I understand.

From Table 10-1 and Table 10-2, it can be seen that the recovery rate when the Dy-dbp coordination polymer is converted to dysprosium oxalate is 70%. From Table 10-3 and Table 10-4, it can be seen that the recovery rate when dysprosium oxalate decahydrate is converted to dysprosium oxide is 100%.

(Example 11)
In this example, the Nd and Dy precipitation rates when the Dy concentration and the Nadbp concentration were reduced to 1/5 in Experiment No. 7-3 in Example 7 were examined.
The solutions were mixed as shown in Table 11-1.

The mixed solution is allowed to stand at 80 ° C. for 72 hours, and then the precipitated coordination polymer is washed and filtered to measure the weight, and the precipitate is filtered by the same procedure as described in [0047]. Disassembled.
The obtained P / (Dy + Nd) molar ratio, Nd and Dy precipitation rates calculated from the Nd and Dy concentrations in the solution are summarized in Table 11-2.

When the concentration of Nd and Dy is 5: 1, the precipitation rate of Dy is low, but only Dy can be selectively precipitated.

Example 12
In this example, in order to investigate whether the coordination polymer forming agent of the present invention can be applied to recover indium (In) from a liquid crystal panel, In and transition metals (aluminum (Al), copper ( The acid concentration dependence of the precipitation rate from a mixed solution of Cu) and zinc (Zn) was investigated.
In Example 2, the precipitation rate of each metal element was examined under the condition that the mixed solution of Nd and Dy was changed to a mixed solution of In, Al, Cu, and Zn.
Four types of solutions were mixed as shown in Table 12-1 below, and each weight was recorded.

After allowing the solution to stand overnight, the precipitated coordination polymer was washed and filtered to measure the weight, and the precipitate was filtered and decomposed in the same manner as described above.
Table 12-2 summarizes the precipitation rates of each metal element from the obtained P / M molar ratio (M is the total concentration of metal ions), HCl concentration, and the weight of the precipitate.

As shown in Table 12-2, even if a transition metal having a higher concentration than In is mixed, only In is selectively precipitated. Since the precipitation rate of Cu and Zn is 0%, it is considered that divalent metal ions do not form coordination polymers, and Al is trivalent, but only In precipitates selectively. From this, it can be seen that selective separation is possible even for metal ions having the same valence.

(Example 13)
In this example, Nd / Dy separation using hydrogen phosphate = bis [2- (methacryloyloxy) ethyl] as a water-soluble phosphate diester was examined.
In Example 2, the precipitation rate of each metal element from the mixed solution of Nd and Dy was examined by changing the hydrogen phosphate Nadbp to Na-type hydrogen phosphate = bis [2- (methacryloyloxy) ethyl (Napmoe).
Four types of solutions were mixed as shown in Table 13-1 below, and each weight was recorded.

After allowing the solution to stand overnight, the precipitated coordination polymer was washed and filtered to measure the weight, and the precipitate was filtered and decomposed in the same manner as described above.
Table 13-2 summarizes the precipitation rates of Nd and Dy calculated from the obtained P / (Dy + Nd) molar ratio, HCl concentration, and the weight of the precipitate.

As shown in Table 13-2, when the acid concentration is 3.0 mol·L ⁻¹ , neither Dy nor Nd is precipitated.
Compared to Example 2, it can be seen that Nadbp has a higher precipitation rate even at higher acid concentrations than Napmoe. In addition, when the acid concentration is 0.30 mol·L ⁻¹ and 0.17 mol·L ⁻¹ , Dy is selectively precipitated, but the precipitation rate is low.

Claims

A method for separating rare metals by fractional precipitation from an aqueous solution containing ions of rare metals,
A fractional precipitation method characterized in that a water-soluble phosphoric acid diester is used as a coordination polymer forming agent, and trivalent rare metal ions are selectively converted into a coordination polymer in an aqueous solution for fractional precipitation.
The fractional precipitation method according to claim 1, wherein the water-soluble phosphate diester is dibutyl phosphate or hydrogen phosphate = bis [2- (methacryloyloxy) ethyl].
The fractional precipitation method according to claim 1 or 2, wherein the trivalent rare metal is rare earth or indium.
3. The fractional precipitation method according to claim 1, wherein the dysprosium ions are selectively coordinated and polymerized in an aqueous solution containing at least neodymium ions and dysprosium ions.
The fractional precipitation method according to claim 4, wherein the aqueous solution is further mixed with an acid to adjust the dissociation degree of the phosphoric acid diester in the aqueous solution.
The fractional precipitation method according to claim 4 or 5, wherein the aqueous solution is heated to less than 100 ° C.
A method for recovering dysprosium oxide by converting the dysprosium coordination polymer fractionally precipitated by the method according to any one of claims 4 to 6 into oxalate or carbonate, followed by baking.